xref: /freebsd/sys/net80211/ieee80211_scan_sw.c (revision 39ee7a7a6bdd1557b1c3532abf60d139798ac88b)
1 /*-
2  * Copyright (c) 2002-2008 Sam Leffler, Errno Consulting
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24  */
25 
26 #include <sys/cdefs.h>
27 __FBSDID("$FreeBSD$");
28 
29 /*
30  * IEEE 802.11 scanning support.
31  */
32 #include "opt_wlan.h"
33 
34 #include <sys/param.h>
35 #include <sys/systm.h>
36 #include <sys/proc.h>
37 #include <sys/kernel.h>
38 #include <sys/condvar.h>
39 
40 #include <sys/socket.h>
41 
42 #include <net/if.h>
43 #include <net/if_var.h>
44 #include <net/if_media.h>
45 #include <net/ethernet.h>
46 
47 #include <net80211/ieee80211_var.h>
48 
49 #include <net80211/ieee80211_scan_sw.h>
50 
51 #include <net/bpf.h>
52 
53 struct scan_state {
54 	struct ieee80211_scan_state base;	/* public state */
55 
56 	u_int		ss_iflags;		/* flags used internally */
57 #define	ISCAN_MINDWELL 	0x0001		/* min dwell time reached */
58 #define	ISCAN_DISCARD	0x0002		/* discard rx'd frames */
59 #define	ISCAN_CANCEL	0x0004		/* cancel current scan */
60 #define	ISCAN_ABORT	0x0008		/* end the scan immediately */
61 	unsigned long	ss_chanmindwell;	/* min dwell on curchan */
62 	unsigned long	ss_scanend;		/* time scan must stop */
63 	u_int		ss_duration;		/* duration for next scan */
64 	struct task	ss_scan_task;		/* scan execution */
65 	struct cv	ss_scan_cv;		/* scan signal */
66 	struct callout	ss_scan_timer;		/* scan timer */
67 };
68 #define	SCAN_PRIVATE(ss)	((struct scan_state *) ss)
69 
70 /*
71  * Amount of time to go off-channel during a background
72  * scan.  This value should be large enough to catch most
73  * ap's but short enough that we can return on-channel
74  * before our listen interval expires.
75  *
76  * XXX tunable
77  * XXX check against configured listen interval
78  */
79 #define	IEEE80211_SCAN_OFFCHANNEL	msecs_to_ticks(150)
80 
81 /*
82  * Roaming-related defaults.  RSSI thresholds are as returned by the
83  * driver (.5dBm).  Transmit rate thresholds are IEEE rate codes (i.e
84  * .5M units) or MCS.
85  */
86 /* rssi thresholds */
87 #define	ROAM_RSSI_11A_DEFAULT		14	/* 11a bss */
88 #define	ROAM_RSSI_11B_DEFAULT		14	/* 11b bss */
89 #define	ROAM_RSSI_11BONLY_DEFAULT	14	/* 11b-only bss */
90 /* transmit rate thresholds */
91 #define	ROAM_RATE_11A_DEFAULT		2*12	/* 11a bss */
92 #define	ROAM_RATE_11B_DEFAULT		2*5	/* 11b bss */
93 #define	ROAM_RATE_11BONLY_DEFAULT	2*1	/* 11b-only bss */
94 #define	ROAM_RATE_HALF_DEFAULT		2*6	/* half-width 11a/g bss */
95 #define	ROAM_RATE_QUARTER_DEFAULT	2*3	/* quarter-width 11a/g bss */
96 #define	ROAM_MCS_11N_DEFAULT		(1 | IEEE80211_RATE_MCS) /* 11n bss */
97 
98 static	void scan_curchan(struct ieee80211_scan_state *, unsigned long);
99 static	void scan_mindwell(struct ieee80211_scan_state *);
100 static	void scan_signal(void *);
101 static	void scan_task(void *, int);
102 
103 MALLOC_DEFINE(M_80211_SCAN, "80211scan", "802.11 scan state");
104 
105 static void
106 ieee80211_swscan_detach(struct ieee80211com *ic)
107 {
108 	struct ieee80211_scan_state *ss = ic->ic_scan;
109 
110 	if (ss != NULL) {
111 		IEEE80211_LOCK(ic);
112 		SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_ABORT;
113 		scan_signal(ss);
114 		IEEE80211_UNLOCK(ic);
115 		ieee80211_draintask(ic, &SCAN_PRIVATE(ss)->ss_scan_task);
116 		callout_drain(&SCAN_PRIVATE(ss)->ss_scan_timer);
117 		KASSERT((ic->ic_flags & IEEE80211_F_SCAN) == 0,
118 		    ("scan still running"));
119 
120 		/*
121 		 * For now, do the ss_ops detach here rather
122 		 * than ieee80211_scan_detach().
123 		 *
124 		 * I'll figure out how to cleanly split things up
125 		 * at a later date.
