doc: update NEWS

doc: mention maxdelayquant in FAQ
test: extend 106-refclock test
2025-12-03 18:45:07 -05:00 · 2022-08-11 10:32:58 +02:00 · 2022-08-10 15:32:54 +02:00 · 2022-08-09 16:53:12 +02:00 · 2022-08-03 15:23:38 +02:00 · 2022-08-03 14:53:35 +02:00
256 changed files with 31083 additions and 7598 deletions
--- a/.gitignore
+++ b/.gitignore
@@ -1,9 +1,12 @@
 .deps
 .vimrc
+*.gcda
+*.gcno
 *.o
 *.swp
 *.dSYM
 *.DS_Store
+core.*
 tags
 /RELEASES
 /Makefile
--- a/Makefile.in
+++ b/Makefile.in
@@ -21,56 +21,56 @@
 #
 # Makefile template

-SYSCONFDIR=@SYSCONFDIR@
-BINDIR=@BINDIR@
-SBINDIR=@SBINDIR@
-LOCALSTATEDIR=@LOCALSTATEDIR@
-CHRONYVARDIR=@CHRONYVARDIR@
+SYSCONFDIR = @SYSCONFDIR@
+BINDIR = @BINDIR@
+SBINDIR = @SBINDIR@
+LOCALSTATEDIR = @LOCALSTATEDIR@
+CHRONYVARDIR = @CHRONYVARDIR@
+DESTDIR =

 CC = @CC@
 CFLAGS = @CFLAGS@
 CPPFLAGS = @CPPFLAGS@
+LDFLAGS = @LDFLAGS@

-DESTDIR=
+EXTRA_OBJS = @EXTRA_OBJS@

-HASH_OBJ = @HASH_OBJ@
+OBJS = array.o cmdparse.o conf.o local.o logging.o main.o memory.o quantiles.o \
+       reference.o regress.o rtc.o samplefilt.o sched.o socket.o sources.o sourcestats.o \
+       stubs.o smooth.o sys.o sys_null.o tempcomp.o util.o $(EXTRA_OBJS)

-OBJS = array.o cmdparse.o conf.o local.o logging.o main.o memory.o \
-       reference.o regress.o rtc.o sched.o sources.o sourcestats.o stubs.o \
-       sys.o smooth.o tempcomp.o util.o $(HASH_OBJ)
-
-EXTRA_OBJS=@EXTRA_OBJECTS@
+EXTRA_CLI_OBJS = @EXTRA_CLI_OBJS@

 CLI_OBJS = array.o client.o cmdparse.o getdate.o memory.o nameserv.o \
-           pktlength.o util.o $(HASH_OBJ)
+           pktlength.o socket.o util.o $(EXTRA_CLI_OBJS)

-ALL_OBJS = $(OBJS) $(EXTRA_OBJS) $(CLI_OBJS)
+ALL_OBJS = $(OBJS) $(CLI_OBJS)

-LDFLAGS = @LDFLAGS@
 LIBS = @LIBS@
-
-EXTRA_LIBS=@EXTRA_LIBS@
-EXTRA_CLI_LIBS=@EXTRA_CLI_LIBS@
+EXTRA_LIBS = @EXTRA_LIBS@
+EXTRA_CLI_LIBS = @EXTRA_CLI_LIBS@

 # Until we have a main procedure we can link, just build object files
 # to test compilation

 all : chronyd chronyc

-chronyd : $(OBJS) $(EXTRA_OBJS)
-	$(CC) $(CFLAGS) -o chronyd $(OBJS) $(EXTRA_OBJS) $(LDFLAGS) $(LIBS) $(EXTRA_LIBS)
+chronyd : $(OBJS)
+	$(CC) $(CFLAGS) -o chronyd $(OBJS) $(LDFLAGS) $(LIBS) $(EXTRA_LIBS)

 chronyc : $(CLI_OBJS)
 	$(CC) $(CFLAGS) -o chronyc $(CLI_OBJS) $(LDFLAGS) $(LIBS) $(EXTRA_CLI_LIBS)

 distclean : clean
-	-rm -f .DS_Store
-	-rm -f Makefile config.h config.log
 	$(MAKE) -C doc distclean
 	$(MAKE) -C test/unit distclean
+	-rm -f .DS_Store
+	-rm -f Makefile config.h config.log

 clean :
-	-rm -f *.o *.s chronyc chronyd core *~
+	$(MAKE) -C test/unit clean
+	-rm -f *.o *.s chronyc chronyd core.* *~
+	-rm -f *.gcda *.gcno
 	-rm -rf .deps
 	-rm -rf *.dSYM

@@ -109,9 +109,18 @@ install-docs :
 %.s : %.c
 	$(CC) $(CFLAGS) $(CPPFLAGS) -S $<

-check : chronyd chronyc
+quickcheck : chronyd chronyc
 	$(MAKE) -C test/unit check
 	cd test/simulation && ./run
+	cd test/system && ./run
+
+check : chronyd chronyc
+	$(MAKE) -C test/unit check
+	cd test/simulation && ./run -i 20 -m 2
+	cd test/system && ./run
+
+print-chronyd-objects :
+	@echo $(OBJS)

 Makefile : Makefile.in configure
 	@echo
@@ -125,4 +134,6 @@ Makefile : Makefile.in configure
 .deps/%.d: %.c | .deps
 	@$(CC) -MM $(CPPFLAGS) -MT '$(<:%.c=%.o) $@' $< -o $@

+ifndef NODEPS
 -include $(ALL_OBJS:%.o=.deps/%.d)
+endif
--- a/242
+++ b/242
@@ -1,3 +1,245 @@
+New in version 4.3
+==================
+
+Enhancements
+------------
+* Add local option to refclock directive to stabilise system clock
+  with more stable free-running clock (e.g. TCXO, OCXO)
+* Add maxdelayquant option to server/pool/peer directive to replace
+  maxdelaydevratio filter with long-term quantile-based filtering
+* Add selection option to log directive
+* Allow external PPS in PHC refclock without configurable pin
+* Don't accept first interleaved response to minimise error in delay
+* Don't use arc4random on Linux to avoid server performance loss
+* Improve filter option to better handle missing NTP samples
+* Improve stability with hardware timestamping and PHC refclock
+* Update seccomp filter
+
+Bug fixes
+---------
+* Fix waitsync command to reconnect when not getting response
+
+New in version 4.2
+==================
+
+Enhancements
+------------
+* Add support for NTPv4 extension field improving synchronisation
+  stability and resolution of root delay and dispersion (experimental)
+* Add support for NTP over PTP (experimental)
+* Add support for AES-CMAC and hash functions in GnuTLS
+* Improve server interleaved mode to be more reliable and support
+  multiple clients behind NAT
+* Update seccomp filter
+* Add statistics about interleaved mode to serverstats report
+
+Bug fixes
+---------
+* Fix RTC support with 64-bit time_t on 32-bit Linux
+* Fix seccomp filter to work correctly with bind*device directives
+* Suppress kernel adjustments of system clock (dosynctodr) on illumos
+
+Other changes
+-------------
+* Switch Solaris support to illumos
+
+New in version 4.1
+==================
+
+Enhancements
+------------
+* Add support for NTS servers specified by IP address (matching
+  Subject Alternative Name in server certificate)
+* Add source-specific configuration of trusted certificates
+* Allow multiple files and directories with trusted certificates
+* Allow multiple pairs of server keys and certificates
+* Add copy option to server/pool directive
+* Increase PPS lock limit to 40% of pulse interval
+* Perform source selection immediately after loading dump files
+* Reload dump files for addresses negotiated by NTS-KE server
+* Update seccomp filter and add less restrictive level
+* Restart ongoing name resolution on online command
+
+Bug fixes
+---------
+* Fix responding to IPv4 command requests on FreeBSD
+* Fix dump files to not include uncorrected offset
+* Fix initstepslew to accept time from own NTP clients
+* Reset NTP address and port when no longer negotiated by NTS-KE server
+
+New in version 4.0
+==================
+
+Enhancements
+------------
+* Add support for Network Time Security (NTS) authentication
+* Add support for AES-CMAC keys (AES128, AES256) with Nettle
+* Add authselectmode directive to control selection of unauthenticated sources
+* Add binddevice, bindacqdevice, bindcmddevice directives
+* Add confdir directive to better support fragmented configuration
+* Add sourcedir directive and "reload sources" command to support dynamic
+  NTP sources specified in files
+* Add clockprecision directive
+* Add dscp directive to set Differentiated Services Code Point (DSCP)
+* Add -L option to limit log messages by severity
+* Add -p option to print whole configuration with included files
+* Add -U option to allow start under non-root user
+* Allow maxsamples to be set to 1 for faster update with -q/-Q option
+* Avoid replacing NTP sources with sources that have unreachable address
+* Improve pools to repeat name resolution to get "maxsources" sources
+* Improve source selection with trusted sources
+* Improve NTP loop test to prevent synchronisation to itself
+* Repeat iburst when NTP source is switched from offline state to online
+* Update clock synchronisation status and leap status more frequently
+* Update seccomp filter
+* Add "add pool" command
+* Add "reset sources" command to drop all measurements
+* Add authdata command to print details about NTP authentication
+* Add selectdata command to print details about source selection
+* Add -N option and sourcename command to print original names of sources
+* Add -a option to some commands to print also unresolved sources
+* Add -k, -p, -r options to clients command to select, limit, reset data
+
+Bug fixes
+---------
+* Don't set interface for NTP responses to allow asymmetric routing
+* Handle RTCs that don't support interrupts
+* Respond to command requests with correct address on multihomed hosts
+
+Removed features
+----------------
+* Drop support for RIPEMD keys (RMD128, RMD160, RMD256, RMD320)
+* Drop support for long (non-standard) MACs in NTPv4 packets (chrony 2.x
+  clients using non-MD5/SHA1 keys need to use option "version 3")
+* Drop support for line editing with GNU Readline
+
+New in version 3.5.1
+====================
+
+Security fixes
+--------------
+* Create new file when writing pidfile (CVE-2020-14367)
+
+New in version 3.5
+==================
+
+Enhancements
+------------
+* Add support for more accurate reading of PHC on Linux 5.0
+* Add support for hardware timestamping on interfaces with read-only
+  timestamping configuration
+* Add support for memory locking and real-time priority on FreeBSD,
+  NetBSD, Solaris
+* Update seccomp filter to work on more architectures
+* Validate refclock driver options
+
+Bug fixes
+---------
+* Fix bindaddress directive on FreeBSD
+* Fix transposition of hardware RX timestamp on Linux 4.13 and later
+* Fix building on non-glibc systems
+
+New in version 3.4
+==================
+
+Enhancements
+------------
+* Add filter option to server/pool/peer directive
+* Add minsamples and maxsamples options to hwtimestamp directive
+* Add support for faster frequency adjustments in Linux 4.19
+* Change default pidfile to /var/run/chrony/chronyd.pid to allow
+  chronyd without root privileges to remove it on exit
+* Disable sub-second polling intervals for distant NTP sources
+* Extend range of supported sub-second polling intervals
+* Get/set IPv4 destination/source address of NTP packets on FreeBSD
+* Make burst options and command useful with short polling intervals
+* Modify auto_offline option to activate when sending request failed
+* Respond from interface that received NTP request if possible
+* Add onoffline command to switch between online and offline state
+  according to current system network configuration
+* Improve example NetworkManager dispatcher script
+
+Bug fixes
+---------
+* Avoid waiting in Linux getrandom system call
+* Fix PPS support on FreeBSD and NetBSD
+
+New in version 3.3
+==================
+
+Enhancements
+------------
+* Add burst option to server/pool directive
+* Add stratum and tai options to refclock directive
+* Add support for Nettle crypto library
+* Add workaround for missing kernel receive timestamps on Linux
+* Wait for late hardware transmit timestamps
+* Improve source selection with unreachable sources
+* Improve protection against replay attacks on symmetric mode
+* Allow PHC refclock to use socket in /var/run/chrony
+* Add shutdown command to stop chronyd
+* Simplify format of response to manual list command
+* Improve handling of unknown responses in chronyc
+
+Bug fixes
+---------
+* Respond to NTPv1 client requests with zero mode
+* Fix -x option to not require CAP_SYS_TIME under non-root user
+* Fix acquisitionport directive to work with privilege separation
+* Fix handling of socket errors on Linux to avoid high CPU usage
+* Fix chronyc to not get stuck in infinite loop after clock step
+
+New in version 3.2
+==================
+
+Enhancements
+------------
+* Improve stability with NTP sources and reference clocks
+* Improve stability with hardware timestamping
+* Improve support for NTP interleaved modes
+* Control frequency of system clock on macOS 10.13 and later
+* Set TAI-UTC offset of system clock with leapsectz directive
+* Minimise data in client requests to improve privacy
+* Allow transmit-only hardware timestamping
+* Add support for new timestamping options introduced in Linux 4.13
+* Add root delay, root dispersion and maximum error to tracking log
+* Add mindelay and asymmetry options to server/peer/pool directive
+* Add extpps option to PHC refclock to timestamp external PPS signal
+* Add pps option to refclock directive to treat any refclock as PPS
+* Add width option to refclock directive to filter wrong pulse edges
+* Add rxfilter option to hwtimestamp directive
+* Add -x option to disable control of system clock
+* Add -l option to log to specified file instead of syslog
+* Allow multiple command-line options to be specified together
+* Allow starting without root privileges with -Q option
+* Update seccomp filter for new glibc versions
+* Dump history on exit by default with dumpdir directive
+* Use hardening compiler options by default
+
+Bug fixes
+---------
+* Don't drop PHC samples with low-resolution system clock
+* Ignore outliers in PHC tracking, RTC tracking, manual input
+* Increase polling interval when peer is not responding
+* Exit with error message when include directive fails
+* Don't allow slash after hostname in allow/deny directive/command
+* Try to connect to all addresses in chronyc before giving up
+
+New in version 3.1
+==================
+
+Enhancements
+------------
+* Add support for precise cross timestamping of PHC on Linux
+* Add minpoll, precision, nocrossts options to hwtimestamp directive
+* Add rawmeasurements option to log directive and modify measurements
+  option to log only valid measurements from synchronised sources
+* Allow sub-second polling interval with NTP sources
+
+Bug fixes
+---------
+* Fix time smoothing in interleaved mode
+
 New in version 3.0
 ==================

--- a/174
+++ b/174
@@ -4,7 +4,7 @@ What is chrony?
 ===============

 chrony is a versatile implementation of the Network Time Protocol (NTP).
-It can synchronize the system clock with NTP servers, reference clocks
+It can synchronise the system clock with NTP servers, reference clocks
 (e.g. GPS receiver), and manual input using wristwatch and keyboard.
 It can also operate as an NTPv4 (RFC 5905) server and peer to provide
 a time service to other computers in the network.
@@ -28,29 +28,23 @@ What will chrony run on?
 ========================

 The software is known to work on Linux, FreeBSD, NetBSD, macOS and
-Solaris.  Closely related systems may work too.  Any other system will
-likely require a porting exercise.  You would need to start from one
-of the existing system-specific drivers and look into the quirks of
-certain system calls and the kernel on your target system.
+illumos.  Closely related systems may work too.  Any other system will
+likely require a porting exercise.

 How do I set it up?
 ===================

 The file INSTALL gives instructions.  On supported systems the
-compilation process should be automatic.
-
-You will need an ANSI C compiler -- gcc is recommended.
-
-The manual (in texinfo and text formats) describes how to set the
-software up for the less straightforward cases.
+compilation process should be automatic.  You will need a C compiler,
+e.g. gcc or clang.

 What documentation is there?
 ============================

-A manual is supplied in Texinfo format (chrony.texi) and
-ready-formatted plain text (chrony.txt) in the distribution.
+The distribution includes manual pages and a document containing
+Frequently Asked Questions (FAQ).

-There is also information available on the chrony web pages, accessible
+The documentation is also available on the chrony web pages, accessible
 through the URL 

    https://chrony.tuxfamily.org/
@@ -59,24 +53,20 @@ Where are new versions announced?
 =================================

 There is a low volume mailing list where new versions and other
-important news relating to chrony is announced.  You can join this list
+important news relating to chrony are announced.  You can join this list
 by sending mail with the subject "subscribe" to

 chrony-announce-request@chrony.tuxfamily.org

-These messages will be copied to chrony-users (see below).
-
 How can I get support for chrony?
-and where can I discuss new features, possible bugs etc?
-========================================================
+=================================

-There are 3 mailing lists relating to chrony.  chrony-announce was
-mentioned above.  chrony-users is a users' discussion list, e.g. for
-general questions and answers about using chrony.  chrony-dev is a more
-technical list, e.g. for discussing how new features should be
-implemented, exchange of information between developers etc.  To
-subscribe to either of these lists, send a message with the subject
-"subscribe" to
+There are two other mailing lists relating to chrony.  chrony-users is a
+discussion list for users, e.g. for questions about chrony configuration
+and bug reports.  chrony-dev is a more technical list for developers,
+e.g. for submitting patches and discussing how new features should be
+implemented.  To subscribe to either of these lists, send a message with
+the subject "subscribe" to

 chrony-users-request@chrony.tuxfamily.org
 or
@@ -84,12 +74,6 @@ chrony-dev-request@chrony.tuxfamily.org

 as applicable.

-When you are reporting a bug, please send us all the information you can.
-Unfortunately, chrony has proven to be one of those programs where it is very
-difficult to reproduce bugs in a different environment. So we may have to
-interact with you quite a lot to obtain enough extra logging and tracing to
-pin-point the problem in some cases. Please be patient and plan for this!
-
 License
 =======

@@ -104,135 +88,73 @@ Miroslav Lichvar <mlichvar@redhat.com>
 Acknowledgements
 ================

-In writing the chronyd program, extensive use has been made of RFC 1305
-and RFC 5905, written by David Mills. The source code of the NTP reference
-implementation has been used to check the details of the protocol.
+In writing the chronyd program, extensive use has been made of the NTPv3 (RFC
+1305) and NTPv4 (RFC 5905) specification.  The source code of the xntpd/ntpd
+implementation written by Dennis Fergusson, Lars Mathiesen, David Mills, and
+others has been used to check the details of the protocol.

 The following people have provided patches and other major contributions
-to the program :
+to chrony:

 Lonnie Abelbeck <lonnie@abelbeck.com>
-    Patch to add tab-completion to chronyc
-
 Benny Lyne Amorsen <benny@amorsen.dk>
-    Patch to add minstratum option
-
 Andrew Bishop <amb@gedanken.demon.co.uk>
-    Fixes for bugs in logging when in daemon mode
-    Fixes for compiler warnings
-    Robustness improvements for drift file
-    Improve installation (directory checking etc)
-    Entries in contrib directory
-    Improvements to 'sources' and 'sourcestats' output from chronyc
-    Improvements to documentation
-    Investigation of required dosynctodr behaviour for various Solaris
-      versions.
-
+Vincent Blut <vincent.debian@free.fr>
 Stephan I. Boettcher <stephan@nevis1.columbia.edu>
-    Entries in contrib directory
-
+David Bohman <debohman@gmail.com>
+Goswin Brederlow <brederlo@informatik.uni-tuebingen.de>
+Leigh Brown <leigh@solinno.co.uk>
 Erik Bryer <ebryer@spots.ab.ca>
-    Entries in contrib directory
-
+Jonathan Cameron <jic23@cam.ac.uk>
 Bryan Christianson <bryan@whatroute.net>
-    Support for macOS
-    Support for privilege separation
-    Entries in contrib directory
-
 Juliusz Chroboczek <jch@pps.jussieu.fr>
-    Fix install rule in Makefile if chronyd file is in use.
-
+Kamil Dudka <kdudka@redhat.com>
+Christian Ehrhardt <christian.ehrhardt@canonical.com>
 Paul Elliott <pelliott@io.com>
-    DNSchrony (in contrib directory), a tool for handling NTP servers
-    with variable IP addresses.
-
+Robert Fairley <rfairley@redhat.com>
+Stefan R. Filipek <srfilipek@gmail.com>
 Mike Fleetwood <mike@rockover.demon.co.uk>
-    Fixes for compiler warnings
-
 Alexander Gretencord <arutha@gmx.de>
-    Changes to installation directory system to make it easier for
-    package builders.
-
 Andrew Griffiths <agriffit@redhat.com>
-    Patch to add support for seccomp filter
-
 Walter Haidinger <walter.haidinger@gmx.at>
-    Providing me with login access to a Linux installation where v1.12
-    wouldn't compile, so I could develop the fixes for v1.13.  Also, for
-    providing the disc space so I can keep an independent backup of the
-    sources.
-
 Juergen Hannken-Illjes <hannken@eis.cs.tu-bs.de>
-    Port to NetBSD
-
 John Hasler <john@dhh.gt.org>
-    Project and website at tuxfamily.org
-    Changes to support 64 bit machines (i.e. those where
-      sizeof(unsigned long) > 4)
-    Bug fix to initstepslew directive
-    Fix to remove potential buffer overrun errors.
-    Memory locking and real-time scheduler support
-    Fix fault where chronyd enters an endless loop
-
 Tjalling Hattink <t.hattink@fugro.nl>
-    Fix scheduler to allow stepping clock from timeout handler
-    Patch to take leap second in PPS refclock from locked source
-    Patch to make reading of RTC for initial trim more reliable
-
 Liam Hatton <me@liamhatton.com>
-    Advice on configuring for Linux on PPC
-
 Jachym Holecek <jakym@volny.cz>
-    Patch to make Linux real time clock work with devfs
-
 Håkan Johansson <f96hajo@chalmers.se>
-    Patch to avoid large values in sources and sourcestats output
-
 Jim Knoble <jmknoble@pobox.com>
-    Fixes for compiler warnings
-
 Antti Jrvinen <costello@iki.fi>
-    Advice on configuring for BSD/386
-
+Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
+Eric Lammerts <eric@lammerts.org>
+Stefan Lucke <stefan@lucke.in-berlin.de>
+Victor Lum <viclum@vanu.com>
+Kevin Lyda <kevin@ie.suberic.net>
+Paul Menzel <paulepanter@users.sourceforge.net>
+Vladimir Michl <vladimir.michl@seznam.cz>
 Victor Moroz <vim@prv.adlum.ru>
-    Patch to support Linux with HZ!=100
-
 Kalle Olavi Niemitalo  <tosi@stekt.oulu.fi>
-    acquisitionport support
-
 Frank Otto <sandwichmacher@web.de>
-    Handling arbitrary HZ values
-
 Denny Page <dennypage@me.com>
-    Advice on support for hardware timestamping
-
+Chris Perl <cperl@janestreet.com>
 Gautier PHILIPPON <gautier.philippon@ensimag.grenoble-inp.fr>
-    Patch to add refresh command to chronyc
-
 Andreas Piesk <apiesk@virbus.de>
-    Patch to make chronyc use the readline library if available
-
+Baruch Siach <baruch@tkos.co.il>
+Foster Snowhill <forst@forstwoof.ru>
+Andreas Steinmetz <ast@domdv.de>
+NAKAMURA Takumi <takumi@ps.sakura.ne.jp>
 Timo Teras <timo.teras@iki.fi>
-    Patch to reply correctly on multihomed hosts
-
 Bill Unruh <unruh@physics.ubc.ca>
-    Advice on statistics
-
 Stephen Wadeley <swadeley@redhat.com>
-    Improvements to man pages
-
+Bernhard Weiss <lisnablagh@web.de>
 Wolfgang Weisselberg <weissel@netcologne.de>
-    Entries in contrib directory
-
+Bernhard M. Wiedemann <bwiedemann@suse.de>
+Joachim Wiedorn <ad_debian@joonet.de>
 Ralf Wildenhues <Ralf.Wildenhues@gmx.de>
-    Many robustness and security improvements
-    
-Ulrich Windl <ulrich.windl@rz.uni-regensburg.de> for the
-    Providing me with information about the Linux 2.2 kernel
-    functionality compared to 2.0.
-
+Ulrich Windl <ulrich.windl@rz.uni-regensburg.de>
+Michael Witten <mfwitten@gmail.com>
 Doug Woodward <dougw@whistler.com>
-    Advice on configuring for Solaris 2.8 on x86
+Thomas Zajic <zlatko@zlatko.fdns.net>

 Many other people have contributed bug reports and suggestions.  We are sorry
 we cannot identify all of you individually.
--- a/addressing.h
+++ b/addressing.h
@@ -30,16 +30,19 @@
 #include "sysincl.h"

 /* This type is used to represent an IPv4 address or IPv6 address.
+   Addresses which are not resolved yet can be represented with an ID.
   All parts are in HOST order, NOT network order. */

 #define IPADDR_UNSPEC 0
 #define IPADDR_INET4 1
 #define IPADDR_INET6 2
+#define IPADDR_ID 3

 typedef struct {
  union { 
    uint32_t in4;
    uint8_t in6[16];
+    uint32_t id;
  } addr;
  uint16_t family;
  uint16_t _pad;
@@ -47,11 +50,16 @@ typedef struct {

 typedef struct {
  IPAddr ip_addr;
-  unsigned short port;
-} NTP_Remote_Address;
+  uint16_t port;
+} IPSockAddr;
+
+typedef IPSockAddr NTP_Remote_Address;
+
+#define INVALID_IF_INDEX -1

 typedef struct {
  IPAddr ip_addr;
+  int if_index;
  int sock_fd;
 } NTP_Local_Address;

--- a/addrfilt.c
+++ b/addrfilt.c
@@ -247,6 +247,8 @@ set_subnet_(ADF_AuthTable table,
          set_subnet(&table->base6, ip6, 4, 0, new_state, delete_children) == ADF_SUCCESS)
        return ADF_SUCCESS;
      break;
+    default:
+      break;
  }

  return ADF_BADSUBNET;
@@ -359,9 +361,9 @@ ADF_IsAllowed(ADF_AuthTable table,
    case IPADDR_INET6:
      split_ip6(ip_addr, ip6);
      return check_ip_in_node(&table->base6, ip6);
+    default:
+      return 0;
  }
-
-  return 0;
 }

 /* ================================================== */
--- a/array.c
+++ b/array.c
@@ -66,8 +66,6 @@ ARR_DestroyInstance(ARR_Instance array)
 static void
 realloc_array(ARR_Instance array, unsigned int min_size)
 {
-  size_t data_size;
-
  assert(min_size <= 2 * min_size);
  if (array->allocated >= min_size && array->allocated <= 2 * min_size)
    return;
@@ -79,10 +77,7 @@ realloc_array(ARR_Instance array, unsigned int min_size)
    array->allocated = min_size;
  }

-  data_size = (size_t)array->elem_size * array->allocated;
-  assert(data_size / array->elem_size == array->allocated);
-
-  array->data = Realloc(array->data, data_size);
+  array->data = Realloc2(array->data, array->allocated, array->elem_size);
 }

 void *
--- a/candm.h
+++ b/candm.h
@@ -97,7 +97,19 @@
 #define REQ_NTP_DATA 57
 #define REQ_ADD_SERVER2 58
 #define REQ_ADD_PEER2 59
-#define N_REQUEST_TYPES 60
+#define REQ_ADD_SERVER3 60
+#define REQ_ADD_PEER3 61
+#define REQ_SHUTDOWN 62
+#define REQ_ONOFFLINE 63
+#define REQ_ADD_SOURCE 64
+#define REQ_NTP_SOURCE_NAME 65
+#define REQ_RESET_SOURCES 66
+#define REQ_AUTH_DATA 67
+#define REQ_CLIENT_ACCESSES_BY_INDEX3 68
+#define REQ_SELECT_DATA 69
+#define REQ_RELOAD_SOURCES 70
+#define REQ_DOFFSET2 71
+#define N_REQUEST_TYPES 72

 /* Structure used to exchange timespecs independent of time_t size */
 typedef struct {
@@ -241,6 +253,11 @@ typedef struct {
  int32_t EOR;
 } REQ_Ac_Check;

+/* Source types in NTP source requests */
+#define REQ_ADDSRC_SERVER 1
+#define REQ_ADDSRC_PEER 2
+#define REQ_ADDSRC_POOL 3
+
 /* Flags used in NTP source requests */
 #define REQ_ADDSRC_ONLINE 0x1
 #define REQ_ADDSRC_AUTOOFFLINE 0x2
@@ -250,9 +267,14 @@ typedef struct {
 #define REQ_ADDSRC_TRUST 0x20
 #define REQ_ADDSRC_REQUIRE 0x40
 #define REQ_ADDSRC_INTERLEAVED 0x80
+#define REQ_ADDSRC_BURST 0x100
+#define REQ_ADDSRC_NTS 0x200
+#define REQ_ADDSRC_COPY 0x400
+#define REQ_ADDSRC_EF_EXP1 0x800

 typedef struct {
-  IPAddr ip_addr;
+  uint32_t type;
+  uint8_t name[256];
  uint32_t port;
  int32_t minpoll;
  int32_t maxpoll;
@@ -264,11 +286,18 @@ typedef struct {
  int32_t min_samples;
  int32_t max_samples;
  uint32_t authkey;
+  uint32_t nts_port;
  Float max_delay;
  Float max_delay_ratio;
  Float max_delay_dev_ratio;
+  Float min_delay;
+  Float asymmetry;
  Float offset;
  uint32_t flags;
+  int32_t filter_length;
+  uint32_t cert_set;
+  Float max_delay_quant;
+  uint32_t reserved[1];
  int32_t EOR;
 } REQ_NTP_Source;

@@ -283,8 +312,7 @@ typedef struct {
 } REQ_Dfreq;

 typedef struct {
-  int32_t sec;
-  int32_t usec;
+  Float doffset;
  int32_t EOR;
 } REQ_Doffset;

@@ -300,6 +328,8 @@ typedef struct {
 typedef struct {
  uint32_t first_index;
  uint32_t n_clients;
+  uint32_t min_hits;
+  uint32_t reset;
  int32_t EOR;
 } REQ_ClientAccessesByIndex;

@@ -326,6 +356,21 @@ typedef struct {
  int32_t EOR;
 } REQ_NTPData;

+typedef struct {
+  IPAddr ip_addr;
+  int32_t EOR;
+} REQ_NTPSourceName;
+
+typedef struct {
+  IPAddr ip_addr;
+  int32_t EOR;
+} REQ_AuthData;
+
+typedef struct {
+  uint32_t index;
+  int32_t EOR;
+} REQ_SelectData;
+
 /* ================================================== */

 #define PKT_TYPE_CMD_REQUEST 1
@@ -362,8 +407,10 @@ typedef struct {
   domain socket.

   Version 6 (no authentication) : changed format of client accesses by index
-   (using new request/reply types), new fields and flags in NTP source request
-   and report, new commands: ntpdata, refresh, serverstats
+   (two times), delta offset, and manual timestamp, added new fields and
+   flags to NTP source request and report, made length of manual list constant,
+   added new commands: authdata, ntpdata, onoffline, refresh, reset,
+   selectdata, serverstats, shutdown, sourcename
 */

 #define PROTO_VERSION_NUMBER 6
@@ -377,8 +424,8 @@ typedef struct {
 #define PROTO_VERSION_PADDING 6

 /* The maximum length of padding in request packet, currently
-   defined by MANUAL_LIST */
-#define MAX_PADDING_LENGTH 396
+   defined by CLIENT_ACCESSES_BY_INDEX3 */
+#define MAX_PADDING_LENGTH 484

 /* ================================================== */

@@ -427,6 +474,9 @@ typedef struct {
    REQ_ReselectDistance reselect_distance;
    REQ_SmoothTime smoothtime;
    REQ_NTPData ntp_data;
+    REQ_NTPSourceName ntp_source_name;
+    REQ_AuthData auth_data;
+    REQ_SelectData select_data;
  } data; /* Command specific parameters */

  /* Padding used to prevent traffic amplification.  It only defines the
@@ -461,7 +511,15 @@ typedef struct {
 #define RPY_SERVER_STATS 14
 #define RPY_CLIENT_ACCESSES_BY_INDEX2 15
 #define RPY_NTP_DATA 16
-#define N_REPLY_TYPES 17
+#define RPY_MANUAL_TIMESTAMP2 17
+#define RPY_MANUAL_LIST2 18
+#define RPY_NTP_SOURCE_NAME 19
+#define RPY_AUTH_DATA 20
+#define RPY_CLIENT_ACCESSES_BY_INDEX3 21
+#define RPY_SERVER_STATS2 22
+#define RPY_SELECT_DATA 23
+#define RPY_SERVER_STATS3 24
+#define N_REPLY_TYPES 25

 /* Status codes */
 #define STT_SUCCESS 0
@@ -474,8 +532,7 @@ typedef struct {
 #define STT_BADSUBNET 7
 #define STT_ACCESSALLOWED 8
 #define STT_ACCESSDENIED 9
-/* Deprecated */
-#define STT_NOHOSTACCESS 10
+#define STT_NOHOSTACCESS 10 /* Deprecated */
 #define STT_SOURCEALREADYKNOWN 11
 #define STT_TOOMANYSOURCES 12
 #define STT_NORTC 13
@@ -485,6 +542,7 @@ typedef struct {
 #define STT_INVALIDAF 17
 #define STT_BADPKTVERSION 18
 #define STT_BADPKTLENGTH 19
+#define STT_INVALIDNAME 21

 typedef struct {
  int32_t EOR;
@@ -499,17 +557,12 @@ typedef struct {
 #define RPY_SD_MD_PEER   1
 #define RPY_SD_MD_REF    2

-#define RPY_SD_ST_SYNC 0
-#define RPY_SD_ST_UNREACH 1
+#define RPY_SD_ST_SELECTED 0
+#define RPY_SD_ST_NONSELECTABLE 1
 #define RPY_SD_ST_FALSETICKER 2
 #define RPY_SD_ST_JITTERY 3
-#define RPY_SD_ST_CANDIDATE 4
-#define RPY_SD_ST_OUTLIER 5
-
-#define RPY_SD_FLAG_NOSELECT 0x1
-#define RPY_SD_FLAG_PREFER 0x2
-#define RPY_SD_FLAG_TRUST 0x4
-#define RPY_SD_FLAG_REQUIRE 0x8
+#define RPY_SD_ST_UNSELECTED 4
+#define RPY_SD_ST_SELECTABLE 5

 typedef struct {
  IPAddr ip_addr;
@@ -569,7 +622,7 @@ typedef struct {
 } RPY_Rtc;

 typedef struct {
-  uint32_t centiseconds;
+  Float offset;
  Float dfreq_ppm;
  Float new_afreq_ppm;
  int32_t EOR;
@@ -578,14 +631,17 @@ typedef struct {
 typedef struct {
  IPAddr ip;
  uint32_t ntp_hits;
+  uint32_t nke_hits;
  uint32_t cmd_hits;
  uint32_t ntp_drops;
+  uint32_t nke_drops;
  uint32_t cmd_drops;
  int8_t ntp_interval;
+  int8_t nke_interval;
  int8_t cmd_interval;
  int8_t ntp_timeout_interval;
-  int8_t pad;
  uint32_t last_ntp_hit_ago;
+  uint32_t last_nke_hit_ago;
  uint32_t last_cmd_hit_ago;
 } RPY_ClientAccesses_Client;

@@ -599,10 +655,16 @@ typedef struct {

 typedef struct {
  uint32_t ntp_hits;
+  uint32_t nke_hits;
  uint32_t cmd_hits;
  uint32_t ntp_drops;
+  uint32_t nke_drops;
  uint32_t cmd_drops;
  uint32_t log_drops;
+  uint32_t ntp_auth_hits;
+  uint32_t ntp_interleaved_hits;
+  uint32_t ntp_timestamps;
+  uint32_t ntp_span_seconds;
  int32_t EOR;
 } RPY_ServerStats;

@@ -676,6 +738,50 @@ typedef struct {
  int32_t EOR;
 } RPY_NTPData;

+typedef struct {
+  uint8_t name[256];
+  int32_t EOR;
+} RPY_NTPSourceName;
+
+#define RPY_AD_MD_NONE 0
+#define RPY_AD_MD_SYMMETRIC 1
+#define RPY_AD_MD_NTS 2
+
+typedef struct {
+  uint16_t mode;
+  uint16_t key_type;
+  uint32_t key_id;
+  uint16_t key_length;
+  uint16_t ke_attempts;
+  uint32_t last_ke_ago;
+  uint16_t cookies;
+  uint16_t cookie_length;
+  uint16_t nak;
+  uint16_t pad;
+  int32_t EOR;
+} RPY_AuthData;
+
+#define RPY_SD_OPTION_NOSELECT 0x1
+#define RPY_SD_OPTION_PREFER 0x2
+#define RPY_SD_OPTION_TRUST 0x4
+#define RPY_SD_OPTION_REQUIRE 0x8
+
+typedef struct {
+  uint32_t ref_id;
+  IPAddr ip_addr;
+  uint8_t state_char;
+  uint8_t authentication;
+  uint8_t leap;
+  uint8_t pad;
+  uint16_t conf_options;
+  uint16_t eff_options;
+  uint32_t last_sample_ago;
+  Float score;
+  Float lo_limit;
+  Float hi_limit;
+  int32_t EOR;
+} RPY_SelectData;
+
 typedef struct {
  uint8_t version;
  uint8_t pkt_type;
@@ -705,6 +811,9 @@ typedef struct {
    RPY_Activity activity;
    RPY_Smoothing smoothing;
    RPY_NTPData ntp_data;
+    RPY_NTPSourceName ntp_source_name;
+    RPY_AuthData auth_data;
+    RPY_SelectData select_data;
  } data; /* Reply specific parameters */

 } CMD_Reply;
--- a/client.c
+++ b/client.c
--- a/clientlog.c
+++ b/clientlog.c
@@ -3,7 +3,7 @@

 **********************************************************************
 * Copyright (C) Richard P. Curnow  1997-2003
- * Copyright (C) Miroslav Lichvar  2009, 2015-2016
+ * Copyright (C) Miroslav Lichvar  2009, 2015-2017, 2021
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
@@ -38,28 +38,24 @@
 #include "array.h"
 #include "clientlog.h"
 #include "conf.h"
+#include "local.h"
 #include "memory.h"
 #include "ntp.h"
 #include "reports.h"
 #include "util.h"
 #include "logging.h"

+#define MAX_SERVICES 3
+
 typedef struct {
  IPAddr ip_addr;
-  uint32_t last_ntp_hit;
-  uint32_t last_cmd_hit;
-  uint32_t ntp_hits;
-  uint32_t cmd_hits;
-  uint16_t ntp_drops;
-  uint16_t cmd_drops;
-  uint16_t ntp_tokens;
-  uint16_t cmd_tokens;
-  int8_t ntp_rate;
-  int8_t cmd_rate;
+  uint32_t last_hit[MAX_SERVICES];
+  uint32_t hits[MAX_SERVICES];
+  uint16_t drops[MAX_SERVICES];
+  uint16_t tokens[MAX_SERVICES];
+  int8_t rate[MAX_SERVICES];
  int8_t ntp_timeout_rate;
-  uint8_t flags;
-  NTP_int64 ntp_rx_ts;
-  NTP_int64 ntp_tx_ts;
+  uint8_t drop_flags;
 } Record;

 /* Hash table of records, there is a fixed number of records per slot */
@@ -104,15 +100,12 @@ static uint32_t ts_offset;
 #define MIN_LIMIT_BURST 1
 #define MAX_LIMIT_BURST 255

-static uint16_t max_ntp_tokens;
-static uint16_t max_cmd_tokens;
-static uint16_t ntp_tokens_per_packet;
-static uint16_t cmd_tokens_per_packet;
+static uint16_t max_tokens[MAX_SERVICES];
+static uint16_t tokens_per_hit[MAX_SERVICES];

 /* Reduction of token rates to avoid overflow of 16-bit counters.  Negative
   shift is used for coarse limiting with intervals shorter than -TS_FRAC. */
-static int ntp_token_shift;
-static int cmd_token_shift;
+static int token_shift[MAX_SERVICES];

 /* Rates at which responses are randomly allowed (in log2) when the
   buckets don't have enough tokens.  This is necessary in order to
@@ -122,20 +115,51 @@ static int cmd_token_shift;
 #define MIN_LEAK_RATE 1
 #define MAX_LEAK_RATE 4

-static int ntp_leak_rate;
-static int cmd_leak_rate;
+static int leak_rate[MAX_SERVICES];

-/* Flag indicating whether the last response was dropped */
-#define FLAG_NTP_DROPPED 0x1
+/* Limit intervals in log2 */
+static int limit_interval[MAX_SERVICES];

 /* Flag indicating whether facility is turned on or not */
 static int active;

+/* RX and TX timestamp saved for clients using interleaved mode */
+typedef struct {
+  uint64_t rx_ts;
+  uint16_t flags;
+  uint16_t slew_epoch;
+  int32_t tx_ts_offset;
+} NtpTimestamps;
+
+/* Flags for NTP timestamps */
+#define NTPTS_DISABLED 1
+#define NTPTS_VALID_TX 2
+
+/* RX->TX map using a circular buffer with ordered timestamps */
+typedef struct {
+  ARR_Instance timestamps;
+  uint32_t first;
+  uint32_t size;
+  uint32_t max_size;
+  uint32_t cached_index;
+  uint64_t cached_rx_ts;
+  uint16_t slew_epoch;
+  double slew_offset;
+} NtpTimestampMap;
+
+static NtpTimestampMap ntp_ts_map;
+
+/* Maximum interval of NTP timestamps in future after a backward step */
+#define NTPTS_FUTURE_LIMIT (1LL << 32) /* 1 second */
+
+/* Maximum number of timestamps moved in the array to insert a new timestamp */
+#define NTPTS_INSERT_LIMIT 64
+
 /* Global statistics */
-static uint32_t total_ntp_hits;
-static uint32_t total_cmd_hits;
-static uint32_t total_ntp_drops;
-static uint32_t total_cmd_drops;
+static uint32_t total_hits[MAX_SERVICES];
+static uint32_t total_drops[MAX_SERVICES];
+static uint32_t total_ntp_auth_hits;
+static uint32_t total_ntp_interleaved_hits;
 static uint32_t total_record_drops;

 #define NSEC_PER_SEC 1000000000U
@@ -143,6 +167,8 @@ static uint32_t total_record_drops;
 /* ================================================== */

 static int expand_hashtable(void);
+static void handle_slew(struct timespec *raw, struct timespec *cooked, double dfreq,
+                        double doffset, LCL_ChangeType change_type, void *anything);

 /* ================================================== */

@@ -158,12 +184,28 @@ compare_ts(uint32_t x, uint32_t y)

 /* ================================================== */

+static int
+compare_total_hits(Record *x, Record *y)
+{
+  uint32_t x_hits, y_hits;
+  int i;
+
+  for (i = 0, x_hits = y_hits = 0; i < MAX_SERVICES; i++) {
+    x_hits += x->hits[i];
+    y_hits += y->hits[i];
+  }
+
+  return x_hits > y_hits ? 1 : -1;
+}
+
+/* ================================================== */
+
 static Record *
 get_record(IPAddr *ip)
 {
-  unsigned int first, i;
-  time_t last_hit, oldest_hit = 0;
+  uint32_t last_hit = 0, oldest_hit = 0;
  Record *record, *oldest_record;
+  unsigned int first, i, j;

  if (!active || (ip->family != IPADDR_INET4 && ip->family != IPADDR_INET6))
    return NULL;
@@ -181,12 +223,13 @@ get_record(IPAddr *ip)
      if (record->ip_addr.family == IPADDR_UNSPEC)
        break;

-      last_hit = compare_ts(record->last_ntp_hit, record->last_cmd_hit) > 0 ?
-                 record->last_ntp_hit : record->last_cmd_hit;
+      for (j = 0; j < MAX_SERVICES; j++) {
+        if (j == 0 || compare_ts(last_hit, record->last_hit[j]) < 0)
+          last_hit = record->last_hit[j];
+      }

      if (!oldest_record || compare_ts(oldest_hit, last_hit) > 0 ||
-          (oldest_hit == last_hit && record->ntp_hits + record->cmd_hits <
-           oldest_record->ntp_hits + oldest_record->cmd_hits)) {
+          (oldest_hit == last_hit && compare_total_hits(oldest_record, record) > 0)) {
        oldest_record = record;
        oldest_hit = last_hit;
      }
@@ -208,16 +251,18 @@ get_record(IPAddr *ip)
  }

  record->ip_addr = *ip;
-  record->last_ntp_hit = record->last_cmd_hit = INVALID_TS;
-  record->ntp_hits = record->cmd_hits = 0;
-  record->ntp_drops = record->cmd_drops = 0;
-  record->ntp_tokens = max_ntp_tokens;
-  record->cmd_tokens = max_cmd_tokens;
-  record->ntp_rate = record->cmd_rate = INVALID_RATE;
+  for (i = 0; i < MAX_SERVICES; i++)
+    record->last_hit[i] = INVALID_TS;
+  for (i = 0; i < MAX_SERVICES; i++)
+    record->hits[i] = 0;
+  for (i = 0; i < MAX_SERVICES; i++)
+    record->drops[i] = 0;
+  for (i = 0; i < MAX_SERVICES; i++)
+    record->tokens[i] = max_tokens[i];
+  for (i = 0; i < MAX_SERVICES; i++)
+    record->rate[i] = INVALID_RATE;
  record->ntp_timeout_rate = INVALID_RATE;
-  record->flags = 0;
-  UTI_ZeroNtp64(&record->ntp_rx_ts);
-  UTI_ZeroNtp64(&record->ntp_tx_ts);
+  record->drop_flags = 0;

  return record;
 }
@@ -294,7 +339,7 @@ set_bucket_params(int interval, int burst, uint16_t *max_tokens,
  *tokens_per_packet = 1U << (TS_FRAC + interval - *token_shift);
  *max_tokens = *tokens_per_packet * burst;

-  DEBUG_LOG(LOGF_ClientLog, "Tokens max %d packet %d shift %d",
+  DEBUG_LOG("Tokens max %d packet %d shift %d",
            *max_tokens, *tokens_per_packet, *token_shift);
 }

@@ -303,37 +348,56 @@ set_bucket_params(int interval, int burst, uint16_t *max_tokens,
 void
 CLG_Initialise(void)
 {
-  int interval, burst, leak_rate;
+  int i, interval, burst, lrate, slots2;

-  max_ntp_tokens = max_cmd_tokens = 0;
-  ntp_tokens_per_packet = cmd_tokens_per_packet = 0;
-  ntp_token_shift = cmd_token_shift = 0;
-  ntp_leak_rate = cmd_leak_rate = 0;
+  for (i = 0; i < MAX_SERVICES; i++) {
+    max_tokens[i] = 0;
+    tokens_per_hit[i] = 0;
+    token_shift[i] = 0;
+    leak_rate[i] = 0;
+    limit_interval[i] = MIN_LIMIT_INTERVAL;

-  if (CNF_GetNTPRateLimit(&interval, &burst, &leak_rate)) {
-    set_bucket_params(interval, burst, &max_ntp_tokens, &ntp_tokens_per_packet,
-                      &ntp_token_shift);
-    ntp_leak_rate = CLAMP(MIN_LEAK_RATE, leak_rate, MAX_LEAK_RATE);
-  }
+    switch (i) {
+      case CLG_NTP:
+        if (!CNF_GetNTPRateLimit(&interval, &burst, &lrate))
+          continue;
+        break;
+      case CLG_NTSKE:
+        if (!CNF_GetNtsRateLimit(&interval, &burst, &lrate))
+          continue;
+        break;
+      case CLG_CMDMON:
+        if (!CNF_GetCommandRateLimit(&interval, &burst, &lrate))
+          continue;
+        break;
+      default:
+        assert(0);
+    }

-  if (CNF_GetCommandRateLimit(&interval, &burst, &leak_rate)) {
-    set_bucket_params(interval, burst, &max_cmd_tokens, &cmd_tokens_per_packet,
-                      &cmd_token_shift);
-    cmd_leak_rate = CLAMP(MIN_LEAK_RATE, leak_rate, MAX_LEAK_RATE);
+    set_bucket_params(interval, burst, &max_tokens[i], &tokens_per_hit[i], &token_shift[i]);
+    leak_rate[i] = CLAMP(MIN_LEAK_RATE, lrate, MAX_LEAK_RATE);
+    limit_interval[i] = CLAMP(MIN_LIMIT_INTERVAL, interval, MAX_LIMIT_INTERVAL);
  }

  active = !CNF_GetNoClientLog();
  if (!active) {
-    if (ntp_leak_rate || cmd_leak_rate)
-      LOG_FATAL(LOGF_ClientLog, "ratelimit cannot be used with noclientlog");
+    for (i = 0; i < MAX_SERVICES; i++) {
+      if (leak_rate[i] != 0)
+        LOG_FATAL("Rate limiting cannot be enabled with noclientlog");
+    }
    return;
  }

  /* Calculate the maximum number of slots that can be allocated in the
     configured memory limit.  Take into account expanding of the hash
     table where two copies exist at the same time. */
-  max_slots = CNF_GetClientLogLimit() / (sizeof (Record) * SLOT_SIZE * 3 / 2);
+  max_slots = CNF_GetClientLogLimit() /
+              ((sizeof (Record) + sizeof (NtpTimestamps)) * SLOT_SIZE * 3 / 2);
  max_slots = CLAMP(MIN_SLOTS, max_slots, MAX_SLOTS);
+  for (slots2 = 0; 1U << (slots2 + 1) <= max_slots; slots2++)
+    ;
+
+  DEBUG_LOG("Max records %u", 1U << (slots2 + SLOT_BITS));

  slots = 0;
  records = NULL;
@@ -342,6 +406,17 @@ CLG_Initialise(void)

  UTI_GetRandomBytes(&ts_offset, sizeof (ts_offset));
  ts_offset %= NSEC_PER_SEC / (1U << TS_FRAC);
+
+  ntp_ts_map.timestamps = NULL;
+  ntp_ts_map.first = 0;
+  ntp_ts_map.size = 0;
+  ntp_ts_map.max_size = 1U << (slots2 + SLOT_BITS);
+  ntp_ts_map.cached_index = 0;
+  ntp_ts_map.cached_rx_ts = 0ULL;
+  ntp_ts_map.slew_epoch = 0;
+  ntp_ts_map.slew_offset = 0.0;
+
+  LCL_AddParameterChangeHandler(handle_slew, NULL);
 }

 /* ================================================== */
@@ -353,6 +428,10 @@ CLG_Finalise(void)
    return;

  ARR_DestroyInstance(records);
+  if (ntp_ts_map.timestamps)
+    ARR_DestroyInstance(ntp_ts_map.timestamps);
+
+  LCL_RemoveParameterChangeHandler(handle_slew, NULL);
 }

 /* ================================================== */
@@ -375,30 +454,33 @@ get_ts_from_timespec(struct timespec *ts)
 /* ================================================== */

 static void
-update_record(struct timespec *now, uint32_t *last_hit, uint32_t *hits,
-              uint16_t *tokens, uint32_t max_tokens, int token_shift, int8_t *rate)
+update_record(CLG_Service service, Record *record, struct timespec *now)
 {
-  uint32_t interval, now_ts, prev_hit, new_tokens;
-  int interval2;
+  uint32_t interval, now_ts, prev_hit, tokens;
+  int interval2, tshift, mtokens;
+  int8_t *rate;

  now_ts = get_ts_from_timespec(now);

-  prev_hit = *last_hit;
-  *last_hit = now_ts;
-  (*hits)++;
+  prev_hit = record->last_hit[service];
+  record->last_hit[service] = now_ts;
+  record->hits[service]++;

  interval = now_ts - prev_hit;

  if (prev_hit == INVALID_TS || (int32_t)interval < 0)
    return;

-  if (token_shift >= 0)
-    new_tokens = (now_ts >> token_shift) - (prev_hit >> token_shift);
-  else if (now_ts - prev_hit > max_tokens)
-    new_tokens = max_tokens;
+  tshift = token_shift[service];
+  mtokens = max_tokens[service];
+
+  if (tshift >= 0)
+    tokens = (now_ts >> tshift) - (prev_hit >> tshift);
+  else if (now_ts - prev_hit > mtokens)
+    tokens = mtokens;
  else
-    new_tokens = (now_ts - prev_hit) << -token_shift;
-  *tokens = MIN(*tokens + new_tokens, max_tokens);
+    tokens = (now_ts - prev_hit) << -tshift;
+  record->tokens[service] = MIN(record->tokens[service] + tokens, mtokens);

  /* Convert the interval to scaled and rounded log2 */
  if (interval) {
@@ -413,6 +495,11 @@ update_record(struct timespec *now, uint32_t *last_hit, uint32_t *hits,
    interval2 = -RATE_SCALE * (TS_FRAC + 1);
  }

+  /* For the NTP service, update one of the two rates depending on whether
+     the previous request of the client had a reply or it timed out */
+  rate = service == CLG_NTP && record->drop_flags & (1U << service) ?
+           &record->ntp_timeout_rate : &record->rate[service];
+
  /* Update the rate in a rough approximation of exponential moving average */
  if (*rate == INVALID_RATE) {
    *rate = -interval2;
@@ -452,50 +539,33 @@ CLG_GetClientIndex(IPAddr *client)

 /* ================================================== */

-int
-CLG_LogNTPAccess(IPAddr *client, struct timespec *now)
+static void
+check_service_number(CLG_Service service)
 {
-  Record *record;
-
-  total_ntp_hits++;
-
-  record = get_record(client);
-  if (record == NULL)
-    return -1;
-
-  /* Update one of the two rates depending on whether the previous request
-     of the client had a reply or it timed out */
-  update_record(now, &record->last_ntp_hit, &record->ntp_hits,
-                &record->ntp_tokens, max_ntp_tokens, ntp_token_shift,
-                record->flags & FLAG_NTP_DROPPED ?
-                &record->ntp_timeout_rate : &record->ntp_rate);
-
-  DEBUG_LOG(LOGF_ClientLog, "NTP hits %"PRIu32" rate %d trate %d tokens %d",
-            record->ntp_hits, record->ntp_rate, record->ntp_timeout_rate,
-            record->ntp_tokens);
-
-  return get_index(record);
+  assert(service >= 0 && service <= MAX_SERVICES);
 }

 /* ================================================== */

 int
-CLG_LogCommandAccess(IPAddr *client, struct timespec *now)
+CLG_LogServiceAccess(CLG_Service service, IPAddr *client, struct timespec *now)
 {
  Record *record;

-  total_cmd_hits++;
+  check_service_number(service);
+
+  total_hits[service]++;

  record = get_record(client);
  if (record == NULL)
    return -1;

-  update_record(now, &record->last_cmd_hit, &record->cmd_hits,
-                &record->cmd_tokens, max_cmd_tokens, cmd_token_shift,
-                &record->cmd_rate);
+  update_record(service, record, now);

-  DEBUG_LOG(LOGF_ClientLog, "Cmd hits %"PRIu32" rate %d tokens %d",
-            record->cmd_hits, record->cmd_rate, record->cmd_tokens);
+  DEBUG_LOG("service %d hits %"PRIu32" rate %d trate %d tokens %d",
+            (int)service, record->hits[service], record->rate[service],
+            service == CLG_NTP ? record->ntp_timeout_rate : INVALID_RATE,
+            record->tokens[service]);

  return get_index(record);
 }
@@ -525,83 +595,385 @@ limit_response_random(int leak_rate)
 /* ================================================== */

 int
-CLG_LimitNTPResponseRate(int index)
+CLG_LimitServiceRate(CLG_Service service, int index)
 {
  Record *record;
  int drop;

-  if (!ntp_tokens_per_packet)
+  check_service_number(service);
+
+  if (tokens_per_hit[service] == 0)
    return 0;

  record = ARR_GetElement(records, index);
-  record->flags &= ~FLAG_NTP_DROPPED;
+  record->drop_flags &= ~(1U << service);

-  if (record->ntp_tokens >= ntp_tokens_per_packet) {
-    record->ntp_tokens -= ntp_tokens_per_packet;
+  if (record->tokens[service] >= tokens_per_hit[service]) {
+    record->tokens[service] -= tokens_per_hit[service];
    return 0;
  }

-  drop = limit_response_random(ntp_leak_rate);
+  drop = limit_response_random(leak_rate[service]);

-  /* Poorly implemented clients may send new requests at even a higher rate
+  /* Poorly implemented NTP clients can send requests at a higher rate
     when they are not getting replies.  If the request rate seems to be more
     than twice as much as when replies are sent, give up on rate limiting to
     reduce the amount of traffic.  Invert the sense of the leak to respond to
     most of the requests, but still keep the estimated rate updated. */
-  if (record->ntp_timeout_rate != INVALID_RATE &&
-      record->ntp_timeout_rate > record->ntp_rate + RATE_SCALE)
+  if (service == CLG_NTP && record->ntp_timeout_rate != INVALID_RATE &&
+      record->ntp_timeout_rate > record->rate[service] + RATE_SCALE)
    drop = !drop;

  if (!drop) {
-    record->ntp_tokens = 0;
+    record->tokens[service] = 0;
    return 0;
  }

-  record->flags |= FLAG_NTP_DROPPED;
-  record->ntp_drops++;
-  total_ntp_drops++;
+  record->drop_flags |= 1U << service;
+  record->drops[service]++;
+  total_drops[service]++;

  return 1;
 }

 /* ================================================== */

+void
+CLG_LogAuthNtpRequest(void)
+{
+  total_ntp_auth_hits++;
+}
+
+/* ================================================== */
+
 int
-CLG_LimitCommandResponseRate(int index)
+CLG_GetNtpMinPoll(void)
 {
-  Record *record;
+  return limit_interval[CLG_NTP];
+}

-  if (!cmd_tokens_per_packet)
-    return 0;
+/* ================================================== */

-  record = ARR_GetElement(records, index);
+static NtpTimestamps *
+get_ntp_tss(uint32_t index)
+{
+  return ARR_GetElement(ntp_ts_map.timestamps,
+                        (ntp_ts_map.first + index) & (ntp_ts_map.max_size - 1));
+}

-  if (record->cmd_tokens >= cmd_tokens_per_packet) {
-    record->cmd_tokens -= cmd_tokens_per_packet;
+/* ================================================== */
+
+static int
+find_ntp_rx_ts(uint64_t rx_ts, uint32_t *index)
+{
+  uint64_t rx_x, rx_lo, rx_hi, step;
+  uint32_t i, x, lo, hi;
+
+  if (ntp_ts_map.cached_rx_ts == rx_ts && rx_ts != 0ULL) {
+    *index = ntp_ts_map.cached_index;
+    return 1;
+  }
+
+  if (ntp_ts_map.size == 0) {
+    *index = 0;
    return 0;
  }

-  if (!limit_response_random(cmd_leak_rate)) {
-    record->cmd_tokens = 0;
+  lo = 0;
+  hi = ntp_ts_map.size - 1;
+  rx_lo = get_ntp_tss(lo)->rx_ts;
+  rx_hi = get_ntp_tss(hi)->rx_ts;
+
+  /* Check for ts < lo before ts > hi to trim timestamps from "future" later
+     if both conditions are true to not break the order of the endpoints.
+     Compare timestamps by their difference to allow adjacent NTP eras. */
+  if ((int64_t)(rx_ts - rx_lo) < 0) {
+    *index = 0;
+    return 0;
+  } else if ((int64_t)(rx_ts - rx_hi) > 0) {
+    *index = ntp_ts_map.size;
    return 0;
  }

-  record->cmd_drops++;
-  total_cmd_drops++;
+  /* Perform a combined linear interpolation and binary search */
+
+  for (i = 0; ; i++) {
+    if (rx_ts == rx_hi) {
+      *index = ntp_ts_map.cached_index = hi;
+      ntp_ts_map.cached_rx_ts = rx_ts;
+      return 1;
+    } else if (rx_ts == rx_lo) {
+      *index = ntp_ts_map.cached_index = lo;
+      ntp_ts_map.cached_rx_ts = rx_ts;
+      return 1;
+    } else if (lo + 1 == hi) {
+      *index = hi;
+      return 0;
+    }
+
+    if (hi - lo > 3 && i % 2 == 0) {
+      step = (rx_hi - rx_lo) / (hi - lo);
+      if (step == 0)
+        step = 1;
+      x = lo + (rx_ts - rx_lo) / step;
+    } else {
+      x = lo + (hi - lo) / 2;
+    }
+
+    if (x <= lo)
+      x = lo + 1;
+    else if (x >= hi)
+      x = hi - 1;
+
+    rx_x = get_ntp_tss(x)->rx_ts;
+
+    if ((int64_t)(rx_x - rx_ts) <= 0) {
+      lo = x;
+      rx_lo = rx_x;
+    } else {
+      hi = x;
+      rx_hi = rx_x;
+    }
+  }
+}
+
+/* ================================================== */
+
+static uint64_t
+ntp64_to_int64(NTP_int64 *ts)
+{
+  return (uint64_t)ntohl(ts->hi) << 32 | ntohl(ts->lo);
+}
+
+/* ================================================== */
+
+static void
+int64_to_ntp64(uint64_t ts, NTP_int64 *ntp_ts)
+{
+  ntp_ts->hi = htonl(ts >> 32);
+  ntp_ts->lo = htonl(ts);
+}
+
+/* ================================================== */
+
+static uint32_t
+push_ntp_tss(uint32_t index)
+{
+  if (ntp_ts_map.size < ntp_ts_map.max_size) {
+    ntp_ts_map.size++;
+  } else {
+    ntp_ts_map.first = (ntp_ts_map.first + 1) % (ntp_ts_map.max_size);
+    if (index > 0)
+      index--;
+  }
+
+  return index;
+}
+
+/* ================================================== */
+
+static void
+set_ntp_tx_offset(NtpTimestamps *tss, NTP_int64 *rx_ts, struct timespec *tx_ts)
+{
+  struct timespec ts;
+
+  if (!tx_ts) {
+    tss->flags &= ~NTPTS_VALID_TX;
+    return;
+  }
+
+  UTI_Ntp64ToTimespec(rx_ts, &ts);
+  UTI_DiffTimespecs(&ts, tx_ts, &ts);
+
+  if (ts.tv_sec < -2 || ts.tv_sec > 1) {
+    tss->flags &= ~NTPTS_VALID_TX;
+    return;
+  }
+
+  tss->tx_ts_offset = (int32_t)ts.tv_nsec + (int32_t)ts.tv_sec * (int32_t)NSEC_PER_SEC;
+  tss->flags |= NTPTS_VALID_TX;
+}
+
+/* ================================================== */
+
+static void
+get_ntp_tx(NtpTimestamps *tss, struct timespec *tx_ts)
+{
+  int32_t offset = tss->tx_ts_offset;
+  NTP_int64 ntp_ts;
+
+  if (tss->flags & NTPTS_VALID_TX) {
+    int64_to_ntp64(tss->rx_ts, &ntp_ts);
+    UTI_Ntp64ToTimespec(&ntp_ts, tx_ts);
+    if (offset >= (int32_t)NSEC_PER_SEC) {
+      offset -= NSEC_PER_SEC;
+      tx_ts->tv_sec++;
+    }
+    tx_ts->tv_nsec += offset;
+    UTI_NormaliseTimespec(tx_ts);
+  } else {
+    UTI_ZeroTimespec(tx_ts);
+  }
+}
+
+/* ================================================== */
+
+void
+CLG_SaveNtpTimestamps(NTP_int64 *rx_ts, struct timespec *tx_ts)
+{
+  NtpTimestamps *tss;
+  uint32_t i, index;
+  uint64_t rx;
+
+  if (!active)
+    return;
+
+  /* Allocate the array on first use */
+  if (!ntp_ts_map.timestamps) {
+    ntp_ts_map.timestamps = ARR_CreateInstance(sizeof (NtpTimestamps));
+    ARR_SetSize(ntp_ts_map.timestamps, ntp_ts_map.max_size);
+  }
+
+  rx = ntp64_to_int64(rx_ts);
+
+  if (rx == 0ULL)
+    return;
+
+  /* Disable the RX timestamp if it already exists to avoid responding
+     with a wrong TX timestamp */
+  if (find_ntp_rx_ts(rx, &index)) {
+    get_ntp_tss(index)->flags |= NTPTS_DISABLED;
+    return;
+  }
+
+  assert(index <= ntp_ts_map.size);
+
+  if (index == ntp_ts_map.size) {
+    /* Increase the size or drop the oldest timestamp to make room for
+       the new timestamp */
+    index = push_ntp_tss(index);
+  } else {
+    /* Trim timestamps in distant future after backward step */
+    while (index < ntp_ts_map.size &&
+           get_ntp_tss(ntp_ts_map.size - 1)->rx_ts - rx > NTPTS_FUTURE_LIMIT)
+      ntp_ts_map.size--;
+
+    /* Insert the timestamp if it is close to the latest timestamp.
+       Otherwise, replace the closest older or the oldest timestamp. */
+    if (index + NTPTS_INSERT_LIMIT >= ntp_ts_map.size) {
+      index = push_ntp_tss(index);
+      for (i = ntp_ts_map.size - 1; i > index; i--)
+        *get_ntp_tss(i) = *get_ntp_tss(i - 1);
+    } else {
+      if (index > 0)
+        index--;
+    }
+  }
+
+  ntp_ts_map.cached_index = index;
+  ntp_ts_map.cached_rx_ts = rx;
+
+  tss = get_ntp_tss(index);
+  tss->rx_ts = rx;
+  tss->flags = 0;
+  tss->slew_epoch = ntp_ts_map.slew_epoch;
+  set_ntp_tx_offset(tss, rx_ts, tx_ts);
+
+  DEBUG_LOG("Saved RX+TX index=%"PRIu32" first=%"PRIu32" size=%"PRIu32,
+            index, ntp_ts_map.first, ntp_ts_map.size);
+}
+
+/* ================================================== */
+
+static void
+handle_slew(struct timespec *raw, struct timespec *cooked, double dfreq,
+            double doffset, LCL_ChangeType change_type, void *anything)
+{
+  /* Drop all timestamps on unknown step */
+  if (change_type == LCL_ChangeUnknownStep) {
+    ntp_ts_map.size = 0;
+    ntp_ts_map.cached_rx_ts = 0ULL;
+  }
+
+  ntp_ts_map.slew_epoch++;
+  ntp_ts_map.slew_offset = doffset;
+}
+
+/* ================================================== */
+
+void
+CLG_UndoNtpTxTimestampSlew(NTP_int64 *rx_ts, struct timespec *tx_ts)
+{
+  uint32_t index;
+
+  if (!ntp_ts_map.timestamps)
+    return;
+
+  if (!find_ntp_rx_ts(ntp64_to_int64(rx_ts), &index))
+    return;
+
+  /* If the RX timestamp was captured before the last correction of the clock,
+     remove the adjustment from the TX timestamp */
+  if ((uint16_t)(get_ntp_tss(index)->slew_epoch + 1U) == ntp_ts_map.slew_epoch)
+    UTI_AddDoubleToTimespec(tx_ts, ntp_ts_map.slew_offset, tx_ts);
+}
+
+/* ================================================== */
+
+void
+CLG_UpdateNtpTxTimestamp(NTP_int64 *rx_ts, struct timespec *tx_ts)
+{
+  uint32_t index;
+
+  if (!ntp_ts_map.timestamps)
+    return;
+
+  if (!find_ntp_rx_ts(ntp64_to_int64(rx_ts), &index))
+    return;
+
+  set_ntp_tx_offset(get_ntp_tss(index), rx_ts, tx_ts);
+}
+
+/* ================================================== */
+
+int
+CLG_GetNtpTxTimestamp(NTP_int64 *rx_ts, struct timespec *tx_ts)
+{
+  NtpTimestamps *tss;
+  uint32_t index;
+
+  if (!ntp_ts_map.timestamps)
+    return 0;
+
+  if (!find_ntp_rx_ts(ntp64_to_int64(rx_ts), &index))
+    return 0;
+
+  tss = get_ntp_tss(index);
+
+  if (tss->flags & NTPTS_DISABLED)
+    return 0;
+
+  get_ntp_tx(tss, tx_ts);

  return 1;
 }

 /* ================================================== */

-void CLG_GetNtpTimestamps(int index, NTP_int64 **rx_ts, NTP_int64 **tx_ts)
+void
+CLG_DisableNtpTimestamps(NTP_int64 *rx_ts)
 {
-  Record *record;
+  uint32_t index;

-  record = ARR_GetElement(records, index);
+  if (!ntp_ts_map.timestamps)
+    return;

-  *rx_ts = &record->ntp_rx_ts;
-  *tx_ts = &record->ntp_tx_ts;
+  if (find_ntp_rx_ts(ntp64_to_int64(rx_ts), &index))
+    get_ntp_tss(index)->flags |= NTPTS_DISABLED;
+
+  /* This assumes the function is called only to prevent multiple
+     interleaved responses to the same timestamp */
+  total_ntp_interleaved_hits++;
 }

 /* ================================================== */
@@ -640,10 +1012,12 @@ static uint32_t get_last_ago(uint32_t x, uint32_t y)
 /* ================================================== */

 int
-CLG_GetClientAccessReportByIndex(int index, RPT_ClientAccessByIndex_Report *report, struct timespec *now)
+CLG_GetClientAccessReportByIndex(int index, int reset, uint32_t min_hits,
+                                 RPT_ClientAccessByIndex_Report *report, struct timespec *now)
 {
  Record *record;
  uint32_t now_ts;
+  int i, r;

  if (!active || index < 0 || index >= ARR_GetSize(records))
    return 0;
@@ -653,20 +1027,44 @@ CLG_GetClientAccessReportByIndex(int index, RPT_ClientAccessByIndex_Report *repo
  if (record->ip_addr.family == IPADDR_UNSPEC)
    return 0;

-  now_ts = get_ts_from_timespec(now);
+  if (min_hits == 0) {
+    r = 1;
+  } else {
+    for (i = r = 0; i < MAX_SERVICES; i++) {
+      if (record->hits[i] >= min_hits) {
+        r = 1;
+        break;
+      }
+    }
+  }

-  report->ip_addr = record->ip_addr;
-  report->ntp_hits = record->ntp_hits;
-  report->cmd_hits = record->cmd_hits;
-  report->ntp_drops = record->ntp_drops;
-  report->cmd_drops = record->cmd_drops;
-  report->ntp_interval = get_interval(record->ntp_rate);
-  report->cmd_interval = get_interval(record->cmd_rate);
-  report->ntp_timeout_interval = get_interval(record->ntp_timeout_rate);
-  report->last_ntp_hit_ago = get_last_ago(now_ts, record->last_ntp_hit);
-  report->last_cmd_hit_ago = get_last_ago(now_ts, record->last_cmd_hit);
+  if (r) {
+    now_ts = get_ts_from_timespec(now);

-  return 1;
+    report->ip_addr = record->ip_addr;
+    report->ntp_hits = record->hits[CLG_NTP];
+    report->nke_hits = record->hits[CLG_NTSKE];
+    report->cmd_hits = record->hits[CLG_CMDMON];
+    report->ntp_drops = record->drops[CLG_NTP];
+    report->nke_drops = record->drops[CLG_NTSKE];
+    report->cmd_drops = record->drops[CLG_CMDMON];
+    report->ntp_interval = get_interval(record->rate[CLG_NTP]);
+    report->nke_interval = get_interval(record->rate[CLG_NTSKE]);
+    report->cmd_interval = get_interval(record->rate[CLG_CMDMON]);
+    report->ntp_timeout_interval = get_interval(record->ntp_timeout_rate);
+    report->last_ntp_hit_ago = get_last_ago(now_ts, record->last_hit[CLG_NTP]);
+    report->last_nke_hit_ago = get_last_ago(now_ts, record->last_hit[CLG_NTSKE]);
+    report->last_cmd_hit_ago = get_last_ago(now_ts, record->last_hit[CLG_CMDMON]);
+  }
+
+  if (reset) {
+    for (i = 0; i < MAX_SERVICES; i++) {
+      record->hits[i] = 0;
+      record->drops[i] = 0;
+    }
+  }
+
+  return r;
 }

