Add detach routine and turn driver into a module so it can be loaded
and unloaded. Also take a stab at implementing multicast packet
reception so that this NIC will work with IPv6. Promiscuous mode
doesn't seem to work, but I'm not sure why. It works well enough that
I can run dhclient on it and put it on the office network though.
Also ripped out spl stuff and replaced it with mutexes.
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
