joinBridge bridge interface = unless (null bridge) $ void $ do
    debug $ printf "Joining %s to %s" interface bridge
    spawnShell $ printf "brctl setfd %s 0" bridge
    spawnShell $ printf "brctl addif %s %s" bridge interface
    spawnShell $ printf "ifconfig %s inet 0.0.0.0 promisc up" interface
joinBridge bridge interface = unless (null bridge) $ void $ do
    debug $ printf "Joining %s to %s" interface bridge
    spawnShell $ printf "brctl setfd %s 0" bridge
    spawnShell $ printf "brctl addif %s %s" bridge interface
    spawnShell $ printf "ifconfig %s inet 0.0.0.0 promisc up" interface
joinBridge bridge interface = unless (null bridge) $ void $ do
    debug $ printf "Joining %s to %s" interface bridge
    spawnShell $ printf "brctl setfd %s 0" bridge
    spawnShell $ printf "brctl addif %s %s" bridge interface
    spawnShell $ printf "ifconfig %s inet 0.0.0.0 promisc up" interface