Fix reach of maximum buffers in asio::send_to (#5472)

* Refs #22439. Fix

Signed-off-by: Ricardo González Moreno <[email protected]>

* Apply suggestions from code review

Co-authored-by: Carlos Ferreira González <[email protected]>

---------

Signed-off-by: Ricardo González Moreno <[email protected]>
Co-authored-by: Carlos Ferreira González <[email protected]>
(cherry picked from commit 885878d)

Co-authored-by: Ricardo González <[email protected]>

Author: mergify[bot]

src/cpp/rtps/messages/RTPSMessageGroup.cpp

@@ -34,6 +34,12 @@
 
 #include <statistics/rtps/messages/RTPSStatisticsMessages.hpp>
 
+#ifdef FASTDDS_STATISTICS
+const size_t max_boost_buffers = 61; // ... + SubMsg header + SubMsg body + Statistics message
+#else
+const size_t max_boost_buffers = 62; // ... + SubMsg header + SubMsg body
+#endif // ifdef FASTDDS_STATISTICS
+
 namespace eprosima {
 namespace fastdds {
 namespace rtps {
@@ -454,8 +460,8 @@ bool RTPSMessageGroup::insert_submessage(
         return false;
     }
 
-    // Messages with a submessage bigger than 64KB cannot have more submessages and should be flushed
-    if (is_big_submessage)
+    // Flush when the submessage is bigger than 64KB OR if the number of buffers to send is 64 (boost limit)
+    if (is_big_submessage || max_boost_buffers < buffers_to_send_->size())
     {
         flush();
     }

src/cpp/rtps/transport/UDPTransportInterface.cpp

@@ -592,6 +592,11 @@ bool UDPTransportInterface::send(
                 EPROSIMA_LOG_WARNING(TRANSPORT_UDP, ec.message());
                 return false;
             }
+
+            if (bytesSent != total_bytes)
+            {
+                EPROSIMA_LOG_WARNING(TRANSPORT_UDP, "Boost send_to wasn't able to send all bytes");
+            }
         }
         catch (const std::exception& error)
         {