SUMMARY: MAC/Link layer Ethernet access in Unix

[Jerry Lahti]

Two weeks ago I posted a question which other Unix systems have equivalent
facilities for Ethernet MAC layer access as those provided by SunOS NIT.
I got only two replies but they seem to cover the field pretty well.
Many other systems seem to have similar facilities but the interfaces
seem to be somewhat different.  The 4.3Bsd/CMU packet filter may be
the most common approach in Bsd based systems.

I have appended the original replies since they provide quite a lot
of details. Many thanks to Doug and Jonathan!

Jerry Lahti
Nokia Data Systems Oy, Workgroup Systems/LAN
Domains: jel at tuura.data.nokia.fi
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>From tut!relay.EU.net!ico!dougm Wed Jul 18 12:53:17 1990

System V.3 has an interface referred to by several names (LLI, DLPI,
LPI, etc).  Sysetm V.4 has DLPI (Data Link Provider Interface) which
is a refined superset of the V.3 stuff.

Ultrix has a DLI (Data Link Interface) available as a configurable
option.  It lets you use sockets to get at the link interface.  Note
that these are link level interfaces and not MAC level.  MAC level
implies talking directly to the hardware and not doing the link level
multiplexing that you probably mean.

Doug McCallum
Interactive Systems Corp.
dougm at ico.isc.com
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>From tut!comp.vuw.ac.nz!jonathan Mon Jul 16 01:26:34 1990

HP-UX on series 300s and I assume 400s (since they're 300s that also
run Apollo's Domain)  and 500s (f you have such a dinosaur), have
something called lan(4) that gives one access to either or both
of 802 LLC or Xerox/Intel/DEc Ethernet.  Ethernet packets
are demultiplexed on input by Ethernet packet type, with little
regard for the sender ; 802 enforces a virtual-circuit interface,
where an SSAP and DSAP are specified once per open file,
and then a specific remote host selected.   Only packets
from the selected host are delivered to an open file, though
datagram service can be obtained by changing the selected host.

HP supports reciept of multicasts on some, but not all,
Ethernet interfaces.

The CMU packet filter provides similar functionality for stock
4.3bsd: it's shipped as part of the user contributed software.
i have ported it locally to HPs running 4.3-tahoe from Mt. Xinu: it
wasn't hard.  My port includes multicast support, through
my port of Stanford's IP multicasting.  I don't think any others do.

Van Jacobsen is rumoured to be contributing an improved version,
with functionality similar to but better than NIT, to 4.4BSD, but I
don't know if that made it into 4.3-reno; I suspect not.

I think the packet filter source should slide fairly easily into
Ultrix on a Vax, with the 4.3 drivers, provided you dont mind losing
Decnet-ULTRIX and/or LAT.  DEC apparently changed the ethernet interface
to support their own protocols.

--Jonathan Stone
Organization: Comp Sci, Victoria University, Wellington, New Zealand.
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