/* * ACS - Automatic Channel Selection module * Copyright (c) 2011, Atheros Communications * Copyright (c) 2013, Qualcomm Atheros, Inc. * * This software may be distributed under the terms of the BSD license. * See README for more details. */ #include "utils/includes.h" #include #include "utils/common.h" #include "utils/list.h" #include "utils/eloop.h" #include "common/ieee802_11_defs.h" #include "common/hw_features_common.h" #include "common/wpa_ctrl.h" #include "drivers/driver.h" #include "hostapd.h" #include "ap_drv_ops.h" #include "ap_config.h" #include "hw_features.h" #include "acs.h" /* * Automatic Channel Selection * =========================== * * More info at * ------------ * http://wireless.kernel.org/en/users/Documentation/acs * * How to use * ---------- * - make sure you have CONFIG_ACS=y in hostapd's .config * - use channel=0 or channel=acs to enable ACS * * How does it work * ---------------- * 1. passive scans are used to collect survey data * (it is assumed that scan trigger collection of survey data in driver) * 2. interference factor is calculated for each channel * 3. ideal channel is picked depending on channel width by using adjacent * channel interference factors * * Known limitations * ----------------- * - Current implementation depends heavily on the amount of time willing to * spend gathering survey data during hostapd startup. Short traffic bursts * may be missed and a suboptimal channel may be picked. * - Ideal channel may end up overlapping a channel with 40 MHz intolerant BSS * * Todo / Ideas * ------------ * - implement other interference computation methods * - BSS/RSSI based * - spectral scan based * (should be possibly to hook this up with current ACS scans) * - add wpa_supplicant support (for P2P) * - collect a histogram of interference over time allowing more educated * guess about an ideal channel (perhaps CSA could be used to migrate AP to a * new "better" channel while running) * - include neighboring BSS scan to avoid conflicts with 40 MHz intolerant BSSs * when choosing the ideal channel * * Survey interference factor implementation details * ------------------------------------------------- * Generic interference_factor in struct hostapd_channel_data is used. * * The survey interference factor is defined as the ratio of the * observed busy time over the time we spent on the channel, * this value is then amplified by the observed noise floor on * the channel in comparison to the lowest noise floor observed * on the entire band. * * This corresponds to: * --- * (busy time - tx time) / (active time - tx time) * 2^(chan_nf - band_min_nf) * --- * * The coefficient of 2 reflects the way power in "far-field" * radiation decreases as the square of distance from the antenna [1]. * What this does is it decreases the observed busy time ratio if the * noise observed was low but increases it if the noise was high, * proportionally to the way "far field" radiation changes over * distance. * * If channel busy time is not available the fallback is to use channel RX time. * * Since noise floor is in dBm it is necessary to convert it into Watts so that * combined channel interference (e.g., HT40, which uses two channels) can be * calculated easily. * --- * (busy time - tx time) / (active time - tx time) * * 2^(10^(chan_nf/10) - 10^(band_min_nf/10)) * --- * * However to account for cases where busy/rx time is 0 (channel load is then * 0%) channel noise floor signal power is combined into the equation so a * channel with lower noise floor is preferred. The equation becomes: * --- * 10^(chan_nf/5) + (busy time - tx time) / (active time - tx time) * * 2^(10^(chan_nf/10) - 10^(band_min_nf/10)) * --- * * All this "interference factor" is purely subjective and only time * will tell how usable this is. By using the minimum noise floor we * remove any possible issues due to card calibration. The computation * of the interference factor then is dependent on what the card itself * picks up as the minimum noise, not an actual real possible card * noise value. * * Total interference computation details * -------------------------------------- * The above channel interference factor is calculated with no respect to * target operational bandwidth. * * To find an ideal channel the above data is combined by taking into account * the target operational bandwidth and selected band. E.g., on 2.4 GHz channels * overlap with 20 MHz bandwidth, but there is no overlap for 20 MHz bandwidth * on 5 GHz. * * Each valid and possible channel spec (i.e., channel + width) is taken and its * interference factor is computed by summing up interferences of each channel * it overlaps. The one with least total interference is picked up. * * Note: This implies base channel interference factor must be non-negative * allowing easy summing up. * * Example ACS analysis printout * ----------------------------- * * ACS: Trying survey-based ACS * ACS: Survey analysis for channel 1 (2412 MHz) * ACS: 1: min_nf=-113 interference_factor=0.0802469 nf=-113 time=162 busy=0 rx=13 * ACS: 2: min_nf=-113 interference_factor=0.0745342 nf=-113 time=161 busy=0 rx=12 * ACS: 3: min_nf=-113 interference_factor=0.0679012 