#!/bin/sh
#
# This script takes care of setting up the rules and routing table for
# eth0 and eth1 which are our wan port
#

# Programs
IPTABLES="/sbin/iptables"
IP="/sbin/ip"

# Enable ip_forwarding
echo 1 > /proc/sys/net/ipv4/ip_forward

# Script variables
wan0="eth0"
wan1="eth1"

# File for marking/demarking expiration/failure of interface
# so when its bound/rebound again it will by pass the new/old IP
# address checks
wan0_file="/var/run/wan0.expired"
wan1_file="/var/run/wan1.expired"

# Sets up the wan0 rules and routes
set_wan0 () {

	$IP rule add from 172.20.0.5 lookup 100

	for router in $new_routers; do
		$IP route add default via $router dev $wan0 table 100
	done
}

# Remove the wan0 rules and routes
unset_wan0 () {

	$IP rule del from 172.20.0.5 lookup 100
	$IP route flush table 100
}

# Sets up the wan1 rules and routes
set_wan1 () {

	$IP rule add from 172.20.0.3 lookup 101

	for router in $new_routers; do
		$IP route add default via $router dev $wan1 table 101
	done
}

# Remove the wan1 rules and routes
unset_wan1 () {

	$IP rule del from 172.20.0.3 lookup 101
	$IP route flush table 101
}

# Setup the IPTABLE rules for wan0
iptable_wan0 () {

	$IPTABLES -t nat -A wan0_dnat -d $new_ip_address -j DNAT --to-destination 172.20.0.5
	$IPTABLES -t nat -A wan0_snat -s 172.20.0.5 -j SNAT --to-source $new_ip_address
}

# Setup the IPTABLE rules for wan1
iptable_wan1 () {

	$IPTABLES -t nat -A wan1_dnat -d $new_ip_address -j DNAT --to-destination 172.20.0.3
	$IPTABLES -t nat -A wan1_snat -s 172.20.0.3 -j SNAT --to-source $new_ip_address
}

##################################################################################################
#
# Below this section shouldn't needs to be changed as long as the basic logic/stuff are the
# same in the above variables/functions
#
##################################################################################################

# Setup the indivual wan0 & wan1 chains and add it to the NAT tables
setup_NAT () {
	
	$IPTABLES -t nat -N wan0_dnat
	$IPTABLES -t nat -N wan0_snat

	$IPTABLES -t nat -N wan1_dnat
	$IPTABLES -t nat -N wan1_snat

	$IPTABLES -t nat -A PREROUTING -j wan0_dnat
	$IPTABLES -t nat -A POSTROUTING -j wan0_snat

	$IPTABLES -t nat -A PREROUTING -j wan1_dnat
	$IPTABLES -t nat -A POSTROUTING -j wan1_snat
}


# Flushes the NAT tables
flush_NAT () {

	# First this function needs to make sure that the
	# proper NAT chains actually exists, if not then
	# create them and exit
	echo `$IPTABLES -n -L -t nat` | grep -F -q "Chain wan1_snat"

	if [[ $? -eq 0 ]]; then
		
		# The NAT chain was found so find out which interface
		# is being flushed then flush that chain
		if [[ "$interface" == "$wan0" ]]; then
			
			$IPTABLES -t nat -F wan0_dnat
			$IPTABLES -t nat -F wan0_snat

		elif [[ "$interface" == "$wan1" ]]; then
			
			$IPTABLES -t nat -F wan1_dnat
			$IPTABLES -t nat -F wan1_snat
		
		fi
	else
		# The NAT chain was not found so create it
		setup_NAT
	fi
}



# Flushes the routing tables
flush_routing () {

	# find out which interface to flush
	if [[ "$interface" == "$wan0" ]]; then

		unset_wan0

	elif [[ "$interface" == "$wan1" ]]; then
	
		unset_wan1
	
	fi
	
	$IP route flush cache
}


# Sets up the NAT tables
set_NAT () {

	# Determite if the NAT tables needs to be flushed
	# and updated, also determite if the interface was
	# previously expired
	if [[ "$old_ip_address" != "$new_ip_address" ||
		-e $wan0_file || -e $wan1_file ]]; then

		# The old and new ip address are not the same, update
		# the NAT table, or the interface was expired/failed
		flush_NAT
		
		# Find out which interface to set
		if [[ "$interface" == "$wan0" ]]; then
			
			iptable_wan0
			$IPTABLES -t nat -A wan0_dnat -j RETURN
			$IPTABLES -t nat -A wan0_snat -j RETURN

			# Remove the expired file
			rm -f $wan0_file

		elif [[ "$interface" == "$wan1" ]]; then

			iptable_wan1
			$IPTABLES -t nat -A wan1_dnat -j RETURN
			$IPTABLES -t nat -A wan1_snat -j RETURN

			# Remove the expired file
			rm -f $wan1_file
		fi

	fi

	#if [[ "$old_routers" != "$new_routers" ]]; then
	#	
	#	# The old and new routers does not match, so update the
	#	# nat TABLE
	#fi
}

# Sets up the routing tables
set_routing () {

	# Determite which interface needs the tables be set
	if [[ "$interface" == "$wan0" ]]; then

		set_wan0

	elif [[ "$interface" == "$wan1" ]]; then
	
		set_wan1
	
	fi

	$IP route flush cache
}

# This block determite which $reason code is passed to this script
case "$reason" in

        # MEDIUM - Ignore, linux does not do medium (media)
        "MEDIUM" )
                exit 0
        ;;

        # PREINIT - Initalizes interface for action
        "PREINIT" )

                # Touch the file for the expired interface
                if [[ "$interface" == "$wan0" ]]; then
                        touch $wan0_file
                elif [[ "$interface" == "$wan1" ]]; then
                        touch $wan1_file
                fi
        ;;

	# BOUND - Flushes and reset the routing tables, then find out
	# 	  If the ip address of the interface has changed and update
	#	  the NAT table if needed
	# RENEW - Same as BOUND
	# REBIND - Same as BOUND
	# REBOOT - Same as BOUND
	"BOUND" | "RENEW" | "REBIND" | "REBOOT" ) 
		set_NAT
		flush_routing
		set_routing
	;;

	# EXPIRE - No IP address on interface, flush NAT & Routing
	# FAIL - Same as EXPIRE
	"EXPIRE" | "FAIL" ) 
		flush_NAT
		flush_routing

		# Touch the file for the expired interface
		if [[ "$interface" == "$wan0" ]]; then
			touch $wan0_file
		elif [[ "$interface" == "$wan1" ]]; then
			touch $wan1_file
		fi
	;;

	# TIMEOUT - If the exit value is 0, the NAT & routing needs to be setup/fixed
	# otherwise if the exit value is 1, we need to flush NAT & routing like EXPIRE/FAIL
	"TIMEOUT" )

		# Determite the exit value
		if [[ "$exit_status" -eq "0" ]]; then
			
			set_NAT
			flush_routing
			set_routing
		else
			flush_NAT
			flush_routing
		fi
	;;

esac