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sourcestats: don't fudge refclock LastRx in sources report

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The sample time used in calculation of the last_meas_ago (LastRx) value
in the sources report is aligned to the second to minimize the leak
of the NTP receive timestamp, which could be useful in some attacks.

There is no need to do that with reference clocks, which are often used
with very short polling intervals and an extra second in the LastRx
value can be misinterpreted as a missed sample.
This commit is contained in:
Miroslav Lichvar 2023-02-02 11:12:31 +01:00
parent 5b3d4dfe76
commit dec07aa844
1 changed files with 4 additions and 3 deletions
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7
sourcestats.c
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@ -80,7 +80,7 @@ static LOG_FileID logfileid;
struct SST_Stats_Record {
/* Reference ID and IP address of source, used for logging to statistics log */
/* Reference ID and IP address (NULL if not an NTP source) */
uint32_t refid;
IPAddr *ip_addr;
@ -964,9 +964,10 @@ SST_DoSourceReport(SST_Stats inst, RPT_SourceReport *report, struct timespec *no
report->latest_meas = inst->offsets[i];
report->latest_meas_err = 0.5*inst->root_delays[j] + inst->root_dispersions[j];
/* Align the sample time to reduce the leak of the receive timestamp */
/* Align the sample time to reduce the leak of the NTP receive timestamp */
last_sample_time = inst->sample_times[i];
last_sample_time.tv_nsec = 0;
if (inst->ip_addr)
last_sample_time.tv_nsec = 0;
report->latest_meas_ago = UTI_DiffTimespecsToDouble(now, &last_sample_time);
} else {
report->latest_meas_ago = (uint32_t)-1;