 /* ================================================== */
@@ -674,9 +1072,17 @@ CLG_GetClientAccessReportByIndex(int index, RPT_ClientAccessByIndex_Report *repo
 void
 CLG_GetServerStatsReport(RPT_ServerStatsReport *report)
 {
-  report->ntp_hits = total_ntp_hits;
-  report->cmd_hits = total_cmd_hits;
-  report->ntp_drops = total_ntp_drops;
-  report->cmd_drops = total_cmd_drops;
+  report->ntp_hits = total_hits[CLG_NTP];
+  report->nke_hits = total_hits[CLG_NTSKE];
+  report->cmd_hits = total_hits[CLG_CMDMON];
+  report->ntp_drops = total_drops[CLG_NTP];
+  report->nke_drops = total_drops[CLG_NTSKE];
+  report->cmd_drops = total_drops[CLG_CMDMON];
  report->log_drops = total_record_drops;
+  report->ntp_auth_hits = total_ntp_auth_hits;
+  report->ntp_interleaved_hits = total_ntp_interleaved_hits;
+  report->ntp_timestamps = ntp_ts_map.size;
+  report->ntp_span_seconds = ntp_ts_map.size > 1 ?
+                             (get_ntp_tss(ntp_ts_map.size - 1)->rx_ts -
+                              get_ntp_tss(0)->rx_ts) >> 32 : 0;
 }
--- a/clientlog.h
+++ b/clientlog.h
@@ -31,19 +31,33 @@
 #include "sysincl.h"
 #include "reports.h"

+typedef enum {
+  CLG_NTP = 0,
+  CLG_NTSKE,
+  CLG_CMDMON,
+} CLG_Service;
+
 extern void CLG_Initialise(void);
 extern void CLG_Finalise(void);
 extern int CLG_GetClientIndex(IPAddr *client);
-extern int CLG_LogNTPAccess(IPAddr *client, struct timespec *now);
-extern int CLG_LogCommandAccess(IPAddr *client, struct timespec *now);
-extern int CLG_LimitNTPResponseRate(int index);
-extern int CLG_LimitCommandResponseRate(int index);
-extern void CLG_GetNtpTimestamps(int index, NTP_int64 **rx_ts, NTP_int64 **tx_ts);
+extern int CLG_LogServiceAccess(CLG_Service service, IPAddr *client, struct timespec *now);
+extern int CLG_LimitServiceRate(CLG_Service service, int index);
+extern void CLG_LogAuthNtpRequest(void);
+extern int CLG_GetNtpMinPoll(void);
+
+/* Functions to save and retrieve timestamps for server interleaved mode */
+extern void CLG_SaveNtpTimestamps(NTP_int64 *rx_ts, struct timespec *tx_ts);
+extern void CLG_UndoNtpTxTimestampSlew(NTP_int64 *rx_ts, struct timespec *tx_ts);
+extern void CLG_UpdateNtpTxTimestamp(NTP_int64 *rx_ts, struct timespec *tx_ts);
+extern int CLG_GetNtpTxTimestamp(NTP_int64 *rx_ts, struct timespec *tx_ts);
+extern void CLG_DisableNtpTimestamps(NTP_int64 *rx_ts);

 /* And some reporting functions, for use by chronyc. */

 extern int CLG_GetNumberOfIndices(void);
-extern int CLG_GetClientAccessReportByIndex(int index, RPT_ClientAccessByIndex_Report *report, struct timespec *now);
+extern int CLG_GetClientAccessReportByIndex(int index, int reset, uint32_t min_hits,
+                                            RPT_ClientAccessByIndex_Report *report,
+                                            struct timespec *now);
 extern void CLG_GetServerStatsReport(RPT_ServerStatsReport *report);

 #endif /* GOT_CLIENTLOG_H */
--- a/cmac.h
+++ b/cmac.h
@@ -0,0 +1,48 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2019
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Header file for CMAC.
+
+  */
+
+#ifndef GOT_CMAC_H
+#define GOT_CMAC_H
+
+/* Avoid overlapping with the hash enumeration */
+typedef enum {
+  CMC_INVALID = 0,
+  CMC_AES128 = 13,
+  CMC_AES256 = 14,
+} CMC_Algorithm;
+
+typedef struct CMC_Instance_Record *CMC_Instance;
+
+extern int CMC_GetKeyLength(CMC_Algorithm algorithm);
+extern CMC_Instance CMC_CreateInstance(CMC_Algorithm algorithm, const unsigned char *key,
+                                       int length);
+extern int CMC_Hash(CMC_Instance inst, const void *in, int in_len,
+                    unsigned char *out, int out_len);
+extern void CMC_DestroyInstance(CMC_Instance inst);
+
+#endif
+
--- a/cmac_gnutls.c
+++ b/cmac_gnutls.c
@@ -0,0 +1,189 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2021
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ **********************************************************************
+
+  =======================================================================
+
+  CMAC using the GnuTLS library
+  */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include <gnutls/crypto.h>
+
+#include "cmac.h"
+#include "hash.h"
+#include "logging.h"
+#include "memory.h"
+
+struct CMC_Instance_Record {
+  gnutls_mac_algorithm_t algorithm;
+  gnutls_hmac_hd_t mac;
+};
+
+/* ================================================== */
+
+static int instance_counter = 0;
+static int gnutls_initialised = 0;
+
+/* ================================================== */
+
+static void
+init_gnutls(void)
+{
+  int r;
+
+  if (gnutls_initialised)
+    return;
+
+  r = gnutls_global_init();
+  if (r < 0)
+    LOG_FATAL("Could not initialise %s : %s", "gnutls", gnutls_strerror(r));
+
+  DEBUG_LOG("Initialised");
+  gnutls_initialised = 1;
+}
+
+/* ================================================== */
+
+static void
+deinit_gnutls(void)
+{
+  assert(gnutls_initialised);
+  gnutls_global_deinit();
+  gnutls_initialised = 0;
+  DEBUG_LOG("Deinitialised");
+}
+
+/* ================================================== */
+
+static gnutls_mac_algorithm_t
+get_mac_algorithm(CMC_Algorithm algorithm)
+{
+  switch (algorithm) {
+    case CMC_AES128:
+      return GNUTLS_MAC_AES_CMAC_128;
+    case CMC_AES256:
+      return GNUTLS_MAC_AES_CMAC_256;
+    default:
+      return GNUTLS_MAC_UNKNOWN;
+  }
+}
+
+/* ================================================== */
+
+int
+CMC_GetKeyLength(CMC_Algorithm algorithm)
+{
+  gnutls_mac_algorithm_t malgo = get_mac_algorithm(algorithm);
+  int len;
+
+  if (malgo == GNUTLS_MAC_UNKNOWN)
+    return 0;
+
+  len = gnutls_hmac_get_key_size(malgo);
+
+  if (len < 0)
+    return 0;
+
+  return len;
+}
+
+/* ================================================== */
+
+CMC_Instance
+CMC_CreateInstance(CMC_Algorithm algorithm, const unsigned char *key, int length)
+{
+  gnutls_hmac_hd_t handle;
+  CMC_Instance inst;
+
+  int r;
+
+  if (instance_counter == 0)
+    init_gnutls();
+
+  if (length <= 0 || length != CMC_GetKeyLength(algorithm))
+    goto error;
+
+  r = gnutls_hmac_init(&handle, get_mac_algorithm(algorithm), key, length);
+  if (r < 0) {
+    DEBUG_LOG("Could not initialise %s : %s", "mac", gnutls_strerror(r));
+    goto error;
+  }
+
+  inst = MallocNew(struct CMC_Instance_Record);
+  inst->algorithm = get_mac_algorithm(algorithm);
+  inst->mac = handle;
+
+  instance_counter++;
+
+  return inst;
+
+error:
+  if (instance_counter == 0)
+    deinit_gnutls();
+  return NULL;
+}
+
+/* ================================================== */
+
+int
+CMC_Hash(CMC_Instance inst, const void *in, int in_len, unsigned char *out, int out_len)
+{
+  unsigned char buf[MAX_HASH_LENGTH];
+  int hash_len;
+
+  if (in_len < 0 || out_len < 0)
+    return 0;
+
+  hash_len = gnutls_hmac_get_len(inst->algorithm);
+
+  if (out_len > hash_len)
+    out_len = hash_len;
+
+  if (hash_len > sizeof (buf))
+    return 0;
+
+  if (gnutls_hmac(inst->mac, in, in_len) < 0) {
+    /* Reset the state */
+    gnutls_hmac_output(inst->mac, buf);
+    return 0;
+  }
+
+  gnutls_hmac_output(inst->mac, buf);
+  memcpy(out, buf, out_len);
+
+  return out_len;
+}
+
+/* ================================================== */
+
+void
+CMC_DestroyInstance(CMC_Instance inst)
+{
+  gnutls_hmac_deinit(inst->mac, NULL);
+  Free(inst);
+
+  instance_counter--;
+  if (instance_counter == 0)
+    deinit_gnutls();
+}
--- a/cmac_nettle.c
+++ b/cmac_nettle.c
@@ -0,0 +1,117 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2019
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Support for AES128 and AES256 CMAC in Nettle.
+
+  */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include <nettle/cmac.h>
+
+#include "cmac.h"
+#include "memory.h"
+
+struct CMC_Instance_Record {
+  int key_length;
+  union {
+    struct cmac_aes128_ctx aes128;
+    struct cmac_aes256_ctx aes256;
+  } context;
+};
+
+/* ================================================== */
+
+int
+CMC_GetKeyLength(CMC_Algorithm algorithm)
+{
+  if (algorithm == CMC_AES128)
+    return AES128_KEY_SIZE;
+  else if (algorithm == CMC_AES256)
+    return AES256_KEY_SIZE;
+  return 0;
+}
+
+/* ================================================== */
+
+CMC_Instance
+CMC_CreateInstance(CMC_Algorithm algorithm, const unsigned char *key, int length)
+{
+  CMC_Instance inst;
+
+  if (length <= 0 || length != CMC_GetKeyLength(algorithm))
+    return NULL;
+
+  inst = MallocNew(struct CMC_Instance_Record);
+  inst->key_length = length;
+
+  switch (length) {
+    case AES128_KEY_SIZE:
+      cmac_aes128_set_key(&inst->context.aes128, key);
+      break;
+    case AES256_KEY_SIZE:
+      cmac_aes256_set_key(&inst->context.aes256, key);
+      break;
+    default:
+      assert(0);
+  }
+
+  return inst;
+}
+
+/* ================================================== */
+
+int
+CMC_Hash(CMC_Instance inst, const void *in, int in_len, unsigned char *out, int out_len)
+{
+  if (in_len < 0 || out_len < 0)
+    return 0;
+
+  if (out_len > CMAC128_DIGEST_SIZE)
+    out_len = CMAC128_DIGEST_SIZE;
+
+  switch (inst->key_length) {
+    case AES128_KEY_SIZE:
+      cmac_aes128_update(&inst->context.aes128, in_len, in);
+      cmac_aes128_digest(&inst->context.aes128, out_len, out);
+      break;
+    case AES256_KEY_SIZE:
+      cmac_aes256_update(&inst->context.aes256, in_len, in);
+      cmac_aes256_digest(&inst->context.aes256, out_len, out);
+      break;
+    default:
+      assert(0);
+  }
+
+  return out_len;
+}
+
+/* ================================================== */
+
+void
+CMC_DestroyInstance(CMC_Instance inst)
+{
+  Free(inst);
+}
--- a/cmdmon.c
+++ b/cmdmon.c
--- a/cmdmon.h
+++ b/cmdmon.h
@@ -29,7 +29,7 @@

 #include "addressing.h"

-extern void CAM_Initialise(int family);
+extern void CAM_Initialise(void);

 extern void CAM_Finalise(void);

--- a/cmdparse.c
+++ b/cmdparse.c
@@ -3,7 +3,7 @@

 **********************************************************************
 * Copyright (C) Richard P. Curnow  1997-2003
- * Copyright (C) Miroslav Lichvar  2013-2014, 2016
+ * Copyright (C) Miroslav Lichvar  2013-2014, 2016, 2021
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
@@ -43,14 +43,16 @@ int
 CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)
 {
  char *hostname, *cmd;
+  uint32_t ef_type;
  int n;
  
  src->port = SRC_DEFAULT_PORT;
  src->params.minpoll = SRC_DEFAULT_MINPOLL;
  src->params.maxpoll = SRC_DEFAULT_MAXPOLL;
-  src->params.online = 1;
+  src->params.connectivity = SRC_ONLINE;
  src->params.auto_offline = 0;
  src->params.presend_minpoll = SRC_DEFAULT_PRESEND_MINPOLL;
+  src->params.burst = 0;
  src->params.iburst = 0;
  src->params.min_stratum = SRC_DEFAULT_MINSTRATUM;
  src->params.poll_target = SRC_DEFAULT_POLLTARGET;
@@ -58,12 +60,21 @@ CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)
  src->params.max_sources = SRC_DEFAULT_MAXSOURCES;
  src->params.min_samples = SRC_DEFAULT_MINSAMPLES;
  src->params.max_samples = SRC_DEFAULT_MAXSAMPLES;
+  src->params.filter_length = 0;
  src->params.interleaved = 0;
  src->params.sel_options = 0;
+  src->params.nts = 0;
+  src->params.nts_port = SRC_DEFAULT_NTSPORT;
+  src->params.copy = 0;
+  src->params.ext_fields = 0;
  src->params.authkey = INACTIVE_AUTHKEY;
+  src->params.cert_set = SRC_DEFAULT_CERTSET;
  src->params.max_delay = SRC_DEFAULT_MAXDELAY;
  src->params.max_delay_ratio = SRC_DEFAULT_MAXDELAYRATIO;
  src->params.max_delay_dev_ratio = SRC_DEFAULT_MAXDELAYDEVRATIO;
+  src->params.max_delay_quant = 0.0;
+  src->params.min_delay = 0.0;
+  src->params.asymmetry = SRC_DEFAULT_ASYMMETRY;
  src->params.offset = 0.0;

  hostname = line;
@@ -82,10 +93,14 @@ CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)

    if (!strcasecmp(cmd, "auto_offline")) {
      src->params.auto_offline = 1;
+    } else if (!strcasecmp(cmd, "burst")) {
+      src->params.burst = 1;
+    } else if (!strcasecmp(cmd, "copy")) {
+      src->params.copy = 1;
    } else if (!strcasecmp(cmd, "iburst")) {
      src->params.iburst = 1;
    } else if (!strcasecmp(cmd, "offline")) {
-      src->params.online = 0;
+      src->params.connectivity = SRC_OFFLINE;
    } else if (!strcasecmp(cmd, "noselect")) {
      src->params.sel_options |= SRC_SELECT_NOSELECT;
    } else if (!strcasecmp(cmd, "prefer")) {
@@ -94,10 +109,29 @@ CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)
      src->params.sel_options |= SRC_SELECT_REQUIRE;
    } else if (!strcasecmp(cmd, "trust")) {
      src->params.sel_options |= SRC_SELECT_TRUST;
+    } else if (!strcasecmp(cmd, "certset")) {
+      if (sscanf(line, "%"SCNu32"%n", &src->params.cert_set, &n) != 1)
+        return 0;
    } else if (!strcasecmp(cmd, "key")) {
      if (sscanf(line, "%"SCNu32"%n", &src->params.authkey, &n) != 1 ||
          src->params.authkey == INACTIVE_AUTHKEY)
        return 0;
+    } else if (!strcasecmp(cmd, "asymmetry")) {
+      if (sscanf(line, "%lf%n", &src->params.asymmetry, &n) != 1)
+        return 0;
+    } else if (!strcasecmp(cmd, "extfield")) {
+      if (sscanf(line, "%"SCNx32"%n", &ef_type, &n) != 1)
+        return 0;
+      switch (ef_type) {
+        case NTP_EF_EXP1:
+          src->params.ext_fields |= NTP_EF_FLAG_EXP1;
+          break;
+        default:
+          return 0;
+      }
+    } else if (!strcasecmp(cmd, "filter")) {
+      if (sscanf(line, "%d%n", &src->params.filter_length, &n) != 1)
+        return 0;
    } else if (!strcasecmp(cmd, "maxdelay")) {
      if (sscanf(line, "%lf%n", &src->params.max_delay, &n) != 1)
        return 0;
@@ -107,6 +141,9 @@ CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)
    } else if (!strcasecmp(cmd, "maxdelaydevratio")) {
      if (sscanf(line, "%lf%n", &src->params.max_delay_dev_ratio, &n) != 1)
        return 0;
+    } else if (!strcasecmp(cmd, "maxdelayquant")) {
+      if (sscanf(line, "%lf%n", &src->params.max_delay_quant, &n) != 1)
+        return 0;
    } else if (!strcasecmp(cmd, "maxpoll")) {
      if (sscanf(line, "%d%n", &src->params.maxpoll, &n) != 1)
        return 0;
@@ -116,6 +153,9 @@ CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)
    } else if (!strcasecmp(cmd, "maxsources")) {
      if (sscanf(line, "%d%n", &src->params.max_sources, &n) != 1)
        return 0;
+    } else if (!strcasecmp(cmd, "mindelay")) {
+      if (sscanf(line, "%lf%n", &src->params.min_delay, &n) != 1)
+        return 0;
    } else if (!strcasecmp(cmd, "minpoll")) {
      if (sscanf(line, "%d%n", &src->params.minpoll, &n) != 1)
        return 0;
@@ -125,11 +165,16 @@ CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)
    } else if (!strcasecmp(cmd, "minstratum")) {
      if (sscanf(line, "%d%n", &src->params.min_stratum, &n) != 1)
        return 0;
+    } else if (!strcasecmp(cmd, "nts")) {
+      src->params.nts = 1;
+    } else if (!strcasecmp(cmd, "ntsport")) {
+      if (sscanf(line, "%d%n", &src->params.nts_port, &n) != 1)
+        return 0;
    } else if (!strcasecmp(cmd, "offset")) {
      if (sscanf(line, "%lf%n", &src->params.offset, &n) != 1)
        return 0;
    } else if (!strcasecmp(cmd, "port")) {
-      if (sscanf(line, "%hu%n", &src->port, &n) != 1)
+      if (sscanf(line, "%d%n", &src->port, &n) != 1)
        return 0;
    } else if (!strcasecmp(cmd, "polltarget")) {
      if (sscanf(line, "%d%n", &src->params.poll_target, &n) != 1)
@@ -152,6 +197,85 @@ CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)

 /* ================================================== */

+int
+CPS_ParseAllowDeny(char *line, int *all, IPAddr *ip, int *subnet_bits)
+{
+  char *p, *net, *slash;
+  uint32_t a, b, c;
+  int bits, len, n;
+
+  p = CPS_SplitWord(line);
+
+  if (strcmp(line, "all") == 0) {
+    *all = 1;
+    net = p;
+    p = CPS_SplitWord(p);
+  } else {
+    *all = 0;
+    net = line;
+  }
+
+  /* Make sure there are no other arguments */
+  if (*p)
+    return 0;
+
+  /* No specified address or network means all IPv4 and IPv6 addresses */
+  if (!*net) {
+    ip->family = IPADDR_UNSPEC;
+    *subnet_bits = 0;
+    return 1;
+  }
+
+  slash = strchr(net, '/');
+  if (slash) {
+    if (sscanf(slash + 1, "%d%n", &bits, &len) != 1 || slash[len + 1] || bits < 0)
+      return 0;
+    *slash = '\0';
+  } else {
+    bits = -1;
+  }
+
+  if (UTI_StringToIP(net, ip)) {
+    if (bits >= 0)
+      *subnet_bits = bits;
+    else
+      *subnet_bits = ip->family == IPADDR_INET6 ? 128 : 32;
+    return 1;
+  }
+
+  /* Check for a shortened IPv4 network notation using only 1, 2, or 3 decimal
+     numbers.  This is different than the numbers-and-dots notation accepted
+     by inet_aton()! */
+
+  a = b = c = 0;
+  n = sscanf(net, "%"PRIu32"%n.%"PRIu32"%n.%"PRIu32"%n", &a, &len, &b, &len, &c, &len);
+
+  if (n > 0 && !net[len]) {
+    if (a > 255 || b > 255 || c > 255)
+      return 0;
+
+    ip->family = IPADDR_INET4;
+    ip->addr.in4 = (a << 24) | (b << 16) | (c << 8);
+
+    if (bits >= 0)
+      *subnet_bits = bits;
+    else
+      *subnet_bits = n * 8;
+
+    return 1;
+  }
+
+  /* The last possibility is a hostname */
+  if (bits < 0 && DNS_Name2IPAddress(net, ip, 1) == DNS_Success) {
+    *subnet_bits = ip->family == IPADDR_INET6 ? 128 : 32;
+    return 1;
+  }
+
+  return 0;
+}
+
+/* ================================================== */
+
 int
 CPS_ParseLocal(char *line, int *stratum, int *orphan, double *distance)
 {
@@ -246,7 +370,7 @@ CPS_SplitWord(char *line)
 /* ================================================== */

 int
-CPS_ParseKey(char *line, uint32_t *id, const char **hash, char **key)
+CPS_ParseKey(char *line, uint32_t *id, const char **type, char **key)
 {
  char *s1, *s2, *s3, *s4;

@@ -263,10 +387,10 @@ CPS_ParseKey(char *line, uint32_t *id, const char **hash, char **key)
    return 0;

  if (*s3) {
-    *hash = s2;
+    *type = s2;
    *key = s3;
  } else {
-    *hash = "MD5";
+    *type = "MD5";
    *key = s2;
  }

--- a/cmdparse.h
+++ b/cmdparse.h
@@ -32,13 +32,16 @@

 typedef struct {
  char *name;
-  unsigned short port;
+  int port;
  SourceParameters params;
 } CPS_NTP_Source;

 /* Parse a command to add an NTP server or peer */
 extern int CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src);
  
+/* Parse a command to allow/deny access */
+extern int CPS_ParseAllowDeny(char *line, int *all, IPAddr *ip, int *subnet_bits);
+
 /* Parse a command to enable local reference */
 extern int CPS_ParseLocal(char *line, int *stratum, int *orphan, double *distance);

@@ -49,6 +52,6 @@ extern void CPS_NormalizeLine(char *line);
 extern char *CPS_SplitWord(char *line);

 /* Parse a key from keyfile */
-extern int CPS_ParseKey(char *line, uint32_t *id, const char **hash, char **key);
+extern int CPS_ParseKey(char *line, uint32_t *id, const char **type, char **key);

 #endif /* GOT_CMDPARSE_H */
--- a/conf.c
+++ b/conf.c
--- a/conf.h
+++ b/conf.h
@@ -30,10 +30,13 @@

 #include "addressing.h"
 #include "reference.h"
+#include "sources.h"

-extern void CNF_Initialise(int restarted);
+extern void CNF_Initialise(int restarted, int client_only);
 extern void CNF_Finalise(void);

+extern void CNF_EnablePrint(void);
+
 extern char *CNF_GetRtcDevice(void);

 extern void CNF_ReadFile(const char *filename);
@@ -46,13 +49,16 @@ extern void CNF_AddSources(void);
 extern void CNF_AddBroadcasts(void);
 extern void CNF_AddRefclocks(void);

+extern void CNF_ReloadSources(void);
+
 extern int CNF_GetAcquisitionPort(void);
 extern int CNF_GetNTPPort(void);
 extern char *CNF_GetDriftFile(void);
 extern char *CNF_GetLogDir(void);
 extern char *CNF_GetDumpDir(void);
 extern int CNF_GetLogBanner(void);
-extern int CNF_GetLogMeasurements(void);
+extern int CNF_GetLogMeasurements(int *raw);
+extern int CNF_GetLogSelection(void);
 extern int CNF_GetLogStatistics(void);
 extern int CNF_GetLogTracking(void);
 extern int CNF_GetLogRtc(void);
@@ -60,7 +66,6 @@ extern int CNF_GetLogRefclocks(void);
 extern int CNF_GetLogTempComp(void);
 extern char *CNF_GetKeysFile(void);
 extern char *CNF_GetRtcFile(void);
-extern int CNF_GetDumpOnExit(void);
 extern int CNF_GetManualEnabled(void);
 extern int CNF_GetCommandPort(void);
 extern int CNF_GetRtcOnUtc(void);
@@ -75,7 +80,11 @@ extern void CNF_GetFallbackDrifts(int *min, int *max);
 extern void CNF_GetBindAddress(int family, IPAddr *addr);
 extern void CNF_GetBindAcquisitionAddress(int family, IPAddr *addr);
 extern void CNF_GetBindCommandAddress(int family, IPAddr *addr);
+extern char *CNF_GetBindNtpInterface(void);
+extern char *CNF_GetBindAcquisitionInterface(void);
+extern char *CNF_GetBindCommandInterface(void);
 extern char *CNF_GetBindCommandPath(void);
+extern int CNF_GetNtpDscp(void);
 extern char *CNF_GetNtpSigndSocket(void);
 extern char *CNF_GetPidFile(void);
 extern REF_LeapMode CNF_GetLeapSecMode(void);
@@ -87,7 +96,9 @@ extern double CNF_GetMaxClockError(void);
 extern double CNF_GetMaxDrift(void);
 extern double CNF_GetCorrectionTimeRatio(void);
 extern double CNF_GetMaxSlewRate(void);
+extern double CNF_GetClockPrecision(void);

+extern SRC_AuthSelectMode CNF_GetAuthSelectMode(void);
 extern double CNF_GetMaxDistance(void);
 extern double CNF_GetMaxJitter(void);
 extern double CNF_GetReselectDistance(void);
@@ -102,6 +113,7 @@ extern int CNF_GetSchedPriority(void);
 extern int CNF_GetLockMemory(void);

 extern int CNF_GetNTPRateLimit(int *interval, int *burst, int *leak);
+extern int CNF_GetNtsRateLimit(int *interval, int *burst, int *leak);
 extern int CNF_GetCommandRateLimit(int *interval, int *burst, int *leak);
 extern void CNF_GetSmooth(double *max_freq, double *max_wander, int *leap_only);
 extern void CNF_GetTempComp(char **file, double *interval, char **point_file, double *T0, double *k0, double *k1, double *k2);
@@ -119,6 +131,40 @@ extern char *CNF_GetHwclockFile(void);
 extern int CNF_GetInitSources(void);
 extern double CNF_GetInitStepThreshold(void);

-extern int CNF_GetHwTsInterface(unsigned int index, char **name, double *tx_comp, double *rx_comp);
+typedef enum {
+  CNF_HWTS_RXFILTER_ANY,
+  CNF_HWTS_RXFILTER_NONE,
+  CNF_HWTS_RXFILTER_NTP,
+  CNF_HWTS_RXFILTER_PTP,
+  CNF_HWTS_RXFILTER_ALL,
+} CNF_HwTs_RxFilter;
+
+typedef struct {
+  char *name;
+  int minpoll;
+  int min_samples;
+  int max_samples;
+  int nocrossts;
+  CNF_HwTs_RxFilter rxfilter;
+  double precision;
+  double tx_comp;
+  double rx_comp;
+} CNF_HwTsInterface;
+
+extern int CNF_GetHwTsInterface(unsigned int index, CNF_HwTsInterface **iface);
+
+extern int CNF_GetPtpPort(void);
+
+extern char *CNF_GetNtsDumpDir(void);
+extern char *CNF_GetNtsNtpServer(void);
+extern int CNF_GetNtsServerCertAndKeyFiles(const char ***certs, const char ***keys);
+extern int CNF_GetNtsServerPort(void);
+extern int CNF_GetNtsServerProcesses(void);
+extern int CNF_GetNtsServerConnections(void);
+extern int CNF_GetNtsRefresh(void);
+extern int CNF_GetNtsRotate(void);
+extern int CNF_GetNtsTrustedCertsPaths(const char ***paths, uint32_t **ids);
+extern int CNF_GetNoSystemCert(void);
+extern int CNF_GetNoCertTimeCheck(void);

 #endif /* GOT_CONF_H */
--- a/451
+++ b/451
@@ -5,7 +5,8 @@
 #
 # Copyright (C) Richard P. Curnow  1997-2003
 # Copyright (C) Bryan Christianson  2016
-# Copyright (C) Miroslav Lichvar  2009, 2012-2016
+# Copyright (C) Miroslav Lichvar  2009, 2012-2021
+# Copyright (C) Stefan R. Filipek  2019
 #
 # =======================================================================

@@ -32,13 +33,13 @@ test_code () {
    echo "int main(int argc, char **argv) {"
    echo "$code"
    echo "return 0; }"
-  ) > docheck.c
+  ) > conftest.c

-  echo "docheck.c:" >> config.log
-  cat docheck.c >> config.log
-  echo $MYCC $MYCFLAGS $MYCPPFLAGS $cflags -o docheck docheck.c $ldflags \
+  echo "conftest.c:" >> config.log
+  cat conftest.c >> config.log
+  echo $MYCC $MYCFLAGS $MYCPPFLAGS $cflags -o conftest conftest.c $ldflags \
    $MYLDFLAGS >> config.log
-  $MYCC $MYCFLAGS $MYCPPFLAGS $cflags -o docheck docheck.c $ldflags \
+  $MYCC $MYCFLAGS $MYCPPFLAGS $cflags -o conftest conftest.c $ldflags \
    $MYLDFLAGS >> config.log 2>&1

  if [ $? -eq 0 ]
@@ -49,11 +50,39 @@ test_code () {
    echo "No"
    result=1
  fi
-  rm -f docheck.c docheck
+  rm -f conftest.c conftest
  echo >> config.log
  return $result
 }
 #}}}
+#{{{ test_executable
+test_executable () {
+  name=$1
+  executable=$2
+  options=$3
+
+  printf "%s" "Checking for $name : "
+
+  echo $executable $options >> config.log
+  $executable $options >> config.log 2>&1
+
+  if [ $? -eq 0 ]
+  then
+    echo "Yes"
+    result=0
+  else
+    echo "No"
+    result=1
+  fi
+  echo >> config.log
+  return $result
+}
+#}}}
+#{{{ pkg_config
+pkg_config () {
+  $PKG_CONFIG "$@" 2>> config.log
+}
+#}}}
 #{{{ usage
 usage () {
  cat <<EOF
@@ -79,14 +108,13 @@ for instance \`--prefix=$HOME'.

 For better control, use the options below.
  --disable-readline     Disable line editing support
-  --without-readline     Don't use GNU readline even if it is available
  --without-editline     Don't use editline even if it is available
-  --with-readline-includes=DIR Specify where readline include directory is
-  --with-readline-library=DIR Specify where readline lib directory is
-  --with-ncurses-library=DIR Specify where ncurses lib directory is
  --disable-sechash      Disable support for hashes other than MD5
+  --without-nettle       Don't use nettle even if it is available
  --without-nss          Don't use NSS even if it is available
  --without-tomcrypt     Don't use libtomcrypt even if it is available
+  --disable-nts          Disable NTS support
+  --without-gnutls       Don't use gnutls even if it is available
  --disable-cmdmon       Disable command and monitoring support
  --disable-ntp          Disable NTP support
  --disable-refclock     Disable reference clock support
@@ -107,7 +135,7 @@ For better control, use the options below.
                         since 1970-01-01 [50*365 days ago]
  --with-user=USER       Specify default chronyd user [root]
  --with-hwclockfile=PATH Specify default path to hwclock(8) adjtime file
-  --with-pidfile=PATH    Specify default pidfile [/var/run/chronyd.pid]
+  --with-pidfile=PATH    Specify default pidfile [/var/run/chrony/chronyd.pid]
  --with-rtcdevice=PATH  Specify default path to RTC device [/dev/rtc]
  --with-sendmail=PATH   Path to sendmail binary [/usr/lib/sendmail]
  --enable-debug         Enable debugging support
@@ -135,6 +163,11 @@ Some influential environment variables:
              headers in a nonstandard directory <include dir>
  LDFLAGS     linker flags, e.g. -L<lib dir> if you have libraries in a
              nonstandard directory <lib dir>
+  PKG_CONFIG  path to pkg-config utility
+  PKG_CONFIG_PATH
+              directories to add to pkg-config's search path
+  PKG_CONFIG_LIBDIR
+              path overriding pkg-config's built-in search path

 Use these variables to override the choices made by \`configure' or to help
 it to find libraries and programs with nonstandard names/locations.
@@ -152,13 +185,6 @@ add_def () {
  fi
 }
 #}}}
-#{{{ pkg_config
-pkg_config () {
-  type pkg-config > /dev/null 2> /dev/null || return 1
-
-  pkg-config $@ 2> /dev/null
-}
-#}}}
 #{{{ get_features
 get_features () {
  ff=1
@@ -184,22 +210,24 @@ OPERATINGSYSTEM=`uname -s`
 VERSION=`uname -r`
 MACHINE=`uname -m`

+LIBS=""
 EXTRA_LIBS=""
 EXTRA_CLI_LIBS=""
 EXTRA_OBJECTS=""
-EXTRA_DEFS=""
-SYSDEFS=""
+EXTRA_CLI_OBJECTS=""

 feat_debug=0
 feat_cmdmon=1
 feat_ntp=1
 feat_refclock=1
 feat_readline=1
-try_readline=1
 try_editline=1
 feat_sechash=1
+try_nettle=1
 try_nss=1
 try_tomcrypt=1
+feat_nts=1
+try_gnutls=1
 feat_rtc=1
 try_rtc=0
 feat_droproot=1
@@ -208,9 +236,6 @@ try_clockctl=0
 feat_scfilter=0
 try_seccomp=-1
 priv_ops=""
-readline_lib=""
-readline_inc=""
-ncurses_lib=""
 feat_ipv6=1
 feat_phc=1
 try_phc=0
@@ -220,14 +245,16 @@ try_lockmem=0
 feat_asyncdns=1
 feat_forcednsretry=1
 try_clock_gettime=1
+try_arc4random=1
 try_recvmmsg=1
 feat_timestamping=1
 try_timestamping=0
 feat_ntp_signd=0
 ntp_era_split=""
+use_pthread=0
 default_user="root"
 default_hwclockfile=""
-default_pidfile="/var/run/chronyd.pid"
+default_pidfile="/var/run/chrony/chronyd.pid"
 default_rtcdevice="/dev/rtc"
 mail_program="/usr/lib/sendmail"

@@ -240,21 +267,9 @@ do
    --disable-readline )
      feat_readline=0
    ;;
-    --without-readline )
-      try_readline=0
-    ;;
    --without-editline )
      try_editline=0
    ;;
-    --with-readline-library=* )
-      readline_lib=-L`echo $option | sed -e 's/^.*=//;'`
-    ;;
-    --with-readline-includes=* )
-      readline_inc=-I`echo $option | sed -e 's/^.*=//;'`
-    ;;
-    --with-ncurses-library=* )
-      ncurses_lib=-L`echo $option | sed -e 's/^.*=//;'`
-    ;;
    --prefix=* | --install_prefix=* )
      SETPREFIX=`echo $option | sed -e 's/[^=]*=//;'`
    ;;
@@ -360,12 +375,21 @@ do
    --disable-sechash )
      feat_sechash=0
    ;;
+    --without-nettle )
+      try_nettle=0
+    ;;
    --without-nss )
      try_nss=0
    ;;
    --without-tomcrypt )
      try_tomcrypt=0
    ;;
+    --disable-nts )
+      feat_nts=0
+    ;;
+    --without-gnutls )
+      try_gnutls=0
+    ;;
    --host-system=* )
      OPERATINGSYSTEM=`echo $option | sed -e 's/^.*=//;'`
    ;;
@@ -390,7 +414,7 @@ SYSTEM=${OPERATINGSYSTEM}-${MACHINE}

 case $OPERATINGSYSTEM in
    Linux)
-        EXTRA_OBJECTS="sys_generic.o sys_linux.o sys_timex.o"
+        EXTRA_OBJECTS="sys_generic.o sys_linux.o sys_timex.o sys_posix.o"
        [ $try_libcap != "0" ] && try_libcap=1
        try_rtc=1
        [ $try_seccomp != "0" ] && try_seccomp=1
@@ -398,6 +422,7 @@ case $OPERATINGSYSTEM in
        try_setsched=1
        try_lockmem=1
        try_phc=1
+        try_arc4random=0
        add_def LINUX
        echo "Configuring for " $SYSTEM
    ;;
@@ -405,7 +430,9 @@ case $OPERATINGSYSTEM in
        # recvmmsg() seems to be broken on FreeBSD 11.0 and it's just
        # a wrapper around recvmsg()
        try_recvmmsg=0
-        EXTRA_OBJECTS="sys_generic.o sys_netbsd.o sys_timex.o"
+        EXTRA_OBJECTS="sys_generic.o sys_netbsd.o sys_timex.o sys_posix.o"
+        try_setsched=1
+        try_lockmem=1
        add_def FREEBSD
        if [ $feat_droproot = "1" ]; then
          add_def FEAT_PRIVDROP
@@ -414,26 +441,37 @@ case $OPERATINGSYSTEM in
        echo "Configuring for $SYSTEM"
    ;;
    NetBSD)
-        EXTRA_OBJECTS="sys_generic.o sys_netbsd.o sys_timex.o"
+        EXTRA_OBJECTS="sys_generic.o sys_netbsd.o sys_timex.o sys_posix.o"
        try_clockctl=1
+        try_setsched=1
+        try_lockmem=1
        add_def NETBSD
        echo "Configuring for $SYSTEM"
    ;;
    Darwin)
        EXTRA_OBJECTS="sys_macosx.o"
-        EXTRA_LIBS="-lresolv"
-        EXTRA_CLI_LIBS="-lresolv"
+        LIBS="$LIBS -lresolv"
        add_def MACOSX
        if [ $feat_droproot = "1" ]; then
          add_def FEAT_PRIVDROP
          priv_ops="ADJUSTTIME SETTIME BINDSOCKET"
        fi
+        major=`echo $VERSION | cut -d. -f1`
+        # ntp_adjtime is not available in macOS 10.12 (Darwin 16.x.x) and earlier
+        if [ $major -gt "16" ]; then
+          add_def HAVE_MACOS_SYS_TIMEX
+          EXTRA_OBJECTS="$EXTRA_OBJECTS sys_generic.o sys_netbsd.o sys_timex.o"
+          if [ $feat_droproot = "1" ]; then
+            priv_ops="$priv_ops ADJUSTTIMEX"
+          fi
+        fi
        echo "Configuring for macOS (" $SYSTEM "macOS version" $VERSION ")"
    ;;
    SunOS)
-        EXTRA_OBJECTS="sys_generic.o sys_solaris.o sys_timex.o"
-        EXTRA_LIBS="-lsocket -lnsl -lresolv"
-        EXTRA_CLI_LIBS="-lsocket -lnsl -lresolv"
+        EXTRA_OBJECTS="sys_generic.o sys_solaris.o sys_timex.o sys_posix.o"
+        LIBS="$LIBS -lsocket -lnsl -lkvm -lelf -lresolv"
+        try_setsched=1
+        try_lockmem=1
        add_def SOLARIS
        # These are needed to have msg_control in struct msghdr
        add_def __EXTENSIONS__
@@ -443,7 +481,7 @@ case $OPERATINGSYSTEM in
          add_def FEAT_PRIVDROP
          priv_ops="ADJUSTTIMEX SETTIME BINDSOCKET"
        fi
-        echo "Configuring for Solaris (" $SYSTEM "SunOS version" $VERSION ")" 
+        echo "Configuring for illumos (" $SYSTEM "SunOS version" $VERSION ")"
    ;;                                                                        
    * )
        echo "error: $SYSTEM is not supported (yet?)"
@@ -463,7 +501,7 @@ fi

 if [ $feat_ntp = "1" ]; then
  add_def FEAT_NTP
-  EXTRA_OBJECTS="$EXTRA_OBJECTS ntp_core.o ntp_io.o ntp_sources.o"
+  EXTRA_OBJECTS="$EXTRA_OBJECTS ntp_auth.o ntp_core.o ntp_ext.o ntp_io.o ntp_sources.o"
  if [ $feat_ntp_signd = "1" ]; then
    add_def FEAT_SIGND
    EXTRA_OBJECTS="$EXTRA_OBJECTS ntp_signd.o"
@@ -490,14 +528,16 @@ MYCPPFLAGS="$CPPFLAGS"
 MYLDFLAGS="$LDFLAGS"

 if [ "x$MYCC" = "x" ]; then
-  MYCC=gcc
-  if ! test_code "$MYCC" '' '' '' ''; then
-    MYCC=cc
-    if ! test_code "$MYCC" '' '' '' ''; then
+  for cc in gcc clang cc ""; do
+    if [ "x$cc" = "x" ]; then
      echo "error: no C compiler found"
      exit 1
    fi
-  fi
+    MYCC=$cc
+    if test_code "$MYCC" '' '' '' ''; then
+      break
+    fi
+  done
 else
  if ! test_code "$MYCC" '' '' '' ''; then
    echo "error: C compiler $MYCC cannot create executables"
@@ -507,12 +547,38 @@ fi

 if [ "x$MYCFLAGS" = "x" ]; then
  MYCFLAGS="-O2 -g"
+
+  TESTCFLAGS="-D_FORTIFY_SOURCE=2 -fPIE"
+  TESTLDFLAGS="-pie -Wl,-z,relro,-z,now"
+  if test_code 'hardening compiler options' '' "$TESTCFLAGS" "$TESTLDFLAGS" ''; then
+    MYCFLAGS="$MYCFLAGS $TESTCFLAGS"
+    MYLDFLAGS="$MYLDFLAGS $TESTLDFLAGS"
+  fi
+  TESTCFLAGS="-fstack-protector-strong --param=ssp-buffer-size=4"
+  if test_code '-fstack-protector-strong' '' "$TESTCFLAGS" '' ''; then
+    MYCFLAGS="$MYCFLAGS $TESTCFLAGS"
+  else
+    TESTCFLAGS="-fstack-protector --param=ssp-buffer-size=4"
+    if test_code '-fstack-protector' '' "$TESTCFLAGS" '' ''; then
+      MYCFLAGS="$MYCFLAGS $TESTCFLAGS"
+    fi
+  fi
 fi

-if [ "x$MYCC" = "xgcc" ]; then
+if [ "x$MYCC" = "xgcc" ] || [ "x$MYCC" = "xclang" ]; then
  MYCFLAGS="$MYCFLAGS -Wmissing-prototypes -Wall"
 fi

+if [ "x$PKG_CONFIG" = "x" ]; then
+  PKG_CONFIG=pkg-config
+fi
+
+if ! test_executable "pkg-config" $PKG_CONFIG --version; then
+  try_nettle=0
+  try_nss=0
+  try_gnutls=0
+fi
+
 if test_code '64-bit time_t' 'time.h' '' '' '
  char x[sizeof(time_t) > 4 ? 1 : -1] = {0};
  return x[0];'
@@ -523,7 +589,11 @@ then
    split_seconds=$ntp_era_split
    split_days=0
  else
-    split_seconds=`date '+%s'`
+    if [ "x$SOURCE_DATE_EPOCH" != "x" ]; then
+      split_seconds=$SOURCE_DATE_EPOCH
+    else
+      split_seconds=`date '+%s'`
+    fi
    if [ "x$split_seconds" = "x" ]; then
      echo "error: could not get current time, --with-ntp-era option is needed"
      exit 1
@@ -548,25 +618,15 @@ then
 fi

 MATHCODE='return (int) pow(2.0, log(sqrt((double)argc)));'
-if test_code 'math' 'math.h' '' '' "$MATHCODE"; then
-  LIBS=""
-else
+if ! test_code 'math' 'math.h' '' '' "$MATHCODE"; then
  if test_code 'math in -lm' 'math.h' '' '-lm' "$MATHCODE"; then
-    LIBS="-lm"
+    LIBS="$LIBS -lm"
  else
    echo "error: could not compile/link a program which uses sqrt(), log(), pow()"
    exit 1
  fi
 fi
  
-if test_code '<stdint.h>' 'stdint.h' '' '' ''; then
-  add_def HAVE_STDINT_H
-fi
-
-if test_code '<inttypes.h>' 'inttypes.h' '' '' ''; then
-  add_def HAVE_INTTYPES_H
-fi
-
 if test_code 'struct in_pktinfo' 'sys/socket.h netinet/in.h' '' '' '
  struct in_pktinfo ipi;
  return sizeof (ipi.ipi_spec_dst.s_addr) + IP_PKTINFO;'
@@ -575,10 +635,11 @@ then
 fi

 if [ $feat_ipv6 = "1" ] && \
-  test_code 'IPv6 support' 'arpa/inet.h sys/socket.h netinet/in.h' '' "$EXTRA_LIBS" '
+  test_code 'IPv6 support' 'arpa/inet.h sys/socket.h netinet/in.h' '' "$LIBS" '
    struct sockaddr_in6 n;
    char p[100];
    n.sin6_addr = in6addr_any;
+    n.sin6_scope_id = 0;
    return !inet_ntop(AF_INET6, &n.sin6_addr.s6_addr, p, sizeof(p));'
 then
  add_def FEAT_IPV6
@@ -596,14 +657,28 @@ then
  fi
 fi

+if ! test_code 'O_NOFOLLOW flag' 'sys/types.h sys/stat.h fcntl.h' '' "$LIBS" \
+  'return open("/dev/null", O_NOFOLLOW);'
+then
+  if test_code 'O_NOFOLLOW flag with _GNU_SOURCE' 'sys/types.h sys/stat.h fcntl.h' \
+    '-D_GNU_SOURCE' "$LIBS" \
+    'return open("/dev/null", O_NOFOLLOW);'
+  then
+    add_def _GNU_SOURCE
+  else
+    echo "error: open() does not support O_NOFOLLOW flag"
+    exit 1
+  fi
+fi
+
 if [ $try_clock_gettime = "1" ]; then
  if test_code 'clock_gettime()' 'time.h' '' '' \
-    'clock_gettime(CLOCK_REALTIME, NULL);'
+    'clock_gettime(CLOCK_REALTIME, (void *)1);'
  then
    add_def HAVE_CLOCK_GETTIME
  else
    if test_code 'clock_gettime() in -lrt' 'time.h' '' '-lrt' \
-      'clock_gettime(CLOCK_REALTIME, NULL);'
+      'clock_gettime(CLOCK_REALTIME, (void *)1);'
    then
      add_def HAVE_CLOCK_GETTIME
      EXTRA_LIBS="$EXTRA_LIBS -lrt"
@@ -611,35 +686,45 @@ if [ $try_clock_gettime = "1" ]; then
  fi
 fi

-if test_code 'getaddrinfo()' 'sys/types.h sys/socket.h netdb.h' '' "$EXTRA_LIBS" \
+if ! test_code 'getaddrinfo()' 'sys/types.h sys/socket.h netdb.h' '' "$LIBS" \
  'return getaddrinfo(0, 0, 0, 0);'
 then
-  add_def HAVE_GETADDRINFO
+  echo "error: getaddrinfo() not found"
+  exit 1
 fi

 if [ $feat_asyncdns = "1" ] && \
-  test_code 'pthread' 'pthread.h' '-pthread' '' \
-    'return pthread_create((void *)1, NULL, (void *)1, NULL);'
+  test_code 'pthread' 'pthread.h' '-pthread' '' '
+    pthread_t thread;
+    return (int)pthread_create(&thread, NULL, (void *)1, NULL);'
 then
  add_def FEAT_ASYNCDNS
  add_def USE_PTHREAD_ASYNCDNS
  EXTRA_OBJECTS="$EXTRA_OBJECTS nameserv_async.o"
-  MYCFLAGS="$MYCFLAGS -pthread"
+  use_pthread=1
 fi

-if test_code 'arc4random_buf()' 'stdlib.h' '' '' 'arc4random_buf(NULL, 0);'; then
+if [ $try_arc4random = "1" ] && \
+  test_code 'arc4random_buf()' 'stdlib.h' '' '' \
+    'arc4random_buf((void *)1, 1);'
+then
  add_def HAVE_ARC4RANDOM
+else
+  if test_code 'getrandom()' 'stdlib.h sys/random.h' '' '' \
+      'return getrandom((void *)1, 1, 0);'; then
+    add_def HAVE_GETRANDOM
+  fi
 fi

 RECVMMSG_CODE='
  struct mmsghdr hdr;
  return !recvmmsg(0, &hdr, 1, MSG_DONTWAIT, 0);'
 if [ $try_recvmmsg = "1" ]; then
-  if test_code 'recvmmsg()' 'sys/socket.h' '' "$EXTRA_LIBS" "$RECVMMSG_CODE"; then
+  if test_code 'recvmmsg()' 'sys/socket.h' '' "$LIBS" "$RECVMMSG_CODE"; then
    add_def HAVE_RECVMMSG
  else
    if test_code 'recvmmsg() with _GNU_SOURCE' 'sys/socket.h' '-D_GNU_SOURCE' \
-      "$EXTRA_LIBS" "$RECVMMSG_CODE"
+      "$LIBS" "$RECVMMSG_CODE"
    then
      add_def _GNU_SOURCE
      add_def HAVE_RECVMMSG
@@ -658,15 +743,27 @@ if [ $feat_timestamping = "1" ] && [ $try_timestamping = "1" ] &&
 then
  add_def HAVE_LINUX_TIMESTAMPING
  EXTRA_OBJECTS="$EXTRA_OBJECTS hwclock.o ntp_io_linux.o"
+
+  if test_code 'other timestamping options' \
+    'sys/types.h sys/socket.h linux/net_tstamp.h' '' '' '
+    struct scm_ts_pktinfo pktinfo;
+    pktinfo.if_index = pktinfo.pkt_length = 0;
+    return pktinfo.if_index + pktinfo.pkt_length + HWTSTAMP_FILTER_NTP_ALL +
+           SCM_TIMESTAMPING_PKTINFO +
+           SOF_TIMESTAMPING_OPT_PKTINFO + SOF_TIMESTAMPING_OPT_TX_SWHW;'; then
+    add_def HAVE_LINUX_TIMESTAMPING_RXFILTER_NTP 1
+    add_def HAVE_LINUX_TIMESTAMPING_OPT_PKTINFO 1
+    add_def HAVE_LINUX_TIMESTAMPING_OPT_TX_SWHW 1
+  fi
 fi

 timepps_h=""
 if [ $feat_refclock = "1" ] && [ $feat_pps = "1" ]; then
-  if test_code '<sys/timepps.h>' 'sys/timepps.h' '' '' ''; then
+  if test_code '<sys/timepps.h>' 'inttypes.h time.h sys/timepps.h' '' '' ''; then
    timepps_h="sys/timepps.h"
    add_def HAVE_SYS_TIMEPPS_H
  else
-    if test_code '<timepps.h>' 'timepps.h' '' '' ''; then
+    if test_code '<timepps.h>' 'inttypes.h time.h timepps.h' '' '' ''; then
      timepps_h="timepps.h"
      add_def HAVE_TIMEPPS_H
    fi
@@ -674,10 +771,11 @@ if [ $feat_refclock = "1" ] && [ $feat_pps = "1" ]; then
 fi

 if [ "x$timepps_h" != "x" ] && \
-  test_code 'PPSAPI' "string.h $timepps_h" '' '' '
+  test_code 'PPSAPI' "inttypes.h string.h time.h $timepps_h" '' '' '
    pps_handle_t h = 0;
    pps_info_t i;
    struct timespec ts;
+    ts.tv_sec = ts.tv_nsec = 0;
    return time_pps_fetch(h, PPS_TSFMT_TSPEC, &i, &ts);'
 then
  add_def FEAT_PPS
@@ -706,10 +804,12 @@ if [ $feat_scfilter = "1" ] && [ $try_seccomp = "1" ] && \
    'seccomp_init(SCMP_ACT_KILL);'
 then
  add_def FEAT_SCFILTER
-  # NAME2IPADDRESS shouldn't be enabled with other operations as the helper
-  # process works on one request at the time and the async resolver could
-  # block the main thread
-  priv_ops="NAME2IPADDRESS"
+  if [ $feat_ntp = "1" ]; then
+    # NAME2IPADDRESS shouldn't be enabled together with a privops operation
+    # used by the main thread as the helper process works on one request at
+    # a time and the async resolver would block the main thread
+    priv_ops="NAME2IPADDRESS RELOADDNS"
+  fi
  EXTRA_LIBS="$EXTRA_LIBS -lseccomp"
 fi

@@ -732,32 +832,43 @@ fi
 if [ $feat_refclock = "1" ] && [ $feat_phc = "1" ] && [ $try_phc = "1" ] && \
  grep '#define HAVE_CLOCK_GETTIME' config.h > /dev/null && \
  test_code '<linux/ptp_clock.h>' 'sys/ioctl.h linux/ptp_clock.h' '' '' \
-    'ioctl(1, PTP_CLOCK_GETCAPS, 0);'
+    'ioctl(1, PTP_CLOCK_GETCAPS + PTP_SYS_OFFSET, 0);'
 then
+  grep 'HAVE_LINUX_TIMESTAMPING' config.h > /dev/null ||
+    EXTRA_OBJECTS="$EXTRA_OBJECTS hwclock.o"
  add_def FEAT_PHC
 fi

 if [ $try_setsched = "1" ] && \
  test_code \
-    'sched_setscheduler()' \
-    'sched.h' '' '' '
+    'pthread_setschedparam()' \
+    'pthread.h sched.h' '-pthread' '' '
     struct sched_param sched;
     sched_get_priority_max(SCHED_FIFO);
-     sched_setscheduler(0, SCHED_FIFO, &sched);'
+     pthread_setschedparam(pthread_self(), SCHED_FIFO, &sched);'
 then
-  add_def HAVE_SCHED_SETSCHEDULER
+  add_def HAVE_PTHREAD_SETSCHEDPARAM
+  use_pthread=1
 fi

 if [ $try_lockmem = "1" ] && \
  test_code \
    'mlockall()' \
-    'sys/mman.h sys/resource.h' '' '' '
-     struct rlimit rlim;
-     setrlimit(RLIMIT_MEMLOCK, &rlim);
+    'sys/mman.h' '' '' '
     mlockall(MCL_CURRENT|MCL_FUTURE);'
 then
  add_def HAVE_MLOCKALL
 fi
+if [ $try_lockmem = "1" ] && \
+  test_code \
+    'setrlimit(RLIMIT_MEMLOCK, ...)' \
+    'sys/resource.h' '' '' '
+     struct rlimit rlim;
+     rlim.rlim_max = rlim.rlim_cur = RLIM_INFINITY;
+     setrlimit(RLIMIT_MEMLOCK, &rlim);'
+then
+  add_def HAVE_SETRLIMIT_MEMLOCK
+fi

 if [ $feat_forcednsretry = "1" ]
 then
@@ -767,37 +878,11 @@ fi
 READLINE_LINK=""
 if [ $feat_readline = "1" ]; then
  if [ $try_editline = "1" ]; then
-    if test_code editline 'stdio.h editline/readline.h' \
-      "$readline_inc" "$readline_lib -ledit" \
+    if test_code editline 'stdio.h editline/readline.h' '' '-ledit' \
      'add_history(readline("prompt"));'
    then
      add_def FEAT_READLINE
-      add_def USE_EDITLINE
-      MYCPPFLAGS="$MYCPPFLAGS $readline_inc"
-      READLINE_LINK="$readline_lib -ledit"
-    fi
-  fi
-
-  if [ "x$READLINE_LINK" = "x" ] && [ $try_readline = "1" ]; then
-    if test_code readline 'stdio.h readline/readline.h readline/history.h' \
-      "$readline_inc" "$readline_lib -lreadline" \
-      'add_history(readline("prompt"));'
-    then
-      add_def FEAT_READLINE
-      MYCPPFLAGS="$MYCPPFLAGS $readline_inc"
-      READLINE_LINK="$readline_lib -lreadline"
-    fi
-  fi
-
-  if [ "x$READLINE_LINK" = "x" ] && [ $try_readline = "1" ]; then
-    if test_code 'readline with -lncurses' \
-      'stdio.h readline/readline.h readline/history.h' \
-      "$readline_inc" "$readline_lib $ncurses_lib -lreadline -lncurses" \
-      'add_history(readline("prompt"));'
-    then
-      add_def FEAT_READLINE
-      MYCPPFLAGS="$MYCPPFLAGS $readline_inc"
-      READLINE_LINK="$readline_lib $ncurses_lib -lreadline -lncurses"
+      READLINE_LINK="-ledit"
    fi
  fi

@@ -807,16 +892,37 @@ fi
 HASH_OBJ="hash_intmd5.o"
 HASH_LINK=""

-if [ $feat_sechash = "1" ] && [ $try_nss = "1" ]; then
+if [ $feat_sechash = "1" ] && [ "x$HASH_LINK" = "x" ]  && [ $try_nettle = "1" ]; then
+  test_cflags="`pkg_config --cflags nettle`"
+  test_link="`pkg_config --libs nettle`"
+  if test_code 'nettle' 'nettle/nettle-meta.h nettle/sha2.h' \
+    "$test_cflags" "$test_link" \
+    'return nettle_hashes[0]->context_size;'
+  then
+    HASH_OBJ="hash_nettle.o"
+    HASH_LINK="$test_link"
+    MYCPPFLAGS="$MYCPPFLAGS $test_cflags"
+    add_def FEAT_SECHASH
+
+    if test_code 'CMAC in nettle' 'nettle/cmac.h' "$test_cflags" "$test_link" \
+      'cmac128_update((void *)1, (void *)2, (void *)3, 1, (void *)4);'
+    then
+      add_def HAVE_CMAC
+      EXTRA_OBJECTS="$EXTRA_OBJECTS cmac_nettle.o"
+      EXTRA_CLI_OBJECTS="$EXTRA_CLI_OBJECTS cmac_nettle.o"
+    fi
+  fi
+fi
+
+if [ $feat_sechash = "1" ] && [ "x$HASH_LINK" = "x" ]  && [ $try_nss = "1" ]; then
  test_cflags="`pkg_config --cflags nss`"
-  test_link="`pkg_config --libs-only-L nss` -lfreebl3"
+  test_link="`pkg_config --libs-only-L nss` -lfreebl3 -lnssutil3"
  if test_code 'NSS' 'nss.h hasht.h nsslowhash.h' \
    "$test_cflags" "$test_link" \
    'NSSLOWHASH_Begin(NSSLOWHASH_NewContext(NSSLOW_Init(), HASH_AlgSHA512));'
  then
    HASH_OBJ="hash_nss.o"
    HASH_LINK="$test_link"
-    LIBS="$LIBS $HASH_LINK"
    MYCPPFLAGS="$MYCPPFLAGS $test_cflags"
    add_def FEAT_SECHASH
  fi
@@ -824,16 +930,99 @@ fi

 if [ $feat_sechash = "1" ] && [ "x$HASH_LINK" = "x" ] && [ $try_tomcrypt = "1" ]; then
  if test_code 'tomcrypt' 'tomcrypt.h' '-I/usr/include/tomcrypt' '-ltomcrypt' \
-    'hash_memory_multi(find_hash("md5"), NULL, NULL, NULL, 0, NULL, 0);'
+    'hash_memory_multi(find_hash("md5"), (void *)1, (void *)2, (void *)3, 1, (void *)4, 1);'
  then
    HASH_OBJ="hash_tomcrypt.o"
    HASH_LINK="-ltomcrypt"
-    LIBS="$LIBS $HASH_LINK"
    MYCPPFLAGS="$MYCPPFLAGS -I/usr/include/tomcrypt"
    add_def FEAT_SECHASH
  fi
 fi

+if [ $feat_sechash = "1" ] && [ "x$HASH_LINK" = "x" ] && [ $try_gnutls = "1" ]; then
+  test_cflags="`pkg_config --cflags gnutls`"
+  test_link="`pkg_config --libs gnutls`"
+  if test_code 'gnutls' 'gnutls/crypto.h' \
+    "$test_cflags" "$test_link" '
+      return gnutls_hash((void *)1, (void *)2, 1);'
+  then
+    HASH_OBJ="hash_gnutls.o"
+    HASH_LINK="$test_link"
+    MYCPPFLAGS="$MYCPPFLAGS $test_cflags"
+    add_def FEAT_SECHASH
+
+    if test_code 'CMAC in gnutls' 'gnutls/crypto.h' "$test_cflags" "$test_link" \
+      'return gnutls_hmac_init((void *)1, GNUTLS_MAC_AES_CMAC_128, (void *)2, 0);'
+    then
+      add_def HAVE_CMAC
+      EXTRA_OBJECTS="$EXTRA_OBJECTS cmac_gnutls.o"
+      EXTRA_CLI_OBJECTS="$EXTRA_CLI_OBJECTS cmac_gnutls.o"
+    fi
+  fi
+fi
+
+EXTRA_OBJECTS="$EXTRA_OBJECTS $HASH_OBJ"
+EXTRA_CLI_OBJECTS="$EXTRA_CLI_OBJECTS $HASH_OBJ"
+LIBS="$LIBS $HASH_LINK"
+
+if [ $feat_ntp = "1" ] && [ $feat_nts = "1" ] && [ $try_gnutls = "1" ]; then
+  if [ "$HASH_OBJ" = "hash_gnutls.o" ]; then
+    test_cflags=""
+    test_link=""
+  else
+    test_cflags="`pkg_config --cflags gnutls`"
+    test_link="`pkg_config --libs gnutls`"
+  fi
+  if test_code 'TLS1.3 in gnutls' 'gnutls/gnutls.h' \
+    "$test_cflags" "$test_link $LIBS" '
+      return gnutls_init((void *)1, 0) + GNUTLS_TLS1_3 +
+        gnutls_priority_init2((void *)1, "", NULL, GNUTLS_PRIORITY_INIT_DEF_APPEND) +
+        gnutls_prf_rfc5705((void *)1, 0, "", 0, "", 16, (void *)2);'
+  then
+    if test_code 'SIV in nettle' \
+      'nettle/siv-cmac.h' "" "$LIBS" \
+      'siv_cmac_aes128_set_key((void *)1, (void *)2);'
+    then
+      EXTRA_OBJECTS="$EXTRA_OBJECTS siv_nettle.o"
+      add_def HAVE_SIV
+      add_def HAVE_NETTLE_SIV_CMAC
+    else
+      if test_code 'SIV in gnutls' 'gnutls/crypto.h' \
+        "$test_cflags" "$test_link $LIBS" '
+          return gnutls_aead_cipher_init((void *)1, GNUTLS_CIPHER_AES_128_SIV, (void *)2);'
+      then
+        EXTRA_OBJECTS="$EXTRA_OBJECTS siv_gnutls.o"
+        add_def HAVE_SIV
+        if test_code 'gnutls_aead_cipher_set_key()' 'gnutls/crypto.h' \
+          "$test_cflags" "$test_link $LIBS" '
+            return gnutls_aead_cipher_set_key((void *)1, (void *)2);'
+        then
+          add_def HAVE_GNUTLS_AEAD_CIPHER_SET_KEY
+        fi
+      else
+        if test_code 'AES128 in nettle' 'nettle/aes.h' '' "$LIBS" \
+          'aes128_set_encrypt_key((void *)1, (void *)2);'
+        then
+          EXTRA_OBJECTS="$EXTRA_OBJECTS siv_nettle.o"
+          add_def HAVE_SIV
+        fi
+      fi
+    fi
+
+    if grep '#define HAVE_SIV' config.h > /dev/null; then
+      EXTRA_OBJECTS="$EXTRA_OBJECTS nts_ke_client.o nts_ke_server.o nts_ke_session.o"
+      EXTRA_OBJECTS="$EXTRA_OBJECTS nts_ntp_auth.o nts_ntp_client.o nts_ntp_server.o"
+      LIBS="$LIBS $test_link"
+      MYCPPFLAGS="$MYCPPFLAGS $test_cflags"
+      add_def FEAT_NTS
+    fi
+  fi
+fi
+
+if [ $use_pthread = "1" ]; then
+  MYCFLAGS="$MYCFLAGS -pthread"
+fi
+
 SYSCONFDIR=/etc
 if [ "x$SETSYSCONFDIR" != "x" ]; then
  SYSCONFDIR=$SETSYSCONFDIR
@@ -897,9 +1086,9 @@ add_def DEFAULT_USER "\"$default_user\""
 add_def DEFAULT_COMMAND_SOCKET "\"$CHRONYRUNDIR/chronyd.sock\""
 add_def MAIL_PROGRAM "\"$mail_program\""

-common_features="`get_features IPV6 DEBUG`"
+common_features="`get_features SECHASH IPV6 DEBUG`"
 chronyc_features="`get_features READLINE`"
-chronyd_features="`get_features CMDMON NTP REFCLOCK RTC PRIVDROP SCFILTER SECHASH SIGND ASYNCDNS`"
+chronyd_features="`get_features CMDMON NTP REFCLOCK RTC PRIVDROP SCFILTER SIGND ASYNCDNS NTS`"
 add_def CHRONYC_FEATURES "\"$chronyc_features $common_features\""
 add_def CHRONYD_FEATURES "\"$chronyd_features $common_features\""
 echo "Features : $chronyd_features $chronyc_features $common_features"
@@ -915,15 +1104,15 @@ add_def CHRONY_VERSION "\"${CHRONY_VERSION}\""
 for f in Makefile doc/Makefile test/unit/Makefile
 do
  echo Creating $f
-  sed -e "s%@EXTRA_OBJECTS@%${EXTRA_OBJECTS}%;\
+  sed -e "s%@EXTRA_OBJS@%${EXTRA_OBJECTS}%;\
+          s%@EXTRA_CLI_OBJS@%${EXTRA_CLI_OBJECTS}%;\
          s%@CC@%${MYCC}%;\
          s%@CFLAGS@%${MYCFLAGS}%;\
          s%@CPPFLAGS@%${MYCPPFLAGS}%;\
-          s%@LIBS@%${LIBS}%;\
          s%@LDFLAGS@%${MYLDFLAGS}%;\
+          s%@LIBS@%${LIBS}%;\
          s%@EXTRA_LIBS@%${EXTRA_LIBS}%;\
          s%@EXTRA_CLI_LIBS@%${EXTRA_CLI_LIBS}%;\
-          s%@HASH_OBJ@%${HASH_OBJ}%;\
          s%@SYSCONFDIR@%${SYSCONFDIR}%;\
          s%@BINDIR@%${BINDIR}%;\
          s%@SBINDIR@%${SBINDIR}%;\
--- a/doc/chrony.conf.adoc
+++ b/doc/chrony.conf.adoc
--- a/doc/chronyc.adoc
+++ b/doc/chronyc.adoc
@@ -2,7 +2,7 @@
 //
 // Copyright (C) Richard P. Curnow  1997-2003
 // Copyright (C) Stephen Wadeley  2016
-// Copyright (C) Miroslav Lichvar  2009-2016
+// Copyright (C) Miroslav Lichvar  2009-2017, 2019-2020
 //
 // This program is free software; you can redistribute it and/or modify
 // it under the terms of version 2 of the GNU General Public License as
@@ -39,7 +39,7 @@ running.
 If no commands are specified on the command line, *chronyc* will expect input
 from the user. The prompt _chronyc>_ will be displayed when it is being run
 from a terminal. If *chronyc*'s input or output are redirected from or to a file,
-the prompt is not shown.
+the prompt will not be shown.

 There are two ways *chronyc* can access *chronyd*. One is the Internet
 Protocol (IPv4 or IPv6) and the other is a Unix domain socket, which is
@@ -51,7 +51,8 @@ running under a non-root user), it will try to connect to 127.0.0.1 and then

 Only the following monitoring commands, which do not affect the behaviour of
 *chronyd*, are allowed from the network: *activity*, *manual list*,
-*rtcdata*, *smoothing*, *sources*, *sourcestats*, *tracking*, *waitsync*. The
+*rtcdata*, *smoothing*, *sourcename*, *sources*, *sourcestats*, *tracking*,
+*waitsync*. The
 set of hosts from which *chronyd* will accept these commands can be configured
 with the <<chrony.conf.adoc#cmdallow,*cmdallow*>> directive in the *chronyd*'s
 configuration file or the <<cmdallow,*cmdallow*>> command in *chronyc*. By
@@ -59,9 +60,7 @@ default, the commands are accepted only from localhost (127.0.0.1 or ::1).

 All other commands are allowed only through the Unix domain socket. When sent
 over the network, *chronyd* will respond with a '`Not authorised`' error, even
-if it is from localhost. In chrony versions before 2.2 they were allowed
-from the network if they were authenticated with a password, but that is no
-longer supported.
+if it is from localhost.

 Having full access to *chronyd* via *chronyc* is more or less equivalent to
 being able to modify the *chronyd*'s configuration file and restart it.
@@ -78,11 +77,17 @@ With this option hostnames will be resolved only to IPv6 addresses.
 This option disables resolving of IP addresses to hostnames, e.g. to avoid slow
 DNS lookups. Long addresses will not be truncated to fit into the column.

+*-N*::
+This option enables printing of original hostnames or IP addresses of NTP
+sources that were specified in the configuration file, or *chronyc* commands.
+Without the *-n* and *-N* option, the printed hostnames are obtained from
+reverse DNS lookups and can be different from the specified hostnames.
+
 *-c*::
 This option enables printing of reports in a comma-separated values (CSV)
-format. IP addresses will not be resolved to hostnames, time will be printed as
-number of seconds since the epoch and values in seconds will not be converted
-to other units.
+format. Reverse DNS lookups will be disabled, time will be printed as number of
+seconds since the epoch, and values in seconds will not be converted to other
+units.

 *-d*::
 This option enables printing of debugging messages if *chronyc* was compiled
@@ -94,12 +99,15 @@ With this option multiple commands can be specified. Each argument will be
 interpreted as a whole command.

 *-h* _host_::
-This option allows the user to specify which host (or comma-separated list of
-addresses) running the *chronyd* program is to be contacted. This allows for
-remote monitoring, without having to connect over SSH to the other host first.
+This option specifies the host to be contacted by *chronyc*. It can be
+specified with a hostname, IP address, or path to the local Unix domain socket.
+Multiple values can be specified as a comma-separated list to provide a
+fallback.
 +
-The default is to contact *chronyd* running on the same host where
-*chronyc* is being run.
+The default value is _@CHRONYRUNDIR@/chronyd.sock,127.0.0.1,::1_, i.e. the host
+where *chronyc* is being run. First, it tries to connect to the Unix domain
+socket and if that fails (e.g. due to running under a non-root user), it
+will try to connect to 127.0.0.1 and then ::1.

 *-p* _port_::
 This option allows the user to specify the UDP port number which the target
@@ -112,10 +120,14 @@ This option is ignored and is provided only for compatibility.
 *-a*::
 This option is ignored and is provided only for compatibility.

-*-v*::
+*-v*, *--version*::
 With this option *chronyc* displays its version number on the terminal and
 exits.

+*--help*::
+With this option *chronyc* displays a help message on the terminal and
+exits.
+
 == COMMANDS

 This section describes each of the commands available within the *chronyc*
@@ -130,15 +142,15 @@ performance. An example of the output is shown below.
 ----
 Reference ID    : CB00710F (foo.example.net)
 Stratum         : 3
-Ref time (UTC)  : Fri Feb  3 15:00:29 2012
-System time     : 0.000001501 seconds slow of NTP time
-Last offset     : -0.000001632 seconds
-RMS offset      : 0.000002360 seconds
-Frequency       : 331.898 ppm fast
-Residual freq   : 0.004 ppm
-Skew            : 0.154 ppm
-Root delay      : 0.373169 seconds
-Root dispersion : 0.024780 seconds
+Ref time (UTC)  : Fri Jan 27 09:49:17 2017
+System time     : 0.000006523 seconds slow of NTP time
+Last offset     : -0.000006747 seconds
+RMS offset      : 0.000035822 seconds
+Frequency       : 3.225 ppm slow
+Residual freq   : -0.000 ppm
+Skew            : 0.129 ppm
+Root delay      : 0.013639022 seconds
+Root dispersion : 0.001100737 seconds
 Update interval : 64.2 seconds
 Leap status     : Normal
 ----
@@ -175,10 +187,12 @@ speeding up or slowing down the system clock until the error has been removed,
 and then returning to the system clock's normal speed. A consequence of this is
 that there will be a period when the system clock (as read by other programs)
 will be different from *chronyd*'s estimate of the current true time (which it
-reports to NTP clients when it is operating in server mode). The value reported
+reports to NTP clients when it is operating as a server). The value reported
 on this line is the difference due to this effect.
 *Last offset*:::
-This is the estimated local offset on the last clock update.
+This is the estimated local offset on the last clock update. A positive value
+indicates the local time (as previously estimated true time) was ahead of the
+time sources.
 *RMS offset*:::
 This is a long-term average of the offset value.
 *Frequency*:::
@@ -187,9 +201,6 @@ The '`frequency`' is the rate by which the system's clock would be wrong if
 For example, a value of 1 ppm would mean that when the system's clock thinks it
 has advanced 1 second, it has actually advanced by 1.000001 seconds relative to
 true time.
-+
-As you can see in the example, the clock in the computer is not a very
-good one; it would gain about 30 seconds per day if it was not corrected!
 *Residual freq*:::
 This shows the '`residual frequency`' for the currently selected reference
 source. This reflects any difference between what the measurements from the
@@ -219,7 +230,7 @@ An absolute bound on the computer's clock accuracy (assuming the stratum-1
 computer is correct) is given by:
 +
 ----
-clock_error <= root_dispersion + (0.5 * |root_delay|)
+clock_error <= |system_time_offset| + root_dispersion + (0.5 * root_delay)
 ----
 *Update interval*:::
 This is the interval between the last two clock updates.
@@ -287,15 +298,18 @@ milliseconds.

