[ntp:questions] Regarding step_systime call

Charles Elliott elliott.ch at comcast.net
Mon Jan 27 13:28:43 UTC 2020


Hello:
	It is very difficult to help you if
you don't specify the platform being used,
i.e.,  O/S (publisher, version and updates)
and CPU if at all unusual.

	What does this mean: "more than 1000s
clock change done erroneously at the
head-end"?  Does 1000s mean 1000 seconds or
is it an abbreviation for the word
"thousands"?  It is common and natural (i.e.,
planned that way) for NTPD to step the time
on initial startup.

	If the O/S is Windows, what does the
Event Log say?  Normally, there will be a
message in the Event Log for every NTPD time
step change.

	Is there another clock program in the
system (such as Windows Time) that is also
trying to control the time, so that NTPD and
the other program are fighting?

	Have you tried a packet sniffer (such
as Wireshark) to see if an external program
is somehow affecting the time?

Charles Elliott

-----Original Message-----
From: questions
[mailto:questions-bounces+elliott.ch=comcast.
net at lists.ntp.org] On Behalf Of Srihari
Raghavan
Sent: Tuesday, January 21, 2020 1:03 AM
To: questions at lists.ntp.org
Subject: [ntp:questions] Regarding
step_systime call

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.

Regards
SR
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