AX.25 packages for Openwrt -- ax25-tools and libax25.
I use them to do IP-based wireless mesh networking with batmand (Layer 3 version of the B.A.T.M.A.N. mesh protocol - IPv4 only) with HC-12 serial RF transceiver modules attached to serial ports of WiFi routers.
At the moment, AX.25 kernel support has to be added manually using the make kernel_menuconfig command inside the Openwrt build environment.
Choose Networking support
Choose Amateur Radio support
Select Amateur Radio AX.25 Level 2 protocol
Select AX.25 network device drivers
For HC-12 or similar serial modules, select Serial port Kiss driver.
Disable the serial TTY console line in inittab, like this:
::sysinit:/etc/init.d/rcS S boot
::shutdown:/etc/init.d/rcS K shutdown
#::askconsole:/usr/libexec/login.sh
Restart init or reboot.
Edit AX.25 configuration in /etc/ax25/axports for callsign, baud rate and so on.
Bring the interface up with the kissattach command. If you want to do mesh networking, enable broadcasts.
All radio transmissions are broadcasts anyway ;)
Happy AX.25 networking / meshing!