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