🚀 go-pugleaf

Archive-name: linux/howto/AX25-HOWTO/part2
Last-modified: 3 Dec 96

-----BEGIN PGP SIGNED MESSAGE-----

*** The `Linux AX25 HOWTO' is posted automatically by the
*** Linux HOWTO coordinator, Greg Hankins <gregh@sunsite.unc.edu>.  Please
*** direct any comments or questions about this HOWTO to the author,
*** Terry Dawson <terry@perf.no.itg.telecom.com.au>.

- --- BEGIN Linux AX25 HOWTO part 2/2 ---

  14.3.  Starting ax25d

  When you have the two configuration files completed you start ax25d
  with the command:

       # /usr/local/sbin/ax25d

  When this is run people should be able to make AX.25 connections to
  your Linux machine. Remember to put the ax25d command in your rc files
  so that it is started automatically when you reboot each time.

  14.4.  Configuring the node software.

  The node software was developed by Tomi Manninen
  <tomi.manninen@hut.fi> and was based on the original PMS program.  It
  provides a fairly complete and flexible node capability that is easily
  configured. It allows users once they are connected to make telnet,
  netrom or telnet connections out and to obtain various sorts of
  information such as Finger, Nodes and Heard lists etc.

  The node would normally be invoked from the ax25d program although it
  is also capable of being invoked from the tcp/ip inetd program to
  allow users to telnet to your machine and obtain access to it, or by
  running it from the command line.

  14.4.1.  Creating the /usr/local/node/node.conf file.

  The node.conf file is where the main configuration of the node takes
  place. It is a simple text file and its format is as follows:

  # /usr/local/node/node.conf
  # configuration file for the node(8) program.
  #
  # Lines beginning with '#' are comments and are ignored.

  # Hostname
  # Specifies the hostname of the node machine
  hostname        radio.gw.vk2ktj.ampr.org

  # Local Network
  # allows you to specify what is consider 'local' for the
  # purposes of permission checking using nodes.perms.
  localnet        44.136.8.96/29

  # Hide Ports
  # If specified allows you to make ports invisible to users. The
  # listed ports will not be listed by the (P)orts command.
  hiddenports     70cm 2m

  # Callserver
  # If configured the node provides users with access to a callserver.
  callserver      zone.oh7rba.ampr.org

  # Node Idle Timeout
  # Specifies the idle time for connections to this node in seconds.
  idletimout      1800

  # Connection Idle Timeout
  # Specifies the idle timer for connections made via this node in
  # seconds.
  conntimeout     1800

  # Reconnect
  # Specifies whether users should be reconnected to the node
  # when their remote connections disconnect, or whether they
  # should be disconnected complete.
  reconnect       on

  # Command Aliases
  # Provide a way of making complex commands simple.
  alias           CONV    "telnet vk1xwt.ampr.org 3600"
  alias           BBS     "connect radio vk2xsb"

  14.4.2.  Creating the /usr/local/node/node.perms file.

  The node allows you to assign permissions to users. These permissions
  allow you to determine which users should be allowed to make use of
  options such as the (T)elnet, and (C)onnect commands, for example, and
  which shouldn't. The node.perms file is where this information is
  stored and contains five key fields. For all fields an asterisk `*'
  character matches anything. This is useful for building default rules.

     user
        The first field is the callsign or user to which the permissions
        should apply.  Any SSID value is ignored, so you should just
        place the base callsign here.

     method
        Each protocol or access method is also given permissions. For
        example you might allow users who have connected via AX.25 or
        NetRom to use the (C)onnect option, but prevent others, such as
        those who are telnet connected from a non-local node from having
        access to it. The second field therefore allows you to select
        which access method this permissions rule should apply to.  The
        access methods allowed are:

          method  description
          ------  -----------------------------------------------------------
          ax25    User connected by AX.25
          netrom  User connected by NetRom
          host    User started node from command line
          local   User is telnet connected from a 'local' host
          ampr    User is telnet connected from an amprnet address (44.0.0.0)
          inet    user is telnet connected from a non-loca, non-ampr address.

     port
        For AX.25 users you can control permissions on a port by port
        basis too if you choose. This allows you to determine what AX.25
        are allowed to do based on which of your ports they have
        connected to. The third field contains the port name if you are
        using this facility. This is useful only for AX.25 connections.

