mac80211_hwsim: 802.11 radio simulator for mac80211

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.
Signed-off-by: Jouni Malinen <j@w1.fi>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

Documentation/networking/mac80211_hwsim/README

+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

Documentation/networking/mac80211_hwsim/hostapd.conf

+interface=wlan0
+driver=nl80211
+
+hw_mode=g
+channel=1
+ssid=mac80211 test
+
+wpa=2
+wpa_key_mgmt=WPA-PSK
+wpa_pairwise=CCMP
+wpa_passphrase=12345678

Documentation/networking/mac80211_hwsim/wpa_supplicant.conf

+ctrl_interface=/var/run/wpa_supplicant
+
+network={
+	ssid="mac80211 test"
+	psk="12345678"
+	key_mgmt=WPA-PSK
+	proto=WPA2
+	pairwise=CCMP
+	group=CCMP
+}

drivers/net/wireless/Kconfig

@@ -673,6 +673,19 @@ config ADM8211
 
 	  Thanks to Infineon-ADMtek for their support of this driver.
 
+config MAC80211_HWSIM
+	tristate "Simulated radio testing tool for mac80211"
+	depends on MAC80211 && WLAN_80211
+	---help---
+	  This driver is a developer testing tool that can be used to test
+	  IEEE 802.11 networking stack (mac80211) functionality. This is not
+	  needed for normal wireless LAN usage and is only for testing. See
+	  Documentation/networking/mac80211_hwsim for more information on how
+	  to use this tool.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called mac80211_hwsim.  If unsure, say N.
+
 source "drivers/net/wireless/p54/Kconfig"
 source "drivers/net/wireless/ath5k/Kconfig"
 source "drivers/net/wireless/iwlwifi/Kconfig"

drivers/net/wireless/Makefile

@@ -62,3 +62,5 @@ obj-$(CONFIG_RT2X00)	+= rt2x00/
 obj-$(CONFIG_P54_COMMON)	+= p54/
 
 obj-$(CONFIG_ATH5K)	+= ath5k/
+
+obj-$(CONFIG_MAC80211_HWSIM)	+= mac80211_hwsim.o

