remove_old()
{
	# remove the rules from PREROUTING
	$IPT -t nat -F $CHAIN_FORWARD_CHECK 2>/dev/null && $IPT -t nat -D PREROUTING -i $IF_SRC -j $CHAIN_FORWARD_CHECK
	$IPT -t nat -F $CHAIN_REDIRECT 2>/dev/null && $IPT -t nat -D PREROUTING -i $IF_SRC -j $CHAIN_REDIRECT
	
	# empty and remove chains if they exist
	for a in $CHAIN_FORWARD_ACTION $CHAIN_FORWARD_CHECK $CHAIN_REDIRECT
		do	$IPT -t nat -F $a 2>/dev/null && $IPT -t nat -X $a
			true
	  done
}


init_chains()
{
	# create chains
	for a in $CHAIN_FORWARD_ACTION $CHAIN_FORWARD_CHECK $CHAIN_REDIRECT
		do	$IPT -t nat -N $a
	  done
	
	# all packets from the specified interface go to the general chain
	$IPT -t nat -A PREROUTING -i $IF_SRC -j $CHAIN_FORWARD_CHECK
	$IPT -t nat -A PREROUTING -i $IF_SRC -j $CHAIN_REDIRECT

	# rules for CHAIN_REDIRECT
	$IPT -t nat -A $CHAIN_REDIRECT -p tcp --dport 80 -j DNAT --to-destination $SPLASH_SERVER
	$IPT -t nat -A $CHAIN_REDIRECT -p tcp --dport 80 -j ACCEPT
	$IPT -t nat -A $CHAIN_REDIRECT -j $REJECT_ACTION

	# all registered senders are simply accepted
	$IPT -t nat -A $CHAIN_FORWARD_ACTION -j ACCEPT
}


get_IPs()
# prints out all active forwards line by line
# every line consists of: "Number of Packets" and "IP"
{
	iptables -t nat -L "$CHAIN_FORWARD_CHECK" -vnx | sed "1,2d; s/  */ /g" | cut -d " " -f 2,9
	# get all active forward chains
	# remove the first two lines
	# remove multiple spaces
	# take only the number of packets and the IP
}


register_IP()
# add a new allowed IP
{
	eval `echo "$RULE_ADD" | sed "s/_IP_/$1/g"`
}


unregister_IP()
# remove the specified IP
{
	eval `echo "$RULE_DEL" | sed "s/_IP_/$1/g"`
}


refresh_IP_list()
{
	local NUM
	local IP
	get_IPs | while read NUM IP
		do	[ "$NUM" = "0" ] && unregister_IP "$IP"
	  done
}