Hi,

I found out the problem already. My driver was set up to transfer out one 
buffer per frame only (1520 bytes) since 
we want to spare processing power as much as we can and also due to the fact we 
have ample memory, 
and the 1.3.0 seems to chain the TCP packets to form frames(multiple buffers 
per frame). Is there any thing i can setup to force
TCP packs 1520 bytes per buffer (pbufs) ?

Thanks

M Ikhwan Ismail
ABB STOTZ KONTAKT GmbH



From: [EMAIL PROTECTED]
To: [email protected]
Date: Tue, 6 May 2008 07:36:13 +0000
Subject: [lwip-users] TCP checksum error for big sized packets on lwip 1.3.0








Hi,

I have ported the version 1.3.0 to my PowerPC running SMX RTOS and a runtime 
system which enables me to input and save
commands over telnet into the runtime system. The connection between the 
programming pc and the runtime system in PowerPC 
is done over Ethernet. Everything is well until the PowerPC  sends a big packet 
(the biggest so far is 500+ bytes)
with checksum error (retransmissions also have checksum error) 
and halts the programming interface of the prog.pc since it awaits response 
from the PowerPC.

At the same time I have a small HTTP server running on the PowerPC and the same 
case is noticed when the server needs to send
a big packet. Anyways the stack didnt crash due to the error. I sent some stray 
IP packets and the ICMP module returned me
the normal Destination Unavailable message. Has anyone faced the same problem ?

I enclosed my opt.h and a wireshark trace as an example. I hope someone can 
give me some tips on the problem as I have been
spending days trying to figure out the problem. I d appreciate any help I can 
get.

Thanks in advance

M Ikhwan Ismail
ABB STOTZ KONTAKT GmbH
Heidelberg, Germany



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