xref: /openbmc/linux/net/mac80211/scan.c (revision b6dcefde)
1 /*
2  * Scanning implementation
3  *
4  * Copyright 2003, Jouni Malinen <jkmaline@cc.hut.fi>
5  * Copyright 2004, Instant802 Networks, Inc.
6  * Copyright 2005, Devicescape Software, Inc.
7  * Copyright 2006-2007	Jiri Benc <jbenc@suse.cz>
8  * Copyright 2007, Michael Wu <flamingice@sourmilk.net>
9  *
10  * This program is free software; you can redistribute it and/or modify
11  * it under the terms of the GNU General Public License version 2 as
12  * published by the Free Software Foundation.
13  */
14 
15 #include <linux/wireless.h>
16 #include <linux/if_arp.h>
17 #include <linux/rtnetlink.h>
18 #include <net/mac80211.h>
19 
20 #include "ieee80211_i.h"
21 #include "driver-ops.h"
22 #include "mesh.h"
23 
24 #define IEEE80211_PROBE_DELAY (HZ / 33)
25 #define IEEE80211_CHANNEL_TIME (HZ / 33)
26 #define IEEE80211_PASSIVE_CHANNEL_TIME (HZ / 8)
27 
28 struct ieee80211_bss *
29 ieee80211_rx_bss_get(struct ieee80211_local *local, u8 *bssid, int freq,
30 		     u8 *ssid, u8 ssid_len)
31 {
32 	return (void *)cfg80211_get_bss(local->hw.wiphy,
33 					ieee80211_get_channel(local->hw.wiphy,
34 							      freq),
35 					bssid, ssid, ssid_len,
36 					0, 0);
37 }
38 
39 static void ieee80211_rx_bss_free(struct cfg80211_bss *cbss)
40 {
41 	struct ieee80211_bss *bss = (void *)cbss;
42 
43 	kfree(bss_mesh_id(bss));
44 	kfree(bss_mesh_cfg(bss));
45 }
46 
47 void ieee80211_rx_bss_put(struct ieee80211_local *local,
48 			  struct ieee80211_bss *bss)
49 {
50 	cfg80211_put_bss((struct cfg80211_bss *)bss);
51 }
52 
53 struct ieee80211_bss *
54 ieee80211_bss_info_update(struct ieee80211_local *local,
55 			  struct ieee80211_rx_status *rx_status,
56 			  struct ieee80211_mgmt *mgmt,
57 			  size_t len,
58 			  struct ieee802_11_elems *elems,
59 			  struct ieee80211_channel *channel,
60 			  bool beacon)
61 {
62 	struct ieee80211_bss *bss;
63 	int clen;
64 	s32 signal = 0;
65 
66 	if (local->hw.flags & IEEE80211_HW_SIGNAL_DBM)
67 		signal = rx_status->signal * 100;
68 	else if (local->hw.flags & IEEE80211_HW_SIGNAL_UNSPEC)
69 		signal = (rx_status->signal * 100) / local->hw.max_signal;
70 
71 	bss = (void *)cfg80211_inform_bss_frame(local->hw.wiphy, channel,
72 						mgmt, len, signal, GFP_ATOMIC);
73 
74 	if (!bss)
75 		return NULL;
76 
77 	bss->cbss.free_priv = ieee80211_rx_bss_free;
78 
79 	/* save the ERP value so that it is available at association time */
80 	if (elems->erp_info && elems->erp_info_len >= 1) {
81 		bss->erp_value = elems->erp_info[0];
82 		bss->has_erp_value = 1;
83 	}
84 
85 	if (elems->tim) {
86 		struct ieee80211_tim_ie *tim_ie =
87 			(struct ieee80211_tim_ie *)elems->tim;
88 		bss->dtim_period = tim_ie->dtim_period;
89 	}
90 
91 	/* set default value for buggy AP/no TIM element */
92 	if (bss->dtim_period == 0)
93 		bss->dtim_period = 1;
94 
95 	bss->supp_rates_len = 0;
96 	if (elems->supp_rates) {
97 		clen = IEEE80211_MAX_SUPP_RATES - bss->supp_rates_len;
98 		if (clen > elems->supp_rates_len)
99 			clen = elems->supp_rates_len;