     password
        You may optionally configure the node so that it prompts users
        to enter a password when they connect. This might be useful to
        help protect specially configured users who have high authority
        levels. If the fourth field is set then its value will be the
        password that will be accepted.

     permissions
        The permissions field is the final field in each entry in the
        file.  The permissions field is coded as a bit field, with each
        facility having a bit value which if set allows the option to be
        used and if not set prevents the facility being used. The list
        of controllable facilities and their corresponding bit values
        are:

          value   description
          -----   -------------------------------------------------
           1      Login allowed.
           2      AX25 (C)onnects allowed.
           4      NetRom (C)onnects allowed.
           8      (T)elnet to local hosts allowed.
           16     (T)elnet to amprnet (44.0.0.0) hosts allowed.
           32     (T)elnet to non-local, non-amprnet hosts allowed.
           64     Hidden ports allowed for AX.25 (C)onnects.

     To code the permissions value for a rule, simply take each of the
     permissions you want that user to have and add their values
     together. The resulting number is what you place in field five.

  A sample nodes.perms might look like:

  # /usr/local/node/node.perms
  #
  # The node operator is VK2KTJ, has a password of 'secret' and
  # is allowed all permissions by all connection methods
  vk2ktj  *       *       secret  127

  # The following users are banned from connecting
  NOCALL  *       *       *       0
  PK232   *       *       *       0
  PMS     *       *       *       0

  # INET users are banned from connecting.
  *       inet    *       *       0

  # AX.25, NetRom, Local, Host and AMPR users may (C)onnect and (T)elnet
  # to local and ampr hosts but not to other IP addresses.
  *       ax25    *       *       31
  *       netrom  *       *       31
  *       local   *       *       31
  *       host    *       *       31
  *       ampr    *       *       31

  14.4.3.  Configuring node to run from ax25d

  The node program would normally be run by the ax25d program.  To do
  this you need to add appropriate rules to the /etc/ax25/ax25d.conf
  file. In my configuration I wanted users to have a choice of either
  connecting to the node or connecting to other services. ax25d allows
  you to do this by cleverly creating creating port aliases. For
  example, given the ax25d configuration presented above, I want to
  configure node so that all users who connect to VK2KTJ-1 are given the
  node. To do this I add the following to my /etc/ax25/ax25d.conf file:

       [VK2KTJ-1 VIA VK2KTJ-0]
       default         * *    *   *   *   0    root /usr/local/bin/node node radio

  This simply says that all users who connect to VK2KTJ-1 on the same
  device (by the same port) as VK2KTJ-0 should cause the node program to
  be run with the name of the port they have connected via, in this case
  you will recall the /etc/ax25/axports specifies the port name as radio
  that supports the callsign VK2KTJ-0.

  14.4.4.  Configuring node to run from inetd

  If you want users to be able to telnet a port on your machine and
  obtain access to the node you can go this fairly easily. The first
  thing to decide is what port users should connect to. In this example
  I've arbitrarily chosen port 4000, though Tomi gives details on how
  you could replace the normal telnet daemon with the node in his
  documentation.

  You need to modify two files.

  To /etc/services you should add:

  node    4000/tcp        #OH2BNS's node software

  and to /etc/inetd.conf you should add:

       node    stream  tcp     nowait  root    /usr/local/bin/node node

  When this is done, and you have restarted the inetd program any user
  who telnet connects to port 4000 of your machine will be prompted to
  login and if configured, their password and then they will be con�
  nected to the node.

  14.5.  Configuring axspawn.

  The axspawn program is a simple program that allows AX.25 stations who
  connect to be log in to your machine. It is invoked from the ax25d
  program as described above. To allow a user to log in to your machine
  you should add a line similar to the following into your
  /etc/ax25/ax25d.conf file:

       default * * * * * 1 root /usr/local/sbin/axspawn axspawn %u

  If the line ends in the + character then the connecting user must hit
  return before they will be allowed to login. The default is to not
  wait.  Any individual host configurations that follow this line will
  have the axspawn program run when they connect. When axspawn is run it
  first checks that the command line argument it is supplied is a legal
  callsign, strips the SSID, then it checks that /etc/passwd file to see
  if that user has an account configured. If there is an account, and
  the password is either "" (null) or + then the user is logged in, if
  there is anything in the password field the user is prompted to enter
  a password. If there is not an existing account in the /etc/passwd
  file then axspawn may be configured to automatically create one.

