Establishing an IPv6 tunnel using 6to4

6to4-daemon

#!/bin/bash
# 6to4-daemon - Establishing an IPv6 tunnel using 6to4
# Copyright (C) 2011  Daniel Rudolf <http://www.daniel-rudolf.de/>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

function showHelp() {
	echo "Usage: $0 (start|stop|reload|restart|status) device"
	echo
	echo "Available devices:"

	IFS=$'\n'
	for AVAILABLE_DEVICE in $(ls -w 1 "/sys/class/net"); do
		echo -e "\t$AVAILABLE_DEVICE"
	done
}

function log() {
	NOW=$(date +"%F %T%z")
	if [ "$1" == "notice" ]; then
		echo "$NOW: $2" >> "$LOG_FILE"
		echo "$NOW: $2"
	elif [ "$1" == "error" ]; then
		echo "$NOW: $2" >> "$LOG_FILE"
		echo "$NOW: $2" >&2
	else
		echo "$NOW: $2" >> "$LOG_FILE"
	fi
}

function createDaemonDirectories() {
	# directory of PID files
	if [ ! -d "$PID_DIRECTORY" ]; then
		mkdir "$PID_DIRECTORY"
		if [ ! -d "$PID_DIRECTORY" ]; then
			echo "Unable to create '$PID_DIRECTORY': Permission denied" >&2
			exit 1
		fi
	fi
	if [ ! -w "$PID_DIRECTORY" ]; then
		echo "Unable to write to '$PID_DIRECTORY': Permission denied" >&2
		exit 1
	fi

	# directory of storage files
	if [ ! -d "$STORAGE_DIRECTORY" ]; then
		mkdir "$STORAGE_DIRECTORY"
		if [ ! -d "$STORAGE_DIRECTORY" ]; then
			echo "Unable to create '$STORAGE_DIRECTORY': Permission denied" >&2
			exit 1
		fi
	fi
	if [ ! -w "$STORAGE_DIRECTORY" ]; then
		echo "Unable to write to '$STORAGE_DIRECTORY': Permission denied" >&2
		exit 1
	fi

	# directory of log files
	if [ ! -d "$LOG_DIRECTORY" ]; then
		mkdir "$LOG_DIRECTORY"
		if [ ! -d "$LOG_DIRECTORY" ]; then
			echo "Unable to create '$LOG_DIRECTORY': Permission denied" >&2
			exit 1
		fi
	fi
	if [ ! -w "$LOG_DIRECTORY" ]; then
		echo "Unable to write to '$LOG_DIRECTORY': Permission denied" >&2
		exit 1
	fi
}

function removeDaemonFiles() {
	if [ -e "$PID_FILE" ]; then
		rm -f "$PID_FILE"
	fi	
	if [ -e "$STORAGE_FILE" ]; then
		rm -f "$STORAGE_FILE"
	fi
}

function createLogFile() {
	if [ ! -f "$LOG_FILE" ]; then
		touch "$LOG_FILE"
	fi
}

function determineInternalIPv4Address() {
	IP4_INTERNAL=$(/sbin/ip addr show "$DEVICE" | grep -e "^    inet " | cut -d " " -f 6)
	IP4_INTERNAL_ADDRESS=$(echo "$IP4_INTERNAL" | cut -d "/" -f 1)
	IP4_INTERNAL_NETMASK=$(echo "$IP4_INTERNAL" | cut -d "/" -f 2)

	# check if IPv4 address is valid
	if [[ ! "$IP4_INTERNAL_ADDRESS" =~ ^((([1-9]?|1[0-9]|2[0-4])[0-9]|25[0-5])\.){3}(([1-9]?|1[0-9]|2[0-4])[0-9]|25[0-5])$ ]]; then
		log "error" "Unable to determine internal IPv4 address: '$IP4_INTERNAL_ADDRESS' is not a valid IPv4 address"
		exit 1
	fi