100 		memcpy(&bss->supp_rates[bss->supp_rates_len], elems->supp_rates,
101 		       clen);
102 		bss->supp_rates_len += clen;
103 	}
104 	if (elems->ext_supp_rates) {
105 		clen = IEEE80211_MAX_SUPP_RATES - bss->supp_rates_len;
106 		if (clen > elems->ext_supp_rates_len)
107 			clen = elems->ext_supp_rates_len;
108 		memcpy(&bss->supp_rates[bss->supp_rates_len],
109 		       elems->ext_supp_rates, clen);
110 		bss->supp_rates_len += clen;
111 	}
112 
113 	bss->wmm_used = elems->wmm_param || elems->wmm_info;
114 
115 	if (!beacon)
116 		bss->last_probe_resp = jiffies;
117 
118 	return bss;
119 }
120 
121 ieee80211_rx_result
122 ieee80211_scan_rx(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb)
123 {
124 	struct ieee80211_rx_status *rx_status = IEEE80211_SKB_RXCB(skb);
125 	struct ieee80211_mgmt *mgmt;
126 	struct ieee80211_bss *bss;
127 	u8 *elements;
128 	struct ieee80211_channel *channel;
129 	size_t baselen;
130 	int freq;
131 	__le16 fc;
132 	bool presp, beacon = false;
133 	struct ieee802_11_elems elems;
134 
135 	if (skb->len < 2)
136 		return RX_DROP_UNUSABLE;
137 
138 	mgmt = (struct ieee80211_mgmt *) skb->data;
139 	fc = mgmt->frame_control;
140 
141 	if (ieee80211_is_ctl(fc))
142 		return RX_CONTINUE;
143 
144 	if (skb->len < 24)
145 		return RX_DROP_MONITOR;
146 
147 	presp = ieee80211_is_probe_resp(fc);
148 	if (presp) {
149 		/* ignore ProbeResp to foreign address */
150 		if (memcmp(mgmt->da, sdata->dev->dev_addr, ETH_ALEN))
151 			return RX_DROP_MONITOR;
152 
153 		presp = true;
154 		elements = mgmt->u.probe_resp.variable;
155 		baselen = offsetof(struct ieee80211_mgmt, u.probe_resp.variable);
156 	} else {
157 		beacon = ieee80211_is_beacon(fc);
158 		baselen = offsetof(struct ieee80211_mgmt, u.beacon.variable);
159 		elements = mgmt->u.beacon.variable;
160 	}
161 
162 	if (!presp && !beacon)
163 		return RX_CONTINUE;
164 
165 	if (baselen > skb->len)
166 		return RX_DROP_MONITOR;
167 
168 	ieee802_11_parse_elems(elements, skb->len - baselen, &elems);
169 
170 	if (elems.ds_params && elems.ds_params_len == 1)
171 		freq = ieee80211_channel_to_frequency(elems.ds_params[0]);
172 	else
173 		freq = rx_status->freq;
174 
175 	channel = ieee80211_get_channel(sdata->local->hw.wiphy, freq);
176 
177 	if (!channel || channel->flags & IEEE80211_CHAN_DISABLED)
178 		return RX_DROP_MONITOR;
179 
180 	bss = ieee80211_bss_info_update(sdata->local, rx_status,
181 					mgmt, skb->len, &elems,
182 					channel, beacon);
183 	if (bss)
184 		ieee80211_rx_bss_put(sdata->local, bss);
185 
186 	dev_kfree_skb(skb);
187 	return RX_QUEUED;
188 }
189 
190 /* return false if no more work */
191 static bool ieee80211_prep_hw_scan(struct ieee80211_local *local)
192 {
193 	struct cfg80211_scan_request *req = local->scan_req;
194 	enum ieee80211_band band;
195 	int i, ielen, n_chans;
196 
197 	do {
198 		if (local->hw_scan_band == IEEE80211_NUM_BANDS)
199 			return false;
200 
201 		band = local->hw_scan_band;
202 		n_chans = 0;
203 		for (i = 0; i < req->n_channels; i++) {
204 			if (req->channels[i]->band == band) {