drivers/net/wireless/mac80211_hwsim.c

+/*
+ * 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.
+ */
+
+/*
+ * TODO:
+ * - IBSS mode simulation (Beacon transmission with competition for "air time")
+ * - IEEE 802.11a and 802.11n modes
+ * - RX filtering based on filter configuration (data->rx_filter)
+ */
+
+#include <net/mac80211.h>
+#include <net/ieee80211_radiotap.h>
+#include <linux/if_arp.h>
+#include <linux/rtnetlink.h>
+#include <linux/etherdevice.h>
+
+MODULE_AUTHOR("Jouni Malinen");
+MODULE_DESCRIPTION("Software simulator of 802.11 radio(s) for mac80211");
+MODULE_LICENSE("GPL");
+
+static int radios = 2;
+module_param(radios, int, 0444);
+MODULE_PARM_DESC(radios, "Number of simulated radios");
+
+
+static struct class *hwsim_class;
+
+static struct ieee80211_hw **hwsim_radios;
+static int hwsim_radio_count;
+static struct net_device *hwsim_mon; /* global monitor netdev */
+
+
+static const struct ieee80211_channel hwsim_channels[] = {
+	{ .center_freq = 2412 },
+	{ .center_freq = 2417 },
+	{ .center_freq = 2422 },
+	{ .center_freq = 2427 },
+	{ .center_freq = 2432 },
+	{ .center_freq = 2437 },
+	{ .center_freq = 2442 },
+	{ .center_freq = 2447 },
+	{ .center_freq = 2452 },
+	{ .center_freq = 2457 },
+	{ .center_freq = 2462 },
+	{ .center_freq = 2467 },
+	{ .center_freq = 2472 },
+	{ .center_freq = 2484 },
+};
+
+static const struct ieee80211_rate hwsim_rates[] = {
+	{ .bitrate = 10 },
+	{ .bitrate = 20, .flags = IEEE80211_RATE_SHORT_PREAMBLE },
+	{ .bitrate = 55, .flags = IEEE80211_RATE_SHORT_PREAMBLE },
+	{ .bitrate = 110, .flags = IEEE80211_RATE_SHORT_PREAMBLE },
+	{ .bitrate = 60 },
+	{ .bitrate = 90 },
+	{ .bitrate = 120 },
+	{ .bitrate = 180 },
+	{ .bitrate = 240 },
+	{ .bitrate = 360 },
+	{ .bitrate = 480 },
+	{ .bitrate = 540 }
+};
+
+struct mac80211_hwsim_data {
+	struct device *dev;
+	struct ieee80211_supported_band band;
+	struct ieee80211_channel channels[ARRAY_SIZE(hwsim_channels)];
+	struct ieee80211_rate rates[ARRAY_SIZE(hwsim_rates)];
+
+	struct ieee80211_channel *channel;
+	int radio_enabled;
+	unsigned long beacon_int; /* in jiffies unit */
+	unsigned int rx_filter;
+	int started;
+	struct timer_list beacon_timer;
+};
+
+
+struct hwsim_radiotap_hdr {
+	struct ieee80211_radiotap_header hdr;
+	u8 rt_flags;
+	u8 rt_rate;
+	__le16 rt_channel;
+	__le16 rt_chbitmask;
+} __attribute__ ((packed));
+
+
+static int hwsim_mon_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	/* TODO: allow packet injection */
+	dev_kfree_skb(skb);
+	return 0;
+}
+
+
+static void mac80211_hwsim_monitor_rx(struct ieee80211_hw *hw,
+				      struct sk_buff *tx_skb)
+{
+	struct mac80211_hwsim_data *data = hw->priv;
+	struct sk_buff *skb;
+	struct hwsim_radiotap_hdr *hdr;
+	u16 flags;
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(tx_skb);
+	struct ieee80211_rate *txrate = ieee80211_get_tx_rate(hw, info);
+
+	if (!netif_running(hwsim_mon))
+		return;
+
+	skb = skb_copy_expand(tx_skb, sizeof(*hdr), 0, GFP_ATOMIC);
+	if (skb == NULL)
+		return;
+
+	hdr = (struct hwsim_radiotap_hdr *) skb_push(skb, sizeof(*hdr));
+	hdr->hdr.it_version = PKTHDR_RADIOTAP_VERSION;
+	hdr->hdr.it_pad = 0;
+	hdr->hdr.it_len = cpu_to_le16(sizeof(*hdr));
+	hdr->hdr.it_present = __constant_cpu_to_le32(
+	     (1 << IEEE80211_RADIOTAP_FLAGS) |
+	     (1 << IEEE80211_RADIOTAP_RATE) |
+	     (1 << IEEE80211_RADIOTAP_CHANNEL));
+	hdr->rt_flags = 0;
+	hdr->rt_rate = txrate->bitrate / 5;
+	hdr->rt_channel = data->channel->center_freq;
+	flags = IEEE80211_CHAN_2GHZ;
