1 /*
2  * WPA Supplicant - background scan and roaming module: learn
3  * Copyright (c) 2009-2010, Jouni Malinen <j@w1.fi>
4  *
5  * This software may be distributed under the terms of the BSD license.
6  * See README for more details.
7  */
8 
9 #include "includes.h"
10 
11 #include "common.h"
12 #include "eloop.h"
13 #include "list.h"
14 #include "common/ieee802_11_defs.h"
15 #include "drivers/driver.h"
16 #include "config_ssid.h"
17 #include "wpa_supplicant_i.h"
18 #include "driver_i.h"
19 #include "scan.h"
20 #include "bgscan.h"
21 
22 struct bgscan_learn_bss {
23 	struct dl_list list;
24 	u8 bssid[ETH_ALEN];
25 	int freq;
26 	u8 *neigh; /* num_neigh * ETH_ALEN buffer */
27 	size_t num_neigh;
28 };
29 
30 struct bgscan_learn_data {
31 	struct wpa_supplicant *wpa_s;
32 	const struct wpa_ssid *ssid;
33 	int scan_interval;
34 	int signal_threshold;
35 	int short_interval; /* use if signal < threshold */
36 	int long_interval; /* use if signal > threshold */
37 	struct os_reltime last_bgscan;
38 	char *fname;
39 	struct dl_list bss;
40 	int *supp_freqs;
41 	int probe_idx;
42 };
43 
44 
bss_free(struct bgscan_learn_bss * bss)45 static void bss_free(struct bgscan_learn_bss *bss)
46 {
47 	os_free(bss->neigh);
48 	os_free(bss);
49 }
50 
51 
bssid_in_array(u8 * array,size_t array_len,const u8 * bssid)52 static int bssid_in_array(u8 *array, size_t array_len, const u8 *bssid)
53 {
54 	size_t i;
55 
56 	if (array == NULL || array_len == 0)
57 		return 0;
58 
59 	for (i = 0; i < array_len; i++) {
60 		if (os_memcmp(array + i * ETH_ALEN, bssid, ETH_ALEN) == 0)
61 			return 1;
62 	}
63 
64 	return 0;
65 }
66 
67 
bgscan_learn_add_neighbor(struct bgscan_learn_bss * bss,const u8 * bssid)68 static void bgscan_learn_add_neighbor(struct bgscan_learn_bss *bss,
69 				      const u8 *bssid)
70 {
71 	u8 *n;
72 
73 	if (os_memcmp(bss->bssid, bssid, ETH_ALEN) == 0)
74 		return;
75 	if (bssid_in_array(bss->neigh, bss->num_neigh, bssid))
76 		return;
77 
78 	n = os_realloc_array(bss->neigh, bss->num_neigh + 1, ETH_ALEN);
79 	if (n == NULL)
80 		return;
81 
82 	os_memcpy(n + bss->num_neigh * ETH_ALEN, bssid, ETH_ALEN);
83 	bss->neigh = n;
84 	bss->num_neigh++;
85 }
86 
87 
bgscan_learn_get_bss(struct bgscan_learn_data * data,const u8 * bssid)88 static struct bgscan_learn_bss * bgscan_learn_get_bss(
89 	struct bgscan_learn_data *data, const u8 *bssid)
90 {
91 	struct bgscan_learn_bss *bss;
92 
93 	dl_list_for_each(bss, &data->bss, struct bgscan_learn_bss, list) {
94 		if (os_memcmp(bss->bssid, bssid, ETH_ALEN) == 0)
95 			return bss;
96 	}
97 	return NULL;
98 }
99 
100 
bgscan_learn_load(struct bgscan_learn_data * data)101 static int bgscan_learn_load(struct bgscan_learn_data *data)
102 {
103 	FILE *f;
104 	char buf[128];
105 	struct bgscan_learn_bss *bss;
106 
107 	if (data->fname == NULL)
108 		return 0;
109 
110 	f = fopen(data->fname, "r");
111 	if (f == NULL)
112 		return 0;
113 
114 	wpa_printf(MSG_DEBUG, "bgscan learn: Loading data from %s",
115 		   data->fname);
116 
117 	if (fgets(buf, sizeof(buf), f) == NULL ||
118 	    os_strncmp(buf, "wpa_supplicant-bgscan-learn\n", 28) != 0) {
