1 /*
2 * ACS - Automatic Channel Selection module
3 * Copyright (c) 2011, Atheros Communications
4 * Copyright (c) 2013, Qualcomm Atheros, Inc.
5 *
6 * This software may be distributed under the terms of the BSD license.
7 * See README for more details.
8 */
9
10 #include "utils/includes.h"
11 #include <math.h>
12
13 #include "utils/common.h"
14 #include "utils/list.h"
15 #include "common/ieee802_11_defs.h"
16 #include "common/wpa_ctrl.h"
17 #include "drivers/driver.h"
18 #include "hostapd.h"
19 #include "ap_drv_ops.h"
20 #include "ap_config.h"
21 #include "hw_features.h"
22 #include "acs.h"
23
24 /*
25 * Automatic Channel Selection
26 * ===========================
27 *
28 * More info at
29 * ------------
30 * http://wireless.kernel.org/en/users/Documentation/acs
31 *
32 * How to use
33 * ----------
34 * - make sure you have CONFIG_ACS=y in hostapd's .config
35 * - use channel=0 or channel=acs to enable ACS
36 *
37 * How does it work
38 * ----------------
39 * 1. passive scans are used to collect survey data
40 * (it is assumed that scan trigger collection of survey data in driver)
41 * 2. interference factor is calculated for each channel
42 * 3. ideal channel is picked depending on channel width by using adjacent
43 * channel interference factors
44 *
45 * Known limitations
46 * -----------------
47 * - Current implementation depends heavily on the amount of time willing to
48 * spend gathering survey data during hostapd startup. Short traffic bursts
49 * may be missed and a suboptimal channel may be picked.
50 * - Ideal channel may end up overlapping a channel with 40 MHz intolerant BSS
51 *
52 * Todo / Ideas
53 * ------------
54 * - implement other interference computation methods
55 * - BSS/RSSI based
56 * - spectral scan based
57 * (should be possibly to hook this up with current ACS scans)
58 * - add wpa_supplicant support (for P2P)
59 * - collect a histogram of interference over time allowing more educated
60 * guess about an ideal channel (perhaps CSA could be used to migrate AP to a
61 * new "better" channel while running)
62 * - include neighboring BSS scan to avoid conflicts with 40 MHz intolerant BSSs
63 * when choosing the ideal channel
64 *
65 * Survey interference factor implementation details
66 * -------------------------------------------------
67 * Generic interference_factor in struct hostapd_channel_data is used.
68 *
69 * The survey interference factor is defined as the ratio of the
70 * observed busy time over the time we spent on the channel,
71 * this value is then amplified by the observed noise floor on
72 * the channel in comparison to the lowest noise floor observed
73 * on the entire band.
74 *
75 * This corresponds to:
76 * ---
77 * (busy time - tx time) / (active time - tx time) * 2^(chan_nf + band_min_nf)
78 * ---
79 *
80 * The coefficient of 2 reflects the way power in "far-field"
81 * radiation decreases as the square of distance from the antenna [1].
82 * What this does is it decreases the observed busy time ratio if the
83 * noise observed was low but increases it if the noise was high,
84 * proportionally to the way "far field" radiation changes over
85 * distance.
86 *
87 * If channel busy time is not available the fallback is to use channel RX time.
88 *
89 * Since noise floor is in dBm it is necessary to convert it into Watts so that
90 * combined channel interference (e.g., HT40, which uses two channels) can be
91 * calculated easily.
92 * ---
93 * (busy time - tx time) / (active time - tx time) *
94 * 2^(10^(chan_nf/10) + 10^(band_min_nf/10))
95 * ---
96 *
97 * However to account for cases where busy/rx time is 0 (channel load is then
98 * 0%) channel noise floor signal power is combined into the equation so a
99 * channel with lower noise floor is preferred. The equation becomes:
100 * ---
101 * 10^(chan_nf/5) + (busy time - tx time) / (active time - tx time) *
102 * 2^(10^(chan_nf/10) + 10^(band_min_nf/10))
103 * ---
104 *
105 * All this "interference factor" is purely subjective and only time
106 * will tell how usable this is. By using the minimum noise floor we
107 * remove any possible issues due to card calibration. The computation
108 * of the interference factor then is dependent on what the card itself
109 * picks up as the minimum noise, not an actual real possible card
110 * noise value.
111 *
112 * Total interference computation details
113 * --------------------------------------
114 * The above channel interference factor is calculated with no respect to
115 * target operational bandwidth.