nf=-113 time=162 busy=0 rx=11 * ACS: 4: min_nf=-113 interference_factor=0.0310559 nf=-113 time=161 busy=0 rx=5 * ACS: 5: min_nf=-113 interference_factor=0.0248447 nf=-113 time=161 busy=0 rx=4 * ACS: * interference factor average: 0.0557166 * ACS: Survey analysis for channel 2 (2417 MHz) * ACS: 1: min_nf=-113 interference_factor=0.0185185 nf=-113 time=162 busy=0 rx=3 * ACS: 2: min_nf=-113 interference_factor=0.0246914 nf=-113 time=162 busy=0 rx=4 * ACS: 3: min_nf=-113 interference_factor=0.037037 nf=-113 time=162 busy=0 rx=6 * ACS: 4: min_nf=-113 interference_factor=0.149068 nf=-113 time=161 busy=0 rx=24 * ACS: 5: min_nf=-113 interference_factor=0.0248447 nf=-113 time=161 busy=0 rx=4 * ACS: * interference factor average: 0.050832 * ACS: Survey analysis for channel 3 (2422 MHz) * ACS: 1: min_nf=-113 interference_factor=2.51189e-23 nf=-113 time=162 busy=0 rx=0 * ACS: 2: min_nf=-113 interference_factor=0.0185185 nf=-113 time=162 busy=0 rx=3 * ACS: 3: min_nf=-113 interference_factor=0.0186335 nf=-113 time=161 busy=0 rx=3 * ACS: 4: min_nf=-113 interference_factor=0.0186335 nf=-113 time=161 busy=0 rx=3 * ACS: 5: min_nf=-113 interference_factor=0.0186335 nf=-113 time=161 busy=0 rx=3 * ACS: * interference factor average: 0.0148838 * ACS: Survey analysis for channel 4 (2427 MHz) * ACS: 1: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0 * ACS: 2: min_nf=-114 interference_factor=0.0555556 nf=-114 time=162 busy=0 rx=9 * ACS: 3: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=161 busy=0 rx=0 * ACS: 4: min_nf=-114 interference_factor=0.0186335 nf=-114 time=161 busy=0 rx=3 * ACS: 5: min_nf=-114 interference_factor=0.00621118 nf=-114 time=161 busy=0 rx=1 * ACS: * interference factor average: 0.0160801 * ACS: Survey analysis for channel 5 (2432 MHz) * ACS: 1: min_nf=-114 interference_factor=0.409938 nf=-113 time=161 busy=0 rx=66 * ACS: 2: min_nf=-114 interference_factor=0.0432099 nf=-113 time=162 busy=0 rx=7 * ACS: 3: min_nf=-114 interference_factor=0.0124224 nf=-113 time=161 busy=0 rx=2 * ACS: 4: min_nf=-114 interference_factor=0.677019 nf=-113 time=161 busy=0 rx=109 * ACS: 5: min_nf=-114 interference_factor=0.0186335 nf=-114 time=161 busy=0 rx=3 * ACS: * interference factor average: 0.232244 * ACS: Survey analysis for channel 6 (2437 MHz) * ACS: 1: min_nf=-113 interference_factor=0.552795 nf=-113 time=161 busy=0 rx=89 * ACS: 2: min_nf=-113 interference_factor=0.0807453 nf=-112 time=161 busy=0 rx=13 * ACS: 3: min_nf=-113 interference_factor=0.0310559 nf=-113 time=161 busy=0 rx=5 * ACS: 4: min_nf=-113 interference_factor=0.434783 nf=-112 time=161 busy=0 rx=70 * ACS: 5: min_nf=-113 interference_factor=0.0621118 nf=-113 time=161 busy=0 rx=10 * ACS: * interference factor average: 0.232298 * ACS: Survey analysis for channel 7 (2442 MHz) * ACS: 1: min_nf=-113 interference_factor=0.440994 nf=-112 time=161 busy=0 rx=71 * ACS: 2: min_nf=-113 interference_factor=0.385093 nf=-113 time=161 busy=0 rx=62 * ACS: 3: min_nf=-113 interference_factor=0.0372671 nf=-113 time=161 busy=0 rx=6 * ACS: 4: min_nf=-113 interference_factor=0.0372671 nf=-113 time=161 busy=0 rx=6 * ACS: 5: min_nf=-113 interference_factor=0.0745342 nf=-113 time=161 busy=0 rx=12 * ACS: * interference factor average: 0.195031 * ACS: Survey analysis for channel 8 (2447 MHz) * ACS: 1: min_nf=-114 interference_factor=0.0496894 nf=-112 time=161 busy=0 rx=8 * ACS: 2: min_nf=-114 interference_factor=0.0496894 nf=-114 time=161 busy=0 rx=8 * ACS: 3: min_nf=-114 interference_factor=0.0372671 nf=-113 time=161 busy=0 rx=6 * ACS: 4: min_nf=-114 interference_factor=0.12963 nf=-113 time=162 busy=0 rx=21 * ACS: 5: min_nf=-114 interference_factor=0.166667 nf=-114 time=162 busy=0 rx=27 * ACS: * interference factor average: 0.0865885 * ACS: Survey analysis for channel 9 (2452 MHz) * ACS: 1: min_nf=-114 interference_factor=0.0124224 nf=-114 time=161 busy=0 rx=2 * ACS: 2: min_nf=-114 interference_factor=0.0310559 nf=-114 time=161 busy=0 rx=5 * ACS: 3: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=161 busy=0 rx=0 * ACS: 4: min_nf=-114 interference_factor=0.00617284 nf=-114 time=162 busy=0 rx=1 * ACS: 5: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0 * ACS: * interference factor average: 0.00993022 * ACS: Survey analysis for channel 10 (2457 MHz) * ACS: 1: min_nf=-114 interference_factor=0.00621118 nf=-114 time=161 busy=0 rx=1 * ACS: 2: min_nf=-114 interference_factor=0.00621118 nf=-114 time=161 busy=0 rx=1 * ACS: 3: min_nf=-114 interference_factor=0.00621118 nf=-114 time=161 busy=0 rx=1 * ACS: 4: min_nf=-114 interference_factor=0.0493827 nf=-114 time=162 busy=0 rx=8 * ACS: 5: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0 * ACS: * interference factor average: 0.0136033 * ACS: Survey analysis for channel 11 (2462 MHz) * ACS: 1: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=161 busy=0 rx=0 * ACS: 2: min_nf=-114 interference_factor=2.51189e-23 nf=-113 time=161 busy=0 rx=0 * ACS: 3: min_nf=-114 interference_factor=2.51189e-23 nf=-113 time=161 busy=0 rx=0 * ACS: 4: min_nf=-114 interference_factor=0.0432099 nf=-114 time=162 busy=0 rx=7 * ACS: 5: min_nf=-114 interference_factor=0.0925926 nf=-114 time=162 busy=0 rx=15 * ACS: * interference factor average: 0.0271605 * ACS: Survey analysis for channel 12 (2467 MHz) * ACS: 1: min_nf=-114 interference_factor=0.0621118 nf=-113 time=161 busy=0 rx=10 * ACS: 2: min_nf=-114 interference_factor=0.00621118 nf=-114 time=161 busy=0 rx=1 * ACS: 3: min_nf=-114 interference_factor=2.51189e-23 nf=-113 time=162 busy=0 rx=0 * ACS: 4: min_nf=-114 interference_factor=2.51189e-23 nf=-113 time=162 busy=0 rx=0 * ACS: 5: min_nf=-114 interference_factor=0.00617284 nf=-113 time=162 busy=0 rx=1 * ACS: * interference factor average: 0.0148992 * ACS: Survey analysis for channel 13 (2472 MHz) * ACS: 1: min_nf=-114 interference_factor=0.0745342 nf=-114 time=161 busy=0 rx=12 * ACS: 2: min_nf=-114 interference_factor=0.0555556 nf=-114 time=162 busy=0 rx=9 * ACS: 3: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0 * ACS: 4: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0 * ACS: 5: min_nf=-114 interference_factor=1.58489e-23 nf=-114 time=162 busy=0 rx=0 * ACS: * interference factor average: 0.0260179 * ACS: Survey analysis for selected bandwidth 20MHz * ACS: * channel 1: total interference = 0.121432 * ACS: * channel 2: total interference = 0.137512 * ACS: * channel 3: total interference = 0.369757 * ACS: * channel 4: total interference = 0.546338 * ACS: * channel 5: total interference = 0.690538 * ACS: * channel 6: total interference = 0.762242 * ACS: * channel 7: total interference = 0.756092 * ACS: * channel 8: total interference = 0.537451 * ACS: * channel 9: total interference = 0.332313 * ACS: * channel 10: total interference = 0.152182 * ACS: * channel 11: total interference = 0.0916111 * ACS: * channel 12: total interference = 0.0816809 * ACS: * channel 13: total interference = 0.0680776 * ACS: Ideal channel is 13 (2472 MHz) with total interference factor of 0.0680776 * * [1] http://en.wikipedia.org/wiki/Near_and_far_field */ enum bw_type { ACS_BW40, ACS_BW80, ACS_BW160, ACS_BW320_1, ACS_BW320_2, }; struct bw_item { int first; int last; int center_chan; }; static const struct bw_item bw_40[] = { { 5180, 5200, 38 }, { 5220, 5240, 46 }, { 5260, 5280, 54 }, { 5300, 5320, 62 }, { 5500, 5520, 102 }, { 5540, 5560, 110 }, { 5580, 5600, 118 }, { 5620, 5640, 126 }, { 5660, 5680, 134 }, { 5700, 5720, 142 }, { 5745, 5765, 151 }, { 5785, 5805, 159 }, { 5825, 5845, 167 }, { 5865, 5885, 175 }, { 5955, 5975, 3 }, { 5995, 6015, 11 }, { 6035, 6055, 19 }, { 6075, 6095, 27 }, { 6115, 6135, 35 }, { 6155, 6175, 43 }, { 6195, 6215, 51 }, { 6235, 6255, 59 }, { 6275, 6295, 67 }, { 6315, 6335, 75 }, { 6355, 6375, 83 }, { 6395, 6415, 91 }, { 6435, 6455, 99 }, { 6475, 6495, 107 }, { 6515, 6535, 115 }, { 6555, 6575, 123 }, { 6595, 6615, 131 }, { 6635, 6655, 139 }, { 6675, 6695, 147 }, { 6715, 6735, 155 }, { 6755, 6775, 163 }, { 6795, 6815, 171 }, { 6835, 6855, 179 }, { 6875, 6895, 187 }, { 6915, 6935, 195 }, { 6955, 6975, 203 }, { 6995, 7015, 211 }, { 7035, 7055, 219 }, { 7075, 7095, 227}, { -1, -1, -1 } }; static const struct bw_item bw_80[] = { { 5180, 5240, 42 }, { 5260, 5320, 58 }, { 5500, 5560, 106 }, { 5580, 5640, 122 }, { 5660, 5720, 138 }, { 5745, 5805, 155 }, { 5825, 5885, 171}, { 5955, 6015, 7 }, { 6035, 6095, 23 }, { 6115, 6175, 39 }, { 6195, 6255, 55 }, { 6275, 6335, 71 }, { 6355, 6415, 87 }, { 6435, 6495, 103 }, { 6515, 6575, 119 }, { 6595, 6655, 135 }, { 6675, 6735, 151 }, { 6755, 6815, 167 }, { 6835, 6895, 183 }, { 6915, 6975, 199 }, { 6995, 7055, 215 }, { -1, -1, -1 } }; static const struct bw_item bw_160[] = { { 5180, 5320, 50 }, { 5500, 5640, 114 }, { 5745, 5885, 163 }, { 5955, 6095, 15 }, { 6115, 6255, 47 }, { 6275, 6415, 79 }, { 6435, 6575, 111 }, { 6595, 6735, 143 }, { 6755, 6895, 175 }, { 6915, 7055, 207 }, { -1, -1, -1 } }; static const struct bw_item bw_320_1[] = { { 5955, 6255, 31 }, { 6275, 6575, 95 }, { 6595, 6895, 159 }, { -1, -1, -1 } }; static const struct bw_item bw_320_2[] = { { 6115, 6415, 63 }, { 6435, 6735, 127 }, { 6755, 7055, 191 }, { -1, -1, -1 } }; static const struct bw_item *bw_desc[] = { [ACS_BW40] = bw_40, [ACS_BW80] = bw_80, [ACS_BW160] = bw_160, [ACS_BW320_1] = bw_320_1, [ACS_BW320_2] = bw_320_2, }; static int acs_request_scan(struct hostapd_iface *iface); static int acs_survey_is_sufficient(struct freq_survey *survey); static void acs_scan_retry(void *eloop_data, void *user_data); static void acs_clean_chan_surveys(struct hostapd_channel_data *chan) { struct freq_survey *survey, *tmp; if (dl_list_empty(&chan->survey_list)) return; dl_list_for_each_safe(survey, tmp, &chan->survey_list, struct freq_survey, list) { dl_list_del(&survey->list); os_free(survey); } } static void acs_cleanup_mode(struct hostapd_hw_modes *mode) { int i; struct hostapd_channel_data *chan; for (i = 0; i < mode->num_channels; i++) { chan = &mode->channels[i]; if (chan->flag & HOSTAPD_CHAN_SURVEY_LIST_INITIALIZED) acs_clean_chan_surveys(chan); dl_list_init(&chan->survey_list); chan->flag |= HOSTAPD_CHAN_SURVEY_LIST_INITIALIZED; chan->min_nf = 0; chan->punct_bitmap = 0; } } void acs_cleanup(struct hostapd_iface *iface) { int i; for (i = 0; i < iface->num_hw_features; i++) acs_cleanup_mode(&iface->hw_features[i]); iface->chans_surveyed = 0; iface->acs_num_completed_scans = 0; iface->acs_num_retries = 0; eloop_cancel_timeout(acs_scan_retry, iface, NULL); } static void acs_fail(struct hostapd_iface *iface) { wpa_printf(MSG_ERROR, "ACS: Failed to start"); acs_cleanup(iface); hostapd_disable_iface(iface); } static long double acs_survey_interference_factor(struct freq_survey *survey, s8 min_nf) { long double factor, busy, total; if (survey->filled & SURVEY_HAS_CHAN_TIME_BUSY) busy = survey->channel_time_busy; else if (survey->filled & SURVEY_HAS_CHAN_TIME_RX) busy = survey->channel_time_rx; else { wpa_printf(MSG_ERROR, "ACS: Survey data missing"); return 0; } total = survey->channel_time; if (survey->filled & SURVEY_HAS_CHAN_TIME_TX) { busy -= survey->channel_time_tx; total -= survey->channel_time_tx; } /* TODO: figure out the best multiplier for noise floor base */ factor = pow(10, survey->nf / 5.0L) + (total ? (busy / total) : 0) * pow(2, pow(10, (long double) survey->nf / 10.0L) - pow(10, (long double) min_nf / 10.0L)); return factor; } static void acs_survey_chan_interference_factor(struct hostapd_iface *iface, struct hostapd_channel_data *chan) { struct freq_survey *survey; unsigned int i = 0; long double int_factor = 0; unsigned count = 0; if (dl_list_empty(&chan->survey_list) || (chan->flag & HOSTAPD_CHAN_DISABLED)) return; chan->interference_factor = 0; dl_list_for_each(survey, &chan->survey_list, struct freq_survey, list) { i++; if (!acs_survey_is_sufficient(survey)) { wpa_printf(MSG_DEBUG, "ACS: %d: insufficient data", i); continue; } count++; int_factor = acs_survey_interference_factor(survey, iface->lowest_nf); chan->interference_factor += int_factor; wpa_printf(MSG_DEBUG, "ACS: %d: min_nf=%d interference_factor=%Lg nf=%d time=%lu busy=%lu rx=%lu", i, chan->min_nf, int_factor, survey->nf, (unsigned long) survey->channel_time, (unsigned long) survey->channel_time_busy, (unsigned long) survey->channel_time_rx); } if (count) chan->interference_factor /= count; } static bool acs_usable_bw_chan(const struct hostapd_channel_data *chan, enum bw_type bw) { unsigned int i = 0; while (bw_desc[bw][i].first != -1) { if (chan->freq == bw_desc[bw][i].first) return true; i++; } return false; } static int acs_get_bw_center_chan(int freq, enum bw_type bw) { unsigned int i = 0; while (bw_desc[bw][i].first != -1) { if (freq >= bw_desc[bw][i].first && freq <= bw_desc[bw][i].last) return bw_desc[bw][i].center_chan; i++; } return 0; } static int acs_survey_is_sufficient(struct freq_survey *survey) { if (!(survey->filled & SURVEY_HAS_NF)) { wpa_printf(MSG_INFO, "ACS: Survey for freq %d is missing noise floor", survey->freq); return 0; } if (!(survey->filled & SURVEY_HAS_CHAN_TIME)) { wpa_printf(MSG_INFO, "ACS: Survey for freq %d is missing channel time", survey->freq); return 0; } if (!(survey->filled & SURVEY_HAS_CHAN_TIME_BUSY) && !(survey->filled & SURVEY_HAS_CHAN_TIME_RX)) { wpa_printf(MSG_INFO, "ACS: Survey for freq %d is missing RX and busy time (at least one is required)", survey->freq); return 0; } return 1; } static int acs_survey_list_is_sufficient(struct hostapd_channel_data *chan) { struct freq_survey *survey; int ret = -1; dl_list_for_each(survey, &chan->survey_list, struct freq_survey, list) { if (acs_survey_is_sufficient(survey)) { ret = 1; break; } ret = 0; } if (ret == -1) ret = 0; /* no survey list entries */ if (!ret) { wpa_printf(MSG_INFO, "ACS: Channel %d has insufficient survey data", chan->chan); } return ret; } static int acs_surveys_are_sufficient_mode(struct hostapd_hw_modes *mode) { int i; struct hostapd_channel_data *chan; for (i = 0; i < mode->num_channels; i++) { chan = &mode->channels[i]; if (!(chan->flag & HOSTAPD_CHAN_DISABLED) && acs_survey_list_is_sufficient(chan)) return 1; } return 0; } static int acs_surveys_are_sufficient(struct hostapd_iface *iface) { int i; struct hostapd_hw_modes *mode; for (i = 0; i < iface->num_hw_features; i++) { mode = &iface->hw_features[i]; if (!hostapd_hw_skip_mode(iface, mode) && acs_surveys_are_sufficient_mode(mode)) return 1; } return 0; } static int acs_usable_chan(struct hostapd_channel_data *chan) { return !dl_list_empty(&chan->survey_list) && !(chan->flag & HOSTAPD_CHAN_DISABLED) && acs_survey_list_is_sufficient(chan); } static int is_in_chanlist(struct hostapd_iface *iface, struct hostapd_channel_data *chan) { if (!iface->conf->acs_ch_list.num) return 1; return freq_range_list_includes(&iface->conf->acs_ch_list, chan->chan); } static int is_in_freqlist(struct hostapd_iface *iface, struct hostapd_channel_data *chan) { if (!iface->conf->acs_freq_list.num) return 1; return freq_range_list_includes(&iface->conf->acs_freq_list, chan->freq); } static void acs_survey_mode_interference_factor( struct hostapd_iface *iface, struct hostapd_hw_modes *mode) { int i; struct hostapd_channel_data *chan; for (i = 0; i < mode->num_channels; i++) { chan = &mode->channels[i]; if (!acs_usable_chan(chan)) continue; if ((chan->flag & HOSTAPD_CHAN_RADAR) && iface->conf->acs_exclude_dfs) continue; if (!is_in_chanlist(iface, chan)) continue; if (!is_in_freqlist(iface, chan)) continue; if (chan->max_tx_power < iface->conf->min_tx_power) continue; if ((chan->flag & HOSTAPD_CHAN_INDOOR_ONLY) && iface->conf->country[2] == 