Configuring the node software

Linux Amateur Radio AX.25 HOWTO
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# 13. Configuring the node software

The node software was developed by Tomi Manninen 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, NET/ROM, ROSE, and AX.25 connections out and to obtain various sorts of information such as Finger, Nodes and Heard lists etc. You can configure the node to execute any Linux command you wish fairly simply.

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.

## 13.1. Creating the `/etc/ax25/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:

    # /etc/ax25/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	rose netrom

    # Node Identification.
    # this will appear in the node prompt
    NodeId		LINUX:VK2KTJ-9

    # NET/ROM port
    # This is the name of the NET/ROM port that will be used for
    # outgoing NET/ROM connections from the node.
    NrPort		netrom

    # 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 node commands simple.
    alias		CONV	"telnet vk1xwt.ampr.org 3600"
    alias		BBS	"connect radio vk2xsb"

    # External Command Aliases
    # Provide a means of executing external commands under the node.
    # extcmd <cmdname> <flag> <userid> <command>
    # Flag == 1 is the only implemented function.
    # <command> is formatted as per ax25d.conf
    extcmd		PMS	1	root	/usr/sbin/pms pms -u %U -o VK2KTJ

    # Logging
    # Set logging to the system log. 3 is the noisiest, 0 is disabled.
    loglevel	3

    # The escape character
    # 20 = (Control-T)
    EscapeChar      20

## 13.2. Creating the `/etc/ax25/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 NET/ROM 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
  --- | ---
  ampr | User is telnet connected from an amprnet address (44.0.0.0)
  ax25 | User connected by AX.25
  host | User started node from command line
  inet | user is telnet connected from a non-loca, non-ampr address.
  local | User is telnet connected from a 'local' host
  netrom | User connected by NET/ROM
  rose | User connected by ROSE
  * | User connected by any means.

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 | AX.25 (C)onnects allowed.
  4 | NET/ROM (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.
  128 | ROSE (C)onnects allowed.

  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:

    # /etc/ax25/node.perms
    #
    # The node operator is VK2KTJ, has a password of 'secret' and
    # is allowed all permissions by all connection methods
    vk2ktj	*	*	secret	255

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

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

    # AX.25, NET/ROM, Local, Host and AMPR users may (C)onnect and (T)elnet
    # to local and ampr hosts but not to other IP addresses.
    *	ax25	*	*	159
    *	netrom	*	*	159
    *	local	*	*	159
    *	host	*	*	159
    *	ampr	*	*	159

## 13.3. 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 radio]
    default    *     *    *   *   *   0    root /usr/sbin/node node

This says that the Linux kernel code will answer any connection requests for the callsign ``VK2KTJ-1`' heard on the AX.25 port named ``radio`', and will cause the node program to be run.

## 13.4. 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	3694/tcp	#OH2BNS's node software

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

    node	stream	tcp	nowait	root	/usr/sbin/node node

When this is done, and you have restarted the inetd program any user who telnet connects to port 3694 of your machine will be prompted to login and if configured, their password and then they will be connected to the node.

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