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clientlog: undo clock adjustments in updated TX timestamps

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When the server clock was updated between saving of the RX timestamp and
updating the TX timestamp, a client using interleaved mode with the four
timestamps which minimize error in measured delay (e.g. chrony) had the
server clock adjustment included in the measured delay, which could
disrupt the sample filtering and weighting.

Add a handler to track the slew epoch and remember the last offset. Undo
the adjustment in TX timestamps which have their RX timestamp in the
previous epoch to fix the delay observed by the clients.

If an unknown clock step is detected, drop all timestamps.
This commit is contained in:
Miroslav Lichvar
2021-10-25 17:00:28 +02:00
parent 189bf9c536
commit bc33e1cda1
4 changed files with 94 additions and 6 deletions
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clientlog.h
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@@ -47,6 +47,7 @@ extern int CLG_GetNtpMinPoll(void);
/* Functions to save and retrieve timestamps for server interleaved mode */
extern void CLG_SaveNtpTimestamps(NTP_int64 *rx_ts, struct timespec *tx_ts);
extern void CLG_UndoNtpTxTimestampSlew(NTP_int64 *rx_ts, struct timespec *tx_ts);
extern void CLG_UpdateNtpTxTimestamp(NTP_int64 *rx_ts, struct timespec *tx_ts);
extern int CLG_GetNtpTxTimestamp(NTP_int64 *rx_ts, struct timespec *tx_ts);
extern void CLG_DisableNtpTimestamps(NTP_int64 *rx_ts);