Open a terminal and type:
kedit /usr/include/linux/wireless.h

This will open a text editor. Locate the lines:
Code:
#ifndef _LINUX_WIRELESS_H
#define _LINUX_WIRELESS_H
and after add:
#include <linux/if.h>

Should now look like:
Code:
#ifndef _LINUX_WIRELESS_H
#define _LINUX_WIRELESS_H
#include <linux/if.h>
Save and exit. In that same terminal follow these steps:

Code:
cd ~
wget kent.dl.sourceforge.net/sourceforge/airpwn/airpwn-1.3.tgz
tar -xzf airpwn-1.3.tgz
cd airpwn-1.3
tar -xzf lorcon-current.tgz
cd lorcon
./configure && make && make install    
cd ..
configure
make
madwifing_prep.sh
Finally, lets give it a go:
Code:
airpwn -c conf/greet_html -d madwifi -i ath1 -v -v