From owner-freebsd-hackers Fri Jan 4 15:12:32 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from swan.prod.itd.earthlink.net (swan.mail.pas.earthlink.net [207.217.120.123]) by hub.freebsd.org (Postfix) with ESMTP id E0EAC37B417 for ; Fri, 4 Jan 2002 15:11:56 -0800 (PST) Received: from pool0477.cvx22-bradley.dialup.earthlink.net ([209.179.199.222] helo=mindspring.com) by swan.prod.itd.earthlink.net with esmtp (Exim 3.33 #1) id 16MdV3-0004Mr-00; Fri, 04 Jan 2002 15:11:45 -0800 Message-ID: <3C3636B1.4D5F42A4@mindspring.com> Date: Fri, 04 Jan 2002 15:11:45 -0800 From: Terry Lambert X-Mailer: Mozilla 4.7 [en]C-CCK-MCD {Sony} (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: Guido van Rooij Cc: William Carrel , freebsd-hackers@freebsd.org Subject: Re: path_mtu_discovery References: <26E71536-013D-11D6-8ED3-003065D5E9A4@infospace.com> <3C36149B.B9C02DCF@mindspring.com> <20020104223235.GA64301@gvr.gvr.org> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Guido van Rooij wrote: > > > ipfilter with 'keep state' on the connections will automatically allow > > > back in relevant ICMP messages such as mustfrag. > > > > Heh... I need to try to write a "mustfrag" daemon, which will > > spoof them back whenever it sees traffic... and see what happens. > > The sender will start sending smaller segments. That's it. > But if you are in the patch between sender and receiver you can do worse > things than that. I knew that I could multiply the number of packets sent by a factor of 5... I was pointing out a flaw in the idea of allowing path MTU ICMP back in, unconditionally... Now ask me how to DOS attack any server daemon that works by using the "sendfile" interface... PS: *Don't* ask me how the SYN-cache overflow SYN-cookie code can be ACK-flooded, to make the kernel spend all its time doing MD5 calculations, since that one is obvious... -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message