+static
+bool is_discarded_packet_or_event_message(const bt_message *msg)
+{
+ const enum bt_message_type msg_type = bt_message_get_type(msg);
+
+ return msg_type == BT_MESSAGE_TYPE_DISCARDED_EVENTS ||
+ msg_type == BT_MESSAGE_TYPE_DISCARDED_PACKETS;
+}
+
+static
+enum lttng_live_iterator_status adjust_discarded_packets_message(
+ bt_self_message_iterator *iter,
+ const bt_stream *stream,
+ const bt_message *msg_in, bt_message **msg_out,
+ uint64_t new_begin_ts)
+{
+ enum lttng_live_iterator_status status = LTTNG_LIVE_ITERATOR_STATUS_OK;
+ enum bt_property_availability availability;
+ const bt_clock_snapshot *clock_snapshot;
+ uint64_t end_ts;
+ uint64_t count;
+
+ clock_snapshot = bt_message_discarded_packets_borrow_end_default_clock_snapshot_const(msg_in);
+ end_ts = bt_clock_snapshot_get_value(clock_snapshot);
+
+ availability = bt_message_discarded_packets_get_count(msg_in, &count);
+ BT_ASSERT_DBG(availability == BT_PROPERTY_AVAILABILITY_AVAILABLE);
+
+ *msg_out = bt_message_discarded_packets_create_with_default_clock_snapshots(
+ iter, stream, new_begin_ts, end_ts);
+ if (!*msg_out) {
+ status = LTTNG_LIVE_ITERATOR_STATUS_NOMEM;
+ goto end;
+ }
+
+ bt_message_discarded_packets_set_count(*msg_out, count);
+end:
+ return status;
+}
+
+static
+enum lttng_live_iterator_status adjust_discarded_events_message(
+ bt_self_message_iterator *iter,
+ const bt_stream *stream,
+ const bt_message *msg_in, bt_message **msg_out,
+ uint64_t new_begin_ts)
+{
+ enum lttng_live_iterator_status status = LTTNG_LIVE_ITERATOR_STATUS_OK;
+ enum bt_property_availability availability;
+ const bt_clock_snapshot *clock_snapshot;
+ uint64_t end_ts;
+ uint64_t count;
+
+ clock_snapshot = bt_message_discarded_events_borrow_end_default_clock_snapshot_const(msg_in);
+ end_ts = bt_clock_snapshot_get_value(clock_snapshot);
+
+ availability = bt_message_discarded_events_get_count(msg_in, &count);
+ BT_ASSERT_DBG(availability == BT_PROPERTY_AVAILABILITY_AVAILABLE);
+
+ *msg_out = bt_message_discarded_events_create_with_default_clock_snapshots(
+ iter, stream, new_begin_ts, end_ts);
+ if (!*msg_out) {
+ status = LTTNG_LIVE_ITERATOR_STATUS_NOMEM;
+ goto end;
+ }
+
+ bt_message_discarded_events_set_count(*msg_out, count);
+end:
+ return status;
+}
+
+static
+enum lttng_live_iterator_status handle_late_message(
+ struct lttng_live_msg_iter *lttng_live_msg_iter,
+ struct lttng_live_stream_iterator *stream_iter,
+ int64_t late_msg_ts_ns, const bt_message *late_msg)
+{
+ bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
+ bt_logging_level log_level = lttng_live_msg_iter->log_level;
+ const bt_clock_class *clock_class;
+ const bt_stream_class *stream_class;
+ enum bt_clock_class_cycles_to_ns_from_origin_status ts_ns_status;
+ int64_t last_inactivity_ts_ns;
+ enum lttng_live_iterator_status stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_OK;
+ enum lttng_live_iterator_status adjust_status;
+ bt_message *adjusted_message;
+
+ /*
+ * The timestamp of the current message is before the last message sent
+ * by this component. We CANNOT send it as is.
+ *
+ * The only expected scenario in which that could happen is the
+ * following, everything else is a bug in this component, relay deamon,
+ * or CTF parser.
+ *
+ * Expected scenario: The CTF message iterator emitted discarded
+ * packets and discarded events with synthesized beginning and end
+ * timestamps from the bounds of the last known packet and the newly
+ * decoded packet header. The CTF message iterator is not aware of
+ * stream inactivity beacons. Hence, we have to adjust the beginning
+ * timestamp of those types of messages if a stream signalled its
+ * inactivity up until _after_ the last known packet's beginning
+ * timestamp.