119 		wpa_printf(MSG_INFO, "bgscan learn: Invalid data file %s",
120 			   data->fname);
121 		fclose(f);
122 		return -1;
123 	}
124 
125 	while (fgets(buf, sizeof(buf), f)) {
126 		if (os_strncmp(buf, "BSS ", 4) == 0) {
127 			bss = os_zalloc(sizeof(*bss));
128 			if (!bss)
129 				continue;
130 			if (hwaddr_aton(buf + 4, bss->bssid) < 0) {
131 				bss_free(bss);
132 				continue;
133 			}
134 			bss->freq = atoi(buf + 4 + 18);
135 			dl_list_add(&data->bss, &bss->list);
136 			wpa_printf(MSG_DEBUG, "bgscan learn: Loaded BSS "
137 				   "entry: " MACSTR " freq=%d",
138 				   MAC2STR(bss->bssid), bss->freq);
139 		}
140 
141 		if (os_strncmp(buf, "NEIGHBOR ", 9) == 0) {
142 			u8 addr[ETH_ALEN];
143 
144 			if (hwaddr_aton(buf + 9, addr) < 0)
145 				continue;
146 			bss = bgscan_learn_get_bss(data, addr);
147 			if (bss == NULL)
148 				continue;
149 			if (hwaddr_aton(buf + 9 + 18, addr) < 0)
150 				continue;
151 
152 			bgscan_learn_add_neighbor(bss, addr);
153 		}
154 	}
155 
156 	fclose(f);
157 	return 0;
158 }
159 
160 
bgscan_learn_save(struct bgscan_learn_data * data)161 static void bgscan_learn_save(struct bgscan_learn_data *data)
162 {
163 	FILE *f;
164 	struct bgscan_learn_bss *bss;
165 
166 	if (data->fname == NULL)
167 		return;
168 
169 	wpa_printf(MSG_DEBUG, "bgscan learn: Saving data to %s",
170 		   data->fname);
171 
172 	f = fopen(data->fname, "w");
173 	if (f == NULL)
174 		return;
175 	fprintf(f, "wpa_supplicant-bgscan-learn\n");
176 
177 	dl_list_for_each(bss, &data->bss, struct bgscan_learn_bss, list) {
178 		fprintf(f, "BSS " MACSTR " %d\n",
179 			MAC2STR(bss->bssid), bss->freq);
180 	}
181 
182 	dl_list_for_each(bss, &data->bss, struct bgscan_learn_bss, list) {
183 		size_t i;
184 		for (i = 0; i < bss->num_neigh; i++) {
185 			fprintf(f, "NEIGHBOR " MACSTR " " MACSTR "\n",
186 				MAC2STR(bss->bssid),
187 				MAC2STR(bss->neigh + i * ETH_ALEN));
188 		}
189 	}
190 
191 	fclose(f);
192 }
193 
194 
in_array(int * array,int val)195 static int in_array(int *array, int val)
196 {
197 	int i;
198 
199 	if (array == NULL)
200 		return 0;
201 
202 	for (i = 0; array[i]; i++) {
203 		if (array[i] == val)
204 			return 1;
205 	}
206 
207 	return 0;
208 }
209 
210 
bgscan_learn_get_freqs(struct bgscan_learn_data * data,size_t * count)211 static int * bgscan_learn_get_freqs(struct bgscan_learn_data *data,
212 				    size_t *count)
213 {
214 	struct bgscan_learn_bss *bss;
215 	int *freqs = NULL, *n;
216 
217 	*count = 0;
218 
219 	dl_list_for_each(bss, &data->bss, struct bgscan_learn_bss, list) {
220 		if (in_array(freqs, bss->freq))
221 			continue;
222 		n = os_realloc_array(freqs, *count + 2, sizeof(int));
223 		if (n == NULL)
224 			return freqs;
225 		freqs = n;
226 		freqs[*count] = bss->freq;
227 		(*count)++;
228 		freqs[*count] = 0;
229 	}
230 
231 	return freqs;
232 }
233 
234 
bgscan_learn_get_probe_freq(struct bgscan_learn_data * data,int * freqs,size_t count)235 static int * bgscan_learn_get_probe_freq(struct bgscan_learn_data *data,
236 					 int *freqs, size_t count)
237 {
