#!/bin/bash

# Scriptname:       network-discovery
# Intention:		Try to find some kind of network connection providing a link to
#					the internet. For this a list of wired interfaces is checked first.
#					Afterwards a list of wireless devices is checked whereas a list of 
#					provided ESSIDs is prefered for the connection. 
#					Optionally the script also tries to connect to whatever ESSID it can find
#					to get a connection (-> ESSID 'any' ).
# Version:			0.1		(3.11.2007)
# 					0.2		(5.11.2007)
#						- added several sleeps
#						- implemented 5 retries to get the interface up with $IFCONFIG $IF up
#						- added a complete shutdown of all involved network interfaces at startup to get a clean start
#					0.3		(13.11.2007)
#						- cut back the number of retries to 3 to shorten the waiting time
#						- added wrapper funktions 'error' and 'verbose'
#						- made output more compact
#						- added nice stuff for passing options to the script
#						- verbose (-v), usage (-h) and precheck_for_internet_connection (-p) switches
#						- availability check + global variables holding absolute paths for all needed external tools
#						- discovery of hidden ESSIDs now possible by setting the ESSID before the scan
#						- added hack for wpa support

echo -ne "### network-discovery(v0.3) ###\n"


#####################
# open improvements #
#####################

# FIXME Log error/status messages via syslog --> logger
# FIXME Trying DHCP on a network without DHCP takes an awfully long time until it aborts
# FIXME Think of something better to test network connectivity 
# FIXME Add generic VPN support
# FIXME Add generic wpa support
# FIXME check if the tun module is loaded when using VPN
# FIXME Add static configuration support
# FIXME Check output of dhclient for what really happened 
#		success + received ip:
#			DHCPACK from 192.168.0.2
#			bound to 192.168.0.245 -- renewal in 1636 seconds.
#		no success:
#			No DHCPOFFERS received.
# FIXME dhclient processes stay in background after trying to get an ip unsuccessfully (-> quick solution: $KILLALL at the end of the file)


##################
# configuration  #
##################

# config for wired network interface
IF_WIRED_LIST="eth0"

# config for wireless network interface
IF_WIRELESS_LIST="ath0"
#IF_WIRELESS_ESSID_LIST="FAU-VPN HOME any"		# adding 'any' to the list also tries to connect through other WLANs in range
IF_WIRELESS_ESSID_LIST="FAU-VPN HOME GENTOO"

# OpenVPN config for FAU-VPN
FAU_VPN_PATH="/root/RRZE"


####################
# global variables #
####################

SCRIPTNAME=`basename $0 .sh`
MIN_ARGS=0

# exit codes
EXIT_SUCCESS=0
EXIT_FAILURE=1
EXIT_ERROR=2
EXIT_BUG=10

# set correct delimiter
IFS=" "

# pre-initialization of option variables with defaults
IS_CONNECTED=0
FLAG_VERBOSE=0
FLAG_PRECHECK=0


#############
# functions #
#############

# error output
function error {
	if [ $# -ge 1 ]
	then
		echo -ne "$*" >&2
	fi
}

# verbose output controlled by $FLAG_VERBOSE
function verbose {
	if [ $# -ge 1 ]
	then
		if (( $FLAG_VERBOSE ))
		then
			#echo "Got '$*'"
			echo -ne "$*" >&1
		fi
	fi
}

# usage
function usage {
	error "Usage: $SCRIPTNAME [-h] [-v]\n"
	
	if [ $# = 1 ]
	then
		exit $1
	else
		exit $EXIT_FAILURE
	fi
}


# check if the specified file is there and executable
function check_tool {
	if [ $# = 1 ]
	then
		verbose "Checking for '$1'..."
		if [ -x $1 ]
		then
			verbose "OK\n"
		else
			verbose "NOT FOUND\n"
			error "Needed external programm not found: ${1}\n"
			exit $EXIT_ERROR
		fi
	else
		exit $EXIT_BUG
	fi

}


# test routine for network/internet setup
function check_network_connection {
	verbose "\052 Checking for a working internet connection..."

