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

[Oleg Tyshev]

Follow-up Comment #22, bug #20515 (project lwip):

I think exists one more error in implementation window update.

To the other side would be sent always rcv_ann_wnd.
It is means, other side is not allowed to send something out of the window.
But in tcp_in.c will be always used rcv_wnd.
It is not correct.

For exampe in tcp_receive()

  /* The sequence number must be within the window (above rcv_nxt
     and below rcv_nxt + rcv_wnd) in order to be further
     processed. */
  if (TCP_SEQ_BETWEEN(seqno, pcb->rcv_nxt, 
                      pcb->rcv_nxt + pcb->rcv_wnd - 1)){

in my case
  rcv_ann_wnd == 0, rcv_wnd == 1000
I get zero window probe packet (tcplen == 1)

and then in tcp_update_rcv_ann_wnd() we go to the the second branch,
rcv_ann_wnd = 65535

  


(file #17836)
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Additional Item Attachment:

File name: tcp_zerowin65535.pcap          Size:153 KB


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