ynl_msg_start
nlh = ynl_msg_start(ys, id, flags);
return ynl_msg_start(ys, id, NLM_F_REQUEST | NLM_F_ACK | flags);
return ynl_msg_start(ys, id, NLM_F_REQUEST | NLM_F_ACK | NLM_F_DUMP);