Re: [PATCH ghak10 v5 2/2] timekeeping/ntp: Audit clock/NTP params adjustments

From: Thomas Gleixner
Date: Mon Aug 27 2018 - 17:42:48 EST

On Mon, 27 Aug 2018, Miroslav Lichvar wrote:

> On Mon, Aug 27, 2018 at 01:35:09PM +0200, Ondrej Mosnacek wrote:
> > On Fri, Aug 24, 2018 at 9:51 PM Richard Guy Briggs <rgb@xxxxxxxxxx> wrote:
> > > It appears this time_tai use of "constant" is different than
> > > time_constant, the former not mentioned by Miroslav Lichvar. What is it
> > > and is it important to log for security? It sounds like it is
> > > important.
> > The TAI offset is the offset of the clock from the International
> > Atomic Time, so basically the time zone offset. I suppose it can't
> > influence the audit timestamps, but changing timezones can still cause
> > all sorts of confusion throughout the system, so intuitively I would
> > say we should log it.
> It's not related to timezones. ADJ_TAI sets the offset of the system
> TAI clock (CLOCK_TAI) relative to the standard UTC clock
> (CLOCK_REALTIME). CLOCK_TAI is rarely used by applications. Setting
> the TAI offset effectively injects a whole-second offset to the TAI
> time.

Rarely used today, but with TSN it's going to get more usage in not so
distant future.