126 		 */
127 		if (ss->ss_ops != NULL) {
128 			ss->ss_ops->scan_detach(ss);
129 			ss->ss_ops = NULL;
130 		}
131 		ic->ic_scan = NULL;
132 		IEEE80211_FREE(SCAN_PRIVATE(ss), M_80211_SCAN);
133 	}
134 }
135 
136 static void
137 ieee80211_swscan_vattach(struct ieee80211vap *vap)
138 {
139 	/* nothing to do for now */
140 	/*
141 	 * TODO: all of the vap scan calls should be methods!
142 	 */
143 
144 }
145 
146 static void
147 ieee80211_swscan_vdetach(struct ieee80211vap *vap)
148 {
149 	struct ieee80211com *ic = vap->iv_ic;
150 	struct ieee80211_scan_state *ss;
151 
152 	IEEE80211_LOCK_ASSERT(ic);
153 	ss = ic->ic_scan;
154 	if (ss != NULL && ss->ss_vap == vap) {
155 		if (ic->ic_flags & IEEE80211_F_SCAN) {
156 			SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_ABORT;
157 			scan_signal(ss);
158 		}
159 	}
160 }
161 
162 static void
163 ieee80211_swscan_set_scan_duration(struct ieee80211vap *vap, u_int duration)
164 {
165 	struct ieee80211com *ic = vap->iv_ic;
166 	struct ieee80211_scan_state *ss = ic->ic_scan;
167 
168 	IEEE80211_LOCK_ASSERT(ic);
169 
170 	/* NB: flush frames rx'd before 1st channel change */
171 	SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_DISCARD;
172 	SCAN_PRIVATE(ss)->ss_duration = duration;
173 }
174 
175 /*
176  * Start a scan unless one is already going.
177  */
178 static int
179 ieee80211_swscan_start_scan_locked(const struct ieee80211_scanner *scan,
180 	struct ieee80211vap *vap, int flags, u_int duration,
181 	u_int mindwell, u_int maxdwell,
182 	u_int nssid, const struct ieee80211_scan_ssid ssids[])
183 {
184 	struct ieee80211com *ic = vap->iv_ic;
185 	struct ieee80211_scan_state *ss = ic->ic_scan;
186 
187 	IEEE80211_LOCK_ASSERT(ic);
188 
189 	if (ic->ic_flags & IEEE80211_F_CSAPENDING) {
190 		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
191 		    "%s: scan inhibited by pending channel change\n", __func__);
192 	} else if ((ic->ic_flags & IEEE80211_F_SCAN) == 0) {
193 		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
194 		    "%s: %s scan, duration %u mindwell %u maxdwell %u, desired mode %s, %s%s%s%s%s%s\n"
195 		    , __func__
196 		    , flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive"
197 		    , duration, mindwell, maxdwell
198 		    , ieee80211_phymode_name[vap->iv_des_mode]
199 		    , flags & IEEE80211_SCAN_FLUSH ? "flush" : "append"
200 		    , flags & IEEE80211_SCAN_NOPICK ? ", nopick" : ""
201 		    , flags & IEEE80211_SCAN_NOJOIN ? ", nojoin" : ""
202 		    , flags & IEEE80211_SCAN_NOBCAST ? ", nobcast" : ""
203 		    , flags & IEEE80211_SCAN_PICK1ST ? ", pick1st" : ""
204 		    , flags & IEEE80211_SCAN_ONCE ? ", once" : ""
205 		);
206 
207 		ieee80211_scan_update_locked(vap, scan);
208 		if (ss->ss_ops != NULL) {
209 			if ((flags & IEEE80211_SCAN_NOSSID) == 0)
210 				ieee80211_scan_copy_ssid(vap, ss, nssid, ssids);
211 
212 			/* NB: top 4 bits for internal use */
213 			ss->ss_flags = flags & 0xfff;
214 			if (ss->ss_flags & IEEE80211_SCAN_ACTIVE)
215 				vap->iv_stats.is_scan_active++;
216 			else
217 				vap->iv_stats.is_scan_passive++;
218 			if (flags & IEEE80211_SCAN_FLUSH)
219 				ss->ss_ops->scan_flush(ss);
220 			if (flags & IEEE80211_SCAN_BGSCAN)
221 				ic->ic_flags_ext |= IEEE80211_FEXT_BGSCAN;
222 
223 			/* Set duration for this particular scan */
224 			ieee80211_swscan_set_scan_duration(vap, duration);
225 
226 			ss->ss_next = 0;
227 			ss->ss_mindwell = mindwell;
228 			ss->ss_maxdwell = maxdwell;
229 			/* NB: scan_start must be before the scan runtask */
230 			ss->ss_ops->scan_start(ss, vap);
231 #ifdef IEEE80211_DEBUG
232 			if (ieee80211_msg_scan(vap))
233 				ieee80211_scan_dump(ss);
234 #endif /* IEEE80211_DEBUG */
235 			ic->ic_flags |= IEEE80211_F_SCAN;
236 
237 			/* Start scan task */
238 			ieee80211_runtask(ic, &SCAN_PRIVATE(ss)->ss_scan_task);
239 		}
240 		return 1;
241 	} else {
242 		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
243 		    "%s: %s scan already in progress\n", __func__,
244 		    ss->ss_flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive");
245 	}
246 	return 0;
247 }
248 
249 
250 /*
251  * Start a scan unless one is already going.
