Christopher J. Buckley

This article has primarily been written to allow other users to share their iTunes playlists from outside their local LAN. I write this entry not to cover the initial setting up of OpenVPN, there’s plenty documentation to aid you here, but rather the implementation of a bridged solution for OpenVPN. Whilst a routed approach scales better, Windows users will find themselves unable to resolve NetBIOS names – a critial part of iTunes’ successful operation across a LAN.

We aren’t even able to use a WINS Server to assist us here, as broadcast packets need to traverse across different LAN’s – impossible using a routed OpenVPN. No, we must configure a VPN solution deployed to use a bridged adapter, allowing full NetBIOS name resolution.

1. Install the bridge utilities. Without this package, our solution will not work.
2. Create a file called openvpn-bridge within /usr/local/bin/. Paste this shell code into the newly created file. Remember, if using VIM to ‘:set paste‘.

   #!/bin/bash
   
   # Define Bridge Interface
   br="br0"
   
   # Define list of TAP interfaces to be bridged,
   # for example tap="tap0 tap1 tap2".
   tap="tap0"
   
   # Define physical ethernet interface to be bridged
   # with TAP interface(s) above.
   eth="eth0"
   
   eth_ip=".."
   eth_netmask=".."
   eth_broadcast=".."
   gw=".."
   
   case "$1" in
     start)
     for t in $tap; do
         openvpn --mktun --dev $t
     done
   
     brctl addbr $br
     brctl addif $br $eth
   
     for t in $tap; do
         brctl addif $br $t
     done
   
     for t in $tap; do
         ifconfig $t 0.0.0.0 promisc up
     done
   
     ifconfig $eth 0.0.0.0 promisc up
   
     ifconfig $br $eth_ip netmask $eth_netmask broadcast $eth_broadcast
     route add default gw $gw
     ;;
     stop)
     ifconfig $br down
     brctl delbr $br
   
     for t in $tap; do
         openvpn --rmtun --dev $t
     done
     ifconfig $eth $eth_ip netmask $eth_netmask broadcast $eth_broadcast
     route add default gw $gw
     ;;
     *)
     echo "usage openvpn-bridge {start|stop}"
   
     exit 1
     ;;
   esac
   exit 0
   # < ---END--->