116 *
117 * To find an ideal channel the above data is combined by taking into account
118 * the target operational bandwidth and selected band. E.g., on 2.4 GHz channels
119 * overlap with 20 MHz bandwidth, but there is no overlap for 20 MHz bandwidth
120 * on 5 GHz.
121 *
122 * Each valid and possible channel spec (i.e., channel + width) is taken and its
123 * interference factor is computed by summing up interferences of each channel
124 * it overlaps. The one with least total interference is picked up.
125 *
126 * Note: This implies base channel interference factor must be non-negative
127 * allowing easy summing up.
128 *
129 * Example ACS analysis printout
130 * -----------------------------
131 *
132 * ACS: Trying survey-based ACS
133 * ACS: Survey analysis for channel 1 (2412 MHz)
134 * ACS: 1: min_nf=-113 interference_factor=0.0802469 nf=-113 time=162 busy=0 rx=13
135 * ACS: 2: min_nf=-113 interference_factor=0.0745342 nf=-113 time=161 busy=0 rx=12
136 * ACS: 3: min_nf=-113 interference_factor=0.0679012 nf=-113 time=162 busy=0 rx=11
137 * ACS: 4: min_nf=-113 interference_factor=0.0310559 nf=-113 time=161 busy=0 rx=5
138 * ACS: 5: min_nf=-113 interference_factor=0.0248447 nf=-113 time=161 busy=0 rx=4
139 * ACS: * interference factor average: 0.0557166
140 * ACS: Survey analysis for channel 2 (2417 MHz)
141 * ACS: 1: min_nf=-113 interference_factor=0.0185185 nf=-113 time=162 busy=0 rx=3
142 * ACS: 2: min_nf=-113 interference_factor=0.0246914 nf=-113 time=162 busy=0 rx=4
143 * ACS: 3: min_nf=-113 interference_factor=0.037037 nf=-113 time=162 busy=0 rx=6
144 * ACS: 4: min_nf=-113 interference_factor=0.149068 nf=-113 time=161 busy=0 rx=24
145 * ACS: 5: min_nf=-113 interference_factor=0.0248447 nf=-113 time=161 busy=0 rx=4
146 * ACS: * interference factor average: 0.050832
147 * ACS: Survey analysis for channel 3 (2422 MHz)
148 * ACS: 1: min_nf=-113 interference_factor=2.51189e-23 nf=-113 time=162 busy=0 rx=0
149 * ACS: 2: min_nf=-113 interference_factor=0.0185185 nf=-113 time=162 busy=0 rx=3
150 * ACS: 3: min_nf=-113 interference_factor=0.0186335 nf=-113 time=161 busy=0 rx=3
151 * ACS: 4: min_nf=-113 interference_factor=0.0186335 nf=-113 time=161 busy=0 rx=3
152 * ACS: 5: min_nf=-113 interference_factor=0.0186335 nf=-113 time=161 busy=0 rx=3
153 * ACS: * interference factor average: 0.0148838
154 * ACS: Survey analysis for channel 4 (2427 MHz)
155 * ACS: 1: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0
156 * ACS: 2: min_nf=-114 interference_factor=0.0555556 nf=-114 time=162 busy=0 rx=9
157 * ACS: 3: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=161 busy=0 rx=0
158 * ACS: 4: min_nf=-114 interference_factor=0.0186335 nf=-114 time=161 busy=0 rx=3
159 * ACS: 5: min_nf=-114 interference_factor=0.00621118 nf=-114 time=161 busy=0 rx=1
160 * ACS: * interference factor average: 0.0160801
161 * ACS: Survey analysis for channel 5 (2432 MHz)
162 * ACS: 1: min_nf=-114 interference_factor=0.409938 nf=-113 time=161 busy=0 rx=66
163 * ACS: 2: min_nf=-114 interference_factor=0.0432099 nf=-113 time=162 busy=0 rx=7
164 * ACS: 3: min_nf=-114 interference_factor=0.0124224 nf=-113 time=161 busy=0 rx=2
165 * ACS: 4: min_nf=-114 interference_factor=0.677019 nf=-113 time=161 busy=0 rx=109
166 * ACS: 5: min_nf=-114 interference_factor=0.0186335 nf=-114 time=161 busy=0 rx=3
167 * ACS: * interference factor average: 0.232244
168 * ACS: Survey analysis for channel 6 (2437 MHz)
169 * ACS: 1: min_nf=-113 interference_factor=0.552795 nf=-113 time=161 busy=0 rx=89
170 * ACS: 2: min_nf=-113 interference_factor=0.0807453 nf=-112 time=161 busy=0 rx=13
