[GitHub] [incubator-nuttx] a-lunev edited a comment on pull request #5272: net/tcp/sendfile: retransmit only one the earliest not acknowledged segment

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a-lunev edited a comment on pull request #5272:
URL: https://github.com/apache/incubator-nuttx/pull/5272#issuecomment-1017523763


   > LGTM. @a-lunev Seems the TCP stack adds too much of sendfile handling, I do not think this is a good trend, since tcp is inherently streaming, the stack should not need to know if a file is being to sent, could we try to hide these details in the tcp_sendfile.c?
   
   @anchao If you mean the introduced conn->sendfile variable in #5239, unfortunately NET_TCP_WRITE_BUFFERS and NET_SENDFILE modes were totally inconsistent to each other (some part of tcp_sendfile relied on NET_TCP_WRITE_BUFFERS=n functionality and the other part of tcp_sendfile relied on NET_TCP_WRITE_BUFFERS=y functionality, however it is a nonsense).
   I have analyzed NuttX git repo history and concluded that these two simultaneously enabled options (NET_TCP_WRITE_BUFFERS and NET_SENDFILE) have never worked in NuttX (never supported by design), however some of the boards (sama5 and sim based) has these two options simultaneously enabled. That means tcp_sendfile was broken for those boards and could not work for any other board if these two options got enabled in the same config.
   In #5239 I supported the possibility to use NET_SENDFILE option if NET_TCP_WRITE_BUFFERS=y, and introducing conn->sendfile variable was a required measure to do that.
   On another hand, I am going to rework tcp_send_buffered.c as well, or at least to do a mutual unification of all 3 parts: tcp_send_buffered.c, tcp_send_unbuffered.c and tcp_sendfile.c. As a result of the intended unification I expect that the conn->sendfile variable may be removed at a later step.


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