From owner-freebsd-net@FreeBSD.ORG  Fri Jul 31 16:41:38 2009
Return-Path: <owner-freebsd-net@FreeBSD.ORG>
Delivered-To: net@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 39805106566B
	for <net@freebsd.org>; Fri, 31 Jul 2009 16:41:38 +0000 (UTC)
	(envelope-from julian@elischer.org)
Received: from outW.internet-mail-service.net (outw.internet-mail-service.net
	[216.240.47.246])
	by mx1.freebsd.org (Postfix) with ESMTP id 21F568FC23
	for <net@freebsd.org>; Fri, 31 Jul 2009 16:41:38 +0000 (UTC)
	(envelope-from julian@elischer.org)
Received: from idiom.com (mx0.idiom.com [216.240.32.160])
	by out.internet-mail-service.net (Postfix) with ESMTP id 4E1E7B4EAF;
	Fri, 31 Jul 2009 09:27:06 -0700 (PDT)
X-Client-Authorized: MaGic Cook1e
X-Client-Authorized: MaGic Cook1e
Received: from julian-mac.elischer.org (home.elischer.org [216.240.48.38])
	by idiom.com (Postfix) with ESMTP id 027DF2D6004;
	Fri, 31 Jul 2009 09:27:05 -0700 (PDT)
Message-ID: <4A731B5F.6060301@elischer.org>
Date: Fri, 31 Jul 2009 09:27:11 -0700
From: Julian Elischer <julian@elischer.org>
User-Agent: Thunderbird 2.0.0.22 (Macintosh/20090605)
MIME-Version: 1.0
To: Hartmut.Brandt@dlr.de
References: <E086A96846579E4F932C168218DB1E550243BA@exbe5.intra.dlr.de>
In-Reply-To: <E086A96846579E4F932C168218DB1E550243BA@exbe5.intra.dlr.de>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Cc: net@freebsd.org
Subject: Re: TCP RST question
X-BeenThere: freebsd-net@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Networking and TCP/IP with FreeBSD <freebsd-net.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-net>,
	<mailto:freebsd-net-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-net>
List-Post: <mailto:freebsd-net@freebsd.org>
List-Help: <mailto:freebsd-net-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-net>,
	<mailto:freebsd-net-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Fri, 31 Jul 2009 16:41:38 -0000

Hartmut.Brandt@dlr.de wrote:
> Hi all,
> 
> I'm looking at our TCP stack and found a change that was introduced with
> the syncache. The original BSD code did send an RST segment when the
> connection timed out in SYN-RECEIVED. The TCP would retransmit the
> SYN+ACK several times and then give up and RST the peer.
> 
> With syncache, however, our TCP doesn't send the RST anymore. It just
> silently discards local state.
> 
> So the question is whether TCP is supposed to RST or not. Looking at
> RFC793 I found nothing useful. It talks about sending RSTs as response
> to incoming segments and it looks like TCP is never supposed to give up
> retransmitting. The state diagram has no line from SYN-RECEIVED to
> CLOSED. Stevens, on the other hand, has this line and it is labeled
> 'send: RST'.
> 
> So the questions are:
> 
>  - is TCP supposed to send an RST when it times out in SYN-RECEIVED?
>  - why was this changed (I suppose it is just one of the regressions
> introduced with the syn-cache).

maybe something to do with avoiding DOS or something?

> harti
> 
> NB: does anybody know a good mailing list where this kind of questions
> can be discussed?
> _______________________________________________
> freebsd-net@freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-net
> To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org"