path: root/net/mac80211/iface.c

/*
 * Interface handling (except master interface)
 *
 * Copyright 2002-2005, Instant802 Networks, Inc.
 * Copyright 2005-2006, Devicescape Software, Inc.
 * Copyright (c) 2006 Jiri Benc <jbenc@suse.cz>
 * Copyright 2008, Johannes Berg <johannes@sipsolutions.net>
 *
 * 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.
 */
#include <linux/kernel.h>
#include <linux/if_arp.h>
#include <linux/netdevice.h>
#include <linux/rtnetlink.h>
#include <net/mac80211.h>
#include "ieee80211_i.h"
#include "sta_info.h"
#include "debugfs_netdev.h"
#include "mesh.h"
#include "led.h"

static int ieee80211_change_mtu(struct net_device *dev, int new_mtu)
{
	int meshhdrlen;
	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);

	meshhdrlen = (sdata->vif.type == NL80211_IFTYPE_MESH_POINT) ? 5 : 0;

	/* FIX: what would be proper limits for MTU?
	 * This interface uses 802.3 frames. */
	if (new_mtu < 256 ||
	    new_mtu > IEEE80211_MAX_DATA_LEN - 24 - 6 - meshhdrlen) {
		return -EINVAL;
	}

#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
	printk(KERN_DEBUG "%s: setting MTU %d\n", dev->name, new_mtu);
#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
	dev->mtu = new_mtu;
	return 0;
}

static inline int identical_mac_addr_allowed(int type1, int type2)
{
	return type1 == NL80211_IFTYPE_MONITOR ||
		type2 == NL80211_IFTYPE_MONITOR ||
		(type1 == NL80211_IFTYPE_AP && type2 == NL80211_IFTYPE_WDS) ||
		(type1 == NL80211_IFTYPE_WDS &&
			(type2 == NL80211_IFTYPE_WDS ||
			 type2 == NL80211_IFTYPE_AP)) ||
		(type1 == NL80211_IFTYPE_AP && type2 == NL80211_IFTYPE_AP_VLAN) ||
		(type1 == NL80211_IFTYPE_AP_VLAN &&
			(type2 == NL80211_IFTYPE_AP ||
			 type2 == NL80211_IFTYPE_AP_VLAN));
}

static int ieee80211_open(struct net_device *dev)
{
	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
	struct ieee80211_sub_if_data *nsdata;
	struct ieee80211_local *local = sdata->local;
	struct sta_info *sta;
	struct ieee80211_if_init_conf conf;
	u32 changed = 0;
	int res;
	u32 hw_reconf_flags = 0;
	u8 null_addr[ETH_ALEN] = {0};

	/* fail early if user set an invalid address */
	if (compare_ether_addr(dev->dev_addr, null_addr) &&
	    !is_valid_ether_addr(dev->dev_addr))
		return -EADDRNOTAVAIL;

	/* we hold the RTNL here so can safely walk the list */
	list_for_each_entry(nsdata, &local->interfaces, list) {
		struct net_device *ndev = nsdata->dev;

		if (ndev != dev && netif_running(ndev)) {
			/*
			 * Allow only a single IBSS interface to be up at any
			 * time. This is restricted because beacon distribution
			 * cannot work properly if both are in the same IBSS.
			 *
			 * To remove this restriction we'd have to disallow them
			 * from setting the same SSID on different IBSS interfaces
			 * belonging to the same hardware. Then, however, we're
			 * faced with having to adopt two different TSF timers...
			 */
			if (sdata->vif.type == NL80211_IFTYPE_ADHOC &&
			    nsdata->vif.type == NL80211_IFTYPE_ADHOC)
				return -EBUSY;

			/*
			 * The remaining checks are only performed for interfaces
			 * with the same MAC address.
			 */
			if (compare_ether_addr(dev->dev_addr, ndev->dev_addr))
				continue;

			/*
			 * check whether it may have the same address
			 */
			if (!identical_mac_addr_allowed(sdata->vif.type,
							nsdata->vif.type))
				return -ENOTUNIQ;

