BPF and buffering

[Ghislain]

Hi,

I'd like to write a specific BPF filter in order to read all packets  
( before routing them ) on a network interface and buffering them in  
order to process them and after routing them if I decide that they  
are correct. But I don't know how to intercept them ( then they are  
not processed immediatly by the kernel ) in order to buffering them  
before giving them back to the kernel.

Can you show me example, tutorials or documentation.

Thanks

Ghislain