+	if (txrate->flags & IEEE80211_RATE_ERP_G)
+		flags |= IEEE80211_CHAN_OFDM;
+	else
+		flags |= IEEE80211_CHAN_CCK;
+	hdr->rt_chbitmask = cpu_to_le16(flags);
+
+	skb->dev = hwsim_mon;
+	skb_set_mac_header(skb, 0);
+	skb->ip_summed = CHECKSUM_UNNECESSARY;
+	skb->pkt_type = PACKET_OTHERHOST;
+	skb->protocol = __constant_htons(ETH_P_802_2);
+	memset(skb->cb, 0, sizeof(skb->cb));
+	netif_rx(skb);
+}
+
+
+static int mac80211_hwsim_tx(struct ieee80211_hw *hw, struct sk_buff *skb)
+{
+	struct mac80211_hwsim_data *data = hw->priv;
+	struct ieee80211_rx_status rx_status;
+	int i, ack = 0;
+	struct ieee80211_hdr *hdr;
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	struct ieee80211_tx_info *txi;
+
+	mac80211_hwsim_monitor_rx(hw, skb);
+
+	if (skb->len < 10) {
+		/* Should not happen; just a sanity check for addr1 use */
+		dev_kfree_skb(skb);
+		return NETDEV_TX_OK;
+	}
+
+	if (!data->radio_enabled) {
+		printk(KERN_DEBUG "%s: dropped TX frame since radio "
+		       "disabled\n", wiphy_name(hw->wiphy));
+		dev_kfree_skb(skb);
+		return NETDEV_TX_OK;
+	}
+
+	hdr = (struct ieee80211_hdr *) skb->data;
+
+	memset(&rx_status, 0, sizeof(rx_status));
+	/* TODO: set mactime */
+	rx_status.freq = data->channel->center_freq;
+	rx_status.band = data->channel->band;
+	rx_status.rate_idx = info->tx_rate_idx;
+	/* TODO: simulate signal strength (and optional packet drop) */
+
+	/* Copy skb to all enabled radios that are on the current frequency */
+	for (i = 0; i < hwsim_radio_count; i++) {
+		struct mac80211_hwsim_data *data2;
+		struct sk_buff *nskb;
+
+		if (hwsim_radios[i] == NULL || hwsim_radios[i] == hw)
+			continue;
+		data2 = hwsim_radios[i]->priv;
+		if (!data2->started || !data2->radio_enabled ||
+		    data->channel->center_freq != data2->channel->center_freq)
+			continue;
+
+		nskb = skb_copy(skb, GFP_ATOMIC);
+		if (nskb == NULL)
+			continue;
+
+		if (memcmp(hdr->addr1, hwsim_radios[i]->wiphy->perm_addr,
+			   ETH_ALEN) == 0)
+			ack = 1;
+		ieee80211_rx_irqsafe(hwsim_radios[i], nskb, &rx_status);
+	}
+
+	txi = IEEE80211_SKB_CB(skb);
+	memset(&txi->status, 0, sizeof(txi->status));
+	if (!(txi->flags & IEEE80211_TX_CTL_NO_ACK)) {
+		if (ack)
+			txi->flags |= IEEE80211_TX_STAT_ACK;
+		else
+			txi->status.excessive_retries = 1;
+	}
+	ieee80211_tx_status_irqsafe(hw, skb);
+	return NETDEV_TX_OK;
+}
+
+
+static int mac80211_hwsim_start(struct ieee80211_hw *hw)
+{
+	struct mac80211_hwsim_data *data = hw->priv;
+	printk(KERN_DEBUG "%s:%s\n", wiphy_name(hw->wiphy), __func__);
+	data->started = 1;
+	return 0;
+}
+
+
+static void mac80211_hwsim_stop(struct ieee80211_hw *hw)
+{
+	struct mac80211_hwsim_data *data = hw->priv;
+	data->started = 0;
+	printk(KERN_DEBUG "%s:%s\n", wiphy_name(hw->wiphy), __func__);
+}
+
+
+static int mac80211_hwsim_add_interface(struct ieee80211_hw *hw,
+					struct ieee80211_if_init_conf *conf)
+{
+	DECLARE_MAC_BUF(mac);
+	printk(KERN_DEBUG "%s:%s (type=%d mac_addr=%s)\n",
+	       wiphy_name(hw->wiphy), __func__, conf->type,
+	       print_mac(mac, conf->mac_addr));
+	return 0;
+}
+
+
+static void mac80211_hwsim_remove_interface(
+	struct ieee80211_hw *hw, struct ieee80211_if_init_conf *conf)
+{
+	DECLARE_MAC_BUF(mac);
+	printk(KERN_DEBUG "%s:%s (type=%d mac_addr=%s)\n",
+	       wiphy_name(hw->wiphy), __func__, conf->type,
+	       print_mac(mac, conf->mac_addr));
+}
+
+
+static void mac80211_hwsim_beacon_tx(void *arg, u8 *mac,
+				     struct ieee80211_vif *vif)
+{
+	struct ieee80211_hw *hw = arg;