	# check if IPv4 netmask is valid
	if [[ ! "$IP4_INTERNAL_NETMASK" =~ ^([1-2]?[0-9]|3[0-2])$ ]]; then
		log "error" "Unable to determine internal IPv4 address: '$IP4_INTERNAL_NETMASK' is not a valid IPv4 netmask"
		exit 1
	fi

	if [ "$1" != "--quiet" ]; then
		log "notice" "Internal IPv4 address determined: $IP4_INTERNAL"
	fi
}

function determineGlobalIPv4Address() {
	# check if the given internal IPv4 address is a global IPv4 address
	if [ "${IP4_INTERNAL:0:3}" != "10." ] && [[ ! "$IP4_INTERNAL" =~ ^172\.(1[6-9]|2[0-9]|3[0-1])\. ]] && [ "${IP4_INTERNAL:0:8}" != "192.168." ]; then
		log "notice" "Determined internal IPv4 address ($IP4_INTERNAL) is already a global address"

		IP4_GLOBAL="$IP4_INTERNAL"
		IP4_GLOBAL_ADDRESS="$IP4_INTERNAL_ADDRESS"
		IP4_GLOBAL_NETMASK="$IP4_INTERNAL_NETMASK"

	# determine global IPv4 address
	else
		i=1
		while [ true ]; do
			determineGlobalIPv4AddressDyndnsDotOrg

			# no answer received
			if [ -z "$IP4_GLOBAL_ADDRESS" ]; then
				# try again up to 50 times...
				if [ $i -le 50 ]; then
					log "notice" "Unable to determine global IPv4 address: Try $i of 50"
					sleep 3

					((i++))
					continue
	
				# but give up after some time
				else
					log "error" "Unable to determine global IPv4 address: Giving up"
					exit 1
				fi

			# we received something
			else
				if [[ "$IP4_GLOBAL_ADDRESS" =~ ^((([1-9]?|1[0-9]|2[0-4])[0-9]|25[0-5])\.){3}(([1-9]?|1[0-9]|2[0-4])[0-9]|25[0-5])$ ]]; then
					IP4_GLOBAL_NETMASK="32"
					IP4_GLOBAL="$IP4_GLOBAL_ADDRESS/$IP4_GLOBAL_NETMASK"
	
					if [ "$1" != "--quiet" ] || [ $i != 1 ]; then
						log "notice" "Global IPv4 address determined: $IP4_GLOBAL"
					fi
					break
	
				# but not a valid IPv4 address
				else
					log "error" "Unable to determine global IPv4 address: '$IP4_GLOBAL_ADDRESS' is not a valid IPv4 address"
					exit 1
				fi
			fi
		done
	fi
}

function determineGlobalIPv4AddressDyndnsDotOrg() {
	IP4_GLOBAL_ADDRESS=$(wget -q -t 1 -O - http://checkip.dyndns.org/)
	if [[ "$IP4_GLOBAL_ADDRESS" =~ \<body\>Current\ IP\ Address:\ (.*)\</body\> ]]; then
		IP4_GLOBAL_ADDRESS="${BASH_REMATCH[1]}"
	fi
}

function computeIPv6Address() {
	IP6_GLOBAL_NETMASK="48"
	IP6_GLOBAL_ADDRESS=$(printf "2002:%02x%02x:%02x%02x::1" $(echo "$IP4_GLOBAL_ADDRESS" | tr "." " "))
	IP6_GLOBAL="$IP6_GLOBAL_ADDRESS/$IP6_GLOBAL_NETMASK"

	log "notice" "Global IPv6 address computed: $IP6_GLOBAL"
}

function createVirtualTunnelDevice() {
	# check if there is already a network device
	if [ -e "/sys/class/net/$VIRTUAL_TUNNEL_DEVICE" ]; then
		log "error" "Unable to create virtual 6to4 tunnel device: There is already a network device called '$VIRTUAL_TUNNEL_DEVICE'"
		exit 1
	fi