+ *
+ * Otherwise, the monotonicity guarantee of message timestamps would
+ * not be preserved.
+ *
+ * In short, the only scenario in which it's okay and fixable to
+ * received a late message is when:
+ * 1. the late message is a discarded packets or discarded events
+ * message,
+ * 2. this stream produced an inactivity message downstream, and
+ * 3. the timestamp of the late message is within the inactivity
+ * timespan we sent downstream through the inactivity message.
+ */
+
+ BT_COMP_LOGD("Handling late message on live stream iterator: "
+ "stream-name=\"%s\", viewer-stream-id=%" PRIu64,
+ stream_iter->name->str, stream_iter->viewer_stream_id);
+
+ if (!stream_iter->last_inactivity_ts.is_set) {
+ BT_COMP_LOGE_APPEND_CAUSE(self_comp, "Invalid live stream state: "
+ "have a late message when no inactivity message "
+ "was ever sent for that stream.");
+ stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
+ goto end;
+ }
+
+ if (!is_discarded_packet_or_event_message(late_msg)) {
+ BT_COMP_LOGE_APPEND_CAUSE(self_comp, "Invalid live stream state: "
+ "have a late message that is not a packet discarded or "
+ "event discarded message: late-msg-type=%s",
+ bt_common_message_type_string(bt_message_get_type(late_msg)));
+ stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
+ goto end;
+ }
+
+ stream_class = bt_stream_borrow_class_const(stream_iter->stream);
+ clock_class = bt_stream_class_borrow_default_clock_class_const(stream_class);
+
+ ts_ns_status = bt_clock_class_cycles_to_ns_from_origin(clock_class,
+ stream_iter->last_inactivity_ts.value, &last_inactivity_ts_ns);
+ if (ts_ns_status != BT_CLOCK_CLASS_CYCLES_TO_NS_FROM_ORIGIN_STATUS_OK) {
+ BT_COMP_LOGE_APPEND_CAUSE(self_comp,"Error converting last "
+ "inactivity message timestamp to nanoseconds");
+ stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
+ goto end;
+ }
+
+ if (last_inactivity_ts_ns <= late_msg_ts_ns) {
+ BT_COMP_LOGE_APPEND_CAUSE(self_comp, "Invalid live stream state: "
+ "have a late message that is none included in a stream "
+ "inactivity timespan: last-inactivity-ts-ns=%" PRIu64
+ "late-msg-ts-ns=%" PRIu64, last_inactivity_ts_ns, late_msg_ts_ns);
+ stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
+ goto end;
+ }
+
+ /*
+ * We now know that it's okay for this message to be late, we can now
+ * adjust its timestamp to ensure monotonicity.
+ */
+ BT_COMP_LOGD("Adjusting the timestamp of late message: late-msg-type=%s, "
+ "msg-new-ts-ns=%" PRIu64,
+ bt_common_message_type_string(bt_message_get_type(late_msg)),
+ stream_iter->last_inactivity_ts.value);
+ switch (bt_message_get_type(late_msg)) {
+ case BT_MESSAGE_TYPE_DISCARDED_EVENTS:
+ adjust_status = adjust_discarded_events_message(
+ lttng_live_msg_iter->self_msg_iter,
+ stream_iter->stream,
+ late_msg, &adjusted_message,
+ stream_iter->last_inactivity_ts.value);
+ break;
+ case BT_MESSAGE_TYPE_DISCARDED_PACKETS:
+ adjust_status = adjust_discarded_packets_message(
+ lttng_live_msg_iter->self_msg_iter,
+ stream_iter->stream,
+ late_msg, &adjusted_message,
+ stream_iter->last_inactivity_ts.value);
+ break;
+ default:
+ bt_common_abort();
+ }
+
+ if (adjust_status != LTTNG_LIVE_ITERATOR_STATUS_OK) {
+ stream_iter_status = adjust_status;
+ goto end;
+ }
+
+ BT_ASSERT_DBG(adjusted_message);
+ stream_iter->current_msg = adjusted_message;
+ stream_iter->current_msg_ts_ns = last_inactivity_ts_ns;
+
+end:
+ return stream_iter_status;
+}
+