	$HOST -W1 google.com 1>/dev/null 2>&1	# FIXME should not end in a DDOS for google ;)
	EXIT_STATUS=$?

	if ( test $EXIT_STATUS = 1 )
	then
		# no connectivity -> do nothing
		verbose "none found\n"
	fi

	if ( test $EXIT_STATUS = 0 )
	then
		# YEEHA! - got a connection
		verbose "found\n"
		IS_CONNECTED=1
	fi
}


########
# init #
########

# test minimal number of arguments
if (( $# < $MIN_ARGS ))
then
	error "Too few arguments.\n"
	usage $EXIT_ERROR
fi

# parse arguments and set flags if necessary
while getopts ':vph' OPTION
do
	case $OPTION in
		v)	# verbosity	
			FLAG_VERBOSE=1
		;;

		h)	# help	
			usage $EXIT_SUCCESS
		;;

		\?)	# unknown option	
			error "Unknown option \"-$OPTARG\".\n"
			usage $EXIT_ERROR
		;;
		
		:)	# missing argument for an option
			error "Option \"-$OPTARG\" is missing an argument.\n"
			usage $EXIT_ERROR
		;;
		
		*)	# this should not be reached (because AFAIK \? catches unknown options if ':' is specified)
			error "Option not implemented.\n"
			usage $EXIT_BUG
		;;
	esac
done
shift `expr $OPTIND - 1`

# notifications
verbose "\052 Beeing verbose.\n"


#########
# tools #
#########

verbose "\052 Checking for needed external programs.\n"

# list of used tools - these have to be installed of course ;)
HOST="/usr/bin/host"; check_tool $HOST;
CAT="/usr/bin/cat"; check_tool $CAT;
IFCONFIG="/sbin/ifconfig"; check_tool $IFCONFIG;
KILLALL="/usr/bin/killall"; check_tool $KILLALL;
IWLIST="/sbin/iwlist"; check_tool $IWLIST;
GREP="/bin/grep"; check_tool $GREP;
AWK="/bin/awk"; check_tool $AWK;
TR="/bin/tr"; check_tool $TR;
DHCLIENT="/sbin/dhclient"; check_tool $DHCLIENT;
OPENVPN="/usr/sbin/openvpn"; check_tool $OPENVPN;
IWCONFIG="/sbin/iwconfig"; check_tool $IWCONFIG;
##########
# script #
##########


# do a pre-check
if (( $FLAG_PRECHECK ))
then
	verbose "\052 Prechecking.\n"
	check_network_connection;
	if (( $IS_CONNECTED ))
	then
		exit $EXIT_SUCCESS
	fi
fi



# FIXME
# shutdown all network related stuff to have a clean starting point for reconfiguring
verbose "\052 Shutting down all network interfaces/DHCP Clients/OpenVPN Clients that might be up/running.\n"
for IF in $IF_WIRED_LIST
do
	$IFCONFIG $IF down 1>/dev/null 2>&1
done

for IF in $IF_WIRELESS_LIST
do
	$IFCONFIG $IF down 1>/dev/null 2>&1
done

$KILLALL dhclient 1>/dev/null 2>&1
$KILLALL openvpn 1>/dev/null 2>&1
$KILLALL wpa_supplicant 1>/dev/null 2>&1



###### WIRED INTERFACES
echo -ne "\n### WIRED INTERFACES ###\n"
for IF_WIRED in $IF_WIRED_LIST
do
	echo -ne "--> Trying wired interface ${IF_WIRED}..."

	# 1. check if interface exists
	verbose "\n\052 Checking if ${IF_WIRED} exists..."
	if [ ! -e /sys/class/net/${IF_WIRED} ]
	then
		# interface does not exist -> skip
		error "\nInterface ${IF_WIRED} not found- skipping\n"
		continue
	fi
	verbose "OK\n"


	# 2. check interface state (up/down)
	verbose "\052 Checking ${IF_WIRED}'s operation status..."
	IF_OPERSTATE=`$CAT /sys/class/net/${IF_WIRED}/operstate`
	verbose "${IF_OPERSTATE}\n"
	if [ "${IF_OPERSTATE}" = "down" ]
	then
		# interface is down
		verbose "Trying to bring ${IF_WIRED} up..."
		
		for i in 1 2 3
		do 
			verbose "#${i} "
			$IFCONFIG $IF_WIRED up 1>/dev/null 2>&1
			sleep 1
			IF_OPERSTATE=`$CAT /sys/class/net/${IF_WIRED}/operstate`
			if [ "${IF_OPERSTATE}" != "down" ]
			then
				break
			fi
			$IFCONFIG $IF_WIRED down 1>/dev/null 2>&1
		done
		
		if [ "${IF_OPERSTATE}" = "down" ]
		then
			# trying to bring up the interface didn't work -> skip
			verbose "FAILED\n"
			error "Could not bring up interface ${IF_WIRED} - skipping\n"
			$IFCONFIG $IF_WIRED down
			continue
		else
			verbose "OK\n"
		fi
	fi

	# 3. check if the interface is actually connected to a network
	verbose "\052 Checking if ${IF_WIRED} is physically connected to a network..."
	IF_CARRIER=`$CAT /sys/class/net/${IF_WIRED}/carrier`
	EXIT_STATUS=$?

