net/mac80211/scan.c - kernel/msm-4.9 - Gitiles

 /*
  * Scanning implementation
  *
  * Copyright 2003, Jouni Malinen <jkmaline@cc.hut.fi>
  * Copyright 2004, Instant802 Networks, Inc.
  * Copyright 2005, Devicescape Software, Inc.
  * Copyright 2006-2007	Jiri Benc <jbenc@suse.cz>
  * Copyright 2007, Michael Wu <flamingice@sourmilk.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/wireless.h>
 #include <linux/if_arp.h>
 #include <linux/rtnetlink.h>
 #include <net/mac80211.h>

 #include "ieee80211_i.h"
 #include "driver-ops.h"
 #include "mesh.h"

 #define IEEE80211_PROBE_DELAY (HZ / 33)
 #define IEEE80211_CHANNEL_TIME (HZ / 33)
 #define IEEE80211_PASSIVE_CHANNEL_TIME (HZ / 8)

 struct ieee80211_bss *
 ieee80211_rx_bss_get(struct ieee80211_local *local, u8 *bssid, int freq,
 		     u8 *ssid, u8 ssid_len)
 {
 	return (void *)cfg80211_get_bss(local->hw.wiphy,
 					ieee80211_get_channel(local->hw.wiphy,
 							      freq),
 					bssid, ssid, ssid_len,
 					0, 0);
 }

 static void ieee80211_rx_bss_free(struct cfg80211_bss *cbss)
 {
 	struct ieee80211_bss *bss = (void *)cbss;

 	kfree(bss_mesh_id(bss));
 	kfree(bss_mesh_cfg(bss));
 }

 void ieee80211_rx_bss_put(struct ieee80211_local *local,
 			  struct ieee80211_bss *bss)
 {
 	cfg80211_put_bss((struct cfg80211_bss *)bss);
 }

 struct ieee80211_bss *
 ieee80211_bss_info_update(struct ieee80211_local *local,
 			  struct ieee80211_rx_status *rx_status,
 			  struct ieee80211_mgmt *mgmt,
 			  size_t len,
 			  struct ieee802_11_elems *elems,
 			  struct ieee80211_channel *channel,
 			  bool beacon)
 {
 	struct ieee80211_bss *bss;
 	int clen;
 	s32 signal = 0;

 	if (local->hw.flags & IEEE80211_HW_SIGNAL_DBM)
 		signal = rx_status->signal * 100;
 	else if (local->hw.flags & IEEE80211_HW_SIGNAL_UNSPEC)
 		signal = (rx_status->signal * 100) / local->hw.max_signal;

 	bss = (void *)cfg80211_inform_bss_frame(local->hw.wiphy, channel,
 						mgmt, len, signal, GFP_ATOMIC);

 	if (!bss)
 		return NULL;

 	bss->cbss.free_priv = ieee80211_rx_bss_free;

 	/* save the ERP value so that it is available at association time */
 	if (elems->erp_info && elems->erp_info_len >= 1) {
 		bss->erp_value = elems->erp_info[0];
 		bss->has_erp_value = 1;
 	}

 	if (elems->tim) {
 		struct ieee80211_tim_ie *tim_ie =
 			(struct ieee80211_tim_ie *)elems->tim;
 		bss->dtim_period = tim_ie->dtim_period;
 	}

 	/* set default value for buggy AP/no TIM element */
 	if (bss->dtim_period == 0)
 		bss->dtim_period = 1;

 	bss->supp_rates_len = 0;
 	if (elems->supp_rates) {
 		clen = IEEE80211_MAX_SUPP_RATES - bss->supp_rates_len;
 		if (clen > elems->supp_rates_len)
 			clen = elems->supp_rates_len;
 		memcpy(&bss->supp_rates[bss->supp_rates_len], elems->supp_rates,
 		       clen);
 		bss->supp_rates_len += clen;
 	}
 	if (elems->ext_supp_rates) {
 		clen = IEEE80211_MAX_SUPP_RATES - bss->supp_rates_len;
 		if (clen > elems->ext_supp_rates_len)
 			clen = elems->ext_supp_rates_len;
 		memcpy(&bss->supp_rates[bss->supp_rates_len],
 		       elems->ext_supp_rates, clen);
 		bss->supp_rates_len += clen;
 	}

 	bss->wmm_used = elems->wmm_param || elems->wmm_info;

 	if (!beacon)
 		bss->last_probe_resp = jiffies;

 	return bss;
 }

 ieee80211_rx_result
 ieee80211_scan_rx(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb)
 {
 	struct ieee80211_rx_status *rx_status = IEEE80211_SKB_RXCB(skb);
 	struct ieee80211_mgmt *mgmt;
 	struct ieee80211_bss *bss;
 	u8 *elements;
 	struct ieee80211_channel *channel;
 	size_t baselen;
 	int freq;
 	__le16 fc;
 	bool presp, beacon = false;
 	struct ieee802_11_elems elems;

 	if (skb->len < 2)
 		return RX_DROP_UNUSABLE;

 	mgmt = (struct ieee80211_mgmt *) skb->data;
 	fc = mgmt->frame_control;

 	if (ieee80211_is_ctl(fc))
 		return RX_CONTINUE;

 	if (skb->len < 24)
 		return RX_DROP_MONITOR;

 	presp = ieee80211_is_probe_resp(fc);
 	if (presp) {
 		/* ignore ProbeResp to foreign address */
 		if (memcmp(mgmt->da, sdata->vif.addr, ETH_ALEN))
 			return RX_DROP_MONITOR;

 		presp = true;
 		elements = mgmt->u.probe_resp.variable;
 		baselen = offsetof(struct ieee80211_mgmt, u.probe_resp.variable);
 	} else {
 		beacon = ieee80211_is_beacon(fc);
 		baselen = offsetof(struct ieee80211_mgmt, u.beacon.variable);
 		elements = mgmt->u.beacon.variable;
 	}

 	if (!presp && !beacon)
 		return RX_CONTINUE;

 	if (baselen > skb->len)
 		return RX_DROP_MONITOR;

 	ieee802_11_parse_elems(elements, skb->len - baselen, &elems);

 	if (elems.ds_params && elems.ds_params_len == 1)
 		freq = ieee80211_channel_to_frequency(elems.ds_params[0]);
 	else
 		freq = rx_status->freq;

 	channel = ieee80211_get_channel(sdata->local->hw.wiphy, freq);

 	if (!channel || channel->flags & IEEE80211_CHAN_DISABLED)
 		return RX_DROP_MONITOR;

 	bss = ieee80211_bss_info_update(sdata->local, rx_status,
 					mgmt, skb->len, &elems,
 					channel, beacon);
 	if (bss)
 		ieee80211_rx_bss_put(sdata->local, bss);

