From owner-freebsd-net@FreeBSD.ORG Thu Sep 14 09:30:11 2006 Return-Path: X-Original-To: freebsd-net@FreeBSD.org Delivered-To: freebsd-net@FreeBSD.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 63A5916A4AB; Thu, 14 Sep 2006 09:30:11 +0000 (UTC) (envelope-from ru@rambler-co.ru) Received: from relay0.rambler.ru (relay0.rambler.ru [81.19.66.187]) by mx1.FreeBSD.org (Postfix) with ESMTP id BEEDC43D55; Thu, 14 Sep 2006 09:30:03 +0000 (GMT) (envelope-from ru@rambler-co.ru) Received: from relay0.rambler.ru (localhost [127.0.0.1]) by relay0.rambler.ru (Postfix) with ESMTP id A3AC85C96; Thu, 14 Sep 2006 13:30:02 +0400 (MSD) Received: from edoofus.park.rambler.ru (unknown [81.19.65.108]) by relay0.rambler.ru (Postfix) with ESMTP id 971365C67; Thu, 14 Sep 2006 13:30:02 +0400 (MSD) Received: (from ru@localhost) by edoofus.park.rambler.ru (8.13.8/8.13.8) id k8E9U6tZ026801; Thu, 14 Sep 2006 13:30:06 +0400 (MSD) (envelope-from ru) Date: Thu, 14 Sep 2006 13:30:06 +0400 From: Ruslan Ermilov To: Andre Oppermann Message-ID: <20060914093006.GE26261@rambler-co.ru> References: <44FAE332.4010209@freebsd.org> <20060913190241.S13138@is.park.rambler.ru> <45085472.5040903@freebsd.org> <20060913230748.P14337@is.park.rambler.ru> <45086AAF.108@freebsd.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="ZwgA9U+XZDXt4+m+" Content-Disposition: inline In-Reply-To: <45086AAF.108@freebsd.org> User-Agent: Mutt/1.5.13 (2006-08-11) X-Virus-Scanned: No virus found Cc: freebsd-net@FreeBSD.org, Igor Sysoev , silby@FreeBSD.org Subject: Re: Improved TCP syncookie implementation 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: Thu, 14 Sep 2006 09:30:11 -0000 --ZwgA9U+XZDXt4+m+ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Sep 13, 2006 at 10:31:43PM +0200, Andre Oppermann wrote: > Igor Sysoev wrote: > >Well, suppose protocol similar to SSH or SMTP: > > > >1) the client calls connect(), it sends SYN; > >2) the server receives SYN and sends SYN/ACK with cookie; > >3) the client receives SYN/ACK and sends ACK; > >4) the client returns successfully from connect() and calls read(); > >5) the ACK is lost; > >6) the server does not about this connection, so application can not > > accept() it, and it can not send() HELO message. > >7) the client gets ETIMEDOUT from read(). > > > >Where in this sequence client may retransmit its ACK ? >=20 > Never. You're correct. There is no data that would cause a retransmit > if the application is waiting for a server prompt first. I shouldn't > write wrong explanations when I'm tired, hungry and in between two tasks.= ;) >=20 > This problem is the reason why we don't switch entirely to syncookies > and still keep syncache as is. >=20 Perhaps it would be a good idea to remove net.inet.tcp.syncookies_only then? In any case, please don't forget to update the syncache(4) manpage to reflect your changes, and if you decide not to remove this sysctl, please add a warning of its potential to break a protocol. Cheers, --=20 Ruslan Ermilov ru@FreeBSD.org FreeBSD committer --ZwgA9U+XZDXt4+m+ Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (FreeBSD) iD8DBQFFCSEeqRfpzJluFF4RAts1AJ9RMcvus0lo8ag4/X41W1+gSip2jQCZAU+9 QuQJsMytIv7ja4rzuOEY8XY= =4K+D -----END PGP SIGNATURE----- --ZwgA9U+XZDXt4+m+--