+	struct mac80211_hwsim_data *data = hw->priv;
+	struct sk_buff *skb;
+	struct ieee80211_rx_status rx_status;
+	int i;
+	struct ieee80211_tx_info *info;
+
+	if (vif->type != IEEE80211_IF_TYPE_AP)
+		return;
+
+	skb = ieee80211_beacon_get(hw, vif);
+	if (skb == NULL)
+		return;
+	info = IEEE80211_SKB_CB(skb);
+
+	mac80211_hwsim_monitor_rx(hw, skb);
+
+	memset(&rx_status, 0, sizeof(rx_status));
+	/* TODO: set mactime */
+	rx_status.freq = data->channel->center_freq;
+	rx_status.band = data->channel->band;
+	rx_status.rate_idx = info->tx_rate_idx;
+	/* TODO: simulate signal strength (and optional packet drop) */
+
+	/* Copy skb to all enabled radios that are on the current frequency */
+	for (i = 0; i < hwsim_radio_count; i++) {
+		struct mac80211_hwsim_data *data2;
+		struct sk_buff *nskb;
+
+		if (hwsim_radios[i] == NULL || hwsim_radios[i] == hw)
+			continue;
+		data2 = hwsim_radios[i]->priv;
+		if (!data2->started || !data2->radio_enabled ||
+		    data->channel->center_freq != data2->channel->center_freq)
+			continue;
+
+		nskb = skb_copy(skb, GFP_ATOMIC);
+		if (nskb == NULL)
+			continue;
+
+		ieee80211_rx_irqsafe(hwsim_radios[i], nskb, &rx_status);
+	}
+
+	dev_kfree_skb(skb);
+}
+
+
+static void mac80211_hwsim_beacon(unsigned long arg)
+{
+	struct ieee80211_hw *hw = (struct ieee80211_hw *) arg;
+	struct mac80211_hwsim_data *data = hw->priv;
+
+	if (!data->started || !data->radio_enabled)
+		return;
+
+	ieee80211_iterate_active_interfaces(hw, mac80211_hwsim_beacon_tx, hw);
+
+	data->beacon_timer.expires = jiffies + data->beacon_int;
+	add_timer(&data->beacon_timer);
+}
+
+
+static int mac80211_hwsim_config(struct ieee80211_hw *hw,
+				 struct ieee80211_conf *conf)
+{
+	struct mac80211_hwsim_data *data = hw->priv;
+
+	printk(KERN_DEBUG "%s:%s (freq=%d radio_enabled=%d beacon_int=%d)\n",
+	       wiphy_name(hw->wiphy), __func__,
+	       conf->channel->center_freq, conf->radio_enabled,
+	       conf->beacon_int);
+
+	data->channel = conf->channel;
+	data->radio_enabled = conf->radio_enabled;
+	data->beacon_int = 1024 * conf->beacon_int / 1000 * HZ / 1000;
+	if (data->beacon_int < 1)
+		data->beacon_int = 1;
+
+	if (!data->started || !data->radio_enabled)
+		del_timer(&data->beacon_timer);
+	else
+		mod_timer(&data->beacon_timer, jiffies + data->beacon_int);
+
+	return 0;
+}
+
+
+static void mac80211_hwsim_configure_filter(struct ieee80211_hw *hw,
+					    unsigned int changed_flags,
+					    unsigned int *total_flags,
+					    int mc_count,
+					    struct dev_addr_list *mc_list)
+{
+	struct mac80211_hwsim_data *data = hw->priv;
+
+	printk(KERN_DEBUG "%s:%s\n", wiphy_name(hw->wiphy), __func__);
+
+	data->rx_filter = 0;
+	if (*total_flags & FIF_PROMISC_IN_BSS)
+		data->rx_filter |= FIF_PROMISC_IN_BSS;
+	if (*total_flags & FIF_ALLMULTI)
+		data->rx_filter |= FIF_ALLMULTI;
+
+	*total_flags = data->rx_filter;
+}
+
+
+
+static const struct ieee80211_ops mac80211_hwsim_ops =
+{
+	.tx = mac80211_hwsim_tx,
+	.start = mac80211_hwsim_start,
+	.stop = mac80211_hwsim_stop,
+	.add_interface = mac80211_hwsim_add_interface,
+	.remove_interface = mac80211_hwsim_remove_interface,
+	.config = mac80211_hwsim_config,
+	.configure_filter = mac80211_hwsim_configure_filter,
+};
+
+
+static void mac80211_hwsim_free(void)
+{
+	int i;
+
+	for (i = 0; i < hwsim_radio_count; i++) {
+		if (hwsim_radios[i]) {
+			struct mac80211_hwsim_data *data;
+			data = hwsim_radios[i]->priv;
+			ieee80211_unregister_hw(hwsim_radios[i]);
+			if (!IS_ERR(data->dev))
