[lwip-users] ip_input

[Pepe Prisas]

Hi there,

I hope this is not a far too simple question for you since I'm a newbie 
with lwIP and with FPGA programming. Any advice would be really appreciated.

I'm actually working on a EDK network project for use on a Virtex-II Pro 
FPGA using Micoblaze soft-core. This project intends to read every 
incoming packet/frame on the network to be analyzed later on, something 
like a sniffer. I'm using EDK 6.3 with the lwIP stack.

I am able to initialize the lwIP TCP/IP stack correctly with the lwIP 
initalization routines: sys_init(); mem_init(); memp_init(); 
pbuf_init(); netif_init(); tcp_init();
I can also activate the network interface correctly with netif_add and 
netif_set_default.
I have been able to run other lwIP applications on my development card 
like the application note "TCP/IP on Virtex-II Pro Devices Using lwIP" 
that work 100% correctly.

My idea was to modify the ip_input function included in ip.c.
This function is the one in charge of reading every incoming packet and 
checking headers, packet length, etc.
But I think this is not the correct way to do it since any changes that 
I make on this file do not seem to apply. I assume that once the lwIP 
files and headers are generated with LibGen these can not be changed.

Some TCP level functions are used to register callback functions which 
can be included in the project code such as tcp_arg, tcp_bind,...The 
callback functions then can be programmed in the project to work on a 
TCP level, but my intention is to capture every packet, not only those 
from a certain TCP connection

Is there any way of registering callback functions on IP level? How can 
I modify ip_input function so that the changes can apply on my project? 
Any advice?

Sorry if I haven't explained myself correctly but English isn't my first 
language.

Thanks in advance.

Adrian