acs.c revision 281681
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 244static int acs_request_scan(struct hostapd_iface *iface); 245static int acs_survey_is_sufficient(struct freq_survey *survey); 246 247 248static 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 263static 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 284static 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 292static long double 293acs_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 325static void 326acs_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 368static 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 382static 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 395static 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 418static 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 445static 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 467static 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 479static int is_in_chanlist(struct hostapd_iface *iface, 480 struct hostapd_channel_data *chan) 481{ 482 int *entry; 483 484 if (!iface->conf->chanlist) 485 return 1; 486 487 for (entry = iface->conf->chanlist; *entry != -1; entry++) { 488 if (*entry == chan->chan) 489 return 1; 490 } 491 return 0; 492} 493 494 495static void acs_survey_all_chans_intereference_factor( 496 struct hostapd_iface *iface) 497{ 498 int i; 499 struct hostapd_channel_data *chan; 500 501 for (i = 0; i < iface->current_mode->num_channels; i++) { 502 chan = &iface->current_mode->channels[i]; 503 504 if (!acs_usable_chan(chan)) 505 continue; 506 507 if (!is_in_chanlist(iface, chan)) 508 continue; 509 510 wpa_printf(MSG_DEBUG, "ACS: Survey analysis for channel %d (%d MHz)", 511 chan->chan, chan->freq); 512 513 acs_survey_chan_interference_factor(iface, chan); 514 515 wpa_printf(MSG_DEBUG, "ACS: * interference factor average: %Lg", 516 chan->interference_factor); 517 } 518} 519 520 521static struct hostapd_channel_data *acs_find_chan(struct hostapd_iface *iface, 522 int freq) 523{ 524 struct hostapd_channel_data *chan; 525 int i; 526 527 for (i = 0; i < iface->current_mode->num_channels; i++) { 528 chan = &iface->current_mode->channels[i]; 529 530 if (chan->flag & HOSTAPD_CHAN_DISABLED) 531 continue; 532 533 if (chan->freq == freq) 534 return chan; 535 } 536 537 return NULL; 538} 539 540 541static int is_24ghz_mode(enum hostapd_hw_mode mode) 542{ 543 return mode == HOSTAPD_MODE_IEEE80211B || 544 mode == HOSTAPD_MODE_IEEE80211G; 545} 546 547 548static int is_common_24ghz_chan(int chan) 549{ 550 return chan == 1 || chan == 6 || chan == 11; 551} 552 553 554#ifndef ACS_ADJ_WEIGHT 555#define ACS_ADJ_WEIGHT 0.85 556#endif /* ACS_ADJ_WEIGHT */ 557 558#ifndef ACS_NEXT_ADJ_WEIGHT 559#define ACS_NEXT_ADJ_WEIGHT 0.55 560#endif /* ACS_NEXT_ADJ_WEIGHT */ 561 562#ifndef ACS_24GHZ_PREFER_1_6_11 563/* 564 * Select commonly used channels 1, 6, 11 by default even if a neighboring 565 * channel has a smaller interference factor as long as it is not better by more 566 * than this multiplier. 567 */ 568#define ACS_24GHZ_PREFER_1_6_11 0.8 569#endif /* ACS_24GHZ_PREFER_1_6_11 */ 570 571/* 572 * At this point it's assumed chan->interface_factor has been computed. 