From owner-freebsd-net@FreeBSD.ORG Mon Sep 10 17:59:38 2007 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2F69816A41B for ; Mon, 10 Sep 2007 17:59:38 +0000 (UTC) (envelope-from tom@tomjudge.com) Received: from smtp810.mail.ird.yahoo.com (smtp810.mail.ird.yahoo.com [217.146.188.70]) by mx1.freebsd.org (Postfix) with SMTP id 6C01113C458 for ; Mon, 10 Sep 2007 17:59:37 +0000 (UTC) (envelope-from tom@tomjudge.com) Received: (qmail 88504 invoked from network); 10 Sep 2007 17:59:36 -0000 Received: from unknown (HELO ?192.168.1.2?) (thomasjudge@btinternet.com@217.44.142.35 with plain) by smtp810.mail.ird.yahoo.com with SMTP; 10 Sep 2007 17:59:35 -0000 X-YMail-OSG: 9b5jC9IVM1kTpRfLQcfMKsIz7Luo8G4x9dpZxjI1lcKwXV_8 Message-ID: <46E59494.7040507@tomjudge.com> Date: Mon, 10 Sep 2007 20:01:40 +0100 From: Tom Judge User-Agent: Thunderbird 1.5.0.13 (X11/20070824) MIME-Version: 1.0 To: Ivan Alexandrovich References: In-Reply-To: Content-Type: text/plain; charset=KOI8-R; format=flowed Content-Transfer-Encoding: 7bit Cc: freebsd-net@freebsd.org Subject: Re: nested vlans and ethernet frame size 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: Mon, 10 Sep 2007 17:59:38 -0000 Ivan Alexandrovich wrote: > Hi > > I'd like to ask for advice - what is the right place for > setting maximum ethernet frame size in freebsd? > It needs 1526 bytes to allow two vlan tags per packet. > Those tags must be processed by ng_vlan code so > it seems that vlanmtu interface flag will be of no use here. > We're running freebsd6.2-stable and use some Intel pro 100 > card for testing purposes along with QinQ-capable switch. > > Currently frames of 1526 length are sent without problems but > incoming packets of such a size are lost. Since fxp driver > complains about 'discarding oversize frame' it can be supposed that > the problem in this case is not in nic hardware but in > driver. > > As far as I can see in kernel sources (it's a pity I'm not a > programmer :) many ethernet drivers use ETHERNET_MAX_FRAME macro > to define size checks. > Possibly I could replace "1518" by "1526" in sys/net/ethernet.h > but it must be considered brutal, isn't it ? :) > > > Thanks in advance, > Ivan This fix does not support N depth nesting, also if you are exceeding 1518 does that not imply at you require hardware that supports jumbo frames to do VLAN tag nesting? Tom