[Simh] 3B2 Simulator NI Card Update

[Seth J. Morabito]

Hello everyone,

I think the NI Ethernet card for the 3B2 Simulator is shaping up very
nicely. I've been using it quite a bit recently and I've ironed out a
few bugs. If you've been using it, please upgrade to the latest checkout
from GitHub and give it another build.

One feature that has NOT been implemented yet is Multicast address
enable. The only reason I haven't implemented it is because I don't have
a way to test it, as I don't seem to have any software that wants
Ethernet multicast enabled!

Some background: By default, the NI card only listens for Ethernet
frames where the destination address is the NI's MAC address, or the
broadcast address ff:ff:ff:ff:ff:ff. The driver and NI card support
adding a set of multicast Ethernet addresses that the card will listen
for in addition to these. There's an ioctl you can call to do this, but
I have absolutely no idea how to actually trigger this in practice.
(And, sadly, the NI driver doesn't include development headers, so I
can't easily write my own 3B2 test software. D'oh.)

If anyone has any experience with this, please do get in touch with me!

-Seth
--
  Seth Morabito
  Poulsbo, WA, USA
  web at loomcom.com