573 * This function should be reusable regardless of interference computation 574 * option (survey, BSS, spectral, ...). chan->interference factor must be 575 * summable (i.e., must be always greater than zero). 576 */ 577static struct hostapd_channel_data * 578acs_find_ideal_chan(struct hostapd_iface *iface) 579{ 580 struct hostapd_channel_data *chan, *adj_chan, *ideal_chan = NULL, 581 *rand_chan = NULL; 582 long double factor, ideal_factor = 0; 583 int i, j; 584 int n_chans = 1; 585 unsigned int k; 586 587 /* TODO: HT40- support */ 588 589 if (iface->conf->ieee80211n && 590 iface->conf->secondary_channel == -1) { 591 wpa_printf(MSG_ERROR, "ACS: HT40- is not supported yet. Please try HT40+"); 592 return NULL; 593 } 594 595 if (iface->conf->ieee80211n && 596 iface->conf->secondary_channel) 597 n_chans = 2; 598 599 if (iface->conf->ieee80211ac && 600 iface->conf->vht_oper_chwidth == 1) 601 n_chans = 4; 602 603 /* TODO: VHT80+80, VHT160. Update acs_adjust_vht_center_freq() too. */ 604 605 wpa_printf(MSG_DEBUG, "ACS: Survey analysis for selected bandwidth %d MHz", 606 n_chans == 1 ? 20 : 607 n_chans == 2 ? 40 : 608 n_chans == 4 ? 80 : 609 -1); 610 611 for (i = 0; i < iface->current_mode->num_channels; i++) { 612 double total_weight; 613 struct acs_bias *bias, tmp_bias; 614 615 chan = &iface->current_mode->channels[i]; 616 617 if (chan->flag & HOSTAPD_CHAN_DISABLED) 618 continue; 619 620 if (!is_in_chanlist(iface, chan)) 621 continue; 622 623 /* HT40 on 5 GHz has a limited set of primary channels as per 624 * 11n Annex J */ 625 if (iface->current_mode->mode == HOSTAPD_MODE_IEEE80211A && 626 iface->conf->ieee80211n && 627 iface->conf->secondary_channel && 628 !acs_usable_ht40_chan(chan)) { 629 wpa_printf(MSG_DEBUG, "ACS: Channel %d: not allowed as primary channel for HT40", 630 chan->chan); 631 continue; 632 } 633 634 if (iface->current_mode->mode == HOSTAPD_MODE_IEEE80211A && 635 iface->conf->ieee80211ac && 636 iface->conf->vht_oper_chwidth == 1 && 637 !acs_usable_vht80_chan(chan)) { 638 wpa_printf(MSG_DEBUG, "ACS: Channel %d: not allowed as primary channel for VHT80", 639 chan->chan); 640 continue; 641 } 642 643 factor = 0; 644 if (acs_usable_chan(chan)) 645 factor = chan->interference_factor; 646 total_weight = 1; 647 648 for (j = 1; j < n_chans; j++) { 649 adj_chan = acs_find_chan(iface, chan->freq + (j * 20)); 650 if (!adj_chan) 651 break; 652 653 if (acs_usable_chan(adj_chan)) { 654 factor += adj_chan->interference_factor; 655 total_weight += 1; 656 } 657 } 658 659 if (j != n_chans) { 660 wpa_printf(MSG_DEBUG, "ACS: Channel %d: not enough bandwidth", 661 chan->chan); 662 continue; 663 } 664 665 /* 2.4 GHz has overlapping 20 MHz channels. Include adjacent 666 * channel interference factor. */ 667 if (is_24ghz_mode(iface->current_mode->mode)) { 668 for (j = 0; j < n_chans; j++) { 669 adj_chan = acs_find_chan(iface, chan->freq + 670 (j * 20) - 5); 671 if (adj_chan && acs_usable_chan(adj_chan)) { 672 factor += ACS_ADJ_WEIGHT * 673 adj_chan->interference_factor; 674 total_weight += ACS_ADJ_WEIGHT; 675 } 676 677 adj_chan = acs_find_chan(iface, chan->freq + 678 (j * 20) - 10); 679 if (adj_chan && acs_usable_chan(adj_chan)) { 680 factor += ACS_NEXT_ADJ_WEIGHT * 681 adj_chan->interference_factor; 682 total_weight += ACS_NEXT_ADJ_WEIGHT; 683 } 684 685 adj_chan = acs_find_chan(iface, chan->freq + 686 (j * 20) + 5); 687 if (adj_chan && acs_usable_chan(adj_chan)) { 