[openib-general] question regarding GRH flag in ib_ah_attr

[Roland Dreier]

    Sean> Does anyone know how the user determines if the grh flag
    Sean> should be set in the ib_ah_attr when allocating an ib_ah?
    Sean> Do they do this by examining the GIDs in a path record?

Good question.  It's always needed for multicast, of course.  For
unicast, I guess one could look at whether the subnet prefixes of the
SGID and DGID are the same, but I'm not sure that's sufficient -- a
router could conceivably sit between two subnets with the same subnet
prefix.

Perhaps some of the Obsidian guys could comment?

 - R.