Hello all, I’m not sure if this the right place to ask, but I will give it a try. I have a system with many initialized UD queue pairs (info for address handle creations and qp numbers exchanged out-of-band). I am only using libibverbs for establishment (purposefully not using librdmacm, to allow for more flexible environment configuration) — everything is working smoothly for unicast. Now I would like to create a multicast group and attach some of these queue pairs (ibv_mcast_attach); however I am struggling to find any details on how to create such a group (and obtain a proper MGID and MLID). I found a few examples online but am left with questions: - There is code within perftest's "multicast_resources.c", but this seems a bit hacky and oddly verbose - There is code within Nvidia Docs’ "Programming Examples using IBV” showcasing joining an already created multicast group at a given IP address using rdma_cm, but It is unclear how to create the group in the first place Questions (please correct me if these do not make sense): 1. What is the role of the OpenSM — is there a C API? - Are there any examples using opensm programmatically and not with CLI? - Does the API differ on InfiniBand vs. RoCEv2 fabric? 2. Is there any high-level documentation to describe the role of libibumad? (Looking at the man pages on a per-function basis is a bit too fine-grained for my understanding as of now). - I also see libibmad — what is the responsibility breakdown between these two? - How do they relate to OpenSM? Any guidance is greatly appreciated. Thanks, Andrew Sheinberg
