Re: [lwip-users] Delayed ACK behavior

[JM]

TCP_QUEUE_OOSEQ is set at default, enabled.

In order to keep the amount of generated debug output to a minimum since this extra processing (delay) somehow reduces the occurrence of these issues, I have only TCP_INPUT_DEBUG and MEMP_DEBUG enabled, and also commented the following lines:

  LWIP_DEBUGF(TCP_INPUT_DEBUG, ("+-+-+-+-+-+-+-+-+-+-+-+-+-+- tcp_input: flags "));
  tcp_debug_print_flags(TCPH_FLAGS(tcphdr));
  LWIP_DEBUGF(TCP_INPUT_DEBUG, ("-+-+-+-+-+-+-+-+-+-+-+-+-+-+\n"));

Otherwise, no code changes were performed.  The debug output:

SYN-SENT: ackno 6558 pcb->snd_nxt 6558 unacked 6557
tcp_receive: ACK for 6662, unacked->seqno 6558:6662
tcp_receive: removing 6558:6662 from pcb->unacked
tcp_input: packet discarded due to failing checksum 0xe4db
tcp_receive: duplicate seqno 2971771236
tcp_input: packet discarded due to failing checksum 0x3b18
tcp_receive: duplicate seqno 2971772867
tcp_input: packet discarded due to failing checksum 0x0e15

The capture is attached.  192.168.0.169 is lwIP.  In the previous emails I had TCP_WND = 2*MSS, where MSS=1460, but for this capture I thought I could simplify and have changed TCP_WND=MSS. 

I'm not sure if there's enough information here to come to any conclusions.  The problem in my case is too much debug output partially fixes these issues, even if I insert delays instead of the UART output function.  Again this is v1.3.0, no RTOS.  Thanks for your help.

--- On Thu, 8/20/09, Kieran Mansley <address@hidden> wrote:

From: Kieran Mansley <address@hidden>
Subject: Re: [lwip-users] Delayed ACK behavior
To: "Mailing list for lwIP users" <address@hidden>
Date: Thursday, August 20, 2009, 3:48 AM

On Wed, 2009-08-19 at 09:27 -0700, JM wrote:
> I've attached the capture here again in case you don't have the older
> messages where it was originally sent.  I did forget some pertinent
> info that might be helpful: it's v1.3.0, no RTOS, all processing is
> done in the ethernet interrupt.  In the capture: .112 is the
> "transmitter" (my computer, .169 is the lwIP (Stellaris micro)
> board. 
>
> Although I should have the debug output to include, in summary it
> complained of duplicate seqno when a packet was retransmitted
> from .112.

The debug output would be useful to see which of the retransmissions it
is complaining about.

Also, do you have TCP_QUEUE_OOSEQ on or off?

Kieran



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