			/*
			 * can only add VLANs to enabled APs
			 */
			if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN &&
			    nsdata->vif.type == NL80211_IFTYPE_AP)
				sdata->bss = &nsdata->u.ap;
		}
	}

	switch (sdata->vif.type) {
	case NL80211_IFTYPE_WDS:
		if (!is_valid_ether_addr(sdata->u.wds.remote_addr))
			return -ENOLINK;
		break;
	case NL80211_IFTYPE_AP_VLAN:
		if (!sdata->bss)
			return -ENOLINK;
		list_add(&sdata->u.vlan.list, &sdata->bss->vlans);
		break;
	case NL80211_IFTYPE_AP:
		sdata->bss = &sdata->u.ap;
		break;
	case NL80211_IFTYPE_MESH_POINT:
		if (!ieee80211_vif_is_mesh(&sdata->vif))
			break;
		/* mesh ifaces must set allmulti to forward mcast traffic */
		atomic_inc(&local->iff_allmultis);
		break;
	case NL80211_IFTYPE_STATION:
	case NL80211_IFTYPE_MONITOR:
	case NL80211_IFTYPE_ADHOC:
		/* no special treatment */
		break;
	case NL80211_IFTYPE_UNSPECIFIED:
	case __NL80211_IFTYPE_AFTER_LAST:
		/* cannot happen */
		WARN_ON(1);
		break;
	}

	if (local->open_count == 0) {
		res = 0;
		if (local->ops->start)
			res = local->ops->start(local_to_hw(local));
		if (res)
			goto err_del_bss;
		/* we're brought up, everything changes */
		hw_reconf_flags = ~0;
		ieee80211_led_radio(local, local->hw.conf.radio_enabled);
	}

	/*
	 * Check all interfaces and copy the hopefully now-present
	 * MAC address to those that have the special null one.
	 */
	list_for_each_entry(nsdata, &local->interfaces, list) {
		struct net_device *ndev = nsdata->dev;

		/*
		 * No need to check netif_running since we do not allow
		 * it to start up with this invalid address.
		 */
		if (compare_ether_addr(null_addr, ndev->dev_addr) == 0)
			memcpy(ndev->dev_addr,
			       local->hw.wiphy->perm_addr,
			       ETH_ALEN);
	}

	if (compare_ether_addr(null_addr, local->mdev->dev_addr) == 0)
		memcpy(local->mdev->dev_addr, local->hw.wiphy->perm_addr,
		       ETH_ALEN);

	/*
	 * Validate the MAC address for this device.
	 */
	if (!is_valid_ether_addr(dev->dev_addr)) {
		if (!local->open_count && local->ops->stop)
			local->ops->stop(local_to_hw(local));
		return -EADDRNOTAVAIL;
	}

	switch (sdata->vif.type) {
	case NL80211_IFTYPE_AP_VLAN:
		/* no need to tell driver */
		break;
	case NL80211_IFTYPE_MONITOR:
		if (sdata->u.mntr_flags & MONITOR_FLAG_COOK_FRAMES) {
			local->cooked_mntrs++;
			break;
		}

		/* must be before the call to ieee80211_configure_filter */
		local->monitors++;
		if (local->monitors == 1) {
			local->hw.conf.flags |= IEEE80211_CONF_RADIOTAP;
			hw_reconf_flags |= IEEE80211_CONF_CHANGE_RADIOTAP;
		}

		if (sdata->u.mntr_flags & MONITOR_FLAG_FCSFAIL)
			local->fif_fcsfail++;
		if (sdata->u.mntr_flags & MONITOR_FLAG_PLCPFAIL)
			local->fif_plcpfail++;
		if (sdata->u.mntr_flags & MONITOR_FLAG_CONTROL)
			local->fif_control++;
		if (sdata->u.mntr_flags & MONITOR_FLAG_OTHER_BSS)
			local->fif_other_bss++;

		netif_addr_lock_bh(local->mdev);
		ieee80211_configure_filter(local);
		netif_addr_unlock_bh(local->mdev);
		break;
	case NL80211_IFTYPE_STATION:
	case NL80211_IFTYPE_ADHOC:
		sdata->u.sta.flags &= ~IEEE80211_STA_PREV_BSSID_SET;
		/* fall through */
	default:
		conf.vif = &sdata->vif;
		conf.type = sdata->vif.type;
		conf.mac_addr = dev->dev_addr;
		res = local->ops->add_interface(local_to_hw(local), &conf);
		if (res)
			goto err_stop;

