Date: Wed, 31 Jan 2007 23:05:40 +0100 From: =?ISO-8859-1?Q?C=E9dric?= Jonas <cedric@decemplex.net> To: Erik Trulsson <ertr1013@student.uu.se> Cc: freebsd-net@freebsd.org, freebsd-current@freebsd.org Subject: Re: fxp(4) checksum (offloading?) errors Message-ID: <20070131230540.2141488e@ganymed> In-Reply-To: <20070131212411.GA86267@owl.midgard.homeip.net> References: <20070131214705.0ee0ba67@ganymed> <20070131212411.GA86267@owl.midgard.homeip.net>
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[-- Attachment #1 --] On Wed, 31 Jan 2007 22:24:11 +0100 Erik Trulsson <ertr1013@student.uu.se> wrote: > On Wed, Jan 31, 2007 at 09:47:05PM +0100, Cédric 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. > > 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.) Arghs, shame on me. You are fully right... I needed to know it, my first mail contains quasi the reason of the "bug" :) However, thank you! > > If it is for incoming packets it could be a real problem. > > > > > > 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 :) > > > > Used NIC: > > > > fxp0: <Intel 82550 Pro/100 Ethernet> port 0xa400-0xa43f mem > > 0xfb030000-0xfb030fff,0xfb000000-0xfb01ffff irq 16 at device > > 7.0 on pci2 > > > > Used system: > > > > 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 > > > > > > -- Cédric Jonas cedric@decemplex.net Mobile Phone: (32-494) 08 92 64 GPG ID: 30CCFE8D GPG Key: http://box.decemplex.net/~cedric/cedric.key.asc GPG Fingerprint: CF03 E1FD 9428 1B6B E971 B107 9044 AA99 30CC FE8D Jabber-ID: cedric@decemplex.net [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (FreeBSD) iD8DBQFFwRLQkESqmTDM/o0RAg/EAJ9oqW84KKbOWTfp36blRvvBl1PESwCdFeqE 5DGJU9ooRX5ChM6R0AW9P3I= =nBDS -----END PGP SIGNATURE-----
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