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hostap/src/ap/acs.c
Jouni Malinen 0d7eb4344f ACS: Accept channel if any (rather than all) survey results are valid 
Previously, a channel with even a single scan/survey result missing
information was skipped in ACS. This may not be desirable in cases when
multiple scan iterations are used (which is the case by default in
hostapd). Instead, use all channels that provided at least one complete
set of results. Calculate the average interference factor as an average
of the iterations that did provide complete values.

This seems to help with some cases, e.g., when ath9k may not be able to
report the noise floor for all channels from the first scan iteration
immediately after the driver has been loaded, but then returns it for
all other scan iterations.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
2015-02-06 21:26:32 +02:00

949 lines
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/*
* 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 <math.h>
#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)
{
int *entry;
if (!iface->conf->chanlist)
return 1;
for (entry = iface->conf->chanlist; *entry != -1; entry++) {
if (*entry == chan->chan)
return 1;
}
return 0;
}
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(&params, 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], &params) < 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;
}
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