Re: TCP-MD5 checksum failure on x86_64 SMP

Stephen Hemminger
2010-05-04T16:12:19Z

On Tue, 4 May 2010 19:58:32 +0530
Bhaskar Dutta <bhaskie@gmail.com> wrote:

> On Tue, May 4, 2010 at 5:02 PM, Ben Hutchings <bhutchings@solarflare.com> wrote:
> > On Tue, 2010-05-04 at 09:00 +0530, Bhaskar Dutta wrote:
> >> Hi,
> >>
> >> I am observing intermittent TCP-MD5 checksum failures
> >> (CONFIG_TCP_MD5SIG)  on kernel 2.6.31 while talking to a BGP router.
> >>
> >> The problem is only seen in multi-core 64 bit machines.
> >> Is there any known bug in the per_cpu_ptr implementation (I am aware
> >> that the percpu allocator has been re-implemented in 2.6.33) that
> >> might cause a corruption in 64 bit SMP machines?
> >>
> >> Any pointers would be appreciated.
> >
> > There was another recent report of incorrect MD5 signatures in
> > <http://thread.gmane.org/gmane.linux.network/159556>, but without any
> > response.
> >
> > Ben.
> >
>
> I found another thread posted back in Jan 2007 with a similar bug
> (x86_64 on 2.6.20) but no replies to that as well.
> http://lkml.org/lkml/2007/1/20/56

2.6.20 had lots of other MD5 bugs. Your problem might be related to
GRO. MD5 may not handle multi-fragment packets.