On Fri, Apr 24, 2009 at 11:55:19PM -0700, Boris Derzhavets wrote:
> Chris,
>
> I have to apologize. Turning off segmentation offloading may work as well.
> Just now it fixed VNC issue on bare metal - CentOS 5.2 with Atansic Gigabit
> Ethernet driver (ASUS P5KR) . I gonna try it at DomUs at my earliest
> convenience.
>
Have you tried another NICs? It could be a bug in the driver for that NIC..
-- Pasi
> Boris.
>
> --- On Fri, 4/24/09, Christophe Saout <christophe@xxxxxxxx> wrote:
> From: Christophe Saout <christophe@xxxxxxxx>
> Subject: Re: [Xen-devel] xen.git branch reorg
> To: "Jeremy Fitzhardinge" <jeremy@xxxxxxxx>
> Cc: bderzhavets@xxxxxxxxx, "Xen-devel" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Ian
> Campbell" <Ian.Campbell@xxxxxxxxxx>
> Date: Friday, April 24, 2009, 6:39 PM
>
> Hi Jeremy,
>
> > > In meantime time i see, that 2.6.30-rc3&rc2&rc1-tip are
> affected.
> > > Solution is the same as on Solaris xVM Linux DomUs about one
> > > year ago - is to disable checksum (nothing else) offloading at
> Linux
> > > DomUs ( CentOS 5.3, Ubuntu 9.04)
> > >
> > > /usr/local/sbin/ethtool -K etho tx off
> >
> > OK, that's a good lead.
>
> Yes, I've been seeing this too (and meant to investigate it before
> claiming there's abug) and I can confirm that turning off segmentation
> offloading "cures" the problem here too.
>
> Now the tcpdump on Dom0 looks interesting. It repeatedly sees a packet
> with 2880 byte from DomU coming in, which is then dropped and ICMP
> "fragmentation needed" sent back, the DomU resends a 1440 byte packet
> (after some delay), which then goes through, but then the next one is a
> 2880 byte one again, and so on.
>
> FYI: My Dom0 is running NAT, in case this is relevant.
>
> Christophe
>
>
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