[OpenAFS] Re: client hangs with 1.2.13 redhat 9 servers

[Jeffrey Hutzelman]

On Friday, February 04, 2005 01:58:06 PM -0500 Joe Buehler 
<jbuehler@spirentcom.com> wrote:

> A further point of information.  Using tcpdump on the main
> two fileservers I see a lot of udp checksum errors.
> One of the machines has fragment reassembly timeouts, which
> probably explains the AFS delays.
>
> I am a bit puzzled by tcpdump claiming errors in the UDP
> checksum for *outgoing* packets on one of the machines,
> however.  At what point does tcpdump hook into the
> ethernet hardware?  Seems like UDP checksums in outgoing
> packets should be impossible...

I've noticed that too in some cases, and not just with AFS.
It seems that in at least some situations, tcpdump does not get to see the 
real UDP checksum that will appear on the wire for outgoing traffic.  This 
is entirely dependent on how the operating system implements its packet 
tracing facility.

-- Jeffrey T. Hutzelman (N3NHS) <jhutz+@cmu.edu>
   Sr. Research Systems Programmer
   School of Computer Science - Research Computing Facility
   Carnegie Mellon University - Pittsburgh, PA