0x4f) continue; wpa_printf(MSG_DEBUG, "ACS: Survey analysis for channel %d (%d MHz)", chan->chan, chan->freq); acs_survey_chan_interference_factor(iface, chan); wpa_printf(MSG_DEBUG, "ACS: * interference factor average: %Lg", chan->interference_factor); } } static void acs_survey_all_chans_interference_factor( struct hostapd_iface *iface) { int i; struct hostapd_hw_modes *mode; for (i = 0; i < iface->num_hw_features; i++) { mode = &iface->hw_features[i]; if (!hostapd_hw_skip_mode(iface, mode)) acs_survey_mode_interference_factor(iface, mode); } } static struct hostapd_channel_data * acs_find_chan_mode(struct hostapd_hw_modes *mode, int freq) { struct hostapd_channel_data *chan; int i; for (i = 0; i < mode->num_channels; i++) { chan = &mode->channels[i]; if (chan->flag & HOSTAPD_CHAN_DISABLED) continue; if (chan->freq == freq) return chan; } return NULL; } static enum hostapd_hw_mode acs_find_mode(struct hostapd_iface *iface, int freq) { int i; struct hostapd_hw_modes *mode; struct hostapd_channel_data *chan; for (i = 0; i < iface->num_hw_features; i++) { mode = &iface->hw_features[i]; if (!hostapd_hw_skip_mode(iface, mode)) { chan = acs_find_chan_mode(mode, freq); if (chan) return mode->mode; } } return HOSTAPD_MODE_IEEE80211ANY; } static struct hostapd_channel_data * acs_find_chan(struct hostapd_iface *iface, int freq) { int i; struct hostapd_hw_modes *mode; struct hostapd_channel_data *chan; for (i = 0; i < iface->num_hw_features; i++) { mode = &iface->hw_features[i]; if (!hostapd_hw_skip_mode(iface, mode)) { chan = acs_find_chan_mode(mode, freq); if (chan) return chan; } } return NULL; } static int is_24ghz_mode(enum hostapd_hw_mode mode) { return mode == HOSTAPD_MODE_IEEE80211B || mode == HOSTAPD_MODE_IEEE80211G; } static int is_common_24ghz_chan(int chan) { return chan == 1 || chan == 6 || chan == 11; } #ifndef ACS_ADJ_WEIGHT #define ACS_ADJ_WEIGHT 0.85 #endif /* ACS_ADJ_WEIGHT */ #ifndef ACS_NEXT_ADJ_WEIGHT #define ACS_NEXT_ADJ_WEIGHT 0.55 #endif /* ACS_NEXT_ADJ_WEIGHT */ #ifndef ACS_24GHZ_PREFER_1_6_11 /* * Select commonly used channels 1, 6, 11 by default even if a neighboring * channel has a smaller interference factor as long as it is not better by more * than this multiplier. */ #define ACS_24GHZ_PREFER_1_6_11 0.8 #endif /* ACS_24GHZ_PREFER_1_6_11 */ #ifdef CONFIG_IEEE80211BE static void acs_update_puncturing_bitmap(struct hostapd_iface *iface, struct hostapd_hw_modes *mode, u32 bw, int n_chans, struct hostapd_channel_data *chan, long double factor, int index_primary) { struct hostapd_config *conf = iface->conf; struct hostapd_channel_data *adj_chan = NULL, *first_chan = chan; int i; long double threshold; /* * If threshold is 0 or user configured puncturing pattern is * available then don't add additional puncturing. */ if (!conf->punct_acs_threshold || conf->punct_bitmap) return; if (is_24ghz_mode(mode->mode) || bw < 80) return; threshold = factor * conf->punct_acs_threshold / 100; for (i = 0; i < n_chans; i++) { int adj_freq; if (i == index_primary) continue; /* Cannot puncture primary channel */ if (i > index_primary) adj_freq = chan->freq + (i - index_primary) * 20; else adj_freq = chan->freq - (index_primary - i) * 20; adj_chan = acs_find_chan(iface, adj_freq); if (!adj_chan) { chan->punct_bitmap = 0; return; } if (i == 0) first_chan = adj_chan; if (adj_chan->interference_factor > threshold) chan->punct_bitmap |= BIT(i); } if (!is_punct_bitmap_valid(bw, (chan->freq - first_chan->freq) / 20, chan->punct_bitmap)) chan->punct_bitmap = 0; } #endif /* CONFIG_IEEE80211BE */ static bool acs_usable_bw320_chan(struct hostapd_iface *iface, struct hostapd_channel_data *chan, int *bw320_offset) { const char *bw320_str[] = { "320 MHz", "320 MHz-1", "320 MHz-2" }; int conf_bw320_offset = hostapd_get_bw320_offset(iface->conf); *bw320_offset = 0; switch (conf_bw320_offset) { case 1: if (acs_usable_bw_chan(chan, ACS_BW320_1)) *bw320_offset = 1; break; case 2: if (acs_usable_bw_chan(chan, ACS_BW320_2)) *bw320_offset = 2; break; case 0: default: conf_bw320_offset = 0; if (acs_usable_bw_chan(chan, ACS_BW320_1)) *bw320_offset = 1; else if (acs_usable_bw_chan(chan, ACS_BW320_2)) *bw320_offset = 2; break; } if (!*bw320_offset) wpa_printf(MSG_DEBUG, "ACS: Channel %d: not allowed as primary channel for %s bandwidth", chan->chan, bw320_str[conf_bw320_offset]); return *bw320_offset != 0; } static void acs_find_ideal_chan_mode(struct hostapd_iface *iface, struct hostapd_hw_modes *mode, int n_chans, u32 bw, struct hostapd_channel_data **rand_chan, struct hostapd_channel_data **ideal_chan, long double *ideal_factor) { struct hostapd_channel_data *chan, *adj_chan = NULL, *best; long double factor; int i, j; int bw320_offset = 0, ideal_bw320_offset = 0; unsigned int k; int secondary_channel = 1, freq_offset; #ifdef CONFIG_IEEE80211BE int index_primary = 0; #endif /* CONFIG_IEEE80211BE */ if (is_24ghz_mode(mode->mode)) secondary_channel = iface->conf->secondary_channel; for (i = 0; i < mode->num_channels; i++) { double total_weight = 0; struct acs_bias *bias, tmp_bias; chan = &mode->channels[i]; /* Since in the current ACS implementation the first channel is * always