 	dev_kfree_skb(skb);
 	return RX_QUEUED;
 }

 /* return false if no more work */
 static bool ieee80211_prep_hw_scan(struct ieee80211_local *local)
 {
 	struct cfg80211_scan_request *req = local->scan_req;
 	enum ieee80211_band band;
 	int i, ielen, n_chans;

 	do {
 		if (local->hw_scan_band == IEEE80211_NUM_BANDS)
 			return false;

 		band = local->hw_scan_band;
 		n_chans = 0;
 		for (i = 0; i < req->n_channels; i++) {
 			if (req->channels[i]->band == band) {
 				local->hw_scan_req->channels[n_chans] =
 							req->channels[i];
 				n_chans++;
 			}
 		}

 		local->hw_scan_band++;
 	} while (!n_chans);

 	local->hw_scan_req->n_channels = n_chans;

 	ielen = ieee80211_build_preq_ies(local, (u8 *)local->hw_scan_req->ie,
 					 req->ie, req->ie_len, band);
 	local->hw_scan_req->ie_len = ielen;

 	return true;
 }

 /*
  * inform AP that we will go to sleep so that it will buffer the frames
  * while we scan
  */
 static void ieee80211_scan_ps_enable(struct ieee80211_sub_if_data *sdata)
 {
 	struct ieee80211_local *local = sdata->local;

 	local->scan_ps_enabled = false;

 	/* FIXME: what to do when local->pspolling is true? */

 	del_timer_sync(&local->dynamic_ps_timer);
 	cancel_work_sync(&local->dynamic_ps_enable_work);

 	if (local->hw.conf.flags & IEEE80211_CONF_PS) {
 		local->scan_ps_enabled = true;
 		local->hw.conf.flags &= ~IEEE80211_CONF_PS;
 		ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
 	}

 	if (!(local->scan_ps_enabled) ||
 	    !(local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK))
 		/*
 		 * If power save was enabled, no need to send a nullfunc
 		 * frame because AP knows that we are sleeping. But if the
 		 * hardware is creating the nullfunc frame for power save
 		 * status (ie. IEEE80211_HW_PS_NULLFUNC_STACK is not
 		 * enabled) and power save was enabled, the firmware just
 		 * sent a null frame with power save disabled. So we need
 		 * to send a new nullfunc frame to inform the AP that we
 		 * are again sleeping.
 		 */
 		ieee80211_send_nullfunc(local, sdata, 1);
 }

 /* inform AP that we are awake again, unless power save is enabled */
 static void ieee80211_scan_ps_disable(struct ieee80211_sub_if_data *sdata)
 {
 	struct ieee80211_local *local = sdata->local;

 	if (!local->ps_sdata)
 		ieee80211_send_nullfunc(local, sdata, 0);
 	else if (local->scan_ps_enabled) {
 		/*
 		 * In !IEEE80211_HW_PS_NULLFUNC_STACK case the hardware
 		 * will send a nullfunc frame with the powersave bit set
 		 * even though the AP already knows that we are sleeping.
 		 * This could be avoided by sending a null frame with power
 		 * save bit disabled before enabling the power save, but
 		 * this doesn't gain anything.
 		 *
 		 * When IEEE80211_HW_PS_NULLFUNC_STACK is enabled, no need
 		 * to send a nullfunc frame because AP already knows that
 		 * we are sleeping, let's just enable power save mode in
 		 * hardware.
 		 */
 		local->hw.conf.flags |= IEEE80211_CONF_PS;
 		ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
 	} else if (local->hw.conf.dynamic_ps_timeout > 0) {
 		/*
 		 * If IEEE80211_CONF_PS was not set and the dynamic_ps_timer
 		 * had been running before leaving the operating channel,
 		 * restart the timer now and send a nullfunc frame to inform
 		 * the AP that we are awake.
 		 */
 		ieee80211_send_nullfunc(local, sdata, 0);
 		mod_timer(&local->dynamic_ps_timer, jiffies +
 			  msecs_to_jiffies(local->hw.conf.dynamic_ps_timeout));
 	}
 }

 void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
 {
 	struct ieee80211_local *local = hw_to_local(hw);
 	struct ieee80211_sub_if_data *sdata;
 	bool was_hw_scan;

 	mutex_lock(&local->scan_mtx);

 	/*
 	 * It's ok to abort a not-yet-running scan (that
 	 * we have one at all will be verified by checking
 	 * local->scan_req next), but not to complete it
 	 * successfully.
 	 */
 	if (WARN_ON(!local->scanning && !aborted))
 		aborted = true;

 	if (WARN_ON(!local->scan_req)) {
 		mutex_unlock(&local->scan_mtx);
 		return;
 	}

 	was_hw_scan = test_bit(SCAN_HW_SCANNING, &local->scanning);
 	if (was_hw_scan && !aborted && ieee80211_prep_hw_scan(local)) {
 		ieee80211_queue_delayed_work(&local->hw,
 					     &local->scan_work, 0);
 		mutex_unlock(&local->scan_mtx);
 		return;
 	}

 	kfree(local->hw_scan_req);
 	local->hw_scan_req = NULL;

 	if (local->scan_req != local->int_scan_req)
 		cfg80211_scan_done(local->scan_req, aborted);
 	local->scan_req = NULL;
 	local->scan_sdata = NULL;

 	local->scanning = 0;
 	local->scan_channel = NULL;

 	/* we only have to protect scan_req and hw/sw scan */
 	mutex_unlock(&local->scan_mtx);

 	ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
 	if (was_hw_scan)
 		goto done;

 	ieee80211_configure_filter(local);

 	drv_sw_scan_complete(local);

 	mutex_lock(&local->iflist_mtx);
 	list_for_each_entry(sdata, &local->interfaces, list) {
 		if (!ieee80211_sdata_running(sdata))
 			continue;

 		/* Tell AP we're back */
 		if (sdata->vif.type == NL80211_IFTYPE_STATION) {
 			if (sdata->u.mgd.associated) {
 				ieee80211_scan_ps_disable(sdata);
 				netif_wake_queue(sdata->dev);
 			}
 		} else
 			netif_wake_queue(sdata->dev);

 		/* re-enable beaconing */
 		if (sdata->vif.type == NL80211_IFTYPE_AP ||
 		    sdata->vif.type == NL80211_IFTYPE_ADHOC ||
 		    sdata->vif.type == NL80211_IFTYPE_MESH_POINT)
 			ieee80211_bss_info_change_notify(
 				sdata, BSS_CHANGED_BEACON_ENABLED);
 	}
 	mutex_unlock(&local->iflist_mtx);

  done:
 	ieee80211_recalc_idle(local);
 	ieee80211_mlme_notify_scan_completed(local);
 	ieee80211_ibss_notify_scan_completed(local);
 	ieee80211_mesh_notify_scan_completed(local);
 }
 EXPORT_SYMBOL(ieee80211_scan_completed);

 static int ieee80211_start_sw_scan(struct ieee80211_local *local)
 {
 	struct ieee80211_sub_if_data *sdata;

