update copyright years

doc: improve description of server directive
doc: improve description of system time in tracking report
2025-12-04 06:15:07 -05:00 · 2022-08-29 15:04:33 +02:00 · 2022-08-29 15:03:59 +02:00 · 2022-08-29 12:39:22 +02:00 · 2022-08-18 11:59:40 +02:00 · 2022-08-17 16:14:38 +02:00
183 changed files with 7591 additions and 2220 deletions
--- a/Makefile.in
+++ b/Makefile.in
@@ -35,7 +35,7 @@ LDFLAGS = @LDFLAGS@

 EXTRA_OBJS = @EXTRA_OBJS@

-OBJS = array.o cmdparse.o conf.o local.o logging.o main.o memory.o \
+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)

--- a/69
+++ b/69
@@ -1,3 +1,72 @@
+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
 ==================

--- a/9
+++ b/9
@@ -28,7 +28,7 @@ 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
+illumos.  Closely related systems may work too.  Any other system will
 likely require a porting exercise.

 How do I set it up?
@@ -91,7 +91,7 @@ Acknowledgements
 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.
+others has been used to check the details of the protocol.

 The following people have provided patches and other major contributions
 to chrony:
@@ -108,6 +108,7 @@ Erik Bryer <ebryer@spots.ab.ca>
 Jonathan Cameron <jic23@cam.ac.uk>
 Bryan Christianson <bryan@whatroute.net>
 Juliusz Chroboczek <jch@pps.jussieu.fr>
+Kamil Dudka <kdudka@redhat.com>
 Christian Ehrhardt <christian.ehrhardt@canonical.com>
 Paul Elliott <pelliott@io.com>
 Robert Fairley <rfairley@redhat.com>
@@ -124,6 +125,7 @@ Jachym Holecek <jakym@volny.cz>
 Håkan Johansson <f96hajo@chalmers.se>
 Jim Knoble <jmknoble@pobox.com>
 Antti Jrvinen <costello@iki.fi>
+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>
@@ -137,6 +139,8 @@ Denny Page <dennypage@me.com>
 Chris Perl <cperl@janestreet.com>
 Gautier PHILIPPON <gautier.philippon@ensimag.grenoble-inp.fr>
 Andreas Piesk <apiesk@virbus.de>
+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>
@@ -148,6 +152,7 @@ Bernhard M. Wiedemann <bwiedemann@suse.de>
 Joachim Wiedorn <ad_debian@joonet.de>
 Ralf Wildenhues <Ralf.Wildenhues@gmx.de>
 Ulrich Windl <ulrich.windl@rz.uni-regensburg.de>
+Michael Witten <mfwitten@gmail.com>
 Doug Woodward <dougw@whistler.com>
 Thomas Zajic <zlatko@zlatko.fdns.net>

--- a/candm.h
+++ b/candm.h
@@ -108,7 +108,8 @@
 #define REQ_CLIENT_ACCESSES_BY_INDEX3 68
 #define REQ_SELECT_DATA 69
 #define REQ_RELOAD_SOURCES 70
-#define N_REQUEST_TYPES 71
+#define REQ_DOFFSET2 71
+#define N_REQUEST_TYPES 72

 /* Structure used to exchange timespecs independent of time_t size */
 typedef struct {
@@ -268,6 +269,8 @@ typedef struct {
 #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 {
  uint32_t type;
@@ -292,7 +295,9 @@ typedef struct {
  Float offset;
  uint32_t flags;
  int32_t filter_length;
-  uint32_t reserved[3];
+  uint32_t cert_set;
+  Float max_delay_quant;
+  uint32_t reserved[1];
  int32_t EOR;
 } REQ_NTP_Source;

@@ -307,8 +312,7 @@ typedef struct {
 } REQ_Dfreq;

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

@@ -403,7 +407,7 @@ typedef struct {
   domain socket.

   Version 6 (no authentication) : changed format of client accesses by index
-   (using new request/reply types) and manual timestamp, added new fields and
+   (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
@@ -514,7 +518,8 @@ typedef struct {
 #define RPY_CLIENT_ACCESSES_BY_INDEX3 21
 #define RPY_SERVER_STATS2 22
 #define RPY_SELECT_DATA 23
-#define N_REPLY_TYPES 24
+#define RPY_SERVER_STATS3 24
+#define N_REPLY_TYPES 25

 /* Status codes */
 #define STT_SUCCESS 0
@@ -527,8 +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
@@ -658,6 +662,9 @@ typedef struct {
  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;

@@ -727,7 +734,8 @@ typedef struct {
  uint32_t total_tx_count;
  uint32_t total_rx_count;
  uint32_t total_valid_count;
-  uint32_t reserved[4];
+  uint32_t total_good_count;
+  uint32_t reserved[3];
  int32_t EOR;
 } RPY_NTPData;

@@ -764,7 +772,8 @@ typedef struct {
  IPAddr ip_addr;
  uint8_t state_char;
  uint8_t authentication;
-  uint8_t pad[2];
+  uint8_t leap;
+  uint8_t pad;
  uint16_t conf_options;
  uint16_t eff_options;
  uint32_t last_sample_ago;
--- a/client.c
+++ b/client.c
@@ -4,7 +4,7 @@
 **********************************************************************
 * Copyright (C) Richard P. Curnow  1997-2003
 * Copyright (C) Lonnie Abelbeck  2016, 2018
- * Copyright (C) Miroslav Lichvar  2009-2020
+ * Copyright (C) Miroslav Lichvar  2009-2021
 * 
 * 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
@@ -61,7 +61,7 @@ static ARR_Instance server_addresses;

 static int sock_fd = -1;

-static int quit = 0;
+static volatile int quit = 0;

 static int on_terminal = 0;

@@ -283,6 +283,9 @@ open_io(void)
    close_io();
  }

+  /* Start from the first address if called again */
+  address_index = 0;
+
  return 0;
 }

@@ -779,182 +782,25 @@ process_cmd_manual(CMD_Request *msg, const char *line)
 /* ================================================== */

 static int
-parse_allow_deny(CMD_Request *msg, char *line)
+process_cmd_allowdeny(CMD_Request *msg, char *line, int cmd, int allcmd)
 {
-  unsigned long a, b, c, d;
-  int n, specified_subnet_bits;
+  int all, subnet_bits;
  IPAddr ip;
-  char *p;
  
-  p = line;
-  if (!*p) {
-    /* blank line - applies to all addresses */
-    ip.family = IPADDR_UNSPEC;
-    UTI_IPHostToNetwork(&ip, &msg->data.allow_deny.ip);
-    msg->data.allow_deny.subnet_bits = htonl(0);
-  } else {
-    char *slashpos;
-    slashpos = strchr(p, '/');
-    if (slashpos) *slashpos = 0;
-    
-    n = 0;
-    if (!UTI_StringToIP(p, &ip) &&
-        (n = sscanf(p, "%lu.%lu.%lu.%lu", &a, &b, &c, &d)) <= 0) {
-
-      /* Try to parse as the name of a machine */
-      if (slashpos || DNS_Name2IPAddress(p, &ip, 1) != DNS_Success) {
+  if (!CPS_ParseAllowDeny(line, &all, &ip, &subnet_bits)) {
    LOG(LOGS_ERR, "Could not read address");
    return 0;
-      } else {
+  }
+
+  msg->command = htons(all ? allcmd : cmd);
  UTI_IPHostToNetwork(&ip, &msg->data.allow_deny.ip);
-        if (ip.family == IPADDR_INET6)
-          msg->data.allow_deny.subnet_bits = htonl(128);
-        else
-          msg->data.allow_deny.subnet_bits = htonl(32);
-      }        
-    } else {
+  msg->data.allow_deny.subnet_bits = htonl(subnet_bits);

-      if (n == 0) {
-        if (ip.family == IPADDR_INET6)
-          msg->data.allow_deny.subnet_bits = htonl(128);
-        else
-          msg->data.allow_deny.subnet_bits = htonl(32);
-      } else {
-        ip.family = IPADDR_INET4;
-
-        a &= 0xff;
-        b &= 0xff;
-        c &= 0xff;
-        d &= 0xff;
-        
-        switch (n) {
-          case 1:
-            ip.addr.in4 = htonl((a<<24));
-            msg->data.allow_deny.subnet_bits = htonl(8);
-            break;
-          case 2:
-            ip.addr.in4 = htonl((a<<24) | (b<<16));
-            msg->data.allow_deny.subnet_bits = htonl(16);
-            break;
-          case 3:
-            ip.addr.in4 = htonl((a<<24) | (b<<16) | (c<<8));
-            msg->data.allow_deny.subnet_bits = htonl(24);
-            break;
-          case 4:
-            ip.addr.in4 = htonl((a<<24) | (b<<16) | (c<<8) | d);
-            msg->data.allow_deny.subnet_bits = htonl(32);
-            break;
-          default:
-            assert(0);
-        }
-      }
-
-      UTI_IPHostToNetwork(&ip, &msg->data.allow_deny.ip);
-
-      if (slashpos) {
-        n = sscanf(slashpos+1, "%d", &specified_subnet_bits);
-        if (n == 1) {
-          msg->data.allow_deny.subnet_bits = htonl(specified_subnet_bits);
-        } else {
-          LOG(LOGS_WARN, "Warning: badly formatted subnet size, using %d",
-              (int)ntohl(msg->data.allow_deny.subnet_bits));
-        }
-      } 
-    }
-  }
  return 1;
 }

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

-static int
-process_cmd_allow(CMD_Request *msg, char *line)
-{
-  int status;
-  msg->command = htons(REQ_ALLOW);
-  status = parse_allow_deny(msg, line);
-  return status;
-}
-
-/* ================================================== */
-
-static int
-process_cmd_allowall(CMD_Request *msg, char *line)
-{
-  int status;
-  msg->command = htons(REQ_ALLOWALL);
-  status = parse_allow_deny(msg, line);
-  return status;
-}
-
-/* ================================================== */
-
-static int
-process_cmd_deny(CMD_Request *msg, char *line)
-{
-  int status;
-  msg->command = htons(REQ_DENY);
-  status = parse_allow_deny(msg, line);
-  return status;
-}
-
-/* ================================================== */
-
-static int
-process_cmd_denyall(CMD_Request *msg, char *line)
-{
-  int status;
-  msg->command = htons(REQ_DENYALL);
-  status = parse_allow_deny(msg, line);
-  return status;
-}
-
-/* ================================================== */
-
-static int
-process_cmd_cmdallow(CMD_Request *msg, char *line)
-{
-  int status;
-  msg->command = htons(REQ_CMDALLOW);
-  status = parse_allow_deny(msg, line);
-  return status;
-}
-
-/* ================================================== */
-
-static int
-process_cmd_cmdallowall(CMD_Request *msg, char *line)
-{
-  int status;
-  msg->command = htons(REQ_CMDALLOWALL);
-  status = parse_allow_deny(msg, line);
-  return status;
-}
-
-/* ================================================== */
-
-static int
-process_cmd_cmddeny(CMD_Request *msg, char *line)
-{
-  int status;
-  msg->command = htons(REQ_CMDDENY);
-  status = parse_allow_deny(msg, line);
-  return status;
-}
-
-/* ================================================== */
-
-static int
-process_cmd_cmddenyall(CMD_Request *msg, char *line)
-{
-  int status;
-  msg->command = htons(REQ_CMDDENYALL);
-  status = parse_allow_deny(msg, line);
-  return status;
-}
-
-/* ================================================== */
-
 static int
 process_cmd_accheck(CMD_Request *msg, char *line)
 {
@@ -987,54 +833,38 @@ process_cmd_cmdaccheck(CMD_Request *msg, char *line)

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

-static void
+static int
 process_cmd_dfreq(CMD_Request *msg, char *line)
 {
  double dfreq;
+
  msg->command = htons(REQ_DFREQ);
-  if (sscanf(line, "%lf", &dfreq) == 1) {
+
+  if (sscanf(line, "%lf", &dfreq) != 1) {
+    LOG(LOGS_ERR, "Invalid value");
+    return 0;
+  }
+
  msg->data.dfreq.dfreq = UTI_FloatHostToNetwork(dfreq);
-  } else {
-    msg->data.dfreq.dfreq = UTI_FloatHostToNetwork(0.0);
-  }
+  return 1;
 }

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

-static void
-cvt_to_sec_usec(double x, long *sec, long *usec) {
-  long s, us;
-  s = (long) x;
-  us = (long)(0.5 + 1.0e6 * (x - (double) s));
-  while (us >= 1000000) {
-    us -= 1000000;
-    s += 1;
-  }
-  while (us < 0) {
-    us += 1000000;
-    s -= 1;
-  }
-  
-  *sec = s;
-  *usec = us;
-}
-
-/* ================================================== */
-
-static void
+static int
 process_cmd_doffset(CMD_Request *msg, char *line)
 {
  double doffset;
-  long sec, usec;
-  msg->command = htons(REQ_DOFFSET);
-  if (sscanf(line, "%lf", &doffset) == 1) {
-    cvt_to_sec_usec(doffset, &sec, &usec);
-    msg->data.doffset.sec = htonl(sec);
-    msg->data.doffset.usec = htonl(usec);
-  } else {
-    msg->data.doffset.sec = htonl(0);
-    msg->data.doffset.usec = htonl(0);
+
+  msg->command = htons(REQ_DOFFSET2);
+
+  if (sscanf(line, "%lf", &doffset) != 1) {
+    LOG(LOGS_ERR, "Invalid value");
+    return 0;
  }
+
+  msg->data.doffset.doffset = UTI_FloatHostToNetwork(doffset);
+  return 1;
 }

 /* ================================================== */
@@ -1114,11 +944,16 @@ process_cmd_add_source(CMD_Request *msg, char *line)
          (data.params.interleaved ? REQ_ADDSRC_INTERLEAVED : 0) |
          (data.params.burst ? REQ_ADDSRC_BURST : 0) |
          (data.params.nts ? REQ_ADDSRC_NTS : 0) |
+          (data.params.copy ? REQ_ADDSRC_COPY : 0) |
+          (data.params.ext_fields & NTP_EF_FLAG_EXP1 ? REQ_ADDSRC_EF_EXP1 : 0) |
          (data.params.sel_options & SRC_SELECT_PREFER ? REQ_ADDSRC_PREFER : 0) |
          (data.params.sel_options & SRC_SELECT_NOSELECT ? REQ_ADDSRC_NOSELECT : 0) |
          (data.params.sel_options & SRC_SELECT_TRUST ? REQ_ADDSRC_TRUST : 0) |
          (data.params.sel_options & SRC_SELECT_REQUIRE ? REQ_ADDSRC_REQUIRE : 0));
      msg->data.ntp_source.filter_length = htonl(data.params.filter_length);
+      msg->data.ntp_source.cert_set = htonl(data.params.cert_set);
+      msg->data.ntp_source.max_delay_quant =
+        UTI_FloatHostToNetwork(data.params.max_delay_quant);
      memset(msg->data.ntp_source.reserved, 0, sizeof (msg->data.ntp_source.reserved));

      result = 1;
@@ -1882,19 +1717,19 @@ print_report(const char *format, ...)
        integer = va_arg(ap, int);
        switch (integer) {
          case LEAP_Normal:
-            string = "Normal";
+            string = width != 1 ? "Normal" : "N";
            break;
          case LEAP_InsertSecond:
-            string = "Insert second";
+            string = width != 1 ? "Insert second" : "+";
            break;
          case LEAP_DeleteSecond:
-            string = "Delete second";
+            string = width != 1 ? "Delete second" : "-";
            break;
          case LEAP_Unsynchronised:
-            string = "Not synchronised";
+            string = width != 1 ? "Not synchronised" : "?";
            break;
          default:
-            string = "Invalid";
+            string = width != 1 ? "Invalid" : "?";
            break;
        }
        printf("%s", string);
@@ -2049,7 +1884,7 @@ get_source_name(IPAddr *ip_addr, char *buf, int size)

  /* Make sure the name is printable */
  for (i = 0; i < size && buf[i] != '\0'; i++) {
-    if (!isgraph(buf[i]))
+    if (!isgraph((unsigned char)buf[i]))
      return 0;
  }

@@ -2105,7 +1940,7 @@ process_cmd_sourcename(char *line)
  IPAddr ip_addr;
  char name[256];

-  if (!UTI_StringToIP(line, &ip_addr)) {
+  if (!parse_source_address(line, &ip_addr)) {
    LOG(LOGS_ERR, "Could not read address");
    return 0;
  }
@@ -2511,7 +2346,8 @@ process_cmd_ntpdata(char *line)
                 "RX timestamping : %N\n"
                 "Total TX        : %U\n"
                 "Total RX        : %U\n"
-                 "Total valid RX  : %U\n",
+                 "Total valid RX  : %U\n"
+                 "Total good RX   : %U\n",
                 UTI_IPToString(&remote_addr), (unsigned long)UTI_IPToRefid(&remote_addr),
                 ntohs(reply.data.ntp_data.remote_port),
                 UTI_IPToString(&local_addr), (unsigned long)UTI_IPToRefid(&local_addr),
@@ -2539,6 +2375,7 @@ process_cmd_ntpdata(char *line)
                 (unsigned long)ntohl(reply.data.ntp_data.total_tx_count),
                 (unsigned long)ntohl(reply.data.ntp_data.total_rx_count),
                 (unsigned long)ntohl(reply.data.ntp_data.total_valid_count),
+                 (unsigned long)ntohl(reply.data.ntp_data.total_good_count),
                 REPORT_END);
  }

@@ -2566,19 +2403,19 @@ process_cmd_selectdata(char *line)
  n_sources = ntohl(reply.data.n_sources.n_sources);

  if (verbose) {
-    printf(    "  .-- State: N - noselect, M - missing samples, d/D - large distance,\n");
-    printf(    " /           ~ - jittery, w/W - waits for others, T - not trusted,\n");
-    printf(    "|            x - falseticker, P - not preferred, U - waits for update,\n");
-    printf(    "|            S - stale, O - orphan, + - combined, * - best.\n");
-    printf(    "|        Effective options ------.  (N - noselect, P - prefer\n");
-    printf(    "|       Configured options -.     \\  T - trust, R - require)\n");
+    printf(    "  . State: N - noselect, s - unsynchronised, M - missing samples,\n");
+    printf(    " /         d/D - large distance, ~ - jittery, w/W - waits for others,\n");
+    printf(    "|          S - stale, O - orphan, T - not trusted, P - not preferred,\n");
+    printf(    "|          U - waits for update,, x - falseticker, + - combined, * - best.\n");
+    printf(    "|   Effective options   ---------.  (N - noselect, P - prefer\n");
+    printf(    "|   Configured options  ----.     \\  T - trust, R - require)\n");
    printf(    "|   Auth. enabled (Y/N) -.   \\     \\     Offset interval --.\n");
    printf(    "|                        |    |     |                       |\n");
  }

-  print_header("S Name/IP Address        Auth COpts EOpts Last Score     Interval   ");
+  print_header("S Name/IP Address        Auth COpts EOpts Last Score     Interval  Leap");

-  /*           "S NNNNNNNNNNNNNNNNNNNNNNNNN A OOOO- OOOO- LLLL SSSSS LLLLLLL LLLLLLL" */
+  /*           "S NNNNNNNNNNNNNNNNNNNNNNNNN A OOOO- OOOO- LLLL SSSSS IIIIIII IIIIIII  L" */

  for (i = 0; i < n_sources; i++) {
    request.command = htons(REQ_SELECT_DATA);
@@ -2596,7 +2433,7 @@ process_cmd_selectdata(char *line)
    conf_options = ntohs(reply.data.select_data.conf_options);
    eff_options = ntohs(reply.data.select_data.eff_options);

-    print_report("%c %-25s %c %c%c%c%c%c %c%c%c%c%c %I %5.1f %+S %+S\n",
+    print_report("%c %-25s %c %c%c%c%c%c %c%c%c%c%c %I %5.1f %+S %+S  %1L\n",
                 reply.data.select_data.state_char,
                 name,
                 reply.data.select_data.authentication ? 'Y' : 'N',
@@ -2614,6 +2451,7 @@ process_cmd_selectdata(char *line)
                 UTI_FloatNetworkToHost(reply.data.select_data.score),
                 UTI_FloatNetworkToHost(reply.data.select_data.lo_limit),
                 UTI_FloatNetworkToHost(reply.data.select_data.hi_limit),
+                 reply.data.select_data.leap,
                 REPORT_END);
  }

@@ -2629,7 +2467,7 @@ process_cmd_serverstats(char *line)
  CMD_Reply reply;

  request.command = htons(REQ_SERVER_STATS);
-  if (!request_reply(&request, &reply, RPY_SERVER_STATS2, 0))
+  if (!request_reply(&request, &reply, RPY_SERVER_STATS3, 0))
    return 0;

  print_report("NTP packets received       : %U\n"
@@ -2639,7 +2477,10 @@ process_cmd_serverstats(char *line)
               "Client log records dropped : %U\n"
               "NTS-KE connections accepted: %U\n"
               "NTS-KE connections dropped : %U\n"
-               "Authenticated NTP packets  : %U\n",
+               "Authenticated NTP packets  : %U\n"
+               "Interleaved NTP packets    : %U\n"
+               "NTP timestamps held        : %U\n"
+               "NTP timestamp span         : %U\n",
               (unsigned long)ntohl(reply.data.server_stats.ntp_hits),
               (unsigned long)ntohl(reply.data.server_stats.ntp_drops),
               (unsigned long)ntohl(reply.data.server_stats.cmd_hits),
@@ -2648,6 +2489,9 @@ process_cmd_serverstats(char *line)
               (unsigned long)ntohl(reply.data.server_stats.nke_hits),
               (unsigned long)ntohl(reply.data.server_stats.nke_drops),
               (unsigned long)ntohl(reply.data.server_stats.ntp_auth_hits),
+               (unsigned long)ntohl(reply.data.server_stats.ntp_interleaved_hits),
+               (unsigned long)ntohl(reply.data.server_stats.ntp_timestamps),
+               (unsigned long)ntohl(reply.data.server_stats.ntp_span_seconds),
               REPORT_END);

  return 1;
@@ -3245,11 +3089,7 @@ process_line(char *line)
  } else if (!strcmp(command, "add")) {
    do_normal_submit = process_cmd_add_source(&tx_message, line);
  } else if (!strcmp(command, "allow")) {
-    if (!strncmp(line, "all", 3)) {
-      do_normal_submit = process_cmd_allowall(&tx_message, CPS_SplitWord(line));
-    } else {
-      do_normal_submit = process_cmd_allow(&tx_message, line);
-    }
+    do_normal_submit = process_cmd_allowdeny(&tx_message, line, REQ_ALLOW, REQ_ALLOWALL);
  } else if (!strcmp(command, "authdata")) {
    do_normal_submit = 0;
    ret = process_cmd_authdata(line);
@@ -3261,35 +3101,22 @@ process_line(char *line)
  } else if (!strcmp(command, "cmdaccheck")) {
    do_normal_submit = process_cmd_cmdaccheck(&tx_message, line);
  } else if (!strcmp(command, "cmdallow")) {
-    if (!strncmp(line, "all", 3)) {
-      do_normal_submit = process_cmd_cmdallowall(&tx_message, CPS_SplitWord(line));
-    } else {
-      do_normal_submit = process_cmd_cmdallow(&tx_message, line);
-    }
+    do_normal_submit = process_cmd_allowdeny(&tx_message, line, REQ_CMDALLOW, REQ_CMDALLOWALL);
  } else if (!strcmp(command, "cmddeny")) {
-    if (!strncmp(line, "all", 3)) {
-      line = CPS_SplitWord(line);
-      do_normal_submit = process_cmd_cmddenyall(&tx_message, line);
-    } else {
-      do_normal_submit = process_cmd_cmddeny(&tx_message, line);
-    }
+    do_normal_submit = process_cmd_allowdeny(&tx_message, line, REQ_CMDDENY, REQ_CMDDENYALL);
  } else if (!strcmp(command, "cyclelogs")) {
    process_cmd_cyclelogs(&tx_message, line);
  } else if (!strcmp(command, "delete")) {
    do_normal_submit = process_cmd_delete(&tx_message, line);
  } else if (!strcmp(command, "deny")) {
-    if (!strncmp(line, "all", 3)) {
-      do_normal_submit = process_cmd_denyall(&tx_message, CPS_SplitWord(line));
-    } else {
-      do_normal_submit = process_cmd_deny(&tx_message, line);
-    }
+    do_normal_submit = process_cmd_allowdeny(&tx_message, line, REQ_DENY, REQ_DENYALL);
  } else if (!strcmp(command, "dfreq")) {
-    process_cmd_dfreq(&tx_message, line);
+    do_normal_submit = process_cmd_dfreq(&tx_message, line);
  } else if (!strcmp(command, "dns")) {
    ret = process_cmd_dns(line);
    do_normal_submit = 0;
  } else if (!strcmp(command, "doffset")) {
-    process_cmd_doffset(&tx_message, line);
+    do_normal_submit = process_cmd_doffset(&tx_message, line);
  } else if (!strcmp(command, "dump")) {
    process_cmd_dump(&tx_message, line);
  } else if (!strcmp(command, "exit")) {
@@ -3415,44 +3242,46 @@ process_line(char *line)
  if (do_normal_submit) {
    ret = request_reply(&tx_message, &rx_message, RPY_NULL, 1);
  }
+
  fflush(stderr);
-  fflush(stdout);
+
+  if (fflush(stdout) != 0 || ferror(stdout) != 0) {
+    LOG(LOGS_ERR, "Could not write to stdout");
+
+    /* Return error for commands that print data */
+    if (!do_normal_submit)
+      return 0;
+  }
+
  return ret;
 }

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

+#define MAX_LINE_LENGTH 2048
+
 static int
 process_args(int argc, char **argv, int multi)
 {
-  int total_length, i, ret = 0;
-  char *line;
+  char line[MAX_LINE_LENGTH];
+  int i, l, ret = 0;

-  total_length = 0;
-  for(i=0; i<argc; i++) {
-    total_length += strlen(argv[i]) + 1;
+  for (i = l = 0; i < argc; i++) {
+    l += snprintf(line + l, sizeof (line) - l, "%s ", argv[i]);
+    if (l >= sizeof (line)) {
+      LOG(LOGS_ERR, "Command too long");
+      return 0;
    }

-  line = (char *) Malloc((2 + total_length) * sizeof(char));
-
-  for (i = 0; i < argc; i++) {
-    line[0] = '\0';
-    if (multi) {
-      strcat(line, argv[i]);
-    } else {
-      for (; i < argc; i++) {
-        strcat(line, argv[i]);
-        if (i + 1 < argc)
-          strcat(line, " ");
-      }
-    }
+    if (!multi && i + 1 < argc)
+      continue;

    ret = process_line(line);
    if (!ret || quit)
      break;
-  }

-  Free(line);
+    l = 0;
+  }

  return ret;
 }
@@ -3471,7 +3300,7 @@ static void
 display_gpl(void)
 {
    printf("chrony version %s\n"
-           "Copyright (C) 1997-2003, 2007, 2009-2020 Richard P. Curnow and others\n"
+           "Copyright (C) 1997-2003, 2007, 2009-2022 Richard P. Curnow and others\n"
           "chrony comes with ABSOLUTELY NO WARRANTY.  This is free software, and\n"
           "you are welcome to redistribute it under certain conditions.  See the\n"
           "GNU General Public License version 2 for details.\n\n",
@@ -3483,8 +3312,22 @@ display_gpl(void)
 static void
 print_help(const char *progname)
 {
-      printf("Usage: %s [-h HOST] [-p PORT] [-n] [-N] [-c] [-d] [-4|-6] [-m] [COMMAND]\n",
-             progname);
+      printf("Usage: %s [OPTION]... [COMMAND]...\n\n"
+             "Options:\n"
+             "  -4\t\tUse IPv4 addresses only\n"
+             "  -6\t\tUse IPv6 addresses only\n"
+             "  -n\t\tDon't resolve hostnames\n"
+             "  -N\t\tPrint original source names\n"
+             "  -c\t\tEnable CSV format\n"
+#if DEBUG > 0
+             "  -d\t\tEnable debug messages\n"
+#endif
+             "  -m\t\tAccept multiple commands\n"
+             "  -h HOST\tSpecify server (%s)\n"
+             "  -p PORT\tSpecify UDP port (%d)\n"
+             "  -v, --version\tPrint version and exit\n"
+             "      --help\tPrint usage and exit\n",
+             progname, DEFAULT_COMMAND_SOCKET",127.0.0.1,::1", DEFAULT_CANDM_PORT);
 }

 /* ================================================== */
@@ -3506,7 +3349,7 @@ main(int argc, char **argv)
  int opt, ret = 1, multi = 0, family = IPADDR_UNSPEC;
  int port = DEFAULT_CANDM_PORT;

-  /* Parse (undocumented) long command-line options */
+  /* Parse long command-line options */
  for (optind = 1; optind < argc; optind++) {
    if (!strcmp("--help", argv[optind])) {
      print_help(progname);
--- a/clientlog.c
+++ b/clientlog.c
@@ -3,7 +3,7 @@

 **********************************************************************
 * Copyright (C) Richard P. Curnow  1997-2003
- * Copyright (C) Miroslav Lichvar  2009, 2015-2017
+ * 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
@@ -38,6 +38,7 @@
 #include "array.h"
 #include "clientlog.h"
 #include "conf.h"
+#include "local.h"
 #include "memory.h"
 #include "ntp.h"
 #include "reports.h"
@@ -55,8 +56,6 @@ typedef struct {
  int8_t rate[MAX_SERVICES];
  int8_t ntp_timeout_rate;
  uint8_t drop_flags;
-  NTP_int64 ntp_rx_ts;
-  NTP_int64 ntp_tx_ts;
 } Record;

 /* Hash table of records, there is a fixed number of records per slot */
@@ -124,10 +123,43 @@ 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_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
@@ -135,6 +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);

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

@@ -169,7 +203,7 @@ compare_total_hits(Record *x, Record *y)
 static Record *
 get_record(IPAddr *ip)
 {
-  uint32_t last_hit, oldest_hit = 0;
+  uint32_t last_hit = 0, oldest_hit = 0;
  Record *record, *oldest_record;
  unsigned int first, i, j;

@@ -229,8 +263,6 @@ get_record(IPAddr *ip)
    record->rate[i] = INVALID_RATE;
  record->ntp_timeout_rate = INVALID_RATE;
  record->drop_flags = 0;
-  UTI_ZeroNtp64(&record->ntp_rx_ts);
-  UTI_ZeroNtp64(&record->ntp_tx_ts);

  return record;
 }
@@ -316,7 +348,7 @@ set_bucket_params(int interval, int burst, uint16_t *max_tokens,
 void
 CLG_Initialise(void)
 {
-  int i, interval, burst, lrate;
+  int i, interval, burst, lrate, slots2;

  for (i = 0; i < MAX_SERVICES; i++) {
    max_tokens[i] = 0;
@@ -359,9 +391,13 @@ CLG_Initialise(void)
  /* 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);
-  DEBUG_LOG("Max records %u", 1U << ((int)round(log(max_slots) / log(2)) + SLOT_BITS));
+  for (slots2 = 0; 1U << (slots2 + 1) <= max_slots; slots2++)
+    ;
+
+  DEBUG_LOG("Max records %u", 1U << (slots2 + SLOT_BITS));

  slots = 0;
  records = NULL;
@@ -370,6 +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);
 }

 /* ================================================== */
@@ -381,6 +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);
 }

 /* ================================================== */
@@ -595,22 +646,334 @@ CLG_LogAuthNtpRequest(void)

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

-void CLG_GetNtpTimestamps(int index, NTP_int64 **rx_ts, NTP_int64 **tx_ts)
+int
+CLG_GetNtpMinPoll(void)
 {
-  Record *record;
+  return limit_interval[CLG_NTP];
+}

-  record = ARR_GetElement(records, index);
+/* ================================================== */

-  *rx_ts = &record->ntp_rx_ts;
-  *tx_ts = &record->ntp_tx_ts;
+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));
+}
+
+/* ================================================== */
+
+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;
+  }
+
+  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;
+  }
+
+  /* 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_GetNtpMinPoll(void)
+CLG_GetNtpTxTimestamp(NTP_int64 *rx_ts, struct timespec *tx_ts)
 {
-  return limit_interval[CLG_NTP];
+  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_DisableNtpTimestamps(NTP_int64 *rx_ts)
+{
+  uint32_t index;
+
+  if (!ntp_ts_map.timestamps)
+    return;
+
+  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++;
 }

 /* ================================================== */
@@ -717,4 +1080,9 @@ CLG_GetServerStatsReport(RPT_ServerStatsReport *report)
  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
@@ -43,9 +43,15 @@ extern int CLG_GetClientIndex(IPAddr *client);
 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 void CLG_GetNtpTimestamps(int index, NTP_int64 **rx_ts, NTP_int64 **tx_ts);
 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);
--- 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/cmdmon.c
+++ b/cmdmon.c
@@ -3,7 +3,7 @@

 **********************************************************************
 * Copyright (C) Richard P. Curnow  1997-2003
- * Copyright (C) Miroslav Lichvar  2009-2016, 2018-2020
+ * Copyright (C) Miroslav Lichvar  2009-2016, 2018-2021
 * 
 * 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
@@ -62,6 +62,9 @@ static int sock_fdu;
 static int sock_fd4;
 static int sock_fd6;

+/* Flag indicating the IPv4 socket is bound to an address */
+static int bound_sock_fd4;
+
 /* Flag indicating whether this module has been initialised or not */
 static int initialised = 0;

@@ -140,6 +143,7 @@ static const char permissions[] = {
  PERMIT_AUTH, /* CLIENT_ACCESSES_BY_INDEX3 */
  PERMIT_AUTH, /* SELECT_DATA */
  PERMIT_AUTH, /* RELOAD_SOURCES */
+  PERMIT_AUTH, /* DOFFSET2 */
 };

 /* ================================================== */
@@ -179,6 +183,9 @@ open_socket(int family)
        return INVALID_SOCK_FD;
      }

+      if (family == IPADDR_INET4)
+        bound_sock_fd4 = local_addr.ip_addr.addr.in4 != INADDR_ANY;
+
      break;
    case IPADDR_UNSPEC:
      local_path = CNF_GetBindCommandPath();
@@ -244,6 +251,8 @@ CAM_Initialise(void)

  initialised = 1;

+  bound_sock_fd4 = 0;
+
  sock_fdu = INVALID_SOCK_FD;
  sock_fd4 = open_socket(IPADDR_INET4);
  sock_fd6 = open_socket(IPADDR_INET6);
@@ -306,9 +315,17 @@ transmit_reply(int sock_fd, int request_length, SCK_Message *message)

  /* Don't require responses to non-link-local addresses to use the same
     interface */
-  if (!SCK_IsLinkLocalIPAddress(&message->remote_addr.ip.ip_addr))
+  if (message->addr_type == SCK_ADDR_IP &&
+      !SCK_IsLinkLocalIPAddress(&message->remote_addr.ip.ip_addr))
    message->if_index = INVALID_IF_INDEX;

+#if !defined(HAVE_IN_PKTINFO) && defined(IP_SENDSRCADDR)
+  /* On FreeBSD a local IPv4 address cannot be specified on bound socket */
+  if (message->addr_type == SCK_ADDR_IP && message->local_addr.ip.family == IPADDR_INET4 &&
+      (sock_fd != sock_fd4 || bound_sock_fd4))
+    message->local_addr.ip.family = IPADDR_UNSPEC;
+#endif
+
  if (!SCK_SendMessage(sock_fd, message, 0))
    return;
 }
@@ -734,11 +751,14 @@ handle_add_source(CMD_Request *rx_message, CMD_Reply *tx_message)
  params.filter_length = ntohl(rx_message->data.ntp_source.filter_length);
  params.authkey = ntohl(rx_message->data.ntp_source.authkey);
  params.nts_port = ntohl(rx_message->data.ntp_source.nts_port);
+  params.cert_set = ntohl(rx_message->data.ntp_source.cert_set);
  params.max_delay = UTI_FloatNetworkToHost(rx_message->data.ntp_source.max_delay);
  params.max_delay_ratio =
    UTI_FloatNetworkToHost(rx_message->data.ntp_source.max_delay_ratio);
  params.max_delay_dev_ratio =
    UTI_FloatNetworkToHost(rx_message->data.ntp_source.max_delay_dev_ratio);
+  params.max_delay_quant =
+    UTI_FloatNetworkToHost(rx_message->data.ntp_source.max_delay_quant);
  params.min_delay = UTI_FloatNetworkToHost(rx_message->data.ntp_source.min_delay);
  params.asymmetry = UTI_FloatNetworkToHost(rx_message->data.ntp_source.asymmetry);
  params.offset = UTI_FloatNetworkToHost(rx_message->data.ntp_source.offset);
@@ -750,6 +770,9 @@ handle_add_source(CMD_Request *rx_message, CMD_Reply *tx_message)
  params.interleaved = ntohl(rx_message->data.ntp_source.flags) & REQ_ADDSRC_INTERLEAVED ? 1 : 0;
  params.burst = ntohl(rx_message->data.ntp_source.flags) & REQ_ADDSRC_BURST ? 1 : 0;
  params.nts = ntohl(rx_message->data.ntp_source.flags) & REQ_ADDSRC_NTS ? 1 : 0;
+  params.copy = ntohl(rx_message->data.ntp_source.flags) & REQ_ADDSRC_COPY ? 1 : 0;
+  params.ext_fields =
+    ntohl(rx_message->data.ntp_source.flags) & REQ_ADDSRC_EF_EXP1 ? NTP_EF_FLAG_EXP1 : 0;
  params.sel_options =
    (ntohl(rx_message->data.ntp_source.flags) & REQ_ADDSRC_PREFER ? SRC_SELECT_PREFER : 0) |
    (ntohl(rx_message->data.ntp_source.flags) & REQ_ADDSRC_NOSELECT ? SRC_SELECT_NOSELECT : 0) |
@@ -840,13 +863,14 @@ handle_dfreq(CMD_Request *rx_message, CMD_Reply *tx_message)
 static void
 handle_doffset(CMD_Request *rx_message, CMD_Reply *tx_message)
 {
-  long sec, usec;
  double doffset;
-  sec = (int32_t)ntohl(rx_message->data.doffset.sec);
-  usec = (int32_t)ntohl(rx_message->data.doffset.usec);
-  doffset = (double) sec + 1.0e-6 * (double) usec;
+
+  doffset = UTI_FloatNetworkToHost(rx_message->data.doffset.doffset);
+  if (!LCL_AccumulateOffset(doffset, 0.0)) {
+    tx_message->status = htons(STT_FAILED);
+  } else {
    LOG(LOGS_INFO, "Accumulated delta offset of %.6f seconds", doffset);
-  LCL_AccumulateOffset(doffset, 0.0);
+  }
 }

