ntp: don't check reference timestamp in received packets

When ntpd as an NTP server has active orphan mode, it doesn't update
its reference time and the reference timestamp may fail the NTP test
3 and 7. (https://bugs.ntp.org/show_bug.cgi?id=1098)

Remove both checks of the timestamp to allow chronyd to operate as
a client of ntpd server in the orphan mode. When ntpd is fixed and
old versions are no longer used, this may be reverted.

diff --git a/ntp_core.c b/ntp_core.c
index 8bcd292eaa07f67d2b4e4363269d46c5a1d99b29..8f3c3e827eac7605a66497d3bb33319a1e781d36 100644 (file)
--- a/ntp_core.c
+++ b/ntp_core.c
@@ -1190,7 +1190,6 @@ receive_packet(NTP_Packet *message, struct timeval *now, double now_err, NCR_Ins
 
   /* These are the timeval equivalents of the remote epochs */  
   struct timeval remote_receive_tv, remote_transmit_tv;
-  struct timeval remote_reference_tv;
   struct timeval local_average, remote_average;
   double local_interval, remote_interval;
 
@@ -1229,7 +1228,6 @@ receive_packet(NTP_Packet *message, struct timeval *now, double now_err, NCR_Ins
 
   UTI_Int64ToTimeval(&message->receive_ts, &remote_receive_tv);
   UTI_Int64ToTimeval(&message->transmit_ts, &remote_transmit_tv);
-  UTI_Int64ToTimeval(&message->reference_ts, &remote_reference_tv);
 
   /* Check if the packet is valid per RFC 5905, section 8.
      The test values are 1 when passed and 0 when failed. */
@@ -1247,7 +1245,6 @@ receive_packet(NTP_Packet *message, struct timeval *now, double now_err, NCR_Ins
      association if not properly 'up'. */
   test3 = (message->originate_ts.hi || message->originate_ts.lo) &&
           (message->receive_ts.hi || message->receive_ts.lo) &&
-          (message->reference_ts.hi || message->reference_ts.lo) &&
           (message->transmit_ts.hi || message->transmit_ts.lo);
 
   /* Test 4 would check for denied access.  It would always pass as this
@@ -1268,10 +1265,8 @@ receive_packet(NTP_Packet *message, struct timeval *now, double now_err, NCR_Ins
           message->stratum != NTP_INVALID_STRATUM; 
 
   /* Test 7 checks for bad data.  The root distance must be smaller than a
-     defined maximum and the transmit time must not be before the time of
-     the last synchronisation update. */
-  test7 = pkt_root_delay / 2.0 + pkt_root_dispersion < NTP_MAX_DISPERSION &&
-          UTI_CompareTimevals(&remote_reference_tv, &remote_transmit_tv) < 1;
+     defined maximum. */
+  test7 = pkt_root_delay / 2.0 + pkt_root_dispersion < NTP_MAX_DISPERSION;
 
   /* The packet is considered valid if the tests above passed */
   valid_packet = test1 && test2 && test3 && test5 && test6 && test7;