On 06/24/2011 09:13 AM, John x wrote:
> Hi, folks,
>
> I am developing a dissector, my tasks are:
>
> 1. to get the 锟斤拷ip.len锟斤拷 (the total length in IP header),
> 2. using the ip.len to know how long the packet would be and extract the last
> byte to my local variable.
>
> *Could you guys please tell me how to get the IP锟斤拷s total length from IP header? *
> *How to extract the last byte of my packet? *
>
> Any suggestions or advices would be appreciated.
>
> Thanks for your help
> John
>
So your dissector sits on top of the IP dissector. It gets a TVB (Testy, Virtual
Buffer) with the IP packet data. Then you can use all the wonderful functions in
epan/tvbuff.h to get access to that (meta-)data.
Like tvb_length() and tvb_reported_length().
Two things: Never go into the TVB data directly, always find the proper access
function. Be aware that captured packets can be cut short, so the length you
have (tvb_length) might be smaller than the original (tvb_reported_length).
Thanks,
Jaap
