From owner-freebsd-net@FreeBSD.ORG Wed Jan 31 22:48:53 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 311DE16A403 for ; Wed, 31 Jan 2007 22:48:53 +0000 (UTC) (envelope-from erikt@midgard.homeip.net) Received: from ch-smtp02.sth.basefarm.net (ch-smtp02.sth.basefarm.net [80.76.149.213]) by mx1.freebsd.org (Postfix) with ESMTP id B5F1313C46B for ; Wed, 31 Jan 2007 22:48:52 +0000 (UTC) (envelope-from erikt@midgard.homeip.net) Received: from c83-253-29-241.bredband.comhem.se ([83.253.29.241]:56778 helo=falcon.midgard.homeip.net) by ch-smtp02.sth.basefarm.net with smtp (Exim 4.63) (envelope-from ) id 1HCOG3-0002Vs-8s for freebsd-net@freebsd.org; Wed, 31 Jan 2007 23:48:51 +0100 Received: (qmail 30419 invoked from network); 31 Jan 2007 23:48:49 +0100 Received: from owl.midgard.homeip.net (10.1.5.7) by falcon.midgard.homeip.net with SMTP; 31 Jan 2007 23:48:49 +0100 Received: (qmail 86910 invoked by uid 1001); 31 Jan 2007 23:48:49 +0100 Date: Wed, 31 Jan 2007 23:48:49 +0100 From: Erik Trulsson To: Wesley Shields Message-ID: <20070131224849.GA86858@owl.midgard.homeip.net> Mail-Followup-To: Wesley Shields , C?dric Jonas , freebsd-net@freebsd.org, freebsd-current@freebsd.org References: <20070131214705.0ee0ba67@ganymed> <20070131212534.GC58404@atarininja.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070131212534.GC58404@atarininja.org> User-Agent: Mutt/1.5.13 (2006-08-11) X-Scan-Result: No virus found in message 1HCOG3-0002Vs-8s. X-Scan-Signature: ch-smtp02.sth.basefarm.net 1HCOG3-0002Vs-8s 24e988f5f4e6b1ae9e28fba7c066a46b Cc: C?dric Jonas , 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 22:48:53 -0000 On Wed, Jan 31, 2007 at 04:25:34PM -0500, Wesley Shields wrote: > On Wed, Jan 31, 2007 at 09:47:05PM +0100, C?dric Jonas wrote: > > Hi, > > > > I get TCP/UDP checksum errors with fxp(4). I noticed it after using > > Wireshark today: > > > > Checksum: 0xac18 [incorrect, should be 0xfbc7 (maybe caused by > > checksum offloading?)] > > > > for example. > > > > 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... > > Yes, the checksums are offloaded to the card. Maybe I missed it, but > you were not very clear on where you were seeing the invalid checksums. > In the case of wireshark running on the machine which is doing the > offloading then this makes sense as the checksums are computed AFTER > wireshark sees them. The best way to know for sure if the checksums > were computed correctly is to check them on the destination or somewhere > along the wire to the destination. > > > 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 :) > > According to ifconfig(8) they can be toggled using -rxcsum and -txcsum, > but it is dependent upon the NIC/driver in use. A quick glance through > fxp(4) indicates that it doesn't do checksum offloading. I'm sure > someone will correct me if I am wrong. :) Some fxp(4) NICs support checksum offloading, but most don't. The fairly common 82559 controller chip does not support checksum offloading. The 82550 (which can be found on the Intel PRO/100 S cards) does support checksum offloading. -- Erik Trulsson ertr1013@student.uu.se