		if (ieee80211_vif_is_mesh(&sdata->vif)) {
			local->fif_other_bss++;
			netif_addr_lock_bh(local->mdev);
			ieee80211_configure_filter(local);
			netif_addr_unlock_bh(local->mdev);

			ieee80211_start_mesh(sdata);
		}
		changed |= ieee80211_reset_erp_info(sdata);
		ieee80211_bss_info_change_notify(sdata, changed);
		ieee80211_enable_keys(sdata);

		if (sdata->vif.type == NL80211_IFTYPE_STATION &&
		    !(sdata->flags & IEEE80211_SDATA_USERSPACE_MLME))
			netif_carrier_off(dev);
		else
			netif_carrier_on(dev);
	}

	if (sdata->vif.type == NL80211_IFTYPE_WDS) {
		/* Create STA entry for the WDS peer */
		sta = sta_info_alloc(sdata, sdata->u.wds.remote_addr,
				     GFP_KERNEL);
		if (!sta) {
			res = -ENOMEM;
			goto err_del_interface;
		}

		/* no locking required since STA is not live yet */
		sta->flags |= WLAN_STA_AUTHORIZED;

		res = sta_info_insert(sta);
		if (res) {
			/* STA has been freed */
			goto err_del_interface;
		}
	}

	if (local->open_count == 0) {
		res = dev_open(local->mdev);
		WARN_ON(res);
		if (res)
			goto err_del_interface;
		tasklet_enable(&local->tx_pending_tasklet);
		tasklet_enable(&local->tasklet);
	}

	/*
	 * set_multicast_list will be invoked by the networking core
	 * which will check whether any increments here were done in
	 * error and sync them down to the hardware as filter flags.
	 */
	if (sdata->flags & IEEE80211_SDATA_ALLMULTI)
		atomic_inc(&local->iff_allmultis);

	if (sdata->flags & IEEE80211_SDATA_PROMISC)
		atomic_inc(&local->iff_promiscs);

	local->open_count++;
	if (hw_reconf_flags) {
		ieee80211_hw_config(local, hw_reconf_flags);
		/*
		 * set default queue parameters so drivers don't
		 * need to initialise the hardware if the hardware
		 * doesn't start up with sane defaults
		 */
		ieee80211_set_wmm_default(sdata);
	}

	/*
	 * ieee80211_sta_work is disabled while network interface
	 * is down. Therefore, some configuration changes may not
	 * yet be effective. Trigger execution of ieee80211_sta_work
	 * to fix this.
	 */
	if (sdata->vif.type == NL80211_IFTYPE_STATION ||
	    sdata->vif.type == NL80211_IFTYPE_ADHOC) {
		struct ieee80211_if_sta *ifsta = &sdata->u.sta;
		queue_work(local->hw.workqueue, &ifsta->work);
	}

	netif_tx_start_all_queues(dev);

	return 0;
 err_del_interface:
	local->ops->remove_interface(local_to_hw(local), &conf);
 err_stop:
	if (!local->open_count && local->ops->stop)
		local->ops->stop(local_to_hw(local));
 err_del_bss:
	sdata->bss = NULL;
	if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN)
		list_del(&sdata->u.vlan.list);
	return res;
}

static int ieee80211_stop(struct net_device *dev)
{
	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
	struct ieee80211_local *local = sdata->local;
	struct ieee80211_if_init_conf conf;
	struct sta_info *sta;
	u32 hw_reconf_flags = 0;

	/*
	 * Stop TX on this interface first.
	 */
	netif_tx_stop_all_queues(dev);

	/*
	 * Now delete all active aggregation sessions.
	 */
	rcu_read_lock();

	list_for_each_entry_rcu(sta, &local->sta_list, list) {
		if (sta->sdata == sdata)
			ieee80211_sta_tear_down_BA_sessions(sdata,
							    sta->sta.addr);
	}

	rcu_read_unlock();