171 * ACS: 3: min_nf=-113 interference_factor=0.0310559 nf=-113 time=161 busy=0 rx=5
172 * ACS: 4: min_nf=-113 interference_factor=0.434783 nf=-112 time=161 busy=0 rx=70
173 * ACS: 5: min_nf=-113 interference_factor=0.0621118 nf=-113 time=161 busy=0 rx=10
174 * ACS: * interference factor average: 0.232298
175 * ACS: Survey analysis for channel 7 (2442 MHz)
176 * ACS: 1: min_nf=-113 interference_factor=0.440994 nf=-112 time=161 busy=0 rx=71
177 * ACS: 2: min_nf=-113 interference_factor=0.385093 nf=-113 time=161 busy=0 rx=62
178 * ACS: 3: min_nf=-113 interference_factor=0.0372671 nf=-113 time=161 busy=0 rx=6
179 * ACS: 4: min_nf=-113 interference_factor=0.0372671 nf=-113 time=161 busy=0 rx=6
180 * ACS: 5: min_nf=-113 interference_factor=0.0745342 nf=-113 time=161 busy=0 rx=12
181 * ACS: * interference factor average: 0.195031
182 * ACS: Survey analysis for channel 8 (2447 MHz)
183 * ACS: 1: min_nf=-114 interference_factor=0.0496894 nf=-112 time=161 busy=0 rx=8
184 * ACS: 2: min_nf=-114 interference_factor=0.0496894 nf=-114 time=161 busy=0 rx=8
185 * ACS: 3: min_nf=-114 interference_factor=0.0372671 nf=-113 time=161 busy=0 rx=6
186 * ACS: 4: min_nf=-114 interference_factor=0.12963 nf=-113 time=162 busy=0 rx=21
187 * ACS: 5: min_nf=-114 interference_factor=0.166667 nf=-114 time=162 busy=0 rx=27
188 * ACS: * interference factor average: 0.0865885
189 * ACS: Survey analysis for channel 9 (2452 MHz)
190 * ACS: 1: min_nf=-114 interference_factor=0.0124224 nf=-114 time=161 busy=0 rx=2
191 * ACS: 2: min_nf=-114 interference_factor=0.0310559 nf=-114 time=161 busy=0 rx=5
192 * ACS: 3: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=161 busy=0 rx=0
193 * ACS: 4: min_nf=-114 interference_factor=0.00617284 nf=-114 time=162 busy=0 rx=1
194 * ACS: 5: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0
195 * ACS: * interference factor average: 0.00993022
196 * ACS: Survey analysis for channel 10 (2457 MHz)
197 * ACS: 1: min_nf=-114 interference_factor=0.00621118 nf=-114 time=161 busy=0 rx=1
198 * ACS: 2: min_nf=-114 interference_factor=0.00621118 nf=-114 time=161 busy=0 rx=1
199 * ACS: 3: min_nf=-114 interference_factor=0.00621118 nf=-114 time=161 busy=0 rx=1
200 * ACS: 4: min_nf=-114 interference_factor=0.0493827 nf=-114 time=162 busy=0 rx=8
201 * ACS: 5: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0
202 * ACS: * interference factor average: 0.0136033
203 * ACS: Survey analysis for channel 11 (2462 MHz)
204 * ACS: 1: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=161 busy=0 rx=0
205 * ACS: 2: min_nf=-114 interference_factor=2.51189e-23 nf=-113 time=161 busy=0 rx=0
206 * ACS: 3: min_nf=-114 interference_factor=2.51189e-23 nf=-113 time=161 busy=0 rx=0
207 * ACS: 4: min_nf=-114 interference_factor=0.0432099 nf=-114 time=162 busy=0 rx=7
208 * ACS: 5: min_nf=-114 interference_factor=0.0925926 nf=-114 time=162 busy=0 rx=15
209 * ACS: * interference factor average: 0.0271605
210 * ACS: Survey analysis for channel 12 (2467 MHz)
211 * ACS: 1: min_nf=-114 interference_factor=0.0621118 nf=-113 time=161 busy=0 rx=10
212 * ACS: 2: min_nf=-114 interference_factor=0.00621118 nf=-114 time=161 busy=0 rx=1
213 * ACS: 3: min_nf=-114 interference_factor=2.51189e-23 nf=-113 time=162 busy=0 rx=0
214 * ACS: 4: min_nf=-114 interference_factor=2.51189e-23 nf=-113 time=162 busy=0 rx=0
215 * ACS: 5: min_nf=-114 interference_factor=0.00617284 nf=-113 time=162 busy=0 rx=1
216 * ACS: * interference factor average: 0.0148992
217 * ACS: Survey analysis for channel 13 (2472 MHz)