205 				local->hw_scan_req->channels[n_chans] =
206 							req->channels[i];
207 				n_chans++;
208 			}
209 		}
210 
211 		local->hw_scan_band++;
212 	} while (!n_chans);
213 
214 	local->hw_scan_req->n_channels = n_chans;
215 
216 	ielen = ieee80211_build_preq_ies(local, (u8 *)local->hw_scan_req->ie,
217 					 req->ie, req->ie_len, band);
218 	local->hw_scan_req->ie_len = ielen;
219 
220 	return true;
221 }
222 
223 /*
224  * inform AP that we will go to sleep so that it will buffer the frames
225  * while we scan
226  */
227 static void ieee80211_scan_ps_enable(struct ieee80211_sub_if_data *sdata)
228 {
229 	struct ieee80211_local *local = sdata->local;
230 
231 	local->scan_ps_enabled = false;
232 
233 	/* FIXME: what to do when local->pspolling is true? */
234 
235 	del_timer_sync(&local->dynamic_ps_timer);
236 	cancel_work_sync(&local->dynamic_ps_enable_work);
237 
238 	if (local->hw.conf.flags & IEEE80211_CONF_PS) {
239 		local->scan_ps_enabled = true;
240 		local->hw.conf.flags &= ~IEEE80211_CONF_PS;
241 		ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
242 	}
243 
244 	if (!(local->scan_ps_enabled) ||
245 	    !(local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK))
246 		/*
247 		 * If power save was enabled, no need to send a nullfunc
248 		 * frame because AP knows that we are sleeping. But if the
249 		 * hardware is creating the nullfunc frame for power save
250 		 * status (ie. IEEE80211_HW_PS_NULLFUNC_STACK is not
251 		 * enabled) and power save was enabled, the firmware just
252 		 * sent a null frame with power save disabled. So we need
253 		 * to send a new nullfunc frame to inform the AP that we
254 		 * are again sleeping.
255 		 */
256 		ieee80211_send_nullfunc(local, sdata, 1);
257 }
258 
259 /* inform AP that we are awake again, unless power save is enabled */
260 static void ieee80211_scan_ps_disable(struct ieee80211_sub_if_data *sdata)
261 {
262 	struct ieee80211_local *local = sdata->local;
263 
264 	if (!local->ps_sdata)
265 		ieee80211_send_nullfunc(local, sdata, 0);
266 	else if (local->scan_ps_enabled) {
267 		/*
268 		 * In !IEEE80211_HW_PS_NULLFUNC_STACK case the hardware
269 		 * will send a nullfunc frame with the powersave bit set
270 		 * even though the AP already knows that we are sleeping.
271 		 * This could be avoided by sending a null frame with power
272 		 * save bit disabled before enabling the power save, but
273 		 * this doesn't gain anything.
274 		 *
275 		 * When IEEE80211_HW_PS_NULLFUNC_STACK is enabled, no need
276 		 * to send a nullfunc frame because AP already knows that
277 		 * we are sleeping, let's just enable power save mode in
278 		 * hardware.
279 		 */
280 		local->hw.conf.flags |= IEEE80211_CONF_PS;
281 		ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
282 	} else if (local->hw.conf.dynamic_ps_timeout > 0) {
283 		/*
284 		 * If IEEE80211_CONF_PS was not set and the dynamic_ps_timer
285 		 * had been running before leaving the operating channel,
286 		 * restart the timer now and send a nullfunc frame to inform
287 		 * the AP that we are awake.