	if [ $EXIT_STATUS != 0 ]
	then
		# if the interface is down reading from /sys/class/net/${IF_WIRED}/carrier results in an error
		# but since we should have brought it up in step 2 this should not happen ;)
		verbose "FAILED\n"
		error "This is weird. Could not read /sys/class/net/${IF_WIRED}/carrier - skipping\n"
		continue
	fi

	verbose "${IF_CARRIER}\n"
	if [ $IF_CARRIER = 0 ]
	then
		# device is not connected to a network
		error "Interface ${IF_WIRED} is not connected to a network - skipping\n"
		$IFCONFIG ${IF_WIRED} down
		continue
	fi

	# 4. try to setup a working network connection
	verbose "\052 Trying to setup a working network connection for ${IF_WIRED}..."


	# try to setup the interface through DHCP
	verbose "DHCP-"
	$DHCLIENT $IF_WIRED 1>/dev/null 2>&1
	EXIT_STATUS=$?

	if [ $EXIT_STATUS = 0 ]
	then
		verbose "OK\n"
	else
		verbose "FAILED\n"
		error "Error setting up ${IF_WIRED} through DHCP (exit code ${EXIT_STATUS}) - skipping\n"
		continue
	fi
	
	check_network_connection;
	if (( $IS_CONNECTED ))
	then
		echo -ne "OK\n"
		exit $EXIT_SUCCESS
	else
		# FIXME
		# if we get to this point there was no connection found so we shut down the tried interface again
		verbose "Shutting down interface ${IF_WIRED}..."
		$IFCONFIG ${IF_WIRED} down
		$KILLALL dhclient
		verbose "OK\n\n"
	fi


done

###### WIRELESS INTERFACES
echo -ne "\n### WIRELESS INTERFACES ###\n"
for IF_WIRELESS in $IF_WIRELESS_LIST
do

	echo -ne "--> Trying interface ${IF_WIRELESS}..."

	# 1. check if interface exists
	verbose "\n\052 Checking if ${IF_WIRELESS} exists..."
	if [ ! -e /sys/class/net/${IF_WIRELESS} ]
	then
		# interface does not exist -> skip
		error  "\nInterface ${IF_WIRELESS} not found - skipping\n"
		continue
	fi
	verbose "OK\n"


	# 2. check interface state (up/down)
	verbose "\052 Checking ${IF_WIRELESS}'s operation status..."
	IF_OPERSTATE=`$CAT /sys/class/net/${IF_WIRELESS}/operstate`
	verbose "${IF_OPERSTATE}\n"
	if [ "${IF_OPERSTATE}" = "down" ]
	then
		# interface is down
		verbose "Trying to bring ${IF_WIRELESS} up..."
		
		for i in 1 2 3
		do 
			verbose "#${i} "
			$IFCONFIG $IF_WIRELESS up 1>/dev/null 2>&1
			sleep 1
			IF_OPERSTATE=`$CAT /sys/class/net/${IF_WIRELESS}/operstate`
			if [ "${IF_OPERSTATE}" != "down" ]
			then
				break
			fi
			$IFCONFIG ${IF_WIRELESS} down 1>/dev/null 2>&1
		done
		
		IF_OPERSTATE=`$CAT /sys/class/net/${IF_WIRELESS}/operstate`
		if [ "${IF_OPERSTATE}" = "down" ]
		then
			# trying to bring up the interface didn't work -> skip
			verbose "FAILED\n"
			error "\nCould not bring up interface ${IF_WIRELESS} - skipping\n"
			$IFCONFIG $IF_WIRELESS down
			continue
		else
			verbose "OK\n"
		fi
	fi


	# 3. scan for desired ESSIDs in range
	verbose "\052 Scanning..."
	ESSID_LIST=""
	for IF_WIRELESS_ESSID in $IF_WIRELESS_ESSID_LIST
	do
		verbose "${IF_WIRELESS_ESSID} "

		if [ "${IF_WIRELESS_ESSID}" == "any" ]
		then
			# scan for all ESSIDs in range
			MATCHES=`${IWLIST} ${IF_WIRELESS} scan | ${GREP} ESSID | ${AWK} -F '"' '{print $2}' | ${TR} '\n' ' ' 2>/dev/null`
			
