(usagi-users 02621) UDP IPv6 Multicast

[Brian Buesker <bbuesker@xxxxxxxxxxxx>]

I am noticing strange behavior on the 2.6 series kernel (I tested on 
2.6.0-test9). When I have two sockets which bind to and join different 
multicast addresses but with the same UDP port, and then I send a packet 
to one of those multicast addresses, the packet gets delivered to both 
of them. For example, if one socket is bound to ff01::1:1 UDP port 2000 
and joins multicast group ff01::1:1, and a second socket is bound to 
ff01::1:2 UDP port 2000 and joins multicast group ff01::1:2, and then I 
send a packet to ff01::1:1 UDP port 2000, it actually gets delivered to 
both sockets. This does not happen in the 2.4 series kernel.

I have narrowed it down to the interaction between the following two 
functions in the kernel: inet6_mc_check and and udp_v6_mcast_next. It 
seems that the return semantics were changed for inet6_mc_check in the 
2.6 series kernel without changing the logic used when calling it in 
udp_v6_mcast_next. Is there a reason for this change, or is this just a bug?

Thanks,
Brian Buesker