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ntp: get TX timestamp after authentication

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If the daemon transmit timestamp is saved for processing of a future
response or responding in the interleaved mode, get a more accurate
timestamp right before calling NIO_SendPacket(). Avoid unnecessary
reading of the clock for the transmit timestamp in the packet (i.e.
in interleaved modes and client basic mode).

This should improve accuracy and stability when authentication is
enabled in the client and symmetric basic modes and also interleaved
modes if kernel/hardware timestamps are not available.
This commit is contained in:
Miroslav Lichvar
2020-07-02 15:18:23 +02:00
parent 4e747da4b4
commit ff03b813b0
2 changed files with 29 additions and 21 deletions
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41
ntp_core.c
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@@ -961,6 +961,10 @@ transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */
smooth_time = 0;
smooth_offset = 0.0;
/* Get an initial transmit timestamp. A more accurate timestamp will be
taken later in this function. */
SCH_GetLastEventTime(&local_transmit, NULL, NULL);
if (my_mode == MODE_CLIENT) {
/* Don't reveal local time or state of the clock in client packets */
precision = 32;
@@ -968,10 +972,6 @@ transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */
our_root_delay = our_root_dispersion = 0.0;
UTI_ZeroTimespec(&our_ref_time);
} else {
/* This is accurate enough and cheaper than calling LCL_ReadCookedTime.
A more accurate timestamp will be taken later in this function. */
SCH_GetLastEventTime(&local_transmit, NULL, NULL);
REF_GetReferenceParams(&local_transmit,
&are_we_synchronised, &leap_status,
&our_stratum,
@@ -1062,20 +1062,20 @@ transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */
/* Prepare random bits which will be added to the transmit timestamp */
UTI_GetNtp64Fuzz(&ts_fuzz, precision);
/* Transmit - this our local time right now! Also, we might need to
store this for our own use later, next time we receive a message
from the source we're sending to now. */
LCL_ReadCookedTime(&local_transmit, &local_transmit_err);
/* Get a more accurate transmit timestamp if it needs to be saved in the
packet (i.e. in the server, symmetric, and broadcast basic modes) */
if (!interleaved && precision < 32) {
LCL_ReadCookedTime(&local_transmit, &local_transmit_err);
if (smooth_time)
UTI_AddDoubleToTimespec(&local_transmit, smooth_offset, &local_transmit);
if (smooth_time)
UTI_AddDoubleToTimespec(&local_transmit, smooth_offset, &local_transmit);
/* Pre-compensate the transmit time by approximately how long it will take
to generate the authentication data */
if (auth)
NAU_AdjustRequestTimestamp(auth, &local_transmit);
else
NAU_AdjustResponseTimestamp(request, request_info, &local_transmit);
/* Pre-compensate the transmit time by approximately how long it will
take to generate the authentication data */
if (auth)
NAU_AdjustRequestTimestamp(auth, &local_transmit);
else
NAU_AdjustResponseTimestamp(request, request_info, &local_transmit);
}
UTI_TimespecToNtp64(interleaved ? &local_tx->ts : &local_transmit,
&message.transmit_ts, &ts_fuzz);
@@ -1111,9 +1111,16 @@ transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */
return 0;
}
/* If the transmit timestamp will be saved, get an even more
accurate daemon timestamp closer to the transmission */
if (local_tx)
LCL_ReadCookedTime(&local_transmit, &local_transmit_err);
ret = NIO_SendPacket(&message, where_to, from, info.length, local_tx != NULL);
if (local_tx) {
if (smooth_time)
UTI_AddDoubleToTimespec(&local_transmit, smooth_offset, &local_transmit);
local_tx->ts = local_transmit;
local_tx->err = local_transmit_err;
local_tx->source = NTP_TS_DAEMON;