238 	int idx, *n;
239 
240 	if (data->supp_freqs == NULL)
241 		return freqs;
242 
243 	idx = data->probe_idx;
244 	do {
245 		if (!in_array(freqs, data->supp_freqs[idx])) {
246 			wpa_printf(MSG_DEBUG, "bgscan learn: Probe new freq "
247 				   "%u", data->supp_freqs[idx]);
248 			data->probe_idx = idx + 1;
249 			if (data->supp_freqs[data->probe_idx] == 0)
250 				data->probe_idx = 0;
251 			n = os_realloc_array(freqs, count + 2, sizeof(int));
252 			if (n == NULL)
253 				return freqs;
254 			freqs = n;
255 			freqs[count] = data->supp_freqs[idx];
256 			count++;
257 			freqs[count] = 0;
258 			break;
259 		}
260 
261 		idx++;
262 		if (data->supp_freqs[idx] == 0)
263 			idx = 0;
264 	} while (idx != data->probe_idx);
265 
266 	return freqs;
267 }
268 
269 
bgscan_learn_timeout(void * eloop_ctx,void * timeout_ctx)270 static void bgscan_learn_timeout(void *eloop_ctx, void *timeout_ctx)
271 {
272 	struct bgscan_learn_data *data = eloop_ctx;
273 	struct wpa_supplicant *wpa_s = data->wpa_s;
274 	struct wpa_driver_scan_params params;
275 	int *freqs = NULL;
276 	size_t count, i;
277 	char msg[100], *pos;
278 
279 	os_memset(&params, 0, sizeof(params));
280 	params.num_ssids = 1;
281 	params.ssids[0].ssid = data->ssid->ssid;
282 	params.ssids[0].ssid_len = data->ssid->ssid_len;
283 	if (data->ssid->scan_freq)
284 		params.freqs = data->ssid->scan_freq;
285 	else {
286 		freqs = bgscan_learn_get_freqs(data, &count);
287 		wpa_printf(MSG_DEBUG, "bgscan learn: BSSes in this ESS have "
288 			   "been seen on %u channels", (unsigned int) count);
289 		freqs = bgscan_learn_get_probe_freq(data, freqs, count);
290 
291 		msg[0] = '\0';
292 		pos = msg;
293 		for (i = 0; freqs && freqs[i]; i++) {
294 			int ret;
295 			ret = os_snprintf(pos, msg + sizeof(msg) - pos, " %d",
296 					  freqs[i]);
297 			if (os_snprintf_error(msg + sizeof(msg) - pos, ret))
298 				break;
299 			pos += ret;
300 		}
301 		pos[0] = '\0';
302 		wpa_printf(MSG_DEBUG, "bgscan learn: Scanning frequencies:%s",
303 			   msg);
304 		params.freqs = freqs;
305 	}
306 
307 	wpa_printf(MSG_DEBUG, "bgscan learn: Request a background scan");
308 	if (wpa_supplicant_trigger_scan(wpa_s, &params)) {
309 		wpa_printf(MSG_DEBUG, "bgscan learn: Failed to trigger scan");
310 		eloop_register_timeout(data->scan_interval, 0,
311 				       bgscan_learn_timeout, data, NULL);
312 	} else
313 		os_get_reltime(&data->last_bgscan);
314 	os_free(freqs);
315 }
316 
317 
bgscan_learn_get_params(struct bgscan_learn_data * data,const char * params)318 static int bgscan_learn_get_params(struct bgscan_learn_data *data,
319 				   const char *params)
320 {
321 	const char *pos;
322 
323 	data->short_interval = atoi(params);
324 
325 	pos = os_strchr(params, ':');
326 	if (pos == NULL)
327 		return 0;
328 	pos++;
329 	data->signal_threshold = atoi(pos);
330 	pos = os_strchr(pos, ':');
331 	if (pos == NULL) {
332 		wpa_printf(MSG_ERROR, "bgscan learn: Missing scan interval "
333 			   "for high signal");
334 		return -1;
335 	}
336 	pos++;
337 	data->long_interval = atoi(pos);
338 	pos = os_strchr(pos, ':');
