Linux Native AX.25 Stack¶
For Debian-alikes, see installation instructions.
Each of the below components are required to make the complete node, but they are (generally) not all interdependent, and most of the unique components will work to make a stripped down version.
axports¶
Setting up basic AX.25 on Debian is relatively simple - the key file to edit here is /etc/ax25/axports.
GB7HIB currently runs the following below config. Each port has been given an internal reference, I like to detail what connection they are providing. Other people map them out by number or other methods, but I find having a pretty consistent set of references to the radio/interface I'm using keeps my brain in check.
The callsign&SSID is, in this case, the physical address for the port, akin to a MAC address on ethernet. It shows under ifconfig as a mac address for the link.
Speed is the speed of the serial port on the interface. In the case of the NinoTNC, this is 57600.
Paclen is the packet length - for V/UHF links, 255 bytes is a nice length. For HF, 60-80 is more common. It means for shorter packets that aren't as likely to be impacted by changes in propagation.
Window is the number of packets that can be sent in one burst. The more reliable the link,the higher the number. This is limited by the version of ax25 you're running - 2.0 has a lower window than 2.0. If you're running Linux, at the moment you're on ax25 2.0.
hibby@raspberrypi:~ $ cat /etc/ax25/axports
# /etc/ax25/axports
#
# The format of this file is:
#
# name callsign speed paclen window description
#
uhf GB7HIB-10 57600 255 2 UHF 9600bd
ip GB7HIB-11 115200 255 7 IP
kissattach¶
kissattach binds the axport to a physical kiss device.
I attach my UHF port to my NinoTNC with:
kissattach /dev/ttyACM0 uhf
axcall¶
With the basic port configured, you can use axcall to place a call.
hibby@raspberrypi:~ $ axcall uhf gm0nrt-7 calls my neighbour bill over layer 2/ax.25 point to point.
You can go via someone too as a digipeter, axcall uhf gm0cqv-7 via gm0nrt calls gm0cqv using gm0nrt as a digipeter!
ax25ipd¶
ax25ipd manages point to point links over the internet between myself and other stations. These can be UDP and TCP. In effect, we are creating a virtual modem to handle communication with other stations, just like we are doing with software or hardware modems when dealing with 'real radios'.
There are a couple of parts needed to make this work as an interface on my system - socat, ax25ipd and kissattach.
This can be a little abstract, but the mode of interaction as is follows:
We create a virtual modem with ax25ipd, a virtual pipe with socat that lets us connect to it similar to a physically attached modem and then run kissattach to make that relationship.
socat¶
I create a socket pair to connect ax25ipd and kissattach to connect the ip ax25 port to the axudp tunnel.
The command I run for this is:
socat -d -d -ly pty,raw,echo=0,link=/var/ax25/pty/axip1 pty,raw,echo=0,link=/var/ax25/pty/axip2
If you are copying this, you might need to make the /var/ax25/pty - mkdir -p /var/ax25/pty
This is brought up at boottime by systemd:
hibby@raspberrypi:~ $ cat /etc/systemd/system/kiss-socat-axip.service
[Unit]
Description=Socat interconnect for AX25 AXIP
After=network-online.target
Wants=network-online.target
[Service]
WorkingDirectory=/var/ax25
ExecStart=socat -d -d -ly pty,raw,echo=0,link=/var/ax25/pty/axip1 pty,raw,echo=0,link=/var/ax25/pty/axip2
ExecStartPost=/usr/bin/bash -c 'while ! [ -h /var/ax25/pty/axip2 ]; do sleep 1 ; done'
ExecStopPost=rm /var/ax25/pty/axip1 /var/ax25/pty/axip2
[Install]
WantedBy=multi-user.target
ax25ipd.conf¶
ax25ipd.conf is the core configuration file for this component. Below you can see that I connect to udp port 10095 of the remote station, and locally ax25ipd is in 'tnc' mode, binding to the previously created axip1. The route allows broadcasts b and is my default route d.
