netdev - Re: NAT stops forwarding ACKs after PMTU discovery

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Message-ID: <alpine.DEB.2.00.1308192207130.27869@blackhole.kfki.hu>
Date:	Mon, 19 Aug 2013 22:13:59 +0200 (CEST)
From:	Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>
To:	Eric Dumazet <eric.dumazet@...il.com>
cc:	Christoph Paasch <christoph.paasch@...ouvain.be>,
	Corey Hickey <bugfood-ml@...ooh.org>,
	Linux Netdev List <netdev@...r.kernel.org>,
	netfilter-devel@...r.kernel.org
Subject: Re: NAT stops forwarding ACKs after PMTU discovery

On Mon, 19 Aug 2013, 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.
> 
> 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.

I beg you pardon: why conntrack should be relaxed, when it is expected
to do more strict TCP checkings (RFC5961, Section 5.).

Also, it's clearly a broken middle box. Don't shoot the messenger.

Best regards,
Jozsef
-
E-mail  : kadlec@...ckhole.kfki.hu, kadlecsik.jozsef@...ner.mta.hu
PGP key : http://www.kfki.hu/~kadlec/pgp_public_key.txt
Address : Wigner Research Centre for Physics, Hungarian Academy of Sciences
          H-1525 Budapest 114, POB. 49, Hungary
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