218 * ACS: 1: min_nf=-114 interference_factor=0.0745342 nf=-114 time=161 busy=0 rx=12
219 * ACS: 2: min_nf=-114 interference_factor=0.0555556 nf=-114 time=162 busy=0 rx=9
220 * ACS: 3: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0
221 * ACS: 4: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0
222 * ACS: 5: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0
223 * ACS: * interference factor average: 0.0260179
224 * ACS: Survey analysis for selected bandwidth 20MHz
225 * ACS: * channel 1: total interference = 0.121432
226 * ACS: * channel 2: total interference = 0.137512
227 * ACS: * channel 3: total interference = 0.369757
228 * ACS: * channel 4: total interference = 0.546338
229 * ACS: * channel 5: total interference = 0.690538
230 * ACS: * channel 6: total interference = 0.762242
231 * ACS: * channel 7: total interference = 0.756092
232 * ACS: * channel 8: total interference = 0.537451
233 * ACS: * channel 9: total interference = 0.332313
234 * ACS: * channel 10: total interference = 0.152182
235 * ACS: * channel 11: total interference = 0.0916111
236 * ACS: * channel 12: total interference = 0.0816809
237 * ACS: * channel 13: total interference = 0.0680776
238 * ACS: Ideal channel is 13 (2472 MHz) with total interference factor of 0.0680776
239 *
240 * [1] http://en.wikipedia.org/wiki/Near_and_far_field
241 */
242
243
244 static int acs_request_scan(struct hostapd_iface *iface);
245
246
acs_clean_chan_surveys(struct hostapd_channel_data * chan)247 static void acs_clean_chan_surveys(struct hostapd_channel_data *chan)
248 {
249 struct freq_survey *survey, *tmp;
250
251 if (dl_list_empty(&chan->survey_list))
252 return;
253
254 dl_list_for_each_safe(survey, tmp, &chan->survey_list,
255 struct freq_survey, list) {
256 dl_list_del(&survey->list);
257 os_free(survey);
258 }
259 }
260
261
acs_cleanup(struct hostapd_iface * iface)262 static void acs_cleanup(struct hostapd_iface *iface)
263 {
264 int i;
265 struct hostapd_channel_data *chan;
266
267 for (i = 0; i < iface->current_mode->num_channels; i++) {
268 chan = &iface->current_mode->channels[i];
269
270 if (chan->flag & HOSTAPD_CHAN_SURVEY_LIST_INITIALIZED)
271 acs_clean_chan_surveys(chan);
272
273 dl_list_init(&chan->survey_list);
274 chan->flag |= HOSTAPD_CHAN_SURVEY_LIST_INITIALIZED;
275 chan->min_nf = 0;
276 }
277
278 iface->chans_surveyed = 0;
279 iface->acs_num_completed_scans = 0;
280 }
281
282
acs_fail(struct hostapd_iface * iface)283 static void acs_fail(struct hostapd_iface *iface)
284 {
285 wpa_printf(MSG_ERROR, "ACS: Failed to start");
286 acs_cleanup(iface);
287 hostapd_disable_iface(iface);
288 }
289
290
291 static long double
acs_survey_interference_factor(struct freq_survey * survey,s8 min_nf)292 acs_survey_interference_factor(struct freq_survey *survey, s8 min_nf)
293 {
294 long double factor, busy, total;
295
296 if (survey->filled & SURVEY_HAS_CHAN_TIME_BUSY)
297 busy = survey->channel_time_busy;
298 else if (survey->filled & SURVEY_HAS_CHAN_TIME_RX)
299 busy = survey->channel_time_rx;
300 else {
301 /* This shouldn't really happen as survey data is checked in
302 * acs_sanity_check() */
303 wpa_printf(MSG_ERROR, "ACS: Survey data missing");
304 return 0;
305 }
306
307 total = survey->channel_time;
308
309 if (survey->filled & SURVEY_HAS_CHAN_TIME_TX) {
310 busy -= survey->channel_time_tx;
311 total -= survey->channel_time_tx;
312 }
313
314 /* TODO: figure out the best multiplier for noise floor base */
315 factor = pow(10, survey->nf / 5.0L) +
316 (busy / total) *
317 pow(2, pow(10, (long double) survey->nf / 10.0L) -
