From owner-freebsd-net@FreeBSD.ORG Wed Jan 31 21:40:58 2007 Return-Path: X-Original-To: freebsd-net@freebsd.org Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 2914516A401 for ; Wed, 31 Jan 2007 21:40:58 +0000 (UTC) (envelope-from erikt@midgard.homeip.net) Received: from ch-smtp01.sth.basefarm.net (ch-smtp01.sth.basefarm.net [80.76.149.212]) by mx1.freebsd.org (Postfix) with ESMTP id AC5D513C491 for ; Wed, 31 Jan 2007 21:40:57 +0000 (UTC) (envelope-from erikt@midgard.homeip.net) Received: from c83-253-29-241.bredband.comhem.se ([83.253.29.241]:51173 helo=falcon.midgard.homeip.net) by ch-smtp01.sth.basefarm.net with smtp (Exim 4.63) (envelope-from ) id 1HCMwA-0004wB-5J for freebsd-net@freebsd.org; Wed, 31 Jan 2007 22:24:14 +0100 Received: (qmail 29819 invoked from network); 31 Jan 2007 22:24:11 +0100 Received: from owl.midgard.homeip.net (10.1.5.7) by falcon.midgard.homeip.net with SMTP; 31 Jan 2007 22:24:11 +0100 Received: (qmail 86304 invoked by uid 1001); 31 Jan 2007 22:24:11 +0100 Date: Wed, 31 Jan 2007 22:24:11 +0100 From: Erik Trulsson To: =?iso-8859-1?Q?C=E9dric?= Jonas Message-ID: <20070131212411.GA86267@owl.midgard.homeip.net> Mail-Followup-To: =?iso-8859-1?Q?C=E9dric?= Jonas , freebsd-net@freebsd.org, freebsd-current@freebsd.org References: <20070131214705.0ee0ba67@ganymed> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <20070131214705.0ee0ba67@ganymed> User-Agent: Mutt/1.5.13 (2006-08-11) X-Scan-Result: No virus found in message 1HCMwA-0004wB-5J. X-Scan-Signature: ch-smtp01.sth.basefarm.net 1HCMwA-0004wB-5J 8edeaa7eda6f7ef52c92be5dcce43b71 Cc: freebsd-net@freebsd.org, freebsd-current@freebsd.org Subject: Re: fxp(4) checksum (offloading?) errors 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: Wed, 31 Jan 2007 21:40:58 -0000 On Wed, Jan 31, 2007 at 09:47:05PM +0100, C=E9dric Jonas wrote: > Hi, >=20 > I get TCP/UDP checksum errors with fxp(4). I noticed it after using > Wireshark today: >=20 > Checksum: 0xac18 [incorrect, should be 0xfbc7 (maybe caused by > checksum offloading?)] >=20 > for example. Is that for incoming or outgoing packets? If it is for outgoing it is perfectly normal and nothing to be worried about (assuming that your NIC does checksum offloading.) If it is for incoming packets it could be a real problem. >=20 > If I understand it more or less correctly, checksum offloading is > performed by or with help of the NIC - only for TCP and UDP, where the > checksum fails exactly... Checksum offloading means that the calculation of the checksum is done by the NIC instead of by the main CPU. For outgoing packets this means that wireshark or tcpdump and all similar programs see the packets before they have been handed over to the NIC, which means that the correct checksum has not yet been calculated and probably contains garbage. > I didn't found a way to disable it, so I assume it's a bug in the > driver... I don't know exactly which infos I must provide additionally > to the following, so don't hesitate to ask more :) >=20 > Used NIC: >=20 > fxp0: port 0xa400-0xa43f mem > 0xfb030000-0xfb030fff,0xfb000000-0xfb01ffff irq 16 at device > 7.0 on pci2 >=20 > Used system: >=20 > FreeBSD ganymed 7.0-CURRENT FreeBSD 7.0-CURRENT #0: Sun Jan 21 > 16:07:51 CET 2007 > root@ganymed:/usr/obj/usr/src/sys/GANYMED i386 >=20 --=20 Erik Trulsson ertr1013@student.uu.se