where and which is the packet to modify the IP layer in qnx?

I want to take the timestamp at IP layer (may be i.e. ip_rcv api). I dont know where and how to take the timestamp at ip Layer in QNX. could someone please explain how to do that ??
If there is any code regarding that then please post it. Its very important and having deadline tomorrow.
I am having io-pkt source code for qnx but dont know which is the file to modify and how to read the timestamp on user application ??

PLEASE HELP ME.

ADMIN : PLEASE POST THIS QUESTION SOON.