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[lwip-users] LwIP help needed

From: Chris Williams
Subject: [lwip-users] LwIP help needed
Date: Tue, 16 Dec 2008 15:45:21 +0000

In message <address@hidden>
, Abhinay Patil <address@hidden> writes
>    Hello, 
>    I am in need of some support in using lwIP for my application. I 
>    hope you will be able to reply on the queries, or atleast guide me 
>    to the proper channel for such queries (if this is not the one!). 
>    Thanks in advance. 
>    Here's what I intend to do in my application: 
>    I have a DSP processor with 2 ethernet ports and running lwIP 
>    stack. One port is to receive the incoming traffic and other port 
>    for outgoing traffic. The processor is expected to either filter or 
>    pass through the incoming traffic to the output port based on 
>    certain conditions. For this, the DSP should receive all the IP 
>    packets coming to the input port, regardless of the fact whether 
>    those packets were addressed to that port or not. The DSP will then 
>    analyse the packets and use some proprietary conditions to 
>    determine whether that packet has to be processed or just passed on 
>    to the output port. While passing on the packets to the output 
>    port, the DSP should ensure that the packets are in exactly the 
>    same format as they were when they entered the input port (i.e. the 
>    original source address and other control data etc..) 
>    I hope I have explained my application clearly. I need your help in 
>    understanding where exactly to modify the lwIP stack to achieve 
>    this. (Just for your information, I already have a project with 2 
>    ethernet ports running under lwIP. I need your help in the packet 
>    handling and forwarding part of the application.) 

If you want to do packet filtering you should look at bpf filters
(Google bpf filter). These provide a fast and consistent way of
filtering packets quickly. You feed packets straight from the ethernet
driver etc. You would not need lwip.

Hope that helps.

>    Thanks and regards, 
>    Abhinay
>lwip-users mailing list

| Chris Williams    EMail address@hidden                            |
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