OpenWRT上的wireguard_watchdog补丁

[nickrunning]

通过Openwrt进行Wireguard组网时，可通过修改/usr/bin/wireguard_watchdog脚本，实现自动更新对端ip和端口：

--- /usr/bin/wireguard_watchdog   2024-05-20 14:21:51.233113205 +0800
+++ /usr/bin/wireguard_watchdog     2024-05-20 14:16:52.044368091 +0800
@@ -47,6 +47,14 @@
   idle_seconds=$(($(date +%s)-${last_handshake}))
   [ ${idle_seconds} -lt 150 ] && return 0;
   logger -t "wireguard_monitor" "${iface} endpoint ${endpoint_host}:${endpoint_port} is not responding for ${idle_seconds} seconds, trying to re-resolve hostname"
+  # if endpoint_port is 0, fetch from IP4P
+  if [ ${endpoint_port} -eq 0 ]; then
+    IP4P=$(nslookup ${endpoint_host} | grep -m 1 -o "$IPV6_REGEX")
+    endpoint_port=$(echo ${IP4P} | awk -F '::' '{split($2, a, ":"); printf "%d\n", "0x" a[1]}')
+    ipv4_segment=$(echo "${IP4P}" | awk -F ':' '{print $4":"$5}')
+    endpoint_host=$(printf "%d.%d.%d.%d\n" 0x${ipv4_segment:0:2} 0x${ipv4_segment:2:2} 0x${ipv4_segment:5:2} 0x${ipv4_segment:7:2})
+    logger -t "wireguard_monitor" "${iface} resolved ${endpoint_host}:${endpoint_port}"
+  fi
   wg set ${iface} peer ${public_key} endpoint "${endpoint_host}:${endpoint_port}"
 }