def unbind_eip(bindings):
    """
    Delete NAT rules for each internal IP to EIP
    """
    global used_ports
    handler = DBHandler()
    for int_ip in bindings['int_ip']:
        handler.add(int_ip)
    if not len(handler.get(ext_ip=bindings['ext_ip'])):
        used_ports.pop(bindings['ext_ip'])
def bind_eip(bindings):
    """
    Add NAT rules for each internal IP to EIP
    """
    global used_ports
    handler = DBHandler()
    for int_ip in bindings['int_ip']:
        #FIXME judge if the int_ip or ext_ip exists first
        handler.add(int_ip, bindings['ext_ip'])
    used_ports.setdefault(bindings['ext_ip'], {})