	/*
	 * Remove all stations associated with this interface.
	 *
	 * This must be done before calling ops->remove_interface()
	 * because otherwise we can later invoke ops->sta_notify()
	 * whenever the STAs are removed, and that invalidates driver
	 * assumptions about always getting a vif pointer that is valid
	 * (because if we remove a STA after ops->remove_interface()
	 * the driver will have removed the vif info already!)
	 *
	 * We could relax this and only unlink the stations from the
	 * hash table and list but keep them on a per-sdata list that
	 * will be inserted back again when the interface is brought
	 * up again, but I don't currently see a use case for that,
	 * except with WDS which gets a STA entry created when it is
	 * brought up.
	 */
	sta_info_flush(local, sdata);

	/*
	 * Don't count this interface for promisc/allmulti while it
	 * is down. dev_mc_unsync() will invoke set_multicast_list
	 * on the master interface which will sync these down to the
	 * hardware as filter flags.
	 */
	if (sdata->flags & IEEE80211_SDATA_ALLMULTI)
		atomic_dec(&local->iff_allmultis);

	if (sdata->flags & IEEE80211_SDATA_PROMISC)
		atomic_dec(&local->iff_promiscs);

	dev_mc_unsync(local->mdev, dev);

	/* APs need special treatment */
	if (sdata->vif.type == NL80211_IFTYPE_AP) {
		struct ieee80211_sub_if_data *vlan, *tmp;
		struct beacon_data *old_beacon = sdata->u.ap.beacon;

		/* remove beacon */
		rcu_assign_pointer(sdata->u.ap.beacon, NULL);
		synchronize_rcu();
		kfree(old_beacon);

		/* down all dependent devices, that is VLANs */
		list_for_each_entry_safe(vlan, tmp, &sdata->u.ap.vlans,
					 u.vlan.list)
			dev_close(vlan->dev);
		WARN_ON(!list_empty(&sdata->u.ap.vlans));
	}

	local->open_count--;

	switch (sdata->vif.type) {
	case NL80211_IFTYPE_AP_VLAN:
		list_del(&sdata->u.vlan.list);
		/* no need to tell driver */
		break;
	case NL80211_IFTYPE_MONITOR:
		if (sdata->u.mntr_flags & MONITOR_FLAG_COOK_FRAMES) {
			local->cooked_mntrs--;
			break;
		}

		local->monitors--;
		if (local->monitors == 0) {
			local->hw.conf.flags &= ~IEEE80211_CONF_RADIOTAP;
			hw_reconf_flags |= IEEE80211_CONF_CHANGE_RADIOTAP;
		}

		if (sdata->u.mntr_flags & MONITOR_FLAG_FCSFAIL)
			local->fif_fcsfail--;
		if (sdata->u.mntr_flags & MONITOR_FLAG_PLCPFAIL)
			local->fif_plcpfail--;
		if (sdata->u.mntr_flags & MONITOR_FLAG_CONTROL)
			local->fif_control--;
		if (sdata->u.mntr_flags & MONITOR_FLAG_OTHER_BSS)
			local->fif_other_bss--;

		netif_addr_lock_bh(local->mdev);
		ieee80211_configure_filter(local);
		netif_addr_unlock_bh(local->mdev);
		break;
	case NL80211_IFTYPE_STATION:
	case NL80211_IFTYPE_ADHOC:
		sdata->u.sta.state = IEEE80211_STA_MLME_DISABLED;
		memset(sdata->u.sta.bssid, 0, ETH_ALEN);
		del_timer_sync(&sdata->u.sta.timer);
		/*
		 * If the timer fired while we waited for it, it will have
		 * requeued the work. Now the work will be running again
		 * but will not rearm the timer again because it checks
		 * whether the interface is running, which, at this point,
		 * it no longer is.
		 */
		cancel_work_sync(&sdata->u.sta.work);
		/*
		 * When we get here, the interface is marked down.
		 * Call synchronize_rcu() to wait for the RX path
		 * should it be using the interface and enqueuing
		 * frames at this very time on another CPU.
		 */
		synchronize_rcu();
		skb_queue_purge(&sdata->u.sta.skb_queue);

