[lwip-devel] [bug #29080] Burst of duplicate ACKs

[Petr Cernin]

URL:
  <http://savannah.nongnu.org/bugs/?29080>

                 Summary: Burst of duplicate ACKs
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: cerninp
            Submitted on: Fri 05 Mar 2010 03:42:41 PM GMT
                Category: TCP
                Severity: 3 - Normal
              Item Group: Crash Error
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: 
            lwIP version: CVS Head

    _______________________________________________________

Details:

Hello,

I've met two strange bugs inside the tcp while sending a large file (cca 4MB)
from pc (192.168.3.53) to the device with lwip (192.168.23.2). 

-----
(1) In periodic intervals tcp sends burst of duplicate acks. See attached
document (packets 124, 693,1283, 1897, 2505, 3168, 3787). 

-----
(2) After upgrading to 1.3.2, lwip stack crashes on following assert during
sending this file:

tcp_in.c:

1278:     pcb->rcv_nxt += TCP_TCPLEN(cseg);
1279:     LWIP_ASSERT("tcp_receive: ooseq tcplen > rcv_wnd\n",
1280:                  pcb->rcv_wnd >= TCP_TCPLEN(cseg));
1281:     pcb->rcv_wnd -= TCP_TCPLEN(cseg);

It happens very often when I switch ethernet to 10Mbps and is very rare when
ethernet is 100Mbps. 

When I switch off out of order queue (by setting TCP_QUEUE_OOSEQ to 0)
everything is ok. 

Maybe there's some ralation between this two bugs.

I have tested it with  1.3.2 and also with head, the result is the same. I
can provide complete wireshark trace. Text version of the trace and lwip
configuration file is attached.

Please help. Now I am going to dig inside the code TCP_QUEUE_OOSEQ.







    _______________________________________________________

File Attachments:


-------------------------------------------------------
Date: Fri 05 Mar 2010 03:42:41 PM GMT  Name: dupack.txt  Size: 463kB   By:
cerninp

<http://savannah.nongnu.org/bugs/download.php?file_id=19853>
-------------------------------------------------------
Date: Fri 05 Mar 2010 03:42:41 PM GMT  Name: lwipopts.h  Size: 14kB   By:
cerninp

<http://savannah.nongnu.org/bugs/download.php?file_id=19854>

    _______________________________________________________

Reply to this item at:

  <http://savannah.nongnu.org/bugs/?29080>

_______________________________________________
  Message sent via/by Savannah
  http://savannah.nongnu.org/