252  *
253  * Called without the comlock held; grab the comlock as appropriate.
254  */
255 static int
256 ieee80211_swscan_start_scan(const struct ieee80211_scanner *scan,
257     struct ieee80211vap *vap, int flags,
258     u_int duration, u_int mindwell, u_int maxdwell,
259     u_int nssid, const struct ieee80211_scan_ssid ssids[])
260 {
261 	struct ieee80211com *ic = vap->iv_ic;
262 	int result;
263 
264 	IEEE80211_UNLOCK_ASSERT(ic);
265 
266 	IEEE80211_LOCK(ic);
267 	result = ieee80211_swscan_start_scan_locked(scan, vap, flags, duration,
268 	    mindwell, maxdwell, nssid, ssids);
269 	IEEE80211_UNLOCK(ic);
270 
271 	return result;
272 }
273 
274 /*
275  * Check the scan cache for an ap/channel to use; if that
276  * fails then kick off a new scan.
277  *
278  * Called with the comlock held.
279  *
280  * XXX TODO: split out!
281  */
282 static int
283 ieee80211_swscan_check_scan(const struct ieee80211_scanner *scan,
284     struct ieee80211vap *vap, int flags,
285     u_int duration, u_int mindwell, u_int maxdwell,
286     u_int nssid, const struct ieee80211_scan_ssid ssids[])
287 {
288 	struct ieee80211com *ic = vap->iv_ic;
289 	struct ieee80211_scan_state *ss = ic->ic_scan;
290 	int result;
291 
292 	IEEE80211_LOCK_ASSERT(ic);
293 
294 	if (ss->ss_ops != NULL) {
295 		/* XXX verify ss_ops matches vap->iv_opmode */
296 		if ((flags & IEEE80211_SCAN_NOSSID) == 0) {
297 			/*
298 			 * Update the ssid list and mark flags so if
299 			 * we call start_scan it doesn't duplicate work.
300 			 */
301 			ieee80211_scan_copy_ssid(vap, ss, nssid, ssids);
302 			flags |= IEEE80211_SCAN_NOSSID;
303 		}
304 		if ((ic->ic_flags & IEEE80211_F_SCAN) == 0 &&
305 		    (flags & IEEE80211_SCAN_FLUSH) == 0 &&
306 		    time_before(ticks, ic->ic_lastscan + vap->iv_scanvalid)) {
307 			/*
308 			 * We're not currently scanning and the cache is
309 			 * deemed hot enough to consult.  Lock out others
310 			 * by marking IEEE80211_F_SCAN while we decide if
311 			 * something is already in the scan cache we can
312 			 * use.  Also discard any frames that might come
313 			 * in while temporarily marked as scanning.
314 			 */
315 			SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_DISCARD;
316 			ic->ic_flags |= IEEE80211_F_SCAN;
317 
318 			/* NB: need to use supplied flags in check */
319 			ss->ss_flags = flags & 0xff;
320 			result = ss->ss_ops->scan_end(ss, vap);
321 
322 			ic->ic_flags &= ~IEEE80211_F_SCAN;
323 			SCAN_PRIVATE(ss)->ss_iflags &= ~ISCAN_DISCARD;
324 			if (result) {
325 				ieee80211_notify_scan_done(vap);
326 				return 1;
327 			}
328 		}
329 	}
330 	result = ieee80211_swscan_start_scan_locked(scan, vap, flags, duration,
331 	    mindwell, maxdwell, nssid, ssids);
332 
333 	return result;
334 }
335 
336 /*
337  * Restart a previous scan.  If the previous scan completed
338  * then we start again using the existing channel list.
339  */
340 static int
341 ieee80211_swscan_bg_scan(const struct ieee80211_scanner *scan,
342     struct ieee80211vap *vap, int flags)
343 {
344 	struct ieee80211com *ic = vap->iv_ic;
345 	struct ieee80211_scan_state *ss = ic->ic_scan;
346 
347 	/* XXX assert unlocked? */
348 	// IEEE80211_UNLOCK_ASSERT(ic);
349 
350 	IEEE80211_LOCK(ic);
351 	if ((ic->ic_flags & IEEE80211_F_SCAN) == 0) {
352 		u_int duration;
353 		/*
354 		 * Go off-channel for a fixed interval that is large
355 		 * enough to catch most ap's but short enough that
356 		 * we can return on-channel before our listen interval
357 		 * expires.
358 		 */
359 		duration = IEEE80211_SCAN_OFFCHANNEL;
360 
361 		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
362 		    "%s: %s scan, ticks %u duration %lu\n", __func__,
363 		    ss->ss_flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive",
364 		    ticks, duration);
365 
366 		ieee80211_scan_update_locked(vap, scan);
367 		if (ss->ss_ops != NULL) {
368 			ss->ss_vap = vap;
369 			/*
370 			 * A background scan does not select a new sta; it
371 			 * just refreshes the scan cache.  Also, indicate
372 			 * the scan logic should follow the beacon schedule:
373 			 * we go off-channel and scan for a while, then
374 			 * return to the bss channel to receive a beacon,
375 			 * then go off-channel again.  All during this time
376 			 * we notify the ap we're in power save mode.  When
377 			 * the scan is complete we leave power save mode.
