Add sequence numbers to message info structure

rmw/include/rmw/types.h

@@ -518,8 +518,21 @@ typedef struct RMW_PUBLIC_TYPE rmw_gid_s
 /// Information describing an rmw message
 typedef struct RMW_PUBLIC_TYPE rmw_message_info_s
 {
+  /// Time when the DDS sample was written in the publisher queue.
   rmw_time_point_value_t source_timestamp;
+  /// Time when the message was added to the subscription queue.
   rmw_time_point_value_t received_timestamp;
+  /// Sequence number of the received message for the publisher.
+  /**
+   * If the rmw implementation doesn't support sequence numbers, it's value will be UINT64_MAX.
+   */
+  int64_t publication_sequence_number;
+  /// Sequence number of the received message for the subscription,
+  /**
+   * If the rmw implementation doesn't support sequence numbers, it's value will be UINT64_MAX.
+   */
+  int64_t reception_sequence_number;
+  /// Global unique identifier of the publisher that sent the message.
   rmw_gid_t publisher_gid;
 
   /// Whether this message is from intra_process communication or not

rmw/src/types.c

@@ -19,6 +19,6 @@ RMW_WARN_UNUSED
 rmw_message_info_t
 rmw_get_zero_initialized_message_info(void)
 {
-  rmw_message_info_t zero_initialized_message_info = {0, 0, {NULL, {0}}, false};
+  rmw_message_info_t zero_initialized_message_info = {0, 0, INT64_MAX, INT64_MAX, {NULL, {0}}, false};
   return zero_initialized_message_info;
 }