I beacon what the station is periodically, and I also allow NET/ROM NODES broadcasts and FBB broadcasts to go over the link.
hibby@raspberrypi:~ $ cat /etc/ax25/ax25ipd.conf
socket udp 10095
mode tnc
device /var/ax25/pty/axip1
speed 115200
loglevel 2
beacon after 3600
loglevel 2
btext ax25ip -- hibby/GB7HIB-2 -- AXIP Interface
broadcast QST-0 NODES-0 FBB-0
route MM3NDH 10.13.37.2 bd
Running ax25ipd¶
This is run from the command line as follows:
ax25ipd
kissattach¶
We need to attach the axip port to the virtual modem we've created with ax25ipd once it's running, and this is a simple case of:
kissattach /var/ax25/pty/axip2 axip
NET/ROM¶
NET/ROM covers functionality analogous to OSI layer3/layer 4.
What it means in reality is that my node has a knowledge of its neighbours and what their neighbours are, and automates routing calls. To use the earlier example, I can call directly to gm0cqv and my machine will know the best path -
axcall nrnod GM0CQV-7
Each NET/ROM sends a 'NODES' broadcast periodically. This details what systems it can hear, what the gateway to the remote nodes is and a 'quality' value. Nodes on the network can have an alias too - GM0CQV's node on -7 above is PTRNOD, so I can do the following -
axcall nrnod PTRNOD
and end up at the same location.
NET/ROM ports are largely independent of ax25 ports in that a user can call any given nrport without going through a specific axport. You can essentially define per-application nrports, and as many as you wish (assuming you have free unique SSIDs to offer them as mac addresses).
nrports¶
/etc/ax25/nrports,similar to axports, defines the netrom ports the system has available. I expect primary incoming connections to be through netrom, so mine are lower numbered.
netrom ports should not share SSID numbers with axports. This will make your system rather unstable.
hibby@raspberrypi:~ $ cat /etc/ax25/nrports
# /etc/ax25/nrports
#
# The format of this file is:
#
# name callsign alias paclen description
#
nrnod GB7HIB-1 HIBNOD 235 Netrom node Port
nrbbs GB7HIB-2 HIBBBS 235 Netrom BBS Port
I have a port for my service, the callsign and port, and an up to 6 letter alias for the service. The packet length is 20 bytes shorter than the ax25 packet to account for overheads, and then there's a wee description.
nrbroadcast¶
/etc/ax25/nrbroadcast defines how often netromd sends a NODES broadcast and what port it sends them over.
It also defines the default quality of stations received directly over that port, the worst quality it will broadcast, how long without hearing a nodes broadcast the station will remain in your routing table.
I have set some sensible defaults, things that come over the ip link are quite high, but I limit the worst quality so that my NODES table isn't too big.
hibby@raspberrypi:~ $ cat /etc/ax25/nrbroadcast
# /etc/ax25/nrbroadcast
#
# The format of this file is:
#
# ax25_name min_obs def_qual worst_qual verbose
#
uhf 5 192 100 1
ip 3 200 130 1
nrattach¶
Like AX.25, we need to attach the port to a device - our tool for this is nrattach.
nrattach is simple - you nrattach a port and that's it.
nrattach nrnod
netromd¶
netromd handles incoming and outgoing broadcasts.
I should really make this systemd unit come up after nrattach.
I run it as netromd -i -l -d -t 30, which broadcasts almost immidiately, creates debug logs and broadcasts every 30 minutes.
ax25d¶
ax25d is the Daemon that routes incoming connection requests and spins up a process for the caller.
Interestingly, it isn't tied to the incoming port that the call is coming through, so you can have any port or interface handle calls to any callsign, alias or other word.
/etc/ax25/ax25d.conf is the config file that controls this, and it handles ax25 ports and netrom ports slightly differently. The default config we ship with debian is full of great examples, see online here - mine is configured as below.
