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Re: [Xen-devel] skb_checksum_setup and NAT

To: Christophe Saout <christophe@xxxxxxxx>, Xen Devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] skb_checksum_setup and NAT
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Thu, 28 Sep 2006 18:35:27 +0100
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On 28/9/06 17:12, "Christophe Saout" <christophe@xxxxxxxx> wrote:

> Why do you need this mess? Isn't the normal ip_summed sufficient? The
> patches don't contain any annotations.

The Linux network stack doesn't expect to be able to receive packets that
have their protocol-checksum field empty. So we have to add extra packet
flags to signal this situation. It does create something of a mess unless
all parts of the network stack know what's going on. I heard that the
networking maintainers were working on a more generic scheme that we should
be able to make use of. Apart from that, the stack needs to make sure that
the proto_csum_blank field is cleared whenever it fills in the full

For now, if it causes you problems and you just want stuff to work, you can
run ethtool on your interface in domU: 'ethtool -K eth0 tx off'.

 -- Keir

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