#!/bin/sh
# SPDX-License-Identifier: GPL-2.0
#
# Copyright (C) 2018 Aleksandr V. Piskunov <aleksandr.v.piskunov@gmail.com>.
# Copyright (C) 2015-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
#
# This watchdog script tries to re-resolve hostnames for inactive WireGuard peers.
# Use it for peers with a frequently changing dynamic IP.
# persistent_keepalive must be set, recommended value is 25 seconds.
#


. /lib/functions.sh

check_peer_activity() {
	local cfg=$1
	local iface=$2
	local disabled
	local public_key
	local endpoint_host
	local endpoint_port
	local persistent_keepalive
	local last_handshake
	local last_idle_seconds
	local idle_seconds

	config_get_bool disabled "${cfg}" "disabled" 0
	config_get public_key "${cfg}" "public_key"
	config_get endpoint_host "${cfg}" "endpoint_host"
	config_get endpoint_port "${cfg}" "endpoint_port" 51820
	config_get idle_seconds "${cfg}" "idle_seconds" 150

	if [ "${disabled}" -eq 1 ]; then
		# skip disabled peers
		return 0
	fi

	persistent_keepalive=$(wg show ${iface} persistent-keepalive | grep ${public_key} | awk '{print $2}')

	# only process peers with endpoints and keepalive set
	[ -z ${endpoint_host} ] && return 0;
	[ "${persistent_keepalive:-off}" = "off" ] && return 0;

	# skip IP addresses
	# check taken from packages/net/ddns-scripts/files/dynamic_dns_functions.sh
	local IPV4_REGEX="[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}"
	local IPV6_REGEX="\(\([0-9A-Fa-f]\{1,4\}:\)\{1,\}\)\(\([0-9A-Fa-f]\{1,4\}\)\{0,1\}\)\(\(:[0-9A-Fa-f]\{1,4\}\)\{1,\}\)"
	local IPV4=$(echo ${endpoint_host} | grep -m 1 -o "$IPV4_REGEX$")    # do not detect ip in 0.0.0.0.example.com
	local IPV6=$(echo ${endpoint_host} | grep -m 1 -o "$IPV6_REGEX")
	[ -n "${IPV4}${IPV6}" ] && return 0;

	# re-resolve endpoint hostname if not responding for too long
	last_handshake=$(wg show ${iface} latest-handshakes | grep ${public_key} | awk '{print $2}')
	[ -z ${last_handshake} ] && return 0;
	last_idle_seconds=$(($(date +%s)-${last_handshake}))
	[ ${last_idle_seconds} -lt ${idle_seconds} ] && return 0;
	logger -t "wireguard_monitor" "${iface} endpoint ${endpoint_host}:${endpoint_port} is not responding for ${last_idle_seconds} seconds, restarting"
	ifup "${iface}"
}

# query ubus for all active wireguard interfaces
eval $(ubus -S call network.interface dump | jsonfilter -e 'wg_ifaces=@.interface[@.up=true && @.proto="wireguard"].interface')

# check every peer in every active wireguard interface
config_load network
for iface in $wg_ifaces; do
	config_foreach check_peer_activity "wireguard_${iface}" "${iface}"
done
