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/hw_features_common.h" 17 #include "common/wpa_ctrl.h" 18 #include "drivers/driver.h" 19 #include "hostapd.h" 20 #include "ap_drv_ops.h" 21 #include "ap_config.h" 22 #include "hw_features.h" 23 #include "acs.h" 24 25 /* 26 * Automatic Channel Selection 27 * =========================== 28 * 29 * More info at 30 * ------------ 31 * http://wireless.kernel.org/en/users/Documentation/acs 32 * 33 * How to use 34 * ---------- 35 * - make sure you have CONFIG_ACS=y in hostapd's .config 36 * - use channel=0 or channel=acs to enable ACS 37 * 38 * How does it work 39 * ---------------- 40 * 1. passive scans are used to collect survey data 41 * (it is assumed that scan trigger collection of survey data in driver) 42 * 2. interference factor is calculated for each channel 43 * 3. ideal channel is picked depending on channel width by using adjacent 44 * channel interference factors 45 * 46 * Known limitations 47 * ----------------- 48 * - Current implementation depends heavily on the amount of time willing to 49 * spend gathering survey data during hostapd startup. Short traffic bursts 50 * may be missed and a suboptimal channel may be picked. 51 * - Ideal channel may end up overlapping a channel with 40 MHz intolerant BSS 52 * 53 * Todo / Ideas 54 * ------------ 55 * - implement other interference computation methods 56 * - BSS/RSSI based 57 * - spectral scan based 58 * (should be possibly to hook this up with current ACS scans) 59 * - add wpa_supplicant support (for P2P) 60 * - collect a histogram of interference over time allowing more educated 61 * guess about an ideal channel (perhaps CSA could be used to migrate AP to a 62 * new "better" channel while running) 63 * - include neighboring BSS scan to avoid conflicts with 40 MHz intolerant BSSs 64 * when choosing the ideal channel 65 * 66 * Survey interference factor implementation details 67 * ------------------------------------------------- 68 * Generic interference_factor in struct hostapd_channel_data is used. 69 * 70 * The survey interference factor is defined as the ratio of the 71 * observed busy time over the time we spent on the channel, 72 * this value is then amplified by the observed noise floor on 73 * the channel in comparison to the lowest noise floor observed 74 * on the entire band. 75 * 76 * This corresponds to: 77 * --- 78 * (busy time - tx time) / (active time - tx time) * 2^(chan_nf + band_min_nf) 79 * --- 80 * 81 * The coefficient of 2 reflects the way power in "far-field" 82 * radiation decreases as the square of distance from the antenna [1]. 83 * What this does is it decreases the observed busy time ratio if the 84 * noise observed was low but increases it if the noise was high, 85 * proportionally to the way "far field" radiation changes over 86 * distance. 87 * 88 * If channel busy time is not available the fallback is to use channel RX time. 89 * 90 * Since noise floor is in dBm it is necessary to convert it into Watts so that 91 * combined channel interference (e.g., HT40, which uses two channels) can be 92 * calculated easily. 93 * --- 94 * (busy time - tx time) / (active time - tx time) * 95 * 2^(10^(chan_nf/10) + 10^(band_min_nf/10)) 96 * --- 97 * 98 * However to account for cases where busy/rx time is 0 (channel load is then 99 * 0%) channel noise floor signal power is combined into the equation so a 100 * channel with lower noise floor is preferred. The equation becomes: 101 * --- 102 * 10^(chan_nf/5) + (busy time - tx time) / (active time - tx time) * 103 * 2^(10^(chan_nf/10) + 10^(band_min_nf/10)) 104 * --- 105 * 106 * All this "interference factor" is purely subjective and only time 107 * will tell how usable this is. By using the minimum noise floor we 108 * remove any possible issues due to card calibration. The computation 109 * of the interference factor then is dependent on what the card itself 110 * picks up as the minimum noise, not an actual real possible card 111 * noise value. 