Re: [lwip-users] Try to manipulate the pbuf payload

[Sergio R. Caprile]

Well...
You do know that p->payload is a void*, that is, a pointer to some 
bytes, do you ?
http://www.nongnu.org/lwip/2_0_x/structpbuf.html#a8d32dc3e964369d4eec638fc37fbc460

Then, why do you want to peek at data between your driver and lwip ? You 
are not using the RAW API, you are looking at raw frame payload contents 
before being passed on to lwIP. You either use UDP or TCP (unless you 
really need to use raw IP, but then you will not probably do what you 
are doing now, or raw frames, but I can't help you there)
Anyway, incoming pbufs are of type PBUF_RAM, that means they can 
actually a chain of pbufs, any action on them must be through the 
pbuf_...() functions:
http://www.nongnu.org/lwip/2_0_x/group__pbuf.html#ggab7e0e32fcc292c0d7107721766ed92fbae969347127387b9b59a23ccd24b76d21

You should see what the examples do and study them.
Also, there is a nice wiki covering whatever the official docs might not 
be verbose at, you could start by understanding the RAW API here:
http://lwip.wikia.com/wiki/Raw/native_API