[lwip-devel] [bug #22110] Recv() makes receive window update for data, that was not received by application

[Simon Goldschmidt]

Follow-up Comment #6, bug #22110 (project lwip):

> The change needed here - being able to find out if the layer
> above is buffering data - is similar to the one needed to
> support shutdown and close properly.

You could implement it that way, but I'd rather think of it as a limitation
of the sockets API being built upon the netconn API: the netconn API simply
does not provide the functionality that we need here: we would need a
netconn_recved callback that effectively does the window update.


A little off topic: I think this is a major performance whole in TCP RX: we
should try to prevent calling back into the stack (do_recv) every time a
packet is received. Most of the time, tcp_recved does nothing and the places
where tcp_ack_now is called that could maybe also be solved differently (e.g.
on next input packet)?

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