 	/*
 	 * Hardware/driver doesn't support hw_scan, so use software
 	 * scanning instead. First send a nullfunc frame with power save
 	 * bit on so that AP will buffer the frames for us while we are not
 	 * listening, then send probe requests to each channel and wait for
 	 * the responses. After all channels are scanned, tune back to the
 	 * original channel and send a nullfunc frame with power save bit
 	 * off to trigger the AP to send us all the buffered frames.
 	 *
 	 * Note that while local->sw_scanning is true everything else but
 	 * nullfunc frames and probe requests will be dropped in
 	 * ieee80211_tx_h_check_assoc().
 	 */
 	drv_sw_scan_start(local);

 	mutex_lock(&local->iflist_mtx);
 	list_for_each_entry(sdata, &local->interfaces, list) {
 		if (!ieee80211_sdata_running(sdata))
 			continue;

 		/* disable beaconing */
 		if (sdata->vif.type == NL80211_IFTYPE_AP ||
 		    sdata->vif.type == NL80211_IFTYPE_ADHOC ||
 		    sdata->vif.type == NL80211_IFTYPE_MESH_POINT)
 			ieee80211_bss_info_change_notify(
 				sdata, BSS_CHANGED_BEACON_ENABLED);

 		/*
 		 * only handle non-STA interfaces here, STA interfaces
 		 * are handled in the scan state machine
 		 */
 		if (sdata->vif.type != NL80211_IFTYPE_STATION)
 			netif_stop_queue(sdata->dev);
 	}
 	mutex_unlock(&local->iflist_mtx);

 	local->next_scan_state = SCAN_DECISION;
 	local->scan_channel_idx = 0;

 	drv_flush(local, false);

 	ieee80211_configure_filter(local);

 	ieee80211_queue_delayed_work(&local->hw,
 				     &local->scan_work,
 				     IEEE80211_CHANNEL_TIME);

 	return 0;
 }


 static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
 				  struct cfg80211_scan_request *req)
 {
 	struct ieee80211_local *local = sdata->local;
 	int rc;

 	if (local->scan_req)
 		return -EBUSY;

 	if (local->ops->hw_scan) {
 		u8 *ies;

 		local->hw_scan_req = kmalloc(
 				sizeof(*local->hw_scan_req) +
 				req->n_channels * sizeof(req->channels[0]) +
 				2 + IEEE80211_MAX_SSID_LEN + local->scan_ies_len +
 				req->ie_len, GFP_KERNEL);
 		if (!local->hw_scan_req)
 			return -ENOMEM;

 		local->hw_scan_req->ssids = req->ssids;
 		local->hw_scan_req->n_ssids = req->n_ssids;
 		ies = (u8 *)local->hw_scan_req +
 			sizeof(*local->hw_scan_req) +
 			req->n_channels * sizeof(req->channels[0]);
 		local->hw_scan_req->ie = ies;

 		local->hw_scan_band = 0;
 	}

 	local->scan_req = req;
 	local->scan_sdata = sdata;

 	if (!list_empty(&local->work_list)) {
 		/* wait for the work to finish/time out */
 		return 0;
 	}

 	if (local->ops->hw_scan)
 		__set_bit(SCAN_HW_SCANNING, &local->scanning);
 	else
 		__set_bit(SCAN_SW_SCANNING, &local->scanning);
 	/*
 	 * Kicking off the scan need not be protected,
 	 * only the scan variable stuff, since now
 	 * local->scan_req is assigned and other callers
 	 * will abort their scan attempts.
 	 *
 	 * This avoids getting a scan_mtx -> iflist_mtx
 	 * dependency, so that the scan completed calls
 	 * have more locking freedom.
 	 */

 	ieee80211_recalc_idle(local);
 	mutex_unlock(&local->scan_mtx);

 	if (local->ops->hw_scan) {
 		WARN_ON(!ieee80211_prep_hw_scan(local));
 		rc = drv_hw_scan(local, local->hw_scan_req);
 	} else
 		rc = ieee80211_start_sw_scan(local);

 	mutex_lock(&local->scan_mtx);

 	if (rc) {
 		kfree(local->hw_scan_req);
 		local->hw_scan_req = NULL;
 		local->scanning = 0;

 		ieee80211_recalc_idle(local);

 		local->scan_req = NULL;
 		local->scan_sdata = NULL;
 	}

 	return rc;
 }

 static int ieee80211_scan_state_decision(struct ieee80211_local *local,
 					 unsigned long *next_delay)
 {
 	bool associated = false;
 	struct ieee80211_sub_if_data *sdata;

 	/* if no more bands/channels left, complete scan and advance to the idle state */
 	if (local->scan_channel_idx >= local->scan_req->n_channels) {
 		ieee80211_scan_completed(&local->hw, false);
 		return 1;
 	}

 	/* check if at least one STA interface is associated */
 	mutex_lock(&local->iflist_mtx);
 	list_for_each_entry(sdata, &local->interfaces, list) {
 		if (!ieee80211_sdata_running(sdata))
 			continue;

 		if (sdata->vif.type == NL80211_IFTYPE_STATION) {
 			if (sdata->u.mgd.associated) {
 				associated = true;
 				break;
 			}
 		}
 	}
 	mutex_unlock(&local->iflist_mtx);

 	if (local->scan_channel) {
 		/*
 		 * we're currently scanning a different channel, let's
 		 * switch back to the operating channel now if at least
 		 * one interface is associated. Otherwise just scan the
 		 * next channel
 		 */
 		if (associated)
 			local->next_scan_state = SCAN_ENTER_OPER_CHANNEL;
 		else
 			local->next_scan_state = SCAN_SET_CHANNEL;
 	} else {
 		/*
 		 * we're on the operating channel currently, let's
 		 * leave that channel now to scan another one
 		 */
 		local->next_scan_state = SCAN_LEAVE_OPER_CHANNEL;
 	}

 	*next_delay = 0;
 	return 0;
 }

 static void ieee80211_scan_state_leave_oper_channel(struct ieee80211_local *local,
 						    unsigned long *next_delay)
 {
 	struct ieee80211_sub_if_data *sdata;

 	/*
 	 * notify the AP about us leaving the channel and stop all STA interfaces
 	 */
 	mutex_lock(&local->iflist_mtx);
 	list_for_each_entry(sdata, &local->interfaces, list) {
 		if (!ieee80211_sdata_running(sdata))
 			continue;

 		if (sdata->vif.type == NL80211_IFTYPE_STATION) {
 			netif_stop_queue(sdata->dev);
 			if (sdata->u.mgd.associated)
 				ieee80211_scan_ps_enable(sdata);
 		}
 	}
 	mutex_unlock(&local->iflist_mtx);