378 			 * If any beacon indicates there are frames pending
379 			 * for us then we drop out of power save mode
380 			 * (and background scan) automatically by way of the
381 			 * usual sta power save logic.
382 			 */
383 			ss->ss_flags |= IEEE80211_SCAN_NOPICK
384 				     |  IEEE80211_SCAN_BGSCAN
385 				     |  flags
386 				     ;
387 			/* if previous scan completed, restart */
388 			if (ss->ss_next >= ss->ss_last) {
389 				if (ss->ss_flags & IEEE80211_SCAN_ACTIVE)
390 					vap->iv_stats.is_scan_active++;
391 				else
392 					vap->iv_stats.is_scan_passive++;
393 				/*
394 				 * NB: beware of the scan cache being flushed;
395 				 *     if the channel list is empty use the
396 				 *     scan_start method to populate it.
397 				 */
398 				ss->ss_next = 0;
399 				if (ss->ss_last != 0)
400 					ss->ss_ops->scan_restart(ss, vap);
401 				else {
402 					ss->ss_ops->scan_start(ss, vap);
403 #ifdef IEEE80211_DEBUG
404 					if (ieee80211_msg_scan(vap))
405 						ieee80211_scan_dump(ss);
406 #endif /* IEEE80211_DEBUG */
407 				}
408 			}
409 			ieee80211_swscan_set_scan_duration(vap, duration);
410 			ss->ss_maxdwell = duration;
411 			ic->ic_flags |= IEEE80211_F_SCAN;
412 			ic->ic_flags_ext |= IEEE80211_FEXT_BGSCAN;
413 			ieee80211_runtask(ic, &SCAN_PRIVATE(ss)->ss_scan_task);
414 		} else {
415 			/* XXX msg+stat */
416 		}
417 	} else {
418 		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
419 		    "%s: %s scan already in progress\n", __func__,
420 		    ss->ss_flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive");
421 	}
422 	IEEE80211_UNLOCK(ic);
423 
424 	/* NB: racey, does it matter? */
425 	return (ic->ic_flags & IEEE80211_F_SCAN);
426 }
427 
428 /*
429  * Cancel any scan currently going on for the specified vap.
430  */
431 static void
432 ieee80211_swscan_cancel_scan(struct ieee80211vap *vap)
433 {
434 	struct ieee80211com *ic = vap->iv_ic;
435 	struct ieee80211_scan_state *ss = ic->ic_scan;
436 
437 	IEEE80211_LOCK(ic);
438 	if ((ic->ic_flags & IEEE80211_F_SCAN) &&
439 	    ss->ss_vap == vap &&
440 	    (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) == 0) {
441 		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
442 		    "%s: cancel %s scan\n", __func__,
443 		    ss->ss_flags & IEEE80211_SCAN_ACTIVE ?
444 			"active" : "passive");
445 
446 		/* clear bg scan NOPICK and mark cancel request */
447 		ss->ss_flags &= ~IEEE80211_SCAN_NOPICK;
448 		SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_CANCEL;
449 		/* wake up the scan task */
450 		scan_signal(ss);
451 	} else {
452 		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
453 		    "%s: called; F_SCAN=%d, vap=%s, CANCEL=%d\n",
454 		        __func__,
455 			!! (ic->ic_flags & IEEE80211_F_SCAN),
456 			(ss->ss_vap == vap ? "match" : "nomatch"),
457 			!! (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL));
458 	}
459 	IEEE80211_UNLOCK(ic);
460 }
461 
462 /*
463  * Cancel any scan currently going on.
464  */
465 static void
466 ieee80211_swscan_cancel_anyscan(struct ieee80211vap *vap)
467 {
468 	struct ieee80211com *ic = vap->iv_ic;
469 	struct ieee80211_scan_state *ss = ic->ic_scan;
470 
471 	IEEE80211_LOCK(ic);
472 	if ((ic->ic_flags & IEEE80211_F_SCAN) &&
473 	    (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) == 0) {
474 		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
475 		    "%s: cancel %s scan\n", __func__,
476 		    ss->ss_flags & IEEE80211_SCAN_ACTIVE ?
477 			"active" : "passive");
478 
479 		/* clear bg scan NOPICK and mark cancel request */
480 		ss->ss_flags &= ~IEEE80211_SCAN_NOPICK;
481 		SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_CANCEL;
482 		/* wake up the scan task */
483 		scan_signal(ss);
484 	} else {
485 		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
486 		    "%s: called; F_SCAN=%d, vap=%s, CANCEL=%d\n",
487 		        __func__,
488 			!! (ic->ic_flags & IEEE80211_F_SCAN),
489 			(ss->ss_vap == vap ? "match" : "nomatch"),
490 			!! (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL));
491 	}
492 	IEEE80211_UNLOCK(ic);
493 }
494 
495 /*
496  * Public access to scan_next for drivers that manage
497  * scanning themselves (e.g. for firmware-based devices).
