update copyright years

doc: update FAQ on improving accuracy
doc: mention dependency of net corrections on HW timestamping
2025-12-03 17:45:07 -05:00 · 2023-12-05 14:22:10 +01:00 · 2023-12-05 14:22:10 +01:00 · 2023-12-05 14:22:08 +01:00 · 2023-12-04 16:50:51 +01:00 · 2023-11-28 12:21:23 +01:00
46 changed files with 1228 additions and 309 deletions
--- a/14
+++ b/14
@@ -1,3 +1,17 @@
+New in version 4.5
+==================
+
+Enhancements
+------------
+* Add support for AES-GCM-SIV in GnuTLS
+* Add support for corrections from PTP transparent clocks
+* Add support for systemd socket activation
+
+Bug fixes
+---------
+* Fix presend in interleaved mode
+* Fix reloading of modified sources from sourcedir
+
 New in version 4.4
 ==================

--- a/1
+++ b/1
@@ -125,6 +125,7 @@ Andreas Steinmetz <ast@domdv.de>
 NAKAMURA Takumi <takumi@ps.sakura.ne.jp>
 Timo Teras <timo.teras@iki.fi>
 Bill Unruh <unruh@physics.ubc.ca>
+Luke Valenta <lvalenta@cloudflare.com>
 Stephen Wadeley <swadeley@redhat.com>
 Bernhard Weiss <lisnablagh@web.de>
 Wolfgang Weisselberg <weissel@netcologne.de>
--- a/candm.h
+++ b/candm.h
@@ -277,7 +277,8 @@ typedef struct {
 #define REQ_ADDSRC_BURST 0x100
 #define REQ_ADDSRC_NTS 0x200
 #define REQ_ADDSRC_COPY 0x400
-#define REQ_ADDSRC_EF_EXP1 0x800
+#define REQ_ADDSRC_EF_EXP_MONO_ROOT 0x800
+#define REQ_ADDSRC_EF_EXP_NET_CORRECTION 0x1000

 typedef struct {
  uint32_t type;
--- a/client.c
+++ b/client.c
@@ -958,7 +958,10 @@ process_cmd_add_source(CMD_Request *msg, char *line)
          (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.ext_fields & NTP_EF_FLAG_EXP_MONO_ROOT ?
+           REQ_ADDSRC_EF_EXP_MONO_ROOT : 0) |
+          (data.params.ext_fields & NTP_EF_FLAG_EXP_NET_CORRECTION ?
+           REQ_ADDSRC_EF_EXP_NET_CORRECTION : 0) |
          convert_addsrc_sel_options(data.params.sel_options));
      msg->data.ntp_source.filter_length = htonl(data.params.filter_length);
      msg->data.ntp_source.cert_set = htonl(data.params.cert_set);
--- a/cmdmon.c
+++ b/cmdmon.c
@@ -783,8 +783,10 @@ handle_add_source(CMD_Request *rx_message, CMD_Reply *tx_message)
  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.ext_fields = (ntohl(rx_message->data.ntp_source.flags) & REQ_ADDSRC_EF_EXP_MONO_ROOT ?
+                      NTP_EF_FLAG_EXP_MONO_ROOT : 0) |
+                      (ntohl(rx_message->data.ntp_source.flags) & REQ_ADDSRC_EF_EXP_NET_CORRECTION ?
+                      NTP_EF_FLAG_EXP_NET_CORRECTION : 0);
  params.sel_options = convert_addsrc_select_options(ntohl(rx_message->data.ntp_source.flags));

  status = NSR_AddSourceByName(name, port, pool, type, &params, NULL);
--- a/cmdparse.c
+++ b/cmdparse.c
@@ -115,8 +115,11 @@ CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)
      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;
+        case NTP_EF_EXP_MONO_ROOT:
+          src->params.ext_fields |= NTP_EF_FLAG_EXP_MONO_ROOT;
+          break;
+        case NTP_EF_EXP_NET_CORRECTION:
+          src->params.ext_fields |= NTP_EF_FLAG_EXP_NET_CORRECTION;
          break;
        default:
          return 0;
--- a/conf.c
+++ b/conf.c
@@ -1660,11 +1660,11 @@ compare_sources(const void *a, const void *b)
    return 1;
  if ((d = strcmp(sa->params.name, sb->params.name)) != 0)
    return d;
-  if ((d = (int)(sa->type) - (int)(sb->type)) != 0)
+  if ((d = (int)sa->type - (int)sb->type) != 0)
    return d;
-  if ((d = sa->pool - sb->pool) != 0)
+  if ((d = (int)sa->pool - (int)sb->pool) != 0)
    return d;
-  if ((d = sa->params.port - sb->params.port) != 0)
+  if ((d = (int)sa->params.port - (int)sb->params.port) != 0)
    return d;
  return memcmp(&sa->params.params, &sb->params.params, sizeof (sa->params.params));
 }
@@ -1679,7 +1679,7 @@ reload_source_dirs(void)
  uint32_t *prev_ids, *new_ids;
  char buf[MAX_LINE_LENGTH];
  NSR_Status s;
-  int d;
+  int d, pass;

  prev_size = ARR_GetSize(ntp_source_ids);
  if (prev_size > 0 && ARR_GetSize(ntp_sources) != prev_size)
@@ -1713,36 +1713,38 @@ reload_source_dirs(void)

  qsort(new_sources, new_size, sizeof (new_sources[0]), compare_sources);

-  for (i = j = 0; i < prev_size || j < new_size; ) {
-    if (i < prev_size && j < new_size)
-      d = compare_sources(&prev_sources[i], &new_sources[j]);
-    else
-      d = i < prev_size ? -1 : 1;
+  for (pass = 0; pass < 2; pass++) {
+    for (i = j = 0; i < prev_size || j < new_size; i += d <= 0, j += d >= 0) {
+      if (i < prev_size && j < new_size)
+        d = compare_sources(&prev_sources[i], &new_sources[j]);
+      else
+        d = i < prev_size ? -1 : 1;

-    if (d < 0) {
-      /* Remove the missing source */
-      if (prev_sources[i].params.name[0] != '\0')
+      /* Remove missing sources before adding others to avoid conflicts */
+      if (pass == 0 && d < 0 && prev_sources[i].params.name[0] != '\0') {
        NSR_RemoveSourcesById(prev_ids[i]);
-      i++;
-    } else if (d > 0) {
-      /* Add a newly configured source */
-      source = &new_sources[j];
-      s = NSR_AddSourceByName(source->params.name, source->params.port, source->pool,
-                              source->type, &source->params.params, &new_ids[j]);
-
-      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';
      }
-      j++;
-    } else {
-      /* Keep the existing source */
-      new_ids[j] = prev_ids[i];
-      i++, j++;
+
+      /* Add new sources */
+      if (pass == 1 && d > 0) {
+        source = &new_sources[j];
+        s = NSR_AddSourceByName(source->params.name, source->params.port, source->pool,
+                                source->type, &source->params.params, &new_ids[j]);
+
+        if (s == NSR_UnresolvedName) {
+          unresolved++;
+        } else if (s != NSR_Success) {
+          LOG(LOGS_ERR, "Could not add source %s : %s",
+              source->params.name, NSR_StatusToString(s));
+
+          /* Mark the source as not present */
+          source->params.name[0] = '\0';
+        }
+      }
+
+      /* Keep unchanged sources */
+      if (pass == 1 && d == 0)
+        new_ids[j] = prev_ids[i];
    }
  }

--- a/55
+++ b/55
@@ -111,10 +111,10 @@ For better control, use the options below.
  --without-editline     Don't use editline even if it is available
  --disable-sechash      Disable support for hashes other than MD5
  --without-nettle       Don't use nettle even if it is available
+  --without-gnutls       Don't use gnutls even if it is available
  --without-nss          Don't use NSS even if it is available
  --without-tomcrypt     Don't use libtomcrypt even if it is available
  --disable-nts          Disable NTS support
-  --without-gnutls       Don't use gnutls even if it is available
  --disable-cmdmon       Disable command and monitoring support
  --disable-ntp          Disable NTP support
  --disable-refclock     Disable reference clock support
@@ -926,6 +926,28 @@ if [ $feat_sechash = "1" ] && [ "x$HASH_LINK" = "x" ]  && [ $try_nettle = "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
+
 if [ $feat_sechash = "1" ] && [ "x$HASH_LINK" = "x" ]  && [ $try_nss = "1" ]; then
  test_cflags="`pkg_config --cflags nss`"
  test_link="`pkg_config --libs-only-L nss` -lfreebl3 -lnssutil3"
@@ -951,28 +973,6 @@ 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"
@@ -991,7 +991,7 @@ if [ $feat_ntp = "1" ] && [ $feat_nts = "1" ] && [ $try_gnutls = "1" ]; then
        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 'AES-SIV-CMAC in nettle' \
+    if [ $try_nettle = "1" ] && test_code 'AES-SIV-CMAC in nettle' \
      'nettle/siv-cmac.h' "" "$LIBS" \
      'siv_cmac_aes128_set_key((void *)1, (void *)2);'
    then
@@ -1012,6 +1012,13 @@ if [ $feat_ntp = "1" ] && [ $feat_nts = "1" ] && [ $try_gnutls = "1" ]; then
      then
        EXTRA_OBJECTS="$EXTRA_OBJECTS siv_gnutls.o"
        add_def HAVE_SIV
+        if [ $try_aes_gcm_siv = "1" ] && test_code 'AES-GCM-SIV in gnutls' \
+          'gnutls/crypto.h' "$test_cflags" "$test_link $LIBS" '
+            return gnutls_aead_cipher_init((void *)1, GNUTLS_CIPHER_AES_128_SIV_GCM,
+                                           (void *)2);'
+        then
+          add_def HAVE_GNUTLS_SIV_GCM
+        fi
        if test_code 'gnutls_aead_cipher_set_key()' 'gnutls/crypto.h' \
          "$test_cflags" "$test_link $LIBS" '
            return gnutls_aead_cipher_set_key((void *)1, (void *)2);'
--- a/doc/chrony.conf.adoc
+++ b/doc/chrony.conf.adoc
@@ -322,16 +322,27 @@ server implementations do not respond to requests containing an unknown
 extension field (*chronyd* as a server responded to such requests since
 version 2.0).
 +
-The following extension field can be enabled by this option:
+This option can be used multiple times to enable multiple extension fields.
+
+The following extension fields are supported:
 +
 _F323_::::
-This is an experimental extension field for some improvements that were
+An experimental extension field to enable several improvements that were
 proposed for the next version of the NTP protocol (NTPv5). The field contains
 root delay and dispersion in higher resolution and a monotonic receive
-timestamp, which enables a frequency transfer between the server and client. It
-can significantly improve stability of the synchronization. Generally, it
-should be expected to work only between servers and clients running the same
-version of *chronyd*.
+timestamp, which enables a frequency transfer between the server and client to
+significantly improve stability of the synchronisation. This field should be
+enabled only for servers known to be running *chronyd* version 4.2 or later.
+_F324_::::
+An experimental extension field to enable the use of the Precision Time
+Protocol (PTP) correction field in NTP-over-PTP messages updated by one-step
+end-to-end transparent clocks in network switches and routers to significantly
+improve accuracy and stability of the synchronisation. NTP-over-PTP can be
+enabled by the <<ptpport,*ptpport*>> directive and setting the *port* option to
+the PTP port. The corrections are applied only to NTP measurements with HW
+timestamps (enabled by the <<hwtimestamp,*hwtimestamp*>> directive). This
+field should be enabled only for servers known to be running *chronyd* version
+4.5 or later.
 {blank}:::

 [[pool]]*pool* _name_ [_option_]...::
@@ -418,7 +429,7 @@ error. *chronyd* then enters its normal operating mode.
 An example of the use of the directive is:
 +
 ----
-initstepslew 30 foo.example.net bar.example.net baz.example.net
+initstepslew 30 ntp1.example.net ntp2.example.net ntp3.example.net
 ----
 +
 where 3 NTP servers are used to make the measurement. The _30_ indicates that
@@ -833,9 +844,10 @@ sources using NTS, otherwise the source with a longer polling interval will
 refresh the keys on each poll and no NTP packets will be exchanged.

 [[ntstrustedcerts]]*ntstrustedcerts* [_set-ID_] _file_|_directory_::
-This directive specifies a file or directory containing certificates (in the
-PEM format) of trusted certificate authorities (CA) which can be used to
-verify certificates of NTS servers.
+This directive specifies a file or directory containing trusted certificates
+(in the PEM format) which are needed to verify certificates of NTS-KE servers,
+e.g. certificates of trusted certificate authorities (CA) or self-signed
+certificates of the servers.
 +
 The optional _set-ID_ argument is a number in the range 0 through 2^32-1, which
 selects the set of certificates where certificates from the specified file
@@ -855,10 +867,10 @@ they change (e.g. after a renewal).
 An example is:
 +
 ----
-ntstrustedcerts /etc/pki/nts/foo.crt
-ntstrustedcerts 1 /etc/pki/nts/bar.crt
-ntstrustedcerts 1 /etc/pki/nts/baz.crt
-ntstrustedcerts 2 /etc/pki/nts/qux.crt
+ntstrustedcerts /etc/pki/nts/ca1.example.net.crt
+ntstrustedcerts 1 /etc/pki/nts/ca2.example.net.crt
+ntstrustedcerts 1 /etc/pki/nts/ca3.example.net.crt
+ntstrustedcerts 2 /etc/pki/nts/ntp2.example.net.crt
 ----

 [[nosystemcert]]*nosystemcert*::
@@ -955,9 +967,9 @@ before 4.0.
 As an example, the following configuration using the default *mix* mode:
 +
 ----
-server foo.example.net nts
-server bar.example.net nts
-server baz.example.net
+server ntp1.example.net nts
+server ntp2.example.net nts
+server ntp3.example.net
 refclock SOCK /var/run/chrony.ttyS0.sock
 ----
 +
@@ -965,9 +977,9 @@ is equivalent to the following configuration using the *ignore* mode:
 +
 ----
 authselectmode ignore
-server foo.example.net nts require trust
-server bar.example.net nts require trust
-server baz.example.net
+server ntp1.example.net nts require trust
+server ntp2.example.net nts require trust
+server ntp3.example.net
 refclock /var/run/chrony.ttyS0.sock require trust
 ----

@@ -1976,8 +1988,9 @@ all* directive.
 [[cmdport]]*cmdport* _port_::
 The *cmdport* directive allows the port that is used for run-time monitoring
 (via the *chronyc* program) to be altered from its default (323). If set to 0,
-*chronyd* will not open the port, this is useful to disable *chronyc*
-access from the Internet. (It does not disable the Unix domain command socket.)
+*chronyd* will not open the port, which disables remote *chronyc* access (with
+a non-default *bindcmdaddress*) and local access for unprivileged users. It
+does not disable the Unix domain command socket.
 +
 An example shows the syntax:
 +
@@ -1986,7 +1999,7 @@ cmdport 257
 ----
 +
 This would make *chronyd* use UDP 257 as its command port. (*chronyc* would
-need to be run with the *-p 257* switch to inter-operate correctly.)
+need to be run with the *-p 257* option to inter-operate correctly.)

