[Simh] Alternative VMS Ethernet Support

[Graham Burley]

I knocked up some ethernet support for use with SIMH on VMS before
hearing of the VMS PCAP port, I've just updated this for V3.2-3 and
thought I'd share.

The routines emulate just enough PCAP calls to support SIMH, they
require a dedicated ethernet interface [1]. but on the plus side
it's all user mode code, doesn't require promiscuous mode, and
should work on older versions of VMS, on VAX (or whatever).

A kit that builds with SIMH V3.2-3 can be found here:

	http://www.encompasserve.org/~burley/vms_pcap_emu.zip

This should be unpacked into the SIMH source directory, the mods to
SIM_ETHER.C and DESCRIP.MMS are very minor. To build:

$ MMx/MACRO=USE_PCAP_EMU=1 foo


[1] The routines use the QIO interface to the LAN drivers. They work
    by inspecting the ethernet protocol type of outbound packets and
    starting ports as needed. When a port is started an attempt is
    made to change the physical address to that requested by SIMH.
    Some sharing between SIMH and host might be possible as long as
    protocol types and physical addresses don't conflict.