[openib-general] IPoIB broadcast MC group membership

[Roland Dreier]

    Fabian> If I understand the code correctly, IPoIB depends on the
    Fabian> broadcast MC group existing, as it only ever issues a MC
    Fabian> join that does not create the group to the SA.

    Fabian> First, is this correct?

Yes.

    Fabian> Second, if so, how is IPoIB supposed to interact with
    Fabian> subnet managers that don't pre-create an empty broadcast
    Fabian> group?

    Fabian> Shouldn't IPoIB first do a GET for the broadcast group,
    Fabian> and use those settings if it exist, otherwise create it?

What parameters should it use to create it?

The IETF drafts for IPoIB say that the IPv4 broadcast group must be
created administratively before an IPoIB interface can be brought up.

What subnet managers exist that don't have some sort of special
handling for the IPoIB broadcast group?

 - R.