 === Time sources

-[[sources]]*sources* [*-v*]::
+[[sources]]*sources* [*-a*] [*-v*]::
 This command displays information about the current time sources that *chronyd*
 is accessing.
 +
-The optional argument *-v* can be specified, meaning _verbose_. In this case,
+If the *-a* option is specified, all sources are displayed, including those that
+do not have a known address yet. Such sources have an identifier in the format
+_ID#XXXXXXXXXX_, which can be used in other commands expecting a source address.
+
+The *-v* option enables a verbose output. In this case,
 extra caption lines are shown as a reminder of the meanings of the columns.
 +
 ----
-210 Number of sources = 3
 MS Name/IP address         Stratum Poll Reach LastRx Last sample
 ===============================================================================
 #* GPS0                          0   4   377    11   -479ns[ -621ns] +/-  134ns
@@ -309,18 +323,23 @@ The columns are as follows:
 This indicates the mode of the source. _^_ means a server, _=_ means a peer
 and _#_ indicates a locally connected reference clock.
 *S*:::
-This column indicates the state of the source.
-* _*_ indicates the source to which *chronyd* is currently synchronised.
-* _+_ indicates acceptable sources which are combined with the selected
-  source.
-* _-_ indicates acceptable sources which are excluded by the combining
-  algorithm.
-* _?_ indicates sources to which connectivity has been lost or whose packets
-  do not pass all tests. It is also shown at start-up, until at least 3 samples
-  have been gathered from it.
-* _x_ indicates a clock which *chronyd* thinks is a falseticker (i.e. its
-  time is inconsistent with a majority of other sources).
+This column indicates the selection state of the source.
+* _*_ indicates the best source which is currently selected for
+  synchronisation.
+* _+_ indicates other sources selected for synchronisation, which are combined
+  with the best source.
+* _-_ indicates a source which is considered to be selectable for
+  synchronisation, but not currently selected.
+* _x_ indicates a source which *chronyd* thinks is a falseticker (i.e. its
+  time is inconsistent with a majority of other sources, or sources specified
+  with the *trust* option).
 * _~_ indicates a source whose time appears to have too much variability.
+* _?_ indicates a source which is not considered to be selectable for
+  synchronisation for other reasons (e.g. unreachable, not synchronised, or
+  does not have enough measurements).
+{blank}:::
+The <<selectdata,*selectdata*>> command can be used to get more details about
+the selection state.
 *Name/IP address*:::
 This shows the name or the IP address of the source, or reference ID for reference
 clocks.
@@ -341,8 +360,9 @@ register has 8 bits and is updated on every received or missed packet from
 the source. A value of 377 indicates that a valid reply was received for all
 from the last eight transmissions.
 *LastRx*:::
-This column shows how long ago the last sample was received from the source.
-This is normally in seconds. The letters _m_, _h_, _d_ or _y_ indicate
+This column shows how long ago the last good sample (which is shown in the next
+column) was received from the source. Measurements that failed some tests are
+ignored. This is normally in seconds. The letters _m_, _h_, _d_ or _y_ indicate
 minutes, hours, days, or years.
 *Last sample*:::
 This column shows the offset between the local clock and the source at the
@@ -355,18 +375,21 @@ since. The number following the _+/-_ indicator shows the margin of error in
 the measurement. Positive offsets indicate that the local clock is ahead of
 the source.

-[[sourcestats]]*sourcestats* [*-v*]::
+[[sourcestats]]*sourcestats* [*-a*] [*-v*]::
 The *sourcestats* command displays information about the drift rate and offset
 estimation process for each of the sources currently being examined by
 *chronyd*.
 +
-The optional argument *-v* can be specified, meaning _verbose_. In this case,
+If the *-a* option is specified, all sources are displayed, including those that
+do not have a known address yet. Such sources have an identifier in the format
+_ID#XXXXXXXXXX_, which can be used in other commands expecting a source address.
+
+The *-v* option enables a verbose output. In this case,
 extra caption lines are shown as a reminder of the meanings of the columns.
 +
 An example report is:
 +
 ----
-210 Number of sources = 1
 Name/IP Address            NP  NR  Span  Frequency  Freq Skew  Offset  Std Dev
 ===============================================================================
 foo.example.net            11   5   46m     -0.001      0.045      1us    25us
@@ -402,6 +425,99 @@ This is the estimated offset of the source.
 *Std Dev*:::
 This is the estimated sample standard deviation.

+[[selectdata]]*selectdata* [*-a*] [*-v*]::
+The *selectdata* command displays information specific to the selection of time
+sources. If the *-a* option is specified, all sources are displayed, including
+those that do not have a known address yet. With the *-v* option, extra caption
+lines are shown as a reminder of the meanings of the columns.
+
+An example of the output is shown below.
+
+----
+S Name/IP Address        Auth COpts EOpts Last Score     Interval  Leap
+=======================================================================
+D foo.example.net           Y ----- --TR-    4   1.0   -61ms   +62ms  N
+* bar.example.net           N ----- -----    0   1.0 -6846us +7305us  N
+ baz.example.net           N ----- -----   10   1.0 -7381us +7355us  N
+----
+
+The columns are as follows:
+
+*S*:::
+This column indicates the state of the source after the last source selection.
+It is similar to the state reported by the *sources* command, but more
+states are reported.
+{blank}:::
+The following states indicate the source is not considered selectable for
+synchronisation:
+* _N_ - has the *noselect* option.
+* _s_ - is not synchronised.
+* _M_ - does not have enough measurements.
+* _d_ - has a root distance larger than the maximum distance (configured by the
+        <<chrony.conf.adoc#maxdistance,*maxdistance*>> directive).
+* _~_ - has a jitter larger than the maximum jitter (configured by the
+        <<chrony.conf.adoc#maxjitter,*maxjitter*>> directive).
+* _w_ - waits for other sources to get out of the _M_ state.
+* _S_ - has older measurements than other sources.
+* _O_ - has a stratum equal or larger than the orphan stratum (configured by
+        the <<chrony.conf.adoc#local,*local*>> directive).
+* _T_ - does not fully agree with sources that have the *trust* option.
+* _x_ - does not agree with other sources (falseticker).
+{blank}:::
+The following states indicate the source is considered selectable, but it is
+not currently used for synchronisation:
+* _W_ - waits for other sources to be selectable (required by the
+        <<chrony.conf.adoc#minsources,*minsources*>> directive, or
+        the *require* option of another source).
+* _P_ - another selectable source is preferred due to the *prefer* option.
+* _U_ - waits for a new measurement (after selecting a different best source).
+* _D_ - has, or recently had, a root distance which is too large to be combined
+        with other sources (configured by the
+        <<chrony.conf.adoc#combinelimit,*combinelimit*>> directive).
+{blank}:::
+The following states indicate the source is used for synchronisation of the
+local clock:
+* _+_ - combined with the best source.
+* _*_ - selected as the best source to update the reference data (e.g. root
+        delay, root dispersion).
+*Name/IP address*:::
+This column shows the name or IP address of the source if it is an NTP server,
+or the reference ID if it is a reference clock.
+*Auth*:::
+This column indicites whether an authentication mechanism is enabled for the
+source. _Y_ means yes and _N_ means no.
+*COpts*:::
+This column displays the configured selection options of the source.
+* _N_ indicates the *noselect* option.
+* _P_ indicates the *prefer* option.
+* _T_ indicates the *trust* option.
+* _R_ indicates the *require* option.
+*EOpts*:::
+This column displays the current effective selection options of the source,
+which can be different from the configured options due to the authentication
+selection mode (configured by the
+<<chrony.conf.adoc#authselmode,*authselmode*>> directive). The symbols are the
+same as in the *COpts* column.
+*Last*:::
+This column displays how long ago was the last measurement of the source made
+when the selection was performed.
+*Score*:::
+This column displays the current score against the source in the _*_ state. The
+scoring system avoids frequent reselection when multiple sources have a similar
+root distance. A value larger than 1 indicates this source was better than the
+_*_ source in recent selections. If the score reaches 10, the best source will
+be reselected and the scores will be reset to 1.
+*Interval*:::
+This column displays the lower and upper endpoint of the interval which was
+expected to contain the true offset of the local clock considering the root
+distance at the time of the selection.
+*Leap*:::
+This column displays the current leap status of the source.
+* _N_ indicates the normal status (no leap second).
+* _+_ indicates that a leap second will be inserted at the end of the month.
+* _-_ indicates that a leap second will be deleted at the end of the month.
+* _?_ indicates the unknown status (i.e. no valid measurement was made).
+
 [[reselect]]*reselect*::
 To avoid excessive switching between sources, *chronyd* can stay synchronised
 to a source even when it is not currently the best one among the available
@@ -442,10 +558,82 @@ the offline state.
 the name of the server or peer was not resolved to an address yet; this source is
 not visible in the *sources* and *sourcestats* reports.

+[[authdata]]*authdata* [*-a*]::
+The *authdata* command displays information specific to authentication of NTP
+sources. If the *-a* option is specified, all sources are displayed, including
+those that do not have a known address yet. An example of the output is
+shown below.
+
+----
+Name/IP address             Mode KeyID Type KLen Last Atmp  NAK Cook CLen
+=========================================================================
+foo.example.net              NTS     1   15  256 135m    0    0    8  100
+bar.example.net               SK    30   13  128    -    0    0    0    0
+baz.example.net                -     0    0    0    -    0    0    0    0
+----
+
+The columns are as follows:
+
+*Name/IP address*:::
+This column shows the name or the IP address of the source.
+*Mode*:::
+This column shows which mechanism authenticates NTP packets received from the
+source. _NTS_ means Network Time Security, _SK_ means a symmetric key, and _-_
+means authentication is disabled.
+*KeyID*:::
+This column shows an identifier of the key used for authentication. With a
+symmetric key, it is the ID from the <<chrony.conf.adoc#keyfile,key file>>.
+With NTS, it is a number starting at zero and incremented by one with each
+successful key establishment using the NTS-KE protocol, i.e. it shows how many
+times the key establishment was performed with this source.
+*Type*:::
+This columns shows an identifier of the algorithm used for authentication.
+With a symmetric key, it is the hash function or cipher specified in the key
+file. With NTS, it is an authenticated encryption with associated data (AEAD)
+algorithm, which is negotiated in the NTS-KE protocol. The following values can
+be reported:
+* 1: MD5
+* 2: SHA1
+* 3: SHA256
+* 4: SHA384
+* 5: SHA512
+* 6: SHA3-224
+* 7: SHA3-256
+* 8: SHA3-384
+* 9: SHA3-512
+* 10: TIGER
+* 11: WHIRLPOOL
+* 13: AES128
+* 14: AES256
+* 15: AEAD-AES-SIV-CMAC-256
+*KLen*:::
+This column shows the length of the key in bits.
+*Last*:::
+This column shows how long ago the last successful key establishment was
+performed. It is in seconds, or letters _m_, _h_, _d_ or _y_ indicate minutes,
+hours, days, or years.
+*Atmp*:::
+This column shows the number of attempts to perform the key establishment since
+the last successful key establishment. A number larger than 1 indicates a
+problem with the network or server.
+*NAK*:::
+This column shows whether an NTS NAK was received since the last request.
+A NAK indicates that authentication failed on the server side due to
+*chronyd* using a cookie which is no longer valid and that it needs to perform
+the key establishment again in order to get new cookies.
+*Cook*:::
+This column shows the number of NTS cookies that *chronyd* currently has. If
+the key establishment was successful, a number smaller than 8 indicates a
+problem with the network or server.
+*CLen*:::
+This column shows the length in bytes of the NTS cookie which will be used in
+the next request.
+
 [[ntpdata]]*ntpdata* [_address_]::
 The *ntpdata* command displays the last valid measurement and other
-NTP-specific information about the specified NTP source, or all NTP sources if
-no address was specified. An example of the output is shown below.
+NTP-specific information about the specified NTP source, or all NTP sources
+(with a known address) if no address was specified. An example of the output is
+shown below.
 +
 ----
 Remote address  : 203.0.113.15 (CB00710F)
@@ -511,7 +699,8 @@ packets sent to the source is more variable than the delay of packets sent
 from the source back.
 *NTP tests*:::
 Results of RFC 5905 tests 1 through 3, 5 through 7, and tests for maximum
-delay, delay ratio, delay dev ratio, and synchronisation loop.
+delay, delay ratio, delay dev ratio (or delay quantile), and synchronisation
+loop.
 *Interleaved*:::
 This shows if the response was in the interleaved mode.
 *Authenticated*:::
@@ -528,15 +717,13 @@ The number of all packets received from the source.
 *Total valid RX*:::
 The number of valid packets received from the source.

-[[add_peer]]*add peer* _address_ [_option_]...::
+[[add_peer]]*add peer* _name_ [_option_]...::
 The *add peer* command allows a new NTP peer to be added whilst
 *chronyd* is running.
 +
 Following the words *add peer*, the syntax of the following
-parameters and options is similar to that for the
+parameters and options is identical to that for the
 <<chrony.conf.adoc#peer,*peer*>> directive in the configuration file.
-The following peer options can be set in the command: *port*, *minpoll*,
-*maxpoll*, *presend*, *maxdelayratio*, *maxdelay*, *key*.
 +
 An example of using this command is shown below.
 +
@@ -544,15 +731,27 @@ An example of using this command is shown below.
 add peer foo.example.net minpoll 6 maxpoll 10 key 25
 ----

-[[add_server]]*add server* _address_ [_option_]...::
+[[add_pool]]*add pool* _name_ [_option_]...::
+The *add pool* command allows a pool of NTP servers to be added whilst
+*chronyd* is running.
+
+Following the words *add pool*, the syntax of the following parameters and
+options is identical to that for the <<chrony.conf.adoc#pool,*pool*>>
+directive in the configuration file.
+
+An example of using this command is shown below:
+
+----
+add pool foo.example.net maxsources 3 iburst
+----
+
+[[add_server]]*add server* _name_ [_option_]...::
 The *add server* command allows a new NTP server to be added whilst
 *chronyd* is running.
 +
 Following the words *add server*, the syntax of the following parameters and
-options is similar to that for the <<chrony.conf.adoc#server,*server*>>
+options is identical to that for the <<chrony.conf.adoc#server,*server*>>
 directive in the configuration file.
-The following server options can be set in the command: *port*, *minpoll*,
-*maxpoll*, *presend*, *maxdelayratio*, *maxdelay*, *key*.
 +
 An example of using this command is shown below:
 +
@@ -603,7 +802,7 @@ alternative to the form with mask.
 _address_:::
 This is an IP address or a hostname. The burst command is applied only to
 that source.
-::
+{blank}::
 +
 If no _mask_ or _masked-address_ arguments are provided, every source will be
 matched.
@@ -690,7 +889,8 @@ the loaded periods. The *offline* and *online* commands can be used to achieve
 this.
 +
 There are four forms of the *offline* command. The first form is a wildcard,
-meaning all sources. The second form allows an IP address mask and a masked
+meaning all sources (including sources that do not have a known address yet).
+The second form allows an IP address mask and a masked
 address to be specified. The third form uses CIDR notation. The fourth form
 uses an IP address or a hostname. These forms are illustrated below.
 +
@@ -725,6 +925,14 @@ particular source or sources has been restored.
 +
 The syntax is identical to that of the <<offline,*offline*>> command.

+[[onoffline]]
+*onoffline*::
+The *onoffline* command tells *chronyd* to switch all sources that have a known
+address to the online or
+offline status according to the current network configuration. A source is
+considered online if it is possible to send requests to it, i.e. a network
+route to the source is present.
+
 [[polltarget]]*polltarget* _address_ _polltarget_::
 The *polltarget* command is used to modify the poll target for one of the
 current set of sources. It is equivalent to the *polltarget* option in the
@@ -739,6 +947,20 @@ Sources that stop responding will be replaced with newly resolved addresses
 automatically after 8 polling intervals, but this command can still be useful
 to replace them immediately and not wait until they are marked as unreachable.

+[[reload]]*reload* *sources*::
+The *reload sources* command causes *chronyd* to re-read all _*.sources_ files
+from the directories specified by the
+<<chrony.conf.adoc#sourcedir,*sourcedir*>> directive.
+
+[[sourcename]]*sourcename* _address_::
+The *sourcename* command prints the original hostname or address that was
+specified for an NTP source in the configuration file, or the *add* command.
+This command is an alternative to the *-N* option, which can be useful in
+scripts.
+
+Note that different NTP sources can share the same name, e.g. servers from a
+pool.
+
 === Manual time input

 [[manual]]
@@ -775,7 +997,7 @@ The columns are as as follows:
 . The regression residual at this point, in seconds. This allows '`outliers`'
  to be easily spotted, so that they can be deleted using the *manual delete*
  command.
-::
+{blank}::
 +
 The *delete* form of the command deletes a single sample. The parameter is the
 index of the sample, as shown in the first column of the output from *manual
@@ -846,10 +1068,17 @@ This command can be used to examine the effect of a series of *allow*, *allow
 all*, *deny*, and *deny all* commands specified either via *chronyc*, or in
 *chronyd*'s configuration file.

-[[clients]]*clients*::
+[[clients]]*clients* [*-p* _packets_] [*-k*] [*-r*]::
 This command shows a list of clients that have accessed the server, through
-either the NTP or command ports. It does not include accesses over
-the Unix domain command socket. There are no arguments.
+the NTP, command, or NTS-KE port. It does not include accesses over the Unix
+domain command socket.
+
+The *-p* option specifies the minimum number of received NTP or command
+packets, or accepted NTS-KE connections, needed to include a client in the
+list. The default value is 0, i.e. all clients are reported. With the *-k*
+option the last four columns will show the NTS-KE accesses instead of command
+accesses. If the *-r* option is specified, *chronyd* will reset the counters of
+received and dropped packets or connections after reporting the current values.
 +
 An example of the output is:
 +
@@ -874,20 +1103,18 @@ The columns are as follows:
 . The average interval between NTP packets.
 . The average interval between NTP packets after limiting the response rate.
 . Time since the last NTP packet was received
-. The number of command packets received from the client.
-. The number of command packets dropped to limit the response rate.
-. The average interval between command packets.
-. Time since the last command packet was received.
+. The number of command packets or NTS-KE connections received/accepted from
+  the client.
+. The number of command packets or NTS-KE connections dropped to limit the
+  response rate.
+. The average interval between command packets or NTS-KE connections.
+. Time since the last command packet or NTS-KE connection was
+  received/accepted.

 [[serverstats]]*serverstats*::
-The *serverstats* command displays how many valid NTP and command requests
-*chronyd* as a server received from clients, how many of them were dropped to
-limit the response rate as configured by the
-<<chrony.conf.adoc#ratelimit,*ratelimit*>> and
-<<chrony.conf.adoc#cmdratelimit,*cmdratelimit*>> directives, and how many
-client log records were dropped due to the memory limit configured by the
-<<chrony.conf.adoc#clientloglimit,*clientloglimit*>> directive. An example of
-the output is shown below.
+The *serverstats* command displays NTP and command server statistics.
+
+An example of the output is shown below.
 +
 ----
 NTP packets received       : 1598
@@ -895,7 +1122,50 @@ NTP packets dropped        : 8
 Command packets received   : 19
 Command packets dropped    : 0
 Client log records dropped : 0
+NTS-KE connections accepted: 3
+NTS-KE connections dropped : 0
+Authenticated NTP packets  : 189
+Interleaved NTP packets    : 43
+NTP timestamps held        : 44
+NTP timestamp span         : 120
 ----
+
+The fields have the following meaning:
+
+*NTP packets received*:::
+The number of valid NTP requests received by the server.
+*NTP packets dropped*:::
+The number of NTP requests dropped by the server due to rate limiting
+(configured by the <<chrony.conf.adoc#ratelimit,*ratelimit*>> directive).
+*Command packets received*:::
+The number of command requests received by the server.
+*Command packets dropped*:::
+The number of command requests dropped by the server due to rate limiting
+(configured by the <<chrony.conf.adoc#cmdratelimit,*cmdratelimit*>> directive).
+*Client log records dropped*:::
+The number of client log records dropped by the server to limit the memory use
+(configured by the <<chrony.conf.adoc#clientloglimit,*clientloglimit*>>
+directive).
+*NTS-KE connections accepted*:::
+The number of NTS-KE connections accepted by the server.
+*NTS-KE connections dropped*:::
+The number of NTS-KE connections dropped by the server due to rate limiting
+(configured by the <<chrony.conf.adoc#ntsratelimit,*ntsratelimit*>> directive).
+*Authenticated NTP packets*:::
+The number of received NTP requests that were authenticated (with a symmetric
+key or NTS).
+*Interleaved NTP packets*:::
+The number of received NTP requests that were detected to be in the interleaved
+mode.
+*NTP timestamps held*:::
+The number of pairs of receive and transmit timestamps that the server is
+currently holding in memory for clients using the interleaved mode.
+*NTP timestamp span*:::
+The interval (in seconds) covered by the currently held NTP timestamps.
+{blank}::
+
+Note that the numbers reported by this overflow to zero after 4294967295
+(32-bit values).

 [[allow]]*allow* [*all*] [_subnet_]::
 The effect of the allow command is identical to the
@@ -904,11 +1174,8 @@ The effect of the allow command is identical to the
 The syntax is illustrated in the following examples:
 +
 ----
-allow foo.example.net
-allow all 1.2
-allow 3.4.5
-allow 6.7.8/22
-allow 6.7.8.9/22
+allow 1.2.3.4
+allow all 3.4.5.0/24
 allow 2001:db8:789a::/48
 allow 0/0
 allow ::/0
@@ -923,11 +1190,8 @@ The effect of the allow command is identical to the
 The syntax is illustrated in the following examples:
 +
 ----
-deny foo.example.net
-deny all 1.2
-deny 3.4.5
-deny 6.7.8/22
-deny 6.7.8.9/22
+deny 1.2.3.4
+deny all 3.4.5.0/24
 deny 2001:db8:789a::/48
 deny 0/0
 deny ::/0
@@ -1080,7 +1344,7 @@ more than 1 second away from the system clock):
  error).
 . Save the RTC parameters to the RTC file (specified with the
  <<chrony.conf.adoc#rtcfile,*rtcfile*>> directive in the configuration file).
-::
+{blank}::
 +
 The last step is done as a precaution against the computer suffering a power
 failure before either the daemon exits or the <<writertc,*writertc*>> command
@@ -1113,25 +1377,38 @@ purged. An example of how to do this is shown below.
 ----
 # mv /var/log/chrony/measurements.log /var/log/chrony/measurements1.log
 # chronyc cyclelogs
-# ls -l /var/log/chrony
-rw-r--r--   1 root     root            0 Jun  8 18:17 measurements.log
-rw-r--r--   1 root     root        12345 Jun  8 18:17 measurements1.log
-# rm -f measurements1.log
+# rm /var/log/chrony/measurements1.log
 ----

 [[dump]]*dump*::
 The *dump* command causes *chronyd* to write its current history of
-measurements for each of its sources to dump files, either for inspection or to
-support the *-r* option when *chronyd* is restarted.
-+
-The *dump* command is somewhat equivalent to the
-<<chrony.conf.adoc#dumponexit,*dumponexit*>> directive in the configuration
-file.
-+
-To use the *dump* command, you might want to configure the name of the
-directory into which the dump files will be written. This can only be
-done in the configuration file with the <<chrony.conf.adoc#dumpdir,*dumpdir*>>
-directive.
+measurements for each of its sources to dump files in the directory specified
+in the configuration file by the <<chrony.conf.adoc#dumpdir,*dumpdir*>>
+directive and also write server NTS keys and client NTS cookies to the
+directory specified by the <<chrony.conf.adoc#ntsdumpdir1,*ntsdumpdir*>>
+directive. Note that *chronyd* does this automatically when it exits. This
+command is mainly useful for inspection whilst *chronyd* is running.
+
+[[rekey]]*rekey*::
+The *rekey* command causes *chronyd* to re-read the key file specified in the
+configuration file by the <<chrony.conf.adoc#keyfile,*keyfile*>> directive. It
+also re-reads the server NTS keys if
+<<chrony.conf.adoc#ntsdumpdir2,*ntsdumpdir*>> is specified and
+<<chrony.conf.adoc#ntsrotate,automatic rotation>> is disabled in the
+configuration file.
+
+[[reset]]*reset* *sources*::
+The *reset sources* command causes *chronyd* to drop all measurements and
+switch to the unsynchronised state. This command can help *chronyd* with
+recovery when the measurements are known to be no longer valid or accurate,
+e.g. due to moving the computer to a different network, or resuming the
+computer from a low-power state (which resets the system clock). *chronyd* will
+drop the measurements automatically when it detects the clock has made an
+unexpected jump, but the detection is not completely reliable.
+
+[[shutdown]]*shutdown*::
+The *shutdown* command causes *chronyd* to exit. This is equivalent to sending
+the process the SIGTERM signal.

 === Client commands

@@ -1181,10 +1458,10 @@ generated from the _/dev/urandom_ device and it is printed to standard output.
 +
 The command has three optional arguments. The first argument is the key number
 (by default 1), which will be specified with the *key* option of the *server*
-or *peer* directives in the configuration file. The second argument is the hash
-function (by default SHA1 or MD5 if SHA1 is not available) and the third
-argument is the number of bits the key should have, between 80 and 4096 bits
-(by default 160 bits).
+or *peer* directives in the configuration file. The second argument is the name
+of the hash function or cipher (by default SHA1, or MD5 if SHA1 is not
+available). The third argument is the length of the key in bits if a hash
+function was selected, between 80 and 4096 bits (by default 160 bits).
 +
 An example is:
 +
@@ -1194,7 +1471,13 @@ keygen 73 SHA1 256
 +
 which generates a 256-bit SHA1 key with number 73. The printed line should
 then be securely transferred and added to the key files on both server and
-client, or peers.
+client, or peers. A different key should be generated for each client or peer.
+
+An example using the AES128 cipher is:
+
+----
+keygen 151 AES128
+----

 [[exit]]*exit*::
 [[quit]]*quit*::
--- a/doc/chronyd.adoc
+++ b/doc/chronyd.adoc
@@ -1,7 +1,7 @@
 // This file is part of chrony
 //
 // Copyright (C) Richard P. Curnow  1997-2003
-// Copyright (C) Miroslav Lichvar  2009-2016
+// Copyright (C) Miroslav Lichvar  2009-2017
 //
 // This program is free software; you can redistribute it and/or modify
 // it under the terms of version 2 of the GNU General Public License as
@@ -41,7 +41,7 @@ If no configuration directives are specified on the command line, *chronyd*
 will read them from a configuration file. The compiled-in default location of
 the file is _@SYSCONFDIR@/chrony.conf_.

-Information messages and warnings will be logged to syslog.
+Informational messages, warnings, and errors will be logged to syslog.

 == OPTIONS

@@ -55,35 +55,52 @@ IPv6 sockets will be created.

 *-f* _file_::
 This option can be used to specify an alternate location for the configuration
-file (default _@SYSCONFDIR@/chrony.conf_).
+file. The compiled-in default value is _@SYSCONFDIR@/chrony.conf_.

 *-n*::
 When run in this mode, the program will not detach itself from the terminal.

 *-d*::
 When run in this mode, the program will not detach itself from the terminal,
-and all messages will be sent to the terminal instead of to syslog. When
-*chronyd* was compiled with debugging support, this option can be used twice to
-print also debugging messages.
+and all messages will be written to the terminal instead of syslog. If
+*chronyd* was compiled with enabled support for debugging, this option can be
+used twice to enable debug messages.
+
+*-l* _file_::
+This option enables writing of log messages to a file instead of syslog or the
+terminal.
+
+*-L* _level_::
+This option specifies the minimum severity level of messages to be written to
+the log file, syslog, or terminal. The following levels can be specified:
+0 (informational), 1 (warning), 2 (non-fatal error), and 3 (fatal error). The
+default value is 0.
+
+*-p*::
+When run in this mode, *chronyd* will print the configuration and exit. It will
+not detach from the terminal. This option can be used to verify the syntax of
+the configuration and get the whole configuration, even if it is split into
+multiple files and read by the *include* or *confdir* directive.

 *-q*::
 When run in this mode, *chronyd* will set the system clock once and exit. It
 will not detach from the terminal.

 *-Q*::
-This option is similar to *-q*, but it will only print the offset without any
-corrections of the clock.
+This option is similar to the *-q* option, except it only prints the offset
+without making any corrections of the clock and it allows *chronyd* to be
+started without root privileges.

 *-r*::
 This option will try to reload and then delete files containing sample
-histories for each of the servers and reference clocks being used. These
-histories are created by using the <<chronyc.adoc#dump,*dump*>> command in
-*chronyc*, or by setting the <<chrony.conf.adoc#dumponexit,*dumponexit*>>
+histories for each of the servers and reference clocks being used. The
+files are expected to be in the directory specified by the
+<<chrony.conf.adoc#dumpdir,*dumpdir*>>
 directive in the configuration file. This option is useful if you want to stop
 and restart *chronyd* briefly for any reason, e.g. to install a new version.
 However, it should be used only on systems where the kernel can maintain clock
-compensation whilst not under *chronyd*'s control (i.e. Linux, FreeBSD, NetBSD
-and Solaris).
+compensation whilst not under *chronyd*'s control (i.e. Linux, FreeBSD, NetBSD,
+illumos, and macOS 10.13 or later).

 *-R*::
 When this option is used, the <<chrony.conf.adoc#initstepslew,*initstepslew*>>
@@ -120,40 +137,73 @@ running, but still allow it to adjust the frequency of the system clock.
 *-u* _user_::
 This option sets the name of the system user to which *chronyd* will switch
 after start in order to drop root privileges. It overrides the
-<<chrony.conf.adoc#user,*user*>> directive (default _@DEFAULT_USER@_).
+<<chrony.conf.adoc#user,*user*>> directive. The compiled-in default value is
+_@DEFAULT_USER@_.
 +
 On Linux, *chronyd* needs to be compiled with support for the *libcap* library.
-On macOS, FreeBSD, NetBSD and Solaris *chronyd* forks into two processes.
+On macOS, FreeBSD, NetBSD, and illumos *chronyd* forks into two processes.
 The child process retains root privileges, but can only perform a very limited
 range of privileged system calls on behalf of the parent.

+*-U*::
+This option disables a check for root privileges to allow *chronyd* to be
+started under a non-root user, assuming the process will have all capabilities
+(e.g. provided by the service manager) and access to all files, directories,
+and devices, needed to operate correctly in the specified configuration. Note
+that different capabilities might be needed with different configurations and
+different Linux kernel versions. Starting *chronyd* under a non-root user is
+not recommended when the configuration is not known, or at least limited to
+specific directives.
+
 *-F* _level_::
-This option configures a system call filter when *chronyd* is compiled with
-support for the Linux secure computing (seccomp) facility. In level 1 the
-process is killed when a forbidden system call is made, in level -1 the SYSSIG
-signal is thrown instead and in level 0 the filter is disabled (default 0).
+This option configures system call filters loaded by *chronyd* processes if it
+was compiled with support for the Linux secure computing (seccomp) facility.
+Three levels are defined: 0, 1, 2. The filters are disabled at level 0. At
+levels 1 and 2, *chronyd* will be killed if it makes a system call which is
+blocked by the filters. The level can be specified as a negative number to
+trigger the SIGSYS signal instead of SIGKILL, which can be useful for
+debugging. The default value is 0.
 +
-It's recommended to enable the filter only when it's known to work on the
-version of the system where *chrony* is installed as the filter needs to allow
-also system calls made from libraries that *chronyd* is using (e.g. libc) and
-different versions or implementations of the libraries may make different
-system calls. If the filter is missing some system call, *chronyd* could be
-killed even in normal operation.
+At level 1, the filters allow only selected system calls that are normally
+expected to be made by *chronyd*. Other system calls are blocked. This level is
+recommended only if it is known to work on the version of the system where
+*chrony* is installed. The filters need to allow also system calls made by
+libraries that *chronyd* is using (e.g. libc), but different versions or
+implementations of the libraries might make different system calls. If the
+filters are missing a system call, *chronyd* could be killed even in normal
+operation.
+
+At level 2, the filters block only a small number of specific system calls
+(e.g. fork and exec). This approach should avoid false positives, but the
+protection of the system against a compromised *chronyd* process is much more
+limited.
+
+The filters cannot be enabled with the *mailonchange* directive.

 *-P* _priority_::
-On Linux, this option will select the SCHED_FIFO real-time scheduler at the
-specified priority (which must be between 0 and 100). On macOS, this option
-must have either a value of 0 (the default) to disable the thread time
-constraint policy or 1 for the policy to be enabled. Other systems do not
-support this option.
+On Linux, FreeBSD, NetBSD, and illumos this option will select the SCHED_FIFO
+real-time scheduler at the specified priority (which must be between 0 and
+100). On macOS, this option must have either a value of 0 to disable the thread
+time constraint policy or 1 for the policy to be enabled. Other systems do not
+support this option. The default value is 0.

 *-m*::
 This option will lock *chronyd* into RAM so that it will never be paged out.
-This mode is only supported on Linux.
+This mode is only supported on Linux, FreeBSD, NetBSD, and illumos.

-*-v*::
+*-x*::
+This option disables the control of the system clock. *chronyd* will not try to
+make any adjustments of the clock. It will assume the clock is free running and
+still track its offset and frequency relative to the estimated true time. This
+option allows *chronyd* to be started without the capability to adjust or set
+the system clock (e.g. in some containers) to operate as an NTP server.
+
+*-v*, *--version*::
 With this option *chronyd* will print version number to the terminal and exit.

+*-h*, *--help*::
+With this option *chronyd* will print a help message to the terminal and exit.
+
 == FILES

 _@SYSCONFDIR@/chrony.conf_
--- a/doc/faq.adoc
+++ b/doc/faq.adoc
--- a/doc/installation.adoc
+++ b/doc/installation.adoc
@@ -22,6 +22,26 @@ The software is distributed as source code which has to be compiled. The source
 code is supplied in the form of a gzipped tar file, which unpacks to a
 subdirectory identifying the name and version of the program.

+A C compiler (e.g. `gcc` or `clang`) and GNU Make are needed to build `chrony`.
+The following libraries with their development files, and programs, are needed
+to enable optional features:
+
+* pkg-config: detection of development libraries
+* Nettle, GnuTLS, NSS, or LibTomCrypt: secure hash functions (`SECHASH`)
+* libcap: dropping root privileges on Linux (`DROPROOT`)
+* libseccomp: system call filter on Linux (`SCFILTER`)
+* GnuTLS and Nettle: Network Time Security (`NTS`)
+* Editline: line editing in `chronyc` (`READLINE`)
+* timepps.h header: PPS reference clock
+* Asciidoctor: documentation in HTML format
+* Bash: test suite
+
+The following programs are needed when building `chrony` from the git
+repository instead of a released tar file:
+
+* Asciidoctor: manual pages
+* Bison: parser for chronyc settime command
+
 After unpacking the source code, change directory into it, and type

 ----
@@ -29,8 +49,8 @@ After unpacking the source code, change directory into it, and type
 ----

 This is a shell script that automatically determines the system type. There is
-a single optional parameter, `--prefix` which indicates the directory tree
-where the software should be installed. For example,
+an optional parameter `--prefix`, which indicates the directory tree where the
+software should be installed. For example,

 ----
 ./configure --prefix=/opt/free
@@ -40,11 +60,11 @@ will install the `chronyd` daemon into `/opt/free/sbin` and the `chronyc`
 control program into `/opt/free/bin`. The default value for the prefix is
 `/usr/local`.

-The configure script assumes you want to use gcc as your compiler. If you want
-to use a different compiler, you can configure this way:
+The `configure` script assumes you want to use `gcc` as your compiler. If you
+want to use a different compiler, you can configure this way:

 ----
-CC=cc CFLAGS=-O ./configure --prefix=/opt/free
+CC=cc ./configure --prefix=/opt/free
 ----

 for Bourne-family shells, or
@@ -63,11 +83,26 @@ shown. Otherwise, `Makefile` will be generated.
 On Linux, if development files for the libcap library are available, `chronyd`
 will be built with support for dropping root privileges. On other systems no
 extra library is needed. The default user which `chronyd` should run as can be
-specified with the `--with-user` option of the configure script.
+specified with the `--with-user` option of the `configure` script.

-If development files for the editline or readline library are available,
+If development files for the POSIX threads library are available, `chronyd`
+will be built with support for asynchronous resolving of hostnames specified in
+the `server`, `peer`, and `pool` directives. This allows `chronyd` operating as
+a server to respond to client requests when resolving a hostname. If you don't
+want to enable the support, specify the `--disable-asyncdns` flag to
+`configure`.
+
+If development files for the https://www.lysator.liu.se/~nisse/nettle/[Nettle],
+https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS[NSS], or
+https://www.libtom.net/LibTomCrypt/[libtomcrypt] library are available,
+`chronyd` will be built with support for other cryptographic hash functions
+than MD5, which can be used for NTP authentication with a symmetric key. If you
+don't want to enable the support, specify the `--disable-sechash` flag to
+`configure`.
+
+If development files for the editline library are available,
 `chronyc` will be built with line editing support. If you don't want this,
-specify the `--disable-readline` flag to configure.
+specify the `--disable-readline` flag to `configure`.

 If a `timepps.h` header is available (e.g. from the
 http://linuxpps.org[LinuxPPS project]), `chronyd` will be built with PPS API
@@ -75,6 +110,9 @@ reference clock driver. If the header is installed in a location that isn't
 normally searched by the compiler, you can add it to the searched locations by
 setting the `CPPFLAGS` variable to `-I/path/to/timepps`.

+The `--help` option can be specified to `configure` to print all options
+supported by the script.
+
 Now type

 ----
@@ -122,51 +160,24 @@ unprivileged user for `chronyd` and specify it with the `-u` command-line
 option or the `user` directive in the configuration file, or set the default
 user with the `--with-user` configure option before building.

-== Support for line editing libraries
+== Support for system call filtering

-`chronyc` can be built with support for line editing, this allows you to use
-the cursor keys to replay and edit old commands. Two libraries are supported
-which provide such functionality, editline and GNU readline.
-
-Please note that readline since version 6.0 is licensed under GPLv3+ which is
-incompatible with chrony's license GPLv2. You should use editline instead if
-you don't want to use older readline versions.
-
-The configure script will automatically enable the line editing support if one
-of the supported libraries is available. If they are both available, the
-editline library will be used.
-
-If you don't want to use it (in which case chronyc will use a minimal command
-line interface), invoke configure like this:
-
----
-./configure --disable-readline other-options...
----
-
-If you have editline, readline or ncurses installed in locations that aren't
-normally searched by the compiler and linker, you need to use extra options:
-
-`--with-readline-includes=directory_name`::
-  This defines the name of the directory above the one where `readline.h` is.
-  `readline.h` is assumed to be in `editline` or `readline` subdirectory of the
-  named directory.
-
-`--with-readline-library=directory_name`::
-  This defines the directory containing the `libedit.a` or `libedit.so` file,
-  or `libreadline.a` or `libreadline.so` file.
-
-`--with-ncurses-library=directory_name`::
-  This defines the directory containing the `libncurses.a` or `libncurses.so`
-  file.
+`chronyd` can be built with support for the Linux secure computing (seccomp)
+facility. This requires development files for the
+https://github.com/seccomp/libseccomp[libseccomp] library and the
+`--enable-scfilter` option specified to `configure`. The `-F` option of
+`chronyd` will enable a system call filter, which should significantly reduce
+the kernel attack surface and possibly prevent kernel exploits from `chronyd`
+if it is compromised.

 == Extra options for package builders

-The configure and make procedures have some extra options that may be useful if
-you are building a distribution package for chrony.
+The `configure` and `make` procedures have some extra options that may be
+useful if you are building a distribution package for `chrony`.

-The `--mandir=DIR` option to configure specifies an install directory for the
-man pages. This overrides the `man` subdirectory of the argument to the
--prefix option.
+The `--mandir=DIR` option to `configure` specifies an installation directory
+for the man pages. This overrides the `man` subdirectory of the argument to the
+`--prefix` option.

 ----
 ./configure --prefix=/usr --mandir=/usr/share/man
@@ -174,8 +185,8 @@ man pages. This overrides the `man` subdirectory of the argument to the

 to set both options together.

-The final option is the `DESTDIR` option to the make command. For example, you
-could use the commands
+The final option is the `DESTDIR` option to the `make` command. For example,
+you could use the commands

 ----
 ./configure --prefix=/usr --mandir=/usr/share/man
--- a/examples/chrony-wait.service
+++ b/examples/chrony-wait.service
@@ -1,5 +1,6 @@
 [Unit]
 Description=Wait for chrony to synchronize system clock
+Documentation=man:chronyc(1)
 After=chronyd.service
 Requires=chronyd.service
 Before=time-sync.target
@@ -7,11 +8,40 @@ Wants=time-sync.target

 [Service]
 Type=oneshot
-# Wait up to ~10 minutes for chronyd to synchronize and the remaining
-# clock correction to be less than 0.1 seconds
-ExecStart=/usr/bin/chronyc -h 127.0.0.1,::1 waitsync 600 0.1 0.0 1
+# Wait for chronyd to update the clock and the remaining
+# correction to be less than 0.1 seconds
+ExecStart=/usr/bin/chronyc -h 127.0.0.1,::1 waitsync 0 0.1 0.0 1
+# Wait for at most 3 minutes
+TimeoutStartSec=180
 RemainAfterExit=yes
 StandardOutput=null

+CapabilityBoundingSet=
+DevicePolicy=closed
+DynamicUser=yes
+IPAddressAllow=localhost
+IPAddressDeny=any
+LockPersonality=yes
+MemoryDenyWriteExecute=yes
+PrivateDevices=yes
+PrivateUsers=yes
+ProcSubset=pid
+ProtectClock=yes
+ProtectControlGroups=yes
+ProtectHome=yes
+ProtectHostname=yes
+ProtectKernelLogs=yes
+ProtectKernelModules=yes
+ProtectKernelTunables=yes
+ProtectProc=invisible
+ProtectSystem=strict
+RestrictAddressFamilies=AF_INET AF_INET6
+RestrictNamespaces=yes
+RestrictRealtime=yes
+SystemCallArchitectures=native
+SystemCallFilter=@system-service
+SystemCallFilter=~@privileged @resources
+UMask=0777
+
 [Install]
 WantedBy=multi-user.target
--- a/examples/chrony.conf.example1
+++ b/examples/chrony.conf.example1
@@ -4,8 +4,8 @@ pool pool.ntp.org iburst
 # Record the rate at which the system clock gains/losses time.
 driftfile /var/lib/chrony/drift

-# In first three updates step the system clock instead of slew
-# if the adjustment is larger than 1 second.
+# Allow the system clock to be stepped in the first three updates
+# if its offset is larger than 1 second.
 makestep 1.0 3

 # Enable kernel synchronization of the real-time clock (RTC).
--- a/examples/chrony.conf.example2
+++ b/examples/chrony.conf.example2
@@ -1,26 +1,45 @@
 # Use public servers from the pool.ntp.org project.
-# Please consider joining the pool (http://www.pool.ntp.org/join.html).
+# Please consider joining the pool (https://www.pool.ntp.org/join.html).
 pool pool.ntp.org iburst

 # Record the rate at which the system clock gains/losses time.
 driftfile /var/lib/chrony/drift

-# In first three updates step the system clock instead of slew
-# if the adjustment is larger than 1 second.
+# Allow the system clock to be stepped in the first three updates
+# if its offset is larger than 1 second.
 makestep 1.0 3

 # Enable kernel synchronization of the real-time clock (RTC).
 rtcsync

-# Allow NTP client access from local network.
-#allow 192.168/16
+# Enable hardware timestamping on all interfaces that support it.
+#hwtimestamp *

-# Serve time even if not synchronized to any NTP server.
+# Increase the minimum number of selectable sources required to adjust
+# the system clock.
+#minsources 2
+
+# Allow NTP client access from local network.
+#allow 192.168.0.0/16
+
+# Serve time even if not synchronized to a time source.
 #local stratum 10

+# Require authentication (nts or key option) for all NTP sources.
+#authselectmode require
+
 # Specify file containing keys for NTP authentication.
 #keyfile /etc/chrony.keys

+# Save NTS keys and cookies.
+ntsdumpdir /var/lib/chrony
+
+# Insert/delete leap seconds by slewing instead of stepping.
+#leapsecmode slew
+
+# Get TAI-UTC offset and leap seconds from the system tz database.
+#leapsectz right/UTC
+
 # Specify directory for log files.
 logdir /var/log/chrony

--- a/examples/chrony.conf.example3
+++ b/examples/chrony.conf.example3
@@ -33,42 +33,44 @@

 ! pool pool.ntp.org iburst
 
-# However, for dial-up use you probably want these instead.  The word
-# 'offline' means that the server is not visible at boot time.  Use
-# chronyc's 'online' command to tell chronyd that these servers have
-# become visible after you go on-line.
-
-! server foo.example.net offline
-! server bar.example.net offline
-! server baz.example.net offline
-
-! pool pool.ntp.org offline
-
-# You may want to specify NTP 'peers' instead.  If you run a network
-# with a lot of computers and want several computers running chrony to
-# have the 'front-line' interface to the public NTP servers, you can
-# 'peer' these machines together to increase robustness.
-
-! peer foo.example.net
-
-# There are other options to the 'server' and 'peer' directives that you
-# might want to use.  For example, you can ignore measurements whose
-# round-trip-time is too large (indicating that the measurement is
-# probably useless, because you don't know which way the measurement
-# message got held up.)  Consult the full documentation for details.
-
 #######################################################################
 ### AVOIDING POTENTIALLY BOGUS CHANGES TO YOUR CLOCK
 #
 # To avoid changes being made to your computer's gain/loss compensation
 # when the measurement history is too erratic, you might want to enable
-# one of the following lines.  The first seems good for dial-up (or
-# other high-latency connections like slow leased lines), the second
-# seems OK for a LAN environment.
+# one of the following lines.  The first seems good with servers on the
+# Internet, the second seems OK for a LAN environment.

 ! maxupdateskew 100
 ! maxupdateskew 5

+# If you want to increase the minimum number of selectable sources
+# required to update the system clock in order to make the
+# synchronisation more reliable, uncomment (and edit) the following
+# line.
+
+! minsources 2
+
+# If your computer has a good stable clock (e.g. it is not a virtual
+# machine), you might also want to reduce the maximum assumed drift
+# (frequency error) of the clock (the value is specified in ppm).
+
+! maxdrift 100
+
+# By default, chronyd allows synchronisation to an unauthenticated NTP
+# source (i.e. specified without the nts and key options) if it agrees with
+# a majority of authenticated NTP sources, or if no authenticated source is
+# specified.  If you don't want chronyd to ever synchronise to an
+# unauthenticated NTP source, uncomment the first from the following lines.
+# If you don't want to synchronise to an unauthenticated NTP source only
+# when an authenticated source is specified, uncomment the second line.
+# If you want chronyd to ignore authentication in the source selection,
+# uncomment the third line.
+
+! authselectmode require
+! authselectmode prefer
+! authselectmode ignore
+
 #######################################################################
 ### FILENAMES ETC
 # Chrony likes to keep information about your computer's clock in files.
@@ -84,22 +86,37 @@ driftfile /var/lib/chrony/drift

 ! keyfile /etc/chrony.keys

+# If you specify an NTP server with the nts option to enable authentication
+# with the Network Time Security (NTS) mechanism, or enable server NTS with
+# the ntsservercert and ntsserverkey directives below, the following line will
+# allow the client/server to save the NTS keys and cookies in order to reduce
+# the number of key establishments (NTS-KE sessions).
+
+ntsdumpdir /var/lib/chrony
+
+# If chronyd is configured to act as an NTP server and you want to enable NTS
+# for its clients, you will need a TLS certificate and private key.  Uncomment
+# and edit the following lines to specify the locations of the certificate and
+# key.
+
+! ntsservercert /etc/.../foo.example.net.crt
+! ntsserverkey /etc/.../foo.example.net.key
+
 # chronyd can save the measurement history for the servers to files when
-# it it exits.  This is useful in 2 situations:
+# it exits.  This is useful in 2 situations:
 #
-# 1. On Linux, if you stop chronyd and restart it with '-r' (e.g. after
+# 1. If you stop chronyd and restart it with the '-r' option (e.g. after
 # an upgrade), the old measurements will still be relevant when chronyd
 # is restarted.  This will reduce the time needed to get accurate
-# gain/loss measurements, especially with a dial-up link.
+# gain/loss measurements.
 #
-# 2. Again on Linux, if you use the RTC support and start chronyd with
+# 2. On Linux, if you use the RTC support and start chronyd with
 # '-r -s' on bootup, measurements from the last boot will still be
 # useful (the real time clock is used to 'flywheel' chronyd between
 # boots).
 #
-# Enable these two options to use this.
+# Uncomment the following line to use this.

-! dumponexit
 ! dumpdir /var/lib/chrony

 # chronyd writes its process ID to a file.  If you try to start a second
@@ -107,7 +124,13 @@ driftfile /var/lib/chrony/drift
 # still running and bail out.  If you want to change the path to the PID
 # file, uncomment this line and edit it.  The default path is shown.

-! pidfile /var/run/chronyd.pid
+! pidfile /var/run/chrony/chronyd.pid
+
+# If the system timezone database is kept up to date and includes the
+# right/UTC timezone, chronyd can use it to determine the current
+# TAI-UTC offset and when will the next leap second occur.
+
+! leapsectz right/UTC

 #######################################################################
 ### INITIAL CLOCK CORRECTION
@@ -122,6 +145,18 @@ driftfile /var/lib/chrony/drift

 ! makestep 1.0 3

+#######################################################################
+### LEAP SECONDS
+# A leap second is an occasional one-second correction of the UTC
+# time scale.  By default, chronyd tells the kernel to insert/delete
+# the leap second, which makes a backward/forward step to correct the
+# clock for it.  As with the makestep directive, this jump can upset
+# some applications.  If you prefer chronyd to make a gradual
+# correction, causing the clock to be off for a longer time, uncomment
+# the following line.
+
+! leapsecmode slew
+
 #######################################################################
 ### LOGGING
 # If you want to log information about the time measurements chronyd has
@@ -141,8 +176,6 @@ driftfile /var/lib/chrony/drift
 #######################################################################
 ### ACTING AS AN NTP SERVER
 # You might want the computer to be an NTP server for other computers.
-# e.g.  you might be running chronyd on a dial-up machine that has a LAN
-# sitting behind it with several 'satellite' computers on it.
 #
 # By default, chronyd does not allow any clients to access it.  You need
 # to explicitly enable access using 'allow' and 'deny' directives.
@@ -158,15 +191,6 @@ driftfile /var/lib/chrony/drift
 # You can have as many allow and deny directives as you need.  The order
 # is unimportant.

-# If you want chronyd to act as an NTP broadcast server, enable and edit
-# (and maybe copy) the following line.  This means that a broadcast
-# packet is sent to the address 192.168.1.255 every 60 seconds.  The
-# address MUST correspond to the broadcast address of one of the network
-# interfaces on your machine.  If you have multiple network interfaces,
-# add a broadcast line for each.
-
-! broadcast 60 192.168.1.255
-
 # If you want to present your computer's time for others to synchronise
 # with, even if you don't seem to be synchronised to any NTP servers
 # yourself, enable the following line.  The value 10 may be varied
@@ -181,13 +205,12 @@ driftfile /var/lib/chrony/drift
 # machine accesses it.  The information can be accessed by the 'clients'
 # command of chronyc.  You can disable this facility by uncommenting the
 # following line.  This will save a bit of memory if you have many
-# clients.
+# clients and it will also disable support for the interleaved mode.

 ! noclientlog

 # The clientlog size is limited to 512KB by default.  If you have many
-# clients, especially in many different subnets, you might want to
-# increase the limit. 
+# clients, you might want to increase the limit.

 ! clientloglimit 4194304

@@ -196,7 +219,7 @@ driftfile /var/lib/chrony/drift
 # clients that are sending requests too frequently, uncomment and edit
 # the following line.

-! limitrate interval 3 burst 8
+! ratelimit interval 3 burst 8

 #######################################################################
 ### REPORTING BIG CLOCK CHANGES
@@ -243,7 +266,17 @@ driftfile /var/lib/chrony/drift
 # Rate limiting can be enabled also for command packets.  (Note,
 # commands from localhost are never limited.)

-! cmdratelimit interval 1 burst 16
+! cmdratelimit interval -4 burst 16
+
+#######################################################################
+### HARDWARE TIMESTAMPING
+# On Linux, if the network interface controller and its driver support
+# hardware timestamping, it can significantly improve the accuracy of
+# synchronisation. It can be enabled on specified interfaces only, or it
+# can be enabled on all interfaces that support it.
+
+! hwtimestamp eth0
+! hwtimestamp *

 #######################################################################
 ### REAL TIME CLOCK
@@ -274,6 +307,12 @@ driftfile /var/lib/chrony/drift

 ! rtcdevice /dev/misc/rtc

+# Alternatively, if not using the -s option, this directive can be used
+# to enable a mode in which the RTC is periodically set to the system
+# time, with no tracking of its drift.
+
+! rtcsync
+
 #######################################################################
 ### REAL TIME SCHEDULER
 # This directive tells chronyd to use the real-time FIFO scheduler with the
--- a/examples/chrony.keys.example
+++ b/examples/chrony.keys.example
@@ -1,6 +1,7 @@
-# This is an example chrony keys file.  It is used for NTP authentication with
-# symmetric keys.  It should be readable only by root or the user to which
-# chronyd is configured to switch to after start.
+# This is an example chrony keys file.  It enables authentication of NTP
+# packets with symmetric keys when its location is specified by the keyfile
+# directive in chrony.conf(5).  It should be readable only by root and the
+# user under which chronyd is running.
 #
 # Don't use the example keys!  It's recommended to generate random keys using
 # the chronyc keygen command.
--- a/examples/chrony.nm-dispatcher
+++ b/examples/chrony.nm-dispatcher
@@ -1,17 +0,0 @@
-#!/bin/sh
-# This is a NetworkManager dispatcher script for chronyd to set its NTP sources
-# online/offline when a default route is configured/removed on the system.
-
-export LC_ALL=C
-
-if [ "$2" = "up" ]; then
-	/sbin/ip route list dev "$1" | grep -q '^default' &&
-		/usr/bin/chronyc online > /dev/null 2>&1
-fi
-
-if [ "$2" = "down" ]; then
-	/sbin/ip route list | grep -q '^default' ||
-		/usr/bin/chronyc offline > /dev/null 2>&1
-fi
-
-exit 0
--- a/examples/chrony.nm-dispatcher.dhcp
+++ b/examples/chrony.nm-dispatcher.dhcp
@@ -0,0 +1,49 @@
+#!/bin/sh
+# This is a NetworkManager dispatcher script for chronyd to update
+# its NTP sources with servers from DHCP options passed by NetworkManager
+# in the DHCP4_NTP_SERVERS and DHCP6_DHCP6_NTP_SERVERS environment variables.
+
+export LC_ALL=C
+
+interface=$1
+action=$2
+
+chronyc=/usr/bin/chronyc
+server_options=iburst
+server_dir=/var/run/chrony-dhcp
+
+dhcp_server_file=$server_dir/$interface.sources
+dhcp_ntp_servers="$DHCP4_NTP_SERVERS $DHCP6_DHCP6_NTP_SERVERS"
+
+add_servers_from_dhcp() {
+    rm -f "$dhcp_server_file"
+    for server in $dhcp_ntp_servers; do
+        # Check for invalid characters (from the DHCPv6 NTP FQDN suboption)
+        len1=$(printf '%s' "$server" | wc -c)
+        len2=$(printf '%s' "$server" | tr -d -c 'A-Za-z0-9:.-' | wc -c)
+        if [ "$len1" -ne "$len2" ] || [ "$len2" -lt 1 ] || [ "$len2" -gt 255 ]; then
+          continue
+        fi
+
+        printf 'server %s %s\n' "$server" "$server_options" >> "$dhcp_server_file"
+    done
+    $chronyc reload sources > /dev/null 2>&1 || :
+}
+
+clear_servers_from_dhcp() {
+    if [ -f "$dhcp_server_file" ]; then
+        rm -f "$dhcp_server_file"
+        $chronyc reload sources > /dev/null 2>&1 || :
+    fi
+}
+
+mkdir -p $server_dir
+
+case "$action" in
+    up|dhcp4-change|dhcp6-change)
+        add_servers_from_dhcp;;
+    down)
+        clear_servers_from_dhcp;;
+esac
+
+exit 0
--- a/examples/chrony.nm-dispatcher.onoffline
+++ b/examples/chrony.nm-dispatcher.onoffline
@@ -0,0 +1,27 @@
+#!/bin/sh
+# This is a NetworkManager dispatcher / networkd-dispatcher script for
+# chronyd to set its NTP sources online or offline when a network interface
+# is configured or removed
+
+export LC_ALL=C
+
+chronyc=/usr/bin/chronyc
+
+# For NetworkManager consider only selected events
+if [ $# -ge 2 ]; then
+    case "$2" in
+        up|down|connectivity-change)
+            ;;
+        dhcp6-change)
+            # No other action is reported for routable IPv6
+            ;;
+        *)
+            exit 0;;
+    esac
+fi
+
+# Note: for networkd-dispatcher routable.d ~= on and off.d ~= off
+
+$chronyc onoffline > /dev/null 2>&1
+
+exit 0
--- a/examples/chrony.spec
+++ b/examples/chrony.spec
@@ -1,46 +0,0 @@
-%global chrony_version @@VERSION@@
-%if 0%(echo %{chrony_version} | grep -q pre && echo 1)
-%global prerelease %(echo %{chrony_version} | sed 's/.*-//')
-%endif
-Summary: An NTP client/server
-Name: chrony
-Version: %(echo %{chrony_version} | sed 's/-.*//')
-Release: %{!?prerelease:1}%{?prerelease:0.1.%{prerelease}}
-Source: chrony-%{version}%{?prerelease:-%{prerelease}}.tar.gz
-License: GPLv2
-Group: Applications/Utilities
-BuildRoot: %{_tmppath}/%{name}-%{version}-root-%(id -u -n)
-
-%description
-chrony is a client and server for the Network Time Protocol (NTP).
-This program keeps your computer's clock accurate. It was specially
-designed to support systems with intermittent Internet connections,
-but it also works well in permanently connected environments. It can
-also use hardware reference clocks, the system real-time clock, or
-manual input as time references.
-
-%prep
-%setup -q -n %{name}-%{version}%{?prerelease:-%{prerelease}}
-
-%build
-./configure \
-	--prefix=%{_prefix} \
-	--bindir=%{_bindir} \
-	--sbindir=%{_sbindir} \
-	--mandir=%{_mandir}
-make
-
-%install
-rm -rf $RPM_BUILD_ROOT
-make install DESTDIR=$RPM_BUILD_ROOT
-
-%files
-%{_sbindir}/chronyd
-%{_bindir}/chronyc
-%{_mandir}/man1/chronyc.1.gz
-%{_mandir}/man5/chrony.conf.5.gz
-%{_mandir}/man8/chronyd.8.gz
-%doc README FAQ NEWS COPYING
-%doc examples/chrony.conf.example*
-%doc examples/chrony.keys.example
-
--- a/examples/chronyd.service
+++ b/examples/chronyd.service
@@ -1,13 +1,49 @@
 [Unit]
 Description=NTP client/server
+Documentation=man:chronyd(8) man:chrony.conf(5)
 After=ntpdate.service sntp.service ntpd.service
 Conflicts=ntpd.service systemd-timesyncd.service
+ConditionCapability=CAP_SYS_TIME

 [Service]
 Type=forking
-PIDFile=/var/run/chronyd.pid
+PIDFile=/run/chrony/chronyd.pid
 EnvironmentFile=-/etc/sysconfig/chronyd
 ExecStart=/usr/sbin/chronyd $OPTIONS

+CapabilityBoundingSet=~CAP_AUDIT_CONTROL CAP_AUDIT_READ CAP_AUDIT_WRITE
+CapabilityBoundingSet=~CAP_BLOCK_SUSPEND CAP_KILL CAP_LEASE CAP_LINUX_IMMUTABLE
+CapabilityBoundingSet=~CAP_MAC_ADMIN CAP_MAC_OVERRIDE CAP_MKNOD CAP_SYS_ADMIN
+CapabilityBoundingSet=~CAP_SYS_BOOT CAP_SYS_CHROOT CAP_SYS_MODULE CAP_SYS_PACCT
+CapabilityBoundingSet=~CAP_SYS_PTRACE CAP_SYS_RAWIO CAP_SYS_TTY_CONFIG CAP_WAKE_ALARM
+DeviceAllow=char-pps rw
+DeviceAllow=char-ptp rw
+DeviceAllow=char-rtc rw
+DevicePolicy=closed
+LockPersonality=yes
+MemoryDenyWriteExecute=yes
+NoNewPrivileges=yes
+PrivateTmp=yes
+ProcSubset=pid
+ProtectControlGroups=yes
+ProtectHome=yes
+ProtectHostname=yes
+ProtectKernelLogs=yes
+ProtectKernelModules=yes
+ProtectKernelTunables=yes
+ProtectProc=invisible
+ProtectSystem=strict
+ReadWritePaths=/run /var/lib/chrony -/var/log
+RestrictAddressFamilies=AF_INET AF_INET6 AF_UNIX
+RestrictNamespaces=yes
+RestrictSUIDSGID=yes
+SystemCallArchitectures=native
+SystemCallFilter=~@cpu-emulation @debug @module @mount @obsolete @raw-io @reboot @swap
+
+# Adjust restrictions for /usr/sbin/sendmail (mailonchange directive)
+NoNewPrivileges=no
+ReadWritePaths=-/var/spool
+RestrictAddressFamilies=AF_NETLINK
+
 [Install]
 WantedBy=multi-user.target
--- a/hash.h
+++ b/hash.h
@@ -31,12 +31,26 @@
 /* length of hash values produced by SHA512 */
 #define MAX_HASH_LENGTH 64

-extern int HSH_GetHashId(const char *name);
+typedef enum {
+  HSH_INVALID = 0,
+  HSH_MD5 = 1,
+  HSH_SHA1 = 2,
+  HSH_SHA256 = 3,
+  HSH_SHA384 = 4,
+  HSH_SHA512 = 5,
+  HSH_SHA3_224 = 6,
+  HSH_SHA3_256 = 7,
+  HSH_SHA3_384 = 8,
+  HSH_SHA3_512 = 9,
+  HSH_TIGER = 10,
+  HSH_WHIRLPOOL = 11,
+  HSH_MD5_NONCRYPTO = 10000, /* For NTPv4 reference ID */
+} HSH_Algorithm;

-extern unsigned int HSH_Hash(int id,
-    const unsigned char *in1, unsigned int in1_len,
-    const unsigned char *in2, unsigned int in2_len,
-    unsigned char *out, unsigned int out_len);
+extern int HSH_GetHashId(HSH_Algorithm algorithm);
+
+extern int HSH_Hash(int id, const void *in1, int in1_len, const void *in2, int in2_len,
+                    unsigned char *out, int out_len);

 extern void HSH_Finalise(void);

--- a/hash_gnutls.c
+++ b/hash_gnutls.c
@@ -0,0 +1,145 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2021
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ **********************************************************************
+
+  =======================================================================
+
+  Crypto hashing using the GnuTLS library
+  */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include <gnutls/crypto.h>
+
+#include "hash.h"
+#include "logging.h"
+
+struct hash {
+  const HSH_Algorithm algorithm;
+  const gnutls_digest_algorithm_t type;
+  gnutls_hash_hd_t handle;
+};
+
+static struct hash hashes[] = {
+  { HSH_MD5_NONCRYPTO, GNUTLS_DIG_MD5, NULL },
+  { HSH_MD5, GNUTLS_DIG_MD5, NULL },
+  { HSH_SHA1, GNUTLS_DIG_SHA1, NULL },
+  { HSH_SHA256, GNUTLS_DIG_SHA256, NULL },
+  { HSH_SHA384, GNUTLS_DIG_SHA384, NULL },
+  { HSH_SHA512, GNUTLS_DIG_SHA512, NULL },
+  { HSH_SHA3_224, GNUTLS_DIG_SHA3_224, NULL },
+  { HSH_SHA3_256, GNUTLS_DIG_SHA3_256, NULL },
+  { HSH_SHA3_384, GNUTLS_DIG_SHA3_384, NULL },
+  { HSH_SHA3_512, GNUTLS_DIG_SHA3_512, NULL },
+  { 0, 0, NULL }
+};
+
+static int gnutls_initialised = 0;
+
+int
+HSH_GetHashId(HSH_Algorithm algorithm)
+{
+  int id, r;
+
+  if (!gnutls_initialised) {
+    r = gnutls_global_init();
+    if (r < 0)
+      LOG_FATAL("Could not initialise %s : %s", "gnutls", gnutls_strerror(r));
+    gnutls_initialised = 1;
+  }
+
+  for (id = 0; hashes[id].algorithm != 0; id++) {
+    if (hashes[id].algorithm == algorithm)
+      break;
+  }
+
+  if (hashes[id].algorithm == 0)
+    return -1;
+
+  if (hashes[id].handle)
+    return id;
+
+  if (algorithm == HSH_MD5_NONCRYPTO)
+    GNUTLS_FIPS140_SET_LAX_MODE();
+
+  r = gnutls_hash_init(&hashes[id].handle, hashes[id].type);
+
+  if (algorithm == HSH_MD5_NONCRYPTO)
+    GNUTLS_FIPS140_SET_STRICT_MODE();
+
+  if (r < 0) {
+    DEBUG_LOG("Could not initialise %s : %s", "hash", gnutls_strerror(r));
+    hashes[id].handle = NULL;
+    return -1;
+  }
+
+  return id;
+}
+
+int
+HSH_Hash(int id, const void *in1, int in1_len, const void *in2, int in2_len,
+         unsigned char *out, int out_len)
+{
+  unsigned char buf[MAX_HASH_LENGTH];
+  gnutls_hash_hd_t handle;
+  int hash_len;
+
+  if (in1_len < 0 || in2_len < 0 || out_len < 0)
+    return 0;
+
+  handle = hashes[id].handle;
+  hash_len = gnutls_hash_get_len(hashes[id].type);
+
+  if (out_len > hash_len)
+    out_len = hash_len;
+
+  if (hash_len > sizeof (buf))
+    return 0;
+
+  if (gnutls_hash(handle, in1, in1_len) < 0 ||
+      (in2 && gnutls_hash(handle, in2, in2_len) < 0)) {
+    /* Reset the state */
+    gnutls_hash_output(handle, buf);
+    return 0;
+  }
+
+  gnutls_hash_output(handle, buf);
+  memcpy(out, buf, out_len);
+
+  return out_len;
+}
+
+void
+HSH_Finalise(void)
+{
+  int i;
+
+  if (!gnutls_initialised)
+    return;
+
+  for (i = 0; hashes[i].algorithm != 0; i++) {
+    if (hashes[i].handle)
+      gnutls_hash_deinit(hashes[i].handle, NULL);
+  }
+
+  gnutls_global_deinit();
+}
--- a/hash_intmd5.c
+++ b/hash_intmd5.c
@@ -29,27 +29,27 @@
 #include "sysincl.h"
 #include "hash.h"
 #include "memory.h"
+#include "util.h"

 #include "md5.c"

 static MD5_CTX ctx;

 int
-HSH_GetHashId(const char *name)
+HSH_GetHashId(HSH_Algorithm algorithm)
 {
  /* only MD5 is supported */
-  if (strcmp(name, "MD5"))
+  if (algorithm != HSH_MD5 && algorithm != HSH_MD5_NONCRYPTO)
    return -1;

  return 0;
 }

-unsigned int
-HSH_Hash(int id, const unsigned char *in1, unsigned int in1_len,
-    const unsigned char *in2, unsigned int in2_len,
-    unsigned char *out, unsigned int out_len)
+int
+HSH_Hash(int id, const void *in1, int in1_len, const void *in2, int in2_len,
+         unsigned char *out, int out_len)
 {
-  if (out_len < 16)
+  if (in1_len < 0 || in2_len < 0 || out_len < 0)
    return 0;

  MD5Init(&ctx);
@@ -58,9 +58,11 @@ HSH_Hash(int id, const unsigned char *in1, unsigned int in1_len,
    MD5Update(&ctx, in2, in2_len);
  MD5Final(&ctx);

-  memcpy(out, ctx.digest, 16);
+  out_len = MIN(out_len, 16);

-  return 16;
+  memcpy(out, ctx.digest, out_len);
+
+  return out_len;
 }

 void
--- a/hash_nettle.c
+++ b/hash_nettle.c
@@ -0,0 +1,124 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2018
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Routines implementing crypto hashing using the nettle library.
+
+  */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include <nettle/nettle-meta.h>
+
+#include "hash.h"
+#include "memory.h"
+
+struct hash {
+  const HSH_Algorithm algorithm;
+  const char *int_name;
+  const struct nettle_hash *nettle_hash;
+  void *context;
+};
+
+static struct hash hashes[] = {
+  { HSH_MD5, "md5", NULL, NULL },
+  { HSH_SHA1, "sha1", NULL, NULL },
+  { HSH_SHA256, "sha256", NULL, NULL },
+  { HSH_SHA384, "sha384", NULL, NULL },
+  { HSH_SHA512, "sha512", NULL, NULL },
+  { HSH_SHA3_224, "sha3_224", NULL, NULL },
+  { HSH_SHA3_256, "sha3_256", NULL, NULL },
+  { HSH_SHA3_384, "sha3_384", NULL, NULL },
+  { HSH_SHA3_512, "sha3_512", NULL, NULL },
+  { 0, NULL, NULL, NULL }
+};
+
+int
+HSH_GetHashId(HSH_Algorithm algorithm)
+{
+  int id, nid;
+
+  if (algorithm == HSH_MD5_NONCRYPTO)
+    algorithm = HSH_MD5;
+
+  for (id = 0; hashes[id].algorithm != 0; id++) {
+    if (hashes[id].algorithm == algorithm)
+      break;
+  }
+
+  if (hashes[id].algorithm == 0)
+    return -1;
+
+  if (hashes[id].context)
+    return id;
+
+  for (nid = 0; nettle_hashes[nid]; nid++) {
+    if (!strcmp(hashes[id].int_name, nettle_hashes[nid]->name))
+      break;
+  }
+
+  if (!nettle_hashes[nid] || !nettle_hashes[nid]->context_size || !nettle_hashes[nid]->init)
+    return -1;
+
+  hashes[id].nettle_hash = nettle_hashes[nid];
+  hashes[id].context = Malloc(hashes[id].nettle_hash->context_size);
+
+  return id;
+}
+
+int
+HSH_Hash(int id, const void *in1, int in1_len, const void *in2, int in2_len,
+         unsigned char *out, int out_len)
+{
+  const struct nettle_hash *hash;
+  void *context;
+
+  if (in1_len < 0 || in2_len < 0 || out_len < 0)
+    return 0;
+
+  hash = hashes[id].nettle_hash;
+  context = hashes[id].context;
+
+  if (out_len > hash->digest_size)
+    out_len = hash->digest_size;
+
+  hash->init(context);
+  hash->update(context, in1_len, in1);
+  if (in2)
+    hash->update(context, in2_len, in2);
+  hash->digest(context, out_len, out);
+
+  return out_len;
+}
+
+void
+HSH_Finalise(void)
+{
+  int i;
+
+  for (i = 0; hashes[i].algorithm != 0; i++) {
+    if (hashes[i].context)
+      Free(hashes[i].context);
+  }
+}
--- a/hash_nss.c
+++ b/hash_nss.c
@@ -32,35 +32,39 @@
 #include <nsslowhash.h>

 #include "hash.h"
+#include "util.h"

 static NSSLOWInitContext *ictx;

 struct hash {
  HASH_HashType type;
-  const char *name;
+  HSH_Algorithm algorithm;
  NSSLOWHASHContext *context;
 };

 static struct hash hashes[] = {
-  { HASH_AlgMD5, "MD5", NULL },
-  { HASH_AlgSHA1, "SHA1", NULL },
-  { HASH_AlgSHA256, "SHA256", NULL },
-  { HASH_AlgSHA384, "SHA384", NULL },
-  { HASH_AlgSHA512, "SHA512", NULL },
-  { 0, NULL, NULL }
+  { HASH_AlgMD5, HSH_MD5, NULL },
+  { HASH_AlgSHA1, HSH_SHA1, NULL },
+  { HASH_AlgSHA256, HSH_SHA256, NULL },
+  { HASH_AlgSHA384, HSH_SHA384, NULL },
+  { HASH_AlgSHA512, HSH_SHA512, NULL },
+  { 0, 0, NULL }
 };

 int
-HSH_GetHashId(const char *name)
+HSH_GetHashId(HSH_Algorithm algorithm)
 {
  int i;

-  for (i = 0; hashes[i].name; i++) {
-    if (!strcmp(name, hashes[i].name))
+  if (algorithm == HSH_MD5_NONCRYPTO)
+    algorithm = HSH_MD5;
+
+  for (i = 0; hashes[i].algorithm != 0; i++) {
+    if (hashes[i].algorithm == algorithm)
      break;
  }

-  if (!hashes[i].name)
+  if (hashes[i].algorithm == 0)
    return -1; /* not found */

  if (!ictx && !(ictx = NSSLOW_Init()))
@@ -73,18 +77,24 @@ HSH_GetHashId(const char *name)
  return i;
 }

-unsigned int
-HSH_Hash(int id, const unsigned char *in1, unsigned int in1_len,
-    const unsigned char *in2, unsigned int in2_len,
-    unsigned char *out, unsigned int out_len)
+int
+HSH_Hash(int id, const void *in1, int in1_len, const void *in2, int in2_len,
+         unsigned char *out, int out_len)
 {
-  unsigned int ret;
+  unsigned char buf[MAX_HASH_LENGTH];
+  unsigned int ret = 0;
+
+  if (in1_len < 0 || in2_len < 0 || out_len < 0)
+    return 0;

  NSSLOWHASH_Begin(hashes[id].context);
  NSSLOWHASH_Update(hashes[id].context, in1, in1_len);
  if (in2)
    NSSLOWHASH_Update(hashes[id].context, in2, in2_len);
-  NSSLOWHASH_End(hashes[id].context, out, &ret, out_len);
+  NSSLOWHASH_End(hashes[id].context, buf, &ret, sizeof (buf));
+
+  ret = MIN(ret, out_len);
+  memcpy(out, buf, ret);

  return ret;
 }
@@ -94,7 +104,7 @@ HSH_Finalise(void)
 {
  int i;

-  for (i = 0; hashes[i].name; i++) {
+  for (i = 0; hashes[i].algorithm != 0; i++) {
    if (hashes[i].context)
      NSSLOWHASH_Destroy(hashes[i].context);
  }
--- a/hash_tomcrypt.c
+++ b/hash_tomcrypt.c
@@ -2,7 +2,7 @@
  chronyd/chronyc - Programs for keeping computer clocks accurate.