Reading it, you can see that GB7HIB is in [] and nrnod is in <>. They define the type of port. This means if you connect to GB7HIB over ax25, you get uronode. If you connect to HIBNOD, or GB7HIB-1 over netrom, you get uronode!
I am really interested in exploring some other applications, including axspawn, which lets you spawn a bash (or other) shell and effectively gives shell access over ax25/netrom to a user.
There's lots of options here, and it's an incredibly flexible piece of software and is the core of why the Linux stack is so interesting to me. You can present any binary on your system to a connecting user!
hibby@raspberrypi:~ $ cat /etc/ax25/ax25d.conf
# /etc/ax25/ax25d.conf
#
# ax25d Configuration File.
#
# AX.25 Ports begin with a '['.
#
[GB7HIB via uhf]
NOCALL * * * * * * L
default * * * * * * - root /usr/sbin/uronode uronode
#
[GB7HIB via ip]
NOCALL * * * * * * L
default * * * * * * - root /usr/sbin/uronode uronode
#
# NET/ROM Ports begin with a '<'.
#
<nrnod>
NOCALL * * * * * * L
default * * * * * * - root /usr/sbin/uronode uronode
#
Running ax25d¶
This is an easy one to start -
ax25d
Uronode Frontend¶
I use uronode both as a frontend for users connecting and for me connecting to the node and to neighbouring stations, essentially over telnet. When someone connects to my system, Uronode generates the menu that they see.
I also have it configured as my local client - i can run uronode in a terminal and be presented with a helpful control interface.
uronode.conf¶
This is the core config file for uronode that details what uronode can do. I'm running mine very stripped back, and have cut a lot of the defaults out:
You can see the BBS command is just a uronode call out to GB7HIB-2 over netrom, and there are external commands for netstat and the 'nodesearch' program I quite like.
The rest is pretty much default.
hibby@raspberrypi:~ $ cat /etc/ax25/uronode.conf
# /etc/ax25/uronode.conf - URONode example configuration file
#
# see uronode.conf(5)
# "Local" network.
# This is your local amprnet subnet in full. Do NOT use 44.0.0.0/8!
LocalNet 10.66.66.0/24
# Command aliases. See uronode.conf(5) for the meaning of the uppercase
# letters in the name of the alias. Examples below:
Alias BBS "c GB7HIB-2"
# External commands. See uronode.conf(5) for the meaning of the uppercase
# letters in the name of the extcmd.
#
# Flags: 1 Run command through pipe
# 2 Reconnected flag
# 3 Run through pipe and reconnect
#
ExtCmd NEtstat 3 nobody /bin/netstat netstat --ax25 --netrom
ExtCmd NSearch 3 root /usr/local/bin/nodesearch nodesearch %1
# Node ID.
# This displays before all output texts when the user connects into
# your node via NetRom. Set to "" to leave blank.
# Note: This -must- be defined or will display as "(null)". A space
# is hardcoded in. Example: UROHUB:N1URO-2 do NOT add the bracket
# afterwards "}" this is predefined in URONode.
#
NodeId HIBNOD:GB7HIB-1
# Ax25/Flex ID.
# This displays before some strings and at logout to the end user when
# they connect in via ax25 as defined in your ax25d.conf file. If
# you don't define this "(null)" will be presented to the end user. Its
# suggested you take this from your ax25d config which either faces a
# flexnet system OR your 2-meter user interface. Note: do NOT make this
# ssid the same as your NetRom SSID here or in ax25d.conf.
FlexId GB7HIB-10
# Netrom port name. This port is used for outgoing netrom connects.
NrPort nrnod
ReConnect on
# Syslog Logging level - suggest leaving this at 3 for debugging. 0
# halts logging.
LogLevel 3
PassPrompt "yes"
# The default escape character (CTRL-T)
#
EscapeChar ^T
Other Uronode Config Files¶
I have modified some other files that are worth highlighting -
uronode.perms¶
I have added the below line which allows me to login without password from the localhost by starting from shell and gets me nice colours!
mm0rfn host * * 255
uronode.announce¶
This has local announcements in it!
uronode.info¶
This has information about the system in it
uronode.motd¶
This is the welcome message displayed on every login
uronode.users¶
This defines shell access for me as a sysop. I've never actually spawned a shell from uronode, but apparently it's possible?!
