SLIP on a DECStation (BSD style).

[Paul A Vixie]

>>	Ultrix seems to have changed the slattach program to include
>> dial up support, etc. and I do not have source for it.  It is
>> unsupported by DEC.  I would appreciate hints on how one can hook up a
>> Ultrix machine to a BSD machine by SLIP.  Please send me E-Mail if you
>> have done so.

Ultrix and BSD SLIP are protocol-compatible.  This means that if you can
get an Ultrix TTY line into SLIP mode, and the other end is a BSD TTY in
SLIP mode, it will work.

Getting an Ultrix TTY line into SLIP mode is a little bit more complicated
than doing it on BSD.  One thing you can do is get the slattach.c from
UUNET's archives of BSD's networking software.  It should simply compile
and run, at which point you will be dealing at least with an interface
program that you have source for.  Or, if you are willing to read the
/etc/sliphosts file and figure out the "hw" support, you can just use the
(unsupported) /usr/new/slattach that comes with Ultrix.

Compiling if_sl.c from the BSD sources is a little bit tougher, since the
Ultrix-supplied init_main.o does not call slattach().  This is why Ultrix
"slN" devices don't show up in "netstat -i" until they are actually
attached -- slopen() maintains a linked list of interfaces, and until
an interface is opened it doesn't show up on the list.  What this means
is that the BSD version of if_sl.c is useless to you unless you have the
source to the Ultrix version of init_main.c.

Beware that SLIP is unsupported on Ultrix.  If it crashes your machine,
you can't submit bug reports on it.  (Under 3.0, it *will* crash your
machine since there was a bug in the linked list handling in if_sl.c.)
--
Paul Vixie
DEC Western Research Lab	<vixie at decwrl.dec.com>
Palo Alto, California		{ames,att,uunet}!decwrl!vixie