Use collectd-mod-ping on openwrt dumb AP to turn ON a led when internet connectivity is down

openwrt_ping_led.sh

#!/bin/sh
# see https://gist.github.com/davidecavestro/ce54e7bf18b09812c03d109e83dbcc38
# originated from https://chatgpt.com/share/de263a5a-a3df-4dc3-944f-14b911624879

# PLEASE NOTE that the LED_PATH variable should reflect the hardware specific led name

# Install necessary packages
opkg update
opkg install collectd collectd-mod-ping bc

uci set luci_statistics.collectd_network.enable="1"
uci set luci_statistics.collectd_ping.enable="1"
uci set luci_statistics.collectd_ping.Hosts="openwrt.org"
uci set luci_statistics.collectd_ping.AddressFamily="ipv4"
uci commit luci_statistics
/etc/init.d/luci_statistics restart

# Create the script to check ping and control the LED
mkdir -p /etc/custom-scripts
cat << 'EOF' > /etc/custom-scripts/check_collectd_ping.sh
#!/bin/sh

# LED control paths
LED_PATH="/sys/class/leds/red:led4"
LED_TRIGGER="$LED_PATH/trigger"
LED_BRIGHTNESS="$LED_PATH/brightness"

# Collectd RRD data path
RRD_FILE="/tmp/rrd/$(cat /proc/sys/kernel/hostname)/ping/ping_droprate-openwrt.org.rrd"

# Check if the RRD file exists
if [ ! -f "$RRD_FILE" ]; then
  echo "RRD file not found: $RRD_FILE"
  exit 1
fi

# Get the latest ping drop rate value
PING_DROP_RATE=$(rrdtool fetch "$RRD_FILE" AVERAGE -s -30s -e now | head -n 3 | tail -n 1 | awk '{print $2}')

# Convert exponential notation to decimal notation
if echo "$PING_DROP_RATE" | grep -q "e"; then
  PING_DROP_RATE=$(printf "%f" "$PING_DROP_RATE")
fi

# Check if the ping drop rate indicates a connectivity issue
if [ "$PING_DROP_RATE" = "nan" ] || [ "$(echo "$PING_DROP_RATE > 0" | bc)" -eq 1 ]; then
  # Internet is not reachable, turn on the LED
  echo "default-on" > $LED_TRIGGER
  echo "1" > $LED_BRIGHTNESS
else
  # Internet is reachable, turn off the LED
  echo "none" > $LED_TRIGGER
  echo "0" > $LED_BRIGHTNESS
fi
EOF

# Make the script executable
chmod +x /etc/custom-scripts/check_collectd_ping.sh

# Create the cron job
cat << 'EOF' >> /etc/crontabs/root
* * * * * /etc/custom-scripts/check_collectd_ping.sh
EOF

# Ensure persistence across upgrades
cat << 'EOF' >> /etc/sysupgrade.conf
/etc/custom-scripts/
/etc/crontabs/
EOF

# Restart services to apply changes
/etc/init.d/cron restart
/etc/init.d/collectd restart

echo "Setup complete. The LED will now indicate internet connectivity status."