288 		 */
289 		ieee80211_send_nullfunc(local, sdata, 0);
290 		mod_timer(&local->dynamic_ps_timer, jiffies +
291 			  msecs_to_jiffies(local->hw.conf.dynamic_ps_timeout));
292 	}
293 }
294 
295 void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
296 {
297 	struct ieee80211_local *local = hw_to_local(hw);
298 	struct ieee80211_sub_if_data *sdata;
299 	bool was_hw_scan;
300 
301 	mutex_lock(&local->scan_mtx);
302 
303 	/*
304 	 * It's ok to abort a not-yet-running scan (that
305 	 * we have one at all will be verified by checking
306 	 * local->scan_req next), but not to complete it
307 	 * successfully.
308 	 */
309 	if (WARN_ON(!local->scanning && !aborted))
310 		aborted = true;
311 
312 	if (WARN_ON(!local->scan_req)) {
313 		mutex_unlock(&local->scan_mtx);
314 		return;
315 	}
316 
317 	was_hw_scan = test_bit(SCAN_HW_SCANNING, &local->scanning);
318 	if (was_hw_scan && !aborted && ieee80211_prep_hw_scan(local)) {
319 		ieee80211_queue_delayed_work(&local->hw,
320 					     &local->scan_work, 0);
321 		mutex_unlock(&local->scan_mtx);
322 		return;
323 	}
324 
325 	kfree(local->hw_scan_req);
326 	local->hw_scan_req = NULL;
327 
328 	if (local->scan_req != local->int_scan_req)
329 		cfg80211_scan_done(local->scan_req, aborted);
330 	local->scan_req = NULL;
331 	local->scan_sdata = NULL;
332 
333 	local->scanning = 0;
334 	local->scan_channel = NULL;
335 
336 	/* we only have to protect scan_req and hw/sw scan */
337 	mutex_unlock(&local->scan_mtx);
338 
339 	ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
340 	if (was_hw_scan)
341 		goto done;
342 
343 	ieee80211_configure_filter(local);
344 
345 	drv_sw_scan_complete(local);
346 
347 	mutex_lock(&local->iflist_mtx);
348 	list_for_each_entry(sdata, &local->interfaces, list) {
349 		if (!netif_running(sdata->dev))
350 			continue;
351 
352 		/* Tell AP we're back */
353 		if (sdata->vif.type == NL80211_IFTYPE_STATION) {
354 			if (sdata->u.mgd.associated) {
355 				ieee80211_scan_ps_disable(sdata);
356 				netif_tx_wake_all_queues(sdata->dev);
357 			}
358 		} else
359 			netif_tx_wake_all_queues(sdata->dev);
360 
361 		/* re-enable beaconing */
362 		if (sdata->vif.type == NL80211_IFTYPE_AP ||
363 		    sdata->vif.type == NL80211_IFTYPE_ADHOC ||
364 		    sdata->vif.type == NL80211_IFTYPE_MESH_POINT)
365 			ieee80211_bss_info_change_notify(
366 				sdata, BSS_CHANGED_BEACON_ENABLED);
367 	}
368 	mutex_unlock(&local->iflist_mtx);
369 
370  done:
371 	ieee80211_recalc_idle(local);
372 	ieee80211_mlme_notify_scan_completed(local);
373 	ieee80211_ibss_notify_scan_completed(local);
374 	ieee80211_mesh_notify_scan_completed(local);
375 }
376 EXPORT_SYMBOL(ieee80211_scan_completed);
377 
378 static int ieee80211_start_sw_scan(struct ieee80211_local *local)
379 {
380 	struct ieee80211_sub_if_data *sdata;
381 
382 	/*
383 	 * Hardware/driver doesn't support hw_scan, so use software
384 	 * scanning instead. First send a nullfunc frame with power save
385 	 * bit on so that AP will buffer the frames for us while we are not
386 	 * listening, then send probe requests to each channel and wait for
387 	 * the responses. After all channels are scanned, tune back to the
388 	 * original channel and send a nullfunc frame with power save bit
389 	 * off to trigger the AP to send us all the buffered frames.