 **********************************************************************
- * Copyright (C) Miroslav Lichvar  2012
+ * Copyright (C) Miroslav Lichvar  2012, 2018
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
@@ -29,59 +29,57 @@

 #include "config.h"
 #include "hash.h"
+#include "util.h"

 struct hash {
-  const char *name;
+  HSH_Algorithm algorithm;
  const char *int_name;
  const struct ltc_hash_descriptor *desc;
 };

 static const struct hash hashes[] = {
-  { "MD5", "md5", &md5_desc },
-#ifdef LTC_RIPEMD128
-  { "RMD128", "rmd128", &rmd128_desc },
-#endif
-#ifdef LTC_RIPEMD160
-  { "RMD160", "rmd160", &rmd160_desc },
-#endif
-#ifdef LTC_RIPEMD256
-  { "RMD256", "rmd256", &rmd256_desc },
-#endif
-#ifdef LTC_RIPEMD320
-  { "RMD320", "rmd320", &rmd320_desc },
-#endif
+  { HSH_MD5, "md5", &md5_desc },
 #ifdef LTC_SHA1
-  { "SHA1", "sha1", &sha1_desc },
+  { HSH_SHA1, "sha1", &sha1_desc },
 #endif
 #ifdef LTC_SHA256
-  { "SHA256", "sha256", &sha256_desc },
+  { HSH_SHA256, "sha256", &sha256_desc },
 #endif
 #ifdef LTC_SHA384
-  { "SHA384", "sha384", &sha384_desc },
+  { HSH_SHA384, "sha384", &sha384_desc },
 #endif
 #ifdef LTC_SHA512
-  { "SHA512", "sha512", &sha512_desc },
+  { HSH_SHA512, "sha512", &sha512_desc },
+#endif
+#ifdef LTC_SHA3
+  { HSH_SHA3_224, "sha3-224", &sha3_224_desc },
+  { HSH_SHA3_256, "sha3-256", &sha3_256_desc },
+  { HSH_SHA3_384, "sha3-384", &sha3_384_desc },
+  { HSH_SHA3_512, "sha3-512", &sha3_512_desc },
 #endif
 #ifdef LTC_TIGER
-  { "TIGER", "tiger", &tiger_desc },
+  { HSH_TIGER, "tiger", &tiger_desc },
 #endif
 #ifdef LTC_WHIRLPOOL
-  { "WHIRLPOOL", "whirlpool", &whirlpool_desc },
+  { HSH_WHIRLPOOL, "whirlpool", &whirlpool_desc },
 #endif
-  { NULL, NULL, NULL }
+  { 0, NULL, NULL }
 };

 int
-HSH_GetHashId(const char *name)
+HSH_GetHashId(HSH_Algorithm algorithm)
 {
  int i, h;

-  for (i = 0; hashes[i].name; i++) {
-    if (!strcmp(name, hashes[i].name))
+  if (algorithm == HSH_MD5_NONCRYPTO)
+    algorithm = HSH_MD5;
+
+  for (i = 0; hashes[i].algorithm != 0; i++) {
+    if (hashes[i].algorithm == algorithm)
      break;
  }

-  if (!hashes[i].name)
+  if (hashes[i].algorithm == 0)
    return -1; /* not found */

  h = find_hash(hashes[i].int_name);
@@ -94,24 +92,31 @@ HSH_GetHashId(const char *name)
  return find_hash(hashes[i].int_name);
 }

-unsigned int
-HSH_Hash(int id, const unsigned char *in1, unsigned int in1_len,
-    const unsigned char *in2, unsigned int in2_len,
-    unsigned char *out, unsigned int out_len)
+int
+HSH_Hash(int id, const void *in1, int in1_len, const void *in2, int in2_len,
+         unsigned char *out, int out_len)
 {
+  unsigned char buf[MAX_HASH_LENGTH];
  unsigned long len;
  int r;

-  len = out_len;
+  if (in1_len < 0 || in2_len < 0 || out_len < 0)
+    return 0;
+
+  len = sizeof (buf);
  if (in2)
-    r = hash_memory_multi(id, out, &len,
-        in1, (unsigned long)in1_len, in2, (unsigned long)in2_len, NULL, 0);
+    r = hash_memory_multi(id, buf, &len,
+                          in1, (unsigned long)in1_len,
+                          in2, (unsigned long)in2_len, NULL, 0);
  else
-    r = hash_memory(id, in1, in1_len, out, &len);
+    r = hash_memory(id, in1, in1_len, buf, &len);

  if (r != CRYPT_OK)
    return 0;

+  len = MIN(len, out_len);
+  memcpy(out, buf, len);
+
  return len;
 }

--- a/hwclock.c
+++ b/hwclock.c
@@ -2,7 +2,7 @@
  chronyd/chronyc - Programs for keeping computer clocks accurate.

 **********************************************************************
- * Copyright (C) Miroslav Lichvar  2016
+ * Copyright (C) Miroslav Lichvar  2016-2018
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
@@ -33,14 +33,23 @@
 #include "local.h"
 #include "logging.h"
 #include "memory.h"
+#include "quantiles.h"
 #include "regress.h"
 #include "util.h"

-/* Maximum number of samples per clock */
-#define MAX_SAMPLES 16
+/* Minimum and maximum number of samples per clock */
+#define MIN_SAMPLES 2
+#define MAX_SAMPLES 64

-/* Minimum interval between samples (in seconds) */
-#define MIN_SAMPLE_SEPARATION 1.0
+/* Maximum acceptable frequency offset of the clock */
+#define MAX_FREQ_OFFSET (2.0 / 3.0)
+
+/* Quantiles for filtering readings by delay */
+#define DELAY_QUANT_MIN_K 1
+#define DELAY_QUANT_MAX_K 2
+#define DELAY_QUANT_Q 10
+#define DELAY_QUANT_REPEAT 7
+#define DELAY_QUANT_MIN_STEP 1.0e-9

 struct HCL_Instance_Record {
  /* HW and local reference timestamp */
@@ -49,21 +58,32 @@ struct HCL_Instance_Record {

  /* Samples stored as intervals (uncorrected for frequency error)
     relative to local_ref and hw_ref */
-  double x_data[MAX_SAMPLES];
-  double y_data[MAX_SAMPLES];
+  double *x_data;
+  double *y_data;

-  /* Number of samples */
+  /* Minimum, maximum and current number of samples */
+  int min_samples;
+  int max_samples;
  int n_samples;

  /* Maximum error of the last sample */
  double last_err;

+  /* Minimum interval between samples */
+  double min_separation;
+
+  /* Expected precision of readings */
+  double precision;
+
  /* Flag indicating the offset and frequency values are valid */
  int valid_coefs;

  /* Estimated offset and frequency of HW clock relative to local clock */
  double offset;
  double frequency;
+
+  /* Estimated quantiles of reading delay */
+  QNT_Instance delay_quants;
 };

 /* ================================================== */
@@ -86,15 +106,28 @@ handle_slew(struct timespec *raw, struct timespec *cooked, double dfreq,
 /* ================================================== */

 HCL_Instance
-HCL_CreateInstance(void)
+HCL_CreateInstance(int min_samples, int max_samples, double min_separation, double precision)
 {
  HCL_Instance clock;

+  min_samples = CLAMP(MIN_SAMPLES, min_samples, MAX_SAMPLES);
+  max_samples = CLAMP(MIN_SAMPLES, max_samples, MAX_SAMPLES);
+  max_samples = MAX(min_samples, max_samples);
+
  clock = MallocNew(struct HCL_Instance_Record);
-  clock->x_data[MAX_SAMPLES - 1] = 0.0;
-  clock->y_data[MAX_SAMPLES - 1] = 0.0;
+  clock->x_data = MallocArray(double, max_samples);
+  clock->y_data = MallocArray(double, max_samples);
+  clock->x_data[max_samples - 1] = 0.0;
+  clock->y_data[max_samples - 1] = 0.0;
+  clock->min_samples = min_samples;
+  clock->max_samples = max_samples;
  clock->n_samples = 0;
  clock->valid_coefs = 0;
+  clock->min_separation = min_separation;
+  clock->precision = precision;
+  clock->delay_quants = QNT_CreateInstance(DELAY_QUANT_MIN_K, DELAY_QUANT_MAX_K,
+                                           DELAY_QUANT_Q, DELAY_QUANT_REPEAT,
+                                           DELAY_QUANT_MIN_STEP);

  LCL_AddParameterChangeHandler(handle_slew, clock);

@@ -106,6 +139,9 @@ HCL_CreateInstance(void)
 void HCL_DestroyInstance(HCL_Instance clock)
 {
  LCL_RemoveParameterChangeHandler(handle_slew, clock);
+  QNT_DestroyInstance(clock->delay_quants);
+  Free(clock->y_data);
+  Free(clock->x_data);
  Free(clock);
 }

@@ -115,7 +151,7 @@ int
 HCL_NeedsNewSample(HCL_Instance clock, struct timespec *now)
 {
  if (!clock->n_samples ||
-      fabs(UTI_DiffTimespecsToDouble(now, &clock->local_ref)) >= MIN_SAMPLE_SEPARATION)
+      fabs(UTI_DiffTimespecsToDouble(now, &clock->local_ref)) >= clock->min_separation)
    return 1;

  return 0;
@@ -123,6 +159,94 @@ HCL_NeedsNewSample(HCL_Instance clock, struct timespec *now)

 /* ================================================== */

+int
+HCL_ProcessReadings(HCL_Instance clock, int n_readings, struct timespec tss[][3],
+                    struct timespec *hw_ts, struct timespec *local_ts, double *err)
+{
+  double delay, raw_delay, min_delay, low_delay, high_delay, e, pred_err;
+  double delay_sum, hw_sum, local_sum, local_prec, freq;
+  int i, min_reading, combined;
+  struct timespec ts1, ts2;
+
+  if (n_readings < 1)
+    return 0;
+
+  /* Work out the current correction multiplier needed to get cooked delays */
+  LCL_CookTime(&tss[0][0], &ts1, NULL);
+  LCL_CookTime(&tss[n_readings - 1][2], &ts2, NULL);
+  if (UTI_CompareTimespecs(&tss[0][0], &tss[n_readings - 1][2]) < 0)
+    freq = UTI_DiffTimespecsToDouble(&ts1, &ts2) /
+           UTI_DiffTimespecsToDouble(&tss[0][0], &tss[n_readings - 1][2]);
+  else
+    freq = 1.0;
+
+  for (i = 0; i < n_readings; i++) {
+    delay = freq * UTI_DiffTimespecsToDouble(&tss[i][2], &tss[i][0]);
+
+    if (delay < 0.0) {
+      /* Step in the middle of a reading? */
+      DEBUG_LOG("Bad reading delay=%e", delay);
+      return 0;
+    }
+
+    if (i == 0 || min_delay > delay) {
+      min_delay = delay;
+      min_reading = i;
+    }
+
+    QNT_Accumulate(clock->delay_quants, delay);
+  }
+
+  local_prec = LCL_GetSysPrecisionAsQuantum();
+
+  low_delay = QNT_GetQuantile(clock->delay_quants, DELAY_QUANT_MIN_K);
+  high_delay = QNT_GetQuantile(clock->delay_quants, DELAY_QUANT_MAX_K);
+  low_delay = MIN(low_delay, high_delay);
+  high_delay = MAX(high_delay, low_delay + local_prec);
+
+  /* Combine readings with delay in the expected interval */
+  for (i = combined = 0, delay_sum = hw_sum = local_sum = 0.0; i < n_readings; i++) {
+    raw_delay = UTI_DiffTimespecsToDouble(&tss[i][2], &tss[i][0]);
+    delay = freq * raw_delay;
+
+    if (delay < low_delay || delay > high_delay)
+      continue;
+
+    delay_sum += delay;
+    hw_sum += UTI_DiffTimespecsToDouble(&tss[i][1], &tss[0][1]);
+    local_sum += UTI_DiffTimespecsToDouble(&tss[i][0], &tss[0][0]) + raw_delay / 2.0;
+    combined++;
+  }
+
+  DEBUG_LOG("Combined %d readings lo=%e hi=%e", combined, low_delay, high_delay);
+
+  if (combined > 0) {
+    UTI_AddDoubleToTimespec(&tss[0][1], hw_sum / combined, hw_ts);
+    UTI_AddDoubleToTimespec(&tss[0][0], local_sum / combined, local_ts);
+    *err = MAX(delay_sum / combined / 2.0, clock->precision);
+    return 1;
+  }
+
+  /* Accept the reading with minimum delay if its interval does not contain
+     the current offset predicted from previous samples */
+
+  *hw_ts = tss[min_reading][1];
+  UTI_AddDoubleToTimespec(&tss[min_reading][0], min_delay / freq / 2.0, local_ts);
+  *err = MAX(min_delay / 2.0, clock->precision);
+
+  pred_err = 0.0;
+  LCL_CookTime(local_ts, &ts1, NULL);
+  if (!HCL_CookTime(clock, hw_ts, &ts2, &e) ||
+      ((pred_err = UTI_DiffTimespecsToDouble(&ts1, &ts2)) > *err)) {
+    DEBUG_LOG("Accepted reading err=%e prerr=%e", *err, pred_err);
+    return 1;
+  }
+
+  return 0;
+}
+
+/* ================================================== */
+
 void
 HCL_AccumulateSample(HCL_Instance clock, struct timespec *hw_ts,
                     struct timespec *local_ts, double err)
@@ -134,18 +258,18 @@ HCL_AccumulateSample(HCL_Instance clock, struct timespec *hw_ts,

  /* Shift old samples */
  if (clock->n_samples) {
-    if (clock->n_samples >= MAX_SAMPLES)
+    if (clock->n_samples >= clock->max_samples)
      clock->n_samples--;

    hw_delta = UTI_DiffTimespecsToDouble(hw_ts, &clock->hw_ref);
    local_delta = UTI_DiffTimespecsToDouble(local_ts, &clock->local_ref) / local_freq;

-    if (hw_delta <= 0.0 || local_delta < MIN_SAMPLE_SEPARATION / 2.0) {
+    if (hw_delta <= 0.0 || local_delta < clock->min_separation / 2.0) {
      clock->n_samples = 0;
-      DEBUG_LOG(LOGF_HwClocks, "HW clock reset interval=%f", local_delta);
+      DEBUG_LOG("HW clock reset interval=%f", local_delta);
    }

-    for (i = MAX_SAMPLES - clock->n_samples; i < MAX_SAMPLES; i++) {
+    for (i = clock->max_samples - clock->n_samples; i < clock->max_samples; i++) {
      clock->y_data[i - 1] = clock->y_data[i] - hw_delta;
      clock->x_data[i - 1] = clock->x_data[i] - local_delta;
    }
@@ -158,31 +282,33 @@ HCL_AccumulateSample(HCL_Instance clock, struct timespec *hw_ts,

  /* Get new coefficients */
  clock->valid_coefs =
-    RGR_FindBestRobustRegression(clock->x_data + MAX_SAMPLES - clock->n_samples,
-                                 clock->y_data + MAX_SAMPLES - clock->n_samples,
-                                 clock->n_samples, 1.0e-9, &clock->offset, &raw_freq,
+    RGR_FindBestRobustRegression(clock->x_data + clock->max_samples - clock->n_samples,
+                                 clock->y_data + clock->max_samples - clock->n_samples,
+                                 clock->n_samples, 1.0e-10, &clock->offset, &raw_freq,
                                 &n_runs, &best_start);

  if (!clock->valid_coefs) {
-    DEBUG_LOG(LOGF_HwClocks, "HW clock needs more samples");
+    DEBUG_LOG("HW clock needs more samples");
    return;
  }

  clock->frequency = raw_freq / local_freq;

  /* Drop unneeded samples */
-  clock->n_samples -= best_start;
+  if (clock->n_samples > clock->min_samples)
+    clock->n_samples -= MIN(best_start, clock->n_samples - clock->min_samples);

-  /* If the fit doesn't cross the error interval of the last sample, throw away
-     all previous samples and keep only the frequency estimate */
-  if (fabs(clock->offset) > err) {
-    DEBUG_LOG(LOGF_HwClocks, "HW clock reset offset=%e", clock->offset);
-    clock->offset = 0.0;
-    clock->n_samples = 1;
+  /* If the fit doesn't cross the error interval of the last sample,
+     or the frequency is not sane, drop all samples and start again */
+  if (fabs(clock->offset) > err ||
+      fabs(clock->frequency - 1.0) > MAX_FREQ_OFFSET) {
+    DEBUG_LOG("HW clock reset");
+    clock->n_samples = 0;
+    clock->valid_coefs = 0;
  }

-  DEBUG_LOG(LOGF_HwClocks, "HW clock samples=%d offset=%e freq=%.9e raw_freq=%.9e err=%e ref_diff=%e",
-            clock->n_samples, clock->offset, clock->frequency, raw_freq, err,
+  DEBUG_LOG("HW clock samples=%d offset=%e freq=%e raw_freq=%e err=%e ref_diff=%e",
+            clock->n_samples, clock->offset, clock->frequency - 1.0, raw_freq - 1.0, err,
            UTI_DiffTimespecsToDouble(&clock->hw_ref, &clock->local_ref));
 }

@@ -197,7 +323,7 @@ HCL_CookTime(HCL_Instance clock, struct timespec *raw, struct timespec *cooked,
    return 0;

  elapsed = UTI_DiffTimespecsToDouble(raw, &clock->hw_ref);
-  offset = clock->offset + elapsed / clock->frequency;
+  offset = elapsed / clock->frequency - clock->offset;
  UTI_AddDoubleToTimespec(&clock->local_ref, offset, cooked);

  /* Fow now, just return the error of the last sample */
--- a/hwclock.h
+++ b/hwclock.h
@@ -29,7 +29,8 @@
 typedef struct HCL_Instance_Record *HCL_Instance;

 /* Create a new HW clock instance */
-extern HCL_Instance HCL_CreateInstance(void);
+extern HCL_Instance HCL_CreateInstance(int min_samples, int max_samples,
+                                       double min_separation, double precision);

 /* Destroy a HW clock instance */
 extern void HCL_DestroyInstance(HCL_Instance clock);
@@ -37,6 +38,11 @@ extern void HCL_DestroyInstance(HCL_Instance clock);
 /* Check if a new sample should be accumulated at this time */
 extern int HCL_NeedsNewSample(HCL_Instance clock, struct timespec *now);

+/* Process new readings of the HW clock in form of (sys, hw, sys) triplets and
+   produce a sample which can be accumulated */
+extern int HCL_ProcessReadings(HCL_Instance clock, int n_readings, struct timespec tss[][3],
+                               struct timespec *hw_ts, struct timespec *local_ts, double *err);
+
 /* Accumulate a new sample */
 extern void HCL_AccumulateSample(HCL_Instance clock, struct timespec *hw_ts,
                                 struct timespec *local_ts, double err);
--- a/keys.c
+++ b/keys.c
@@ -3,7 +3,7 @@

 **********************************************************************
 * Copyright (C) Richard P. Curnow  1997-2003
- * Copyright (C) Miroslav Lichvar  2012-2016
+ * Copyright (C) Miroslav Lichvar  2012-2016, 2019-2020
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
@@ -32,6 +32,7 @@

 #include "array.h"
 #include "keys.h"
+#include "cmac.h"
 #include "cmdparse.h"
 #include "conf.h"
 #include "memory.h"
@@ -42,12 +43,23 @@
 /* Consider 80 bits as the absolute minimum for a secure key */
 #define MIN_SECURE_KEY_LENGTH 10

+typedef enum {
+  NTP_MAC,
+  CMAC,
+} KeyClass;
+
 typedef struct {
  uint32_t id;
-  char *val;
-  int len;
-  int hash_id;
-  int auth_delay;
+  int type;
+  int length;
+  KeyClass class;
+  union {
+    struct {
+      unsigned char *value;
+      int hash_id;
+    } ntp_mac;
+    CMC_Instance cmac;
+  } data;
 } Key;

 static ARR_Instance keys;
@@ -62,9 +74,21 @@ static void
 free_keys(void)
 {
  unsigned int i;
+  Key *key;

-  for (i = 0; i < ARR_GetSize(keys); i++)
-    Free(((Key *)ARR_GetElement(keys, i))->val);
+  for (i = 0; i < ARR_GetSize(keys); i++) {
+    key = ARR_GetElement(keys, i);
+    switch (key->class) {
+      case NTP_MAC:
+        Free(key->data.ntp_mac.value);
+        break;
+      case CMAC:
+        CMC_DestroyInstance(key->data.cmac);
+        break;
+      default:
+        assert(0);
+    }
+  }

  ARR_SetSize(keys, 0);
  cache_valid = 0;
@@ -98,60 +122,18 @@ get_key(unsigned int index)
 }

 /* ================================================== */
+/* Decode key encoded in ASCII or HEX */

 static int
-determine_hash_delay(uint32_t key_id)
+decode_key(char *key)
 {
-  NTP_Packet pkt;
-  struct timespec before, after;
-  double diff, min_diff;
-  int i, nsecs;
-
-  for (i = 0; i < 10; i++) {
-    LCL_ReadRawTime(&before);
-    KEY_GenerateAuth(key_id, (unsigned char *)&pkt, NTP_NORMAL_PACKET_LENGTH,
-        (unsigned char *)&pkt.auth_data, sizeof (pkt.auth_data));
-    LCL_ReadRawTime(&after);
-
-    diff = UTI_DiffTimespecsToDouble(&after, &before);
-
-    if (i == 0 || min_diff > diff)
-      min_diff = diff;
-  }
-
-  /* Add on a bit extra to allow for copying, conversions etc */
-  nsecs = 1.0625e9 * min_diff;
-
-  DEBUG_LOG(LOGF_Keys, "authentication delay for key %"PRIu32": %d nsecs", key_id, nsecs);
-
-  return nsecs;
-}
-
-/* ================================================== */
-/* Decode password encoded in ASCII or HEX */
-
-static int
-decode_password(char *key)
-{
-  int i, j, len = strlen(key);
-  char buf[3], *p;
+  int len = strlen(key);

  if (!strncmp(key, "ASCII:", 6)) {
    memmove(key, key + 6, len - 6);
    return len - 6;
  } else if (!strncmp(key, "HEX:", 4)) {
-    if ((len - 4) % 2)
-      return 0;
-
-    for (i = 0, j = 4; j + 1 < len; i++, j += 2) {
-      buf[0] = key[j], buf[1] = key[j + 1], buf[2] = '\0';
-      key[i] = strtol(buf, &p, 16);
-
-      if (p != buf + 2)
-        return 0;
-    }
-
-    return i;
+    return UTI_HexToBytes(key + 4, key, len);
  } else {
    /* assume ASCII */
    return len;
@@ -183,11 +165,13 @@ compare_keys_by_id(const void *a, const void *b)
 void
 KEY_Reload(void)
 {
-  unsigned int i, line_number;
+  unsigned int i, line_number, key_length, cmac_key_length;
  FILE *in;
-  uint32_t key_id;
-  char line[2048], *keyval, *key_file;
-  const char *hashname;
+  char line[2048], *key_file, *key_value;
+  const char *key_type;
+  HSH_Algorithm hash_algorithm;
+  CMC_Algorithm cmac_algorithm;
+  int hash_id;
  Key key;

  free_keys();
@@ -198,9 +182,9 @@ KEY_Reload(void)
  if (!key_file)
    return;

-  in = fopen(key_file, "r");
+  in = UTI_OpenFile(NULL, key_file, NULL, 'r', 0);
  if (!in) {
-    LOG(LOGS_WARN, LOGF_Keys, "Could not open keyfile %s", key_file);
+    LOG(LOGS_WARN, "Could not open keyfile %s", key_file);
    return;
  }

@@ -211,26 +195,56 @@ KEY_Reload(void)
    if (!*line)
      continue;

-    if (!CPS_ParseKey(line, &key_id, &hashname, &keyval)) {
-      LOG(LOGS_WARN, LOGF_Keys, "Could not parse key at line %d in file %s", line_number, key_file);
+    memset(&key, 0, sizeof (key));
+
+    if (!CPS_ParseKey(line, &key.id, &key_type, &key_value)) {
+      LOG(LOGS_WARN, "Could not parse key at line %u in file %s", line_number, key_file);
      continue;
    }

-    key.hash_id = HSH_GetHashId(hashname);
-    if (key.hash_id < 0) {
-      LOG(LOGS_WARN, LOGF_Keys, "Unknown hash function in key %"PRIu32, key_id);
+    key_length = decode_key(key_value);
+    if (key_length == 0) {
+      LOG(LOGS_WARN, "Could not decode key %"PRIu32, key.id);
      continue;
    }

-    key.len = decode_password(keyval);
-    if (!key.len) {
-      LOG(LOGS_WARN, LOGF_Keys, "Could not decode password in key %"PRIu32, key_id);
+    hash_algorithm = UTI_HashNameToAlgorithm(key_type);
+    cmac_algorithm = UTI_CmacNameToAlgorithm(key_type);
+
+    if (hash_algorithm != 0) {
+      hash_id = HSH_GetHashId(hash_algorithm);
+      if (hash_id < 0) {
+        LOG(LOGS_WARN, "Unsupported %s in key %"PRIu32, "hash function", key.id);
+        continue;
+      }
+      key.class = NTP_MAC;
+      key.type = hash_algorithm;
+      key.length = key_length;
+      key.data.ntp_mac.value = MallocArray(unsigned char, key_length);
+      memcpy(key.data.ntp_mac.value, key_value, key_length);
+      key.data.ntp_mac.hash_id = hash_id;
+    } else if (cmac_algorithm != 0) {
+      cmac_key_length = CMC_GetKeyLength(cmac_algorithm);
+      if (cmac_key_length == 0) {
+        LOG(LOGS_WARN, "Unsupported %s in key %"PRIu32, "cipher", key.id);
+        continue;
+      } else if (cmac_key_length != key_length) {
+        LOG(LOGS_WARN, "Invalid length of %s key %"PRIu32" (expected %u bits)",
+            key_type, key.id, 8 * cmac_key_length);
+        continue;
+      }
+
+      key.class = CMAC;
+      key.type = cmac_algorithm;
+      key.length = key_length;
+      key.data.cmac = CMC_CreateInstance(cmac_algorithm, (unsigned char *)key_value,
+                                         key_length);
+      assert(key.data.cmac);
+    } else {
+      LOG(LOGS_WARN, "Invalid type in key %"PRIu32, key.id);
      continue;
    }

-    key.id = key_id;
-    key.val = MallocArray(char, key.len);
-    memcpy(key.val, keyval, key.len);
    ARR_AppendElement(keys, &key);
  }

@@ -244,14 +258,11 @@ KEY_Reload(void)
  /* Check for duplicates */
  for (i = 1; i < ARR_GetSize(keys); i++) {
    if (get_key(i - 1)->id == get_key(i)->id)
-      LOG(LOGS_WARN, LOGF_Keys, "Detected duplicate key %"PRIu32, get_key(i - 1)->id);
+      LOG(LOGS_WARN, "Detected duplicate key %"PRIu32, get_key(i - 1)->id);
  }

  /* Erase any passwords from stack */
  memset(line, 0, sizeof (line));
-
-  for (i = 0; i < ARR_GetSize(keys); i++)
-    get_key(i)->auth_delay = determine_hash_delay(get_key(i)->id);
 }

 /* ================================================== */
@@ -307,21 +318,6 @@ KEY_KeyKnown(uint32_t key_id)

 /* ================================================== */

-int
-KEY_GetAuthDelay(uint32_t key_id)
-{
-  Key *key;
-
-  key = get_key_by_id(key_id);
-
-  if (!key)
-    return 0;
-
-  return key->auth_delay;
-}
-
-/* ================================================== */
-
 int
 KEY_GetAuthLength(uint32_t key_id)
 {
@@ -333,7 +329,15 @@ KEY_GetAuthLength(uint32_t key_id)
  if (!key)
    return 0;

-  return HSH_Hash(key->hash_id, buf, 0, buf, 0, buf, sizeof (buf));
+  switch (key->class) {
+    case NTP_MAC:
+      return HSH_Hash(key->data.ntp_mac.hash_id, buf, 0, buf, 0, buf, sizeof (buf));
+    case CMAC:
+      return CMC_Hash(key->data.cmac, buf, 0, buf, sizeof (buf));
+    default:
+      assert(0);
+      return 0;
+  }
 }

 /* ================================================== */
@@ -348,39 +352,13 @@ KEY_CheckKeyLength(uint32_t key_id)
  if (!key)
    return 0;

-  return key->len >= MIN_SECURE_KEY_LENGTH;
-}
-
-/* ================================================== */
-
-static int
-generate_ntp_auth(int hash_id, const unsigned char *key, int key_len,
-                  const unsigned char *data, int data_len,
-                  unsigned char *auth, int auth_len)
-{
-  return HSH_Hash(hash_id, key, key_len, data, data_len, auth, auth_len);
-}
-
-/* ================================================== */
-
-static int
-check_ntp_auth(int hash_id, const unsigned char *key, int key_len,
-               const unsigned char *data, int data_len,
-               const unsigned char *auth, int auth_len, int trunc_len)
-{
-  unsigned char buf[MAX_HASH_LENGTH];
-  int hash_len;
-
-  hash_len = generate_ntp_auth(hash_id, key, key_len, data, data_len, buf, sizeof (buf));
-
-  return MIN(hash_len, trunc_len) == auth_len && !memcmp(buf, auth, auth_len);
+  return key->length >= MIN_SECURE_KEY_LENGTH;
 }

 /* ================================================== */

 int
-KEY_GenerateAuth(uint32_t key_id, const unsigned char *data, int data_len,
-    unsigned char *auth, int auth_len)
+KEY_GetKeyInfo(uint32_t key_id, int *type, int *bits)
 {
  Key *key;

@@ -389,14 +367,62 @@ KEY_GenerateAuth(uint32_t key_id, const unsigned char *data, int data_len,
  if (!key)
    return 0;

-  return generate_ntp_auth(key->hash_id, (unsigned char *)key->val, key->len,
-                           data, data_len, auth, auth_len);
+  *type = key->type;
+  *bits = 8 * key->length;
+
+  return 1;
+}
+
+/* ================================================== */
+
+static int
+generate_auth(Key *key, const void *data, int data_len, unsigned char *auth, int auth_len)
+{
+  switch (key->class) {
+    case NTP_MAC:
+      return HSH_Hash(key->data.ntp_mac.hash_id, key->data.ntp_mac.value,
+                      key->length, data, data_len, auth, auth_len);
+    case CMAC:
+      return CMC_Hash(key->data.cmac, data, data_len, auth, auth_len);
+    default:
+      return 0;
+  }
+}
+
+/* ================================================== */
+
+static int
+check_auth(Key *key, const void *data, int data_len,
+           const unsigned char *auth, int auth_len, int trunc_len)
+{
+  unsigned char buf[MAX_HASH_LENGTH];
+  int hash_len;
+
+  hash_len = generate_auth(key, data, data_len, buf, sizeof (buf));
+
+  return MIN(hash_len, trunc_len) == auth_len && !memcmp(buf, auth, auth_len);
 }

 /* ================================================== */

 int
-KEY_CheckAuth(uint32_t key_id, const unsigned char *data, int data_len,
+KEY_GenerateAuth(uint32_t key_id, const void *data, int data_len,
+                 unsigned char *auth, int auth_len)
+{
+  Key *key;
+
+  key = get_key_by_id(key_id);
+
+  if (!key)
+    return 0;
+
+  return generate_auth(key, data, data_len, auth, auth_len);
+}
+
+/* ================================================== */
+
+int
+KEY_CheckAuth(uint32_t key_id, const void *data, int data_len,
              const unsigned char *auth, int auth_len, int trunc_len)
 {
  Key *key;
@@ -406,6 +432,5 @@ KEY_CheckAuth(uint32_t key_id, const unsigned char *data, int data_len,
  if (!key)
    return 0;

-  return check_ntp_auth(key->hash_id, (unsigned char *)key->val, key->len,
-                        data, data_len, auth, auth_len, trunc_len);
+  return check_auth(key, data, data_len, auth, auth_len, trunc_len);
 }
--- a/keys.h
+++ b/keys.h
@@ -34,15 +34,14 @@ extern void KEY_Finalise(void);

 extern void KEY_Reload(void);

-extern int KEY_GetKey(uint32_t key_id, char **key, int *len);
 extern int KEY_KeyKnown(uint32_t key_id);
-extern int KEY_GetAuthDelay(uint32_t key_id);
 extern int KEY_GetAuthLength(uint32_t key_id);
 extern int KEY_CheckKeyLength(uint32_t key_id);
+extern int KEY_GetKeyInfo(uint32_t key_id, int *type, int *bits);

-extern int KEY_GenerateAuth(uint32_t key_id, const unsigned char *data,
-    int data_len, unsigned char *auth, int auth_len);
-extern int KEY_CheckAuth(uint32_t key_id, const unsigned char *data, int data_len,
+extern int KEY_GenerateAuth(uint32_t key_id, const void *data, int data_len,
+                            unsigned char *auth, int auth_len);
+extern int KEY_CheckAuth(uint32_t key_id, const void *data, int data_len,
                         const unsigned char *auth, int auth_len, int trunc_len);

 #endif /* GOT_KEYS_H */
--- a/local.c
+++ b/local.c
@@ -108,8 +108,8 @@ static double max_clock_error;

 #define NSEC_PER_SEC 1000000000

-static void
-calculate_sys_precision(void)
+static double
+measure_clock_precision(void)
 {
  struct timespec ts, old_ts;
  int iters, diff, best;
@@ -135,18 +135,7 @@ calculate_sys_precision(void)

  assert(best > 0);

-  precision_quantum = 1.0e-9 * best;
-
-  /* Get rounded log2 value of the measured precision */
-  precision_log = 0;
-  while (best < 707106781) {
-    precision_log--;
-    best *= 2;
-  }
-
-  assert(precision_log >= -30);
-
-  DEBUG_LOG(LOGF_Local, "Clock precision %.9f (%d)", precision_quantum, precision_log);
+  return 1.0e-9 * best;
 }

 /* ================================================== */
@@ -170,7 +159,16 @@ LCL_Initialise(void)
  current_freq_ppm = 0.0;
  temp_comp_ppm = 0.0;

-  calculate_sys_precision();
+  precision_quantum = CNF_GetClockPrecision();
+  if (precision_quantum <= 0.0)
+    precision_quantum = measure_clock_precision();
+
+  precision_quantum = CLAMP(1.0e-9, precision_quantum, 1.0);
+  precision_log = round(log(precision_quantum) / log(2.0));
+  /* NTP code doesn't support smaller log than -30 */
+  assert(precision_log >= -30);
+
+  DEBUG_LOG("Clock precision %.9f (%d)", precision_quantum, precision_log);

  /* This is the maximum allowed frequency offset in ppm, the time must
     never stop or run backwards */
@@ -185,13 +183,11 @@ LCL_Initialise(void)
 void
 LCL_Finalise(void)
 {
-  while (change_list.next != &change_list)
-    LCL_RemoveParameterChangeHandler(change_list.next->handler,
-                                     change_list.next->anything);
-
-  while (dispersion_notify_list.next != &dispersion_notify_list)
-    LCL_RemoveDispersionNotifyHandler(dispersion_notify_list.next->handler,
-                                      dispersion_notify_list.next->anything);
+  /* Make sure all handlers have been removed */
+  if (change_list.next != &change_list)
+    assert(0);
+  if (dispersion_notify_list.next != &dispersion_notify_list)
+    assert(0);
 }

 /* ================================================== */
@@ -358,12 +354,12 @@ LCL_ReadRawTime(struct timespec *ts)
 {
 #if HAVE_CLOCK_GETTIME
  if (clock_gettime(CLOCK_REALTIME, ts) < 0)
-    LOG_FATAL(LOGF_Local, "clock_gettime() failed : %s", strerror(errno));
+    LOG_FATAL("clock_gettime() failed : %s", strerror(errno));
 #else
  struct timeval tv;

  if (gettimeofday(&tv, NULL) < 0)
-    LOG_FATAL(LOGF_Local, "gettimeofday() failed : %s", strerror(errno));
+    LOG_FATAL("gettimeofday() failed : %s", strerror(errno));

  UTI_TimevalToTimespec(&tv, ts);
 #endif
@@ -426,7 +422,7 @@ clamp_freq(double freq)
  if (freq <= max_freq_ppm && freq >= -max_freq_ppm)
    return freq;

-  LOG(LOGS_WARN, LOGF_Local, "Frequency %.1f ppm exceeds allowed maximum", freq);
+  LOG(LOGS_WARN, "Frequency %.1f ppm exceeds allowed maximum", freq);

  return CLAMP(-max_freq_ppm, freq, max_freq_ppm);
 }
@@ -440,7 +436,7 @@ check_offset(struct timespec *now, double offset)
  if (UTI_IsTimeOffsetSane(now, -offset))
      return 1;

-  LOG(LOGS_WARN, LOGF_Local, "Adjustment of %.1f seconds is invalid", -offset);
+  LOG(LOGS_WARN, "Adjustment of %.1f seconds is invalid", -offset);
  return 0;
 }

@@ -509,7 +505,7 @@ LCL_AccumulateDeltaFrequency(double dfreq)

 /* ================================================== */

-void
+int
 LCL_AccumulateOffset(double offset, double corr_rate)
 {
  struct timespec raw, cooked;
@@ -521,12 +517,14 @@ LCL_AccumulateOffset(double offset, double corr_rate)
  LCL_CookTime(&raw, &cooked, NULL);

  if (!check_offset(&cooked, offset))
-      return;
+    return 0;

  (*drv_accrue_offset)(offset, corr_rate);

  /* Dispatch to all handlers */
  invoke_parameter_change_handlers(&raw, &cooked, 0.0, offset, LCL_ChangeAdjust);
+
+  return 1;
 }

 /* ================================================== */
@@ -546,7 +544,7 @@ LCL_ApplyStepOffset(double offset)
      return 0;

  if (!(*drv_apply_step_offset)(offset)) {
-    LOG(LOGS_ERR, LOGF_Local, "Could not step clock");
+    LOG(LOGS_ERR, "Could not step system clock");
    return 0;
  }

@@ -565,6 +563,8 @@ void
 LCL_NotifyExternalTimeStep(struct timespec *raw, struct timespec *cooked,
    double offset, double dispersion)
 {
+  LCL_CancelOffsetCorrection();
+
  /* Dispatch to all handlers */
  invoke_parameter_change_handlers(raw, cooked, 0.0, offset, LCL_ChangeUnknownStep);

@@ -590,7 +590,7 @@ LCL_NotifyLeap(int leap)

 /* ================================================== */

-void
+int
 LCL_AccumulateFrequencyAndOffset(double dfreq, double doffset, double corr_rate)
 {
  struct timespec raw, cooked;
@@ -602,7 +602,7 @@ LCL_AccumulateFrequencyAndOffset(double dfreq, double doffset, double corr_rate)
  LCL_CookTime(&raw, &cooked, NULL);

  if (!check_offset(&cooked, doffset))
-      return;
+    return 0;

  old_freq_ppm = current_freq_ppm;

@@ -613,7 +613,7 @@ LCL_AccumulateFrequencyAndOffset(double dfreq, double doffset, double corr_rate)

  current_freq_ppm = clamp_freq(current_freq_ppm);

-  DEBUG_LOG(LOGF_Local, "old_freq=%.3fppm new_freq=%.3fppm offset=%.6fsec",
+  DEBUG_LOG("old_freq=%.3fppm new_freq=%.3fppm offset=%.6fsec",
      old_freq_ppm, current_freq_ppm, doffset);

  /* Call the system-specific driver for setting the frequency */
@@ -624,6 +624,26 @@ LCL_AccumulateFrequencyAndOffset(double dfreq, double doffset, double corr_rate)

  /* Dispatch to all handlers */
  invoke_parameter_change_handlers(&raw, &cooked, dfreq, doffset, LCL_ChangeAdjust);
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+LCL_AccumulateFrequencyAndOffsetNoHandlers(double dfreq, double doffset, double corr_rate)
+{
+  ChangeListEntry *first_handler;
+  int r;
+
+  first_handler = change_list.next;
+  change_list.next = &change_list;
+
+  r = LCL_AccumulateFrequencyAndOffset(dfreq, doffset, corr_rate);
+
+  change_list.next = first_handler;
+
+  return r;
 }

 /* ================================================== */
@@ -660,7 +680,7 @@ lcl_RegisterSystemDrivers(lcl_ReadFrequencyDriver read_freq,

  current_freq_ppm = (*drv_read_freq)();

-  DEBUG_LOG(LOGF_Local, "Local freq=%.3fppm", current_freq_ppm);
+  DEBUG_LOG("Local freq=%.3fppm", current_freq_ppm);
 }

 /* ================================================== */
@@ -684,13 +704,26 @@ LCL_MakeStep(void)
  if (!LCL_ApplyStepOffset(-correction))
    return 0;

-  LOG(LOGS_WARN, LOGF_Local, "System clock was stepped by %.6f seconds", correction);
+  LOG(LOGS_WARN, "System clock was stepped by %.6f seconds", correction);

  return 1;
 }

 /* ================================================== */

+void
+LCL_CancelOffsetCorrection(void)
+{
+  struct timespec raw;
+  double correction;
+
+  LCL_ReadRawTime(&raw);
+  LCL_GetOffsetCorrection(&raw, &correction, NULL);
+  LCL_AccumulateOffset(correction, 0.0);
+}
+
+/* ================================================== */
+
 int
 LCL_CanSystemLeap(void)
 {
@@ -700,10 +733,10 @@ LCL_CanSystemLeap(void)
 /* ================================================== */

 void
-LCL_SetSystemLeap(int leap)
+LCL_SetSystemLeap(int leap, int tai_offset)
 {
  if (drv_set_leap) {
-    (drv_set_leap)(leap);
+    (drv_set_leap)(leap, tai_offset);
  }
 }

--- a/local.h
+++ b/local.h
@@ -149,7 +149,7 @@ extern void LCL_AccumulateDeltaFrequency(double dfreq);
   forwards (i.e. it is currently slow of true time).  Provided is also
   a suggested correction rate (correction time * offset). */

-extern void LCL_AccumulateOffset(double offset, double corr_rate);
+extern int LCL_AccumulateOffset(double offset, double corr_rate);

 /* Routine to apply an immediate offset by doing a sudden step if
   possible. (Intended for use after an initial estimate of offset has
@@ -171,7 +171,12 @@ extern void LCL_NotifyLeap(int leap);

 /* Perform the combination of modifying the frequency and applying
   a slew, in one easy step */
-extern void LCL_AccumulateFrequencyAndOffset(double dfreq, double doffset, double corr_rate);
+extern int LCL_AccumulateFrequencyAndOffset(double dfreq, double doffset, double corr_rate);
+
+/* Same as the routine above, except it does not call the registered
+   parameter change handlers */
+extern int LCL_AccumulateFrequencyAndOffsetNoHandlers(double dfreq, double doffset,
+                                                      double corr_rate);

 /* Routine to read the system precision as a log to base 2 value. */
 extern int LCL_GetSysPrecisionAsLog(void);
@@ -197,14 +202,18 @@ extern void LCL_Finalise(void);
   to a timezone problem. */
 extern int LCL_MakeStep(void);

+/* Routine to cancel the outstanding system clock correction */
+extern void LCL_CancelOffsetCorrection(void);
+
 /* Check if the system driver supports leap seconds, i.e. LCL_SetSystemLeap
   does something */
 extern int LCL_CanSystemLeap(void);

-/* Routine to set the system clock to correct itself for a leap second if
-   supported.  Leap second will be inserted at the end of the day if the
-   argument is positive, deleted if negative, and zero resets the setting. */
-extern void LCL_SetSystemLeap(int leap);
+/* Routine to set the system clock to correct itself for a leap second and also
+   set its TAI-UTC offset.  If supported, leap second will be inserted at the
+   end of the day if the argument is positive, deleted if negative, and zero
+   resets the setting. */
+extern void LCL_SetSystemLeap(int leap, int tai_offset);

 /* Routine to set a frequency correction (in ppm) that should be applied
   to local clock to compensate for temperature changes.  A positive
--- a/localp.h
+++ b/localp.h
@@ -54,8 +54,8 @@ typedef int (*lcl_ApplyStepOffsetDriver)(double offset);
   raw time to get the corrected time */
 typedef void (*lcl_OffsetCorrectionDriver)(struct timespec *raw, double *corr, double *err);

-/* System driver to schedule leap second */
-typedef void (*lcl_SetLeapDriver)(int leap);
+/* System driver to schedule leap seconds and set TAI-UTC offset */
+typedef void (*lcl_SetLeapDriver)(int leap, int tai_offset);

 /* System driver to set the synchronisation status */
 typedef void (*lcl_SetSyncStatusDriver)(int synchronised, double est_error, double max_error);
--- a/logging.c
+++ b/logging.c
@@ -3,7 +3,7 @@

 **********************************************************************
 * Copyright (C) Richard P. Curnow  1997-2003
- * Copyright (C) Miroslav Lichvar  2011-2014
+ * Copyright (C) Miroslav Lichvar  2011-2014, 2018-2020
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
@@ -29,25 +29,25 @@

 #include "sysincl.h"

+#include <syslog.h>
+
 #include "conf.h"
 #include "logging.h"
+#include "memory.h"
 #include "util.h"

 /* This is used by DEBUG_LOG macro */
-int log_debug_enabled = 0;
+LOG_Severity log_min_severity = LOGS_INFO;

 /* ================================================== */
 /* Flag indicating we have initialised */
 static int initialised = 0;

+static FILE *file_log = NULL;
 static int system_log = 0;

 static int parent_fd = 0;

-#define DEBUG_LEVEL_PRINT_FUNCTION 2
-#define DEBUG_LEVEL_PRINT_DEBUG 2
-static int debug_level = 0;
-
 struct LogFile {
  const char *name;
  const char *banner;
@@ -62,13 +62,18 @@ static int n_filelogs = 0;

 static struct LogFile logfiles[MAX_FILELOGS];

+/* Global prefix for debug messages */
+static char *debug_prefix;
+
 /* ================================================== */
 /* Init function */

 void
 LOG_Initialise(void)
 {
+  debug_prefix = Strdup("");
  initialised = 1;
+  LOG_OpenFileLog(NULL);
 }

 /* ================================================== */
@@ -77,12 +82,16 @@ LOG_Initialise(void)
 void
 LOG_Finalise(void)
 {
-  if (system_log) {
+  if (system_log)
    closelog();
-  }
+
+  if (file_log)
+    fclose(file_log);

  LOG_CycleLogFiles();

+  Free(debug_prefix);
+
  initialised = 0;
 }

@@ -112,8 +121,8 @@ static void log_message(int fatal, LOG_Severity severity, const char *message)
        assert(0);
    }
    syslog(priority, fatal ? "Fatal error : %s" : "%s", message);
-  } else {
-    fprintf(stderr, fatal ? "Fatal error : %s\n" : "%s\n", message);
+  } else if (file_log) {
+    fprintf(file_log, fatal ? "Fatal error : %s\n" : "%s\n", message);
  }
 }

@@ -121,25 +130,28 @@ static void log_message(int fatal, LOG_Severity severity, const char *message)

 void LOG_Message(LOG_Severity severity,
 #if DEBUG > 0
-                 LOG_Facility facility, int line_number,
-                 const char *filename, const char *function_name,
+                 int line_number, const char *filename, const char *function_name,
 #endif
                 const char *format, ...)
 {
  char buf[2048];
  va_list other_args;
  time_t t;
-  struct tm stm;
+  struct tm *tm;

-  if (!system_log) {
+  assert(initialised);
+
+  if (!system_log && file_log && severity >= log_min_severity) {
    /* Don't clutter up syslog with timestamps and internal debugging info */
    time(&t);
-    stm = *gmtime(&t);
-    strftime(buf, sizeof(buf), "%Y-%m-%dT%H:%M:%SZ", &stm);
-    fprintf(stderr, "%s ", buf);
+    tm = gmtime(&t);
+    if (tm) {
+      strftime(buf, sizeof (buf), "%Y-%m-%dT%H:%M:%SZ", tm);
+      fprintf(file_log, "%s ", buf);
+    }
 #if DEBUG > 0
-    if (debug_level >= DEBUG_LEVEL_PRINT_FUNCTION)
-      fprintf(stderr, "%s:%d:(%s) ", filename, line_number, function_name);
+    if (log_min_severity <= LOGS_DEBUG)
+      fprintf(file_log, "%s%s:%d:(%s) ", debug_prefix, filename, line_number, function_name);
 #endif
  }

@@ -152,28 +164,52 @@ void LOG_Message(LOG_Severity severity,
    case LOGS_INFO:
    case LOGS_WARN:
    case LOGS_ERR:
-      log_message(0, severity, buf);
+      if (severity >= log_min_severity)
+        log_message(0, severity, buf);
      break;
    case LOGS_FATAL:
-      log_message(1, severity, buf);
+      if (severity >= log_min_severity)
+        log_message(1, severity, buf);

-      /* With syslog, send the message also to the grandparent
-         process or write it to stderr if not detached */
-      if (system_log) {
-        if (parent_fd > 0) {
-          if (write(parent_fd, buf, strlen(buf) + 1) < 0)
-            ; /* Not much we can do here */
-        } else if (parent_fd == 0) {
-          system_log = 0;
-          log_message(1, severity, buf);
-        }
+      /* Send the message also to the foreground process if it is
+         still running, or stderr if it is still open */
+      if (parent_fd > 0) {
+        if (write(parent_fd, buf, strlen(buf) + 1) < 0)
+          ; /* Not much we can do here */
+      } else if (system_log && parent_fd == 0) {
+        system_log = 0;
+        log_message(1, severity, buf);
      }
+      exit(1);
      break;
    default:
      assert(0);
  }
 }

+/* ================================================== */
+
+void
+LOG_OpenFileLog(const char *log_file)
+{
+  FILE *f;
+
+  if (log_file) {
+    f = UTI_OpenFile(NULL, log_file, NULL, 'A', 0640);
+  } else {
+    f = stderr;
+  }
+
+  /* Enable line buffering */
+  setvbuf(f, NULL, _IOLBF, BUFSIZ);
+
+  if (file_log && file_log != stderr)
+    fclose(file_log);
+
+  file_log = f;
+}
+
+
 /* ================================================== */

 void
@@ -185,12 +221,27 @@ LOG_OpenSystemLog(void)

 /* ================================================== */

-void LOG_SetDebugLevel(int level)
+void LOG_SetMinSeverity(LOG_Severity severity)
 {
-  debug_level = level;
-  if (level >= DEBUG_LEVEL_PRINT_DEBUG) {
-    log_debug_enabled = 1;
-  }
+  /* Don't print any debug messages in a non-debug build */
+  log_min_severity = CLAMP(DEBUG > 0 ? LOGS_DEBUG : LOGS_INFO, severity, LOGS_FATAL);
+}
+
+/* ================================================== */
+
+LOG_Severity
+LOG_GetMinSeverity(void)
+{
+  return log_min_severity;
+}
+
+/* ================================================== */
+
+void
+LOG_SetDebugPrefix(const char *prefix)
+{
+  Free(debug_prefix);
+  debug_prefix = Strdup(prefix);
 }

 /* ================================================== */
@@ -199,6 +250,8 @@ void
 LOG_SetParentFd(int fd)
 {
  parent_fd = fd;
+  if (file_log == stderr)
+    file_log = NULL;
 }

 /* ================================================== */
@@ -216,7 +269,10 @@ LOG_CloseParentFd()
 LOG_FileID
 LOG_FileOpen(const char *name, const char *banner)
 {
-  assert(n_filelogs < MAX_FILELOGS);
+  if (n_filelogs >= MAX_FILELOGS) {
+    assert(0);
+    return -1;
+  }

  logfiles[n_filelogs].name = name;
  logfiles[n_filelogs].banner = banner;
@@ -238,24 +294,20 @@ LOG_FileWrite(LOG_FileID id, const char *format, ...)
    return;

  if (!logfiles[id].file) {
-    char filename[512], *logdir = CNF_GetLogDir();
+    char *logdir = CNF_GetLogDir();

-    if (logdir[0] == '\0') {
-      LOG(LOGS_WARN, LOGF_Logging, "logdir not specified");
+    if (!logdir) {
+      LOG(LOGS_WARN, "logdir not specified");
      logfiles[id].name = NULL;
      return;
    }

-    if (snprintf(filename, sizeof(filename), "%s/%s.log",
-                 logdir, logfiles[id].name) >= sizeof (filename) ||
-        !(logfiles[id].file = fopen(filename, "a"))) {
-      LOG(LOGS_WARN, LOGF_Logging, "Could not open log file %s", filename);
+    logfiles[id].file = UTI_OpenFile(logdir, logfiles[id].name, ".log", 'a', 0644);
+    if (!logfiles[id].file) {
+      /* Disable the log */
      logfiles[id].name = NULL;
      return;
    }
-
-    /* Close on exec */
-    UTI_FdSetCloexec(fileno(logfiles[id].file));
  }

  banner = CNF_GetLogBanner();
@@ -263,7 +315,7 @@ LOG_FileWrite(LOG_FileID id, const char *format, ...)
    char bannerline[256];
    int i, bannerlen;

-    bannerlen = strlen(logfiles[id].banner);
+    bannerlen = MIN(strlen(logfiles[id].banner), sizeof (bannerline) - 1);

    for (i = 0; i < bannerlen; i++)
      bannerline[i] = '=';
--- a/logging.h
+++ b/logging.h
@@ -31,9 +31,6 @@

 #include "sysincl.h"

-/* Flag indicating whether debug messages are logged */
-extern int log_debug_enabled;
-
 /* Line logging macros.  If the compiler is GNU C, we take advantage of
   being able to get the function name also. */

@@ -46,79 +43,38 @@ extern int log_debug_enabled;
 #endif

 #if DEBUG > 0
-#define LOG_MESSAGE(severity, facility, ...) \
-  LOG_Message(severity, facility, __LINE__, __FILE__, FUNCTION_NAME, __VA_ARGS__)
+#define LOG_MESSAGE(severity, ...) \
+  LOG_Message(severity, __LINE__, __FILE__, FUNCTION_NAME, __VA_ARGS__)
 #else
-#define LOG_MESSAGE(severity, facility, ...) \
+#define LOG_MESSAGE(severity, ...) \
  LOG_Message(severity, __VA_ARGS__)
 #endif

-#define DEBUG_LOG(facility, ...) \
+#define DEBUG_LOG(...) \
  do { \
-    if (DEBUG && log_debug_enabled) \
-      LOG_MESSAGE(LOGS_DEBUG, facility, __VA_ARGS__); \
+    if (DEBUG && log_min_severity == LOGS_DEBUG) \
+      LOG_MESSAGE(LOGS_DEBUG, __VA_ARGS__); \
  } while (0)

-#define LOG_FATAL(facility, ...) \
+#define LOG_FATAL(...) \
  do { \
-    LOG_MESSAGE(LOGS_FATAL, facility, __VA_ARGS__); \
+    LOG_MESSAGE(LOGS_FATAL, __VA_ARGS__); \
    exit(1); \
  } while (0)

-#define LOG(severity, facility, ...) LOG_MESSAGE(severity, facility, __VA_ARGS__)
+#define LOG(severity, ...) LOG_MESSAGE(severity, __VA_ARGS__)

 /* Definition of severity */
 typedef enum {
-  LOGS_INFO,
+  LOGS_DEBUG = -1,
+  LOGS_INFO = 0,
  LOGS_WARN,
  LOGS_ERR,
  LOGS_FATAL,
-  LOGS_DEBUG
 } LOG_Severity;

-/* Definition of facility.  Each message is tagged with who generated
-   it, so that the user can customise what level of reporting he gets
-   for each area of the software */
-typedef enum {
-  LOGF_Reference,
-  LOGF_NtpIO,
-  LOGF_NtpIOLinux,
-  LOGF_NtpCore,
-  LOGF_NtpSignd,
-  LOGF_NtpSources,
-  LOGF_Scheduler,
-  LOGF_SourceStats,
-  LOGF_Sources,
-  LOGF_Local,
-  LOGF_Util,
-  LOGF_Main,
-  LOGF_Memory,
-  LOGF_Client,
-  LOGF_ClientLog,
-  LOGF_Configure,
-  LOGF_CmdMon,
-  LOGF_Acquire,
-  LOGF_Manual,
-  LOGF_Keys,
-  LOGF_Logging,
-  LOGF_Nameserv,
-  LOGF_PrivOps,
-  LOGF_Rtc,
-  LOGF_Regress,
-  LOGF_Sys,
-  LOGF_SysGeneric,
-  LOGF_SysLinux,
-  LOGF_SysMacOSX,
-  LOGF_SysNetBSD,
-  LOGF_SysSolaris,
-  LOGF_SysTimex,
-  LOGF_SysWinnt,
-  LOGF_TempComp,
-  LOGF_RtcLinux,
-  LOGF_Refclock,
-  LOGF_HwClocks,
-  LOGF_Smooth,
-} LOG_Facility;
+/* Minimum severity of messages to be logged */
+extern LOG_Severity log_min_severity;

 /* Init function */
 extern void LOG_Initialise(void);
@@ -128,26 +84,32 @@ extern void LOG_Finalise(void);

 /* Line logging function */
 #if DEBUG > 0
-FORMAT_ATTRIBUTE_PRINTF(6, 7)
-extern void LOG_Message(LOG_Severity severity, LOG_Facility facility,
-                        int line_number, const char *filename,
+FORMAT_ATTRIBUTE_PRINTF(5, 6)
+extern void LOG_Message(LOG_Severity severity, int line_number, const char *filename,
                        const char *function_name, const char *format, ...);
 #else
 FORMAT_ATTRIBUTE_PRINTF(2, 3)
 extern void LOG_Message(LOG_Severity severity, const char *format, ...);
 #endif

-/* Set debug level:
-   0, 1 - only non-debug messages are logged
-   2    - debug messages are logged too, all messages are prefixed with
-          filename, line, and function name
-   */
-extern void LOG_SetDebugLevel(int level);
+/* Set the minimum severity of a message to be logged or printed to terminal.
+   If the severity is LOGS_DEBUG and DEBUG is enabled, all messages will be
+   prefixed with the filename, line number, and function name. */
+extern void LOG_SetMinSeverity(LOG_Severity severity);
+
+/* Get the minimum severity */
+extern LOG_Severity LOG_GetMinSeverity(void);
+
+/* Set a prefix for debug messages */
+extern void LOG_SetDebugPrefix(const char *prefix);
+
+/* Log messages to a file instead of stderr, or stderr again if NULL */
+extern void LOG_OpenFileLog(const char *log_file);

 /* Log messages to syslog instead of stderr */
 extern void LOG_OpenSystemLog(void);

-/* Send fatal message also to the foreground process */
+/* Stop using stderr and send fatal message to the foreground process */
 extern void LOG_SetParentFd(int fd);

 /* Close the pipe to the foreground process so it can exit */
--- a/main.c
+++ b/main.c
@@ -4,7 +4,7 @@
 **********************************************************************
 * Copyright (C) Richard P. Curnow  1997-2003
 * Copyright (C) John G. Hasler  2009
- * Copyright (C) Miroslav Lichvar  2012-2015
+ * Copyright (C) Miroslav Lichvar  2012-2020
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
@@ -38,6 +38,9 @@
 #include "ntp_signd.h"
 #include "ntp_sources.h"
 #include "ntp_core.h"
+#include "nts_ke_server.h"
+#include "nts_ntp_server.h"
+#include "socket.h"
 #include "sources.h"
 #include "sourcestats.h"
 #include "reference.h"
@@ -73,11 +76,18 @@ static REF_Mode ref_mode = REF_ModeNormal;
 static void
 do_platform_checks(void)
 {
+  struct timespec ts;
+
  /* Require at least 32-bit integers, two's complement representation and
     the usual implementation of conversion of unsigned integers */
  assert(sizeof (int) >= 4);
  assert(-1 == ~0);
  assert((int32_t)4294967295U == (int32_t)-1);
+
+  /* Require time_t and tv_nsec in timespec to be signed */
+  ts.tv_sec = -1;
+  ts.tv_nsec = -1;
+  assert(ts.tv_sec < 0 && ts.tv_nsec < 0);
 }

 /* ================================================== */
@@ -86,8 +96,12 @@ static void
 delete_pidfile(void)
 {
  const char *pidfile = CNF_GetPidFile();
-  /* Don't care if this fails, there's not a lot we can do */
-  unlink(pidfile);
+
+  if (!pidfile)
+    return;
+
+  if (!UTI_RemoveFile(NULL, pidfile, NULL))
+    ;
 }

 /* ================================================== */
@@ -97,9 +111,8 @@ MAI_CleanupAndExit(void)
 {
  if (!initialised) exit(exit_status);
  
-  if (CNF_GetDumpOnExit()) {
-    SRC_DumpSources();
-  }
+  LCL_CancelOffsetCorrection();
+  SRC_DumpSources();

  /* Don't update clock when removing sources */
  REF_SetMode(REF_ModeIgnore);
@@ -108,18 +121,23 @@ MAI_CleanupAndExit(void)
  TMC_Finalise();
  MNL_Finalise();
  CLG_Finalise();
+  NKS_Finalise();
+  NNS_Finalise();
  NSD_Finalise();
  NSR_Finalise();
  SST_Finalise();
  NCR_Finalise();
  NIO_Finalise();
  CAM_Finalise();
+
  KEY_Finalise();
  RCL_Finalise();
  SRC_Finalise();
  REF_Finalise();
  RTC_Finalise();
  SYS_Finalise();
+
+  SCK_Finalise();
  SCH_Finalise();
  LCL_Finalise();
  PRV_Finalise();
@@ -127,9 +145,10 @@ MAI_CleanupAndExit(void)
  delete_pidfile();
  
  CNF_Finalise();
+  HSH_Finalise();
  LOG_Finalise();

-  HSH_Finalise();
+  UTI_ResetGetRandomFunctions();

  exit(exit_status);
 }
@@ -139,7 +158,6 @@ MAI_CleanupAndExit(void)
 static void
 signal_cleanup(int x)
 {
-  if (!initialised) exit(0);
  SCH_QuitProgram();
 }

@@ -148,6 +166,8 @@ signal_cleanup(int x)
 static void
 quit_timeout(void *arg)
 {
+  LOG(LOGS_INFO, "Timeout reached");
+
  /* Return with non-zero status if the clock is not synchronised */
  exit_status = REF_GetOurStratum() >= NTP_MAX_STRATUM;
  SCH_QuitProgram();
@@ -175,7 +195,7 @@ ntp_source_resolving_end(void)
  NSR_AutoStartSources();

  /* Special modes can end only when sources update their reachability.
-     Give up immediatelly if there are no active sources. */
+     Give up immediately if there are no active sources. */
  if (ref_mode != REF_ModeNormal && !SRC_ActiveSources()) {
    REF_SetUnsynchronised();
  }
@@ -242,63 +262,54 @@ post_init_rtc_hook(void *anything)
 }

 /* ================================================== */
-/* Return 1 if the process exists on the system. */

-static int
-does_process_exist(int pid)
-{
-  int status;
-  status = getsid(pid);
-  if (status >= 0) {
-    return 1;
-  } else {
-    return 0;
-  }
-}
-
-/* ================================================== */
-
-static int
-maybe_another_chronyd_running(int *other_pid)
+static void
+check_pidfile(void)
 {
  const char *pidfile = CNF_GetPidFile();
  FILE *in;
  int pid, count;
  
-  *other_pid = 0;
+  if (!pidfile)
+    return;

-  in = fopen(pidfile, "r");
-  if (!in) return 0;
+  in = UTI_OpenFile(NULL, pidfile, NULL, 'r', 0);
+  if (!in)
+    return;

  count = fscanf(in, "%d", &pid);
  fclose(in);
  
-  if (count != 1) return 0;
+  if (count != 1)
+    return;

-  *other_pid = pid;
-  return does_process_exist(pid);
-  
+  if (getsid(pid) < 0)
+    return;
+
+  LOG_FATAL("Another chronyd may already be running (pid=%d), check %s",
+            pid, pidfile);
 }

 /* ================================================== */

 static void
-write_lockfile(void)
+write_pidfile(void)
 {
  const char *pidfile = CNF_GetPidFile();
  FILE *out;

-  out = fopen(pidfile, "w");
-  if (!out) {
-    LOG_FATAL(LOGF_Main, "could not open lockfile %s for writing", pidfile);
-  } else {
-    fprintf(out, "%d\n", (int)getpid());
-    fclose(out);
-  }
+  if (!pidfile)
+    return;
+
+  out = UTI_OpenFile(NULL, pidfile, NULL, 'W', 0644);
+  fprintf(out, "%d\n", (int)getpid());
+  fclose(out);
 }

 /* ================================================== */

+#define DEV_NULL "/dev/null"
+
 static void
 go_daemon(void)
 {
@@ -307,14 +318,14 @@ go_daemon(void)
  /* Create pipe which will the daemon use to notify the grandparent
     when it's initialised or send an error message */
  if (pipe(pipefd)) {
-    LOG_FATAL(LOGF_Main, "Could not detach, pipe failed : %s", strerror(errno));
+    LOG_FATAL("pipe() failed : %s", strerror(errno));
  }

  /* Does this preserve existing signal handlers? */
  pid = fork();

  if (pid < 0) {
-    LOG_FATAL(LOGF_Main, "Could not detach, fork failed : %s", strerror(errno));
+    LOG_FATAL("fork() failed : %s", strerror(errno));
  } else if (pid > 0) {
    /* In the 'grandparent' */
    char message[1024];
@@ -340,7 +351,7 @@ go_daemon(void)
    pid = fork();

    if (pid < 0) {
-      LOG_FATAL(LOGF_Main, "Could not detach, fork failed : %s", strerror(errno));
+      LOG_FATAL("fork() failed : %s", strerror(errno));
    } else if (pid > 0) {
      exit(0); /* In the 'parent' */
    } else {
@@ -348,7 +359,7 @@ go_daemon(void)

      /* Change current directory to / */
      if (chdir("/") < 0) {
-        LOG_FATAL(LOGF_Main, "Could not chdir to / : %s", strerror(errno));
+        LOG_FATAL("chdir() failed : %s", strerror(errno));
      }

      /* Don't keep stdin/out/err from before. But don't close
@@ -359,156 +370,257 @@ go_daemon(void)
      }

      LOG_SetParentFd(pipefd[1]);
+
+      /* Open /dev/null as new stdin/out/err */
+      errno = 0;
+      if (open(DEV_NULL, O_RDONLY) != STDIN_FILENO ||
+          open(DEV_NULL, O_WRONLY) != STDOUT_FILENO ||
+          open(DEV_NULL, O_RDWR) != STDERR_FILENO)
+        LOG_FATAL("Could not open %s : %s", DEV_NULL, strerror(errno));
    }
  }
 }