318 pow(10, (long double) min_nf / 10.0L));
319
320 return factor;
321 }
322
323
324 static void
acs_survey_chan_interference_factor(struct hostapd_iface * iface,struct hostapd_channel_data * chan)325 acs_survey_chan_interference_factor(struct hostapd_iface *iface,
326 struct hostapd_channel_data *chan)
327 {
328 struct freq_survey *survey;
329 unsigned int i = 0;
330 long double int_factor = 0;
331
332 if (dl_list_empty(&chan->survey_list))
333 return;
334
335 if (chan->flag & HOSTAPD_CHAN_DISABLED)
336 return;
337
338 chan->interference_factor = 0;
339
340 dl_list_for_each(survey, &chan->survey_list, struct freq_survey, list)
341 {
342 int_factor = acs_survey_interference_factor(survey,
343 iface->lowest_nf);
344 chan->interference_factor += int_factor;
345 wpa_printf(MSG_DEBUG, "ACS: %d: min_nf=%d interference_factor=%Lg nf=%d time=%lu busy=%lu rx=%lu",
346 ++i, chan->min_nf, int_factor,
347 survey->nf, (unsigned long) survey->channel_time,
348 (unsigned long) survey->channel_time_busy,
349 (unsigned long) survey->channel_time_rx);
350 }
351
352 chan->interference_factor = chan->interference_factor /
353 dl_list_len(&chan->survey_list);
354 }
355
356
acs_usable_ht40_chan(struct hostapd_channel_data * chan)357 static int acs_usable_ht40_chan(struct hostapd_channel_data *chan)
358 {
359 const int allowed[] = { 36, 44, 52, 60, 100, 108, 116, 124, 132, 149,
360 157, 184, 192 };
361 unsigned int i;
362
363 for (i = 0; i < ARRAY_SIZE(allowed); i++)
364 if (chan->chan == allowed[i])
365 return 1;
366
367 return 0;
368 }
369
370
acs_usable_vht80_chan(struct hostapd_channel_data * chan)371 static int acs_usable_vht80_chan(struct hostapd_channel_data *chan)
372 {
373 const int allowed[] = { 36, 52, 100, 116, 132, 149 };
374 unsigned int i;
375
376 for (i = 0; i < ARRAY_SIZE(allowed); i++)
377 if (chan->chan == allowed[i])
378 return 1;
379
380 return 0;
381 }
382
383
acs_survey_is_sufficient(struct freq_survey * survey)384 static int acs_survey_is_sufficient(struct freq_survey *survey)
385 {
386 if (!(survey->filled & SURVEY_HAS_NF)) {
387 wpa_printf(MSG_ERROR, "ACS: Survey is missing noise floor");
388 return 0;
389 }
390
391 if (!(survey->filled & SURVEY_HAS_CHAN_TIME)) {
392 wpa_printf(MSG_ERROR, "ACS: Survey is missing channel time");
393 return 0;
394 }
395
396 if (!(survey->filled & SURVEY_HAS_CHAN_TIME_BUSY) &&
397 !(survey->filled & SURVEY_HAS_CHAN_TIME_RX)) {
398 wpa_printf(MSG_ERROR, "ACS: Survey is missing RX and busy time (at least one is required)");
399 return 0;
400 }
401
402 return 1;
403 }
404
405
acs_survey_list_is_sufficient(struct hostapd_channel_data * chan)406 static int acs_survey_list_is_sufficient(struct hostapd_channel_data *chan)
407 {
408 struct freq_survey *survey;
409
410 dl_list_for_each(survey, &chan->survey_list, struct freq_survey, list)
411 {
412 if (!acs_survey_is_sufficient(survey)) {
413 wpa_printf(MSG_ERROR, "ACS: Channel %d has insufficient survey data",
414 chan->chan);
415 return 0;
416 }
417 }
418
419 return 1;
420
421 }
422
423
acs_surveys_are_sufficient(struct hostapd_iface * iface)424 static int acs_surveys_are_sufficient(struct hostapd_iface *iface)
425 {
426 int i;
427 struct hostapd_channel_data *chan;
428 int valid = 0;
429
430 for (i = 0; i < iface->current_mode->num_channels; i++) {
431 chan = &iface->current_mode->channels[i];
432 if (chan->flag & HOSTAPD_CHAN_DISABLED)
433 continue;
434
435 if (!acs_survey_list_is_sufficient(chan))
436 continue;
437
438 valid++;
439 }
440
441 /* We need at least survey data for one channel */
442 return !!valid;
443 }
444
445