	/sbin/ip tunnel add "$VIRTUAL_TUNNEL_DEVICE" mode sit ttl 200 remote any local "$IP4_INTERNAL_ADDRESS"
	/sbin/ip link set dev "$VIRTUAL_TUNNEL_DEVICE" up

	log "notice" "Virtual 6to4 tunnel device created"
}

function destroyVirtualTunnelDevice() {
	/sbin/ip -6 addr flush dev "$VIRTUAL_TUNNEL_DEVICE"
	/sbin/ip -6 route flush dev "$VIRTUAL_TUNNEL_DEVICE"
	/sbin/ip link set dev "$VIRTUAL_TUNNEL_DEVICE" down
	/sbin/ip tunnel del "$VIRTUAL_TUNNEL_DEVICE"

	log "notice" "Virtual 6to4 tunnel device has been destroyed"
}

function routeIPv6ConnectionsThroughVirtualTunnelDevice() {
	/sbin/ip -6 route add 2000::/3 via "::192.88.99.1" dev "$VIRTUAL_TUNNEL_DEVICE" metric 1
}

function addIPv6Address() {
	/sbin/ip -6 addr add "$IP6_GLOBAL" dev "$VIRTUAL_TUNNEL_DEVICE"
}

function removeIPv6Address() {
	/sbin/ip -6 addr del "$1" dev "$VIRTUAL_TUNNEL_DEVICE"
}

function storeData() {
	echo $IP4_INTERNAL > "$STORAGE_FILE"
	echo $IP4_GLOBAL >> "$STORAGE_FILE"
	echo $IP6_GLOBAL >> "$STORAGE_FILE"
}

function getStoredData() {
	# check if storage file exists
	if [ ! -f "$STORAGE_FILE" ]; then
		log "error" "Unable to read contents of storage file '$STORAGE_FILE': No such file or directory"
	fi

	# check if storage file is readable
	if [ ! -r "$STORAGE_FILE" ]; then
		log "error" "Unable to read contents of storage file '$STORAGE_FILE': Permission denied"
	fi

	OLD_IP4_INTERNAL=$(sed -n 1p "$STORAGE_FILE")
	OLD_IP4_GLOBAL=$(sed -n 2p "$STORAGE_FILE")
	OLD_IP6_GLOBAL=$(sed -n 3p "$STORAGE_FILE")
}



# parameter count
if [ $# != 2 ]; then
	echo "Wrong parameter count" >&2
	echo
	showHelp
	exit 1
fi

# root rights
if [ $(id -u) -ne 0 ]; then
	echo "You must have root rights" >&2
	exit 1
fi

DEVICE=$2
VIRTUAL_TUNNEL_DEVICE="$DEVICE-6to4"

# network device exists
if [ ! -e "/sys/class/net/$DEVICE" ]; then
	echo "There is no network device called '$DEVICE'" >&2
	exit 1
fi

PID_DIRECTORY="/var/run/6to4-daemon"
PID_FILE="$PID_DIRECTORY/$DEVICE"

STORAGE_DIRECTORY="/tmp/6to4-daemon"
STORAGE_FILE="$STORAGE_DIRECTORY/$DEVICE"

LOG_DIRECTORY="/var/log/6to4-daemon"
LOG_FILE="$LOG_DIRECTORY/$DEVICE"

case "$1" in
	start)
		if [ -f "$PID_FILE" ]; then
			if (kill -0 $(cat "$PID_FILE") 2> /dev/null); then
				echo "Daemon is already running" >&2
				exit 1
			else
				echo "'$PID_FILE' found but daemon is not running." >&2
				echo "Propably your previously started daemon crashed. Please view the logfile for details."
				echo "If you want to start the daemon please try again."
				rm -f "$PID_FILE"
				exit 1
			fi
		fi

		# check if network device is already using IPv6
		if [ $(/sbin/ip addr show "$DEVICE" | grep -e "^    inet6 .* scope global" | wc -l) -gt 0 ]; then
			echo "It seems that you are already using IPv6 on '$DEVICE'" >&2
			exit 1
		fi

		createDaemonDirectories

		createLogFile
		log "notice" "Establishing 6to4 tunnel..."

