/*
* The function assumes HT40+ operation.
* Make sure to adjust the following variables after calling this:
* - hapd->secondary_channel
* - hapd->vht_oper_centr_freq_seg0_idx
* - hapd->vht_oper_centr_freq_seg1_idx
*/
static int dfs_find_channel(struct hostapd_iface *iface,
struct hostapd_channel_data **ret_chan,
int idx, int skip_radar)
{
struct hostapd_hw_modes *mode;
struct hostapd_channel_data *chan;
int i, channel_idx = 0, n_chans, n_chans1;
mode = iface->current_mode;
n_chans = dfs_get_used_n_chans(iface, &n_chans1);
wpa_printf(MSG_DEBUG, "DFS new chan checking %d channels", n_chans);
for (i = 0; i < mode->num_channels; i++) {
chan = &mode->channels[i];
/* Skip HT40/VHT incompatible channels */
if (iface->conf->ieee80211n &&
iface->conf->secondary_channel &&
!dfs_is_chan_allowed(chan, n_chans))
continue;
/* Skip incompatible chandefs */
if (!dfs_chan_range_available(mode, i, n_chans, skip_radar))
continue;
if (!is_in_chanlist(iface, chan))
continue;
if (ret_chan && idx == channel_idx) {
wpa_printf(MSG_DEBUG, "Selected ch. #%d", chan->chan);
*ret_chan = chan;
return idx;
}
wpa_printf(MSG_DEBUG, "Adding channel: %d", chan->chan);
channel_idx++;
}
return channel_idx;
}
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);
}
}
/*
* 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;
}