 /* ================================================== */
@@ -1145,7 +1169,7 @@ handle_server_stats(CMD_Request *rx_message, CMD_Reply *tx_message)
  RPT_ServerStatsReport report;

  CLG_GetServerStatsReport(&report);
-  tx_message->reply = htons(RPY_SERVER_STATS2);
+  tx_message->reply = htons(RPY_SERVER_STATS3);
  tx_message->data.server_stats.ntp_hits = htonl(report.ntp_hits);
  tx_message->data.server_stats.nke_hits = htonl(report.nke_hits);
  tx_message->data.server_stats.cmd_hits = htonl(report.cmd_hits);
@@ -1154,6 +1178,9 @@ handle_server_stats(CMD_Request *rx_message, CMD_Reply *tx_message)
  tx_message->data.server_stats.cmd_drops = htonl(report.cmd_drops);
  tx_message->data.server_stats.log_drops = htonl(report.log_drops);
  tx_message->data.server_stats.ntp_auth_hits = htonl(report.ntp_auth_hits);
+  tx_message->data.server_stats.ntp_interleaved_hits = htonl(report.ntp_interleaved_hits);
+  tx_message->data.server_stats.ntp_timestamps = htonl(report.ntp_timestamps);
+  tx_message->data.server_stats.ntp_span_seconds = htonl(report.ntp_span_seconds);
 }

 /* ================================================== */
@@ -1197,6 +1224,7 @@ handle_ntp_data(CMD_Request *rx_message, CMD_Reply *tx_message)
  tx_message->data.ntp_data.total_tx_count = htonl(report.total_tx_count);
  tx_message->data.ntp_data.total_rx_count = htonl(report.total_rx_count);
  tx_message->data.ntp_data.total_valid_count = htonl(report.total_valid_count);
+  tx_message->data.ntp_data.total_good_count = htonl(report.total_good_count);
  memset(tx_message->data.ntp_data.reserved, 0xff, sizeof (tx_message->data.ntp_data.reserved));
 }

@@ -1326,6 +1354,7 @@ handle_select_data(CMD_Request *rx_message, CMD_Reply *tx_message)
  UTI_IPHostToNetwork(&report.ip_addr, &tx_message->data.select_data.ip_addr);
  tx_message->data.select_data.state_char = report.state_char;
  tx_message->data.select_data.authentication = report.authentication;
+  tx_message->data.select_data.leap = report.leap;
  tx_message->data.select_data.conf_options = htons(convert_select_options(report.conf_options));
  tx_message->data.select_data.eff_options = htons(convert_select_options(report.eff_options));
  tx_message->data.select_data.last_sample_ago = htonl(report.last_sample_ago);
@@ -1620,7 +1649,7 @@ read_from_cmd_socket(int sock_fd, int event, void *anything)
          handle_dfreq(&rx_message, &tx_message);
          break;

-        case REQ_DOFFSET:
+        case REQ_DOFFSET2:
          handle_doffset(&rx_message, &tx_message);
          break;

--- 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
@@ -43,6 +43,7 @@ int
 CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)
 {
  char *hostname, *cmd;
+  uint32_t ef_type;
  int n;
  
  src->port = SRC_DEFAULT_PORT;
@@ -64,10 +65,14 @@ CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)
  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;
@@ -90,6 +95,8 @@ CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)
      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")) {
@@ -102,6 +109,9 @@ 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)
@@ -109,6 +119,16 @@ CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)
    } 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;
@@ -121,6 +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;
@@ -174,6 +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)
 {
--- a/cmdparse.h
+++ b/cmdparse.h
@@ -39,6 +39,9 @@ typedef struct {
 /* 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);

--- a/conf.c
+++ b/conf.c
@@ -76,6 +76,8 @@ static void parse_log(char *);
 static void parse_mailonchange(char *);
 static void parse_makestep(char *);
 static void parse_maxchange(char *);
+static void parse_ntsserver(char *, ARR_Instance files);
+static void parse_ntstrustedcerts(char *);
 static void parse_ratelimit(char *line, int *enabled, int *interval,
                            int *burst, int *leak);
 static void parse_refclock(char *);
@@ -113,6 +115,7 @@ static int cmd_port = DEFAULT_CANDM_PORT;

 static int raw_measurements = 0;
 static int do_log_measurements = 0;
+static int do_log_selection = 0;
 static int do_log_statistics = 0;
 static int do_log_tracking = 0;
 static int do_log_rtc = 0;
@@ -252,14 +255,15 @@ static char *user;
 /* NTS server and client configuration */
 static char *nts_dump_dir = NULL;
 static char *nts_ntp_server = NULL;
-static char *nts_server_cert_file = NULL;
-static char *nts_server_key_file = NULL;
+static ARR_Instance nts_server_cert_files; /* array of (char *) */
+static ARR_Instance nts_server_key_files; /* array of (char *) */
 static int nts_server_port = NKE_PORT;
 static int nts_server_processes = 1;
 static int nts_server_connections = 100;
 static int nts_refresh = 2419200; /* 4 weeks */
 static int nts_rotate = 604800; /* 1 week */
-static char *nts_trusted_cert_file = NULL;
+static ARR_Instance nts_trusted_certs_paths; /* array of (char *) */
+static ARR_Instance nts_trusted_certs_ids; /* array of uint32_t */

 /* Number of clock updates needed to enable certificate time checks */
 static int no_cert_time_check = 0;
@@ -270,6 +274,9 @@ static int no_system_cert = 0;
 /* Array of CNF_HwTsInterface */
 static ARR_Instance hwts_interfaces;

+/* PTP event port (disabled by default) */
+static int ptp_port = 0;
+
 typedef struct {
  NTP_Source_Type type;
  int pool;
@@ -388,6 +395,11 @@ CNF_Initialise(int r, int client_only)
  ntp_restrictions = ARR_CreateInstance(sizeof (AllowDeny));
  cmd_restrictions = ARR_CreateInstance(sizeof (AllowDeny));

+  nts_server_cert_files = ARR_CreateInstance(sizeof (char *));
+  nts_server_key_files = ARR_CreateInstance(sizeof (char *));
+  nts_trusted_certs_paths = ARR_CreateInstance(sizeof (char *));
+  nts_trusted_certs_ids = ARR_CreateInstance(sizeof (uint32_t));
+
  rtc_device = Strdup(DEFAULT_RTC_DEVICE);
  hwclock_file = Strdup(DEFAULT_HWCLOCK_FILE);
  user = Strdup(DEFAULT_USER);
@@ -422,6 +434,16 @@ CNF_Finalise(void)
    Free(((NTP_Source *)ARR_GetElement(ntp_sources, i))->params.name);
  for (i = 0; i < ARR_GetSize(ntp_source_dirs); i++)
    Free(*(char **)ARR_GetElement(ntp_source_dirs, i));
+  for (i = 0; i < ARR_GetSize(refclock_sources); i++) {
+    Free(((RefclockParameters *)ARR_GetElement(refclock_sources, i))->driver_name);
+    Free(((RefclockParameters *)ARR_GetElement(refclock_sources, i))->driver_parameter);
+  }
+  for (i = 0; i < ARR_GetSize(nts_server_cert_files); i++)
+    Free(*(char **)ARR_GetElement(nts_server_cert_files, i));
+  for (i = 0; i < ARR_GetSize(nts_server_key_files); i++)
+    Free(*(char **)ARR_GetElement(nts_server_key_files, i));
+  for (i = 0; i < ARR_GetSize(nts_trusted_certs_paths); i++)
+    Free(*(char **)ARR_GetElement(nts_trusted_certs_paths, i));

  ARR_DestroyInstance(init_sources);
  ARR_DestroyInstance(ntp_sources);
@@ -433,6 +455,11 @@ CNF_Finalise(void)
  ARR_DestroyInstance(ntp_restrictions);
  ARR_DestroyInstance(cmd_restrictions);

+  ARR_DestroyInstance(nts_server_cert_files);
+  ARR_DestroyInstance(nts_server_key_files);
+  ARR_DestroyInstance(nts_trusted_certs_paths);
+  ARR_DestroyInstance(nts_trusted_certs_ids);
+
  Free(drift_file);
  Free(dumpdir);
  Free(hwclock_file);
@@ -453,9 +480,6 @@ CNF_Finalise(void)
  Free(tempcomp_point_file);
  Free(nts_dump_dir);
  Free(nts_ntp_server);
-  Free(nts_server_cert_file);
-  Free(nts_server_key_file);
-  Free(nts_trusted_cert_file);
 }

 /* ================================================== */
@@ -639,8 +663,6 @@ CNF_ParseLine(const char *filename, int number, char *line)
  } else if (!strcasecmp(command, "ntsratelimit")) {
    parse_ratelimit(p, &nts_ratelimit_enabled, &nts_ratelimit_interval,
                    &nts_ratelimit_burst, &nts_ratelimit_leak);
-  } else if (!strcasecmp(command, "ntstrustedcerts")) {
-    parse_string(p, &nts_trusted_cert_file);
  } else if (!strcasecmp(command, "ntscachedir") ||
             !strcasecmp(command, "ntsdumpdir")) {
    parse_string(p, &nts_dump_dir);
@@ -655,9 +677,11 @@ CNF_ParseLine(const char *filename, int number, char *line)
  } else if (!strcasecmp(command, "ntsrotate")) {
    parse_int(p, &nts_rotate);
  } else if (!strcasecmp(command, "ntsservercert")) {
-    parse_string(p, &nts_server_cert_file);
+    parse_ntsserver(p, nts_server_cert_files);
  } else if (!strcasecmp(command, "ntsserverkey")) {
-    parse_string(p, &nts_server_key_file);
+    parse_ntsserver(p, nts_server_key_files);
+  } else if (!strcasecmp(command, "ntstrustedcerts")) {
+    parse_ntstrustedcerts(p);
  } else if (!strcasecmp(command, "peer")) {
    parse_source(p, command, 1);
  } else if (!strcasecmp(command, "pidfile")) {
@@ -666,6 +690,8 @@ CNF_ParseLine(const char *filename, int number, char *line)
    parse_source(p, command, 1);
  } else if (!strcasecmp(command, "port")) {
    parse_int(p, &ntp_port);
+  } else if (!strcasecmp(command, "ptpport")) {
+    parse_int(p, &ptp_port);
  } else if (!strcasecmp(command, "ratelimit")) {
    parse_ratelimit(p, &ntp_ratelimit_enabled, &ntp_ratelimit_interval,
                    &ntp_ratelimit_burst, &ntp_ratelimit_leak);
@@ -836,7 +862,7 @@ static void
 parse_refclock(char *line)
 {
  int n, poll, dpoll, filter_length, pps_rate, min_samples, max_samples, sel_options;
-  int max_lock_age, pps_forced, stratum, tai;
+  int local, max_lock_age, pps_forced, stratum, tai;
  uint32_t ref_id, lock_ref_id;
  double offset, delay, precision, max_dispersion, pulse_width;
  char *p, *cmd, *name, *param;
@@ -846,6 +872,7 @@ parse_refclock(char *line)
  poll = 4;
  dpoll = 0;
  filter_length = 64;
+  local = 0;
  pps_forced = 0;
  pps_rate = 0;
  min_samples = SRC_DEFAULT_MINSAMPLES;
@@ -904,6 +931,9 @@ parse_refclock(char *line)
      if (sscanf(line, "%d%n", &filter_length, &n) != 1) {
        break;
      }
+    } else if (!strcasecmp(cmd, "local")) {
+      n = 0;
+      local = 1;
    } else if (!strcasecmp(cmd, "rate")) {
      if (sscanf(line, "%d%n", &pps_rate, &n) != 1)
        break;
@@ -970,6 +1000,7 @@ parse_refclock(char *line)
  refclock->driver_poll = dpoll;
  refclock->poll = poll;
  refclock->filter_length = filter_length;
+  refclock->local = local;
  refclock->pps_forced = pps_forced;
  refclock->pps_rate = pps_rate;
  refclock->min_samples = min_samples;
@@ -1002,6 +1033,8 @@ parse_log(char *line)
        raw_measurements = 1;
      } else if (!strcmp(log_name, "measurements")) {
        do_log_measurements = 1;
+      } else if (!strcmp(log_name, "selection")) {
+        do_log_selection = 1;
      } else if (!strcmp(log_name, "statistics")) {
        do_log_statistics = 1;
      } else if (!strcmp(log_name, "tracking")) {
@@ -1154,103 +1187,56 @@ parse_mailonchange(char *line)

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

+static void
+parse_ntsserver(char *line, ARR_Instance files)
+{
+  char *file = NULL;
+
+  parse_string(line, &file);
+  ARR_AppendElement(files, &file);
+}
+
+/* ================================================== */
+
+static void
+parse_ntstrustedcerts(char *line)
+{
+  uint32_t id;
+  char *path;
+
+  if (get_number_of_args(line) == 2) {
+    path = CPS_SplitWord(line);
+    if (sscanf(line, "%"SCNu32, &id) != 1)
+      command_parse_error();
+  } else {
+    check_number_of_args(line, 1);
+    path = line;
+    id = 0;
+  }
+
+  path = Strdup(path);
+
+  ARR_AppendElement(nts_trusted_certs_paths, &path);
+  ARR_AppendElement(nts_trusted_certs_ids, &id);
+}
+
+/* ================================================== */
+
 static void
 parse_allow_deny(char *line, ARR_Instance restrictions, int allow)
 {
-  char *p;
-  unsigned long a, b, c, d, n;
-  int all = 0;
-  AllowDeny *new_node = NULL;
-  IPAddr ip_addr;
+  int all, subnet_bits;
+  AllowDeny *node;
+  IPAddr ip;

-  p = line;
-
-  if (!strncmp(p, "all", 3)) {
-    all = 1;
-    p = CPS_SplitWord(line);
-  }
-
-  if (!*p) {
-    /* Empty line applies to all addresses */
-    new_node = (AllowDeny *)ARR_GetNewElement(restrictions);
-    new_node->allow = allow;
-    new_node->all = all;
-    new_node->ip.family = IPADDR_UNSPEC;
-    new_node->subnet_bits = 0;
-  } else {
-    char *slashpos;
-    slashpos = strchr(p, '/');
-    if (slashpos) *slashpos = 0;
-
-    check_number_of_args(p, 1);
-    n = 0;
-    if (UTI_StringToIP(p, &ip_addr) ||
-        (n = sscanf(p, "%lu.%lu.%lu.%lu", &a, &b, &c, &d)) >= 1) {
-      new_node = (AllowDeny *)ARR_GetNewElement(restrictions);
-      new_node->allow = allow;
-      new_node->all = all;
-
-      if (n == 0) {
-        new_node->ip = ip_addr;
-        if (ip_addr.family == IPADDR_INET6)
-          new_node->subnet_bits = 128;
-        else
-          new_node->subnet_bits = 32;
-      } else {
-        new_node->ip.family = IPADDR_INET4;
-
-        a &= 0xff;
-        b &= 0xff;
-        c &= 0xff;
-        d &= 0xff;
-        
-        switch (n) {
-          case 1:
-            new_node->ip.addr.in4 = (a<<24);
-            new_node->subnet_bits = 8;
-            break;
-          case 2:
-            new_node->ip.addr.in4 = (a<<24) | (b<<16);
-            new_node->subnet_bits = 16;
-            break;
-          case 3:
-            new_node->ip.addr.in4 = (a<<24) | (b<<16) | (c<<8);
-            new_node->subnet_bits = 24;
-            break;
-          case 4:
-            new_node->ip.addr.in4 = (a<<24) | (b<<16) | (c<<8) | d;
-            new_node->subnet_bits = 32;
-            break;
-          default:
-            assert(0);
-        }
-      }
-      
-      if (slashpos) {
-        int specified_subnet_bits, n;
-        n = sscanf(slashpos+1, "%d", &specified_subnet_bits);
-        if (n == 1) {
-          new_node->subnet_bits = specified_subnet_bits;
-        } else {
+  if (!CPS_ParseAllowDeny(line, &all, &ip, &subnet_bits))
    command_parse_error();
-        }
-      }

-    } else {
-      if (!slashpos && DNS_Name2IPAddress(p, &ip_addr, 1) == DNS_Success) {
-        new_node = (AllowDeny *)ARR_GetNewElement(restrictions);
-        new_node->allow = allow;
-        new_node->all = all;
-        new_node->ip = ip_addr;
-        if (ip_addr.family == IPADDR_INET6)
-          new_node->subnet_bits = 128;
-        else
-          new_node->subnet_bits = 32;
-      } else {
-        command_parse_error();
-      }      
-    }
-  }
+  node = ARR_GetNewElement(restrictions);
+  node->allow = allow;
+  node->all = all;
+  node->ip = ip;
+  node->subnet_bits = subnet_bits;
 }
  
 /* ================================================== */
@@ -1501,6 +1487,8 @@ parse_hwtimestamp(char *line)
        iface->rxfilter = CNF_HWTS_RXFILTER_NONE;
      else if (!strcasecmp(filter, "ntp"))
        iface->rxfilter = CNF_HWTS_RXFILTER_NTP;
+      else if (!strcasecmp(filter, "ptp"))
+        iface->rxfilter = CNF_HWTS_RXFILTER_PTP;
      else if (!strcasecmp(filter, "all"))
        iface->rxfilter = CNF_HWTS_RXFILTER_ALL;
      else
@@ -1639,8 +1627,9 @@ load_source_file(const char *filename)
    return;

  while (fgets(line, sizeof (line), f)) {
-    if (strlen(line) >= MAX_LINE_LENGTH)
-      continue;
+    /* Require lines to be terminated */
+    if (line[0] == '\0' || line[strlen(line) - 1] != '\n')
+      break;

    CPS_NormalizeLine(line);
    if (line[0] == '\0')
@@ -1737,6 +1726,8 @@ reload_source_dirs(void)
      if (s == NSR_UnresolvedName) {
        unresolved++;
      } else if (s != NSR_Success) {
+        LOG(LOGS_ERR, "Could not add source %s", source->params.name);
+
        /* Mark the source as not present */
        source->params.name[0] = '\0';
      }
@@ -1808,7 +1799,8 @@ CNF_AddInitSources(void)
    ntp_addr.port = cps_source.port;
    cps_source.params.iburst = 1;

-    NSR_AddSource(&ntp_addr, NTP_SERVER, &cps_source.params, NULL);
+    if (NSR_AddSource(&ntp_addr, NTP_SERVER, &cps_source.params, NULL) != NSR_Success)
+      LOG(LOGS_ERR, "Could not add source %s", UTI_IPToString(&ntp_addr.ip_addr));
  }

  ARR_SetSize(init_sources, 0);
@@ -1821,11 +1813,16 @@ CNF_AddSources(void)
 {
  NTP_Source *source;
  unsigned int i;
+  NSR_Status s;

  for (i = 0; i < ARR_GetSize(ntp_sources); i++) {
    source = (NTP_Source *)ARR_GetElement(ntp_sources, i);
-    NSR_AddSourceByName(source->params.name, source->params.port,
-                        source->pool, source->type, &source->params.params, NULL);
+
+    s = NSR_AddSourceByName(source->params.name, source->params.port, source->pool,
+                            source->type, &source->params.params, NULL);
+    if (s != NSR_Success && s != NSR_UnresolvedName)
+      LOG(LOGS_ERR, "Could not add source %s", source->params.name);
+
    Free(source->params.name);
  }

@@ -1839,10 +1836,14 @@ CNF_AddSources(void)
 void
 CNF_AddRefclocks(void)
 {
+  RefclockParameters *refclock;
  unsigned int i;

  for (i = 0; i < ARR_GetSize(refclock_sources); i++) {
-    RCL_AddRefclock((RefclockParameters *)ARR_GetElement(refclock_sources, i));
+    refclock = ARR_GetElement(refclock_sources, i);
+    RCL_AddRefclock(refclock);
+    Free(refclock->driver_name);
+    Free(refclock->driver_parameter);
  }

  ARR_SetSize(refclock_sources, 0);
@@ -1931,6 +1932,14 @@ CNF_GetLogMeasurements(int *raw)

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

+int
+CNF_GetLogSelection(void)
+{
+  return do_log_selection;
+}
+
+/* ================================================== */
+
 int
 CNF_GetLogStatistics(void)
 {
@@ -2491,6 +2500,14 @@ CNF_GetHwTsInterface(unsigned int index, CNF_HwTsInterface **iface)

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

+int
+CNF_GetPtpPort(void)
+{
+  return ptp_port;
+}
+
+/* ================================================== */
+
 char *
 CNF_GetNtsDumpDir(void)
 {
@@ -2507,18 +2524,16 @@ CNF_GetNtsNtpServer(void)

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

-char *
-CNF_GetNtsServerCertFile(void)
+int
+CNF_GetNtsServerCertAndKeyFiles(const char ***certs, const char ***keys)
 {
-  return nts_server_cert_file;
-}
+  *certs = ARR_GetElements(nts_server_cert_files);
+  *keys = ARR_GetElements(nts_server_key_files);

-/* ================================================== */
+  if (ARR_GetSize(nts_server_cert_files) != ARR_GetSize(nts_server_key_files))
+    LOG_FATAL("Uneven number of NTS certs and keys");

-char *
-CNF_GetNtsServerKeyFile(void)
-{
-  return nts_server_key_file;
+  return ARR_GetSize(nts_server_cert_files);
 }

 /* ================================================== */
@@ -2563,10 +2578,16 @@ CNF_GetNtsRotate(void)

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

-char *
-CNF_GetNtsTrustedCertFile(void)
+int
+CNF_GetNtsTrustedCertsPaths(const char ***paths, uint32_t **ids)
 {
-  return nts_trusted_cert_file;
+  *paths = ARR_GetElements(nts_trusted_certs_paths);
+  *ids = ARR_GetElements(nts_trusted_certs_ids);
+
+  if (ARR_GetSize(nts_trusted_certs_paths) != ARR_GetSize(nts_trusted_certs_ids))
+    assert(0);
+
+  return ARR_GetSize(nts_trusted_certs_paths);
 }

 /* ================================================== */
--- a/conf.h
+++ b/conf.h
@@ -58,6 +58,7 @@ extern char *CNF_GetLogDir(void);
 extern char *CNF_GetDumpDir(void);
 extern int CNF_GetLogBanner(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);
@@ -134,6 +135,7 @@ 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;

@@ -151,16 +153,17 @@ typedef struct {

 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 char *CNF_GetNtsServerCertFile(void);
-extern char *CNF_GetNtsServerKeyFile(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 char *CNF_GetNtsTrustedCertFile(void);
+extern int CNF_GetNtsTrustedCertsPaths(const char ***paths, uint32_t **ids);
 extern int CNF_GetNoSystemCert(void);
 extern int CNF_GetNoCertTimeCheck(void);

--- a/113
+++ b/113
@@ -5,7 +5,7 @@
 #
 # Copyright (C) Richard P. Curnow  1997-2003
 # Copyright (C) Bryan Christianson  2016
-# Copyright (C) Miroslav Lichvar  2009, 2012-2020
+# Copyright (C) Miroslav Lichvar  2009, 2012-2021
 # Copyright (C) Stefan R. Filipek  2019
 #
 # =======================================================================
@@ -33,13 +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 ]
@@ -50,7 +50,7 @@ test_code () {
    echo "No"
    result=1
  fi
-  rm -f docheck.c docheck
+  rm -f conftest.c conftest
  echo >> config.log
  return $result
 }
@@ -245,6 +245,7 @@ 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
@@ -421,6 +422,7 @@ case $OPERATINGSYSTEM in
        try_setsched=1
        try_lockmem=1
        try_phc=1
+        try_arc4random=0
        add_def LINUX
        echo "Configuring for " $SYSTEM
    ;;
@@ -467,7 +469,7 @@ case $OPERATINGSYSTEM in
    ;;
    SunOS)
        EXTRA_OBJECTS="sys_generic.o sys_solaris.o sys_timex.o sys_posix.o"
-        LIBS="$LIBS -lsocket -lnsl -lresolv"
+        LIBS="$LIBS -lsocket -lnsl -lkvm -lelf -lresolv"
        try_setsched=1
        try_lockmem=1
        add_def SOLARIS
@@ -479,7 +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?)"
@@ -655,14 +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"
@@ -670,10 +686,11 @@ if [ $try_clock_gettime = "1" ]; then
  fi
 fi

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

 if [ $feat_asyncdns = "1" ] && \
@@ -687,13 +704,16 @@ then
  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
-fi
-
-if test_code 'getrandom()' 'stdlib.h sys/random.h' '' '' \
-    'return getrandom(NULL, 256, 0);'; then
+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='
@@ -885,7 +905,7 @@ if [ $feat_sechash = "1" ] && [ "x$HASH_LINK" = "x" ]  && [ $try_nettle = "1" ];
    add_def FEAT_SECHASH

    if test_code 'CMAC in nettle' 'nettle/cmac.h' "$test_cflags" "$test_link" \
-      'cmac128_update(NULL, NULL, NULL, 0, NULL);'
+      'cmac128_update((void *)1, (void *)2, (void *)3, 1, (void *)4);'
    then
      add_def HAVE_CMAC
      EXTRA_OBJECTS="$EXTRA_OBJECTS cmac_nettle.o"
@@ -910,7 +930,7 @@ 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"
@@ -919,36 +939,69 @@ if [ $feat_sechash = "1" ] && [ "x$HASH_LINK" = "x" ] && [ $try_tomcrypt = "1" ]
  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`"
-  if test_code 'gnutls' 'gnutls/gnutls.h' \
-    "$test_cflags" "$test_link" '
-      return gnutls_init(NULL, 0) + GNUTLS_TLS1_3 +
-        gnutls_priority_init2(NULL, "", NULL, GNUTLS_PRIORITY_INIT_DEF_APPEND) +
-        gnutls_prf_rfc5705(NULL, 0, "", 0, "", 16, NULL);'
+  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(NULL, NULL);'
+      'siv_cmac_aes128_set_key((void *)1, (void *)2);'
    then
      EXTRA_OBJECTS="$EXTRA_OBJECTS siv_nettle.o"
      add_def HAVE_SIV
      add_def HAVE_NETTLE_SIV_CMAC
    else
-      if test_code 'SIV in gnutls' 'gnutls/gnutls.h' \
-        "$test_cflags" "$test_link" '
-          return gnutls_aead_cipher_init(NULL, GNUTLS_CIPHER_AES_128_SIV, NULL);'
+      if test_code 'SIV in gnutls' 'gnutls/crypto.h' \
+        "$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(NULL, NULL);'
+          'aes128_set_encrypt_key((void *)1, (void *)2);'
        then
          EXTRA_OBJECTS="$EXTRA_OBJECTS siv_nettle.o"
          add_def HAVE_SIV
--- 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  2009-2017, 2019-2020
+// Copyright (C) Miroslav Lichvar  2009-2017, 2019-2022
 //
 // 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
@@ -78,11 +78,10 @@ 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 the original names of NTP sources that were
-specified in the configuration file, or *chronyc* commands, and are internally
-used by *chronyd*. Without the *-n* and *-N* option, the names of NTP sources
-are obtained from reverse DNS lookups and can be different from the original
-names.
+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)
@@ -100,12 +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
@@ -118,10 +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*
@@ -174,15 +180,19 @@ stratum-2 and is synchronised from a stratum-1).
 This is the time (UTC) at which the last measurement from the reference
 source was processed.
 *System time*:::
-In normal operation, *chronyd* by default never steps the system clock, because
-any jump in the time can have adverse consequences for certain application
-programs. Instead, any error in the system clock is corrected by slightly
-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 as a server). The value reported
-on this line is the difference due to this effect.
+This is the current offset between the NTP clock and system clock. The NTP
+clock is a software (virtual) clock maintained by *chronyd*, which is
+synchronised to the configured time sources and provides time to NTP clients.
+The system clock is synchronised to the NTP clock. To avoid steps in the
+system time, which might have adverse consequences for certain applications,
+the system clock is normally corrected only by speeding up or slowing down (up
+to the rate configured by the <<chrony.conf.adoc#maxslewrate,*maxslewrate*>>
+directive). If the offset is too large, this correction will take a very long
+time. A step can be forced by the <<makestep,*makestep*>> command, or the
+<<chrony.conf.adoc#makestep,*makestep*>> directive in the configuration file.
+
+Note that all other offsets reported by *chronyc* and most offsets in the log
+files are relative to the NTP clock, not the system clock.
 *Last offset*:::
 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
@@ -428,11 +438,11 @@ 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   
-====================================================================
-D foo.example.net           Y ----- --TR-    4   1.0   -61ms   +62ms
-* bar.example.net           N ----- -----    0   1.0 -6846us +7305us
-+ baz.example.net           N ----- -----   10   1.0 -7381us +7355us
+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:
@@ -445,6 +455,7 @@ states are reported.
 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).
@@ -504,6 +515,12 @@ be reselected and the scores will be reset to 1.
 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
@@ -649,6 +666,7 @@ RX timestamping : Kernel
 Total TX        : 24
 Total RX        : 24
 Total valid RX  : 24
+Total good RX   : 22
 ----
 +
 The fields are explained as follows:
@@ -686,7 +704,8 @@ 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*:::
@@ -701,7 +720,10 @@ The number of packets sent to the source.
 *Total RX*:::
 The number of all packets received from the source.
 *Total valid RX*:::
-The number of valid packets received from the source.
+The number of packets which passed the first two groups of NTP tests.
+*Total good RX*:::
+The number of packets which passed all three groups of NTP tests, i.e. the NTP
+measurement was accepted.

 [[add_peer]]*add peer* _name_ [_option_]...::
 The *add peer* command allows a new NTP peer to be added whilst
@@ -1098,13 +1120,9 @@ The columns are as follows:
  received/accepted.

 [[serverstats]]*serverstats*::
-The *serverstats* command displays how many valid NTP and command requests, and
-NTS-KE connections, *chronyd* operating as a server received from clients, and
-how many of them were dropped due to rate limiting. It also displays how many
-client log records were dropped due to the memory limit configured by the
-<<chrony.conf.adoc#clientloglimit,*clientloglimit*>> directive and how many of
-the NTP requests (from those which were not dropped) were authenticated. 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
@@ -1115,7 +1133,47 @@ 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
@@ -1124,11 +1182,8 @@ 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
@@ -1143,11 +1198,8 @@ 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
--- a/doc/chronyd.adoc
+++ b/doc/chronyd.adoc
@@ -100,7 +100,7 @@ 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,
-Solaris, and macOS 10.13 or later).
+illumos, and macOS 10.13 or later).

 *-R*::
 When this option is used, the <<chrony.conf.adoc#initstepslew,*initstepslew*>>
@@ -141,7 +141,7 @@ after start in order to drop root privileges. It overrides the
 _@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.

@@ -156,29 +156,40 @@ 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 SIGSYS
-signal is thrown instead and in level 0 the filter is disabled. The default
-value is 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 is recommended to enable the filter only when it is 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 might 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 to disable the thread time
-constraint policy or 1 for the policy to be enabled. Other systems do not
+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.

 *-x*::
 This option disables the control of the system clock. *chronyd* will not try to
@@ -187,9 +198,12 @@ 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*::
+*-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
@@ -1,7 +1,7 @@
 // This file is part of chrony
 //
 // Copyright (C) Richard P. Curnow  1997-2003
-// Copyright (C) Miroslav Lichvar  2014-2016, 2020
+// Copyright (C) Miroslav Lichvar  2014-2016, 2020-2022
 //
 // 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
@@ -49,9 +49,11 @@ website.

 First, the client needs to know which NTP servers it should ask for the current
 time. They are specified by the `server` or `pool` directive. The `pool`
-directive can be used for names that resolve to multiple addresses. For good
-reliability the client should have at least three servers. The `iburst` option
-speeds up the initial synchronisation.
+directive is used with names that resolve to multiple addresses of different
+servers. For reliable operation, the client should have at least three servers.
+
+The `iburst` option enables a burst of requests to speed up the initial
+synchronisation.

 To stabilise the initial synchronisation on the next start, the estimated drift
 of the system clock is saved to a file specified by the `driftfile` directive.
@@ -67,8 +69,8 @@ next boot from the RTC, the `rtcsync` directive enables a mode in which the
 system time is periodically copied to the RTC. It is supported on Linux and
 macOS.

-If you want to use public NTP servers from the
-http://www.pool.ntp.org/[pool.ntp.org] project, the minimal _chrony.conf_ file
+If you wanted to use public NTP servers from the
+https://www.pool.ntp.org/[pool.ntp.org] project, the minimal _chrony.conf_ file
 could be:

 ----
@@ -80,9 +82,16 @@ rtcsync

 === How do I make an NTP server?

-You need to add an `allow` directive to the _chrony.conf_ file in order to open
-the NTP port and allow `chronyd` to reply to client requests. `allow` with no
-specified subnet allows access from all IPv4 and IPv6 addresses.
+By default, `chronyd` does not operate as an NTP server. You need to add an
+`allow` directive to the _chrony.conf_ file in order for `chronyd` to open the
+server NTP port and respond to client requests.
+
+----
+allow 192.168.1.0/24
+----
+
+An `allow` directive with no specified subnet allows access from all IPv4 and
+IPv6 addresses.

 === Should all computers on a LAN be clients of an external server?

@@ -128,21 +137,136 @@ versions or implementations of the libraries might make different system calls.
 If the filter is missing some system call, `chronyd` could be killed even in
 normal operation.

