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RE: [lwip-users] netconn api problem

From: Andrew Foster
Subject: RE: [lwip-users] netconn api problem
Date: Wed, 24 Nov 2010 11:31:56 -0500


You may also want to look into the STATS define in lwipopts.h. You could 
invoke the stats_display function after you've detected the error. This 
would allow you to observe the important stack structures without 
drastically changing execution times.

If I've stated the obvious, I apologize.


-----Original Message-----
From: Tyrel Newton [mailto:address@hidden 
Sent: Wednesday, November 24, 2010 10:46
To: Mailing list for lwIP users
Subject: Re: [lwip-users] netconn api problem

> You could add a UDP broadcast after the big write and use that in 
> to find the smaller packet that follows.

I like the UDP broadcast approach as it will give something unique to 
trigger wireshark (and potentially my python scripts) against.

> Wouldn't you hate to go down this
> path for a long time to find out byte ends up being in the WireShark
> capture?  Sure, I agree, it's 99.9% sure not going to be there.  But 
> Wireshark capture might show other problems in and around that area.  
> are there errors in the capture or is it clean?
> Can you shrink iteratively the size of the first large send until the 
> send works?  This might point to some size or boundary condition when 
> problem appears.

Sure, but the problem is random enough that I'm not sure I could 
reproduce anything useful in a controlled manner. At this point, I 
really think the problem is a third party on our network that broadcasts 
something while lwIP is sending the large chunk of data. And that 
something is somehow screwing with lwIP's internals. I'm sure that 
turning on asserts and debugging in lwIP would show what's wrong, but 
that would change the dynamics of the situation by bringing throughput 
to a screeching halt.

I'll add the UDP broadcast thing and capture it my python scripts in 
parallel, hopefully that will shed some light.

Thanks for the tip!

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