  14.5.1.  Creating the /etc/ax25/axspawn.conf file.

  You can alter the behaviour of axspawn in various ways by use of the
  /etc/ax25/axspawn.conf file. This file is formatted as follows:

  # /etc/ax25/axspawn.conf
  #
  # allow automatic creation of user accounts
  create    yes
  #
  # guest user if above is 'no' or everything else fails. Disable with "no"
  guest     no
  #
  # group id or name for autoaccount
  group     ax25
  #
  # first user id to use
  first_uid 2001
  #
  # maximum user id
  max_uid   3000
  #
  # where to add the home directory for the new users
  home      /home/ax25
  #
  # user shell
  shell     /bin/bash
  #
  # bind user id to callsign for outgoing connects.
  associate yes

  The eight configurable characteristics of axspawn are as follows:

     #  indicates a comment.

     create
        if this field is set to yes then axspawn will attempt to
        automatically create a user account for any user who connects
        and does not already have an entry in the /etc/passwd file.

     guest
        this field names the login name of the account that will be used
        for people who connect who do not already have accounts if
        create is set to no. This is usually ax25 or guest.

     group
        this field names the group name that will be used for any users
        who connect and do not already have an entry in the /etc/passwd
        file.

     first_uid
        this is the number of the first userid that will be
        automatically created for new users.

     max_uid
        this is the maximum number that will be used for the userid of
        new users.

     home
        this is the home (login) directory of new users.

     shell
        this is the login shell of any new users.

     associate
        this flag indicates whether outgoing AX.25 connections made by
        this user after they login will use their own callsign, or your
        stations callsign.

  14.6.  Configuring the pms

  The pms program is an implementation of a simple personal message
  system. It was originally written by Alan Cox. Dave Brown, N2RJT,
  <dcb@vectorbd.com> has taken on further development of it.  At present
  it is still very simple, supporting only the ability to send mail to
  the owner of the system and to obtain some limited system information
  but Dave is working to expand its capability to make it more useful.

  Configuring the pms program is still a little clumsy at the moment
  because it is new but bare with it while Dave works on it. The only
  difficult part is modifying the source code to support your local mail
  delivery agent and whether you use the ttylinkd program or the talk-
  ax25 program.

  After that is done there are a couple of simple files that you should
  create that give users some information about the system and then you
  need to add appropriate entries into the ax25d.conf file so that
  connected users are presented with the PMS.

  14.6.1.  Customising pms.c

  If you take a look at the pms.c file in the ax25-utils package you
  will see that there a few items that you can configure.  Perhaps the
  most important to configure is the one that allows you to specify what
  local mail delivery agent you use. In most installations the deliver
  program may well work, but in the minimal installation on my gateway
  machine I needed to modify the line that previously said:

  #define MAIL_DELIVERY_AGENT     "deliver %s"

  to:

  #define MAIL_DELIVERY_AGENT     "/bin/mail.local %s"

  There is no easy way of knowing what local delivery agent your machine
  is configured to use, so perhaps you could simply look for either of
  these files in the obvious places and choose whichever seems to be
  there.

  I also have the ttylinkd program installed, so I needed to modify the
  section relating to it. I keep my copy of the ttylinkd program in my
  /usr/sbin directory, so I modified the line that previously said:

  /* #define MY_TALK              "/usr/local/sbin/ttylinkd" */

  to:

  #define MY_TALK              "/usr/sbin/ttylinkd"

  If you use the talk-ax25 program then you would remove the /* and */
  from around that line instead.

  There is one last definition that might be useful to you, and that is
  if you have a default email gateway. This line is the line containing
  the string MY_GATEWAY. If you have an email gateway that you use, then
  you should remove the comments from this line and change the address
  to that of your gateway.

  14.6.2.  Create the /usr/local/pms/motd file.

  The /usr/local/pms/motd file contains the `message of the day' that
  users will be presented with after they connect and receive the usual
  BBS id header. The file is a simple text file, any text you include in
  this file will be sent to users.

  14.6.3.  Create the /usr/local/pms/info file.

  The /usr/local/pms/info file is also a simple text file in which you
  would put more detailed information about your station or
  configuration.  This file is presented to users in response to their
  issuing of the Info command from the PMS> prompt.

  14.6.4.  Associate AX.25 callsigns with system users.

  When a connected user sends mail to an AX.25 callsign, the pms expects
  that callsign to be mapped, or associated with a real system user on
  your machine.

