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 static int acs_survey_is_sufficient(struct freq_survey *survey); 246 247 248 static void acs_clean_chan_surveys(struct hostapd_channel_data *chan) 249 { 250 struct freq_survey *survey, *tmp; 251 252 if (dl_list_empty(&chan->survey_list)) 253 return; 254 255 dl_list_for_each_safe(survey, tmp, &chan->survey_list, 256 struct freq_survey, list) { 257 dl_list_del(&survey->list); 258 os_free(survey); 259 } 260 } 261 262 263 static void acs_cleanup(struct hostapd_iface *iface) 264 { 265 int i; 266 struct hostapd_channel_data *chan; 267 268 for (i = 0; i < iface->current_mode->num_channels; i++) { 269 chan = &iface->current_mode->channels[i]; 270 271 if (chan->flag & HOSTAPD_CHAN_SURVEY_LIST_INITIALIZED) 272 acs_clean_chan_surveys(chan); 273 274 dl_list_init(&chan->survey_list); 275 chan->flag |= HOSTAPD_CHAN_SURVEY_LIST_INITIALIZED; 276 chan->min_nf = 0; 277 } 278 279 iface->chans_surveyed = 0; 280 iface->acs_num_completed_scans = 0; 281 } 282 283 284 static void acs_fail(struct hostapd_iface *iface) 285 { 286 wpa_printf(MSG_ERROR, "ACS: Failed to start"); 287 acs_cleanup(iface); 288 hostapd_disable_iface(iface); 289 } 290 291 292 static long double 293 acs_survey_interference_factor(struct freq_survey *survey, s8 min_nf) 294 { 295 long double factor, busy, total; 296 297 if (survey->filled & SURVEY_HAS_CHAN_TIME_BUSY) 298 busy = survey->channel_time_busy; 299 else if (survey->filled & SURVEY_HAS_CHAN_TIME_RX) 300 busy = survey->channel_time_rx; 301 else { 302 /* This shouldn't really happen as survey data is checked in 303 * acs_sanity_check() */ 304 wpa_printf(MSG_ERROR, "ACS: Survey data missing"); 305 return 0; 306 } 307 308 total = survey->channel_time; 309 310 if (survey->filled & SURVEY_HAS_CHAN_TIME_TX) { 311 busy -= survey->channel_time_tx; 312 total -= survey->channel_time_tx; 313 } 314 315 /* TODO: figure out the best multiplier for noise floor base */ 316 factor = pow(10, survey->nf / 5.0L) + 317 (busy / total) * 318 pow(2, pow(10, (long double) survey->nf / 10.0L) - 319 pow(10, (long double) min_nf / 10.0L)); 320 321 return factor; 322 } 323 324 325 static void 326 acs_survey_chan_interference_factor(struct hostapd_iface *iface, 327 struct hostapd_channel_data *chan) 328 { 329 struct freq_survey *survey; 330 unsigned int i = 0; 331 long double int_factor = 0; 332 unsigned count = 0; 333 334 if (dl_list_empty(&chan->survey_list)) 335 return; 336 337 if (chan->flag & HOSTAPD_CHAN_DISABLED) 338 return; 339 340 chan->interference_factor = 0; 341 342 dl_list_for_each(survey, &chan->survey_list, struct freq_survey, list) 343 { 344 i++; 345 346 if (!acs_survey_is_sufficient(survey)) { 347 wpa_printf(MSG_DEBUG, "ACS: %d: insufficient data", i); 348 continue; 349 } 350 351 count++; 352 int_factor = acs_survey_interference_factor(survey, 353 iface->lowest_nf); 354 chan->interference_factor += int_factor; 355 wpa_printf(MSG_DEBUG, "ACS: %d: min_nf=%d interference_factor=%Lg nf=%d time=%lu busy=%lu rx=%lu", 356 