From mboxrd@z Thu Jan  1 00:00:00 1970
From: John Heffner <jheffner@psc.edu>
Subject: Re: Possible BUG in IPv4 TCP window handling, all recent 2.4.x/2.6.x kernels
Date: Fri, 2 Sep 2005 10:16:57 -0400
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References: <Pine.LNX.4.61.0509011713240.6083@guppy.limebrokerage.com> <20050901.154300.118239765.davem@davemloft.net> <Pine.LNX.4.61.0509011845040.6083@guppy.limebrokerage.com> <2d02c76a84655d212634a91002b3eccd@psc.edu> <20050902134807.GB12617@yakov.inr.ac.ru>
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Cc: Ion Badulescu <lists@limebrokerage.com>,
	linux-kernel@vger.kernel.org,
	"David S. Miller" <davem@davemloft.net>, linux-net@vger.kernel.org,
	netdev@vger.kernel.org
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In-Reply-To: <20050902134807.GB12617@yakov.inr.ac.ru>
To: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: netdev.vger.kernel.org

On Sep 2, 2005, at 9:48 AM, Alexey Kuznetsov wrote:

> Hello!
>
>> If you overflow the socket's memory bound, it ends up calling
>> tcp_clamp_window().  (I'm not sure this is really the right thing to 
>> do
>> here before trying to collapse the queue.)
>
> Collapsing is too expensive procedure, it is rather an emergency 
> measure.
> So, tcp collapses queue, when it is necessary, but it must reduce 
> window
> as well.

Right.

I wonder if clamping the window though is too harsh.  Maybe just 
setting the rcv_ssthresh down is better?  Why the distinction between 
in-order and out-of-order data?  Because you expect in-order data to be 
a persistent case?

   -John