network: Add function to check if a queue would overflow

src/network/utils/net-device-queue-interface.h

@@ -347,12 +347,10 @@ NetDeviceQueue::PacketEnqueued (QueueType* queue, Ptr<const typename QueueType::
   NotifyQueuedBytes (item->GetSize ());
 
   NS_ASSERT_MSG (m_device, "Aggregated NetDevice not set");
-  Ptr<Packet> p = Create<Packet> (m_device->GetMtu ());
-
   // After enqueuing a packet, we need to check whether the queue is able to
   // store another packet. If not, we stop the queue
 
-  if (queue->GetCurrentSize () + p > queue->GetMaxSize ())
+  if (queue->WouldOverflow (1, m_device->GetMtu ()))
     {
       NS_LOG_DEBUG ("The device queue is being stopped (" << queue->GetCurrentSize ()
                     << " inside)");
@@ -370,13 +368,11 @@ NetDeviceQueue::PacketDequeued (QueueType* queue, Ptr<const typename QueueType::
   NotifyTransmittedBytes (item->GetSize ());
 
   NS_ASSERT_MSG (m_device, "Aggregated NetDevice not set");
-  Ptr<Packet> p = Create<Packet> (m_device->GetMtu ());
-
   // After dequeuing a packet, if there is room for another packet we
   // call Wake () that ensures that the queue is not stopped and restarts
   // the queue disc if the queue was stopped
 
-  if (queue->GetCurrentSize () + p <= queue->GetMaxSize ())
+  if (!queue->WouldOverflow (1, m_device->GetMtu ()))
     {
       Wake ();
     }

src/network/utils/queue.cc

@@ -220,4 +220,17 @@ QueueBase::GetMaxSize (void) const
   return m_maxSize;
 }
 
+bool
+QueueBase::WouldOverflow (uint32_t nPackets, uint32_t nBytes) const
+{
+  if (m_maxSize.GetUnit () == QueueSizeUnit::PACKETS)
+    {
+      return (m_nPackets + nPackets > m_maxSize.GetValue ());
+    }
+  else
+    {
+      return (m_nBytes + nBytes > m_maxSize.GetValue ());
+    }
+}
+
 } // namespace ns3

src/network/utils/queue.h

@@ -178,6 +178,15 @@ public:
    */
   QueueSize GetMaxSize (void) const;
 
+  /**
+   * \brief Check if the queue would overflow with additional bytes or packets
+   * Note: the check is performed according to the queue's operating mode (bytes or packets).
+   * \param nPackets number of additional packets
+   * \param nBytes number of additional bytes
+   * \return true if the queue should overflow, false otherwise.
+   */
+  bool WouldOverflow (uint32_t nPackets, uint32_t nBytes) const;
+
 #if 0
   // average calculation requires keeping around
   // a buffer with the date of arrival of past received packets