		sdata->u.sta.flags &= ~IEEE80211_STA_PRIVACY_INVOKED;
		kfree(sdata->u.sta.extra_ie);
		sdata->u.sta.extra_ie = NULL;
		sdata->u.sta.extra_ie_len = 0;
		/* fall through */
	case NL80211_IFTYPE_MESH_POINT:
		if (ieee80211_vif_is_mesh(&sdata->vif)) {
			/* other_bss and allmulti are always set on mesh
			 * ifaces */
			local->fif_other_bss--;
			atomic_dec(&local->iff_allmultis);

			netif_addr_lock_bh(local->mdev);
			ieee80211_configure_filter(local);
			netif_addr_unlock_bh(local->mdev);

			ieee80211_stop_mesh(sdata);
		}
		/* fall through */
	default:
		if (local->scan_sdata == sdata) {
			if (!local->ops->hw_scan)
				cancel_delayed_work_sync(&local->scan_work);
			/*
			 * The software scan can no longer run now, so we can
			 * clear out the scan_sdata reference. However, the
			 * hardware scan may still be running. The complete
			 * function must be prepared to handle a NULL value.
			 */
			local->scan_sdata = NULL;
			/*
			 * The memory barrier guarantees that another CPU
			 * that is hardware-scanning will now see the fact
			 * that this interface is gone.
			 */
			smp_mb();
			/*
			 * If software scanning, complete the scan but since
			 * the scan_sdata is NULL already don't send out a
			 * scan event to userspace -- the scan is incomplete.
			 */
			if (local->sw_scanning)
				ieee80211_scan_completed(&local->hw);
		}

		conf.vif = &sdata->vif;
		conf.type = sdata->vif.type;
		conf.mac_addr = dev->dev_addr;
		/* disable all keys for as long as this netdev is down */
		ieee80211_disable_keys(sdata);
		local->ops->remove_interface(local_to_hw(local), &conf);
	}

	sdata->bss = NULL;

	if (local->open_count == 0) {
		if (netif_running(local->mdev))
			dev_close(local->mdev);

		if (local->ops->stop)
			local->ops->stop(local_to_hw(local));

		ieee80211_led_radio(local, 0);

		flush_workqueue(local->hw.workqueue);

		tasklet_disable(&local->tx_pending_tasklet);
		tasklet_disable(&local->tasklet);

		/* no reconfiguring after stop! */
		hw_reconf_flags = 0;
	}

	/* do after stop to avoid reconfiguring when we stop anyway */
	if (hw_reconf_flags)
		ieee80211_hw_config(local, hw_reconf_flags);

	return 0;
}

static void ieee80211_set_multicast_list(struct net_device *dev)
{
	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
	struct ieee80211_local *local = sdata->local;
	int allmulti, promisc, sdata_allmulti, sdata_promisc;

	allmulti = !!(dev->flags & IFF_ALLMULTI);
	promisc = !!(dev->flags & IFF_PROMISC);
	sdata_allmulti = !!(sdata->flags & IEEE80211_SDATA_ALLMULTI);
	sdata_promisc = !!(sdata->flags & IEEE80211_SDATA_PROMISC);

	if (allmulti != sdata_allmulti) {
		if (dev->flags & IFF_ALLMULTI)
			atomic_inc(&local->iff_allmultis);
		else
			atomic_dec(&local->iff_allmultis);
		sdata->flags ^= IEEE80211_SDATA_ALLMULTI;
	}

	if (promisc != sdata_promisc) {
		if (dev->flags & IFF_PROMISC)
			atomic_inc(&local->iff_promiscs);
		else
			atomic_dec(&local->iff_promiscs);
		sdata->flags ^= IEEE80211_SDATA_PROMISC;
	}

	dev_mc_sync(local->mdev, dev);
}

static void ieee80211_if_setup(struct net_device *dev)
{
	ether_setup(dev);
	dev->hard_start_xmit = ieee80211_subif_start_xmit;
	dev->wireless_handlers = &ieee80211_iw_handler_def;
	dev->set_multicast_list = ieee80211_set_multicast_list;
	dev->change_mtu = ieee80211_change_mtu;
	dev->open = ieee80211_open;
	dev->stop = ieee80211_stop;
	dev->destructor = free_netdev;
	/* we will validate the address ourselves in ->open */
	dev->validate_addr = NULL;
}
/*
 * Called when the netdev is removed or, by the code below, before
 * the interface type changes.
 */
static void ieee80211_teardown_sdata(struct net_device *dev)
{
	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
	struct ieee80211_local *local = sdata->local;
	struct beacon_data *beacon;
	struct sk_buff *skb;
	int flushed;
	int i;

