#!/bin/bash
# OpenMPTCProuter VPS 6in4 service script

if [ "$1" = "stop" ] && [ "$(ip link show omr-6in4 up)" ]; then
	ip route del fd00::/8 via fe80::a00:2 dev omr-6in4
	ip link set omr-6in4 down
	ip tunnel del omr-6in4
	exit 0
fi

# Add IPv6 tunnel
if [ "$(ip link show omr-6in4 up)" ]; then
	ip tunnel change omr-6in4 mode sit remote 10.0.0.2 local 10.0.0.1
else
	ip tunnel add omr-6in4 mode sit remote 10.0.0.2 local 10.0.0.1
fi
ip link set omr-6in4 up
ip route replace fd00::/8 via fe80::a00:2 dev omr-6in4

_ping() {
	local host=$1
	ret=$(ping -4 "${host}" \
		-W 5 \
		-c 1 \
		-q
	) && echo "$ret" | grep -sq "0% packet loss" && {
		return
	}
	false
}

while true; do
	currentaddr=$(ip addr show omr-6in4 | grep link/sit | awk '{print $2}' | tr -d "\n")
	currentpeer=$(ip addr show omr-6in4 | grep link/sit | awk '{print $4}' | tr -d "\n")
	if [ -n "$currentpeer" ]; then
		_ping $currentpeer
		status=$?
		if ! $(exit $status); then
			allip_tcp=$(ip -4 addr show gt-tun0 | grep inet)
			allip_udp=$(ip -4 addr show gt-udp-tun0 | grep inet)
			allip="$allip_tcp
$allip_udp"
			while IFS= read -r inet; do
				ip=$(echo $inet | awk '{print $2}' | cut -d/ -f1 | tr -d "\n")
				ipd=$(echo $ip | sed 's/.1/.2/' | tr -d "\n")
				_ping $ipd
				status=$?
				if $(exit $status); then
					ip tunnel change omr-6in4 mode sit remote $ipd local $ip
					break
				fi
			done < <(printf '%s\n' "$allip")
		fi
	fi
	sleep 5
done