#!/bin/bash
#Copyright 1999-2002, William Stearns <wstearns@pobox.com>
#Released under the GPL.

TunnelClientVer='0.4.0'

#sudo needed for: dd, insmod, ip, tc if using tc mode
export PATH="/sbin:/usr/sbin:/bin:/usr/bin"
MODE="equal"		#tc or equal

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

Action="start"
unset TunnelName
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
		;;	
	*)
		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

for OneIF in $ClientCandidateIFs ; do
	if [ -n "`ifconfig | grep '^'$OneIF | awk '{print $1}'`" ]; then
		ClientIFs="${ClientIFs} `ifconfig | grep '^'$OneIF | awk '{print $1}'`"
	fi
done

if [ -z "$ClientIFs" ] && [ "$Action" != 'stop' ]; then
	logger -s -t client_tunnel "No live interfaces, forcing a stop."
	Action='stop'
fi

logger -s -t client_tunnel "Attempting to $Action tunnel Client perm $ClientPermanentIP ($TunnelName) through interfaces $ClientIFs to Server $TunnelServerIP."

case "$Action" in
start)
	set -x
	if [ "$MODE" = 'tc' ]; then
		if [ `cat /proc/sys/net/ipv4/conf/all/rp_filter` -ne 0 ]; then
			echo 0 | sudo dd of=/proc/sys/net/ipv4/conf/all/rp_filter	#required?
		fi
	fi
	if [ `lsmod | grep '^ip_gre' | wc -l` -eq 0 ]; then
		sudo insmod ip_gre >/dev/null 2>/dev/null
	fi
	if [ `cat /proc/sys/net/ipv4/ip_forward` -ne 1 ]; then
		echo 1 | sudo dd of=/proc/sys/net/ipv4/ip_forward 2>/dev/null		#a sudo-friendly version of:  echo 1 >/proc/sys/net/ipv4/ip_forward
	fi

	for OneIF in $ClientIFs ; do
		ClientTransientIPs="${ClientTransientIPs} `ifconfig $OneIF | grep 'inet addr' | awk '{print $2}' | sed -e 's/.*://'`"
	done
	echo $ClientTransientIPs	#Sent to stdout so caller knows what transient IP's to give to server.

	if [ "$MODE" = 'equal' ]; then
		DefaultRouteCommand="sudo ip route add default equalize "	#proto static doesn't seem to help, nor does scope global
	fi
	TunnelServerRouteCommand="sudo ip route add \"$TunnelServerIP/32\" equalize "
	for OneIF in $ClientIFs ; do
		sudo ip tunnel add "t$OneIF" mode gre remote "$TunnelServerIP" local `ifconfig "$OneIF" | grep 'inet addr' | awk '{print $2}' | sed -e 's/.*://'` ttl 255
		sudo ip link set "t$OneIF" up
		sudo ip addr add "$ClientPermanentIP" dev "t$OneIF"
		if [ "$MODE" = 'equal' ]; then
			DefaultRouteCommand="${DefaultRouteCommand} nexthop dev \"t$OneIF\""
		elif [ "$MODE" = 'tc' ]; then
			sudo tc qdisc add dev "t$OneIF" root teql0		#FIXME hardcoded teql0
		fi
		TunnelServerRouteCommand="${TunnelServerRouteCommand} nexthop dev \"$OneIF\""
	done
	if [ "$MODE" = 'tc' ]; then
		sudo ip link set dev teql0 up
		sudo ip addr add "$ClientPermanentIP" dev teql0
	fi
	sudo ip route del "$TunnelServerIP/32"
	eval "$TunnelServerRouteCommand"
	sudo ip route del 0/0
	if [ "$MODE" = 'equal' ]; then
		eval "$DefaultRouteCommand"
	elif [ "$MODE" = 'tc' ]; then
		sudo ip route add default dev teql0
	fi
	;;
stop)
	set -x
	for OneIF in $ClientIFs ; do
		sudo ip link set "t$OneIF" down
		sudo ip tunnel del "t$OneIF"
		#sudo ip route del "$TunnelServerIP/32"
	done
	if [ "$MODE" = 'tc' ]; then
		sudo ip link set teql0 down
	fi
	#FIXME - reinstate default route.
	;;
restart)
	$0 stop -n "$TunnelName"
	$0 start -n "$TunnelName"
	;;
*)
	fail "Use \"$0 start\", \"$0 stop\" or \"$0 restart\""
	;;
esac

exit 0









#Graveyard:
#OutIF="ppp0"
#MODULE="ipip" ;		TDev="tunl0"
#MODULE="ip_gre" ;	TDev="gre0"

