openvpn/openvpn_init.sh

#!/bin/sh

set -eu

umask 002

: "${VPN_IP:?VPN_IP must be set to the VPN server address}"
LOCAL_NET="${LOCAL_NET:-192.168.0.0/16}"
DNS_SERVER="${DNS_SERVER:-8.8.8.8}"

VPN_GW=$(ip route | awk '/^default/ { print $3; exit }')
if [ -z "$VPN_GW" ]; then
    echo "No default gateway found" >&2
    exit 1
fi
echo "Saving gateway $VPN_GW"

echo "Deleting default gateway"
ip route del default

echo "Routing only $VPN_IP through $VPN_GW"
ip route replace "$VPN_IP" via "$VPN_GW"

echo "Routing $LOCAL_NET through $VPN_GW"
ip route replace "$LOCAL_NET" via "$VPN_GW"

echo "nameserver $DNS_SERVER" > /etc/resolv.conf

ip route
echo "Starting openvpn"
cd /vpn

until openvpn --config vpn; do
    echo "Openvpn crashed, respawning"
    sleep 10
done