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ntp: check software timestamps on Linux

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Apparently some routers with hardware NAT acceleration have a bug
causing the kernel timestamps to be corrupted and break NTP. Similarly
to the sanity check applied to hardware timestamps, require the
kernel/driver timestamps to be within one second of the daemon timestamp
to be accepted.
This commit is contained in:
Miroslav Lichvar 2021-09-23 13:00:24 +02:00
parent 7ee5f4888e
commit 127826a399
1 changed files with 24 additions and 3 deletions
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27
ntp_io_linux.c
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@ -73,7 +73,7 @@ struct Interface {
/* Minimum interval between PHC readings */
#define MIN_PHC_POLL -6
/* Maximum acceptable offset between HW and daemon/kernel timestamp */
/* Maximum acceptable offset between SW/HW and daemon timestamp */
#define MAX_TS_DELAY 1.0
/* Array of Interfaces */
@ -619,6 +619,28 @@ process_hw_timestamp(struct Interface *iface, struct timespec *hw_ts,
local_ts->source = NTP_TS_HARDWARE;
}
/* ================================================== */
static void
process_sw_timestamp(struct timespec *sw_ts, NTP_Local_Timestamp *local_ts)
{
double ts_delay, local_err;
struct timespec ts;
LCL_CookTime(sw_ts, &ts, &local_err);
ts_delay = UTI_DiffTimespecsToDouble(&local_ts->ts, &ts);
if (fabs(ts_delay) > MAX_TS_DELAY) {
DEBUG_LOG("Unacceptable timestamp delay %.9f", ts_delay);
return;
}
local_ts->ts = ts;
local_ts->err = local_err;
local_ts->source = NTP_TS_KERNEL;
}
/* ================================================== */
/* Extract UDP data from a layer 2 message. Supported is Ethernet
with optional VLAN tags. */
@ -744,8 +766,7 @@ NIO_Linux_ProcessMessage(SCK_Message *message, NTP_Local_Address *local_addr,
if (local_ts->source == NTP_TS_DAEMON && !UTI_IsZeroTimespec(&message->timestamp.kernel) &&
(!is_tx || UTI_IsZeroTimespec(&message->timestamp.hw))) {
LCL_CookTime(&message->timestamp.kernel, &local_ts->ts, &local_ts->err);
local_ts->source = NTP_TS_KERNEL;
process_sw_timestamp(&message->timestamp.kernel, local_ts);
}
/* If the kernel is slow with enabling RX timestamping, open a dummy