[ofw] rdma_join_multicast not implemented??

[Hefty, Sean]

> I just attended the RDMA programming class that OpenFabrics held.  I was
> interested in applying what I had learned to create an application that
> uses UD and multicast using the new WinOF 2.3 release.  I have not had much
> success in doing so, so I downloaded the source code and searched for the
> rdma_join_multicast() and rdma_leave_multicast() functions.  It looks like
> these functions are not currently implemented as they just have the
> following code: return rdma_seterrno(ENOSYS);

Correct - there were no current in-tree users of that code, so their implementations were deferred.

> I got the impression, from my class, that multicast should be there on the
> Linux side so this would appear to be a difference in functionality between
> Linux and Windows.  Is there any plan to implement these in the next
> release, or am I completely missing something.

OFED-Windows does support multicast at the verbs level (somewhat) and UD; it's the librdmacm port that does not.  The issue is that the underlying libraries and kernel drivers are missing the necessary features to support user space multicast.  To date, there haven't been requests to add this feature, so no plans have been made to implement UD support through the librdmacm.

This is not something I have time at the moment to implement, but I would be able to work with another developer to review any patches and merge them into the tree.

- Sean