WireGuar Watchdog for DDNS endpoint update

wireguard-watchdog.sh

#!/bin/bash
set -e

## Put this script in /usr/local/bin/wireguard-watchdog.sh

## Create a service file
# sudo nano /etc/systemd/system/wireguard-watchdog.service

# [Unit]
# Description=WireGuard Watchdog for DDNS endpoint update
# After=network.target

# [Service]
# ExecStart=/usr/local/bin/wireguard-watchdog.sh
# Restart=always
# User=root

# [Install]
# WantedBy=multi-user.target

## Reload systemd and enable the service
# sudo systemctl daemon-reload
# sudo systemctl enable wireguard-watchdog.service
# sudo systemctl start wireguard-watchdog.service

log() {
    local message="$(date '+%Y-%m-%d %H:%M:%S') - $*"
    echo "$message" >> "$LOG_FILE"  # Write to custom log file
    logger -t "wireguard-watchdog" "$@"  # Keep syslog entry if needed
}

watchdog(){
	# Configuration
	HOSTNAME="WIREGUARD_PUBLIC_ENDPOINT"  # Wireguard hostname
	IP_FILE="/var/tmp/last_known_ip"     # Storage for previous IP
	SLEEP=300  # 5 minutes between checks
	LOG_FILE="/var/log/wireguard-watchdog.log"
	LOG_LEVEL=3
	[ -f "$LOG_FILE" ] || touch "$LOG_FILE" && chmod 644 "$LOG_FILE"

	echo "WireGuard watchdog: started, checking $HOSTNAME every $SLEEP seconds"
	log "Service started, checking $HOSTNAME every $SLEEP seconds"
	while sleep "$SLEEP"; do
		for i in {1..3}; do
			current_ip=$(dig +short "$HOSTNAME" @119.29.29.29 | head -n1) || true
			if [ -n "$current_ip" ]; then
				break
			fi
			sleep 2
		done
		if [ -z "$current_ip" ]; then
			log "Failed to resolve IP address after 3 attempts" >&2
		fi
		previous_ip=$(cat "$IP_FILE" 2>/dev/null)
		
		if [ "$current_ip" != "$previous_ip" ]; then
			echo "IP changed from ${previous_ip:-none} to $current_ip"
			log "IP changed from ${previous_ip:-none} to $current_ip"
			echo "$current_ip" > "$IP_FILE"
			systemctl restart wg-quick@wg0  # Make sure wg0 is the correct wireguard interface
			echo "Successfully restarted service with new IP $current_ip"
			log "Successfully restarted service with new IP $current_ip"
		else
			echo "No IP change detected for $HOSTNAME"
			log "No IP change detected for $HOSTNAME"
		fi
	done
}

# Start the watchdog
watchdog