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ntp: improve maxdelayratio test

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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.
This commit is contained in:
Miroslav Lichvar
2017-08-25 14:57:25 +02:00
parent 51fe80ad95
commit c68ca40ce4
3 changed files with 27 additions and 6 deletions
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28
ntp_core.c
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@@ -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