/* * 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 "common/ieee802_11_defs.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 */ static int acs_request_scan(struct hostapd_iface *iface); static int acs_survey_is_sufficient(struct freq_survey *survey); 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(struct hostapd_iface *iface) { int i; struct hostapd_channel_data *chan; for (i = 0; i < iface->current_mode->num_channels; i++) { chan = &iface->current_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; } iface->chans_surveyed = 0; iface->acs_num_completed_scans = 0; } 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 { /* This shouldn't really happen as survey data is checked in * acs_sanity_check() */ 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) + (busy / total) * 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)) return; if (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) return; chan->interference_factor /= count; } static int acs_usable_ht40_chan(struct hostapd_channel_data *chan) { const int allowed[] = { 36, 44, 52, 60, 100, 108, 116, 124, 132, 149, 157, 184, 192 }; unsigned int i; for (i = 0; i < ARRAY_SIZE(allowed); i++) if (chan->chan == allowed[i]) return 1; return 0; } static int acs_usable_vht80_chan(struct hostapd_channel_data *chan) { const int allowed[] = { 36, 52, 100, 116, 132, 149 }; unsigned int i; for (i = 0; i < ARRAY_SIZE(allowed); i++) if (chan->chan == allowed[i]) return 1; return 0; } static int acs_survey_is_sufficient(struct freq_survey *survey) { if (!(survey->filled & SURVEY_HAS_NF)) { wpa_printf(MSG_INFO, "ACS: Survey is missing noise floor"); return 0; } if (!(survey->filled & SURVEY_HAS_CHAN_TIME)) { wpa_printf(MSG_INFO, "ACS: Survey is missing channel time"); return 0; } if (!(survey->filled & SURVEY_HAS_CHAN_TIME_BUSY) && !(survey->filled & SURVEY_HAS_CHAN_TIME_RX)) { wpa_printf(MSG_INFO, "ACS: Survey is missing RX and busy time (at least one is required)"); 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 = 1; /* 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(struct hostapd_iface *iface) { int i; struct hostapd_channel_data *chan; int valid = 0; for (i = 0; i < iface->current_mode->num_channels; i++) { chan = &iface->current_mode->channels[i]; if (chan->flag & HOSTAPD_CHAN_DISABLED) continue; if (!acs_survey_list_is_sufficient(chan)) continue; valid++; } /* We need at least survey data for one channel */ return !!valid; } static int acs_usable_chan(struct hostapd_channel_data *chan) { if (dl_list_empty(&chan->survey_list)) return 0; if (chan->flag & HOSTAPD_CHAN_DISABLED) return 0; if (!acs_survey_list_is_sufficient(chan)) return 0; return 1; } 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 void acs_survey_all_chans_intereference_factor( struct hostapd_iface *iface) { int i; struct hostapd_channel_data *chan; for (i = 0; i < iface->current_mode->num_channels; i++) { chan = &iface->current_mode->channels[i]; if (!acs_usable_chan(chan)) continue; if (!is_in_chanlist(iface, chan)) 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 struct hostapd_channel_data *acs_find_chan(struct hostapd_iface *iface, int freq) { struct hostapd_channel_data *chan; int i; for (i = 0; i < iface->current_mode->num_channels; i++) { chan = &iface->current_mode->channels[i]; if (chan->flag & HOSTAPD_CHAN_DISABLED) continue; if (chan->freq == freq) 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 */ /* * At this point it's assumed chan->interface_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 *chan, *adj_chan, *ideal_chan = NULL, *rand_chan = NULL; long double factor, ideal_factor = 0; int i, j; int n_chans = 1; unsigned int k; /* TODO: HT40- support */ if (iface->conf->ieee80211n && iface->conf->secondary_channel == -1) { wpa_printf(MSG_ERROR, "ACS: HT40- is not supported yet. Please try HT40+"); return NULL; } if (iface->conf->ieee80211n && iface->conf->secondary_channel) n_chans = 2; if (iface->conf->ieee80211ac && iface->conf->vht_oper_chwidth == 1) n_chans = 4; /* TODO: VHT80+80, VHT160. Update acs_adjust_vht_center_freq() too. */ wpa_printf(MSG_DEBUG, "ACS: Survey analysis for selected bandwidth %d MHz", n_chans == 1 ? 20 : n_chans == 2 ? 40 : n_chans == 4 ? 