 [[cmdratelimit]]*cmdratelimit* [_option_]...::
 This directive enables response rate limiting for command packets. It is
@@ -2728,24 +2741,27 @@ pidfile /run/chronyd.pid
 The *ptpport* directive enables *chronyd* to send and receive NTP messages
 contained in PTP event messages (NTP-over-PTP) to enable hardware timestamping
 on NICs which cannot timestamp NTP packets, but can timestamp unicast PTP
-packets. The port recognized by the NICs is 319 (PTP event port). The default
-value is 0 (disabled).
+packets, and also use corrections provided by PTP one-step end-to-end
+transparent clocks in network switches and routers. The port recognized by the
+NICs and PTP transparent clocks is 319 (PTP event port). The default value is 0
+(disabled).
 +
 The NTP-over-PTP support is experimental. The protocol and configuration can
-change in future. It should be used only in local networks and expected to work
-only between servers and clients running the same version of *chronyd*.
+change in future. It should be used only in local networks.
 +
 The PTP port will be open even if *chronyd* is not configured to operate as a
 server or client. The directive does not change the default protocol of
 specified NTP sources. Each NTP source that should use NTP-over-PTP needs to
 be specified with the *port* option set to the PTP port. To actually enable
 hardware timestamping on NICs which can timestamp PTP packets only, the
-*rxfilter* option of the *hwtimestamp* directive needs to be set to _ptp_.
+*rxfilter* option of the *hwtimestamp* directive needs to be set to _ptp_. The
+extension field _F324_ needs to be enabled to use the corrections provided by
+the PTP transparent clocks.
 +
 An example of client configuration is:
 +
 ----
-server foo.example.net minpoll 0 maxpoll 0 xleave port 319
+server ntp1.example.net minpoll 0 maxpoll 0 xleave port 319 extfield F324
 hwtimestamp * rxfilter ptp
 ptpport 319
 ----
@@ -2806,13 +2822,13 @@ the following methods:
  facilities.
 * Use public servers from the https://www.pool.ntp.org/[pool.ntp.org] project.

-Assuming that your NTP servers are called _foo.example.net_, _bar.example.net_
-and _baz.example.net_, your _chrony.conf_ file could contain as a minimum:
+Assuming that your NTP servers are called _ntp1.example.net_, _ntp2.example.net_
+and _ntp3.example.net_, your _chrony.conf_ file could contain as a minimum:

 ----
-server foo.example.net
-server bar.example.net
-server baz.example.net
+server ntp1.example.net
+server ntp2.example.net
+server ntp3.example.net
 ----

 However, you will probably want to include some of the other directives. The
@@ -2823,9 +2839,9 @@ synchronisation. The smallest useful configuration file would look something
 like:

 ----
-server foo.example.net iburst
-server bar.example.net iburst
-server baz.example.net iburst
+server ntp1.example.net iburst
+server ntp2.example.net iburst
+server ntp3.example.net iburst
 driftfile @CHRONYVARDIR@/drift
 makestep 1.0 3
 rtcsync
@@ -2849,9 +2865,9 @@ option will enable a secure synchronisation to the servers. The configuration
 file could look like:

 ----
-server foo.example.net iburst nts
-server bar.example.net iburst nts
-server baz.example.net iburst nts
+server ntp1.example.net iburst nts
+server ntp2.example.net iburst nts
+server ntp3.example.net iburst nts
 driftfile @CHRONYVARDIR@/drift
 makestep 1.0 3
 rtcsync
@@ -2865,14 +2881,14 @@ additional configuration to tell *chronyd* when the connection goes up and
 down. This saves the program from continuously trying to poll the servers when
 they are inaccessible.

-Again, assuming that your NTP servers are called _foo.example.net_,
-_bar.example.net_ and _baz.example.net_, your _chrony.conf_ file would now
+Again, assuming that your NTP servers are called _ntp1.example.net_,
+_ntp2.example.net_ and _ntp3.example.net_, your _chrony.conf_ file would now
 contain:

 ----
-server foo.example.net offline
-server bar.example.net offline
-server baz.example.net offline
+server ntp1.example.net offline
+server ntp2.example.net offline
+server ntp3.example.net offline
 driftfile @CHRONYVARDIR@/drift
 makestep 1.0 3
 rtcsync
@@ -3056,9 +3072,9 @@ configuration files are shown.
 For the _chrony.conf_ file, the following can be used as an example.

 ----
-server foo.example.net maxdelay 0.4 offline
-server bar.example.net maxdelay 0.4 offline
-server baz.example.net maxdelay 0.4 offline
+server ntp1.example.net maxdelay 0.4 offline
+server ntp2.example.net maxdelay 0.4 offline
+server ntp3.example.net maxdelay 0.4 offline
 logdir /var/log/chrony
 log statistics measurements tracking
 driftfile @CHRONYVARDIR@/drift
@@ -3117,10 +3133,10 @@ configuration).
 The configuration file could look like:

 ----
-server foo.example.net iburst
-server bar.example.net iburst
-server baz.example.net iburst
-server qux.example.net iburst
+server ntp1.example.net iburst
+server ntp2.example.net iburst
+server ntp3.example.net iburst
+server ntp4.example.net iburst
 makestep 1.0 3
 rtcsync
 allow
--- a/doc/chronyc.adoc
+++ b/doc/chronyc.adoc
@@ -144,7 +144,7 @@ The *tracking* command displays parameters about the system's clock
 performance. An example of the output is shown below.
 +
 ----
-Reference ID    : CB00710F (foo.example.net)
+Reference ID    : CB00710F (ntp1.example.net)
 Stratum         : 3
 Ref time (UTC)  : Fri Jan 27 09:49:17 2017
 System time     : 0.000006523 seconds slow of NTP time
@@ -178,7 +178,7 @@ with an IPv4 address.
 *Stratum*:::
 The stratum indicates how many hops away from a computer with an attached
 reference clock we are. Such a computer is a stratum-1 computer, so the
-computer in the example is two hops away (i.e. _foo.example.net_ is a
+computer in the example is two hops away (i.e. _ntp1.example.net_ is a
 stratum-2 and is synchronised from a stratum-1).
 *Ref time*:::
 This is the time (UTC) at which the last measurement from the reference
@@ -321,8 +321,8 @@ extra caption lines are shown as a reminder of the meanings of the columns.
 MS Name/IP address         Stratum Poll Reach LastRx Last sample
 ===============================================================================
 #* GPS0                          0   4   377    11   -479ns[ -621ns] +/-  134ns
-^? foo.example.net               2   6   377    23   -923us[ -924us] +/-   43ms
-^+ bar.example.net               1   6   377    21  -2629us[-2619us] +/-   86ms
+^? ntp1.example.net              2   6   377    23   -923us[ -924us] +/-   43ms
+^+ ntp2.example.net              1   6   377    21  -2629us[-2619us] +/-   86ms
 ----
 +
 The columns are as follows:
@@ -400,7 +400,7 @@ An example report is:
 ----
 Name/IP Address            NP  NR  Span  Frequency  Freq Skew  Offset  Std Dev
 ===============================================================================
-foo.example.net            11   5   46m     -0.001      0.045      1us    25us
+ntp1.example.net           11   5   46m     -0.001      0.045      1us    25us
 ----
 +
 The columns are as follows:
@@ -444,9 +444,9 @@ An example of the output is shown below.
 ----
 S Name/IP Address        Auth COpts EOpts Last Score     Interval  Leap
 =======================================================================
-D foo.example.net           Y ----- --TR-    4   1.0   -61ms   +62ms  N
-* bar.example.net           N ----- -----    0   1.0 -6846us +7305us  N
-+ baz.example.net           N ----- -----   10   1.0 -7381us +7355us  N
+D ntp1.example.net          Y ----- --TR-    4   1.0   -61ms   +62ms  N
+* ntp2.example.net          N ----- -----    0   1.0 -6846us +7305us  N
+ ntp3.example.net          N ----- -----   10   1.0 -7381us +7355us  N
 ----
 +
 The columns are as follows:
@@ -592,9 +592,9 @@ shown below.
 ----
 Name/IP address             Mode KeyID Type KLen Last Atmp  NAK Cook CLen
 =========================================================================
-foo.example.net              NTS     1   15  256 135m    0    0    8  100
-bar.example.net               SK    30   13  128    -    0    0    0    0
-baz.example.net                -     0    0    0    -    0    0    0    0
+ntp1.example.net             NTS     1   15  256 135m    0    0    8  100
+ntp2.example.net              SK    30   13  128    -    0    0    0    0
+ntp3.example.net               -     0    0    0    -    0    0    0    0
 ----
 +
 The columns are as follows:
@@ -758,7 +758,7 @@ parameters and options is identical to that for the
 An example of using this command is shown below.
 +
 ----
-add peer foo.example.net minpoll 6 maxpoll 10 key 25
+add peer ntp1.example.net minpoll 6 maxpoll 10 key 25
 ----

 [[add_pool]]*add pool* _name_ [_option_]...::
@@ -772,7 +772,7 @@ directive in the configuration file.
 An example of using this command is shown below:
 +
 ----
-add pool foo.example.net maxsources 3 iburst
+add pool ntp1.example.net maxsources 3 iburst
 ----

 [[add_server]]*add server* _name_ [_option_]...::
@@ -786,7 +786,7 @@ directive in the configuration file.
 An example of using this command is shown below:
 +
 ----
-add server foo.example.net minpoll 6 maxpoll 10 key 25
+add server ntp1.example.net minpoll 6 maxpoll 10 key 25
 ----

 [[delete]]*delete* _address_::
@@ -862,7 +862,7 @@ IPv6 addresses have first 48 bits equal to _2001:db8:789a_.
 Example of the three-argument form of the command is:
 +
 ----
-burst 2/10 foo.example.net
+burst 2/10 ntp1.example.net
 ----

 [[maxdelay]]*maxdelay* _address_ _delay_::
@@ -928,7 +928,7 @@ uses an IP address or a hostname. These forms are illustrated below.
 offline
 offline 255.255.255.0/1.2.3.0
 offline 2001:db8:789a::/48
-offline foo.example.net
+offline ntp1.example.net
 ----
 +
 The second form means that the *offline* command is to be applied to any source
@@ -986,6 +986,10 @@ command might replace the addresses even if they are still in the pool.
 The *reload sources* command causes *chronyd* to re-read all _*.sources_ files
 from the directories specified by the
 <<chrony.conf.adoc#sourcedir,*sourcedir*>> directive.
+
+Note that modified sources (e.g. specified with a new option) are not modified
+in memory. They are removed and added again, which causes them to lose old
+measurements and reset the selection state.

 [[sourcename]]*sourcename* _address_::
 The *sourcename* command prints the original hostname or address that was
@@ -1094,7 +1098,7 @@ particular host.
 Examples of use, showing a named host and a numeric IP address, are as follows:
 +
 ----
-accheck foo.example.net
+accheck ntp1.example.net
 accheck 1.2.3.4
 accheck 2001:db8::1
 ----
@@ -1121,7 +1125,7 @@ An example of the output is:
 Hostname                      NTP   Drop Int IntL Last     Cmd   Drop Int  Last
 ===============================================================================
 localhost                       2      0   2   -   133      15      0  -1     7
-foo.example.net                12      0   6   -    23       0      0   -     -
+ntp1.example.net               12      0   6   -    23       0      0   -     -
 ----
 +
 Each row shows the data for a single host. Only hosts that have passed the host
@@ -1321,7 +1325,7 @@ used to check whether monitoring access is permitted from a named host.
 Examples of use are as follows:
 +
 ----
-cmdaccheck foo.example.net
+cmdaccheck ntp1.example.net
 cmdaccheck 1.2.3.4
 cmdaccheck 2001:db8::1
 ----
--- a/doc/chronyd.adoc
+++ b/doc/chronyd.adoc
@@ -72,9 +72,9 @@ terminal.

 *-L* _level_::
 This option specifies the minimum severity level of messages to be written to
-the log file, syslog, or terminal. The following levels can be specified:
-0 (informational), 1 (warning), 2 (non-fatal error), and 3 (fatal error). The
-default value is 0.
+the log file, syslog, or terminal. The following levels can be specified: -1
+(debug, if compiled with enabled support for debugging), 0 (informational), 1
+(warning), 2 (non-fatal error), and 3 (fatal error). The default value is 0.

 *-p*::
 When run in this mode, *chronyd* will print the configuration and exit. It will
@@ -206,6 +206,17 @@ 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.

+== ENVIRONMENT VARIABLES
+
+*LISTEN_FDS*::
+On Linux systems, the systemd service manager may pass file descriptors for
+pre-initialised sockets to *chronyd*. The service manager allocates and binds
+the file descriptors, and passes a copy to each spawned instance of the
+service. This allows for zero-downtime service restarts as the sockets buffer
+client requests until the service is able to handle them. The service manager
+sets the LISTEN_FDS environment variable to the number of passed file
+descriptors.
+
 == FILES

 _@SYSCONFDIR@/chrony.conf_
--- a/doc/faq.adoc
+++ b/doc/faq.adoc
@@ -1,6 +1,7 @@
 // This file is part of chrony
 //
 // Copyright (C) Richard P. Curnow  1997-2003
+// Copyright (C) Luke Valenta  2023
 // Copyright (C) Miroslav Lichvar  2014-2016, 2020-2023
 //
 // This program is free software; you can redistribute it and/or modify
@@ -265,11 +266,11 @@ 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
+server ntp1.example.net iburst nts maxdelay 0.1
+server ntp2.example.net iburst nts maxdelay 0.2
+server ntp3.example.net iburst nts maxdelay 0.05
+server ntp4.example.net iburst nts maxdelay 0.1
+server ntp5.example.net iburst nts maxdelay 0.1
 minsources 3
 maxchange 100 0 0
 makestep 0.001 1
@@ -318,7 +319,7 @@ An example of the directive for an NTP server on the Internet that you are
 allowed to poll frequently could be

 ----
-server foo.example.net minpoll 4 maxpoll 6 polltarget 16
+server ntp.example.net minpoll 4 maxpoll 6 polltarget 16
 ----

 An example using shorter polling intervals with a server located in the same
@@ -381,7 +382,7 @@ 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
+Since 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:
@@ -390,6 +391,18 @@ the `extfield F323` option. For example:
 server ntp.local minpoll 0 maxpoll 0 xleave extfield F323
 ----

+Since version 4.5, `chronyd` can apply corrections from PTP one-step end-to-end
+transparent clocks (e.g. network switches) to significantly improve accuracy of
+synchronisation in local networks. It requires the PTP transport to be enabled
+by the `ptpport` directive, HW timestamping, and the `extfield F324` option.
+For example:
+
+----
+server ntp.local minpoll -4 maxpoll -4 xleave extfield F323 extfield F324 port 319
+ptpport 319
+hwtimestamp eth0 minpoll -4
+----
+
 === Does `chronyd` have an ntpdate mode?

 Yes. With the `-q` option `chronyd` will set the system clock once and exit.
@@ -497,6 +510,59 @@ pidfile /var/run/chronyd-server1.pid
 driftfile /var/lib/chrony/drift-server1
 ----

+=== How can `chronyd` be configured to minimise downtime during restarts?
+
+The `dumpdir` directive in _chrony.conf_ provides `chronyd` a location to save
+a measurement history of the sources it uses when the service exits. The `-r`
+option then enables `chronyd` to load state from the dump files, reducing the
+synchronisation time after a restart.
+
+Similarly, the `ntsdumpdir` directive provides a location for `chronyd` to save
+NTS cookies received from the server to avoid making a NTS-KE request when
+`chronyd` is started. When operating as an NTS server, `chronyd` also saves
+cookies keys to this directory to allow clients to continue to use the old keys
+after a server restart for a more seamless experience.
+
+On Linux systems,
+https://www.freedesktop.org/software/systemd/man/latest/sd_listen_fds.html[systemd
+socket activation] provides a mechanism to reuse server sockets across
+`chronyd` restarts, so that client requests will be buffered until the service
+is again able to handle the requests. This allows for zero-downtime service
+restarts, simplified dependency logic at boot, and on-demand service spawning
+(for instance, for separated server `chronyd` instances run with the `-x`
+flag).
+
+Socket activation is supported since `chrony` version 4.5.
+The service manager (systemd) creates sockets and
+passes file descriptors to them to the process via the `LISTEN_FDS` environment
+variable. Before opening new sockets, `chronyd` first checks for and attempts
+to reuse matching sockets passed from the service manager. For instance, if an
+IPv4 datagram socket bound on `bindaddress` and `port` is available, it will be
+used by the NTP server to accept incoming IPv4 requests.
+
+An example systemd socket unit is below, where `chronyd` is configured with
+`bindaddress 0.0.0.0`, `bindaddress ::`, `port 123`, and `ntsport 4460`.
+
+----
+[Unit]
+Description=chronyd server sockets
+
+[Socket]
+Service=chronyd.service
+# IPv4 NTP server
+ListenDatagram=0.0.0.0:123
+# IPv6 NTP server
+ListenDatagram=[::]:123
+# IPv4 NTS-KE server
+ListenStream=0.0.0.0:4460
+# IPv6 NTS-KE server
+ListenStream=[::]:4460
+BindIPv6Only=ipv6-only
+
+[Install]
+WantedBy=sockets.target
+----
+
 === Should be a leap smear enabled on NTP server?

