From owner-freebsd-net@FreeBSD.ORG  Thu Dec 17 19:28:46 2009
Return-Path: <owner-freebsd-net@FreeBSD.ORG>
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 797771065670
	for <freebsd-net@freebsd.org>; Thu, 17 Dec 2009 19:28:46 +0000 (UTC)
	(envelope-from qing.li@bluecoat.com)
Received: from whisker.bluecoat.com (whisker.bluecoat.com [216.52.23.28])
	by mx1.freebsd.org (Postfix) with ESMTP id 619D88FC17
	for <freebsd-net@freebsd.org>; Thu, 17 Dec 2009 19:28:46 +0000 (UTC)
Received: from bcs-mail03.internal.cacheflow.com ([10.2.2.95])
	by whisker.bluecoat.com (8.14.2/8.14.2) with ESMTP id nBHJSgwH014161;
	Thu, 17 Dec 2009 11:28:42 -0800 (PST)
X-MimeOLE: Produced By Microsoft Exchange V6.5
Content-class: urn:content-classes:message
MIME-Version: 1.0
Content-Type: text/plain;
	charset="gb2312"
Content-Transfer-Encoding: quoted-printable
Date: Thu, 17 Dec 2009 11:28:36 -0800
Message-ID: <B583FBF374231F4A89607B4D08578A4306236179@bcs-mail03.internal.cacheflow.com>
In-Reply-To: <31264189.456321261063444556.JavaMail.coremail@bj126app49.126.com>
X-MS-Has-Attach: 
X-MS-TNEF-Correlator: 
Thread-Topic: Bug discussion:Tcp snd_nxt will not be increased.
Thread-Index: Acp/SY4IAyf5MlVuTLeGlVWWUClLyAABIxNA
References: <31264189.456321261063444556.JavaMail.coremail@bj126app49.126.com>
From: "Li, Qing" <qing.li@bluecoat.com>
To: =?gb2312?B?zfW0urfn?= <fengdreamer@126.com>,
	"freebsd-net" <freebsd-net@freebsd.org>
Cc: 
Subject: RE: Bug discussion:Tcp snd_nxt will not be increased.
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: Thu, 17 Dec 2009 19:28:46 -0000

Hi,

Could you please tell us what version you are running?

>
> If the tcp_output just have some error, for example: when alloc mbuf,
> it returns NULL, and then the snd_nxt number will not be return to
> normal.
> If just in this time, SYN Ack arrives, freeBSD can't handle this
> situdition.
>

I have seen a related issue in older versions that I fixed, but it's =
from=20
the SYN+ACK perspective. If my memory serves me right, local listener =
receives
a SYN packet, transmits the SYN+ACK, but memory allocation fails, so the
SYN+ACK packet was never transmitted onto the wire, however, the SEQ =
advanced
by 1. As a result of SEQ update, the retransmitted SYN packet from the =
other=20
end were discard as duplicates, eventually the connection times out.

-- Qing