 /* ================================================== */

+static void
+print_help(const char *progname)
+{
+      printf("Usage: %s [OPTION]... [DIRECTIVE]...\n\n"
+             "Options:\n"
+             "  -4\t\tUse IPv4 addresses only\n"
+             "  -6\t\tUse IPv6 addresses only\n"
+             "  -f FILE\tSpecify configuration file (%s)\n"
+             "  -n\t\tDon't run as daemon\n"
+             "  -d\t\tDon't run as daemon and log to stderr\n"
+#if DEBUG > 0
+             "  -d -d\t\tEnable debug messages\n"
+#endif
+             "  -l FILE\tLog to file\n"
+             "  -L LEVEL\tSet logging threshold (0)\n"
+             "  -p\t\tPrint configuration and exit\n"
+             "  -q\t\tSet clock and exit\n"
+             "  -Q\t\tLog offset and exit\n"
+             "  -r\t\tReload dump files\n"
+             "  -R\t\tAdapt configuration for restart\n"
+             "  -s\t\tSet clock from RTC\n"
+             "  -t SECONDS\tExit after elapsed time\n"
+             "  -u USER\tSpecify user (%s)\n"
+             "  -U\t\tDon't check for root\n"
+             "  -F LEVEL\tSet system call filter level (0)\n"
+             "  -P PRIORITY\tSet process priority (0)\n"
+             "  -m\t\tLock memory\n"
+             "  -x\t\tDon't control clock\n"
+             "  -v, --version\tPrint version and exit\n"
+             "  -h, --help\tPrint usage and exit\n",
+             progname, DEFAULT_CONF_FILE, DEFAULT_USER);
+}
+
+/* ================================================== */
+
+static void
+print_version(void)
+{
+  printf("chronyd (chrony) version %s (%s)\n", CHRONY_VERSION, CHRONYD_FEATURES);
+}
+
+/* ================================================== */
+
+static int
+parse_int_arg(const char *arg)
+{
+  int i;
+
+  if (sscanf(arg, "%d", &i) != 1)
+    LOG_FATAL("Invalid argument %s", arg);
+  return i;
+}
+
+/* ================================================== */
+
 int main
 (int argc, char **argv)
 {
  const char *conf_file = DEFAULT_CONF_FILE;
  const char *progname = argv[0];
-  char *user = NULL;
+  char *user = NULL, *log_file = NULL;
  struct passwd *pw;
-  int debug = 0, nofork = 0, address_family = IPADDR_UNSPEC;
-  int do_init_rtc = 0, restarted = 0, timeout = 0;
-  int other_pid;
+  int opt, debug = 0, nofork = 0, address_family = IPADDR_UNSPEC;
+  int do_init_rtc = 0, restarted = 0, client_only = 0, timeout = -1;
  int scfilter_level = 0, lock_memory = 0, sched_priority = 0;
-  int system_log = 1;
-  int config_args = 0;
+  int clock_control = 1, system_log = 1, log_severity = LOGS_INFO;
+  int user_check = 1, config_args = 0, print_config = 0;

  do_platform_checks();

  LOG_Initialise();

-  /* Parse command line options */
-  while (++argv, (--argc)>0) {
-
-    if (!strcmp("-f", *argv)) {
-      ++argv, --argc;
-      conf_file = *argv;
-    } else if (!strcmp("-P", *argv)) {
-      ++argv, --argc;
-      if (argc == 0 || sscanf(*argv, "%d", &sched_priority) != 1) {
-        LOG_FATAL(LOGF_Main, "Bad scheduler priority");
-      }
-    } else if (!strcmp("-m", *argv)) {
-      lock_memory = 1;
-    } else if (!strcmp("-r", *argv)) {
-      reload = 1;
-    } else if (!strcmp("-R", *argv)) {
-      restarted = 1;
-    } else if (!strcmp("-u", *argv)) {
-      ++argv, --argc;
-      if (argc == 0) {
-        LOG_FATAL(LOGF_Main, "Missing user name");
-      } else {
-        user = *argv;
-      }
-    } else if (!strcmp("-F", *argv)) {
-      ++argv, --argc;
-      if (argc == 0 || sscanf(*argv, "%d", &scfilter_level) != 1)
-        LOG_FATAL(LOGF_Main, "Bad syscall filter level");
-    } else if (!strcmp("-s", *argv)) {
-      do_init_rtc = 1;
-    } else if (!strcmp("-v", *argv) || !strcmp("--version",*argv)) {
-      /* This write to the terminal is OK, it comes before we turn into a daemon */
-      printf("chronyd (chrony) version %s (%s)\n", CHRONY_VERSION, CHRONYD_FEATURES);
+  /* Parse long command-line options */
+  for (optind = 1; optind < argc; optind++) {
+    if (!strcmp("--help", argv[optind])) {
+      print_help(progname);
      return 0;
-    } else if (!strcmp("-n", *argv)) {
-      nofork = 1;
-    } else if (!strcmp("-d", *argv)) {
-      debug++;
-      nofork = 1;
-      system_log = 0;
-    } else if (!strcmp("-q", *argv)) {
-      ref_mode = REF_ModeUpdateOnce;
-      nofork = 1;
-      system_log = 0;
-    } else if (!strcmp("-Q", *argv)) {
-      ref_mode = REF_ModePrintOnce;
-      nofork = 1;
-      system_log = 0;
-    } else if (!strcmp("-t", *argv)) {
-      ++argv, --argc;
-      if (argc == 0 || sscanf(*argv, "%d", &timeout) != 1 || timeout <= 0)
-        LOG_FATAL(LOGF_Main, "Bad timeout");
-    } else if (!strcmp("-4", *argv)) {
-      address_family = IPADDR_INET4;
-    } else if (!strcmp("-6", *argv)) {
-      address_family = IPADDR_INET6;
-    } else if (!strcmp("-h", *argv) || !strcmp("--help", *argv)) {
-      printf("Usage: %s [-4|-6] [-n|-d] [-q|-Q] [-r] [-R] [-s] [-t TIMEOUT] [-f FILE|COMMAND...]\n",
-             progname);
+    } else if (!strcmp("--version", argv[optind])) {
+      print_version();
      return 0;
-    } else if (*argv[0] == '-') {
-      LOG_FATAL(LOGF_Main, "Unrecognized command line option [%s]", *argv);
-    } else {
-      /* Process remaining arguments and configuration lines */
-      config_args = argc;
-      break;
    }
  }

-  if (getuid() != 0) {
-    /* This write to the terminal is OK, it comes before we turn into a daemon */
-    fprintf(stderr,"Not superuser\n");
-    return 1;
+  optind = 1;
+
+  /* Parse short command-line options */
+  while ((opt = getopt(argc, argv, "46df:F:hl:L:mnpP:qQrRst:u:Uvx")) != -1) {
+    switch (opt) {
+      case '4':
+      case '6':
+        address_family = opt == '4' ? IPADDR_INET4 : IPADDR_INET6;
+        break;
+      case 'd':
+        debug++;
+        nofork = 1;
+        system_log = 0;
+        break;
+      case 'f':
+        conf_file = optarg;
+        break;
+      case 'F':
+        scfilter_level = parse_int_arg(optarg);
+        break;
+      case 'l':
+        log_file = optarg;
+        break;
+      case 'L':
+        log_severity = parse_int_arg(optarg);
+        break;
+      case 'm':
+        lock_memory = 1;
+        break;
+      case 'n':
+        nofork = 1;
+        break;
+      case 'p':
+        print_config = 1;
+        user_check = 0;
+        nofork = 1;
+        system_log = 0;
+        log_severity = LOGS_WARN;
+        break;
+      case 'P':
+        sched_priority = parse_int_arg(optarg);
+        break;
+      case 'q':
+        ref_mode = REF_ModeUpdateOnce;
+        nofork = 1;
+        client_only = 0;
+        system_log = 0;
+        break;
+      case 'Q':
+        ref_mode = REF_ModePrintOnce;
+        nofork = 1;
+        client_only = 1;
+        user_check = 0;
+        clock_control = 0;
+        system_log = 0;
+        break;
+      case 'r':
+        reload = 1;
+        break;
+      case 'R':
+        restarted = 1;
+        break;
+      case 's':
+        do_init_rtc = 1;
+        break;
+      case 't':
+        timeout = parse_int_arg(optarg);
+        break;
+      case 'u':
+        user = optarg;
+        break;
+      case 'U':
+        user_check = 0;
+        break;
+      case 'v':
+        print_version();
+        return 0;
+      case 'x':
+        clock_control = 0;
+        break;
+      default:
+        print_help(progname);
+        return opt != 'h';
+    }
  }

+  if (user_check && getuid() != 0)
+    LOG_FATAL("Not superuser");
+
  /* Turn into a daemon */
  if (!nofork) {
    go_daemon();
  }

-  if (system_log) {
+  if (log_file) {
+    LOG_OpenFileLog(log_file);
+  } else if (system_log) {
    LOG_OpenSystemLog();
  }
  
-  LOG_SetDebugLevel(debug);
+  LOG_SetMinSeverity(debug >= 2 ? LOGS_DEBUG : log_severity);
  
-  LOG(LOGS_INFO, LOGF_Main, "chronyd version %s starting (%s)",
-      CHRONY_VERSION, CHRONYD_FEATURES);
+  LOG(LOGS_INFO, "chronyd version %s starting (%s)", CHRONY_VERSION, CHRONYD_FEATURES);

  DNS_SetAddressFamily(address_family);

-  CNF_Initialise(restarted);
+  CNF_Initialise(restarted, client_only);
+  if (print_config)
+    CNF_EnablePrint();

  /* Parse the config file or the remaining command line arguments */
+  config_args = argc - optind;
  if (!config_args) {
    CNF_ReadFile(conf_file);
  } else {
-    do {
-      CNF_ParseLine(NULL, config_args - argc + 1, *argv);
-    } while (++argv, --argc);
+    for (; optind < argc; optind++)
+      CNF_ParseLine(NULL, config_args + optind - argc + 1, argv[optind]);
  }

-  /* Check whether another chronyd may already be running.  Do this after
-   * forking, so that message logging goes to the right place (i.e. syslog), in
-   * case this chronyd is being run from a boot script. */
-  if (maybe_another_chronyd_running(&other_pid)) {
-    LOG_FATAL(LOGF_Main, "Another chronyd may already be running (pid=%d), check lockfile (%s)",
-              other_pid, CNF_GetPidFile());
-  }
+  if (print_config)
+    return 0;

-  /* Write our lockfile to prevent other chronyds running.  This has *GOT* to
-   * be done *AFTER* the daemon-creation fork() */
-  write_lockfile();
+  /* Check whether another chronyd may already be running */
+  check_pidfile();
+
+  if (!user)
+    user = CNF_GetUser();
+
+  pw = getpwnam(user);
+  if (!pw)
+    LOG_FATAL("Could not get user/group ID of %s", user);
+
+  /* Create directories for sockets, log files, and dump files */
+  CNF_CreateDirs(pw->pw_uid, pw->pw_gid);
+
+  /* Write our pidfile to prevent other instances from running */
+  write_pidfile();

  PRV_Initialise();
  LCL_Initialise();
  SCH_Initialise();
-  SYS_Initialise();
+  SCK_Initialise(address_family);
+
+  /* Start helper processes if needed */
+  NKS_PreInitialise(pw->pw_uid, pw->pw_gid, scfilter_level);
+
+  SYS_Initialise(clock_control);
  RTC_Initialise(do_init_rtc);
  SRC_Initialise();
  RCL_Initialise();
  KEY_Initialise();

  /* Open privileged ports before dropping root */
-  CAM_Initialise(address_family);
-  NIO_Initialise(address_family);
+  CAM_Initialise();
+  NIO_Initialise();
  NCR_Initialise();
  CNF_SetupAccessRestrictions();

@@ -524,24 +636,19 @@ int main
    SYS_LockMemory();
  }

-  if (!user) {
-    user = CNF_GetUser();
-  }
+  /* Drop root privileges if the specified user has a non-zero UID */
+  if (!geteuid() && (pw->pw_uid || pw->pw_gid))
+    SYS_DropRoot(pw->pw_uid, pw->pw_gid, SYS_MAIN_PROCESS);

-  if ((pw = getpwnam(user)) == NULL)
-    LOG_FATAL(LOGF_Main, "Could not get %s uid/gid", user);
-
-  /* Create all directories before dropping root */
-  CNF_CreateDirs(pw->pw_uid, pw->pw_gid);
-
-  /* Drop root privileges if the user has non-zero uid or gid */
-  if (pw->pw_uid || pw->pw_gid)
-    SYS_DropRoot(pw->pw_uid, pw->pw_gid);
+  if (!geteuid())
+    LOG(LOGS_WARN, "Running with root privileges");

  REF_Initialise();
  SST_Initialise();
  NSR_Initialise();
  NSD_Initialise();
+  NNS_Initialise();
+  NKS_Initialise();
  CLG_Initialise();
  MNL_Initialise();
  TMC_Initialise();
@@ -550,12 +657,12 @@ int main
  /* From now on, it is safe to do finalisation on exit */
  initialised = 1;

-  UTI_SetQuitSignalsHandler(signal_cleanup);
+  UTI_SetQuitSignalsHandler(signal_cleanup, 1);

  CAM_OpenUnixSocket();

  if (scfilter_level)
-    SYS_EnableSystemCallFilter(scfilter_level);
+    SYS_EnableSystemCallFilter(scfilter_level, SYS_MAIN_PROCESS);

  if (ref_mode == REF_ModeNormal && CNF_GetInitSources() > 0) {
    ref_mode = REF_ModeInitStepSlew;
@@ -564,7 +671,7 @@ int main
  REF_SetModeEndHandler(reference_mode_end);
  REF_SetMode(ref_mode);

-  if (timeout)
+  if (timeout >= 0)
    SCH_AddTimeoutByDelay(timeout, quit_timeout, NULL);

  if (do_init_rtc) {
@@ -577,7 +684,7 @@ int main
     the scheduler. */
  SCH_MainLoop();

-  LOG(LOGS_INFO, LOGF_Main, "chronyd exiting");
+  LOG(LOGS_INFO, "chronyd exiting");

  MAI_CleanupAndExit();

--- a/2
+++ b/2
@@ -36,8 +36,6 @@ cd RELEASES/$subdir || exit 1

 echo $version > version.txt

-sed -i -e "s%@@VERSION@@%${version}%" examples/chrony.spec
-
 ./configure && make -C doc man txt || exit 1

 iconv -f utf-8 -t ascii//TRANSLIT < doc/installation.txt > INSTALL
--- a/manual.c
+++ b/manual.c
@@ -92,12 +92,14 @@ MNL_Initialise(void)
 void
 MNL_Finalise(void)
 {
+  LCL_RemoveParameterChangeHandler(slew_samples, NULL);
 }

 /* ================================================== */

 static void
-estimate_and_set_system(struct timespec *now, int offset_provided, double offset, long *offset_cs, double *dfreq_ppm, double *new_afreq_ppm)
+estimate_and_set_system(struct timespec *now, int offset_provided, double offset,
+                        double *reg_offset, double *dfreq_ppm, double *new_afreq_ppm)
 {
  double agos[MAX_SAMPLES], offsets[MAX_SAMPLES];
  double b0, b1;
@@ -108,32 +110,26 @@ estimate_and_set_system(struct timespec *now, int offset_provided, double offset
  int found_freq;
  double slew_by;

+  b0 = offset_provided ? offset : 0.0;
+  b1 = freq = 0.0;
+  found_freq = 0;
+
  if (n_samples > 1) {
    for (i=0; i<n_samples; i++) {
      agos[i] = UTI_DiffTimespecsToDouble(&samples[n_samples - 1].when, &samples[i].when);
      offsets[i] = samples[i].offset;
    }
    
-    RGR_FindBestRobustRegression(agos, offsets, n_samples,
-                                 1.0e-8, /* 0.01ppm easily good enough for this! */
-                                 &b0, &b1, &n_runs, &best_start);
-    
-    
-    /* Ignore b0 from regression; treat offset as being the most
-       recently entered value.  (If the administrator knows he's put
-       an outlier in, he will rerun the settime operation.)   However,
-       the frequency estimate comes from the regression. */
-    
-    freq = -b1;
-    found_freq = 1;
-  } else {
-    if (offset_provided) {
-      b0 = offset;
-    } else {
-      b0 = 0.0;
+    if (RGR_FindBestRobustRegression(agos, offsets, n_samples, 1.0e-8,
+                                     &b0, &b1, &n_runs, &best_start)) {
+      /* Ignore b0 from regression; treat offset as being the most
+         recently entered value.  (If the administrator knows he's put
+         an outlier in, he will rerun the settime operation.)   However,
+         the frequency estimate comes from the regression. */
+      freq = -b1;
+      found_freq = 1;
    }
-    b1 = freq = 0.0;
-    found_freq = 0;
+  } else {
    agos[0] = 0.0;
    offsets[0] = b0;
  }
@@ -145,21 +141,20 @@ estimate_and_set_system(struct timespec *now, int offset_provided, double offset
  }
  
  if (found_freq) {
-    LOG(LOGS_INFO, LOGF_Manual,
-        "Making a frequency change of %.3f ppm and a slew of %.6f",
+    LOG(LOGS_INFO, "Making a frequency change of %.3f ppm and a slew of %.6f",
        1.0e6 * freq, slew_by);
    
    REF_SetManualReference(now,
                           slew_by,
                           freq, skew);
  } else {
-    LOG(LOGS_INFO, LOGF_Manual, "Making a slew of %.6f", slew_by);
+    LOG(LOGS_INFO, "Making a slew of %.6f", slew_by);
    REF_SetManualReference(now,
                           slew_by,
                           0.0, skew);
  }
  
-  if (offset_cs) *offset_cs = (long)(0.5 + 100.0 * b0);
+  if (reg_offset) *reg_offset = b0;
  if (dfreq_ppm) *dfreq_ppm = 1.0e6 * freq;
  if (new_afreq_ppm) *new_afreq_ppm = LCL_ReadAbsoluteFrequency();
  
@@ -173,7 +168,7 @@ estimate_and_set_system(struct timespec *now, int offset_provided, double offset
 /* ================================================== */

 int
-MNL_AcceptTimestamp(struct timespec *ts, long *offset_cs, double *dfreq_ppm, double *new_afreq_ppm)
+MNL_AcceptTimestamp(struct timespec *ts, double *reg_offset, double *dfreq_ppm, double *new_afreq_ppm)
 {
  struct timespec now;
  double offset, diff;
@@ -210,7 +205,7 @@ MNL_AcceptTimestamp(struct timespec *ts, long *offset_cs, double *dfreq_ppm, dou
    samples[n_samples].orig_offset = offset;
    ++n_samples;

-    estimate_and_set_system(&now, 1, offset, offset_cs, dfreq_ppm, new_afreq_ppm);
+    estimate_and_set_system(&now, 1, offset, reg_offset, dfreq_ppm, new_afreq_ppm);

    return 1;

--- a/manual.h
+++ b/manual.h
@@ -33,7 +33,7 @@

 extern void MNL_Initialise(void);
 extern void MNL_Finalise(void);
-extern int MNL_AcceptTimestamp(struct timespec *ts, long *offset_cs, double *dfreq_ppm, double *new_afreq_ppm);
+extern int MNL_AcceptTimestamp(struct timespec *ts, double *reg_offset, double *dfreq_ppm, double *new_afreq_ppm);

 extern void MNL_Enable(void);
 extern void MNL_Disable(void);
--- a/memory.c
+++ b/memory.c
@@ -2,7 +2,7 @@
  chronyd/chronyc - Programs for keeping computer clocks accurate.

 **********************************************************************
- * Copyright (C) Miroslav Lichvar  2014
+ * Copyright (C) Miroslav Lichvar  2014, 2017
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
@@ -37,7 +37,7 @@ Malloc(size_t size)

  r = malloc(size);
  if (!r && size)
-    LOG_FATAL(LOGF_Memory, "Could not allocate memory");
+    LOG_FATAL("Could not allocate memory");

  return r;
 }
@@ -49,11 +49,37 @@ Realloc(void *ptr, size_t size)

  r = realloc(ptr, size);
  if (!r && size)
-    LOG_FATAL(LOGF_Memory, "Could not allocate memory");
+    LOG_FATAL("Could not allocate memory");

  return r;
 }

+static size_t
+get_array_size(size_t nmemb, size_t size)
+{
+  size_t array_size;
+
+  array_size = nmemb * size;
+
+  /* Check for overflow */
+  if (nmemb > 0 && array_size / nmemb != size)
+    LOG_FATAL("Could not allocate memory");
+
+  return array_size;
+}
+
+void *
+Malloc2(size_t nmemb, size_t size)
+{
+  return Malloc(get_array_size(nmemb, size));
+}
+
+void *
+Realloc2(void *ptr, size_t nmemb, size_t size)
+{
+  return Realloc(ptr, get_array_size(nmemb, size));
+}
+
 char *
 Strdup(const char *s)
 {
@@ -61,7 +87,7 @@ Strdup(const char *s)

  r = strdup(s);
  if (!r)
-    LOG_FATAL(LOGF_Memory, "Could not allocate memory");
+    LOG_FATAL("Could not allocate memory");

  return r;
 }
--- a/memory.h
+++ b/memory.h
@@ -27,15 +27,19 @@
 #ifndef GOT_MEMORY_H
 #define GOT_MEMORY_H

+#include "sysincl.h"
+
 /* Wrappers checking for errors */
 extern void *Malloc(size_t size);
 extern void *Realloc(void *ptr, size_t size);
+extern void *Malloc2(size_t nmemb, size_t size);
+extern void *Realloc2(void *ptr, size_t nmemb, size_t size);
 extern char *Strdup(const char *s);

 /* Convenient macros */
 #define MallocNew(T) ((T *) Malloc(sizeof(T)))
-#define MallocArray(T, n) ((T *) Malloc((n) * sizeof(T)))
-#define ReallocArray(T,n,x) ((T *) Realloc((void *)(x), (n)*sizeof(T)))
+#define MallocArray(T, n) ((T *) Malloc2(n, sizeof(T)))
+#define ReallocArray(T, n, x) ((T *) Realloc2((void *)(x), n, sizeof(T)))
 #define Free(x) free(x)

 #endif /* GOT_MEMORY_H */
--- a/nameserv.c
+++ b/nameserv.c
@@ -30,7 +30,11 @@

 #include "sysincl.h"

+#include <netdb.h>
+#include <resolv.h>
+
 #include "nameserv.h"
+#include "socket.h"
 #include "util.h"

 /* ================================================== */
@@ -46,15 +50,39 @@ DNS_SetAddressFamily(int family)
 DNS_Status 
 DNS_Name2IPAddress(const char *name, IPAddr *ip_addrs, int max_addrs)
 {
-#ifdef HAVE_GETADDRINFO
  struct addrinfo hints, *res, *ai;
  int i, result;
+  IPAddr ip;

  max_addrs = MIN(max_addrs, DNS_MAX_ADDRESSES);

+  for (i = 0; i < max_addrs; i++)
+    ip_addrs[i].family = IPADDR_UNSPEC;
+
+  /* Avoid calling getaddrinfo() if the name is an IP address */
+  if (UTI_StringToIP(name, &ip)) {
+    if (address_family != IPADDR_UNSPEC && ip.family != address_family)
+      return DNS_Failure;
+    if (max_addrs >= 1)
+      ip_addrs[0] = ip;
+    return DNS_Success;
+  }
+
  memset(&hints, 0, sizeof (hints));
-  hints.ai_family = AF_UNSPEC;
-  hints.ai_socktype = SOCK_STREAM;
+
+  switch (address_family) {
+    case IPADDR_INET4:
+      hints.ai_family = AF_INET;
+      break;
+#ifdef FEAT_IPV6
+    case IPADDR_INET6:
+      hints.ai_family = AF_INET6;
+      break;
+#endif
+    default:
+      hints.ai_family = AF_UNSPEC;
+  }
+  hints.ai_socktype = SOCK_DGRAM;

  result = getaddrinfo(name, NULL, &hints, &res);

@@ -79,6 +107,9 @@ DNS_Name2IPAddress(const char *name, IPAddr *ip_addrs, int max_addrs)
      case AF_INET6:
        if (address_family != IPADDR_UNSPEC && address_family != IPADDR_INET6)
          continue;
+        /* Don't return an address that would lose a scope ID */
+        if (((struct sockaddr_in6 *)ai->ai_addr)->sin6_scope_id != 0)
+          continue;
        ip_addrs[i].family = IPADDR_INET6;
        memcpy(&ip_addrs[i].addr.in6, &((struct sockaddr_in6 *)ai->ai_addr)->sin6_addr.s6_addr,
               sizeof (ip_addrs->addr.in6));
@@ -88,48 +119,9 @@ DNS_Name2IPAddress(const char *name, IPAddr *ip_addrs, int max_addrs)
    }
  }

-  for (; i < max_addrs; i++)
-        ip_addrs[i].family = IPADDR_UNSPEC;
-
  freeaddrinfo(res);

  return !max_addrs || ip_addrs[0].family != IPADDR_UNSPEC ? DNS_Success : DNS_Failure;
-#else
-  struct hostent *host;
-  int i;
-  
-  if (address_family != IPADDR_UNSPEC && address_family != IPADDR_INET4)
-    return DNS_Failure;
-
-  max_addrs = MIN(max_addrs, DNS_MAX_ADDRESSES);
-
-  host = gethostbyname(name);
-
-  if (host == NULL) {
-    if (h_errno == TRY_AGAIN)
-      return DNS_TryAgain;
-  } else {
-    if (host->h_addrtype != AF_INET || !host->h_addr_list[0])
-      return DNS_Failure;
-
-    for (i = 0; host->h_addr_list[i] && i < max_addrs; i++) {
-      ip_addrs[i].family = IPADDR_INET4;
-      ip_addrs[i].addr.in4 = ntohl(*(uint32_t *)host->h_addr_list[i]);
-    }
-
-    for (; i < max_addrs; i++)
-      ip_addrs[i].family = IPADDR_UNSPEC;
-
-    return DNS_Success;
-  }
-
-#ifdef FORCE_DNSRETRY
-  return DNS_TryAgain;
-#else
-  return DNS_Failure;
-#endif
-
-#endif
 }

 /* ================================================== */
@@ -138,35 +130,21 @@ int
 DNS_IPAddress2Name(IPAddr *ip_addr, char *name, int len)
 {
  char *result = NULL;
-
 #ifdef FEAT_IPV6
-  struct sockaddr_in6 in6;
+  struct sockaddr_in6 saddr;
+#else
+  struct sockaddr_in saddr;
+#endif
+  IPSockAddr ip_saddr;
  socklen_t slen;
  char hbuf[NI_MAXHOST];

-  slen = UTI_IPAndPortToSockaddr(ip_addr, 0, (struct sockaddr *)&in6);
-  if (!getnameinfo((struct sockaddr *)&in6, slen, hbuf, sizeof (hbuf), NULL, 0, 0))
-    result = hbuf;
-#else
-  struct hostent *host;
-  uint32_t addr;
+  ip_saddr.ip_addr = *ip_addr;
+  ip_saddr.port = 0;

-  switch (ip_addr->family) {
-    case IPADDR_INET4:
-      addr = htonl(ip_addr->addr.in4);
-      host = gethostbyaddr((const char *) &addr, sizeof (ip_addr), AF_INET);
-      break;
-#ifdef FEAT_IPV6
-    case IPADDR_INET6:
-      host = gethostbyaddr((const void *) ip_addr->addr.in6, sizeof (ip_addr->addr.in6), AF_INET6);
-      break;
-#endif
-    default:
-      host = NULL;
-  }
-  if (host)
-    result = host->h_name;
-#endif
+  slen = SCK_IPSockAddrToSockaddr(&ip_saddr, (struct sockaddr *)&saddr, sizeof (saddr));
+  if (!getnameinfo((struct sockaddr *)&saddr, slen, hbuf, sizeof (hbuf), NULL, 0, 0))
+    result = hbuf;

  if (result == NULL)
    result = UTI_IPToString(ip_addr);
--- a/nameserv_async.c
+++ b/nameserv_async.c
@@ -51,7 +51,7 @@ struct DNS_Async_Instance {
  int pipe[2];
 };

-static int resolving_threads = 0;
+static pthread_mutex_t privops_lock = PTHREAD_MUTEX_INITIALIZER;

 /* ================================================== */

@@ -60,7 +60,9 @@ start_resolving(void *anything)
 {
  struct DNS_Async_Instance *inst = (struct DNS_Async_Instance *)anything;

+  pthread_mutex_lock(&privops_lock);
  inst->status = PRV_Name2IPAddress(inst->name, inst->addresses, DNS_MAX_ADDRESSES);
+  pthread_mutex_unlock(&privops_lock);

  /* Notify the main thread that the result is ready */
  if (write(inst->pipe[1], "", 1) < 0)
@@ -78,11 +80,9 @@ end_resolving(int fd, int event, void *anything)
  int i;

  if (pthread_join(inst->thread, NULL)) {
-    LOG_FATAL(LOGF_Nameserv, "pthread_join() failed");
+    LOG_FATAL("pthread_join() failed");
  }

-  resolving_threads--;
-
  SCH_RemoveFileHandler(inst->pipe[0]);
  close(inst->pipe[0]);
  close(inst->pipe[1]);
@@ -110,17 +110,14 @@ DNS_Name2IPAddressAsync(const char *name, DNS_NameResolveHandler handler, void *
  inst->status = DNS_Failure;

  if (pipe(inst->pipe)) {
-    LOG_FATAL(LOGF_Nameserv, "pipe() failed");
+    LOG_FATAL("pipe() failed");
  }

  UTI_FdSetCloexec(inst->pipe[0]);
  UTI_FdSetCloexec(inst->pipe[1]);

-  resolving_threads++;
-  assert(resolving_threads <= 1);
-
  if (pthread_create(&inst->thread, NULL, start_resolving, inst)) {
-    LOG_FATAL(LOGF_Nameserv, "pthread_create() failed");
+    LOG_FATAL("pthread_create() failed");
  }

  SCH_AddFileHandler(inst->pipe[0], SCH_FILE_INPUT, end_resolving, inst);
--- a/ntp.h
+++ b/ntp.h
@@ -38,24 +38,30 @@ typedef struct {

 typedef uint32_t NTP_int32;

+/* The UDP port number used by NTP */
+#define NTP_PORT 123
+
 /* The NTP protocol version that we support */
 #define NTP_VERSION 4

 /* Maximum stratum number (infinity) */
 #define NTP_MAX_STRATUM 16

-/* The minimum valid length of an extension field */
-#define NTP_MIN_EXTENSION_LENGTH 16
-
-/* The maximum assumed length of all extension fields in received
-   packets (RFC 5905 doesn't specify a limit on length or number of
-   extension fields in one packet) */
-#define NTP_MAX_EXTENSIONS_LENGTH 1024
+/* Invalid stratum number */
+#define NTP_INVALID_STRATUM 0

 /* The minimum and maximum supported length of MAC */
 #define NTP_MIN_MAC_LENGTH (4 + 16)
 #define NTP_MAX_MAC_LENGTH (4 + MAX_HASH_LENGTH)

+/* The minimum valid length of an extension field */
+#define NTP_MIN_EF_LENGTH 16
+
+/* The maximum assumed length of all extension fields in an NTP packet,
+   including a MAC (RFC 5905 doesn't specify a limit on length or number of
+   extension fields in one packet) */
+#define NTP_MAX_EXTENSIONS_LENGTH (1024 + NTP_MAX_MAC_LENGTH)
+
 /* The maximum length of MAC in NTPv4 packets which allows deterministic
   parsing of extension fields (RFC 7822) */
 #define NTP_MAX_V4_MAC_LENGTH (4 + 20)
@@ -90,21 +96,10 @@ typedef struct {
  NTP_int64 receive_ts;
  NTP_int64 transmit_ts;

-  /* Optional extension fields, we don't send packets with them yet */
-  /* uint8_t extensions[] */
-
-  /* Optional message authentication code (MAC) */
-  NTP_int32 auth_keyid;
-  uint8_t auth_data[NTP_MAX_MAC_LENGTH - 4];
+  uint8_t extensions[NTP_MAX_EXTENSIONS_LENGTH];
 } NTP_Packet;

-#define NTP_NORMAL_PACKET_LENGTH (int)offsetof(NTP_Packet, auth_keyid)
-
-/* The buffer used to hold a datagram read from the network */
-typedef struct {
-  NTP_Packet ntp_pkt;
-  uint8_t extensions[NTP_MAX_EXTENSIONS_LENGTH];
-} NTP_Receive_Buffer;
+#define NTP_HEADER_LENGTH (int)offsetof(NTP_Packet, extensions)

 /* Macros to work with the lvm field */
 #define NTP_LVM_TO_LEAP(lvm) (((lvm) >> 6) & 0x3)
@@ -118,4 +113,70 @@ typedef struct {
 #define NTP_REFID_LOCAL 0x7F7F0101UL /* 127.127.1.1 */
 #define NTP_REFID_SMOOTH 0x7F7F01FFUL /* 127.127.1.255 */

+/* Non-authentication extension fields and corresponding internal flags */
+
+#define NTP_EF_EXP1                     0xF323
+
+#define NTP_EF_FLAG_EXP1                0x1
+
+/* Pre-NTPv5 experimental extension field */
+typedef struct {
+  uint32_t magic;
+  NTP_int32 root_delay;
+  NTP_int32 root_dispersion;
+  NTP_int64 mono_receive_ts;
+  uint32_t mono_epoch;
+} NTP_ExtFieldExp1;
+
+#define NTP_EF_EXP1_MAGIC 0xF5BEDD9AU
+
+/* Authentication extension fields */
+
+#define NTP_EF_NTS_UNIQUE_IDENTIFIER    0x0104
+#define NTP_EF_NTS_COOKIE               0x0204
+#define NTP_EF_NTS_COOKIE_PLACEHOLDER   0x0304
+#define NTP_EF_NTS_AUTH_AND_EEF         0x0404
+
+/* Enumeration for authentication modes of NTP packets */
+typedef enum {
+  NTP_AUTH_NONE = 0,            /* No authentication */
+  NTP_AUTH_SYMMETRIC,           /* NTP MAC or CMAC using a symmetric key
+                                   (RFC 1305, RFC 5905, RFC 8573) */
+  NTP_AUTH_MSSNTP,              /* MS-SNTP authenticator field */
+  NTP_AUTH_MSSNTP_EXT,          /* MS-SNTP extended authenticator field */
+  NTP_AUTH_NTS,                 /* Network Time Security (RFC 8915) */
+} NTP_AuthMode;
+
+/* Structure describing an NTP packet */
+typedef struct {
+  int length;
+  int version;
+  NTP_Mode mode;
+
+  int ext_fields;
+  int ext_field_flags;
+
+  struct {
+    NTP_AuthMode mode;
+    struct {
+      int start;
+      int length;
+      uint32_t key_id;
+    } mac;
+  } auth;
+} NTP_PacketInfo;
+
+/* Structure used to save NTP measurements.  time is the local time at which
+   the sample is to be considered to have been made and offset is the offset at
+   the time (positive indicates that the local clock is slow relative to the
+   source).  root_delay/root_dispersion include peer_delay/peer_dispersion. */
+typedef struct {
+  struct timespec time;
+  double offset;
+  double peer_delay;
+  double peer_dispersion;
+  double root_delay;
+  double root_dispersion;
+} NTP_Sample;
+
 #endif /* GOT_NTP_H */
--- a/ntp_auth.c
+++ b/ntp_auth.c
@@ -0,0 +1,386 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2019-2020
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  NTP authentication
+  */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include "keys.h"
+#include "logging.h"
+#include "memory.h"
+#include "ntp_auth.h"
+#include "ntp_signd.h"
+#include "nts_ntp.h"
+#include "nts_ntp_client.h"
+#include "nts_ntp_server.h"
+#include "srcparams.h"
+#include "util.h"
+
+/* Structure to hold authentication configuration and state */
+
+struct NAU_Instance_Record {
+  NTP_AuthMode mode;            /* Authentication mode of NTP packets */
+  uint32_t key_id;              /* Identifier of a symmetric key */
+  NNC_Instance nts;             /* Client NTS state */
+};
+
+/* ================================================== */
+
+static int
+generate_symmetric_auth(uint32_t key_id, NTP_Packet *packet, NTP_PacketInfo *info)
+{
+  int auth_len, max_auth_len;
+
+  if (info->length + NTP_MIN_MAC_LENGTH > sizeof (*packet)) {
+    DEBUG_LOG("Packet too long");
+    return 0;
+  }
+
+  /* Truncate long MACs in NTPv4 packets to allow deterministic parsing
+     of extension fields (RFC 7822) */
+  max_auth_len = (info->version == 4 ? NTP_MAX_V4_MAC_LENGTH : NTP_MAX_MAC_LENGTH) - 4;
+  max_auth_len = MIN(max_auth_len, sizeof (*packet) - info->length - 4);
+
+  auth_len = KEY_GenerateAuth(key_id, packet, info->length,
+                              (unsigned char *)packet + info->length + 4, max_auth_len);
+  if (auth_len < NTP_MIN_MAC_LENGTH - 4) {
+    DEBUG_LOG("Could not generate auth data with key %"PRIu32, key_id);
+    return 0;
+  }
+
+  *(uint32_t *)((unsigned char *)packet + info->length) = htonl(key_id);
+
+  info->auth.mac.start = info->length;
+  info->auth.mac.length = 4 + auth_len;
+  info->auth.mac.key_id = key_id;
+  info->length += info->auth.mac.length;
+
+  return 1;
+}
+
+/* ================================================== */
+
+static int
+check_symmetric_auth(NTP_Packet *packet, NTP_PacketInfo *info)
+{
+  int trunc_len;
+
+  if (info->auth.mac.length < NTP_MIN_MAC_LENGTH)
+    return 0;
+
+  trunc_len = info->version == 4 && info->auth.mac.length <= NTP_MAX_V4_MAC_LENGTH ?
+              NTP_MAX_V4_MAC_LENGTH : NTP_MAX_MAC_LENGTH;
+
+  if (!KEY_CheckAuth(info->auth.mac.key_id, packet, info->auth.mac.start,
+                     (unsigned char *)packet + info->auth.mac.start + 4,
+                     info->auth.mac.length - 4, trunc_len - 4))
+    return 0;
+
+  return 1;
+}
+
+/* ================================================== */
+
+static NAU_Instance
+create_instance(NTP_AuthMode mode)
+{
+  NAU_Instance instance;
+
+  instance = MallocNew(struct NAU_Instance_Record);
+  instance->mode = mode;
+  instance->key_id = INACTIVE_AUTHKEY;
+  instance->nts = NULL;
+
+  assert(sizeof (instance->key_id) == 4);
+
+  return instance;
+}
+
+/* ================================================== */
+
+NAU_Instance
+NAU_CreateNoneInstance(void)
+{
+  return create_instance(NTP_AUTH_NONE);
+}
+
+/* ================================================== */
+
+NAU_Instance
+NAU_CreateSymmetricInstance(uint32_t key_id)
+{
+  NAU_Instance instance = create_instance(NTP_AUTH_SYMMETRIC);
+
+  instance->key_id = key_id;
+
+  if (!KEY_KeyKnown(key_id))
+    LOG(LOGS_WARN, "Key %"PRIu32" is %s", key_id, "missing");
+  else if (!KEY_CheckKeyLength(key_id))
+    LOG(LOGS_WARN, "Key %"PRIu32" is %s", key_id, "too short");
+
+  return instance;
+}
+
+/* ================================================== */
+
+NAU_Instance
+NAU_CreateNtsInstance(IPSockAddr *nts_address, const char *name, uint32_t cert_set,
+                      uint16_t ntp_port)
+{
+  NAU_Instance instance = create_instance(NTP_AUTH_NTS);
+
+  instance->nts = NNC_CreateInstance(nts_address, name, cert_set, ntp_port);
+
+  return instance;
+}
+
+/* ================================================== */
+
+void
+NAU_DestroyInstance(NAU_Instance instance)
+{
+  if (instance->mode == NTP_AUTH_NTS)
+    NNC_DestroyInstance(instance->nts);
+  Free(instance);
+}
+
+/* ================================================== */
+
+int
+NAU_IsAuthEnabled(NAU_Instance instance)
+{
+  return instance->mode != NTP_AUTH_NONE;
+}
+
+/* ================================================== */
+
+int
+NAU_GetSuggestedNtpVersion(NAU_Instance instance)
+{
+  /* If the MAC in NTPv4 packets would be truncated, prefer NTPv3 for
+     compatibility with older chronyd servers */
+  if (instance->mode == NTP_AUTH_SYMMETRIC &&
+      KEY_GetAuthLength(instance->key_id) + sizeof (instance->key_id) > NTP_MAX_V4_MAC_LENGTH)
+    return 3;
+
+  return NTP_VERSION;
+}
+
+/* ================================================== */
+
+int
+NAU_PrepareRequestAuth(NAU_Instance instance)
+{
+  switch (instance->mode) {
+    case NTP_AUTH_NTS:
+      if (!NNC_PrepareForAuth(instance->nts))
+        return 0;
+      break;
+    default:
+      break;
+  }
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NAU_GenerateRequestAuth(NAU_Instance instance, NTP_Packet *request, NTP_PacketInfo *info)
+{
+  switch (instance->mode) {
+    case NTP_AUTH_NONE:
+      break;
+    case NTP_AUTH_SYMMETRIC:
+      if (!generate_symmetric_auth(instance->key_id, request, info))
+        return 0;
+      break;
+    case NTP_AUTH_NTS:
+      if (!NNC_GenerateRequestAuth(instance->nts, request, info))
+        return 0;
+      break;
+    default:
+      assert(0);
+  }
+
+  info->auth.mode = instance->mode;
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NAU_CheckRequestAuth(NTP_Packet *request, NTP_PacketInfo *info, uint32_t *kod)
+{
+  *kod = 0;
+
+  switch (info->auth.mode) {
+    case NTP_AUTH_NONE:
+      break;
+    case NTP_AUTH_SYMMETRIC:
+      if (!check_symmetric_auth(request, info))
+        return 0;
+      break;
+    case NTP_AUTH_MSSNTP:
+      /* MS-SNTP requests are not authenticated */
+      break;
+    case NTP_AUTH_MSSNTP_EXT:
+      /* Not supported yet */
+      return 0;
+    case NTP_AUTH_NTS:
+      if (!NNS_CheckRequestAuth(request, info, kod))
+        return 0;
+      break;
+    default:
+      return 0;
+  }
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NAU_GenerateResponseAuth(NTP_Packet *request, NTP_PacketInfo *request_info,
+                         NTP_Packet *response, NTP_PacketInfo *response_info,
+                         NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr,
+                         uint32_t kod)
+{
+  switch (request_info->auth.mode) {
+    case NTP_AUTH_NONE:
+      break;
+    case NTP_AUTH_SYMMETRIC:
+      if (!generate_symmetric_auth(request_info->auth.mac.key_id, response, response_info))
+        return 0;
+      break;
+    case NTP_AUTH_MSSNTP:
+      /* Sign the packet asynchronously by ntp_signd */
+      if (!NSD_SignAndSendPacket(request_info->auth.mac.key_id, response, response_info,
+                                 remote_addr, local_addr))
+        return 0;
+      /* Don't send the original packet */
+      return 0;
+    case NTP_AUTH_NTS:
+      if (!NNS_GenerateResponseAuth(request, request_info, response, response_info, kod))
+        return 0;
+      break;
+    default:
+      DEBUG_LOG("Could not authenticate response auth_mode=%d", (int)request_info->auth.mode);
+      return 0;
+  }
+
+  response_info->auth.mode = request_info->auth.mode;
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NAU_CheckResponseAuth(NAU_Instance instance, NTP_Packet *response, NTP_PacketInfo *info)
+{
+  /* The authentication must match the expected mode */
+  if (info->auth.mode != instance->mode)
+    return 0;
+
+  switch (info->auth.mode) {
+    case NTP_AUTH_NONE:
+      break;
+    case NTP_AUTH_SYMMETRIC:
+      /* Check if it is authenticated with the specified key */
+      if (info->auth.mac.key_id != instance->key_id)
+        return 0;
+      /* and that the MAC is valid */
+      if (!check_symmetric_auth(response, info))
+        return 0;
+      break;
+    case NTP_AUTH_NTS:
+      if (!NNC_CheckResponseAuth(instance->nts, response, info))
+        return 0;
+      break;
+    default:
+      return 0;
+  }
+
+  return 1;
+}
+
+/* ================================================== */
+
+void
+NAU_ChangeAddress(NAU_Instance instance, IPAddr *address)
+{
+  switch (instance->mode) {
+    case NTP_AUTH_NONE:
+    case NTP_AUTH_SYMMETRIC:
+      break;
+    case NTP_AUTH_NTS:
+      NNC_ChangeAddress(instance->nts, address);
+      break;
+    default:
+      assert(0);
+  }
+}
+
+/* ================================================== */
+
+void
+NAU_DumpData(NAU_Instance instance)
+{
+  switch (instance->mode) {
+    case NTP_AUTH_NTS:
+      NNC_DumpData(instance->nts);
+      break;
+    default:
+      break;
+  }
+}
+
+/* ================================================== */
+
+void
+NAU_GetReport(NAU_Instance instance, RPT_AuthReport *report)
+{
+  memset(report, 0, sizeof (*report));
+
+  report->mode = instance->mode;
+  report->last_ke_ago = -1;
+
+  switch (instance->mode) {
+    case NTP_AUTH_NONE:
+      break;
+    case NTP_AUTH_SYMMETRIC:
+      report->key_id = instance->key_id;
+      KEY_GetKeyInfo(instance->key_id, &report->key_type, &report->key_length);
+      break;
+    case NTP_AUTH_NTS:
+      NNC_GetReport(instance->nts, report);
+      break;
+    default:
+      assert(0);
+  }
+}
--- a/ntp_auth.h
+++ b/ntp_auth.h
@@ -0,0 +1,84 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2019
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Header file for NTP authentication
+  */
+
+#ifndef GOT_NTP_AUTH_H
+#define GOT_NTP_AUTH_H
+
+#include "addressing.h"
+#include "ntp.h"
+#include "reports.h"
+
+typedef struct NAU_Instance_Record *NAU_Instance;
+
+/* Create an authenticator instance in a specific mode */
+extern NAU_Instance NAU_CreateNoneInstance(void);
+extern NAU_Instance NAU_CreateSymmetricInstance(uint32_t key_id);
+extern NAU_Instance NAU_CreateNtsInstance(IPSockAddr *nts_address, const char *name,
+                                          uint32_t cert_set, uint16_t ntp_port);
+
+/* Destroy an instance */
+extern void NAU_DestroyInstance(NAU_Instance instance);
+
+/* Check if an instance is not in the None mode */
+extern int NAU_IsAuthEnabled(NAU_Instance instance);
+
+/* Get NTP version recommended for better compatibility */
+extern int NAU_GetSuggestedNtpVersion(NAU_Instance instance);
+
+/* Perform operations necessary for NAU_GenerateRequestAuth() */
+extern int NAU_PrepareRequestAuth(NAU_Instance instance);
+
+/* Extend a request with data required by the authentication mode */
+extern int NAU_GenerateRequestAuth(NAU_Instance instance, NTP_Packet *request,
+                                   NTP_PacketInfo *info);
+
+/* Verify that a request is authentic.  If it is not authentic and a non-zero
+   kod code is returned, a KoD response should be sent back. */
+extern int NAU_CheckRequestAuth(NTP_Packet *request, NTP_PacketInfo *info, uint32_t *kod);
+
+/* Extend a response with data required by the authentication mode.  This
+   function can be called only if the previous call of NAU_CheckRequestAuth()
+   was on the same request. */
+extern int NAU_GenerateResponseAuth(NTP_Packet *request, NTP_PacketInfo *request_info,
+                                    NTP_Packet *response, NTP_PacketInfo *response_info,
+                                    NTP_Remote_Address *remote_addr,
+                                    NTP_Local_Address *local_addr,
+                                    uint32_t kod);
+
+/* Verify that a response is authentic */
+extern int NAU_CheckResponseAuth(NAU_Instance instance, NTP_Packet *response,
+                                 NTP_PacketInfo *info);
+
+/* Change an authentication-specific address (e.g. after replacing a source) */
+extern void NAU_ChangeAddress(NAU_Instance instance, IPAddr *address);
+
+/* Save authentication-specific data to speed up the next start */
+extern void NAU_DumpData(NAU_Instance instance);
+
+/* Provide a report about the current authentication state */
+extern void NAU_GetReport(NAU_Instance instance, RPT_AuthReport *report);
+
+#endif
--- a/ntp_core.c
+++ b/ntp_core.c
--- a/ntp_core.h
+++ b/ntp_core.h
@@ -59,7 +59,8 @@ extern void NCR_Initialise(void);
 extern void NCR_Finalise(void);

 /* Get a new instance for a server or peer */
-extern NCR_Instance NCR_GetInstance(NTP_Remote_Address *remote_addr, NTP_Source_Type type, SourceParameters *params);
+extern NCR_Instance NCR_CreateInstance(NTP_Remote_Address *remote_addr, NTP_Source_Type type,
+                                       SourceParameters *params, const char *name);

 /* Destroy an instance */
 extern void NCR_DestroyInstance(NCR_Instance instance);
@@ -74,7 +75,8 @@ extern void NCR_ResetInstance(NCR_Instance inst);
 extern void NCR_ResetPoll(NCR_Instance instance);

 /* Change the remote address of an instance */
-extern void NCR_ChangeRemoteAddress(NCR_Instance inst, NTP_Remote_Address *remote_addr);
+extern void NCR_ChangeRemoteAddress(NCR_Instance inst, NTP_Remote_Address *remote_addr,
+                                    int ntp_only);

 /* This routine is called when a new packet arrives off the network,
   and it relates to a source we have an ongoing protocol exchange with */
@@ -99,12 +101,9 @@ extern void NCR_ProcessTxUnknown(NTP_Remote_Address *remote_addr, NTP_Local_Addr
 /* Slew receive and transmit times in instance records */
 extern void NCR_SlewTimes(NCR_Instance inst, struct timespec *when, double dfreq, double doffset);

-/* Take a particular source online (i.e. start sampling it) */
-extern void NCR_TakeSourceOnline(NCR_Instance inst);
-
-/* Take a particular source offline (i.e. stop sampling it, without
-   marking it unreachable in the source selection stuff) */
-extern void NCR_TakeSourceOffline(NCR_Instance inst);
+/* Take a particular source online (i.e. start sampling it) or offline
+   (i.e. stop sampling it) */
+extern void NCR_SetConnectivity(NCR_Instance inst, SRC_Connectivity connectivity);

 extern void NCR_ModifyMinpoll(NCR_Instance inst, int new_minpoll);

@@ -123,6 +122,7 @@ extern void NCR_ModifyPolltarget(NCR_Instance inst, int new_poll_target);
 extern void NCR_InitiateSampleBurst(NCR_Instance inst, int n_good_samples, int n_total_samples);

 extern void NCR_ReportSource(NCR_Instance inst, RPT_SourceReport *report, struct timespec *now);
+extern void NCR_GetAuthReport(NCR_Instance inst, RPT_AuthReport *report);
 extern void NCR_GetNTPReport(NCR_Instance inst, RPT_NTPReport *report);

 extern int NCR_AddAccessRestriction(IPAddr *ip_addr, int subnet_bits, int allow, int all);
@@ -137,6 +137,8 @@ extern uint32_t NCR_GetLocalRefid(NCR_Instance inst);

 extern int NCR_IsSyncPeer(NCR_Instance instance);

-extern void NCR_AddBroadcastDestination(IPAddr *addr, unsigned short port, int interval);
+extern void NCR_DumpAuthData(NCR_Instance inst);
+
+extern void NCR_AddBroadcastDestination(NTP_Remote_Address *addr, int interval);

 #endif /* GOT_NTP_CORE_H */
--- a/ntp_ext.c
+++ b/ntp_ext.c
@@ -0,0 +1,192 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2019-2020
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Functions for adding and parsing NTPv4 extension fields
+  */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include "ntp_ext.h"
+
+struct ExtFieldHeader {
+  uint16_t type;
+  uint16_t length;
+};
+
+/* ================================================== */
+
+static int
+format_field(unsigned char *buffer, int buffer_length, int start,
+             int type, int body_length, int *length, void **body)
+{
+  struct ExtFieldHeader *header;
+
+  if (buffer_length < 0 || start < 0 || buffer_length <= start ||
+      buffer_length - start < sizeof (*header) || start % 4 != 0)
+    return 0;
+
+  header = (struct ExtFieldHeader *)(buffer + start);
+
+  if (body_length < 0 || sizeof (*header) + body_length > 0xffff ||
+      start + sizeof (*header) + body_length > buffer_length || body_length % 4 != 0)
+    return 0;
+
+  header->type = htons(type);
+  header->length = htons(sizeof (*header) + body_length);
+  *length = sizeof (*header) + body_length;
+  *body = header + 1;
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NEF_SetField(unsigned char *buffer, int buffer_length, int start,
+             int type, void *body, int body_length, int *length)
+{
+  void *ef_body;
+
+  if (!format_field(buffer, buffer_length, start, type, body_length, length, &ef_body))
+    return 0;
+
+  memcpy(ef_body, body, body_length);
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NEF_AddBlankField(NTP_Packet *packet, NTP_PacketInfo *info, int type, int body_length, void **body)
+{
+  int ef_length, length = info->length;
+
+  if (length < NTP_HEADER_LENGTH || length >= sizeof (*packet) || length % 4 != 0)
+    return 0;
+
+  /* Only NTPv4 packets can have extension fields */
+  if (info->version != 4)
+    return 0;
+
+  if (!format_field((unsigned char *)packet, sizeof (*packet), length,
+                    type, body_length, &ef_length, body))
+    return 0;
+
+  if (ef_length < NTP_MIN_EF_LENGTH)
+    return 0;
+
+  info->length += ef_length;
+  info->ext_fields++;
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NEF_AddField(NTP_Packet *packet, NTP_PacketInfo *info,
+             int type, void *body, int body_length)
+{
+  void *ef_body;
+
+  if (!NEF_AddBlankField(packet, info, type, body_length, &ef_body))
+    return 0;
+
+  memcpy(ef_body, body, body_length);
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NEF_ParseSingleField(unsigned char *buffer, int buffer_length, int start,
+                     int *length, int *type, void **body, int *body_length)
+{
+  struct ExtFieldHeader *header;
+  int ef_length;
+
+  if (buffer_length < 0 || start < 0 || buffer_length <= start ||
+      buffer_length - start < sizeof (*header))
+    return 0;
+
+  header = (struct ExtFieldHeader *)(buffer + start);
+
+  assert(sizeof (*header) == 4);
+
+  ef_length = ntohs(header->length);
+
+  if (ef_length < (int)(sizeof (*header)) || start + ef_length > buffer_length ||
+      ef_length % 4 != 0)
+    return 0;
+
+  if (length)
+    *length = ef_length;
+  if (type)
+    *type = ntohs(header->type);
+  if (body)
+    *body = header + 1;
+  if (body_length)
+    *body_length = ef_length - sizeof (*header);
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NEF_ParseField(NTP_Packet *packet, int packet_length, int start,
+               int *length, int *type, void **body, int *body_length)
+{
+  int ef_length;
+
+  if (packet_length <= NTP_HEADER_LENGTH || packet_length > sizeof (*packet) ||
+      packet_length <= start || packet_length % 4 != 0 ||
+      start < NTP_HEADER_LENGTH || start % 4 != 0)
+    return 0;
+
+  /* Only NTPv4 packets have extension fields */
+  if (NTP_LVM_TO_VERSION(packet->lvm) != 4)
+    return 0;
+
+  /* Check if the remaining data is a MAC.  RFC 7822 specifies the maximum
+     length of a MAC in NTPv4 packets in order to enable deterministic
+     parsing. */
+  if (packet_length - start <= NTP_MAX_V4_MAC_LENGTH)
+    return 0;
+
+  if (!NEF_ParseSingleField((unsigned char *)packet, packet_length, start,
+                            &ef_length, type, body, body_length))
+    return 0;
+
+  if (ef_length < NTP_MIN_EF_LENGTH)
+    return 0;
+
+  if (length)
+    *length = ef_length;
+
+  return 1;
+}
--- a/ntp_ext.h
+++ b/ntp_ext.h
@@ -0,0 +1,43 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2019
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Header file for NTP extension fields
+  */
+
+#ifndef GOT_NTP_EXT_H
+#define GOT_NTP_EXT_H
+
+#include "ntp.h"
+
+extern int NEF_SetField(unsigned char *buffer, int buffer_length, int start,
+                        int type, void *body, int body_length, int *length);
+extern int NEF_AddBlankField(NTP_Packet *packet, NTP_PacketInfo *info, int type,
+                             int body_length, void **body);
+extern int NEF_AddField(NTP_Packet *packet, NTP_PacketInfo *info,
+                        int type, void *body, int body_length);
+extern int NEF_ParseSingleField(unsigned char *buffer, int buffer_length, int start,
+                                int *length, int *type, void **body, int *body_length);
+extern int NEF_ParseField(NTP_Packet *packet, int packet_length, int start,
+                          int *length, int *type, void **body, int *body_length);
+
+#endif
--- a/ntp_io.c
+++ b/ntp_io.c
--- a/ntp_io.h
+++ b/ntp_io.h
@@ -31,9 +31,10 @@

 #include "ntp.h"
 #include "addressing.h"
+#include "socket.h"

 /* Function to initialise the module. */
-extern void NIO_Initialise(int family);
+extern void NIO_Initialise(void);

 /* Function to finalise the module */
 extern void NIO_Finalise(void);
@@ -53,6 +54,15 @@ extern void NIO_CloseServerSocket(int sock_fd);
 /* Function to check if socket is a server socket */
 extern int NIO_IsServerSocket(int sock_fd);

+/* Function to check if a server socket is currently open */
+extern int NIO_IsServerSocketOpen(void);
+
+/* Function to check if client packets can be sent to a server */
+extern int NIO_IsServerConnectable(NTP_Remote_Address *remote_addr);
+
+/* Function to unwrap an NTP message from non-native transport (e.g. PTP) */
+extern int NIO_UnwrapMessage(SCK_Message *message, int sock_fd);
+
 /* Function to transmit a packet */
 extern int NIO_SendPacket(NTP_Packet *packet, NTP_Remote_Address *remote_addr,
                          NTP_Local_Address *local_addr, int length, int process_tx);
--- a/ntp_io_linux.c
+++ b/ntp_io_linux.c
@@ -2,7 +2,7 @@
  chronyd/chronyc - Programs for keeping computer clocks accurate.

 **********************************************************************
- * Copyright (C) Miroslav Lichvar  2016-2017
+ * Copyright (C) Miroslav Lichvar  2016-2019
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
@@ -29,10 +29,8 @@
 #include "sysincl.h"

 #include <ifaddrs.h>
-#include <linux/errqueue.h>
 #include <linux/ethtool.h>
 #include <linux/net_tstamp.h>
-#include <linux/ptp_clock.h>
 #include <linux/sockios.h>
 #include <net/if.h>

@@ -46,21 +44,16 @@
 #include "ntp_io_linux.h"
 #include "ntp_sources.h"
 #include "sched.h"
+#include "socket.h"
 #include "sys_linux.h"
 #include "util.h"

-union sockaddr_in46 {
-  struct sockaddr_in in4;
-#ifdef FEAT_IPV6
-  struct sockaddr_in6 in6;
-#endif
-  struct sockaddr u;
-};
-
 struct Interface {
  char name[IF_NAMESIZE];
  int if_index;
  int phc_fd;
+  int phc_mode;
+  int phc_nocrossts;
  /* Link speed in mbit/s */
  int link_speed;
  /* Start of UDP data at layer 2 for IPv4 and IPv6 */
@@ -73,9 +66,12 @@ struct Interface {
 };

 /* Number of PHC readings per HW clock sample */
-#define PHC_READINGS 10
+#define PHC_READINGS 25

-/* Maximum acceptable offset between HW and daemon/kernel timestamp */
+/* Minimum interval between PHC readings */
+#define MIN_PHC_POLL -6
+
+/* Maximum acceptable offset between SW/HW and daemon timestamp */
 #define MAX_TS_DELAY 1.0

 /* Array of Interfaces */
@@ -88,40 +84,61 @@ static int ts_tx_flags;
 /* Flag indicating the socket options can't be changed in control messages */
 static int permanent_ts_options;

+/* When sending client requests to a close and fast server, it is possible that
+   a response will be received before the HW transmit timestamp of the request
+   itself.  To avoid processing of the response without the HW timestamp, we
+   monitor events returned by select() and suspend reading of packets from the
+   receive queue for up to 200 microseconds.  As the requests are normally
+   separated by at least 200 milliseconds, it is sufficient to monitor and
+   suspend one socket at a time. */
+static int monitored_socket;
+static int suspended_socket;
+static SCH_TimeoutID resume_timeout_id;
+
+#define RESUME_TIMEOUT 200.0e-6
+
+/* Unbound socket keeping the kernel RX timestamping permanently enabled
+   in order to avoid a race condition between receiving a server response
+   and the kernel actually starting to timestamp received packets after
+   enabling the timestamping and sending a request */
+static int dummy_rxts_socket;
+
+#define INVALID_SOCK_FD -3
+
 /* ================================================== */

 static int
-add_interface(const char *name, double tx_comp, double rx_comp)
+add_interface(CNF_HwTsInterface *conf_iface)
 {
  struct ethtool_ts_info ts_info;
  struct hwtstamp_config ts_config;
  struct ifreq req;
-  int sock_fd, if_index, phc_index, phc_fd;
+  int sock_fd, if_index, phc_fd, req_hwts_flags, rx_filter;
  unsigned int i;
  struct Interface *iface;
-  char phc_path[64];

  /* Check if the interface was not already added */
  for (i = 0; i < ARR_GetSize(interfaces); i++) {
-    if (!strcmp(name, ((struct Interface *)ARR_GetElement(interfaces, i))->name))
+    if (!strcmp(conf_iface->name, ((struct Interface *)ARR_GetElement(interfaces, i))->name))
      return 1;
  }

-  sock_fd = socket(AF_INET, SOCK_DGRAM, 0);
+  sock_fd = SCK_OpenUdpSocket(NULL, NULL, NULL, 0);
  if (sock_fd < 0)
    return 0;

  memset(&req, 0, sizeof (req));
  memset(&ts_info, 0, sizeof (ts_info));

-  if (snprintf(req.ifr_name, sizeof (req.ifr_name), "%s", name) >= sizeof (req.ifr_name)) {
-    close(sock_fd);
+  if (snprintf(req.ifr_name, sizeof (req.ifr_name), "%s", conf_iface->name) >=
+      sizeof (req.ifr_name)) {
+    SCK_CloseSocket(sock_fd);
    return 0;
  }

  if (ioctl(sock_fd, SIOCGIFINDEX, &req)) {
-    DEBUG_LOG(LOGF_NtpIOLinux, "ioctl(%s) failed : %s", "SIOCGIFINDEX", strerror(errno));
-    close(sock_fd);
+    DEBUG_LOG("ioctl(%s) failed : %s", "SIOCGIFINDEX", strerror(errno));
+    SCK_CloseSocket(sock_fd);
    return 0;
  }

@@ -131,53 +148,109 @@ add_interface(const char *name, double tx_comp, double rx_comp)
  req.ifr_data = (char *)&ts_info;

  if (ioctl(sock_fd, SIOCETHTOOL, &req)) {
-    DEBUG_LOG(LOGF_NtpIOLinux, "ioctl(%s) failed : %s", "SIOCETHTOOL", strerror(errno));
-    close(sock_fd);
+    DEBUG_LOG("ioctl(%s) failed : %s", "SIOCETHTOOL", strerror(errno));
+    SCK_CloseSocket(sock_fd);
    return 0;
  }

+  req_hwts_flags = SOF_TIMESTAMPING_RX_HARDWARE | SOF_TIMESTAMPING_TX_HARDWARE |
+                   SOF_TIMESTAMPING_RAW_HARDWARE;
+  if ((ts_info.so_timestamping & req_hwts_flags) != req_hwts_flags) {
+    DEBUG_LOG("HW timestamping not supported on %s", req.ifr_name);
+    SCK_CloseSocket(sock_fd);
+    return 0;
+  }
+
+  if (ts_info.phc_index < 0) {
+    DEBUG_LOG("PHC missing on %s", req.ifr_name);
+    SCK_CloseSocket(sock_fd);
+    return 0;
+  }
+
+  switch (conf_iface->rxfilter) {
+    case CNF_HWTS_RXFILTER_ANY:
+#ifdef HAVE_LINUX_TIMESTAMPING_RXFILTER_NTP
+      if (ts_info.rx_filters & (1 << HWTSTAMP_FILTER_NTP_ALL))
+        rx_filter = HWTSTAMP_FILTER_NTP_ALL;
+      else
+#endif
+      if (ts_info.rx_filters & (1 << HWTSTAMP_FILTER_ALL))
+        rx_filter = HWTSTAMP_FILTER_ALL;
+      else
+        rx_filter = HWTSTAMP_FILTER_NONE;
+      break;
+    case CNF_HWTS_RXFILTER_NONE:
+      rx_filter = HWTSTAMP_FILTER_NONE;
+      break;
+#ifdef HAVE_LINUX_TIMESTAMPING_RXFILTER_NTP
+    case CNF_HWTS_RXFILTER_NTP:
+      rx_filter = HWTSTAMP_FILTER_NTP_ALL;
+      break;
+#endif
+    case CNF_HWTS_RXFILTER_PTP:
+      if (ts_info.rx_filters & (1 << HWTSTAMP_FILTER_PTP_V2_L4_EVENT))
+        rx_filter = HWTSTAMP_FILTER_PTP_V2_L4_EVENT;
+      else if (ts_info.rx_filters & (1 << HWTSTAMP_FILTER_PTP_V2_EVENT))
+        rx_filter = HWTSTAMP_FILTER_PTP_V2_EVENT;
+      else
+        rx_filter = HWTSTAMP_FILTER_NONE;
+      break;
+    default:
+      rx_filter = HWTSTAMP_FILTER_ALL;
+      break;
+  }
+
  ts_config.flags = 0;
  ts_config.tx_type = HWTSTAMP_TX_ON;
-  ts_config.rx_filter = HWTSTAMP_FILTER_ALL;
+  ts_config.rx_filter = rx_filter;
  req.ifr_data = (char *)&ts_config;

  if (ioctl(sock_fd, SIOCSHWTSTAMP, &req)) {
-    DEBUG_LOG(LOGF_NtpIOLinux, "ioctl(%s) failed : %s", "SIOCSHWTSTAMP", strerror(errno));
-    close(sock_fd);
-    return 0;
+    LOG(errno == EPERM ? LOGS_ERR : LOGS_DEBUG,
+        "ioctl(%s) failed : %s", "SIOCSHWTSTAMP", strerror(errno));
+
+    /* Check the current timestamping configuration in case this interface
+       allows only reading of the configuration and it was already configured
+       as requested */
+    req.ifr_data = (char *)&ts_config;
+#ifdef SIOCGHWTSTAMP
+    if (ioctl(sock_fd, SIOCGHWTSTAMP, &req) ||
+        ts_config.tx_type != HWTSTAMP_TX_ON || ts_config.rx_filter != rx_filter)
+#endif
+    {
+      SCK_CloseSocket(sock_fd);
+      return 0;
+    }
  }

-  close(sock_fd);
-  phc_index = ts_info.phc_index;
+  SCK_CloseSocket(sock_fd);

-  if (snprintf(phc_path, sizeof (phc_path), "/dev/ptp%d", phc_index) >= sizeof (phc_path))
+  phc_fd = SYS_Linux_OpenPHC(NULL, ts_info.phc_index);
+  if (phc_fd < 0)
    return 0;

-  phc_fd = open(phc_path, O_RDONLY);
-  if (phc_fd < 0) {
-    LOG(LOGS_ERR, LOGF_NtpIOLinux, "Could not open %s : %s", phc_path, strerror(errno));
-    return 0;
-  }
-
-  UTI_FdSetCloexec(phc_fd);
-
  iface = ARR_GetNewElement(interfaces);

-  snprintf(iface->name, sizeof (iface->name), "%s", name);
+  snprintf(iface->name, sizeof (iface->name), "%s", conf_iface->name);
  iface->if_index = if_index;
  iface->phc_fd = phc_fd;
+  iface->phc_mode = 0;
+  iface->phc_nocrossts = conf_iface->nocrossts;

  /* Start with 1 gbit and no VLANs or IPv4/IPv6 options */
  iface->link_speed = 1000;
  iface->l2_udp4_ntp_start = 42;
  iface->l2_udp6_ntp_start = 62;

-  iface->tx_comp = tx_comp;
-  iface->rx_comp = rx_comp;
+  iface->tx_comp = conf_iface->tx_comp;
+  iface->rx_comp = conf_iface->rx_comp;

-  iface->clock = HCL_CreateInstance();
+  iface->clock = HCL_CreateInstance(conf_iface->min_samples, conf_iface->max_samples,
+                                    UTI_Log2ToDouble(MAX(conf_iface->minpoll, MIN_PHC_POLL)),
+                                    conf_iface->precision);

-  DEBUG_LOG(LOGF_NtpIOLinux, "Enabled HW timestamping on %s", name);
+  LOG(LOGS_INFO, "Enabled HW timestamping %son %s",
+      ts_config.rx_filter == HWTSTAMP_FILTER_NONE ? "(TX only) " : "", iface->name);

  return 1;
 }
@@ -185,18 +258,22 @@ add_interface(const char *name, double tx_comp, double rx_comp)
 /* ================================================== */

 static int
-add_all_interfaces(double tx_comp, double rx_comp)
+add_all_interfaces(CNF_HwTsInterface *conf_iface_all)
 {
+  CNF_HwTsInterface conf_iface;
  struct ifaddrs *ifaddr, *ifa;
  int r;

+  conf_iface = *conf_iface_all;
+
  if (getifaddrs(&ifaddr)) {
-    DEBUG_LOG(LOGF_NtpIOLinux, "getifaddrs() failed : %s", strerror(errno));
+    DEBUG_LOG("getifaddrs() failed : %s", strerror(errno));
    return 0;
  }

  for (r = 0, ifa = ifaddr; ifa; ifa = ifa->ifa_next) {
-    if (add_interface(ifa->ifa_name, tx_comp, rx_comp))
+    conf_iface.name = ifa->ifa_name;
+    if (add_interface(&conf_iface))
      r = 1;
  }
  
@@ -213,9 +290,9 @@ update_interface_speed(struct Interface *iface)
 {
  struct ethtool_cmd cmd;
  struct ifreq req;
-  int sock_fd;
+  int sock_fd, link_speed;

-  sock_fd = socket(AF_INET, SOCK_DGRAM, 0);
+  sock_fd = SCK_OpenUdpSocket(NULL, NULL, NULL, 0);
  if (sock_fd < 0)
    return;

@@ -227,14 +304,60 @@ update_interface_speed(struct Interface *iface)
  req.ifr_data = (char *)&cmd;

  if (ioctl(sock_fd, SIOCETHTOOL, &req)) {
-    DEBUG_LOG(LOGF_NtpIOLinux, "ioctl(%s) failed : %s", "SIOCETHTOOL", strerror(errno));
-    close(sock_fd);
+    DEBUG_LOG("ioctl(%s) failed : %s", "SIOCETHTOOL", strerror(errno));
+    SCK_CloseSocket(sock_fd);
    return;
  }

-  close(sock_fd);
+  SCK_CloseSocket(sock_fd);

-  iface->link_speed = ethtool_cmd_speed(&cmd);
+  link_speed = ethtool_cmd_speed(&cmd);
+
+  if (iface->link_speed != link_speed) {
+    iface->link_speed = link_speed;
+    DEBUG_LOG("Updated speed of %s to %d Mb/s", iface->name, link_speed);
+  }
+}
+
+/* ================================================== */
+
+#if defined(HAVE_LINUX_TIMESTAMPING_OPT_PKTINFO) || defined(HAVE_LINUX_TIMESTAMPING_OPT_TX_SWHW)
+static int
+check_timestamping_option(int option)
+{
+  int sock_fd;
+
+  sock_fd = SCK_OpenUdpSocket(NULL, NULL, NULL, 0);
+  if (sock_fd < 0)
+    return 0;
+
+  if (!SCK_SetIntOption(sock_fd, SOL_SOCKET, SO_TIMESTAMPING, option)) {
+    SCK_CloseSocket(sock_fd);
+    return 0;
+  }
+
+  SCK_CloseSocket(sock_fd);
+  return 1;
+}
+#endif
+
+/* ================================================== */
+
+static int
+open_dummy_socket(void)
+{
+  int sock_fd, events = 0;
+
+  sock_fd = SCK_OpenUdpSocket(NULL, NULL, NULL, 0);
+  if (sock_fd < 0)
+    return INVALID_SOCK_FD;
+
+  if (!NIO_Linux_SetTimestampSocketOptions(sock_fd, 1, &events)) {
+    SCK_CloseSocket(sock_fd);
+    return INVALID_SOCK_FD;
+  }
+
+  return sock_fd;
 }