498  */
499 static void
500 ieee80211_swscan_scan_next(struct ieee80211vap *vap)
501 {
502 	struct ieee80211com *ic = vap->iv_ic;
503 	struct ieee80211_scan_state *ss = ic->ic_scan;
504 
505 	IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN, "%s: called\n", __func__);
506 
507 	/* wake up the scan task */
508 	IEEE80211_LOCK(ic);
509 	scan_signal(ss);
510 	IEEE80211_UNLOCK(ic);
511 }
512 
513 /*
514  * Public access to scan_next for drivers that are not able to scan single
515  * channels (e.g. for firmware-based devices).
516  */
517 static void
518 ieee80211_swscan_scan_done(struct ieee80211vap *vap)
519 {
520 	struct ieee80211com *ic = vap->iv_ic;
521 	struct ieee80211_scan_state *ss;
522 
523 	IEEE80211_LOCK_ASSERT(ic);
524 
525 	ss = ic->ic_scan;
526 	scan_signal(ss);
527 }
528 
529 /*
530  * Probe the curent channel, if allowed, while scanning.
531  * If the channel is not marked passive-only then send
532  * a probe request immediately.  Otherwise mark state and
533  * listen for beacons on the channel; if we receive something
534  * then we'll transmit a probe request.
535  */
536 static void
537 ieee80211_swscan_probe_curchan(struct ieee80211vap *vap, int force)
538 {
539 	struct ieee80211com *ic = vap->iv_ic;
540 	struct ieee80211_scan_state *ss = ic->ic_scan;
541 	struct ifnet *ifp = vap->iv_ifp;
542 	int i;
543 
544 	/*
545 	 * Send directed probe requests followed by any
546 	 * broadcast probe request.
547 	 * XXX remove dependence on ic/vap->iv_bss
548 	 */
549 	for (i = 0; i < ss->ss_nssid; i++)
550 		ieee80211_send_probereq(vap->iv_bss,
551 			vap->iv_myaddr, ifp->if_broadcastaddr,
552 			ifp->if_broadcastaddr,
553 			ss->ss_ssid[i].ssid, ss->ss_ssid[i].len);
554 	if ((ss->ss_flags & IEEE80211_SCAN_NOBCAST) == 0)
555 		ieee80211_send_probereq(vap->iv_bss,
556 			vap->iv_myaddr, ifp->if_broadcastaddr,
557 			ifp->if_broadcastaddr,
558 			"", 0);
559 }
560 
561 /*
562  * Scan curchan.  If this is an active scan and the channel
563  * is not marked passive then send probe request frame(s).
564  * Arrange for the channel change after maxdwell ticks.
565  */
566 static void
567 scan_curchan(struct ieee80211_scan_state *ss, unsigned long maxdwell)
568 {
569 	struct ieee80211vap *vap  = ss->ss_vap;
570 
571 	IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
572 	    "%s: calling; maxdwell=%lu\n",
573 	    __func__,
574 	    maxdwell);
575 	IEEE80211_LOCK(vap->iv_ic);
576 	if (ss->ss_flags & IEEE80211_SCAN_ACTIVE)
577 		ieee80211_probe_curchan(vap, 0);
578 	callout_reset(&SCAN_PRIVATE(ss)->ss_scan_timer,
579 	    maxdwell, scan_signal, ss);
580 	IEEE80211_UNLOCK(vap->iv_ic);
581 }
582 
583 static void
584 scan_signal(void *arg)
585 {
586 	struct ieee80211_scan_state *ss = (struct ieee80211_scan_state *) arg;
587 
588 	IEEE80211_LOCK_ASSERT(ss->ss_ic);
589 	cv_signal(&SCAN_PRIVATE(ss)->ss_scan_cv);
590 }
591 
592 /*
593  * Handle mindwell requirements completed; initiate a channel
594  * change to the next channel asap.
595  */
596 static void
597 scan_mindwell(struct ieee80211_scan_state *ss)
598 {
599 	struct ieee80211com *ic = ss->ss_ic;
600 
601 	IEEE80211_DPRINTF(ss->ss_vap, IEEE80211_MSG_SCAN, "%s: called\n", __func__);
602 
603 	IEEE80211_LOCK(ic);
604 	scan_signal(ss);
605 	IEEE80211_UNLOCK(ic);
606 }
607 
608 static void
609 scan_task(void *arg, int pending)
610 {
611 #define	ISCAN_REP	(ISCAN_MINDWELL | ISCAN_DISCARD)
612 	struct ieee80211_scan_state *ss = (struct ieee80211_scan_state *) arg;
613 	struct ieee80211vap *vap = ss->ss_vap;
614 	struct ieee80211com *ic = ss->ss_ic;
615 	struct ieee80211_channel *chan;
616 	unsigned long maxdwell, scanend;
617 	int scandone = 0;
618 
619 	IEEE80211_LOCK(ic);
620 	if (vap == NULL || (ic->ic_flags & IEEE80211_F_SCAN) == 0 ||
621 	    (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_ABORT)) {
622 		/* Cancelled before we started */
623 		goto done;
624 	}
625 
626 	if (ss->ss_next == ss->ss_last) {
627 		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
628 			"%s: no channels to scan\n", __func__);
629 		scandone = 1;
630 		goto done;
631 	}
632 
633 	if (vap->iv_opmode == IEEE80211_M_STA &&
634 	    vap->iv_state == IEEE80211_S_RUN) {
635 		if ((vap->iv_bss->ni_flags & IEEE80211_NODE_PWR_MGT) == 0) {
636 			/* Enable station power save mode */
637 			vap->iv_sta_ps(vap, 1);
638 			/*
639 			 * Use an 1ms delay so the null data frame has a chance
640 			 * to go out.