 	__set_bit(SCAN_OFF_CHANNEL, &local->scanning);

 	/*
 	 * What if the nullfunc frames didn't arrive?
 	 */
 	drv_flush(local, false);
 	if (local->ops->flush)
 		*next_delay = 0;
 	else
 		*next_delay = HZ / 10;

 	/* advance to the next channel to be scanned */
 	local->next_scan_state = SCAN_SET_CHANNEL;
 }

 static void ieee80211_scan_state_enter_oper_channel(struct ieee80211_local *local,
 						    unsigned long *next_delay)
 {
 	struct ieee80211_sub_if_data *sdata = local->scan_sdata;

 	/* switch back to the operating channel */
 	local->scan_channel = NULL;
 	ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);

 	/*
 	 * notify the AP about us being back and restart all STA interfaces
 	 */
 	mutex_lock(&local->iflist_mtx);
 	list_for_each_entry(sdata, &local->interfaces, list) {
 		if (!ieee80211_sdata_running(sdata))
 			continue;

 		/* Tell AP we're back */
 		if (sdata->vif.type == NL80211_IFTYPE_STATION) {
 			if (sdata->u.mgd.associated)
 				ieee80211_scan_ps_disable(sdata);
 			netif_wake_queue(sdata->dev);
 		}
 	}
 	mutex_unlock(&local->iflist_mtx);

 	__clear_bit(SCAN_OFF_CHANNEL, &local->scanning);

 	*next_delay = HZ / 5;
 	local->next_scan_state = SCAN_DECISION;
 }

 static void ieee80211_scan_state_set_channel(struct ieee80211_local *local,
 					     unsigned long *next_delay)
 {
 	int skip;
 	struct ieee80211_channel *chan;

 	skip = 0;
 	chan = local->scan_req->channels[local->scan_channel_idx];

 	local->scan_channel = chan;
 	if (ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL))
 		skip = 1;

 	/* advance state machine to next channel/band */
 	local->scan_channel_idx++;

 	if (skip) {
 		/* if we skip this channel return to the decision state */
 		local->next_scan_state = SCAN_DECISION;
 		return;
 	}

 	/*
 	 * Probe delay is used to update the NAV, cf. 11.1.3.2.2
 	 * (which unfortunately doesn't say _why_ step a) is done,
 	 * but it waits for the probe delay or until a frame is
 	 * received - and the received frame would update the NAV).
 	 * For now, we do not support waiting until a frame is
 	 * received.
 	 *
 	 * In any case, it is not necessary for a passive scan.
 	 */
 	if (chan->flags & IEEE80211_CHAN_PASSIVE_SCAN ||
 	    !local->scan_req->n_ssids) {
 		*next_delay = IEEE80211_PASSIVE_CHANNEL_TIME;
 		local->next_scan_state = SCAN_DECISION;
 		return;
 	}

 	/* active scan, send probes */
 	*next_delay = IEEE80211_PROBE_DELAY;
 	local->next_scan_state = SCAN_SEND_PROBE;
 }

 static void ieee80211_scan_state_send_probe(struct ieee80211_local *local,
 					    unsigned long *next_delay)
 {
 	int i;
 	struct ieee80211_sub_if_data *sdata = local->scan_sdata;

 	for (i = 0; i < local->scan_req->n_ssids; i++)
 		ieee80211_send_probe_req(
 			sdata, NULL,
 			local->scan_req->ssids[i].ssid,
 			local->scan_req->ssids[i].ssid_len,
 			local->scan_req->ie, local->scan_req->ie_len);

 	/*
 	 * After sending probe requests, wait for probe responses
 	 * on the channel.
 	 */
 	*next_delay = IEEE80211_CHANNEL_TIME;
 	local->next_scan_state = SCAN_DECISION;
 }

 void ieee80211_scan_work(struct work_struct *work)
 {
 	struct ieee80211_local *local =
 		container_of(work, struct ieee80211_local, scan_work.work);
 	struct ieee80211_sub_if_data *sdata = local->scan_sdata;
 	unsigned long next_delay = 0;

 	mutex_lock(&local->scan_mtx);
 	if (!sdata || !local->scan_req) {
 		mutex_unlock(&local->scan_mtx);
 		return;
 	}

 	if (local->hw_scan_req) {
 		int rc = drv_hw_scan(local, local->hw_scan_req);
 		mutex_unlock(&local->scan_mtx);
 		if (rc)
 			ieee80211_scan_completed(&local->hw, true);
 		return;
 	}

 	if (local->scan_req && !local->scanning) {
 		struct cfg80211_scan_request *req = local->scan_req;
 		int rc;

 		local->scan_req = NULL;
 		local->scan_sdata = NULL;

 		rc = __ieee80211_start_scan(sdata, req);
 		mutex_unlock(&local->scan_mtx);

 		if (rc)
 			ieee80211_scan_completed(&local->hw, true);
 		return;
 	}

 	mutex_unlock(&local->scan_mtx);

 	/*
 	 * Avoid re-scheduling when the sdata is going away.
 	 */
 	if (!ieee80211_sdata_running(sdata)) {
 		ieee80211_scan_completed(&local->hw, true);
 		return;
 	}

 	/*
 	 * as long as no delay is required advance immediately
 	 * without scheduling a new work
 	 */
 	do {
 		switch (local->next_scan_state) {
 		case SCAN_DECISION:
 			if (ieee80211_scan_state_decision(local, &next_delay))
 				return;
 			break;
 		case SCAN_SET_CHANNEL:
 			ieee80211_scan_state_set_channel(local, &next_delay);
 			break;
 		case SCAN_SEND_PROBE:
 			ieee80211_scan_state_send_probe(local, &next_delay);
 			break;
 		case SCAN_LEAVE_OPER_CHANNEL:
 			ieee80211_scan_state_leave_oper_channel(local, &next_delay);
 			break;
 		case SCAN_ENTER_OPER_CHANNEL:
 			ieee80211_scan_state_enter_oper_channel(local, &next_delay);
 			break;
 		}
 	} while (next_delay == 0);

 	ieee80211_queue_delayed_work(&local->hw, &local->scan_work, next_delay);
 }

 int ieee80211_request_scan(struct ieee80211_sub_if_data *sdata,
 			   struct cfg80211_scan_request *req)
 {
 	int res;

 	mutex_lock(&sdata->local->scan_mtx);
 	res = __ieee80211_start_scan(sdata, req);
 	mutex_unlock(&sdata->local->scan_mtx);

 	return res;
 }

 int ieee80211_request_internal_scan(struct ieee80211_sub_if_data *sdata,
 				    const u8 *ssid, u8 ssid_len)
 {
 	struct ieee80211_local *local = sdata->local;
 	int ret = -EBUSY;

 	mutex_lock(&local->scan_mtx);

