mac80211_hwsim - software simulator of 802.11 radio(s) for mac80211
Copyright (c) 2008, Jouni Malinen <j@w1.fi>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License version 2 as
published by the Free Software Foundation.


Introduction

mac80211_hwsim is a Linux kernel module that can be used to simulate
arbitrary number of IEEE 802.11 radios for mac80211 on a single
device. It can be used to test most of the mac80211 functionality and
user space tools (e.g., hostapd and wpa_supplicant) in a way that
matches very closely with the normal case of using real WLAN
hardware. From the mac80211 view point, mac80211_hwsim is yet another
hardware driver, i.e., no changes to mac80211 are needed to use this
testing tool.

The main goal for mac80211_hwsim is to make it easier for developers
to test their code and work with new features to mac80211, hostapd,
and wpa_supplicant. The simulated radios do not have the limitations
of real hardware, so it is easy to generate an arbitrary test setup
and always reproduce the same setup for future tests. In addition,
since all radio operation is simulated, any channel can be used in
tests regardless of regulatory rules.

mac80211_hwsim kernel module has a parameter 'radios' that can be used
to select how many radios are simulates (default 2). This allows
configuration of both very simply setups (e.g., just a single access
point and a station) or large scale tests (multiple access points with
hundreds of stations).

mac80211_hwsim works by tracking the current channel of each virtual
radio and copying all transmitted frames to all other radios that are
currently enabled and on the same channel as the transmitting
radio. Software encryption in mac80211 is used so that the frames are
actually encrypted over the virtual air interface to allow more
complete testing of encryption.

A global monitoring netdev, hwsim#, is created independent of
mac80211. This interface can be used to monitor all transmitted frames
regardless of channel.


Simple example

This example shows how to use mac80211_hwsim to simulate two radios:
one to act as an access point and the other as a station that
associates with the AP. hostapd and wpa_supplicant are used to take
care of WPA2-PSK authentication. In addition, hostapd is also
processing access point side of association.

Please note that the current Linux kernel does not enable AP mode, so a
simple patch is needed to enable AP mode selection:
http://johannes.sipsolutions.net/patches/kernel/all/LATEST/006-allow-ap-vlan-modes.patch


# Build mac80211_hwsim as part of kernel configuration

# Load the module
modprobe mac80211_hwsim

# Run hostapd (AP) for wlan0
hostapd hostapd.conf

# Run wpa_supplicant (station) for wlan1
wpa_supplicant -Dwext -iwlan1 -c wpa_supplicant.conf