 /* ================================================== */
@@ -242,8 +365,7 @@ update_interface_speed(struct Interface *iface)
 void
 NIO_Linux_Initialise(void)
 {
-  double tx_comp, rx_comp;
-  char *name;
+  CNF_HwTsInterface *conf_iface;
  unsigned int i;
  int hwts;

@@ -252,28 +374,36 @@ NIO_Linux_Initialise(void)
  /* Enable HW timestamping on specified interfaces.  If "*" was specified, try
     all interfaces.  If no interface was specified, enable SW timestamping. */

-  for (i = hwts = 0; CNF_GetHwTsInterface(i, &name, &tx_comp, &rx_comp); i++) {
-    if (!strcmp("*", name))
+  for (i = hwts = 0; CNF_GetHwTsInterface(i, &conf_iface); i++) {
+    if (!strcmp("*", conf_iface->name))
      continue;
-    if (!add_interface(name, tx_comp, rx_comp))
-      LOG_FATAL(LOGF_NtpIO, "Could not enable HW timestamping on %s", name);
+    if (!add_interface(conf_iface))
+      LOG_FATAL("Could not enable HW timestamping on %s", conf_iface->name);
    hwts = 1;
  }

-  for (i = 0; CNF_GetHwTsInterface(i, &name, &tx_comp, &rx_comp); i++) {
-    if (strcmp("*", name))
+  for (i = 0; CNF_GetHwTsInterface(i, &conf_iface); i++) {
+    if (strcmp("*", conf_iface->name))
      continue;
-    if (add_all_interfaces(tx_comp, rx_comp))
+    if (add_all_interfaces(conf_iface))
      hwts = 1;
    break;
  }

+  ts_flags = SOF_TIMESTAMPING_SOFTWARE | SOF_TIMESTAMPING_RX_SOFTWARE;
+  ts_tx_flags = SOF_TIMESTAMPING_TX_SOFTWARE;
+
  if (hwts) {
-    ts_flags = SOF_TIMESTAMPING_RAW_HARDWARE | SOF_TIMESTAMPING_RX_HARDWARE;
-    ts_tx_flags = SOF_TIMESTAMPING_TX_HARDWARE;
-  } else {
-    ts_flags = SOF_TIMESTAMPING_SOFTWARE | SOF_TIMESTAMPING_RX_SOFTWARE;
-    ts_tx_flags = SOF_TIMESTAMPING_TX_SOFTWARE;
+    ts_flags |= SOF_TIMESTAMPING_RAW_HARDWARE | SOF_TIMESTAMPING_RX_HARDWARE;
+    ts_tx_flags |= SOF_TIMESTAMPING_TX_HARDWARE;
+#ifdef HAVE_LINUX_TIMESTAMPING_OPT_PKTINFO
+    if (check_timestamping_option(SOF_TIMESTAMPING_OPT_PKTINFO))
+      ts_flags |= SOF_TIMESTAMPING_OPT_PKTINFO;
+#endif
+#ifdef HAVE_LINUX_TIMESTAMPING_OPT_TX_SWHW
+    if (check_timestamping_option(SOF_TIMESTAMPING_OPT_TX_SWHW))
+      ts_flags |= SOF_TIMESTAMPING_OPT_TX_SWHW;
+#endif
  }

  /* Enable IP_PKTINFO in messages looped back to the error queue */
@@ -281,6 +411,10 @@ NIO_Linux_Initialise(void)

  /* Kernels before 4.7 ignore timestamping flags set in control messages */
  permanent_ts_options = !SYS_Linux_CheckKernelVersion(4, 7);
+
+  monitored_socket = INVALID_SOCK_FD;
+  suspended_socket = INVALID_SOCK_FD;
+  dummy_rxts_socket = INVALID_SOCK_FD;
 }

 /* ================================================== */
@@ -291,6 +425,9 @@ NIO_Linux_Finalise(void)
  struct Interface *iface;
  unsigned int i;

+  if (dummy_rxts_socket != INVALID_SOCK_FD)
+    SCK_CloseSocket(dummy_rxts_socket);
+
  for (i = 0; i < ARR_GetSize(interfaces); i++) {
    iface = ARR_GetElement(interfaces, i);
    HCL_DestroyInstance(iface->clock);
@@ -319,14 +456,12 @@ NIO_Linux_SetTimestampSocketOptions(int sock_fd, int client_only, int *events)
  if (client_only || permanent_ts_options)
    flags |= ts_tx_flags;

-  if (setsockopt(sock_fd, SOL_SOCKET, SO_SELECT_ERR_QUEUE, &val, sizeof (val)) < 0) {
-    LOG(LOGS_ERR, LOGF_NtpIOLinux, "Could not set %s socket option", "SO_SELECT_ERR_QUEUE");
+  if (!SCK_SetIntOption(sock_fd, SOL_SOCKET, SO_SELECT_ERR_QUEUE, val)) {
    ts_flags = 0;
    return 0;
  }

-  if (setsockopt(sock_fd, SOL_SOCKET, SO_TIMESTAMPING, &flags, sizeof (flags)) < 0) {
-    LOG(LOGS_ERR, LOGF_NtpIOLinux, "Could not set %s socket option", "SO_TIMESTAMPING");
+  if (!SCK_SetIntOption(sock_fd, SOL_SOCKET, SO_TIMESTAMPING, flags)) {
    ts_flags = 0;
    return 0;
  }
@@ -337,64 +472,69 @@ NIO_Linux_SetTimestampSocketOptions(int sock_fd, int client_only, int *events)

 /* ================================================== */

-static int
-get_phc_sample(int phc_fd, struct timespec *phc_ts, struct timespec *local_ts, double *p_delay)
+static void
+resume_socket(int sock_fd)
 {
-  struct ptp_sys_offset sys_off;
-  struct timespec ts1, ts2, ts3, phc_tss[PHC_READINGS], sys_tss[PHC_READINGS];
-  double min_delay = 0.0, delays[PHC_READINGS], phc_sum, local_sum, local_prec;
-  int i, n;
+  if (monitored_socket == sock_fd)
+    monitored_socket = INVALID_SOCK_FD;

-  /* Silence valgrind */
-  memset(&sys_off, 0, sizeof (sys_off));
+  if (sock_fd == INVALID_SOCK_FD || sock_fd != suspended_socket)
+    return;

-  sys_off.n_samples = PHC_READINGS;
+  suspended_socket = INVALID_SOCK_FD;

-  if (ioctl(phc_fd, PTP_SYS_OFFSET, &sys_off)) {
-    DEBUG_LOG(LOGF_NtpIOLinux, "ioctl(%s) failed : %s", "PTP_SYS_OFFSET", strerror(errno));
+  SCH_SetFileHandlerEvent(sock_fd, SCH_FILE_INPUT, 1);
+
+  DEBUG_LOG("Resumed RX processing %s timeout fd=%d",
+            resume_timeout_id ? "before" : "on", sock_fd);
+
+  if (resume_timeout_id) {
+    SCH_RemoveTimeout(resume_timeout_id);
+    resume_timeout_id = 0;
+  }
+}
+
+/* ================================================== */
+
+static void
+resume_timeout(void *arg)
+{
+  resume_timeout_id = 0;
+  resume_socket(suspended_socket);
+}
+
+/* ================================================== */
+
+static void
+suspend_socket(int sock_fd)
+{
+  resume_socket(suspended_socket);
+
+  suspended_socket = sock_fd;
+
+  SCH_SetFileHandlerEvent(suspended_socket, SCH_FILE_INPUT, 0);
+  resume_timeout_id = SCH_AddTimeoutByDelay(RESUME_TIMEOUT, resume_timeout, NULL);
+
+  DEBUG_LOG("Suspended RX processing fd=%d", sock_fd);
+}
+
+/* ================================================== */
+
+int
+NIO_Linux_ProcessEvent(int sock_fd, int event)
+{
+  if (sock_fd != monitored_socket)
    return 0;
+
+  if (event == SCH_FILE_INPUT) {
+    suspend_socket(monitored_socket);
+    monitored_socket = INVALID_SOCK_FD;
+
+    /* Don't process the message yet */
+    return 1;
  }

-  for (i = 0; i < PHC_READINGS; i++) {
-    ts1.tv_sec = sys_off.ts[i * 2].sec;
-    ts1.tv_nsec = sys_off.ts[i * 2].nsec;
-    ts2.tv_sec = sys_off.ts[i * 2 + 1].sec;
-    ts2.tv_nsec = sys_off.ts[i * 2 + 1].nsec;
-    ts3.tv_sec = sys_off.ts[i * 2 + 2].sec;
-    ts3.tv_nsec = sys_off.ts[i * 2 + 2].nsec;
-
-    sys_tss[i] = ts1;
-    phc_tss[i] = ts2;
-    delays[i] = UTI_DiffTimespecsToDouble(&ts3, &ts1);
-
-    if (delays[i] <= 0.0)
-      /* Step in the middle of a PHC reading? */
-      return 0;
-
-    if (!i || delays[i] < min_delay)
-      min_delay = delays[i];
-  }
-
-  local_prec = LCL_GetSysPrecisionAsQuantum();
-
-  /* Combine best readings */
-  for (i = n = 0, phc_sum = local_sum = 0.0; i < PHC_READINGS; i++) {
-    if (delays[i] > min_delay + local_prec)
-      continue;
-
-    phc_sum += UTI_DiffTimespecsToDouble(&phc_tss[i], &phc_tss[0]);
-    local_sum += UTI_DiffTimespecsToDouble(&sys_tss[i], &sys_tss[0]) + delays[i] / 2.0;
-    n++;
-  }
-
-  assert(n);
-
-  UTI_AddDoubleToTimespec(&phc_tss[0], phc_sum / n, phc_ts);
-  UTI_AddDoubleToTimespec(&sys_tss[0], local_sum / n, &ts1);
-  LCL_CookTime(&ts1, local_ts, NULL);
-  *p_delay = min_delay;
-
-  return 1;
+  return 0;
 }

 /* ================================================== */
@@ -420,55 +560,88 @@ get_interface(int if_index)

 static void
 process_hw_timestamp(struct Interface *iface, struct timespec *hw_ts,
-                     NTP_Local_Timestamp *local_ts, int rx_ntp_length, int family)
+                     NTP_Local_Timestamp *local_ts, int rx_ntp_length, int family,
+                     int l2_length)
 {
-  struct timespec sample_phc_ts, sample_local_ts, ts;
-  double sample_delay, rx_correction, ts_delay, err;
-  int l2_length;
+  struct timespec sample_phc_ts, sample_sys_ts, sample_local_ts, ts;
+  struct timespec phc_readings[PHC_READINGS][3];
+  double rx_correction, ts_delay, phc_err, local_err;
+  int n_readings;

  if (HCL_NeedsNewSample(iface->clock, &local_ts->ts)) {
-    if (!get_phc_sample(iface->phc_fd, &sample_phc_ts, &sample_local_ts, &sample_delay))
-      return;
+    n_readings = SYS_Linux_GetPHCReadings(iface->phc_fd, iface->phc_nocrossts,
+                                          &iface->phc_mode, PHC_READINGS, phc_readings);
+    if (n_readings > 0 &&
+        HCL_ProcessReadings(iface->clock, n_readings, phc_readings,
+                             &sample_phc_ts, &sample_sys_ts, &phc_err)) {
+      LCL_CookTime(&sample_sys_ts, &sample_local_ts, &local_err);
+      HCL_AccumulateSample(iface->clock, &sample_phc_ts, &sample_local_ts,
+                           phc_err + local_err);

-    HCL_AccumulateSample(iface->clock, &sample_phc_ts, &sample_local_ts,
-                         sample_delay / 2.0);
-
-    update_interface_speed(iface);
+      update_interface_speed(iface);
+    }
  }

  /* We need to transpose RX timestamps as hardware timestamps are normally
     preamble timestamps and RX timestamps in NTP are supposed to be trailer
-     timestamps.  Without raw sockets we don't know the length of the packet
-     at layer 2, so we make an assumption that UDP data start at the same
-     position as in the last transmitted packet which had a HW TX timestamp. */
+     timestamps.  If we don't know the length of the packet at layer 2, we
+     make an assumption that UDP data start at the same position as in the
+     last transmitted packet which had a HW TX timestamp. */
  if (rx_ntp_length && iface->link_speed) {
-    l2_length = (family == IPADDR_INET4 ? iface->l2_udp4_ntp_start :
-                 iface->l2_udp6_ntp_start) + rx_ntp_length + 4;
+    if (!l2_length)
+      l2_length = (family == IPADDR_INET4 ? iface->l2_udp4_ntp_start :
+                   iface->l2_udp6_ntp_start) + rx_ntp_length;
+
+    /* Include the frame check sequence (FCS) */
+    l2_length += 4;
+
    rx_correction = l2_length / (1.0e6 / 8 * iface->link_speed);

    UTI_AddDoubleToTimespec(hw_ts, rx_correction, hw_ts);
  }

-  if (!rx_ntp_length && iface->tx_comp)
-    UTI_AddDoubleToTimespec(hw_ts, iface->tx_comp, hw_ts);
-  else if (rx_ntp_length && iface->rx_comp)
-    UTI_AddDoubleToTimespec(hw_ts, -iface->rx_comp, hw_ts);
-
-  if (!HCL_CookTime(iface->clock, hw_ts, &ts, &err))
+  if (!HCL_CookTime(iface->clock, hw_ts, &ts, &local_err))
    return;

+  if (!rx_ntp_length && iface->tx_comp)
+    UTI_AddDoubleToTimespec(&ts, iface->tx_comp, &ts);
+  else if (rx_ntp_length && iface->rx_comp)
+    UTI_AddDoubleToTimespec(&ts, -iface->rx_comp, &ts);
+
  ts_delay = UTI_DiffTimespecsToDouble(&local_ts->ts, &ts);

  if (fabs(ts_delay) > MAX_TS_DELAY) {
-    DEBUG_LOG(LOGF_NtpIOLinux, "Unacceptable timestamp delay %.9f", ts_delay);
+    DEBUG_LOG("Unacceptable timestamp delay %.9f", ts_delay);
    return;
  }

  local_ts->ts = ts;
-  local_ts->err = err;
+  local_ts->err = local_err;
  local_ts->source = NTP_TS_HARDWARE;
 }

+/* ================================================== */
+
+static void
+process_sw_timestamp(struct timespec *sw_ts, NTP_Local_Timestamp *local_ts)
+{
+  double ts_delay, local_err;
+  struct timespec ts;
+
+  LCL_CookTime(sw_ts, &ts, &local_err);
+
+  ts_delay = UTI_DiffTimespecsToDouble(&local_ts->ts, &ts);
+
+  if (fabs(ts_delay) > MAX_TS_DELAY) {
+    DEBUG_LOG("Unacceptable timestamp delay %.9f", ts_delay);
+    return;
+  }
+
+  local_ts->ts = ts;
+  local_ts->err = local_err;
+  local_ts->source = NTP_TS_KERNEL;
+}
+
 /* ================================================== */
 /* Extract UDP data from a layer 2 message.  Supported is Ethernet
   with optional VLAN tags. */
@@ -477,7 +650,6 @@ static int
 extract_udp_data(unsigned char *msg, NTP_Remote_Address *remote_addr, int len)
 {
  unsigned char *msg_start = msg;
-  union sockaddr_in46 addr;

  remote_addr->ip_addr.family = IPADDR_UNSPEC;
  remote_addr->port = 0;
@@ -500,31 +672,60 @@ extract_udp_data(unsigned char *msg, NTP_Remote_Address *remote_addr, int len)
  /* Parse destination address and port from IPv4/IPv6 and UDP headers */
  if (len >= 20 && msg[0] >> 4 == 4) {
    int ihl = (msg[0] & 0xf) * 4;
+    uint32_t addr;

    if (len < ihl + 8 || msg[9] != 17)
      return 0;

-    memcpy(&addr.in4.sin_addr.s_addr, msg + 16, sizeof (uint32_t));
-    addr.in4.sin_port = *(uint16_t *)(msg + ihl + 2);
-    addr.in4.sin_family = AF_INET;
+    memcpy(&addr, msg + 16, sizeof (addr));
+    remote_addr->ip_addr.addr.in4 = ntohl(addr);
+    remote_addr->port = ntohs(*(uint16_t *)(msg + ihl + 2));
+    remote_addr->ip_addr.family = IPADDR_INET4;
    len -= ihl + 8, msg += ihl + 8;
 #ifdef FEAT_IPV6
  } else if (len >= 48 && msg[0] >> 4 == 6) {
-    /* IPv6 extension headers are not supported */
-    if (msg[6] != 17)
-      return 0;
+    int eh_len, next_header = msg[6];

-    memcpy(&addr.in6.sin6_addr.s6_addr, msg + 24, 16);
-    addr.in6.sin6_port = *(uint16_t *)(msg + 40 + 2);
-    addr.in6.sin6_family = AF_INET6;
-    len -= 48, msg += 48;
+    memcpy(&remote_addr->ip_addr.addr.in6, msg + 24, sizeof (remote_addr->ip_addr.addr.in6));
+    len -= 40, msg += 40;
+
+    /* Skip IPv6 extension headers if present */
+    while (next_header != 17) {
+      switch (next_header) {
+        case 44:  /* Fragment Header */
+          /* Process only the first fragment */
+          if (ntohs(*(uint16_t *)(msg + 2)) >> 3 != 0)
+            return 0;
+          eh_len = 8;
+          break;
+        case 0:   /* Hop-by-Hop Options */
+        case 43:  /* Routing Header */
+        case 60:  /* Destination Options */
+        case 135: /* Mobility Header */
+          eh_len = 8 * (msg[1] + 1);
+          break;
+        case 51:  /* Authentication Header */
+          eh_len = 4 * (msg[1] + 2);
+          break;
+        default:
+          return 0;
+      }
+
+      if (eh_len < 8 || len < eh_len + 8)
+        return 0;
+
+      next_header = msg[0];
+      len -= eh_len, msg += eh_len;
+    }
+
+    remote_addr->port = ntohs(*(uint16_t *)(msg + 2));
+    remote_addr->ip_addr.family = IPADDR_INET6;
+    len -= 8, msg += 8;
 #endif
  } else {
    return 0;
  }

-  UTI_SockaddrToIPAndPort(&addr.u, &remote_addr->ip_addr, &remote_addr->port);
-
  /* Move the message to fix alignment of its fields */
  if (len > 0)
    memmove(msg_start, msg, len);
@@ -535,50 +736,46 @@ extract_udp_data(unsigned char *msg, NTP_Remote_Address *remote_addr, int len)
 /* ================================================== */

 int
-NIO_Linux_ProcessMessage(NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr,
-                         NTP_Local_Timestamp *local_ts, struct msghdr *hdr,
-                         int length, int sock_fd, int if_index)
+NIO_Linux_ProcessMessage(SCK_Message *message, NTP_Local_Address *local_addr,
+                         NTP_Local_Timestamp *local_ts, int event)
 {
  struct Interface *iface;
-  struct cmsghdr *cmsg;
-  int is_tx, l2_length;
+  int is_tx, ts_if_index, l2_length;

-  is_tx = hdr->msg_flags & MSG_ERRQUEUE;
+  is_tx = event == SCH_FILE_EXCEPTION;
  iface = NULL;

-  for (cmsg = CMSG_FIRSTHDR(hdr); cmsg; cmsg = CMSG_NXTHDR(hdr, cmsg)) {
-    if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_TIMESTAMPING) {
-      struct scm_timestamping ts3;
+  ts_if_index = message->timestamp.if_index;
+  if (ts_if_index == INVALID_IF_INDEX)
+    ts_if_index = message->if_index;
+  l2_length = message->timestamp.l2_length;

-      memcpy(&ts3, CMSG_DATA(cmsg), sizeof (ts3));
-
-      if (!UTI_IsZeroTimespec(&ts3.ts[0])) {
-        LCL_CookTime(&ts3.ts[0], &local_ts->ts, &local_ts->err);
-        local_ts->source = NTP_TS_KERNEL;
-      } else if (!UTI_IsZeroTimespec(&ts3.ts[2])) {
-        iface = get_interface(if_index);
-        if (iface) {
-          process_hw_timestamp(iface, &ts3.ts[2], local_ts, !is_tx ? length : 0,
-                               remote_addr->ip_addr.family);
-        } else {
-          DEBUG_LOG(LOGF_NtpIOLinux, "HW clock not found for interface %d", if_index);
-        }
-      }
+  if (!UTI_IsZeroTimespec(&message->timestamp.hw)) {
+    iface = get_interface(ts_if_index);
+    if (iface) {
+      process_hw_timestamp(iface, &message->timestamp.hw, local_ts, !is_tx ? message->length : 0,
+                           message->remote_addr.ip.ip_addr.family, l2_length);
+    } else {
+      DEBUG_LOG("HW clock not found for interface %d", ts_if_index);
    }

-    if ((cmsg->cmsg_level == SOL_IP && cmsg->cmsg_type == IP_RECVERR) ||
-        (cmsg->cmsg_level == SOL_IPV6 && cmsg->cmsg_type == IPV6_RECVERR)) {
-      struct sock_extended_err err;
+    /* If a HW transmit timestamp was received, resume processing
+       of non-error messages on this socket */
+    if (is_tx)
+      resume_socket(local_addr->sock_fd);
+  }

-      memcpy(&err, CMSG_DATA(cmsg), sizeof (err));
+  if (local_ts->source == NTP_TS_DAEMON && !UTI_IsZeroTimespec(&message->timestamp.kernel) &&
+      (!is_tx || UTI_IsZeroTimespec(&message->timestamp.hw))) {
+    process_sw_timestamp(&message->timestamp.kernel, local_ts);
+  }

-      if (err.ee_errno != ENOMSG || err.ee_info != SCM_TSTAMP_SND ||
-          err.ee_origin != SO_EE_ORIGIN_TIMESTAMPING) {
-        DEBUG_LOG(LOGF_NtpIOLinux, "Unknown extended error");
-        /* Drop the message */
-        return 1;
-      }
-    }
+  /* If the kernel is slow with enabling RX timestamping, open a dummy
+     socket to keep the kernel RX timestamping permanently enabled */
+  if (!is_tx && local_ts->source == NTP_TS_DAEMON && ts_flags) {
+    DEBUG_LOG("Missing kernel RX timestamp");
+    if (dummy_rxts_socket == INVALID_SOCK_FD)
+      dummy_rxts_socket = open_dummy_socket();
  }

  /* Return the message if it's not received from the error queue */
@@ -588,59 +785,63 @@ NIO_Linux_ProcessMessage(NTP_Remote_Address *remote_addr, NTP_Local_Address *loc
  /* The data from the error queue includes all layers up to UDP.  We have to
     extract the UDP data and also the destination address with port as there
     currently doesn't seem to be a better way to get them both. */
-  l2_length = length;
-  length = extract_udp_data(hdr->msg_iov[0].iov_base, remote_addr, length);
+  l2_length = message->length;
+  message->length = extract_udp_data(message->data, &message->remote_addr.ip, message->length);

-  DEBUG_LOG(LOGF_NtpIOLinux, "Received %d (%d) bytes from error queue for %s:%d fd=%d if=%d tss=%d",
-            l2_length, length, UTI_IPToString(&remote_addr->ip_addr), remote_addr->port,
-            sock_fd, if_index, local_ts->source);
+  DEBUG_LOG("Extracted message for %s fd=%d len=%d",
+            UTI_IPSockAddrToString(&message->remote_addr.ip),
+            local_addr->sock_fd, message->length);

  /* Update assumed position of UDP data at layer 2 for next received packet */
-  if (iface && length) {
-    if (remote_addr->ip_addr.family == IPADDR_INET4)
-      iface->l2_udp4_ntp_start = l2_length - length;
-    else if (remote_addr->ip_addr.family == IPADDR_INET6)
-      iface->l2_udp6_ntp_start = l2_length - length;
+  if (iface && message->length) {
+    if (message->remote_addr.ip.ip_addr.family == IPADDR_INET4)
+      iface->l2_udp4_ntp_start = l2_length - message->length;
+    else if (message->remote_addr.ip.ip_addr.family == IPADDR_INET6)
+      iface->l2_udp6_ntp_start = l2_length - message->length;
  }

-  /* Drop the message if HW timestamp is missing or its processing failed */
-  if ((ts_flags & SOF_TIMESTAMPING_RAW_HARDWARE) && local_ts->source != NTP_TS_HARDWARE) {
-    DEBUG_LOG(LOGF_NtpIOLinux, "Missing HW timestamp");
+  /* Drop the message if it has no timestamp or its processing failed */
+  if (local_ts->source == NTP_TS_DAEMON) {
+    DEBUG_LOG("Missing TX timestamp");
    return 1;
  }

-  if (length < NTP_NORMAL_PACKET_LENGTH)
+  if (!NIO_UnwrapMessage(message, local_addr->sock_fd))
    return 1;

-  NSR_ProcessTx(remote_addr, local_addr, local_ts,
-                (NTP_Packet *)hdr->msg_iov[0].iov_base, length);
+  if (message->length < NTP_HEADER_LENGTH || message->length > sizeof (NTP_Packet))
+    return 1;
+
+  NSR_ProcessTx(&message->remote_addr.ip, local_addr, local_ts, message->data, message->length);

  return 1;
 }

 /* ================================================== */

-int
-NIO_Linux_RequestTxTimestamp(struct msghdr *msg, int cmsglen, int sock_fd)
+void
+NIO_Linux_RequestTxTimestamp(SCK_Message *message, int sock_fd)
 {
-  struct cmsghdr *cmsg;
+  if (!ts_flags)
+    return;
+
+  /* If a HW transmit timestamp is requested on a client socket, monitor
+     events on the socket in order to avoid processing of a fast response
+     without the HW timestamp of the request */
+  if (ts_tx_flags & SOF_TIMESTAMPING_TX_HARDWARE && !NIO_IsServerSocket(sock_fd))
+    monitored_socket = sock_fd;

  /* Check if TX timestamping is disabled on this socket */
  if (permanent_ts_options || !NIO_IsServerSocket(sock_fd))
-    return cmsglen;
+    return;

-  /* Add control message that will enable TX timestamping for this message.
-     Don't use CMSG_NXTHDR as the one in glibc is buggy for creating new
-     control messages. */
-  cmsg = (struct cmsghdr *)((char *)CMSG_FIRSTHDR(msg) + cmsglen);
-  memset(cmsg, 0, CMSG_SPACE(sizeof (ts_tx_flags)));
-  cmsglen += CMSG_SPACE(sizeof (ts_tx_flags));
-
-  cmsg->cmsg_level = SOL_SOCKET;
-  cmsg->cmsg_type = SO_TIMESTAMPING;
-  cmsg->cmsg_len = CMSG_LEN(sizeof (ts_tx_flags));
-
-  memcpy(CMSG_DATA(cmsg), &ts_tx_flags, sizeof (ts_tx_flags));
-
-  return cmsglen;
+  message->timestamp.tx_flags = ts_tx_flags;
+}
+
+/* ================================================== */
+
+void
+NIO_Linux_NotifySocketClosing(int sock_fd)
+{
+  resume_socket(sock_fd);
 }
--- a/ntp_io_linux.h
+++ b/ntp_io_linux.h
@@ -24,14 +24,24 @@
  This is the header file for the Linux-specific NTP socket I/O bits.
  */

+#ifndef GOT_NTP_IO_LINUX_H
+#define GOT_NTP_IO_LINUX_H
+
+#include "socket.h"
+
 extern void NIO_Linux_Initialise(void);

 extern void NIO_Linux_Finalise(void);

 extern int NIO_Linux_SetTimestampSocketOptions(int sock_fd, int client_only, int *events);

-extern int NIO_Linux_ProcessMessage(NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr,
-                                    NTP_Local_Timestamp *local_ts, struct msghdr *hdr, int length,
-                                    int sock_fd, int if_index);
+extern int NIO_Linux_ProcessEvent(int sock_fd, int event);

-extern int NIO_Linux_RequestTxTimestamp(struct msghdr *msg, int cmsglen, int sock_fd);
+extern int NIO_Linux_ProcessMessage(SCK_Message *message, NTP_Local_Address *local_addr,
+                                    NTP_Local_Timestamp *local_ts, int event);
+
+extern void NIO_Linux_RequestTxTimestamp(SCK_Message *message, int sock_fd);
+
+extern void NIO_Linux_NotifySocketClosing(int sock_fd);
+
+#endif
--- a/ntp_signd.c
+++ b/ntp_signd.c
@@ -34,6 +34,7 @@
 #include "ntp_io.h"
 #include "ntp_signd.h"
 #include "sched.h"
+#include "socket.h"
 #include "util.h"

 /* Declarations per samba/source4/librpc/idl/ntp_signd.idl */
@@ -90,19 +91,11 @@ static ARR_Instance queue;
 static unsigned int queue_head;
 static unsigned int queue_tail;

-#define INVALID_SOCK_FD -1
+#define INVALID_SOCK_FD (-6)

 /* Unix domain socket connected to ntp_signd */
 static int sock_fd;

-#define MIN_AUTH_DELAY 1.0e-5
-#define MAX_AUTH_DELAY 1.0e-2
-
-/* Average time needed for signing one packet.  This is used to adjust the
-   transmit timestamp in NTP packets.  The timestamp won't be very accurate as
-   the delay is variable, but it should be good enough for MS-SNTP clients. */
-static double auth_delay;
-
 /* Flag indicating if the MS-SNTP authentication is enabled */
 static int enabled;

@@ -116,7 +109,7 @@ static void
 close_socket(void)
 {
  SCH_RemoveFileHandler(sock_fd);
-  close(sock_fd);
+  SCK_CloseSocket(sock_fd);
  sock_fd = INVALID_SOCK_FD;

  /* Empty the queue */
@@ -128,36 +121,24 @@ close_socket(void)
 static int
 open_socket(void)
 {
-  struct sockaddr_un s;
+  char path[PATH_MAX];

-  if (sock_fd >= 0)
+  if (sock_fd != INVALID_SOCK_FD)
    return 1;

-  sock_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+  if (snprintf(path, sizeof (path), "%s/socket", CNF_GetNtpSigndSocket()) >= sizeof (path)) {
+    DEBUG_LOG("signd socket path too long");
+    return 0;
+  }
+
+  sock_fd = SCK_OpenUnixStreamSocket(path, NULL, 0);
  if (sock_fd < 0) {
-    DEBUG_LOG(LOGF_NtpSignd, "Could not open signd socket : %s", strerror(errno));
+    sock_fd = INVALID_SOCK_FD;
    return 0;
  }

-  UTI_FdSetCloexec(sock_fd);
  SCH_AddFileHandler(sock_fd, SCH_FILE_INPUT, read_write_socket, NULL);

-  s.sun_family = AF_UNIX;
-  if (snprintf(s.sun_path, sizeof (s.sun_path), "%s/socket",
-               CNF_GetNtpSigndSocket()) >= sizeof (s.sun_path)) {
-    DEBUG_LOG(LOGF_NtpSignd, "signd socket path too long");
-    close_socket();
-    return 0;
-  }
-
-  if (connect(sock_fd, (struct sockaddr *)&s, sizeof (s)) < 0) {
-    DEBUG_LOG(LOGF_NtpSignd, "Could not connect to signd : %s", strerror(errno));
-    close_socket();
-    return 0;
-  }
-
-  DEBUG_LOG(LOGF_NtpSignd, "Connected to signd");
-
  return 1;
 }

@@ -170,34 +151,30 @@ process_response(SignInstance *inst)
  double delay;

  if (ntohs(inst->request.packet_id) != ntohl(inst->response.packet_id)) {
-    DEBUG_LOG(LOGF_NtpSignd, "Invalid response ID");
+    DEBUG_LOG("Invalid response ID");
    return;
  }

  if (ntohl(inst->response.op) != SIGNING_SUCCESS) {
-    DEBUG_LOG(LOGF_NtpSignd, "Signing failed");
+    DEBUG_LOG("Signing failed");
    return;
  }

  /* Check if the file descriptor is still valid */
  if (!NIO_IsServerSocket(inst->local_addr.sock_fd)) {
-    DEBUG_LOG(LOGF_NtpSignd, "Invalid NTP socket");
+    DEBUG_LOG("Invalid NTP socket");
    return;
  }

  SCH_GetLastEventTime(NULL, NULL, &ts);
  delay = UTI_DiffTimespecsToDouble(&ts, &inst->request_ts);

-  DEBUG_LOG(LOGF_NtpSignd, "Signing succeeded (delay %f)", delay);
+  DEBUG_LOG("Signing succeeded (delay %f)", delay);

  /* Send the signed NTP packet */
  NIO_SendPacket(&inst->response.signed_packet, &inst->remote_addr, &inst->local_addr,
                 ntohl(inst->response.length) + sizeof (inst->response.length) -
                 offsetof(SigndResponse, signed_packet), 0);
-
-  /* Update exponential moving average of the authentication delay */
-  delay = CLAMP(MIN_AUTH_DELAY, delay, MAX_AUTH_DELAY);
-  auth_delay += 0.1 * (delay - auth_delay);
 }

 /* ================================================== */
@@ -218,16 +195,14 @@ read_write_socket(int sock_fd, int event, void *anything)
    if (!inst->sent)
      SCH_GetLastEventTime(NULL, NULL, &inst->request_ts);

-    s = send(sock_fd, (char *)&inst->request + inst->sent,
-             inst->request_length - inst->sent, 0);
+    s = SCK_Send(sock_fd, (char *)&inst->request + inst->sent,
+                 inst->request_length - inst->sent, 0);

    if (s < 0) {
-      DEBUG_LOG(LOGF_NtpSignd, "signd socket error: %s", strerror(errno));
      close_socket();
      return;
    }

-    DEBUG_LOG(LOGF_NtpSignd, "Sent %d bytes to signd", s);
    inst->sent += s;

    /* Try again later if the request is not complete yet */
@@ -235,31 +210,25 @@ read_write_socket(int sock_fd, int event, void *anything)
      return;

    /* Disable output and wait for a response */
-    SCH_SetFileHandlerEvents(sock_fd, SCH_FILE_INPUT);
+    SCH_SetFileHandlerEvent(sock_fd, SCH_FILE_OUTPUT, 0);
  }

  if (event == SCH_FILE_INPUT) {
    if (IS_QUEUE_EMPTY()) {
-        DEBUG_LOG(LOGF_NtpSignd, "Unexpected signd response");
+        DEBUG_LOG("Unexpected signd response");
        close_socket();
        return;
    }

    assert(inst->received < sizeof (inst->response));
-    s = recv(sock_fd, (char *)&inst->response + inst->received,
-             sizeof (inst->response) - inst->received, 0);
+    s = SCK_Receive(sock_fd, (char *)&inst->response + inst->received,
+                    sizeof (inst->response) - inst->received, 0);

    if (s <= 0) {
-      if (s < 0)
-        DEBUG_LOG(LOGF_NtpSignd, "signd socket error: %s", strerror(errno));
-      else
-        DEBUG_LOG(LOGF_NtpSignd, "signd socket closed");
-
      close_socket();
      return;
    }

-    DEBUG_LOG(LOGF_NtpSignd, "Received %d bytes from signd", s);
    inst->received += s;

    if (inst->received < sizeof (inst->response.length))
@@ -269,7 +238,7 @@ read_write_socket(int sock_fd, int event, void *anything)

    if (response_length < offsetof(SigndResponse, signed_packet) ||
        response_length > sizeof (SigndResponse)) {
-      DEBUG_LOG(LOGF_NtpSignd, "Invalid response length");
+      DEBUG_LOG("Invalid response length");
      close_socket();
      return;
    }
@@ -283,7 +252,7 @@ read_write_socket(int sock_fd, int event, void *anything)
    /* Move the head and enable output for the next packet */
    queue_head = NEXT_QUEUE_INDEX(queue_head);
    if (!IS_QUEUE_EMPTY())
-      SCH_SetFileHandlerEvents(sock_fd, SCH_FILE_INPUT | SCH_FILE_OUTPUT);
+      SCH_SetFileHandlerEvent(sock_fd, SCH_FILE_OUTPUT, 1);
  }
 }

@@ -293,7 +262,6 @@ void
 NSD_Initialise()
 {
  sock_fd = INVALID_SOCK_FD;
-  auth_delay = MIN_AUTH_DELAY;
  enabled = CNF_GetNtpSigndSocket() && CNF_GetNtpSigndSocket()[0];

  if (!enabled)
@@ -303,7 +271,7 @@ NSD_Initialise()
  ARR_SetSize(queue, MAX_QUEUE_LENGTH);
  queue_head = queue_tail = 0;

-  LOG(LOGS_INFO, LOGF_NtpSignd, "MS-SNTP authentication enabled");
+  LOG(LOGS_INFO, "MS-SNTP authentication enabled");
 }

 /* ================================================== */
@@ -320,30 +288,24 @@ NSD_Finalise()

 /* ================================================== */

-extern int NSD_GetAuthDelay(uint32_t key_id)
-{
-  return 1.0e9 * auth_delay;
-}
-
-/* ================================================== */
-
 int
-NSD_SignAndSendPacket(uint32_t key_id, NTP_Packet *packet, NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr, int length)
+NSD_SignAndSendPacket(uint32_t key_id, NTP_Packet *packet, NTP_PacketInfo *info,
+                      NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr)
 {
  SignInstance *inst;

  if (!enabled) {
-    DEBUG_LOG(LOGF_NtpSignd, "signd disabled");
+    DEBUG_LOG("signd disabled");
    return 0;
  }

  if (queue_head == NEXT_QUEUE_INDEX(queue_tail)) {
-    DEBUG_LOG(LOGF_NtpSignd, "signd queue full");
+    DEBUG_LOG("signd queue full");
    return 0;
  }

-  if (length != NTP_NORMAL_PACKET_LENGTH) {
-    DEBUG_LOG(LOGF_NtpSignd, "Invalid packet length");
+  if (info->length != NTP_HEADER_LENGTH) {
+    DEBUG_LOG("Invalid packet length");
    return 0;
  }

@@ -355,7 +317,7 @@ NSD_SignAndSendPacket(uint32_t key_id, NTP_Packet *packet, NTP_Remote_Address *r
  inst->local_addr = *local_addr;
  inst->sent = 0;
  inst->received = 0;
-  inst->request_length = offsetof(SigndRequest, packet_to_sign) + length;
+  inst->request_length = offsetof(SigndRequest, packet_to_sign) + info->length;

  /* The length field doesn't include itself */
  inst->request.length = htonl(inst->request_length - sizeof (inst->request.length));
@@ -365,16 +327,15 @@ NSD_SignAndSendPacket(uint32_t key_id, NTP_Packet *packet, NTP_Remote_Address *r
  inst->request._pad = 0;
  inst->request.key_id = htonl(key_id);

-  memcpy(&inst->request.packet_to_sign, packet, length);
+  memcpy(&inst->request.packet_to_sign, packet, info->length);

  /* Enable output if there was no pending request */
  if (IS_QUEUE_EMPTY())
-    SCH_SetFileHandlerEvents(sock_fd, SCH_FILE_INPUT | SCH_FILE_OUTPUT);
+    SCH_SetFileHandlerEvent(sock_fd, SCH_FILE_OUTPUT, 1);

  queue_tail = NEXT_QUEUE_INDEX(queue_tail);

-  DEBUG_LOG(LOGF_NtpSignd, "Packet added to signd queue (%u:%u)",
-            queue_head, queue_tail);
+  DEBUG_LOG("Packet added to signd queue (%u:%u)", queue_head, queue_tail);

  return 1;
 }
--- a/ntp_signd.h
+++ b/ntp_signd.h
@@ -35,10 +35,8 @@ extern void NSD_Initialise(void);
 /* Finalisation function */
 extern void NSD_Finalise(void);

-/* Function to get an estimate of delay due to signing */
-extern int NSD_GetAuthDelay(uint32_t key_id);
-
 /* Function to sign an NTP packet and send it */
-extern int NSD_SignAndSendPacket(uint32_t key_id, NTP_Packet *packet, NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr, int length);
+extern int NSD_SignAndSendPacket(uint32_t key_id, NTP_Packet *packet, NTP_PacketInfo *info,
+                                 NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr);

 #endif
--- a/ntp_sources.c
+++ b/ntp_sources.c
--- a/ntp_sources.h
+++ b/ntp_sources.h
@@ -44,16 +44,21 @@ typedef enum {
  NSR_NoSuchSource, /* Remove - attempt to remove a source that is not known */
  NSR_AlreadyInUse, /* AddSource - attempt to add a source that is already known */ 
  NSR_TooManySources, /* AddSource - too many sources already present */
-  NSR_InvalidAF /* AddSource - attempt to add a source with invalid address family */
+  NSR_InvalidAF, /* AddSource - attempt to add a source with invalid address family */
+  NSR_InvalidName, /* AddSourceByName - attempt to add a source with invalid name */
+  NSR_UnresolvedName, /* AddSourceByName - name will be resolved later */
 } NSR_Status;

 /* Procedure to add a new server or peer source. */
-extern NSR_Status NSR_AddSource(NTP_Remote_Address *remote_addr, NTP_Source_Type type, SourceParameters *params);
+extern NSR_Status NSR_AddSource(NTP_Remote_Address *remote_addr, NTP_Source_Type type,
+                                SourceParameters *params, uint32_t *conf_id);

 /* Procedure to add a new server, peer source, or pool of servers specified by
   name instead of address.  The name is resolved in exponentially increasing
-   intervals until it succeeds or fails with a non-temporary error. */
-extern void NSR_AddSourceByName(char *name, int port, int pool, NTP_Source_Type type, SourceParameters *params);
+   intervals until it succeeds or fails with a non-temporary error.  If the
+   name is an address, it is equivalent to NSR_AddSource(). */
+extern NSR_Status NSR_AddSourceByName(char *name, int port, int pool, NTP_Source_Type type,
+                                      SourceParameters *params, uint32_t *conf_id);

 /* Function type for handlers to be called back when an attempt
 * (possibly unsuccessful) to resolve unresolved sources ends */
@@ -72,7 +77,10 @@ extern void NSR_StartSources(void);
 extern void NSR_AutoStartSources(void);

 /* Procedure to remove a source */
-extern NSR_Status NSR_RemoveSource(NTP_Remote_Address *remote_addr);
+extern NSR_Status NSR_RemoveSource(IPAddr *address);
+
+/* Procedure to remove all sources matching a configuration ID */
+extern void NSR_RemoveSourcesById(uint32_t conf_id);

 /* Procedure to remove all sources */
 extern void NSR_RemoveAllSources(void);
@@ -83,9 +91,18 @@ extern void NSR_HandleBadSource(IPAddr *address);
 /* Procedure to resolve all names again */
 extern void NSR_RefreshAddresses(void);

+/* Procedure to update the address of a source.  The update may be
+   postponed. */
+extern NSR_Status NSR_UpdateSourceNtpAddress(NTP_Remote_Address *old_addr,
+                                             NTP_Remote_Address *new_addr);
+
 /* Procedure to get local reference ID corresponding to a source */
 extern uint32_t NSR_GetLocalRefid(IPAddr *address);

+/* Procedure to get the name of a source as it was specified (it may be
+   an IP address) */
+extern char *NSR_GetName(IPAddr *address);
+
 /* This routine is called by ntp_io when a new packet arrives off the network */
 extern void NSR_ProcessRx(NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr,
                          NTP_Local_Timestamp *rx_ts, NTP_Packet *message, int length);
@@ -102,14 +119,9 @@ extern void NSR_Initialise(void);
 extern void NSR_Finalise(void);

 /* This routine is used to indicate that sources whose IP addresses
-   match a particular subnet should be set online again.  Returns a
-   flag indicating whether any hosts matched the address */
-extern int NSR_TakeSourcesOnline(IPAddr *mask, IPAddr *address);
-
-/* This routine is used to indicate that sources whose IP addresses
-   match a particular subnet should be set offline.  Returns a flag
-   indicating whether any hosts matched the address */
-extern int NSR_TakeSourcesOffline(IPAddr *mask, IPAddr *address);
+   match a particular subnet should be set online or offline.  It returns
+   a flag indicating whether any hosts matched the address. */
+extern int NSR_SetConnectivity(IPAddr *mask, IPAddr *address, SRC_Connectivity connectivity);

 extern int NSR_ModifyMinpoll(IPAddr *address, int new_minpoll);

@@ -129,8 +141,12 @@ extern int NSR_InitiateSampleBurst(int n_good_samples, int n_total_samples, IPAd

 extern void NSR_ReportSource(RPT_SourceReport *report, struct timespec *now);

+extern int NSR_GetAuthReport(IPAddr *address, RPT_AuthReport *report);
+
 extern int NSR_GetNTPReport(RPT_NTPReport *report);

 extern void NSR_GetActivityReport(RPT_ActivityReport *report);