339 	if (pos) {
340 		pos++;
341 		data->fname = os_strdup(pos);
342 	}
343 
344 	return 0;
345 }
346 
347 
bgscan_learn_get_supp_freqs(struct wpa_supplicant * wpa_s)348 static int * bgscan_learn_get_supp_freqs(struct wpa_supplicant *wpa_s)
349 {
350 	struct hostapd_hw_modes *modes;
351 	int i, j, *freqs = NULL, *n;
352 	size_t count = 0;
353 
354 	modes = wpa_s->hw.modes;
355 	if (modes == NULL)
356 		return NULL;
357 
358 	for (i = 0; i < wpa_s->hw.num_modes; i++) {
359 		for (j = 0; j < modes[i].num_channels; j++) {
360 			if (modes[i].channels[j].flag & HOSTAPD_CHAN_DISABLED)
361 				continue;
362 			/* some hw modes (e.g. 11b & 11g) contain same freqs */
363 			if (in_array(freqs, modes[i].channels[j].freq))
364 				continue;
365 			n = os_realloc_array(freqs, count + 2, sizeof(int));
366 			if (n == NULL)
367 				continue;
368 
369 			freqs = n;
370 			freqs[count] = modes[i].channels[j].freq;
371 			count++;
372 			freqs[count] = 0;
373 		}
374 	}
375 
376 	return freqs;
377 }
378 
379 
bgscan_learn_init(struct wpa_supplicant * wpa_s,const char * params,const struct wpa_ssid * ssid)380 static void * bgscan_learn_init(struct wpa_supplicant *wpa_s,
381 				const char *params,
382 				const struct wpa_ssid *ssid)
383 {
384 	struct bgscan_learn_data *data;
385 
386 	data = os_zalloc(sizeof(*data));
387 	if (data == NULL)
388 		return NULL;
389 	dl_list_init(&data->bss);
390 	data->wpa_s = wpa_s;
391 	data->ssid = ssid;
392 	if (bgscan_learn_get_params(data, params) < 0) {
393 		os_free(data->fname);
394 		os_free(data);
395 		return NULL;
396 	}
397 	if (data->short_interval <= 0)
398 		data->short_interval = 30;
399 	if (data->long_interval <= 0)
400 		data->long_interval = 30;
401 
402 	if (bgscan_learn_load(data) < 0) {
403 		os_free(data->fname);
404 		os_free(data);
405 		return NULL;
406 	}
407 
408 	wpa_printf(MSG_DEBUG, "bgscan learn: Signal strength threshold %d  "
409 		   "Short bgscan interval %d  Long bgscan interval %d",
410 		   data->signal_threshold, data->short_interval,
411 		   data->long_interval);
412 
413 	if (data->signal_threshold &&
414 	    wpa_drv_signal_monitor(wpa_s, data->signal_threshold, 4) < 0) {
415 		wpa_printf(MSG_ERROR, "bgscan learn: Failed to enable "
416 			   "signal strength monitoring");
417 	}
418 
419 	data->supp_freqs = bgscan_learn_get_supp_freqs(wpa_s);
420 	data->scan_interval = data->short_interval;
421 	if (data->signal_threshold) {
422 		/* Poll for signal info to set initial scan interval */
423 		struct wpa_signal_info siginfo;
424 		if (wpa_drv_signal_poll(wpa_s, &siginfo) == 0 &&
425 		    siginfo.current_signal >= data->signal_threshold)
426 			data->scan_interval = data->long_interval;
427 	}
428 
429 	eloop_register_timeout(data->scan_interval, 0, bgscan_learn_timeout,
430 			       data, NULL);
431 
432 	/*
433 	 * This function is called immediately after an association, so it is
434 	 * reasonable to assume that a scan was completed recently. This makes
435 	 * us skip an immediate new scan in cases where the current signal
436 	 * level is below the bgscan threshold.
