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

[Simon Goldschmidt]

Update of bug #20515 (project lwip):

                 Summary: TCP delyed ack does not work as expected => TCP
delayed ack does not work as expected

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Follow-up Comment #2:

I propose the following change in tcp_recved():

Replace
>>>
  if (!(pcb->flags & TF_ACK_DELAY) &&
     !(pcb->flags & TF_ACK_NOW)) {
    tcp_ack(pcb);
  } 
  else if (pcb->flags & TF_ACK_DELAY && pcb->rcv_wnd >= TCP_WND/2){
    tcp_ack_now(pcb);
  }
<<<

by

>>>
  if (old_win <= TCP_WND/2) { 
    tcp_ack_now(pcb);
  else {
    pcb->flags |= TF_ACK_DELAY;
  }
<<<

That way, we send a TCP-window-update-ACK only if the previous window size
was very small.

Note that the current code, the 'tcp_ack(pcb)' effectively resolves to
'pcb->flags |= TF_ACK_DELAY'.

I'm getting better results with the change, but like to have it tested, so
I'm attaching a patch to tcp.c!

(file #13383)
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