From owner-freebsd-net@FreeBSD.ORG Sat Mar 31 08:06:41 2012 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 729171065747 for ; Sat, 31 Mar 2012 08:06:41 +0000 (UTC) (envelope-from darernr@freebsd.org) Received: from out1-smtp.messagingengine.com (out1-smtp.messagingengine.com [66.111.4.25]) by mx1.freebsd.org (Postfix) with ESMTP id 378D68FC08 for ; Sat, 31 Mar 2012 08:06:41 +0000 (UTC) Received: from compute3.internal (compute3.nyi.mail.srv.osa [10.202.2.43]) by gateway1.nyi.mail.srv.osa (Postfix) with ESMTP id C5461203C3 for ; Sat, 31 Mar 2012 04:06:40 -0400 (EDT) Received: from frontend1.nyi.mail.srv.osa ([10.202.2.160]) by compute3.internal (MEProxy); Sat, 31 Mar 2012 04:06:40 -0400 DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d= messagingengine.com; h=message-id:date:from:mime-version:to:cc :subject:references:in-reply-to:content-type :content-transfer-encoding; s=smtpout; bh=kTz8FQ8pTe58AD4Tl7TtrU g3yso=; b=NE+hix5W4J44lJb5JWywMCdfDOi2B7iJA3zZ3Ll5xCO8+mn6WSv8hD PUiyyCESg7JplZeWXBbMMfItlqRiNcNuC6/5xBnLZojNEr2gYWjcz1zTNHUrvsgS AuReye7KIvAx7OLxG5EtSLMXF1SQjX+Jk11GPcryP4Pnz3eTMujAs= X-Sasl-enc: sMXR68jt46DJvYlcGV0Y3Q+hAJEYQUINI4lmR/stROo2 1333181200 Received: from [192.168.1.23] (dsl-202-45-110-141-static.VIC.netspace.net.au [202.45.110.141]) by mail.messagingengine.com (Postfix) with ESMTPSA id 452238E0201; Sat, 31 Mar 2012 04:06:38 -0400 (EDT) Message-ID: <4F76C929.5080400@freebsd.org> Date: Sat, 31 Mar 2012 20:06:49 +1100 From: Darren Reed User-Agent: Thunderbird 2.0.0.24 (Windows/20100228) MIME-Version: 1.0 To: Andre Oppermann References: <4F75C1A3.4030401@freebsd.org> <4F75D9ED.7080707@freebsd.org> In-Reply-To: <4F75D9ED.7080707@freebsd.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: darrenr@freebsd.org, freebsd-net@freebsd.org Subject: Re: FreeBSD TCP ignores zero window size X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 31 Mar 2012 08:06:41 -0000 Andre Oppermann wrote: > On 30.03.2012 16:22, Darren Reed wrote: >> I've been tracking down some problems with FreeBSD's sending >> of TCP packets and seem to have come to the conclusion that >> in FreeBSD 8.2-RELEASE, when the system is working with a >> TCP connection that has a moderate delay in it, FreeBSD's >> TCP ignores the other end telling it that the window size >> is now 0 and continues to send data. I suspect that this is >> meant to make sense because it is expecting that the ACK >> that will open up the window is already in transit. But that >> only accounts for the condition where the TCP on FreeBSD can >> compute and decide that the remote TCP will have its buffer >> full. What I find harder to accept is that when FreeBSD's >> TCP receives a TCP packet from the remote end advertising >> a window of 0, FreeBSD's response is to send more data and >> not a window probe or is that now the expected behaviour? >> And whilst you might say "ok" for a packet of data, I'm >> somewhat hard pressed to explain why FreeBSD's TCP sends >> multiple packets with data in them after receiving a TCP >> packet from the other end advertising a zero window size. >> >> However this causes a problem with firewalls (;_) that are >> close to the FreeBSD end because for them, it appears that >> FreeBSD is sending data outside of its window. >> >> Is this a known problem? >> If so, has it been fixed in a later version of FreeBSD? >> (No, I haven't tested anything other than 8.2) > > The window update acceptance test is too restrictive. In your case > the last updated seq# tracking gets it wrong and prevents the update. > > The code hasn't changed for a long time and newer versions behave the > same. > > The concept patch below simplifies the logic, better tracks the seq# > and is a bit more permissive. > This patch does not apply cleanly against 8.2 (BYTES_THIS_ACK is not present in 8.2.) I'll add in the obvious missing #defines and see how I go. Darren