437 	 */
438 	os_get_reltime(&data->last_bgscan);
439 
440 	return data;
441 }
442 
443 
bgscan_learn_deinit(void * priv)444 static void bgscan_learn_deinit(void *priv)
445 {
446 	struct bgscan_learn_data *data = priv;
447 	struct bgscan_learn_bss *bss, *n;
448 
449 	bgscan_learn_save(data);
450 	eloop_cancel_timeout(bgscan_learn_timeout, data, NULL);
451 	if (data->signal_threshold)
452 		wpa_drv_signal_monitor(data->wpa_s, 0, 0);
453 	os_free(data->fname);
454 	dl_list_for_each_safe(bss, n, &data->bss, struct bgscan_learn_bss,
455 			      list) {
456 		dl_list_del(&bss->list);
457 		bss_free(bss);
458 	}
459 	os_free(data->supp_freqs);
460 	os_free(data);
461 }
462 
463 
bgscan_learn_bss_match(struct bgscan_learn_data * data,struct wpa_scan_res * bss)464 static int bgscan_learn_bss_match(struct bgscan_learn_data *data,
465 				  struct wpa_scan_res *bss)
466 {
467 	const u8 *ie;
468 
469 	ie = wpa_scan_get_ie(bss, WLAN_EID_SSID);
470 	if (ie == NULL)
471 		return 0;
472 
473 	if (data->ssid->ssid_len != ie[1] ||
474 	    os_memcmp(data->ssid->ssid, ie + 2, ie[1]) != 0)
475 		return 0; /* SSID mismatch */
476 
477 	return 1;
478 }
479 
480 
bgscan_learn_notify_scan(void * priv,struct wpa_scan_results * scan_res)481 static int bgscan_learn_notify_scan(void *priv,
482 				    struct wpa_scan_results *scan_res)
483 {
484 	struct bgscan_learn_data *data = priv;
485 	size_t i, j;
486 #define MAX_BSS 50
487 	u8 bssid[MAX_BSS * ETH_ALEN];
488 	size_t num_bssid = 0;
489 
490 	wpa_printf(MSG_DEBUG, "bgscan learn: scan result notification");
491 
492 	eloop_cancel_timeout(bgscan_learn_timeout, data, NULL);
493 	eloop_register_timeout(data->scan_interval, 0, bgscan_learn_timeout,
494 			       data, NULL);
495 
496 	for (i = 0; i < scan_res->num; i++) {
497 		struct wpa_scan_res *res = scan_res->res[i];
498 		if (!bgscan_learn_bss_match(data, res))
499 			continue;
500 
501 		if (num_bssid < MAX_BSS) {
502 			os_memcpy(bssid + num_bssid * ETH_ALEN, res->bssid,
503 				  ETH_ALEN);
504 			num_bssid++;
505 		}
506 	}
507 	wpa_printf(MSG_DEBUG, "bgscan learn: %u matching BSSes in scan "
508 		   "results", (unsigned int) num_bssid);
509 
510 	for (i = 0; i < scan_res->num; i++) {
511 		struct wpa_scan_res *res = scan_res->res[i];
512 		struct bgscan_learn_bss *bss;
513 
514 		if (!bgscan_learn_bss_match(data, res))
515 			continue;
516 
517 		bss = bgscan_learn_get_bss(data, res->bssid);
518 		if (bss && bss->freq != res->freq) {
519 			wpa_printf(MSG_DEBUG, "bgscan learn: Update BSS "
520 			   MACSTR " freq %d -> %d",
521 				   MAC2STR(res->bssid), bss->freq, res->freq);
522 			bss->freq = res->freq;
523 		} else if (!bss) {
524 			wpa_printf(MSG_DEBUG, "bgscan learn: Add BSS " MACSTR
525 				   " freq=%d", MAC2STR(res->bssid), res->freq);
526 			bss = os_zalloc(sizeof(*bss));
527 			if (!bss)
528 				continue;
529 			os_memcpy(bss->bssid, res->bssid, ETH_ALEN);
530 			bss->freq = res->freq;
531 			dl_list_add(&data->bss, &bss->list);
532 		}
533 
534 		for (j = 0; j < num_bssid; j++) {
535 			u8 *addr = bssid + j * ETH_ALEN;
536 			bgscan_learn_add_neighbor(bss, addr);
537 		}
538 	}
539 
540 	/*
541 	 * A more advanced bgscan could process scan results internally, select
542 	 * the BSS and request roam if needed. This sample uses the existing
543 	 * BSS/ESS selection routine. Change this to return 1 if selection is
544 	 * done inside the bgscan module.
