netdev - Re: [PATCH] tcp FRTO: in-order-only "TCP proxy" fragility workaround

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Message-Id: <20080822.143709.65615512.davem@davemloft.net>
Date:	Fri, 22 Aug 2008 14:37:09 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	fragabr@...il.com
Cc:	ilpo.jarvinen@...sinki.fi, thomas.jarosch@...ra2net.com,
	billfink@...dspring.com, netdev@...r.kernel.org, kaber@...sh.net,
	netfilter-devel@...r.kernel.org, kadlec@...ckhole.kfki.hu
Subject: Re: [PATCH] tcp FRTO: in-order-only "TCP proxy" fragility
 workaround

From: Dâniel Fraga <fragabr@...il.com>
Date: Fri, 22 Aug 2008 18:32:24 -0300

> On Wed, 20 Aug 2008 15:37:13 +0300 (EEST)
> "Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi> wrote:
> 
> > Based on irc discussion with davem, there is a htb bug which can cause 
> > corruption of the retransmitted TCP packets (and then a discard due to 
> > checksum mismatch). That would also explain the strange headers I noticed 
> > earlier. There's a patch below (should apply to 2.6.26), please put it at 
> > least on the host(s) which use htb (I don't know if both server and the 
> > client do use wondershaper script or just the client). An different 
> > failure symptoms (one could be somehow frto related as FRTO is used while 
> > retransmitting) are also quite well explainable.
> > 
> > But FRTO is mostly not a suspect based on the tcpdump you provided (no 
> > FRTO workaround would help in that).
> 
> 	Ilpo, I have good news. I decided to disable completely HTB and
> the problem seems to have gone. And frto is enabled, of course. So the
> problem was with HTB, not frto as I thought.
> 
> 	The HTB patches you provided are going to be included in the
> next 2.6.27 kernel, right?

Yes, but it's important that you verify that the patch makes the
problem go away when HTB is enabled.  Please make this test if you
can.
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