add a bash script to run with systemd for digirig and ICOM dedicated VHF packet station

ansible/roles/scanner_digirig/templates/digirig-direwolf.sh

@@ -0,0 +1,119 @@
+#!/bin/bash
+# @author Craig McDaniel
+#
+# This script runs Direwolf, socat and kissatach. It starts them in that order and makes sure they
+# all stay running and work together. If one crashes, this script stops everything. This effectively
+# sets up a AX.25 interface on a Linux computer using the Linux AX.25 stack.
+#
+# It's designed to be uses with systemd for things like auto start, auto re-start.
+#
+# 
+# RF signals!   _ RF signals!
+#  \          _/
+#   \       /
+#  +-------+
+#  | Radio | ----- RF signals!
+#  +-------+
+#      |
+#      | Analog cable
+#      |
+# +---------+
+# | Digirig |
+# +---------+
+#      |
+#      | USB sound card
+#      |
+# +----|---------------------------------------------------------------------------+
+# |    |    This is your computer. The things in here are virtual components.      |
+# |    |                                                                           |
+# |  +-----------+       +-------+        +------------+            Linux kernel   |
+# |  | Direwolf  | <---> | Socat | <----> | Kissattach | <------>   ax0 interface  |
+# |  +-----------+       +-------+        +------------+                           |
+# |                                                                                |
+# +--------------------------------------------------------------------------------+
+
+# Configuration
+DIREWOLF_CMD="/usr/local/bin/direwolf -t 0 -X 1 -c /opt/busnet/direwolf/config/digirig.conf"
+SOCAT_CMD="/usr/bin/socat PTY,raw,echo=0,link=/dev/radio/digirig-tnc TCP4:127.0.0.1:8001"
+KISSATTACH_CMD="/usr/sbin/kissattach /dev/radio/digirig-tnc digirig"
+KISSPARAMS_CMD="kissparms -c 1 -p digirig"
+INTERFACE_NAME="ax0"
+
+cleanup() {
+    echo
+    echo "Exit signal detected. Cleaning up..."
+    trap - SIGTERM # prevent recursion
+    kill 0
+    exit
+}
+
+# Trap exit signals
+trap cleanup SIGINT SIGTERM
+
+echo
+echo "======================================================================"
+echo "Starting Direwolf..."
+echo "======================================================================"
+echo
+$DIREWOLF_CMD &
+DIREWOLF_PID=$!
+sleep 1
+if ! kill -0 $DIREWOLF_PID; then
+    echo "Direwolf failed to start."
+    exit 1
+fi
+
+# Wait 3 seconds for Direwolf to initialize, then start socat.
+# socat creates a full duplex/bidirectional pipe between a serial port /dev/radio/digirig-tnc and
+# Direwolf's KISS TCP interface, which is running on localhost:8001. The kissattach program needs
+# a serial port to work, and this is how we accomplish connecting kissattach to direwolf.
+sleep 3
+
+echo
+echo "======================================================================"
+echo "Starting socat..."
+echo "======================================================================"
+echo
+sudo $SOCAT_CMD &
+SOCAT_PID=$!
+if ! kill -0 $SOCAT_PID; then
+    echo "Socat failed to start."
+    kill $DIREWOLF_PID
+    exit 1
+fi
+
+
+# Run kissatach to create an AX.25 network interface on the system.
+#
+# Kissattach annoyingly forks itself in the background, so we can't directly monitor the process.
+# We rely on the control-group feature of systemd to kill all child processes for us, even if 
+# they fork!
+#
+# Kissattach cannot use KISS over TCP directly to Direwolf. It expects a serial terminal to exist,
+# which is why we use socat to create the pipe between Direwolf's KISS TCP port and this serial
+# device.
+sleep 1
+
+echo
+echo "======================================================================"
+echo "Starting kissattach and setting kissparams..."
+echo "======================================================================"
+echo
+sudo $KISSATTACH_CMD
+if [ $? -ne 0 ]; then
+    echo "kissattach failed to start."
+    cleanup
+fi
+
+# We have to set something on the AX.25 interface that Direwolf requires.
+sudo $KISSPARAMS_CMD
+
+echo
+echo "All processes started. Monitoring via wait..."
+
+# 'wait -n' waits for ANY background process to exit.
+# It returns as soon as Direwolf or Socat dies.
+wait -n
+
+# If we get here, one of the processes died.
+cleanup