docs: def nl_socket_get_local_port(sk):
      """https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L357.
  
      Also https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L338
      """
      if not sk.s_local.nl_pid:
          port = generate_local_port()
          sk.s_flags &= ~NL_OWN_PORT
          sk.s_local.nl_pid = port
          return port
      return sk.s_local.nl_pid