From owner-freebsd-net@FreeBSD.ORG Fri Apr 1 12:43:48 2011 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 EEC8A1065703 for ; Fri, 1 Apr 2011 12:43:48 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42]) by mx1.freebsd.org (Postfix) with ESMTP id C75928FC14 for ; Fri, 1 Apr 2011 12:43:48 +0000 (UTC) Received: from bigwig.baldwin.cx (66.111.2.69.static.nyinternet.net [66.111.2.69]) by cyrus.watson.org (Postfix) with ESMTPSA id 79E0346BA4; Fri, 1 Apr 2011 08:43:48 -0400 (EDT) Received: from jhbbsd.localnet (unknown [209.249.190.124]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id 104988A01B; Fri, 1 Apr 2011 08:43:48 -0400 (EDT) From: John Baldwin To: "Stefan `Sec` Zehl" Date: Fri, 1 Apr 2011 08:32:49 -0400 User-Agent: KMail/1.13.5 (FreeBSD/8.2-CBSD-20110325; KDE/4.5.5; amd64; ; ) References: <4D8B99B4.4070404@FreeBSD.org> <201103300838.09608.jhb@freebsd.org> <20110331234017.GC3308@ice.42.org> In-Reply-To: <20110331234017.GC3308@ice.42.org> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201104010832.49214.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.6 (bigwig.baldwin.cx); Fri, 01 Apr 2011 08:43:48 -0400 (EDT) Cc: freebsd-net@freebsd.org Subject: Re: The tale of a TCP bug 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: Fri, 01 Apr 2011 12:43:49 -0000 On Thursday, March 31, 2011 7:40:17 pm Stefan `Sec` Zehl wrote: > On Wed, Mar 30, 2011 at 08:38 -0400, John Baldwin wrote: > > There is at least one case I know of related to a bug I reported earlier > > where a window probe from a remote connection can cause rcv_nxt to advance > > past rcv_adv by one. However, I think we want to know about those cases, > > and we should probably be treating rcv_adv - rcv_nxt as if it is zero in > > that case, not -1 (my patch in my original e-mail does just that in a > > different place in tcp_output() when we calculate the window "for real"). > > I've been running for about a day now with the committed patch and > adv_neg is still zero: Well, after thinking some more, rcv_nxt == rcv_adv + 1 will not make adv negative. > | ice:~>uptime; sysctl net.inet.tcp.adv_neg > | 1:36AM up 1 day, 4:52, 1 user, load averages: 0.12, 0.06, 0.05 > | net.inet.tcp.adv_neg: 0 > > I'll of course monitor this value and report back if I ever see it > increase :-) Great, thanks! -- John Baldwin