 	/* busy scanning */
 	if (local->scan_req)
 		goto unlock;

 	memcpy(local->int_scan_req->ssids[0].ssid, ssid, IEEE80211_MAX_SSID_LEN);
 	local->int_scan_req->ssids[0].ssid_len = ssid_len;

 	ret = __ieee80211_start_scan(sdata, sdata->local->int_scan_req);
  unlock:
 	mutex_unlock(&local->scan_mtx);
 	return ret;
 }

 void ieee80211_scan_cancel(struct ieee80211_local *local)
 {
 	bool abortscan;

 	cancel_delayed_work_sync(&local->scan_work);

 	/*
 	 * Only call this function when a scan can't be
 	 * queued -- mostly at suspend under RTNL.
 	 */
 	mutex_lock(&local->scan_mtx);
 	abortscan = test_bit(SCAN_SW_SCANNING, &local->scanning) ||
 		    (!local->scanning && local->scan_req);
 	mutex_unlock(&local->scan_mtx);

 	if (abortscan)
 		ieee80211_scan_completed(&local->hw, true);
 }
	/*
	* Scanning implementation
	*
	* Copyright 2003, Jouni Malinen <jkmaline@cc.hut.fi>
	* Copyright 2004, Instant802 Networks, Inc.
	* Copyright 2005, Devicescape Software, Inc.
	* Copyright 2006-2007 Jiri Benc <jbenc@suse.cz>
	* Copyright 2007, Michael Wu <flamingice@sourmilk.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/wireless.h>
	#include <linux/if_arp.h>
	#include <linux/rtnetlink.h>
	#include <net/mac80211.h>

	#include "ieee80211_i.h"
	#include "driver-ops.h"
	#include "mesh.h"

	#define IEEE80211_PROBE_DELAY (HZ / 33)
	#define IEEE80211_CHANNEL_TIME (HZ / 33)
	#define IEEE80211_PASSIVE_CHANNEL_TIME (HZ / 8)

	struct ieee80211_bss *
	ieee80211_rx_bss_get(struct ieee80211_local local, u8 bssid, int freq,
	u8 *ssid, u8 ssid_len)
	{
	return (void *)cfg80211_get_bss(local->hw.wiphy,
	ieee80211_get_channel(local->hw.wiphy,
	freq),
	bssid, ssid, ssid_len,
	0, 0);
	}

	static void ieee80211_rx_bss_free(struct cfg80211_bss *cbss)
	{
	struct ieee80211_bss bss = (void )cbss;

	kfree(bss_mesh_id(bss));
	kfree(bss_mesh_cfg(bss));
	}

	void ieee80211_rx_bss_put(struct ieee80211_local *local,
	struct ieee80211_bss *bss)
	{
	cfg80211_put_bss((struct cfg80211_bss *)bss);
	}

	struct ieee80211_bss *
	ieee80211_bss_info_update(struct ieee80211_local *local,
	struct ieee80211_rx_status *rx_status,
	struct ieee80211_mgmt *mgmt,
	size_t len,
	struct ieee802_11_elems *elems,
	struct ieee80211_channel *channel,
	bool beacon)
	{
	struct ieee80211_bss *bss;
	int clen;
	s32 signal = 0;

	if (local->hw.flags & IEEE80211_HW_SIGNAL_DBM)
	signal = rx_status->signal * 100;
	else if (local->hw.flags & IEEE80211_HW_SIGNAL_UNSPEC)
	signal = (rx_status->signal * 100) / local->hw.max_signal;

	bss = (void *)cfg80211_inform_bss_frame(local->hw.wiphy, channel,
	mgmt, len, signal, GFP_ATOMIC);

	if (!bss)
	return NULL;

	bss->cbss.free_priv = ieee80211_rx_bss_free;

	/* save the ERP value so that it is available at association time */
	if (elems->erp_info && elems->erp_info_len >= 1) {
	bss->erp_value = elems->erp_info[0];
	bss->has_erp_value = 1;
	}

	if (elems->tim) {
	struct ieee80211_tim_ie *tim_ie =
	(struct ieee80211_tim_ie *)elems->tim;
	bss->dtim_period = tim_ie->dtim_period;
	}

	/* set default value for buggy AP/no TIM element */
	if (bss->dtim_period == 0)
	bss->dtim_period = 1;

	bss->supp_rates_len = 0;
	if (elems->supp_rates) {
	clen = IEEE80211_MAX_SUPP_RATES - bss->supp_rates_len;
	if (clen > elems->supp_rates_len)
	clen = elems->supp_rates_len;
	memcpy(&bss->supp_rates[bss->supp_rates_len], elems->supp_rates,
	clen);
	bss->supp_rates_len += clen;
	}
	if (elems->ext_supp_rates) {
	clen = IEEE80211_MAX_SUPP_RATES - bss->supp_rates_len;
	if (clen > elems->ext_supp_rates_len)
	clen = elems->ext_supp_rates_len;
	memcpy(&bss->supp_rates[bss->supp_rates_len],
	elems->ext_supp_rates, clen);
	bss->supp_rates_len += clen;
	}

	bss->wmm_used = elems->wmm_param \|\| elems->wmm_info;

	if (!beacon)
	bss->last_probe_resp = jiffies;

	return bss;
	}

	ieee80211_rx_result
	ieee80211_scan_rx(struct ieee80211_sub_if_data sdata, struct sk_buff skb)
	{
	struct ieee80211_rx_status *rx_status = IEEE80211_SKB_RXCB(skb);
	struct ieee80211_mgmt *mgmt;
	struct ieee80211_bss *bss;
	u8 *elements;
	struct ieee80211_channel *channel;
	size_t baselen;
	int freq;
	__le16 fc;
	bool presp, beacon = false;
	struct ieee802_11_elems elems;

	if (skb->len < 2)
	return RX_DROP_UNUSABLE;

	mgmt = (struct ieee80211_mgmt *) skb->data;
	fc = mgmt->frame_control;

	if (ieee80211_is_ctl(fc))
	return RX_CONTINUE;

	if (skb->len < 24)
	return RX_DROP_MONITOR;

	presp = ieee80211_is_probe_resp(fc);
	if (presp) {
	/* ignore ProbeResp to foreign address */
	if (memcmp(mgmt->da, sdata->vif.addr, ETH_ALEN))
	return RX_DROP_MONITOR;

	presp = true;
	elements = mgmt->u.probe_resp.variable;
	baselen = offsetof(struct ieee80211_mgmt, u.probe_resp.variable);
	} else {
	beacon = ieee80211_is_beacon(fc);
	baselen = offsetof(struct ieee80211_mgmt, u.beacon.variable);
	elements = mgmt->u.beacon.variable;
	}

	if (!presp && !beacon)
	return RX_CONTINUE;

	if (baselen > skb->len)
	return RX_DROP_MONITOR;

	ieee802_11_parse_elems(elements, skb->len - baselen, &elems);

	if (elems.ds_params && elems.ds_params_len == 1)
	freq = ieee80211_channel_to_frequency(elems.ds_params[0]);
	else
	freq = rx_status->freq;

