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Date:      Thu, 6 Dec 2001 20:48:16 +0800 (CST)
From:      Yung-Sheng Tang <freebsd@hoolan.org>
To:        freebsd-questions@freebsd.org
Subject:   UDP checksum error after encapsulating multicast packet
Message-ID:  <Pine.BSF.4.05.10112062031300.88337-100000@hoolan.org>

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I am setting up a multicast router. Recompiling kernel with MROUTING
option and enabling mrouted are done. Basically, my multicast AP runs
well, but if that AP and mrouted run on the same machine, forwarded 
packets would get udp checksum error. Here is the result from tcpdump:


18:27:12.968167 192.9.200.127.1399 > 224.2.3.4.1234: [udp sum ok] udp 
16 (ttl 16, id 38554, len 44)
                         4500 002c 969a 0000 1011 a897 c009 c87f
                         e002 0304 0577 04d2 0018 22c5 ea02 0400
                         3c0f 4401 0001 3145 c7c6 0000
18:27:12.968185 192.9.200.127 > 150.9.120.183: 192.9.200.127.1399 > 
224.2.3.4.1234:  [bad udp cksum bb7!] udp 16 (ttl 15, id 38554, len 44)
(ttl 64, id 38555, len 64)
                         4500 0040 969b 0000 4004 4cd5 c009 c87f
                         9609 78b7 4500 002c 969a 0000 0f11 a997
                         c009 c87f e002 0304 0577 04d2 0018 6bb9
                         ea02 0400 3c0f 4401 0001 3145 c7c6 0000

Did I make some mistake? I have not subscribe freebsd-questions, please
CC me. Thank you for your attention.

Regards,
Yung-Sheng Jeff Tang


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