[ntp:questions] Regarding step_systime call

Srihari Raghavan srihari.raghavan at gmail.com
Tue Jan 21 06:03:21 UTC 2020

Hi all

In one of our research network lab devices, that use an implementation
based off of ntp.org 4.2.8p12 in NTP client mode - I see a spurious
"stepped" system clock change under certain conditions (more than 1000s
clock change done erroneously at the head-end) BEFORE the actual NTP
triggered clock change via known NTP log message around "step_systime" call
- and am trying to track down the spurious clock change that happened
first.  There could be other actors that could have changed the system
clock via 'date' etc., but I am trying to rule out the obvious.

I have added logs around step_systime call in the code ntp_loopfilter.c and
also in ntp_timer.c and also via ntpd_time_stepped and I don't see any of
them being being triggered for the 'spurious' case.

Are there any other calls/paths/APIs in NTP.org code, besides step_systime
way, that can potentially step the system clock?   Scoured the NTP.org code
(ntpdate is not being used) for the same without success and hence my
request and email.

Thanks in advance for any help.


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