[CentOS] Dag repo

Dag Wieers dag at wieers.com
Wed Nov 9 11:19:23 UTC 2005

On Wed, 9 Nov 2005, Colm MacCarthaigh wrote:

> On Tue, Nov 08, 2005 at 12:36:04PM +0100, Dag Wieers wrote:
> > I don't know what the problem is. Either the file is empty on the 
> > filesystem (corruption on the filesystem level or problems with rsync or 
> > NFS) or the web server is handing out empty files under certain 
> > conditions.
> It's the latter, and the problem has been traced to yet another bug to
> do with sendfile() and TCP checksum offloading. Basically ... the
> packets were being sent, but with invalid checksums. So the clients were
> rejecting the packets. 
> > Without access to the system I have no clue whether the filesystem is the 
> > problem or it is Apache related. I bet it is Apache's problem as mirrors 
> > of Heanet do not seem to have this problem. (This is different than when 
> > it was a NFS problem with the same symptoms)
> Turned out not to be an Apache problem, as anything which used
> sendfile() would have been effected. The problem is really in the
> network cards - and how they handle offloaded checksums when DSCP
> headers are set.

Thanks Colm, I'm very interested to learn how you figured this out.

Also, are there any tests/monitors to find the same cause in the future ?
It could be something that is silently bothering other people as well, and 
a technical explanation together with Google might make this valuable 

Kind regards,
--   dag wieers,  dag at wieers.com,  http://dag.wieers.com/   --
[all I want is a warm bed and a kind word and unlimited power]

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