serial-ip - Serial IP (SLIP or PPP) setup

     Note: This text and the serial IP code is not finished.  Code needs to be
     added  to  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...

     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
     slip(8) program, or PPP (Point-to-Point Protocol), the newer  and  better
     serial  IP  protocol  implemented  by  the ppp(8) program.  Alas standard
     Minix only supports SLIP.

     In the following text all descriptions and examples will name SLIP or the
     slip  program, but one may just as well read PPP or ppp.  Where necessary
     the differences will be noted.

     A typical use of the slip program is like this:

          slip /dev/psip2 </dev/tty01 >/dev/tty01

     The argument of the program, the /dev/psip2 device, is  one  of  the  so-
     called "Pseudo IP" devices that the Minix TCP/IP driver 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  slip.   Standard  input and output are used by slip to exchange
     packets with another SLIP implementation.  This is  normally  through  an
     RS-232  serial line like the second serial line /dev/tty01 as used in the
     example above.

     If we look at the flow of data over normal ethernet then this is  what  a
     TCP  connection  between  two  Minix machines, telnet for instance, looks



     One-half (!) of a SLIP connection would look like this:

                                [serial line]

  Configuration for a SLIP network only
     It is important to know that as far as inet is concerned  the  pseudo  IP
     network  is  just  another  network,  nothing  special.   So  you have to
     convince inet that it has to send packets out  over  that  network.   One
     does  this  by setting a default route that makes inet believe that there
     is a router somewhere on the pseudo-IP network.

     Assume your machine has been given the IP address  by  your
     service   provider.   Let's  choose  another  address  on  that  network, 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 if-then-else-fi code in /usr/etc/rc  that  tests  if  /etc/
     should  be  run.   Copy  the lines in the else clause that starts network
     daemons to /etc/ and add the following lines to make it  look  like

          # My SLIP interface address.
          ifconfig -h -n

          # Standard network daemons.
          daemonize rarpd $named irdpd rip inetd

          # Default route to the outside world.
          add_route -g

     For standard Minix one has to edit /etc/rc instead at the  point  of  the
     XXX  comments.   The ifconfig goes at the first XXX, the 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.)

     Just one thing left to do.  The system uses the  first  ethernet  network
     (eth0,  ip0,  tcp0,  and  udp0) as the default network.  With the program
     netdefault(8) you have  to  change  the  links  to  the  default  devices
     (eth/psip,  ip,  tcp,  and  udp)  to point to the first pseudo IP network
     (psip2, ip2, tcp2, and udp2):

          netdefault psip2

     In /etc/hosts list at least 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:

          List the names and addresses of any other machine you wish  to  talk
          to  in /etc/hosts.  Drawback: This will quickly become a pretty long

          Create an /etc/resolv.conf that lists a nameserver at your  ISP  and
  (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.

          Install the above /etc/resolv.conf when slip is started, and  remove
          it  when  slip  exits.   Drawback:  Long  running programs only read
          /etc/resolv.conf at startup, so they don't notice it changing.

          Run a real Internet name daemon from the named  package.   Drawback:
          Nontrivial to set up.

  Configuration for a SLIP - Ethernet router (simple case)

  Configuration for a SLIP - Ethernet router (complex case)


     /dev/psip*     Pseudo-IP devices for use by slip and ppp.

     boot(8), inet(8), netdefault(8), term(1), chat(1).


     Kees J. Bot (