390 	 *
391 	 * Note that while local->sw_scanning is true everything else but
392 	 * nullfunc frames and probe requests will be dropped in
393 	 * ieee80211_tx_h_check_assoc().
394 	 */
395 	drv_sw_scan_start(local);
396 
397 	mutex_lock(&local->iflist_mtx);
398 	list_for_each_entry(sdata, &local->interfaces, list) {
399 		if (!netif_running(sdata->dev))
400 			continue;
401 
402 		/* disable beaconing */
403 		if (sdata->vif.type == NL80211_IFTYPE_AP ||
404 		    sdata->vif.type == NL80211_IFTYPE_ADHOC ||
405 		    sdata->vif.type == NL80211_IFTYPE_MESH_POINT)
406 			ieee80211_bss_info_change_notify(
407 				sdata, BSS_CHANGED_BEACON_ENABLED);
408 
409 		/*
410 		 * only handle non-STA interfaces here, STA interfaces
411 		 * are handled in the scan state machine
412 		 */
413 		if (sdata->vif.type != NL80211_IFTYPE_STATION)
414 			netif_tx_stop_all_queues(sdata->dev);
415 	}
416 	mutex_unlock(&local->iflist_mtx);
417 
418 	local->next_scan_state = SCAN_DECISION;
419 	local->scan_channel_idx = 0;
420 
421 	ieee80211_configure_filter(local);
422 
423 	/* TODO: start scan as soon as all nullfunc frames are ACKed */
424 	ieee80211_queue_delayed_work(&local->hw,
425 				     &local->scan_work,
426 				     IEEE80211_CHANNEL_TIME);
427 
428 	return 0;
429 }
430 
431 
432 static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
433 				  struct cfg80211_scan_request *req)
434 {
435 	struct ieee80211_local *local = sdata->local;
436 	struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
437 	int rc;
438 
439 	if (local->scan_req)
440 		return -EBUSY;
441 
442 	if (req != local->int_scan_req &&
443 	    sdata->vif.type == NL80211_IFTYPE_STATION &&
444 	    !list_empty(&ifmgd->work_list)) {
445 		/* actually wait for the work it's doing to finish/time out */
446 		set_bit(IEEE80211_STA_REQ_SCAN, &ifmgd->request);
447 		local->scan_req = req;
448 		local->scan_sdata = sdata;
449 		return 0;
450 	}
451 
452 	if (local->ops->hw_scan) {
453 		u8 *ies;
454 
455 		local->hw_scan_req = kmalloc(
456 				sizeof(*local->hw_scan_req) +
457 				req->n_channels * sizeof(req->channels[0]) +
458 				2 + IEEE80211_MAX_SSID_LEN + local->scan_ies_len +
459 				req->ie_len, GFP_KERNEL);
460 		if (!local->hw_scan_req)
461 			return -ENOMEM;
462 
463 		local->hw_scan_req->ssids = req->ssids;
464 		local->hw_scan_req->n_ssids = req->n_ssids;
465 		ies = (u8 *)local->hw_scan_req +
466 			sizeof(*local->hw_scan_req) +
467 			req->n_channels * sizeof(req->channels[0]);
468 		local->hw_scan_req->ie = ies;
469 
470 		local->hw_scan_band = 0;
471 	}
472 
473 	local->scan_req = req;
474 	local->scan_sdata = sdata;
475 
476 	if (local->ops->hw_scan)
477 		__set_bit(SCAN_HW_SCANNING, &local->scanning);
478 	else
479 		__set_bit(SCAN_SW_SCANNING, &local->scanning);
480 	/*
481 	 * Kicking off the scan need not be protected,
482 	 * only the scan variable stuff, since now
483 	 * local->scan_req is assigned and other callers
484 	 * will abort their scan attempts.
485 	 *
486 	 * This avoids getting a scan_mtx -> iflist_mtx
487 	 * dependency, so that the scan completed calls
488 	 * have more locking freedom.
