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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.