 With the `smoothtime` and `leapsecmode` directives it is possible to enable a
@@ -598,7 +664,10 @@ 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.
+`ptpport` directive. Since version 4.5, `chrony` can also apply corrections
+provided by PTP one-step end-to-end transparent clocks to reach the accuracy of
+ordinary PTP clocks. The application of PTP corrections can be enabled by the
+`extfield F324` option.

 === How can I avoid using wrong PHC refclock?

@@ -669,9 +738,9 @@ this:
 ----
 MS Name/IP address         Stratum Poll Reach LastRx Last sample
 ===============================================================================
-^* foo.example.net               2   6   377    34   +484us[ -157us] +/-   30ms
-^- bar.example.net               2   6   377    34    +33ms[  +32ms] +/-   47ms
-^+ baz.example.net               3   6   377    35  -1397us[-2033us] +/-   60ms
+^* ntp1.example.net              2   6   377    34   +484us[ -157us] +/-   30ms
+^- ntp2.example.net              2   6   377    34    +33ms[  +32ms] +/-   47ms
+^+ ntp3.example.net              3   6   377    35  -1397us[-2033us] +/-   60ms
 ----

 === Are NTP servers specified with the `offline` option?
@@ -741,9 +810,9 @@ 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
+ntp1.example.net             NTS     1   15  256  33m    0    0    8  100
+ntp2.example.net             NTS     1   15  256  33m    0    0    8  100
+ntp3.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
@@ -867,7 +936,7 @@ Name/IP Address            NP  NR  Span  Frequency  Freq Skew  Offset  Std Dev
 ==============================================================================
 PPS0                        0   0     0     +0.000   2000.000     +0ns  4000ms
 NMEA                       58  30   231    -96.494     38.406   +504ms  6080us
-foo.example.net             7   3   200     -2.991     16.141   -107us   492us
+ntp1.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
--- a/examples/chrony.conf.example3
+++ b/examples/chrony.conf.example3
@@ -27,9 +27,9 @@
 # you can access at http://support.ntp.org/bin/view/Servers/WebHome or
 # you can use servers from the pool.ntp.org project.

-! server foo.example.net iburst
-! server bar.example.net iburst
-! server baz.example.net iburst
+! server ntp1.example.net iburst
+! server ntp2.example.net iburst
+! server ntp3.example.net iburst

 ! pool pool.ntp.org iburst
 
@@ -99,8 +99,8 @@ ntsdumpdir /var/lib/chrony
 # and edit the following lines to specify the locations of the certificate and
 # key.

-! ntsservercert /etc/.../foo.example.net.crt
-! ntsserverkey /etc/.../foo.example.net.key
+! ntsservercert /etc/.../nts-server.crt
+! ntsserverkey /etc/.../nts-server.key

 # chronyd can save the measurement history for the servers to files when
 # it exits.  This is useful in 2 situations:
@@ -238,7 +238,7 @@ ntsdumpdir /var/lib/chrony
 # several people, you need to set up a mailing list or sendmail alias
 # for them and use the address of that.)

-! mailonchange wibble@foo.example.net 0.5
+! mailonchange wibble@example.net 0.5

 #######################################################################
 ### COMMAND ACCESS
--- a/logging.c
+++ b/logging.c
@@ -145,6 +145,7 @@ void LOG_Message(LOG_Severity severity,
  struct tm *tm;

  assert(initialised);
+  severity = CLAMP(LOGS_DEBUG, severity, LOGS_FATAL);

  if (!system_log && file_log && severity >= log_min_severity) {
    /* Don't clutter up syslog with timestamps and internal debugging info */
@@ -155,8 +156,13 @@ void LOG_Message(LOG_Severity severity,
      fprintf(file_log, "%s ", buf);
    }
 #if DEBUG > 0
-    if (log_min_severity <= LOGS_DEBUG)
-      fprintf(file_log, "%s%s:%d:(%s) ", debug_prefix, filename, line_number, function_name);
+    if (log_min_severity <= LOGS_DEBUG) {
+      /* Log severity to character mapping (debug, info, warn, err, fatal) */
+      const char severity_chars[LOGS_FATAL - LOGS_DEBUG + 1] = {'D', 'I', 'W', 'E', 'F'};
+
+      fprintf(file_log, "%c:%s%s:%d:(%s) ", severity_chars[severity - LOGS_DEBUG],
+              debug_prefix, filename, line_number, function_name);
+    }
 #endif
  }

--- a/main.c
+++ b/main.c
@@ -368,9 +368,9 @@ go_daemon(void)
      }

      /* Don't keep stdin/out/err from before. But don't close
-         the parent pipe yet. */
+         the parent pipe yet, or reusable file descriptors. */
      for (fd=0; fd<1024; fd++) {
-        if (fd != pipefd[1])
+        if (fd != pipefd[1] && !SCK_IsReusable(fd))
          close(fd);
      }

@@ -560,6 +560,9 @@ int main
  if (user_check && getuid() != 0)
    LOG_FATAL("Not superuser");

+  /* Initialise reusable file descriptors before fork */
+  SCK_PreInitialise();
+
  /* Turn into a daemon */
  if (!nofork) {
    go_daemon();
--- a/ntp.h
+++ b/ntp.h
@@ -115,9 +115,11 @@ typedef struct {

 /* Non-authentication extension fields and corresponding internal flags */

-#define NTP_EF_EXP1                     0xF323
+#define NTP_EF_EXP_MONO_ROOT            0xF323
+#define NTP_EF_EXP_NET_CORRECTION       0xF324

-#define NTP_EF_FLAG_EXP1                0x1
+#define NTP_EF_FLAG_EXP_MONO_ROOT       0x1
+#define NTP_EF_FLAG_EXP_NET_CORRECTION  0x2

 /* Pre-NTPv5 experimental extension field */
 typedef struct {
@@ -126,9 +128,18 @@ typedef struct {
  NTP_int32 root_dispersion;
  NTP_int64 mono_receive_ts;
  uint32_t mono_epoch;
-} NTP_ExtFieldExp1;
+} NTP_EFExpMonoRoot;

-#define NTP_EF_EXP1_MAGIC 0xF5BEDD9AU
+#define NTP_EF_EXP_MONO_ROOT_MAGIC      0xF5BEDD9AU
+
+/* Experimental extension field to provide PTP corrections */
+typedef struct {
+  uint32_t magic;
+  NTP_int64 correction;
+  uint32_t reserved[3];
+} NTP_EFExpNetCorrection;
+
+#define NTP_EF_EXP_NET_CORRECTION_MAGIC 0x07AC2CEBU

 /* Authentication extension fields */

--- a/ntp_core.c
+++ b/ntp_core.c
@@ -314,6 +314,9 @@ static ARR_Instance broadcasts;
 /* Maximum acceptable change in server mono<->real offset */
 #define MAX_MONO_DOFFSET 16.0

+/* Maximum assumed frequency error in network corrections */
+#define MAX_NET_CORRECTION_FREQ 100.0e-6
+
 /* Invalid socket, different from the one in ntp_io.c */
 #define INVALID_SOCK_FD -2

@@ -373,6 +376,9 @@ do_size_checks(void)
  assert(offsetof(NTP_Packet, originate_ts)    == 24);
  assert(offsetof(NTP_Packet, receive_ts)      == 32);
  assert(offsetof(NTP_Packet, transmit_ts)     == 40);
+
+  assert(sizeof (NTP_EFExpMonoRoot) == 24);
+  assert(sizeof (NTP_EFExpNetCorrection) == 24);
 }

 /* ================================================== */
@@ -418,6 +424,8 @@ zero_local_timestamp(NTP_Local_Timestamp *ts)
  UTI_ZeroTimespec(&ts->ts);
  ts->err = 0.0;
  ts->source = NTP_TS_DAEMON;
+  ts->rx_duration = 0.0;
+  ts->net_correction = 0.0;
 }

 /* ================================================== */
@@ -1045,34 +1053,64 @@ receive_timeout(void *arg)
 /* ================================================== */

 static int
-add_ext_exp1(NTP_Packet *message, NTP_PacketInfo *info, struct timespec *rx,
-             double root_delay, double root_dispersion)
+add_ef_mono_root(NTP_Packet *message, NTP_PacketInfo *info, struct timespec *rx,
+                 double root_delay, double root_dispersion)
 {
  struct timespec mono_rx;
-  NTP_ExtFieldExp1 exp1;
+  NTP_EFExpMonoRoot ef;
  NTP_int64 ts_fuzz;

-  memset(&exp1, 0, sizeof (exp1));
-  exp1.magic = htonl(NTP_EF_EXP1_MAGIC);
+  memset(&ef, 0, sizeof (ef));
+  ef.magic = htonl(NTP_EF_EXP_MONO_ROOT_MAGIC);

  if (info->mode != MODE_CLIENT) {
-    exp1.root_delay = UTI_DoubleToNtp32f28(root_delay);
-    exp1.root_dispersion = UTI_DoubleToNtp32f28(root_dispersion);
+    ef.root_delay = UTI_DoubleToNtp32f28(root_delay);
+    ef.root_dispersion = UTI_DoubleToNtp32f28(root_dispersion);
    if (rx)
      UTI_AddDoubleToTimespec(rx, server_mono_offset, &mono_rx);
    else
      UTI_ZeroTimespec(&mono_rx);
    UTI_GetNtp64Fuzz(&ts_fuzz, message->precision);
-    UTI_TimespecToNtp64(&mono_rx, &exp1.mono_receive_ts, &ts_fuzz);
-    exp1.mono_epoch = htonl(server_mono_epoch);
+    UTI_TimespecToNtp64(&mono_rx, &ef.mono_receive_ts, &ts_fuzz);
+    ef.mono_epoch = htonl(server_mono_epoch);
  }

-  if (!NEF_AddField(message, info, NTP_EF_EXP1, &exp1, sizeof (exp1))) {
+  if (!NEF_AddField(message, info, NTP_EF_EXP_MONO_ROOT, &ef, sizeof (ef))) {
    DEBUG_LOG("Could not add EF");
    return 0;
  }

-  info->ext_field_flags |= NTP_EF_FLAG_EXP1;
+  info->ext_field_flags |= NTP_EF_FLAG_EXP_MONO_ROOT;
+
+  return 1;
+}
+
+/* ================================================== */
+
+static int
+add_ef_net_correction(NTP_Packet *message, NTP_PacketInfo *info,
+                      NTP_Local_Timestamp *local_rx)
+{
+  NTP_EFExpNetCorrection ef;
+
+  if (CNF_GetPtpPort() == 0) {
+    DEBUG_LOG("ptpport disabled");
+    return 1;
+  }
+
+  memset(&ef, 0, sizeof (ef));
+  ef.magic = htonl(NTP_EF_EXP_NET_CORRECTION_MAGIC);
+
+  if (info->mode != MODE_CLIENT && local_rx->net_correction > local_rx->rx_duration) {
+    UTI_DoubleToNtp64(local_rx->net_correction, &ef.correction);
+  }
+
+  if (!NEF_AddField(message, info, NTP_EF_EXP_NET_CORRECTION, &ef, sizeof (ef))) {
+    DEBUG_LOG("Could not add EF");
+    return 0;
+  }
+
+  info->ext_field_flags |= NTP_EF_FLAG_EXP_NET_CORRECTION;

  return 1;
 }
@@ -1224,9 +1262,13 @@ transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */
    return 0;

  if (ext_field_flags) {
-    if (ext_field_flags & NTP_EF_FLAG_EXP1) {
-      if (!add_ext_exp1(&message, &info, smooth_time ? NULL : &local_receive,
-                        our_root_delay, our_root_dispersion))
+    if (ext_field_flags & NTP_EF_FLAG_EXP_MONO_ROOT) {
+      if (!add_ef_mono_root(&message, &info, smooth_time ? NULL : &local_receive,
+                            our_root_delay, our_root_dispersion))
+        return 0;
+    }
+    if (ext_field_flags & NTP_EF_FLAG_EXP_NET_CORRECTION) {
+      if (!add_ef_net_correction(&message, &info, local_rx))
        return 0;
    }
  }
@@ -1297,6 +1339,8 @@ transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */
    local_tx->ts = local_transmit;
    local_tx->err = local_transmit_err;
    local_tx->source = NTP_TS_DAEMON;
+    local_tx->rx_duration = 0.0;
+    local_tx->net_correction = 0.0;
  }

  if (local_ntp_rx)
@@ -1490,6 +1534,14 @@ is_zero_data(unsigned char *data, int length)

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

+static int
+is_exp_ef(void *body, int body_length, int expected_body_length, uint32_t magic)
+{
+  return body_length == expected_body_length && *(uint32_t *)body == htonl(magic);
+}
+
+/* ================================================== */
+
 static int
 parse_packet(NTP_Packet *packet, int length, NTP_PacketInfo *info)
 {
@@ -1576,10 +1628,15 @@ parse_packet(NTP_Packet *packet, int length, NTP_PacketInfo *info)
      case NTP_EF_NTS_AUTH_AND_EEF:
        info->auth.mode = NTP_AUTH_NTS;
        break;
-      case NTP_EF_EXP1:
-        if (ef_body_length == sizeof (NTP_ExtFieldExp1) &&
-            ntohl(((NTP_ExtFieldExp1 *)ef_body)->magic) == NTP_EF_EXP1_MAGIC)
-          info->ext_field_flags |= NTP_EF_FLAG_EXP1;
+      case NTP_EF_EXP_MONO_ROOT:
+        if (is_exp_ef(ef_body, ef_body_length, sizeof (NTP_EFExpMonoRoot),
+                      NTP_EF_EXP_MONO_ROOT_MAGIC))
+          info->ext_field_flags |= NTP_EF_FLAG_EXP_MONO_ROOT;
+        break;
+      case NTP_EF_EXP_NET_CORRECTION:
+        if (is_exp_ef(ef_body, ef_body_length, sizeof (NTP_EFExpNetCorrection),
+                      NTP_EF_EXP_NET_CORRECTION_MAGIC))
+          info->ext_field_flags |= NTP_EF_FLAG_EXP_NET_CORRECTION;
        break;
      default:
        DEBUG_LOG("Unknown extension field type=%x", (unsigned int)ef_type);
@@ -1607,6 +1664,53 @@ parse_packet(NTP_Packet *packet, int length, NTP_PacketInfo *info)

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

+static void
+apply_net_correction(NTP_Sample *sample, NTP_Local_Timestamp *rx, NTP_Local_Timestamp *tx,
+                     double precision)
+{
+  double rx_correction, tx_correction, low_delay_correction;
+
+  /* Require some correction from transparent clocks to be present
+     in both directions (not just the local RX timestamp correction) */
+  if (rx->net_correction <= rx->rx_duration || tx->net_correction <= 0.0)
+    return;
+
+  /* With perfect corrections from PTP transparent clocks and short cables
+     the peer delay would be close to zero, or even negative if the server or
+     transparent clocks were running faster than client, which would invert the
+     sample weighting.  Adjust the correction to get a delay corresponding to
+     a direct connection to the server.  For simplicity, assume the TX and RX
+     link speeds are equal.  If not, the reported delay will be wrong, but it
+     will not cause an error in the offset. */
+  rx_correction = rx->net_correction - rx->rx_duration;
+  tx_correction = tx->net_correction - rx->rx_duration;
+
+  /* Use a slightly smaller value in the correction of delay to not overcorrect
+     if the transparent clocks run up to 100 ppm fast and keep a part of the
+     uncorrected delay for the sample weighting */
+  low_delay_correction = (rx_correction + tx_correction) *
+                         (1.0 - MAX_NET_CORRECTION_FREQ);
+
+  /* Make sure the correction is sane.  The values are not authenticated! */
+  if (low_delay_correction < 0.0 || low_delay_correction > sample->peer_delay) {
+    DEBUG_LOG("Invalid correction %.9f peer_delay=%.9f",
+              low_delay_correction, sample->peer_delay);
+    return;
+  }
+
+  /* Correct the offset and peer delay, but not the root delay to not
+     change the estimated maximum error */
+  sample->offset += (rx_correction - tx_correction) / 2.0;
+  sample->peer_delay -= low_delay_correction;
+  if (sample->peer_delay < precision)
+    sample->peer_delay = precision;
+
+  DEBUG_LOG("Applied correction rx=%.9f tx=%.9f dur=%.9f",
+            rx->net_correction, tx->net_correction, rx->rx_duration);
+}
+
+/* ================================================== */
+
 static int
 check_delay_ratio(NCR_Instance inst, SST_Stats stats,
                struct timespec *sample_time, double delay)
@@ -1868,18 +1972,20 @@ process_response(NCR_Instance inst, int saved, NTP_Local_Address *local_addr,
  /* Extension fields */
  int parsed, ef_length, ef_type, ef_body_length;
  void *ef_body;
-  NTP_ExtFieldExp1 *ef_exp1;
+  NTP_EFExpMonoRoot *ef_mono_root;
+  NTP_EFExpNetCorrection *ef_net_correction;