+=== How can I make the system clock more secure?
+
+An NTP client synchronising the system clock to an NTP server is susceptible to
+various attacks, which can break applications and network protocols relying on
+accuracy of the clock (e.g. DNSSEC, Kerberos, TLS, WireGuard).
+
+Generally, a man-in-the-middle (MITM) attacker between the client and server
+can
+
+* make fake responses, or modify real responses from the server, to create an
+  arbitrarily large time and frequency offset, make the server appear more
+  accurate, insert a leap second, etc.
+* delay the requests and/or responses to create a limited time offset and
+  temporarily also a limited frequency offset
+* drop the requests or responses to prevent updates of the clock with new
+  measurements
+* redirect the requests to a different server
+
+The attacks can be combined for a greater effect. The attacker can delay
+packets to create a significant frequency offset first and then drop all
+subsequent packets to let the clock quickly drift away from the true time.
+The attacker might also be able to control the server's clock.
+
+Some attacks cannot be prevented. Monitoring is needed for detection, e.g. the
+reachability register in the `sources` report shows missing packets. The extent
+to which the attacker can control the client's clock depends on its
+configuration.
+
+Enable authentication to prevent `chronyd` from accepting modified, fake, or
+redirected packets. It can be enabled with a symmetric key specified by the
+`key` option, or Network Time Security (NTS) by the `nts` option (supported
+since `chrony` version 4.0). The server needs to support the selected
+authentication mechanism. Symmetric keys have to be configured on both client
+and server, and each client must have its own key (one per server).
+
+The maximum offset that the attacker can insert in an NTP measurement by
+delaying packets can be limited by the `maxdelay` option. The default value is
+3 seconds. The measured delay is reported as the peer delay in the `ntpdata`
+report and `measurements` log. Set the `maxdelay` option to a value larger than
+the maximum value that is normally observed. Note that the delay can increase
+significantly even when not under an attack, e.g. when the network is congested
+or the routing has changed.
+
+The maximum accepted change in time offset between clock updates can be limited
+by the `maxchange` directive. Larger changes in the offset will be ignored or
+cause `chronyd` to exit. Note that the attacker can get around this limit by
+splitting the offset into multiple smaller offsets and/or creating a large
+frequency offset. When this directive is used, `chronyd` will have to be
+restarted after a successful attack. It will not be able to recover on its own.
+It must not be restarted automatically (e.g. by the service manager).
+
+The impact of a large accepted time offset can be reduced by disabling clock
+steps, i.e. by not using the `makestep` and `initstepslew` directives. The
+offset will be slowly corrected by speeding up or slowing down the clock at a
+rate which can be limited by the `maxslewrate` directive. Disabling clock steps
+completely is practical only if the clock cannot gain a larger error on its
+own, e.g. when the computer is shut down or suspended, and the `maxslewrate`
+limit is large enough to correct an expected error in an acceptable time. The
+`rtcfile` directive with the `-s` option can be used to compensate for the RTC
+drift.
+
+A more practical approach is to enable `makestep` for a limited number of clock
+updates (the 2nd argument of the directive) and limit the offset change in all
+updates by the `maxchange` directive. The attacker will be able to make only a
+limited step and only if the attack starts in a short window after booting the
+computer, or when `chronyd` is restarted without the `-R` option.
+
+The frequency offset can be limited by the `maxdrift` directive. The measured
+frequency offset is reported in the drift file, `tracking` report, and
+`tracking` log. Set `maxdrift` to a value larger than the maximum absolute
+value that is normally observed. Note that the frequency of the clock can
+change due to aging of the crystal, differences in calibration of the clock
+source between reboots, migrated virtual machine, etc. A typical computer clock
+has a drift smaller than 100 parts per million (ppm), but much larger drifts
+are possible (e.g. in some virtual machines).
+
+Use only trusted servers, which you expect to be well configured and managed,
+using authentication for their own servers, etc. Use multiple servers, ideally
+in different locations. The attacker will have to deal with a majority of the
+servers in order to pass the source selection and update the clock with a large
+offset. Use the `minsources` directive to increase the required number of
+selectable sources to make the selection more robust.
+
+Do not specify servers as peers. The symmetric mode is less secure than the
+client/server mode. If not authenticated, it is vulnerable to off-path
+denial-of-service attacks, and even when it is authenticated, it is still
+susceptible to replay attacks.
+
+Mixing of authenticated and unauthenticated servers should generally be
+avoided. If mixing is necessary (e.g. for a more accurate and stable
+synchronisation to a closer server which does not support authentication), the
+authenticated servers should be configured as trusted and required to not allow
+the unauthenticated servers to override the authenticated servers in the source
+selection. Since `chrony` version 4.0, the selection options are enabled in
+such a case automatically. This behaviour can be disabled or modified by the
+`authselmode` directive.
+
+An example of a client configuration limiting the impact of the attacks could
+be
+
+----
+server foo.example.net iburst nts maxdelay 0.1
+server bar.example.net iburst nts maxdelay 0.2
+server baz.example.net iburst nts maxdelay 0.05
+server qux.example.net iburst nts maxdelay 0.1
+server quux.example.net iburst nts maxdelay 0.1
+minsources 3
+maxchange 100 0 0
+makestep 0.001 1
+maxdrift 100
+maxslewrate 100
+driftfile /var/lib/chrony/drift
+ntsdumpdir /var/lib/chrony
+rtcsync
+----
+
 === How can I improve the accuracy of the system clock with NTP sources?

 Select NTP servers that are well synchronised, stable and close to your
-network. It is better to use more than one server, three or four is usually
+network. It is better to use more than one server. Three or four is usually
 recommended as the minimum, so `chronyd` can detect servers that serve false
 time and combine measurements from multiple sources.

 If you have a network card with hardware timestamping supported on Linux, it
-can be enabled by the `hwtimestamp` directive in the _chrony.conf_ file. It
-should make local receive and transmit timestamps of NTP packets much more
-accurate.
+can be enabled by the `hwtimestamp` directive. It should make local receive and
+transmit timestamps of NTP packets much more stable and accurate.

-There are also useful options which can be set in the `server` directive, they
-are `minpoll`, `maxpoll`, `polltarget`, `maxdelay`, `maxdelayratio`,
-`maxdelaydevratio`, and `xleave`.
+The `server` directive has some useful options: `minpoll`, `maxpoll`,
+`polltarget`, `maxdelay`, `maxdelayratio`, `maxdelaydevratio`, `xleave`,
+`filter`.

 The first three options set the minimum and maximum allowed polling interval,
 and how should be the actual interval adjusted in the specified range. Their
@@ -177,7 +301,7 @@ LAN could be
 server ntp.local minpoll 2 maxpoll 4 polltarget 30
 ----

-The maxdelay options are useful to ignore measurements with an unusally large
+The maxdelay options are useful to ignore measurements with an unusually large
 delay (e.g. due to congestion in the network) and improve the stability of the
 synchronisation. The `maxdelaydevratio` option could be added to the example
 with local NTP server
@@ -187,8 +311,8 @@ server ntp.local minpoll 2 maxpoll 4 polltarget 30 maxdelaydevratio 2
 ----

 If your server supports the interleaved mode (e.g. it is running `chronyd`),
-the `xleave` option should be added to the `server` directive in order to allow
-the server to send the client more accurate transmit timestamps (kernel or
+the `xleave` option should be added to the `server` directive to enable the
+server to provide the client with more accurate transmit timestamps (kernel or
 preferably hardware). For example:

 ----
@@ -221,6 +345,24 @@ server ntp.local minpoll -6 maxpoll -6 filter 15 xleave
 hwtimestamp eth0 minpoll -6
 ----

+Since `chrony` version 4.3, the minimum `minpoll` is -7 and a filter using a
+long-term estimate of a delay quantile can be enabled by the `maxdelayquant`
+option to replace the default `maxdelaydevratio` filter, which is sensitive to
+outliers corrupting the minimum delay. For example:
+
+----
+server ntp.local minpoll -7 maxpoll -7 filter 31 maxdelayquant 0.3 xleave
+----
+
+As an experimental feature added in version 4.2, `chronyd` supports an NTPv4
+extension field containing an additional timestamp to enable frequency transfer
+and significantly improve stability of synchronisation. It can be enabled by
+the `extfield F323` option. For example:
+
+----
+server ntp.local minpoll 0 maxpoll 0 xleave extfield F323
+----
+
 === Does `chronyd` have an ntpdate mode?

 Yes. With the `-q` option `chronyd` will set the system clock once and exit.
@@ -237,7 +379,7 @@ well synchronised and responding to all requests. If not synchronised or
 responding, it would take about 10 seconds for `chronyd` to give up and exit
 with a non-zero status. A faster configuration is possible. A single server can
 be used instead of four servers, the number of measurements can be reduced with
-the `maxsamples` option to one (supported in `chrony` version 4.0), and a
+the `maxsamples` option to one (supported since `chrony` version 4.0), and a
 timeout can be specified with the `-t` option. The following command would take
 only up to about one second.

@@ -284,18 +426,49 @@ and be unsuitable for monitoring.

 === Can NTP server be separated from NTP client?

-Yes, it is possible to run multiple instances of `chronyd` on the same
-computer. One can be configured as an NTP client, and another as a server. They
-need to use different pidfiles, NTP ports, command ports, and Unix domain
-command sockets. The server instance should be started with the `-x` option to
-avoid touching the clock. It can be configured to serve the system time with
-the `local` directive, or synchronise its NTP clock to the client instance
-running on localhost using a non-standard NTP port.
+Yes, it is possible to run multiple instances of `chronyd` on a computer at the
+same time. One can operate primarily as an NTP client to synchronise the system
+clock and another as a server for other computers. If they use the same
+filesystem, they need to be configured with different pidfiles, Unix domain
+command sockets, and any other file or directory specified in the configuration
+file. If they run in the same network namespace, they need to use different NTP
+and command ports, or bind the ports to different addresses or interfaces.

-On Linux, starting with `chrony` version 4.0, it is also possible to run
-multiple server instances sharing a port to utilise multiple cores of the CPU.
-Note that the client/server interleaved mode requires that all packets from an
-address are handled by the same server instance.
+The server instance should be started with the `-x` option to prevent it from
+adjusting the system clock and interfering with the client instance. It can be
+configured as a client to synchronise its NTP clock to other servers, or the
+client instance running on the same computer. In the latter case, the `copy`
+option (added in `chrony` version 4.1) can be used to assume the reference ID
+and stratum of the client instance, which enables detection of synchronisation
+loops with its own clients.
+
+On Linux, starting with `chrony` version 4.0, it is possible to run multiple
+server instances sharing a port to better utilise multiple cores of the CPU.
+Note that for rate limiting and client/server interleaved mode to work well
+it is necessary that all packets received from the same address are handled by
+the same server instance.
+
+An example configuration of the client instance could be
+
+----
+pool pool.ntp.org iburst
+allow 127.0.0.1
+port 11123
+driftfile /var/lib/chrony/drift
+makestep 1 3
+rtcsync
+----
+
+and configuration of the first server instance could be
+
+----
+server 127.0.0.1 port 11123 minpoll 0 maxpoll 0 copy
+allow
+cmdport 11323
+bindcmdaddress /var/run/chrony/chronyd-server1.sock
+pidfile /var/run/chronyd-server1.pid
+driftfile /var/lib/chrony/drift-server1
+----

 === Should be a leap smear enabled on NTP server?

@@ -308,12 +481,71 @@ e.g. when the clients cannot be configured to handle the leap seconds as
 needed, or their number is so large that configuring them all would be
 impractical. The clients should use only one leap-smearing server, or multiple
 identically configured leap-smearing servers. Note that some clients can get
-leap seconds from external sources (e.g. with the `leapsectz` directive in
+leap seconds from other sources (e.g. with the `leapsectz` directive in
 `chrony`) and they will not work correctly with a leap smearing server.

+=== How should `chronyd` be configuration with `gpsd`?
+
+A GPS or other GNSS receiver can be used as a reference clock with `gpsd`. It
+can work as one or two separate time sources for each connected receiver. The
+first time source is based on timestamping of messages sent by the receiver.
+Typically, it is accurate to milliseconds. The other source is much more
+accurate. It is timestamping a pulse-per-second (PPS) signal, usually connected
+to a serial port (e.g. DCD pin) or GPIO pin.
+
+If the PPS signal is connected to the serial port which is receiving messages
+from the GPS/GNSS receiver, `gpsd` should detect and use it automatically. If
+it is connected to a GPIO pin, or another serial port, the PPS device needs to
+be specified on the command line as an additional data source. On Linux, the
+`ldattach` utility can be used to create a PPS device for a serial device.
+
+The message-based time source provided by `gpsd` is specified as a `SHM 0`
+refclock, or other even number if `gpsd` is configured with multiple receivers.
+
+The PPS-based time source is specified as a `SHM 1` refclock (or other odd
+number), or `SOCK /var/run/chrony.DEV.sock` where `DEV` is the name of the
+serial device (e.g. ttyS0).
+
+With `chronyd` and `gpsd` both supporting PPS, and `gpsd` providing two
+different refclocks for PPS, there are three different recommended
+configurations:
+
+----
+# First option
+refclock SOCK /var/run/chrony.ttyS0.sock refid GPS
+
+# Second option
+refclock SHM 1 refid GPS
+
+# Third option
+refclock PPS /dev/pps0 lock NMEA refid GPS
+refclock SHM 0 offset 0.5 delay 0.1 refid NMEA noselect
+----
+
+Each option has some advantages:
+
+* `SOCK` does not use polling (i.e. it can get samples earlier than `SHM`),
+  but it requires `gpsd` to be started after `chronyd` in order to connect to
+  its socket
+* `SOCK` and `SHM 1` can be more accurate than `PPS` if `gpsd` corrects for the
+  sawtooth error provided by the receiver in serial data
+* `PPS` can be used with higher PPS rates (specified by the `rate` option),
+  but it requires a second refclock or another time source to pair pulses
+  with seconds, and the `SHM 0` offset needs to be specified
+  <<using-pps-refclock,correctly>> to compensate for the message delay, while
+  `gpsd` can apply HW-specific information
+
+If the PPS signal is not available, or cannot be used for some reason, the only
+option is the message-based timing
+
+----
+refclock SHM 0 offset 0.5 delay 0.1 refid GPS
+----
+
 === Does `chrony` support PTP?

-No, the Precision Time Protocol (PTP) is not supported and there are no plans
+No, the Precision Time Protocol (PTP) is not supported as a protocol for
+synchronisation of clocks and there are no plans
 to support it. It is a complex protocol, which shares some issues with the
 NTP broadcast mode. One of the main differences between NTP and PTP is that PTP
 was designed to be easily supported in hardware (e.g. network switches and
@@ -328,6 +560,32 @@ packets (enabled by the `hwtimestamp` directive) if the NIC can timestamp other
 packets than PTP, which is usually the case at least for transmitted packets.
 The `ethtool -T` command can be used to verify the timestamping support.

+As an experimental feature added in version 4.2, `chrony` can use PTP as a
+transport for NTP messages (NTP over PTP) to enable hardware timestamping on
+hardware which can timestamp PTP packets only. It can be enabled by the
+`ptpport` directive.
+
+=== Why are client log records dropped before reaching `clientloglimit`?
+
+The number of dropped client log records reported by the `serverstats` command
+can be increasing before the number of clients reported by the `clients` command
+reaches the maximum value corresponding to the memory limit set by the
+`clientloglimit` directive.
+
+This is due to the design of the data structure keeping the client records. It
+is a hash table which can store only up to 16 colliding addresses per slot. If
+a slot has more collisions and the table already has the maximum size, the
+oldest record will be dropped and replaced by the new client.
+
+Note that the size of the table is always a power of two and it can only grow.
+The limit set by the `clientloglimit` directive takes into account that two
+copies of the table exist when it is being resized. This means the actual
+memory usage reported by `top` and other utilities can be significantly smaller
+than the limit even when the maximum number of records is used.
+
+The absolute maximum number of client records kept at the same time is
+16777216.
+
 === What happened to the `commandkey` and `generatecommandkey` directives?

 They were removed in version 2.2. Authentication is no longer supported in the
@@ -355,7 +613,6 @@ When `chronyd` is receiving responses from the servers, the output of the
 this:

 ----
-210 Number of sources = 3
 MS Name/IP address         Stratum Poll Reach LastRx Last sample
 ===============================================================================
 ^* foo.example.net               2   6   377    34   +484us[ -157us] +/-   30ms
@@ -379,6 +636,19 @@ example:
 0 sources with unknown address
 ----

+=== Is name resolution working correctly?
+
+NTP servers specified by their hostname (instead of an IP address) have to have
+their names resolved before `chronyd` can send any requests to them. If the
+`activity` command prints a non-zero number of sources with unknown address,
+there is an issue with the resolution. Typically, a DNS server is specified in
+_/etc/resolv.conf_. Make sure it is working correctly.
+
+Since `chrony` version 4.0, you can run `chronyc -N sources -a` command to
+print all sources, even those that do not have a known address yet, with their
+names as they were specified in the configuration. This can be useful to verify
+that the names specified in the configuration are used as expected.
+
 === Is `chronyd` allowed to step the system clock?

 By default, `chronyd` adjusts the clock gradually by slowing it down or
@@ -405,6 +675,62 @@ to
 makestep 1 -1
 ----

+=== Using NTS?
+
+The Network Time Security (NTS) mechanism uses Transport Layer Security (TLS)
+to establish the keys needed for authentication of NTP packets.
+
+Run the `authdata` command to check whether the key establishment was
+successful:
+
+----
+# chronyc -N authdata
+Name/IP address             Mode KeyID Type KLen Last Atmp  NAK Cook CLen
+=========================================================================
+foo.example.net              NTS     1   15  256  33m    0    0    8  100
+bar.example.net              NTS     1   15  256  33m    0    0    8  100
+baz.example.net              NTS     1   15  256  33m    0    0    8  100
+----
+
+The KeyID, Type, and KLen columns should have non-zero values. If they are
+zero, check the system log for error messages from `chronyd`. One possible
+cause of failure is a firewall blocking the client's connection to the server's
+TCP port 4460.
+
+Another possible cause of failure is a certificate that is failing to verify
+because the client's clock is wrong. This is a chicken-and-egg problem with NTS.
+You might need to manually correct the date, or temporarily disable NTS, in
+order to get NTS working. If your computer has an RTC and it is backed up by a
+good battery, this operation should be needed only once, assuming the RTC will
+be set periodically with the `rtcsync` directive, or compensated with the
+`rtcfile` directive and the `-s` option.
+
+If the computer does not have an RTC or battery, you can use the `-s` option
+without `rtcfile` directive to restore time of the last shutdown or reboot from
+the drift file. The clock will start behind the true time, but if the computer
+was not shut down for too long and the server's certificate was not renewed too
+close to its expiration, it should be sufficient for the time checks to
+succeed.
+
+If you run your own server, you can use a self-signed certificate covering
+all dates where the client can start (e.g. years 1970-2100). The certificate
+needs to be installed on the client and specified with the `ntstrustedcerts`
+directive. The server can have multiple names and certificates. To avoid
+trusting a certificate for too long, a new certificate can be added to the
+server periodically (e.g. once per year) and the client can have the server
+name and trusted certificate updated automatically (e.g. using a package
+repository, or a cron script downloading the files directly from the server
+over HTTPS). A client that was shut down for years will still be able to
+synchronise its clock and perform the update as long as the server keeps
+the old certificate.
+
+As a last resort, you can disable the time checks by the `nocerttimecheck`
+directive. This has some important security implications. To reduce the
+security risk, you can use the `nosystemcert` and `ntstrustedcerts` directives
+to disable the system's default trusted certificate authorities and trust only
+a minimal set of selected authorities needed to validate the certificates of
+used NTP servers.
+
 === Using a Windows NTP server?

 A common issue with Windows NTP servers is that they report a very large root
@@ -428,8 +754,7 @@ are marked with the _*_ or _+_ symbol in the report printed by the `sources`
 command.

 When the best source (marked with the _*_ symbol) becomes unreachable (e.g. NTP
-server stops responding), or the measurements are no longer accepted (e.g. a
-change in network routing adds a delay), `chronyd` will not immediately switch
+server stops responding), `chronyd` will not immediately switch
 to the second best source in an attempt to minimise the error of the clock. It
 will let the clock run free for as long as its estimated error (in terms of
 root distance) based on previous measurements is smaller than the estimated
@@ -437,18 +762,44 @@ error of the second source, and there is still an interval which contains some
 measurements from both sources.

 If the first source was significantly better than the second source, it can
-take many hours (up to 64 times the maximum polling interval) before the second
-source is selected. If you do not like this behaviour, you can force a faster
-reselection by increasing the clock error rate (`maxclockerror` directive),
-shortening the polling interval (`maxpoll` option), or reducing the number of
-samples (`maxsamples` option).
+take many hours before the second source is selected, depending on its polling
+interval. You can force a faster reselection by increasing the clock error rate
+(`maxclockerror` directive), shortening the polling interval (`maxpoll`
+option), or reducing the number of samples (`maxsamples` option).

+=== Does selected source drop new measurements?
+
+`chronyd` can drop a large number of successive NTP measurements if they are
+not passing some of the NTP tests. The `sources` command can report for a
+selected source the fully-reachable value of 377 in the Reach column and at the
+same time a LastRx value that is much larger than the current polling interval.
+If the source is online, this indicates that a number of measurements was
+dropped. You can use the `ntpdata` command to check the NTP tests for the last
+measurement. Usually, it is the test C which fails.
+
+This can be an issue when there is a long-lasting increase in the measured
+delay, e.g. due to a routing change in the network. Unfortunately, `chronyd`
+does not know for how long it should wait for the delay to come back to the
+original values, or whether it is a permanent increase and it should start from
+scratch.
+
+The test C is an adaptive filter. It can take many hours before it accepts
+a measurement with the larger delay, and even much longer before it drops all
+measurements with smaller delay, which determine an expected delay used by the
+test. You can use the `reset sources` command to drop all measurements
+immediately (available in chrony 4.0 and later). If this issue happens
+frequently, you can effectively disable the test by setting the
+`maxdelaydevratio` option to a very large value (e.g. 1000000), or speed up the
+recovery by increasing the clock error rate with the `maxclockerror` directive.
+
+[[using-pps-refclock]]
 === Using a PPS reference clock?

 A pulse-per-second (PPS) reference clock requires a non-PPS time source to
 determine which second of UTC corresponds to each pulse. If it is another
 reference clock specified with the `lock` option in the `refclock` directive,
-the offset between the two reference clocks must be smaller than 0.2 seconds in
+the offset between the two reference clocks must be smaller than 0.4 seconds
+(0.2 seconds with `chrony` versions before 4.1) in
 order for the PPS reference clock to work. With NMEA reference clocks it is
 common to have a larger offset. It needs to be corrected with the `offset`
 option.
@@ -467,7 +818,7 @@ foo.example.net             7   3   200     -2.991     16.141   -107us   492us

 the offset of the NMEA source would need to be increased by about 0.504
 seconds. It does not have to be very accurate. As long as the offset of the
-NMEA reference clock stays below 0.2 seconds, the PPS reference clock should be
+NMEA reference clock stays below the limit, the PPS reference clock should be
 able to determine the seconds corresponding to the pulses and allow the samples
 to be used for synchronisation.

@@ -523,6 +874,10 @@ in parentheses) on the `Reference ID` line.
 Only by the source code. See _cmdmon.c_ (`chronyd` side) and _client.c_
 (`chronyc` side).

+Note that this protocol is not compatible with the mode 6 or mode 7 protocol
+supported by `ntpd`, i.e. the `ntpq` or `ntpdc` utility cannot be used to
+monitor `chronyd`, and `chronyc` cannot be used to monitor `ntpd`.
+
 == Real-time clock issues

 === What is the real-time clock (RTC)?
@@ -533,7 +888,7 @@ more than few seconds per day.

 There are two approaches how `chronyd` can work with it. One is to use the
 `rtcsync` directive, which tells `chronyd` to enable a kernel mode which sets
-the RTC from the system clock every 11 minutes. `chronyd` itself won't touch
+the RTC from the system clock every 11 minutes. `chronyd` itself will not touch
 the RTC. If the computer is not turned off for a long time, the RTC should
 still be close to the true time when the system clock will be initialised from
 it on the next boot.
@@ -548,12 +903,12 @@ it is not strictly necessary if its only purpose is to set the system clock when

 === Does `hwclock` have to be disabled?

-The `hwclock` program is often set-up by default in the boot and shutdown
-scripts with many Linux installations. With the kernel RTC synchronisation
+The `hwclock` program is run by default in the boot and/or shutdown
+scripts in some Linux installations. With the kernel RTC synchronisation
 (`rtcsync` directive), the RTC will be set also every 11 minutes as long as the
 system clock is synchronised. If you want to use ``chronyd``'s RTC monitoring
 (`rtcfile` directive), it is important to disable `hwclock` in the shutdown
-procedure. If you do not that, it will over-write the RTC with a new value, unknown
+procedure. If you do not do that, it will overwrite the RTC with a new value, unknown
 to `chronyd`. At the next reboot, `chronyd` started with the `-s` option will
 compensate this (wrong) time with its estimate of how far the RTC has drifted
 whilst the power was off, giving a meaningless initial system time.
@@ -574,6 +929,19 @@ things

 Some other program running on the system might be using the device.

+=== When I start `chronyd`, the log says `Could not enable RTC interrupt : Invalid argument` (or it may say `disable`)
+
+Your real-time clock hardware might not support the required ioctl requests:
+
+* `RTC_UIE_ON`
+* `RTC_UIE_OFF`
+
+A possible solution could be to build the Linux kernel with support for software
+emulation instead; try enabling the following configuration option when building
+the Linux kernel:
+
+* `CONFIG_RTC_INTF_DEV_UIE_EMUL`
+
 === What if my computer does not have an RTC or backup battery?

 In this case you can still use the `-s` option to set the system clock to the
@@ -630,11 +998,39 @@ When two computers are synchronised to each other using the client/server or
 symmetric NTP mode, there is an expectation that NTP measurements between the
 two computers made on both ends show an average offset close to zero.

-With `chronyd` that can be expected only when the interleaved mode (`xleave`
-option) is enabled. Otherwise, `chronyd` will use different transmit timestamps
-(e.g. daemon timestamp vs kernel timestamp) for serving time and
-synchronisation of its own clock, which creates an asymmetry in the
-timestamping and causes the other end to measure a significant offset.
+With `chronyd` that can be expected only when the interleaved mode is enabled
+by the `xleave` option. Otherwise, `chronyd` will use different transmit
+timestamps (e.g. daemon timestamp vs kernel timestamp) for serving time and
+synchronisation of its own clock, which will cause the other computer to
+measure a significant offset.
+
+== Operation
+
+=== What clocks does `chronyd` use?
+
+There are several different clocks used by `chronyd`:
+
+* *System clock:* software clock maintained by the kernel. It is the main clock
+  used by applications running on the computer. It is synchronised by `chronyd`
+  to its NTP clock, unless started with the *-x* option.
+* *NTP clock:* software clock (virtual) based on the system clock and internal
+  to `chronyd`. It keeps the best estimate of the true time according to the
+  configured time sources, which is served to NTP clients unless time smoothing
+  is enabled by the *smoothtime* directive. The *System time* value in the
+  `tracking` report is the current offset between the system and NTP clock.
+* *Real-time clock (RTC):* hardware clock keeping time even when the
+  computer is turned off. It is used by the kernel to initialise the system
+  clock on boot and also by `chronyd` to compensate for its measured drift if
+  configured with the `rtcfile` directive and started with the `-s` option.
+  The clock can be kept accurate only by stepping enabled by the `rtcsync` or
+  `rtcautotrim` directive.
+* *Reference clock:* hardware clock used as a time source. It is specified by
+  the `refclock` directive.
+* *NIC clock (also known as PTP hardware clock):* hardware clock timestamping
+  packets received and transmitted by a network device specified by the
+  *hwtimestamp* directive. The clock is expected to be running free. It is not
+  synchronised by `chronyd`. Its offset is tracked relative to the NTP clock in
+  order to convert the hardware timestamps.

 == Operating systems

--- a/doc/installation.adoc
+++ b/doc/installation.adoc
@@ -27,7 +27,7 @@ The following libraries with their development files, and programs, are needed
 to enable optional features:

 * pkg-config: detection of development libraries
-* Nettle, NSS, or LibTomCrypt: secure hash functions (`SECHASH`)
+* 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`)
@@ -94,7 +94,7 @@ want to enable the support, specify the `--disable-asyncdns` flag to

 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
-http://www.libtom.net/LibTomCrypt/[libtomcrypt] library are available,
+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
--- a/examples/chrony-wait.service
+++ b/examples/chrony-wait.service
@@ -16,5 +16,32 @@ 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.example2
+++ b/examples/chrony.conf.example2
@@ -1,5 +1,5 @@
 # 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.
--- a/examples/chrony.nm-dispatcher.dhcp
+++ b/examples/chrony.nm-dispatcher.dhcp
@@ -1,8 +1,7 @@
 #!/bin/sh
 # This is a NetworkManager dispatcher script for chronyd to update
-# its NTP sources passed from DHCP options. Note that this script is
-# specific to NetworkManager-dispatcher due to use of the
-# DHCP4_NTP_SERVERS environment variable.
+# 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

@@ -10,17 +9,23 @@ interface=$1
 action=$2

 chronyc=/usr/bin/chronyc
-default_server_options=iburst
+server_options=iburst
 server_dir=/var/run/chrony-dhcp

 dhcp_server_file=$server_dir/$interface.sources
-# DHCP4_NTP_SERVERS is passed from DHCP options by NetworkManager.
-nm_dhcp_servers=$DHCP4_NTP_SERVERS
+dhcp_ntp_servers="$DHCP4_NTP_SERVERS $DHCP6_DHCP6_NTP_SERVERS"

 add_servers_from_dhcp() {
    rm -f "$dhcp_server_file"
-    for server in $nm_dhcp_servers; do
-        echo "server $server $default_server_options" >> "$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 || :
 }
@@ -34,10 +39,11 @@ clear_servers_from_dhcp() {

 mkdir -p $server_dir

-if [ "$action" = "up" ] || [ "$action" = "dhcp4-change" ]; then
-    add_servers_from_dhcp
-elif [ "$action" = "down" ]; then
-    clear_servers_from_dhcp
-fi
+case "$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
@@ -7,8 +7,18 @@ export LC_ALL=C

 chronyc=/usr/bin/chronyc

-# For NetworkManager consider only up/down events
-[ $# -ge 2 ] && [ "$2" != "up" ] && [ "$2" != "down" ] && exit 0
+# 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

--- a/examples/chronyd.service
+++ b/examples/chronyd.service
@@ -10,9 +10,40 @@ Type=forking
 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
-ProtectSystem=full
+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
@@ -44,6 +44,7 @@ typedef enum {
  HSH_SHA3_512 = 9,
  HSH_TIGER = 10,
  HSH_WHIRLPOOL = 11,
+  HSH_MD5_NONCRYPTO = 10000, /* For NTPv4 reference ID */
 } HSH_Algorithm;

 extern int HSH_GetHashId(HSH_Algorithm algorithm);
--- 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
@@ -39,7 +39,7 @@ int
 HSH_GetHashId(HSH_Algorithm algorithm)
 {
  /* only MD5 is supported */
-  if (algorithm != HSH_MD5)
+  if (algorithm != HSH_MD5 && algorithm != HSH_MD5_NONCRYPTO)
    return -1;

  return 0;
--- a/hash_nettle.c
+++ b/hash_nettle.c
@@ -59,6 +59,9 @@ 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;
--- a/hash_nss.c
+++ b/hash_nss.c
@@ -56,6 +56,9 @@ HSH_GetHashId(HSH_Algorithm algorithm)
 {
  int i;

+  if (algorithm == HSH_MD5_NONCRYPTO)
+    algorithm = HSH_MD5;
+
  for (i = 0; hashes[i].algorithm != 0; i++) {
    if (hashes[i].algorithm == algorithm)
      break;
--- a/hash_tomcrypt.c
+++ b/hash_tomcrypt.c
@@ -71,6 +71,9 @@ HSH_GetHashId(HSH_Algorithm algorithm)
 {
  int i, h;

+  if (algorithm == HSH_MD5_NONCRYPTO)
+    algorithm = HSH_MD5;
+
  for (i = 0; hashes[i].algorithm != 0; i++) {
    if (hashes[i].algorithm == algorithm)
      break;
--- a/hwclock.c
+++ b/hwclock.c
@@ -2,7 +2,7 @@
  chronyd/chronyc - Programs for keeping computer clocks accurate.

 **********************************************************************
- * Copyright (C) Miroslav Lichvar  2016-2018
+ * Copyright (C) Miroslav Lichvar  2016-2018, 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
@@ -33,6 +33,7 @@
 #include "local.h"
 #include "logging.h"
 #include "memory.h"
+#include "quantiles.h"
 #include "regress.h"
 #include "util.h"

@@ -43,6 +44,13 @@
 /* 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 */
  struct timespec hw_ref;
@@ -64,12 +72,18 @@ struct HCL_Instance_Record {
  /* 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;
 };

 /* ================================================== */
@@ -92,7 +106,7 @@ handle_slew(struct timespec *raw, struct timespec *cooked, double dfreq,
 /* ================================================== */

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

@@ -110,6 +124,10 @@ HCL_CreateInstance(int min_samples, int max_samples, double min_separation)
  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);

@@ -121,6 +139,7 @@ HCL_CreateInstance(int min_samples, int max_samples, double min_separation)
 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);
@@ -140,6 +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)
--- a/hwclock.h
+++ b/hwclock.h
@@ -30,7 +30,7 @@ typedef struct HCL_Instance_Record *HCL_Instance;

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

 /* Destroy a HW clock instance */
 extern void HCL_DestroyInstance(HCL_Instance clock);
@@ -38,6 +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/local.c
+++ b/local.c
@@ -505,7 +505,7 @@ LCL_AccumulateDeltaFrequency(double dfreq)

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

-void
+int
 LCL_AccumulateOffset(double offset, double corr_rate)
 {
  struct timespec raw, cooked;
@@ -517,12 +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;
 }

 /* ================================================== */
@@ -561,6 +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);

@@ -586,7 +590,7 @@ LCL_NotifyLeap(int leap)

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

-void
+int
 LCL_AccumulateFrequencyAndOffset(double dfreq, double doffset, double corr_rate)
 {
  struct timespec raw, cooked;
@@ -598,7 +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;

@@ -620,6 +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;
 }

 /* ================================================== */
@@ -687,6 +711,19 @@ LCL_MakeStep(void)

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

+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)
 {
--- 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);
@@ -197,6 +202,9 @@ 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);
--- a/main.c
+++ b/main.c
@@ -76,11 +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);
 }

 /* ================================================== */
@@ -104,6 +111,7 @@ MAI_CleanupAndExit(void)
 {
  if (!initialised) exit(exit_status);
  
+  LCL_CancelOffsetCorrection();
  SRC_DumpSources();

  /* Don't update clock when removing sources */
@@ -140,6 +148,8 @@ MAI_CleanupAndExit(void)
  HSH_Finalise();
  LOG_Finalise();

+  UTI_ResetGetRandomFunctions();
+
  exit(exit_status);
 }

@@ -156,6 +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();
@@ -183,7 +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();
  }
@@ -374,8 +386,34 @@ go_daemon(void)
 static void
 print_help(const char *progname)
 {
-      printf("Usage: %s [-4|-6] [-n|-d] [-p|-q|-Q] [-r] [-R] [-s] [-t TIMEOUT] [-f FILE|COMMAND...]\n",
-             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);
 }

 /* ================================================== */
@@ -417,7 +455,7 @@ int main

  LOG_Initialise();

-  /* Parse (undocumented) long command-line options */
+  /* Parse long command-line options */
  for (optind = 1; optind < argc; optind++) {
    if (!strcmp("--help", argv[optind])) {
      print_help(progname);
@@ -465,6 +503,7 @@ int main
        user_check = 0;
        nofork = 1;
        system_log = 0;
+        log_severity = LOGS_WARN;
        break;
      case 'P':
        sched_priority = parse_int_arg(optarg);
@@ -599,7 +638,10 @@ int main

  /* 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_DropRoot(pw->pw_uid, pw->pw_gid, SYS_MAIN_PROCESS);
+
+  if (!geteuid())
+    LOG(LOGS_WARN, "Running with root privileges");

  REF_Initialise();
  SST_Initialise();
--- a/nameserv.c
+++ b/nameserv.c
@@ -50,12 +50,24 @@ 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));

  switch (address_family) {
@@ -107,48 +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
 }

 /* ================================================== */
@@ -157,9 +130,11 @@ 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];
@@ -167,29 +142,9 @@ DNS_IPAddress2Name(IPAddr *ip_addr, char *name, int len)
  ip_saddr.ip_addr = *ip_addr;
  ip_saddr.port = 0;

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

  if (result == NULL)
    result = UTI_IPToString(ip_addr);
--- a/ntp.h
+++ b/ntp.h
@@ -113,13 +113,38 @@ 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,           /* MAC using symmetric key (RFC 1305, RFC 5905) */
+  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 ????) */
+  NTP_AUTH_NTS,                 /* Network Time Security (RFC 8915) */
 } NTP_AuthMode;

 /* Structure describing an NTP packet */
@@ -129,6 +154,7 @@ typedef struct {
  NTP_Mode mode;

  int ext_fields;
+  int ext_field_flags;

  struct {
    NTP_AuthMode mode;
@@ -151,7 +177,6 @@ typedef struct {
  double peer_dispersion;
  double root_delay;
  double root_dispersion;
-  int stratum;
 } NTP_Sample;

 #endif /* GOT_NTP_H */
--- a/ntp_auth.c
+++ b/ntp_auth.c
@@ -32,7 +32,6 @@
 #include "logging.h"
 #include "memory.h"
 #include "ntp_auth.h"
-#include "ntp_ext.h"
 #include "ntp_signd.h"
 #include "nts_ntp.h"
 #include "nts_ntp_client.h"
@@ -105,19 +104,6 @@ check_symmetric_auth(NTP_Packet *packet, NTP_PacketInfo *info)

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

-static int
-is_zero_data(unsigned char *data, int length)
-{
-  int i;
-
-  for (i = 0; i < length; i++)
-    if (data[i] != 0)
-      return 0;
-  return 1;
-}
-
-/* ================================================== */
-
 static NAU_Instance
 create_instance(NTP_AuthMode mode)
 {
@@ -161,11 +147,12 @@ NAU_CreateSymmetricInstance(uint32_t key_id)
 /* ================================================== */