#TDev="bill"
#TunnelServerIP="Z.Z.Z.Z"
#ClientPermanentIP="Z.Z.Z.Y"

#DefaultRouteDevs="`/sbin/route -n | grep '^0\.0\.0\.0[ \t]' | awk '{print $8}' | sort | uniq`"
#DefaultRouteGws="`/sbin/route -n | grep '^0\.0\.0\.0[ \t]' | awk '{print $2}' | sort | uniq`"

#if [ `echo "$DefaultRouteDevs" | wc -l` -ne 1 ]; then
#	echo Too many or few default route interfaces, exiting. >>/dev/stderr
#	exit 1
#fi
#if [ `echo "$DefaultRouteGws" | wc -l` -ne 1 ]; then
#	echo Too many or few default route ips, exiting. >>/dev/stderr
#	exit 1
#fi

#DESTS="${DESTS} Onetargetmachine Anothertargetmachine"
#DESTS="${DESTS} 0.0.0.0/0.0.0.0"

#Start
#	sudo insmod ip_gre >/dev/null 2>/dev/null
#	sudo ifconfig "$TDev" "$ClientPermanentIP" pointopoint "$TunnelServerIP" netmask 255.255.255.255 up
#
#	sudo route del -host "$TunnelServerIP" "$TDev"
#	sudo route add -host "$TunnelServerIP" "$TDev"
#	for AHOST in $DESTS ; do
#		case "$AHOST" in
#		*/*)
#			Network=${AHOST%%/*}
#			Netmask=${AHOST##*/}
#			sudo route add -net "$Network" netmask "$Netmask" gw "$TunnelServerIP" "$TDev"
#			if [ "$AHOST" = "0.0.0.0/0.0.0.0" ]; then
#				sudo route del default "$OutIF"
#			fi
#			;;
#		*)
#			sudo route add -host "$AHOST" gw "$TunnelServerIP" "$TDev"
#			;;
#		esac
#	done
#	sudo route del -host "$TunnelServerIP" "$TDev"
#	sudo route del -host "$TunnelServerIP" "$TDev" >/dev/null 2>/dev/null
#
#	sudo route add -host "$TunnelServerIP" "$OutIF"


#Stop
#	sudo route del -host "$TunnelServerIP" "$OutIF"
#
#	for AHOST in $DESTS ; do
#		case "$AHOST" in
#		*/*)
#			Network=${AHOST%%/*}
#			Netmask=${AHOST##*/}
#			#echo "Routing to network $Network, netmask $Netmask" >>/dev/stderr
#			sudo route del -net "$Network" netmask "$Netmask" gw "$TunnelServerIP" "$TDev"
#			if [ "$AHOST" = "0.0.0.0/0.0.0.0" ]; then
#				sudo route add default "$OutIF"
#			fi
#			;;
#		*)
#			sudo route del -host "$AHOST" gw "$TunnelServerIP" "$TDev"
#			;;
#		esac
#	done
#
#	sudo ifconfig "$TDev" down
#	#sudo route add default "$OutIF"	#Done above
#	sudo rmmod ip_gre


#ip/tc notes.
	#for OneIF in $ClientIFs ; do
	#	sudo tc qdisc add dev "$OneIF" root teql0
	#done
	#sudo ip link set dev teql0 up
	#sudo ip addr add dev teql0 "$ClientPermanentIP"
	#sudo ip route add 0/0 dev teql0

	#sudo ip route add default scope global nexthop via "$P1" dev "$IF1" weight 1 nexthop via "$P2" dev "$IF2" weight 1

# sudo tc qdisc add dev eth1 root teql0
# sudo tc qdisc add dev eth2 root teql0
# sudo ip link set dev teql0 up

#Don't forget the 'ip link set up' command!

#This needs to be done on both hosts. The device teql0 is basically a
#roundrobin distributor over eth1 and eth2, for sending packets. No data
#ever comes in over an teql device, that just appears on the 'raw' eth1
#and eth2.

#But now we just have devices, we also need proper routing. One way to do
#this is to assign a /31 network to both links, and a /31 to the teql0
#device as well:

#FIXME: does this need something like 'nobroadcast'? A /31 is too small
#to house a network address and a broadcast address - if this doesn't
#work as planned, try a /30, and adjust the ip adresses accordingly. You
#might even try to make eth1 and eth2 do without an IP address!

#On router A: 

# ip addr add dev eth1 10.0.0.0/31
# ip addr add dev eth2 10.0.0.2/31
# ip addr add dev teql0 10.0.0.4/31