ntp: improve maxdelayratio test

Similarly to the maxdelaydevratio test, include in the maximum delay
dispersion which accumulated in the interval since the last sample.
Also, enable the test for symmetric associations.

diff --git a/doc/chrony.conf.adoc b/doc/chrony.conf.adoc
index 612bc00d172f1222ef832bf3fd250db393ba6204..6b65445c24a72ccc383d79ce3bc43d87d4725d22 100644 (file)
--- a/doc/chrony.conf.adoc
+++ b/doc/chrony.conf.adoc
@@ -115,8 +115,7 @@ round-trip delay of 0.3 seconds or more should be ignored. The default value is
 This option is similar to the maxdelay option above. *chronyd* keeps a record
 of the minimum round-trip delay amongst the previous measurements that it has
 buffered. If a measurement has a round trip delay that is greater than the
-maxdelayratio times the minimum delay, it will be rejected. This option does
-not work in the *peer* directive.
+maxdelayratio times the minimum delay, it will be rejected.
 *maxdelaydevratio* _ratio_:::
 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

diff --git a/ntp_core.c b/ntp_core.c
index af475165e84b5e8399865f852657ca9d953a4d9b..d73111fbcf88f0340b7ef6d9308764428431f42d 100644 (file)
--- a/ntp_core.c
+++ b/ntp_core.c
@@ -1325,6 +1325,30 @@ check_packet_auth(NTP_Packet *pkt, int length,
 
 /* ================================================== */
 
+static int
+check_delay_ratio(NCR_Instance inst, SST_Stats stats,
+                struct timespec *sample_time, double delay)
+{
+  double last_sample_ago, predicted_offset, min_delay, skew, std_dev;
+  double max_delay;
+
+  if (inst->max_delay_ratio < 1.0 ||
+      !SST_GetDelayTestData(stats, sample_time, &last_sample_ago,
+                            &predicted_offset, &min_delay, &skew, &std_dev))
+    return 1;
+
+  max_delay = min_delay * inst->max_delay_ratio +
+              last_sample_ago * (skew + LCL_GetMaxClockError());
+
+  if (delay <= max_delay)
+    return 1;
+
+  DEBUG_LOG("maxdelayratio: delay=%e max_delay=%e", delay, max_delay);
+  return 0;
+}
+
+/* ================================================== */
+
 static int
 check_delay_dev_ratio(NCR_Instance inst, SST_Stats stats,
                       struct timespec *sample_time, double offset, double delay)
@@ -1582,9 +1606,7 @@ receive_packet(NCR_Instance inst, NTP_Local_Address *local_addr,
     /* Test B requires in client mode that the ratio of the round trip delay
        to the minimum one currently in the stats data register is less than an
        administrator-defined value */
-    testB = inst->max_delay_ratio <= 1.0 ||
-            !(inst->mode == MODE_CLIENT &&
-              (delay - dispersion) / SST_MinRoundTripDelay(stats) > inst->max_delay_ratio);
+    testB = check_delay_ratio(inst, stats, &sample_time, delay);
 
     /* Test C requires that the ratio of the increase in delay from the minimum
        one in the stats data register to the standard deviation of the offsets

diff --git a/test/simulation/118-maxdelay b/test/simulation/118-maxdelay
index 18fcdfa31093391567114a42c694cae7a28dff46..22b9a502c975fa8bf8a1ccce52a8bfd223cf954e 100755 (executable)
--- a/test/simulation/118-maxdelay
+++ b/test/simulation/118-maxdelay
@@ -18,7 +18,7 @@ check_source_selection || test_fail
 check_packet_interval || test_fail
 check_sync || test_fail
 
-for client_server_options in "maxpoll 6 maxdelay 2e-5" "maxpoll 6 maxdelayratio 1.001"; do
+for client_server_options in "maxpoll 6 maxdelay 2e-5"; do
        run_test || test_fail
        check_chronyd_exit || test_fail
        check_packet_interval || test_fail