[GitHub] [incubator-nuttx] yamt commented on a change in pull request #2414: net/tcp: implement the fast retransmit

[GitBox <gi...@apache.org>]

yamt commented on a change in pull request #2414:
URL: https://github.com/apache/incubator-nuttx/pull/2414#discussion_r671039119



##########
File path: net/tcp/tcp_send_buffered.c
##########
@@ -484,6 +485,26 @@ static uint16_t psock_send_eventhandler(FAR struct net_driver_s *dev,
                         wrb, TCP_WBSEQNO(wrb), TCP_WBPKTLEN(wrb));
                 }
             }
+          else if (ackno == TCP_WBSEQNO(wrb))
+            {
+              /* Duplicate ACK? Retransmit data if need */
+
+              if (++TCP_WBNACK(wrb) ==
+                  CONFIG_NET_TCP_FAST_RETRANSMIT_WATERMARK)
+                {
+                  /* Do fast retransmit */
+
+                  rexmit = true;
+                }
+              else if ((TCP_WBNACK(wrb) >
+                       CONFIG_NET_TCP_FAST_RETRANSMIT_WATERMARK) &&
+                       TCP_WBNACK(wrb) == sq_count(&conn->unacked_q) - 1)

Review comment:
       @anchao can you explain the intention of this condition?




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