+				device_unregister(data->dev);
+			ieee80211_free_hw(hwsim_radios[i]);
+		}
+	}
+	kfree(hwsim_radios);
+	class_destroy(hwsim_class);
+}
+
+
+static struct device_driver mac80211_hwsim_driver = {
+	.name = "mac80211_hwsim"
+};
+
+
+static void hwsim_mon_setup(struct net_device *dev)
+{
+	dev->hard_start_xmit = hwsim_mon_xmit;
+	dev->destructor = free_netdev;
+	ether_setup(dev);
+	dev->tx_queue_len = 0;
+	dev->type = ARPHRD_IEEE80211_RADIOTAP;
+	memset(dev->dev_addr, 0, ETH_ALEN);
+	dev->dev_addr[0] = 0x12;
+}
+
+
+static int __init init_mac80211_hwsim(void)
+{
+	int i, err = 0;
+	u8 addr[ETH_ALEN];
+	struct mac80211_hwsim_data *data;
+	struct ieee80211_hw *hw;
+	DECLARE_MAC_BUF(mac);
+
+	if (radios < 1 || radios > 65535)
+		return -EINVAL;
+
+	hwsim_radio_count = radios;
+	hwsim_radios = kcalloc(hwsim_radio_count,
+			       sizeof(struct ieee80211_hw *), GFP_KERNEL);
+	if (hwsim_radios == NULL)
+		return -ENOMEM;
+
+	hwsim_class = class_create(THIS_MODULE, "mac80211_hwsim");
+	if (IS_ERR(hwsim_class)) {
+		kfree(hwsim_radios);
+		return PTR_ERR(hwsim_class);
+	}
+
+	memset(addr, 0, ETH_ALEN);
+	addr[0] = 0x02;
+
+	for (i = 0; i < hwsim_radio_count; i++) {
+		printk(KERN_DEBUG "mac80211_hwsim: Initializing radio %d\n",
+		       i);
+		hw = ieee80211_alloc_hw(sizeof(*data), &mac80211_hwsim_ops);
+		if (hw == NULL) {
+			printk(KERN_DEBUG "mac80211_hwsim: ieee80211_alloc_hw "
+			       "failed\n");
+			err = -ENOMEM;
+			goto failed;
+		}
+		hwsim_radios[i] = hw;
+
+		data = hw->priv;
+		data->dev = device_create(hwsim_class, NULL, 0, "hwsim%d", i);
+		if (IS_ERR(data->dev)) {
+			printk(KERN_DEBUG "mac80211_hwsim: device_create "
+			       "failed (%ld)\n", PTR_ERR(data->dev));
+			err = -ENOMEM;
+			goto failed;
+		}
+		data->dev->driver = &mac80211_hwsim_driver;
+		dev_set_drvdata(data->dev, hw);
+
+		SET_IEEE80211_DEV(hw, data->dev);
+		addr[3] = i >> 8;
+		addr[4] = i;
+		SET_IEEE80211_PERM_ADDR(hw, addr);
+
+		hw->channel_change_time = 1;
+		hw->queues = 1;
+
+		memcpy(data->channels, hwsim_channels, sizeof(hwsim_channels));
+		memcpy(data->rates, hwsim_rates, sizeof(hwsim_rates));
+		data->band.channels = data->channels;
+		data->band.n_channels = ARRAY_SIZE(hwsim_channels);
+		data->band.bitrates = data->rates;
+		data->band.n_bitrates = ARRAY_SIZE(hwsim_rates);
+		hw->wiphy->bands[IEEE80211_BAND_2GHZ] = &data->band;
+
+		err = ieee80211_register_hw(hw);
+		if (err < 0) {
+			printk(KERN_DEBUG "mac80211_hwsim: "
+			       "ieee80211_register_hw failed (%d)\n", err);
+			goto failed;
+		}
+
+		printk(KERN_DEBUG "%s: hwaddr %s registered\n",
+		       wiphy_name(hw->wiphy),
+		       print_mac(mac, hw->wiphy->perm_addr));
+
+		setup_timer(&data->beacon_timer, mac80211_hwsim_beacon,
+			    (unsigned long) hw);
+	}
+
+	hwsim_mon = alloc_netdev(0, "hwsim%d", hwsim_mon_setup);
+	if (hwsim_mon == NULL)
+		goto failed;
+
+	rtnl_lock();
+
+	err = dev_alloc_name(hwsim_mon, hwsim_mon->name);
+	if (err < 0) {
+		goto failed_mon;
+	}
+
+	err = register_netdevice(hwsim_mon);
+	if (err < 0)
+		goto failed_mon;
+
+	rtnl_unlock();
+
+	return 0;
+
+failed_mon:
+	rtnl_unlock();
+	free_netdev(hwsim_mon);
+
+failed:
+	mac80211_hwsim_free();
+	return err;
+}
+
+
+static void __exit exit_mac80211_hwsim(void)
+{
+	printk(KERN_DEBUG "mac80211_hwsim: unregister %d radios\n",
+	       hwsim_radio_count);
+
+	unregister_netdev(hwsim_mon);
+	mac80211_hwsim_free();
+}
+
+
+module_init(init_mac80211_hwsim);
+module_exit(exit_mac80211_hwsim);