 NAU_Instance
-NAU_CreateNtsInstance(IPSockAddr *nts_address, const char *name, const IPSockAddr *ntp_address)
+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, ntp_address);
+  instance->nts = NNC_CreateInstance(nts_address, name, cert_set, ntp_port);

  return instance;
 }
@@ -175,7 +162,7 @@ NAU_CreateNtsInstance(IPSockAddr *nts_address, const char *name, const IPSockAdd
 void
 NAU_DestroyInstance(NAU_Instance instance)
 {
-  if (instance->nts)
+  if (instance->mode == NTP_AUTH_NTS)
    NNC_DestroyInstance(instance->nts);
  Free(instance);
 }
@@ -246,101 +233,6 @@ NAU_GenerateRequestAuth(NAU_Instance instance, NTP_Packet *request, NTP_PacketIn

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

-int
-NAU_ParsePacket(NTP_Packet *packet, NTP_PacketInfo *info)
-{
-  int parsed, remainder, ef_length, ef_type;
-  unsigned char *data;
-
-  data = (void *)packet;
-  parsed = NTP_HEADER_LENGTH;
-  remainder = info->length - parsed;
-
-  info->ext_fields = 0;
-
-  /* Check if this is a plain NTP packet with no extension fields or MAC */
-  if (remainder <= 0)
-    return 1;
-
-  assert(remainder % 4 == 0);
-
-  /* In NTPv3 and older packets don't have extension fields.  Anything after
-     the header is assumed to be a MAC. */
-  if (info->version <= 3) {
-    info->auth.mode = NTP_AUTH_SYMMETRIC;
-    info->auth.mac.start = parsed;
-    info->auth.mac.length = remainder;
-    info->auth.mac.key_id = ntohl(*(uint32_t *)(data + parsed));
-
-    /* Check if it is an MS-SNTP authenticator field or extended authenticator
-       field with zeroes as digest */
-    if (info->version == 3 && info->auth.mac.key_id != 0) {
-      if (remainder == 20 && is_zero_data(data + parsed + 4, remainder - 4))
-        info->auth.mode = NTP_AUTH_MSSNTP;
-      else if (remainder == 72 && is_zero_data(data + parsed + 8, remainder - 8))
-        info->auth.mode = NTP_AUTH_MSSNTP_EXT;
-    }
-
-    return 1;
-  }
-
-  /* Check for a crypto NAK */
-  if (remainder == 4 && ntohl(*(uint32_t *)(data + parsed)) == 0) {
-    info->auth.mode = NTP_AUTH_SYMMETRIC;
-    info->auth.mac.start = parsed;
-    info->auth.mac.length = remainder;
-    info->auth.mac.key_id = 0;
-    return 1;
-  }
-
-  /* Parse the rest of the NTPv4 packet */
-
-  while (remainder > 0) {
-    /* Check if the remaining data is a MAC */
-    if (remainder >= NTP_MIN_MAC_LENGTH && remainder <= NTP_MAX_V4_MAC_LENGTH)
-      break;
-
-    /* Check if this is a valid NTPv4 extension field and skip it */
-    if (!NEF_ParseField(packet, info->length, parsed, &ef_length, &ef_type, NULL, NULL)) {
-      DEBUG_LOG("Invalid format");
-      return 0;
-    }
-
-    assert(ef_length > 0 && ef_length % 4 == 0);
-
-    switch (ef_type) {
-      case NTP_EF_NTS_UNIQUE_IDENTIFIER:
-      case NTP_EF_NTS_COOKIE:
-      case NTP_EF_NTS_COOKIE_PLACEHOLDER:
-      case NTP_EF_NTS_AUTH_AND_EEF:
-        info->auth.mode = NTP_AUTH_NTS;
-        break;
-      default:
-        DEBUG_LOG("Unknown extension field type=%x", (unsigned int)ef_type);
-    }
-
-    info->ext_fields++;
-    parsed += ef_length;
-    remainder = info->length - parsed;
-  }
-
-  if (remainder == 0) {
-    /* No MAC */
-    return 1;
-  } else if (remainder >= NTP_MIN_MAC_LENGTH) {
-    info->auth.mode = NTP_AUTH_SYMMETRIC;
-    info->auth.mac.start = parsed;
-    info->auth.mac.length = remainder;
-    info->auth.mac.key_id = ntohl(*(uint32_t *)(data + parsed));
-    return 1;
-  }
-
-  DEBUG_LOG("Invalid format");
-  return 0;
-}
-
-/* ================================================== */
-
 int
 NAU_CheckRequestAuth(NTP_Packet *request, NTP_PacketInfo *info, uint32_t *kod)
 {
--- a/ntp_auth.h
+++ b/ntp_auth.h
@@ -37,7 +37,7 @@ typedef struct NAU_Instance_Record *NAU_Instance;
 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,
-                                          const IPSockAddr *ntp_address);
+                                          uint32_t cert_set, uint16_t ntp_port);

 /* Destroy an instance */
 extern void NAU_DestroyInstance(NAU_Instance instance);
@@ -55,9 +55,6 @@ extern int NAU_PrepareRequestAuth(NAU_Instance instance);
 extern int NAU_GenerateRequestAuth(NAU_Instance instance, NTP_Packet *request,
                                   NTP_PacketInfo *info);

-/* Parse a request or response to detect the authentication mode */
-extern int NAU_ParsePacket(NTP_Packet *packet, 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);
--- a/ntp_core.c
+++ b/ntp_core.c
--- a/ntp_io.c
+++ b/ntp_io.c
@@ -4,7 +4,7 @@
 **********************************************************************
 * Copyright (C) Richard P. Curnow  1997-2003
 * Copyright (C) Timo Teras  2009
- * Copyright (C) Miroslav Lichvar  2009, 2013-2016, 2018-2020
+ * Copyright (C) Miroslav Lichvar  2009, 2013-2016, 2018-2021
 * 
 * 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
@@ -30,9 +30,11 @@

 #include "sysincl.h"

+#include "memory.h"
 #include "ntp_io.h"
 #include "ntp_core.h"
 #include "ntp_sources.h"
+#include "ptp.h"
 #include "sched.h"
 #include "socket.h"
 #include "local.h"
@@ -70,6 +72,16 @@ static int permanent_server_sockets;
 /* Flag indicating the server IPv4 socket is bound to an address */
 static int bound_server_sock_fd4;

+/* PTP event port, or 0 if disabled */
+static int ptp_port;
+
+/* Shared server/client sockets for NTP-over-PTP */
+static int ptp_sock_fd4;
+static int ptp_sock_fd6;
+
+/* Buffer for transmitted NTP-over-PTP messages */
+static PTP_NtpMessage *ptp_message;
+
 /* Flag indicating that we have been initialised */
 static int initialised=0;

@@ -221,6 +233,17 @@ NIO_Initialise(void)
       client_sock_fd4 == INVALID_SOCK_FD && client_sock_fd6 == INVALID_SOCK_FD)) {
    LOG_FATAL("Could not open NTP sockets");
  }
+
+  ptp_port = CNF_GetPtpPort();
+  ptp_sock_fd4 = INVALID_SOCK_FD;
+  ptp_sock_fd6 = INVALID_SOCK_FD;
+  ptp_message = NULL;
+
+  if (ptp_port > 0) {
+    ptp_sock_fd4 = open_socket(IPADDR_INET4, ptp_port, 0, NULL);
+    ptp_sock_fd6 = open_socket(IPADDR_INET6, ptp_port, 0, NULL);
+    ptp_message = MallocNew(PTP_NtpMessage);
+  }
 }

 /* ================================================== */
@@ -238,6 +261,11 @@ NIO_Finalise(void)
  close_socket(server_sock_fd6);
  server_sock_fd6 = client_sock_fd6 = INVALID_SOCK_FD;

+  close_socket(ptp_sock_fd4);
+  close_socket(ptp_sock_fd6);
+  ptp_sock_fd4 = ptp_sock_fd6 = INVALID_SOCK_FD;
+  Free(ptp_message);
+
 #ifdef HAVE_LINUX_TIMESTAMPING
  NIO_Linux_Finalise();
 #endif
@@ -250,18 +278,22 @@ NIO_Finalise(void)
 int
 NIO_OpenClientSocket(NTP_Remote_Address *remote_addr)
 {
-  if (separate_client_sockets) {
-    return open_separate_client_socket(remote_addr);
-  } else {
  switch (remote_addr->ip_addr.family) {
    case IPADDR_INET4:
+      if (ptp_port > 0 && remote_addr->port == ptp_port)
+        return ptp_sock_fd4;
+      if (separate_client_sockets)
+        return open_separate_client_socket(remote_addr);
      return client_sock_fd4;
    case IPADDR_INET6:
+      if (ptp_port > 0 && remote_addr->port == ptp_port)
+        return ptp_sock_fd6;
+      if (separate_client_sockets)
+        return open_separate_client_socket(remote_addr);
      return client_sock_fd6;
    default:
      return INVALID_SOCK_FD;
  }
-  }
 }

 /* ================================================== */
@@ -271,6 +303,8 @@ NIO_OpenServerSocket(NTP_Remote_Address *remote_addr)
 {
  switch (remote_addr->ip_addr.family) {
    case IPADDR_INET4:
+      if (ptp_port > 0 && remote_addr->port == ptp_port)
+        return ptp_sock_fd4;
      if (permanent_server_sockets)
        return server_sock_fd4;
      if (server_sock_fd4 == INVALID_SOCK_FD)
@@ -279,6 +313,8 @@ NIO_OpenServerSocket(NTP_Remote_Address *remote_addr)
        server_sock_ref4++;
      return server_sock_fd4;
    case IPADDR_INET6:
+      if (ptp_port > 0 && remote_addr->port == ptp_port)
+        return ptp_sock_fd6;
      if (permanent_server_sockets)
        return server_sock_fd6;
      if (server_sock_fd6 == INVALID_SOCK_FD)
@@ -293,9 +329,21 @@ NIO_OpenServerSocket(NTP_Remote_Address *remote_addr)

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

+static int
+is_ptp_socket(int sock_fd)
+{
+  return ptp_port > 0 && sock_fd != INVALID_SOCK_FD &&
+    (sock_fd == ptp_sock_fd4 || sock_fd == ptp_sock_fd6);
+}
+
+/* ================================================== */
+
 void
 NIO_CloseClientSocket(int sock_fd)
 {
+  if (is_ptp_socket(sock_fd))
+    return;
+
  if (separate_client_sockets)
    close_socket(sock_fd);
 }
@@ -305,7 +353,7 @@ NIO_CloseClientSocket(int sock_fd)
 void
 NIO_CloseServerSocket(int sock_fd)
 {
-  if (permanent_server_sockets || sock_fd == INVALID_SOCK_FD)
+  if (permanent_server_sockets || sock_fd == INVALID_SOCK_FD || is_ptp_socket(sock_fd))
    return;

  if (sock_fd == server_sock_fd4) {
@@ -329,7 +377,7 @@ int
 NIO_IsServerSocket(int sock_fd)
 {
  return sock_fd != INVALID_SOCK_FD &&
-    (sock_fd == server_sock_fd4 || sock_fd == server_sock_fd6);
+    (sock_fd == server_sock_fd4 || sock_fd == server_sock_fd6 || is_ptp_socket(sock_fd));
 }

 /* ================================================== */
@@ -337,7 +385,8 @@ NIO_IsServerSocket(int sock_fd)
 int
 NIO_IsServerSocketOpen(void)
 {
-  return server_sock_fd4 != INVALID_SOCK_FD || server_sock_fd6 != INVALID_SOCK_FD;
+  return server_sock_fd4 != INVALID_SOCK_FD || server_sock_fd6 != INVALID_SOCK_FD ||
+    ptp_sock_fd4 != INVALID_SOCK_FD || ptp_sock_fd6 != INVALID_SOCK_FD;
 }

 /* ================================================== */
@@ -392,6 +441,9 @@ process_message(SCK_Message *message, int sock_fd, int event)
    DEBUG_LOG("Updated RX timestamp delay=%.9f tss=%u",
              UTI_DiffTimespecsToDouble(&sched_ts, &local_ts.ts), local_ts.source);

+  if (!NIO_UnwrapMessage(message, sock_fd))
+    return;
+
  /* Just ignore the packet if it's not of a recognized length */
  if (message->length < NTP_HEADER_LENGTH || message->length > sizeof (NTP_Packet)) {
    DEBUG_LOG("Unexpected length");
@@ -430,6 +482,78 @@ read_from_socket(int sock_fd, int event, void *anything)
    process_message(&messages[i], sock_fd, event);
 }

+/* ================================================== */
+
+int
+NIO_UnwrapMessage(SCK_Message *message, int sock_fd)
+{
+  PTP_NtpMessage *msg;
+
+  if (!is_ptp_socket(sock_fd))
+    return 1;
+
+  if (message->length <= PTP_NTP_PREFIX_LENGTH) {
+    DEBUG_LOG("Unexpected length");
+    return 0;
+  }
+
+  msg = message->data;
+
+  if (msg->header.type != PTP_TYPE_DELAY_REQ || msg->header.version != PTP_VERSION ||
+      ntohs(msg->header.length) != message->length ||
+      msg->header.domain != PTP_DOMAIN_NTP ||
+      ntohs(msg->header.flags) != PTP_FLAG_UNICAST ||
+      ntohs(msg->tlv_header.type) != PTP_TLV_NTP ||
+      ntohs(msg->tlv_header.length) != message->length - PTP_NTP_PREFIX_LENGTH) {
+    DEBUG_LOG("Unexpected PTP message");
+    return 0;
+  }
+
+  message->data = (char *)message->data + PTP_NTP_PREFIX_LENGTH;
+  message->length -= PTP_NTP_PREFIX_LENGTH;
+
+  DEBUG_LOG("Unwrapped PTP->NTP len=%d", message->length);
+
+  return 1;
+}
+
+/* ================================================== */
+
+static int
+wrap_message(SCK_Message *message, int sock_fd)
+{
+  assert(PTP_NTP_PREFIX_LENGTH == 48);
+
+  if (!is_ptp_socket(sock_fd))
+    return 1;
+
+  if (!ptp_message)
+    return 0;
+
+  if (message->length < NTP_HEADER_LENGTH ||
+      message->length + PTP_NTP_PREFIX_LENGTH > sizeof (*ptp_message)) {
+    DEBUG_LOG("Unexpected length");
+    return 0;
+  }
+
+  memset(ptp_message, 0, PTP_NTP_PREFIX_LENGTH);
+  ptp_message->header.type = PTP_TYPE_DELAY_REQ;
+  ptp_message->header.version = PTP_VERSION;
+  ptp_message->header.length = htons(PTP_NTP_PREFIX_LENGTH + message->length);
+  ptp_message->header.domain = PTP_DOMAIN_NTP;
+  ptp_message->header.flags = htons(PTP_FLAG_UNICAST);
+  ptp_message->tlv_header.type = htons(PTP_TLV_NTP);
+  ptp_message->tlv_header.length = htons(message->length);
+  memcpy((char *)ptp_message + PTP_NTP_PREFIX_LENGTH, message->data, message->length);
+
+  message->data = ptp_message;
+  message->length += PTP_NTP_PREFIX_LENGTH;
+
+  DEBUG_LOG("Wrapped NTP->PTP len=%d", message->length - PTP_NTP_PREFIX_LENGTH);
+
+  return 1;
+}
+
 /* ================================================== */
 /* Send a packet to remote address from local address */

@@ -451,6 +575,9 @@ NIO_SendPacket(NTP_Packet *packet, NTP_Remote_Address *remote_addr,
  message.data = packet;
  message.length = length;

+  if (!wrap_message(&message, local_addr->sock_fd))
+    return 0;
+
  /* Specify remote address if the socket is not connected */
  if (NIO_IsServerSocket(local_addr->sock_fd) || !separate_client_sockets) {
    message.remote_addr.ip.ip_addr = remote_addr->ip_addr;
@@ -467,7 +594,7 @@ NIO_SendPacket(NTP_Packet *packet, NTP_Remote_Address *remote_addr,
 #if !defined(HAVE_IN_PKTINFO) && defined(IP_SENDSRCADDR)
  /* On FreeBSD a local IPv4 address cannot be specified on bound socket */
  if (message.local_addr.ip.family == IPADDR_INET4 &&
-      (local_addr->sock_fd != server_sock_fd4 || bound_server_sock_fd4))
+      (bound_server_sock_fd4 || !NIO_IsServerSocket(local_addr->sock_fd)))
    message.local_addr.ip.family = IPADDR_UNSPEC;
 #endif

--- a/ntp_io.h
+++ b/ntp_io.h
@@ -31,6 +31,7 @@

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

 /* Function to initialise the module. */
 extern void NIO_Initialise(void);
@@ -59,6 +60,9 @@ 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  2016-2019
+ * Copyright (C) Miroslav Lichvar  2016-2019, 2021-2022
 * 
 * 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
@@ -59,8 +59,6 @@ struct Interface {
  /* Start of UDP data at layer 2 for IPv4 and IPv6 */
  int l2_udp4_ntp_start;
  int l2_udp6_ntp_start;
-  /* Precision of PHC readings */
-  double precision;
  /* Compensation of errors in TX and RX timestamping */
  double tx_comp;
  double rx_comp;
@@ -68,12 +66,12 @@ struct Interface {
 };

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

 /* Minimum interval between PHC readings */
 #define MIN_PHC_POLL -6

-/* Maximum acceptable offset between HW and daemon/kernel timestamp */
+/* Maximum acceptable offset between SW/HW and daemon timestamp */
 #define MAX_TS_DELAY 1.0

 /* Array of Interfaces */
@@ -189,6 +187,14 @@ add_interface(CNF_HwTsInterface *conf_iface)
      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;
@@ -236,12 +242,12 @@ add_interface(CNF_HwTsInterface *conf_iface)
  iface->l2_udp4_ntp_start = 42;
  iface->l2_udp6_ntp_start = 62;

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

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

  LOG(LOGS_INFO, "Enabled HW timestamping %son %s",
      ts_config.rx_filter == HWTSTAMP_FILTER_NONE ? "(TX only) " : "", iface->name);
@@ -558,20 +564,23 @@ process_hw_timestamp(struct Interface *iface, struct timespec *hw_ts,
                     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 (!SYS_Linux_GetPHCSample(iface->phc_fd, iface->phc_nocrossts, iface->precision,
-                                &iface->phc_mode, &sample_phc_ts, &sample_sys_ts,
-                                &phc_err))
-      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);

      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
@@ -611,6 +620,28 @@ process_hw_timestamp(struct Interface *iface, struct timespec *hw_ts,
  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. */
@@ -736,8 +767,7 @@ NIO_Linux_ProcessMessage(SCK_Message *message, NTP_Local_Address *local_addr,

  if (local_ts->source == NTP_TS_DAEMON && !UTI_IsZeroTimespec(&message->timestamp.kernel) &&
      (!is_tx || UTI_IsZeroTimespec(&message->timestamp.hw))) {
-    LCL_CookTime(&message->timestamp.kernel, &local_ts->ts, &local_ts->err);
-    local_ts->source = NTP_TS_KERNEL;
+    process_sw_timestamp(&message->timestamp.kernel, local_ts);
  }

  /* If the kernel is slow with enabling RX timestamping, open a dummy
@@ -776,7 +806,10 @@ NIO_Linux_ProcessMessage(SCK_Message *message, NTP_Local_Address *local_addr,
    return 1;
  }

-  if (message->length < NTP_HEADER_LENGTH)
+  if (!NIO_UnwrapMessage(message, local_addr->sock_fd))
+    return 1;
+
+  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);
--- a/ntp_sources.c
+++ b/ntp_sources.c
@@ -3,7 +3,7 @@

 **********************************************************************
 * Copyright (C) Richard P. Curnow  1997-2003
- * Copyright (C) Miroslav Lichvar  2011-2012, 2014, 2016, 2020
+ * Copyright (C) Miroslav Lichvar  2011-2012, 2014, 2016, 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
@@ -45,6 +45,9 @@

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

+/* Maximum number of sources */
+#define MAX_SOURCES 65536
+
 /* Record type private to this file, used to store information about
   particular sources */
 typedef struct {
@@ -53,7 +56,8 @@ typedef struct {
                                      (an IPADDR_ID address means the address
                                      is not resolved yet) */
  NCR_Instance data;            /* Data for the protocol engine for this source */
-  char *name;                   /* Name of the source, may be NULL */
+  char *name;                   /* Name of the source as it was specified
+                                   (may be an IP address) */
  int pool_id;                  /* ID of the pool from which was this source
                                   added or INVALID_POOL */
  int tentative;                /* Flag indicating there was no valid response
@@ -72,6 +76,9 @@ static int n_sources;
 /* Flag indicating new sources will be started automatically when added */
 static int auto_start_sources = 0;

+/* Flag indicating a record is currently being modified */
+static int record_lock;
+
 /* Last assigned address ID */
 static uint32_t last_address_id = 0;

@@ -100,6 +107,7 @@ struct UnresolvedSource {

 static struct UnresolvedSource *unresolved_sources = NULL;
 static int resolving_interval = 0;
+static int resolving_restart = 0;
 static SCH_TimeoutID resolving_id;
 static struct UnresolvedSource *resolving_source = NULL;
 static NSR_SourceResolvingEndHandler resolving_end_handler = NULL;
@@ -122,11 +130,21 @@ struct SourcePool {
 /* Array of SourcePool (indexed by their ID) */
 static ARR_Instance pools;

+/* Requested update of a source's address */
+struct AddressUpdate {
+  NTP_Remote_Address old_address;
+  NTP_Remote_Address new_address;
+};
+
+/* Update saved when record_lock is true */
+static struct AddressUpdate saved_address_update;
+
 /* ================================================== */
 /* Forward prototypes */

 static void resolve_sources(void);
 static void rehash_records(void);
+static void handle_saved_address_update(void);
 static void clean_source_record(SourceRecord *record);
 static void remove_pool_sources(int pool_id, int tentative, int unresolved);
 static void remove_unresolved_source(struct UnresolvedSource *us);
@@ -181,14 +199,7 @@ NSR_Initialise(void)
 void
 NSR_Finalise(void)
 {
-  SourceRecord *record;
-  unsigned int i;
-
-  for (i = 0; i < ARR_GetSize(records); i++) {
-    record = get_record(i);
-    if (record->remote_addr)
-      clean_source_record(record);
-  }
+  NSR_RemoveAllSources();

  LCL_RemoveParameterChangeHandler(slew_sources, NULL);

@@ -275,6 +286,8 @@ rehash_records(void)
  unsigned int i, old_size, new_size;
  int slot;

+  assert(!record_lock);
+
  old_size = ARR_GetSize(records);

  temp_records = MallocArray(SourceRecord, old_size);
@@ -317,6 +330,11 @@ add_source(NTP_Remote_Address *remote_addr, char *name, NTP_Source_Type type,
  /* Find empty bin & check that we don't have the address already */
  if (find_slot2(remote_addr, &slot) != 0) {
    return NSR_AlreadyInUse;
+  } else if (!name && !UTI_IsIPReal(&remote_addr->ip_addr)) {
+    /* Name is required for non-real addresses */
+    return NSR_InvalidName;
+  } else if (n_sources >= MAX_SOURCES) {
+    return NSR_TooManySources;
  } else {
    if (remote_addr->ip_addr.family != IPADDR_INET4 &&
        remote_addr->ip_addr.family != IPADDR_INET6 &&
@@ -331,14 +349,19 @@ add_source(NTP_Remote_Address *remote_addr, char *name, NTP_Source_Type type,
          assert(0);
      }

+      assert(!record_lock);
+      record_lock = 1;
+
      record = get_record(slot);
-      record->data = NCR_CreateInstance(remote_addr, type, params, name);
+      record->name = Strdup(name ? name : UTI_IPToString(&remote_addr->ip_addr));
+      record->data = NCR_CreateInstance(remote_addr, type, params, record->name);
      record->remote_addr = NCR_GetRemoteAddress(record->data);
-      record->name = name ? Strdup(name) : NULL;
      record->pool_id = pool_id;
      record->tentative = 1;
      record->conf_id = conf_id;

+      record_lock = 0;
+
      if (record->pool_id != INVALID_POOL) {
        get_pool(record->pool_id)->sources++;
        if (!UTI_IsIPReal(&remote_addr->ip_addr))
@@ -348,6 +371,9 @@ add_source(NTP_Remote_Address *remote_addr, char *name, NTP_Source_Type type,
      if (auto_start_sources && UTI_IsIPReal(&remote_addr->ip_addr))
        NCR_StartInstance(record->data);

+      /* The new instance is allowed to change its address immediately */
+      handle_saved_address_update();
+
      return NSR_Success;
    }
  }
@@ -365,7 +391,7 @@ change_source_address(NTP_Remote_Address *old_addr, NTP_Remote_Address *new_addr
  char *name;

  found = find_slot2(old_addr, &slot1);
-  if (found == 0)
+  if (found != 2)
    return NSR_NoSuchSource;

  /* Make sure there is no other source using the new address (with the same
@@ -374,9 +400,16 @@ change_source_address(NTP_Remote_Address *old_addr, NTP_Remote_Address *new_addr
  if (found == 2 || (found != 0 && slot1 != slot2))
    return NSR_AlreadyInUse;

+  assert(!record_lock);
+  record_lock = 1;
+
  record = get_record(slot1);
  NCR_ChangeRemoteAddress(record->data, new_addr, !replacement);
-  record->remote_addr = NCR_GetRemoteAddress(record->data);
+
+  if (record->remote_addr != NCR_GetRemoteAddress(record->data) ||
+      UTI_CompareIPs(&record->remote_addr->ip_addr, &new_addr->ip_addr, NULL) != 0)
+    assert(0);
+
  if (!UTI_IsIPReal(&old_addr->ip_addr) && UTI_IsIPReal(&new_addr->ip_addr)) {
    if (auto_start_sources)
      NCR_StartInstance(record->data);
@@ -391,6 +424,8 @@ change_source_address(NTP_Remote_Address *old_addr, NTP_Remote_Address *new_addr
      get_pool(record->pool_id)->confirmed_sources--;
  }

+  record_lock = 0;
+
  name = record->name;
  severity = UTI_IsIPReal(&old_addr->ip_addr) ? LOGS_INFO : LOGS_DEBUG;

@@ -400,10 +435,10 @@ change_source_address(NTP_Remote_Address *old_addr, NTP_Remote_Address *new_addr

    LOG(severity, "Source %s %s %s (%s)", UTI_IPToString(&old_addr->ip_addr),
        replacement ? "replaced with" : "changed to",
-        UTI_IPToString(&new_addr->ip_addr), name ? name : "");
+        UTI_IPToString(&new_addr->ip_addr), name);
  } else {
    LOG(severity, "Source %s (%s) changed port to %d",
-        UTI_IPToString(&new_addr->ip_addr), name ? name : "", new_addr->port);
+        UTI_IPToString(&new_addr->ip_addr), name, new_addr->port);
  }

  return NSR_Success;
@@ -411,6 +446,24 @@ change_source_address(NTP_Remote_Address *old_addr, NTP_Remote_Address *new_addr

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

+static void
+handle_saved_address_update(void)
+{
+  if (!UTI_IsIPReal(&saved_address_update.old_address.ip_addr))
+    return;
+
+  if (change_source_address(&saved_address_update.old_address,
+                            &saved_address_update.new_address, 0) != NSR_Success)
+    /* This is expected to happen only if the old address is wrong */
+    LOG(LOGS_ERR, "Could not change %s to %s",
+        UTI_IPSockAddrToString(&saved_address_update.old_address),
+        UTI_IPSockAddrToString(&saved_address_update.new_address));
+
+  saved_address_update.old_address.ip_addr.family = IPADDR_UNSPEC;
+}
+
+/* ================================================== */
+
 static int
 replace_source_connectable(NTP_Remote_Address *old_addr, NTP_Remote_Address *new_addr)
 {
@@ -422,6 +475,8 @@ replace_source_connectable(NTP_Remote_Address *old_addr, NTP_Remote_Address *new
  if (change_source_address(old_addr, new_addr, 1) == NSR_AlreadyInUse)
    return 0;

+  handle_saved_address_update();
+
  return 1;
 }

@@ -444,8 +499,8 @@ process_resolved_name(struct UnresolvedSource *us, IPAddr *ip_addrs, int n_addrs
    DEBUG_LOG("(%d) %s", i + 1, UTI_IPToString(&new_addr.ip_addr));

    if (us->pool_id != INVALID_POOL) {
-      /* In the pool resolving mode, try to replace all sources from
-         the pool which don't have a real address yet */
+      /* In the pool resolving mode, try to replace a source from
+         the pool which does not have a real address yet */
      for (j = 0; j < ARR_GetSize(records); j++) {
        record = get_record(j);
        if (!record->remote_addr || record->pool_id != us->pool_id ||
@@ -454,6 +509,7 @@ process_resolved_name(struct UnresolvedSource *us, IPAddr *ip_addrs, int n_addrs
        old_addr = *record->remote_addr;
        new_addr.port = old_addr.port;
        if (replace_source_connectable(&old_addr, &new_addr))
+          ;
        break;
      }
    } else {
@@ -523,6 +579,13 @@ name_resolve_handler(DNS_Status status, int n_addrs, IPAddr *ip_addrs, void *any
  if (status == DNS_Failure || UTI_IsIPReal(&us->address.ip_addr) || is_resolved(us))
    remove_unresolved_source(us);

+  /* If a restart was requested and this was the last source in the list,
+     start with the first source again (if there still is one) */
+  if (!next && resolving_restart) {
+    next = unresolved_sources;
+    resolving_restart = 0;
+  }
+
  resolving_source = next;

  if (next) {
@@ -634,21 +697,25 @@ static int get_unused_pool_id(void)

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

+static uint32_t
+get_next_conf_id(uint32_t *conf_id)
+{
+  last_conf_id++;
+
+  if (conf_id)
+    *conf_id = last_conf_id;
+
+  return last_conf_id;
+}
+
+/* ================================================== */
+
 NSR_Status
 NSR_AddSource(NTP_Remote_Address *remote_addr, NTP_Source_Type type,
              SourceParameters *params, uint32_t *conf_id)
 {
-  NSR_Status s;
-
-  s = add_source(remote_addr, NULL, type, params, INVALID_POOL, last_conf_id + 1);
-  if (s != NSR_Success)
-    return s;
-
-  last_conf_id++;
-  if (conf_id)
-    *conf_id = last_conf_id;
-
-  return s;
+  return add_source(remote_addr, NULL, type, params, INVALID_POOL,
+                    get_next_conf_id(conf_id));
 }

 /* ================================================== */
@@ -661,17 +728,18 @@ NSR_AddSourceByName(char *name, int port, int pool, NTP_Source_Type type,
  struct SourcePool *sp;
  NTP_Remote_Address remote_addr;
  int i, new_sources, pool_id;
+  uint32_t cid;

-  /* If the name is an IP address, don't bother with full resolving now
-     or later when trying to replace the source */
+  /* If the name is an IP address, add the source with the address directly */
  if (UTI_StringToIP(name, &remote_addr.ip_addr)) {
    remote_addr.port = port;
-    return NSR_AddSource(&remote_addr, type, params, conf_id);
+    return add_source(&remote_addr, name, type, params, INVALID_POOL,
+                      get_next_conf_id(conf_id));
  }

  /* Make sure the name is at least printable and has no spaces */
  for (i = 0; name[i] != '\0'; i++) {
-    if (!isgraph(name[i]))
+    if (!isgraph((unsigned char)name[i]))
      return NSR_InvalidName;
  }

@@ -707,14 +775,12 @@ NSR_AddSourceByName(char *name, int port, int pool, NTP_Source_Type type,

  append_unresolved_source(us);

-  last_conf_id++;
-  if (conf_id)
-    *conf_id = last_conf_id;
+  cid = get_next_conf_id(conf_id);

  for (i = 0; i < new_sources; i++) {
    if (i > 0)
      remote_addr.ip_addr.addr.id = ++last_address_id;
-    if (add_source(&remote_addr, name, type, params, us->pool_id, last_conf_id) != NSR_Success)
+    if (add_source(&remote_addr, name, type, params, us->pool_id, cid) != NSR_Success)
      return NSR_TooManySources;
  }

@@ -736,7 +802,7 @@ NSR_ResolveSources(void)
 {
  /* Try to resolve unresolved sources now */
  if (unresolved_sources) {
-    /* Make sure no resolving is currently running */
+    /* Allow only one resolving to be running at a time */
    if (!resolving_source) {
      if (resolving_id != 0) {
        SCH_RemoveTimeout(resolving_id);
@@ -744,6 +810,9 @@ NSR_ResolveSources(void)
        resolving_interval--;
      }
      resolve_sources();
+    } else {
+      /* Try again as soon as the current resolving ends */
+      resolving_restart = 1;
    }
  } else {
    /* No unresolved sources, we are done */
@@ -795,7 +864,6 @@ clean_source_record(SourceRecord *record)

  record->remote_addr = NULL;
  NCR_DestroyInstance(record->data);
-  if (record->name)
  Free(record->name);

  n_sources--;
@@ -869,7 +937,8 @@ resolve_source_replacement(SourceRecord *record)
 {
  struct UnresolvedSource *us;

-  DEBUG_LOG("trying to replace %s", UTI_IPToString(&record->remote_addr->ip_addr));
+  DEBUG_LOG("trying to replace %s (%s)",
+            UTI_IPToString(&record->remote_addr->ip_addr), record->name);

  us = MallocNew(struct UnresolvedSource);
  us->name = Strdup(record->name);
@@ -893,6 +962,7 @@ NSR_HandleBadSource(IPAddr *address)
  static struct timespec last_replacement;
  struct timespec now;
  SourceRecord *record;
+  IPAddr ip_addr;
  double diff;
  int slot;

@@ -901,8 +971,10 @@ NSR_HandleBadSource(IPAddr *address)

  record = get_record(slot);

-  /* Only sources with a name can be replaced */
-  if (!record->name)
+  /* Don't try to replace a source specified by an IP address unless the
+     address changed since the source was added (e.g. by NTS-KE) */
+  if (UTI_StringToIP(record->name, &ip_addr) &&
+      UTI_CompareIPs(&record->remote_addr->ip_addr, &ip_addr, NULL) == 0)
    return;

  /* Don't resolve names too frequently */
@@ -927,7 +999,7 @@ NSR_RefreshAddresses(void)

  for (i = 0; i < ARR_GetSize(records); i++) {
    record = get_record(i);
-    if (!record->remote_addr || !record->name)
+    if (!record->remote_addr)
      continue;

    resolve_source_replacement(record);
@@ -939,10 +1011,28 @@ NSR_RefreshAddresses(void)
 NSR_Status
 NSR_UpdateSourceNtpAddress(NTP_Remote_Address *old_addr, NTP_Remote_Address *new_addr)
 {
-  if (new_addr->ip_addr.family == IPADDR_UNSPEC)
+  int slot;
+
+  if (!UTI_IsIPReal(&old_addr->ip_addr) || !UTI_IsIPReal(&new_addr->ip_addr))
    return NSR_InvalidAF;

+  if (UTI_CompareIPs(&old_addr->ip_addr, &new_addr->ip_addr, NULL) != 0 &&
+      find_slot(&new_addr->ip_addr, &slot))
+    return NSR_AlreadyInUse;
+
+  /* If a record is being modified (e.g. by change_source_address(), or the
+     source is just being created), postpone the change to avoid corruption */
+
+  if (!record_lock)
    return change_source_address(old_addr, new_addr, 0);
+
+  if (UTI_IsIPReal(&saved_address_update.old_address.ip_addr))
+    return NSR_TooManySources;
+
+  saved_address_update.old_address = *old_addr;
+  saved_address_update.new_address = *new_addr;
+
+  return NSR_Success;
 }

 /* ================================================== */
@@ -991,17 +1081,12 @@ NSR_GetLocalRefid(IPAddr *address)
 char *
 NSR_GetName(IPAddr *address)
 {
-  SourceRecord *record;
  int slot;

  if (!find_slot(address, &slot))
-    return 0;
+    return NULL;

-  record = get_record(slot);
-  if (record->name)
-    return record->name;
-
-  return UTI_IPToString(&record->remote_addr->ip_addr); 
+  return get_record(slot)->name;
 }

 /* ================================================== */
@@ -1018,8 +1103,10 @@ NSR_ProcessRx(NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr,

  assert(initialised);

-  /* Must match IP address AND port number */
-  if (find_slot2(remote_addr, &slot) == 2) {
+  /* Avoid unnecessary lookup if the packet cannot be a response from our
+     source.  Otherwise, it must match both IP address and port number. */
+  if (NTP_LVM_TO_MODE(message->lvm) != MODE_CLIENT &&
+      find_slot2(remote_addr, &slot) == 2) {
    record = get_record(slot);

    if (!NCR_ProcessRxKnown(record->data, local_addr, rx_ts, message, length))
@@ -1055,8 +1142,10 @@ NSR_ProcessTx(NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr,
  SourceRecord *record;
  int slot;

-  /* Must match IP address AND port number */
-  if (find_slot2(remote_addr, &slot) == 2) {
+  /* Avoid unnecessary lookup if the packet cannot be a request to our
+     source.  Otherwise, it must match both IP address and port number. */
+  if (NTP_LVM_TO_MODE(message->lvm) != MODE_SERVER &&
+      find_slot2(remote_addr, &slot) == 2) {
    record = get_record(slot);
    NCR_ProcessTxKnown(record->data, local_addr, tx_ts, message, length);
  } else {
--- a/ntp_sources.h
+++ b/ntp_sources.h
@@ -91,15 +91,16 @@ 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 */
+/* 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.  If the source doesn't have a name,
-   it returns a temporary string containing formatted 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 */
--- a/nts_ke_client.c
+++ b/nts_ke_client.c
@@ -2,7 +2,7 @@
  chronyd/chronyc - Programs for keeping computer clocks accurate.

