netdev - Re: NAT stops forwarding ACKs after PMTU discovery

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Date:	Mon, 19 Aug 2013 16:43:33 +0200
From:	Christoph Paasch <christoph.paasch@...ouvain.be>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	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 19/08/13 - 06:58:05, Eric Dumazet wrote:
> On Mon, 2013-08-19 at 15:49 +0200, Christoph Paasch wrote:
> > It's a TCP-patch, that interprets duplicate-acks with invalid SACK-blocks as
> > duplicate acks in tcp_sock->sacked_out.
> 
> Yeah, but here, this is conntrack who is blocking the thing.

Yes, of course. I know that here conntrack is blocking the dup-ACKs.

Sorry for having added TCP-stack specific things in a conntrack-thread.
I just wanted to highlight that the TCP-stack has also problems with
sequence-number rewriting middleboxes.

> 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.
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