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ntp: don't use first response in interleaved mode

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With the first interleaved response coming after a basic response the
client is forced to select the four timestamps covering most of the last
polling interval, which makes measured delay very sensitive to the
frequency offset between server and client. To avoid corrupting the
minimum delay held in sourcestats (which can cause testC failures),
reject the first interleaved response in the client/server mode as
failing the test A.

This does not change anything for the symmetric mode, where both sets of
the four timestamps generally cover a significant part of the polling
interval.
This commit is contained in:
Miroslav Lichvar 2022-06-30 10:18:48 +02:00
parent 52ec694d2b
commit 0ae6f2485b
3 changed files with 13 additions and 3 deletions
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7
ntp_core.c
View file

@ -1907,12 +1907,17 @@ process_response(NCR_Instance inst, NTP_Local_Address *local_addr,
/* Test A requires that the minimum estimate of the peer delay is not
larger than the configured maximum, in both client modes that the server
processing time is sane, and in interleaved symmetric mode that the
processing time is sane, in interleaved client/server mode that the
previous response was not in basic mode (which prevents using timestamps
that minimise delay error), and in interleaved symmetric mode that the
measured delay and intervals between remote timestamps don't indicate
a missed response */
testA = sample.peer_delay - sample.peer_dispersion <= inst->max_delay &&
precision <= inst->max_delay &&
!(inst->mode == MODE_CLIENT && response_time > MAX_SERVER_INTERVAL) &&
!(inst->mode == MODE_CLIENT && interleaved_packet &&
UTI_IsZeroTimespec(&inst->prev_local_tx.ts) &&
UTI_CompareTimespecs(&local_transmit.ts, &inst->local_tx.ts) == 0) &&
!(inst->mode == MODE_ACTIVE && interleaved_packet &&
(sample.peer_delay > 0.5 * prev_remote_poll_interval ||
UTI_CompareNtp64(&message->receive_ts, &message->transmit_ts) <= 0 ||

4
test/simulation/122-xleave
View file

@ -15,10 +15,11 @@ check_chronyd_exit || test_fail
check_source_selection || test_fail
check_sync || test_fail
check_file_messages "111 111 1111.* 4I [DKH] [DKH]\$" 0 0 measurements.log || test_fail
check_file_messages "111 111 .111.* 4I [DKH] [DKH]\$" 0 0 measurements.log || test_fail
rm -f tmp/measurements.log
server_conf=""
max_sync_time=270
run_test || test_fail
check_chronyd_exit || test_fail
@ -28,6 +29,7 @@ check_sync || test_fail
check_file_messages "111 111 1111.* 4B [DKH] [DKH]\$" 2 2 measurements.log || test_fail
check_file_messages "111 111 1111.* 4I [DKH] [DKH]\$" 30 200 measurements.log || test_fail
check_file_messages "111 111 0111.* 4I [DKH] [DKH]\$" 1 1 measurements.log || test_fail
rm -f tmp/measurements.log
clients=2

5
test/unit/ntp_core.c
View file

@ -496,7 +496,10 @@ test_unit(void)
send_request(inst1);
process_request(&remote_addr);
proc_response(inst1, 1, 1, 1, 0);
proc_response(inst1,
!source.params.interleaved || source.params.version != 4 ||
inst1->mode == MODE_ACTIVE || j != 2,
1, 1, 0);
advance_time(1 << inst1->local_poll);
}