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List:       freebsd-security
Subject:    Re: Leap Second
From:       Mark Felder <feld () FreeBSD ! org>
Date:       2015-06-24 13:57:54
Message-ID: 1435154274.964221.306546033.052903CD () webmail ! messagingengine ! com
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On Tue, Jun 23, 2015, at 14:03, Pawel Biernacki wrote:
> Hi,
> 
> As we (hopefully) all know on 30th of June we'll observe leap second.
>  tzdata information was updated in release 2015a in January.  This
>  version
> was imported in FreeBSD HEAD (r279706), 10-STABLE (r279707), 9-STABLE
> (r279708) and 8-STABLE (r279709) on 6th of March.  Since then there were
> no
> releases and therefore users of _supported_ releases don't have tzdata
> information about incoming leap second.
> RedHat published a very detailed guide about that:
> https://access.redhat.com/articles/15145.
> I believe that FreeBSD Project should issue Errata Notices for all
> supported version with update to share/zoneinfo/leap-seconds.list file.
> This also means update to 8.4-R that will be supported till the last (and
> leap) second of 30th of June.
> 

I'm not an expert on the leapsecond operation, but if I understand it
correctly there are two ways a system can be notified of a leapsecond:
via a tzdata update or through NTP.

I *think* if the tzdata was missing the leapsecond information but the
server was syncing to an NTP server that is aware of the leapsecond, the
leapsecond info is passed to the NTP client ~24 hours before it happens.

This would mean there are three potential scenarios:

1) FreeBSD server unaware of leapsecond due to no tzdata entry and not
synced to NTP ends up 1 second off
2) FreeBSD server unaware of leapsecond due to no tzdata entry synced to
leapsecond-aware NTP server successfully handles leapsecond
3) FreeBSD server unaware of leapsecond due to no tzdata entry acting as
NTP server doesn't notify clients of leapsecond and they end up 1 second
off


Can anyone confirm/deny if this summary is accurate?
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