netdev - Re: [PATCH net-next] ipv4: fix tunneled VM traffic over hw VXLAN/GRE GSO NIC

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Date:	Wed, 18 Dec 2013 16:35:33 -0800
From:	Stephen Hemminger <stephen@...workplumber.org>
To:	Wei-Chun Chao <weichunc@...mgrid.com>
Cc:	davem@...emloft.net, eric.dumazet@...il.com, ast@...mgrid.com,
	netdev@...r.kernel.org, joseph.gasparakis@...el.com,
	or.gerlitz@...il.com
Subject: Re: [PATCH net-next] ipv4: fix tunneled VM traffic over hw
 VXLAN/GRE GSO NIC

On Wed, 18 Dec 2013 11:02:48 -0800
Wei-Chun Chao <weichunc@...mgrid.com> wrote:

> This is also seen on 'net'.
> 
> VM to VM GSO traffic is broken if it goes through VXLAN or GRE
> tunnel and the physical NIC on the host supports hardware VXLAN/GRE
> GSO offload (e.g. bnx2x and next-gen mlx4).
> 
> Two issues -
> (VXLAN) VM traffic has SKB_GSO_DODGY and SKB_GSO_UDP_TUNNEL with
> SKB_GSO_TCP/UDP set depending on the inner protocol. GSO header
> integrity check fails in udp4_ufo_fragment if inner protocol is
> TCP. Also gso_segs is calculated incorrectly using skb->len that
> includes tunnel header. Fix: robust check should only be applied
> to the inner packet.
> 
> (VXLAN & GRE) Once GSO header integrity check passes, NULL segs
> is returned and the original skb is sent to hardware. However the
> tunnel header is already pulled. Fix: tunnel header needs to be
> restored so that hardware can perform GSO properly on the original
> packet.
> 
> Signed-off-by: Wei-Chun Chao <weichunc@...mgrid.com>
> ---

Is there someway the tunnel could fixup the GSO bits?
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