641 			 * XXX Should use M_TXCB mechanism to eliminate this.
642 			 */
643 			cv_timedwait(&SCAN_PRIVATE(ss)->ss_scan_cv,
644 			    IEEE80211_LOCK_OBJ(ic), hz / 1000);
645 			if (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_ABORT)
646 				goto done;
647 		}
648 	}
649 
650 	scanend = ticks + SCAN_PRIVATE(ss)->ss_duration;
651 
652 	/* XXX scan state can change! Re-validate scan state! */
653 
654 	IEEE80211_UNLOCK(ic);
655 	ic->ic_scan_start(ic);		/* notify driver */
656 	IEEE80211_LOCK(ic);
657 
658 	for (;;) {
659 
660 		scandone = (ss->ss_next >= ss->ss_last) ||
661 		    (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) != 0;
662 
663 		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
664 		    "%s: loop start; scandone=%d\n",
665 		    __func__,
666 		    scandone);
667 
668 		if (scandone || (ss->ss_flags & IEEE80211_SCAN_GOTPICK) ||
669 		    (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_ABORT) ||
670 		     time_after(ticks + ss->ss_mindwell, scanend))
671 			break;
672 
673 		chan = ss->ss_chans[ss->ss_next++];
674 
675 		/*
676 		 * Watch for truncation due to the scan end time.
677 		 */
678 		if (time_after(ticks + ss->ss_maxdwell, scanend))
679 			maxdwell = scanend - ticks;
680 		else
681 			maxdwell = ss->ss_maxdwell;
682 
683 		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
684 		    "%s: chan %3d%c -> %3d%c [%s, dwell min %lums max %lums]\n",
685 		    __func__,
686 		    ieee80211_chan2ieee(ic, ic->ic_curchan),
687 		    ieee80211_channel_type_char(ic->ic_curchan),
688 		    ieee80211_chan2ieee(ic, chan),
689 		    ieee80211_channel_type_char(chan),
690 		    (ss->ss_flags & IEEE80211_SCAN_ACTIVE) &&
691 			(chan->ic_flags & IEEE80211_CHAN_PASSIVE) == 0 ?
692 			"active" : "passive",
693 		    ticks_to_msecs(ss->ss_mindwell), ticks_to_msecs(maxdwell));
694 
695 		/*
696 		 * Potentially change channel and phy mode.
697 		 */
698 		ic->ic_curchan = chan;
699 		ic->ic_rt = ieee80211_get_ratetable(chan);
700 		IEEE80211_UNLOCK(ic);
701 		/*
702 		 * Perform the channel change and scan unlocked so the driver
703 		 * may sleep. Once set_channel returns the hardware has
704 		 * completed the channel change.
705 		 */
706 		ic->ic_set_channel(ic);
707 		ieee80211_radiotap_chan_change(ic);
708 
709 		/*
710 		 * Scan curchan.  Drivers for "intelligent hardware"
711 		 * override ic_scan_curchan to tell the device to do
712 		 * the work.  Otherwise we manage the work outselves;
713 		 * sending a probe request (as needed), and arming the
714 		 * timeout to switch channels after maxdwell ticks.
715 		 *
716 		 * scan_curchan should only pause for the time required to
717 		 * prepare/initiate the hardware for the scan (if at all), the
718 		 * below condvar is used to sleep for the channels dwell time
719 		 * and allows it to be signalled for abort.
720 		 */
721 		ic->ic_scan_curchan(ss, maxdwell);
722 		IEEE80211_LOCK(ic);
723 
724 		/* XXX scan state can change! Re-validate scan state! */
725 
726 		SCAN_PRIVATE(ss)->ss_chanmindwell = ticks + ss->ss_mindwell;
727 		/* clear mindwell lock and initial channel change flush */
728 		SCAN_PRIVATE(ss)->ss_iflags &= ~ISCAN_REP;
729 
730 		if ((SCAN_PRIVATE(ss)->ss_iflags & (ISCAN_CANCEL|ISCAN_ABORT)))
731 			continue;
732 
733 		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN, "%s: waiting\n", __func__);
734 		/* Wait to be signalled to scan the next channel */
735 		cv_wait(&SCAN_PRIVATE(ss)->ss_scan_cv, IEEE80211_LOCK_OBJ(ic));
736 	}
737 
738 	IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN, "%s: out\n", __func__);
739 
740 	if (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_ABORT)
741 		goto done;
742 
743 	IEEE80211_UNLOCK(ic);
744 	ic->ic_scan_end(ic);		/* notify driver */
745 	IEEE80211_LOCK(ic);
746 	/* XXX scan state can change! Re-validate scan state! */
747 
748 	/*
749 	 * Since a cancellation may have occured during one of the
750 	 * driver calls (whilst unlocked), update scandone.
