How can I get these packets in the user space application? Performance Issues?

[Henrik Nordstrom]

On Thu, 9 Dec 2004, Steven J Scott wrote:

> I have a side question on this.  I have a kernel module that creates a
> netfilter hook that looks for packets with a certain source port, and then
> directs them to NF_QUEUE, and I have a user space application that receives the queued packets.
> Since I am only queuing packets I want to monitor/modify is my performance
> hit significant?  Or am I better off doing everything within the kernel
> module?

Only the packets you return NF_QUEUE on receives a noticeable performance 
penalty.

But if all you do is to look into the source port then why not use plain 
iptables for the match?

Regards
Henrik