  You make this association with the axparms command. An example looks
  like:

       # axparms -assoc vk2ktj terry

  This command associates that AX.25 callsign vk2ktj with the user terry
  on the machine, so any mail for vk2ktj on the pms will be sent to
  terry.

  Remember to put these associations into your rc file so that they are
  available each time your reboot.

  14.6.5.  Add the PMS to the /etc/ax25/ax25d.conf file.

  Adding the pms to your ax25d.conf file is very simple.  There is one
  small thing you need to think about though. Dave has added command
  line arguments to the PMS to allow it to handle a number of different
  text end-of-line conventions. AX.25 and NetRom by convention expect
  the end-of-line to be carriage return, linefeed while the standard
  unix end-of-line is just newline. So, for example, if you wanted to
  add an entry that meant that the default action for a connection
  received on an AX.25 port is to start the PMS then you would add a
  line that looked something like:

       default  1  10 5 100 5   0    root  /usr/local/bin/pms pms -a -o vk2ktj

  This simply runs the pms program, telling it that it is an AX.25
  connection it is connected to and that the PMS owner is vk2ktj.  Check
  the man page for what you should specify for other connection methods.
  14.6.6.  Test the PMS.

  To test the PMS, you can try the following command from the command
  line:

  # /usr/local/bin/pms -u vk2ktj -o vk2ktj

  Substitute your own callsign for mine and this will run the pms,
  telling it that it is to use the unix end-of-line convention, and that
  user logging in is vk2ktj. You can do all the things connected users
  can.

  Additionally you might try getting some other node to connect to you
  to confirm that your ax25d.conf configuration works.

  15.  HOWTO link NOS and the Linux kernel networking software

  Many people like to run some version of NOS under Linux because it has
  all of the features and facilities they are used to. Most of those
  people would also like to have the NOS running on their machine
  capable of talking to the Linux kernel so that they can offer some of
  the linux capabilities to radio users.

  15.1.  Linking NOS and Linux using a pipe device

  Brandon S. Allbery, KF8NH, contributed the following information to
  explain how to interconnect the NOS running on a Linux machine with
  the kernel code using the Linux pipe device.

  Since both Linux and NOS support the slip protocol it is possible to
  link the two together by creating a slip link. You could do this by
  using two serial ports with a loopback cable between them, but this
  would be slow and costly. Linux provides a feature that many other
  Unix-like operating systems provide called `pipes'. These are special
  pseudo devices that look like a standard tty device to software but in
  fact loopback to another pipe device. To use these pipes the first
  program must open the master end of the pipe, and the open then the
  second program can open the slave end of the pipe. When both ends are
  open the programs can communicate with each other simply by writing
  characters to the pipes in the way they would if they were terminal
  devices.

  To use this feature to connect the Linux Kernel and a copy of NOS, or
  some other program you first must choose a pipe device to use. You can
  find one by looking in your /dev directory. The master end of the
  pipes are named: ptyp[1-f] and the slave end of the pipes are known
  as: ttyp[1-f]. Remember they come in pairs, so if you select
  /dev/ptypf as your master end then you must use /dev/ttypf as the
  slave end.

  Once you have chosen a pipe device pair to use you should allocate the
  master end to you linux kernel and the slave end to the NOS program,
  as the Linux kernel starts first and the master end of the pipe must
  be opened first.  You must also remember that your Linux kernel must
  have a different IP address to your NOS, so you will need to allocate
  a unique address for it if you haven't already.

  You configure the pipe just as if it were a serial device, so to
  create the slip link from your linux kernel you can use commands
  similar to the following:

  # /sbin/slattach -s 38400 -p slip /dev/ptypf &
  # /sbin/ifconfig sl0 broadcast 44.255.255.255 pointopoint 44.70.248.67 /
          mtu 1536 44.70.4.88
  # /sbin/route add 44.70.248.67 sl0
  # /sbin/route add -net 44.0.0.0 gw 44.70.248.67

  In this example the Linux kernel has been given IP address 44.70.4.88
  and the NOS program is using IP address 44.70.248.67. The route
  command in the last line simply tells your linux kernel to route all
  datagrams for the amprnet via the slip link created by the slattach
  command. Normally you would put these commands into your
  /etc/rc.d/rc.inet2 file after all your other network configuration is
  complete so that the slip link is created automatically when you
  reboot.  Note: there is no advantage in using cslip instead of slip as
  it actually reduces performance because the link is only a virtual one
  and occurs fast enough that having to compress the headers first takes
  longer than transmitting the uncompressed datagram.