489 	 */
490 
491 	ieee80211_recalc_idle(local);
492 	mutex_unlock(&local->scan_mtx);
493 
494 	if (local->ops->hw_scan) {
495 		WARN_ON(!ieee80211_prep_hw_scan(local));
496 		rc = drv_hw_scan(local, local->hw_scan_req);
497 	} else
498 		rc = ieee80211_start_sw_scan(local);
499 
500 	mutex_lock(&local->scan_mtx);
501 
502 	if (rc) {
503 		kfree(local->hw_scan_req);
504 		local->hw_scan_req = NULL;
505 		local->scanning = 0;
506 
507 		ieee80211_recalc_idle(local);
508 
509 		local->scan_req = NULL;
510 		local->scan_sdata = NULL;
511 	}
512 
513 	return rc;
514 }
515 
516 static int ieee80211_scan_state_decision(struct ieee80211_local *local,
517 					 unsigned long *next_delay)
518 {
519 	bool associated = false;
520 	struct ieee80211_sub_if_data *sdata;
521 
522 	/* if no more bands/channels left, complete scan and advance to the idle state */
523 	if (local->scan_channel_idx >= local->scan_req->n_channels) {
524 		ieee80211_scan_completed(&local->hw, false);
525 		return 1;
526 	}
527 
528 	/* check if at least one STA interface is associated */
529 	mutex_lock(&local->iflist_mtx);
530 	list_for_each_entry(sdata, &local->interfaces, list) {
531 		if (!netif_running(sdata->dev))
532 			continue;
533 
534 		if (sdata->vif.type == NL80211_IFTYPE_STATION) {
535 			if (sdata->u.mgd.associated) {
536 				associated = true;
537 				break;
538 			}
539 		}
540 	}
541 	mutex_unlock(&local->iflist_mtx);
542 
543 	if (local->scan_channel) {
544 		/*
545 		 * we're currently scanning a different channel, let's
546 		 * switch back to the operating channel now if at least
547 		 * one interface is associated. Otherwise just scan the
548 		 * next channel
549 		 */
550 		if (associated)
551 			local->next_scan_state = SCAN_ENTER_OPER_CHANNEL;
552 		else
553 			local->next_scan_state = SCAN_SET_CHANNEL;
554 	} else {
555 		/*
556 		 * we're on the operating channel currently, let's
557 		 * leave that channel now to scan another one
558 		 */
559 		local->next_scan_state = SCAN_LEAVE_OPER_CHANNEL;
560 	}
561 
562 	*next_delay = 0;
563 	return 0;
564 }
565 
566 static void ieee80211_scan_state_leave_oper_channel(struct ieee80211_local *local,
567 						    unsigned long *next_delay)
568 {
569 	struct ieee80211_sub_if_data *sdata;
570 
571 	/*
572 	 * notify the AP about us leaving the channel and stop all STA interfaces
573 	 */
574 	mutex_lock(&local->iflist_mtx);
575 	list_for_each_entry(sdata, &local->interfaces, list) {
576 		if (!netif_running(sdata->dev))
577 			continue;
578 
579 		if (sdata->vif.type == NL80211_IFTYPE_STATION) {
580 			netif_tx_stop_all_queues(sdata->dev);
581 			if (sdata->u.mgd.associated)
582 				ieee80211_scan_ps_enable(sdata);
583 		}
584 	}
585 	mutex_unlock(&local->iflist_mtx);
586 
587 	__set_bit(SCAN_OFF_CHANNEL, &local->scanning);
588 
589 	/* advance to the next channel to be scanned */
590 	*next_delay = HZ / 10;
591 	local->next_scan_state = SCAN_SET_CHANNEL;
592 }
593 
