bad tcp/udp checksums with broadcom cards.
mipam at ibb.net
Mon Apr 5 08:01:08 PDT 2004
(I allready posted this message without a subject, which isnt nice so i
post it again, forgive me).
I've some dell poweredges with broadcomcards in them:
bge0: <Broadcom BCM5704C Dual Gigabit Ethernet, ASIC rev. 0x2002> mem
-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,
However on all of these systems i encounter this in tcpdump:
14:51:49.845 x.x.x.x.22 > x.x.x.x.3599: P 444:784(340) ack
53 win 32850 (DF) [tos 0x10] (ttl 64, id 21535, len 380, bad cksum 0!)
14:51:49.863740 x.x.x.x.3599 > x.x.x.x.22: P 53:105(52) ack 280
win 64128 (ttl 126, id 24085, len 92)
14:51:49.864327 x.x.x.x.3599 > x.x.x.x.22: . [tcp sum ok]
105:105(0) ack 784 win 63624 (ttl 126, id 24086, len 40)
14:51:49.865208 x.x.x.x.3599 > x.x.x.x.22: P 105:157(52) ack
784 win 63624 (ttl 126, id 24088, len 92)
14:51:49.865231 x.x.x.x.22 > x.x.x.x.3599: . [bad tcp cksum
505b!] 784:784(0) ack 157 win 32824 (DF) [tos 0x10] (ttl 64, id 21536,
len 40, bad cksum 0!)
Has this to do with tcp checksum offloading?
Should i turn it off? And if so, how to turn it off?
Or is this correct and no problem?
Does this card got segmentation offload and other offloads?
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