On Fri, Mar 18, 2005 at 03:48:54PM +0000, Patrick Welche wrote:
> > Good point..
> 
> How about this:
> 
> 15:35:15.825614 IP (tos 0x0, ttl  63, id 4649, offset 0, flags [none], length: 240, bad cksum 0 (->8cda)!) quartz.newn.cam.ac.uk.domain > 192.168.203.45.1072:  51958 1/5/4 time.windows.com. A time.windows.com (212)
> 
> It comes from tcpdump running on a -current box between quartz.newn and
> 192.168.203.45. Is the bad checksum from quartz.newn, or because the box
> running tcpdump has an ex(4) with hardware checksumming? All seems to
> work, so I would guess the later.. (BTW nfs seems OK for me, but the loads
> are very low)

Where are you running the tcpdump ? quartz.newn.cam.ac.uk or 192.168.203.45 ?
For packets transmitted, the checksum is always 0, this is OK.
For packets received, I think is should be correct. At last this is how I
see it on a 1.6.2 box with ex(4):
17:45:59.444719 132.227.63.60.58861 > 132.227.63.66.111: udp 56 (ttl 64, id 29811, len 84)
17:45:59.444861 132.227.63.66.111 > 132.227.63.60.58861: [bad udp cksum a159!] udp 28 (ttl 64, id 13314, len 56, bad cksum 0!)
the tcpdump was running on 132.227.63.66 so the first packet was received,
the second transmitted by the box running the tcpdump.

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
     NetBSD: 26 ans d'experience feront toujours la difference
--