594 static void ieee80211_scan_state_enter_oper_channel(struct ieee80211_local *local,
595 						    unsigned long *next_delay)
596 {
597 	struct ieee80211_sub_if_data *sdata = local->scan_sdata;
598 
599 	/* switch back to the operating channel */
600 	local->scan_channel = NULL;
601 	ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
602 
603 	/*
604 	 * notify the AP about us being back and restart all STA interfaces
605 	 */
606 	mutex_lock(&local->iflist_mtx);
607 	list_for_each_entry(sdata, &local->interfaces, list) {
608 		if (!netif_running(sdata->dev))
609 			continue;
610 
611 		/* Tell AP we're back */
612 		if (sdata->vif.type == NL80211_IFTYPE_STATION) {
613 			if (sdata->u.mgd.associated)
614 				ieee80211_scan_ps_disable(sdata);
615 			netif_tx_wake_all_queues(sdata->dev);
616 		}
617 	}
618 	mutex_unlock(&local->iflist_mtx);
619 
620 	__clear_bit(SCAN_OFF_CHANNEL, &local->scanning);
621 
622 	*next_delay = HZ / 5;
623 	local->next_scan_state = SCAN_DECISION;
624 }
625 
626 static void ieee80211_scan_state_set_channel(struct ieee80211_local *local,
627 					     unsigned long *next_delay)
628 {
629 	int skip;
630 	struct ieee80211_channel *chan;
631 
632 	skip = 0;
633 	chan = local->scan_req->channels[local->scan_channel_idx];
634 
635 	local->scan_channel = chan;
636 	if (ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL))
637 		skip = 1;
638 
639 	/* advance state machine to next channel/band */
640 	local->scan_channel_idx++;
641 
642 	if (skip) {
643 		/* if we skip this channel return to the decision state */
644 		local->next_scan_state = SCAN_DECISION;
645 		return;
646 	}
647 
648 	/*
649 	 * Probe delay is used to update the NAV, cf. 11.1.3.2.2
650 	 * (which unfortunately doesn't say _why_ step a) is done,
651 	 * but it waits for the probe delay or until a frame is
652 	 * received - and the received frame would update the NAV).
653 	 * For now, we do not support waiting until a frame is
654 	 * received.
655 	 *
656 	 * In any case, it is not necessary for a passive scan.
657 	 */
658 	if (chan->flags & IEEE80211_CHAN_PASSIVE_SCAN ||
659 	    !local->scan_req->n_ssids) {
660 		*next_delay = IEEE80211_PASSIVE_CHANNEL_TIME;
661 		local->next_scan_state = SCAN_DECISION;
662 		return;
663 	}
664 
665 	/* active scan, send probes */
666 	*next_delay = IEEE80211_PROBE_DELAY;
667 	local->next_scan_state = SCAN_SEND_PROBE;
668 }
669 
670 static void ieee80211_scan_state_send_probe(struct ieee80211_local *local,
671 					    unsigned long *next_delay)
672 {
673 	int i;
674 	struct ieee80211_sub_if_data *sdata = local->scan_sdata;
675 
676 	for (i = 0; i < local->scan_req->n_ssids; i++)
677 		ieee80211_send_probe_req(
678 			sdata, NULL,
679 			local->scan_req->ssids[i].ssid,
680 			local->scan_req->ssids[i].ssid_len,
681 			local->scan_req->ie, local->scan_req->ie_len);
682 
683 	/*
684 	 * After sending probe requests, wait for probe responses
685 	 * on the channel.