688 factor += ACS_ADJ_WEIGHT * 689 adj_chan->interference_factor; 690 total_weight += ACS_ADJ_WEIGHT; 691 } 692 693 adj_chan = acs_find_chan(iface, chan->freq + 694 (j * 20) + 10); 695 if (adj_chan && acs_usable_chan(adj_chan)) { 696 factor += ACS_NEXT_ADJ_WEIGHT * 697 adj_chan->interference_factor; 698 total_weight += ACS_NEXT_ADJ_WEIGHT; 699 } 700 } 701 } 702 703 factor /= total_weight; 704 705 bias = NULL; 706 if (iface->conf->acs_chan_bias) { 707 for (k = 0; k < iface->conf->num_acs_chan_bias; k++) { 708 bias = &iface->conf->acs_chan_bias[k]; 709 if (bias->channel == chan->chan) 710 break; 711 bias = NULL; 712 } 713 } else if (is_24ghz_mode(iface->current_mode->mode) && 714 is_common_24ghz_chan(chan->chan)) { 715 tmp_bias.channel = chan->chan; 716 tmp_bias.bias = ACS_24GHZ_PREFER_1_6_11; 717 bias = &tmp_bias; 718 } 719 720 if (bias) { 721 factor *= bias->bias; 722 wpa_printf(MSG_DEBUG, 723 "ACS: * channel %d: total interference = %Lg (%f bias)", 724 chan->chan, factor, bias->bias); 725 } else { 726 wpa_printf(MSG_DEBUG, 727 "ACS: * channel %d: total interference = %Lg", 728 chan->chan, factor); 729 } 730 731 if (acs_usable_chan(chan) && 732 (!ideal_chan || factor < ideal_factor)) { 733 ideal_factor = factor; 734 ideal_chan = chan; 735 } 736 737 /* This channel would at least be usable */ 738 if (!rand_chan) 739 rand_chan = chan; 740 } 741 742 if (ideal_chan) { 743 wpa_printf(MSG_DEBUG, "ACS: Ideal channel is %d (%d MHz) with total interference factor of %Lg", 744 ideal_chan->chan, ideal_chan->freq, ideal_factor); 745 return ideal_chan; 746 } 747 748 return rand_chan; 749} 750 751 752static void acs_adjust_vht_center_freq(struct hostapd_iface *iface) 753{ 754 int offset; 755 756 wpa_printf(MSG_DEBUG, "ACS: Adjusting VHT center frequency"); 757 758 switch (iface->conf->vht_oper_chwidth) { 759 case VHT_CHANWIDTH_USE_HT: 760 offset = 2 * iface->conf->secondary_channel; 761 break; 762 case VHT_CHANWIDTH_80MHZ: 763 offset = 6; 764 break; 765 default: 766 /* TODO: How can this be calculated? Adjust 767 * acs_find_ideal_chan() */ 768 wpa_printf(MSG_INFO, "ACS: Only VHT20/40/80 is supported now"); 769 return; 770 } 771 772 iface->conf->vht_oper_centr_freq_seg0_idx = 773 iface->conf->channel + offset; 774} 775 776 777static int acs_study_survey_based(struct hostapd_iface *iface) 778{ 779 wpa_printf(MSG_DEBUG, "ACS: Trying survey-based ACS"); 780 781 if (!iface->chans_surveyed) { 782 wpa_printf(MSG_ERROR, "ACS: Unable to collect survey data"); 783 return -1; 784 } 785 786 if (!acs_surveys_are_sufficient(iface)) { 787 wpa_printf(MSG_ERROR, "ACS: Surveys have insufficient data"); 788 return -1; 789 } 790 791 acs_survey_all_chans_intereference_factor(iface); 792 return 0; 793} 794 795 796static int acs_study_options(struct hostapd_iface *iface) 797{ 798 int err; 799 800 err = acs_study_survey_based(iface); 801 if (err == 0) 802 return 0; 803 804 /* TODO: If no surveys are available/sufficient this is a good 805 * place to fallback to BSS-based ACS */ 806 807 return -1; 808} 809 810 811static void acs_study(struct hostapd_iface *iface) 812{ 813 struct hostapd_channel_data *ideal_chan; 814 int err; 815 816 err = acs_study_options(iface); 817 if (err < 0) { 818 wpa_printf(MSG_ERROR, "ACS: All study options have failed"); 819 goto fail; 820 } 