relay_handle_reply
return relay_handle_reply(relay, origin, rid, error ?: -EREMOTEIO, NULL, 0);
err = relay_handle_reply(relay, origin, rid, 0, msg, len);
err = relay_handle_reply(relay, origin, rid, -EBUSY, NULL, 0);
err = relay_handle_reply(relay, origin, rid, -EAGAIN, NULL, 0);