#!/bin/bash
#
# Copyright 2012 - Jean-Sebastien Morisset - http://surniaulula.com/
#
# This script 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 script 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 at http://www.gnu.org/licenses/.
#
# --- START OF CONFIGURATION SECTION ---

rt_tables[100]="intern"
rt_tables[200]="prov_1"
rt_tables[300]="prov_2"

NetInfo () {
	# ------------------------------gateway---------metric--table---prio----fwd'ing
	case "$1" in
        17.10.20.0/23)      echo    17.10.20.1      100     prov_1  5000    1 ;;
        84.70.129.64/28)    echo    84.70.129.65    100     prov_2  4000    1 ;;
        105.104.78.152/29)  echo    105.104.78.153  100     prov_2  3000    1 ;;
        105.104.72.16/28)   echo    105.104.72.17   100     prov_2  2000    1 ;;
        192.168.0.0/24)     echo    192.168.0.1     100     intern  1100    0 ;;
        10.201.50.0/24)     echo    10.201.50.1     200     intern  1200    0 ;;
	esac
}

# --- END OF CONFIGURATION SECTION ---

RouteNet () {
	# return if we don't have all 8 arguments
	[ "${#@}" != 8 ] && return

	# name the arguments to keep things clear
	dev="$1" ip="$2" net_mask="$3" gw="$4" metric="$5" table="$6" prio="$7" fwd="$8"

	echo sysctl -w net.ipv4.conf.$dev.forwarding=$fwd

	for action in del add
	do
		cat <<EOF
		ip route $action $net_mask dev $dev scope link src $ip table $table
		ip route $action default via $gw dev $dev metric $metric table $table
		ip rule $action from $net_mask table $table prio $prio
		ip rule $action to $net_mask table $table prio $prio
EOF
	done
}

ShowTables () {
	echo -e "\n$1 RULES"
	ip rule list
	for rt in main "${rt_tables[@]}"
	do
		echo -e "\n$1 TABLE $rt"
		ip route show table $rt
	done
	echo ""
}

CheckDeps () {
	if [ -z "`which ip`" ]
	then
		echo "\"ip\" binary not found!" >/dev/stderr
		exit 1
	elif [ -z "`which ipcalc`" ]
	then
		echo "\"ipcalc\" binary not found!" >/dev/stderr
		exit 1
	elif [ -z "`ip rule list|grep 'from all lookup main'`" ]
	then
		echo "kernel does not appear to support policy routing" >/dev/stderr
		exit 1
	fi
}

# parse the command line, skipping stuff we don't know, until there's nothing left
while :
do
	for arg in "$@"
        do
                case $arg in
                        -t) no_change="1"; shift 1;;
                        *)  shift 1 ;;
                esac
                continue 2
        done
        break
done

CheckDeps

echo ""
[ -z "$no_change" ] && \
	cat /dev/null > /etc/iproute2/rt_tables

for rt in "${!rt_tables[@]}"
do
	echo "adding routing table: $rt ${rt_tables[$rt]}" 
	[ -z "$no_change" ] && \
		echo "$rt ${rt_tables[$rt]}" >> /etc/iproute2/rt_tables
done

interfaces="`ip addr show | sed -n 's/^[0-9][0-9]*: \([^:]*\): .*$/\1/p'`"

# reset the command-line arguments with the interface names
set -- $interfaces

ShowTables "BEFORE"

echo "EXEC RULES AND ROUTES"
{
	for dev in "$@"
	do
		for ip_mask in `ip addr show $dev | sed -n 's/^\s*inet \([0-9\.\/]*\) .*$/\1/p'`
		do
			ip=${ip_mask%/*}
			mask=${ip_mask#*/}
			[ -z "$ip" -o -z "$mask" ] && echo "error reading \"ip addr show $dev\" info" >/dev/stderr

			[ "$mask" -eq "32" ] && net="$ip" || \
				net="`ipcalc -n $ip/$mask|sed -n 's/^network[=:][[:space:]]*\([0-9\.]*\).*$/\1/ip'`"
			[ -z "$net" ] && echo "error reading \"ipcalc -n $ip/$mask\" output" >/dev/stderr

			RouteNet $dev $ip $net/$mask `NetInfo $net/$mask`
		done
	done

# remove possible duplicate default routes etc from multiple ips on same network
# sort reverse to exec the deletes first, then the adds
} | sort -u -r | while read line
do
	echo "$line"
	[ -z "$no_change" ] && \
		eval $line >/dev/null 2>&1
done

ShowTables "AFTER"

ip route flush cache

echo "FORWARDING"
sysctl -a 2>/dev/null |  grep '^net\.ipv4\..*\.forwarding'
echo ""