acs_usable_chan(struct hostapd_channel_data * chan)446 static int acs_usable_chan(struct hostapd_channel_data *chan)
447 {
448 if (dl_list_empty(&chan->survey_list))
449 return 0;
450 if (chan->flag & HOSTAPD_CHAN_DISABLED)
451 return 0;
452 if (!acs_survey_list_is_sufficient(chan))
453 return 0;
454 return 1;
455 }
456
457
acs_survey_all_chans_intereference_factor(struct hostapd_iface * iface)458 static void acs_survey_all_chans_intereference_factor(
459 struct hostapd_iface *iface)
460 {
461 int i;
462 struct hostapd_channel_data *chan;
463
464 for (i = 0; i < iface->current_mode->num_channels; i++) {
465 chan = &iface->current_mode->channels[i];
466
467 if (!acs_usable_chan(chan))
468 continue;
469
470 wpa_printf(MSG_DEBUG, "ACS: Survey analysis for channel %d (%d MHz)",
471 chan->chan, chan->freq);
472
473 acs_survey_chan_interference_factor(iface, chan);
474
475 wpa_printf(MSG_DEBUG, "ACS: * interference factor average: %Lg",
476 chan->interference_factor);
477 }
478 }
479
480
acs_find_chan(struct hostapd_iface * iface,int freq)481 static struct hostapd_channel_data *acs_find_chan(struct hostapd_iface *iface,
482 int freq)
483 {
484 struct hostapd_channel_data *chan;
485 int i;
486
487 for (i = 0; i < iface->current_mode->num_channels; i++) {
488 chan = &iface->current_mode->channels[i];
489
490 if (chan->flag & HOSTAPD_CHAN_DISABLED)
491 continue;
492
493 if (chan->freq == freq)
494 return chan;
495 }
496
497 return NULL;
498 }
499
500
501 /*
502 * At this point it's assumed chan->interface_factor has been computed.
503 * This function should be reusable regardless of interference computation
504 * option (survey, BSS, spectral, ...). chan->interference factor must be
505 * summable (i.e., must be always greater than zero).
506 */
507 static struct hostapd_channel_data *
acs_find_ideal_chan(struct hostapd_iface * iface)508 acs_find_ideal_chan(struct hostapd_iface *iface)
509 {
510 struct hostapd_channel_data *chan, *adj_chan, *ideal_chan = NULL,
511 *rand_chan = NULL;
512 long double factor, ideal_factor = 0;
513 int i, j;
514 int n_chans = 1;
515
516 /* TODO: HT40- support */
517
518 if (iface->conf->ieee80211n &&
519 iface->conf->secondary_channel == -1) {
520 wpa_printf(MSG_ERROR, "ACS: HT40- is not supported yet. Please try HT40+");
521 return NULL;
522 }
523
524 if (iface->conf->ieee80211n &&
525 iface->conf->secondary_channel)
526 n_chans = 2;
527
528 if (iface->conf->ieee80211ac &&
529 iface->conf->vht_oper_chwidth == 1)
530 n_chans = 4;
531
532 /* TODO: VHT80+80, VHT160. Update acs_adjust_vht_center_freq() too. */
533
534 wpa_printf(MSG_DEBUG, "ACS: Survey analysis for selected bandwidth %d MHz",
535 n_chans == 1 ? 20 :
536 n_chans == 2 ? 40 :
537 n_chans == 4 ? 80 :
538 -1);
539
540 for (i = 0; i < iface->current_mode->num_channels; i++) {
541 chan = &iface->current_mode->channels[i];
542
543 if (chan->flag & HOSTAPD_CHAN_DISABLED)
544 continue;
545
546
547 /* HT40 on 5 GHz has a limited set of primary channels as per
548 * 11n Annex J */
549 if (iface->current_mode->mode == HOSTAPD_MODE_IEEE80211A &&
550 iface->conf->ieee80211n &&
551 iface->conf->secondary_channel &&
552 !acs_usable_ht40_chan(chan)) {
553 wpa_printf(MSG_DEBUG, "ACS: Channel %d: not allowed as primary channel for HT40",
554 chan->chan);
555 continue;
556 }
557
558 if (iface->current_mode->mode == HOSTAPD_MODE_IEEE80211A &&
559 iface->conf->ieee80211ac &&
560 iface->conf->vht_oper_chwidth == 1 &&
561 !acs_usable_vht80_chan(chan)) {
562 wpa_printf(MSG_DEBUG, "ACS: Channel %d: not allowed as primary channel for VHT80",
563 chan->chan);
