yamt commented on a change in pull request #2414:
URL: https://github.com/apache/incubator-nuttx/pull/2414#discussion_r676424780
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File path: net/tcp/tcp_send_buffered.c
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@@ -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:
in that case, we have likely already started fast retransmit.
* do you mean the segment fast-retransmitted has lost again? such a case is
simpler to leave to the usual "slow retransmit".
* this implementation of fast retransmit can retransmit multiple segments.
(usually fast retransmit only retransmit one segment. but to me this
implementation doesn't seem to have such a mechanism.) so the calculation here
doesn't seem to make much sense to me.
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