[openib-general] [RFC][PATCH] rdma_cm: allow joins to return a unique address

[Sean Hefty]

>>To allow others to join this group, we need a way to determine
>>if additional join requests are for a specific MGID, or require
>>IP to MGID mapping.  This is done by comparing the requested
>>join address against SA assigned MGIDs.
> 
> 
> Still not understanding this part -- this means that I'm not able to get 
> some sort of portable handle for the group on the process that initially 
> joins the group, and pass it to other processes who would then use that 
> to join the group?

I believe that this patch lets you can do what you're trying to do.  The group 
handle would be the returned mgid from the initial join that created the group. 
  The mgid would need to be passed to other processes as an IPv6 address, who 
issue a join request on that group.  (The mgid is available from the 
rdma_cm_event.param.ud.ah_attr.grh.dgid.)

Typically, the rdma_cm maps IP addresses to mgids using the ipoib ip mapping 
algorithm.  This patch avoids that mapping if the upper 32-bits of the IP 
address match a specific pattern.

- Sean