112 * 113 * Total interference computation details 114 * -------------------------------------- 115 * The above channel interference factor is calculated with no respect to 116 * target operational bandwidth. 117 * 118 * To find an ideal channel the above data is combined by taking into account 119 * the target operational bandwidth and selected band. E.g., on 2.4 GHz channels 120 * overlap with 20 MHz bandwidth, but there is no overlap for 20 MHz bandwidth 121 * on 5 GHz. 122 * 123 * Each valid and possible channel spec (i.e., channel + width) is taken and its 124 * interference factor is computed by summing up interferences of each channel 125 * it overlaps. The one with least total interference is picked up. 126 * 127 * Note: This implies base channel interference factor must be non-negative 128 * allowing easy summing up. 129 * 130 * Example ACS analysis printout 131 * ----------------------------- 132 * 133 * ACS: Trying survey-based ACS 134 * ACS: Survey analysis for channel 1 (2412 MHz) 135 * ACS: 1: min_nf=-113 interference_factor=0.0802469 nf=-113 time=162 busy=0 rx=13 136 * ACS: 2: min_nf=-113 interference_factor=0.0745342 nf=-113 time=161 busy=0 rx=12 137 * ACS: 3: min_nf=-113 interference_factor=0.0679012 nf=-113 time=162 busy=0 rx=11 138 * ACS: 4: min_nf=-113 interference_factor=0.0310559 nf=-113 time=161 busy=0 rx=5 139 * ACS: 5: min_nf=-113 interference_factor=0.0248447 nf=-113 time=161 busy=0 rx=4 140 * ACS: * interference factor average: 0.0557166 141 * ACS: Survey analysis for channel 2 (2417 MHz) 142 * ACS: 1: min_nf=-113 interference_factor=0.0185185 nf=-113 time=162 busy=0 rx=3 143 * ACS: 2: min_nf=-113 interference_factor=0.0246914 nf=-113 time=162 busy=0 rx=4 144 * ACS: 3: min_nf=-113 interference_factor=0.037037 nf=-113 time=162 busy=0 rx=6 145 * ACS: 4: min_nf=-113 interference_factor=0.149068 nf=-113 time=161 busy=0 rx=24 146 * ACS: 5: min_nf=-113 interference_factor=0.0248447 nf=-113 time=161 busy=0 rx=4 147 * ACS: * interference factor average: 0.050832 148 * ACS: Survey analysis for channel 3 (2422 MHz) 149 * ACS: 1: min_nf=-113 interference_factor=2.51189e-23 nf=-113 time=162 busy=0 rx=0 150 * ACS: 2: min_nf=-113 interference_factor=0.0185185 nf=-113 time=162 busy=0 rx=3 151 * ACS: 3: min_nf=-113 interference_factor=0.0186335 nf=-113 time=161 busy=0 rx=3 152 * ACS: 4: min_nf=-113 interference_factor=0.0186335 nf=-113 time=161 busy=0 rx=3 153 * ACS: 5: min_nf=-113 interference_factor=0.0186335 nf=-113 time=161 busy=0 rx=3 154 * ACS: * interference factor average: 0.0148838 155 * ACS: Survey analysis for channel 4 (2427 MHz) 156 * ACS: 1: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0 157 * ACS: 2: min_nf=-114 interference_factor=0.0555556 nf=-114 time=162 busy=0 rx=9 158 * ACS: 3: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=161 busy=0 rx=0 159 * ACS: 4: min_nf=-114 interference_factor=0.0186335 nf=-114 time=161 busy=0 rx=3 160 * ACS: 5: min_nf=-114 interference_factor=0.00621118 nf=-114 time=161 busy=0 rx=1 161 * ACS: * interference factor average: 0.0160801 162 * ACS: Survey analysis for channel 5 (2432 MHz) 163 * ACS: 1: min_nf=-114 interference_factor=0.409938 nf=-113 time=161 busy=0 rx=66 164 * ACS: 2: min_nf=-114 interference_factor=0.0432099 nf=-113 time=162 busy=0 rx=7 165 * ACS: 3: min_nf=-114 interference_factor=0.0124224 nf=-113 time=161 busy=0 rx=2 166 * ACS: 4: min_nf=-114 interference_factor=0.677019 nf=-113 time=161 busy=0 rx=109 167 * ACS: 5: min_nf=-114 interference_factor=0.0186335 nf=-114 time=161 busy=0 rx=3 168 * ACS: * interference factor average: 0.232244 169 * ACS: Survey analysis for channel 6 (2437 MHz) 170 * ACS: 1: min_nf=-113 interference_factor=0.552795 nf=-113 time=161 busy=0 rx=89 171 * ACS: 2: min_nf=-113 interference_factor=0.0807453 nf=-112 time=161 busy=0 rx=13 172 * ACS: 3: min_nf=-113 interference_factor=0.0310559 nf=-113 time=161 busy=0 rx=5 173 * ACS: 4: min_nf=-113 interference_factor=0.434783 nf=-112 time=161 busy=0 rx=70 174 * ACS: 5: