[openib-general] ip_ib_mc_map?

[Or Gerlitz]

Michael S. Tsirkin wrote:
>> 1) adding a backport to the rdma_cm containing ip_ib_mc_map, period.

>> 2) having the rdma cm follow the net stack and make its consumer use the 
>> broadcast group.

> Correct. Since multicast is broken in other respects on U4
> (sockets can't join multicast groups), I think 2 is the simplest approach.

The situation in U4 is kind of more involved, sockets doing 
IP_ADD_MEMBERSHIP to some multicast group are actually sending and 
receiving traffic over the IPoIB broadcast group which makes this 
cluster IPoIB kind of hell.

> Anyone who wants IPoIB milticast should just stay away from U4.

We are still interested to be able to run our multicast app over the 
RDMA CM and we want it to be done over the correct multicast group and 
not over a broadcast group. So option 2 is real problem for us.

Or.