[openib-general] [PATCH] librdmacm: fix bug causing failure to work with partial membership pkey

[Sean Hefty]

>>Can someone help my understanding here?  Is ipoib joining a multicast group
>>using the full membership PKey, even if the node that it joins from only has the
>>limited membership PKey configured? And the code in ib_find_cached_pkey helps
>>enable this?
> 
> Yep. The ipoib create_child  function Or-s 0x8000  to the device pkey
> which was provided by the user. Now, IPoIB uses the device pkey when
> forming MGIDs and when doing modify qp to init. Indeed the way
> ib_find_cached_pkey() is implemented, make the latter use trivial.

Doesn't this allow ipoib to join a multicast group for which it may not be able 
to communicate with all members?  For the broadcast group, this seems like an 
error to me.  Can ipoib work in such a configuration?  If all nodes were 
assigned a partial membership PKey, none of them could communicate, but no 
errors would be generated anywhere.

Joining a multicast group requires specifying the full membership PKey.  I don't 
see anything in the spec that explicitly prohibits joining the group from a node 
with only a partial membership PKey, but at first glance, this seems like a 
subnet configuration issue.  Is there some use of this I'm overlooking?

- Sean