xref: /freebsd/sys/net80211/ieee80211_scan.c (revision 1e413cf93298b5b97441a21d9a50fdcd0ee9945e)
1 /*-
2  * Copyright (c) 2002-2007 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 <sys/param.h>
33 #include <sys/systm.h>
34 #include <sys/kernel.h>
35 
36 #include <sys/socket.h>
37 
38 #include <net/if.h>
39 #include <net/if_media.h>
40 #include <net/ethernet.h>
41 
42 #include <net80211/ieee80211_var.h>
43 
44 #include <net/bpf.h>
45 
46 struct scan_state {
47 	struct ieee80211_scan_state base;	/* public state */
48 
49 	u_int		ss_iflags;		/* flags used internally */
50 #define	ISCAN_MINDWELL 	0x0001		/* min dwell time reached */
51 #define	ISCAN_DISCARD	0x0002		/* discard rx'd frames */
52 #define	ISCAN_CANCEL	0x0004		/* cancel current scan */
53 #define	ISCAN_START	0x0008		/* 1st time through next_scan */
54 	unsigned long	ss_chanmindwell;	/* min dwell on curchan */
55 	unsigned long	ss_scanend;		/* time scan must stop */
56 	u_int		ss_duration;		/* duration for next scan */
57 	struct callout	ss_scan_timer;		/* scan timer */
58 };
59 #define	SCAN_PRIVATE(ss)	((struct scan_state *) ss)
60 
61 /*
62  * Amount of time to go off-channel during a background
63  * scan.  This value should be large enough to catch most
64  * ap's but short enough that we can return on-channel
65  * before our listen interval expires.
66  *
67  * XXX tunable
68  * XXX check against configured listen interval
69  */
70 #define	IEEE80211_SCAN_OFFCHANNEL	msecs_to_ticks(150)
71 
72 /*
73  * Roaming-related defaults.  RSSI thresholds are as returned by the
74  * driver (dBm).  Transmit rate thresholds are IEEE rate codes (i.e
75  * .5M units).
76  */
77 #define	ROAM_RSSI_11A_DEFAULT		14	/* rssi threshold for 11a bss */
78 #define	ROAM_RSSI_11B_DEFAULT		14	/* rssi threshold for 11b bss */
79 #define	ROAM_RSSI_11BONLY_DEFAULT	14	/* rssi threshold for 11b-only bss */
80 #define	ROAM_RATE_11A_DEFAULT		2*12	/* tx rate thresh for 11a bss */
81 #define	ROAM_RATE_11B_DEFAULT		2*5	/* tx rate thresh for 11b bss */
82 #define	ROAM_RATE_11BONLY_DEFAULT	2*1	/* tx rate thresh for 11b-only bss */
83 
84 static	void scan_restart_pwrsav(void *);
85 static	void scan_curchan(struct ieee80211com *, unsigned long);
86 static	void scan_mindwell(struct ieee80211com *);
87 static	void scan_next(void *);
88 
89 MALLOC_DEFINE(M_80211_SCAN, "80211scan", "802.11 scan state");
90 
91 void
92 ieee80211_scan_attach(struct ieee80211com *ic)
93 {
94 	struct scan_state *ss;
95 
96 	ic->ic_roaming = IEEE80211_ROAMING_AUTO;
97 
98 	MALLOC(ss, struct scan_state *, sizeof(struct scan_state),
99 		M_80211_SCAN, M_NOWAIT | M_ZERO);
100 	if (ss == NULL) {
101 		ic->ic_scan = NULL;
102 		return;
103 	}
104 	callout_init(&ss->ss_scan_timer, CALLOUT_MPSAFE);
105 	ic->ic_scan = &ss->base;
106 
107 	ic->ic_scan_curchan = scan_curchan;
108 	ic->ic_scan_mindwell = scan_mindwell;
109 
110 	ic->ic_bgscanidle = (IEEE80211_BGSCAN_IDLE_DEFAULT*1000)/hz;
111 	ic->ic_bgscanintvl = IEEE80211_BGSCAN_INTVAL_DEFAULT*hz;
112 	ic->ic_scanvalid = IEEE80211_SCAN_VALID_DEFAULT*hz;
113 	ic->ic_roam.rssi11a = ROAM_RSSI_11A_DEFAULT;
114 	ic->ic_roam.rssi11b = ROAM_RSSI_11B_DEFAULT;
115 	ic->ic_roam.rssi11bOnly = ROAM_RSSI_11BONLY_DEFAULT;
116 	ic->ic_roam.rate11a = ROAM_RATE_11A_DEFAULT;
117 	ic->ic_roam.rate11b = ROAM_RATE_11B_DEFAULT;
118 	ic->ic_roam.rate11bOnly = ROAM_RATE_11BONLY_DEFAULT;
119 }
120 
121 void
122 ieee80211_scan_detach(struct ieee80211com *ic)
123 {
124 	struct ieee80211_scan_state *ss = ic->ic_scan;
125 
126 	if (ss != NULL) {
127 		callout_drain(&SCAN_PRIVATE(ss)->ss_scan_timer);
128 		if (ss->ss_ops != NULL) {
129 			ss->ss_ops->scan_detach(ss);
130 			ss->ss_ops = NULL;
131 		}
132 		ic->ic_flags &= ~IEEE80211_F_SCAN;
133 		ic->ic_scan = NULL;
134 		FREE(SCAN_PRIVATE(ss), M_80211_SCAN);
135 	}
136 }
137 
138 /*
139  * Simple-minded scanner module support.