min_nf=-113 interference_factor=0.0621118 nf=-113 time=161 busy=0 rx=10 175 * ACS: * interference factor average: 0.232298 176 * ACS: Survey analysis for channel 7 (2442 MHz) 177 * ACS: 1: min_nf=-113 interference_factor=0.440994 nf=-112 time=161 busy=0 rx=71 178 * ACS: 2: min_nf=-113 interference_factor=0.385093 nf=-113 time=161 busy=0 rx=62 179 * ACS: 3: min_nf=-113 interference_factor=0.0372671 nf=-113 time=161 busy=0 rx=6 180 * ACS: 4: min_nf=-113 interference_factor=0.0372671 nf=-113 time=161 busy=0 rx=6 181 * ACS: 5: min_nf=-113 interference_factor=0.0745342 nf=-113 time=161 busy=0 rx=12 182 * ACS: * interference factor average: 0.195031 183 * ACS: Survey analysis for channel 8 (2447 MHz) 184 * ACS: 1: min_nf=-114 interference_factor=0.0496894 nf=-112 time=161 busy=0 rx=8 185 * ACS: 2: min_nf=-114 interference_factor=0.0496894 nf=-114 time=161 busy=0 rx=8 186 * ACS: 3: min_nf=-114 interference_factor=0.0372671 nf=-113 time=161 busy=0 rx=6 187 * ACS: 4: min_nf=-114 interference_factor=0.12963 nf=-113 time=162 busy=0 rx=21 188 * ACS: 5: min_nf=-114 interference_factor=0.166667 nf=-114 time=162 busy=0 rx=27 189 * ACS: * interference factor average: 0.0865885 190 * ACS: Survey analysis for channel 9 (2452 MHz) 191 * ACS: 1: min_nf=-114 interference_factor=0.0124224 nf=-114 time=161 busy=0 rx=2 192 * ACS: 2: min_nf=-114 interference_factor=0.0310559 nf=-114 time=161 busy=0 rx=5 193 * ACS: 3: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=161 busy=0 rx=0 194 * ACS: 4: min_nf=-114 interference_factor=0.00617284 nf=-114 time=162 busy=0 rx=1 195 * ACS: 5: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0 196 * ACS: * interference factor average: 0.00993022 197 * ACS: Survey analysis for channel 10 (2457 MHz) 198 * ACS: 1: min_nf=-114 interference_factor=0.00621118 nf=-114 time=161 busy=0 rx=1 199 * ACS: 2: min_nf=-114 interference_factor=0.00621118 nf=-114 time=161 busy=0 rx=1 200 * ACS: 3: min_nf=-114 interference_factor=0.00621118 nf=-114 time=161 busy=0 rx=1 201 * ACS: 4: min_nf=-114 interference_factor=0.0493827 nf=-114 time=162 busy=0 rx=8 202 * ACS: 5: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0 203 * ACS: * interference factor average: 0.0136033 204 * ACS: Survey analysis for channel 11 (2462 MHz) 205 * ACS: 1: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=161 busy=0 rx=0 206 * ACS: 2: min_nf=-114 interference_factor=2.51189e-23 nf=-113 time=161 busy=0 rx=0 207 * ACS: 3: min_nf=-114 interference_factor=2.51189e-23 nf=-113 time=161 busy=0 rx=0 208 * ACS: 4: min_nf=-114 interference_factor=0.0432099 nf=-114 time=162 busy=0 rx=7 209 * ACS: 5: min_nf=-114 interference_factor=0.0925926 nf=-114 time=162 busy=0 rx=15 210 * ACS: * interference factor average: 0.0271605 211 * ACS: Survey analysis for channel 12 (2467 MHz) 212 * ACS: 1: min_nf=-114 interference_factor=0.0621118 nf=-113 time=161 busy=0 rx=10 213 * ACS: 2: min_nf=-114 interference_factor=0.00621118 nf=-114 time=161 busy=0 rx=1 214 * ACS: 3: min_nf=-114 interference_factor=2.51189e-23 nf=-113 time=162 busy=0 rx=0 215 * ACS: 4: min_nf=-114 interference_factor=2.51189e-23 nf=-113 time=162 busy=0 rx=0 216 * ACS: 5: min_nf=-114 interference_factor=0.00617284 nf=-113 time=162 busy=0 rx=1 217 * ACS: * interference factor average: 0.0148992 218 * ACS: Survey analysis for channel 13 (2472 MHz) 219 * ACS: 1: min_nf=-114 interference_factor=0.0745342 nf=-114 time=161 busy=0 rx=12 220 * ACS: 2: min_nf=-114 interference_factor=0.0555556 nf=-114 time=162 busy=0 rx=9 221 * ACS: 3: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0 222 * ACS: 4: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0 223 * ACS: 5: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0 224 * ACS: * interference factor average: 0.0260179 225 * ACS: Survey analysis for selected bandwidth 20MHz 226 * ACS: * channel 1: total interference = 0.121432 227 * ACS: * channel 2: total interference = 0.137512 228 * ACS: * channel 3: total interference = 0.369757 229 * ACS: * channel 