Berkeley, CA,  Sun Dec 31 08:54:07 PST 1989

This directory contains as slip driver that seems to work
with Sun OS 4.0 on Sun-3s and Sun-4s.  This driver consists
of the minimal modifications we could make to the "streams"
driver written by Doug Kingston and Rayan Zachariassen.
You probably want to anonymous ftp their complete distribution
from ai.toronto.edu (128.100.1.65), either pub/slip-4.0.tar.Z
or pub/slipware.tar.Z.

Unpack their slip-4.0 directory, replace the tty_slip.c in it
with the one here, remove the slip.h from their directory and
copy this slip_var.h from here to there.  (We changed the name
of this file because otherwise you end up with two includes
named "slip.h" -- one in /sys/sys and one in the target system
directory.  Some programs need to include both these files and,
depending on which flavor of cpp you run, can easily get the
wrong one.  Also, some strange uses of VPATH will show up in the
near future and these duplicate names are an invitation to
disaster.)

Then follow their directions but,

 - in step 1, also add the line
	os/slcompress.c		optional slip
   to /sys/conf.common/files.cmn and copy ../slcompress.[ch] to /sys/os.

 - in step 5, change slip.h to slip_var.h.

 - in step 7, if you compile their sliplogin.c, you'll need to
   change the "#include <sys/slip.h>" to <sys/slip_var.h>.
   But you may want to use the slattach in the directory above
   this one instead of sliplogin.  "make slattach" in this
   directory should build a sunos4 version.


Note that in Sun OS 4.x, slip runs over a "streams" tty driver 
where much of the underlying support code was taken from AT&T's
System-V Unix.  This support code is incredibly bad:  A Sun-3/50
will run both it's serial ports at 38,400 baud with no problems
under Sun OS 3.x (which uses the Berkeley/V7 tty driver).  That
same 3/50 can not keep up with one serial port running at 9600 baud
under Sun OS 4.0.3.  The AT&T code also doesn't handle any kind of
exception correctly:  If it runs out of stream buffers or gets a signal
or interrupt at the wrong time, the system will crash.  So, run
Sun OS 3 if you have any choice.  If you have no choice, try this
stuff but don't expect reasonable performance or robustness.

 - VJ
