conf: add mindelay and asymmetry options to NTP sources

diff --git a/cmdparse.c b/cmdparse.c
index 700da327950614172ded0c3614b7fd806f89db24..c4e26bf977b985dabe385fbfc47175339934b8be 100644 (file)
--- a/cmdparse.c
+++ b/cmdparse.c
@@ -64,6 +64,8 @@ CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)
   src->params.max_delay = SRC_DEFAULT_MAXDELAY;
   src->params.max_delay_ratio = SRC_DEFAULT_MAXDELAYRATIO;
   src->params.max_delay_dev_ratio = SRC_DEFAULT_MAXDELAYDEVRATIO;
+  src->params.min_delay = 0.0;
+  src->params.asymmetry = SRC_DEFAULT_ASYMMETRY;
   src->params.offset = 0.0;
 
   hostname = line;
@@ -98,6 +100,9 @@ CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)
       if (sscanf(line, "%"SCNu32"%n", &src->params.authkey, &n) != 1 ||
           src->params.authkey == INACTIVE_AUTHKEY)
         return 0;
+    } else if (!strcasecmp(cmd, "asymmetry")) {
+      if (sscanf(line, "%lf%n", &src->params.asymmetry, &n) != 1)
+        return 0;
     } else if (!strcasecmp(cmd, "maxdelay")) {
       if (sscanf(line, "%lf%n", &src->params.max_delay, &n) != 1)
         return 0;
@@ -116,6 +121,9 @@ CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)
     } else if (!strcasecmp(cmd, "maxsources")) {
       if (sscanf(line, "%d%n", &src->params.max_sources, &n) != 1)
         return 0;
+    } else if (!strcasecmp(cmd, "mindelay")) {
+      if (sscanf(line, "%lf%n", &src->params.min_delay, &n) != 1)
+        return 0;
     } else if (!strcasecmp(cmd, "minpoll")) {
       if (sscanf(line, "%d%n", &src->params.minpoll, &n) != 1)
         return 0;

diff --git a/doc/chrony.conf.adoc b/doc/chrony.conf.adoc
index b689fb1c858b2eb42ae36c9706e5bfac76e7a408..7b2ee757d92e8ef8f6a4fca007381115d3d6a13c 100644 (file)
--- a/doc/chrony.conf.adoc
+++ b/doc/chrony.conf.adoc
@@ -122,6 +122,19 @@ If a measurement has a ratio of the increase in the round-trip delay from the
 minimum delay amongst the previous measurements to the standard deviation of
 the previous measurements that is greater than the specified ratio, it will be
 rejected. The default is 10.0.
+*mindelay* _delay_:::
+This options specifies a fixed minimum round-trip delay to be used instead of
+the minimum amongst the previous measurements. This can be useful in networks
+with static configuration to improve the stability of corrections for
+asymmetric jitter, weighting of the measurements, and the *maxdelayratio* and
+*maxdelaydevratio* tests. The value should be set accurately in order to have a
+positive effect on the synchronisation.
+*asymmetry* _ratio_:::
+This options specifies the asymmetry of the network jitter on the path to the
+source, which is used to correct the measured offset according to the delay.
+The asymmetry can be between -0.5 and +0.5. A negative value means the delay of
+packets sent to the source is more variable than the delay of packets sent from
+the source back. By default, *chronyd* estimates the asymmetry automatically.
 *offset* _offset_:::
 This option specifies a correction (in seconds) which will be applied to
 offsets measured with this source. It's particularly useful to compensate for a
@@ -1664,11 +1677,11 @@ from the example line above):
   to be discarded. The number of runs for the data that is being retained is
   tabulated. Values of approximately half the number of samples are expected.
   [8]
-. The estimated asymmetry of network jitter on the path to the source which was
-  used to correct the measured offsets. The asymmetry can be between -0.5 and
-  0.5. A negative value means the delay of packets sent to the source is
-  more variable than the delay of packets sent from the source back. [0.00,
-  i.e. no correction for asymmetry]
+. The estimated or configured asymmetry of network jitter on the path to the
+  source which was used to correct the measured offsets. The asymmetry can be
+  between -0.5 and +0.5. A negative value means the delay of packets sent to
+  the source is more variable than the delay of packets sent from the source
+  back. [0.00, i.e. no correction for asymmetry]
 +
 *tracking*:::
 This option logs changes to the estimate of the system's gain or loss rate, and

diff --git a/ntp_core.c b/ntp_core.c
index f981953acca29e0483c79e73186465e47f4a4794..a1985453b02198ea4c0e7399dea1a83e3c59e3df 100644 (file)
--- a/ntp_core.c
+++ b/ntp_core.c
@@ -586,7 +586,7 @@ NCR_GetInstance(NTP_Remote_Address *remote_addr, NTP_Source_Type type, SourcePar
                                          SRC_NTP, params->sel_options,
                                          &result->remote_addr.ip_addr,
                                          params->min_samples, params->max_samples,
-                                         0.0, 1.0);
+                                         params->min_delay, params->asymmetry);
 
   result->rx_timeout_id = 0;
   result->tx_timeout_id = 0;

diff --git a/srcparams.h b/srcparams.h
index bdf13a8f166f1126019c70d1e836d3255fd011eb..5bd591df7b2bad4d3c1b60a16f3b588f20aeccb9 100644 (file)
--- a/srcparams.h
+++ b/srcparams.h
@@ -48,6 +48,8 @@ typedef struct {
   double max_delay;
   double max_delay_ratio;
   double max_delay_dev_ratio;
+  double min_delay;
+  double asymmetry;
   double offset;
 } SourceParameters;
 
@@ -63,6 +65,7 @@ typedef struct {
 #define SRC_DEFAULT_MAXSOURCES 4
 #define SRC_DEFAULT_MINSAMPLES (-1)
 #define SRC_DEFAULT_MAXSAMPLES (-1)
+#define SRC_DEFAULT_ASYMMETRY 1.0
 #define INACTIVE_AUTHKEY 0
 
 /* Flags for source selection */