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SubjectMulticast MAC when sending via gateway
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I observe some strange behavior when sending multicast datagrams 

via gateway. It appears that destination MAC in UDP packets differs

when using connected and connectionless socket. In case of

connectionless socket destination MAC field of UDP header is filled

with MAC address of gateway, but in case we use connect()

with multicast address, destination MAC is set to multicast MAC.

I don't know, which behavior is right, but different behavior seems

strange.



I run the attached test on thorin1 machine and use thorin2 as a gateway.

thorin1 is running 2.6.26-2-686 kernel, thorin2 is 2.6.26-2-amd64.

I also attach ifconfig and route output for this machines and tcpdump

output on thorin2 when running test. There we can see the following:



16:02:30.567909 00:27:0e:09:01:2a > 00:27:0e:09:02:2a, ethertype IPv4

(0x0800), length 58: 10.54.10.1.40074 > 237.92.130.210.51721: UDP, length

16

16:02:30.567984 00:27:0e:09:01:2a > 01:00:5e:5c:82:d2, ethertype IPv4

(0x0800), length 74: 10.54.10.1.43360 > 237.92.130.210.51721: UDP, length

32



Is it a bug or is this kind of behavior expected?



I wish to be personally CC'ed the answers/comments posted to the list in

response to this posting.



Nikita Rastegaev <Nikita.Rastegaev@oktetlabs.ru>
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