686 	 */
687 	*next_delay = IEEE80211_CHANNEL_TIME;
688 	local->next_scan_state = SCAN_DECISION;
689 }
690 
691 void ieee80211_scan_work(struct work_struct *work)
692 {
693 	struct ieee80211_local *local =
694 		container_of(work, struct ieee80211_local, scan_work.work);
695 	struct ieee80211_sub_if_data *sdata = local->scan_sdata;
696 	unsigned long next_delay = 0;
697 
698 	mutex_lock(&local->scan_mtx);
699 	if (!sdata || !local->scan_req) {
700 		mutex_unlock(&local->scan_mtx);
701 		return;
702 	}
703 
704 	if (local->hw_scan_req) {
705 		int rc = drv_hw_scan(local, local->hw_scan_req);
706 		mutex_unlock(&local->scan_mtx);
707 		if (rc)
708 			ieee80211_scan_completed(&local->hw, true);
709 		return;
710 	}
711 
712 	if (local->scan_req && !local->scanning) {
713 		struct cfg80211_scan_request *req = local->scan_req;
714 		int rc;
715 
716 		local->scan_req = NULL;
717 		local->scan_sdata = NULL;
718 
719 		rc = __ieee80211_start_scan(sdata, req);
720 		mutex_unlock(&local->scan_mtx);
721 
722 		if (rc)
723 			ieee80211_scan_completed(&local->hw, true);
724 		return;
725 	}
726 
727 	mutex_unlock(&local->scan_mtx);
728 
729 	/*
730 	 * Avoid re-scheduling when the sdata is going away.
731 	 */
732 	if (!netif_running(sdata->dev)) {
733 		ieee80211_scan_completed(&local->hw, true);
734 		return;
735 	}
736 
737 	/*
738 	 * as long as no delay is required advance immediately
739 	 * without scheduling a new work
740 	 */
741 	do {
742 		switch (local->next_scan_state) {
743 		case SCAN_DECISION:
744 			if (ieee80211_scan_state_decision(local, &next_delay))
745 				return;
746 			break;
747 		case SCAN_SET_CHANNEL:
748 			ieee80211_scan_state_set_channel(local, &next_delay);
749 			break;
750 		case SCAN_SEND_PROBE:
751 			ieee80211_scan_state_send_probe(local, &next_delay);
752 			break;
753 		case SCAN_LEAVE_OPER_CHANNEL:
754 			ieee80211_scan_state_leave_oper_channel(local, &next_delay);
755 			break;
756 		case SCAN_ENTER_OPER_CHANNEL:
757 			ieee80211_scan_state_enter_oper_channel(local, &next_delay);
758 			break;
759 		}
760 	} while (next_delay == 0);
761 
762 	ieee80211_queue_delayed_work(&local->hw, &local->scan_work, next_delay);
763 }
764 
765 int ieee80211_request_scan(struct ieee80211_sub_if_data *sdata,
766 			   struct cfg80211_scan_request *req)
767 {
768 	int res;
769 
770 	mutex_lock(&sdata->local->scan_mtx);
771 	res = __ieee80211_start_scan(sdata, req);
772 	mutex_unlock(&sdata->local->scan_mtx);
773 
774 	return res;
775 }
776 
777 int ieee80211_request_internal_scan(struct ieee80211_sub_if_data *sdata,
778 				    const u8 *ssid, u8 ssid_len)
779 {
780 	struct ieee80211_local *local = sdata->local;
781 	int ret = -EBUSY;
782 
783 	mutex_lock(&local->scan_mtx);
784 
785 	/* busy scanning */
786 	if (local->scan_req)
787 		goto unlock;
788 
789 	memcpy(local->int_scan_req->ssids[0].ssid, ssid, IEEE80211_MAX_SSID_LEN);
790 	local->int_scan_req->ssids[0].ssid_len = ssid_len;
791 
792 	ret = __ieee80211_start_scan(sdata, sdata->local->int_scan_req);
793  unlock:
794 	mutex_unlock(&local->scan_mtx);
795 	return ret;
796 }
797 
798 void ieee80211_scan_cancel(struct ieee80211_local *local)
799 {
800 	bool abortscan;
801 
802 	cancel_delayed_work_sync(&local->scan_work);
803 
804 	/*
805 	 * Only call this function when a scan can't be
806 	 * queued -- mostly at suspend under RTNL.
807 	 */
808 	mutex_lock(&local->scan_mtx);
809 	abortscan = test_bit(SCAN_SW_SCANNING, &local->scanning) ||
810 		    (!local->scanning && local->scan_req);
811 	mutex_unlock(&local->scan_mtx);
812 
813 	if (abortscan)
814 		ieee80211_scan_completed(&local->hw, true);
815 }
816