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

[Sean Hefty]

Or Gerlitz wrote:
> Modify librdmacm use a qkey for its UD IDs/QPs delivered to it by the
> rdma cm kernel code instead the a hard coded RDMA_UD_QKEY. For RDMA_PS_UDP
> ID, the qkey is provided by the kernel in ADDR_RESOLVED and CONNECT_REQUEST
> events and is stored by the library in struct cma_id_private. Later
> the library use the qkey when it is called to create a UD QP.

Reading the code, the following sequence does not work: rdma_join_multicast then 
rdma_create_qp.  The QP does not automatically attach to previously joined 
multicast groups on creation.  (This is a problem with the existing code.)  The 
reverse sequence (create then join) does work.  I'm adding the ipoib support to 
the librdmacm now, but we will still need a separate patch to fix attaching to 
joined multicast groups when the QP is created.

- Sean