[lwip-devel] [bug #20515] TCP delayed ack does not work as expected

[Simon Goldschmidt]

Follow-up Comment #19, bug #20515 (project lwip):

Nice work! Let me summarize what I understood from reading the code, only to
make sure I understood it correctly:

- until now, tcp_ack was responsible for window-update-acks
- until now, we called tcp_ack from tcp_received and tcp_receive

- now, tcp_received calculates the window-update-ack on its own
- tcp_receive still uses the 'old' tcp_ack -> called for every packet
received

If I remember the RFC correctly, the goal should be to send ACKs/window
updates for every 2nd packet at least (no matter how big it is) and again if
the window increase is notably high.

I *guess* this is achieved with your patch (although I would rather test it
before releasing lwIP with this).


Only one comment on the code: To let future developers know what's going on,
I'd rename the function tcp_set_header to tcp_output_set_header: We already
had the idea to set the header when enqueueing (not sending) a segment to
update chksum on-the-fly and we should prevent tcp_set_header being used in
this case (as the value of rcv_ann_right_edge would then be wrong).

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