[lwip-users] re assembly problems

[Michel SIMIAN]

Hi,

We have designed an embedded application using LWIP, running on ARM 
based board, compiled with Keil uvision and freeRTOS.
The stack used was the 1.3.0 release.

The application is connected to a single PC Windows.

We have detected some problems when a routeur sometimes changes the MTU. 
A net sniffer indicates that some frames are broken into 2 parts, which 
causes our highlevel protocol crashes.

for example when the PC send 806 bytes with an MTU  of 536, the 
application read first the total length stored at the frame begining as 
a short, then try to read the last 804 bytes.

It is very difficult to debug because of the embedded depth of code. 
Perhaps we may mis-use the API, perhaps whe should use another way to 
recv(). But the application is a closed component running grafcet blocks 
and we can't easily debug it.

We have designed a very small test application on the two sides. The PC 
sends N frames from B bytes at S interval.

The embedded application receives more than N frames, but always B * N 
bytes, which is normal. Why more then N frames ? And N increases as S 
decreases.

So, my question is : were should we look if we have re assembly problem ?

Thanks...

--
Michel SIMIAN
XOOL Technologies
04.75.42.29.70