another bug: system time change

Andrew Lemin andrew.lemin at
Fri Apr 9 17:37:06 CEST 2010

This is my first time so sorry if I have not done this right.

I have seen this problem before.
I have seen this in Linux when the BIOS synchronises its time with the OS.

The Linux OS could have been fine and have had a valid NTP source, but periodically there is some form of synchronisation that occurs between the BIOS and the OS and weird things can happen.

This is probably nothing to do with bird.

PS; A Virtual BIOS does exactly the same thing.
Ie. the real BIOS time gets synchronised with all the Virtual BIOS clocks (one for each VM), which each in turn synchronise with their respective guest.

Check all your BIOS times (physical BIOS and virtual Guest BIOS').

Hope this helps.

-----Original Message-----
From: owner-bird-users at [mailto:owner-bird-users at] On Behalf Of Wolfgang Hennerbichler
Sent: 09 April 2010 09:49
To: Ondrej Zajicek
Cc: Bird Users
Subject: Re: another bug: system time change

On Apr 9, 2010, at 10:49 , Ondrej Zajicek wrote:

> On Fri, Apr 09, 2010 at 10:22:05AM +0200, Wolfgang Hennerbichler wrote:
>> Hi Ondrejs,
>> I think I found another bug. For some mysterious reason our system time jumped forward (more than 30.000 seconds) on one of our route-servers. I don't know why this happened, but I suspect a broken ntp server could have caused this. Nevetheless, this was reason enough for BIRD to drop the BGP peerings:
>> You see the log-entries from the wtachdog, which is run every minute,
>> all of a sudden the time jumps to 10:08 UTC, and BIRD brings down BGP
>> sessions. Are the session hold timers dependent on the system time?
> That is really strange. On Linux 2.6, we use monotonic timers, which
> shouldn't be affected by system time change. If monotonic timers are not
> available (on Linux 2.4), we use system time but we detect time jumps
> and ignore them.

Hm. Now this is strange indeed. I run linux (amd64) - but it is a virtualized host (with xen). Maybe it was xen's fault, but the logs don't reveal much as you see. Hm. this sucks.

> --
> Elen sila lumenn' omentielvo
> Ondrej 'SanTiago' Zajicek (email: santiago at
> OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3,
> "To err is human -- to blame it on a computer is even more so."

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