	channel = ieee80211_get_channel(sdata->local->hw.wiphy, freq);

	if (!channel \|\| channel->flags & IEEE80211_CHAN_DISABLED)
	return RX_DROP_MONITOR;

	bss = ieee80211_bss_info_update(sdata->local, rx_status,
	mgmt, skb->len, &elems,
	channel, beacon);
	if (bss)
	ieee80211_rx_bss_put(sdata->local, bss);

	dev_kfree_skb(skb);
	return RX_QUEUED;
	}

	/* return false if no more work */
	static bool ieee80211_prep_hw_scan(struct ieee80211_local *local)
	{
	struct cfg80211_scan_request *req = local->scan_req;
	enum ieee80211_band band;
	int i, ielen, n_chans;

	do {
	if (local->hw_scan_band == IEEE80211_NUM_BANDS)
	return false;

	band = local->hw_scan_band;
	n_chans = 0;
	for (i = 0; i < req->n_channels; i++) {
	if (req->channels[i]->band == band) {
	local->hw_scan_req->channels[n_chans] =
	req->channels[i];
	n_chans++;
	}
	}

	local->hw_scan_band++;
	} while (!n_chans);

	local->hw_scan_req->n_channels = n_chans;

	ielen = ieee80211_build_preq_ies(local, (u8 *)local->hw_scan_req->ie,
	req->ie, req->ie_len, band);
	local->hw_scan_req->ie_len = ielen;

	return true;
	}

	/*
	* inform AP that we will go to sleep so that it will buffer the frames
	* while we scan
	*/
	static void ieee80211_scan_ps_enable(struct ieee80211_sub_if_data *sdata)
	{
	struct ieee80211_local *local = sdata->local;

	local->scan_ps_enabled = false;

	/* FIXME: what to do when local->pspolling is true? */

	del_timer_sync(&local->dynamic_ps_timer);
	cancel_work_sync(&local->dynamic_ps_enable_work);

	if (local->hw.conf.flags & IEEE80211_CONF_PS) {
	local->scan_ps_enabled = true;
	local->hw.conf.flags &= ~IEEE80211_CONF_PS;
	ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
	}

	if (!(local->scan_ps_enabled) \|\|
	!(local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK))
	/*
	* If power save was enabled, no need to send a nullfunc
	* frame because AP knows that we are sleeping. But if the
	* hardware is creating the nullfunc frame for power save
	* status (ie. IEEE80211_HW_PS_NULLFUNC_STACK is not
	* enabled) and power save was enabled, the firmware just
	* sent a null frame with power save disabled. So we need
	* to send a new nullfunc frame to inform the AP that we
	* are again sleeping.
	*/
	ieee80211_send_nullfunc(local, sdata, 1);
	}

	/* inform AP that we are awake again, unless power save is enabled */
	static void ieee80211_scan_ps_disable(struct ieee80211_sub_if_data *sdata)
	{
	struct ieee80211_local *local = sdata->local;

	if (!local->ps_sdata)
	ieee80211_send_nullfunc(local, sdata, 0);
	else if (local->scan_ps_enabled) {
	/*
	* In !IEEE80211_HW_PS_NULLFUNC_STACK case the hardware
	* will send a nullfunc frame with the powersave bit set
	* even though the AP already knows that we are sleeping.
	* This could be avoided by sending a null frame with power
	* save bit disabled before enabling the power save, but
	* this doesn't gain anything.
	*
	* When IEEE80211_HW_PS_NULLFUNC_STACK is enabled, no need
	* to send a nullfunc frame because AP already knows that
	* we are sleeping, let's just enable power save mode in
	* hardware.
	*/
	local->hw.conf.flags \|= IEEE80211_CONF_PS;
	ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
	} else if (local->hw.conf.dynamic_ps_timeout > 0) {
	/*
	* If IEEE80211_CONF_PS was not set and the dynamic_ps_timer
	* had been running before leaving the operating channel,
	* restart the timer now and send a nullfunc frame to inform
	* the AP that we are awake.
	*/
	ieee80211_send_nullfunc(local, sdata, 0);
	mod_timer(&local->dynamic_ps_timer, jiffies +
	msecs_to_jiffies(local->hw.conf.dynamic_ps_timeout));
	}
	}

	void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
	{
	struct ieee80211_local *local = hw_to_local(hw);
	struct ieee80211_sub_if_data *sdata;
	bool was_hw_scan;

	mutex_lock(&local->scan_mtx);

	/*
	* It's ok to abort a not-yet-running scan (that
	* we have one at all will be verified by checking
	* local->scan_req next), but not to complete it
	* successfully.
	*/
	if (WARN_ON(!local->scanning && !aborted))
	aborted = true;

	if (WARN_ON(!local->scan_req)) {
	mutex_unlock(&local->scan_mtx);
	return;
	}

	was_hw_scan = test_bit(SCAN_HW_SCANNING, &local->scanning);
	if (was_hw_scan && !aborted && ieee80211_prep_hw_scan(local)) {
	ieee80211_queue_delayed_work(&local->hw,
	&local->scan_work, 0);
	mutex_unlock(&local->scan_mtx);
	return;
	}

	kfree(local->hw_scan_req);
	local->hw_scan_req = NULL;

	if (local->scan_req != local->int_scan_req)
	cfg80211_scan_done(local->scan_req, aborted);
	local->scan_req = NULL;
	local->scan_sdata = NULL;

	local->scanning = 0;
	local->scan_channel = NULL;

	/* we only have to protect scan_req and hw/sw scan */
	mutex_unlock(&local->scan_mtx);

	ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
	if (was_hw_scan)
	goto done;

	ieee80211_configure_filter(local);

	drv_sw_scan_complete(local);

	mutex_lock(&local->iflist_mtx);
	list_for_each_entry(sdata, &local->interfaces, list) {
	if (!ieee80211_sdata_running(sdata))
	continue;

	/* Tell AP we're back */
	if (sdata->vif.type == NL80211_IFTYPE_STATION) {
	if (sdata->u.mgd.associated) {
	ieee80211_scan_ps_disable(sdata);
	netif_wake_queue(sdata->dev);
	}
	} else
	netif_wake_queue(sdata->dev);

	/* re-enable beaconing */
	if (sdata->vif.type == NL80211_IFTYPE_AP \|\|
	sdata->vif.type == NL80211_IFTYPE_ADHOC \|\|
	sdata->vif.type == NL80211_IFTYPE_MESH_POINT)
	ieee80211_bss_info_change_notify(
	sdata, BSS_CHANGED_BEACON_ENABLED);
	}
	mutex_unlock(&local->iflist_mtx);

	done:
	ieee80211_recalc_idle(local);
	ieee80211_mlme_notify_scan_completed(local);
	ieee80211_ibss_notify_scan_completed(local);
	ieee80211_mesh_notify_scan_completed(local);
	}
	EXPORT_SYMBOL(ieee80211_scan_completed);

	static int ieee80211_start_sw_scan(struct ieee80211_local *local)
	{
	struct ieee80211_sub_if_data *sdata;