  To configure the NOS end of the link you could try the following:

       # you can call the interface anything you want; I use "linux" for convenience.
       attach asy ttypf - slip linux 1024 1024 38400
       route addprivate 44.70.4.88 linux

  These commands will create a slip port named `linux' via the slave end
  of the pipe device pair to your linux kernel, and a route to it to
  make it work. When you have started NOS you should be able to ping and
  telnet to your NOS from your Linux machine and vice versa. If not,
  double check that you have made no mistakes especially that you have
  the addresses configured properly and have the pipe devices around the
  right way.

  16.  The /proc/ file system entries.

  The /proc filesystem contains a number of files specifically related
  to the AX25 and NetRom kernel software. These files are normally used
  by the AX52 utilities, but they are plainly formatted so you may be
  interested in reading them. The format is fairly easily understood so
  I don't think much explanation will be necessary.

     arp
        contains the list of Address Resolution Protocol mappings of IP
        addresses to MAC layer protocol addresses. These can can AX.25,
        ethernet or some other MAC layer protocol.

     ax25
        contains the AX.25 port configuration information.

     ax25%lowbar;bpqether
        contains the AX25 over ethernet BPQ style callsign mappings.

     ax25_calls
        contains the linux userid to callsign mappings set my the
        axparms -assoc command.

     ax25_route
        contains AX.25 digipeater path information.

     nr contains the NetRom port configuration information.

     nr_neigh
        contains information about the  NetRom neighbours known to the
        NetRom software.

     nr_nodes
        contains information about the NetRom nodes known to the NetRom
        software.

  17.  Walking on the wilder side .. the developmental software

  If all of the above doesn't satisfy your desire to push the limits
  there is plenty more for you to play with.

  There have a been a number of enhancements that are available as
  experimental software for you to try. They come either as patches
  against the 2.0.*  kernels, or in the alpha 2.1.* kernels.

  Be warned though, this software is new, pretty much untested and
  likely to contain bugs. If that worries you, then ignore this section
  of the document.

  17.1.  Enhanced versions of just about everything.

  The 2.1.* kernels have enhanced versions of nearly all of the
  protocols and drivers. The most significant of the enhancements are:

     modularised
        the protocols and drivers have all been modularised so that you
        can insmod and rmmod them whenever you wish. This reduces the
        kernel memory requirements for infrequently used modules and
        makes development and bug hunting much simpler.

     all drivers are now network drivers
        all of the network devices such as Baycom, SCC, PI, Packettwin
        etc now present a normal network interface, that is they now
        look like the ethernet driver does, they no longer look like
        KISS TNC's. A new utility called net2kiss allows you to build a
        kiss interface to these devices if you wish.

     bug fixed
        there have been many bug fixes and new features added to the
        drivers and protocols.

  To take advantage of the features of the 2.1.* AX.25 support you must
  use the new ax25-utils package. You shouldn't use a kernel older than
  2.1.9 and you should use ax25-utils-2.1.9a.tar.gz which is available
  from Jonathons home site.

  17.2.  ROSE Packet Layer Support

  The Rose packet layer protocol is similar to layer three of the X.25
  specification. The kernel based Rose support is a modified version of
  the FPAC Rose implementation
  <http://fpac.lmi.ecp.fr/f1oat/f1oat.html>.  You will need
  ax25-utils-2.1.9a.tar.gz to configure the rose interface.

  17.3.  Soundcard DSP based modem

  Thomas Sailor has built a new driver for the kernel that allows you to
  use your soundcard as a modem. Connect your radio directly to your
  soundcard to play packet!

  18.  Some sample configurations.

  Following are examples of the most common types of configurations.
  These are guides only as there are as many ways of configuring your
  network as there are networks to configure, but they may give you a
  start.