  NTP_Local_Timestamp local_receive, local_transmit;
  double remote_interval, local_interval, response_time;
-  double delay_time, precision, mono_doffset;
+  double delay_time, precision, mono_doffset, net_correction;
  int updated_timestamps;

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

  stats = SRC_GetSourcestats(inst->source);

-  ef_exp1 = NULL;
+  ef_mono_root = NULL;
+  ef_net_correction = NULL;

  /* Find requested non-authentication extension fields */
  if (inst->ext_field_flags & info->ext_field_flags) {
@@ -1889,11 +1995,17 @@ process_response(NCR_Instance inst, int saved, NTP_Local_Address *local_addr,
        break;

      switch (ef_type) {
-        case NTP_EF_EXP1:
-          if (inst->ext_field_flags & NTP_EF_FLAG_EXP1 &&
-              ef_body_length == sizeof (*ef_exp1) &&
-              ntohl(((NTP_ExtFieldExp1 *)ef_body)->magic) == NTP_EF_EXP1_MAGIC)
-            ef_exp1 = ef_body;
+        case NTP_EF_EXP_MONO_ROOT:
+          if (inst->ext_field_flags & NTP_EF_FLAG_EXP_MONO_ROOT &&
+              is_exp_ef(ef_body, ef_body_length, sizeof (*ef_mono_root),
+                        NTP_EF_EXP_MONO_ROOT_MAGIC))
+            ef_mono_root = ef_body;
+          break;
+        case NTP_EF_EXP_NET_CORRECTION:
+          if (inst->ext_field_flags & NTP_EF_FLAG_EXP_NET_CORRECTION &&
+              is_exp_ef(ef_body, ef_body_length, sizeof (*ef_net_correction),
+                        NTP_EF_EXP_NET_CORRECTION_MAGIC))
+            ef_net_correction = ef_body;
          break;
      }
    }
@@ -1902,9 +2014,9 @@ process_response(NCR_Instance inst, int saved, NTP_Local_Address *local_addr,
  pkt_leap = NTP_LVM_TO_LEAP(message->lvm);
  pkt_version = NTP_LVM_TO_VERSION(message->lvm);
  pkt_refid = ntohl(message->reference_id);
-  if (ef_exp1) {
-    pkt_root_delay = UTI_Ntp32f28ToDouble(ef_exp1->root_delay);
-    pkt_root_dispersion = UTI_Ntp32f28ToDouble(ef_exp1->root_dispersion);
+  if (ef_mono_root) {
+    pkt_root_delay = UTI_Ntp32f28ToDouble(ef_mono_root->root_delay);
+    pkt_root_dispersion = UTI_Ntp32f28ToDouble(ef_mono_root->root_dispersion);
  } else {
    pkt_root_delay = UTI_Ntp32ToDouble(message->root_delay);
    pkt_root_dispersion = UTI_Ntp32ToDouble(message->root_dispersion);
@@ -1989,11 +2101,11 @@ process_response(NCR_Instance inst, int saved, NTP_Local_Address *local_addr,
       the new sample.  In the interleaved mode, cancel the correction out in
       remote timestamps of the previous request and response, which were
       captured before the source accumulated the new time corrections. */
-    if (ef_exp1 && inst->remote_mono_epoch == ntohl(ef_exp1->mono_epoch) &&
-        !UTI_IsZeroNtp64(&ef_exp1->mono_receive_ts) &&
+    if (ef_mono_root && inst->remote_mono_epoch == ntohl(ef_mono_root->mono_epoch) &&
+        !UTI_IsZeroNtp64(&ef_mono_root->mono_receive_ts) &&
        !UTI_IsZeroNtp64(&inst->remote_ntp_monorx)) {
      mono_doffset =
-          UTI_DiffNtp64ToDouble(&ef_exp1->mono_receive_ts, &inst->remote_ntp_monorx) -
+          UTI_DiffNtp64ToDouble(&ef_mono_root->mono_receive_ts, &inst->remote_ntp_monorx) -
          UTI_DiffNtp64ToDouble(&message->receive_ts, &inst->remote_ntp_rx);
      if (fabs(mono_doffset) > MAX_MONO_DOFFSET)
        mono_doffset = 0.0;
@@ -2001,6 +2113,12 @@ process_response(NCR_Instance inst, int saved, NTP_Local_Address *local_addr,
      mono_doffset = 0.0;
    }

+    if (ef_net_correction) {
+      net_correction = UTI_Ntp64ToDouble(&ef_net_correction->correction);
+    } else {
+      net_correction = 0.0;
+    }
+
    /* Select remote and local timestamps for the new sample */
    if (interleaved_packet) {
      /* Prefer previous local TX and remote RX timestamps if it will make
@@ -2020,6 +2138,7 @@ process_response(NCR_Instance inst, int saved, NTP_Local_Address *local_addr,
        UTI_Ntp64ToTimespec(&message->receive_ts, &remote_receive);
        UTI_Ntp64ToTimespec(&inst->remote_ntp_rx, &remote_request_receive);
        local_transmit = inst->local_tx;
+        local_transmit.net_correction = net_correction;
        root_delay = MAX(pkt_root_delay, inst->remote_root_delay);
        root_dispersion = MAX(pkt_root_dispersion, inst->remote_root_dispersion);
      }
@@ -2034,6 +2153,7 @@ process_response(NCR_Instance inst, int saved, NTP_Local_Address *local_addr,
      remote_request_receive = remote_receive;
      local_receive = *rx_ts;
      local_transmit = inst->local_tx;
+      local_transmit.net_correction = net_correction;
      root_delay = pkt_root_delay;
      root_dispersion = pkt_root_dispersion;
    }
@@ -2077,6 +2197,9 @@ process_response(NCR_Instance inst, int saved, NTP_Local_Address *local_addr,
                             skew * fabs(local_interval);
    sample.root_delay = root_delay + sample.peer_delay;
    sample.root_dispersion = root_dispersion + sample.peer_dispersion;
+
+    /* Apply corrections from PTP transparent clocks if available and sane */
+    apply_net_correction(&sample, &local_receive, &local_transmit, precision);
    
    /* If the source is an active peer, this is the minimum assumed interval
       between previous two transmissions (if not constrained by minpoll) */
@@ -2085,8 +2208,10 @@ process_response(NCR_Instance inst, int saved, NTP_Local_Address *local_addr,

    /* Additional tests required to pass before accumulating the sample */

-    /* Test A requires that the minimum estimate of the peer delay is not
-       larger than the configured maximum, in both client modes that the server
+    /* Test A combines multiple tests to avoid changing the measurements log
+       format and ntpdata report.  It requires that the minimum estimate of the
+       peer delay is not larger than the configured maximum, it is not a
+       response in the 'warm up' exchange, in both client modes that the server
       processing time is sane, in interleaved client/server mode that the
       previous response was not in basic mode (which prevents using timestamps
       that minimise delay error), and in interleaved symmetric mode that the
@@ -2094,6 +2219,7 @@ process_response(NCR_Instance inst, int saved, NTP_Local_Address *local_addr,
       a missed response */
    testA = sample.peer_delay - sample.peer_dispersion <= inst->max_delay &&
            precision <= inst->max_delay &&
+            inst->presend_done <= 0 &&
            !(inst->mode == MODE_CLIENT && response_time > MAX_SERVER_INTERVAL) &&
            !(inst->mode == MODE_CLIENT && interleaved_packet &&
              UTI_IsZeroTimespec(&inst->prev_local_tx.ts) &&
@@ -2132,6 +2258,7 @@ process_response(NCR_Instance inst, int saved, NTP_Local_Address *local_addr,
    sample.root_delay = sample.root_dispersion = 0.0;
    sample.time = rx_ts->ts;
    mono_doffset = 0.0;
+    net_correction = 0.0;
    local_receive = *rx_ts;
    local_transmit = inst->local_tx;
    testA = testB = testC = testD = 0;
@@ -2165,9 +2292,9 @@ process_response(NCR_Instance inst, int saved, NTP_Local_Address *local_addr,
    /* If available, update the monotonic timestamp and accumulate the offset.
       This needs to be done here to not lose changes in remote_ntp_rx in
       symmetric mode when there are multiple responses per request. */
-    if (ef_exp1 && !UTI_IsZeroNtp64(&ef_exp1->mono_receive_ts)) {
-      inst->remote_mono_epoch = ntohl(ef_exp1->mono_epoch);
-      inst->remote_ntp_monorx = ef_exp1->mono_receive_ts;
+    if (ef_mono_root && !UTI_IsZeroNtp64(&ef_mono_root->mono_receive_ts)) {
+      inst->remote_mono_epoch = ntohl(ef_mono_root->mono_epoch);
+      inst->remote_ntp_monorx = ef_mono_root->mono_receive_ts;
      inst->mono_doffset += mono_doffset;
    } else {
      inst->remote_mono_epoch = 0;
@@ -2175,8 +2302,11 @@ process_response(NCR_Instance inst, int saved, NTP_Local_Address *local_addr,
      inst->mono_doffset = 0.0;
    }

-    /* Don't use the same set of timestamps for the next sample */
-    if (interleaved_packet)
+    inst->local_tx.net_correction = net_correction;
+
+    /* Avoid reusing timestamps of an accumulated sample when switching
+       from basic mode to interleaved mode */
+    if (interleaved_packet || !good_packet)
      inst->prev_local_tx = inst->local_tx;
    else
      zero_local_timestamp(&inst->prev_local_tx);
@@ -2195,15 +2325,11 @@ process_response(NCR_Instance inst, int saved, NTP_Local_Address *local_addr,
  /* Accept at most one response per request.  The NTP specification recommends
     resetting local_ntp_tx to make the following packets fail test2 or test3,
     but that would not allow the code above to make multiple updates of the
-     timestamps in symmetric mode.  Also, ignore presend responses. */
+     timestamps in symmetric mode. */
  if (inst->valid_rx) {
    test2 = test3 = 0;
    valid_packet = synced_packet = good_packet = 0;
  } else if (valid_packet) {
-    if (inst->presend_done) {
-      testA = 0;
-      good_packet = 0;
-    }
    inst->valid_rx = 1;
  }

@@ -2602,8 +2728,7 @@ NCR_ProcessRxUnknown(NTP_Remote_Address *remote_addr, NTP_Local_Address *local_a
      UTI_CompareNtp64(&message->receive_ts, &message->transmit_ts) != 0) {
    ntp_rx = message->originate_ts;
    local_ntp_rx = &ntp_rx;
-    UTI_ZeroTimespec(&local_tx.ts);
-    local_tx.source = NTP_TS_DAEMON;
+    zero_local_timestamp(&local_tx);
    interleaved = CLG_GetNtpTxTimestamp(&ntp_rx, &local_tx.ts, &local_tx.source);

    tx_ts = &local_tx;
--- a/ntp_core.h
+++ b/ntp_core.h
@@ -42,6 +42,8 @@ typedef struct {
  struct timespec ts;
  double err;
  NTP_Timestamp_Source source;
+  double rx_duration;
+  double net_correction;
 } NTP_Local_Timestamp;

 /* This is a private data type used for storing the instance record for
--- a/ntp_io.c
+++ b/ntp_io.c
@@ -431,6 +431,9 @@ process_message(SCK_Message *message, int sock_fd, int event)

  SCH_GetLastEventTime(&local_ts.ts, &local_ts.err, NULL);
  local_ts.source = NTP_TS_DAEMON;
+  local_ts.rx_duration = 0.0;
+  local_ts.net_correction = 0.0;
+
  sched_ts = local_ts.ts;

  if (message->addr_type != SCK_ADDR_IP) {
@@ -456,7 +459,7 @@ 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))
+  if (!NIO_UnwrapMessage(message, sock_fd, &local_ts.net_correction))
    return;

  /* Just ignore the packet if it's not of a recognized length */
@@ -495,8 +498,9 @@ read_from_socket(int sock_fd, int event, void *anything)
 /* ================================================== */

 int
-NIO_UnwrapMessage(SCK_Message *message, int sock_fd)
+NIO_UnwrapMessage(SCK_Message *message, int sock_fd, double *net_correction)
 {
+  double ptp_correction;
  PTP_NtpMessage *msg;

  if (!is_ptp_socket(sock_fd))
@@ -522,7 +526,14 @@ NIO_UnwrapMessage(SCK_Message *message, int sock_fd)
  message->data = (char *)message->data + PTP_NTP_PREFIX_LENGTH;
  message->length -= PTP_NTP_PREFIX_LENGTH;

-  DEBUG_LOG("Unwrapped PTP->NTP len=%d", message->length);
+  ptp_correction = UTI_Integer64NetworkToHost(*(Integer64 *)msg->header.correction) /
+                   ((1 << 16) * 1.0e9);
+
+  /* Use the correction only if the RX duration is known (i.e. HW timestamp) */
+  if (*net_correction > 0.0)
+    *net_correction += ptp_correction;
+
+  DEBUG_LOG("Unwrapped PTP->NTP len=%d corr=%.9f", message->length, ptp_correction);

  return 1;
 }
--- a/ntp_io.h
+++ b/ntp_io.h
@@ -64,7 +64,7 @@ extern int NIO_IsServerSocketOpen(void);
 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);
+extern int NIO_UnwrapMessage(SCK_Message *message, int sock_fd, double *net_correction);

 /* Function to transmit a packet */
 extern int NIO_SendPacket(NTP_Packet *packet, NTP_Remote_Address *remote_addr,
--- a/ntp_io_linux.c
+++ b/ntp_io_linux.c
@@ -559,7 +559,7 @@ process_hw_timestamp(struct Interface *iface, struct timespec *hw_ts,
                     NTP_Local_Timestamp *local_ts, int rx_ntp_length, int family,
                     int l2_length)
 {
-  double rx_correction, ts_delay, local_err;
+  double rx_correction = 0.0, ts_delay, local_err;
  struct timespec ts;

  poll_phc(iface, &local_ts->ts);
@@ -600,6 +600,10 @@ process_hw_timestamp(struct Interface *iface, struct timespec *hw_ts,
  local_ts->ts = ts;
  local_ts->err = local_err;
  local_ts->source = NTP_TS_HARDWARE;
+  local_ts->rx_duration = rx_correction;
+  /* Network correction needs to include the RX duration to avoid
+     asymmetric correction with asymmetric link speeds */
+  local_ts->net_correction = rx_correction;
 }

 /* ================================================== */
@@ -723,6 +727,7 @@ NIO_Linux_ProcessMessage(SCK_Message *message, NTP_Local_Address *local_addr,
 {
  struct Interface *iface;
  int is_tx, ts_if_index, l2_length;
+  double c = 0.0;

  is_tx = event == SCH_FILE_EXCEPTION;
  iface = NULL;
@@ -783,7 +788,7 @@ NIO_Linux_ProcessMessage(SCK_Message *message, NTP_Local_Address *local_addr,
    return 1;
  }

-  if (!NIO_UnwrapMessage(message, local_addr->sock_fd))
+  if (!NIO_UnwrapMessage(message, local_addr->sock_fd, &c))
    return 1;

  if (message->length < NTP_HEADER_LENGTH || message->length > sizeof (NTP_Packet))
--- a/ntp_sources.c
+++ b/ntp_sources.c
@@ -844,6 +844,31 @@ NSR_AddSourceByName(char *name, int port, int pool, NTP_Source_Type type,

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

+const char *
+NSR_StatusToString(NSR_Status status)
+{
+  switch (status) {
+    case NSR_Success:
+      return "Success";
+    case NSR_NoSuchSource:
+      return "No such source";
+    case NSR_AlreadyInUse:
+      return "Already in use";
+    case NSR_TooManySources:
+      return "Too many sources";
+    case NSR_InvalidAF:
+      return "Invalid address";
+    case NSR_InvalidName:
+      return "Invalid name";
+    case NSR_UnresolvedName:
+      return "Unresolved name";
+    default:
+      return "?";
+  }
+}
+
+/* ================================================== */
+
 void
 NSR_SetSourceResolvingEndHandler(NSR_SourceResolvingEndHandler handler)
 {
--- a/ntp_sources.h
+++ b/ntp_sources.h
@@ -60,6 +60,8 @@ extern NSR_Status NSR_AddSource(NTP_Remote_Address *remote_addr, NTP_Source_Type
 extern NSR_Status NSR_AddSourceByName(char *name, int port, int pool, NTP_Source_Type type,
                                      SourceParameters *params, uint32_t *conf_id);

+extern const char *NSR_StatusToString(NSR_Status status);
+
 /* Function type for handlers to be called back when an attempt
 * (possibly unsuccessful) to resolve unresolved sources ends */
 typedef void (*NSR_SourceResolvingEndHandler)(void);
--- a/nts_ke_server.c
+++ b/nts_ke_server.c
@@ -685,6 +685,8 @@ run_helper(uid_t uid, gid_t gid, int scfilter_level)

  DEBUG_LOG("Helper started");

+  SCK_CloseReusableSockets();
+
  /* Suppress a log message about disabled clock control */
  log_severity = LOG_GetMinSeverity();
  LOG_SetMinSeverity(LOGS_ERR);
--- a/siv_gnutls.c
+++ b/siv_gnutls.c
@@ -2,7 +2,7 @@
  chronyd/chronyc - Programs for keeping computer clocks accurate.

