netdev - Re: NAT stops forwarding ACKs after PMTU discovery

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Date:	Mon, 19 Aug 2013 08:32:05 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Phil Oester <kernel@...uxace.com>
Cc:	Christoph Paasch <christoph.paasch@...ouvain.be>,
	Corey Hickey <bugfood-ml@...ooh.org>,
	Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
	Linux Netdev List <netdev@...r.kernel.org>,
	netfilter-devel@...r.kernel.org
Subject: Re: NAT stops forwarding ACKs after PMTU discovery

On Mon, 2013-08-19 at 07:35 -0700, Phil Oester wrote:
> On Mon, Aug 19, 2013 at 06:58:05AM -0700, Eric Dumazet wrote:
> > Yeah, but here, this is conntrack who is blocking the thing.
> > 
> > TCP receiver has no chance to 'fix' it.
> > 
> > See conntrack is one of those buggy middle box as well.
> > 
> > So if you want to properly handle this mess, you'll also have to fix
> > conntrack.
> 
> Better to fix the box which is randomizing the acks and ignoring
> the SACKs.  Usually these are older Cisco PIX/ASA devices which just
> need a code upgrade.  


Having a patch to relax things could be evaluated, if not adding new
problems ( http://en.wikipedia.org/wiki/Robustness_principle ) 



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