	/* free extra data */
	ieee80211_free_keys(sdata);

	ieee80211_debugfs_remove_netdev(sdata);

	for (i = 0; i < IEEE80211_FRAGMENT_MAX; i++)
		__skb_queue_purge(&sdata->fragments[i].skb_list);
	sdata->fragment_next = 0;

	switch (sdata->vif.type) {
	case NL80211_IFTYPE_AP:
		beacon = sdata->u.ap.beacon;
		rcu_assign_pointer(sdata->u.ap.beacon, NULL);
		synchronize_rcu();
		kfree(beacon);

		while ((skb = skb_dequeue(&sdata->u.ap.ps_bc_buf))) {
			local->total_ps_buffered--;
			dev_kfree_skb(skb);
		}

		break;
	case NL80211_IFTYPE_MESH_POINT:
		if (ieee80211_vif_is_mesh(&sdata->vif))
			mesh_rmc_free(sdata);
		break;
	case NL80211_IFTYPE_STATION:
	case NL80211_IFTYPE_ADHOC:
		kfree(sdata->u.sta.extra_ie);
		kfree(sdata->u.sta.assocreq_ies);
		kfree(sdata->u.sta.assocresp_ies);
		kfree_skb(sdata->u.sta.probe_resp);
		break;
	case NL80211_IFTYPE_WDS:
	case NL80211_IFTYPE_AP_VLAN:
	case NL80211_IFTYPE_MONITOR:
		break;
	case NL80211_IFTYPE_UNSPECIFIED:
	case __NL80211_IFTYPE_AFTER_LAST:
		BUG();
		break;
	}

	flushed = sta_info_flush(local, sdata);
	WARN_ON(flushed);
}

/*
 * Helper function to initialise an interface to a specific type.
 */
static void ieee80211_setup_sdata(struct ieee80211_sub_if_data *sdata,
				  enum nl80211_iftype type)
{
	/* clear type-dependent union */
	memset(&sdata->u, 0, sizeof(sdata->u));

	/* and set some type-dependent values */
	sdata->vif.type = type;
	sdata->dev->hard_start_xmit = ieee80211_subif_start_xmit;
	sdata->wdev.iftype = type;

	/* only monitor differs */
	sdata->dev->type = ARPHRD_ETHER;

	switch (type) {
	case NL80211_IFTYPE_AP:
		skb_queue_head_init(&sdata->u.ap.ps_bc_buf);
		INIT_LIST_HEAD(&sdata->u.ap.vlans);
		break;
	case NL80211_IFTYPE_STATION:
	case NL80211_IFTYPE_ADHOC:
		ieee80211_sta_setup_sdata(sdata);
		break;
	case NL80211_IFTYPE_MESH_POINT:
		if (ieee80211_vif_is_mesh(&sdata->vif))
			ieee80211_mesh_init_sdata(sdata);
		break;
	case NL80211_IFTYPE_MONITOR:
		sdata->dev->type = ARPHRD_IEEE80211_RADIOTAP;
		sdata->dev->hard_start_xmit = ieee80211_monitor_start_xmit;
		sdata->u.mntr_flags = MONITOR_FLAG_CONTROL |
				      MONITOR_FLAG_OTHER_BSS;
		break;
	case NL80211_IFTYPE_WDS:
	case NL80211_IFTYPE_AP_VLAN:
		break;
	case NL80211_IFTYPE_UNSPECIFIED:
	case __NL80211_IFTYPE_AFTER_LAST:
		BUG();
		break;
	}

	ieee80211_debugfs_add_netdev(sdata);
}

int ieee80211_if_change_type(struct ieee80211_sub_if_data *sdata,
			     enum nl80211_iftype type)
{
	ASSERT_RTNL();

	if (type == sdata->vif.type)
		return 0;