545 	 */
546 
547 	return 0;
548 }
549 
550 
bgscan_learn_notify_beacon_loss(void * priv)551 static void bgscan_learn_notify_beacon_loss(void *priv)
552 {
553 	wpa_printf(MSG_DEBUG, "bgscan learn: beacon loss");
554 	/* TODO: speed up background scanning */
555 }
556 
557 
bgscan_learn_notify_signal_change(void * priv,int above,int current_signal,int current_noise,int current_txrate)558 static void bgscan_learn_notify_signal_change(void *priv, int above,
559 					      int current_signal,
560 					      int current_noise,
561 					      int current_txrate)
562 {
563 	struct bgscan_learn_data *data = priv;
564 	int scan = 0;
565 	struct os_reltime now;
566 
567 	if (data->short_interval == data->long_interval ||
568 	    data->signal_threshold == 0)
569 		return;
570 
571 	wpa_printf(MSG_DEBUG, "bgscan learn: signal level changed "
572 		   "(above=%d current_signal=%d current_noise=%d "
573 		   "current_txrate=%d)", above, current_signal,
574 		   current_noise, current_txrate);
575 	if (data->scan_interval == data->long_interval && !above) {
576 		wpa_printf(MSG_DEBUG, "bgscan learn: Start using short bgscan "
577 			   "interval");
578 		data->scan_interval = data->short_interval;
579 		os_get_reltime(&now);
580 		if (now.sec > data->last_bgscan.sec + 1)
581 			scan = 1;
582 	} else if (data->scan_interval == data->short_interval && above) {
583 		wpa_printf(MSG_DEBUG, "bgscan learn: Start using long bgscan "
584 			   "interval");
585 		data->scan_interval = data->long_interval;
586 		eloop_cancel_timeout(bgscan_learn_timeout, data, NULL);
587 		eloop_register_timeout(data->scan_interval, 0,
588 				       bgscan_learn_timeout, data, NULL);
589 	} else if (!above) {
590 		/*
591 		 * Signal dropped further 4 dB. Request a new scan if we have
592 		 * not yet scanned in a while.
593 		 */
594 		os_get_reltime(&now);
595 		if (now.sec > data->last_bgscan.sec + 10)
596 			scan = 1;
597 	}
598 
599 	if (scan) {
600 		wpa_printf(MSG_DEBUG, "bgscan learn: Trigger immediate scan");
601 		eloop_cancel_timeout(bgscan_learn_timeout, data, NULL);
602 		eloop_register_timeout(0, 0, bgscan_learn_timeout, data, NULL);
603 	}
604 }
605 
606 
607 const struct bgscan_ops bgscan_learn_ops = {
608 	.name = "learn",
609 	.init = bgscan_learn_init,
610 	.deinit = bgscan_learn_deinit,
611 	.notify_scan = bgscan_learn_notify_scan,
612 	.notify_beacon_loss = bgscan_learn_notify_beacon_loss,
613 	.notify_signal_change = bgscan_learn_notify_signal_change,
614 };
615