  18.1.  Small Ethernet LAN with Linux as a router to Radio LAN

  Many of you may have small local area networks at home and want to
  connect the machines on that network to your local radio LAN. This is
  the type of configuration I use at home. I arranged to have a suitable
  block of addresses allocated to me that I could capture in a single
  route for convenience and I use these on my Ethernet LAN. Your local
  IP coordinator will assist you in doing this if you want to try it as
  well. The addresses for the Ethernet LAN form a subset of the radio
  LAN addresses. The following configuration is the actual one for my
  linux router on my network at home:

                                                 .      .   .    .    . .
         ---                                .
          | Network       /---------\     .    Network
          | 44.136.8.96/29|         |    .     44.136.8/24        \ | /
          |               | Linux   |   .                          \|/
          |               |         |  .                            |
          |          eth0 | Router  |  .  /-----\    /----------\   |
          |---------------|         |-----| TNC |----| Radio    |---/
          |   44.136.8.97 |  and    |  .  \-----/    \----------/
          |               |         | sl0
          |               | Server  | 44.136.8.5
          |               |         |    .
          |               |         |     .
          |               \_________/       .
         ---                                     .      .   .    .    . .

  #!/bin/sh
  # /etc/rc.net
  # This configuration provides one KISS based AX.25 port and one
  # Ethernet device.

  echo "/etc/rc.net"
  echo "  Configuring:"

  echo -n "    loopback:"
  /sbin/ifconfig lo 127.0.0.1
  /sbin/route add 127.0.0.1
  echo " done."

  echo -n "    ethernet:"
  /sbin/ifconfig eth0 44.136.8.97 netmask 255.255.255.248 \
                  broadcast 44.136.8.103 up
  /sbin/route add 44.136.8.97 eth0
  /sbin/route add -net 44.136.8.96 netmask 255.255.255.248 eth0
  echo " done."

  echo -n "    AX.25: "
  axattach -i 44.136.8.5 -m 512 /dev/ttyS1 4800
  ifconfig sl0 netmask 255.255.255.0 broadcast 44.136.8.255
  route add -host 44.136.8.5 sl0
  route add -net 44.136.8.0 window 1024 sl0

  echo -n "    Netrom: "
  nrattach -i 44.136.8.5 netrom

  echo "  Routing:"
  /sbin/route add default gw 44.136.8.68 window 1024 sl0
  echo "    default route."
  echo done.

  # end

  /etc/ax25/axports

       # name  callsign        speed   paclen  window  description
       4800    VK2KTJ-0        4800    256     2       144.800 MHz

  /etc/ax25/nrports

       # name  callsign        alias   paclen  description
       netrom  VK2KTJ-9        LINUX   235     Linux Switch Port

  /etc/ax25/nrbroadcast

       # ax25_name     min_obs def_qual        worst_qual      verbose
       4800            1       120             10              1

  �  You must have IP_FORWARDING enabled in your kernel.

  �  The AX.25 configuration files are pretty much those used as
     examples in the earlier sections, refer to those where necessary.

  �  I've chosen to use an IP address for my radio port that is not
     within my home network block. I needn't have done so, I could have
     easily used 44.136.8.97 for that port too.

  �  44.136.8.68 is my local IPIP encapsulated gateway and hence is
     where I point my default route.

  �  Each of the machines on my Ethernet network have a route:

       route add -net 44.0.0.0 gw 44.136.8.97 window 512 mss 512 eth0

  The use of the mss and window parameters means that I can get optimum
  performance from both local Ethernet and radio based connections.

  �  I also run my sendmail, http, ftp and other daemons on the router
     machine so that it needs to be the only machine to provide others
     with facilities.

  �  The router machine is a lowly 386DX20 with a 20Mb harddrive and a
     very minimal linux configuration.

  18.2.  IPIP encapsulated gateway configuration.

  Linux is now very commonly used for tcp/ip encapsulated gateways
  around the world. The new tunnel driver supports multiple encapsulated
  routes and makes the older ipip daemon obsolete.

  A typical configuration would look similar to the following.

                                                 .      .   .    .    . .
         ---                                .
          | Network       /---------\     .    Network
          | 154.27.3/24   |         |    .     44.136.16/24       \ | /
          |               | Linux   |   .                          \|/
          |               |         |  .                            |
          |          eth0 | IPIP    |  .  /-----\    /----------\   |
       ---|---------------|         |-----| TNC |----| Radio    |---/
          |   154.27.3.20 | Gateway |  .  \-----/    \----------/
          |               |         | sl0
          |               |         | 44.136.16.1
          |               |         |    .
          |               |         |     .
          |               \_________/       .
         ---                                     .      .   .    .    . .