4: total interference = 0.546338 230 * ACS: * channel 5: total interference = 0.690538 231 * ACS: * channel 6: total interference = 0.762242 232 * ACS: * channel 7: total interference = 0.756092 233 * ACS: * channel 8: total interference = 0.537451 234 * ACS: * channel 9: total interference = 0.332313 235 * ACS: * channel 10: total interference = 0.152182 236 * ACS: * channel 11: total interference = 0.0916111 237 * ACS: * channel 12: total interference = 0.0816809 238 * ACS: * channel 13: total interference = 0.0680776 239 * ACS: Ideal channel is 13 (2472 MHz) with total interference factor of 0.0680776 240 * 241 * [1] http://en.wikipedia.org/wiki/Near_and_far_field 242 */ 243 244 245 static int acs_request_scan(struct hostapd_iface *iface); 246 static int acs_survey_is_sufficient(struct freq_survey *survey); 247 248 249 static void acs_clean_chan_surveys(struct hostapd_channel_data *chan) 250 { 251 struct freq_survey *survey, *tmp; 252 253 if (dl_list_empty(&chan->survey_list)) 254 return; 255 256 dl_list_for_each_safe(survey, tmp, &chan->survey_list, 257 struct freq_survey, list) { 258 dl_list_del(&survey->list); 259 os_free(survey); 260 } 261 } 262 263 264 void acs_cleanup(struct hostapd_iface *iface) 265 { 266 int i; 267 struct hostapd_channel_data *chan; 268 269 for (i = 0; i < iface->current_mode->num_channels; i++) { 270 chan = &iface->current_mode->channels[i]; 271 272 if (chan->flag & HOSTAPD_CHAN_SURVEY_LIST_INITIALIZED) 273 acs_clean_chan_surveys(chan); 274 275 dl_list_init(&chan->survey_list); 276 chan->flag |= HOSTAPD_CHAN_SURVEY_LIST_INITIALIZED; 277 chan->min_nf = 0; 278 } 279 280 iface->chans_surveyed = 0; 281 iface->acs_num_completed_scans = 0; 282 } 283 284 285 static void acs_fail(struct hostapd_iface *iface) 286 { 287 wpa_printf(MSG_ERROR, "ACS: Failed to start"); 288 acs_cleanup(iface); 289 hostapd_disable_iface(iface); 290 } 291 292 293 static long double 294 acs_survey_interference_factor(struct freq_survey *survey, s8 min_nf) 295 { 296 long double factor, busy, total; 297 298 if (survey->filled & SURVEY_HAS_CHAN_TIME_BUSY) 299 busy = survey->channel_time_busy; 300 else if (survey->filled & SURVEY_HAS_CHAN_TIME_RX) 301 busy = survey->channel_time_rx; 302 else { 303 /* This shouldn't really happen as survey data is checked in 304 * acs_sanity_check() */ 305 wpa_printf(MSG_ERROR, "ACS: Survey data missing"); 306 return 0; 307 } 308 309 total = survey->channel_time; 310 311 if (survey->filled & SURVEY_HAS_CHAN_TIME_TX) { 312 busy -= survey->channel_time_tx; 313 total -= survey->channel_time_tx; 314 } 315 316 /* TODO: figure out the best multiplier for noise floor base */ 317 factor = pow(10, survey->nf / 5.0L) + 318 (total ? (busy / total) : 0) * 319 pow(2, pow(10, (long double) survey->nf / 10.0L) - 320 pow(10, (long double) min_nf / 10.0L)); 321 322 return factor; 323 } 324 325 326 static void 327 acs_survey_chan_interference_factor(struct hostapd_iface *iface, 328 struct hostapd_channel_data *chan) 329 { 330 struct freq_survey *survey; 331 unsigned int i = 0; 332 long double int_factor = 0; 333 unsigned count = 0; 334 335 if (dl_list_empty(&chan->survey_list) || 336 (chan->flag & HOSTAPD_CHAN_DISABLED)) 337 return; 338 339 chan->interference_factor = 0; 340 341 dl_list_for_each(survey, &chan->survey_list, struct freq_survey, list) 342 { 343 i++; 344 345 if (!acs_survey_is_sufficient(survey)) { 346 wpa_printf(MSG_DEBUG, "ACS: %d: insufficient data", i); 347 continue; 348 } 349 350 count++; 351 int_factor = acs_survey_interference_factor(survey, 352 iface->lowest_nf); 353 chan->interference_factor += int_factor; 354 wpa_printf(MSG_DEBUG, "ACS: %d: min_nf=%d interference_factor=%Lg nf=%d time=%lu busy=%lu rx=%lu", 355 i, chan->min_nf, int_factor, 356 survey->nf, (unsigned long) survey->channel_time, 357 (unsigned long) survey->channel_time_busy, 358 (unsigned long) survey->channel_time_rx); 359 } 360 361 if (count) 362 chan->interference_factor /= count; 363 } 364 365 366 static int acs_usable_ht40_chan(const