netdev - Re: TCP connection stalls under 2.6.24.7

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Message-Id: <200807151810.45942.thomas.jarosch@intra2net.com>
Date:	Tue, 15 Jul 2008 18:10:42 +0200
From:	Thomas Jarosch <thomas.jarosch@...ra2net.com>
To:	Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>
Cc:	netdev@...r.kernel.org, Patrick McHardy <kaber@...sh.net>,
	Sven Riedel <sr@...urenet.de>,
	Netfilter Developer Mailing List 
	<netfilter-devel@...r.kernel.org>,
	Dâniel Fraga <fragabr@...il.com>
Subject: Re: TCP connection stalls under 2.6.24.7

> Luckily I'm able to reproduce the problem locally using an ADSL line from
> the same provider, so I'll now bisect the kernel from 2.6.23.17 to 2.6.24.

After bisecting for hours, l only had ten revisions left to test.
There was this commit that caught my eye:

------------------------------
commit c96fd3d461fa495400df24be3b3b66f0e0b152f9
Author: Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
Date:   Thu Sep 20 11:36:37 2007 -0700

    [TCP]: Enable SACK enhanced FRTO (RFC4138) by default
------------------------------

This change sets the value of "tcp_frto" to 2 by default.
If I reset it to zero, the connection works immediately.
@Dâniel Fraga: Does disabling tcp_frto work for you, too?

Disabling tcp_sack makes no difference. To summarize the situation,
I had two different cases of stalling TCP connections, both connecting
to busy SMTP relays servers which probably drop some packets here and there.

I can easily reproduce the problem, so how do we go from here?

Cheers,
Thomas
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