+extern void NSR_DumpAuthData(void);
+
 #endif /* GOT_NTP_SOURCES_H */
--- a/nts_ke.h
+++ b/nts_ke.h
@@ -0,0 +1,81 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2020
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Header file for the NTS Key Establishment protocol
+  */
+
+#ifndef GOT_NTS_KE_H
+#define GOT_NTS_KE_H
+
+#include "siv.h"
+
+#define NKE_PORT                        4460
+
+#define NKE_RECORD_CRITICAL_BIT         (1U << 15)
+#define NKE_RECORD_END_OF_MESSAGE       0
+#define NKE_RECORD_NEXT_PROTOCOL        1
+#define NKE_RECORD_ERROR                2
+#define NKE_RECORD_WARNING              3
+#define NKE_RECORD_AEAD_ALGORITHM       4
+#define NKE_RECORD_COOKIE               5
+#define NKE_RECORD_NTPV4_SERVER_NEGOTIATION 6
+#define NKE_RECORD_NTPV4_PORT_NEGOTIATION 7
+
+#define NKE_NEXT_PROTOCOL_NTPV4         0
+
+#define NKE_ERROR_UNRECOGNIZED_CRITICAL_RECORD 0
+#define NKE_ERROR_BAD_REQUEST           1
+#define NKE_ERROR_INTERNAL_SERVER_ERROR 2
+
+#define NKE_ALPN_NAME                   "ntske/1"
+#define NKE_EXPORTER_LABEL              "EXPORTER-network-time-security"
+#define NKE_EXPORTER_CONTEXT_C2S        "\x0\x0\x0\xf\x0"
+#define NKE_EXPORTER_CONTEXT_S2C        "\x0\x0\x0\xf\x1"
+
+#define NKE_MAX_MESSAGE_LENGTH          16384
+#define NKE_MAX_RECORD_BODY_LENGTH      256
+#define NKE_MAX_COOKIE_LENGTH           256
+#define NKE_MAX_COOKIES                 8
+#define NKE_MAX_KEY_LENGTH SIV_MAX_KEY_LENGTH
+
+#define NKE_RETRY_FACTOR2_CONNECT       4
+#define NKE_RETRY_FACTOR2_TLS           10
+#define NKE_MAX_RETRY_INTERVAL2         19
+
+typedef struct {
+  int length;
+  unsigned char key[NKE_MAX_KEY_LENGTH];
+} NKE_Key;
+
+typedef struct {
+  SIV_Algorithm algorithm;
+  NKE_Key c2s;
+  NKE_Key s2c;
+} NKE_Context;
+
+typedef struct {
+  int length;
+  unsigned char cookie[NKE_MAX_COOKIE_LENGTH];
+} NKE_Cookie;
+
+#endif
--- a/nts_ke_client.c
+++ b/nts_ke_client.c
@@ -0,0 +1,442 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2020-2021
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  NTS-KE client
+  */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include "nts_ke_client.h"
+
+#include "conf.h"
+#include "logging.h"
+#include "memory.h"
+#include "nameserv_async.h"
+#include "nts_ke_session.h"
+#include "siv.h"
+#include "socket.h"
+#include "util.h"
+
+#define CLIENT_TIMEOUT 16.0
+
+struct NKC_Instance_Record {
+  char *name;
+  IPSockAddr address;
+  NKSN_Credentials credentials;
+  NKSN_Instance session;
+  int destroying;
+  int got_response;
+  int resolving_name;
+
+  NKE_Context context;
+  NKE_Cookie cookies[NKE_MAX_COOKIES];
+  int num_cookies;
+  char server_name[NKE_MAX_RECORD_BODY_LENGTH + 2];
+  IPSockAddr ntp_address;
+};
+
+/* ================================================== */
+
+static NKSN_Credentials default_credentials = NULL;
+static int default_credentials_refs = 0;
+
+/* ================================================== */
+
+static void
+name_resolve_handler(DNS_Status status, int n_addrs, IPAddr *ip_addrs, void *arg)
+{
+  NKC_Instance inst = arg;
+  int i;
+
+  inst->resolving_name = 0;
+
+  if (inst->destroying) {
+    Free(inst);
+    return;
+  }
+
+  if (status != DNS_Success || n_addrs < 1) {
+    LOG(LOGS_ERR, "Could not resolve NTP server %s from %s", inst->server_name, inst->name);
+    /* Force restart */
+    inst->got_response = 0;
+    return;
+  }
+
+  inst->ntp_address.ip_addr = ip_addrs[0];
+
+  /* Prefer an address in the same family as the NTS-KE server */
+  for (i = 0; i < n_addrs; i++) {
+    DEBUG_LOG("%s resolved to %s", inst->server_name, UTI_IPToString(&ip_addrs[i]));
+    if (ip_addrs[i].family == inst->address.ip_addr.family) {
+      inst->ntp_address.ip_addr = ip_addrs[i];
+      break;
+    }
+  }
+}
+
+/* ================================================== */
+
+static int
+prepare_request(NKC_Instance inst)
+{
+  NKSN_Instance session = inst->session;
+  uint16_t datum;
+
+  NKSN_BeginMessage(session);
+
+  datum = htons(NKE_NEXT_PROTOCOL_NTPV4);
+  if (!NKSN_AddRecord(session, 1, NKE_RECORD_NEXT_PROTOCOL, &datum, sizeof (datum)))
+    return 0;
+
+  datum = htons(AEAD_AES_SIV_CMAC_256);
+  if (!NKSN_AddRecord(session, 1, NKE_RECORD_AEAD_ALGORITHM, &datum, sizeof (datum)))
+    return 0;
+
+  if (!NKSN_EndMessage(session))
+    return 0;
+
+  return 1;
+}
+
+/* ================================================== */
+
+static int
+process_response(NKC_Instance inst)
+{
+  int next_protocol = -1, aead_algorithm = -1, error = 0;
+  int i, critical, type, length;
+  uint16_t data[NKE_MAX_RECORD_BODY_LENGTH / sizeof (uint16_t)];
+
+  assert(NKE_MAX_COOKIE_LENGTH <= NKE_MAX_RECORD_BODY_LENGTH);
+  assert(sizeof (data) % sizeof (uint16_t) == 0);
+  assert(sizeof (uint16_t) == 2);
+
+  inst->num_cookies = 0;
+  inst->ntp_address.ip_addr.family = IPADDR_UNSPEC;
+  inst->ntp_address.port = 0;
+  inst->server_name[0] = '\0';
+
+  while (!error) {
+    if (!NKSN_GetRecord(inst->session, &critical, &type, &length, &data, sizeof (data)))
+      break;
+
+    if (length > sizeof (data)) {
+      DEBUG_LOG("Record too long type=%d length=%d critical=%d", type, length, critical);
+      if (critical)
+        error = 1;
+      continue;
+    }
+
+    switch (type) {
+      case NKE_RECORD_NEXT_PROTOCOL:
+        if (!critical || length != 2 || ntohs(data[0]) != NKE_NEXT_PROTOCOL_NTPV4) {
+          DEBUG_LOG("Unexpected NTS-KE next protocol");
+          error = 1;
+          break;
+        }
+        next_protocol = NKE_NEXT_PROTOCOL_NTPV4;
+        break;
+      case NKE_RECORD_AEAD_ALGORITHM:
+        if (length != 2 || ntohs(data[0]) != AEAD_AES_SIV_CMAC_256) {
+          DEBUG_LOG("Unexpected NTS-KE AEAD algorithm");
+          error = 1;
+          break;
+        }
+        aead_algorithm = AEAD_AES_SIV_CMAC_256;
+        inst->context.algorithm = aead_algorithm;
+        break;
+      case NKE_RECORD_ERROR:
+        if (length == 2)
+          DEBUG_LOG("NTS-KE error %d", ntohs(data[0]));
+        error = 1;
+        break;
+      case NKE_RECORD_WARNING:
+        if (length == 2)
+          DEBUG_LOG("NTS-KE warning %d", ntohs(data[0]));
+        error = 1;
+        break;
+      case NKE_RECORD_COOKIE:
+        DEBUG_LOG("Got cookie length=%d", length);
+
+        if (length < 1 || length > NKE_MAX_COOKIE_LENGTH || length % 4 != 0 ||
+            inst->num_cookies >= NKE_MAX_COOKIES) {
+          DEBUG_LOG("Unexpected length/cookie");
+          break;
+        }
+
+        assert(NKE_MAX_COOKIE_LENGTH == sizeof (inst->cookies[inst->num_cookies].cookie));
+        assert(NKE_MAX_COOKIES == sizeof (inst->cookies) /
+                                  sizeof (inst->cookies[inst->num_cookies]));
+        inst->cookies[inst->num_cookies].length = length;
+        memcpy(inst->cookies[inst->num_cookies].cookie, data, length);
+
+        inst->num_cookies++;
+        break;
+      case NKE_RECORD_NTPV4_SERVER_NEGOTIATION:
+        if (length < 1 || length >= sizeof (inst->server_name)) {
+          DEBUG_LOG("Invalid server name");
+          error = 1;
+          break;
+        }
+
+        memcpy(inst->server_name, data, length);
+        inst->server_name[length] = '\0';
+
+        /* Make sure the name is printable and has no spaces */
+        for (i = 0; i < length && isgraph((unsigned char)inst->server_name[i]); i++)
+          ;
+        if (i != length) {
+          DEBUG_LOG("Invalid server name");
+          error = 1;
+          break;
+        }
+
+        DEBUG_LOG("Negotiated server %s", inst->server_name);
+        break;
+      case NKE_RECORD_NTPV4_PORT_NEGOTIATION:
+        if (length != 2) {
+          DEBUG_LOG("Invalid port");
+          error = 1;
+          break;
+        }
+        inst->ntp_address.port = ntohs(data[0]);
+        DEBUG_LOG("Negotiated port %d", inst->ntp_address.port);
+        break;
+      default:
+        DEBUG_LOG("Unknown record type=%d length=%d critical=%d", type, length, critical);
+        if (critical)
+          error = 1;
+    }
+  }
+
+  DEBUG_LOG("NTS-KE response: error=%d next=%d aead=%d",
+            error, next_protocol, aead_algorithm);
+
+  if (error || inst->num_cookies == 0 ||
+      next_protocol != NKE_NEXT_PROTOCOL_NTPV4 ||
+      aead_algorithm != AEAD_AES_SIV_CMAC_256)
+    return 0;
+
+  return 1;
+}
+
+/* ================================================== */
+
+static int
+handle_message(void *arg)
+{
+  NKC_Instance inst = arg;
+
+  if (!process_response(inst)) {
+    LOG(LOGS_ERR, "Received invalid NTS-KE response from %s", inst->name);
+    return 0;
+  }
+
+  if (!NKSN_GetKeys(inst->session, inst->context.algorithm,
+                    &inst->context.c2s, &inst->context.s2c))
+    return 0;
+
+  if (inst->server_name[0] != '\0') {
+    if (inst->resolving_name)
+      return 0;
+    if (!UTI_StringToIP(inst->server_name, &inst->ntp_address.ip_addr)) {
+      int length = strlen(inst->server_name);
+
+      /* Add a trailing dot if not present to force the name to be
+         resolved as a fully qualified domain name */
+      if (length < 1 || length + 1 >= sizeof (inst->server_name))
+        return 0;
+      if (inst->server_name[length - 1] != '.') {
+        inst->server_name[length] = '.';
+        inst->server_name[length + 1] = '\0';
+      }
+
+      DNS_Name2IPAddressAsync(inst->server_name, name_resolve_handler, inst);
+      inst->resolving_name = 1;
+    }
+  }
+
+  inst->got_response = 1;
+
+  return 1;
+}
+
+/* ================================================== */
+
+NKC_Instance
+NKC_CreateInstance(IPSockAddr *address, const char *name, uint32_t cert_set)
+{
+  const char **trusted_certs;
+  uint32_t *certs_ids;
+  NKC_Instance inst;
+  int n_certs;
+
+  inst = MallocNew(struct NKC_Instance_Record);
+
+  inst->address = *address;
+  inst->name = Strdup(name);
+  inst->session = NKSN_CreateInstance(0, inst->name, handle_message, inst);
+  inst->resolving_name = 0;
+  inst->destroying = 0;
+  inst->got_response = 0;
+
+  n_certs = CNF_GetNtsTrustedCertsPaths(&trusted_certs, &certs_ids);
+
+  /* Share the credentials among clients using the default set of trusted
+     certificates, which likely contains most certificates */
+  if (cert_set == 0) {
+    if (!default_credentials)
+      default_credentials = NKSN_CreateClientCertCredentials(trusted_certs, certs_ids,
+                                                             n_certs, cert_set);
+    inst->credentials = default_credentials;
+    if (default_credentials)
+      default_credentials_refs++;
+  } else {
+    inst->credentials = NKSN_CreateClientCertCredentials(trusted_certs, certs_ids,
+                                                         n_certs, cert_set);
+  }
+
+  return inst;
+}
+
+/* ================================================== */
+
+void
+NKC_DestroyInstance(NKC_Instance inst)
+{
+  NKSN_DestroyInstance(inst->session);
+
+  Free(inst->name);
+
+  if (inst->credentials) {
+    if (inst->credentials == default_credentials) {
+      default_credentials_refs--;
+      if (default_credentials_refs <= 0) {
+        NKSN_DestroyCertCredentials(default_credentials);
+        default_credentials = NULL;
+      }
+    } else {
+      NKSN_DestroyCertCredentials(inst->credentials);
+    }
+  }
+
+  /* If the asynchronous resolver is running, let the handler free
+     the instance later */
+  if (inst->resolving_name) {
+    inst->destroying = 1;
+    return;
+  }
+
+  Free(inst);
+}
+
+/* ================================================== */
+
+int
+NKC_Start(NKC_Instance inst)
+{
+  IPSockAddr local_addr;
+  char label[512], *iface;
+  int sock_fd;
+
+  assert(!NKC_IsActive(inst));
+
+  inst->got_response = 0;
+
+  if (!inst->credentials) {
+    DEBUG_LOG("Missing client credentials");
+    return 0;
+  }
+
+  /* Follow the bindacqaddress and bindacqdevice settings */
+  CNF_GetBindAcquisitionAddress(inst->address.ip_addr.family, &local_addr.ip_addr);
+  local_addr.port = 0;
+  iface = CNF_GetBindAcquisitionInterface();
+
+  /* Make a label containing both the address and name of the server */
+  if (snprintf(label, sizeof (label), "%s (%s)",
+               UTI_IPSockAddrToString(&inst->address), inst->name) >= sizeof (label))
+    ;
+
+  sock_fd = SCK_OpenTcpSocket(&inst->address, &local_addr, iface, 0);
+  if (sock_fd < 0) {
+    LOG(LOGS_ERR, "Could not connect to %s", label);
+    return 0;
+  }
+
+  /* Start an NTS-KE session */
+  if (!NKSN_StartSession(inst->session, sock_fd, label, inst->credentials, CLIENT_TIMEOUT)) {
+    SCK_CloseSocket(sock_fd);
+    return 0;
+  }
+
+  /* Send a request */
+  if (!prepare_request(inst)) {
+    DEBUG_LOG("Could not prepare NTS-KE request");
+    NKSN_StopSession(inst->session);
+    return 0;
+  }
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NKC_IsActive(NKC_Instance inst)
+{
+  return !NKSN_IsStopped(inst->session) || inst->resolving_name;
+}
+
+/* ================================================== */
+
+int
+NKC_GetNtsData(NKC_Instance inst, NKE_Context *context,
+               NKE_Cookie *cookies, int *num_cookies, int max_cookies,
+               IPSockAddr *ntp_address)
+{
+  int i;
+
+  if (!inst->got_response || inst->resolving_name)
+    return 0;
+
+  *context = inst->context;
+
+  for (i = 0; i < inst->num_cookies && i < max_cookies; i++)
+    cookies[i] = inst->cookies[i];
+  *num_cookies = i;
+
+  *ntp_address = inst->ntp_address;
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NKC_GetRetryFactor(NKC_Instance inst)
+{
+  return NKSN_GetRetryFactor(inst->session);
+}
--- a/nts_ke_client.h
+++ b/nts_ke_client.h
@@ -0,0 +1,56 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2020
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Header file for the NTS-KE client
+  */
+
+#ifndef GOT_NTS_KE_CLIENT_H
+#define GOT_NTS_KE_CLIENT_H
+
+#include "addressing.h"
+#include "nts_ke.h"
+
+typedef struct NKC_Instance_Record *NKC_Instance;
+
+/* Create a client NTS-KE instance */
+extern NKC_Instance NKC_CreateInstance(IPSockAddr *address, const char *name, uint32_t cert_set);
+
+/* Destroy an instance */
+extern void NKC_DestroyInstance(NKC_Instance inst);
+
+/* Connect to the server, start an NTS-KE session, send an NTS-KE request, and
+   process the response (asynchronously) */
+extern int NKC_Start(NKC_Instance inst);
+
+/* Check if the client is still running */
+extern int NKC_IsActive(NKC_Instance inst);
+
+/* Get the NTS data if the session was successful */
+extern int NKC_GetNtsData(NKC_Instance inst, NKE_Context *context,
+                          NKE_Cookie *cookies, int *num_cookies, int max_cookies,
+                          IPSockAddr *ntp_address);
+
+/* Get a factor to calculate retry interval (in log2 seconds) */
+extern int NKC_GetRetryFactor(NKC_Instance inst);
+
+#endif
--- a/nts_ke_server.c
+++ b/nts_ke_server.c
@@ -0,0 +1,967 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2020
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  NTS-KE server
+  */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include "nts_ke_server.h"
+
+#include "array.h"
+#include "conf.h"
+#include "clientlog.h"
+#include "local.h"
+#include "logging.h"
+#include "memory.h"
+#include "ntp_core.h"
+#include "nts_ke_session.h"
+#include "privops.h"
+#include "siv.h"
+#include "socket.h"
+#include "sched.h"
+#include "sys.h"
+#include "util.h"
+
+#define SERVER_TIMEOUT 2.0
+
+#define SERVER_COOKIE_SIV AEAD_AES_SIV_CMAC_256
+#define SERVER_COOKIE_NONCE_LENGTH 16
+
+#define KEY_ID_INDEX_BITS 2
+#define MAX_SERVER_KEYS (1U << KEY_ID_INDEX_BITS)
+#define FUTURE_KEYS 1
+
+#define DUMP_FILENAME "ntskeys"
+#define DUMP_IDENTIFIER "NKS0\n"
+
+#define INVALID_SOCK_FD (-7)
+
+typedef struct {
+  uint32_t key_id;
+  unsigned char nonce[SERVER_COOKIE_NONCE_LENGTH];
+} ServerCookieHeader;
+
+typedef struct {
+  uint32_t id;
+  unsigned char key[SIV_MAX_KEY_LENGTH];
+  SIV_Instance siv;
+} ServerKey;
+
+typedef struct {
+  uint32_t key_id;
+  unsigned char key[SIV_MAX_KEY_LENGTH];
+  IPAddr client_addr;
+  uint16_t client_port;
+  uint16_t _pad;
+} HelperRequest;
+
+/* ================================================== */
+
+static ServerKey server_keys[MAX_SERVER_KEYS];
+static int current_server_key;
+static double last_server_key_ts;
+static int key_rotation_interval;
+
+static int server_sock_fd4;
+static int server_sock_fd6;
+
+static int helper_sock_fd;
+static int is_helper;
+
+static int initialised = 0;
+
+/* Array of NKSN instances */
+static ARR_Instance sessions;
+static NKSN_Credentials server_credentials;
+
+/* ================================================== */
+
+static int handle_message(void *arg);
+
+/* ================================================== */
+
+static int
+handle_client(int sock_fd, IPSockAddr *addr)
+{
+  NKSN_Instance inst, *instp;
+  int i;
+
+  /* Leave at least half of the descriptors which can handled by select()
+     to other use */
+  if (sock_fd > FD_SETSIZE / 2) {
+    DEBUG_LOG("Rejected connection from %s (%s)",
+              UTI_IPSockAddrToString(addr), "too many descriptors");
+    return 0;
+  }
+
+  /* Find an unused server slot or one with an already stopped session */
+  for (i = 0, inst = NULL; i < ARR_GetSize(sessions); i++) {
+    instp = ARR_GetElement(sessions, i);
+    if (!*instp) {
+      /* NULL handler arg will be replaced with the session instance */
+      inst = NKSN_CreateInstance(1, NULL, handle_message, NULL);
+      *instp = inst;
+      break;
+    } else if (NKSN_IsStopped(*instp)) {
+      inst = *instp;
+      break;
+    }
+  }
+
+  if (!inst) {
+    DEBUG_LOG("Rejected connection from %s (%s)",
+              UTI_IPSockAddrToString(addr), "too many connections");
+    return 0;
+  }
+
+  assert(server_credentials);
+
+  if (!NKSN_StartSession(inst, sock_fd, UTI_IPSockAddrToString(addr),
+                         server_credentials, SERVER_TIMEOUT))
+    return 0;
+
+  return 1;
+}
+
+/* ================================================== */
+
+static void
+handle_helper_request(int fd, int event, void *arg)
+{
+  SCK_Message *message;
+  HelperRequest *req;
+  IPSockAddr client_addr;
+  int sock_fd;
+
+  /* Receive the helper request with the NTS-KE session socket.
+     With multiple helpers EAGAIN errors are expected here. */
+  message = SCK_ReceiveMessage(fd, SCK_FLAG_MSG_DESCRIPTOR);
+  if (!message)
+    return;
+
+  sock_fd = message->descriptor;
+  if (sock_fd < 0) {
+    /* Message with no descriptor is a shutdown command */
+    SCH_QuitProgram();
+    return;
+  }
+
+  if (!initialised) {
+    DEBUG_LOG("Uninitialised helper");
+    SCK_CloseSocket(sock_fd);
+    return;
+  }
+
+  if (message->length != sizeof (HelperRequest))
+    LOG_FATAL("Invalid helper request");
+
+  req = message->data;
+
+  /* Extract the current server key and client address from the request */
+  server_keys[current_server_key].id = ntohl(req->key_id);
+  assert(sizeof (server_keys[current_server_key].key) == sizeof (req->key));
+  memcpy(server_keys[current_server_key].key, req->key,
+         sizeof (server_keys[current_server_key].key));
+  UTI_IPNetworkToHost(&req->client_addr, &client_addr.ip_addr);
+  client_addr.port = ntohs(req->client_port);
+
+  if (!SIV_SetKey(server_keys[current_server_key].siv, server_keys[current_server_key].key,
+                  SIV_GetKeyLength(SERVER_COOKIE_SIV)))
+    LOG_FATAL("Could not set SIV key");
+
+  if (!handle_client(sock_fd, &client_addr)) {
+    SCK_CloseSocket(sock_fd);
+    return;
+  }
+
+  DEBUG_LOG("Accepted helper request fd=%d", sock_fd);
+}
+
+/* ================================================== */
+
+static void
+accept_connection(int listening_fd, int event, void *arg)
+{
+  SCK_Message message;
+  IPSockAddr addr;
+  int log_index, sock_fd;
+  struct timespec now;
+
+  sock_fd = SCK_AcceptConnection(listening_fd, &addr);
+  if (sock_fd < 0)
+    return;
+
+  if (!NCR_CheckAccessRestriction(&addr.ip_addr)) {
+    DEBUG_LOG("Rejected connection from %s (%s)",
+              UTI_IPSockAddrToString(&addr), "access denied");
+    SCK_CloseSocket(sock_fd);
+    return;
+  }
+
+  SCH_GetLastEventTime(&now, NULL, NULL);
+
+  log_index = CLG_LogServiceAccess(CLG_NTSKE, &addr.ip_addr, &now);
+  if (log_index >= 0 && CLG_LimitServiceRate(CLG_NTSKE, log_index)) {
+    DEBUG_LOG("Rejected connection from %s (%s)",
+              UTI_IPSockAddrToString(&addr), "rate limit");
+    SCK_CloseSocket(sock_fd);
+    return;
+  }
+
+  /* Pass the socket to a helper process if enabled.  Otherwise, handle the
+     client in the main process. */
+  if (helper_sock_fd != INVALID_SOCK_FD) {
+    HelperRequest req;
+
+    memset(&req, 0, sizeof (req));
+
+    /* Include the current server key and client address in the request */
+    req.key_id = htonl(server_keys[current_server_key].id);
+    assert(sizeof (req.key) == sizeof (server_keys[current_server_key].key));
+    memcpy(req.key, server_keys[current_server_key].key, sizeof (req.key));
+    UTI_IPHostToNetwork(&addr.ip_addr, &req.client_addr);
+    req.client_port = htons(addr.port);
+
+    SCK_InitMessage(&message, SCK_ADDR_UNSPEC);
+    message.data = &req;
+    message.length = sizeof (req);
+    message.descriptor = sock_fd;
+
+    errno = 0;
+    if (!SCK_SendMessage(helper_sock_fd, &message, SCK_FLAG_MSG_DESCRIPTOR)) {
+      /* If sending failed with EPIPE, it means all helpers closed their end of
+         the socket (e.g. due to a fatal error) */
+      if (errno == EPIPE)
+        LOG_FATAL("NTS-KE helpers failed");
+      SCK_CloseSocket(sock_fd);
+      return;
+    }
+
+    SCK_CloseSocket(sock_fd);
+  } else {
+    if (!handle_client(sock_fd, &addr)) {
+      SCK_CloseSocket(sock_fd);
+      return;
+    }
+  }
+
+  DEBUG_LOG("Accepted connection from %s fd=%d", UTI_IPSockAddrToString(&addr), sock_fd);
+}
+
+/* ================================================== */
+
+static int
+open_socket(int family)
+{
+  IPSockAddr local_addr;
+  int backlog, sock_fd;
+  char *iface;
+
+  if (!SCK_IsIpFamilyEnabled(family))
+    return INVALID_SOCK_FD;
+
+  CNF_GetBindAddress(family, &local_addr.ip_addr);
+  local_addr.port = CNF_GetNtsServerPort();
+  iface = CNF_GetBindNtpInterface();
+
+  sock_fd = SCK_OpenTcpSocket(NULL, &local_addr, iface, 0);
+  if (sock_fd < 0) {
+    LOG(LOGS_ERR, "Could not open NTS-KE socket on %s", UTI_IPSockAddrToString(&local_addr));
+    return INVALID_SOCK_FD;
+  }
+
+  /* Set the maximum number of waiting connections on the socket to the maximum
+     number of concurrent sessions */
+  backlog = MAX(CNF_GetNtsServerProcesses(), 1) * CNF_GetNtsServerConnections();
+
+  if (!SCK_ListenOnSocket(sock_fd, backlog)) {
+    SCK_CloseSocket(sock_fd);
+    return INVALID_SOCK_FD;
+  }
+
+  SCH_AddFileHandler(sock_fd, SCH_FILE_INPUT, accept_connection, NULL);
+
+  return sock_fd;
+}
+
+/* ================================================== */
+
+static void
+helper_signal(int x)
+{
+  SCH_QuitProgram();
+}
+
+/* ================================================== */
+
+static int
+prepare_response(NKSN_Instance session, int error, int next_protocol, int aead_algorithm)
+{
+  NKE_Context context;
+  NKE_Cookie cookie;
+  char *ntp_server;
+  uint16_t datum;
+  int i;
+
+  DEBUG_LOG("NTS KE response: error=%d next=%d aead=%d", error, next_protocol, aead_algorithm);
+
+  NKSN_BeginMessage(session);
+
+  if (error >= 0) {
+    datum = htons(error);
+    if (!NKSN_AddRecord(session, 1, NKE_RECORD_ERROR, &datum, sizeof (datum)))
+      return 0;
+  } else if (next_protocol < 0) {
+    if (!NKSN_AddRecord(session, 1, NKE_RECORD_NEXT_PROTOCOL, NULL, 0))
+      return 0;
+  } else if (aead_algorithm < 0) {
+    datum = htons(next_protocol);
+    if (!NKSN_AddRecord(session, 1, NKE_RECORD_NEXT_PROTOCOL, &datum, sizeof (datum)))
+      return 0;
+    if (!NKSN_AddRecord(session, 1, NKE_RECORD_AEAD_ALGORITHM, NULL, 0))
+      return 0;
+  } else {
+    datum = htons(next_protocol);
+    if (!NKSN_AddRecord(session, 1, NKE_RECORD_NEXT_PROTOCOL, &datum, sizeof (datum)))
+      return 0;
+
+    datum = htons(aead_algorithm);
+    if (!NKSN_AddRecord(session, 1, NKE_RECORD_AEAD_ALGORITHM, &datum, sizeof (datum)))
+      return 0;
+
+    if (CNF_GetNTPPort() != NTP_PORT) {
+      datum = htons(CNF_GetNTPPort());
+      if (!NKSN_AddRecord(session, 1, NKE_RECORD_NTPV4_PORT_NEGOTIATION, &datum, sizeof (datum)))
+        return 0;
+    }
+
+    ntp_server = CNF_GetNtsNtpServer();
+    if (ntp_server) {
+      if (!NKSN_AddRecord(session, 1, NKE_RECORD_NTPV4_SERVER_NEGOTIATION,
+                          ntp_server, strlen(ntp_server)))
+        return 0;
+    }
+
+    context.algorithm = aead_algorithm;
+
+    if (!NKSN_GetKeys(session, aead_algorithm, &context.c2s, &context.s2c))
+      return 0;
+
+    for (i = 0; i < NKE_MAX_COOKIES; i++) {
+      if (!NKS_GenerateCookie(&context, &cookie))
+        return 0;
+      if (!NKSN_AddRecord(session, 0, NKE_RECORD_COOKIE, cookie.cookie, cookie.length))
+        return 0;
+    }
+  }
+
+  if (!NKSN_EndMessage(session))
+    return 0;
+
+  return 1;
+}
+
+/* ================================================== */
+
+static int
+process_request(NKSN_Instance session)
+{
+  int next_protocol_records = 0, aead_algorithm_records = 0;
+  int next_protocol_values = 0, aead_algorithm_values = 0;
+  int next_protocol = -1, aead_algorithm = -1, error = -1;
+  int i, critical, type, length;
+  uint16_t data[NKE_MAX_RECORD_BODY_LENGTH / sizeof (uint16_t)];
+
+  assert(NKE_MAX_RECORD_BODY_LENGTH % sizeof (uint16_t) == 0);
+  assert(sizeof (uint16_t) == 2);
+
+  while (error < 0) {
+    if (!NKSN_GetRecord(session, &critical, &type, &length, &data, sizeof (data)))
+      break;
+
+    switch (type) {
+      case NKE_RECORD_NEXT_PROTOCOL:
+        if (!critical || length < 2 || length % 2 != 0) {
+          error = NKE_ERROR_BAD_REQUEST;
+          break;
+        }
+
+        next_protocol_records++;
+
+        for (i = 0; i < MIN(length, sizeof (data)) / 2; i++) {
+          next_protocol_values++;
+          if (ntohs(data[i]) == NKE_NEXT_PROTOCOL_NTPV4)
+            next_protocol = NKE_NEXT_PROTOCOL_NTPV4;
+        }
+        break;
+      case NKE_RECORD_AEAD_ALGORITHM:
+        if (length < 2 || length % 2 != 0) {
+          error = NKE_ERROR_BAD_REQUEST;
+          break;
+        }
+
+        aead_algorithm_records++;
+
+        for (i = 0; i < MIN(length, sizeof (data)) / 2; i++) {
+          aead_algorithm_values++;
+          if (ntohs(data[i]) == AEAD_AES_SIV_CMAC_256)
+            aead_algorithm = AEAD_AES_SIV_CMAC_256;
+        }
+        break;
+      case NKE_RECORD_ERROR:
+      case NKE_RECORD_WARNING:
+      case NKE_RECORD_COOKIE:
+        error = NKE_ERROR_BAD_REQUEST;
+        break;
+      default:
+        if (critical)
+          error = NKE_ERROR_UNRECOGNIZED_CRITICAL_RECORD;
+    }
+  }
+
+  if (error < 0) {
+    if (next_protocol_records != 1 || next_protocol_values < 1 ||
+        (next_protocol == NKE_NEXT_PROTOCOL_NTPV4 &&
+         (aead_algorithm_records != 1 || aead_algorithm_values < 1)))
+      error = NKE_ERROR_BAD_REQUEST;
+  }
+
+  if (!prepare_response(session, error, next_protocol, aead_algorithm))
+    return 0;
+
+  return 1;
+}
+
+/* ================================================== */
+
+static int
+handle_message(void *arg)
+{
+  NKSN_Instance session = arg;
+
+  return process_request(session);
+}
+
+/* ================================================== */
+
+static void
+generate_key(int index)
+{
+  int key_length;
+
+  if (index < 0 || index >= MAX_SERVER_KEYS)
+    assert(0);
+
+  key_length = SIV_GetKeyLength(SERVER_COOKIE_SIV);
+  if (key_length > sizeof (server_keys[index].key))
+    assert(0);
+
+  UTI_GetRandomBytesUrandom(server_keys[index].key, key_length);
+
+  if (!server_keys[index].siv ||
+      !SIV_SetKey(server_keys[index].siv, server_keys[index].key, key_length))
+    LOG_FATAL("Could not set SIV key");
+
+  UTI_GetRandomBytes(&server_keys[index].id, sizeof (server_keys[index].id));
+
+  /* Encode the index in the lowest bits of the ID */
+  server_keys[index].id &= -1U << KEY_ID_INDEX_BITS;
+  server_keys[index].id |= index;
+
+  DEBUG_LOG("Generated server key %"PRIX32, server_keys[index].id);
+
+  last_server_key_ts = SCH_GetLastEventMonoTime();
+}
+
+/* ================================================== */
+
+static void
+save_keys(void)
+{
+  char buf[SIV_MAX_KEY_LENGTH * 2 + 1], *dump_dir;
+  int i, index, key_length;
+  double last_key_age;
+  FILE *f;
+
+  /* Don't save the keys if rotation is disabled to enable an external
+     management of the keys (e.g. share them with another server) */
+  if (key_rotation_interval == 0)
+    return;
+
+  dump_dir = CNF_GetNtsDumpDir();
+  if (!dump_dir)
+    return;
+
+  f = UTI_OpenFile(dump_dir, DUMP_FILENAME, ".tmp", 'w', 0600);
+  if (!f)
+    return;
+
+  key_length = SIV_GetKeyLength(SERVER_COOKIE_SIV);
+  last_key_age = SCH_GetLastEventMonoTime() - last_server_key_ts;
+
+  if (fprintf(f, "%s%d %.1f\n", DUMP_IDENTIFIER, SERVER_COOKIE_SIV, last_key_age) < 0)
+    goto error;
+
+  for (i = 0; i < MAX_SERVER_KEYS; i++) {
+    index = (current_server_key + i + 1 + FUTURE_KEYS) % MAX_SERVER_KEYS;
+
+    if (key_length > sizeof (server_keys[index].key) ||
+        !UTI_BytesToHex(server_keys[index].key, key_length, buf, sizeof (buf)) ||
+        fprintf(f, "%08"PRIX32" %s\n", server_keys[index].id, buf) < 0)
+      goto error;
+  }
+
+  fclose(f);
+
+  /* Rename the temporary file, or remove it if that fails */
+  if (!UTI_RenameTempFile(dump_dir, DUMP_FILENAME, ".tmp", NULL)) {
+    if (!UTI_RemoveFile(dump_dir, DUMP_FILENAME, ".tmp"))
+      ;
+  }
+
+  return;
+
+error:
+  DEBUG_LOG("Could not %s server keys", "save");
+  fclose(f);
+
+  if (!UTI_RemoveFile(dump_dir, DUMP_FILENAME, NULL))
+    ;
+}
+
+/* ================================================== */
+
+#define MAX_WORDS 2
+
+static int
+load_keys(void)
+{
+  char *dump_dir, line[1024], *words[MAX_WORDS];
+  unsigned char key[SIV_MAX_KEY_LENGTH];
+  int i, index, key_length, algorithm;
+  double key_age;
+  FILE *f;
+  uint32_t id;
+
+  dump_dir = CNF_GetNtsDumpDir();
+  if (!dump_dir)
+    return 0;
+
+  f = UTI_OpenFile(dump_dir, DUMP_FILENAME, NULL, 'r', 0);
+  if (!f)
+    return 0;
+
+  if (!fgets(line, sizeof (line), f) || strcmp(line, DUMP_IDENTIFIER) != 0 ||
+      !fgets(line, sizeof (line), f) || UTI_SplitString(line, words, MAX_WORDS) != 2 ||
+        sscanf(words[0], "%d", &algorithm) != 1 || algorithm != SERVER_COOKIE_SIV ||
+        sscanf(words[1], "%lf", &key_age) != 1)
+    goto error;
+
+  key_length = SIV_GetKeyLength(SERVER_COOKIE_SIV);
+  last_server_key_ts = SCH_GetLastEventMonoTime() - MAX(key_age, 0.0);
+
+  for (i = 0; i < MAX_SERVER_KEYS && fgets(line, sizeof (line), f); i++) {
+    if (UTI_SplitString(line, words, MAX_WORDS) != 2 ||
+        sscanf(words[0], "%"PRIX32, &id) != 1)
+      goto error;
+
+    if (UTI_HexToBytes(words[1], key, sizeof (key)) != key_length)
+      goto error;
+
+    index = id % MAX_SERVER_KEYS;
+
+    server_keys[index].id = id;
+    assert(sizeof (server_keys[index].key) == sizeof (key));
+    memcpy(server_keys[index].key, key, key_length);
+
+    if (!SIV_SetKey(server_keys[index].siv, server_keys[index].key, key_length))
+      LOG_FATAL("Could not set SIV key");
+
+    DEBUG_LOG("Loaded key %"PRIX32, id);
+
+    current_server_key = (index + MAX_SERVER_KEYS - FUTURE_KEYS) % MAX_SERVER_KEYS;
+  }
+
+  fclose(f);
+
+  return 1;
+
+error:
+  DEBUG_LOG("Could not %s server keys", "load");
+  fclose(f);
+
+  return 0;
+}
+
+/* ================================================== */
+
+static void
+key_timeout(void *arg)
+{
+  current_server_key = (current_server_key + 1) % MAX_SERVER_KEYS;
+  generate_key((current_server_key + FUTURE_KEYS) % MAX_SERVER_KEYS);
+  save_keys();
+
+  SCH_AddTimeoutByDelay(key_rotation_interval, key_timeout, NULL);
+}
+
+/* ================================================== */
+
+static void
+run_helper(uid_t uid, gid_t gid, int scfilter_level)
+{
+  LOG_Severity log_severity;
+
+  /* Finish minimal initialisation and run using the scheduler loop
+     similarly to the main process */
+
+  DEBUG_LOG("Helper started");
+
+  /* Suppress a log message about disabled clock control */
+  log_severity = LOG_GetMinSeverity();
+  LOG_SetMinSeverity(LOGS_ERR);
+
+  SYS_Initialise(0);
+  LOG_SetMinSeverity(log_severity);
+
+  if (!geteuid() && (uid || gid))
+    SYS_DropRoot(uid, gid, SYS_NTSKE_HELPER);
+
+  NKS_Initialise();
+
+  UTI_SetQuitSignalsHandler(helper_signal, 1);
+  if (scfilter_level != 0)
+    SYS_EnableSystemCallFilter(scfilter_level, SYS_NTSKE_HELPER);
+
+  SCH_MainLoop();
+
+  DEBUG_LOG("Helper exiting");
+
+  NKS_Finalise();
+  SCK_Finalise();
+  SYS_Finalise();
+  SCH_Finalise();
+  LCL_Finalise();
+  PRV_Finalise();
+  CNF_Finalise();
+  LOG_Finalise();
+
+  UTI_ResetGetRandomFunctions();
+
+  exit(0);
+}
+
+/* ================================================== */
+
+void
+NKS_PreInitialise(uid_t uid, gid_t gid, int scfilter_level)
+{
+  int i, processes, sock_fd1, sock_fd2;
+  const char **certs, **keys;
+  char prefix[16];
+  pid_t pid;
+
+  helper_sock_fd = INVALID_SOCK_FD;
+  is_helper = 0;
+
+  if (CNF_GetNtsServerCertAndKeyFiles(&certs, &keys) <= 0)
+    return;
+
+  processes = CNF_GetNtsServerProcesses();
+  if (processes <= 0)
+    return;
+
+  /* Start helper processes to perform (computationally expensive) NTS-KE
+     sessions with clients on sockets forwarded from the main process */
+
+  sock_fd1 = SCK_OpenUnixSocketPair(0, &sock_fd2);
+  if (sock_fd1 < 0)
+    LOG_FATAL("Could not open socket pair");
+
+  for (i = 0; i < processes; i++) {
+    pid = fork();
+
+    if (pid < 0)
+      LOG_FATAL("fork() failed : %s", strerror(errno));
+
+    if (pid > 0)
+      continue;
+
+    is_helper = 1;
+
+    UTI_ResetGetRandomFunctions();
+
+    snprintf(prefix, sizeof (prefix), "nks#%d:", i + 1);
+    LOG_SetDebugPrefix(prefix);
+    LOG_CloseParentFd();
+
+    SCK_CloseSocket(sock_fd1);
+    SCH_AddFileHandler(sock_fd2, SCH_FILE_INPUT, handle_helper_request, NULL);
+
+    run_helper(uid, gid, scfilter_level);
+  }
+
+  SCK_CloseSocket(sock_fd2);
+  helper_sock_fd = sock_fd1;
+}
+
+/* ================================================== */
+
+void
+NKS_Initialise(void)
+{
+  const char **certs, **keys;
+  int i, n_certs_keys;
+  double key_delay;
+
+  server_sock_fd4 = INVALID_SOCK_FD;
+  server_sock_fd6 = INVALID_SOCK_FD;
+
+  n_certs_keys = CNF_GetNtsServerCertAndKeyFiles(&certs, &keys);
+  if (n_certs_keys <= 0)
+    return;
+
+  if (helper_sock_fd == INVALID_SOCK_FD) {
+    server_credentials = NKSN_CreateServerCertCredentials(certs, keys, n_certs_keys);
+    if (!server_credentials)
+      return;
+  } else {
+    server_credentials = NULL;
+  }
+
+  sessions = ARR_CreateInstance(sizeof (NKSN_Instance));
+  for (i = 0; i < CNF_GetNtsServerConnections(); i++)
+    *(NKSN_Instance *)ARR_GetNewElement(sessions) = NULL;
+
+  /* Generate random keys, even if they will be replaced by reloaded keys,
+     or unused (in the helper) */
+  for (i = 0; i < MAX_SERVER_KEYS; i++) {
+    server_keys[i].siv = SIV_CreateInstance(SERVER_COOKIE_SIV);
+    generate_key(i);
+  }
+
+  current_server_key = MAX_SERVER_KEYS - 1;
+
+  if (!is_helper) {
+    server_sock_fd4 = open_socket(IPADDR_INET4);
+    server_sock_fd6 = open_socket(IPADDR_INET6);
+
+    key_rotation_interval = MAX(CNF_GetNtsRotate(), 0);
+
+    /* Reload saved keys, or save the new keys */
+    if (!load_keys())
+      save_keys();
+
+    if (key_rotation_interval > 0) {
+      key_delay = key_rotation_interval - (SCH_GetLastEventMonoTime() - last_server_key_ts);
+      SCH_AddTimeoutByDelay(MAX(key_delay, 0.0), key_timeout, NULL);
+    }
+  }
+
+  initialised = 1;
+}
+
+/* ================================================== */
+
+void
+NKS_Finalise(void)
+{
+  int i;
+
+  if (!initialised)
+    return;
+
+  if (helper_sock_fd != INVALID_SOCK_FD) {
+    /* Send the helpers a request to exit */
+    for (i = 0; i < CNF_GetNtsServerProcesses(); i++) {
+      if (!SCK_Send(helper_sock_fd, "", 1, 0))
+        ;
+    }
+    SCK_CloseSocket(helper_sock_fd);
+  }
+  if (server_sock_fd4 != INVALID_SOCK_FD)
+    SCK_CloseSocket(server_sock_fd4);
+  if (server_sock_fd6 != INVALID_SOCK_FD)
+    SCK_CloseSocket(server_sock_fd6);
+
+  if (!is_helper)
+    save_keys();
+
+  for (i = 0; i < MAX_SERVER_KEYS; i++)
+    SIV_DestroyInstance(server_keys[i].siv);
+
+  for (i = 0; i < ARR_GetSize(sessions); i++) {
+    NKSN_Instance session = *(NKSN_Instance *)ARR_GetElement(sessions, i);
+    if (session)
+      NKSN_DestroyInstance(session);
+  }
+  ARR_DestroyInstance(sessions);
+
+  if (server_credentials)
+    NKSN_DestroyCertCredentials(server_credentials);
+}
+
+/* ================================================== */
+
+void
+NKS_DumpKeys(void)
+{
+  save_keys();
+}
+
+/* ================================================== */
+
+void
+NKS_ReloadKeys(void)
+{
+  /* Don't load the keys if they are expected to be generated by this server
+     instance (i.e. they are already loaded) to not delay the next rotation */
+  if (key_rotation_interval > 0)
+    return;
+
+  load_keys();
+}
+
+/* ================================================== */
+
+/* A server cookie consists of key ID, nonce, and encrypted C2S+S2C keys */
+
+int
+NKS_GenerateCookie(NKE_Context *context, NKE_Cookie *cookie)
+{
+  unsigned char plaintext[2 * NKE_MAX_KEY_LENGTH], *ciphertext;
+  int plaintext_length, tag_length;
+  ServerCookieHeader *header;
+  ServerKey *key;
+
+  if (!initialised) {
+    DEBUG_LOG("NTS server disabled");
+    return 0;
+  }
+
+  /* The algorithm is hardcoded for now */
+  if (context->algorithm != AEAD_AES_SIV_CMAC_256) {
+    DEBUG_LOG("Unexpected SIV algorithm");
+    return 0;
+  }
+
+  if (context->c2s.length < 0 || context->c2s.length > NKE_MAX_KEY_LENGTH ||
+      context->s2c.length < 0 || context->s2c.length > NKE_MAX_KEY_LENGTH) {
+    DEBUG_LOG("Invalid key length");
+    return 0;
+  }
+
+  key = &server_keys[current_server_key];
+
+  header = (ServerCookieHeader *)cookie->cookie;
+
+  header->key_id = htonl(key->id);
+  UTI_GetRandomBytes(header->nonce, sizeof (header->nonce));
+
+  plaintext_length = context->c2s.length + context->s2c.length;
+  assert(plaintext_length <= sizeof (plaintext));
+  memcpy(plaintext, context->c2s.key, context->c2s.length);
+  memcpy(plaintext + context->c2s.length, context->s2c.key, context->s2c.length);
+
+  tag_length = SIV_GetTagLength(key->siv);
+  cookie->length = sizeof (*header) + plaintext_length + tag_length;
+  assert(cookie->length <= sizeof (cookie->cookie));
+  ciphertext = cookie->cookie + sizeof (*header);
+
+  if (!SIV_Encrypt(key->siv, header->nonce, sizeof (header->nonce),
+                   "", 0,
+                   plaintext, plaintext_length,
+                   ciphertext, plaintext_length + tag_length)) {
+    DEBUG_LOG("Could not encrypt cookie");
+    return 0;
+  }
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NKS_DecodeCookie(NKE_Cookie *cookie, NKE_Context *context)
+{
+  unsigned char plaintext[2 * NKE_MAX_KEY_LENGTH], *ciphertext;
+  int ciphertext_length, plaintext_length, tag_length;
+  ServerCookieHeader *header;
+  ServerKey *key;
+  uint32_t key_id;
+
+  if (!initialised) {
+    DEBUG_LOG("NTS server disabled");
+    return 0;
+  }
+
+  if (cookie->length <= (int)sizeof (*header)) {
+    DEBUG_LOG("Invalid cookie length");
+    return 0;
+  }
+
+  header = (ServerCookieHeader *)cookie->cookie;
+  ciphertext = cookie->cookie + sizeof (*header);
+  ciphertext_length = cookie->length - sizeof (*header);
+
+  key_id = ntohl(header->key_id);
+  key = &server_keys[key_id % MAX_SERVER_KEYS];
+  if (key_id != key->id) {
+    DEBUG_LOG("Unknown key %"PRIX32, key_id);
+    return 0;
+  }
+
+  tag_length = SIV_GetTagLength(key->siv);
+  if (tag_length >= ciphertext_length) {
+    DEBUG_LOG("Invalid cookie length");
+    return 0;
+  }
+
+  plaintext_length = ciphertext_length - tag_length;
+  if (plaintext_length > sizeof (plaintext) || plaintext_length % 2 != 0) {
+    DEBUG_LOG("Invalid cookie length");
+    return 0;
+  }
+
+  if (!SIV_Decrypt(key->siv, header->nonce, sizeof (header->nonce),
+                   "", 0,
+                   ciphertext, ciphertext_length,
+                   plaintext, plaintext_length)) {
+    DEBUG_LOG("Could not decrypt cookie");
+    return 0;
+  }
+
+  context->algorithm = AEAD_AES_SIV_CMAC_256;
+
+  context->c2s.length = plaintext_length / 2;
+  context->s2c.length = plaintext_length / 2;
+  assert(context->c2s.length <= sizeof (context->c2s.key));
+
+  memcpy(context->c2s.key, plaintext, context->c2s.length);
+  memcpy(context->s2c.key, plaintext + context->c2s.length, context->s2c.length);
+
+  return 1;
+}
--- a/nts_ke_server.h
+++ b/nts_ke_server.h
@@ -0,0 +1,49 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2020
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Header file for the NTS-KE server
+  */
+
+#ifndef GOT_NTS_KE_SERVER_H
+#define GOT_NTS_KE_SERVER_H
+
+#include "nts_ke.h"
+
+/* Init and fini functions */
+extern void NKS_PreInitialise(uid_t uid, gid_t gid, int scfilter_level);
+extern void NKS_Initialise(void);
+extern void NKS_Finalise(void);
+
+/* Save the current server keys */
+extern void NKS_DumpKeys(void);
+
+/* Reload the keys */
+extern void NKS_ReloadKeys(void);
+
+/* Generate an NTS cookie with a given context */
+extern int NKS_GenerateCookie(NKE_Context *context, NKE_Cookie *cookie);
+
+/* Validate a cookie and decode the context */
+extern int NKS_DecodeCookie(NKE_Cookie *cookie, NKE_Context *context);
+
+#endif
--- a/nts_ke_session.c
+++ b/nts_ke_session.c
@@ -0,0 +1,927 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2020-2021
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  NTS-KE session used by server and client
+  */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include "nts_ke_session.h"
+
+#include "conf.h"
+#include "local.h"
+#include "logging.h"
+#include "memory.h"
+#include "siv.h"
+#include "socket.h"
+#include "sched.h"
+#include "util.h"
+
+#include <gnutls/gnutls.h>
+#include <gnutls/x509.h>
+
+#define INVALID_SOCK_FD (-8)
+
+struct RecordHeader {
+  uint16_t type;
+  uint16_t body_length;
+};
+
+struct Message {
+  int length;
+  int sent;
+  int parsed;
+  int complete;
+  unsigned char data[NKE_MAX_MESSAGE_LENGTH];
+};
+
+typedef enum {
+  KE_WAIT_CONNECT,
+  KE_HANDSHAKE,
+  KE_SEND,
+  KE_RECEIVE,
+  KE_SHUTDOWN,
+  KE_STOPPED,
+} KeState;
+
+struct NKSN_Instance_Record {
+  int server;
+  char *server_name;
+  NKSN_MessageHandler handler;
+  void *handler_arg;
+
+  KeState state;
+  int sock_fd;
+  char *label;
+  gnutls_session_t tls_session;
+  SCH_TimeoutID timeout_id;
+  int retry_factor;
+
+  struct Message message;
+  int new_message;
+};
+
+/* ================================================== */
+
+static gnutls_priority_t priority_cache;
+
+static int credentials_counter = 0;
+
+static int clock_updates = 0;
+
+/* ================================================== */
+
+static void
+reset_message(struct Message *message)
+{
+  message->length = 0;
+  message->sent = 0;
+  message->parsed = 0;
+  message->complete = 0;
+}
+
+/* ================================================== */
+
+static int
+add_record(struct Message *message, int critical, int type, const void *body, int body_length)
+{
+  struct RecordHeader header;
+
+  assert(message->length <= sizeof (message->data));
+
+  if (body_length < 0 || body_length > 0xffff || type < 0 || type > 0x7fff ||
+      message->length + sizeof (header) + body_length > sizeof (message->data))
+    return 0;
+
+  header.type = htons(!!critical * NKE_RECORD_CRITICAL_BIT | type);
+  header.body_length = htons(body_length);
+
+  memcpy(&message->data[message->length], &header, sizeof (header));
+  message->length += sizeof (header);
+
+  if (body_length > 0) {
+    memcpy(&message->data[message->length], body, body_length);
+    message->length += body_length;
+  }
+
+  return 1;
+}
+
+/* ================================================== */
+
+static void
+reset_message_parsing(struct Message *message)
+{
+  message->parsed = 0;
+}
+
+/* ================================================== */
+
+static int
+get_record(struct Message *message, int *critical, int *type, int *body_length,
+           void *body, int buffer_length)
+{
+  struct RecordHeader header;
+  int blen, rlen;
+
+  if (message->length < message->parsed + sizeof (header) ||
+      buffer_length < 0)
+    return 0;
+
+  memcpy(&header, &message->data[message->parsed], sizeof (header));
+
+  blen = ntohs(header.body_length);
+  rlen = sizeof (header) + blen;
+  assert(blen >= 0 && rlen > 0);
+
+  if (message->length < message->parsed + rlen)
+    return 0;
+
+  if (critical)
+    *critical = !!(ntohs(header.type) & NKE_RECORD_CRITICAL_BIT);
+  if (type)
+    *type = ntohs(header.type) & ~NKE_RECORD_CRITICAL_BIT;
+  if (body)
+    memcpy(body, &message->data[message->parsed + sizeof (header)], MIN(buffer_length, blen));
+  if (body_length)
+    *body_length = blen;
+
+  message->parsed += rlen;
+
+  return 1;
+}
+
+/* ================================================== */
+
+static int
+check_message_format(struct Message *message, int eof)
+{
+  int critical = 0, type = -1, length = -1, ends = 0;
+
+  reset_message_parsing(message);
+  message->complete = 0;
+
+  while (get_record(message, &critical, &type, &length, NULL, 0)) {
+    if (type == NKE_RECORD_END_OF_MESSAGE) {
+      if (!critical || length != 0 || ends > 0)
+        return 0;
+      ends++;
+    }
+  }
+
+  /* If the message cannot be fully parsed, but more data may be coming,
+     consider the format to be ok */
+  if (message->length == 0 || message->parsed < message->length)
+    return !eof;
+
+  if (type != NKE_RECORD_END_OF_MESSAGE)
+    return !eof;
+
+  message->complete = 1;
+
+  return 1;
+}
+
+/* ================================================== */
+
+static gnutls_session_t
+create_tls_session(int server_mode, int sock_fd, const char *server_name,
+                   gnutls_certificate_credentials_t credentials,
+                   gnutls_priority_t priority)
+{
+  unsigned char alpn_name[sizeof (NKE_ALPN_NAME)];
+  gnutls_session_t session;
+  gnutls_datum_t alpn;
+  unsigned int flags;
+  int r;
+
+  r = gnutls_init(&session, GNUTLS_NONBLOCK | GNUTLS_NO_TICKETS |
+                  (server_mode ? GNUTLS_SERVER : GNUTLS_CLIENT));
+  if (r < 0) {
+    LOG(LOGS_ERR, "Could not %s TLS session : %s", "create", gnutls_strerror(r));
+    return NULL;
+  }
+
+  if (!server_mode) {
+    assert(server_name);
+
+    if (!UTI_IsStringIP(server_name)) {
+      r = gnutls_server_name_set(session, GNUTLS_NAME_DNS, server_name, strlen(server_name));
+      if (r < 0)
+        goto error;
+    }
+
+    flags = 0;
+
+    if (clock_updates < CNF_GetNoCertTimeCheck()) {
+      flags |= GNUTLS_VERIFY_DISABLE_TIME_CHECKS | GNUTLS_VERIFY_DISABLE_TRUSTED_TIME_CHECKS;
+      DEBUG_LOG("Disabled time checks");
+    }
+
+    gnutls_session_set_verify_cert(session, server_name, flags);
+  }
+
+  r = gnutls_priority_set(session, priority);
+  if (r < 0)
+    goto error;
+
+  r = gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE, credentials);
+  if (r < 0)
+    goto error;
+
+  memcpy(alpn_name, NKE_ALPN_NAME, sizeof (alpn_name));
+  alpn.data = alpn_name;
+  alpn.size = sizeof (alpn_name) - 1;
+
+  r = gnutls_alpn_set_protocols(session, &alpn, 1, 0);
+  if (r < 0)
+    goto error;
+
+  gnutls_transport_set_int(session, sock_fd);
+
+  return session;
+
+error:
+  LOG(LOGS_ERR, "Could not %s TLS session : %s", "set", gnutls_strerror(r));
+  gnutls_deinit(session);
+  return NULL;
+}
+
+/* ================================================== */
+
+static void
+stop_session(NKSN_Instance inst)
+{
+  if (inst->state == KE_STOPPED)
+    return;
+
+  inst->state = KE_STOPPED;
+
+  SCH_RemoveFileHandler(inst->sock_fd);
+  SCK_CloseSocket(inst->sock_fd);
+  inst->sock_fd = INVALID_SOCK_FD;
+
+  Free(inst->label);
+  inst->label = NULL;
+
+  gnutls_deinit(inst->tls_session);
+  inst->tls_session = NULL;
+
+  SCH_RemoveTimeout(inst->timeout_id);
+  inst->timeout_id = 0;
+}
+
+/* ================================================== */
+
+static void
+session_timeout(void *arg)
+{
+  NKSN_Instance inst = arg;
+
+  LOG(inst->server ? LOGS_DEBUG : LOGS_ERR, "NTS-KE session with %s timed out", inst->label);
+
+  inst->timeout_id = 0;
+  stop_session(inst);
+}
+
+/* ================================================== */
+
+static int
+check_alpn(NKSN_Instance inst)
+{
+  gnutls_datum_t alpn;
+
+  if (gnutls_alpn_get_selected_protocol(inst->tls_session, &alpn) < 0 ||
+      alpn.size != sizeof (NKE_ALPN_NAME) - 1 ||
+      memcmp(alpn.data, NKE_ALPN_NAME, sizeof (NKE_ALPN_NAME) - 1) != 0)
+    return 0;
+
+  return 1;
+}
+
+/* ================================================== */
+
+static void
+set_input_output(NKSN_Instance inst, int output)
+{
+  SCH_SetFileHandlerEvent(inst->sock_fd, SCH_FILE_INPUT, !output);
+  SCH_SetFileHandlerEvent(inst->sock_fd, SCH_FILE_OUTPUT, output);
+}
+
+/* ================================================== */
+
+static void
+change_state(NKSN_Instance inst, KeState state)
+{
+  int output;
+
+  switch (state) {
+    case KE_HANDSHAKE:
+      output = !inst->server;
+      break;
+    case KE_WAIT_CONNECT:
+    case KE_SEND:
+    case KE_SHUTDOWN:
+      output = 1;
+      break;
+    case KE_RECEIVE:
+      output = 0;
+      break;
+    default:
+      assert(0);
+  }
+
+  set_input_output(inst, output);
+
+  inst->state = state;
+}
+
+/* ================================================== */
+
+static int
+handle_event(NKSN_Instance inst, int event)
+{
+  struct Message *message = &inst->message;
+  int r;
+
+  DEBUG_LOG("Session event %d fd=%d state=%d", event, inst->sock_fd, (int)inst->state);
+
+  switch (inst->state) {
+    case KE_WAIT_CONNECT:
+      /* Check if connect() succeeded */
+      if (event != SCH_FILE_OUTPUT)
+        return 0;
+
+      /* Get the socket error */
+      if (!SCK_GetIntOption(inst->sock_fd, SOL_SOCKET, SO_ERROR, &r))
+        r = EINVAL;
+
+      if (r != 0) {
+        LOG(LOGS_ERR, "Could not connect to %s : %s", inst->label, strerror(r));
+        stop_session(inst);
+        return 0;
+      }
+
+      DEBUG_LOG("Connected to %s", inst->label);
+
+      change_state(inst, KE_HANDSHAKE);
+      return 0;
+
+    case KE_HANDSHAKE:
+      r = gnutls_handshake(inst->tls_session);
+
+      if (r < 0) {
+        if (gnutls_error_is_fatal(r)) {
+          gnutls_datum_t cert_error;
+
+          /* Get a description of verification errors */
+          if (r != GNUTLS_E_CERTIFICATE_VERIFICATION_ERROR ||
+              gnutls_certificate_verification_status_print(
+                          gnutls_session_get_verify_cert_status(inst->tls_session),
+                          gnutls_certificate_type_get(inst->tls_session), &cert_error, 0) < 0)
+            cert_error.data = NULL;
+
+          LOG(inst->server ? LOGS_DEBUG : LOGS_ERR,
+              "TLS handshake with %s failed : %s%s%s", inst->label, gnutls_strerror(r),
+              cert_error.data ? " " : "", cert_error.data ? (const char *)cert_error.data : "");
+
+          if (cert_error.data)
+            gnutls_free(cert_error.data);
+
+          stop_session(inst);
+
+          /* Increase the retry interval if the handshake did not fail due
+             to the other end closing the connection */
+          if (r != GNUTLS_E_PULL_ERROR && r != GNUTLS_E_PREMATURE_TERMINATION)
+            inst->retry_factor = NKE_RETRY_FACTOR2_TLS;
+
+          return 0;
+        }
+
+        /* Disable output when the handshake is trying to receive data */
+        set_input_output(inst, gnutls_record_get_direction(inst->tls_session));
+        return 0;
+      }
+
+      inst->retry_factor = NKE_RETRY_FACTOR2_TLS;
+
+      if (DEBUG) {
+        char *description = gnutls_session_get_desc(inst->tls_session);
+        DEBUG_LOG("Handshake with %s completed %s",
+                  inst->label, description ? description : "");
+        gnutls_free(description);
+      }
+
+      if (!check_alpn(inst)) {
+        LOG(inst->server ? LOGS_DEBUG : LOGS_ERR, "NTS-KE not supported by %s", inst->label);
+        stop_session(inst);
+        return 0;
+      }
+
+      /* Client will send a request to the server */
+      change_state(inst, inst->server ? KE_RECEIVE : KE_SEND);
+      return 0;
+
+    case KE_SEND:
+      assert(inst->new_message && message->complete);
+      assert(message->length <= sizeof (message->data) && message->length > message->sent);
+
+      r = gnutls_record_send(inst->tls_session, &message->data[message->sent],
+                             message->length - message->sent);
+
+      if (r < 0) {
+        if (gnutls_error_is_fatal(r)) {
+          LOG(inst->server ? LOGS_DEBUG : LOGS_ERR,
+              "Could not send NTS-KE message to %s : %s", inst->label, gnutls_strerror(r));
+          stop_session(inst);
+        }
+        return 0;
+      }
+
+      DEBUG_LOG("Sent %d bytes to %s", r, inst->label);
+
+      message->sent += r;
+      if (message->sent < message->length)
+        return 0;
+
+      /* Client will receive a response */
+      change_state(inst, inst->server ? KE_SHUTDOWN : KE_RECEIVE);
+      reset_message(&inst->message);
+      inst->new_message = 0;
+      return 0;
+
+    case KE_RECEIVE:
+      do {
+        if (message->length >= sizeof (message->data)) {
+          DEBUG_LOG("Message is too long");
+          stop_session(inst);
+          return 0;
+        }
+
+        r = gnutls_record_recv(inst->tls_session, &message->data[message->length],
+                               sizeof (message->data) - message->length);
+
+        if (r < 0) {
+          /* Handle a renegotiation request on both client and server as
+             a protocol error */
+          if (gnutls_error_is_fatal(r) || r == GNUTLS_E_REHANDSHAKE) {
+            LOG(inst->server ? LOGS_DEBUG : LOGS_ERR,
+                "Could not receive NTS-KE message from %s : %s",
+                inst->label, gnutls_strerror(r));
+            stop_session(inst);
+          }
+          return 0;
+        }
+
+        DEBUG_LOG("Received %d bytes from %s", r, inst->label);
+
+        message->length += r;
+
+      } while (gnutls_record_check_pending(inst->tls_session) > 0);
+
+      if (!check_message_format(message, r == 0)) {
+        LOG(inst->server ? LOGS_DEBUG : LOGS_ERR,
+            "Received invalid NTS-KE message from %s", inst->label);
+        stop_session(inst);
+        return 0;
+      }
+
+      /* Wait for more data if the message is not complete yet */
+      if (!message->complete)
+        return 0;
+
+      /* Server will send a response to the client */
+      change_state(inst, inst->server ? KE_SEND : KE_SHUTDOWN);
+
+      /* Return success to process the received message */
+      return 1;
+
+    case KE_SHUTDOWN:
+      r = gnutls_bye(inst->tls_session, GNUTLS_SHUT_RDWR);
+
+      if (r < 0) {
+        if (gnutls_error_is_fatal(r)) {
+          DEBUG_LOG("Shutdown with %s failed : %s", inst->label, gnutls_strerror(r));
+          stop_session(inst);
+          return 0;
+        }
+
+        /* Disable output when the TLS shutdown is trying to receive data */
+        set_input_output(inst, gnutls_record_get_direction(inst->tls_session));
+        return 0;
+      }
+
+      SCK_ShutdownConnection(inst->sock_fd);
+      stop_session(inst);
+
+      DEBUG_LOG("Shutdown completed");
+      return 0;
+
+    default:
+      assert(0);
+      return 0;
+  }
+}
+
+/* ================================================== */
+
+static void
+read_write_socket(int fd, int event, void *arg)
+{
+  NKSN_Instance inst = arg;
+
+  if (!handle_event(inst, event))
+    return;
+
+  /* A valid message was received.  Call the handler to process the message,
+     and prepare a response if it is a server. */
+
+  reset_message_parsing(&inst->message);
+
+  if (!(inst->handler)(inst->handler_arg)) {
+    stop_session(inst);
+    return;
+  }
+}
+
+/* ================================================== */
+
+static time_t
+get_time(time_t *t)
+{
+  struct timespec now;
+
+  LCL_ReadCookedTime(&now, NULL);
+  if (t)
+    *t = now.tv_sec;
+
+  return now.tv_sec;
+}
+
+/* ================================================== */
+
+static void
+handle_step(struct timespec *raw, struct timespec *cooked, double dfreq,
+            double doffset, LCL_ChangeType change_type, void *anything)
+{
+  if (change_type != LCL_ChangeUnknownStep && clock_updates < INT_MAX)
+    clock_updates++;
+}
+
+/* ================================================== */
+
+static int gnutls_initialised = 0;
+
+static int
+init_gnutls(void)
+{
+  int r;
+
+  if (gnutls_initialised)
+    return 1;
+
+  r = gnutls_global_init();
+  if (r < 0)
+    LOG_FATAL("Could not initialise %s : %s", "gnutls", gnutls_strerror(r));
+
+  /* Prepare a priority cache for server and client NTS-KE sessions
+     (the NTS specification requires TLS1.3 or later) */
+  r = gnutls_priority_init2(&priority_cache,
+                            "-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1:-VERS-TLS1.2:-VERS-DTLS-ALL",
+                            NULL, GNUTLS_PRIORITY_INIT_DEF_APPEND);
+  if (r < 0) {
+    LOG(LOGS_ERR, "Could not initialise %s : %s",
+        "priority cache for TLS", gnutls_strerror(r));
+    gnutls_global_deinit();
+    return 0;
+  }
+
+  /* Use our clock instead of the system clock in certificate verification */
+  gnutls_global_set_time_function(get_time);
+
+  gnutls_initialised = 1;
+  DEBUG_LOG("Initialised");
+
+  LCL_AddParameterChangeHandler(handle_step, NULL);
+
+  return 1;
+}
+
+/* ================================================== */
+
+static void
+deinit_gnutls(void)
+{
+  if (!gnutls_initialised || credentials_counter > 0)
+    return;
+
+  LCL_RemoveParameterChangeHandler(handle_step, NULL);
+
+  gnutls_priority_deinit(priority_cache);
+  gnutls_global_deinit();
+  gnutls_initialised = 0;
+  DEBUG_LOG("Deinitialised");
+}
+
+/* ================================================== */
+
+static NKSN_Credentials
+create_credentials(const char **certs, const char **keys, int n_certs_keys,
+                   const char **trusted_certs, uint32_t *trusted_certs_ids,
+                   int n_trusted_certs, uint32_t trusted_cert_set)
+{
+  gnutls_certificate_credentials_t credentials = NULL;
+  int i, r;
+
+  if (!init_gnutls())
+    return NULL;
+
+  r = gnutls_certificate_allocate_credentials(&credentials);
+  if (r < 0)
+    goto error;
+
+  if (certs && keys) {
+    if (trusted_certs || trusted_certs_ids)
+      assert(0);
+
+    for (i = 0; i < n_certs_keys; i++) {
+      r = gnutls_certificate_set_x509_key_file(credentials, certs[i], keys[i],
+                                               GNUTLS_X509_FMT_PEM);
+      if (r < 0)
+        goto error;
+    }
+  } else {
+    if (certs || keys || n_certs_keys > 0)
+      assert(0);
+
+    if (trusted_cert_set == 0 && !CNF_GetNoSystemCert()) {
+      r = gnutls_certificate_set_x509_system_trust(credentials);
+      if (r < 0)
+        goto error;
+    }
+
+    if (trusted_certs && trusted_certs_ids) {
+      for (i = 0; i < n_trusted_certs; i++) {
+        struct stat buf;
+
+        if (trusted_certs_ids[i] != trusted_cert_set)
+          continue;
+
+        if (stat(trusted_certs[i], &buf) == 0 && S_ISDIR(buf.st_mode))
+          r = gnutls_certificate_set_x509_trust_dir(credentials, trusted_certs[i],
+                                                    GNUTLS_X509_FMT_PEM);
+        else
+          r = gnutls_certificate_set_x509_trust_file(credentials, trusted_certs[i],
+                                                     GNUTLS_X509_FMT_PEM);
+        if (r < 0)
+          goto error;
+
+        DEBUG_LOG("Added %d trusted certs from %s", r, trusted_certs[i]);
+      }
+    }
+  }
+
+  credentials_counter++;
+
+  return (NKSN_Credentials)credentials;
+
+error:
+  LOG(LOGS_ERR, "Could not set credentials : %s", gnutls_strerror(r));
+  if (credentials)
+    gnutls_certificate_free_credentials(credentials);
+  deinit_gnutls();
+  return NULL;
+}
+
+/* ================================================== */
+
+NKSN_Credentials
+NKSN_CreateServerCertCredentials(const char **certs, const char **keys, int n_certs_keys)
+{
+  return create_credentials(certs, keys, n_certs_keys, NULL, NULL, 0, 0);
+}
+
+/* ================================================== */
+
+NKSN_Credentials
+NKSN_CreateClientCertCredentials(const char **certs, uint32_t *ids,
+                                 int n_certs_ids, uint32_t trusted_cert_set)
+{
+  return create_credentials(NULL, NULL, 0, certs, ids, n_certs_ids, trusted_cert_set);
+}
+
+/* ================================================== */
+
+void
+NKSN_DestroyCertCredentials(NKSN_Credentials credentials)
+{
+  gnutls_certificate_free_credentials((gnutls_certificate_credentials_t)credentials);
+  credentials_counter--;
+  deinit_gnutls();
+}
+
+/* ================================================== */
+
+NKSN_Instance
+NKSN_CreateInstance(int server_mode, const char *server_name,
+                    NKSN_MessageHandler handler, void *handler_arg)
+{
+  NKSN_Instance inst;
+
+  inst = MallocNew(struct NKSN_Instance_Record);
+
+  inst->server = server_mode;
+  inst->server_name = server_name ? Strdup(server_name) : NULL;
+  inst->handler = handler;
+  inst->handler_arg = handler_arg;
+  /* Replace a NULL argument with the session itself */
+  if (!inst->handler_arg)
+    inst->handler_arg = inst;
+
+  inst->state = KE_STOPPED;
+  inst->sock_fd = INVALID_SOCK_FD;
+  inst->label = NULL;
+  inst->tls_session = NULL;
+  inst->timeout_id = 0;
+  inst->retry_factor = NKE_RETRY_FACTOR2_CONNECT;
+
+  return inst;
+}
+
+/* ================================================== */
+
+void
+NKSN_DestroyInstance(NKSN_Instance inst)
+{
+  stop_session(inst);
+
+  Free(inst->server_name);
+  Free(inst);
+}
+
+/* ================================================== */
+
+int
+NKSN_StartSession(NKSN_Instance inst, int sock_fd, const char *label,
+                  NKSN_Credentials credentials, double timeout)
+{
+  assert(inst->state == KE_STOPPED);
+
+  inst->tls_session = create_tls_session(inst->server, sock_fd, inst->server_name,
+                                         (gnutls_certificate_credentials_t)credentials,
+                                         priority_cache);
+  if (!inst->tls_session)
+    return 0;
+
+  inst->sock_fd = sock_fd;
+  SCH_AddFileHandler(sock_fd, SCH_FILE_INPUT, read_write_socket, inst);
+
+  inst->label = Strdup(label);
+  inst->timeout_id = SCH_AddTimeoutByDelay(timeout, session_timeout, inst);
+  inst->retry_factor = NKE_RETRY_FACTOR2_CONNECT;
+
+  reset_message(&inst->message);
+  inst->new_message = 0;
+
+  change_state(inst, inst->server ? KE_HANDSHAKE : KE_WAIT_CONNECT);
+
+  return 1;
+}
+
+/* ================================================== */
+
+void
+NKSN_BeginMessage(NKSN_Instance inst)
+{
+  reset_message(&inst->message);
+  inst->new_message = 1;
+}
+
+/* ================================================== */
+
+int
+NKSN_AddRecord(NKSN_Instance inst, int critical, int type, const void *body, int body_length)
+{
+  assert(inst->new_message && !inst->message.complete);
+  assert(type != NKE_RECORD_END_OF_MESSAGE);
+
+  return add_record(&inst->message, critical, type, body, body_length);
+}
+
+/* ================================================== */
+
+int
+NKSN_EndMessage(NKSN_Instance inst)
+{
+  assert(!inst->message.complete);
+
+  /* Terminate the message */
+  if (!add_record(&inst->message, 1, NKE_RECORD_END_OF_MESSAGE, NULL, 0))
+    return 0;
+
+  inst->message.complete = 1;
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NKSN_GetRecord(NKSN_Instance inst, int *critical, int *type, int *body_length,
+               void *body, int buffer_length)
+{
+  int type2;
+
+  assert(inst->message.complete);
+
+  if (body_length)
+    *body_length = 0;
+
+  if (!get_record(&inst->message, critical, &type2, body_length, body, buffer_length))
+    return 0;
+
+  /* Hide the end-of-message record */
+  if (type2 == NKE_RECORD_END_OF_MESSAGE)
+    return 0;
+
+  if (type)
+    *type = type2;
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NKSN_GetKeys(NKSN_Instance inst, SIV_Algorithm siv, NKE_Key *c2s, NKE_Key *s2c)
+{
+  int length = SIV_GetKeyLength(siv);
+
+  if (length <= 0 || length > sizeof (c2s->key) || length > sizeof (s2c->key)) {
+    DEBUG_LOG("Invalid algorithm");
+    return 0;
+  }
+
+  if (gnutls_prf_rfc5705(inst->tls_session,
+                         sizeof (NKE_EXPORTER_LABEL) - 1, NKE_EXPORTER_LABEL,
+                         sizeof (NKE_EXPORTER_CONTEXT_C2S) - 1, NKE_EXPORTER_CONTEXT_C2S,
+                         length, (char *)c2s->key) < 0 ||
+      gnutls_prf_rfc5705(inst->tls_session,
+                         sizeof (NKE_EXPORTER_LABEL) - 1, NKE_EXPORTER_LABEL,
+                         sizeof (NKE_EXPORTER_CONTEXT_S2C) - 1, NKE_EXPORTER_CONTEXT_S2C,
+                         length, (char *)s2c->key) < 0) {
+    DEBUG_LOG("Could not export key");
+    return 0;
+  }
+
+  c2s->length = length;
+  s2c->length = length;
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NKSN_IsStopped(NKSN_Instance inst)
+{
+  return inst->state == KE_STOPPED;
+}
+
+/* ================================================== */
+
+void
+NKSN_StopSession(NKSN_Instance inst)
+{
+  stop_session(inst);
+}
+
+/* ================================================== */
+
+int
+NKSN_GetRetryFactor(NKSN_Instance inst)
+{
+  return inst->retry_factor;
+}
--- a/nts_ke_session.h
+++ b/nts_ke_session.h
@@ -0,0 +1,93 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2020
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Header file for the NTS-KE session
+  */
+
+#ifndef GOT_NTS_KE_SESSION_H
+#define GOT_NTS_KE_SESSION_H
+
+#include "nts_ke.h"
+#include "siv.h"
+
+typedef struct NKSN_Credentials_Record *NKSN_Credentials;
+
+typedef struct NKSN_Instance_Record *NKSN_Instance;
+
+/* Handler for received NTS-KE messages.  A zero return code stops
+   the session. */
+typedef int (*NKSN_MessageHandler)(void *arg);
+
+/* Get server or client credentials using a server certificate and key,
+   or certificates of trusted CAs.  The credentials may be shared between
+   different clients or servers. */
+extern NKSN_Credentials NKSN_CreateServerCertCredentials(const char **certs, const char **keys,
+                                                         int n_certs_keys);
+extern NKSN_Credentials NKSN_CreateClientCertCredentials(const char **certs, uint32_t *ids,
+                                                         int n_certs_ids,
+                                                         uint32_t trusted_cert_set);
+
+/* Destroy the credentials */
+extern void NKSN_DestroyCertCredentials(NKSN_Credentials credentials);
+
+/* Create an instance */
+extern NKSN_Instance NKSN_CreateInstance(int server_mode, const char *server_name,
+                                         NKSN_MessageHandler handler, void *handler_arg);
+
+/* Destroy an instance */
+extern void NKSN_DestroyInstance(NKSN_Instance inst);
+
+/* Start a new NTS-KE session */
+extern int NKSN_StartSession(NKSN_Instance inst, int sock_fd, const char *label,
+                             NKSN_Credentials credentials, double timeout);
+
+/* Begin an NTS-KE message.  A request should be made right after starting
+   the session and response should be made in the message handler. */
+extern void NKSN_BeginMessage(NKSN_Instance inst);
+
+/* Add a record to the message */
+extern int NKSN_AddRecord(NKSN_Instance inst, int critical, int type,
+                          const void *body, int body_length);
+
+/* Terminate the message */
+extern int NKSN_EndMessage(NKSN_Instance inst);
+
+/* Get the next record from the received message.  This function should be
+   called from the message handler. */
+extern int NKSN_GetRecord(NKSN_Instance inst, int *critical, int *type, int *body_length,
+                          void *body, int buffer_length);
+
+/* Export NTS keys for a specified algorithm */
+extern int NKSN_GetKeys(NKSN_Instance inst, SIV_Algorithm siv, NKE_Key *c2s, NKE_Key *s2c);
+
+/* Check if the session has stopped */
+extern int NKSN_IsStopped(NKSN_Instance inst);
+
+/* Stop the session */
+extern void NKSN_StopSession(NKSN_Instance inst);
+
+/* Get a factor to calculate retry interval (in log2 seconds)
+   based on the session state or how it was terminated */
+extern int NKSN_GetRetryFactor(NKSN_Instance inst);
+
+#endif
--- a/nts_ntp.h
+++ b/nts_ntp.h
@@ -0,0 +1,36 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2020
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Header file for the NTS-NTP protocol
+  */
+
+#ifndef GOT_NTS_NTP_H
+#define GOT_NTS_NTP_H
+
+#define NTP_KOD_NTS_NAK                 0x4e54534e
+
+#define NTS_MIN_UNIQ_ID_LENGTH          32
+#define NTS_MIN_UNPADDED_NONCE_LENGTH   16
+#define NTS_MAX_COOKIES                 8
+
+#endif
--- a/nts_ntp_auth.c
+++ b/nts_ntp_auth.c
@@ -0,0 +1,183 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2020
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  NTS Authenticator and Encrypted Extension Fields extension field
+  */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include "nts_ntp_auth.h"
+
+#include "logging.h"
+#include "ntp_ext.h"
+#include "nts_ntp.h"
+#include "siv.h"
+#include "util.h"
+
+struct AuthHeader {
+  uint16_t nonce_length;
+  uint16_t ciphertext_length;
+};
+
+/* ================================================== */
+
+static int
+get_padding_length(int length)
+{
+  return length % 4U ? 4 - length % 4U : 0;
+}
+
+/* ================================================== */
+
+static int
+get_padded_length(int length)
+{
+  return length + get_padding_length(length);
+}
+
+/* ================================================== */
+
+int
+NNA_GenerateAuthEF(NTP_Packet *packet, NTP_PacketInfo *info, SIV_Instance siv,
+                   const unsigned char *nonce, int nonce_length,
+                   const unsigned char *plaintext, int plaintext_length,
+                   int min_ef_length)
+{
+  int auth_length, ciphertext_length, assoc_length;
+  int nonce_padding, ciphertext_padding, additional_padding;
+  unsigned char *ciphertext, *body;
+  struct AuthHeader *header;
+
+  assert(sizeof (*header) == 4);
+
+  if (nonce_length <= 0 || plaintext_length < 0) {
+    DEBUG_LOG("Invalid nonce/plaintext length");
+    return 0;
+  }
+
+  assoc_length = info->length;
+  ciphertext_length = SIV_GetTagLength(siv) + plaintext_length;
+  nonce_padding = get_padding_length(nonce_length);
+  ciphertext_padding = get_padding_length(ciphertext_length);
+  min_ef_length = get_padded_length(min_ef_length);
+
+  auth_length = sizeof (*header) + nonce_length + nonce_padding +
+                ciphertext_length + ciphertext_padding;
+  additional_padding = MAX(min_ef_length - auth_length - 4, 0);
+  additional_padding = MAX(NTS_MIN_UNPADDED_NONCE_LENGTH - nonce_length - nonce_padding,
+                           additional_padding);
+  auth_length += additional_padding;
+
+  if (!NEF_AddBlankField(packet, info, NTP_EF_NTS_AUTH_AND_EEF, auth_length,
+                         (void **)&header)) {
+    DEBUG_LOG("Could not add EF");
+    return 0;
+  }
+
+  header->nonce_length = htons(nonce_length);
+  header->ciphertext_length = htons(ciphertext_length);
+
+  body = (unsigned char *)(header + 1);
+  ciphertext = body + nonce_length + nonce_padding;
+
+  if ((unsigned char *)header + auth_length !=
+      ciphertext + ciphertext_length + ciphertext_padding + additional_padding)
+    assert(0);
+
+  memcpy(body, nonce, nonce_length);
+  memset(body + nonce_length, 0, nonce_padding);
+
+  if (!SIV_Encrypt(siv, nonce, nonce_length, packet, assoc_length,
+                   plaintext, plaintext_length, ciphertext, ciphertext_length)) {
+    DEBUG_LOG("SIV encrypt failed");
+    info->length = assoc_length;
+    return 0;
+  }
+
+  memset(ciphertext + ciphertext_length, 0, ciphertext_padding + additional_padding);
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NNA_DecryptAuthEF(NTP_Packet *packet, NTP_PacketInfo *info, SIV_Instance siv, int ef_start,
+                  unsigned char *plaintext, int buffer_length, int *plaintext_length)
+{
+  unsigned int siv_tag_length, nonce_length, ciphertext_length;
+  unsigned char *nonce, *ciphertext;
+  int ef_type, ef_body_length;
+  void *ef_body;
+  struct AuthHeader *header;
+
+  if (buffer_length < 0)
+    return 0;
+
+  if (!NEF_ParseField(packet, info->length, ef_start,
+                      NULL, &ef_type, &ef_body, &ef_body_length))
+    return 0;
+
+  if (ef_type != NTP_EF_NTS_AUTH_AND_EEF || ef_body_length < sizeof (*header))
+    return 0;
+
+  header = ef_body;
+
+  nonce_length = ntohs(header->nonce_length);
+  ciphertext_length = ntohs(header->ciphertext_length);
+
+  if (get_padded_length(nonce_length) +
+      get_padded_length(ciphertext_length) > ef_body_length)
+    return 0;
+
+  nonce = (unsigned char *)(header + 1);
+  ciphertext = nonce + get_padded_length(nonce_length);
+
+  siv_tag_length = SIV_GetTagLength(siv);
+
+  if (nonce_length < 1 ||
+      ciphertext_length < siv_tag_length ||
+      ciphertext_length - siv_tag_length > buffer_length) {
+    DEBUG_LOG("Unexpected nonce/ciphertext length");
+    return 0;
+  }
+
+  if (ef_body_length < sizeof (*header) +
+        NTS_MIN_UNPADDED_NONCE_LENGTH + get_padded_length(ciphertext_length)) {
+    DEBUG_LOG("Missing padding");
+    return 0;
+  }
+
+  *plaintext_length = ciphertext_length - siv_tag_length;
+  assert(*plaintext_length >= 0);
+
+  if (!SIV_Decrypt(siv, nonce, nonce_length, packet, ef_start,
+                   ciphertext, ciphertext_length, plaintext, *plaintext_length)) {
+    DEBUG_LOG("SIV decrypt failed");
+    return 0;
+  }
+
+  return 1;
+}
--- a/nts_ntp_auth.h
+++ b/nts_ntp_auth.h
@@ -0,0 +1,43 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2020
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Header for NTS Authenticator and Encrypted Extension Fields
+  extension field
+  */
+
+#ifndef GOT_NTS_NTP_AUTH_H
+#define GOT_NTS_NTP_AUTH_H
+
+#include "ntp.h"
+#include "siv.h"
+
+extern int NNA_GenerateAuthEF(NTP_Packet *packet, NTP_PacketInfo *info, SIV_Instance siv,
+                              const unsigned char *nonce, int nonce_length,
+                              const unsigned char *plaintext, int plaintext_length,
+                              int min_ef_length);
+
+extern int NNA_DecryptAuthEF(NTP_Packet *packet, NTP_PacketInfo *info, SIV_Instance siv,
+                             int ef_start, unsigned char *plaintext, int buffer_length,
+                             int *plaintext_length);
+
+#endif
--- a/nts_ntp_client.c
+++ b/nts_ntp_client.c
@@ -0,0 +1,709 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2020
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Client NTS-NTP authentication
+  */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include "nts_ntp_client.h"
+
+#include "conf.h"
+#include "logging.h"
+#include "memory.h"
+#include "ntp.h"
+#include "ntp_ext.h"
+#include "ntp_sources.h"
+#include "nts_ke_client.h"
+#include "nts_ntp.h"
+#include "nts_ntp_auth.h"
+#include "sched.h"
+#include "siv.h"
+#include "util.h"
+
+/* Maximum length of all cookies to avoid IP fragmentation */
+#define MAX_TOTAL_COOKIE_LENGTH (8 * 108)
+
+/* Magic string of files containing keys and cookies */
+#define DUMP_IDENTIFIER "NNC0\n"
+
+struct NNC_Instance_Record {
+  /* Address of NTS-KE server */
+  IPSockAddr nts_address;
+  /* Hostname or IP address for certificate verification */
+  char *name;
+  /* ID of trusted certificates */
+  uint32_t cert_set;
+  /* Configured NTP port */
+  uint16_t default_ntp_port;
+  /* Address of NTP server (can be negotiated in NTS-KE) */
+  IPSockAddr ntp_address;
+
+  NKC_Instance nke;
+  SIV_Instance siv;
+
+  int nke_attempts;
+  double next_nke_attempt;
+  double last_nke_success;
+
+  NKE_Context context;
+  unsigned int context_id;
+  NKE_Cookie cookies[NTS_MAX_COOKIES];
+  int num_cookies;
+  int cookie_index;
+  int auth_ready;
+  int nak_response;
+  int ok_response;
+  unsigned char nonce[NTS_MIN_UNPADDED_NONCE_LENGTH];
+  unsigned char uniq_id[NTS_MIN_UNIQ_ID_LENGTH];
+};
+
+/* ================================================== */
+
+static void save_cookies(NNC_Instance inst);
+static void load_cookies(NNC_Instance inst);
+
+/* ================================================== */
+
+static void
+reset_instance(NNC_Instance inst)
+{
+  if (inst->nke)
+    NKC_DestroyInstance(inst->nke);
+  inst->nke = NULL;
+  if (inst->siv)
+    SIV_DestroyInstance(inst->siv);
+  inst->siv = NULL;
+
+  inst->nke_attempts = 0;
+  inst->next_nke_attempt = 0.0;
+  inst->last_nke_success = 0.0;
+
+  memset(&inst->context, 0, sizeof (inst->context));
+  inst->context_id = 0;
+  memset(inst->cookies, 0, sizeof (inst->cookies));
+  inst->num_cookies = 0;
+  inst->cookie_index = 0;
+  inst->auth_ready = 0;
+  inst->nak_response = 0;
+  inst->ok_response = 1;
+  memset(inst->nonce, 0, sizeof (inst->nonce));
+  memset(inst->uniq_id, 0, sizeof (inst->uniq_id));
+}
+
+/* ================================================== */
+
+NNC_Instance
+NNC_CreateInstance(IPSockAddr *nts_address, const char *name, uint32_t cert_set, uint16_t ntp_port)
+{
+  NNC_Instance inst;
+
+  inst = MallocNew(struct NNC_Instance_Record);
+
+  inst->nts_address = *nts_address;
+  inst->name = Strdup(name);
+  inst->cert_set = cert_set;
+  inst->default_ntp_port = ntp_port;
+  inst->ntp_address.ip_addr = nts_address->ip_addr;
+  inst->ntp_address.port = ntp_port;
+  inst->siv = NULL;
+  inst->nke = NULL;
+
+  reset_instance(inst);
+
+  /* Try to reload saved keys and cookies */
+  load_cookies(inst);
+
+  return inst;
+}
+
+/* ================================================== */
+
+void
+NNC_DestroyInstance(NNC_Instance inst)
+{
+  save_cookies(inst);
+
+  reset_instance(inst);
+
+  Free(inst->name);
+  Free(inst);
+}
+
+/* ================================================== */
+
+static int
+check_cookies(NNC_Instance inst)
+{
+  /* Force a new NTS-KE session if a NAK was received without a valid response,
+     or the keys encrypting the cookies need to be refreshed */
+  if (inst->num_cookies > 0 &&
+      ((inst->nak_response && !inst->ok_response) ||
+       SCH_GetLastEventMonoTime() - inst->last_nke_success > CNF_GetNtsRefresh())) {
+    inst->num_cookies = 0;
+    DEBUG_LOG("Dropped cookies");
+  }
+
+  return inst->num_cookies > 0;
+}
+
+/* ================================================== */
+
+static int
+set_ntp_address(NNC_Instance inst, NTP_Remote_Address *negotiated_address)
+{
+  NTP_Remote_Address old_address, new_address;
+
+  old_address = inst->ntp_address;
+  new_address = *negotiated_address;
+
+  if (new_address.ip_addr.family == IPADDR_UNSPEC)
+    new_address.ip_addr = inst->nts_address.ip_addr;
+  if (new_address.port == 0)
+    new_address.port = inst->default_ntp_port;
+
+  if (UTI_CompareIPs(&old_address.ip_addr, &new_address.ip_addr, NULL) == 0 &&
+      old_address.port == new_address.port)
+    /* Nothing to do */
+    return 1;
+
+  if (NSR_UpdateSourceNtpAddress(&old_address, &new_address) != NSR_Success) {
+    LOG(LOGS_ERR, "Could not change %s to negotiated address %s",
+        UTI_IPToString(&old_address.ip_addr), UTI_IPToString(&new_address.ip_addr));
+    return 0;
+  }
+
+  inst->ntp_address = new_address;
+
+  return 1;
+}
+
+/* ================================================== */
+
+static void
+update_next_nke_attempt(NNC_Instance inst, double now)
+{
+  int factor, interval;
+
+  if (!inst->nke)
+    return;
+
+  factor = NKC_GetRetryFactor(inst->nke);
+  interval = MIN(factor + inst->nke_attempts - 1, NKE_MAX_RETRY_INTERVAL2);
+  inst->next_nke_attempt = now + UTI_Log2ToDouble(interval);
+}
+
+/* ================================================== */
+
+static int
+get_cookies(NNC_Instance inst)
+{
+  NTP_Remote_Address ntp_address;
+  double now;
+  int got_data;
+
+  assert(inst->num_cookies == 0);
+
+  now = SCH_GetLastEventMonoTime();
+
+  /* Create and start a new NTS-KE session if not already present */
+  if (!inst->nke) {
+    if (now < inst->next_nke_attempt) {
+      DEBUG_LOG("Limiting NTS-KE request rate (%f seconds)",
+                inst->next_nke_attempt - now);
+      return 0;
+    }
+
+    inst->nke = NKC_CreateInstance(&inst->nts_address, inst->name, inst->cert_set);
+
+    inst->nke_attempts++;
+    update_next_nke_attempt(inst, now);
+
+    if (!NKC_Start(inst->nke))
+      return 0;
+  }
+
+  update_next_nke_attempt(inst, now);
+
+  /* Wait until the session stops */
+  if (NKC_IsActive(inst->nke))
+    return 0;
+
+  assert(sizeof (inst->cookies) / sizeof (inst->cookies[0]) == NTS_MAX_COOKIES);
+
+  /* Get the new keys, cookies and NTP address if the session was successful */
+  got_data = NKC_GetNtsData(inst->nke, &inst->context,
+                            inst->cookies, &inst->num_cookies, NTS_MAX_COOKIES,
+                            &ntp_address);
+
+  NKC_DestroyInstance(inst->nke);
+  inst->nke = NULL;
+
+  if (!got_data)
+    return 0;
+
+  if (inst->siv)
+    SIV_DestroyInstance(inst->siv);
+  inst->siv = NULL;
+
+  inst->context_id++;
+
+  /* Force a new session if the NTP address is used by another source, with
+     an expectation that it will eventually get a non-conflicting address */
+  if (!set_ntp_address(inst, &ntp_address)) {
+    inst->num_cookies = 0;
+    return 0;
+  }
+
+  inst->last_nke_success = now;
+  inst->cookie_index = 0;
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NNC_PrepareForAuth(NNC_Instance inst)
+{
+  inst->auth_ready = 0;
+
+  /* Prepare data for the next request and invalidate any responses to the
+     previous request */
+  UTI_GetRandomBytes(inst->uniq_id, sizeof (inst->uniq_id));
+  UTI_GetRandomBytes(inst->nonce, sizeof (inst->nonce));
+
+  /* Get new cookies if there are not any, or they are no longer usable */
+  if (!check_cookies(inst)) {
+    if (!get_cookies(inst))
+      return 0;
+  }
+
+  inst->nak_response = 0;
+
+  if (!inst->siv)
+    inst->siv = SIV_CreateInstance(inst->context.algorithm);
+
+  if (!inst->siv ||
+      !SIV_SetKey(inst->siv, inst->context.c2s.key, inst->context.c2s.length)) {
+    DEBUG_LOG("Could not set SIV key");
+    return 0;
+  }
+
+  inst->auth_ready = 1;
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NNC_GenerateRequestAuth(NNC_Instance inst, NTP_Packet *packet,
+                        NTP_PacketInfo *info)
+{
+  NKE_Cookie *cookie;
+  int i, req_cookies;
+  void *ef_body;
+
+  if (!inst->auth_ready)
+    return 0;
+
+  inst->auth_ready = 0;
+
+  if (inst->num_cookies <= 0 || !inst->siv)
+    return 0;
+
+  if (info->mode != MODE_CLIENT)
+    return 0;
+
+  cookie = &inst->cookies[inst->cookie_index];
+  inst->num_cookies--;
+  inst->cookie_index = (inst->cookie_index + 1) % NTS_MAX_COOKIES;
+
+  req_cookies = MIN(NTS_MAX_COOKIES - inst->num_cookies,
+                    MAX_TOTAL_COOKIE_LENGTH / (cookie->length + 4));
+
+  if (!NEF_AddField(packet, info, NTP_EF_NTS_UNIQUE_IDENTIFIER,
+                    inst->uniq_id, sizeof (inst->uniq_id)))
+    return 0;
+
+  if (!NEF_AddField(packet, info, NTP_EF_NTS_COOKIE,
+                    cookie->cookie, cookie->length))
+    return 0;
+
+  for (i = 0; i < req_cookies - 1; i++) {
+    if (!NEF_AddBlankField(packet, info, NTP_EF_NTS_COOKIE_PLACEHOLDER,
+                           cookie->length, &ef_body))
+      return 0;
+    memset(ef_body, 0, cookie->length);
+  }
+
+  if (!NNA_GenerateAuthEF(packet, info, inst->siv, inst->nonce, sizeof (inst->nonce),
+                          (const unsigned char *)"", 0, NTP_MAX_V4_MAC_LENGTH + 4))
+    return 0;
+
+  inst->ok_response = 0;
+
+  return 1;
+}
+
+/* ================================================== */
+
+static int
+parse_encrypted_efs(NNC_Instance inst, unsigned char *plaintext, int length)
+{
+  int ef_length, parsed;
+
+  for (parsed = 0; parsed < length; parsed += ef_length) {
+    if (!NEF_ParseSingleField(plaintext, length, parsed, &ef_length, NULL, NULL, NULL)) {
+      DEBUG_LOG("Could not parse encrypted EF");
+      return 0;
+    }
+  }
+
+  return 1;
+}
+
+/* ================================================== */
+
+static int
+extract_cookies(NNC_Instance inst, unsigned char *plaintext, int length)
+{
+  int ef_type, ef_body_length, ef_length, parsed, index, acceptable, saved;
+  void *ef_body;
+
+  acceptable = saved = 0;
+
+  for (parsed = 0; parsed < length; parsed += ef_length) {
+    if (!NEF_ParseSingleField(plaintext, length, parsed,
+                              &ef_length, &ef_type, &ef_body, &ef_body_length))
+      return 0;
+
+    if (ef_type != NTP_EF_NTS_COOKIE)
+      continue;
+
+    if (ef_length < NTP_MIN_EF_LENGTH || ef_body_length > sizeof (inst->cookies[0].cookie)) {
+      DEBUG_LOG("Unexpected cookie length %d", ef_body_length);
+      continue;
+    }
+
+    acceptable++;
+
+    if (inst->num_cookies >= NTS_MAX_COOKIES)
+      continue;
+
+    index = (inst->cookie_index + inst->num_cookies) % NTS_MAX_COOKIES;
+    assert(index >= 0 && index < NTS_MAX_COOKIES);
+    assert(sizeof (inst->cookies) / sizeof (inst->cookies[0]) == NTS_MAX_COOKIES);
+
+    memcpy(inst->cookies[index].cookie, ef_body, ef_body_length);
+    inst->cookies[index].length = ef_body_length;
+    inst->num_cookies++;
+
+    saved++;
+  }
+
+  DEBUG_LOG("Extracted %d cookies (saved %d)", acceptable, saved);
+
+  return acceptable > 0;
+}
+
+/* ================================================== */
+
+int
+NNC_CheckResponseAuth(NNC_Instance inst, NTP_Packet *packet,
+                      NTP_PacketInfo *info)
+{
+  int ef_type, ef_body_length, ef_length, parsed, plaintext_length;
+  int has_valid_uniq_id = 0, has_valid_auth = 0;
+  unsigned char plaintext[NTP_MAX_EXTENSIONS_LENGTH];
+  void *ef_body;
+
+  if (info->ext_fields == 0 || info->mode != MODE_SERVER)
+    return 0;
+
+  /* Accept at most one response per request */
+  if (inst->ok_response || inst->auth_ready)
+    return 0;
+
+  if (!inst->siv ||
+      !SIV_SetKey(inst->siv, inst->context.s2c.key, inst->context.s2c.length)) {
+    DEBUG_LOG("Could not set SIV key");
+    return 0;
+  }
+
+  for (parsed = NTP_HEADER_LENGTH; parsed < info->length; parsed += ef_length) {
+    if (!NEF_ParseField(packet, info->length, parsed,
+                        &ef_length, &ef_type, &ef_body, &ef_body_length))
+      /* This is not expected as the packet already passed parsing */
+      return 0;
+
+    switch (ef_type) {
+      case NTP_EF_NTS_UNIQUE_IDENTIFIER:
+        if (ef_body_length != sizeof (inst->uniq_id) ||
+            memcmp(ef_body, inst->uniq_id, sizeof (inst->uniq_id)) != 0) {
+          DEBUG_LOG("Invalid uniq id");
+          return 0;
+        }
+        has_valid_uniq_id = 1;
+        break;
+      case NTP_EF_NTS_COOKIE:
+        DEBUG_LOG("Unencrypted cookie");
+        break;
+      case NTP_EF_NTS_AUTH_AND_EEF:
+        if (parsed + ef_length != info->length) {
+          DEBUG_LOG("Auth not last EF");
+          return 0;
+        }
+
+        if (!NNA_DecryptAuthEF(packet, info, inst->siv, parsed,
+                               plaintext, sizeof (plaintext), &plaintext_length))
+          return 0;
+
+        if (!parse_encrypted_efs(inst, plaintext, plaintext_length))
+          return 0;
+
+        has_valid_auth = 1;
+        break;
+      default:
+        break;
+    }
+  }
+
+  if (!has_valid_uniq_id || !has_valid_auth) {
+    if (has_valid_uniq_id && packet->stratum == NTP_INVALID_STRATUM &&
+        ntohl(packet->reference_id) == NTP_KOD_NTS_NAK) {
+      DEBUG_LOG("NTS NAK");
+      inst->nak_response = 1;
+      return 0;
+    }
+
+    DEBUG_LOG("Missing NTS EF");
+    return 0;
+  }
+
+  if (!extract_cookies(inst, plaintext, plaintext_length))
+    return 0;
+
+  inst->ok_response = 1;
+
+  /* At this point we know the client interoperates with the server.  Allow a
+     new NTS-KE session to be started as soon as the cookies run out. */
+  inst->nke_attempts = 0;
+  inst->next_nke_attempt = 0.0;
+
+  return 1;
+}
+
+/* ================================================== */
+
+void
+NNC_ChangeAddress(NNC_Instance inst, IPAddr *address)
+{
+  save_cookies(inst);
+
+  inst->nts_address.ip_addr = *address;
+  inst->ntp_address.ip_addr = *address;
+
+  reset_instance(inst);
+
+  DEBUG_LOG("NTS reset");
+
+  load_cookies(inst);
+}
+
+/* ================================================== */
+
+static void
+save_cookies(NNC_Instance inst)
+{
+  char buf[2 * NKE_MAX_COOKIE_LENGTH + 2], *dump_dir, *filename;
+  struct timespec now;
+  double context_time;
+  FILE *f;
+  int i;
+
+  if (inst->num_cookies < 1 || !UTI_IsIPReal(&inst->nts_address.ip_addr))
+    return;
+
+  dump_dir = CNF_GetNtsDumpDir();
+  if (!dump_dir)
+    return;
+
+  filename = UTI_IPToString(&inst->nts_address.ip_addr);
+
+  f = UTI_OpenFile(dump_dir, filename, ".tmp", 'w', 0600);
+  if (!f)
+    return;
+
+  SCH_GetLastEventTime(&now, NULL, NULL);
+  context_time = inst->last_nke_success - SCH_GetLastEventMonoTime();
+  context_time += UTI_TimespecToDouble(&now);
+
+  if (fprintf(f, "%s%s\n%.1f\n%s %d\n%u %d ",
+              DUMP_IDENTIFIER, inst->name, context_time,
+              UTI_IPToString(&inst->ntp_address.ip_addr), inst->ntp_address.port,
+              inst->context_id, (int)inst->context.algorithm) < 0 ||
+      !UTI_BytesToHex(inst->context.s2c.key, inst->context.s2c.length, buf, sizeof (buf)) ||
+      fprintf(f, "%s ", buf) < 0 ||
+      !UTI_BytesToHex(inst->context.c2s.key, inst->context.c2s.length, buf, sizeof (buf)) ||
+      fprintf(f, "%s\n", buf) < 0)
+    goto error;
+
+  for (i = 0; i < inst->num_cookies; i++) {
+    if (!UTI_BytesToHex(inst->cookies[i].cookie, inst->cookies[i].length, buf, sizeof (buf)) ||
+        fprintf(f, "%s\n", buf) < 0)
+      goto error;
+  }
+
+  fclose(f);
+
+  if (!UTI_RenameTempFile(dump_dir, filename, ".tmp", ".nts"))
+    ;
+  return;
+
+error:
+  DEBUG_LOG("Could not %s cookies for %s", "save", filename);
+  fclose(f);
+
+  if (!UTI_RemoveFile(dump_dir, filename, ".nts"))
+    ;
+}
+
+/* ================================================== */
+
+#define MAX_WORDS 4
+
+static void
+load_cookies(NNC_Instance inst)
+{
+  char line[2 * NKE_MAX_COOKIE_LENGTH + 2], *dump_dir, *filename, *words[MAX_WORDS];
+  unsigned int context_id;
+  int i, algorithm, port;
+  double context_time;
+  struct timespec now;
+  IPSockAddr ntp_addr;
+  FILE *f;
+
+  dump_dir = CNF_GetNtsDumpDir();
+  if (!dump_dir)
+    return;
+
+  filename = UTI_IPToString(&inst->nts_address.ip_addr);
+
+  f = UTI_OpenFile(dump_dir, filename, ".nts", 'r', 0);
+  if (!f)
+    return;
+
+  /* Don't load this file again */
+  if (!UTI_RemoveFile(dump_dir, filename, ".nts"))
+    ;
+
+  if (inst->siv)
+    SIV_DestroyInstance(inst->siv);
+  inst->siv = NULL;
+
+  if (!fgets(line, sizeof (line), f) || strcmp(line, DUMP_IDENTIFIER) != 0 ||
+      !fgets(line, sizeof (line), f) || UTI_SplitString(line, words, MAX_WORDS) != 1 ||
+        strcmp(words[0], inst->name) != 0 ||
+      !fgets(line, sizeof (line), f) || UTI_SplitString(line, words, MAX_WORDS) != 1 ||
+        sscanf(words[0], "%lf", &context_time) != 1 ||
+      !fgets(line, sizeof (line), f) || UTI_SplitString(line, words, MAX_WORDS) != 2 ||
+        !UTI_StringToIP(words[0], &ntp_addr.ip_addr) || sscanf(words[1], "%d", &port) != 1 ||
+      !fgets(line, sizeof (line), f) || UTI_SplitString(line, words, MAX_WORDS) != 4 ||
+        sscanf(words[0], "%u", &context_id) != 1 || sscanf(words[1], "%d", &algorithm) != 1)
+    goto error;
+
+  inst->context.algorithm = algorithm;
+  inst->context.s2c.length = UTI_HexToBytes(words[2], inst->context.s2c.key,
+                                            sizeof (inst->context.s2c.key));
+  inst->context.c2s.length = UTI_HexToBytes(words[3], inst->context.c2s.key,
+                                            sizeof (inst->context.c2s.key));
+
+  if (inst->context.s2c.length != SIV_GetKeyLength(algorithm) ||
+      inst->context.c2s.length != inst->context.s2c.length)
+    goto error;
+
+  for (i = 0; i < NTS_MAX_COOKIES && fgets(line, sizeof (line), f); i++) {
+    if (UTI_SplitString(line, words, MAX_WORDS) != 1)
+      goto error;
+
+    inst->cookies[i].length = UTI_HexToBytes(words[0], inst->cookies[i].cookie,
+                                             sizeof (inst->cookies[i].cookie));
+    if (inst->cookies[i].length == 0)
+      goto error;
+  }
+
+  inst->num_cookies = i;
+
+  ntp_addr.port = port;
+  if (!set_ntp_address(inst, &ntp_addr))
+    goto error;
+
+  SCH_GetLastEventTime(&now, NULL, NULL);
+  context_time -= UTI_TimespecToDouble(&now);
+  if (context_time > 0)
+    context_time = 0;
+  inst->last_nke_success = context_time + SCH_GetLastEventMonoTime();
+  inst->context_id = context_id;
+
+  fclose(f);
+
+  DEBUG_LOG("Loaded %d cookies for %s", i, filename);
+  return;
+
+error:
+  DEBUG_LOG("Could not %s cookies for %s", "load", filename);
+  fclose(f);
+
+  memset(&inst->context, 0, sizeof (inst->context));
+  inst->num_cookies = 0;
+}
+
+/* ================================================== */
+
+void
+NNC_DumpData(NNC_Instance inst)
+{
+  save_cookies(inst);
+}
+
+/* ================================================== */
+
+void
+NNC_GetReport(NNC_Instance inst, RPT_AuthReport *report)
+{
+  report->key_id = inst->context_id;
+  report->key_type = inst->context.algorithm;
+  report->key_length = 8 * inst->context.s2c.length;
+  report->ke_attempts = inst->nke_attempts;
+  if (report->key_length > 0)
+    report->last_ke_ago = SCH_GetLastEventMonoTime() - inst->last_nke_success;
+  else
+    report->last_ke_ago = -1;
+  report->cookies = inst->num_cookies;
+  report->cookie_length = inst->num_cookies > 0 ? inst->cookies[inst->cookie_index].length : 0;
+  report->nak = inst->nak_response;
+}
--- a/nts_ntp_client.h
+++ b/nts_ntp_client.h
@@ -0,0 +1,51 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2020
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Header file for client NTS-NTP authentication
+  */
+
+#ifndef GOT_NTS_NTP_CLIENT_H
+#define GOT_NTS_NTP_CLIENT_H
+
+#include "addressing.h"
+#include "ntp.h"
+#include "reports.h"
+
+typedef struct NNC_Instance_Record *NNC_Instance;
+
+extern NNC_Instance NNC_CreateInstance(IPSockAddr *nts_address, const char *name,
+                                       uint32_t cert_set, uint16_t ntp_port);
+extern void NNC_DestroyInstance(NNC_Instance inst);
+extern int NNC_PrepareForAuth(NNC_Instance inst);
+extern int NNC_GenerateRequestAuth(NNC_Instance inst, NTP_Packet *packet,
+                                   NTP_PacketInfo *info);
+extern int NNC_CheckResponseAuth(NNC_Instance inst, NTP_Packet *packet,
+                                 NTP_PacketInfo *info);
+
+extern void NNC_ChangeAddress(NNC_Instance inst, IPAddr *address);
+
+extern void NNC_DumpData(NNC_Instance inst);
+
+extern void NNC_GetReport(NNC_Instance inst, RPT_AuthReport *report);
+
+#endif
--- a/nts_ntp_server.c
+++ b/nts_ntp_server.c
@@ -0,0 +1,283 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2020
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Server NTS-NTP authentication
+  */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include "nts_ntp_server.h"
+
+#include "conf.h"
+#include "logging.h"
+#include "memory.h"
+#include "ntp.h"
+#include "ntp_ext.h"
+#include "nts_ke_server.h"
+#include "nts_ntp.h"
+#include "nts_ntp_auth.h"
+#include "siv.h"
+#include "util.h"
+
+#define SERVER_SIV AEAD_AES_SIV_CMAC_256
+
+struct NtsServer {
+  SIV_Instance siv;
+  unsigned char nonce[NTS_MIN_UNPADDED_NONCE_LENGTH];
+  NKE_Cookie cookies[NTS_MAX_COOKIES];
+  int num_cookies;
+  NTP_int64 req_tx;
+};
+
+/* The server instance handling all requests */
+struct NtsServer *server;
+
+/* ================================================== */
+
+void
+NNS_Initialise(void)
+{
+  const char **certs, **keys;
+
+  /* Create an NTS-NTP server instance only if NTS-KE server is enabled */
+  if (CNF_GetNtsServerCertAndKeyFiles(&certs, &keys) <= 0) {
+    server = NULL;
+    return;
+  }
+
+  server = Malloc(sizeof (struct NtsServer));
+  server->siv = SIV_CreateInstance(SERVER_SIV);
+  if (!server->siv)
+    LOG_FATAL("Could not initialise SIV cipher");
+}
+
+/* ================================================== */
+
+void
+NNS_Finalise(void)
+{
+  if (!server)
+    return;
+
+  SIV_DestroyInstance(server->siv);
+  Free(server);
+  server = NULL;
+}
+
+/* ================================================== */
+
+int
+NNS_CheckRequestAuth(NTP_Packet *packet, NTP_PacketInfo *info, uint32_t *kod)
+{
+  int ef_type, ef_body_length, ef_length, has_uniq_id = 0, has_auth = 0, has_cookie = 0;
+  int i, plaintext_length, parsed, requested_cookies, cookie_length = -1, auth_start = 0;
+  unsigned char plaintext[NTP_MAX_EXTENSIONS_LENGTH];
+  NKE_Context context;
+  NKE_Cookie cookie;
+  void *ef_body;
+
+  *kod = 0;
+
+  if (!server)
+    return 0;
+
+  server->num_cookies = 0;
+  server->req_tx = packet->transmit_ts;
+
+  if (info->ext_fields == 0 || info->mode != MODE_CLIENT)
+    return 0;
+
+  requested_cookies = 0;
+
+  for (parsed = NTP_HEADER_LENGTH; parsed < info->length; parsed += ef_length) {
+    if (!NEF_ParseField(packet, info->length, parsed,
+                        &ef_length, &ef_type, &ef_body, &ef_body_length))
+      /* This is not expected as the packet already passed NAU_ParsePacket() */
+      return 0;
+
+    switch (ef_type) {
+      case NTP_EF_NTS_UNIQUE_IDENTIFIER:
+        has_uniq_id = 1;
+        break;
+      case NTP_EF_NTS_COOKIE:
+        if (has_cookie || ef_body_length > sizeof (cookie.cookie)) {
+          DEBUG_LOG("Unexpected cookie/length");
+          return 0;
+        }
+        cookie.length = ef_body_length;
+        memcpy(cookie.cookie, ef_body, ef_body_length);
+        has_cookie = 1;
+        /* Fall through */
+      case NTP_EF_NTS_COOKIE_PLACEHOLDER:
+        requested_cookies++;
+
+        if (cookie_length >= 0 && cookie_length != ef_body_length) {
+          DEBUG_LOG("Invalid cookie/placeholder length");
+          return 0;
+        }
+        cookie_length = ef_body_length;
+        break;
+      case NTP_EF_NTS_AUTH_AND_EEF:
+        if (parsed + ef_length != info->length) {
+          DEBUG_LOG("Auth not last EF");
+          return 0;
+        }
+
+        auth_start = parsed;
+        has_auth = 1;
+        break;
+      default:
+        break;
+    }
+  }
+
+  if (!has_uniq_id || !has_cookie || !has_auth) {
+    DEBUG_LOG("Missing an NTS EF");
+    return 0;
+  }
+
+  if (!NKS_DecodeCookie(&cookie, &context)) {
+    *kod = NTP_KOD_NTS_NAK;
+    return 0;
+  }
+
+  if (context.algorithm != SERVER_SIV) {
+    DEBUG_LOG("Unexpected SIV");
+    return 0;
+  }
+
+  if (!SIV_SetKey(server->siv, context.c2s.key, context.c2s.length)) {
+    DEBUG_LOG("Could not set C2S key");
+    return 0;
+  }
+
+  if (!NNA_DecryptAuthEF(packet, info, server->siv, auth_start,
+                         plaintext, sizeof (plaintext), &plaintext_length)) {
+    *kod = NTP_KOD_NTS_NAK;
+    return 0;
+  }
+
+  for (parsed = 0; parsed < plaintext_length; parsed += ef_length) {
+    if (!NEF_ParseSingleField(plaintext, plaintext_length, parsed,
+                              &ef_length, &ef_type, &ef_body, &ef_body_length)) {
+      DEBUG_LOG("Could not parse encrypted EF");
+      return 0;
+    }
+
+    switch (ef_type) {
+      case NTP_EF_NTS_COOKIE_PLACEHOLDER:
+        if (cookie_length != ef_body_length) {
+          DEBUG_LOG("Invalid cookie/placeholder length");
+          return 0;
+        }
+        requested_cookies++;
+        break;
+      default:
+        break;
+    }
+  }
+
+  if (!SIV_SetKey(server->siv, context.s2c.key, context.s2c.length)) {
+    DEBUG_LOG("Could not set S2C key");
+    return 0;
+  }
+
+  /* Prepare data for NNS_GenerateResponseAuth() to minimise the time spent
+     there (when the TX timestamp is already set) */
+
+  UTI_GetRandomBytes(server->nonce, sizeof (server->nonce));
+
+  assert(sizeof (server->cookies) / sizeof (server->cookies[0]) == NTS_MAX_COOKIES);
+  for (i = 0; i < NTS_MAX_COOKIES && i < requested_cookies; i++)
+    if (!NKS_GenerateCookie(&context, &server->cookies[i]))
+      return 0;
+
+  server->num_cookies = i;
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+NNS_GenerateResponseAuth(NTP_Packet *request, NTP_PacketInfo *req_info,
+                         NTP_Packet *response, NTP_PacketInfo *res_info,
+                         uint32_t kod)
+{
+  int i, ef_type, ef_body_length, ef_length, parsed;
+  void *ef_body;
+  unsigned char plaintext[NTP_MAX_EXTENSIONS_LENGTH];
+  int plaintext_length;
+
+  if (!server || req_info->mode != MODE_CLIENT || res_info->mode != MODE_SERVER)
+    return 0;
+
+  /* Make sure this is a response to the request from the last call
+     of NNS_CheckRequestAuth() */
+  if (UTI_CompareNtp64(&server->req_tx, &request->transmit_ts) != 0)
+    assert(0);
+
+  for (parsed = NTP_HEADER_LENGTH; parsed < req_info->length; parsed += ef_length) {
+    if (!NEF_ParseField(request, req_info->length, parsed,
+                        &ef_length, &ef_type, &ef_body, &ef_body_length))
+      /* This is not expected as the packet already passed parsing */
+      return 0;
+
+    switch (ef_type) {
+      case NTP_EF_NTS_UNIQUE_IDENTIFIER:
+        /* Copy the ID from the request */
+        if (!NEF_AddField(response, res_info, ef_type, ef_body, ef_body_length))
+          return 0;
+      default:
+        break;
+    }
+  }
+
+  /* NTS NAK response does not have any other fields */
+  if (kod)
+    return 1;
+
+  for (i = 0, plaintext_length = 0; i < server->num_cookies; i++) {
+    if (!NEF_SetField(plaintext, sizeof (plaintext), plaintext_length,
+                      NTP_EF_NTS_COOKIE, server->cookies[i].cookie,
+                      server->cookies[i].length, &ef_length))
+      return 0;
+
+    plaintext_length += ef_length;
+    assert(plaintext_length <= sizeof (plaintext));
+  }
+
+  server->num_cookies = 0;
+
+  /* Generate an authenticator field which will make the length
+     of the response equal to the length of the request */
+  if (!NNA_GenerateAuthEF(response, res_info, server->siv,
+                          server->nonce, sizeof (server->nonce),
+                          plaintext, plaintext_length,
+                          req_info->length - res_info->length))
+    return 0;
+
+  return 1;
+}
--- a/nts_ntp_server.h
+++ b/nts_ntp_server.h
@@ -0,0 +1,40 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2020
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Header file for server NTS-NTP authentication
+  */
+
+#ifndef GOT_NTS_NTP_SERVER_H
+#define GOT_NTS_NTP_SERVER_H
+
+#include "ntp.h"
+
+extern void NNS_Initialise(void);
+extern void NNS_Finalise(void);
+
+extern int NNS_CheckRequestAuth(NTP_Packet *packet, NTP_PacketInfo *info, uint32_t *kod);
+extern int NNS_GenerateResponseAuth(NTP_Packet *request, NTP_PacketInfo *req_info,
+                                    NTP_Packet *response, NTP_PacketInfo *res_info,
+                                    uint32_t kod);
+
+#endif
--- a/pktlength.c
+++ b/pktlength.c
@@ -87,7 +87,7 @@ static const struct request_length request_lengths[] = {
  REQ_LENGTH_ENTRY(del_source, null),           /* DEL_SOURCE */
  REQ_LENGTH_ENTRY(null, null),                 /* WRITERTC */
  REQ_LENGTH_ENTRY(dfreq, null),                /* DFREQ */
-  REQ_LENGTH_ENTRY(doffset, null),              /* DOFFSET */
+  { 0, 0 },                                     /* DOFFSET - not supported */
  REQ_LENGTH_ENTRY(null, tracking),             /* TRACKING */
  REQ_LENGTH_ENTRY(sourcestats, sourcestats),   /* SOURCESTATS */
  REQ_LENGTH_ENTRY(null, rtc),                  /* RTCREPORT */
@@ -110,12 +110,25 @@ static const struct request_length request_lengths[] = {
  REQ_LENGTH_ENTRY(smoothtime, null),           /* SMOOTHTIME */
  REQ_LENGTH_ENTRY(null, null),                 /* REFRESH */
  REQ_LENGTH_ENTRY(null, server_stats),         /* SERVER_STATS */
-  REQ_LENGTH_ENTRY(client_accesses_by_index,
-                   client_accesses_by_index),   /* CLIENT_ACCESSES_BY_INDEX2 */
+  { 0, 0 },                                     /* CLIENT_ACCESSES_BY_INDEX2 - not supported */
  REQ_LENGTH_ENTRY(local, null),                /* LOCAL2 */
  REQ_LENGTH_ENTRY(ntp_data, ntp_data),         /* NTP_DATA */
-  REQ_LENGTH_ENTRY(ntp_source, null),           /* ADD_SERVER2 */
-  REQ_LENGTH_ENTRY(ntp_source, null),           /* ADD_PEER2 */
+  { 0, 0 },                                     /* ADD_SERVER2 */
+  { 0, 0 },                                     /* ADD_PEER2 */
+  { 0, 0 },                                     /* ADD_SERVER3 */
+  { 0, 0 },                                     /* ADD_PEER3 */
+  REQ_LENGTH_ENTRY(null, null),                 /* SHUTDOWN */
+  REQ_LENGTH_ENTRY(null, null),                 /* ONOFFLINE */
+  REQ_LENGTH_ENTRY(ntp_source, null),           /* ADD_SOURCE */
+  REQ_LENGTH_ENTRY(ntp_source_name,
+                   ntp_source_name),            /* NTP_SOURCE_NAME */
+  REQ_LENGTH_ENTRY(null, null),                 /* RESET_SOURCES */
+  REQ_LENGTH_ENTRY(auth_data, auth_data),       /* AUTH_DATA */
+  REQ_LENGTH_ENTRY(client_accesses_by_index,
+                   client_accesses_by_index),   /* CLIENT_ACCESSES_BY_INDEX3 */
+  REQ_LENGTH_ENTRY(select_data, select_data),   /* SELECT_DATA */
+  REQ_LENGTH_ENTRY(null, null),                 /* RELOAD_SOURCES */
+  REQ_LENGTH_ENTRY(doffset, null),              /* DOFFSET2 */
 };