  The configuration files of interest are:

  # /etc/rc.net
  # This file is a simple configuration that provides one KISS AX.25
  # radio port, one Ethernet device, and utilises the kernel tunnel driver
  # to perform the IPIP encapsulation/decapsulation
  #
  echo "/etc/rc.net"
  echo "  Configuring:"
  #
  echo -n "    loopback:"
  /sbin/ifconfig lo 127.0.0.1
  /sbin/route add 127.0.0.1
  echo " done."
  #
  echo -n "    ethernet:"
  /sbin/ifconfig eth0 154.27.3.20 netmask 255.255.255.0 \
                  broadcast 154.27.3.255 up
  /sbin/route add 154.27.3.20 eth0
  /sbin/route add -net 154.27.3.0 netmask 255.255.255.0 eth0
  echo " done."
  #
  echo -n "    AX.25: "
  axattach -i 44.136.16.1 -m 512 /dev/ttyS1 4800
  /sbin/ifconfig sl0 netmask 255.255.255.0 broadcast 44.136.16.255
  /sbin/route add -host 44.136.16.1 sl0
  /sbin/route add -net 44.136.16.0 netmask 255.255.255.0 window 1024 sl0
  #
  echo -n "    tunnel:"
  /sbin/ifconfig tunl0 44.136.16.1 mtu 512 up
  #
  echo done.
  #
  echo -n "Routing ... "
  source /etc/ipip.routes
  echo done.
  #
  # end.

  and:

       # /etc/ipip.routes
       # This file is generated using the munge script
       #
       /sbin/route add -net 44.134.8.0 netmask 255.255.255.0 tunl0 gw 134.43.26.1
       /sbin/route add -net 44.34.9.0 netmask 255.255.255.0 tunl0 gw 174.84.6.17
       /sbin/route add -net 44.13.28.0 netmask 255.255.255.0 tunl0 gw 212.37.126.3
          ...
          ...
          ...

  /etc/ax25/axports

       # name  callsign        speed   paclen  window  description
       4800    VK2KTJ-0        4800    256     2       144.800 MHz

  Some points to note here are:

  �  The new tunnel driver uses the gw field in the routing table in
     place of the pointopoint parameter to specify the address of the
     remote IPIP gateway. This is why it now supports multiple routes
     per interface.

  �  You can configure two network devices with the same address.  In
     this example both the sl0 and the tunl0 devices have been
     configured with the IP address of the radio port. This is done so
     that the remote gateway sees the correct address from your gateway
     in encapsulated datagrams sent to it.

  �  The route commands used to specify the encapsulated routes can be
     automatically generated by a modified version of the munge script.
     This is included below. The route commands would then be written to
     a separate file and read in using the bash source /etc/ipip.routes
     command (assuming you called the file with the routing commands
     /etc/ipip.routes) as illustrated. The source file must be in the
     NOS route command format.

  �  Note the use of the window argument on the route command. Setting
     this parameter to an appropriate value improves the performance of
     your radio link.

  The new tunnel-munge script:

  #!/bin/sh
  #
  # From: Ron Atkinson <n8fow@hamgate.cc.wayne.edu>
  #
  #  This script is basically the 'munge' script written by Bdale N3EUA
  #  for the IPIP daemon and is modified by Ron Atkinson N8FOW. It's
  #  purpose is to convert a KA9Q NOS format gateways route file
  #  (usually called 'encap.txt') into a Linux routing table format
  #  for the IP tunnel driver.
  #
  #        Usage: Gateway file on stdin, Linux route format file on stdout.
  #               eg.  tunnel-munge < encap.txt > ampr-routes
  #
  # NOTE: Before you use this script be sure to check or change the
  #       following items:
  #
  #     1) Change the 'Local routes' and 'Misc user routes' sections
  #        to routes that apply to your own area (remove mine please!)
  #     2) On the fgrep line be sure to change the IP address to YOUR
  #        gateway Internet address. Failure to do so will cause serious
  #        routing loops.
  #     3) The default interface name is 'tunl0'. Make sure this is
  #        correct for your system.