751 	 */
752 	if (scandone == 0 &&
753 	    ((SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) != 0)) {
754 		/* XXX printf? */
755 		if_printf(vap->iv_ifp,
756 		    "%s: OOPS! scan cancelled during driver call (1)!\n",
757 		    __func__);
758 		scandone = 1;
759 	}
760 
761 	/*
762 	 * Record scan complete time.  Note that we also do
763 	 * this when canceled so any background scan will
764 	 * not be restarted for a while.
765 	 */
766 	if (scandone)
767 		ic->ic_lastscan = ticks;
768 	/* return to the bss channel */
769 	if (ic->ic_bsschan != IEEE80211_CHAN_ANYC &&
770 	    ic->ic_curchan != ic->ic_bsschan) {
771 		ieee80211_setupcurchan(ic, ic->ic_bsschan);
772 		IEEE80211_UNLOCK(ic);
773 		ic->ic_set_channel(ic);
774 		ieee80211_radiotap_chan_change(ic);
775 		IEEE80211_LOCK(ic);
776 	}
777 	/* clear internal flags and any indication of a pick */
778 	SCAN_PRIVATE(ss)->ss_iflags &= ~ISCAN_REP;
779 	ss->ss_flags &= ~IEEE80211_SCAN_GOTPICK;
780 
781 	/*
782 	 * If not canceled and scan completed, do post-processing.
783 	 * If the callback function returns 0, then it wants to
784 	 * continue/restart scanning.  Unfortunately we needed to
785 	 * notify the driver to end the scan above to avoid having
786 	 * rx frames alter the scan candidate list.
787 	 */
788 	if ((SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) == 0 &&
789 	    !ss->ss_ops->scan_end(ss, vap) &&
790 	    (ss->ss_flags & IEEE80211_SCAN_ONCE) == 0 &&
791 	    time_before(ticks + ss->ss_mindwell, scanend)) {
792 		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
793 		    "%s: done, restart "
794 		    "[ticks %u, dwell min %lu scanend %lu]\n",
795 		    __func__,
796 		    ticks, ss->ss_mindwell, scanend);
797 		ss->ss_next = 0;	/* reset to begining */
798 		if (ss->ss_flags & IEEE80211_SCAN_ACTIVE)
799 			vap->iv_stats.is_scan_active++;
800 		else
801 			vap->iv_stats.is_scan_passive++;
802 
803 		ss->ss_ops->scan_restart(ss, vap);	/* XXX? */
804 		ieee80211_runtask(ic, &SCAN_PRIVATE(ss)->ss_scan_task);
805 		IEEE80211_UNLOCK(ic);
806 		return;
807 	}
808 
809 	/* past here, scandone is ``true'' if not in bg mode */
810 	if ((ss->ss_flags & IEEE80211_SCAN_BGSCAN) == 0)
811 		scandone = 1;
812 
813 	IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
814 	    "%s: %s, [ticks %u, dwell min %lu scanend %lu]\n",
815 	    __func__, scandone ? "done" : "stopped",
816 	    ticks, ss->ss_mindwell, scanend);
817 
818 	/*
819 	 * Since a cancellation may have occured during one of the
820 	 * driver calls (whilst unlocked), update scandone.
821 	 */
822 	if (scandone == 0 &&
823 	    ((SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) != 0)) {
824 		/* XXX printf? */
825 		if_printf(vap->iv_ifp,
826 		    "%s: OOPS! scan cancelled during driver call (2)!\n",
827 		    __func__);
828 		scandone = 1;
829 	}
830 
831 	/*
832 	 * Clear the SCAN bit first in case frames are
833 	 * pending on the station power save queue.  If
834 	 * we defer this then the dispatch of the frames
835 	 * may generate a request to cancel scanning.
836 	 */
837 done:
838 	ic->ic_flags &= ~IEEE80211_F_SCAN;
839 	/*
840 	 * Drop out of power save mode when a scan has
841 	 * completed.  If this scan was prematurely terminated
842 	 * because it is a background scan then don't notify
843 	 * the ap; we'll either return to scanning after we
844 	 * receive the beacon frame or we'll drop out of power
845 	 * save mode because the beacon indicates we have frames
846 	 * waiting for us.