a primary channel, skip channels not available as * primary until more sophisticated channel selection is * implemented. * * If this implementation is changed to allow any channel in * the bandwidth to be the primary one, the last parameter to * acs_update_puncturing_bitmap() should be changed to the index * of the primary channel */ if (!chan_pri_allowed(chan)) continue; if ((chan->flag & HOSTAPD_CHAN_RADAR) && iface->conf->acs_exclude_dfs) continue; if (!is_in_chanlist(iface, chan)) continue; if (!is_in_freqlist(iface, chan)) continue; if (chan->max_tx_power < iface->conf->min_tx_power) continue; if ((chan->flag & HOSTAPD_CHAN_INDOOR_ONLY) && iface->conf->country[2] == 0x4f) continue; if (!chan_bw_allowed(chan, bw, secondary_channel != -1, 1)) { wpa_printf(MSG_DEBUG, "ACS: Channel %d: BW %u is not supported", chan->chan, bw); continue; } /* HT40 on 5 GHz has a limited set of primary channels as per * 11n Annex J */ if (mode->mode == HOSTAPD_MODE_IEEE80211A && ((iface->conf->ieee80211n && iface->conf->secondary_channel) || is_6ghz_freq(chan->freq)) && !acs_usable_bw_chan(chan, ACS_BW40)) { wpa_printf(MSG_DEBUG, "ACS: Channel %d: not allowed as primary channel for 40 MHz bandwidth", chan->chan); continue; } if (mode->mode == HOSTAPD_MODE_IEEE80211A && (iface->conf->ieee80211ac || iface->conf->ieee80211ax || iface->conf->ieee80211be)) { if (hostapd_get_oper_chwidth(iface->conf) == CONF_OPER_CHWIDTH_80MHZ && !acs_usable_bw_chan(chan, ACS_BW80)) { wpa_printf(MSG_DEBUG, "ACS: Channel %d: not allowed as primary channel for 80 MHz bandwidth", chan->chan); continue; } if (hostapd_get_oper_chwidth(iface->conf) == CONF_OPER_CHWIDTH_160MHZ && !acs_usable_bw_chan(chan, ACS_BW160)) { wpa_printf(MSG_DEBUG, "ACS: Channel %d: not allowed as primary channel for 160 MHz bandwidth", chan->chan); continue; } } if (mode->mode == HOSTAPD_MODE_IEEE80211A && iface->conf->ieee80211be) { if (hostapd_get_oper_chwidth(iface->conf) == CONF_OPER_CHWIDTH_320MHZ && !acs_usable_bw320_chan(iface, chan, &bw320_offset)) continue; } factor = 0; best = NULL; if (acs_usable_chan(chan)) { factor = chan->interference_factor; total_weight = 1; best = chan; } for (j = 1; j < n_chans; j++) { adj_chan = acs_find_chan(iface, chan->freq + j * secondary_channel * 20); if (!adj_chan) break; if (!chan_bw_allowed(adj_chan, bw, 1, 0)) { wpa_printf(MSG_DEBUG, "ACS: PRI Channel %d: secondary channel %d BW %u is not supported", chan->chan, adj_chan->chan, bw); break; } if (!acs_usable_chan(adj_chan)) continue; factor += adj_chan->interference_factor; total_weight += 1; /* find the best channel in this segment */ if (!best || adj_chan->interference_factor < best->interference_factor) best = adj_chan; } if (j != n_chans) { wpa_printf(MSG_DEBUG, "ACS: Channel %d: not enough bandwidth", chan->chan); continue; } /* If the AP is in the 5 GHz or 6 GHz band, lets prefer a less * crowded primary channel if one was found in the segment */ if (iface->current_mode && iface->current_mode->mode == HOSTAPD_MODE_IEEE80211A && best && chan != best) { wpa_printf(MSG_DEBUG, "ACS: promoting channel %d over %d (less interference %Lg/%Lg)", best->chan, chan->chan, chan->interference_factor, best->interference_factor); #ifdef CONFIG_IEEE80211BE index_primary = (chan->freq - best->freq) / 20; #endif /* CONFIG_IEEE80211BE */ chan = best; } /* 2.4 GHz has overlapping 20 MHz channels. Include adjacent * channel interference factor. */ if (is_24ghz_mode(mode->mode)) { for (j = 0; j < n_chans; j++) { freq_offset = j * 20 * secondary_channel; adj_chan = acs_find_chan(iface, chan->freq + freq_offset - 5); if (adj_chan && acs_usable_chan(adj_chan)) { factor += ACS_ADJ_WEIGHT * adj_chan->interference_factor; total_weight += ACS_ADJ_WEIGHT; } adj_chan = acs_find_chan(iface, chan->freq + freq_offset - 10); if (adj_chan && acs_usable_chan(adj_chan)) { factor += ACS_NEXT_ADJ_WEIGHT * adj_chan->interference_factor; total_weight += ACS_NEXT_ADJ_WEIGHT; } adj_chan = acs_find_chan(iface, chan->freq + freq_offset + 5); if (adj_chan && acs_usable_chan(adj_chan)) { factor += ACS_ADJ_WEIGHT * adj_chan->interference_factor; total_weight += ACS_ADJ_WEIGHT; } adj_chan = acs_find_chan(iface, chan->freq + freq_offset + 10); if (adj_chan && acs_usable_chan(adj_chan)) { factor += ACS_NEXT_ADJ_WEIGHT * adj_chan->interference_factor; total_weight += ACS_NEXT_ADJ_WEIGHT; } } } if (total_weight == 0) continue; factor /= total_weight; bias = NULL; if (iface->conf->acs_chan_bias) { for (k = 0; k < iface->conf->num_acs_chan_bias; k++) { bias = &iface->conf->acs_chan_bias[k]; if (bias->channel == chan->chan) break; bias = NULL; } } else if (is_24ghz_mode(mode->mode) && is_common_24ghz_chan(chan->chan)) { tmp_bias.channel = chan->chan; tmp_bias.bias = ACS_24GHZ_PREFER_1_6_11; bias = &tmp_bias; } if (bias) { factor *= bias->bias; wpa_printf(MSG_DEBUG, "ACS: * channel %d: total interference = %Lg (%f bias)", chan->chan, factor, bias->bias); } else { wpa_printf(MSG_DEBUG, "ACS: * channel %d: total interference = %Lg", chan->chan, factor); } if (acs_usable_chan(chan) && (!