#!/bin/sh

. /etc/functions.sh
. /usr/share/libubox/jshn.sh

find_iface_address()
{
	local iface="$1"
	local ipaddr="$2"
	local prefix="$3"

	local tmp="$(ubus call network.interface."$iface" status 2>/dev/null)"

	json_load "${tmp:-{}}"
	json_get_type tmp address

	if [ "$tmp" = array ]; then

		json_select address
		json_get_type tmp 1

		if [ "$tmp" = object ]; then

			json_select 1
			[ -n "$ipaddr" ] && json_get_var "$ipaddr" address
			[ -n "$prefix" ] && json_get_var "$prefix" mask

		fi
	fi
}

if [ "$ACTION" = "add" ] && [ "$INTERFACE" = "wan" ]; then
	local wanip
	find_iface_address wan wanip
	[ -n "$wanip" ] || return

	iptables -t nat -F nat_reflection_in 2>/dev/null || {
		iptables -t nat -N nat_reflection_in
		iptables -t nat -A prerouting_rule -j nat_reflection_in
	}

	iptables -t nat -F nat_reflection_out 2>/dev/null || {
		iptables -t nat -N nat_reflection_out
		iptables -t nat -A postrouting_rule -j nat_reflection_out
	}

	iptables -t filter -F nat_reflection_fwd 2>/dev/null || {
		iptables -t filter -N nat_reflection_fwd
		iptables -t filter -A forwarding_rule -j nat_reflection_fwd
	}

	find_networks() {
		find_networks_cb() {
			local cfg="$1"
			local zone="$2"

			local name
			config_get name "$cfg" name

			[ "$name" = "$zone" ] && {
				local network
				config_get network "$cfg" network

				echo ${network:-$zone}
				return 1
			}
		}

		config_foreach find_networks_cb zone "$1"
	}

	setup_fwd() {
		local cfg="$1"

		local reflection
		config_get_bool reflection "$cfg" reflection 1
		[ "$reflection" == 1 ] || return

		local src
		config_get src "$cfg" src

		local target
		config_get target "$cfg" target DNAT

		[ "$src" = wan ] && [ "$target" = DNAT ] && {
			local dest
			config_get dest "$cfg" dest "lan"
			[ "$dest" != "*" ] || return

			local net
			for net in $(find_networks "$dest"); do
				local lanip lanmk
				find_iface_address "$net" lanip lanmk
				[ -n "$lanip" ] || return

				local proto
				config_get proto "$cfg" proto

				local epmin epmax extport
				config_get extport "$cfg" src_dport
				[ -n "$extport" ] || return

				epmin="${extport%[-:]*}"; epmax="${extport#*[-:]}"
				[ "${epmin#!}" != "$epmax" ] || epmax=""

				local ipmin ipmax intport
				config_get intport "$cfg" dest_port "$extport"

				ipmin="${intport%[-:]*}"; ipmax="${intport#*[-:]}"
				[ "${ipmin#!}" != "$ipmax" ] || ipmax=""

				local exthost
				config_get exthost "$cfg" src_dip "$wanip"

				local inthost
				config_get inthost "$cfg" dest_ip
				[ -n "$inthost" ] || return

				[ "$proto" = tcpudp ] && proto="tcp udp"

				[ "${inthost#!}" = "$inthost" ] || return 0
				[ "${exthost#!}" = "$exthost" ] || return 0

				[ "${epmin#!}" != "$epmin" ] && \
					extport="! --dport ${epmin#!}${epmax:+:$epmax}" || \
					extport="--dport $epmin${epmax:+:$epmax}"

				[ "${ipmin#!}" != "$ipmin" ] && \
					intport="! --dport ${ipmin#!}${ipmax:+:$ipmax}" || \
					intport="--dport $ipmin${ipmax:+:$ipmax}"

				local p
				for p in ${proto:-tcp udp}; do
					case "$p" in
						tcp|udp|6|17)
							iptables -t nat -A nat_reflection_in \
								-s $lanip/$lanmk -d $exthost \
								-p $p $extport \
								-j DNAT --to $inthost:${ipmin#!}${ipmax:+-$ipmax}

							iptables -t nat -A nat_reflection_out \
								-s $lanip/$lanmk -d $inthost \
								-p $p $intport \
								-j SNAT --to-source $lanip

							iptables -t filter -A nat_reflection_fwd \
								-s $lanip/$lanmk -d $inthost \
								-p $p $intport \
								-j ACCEPT
						;;
					esac
				done
			done
		}
	}

	config_load firewall
	config_foreach setup_fwd redirect
fi