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ntp: add sanity check for HW timestamps

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Accept HW timestamp only if it doesn't differ from the kernel/daemon
timestamp by more than one second.
This commit is contained in:
Miroslav Lichvar 2017-01-05 16:27:27 +01:00
parent c44d282f0b
commit 8efec1d640
1 changed files with 15 additions and 3 deletions
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18
ntp_io_linux.c
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@ -72,6 +72,9 @@ struct Interface {
/* Number of PHC readings per HW clock sample */ /* Number of PHC readings per HW clock sample */
#define PHC_READINGS 10 #define PHC_READINGS 10
/* Maximum acceptable offset between HW and daemon/kernel timestamp */
#define MAX_TS_DELAY 1.0
/* Array of Interfaces */ /* Array of Interfaces */
static ARR_Instance interfaces; static ARR_Instance interfaces;
@ -417,8 +420,8 @@ static void
process_hw_timestamp(struct Interface *iface, struct timespec *hw_ts, process_hw_timestamp(struct Interface *iface, struct timespec *hw_ts,
NTP_Local_Timestamp *local_ts, int rx_ntp_length, int family) NTP_Local_Timestamp *local_ts, int rx_ntp_length, int family)
{ {
struct timespec sample_phc_ts, sample_local_ts; struct timespec sample_phc_ts, sample_local_ts, ts;
double sample_delay, rx_correction; double sample_delay, rx_correction, ts_delay, err;
int l2_length; int l2_length;
if (HCL_NeedsNewSample(iface->clock, &local_ts->ts)) { if (HCL_NeedsNewSample(iface->clock, &local_ts->ts)) {
@ -444,9 +447,18 @@ process_hw_timestamp(struct Interface *iface, struct timespec *hw_ts,
UTI_AddDoubleToTimespec(hw_ts, rx_correction, hw_ts); UTI_AddDoubleToTimespec(hw_ts, rx_correction, hw_ts);
} }
if (!HCL_CookTime(iface->clock, hw_ts, &local_ts->ts, &local_ts->err)) if (!HCL_CookTime(iface->clock, hw_ts, &ts, &err))
return; return;
ts_delay = UTI_DiffTimespecsToDouble(&local_ts->ts, &ts);
if (fabs(ts_delay) > MAX_TS_DELAY) {
DEBUG_LOG(LOGF_NtpIOLinux, "Unacceptable timestamp delay %.9f", ts_delay);
return;
}
local_ts->ts = ts;
local_ts->err = err;
local_ts->source = NTP_TS_HARDWARE; local_ts->source = NTP_TS_HARDWARE;
} }