140  */
141 #define	IEEE80211_SCANNER_MAX	(IEEE80211_M_MONITOR+1)
142 
143 static const char *scan_modnames[IEEE80211_SCANNER_MAX] = {
144 	"wlan_scan_sta",	/* IEEE80211_M_IBSS */
145 	"wlan_scan_sta",	/* IEEE80211_M_STA */
146 	"wlan_scan_wds",	/* IEEE80211_M_WDS */
147 	"wlan_scan_sta",	/* IEEE80211_M_AHDEMO */
148 	"wlan_scan_4",		/* n/a */
149 	"wlan_scan_5",		/* n/a */
150 	"wlan_scan_ap",		/* IEEE80211_M_HOSTAP */
151 	"wlan_scan_7",		/* n/a */
152 	"wlan_scan_monitor",	/* IEEE80211_M_MONITOR */
153 };
154 static const struct ieee80211_scanner *scanners[IEEE80211_SCANNER_MAX];
155 
156 const struct ieee80211_scanner *
157 ieee80211_scanner_get(enum ieee80211_opmode mode)
158 {
159 	if (mode >= IEEE80211_SCANNER_MAX)
160 		return NULL;
161 	/* NB: avoid monitor mode; there is no scan support */
162 	if (mode != IEEE80211_M_MONITOR && scanners[mode] == NULL)
163 		ieee80211_load_module(scan_modnames[mode]);
164 	return scanners[mode];
165 }
166 
167 void
168 ieee80211_scanner_register(enum ieee80211_opmode mode,
169 	const struct ieee80211_scanner *scan)
170 {
171 	if (mode >= IEEE80211_SCANNER_MAX)
172 		return;
173 	scanners[mode] = scan;
174 }
175 
176 void
177 ieee80211_scanner_unregister(enum ieee80211_opmode mode,
178 	const struct ieee80211_scanner *scan)
179 {
180 	if (mode >= IEEE80211_SCANNER_MAX)
181 		return;
182 	if (scanners[mode] == scan)
183 		scanners[mode] = NULL;
184 }
185 
186 void
187 ieee80211_scanner_unregister_all(const struct ieee80211_scanner *scan)
188 {
189 	int m;
190 
191 	for (m = 0; m < IEEE80211_SCANNER_MAX; m++)
192 		if (scanners[m] == scan)
193 			scanners[m] = NULL;
194 }
195 
196 /*
197  * Update common scanner state to reflect the current
198  * operating mode.  This is called when the state machine
199  * is transitioned to RUN state w/o scanning--e.g. when
200  * operating in monitor mode.  The purpose of this is to
201  * ensure later callbacks find ss_ops set to properly
202  * reflect current operating mode.
203  */
204 int
205 ieee80211_scan_update(struct ieee80211com *ic)
206 {
207 	struct ieee80211_scan_state *ss = ic->ic_scan;
208 	const struct ieee80211_scanner *scan;
209 
210 	scan = ieee80211_scanner_get(ic->ic_opmode);
211 	IEEE80211_LOCK(ic);
212 	if (scan == NULL) {
213 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN,
214 		    "%s: no scanner support for mode %u\n",
215 		    __func__, ic->ic_opmode);
216 		/* XXX stat */
217 	}
218 	ss->ss_ic = ic;
219 	if (ss->ss_ops != scan) {
220 		/* switch scanners; detach old, attach new */
221 		if (ss->ss_ops != NULL)
222 			ss->ss_ops->scan_detach(ss);
223 		if (scan != NULL && !scan->scan_attach(ss)) {
224 			/* XXX attach failure */
225 			/* XXX stat+msg */
226 			ss->ss_ops = NULL;
227 		} else
228 			ss->ss_ops = scan;
229 	}
230 	IEEE80211_UNLOCK(ic);
231 
232 	return (scan != NULL);
233 }
234 
235 static void
236 change_channel(struct ieee80211com *ic,
237 	struct ieee80211_channel *chan)
238 {
239 	ic->ic_curchan = chan;
240 	ic->ic_set_channel(ic);
241 }
242 
243 static char
244 channel_type(const struct ieee80211_channel *c)
245 {
246 	if (IEEE80211_IS_CHAN_ST(c))
247 		return 'S';
248 	if (IEEE80211_IS_CHAN_108A(c))
249 		return 'T';
250 	if (IEEE80211_IS_CHAN_108G(c))
251 		return 'G';
252 	if (IEEE80211_IS_CHAN_HT(c))
253 		return 'n';
254 	if (IEEE80211_IS_CHAN_A(c))
255 		return 'a';
256 	if (IEEE80211_IS_CHAN_ANYG(c))
257 		return 'g';
258 	if (IEEE80211_IS_CHAN_B(c))
259 		return 'b';
260 	return 'f';
261 }
262 
263 void
264 ieee80211_scan_dump_channels(const struct ieee80211_scan_state *ss)
265 {
266 	struct ieee80211com *ic = ss->ss_ic;
267 	const char *sep;
268 	int i;
269 
270 	sep = "";
271 	for (i = ss->ss_next; i < ss->ss_last; i++) {
272 		const struct ieee80211_channel *c = ss->ss_chans[i];
273 
274 		printf("%s%u%c", sep, ieee80211_chan2ieee(ic, c),
275 			channel_type(c));
276 		sep = ", ";
277 	}
278 }
279 
280 /*
281  * Enable station power save mode and start/restart the scanning thread.
