labnat

#!/bin/bash

running_file="/tmp/.labnat_running"

ip_list="/opt/labnat/lab_ips"
ip_assoc="/tmp/.labnat_ip_assoc"

wan_interface="enp0s3"
lan_interface="enp0s8"
temp_interface="_temp_nat_"

msg(){
	>&2 echo $@
}

die(){
	msg "$@";
	exit 1
}


[ "$#" -eq 0 ] && die 'No Arguments provided.';


getAssocIpByInternalIp() {
	int="$1"
	grep "^$1=" "$ip_assoc" | sed 's/^.*\?=\(.*\?\)\#.*$/\1/' 2>/dev/null
	return ${PIPESTATUS[0]}
}
getAssocIpByMac() {
	int="$1"
	grep "^.*=$1#" "$ip_assoc" | sed 's/^.*\?=\(.*\?\)\#.*$/\1/' 2>/dev/null
	return ${PIPESTATUS[0]}
}
updateAssocByInternalIp() {
	int_ip="$1"
	mac="$2"
	new_ip="$3"
	[ -z "$int_ip" ] && { msg 'Invalid Internal IP'; return 1; };
	[ -z "$mac" ] && { msg 'Invalid MAC'; return 1; };
	[ -z "$new_ip" ] && { msg 'Invalid WAN IP'; return 1; };
	grep "^$int_ip" "$ip_assoc" && sed -i 's/^.*\?='"$mac"'\#.*$/'"$int_ip=$mac#$new_ip"'/g' "$ip_assoc" || echo "$int_ip=$mac#$new_ip" >> "$ip_assoc"
}
assocSplit(){
	echo $record | sed 's/^\(.*\?\)=\(.*\?\)\#\(.*\)/\1 \2 \3/g'
}

createInterface(){
	src="$1"
	mac="$2"
	int="$3"
	[ -n "$src" ] && ip link show "$src" &>/dev/null || { msg "Invalid Source."; return 1; }
	[ -n "$temp_interface" ] && ip link show "$temp_interface" &>/dev/null && msg "Interface already exists." && return 2
	assign_mac=""
	[ -n "$mac" ] && assign_mac=" address $mac"
	ip link add dev "$temp_interface" link "$src" $assign_mac up type macvlan &>/dev/null || { msg "Failed to create interface."; return 3; }
	new_ip_mac="$(getInterfaceIp $temp_interface)";
	ret=$?
	new_ip="$(echo $new_ip_mac | cut -d' ' -f 1)"
	new_mac="$(echo $new_ip_mac | cut -d' ' -f 2)"
	ip link delete dev "$temp_interface" &>/dev/null
	ip addr add "$new_ip"/32 dev "$wan_interface" || { msg "Failed to add IP to wan interface."; return 4; }
	updateAssocByInternalIp "$int" "$new_mac" "$new_ip" &>/dev/null
	echo "$new_ip"
	return $ret
}
request_count=0
getInterfaceIp(){
	(( request_count += 1 ))
	res="$(dhclient -v -sf /etc/dhcp/dhclient-clear-routes.sh "$@" 2>&1)";
	ret=$?
	[ $ret -eq 0 ] && {
		if_ip="$(echo "$res" | grep "bound to" | awk '{ print $3 }')"
		if_mac="$(echo "$res" | grep -m1 "Listening on LPF" | awk -F'/' '{ print $NF }')"
		[ -n "$if_ip" ] && [ -n "$if_mac" ] && {
			echo "$if_ip $if_mac";
			request_count=0
			return 0;
		}
		request_count=0
		return 1
	}
	echo "$res" | grep "is already running" &>/dev/null && {
		msg 'DHClient is already running, killing first...';
		pid="$(echo "$res" | grep "is already running" | sed 's/^.*dhclient(\([0-9]\+\)).*$/\1/g')"
		[ -z "$pid" ] && die 'Failed to determine PID, try killing it manually.' || {
			kill $pid && msg 'Killed!' && {
				[ $request_count -gt 2 ] && { msg 'FAILED: Max tries reached.'; request_count=0 return 1; } || { getInterfaceIp $@; request_count=0; return $?; };
			} && { request_count=0; return $?; };
		}
	}
	msg 'Failed to determine interface IP.'
	request_count=0
	return 1
}
addNatRule(){
	int="$1"
	ext="$2"
	[ -z "$int" ] && { msg 'Invalid Internal IP'; return 1; }
	[ -z "$ext" ] && { msg 'Invalid External IP'; return 1; }
	iptables -t nat -A PREROUTING -d "$ext" -i "$wan_interface" -j DNAT --to-destination "$int"
	iptables -t nat -A POSTROUTING -s "$int" -o "$wan_interface" -j SNAT --to "$ext"
}
removeNatRule(){
	int="$1"
	ext="$2"
	[ -z "$int" ] && { msg 'Invalid Internal IP'; return 1; }
	[ -z "$ext" ] && { msg 'Invalid External IP'; return 1; }
	iptables -t nat -D PREROUTING -d "$ext" -i "$wan_interface" -j DNAT --to-destination "$int"
	iptables -t nat -D POSTROUTING -s "$int" -o "$wan_interface" -j SNAT --to "$ext"
}

status() {
	[ -f "$ip_assoc" ] || { msg 'Not Running.'; return 1; };
	cat "$ip_assoc"
}

stop(){
	[ -f "$running_file" ] || { msg 'Not Running.'; return 1; };
	[ -f "$ip_assoc" ] || die 'DB Not found.'
	msg 'Clearing Forwards...'
	iptables -D FORWARD -i "$lan_interface" -o "$wan_interface" -j ACCEPT
	iptables -D FORWARD -i "$wan_interface" -o "$lan_interface" -j ACCEPT
	msg 'Removing IPs...'
	assoc="$(cat "$ip_assoc")"
	for record in $assoc; do
		read int_ip wan_mac wan_ip <<<$(assocSplit $record)
		[ -n "$wan_ip" ] && ip addr del "$wan_ip"/32 dev "$wan_interface"
		removeNatRule "$int_ip" "$wan_ip"
	done
	rm -f "$running_file"
	return 0
}
start() {
	[ -f "$running_file" ] && die 'Already Running.'
	touch "$running_file"
	ips="$@"
	[ "$#" -eq 0 ] && { [ -f "$ip_list" ]  && ips="$(cat "$ip_list")" || { msg "No arguments provided"; return 1; }; };
	


	iptables -A FORWARD -i "$lan_interface" -o "$wan_interface" -j ACCEPT
	iptables -A FORWARD -i "$wan_interface" -o "$lan_interface" -j ACCEPT

	for nat_ip in $ips; do
		msg "Creating NAT for $nat_ip ..."
		wan_mac="$(getAssocIpByInternalIp "$nat_ip")"
		wan_ip="$(createInterface "$wan_interface" "$wan_mac" "$nat_ip")"
		[ $? -eq 0 ] && {
			msg "IP Association $nat_ip > $wan_ip";
			addNatRule "$nat_ip" "$wan_ip"
			msg "Done"
		}
	done
}
[ "$1" == "start" ] && { shift; start $@; exit; }
[ "$1" == "stop" ] && { shift; stop; exit; }
[ "$1" == "restart" ] && { shift; stop; start; exit; }
[ "$1" == "status" ] && { status; exit; }

exit 1