 static const uint16_t reply_lengths[] = {
@@ -123,19 +136,27 @@ static const uint16_t reply_lengths[] = {
  RPY_LENGTH_ENTRY(null),                       /* NULL */
  RPY_LENGTH_ENTRY(n_sources),                  /* N_SOURCES */
  RPY_LENGTH_ENTRY(source_data),                /* SOURCE_DATA */
-  RPY_LENGTH_ENTRY(manual_timestamp),           /* MANUAL_TIMESTAMP */
+  0,                                            /* MANUAL_TIMESTAMP */
  RPY_LENGTH_ENTRY(tracking),                   /* TRACKING */
  RPY_LENGTH_ENTRY(sourcestats),                /* SOURCESTATS */
  RPY_LENGTH_ENTRY(rtc),                        /* RTC */
  0,                                            /* SUBNETS_ACCESSED - not supported */
  0,                                            /* CLIENT_ACCESSES - not supported */
  0,                                            /* CLIENT_ACCESSES_BY_INDEX - not supported */
-  0,                                            /* MANUAL_LIST - variable length */
+  0,                                            /* MANUAL_LIST - not supported */
  RPY_LENGTH_ENTRY(activity),                   /* ACTIVITY */
  RPY_LENGTH_ENTRY(smoothing),                  /* SMOOTHING */
-  RPY_LENGTH_ENTRY(server_stats),               /* SERVER_STATS */
-  RPY_LENGTH_ENTRY(client_accesses_by_index),   /* CLIENT_ACCESSES_BY_INDEX2 */
+  0,                                            /* SERVER_STATS - not supported */
+  0,                                            /* CLIENT_ACCESSES_BY_INDEX2 - not supported */
  RPY_LENGTH_ENTRY(ntp_data),                   /* NTP_DATA */
+  RPY_LENGTH_ENTRY(manual_timestamp),           /* MANUAL_TIMESTAMP2 */
+  RPY_LENGTH_ENTRY(manual_list),                /* MANUAL_LIST2 */
+  RPY_LENGTH_ENTRY(ntp_source_name),            /* NTP_SOURCE_NAME */
+  RPY_LENGTH_ENTRY(auth_data),                  /* AUTH_DATA */
+  RPY_LENGTH_ENTRY(client_accesses_by_index),   /* CLIENT_ACCESSES_BY_INDEX3 */
+  0,                                            /* SERVER_STATS2 - not supported */
+  RPY_LENGTH_ENTRY(select_data),                /* SELECT_DATA */
+  RPY_LENGTH_ENTRY(server_stats),               /* SERVER_STATS3 */
 };

 /* ================================================== */
@@ -192,21 +213,6 @@ PKL_ReplyLength(CMD_Reply *r)
  if (type < 1 || type >= N_REPLY_TYPES)
    return 0;

-  /* Length of MANUAL_LIST depends on number of samples stored in it */
-  if (type == RPY_MANUAL_LIST) {
-    uint32_t ns;
-
-    if (r->status != htons(STT_SUCCESS))
-      return offsetof(CMD_Reply, data);
-
-    ns = ntohl(r->data.manual_list.n_samples);
-    if (ns > MAX_MANUAL_LIST_SAMPLES)
-      return 0;
-
-    return offsetof(CMD_Reply, data.manual_list.samples) +
-           ns * sizeof (RPY_ManualListSample);
-  }
-
  return reply_lengths[type];
 }

--- a/privops.c
+++ b/privops.c
@@ -3,7 +3,7 @@

 **********************************************************************
 * Copyright (C) Bryan Christianson 2015
- * Copyright (C) Miroslav Lichvar  2016
+ * Copyright (C) Miroslav Lichvar  2017
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
@@ -33,6 +33,7 @@
 #include "nameserv.h"
 #include "logging.h"
 #include "privops.h"
+#include "socket.h"
 #include "util.h"

 #define OP_ADJUSTTIME     1024
@@ -40,6 +41,7 @@
 #define OP_SETTIME        1026
 #define OP_BINDSOCKET     1027
 #define OP_NAME2IPADDRESS 1028
+#define OP_RELOADDNS      1029
 #define OP_QUIT           1099

 union sockaddr_in46 {
@@ -157,7 +159,7 @@ res_fatal(PrvResponse *res, const char *fmt, ...)
 static int
 send_response(int fd, const PrvResponse *res)
 {
-  if (send(fd, res, sizeof (*res), 0) != sizeof (*res))
+  if (SCK_Send(fd, res, sizeof (*res), 0) != sizeof (*res))
    return 0;

  return 1;
@@ -169,37 +171,23 @@ send_response(int fd, const PrvResponse *res)
 static int
 receive_from_daemon(int fd, PrvRequest *req)
 {
-  struct msghdr msg;
-  struct cmsghdr *cmsg;
-  struct iovec iov;
-  char cmsgbuf[256];
+  SCK_Message *message;

-  iov.iov_base = req;
-  iov.iov_len = sizeof (*req);
-
-  msg.msg_name = NULL;
-  msg.msg_namelen = 0;
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-  msg.msg_control = (void *)cmsgbuf;
-  msg.msg_controllen = sizeof (cmsgbuf);
-  msg.msg_flags = MSG_WAITALL;
-
-  /* read the data */
-  if (recvmsg(fd, &msg, 0) != sizeof (*req))
+  message = SCK_ReceiveMessage(fd, SCK_FLAG_MSG_DESCRIPTOR);
+  if (!message || message->length != sizeof (*req))
    return 0;

+  memcpy(req, message->data, sizeof (*req));
+
  if (req->op == OP_BINDSOCKET) {
-    /* extract transferred descriptor */
-    req->data.bind_socket.sock = -1;
-    for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
-      if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS)
-        memcpy(&req->data.bind_socket.sock, CMSG_DATA(cmsg), sizeof (int));
-    }
+    req->data.bind_socket.sock = message->descriptor;

    /* return error if valid descriptor not found */
    if (req->data.bind_socket.sock < 0)
      return 0;
+  } else if (message->descriptor >= 0) {
+    SCK_CloseSocket(message->descriptor);
+    return 0;
  }

  return 1;
@@ -256,8 +244,7 @@ do_set_time(const ReqSetTime *req, PrvResponse *res)
 static void
 do_bind_socket(ReqBindSocket *req, PrvResponse *res)
 {
-  unsigned short port;
-  IPAddr ip;
+  IPSockAddr ip_saddr;
  int sock_fd;
  struct sockaddr *sa;
  socklen_t sa_len;
@@ -266,10 +253,11 @@ do_bind_socket(ReqBindSocket *req, PrvResponse *res)
  sa_len = req->sa_len;
  sock_fd = req->sock;

-  UTI_SockaddrToIPAndPort(sa, &ip, &port);
-  if (port && port != CNF_GetNTPPort()) {
-    close(sock_fd);
-    res_fatal(res, "Invalid port %d", port);
+  SCK_SockaddrToIPSockAddr(sa, sa_len, &ip_saddr);
+  if (ip_saddr.port != 0 && ip_saddr.port != CNF_GetNTPPort() &&
+      ip_saddr.port != CNF_GetAcquisitionPort() && ip_saddr.port != CNF_GetPtpPort()) {
+    SCK_CloseSocket(sock_fd);
+    res_fatal(res, "Invalid port %d", ip_saddr.port);
    return;
  }

@@ -278,7 +266,7 @@ do_bind_socket(ReqBindSocket *req, PrvResponse *res)
    res->res_errno = errno;

  /* sock is still open on daemon side, but we're done with it in the helper */
-  close(sock_fd);
+  SCK_CloseSocket(sock_fd);
 }
 #endif

@@ -293,8 +281,6 @@ do_name_to_ipaddress(ReqName2IPAddress *req, PrvResponse *res)
  /* make sure the string is terminated */
  req->name[sizeof (req->name) - 1] = '\0';

-  DNS_Reload();
-
  res->rc = DNS_Name2IPAddress(req->name, res->data.name_to_ipaddress.addresses,
                               DNS_MAX_ADDRESSES);
 }
@@ -302,6 +288,19 @@ do_name_to_ipaddress(ReqName2IPAddress *req, PrvResponse *res)

 /* ======================================================================= */

+/* HELPER - perform DNS_Reload() */
+
+#ifdef PRIVOPS_RELOADDNS
+static void
+do_reload_dns(PrvResponse *res)
+{
+  DNS_Reload();
+  res->rc = 0;
+}
+#endif
+
+/* ======================================================================= */
+
 /* HELPER - main loop - action requests from the daemon */

 static void
@@ -343,6 +342,11 @@ helper_main(int fd)
      case OP_NAME2IPADDRESS:
        do_name_to_ipaddress(&req.data.name_to_ipaddress, &res);
        break;
+#endif
+#ifdef PRIVOPS_RELOADDNS
+      case OP_RELOADDNS:
+        do_reload_dns(&res);
+        break;
 #endif
      case OP_QUIT:
        quit = 1;
@@ -356,7 +360,7 @@ helper_main(int fd)
    send_response(fd, &res);
  }

-  close(fd);
+  SCK_CloseSocket(fd);
  exit(0);
 }

@@ -369,16 +373,16 @@ receive_response(PrvResponse *res)
 {
  int resp_len;

-  resp_len = recv(helper_fd, res, sizeof (*res), 0);
+  resp_len = SCK_Receive(helper_fd, res, sizeof (*res), 0);
  if (resp_len < 0)
-    LOG_FATAL(LOGF_PrivOps, "Could not read from helper : %s", strerror(errno));
+    LOG_FATAL("Could not read from helper : %s", strerror(errno));
  if (resp_len != sizeof (*res))
-    LOG_FATAL(LOGF_PrivOps, "Invalid helper response");
+    LOG_FATAL("Invalid helper response");

  if (res->fatal_error)
-    LOG_FATAL(LOGF_PrivOps, "Error in helper : %s", res->data.fatal_msg.msg);
+    LOG_FATAL("Error in helper : %s", res->data.fatal_msg.msg);

-  DEBUG_LOG(LOGF_PrivOps, "Received response rc=%d", res->rc);
+  DEBUG_LOG("Received response rc=%d", res->rc);

  /* if operation failed in the helper, set errno so daemon can print log message */
  if (res->res_errno)
@@ -392,47 +396,28 @@ receive_response(PrvResponse *res)
 static void
 send_request(PrvRequest *req)
 {
-  struct msghdr msg;
-  struct iovec iov;
-  char cmsgbuf[256];
+  SCK_Message message;
+  int flags;

-  iov.iov_base = req;
-  iov.iov_len = sizeof (*req);
+  SCK_InitMessage(&message, SCK_ADDR_UNSPEC);

-  msg.msg_name = NULL;
-  msg.msg_namelen = 0;
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-  msg.msg_control = NULL;
-  msg.msg_controllen = 0;
-  msg.msg_flags = 0;
+  message.data = req;
+  message.length = sizeof (*req);
+  flags = 0;

  if (req->op == OP_BINDSOCKET) {
    /* send file descriptor as a control message */
-    struct cmsghdr *cmsg;
-    int *ptr_send_fd;
-
-    msg.msg_control = cmsgbuf;
-    msg.msg_controllen = CMSG_SPACE(sizeof (int));
-
-    cmsg = CMSG_FIRSTHDR(&msg);
-    memset(cmsg, 0, CMSG_SPACE(sizeof (int)));
-
-    cmsg->cmsg_level = SOL_SOCKET;
-    cmsg->cmsg_type = SCM_RIGHTS;
-    cmsg->cmsg_len = CMSG_LEN(sizeof (int));
-
-    ptr_send_fd = (int *)CMSG_DATA(cmsg);
-    *ptr_send_fd = req->data.bind_socket.sock;
+    message.descriptor = req->data.bind_socket.sock;
+    flags |= SCK_FLAG_MSG_DESCRIPTOR;
  }

-  if (sendmsg(helper_fd, &msg, 0) < 0) {
+  if (!SCK_SendMessage(helper_fd, &message, flags)) {
    /* don't try to send another request from exit() */
    helper_fd = -1;
-    LOG_FATAL(LOGF_PrivOps, "Could not send to helper : %s", strerror(errno));
+    LOG_FATAL("Could not send to helper : %s", strerror(errno));
  }

-  DEBUG_LOG(LOGF_PrivOps, "Sent request op=%d", req->op);
+  DEBUG_LOG("Sent request op=%d", req->op);
 }

 /* ======================================================================= */
@@ -556,13 +541,14 @@ PRV_SetTime(const struct timeval *tp, const struct timezone *tzp)
 int
 PRV_BindSocket(int sock, struct sockaddr *address, socklen_t address_len)
 {
+  IPSockAddr ip_saddr;
  PrvRequest req;
  PrvResponse res;
-  IPAddr ip;
-  unsigned short port;

-  UTI_SockaddrToIPAndPort(address, &ip, &port);
-  assert(!port || port == CNF_GetNTPPort());
+  SCK_SockaddrToIPSockAddr(address, address_len, &ip_saddr);
+  if (ip_saddr.port != 0 && ip_saddr.port != CNF_GetNTPPort() &&
+      ip_saddr.port != CNF_GetAcquisitionPort() && ip_saddr.port != CNF_GetPtpPort())
+    assert(0);

  if (!have_helper())
    return bind(sock, address, address_len);
@@ -571,6 +557,7 @@ PRV_BindSocket(int sock, struct sockaddr *address, socklen_t address_len)
  req.op = OP_BINDSOCKET;
  req.data.bind_socket.sock = sock;
  req.data.bind_socket.sa_len = address_len;
+  assert(address_len <= sizeof (req.data.bind_socket.sa));
  memcpy(&req.data.bind_socket.sa.u, address, address_len);

  submit_request(&req, &res);
@@ -598,7 +585,6 @@ PRV_Name2IPAddress(const char *name, IPAddr *ip_addrs, int max_addrs)
  req.op = OP_NAME2IPADDRESS;
  if (snprintf(req.data.name_to_ipaddress.name, sizeof (req.data.name_to_ipaddress.name),
               "%s", name) >= sizeof (req.data.name_to_ipaddress.name)) {
-    DEBUG_LOG(LOGF_PrivOps, "Name too long");
    return DNS_Failure;
  }

@@ -613,6 +599,30 @@ PRV_Name2IPAddress(const char *name, IPAddr *ip_addrs, int max_addrs)

 /* ======================================================================= */

+/* DAEMON - request res_init() */
+
+#ifdef PRIVOPS_RELOADDNS
+void
+PRV_ReloadDNS(void)
+{
+  PrvRequest req;
+  PrvResponse res;
+
+  if (!have_helper()) {
+    DNS_Reload();
+    return;
+  }
+
+  memset(&req, 0, sizeof (req));
+  req.op = OP_RELOADDNS;
+
+  submit_request(&req, &res);
+  assert(!res.rc);
+}
+#endif
+
+/* ======================================================================= */
+
 void
 PRV_Initialise(void)
 {
@@ -628,44 +638,41 @@ void
 PRV_StartHelper(void)
 {
  pid_t pid;
-  int fd, sock_pair[2];
+  int fd, sock_fd1, sock_fd2;

  if (have_helper())
-    LOG_FATAL(LOGF_PrivOps, "Helper already running");
+    LOG_FATAL("Helper already running");

-  if (
-#ifdef SOCK_SEQPACKET
-      socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sock_pair) &&
-#endif
-      socketpair(AF_UNIX, SOCK_DGRAM, 0, sock_pair))
-    LOG_FATAL(LOGF_PrivOps, "socketpair() failed : %s", strerror(errno));
-
-  UTI_FdSetCloexec(sock_pair[0]);
-  UTI_FdSetCloexec(sock_pair[1]);
+  sock_fd1 = SCK_OpenUnixSocketPair(SCK_FLAG_BLOCK, &sock_fd2);
+  if (sock_fd1 < 0)
+    LOG_FATAL("Could not open socket pair");

  pid = fork();
  if (pid < 0)
-    LOG_FATAL(LOGF_PrivOps, "fork() failed : %s", strerror(errno));
+    LOG_FATAL("fork() failed : %s", strerror(errno));

  if (pid == 0) {
    /* child process */
-    close(sock_pair[0]);
+    SCK_CloseSocket(sock_fd1);

-    /* close other descriptors inherited from the parent process */
-    for (fd = 0; fd < 1024; fd++) {
-      if (fd != sock_pair[1])
+    /* close other descriptors inherited from the parent process, except
+       stdin, stdout, and stderr */
+    for (fd = STDERR_FILENO + 1; fd < 1024; fd++) {
+      if (fd != sock_fd2)
        close(fd);
    }

-    /* ignore signals, the process will exit on OP_QUIT request */
-    UTI_SetQuitSignalsHandler(SIG_IGN);
+    UTI_ResetGetRandomFunctions();

-    helper_main(sock_pair[1]);
+    /* ignore signals, the process will exit on OP_QUIT request */
+    UTI_SetQuitSignalsHandler(SIG_IGN, 1);
+
+    helper_main(sock_fd2);

  } else {
    /* parent process */
-    close(sock_pair[1]);
-    helper_fd = sock_pair[0];
+    SCK_CloseSocket(sock_fd2);
+    helper_fd = sock_fd1;
    helper_pid = pid;

    /* stop the helper even when not exiting cleanly from the main function */
--- a/privops.h
+++ b/privops.h
@@ -58,6 +58,12 @@ int PRV_Name2IPAddress(const char *name, IPAddr *ip_addrs, int max_addrs);
 #define PRV_Name2IPAddress DNS_Name2IPAddress
 #endif

+#ifdef PRIVOPS_RELOADDNS
+void PRV_ReloadDNS(void);
+#else
+#define PRV_ReloadDNS DNS_Reload
+#endif
+
 #ifdef PRIVOPS_HELPER
 void PRV_Initialise(void);
 void PRV_StartHelper(void);
--- a/ptp.h
+++ b/ptp.h
@@ -0,0 +1,64 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2021
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ **********************************************************************
+
+  =======================================================================
+
+  This is the header file for the Precision Time Protocol (PTP).
+
+  */
+#ifndef GOT_PTP_H
+#define GOT_PTP_H
+
+#include "sysincl.h"
+
+#include "ntp.h"
+
+#define PTP_VERSION 2
+#define PTP_TYPE_DELAY_REQ 1
+#define PTP_DOMAIN_NTP 123
+#define PTP_FLAG_UNICAST (1 << (2 + 8))
+#define PTP_TLV_NTP 0x2023
+
+typedef struct {
+  uint8_t type;
+  uint8_t version;
+  uint16_t length;
+  uint8_t domain;
+  uint8_t min_sdoid;
+  uint16_t flags;
+  uint8_t rest[26];
+} PTP_Header;
+
+typedef struct {
+  uint16_t type;
+  uint16_t length;
+} PTP_TlvHeader;
+
+typedef struct {
+  PTP_Header header;
+  uint8_t origin_ts[10];
+  PTP_TlvHeader tlv_header;
+  NTP_Packet ntp_msg;
+} PTP_NtpMessage;
+
+#define PTP_NTP_PREFIX_LENGTH (int)offsetof(PTP_NtpMessage, ntp_msg)
+
+#endif
--- a/quantiles.c
+++ b/quantiles.c
@@ -0,0 +1,209 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2022
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ **********************************************************************
+
+  =======================================================================
+
+  Estimation of quantiles using the Frugal-2U streaming algorithm
+  (https://arxiv.org/pdf/1407.1121v1.pdf)
+  */
+
+#include "config.h"
+
+#include "logging.h"
+#include "memory.h"
+#include "quantiles.h"
+#include "regress.h"
+#include "util.h"
+
+/* Maximum number of repeated estimates for stabilisation */
+#define MAX_REPEAT 64
+
+struct Quantile {
+  double est;
+  double step;
+  int sign;
+};
+
+struct QNT_Instance_Record {
+  struct Quantile *quants;
+  int n_quants;
+  int repeat;
+  int q;
+  int min_k;
+  double min_step;
+  int n_set;
+};
+
+/* ================================================== */
+
+QNT_Instance
+QNT_CreateInstance(int min_k, int max_k, int q, int repeat, double min_step)
+{
+  QNT_Instance inst;
+  long seed;
+
+  if (q < 2 || min_k > max_k || min_k < 1 || max_k >= q ||
+      repeat < 1 || repeat > MAX_REPEAT || min_step <= 0.0)
+    assert(0);
+
+  inst = MallocNew(struct QNT_Instance_Record);
+  inst->n_quants = (max_k - min_k + 1) * repeat;
+  inst->quants = MallocArray(struct Quantile, inst->n_quants);
+  inst->repeat = repeat;
+  inst->q = q;
+  inst->min_k = min_k;
+  inst->min_step = min_step;
+
+  QNT_Reset(inst);
+
+  /* Seed the random number generator, which will not be isolated from
+     other instances and other random() users */
+  UTI_GetRandomBytes(&seed, sizeof (seed));
+  srandom(seed);
+
+  return inst;
+}
+
+/* ================================================== */
+
+void
+QNT_DestroyInstance(QNT_Instance inst)
+{
+  Free(inst->quants);
+  Free(inst);
+}
+
+/* ================================================== */
+
+void
+QNT_Reset(QNT_Instance inst)
+{
+  int i;
+
+  inst->n_set = 0;
+
+  for (i = 0; i < inst->n_quants; i++) {
+    inst->quants[i].est = 0.0;
+    inst->quants[i].step = inst->min_step;
+    inst->quants[i].sign = 1;
+  }
+}
+
+/* ================================================== */
+
+static void
+insert_initial_value(QNT_Instance inst, double value)
+{
+  int i, j, r = inst->repeat;
+
+  if (inst->n_set * r >= inst->n_quants)
+    assert(0);
+
+  /* Keep the initial estimates repeated and ordered */
+  for (i = inst->n_set; i > 0 && inst->quants[(i - 1) * r].est > value; i--) {
+    for (j = 0; j < r; j++)
+      inst->quants[i * r + j].est = inst->quants[(i - 1) * r].est;
+  }
+
+  for (j = 0; j < r; j++)
+    inst->quants[i * r + j].est = value;
+  inst->n_set++;
+
+  /* Duplicate the largest value in unset quantiles */
+  for (i = inst->n_set * r; i < inst->n_quants; i++)
+    inst->quants[i].est = inst->quants[i - 1].est;
+}
+
+/* ================================================== */
+
+static void
+update_estimate(struct Quantile *quantile, double value, double p, double rand,
+                double min_step)
+{
+  if (value > quantile->est && rand > (1.0 - p)) {
+    quantile->step += quantile->sign > 0 ? min_step : -min_step;
+    quantile->est += quantile->step > 0.0 ? fabs(quantile->step) : min_step;
+    if (quantile->est > value) {
+      quantile->step += value - quantile->est;
+      quantile->est = value;
+    }
+    if (quantile->sign < 0 && quantile->step > min_step)
+      quantile->step = min_step;
+    quantile->sign = 1;
+  } else if (value < quantile->est && rand > p) {
+    quantile->step += quantile->sign < 0 ? min_step : -min_step;
+    quantile->est -= quantile->step > 0.0 ? fabs(quantile->step) : min_step;
+    if (quantile->est < value) {
+      quantile->step += quantile->est - value;
+      quantile->est = value;
+    }
+    if (quantile->sign > 0 && quantile->step > min_step)
+      quantile->step = min_step;
+    quantile->sign = -1;
+  }
+}
+
+/* ================================================== */
+
+void
+QNT_Accumulate(QNT_Instance inst, double value)
+{
+  double p, rand;
+  int i;
+
+  /* Initialise the estimates with first received values */
+  if (inst->n_set * inst->repeat < inst->n_quants) {
+    insert_initial_value(inst, value);
+    return;
+  }
+
+  for (i = 0; i < inst->n_quants; i++) {
+    p = (double)(i / inst->repeat + inst->min_k) / inst->q;
+    rand = (double)random() / ((1U << 31) - 1);
+
+    update_estimate(&inst->quants[i], value, p, rand, inst->min_step);
+  }
+}
+
+/* ================================================== */
+
+int
+QNT_GetMinK(QNT_Instance inst)
+{
+  return inst->min_k;
+}
+
+/* ================================================== */
+
+double
+QNT_GetQuantile(QNT_Instance inst, int k)
+{
+  double estimates[MAX_REPEAT];
+  int i;
+
+  if (k < inst->min_k || k - inst->min_k >= inst->n_quants)
+    assert(0);
+
+  for (i = 0; i < inst->repeat; i++)
+    estimates[i] = inst->quants[(k - inst->min_k) * inst->repeat + i].est;
+
+  return RGR_FindMedian(estimates, inst->repeat);
+}
--- a/quantiles.h
+++ b/quantiles.h
@@ -0,0 +1,41 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2022
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ **********************************************************************
+
+  =======================================================================
+
+  Header file for estimation of quantiles.
+
+  */
+
+#ifndef GOT_QUANTILES_H
+#define GOT_QUANTILES_H
+
+typedef struct QNT_Instance_Record *QNT_Instance;
+
+extern QNT_Instance QNT_CreateInstance(int min_k, int max_k, int q, int repeat, double min_step);
+extern void QNT_DestroyInstance(QNT_Instance inst);
+
+extern void QNT_Reset(QNT_Instance inst);
+extern void QNT_Accumulate(QNT_Instance inst, double value);
+extern int QNT_GetMinK(QNT_Instance inst);
+extern double QNT_GetQuantile(QNT_Instance inst, int k);
+
+#endif
--- a/refclock.c
+++ b/refclock.c
--- a/refclock.h
+++ b/refclock.h
@@ -37,17 +37,22 @@ typedef struct {
  int driver_poll;
  int poll;
  int filter_length;
+  int local;
+  int pps_forced;
  int pps_rate;
  int min_samples;
  int max_samples;
  int sel_options;
  int max_lock_age;
+  int stratum;
+  int tai;
  uint32_t ref_id;
  uint32_t lock_ref_id;
  double offset;
  double delay;
  double precision;
  double max_dispersion;
+  double pulse_width;
 } RefclockParameters;

 typedef struct RCL_Instance_Record *RCL_Instance;
@@ -68,8 +73,14 @@ extern void RCL_ReportSource(RPT_SourceReport *report, struct timespec *now);
 extern void RCL_SetDriverData(RCL_Instance instance, void *data);
 extern void *RCL_GetDriverData(RCL_Instance instance);
 extern char *RCL_GetDriverParameter(RCL_Instance instance);
+extern void RCL_CheckDriverOptions(RCL_Instance instance, const char **options);
 extern char *RCL_GetDriverOption(RCL_Instance instance, char *name);
-extern int RCL_AddSample(RCL_Instance instance, struct timespec *sample_time, double offset, int leap);
+extern int RCL_AddSample(RCL_Instance instance, struct timespec *sample_time,
+                         struct timespec *ref_time, int leap);
 extern int RCL_AddPulse(RCL_Instance instance, struct timespec *pulse_time, double second);
+extern int RCL_AddCookedPulse(RCL_Instance instance, struct timespec *cooked_time,
+                              double second, double dispersion, double raw_correction);
+extern double RCL_GetPrecision(RCL_Instance instance);
+extern int RCL_GetDriverPoll(RCL_Instance instance);

 #endif
--- a/refclock_phc.c
+++ b/refclock_phc.c
@@ -2,7 +2,7 @@
  chronyd/chronyc - Programs for keeping computer clocks accurate.

 **********************************************************************
- * Copyright (C) Miroslav Lichvar  2013
+ * Copyright (C) Miroslav Lichvar  2013, 2017
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
@@ -33,144 +33,142 @@

 #include "sysincl.h"

-#include <linux/ptp_clock.h>
-
 #include "refclock.h"
+#include "hwclock.h"
+#include "local.h"
 #include "logging.h"
+#include "memory.h"
 #include "util.h"
+#include "sched.h"
+#include "sys_linux.h"

-/* From linux/include/linux/posix-timers.h */
-#define CPUCLOCK_MAX            3
-#define CLOCKFD                 CPUCLOCK_MAX
-#define CLOCKFD_MASK            (CPUCLOCK_PERTHREAD_MASK|CPUCLOCK_CLOCK_MASK)
-
-#define FD_TO_CLOCKID(fd)       ((~(clockid_t) (fd) << 3) | CLOCKFD)
-
-#define NUM_READINGS 10
-
-static int no_sys_offset_ioctl = 0;
-
-struct phc_reading {
-  struct timespec sys_ts1;
-  struct timespec phc_ts;;
-  struct timespec sys_ts2;
+struct phc_instance {
+  int fd;
+  int mode;
+  int nocrossts;
+  int extpps;
+  int pin;
+  int channel;
+  HCL_Instance clock;
 };

-static int read_phc_ioctl(struct phc_reading *readings, int phc_fd, int n)
-{
-#if defined(PTP_SYS_OFFSET) && NUM_READINGS <= PTP_MAX_SAMPLES
-  struct ptp_sys_offset sys_off;
-  int i;
-
-  /* Silence valgrind */
-  memset(&sys_off, 0, sizeof (sys_off));
-
-  sys_off.n_samples = n;
-  if (ioctl(phc_fd, PTP_SYS_OFFSET, &sys_off)) {
-    LOG(LOGS_ERR, LOGF_Refclock, "ioctl(PTP_SYS_OFFSET) failed : %s", strerror(errno));
-    return 0;
-  }
-
-  for (i = 0; i < n; i++) {
-    readings[i].sys_ts1.tv_sec = sys_off.ts[i * 2].sec;
-    readings[i].sys_ts1.tv_nsec = sys_off.ts[i * 2].nsec;
-    readings[i].phc_ts.tv_sec = sys_off.ts[i * 2 + 1].sec;
-    readings[i].phc_ts.tv_nsec = sys_off.ts[i * 2 + 1].nsec;
-    readings[i].sys_ts2.tv_sec = sys_off.ts[i * 2 + 2].sec;
-    readings[i].sys_ts2.tv_nsec = sys_off.ts[i * 2 + 2].nsec;
-  }
-
-  return 1;
-#else
-  /* Not available */
-  return 0;
-#endif
-}
-
-static int read_phc_user(struct phc_reading *readings, int phc_fd, int n)
-{
-  clockid_t phc_id;
-  int i;
-
-  phc_id = FD_TO_CLOCKID(phc_fd);
-
-  for (i = 0; i < n; i++) {
-    if (clock_gettime(CLOCK_REALTIME, &readings[i].sys_ts1) ||
-        clock_gettime(phc_id, &readings[i].phc_ts) ||
-        clock_gettime(CLOCK_REALTIME, &readings[i].sys_ts2)) {
-      LOG(LOGS_ERR, LOGF_Refclock, "clock_gettime() failed : %s", strerror(errno));
-      return 0;
-    }
-  }
-
-  return 1;
-}
+static void read_ext_pulse(int sockfd, int event, void *anything);

 static int phc_initialise(RCL_Instance instance)
 {
-  struct ptp_clock_caps caps;
-  int phc_fd;
-  char *path;
+  const char *options[] = {"nocrossts", "extpps", "pin", "channel", "clear", NULL};
+  struct phc_instance *phc;
+  int phc_fd, rising_edge;
+  char *path, *s;
+
+  RCL_CheckDriverOptions(instance, options);

  path = RCL_GetDriverParameter(instance);
 
-  phc_fd = open(path, O_RDONLY);
-  if (phc_fd < 0) {
-    LOG_FATAL(LOGF_Refclock, "open() failed on %s", path);
-    return 0;
+  phc_fd = SYS_Linux_OpenPHC(path, 0);
+  if (phc_fd < 0)
+    LOG_FATAL("Could not open PHC");
+
+  phc = MallocNew(struct phc_instance);
+  phc->fd = phc_fd;
+  phc->mode = 0;
+  phc->nocrossts = RCL_GetDriverOption(instance, "nocrossts") ? 1 : 0;
+  phc->extpps = RCL_GetDriverOption(instance, "extpps") ? 1 : 0;
+
+  phc->clock = HCL_CreateInstance(0, 16, UTI_Log2ToDouble(RCL_GetDriverPoll(instance)),
+                                  RCL_GetPrecision(instance));
+
+  if (phc->extpps) {
+    s = RCL_GetDriverOption(instance, "pin");
+    phc->pin = s ? atoi(s) : 0;
+    s = RCL_GetDriverOption(instance, "channel");
+    phc->channel = s ? atoi(s) : 0;
+    rising_edge = RCL_GetDriverOption(instance, "clear") ? 0 : 1;
+
+    if (!SYS_Linux_SetPHCExtTimestamping(phc->fd, phc->pin, phc->channel,
+                                         rising_edge, !rising_edge, 1))
+      LOG_FATAL("Could not enable external PHC timestamping");
+
+    SCH_AddFileHandler(phc->fd, SCH_FILE_INPUT, read_ext_pulse, instance);
+  } else {
+    phc->pin = phc->channel = 0;
  }

-  /* Make sure it is a PHC */
-  if (ioctl(phc_fd, PTP_CLOCK_GETCAPS, &caps)) {
-    LOG_FATAL(LOGF_Refclock, "ioctl(PTP_CLOCK_GETCAPS) failed : %s", strerror(errno));
-    return 0;
-  }
-
-  UTI_FdSetCloexec(phc_fd);
-
-  RCL_SetDriverData(instance, (void *)(long)phc_fd);
+  RCL_SetDriverData(instance, phc);
  return 1;
 }

 static void phc_finalise(RCL_Instance instance)
 {
-  close((long)RCL_GetDriverData(instance));
+  struct phc_instance *phc;
+
+  phc = (struct phc_instance *)RCL_GetDriverData(instance);
+
+  if (phc->extpps) {
+    SCH_RemoveFileHandler(phc->fd);
+    SYS_Linux_SetPHCExtTimestamping(phc->fd, phc->pin, phc->channel, 0, 0, 0);
+  }
+
+  HCL_DestroyInstance(phc->clock);
+  close(phc->fd);
+  Free(phc);
 }

+static void read_ext_pulse(int fd, int event, void *anything)
+{
+  RCL_Instance instance;
+  struct phc_instance *phc;
+  struct timespec phc_ts, local_ts;
+  double local_err;
+  int channel;
+
+  instance = anything;
+  phc = RCL_GetDriverData(instance);
+
+  if (!SYS_Linux_ReadPHCExtTimestamp(phc->fd, &phc_ts, &channel))
+    return;
+
+  if (channel != phc->channel) {
+    DEBUG_LOG("Unexpected extts channel %d\n", channel);
+    return;
+  }
+
+  if (!HCL_CookTime(phc->clock, &phc_ts, &local_ts, &local_err))
+    return;
+
+  RCL_AddCookedPulse(instance, &local_ts, 1.0e-9 * local_ts.tv_nsec, local_err,
+                     UTI_DiffTimespecsToDouble(&phc_ts, &local_ts));
+}
+
+#define PHC_READINGS 25
+
 static int phc_poll(RCL_Instance instance)
 {
-  struct phc_reading readings[NUM_READINGS];
-  double offset = 0.0, delay, best_delay = 0.0;
-  int i, phc_fd, best;
- 
-  phc_fd = (long)RCL_GetDriverData(instance);
+  struct timespec phc_ts, sys_ts, local_ts, readings[PHC_READINGS][3];
+  struct phc_instance *phc;
+  double phc_err, local_err;
+  int n_readings;

-  if (!no_sys_offset_ioctl) {
-    if (!read_phc_ioctl(readings, phc_fd, NUM_READINGS)) {
-      no_sys_offset_ioctl = 1;
-      return 0;
-    }
-  } else {
-    if (!read_phc_user(readings, phc_fd, NUM_READINGS))
-      return 0;
-  }
+  phc = (struct phc_instance *)RCL_GetDriverData(instance);

-  /* Find the fastest reading */
-  for (i = 0; i < NUM_READINGS; i++) {
-    delay = UTI_DiffTimespecsToDouble(&readings[i].sys_ts2, &readings[i].sys_ts1);
+  n_readings = SYS_Linux_GetPHCReadings(phc->fd, phc->nocrossts, &phc->mode,
+                                        PHC_READINGS, readings);
+  if (n_readings < 1)
+    return 0;

-    if (!i || best_delay > delay) {
-      best = i;
-      best_delay = delay;
-    }
-  }
+  if (!HCL_ProcessReadings(phc->clock, n_readings, readings, &phc_ts, &sys_ts, &phc_err))
+    return 0;

-  offset = UTI_DiffTimespecsToDouble(&readings[best].phc_ts, &readings[best].sys_ts2) +
-           best_delay / 2.0;
+  LCL_CookTime(&sys_ts, &local_ts, &local_err);
+  HCL_AccumulateSample(phc->clock, &phc_ts, &local_ts, phc_err + local_err);

-  DEBUG_LOG(LOGF_Refclock, "PHC offset: %+.9f delay: %.9f", offset, best_delay);
+  if (phc->extpps)
+    return 0;

-  return RCL_AddSample(instance, &readings[best].sys_ts2, offset, LEAP_Normal);
+  DEBUG_LOG("PHC offset: %+.9f err: %.9f",
+            UTI_DiffTimespecsToDouble(&phc_ts, &sys_ts), phc_err);
+
+  return RCL_AddSample(instance, &sys_ts, &phc_ts, LEAP_Normal);
 }

 RefclockDriver RCL_PHC_driver = {
--- a/refclock_pps.c
+++ b/refclock_pps.c
@@ -48,59 +48,49 @@ struct pps_instance {
 };

 static int pps_initialise(RCL_Instance instance) {
+  const char *options[] = {"clear", NULL};
  pps_handle_t handle;
  pps_params_t params;
  struct pps_instance *pps;
  int fd, edge_clear, mode;
  char *path;

+  RCL_CheckDriverOptions(instance, options);
+
  path = RCL_GetDriverParameter(instance);
  edge_clear = RCL_GetDriverOption(instance, "clear") ? 1 : 0;

  fd = open(path, O_RDWR);
-  if (fd < 0) {
-    LOG_FATAL(LOGF_Refclock, "open() failed on %s", path);
-    return 0;
-  }
+  if (fd < 0)
+    LOG_FATAL("Could not open %s : %s", path, strerror(errno));

  UTI_FdSetCloexec(fd);

-  if (time_pps_create(fd, &handle) < 0) {
-    LOG_FATAL(LOGF_Refclock, "time_pps_create() failed on %s", path);
-    return 0;
-  }
+  if (time_pps_create(fd, &handle) < 0)
+    LOG_FATAL("time_pps_create() failed on %s : %s", path, strerror(errno));

-  if (time_pps_getcap(handle, &mode) < 0) {
-    LOG_FATAL(LOGF_Refclock, "time_pps_getcap() failed on %s", path);
-    return 0;
-  }
+  if (time_pps_getcap(handle, &mode) < 0)
+    LOG_FATAL("time_pps_getcap() failed on %s : %s", path, strerror(errno));

-  if (time_pps_getparams(handle, &params) < 0) {
-    LOG_FATAL(LOGF_Refclock, "time_pps_getparams() failed on %s", path);
-    return 0;
-  }
+  if (time_pps_getparams(handle, &params) < 0)
+    LOG_FATAL("time_pps_getparams() failed on %s : %s", path, strerror(errno));

  if (!edge_clear) {
-    if (!(mode & PPS_CAPTUREASSERT)) {
-      LOG_FATAL(LOGF_Refclock, "CAPTUREASSERT not supported on %s", path);
-      return 0;
-    }
+    if (!(mode & PPS_CAPTUREASSERT))
+      LOG_FATAL("CAPTUREASSERT not supported on %s", path);
+
    params.mode |= PPS_CAPTUREASSERT;
    params.mode &= ~PPS_CAPTURECLEAR;
  } else {
-    if (!(mode & PPS_CAPTURECLEAR)) {
-      LOG_FATAL(LOGF_Refclock, "CAPTURECLEAR not supported on %s", path);
-      return 0;
-    }
+    if (!(mode & PPS_CAPTURECLEAR))
+      LOG_FATAL("CAPTURECLEAR not supported on %s", path);
+
    params.mode |= PPS_CAPTURECLEAR;
    params.mode &= ~PPS_CAPTUREASSERT;
  }

-  if (time_pps_setparams(handle, &params) < 0) {
-    LOG_FATAL(LOGF_Refclock, "time_pps_setparams() failed on %s", path);
-    return 0;
-  }
-
+  if (time_pps_setparams(handle, &params) < 0)
+    LOG_FATAL("time_pps_setparams() failed on %s : %s", path, strerror(errno));

  pps = MallocNew(struct pps_instance);
  pps->handle = handle;
@@ -133,7 +123,7 @@ static int pps_poll(RCL_Instance instance)
  ts.tv_nsec = 0;

  if (time_pps_fetch(pps->handle, PPS_TSFMT_TSPEC, &pps_info, &ts) < 0) {
-    LOG(LOGS_ERR, LOGF_Refclock, "time_pps_fetch() failed : %s", strerror(errno));
+    LOG(LOGS_ERR, "time_pps_fetch() failed : %s", strerror(errno));
    return 0;
  }

@@ -146,8 +136,8 @@ static int pps_poll(RCL_Instance instance)
  }

  if (seq == pps->last_seq || UTI_IsZeroTimespec(&ts)) {
-    DEBUG_LOG(LOGF_Refclock, "PPS sample ignored seq=%lu ts=%s",
-              seq, UTI_TimespecToString(&ts));
+    DEBUG_LOG("PPS sample ignored seq=%lu ts=%s",
+              (unsigned long)seq, UTI_TimespecToString(&ts));
    return 0;
  }

--- a/refclock_shm.c
+++ b/refclock_shm.c
@@ -59,23 +59,26 @@ struct shmTime {
 };

 static int shm_initialise(RCL_Instance instance) {
+  const char *options[] = {"perm", NULL};
  int id, param, perm;
  char *s;
  struct shmTime *shm;

+  RCL_CheckDriverOptions(instance, options);
+
  param = atoi(RCL_GetDriverParameter(instance));
  s = RCL_GetDriverOption(instance, "perm");
  perm = s ? strtol(s, NULL, 8) & 0777 : 0600;

  id = shmget(SHMKEY + param, sizeof (struct shmTime), IPC_CREAT | perm);
  if (id == -1) {
-    LOG_FATAL(LOGF_Refclock, "shmget() failed");
+    LOG_FATAL("shmget() failed : %s", strerror(errno));
    return 0;
  }
   
  shm = (struct shmTime *)shmat(id, 0, 0);
  if ((long)shm == -1) {
-    LOG_FATAL(LOGF_Refclock, "shmat() failed");
+    LOG_FATAL("shmat() failed : %s", strerror(errno));
    return 0;
  }

@@ -92,7 +95,6 @@ static int shm_poll(RCL_Instance instance)
 {
  struct timespec receive_ts, clock_ts;
  struct shmTime t, *shm;
-  double offset;

  shm = (struct shmTime *)RCL_GetDriverData(instance);

@@ -100,7 +102,7 @@ static int shm_poll(RCL_Instance instance)
  
  if ((t.mode == 1 && t.count != shm->count) ||
    !(t.mode == 0 || t.mode == 1) || !t.valid) {
-    DEBUG_LOG(LOGF_Refclock, "SHM sample ignored mode=%d count=%d valid=%d",
+    DEBUG_LOG("SHM sample ignored mode=%d count=%d valid=%d",
        t.mode, t.count, t.valid);
    return 0;
  }
@@ -121,9 +123,8 @@ static int shm_poll(RCL_Instance instance)

  UTI_NormaliseTimespec(&clock_ts);
  UTI_NormaliseTimespec(&receive_ts);
-  offset = UTI_DiffTimespecsToDouble(&clock_ts, &receive_ts);

-  return RCL_AddSample(instance, &receive_ts, offset, t.leap);
+  return RCL_AddSample(instance, &receive_ts, &clock_ts, t.leap);
 }

 RefclockDriver RCL_SHM_driver = {
--- a/refclock_sock.c
+++ b/refclock_sock.c
@@ -33,6 +33,7 @@
 #include "logging.h"
 #include "util.h"
 #include "sched.h"
+#include "socket.h"

 #define SOCK_MAGIC 0x534f434b

@@ -59,8 +60,8 @@ struct sock_sample {

 static void read_sample(int sockfd, int event, void *anything)
 {
+  struct timespec sys_ts, ref_ts;
  struct sock_sample sample;
-  struct timespec ts;
  RCL_Instance instance;
  int s;

@@ -69,60 +70,49 @@ static void read_sample(int sockfd, int event, void *anything)
  s = recv(sockfd, &sample, sizeof (sample), 0);

  if (s < 0) {
-    LOG(LOGS_ERR, LOGF_Refclock, "Could not read SOCK sample : %s",
-        strerror(errno));
+    DEBUG_LOG("Could not read SOCK sample : %s", strerror(errno));
    return;
  }

  if (s != sizeof (sample)) {
-    LOG(LOGS_WARN, LOGF_Refclock, "Unexpected length of SOCK sample : %d != %ld",
-        s, (long)sizeof (sample));
+    DEBUG_LOG("Unexpected length of SOCK sample : %d != %ld",
+              s, (long)sizeof (sample));
    return;
  }

  if (sample.magic != SOCK_MAGIC) {
-    LOG(LOGS_WARN, LOGF_Refclock, "Unexpected magic number in SOCK sample : %x != %x",
-        sample.magic, SOCK_MAGIC);
+    DEBUG_LOG("Unexpected magic number in SOCK sample : %x != %x",
+              (unsigned int)sample.magic, (unsigned int)SOCK_MAGIC);
    return;
  }

-  UTI_TimevalToTimespec(&sample.tv, &ts);
-  UTI_NormaliseTimespec(&ts);
+  UTI_TimevalToTimespec(&sample.tv, &sys_ts);
+  UTI_NormaliseTimespec(&sys_ts);
+
+  if (!UTI_IsTimeOffsetSane(&sys_ts, sample.offset))
+    return;
+
+  UTI_AddDoubleToTimespec(&sys_ts, sample.offset, &ref_ts);

  if (sample.pulse) {
-    RCL_AddPulse(instance, &ts, sample.offset);
+    RCL_AddPulse(instance, &sys_ts, sample.offset);
  } else {
-    RCL_AddSample(instance, &ts, sample.offset, sample.leap);
+    RCL_AddSample(instance, &sys_ts, &ref_ts, sample.leap);
  }
 }

 static int sock_initialise(RCL_Instance instance)
 {
-  struct sockaddr_un s;
  int sockfd;
  char *path;

+  RCL_CheckDriverOptions(instance, NULL);
+
  path = RCL_GetDriverParameter(instance);
 
-  s.sun_family = AF_UNIX;
-  if (snprintf(s.sun_path, sizeof (s.sun_path), "%s", path) >= sizeof (s.sun_path)) {
-    LOG_FATAL(LOGF_Refclock, "path %s is too long", path);
-    return 0;
-  }
-
-  sockfd = socket(AF_UNIX, SOCK_DGRAM, 0);
-  if (sockfd < 0) {
-    LOG_FATAL(LOGF_Refclock, "socket() failed");
-    return 0;
-  }
-
-  UTI_FdSetCloexec(sockfd);
-
-  unlink(path);
-  if (bind(sockfd, (struct sockaddr *)&s, sizeof (s)) < 0) {
-    LOG_FATAL(LOGF_Refclock, "bind() failed");
-    return 0;
-  }
+  sockfd = SCK_OpenUnixDatagramSocket(NULL, path, 0);
+  if (sockfd < 0)
+    LOG_FATAL("Could not open socket %s", path);

  RCL_SetDriverData(instance, (void *)(long)sockfd);
  SCH_AddFileHandler(sockfd, SCH_FILE_INPUT, read_sample, instance);
@@ -135,7 +125,8 @@ static void sock_finalise(RCL_Instance instance)

  sockfd = (long)RCL_GetDriverData(instance);
  SCH_RemoveFileHandler(sockfd);
-  close(sockfd);
+  SCK_RemoveSocket(sockfd);
+  SCK_CloseSocket(sockfd);
 }

 RefclockDriver RCL_SOCK_driver = {
--- a/Show More
+++ b/Show More