netdev - Re: [PATCH net] net/core: Handle csum for CHECKSUM

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Message-Id: <20141226.161726.1781237749642541089.davem@davemloft.net>
Date:	Fri, 26 Dec 2014 16:17:26 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	jay.vosburgh@...onical.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net] net/core: Handle csum for CHECKSUM_COMPLETE VXLAN
 forwarding

From: Jay Vosburgh <jay.vosburgh@...onical.com>
Date: Fri, 19 Dec 2014 15:32:00 -0800

> 
> 	When using VXLAN tunnels and a sky2 device, I have experienced
> checksum failures of the following type:
 ...
> 	These are reliably reproduced in a network topology of:
> 
> container:eth0 == host(OVS VXLAN on VLAN) == bond0 == eth0 (sky2) -> switch
> 
> 	When VXLAN encapsulated traffic is received from a similarly
> configured peer, the above warning is generated in the receive
> processing of the encapsulated packet.  Note that the warning is
> associated with the container eth0.
> 
>         The skbs from sky2 have ip_summed set to CHECKSUM_COMPLETE, and
> because the packet is an encapsulated Ethernet frame, the checksum
> generated by the hardware includes the inner protocol and Ethernet
> headers.
> 
> 	The receive code is careful to update the skb->csum, except in
> __dev_forward_skb, as called by dev_forward_skb.  __dev_forward_skb
> calls eth_type_trans, which in turn calls skb_pull_inline(skb, ETH_HLEN)
> to skip over the Ethernet header, but does not update skb->csum when
> doing so.
> 
> 	This patch resolves the problem by adding a call to
> skb_postpull_rcsum to update the skb->csum after the call to
> eth_type_trans.
> 
> Signed-off-by: Jay Vosburgh <jay.vosburgh@...onical.com>

Applied and queued up for -stable, thanks Jay.
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