How to extract source and destination port number from packet in queue of iptables

Question

I am using libnetfilter_queue library. But i couldn't figure out a way to extract port number in the call back function. I am bit new. A detailed help will be highly appreciated!

Answer 1

It can be done in the following manner, in the call back function:

len = nfq_get_payload(nfa, &buffer);
src_port = *((unsigned short*) (buffer + 20));
dst_port = *((unsigned short*) (buffer + 22));