[ewg] Re: [ofa-general] [PATCH 2/9] ib_core: kernel API for GID -->MAC translations

[Roland Dreier]

 > It is like an IPv6 address but it was expressly envisioned to be a
 > seperate space. The IBA authors copied many of the conventions from
 > IPv6 for numbering this new space, like link local, and multicast
 > prefixes, but it was not intended to be co-mingled.

Well (I've quoted this many times): IBA section 4.1:

   "A GID is a valid 128-bit IPv6 address (per RFC 2373) with additional
    properties / restrictions defined within IBA..."

People often try to claim that this sentence doesn't mean what it very
explicitly and clearly says, and certainly I believe that existing
practice doesn't comply with the IBA spec, but I don't see how anyone
can say that a truly compliant IB GID is not a real IPv6 address.

 > So, I didn't look closely enough, but what was the ethertype that is
 > used here in this patch set? Hopefully not IPv6.

I don't think it's specified in the code -- presumably in HCA FW.  Which
is an issue as you say -- do we have an IEEE ethertype yet?  And if we
don't use the IPv6 ethertype, then is multicast going to work well (if
the code is moved away from just broadcasting everything)?  I doubt that
switch IGMP snooping works well for non-IP ethertypes -- in fact I
wonder how well existing switches handle IPv6 multicast ;)

 - R.