[ofw] enable/disable device changes IPoIB physical address??

[Sean Hefty]

>In Windows, IPoIB pretends to be a standard 802.3 NIC.  That means the
>MAC address it reports to the OS for both its local address and in any
>received ARP packets is a 6-byte MAC.  This 6-byte MAC is generated from
>the 20-byte IPoIB MAC that goes over the wire and is made up of the GID
>and QPN.  Shrinking a 20-byte space down to 6 bytes is a bit of a
>challenge.  The driver discards the QPN and the subnet prefix from the
>GID, leaving just the port GUID.  This GUID is then reduced to a 6-byte
>MAC based on the vendor ID in the first 3 bytes.  There are algorithms
>in the IPoIB driver to convert Mellanox, QLogic (ex Sliverstorm), and
>Voltaire GUIDs.  For all other types, the driver generates a locally
>administered address (LAA) which starts with 02 00 (maybe an extra 00,
>too).  The lower bytes are a simple counter that gets incremented every
>time a new LAA is generated.  Note that Cisco HCAs fall into the "all
>other types" category, as there is currently no code in the IPoIB driver
>to handle these GUIDs.

Does this work with non-Windows IPoIB implementations?  It doesn't actually
report a 6-byte MAC address over the wire, does it?  This is just a made up
address to fool Windows, correct?