Re: [Xen-devel] Checksumming problem in pv_ops dom0 kernel / netback

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2010-03-30 at 23:58 +0100, Scott Garron wrote:
> S.H. Verbrugge wrote:
> > Ever since we switched to a pv_ops dom0 kernel (we were using 2.6.26 
> > xenkernel from Debian repo before, with Xen 3.2), we started to have 
> > some problems when attempting to route packets on a domU.
> 
>       I'm having the same problem.  All TCP packets that are forwarded
> through a domU are somehow getting a static checksum (0x9e85) just as
> they're being put out on the wire.  ICMP is dropped by the dom0, as you
> describe, with the "Attempting to checksum a non UDP/TCP packet" message
> in dmesg.  More detail about my situation is in my post to xen-users, here:
> 
> http://lists.xensource.com/archives/html/xen-users/2010-03/msg00846.html
> 
>       It doesn't include a solution, though.
> 
> > This is a tg3 interface
> 
>       I'm also running the tg3 ethernet driver, which may be of
> significance.

According to the driver source some tg3 chipsets are known to have
broken checksumming hardware, in particular 5700 B0 silicon. The
workaround seems to have been present in the driver forever though so
that may be a red-herring.

Ian.



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