Crazy network problem (solved!)

Gabriel Gunderson gabe at
Sat Apr 21 10:52:27 MDT 2012

On Sat, Apr 21, 2012 at 8:40 AM, Steve Meyers <steve-plug at> wrote:
> So why was the checksum wrong?  It turns out that the virtio driver in
> C6 has some optimizations in it.  It waits until a packet actually hits
> the wire to calculate the checksum.  Internally to the physical host, it
> never bothers -- since it's never going on the wire, it doesn't
> calculate it or check it.  The problem was that OpenVPN was sending
> those bad packets to my home network without fixing the checksum, since
> they never hit the physical machine's NIC.

Thanks for sharing! It sounds like you should be able to choose a
different driver and avoid moving this to a physical host, right? If
so, why not do that?


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