564 continue;
565 }
566
567 factor = 0;
568 if (acs_usable_chan(chan))
569 factor = chan->interference_factor;
570
571 for (j = 1; j < n_chans; j++) {
572 adj_chan = acs_find_chan(iface, chan->freq + (j * 20));
573 if (!adj_chan)
574 break;
575
576 if (acs_usable_chan(adj_chan))
577 factor += adj_chan->interference_factor;
578 }
579
580 if (j != n_chans) {
581 wpa_printf(MSG_DEBUG, "ACS: Channel %d: not enough bandwidth",
582 chan->chan);
583 continue;
584 }
585
586 /* 2.4 GHz has overlapping 20 MHz channels. Include adjacent
587 * channel interference factor. */
588 if (iface->current_mode->mode == HOSTAPD_MODE_IEEE80211B ||
589 iface->current_mode->mode == HOSTAPD_MODE_IEEE80211G) {
590 for (j = 0; j < n_chans; j++) {
591 /* TODO: perhaps a multiplier should be used
592 * here? */
593
594 adj_chan = acs_find_chan(iface, chan->freq +
595 (j * 20) - 5);
596 if (adj_chan && acs_usable_chan(adj_chan))
597 factor += adj_chan->interference_factor;
598
599 adj_chan = acs_find_chan(iface, chan->freq +
600 (j * 20) - 10);
601 if (adj_chan && acs_usable_chan(adj_chan))
602 factor += adj_chan->interference_factor;
603
604 adj_chan = acs_find_chan(iface, chan->freq +
605 (j * 20) + 5);
606 if (adj_chan && acs_usable_chan(adj_chan))
607 factor += adj_chan->interference_factor;
608
609 adj_chan = acs_find_chan(iface, chan->freq +
610 (j * 20) + 10);
611 if (adj_chan && acs_usable_chan(adj_chan))
612 factor += adj_chan->interference_factor;
613 }
614 }
615
616 wpa_printf(MSG_DEBUG, "ACS: * channel %d: total interference = %Lg",
617 chan->chan, factor);
618
619 if (acs_usable_chan(chan) &&
620 (!ideal_chan || factor < ideal_factor)) {
621 ideal_factor = factor;
622 ideal_chan = chan;
623 }
624
625 /* This channel would at least be usable */
626 if (!rand_chan)
627 rand_chan = chan;
628 }
629
630 if (ideal_chan) {
631 wpa_printf(MSG_DEBUG, "ACS: Ideal channel is %d (%d MHz) with total interference factor of %Lg",
632 ideal_chan->chan, ideal_chan->freq, ideal_factor);
633 return ideal_chan;
634 }
635
636 return rand_chan;
637 }
638
639
acs_adjust_vht_center_freq(struct hostapd_iface * iface)640 static void acs_adjust_vht_center_freq(struct hostapd_iface *iface)
641 {
642 int offset;
643
644 wpa_printf(MSG_DEBUG, "ACS: Adjusting VHT center frequency");
645
646 switch (iface->conf->vht_oper_chwidth) {
647 case VHT_CHANWIDTH_USE_HT:
648 offset = 2 * iface->conf->secondary_channel;
649 break;
650 case VHT_CHANWIDTH_80MHZ:
651 offset = 6;
652 break;
653 default:
654 /* TODO: How can this be calculated? Adjust
655 * acs_find_ideal_chan() */
656 wpa_printf(MSG_INFO, "ACS: Only VHT20/40/80 is supported now");
657 return;
658 }
659
660 iface->conf->vht_oper_centr_freq_seg0_idx =
661 iface->conf->channel + offset;
662 }
663
664
acs_study_survey_based(struct hostapd_iface * iface)665 static int acs_study_survey_based(struct hostapd_iface *iface)
666 {
667 wpa_printf(MSG_DEBUG, "ACS: Trying survey-based ACS");
668
669 if (!iface->chans_surveyed) {
670 wpa_printf(MSG_ERROR, "ACS: Unable to collect survey data");
671 return -1;
672 }
673
674 if (!acs_surveys_are_sufficient(iface)) {
675 wpa_printf(MSG_ERROR, "ACS: Surveys have insufficient data");
676 return -1;
677 }
678
679 acs_survey_all_chans_intereference_factor(iface);
680 return 0;
681 }
682
683
acs_study_options(struct hostapd_iface * iface)684 static int acs_study_options(struct hostapd_iface *iface)
685 {
686 int err;
687
688 err = acs_study_survey_based(iface);
689 if (err == 0)
690 return 0;
691
692 /* TODO: If no surveys are available/sufficient this is a good
