netdev - Re: IPv6 xfrm GSO fragmentation bug

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Message-ID: <20150907100044.GH25499@secunet.com>
Date:	Mon, 7 Sep 2015 12:00:45 +0200
From:	Steffen Klassert <steffen.klassert@...unet.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
CC:	<netdev@...r.kernel.org>
Subject: Re: IPv6 xfrm GSO fragmentation bug

On Fri, Sep 04, 2015 at 01:21:06PM +0800, Herbert Xu wrote:
> On Mon, Aug 31, 2015 at 03:35:26PM +0800, Herbert Xu wrote:
> > 
> > I see where the bug came from.  Indeed IPv6 does do fragmentation
> > but only for tunnel mode.  While your patch added a check that also
> > affected transport mode.  So in addition to the GSO fix we should
> > also make the MTU check conditional to tunnel mode.
> 
> Here is the patch:
> 
> ---8<---
> ipv6: Fix IPsec pre-encap fragmentation check
> 
> The IPv6 IPsec pre-encap path performs fragmentation for tunnel-mode
> packets.  That is, we perform fragmentation pre-encap rather than
> post-encap.
> 
> A check was added later to ensure that proper MTU information is
> passed back for locally generated traffic.  Unfortunately this
> check was performed on all IPsec packets, including transport-mode
> packets.
> 
> What's more, the check failed to take GSO into account.
> 
> The end result is that transport-mode GSO packets get dropped at
> the check.
> 
> This patch fixes it by moving the tunnel mode check forward as well
> as adding the GSO check.
> 
> Fixes: dd767856a36e ("xfrm6: Don't call icmpv6_send on local error")
> Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

Applied to the ipsec tree, thanks Herbert!
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