			# eleminate duplicates
			LIST="${MATCHES}"
			for i in $LIST
			do
				DUPLICATE_FOUND=0
				for j in $ESSID_LIST
				do
					if [ "$i" = "$j" ]
					then
						DUPLICATE_FOUND=1
						break
					fi
				done
				
				if [ $DUPLICATE_FOUND = 0 ]
				then
					if [ "${ESSID_LIST}" = "" ]
					then
						ESSID_LIST="${i}"
					else
						ESSID_LIST="${ESSID_LIST} ${i}"
					fi
				fi
			done
		else
			# configure interface for the given ESSID _before_ scan (-> also checks for hidden ESSIDs)
			$IWCONFIG $IF_WIRELESS essid $IF_WIRELESS_ESSID
#			$IWCONFIG $IF_WIRELESS essid $IF_WIRELESS_ESSID 1>/dev/null 2>&1
 			EXIT_STATUS=$?
			sleep 1

			# interface configured, start scanning
			if [ $EXIT_STATUS = 0 ]
			then
				# scan only for the currently configured ESSID
				MATCHES=`${IWLIST} ${IF_WIRELESS} scan | ${GREP} ${IF_WIRELESS_ESSID} 2>/dev/null`
				
				# is the essid in range
				if [ "$MATCHES" ]
				then
					# desired WLAN in range found, add it to the list
					if [ "${ESSID_LIST}" = "" ]
					then
						ESSID_LIST="${IF_WIRELESS_ESSID}"
					else
						ESSID_LIST="${ESSID_LIST} ${IF_WIRELESS_ESSID}"
					fi
				fi
			else
				# error configuring interface
				error "\nError during interface setup (code ${EXIT_STATUS}) - skipping\n"
				continue 2
			fi
		fi
	done

	if [ "${ESSID_LIST}" ]
	then
		# found valid WLANs
		verbose "OK\n"
		verbose  "valid ESSIDs in range: ${ESSID_LIST}\n"
	else
		# no valid WLANs found -> try next interface
		verbose "FAILED\n"
		continue	
	fi

	# 4. try to setup a working network connection with one of the found ESSIDs
	
	#FIXME
	$IFCONFIG $IF_WIRELESS down
	$IFCONFIG $IF_WIRELESS up
	sleep 1
	
	verbose "\052 Trying to setup a working network connection for ${IF_WIRELESS}..."
	for ESSID in $ESSID_LIST
	do
		echo -ne "${ESSID}:"
		# configure interface for the given ESSID
		$IWCONFIG $IF_WIRELESS essid $ESSID
		#$IWCONFIG $IF_WIRELESS essid $ESSID 1>/dev/null 2>&1
		EXIT_STATUS=$?
		sleep 1
		
		if (( $EXIT_STATUS > 0 ))
		then
			error "Error during interface setup (code ${EXIT_STATUS}) - skipping\n"
			continue 2
		fi
		
		# FIXME
		# connect through WLAN with WPA2 encryption
		if [ "$ESSID" = "GENTOO" ]
		then
			wpa_supplicant -B -Dwext -iath0 -c/root/wpa_GENTOO.conf
		fi
	
		# try to setup the interface through DHCP
		echo -ne "DHCP-"
		$DHCLIENT $IF_WIRELESS 1>/dev/null 2>&1
		EXIT_STATUS=$?

		if [ $EXIT_STATUS = 0 ]
		then
			verbose "OK\n"
		else
			verbose "FAILED\n"
			error "Error setting up ${IF_WIRELESS} through DHCP (exit code ${EXIT_STATUS}) - skipping\n"
			continue
		fi
		
		
		# FIXME
		# connect through FAU's OpenVPN tunnel
		if [ "$ESSID" = "FAU-VPN" ]
		then
			verbose "\052 Connecting through FAU's OpenVPN tunnel..."
			PWD=`pwd`
			cd $FAU_VPN_PATH
			$OPENVPN --config RRZE-full-tunnel.ovpn --auth-user-pass secret --daemon FAU-VPN 1>/dev/null 2>&1
			EXIT_STATUS=$?
			cd $PWD
			if [ $EXIT_STATUS = 0 ]
			then
				verbose "OK\n"
			else
					error "Error during OpenVPN setup (code ${EXIT_STATUS}) - skipping\n"
					continue 2
			fi
		fi


		check_network_connection;
		if (( $IS_CONNECTED ))
		then
			echo -ne "OK\n"
			exit $EXIT_SUCCESS
		else
			# FIXME
			# if we get to this point there was no connection found so we shut down the tried interface again
			verbose "Shutting down interface ${IF_WIRED}..."
			$IFCONFIG ${IF_WIRED} down
			$KILLALL dhclient
			verbose "OK\n\n"
		fi
	
		echo -ne "\n"
	done

done

# unsuccessful exit
$KILLALL dhclient # FIXME
echo -ne "\nGiving up.\n"
exit $EXIT_FAILURE