(usagi-users 02311) Re: [Ethereal-dev] Incorrect UDP checksum when using router header?

["Martin Regner" <martin.regner@xxxxxxxxx>]

Yaniv Kaul wrote:
>I'm sending UDP packets from 3ffe:0:c0a8:979:290:27ff:febd:6ba9 to 
>3ffe:0:a09:c901:2e0:18ff:fe22:391f via 
>3ffe:0:c0a8:9c9:2a0:8eff:fe0c:2e1, using router header option.
>It seems that the UDP checksum, when going out from the client is 
>incorrect, at least according to Ethereal. They are correct on the 
>server, therefore I think the checksum calc is done prior to taking into 
>account the routing.
>
>I'm using mgen6 as the client producing those packets, perhaps the error 
>is there.
>
>Attached please find client and server tcpdumps. Please take a look at 
>the client's 2nd and 3rd packets.
>
>Any ideas who's fault is it? (IPv6 stack, Ethereal, mgen6) ?
>
>mgen6 is from http://matrix.it.uc3m.es/~long/software/mgen6/mgen6/, 
>version 3.2.6
>IPv6 stack - both vanilla RH 7.3, and USAGI 20030331 kernel.
>Ethereal 0.9.11
>

I think that if you use router header option then Ethereal may not calclutate the checksum correct for
upper level protocols (TCP, UDP, ...):

http://www.ethereal.com/lists/ethereal-dev/200211/msg00015.html

http://www.ethereal.com/lists/ethereal-dev/200211/msg00017.html

http://www.ethereal.com/lists/ethereal-dev/200211/msg00041.html

http://www.ethereal.com/lists/ethereal-dev/200211/msg00042.html