struct hostapd_channel_data *chan) 367 { 368 const int allowed[] = { 36, 44, 52, 60, 100, 108, 116, 124, 132, 149, 369 157, 184, 192 }; 370 unsigned int i; 371 372 for (i = 0; i < ARRAY_SIZE(allowed); i++) 373 if (chan->chan == allowed[i]) 374 return 1; 375 376 return 0; 377 } 378 379 380 static int acs_usable_vht80_chan(const struct hostapd_channel_data *chan) 381 { 382 const int allowed[] = { 36, 52, 100, 116, 132, 149 }; 383 unsigned int i; 384 385 for (i = 0; i < ARRAY_SIZE(allowed); i++) 386 if (chan->chan == allowed[i]) 387 return 1; 388 389 return 0; 390 } 391 392 393 static int acs_usable_vht160_chan(const struct hostapd_channel_data *chan) 394 { 395 const int allowed[] = { 36, 100 }; 396 unsigned int i; 397 398 for (i = 0; i < ARRAY_SIZE(allowed); i++) 399 if (chan->chan == allowed[i]) 400 return 1; 401 402 return 0; 403 } 404 405 406 static int acs_survey_is_sufficient(struct freq_survey *survey) 407 { 408 if (!(survey->filled & SURVEY_HAS_NF)) { 409 wpa_printf(MSG_INFO, "ACS: Survey is missing noise floor"); 410 return 0; 411 } 412 413 if (!(survey->filled & SURVEY_HAS_CHAN_TIME)) { 414 wpa_printf(MSG_INFO, "ACS: Survey is missing channel time"); 415 return 0; 416 } 417 418 if (!(survey->filled & SURVEY_HAS_CHAN_TIME_BUSY) && 419 !(survey->filled & SURVEY_HAS_CHAN_TIME_RX)) { 420 wpa_printf(MSG_INFO, 421 "ACS: Survey is missing RX and busy time (at least one is required)"); 422 return 0; 423 } 424 425 return 1; 426 } 427 428 429 static int acs_survey_list_is_sufficient(struct hostapd_channel_data *chan) 430 { 431 struct freq_survey *survey; 432 int ret = -1; 433 434 dl_list_for_each(survey, &chan->survey_list, struct freq_survey, list) 435 { 436 if (acs_survey_is_sufficient(survey)) { 437 ret = 1; 438 break; 439 } 440 ret = 0; 441 } 442 443 if (ret == -1) 444 ret = 1; /* no survey list entries */ 445 446 if (!ret) { 447 wpa_printf(MSG_INFO, 448 "ACS: Channel %d has insufficient survey data", 449 chan->chan); 450 } 451 452 return ret; 453 } 454 455 456 static int acs_surveys_are_sufficient(struct hostapd_iface *iface) 457 { 458 int i; 459 struct hostapd_channel_data *chan; 460 int valid = 0; 461 462 for (i = 0; i < iface->current_mode->num_channels; i++) { 463 chan = &iface->current_mode->channels[i]; 464 if (!(chan->flag & HOSTAPD_CHAN_DISABLED) && 465 acs_survey_list_is_sufficient(chan)) 466 valid++; 467 } 468 469 /* We need at least survey data for one channel */ 470 return !!valid; 471 } 472 473 474 static int acs_usable_chan(struct hostapd_channel_data *chan) 475 { 476 return !dl_list_empty(&chan->survey_list) && 477 !(chan->flag & HOSTAPD_CHAN_DISABLED) && 478 acs_survey_list_is_sufficient(chan); 479 } 480 481 482 static int is_in_chanlist(struct hostapd_iface *iface, 483 struct hostapd_channel_data *chan) 484 { 485 if (!iface->conf->acs_ch_list.num) 486 return 1; 487 488 return freq_range_list_includes(&iface->conf->acs_ch_list, chan->chan); 489 } 490 491 492 static void acs_survey_all_chans_intereference_factor( 493 struct hostapd_iface *iface) 494 { 495 int i; 496 struct hostapd_channel_data *chan; 497 498 for (i = 0; i < iface->current_mode->num_channels; i++) { 499 chan = &iface->current_mode->channels[i]; 500 501 if (!acs_usable_chan(chan)) 502 continue; 503 504 if (!is_in_chanlist(iface, chan)) 505 continue; 506 507 wpa_printf(MSG_DEBUG, "ACS: Survey analysis for channel %d (%d MHz)", 508 chan->chan, chan->freq); 509 510 acs_survey_chan_interference_factor(iface, chan); 511 512 wpa_printf(MSG_DEBUG, "ACS: * interference factor average: %Lg", 513 chan->interference_factor); 514 } 515 } 516 517 518 static struct hostapd_channel_data *acs_find_chan(struct hostapd_iface *iface, 519 int freq) 520 { 521 struct hostapd_channel_data *chan; 522 int i; 523 524 for (i = 0; i < iface->current_mode->num_channels; i++) { 525 chan = &iface->current_mode->channels[i]; 526 527 if (chan->flag & HOSTAPD_CHAN_DISABLED) 528 continue; 529 530 if (chan->freq == freq) 531 return chan; 532 } 533 534 return