*ideal_chan || factor < *ideal_factor)) { /* Reset puncturing bitmap for the previous ideal * channel */ if (*ideal_chan) (*ideal_chan)->punct_bitmap = 0; *ideal_factor = factor; *ideal_chan = chan; ideal_bw320_offset = bw320_offset; #ifdef CONFIG_IEEE80211BE if (iface->conf->ieee80211be) acs_update_puncturing_bitmap(iface, mode, bw, n_chans, chan, factor, index_primary); #endif /* CONFIG_IEEE80211BE */ } /* This channel would at least be usable */ if (!(*rand_chan)) { *rand_chan = chan; ideal_bw320_offset = bw320_offset; } } hostapd_set_and_check_bw320_offset(iface->conf, ideal_bw320_offset); } /* * At this point it's assumed chan->interference_factor has been computed. * This function should be reusable regardless of interference computation * option (survey, BSS, spectral, ...). chan->interference factor must be * summable (i.e., must be always greater than zero). */ static struct hostapd_channel_data * acs_find_ideal_chan(struct hostapd_iface *iface) { struct hostapd_channel_data *ideal_chan = NULL, *rand_chan = NULL; long double ideal_factor = 0; int i; int n_chans = 1; u32 bw; struct hostapd_hw_modes *mode; if (is_6ghz_op_class(iface->conf->op_class)) { bw = op_class_to_bandwidth(iface->conf->op_class); n_chans = bw / 20; goto bw_selected; } if (iface->conf->ieee80211n && iface->conf->secondary_channel) n_chans = 2; if (iface->conf->ieee80211ac || iface->conf->ieee80211ax || iface->conf->ieee80211be) { switch (hostapd_get_oper_chwidth(iface->conf)) { case CONF_OPER_CHWIDTH_80MHZ: n_chans = 4; break; case CONF_OPER_CHWIDTH_160MHZ: n_chans = 8; break; case CONF_OPER_CHWIDTH_320MHZ: n_chans = 16; break; default: break; } } bw = num_chan_to_bw(n_chans); bw_selected: /* TODO: VHT/HE80+80. Update acs_adjust_center_freq() too. */ wpa_printf(MSG_DEBUG, "ACS: Survey analysis for selected bandwidth %d MHz", bw); for (i = 0; i < iface->num_hw_features; i++) { mode = &iface->hw_features[i]; if (!hostapd_hw_skip_mode(iface, mode)) acs_find_ideal_chan_mode(iface, mode, n_chans, bw, &rand_chan, &ideal_chan, &ideal_factor); } if (ideal_chan) { wpa_printf(MSG_DEBUG, "ACS: Ideal channel is %d (%d MHz) with total interference factor of %Lg", ideal_chan->chan, ideal_chan->freq, ideal_factor); #ifdef CONFIG_IEEE80211BE if (iface->conf->punct_acs_threshold) wpa_printf(MSG_DEBUG, "ACS: RU puncturing bitmap 0x%x", ideal_chan->punct_bitmap); #endif /* CONFIG_IEEE80211BE */ return ideal_chan; } return rand_chan; } static void acs_adjust_secondary(struct hostapd_iface *iface) { unsigned int i; /* When working with bandwidth over 20 MHz on the 5 GHz or 6 GHz band, * ACS can return a secondary channel which is not the first channel of * the segment and we need to adjust. */ if (!iface->conf->secondary_channel || acs_find_mode(iface, iface->freq) != HOSTAPD_MODE_IEEE80211A) return; wpa_printf(MSG_DEBUG, "ACS: Adjusting HT/VHT/HE/EHT secondary frequency"); for (i = 0; bw_desc[ACS_BW40][i].first != -1; i++) { if (iface->freq == bw_desc[ACS_BW40][i].first) iface->conf->secondary_channel = 1; else if (iface->freq == bw_desc[ACS_BW40][i].last) iface->conf->secondary_channel = -1; } } static void acs_adjust_center_freq(struct hostapd_iface *iface) { int center; wpa_printf(MSG_DEBUG, "ACS: Adjusting center frequency"); switch (hostapd_get_oper_chwidth(iface->conf)) { case CONF_OPER_CHWIDTH_USE_HT: if (iface->conf->secondary_channel && iface->freq >= 2400 && iface->freq < 2500) center = iface->conf->channel + 2 * iface->conf->secondary_channel; else if (iface->conf->secondary_channel) center = acs_get_bw_center_chan(iface->freq, ACS_BW40); else center = iface->conf->channel; break; case CONF_OPER_CHWIDTH_80MHZ: center = acs_get_bw_center_chan(iface->freq, ACS_BW80); break; case CONF_OPER_CHWIDTH_160MHZ: center = acs_get_bw_center_chan(iface->freq, ACS_BW160); break; case CONF_OPER_CHWIDTH_320MHZ: switch (hostapd_get_bw320_offset(iface->conf)) { case 1: center = acs_get_bw_center_chan(iface->freq, ACS_BW320_1); break; case 2: center = acs_get_bw_center_chan(iface->freq, ACS_BW320_2); break; default: wpa_printf(MSG_INFO, "ACS: BW320 offset is not selected"); return; } break; default: /* TODO: How can this be calculated? Adjust * acs_find_ideal_chan() */ wpa_printf(MSG_INFO, "ACS: Only VHT20/40/80/160/320 is supported now"); return; } hostapd_set_oper_centr_freq_seg0_idx(iface->conf, center); } static int acs_study_survey_based(struct hostapd_iface *iface) { wpa_printf(MSG_DEBUG, "ACS: Trying survey-based ACS"); if (!iface->chans_surveyed) { wpa_printf(MSG_ERROR, "ACS: Unable to collect survey data"); return -1; } if (!acs_surveys_are_sufficient(iface)) { wpa_printf(MSG_ERROR, "ACS: Surveys have insufficient data"); return -1; } acs_survey_all_chans_interference_factor(iface); return 0; } static int acs_study_options(struct hostapd_iface *iface) { if (acs_study_survey_based(iface) == 0) return 0; /* TODO: If no surveys are available/sufficient this is a good * place to fallback to BSS-based ACS */ return -1; } static void acs_study(struct hostapd_iface *iface) { struct hostapd_channel_data *ideal_chan; int err; err = acs_study_options(iface); if (err < 0) { wpa_printf(MSG_ERROR, "ACS: All study options have failed"); goto fail; } ideal_chan = acs_find_ideal_chan(iface); if (!ideal_chan) { wpa_printf(MSG_ERROR, "ACS: