.TH SERIAL-IP 8
.SH NAME
serial-ip \- Serial IP (SLIP or PPP) setup
.SH DESCRIPTION
.de SP
.if t .sp 0.4
.if n .sp
..
\-\-\-\-\-\-\-
.br
.B Note:
This text and the serial IP code is not finished.  Code needs to be added to
.B nonamed
to allow it to be used both with and without a connection to the Internet,
and by now there is a PPP program for standard Minix "out there" that will
change everything that is said in this text.  So much to do, so little
time...
.br
\-\-\-\-\-\-\-
.PP
This manual page describes the Minix network setup to use serial line IP.
The serial IP protocol used can either be the older SLIP by means of the
.BR slip (8)
program, or PPP (Point-to-Point Protocol), the newer and better serial IP
protocol implemented by the
.BR ppp (8)
program.  Alas standard Minix only supports SLIP.
.PP
In the following text all descriptions and examples will name SLIP or the
.BR slip
program, but one may just as well read PPP or
.BR ppp .
Where necessary the differences will be noted.
.PP
A typical use of the
.B slip
program is like this:
.PP
.RS
.B "slip /dev/psip2 </dev/tty01 >/dev/tty01"
.RE
.PP
The argument of the program, the
.B /dev/psip2
device, is one of the so-called "Pseudo IP" devices that the Minix TCP/IP
driver
.BR inet (8)
offers to implement a virtual network on.  On an ethernet IP packets are
received or transmitted by the ethernet card, but packets on a pseudo IP
network are channeled back to or received from a program running in user
space, such as
.BR slip .
Standard input and output are used by
.B slip
to exchange packets with another SLIP implementation.  This is normally
through an RS-232 serial line like the second serial line
.B /dev/tty01
as used in the example above.
.PP
If we look at the flow of data over normal ethernet then this is what a TCP
connection between two Minix machines,
.B telnet
for instance, looks like:
.PP
.in 0
.ce 13
[telnet]
|
/dev/tcp0
|
inet
|
[ethernet]
|
inet
|
/dev/tcp0
|
[in.telnetd]
.PP
One-half (!) of a SLIP connection would look like this:
.PP
.in 0
.ce 12
[telnet]
|
/dev/tcp2
|
inet
|
/dev/psip2
|
slip
|
[serial line]
\&...
.SS "Configuration for a SLIP network only"
It is important to know that as far as
.B inet
is concerned the pseudo IP network is just another network, nothing special.
So you have to convince
.B inet
that it has to send packets out over that network.  One does this by
setting a default route that makes
.B inet
believe that there is a router somewhere on the pseudo-IP network.
.PP
Assume your machine has been given the IP address
.B 192.168.0.13
by your service provider.  Let's choose another address on that network,
.B 192.168.0.1
for instance.  (You can use the address of the SLIP gateway if you want
to make it look pretty, but it doesn't really matter, anything "out there"
is ok.)
To make Minix aware of the situation you have to configure the pseudo IP
network.  For Minix-vmd you need to look for the
.B if-then-else-fi
code in
.B /usr/etc/rc
that tests if
.B /etc/rc.net
should be run.  Copy the lines in the
.B else
clause that starts network daemons to
.B /etc/rc.net
and add the following lines to make it look like this:
.PP
.RS
.nf
# My SLIP interface address.
ifconfig -h 192.168.0.13 -n 255.255.255.0
.SP
# Standard network daemons.
daemonize rarpd $named irdpd rip inetd
.SP
# Default route to the outside world.
add_route -g 192.168.0.1
.fi
.RE
.PP
For standard Minix one has to edit
.B /etc/rc
instead at the point of the XXX comments.  The
.B ifconfig
goes at the first XXX, the
.B add_route
at the second XXX.  The result is conceptually the same as the example
above.  The important thing is the order: Configuration, Daemons, Routes.
(First give addresses to the networks, let the daemons meditate over the
results and possibly configure more networks (rarpd), then add routes to
the configured networks.)
.PP
Just one thing left to do.  The system uses the first ethernet network
.RB ( eth0 ,
.BR ip0 ,
.BR tcp0 ,
and
.BR udp0 )
as the default network.  With the program
.BR netdefault (8)
you have to change the links to the default devices
.RB ( eth / psip ,
.BR ip ,
.BR tcp ,
and
.BR udp )
to point to the first pseudo IP network
.RB ( psip2 ,
.BR ip2 ,
.BR tcp2 ,
and
.BR udp2 ):
.PP
.RS
.B "netdefault psip2"
.RE
.PP
In
.B /etc/hosts
list at least
.B localhost
and the name of your machine with its SLIP address.  This way your machine
will boot and know its own name.  Now you need to find a way to let your
system know the addresses of other machines.  There are three ways:
.PP
.RS
List the names and addresses of any other machine you wish to talk
to in
.BR /etc/hosts .
Drawback: This will quickly become a pretty long list.
.SP
Create an
.B /etc/resolv.conf
that lists a nameserver at your ISP and
.B 127.0.0.1
(localhost).  Drawback:  With the SLIP link down it takes 5 to 10 seconds for
a name lookup to time out on the remote name server before the local name
server is tried.
.SP
Install the above
.B /etc/resolv.conf
when
.B slip
is started, and remove it when
.B slip
exits.  Drawback: Long running programs only read
.B /etc/resolv.conf
at startup, so they don't notice it changing.
.SP
Run a real Internet name daemon from the
.B named
package.  Drawback: Nontrivial to set up.
.SS "Configuration for a SLIP - Ethernet router (simple case)"
XXX
.SS "Configuration for a SLIP - Ethernet router (complex case)"
XXX
.SH FILES
.TP \w'/dev/psip*'u+5n
.B /dev/psip*
Pseudo-IP devices for use by
.BR slip
and
.BR ppp .
.SH "SEE ALSO"
.BR boot (8),
.BR inet (8),
.BR netdefault (8),
.BR term (1),
.BR chat (1).
.SH BUGS
.SH AUTHOR
Kees J. Bot (kjb@cs.vu.nl)