Generate new packets with NF?

[Sandip Bhattacharya]

Hi!
I have a target which takes X packet as input and Y,Z packet as output. 
In other words,
         X --->my_target --->Y
                                        |
                                       +--> Z

Y, and Z and totally different in a number of ways

Is this possible using netfilter? I mean, I can mangle one packet at a 
time. But can I "steal" a packet and inject
new packets into the netfilter architecture? Ofcourse, being a kernel 
module, I should be able to reinject the packets
using netif_rx() but I was looking for a much cleaner way using netfilter...

Thanks!

- Sandip