  echo "#"
  echo "# IP tunnel route table built by $LOGNAME on `date`"
  echo "# by tunnel-munge script v960307."
  echo "#"
  echo "# Local routes"
  echo "route add -net 44.xxx.xxx.xxx netmask 255.mmm.mmm.mmm dev sl0"
  echo "#"
  echo "# Misc user routes"
  echo "#"
  echo "# remote routes"

  fgrep encap | grep "^route" | grep -v " XXX.XXX.XXX.XXX" | \
  awk '{
          split($3, s, "/")
          split(s[1], n,".")
          if      (n[1] == "")    n[1]="0"
          if      (n[2] == "")    n[2]="0"
          if      (n[3] == "")    n[3]="0"
          if      (n[4] == "")    n[4]="0"
          if      (s[2] == "1")   mask="128.0.0.0"
          else if (s[2] == "2")   mask="192.0.0.0"
          else if (s[2] == "3")   mask="224.0.0.0"
          else if (s[2] == "4")   mask="240.0.0.0"
          else if (s[2] == "5")   mask="248.0.0.0"
          else if (s[2] == "6")   mask="252.0.0.0"
          else if (s[2] == "7")   mask="254.0.0.0"
          else if (s[2] == "8")   mask="255.0.0.0"
          else if (s[2] == "9")   mask="255.128.0.0"
          else if (s[2] == "10")  mask="255.192.0.0"
          else if (s[2] == "11")  mask="255.224.0.0"
          else if (s[2] == "12")  mask="255.240.0.0"
          else if (s[2] == "13")  mask="255.248.0.0"
          else if (s[2] == "14")  mask="255.252.0.0"
          else if (s[2] == "15")  mask="255.254.0.0"
          else if (s[2] == "16")  mask="255.255.0.0"
          else if (s[2] == "17")  mask="255.255.128.0"
          else if (s[2] == "18")  mask="255.255.192.0"
          else if (s[2] == "19")  mask="255.255.224.0"
          else if (s[2] == "20")  mask="255.255.240.0"
          else if (s[2] == "21")  mask="255.255.248.0"
          else if (s[2] == "22")  mask="255.255.252.0"
          else if (s[2] == "23")  mask="255.255.254.0"
          else if (s[2] == "24")  mask="255.255.255.0"
          else if (s[2] == "25")  mask="255.255.255.128"
          else if (s[2] == "26")  mask="255.255.255.192"
          else if (s[2] == "27")  mask="255.255.255.224"
          else if (s[2] == "28")  mask="255.255.255.240"
          else if (s[2] == "29")  mask="255.255.255.248"
          else if (s[2] == "30")  mask="255.255.255.252"
          else if (s[2] == "31")  mask="255.255.255.254"
          else                    mask="255.255.255.255"

  if (mask == "255.255.255.255")
          printf "route add -host %s.%s.%s.%s gw %s dev tunl0\n"\
                  ,n[1],n[2],n[3],n[4],$5
  else
          printf "route add -net %s.%s.%s.%s gw %s netmask %s dev tunl0\n"\
                  ,n[1],n[2],n[3],n[4],$5,mask
   }'

  echo "#"
  echo "# default the rest of amprnet via mirrorshades.ucsd.edu"
  echo "route add -net 44.0.0.0 gw 128.54.16.18 netmask 255.0.0.0 dev tunl0"
  echo "#"
  echo "# the end"

  19.  Discussion relating to Amateur Radio and Linux.

  There are various places that discussion relating to Amateur Radio and
  Linux take place. They take place in the comp.os.linux.* newsgroups,
  they also take place on the HAMS list on vger.rutgers.edu. Other
  places where they are held include the tcp-group mailing list at
  ucsd.edu (the home of amateur radio tcp/ip discussions), and you might
  also try the #linpeople channel on the linuxnet irc network.

  To join the Linux linux-hams channel on the mail list server, send
  mail to:

       Majordomo@vger.rutgers.edu

  with the line:

       subscribe linux-hams

  in the message body. The subject line is ignored.

  To join the tcp-group send mail to:

       listserver@ucsd.edu

  with the line:
       subscribe tcp-group

  in the body of the text.

  Note: Please remember that the tcp-group is primarily for discussion
  of the use of advanced protocols, of which tcp/ip is one, in Amateur
  Radio. Linux specific questions should not ordinarily go there.

  20.  Copyright.

  The AX25-HOWTO, information on how to install and configure some of
  the more important packages providing AX25 support for Linux.
  Copyright (c) 1996 Terry Dawson.

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or (at
  your option) any later version.

  This program is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the:

  Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139,
  USA.


- --- END Linux AX25 HOWTO part 2/2 ---

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