282  */
283 static void
284 scan_restart_pwrsav(void *arg)
285 {
286 	struct scan_state *ss = (struct scan_state *) arg;
287 	struct ieee80211com *ic = ss->base.ss_ic;
288 	int delay;
289 
290 	ieee80211_sta_pwrsave(ic, 1);
291 	/*
292 	 * Use an initial 1ms delay to insure the null
293 	 * data frame has a chance to go out.
294 	 * XXX 1ms is a lot, better to trigger scan
295 	 * on tx complete.
296 	 */
297 	delay = hz/1000;
298 	if (delay < 1)
299 		delay = 1;
300 	ic->ic_scan_start(ic);			/* notify driver */
301 	ss->ss_scanend = ticks + delay + ss->ss_duration;
302 	ss->ss_iflags |= ISCAN_START;
303 	callout_reset(&ss->ss_scan_timer, delay, scan_next, ss);
304 }
305 
306 /*
307  * Start/restart scanning.  If we're operating in station mode
308  * and associated notify the ap we're going into power save mode
309  * and schedule a callback to initiate the work (where there's a
310  * better context for doing the work).  Otherwise, start the scan
311  * directly.
312  */
313 static int
314 scan_restart(struct scan_state *ss, u_int duration)
315 {
316 	struct ieee80211com *ic = ss->base.ss_ic;
317 	int defer = 0;
318 
319 	if (ss->base.ss_next == ss->base.ss_last) {
320 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN,
321 			"%s: no channels to scan\n", __func__);
322 		return 0;
323 	}
324 	if (ic->ic_opmode == IEEE80211_M_STA &&
325 	    ic->ic_state == IEEE80211_S_RUN) {
326 		if ((ic->ic_bss->ni_flags & IEEE80211_NODE_PWR_MGT) == 0) {
327 			/*
328 			 * Initiate power save before going off-channel.
329 			 * Note that we cannot do this directly because
330 			 * of locking issues; instead we defer it to a
331 			 * tasklet.
332 			 */
333 			ss->ss_duration = duration;
334 			defer = 1;
335 		}
336 	}
337 
338 	if (!defer) {
339 		ic->ic_scan_start(ic);		/* notify driver */
340 		ss->ss_scanend = ticks + duration;
341 		ss->ss_iflags |= ISCAN_START;
342 		callout_reset(&ss->ss_scan_timer, 0, scan_next, ss);
343 	} else
344 		scan_restart_pwrsav(ss);
345 	return 1;
346 }
347 
348 static void
349 copy_ssid(struct ieee80211com *ic, struct ieee80211_scan_state *ss,
350 	int nssid, const struct ieee80211_scan_ssid ssids[])
351 {
352 	if (nssid > IEEE80211_SCAN_MAX_SSID) {
353 		/* XXX printf */
354 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN,
355 		    "%s: too many ssid %d, ignoring all of them\n",
356 		    __func__, nssid);
357 		return;
358 	}
359 	memcpy(ss->ss_ssid, ssids, nssid * sizeof(ssids[0]));
360 	ss->ss_nssid = nssid;
361 }
362 
363 /*
364  * Start a scan unless one is already going.