	/*
	* Hardware/driver doesn't support hw_scan, so use software
	* scanning instead. First send a nullfunc frame with power save
	* bit on so that AP will buffer the frames for us while we are not
	* listening, then send probe requests to each channel and wait for
	* the responses. After all channels are scanned, tune back to the
	* original channel and send a nullfunc frame with power save bit
	* off to trigger the AP to send us all the buffered frames.
	*
	* Note that while local->sw_scanning is true everything else but
	* nullfunc frames and probe requests will be dropped in
	* ieee80211_tx_h_check_assoc().
	*/
	drv_sw_scan_start(local);

	mutex_lock(&local->iflist_mtx);
	list_for_each_entry(sdata, &local->interfaces, list) {
	if (!ieee80211_sdata_running(sdata))
	continue;

	/* disable beaconing */
	if (sdata->vif.type == NL80211_IFTYPE_AP \|\|
	sdata->vif.type == NL80211_IFTYPE_ADHOC \|\|
	sdata->vif.type == NL80211_IFTYPE_MESH_POINT)
	ieee80211_bss_info_change_notify(
	sdata, BSS_CHANGED_BEACON_ENABLED);

	/*
	* only handle non-STA interfaces here, STA interfaces
	* are handled in the scan state machine
	*/
	if (sdata->vif.type != NL80211_IFTYPE_STATION)
	netif_stop_queue(sdata->dev);
	}
	mutex_unlock(&local->iflist_mtx);

	local->next_scan_state = SCAN_DECISION;
	local->scan_channel_idx = 0;

	drv_flush(local, false);

	ieee80211_configure_filter(local);

	ieee80211_queue_delayed_work(&local->hw,
	&local->scan_work,
	IEEE80211_CHANNEL_TIME);

	return 0;
	}


	static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
	struct cfg80211_scan_request *req)
	{
	struct ieee80211_local *local = sdata->local;
	int rc;

	if (local->scan_req)
	return -EBUSY;

	if (local->ops->hw_scan) {
	u8 *ies;

	local->hw_scan_req = kmalloc(
	sizeof(*local->hw_scan_req) +
	req->n_channels * sizeof(req->channels[0]) +
	2 + IEEE80211_MAX_SSID_LEN + local->scan_ies_len +
	req->ie_len, GFP_KERNEL);
	if (!local->hw_scan_req)
	return -ENOMEM;

	local->hw_scan_req->ssids = req->ssids;
	local->hw_scan_req->n_ssids = req->n_ssids;
	ies = (u8 *)local->hw_scan_req +
	sizeof(*local->hw_scan_req) +
	req->n_channels * sizeof(req->channels[0]);
	local->hw_scan_req->ie = ies;

	local->hw_scan_band = 0;
	}

	local->scan_req = req;
	local->scan_sdata = sdata;

	if (!list_empty(&local->work_list)) {
	/* wait for the work to finish/time out */
	return 0;
	}

	if (local->ops->hw_scan)
	__set_bit(SCAN_HW_SCANNING, &local->scanning);
	else
	__set_bit(SCAN_SW_SCANNING, &local->scanning);
	/*
	* Kicking off the scan need not be protected,
	* only the scan variable stuff, since now
	* local->scan_req is assigned and other callers
	* will abort their scan attempts.
	*
	* This avoids getting a scan_mtx -> iflist_mtx
	* dependency, so that the scan completed calls
	* have more locking freedom.
	*/

	ieee80211_recalc_idle(local);
	mutex_unlock(&local->scan_mtx);

	if (local->ops->hw_scan) {
	WARN_ON(!ieee80211_prep_hw_scan(local));
	rc = drv_hw_scan(local, local->hw_scan_req);
	} else
	rc = ieee80211_start_sw_scan(local);

	mutex_lock(&local->scan_mtx);

	if (rc) {
	kfree(local->hw_scan_req);
	local->hw_scan_req = NULL;
	local->scanning = 0;

	ieee80211_recalc_idle(local);

	local->scan_req = NULL;
	local->scan_sdata = NULL;
	}

	return rc;
	}

	static int ieee80211_scan_state_decision(struct ieee80211_local *local,
	unsigned long *next_delay)
	{
	bool associated = false;
	struct ieee80211_sub_if_data *sdata;

	/* if no more bands/channels left, complete scan and advance to the idle state */
	if (local->scan_channel_idx >= local->scan_req->n_channels) {
	ieee80211_scan_completed(&local->hw, false);
	return 1;
	}

	/* check if at least one STA interface is associated */
	mutex_lock(&local->iflist_mtx);
	list_for_each_entry(sdata, &local->interfaces, list) {
	if (!ieee80211_sdata_running(sdata))
	continue;

	if (sdata->vif.type == NL80211_IFTYPE_STATION) {
	if (sdata->u.mgd.associated) {
	associated = true;
	break;
	}
	}
	}
	mutex_unlock(&local->iflist_mtx);

	if (local->scan_channel) {
	/*
	* we're currently scanning a different channel, let's
	* switch back to the operating channel now if at least
	* one interface is associated. Otherwise just scan the
	* next channel
	*/
	if (associated)
	local->next_scan_state = SCAN_ENTER_OPER_CHANNEL;
	else
	local->next_scan_state = SCAN_SET_CHANNEL;
	} else {
	/*
	* we're on the operating channel currently, let's
	* leave that channel now to scan another one
	*/
	local->next_scan_state = SCAN_LEAVE_OPER_CHANNEL;
	}

	*next_delay = 0;
	return 0;
	}

	static void ieee80211_scan_state_leave_oper_channel(struct ieee80211_local *local,
	unsigned long *next_delay)
	{
	struct ieee80211_sub_if_data *sdata;

	/*
	* notify the AP about us leaving the channel and stop all STA interfaces
	*/
	mutex_lock(&local->iflist_mtx);
	list_for_each_entry(sdata, &local->interfaces, list) {
	if (!ieee80211_sdata_running(sdata))
	continue;

	if (sdata->vif.type == NL80211_IFTYPE_STATION) {
	netif_stop_queue(sdata->dev);
	if (sdata->u.mgd.associated)
	ieee80211_scan_ps_enable(sdata);
	}
	}
	mutex_unlock(&local->iflist_mtx);

	__set_bit(SCAN_OFF_CHANNEL, &local->scanning);

	/*
	* What if the nullfunc frames didn't arrive?
	*/
	drv_flush(local, false);
	if (local->ops->flush)
	*next_delay = 0;
	else
	*next_delay = HZ / 10;

	/* advance to the next channel to be scanned */
	local->next_scan_state = SCAN_SET_CHANNEL;
	}

	static void ieee80211_scan_state_enter_oper_channel(struct ieee80211_local *local,
	unsigned long *next_delay)
	{
	struct ieee80211_sub_if_data *sdata = local->scan_sdata;