NULL; 535 } 536 537 538 static int is_24ghz_mode(enum hostapd_hw_mode mode) 539 { 540 return mode == HOSTAPD_MODE_IEEE80211B || 541 mode == HOSTAPD_MODE_IEEE80211G; 542 } 543 544 545 static int is_common_24ghz_chan(int chan) 546 { 547 return chan == 1 || chan == 6 || chan == 11; 548 } 549 550 551 #ifndef ACS_ADJ_WEIGHT 552 #define ACS_ADJ_WEIGHT 0.85 553 #endif /* ACS_ADJ_WEIGHT */ 554 555 #ifndef ACS_NEXT_ADJ_WEIGHT 556 #define ACS_NEXT_ADJ_WEIGHT 0.55 557 #endif /* ACS_NEXT_ADJ_WEIGHT */ 558 559 #ifndef ACS_24GHZ_PREFER_1_6_11 560 /* 561 * Select commonly used channels 1, 6, 11 by default even if a neighboring 562 * channel has a smaller interference factor as long as it is not better by more 563 * than this multiplier. 564 */ 565 #define ACS_24GHZ_PREFER_1_6_11 0.8 566 #endif /* ACS_24GHZ_PREFER_1_6_11 */ 567 568 /* 569 * At this point it's assumed chan->interface_factor has been computed. 570 * This function should be reusable regardless of interference computation 571 * option (survey, BSS, spectral, ...). chan->interference factor must be 572 * summable (i.e., must be always greater than zero). 573 */ 574 static struct hostapd_channel_data * 575 acs_find_ideal_chan(struct hostapd_iface *iface) 576 { 577 struct hostapd_channel_data *chan, *adj_chan, *ideal_chan = NULL, 578 *rand_chan = NULL; 579 long double factor, ideal_factor = 0; 580 int i, j; 581 int n_chans = 1; 582 u32 bw; 583 unsigned int k; 584 585 /* TODO: HT40- support */ 586 587 if (iface->conf->ieee80211n && 588 iface->conf->secondary_channel == -1) { 589 wpa_printf(MSG_ERROR, "ACS: HT40- is not supported yet. Please try HT40+"); 590 return NULL; 591 } 592 593 if (iface->conf->ieee80211n && 594 iface->conf->secondary_channel) 595 n_chans = 2; 596 597 if (iface->conf->ieee80211ac) { 598 switch (iface->conf->vht_oper_chwidth) { 599 case VHT_CHANWIDTH_80MHZ: 600 n_chans = 4; 601 break; 602 case VHT_CHANWIDTH_160MHZ: 603 n_chans = 8; 604 break; 605 } 606 } 607 608 bw = num_chan_to_bw(n_chans); 609 610 /* TODO: VHT80+80. Update acs_adjust_vht_center_freq() too. */ 611 612 wpa_printf(MSG_DEBUG, 613 "ACS: Survey analysis for selected bandwidth %d MHz", bw); 614 615 for (i = 0; i < iface->current_mode->num_channels; i++) { 616 double total_weight; 617 struct acs_bias *bias, tmp_bias; 618 619 chan = &iface->current_mode->channels[i]; 620 621 /* Since in the current ACS implementation the first channel is 622 * always a primary channel, skip channels not available as 623 * primary until more sophisticated channel selection is 624 * implemented. */ 625 if (!chan_pri_allowed(chan)) 626 continue; 627 628 if (!is_in_chanlist(iface, chan)) 629 continue; 630 631 if (!chan_bw_allowed(chan, bw, 1, 1)) { 632 wpa_printf(MSG_DEBUG, 633 "ACS: Channel %d: BW %u is not supported", 634 chan->chan, bw); 635 continue; 636 } 637 638 /* HT40 on 5 GHz has a limited set of primary channels as per 639 * 11n Annex J */ 640 if (iface->current_mode->mode == HOSTAPD_MODE_IEEE80211A && 641 iface->conf->ieee80211n && 642 iface->conf->secondary_channel && 643 !acs_usable_ht40_chan(chan)) { 644 wpa_printf(MSG_DEBUG, "ACS: Channel %d: not allowed as primary channel for HT40", 645 chan->chan); 646 continue; 647 } 648 649 if (iface->current_mode->mode == HOSTAPD_MODE_IEEE80211A && 650 iface->conf->ieee80211ac) { 651 if (iface->conf->vht_oper_chwidth == 652 VHT_CHANWIDTH_80MHZ && 653 !acs_usable_vht80_chan(chan)) { 654 wpa_printf(MSG_DEBUG, 655 "ACS: Channel %d: not allowed as primary channel for VHT80", 656 chan->chan); 657 continue; 658 } 659 660 if (iface->conf->vht_oper_chwidth == 661 VHT_CHANWIDTH_160MHZ && 662 !acs_usable_vht160_chan(chan)) { 663 wpa_printf(MSG_DEBUG, 664 "ACS: Channel %d: not allowed as primary channel for VHT160", 665 chan->chan); 666 continue; 667 } 668 } 669 670 factor = 0; 671 if (acs_usable_chan(chan)) 672 factor = chan->interference_factor; 673 total_weight = 1; 674 675 for (j = 1; j < n_chans; j++) { 676 adj_chan = acs_find_chan(iface, chan->freq + (j * 20)); 677 if (!adj_chan) 678 break; 679 680 if (!chan_bw_allowed(adj_chan, bw, 1, 0)) { 681 wpa_printf(MSG_DEBUG, 682 "ACS: PRI Channel %d: secondary channel %d BW %u is not supported", 683 chan->chan, adj_chan->chan, bw); 684 break; 685 } 686 687 if (acs_usable_chan(adj_chan)) { 688 factor += adj_chan->interference_factor; 689 total_weight += 1; 690 } 691 } 692 693 if (j != n_chans) { 694 wpa_printf(MSG_DEBUG, "ACS: Channel %d: not enough bandwidth", 695 chan->chan); 696 continue; 697 } 698 699 /* 2.4 GHz has overlapping 20 MHz channels. Include adjacent 700 * channel interference factor. */ 701 if (is_24ghz_mode(iface->current_mode->mode)) { 702 for (j = 0; j < n_chans; j++) { 703 adj_chan = acs_find_chan(iface, chan->freq + 704 (j * 20) - 5); 705 if (adj_chan && acs_usable_chan(adj_chan)) { 706 factor += ACS_ADJ_WEIGHT * 707 adj_chan->interference_factor; 708 total_weight += ACS_ADJ_WEIGHT; 709 } 710 711 adj_chan = acs_find_chan(iface, chan->freq + 712 (j * 20) - 10); 713 if (adj_chan && acs_usable_chan(adj_chan)) { 714 factor += ACS_NEXT_ADJ_WEIGHT * 715 adj_chan->interference_factor; 716 total_weight += ACS_NEXT_ADJ_WEIGHT; 717 } 718 719 adj_chan = acs_find_chan(iface, chan->freq + 720 (j * 20) + 5); 721 if (adj_chan && acs_usable_chan(adj_chan)) { 722 factor += ACS_ADJ_WEIGHT * 723 adj_chan->interference_factor; 724 total_weight += ACS_ADJ_WEIGHT; 725 } 726 727 adj_chan = acs_find_chan(iface, chan->freq + 728 (j * 20) + 10); 729 if (adj_chan && acs_usable_chan(adj_chan)) { 730 factor += ACS_NEXT_ADJ_WEIGHT * 731 adj_chan->interference_factor; 732 total_weight += ACS_NEXT_ADJ_WEIGHT; 733 } 734 } 735 } 736 737 factor /= total_weight; 738 739 bias = NULL; 740 if (iface->conf->acs_chan_bias) { 741 for (k = 0; k < iface->conf->num_acs_chan_bias; k++) { 742 bias = &iface->conf->acs_chan_bias[k]; 743 if (bias->channel == chan->chan) 744 break; 745 bias = NULL; 746 } 747 } else if (is_24ghz_mode(iface->current_mode->mode) && 748 is_common_24ghz_chan(chan->chan)) { 749 tmp_bias.channel = chan->chan; 750 tmp_bias.bias = ACS_24GHZ_PREFER_1_6_11; 751 bias = &tmp_bias; 752 } 753 754 if (bias) { 755 factor *= bias->bias; 756 wpa_printf(MSG_DEBUG, 757 "ACS: * channel %d: total interference = %Lg (%f bias)", 758 chan->chan, factor, bias->bias); 759 } else { 760 wpa_printf(MSG_DEBUG, 761 "ACS: * channel %d: total interference = %Lg", 762 chan->chan, factor); 763 } 764 765 if (acs_usable_chan(chan) && 766 (!ideal_chan || factor < ideal_factor)) { 767 ideal_factor = factor; 768 ideal_chan = chan; 769 } 770 771 /* This channel would at least be usable */ 772 if (!rand_chan) 773 rand_chan = chan; 774 } 775 776 if (ideal_chan) { 777 wpa_printf(MSG_DEBUG, "ACS: Ideal channel is %d (%d MHz) with total interference factor of %Lg", 778 ideal_chan->chan, ideal_chan->freq, ideal_factor); 779 return ideal_chan; 780 } 781 782 return rand_chan; 783 } 784 785 786 static void acs_adjust_vht_center_freq(struct hostapd_iface *iface) 787 { 788 int offset; 789 790 wpa_printf(MSG_DEBUG, "ACS: Adjusting VHT center frequency"); 791 792 switch (iface->conf->vht_oper_chwidth) { 793 case VHT_CHANWIDTH_USE_HT: 794 offset = 2 * iface->conf->secondary_channel; 795 break; 796 case VHT_CHANWIDTH_80MHZ: 797 offset = 6; 798 break; 799 case VHT_CHANWIDTH_160MHZ: 800 offset = 14; 801 break; 802 default: 803 /* TODO: How can this be calculated? Adjust 804 * acs_find_ideal_chan() */ 805 wpa_printf(MSG_INFO, 806 "ACS: Only VHT20/40/80/160 is supported now"); 807 return; 808 } 809 810 iface->conf->vht_oper_centr_freq_seg0_idx = 811 iface->conf->channel + offset; 812 } 813 814 815 static int acs_study_survey_based(struct hostapd_iface *iface) 816 { 817 wpa_printf(MSG_DEBUG, "ACS: Trying survey-based ACS"); 818 819 if (!iface->chans_surveyed) { 820 wpa_printf(MSG_ERROR, "ACS: Unable to collect survey data"); 821 return -1; 822 } 823 824 if (!acs_surveys_are_sufficient(iface)) { 825 wpa_printf(MSG_ERROR, "ACS: Surveys have insufficient data"); 826 return -1; 827 } 828 829 