From owner-freebsd-net@FreeBSD.ORG Wed Oct 29 01:04:57 2003 Return-Path: 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 DBA6E16A4CF for ; Wed, 29 Oct 2003 01:04:57 -0800 (PST) Received: from mizar.origin-it.net (mizar.origin-it.net [194.8.96.234]) by mx1.FreeBSD.org (Postfix) with ESMTP id 5AFC143F75 for ; Wed, 29 Oct 2003 01:04:56 -0800 (PST) (envelope-from helge.oldach@atosorigin.com) Received: from matar.hbg.de.int.atosorigin.com (dehsfw3e.origin-it.net [194.8.96.68])h9T94mvG017618 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 29 Oct 2003 10:04:54 +0100 (CET) (envelope-from helge.oldach@atosorigin.com) Received: from galaxy.hbg.de.ao-srv.com (galaxy.hbg.de.ao-srv.com [161.89.20.4])ESMTP id h9T94mno086148; Wed, 29 Oct 2003 10:04:48 +0100 (CET) (envelope-from helge.oldach@atosorigin.com) Received: (from hmo@localhost) by galaxy.hbg.de.ao-srv.com (8.9.3p2/8.9.3/hmo30mar03) id KAA09027; Wed, 29 Oct 2003 10:04:46 +0100 (MET) Message-Id: <200310290904.KAA09027@galaxy.hbg.de.ao-srv.com> In-Reply-To: <86n0bllhez.fsf@t39bsdems.interne.kisoft-services.com> from Eric Masson at "Oct 28, 2003 12:40: 4 pm" To: e-masson@kisoft-services.com (Eric Masson) Date: Wed, 29 Oct 2003 10:04:46 +0100 (MET) From: Helge Oldach X-Address: Atos Origin GmbH, Friesenstraße 13, D-20097 Hamburg, Germany X-Phone: +49 40 7886 7464, Fax: +49 40 7886 9464, Mobile: +49 160 4782517 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit cc: freebsd-net@freebsd.org Subject: Re: ipsec tunnels & packet length issues X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 29 Oct 2003 09:04:58 -0000 Eric Masson: >>>>>> "Michael" == Michael Sierchio writes: > > Michael> You should allow for an IP header with options and the ESP > Michael> header, which is smaller than 1450. For SKIP I use 1366 as the > Michael> advertised MTU, and for IPsec usually 1436, unless I need to > Michael> accomodate ESP and AH, in which case it's smaller. > >Ok, that's fine. > > Michael> It's a known feature of any sort of IP encapsulation. > >I understand. > >I'm no kernel hacker at all, I was just thinking about the ability for >the tunnel endpoint to send back an icmp packet type 3 code 4 when the >packet is too long to be encapsulated. Actually this is the case. Or better, it *should* be happening - I don't know if you see the ICMPs or not. Note that this must be done on the local tunnel endpoint, not the remote one. Helge