 **********************************************************************
- * Copyright (C) Miroslav Lichvar  2020
+ * 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
@@ -44,6 +44,7 @@
 struct NKC_Instance_Record {
  char *name;
  IPSockAddr address;
+  NKSN_Credentials credentials;
  NKSN_Instance session;
  int destroying;
  int got_response;
@@ -52,14 +53,14 @@ struct NKC_Instance_Record {
  NKE_Context context;
  NKE_Cookie cookies[NKE_MAX_COOKIES];
  int num_cookies;
-  char server_name[NKE_MAX_RECORD_BODY_LENGTH + 1];
+  char server_name[NKE_MAX_RECORD_BODY_LENGTH + 2];
  IPSockAddr ntp_address;
 };

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

-static void *client_credentials = NULL;
-static int client_credentials_refs = 0;
+static NKSN_Credentials default_credentials = NULL;
+static int default_credentials_refs = 0;

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

@@ -126,9 +127,10 @@ process_response(NKC_Instance inst)
 {
  int next_protocol = -1, aead_algorithm = -1, error = 0;
  int i, critical, type, length;
-  uint16_t data[NKE_MAX_COOKIE_LENGTH / sizeof (uint16_t)];
+  uint16_t data[NKE_MAX_RECORD_BODY_LENGTH / sizeof (uint16_t)];

-  assert(NKE_MAX_COOKIE_LENGTH % sizeof (uint16_t) == 0);
+  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;
@@ -140,6 +142,13 @@ process_response(NKC_Instance inst)
    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) {
@@ -196,7 +205,7 @@ process_response(NKC_Instance inst)
        inst->server_name[length] = '\0';

        /* Make sure the name is printable and has no spaces */
-        for (i = 0; i < length && isgraph(inst->server_name[i]); i++)
+        for (i = 0; i < length && isgraph((unsigned char)inst->server_name[i]); i++)
          ;
        if (i != length) {
          DEBUG_LOG("Invalid server name");
@@ -253,6 +262,17 @@ handle_message(void *arg)
    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;
    }
@@ -266,9 +286,12 @@ handle_message(void *arg)
 /* ================================================== */

 NKC_Instance
-NKC_CreateInstance(IPSockAddr *address, const char *name)
+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);

@@ -279,10 +302,21 @@ NKC_CreateInstance(IPSockAddr *address, const char *name)
  inst->destroying = 0;
  inst->got_response = 0;

-  /* Share the credentials with other client instances */
-  if (!client_credentials)
-    client_credentials = NKSN_CreateCertCredentials(NULL, NULL, CNF_GetNtsTrustedCertFile());
-  client_credentials_refs++;
+  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;
 }
@@ -296,10 +330,16 @@ NKC_DestroyInstance(NKC_Instance inst)

  Free(inst->name);

-  client_credentials_refs--;
-  if (client_credentials_refs <= 0 && client_credentials) {
-    NKSN_DestroyCertCredentials(client_credentials);
-    client_credentials = NULL;
+  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
@@ -325,7 +365,7 @@ NKC_Start(NKC_Instance inst)

  inst->got_response = 0;

-  if (!client_credentials) {
+  if (!inst->credentials) {
    DEBUG_LOG("Missing client credentials");
    return 0;
  }
@@ -347,7 +387,7 @@ NKC_Start(NKC_Instance inst)
  }

  /* Start an NTS-KE session */
-  if (!NKSN_StartSession(inst->session, sock_fd, label, client_credentials, CLIENT_TIMEOUT)) {
+  if (!NKSN_StartSession(inst->session, sock_fd, label, inst->credentials, CLIENT_TIMEOUT)) {
    SCK_CloseSocket(sock_fd);
    return 0;
  }
--- a/nts_ke_client.h
+++ b/nts_ke_client.h
@@ -33,7 +33,7 @@
 typedef struct NKC_Instance_Record *NKC_Instance;

 /* Create a client NTS-KE instance */
-extern NKC_Instance NKC_CreateInstance(IPSockAddr *address, const char *name);
+extern NKC_Instance NKC_CreateInstance(IPSockAddr *address, const char *name, uint32_t cert_set);

 /* Destroy an instance */
 extern void NKC_DestroyInstance(NKC_Instance inst);
--- a/nts_ke_server.c
+++ b/nts_ke_server.c
@@ -95,7 +95,7 @@ static int initialised = 0;

 /* Array of NKSN instances */
 static ARR_Instance sessions;
-static void *server_credentials;
+static NKSN_Credentials server_credentials;

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

@@ -556,7 +556,7 @@ error:

 #define MAX_WORDS 2

-static void
+static int
 load_keys(void)
 {
  char *dump_dir, line[1024], *words[MAX_WORDS];
@@ -568,11 +568,11 @@ load_keys(void)

  dump_dir = CNF_GetNtsDumpDir();
  if (!dump_dir)
-    return;
+    return 0;

  f = UTI_OpenFile(dump_dir, DUMP_FILENAME, NULL, 'r', 0);
  if (!f)
-    return;
+    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 ||
@@ -607,11 +607,13 @@ load_keys(void)

  fclose(f);

-  return;
+  return 1;

 error:
  DEBUG_LOG("Could not %s server keys", "load");
  fclose(f);
+
+  return 0;
 }

 /* ================================================== */
@@ -646,7 +648,7 @@ run_helper(uid_t uid, gid_t gid, int scfilter_level)
  LOG_SetMinSeverity(log_severity);

  if (!geteuid() && (uid || gid))
-    SYS_DropRoot(uid, gid);
+    SYS_DropRoot(uid, gid, SYS_NTSKE_HELPER);

  NKS_Initialise();

@@ -667,6 +669,8 @@ run_helper(uid_t uid, gid_t gid, int scfilter_level)
  CNF_Finalise();
  LOG_Finalise();

+  UTI_ResetGetRandomFunctions();
+
  exit(0);
 }

@@ -676,13 +680,14 @@ 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_GetNtsServerCertFile() || !CNF_GetNtsServerKeyFile())
+  if (CNF_GetNtsServerCertAndKeyFiles(&certs, &keys) <= 0)
    return;

  processes = CNF_GetNtsServerProcesses();
@@ -707,6 +712,8 @@ NKS_PreInitialise(uid_t uid, gid_t gid, int scfilter_level)

    is_helper = 1;

+    UTI_ResetGetRandomFunctions();
+
    snprintf(prefix, sizeof (prefix), "nks#%d:", i + 1);
    LOG_SetDebugPrefix(prefix);
    LOG_CloseParentFd();
@@ -726,21 +733,19 @@ NKS_PreInitialise(uid_t uid, gid_t gid, int scfilter_level)
 void
 NKS_Initialise(void)
 {
-  char *cert, *key;
+  const char **certs, **keys;
+  int i, n_certs_keys;
  double key_delay;
-  int i;

  server_sock_fd4 = INVALID_SOCK_FD;
  server_sock_fd6 = INVALID_SOCK_FD;

-  cert = CNF_GetNtsServerCertFile();
-  key = CNF_GetNtsServerKeyFile();
-
-  if (!cert || !key)
+  n_certs_keys = CNF_GetNtsServerCertAndKeyFiles(&certs, &keys);
+  if (n_certs_keys <= 0)
    return;

  if (helper_sock_fd == INVALID_SOCK_FD) {
-    server_credentials = NKSN_CreateCertCredentials(cert, key, NULL);
+    server_credentials = NKSN_CreateServerCertCredentials(certs, keys, n_certs_keys);
    if (!server_credentials)
      return;
  } else {
@@ -764,10 +769,12 @@ NKS_Initialise(void)
    server_sock_fd4 = open_socket(IPADDR_INET4);
    server_sock_fd6 = open_socket(IPADDR_INET6);

-    load_keys();
-
    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);
--- a/nts_ke_session.c
+++ b/nts_ke_session.c
@@ -2,7 +2,7 @@
  chronyd/chronyc - Programs for keeping computer clocks accurate.

 **********************************************************************
- * Copyright (C) Miroslav Lichvar  2020
+ * 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
@@ -225,9 +225,13 @@ create_tls_session(int server_mode, int sock_fd, const char *server_name,
  }

  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;

@@ -590,13 +594,13 @@ handle_step(struct timespec *raw, struct timespec *cooked, double dfreq,

 static int gnutls_initialised = 0;

-static void
+static int
 init_gnutls(void)
 {
  int r;

  if (gnutls_initialised)
-    return;
+    return 1;

  r = gnutls_global_init();
  if (r < 0)
@@ -607,8 +611,12 @@ init_gnutls(void)
  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_FATAL("Could not initialise %s : %s", "priority cache", gnutls_strerror(r));
+  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);
@@ -617,6 +625,8 @@ init_gnutls(void)
  DEBUG_LOG("Initialised");

  LCL_AddParameterChangeHandler(handle_step, NULL);
+
+  return 1;
 }

 /* ================================================== */
@@ -637,41 +647,65 @@ deinit_gnutls(void)

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

-void *
-NKSN_CreateCertCredentials(char *cert, char *key, char *trusted_certs)
+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 r;
+  int i, r;

-  init_gnutls();
+  if (!init_gnutls())
+    return NULL;

  r = gnutls_certificate_allocate_credentials(&credentials);
  if (r < 0)
    goto error;

-  if (cert && key) {
-    r = gnutls_certificate_set_x509_key_file(credentials, cert, key,
+  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 (!CNF_GetNoSystemCert()) {
+    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) {
-      r = gnutls_certificate_set_x509_trust_file(credentials, trusted_certs,
+    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 credentials;
+  return (NKSN_Credentials)credentials;

 error:
  LOG(LOGS_ERR, "Could not set credentials : %s", gnutls_strerror(r));
@@ -683,10 +717,27 @@ error:

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

-void
-NKSN_DestroyCertCredentials(void *credentials)
+NKSN_Credentials
+NKSN_CreateServerCertCredentials(const char **certs, const char **keys, int n_certs_keys)
 {
-  gnutls_certificate_free_credentials(credentials);
+  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();
 }
@@ -734,12 +785,13 @@ NKSN_DestroyInstance(NKSN_Instance inst)

 int
 NKSN_StartSession(NKSN_Instance inst, int sock_fd, const char *label,
-                  void *credentials, double timeout)
+                  NKSN_Credentials credentials, double timeout)
 {
  assert(inst->state == KE_STOPPED);

  inst->tls_session = create_tls_session(inst->server, sock_fd, inst->server_name,
-                                         credentials, priority_cache);
+                                         (gnutls_certificate_credentials_t)credentials,
+                                         priority_cache);
  if (!inst->tls_session)
    return 0;

@@ -825,21 +877,27 @@ NKSN_GetRecord(NKSN_Instance inst, int *critical, int *type, int *body_length,
 int
 NKSN_GetKeys(NKSN_Instance inst, SIV_Algorithm siv, NKE_Key *c2s, NKE_Key *s2c)
 {
-  c2s->length = SIV_GetKeyLength(siv);
-  s2c->length = SIV_GetKeyLength(siv);
-  assert(c2s->length <= sizeof (c2s->key));
-  assert(s2c->length <= sizeof (s2c->key));
+  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,
-                         c2s->length, (char *)c2s->key) < 0)
-    return 0;
-  if (gnutls_prf_rfc5705(inst->tls_session,
+                         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,
-                         s2c->length, (char *)s2c->key) < 0)
+                         length, (char *)s2c->key) < 0) {
+    DEBUG_LOG("Could not export key");
    return 0;
+  }
+
+  c2s->length = length;
+  s2c->length = length;

  return 1;
 }
--- a/nts_ke_session.h
+++ b/nts_ke_session.h
@@ -30,19 +30,25 @@
 #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 client or server credentials using certificates of trusted CAs,
-   or a server certificate and key.  The credentials may be shared between
+/* 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 void *NKSN_CreateCertCredentials(char *cert, char *key, char *trusted_certs);
+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(void *credentials);
+extern void NKSN_DestroyCertCredentials(NKSN_Credentials credentials);

 /* Create an instance */
 extern NKSN_Instance NKSN_CreateInstance(int server_mode, const char *server_name,
@@ -53,7 +59,7 @@ 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,
-                             void *credentials, double timeout);
+                             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. */
--- a/nts_ntp.h
+++ b/nts_ntp.h
@@ -27,11 +27,6 @@
 #ifndef GOT_NTS_NTP_H
 #define GOT_NTS_NTP_H

-#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
-
 #define NTP_KOD_NTS_NAK                 0x4e54534e

 #define NTS_MIN_UNIQ_ID_LENGTH          32
--- a/nts_ntp_auth.c
+++ b/nts_ntp_auth.c
@@ -112,6 +112,7 @@ NNA_GenerateAuthEF(NTP_Packet *packet, NTP_PacketInfo *info, SIV_Instance siv,
  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;
  }

--- a/nts_ntp_client.c
+++ b/nts_ntp_client.c
@@ -50,14 +50,20 @@
 #define DUMP_IDENTIFIER "NNC0\n"

 struct NNC_Instance_Record {
-  const IPSockAddr *ntp_address;
+  /* 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 load_attempt;
  int nke_attempts;
  double next_nke_attempt;
  double last_nke_success;
@@ -91,7 +97,6 @@ reset_instance(NNC_Instance inst)
    SIV_DestroyInstance(inst->siv);
  inst->siv = NULL;

-  inst->load_attempt = 0;
  inst->nke_attempts = 0;
  inst->next_nke_attempt = 0.0;
  inst->last_nke_success = 0.0;
@@ -111,20 +116,26 @@ reset_instance(NNC_Instance inst)
 /* ================================================== */

 NNC_Instance
-NNC_CreateInstance(IPSockAddr *nts_address, const char *name, const IPSockAddr *ntp_address)
+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->ntp_address = ntp_address;
  inst->nts_address = *nts_address;
-  inst->name = name ? Strdup(name) : NULL;
+  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;
 }

@@ -165,13 +176,13 @@ set_ntp_address(NNC_Instance inst, NTP_Remote_Address *negotiated_address)
 {
  NTP_Remote_Address old_address, new_address;

-  old_address = *inst->ntp_address;
+  old_address = inst->ntp_address;
  new_address = *negotiated_address;

  if (new_address.ip_addr.family == IPADDR_UNSPEC)
-    new_address.ip_addr = old_address.ip_addr;
+    new_address.ip_addr = inst->nts_address.ip_addr;
  if (new_address.port == 0)
-    new_address.port = old_address.port;
+    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)
@@ -184,6 +195,8 @@ set_ntp_address(NNC_Instance inst, NTP_Remote_Address *negotiated_address)
    return 0;
  }

+  inst->ntp_address = new_address;
+
  return 1;
 }

@@ -223,13 +236,7 @@ get_cookies(NNC_Instance inst)
      return 0;
    }

-    if (!inst->name) {
-      LOG(LOGS_ERR, "Missing name of %s for NTS-KE",
-          UTI_IPToString(&inst->nts_address.ip_addr));
-      return 0;
-    }
-
-    inst->nke = NKC_CreateInstance(&inst->nts_address, inst->name);
+    inst->nke = NKC_CreateInstance(&inst->nts_address, inst->name, inst->cert_set);

    inst->nke_attempts++;
    update_next_nke_attempt(inst, now);
@@ -273,8 +280,6 @@ get_cookies(NNC_Instance inst)
  inst->last_nke_success = now;
  inst->cookie_index = 0;

-  inst->nak_response = 0;
-
  return 1;
 }

@@ -285,11 +290,10 @@ NNC_PrepareForAuth(NNC_Instance inst)
 {
  inst->auth_ready = 0;

-  /* Try to reload saved keys and cookies (once for the NTS-KE address) */
-  if (!inst->load_attempt) {
-    load_cookies(inst);
-    inst->load_attempt = 1;
-  }
+  /* 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)) {
@@ -297,6 +301,8 @@ NNC_PrepareForAuth(NNC_Instance inst)
      return 0;
  }

+  inst->nak_response = 0;
+
  if (!inst->siv)
    inst->siv = SIV_CreateInstance(inst->context.algorithm);

@@ -306,10 +312,6 @@ NNC_PrepareForAuth(NNC_Instance inst)
    return 0;
  }

-  /* Prepare data for NNC_GenerateRequestAuth() */
-  UTI_GetRandomBytes(inst->uniq_id, sizeof (inst->uniq_id));
-  UTI_GetRandomBytes(inst->nonce, sizeof (inst->nonce));
-
  inst->auth_ready = 1;

  return 1;
@@ -325,14 +327,22 @@ NNC_GenerateRequestAuth(NNC_Instance inst, NTP_Packet *packet,
  int i, req_cookies;
  void *ef_body;

-  if (!inst->auth_ready || inst->num_cookies == 0 || !inst->siv)
+  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];
-  req_cookies = MIN(NTS_MAX_COOKIES - inst->num_cookies + 1,
+  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,
@@ -354,10 +364,6 @@ NNC_GenerateRequestAuth(NNC_Instance inst, NTP_Packet *packet,
                          (const unsigned char *)"", 0, NTP_MAX_V4_MAC_LENGTH + 4))
    return 0;

-  inst->num_cookies--;
-  inst->cookie_index = (inst->cookie_index + 1) % NTS_MAX_COOKIES;
-  inst->auth_ready = 0;
-  inst->nak_response = 0;
  inst->ok_response = 0;

  return 1;
@@ -451,7 +457,7 @@ NNC_CheckResponseAuth(NNC_Instance inst, NTP_Packet *packet,
  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() */
+      /* This is not expected as the packet already passed parsing */
      return 0;

    switch (ef_type) {
@@ -519,10 +525,13 @@ 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);
 }

 /* ================================================== */
@@ -553,9 +562,10 @@ save_cookies(NNC_Instance inst)
  context_time = inst->last_nke_success - SCH_GetLastEventMonoTime();
  context_time += UTI_TimespecToDouble(&now);

-  if (fprintf(f, "%s%.1f\n%s %d\n%u %d ",
-              DUMP_IDENTIFIER, context_time, UTI_IPToString(&inst->ntp_address->ip_addr),
-              inst->ntp_address->port, inst->context_id, (int)inst->context.algorithm) < 0 ||
+  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)) ||
@@ -616,6 +626,8 @@ load_cookies(NNC_Instance inst)
  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 ||
@@ -657,6 +669,8 @@ load_cookies(NNC_Instance inst)
  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;

--- a/nts_ntp_client.h
+++ b/nts_ntp_client.h
@@ -34,7 +34,7 @@
 typedef struct NNC_Instance_Record *NNC_Instance;

 extern NNC_Instance NNC_CreateInstance(IPSockAddr *nts_address, const char *name,
-                                                   const IPSockAddr *ntp_address);
+                                       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,
--- a/nts_ntp_server.c
+++ b/nts_ntp_server.c
@@ -59,8 +59,10 @@ 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_GetNtsServerCertFile() || !CNF_GetNtsServerKeyFile()) {
+  if (CNF_GetNtsServerCertAndKeyFiles(&certs, &keys) <= 0) {
    server = NULL;
    return;
  }
@@ -96,11 +98,11 @@ NNS_CheckRequestAuth(NTP_Packet *packet, NTP_PacketInfo *info, uint32_t *kod)
  NKE_Cookie cookie;
  void *ef_body;

+  *kod = 0;
+
  if (!server)
    return 0;

-  *kod = 0;
-
  server->num_cookies = 0;
  server->req_tx = packet->transmit_ts;

@@ -240,7 +242,7 @@ NNS_GenerateResponseAuth(NTP_Packet *request, NTP_PacketInfo *req_info,
  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 NAU_ParsePacket() */
+      /* This is not expected as the packet already passed parsing */
      return 0;

    switch (ef_type) {
--- 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 */
@@ -128,6 +128,7 @@ static const struct request_length request_lengths[] = {
                   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[] = {
@@ -153,8 +154,9 @@ static const uint16_t reply_lengths[] = {
  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 */
-  RPY_LENGTH_ENTRY(server_stats),               /* SERVER_STATS2 */
+  0,                                            /* SERVER_STATS2 - not supported */
  RPY_LENGTH_ENTRY(select_data),                /* SELECT_DATA */
+  RPY_LENGTH_ENTRY(server_stats),               /* SERVER_STATS3 */
 };

 /* ================================================== */
--- a/privops.c
+++ b/privops.c
@@ -255,7 +255,7 @@ do_bind_socket(ReqBindSocket *req, PrvResponse *res)

  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_GetAcquisitionPort() && ip_saddr.port != CNF_GetPtpPort()) {
    SCK_CloseSocket(sock_fd);
    res_fatal(res, "Invalid port %d", ip_saddr.port);
    return;
@@ -547,7 +547,7 @@ PRV_BindSocket(int sock, struct sockaddr *address, socklen_t address_len)

  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_GetAcquisitionPort() && ip_saddr.port != CNF_GetPtpPort())
    assert(0);

  if (!have_helper())
@@ -662,6 +662,8 @@ PRV_StartHelper(void)
        close(fd);
    }

+    UTI_ResetGetRandomFunctions();
+
    /* ignore signals, the process will exit on OP_QUIT request */
    UTI_SetQuitSignalsHandler(SIG_IGN, 1);

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

 **********************************************************************
- * Copyright (C) Miroslav Lichvar  2009-2011, 2013-2014, 2016-2019
+ * Copyright (C) Miroslav Lichvar  2009-2011, 2013-2014, 2016-2019, 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
@@ -40,6 +40,9 @@
 #include "samplefilt.h"
 #include "sched.h"

+/* Maximum offset of locked reference as a fraction of the PPS interval */
+#define PPS_LOCK_LIMIT 0.4
+
 /* list of refclock drivers */
 extern RefclockDriver RCL_SHM_driver;
 extern RefclockDriver RCL_SOCK_driver;
@@ -52,21 +55,6 @@ struct FilterSample {
  struct timespec sample_time;
 };

-struct MedianFilter {
-  int length;
-  int index;
-  int used;
-  int last;
-  int avg_var_n;
-  double avg_var;
-  double max_var;
-  struct FilterSample *samples;
-  int *selected;
-  double *x_data;
-  double *y_data;
-  double *w_data;
-};
-
 struct RCL_Instance_Record {
  RefclockDriver *driver;
  void *data;
@@ -76,6 +64,7 @@ struct RCL_Instance_Record {
  int driver_polled;
  int poll;
  int leap_status;
+  int local;
  int pps_forced;
  int pps_rate;
  int pps_active;
@@ -181,12 +170,13 @@ RCL_AddRefclock(RefclockParameters *params)
    LOG_FATAL("refclock tai option requires leapsectz");

  inst->data = NULL;
-  inst->driver_parameter = params->driver_parameter;
+  inst->driver_parameter = Strdup(params->driver_parameter);
  inst->driver_parameter_length = 0;
  inst->driver_poll = params->driver_poll;
  inst->poll = params->poll;
  inst->driver_polled = 0;
  inst->leap_status = LEAP_Normal;
+  inst->local = params->local;
  inst->pps_forced = params->pps_forced;
  inst->pps_rate = params->pps_rate;
  inst->pps_active = 0;
@@ -228,6 +218,13 @@ RCL_AddRefclock(RefclockParameters *params)
    inst->ref_id = (uint32_t)ref[0] << 24 | ref[1] << 16 | ref[2] << 8 | ref[3];
  }

+  if (inst->local) {
+    inst->pps_forced = 1;
+    inst->lock_ref = inst->ref_id;
+    inst->leap_status = LEAP_Unsynchronised;
+    inst->max_lock_age = MAX(inst->max_lock_age, 3);
+  }
+
  if (inst->driver->poll) {
    int max_samples;

@@ -261,15 +258,13 @@ RCL_AddRefclock(RefclockParameters *params)
      params->driver_name, UTI_RefidToString(inst->ref_id),
      inst->poll, inst->driver_poll, params->filter_length);

-  Free(params->driver_name);
-
  return 1;
 }

 void
 RCL_StartRefclocks(void)
 {
-  unsigned int i, j, n;
+  unsigned int i, j, n, lock_index;

  n = ARR_GetSize(refclocks);

@@ -279,13 +274,31 @@ RCL_StartRefclocks(void)
    SRC_SetActive(inst->source);
    inst->timeout_id = SCH_AddTimeoutByDelay(0.0, poll_timeout, (void *)inst);

-    if (inst->lock_ref) {
-      /* Replace lock refid with index to refclocks */
-      for (j = 0; j < n && get_refclock(j)->ref_id != inst->lock_ref; j++)
-        ;
-      inst->lock_ref = j < n ? j : -1;
-    } else
-      inst->lock_ref = -1;
+    /* Replace lock refid with the refclock's index, or -1 if not valid */
+
+    lock_index = -1;
+
+    if (inst->lock_ref != 0) {
+      for (j = 0; j < n; j++) {
+        RCL_Instance inst2 = get_refclock(j);
+
+        if (inst->lock_ref != inst2->ref_id)
+          continue;
+
+        if (inst->driver->poll && inst2->driver->poll &&
+            (double)inst->max_lock_age / inst->pps_rate < UTI_Log2ToDouble(inst2->driver_poll))
+          LOG(LOGS_WARN, "%s maxlockage too small for %s",
+              UTI_RefidToString(inst->ref_id), UTI_RefidToString(inst2->ref_id));
+
+        lock_index = j;
+        break;
+      }
+
+      if (lock_index == -1 || (lock_index == i && !inst->local))
+        LOG(LOGS_WARN, "Invalid lock refid %s", UTI_RefidToString(inst->lock_ref));
+    }
+
+    inst->lock_ref = lock_index;
  }
 }

@@ -417,30 +430,28 @@ accumulate_sample(RCL_Instance instance, struct timespec *sample_time, double of
  sample.peer_dispersion = dispersion;
  sample.root_dispersion = dispersion;

-  /* Handle special case when PPS is used with the local reference */
-  if (instance->pps_active && instance->lock_ref == -1)
-    sample.stratum = pps_stratum(instance, &sample.time);
-  else
-    sample.stratum = instance->stratum;
-
  return SPF_AccumulateSample(instance->filter, &sample);
 }

 int
-RCL_AddSample(RCL_Instance instance, struct timespec *sample_time, double offset, int leap)
+RCL_AddSample(RCL_Instance instance, struct timespec *sample_time,
+              struct timespec *ref_time, int leap)
 {
-  double correction, dispersion;
+  double correction, dispersion, raw_offset, offset;
  struct timespec cooked_time;

  if (instance->pps_forced)
-    return RCL_AddPulse(instance, sample_time, -offset);
+    return RCL_AddPulse(instance, sample_time,
+                        1.0e-9 * (sample_time->tv_nsec - ref_time->tv_nsec));
+
+  raw_offset = UTI_DiffTimespecsToDouble(ref_time, sample_time);

  LCL_GetOffsetCorrection(sample_time, &correction, &dispersion);
  UTI_AddDoubleToTimespec(sample_time, correction, &cooked_time);
  dispersion += instance->precision;

  /* Make sure the timestamp and offset provided by the driver are sane */
-  if (!UTI_IsTimeOffsetSane(sample_time, offset) ||
+  if (!UTI_IsTimeOffsetSane(sample_time, raw_offset) ||
      !valid_sample_time(instance, &cooked_time))
    return 0;

@@ -455,18 +466,24 @@ RCL_AddSample(RCL_Instance instance, struct timespec *sample_time, double offset
      return 0;
  }

+  /* Calculate offset = raw_offset - correction + instance->offset
+     in parts to avoid loss of precision if there are large differences */
+  offset = ref_time->tv_sec - sample_time->tv_sec -
+           (time_t)correction + (time_t)instance->offset;
+  offset += 1.0e-9 * (ref_time->tv_nsec - sample_time->tv_nsec) -
+            (correction - (time_t)correction) + (instance->offset - (time_t)instance->offset);
+
  if (instance->tai && !convert_tai_offset(sample_time, &offset)) {
    DEBUG_LOG("refclock sample ignored unknown TAI offset");
    return 0;
  }

-  if (!accumulate_sample(instance, &cooked_time,
-                         offset - correction + instance->offset, dispersion))
+  if (!accumulate_sample(instance, &cooked_time, offset, dispersion))
    return 0;

  instance->pps_active = 0;

-  log_sample(instance, &cooked_time, 0, 0, offset, offset - correction + instance->offset, dispersion);
+  log_sample(instance, &cooked_time, 0, 0, raw_offset, offset, dispersion);

  /* for logging purposes */
  if (!instance->driver->poll)
@@ -545,29 +562,40 @@ RCL_AddCookedPulse(RCL_Instance instance, struct timespec *cooked_time,
    lock_refclock = get_refclock(instance->lock_ref);

    if (!SPF_GetLastSample(lock_refclock->filter, &ref_sample)) {
+      if (instance->local) {
+        /* Make the first sample in order to lock to itself */
+        ref_sample.time = *cooked_time;
+        ref_sample.offset = offset;
+        ref_sample.peer_delay = ref_sample.peer_dispersion = 0;
+        ref_sample.root_delay = ref_sample.root_dispersion = 0;
+      } else {
        DEBUG_LOG("refclock pulse ignored no ref sample");
        return 0;
      }
+    }

    ref_sample.root_dispersion += SPF_GetAvgSampleDispersion(lock_refclock->filter);

    sample_diff = UTI_DiffTimespecsToDouble(cooked_time, &ref_sample.time);
    if (fabs(sample_diff) >= (double)instance->max_lock_age / rate) {
-      DEBUG_LOG("refclock pulse ignored samplediff=%.9f",
-          sample_diff);
+      DEBUG_LOG("refclock pulse ignored samplediff=%.9f", sample_diff);
+
+      /* Restart the local mode */
+      if (instance->local) {
+        LOG(LOGS_WARN, "Local refclock lost lock");
+        SPF_DropSamples(instance->filter);
+        SRC_ResetInstance(instance->source);
+      }
      return 0;
    }

    /* Align the offset to the reference sample */
-    if ((ref_sample.offset - offset) >= 0.0)
-      shift = (long)((ref_sample.offset - offset) * rate + 0.5) / (double)rate;
-    else
-      shift = (long)((ref_sample.offset - offset) * rate - 0.5) / (double)rate;
+    shift = round((ref_sample.offset - offset) * rate) / rate;

    offset += shift;

    if (fabs(ref_sample.offset - offset) +
-        ref_sample.root_dispersion + dispersion >= 0.2 / rate) {
+        ref_sample.root_dispersion + dispersion > PPS_LOCK_LIMIT / rate) {
      DEBUG_LOG("refclock pulse ignored offdiff=%.9f refdisp=%.9f disp=%.9f",
                ref_sample.offset - offset, ref_sample.root_dispersion, dispersion);
      return 0;
@@ -683,11 +711,57 @@ pps_stratum(RCL_Instance instance, struct timespec *ts)
  return 0;
 }

+static void
+get_local_stats(RCL_Instance inst, struct timespec *ref, double *freq, double *offset)
+{
+  double offset_sd, freq_sd, skew, root_delay, root_disp;
+  SST_Stats stats = SRC_GetSourcestats(inst->source);
+
+  if (SST_Samples(stats) < SST_GetMinSamples(stats)) {
+    UTI_ZeroTimespec(ref);
+    return;
+  }
+
+  SST_GetTrackingData(stats, ref, offset, &offset_sd, freq, &freq_sd,
+                      &skew, &root_delay, &root_disp);
+}
+
+static void
+follow_local(RCL_Instance inst, struct timespec *prev_ref_time, double prev_freq,
+             double prev_offset)
+{
+  SST_Stats stats = SRC_GetSourcestats(inst->source);
+  double freq, dfreq, offset, doffset, elapsed;
+  struct timespec now, ref_time;
+
+  get_local_stats(inst, &ref_time, &freq, &offset);
+
+  if (UTI_IsZeroTimespec(prev_ref_time) || UTI_IsZeroTimespec(&ref_time))
+    return;
+
+  dfreq = (freq - prev_freq) / (1.0 - prev_freq);
+  elapsed = UTI_DiffTimespecsToDouble(&ref_time, prev_ref_time);
+  doffset = offset - elapsed * prev_freq - prev_offset;
+
+  if (!REF_AdjustReference(doffset, dfreq))
+    return;
+
+  LCL_ReadCookedTime(&now, NULL);
+  SST_SlewSamples(stats, &now, dfreq, doffset);
+  SPF_SlewSamples(inst->filter, &now, dfreq, doffset);
+
+  /* Keep the offset close to zero to not lose precision */
+  if (fabs(offset) >= 1.0) {
+    SST_CorrectOffset(stats, -round(offset));
+    SPF_CorrectOffset(inst->filter, -round(offset));
+  }
+}
+
 static void
 poll_timeout(void *arg)
 {
  NTP_Sample sample;
-  int poll;
+  int poll, stratum;

  RCL_Instance inst = (RCL_Instance)arg;

@@ -703,11 +777,28 @@ poll_timeout(void *arg)
    inst->driver_polled = 0;

    if (SPF_GetFilteredSample(inst->filter, &sample)) {
+      double local_freq, local_offset;
+      struct timespec local_ref_time;
+
+      /* Handle special case when PPS is used with the local reference */
+      if (inst->pps_active && inst->lock_ref == -1)
+        stratum = pps_stratum(inst, &sample.time);
+      else
+        stratum = inst->stratum;
+
+      if (inst->local) {
+        get_local_stats(inst, &local_ref_time, &local_freq, &local_offset);
+        inst->leap_status = LEAP_Unsynchronised;
+      }
+
      SRC_UpdateReachability(inst->source, 1);
-      SRC_SetLeapStatus(inst->source, inst->leap_status);
+      SRC_UpdateStatus(inst->source, stratum, inst->leap_status);
      SRC_AccumulateSample(inst->source, &sample);
      SRC_SelectSource(inst->source);

+      if (inst->local)
+        follow_local(inst, &local_ref_time, local_freq, local_offset);
+
      log_sample(inst, &sample.time, 1, 0, 0.0, sample.offset, sample.peer_dispersion);
    } else {
      SRC_UpdateReachability(inst->source, 0);
--- a/refclock.h
+++ b/refclock.h
@@ -37,6 +37,7 @@ typedef struct {
  int driver_poll;
  int poll;
  int filter_length;
+  int local;
  int pps_forced;
  int pps_rate;
  int min_samples;
@@ -74,7 +75,8 @@ 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);
--- a/refclock_phc.c
+++ b/refclock_phc.c
@@ -66,10 +66,8 @@ static int phc_initialise(RCL_Instance instance)
  path = RCL_GetDriverParameter(instance);
 
  phc_fd = SYS_Linux_OpenPHC(path, 0);
-  if (phc_fd < 0) {
+  if (phc_fd < 0)
    LOG_FATAL("Could not open PHC");
-    return 0;
-  }

  phc = MallocNew(struct phc_instance);
  phc->fd = phc_fd;
@@ -77,13 +75,15 @@ static int phc_initialise(RCL_Instance instance)
  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;
-    phc->clock = HCL_CreateInstance(0, 16, UTI_Log2ToDouble(RCL_GetDriverPoll(instance)));

    if (!SYS_Linux_SetPHCExtTimestamping(phc->fd, phc->pin, phc->channel,
                                         rising_edge, !rising_edge, 1))
@@ -92,7 +92,6 @@ static int phc_initialise(RCL_Instance instance)
    SCH_AddFileHandler(phc->fd, SCH_FILE_INPUT, read_ext_pulse, instance);
  } else {
    phc->pin = phc->channel = 0;
-    phc->clock = NULL;
  }

  RCL_SetDriverData(instance, phc);
@@ -108,9 +107,9 @@ static void phc_finalise(RCL_Instance instance)
  if (phc->extpps) {
    SCH_RemoveFileHandler(phc->fd);
    SYS_Linux_SetPHCExtTimestamping(phc->fd, phc->pin, phc->channel, 0, 0, 0);
-    HCL_DestroyInstance(phc->clock);
  }

+  HCL_DestroyInstance(phc->clock);
  close(phc->fd);
  Free(phc);
 }
@@ -141,29 +140,35 @@ static void read_ext_pulse(int fd, int event, void *anything)
                     UTI_DiffTimespecsToDouble(&phc_ts, &local_ts));
 }