acs_survey_all_chans_intereference_factor(iface); 830 return 0; 831 } 832 833 834 static int acs_study_options(struct hostapd_iface *iface) 835 { 836 if (acs_study_survey_based(iface) == 0) 837 return 0; 838 839 /* TODO: If no surveys are available/sufficient this is a good 840 * place to fallback to BSS-based ACS */ 841 842 return -1; 843 } 844 845 846 static void acs_study(struct hostapd_iface *iface) 847 { 848 struct hostapd_channel_data *ideal_chan; 849 int err; 850 851 err = acs_study_options(iface); 852 if (err < 0) { 853 wpa_printf(MSG_ERROR, "ACS: All study options have failed"); 854 goto fail; 855 } 856 857 ideal_chan = acs_find_ideal_chan(iface); 858 if (!ideal_chan) { 859 wpa_printf(MSG_ERROR, "ACS: Failed to compute ideal channel"); 860 err = -1; 861 goto fail; 862 } 863 864 iface->conf->channel = ideal_chan->chan; 865 866 if (iface->conf->ieee80211ac) 867 acs_adjust_vht_center_freq(iface); 868 869 err = 0; 870 fail: 871 /* 872 * hostapd_setup_interface_complete() will return -1 on failure, 873 * 0 on success and 0 is HOSTAPD_CHAN_VALID :) 874 */ 875 if (hostapd_acs_completed(iface, err) == HOSTAPD_CHAN_VALID) { 876 acs_cleanup(iface); 877 return; 878 } 879 880 /* This can possibly happen if channel parameters (secondary 881 * channel, center frequencies) are misconfigured */ 882 wpa_printf(MSG_ERROR, "ACS: Possibly channel configuration is invalid, please report this along with your config file."); 883 acs_fail(iface); 884 } 885 886 887 static void acs_scan_complete(struct hostapd_iface *iface) 888 { 889 int err; 890 891 iface->scan_cb = NULL; 892 893 wpa_printf(MSG_DEBUG, "ACS: Using survey based algorithm (acs_num_scans=%d)", 894 iface->conf->acs_num_scans); 895 896 err = hostapd_drv_get_survey(iface->bss[0], 0); 897 if (err) { 898 wpa_printf(MSG_ERROR, "ACS: Failed to get survey data"); 899 goto fail; 900 } 901 902 if (++iface->acs_num_completed_scans < iface->conf->acs_num_scans) { 903 err = acs_request_scan(iface); 904 if (err) { 905 wpa_printf(MSG_ERROR, "ACS: Failed to request scan"); 906 goto fail; 907 } 908 909 return; 910 } 911 912 acs_study(iface); 913 return; 914 fail: 915 hostapd_acs_completed(iface, 1); 916 acs_fail(iface); 917 } 918 919 920 static int acs_request_scan(struct hostapd_iface *iface) 921 { 922 struct wpa_driver_scan_params params; 923 struct hostapd_channel_data *chan; 924 int i, *freq; 925 926 os_memset(¶ms, 0, sizeof(params)); 927 params.freqs = os_calloc(iface->current_mode->num_channels + 1, 928 sizeof(params.freqs[0])); 929 if (params.freqs == NULL) 930 return -1; 931 932 freq = params.freqs; 933 for (i = 0; i < iface->current_mode->num_channels; i++) { 934 chan = &iface->current_mode->channels[i]; 935 if (chan->flag & HOSTAPD_CHAN_DISABLED) 936 continue; 937 938 if (!is_in_chanlist(iface, chan)) 939 continue; 940 941 *freq++ = chan->freq; 942 } 943 *freq = 0; 944 945 iface->scan_cb = acs_scan_complete; 946 947 wpa_printf(MSG_DEBUG, "ACS: Scanning %d / %d", 948 iface->acs_num_completed_scans + 1, 949 iface->conf->acs_num_scans); 950 951 if (hostapd_driver_scan(iface->bss[0], ¶ms) < 0) { 952 wpa_printf(MSG_ERROR, "ACS: Failed to request initial scan"); 953 acs_cleanup(iface); 954 os_free(params.freqs); 955 return -1; 956 } 957 958 os_free(params.freqs); 959 return 0; 960 } 961 962 963 enum hostapd_chan_status acs_init(struct hostapd_iface *iface) 964 { 965 wpa_printf(MSG_INFO, "ACS: Automatic channel selection started, this may take a bit"); 966 967 if (iface->drv_flags & WPA_DRIVER_FLAGS_ACS_OFFLOAD) { 968 wpa_printf(MSG_INFO, "ACS: Offloading to driver"); 969 if (hostapd_drv_do_acs(iface->bss[0])) 970 return HOSTAPD_CHAN_INVALID; 971 return HOSTAPD_CHAN_ACS; 972 } 973 974 if (!iface->current_mode) 975 return HOSTAPD_CHAN_INVALID; 976 977 acs_cleanup(iface); 978 979 if (acs_request_scan(iface) < 0) 980 return HOSTAPD_CHAN_INVALID; 981 982 hostapd_set_state(iface, HAPD_IFACE_ACS); 983 wpa_msg(iface->bss[0]->msg_ctx, MSG_INFO, ACS_EVENT_STARTED); 984 985 return HOSTAPD_CHAN_ACS; 986 } 987