365  */
366 int
367 ieee80211_start_scan(struct ieee80211com *ic, int flags, u_int duration,
368 	u_int nssid, const struct ieee80211_scan_ssid ssids[])
369 {
370 	const struct ieee80211_scanner *scan;
371 	struct ieee80211_scan_state *ss = ic->ic_scan;
372 
373 	scan = ieee80211_scanner_get(ic->ic_opmode);
374 	if (scan == NULL) {
375 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN,
376 		    "%s: no scanner support for mode %u\n",
377 		    __func__, ic->ic_opmode);
378 		/* XXX stat */
379 		return 0;
380 	}
381 
382 	IEEE80211_LOCK(ic);
383 	if ((ic->ic_flags & IEEE80211_F_SCAN) == 0) {
384 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN,
385 		    "%s: %s scan, duration %u, desired mode %s, %s%s%s%s\n"
386 		    , __func__
387 		    , flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive"
388 		    , duration
389 		    , ieee80211_phymode_name[ic->ic_des_mode]
390 		    , flags & IEEE80211_SCAN_FLUSH ? "flush" : "append"
391 		    , flags & IEEE80211_SCAN_NOPICK ? ", nopick" : ""
392 		    , flags & IEEE80211_SCAN_PICK1ST ? ", pick1st" : ""
393 		    , flags & IEEE80211_SCAN_ONCE ? ", once" : ""
394 		);
395 
396 		ss->ss_ic = ic;
397 		if (ss->ss_ops != scan) {
398 			/* switch scanners; detach old, attach new */
399 			if (ss->ss_ops != NULL)
400 				ss->ss_ops->scan_detach(ss);
401 			if (!scan->scan_attach(ss)) {
402 				/* XXX attach failure */
403 				/* XXX stat+msg */
404 				ss->ss_ops = NULL;
405 			} else
406 				ss->ss_ops = scan;
407 		}
408 		if (ss->ss_ops != NULL) {
409 			if ((flags & IEEE80211_SCAN_NOSSID) == 0)
410 				copy_ssid(ic, ss, nssid, ssids);
411 
412 			/* NB: top 4 bits for internal use */
413 			ss->ss_flags = flags & 0xfff;
414 			if (ss->ss_flags & IEEE80211_SCAN_ACTIVE)
415 				ic->ic_stats.is_scan_active++;
416 			else
417 				ic->ic_stats.is_scan_passive++;
418 			if (flags & IEEE80211_SCAN_FLUSH)
419 				ss->ss_ops->scan_flush(ss);
420 
421 			/* NB: flush frames rx'd before 1st channel change */
422 			SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_DISCARD;
423 			ss->ss_ops->scan_start(ss, ic);
424 			if (scan_restart(SCAN_PRIVATE(ss), duration))
425 				ic->ic_flags |= IEEE80211_F_SCAN;
426 		}
427 	} else {
428 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN,
429 		    "%s: %s scan already in progress\n", __func__,
430 		    ss->ss_flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive");
431 	}
432 	IEEE80211_UNLOCK(ic);
433 
434 	/* NB: racey, does it matter? */
435 	return (ic->ic_flags & IEEE80211_F_SCAN);
436 }
437 
438 /*
439  * Check the scan cache for an ap/channel to use; if that
440  * fails then kick off a new scan.
441  */
442 int
443 ieee80211_check_scan(struct ieee80211com *ic, int flags, u_int duration,
444 	u_int nssid, const struct ieee80211_scan_ssid ssids[])
445 {
446 	struct ieee80211_scan_state *ss = ic->ic_scan;
447 	int checkscanlist = 0;
448 
449 	/*
450 	 * Check if there's a list of scan candidates already.
451 	 * XXX want more than the ap we're currently associated with
452 	 */
453 
454 	IEEE80211_LOCK(ic);
455 	IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN,
456 	    "%s: %s scan, duration %u, desired mode %s, %s%s%s%s\n"
457 	    , __func__
458 	    , flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive"
459 	    , duration
460 	    , ieee80211_phymode_name[ic->ic_des_mode]
461 	    , flags & IEEE80211_SCAN_FLUSH ? "flush" : "append"
462 	    , flags & IEEE80211_SCAN_NOPICK ? ", nopick" : ""
463 	    , flags & IEEE80211_SCAN_PICK1ST ? ", pick1st" : ""
464 	    , flags & IEEE80211_SCAN_ONCE ? ", once" : ""
465 	);
466 
467 	if (ss->ss_ops != NULL) {
468 		/* XXX verify ss_ops matches ic->ic_opmode */
469 		if ((flags & IEEE80211_SCAN_NOSSID) == 0) {
470 			/*
471 			 * Update the ssid list and mark flags so if
472 			 * we call start_scan it doesn't duplicate work.
473 			 */
474 			copy_ssid(ic, ss, nssid, ssids);
475 			flags |= IEEE80211_SCAN_NOSSID;
476 		}
477 		if ((ic->ic_flags & IEEE80211_F_SCAN) == 0 &&
478 		     time_before(ticks, ic->ic_lastscan + ic->ic_scanvalid)) {
479 			/*
480 			 * We're not currently scanning and the cache is
481 			 * deemed hot enough to consult.  Lock out others
482 			 * by marking IEEE80211_F_SCAN while we decide if
483 			 * something is already in the scan cache we can
484 			 * use.  Also discard any frames that might come
485 			 * in while temporarily marked as scanning.
486 			 */
487 			SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_DISCARD;
488 			ic->ic_flags |= IEEE80211_F_SCAN;
489 			checkscanlist = 1;
490 		}
491 	}
492 	IEEE80211_UNLOCK(ic);
493 	if (checkscanlist) {
494 		const struct ieee80211_scanner *scan;
495 
496 		scan = ieee80211_scanner_get(ic->ic_opmode);
497 		if (scan == NULL) {
498 			IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN,
499 			    "%s: no scanner support for mode %u\n",
500 			    __func__, ic->ic_opmode);
501 			/* XXX stat */
502 			return 0;
503 		}
504 		if (scan == ss->ss_ops && ss->ss_ops->scan_end(ss, ic)) {
505 			/* found an ap, just clear the flag */
506 			ic->ic_flags &= ~IEEE80211_F_SCAN;
507 			return 1;
508 		}
509 		/* no ap, clear the flag before starting a scan */
510 		ic->ic_flags &= ~IEEE80211_F_SCAN;
511 	}
512 	return ieee80211_start_scan(ic, flags, duration, nssid, ssids);
513 }
514 
515 /*
516  * Restart a previous scan.  If the previous scan completed
517  * then we start again using the existing channel list.
