netdev - Re: [net PATCH] gro: Allow tunnel stacking in the case of FOU/GUE

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Date:	Mon, 28 Mar 2016 19:54:06 -0700
From:	Jesse Gross <jesse@...nel.org>
To:	Alexander Duyck <aduyck@...antis.com>
Cc:	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Alexander Duyck <alexander.duyck@...il.com>,
	Tom Herbert <tom@...bertland.com>
Subject: Re: [net PATCH] gro: Allow tunnel stacking in the case of FOU/GUE

On Mon, Mar 28, 2016 at 4:58 PM, Alexander Duyck <aduyck@...antis.com> wrote:
> This patch should fix the issues seen with a recent fix to prevent
> tunnel-in-tunnel frames from being generated with GRO.  The fix itself is
> correct for now as long as we do not add any devices that support
> NETIF_F_GSO_GRE_CSUM.  When such a device is added it could have the
> potential to mess things up due to the fact that the outer transport header
> points to the outer UDP header and not the GRE header as would be expected.
>
> Fixes: fac8e0f579695 ("tunnels: Don't apply GRO to multiple layers of encapsulation.")
> Signed-off-by: Alexander Duyck <aduyck@...antis.com>
> ---
>
> This should allow us to keep the fix that Jesse added without breaking the
> 3 cases that Tom called out in terms of FOU/GUE.
>
> Additional work will be needed in net-next as we probably need to make it
> so that offloads work correctly when we get around to supporting
> NETIF_F_GSO_GRE_CSUM.

Thanks, this looks like a reasonable fix to me. I agree that there is
more that can be done in the future to improve things but this should
restore GRO while still avoiding possible issues.