821 822 ideal_chan = acs_find_ideal_chan(iface); 823 if (!ideal_chan) { 824 wpa_printf(MSG_ERROR, "ACS: Failed to compute ideal channel"); 825 err = -1; 826 goto fail; 827 } 828 829 iface->conf->channel = ideal_chan->chan; 830 831 if (iface->conf->ieee80211ac) 832 acs_adjust_vht_center_freq(iface); 833 834 err = 0; 835fail: 836 /* 837 * hostapd_setup_interface_complete() will return -1 on failure, 838 * 0 on success and 0 is HOSTAPD_CHAN_VALID :) 839 */ 840 if (hostapd_acs_completed(iface, err) == HOSTAPD_CHAN_VALID) { 841 acs_cleanup(iface); 842 return; 843 } 844 845 /* This can possibly happen if channel parameters (secondary 846 * channel, center frequencies) are misconfigured */ 847 wpa_printf(MSG_ERROR, "ACS: Possibly channel configuration is invalid, please report this along with your config file."); 848 acs_fail(iface); 849} 850 851 852static void acs_scan_complete(struct hostapd_iface *iface) 853{ 854 int err; 855 856 iface->scan_cb = NULL; 857 858 wpa_printf(MSG_DEBUG, "ACS: Using survey based algorithm (acs_num_scans=%d)", 859 iface->conf->acs_num_scans); 860 861 err = hostapd_drv_get_survey(iface->bss[0], 0); 862 if (err) { 863 wpa_printf(MSG_ERROR, "ACS: Failed to get survey data"); 864 goto fail; 865 } 866 867 if (++iface->acs_num_completed_scans < iface->conf->acs_num_scans) { 868 err = acs_request_scan(iface); 869 if (err) { 870 wpa_printf(MSG_ERROR, "ACS: Failed to request scan"); 871 goto fail; 872 } 873 874 return; 875 } 876 877 acs_study(iface); 878 return; 879fail: 880 hostapd_acs_completed(iface, 1); 881 acs_fail(iface); 882} 883 884 885static int acs_request_scan(struct hostapd_iface *iface) 886{ 887 struct wpa_driver_scan_params params; 888 struct hostapd_channel_data *chan; 889 int i, *freq; 890 891 os_memset(¶ms, 0, sizeof(params)); 892 params.freqs = os_calloc(iface->current_mode->num_channels + 1, 893 sizeof(params.freqs[0])); 894 if (params.freqs == NULL) 895 return -1; 896 897 freq = params.freqs; 898 for (i = 0; i < iface->current_mode->num_channels; i++) { 899 chan = &iface->current_mode->channels[i]; 900 if (chan->flag & HOSTAPD_CHAN_DISABLED) 901 continue; 902 903 *freq++ = chan->freq; 904 } 905 *freq = 0; 906 907 iface->scan_cb = acs_scan_complete; 908 909 wpa_printf(MSG_DEBUG, "ACS: Scanning %d / %d", 910 iface->acs_num_completed_scans + 1, 911 iface->conf->acs_num_scans); 912 913 if (hostapd_driver_scan(iface->bss[0], ¶ms) < 0) { 914 wpa_printf(MSG_ERROR, "ACS: Failed to request initial scan"); 915 acs_cleanup(iface); 916 os_free(params.freqs); 917 return -1; 918 } 919 920 os_free(params.freqs); 921 return 0; 922} 923 924 925enum hostapd_chan_status acs_init(struct hostapd_iface *iface) 926{ 927 int err; 928 929 wpa_printf(MSG_INFO, "ACS: Automatic channel selection started, this may take a bit"); 930 931 if (iface->drv_flags & WPA_DRIVER_FLAGS_ACS_OFFLOAD) { 932 wpa_printf(MSG_INFO, "ACS: Offloading to driver"); 933 err = hostapd_drv_do_acs(iface->bss[0]); 934 if (err) 935 return HOSTAPD_CHAN_INVALID; 936 return HOSTAPD_CHAN_ACS; 937 } 938 939 acs_cleanup(iface); 940 941 err = acs_request_scan(iface); 942 if (err < 0) 943 return HOSTAPD_CHAN_INVALID; 944 945 hostapd_set_state(iface, HAPD_IFACE_ACS); 946 wpa_msg(iface->bss[0]->msg_ctx, MSG_INFO, ACS_EVENT_STARTED); 947 948 return HOSTAPD_CHAN_ACS; 949} 950