80 : -1); for (i = 0; i < iface->current_mode->num_channels; i++) { double total_weight; struct acs_bias *bias, tmp_bias; chan = &iface->current_mode->channels[i]; if (chan->flag & HOSTAPD_CHAN_DISABLED) continue; if (!is_in_chanlist(iface, chan)) continue; /* HT40 on 5 GHz has a limited set of primary channels as per * 11n Annex J */ if (iface->current_mode->mode == HOSTAPD_MODE_IEEE80211A && iface->conf->ieee80211n && iface->conf->secondary_channel && !acs_usable_ht40_chan(chan)) { wpa_printf(MSG_DEBUG, "ACS: Channel %d: not allowed as primary channel for HT40", chan->chan); continue; } if (iface->current_mode->mode == HOSTAPD_MODE_IEEE80211A && iface->conf->ieee80211ac && iface->conf->vht_oper_chwidth == 1 && !acs_usable_vht80_chan(chan)) { wpa_printf(MSG_DEBUG, "ACS: Channel %d: not allowed as primary channel for VHT80", chan->chan); continue; } factor = 0; if (acs_usable_chan(chan)) factor = chan->interference_factor; total_weight = 1; for (j = 1; j < n_chans; j++) { adj_chan = acs_find_chan(iface, chan->freq + (j * 20)); if (!adj_chan) break; if (acs_usable_chan(adj_chan)) { factor += adj_chan->interference_factor; total_weight += 1; } } if (j != n_chans) { wpa_printf(MSG_DEBUG, "ACS: Channel %d: not enough bandwidth", chan->chan); continue; } /* 2.4 GHz has overlapping 20 MHz channels. Include adjacent * channel interference factor. */ if (is_24ghz_mode(iface->current_mode->mode)) { for (j = 0; j < n_chans; j++) { adj_chan = acs_find_chan(iface, chan->freq + (j * 20) - 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 + (j * 20) - 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 + (j * 20) + 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 + (j * 20) + 10); if (adj_chan && acs_usable_chan(adj_chan)) { factor += ACS_NEXT_ADJ_WEIGHT * adj_chan->interference_factor; total_weight += ACS_NEXT_ADJ_WEIGHT; } } } 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(iface->current_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)) { ideal_factor = factor; ideal_chan = chan; } /* This channel would at least be usable */ if (!rand_chan) rand_chan = chan; } 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); return ideal_chan; } return rand_chan; } static void acs_adjust_vht_center_freq(struct hostapd_iface *iface) { int offset; wpa_printf(MSG_DEBUG, "ACS: Adjusting VHT center frequency"); switch (iface->conf->vht_oper_chwidth) { case VHT_CHANWIDTH_USE_HT: offset = 2 * iface->conf->secondary_channel; break; case VHT_CHANWIDTH_80MHZ: offset = 6; break; default: /* TODO: How can this be calculated? Adjust * acs_find_ideal_chan() */ wpa_printf(MSG_INFO, "ACS: Only VHT20/40/80 is supported now"); return; } iface->conf->vht_oper_centr_freq_seg0_idx = iface->conf->channel + offset; } 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_intereference_factor(iface); return 0; } static int acs_study_options(struct hostapd_iface *iface) { int err; err = acs_study_survey_based(iface); if (err == 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; if (iface->conf->ieee80211ac) acs_adjust_vht_center_freq(iface); 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; 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) { 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(struct hostapd_iface *iface) { struct wpa_driver_scan_params params; struct hostapd_channel_data *chan; int i, *freq; os_memset(¶ms, 0, sizeof(params)); params.freqs = os_calloc(iface->current_mode->num_channels + 1, sizeof(params.freqs[0])); if (params.freqs == NULL) return -1; freq = params.freqs; for (i = 0; i < iface->current_mode->num_channels; i++) { chan = &iface->current_mode->channels[i]; if (chan->flag & HOSTAPD_CHAN_DISABLED) continue; *freq++ = chan->freq; } *freq = 0; iface->scan_cb = acs_scan_complete; wpa_printf(MSG_DEBUG, "ACS: Scanning %d / %d", iface->acs_num_completed_scans + 1, iface->conf->acs_num_scans); if (hostapd_driver_scan(iface->bss[0], ¶ms) < 0) { wpa_printf(MSG_ERROR, "ACS: Failed to request initial scan"); acs_cleanup(iface); os_free(params.freqs); return -1; } os_free(params.freqs); return 0; } 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) return HOSTAPD_CHAN_INVALID; return HOSTAPD_CHAN_ACS; } acs_cleanup(iface); err = acs_request_scan(iface); if (err < 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; }