518  */
519 int
520 ieee80211_bg_scan(struct ieee80211com *ic)
521 {
522 	struct ieee80211_scan_state *ss = ic->ic_scan;
523 
524 	IEEE80211_LOCK(ic);
525 	if ((ic->ic_flags & IEEE80211_F_SCAN) == 0) {
526 		u_int duration;
527 		/*
528 		 * Go off-channel for a fixed interval that is large
529 		 * enough to catch most ap's but short enough that
530 		 * we can return on-channel before our listen interval
531 		 * expires.
532 		 */
533 		duration = IEEE80211_SCAN_OFFCHANNEL;
534 
535 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN,
536 		    "%s: %s scan, ticks %u duration %lu\n", __func__,
537 		    ss->ss_flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive",
538 		    ticks, duration);
539 
540 		if (ss->ss_ops != NULL) {
541 			ss->ss_ic = ic;
542 			/*
543 			 * A background scan does not select a new sta; it
544 			 * just refreshes the scan cache.  Also, indicate
545 			 * the scan logic should follow the beacon schedule:
546 			 * we go off-channel and scan for a while, then
547 			 * return to the bss channel to receive a beacon,
548 			 * then go off-channel again.  All during this time
549 			 * we notify the ap we're in power save mode.  When
550 			 * the scan is complete we leave power save mode.
551 			 * If any beacon indicates there are frames pending
552 			 * for us then we drop out of power save mode
553 			 * (and background scan) automatically by way of the
554 			 * usual sta power save logic.
555 			 */
556 			ss->ss_flags |= IEEE80211_SCAN_NOPICK
557 				     |  IEEE80211_SCAN_BGSCAN;
558 			/* if previous scan completed, restart */
559 			if (ss->ss_next >= ss->ss_last) {
560 				ss->ss_next = 0;
561 				if (ss->ss_flags & IEEE80211_SCAN_ACTIVE)
562 					ic->ic_stats.is_scan_active++;
563 				else
564 					ic->ic_stats.is_scan_passive++;
565 				ss->ss_ops->scan_restart(ss, ic);
566 			}
567 			/* NB: flush frames rx'd before 1st channel change */
568 			SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_DISCARD;
569 			ss->ss_maxdwell = duration;
570 			if (scan_restart(SCAN_PRIVATE(ss), duration)) {
571 				ic->ic_flags |= IEEE80211_F_SCAN;
572 				ic->ic_flags_ext |= IEEE80211_FEXT_BGSCAN;
573 			}
574 		} else {
575 			/* XXX msg+stat */
576 		}
577 	} else {
578 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN,
579 		    "%s: %s scan already in progress\n", __func__,
580 		    ss->ss_flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive");
581 	}
582 	IEEE80211_UNLOCK(ic);
583 
584 	/* NB: racey, does it matter? */
585 	return (ic->ic_flags & IEEE80211_F_SCAN);
586 }
587 
588 /*
589  * Cancel any scan currently going on.
590  */
591 void
592 ieee80211_cancel_scan(struct ieee80211com *ic)
593 {
594 	struct ieee80211_scan_state *ss = ic->ic_scan;
595 
596 	IEEE80211_LOCK(ic);
597 	if ((ic->ic_flags & IEEE80211_F_SCAN) &&
598 	    (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) == 0) {
599 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN,
600 		    "%s: cancel %s scan\n", __func__,
601 		    ss->ss_flags & IEEE80211_SCAN_ACTIVE ?
602 			"active" : "passive");
603 
604 		/* clear bg scan NOPICK and mark cancel request */
605 		ss->ss_flags &= ~IEEE80211_SCAN_NOPICK;
606 		SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_CANCEL;
607 		/* force it to fire asap */
608 		callout_reset(&SCAN_PRIVATE(ss)->ss_scan_timer,
609 			0, scan_next, ss);
610 	}
611 	IEEE80211_UNLOCK(ic);
612 }
613 
614 /*
615  * Public access to scan_next for drivers that manage
616  * scanning themselves (e.g. for firmware-based devices).
617  */
618 void
619 ieee80211_scan_next(struct ieee80211com *ic)
620 {
621 	/*
622 	 * XXX: We might need/want to decouple context here by either:
623 	 *  callout_reset(&SCAN_PRIVATE(ss)->ss_scan_timer, 0, scan_next, ss);
624 	 * or using a taskqueue.  Let's see what kind of problems direct
625 	 * dispatch has for now.
