[openib-general] [RFC/PATCH] librdmacm: use the ipoib broadcast group qkey

[Or Gerlitz]

Sean Hefty wrote:
>> Maybe just ask user to always call rdma_join_multicast after rdma_create_qp?
>> Joins are now properly reference counted, so it shouldn't be a problem
>> to repeat this any number of times. Right?
> 
> This is the solution for now, and it should work fine.  I don't think it would
> be hard to support creating the QP after joining if someone ever came up with
> the need, but it doesn't seem like a priority at the moment.

Indeed, since to do multicast RX/TX you need an IB UD QP... naturally an 
IB app (eg IPoIB) would create its QP before doing any join/leave on the 
group, if there would be a demand for a "crazy" use scheme of 1st join 
2nd create qp, you can enhance librdmacm to support it.

Or.