netdev - RE: [PATCH] xen-netfront: reset skb transport header before checksum

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Date:	Tue, 12 May 2015 07:00:16 -0700 (PDT)
From:	Venkat Venkatsubra <venkat.x.venkatsubra@...cle.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org, xen-devel@...ts.xenproject.org,
	davem@...emloft.net, david.vrabel@...rix.com,
	Konrad Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	wei.liu2@...rix.com, paul.durrant@...rix.com
Subject: RE: [PATCH] xen-netfront: reset skb transport header before checksum

> 
> This looks bogus for IPv6.
> 
> I would rather fix skb_checksum_setup_ip() and
> skb_checksum_setup_ipv6(), since you already use correctly
> skb_maybe_pull_tail() there.
> 
> In general, setting network and transport header at this point seems
> extra work.
> 

Yes, I missed the IPv6 case. ;-) Thanks Eric for pointing that out.
Looking further the below commit might have already resolved the issue.

commit e5d5decaedf41f5b03e6819789cc3ba8744d9f54
Author: Jason Wang <jasowang@...hat.com>
Date:   Tue Mar 26 23:11:20 2013 +0000

    net: core: let skb_partial_csum_set() set transport header

    For untrusted packets with partial checksum, we need to set the transport he
    for precise packet length estimation. We can just let skb_pratial_csum_set()
    do this to avoid extra call to skb_flow_dissect() and simplify the caller.

    Cc: Eric Dumazet <edumazet@...gle.com>
    Signed-off-by: Jason Wang <jasowang@...hat.com>
    Acked-by: Eric Dumazet <edumazet@...gle.com>
    Signed-off-by: David S. Miller <davem@...emloft.net>

The guest we were running was older to this and didn't have the above commit.

Thanks.

Venkat
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