	/*
	 * We could, here, on changes between IBSS/STA/MESH modes,
	 * invoke an MLME function instead that disassociates etc.
	 * and goes into the requested mode.
	 */

	if (netif_running(sdata->dev))
		return -EBUSY;

	/* Purge and reset type-dependent state. */
	ieee80211_teardown_sdata(sdata->dev);
	ieee80211_setup_sdata(sdata, type);

	/* reset some values that shouldn't be kept across type changes */
	sdata->vif.bss_conf.basic_rates =
		ieee80211_mandatory_rates(sdata->local,
			sdata->local->hw.conf.channel->band);
	sdata->drop_unencrypted = 0;

	return 0;
}

int ieee80211_if_add(struct ieee80211_local *local, const char *name,
		     struct net_device **new_dev, enum nl80211_iftype type,
		     struct vif_params *params)
{
	struct net_device *ndev;
	struct ieee80211_sub_if_data *sdata = NULL;
	int ret, i;

	ASSERT_RTNL();

	ndev = alloc_netdev(sizeof(*sdata) + local->hw.vif_data_size,
			    name, ieee80211_if_setup);
	if (!ndev)
		return -ENOMEM;

	ndev->needed_headroom = local->tx_headroom +
				4*6 /* four MAC addresses */
				+ 2 + 2 + 2 + 2 /* ctl, dur, seq, qos */
				+ 6 /* mesh */
				+ 8 /* rfc1042/bridge tunnel */
				- ETH_HLEN /* ethernet hard_header_len */
				+ IEEE80211_ENCRYPT_HEADROOM;
	ndev->needed_tailroom = IEEE80211_ENCRYPT_TAILROOM;

	ret = dev_alloc_name(ndev, ndev->name);
	if (ret < 0)
		goto fail;

	memcpy(ndev->dev_addr, local->hw.wiphy->perm_addr, ETH_ALEN);
	SET_NETDEV_DEV(ndev, wiphy_dev(local->hw.wiphy));

	/* don't use IEEE80211_DEV_TO_SUB_IF because it checks too much */
	sdata = netdev_priv(ndev);
	ndev->ieee80211_ptr = &sdata->wdev;

	/* initialise type-independent data */
	sdata->wdev.wiphy = local->hw.wiphy;
	sdata->local = local;
	sdata->dev = ndev;

	for (i = 0; i < IEEE80211_FRAGMENT_MAX; i++)
		skb_queue_head_init(&sdata->fragments[i].skb_list);

	INIT_LIST_HEAD(&sdata->key_list);

	sdata->force_unicast_rateidx = -1;
	sdata->max_ratectrl_rateidx = -1;

	/* setup type-dependent data */
	ieee80211_setup_sdata(sdata, type);

	ret = register_netdevice(ndev);
	if (ret)
		goto fail;

	ndev->uninit = ieee80211_teardown_sdata;

	if (ieee80211_vif_is_mesh(&sdata->vif) &&
	    params && params->mesh_id_len)
		ieee80211_sdata_set_mesh_id(sdata,
					    params->mesh_id_len,
					    params->mesh_id);

	list_add_tail_rcu(&sdata->list, &local->interfaces);

	if (new_dev)
		*new_dev = ndev;

	return 0;

 fail:
	free_netdev(ndev);
	return ret;
}

void ieee80211_if_remove(struct ieee80211_sub_if_data *sdata)
{
	ASSERT_RTNL();

	list_del_rcu(&sdata->list);
	synchronize_rcu();
	unregister_netdevice(sdata->dev);
}

/*
 * Remove all interfaces, may only be called at hardware unregistration
 * time because it doesn't do RCU-safe list removals.
 */
void ieee80211_remove_interfaces(struct ieee80211_local *local)
{
	struct ieee80211_sub_if_data *sdata, *tmp;

	ASSERT_RTNL();

	list_for_each_entry_safe(sdata, tmp, &local->interfaces, list) {
		list_del(&sdata->list);
		unregister_netdevice(sdata->dev);
	}
}