netdev - Re: Possible regression: "gre: Use inner mac length when computing tunnel length"

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Message-ID: <CA+mtBx-WsgMRAYDUaPiVaBt43cRx7tb-0hRJ+6Eao8vjd3j8aQ@mail.gmail.com>
Date:	Tue, 9 Dec 2014 13:23:54 -0800
From:	Tom Herbert <therbert@...gle.com>
To:	Timo Teras <timo.teras@....fi>
Cc:	Alexander Duyck <alexander.h.duyck@...hat.com>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: Possible regression: "gre: Use inner mac length when computing
 tunnel length"

On Mon, Dec 8, 2014 at 10:44 PM, Timo Teras <timo.teras@....fi> wrote:
> On Tue, 9 Dec 2014 08:26:45 +0200
> Timo Teras <timo.teras@....fi> wrote:
>
>> On Thu, 4 Dec 2014 08:00:19 -0800
>> Tom Herbert <therbert@...gle.com> wrote:
>>
>> > A fix is pending for net. Please try if you can.
>>
>> Finally got to testing this. Unfortunately, this does not seem to fix
>> the issue I am experiencing.
>>
>> Any suggestions?
>
> I think this fix is required, but does not fix the issue.
>
> I suspect my problem is with the fact that I have NBMA GRE tunnel.
>
> In ipgre_xmit() it is gre_handle_offloads() that is called first.
> However, in my case, the GRE header was already pushed earlier via
> header_ops. That's why the packet is skb_pull()'ed in the
> "if (dev->header_ops)" path, so that __gre_xmit can push back the
> header again on it.
>
> I wonder if it is correct to just move the gre_handle_offloads() call
> after the if() block, or if additional fixing is needed to make
> offloads work with nbma tunnels.
>
Yes, that probably is a good idea. iptunnel_handle_offloads resets
inner headers so that inner_mac header is probably wrong when there
are dev->header_ops.

Tom

> /Timo
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