leaveBridge bridge interface = unless (null bridge) $ void $ do 
    spawnShell $ printf "brctl delif %s %s" bridge interface
    spawnShell $ printf "ip link set %s down" interface
leaveBridge bridge interface = unless (null bridge) $ void $ do 
    spawnShell $ printf "brctl delif %s %s" bridge interface
    spawnShell $ printf "ip link set %s down" interface
leaveBridge bridge interface = unless (null bridge) $ void $ do 
    spawnShell $ printf "brctl delif %s %s" bridge interface
    spawnShell $ printf "ip link set %s down" interface