626 	 */
627 	scan_next(ic->ic_scan);
628 }
629 
630 /*
631  * Public access to scan_next for drivers that are not able to scan single
632  * channels (e.g. for firmware-based devices).
633  */
634 void
635 ieee80211_scan_done(struct ieee80211com *ic)
636 {
637 	struct ieee80211_scan_state *ss = ic->ic_scan;
638 
639 	ss->ss_next = ss->ss_last; /* all channels are complete */
640 	scan_next(ss);
641 }
642 
643 /*
644  * Scan curchan.  If this is an active scan and the channel
645  * is not marked passive then send probe request frame(s).
646  * Arrange for the channel change after maxdwell ticks.
647  */
648 static void
649 scan_curchan(struct ieee80211com *ic, unsigned long maxdwell)
650 {
651 	struct ieee80211_scan_state *ss = ic->ic_scan;
652 
653 	if ((ss->ss_flags & IEEE80211_SCAN_ACTIVE) &&
654 	    (ic->ic_curchan->ic_flags & IEEE80211_CHAN_PASSIVE) == 0) {
655 		struct ifnet *ifp = ic->ic_ifp;
656 		int i;
657 
658 		/*
659 		 * Send a broadcast probe request followed by
660 		 * any specified directed probe requests.
661 		 * XXX suppress broadcast probe req?
662 		 * XXX remove dependence on ic/ic->ic_bss
663 		 * XXX move to policy code?
664 		 */
665 		ieee80211_send_probereq(ic->ic_bss,
666 			ic->ic_myaddr, ifp->if_broadcastaddr,
667 			ifp->if_broadcastaddr,
668 			"", 0,
669 			ic->ic_opt_ie, ic->ic_opt_ie_len);
670 		for (i = 0; i < ss->ss_nssid; i++)
671 			ieee80211_send_probereq(ic->ic_bss,
672 				ic->ic_myaddr, ifp->if_broadcastaddr,
673 				ifp->if_broadcastaddr,
674 				ss->ss_ssid[i].ssid,
675 				ss->ss_ssid[i].len,
676 				ic->ic_opt_ie, ic->ic_opt_ie_len);
677 	}
678 	callout_reset(&SCAN_PRIVATE(ss)->ss_scan_timer,
679 		maxdwell, scan_next, ss);
680 }
681 
682 /*
683  * Handle mindwell requirements completed; initiate a channel
684  * change to the next channel asap.
685  */
686 static void
687 scan_mindwell(struct ieee80211com *ic)
688 {
689 	struct ieee80211_scan_state *ss = ic->ic_scan;
690 
691 	callout_reset(&SCAN_PRIVATE(ss)->ss_scan_timer, 0, scan_next, ss);
692 }
693 
694 /*
695  * Switch to the next channel marked for scanning.
696  */
697 static void
698 scan_next(void *arg)
699 {
700 #define	ISCAN_REP	(ISCAN_MINDWELL | ISCAN_START | ISCAN_DISCARD)
701 	struct ieee80211_scan_state *ss = (struct ieee80211_scan_state *) arg;
702 	struct ieee80211com *ic = ss->ss_ic;
703 	struct ieee80211_channel *chan;
704 	unsigned long maxdwell, scanend;
705 	int scanning, scandone;
706 
707 	IEEE80211_LOCK(ic);
708 	scanning = (ic->ic_flags & IEEE80211_F_SCAN) != 0;
709 	IEEE80211_UNLOCK(ic);
710 	if (!scanning)			/* canceled */
711 		return;
712 
713 again:
714 	scandone = (ss->ss_next >= ss->ss_last) ||
715 		(SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) != 0;
716 	scanend = SCAN_PRIVATE(ss)->ss_scanend;
717 	if (!scandone &&
718 	    (ss->ss_flags & IEEE80211_SCAN_GOTPICK) == 0 &&
719 	    ((SCAN_PRIVATE(ss)->ss_iflags & ISCAN_START) ||
720 	     time_before(ticks + ss->ss_mindwell, scanend))) {
721 		chan = ss->ss_chans[ss->ss_next++];
722 
723 		/*
724 		 * Watch for truncation due to the scan end time.
725 		 */
726 		if (time_after(ticks + ss->ss_maxdwell, scanend))
727 			maxdwell = scanend - ticks;
728 		else
729 			maxdwell = ss->ss_maxdwell;
730 
731 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN,
732 		    "%s: chan %3d%c -> %3d%c [%s, dwell min %lu max %lu]\n",
733 		    __func__,
734 		    ieee80211_chan2ieee(ic, ic->ic_curchan),
735 		        channel_type(ic->ic_curchan),
736 		    ieee80211_chan2ieee(ic, chan), channel_type(chan),
737 		    (ss->ss_flags & IEEE80211_SCAN_ACTIVE) &&
738 			(chan->ic_flags & IEEE80211_CHAN_PASSIVE) == 0 ?
739 			"active" : "passive",
740 		    ss->ss_mindwell, maxdwell);
741 
742 		/*
743 		 * Potentially change channel and phy mode.
