[openib-general] RDMA CM multicast

[Sean Hefty]

> rdma_join_multicast(0.0.0.0, port 0)	<- exchange group info out of band

Trying to work through this more, having the first node join seems trivial. 
Getting additional nodes to join the same group through the rdma_cm is proving 
more difficult...  The MGID of the group would need to be treated as an IPv6 
address, with a join done using that address directly, versus mapping an IPv6 
address to an MGID using the ipoib algorithm.

I still believe this is doable, it's just going to require more 
thought/discussion to ensure that we get a clean implementation.

- Sean