 **********************************************************************
- * Copyright (C) Miroslav Lichvar  2020
+ * Copyright (C) Miroslav Lichvar  2020, 2023
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
@@ -37,6 +37,8 @@
 struct SIV_Instance_Record {
  gnutls_cipher_algorithm_t algorithm;
  gnutls_aead_cipher_hd_t cipher;
+  int min_nonce_length;
+  int max_nonce_length;
 };

 /* ================================================== */
@@ -81,6 +83,10 @@ get_cipher_algorithm(SIV_Algorithm algorithm)
  switch (algorithm) {
    case AEAD_AES_SIV_CMAC_256:
      return GNUTLS_CIPHER_AES_128_SIV;
+#if HAVE_GNUTLS_SIV_GCM
+    case AEAD_AES_128_GCM_SIV:
+      return GNUTLS_CIPHER_AES_128_SIV_GCM;
+#endif
    default:
      return 0;
  }
@@ -112,6 +118,19 @@ SIV_CreateInstance(SIV_Algorithm algorithm)
  instance->algorithm = calgo;
  instance->cipher = NULL;

+  switch (algorithm) {
+    case AEAD_AES_SIV_CMAC_256:
+      instance->min_nonce_length = 1;
+      instance->max_nonce_length = INT_MAX;
+      break;
+    case AEAD_AES_128_GCM_SIV:
+      instance->min_nonce_length = 12;
+      instance->max_nonce_length = 12;
+      break;
+    default:
+      assert(0);
+  }
+
  instance_counter++;

  return instance;
@@ -143,6 +162,8 @@ SIV_GetKeyLength(SIV_Algorithm algorithm)
    return 0;

  len = gnutls_cipher_get_key_size(calgo);
+  if (len == 0)
+    return 0;

  if (len < 1 || len > SIV_MAX_KEY_LENGTH)
    LOG_FATAL("Invalid key length");
@@ -198,7 +219,7 @@ SIV_SetKey(SIV_Instance instance, const unsigned char *key, int length)
 int
 SIV_GetMinNonceLength(SIV_Instance instance)
 {
-  return 1;
+  return instance->min_nonce_length;
 }

 /* ================================================== */
@@ -206,7 +227,7 @@ SIV_GetMinNonceLength(SIV_Instance instance)
 int
 SIV_GetMaxNonceLength(SIV_Instance instance)
 {
-  return INT_MAX;
+  return instance->max_nonce_length;
 }

 /* ================================================== */
@@ -238,7 +259,8 @@ SIV_Encrypt(SIV_Instance instance,
  if (!instance->cipher)
    return 0;

-  if (nonce_length < 1 || assoc_length < 0 ||
+  if (nonce_length < instance->min_nonce_length ||
+      nonce_length > instance->max_nonce_length || assoc_length < 0 ||
      plaintext_length < 0 || ciphertext_length < 0)
    return 0;

@@ -269,7 +291,8 @@ SIV_Decrypt(SIV_Instance instance,
  if (!instance->cipher)
    return 0;

-  if (nonce_length < 1 || assoc_length < 0 ||
+  if (nonce_length < instance->min_nonce_length ||
+      nonce_length > instance->max_nonce_length || assoc_length < 0 ||
      plaintext_length < 0 || ciphertext_length < 0)
    return 0;

--- a/socket.c
+++ b/socket.c
@@ -5,6 +5,7 @@
 * Copyright (C) Richard P. Curnow  1997-2003
 * Copyright (C) Timo Teras  2009
 * Copyright (C) Miroslav Lichvar  2009, 2013-2020
+ * Copyright (C) Luke Valenta  2023
 * 
 * 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
@@ -89,6 +90,9 @@ struct MessageHeader {

 static int initialised;

+static int first_reusable_fd;
+static int reusable_fds;
+
 /* Flags indicating in which IP families sockets can be requested */
 static int ip4_enabled;
 static int ip6_enabled;
@@ -155,6 +159,59 @@ domain_to_string(int domain)

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

+static int
+get_reusable_socket(int type, IPSockAddr *spec)
+{
+#ifdef LINUX
+  union sockaddr_all sa;
+  IPSockAddr ip_sa;
+  int sock_fd, opt;
+  socklen_t l;
+
+  /* Abort early if not an IPv4/IPv6 server socket */
+  if (!spec || spec->ip_addr.family == IPADDR_UNSPEC || spec->port == 0)
+    return INVALID_SOCK_FD;
+
+  /* Loop over available reusable sockets */
+  for (sock_fd = first_reusable_fd; sock_fd < first_reusable_fd + reusable_fds; sock_fd++) {
+
+    /* Check that types match */
+    l = sizeof (opt);
+    if (getsockopt(sock_fd, SOL_SOCKET, SO_TYPE, &opt, &l) < 0 ||
+        l != sizeof (opt) || opt != type)
+      continue;
+
+    /* Get sockaddr for reusable socket */
+    l = sizeof (sa);
+    if (getsockname(sock_fd, &sa.sa, &l) < 0 || l < sizeof (sa_family_t))
+      continue;
+    SCK_SockaddrToIPSockAddr(&sa.sa, l, &ip_sa);
+
+    /* Check that reusable socket matches specification */
+    if (ip_sa.port != spec->port || UTI_CompareIPs(&ip_sa.ip_addr, &spec->ip_addr, NULL) != 0)
+      continue;
+
+    /* Check that STREAM socket is listening */
+    l = sizeof (opt);
+    if (type == SOCK_STREAM && (getsockopt(sock_fd, SOL_SOCKET, SO_ACCEPTCONN, &opt, &l) < 0 ||
+                                l != sizeof (opt) || opt == 0))
+      continue;
+
+#if defined(FEAT_IPV6) && defined(IPV6_V6ONLY)
+    if (spec->ip_addr.family == IPADDR_INET6 &&
+        (!SCK_GetIntOption(sock_fd, IPPROTO_IPV6, IPV6_V6ONLY, &opt) || opt != 1))
+      LOG(LOGS_WARN, "Reusable IPv6 socket missing IPV6_V6ONLY option");
+#endif
+
+    return sock_fd;
+  }
+#endif
+
+  return INVALID_SOCK_FD;
+}
+
+/* ================================================== */
+
 #if defined(SOCK_CLOEXEC) || defined(SOCK_NONBLOCK)
 static int
 check_socket_flag(int sock_flag, int fd_flag, int fs_flag)
@@ -212,7 +269,7 @@ static int
 set_socket_flags(int sock_fd, int flags)
 {
  /* Close the socket automatically on exec */
-  if (
+  if (!SCK_IsReusable(sock_fd) &&
 #ifdef SOCK_CLOEXEC
      (supported_socket_flags & SOCK_CLOEXEC) == 0 &&
 #endif
@@ -222,7 +279,7 @@ set_socket_flags(int sock_fd, int flags)
  /* Enable non-blocking mode */
  if ((flags & SCK_FLAG_BLOCK) == 0 &&
 #ifdef SOCK_NONBLOCK
-      (supported_socket_flags & SOCK_NONBLOCK) == 0 &&
+      (SCK_IsReusable(sock_fd) || (supported_socket_flags & SOCK_NONBLOCK) == 0) &&
 #endif
      !set_socket_nonblock(sock_fd))
    return 0;
@@ -279,6 +336,32 @@ open_socket_pair(int domain, int type, int flags, int *other_fd)

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

+static int
+get_ip_socket(int domain, int type, int flags, IPSockAddr *ip_sa)
+{
+  int sock_fd;
+
+  /* Check if there is a matching reusable socket */
+  sock_fd = get_reusable_socket(type, ip_sa);
+
+  if (sock_fd < 0) {
+    sock_fd = open_socket(domain, type, flags);
+
+    /* Unexpected, but make sure the new socket is not in the reusable range */
+    if (SCK_IsReusable(sock_fd))
+      LOG_FATAL("Could not open %s socket : file descriptor in reusable range",
+                domain_to_string(domain));
+  } else {
+    /* Set socket flags on reusable socket */
+    if (!set_socket_flags(sock_fd, flags))
+      return INVALID_SOCK_FD;
+  }
+
+  return sock_fd;
+}
+
+/* ================================================== */
+
 static int
 set_socket_options(int sock_fd, int flags)
 {
@@ -295,8 +378,10 @@ static int
 set_ip_options(int sock_fd, int family, int flags)
 {
 #if defined(FEAT_IPV6) && defined(IPV6_V6ONLY)
-  /* Receive only IPv6 packets on an IPv6 socket */
-  if (family == IPADDR_INET6 && !SCK_SetIntOption(sock_fd, IPPROTO_IPV6, IPV6_V6ONLY, 1))
+  /* Receive only IPv6 packets on an IPv6 socket, but do not attempt
+     to set this option on pre-initialised reuseable sockets */
+  if (family == IPADDR_INET6 && !SCK_IsReusable(sock_fd) &&
+      !SCK_SetIntOption(sock_fd, IPPROTO_IPV6, IPV6_V6ONLY, 1))
    return 0;
 #endif

@@ -385,6 +470,10 @@ bind_ip_address(int sock_fd, IPSockAddr *addr, int flags)
    ;
 #endif

+  /* Do not attempt to bind pre-initialised reusable socket */
+  if (SCK_IsReusable(sock_fd))
+    return 1;
+
  saddr_len = SCK_IPSockAddrToSockaddr(addr, (struct sockaddr *)&saddr, sizeof (saddr));
  if (saddr_len == 0)
    return 0;
@@ -457,7 +546,7 @@ open_ip_socket(IPSockAddr *remote_addr, IPSockAddr *local_addr, const char *ifac
      return INVALID_SOCK_FD;
  }

-  sock_fd = open_socket(domain, type, flags);
+  sock_fd = get_ip_socket(domain, type, flags, local_addr);
  if (sock_fd < 0)
    return INVALID_SOCK_FD;

@@ -482,7 +571,8 @@ open_ip_socket(IPSockAddr *remote_addr, IPSockAddr *local_addr, const char *ifac
    goto error;

  if (remote_addr || local_addr)
-    DEBUG_LOG("Opened %s%s socket fd=%d%s%s%s%s",
+    DEBUG_LOG("%s %s%s socket fd=%d%s%s%s%s",
+              SCK_IsReusable(sock_fd) ? "Reusing" : "Opened",
              type == SOCK_DGRAM ? "UDP" : type == SOCK_STREAM ? "TCP" : "?",
              family == IPADDR_INET4 ? "v4" : "v6",
              sock_fd,
@@ -1170,9 +1260,44 @@ send_message(int sock_fd, SCK_Message *message, int flags)

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

+void
+SCK_PreInitialise(void)
+{
+#ifdef LINUX
+  char *s, *ptr;
+
+  /* On Linux systems, the systemd service manager may pass file descriptors
+     for pre-initialised sockets to the chronyd daemon.  The service manager
+     allocates and binds the file descriptors, and passes a copy to each
+     spawned instance of the service.  This allows for zero-downtime service
+     restarts as the sockets buffer client requests until the service is able
+     to handle them.  The service manager sets the LISTEN_FDS environment
+     variable to the number of passed file descriptors, and the integer file
+     descriptors start at 3 (see SD_LISTEN_FDS_START in
+     https://www.freedesktop.org/software/systemd/man/latest/sd_listen_fds.html). */
+  first_reusable_fd = 3;
+  reusable_fds = 0;
+
+  s = getenv("LISTEN_FDS");
+  if (s) {
+    errno = 0;
+    reusable_fds = strtol(s, &ptr, 10);
+    if (errno != 0 || *ptr != '\0' || reusable_fds < 0)
+      reusable_fds = 0;
+  }
+#else
+  first_reusable_fd = 0;
+  reusable_fds = 0;
+#endif
+}
+
+/* ================================================== */
+
 void
 SCK_Initialise(int family)
 {
+  int fd;
+
  ip4_enabled = family == IPADDR_INET4 || family == IPADDR_UNSPEC;
 #ifdef FEAT_IPV6
  ip6_enabled = family == IPADDR_INET6 || family == IPADDR_UNSPEC;
@@ -1201,6 +1326,9 @@ SCK_Initialise(int family)
    supported_socket_flags |= SOCK_NONBLOCK;
 #endif

+  for (fd = first_reusable_fd; fd < first_reusable_fd + reusable_fds; fd++)
+    UTI_FdSetCloexec(fd);
+
  initialised = 1;
 }

@@ -1213,6 +1341,8 @@ SCK_Finalise(void)
  ARR_DestroyInstance(recv_headers);
  ARR_DestroyInstance(recv_messages);

+  SCK_CloseReusableSockets();
+
  initialised = 0;
 }

@@ -1353,6 +1483,27 @@ SCK_OpenUnixSocketPair(int flags, int *other_fd)

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

+int
+SCK_IsReusable(int fd)
+{
+  return fd >= first_reusable_fd && fd < first_reusable_fd + reusable_fds;
+}
+
+/* ================================================== */
+
+void
+SCK_CloseReusableSockets(void)
+{
+  int fd;
+
+  for (fd = first_reusable_fd; fd < first_reusable_fd + reusable_fds; fd++)
+    close(fd);
+  reusable_fds = 0;
+  first_reusable_fd = 0;
+}
+
+/* ================================================== */
+
 int
 SCK_SetIntOption(int sock_fd, int level, int name, int value)
 {
@@ -1410,7 +1561,7 @@ SCK_EnableKernelRxTimestamping(int sock_fd)
 int
 SCK_ListenOnSocket(int sock_fd, int backlog)
 {
-  if (listen(sock_fd, backlog) < 0) {
+  if (!SCK_IsReusable(sock_fd) && listen(sock_fd, backlog) < 0) {
    DEBUG_LOG("listen() failed : %s", strerror(errno));
    return 0;
  }
@@ -1573,6 +1724,10 @@ SCK_RemoveSocket(int sock_fd)
 void
 SCK_CloseSocket(int sock_fd)
 {
+  /* Reusable sockets are closed in finalisation */
+  if (SCK_IsReusable(sock_fd))
+    return;
+
  close(sock_fd);
 }

