From owner-freebsd-security@FreeBSD.ORG Wed Apr 21 14:59:43 2004 Return-Path: Delivered-To: freebsd-security@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 5964916A4CE for ; Wed, 21 Apr 2004 14:59:43 -0700 (PDT) Received: from rwcrmhc12.comcast.net (rwcrmhc12.comcast.net [216.148.227.85]) by mx1.FreeBSD.org (Postfix) with ESMTP id 2761843D55 for ; Wed, 21 Apr 2004 14:59:43 -0700 (PDT) (envelope-from garycor@comcast.net) Received: from comcast.net (pcp09118143pcs.union01.nj.comcast.net[69.142.234.88]) by comcast.net (rwcrmhc12) with SMTP id <2004042121594201400i4dfne> (Authid: garycor); Wed, 21 Apr 2004 21:59:42 +0000 Message-ID: <4086EED7.3070808@comcast.net> Date: Wed, 21 Apr 2004 17:59:51 -0400 From: Gary Corcoran User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.5) Gecko/20031007 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Tillman Hodgson References: <6.0.3.0.0.20040420144001.0723ab80@209.112.4.2> <200404201332.40827.dr@kyx.net> <20040421111003.GB19640@lum.celabo.org> <6.0.3.0.0.20040421121715.04547510@209.112.4.2> <20040421165454.GB20049@lum.celabo.org> <6.0.3.0.0.20040421132605.0901bb40@209.112.4.2> <48FCF8AA-93CF-11D8-9C50-000393C94468@sarenet.es> <6.0.3.0.0.20040421161217.05453308@209.112.4.2> <75226E9B-93D3-11D8-90F9-003065ABFD92@mac.com> <4086E522.7090303@comcast.net> <20040421214445.GX476@seekingfire.com> In-Reply-To: <20040421214445.GX476@seekingfire.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit cc: freebsd-security@freebsd.org Subject: Re: Other possible protection against RST/SYN attacks (was Re: TCP RST attack X-BeenThere: freebsd-security@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Security issues [members-only posting] List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 21 Apr 2004 21:59:43 -0000 Tillman Hodgson wrote: > On Wed, Apr 21, 2004 at 05:18:26PM -0400, Gary Corcoran wrote: > >>Charles Swiger wrote: >> >>>The default TTL gets decremented with every hop, which means that a >>>packet coming in with a TTL of 255 had to be sent by a directly >>>connected system. [ip_ttl is an octet, so it can't hold a larger TTL >>>value.] >> >>Huh? 255-- == 254, not 0. A TTL of 255 just allows the maximum possible >>number of hops, before being declared hopelessly lost. > > > Exactly -- if you see an incoming packet with a TTL of 255, it must've > originated on a directly connected system /or it would've already been > decremented to 254 or lower/. Ah, yes, of course. I thought the original poster was implying that the packet could only exist on a direct connection, and wouldn't be passed along to another hop if it had a TTL of 255. But I guess I just got the wrong impression - sorry for the confusion. In any event, it still seems like 255 is overkill for this application... Gary