+#define PHC_READINGS 25
+
 static int phc_poll(RCL_Instance instance)
 {
+  struct timespec phc_ts, sys_ts, local_ts, readings[PHC_READINGS][3];
  struct phc_instance *phc;
-  struct timespec phc_ts, sys_ts, local_ts;
-  double offset, phc_err, local_err;
+  double phc_err, local_err;
+  int n_readings;

  phc = (struct phc_instance *)RCL_GetDriverData(instance);

-  if (!SYS_Linux_GetPHCSample(phc->fd, phc->nocrossts, RCL_GetPrecision(instance),
-                              &phc->mode, &phc_ts, &sys_ts, &phc_err))
+  n_readings = SYS_Linux_GetPHCReadings(phc->fd, phc->nocrossts, &phc->mode,
+                                        PHC_READINGS, readings);
+  if (n_readings < 1)
+    return 0;
+
+  if (!HCL_ProcessReadings(phc->clock, n_readings, readings, &phc_ts, &sys_ts, &phc_err))
    return 0;

-  if (phc->extpps) {
  LCL_CookTime(&sys_ts, &local_ts, &local_err);
  HCL_AccumulateSample(phc->clock, &phc_ts, &local_ts, phc_err + local_err);
+
+  if (phc->extpps)
    return 0;
-  }

-  offset = UTI_DiffTimespecsToDouble(&phc_ts, &sys_ts);
+  DEBUG_LOG("PHC offset: %+.9f err: %.9f",
+            UTI_DiffTimespecsToDouble(&phc_ts, &sys_ts), phc_err);

-  DEBUG_LOG("PHC offset: %+.9f err: %.9f", offset, phc_err);
-
-  return RCL_AddSample(instance, &sys_ts, offset, LEAP_Normal);
+  return RCL_AddSample(instance, &sys_ts, &phc_ts, LEAP_Normal);
 }

 RefclockDriver RCL_PHC_driver = {
--- a/refclock_pps.c
+++ b/refclock_pps.c
@@ -61,49 +61,36 @@ static int pps_initialise(RCL_Instance instance) {
  edge_clear = RCL_GetDriverOption(instance, "clear") ? 1 : 0;

  fd = open(path, O_RDWR);
-  if (fd < 0) {
+  if (fd < 0)
    LOG_FATAL("Could not open %s : %s", path, strerror(errno));
-    return 0;
-  }

  UTI_FdSetCloexec(fd);

-  if (time_pps_create(fd, &handle) < 0) {
+  if (time_pps_create(fd, &handle) < 0)
    LOG_FATAL("time_pps_create() failed on %s : %s", path, strerror(errno));
-    return 0;
-  }

-  if (time_pps_getcap(handle, &mode) < 0) {
+  if (time_pps_getcap(handle, &mode) < 0)
    LOG_FATAL("time_pps_getcap() failed on %s : %s", path, strerror(errno));
-    return 0;
-  }

-  if (time_pps_getparams(handle, &params) < 0) {
+  if (time_pps_getparams(handle, &params) < 0)
    LOG_FATAL("time_pps_getparams() failed on %s : %s", path, strerror(errno));
-    return 0;
-  }

  if (!edge_clear) {
-    if (!(mode & PPS_CAPTUREASSERT)) {
+    if (!(mode & PPS_CAPTUREASSERT))
      LOG_FATAL("CAPTUREASSERT not supported on %s", path);
-      return 0;
-    }
+
    params.mode |= PPS_CAPTUREASSERT;
    params.mode &= ~PPS_CAPTURECLEAR;
  } else {
-    if (!(mode & PPS_CAPTURECLEAR)) {
+    if (!(mode & PPS_CAPTURECLEAR))
      LOG_FATAL("CAPTURECLEAR not supported on %s", path);
-      return 0;
-    }
+
    params.mode |= PPS_CAPTURECLEAR;
    params.mode &= ~PPS_CAPTUREASSERT;
  }

-  if (time_pps_setparams(handle, &params) < 0) {
+  if (time_pps_setparams(handle, &params) < 0)
    LOG_FATAL("time_pps_setparams() failed on %s : %s", path, strerror(errno));
-    return 0;
-  }
-

  pps = MallocNew(struct pps_instance);
  pps->handle = handle;
--- a/refclock_shm.c
+++ b/refclock_shm.c
@@ -95,7 +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);

@@ -124,9 +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
@@ -60,8 +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;

@@ -86,13 +86,18 @@ static void read_sample(int sockfd, int event, void *anything)
    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);
  }
 }

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

 **********************************************************************
 * Copyright (C) Richard P. Curnow  1997-2003
- * Copyright (C) Miroslav Lichvar  2009-2018, 2020
+ * Copyright (C) Miroslav Lichvar  2009-2018, 2020, 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
@@ -150,6 +150,9 @@ static SCH_TimeoutID fb_drift_timeout_id;
 static double last_ref_update;
 static double last_ref_update_interval;

+static double last_ref_adjustment;
+static int ref_adjustments;
+
 /* ================================================== */

 static NTP_Leap get_tz_leap(time_t when, int *tai_offset);
@@ -286,6 +289,8 @@ REF_Initialise(void)
  UTI_ZeroTimespec(&our_ref_time);
  last_ref_update = 0.0;
  last_ref_update_interval = 0.0;
+  last_ref_adjustment = 0.0;
+  ref_adjustments = 0;

  LCL_AddParameterChangeHandler(handle_slew, NULL);

@@ -960,6 +965,27 @@ fuzz_ref_time(struct timespec *ts)

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

+static double
+get_correction_rate(double offset_sd, double update_interval)
+{
+  /* We want to correct the offset quickly, but we also want to keep the
+     frequency error caused by the correction itself low.
+
+     Define correction rate as the area of the region bounded by the graph of
+     offset corrected in time.  Set the rate so that the time needed to correct
+     an offset equal to the current sourcestats stddev will be equal to the
+     update interval multiplied by the correction time ratio (assuming linear
+     adjustment).  The offset and the time needed to make the correction are
+     inversely proportional.
+
+     This is only a suggestion and it's up to the system driver how the
+     adjustment will be executed. */
+
+  return correction_time_ratio * 0.5 * offset_sd * update_interval;
+}
+
+/* ================================================== */
+
 void
 REF_SetReference(int stratum, NTP_Leap leap, int combined_sources,
                 uint32_t ref_id, IPAddr *ref_ip, struct timespec *ref_time,
@@ -969,7 +995,7 @@ REF_SetReference(int stratum, NTP_Leap leap, int combined_sources,
 {
  double uncorrected_offset, accumulate_offset, step_offset;
  double residual_frequency, local_abs_frequency;
-  double elapsed, mono_now, update_interval, correction_rate, orig_root_distance;
+  double elapsed, mono_now, update_interval, orig_root_distance;
  struct timespec now, raw_now;
  int manual;

@@ -1024,21 +1050,6 @@ REF_SetReference(int stratum, NTP_Leap leap, int combined_sources,
  last_ref_update_interval = update_interval;
  last_offset = offset;

-  /* We want to correct the offset quickly, but we also want to keep the
-     frequency error caused by the correction itself low.
-
-     Define correction rate as the area of the region bounded by the graph of
-     offset corrected in time. Set the rate so that the time needed to correct
-     an offset equal to the current sourcestats stddev will be equal to the
-     update interval multiplied by the correction time ratio (assuming linear
-     adjustment). The offset and the time needed to make the correction are
-     inversely proportional.
-
-     This is only a suggestion and it's up to the system driver how the
-     adjustment will be executed. */
-
-  correction_rate = correction_time_ratio * 0.5 * offset_sd * update_interval;
-
  /* Check if the clock should be stepped */
  if (is_step_limit_reached(offset, uncorrected_offset)) {
    /* Cancel the uncorrected offset and correct the total offset by step */
@@ -1050,7 +1061,8 @@ REF_SetReference(int stratum, NTP_Leap leap, int combined_sources,
  }

  /* Adjust the clock */
-  LCL_AccumulateFrequencyAndOffset(frequency, accumulate_offset, correction_rate);
+  LCL_AccumulateFrequencyAndOffset(frequency, accumulate_offset,
+                                   get_correction_rate(offset_sd, update_interval));
    
  maybe_log_offset(offset, raw_now.tv_sec);

@@ -1095,6 +1107,27 @@ REF_SetReference(int stratum, NTP_Leap leap, int combined_sources,
      avg2_moving = 1;
    avg2_offset = SQUARE(offset);
  }
+
+  ref_adjustments = 0;
+}
+
+/* ================================================== */
+
+int
+REF_AdjustReference(double offset, double frequency)
+{
+  double adj_corr_rate, ref_corr_rate, mono_now;
+
+  mono_now = SCH_GetLastEventMonoTime();
+  ref_adjustments++;
+
+  adj_corr_rate = get_correction_rate(fabs(offset), mono_now - last_ref_adjustment);
+  ref_corr_rate = get_correction_rate(our_offset_sd, last_ref_update_interval) /
+                  ref_adjustments;
+  last_ref_adjustment = mono_now;
+
+  return LCL_AccumulateFrequencyAndOffsetNoHandlers(frequency, offset,
+                                                    MAX(adj_corr_rate, ref_corr_rate));
 }

 /* ================================================== */
@@ -1333,7 +1366,8 @@ REF_DisableLocal(void)
 static int
 is_leap_close(time_t t)
 {
-  return t >= leap_when - LEAP_SECOND_CLOSE && t < leap_when + LEAP_SECOND_CLOSE;
+  return leap_when != 0 &&
+         t >= leap_when - LEAP_SECOND_CLOSE && t < leap_when + LEAP_SECOND_CLOSE;
 }

 /* ================================================== */
--- a/reference.h
+++ b/reference.h
@@ -162,6 +162,10 @@ extern void REF_SetManualReference
 extern void
 REF_SetUnsynchronised(void);

+/* Make a small correction of the clock without updating the reference
+   parameters and calling the clock change handlers */
+extern int REF_AdjustReference(double offset, double frequency);
+
 /* Announce a leap second before the full reference update */
 extern void REF_UpdateLeapStatus(NTP_Leap leap);

--- a/reports.h
+++ b/reports.h
@@ -117,6 +117,9 @@ typedef struct {
  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;
 } RPT_ServerStatsReport;

 typedef struct {
@@ -171,6 +174,7 @@ typedef struct {
  uint32_t total_tx_count;
  uint32_t total_rx_count;
  uint32_t total_valid_count;
+  uint32_t total_good_count;
 } RPT_NTPReport;

 typedef struct {
@@ -190,6 +194,7 @@ typedef struct {
  IPAddr ip_addr;
  char state_char;
  int authentication;
+  NTP_Leap leap;
  int conf_options;
  int eff_options;
  uint32_t last_sample_ago;
--- a/rtc.c
+++ b/rtc.c
@@ -148,6 +148,8 @@ RTC_Initialise(int initial_set)
    if (driver.init) {
      if ((driver.init)()) {
        driver_initialised = 1;
+      } else {
+        LOG(LOGS_ERR, "RTC driver could not be initialised");
      }
    } else {
      LOG(LOGS_ERR, "RTC not supported on this operating system");
--- a/rtc_linux.c
+++ b/rtc_linux.c
@@ -64,7 +64,7 @@ static OperatingMode operating_mode = OM_NORMAL;

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

-static int fd = -1;
+static int fd;

 #define LOWEST_MEASUREMENT_PERIOD 15
 #define HIGHEST_MEASUREMENT_PERIOD 480
@@ -82,16 +82,12 @@ static int skip_interrupts;
 #define MAX_SAMPLES 64

 /* Real time clock samples.  We store the seconds count as originally
-   measured, together with a 'trim' that compensates these values for
-   any steps made to the RTC to bring it back into line
-   occasionally.  The trim is in seconds. */
+   measured. */
 static time_t *rtc_sec = NULL;
-static double *rtc_trim = NULL;

 /* Reference time, against which delta times on the RTC scale are measured */
 static time_t rtc_ref;

-
 /* System clock samples associated with the above samples. */
 static struct timespec *system_times = NULL;

@@ -145,7 +141,7 @@ static double file_ref_offset, file_rate_ppm;
 /* ================================================== */

 /* Flag to remember whether to assume the RTC is running on UTC */
-static int rtc_on_utc = 1;
+static int rtc_on_utc;

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

@@ -168,7 +164,6 @@ discard_samples(int new_first)
  n_to_save = n_samples - new_first;

  memmove(rtc_sec, rtc_sec + new_first, n_to_save * sizeof(time_t));
-  memmove(rtc_trim, rtc_trim + new_first, n_to_save * sizeof(double));
  memmove(system_times, system_times + new_first, n_to_save * sizeof(struct timespec));

  n_samples = n_to_save;
@@ -188,21 +183,16 @@ accumulate_sample(time_t rtc, struct timespec *sys)
  }

  /* Discard all samples if the RTC was stepped back (not our trim) */
-  if (n_samples > 0 && rtc_sec[n_samples - 1] - rtc >= rtc_trim[n_samples - 1]) {
+  if (n_samples > 0 && rtc_sec[n_samples - 1] >= rtc) {
    DEBUG_LOG("RTC samples discarded");
    n_samples = 0;
  }

  /* Always use most recent sample as reference */
-  /* use sample only if n_sample is not negative*/
-  if(n_samples >=0)
-  {
  rtc_ref = rtc;
  rtc_sec[n_samples] = rtc;
-  rtc_trim[n_samples] = 0.0;
  system_times[n_samples] = *sys;
  ++n_samples_since_regression;
-  }
  ++n_samples;
 }

@@ -227,7 +217,7 @@ run_regression(int new_sample,
  if (n_samples > 0) {

    for (i=0; i<n_samples; i++) {
-      rtc_rel[i] = rtc_trim[i] + (double)(rtc_sec[i] - rtc_ref);
+      rtc_rel[i] = (double)(rtc_sec[i] - rtc_ref);
      offsets[i] = ((double) (rtc_ref - system_times[i].tv_sec) -
                    (1.0e-9 * system_times[i].tv_nsec) +
                    rtc_rel[i]);
@@ -434,6 +424,7 @@ setup_config(void)
 static void
 read_coefs_from_file(void)
 {
+  double ref_time;
  FILE *in;

  if (!tried_to_load_coefs) {
@@ -444,11 +435,12 @@ read_coefs_from_file(void)

    if (coefs_file_name &&
        (in = UTI_OpenFile(NULL, coefs_file_name, NULL, 'r', 0))) {
-      if (fscanf(in, "%d%ld%lf%lf",
+      if (fscanf(in, "%d%lf%lf%lf",
                 &valid_coefs_from_file,
-                 &file_ref_time,
+                 &ref_time,
                 &file_ref_offset,
                 &file_rate_ppm) == 4) {
+        file_ref_time = ref_time;
      } else {
        LOG(LOGS_WARN, "Could not read coefficients from %s", coefs_file_name);
      }
@@ -472,7 +464,7 @@ write_coefs_to_file(int valid,time_t ref_time,double offset,double rate)
    return RTC_ST_BADFILE;

  /* Gain rate is written out in ppm */
-  fprintf(out, "%1d %ld %.6f %.3f\n", valid, ref_time, offset, 1.0e6 * rate);
+  fprintf(out, "%1d %.0f %.6f %.3f\n", valid, (double)ref_time, offset, 1.0e6 * rate);
  fclose(out);

  /* Rename the temporary file to the correct location */
@@ -525,7 +517,6 @@ RTC_Linux_Initialise(void)
  UTI_FdSetCloexec(fd);

  rtc_sec = MallocArray(time_t, MAX_SAMPLES);
-  rtc_trim = MallocArray(double, MAX_SAMPLES);
  system_times = MallocArray(struct timespec, MAX_SAMPLES);

  /* Setup details depending on configuration options */
@@ -578,7 +569,6 @@ RTC_Linux_Finalise(void)
    LCL_RemoveParameterChangeHandler(slew_samples, NULL);

  Free(rtc_sec);
-  Free(rtc_trim);
  Free(system_times);
 }

@@ -639,11 +629,7 @@ handle_initial_trim(void)
  run_regression(1, &coefs_valid, &coef_ref_time, &coef_seconds_fast, &coef_gain_rate);

  n_samples_since_regression = 0;
-
-  /* Set sample number to -1 so the next sample is not used, as it will not yet be corrected for System Trim*/
-
-  n_samples = -1;
-
+  n_samples = 0;

  read_coefs_from_file();

@@ -1028,8 +1014,7 @@ RTC_Linux_GetReport(RPT_RTC_Report *report)
  report->n_samples = n_samples;
  report->n_runs = n_runs;
  if (n_samples > 1) {
-    report->span_seconds = ((rtc_sec[n_samples-1] - rtc_sec[0]) +
-                            (long)(rtc_trim[n_samples-1] - rtc_trim[0]));
+    report->span_seconds = rtc_sec[n_samples - 1] - rtc_sec[0];
  } else {
    report->span_seconds = 0;
  }
--- a/samplefilt.c
+++ b/samplefilt.c
@@ -162,6 +162,14 @@ SPF_GetNumberOfSamples(SPF_Instance filter)

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

+int
+SPF_GetMaxSamples(SPF_Instance filter)
+{
+  return filter->max_samples;
+}
+
+/* ================================================== */
+
 double
 SPF_GetAvgSampleDispersion(SPF_Instance filter)
 {
@@ -170,11 +178,21 @@ SPF_GetAvgSampleDispersion(SPF_Instance filter)

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

-void
-SPF_DropSamples(SPF_Instance filter)
+static void
+drop_samples(SPF_Instance filter, int keep_last)
 {
  filter->index = -1;
  filter->used = 0;
+  if (!keep_last)
+    filter->last = -1;
+}
+
+/* ================================================== */
+
+void
+SPF_DropSamples(SPF_Instance filter)
+{
+  drop_samples(filter, 0);
 }

 /* ================================================== */
@@ -386,7 +404,6 @@ combine_selected_samples(SPF_Instance filter, int n, NTP_Sample *result)
  result->root_dispersion = MAX(disp, mean_root_dispersion);
  result->peer_delay = mean_peer_delay;
  result->root_delay = mean_root_delay;
-  result->stratum = last_sample->stratum;

  return 1;
 }
@@ -400,17 +417,40 @@ SPF_GetFilteredSample(SPF_Instance filter, NTP_Sample *sample)

  n = select_samples(filter);

+  DEBUG_LOG("selected %d from %d samples", n, filter->used);
+
  if (n < 1)
    return 0;

  if (!combine_selected_samples(filter, n, sample))
    return 0;

-  SPF_DropSamples(filter);
+  drop_samples(filter, 1);

  return 1;
 }

+/* ================================================== */
+
+static int
+get_first_last(SPF_Instance filter, int *first, int *last)
+{
+  if (filter->last < 0)
+    return 0;
+
+  /* Always slew the last sample as it may be returned even if no new
+     samples were accumulated */
+  if (filter->used > 0) {
+    *first = 0;
+    *last = filter->used - 1;
+  } else {
+    *first = *last = filter->last;
+  }
+
+  return 1;
+}
+
+
 /* ================================================== */

 void
@@ -419,18 +459,9 @@ SPF_SlewSamples(SPF_Instance filter, struct timespec *when, double dfreq, double
  int i, first, last;
  double delta_time;

-  if (filter->last < 0)
+  if (!get_first_last(filter, &first, &last))
    return;

-  /* Always slew the last sample as it may be returned even if no new
-     samples were accumulated */
-  if (filter->used > 0) {
-    first = 0;
-    last = filter->used - 1;
-  } else {
-    first = last = filter->last;
-  }
-
  for (i = first; i <= last; i++) {
    UTI_AdjustTimespec(&filter->samples[i].time, when, &filter->samples[i].time,
                       &delta_time, dfreq, doffset);
@@ -440,6 +471,20 @@ SPF_SlewSamples(SPF_Instance filter, struct timespec *when, double dfreq, double

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

+void
+SPF_CorrectOffset(SPF_Instance filter, double doffset)
+{
+  int i, first, last;
+
+  if (!get_first_last(filter, &first, &last))
+    return;
+
+  for (i = first; i <= last; i++)
+    filter->samples[i].offset -= doffset;
+}
+
+/* ================================================== */
+
 void
 SPF_AddDispersion(SPF_Instance filter, double dispersion)
 {
--- a/samplefilt.h
+++ b/samplefilt.h
@@ -39,11 +39,13 @@ extern void SPF_DestroyInstance(SPF_Instance filter);
 extern int SPF_AccumulateSample(SPF_Instance filter, NTP_Sample *sample);
 extern int SPF_GetLastSample(SPF_Instance filter, NTP_Sample *sample);
 extern int SPF_GetNumberOfSamples(SPF_Instance filter);
+extern int SPF_GetMaxSamples(SPF_Instance filter);
 extern double SPF_GetAvgSampleDispersion(SPF_Instance filter);
 extern void SPF_DropSamples(SPF_Instance filter);
 extern int SPF_GetFilteredSample(SPF_Instance filter, NTP_Sample *sample);
 extern void SPF_SlewSamples(SPF_Instance filter, struct timespec *when,
                            double dfreq, double doffset);
+extern void SPF_CorrectOffset(SPF_Instance filter, double doffset);
 extern void SPF_AddDispersion(SPF_Instance filter, double dispersion);

 #endif
--- a/sched.c
+++ b/sched.c
@@ -111,7 +111,8 @@ static struct timespec last_class_dispatch[SCH_NumberOfClasses];

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

-static int need_to_exit;
+/* Flag terminating the main loop, which can be set from a signal handler */
+static volatile int need_to_exit;

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

@@ -498,12 +499,15 @@ SCH_RemoveTimeout(SCH_TimeoutID id)

 static void
 dispatch_timeouts(struct timespec *now) {
+  unsigned long n_done, n_entries_on_start;
  TimerQueueEntry *ptr;
  SCH_TimeoutHandler handler;
  SCH_ArbitraryArgument arg;
-  int n_done = 0, n_entries_on_start = n_timer_queue_entries;

-  while (1) {
+  n_entries_on_start = n_timer_queue_entries;
+  n_done = 0;
+
+  do {
    LCL_ReadRawTime(now);

    if (!(n_timer_queue_entries > 0 &&
@@ -526,16 +530,21 @@ dispatch_timeouts(struct timespec *now) {
    /* Increment count of timeouts handled */
    ++n_done;

-    /* If more timeouts were handled than there were in the timer queue on
-       start and there are now, assume some code is scheduling timeouts with
-       negative delays and abort.  Make the actual limit higher in case the
-       machine is temporarily overloaded and dispatching the handlers takes
-       more time than was delay of a scheduled timeout. */
-    if (n_done > n_timer_queue_entries * 4 &&
-        n_done > n_entries_on_start * 4) {
+    /* If the number of dispatched timeouts is significantly larger than the
+       length of the queue on start and now, assume there is a bug causing
+       an infinite loop by constantly adding a timeout with a zero or negative
+       delay.  Check the actual rate of timeouts to avoid false positives in
+       case the execution slowed down so much (e.g. due to memory thrashing)
+       that it repeatedly takes more time to handle the timeout than is its
+       delay.  This is a safety mechanism intended to stop a full-speed flood
+       of NTP requests due to a bug in the NTP polling. */
+
+    if (n_done > 20 &&
+        n_done > 4 * MAX(n_timer_queue_entries, n_entries_on_start) &&
+        fabs(UTI_DiffTimespecsToDouble(now, &last_select_ts_raw)) / n_done < 0.01)
      LOG_FATAL("Possible infinite loop in scheduling");
-    }
-  }
+
+  } while (!need_to_exit);
 }

 /* ================================================== */
@@ -799,14 +808,14 @@ SCH_MainLoop(void)
    LCL_ReadRawTime(&now);
    LCL_CookTime(&now, &cooked, &err);

+    update_monotonic_time(&now, &last_select_ts_raw);
+
    /* Check if the time didn't jump unexpectedly */
    if (!check_current_time(&saved_now, &now, status == 0, &saved_tv, ptv)) {
      /* Cook the time again after handling the step */
      LCL_CookTime(&now, &cooked, &err);
    }

-    update_monotonic_time(&cooked, &last_select_ts);
-
    last_select_ts_raw = now;
    last_select_ts = cooked;
    last_select_ts_err = err;
--- a/siv_gnutls.c
+++ b/siv_gnutls.c
@@ -102,8 +102,11 @@ SIV_CreateInstance(SIV_Algorithm algorithm)
    init_gnutls();

  /* Check if the cipher is actually supported */
-  if (gnutls_cipher_get_tag_size(calgo) == 0)
+  if (gnutls_cipher_get_tag_size(calgo) == 0) {
+    if (instance_counter == 0)
+      deinit_gnutls();
    return NULL;
+  }

  instance = MallocNew(struct SIV_Instance_Record);
  instance->algorithm = calgo;
@@ -162,17 +165,29 @@ SIV_SetKey(SIV_Instance instance, const unsigned char *key, int length)
  datum.data = (unsigned char *)key;
  datum.size = length;

-  /* Initialise a new cipher with the provided key (gnutls does not seem to
-     have a function to change the key directly) */
+#ifdef HAVE_GNUTLS_AEAD_CIPHER_SET_KEY
+  if (instance->cipher) {
+    r = gnutls_aead_cipher_set_key(instance->cipher, &datum);
+    if (r < 0) {
+      DEBUG_LOG("Could not set cipher key : %s", gnutls_strerror(r));
+      return 0;
+    }
+
+    return 1;
+  }
+#endif
+
+  /* Initialise a new cipher with the provided key */
  r = gnutls_aead_cipher_init(&cipher, instance->algorithm, &datum);
  if (r < 0) {
    DEBUG_LOG("Could not initialise %s : %s", "cipher", gnutls_strerror(r));
    return 0;
  }

-  /* Replace the previous cipher */
+  /* Destroy the previous cipher (if its key could not be changed directly) */
  if (instance->cipher)
    gnutls_aead_cipher_deinit(instance->cipher);
+
  instance->cipher = cipher;

  return 1;
--- a/socket.c
+++ b/socket.c
@@ -40,6 +40,7 @@
 #include "array.h"
 #include "logging.h"
 #include "privops.h"
+#include "ptp.h"
 #include "util.h"

 #define INVALID_SOCK_FD (-4)
@@ -58,10 +59,16 @@ struct Message {
  union sockaddr_all name;
  struct iovec iov;
  /* Buffer of sufficient length for all expected messages */
+  struct {
+    /* Extra space for Ethernet, IPv4/IPv6, and UDP headers in
+       timestamped messages received from the Linux error queue */
+    uint8_t l234_headers[64];
    union {
      NTP_Packet ntp_msg;
+      PTP_NtpMessage ptp_msg;
      CMD_Request cmd_request;
      CMD_Reply cmd_reply;
+    } msg;
  } msg_buf;
  /* Aligned buffer for control messages */
  struct cmsghdr cmsg_buf[CMSG_BUF_SIZE / sizeof (struct cmsghdr)];
@@ -498,6 +505,8 @@ bind_unix_address(int sock_fd, const char *addr, int flags)
 {
  union sockaddr_all saddr;

+  memset(&saddr, 0, sizeof (saddr));
+
  if (snprintf(saddr.un.sun_path, sizeof (saddr.un.sun_path), "%s", addr) >=
      sizeof (saddr.un.sun_path)) {
    DEBUG_LOG("Unix socket path %s too long", addr);
@@ -530,6 +539,8 @@ connect_unix_address(int sock_fd, const char *addr)
 {
  union sockaddr_all saddr;

+  memset(&saddr, 0, sizeof (saddr));
+
  if (snprintf(saddr.un.sun_path, sizeof (saddr.un.sun_path), "%s", addr) >=
      sizeof (saddr.un.sun_path)) {
    DEBUG_LOG("Unix socket path %s too long", addr);
@@ -737,23 +748,26 @@ init_message_nonaddress(SCK_Message *message)

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

+static int
+match_cmsg(struct cmsghdr *cmsg, int level, int type, size_t length)
+{
+  if (cmsg->cmsg_type == type && cmsg->cmsg_level == level &&
+      (length == 0 || cmsg->cmsg_len == CMSG_LEN(length)))
+    return 1;
+  return 0;
+}
+
+/* ================================================== */
+
 static int
 process_header(struct msghdr *msg, int msg_length, int sock_fd, int flags,
               SCK_Message *message)
 {
  struct cmsghdr *cmsg;
+  int r = 1;

-  if (msg->msg_iovlen != 1) {
-    DEBUG_LOG("Unexpected iovlen");
-    return 0;
-  }
-
-  if (msg->msg_namelen > sizeof (union sockaddr_all)) {
-    DEBUG_LOG("Truncated source address");
-    return 0;
-  }
-
-  if (msg->msg_namelen > sizeof (((struct sockaddr *)msg->msg_name)->sa_family)) {
+  if (msg->msg_namelen <= sizeof (union sockaddr_all) &&
+      msg->msg_namelen > sizeof (((struct sockaddr *)msg->msg_name)->sa_family)) {
    switch (((struct sockaddr *)msg->msg_name)->sa_family) {
      case AF_INET:
 #ifdef FEAT_IPV6
@@ -767,31 +781,45 @@ process_header(struct msghdr *msg, int msg_length, int sock_fd, int flags,
        message->remote_addr.path = ((struct sockaddr_un *)msg->msg_name)->sun_path;
        break;
      default:
+        init_message_addresses(message, SCK_ADDR_UNSPEC);
        DEBUG_LOG("Unexpected address");
-        return 0;
+        r = 0;
+        break;
    }
  } else {
    init_message_addresses(message, SCK_ADDR_UNSPEC);
+
+    if (msg->msg_namelen > sizeof (union sockaddr_all)) {
+      DEBUG_LOG("Truncated source address");
+      r = 0;
+    }
  }

  init_message_nonaddress(message);

+  if (msg->msg_iovlen == 1) {
    message->data = msg->msg_iov[0].iov_base;
    message->length = msg_length;
+  } else {
+    DEBUG_LOG("Unexpected iovlen");
+    r = 0;
+  }

  if (msg->msg_flags & MSG_TRUNC) {
    log_message(sock_fd, 1, message, "Truncated", NULL);
-    return 0;
+    r = 0;
  }

  if (msg->msg_flags & MSG_CTRUNC) {
    log_message(sock_fd, 1, message, "Truncated cmsg in", NULL);
-    return 0;
+    r = 0;
  }

  for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg)) {
+    if (0) {
+    }
 #ifdef HAVE_IN_PKTINFO
-    if (cmsg->cmsg_level == IPPROTO_IP && cmsg->cmsg_type == IP_PKTINFO) {
+    else if (match_cmsg(cmsg, IPPROTO_IP, IP_PKTINFO, sizeof (struct in_pktinfo))) {
      struct in_pktinfo ipi;

      if (message->addr_type != SCK_ADDR_IP)
@@ -803,7 +831,7 @@ process_header(struct msghdr *msg, int msg_length, int sock_fd, int flags,
      message->if_index = ipi.ipi_ifindex;
    }
 #elif defined(IP_RECVDSTADDR)
-    if (cmsg->cmsg_level == IPPROTO_IP && cmsg->cmsg_type == IP_RECVDSTADDR) {
+    else if (match_cmsg(cmsg, IPPROTO_IP, IP_RECVDSTADDR, sizeof (struct in_addr))) {
      struct in_addr addr;

      if (message->addr_type != SCK_ADDR_IP)
@@ -814,9 +842,8 @@ process_header(struct msghdr *msg, int msg_length, int sock_fd, int flags,
      message->local_addr.ip.family = IPADDR_INET4;
    }
 #endif
-
 #ifdef HAVE_IN6_PKTINFO
-    if (cmsg->cmsg_level == IPPROTO_IPV6 && cmsg->cmsg_type == IPV6_PKTINFO) {
+    else if (match_cmsg(cmsg, IPPROTO_IPV6, IPV6_PKTINFO, sizeof (struct in6_pktinfo))) {
      struct in6_pktinfo ipi;

      if (message->addr_type != SCK_ADDR_IP)
@@ -829,25 +856,23 @@ process_header(struct msghdr *msg, int msg_length, int sock_fd, int flags,
      message->if_index = ipi.ipi6_ifindex;
    }
 #endif
-
 #ifdef SCM_TIMESTAMP
-    if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_TIMESTAMP) {
+    else if (match_cmsg(cmsg, SOL_SOCKET, SCM_TIMESTAMP, sizeof (struct timeval))) {
      struct timeval tv;

      memcpy(&tv, CMSG_DATA(cmsg), sizeof (tv));
      UTI_TimevalToTimespec(&tv, &message->timestamp.kernel);
    }
 #endif
-
 #ifdef SCM_TIMESTAMPNS
-    if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_TIMESTAMPNS) {
+    else if (match_cmsg(cmsg, SOL_SOCKET, SCM_TIMESTAMPNS, sizeof (message->timestamp.kernel))) {
      memcpy(&message->timestamp.kernel, CMSG_DATA(cmsg), sizeof (message->timestamp.kernel));
    }
 #endif
-
 #ifdef HAVE_LINUX_TIMESTAMPING
 #ifdef HAVE_LINUX_TIMESTAMPING_OPT_PKTINFO
-    if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_TIMESTAMPING_PKTINFO) {
+    else if (match_cmsg(cmsg, SOL_SOCKET, SCM_TIMESTAMPING_PKTINFO,
+                        sizeof (struct scm_ts_pktinfo))) {
      struct scm_ts_pktinfo ts_pktinfo;

      memcpy(&ts_pktinfo, CMSG_DATA(cmsg), sizeof (ts_pktinfo));
@@ -855,17 +880,17 @@ process_header(struct msghdr *msg, int msg_length, int sock_fd, int flags,
      message->timestamp.l2_length = ts_pktinfo.pkt_length;
    }
 #endif
-
-    if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_TIMESTAMPING) {
+    else if (match_cmsg(cmsg, SOL_SOCKET, SCM_TIMESTAMPING,
+                        sizeof (struct scm_timestamping))) {
      struct scm_timestamping ts3;

      memcpy(&ts3, CMSG_DATA(cmsg), sizeof (ts3));
      message->timestamp.kernel = ts3.ts[0];
      message->timestamp.hw = ts3.ts[2];
    }
-
-    if ((cmsg->cmsg_level == SOL_IP && cmsg->cmsg_type == IP_RECVERR) ||
-        (cmsg->cmsg_level == SOL_IPV6 && cmsg->cmsg_type == IPV6_RECVERR)) {
+    else if ((match_cmsg(cmsg, SOL_IP, IP_RECVERR, 0) ||
+              match_cmsg(cmsg, SOL_IPV6, IPV6_RECVERR, 0)) &&
+             cmsg->cmsg_len >= CMSG_LEN(sizeof (struct sock_extended_err))) {
      struct sock_extended_err err;

      memcpy(&err, CMSG_DATA(cmsg), sizeof (err));
@@ -873,25 +898,34 @@ process_header(struct msghdr *msg, int msg_length, int sock_fd, int flags,
      if (err.ee_errno != ENOMSG || err.ee_info != SCM_TSTAMP_SND ||
          err.ee_origin != SO_EE_ORIGIN_TIMESTAMPING) {
        log_message(sock_fd, 1, message, "Unexpected extended error in", NULL);
-        return 0;
+        r = 0;
      }
    }
 #endif
-
-    if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS) {
+    else if (match_cmsg(cmsg, SOL_SOCKET, SCM_RIGHTS, 0)) {
      if (!(flags & SCK_FLAG_MSG_DESCRIPTOR) || cmsg->cmsg_len != CMSG_LEN(sizeof (int))) {
-        unsigned int i;
+        int i, fd;

        DEBUG_LOG("Unexpected SCM_RIGHTS");
-        for (i = 0; CMSG_LEN((i + 1) * sizeof (int)) <= cmsg->cmsg_len; i++)
-          close(((int *)CMSG_DATA(cmsg))[i]);
-        return 0;
+        for (i = 0; CMSG_LEN((i + 1) * sizeof (int)) <= cmsg->cmsg_len; i++) {
+          memcpy(&fd, (char *)CMSG_DATA(cmsg) + i * sizeof (int), sizeof (fd));
+          close(fd);
        }
-      message->descriptor = *(int *)CMSG_DATA(cmsg);
+        r = 0;
+      } else {
+        memcpy(&message->descriptor, CMSG_DATA(cmsg), sizeof (message->descriptor));
+      }
+    }
+    else {
+      DEBUG_LOG("Unexpected control message level=%d type=%d len=%d",
+                cmsg->cmsg_level, cmsg->cmsg_type, (int)cmsg->cmsg_len);
    }
  }

-  return 1;
+  if (!r && message->descriptor != INVALID_SOCK_FD)
+    close(message->descriptor);
+
+  return r;
 }

 /* ================================================== */
@@ -901,7 +935,7 @@ receive_messages(int sock_fd, int flags, int max_messages, int *num_messages)
 {
  struct MessageHeader *hdr;
  SCK_Message *messages;
-  unsigned int i, n;
+  unsigned int i, n, n_ok;
  int ret, recv_flags = 0;

  assert(initialised);
@@ -945,18 +979,20 @@ receive_messages(int sock_fd, int flags, int max_messages, int *num_messages)

  received_messages = n;