--- a/socket.h
+++ b/socket.h
@@ -73,6 +73,9 @@ typedef struct {
  int descriptor;
 } SCK_Message;

+/* Pre-initialisation function */
+extern void SCK_PreInitialise(void);
+
 /* Initialisation function (the specified IP family is enabled,
   or all if IPADDR_UNSPEC) */
 extern void SCK_Initialise(int family);
@@ -106,6 +109,12 @@ extern int SCK_OpenUnixStreamSocket(const char *remote_addr, const char *local_a
                                    int flags);
 extern int SCK_OpenUnixSocketPair(int flags, int *other_fd);

+/* Check if a file descriptor was passed from the service manager */
+extern int SCK_IsReusable(int sock_fd);
+
+/* Close all reusable sockets before finalisation (e.g. in a helper process) */
+extern void SCK_CloseReusableSockets(void);
+
 /* Set and get a socket option of int size */
 extern int SCK_SetIntOption(int sock_fd, int level, int name, int value);
 extern int SCK_GetIntOption(int sock_fd, int level, int name, int *value);
--- a/sources.c
+++ b/sources.c
@@ -174,6 +174,9 @@ static int selected_source_index; /* Which source index is currently
                                     if no current valid reference) */
 static int reported_no_majority;  /* Flag to avoid repeated log message
                                     about no majority */
+static int report_selection_loss; /* Flag to force logging a message if
+                                     selection is lost in a transient state
+                                     (SRC_WAITS_STATS, SRC_WAITS_UPDATE) */

 /* Score needed to replace the currently selected source */
 #define SCORE_LIMIT 10.0
@@ -201,6 +204,8 @@ static LOG_FileID logfileid;
 /* Forward prototype */

 static void update_sel_options(void);
+static void unselect_selected_source(LOG_Severity severity, const char *format,
+                                     const char *arg);
 static void slew_sources(struct timespec *raw, struct timespec *cooked, double dfreq,
                         double doffset, LCL_ChangeType change_type, void *anything);
 static void add_dispersion(double dispersion, void *anything);
@@ -330,11 +335,12 @@ void SRC_DestroyInstance(SRC_Instance instance)

  update_sel_options();

-  /* If this was the previous reference source, we have to reselect! */
-  if (selected_source_index == dead_index)
-    SRC_ReselectSource();
-  else if (selected_source_index > dead_index)
+  if (selected_source_index > dead_index)
    --selected_source_index;
+  else if (selected_source_index == dead_index)
+    unselect_selected_source(LOGS_INFO, NULL, NULL);
+
+  SRC_SelectSource(NULL);
 }

 /* ================================================== */
@@ -357,6 +363,9 @@ SRC_ResetInstance(SRC_Instance instance)
  memset(&instance->sel_info, 0, sizeof (instance->sel_info));

  SST_ResetInstance(instance->stats);
+
+  if (selected_source_index == instance->index)
+    SRC_SelectSource(NULL);
 }

 /* ================================================== */
@@ -733,6 +742,26 @@ mark_ok_sources(SRC_Status status)
  }
 }

+/* ================================================== */
+/* Reset the index of selected source and report the selection loss.  If no
+   message is provided, assume it is a transient state and wait for another
+   call providing a message or selection of another source, which resets the
+   report_selection_loss flag. */
+
+static void
+unselect_selected_source(LOG_Severity severity, const char *format, const char *arg)
+{
+  if (selected_source_index != INVALID_SOURCE) {
+    selected_source_index = INVALID_SOURCE;
+    report_selection_loss = 1;
+  }
+
+  if (report_selection_loss && format) {
+    log_selection_message(severity, format, arg);
+    report_selection_loss = 0;
+  }
+}
+
 /* ================================================== */

 static int
@@ -850,11 +879,7 @@ SRC_SelectSource(SRC_Instance updated_inst)
  }

  if (n_sources == 0) {
-    /* In this case, we clearly cannot synchronise to anything */
-    if (selected_source_index != INVALID_SOURCE) {
-      log_selection_message(LOGS_INFO, "Can't synchronise: no sources", NULL);
-      selected_source_index = INVALID_SOURCE;
-    }
+    unselect_selected_source(LOGS_INFO, "Can't synchronise: no sources", NULL);
    return;
  }

@@ -1039,15 +1064,13 @@ SRC_SelectSource(SRC_Instance updated_inst)
  if (n_badstats_sources && n_sel_sources && selected_source_index == INVALID_SOURCE &&
      max_sel_reach_size < SOURCE_REACH_BITS && max_sel_reach >> 1 == max_badstat_reach) {
    mark_ok_sources(SRC_WAITS_STATS);
+    unselect_selected_source(LOGS_INFO, NULL, NULL);
    return;
  }

  if (n_endpoints == 0) {
    /* No sources provided valid endpoints */
-    if (selected_source_index != INVALID_SOURCE) {
-      log_selection_message(LOGS_INFO, "Can't synchronise: no selectable sources", NULL);
-      selected_source_index = INVALID_SOURCE;
-    }
+    unselect_selected_source(LOGS_INFO, "Can't synchronise: no selectable sources", NULL);
    return;
  }

@@ -1128,6 +1151,7 @@ SRC_SelectSource(SRC_Instance updated_inst)
    if (!reported_no_majority) {
      log_selection_message(LOGS_WARN, "Can't synchronise: no majority", NULL);
      reported_no_majority = 1;
+      report_selection_loss = 0;
    }

    if (selected_source_index != INVALID_SOURCE) {
@@ -1184,12 +1208,9 @@ SRC_SelectSource(SRC_Instance updated_inst)
  }

  if (!n_sel_sources || sel_req_source || n_sel_sources < CNF_GetMinSources()) {
-    if (selected_source_index != INVALID_SOURCE) {
-      log_selection_message(LOGS_INFO, "Can't synchronise: %s selectable sources",
-                            !n_sel_sources ? "no" :
-                            sel_req_source ? "no required source in" : "not enough");
-      selected_source_index = INVALID_SOURCE;
-    }
+    unselect_selected_source(LOGS_INFO, "Can't synchronise: %s selectable sources",
+                             !n_sel_sources ? "no" :
+                             sel_req_source ? "no required source in" : "not enough");
    mark_ok_sources(SRC_WAITS_SOURCES);
    return;
  }
@@ -1296,7 +1317,7 @@ SRC_SelectSource(SRC_Instance updated_inst)
    /* Before selecting the new synchronisation source wait until the reference
       can be updated */
    if (sources[max_score_index]->updates == 0) {
-      selected_source_index = INVALID_SOURCE;
+      unselect_selected_source(LOGS_INFO, NULL, NULL);
      mark_ok_sources(SRC_WAITS_UPDATE);
      return;
    }
@@ -1312,6 +1333,7 @@ SRC_SelectSource(SRC_Instance updated_inst)
    }

    reported_no_majority = 0;
+    report_selection_loss = 0;
  }

  mark_source(sources[selected_source_index], SRC_SELECTED);
--- a/stubs.c
+++ b/stubs.c
@@ -207,6 +207,12 @@ NSR_AddSourceByName(char *name, int port, int pool, NTP_Source_Type type,
  return NSR_TooManySources;
 }

+const char *
+NSR_StatusToString(NSR_Status status)
+{
+  return "NTP not supported";
+}
+
 NSR_Status
 NSR_RemoveSource(IPAddr *address)
 {
--- a/test/compilation/002-scanbuild
+++ b/test/compilation/002-scanbuild
@@ -7,9 +7,9 @@ for opts in \
 	"--host-system=NetBSD" \
 	"--host-system=FreeBSD" \
 	"--without-nettle" \
-	"--without-nettle --without-nss" \
-	"--without-nettle --without-nss --without-tomcrypt" \
-	"--without-nettle --without-nss --without-tomcrypt --without-gnutls"
+	"--without-nettle --without-gnutls" \
+	"--without-nettle --without-gnutls --without-nss" \
+	"--without-nettle --without-gnutls --without-nss --without-tomcrypt"
 do
 	./configure $opts
 	scan-build make "$@" || exit 1
--- a/test/compilation/003-sanitizers
+++ b/test/compilation/003-sanitizers
@@ -25,13 +25,13 @@ touch Makefile
 for extra_config_opts in \
  "--all-privops" \
  "--disable-ipv6" \
+  "--disable-nts" \
  "--disable-scfilter" \
  "--without-aes-gcm-siv" \
-  "--without-gnutls" \
  "--without-nettle" \
-  "--without-nettle --without-nss" \
-  "--without-nettle --without-nss --without-tomcrypt" \
-  "--without-nettle --without-nss --without-tomcrypt --without-gnutls"; \
+  "--without-nettle --without-gnutls" \
+  "--without-nettle --without-gnutls --without-nss" \
+  "--without-nettle --without-gnutls --without-nss --without-tomcrypt"; \
 do
  for arch_opts in "-m32" ""; do
    pushd test/simulation/clknetsim || exit 1
--- a/test/simulation/110-chronyc
+++ b/test/simulation/110-chronyc
@@ -114,7 +114,7 @@ limit=1
 for chronyc_conf in \
 	"accheck 1.2.3.4" \
 	"add peer 10.0.0.0 minpoll 2 maxpoll 6" \
-	"add server 10.0.0.0 minpoll 6 maxpoll 10 iburst burst key 1 certset 2 maxdelay 1e-3 maxdelayratio 10.0 maxdelaydevratio 10.0 maxdelayquant 0.5 mindelay 1e-4 asymmetry 0.5 offset 1e-5 minsamples 6 maxsamples 6 filter 3 offline auto_offline prefer noselect trust require xleave polltarget 20 port 123 presend 7 minstratum 3 version 4 nts ntsport 4460 copy extfield F323" \
+	"add server 10.0.0.0 minpoll 6 maxpoll 10 iburst burst key 1 certset 2 maxdelay 1e-3 maxdelayratio 10.0 maxdelaydevratio 10.0 maxdelayquant 0.5 mindelay 1e-4 asymmetry 0.5 offset 1e-5 minsamples 6 maxsamples 6 filter 3 offline auto_offline prefer noselect trust require xleave polltarget 20 port 123 presend 7 minstratum 3 version 4 nts ntsport 4460 copy extfield F323 extfield F324" \
 	"add server node1.net1.clk" \
 	"allow 1.2.3.4" \
 	"allow 1.2" \
--- a/test/simulation/114-presend
+++ b/test/simulation/114-presend
@@ -23,4 +23,29 @@ check_source_selection || test_fail
 check_packet_interval || test_fail
 check_sync || test_fail

+limit=10
+base_delay=$default_base_delay
+client_conf="logdir tmp
+log measurements"
+
+client_server_options="presend 5"
+
+run_test || test_fail
+check_chronyd_exit || test_fail
+check_packet_interval || test_fail
+
+check_file_messages "20.*123\.1.* 111 111 0111" 1 1 measurements.log || test_fail
+check_file_messages "20.*123\.1.* 111 111 1111" 1 1 measurements.log || test_fail
+rm -f tmp/measurements.log
+
+client_server_options="presend 5 xleave"
+
+run_test || test_fail
+check_chronyd_exit || test_fail
+check_packet_interval || test_fail
+
+check_file_messages "20.*123\.1.* 111 111 0111" 2 2 measurements.log || test_fail
+check_file_messages "20.*123\.1.* 111 111 1111" 1 1 measurements.log || test_fail
+rm -f tmp/measurements.log
+
 test_pass
--- a/test/simulation/142-ntpoverptp
+++ b/test/simulation/142-ntpoverptp
@@ -0,0 +1,106 @@
+#!/usr/bin/env bash
+
+. ./test.common
+
+test_start "NTP over PTP"
+
+# Block communication between 3 and 1
+base_delay="(+ 1e-4 (* -1 (equal 0.1 from 3) (equal 0.1 to 1)))"
+
+cat > tmp/peer.keys <<-EOF
+1 MD5 1234567890
+EOF
+
+clients=2
+peers=2
+max_sync_time=420
+
+server_conf="
+ptpport 319"
+client_conf="
+ptpport 319
+authselectmode ignore
+keyfile tmp/peer.keys"
+client_server_options="minpoll 6 maxpoll 6 port 319"
+client_peer_options="minpoll 6 maxpoll 6 port 319 key 1"
+
+run_test || test_fail
+check_chronyd_exit || test_fail
+check_source_selection || test_fail
+check_sync || test_fail
+
+check_file_messages "	2	1	.*	319	319	1	96	" 150 160 \
+	log.packets || test_fail
+check_file_messages "	1	2	.*	319	319	1	96	" 150 160 \
+	log.packets || test_fail
+check_file_messages "	2	3	.*	319	319	1	116	" 150 160 \
+	log.packets || test_fail
+check_file_messages "	3	2	.*	319	319	1	116	" 150 160 \
+	log.packets || test_fail
+
+check_config_h 'HAVE_LINUX_TIMESTAMPING 1' || test_skip
+
+export CLKNETSIM_TIMESTAMPING=2
+export CLKNETSIM_LINK_SPEED=100
+
+client_server_options+=" extfield F324 minpoll 0 maxpoll 0"
+client_peer_options+=" extfield F324 minpoll 0 maxpoll 0 maxdelaydevratio 1e6"
+server_conf+="
+clockprecision 1e-9
+hwtimestamp eth0"
+client_conf+="
+clockprecision 1e-9
+hwtimestamp eth0"
+delay_correction="(+ delay (* -8e-8 (+ length 46)))"
+wander=1e-9
+limit=1000
+freq_offset=-1e-4
+min_sync_time=5
+max_sync_time=20
+time_max_limit=1e-7
+time_rms_limit=2e-8
+freq_max_limit=1e-7
+freq_rms_limit=5e-8
+client_chronyd_options="-d"
+
+run_test || test_fail
+check_chronyd_exit || test_fail
+check_source_selection || test_fail
+check_sync || test_fail
+
+if check_config_h 'FEAT_DEBUG 1'; then
+	check_log_messages "apply_net_correction.*Applied" 900 2100 || test_fail
+	check_log_messages "apply_net_correction.*Invalid" 0 4 || test_fail
+fi
+
+client_server_options+=" xleave"
+client_peer_options+=" xleave"
+
+run_test || test_fail
+check_chronyd_exit || test_fail
+check_source_selection || test_fail
+check_sync || test_fail
+
+if check_config_h 'FEAT_DEBUG 1'; then
+	check_log_messages "apply_net_correction.*Applied" 900 2100 || test_fail
+	check_log_messages "apply_net_correction.*Invalid" 0 4 || test_fail
+
+	freq_offset=0.0
+	delay_correction="(+ -1.0e-9 (* 1.0001 delay))"
+
+	run_test || test_fail
+	check_chronyd_exit || test_fail
+
+	check_log_messages "apply_net_correction.*Applied" 350 1400 || test_fail
+	check_log_messages "apply_net_correction.*Invalid" 350 1400 || test_fail
+
+	server_conf="ptpport 319"
+	client_conf="ptpport 319"
+
+	run_test || test_fail
+	check_chronyd_exit || test_fail
+
+	check_log_messages "apply_net_correction.*Applied" 0 0 || test_fail
+fi
+
+test_pass
--- a/test/simulation/142-ptpport
+++ b/test/simulation/142-ptpport
@@ -1,41 +0,0 @@
-#!/usr/bin/env bash
-
-. ./test.common
-
-test_start "PTP port"
-
-# Block communication between 3 and 1
-base_delay="(+ 1e-4 (* -1 (equal 0.1 from 3) (equal 0.1 to 1)))"
-
-cat > tmp/peer.keys <<-EOF
-1 MD5 1234567890
-EOF
-
-clients=2
-peers=2
-max_sync_time=420
-
-server_conf="
-ptpport 319"
-client_conf="
-ptpport 319
-authselectmode ignore
-keyfile tmp/peer.keys"
-client_server_options="minpoll 6 maxpoll 6 port 319"
-client_peer_options="minpoll 6 maxpoll 6 port 319 key 1"
-
-run_test || test_fail
-check_chronyd_exit || test_fail
-check_source_selection || test_fail
-check_sync || test_fail
-
-check_file_messages "	2	1	.*	319	319	1	96	" 150 160 \
-	log.packets || test_fail
-check_file_messages "	1	2	.*	319	319	1	96	" 150 160 \
-	log.packets || test_fail
-check_file_messages "	2	3	.*	319	319	1	116	" 150 160 \
-	log.packets || test_fail
-check_file_messages "	3	2	.*	319	319	1	116	" 150 160 \
-	log.packets || test_fail
-
-test_pass
--- a/test/simulation/144-monoroot
+++ b/test/simulation/144-monoroot
@@ -2,7 +2,7 @@