		determineInternalIPv4Address
		determineGlobalIPv4Address
		computeIPv6Address

		createVirtualTunnelDevice
		routeIPv6ConnectionsThroughVirtualTunnelDevice
		addIPv6Address

		storeData
		log "notice" "6to4 tunnel established"

		(
			while [ true ]; do
				getStoredData

				determineInternalIPv4Address --quiet

				# internal IPv4 address has been changed
				if [ "$IP4_INTERNAL" != "$OLD_IP4_INTERNAL" ]; then
					log "notice" "Internal IPv4 address has been changed: $IP4_INTERNAL"
	
					determineGlobalIPv4Address
					computeIPv6Address
	
					destroyVirtualTunnelDevice

					createVirtualTunnelDevice
					routeIPv6ConnectionsThroughVirtualTunnelDevice
					addIPv6Address

					storeData
	
					sleep 3
					continue
				fi

				determineGlobalIPv4Address --quiet

				# global IPv4 address has been changed
				if [ "$IP4_GLOBAL" != "$OLD_IP4_GLOBAL" ]; then
					log "notice" "Global IPv4 address has been changed: $IP4_GLOBAL"
					computeIPv6Address
	
					removeIPv6Address "$OLD_IP6_GLOBAL"
					addIPv6Address

					storeData
	
					sleep 3
					continue
				fi

				# nothing has been changed
				sleep 3
			done
		) &

		PID=$!
		echo $PID > "$PID_FILE"

		wait $PID
		RETURN=$?

		destroyVirtualTunnelDevice
		removeDaemonFiles

		exit $RETURN
		;;

	stop)
		if [ -f "$PID_FILE" ]; then
			PID=$(cat "$PID_FILE")

			if (kill -0 $PID 2> /dev/null); then
				log "notice" "Daemon shutdown requested..."

				echo -n "Stopping daemon"
				if (kill -TERM $PID 2> /dev/null); then
					i=0
					while [ "$i" -le 40 ]; do
						if (kill -0 $PID 2> /dev/null); then
							echo -n "."
							let "i += 1"
							sleep 0.25
						else
							break
						fi
					done
				fi
				if (kill -0 $PID 2> /dev/null); then
					echo
					echo "Daemon is unable to shut down cleanly - killing" >&2
					kill -KILL $PID
					exit 1
				else
					echo " done"
				fi
			else
				echo "'$PID_FILE' found but daemon is not running." >&2
				echo "Propably your previously started daemon crashed. Please view the logfile for details."
				exit 1
			fi
		else
			echo "Daemon is propably not running" >&2
			exit 1
		fi
		;;

	reload)
		# check if daemon is running
		if [ -f "$PID_FILE" ]; then
			if (kill -0 $(cat "$PID_FILE") 2> /dev/null); then
				log "notice" "Daemon reload requested..."

				determineInternalIPv4Address
				determineGlobalIPv4Address
				computeIPv6Address

				destroyVirtualTunnelDevice

				createVirtualTunnelDevice
				routeIPv6ConnectionsThroughVirtualTunnelDevice
				addIPv6Address

				storeData
				log "notice" "6to4 tunnel established"
			else
				echo "'$PID_FILE' found but daemon is not running." >&2
				echo "Propably your previously started daemon crashed. Please view the logfile for details."
				exit 1
			fi
		else
			echo "Daemon is propably not running" >&2
			exit 1
		fi
		;;

	restart)
		$0 stop
		if [ $? != 0 ]; then
			exit $?
		fi

		$0 start
		if [ $? != 0 ]; then
			exit $?
		fi
		;;

	status)
		if [ -f "$PID_FILE" ]; then
			if (kill -0 $(cat "$PID_FILE") 2> /dev/null); then
				echo "Daemon is running"
			else
				echo "'$PID_FILE' found but daemon is not running."
				echo "Propably your previously started daemon crashed. Please view the logfile for details."
			fi
		else
			echo "Daemon is propably not running"
		fi
		;;

	*)
		showHelp
		;;
esac
exit 0