i, chan->min_nf, int_factor, 357 survey->nf, (unsigned long) survey->channel_time, 358 (unsigned long) survey->channel_time_busy, 359 (unsigned long) survey->channel_time_rx); 360 } 361 362 if (!count) 363 return; 364 chan->interference_factor /= count; 365 } 366 367 368 static int acs_usable_ht40_chan(struct hostapd_channel_data *chan) 369 { 370 const int allowed[] = { 36, 44, 52, 60, 100, 108, 116, 124, 132, 149, 371 157, 184, 192 }; 372 unsigned int i; 373 374 for (i = 0; i < ARRAY_SIZE(allowed); i++) 375 if (chan->chan == allowed[i]) 376 return 1; 377 378 return 0; 379 } 380 381 382 static int acs_usable_vht80_chan(struct hostapd_channel_data *chan) 383 { 384 const int allowed[] = { 36, 52, 100, 116, 132, 149 }; 385 unsigned int i; 386 387 for (i = 0; i < ARRAY_SIZE(allowed); i++) 388 if (chan->chan == allowed[i]) 389 return 1; 390 391 return 0; 392 } 393 394 395 static int acs_survey_is_sufficient(struct freq_survey *survey) 396 { 397 if (!(survey->filled & SURVEY_HAS_NF)) { 398 wpa_printf(MSG_INFO, "ACS: Survey is missing noise floor"); 399 return 0; 400 } 401 402 if (!(survey->filled & SURVEY_HAS_CHAN_TIME)) { 403 wpa_printf(MSG_INFO, "ACS: Survey is missing channel time"); 404 return 0; 405 } 406 407 if (!(survey->filled & SURVEY_HAS_CHAN_TIME_BUSY) && 408 !(survey->filled & SURVEY_HAS_CHAN_TIME_RX)) { 409 wpa_printf(MSG_INFO, 410 "ACS: Survey is missing RX and busy time (at least one is required)"); 411 return 0; 412 } 413 414 return 1; 415 } 416 417 418 static int acs_survey_list_is_sufficient(struct hostapd_channel_data *chan) 419 { 420 struct freq_survey *survey; 421 int ret = -1; 422 423 dl_list_for_each(survey, &chan->survey_list, struct freq_survey, list) 424 { 425 if (acs_survey_is_sufficient(survey)) { 426 ret = 1; 427 break; 428 } 429 ret = 0; 430 } 431 432 if (ret == -1) 433 ret = 1; /* no survey list entries */ 434 435 if (!ret) { 436 wpa_printf(MSG_INFO, 437 "ACS: Channel %d has insufficient survey data", 438 chan->chan); 439 } 440 441 return ret; 442 } 443 444 445 static int acs_surveys_are_sufficient(struct hostapd_iface *iface) 446 { 447 int i; 448 struct hostapd_channel_data *chan; 449 int valid = 0; 450 451 for (i = 0; i < iface->current_mode->num_channels; i++) { 452 chan = &iface->current_mode->channels[i]; 453 if (chan->flag & HOSTAPD_CHAN_DISABLED) 454 continue; 455 456 if (!acs_survey_list_is_sufficient(chan)) 457 continue; 458 459 valid++; 460 } 461 462 /* We need at least survey data for one channel */ 463 return !!valid; 464 } 465 466 467 static int acs_usable_chan(struct hostapd_channel_data *chan) 468 { 469 if (dl_list_empty(&chan->survey_list)) 470 return 0; 471 if (chan->flag & HOSTAPD_CHAN_DISABLED) 472 return 0; 473 if (!acs_survey_list_is_sufficient(chan)) 474 return 0; 475 return 1; 476 } 477 478 479 static int is_in_chanlist(struct hostapd_iface *iface, 480 struct hostapd_channel_data *chan) 481 { 482 if (!iface->conf->acs_ch_list.num) 483 return 1; 484 485 return freq_range_list_includes(&iface->conf->acs_ch_list, chan->chan); 