 . ./test.common

-test_start "experimental extension field"
+test_start "mono+root extension field"

 check_config_h 'FEAT_CMDMON 1' || test_skip

--- a/test/simulation/test.common
+++ b/test/simulation/test.common
@@ -31,6 +31,7 @@ default_primary_time_offset=0.0
 default_time_offset=1e-1
 default_freq_offset=1e-4
 default_base_delay=1e-4
+default_delay_correction=""
 default_jitter=1e-4
 default_jitter_asymmetry=0.0
 default_wander=1e-9
@@ -460,6 +461,10 @@ run_test() {
 		for j in $(seq 1 $nodes); do
 			echo "node${i}_delay${j} = $(get_delay_expr up)"
 			echo "node${j}_delay${i} = $(get_delay_expr down)"
+			if [ -n "$delay_correction" ]; then
+				echo "node${i}_delay_correction${j} = $delay_correction"
+				echo "node${j}_delay_correction${i} = $delay_correction"
+			fi
 		done
 	done > tmp/conf

--- a/test/system/008-confload
+++ b/test/system/008-confload
@@ -30,6 +30,8 @@ echo "server 127.123.4.4" > $TEST_DIR/conf4.d/4.conf
 echo "server 127.123.5.1" > $TEST_DIR/conf5.d/1.sources
 echo "server 127.123.5.2" > $TEST_DIR/conf5.d/2.sources
 echo "server 127.123.5.3" > $TEST_DIR/conf5.d/3.sources
+echo "server 127.123.5.4" > $TEST_DIR/conf5.d/4.sources
+echo "server 127.123.5.5" > $TEST_DIR/conf5.d/5.sources

 start_chronyd || test_fail

@@ -46,12 +48,16 @@ check_chronyc_output "^[^=]*
 .. 127\.123\.1\.2 [^^]*
 .. 127\.123\.5\.1 [^^]*
 .. 127\.123\.5\.2 [^^]*
-.. 127\.123\.5\.3 [^^]*$" || test_fail
+.. 127\.123\.5\.3 [^^]*
+.. 127\.123\.5\.4 [^^]*
+.. 127\.123\.5\.5 [^^]*$" || test_fail

 rm $TEST_DIR/conf5.d/1.sources
-echo "server 127.123.5.2 minpoll 7" > $TEST_DIR/conf5.d/2.sources
-echo > $TEST_DIR/conf5.d/3.sources
-echo "server 127.123.5.4" > $TEST_DIR/conf5.d/4.sources
+echo "server 127.123.5.2 minpoll 5" > $TEST_DIR/conf5.d/2.sources
+echo "server 127.123.5.3 minpoll 7" > $TEST_DIR/conf5.d/3.sources
+echo > $TEST_DIR/conf5.d/4.sources
+echo "server 127.123.5.5" >> $TEST_DIR/conf5.d/5.sources
+echo "server 127.123.5.6" > $TEST_DIR/conf5.d/6.sources

 run_chronyc "reload sources" || test_fail

@@ -66,9 +72,12 @@ check_chronyc_output "^[^=]*
 .. 127\.123\.2\.3 [^^]*
 .. 127\.123\.4\.4 [^^]*
 .. 127\.123\.1\.2 *[05]   6 [^^]*
-.. 127\.123\.5\.2 *[05]   7 [^^]*
-.. 127\.123\.5\.4 [^^]*$" || test_fail
+.. 127\.123\.5\.5 [^^]*
+.. 127\.123\.5\.2 *[05]   5 [^^]*
+.. 127\.123\.5\.3 *[05]   7 [^^]*
+.. 127\.123\.5\.6 [^^]*$" || test_fail

 stop_chronyd || test_fail
+check_chronyd_message_count "Could not add source" 1 1 || test_fail

 test_pass
--- a/test/system/011-systemd
+++ b/test/system/011-systemd
@@ -0,0 +1,140 @@
+#!/usr/bin/env bash
+
+. ./test.common
+
+check_chronyd_features NTS || test_skip "NTS support disabled"
+certtool --help &> /dev/null || test_skip "certtool missing"
+check_chronyd_features DEBUG || test_skip "DEBUG support disabled"
+systemd-socket-activate -h &> /dev/null || test_skip "systemd-socket-activate missing"
+has_ipv6=$(check_chronyd_features IPV6 && ping6 -c 1 ::1 > /dev/null 2>&1 && echo 1 || echo 0)
+
+test_start "systemd socket activation"
+
+cat > $TEST_DIR/cert.cfg <<EOF
+cn = "chrony-nts-test"
+dns_name = "chrony-nts-test"
+ip_address = "$server"
+$([ "$has_ipv6" = "1" ] && echo 'ip_address = "::1"')
+serial = 001
+activation_date = "$[$(date '+%Y') - 1]-01-01 00:00:00 UTC"
+expiration_date = "$[$(date '+%Y') + 2]-01-01 00:00:00 UTC"
+signing_key
+encryption_key
+EOF
+
+certtool --generate-privkey --key-type=ed25519 --outfile $TEST_DIR/server.key \
+	&> $TEST_DIR/certtool.log
+certtool --generate-self-signed --load-privkey $TEST_DIR/server.key \
+	--template $TEST_DIR/cert.cfg --outfile $TEST_DIR/server.crt &>> $TEST_DIR/certtool.log
+chown $user $TEST_DIR/server.*
+
+ntpport=$(get_free_port)
+ntsport=$(get_free_port)
+
+server_options="port $ntpport nts ntsport $ntsport"
+extra_chronyd_directives="
+port $ntpport
+ntsport $ntsport
+ntsserverkey $TEST_DIR/server.key
+ntsservercert $TEST_DIR/server.crt
+ntstrustedcerts $TEST_DIR/server.crt
+ntsdumpdir $TEST_LIBDIR
+ntsprocesses 3"
+
+if [ "$has_ipv6" = "1" ]; then
+  extra_chronyd_directives="$extra_chronyd_directives
+  bindaddress ::1
+  server ::1 minpoll -6 maxpoll -6 $server_options"
+fi
+
+# enable debug logging
+extra_chronyd_options="-L -1"
+# Hack to trigger systemd-socket-activate to activate the service.  Normally,
+# chronyd.service would be configured with the WantedBy= directive so it starts
+# without waiting for socket activation.
+# (https://0pointer.de/blog/projects/socket-activation.html).
+for i in $(seq 10); do
+  sleep 1
+  (echo "wake up" > /dev/udp/127.0.0.1/$ntpport) 2>/dev/null
+  (echo "wake up" > /dev/tcp/127.0.0.1/$ntsport) 2>/dev/null
+done &
+
+# Test with UDP sockets (unfortunately systemd-socket-activate doesn't support
+# both datagram and stream sockets in the same invocation:
+# https://github.com/systemd/systemd/issues/9983).
+CHRONYD_WRAPPER="systemd-socket-activate \
+  --datagram \
+  --listen 127.0.0.1:$ntpport \
+  --listen 127.0.0.1:$ntsport"
+if [ "$has_ipv6" = "1" ]; then
+  CHRONYD_WRAPPER="$CHRONYD_WRAPPER \
+    --listen [::1]:$ntpport \
+    --listen [::1]:$ntsport"
+fi
+
+start_chronyd || test_fail
+wait_for_sync || test_fail
+
+if [ "$has_ipv6" = "1" ]; then
+  run_chronyc "ntpdata ::1" || test_fail
+  check_chronyc_output "Total RX +: [1-9]" || test_fail
+fi
+run_chronyc "authdata" || test_fail
+check_chronyc_output "^Name/IP address             Mode KeyID Type KLen Last Atmp  NAK Cook CLen
+=========================================================================\
+$([ "$has_ipv6" = "1" ] && printf "\n%s\n" '::1                          NTS     1   (30|15)  (128|256)    [0-9]    0    0    [78]  ( 64|100)')
+127\.0\.0\.1                    NTS     1   (30|15)  (128|256)    [0-9]    0    0    [78]  ( 64|100)$" || test_fail
+
+stop_chronyd || test_fail
+# DGRAM ntpport socket should be used
+check_chronyd_message_count "Reusing UDPv4 socket fd=3 local=127.0.0.1:$ntpport" 1 1 || test_fail
+# DGRAM ntsport socket should be ignored
+check_chronyd_message_count "Reusing TCPv4 socket fd=4 local=127.0.0.1:$ntsport" 0 0 || test_fail
+if [ "$has_ipv6" = "1" ]; then
+  # DGRAM ntpport socket should be used
+  check_chronyd_message_count "Reusing UDPv6 socket fd=5 local=\[::1\]:$ntpport" 1 1 || test_fail
+  # DGRAM ntsport socket should be ignored
+  check_chronyd_message_count "Reusing TCPv6 socket fd=6 local=\[::1\]:$ntsport" 0 0 || test_fail
+fi
+
+check_chronyd_messages || test_fail
+check_chronyd_files || test_fail
+
+# Test with TCP sockets
+CHRONYD_WRAPPER="systemd-socket-activate \
+  --listen 127.0.0.1:$ntpport \
+  --listen 127.0.0.1:$ntsport"
+if [ "$has_ipv6" = "1" ]; then
+  CHRONYD_WRAPPER="$CHRONYD_WRAPPER \
+    --listen [::1]:$ntpport \
+    --listen [::1]:$ntsport"
+fi
+
+start_chronyd || test_fail
+wait_for_sync || test_fail
+
+if [ "$has_ipv6" = "1" ]; then
+  run_chronyc "ntpdata ::1" || test_fail
+  check_chronyc_output "Total RX +: [1-9]" || test_fail
+fi
+run_chronyc "authdata" || test_fail
+check_chronyc_output "^Name/IP address             Mode KeyID Type KLen Last Atmp  NAK Cook CLen
+=========================================================================\
+$([ "$has_ipv6" = "1" ] && printf "\n%s\n" '::1                          NTS     1   (30|15)  (128|256)    [0-9]    0    0    [78]  ( 64|100)')
+127\.0\.0\.1                    NTS     1   (30|15)  (128|256)    [0-9]    0    0    [78]  ( 64|100)$" || test_fail
+
+stop_chronyd || test_fail
+# STREAM ntpport should be ignored
+check_chronyd_message_count "Reusing TCPv4 socket fd=3 local=127.0.0.1:$ntpport" 0 0 || test_fail
+# STREAM ntsport should be used
+check_chronyd_message_count "Reusing TCPv4 socket fd=4 local=127.0.0.1:$ntsport" 1 1 || test_fail
+if [ "$has_ipv6" = "1" ]; then
+  # STREAM ntpport should be ignored
+  check_chronyd_message_count "Reusing TCPv6 socket fd=5 local=\[::1\]:$ntpport" 0 0 || test_fail
+  # STREAM ntsport should be used
+  check_chronyd_message_count "Reusing TCPv6 socket fd=6 local=\[::1\]:$ntsport" 1 1 || test_fail
+fi
+check_chronyd_messages || test_fail
+check_chronyd_files || test_fail
+
+test_pass
--- a/test/system/test.common
+++ b/test/system/test.common
@@ -324,7 +324,7 @@ check_chronyd_messages() {
 		([ "$clock_control" -ne 0 ] || grep -q 'Disabled control of system clock' "$logfile") && \
 		([ "$minimal_config" -ne 0 ] || grep -q 'Frequency .* read from' "$logfile") && \
 		grep -q 'chronyd exiting' "$logfile" && \
-		! grep -q 'Could not' "$logfile" && \
+		! (grep -v '^.\{19\}Z D:' "$logfile" | grep -q 'Could not') && \
 		! grep -q 'Disabled command socket' "$logfile" && \
 		test_ok || test_bad
 }
--- a/test/unit/ntp_core.c
+++ b/test/unit/ntp_core.c
@@ -99,8 +99,8 @@ send_request(NCR_Instance inst, int late_hwts)
    local_addr.ip_addr.family = IPADDR_UNSPEC;
    local_addr.if_index = INVALID_IF_INDEX;
    local_addr.sock_fd = 101;
+    zero_local_timestamp(&local_ts);
    local_ts.ts = current_time;
-    local_ts.err = 0.0;
    local_ts.source = NTP_TS_KERNEL;

    NCR_ProcessTxKnown(inst, &local_addr, &local_ts, &req_buffer, req_length);
@@ -122,8 +122,8 @@ process_request(NTP_Remote_Address *remote_addr)
  local_addr.ip_addr.family = IPADDR_UNSPEC;
  local_addr.if_index = INVALID_IF_INDEX;
  local_addr.sock_fd = 100;
+  zero_local_timestamp(&local_ts);
  local_ts.ts = current_time;
-  local_ts.err = 0.0;
  local_ts.source = NTP_TS_KERNEL;

  res_length = 0;
@@ -289,8 +289,8 @@ proc_response(NCR_Instance inst, int good, int valid, int updated_sync,
  local_addr.ip_addr.family = IPADDR_UNSPEC;
  local_addr.if_index = INVALID_IF_INDEX;
  local_addr.sock_fd = NTP_LVM_TO_MODE(res->lvm) != MODE_SERVER ? 100 : 101;
+  zero_local_timestamp(&local_ts);
  local_ts.ts = current_time;
-  local_ts.err = 0.0;
  local_ts.source = NTP_TS_KERNEL;

  prev_rx_count = inst->report.total_rx_count;
--- a/test/unit/ntp_sources.c
+++ b/test/unit/ntp_sources.c
@@ -88,6 +88,8 @@ update_random_address(NTP_Remote_Address *addr, int rand_bits)
    TEST_CHECK(status == NSR_Success || status == NSR_AlreadyInUse);
  }

+  TEST_CHECK(strlen(NSR_StatusToString(status)) > 0);
+
  return status == NSR_Success;
 }

--- a/test/unit/socket.c
+++ b/test/unit/socket.c
@@ -0,0 +1,61 @@
+/*
+ **********************************************************************
+ * Copyright (C) Luke Valenta  2023
+ * 
+ * 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.
+ * 
+ **********************************************************************
+ */
+
+#include <socket.c>
+#include "test.h"
+
+static void
+test_preinitialise(void)
+{
+#ifdef LINUX
+  /* Test LISTEN_FDS environment variable parsing */
+
+  /* normal */
+  putenv("LISTEN_FDS=2");
+  SCK_PreInitialise();
+  TEST_CHECK(reusable_fds == 2);
+
+  /* negative */
+  putenv("LISTEN_FDS=-2");
+  SCK_PreInitialise();
+  TEST_CHECK(reusable_fds == 0);
+
+  /* trailing characters */
+  putenv("LISTEN_FDS=2a");
+  SCK_PreInitialise();
+  TEST_CHECK(reusable_fds == 0);
+
+  /* non-integer */
+  putenv("LISTEN_FDS=a2");
+  SCK_PreInitialise();
+  TEST_CHECK(reusable_fds == 0);
+
+  /* not set */
+  unsetenv("LISTEN_FDS");
+  SCK_PreInitialise();
+  TEST_CHECK(reusable_fds == 0);
+#endif
+}
+
+void
+test_unit(void)
+{
+  test_preinitialise();
+}
--- a/test/unit/util.c
+++ b/test/unit/util.c
@@ -1,6 +1,6 @@
 /*
 **********************************************************************
- * Copyright (C) Miroslav Lichvar  2017-2018, 2021
+ * Copyright (C) Miroslav Lichvar  2017-2018, 2021, 2023
 * 
 * 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
@@ -253,6 +253,47 @@ test_unit(void)
  TEST_CHECK(UTI_IsEqualAnyNtp64(&ntp_ts, NULL, NULL, &ntp_ts));
  TEST_CHECK(!UTI_IsEqualAnyNtp64(&ntp_ts, &ntp_fuzz, &ntp_fuzz, &ntp_fuzz));