-  for (i = 0; i < n; i++) {
+  for (i = n_ok = 0; i < n; i++) {
    hdr = ARR_GetElement(recv_headers, i);
-    if (!process_header(&hdr->msg_hdr, hdr->msg_len, sock_fd, flags, &messages[i]))
-      return NULL;
+    if (!process_header(&hdr->msg_hdr, hdr->msg_len, sock_fd, flags, &messages[n_ok]))
+      continue;

-    log_message(sock_fd, 1, &messages[i],
+    log_message(sock_fd, 1, &messages[n_ok],
                flags & SCK_FLAG_MSG_ERRQUEUE ? "Received error" : "Received", NULL);
+
+    n_ok++;
  }

-  *num_messages = n;
+  *num_messages = n_ok;

-  return messages;
+  return n_ok > 0 ? messages : NULL;
 }

 /* ================================================== */
--- a/sources.c
+++ b/sources.c
@@ -3,7 +3,7 @@

 **********************************************************************
 * Copyright (C) Richard P. Curnow  1997-2003
- * Copyright (C) Miroslav Lichvar  2011-2016, 2018, 2020
+ * Copyright (C) Miroslav Lichvar  2011-2016, 2018, 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
@@ -54,7 +54,6 @@ static int initialised = 0;
 /* ================================================== */
 /* Structure used to hold info for selecting between sources */
 struct SelectInfo {
-  int stratum;
  int select_ok;
  double std_dev;
  double root_distance;
@@ -69,6 +68,7 @@ struct SelectInfo {
 typedef enum {
  SRC_OK,               /* OK so far, not a final status! */
  SRC_UNSELECTABLE,     /* Has noselect option set */
+  SRC_UNSYNCHRONISED,   /* Provides samples but not unsynchronised */
  SRC_BAD_STATS,        /* Doesn't have valid stats data */
  SRC_BAD_DISTANCE,     /* Has root distance longer than allowed maximum */
  SRC_JITTERY,          /* Had std dev larger than allowed maximum */
@@ -132,7 +132,10 @@ struct SRC_Instance_Record {

  struct SelectInfo sel_info;

-  /* Latest leap status */
+  /* Current stratum */
+  int stratum;
+
+  /* Current leap status */
  NTP_Leap leap;

  /* Flag indicating the source has a leap second vote */
@@ -175,6 +178,11 @@ static double reselect_distance;
 static double stratum_weight;
 static double combine_limit;

+static LOG_FileID logfileid;
+
+/* Identifier of the dump file */
+#define DUMP_IDENTIFIER "SRC0\n"
+
 /* ================================================== */
 /* Forward prototype */

@@ -183,6 +191,7 @@ static void slew_sources(struct timespec *raw, struct timespec *cooked, double d
                         double doffset, LCL_ChangeType change_type, void *anything);
 static void add_dispersion(double dispersion, void *anything);
 static char *source_to_string(SRC_Instance inst);
+static char get_status_char(SRC_Status status);

 /* ================================================== */
 /* Initialisation function */
@@ -202,6 +211,10 @@ void SRC_Initialise(void) {

  LCL_AddParameterChangeHandler(slew_sources, NULL);
  LCL_AddDispersionNotifyHandler(add_dispersion, NULL);
+
+  logfileid = CNF_GetLogSelection() ? LOG_FileOpen("selection",
+              "   Date (UTC) Time     IP Address   S EOpts Reach Score Last sample  Low end   High end")
+              : -1;
 }

 /* ================================================== */
@@ -313,6 +326,7 @@ SRC_ResetInstance(SRC_Instance instance)
  instance->distant = 0;
  instance->status = SRC_BAD_STATS;
  instance->sel_score = 1.0;
+  instance->stratum = 0;
  instance->leap = LEAP_Unsynchronised;
  instance->leap_vote = 0;

@@ -371,8 +385,10 @@ get_leap_status(void)
 /* ================================================== */

 void
-SRC_SetLeapStatus(SRC_Instance inst, NTP_Leap leap)
+SRC_UpdateStatus(SRC_Instance inst, int stratum, NTP_Leap leap)
 {
+  inst->stratum = stratum;
+
  if (REF_IsLeapSecondClose(NULL, 0.0))
    return;

@@ -398,9 +414,9 @@ SRC_AccumulateSample(SRC_Instance inst, NTP_Sample *sample)

  assert(initialised);

-  DEBUG_LOG("src=%s ts=%s offset=%e delay=%e disp=%e stratum=%d",
+  DEBUG_LOG("src=%s ts=%s offset=%e delay=%e disp=%e",
            source_to_string(inst), UTI_TimespecToString(&sample->time), -sample->offset,
-            sample->root_delay, sample->root_dispersion, sample->stratum);
+            sample->root_delay, sample->root_dispersion);

  if (REF_IsLeapSecondClose(&sample->time, sample->offset)) {
    LOG(LOGS_INFO, "Dropping sample around leap second");
@@ -631,13 +647,33 @@ source_to_string(SRC_Instance inst)
 static void
 mark_source(SRC_Instance inst, SRC_Status status)
 {
+  struct timespec now;
+
  inst->status = status;

-  DEBUG_LOG("%s status=%d options=%x reach=%o/%d updates=%d distant=%d leap=%d vote=%d lo=%f hi=%f",
-            source_to_string(inst), (int)inst->status, (unsigned int)inst->sel_options,
-            (unsigned int)inst->reachability, inst->reachability_size, inst->updates,
+  DEBUG_LOG("%s status=%c options=%x reach=%o/%d updates=%d distant=%d leap=%d vote=%d lo=%f hi=%f",
+            source_to_string(inst), get_status_char(inst->status),
+            (unsigned int)inst->sel_options, (unsigned int)inst->reachability,
+            inst->reachability_size, inst->updates,
            inst->distant, (int)inst->leap, inst->leap_vote,
            inst->sel_info.lo_limit, inst->sel_info.hi_limit);
+
+  if (logfileid == -1)
+    return;
+
+  SCH_GetLastEventTime(&now, NULL, NULL);
+
+  LOG_FileWrite(logfileid,
+                "%s %-15s %c -%c%c%c%c %4o %5.2f %10.3e %10.3e %10.3e",
+                UTI_TimeToLogForm(now.tv_sec), source_to_string(inst),
+                get_status_char(inst->status),
+                inst->sel_options & SRC_SELECT_NOSELECT ? 'N' : '-',
+                inst->sel_options & SRC_SELECT_PREFER ? 'P' : '-',
+                inst->sel_options & SRC_SELECT_TRUST ? 'T' : '-',
+                inst->sel_options & SRC_SELECT_REQUIRE ? 'R' : '-',
+                (unsigned int)inst->reachability, inst->sel_score,
+                inst->sel_info.last_sample_ago,
+                inst->sel_info.lo_limit, inst->sel_info.hi_limit);
 }

 /* ================================================== */
@@ -714,8 +750,8 @@ combine_sources(int n_sel_sources, struct timespec *ref_time, double *offset,
    offset_weight = 1.0 / sources[index]->sel_info.root_distance;
    frequency_weight = 1.0 / SQUARE(src_frequency_sd);

-    DEBUG_LOG("combining index=%d oweight=%e offset=%e osd=%e fweight=%e freq=%e fsd=%e skew=%e",
-              index, offset_weight, src_offset, src_offset_sd,
+    DEBUG_LOG("combining %s oweight=%e offset=%e osd=%e fweight=%e freq=%e fsd=%e skew=%e",
+              source_to_string(sources[index]), offset_weight, src_offset, src_offset_sd,
              frequency_weight, src_frequency, src_frequency_sd, src_skew);

    sum_offset_weight += offset_weight;
@@ -807,8 +843,14 @@ SRC_SelectSource(SRC_Instance updated_inst)
      continue;
    }

+    /* Ignore sources which are not synchronised */
+    if (sources[i]->leap == LEAP_Unsynchronised) {
+      mark_source(sources[i], SRC_UNSYNCHRONISED);
+      continue;
+    }
+
    si = &sources[i]->sel_info;
-    SST_GetSelectionData(sources[i]->stats, &now, &si->stratum,
+    SST_GetSelectionData(sources[i]->stats, &now,
                         &si->lo_limit, &si->hi_limit, &si->root_distance,
                         &si->std_dev, &first_sample_ago,
                         &si->last_sample_ago, &si->select_ok);
@@ -890,10 +932,10 @@ SRC_SelectSource(SRC_Instance updated_inst)
       source can settle down to a state where only one server is serving its
       local unsychronised time and others are synchronised to it. */

-    if (si->stratum >= orphan_stratum && sources[i]->type == SRC_NTP) {
+    if (sources[i]->stratum >= orphan_stratum && sources[i]->type == SRC_NTP) {
      mark_source(sources[i], SRC_ORPHAN);

-      if (si->stratum == orphan_stratum && sources[i]->reachability &&
+      if (sources[i]->stratum == orphan_stratum && sources[i]->reachability &&
          (orphan_source == INVALID_SOURCE ||
           sources[i]->ref_id < sources[orphan_source]->ref_id))
        orphan_source = i;
@@ -1131,10 +1173,10 @@ SRC_SelectSource(SRC_Instance updated_inst)
  /* Find minimum stratum */

  index = sel_sources[0];
-  min_stratum = sources[index]->sel_info.stratum;
+  min_stratum = sources[index]->stratum;
  for (i = 1; i < n_sel_sources; i++) {
    index = sel_sources[i];
-    stratum = sources[index]->sel_info.stratum;
+    stratum = sources[index]->stratum;
    if (stratum < min_stratum)
      min_stratum = stratum;
  }
@@ -1147,7 +1189,7 @@ SRC_SelectSource(SRC_Instance updated_inst)

  if (selected_source_index != INVALID_SOURCE)
    sel_src_distance = sources[selected_source_index]->sel_info.root_distance +
-      (sources[selected_source_index]->sel_info.stratum - min_stratum) * stratum_weight;
+      (sources[selected_source_index]->stratum - min_stratum) * stratum_weight;

  for (i = 0; i < n_sources; i++) {
    /* Reset score for non-selectable sources */
@@ -1159,7 +1201,7 @@ SRC_SelectSource(SRC_Instance updated_inst)
    }

    distance = sources[i]->sel_info.root_distance +
-      (sources[i]->sel_info.stratum - min_stratum) * stratum_weight;
+      (sources[i]->stratum - min_stratum) * stratum_weight;
    if (sources[i]->type == SRC_NTP)
      distance += reselect_distance;

@@ -1247,7 +1289,7 @@ SRC_SelectSource(SRC_Instance updated_inst)
  combined = combine_sources(n_sel_sources, &ref_time, &src_offset, &src_offset_sd,
                             &src_frequency, &src_frequency_sd, &src_skew);

-  REF_SetReference(sources[selected_source_index]->sel_info.stratum,
+  REF_SetReference(sources[selected_source_index]->stratum,
                   leap_status, combined,
                   sources[selected_source_index]->ref_id,
                   sources[selected_source_index]->ip_addr,
@@ -1320,24 +1362,60 @@ add_dispersion(double dispersion, void *anything)

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

-static
-FILE *open_dumpfile(SRC_Instance inst, char mode)
+static int
+get_dumpfile(SRC_Instance inst, char *filename, size_t len)
 {
-  char filename[64], *dumpdir;
+  /* Use the IP address, or reference ID with reference clocks */
+  switch (inst->type) {
+    case SRC_NTP:
+      if (!UTI_IsIPReal(inst->ip_addr) ||
+          snprintf(filename, len, "%s", source_to_string(inst)) >= len)
+        return 0;
+      break;
+    case SRC_REFCLOCK:
+      if (snprintf(filename, len, "refid:%08"PRIx32, inst->ref_id) >= len)
+        return 0;
+      break;
+    default:
+      assert(0);
+  }
+
+  return 1;
+}
+
+/* ================================================== */
+
+static void
+save_source(SRC_Instance inst)
+{
+  char filename[64], *dumpdir, *ntp_name;
+  FILE *f;

  dumpdir = CNF_GetDumpDir();
  if (!dumpdir)
-    return NULL;
+    return;

-  /* Include IP address in the name for NTP sources, or reference ID in hex */
-  if (inst->type == SRC_NTP && UTI_IsIPReal(inst->ip_addr))
-    snprintf(filename, sizeof (filename), "%s", source_to_string(inst));
-  else if (inst->type == SRC_REFCLOCK)
-    snprintf(filename, sizeof (filename), "refid:%08"PRIx32, inst->ref_id);
-  else
-    return NULL;
+  if (!get_dumpfile(inst, filename, sizeof (filename)))
+    return;

-  return UTI_OpenFile(dumpdir, filename, ".dat", mode, 0644);
+  f = UTI_OpenFile(dumpdir, filename, ".dat", 'w', 0644);
+  if (!f)
+    return;
+
+  ntp_name = inst->type == SRC_NTP ? NSR_GetName(inst->ip_addr) : ".";
+
+  if (fprintf(f, "%s%s\n%d %o %d %d %d\n",
+              DUMP_IDENTIFIER, ntp_name, inst->authenticated,
+              (unsigned int)inst->reachability, inst->reachability_size,
+              inst->stratum, (int)inst->leap) < 0 ||
+      !SST_SaveToFile(inst->stats, f)) {
+    fclose(f);
+    if (!UTI_RemoveFile(dumpdir, filename, ".dat"))
+      ;
+    return;
+  }
+
+  fclose(f);
 }

 /* ================================================== */
@@ -1346,16 +1424,60 @@ FILE *open_dumpfile(SRC_Instance inst, char mode)
 void
 SRC_DumpSources(void)
 {
-  FILE *out;
  int i;

-  for (i = 0; i < n_sources; i++) {
-    out = open_dumpfile(sources[i], 'w');
-    if (!out)
-      continue;
-    SST_SaveToFile(sources[i]->stats, out);
-    fclose(out);
+  for (i = 0; i < n_sources; i++)
+    save_source(sources[i]);
+}
+
+/* ================================================== */
+
+#define MAX_WORDS 1
+
+static void
+load_source(SRC_Instance inst)
+{
+  char filename[64], line[256], *dumpdir, *ntp_name, *words[MAX_WORDS];
+  int auth, leap, reach_size, stratum;
+  unsigned int reach;
+  FILE *f;
+
+  dumpdir = CNF_GetDumpDir();
+  if (!dumpdir)
+    return;
+
+  if (!get_dumpfile(inst, filename, sizeof (filename)))
+    return;
+
+  f = UTI_OpenFile(dumpdir, filename, ".dat", 'r', 0);
+  if (!f)
+    return;
+
+  ntp_name = inst->type == SRC_NTP ? NSR_GetName(inst->ip_addr) : NULL;
+
+  if (!fgets(line, sizeof (line), f) || strcmp(line, DUMP_IDENTIFIER) != 0 ||
+      !fgets(line, sizeof (line), f) || UTI_SplitString(line, words, MAX_WORDS) != 1 ||
+        (inst->type == SRC_NTP && (!ntp_name || strcmp(words[0], ntp_name) != 0)) ||
+      !fgets(line, sizeof (line), f) ||
+        sscanf(words[0], "%d %o %d %d %d",
+               &auth, &reach, &reach_size, &stratum, &leap) != 5 ||
+        (!auth && inst->authenticated) ||
+        stratum < 0 || stratum >= NTP_MAX_STRATUM ||
+        leap < LEAP_Normal || leap >= LEAP_Unsynchronised ||
+      !SST_LoadFromFile(inst->stats, f)) {
+    LOG(LOGS_WARN, "Could not load dump file for %s", source_to_string(inst));
+    fclose(f);
+    return;
  }
+
+  inst->reachability = reach & ((1U << SOURCE_REACH_BITS) - 1);
+  inst->reachability_size = CLAMP(0, reach_size, SOURCE_REACH_BITS);
+  inst->stratum = stratum;
+  inst->leap = leap;
+
+  LOG(LOGS_INFO, "Loaded dump file for %s", source_to_string(inst));
+
+  fclose(f);
 }

 /* ================================================== */
@@ -1363,21 +1485,17 @@ SRC_DumpSources(void)
 void
 SRC_ReloadSources(void)
 {
-  FILE *in;
  int i;

  for (i = 0; i < n_sources; i++) {
-    in = open_dumpfile(sources[i], 'r');
-    if (!in)
-      continue;
-    if (!SST_LoadFromFile(sources[i]->stats, in))
-      LOG(LOGS_WARN, "Could not load dump file for %s",
-          source_to_string(sources[i]));
-    else
-      LOG(LOGS_INFO, "Loaded dump file for %s",
-          source_to_string(sources[i]));
-    fclose(in);
+    load_source(sources[i]);
+
+    /* Allow an immediate update of the reference */
+    sources[i]->updates++;
  }
+
+  /* Select sources and set the reference */
+  SRC_SelectSource(NULL);
 }

 /* ================================================== */
@@ -1492,6 +1610,8 @@ SRC_ReportSource(int index, RPT_SourceReport *report, struct timespec *now)
      report->ip_addr.family = IPADDR_INET4;
    }

+    report->stratum = src->stratum;
+
    switch (src->status) {
      case SRC_FALSETICKER:
        report->state = RPT_FALSETICKER;
@@ -1556,6 +1676,8 @@ get_status_char(SRC_Status status)
  switch (status) {
    case SRC_UNSELECTABLE:
      return 'N';
+    case SRC_UNSYNCHRONISED:
+      return 's';
    case SRC_BAD_STATS:
      return 'M';
    case SRC_BAD_DISTANCE:
@@ -1610,6 +1732,7 @@ SRC_GetSelectReport(int index, RPT_SelectReport *report)
    report->ip_addr.family = IPADDR_UNSPEC;
  report->state_char = get_status_char(inst->status);
  report->authentication = inst->authenticated;
+  report->leap = inst->leap;
  report->conf_options = inst->conf_sel_options;
  report->eff_options = inst->sel_options;
  report->last_sample_ago = inst->sel_info.last_sample_ago;
--- a/sources.h
+++ b/sources.h
@@ -87,8 +87,8 @@ extern void SRC_SetRefid(SRC_Instance instance, uint32_t ref_id, IPAddr *addr);
 /* Function to get access to the sourcestats instance */
 extern SST_Stats SRC_GetSourcestats(SRC_Instance instance);

-/* Function to set the current leap status according to the source */
-extern void SRC_SetLeapStatus(SRC_Instance instance, NTP_Leap leap);
+/* Function to update the stratum and leap status of the source */
+extern void SRC_UpdateStatus(SRC_Instance instance, int stratum, NTP_Leap leap);

 /* Function to accumulate a new sample from the source */
 extern void SRC_AccumulateSample(SRC_Instance instance, NTP_Sample *sample);
--- a/sourcestats.c
+++ b/sourcestats.c
@@ -3,7 +3,7 @@

 **********************************************************************
 * Copyright (C) Richard P. Curnow  1997-2003
- * Copyright (C) Miroslav Lichvar  2011-2014, 2016-2018
+ * Copyright (C) Miroslav Lichvar  2011-2014, 2016-2018, 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
@@ -177,9 +177,6 @@ struct SST_Stats_Record {
  /* This array contains the root dispersions of each sample at the
     time of the measurements */
  double root_dispersions[MAX_SAMPLES];
-
-  /* The stratum from the last accumulated sample */
-  int stratum;
 };

 /* ================================================== */
@@ -214,8 +211,8 @@ SST_CreateInstance(uint32_t refid, IPAddr *addr, int min_samples, int max_sample
  SST_Stats inst;
  inst = MallocNew(struct SST_Stats_Record);

-  inst->min_samples = min_samples;
-  inst->max_samples = max_samples;
+  inst->max_samples = max_samples > 0 ? CLAMP(1, max_samples, MAX_SAMPLES) : MAX_SAMPLES;
+  inst->min_samples = CLAMP(1, min_samples, inst->max_samples);
  inst->fixed_min_delay = min_delay;
  inst->fixed_asymmetry = asymmetry;

@@ -321,7 +318,6 @@ SST_AccumulateSample(SST_Stats inst, NTP_Sample *sample)
  inst->peer_dispersions[m] = sample->peer_dispersion;
  inst->root_delays[m] = sample->root_delay;
  inst->root_dispersions[m] = sample->root_dispersion;
-  inst->stratum = sample->stratum;
 
  if (inst->peer_delays[n] < inst->fixed_min_delay)
    inst->peer_delays[n] = 2.0 * inst->fixed_min_delay - inst->peer_delays[n];
@@ -650,7 +646,6 @@ SST_GetFrequencyRange(SST_Stats inst,

 void
 SST_GetSelectionData(SST_Stats inst, struct timespec *now,
-                     int *stratum,
                     double *offset_lo_limit,
                     double *offset_hi_limit,
                     double *root_distance,
@@ -670,7 +665,6 @@ SST_GetSelectionData(SST_Stats inst, struct timespec *now,
  i = get_runsbuf_index(inst, inst->best_single_sample);
  j = get_buf_index(inst, inst->best_single_sample);

-  *stratum = inst->stratum;
  *std_dev = inst->std_dev;

  sample_elapsed = fabs(UTI_DiffTimespecsToDouble(now, &inst->sample_times[i]));
@@ -704,7 +698,8 @@ SST_GetSelectionData(SST_Stats inst, struct timespec *now,

  /* If maxsamples is too small to have a successful regression, enable the
     selection as a special case for a fast update/print-once reference mode */
-  if (!*select_ok && inst->n_samples < 3 && inst->n_samples == inst->max_samples) {
+  if (!*select_ok && inst->n_samples < MIN_SAMPLES_FOR_REGRESS &&
+      inst->n_samples == inst->max_samples) {
    *std_dev = CNF_GetMaxJitter();
    *select_ok = 1;
  }
@@ -785,6 +780,22 @@ SST_SlewSamples(SST_Stats inst, struct timespec *when, double dfreq, double doff

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

+void
+SST_CorrectOffset(SST_Stats inst, double doffset)
+{
+  int i;
+
+  if (!inst->n_samples)
+    return;
+
+  for (i = -inst->runs_samples; i < inst->n_samples; i++)
+    inst->offsets[get_runsbuf_index(inst, i)] += doffset;
+
+  inst->estimated_offset += doffset;
+}
+
+/* ================================================== */
+
 void 
 SST_AddDispersion(SST_Stats inst, double dispersion)
 {
@@ -804,7 +815,7 @@ SST_PredictOffset(SST_Stats inst, struct timespec *when)
 {
  double elapsed;
  
-  if (inst->n_samples < 3) {
+  if (inst->n_samples < MIN_SAMPLES_FOR_REGRESS) {
    /* We don't have any useful statistics, and presumably the poll
       interval is minimal.  We can't do any useful prediction other
       than use the latest sample or zero if we don't have any samples */
@@ -858,38 +869,30 @@ SST_GetDelayTestData(SST_Stats inst, struct timespec *sample_time,
 /* This is used to save the register to a file, so that we can reload
   it after restarting the daemon */

-void
+int
 SST_SaveToFile(SST_Stats inst, FILE *out)
 {
  int m, i, j;

-  fprintf(out, "%d\n", inst->n_samples);
+  if (inst->n_samples < 1)
+    return 0;
+
+  if (fprintf(out, "%d %d\n", inst->n_samples, inst->asymmetry_run) < 0)
+    return 0;

  for(m = 0; m < inst->n_samples; m++) {
    i = get_runsbuf_index(inst, m);
    j = get_buf_index(inst, m);

-    fprintf(out,
-#ifdef HAVE_LONG_TIME_T
-            "%08"PRIx64" %08lx %.6e %.6e %.6e %.6e %.6e %.6e %.6e %d\n",
-            (uint64_t)inst->sample_times[i].tv_sec,
-#else
-            "%08lx %08lx %.6e %.6e %.6e %.6e %.6e %.6e %.6e %d\n",
-            (unsigned long)inst->sample_times[i].tv_sec,
-#endif
-            (unsigned long)inst->sample_times[i].tv_nsec / 1000,
-            inst->offsets[i],
-            inst->orig_offsets[j],
-            inst->peer_delays[i],
-            inst->peer_dispersions[j],
-            inst->root_delays[j],
-            inst->root_dispersions[j],
-            1.0, /* used to be inst->weights[i] */
-            inst->stratum /* used to be an array */);
-
+    if (fprintf(out, "%s %.6e %.6e %.6e %.6e %.6e %.6e\n",
+                UTI_TimespecToString(&inst->sample_times[i]),
+                inst->offsets[i], inst->orig_offsets[j],
+                inst->peer_delays[i], inst->peer_dispersions[j],
+                inst->root_delays[j], inst->root_dispersions[j]) < 0)
+      return 0;
  }

-  fprintf(out, "%d\n", inst->asymmetry_run);
+  return 1;
 }

 /* ================================================== */
@@ -898,65 +901,47 @@ SST_SaveToFile(SST_Stats inst, FILE *out)
 int
 SST_LoadFromFile(SST_Stats inst, FILE *in)
 {
-#ifdef HAVE_LONG_TIME_T
-  uint64_t sec;
-#else
-  unsigned long sec;
-#endif
-  unsigned long usec;
-  int i;
-  char line[1024];
-  double weight;
+  int i, n_samples, arun;
+  struct timespec now;
+  double sample_time;
+  char line[256];
+
+  if (!fgets(line, sizeof (line), in) ||
+      sscanf(line, "%d %d", &n_samples, &arun) != 2 ||
+      n_samples < 1 || n_samples > MAX_SAMPLES)
+    return 0;

  SST_ResetInstance(inst);

-  if (fgets(line, sizeof(line), in) &&
-      sscanf(line, "%d", &inst->n_samples) == 1 &&
-      inst->n_samples >= 0 && inst->n_samples <= MAX_SAMPLES) {
+  LCL_ReadCookedTime(&now, NULL);

-    for (i=0; i<inst->n_samples; i++) {
-      if (!fgets(line, sizeof(line), in) ||
-          (sscanf(line,
-#ifdef HAVE_LONG_TIME_T
-                  "%"SCNx64"%lx%lf%lf%lf%lf%lf%lf%lf%d\n",
-#else
-                  "%lx%lx%lf%lf%lf%lf%lf%lf%lf%d\n",
-#endif
-                  &(sec), &(usec),
-                  &(inst->offsets[i]),
-                  &(inst->orig_offsets[i]),
-                  &(inst->peer_delays[i]),
-                  &(inst->peer_dispersions[i]),
-                  &(inst->root_delays[i]),
-                  &(inst->root_dispersions[i]),
-                  &weight, /* not used anymore */
-                  &inst->stratum) != 10)) {
-
-        /* This is the branch taken if the read FAILED */
-
-        inst->n_samples = 0; /* Load abandoned if any sign of corruption */
+  for (i = 0; i < n_samples; i++) {
+    if (!fgets(line, sizeof (line), in) ||
+        sscanf(line, "%lf %lf %lf %lf %lf %lf %lf",
+               &sample_time, &inst->offsets[i], &inst->orig_offsets[i],
+               &inst->peer_delays[i], &inst->peer_dispersions[i],
+               &inst->root_delays[i], &inst->root_dispersions[i]) != 7)
      return 0;
-      } else {

-        /* This is the branch taken if the read is SUCCESSFUL */
-        inst->sample_times[i].tv_sec = sec;
-        inst->sample_times[i].tv_nsec = 1000 * usec;
-        UTI_NormaliseTimespec(&inst->sample_times[i]);
-      }
-    }
+    if (!UTI_IsTimeOffsetSane(&now, sample_time - UTI_TimespecToDouble(&now)))
+      return 0;

-    /* This field was not saved in older versions */
-    if (!fgets(line, sizeof(line), in) || sscanf(line, "%d\n", &inst->asymmetry_run) != 1)
-      inst->asymmetry_run = 0;
-  } else {
-    inst->n_samples = 0; /* Load abandoned if any sign of corruption */
+    /* Some resolution is lost in the double format, but that's ok */
+    UTI_DoubleToTimespec(sample_time, &inst->sample_times[i]);
+
+    /* Make sure the samples are sane and they are in order */
+    if (!UTI_IsTimeOffsetSane(&inst->sample_times[i], -inst->offsets[i]) ||
+        UTI_CompareTimespecs(&now, &inst->sample_times[i]) < 0 ||
+        !(fabs(inst->peer_delays[i]) < 1.0e6 && fabs(inst->peer_dispersions[i]) < 1.0e6 &&
+          fabs(inst->root_delays[i]) < 1.0e6 && fabs(inst->root_dispersions[i]) < 1.0e6) ||
+        (i > 0 && UTI_CompareTimespecs(&inst->sample_times[i],
+                                       &inst->sample_times[i - 1]) <= 0))
      return 0;
  }

-  if (!inst->n_samples)
-    return 1;
-
+  inst->n_samples = n_samples;
  inst->last_sample = inst->n_samples - 1;
+  inst->asymmetry_run = CLAMP(-MAX_ASYMMETRY_RUN, arun, MAX_ASYMMETRY_RUN);

  find_min_delay_sample(inst);
  SST_DoNewRegression(inst);
@@ -978,7 +963,6 @@ SST_DoSourceReport(SST_Stats inst, RPT_SourceReport *report, struct timespec *no
    report->orig_latest_meas = inst->orig_offsets[j];
    report->latest_meas = inst->offsets[i];
    report->latest_meas_err = 0.5*inst->root_delays[j] + inst->root_dispersions[j];
-    report->stratum = inst->stratum;

    /* Align the sample time to reduce the leak of the receive timestamp */
    last_sample_time = inst->sample_times[i];
@@ -1003,6 +987,14 @@ SST_Samples(SST_Stats inst)

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

+int
+SST_GetMinSamples(SST_Stats inst)
+{
+  return inst->min_samples;
+}
+
+/* ================================================== */
+
 void
 SST_DoSourcestatsReport(SST_Stats inst, RPT_SourcestatsReport *report, struct timespec *now)
 {
--- a/sourcestats.h
+++ b/sourcestats.h
@@ -69,7 +69,6 @@ extern void SST_GetFrequencyRange(SST_Stats inst, double *lo, double *hi);
 /* Get data needed for selection */
 extern void
 SST_GetSelectionData(SST_Stats inst, struct timespec *now,
-                     int *stratum,
                     double *offset_lo_limit,
                     double *offset_hi_limit,
                     double *root_distance,
@@ -103,6 +102,10 @@ SST_GetTrackingData(SST_Stats inst, struct timespec *ref_time,

 extern void SST_SlewSamples(SST_Stats inst, struct timespec *when, double dfreq, double doffset);

+/* This routine corrects already accumulated samples to improve the
+   frequency estimate when a new sample is accumulated */
+extern void SST_CorrectOffset(SST_Stats inst, double doffset);
+
 /* This routine is called when an indeterminate offset is introduced
   into the local time. */
 extern void SST_AddDispersion(SST_Stats inst, double dispersion);
@@ -120,7 +123,7 @@ extern int SST_GetDelayTestData(SST_Stats inst, struct timespec *sample_time,
                                double *last_sample_ago, double *predicted_offset,
                                double *min_delay, double *skew, double *std_dev);

-extern void SST_SaveToFile(SST_Stats inst, FILE *out);
+extern int SST_SaveToFile(SST_Stats inst, FILE *out);

 extern int SST_LoadFromFile(SST_Stats inst, FILE *in);

@@ -130,6 +133,8 @@ extern void SST_DoSourcestatsReport(SST_Stats inst, RPT_SourcestatsReport *repor

 extern int SST_Samples(SST_Stats inst);

+extern int SST_GetMinSamples(SST_Stats inst);
+
 extern double SST_GetJitterAsymmetry(SST_Stats inst);

 #endif /* GOT_SOURCESTATS_H */
--- a/srcparams.h
+++ b/srcparams.h
@@ -54,10 +54,14 @@ typedef struct {
  int sel_options;
  int nts;
  int nts_port;
+  int copy;
+  int ext_fields;
  uint32_t authkey;
+  uint32_t cert_set;
  double max_delay;
  double max_delay_ratio;
  double max_delay_dev_ratio;
+  double max_delay_quant;
  double min_delay;
  double asymmetry;
  double offset;
@@ -77,6 +81,7 @@ typedef struct {
 #define SRC_DEFAULT_MAXSAMPLES (-1)
 #define SRC_DEFAULT_ASYMMETRY 1.0
 #define SRC_DEFAULT_NTSPORT 4460
+#define SRC_DEFAULT_CERTSET 0
 #define INACTIVE_AUTHKEY 0

 /* Flags for source selection */
--- a/stubs.c
+++ b/stubs.c
@@ -491,7 +491,8 @@ NNS_GenerateResponseAuth(NTP_Packet *request, NTP_PacketInfo *req_info,
 }

 NNC_Instance
-NNC_CreateInstance(IPSockAddr *nts_address, const char *name, const IPSockAddr *ntp_address)
+NNC_CreateInstance(IPSockAddr *nts_address, const char *name, uint32_t cert_set,
+                   uint16_t ntp_port)
 {
  return NULL;
 }
--- a/sys.c
+++ b/sys.c
@@ -97,16 +97,16 @@ SYS_Finalise(void)

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

-void SYS_DropRoot(uid_t uid, gid_t gid)
+void SYS_DropRoot(uid_t uid, gid_t gid, SYS_ProcessContext context)
 {
 #if defined(LINUX) && defined (FEAT_PRIVDROP)
-  SYS_Linux_DropRoot(uid, gid, !null_driver);
+  SYS_Linux_DropRoot(uid, gid, context, !null_driver);
 #elif defined(SOLARIS) && defined(FEAT_PRIVDROP)
-  SYS_Solaris_DropRoot(uid, gid);
+  SYS_Solaris_DropRoot(uid, gid, context);
 #elif (defined(NETBSD) || defined(FREEBSD)) && defined(FEAT_PRIVDROP)
-  SYS_NetBSD_DropRoot(uid, gid);
+  SYS_NetBSD_DropRoot(uid, gid, context, !null_driver);
 #elif defined(MACOSX) && defined(FEAT_PRIVDROP)
-  SYS_MacOSX_DropRoot(uid, gid);
+  SYS_MacOSX_DropRoot(uid, gid, context);
 #else
  LOG_FATAL("dropping root privileges not supported");
 #endif
@@ -114,7 +114,7 @@ void SYS_DropRoot(uid_t uid, gid_t gid)

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

-void SYS_EnableSystemCallFilter(int level, SYS_SystemCallContext context)
+void SYS_EnableSystemCallFilter(int level, SYS_ProcessContext context)
 {
 #if defined(LINUX) && defined(FEAT_SCFILTER)
  SYS_Linux_EnableSystemCallFilter(level, context);
--- a/sys.h
+++ b/sys.h
@@ -35,17 +35,17 @@ extern void SYS_Initialise(int clock_control);
 /* Called at the end of the run to do final clean-up */
 extern void SYS_Finalise(void);

-/* Drop root privileges to the specified user and group */
-extern void SYS_DropRoot(uid_t uid, gid_t gid);
-
 typedef enum {
  SYS_MAIN_PROCESS,
  SYS_NTSKE_HELPER,
-} SYS_SystemCallContext;
+} SYS_ProcessContext;
+
+/* Switch to the specified user and group in given context */
+extern void SYS_DropRoot(uid_t uid, gid_t gid, SYS_ProcessContext context);

 /* Enable a system call filter to allow only system calls
   which chronyd normally needs after initialization */
-extern void SYS_EnableSystemCallFilter(int level, SYS_SystemCallContext context);
+extern void SYS_EnableSystemCallFilter(int level, SYS_ProcessContext context);

 extern void SYS_SetScheduler(int SchedPriority);
 extern void SYS_LockMemory(void);
--- a/sys_generic.c
+++ b/sys_generic.c
@@ -73,13 +73,28 @@ static double slew_freq;
 /* Time (raw) of last update of slewing frequency and offset */
 static struct timespec slew_start;

-/* Limits for the slew timeout */
-#define MIN_SLEW_TIMEOUT 1.0
-#define MAX_SLEW_TIMEOUT 1.0e4
+/* Limits for the slew length */
+#define MIN_SLEW_DURATION 1.0
+#define MAX_SLEW_DURATION 1.0e4

 /* Scheduler timeout ID for ending of the currently running slew */
 static SCH_TimeoutID slew_timeout_id;

+/* Scheduled duration of the currently running slew */
+static double slew_duration;
+
+/* Expected delay in ending of the slew due to process scheduling and
+   execution time, tracked as a decaying maximum value */
+static double slew_excess_duration;
+
+/* Maximum accepted excess duration to ignore large jumps after resuming
+   suspended system and other reasons (which should be handled in the
+   scheduler), a constant to determine the minimum slew duration to avoid
+   oscillations due to the excess, and the decay constant */
+#define MAX_SLEW_EXCESS_DURATION 100.0
+#define MIN_SLEW_DURATION_EXCESS_RATIO 5.0
+#define SLEW_EXCESS_DURATION_DECAY 0.9
+
 /* Suggested offset correction rate (correction time * offset) */
 static double correction_rate;

