netdev - Re: [PATCH] xfrm6: Do not use xfrm_local_error for path MTU issues in tunnels

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Message-ID: <20150528044918.GA4333@gondor.apana.org.au>
Date:	Thu, 28 May 2015 12:49:19 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Alexander Duyck <alexander.h.duyck@...hat.com>
Cc:	steffen.klassert@...unet.com, davem@...emloft.net,
	netdev@...r.kernel.org, linux-crypto@...r.kernel.org
Subject: Re: [PATCH] xfrm6: Do not use xfrm_local_error for path MTU issues
 in tunnels

On Wed, May 27, 2015 at 10:40:32AM -0700, Alexander Duyck wrote:
> This change makes it so that we use icmpv6_send to report PMTU issues back
> into tunnels in the case that the resulting packet is larger than the MTU
> of the outgoing interface.  Previously xfrm_local_error was being used in
> this case, however this was resulting in no changes, I suspect due to the
> fact that the tunnel itself was being kept out of the loop.
> 
> This patch fixes PMTU problems seen on ip6_vti tunnels and is based on the
> behavior seen if the socket was orphaned.  Instead of requiring the socket
> to be orphaned this patch simply defaults to using icmpv6_send in the case
> that the frame came though a tunnel.
> 
> Signed-off-by: Alexander Duyck <alexander.h.duyck@...hat.com>

Does this still work with normal tunnel mode and identical inner
and outer addresses? I recall we used to have a bug where in that
situation the kernel would interpret the ICMP message as a reduction
in outer MTU and thus resulting in a loop where the MTU keeps
getting smaller.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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