+  ntp_ts.hi = htonl(0);
+  ntp_ts.lo = htonl(0);
+  x = UTI_Ntp64ToDouble(&ntp_ts);
+  TEST_CHECK(fabs(x) < 1e-10);
+  UTI_DoubleToNtp64(x, &ntp_ts2);
+  TEST_CHECK(UTI_CompareNtp64(&ntp_ts, &ntp_ts2) == 0);
+
+  ntp_ts.hi = htonl(0);
+  ntp_ts.lo = htonl(0xffffffff);
+  x = UTI_Ntp64ToDouble(&ntp_ts);
+  TEST_CHECK(fabs(x - 1.0 + 0.23e-9) < 1e-10);
+  UTI_DoubleToNtp64(x, &ntp_ts2);
+  TEST_CHECK(fabs(UTI_DiffNtp64ToDouble(&ntp_ts, &ntp_ts2)) < 0.3e-9);
+
+  ntp_ts.hi = htonl(0xffffffff);
+  ntp_ts.lo = htonl(0xffffffff);
+  x = UTI_Ntp64ToDouble(&ntp_ts);
+  TEST_CHECK(fabs(x + 0.23e-9) < 1e-10);
+  UTI_DoubleToNtp64(x, &ntp_ts2);
+  TEST_CHECK(fabs(UTI_DiffNtp64ToDouble(&ntp_ts, &ntp_ts2)) < 0.3e-9);
+
+  ntp_ts.hi = htonl(0x80000000);
+  ntp_ts.lo = htonl(0);
+  x = UTI_Ntp64ToDouble(&ntp_ts);
+  TEST_CHECK(fabs(x + 0x80000000) < 1e-10);
+  UTI_DoubleToNtp64(x, &ntp_ts2);
+  TEST_CHECK(fabs(UTI_DiffNtp64ToDouble(&ntp_ts, &ntp_ts2)) < 0.3e-9);
+
+  ntp_ts.hi = htonl(0x7fffffff);
+  ntp_ts.lo = htonl(0xffffffff);
+  x = UTI_Ntp64ToDouble(&ntp_ts);
+  TEST_CHECK(fabs(x - 2147483648) < 1.0);
+
+  ntp_ts.lo = htonl(0);
+  ntp_ts.hi = htonl(0x7fffffff);
+  UTI_DoubleToNtp64(0x7fffffff + 0.1, &ntp_ts2);
+  TEST_CHECK(UTI_CompareNtp64(&ntp_ts, &ntp_ts2) == 0);
+  ntp_ts.hi = htonl(0x80000000);
+  UTI_DoubleToNtp64(0x80000000 - 0.1, &ntp_ts);
+  TEST_CHECK(UTI_CompareNtp64(&ntp_ts, &ntp_ts2) == 0);
+
  ts.tv_sec = 1;
  ts.tv_nsec = 2;
  ts2.tv_sec = 1;
--- a/util.c
+++ b/util.c
@@ -818,6 +818,33 @@ UTI_DiffNtp64ToDouble(const NTP_int64 *a, const NTP_int64 *b)

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

+double
+UTI_Ntp64ToDouble(NTP_int64 *src)
+{
+  NTP_int64 zero;
+
+  UTI_ZeroNtp64(&zero);
+  return UTI_DiffNtp64ToDouble(src, &zero);
+}
+
+/* ================================================== */
+
+void
+UTI_DoubleToNtp64(double src, NTP_int64 *dest)
+{
+  int32_t hi;
+
+  src = CLAMP(INT32_MIN, src, INT32_MAX);
+  hi = round(src);
+  if (hi > src)
+    hi -= 1;
+
+  dest->hi = htonl(hi);
+  dest->lo = htonl((src - hi) * (1.0e9 * NSEC_PER_NTP64));
+}
+
+/* ================================================== */
+
 /* Maximum offset between two sane times */
 #define MAX_OFFSET 4294967296.0

--- a/util.h
+++ b/util.h
@@ -163,6 +163,10 @@ extern void UTI_Ntp64ToTimespec(const NTP_int64 *src, struct timespec *dest);
 /* Calculate a - b in any epoch */
 extern double UTI_DiffNtp64ToDouble(const NTP_int64 *a, const NTP_int64 *b);

+/* Convert a difference in double (not a timestamp) from and to NTP format */
+extern double UTI_Ntp64ToDouble(NTP_int64 *src);
+extern void UTI_DoubleToNtp64(double src, NTP_int64 *dest);
+
 /* Check if time + offset is sane */
 extern int UTI_IsTimeOffsetSane(const struct timespec *ts, double offset);
Author	SHA1	Message	Date
Miroslav Lichvar	120dfb8b36	update copyright years	2023-12-05 14:22:10 +01:00
Miroslav Lichvar	598b893e1d	doc: update FAQ on improving accuracy	2023-12-05 14:22:10 +01:00
Miroslav Lichvar	89aa8fa342	doc: mention dependency of net corrections on HW timestamping	2023-12-05 14:22:08 +01:00
Miroslav Lichvar	42fdad5dcc	doc: improve description of reload sources command	2023-12-04 16:50:51 +01:00
Miroslav Lichvar	3ee7b3e786	sources: rework logging of selection loss The commit `5dd288dc0c` ("sources: reselect earlier when removing selected source") didn't cover all paths that can lead to a missing log message when all sources are removed. Add a flag to track the loss of selection and postpone the log message in transient states where no message is logged to avoid spamming in normal operation. Call SRC_SelectSource() after removing the source to get a log message if there are no (selectable) sources left. Reported-by: Thomas Lange <thomas@corelatus.se>	2023-11-28 12:21:23 +01:00
Miroslav Lichvar	426fe2ee58	doc: update NEWS	2023-11-22 13:53:23 +01:00
Miroslav Lichvar	3f66202d79	doc: update README	2023-11-22 11:56:16 +01:00
Miroslav Lichvar	ed6b0b55c7	doc: replace foobar naming in examples	2023-11-22 11:56:15 +01:00
Miroslav Lichvar	5e5adbea0c	doc: update description of NTP over PTP in FAQ	2023-11-22 11:56:15 +01:00
Miroslav Lichvar	82959431df	doc: mention version supporting socket activation in FAQ	2023-11-22 11:56:15 +01:00
Miroslav Lichvar	b92b2da24a	doc: improve ntstrustedcerts description	2023-11-22 11:55:27 +01:00
Miroslav Lichvar	68a3d52086	doc: improve cmdport description	2023-11-22 09:48:36 +01:00
Miroslav Lichvar	1a15be1e9e	sources: drop unreachable log message With forced reselection during source removal selected_source_index can only be INVALID_SOURCE if there are no sources. The "Can't synchronise: no sources" message couldn't be logged even before that as SRC_ReselectSource() resets the index before calling SRC_SelectSource(). Replace the message with an assertion.	2023-11-21 12:38:41 +01:00
Miroslav Lichvar	5dd288dc0c	sources: reselect earlier when removing selected source When a selected source is being removed, reset the instance and rerun the selection while the source is still marked as selected. This forces a "Can't synchronise" message to be logged when all sources are removed. Reported-by: Thomas Lange <thomas@corelatus.se>	2023-11-21 12:38:41 +01:00
Miroslav Lichvar	cbee464c75	sources: reselect after resetting selected source Avoid showing in the sources report a selected source which has no samples (e.g. after replacement).	2023-11-21 12:38:41 +01:00
Miroslav Lichvar	4e36295889	ntp: allow reusing timestamps of unused samples When switching from basic mode to interleaved mode following a response which wasn't accumulated due to failed test A, B, C, or D, allow timestamps of the failed sample to be reused in interleaved mode, i.e. replacing the server's less accurate transmit timestamp with a more accurate timestamp server can turn a failed sample into acceptable one. Move the presend check into test A to simplify the code.	2023-11-21 12:38:41 +01:00
Miroslav Lichvar	2d2642bb82	ntp: fix presend in interleaved mode The presend option in interleaved mode uses two presend requests instead of one to get an interleaved response from servers like chrony which delay the first interleaved response due to an optimization saving timestamps only for clients actually using the interleaved mode. After commit `0ae6f2485b` ("ntp: don't use first response in interleaved mode") the first interleaved response following the two presend responses in basic mode is dropped as the preferred set of timestamps minimizing error in delay was already used by the second sample in basic mode. There are only three responses in the burst and no sample is accumulated. Increasing the number of presend requests to three to get a fourth sample would be wasteful. Instead, allow reusing timestamps of the second presend sample in basic mode, which is never accumulated. Reported-by: Aaron Thompson Fixes: `0ae6f2485b` ("ntp: don't use first response in interleaved mode")	2023-11-21 12:38:41 +01:00
Miroslav Lichvar	9c6eaccc32	nts: close reusable sockets in helper process Close all reusable sockets when the NTS-KE server helper is forked. It is not supposed to have access to any of the server sockets, just the socket for getting requests from the main process and the syslog socket.	2023-11-21 12:38:41 +01:00
Miroslav Lichvar	0aa4d5ac14	socket: provide function for closing reusable sockets	2023-11-21 12:38:39 +01:00
Miroslav Lichvar	ee9d721b7b	socket: set close-on-exec on all reusable sockets Set the CLOEXEC flag on all reusable sockets in the initialization to avoid leaking them to sendmail (mailonchange directive) in case the chrony configuration doesn't use all sockets provided by systemd.	2023-11-20 13:33:45 +01:00
Luke Valenta	b6eec0068a	doc: add FAQ section on minimizing service downtime	2023-11-13 17:05:46 +01:00
Luke Valenta	e6a0476eb7	socket: add support for systemd sockets Before opening new IPv4/IPv6 server sockets, chronyd will check for matching reusable sockets passed from the service manager (for example, passed via systemd socket activation: https://www.freedesktop.org/software/systemd/man/latest/sd_listen_fds.html) and use those instead. Aside from IPV6_V6ONLY (which cannot be set on already-bound sockets), the daemon sets the same socket options on reusable sockets as it would on sockets it opens itself. Unit tests test the correct parsing of the LISTEN_FDS environment variable. Add 011-systemd system test to test socket activation for DGRAM and STREAM sockets (both IPv4 and IPv6). The tests use the systemd-socket-activate test tool, which has some limitations requiring workarounds discussed in inline comments.	2023-11-13 17:05:26 +01:00
Luke Valenta	c063b9e78a	logging: move severity_chars to fix compiler warning	2023-11-08 15:09:03 +01:00
Luke Valenta	f6f1863fe2	logging: add log severity to file log prefix when debug is enabled	2023-11-07 15:43:57 +01:00
Miroslav Lichvar	51a621bc2b	ntp: initialize network correction of transmitted packets Initialize the unused value of network correction parsed from own transmitted packets to avoid a use-of-uninitialized-value error in NIO_UnwrapMessage() reported by clang. Fixes: `6372a9f93f` ("ntp: save PTP correction from NTP-over-PTP messages")	2023-11-02 12:53:00 +01:00
Luke Valenta	1488b31a38	doc: document '-L -1' option for debug logging output	2023-10-24 11:37:56 +02:00
Miroslav Lichvar	70cdd8b1ef	ntp: add client support for network correction If the network correction is known for both the request and response, and their sum is not larger that the measured peer delay, allowing the transparent clocks to be running up to 100 ppm faster than the client's clock, apply the corrections to the NTP offset and peer delay. Don't correct the root delay to not change the estimated maximum error.	2023-09-26 15:14:13 +02:00
Miroslav Lichvar	8eef631009	ntp: add server support for network correction Provide the network correction (PTP correction + RX duration) of the request in the new extension field if included in the request and NTP-over-PTP is enabled.	2023-09-26 15:14:13 +02:00
Miroslav Lichvar	d9ae724c60	ntp: add extension field to provide network correction To be able to verify PTP corrections, the client will need to know both the correction of the request received by the server and the correction of the response. Add a new experimental NTP extension field that the clients will use to request the correction and servers return the value.	2023-09-26 15:14:13 +02:00
Miroslav Lichvar	6372a9f93f	ntp: save PTP correction from NTP-over-PTP messages When the RX duration is known (HW timestamping), save the PTP correction from received PTP messages in the local RX timestamp.	2023-09-26 15:14:13 +02:00
Miroslav Lichvar	b0267475e3	ntp: extend local timestamp for PTP correction Add two new fields to the NTP_Local_Timestamp structure: - receive duration as the time it takes to receive the ethernet frame, currently known only with HW timestamping - network correction as a generalized PTP correction The PTP correction is provided by transparent clocks in the correction field of PTP messages to remove the receive, processing and queueing delays of network switches and routers. Only one-step end-to-end unicast transparent clocks are useful for NTP-over-PTP. Two-step transparent clocks use follow-up messages and peer-to-peer transparent clocks don't handle delay requests. The RX duration will be included in the network correction to compensate for asymmetric link speeds of the server and client as the NTP RX timestamp corresponds to the end of the reception (in order to compensate for the asymmetry in the normal case when no corrections are applied).	2023-09-26 15:10:19 +02:00
Miroslav Lichvar	07134f2625	ntp: add function for detection of experimental fields	2023-09-26 15:03:33 +02:00
Miroslav Lichvar	85db8e3a9c	ntp: assert size of exp_mono_root field	2023-09-26 15:02:06 +02:00
Miroslav Lichvar	05f4f79cbf	ntp: rename exp1 extension field Rename the exp1 extension field to exp_mono_root (monotonic timestamp + root delay/dispersion) to better distinguish it from future experimental extension fields.	2023-09-26 15:01:24 +02:00
Miroslav Lichvar	bf616eafa1	util: add conversion between intervals and NTP 64-bit format This will be needed to save PTP correction in NTP timestamp format.	2023-09-26 15:00:06 +02:00
Miroslav Lichvar	e08a0ee668	doc: don't require same version for experimental features	2023-09-26 14:58:42 +02:00
Miroslav Lichvar	f2d7baa94f	configure: prefer gnutls over nss and tomcrypt for hashing Reorder the tests in the configure script to prefer gnutls over nss and tomcrypt as its support includes AES-CMAC.	2023-09-12 10:36:23 +02:00
Miroslav Lichvar	558931524d	configure: don't try AES-SIV-CMAC in nettle when disabled Avoid confusing message when --without-nettle is specified.	2023-09-12 10:31:36 +02:00
Miroslav Lichvar	a74b63277a	siv: add support for AES-GCM-SIV in gnutls Add support for AES-128-GCM-SIV in the current development code of gnutls. There doesn't seem to be an API to get the cipher's minimum and maximum nonce length and it doesn't check for invalid lengths. Hardcode and check the limits in chrony for now.	2023-09-12 10:31:36 +02:00
Miroslav Lichvar	aa8196328c	conf: improve log message for failed additions in sources reload Describe the error status in the log message when adding a source from sourcedir failed.	2023-09-12 08:11:25 +02:00
Miroslav Lichvar	37deee7140	conf: cast subtraction operands in source comparison Cast the values to int to not break the sorting in case they are changed to unsigned types.	2023-09-12 08:03:23 +02:00
Miroslav Lichvar	7ff74d9efe	conf: fix reloading modified sources specified by IP address When reloading a modified source from sourcedir which is ordered before the original source (e.g. maxpoll was decreased), the new source is added before the original one is removed. If the source is specified by IP address, the addition fails due to the conflict with the original source. Sources specified by hostname don't conflict. They are resolved later (repeatedly if the resolver provides only conflicting addresses). Split the processing of sorted source lists into two phases, so all modified sources are removed before they are added again to avoid the conflict. Reported-by: Thomas Lange <thomas@corelatus.se>	2023-09-12 08:02:36 +02:00