Date: Tue, 20 Apr 2004 19:01:35 +0100 From: ian j hart <ianjhart@ntlworld.com> To: freebsd-stable@freebsd.org Cc: Kris Kennaway <kris@obsecurity.org> Subject: Re: bad tcp/udp checksumsc with 5704C Message-ID: <200404201901.35819.ianjhart@ntlworld.com> In-Reply-To: <20040407170932.GA74440@xor.obsecurity.org> References: <Pine.LNX.4.33.0404071450090.22128-100000@ux1.ibb.net> <20040407170932.GA74440@xor.obsecurity.org>
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On Wednesday 07 April 2004 18:09, Kris Kennaway wrote: Sorry about the delay - on holiday. > On Wed, Apr 07, 2004 at 03:09:11PM +0200, Mipam wrote: > > Hi, > > > > I'm running FreeBSD 5.2.1-p4 on a dell system with a Broadcom 5704C Nic > > in it. > > > > bge0: <Broadcom BCM5704C Dual Gigabit Ethernet, ASIC rev. 0x2002> mem > > 0xfcd20000-0xfcd2ffff,0xfcd30000-0xfcd3ffff irq 16 at device 0.0 on pci2 > > bge0: Ethernet address: 00:0b:db:93:c5:c4 > > miibus0: <MII bus> on bge0 > > brgphy0: <BCM5704 10/100/1000baseTX PHY> on miibus0 > > brgphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, 1000baseTX, > > 1000baseTX-FDX, auto > > > > Since version 4.5 tcp checksum offloading is supported with this NIC. > > However, i'm encountering continuous on all packet send from this > > machines bad tdp/udp checksums: > > > > 16:05:41.287764 x.x.x.x.22 > 192.168.2.1.4761: . [bad tcp cksum > > f48!] 984:984(0) ack 313 win 32824 (DF) [tos 0x10] (ttl 64, id 44539, > > len 40, bad cksum 0!) > > 16:05:41.545073 x.x.x.x.123 > y.y.y.y.123: [bad udp cksum > > 6a52!] v3 server strat 2 poll 6 prec -31 dist 0.007049 disp 0.022796 ref > > 195.169.124.69@3290335106.099078394 orig 3290335541.540184020 rec > > +0.004841091 xmt +0.004874050 [tos 0x10] (ttl 64, id 44541, len 76, bad > > cksum 0!) > > > > When tcp csum offloading is turned on, does the networking stack not > > compute the checksum on outgoing packets and hand it to the driver which > > hands it to bpf and libpcap hands it to tcpdump so tcpdump reports an > > invalid checksum? For now i am not sure whether the behaviour is right or > > not.... it worries me. > > I ran into this yesterday with a different NIC, and Peter Wemm told me > that tcpdump indeed gets it wrong for locally-generated packets when > the card does checksum offloading. Indeed, when I ran the tcpdump on > another machine on the LAN it verified that the checksums on those > packets were all correct. In that case, this PR can probably go. http://www.freebsd.org/cgi/query-pr.cgi?pr=63982 > > > There's more: when i set the speed and duplex hard on the switch and nic > > on 100 and full-duplex, the traffic is very slow. > > Sounds like what happens when full-duplex isn't supported by one > end, or isn't actually being set correctly. > > Kris -- ian j hart http://ars.userfriendly.org/cartoons/?id=20031016
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