@@ -109,12 +124,7 @@ 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) {
-    /* Reset offset and slewing */
-    slew_start = *raw;
-    offset_register = 0.0;
-    update_slew();
-  } else if (change_type == LCL_ChangeStep) {
+  if (change_type == LCL_ChangeStep) {
    UTI_AddDoubleToTimespec(&slew_start, -doffset, &slew_start);
  }
 }
@@ -169,8 +179,8 @@ clamp_freq(double freq)
 static void
 update_slew(void)
 {
+  double old_slew_freq, total_freq, corr_freq, duration, excess_duration;
  struct timespec now, end_of_slew;
-  double old_slew_freq, total_freq, corr_freq, duration;

  /* Remove currently running timeout */
  SCH_RemoveTimeout(slew_timeout_id);
@@ -183,13 +193,25 @@ update_slew(void)

  stop_fastslew(&now);

-  /* Estimate how long should the next slew take */
+  /* Update the maximum excess duration, decaying even when the slew did
+     not time out (i.e. frequency was set or offset accrued), but add a small
+     value to avoid denormals */
+  slew_excess_duration = (slew_excess_duration + 1.0e-9) * SLEW_EXCESS_DURATION_DECAY;
+  excess_duration = duration - slew_duration;
+  if (slew_excess_duration < excess_duration &&
+      excess_duration <= MAX_SLEW_EXCESS_DURATION)
+    slew_excess_duration = excess_duration;
+
+  /* Calculate the duration of the new slew, considering the current correction
+     rate and previous delays in stopping of the slew */
  if (fabs(offset_register) < MIN_OFFSET_CORRECTION) {
-    duration = MAX_SLEW_TIMEOUT;
+    duration = MAX_SLEW_DURATION;
  } else {
    duration = correction_rate / fabs(offset_register);
-    if (duration < MIN_SLEW_TIMEOUT)
-      duration = MIN_SLEW_TIMEOUT;
+    if (duration < MIN_SLEW_DURATION)
+      duration = MIN_SLEW_DURATION;
+    if (duration < MIN_SLEW_DURATION_EXCESS_RATIO * slew_excess_duration)
+      duration = MIN_SLEW_DURATION_EXCESS_RATIO * slew_excess_duration;
  }

  /* Get frequency offset needed to slew the offset in the duration
@@ -232,23 +254,25 @@ update_slew(void)
     maximum timeout and try again on the next update. */
  if (fabs(offset_register) < MIN_OFFSET_CORRECTION ||
      offset_register * slew_freq <= 0.0) {
-    duration = MAX_SLEW_TIMEOUT;
+    duration = MAX_SLEW_DURATION;
  } else {
    duration = offset_register / slew_freq;
-    if (duration < MIN_SLEW_TIMEOUT)
-      duration = MIN_SLEW_TIMEOUT;
-    else if (duration > MAX_SLEW_TIMEOUT)
-      duration = MAX_SLEW_TIMEOUT;
+    if (duration < MIN_SLEW_DURATION)
+      duration = MIN_SLEW_DURATION;
+    else if (duration > MAX_SLEW_DURATION)
+      duration = MAX_SLEW_DURATION;
  }

  /* Restart timer for the next update */
  UTI_AddDoubleToTimespec(&now, duration, &end_of_slew);
  slew_timeout_id = SCH_AddTimeout(&end_of_slew, handle_end_of_slew, NULL);
  slew_start = now;
+  slew_duration = duration;

-  DEBUG_LOG("slew offset=%e corr_rate=%e base_freq=%f total_freq=%f slew_freq=%e duration=%f slew_error=%e",
+  DEBUG_LOG("slew offset=%e corr_rate=%e base_freq=%f total_freq=%f slew_freq=%e"
+            " duration=%f excess=%f slew_error=%e",
            offset_register, correction_rate, base_freq, total_freq, slew_freq,
-      duration, slew_error);
+            slew_duration, slew_excess_duration, slew_error);
 }

 /* ================================================== */
@@ -385,6 +409,7 @@ SYS_Generic_CompleteFreqDriver(double max_set_freq_ppm, double max_set_freq_dela
  base_freq = (*drv_read_freq)();
  slew_freq = 0.0;
  offset_register = 0.0;
+  slew_excess_duration = 0.0;

  max_corr_freq = CNF_GetMaxSlewRate() / 1.0e6;

--- a/sys_linux.c
+++ b/sys_linux.c
@@ -97,21 +97,6 @@ static int have_setoffset;
   updated in the kernel */
 static int tick_update_hz;

-/* ================================================== */
-
-inline static long
-our_round(double x)
-{
-  long y;
-
-  if (x > 0.0)
-    y = x + 0.5;
-  else
-    y = x - 0.5;
-
-  return y;
-}
-
 /* ================================================== */
 /* Positive means currently fast of true time, i.e. jump backwards */

@@ -149,7 +134,7 @@ set_frequency(double freq_ppm)
  double required_freq;
  int required_delta_tick;

-  required_delta_tick = our_round(freq_ppm / dhz);
+  required_delta_tick = round(freq_ppm / dhz);

  /* Older kernels (pre-2.6.18) don't apply the frequency offset exactly as
     set by adjtimex() and a scaling constant (that depends on the internal
@@ -426,7 +411,7 @@ SYS_Linux_Finalise(void)

 #ifdef FEAT_PRIVDROP
 void
-SYS_Linux_DropRoot(uid_t uid, gid_t gid, int clock_control)
+SYS_Linux_DropRoot(uid_t uid, gid_t gid, SYS_ProcessContext context, int clock_control)
 {
  char cap_text[256];
  cap_t cap;
@@ -450,6 +435,10 @@ SYS_Linux_DropRoot(uid_t uid, gid_t gid, int clock_control)
               clock_control ? "cap_sys_time=ep" : "") >= sizeof (cap_text))
    assert(0);

+  /* Helpers don't need any capabilities */
+  if (context != SYS_MAIN_PROCESS)
+    cap_text[0] = '\0';
+
  if ((cap = cap_from_text(cap_text)) == NULL) {
    LOG_FATAL("cap_from_text() failed");
  }
@@ -480,9 +469,9 @@ void check_seccomp_applicability(void)
 /* ================================================== */

 void
-SYS_Linux_EnableSystemCallFilter(int level, SYS_SystemCallContext context)
+SYS_Linux_EnableSystemCallFilter(int level, SYS_ProcessContext context)
 {
-  const int syscalls[] = {
+  const int allowed[] = {
    /* Clock */
    SCMP_SYS(adjtimex),
    SCMP_SYS(clock_adjtime),
@@ -499,11 +488,18 @@ SYS_Linux_EnableSystemCallFilter(int level, SYS_SystemCallContext context)

    /* Process */
    SCMP_SYS(clone),
+#ifdef __NR_clone3
+    SCMP_SYS(clone3),
+#endif
    SCMP_SYS(exit),
    SCMP_SYS(exit_group),
    SCMP_SYS(getpid),
    SCMP_SYS(getrlimit),
    SCMP_SYS(getuid),
+    SCMP_SYS(getuid32),
+#ifdef __NR_rseq
+    SCMP_SYS(rseq),
+#endif
    SCMP_SYS(rt_sigaction),
    SCMP_SYS(rt_sigreturn),
    SCMP_SYS(rt_sigprocmask),
@@ -533,6 +529,7 @@ SYS_Linux_EnableSystemCallFilter(int level, SYS_SystemCallContext context)
    SCMP_SYS(fchownat),
    SCMP_SYS(fstat),
    SCMP_SYS(fstat64),
+    SCMP_SYS(fstatat64),
    SCMP_SYS(getdents),
    SCMP_SYS(getdents64),
    SCMP_SYS(lseek),
@@ -543,11 +540,16 @@ SYS_Linux_EnableSystemCallFilter(int level, SYS_SystemCallContext context)
    SCMP_SYS(readlinkat),
    SCMP_SYS(rename),
    SCMP_SYS(renameat),
+#ifdef __NR_renameat2
    SCMP_SYS(renameat2),
+#endif
    SCMP_SYS(stat),
    SCMP_SYS(stat64),
    SCMP_SYS(statfs),
    SCMP_SYS(statfs64),
+#ifdef __NR_statx
+    SCMP_SYS(statx),
+#endif
    SCMP_SYS(unlink),
    SCMP_SYS(unlinkat),

@@ -584,6 +586,7 @@ SYS_Linux_EnableSystemCallFilter(int level, SYS_SystemCallContext context)
 #ifdef __NR_ppoll_time64
    SCMP_SYS(ppoll_time64),
 #endif
+    SCMP_SYS(pread64),
    SCMP_SYS(pselect6),
 #ifdef __NR_pselect6_time64
    SCMP_SYS(pselect6_time64),
@@ -603,6 +606,22 @@ SYS_Linux_EnableSystemCallFilter(int level, SYS_SystemCallContext context)
    SCMP_SYS(uname),
  };

+  const int denied_any[] = {
+    SCMP_SYS(execve),
+#ifdef __NR_execveat
+    SCMP_SYS(execveat),
+#endif
+    SCMP_SYS(fork),
+    SCMP_SYS(ptrace),
+    SCMP_SYS(vfork),
+  };
+
+  const int denied_ntske[] = {
+    SCMP_SYS(ioctl),
+    SCMP_SYS(setsockopt),
+    SCMP_SYS(socket),
+  };
+
  const int socket_domains[] = {
    AF_NETLINK, AF_UNIX, AF_INET,
 #ifdef FEAT_IPV6
@@ -611,9 +630,12 @@ SYS_Linux_EnableSystemCallFilter(int level, SYS_SystemCallContext context)
  };

  const static int socket_options[][2] = {
-    { SOL_IP, IP_PKTINFO }, { SOL_IP, IP_FREEBIND },
+    { SOL_IP, IP_PKTINFO }, { SOL_IP, IP_FREEBIND }, { SOL_IP, IP_TOS },
 #ifdef FEAT_IPV6
    { SOL_IPV6, IPV6_V6ONLY }, { SOL_IPV6, IPV6_RECVPKTINFO },
+#endif
+#ifdef SO_BINDTODEVICE
+    { SOL_SOCKET, SO_BINDTODEVICE },
 #endif
    { SOL_SOCKET, SO_BROADCAST }, { SOL_SOCKET, SO_REUSEADDR },
 #ifdef SO_REUSEPORT
@@ -652,31 +674,65 @@ SYS_Linux_EnableSystemCallFilter(int level, SYS_SystemCallContext context)
 #endif
  };

+  unsigned int default_action, deny_action;
  scmp_filter_ctx *ctx;
  int i;

+  /* Sign of the level determines the deny action (kill or SIGSYS).
+     At level 1, selected syscalls are allowed, others are denied.
+     At level 2, selected syscalls are denied, others are allowed. */
+
+  deny_action = level > 0 ? SCMP_ACT_KILL : SCMP_ACT_TRAP;
+  if (level < 0)
+    level = -level;
+
+  switch (level) {
+    case 1:
+      default_action = deny_action;
+      break;
+    case 2:
+      default_action = SCMP_ACT_ALLOW;
+      break;
+    default:
+      LOG_FATAL("Unsupported filter level");
+  }
+
  if (context == SYS_MAIN_PROCESS) {
    /* Check if the chronyd configuration is supported */
    check_seccomp_applicability();

-    /* Start the helper process, which will run without any seccomp filter.  It
-       will be used for getaddrinfo(), for which it's difficult to maintain a
-       list of required system calls (with glibc it depends on what NSS modules
-       are installed and enabled on the system). */
+    /* At level 1, start a helper process which will not have a seccomp filter.
+       It will be used for getaddrinfo(), for which it is difficult to maintain
+       a list of required system calls (with glibc it depends on what NSS
+       modules are installed and enabled on the system). */
+    if (default_action != SCMP_ACT_ALLOW)
      PRV_StartHelper();
  }

-  ctx = seccomp_init(level > 0 ? SCMP_ACT_KILL : SCMP_ACT_TRAP);
+  ctx = seccomp_init(default_action);
  if (ctx == NULL)
      LOG_FATAL("Failed to initialize seccomp");

-  /* Add system calls that are always allowed */
-  for (i = 0; i < (sizeof (syscalls) / sizeof (*syscalls)); i++) {
-    if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, syscalls[i], 0) < 0)
+  if (default_action != SCMP_ACT_ALLOW) {
+    for (i = 0; i < sizeof (allowed) / sizeof (*allowed); i++) {
+      if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, allowed[i], 0) < 0)
+        goto add_failed;
+    }
+  } else {
+    for (i = 0; i < sizeof (denied_any) / sizeof (*denied_any); i++) {
+      if (seccomp_rule_add(ctx, deny_action, denied_any[i], 0) < 0)
        goto add_failed;
    }

-  if (context == SYS_MAIN_PROCESS) {
+    if (context == SYS_NTSKE_HELPER) {
+      for (i = 0; i < sizeof (denied_ntske) / sizeof (*denied_ntske); i++) {
+        if (seccomp_rule_add(ctx, deny_action, denied_ntske[i], 0) < 0)
+          goto add_failed;
+      }
+    }
+  }
+
+  if (default_action != SCMP_ACT_ALLOW && context == SYS_MAIN_PROCESS) {
    /* Allow opening sockets in selected domains */
    for (i = 0; i < sizeof (socket_domains) / sizeof (*socket_domains); i++) {
      if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 1,
@@ -686,10 +742,9 @@ SYS_Linux_EnableSystemCallFilter(int level, SYS_SystemCallContext context)

    /* Allow selected socket options */
    for (i = 0; i < sizeof (socket_options) / sizeof (*socket_options); i++) {
-      if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(setsockopt), 3,
+      if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(setsockopt), 2,
                           SCMP_A1(SCMP_CMP_EQ, socket_options[i][0]),
-                           SCMP_A2(SCMP_CMP_EQ, socket_options[i][1]),
-                           SCMP_A4(SCMP_CMP_LE, sizeof (int))) < 0)
+                           SCMP_A2(SCMP_CMP_EQ, socket_options[i][1])))
        goto add_failed;
    }

@@ -713,7 +768,8 @@ SYS_Linux_EnableSystemCallFilter(int level, SYS_SystemCallContext context)
  if (seccomp_load(ctx) < 0)
    LOG_FATAL("Failed to load seccomp rules");

-  LOG(context == SYS_MAIN_PROCESS ? LOGS_INFO : LOGS_DEBUG, "Loaded seccomp filter");
+  LOG(context == SYS_MAIN_PROCESS ? LOGS_INFO : LOGS_DEBUG,
+      "Loaded seccomp filter (level %d)", level);
  seccomp_release(ctx);
  return;

@@ -738,73 +794,25 @@ SYS_Linux_CheckKernelVersion(int req_major, int req_minor)

 #if defined(FEAT_PHC) || defined(HAVE_LINUX_TIMESTAMPING)

-#define PHC_READINGS 10
-
 static int
-process_phc_readings(struct timespec ts[][3], int n, double precision,
-                     struct timespec *phc_ts, struct timespec *sys_ts, double *err)
+get_phc_readings(int phc_fd, int max_samples, struct timespec ts[][3])
 {
-  double min_delay = 0.0, delays[PTP_MAX_SAMPLES], phc_sum, sys_sum, sys_prec;
-  int i, combined;
-
-  if (n > PTP_MAX_SAMPLES)
-    return 0;
-
-  for (i = 0; i < n; i++) {
-    delays[i] = UTI_DiffTimespecsToDouble(&ts[i][2], &ts[i][0]);
-
-    if (delays[i] < 0.0) {
-      /* Step in the middle of a PHC reading? */
-      DEBUG_LOG("Bad PTP_SYS_OFFSET sample delay=%e", delays[i]);
-      return 0;
-    }
-
-    if (!i || delays[i] < min_delay)
-      min_delay = delays[i];
-  }
-
-  sys_prec = LCL_GetSysPrecisionAsQuantum();
-
-  /* Combine best readings */
-  for (i = combined = 0, phc_sum = sys_sum = 0.0; i < n; i++) {
-    if (delays[i] > min_delay + MAX(sys_prec, precision))
-      continue;
-
-    phc_sum += UTI_DiffTimespecsToDouble(&ts[i][1], &ts[0][1]);
-    sys_sum += UTI_DiffTimespecsToDouble(&ts[i][0], &ts[0][0]) + delays[i] / 2.0;
-    combined++;
-  }
-
-  assert(combined);
-
-  UTI_AddDoubleToTimespec(&ts[0][1], phc_sum / combined, phc_ts);
-  UTI_AddDoubleToTimespec(&ts[0][0], sys_sum / combined, sys_ts);
-  *err = MAX(min_delay / 2.0, precision);
-
-  return 1;
-}
-
-/* ================================================== */
-
-static int
-get_phc_sample(int phc_fd, double precision, struct timespec *phc_ts,
-               struct timespec *sys_ts, double *err)
-{
-  struct timespec ts[PHC_READINGS][3];
  struct ptp_sys_offset sys_off;
  int i;

+  max_samples = CLAMP(0, max_samples, PTP_MAX_SAMPLES);
+
  /* Silence valgrind */
  memset(&sys_off, 0, sizeof (sys_off));

-  sys_off.n_samples = PHC_READINGS;
+  sys_off.n_samples = max_samples;

  if (ioctl(phc_fd, PTP_SYS_OFFSET, &sys_off)) {
    DEBUG_LOG("ioctl(%s) failed : %s", "PTP_SYS_OFFSET", strerror(errno));
    return 0;
  }

-  for (i = 0; i < PHC_READINGS; i++) {
+  for (i = 0; i < max_samples; i++) {
    ts[i][0].tv_sec = sys_off.ts[i * 2].sec;
    ts[i][0].tv_nsec = sys_off.ts[i * 2].nsec;
    ts[i][1].tv_sec = sys_off.ts[i * 2 + 1].sec;
@@ -813,31 +821,31 @@ get_phc_sample(int phc_fd, double precision, struct timespec *phc_ts,
    ts[i][2].tv_nsec = sys_off.ts[i * 2 + 2].nsec;
  }

-  return process_phc_readings(ts, PHC_READINGS, precision, phc_ts, sys_ts, err);
+  return max_samples;
 }

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

 static int
-get_extended_phc_sample(int phc_fd, double precision, struct timespec *phc_ts,
-                        struct timespec *sys_ts, double *err)
+get_extended_phc_readings(int phc_fd, int max_samples, struct timespec ts[][3])
 {
 #ifdef PTP_SYS_OFFSET_EXTENDED
-  struct timespec ts[PHC_READINGS][3];
  struct ptp_sys_offset_extended sys_off;
  int i;

+  max_samples = CLAMP(0, max_samples, PTP_MAX_SAMPLES);
+
  /* Silence valgrind */
  memset(&sys_off, 0, sizeof (sys_off));

-  sys_off.n_samples = PHC_READINGS;
+  sys_off.n_samples = max_samples;

  if (ioctl(phc_fd, PTP_SYS_OFFSET_EXTENDED, &sys_off)) {
    DEBUG_LOG("ioctl(%s) failed : %s", "PTP_SYS_OFFSET_EXTENDED", strerror(errno));
    return 0;
  }

-  for (i = 0; i < PHC_READINGS; i++) {
+  for (i = 0; i < max_samples; i++) {
    ts[i][0].tv_sec = sys_off.ts[i][0].sec;
    ts[i][0].tv_nsec = sys_off.ts[i][0].nsec;
    ts[i][1].tv_sec = sys_off.ts[i][1].sec;
@@ -846,7 +854,7 @@ get_extended_phc_sample(int phc_fd, double precision, struct timespec *phc_ts,
    ts[i][2].tv_nsec = sys_off.ts[i][2].nsec;
  }

-  return process_phc_readings(ts, PHC_READINGS, precision, phc_ts, sys_ts, err);
+  return max_samples;
 #else
  return 0;
 #endif
@@ -855,12 +863,14 @@ get_extended_phc_sample(int phc_fd, double precision, struct timespec *phc_ts,
 /* ================================================== */

 static int
-get_precise_phc_sample(int phc_fd, double precision, struct timespec *phc_ts,
-		       struct timespec *sys_ts, double *err)
+get_precise_phc_readings(int phc_fd, int max_samples, struct timespec ts[][3])
 {
 #ifdef PTP_SYS_OFFSET_PRECISE
  struct ptp_sys_offset_precise sys_off;

+  if (max_samples < 1)
+    return 0;
+
  /* Silence valgrind */
  memset(&sys_off, 0, sizeof (sys_off));

@@ -870,11 +880,11 @@ get_precise_phc_sample(int phc_fd, double precision, struct timespec *phc_ts,
    return 0;
  }

-  phc_ts->tv_sec = sys_off.device.sec;
-  phc_ts->tv_nsec = sys_off.device.nsec;
-  sys_ts->tv_sec = sys_off.sys_realtime.sec;
-  sys_ts->tv_nsec = sys_off.sys_realtime.nsec;
-  *err = MAX(LCL_GetSysPrecisionAsQuantum(), precision);
+  ts[0][0].tv_sec = sys_off.sys_realtime.sec;
+  ts[0][0].tv_nsec = sys_off.sys_realtime.nsec;
+  ts[0][1].tv_sec = sys_off.device.sec;
+  ts[0][1].tv_nsec = sys_off.device.nsec;
+  ts[0][2] = ts[0][0];

  return 1;
 #else
@@ -918,23 +928,23 @@ SYS_Linux_OpenPHC(const char *path, int phc_index)
 /* ================================================== */

 int
-SYS_Linux_GetPHCSample(int fd, int nocrossts, double precision, int *reading_mode,
-                       struct timespec *phc_ts, struct timespec *sys_ts, double *err)
+SYS_Linux_GetPHCReadings(int fd, int nocrossts, int *reading_mode, int max_readings,
+                         struct timespec tss[][3])
 {
-  if ((*reading_mode == 2 || !*reading_mode) && !nocrossts &&
-      get_precise_phc_sample(fd, precision, phc_ts, sys_ts, err)) {
+  int r = 0;
+
+  if ((*reading_mode == 2 || *reading_mode == 0) && !nocrossts &&
+      (r = get_precise_phc_readings(fd, max_readings, tss)) > 0) {
    *reading_mode = 2;
-    return 1;
-  } else if ((*reading_mode == 3 || !*reading_mode) &&
-      get_extended_phc_sample(fd, precision, phc_ts, sys_ts, err)) {
+  } else if ((*reading_mode == 3 || *reading_mode == 0) &&
+             (r = get_extended_phc_readings(fd, max_readings, tss)) > 0) {
    *reading_mode = 3;
-    return 1;
-  } else if ((*reading_mode == 1 || !*reading_mode) &&
-      get_phc_sample(fd, precision, phc_ts, sys_ts, err)) {
+  } else if ((*reading_mode == 1 || *reading_mode == 0) &&
+             (r = get_phc_readings(fd, max_readings, tss)) > 0) {
    *reading_mode = 1;
-    return 1;
  }
-  return 0;
+
+  return r;
 }

 /* ================================================== */
@@ -952,7 +962,7 @@ SYS_Linux_SetPHCExtTimestamping(int fd, int pin, int channel,
  pin_desc.func = enable ? PTP_PF_EXTTS : PTP_PF_NONE;
  pin_desc.chan = channel;

-  if (ioctl(fd, PTP_PIN_SETFUNC, &pin_desc)) {
+  if (pin >= 0 && ioctl(fd, PTP_PIN_SETFUNC, &pin_desc)) {
    DEBUG_LOG("ioctl(%s) failed : %s", "PTP_PIN_SETFUNC", strerror(errno));
    return 0;
  }
--- a/sys_linux.h
+++ b/sys_linux.h
@@ -33,16 +33,16 @@ extern void SYS_Linux_Initialise(void);

 extern void SYS_Linux_Finalise(void);

-extern void SYS_Linux_DropRoot(uid_t uid, gid_t gid, int clock_control);
+extern void SYS_Linux_DropRoot(uid_t uid, gid_t gid, SYS_ProcessContext context, int clock_control);

-extern void SYS_Linux_EnableSystemCallFilter(int level, SYS_SystemCallContext context);
+extern void SYS_Linux_EnableSystemCallFilter(int level, SYS_ProcessContext context);

 extern int SYS_Linux_CheckKernelVersion(int req_major, int req_minor);

 extern int SYS_Linux_OpenPHC(const char *path, int phc_index);

-extern int SYS_Linux_GetPHCSample(int fd, int nocrossts, double precision, int *reading_mode,
-                                  struct timespec *phc_ts, struct timespec *sys_ts, double *err);
+extern int SYS_Linux_GetPHCReadings(int fd, int nocrossts, int *reading_mode, int max_readings,
+                                    struct timespec tss[][3]);

 extern int SYS_Linux_SetPHCExtTimestamping(int fd, int pin, int channel,
                                           int rising, int falling, int enable);
--- a/sys_macosx.c
+++ b/sys_macosx.c
@@ -415,8 +415,9 @@ SYS_MacOSX_SetScheduler(int SchedPriority)
 /* ================================================== */

 #ifdef FEAT_PRIVDROP
-void SYS_MacOSX_DropRoot(uid_t uid, gid_t gid)
+void SYS_MacOSX_DropRoot(uid_t uid, gid_t gid, SYS_ProcessContext context)
 {
+  if (context == SYS_MAIN_PROCESS)
    PRV_StartHelper();

  UTI_DropRoot(uid, gid);
--- a/sys_macosx.h
+++ b/sys_macosx.h
@@ -30,8 +30,10 @@
 #ifndef GOT_SYS_MACOSX_H
 #define GOT_SYS_MACOSX_H

+#include "sys.h"
+
 void SYS_MacOSX_SetScheduler(int SchedPriority);
-void SYS_MacOSX_DropRoot(uid_t uid, gid_t gid);
+void SYS_MacOSX_DropRoot(uid_t uid, gid_t gid, SYS_ProcessContext context);
 void SYS_MacOSX_Initialise(void);
 void SYS_MacOSX_Finalise(void);

--- a/sys_netbsd.c
+++ b/sys_netbsd.c
@@ -131,7 +131,7 @@ SYS_NetBSD_Finalise(void)

 #ifdef FEAT_PRIVDROP
 void
-SYS_NetBSD_DropRoot(uid_t uid, gid_t gid)
+SYS_NetBSD_DropRoot(uid_t uid, gid_t gid, SYS_ProcessContext context, int clock_control)
 {
 #ifdef NETBSD
  int fd;
@@ -139,11 +139,15 @@ SYS_NetBSD_DropRoot(uid_t uid, gid_t gid)

  /* On NetBSD the helper is used only for socket binding, but on FreeBSD
     it's used also for setting and adjusting the system clock */
+  if (context == SYS_MAIN_PROCESS)
    PRV_StartHelper();

  UTI_DropRoot(uid, gid);

 #ifdef NETBSD
+  if (!clock_control)
+    return;
+
  /* Check if we have write access to /dev/clockctl */
  fd = open("/dev/clockctl", O_WRONLY);
  if (fd < 0)
--- a/sys_netbsd.h
+++ b/sys_netbsd.h
@@ -28,10 +28,12 @@
 #ifndef GOT_SYS_NETBSD_H
 #define GOT_SYS_NETBSD_H

+#include "sys.h"
+
 void SYS_NetBSD_Initialise(void);

 void SYS_NetBSD_Finalise(void);

-void SYS_NetBSD_DropRoot(uid_t uid, gid_t gid);
+void SYS_NetBSD_DropRoot(uid_t uid, gid_t gid, SYS_ProcessContext context, int clock_control);

 #endif
--- a/sys_solaris.c
+++ b/sys_solaris.c
@@ -21,23 +21,54 @@

  =======================================================================

-  Driver file for Solaris operating system
+  Driver file for illumos operating system (previously Solaris)
  */

 #include "config.h"

 #include "sysincl.h"

+#include "logging.h"
 #include "privops.h"
 #include "sys_solaris.h"
 #include "sys_timex.h"
 #include "util.h"

+#include <kvm.h>
+#include <nlist.h>
+
+/* ================================================== */
+
+static void
+set_dosynctodr(int on_off)
+{
+  struct nlist nl[] = { {"dosynctodr"}, {NULL} };
+  kvm_t *kt;
+
+  kt = kvm_open(NULL, NULL, NULL, O_RDWR, NULL);
+  if (!kt)
+    LOG_FATAL("Could not open kvm");
+
+  if (kvm_nlist(kt, nl) < 0 || !nl[0].n_value)
+    LOG_FATAL("Could not get dosynctodr address");
+
+  if (kvm_kwrite(kt, nl[0].n_value, &on_off, sizeof (on_off)) < 0)
+    LOG_FATAL("Could not write to dosynctodr");
+
+  kvm_close(kt);
+}
+
 /* ================================================== */

 void
 SYS_Solaris_Initialise(void)
 {
+  /* The kernel keeps the system clock and hardware clock synchronised to each
+     other.  The dosynctodr variable needs to be set to zero to prevent the
+     the system clock from following the hardware clock when the system clock
+     is not adjusted by adjtime() or ntp_adjtime(modes=MOD_OFFSET). */
+  set_dosynctodr(0);
+
  /* The kernel allows the frequency to be set in the full range off int32_t */
  SYS_Timex_InitialiseWithFunctions(32500, 1.0 / 100, NULL, NULL, NULL,
                                    0.0, 0.0, NULL, NULL);
@@ -55,8 +86,9 @@ SYS_Solaris_Finalise(void)

 #ifdef FEAT_PRIVDROP
 void
-SYS_Solaris_DropRoot(uid_t uid, gid_t gid)
+SYS_Solaris_DropRoot(uid_t uid, gid_t gid, SYS_ProcessContext context)
 {
+  if (context == SYS_MAIN_PROCESS)
    PRV_StartHelper();
  UTI_DropRoot(uid, gid);
 }
--- a/sys_solaris.h
+++ b/sys_solaris.h
@@ -27,10 +27,12 @@
 #ifndef GOT_SYS_SOLARIS_H
 #define GOT_SYS_SOLARIS_H

+#include "sys.h"
+
 void SYS_Solaris_Initialise(void);

 void SYS_Solaris_Finalise(void);

-void SYS_Solaris_DropRoot(uid_t uid, gid_t gid);
+void SYS_Solaris_DropRoot(uid_t uid, gid_t gid, SYS_ProcessContext context);

 #endif
--- a/sys_timex.c
+++ b/sys_timex.c
@@ -75,13 +75,6 @@ convert_timex_frequency(const struct timex *txc)

  freq_ppm = txc->freq / FREQ_SCALE;

-#ifdef MACOSX
-  /* Temporary workaround for Apple bug treating freq as unsigned number */
-  if (freq_ppm > 32767) {
-    freq_ppm -= 65536;
-  }
-#endif
-
  return -freq_ppm;
 }

--- a/sysincl.h
+++ b/sysincl.h
@@ -28,6 +28,7 @@
 #ifndef GOT_SYSINCL_H
 #define GOT_SYSINCL_H

+#include <arpa/inet.h>
 #include <assert.h>
 #include <ctype.h>
 #include <errno.h>
@@ -61,11 +62,6 @@
 #include <sys/timex.h>
 #endif

-#ifdef FEAT_IPV6
-/* For inet_ntop() */
-#include <arpa/inet.h>
-#endif
-
 #ifdef HAVE_GETRANDOM
 #include <sys/random.h>
 #endif
--- a/test/compilation/002-scanbuild
+++ b/test/compilation/002-scanbuild
@@ -8,7 +8,8 @@ for opts in \
 	"--host-system=FreeBSD" \
 	"--without-nettle" \
 	"--without-nettle --without-nss" \
-	"--without-nettle --without-nss --without-tomcrypt"
+	"--without-nettle --without-nss --without-tomcrypt" \
+	"--without-nettle --without-nss --without-tomcrypt --without-gnutls"
 do
 	./configure $opts
 	scan-build make "$@" || exit 1
--- a/test/compilation/003-sanitizers
+++ b/test/compilation/003-sanitizers
@@ -1,7 +1,9 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # Run the unit and simulation tests with different compiler sanitizers
 # and under valgrind

+valgrind_opts="--leak-check=full --errors-for-leak-kinds=definite"
+
 cd ../..

 if [ "$(uname -sm)" != "Linux x86_64" ]; then
@@ -13,16 +15,23 @@ fi

 if [ "$ID" = "fedora" ]; then
  echo Checking test dependencies:
-  rpm -q {valgrind,gcc,clang}.x86_64 {libgcc,clang-libs}.{x86_64,i686} || exit 1
+  rpm -q {gcc,clang}.x86_64 {valgrind,libgcc,clang-libs}.{x86_64,i686} || exit 1
  rpm -q {libseccomp,nettle,nss-softokn-freebl,libtomcrypt,gnutls}-devel.{x86_64,i686} || exit 1
  echo
 fi

 touch Makefile

-for CC in gcc clang; do
-  export CC
-
+for extra_config_opts in \
+  "--all-privops" \
+  "--disable-ipv6" \
+  "--disable-scfilter" \
+  "--without-gnutls" \
+  "--without-nettle" \
+  "--without-nettle --without-nss" \
+  "--without-nettle --without-nss --without-tomcrypt" \
+  "--without-nettle --without-nss --without-tomcrypt --without-gnutls"; \
+do
  for arch_opts in "-m32" ""; do
    pushd test/simulation/clknetsim || exit 1
    make clean > /dev/null 2>&1
@@ -31,26 +40,21 @@ for CC in gcc clang; do

    popd

-    for extra_config_opts in \
-      "--all-privops" \
-      "--disable-scfilter" \
-      "--without-gnutls" \
-      "--without-nettle" \
-      "--without-nettle --without-nss" \
-      "--without-nettle --without-nss --without-tomcrypt"; \
-    do
+    for CC in gcc clang; do
+      export CC
+
      for san_options in "" "-fsanitize=address" "-fsanitize=memory"; do
        export CFLAGS="-O2 -g -fsanitize=undefined -fsanitize=float-divide-by-zero -fno-sanitize-recover=undefined,float-divide-by-zero $san_options $arch_opts"

        # clang msan doesn't work on i686 and otherwise requires patches
        echo $CFLAGS | grep -q 'sanitize=memory' && continue

-        # build fails with clang ubsan on i686 (Fedora only?)
-        [ "$arch_opts" = "-m32" -a "$CC" = "clang" ] && continue
+        [ -n "$TEST_NO_M32_CLANG" -a "$arch_opts" = "-m32" -a "$CC" = "clang" ] && continue

-        [ "$CC" = "gcc" ] && echo $CFLAGS | grep -q 'sanitize=address' && CFLAGS="$CFLAGS -static-libasan"
+        [ -n "$TEST_GCC_STATIC_ASAN" -a "$CC" = "gcc" ] &&
+                echo $CFLAGS | grep -q 'sanitize=address' && CFLAGS="$CFLAGS -static-libasan"

-        config_opts="--with-user=chrony --enable-debug --enable-scfilter --enable-ntp-signd $extra_config_opts"
+        config_opts="--with-user=chrony --with-ntp-era=1000000000 --enable-debug --enable-scfilter --enable-ntp-signd $extra_config_opts"

        echo -----------------------------------------------------------------------------
        echo CC=\"$CC\" CFLAGS=\"$CFLAGS\" ./configure $config_opts
@@ -67,20 +71,31 @@ for CC in gcc clang; do

        make "$@" || exit 1

-        [ -n "$BUILD_TEST_ONLY" ] && continue
+        [ -n "$TEST_BUILD_ONLY" ] && continue

        echo
        pushd test/unit || exit 1
+        make "$@" || exit 1
        if [ "$san_options" = "" ]; then
-          make check TEST_WRAPPER="valgrind --error-exitcode=1" || exit 1
+          make check TEST_WRAPPER="valgrind $valgrind_opts --error-exitcode=1" || exit 1
        else
          make check || exit 1
        fi
        popd

+        [ -n "$TEST_UNIT_ONLY" ] && continue
+
        echo
        pushd test/simulation || exit 1
-        CLKNETSIM_RANDOM_SEED=101 ./run -i 1 || exit 1
+        export CLKNETSIM_RANDOM_SEED=101
+        if [ "$arch_opts" = "" -a "$san_options" = "" ]; then
+          CLKNETSIM_CLIENT_WRAPPER="valgrind $valgrind_opts" ./run -i 1 || exit 1
+        elif [ "$CC" = "gcc" ] && ! echo $CFLAGS | grep -q "-static-libasan"; then
+          libasan=$(ldd ../../chronyd | grep -o '/.*lib.*/libasan.so.[0-9]')
+          CLKNETSIM_PRELOAD=$libasan ./run -i 1 || exit 1
+        else
+          ./run -i 1 || exit 1
+        fi
        popd
      done
    done
--- a/test/simulation/001-defaults
+++ b/test/simulation/001-defaults
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash

 . ./test.common

--- a/test/simulation/002-largenetwork
+++ b/test/simulation/002-largenetwork
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash

 . ./test.common

--- a/test/simulation/003-largefreqoffset
+++ b/test/simulation/003-largefreqoffset
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash

 . ./test.common

--- a/Show More
+++ b/Show More