Re: Bad UDP checksums with 2.6.9

[Martin Josefsson]

On Thu, 4 Nov 2004 foo@xxxxxxxxxxxxxxxxx wrote:

> On Thu, Nov 04, 2004 at 12:48:38AM -0500, foo wrote:
> > 'm seeing the same problem as in:
> > Message-Id: 20041020191203.GA14356@xxxxxxxxxxxxxxxxxxxx
> > or http://www.ussg.iu.edu/hypermail/linux/kernel/0410.2/1310.html
> >
> > I just upgraded a machine from 2.6.5 to 2.6.9, and when the amanda
> > backup server contacts it, it sometimes replies with a UDP packet with a
> > bad checksum.  I'm using e1000 here, so it seems to not be related to
> > the ethernet driver.  I have a binary tcpdump if anyone's interested.
>
> I don't know why I didn't think of this at first, but I have another
> identical machine that I upgraded at the same time that doesn't have the
> problem.
>
> Here's a diff between their .configs - albarino is the one having
> trouble.  Maybe CONFIG_PACKET_MMAP?  If someone can point me at a likely
> config option to change I'll boot a new kernel for the next backup run
> Friday night.

> -CONFIG_IP_NF_AMANDA=y

Disable that and it should work again, there's a bug in that conntrack
helper that was introduced when some performance-fixes for non-linear
packets went in. Davem has a patch for it in his tree, should find it's
way into mainline soonish.

Look at a netfilter-devel archive for the discussion if you are
interested.

/Martin
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