Looks like the patch is all good. I'm marking as ready for commiter.
On a side note, i'm noticing from http://en.wikipedia.org/wiki/MAC_address, that there is three numbering namespace for MAC: MAC-48, EUI-48 and EUI-64. The last one is 64 bits long (8 bytes). Currently PostgreSQL's macaddr is only 6 bytes long. Should we change it to 8 bytes (not in this patch, of course)?