744 		 */
745 		change_channel(ic, chan);
746 
747 		/*
748 		 * Scan curchan.  Drivers for "intelligent hardware"
749 		 * override ic_scan_curchan to tell the device to do
750 		 * the work.  Otherwise we manage the work outselves;
751 		 * sending a probe request (as needed), and arming the
752 		 * timeout to switch channels after maxdwell ticks.
753 		 */
754 		ic->ic_scan_curchan(ic, maxdwell);
755 
756 		SCAN_PRIVATE(ss)->ss_chanmindwell = ticks + ss->ss_mindwell;
757 		/* clear mindwell lock and initial channel change flush */
758 		SCAN_PRIVATE(ss)->ss_iflags &= ~ISCAN_REP;
759 	} else {
760 		ic->ic_scan_end(ic);		/* notify driver */
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 			change_channel(ic, ic->ic_bsschan);
772 		/* clear internal flags and any indication of a pick */
773 		SCAN_PRIVATE(ss)->ss_iflags &= ~ISCAN_REP;
774 		ss->ss_flags &= ~IEEE80211_SCAN_GOTPICK;
775 
776 		/*
777 		 * If not canceled and scan completed, do post-processing.
778 		 * If the callback function returns 0, then it wants to
779 		 * continue/restart scanning.  Unfortunately we needed to
780 		 * notify the driver to end the scan above to avoid having
781 		 * rx frames alter the scan candidate list.
782 		 */
783 		if ((SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) == 0 &&
784 		    !ss->ss_ops->scan_end(ss, ic) &&
785 		    (ss->ss_flags & IEEE80211_SCAN_ONCE) == 0 &&
786 		    time_before(ticks + ss->ss_mindwell, scanend)) {
787 			IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN,
788 			    "%s: done, restart "
789 			    "[ticks %u, dwell min %lu scanend %lu]\n",
790 			    __func__,
791 			    ticks, ss->ss_mindwell, scanend);
792 			ss->ss_next = 0;	/* reset to begining */
793 			if (ss->ss_flags & IEEE80211_SCAN_ACTIVE)
794 				ic->ic_stats.is_scan_active++;
795 			else
796 				ic->ic_stats.is_scan_passive++;
797 
798 			ic->ic_scan_start(ic);	/* notify driver */
799 			goto again;
800 		} else {
801 			/* past here, scandone is ``true'' if not in bg mode */
802 			if ((ss->ss_flags & IEEE80211_SCAN_BGSCAN) == 0)
803 				scandone = 1;
804 
805 			IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN,
806 			    "%s: %s, "
807 			    "[ticks %u, dwell min %lu scanend %lu]\n",
808 			    __func__, scandone ? "done" : "stopped",
809 			    ticks, ss->ss_mindwell, scanend);
810 
811 			/*
812 			 * Clear the SCAN bit first in case frames are
813 			 * pending on the station power save queue.  If
814 			 * we defer this then the dispatch of the frames
815 			 * may generate a request to cancel scanning.
816 			 */
817 			ic->ic_flags &= ~IEEE80211_F_SCAN;
818 			/*
819 			 * Drop out of power save mode when a scan has
820 			 * completed.  If this scan was prematurely terminated
821 			 * because it is a background scan then don't notify
822 			 * the ap; we'll either return to scanning after we
823 			 * receive the beacon frame or we'll drop out of power
824 			 * save mode because the beacon indicates we have frames
825 			 * waiting for us.
826 			 */
827 			if (scandone) {
828 				ieee80211_sta_pwrsave(ic, 0);
829 				if (ss->ss_next >= ss->ss_last) {
830 					ieee80211_notify_scan_done(ic);
831 					ic->ic_flags_ext &= ~IEEE80211_FEXT_BGSCAN;
832 				}
833 			}
834 			SCAN_PRIVATE(ss)->ss_iflags &= ~ISCAN_CANCEL;
835 			ss->ss_flags &=
836 			    ~(IEEE80211_SCAN_ONCE | IEEE80211_SCAN_PICK1ST);
837 		}
838 	}
839 #undef ISCAN_REP
840 }
841 
842 #ifdef IEEE80211_DEBUG
843 static void
844 dump_probe_beacon(uint8_t subtype, int isnew,
845 	const uint8_t mac[IEEE80211_ADDR_LEN],
846 	const struct ieee80211_scanparams *sp)
847 {
848 
849 	printf("[%s] %s%s on chan %u (bss chan %u) ",
850 	    ether_sprintf(mac), isnew ? "new " : "",
851 	    ieee80211_mgt_subtype_name[subtype >> IEEE80211_FC0_SUBTYPE_SHIFT],
852 	    IEEE80211_CHAN2IEEE(sp->curchan), sp->bchan);
853 	ieee80211_print_essid(sp->ssid + 2, sp->ssid[1]);
854 	printf("\n");
855 
856 	if (isnew) {
857 		printf("[%s] caps 0x%x bintval %u erp 0x%x",
858 			ether_sprintf(mac), sp->capinfo, sp->bintval, sp->erp);
859 		if (sp->country != NULL) {
860 #ifdef __FreeBSD__
861 			printf(" country info %*D",
862 				sp->country[1], sp->country+2, " ");
863 #else
864 			int i;
865 			printf(" country info");
866 			for (i = 0; i < sp->country[1]; i++)
867 				printf(" %02x", sp->country[i+2]);
868 #endif
869 		}
870 		printf("\n");
871 	}
872 }
873 #endif /* IEEE80211_DEBUG */
874 
875 /*
876  * Process a beacon or probe response frame.
