#!/bin/sh

main_device=$1
def_eth0_gateway=$2
def_serverip=$3

add_4g_dns()
{
	DNS_4G_PATH="/tmp/resolv.conf"
	DNS_PATH="/mnt/usr/etc/resolv.conf"

	if [ ! -f $DNS_4G_PATH ];then
		return
	fi
	
	if [ "$(sed -n 1p $DNS_4G_PATH)" == "" ];
	then
		return
	fi
	
	if [ "$(sed -n 1p $DNS_4G_PATH)" == "$(sed -n 2p $DNS_PATH)" ];
	then
		return
	fi
	
	if [ "$(sed -n 1p $DNS_4G_PATH)" == "$(sed -n 1p $DNS_PATH)" ];
	then
		return
	fi
	
	
	if [ ! -f $DNS_PATH ];then
		echo $(sed -n 1p $DNS_4G_PATH) > $DNS_PATH
		echo "nameserver 114.114.114.114" >> $DNS_PATH
	else
		echo $(sed -n 1p $DNS_PATH) > $DNS_PATH
		echo $(sed -n 1p $DNS_4G_PATH) >> $DNS_PATH
		echo "nameserver 114.114.114.114" >> $DNS_PATH
	fi
}

check_route()
{
	add_4g_dns
	
	if [ "$(route -n | sed -n '3p;3q' | grep $1 | grep UG)" == "" ];then
			ppp0_gw=$(route -n | grep ppp0 | grep UG | awk '{print $2}')
			while [ "$(route -n | grep UG)" != "" ]
			do 
				route del default
			done
			
			if [ "$2" == "eth1" ];then
				route add default gw $def_eth0_gateway dev $2 metric 20
			else
				route add default gw $ppp0_gw dev $2 metric 20
			fi
			
			if [ "$1" == "eth1" ];then
				route add default gw $def_eth0_gateway dev $1 metric 10
			else
				route add default gw $ppp0_gw dev $1 metric 10
			fi
	fi
}

set_route_default()
{
	ppp0_gw=$(route -n | grep ppp0 | grep UG | awk '{print $2}')
	while [ "$(route -n | grep UG)" != "" ]
	do 
		route del default
	done
			
	if [ "$2" == "eth1" ];then
		route add default gw $def_eth0_gateway dev $2 metric 20
	else
		route add default gw $ppp0_gw dev $2 metric 20
	fi
			
	if [ "$1" == "eth1" ];then
		route add default gw $def_eth0_gateway dev $1 metric 10
	else
		route add default gw $ppp0_gw dev $1 metric 10
	fi
}

sub_device=""

main_device_error=0
sub_device_error=0
route_def_flag=0

nothing=0

if [ "$#" -ne "3" ];then
	echo "usage ./auto_gw_switch <DefaultDev> <Eth0GetWay> <ping ip>"
	exit 1
fi

if [ "$main_device" == "eth1" ];
then
	echo $main_device
elif [ "$main_device" == "ppp0" ];
then
	echo $main_device
else
	echo "Error: No such Main Dev "
	exit 1
fi

if [ "$main_device" == "eth1" ];
then
	sub_device="ppp0";
else
	sub_device="eth1";
fi

echo -n $def_serverip > /tmp/4g_ping.txt

while true
do
	if [ "$(lsusb | grep -E "ID 05c6:9025|ID 05c6:9059|ID 05c6:905a|ID 2949:8241|ID 2949:8242|ID 2949:8243|ID 19d2:0532|ID 19d2:0536|ID 19d2:0542|ID 19d2:0573|ID 19d2:0579|ID 2c7c:0125|ID 19d2:1476|ID 2c7c:6026|ID 2c7c:6002|ID 2c7c:6005")" != "" ];
	then
		if [ "$(ps | grep udhcpc |grep -v grep)" == "" ];
		then
		echo "nothing"
		#udhcpc -i ppp0 &
		fi
	else
		if [ "$(ps | grep udhcpc | grep -v grep)" == "" ];then
			nothing=1
		else
			echo "nothing"
			#killall udhcpc
		fi
		sleep 5
		continue
	fi
	
	if [ $route_def_flag == 0 ];then
		set_route_default $main_device $sub_device
		route_def_flag=1
	fi
	
	ping $def_serverip -I $main_device -c 1 -w 1 >> /dev/null
	if [ "$?" != "0" ]; then
		#echo "ping main device failed" $main_device_error;
		let main_device_error++;
	else
		main_device_error=0;
		#echo "change to Main device"
		check_route $main_device $sub_device
		sleep 5
	fi
	
	if [ $main_device_error -gt 5 ];then
		ping $def_serverip -I $sub_device -c 1 -w 1 >> /dev/null
		if [ "$?" != "0" ]; then
			#echo "ping sub device failed" $sub_device_error;
			let sub_device_error++;
		else
			sub_device_error=0;
			#echo "change to sub device"
			check_route $sub_device $main_device
			sleep 5
		fi
	fi
	
	if [ $sub_device_error -gt 5 ];then
		check_route $main_device $sub_device
	fi

done