486 } 487 488 489 static void acs_survey_all_chans_intereference_factor( 490 struct hostapd_iface *iface) 491 { 492 int i; 493 struct hostapd_channel_data *chan; 494 495 for (i = 0; i < iface->current_mode->num_channels; i++) { 496 chan = &iface->current_mode->channels[i]; 497 498 if (!acs_usable_chan(chan)) 499 continue; 500 501 if (!is_in_chanlist(iface, chan)) 502 continue; 503 504 wpa_printf(MSG_DEBUG, "ACS: Survey analysis for channel %d (%d MHz)", 505 chan->chan, chan->freq); 506 507 acs_survey_chan_interference_factor(iface, chan); 508 509 wpa_printf(MSG_DEBUG, "ACS: * interference factor average: %Lg", 510 chan->interference_factor); 511 } 512 } 513 514 515 static struct hostapd_channel_data *acs_find_chan(struct hostapd_iface *iface, 516 int freq) 517 { 518 struct hostapd_channel_data *chan; 519 int i; 520 521 for (i = 0; i < iface->current_mode->num_channels; i++) { 522 chan = &iface->current_mode->channels[i]; 523 524 if (chan->flag & HOSTAPD_CHAN_DISABLED) 525 continue; 526 527 if (chan->freq == freq) 528 return chan; 529 } 530 531 return NULL; 532 } 533 534 535 static int is_24ghz_mode(enum hostapd_hw_mode mode) 536 { 537 return mode == HOSTAPD_MODE_IEEE80211B || 538 mode == HOSTAPD_MODE_IEEE80211G; 539 } 540 541 542 static int is_common_24ghz_chan(int chan) 543 { 544 return chan == 1 || chan == 6 || chan == 11; 545 } 546 547 548 #ifndef ACS_ADJ_WEIGHT 549 #define ACS_ADJ_WEIGHT 0.85 550 #endif /* ACS_ADJ_WEIGHT */ 551 552 #ifndef ACS_NEXT_ADJ_WEIGHT 553 #define ACS_NEXT_ADJ_WEIGHT 0.55 554 #endif /* ACS_NEXT_ADJ_WEIGHT */ 555 556 #ifndef ACS_24GHZ_PREFER_1_6_11 557 /* 558 * Select commonly used channels 1, 6, 11 by default even if a neighboring 559 * channel has a smaller interference factor as long as it is not better by more 560 * than this multiplier. 561 */ 562 #define ACS_24GHZ_PREFER_1_6_11 0.8 563 #endif /* ACS_24GHZ_PREFER_1_6_11 */ 564 565 /* 566 * At this point it's assumed chan->interface_factor has been computed. 567 * This function should be reusable regardless of interference computation 568 * option (survey, BSS, spectral, ...). chan->interference factor must be 569 * summable (i.e., must be always greater than zero). 570 */ 571 static struct hostapd_channel_data * 572 acs_find_ideal_chan(struct hostapd_iface *iface) 573 { 574 struct hostapd_channel_data *chan, *adj_chan, *ideal_chan = NULL, 575 *rand_chan = NULL; 576 long double factor, ideal_factor = 0; 577 int i, j; 578 int n_chans = 1; 579 unsigned int k; 580 581 /* TODO: HT40- support */ 582 583 if (iface->conf->ieee80211n && 584 iface->conf->secondary_channel == -1) { 585 wpa_printf(MSG_ERROR, "ACS: HT40- is not supported yet. Please try HT40+"); 586 return NULL; 587 } 588 589 if (iface->conf->ieee80211n && 590 iface->conf->secondary_channel) 591 n_chans = 2; 592 593 if (iface->conf->ieee80211ac && 594 iface->conf->vht_oper_chwidth == 1) 595 n_chans = 4; 596 597 /* TODO: VHT80+80, VHT160. Update acs_adjust_vht_center_freq() too. */ 598 599 wpa_printf(MSG_DEBUG, "ACS: Survey analysis for selected bandwidth %d MHz", 600 n_chans == 1 ? 