buglwIP - A Lightweight TCP/IP stack - Bugs: bug #47305, slow load time, DupACK-Problem in...

 
 

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bug #47305: slow load time, DupACK-Problem in TCPIP Thread

Submitter:  Martin Datzmann <martin5523>
Submitted:  Mon 29 Feb 2016 02:43:05 PM UTC
   
 
Category:  TCP Severity:  3 - Normal
Item Group:  None Status:  Works For Me
Privacy:  Public Assigned to:  goldsimon
Open/Closed:  Closed Planned Release:  None
lwIP version:  1.4.1

Fri 04 Mar 2016 08:38:18 PM UTC, comment #1: 

This sounds like a misconfiguration (out of memory?) or a bug in your lwIP-port.

Please send questions on how to use lwIP (if this it what you want?) to the
lwip-users list.

Simon Goldschmidt <goldsimon>
Group administrator
Mon 29 Feb 2016 02:43:05 PM UTC, original submission:  

Dear all,

in my project, I use the lwIP-Stack with FreeRTOS on an ARM-Cortex M4 Mikrocontroller.
There is no problem, to serve a small html-page. (web page load time: 3 ms)
When I try to serve a slightly more complex page (html and two pictures), the following problem can occur resulting

in very slow load time:

In response to a request the webserver sends two data-packets (Con1_data1.1/data1.2) as usual and gets an ACK from

the Browser (Con1_ACK1). If an ACK for another TCP-connection (Con2_ACK1) is received between Con1_data1.1/data1.2

and Con1_ACK1, then Con2_ACK1 is handled correctly.

But now, instead of processing Con1_ACK1 and therefore removing Con1_data1.1/data1.2 from the unacked-list, the

TCP/IP-thread is terminating and still waits for an ACK for Con1_data1.1/data1.2. After timeout (ca. 2 s), the

TCP/IP-thread resends Con1_data1.1, gets an ACK again (Con1_ACK1dup) and removes Con1_data1.1 from the unacked-list

and Con1_data1.2 from the unsent-list and everything seems ok.

After this the next two packets are sent (Con1_data2.1/data2.2) and Con1_ACK2 is received. Now in tcp_receive() the

dupack routine is entered probably because of Con1_ACK1dup ( a) dupacks < 3: do nothing) and the TCP/IP-thread is

terminating without removing Con1_data2.1/data2.2 from the unacked-list. From now on the process is repeating again

with resending Con1_data2.1 after timeout and receiving Con1_ACK2dup as described above.

Once the problem occured, it repeats again and again and one has to do a restart to reset the behaviour.
I used lwip 1.4.1 and also latest source from git.savannah.gnu.org (commit #70f3e5e). In both versions the problem

exists.

Has anybody experienced a similar problem with DupACKs here?
What could be the reason for this behaviour?


Thanks!

Martin Datzmann <martin5523>

 

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Attached Files
file #36504:  wireshark.jpg added by martin5523 (486KiB - image/jpeg)

 

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    Date Changed by Updated Field Previous Value => Replaced by
    2016-03-04 goldsimon StatusNone Works For Me
        Assigned toNone goldsimon
        Open/ClosedOpen Closed
    2016-02-29 martin5523 Attached File- Added wireshark.jpg, #36504
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