847 	 */
848 	if (scandone) {
849 		vap->iv_sta_ps(vap, 0);
850 		if (ss->ss_next >= ss->ss_last) {
851 			ieee80211_notify_scan_done(vap);
852 			ic->ic_flags_ext &= ~IEEE80211_FEXT_BGSCAN;
853 		}
854 	}
855 	SCAN_PRIVATE(ss)->ss_iflags &= ~(ISCAN_CANCEL|ISCAN_ABORT);
856 	ss->ss_flags &= ~(IEEE80211_SCAN_ONCE | IEEE80211_SCAN_PICK1ST);
857 	IEEE80211_UNLOCK(ic);
858 #undef ISCAN_REP
859 }
860 
861 /*
862  * Process a beacon or probe response frame.
863  */
864 static void
865 ieee80211_swscan_add_scan(struct ieee80211vap *vap,
866 	struct ieee80211_channel *curchan,
867 	const struct ieee80211_scanparams *sp,
868 	const struct ieee80211_frame *wh,
869 	int subtype, int rssi, int noise)
870 {
871 	struct ieee80211com *ic = vap->iv_ic;
872 	struct ieee80211_scan_state *ss = ic->ic_scan;
873 
874 	/* XXX locking */
875 	/*
876 	 * Frames received during startup are discarded to avoid
877 	 * using scan state setup on the initial entry to the timer
878 	 * callback.  This can occur because the device may enable
879 	 * rx prior to our doing the initial channel change in the
880 	 * timer routine.
881 	 */
882 	if (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_DISCARD)
883 		return;
884 #ifdef IEEE80211_DEBUG
885 	if (ieee80211_msg_scan(vap) && (ic->ic_flags & IEEE80211_F_SCAN))
886 		ieee80211_scan_dump_probe_beacon(subtype, 1, wh->i_addr2, sp, rssi);
887 #endif
888 	if (ss->ss_ops != NULL &&
889 	    ss->ss_ops->scan_add(ss, curchan, sp, wh, subtype, rssi, noise)) {
890 		/*
891 		 * If we've reached the min dwell time terminate
892 		 * the timer so we'll switch to the next channel.
893 		 */
894 		if ((SCAN_PRIVATE(ss)->ss_iflags & ISCAN_MINDWELL) == 0 &&
895 		    time_after_eq(ticks, SCAN_PRIVATE(ss)->ss_chanmindwell)) {
896 			IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
897 			    "%s: chan %3d%c min dwell met (%u > %lu)\n",
898 			    __func__,
899 			    ieee80211_chan2ieee(ic, ic->ic_curchan),
900 			    ieee80211_channel_type_char(ic->ic_curchan),
901 			    ticks, SCAN_PRIVATE(ss)->ss_chanmindwell);
902 			SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_MINDWELL;
903 			/*
904 			 * NB: trigger at next clock tick or wait for the
905 			 * hardware.
906 			 */
907 			ic->ic_scan_mindwell(ss);
908 		}
909 	}
910 }
911 
912 static struct ieee80211_scan_methods swscan_methods = {
913 	.sc_attach = ieee80211_swscan_attach,
914 	.sc_detach = ieee80211_swscan_detach,
915 	.sc_vattach = ieee80211_swscan_vattach,
916 	.sc_vdetach = ieee80211_swscan_vdetach,
917 	.sc_set_scan_duration = ieee80211_swscan_set_scan_duration,
918 	.sc_start_scan = ieee80211_swscan_start_scan,
919 	.sc_check_scan = ieee80211_swscan_check_scan,
920 	.sc_bg_scan = ieee80211_swscan_bg_scan,
921 	.sc_cancel_scan = ieee80211_swscan_cancel_scan,
922 	.sc_cancel_anyscan = ieee80211_swscan_cancel_anyscan,
923 	.sc_scan_next = ieee80211_swscan_scan_next,
924 	.sc_scan_done = ieee80211_swscan_scan_done,
925 	.sc_scan_probe_curchan = ieee80211_swscan_probe_curchan,
926 	.sc_add_scan = ieee80211_swscan_add_scan
927 };
928 
929 /*
930  * Default scan attach method.
931  */
932 void
933 ieee80211_swscan_attach(struct ieee80211com *ic)
934 {
935 	struct scan_state *ss;
936 
937 	/*
938 	 * Setup the default methods
939 	 */
940 	ic->ic_scan_methods = &swscan_methods;
941 
942 	/* Allocate initial scan state */
943 	ss = (struct scan_state *) IEEE80211_MALLOC(sizeof(struct scan_state),
944 		M_80211_SCAN, IEEE80211_M_NOWAIT | IEEE80211_M_ZERO);
945 	if (ss == NULL) {
946 		ic->ic_scan = NULL;
947 		return;
948 	}
949 	callout_init_mtx(&ss->ss_scan_timer, IEEE80211_LOCK_OBJ(ic), 0);
950 	cv_init(&ss->ss_scan_cv, "scan");
951 	TASK_INIT(&ss->ss_scan_task, 0, scan_task, ss);
952 
953 	ic->ic_scan = &ss->base;
954 	ss->base.ss_ic = ic;
955 
956 	ic->ic_scan_curchan = scan_curchan;
957 	ic->ic_scan_mindwell = scan_mindwell;
958 }
959