	/* switch back to the operating channel */
	local->scan_channel = NULL;
	ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);

	/*
	* notify the AP about us being back and restart all STA interfaces
	*/
	mutex_lock(&local->iflist_mtx);
	list_for_each_entry(sdata, &local->interfaces, list) {
	if (!ieee80211_sdata_running(sdata))
	continue;

	/* Tell AP we're back */
	if (sdata->vif.type == NL80211_IFTYPE_STATION) {
	if (sdata->u.mgd.associated)
	ieee80211_scan_ps_disable(sdata);
	netif_wake_queue(sdata->dev);
	}
	}
	mutex_unlock(&local->iflist_mtx);

	__clear_bit(SCAN_OFF_CHANNEL, &local->scanning);

	*next_delay = HZ / 5;
	local->next_scan_state = SCAN_DECISION;
	}

	static void ieee80211_scan_state_set_channel(struct ieee80211_local *local,
	unsigned long *next_delay)
	{
	int skip;
	struct ieee80211_channel *chan;

	skip = 0;
	chan = local->scan_req->channels[local->scan_channel_idx];

	local->scan_channel = chan;
	if (ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL))
	skip = 1;

	/* advance state machine to next channel/band */
	local->scan_channel_idx++;

	if (skip) {
	/* if we skip this channel return to the decision state */
	local->next_scan_state = SCAN_DECISION;
	return;
	}

	/*
	* Probe delay is used to update the NAV, cf. 11.1.3.2.2
	* (which unfortunately doesn't say _why_ step a) is done,
	* but it waits for the probe delay or until a frame is
	* received - and the received frame would update the NAV).
	* For now, we do not support waiting until a frame is
	* received.
	*
	* In any case, it is not necessary for a passive scan.
	*/
	if (chan->flags & IEEE80211_CHAN_PASSIVE_SCAN \|\|
	!local->scan_req->n_ssids) {
	*next_delay = IEEE80211_PASSIVE_CHANNEL_TIME;
	local->next_scan_state = SCAN_DECISION;
	return;
	}

	/* active scan, send probes */
	*next_delay = IEEE80211_PROBE_DELAY;
	local->next_scan_state = SCAN_SEND_PROBE;
	}

	static void ieee80211_scan_state_send_probe(struct ieee80211_local *local,
	unsigned long *next_delay)
	{
	int i;
	struct ieee80211_sub_if_data *sdata = local->scan_sdata;

	for (i = 0; i < local->scan_req->n_ssids; i++)
	ieee80211_send_probe_req(
	sdata, NULL,
	local->scan_req->ssids[i].ssid,
	local->scan_req->ssids[i].ssid_len,
	local->scan_req->ie, local->scan_req->ie_len);

	/*
	* After sending probe requests, wait for probe responses
	* on the channel.
	*/
	*next_delay = IEEE80211_CHANNEL_TIME;
	local->next_scan_state = SCAN_DECISION;
	}

	void ieee80211_scan_work(struct work_struct *work)
	{
	struct ieee80211_local *local =
	container_of(work, struct ieee80211_local, scan_work.work);
	struct ieee80211_sub_if_data *sdata = local->scan_sdata;
	unsigned long next_delay = 0;

	mutex_lock(&local->scan_mtx);
	if (!sdata \|\| !local->scan_req) {
	mutex_unlock(&local->scan_mtx);
	return;
	}

	if (local->hw_scan_req) {
	int rc = drv_hw_scan(local, local->hw_scan_req);
	mutex_unlock(&local->scan_mtx);
	if (rc)
	ieee80211_scan_completed(&local->hw, true);
	return;
	}

	if (local->scan_req && !local->scanning) {
	struct cfg80211_scan_request *req = local->scan_req;
	int rc;

	local->scan_req = NULL;
	local->scan_sdata = NULL;

	rc = __ieee80211_start_scan(sdata, req);
	mutex_unlock(&local->scan_mtx);

	if (rc)
	ieee80211_scan_completed(&local->hw, true);
	return;
	}

	mutex_unlock(&local->scan_mtx);

	/*
	* Avoid re-scheduling when the sdata is going away.
	*/
	if (!ieee80211_sdata_running(sdata)) {
	ieee80211_scan_completed(&local->hw, true);
	return;
	}

	/*
	* as long as no delay is required advance immediately
	* without scheduling a new work
	*/
	do {
	switch (local->next_scan_state) {
	case SCAN_DECISION:
	if (ieee80211_scan_state_decision(local, &next_delay))
	return;
	break;
	case SCAN_SET_CHANNEL:
	ieee80211_scan_state_set_channel(local, &next_delay);
	break;
	case SCAN_SEND_PROBE:
	ieee80211_scan_state_send_probe(local, &next_delay);
	break;
	case SCAN_LEAVE_OPER_CHANNEL:
	ieee80211_scan_state_leave_oper_channel(local, &next_delay);
	break;
	case SCAN_ENTER_OPER_CHANNEL:
	ieee80211_scan_state_enter_oper_channel(local, &next_delay);
	break;
	}
	} while (next_delay == 0);

	ieee80211_queue_delayed_work(&local->hw, &local->scan_work, next_delay);
	}

	int ieee80211_request_scan(struct ieee80211_sub_if_data *sdata,
	struct cfg80211_scan_request *req)
	{
	int res;

	mutex_lock(&sdata->local->scan_mtx);
	res = __ieee80211_start_scan(sdata, req);
	mutex_unlock(&sdata->local->scan_mtx);

	return res;
	}

	int ieee80211_request_internal_scan(struct ieee80211_sub_if_data *sdata,
	const u8 *ssid, u8 ssid_len)
	{
	struct ieee80211_local *local = sdata->local;
	int ret = -EBUSY;

	mutex_lock(&local->scan_mtx);

	/* busy scanning */
	if (local->scan_req)
	goto unlock;

	memcpy(local->int_scan_req->ssids[0].ssid, ssid, IEEE80211_MAX_SSID_LEN);
	local->int_scan_req->ssids[0].ssid_len = ssid_len;

	ret = __ieee80211_start_scan(sdata, sdata->local->int_scan_req);
	unlock:
	mutex_unlock(&local->scan_mtx);
	return ret;
	}

	void ieee80211_scan_cancel(struct ieee80211_local *local)
	{
	bool abortscan;

	cancel_delayed_work_sync(&local->scan_work);

	/*
	* Only call this function when a scan can't be
	* queued -- mostly at suspend under RTNL.
	*/
	mutex_lock(&local->scan_mtx);
	abortscan = test_bit(SCAN_SW_SCANNING, &local->scanning) \|\|
	(!local->scanning && local->scan_req);
	mutex_unlock(&local->scan_mtx);

	if (abortscan)
	ieee80211_scan_completed(&local->hw, true);
	}