Uronode as a local interface¶
I use uronode as my local packet radio terminal - instead of turning on and typing axcall nrnod salbbs to get to gm0nrt, I log in, type uronode, feed it my callsign and I am met with the uronode command interface, from which I can type c salbbs. It's a much nicer place to be!
This required xinetd for me to set up easily.
xinetd config¶
I think the below two config files are the only things required to make uronode listen on port 3964 -
xinetd must be enabled and started by systemd to be listening (systemctl enable xinetd, systemctl start xinetd)
There is probably a systemd native way of doing this, but I couldn't see that in the docs.
hibby@raspberrypi:~ $ cat /etc/xinetd.d/uronode
service uronode
{
disable = no
socket_type = stream
protocol = tcp
user = root
server = /usr/sbin/uronode
wait = no
instances = 20
}
hibby@raspberrypi:~ $ cat /etc/services | grep uronode
uronode 3694/tcp # Uronode
FBB BBS¶
fbb is my BBS software of choice! It is an oddity in that it binds directly to the ports you tell it exist, so it's listening on my ax25 and netrom ports without an entry in ax25d.conf. This mostly seems like magic to me and I am happy to let it run this way!
It has a few config files - fbb.conf, which is populated by the first run, ports.sys which defines the ports available and then bbs.sys and forward.sys which defines how you route to the outside world.
ports.sys¶
My reference for this file was this website, which was a helpful resource!
I have incremented the number of TNCs where appropriate and added my ports as 1,2,3. I have left the COM 1 Interface 9 etc alone.
hibby@raspberrypi:~ $ cat /etc/ax25/fbb/port.sys
# FBB7.0.11
#
#Ports TNCs
1 3
#
#Com Interface Adress (Hex) Baud
1 9 **** 9600
#
#TNC NbCh Com MultCh Pacln Maxfr NbFwd MxBloc M/P-Fwd Mode Freq
0 0 0 0 0 0 0 0 00/01 ---- File-fwd.
1 8 1 uhf 250 2 1 10 00/15 XUWYL 433.6250
2 8 1 ip 250 2 1 10 00/15 XUWYL ip port
3 8 1 nrbbs 236 2 1 10 00/15 XUWYL netrom port
#
# End of file.
#
bbs.sys, forward.sys¶
The Documentation is the best reference I've got for it, and I can't improve upon it.
Running Everything¶
I used to use systemd to bring things up, but now I run it with a bash script run as root:
#!/bin/bash
echo -n 'Creating socat sockets...'
socat -d -d -ly pty,raw,echo=0,link=/var/ax25/pty/axip1 pty,raw,echo=0,link=/var/ax25/pty/axip2 &
sleep 1
echo Done
echo -n 'Starting ax25ipd'
ax25ipd
sleep 1
kissattach /dev/ttyACM0 uhf
kissattach /var/ax25/pty/axip2 ip
kissparms -c 1 -p uhf
kissparms -c 1 -p ip
sleep 1
echo 'Done'
echo -n 'Bringing up NET/ROM runtime...'
modprobe netrom
nrattach nrnod
nrattach nrbbs
nrattach nrterm
netromd -i -l -d -t 30
echo -n Starting mheard daemon...
mheardd -l
echo Done
echo -n Starting ax25 daemon...
ax25d -l
echo Done
echo -n 'Starting fbb'
sudo fbb -f -l /home/hibby/fbb.log
echo Done