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); 245 246 247 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 } 260 261 262 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 } 281 282 283 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 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 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 } 355 356 357 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 } 369 370 371 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 } 382 383 384 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 } 404 405 406 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 } 422 423 424 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 } 444 445 446 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 } 456 457 458 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 } 479 480 481 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 * 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 } 638 639 640 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 } 663 664 665 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 } 682 683 684 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 } 697 698 699 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 } 738 739 740 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 } 771 772 773 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 } 811 812 813 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
