buglwIP - A Lightweight TCP/IP stack - Bugs: bug #25940, Regarding the Fragmentation issue...


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bug #25940: Regarding the Fragmentation issue in the ICMP packet.

Submitted by:  Arun <arun_rh>
Submitted on:  Fri 20 Mar 2009 03:45:28 PM UTC  
Category:  None Severity:  3 - Normal
Item Group:  Faulty Behaviour Status:  Need Info
Privacy:  Public Assigned to:  None
Open/Closed:  Closed Planned Release:  None
lwIP version:  1.3.0

Sat 09 Jan 2010 12:32:16 PM UTC, comment #3: 

Closing this as there's no more input from the original poster and fragmented ping does not seem to be a problem currently...

Everyone, please reopen if there d appear more problems here!

Simon Goldschmidt <goldsimon>
Project Administrator
Fri 01 May 2009 12:21:20 PM UTC, comment #2: 

Arun, could you tell us a little bit more about this? I don't think this is related to bug #24517, since that completely crashed (on unaligned data) and this one seems to have invalid pbufs somehow (failing in pbuf_header).

This could well be a misconfiguration... but without any further info, we're not able to do anything about it: the function where the assert fails is called from far too many places to know what's happening from your initial post only.

Simon Goldschmidt <goldsimon>
Project Administrator
Fri 03 Apr 2009 10:57:17 AM UTC, comment #1: 

I wonder if this could be related to BUG24517: https://savannah.nongnu.org/bugs/index.php?24517

Is there any chance you could test your code with that bug fix?

Kieran Mansley <kieranm>
Project Member
Fri 20 Mar 2009 03:45:28 PM UTC, original submission:  

Hello All,
Currently I am working on the LWIP stack, which we have ported on to the STR912 processor.
Actually I am facing a strange problem of reassembling process of Fragmented ICMP packet.
My observation was the ping utility is failing at higher packet size (more than 1472 ) say1500.
But the same works if we send the ping command less than 1472.
So I understand that when ever we send the ping command with more than 1472 bytes, it basically splits the packet into and the same Is reassembled on the LWIP stack. I saw the sender sends the ping command with fragmented messages.

These fragmented messages are received on the STR912 that is our target where the LWIP stack will be running.

So the LWIP while in the process of reassembling it is going to some Assert statement. Actually it is going to some assert statement in pbuf_header() function in the pbuf.c file and the code is

if (header_size_increment < 0){

    increment_magnitude = -header_size_increment;

    /* Check that we aren't going to move off the end of the pbuf */

    LWIP_ERROR("increment_magnitude <= p->len", (increment_magnitude <= p->len), return 1;);


I have seen one of the mail asking the same question for the solution in 2006. So could u please suggest me whether the issue of reassembling process and the fragmentation is fixed or not. Currently I am using the 1.0.3 version. Does the LWIP stack is tested with the Ping utility with more than 10000 bytes ?


With Regards

Arun Honnappa

Arun <arun_rh>


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    Follow 2 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2010-01-09 goldsimon Open/ClosedOpen => Closed
    2009-05-01 kieranm StatusNone => Need Info

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