693 * place to fallback to BSS-based ACS */
694
695 return -1;
696 }
697
698
acs_study(struct hostapd_iface * iface)699 static void acs_study(struct hostapd_iface *iface)
700 {
701 struct hostapd_channel_data *ideal_chan;
702 int err;
703
704 err = acs_study_options(iface);
705 if (err < 0) {
706 wpa_printf(MSG_ERROR, "ACS: All study options have failed");
707 goto fail;
708 }
709
710 ideal_chan = acs_find_ideal_chan(iface);
711 if (!ideal_chan) {
712 wpa_printf(MSG_ERROR, "ACS: Failed to compute ideal channel");
713 err = -1;
714 goto fail;
715 }
716
717 iface->conf->channel = ideal_chan->chan;
718
719 if (iface->conf->ieee80211ac)
720 acs_adjust_vht_center_freq(iface);
721
722 err = 0;
723 fail:
724 /*
725 * hostapd_setup_interface_complete() will return -1 on failure,
726 * 0 on success and 0 is HOSTAPD_CHAN_VALID :)
727 */
728 if (hostapd_acs_completed(iface, err) == HOSTAPD_CHAN_VALID) {
729 acs_cleanup(iface);
730 return;
731 }
732
733 /* This can possibly happen if channel parameters (secondary
734 * channel, center frequencies) are misconfigured */
735 wpa_printf(MSG_ERROR, "ACS: Possibly channel configuration is invalid, please report this along with your config file.");
736 acs_fail(iface);
737 }
738
739
acs_scan_complete(struct hostapd_iface * iface)740 static void acs_scan_complete(struct hostapd_iface *iface)
741 {
742 int err;
743
744 iface->scan_cb = NULL;
745
746 wpa_printf(MSG_DEBUG, "ACS: Using survey based algorithm (acs_num_scans=%d)",
747 iface->conf->acs_num_scans);
748
749 err = hostapd_drv_get_survey(iface->bss[0], 0);
750 if (err) {
751 wpa_printf(MSG_ERROR, "ACS: Failed to get survey data");
752 goto fail;
753 }
754
755 if (++iface->acs_num_completed_scans < iface->conf->acs_num_scans) {
756 err = acs_request_scan(iface);
757 if (err) {
758 wpa_printf(MSG_ERROR, "ACS: Failed to request scan");
759 goto fail;
760 }
761
762 return;
763 }
764
765 acs_study(iface);
766 return;
767 fail:
768 hostapd_acs_completed(iface, 1);
769 acs_fail(iface);
770 }
771
772
acs_request_scan(struct hostapd_iface * iface)773 static int acs_request_scan(struct hostapd_iface *iface)
774 {
775 struct wpa_driver_scan_params params;
776 struct hostapd_channel_data *chan;
777 int i, *freq;
778
779 os_memset(¶ms, 0, sizeof(params));
780 params.freqs = os_calloc(iface->current_mode->num_channels + 1,
781 sizeof(params.freqs[0]));
782 if (params.freqs == NULL)
783 return -1;
784
785 freq = params.freqs;
786 for (i = 0; i < iface->current_mode->num_channels; i++) {
787 chan = &iface->current_mode->channels[i];
788 if (chan->flag & HOSTAPD_CHAN_DISABLED)
789 continue;
790
791 *freq++ = chan->freq;
792 }
793 *freq = 0;
794
795 iface->scan_cb = acs_scan_complete;
796
797 wpa_printf(MSG_DEBUG, "ACS: Scanning %d / %d",
798 iface->acs_num_completed_scans + 1,
799 iface->conf->acs_num_scans);
800
801 if (hostapd_driver_scan(iface->bss[0], ¶ms) < 0) {
802 wpa_printf(MSG_ERROR, "ACS: Failed to request initial scan");
803 acs_cleanup(iface);
804 os_free(params.freqs);
805 return -1;
806 }
807
808 os_free(params.freqs);
809 return 0;
810 }
811
812
acs_init(struct hostapd_iface * iface)813 enum hostapd_chan_status acs_init(struct hostapd_iface *iface)
814 {
815 int err;
816
817 wpa_printf(MSG_INFO, "ACS: Automatic channel selection started, this may take a bit");
818
819 acs_cleanup(iface);
820
821 err = acs_request_scan(iface);
822 if (err < 0)
823 return HOSTAPD_CHAN_INVALID;
824
825 hostapd_set_state(iface, HAPD_IFACE_ACS);
826 wpa_msg(iface->bss[0]->msg_ctx, MSG_INFO, ACS_EVENT_STARTED);
827
828 return HOSTAPD_CHAN_ACS;
829 }
830