#!/bin/bash
#Copyright 1999-2002, William Stearns.
#Released under the GPL.

#sudo needed for dd, arp, ip, insmod
export PATH="/sbin:/usr/sbin:/bin:/usr/bin"

fail () {
	logger -s -t server_tunnel "$*, exiting."
	exit 1
}

Action='start'
unset TunnelName ClientTransientIPs
while [ -n "$1" ]; do
	case "$1" in
	[Ss][Tt][Aa][Rr][Tt])
		Action='start'
		;;
	[Rr][Ee][Ss][Tt][Aa][Rr][Tt])
		Action='restart'
		;;
	[Ss][Tt][Oo][Pp])
		Action='stop'	
		;;
	-n)
		if [ -n "$2" ]; then
			TunnelName="$2"
			shift
		else
			fail "Missing -n TunnelName parameter"
		fi
		;;	
	[0-9]*)
		ClientTransientIPs="${ClientTransientIPs} $1"
		;;
	*)
		fail "Unknown parameter \"$1\""
		;;
	esac
	shift
done

if [ -z "$TunnelName" ]; then
	fail 'Missing TunnelName'
fi

unset TunnelServerIP ClientPermanentIP ClientCandidateIFs
if [ -r /etc/tunnel.conf ]; then
	. /etc/tunnel.conf "$TunnelName"
else
	fail 'Missing or unreadable /etc/tunnel.conf'
fi

if [ -z "$TunnelServerIP" ] || [ -z "$ClientPermanentIP" ] || [ -z "$ClientCandidateIFs" ]; then
	fail "Missing configuration TunnelServerIP, ClientPermanentIP, and/or ClientCandidateIFs information for Tunnel $TunnelName"
fi

if [ -z "$ClientTransientIPs" ]; then
	logger -s -t server_tunnel 'No transient IPs specified, forcing a stop.'
	Action='stop'
fi

logger -s -t server_tunnel "Attempting to $Action tunnel Client perm $ClientPermanentIP ($TunnelName) via ips $ClientTransientIPs at Server $TunnelServerIP."

case "$Action" in
start)
	echo 1 | sudo dd of=/proc/sys/net/ipv4/ip_forward 2>/dev/null			#sudo friendly version of:  echo 1 >/proc/sys/net/ipv4/ip_forward
	sudo arp $ClientPermanentIP -Ds eth0 pub					#FIXME - hardcoded eth0 on server
	sudo insmod ip_gre >/dev/null 2>/dev/null
	TunnelServerGw=`route -n | grep '^0\.0\.0\.0\W' | awk '{print $2}' | grep -v '0\.0\.0\.0' | tail -1`

	IFNumber=1
	TunnelClientRouteCommand="sudo ip route add \"$ClientPermanentIP/32\" equalize "
	for OneIP in $ClientTransientIPs ; do
		sudo ip tunnel add "$TunnelName$IFNumber" mode gre remote "$OneIP" local "$TunnelServerIP" ttl 255
		sudo ip link set "$TunnelName$IFNumber" up
		sudo ip addr add "$TunnelServerIP" dev "$TunnelName$IFNumber"
		TunnelClientRouteCommand="${TunnelClientRouteCommand} nexthop dev \"$TunnelName$IFNumber\""	#via \"$TunnelServerGw\" needed?
		IFNumber=$[ $IFNumber + 1 ]
	done
	eval "$TunnelClientRouteCommand"
	;;
stop)
	for OneIF in `ifconfig | grep '^'"$TunnelName" | awk '{print $1}'` ; do
		sudo ip link set "$OneIF" down							#Kills all routes
		sudo ip tunnel del "$OneIF"
	done
	sudo arp -i eth0 -d "$ClientPermanentIP" pub
	;;
restart)
	$0 stop -n "$TunnelName"
	$0 start -n "$TunnelName" $ClientTransientIPs
	;;
*)
	logger -s -t server_tunnel "Use \"$0 start\" or \"$0 stop\"."
	;;
esac




#Graveyard:
#MODULE="ipip" ;		TDEV="tunl0"
#MODULE="ip_gre" ;	TDEV="gre0"

#Start
#	if [ -z "$CLIENTDIALIP" ]; then
#		echo "Please run with CLIENTDIALIP set, exiting." #>>/dev/stderr
#		exit 1
#	fi
#	ifconfig lo:126 down		#Make sure you no longer have ClientPermanentIP live as a loopback alias.
#	echo $CLIENTDIALIP >>/root/bin/CLIENTIPS
#	sudo insmod "$MODULE" >/dev/null 2>/dev/null
#	sudo ifconfig "$TDEV" "$TunnelServerIP" pointopoint "$ClientPermanentIP" netmask 255.255.255.255 up
#
#	sudo route del -host "$ClientPermanentIP"
#	sudo route add -host "$CLIENTDIALIP" "$TDEV"
#	sudo route add -host "$ClientPermanentIP" gw "$CLIENTDIALIP" "$TDEV"
#	sudo route del -host "$CLIENTDIALIP" "$TDEV"
#
#	sudo route add -host "$CLIENTDIALIP" gw "$TunnelServerGw" dev eth0

#Stop
#	for AHOST in `cat /root/bin/CLIENTIPS` ; do
#		sudo route del -host "$AHOST" eth0
#	done
#	rm -f /root/bin/CLIENTIPS
#
#	#sudo route del -host "$ClientPermanentIP" gw "$CLIENTDIALIP" "$TDEV"
#	sudo route del -host "$ClientPermanentIP" "$TDEV"
#
#	sudo ifconfig "$TDEV" down
#	#sudo rmmod "$MODULE"



#ip notes
#ip tunnel add netb mode gre remote 172.19.20.21 local 172.16.17.18 ttl 255
#ip link set netb up
#ip addr add 10.0.1.1 dev netb
#ip route add 10.0.2.0/24 dev netb