Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268033AbUIUUFK (ORCPT ); Tue, 21 Sep 2004 16:05:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268043AbUIUUFJ (ORCPT ); Tue, 21 Sep 2004 16:05:09 -0400 Received: from mail.enyo.de ([212.9.189.167]:13327 "EHLO mail.enyo.de") by vger.kernel.org with ESMTP id S268033AbUIUUFC (ORCPT ); Tue, 21 Sep 2004 16:05:02 -0400 To: "David S. Miller" Cc: herbert@gondor.apana.org.au, paul@clubi.ie, alan@lxorguk.ukuu.org.uk, vph@iki.fi, toon@hout.vanvergehaald.nl, admin@wolfpaw.net, kaukasoi@elektroni.ee.tut.fi, linux-kernel@vger.kernel.org Subject: Re: Linux 2.4.27 SECURITY BUG - TCP Local and REMOTE(verified) Denial of Service Attack References: <873c1bjwwj.fsf@deneb.enyo.de> <20040921125645.05fafd5a.davem@davemloft.net> From: Florian Weimer Date: Tue, 21 Sep 2004 22:04:41 +0200 In-Reply-To: <20040921125645.05fafd5a.davem@davemloft.net> (David S. Miller's message of "Tue, 21 Sep 2004 12:56:45 -0700") Message-ID: <871xgvie1y.fsf@deneb.enyo.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1072 Lines: 31 * David S. Miller: > On Tue, 21 Sep 2004 20:32:12 +0200 > Florian Weimer wrote: > >> > But then you get PMTU problems... >> >> PMTU discovery is not an issue because it's turned off anyway, at >> least by default. > > It's on by default, for both TCP and UDP in the kernel, > and has been so for a long time. Linux is not the reference TCP/IP stack for routers. 8-) > Why would it be off by default? Probably because PMTUD is just a DRAFT STANDARD, and these router folks are usually extremely conservative. Switching the default is dangerous because it's likely to break existing setups, as Herbert noted. > If you disable PMTU discovery, say goodbye to TCP performance. Indeed. On those platforms, the CPU impact is also significant, and the overall increase in BGP convergence time is measurable. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/