20 : 601 n_chans == 2 ? 40 : 602 n_chans == 4 ? 80 : 603 -1); 604 605 for (i = 0; i < iface->current_mode->num_channels; i++) { 606 double total_weight; 607 struct acs_bias *bias, tmp_bias; 608 609 chan = &iface->current_mode->channels[i]; 610 611 if (chan->flag & HOSTAPD_CHAN_DISABLED) 612 continue; 613 614 if (!is_in_chanlist(iface, chan)) 615 continue; 616 617 /* HT40 on 5 GHz has a limited set of primary channels as per 618 * 11n Annex J */ 619 if (iface->current_mode->mode == HOSTAPD_MODE_IEEE80211A && 620 iface->conf->ieee80211n && 621 iface->conf->secondary_channel && 622 !acs_usable_ht40_chan(chan)) { 623 wpa_printf(MSG_DEBUG, "ACS: Channel %d: not allowed as primary channel for HT40", 624 chan->chan); 625 continue; 626 } 627 628 if (iface->current_mode->mode == HOSTAPD_MODE_IEEE80211A && 629 iface->conf->ieee80211ac && 630 iface->conf->vht_oper_chwidth == 1 && 631 !acs_usable_vht80_chan(chan)) { 632 wpa_printf(MSG_DEBUG, "ACS: Channel %d: not allowed as primary channel for VHT80", 633 chan->chan); 634 continue; 635 } 636 637 factor = 0; 638 if (acs_usable_chan(chan)) 639 factor = chan->interference_factor; 640 total_weight = 1; 641 642 for (j = 1; j < n_chans; j++) { 643 adj_chan = acs_find_chan(iface, chan->freq + (j * 20)); 644 if (!adj_chan) 645 break; 646 647 if (acs_usable_chan(adj_chan)) { 648 factor += adj_chan->interference_factor; 649 total_weight += 1; 650 } 651 } 652 653 if (j != n_chans) { 654 wpa_printf(MSG_DEBUG, "ACS: Channel %d: not enough bandwidth", 655 chan->chan); 656 continue; 657 } 658 659 /* 2.4 GHz has overlapping 20 MHz channels. Include adjacent 660 * channel interference factor. */ 661 if (is_24ghz_mode(iface->current_mode->mode)) { 662 for (j = 0; j < n_chans; j++) { 663 adj_chan = acs_find_chan(iface, chan->freq + 664 (j * 20) - 5); 665 if (adj_chan && acs_usable_chan(adj_chan)) { 666 factor += ACS_ADJ_WEIGHT * 667 adj_chan->interference_factor; 668 total_weight += ACS_ADJ_WEIGHT; 669 } 670 671 adj_chan = acs_find_chan(iface, chan->freq + 672 (j * 20) - 10); 673 if (adj_chan && acs_usable_chan(adj_chan)) { 674 factor += ACS_NEXT_ADJ_WEIGHT * 675 adj_chan->interference_factor; 676 total_weight += ACS_NEXT_ADJ_WEIGHT; 677 } 678 679 adj_chan = acs_find_chan(iface, chan->freq + 680 (j * 20) + 5); 681 if (adj_chan && acs_usable_chan(adj_chan)) { 682 factor += ACS_ADJ_WEIGHT * 683 adj_chan->interference_factor; 684 total_weight += ACS_ADJ_WEIGHT; 685 } 686 687 adj_chan = acs_find_chan(iface, chan->freq + 688 (j * 20) + 10); 689 if (adj_chan && acs_usable_chan(adj_chan)) { 690 factor += ACS_NEXT_ADJ_WEIGHT * 691 adj_chan->interference_factor; 692 total_weight += ACS_NEXT_ADJ_WEIGHT; 693 } 694 } 695 } 696 697 factor /= total_weight; 698 699 bias = NULL; 700 if (iface->conf->acs_chan_bias) { 701 for (k = 0; k < iface->conf->num_acs_chan_bias; k++) { 702 bias = &iface->conf->acs_chan_bias[k]; 703 if (bias->channel == chan->chan) 704 break; 705 bias = NULL; 706 } 707 } else if (is_24ghz_mode(iface->current_mode->mode) && 708 is_common_24ghz_chan(chan->chan)) { 709 tmp_bias.channel = chan->chan; 710 tmp_bias.bias = ACS_24GHZ_PREFER_1_6_11; 711 bias = &tmp_bias; 712 } 713 714 if (bias) { 715 factor *= bias->bias; 716 wpa_printf(MSG_DEBUG, 717 "ACS: * channel %d: total interference = %Lg (%f bias)", 718 chan->chan, factor, bias->bias); 719 } else { 720 wpa_printf(MSG_DEBUG, 721 "ACS: * channel %d: total interference = %Lg", 722 chan->chan, factor); 723 } 724 725 if (acs_usable_chan(chan) && 726 (!ideal_chan || factor < ideal_factor)) { 727 ideal_factor = factor; 728 ideal_chan = chan; 729 } 730 731 /* This channel would at least be usable */ 732 if (!rand_chan) 733 rand_chan = chan; 734 } 735 736 if (ideal_chan) { 737 wpa_printf(MSG_DEBUG, "ACS: Ideal channel is %d (%d MHz) with total interference factor of %Lg", 738 ideal_chan->chan, ideal_chan->freq, ideal_factor); 739 return ideal_chan; 740 } 741 742 return rand_chan; 743 } 744 745 746 static void acs_adjust_vht_center_freq(struct hostapd_iface *iface) 747 { 748 int offset; 749 750 wpa_printf(MSG_DEBUG, "ACS: Adjusting VHT center frequency"); 751 752 switch (iface->conf->vht_oper_chwidth) { 753 case VHT_CHANWIDTH_USE_HT: 754 offset = 2 * iface->conf->secondary_channel; 755 break; 756 case VHT_CHANWIDTH_80MHZ: 757 offset = 6; 758 break; 759 default: 760 /* TODO: How can this be calculated? Adjust 761 * acs_find_ideal_chan() */ 762 wpa_printf(MSG_INFO, "ACS: Only VHT20/40/80 is supported now"); 763 return; 764 } 765 766 iface->conf->vht_oper_centr_freq_seg0_idx = 767 iface->conf->channel + offset; 768 } 769 770 771 static int acs_study_survey_based(struct hostapd_iface *iface) 772 { 773 wpa_printf(MSG_DEBUG, "ACS: Trying survey-based ACS"); 774 775 if (!iface->chans_surveyed) { 776 wpa_printf(MSG_ERROR, "ACS: Unable to collect survey data"); 777 return -1; 778 } 779 780 if (!acs_surveys_are_sufficient(iface)) { 781 wpa_printf(MSG_ERROR, "ACS: Surveys have insufficient data"); 782 return -1; 783 } 784 785 acs_survey_all_chans_intereference_factor(iface); 786 return 0; 787 } 788 789 790 static int acs_study_options(struct hostapd_iface *iface) 791 { 792 int err; 793 794 err = acs_study_survey_based(iface); 795 if (err == 0) 796 return 0; 797 798 /* TODO: If no surveys are available/sufficient this is a good 799 * place to fallback to BSS-based ACS */ 800 801 return -1; 802 } 803 804 805 static void acs_study(struct hostapd_iface *iface) 806 { 807 struct hostapd_channel_data *ideal_chan; 808 int err; 809 810 err = acs_study_options(iface); 811 if (err < 0) { 812 wpa_printf(MSG_ERROR, "ACS: All study options have failed"); 813 goto fail; 814 } 815 816 ideal_chan = acs_find_ideal_chan(iface); 817 if (!ideal_chan) { 818 wpa_printf(MSG_ERROR, "ACS: Failed to compute ideal channel"); 819 err = -1; 820 goto fail; 821 } 822 823 iface->conf->channel = ideal_chan->chan; 824 825 if (iface->conf->ieee80211ac) 826 acs_adjust_vht_center_freq(iface); 827 828 err = 0; 829 fail: 830 /* 831 * hostapd_setup_interface_complete() will return -1 on failure, 832 * 0 on success and 0 is HOSTAPD_CHAN_VALID :) 833 */ 834 if (hostapd_acs_completed(iface, err) == HOSTAPD_CHAN_VALID) { 835 acs_cleanup(iface); 836 return; 837 } 838 839 /* This can possibly happen if channel parameters (secondary 840 * channel, center frequencies) are misconfigured */ 841 wpa_printf(MSG_ERROR, "ACS: Possibly channel configuration is invalid, please report this along with your config file."); 842 acs_fail(iface); 843 } 844 845 846 static void acs_scan_complete(struct hostapd_iface *iface) 847 { 848 int err; 849 850 iface->scan_cb = NULL; 851 852 wpa_printf(MSG_DEBUG, "ACS: Using survey based algorithm (acs_num_scans=%d)", 853 iface->conf->acs_num_scans); 854 855 err = hostapd_drv_get_survey(iface->bss[0], 0); 856 if (err) { 857 wpa_printf(MSG_ERROR, "ACS: Failed to get survey data"); 858 goto fail; 859 } 860 861 if (++iface->acs_num_completed_scans < iface->conf->acs_num_scans) { 862 err = acs_request_scan(iface); 863 if (err) { 864 wpa_printf(MSG_ERROR, "ACS: Failed to request scan"); 865 goto fail; 866 } 867 868 return; 869 } 870 871 acs_study(iface); 872 return; 873 fail: 874 hostapd_acs_completed(iface, 1); 875 acs_fail(iface); 876 } 877 878 879 static int acs_request_scan(struct hostapd_iface *iface) 880 { 881 struct wpa_driver_scan_params params; 882 struct hostapd_channel_data *chan; 883 int i, *freq; 884 885 os_memset(¶ms, 0, sizeof(params)); 886 params.freqs = os_calloc(iface->current_mode->num_channels + 1, 887 sizeof(params.freqs[0])); 888 if (params.freqs == NULL) 889 return -1; 890 891 freq = params.freqs; 892 for (i = 0; i < iface->current_mode->num_channels; i++) { 893 chan = &iface->current_mode->channels[i]; 894 if (chan->flag & HOSTAPD_CHAN_DISABLED) 895 continue; 896 897 if (!is_in_chanlist(iface, chan)) 898 continue; 899 900 *freq++ = chan->freq; 901 } 902 *freq = 0; 903 904 iface->scan_cb = acs_scan_complete; 905 906 wpa_printf(MSG_DEBUG, "ACS: Scanning %d / %d", 907 iface->acs_num_completed_scans + 1, 908 iface->conf->acs_num_scans); 909 910 if (hostapd_driver_scan(iface->bss[0], ¶ms) < 0) { 911 wpa_printf(MSG_ERROR, "ACS: Failed to request initial scan"); 912 acs_cleanup(iface); 913 os_free(params.freqs); 914 return -1; 915 } 916 917 os_free(params.freqs); 918 return 0; 919 } 920 921 922 enum hostapd_chan_status acs_init(struct hostapd_iface *iface) 923 { 924 int err; 925 926 wpa_printf(MSG_INFO, "ACS: Automatic channel selection started, this may take a bit"); 927 928 if (iface->drv_flags & WPA_DRIVER_FLAGS_ACS_OFFLOAD) { 929 wpa_printf(MSG_INFO, "ACS: Offloading to driver"); 930 err = hostapd_drv_do_acs(iface->bss[0]); 931 if (err) 932 return HOSTAPD_CHAN_INVALID; 933 return HOSTAPD_CHAN_ACS; 934 } 935 936 acs_cleanup(iface); 937 938 err = acs_request_scan(iface); 939 if (err < 0) 940 return HOSTAPD_CHAN_INVALID; 941 942 hostapd_set_state(iface, HAPD_IFACE_ACS); 943 wpa_msg(iface->bss[0]->msg_ctx, MSG_INFO, ACS_EVENT_STARTED); 944 945 return HOSTAPD_CHAN_ACS; 946 } 947