U2: drop packets from libslirp if the queue is full (we keep at most 10).

Signed-off-by: Andrea Odetti <mariofutire@gmail.com>

source/linux/network/slirp2.cpp

@@ -132,7 +132,14 @@ void SlirpNet::sendFromGuest(const uint8_t *pkt, const int pkt_len)
 
 void SlirpNet::sendToGuest(const uint8_t *pkt, int pkt_len)
 {
-  myQueue.emplace(pkt, pkt + pkt_len);
+  if (myQueue.size() < ourQueueSize)
+  {
+    myQueue.emplace(pkt, pkt + pkt_len);
+  }
+  else
+  {
+    // drop it
+  }
 }
 
 void SlirpNet::process(uint32_t timeout)

source/linux/network/slirp2.h

@@ -21,6 +21,9 @@ public:
   std::queue<std::vector<uint8_t>> & getQueue();
   void clearQueue();
 private:
+
+  static constexpr size_t ourQueueSize = 10;
+
   std::shared_ptr<Slirp> mySlirp;
   std::vector<pollfd> myFDs;
 

source/linux/network/uthernet2.cpp

@@ -355,7 +355,7 @@ namespace
 #ifdef U2_USE_SLIRP
     {
       std::queue<std::vector<uint8_t>> & queue = slirp->getQueue();
-      if (!queue.empty())
+      while (!queue.empty())
       {
         const std::vector<uint8_t> & packet = queue.front();
         if (isThereRoomFor(i, packet.size(), sizeof(uint16_t)))
@@ -366,6 +366,10 @@ namespace
           LogFileOutput("U2: READ MACRAW[%d]: +%d -> %d bytes (%04x)\n", i, packet.size(), socket.sn_rx_rsr, socket.sn_rx_wr);
 #endif
         }
+        else
+        {
+          break;
+        }
       }
     }
 #else
@@ -383,7 +387,7 @@ namespace
         }
         else
         {
-          // ??? we just skip it
+          // drop it
 #ifdef U2_LOG_TRAFFIC
           LogFileOutput("U2: SKIP MACRAW[%d]: %d bytes\n", i, len);
 #endif