vpn-route-external.sh

#!/bin/bash

# Set static routing tables to route some external IP addresses to a different gateway, for example if tend 
# to connect on a VPN and you want to route some traffic to avoid the VPN.
#
# I use this on a Mac - if you're lucky it might work on other operating systems.  This script does update 
# your /etc/hosts files AND route table.   Take appropriate due care.
#
# Usage
# -----
#
# Run the following BEFORE you connect to your VPN :
#
#    export NON_VPN_HOSTS="host1.com host2.com host3.com"
#    export LOCAL_GATEWAY="192.168.1.254"
#    vpn-route-external.sh
# 
# and enter sudo password so that /etc/hosts and route table is updated
#

action=${1:-create}
gateway=${2:-$LOCAL_GATEWAY}
nonVpnHosts=${3:-$NON_VPN_HOSTS}

if [ -z "gateway" ] ; then
    echo "Please set shell variable \$LOCAL_GATEWAY to static gateway IP address"
    exit 1
fi

if [ -z "$nonVpnHosts" ] ; then
    echo "Please set shell variable \$NON_VPN_HOSTS to space separated list of hosts that don't want route through VPN"
    exit 1
fi

echo "Action : $action"

for host in $nonVpnHosts ; do	
    ip=`host $host | awk '/has address/ { print $4 }'`
    nonVpnIps=$nonVpnIps" $ip"	
done

nonVpnIps=`echo $nonVpnIps | tr ' ' '\n' | sort -u | tr '\n' ' '`
echo "Direct Gateway : $gateway"
echo "Non VPN Hosts  : $nonVpnHosts"
echo "Non VPN IPs    : $nonVpnIps"

function deleteVpnRoutes {
    for ip in $nonVpnIps ; do 
        sudo route -n delete $ip/32 $gateway
    done

    echo "External routes REMOVED to route table"

    for host in $nonVpnHosts ; do
        sudo sed -i '' "/$host/d" /etc/hosts
    done

    echo "External IP addresses REMOVED from /etc/hosts"
}

if [ $action == "delete" ] ; then
    deleteVpnRoutes
else
    deleteVpnRoutes
	
    # We should really get these from nslookup
	
    for host in $nonVpnHosts ; do
        ip=`host $host | awk '/has address/ { print $4 }' | head -n 1`
        echo "$ip	$host" | sudo tee -a /etc/hosts 
    done

    echo "External IP addresses ADDED to /etc/hosts"
    echo "External routes ADDED to route table"

    for ip in $nonVpnIps ; do 
        sudo route -n add $ip/32 $gateway		
    done
fi