Failed to compute ideal channel"); err = -1; goto fail; } iface->conf->channel = ideal_chan->chan; iface->freq = ideal_chan->freq; #ifdef CONFIG_IEEE80211BE iface->conf->punct_bitmap = ideal_chan->punct_bitmap; #endif /* CONFIG_IEEE80211BE */ if (iface->conf->ieee80211ac || iface->conf->ieee80211ax || iface->conf->ieee80211be) { acs_adjust_secondary(iface); acs_adjust_center_freq(iface); } err = hostapd_select_hw_mode(iface); if (err) { wpa_printf(MSG_ERROR, "ACS: Could not (err: %d) select hw_mode for freq=%d channel=%d", err, iface->freq, iface->conf->channel); err = -1; goto fail; } err = 0; fail: /* * hostapd_setup_interface_complete() will return -1 on failure, * 0 on success and 0 is HOSTAPD_CHAN_VALID :) */ if (hostapd_acs_completed(iface, err) == HOSTAPD_CHAN_VALID) { acs_cleanup(iface); return; } /* This can possibly happen if channel parameters (secondary * channel, center frequencies) are misconfigured */ wpa_printf(MSG_ERROR, "ACS: Possibly channel configuration is invalid, please report this along with your config file."); acs_fail(iface); } static void acs_scan_complete(struct hostapd_iface *iface) { int err; iface->scan_cb = NULL; iface->acs_num_retries = 0; wpa_printf(MSG_DEBUG, "ACS: Using survey based algorithm (acs_num_scans=%d)", iface->conf->acs_num_scans); err = hostapd_drv_get_survey(iface->bss[0], 0); if (err) { wpa_printf(MSG_ERROR, "ACS: Failed to get survey data"); goto fail; } if (++iface->acs_num_completed_scans < iface->conf->acs_num_scans) { err = acs_request_scan(iface); if (err && err != -EBUSY) { wpa_printf(MSG_ERROR, "ACS: Failed to request scan"); goto fail; } return; } acs_study(iface); return; fail: hostapd_acs_completed(iface, 1); acs_fail(iface); } static int * acs_request_scan_add_freqs(struct hostapd_iface *iface, struct hostapd_hw_modes *mode, int *freq) { struct hostapd_channel_data *chan; int i; for (i = 0; i < mode->num_channels; i++) { chan = &mode->channels[i]; if ((chan->flag & HOSTAPD_CHAN_DISABLED) || ((chan->flag & HOSTAPD_CHAN_RADAR) && iface->conf->acs_exclude_dfs)) continue; if (!is_in_chanlist(iface, chan)) continue; if (!is_in_freqlist(iface, chan)) continue; if (chan->max_tx_power < iface->conf->min_tx_power) continue; if ((chan->flag & HOSTAPD_CHAN_INDOOR_ONLY) && iface->conf->country[2] == 0x4f) continue; *freq++ = chan->freq; } return freq; } static int acs_request_scan(struct hostapd_iface *iface) { struct wpa_driver_scan_params params; int i, *freq, ret; int num_channels; struct hostapd_hw_modes *mode; os_memset(¶ms, 0, sizeof(params)); num_channels = 0; for (i = 0; i < iface->num_hw_features; i++) { mode = &iface->hw_features[i]; if (!hostapd_hw_skip_mode(iface, mode)) num_channels += mode->num_channels; } params.freqs = os_calloc(num_channels + 1, sizeof(params.freqs[0])); if (params.freqs == NULL) return -1; freq = params.freqs; for (i = 0; i < iface->num_hw_features; i++) { mode = &iface->hw_features[i]; if (!hostapd_hw_skip_mode(iface, mode)) freq = acs_request_scan_add_freqs(iface, mode, freq); } *freq = 0; if (params.freqs == freq) { wpa_printf(MSG_ERROR, "ACS: No available channels found"); os_free(params.freqs); return -1; } if (!iface->acs_num_retries) wpa_printf(MSG_DEBUG, "ACS: Scanning %d / %d", iface->acs_num_completed_scans + 1, iface->conf->acs_num_scans); else wpa_printf(MSG_DEBUG, "ACS: Re-try scanning attempt %d (%d / %d)", iface->acs_num_retries, iface->acs_num_completed_scans + 1, iface->conf->acs_num_scans); ret = hostapd_driver_scan(iface->bss[0], ¶ms); os_free(params.freqs); if (ret == -EBUSY) { iface->acs_num_retries++; if (iface->acs_num_retries >= ACS_SCAN_RETRY_MAX_COUNT) { wpa_printf(MSG_ERROR, "ACS: Failed to request initial scan (all re-attempts failed)"); acs_fail(iface); return -1; } wpa_printf(MSG_INFO, "Failed to request acs scan ret=%d (%s) - try to scan after %d seconds", ret, strerror(-ret), ACS_SCAN_RETRY_INTERVAL); eloop_cancel_timeout(acs_scan_retry, iface, NULL); eloop_register_timeout(ACS_SCAN_RETRY_INTERVAL, 0, acs_scan_retry, iface, NULL); return 0; } if (ret < 0) { wpa_printf(MSG_ERROR, "ACS: Failed to request initial scan"); acs_cleanup(iface); return -1; } iface->scan_cb = acs_scan_complete; return 0; } static void acs_scan_retry(void *eloop_data, void *user_data) { struct hostapd_iface *iface = eloop_data; if (acs_request_scan(iface)) { wpa_printf(MSG_ERROR, "ACS: Failed to request re-try of initial scan"); acs_fail(iface); } } enum hostapd_chan_status acs_init(struct hostapd_iface *iface) { int err; wpa_printf(MSG_INFO, "ACS: Automatic channel selection started, this may take a bit"); if (iface->drv_flags & WPA_DRIVER_FLAGS_ACS_OFFLOAD) { wpa_printf(MSG_INFO, "ACS: Offloading to driver"); err = hostapd_drv_do_acs(iface->bss[0]); if (err) { if (err == 1) return HOSTAPD_CHAN_INVALID_NO_IR; return HOSTAPD_CHAN_INVALID; } return HOSTAPD_CHAN_ACS; } if (!iface->current_mode && iface->conf->hw_mode != HOSTAPD_MODE_IEEE80211ANY) return HOSTAPD_CHAN_INVALID; acs_cleanup(iface); if (acs_request_scan(iface) < 0) return HOSTAPD_CHAN_INVALID; hostapd_set_state(iface, HAPD_IFACE_ACS); wpa_msg(iface->bss[0]->msg_ctx, MSG_INFO, ACS_EVENT_STARTED); return HOSTAPD_CHAN_ACS; }