PhrozenByte · April 22, 2020 12:06
diff --git a/6to4-daemon b/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
	#!/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