877  */
878 void
879 ieee80211_add_scan(struct ieee80211com *ic,
880 	const struct ieee80211_scanparams *sp,
881 	const struct ieee80211_frame *wh,
882 	int subtype, int rssi, int noise, int rstamp)
883 {
884 	struct ieee80211_scan_state *ss = ic->ic_scan;
885 
886 	/*
887 	 * Frames received during startup are discarded to avoid
888 	 * using scan state setup on the initial entry to the timer
889 	 * callback.  This can occur because the device may enable
890 	 * rx prior to our doing the initial channel change in the
891 	 * timer routine (we defer the channel change to the timer
892 	 * code to simplify locking on linux).
893 	 */
894 	if (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_DISCARD)
895 		return;
896 #ifdef IEEE80211_DEBUG
897 	if (ieee80211_msg_scan(ic) && (ic->ic_flags & IEEE80211_F_SCAN))
898 		dump_probe_beacon(subtype, 1, wh->i_addr2, sp);
899 #endif
900 	if (ss->ss_ops != NULL &&
901 	    ss->ss_ops->scan_add(ss, sp, wh, subtype, rssi, noise, rstamp)) {
902 		/*
903 		 * If we've reached the min dwell time terminate
904 		 * the timer so we'll switch to the next channel.
905 		 */
906 		if ((SCAN_PRIVATE(ss)->ss_iflags & ISCAN_MINDWELL) == 0 &&
907 		    time_after_eq(ticks, SCAN_PRIVATE(ss)->ss_chanmindwell)) {
908 			IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN,
909 			    "%s: chan %3d%c min dwell met (%u > %lu)\n",
910 			    __func__,
911 			    ieee80211_chan2ieee(ic, ic->ic_curchan),
912 				channel_type(ic->ic_curchan),
913 			    ticks, SCAN_PRIVATE(ss)->ss_chanmindwell);
914 			SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_MINDWELL;
915 			/*
916 			 * NB: trigger at next clock tick or wait for the
917 			 * hardware
918 			 */
919 			ic->ic_scan_mindwell(ic);
920 		}
921 	}
922 }
923 
924 /*
925  * Timeout/age scan cache entries; called from sta timeout
926  * timer (XXX should be self-contained).
927  */
928 void
929 ieee80211_scan_timeout(struct ieee80211com *ic)
930 {
931 	struct ieee80211_scan_state *ss = ic->ic_scan;
932 
933 	if (ss->ss_ops != NULL)
934 		ss->ss_ops->scan_age(ss);
935 }
936 
937 /*
938  * Mark a scan cache entry after a successful associate.
939  */
940 void
941 ieee80211_scan_assoc_success(struct ieee80211com *ic, const uint8_t mac[])
942 {
943 	struct ieee80211_scan_state *ss = ic->ic_scan;
944 
945 	if (ss->ss_ops != NULL) {
946 		IEEE80211_NOTE_MAC(ic, IEEE80211_MSG_SCAN,
947 			mac, "%s",  __func__);
948 		ss->ss_ops->scan_assoc_success(ss, mac);
949 	}
950 }
951 
952 /*
953  * Demerit a scan cache entry after failing to associate.
954  */
955 void
956 ieee80211_scan_assoc_fail(struct ieee80211com *ic,
957 	const uint8_t mac[], int reason)
958 {
959 	struct ieee80211_scan_state *ss = ic->ic_scan;
960 
961 	if (ss->ss_ops != NULL) {
962 		IEEE80211_NOTE_MAC(ic, IEEE80211_MSG_SCAN, mac,
963 			"%s: reason %u", __func__, reason);
964 		ss->ss_ops->scan_assoc_fail(ss, mac, reason);
965 	}
966 }
967 
968 /*
969  * Iterate over the contents of the scan cache.
970  */
971 void
972 ieee80211_scan_iterate(struct ieee80211com *ic,
973 	ieee80211_scan_iter_func *f, void *arg)
974 {
975 	struct ieee80211_scan_state *ss = ic->ic_scan;
976 
977 	if (ss->ss_ops != NULL)
978 		ss->ss_ops->scan_iterate(ss, f, arg);
979 }
980 
981 /*
982  * Flush the contents of the scan cache.
983  */
984 void
985 ieee80211_scan_flush(struct ieee80211com *ic)
986 {
987 	struct ieee80211_scan_state *ss = ic->ic_scan;
988 
989 	if (ss->ss_ops != NULL) {
990 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_SCAN,
991 			"%s\n",  __func__);
992 		ss->ss_ops->scan_flush(ss);
993 	}
994 }
995