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core: allow disabling system time correction if rtc returns time far in the future

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There might be (embedded) systems that get never updated (things like
e.g. entertainment systems of trains, for example) and where the adjustment of
the system clock (introduced by b10abe4bba) would
do the wrong thing even if the difference between the systemd build time and
the rtc is 15 years or more.

This patch allows disabling the adjustment by setting
'clock-valid-range-usec-max' meson option to 0 or to a negative value.
This commit is contained in:
Franck Bui 2022-08-23 17:07:23 +02:00 committed by Luca Boccassi
parent 34683dbdd0
commit 2306b4656a
2 changed files with 2 additions and 2 deletions
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2
meson_options.txt
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@ -223,7 +223,7 @@ option('status-unit-format-default', type : 'combo',
option('time-epoch', type : 'integer', value : 0,
description : 'time epoch for time clients')
option('clock-valid-range-usec-max', type : 'integer', value : 473364000000000, # 15 years
description : 'maximum value in microseconds for the difference between RTC and epoch, exceeding which is considered an RTC error')
description : 'maximum value in microseconds for the difference between RTC and epoch, exceeding which is considered an RTC error ["0" disables]')
option('default-user-shell', type : 'string', value : '/bin/bash',
description : 'default interactive shell')

2
src/shared/clock-util.c
View File

@ -153,7 +153,7 @@ int clock_apply_epoch(ClockChangeDirection *ret_attempted_change) {
now_usec = now(CLOCK_REALTIME);
if (now_usec < epoch_usec)
*ret_attempted_change = CLOCK_CHANGE_FORWARD;
else if (now_usec > usec_add(epoch_usec, CLOCK_VALID_RANGE_USEC_MAX))
else if (CLOCK_VALID_RANGE_USEC_MAX > 0 && now_usec > usec_add(epoch_usec, CLOCK_VALID_RANGE_USEC_MAX))
*ret_attempted_change = CLOCK_CHANGE_BACKWARD;
else {
*ret_attempted_change = CLOCK_CHANGE_NOOP;