From 920a20927f1537ae2a6ce9c7123ef189e83cd0a0 Mon Sep 17 00:00:00 2001
From: Evelyn Tsai <evelyn.tsai@mediatek.com>
Date: Sat, 11 Nov 2023 11:42:59 +0800
Subject: [PATCH] hostapd: mtk: ACS: Fix 2.4GHz HT40 case and channel switch
 fail

Issue#1. Add 2.4G HT40- support
1. Add 2.4G HT40- support
2. Fix issue: selected best channel is out of channels

Issue#2. Fix chan_switch to usable DFS channel fail due to ACS

Step and issue:
1. Enable ACS in hostapd config;
2. Bootup and then use hostapd_cli cmd switch channel to a DFS channel;
3. Will do ACS again, and no work on channel specified in step 2.

Root cause:
When need do DFS-CAC, hostapd will do intf disable, then set the new
channel into running config settings, and finally enable intf;
In the test case, new DFS channel is set to runnint config settings, but
another param "acs" is still 1 (enable), caused the ACS running when
intf enabled.
---
 src/ap/acs.c     | 142 ++++++++++++++++++++++++++---------------------
 src/ap/hostapd.c |   3 +
 2 files changed, 83 insertions(+), 62 deletions(-)

diff --git a/src/ap/acs.c b/src/ap/acs.c
index 130e135..65573b9 100644
--- a/src/ap/acs.c
+++ b/src/ap/acs.c
@@ -712,10 +712,19 @@ acs_find_ideal_chan_mode(struct hostapd_iface *iface,
 			 struct hostapd_channel_data **ideal_chan,
 			 long double *ideal_factor)
 {
-	struct hostapd_channel_data *chan, *adj_chan = NULL, *best;
+	struct hostapd_channel_data *chan, *adj_chan = NULL, *tmp_chan = NULL, *best;
 	long double factor;
 	int i, j;
 	unsigned int k;
+	int ht40_plus = 1, sec_ch_factor = 1;
+
+	if (is_24ghz_mode(mode->mode)) {
+		ht40_plus = (iface->conf->secondary_channel == -1) ? 0 : 1;
+		sec_ch_factor = (iface->conf->secondary_channel == -1) ? -1 : 1;
+	}
+
+	wpa_printf(MSG_INFO, "%s:%d, bw(%u), n_chans(%d), num_channels(%d), sec_ch(%d)",
+		__func__, __LINE__, bw, n_chans, mode->num_channels, iface->conf->secondary_channel);
 
 	for (i = 0; i < mode->num_channels; i++) {
 		double total_weight;
@@ -723,6 +732,9 @@ acs_find_ideal_chan_mode(struct hostapd_iface *iface,
 		bool update_best = true;
 
 		best = chan = &mode->channels[i];
+		wpa_printf(MSG_INFO,
+			   "ACS: Channel[%d] %d: interference_factor %Lg",
+			   i, chan->chan, chan->interference_factor);
 
 		/* Since in the current ACS implementation the first channel is
 		 * always a primary channel, skip channels not available as
@@ -747,7 +759,7 @@ acs_find_ideal_chan_mode(struct hostapd_iface *iface,
 		if (chan->flag & HOSTAPD_CHAN_INDOOR_ONLY && iface->conf->country[2] == 0x4f)
 			continue;
 
-		if (!chan_bw_allowed(chan, bw, 1, 1)) {
+		if (!chan_bw_allowed(chan, bw, ht40_plus, 1)) {
 			wpa_printf(MSG_DEBUG,
 				   "ACS: Channel %d: BW %u is not supported",
 				   chan->chan, bw);
@@ -789,60 +801,73 @@ acs_find_ideal_chan_mode(struct hostapd_iface *iface,
 		}
 
 		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;
+		total_weight = 0;
 
-			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)) {
-				factor += adj_chan->interference_factor;
+		if (!is_24ghz_mode(mode->mode)) {
+			/* 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 (acs_usable_chan(chan)) {
+				factor += chan->interference_factor;
 				total_weight += 1;
-			} else {
-				update_best = false;
 			}
 
-			/* find the best channel in this segment */
-			if (update_best &&
-			    adj_chan->interference_factor <
-			    best->interference_factor)
-				best = adj_chan;
-		}
+			for (j = 1; j < n_chans; j++) {
+				adj_chan = acs_find_chan(iface, chan->freq + j * 20);
+				if (!adj_chan)
+					break;
 
-		if (j != n_chans) {
-			wpa_printf(MSG_DEBUG, "ACS: Channel %d: not enough bandwidth",
-				   chan->chan);
-			continue;
-		}
+				if (!is_in_chanlist(iface, adj_chan) || !is_in_freqlist(iface, adj_chan))
+					break;
 
-		/* 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->mode == HOSTAPD_MODE_IEEE80211A &&
-		    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);
-			chan = best;
-		}
+				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;
+				}
 
-		/* 2.4 GHz has overlapping 20 MHz channels. Include adjacent
-		 * channel interference factor. */
-		if (is_24ghz_mode(mode->mode)) {
+				update_best = true;
+				if (acs_usable_chan(adj_chan)) {
+					factor += adj_chan->interference_factor;
+					total_weight += 1;
+				} else {
+					update_best = false;
+				}
+
+				/* find the best channel in this segment */
+				if (update_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 (chan != best) {
+				wpa_printf(MSG_INFO,
+					   "ACS: promoting channel %d over %d (less interference %Lg/%Lg)",
+					   best->chan, chan->chan,
+					   chan->interference_factor,
+					   best->interference_factor);
+				chan = best;
+			}
+		} else {
 			for (j = 0; j < n_chans; j++) {
+				/* Will set primary_channel / secondary_channel(40M case) weight to 1 */
+				tmp_chan = acs_find_chan(iface, chan->freq +
+							 (j * sec_ch_factor * 20));
+				if (tmp_chan && acs_usable_chan(tmp_chan)) {
+					factor += tmp_chan->interference_factor;
+					total_weight += 1;
+				}
+
+				/* 2.4 GHz has overlapping 20 MHz channels. Include adjacent channel
+				interference factor, separately for primary/secondary channel. */
 				adj_chan = acs_find_chan(iface, chan->freq +
-							 (j * 20) - 5);
+							  (j * sec_ch_factor * 20) - 5);
 				if (adj_chan && acs_usable_chan(adj_chan)) {
 					factor += ACS_ADJ_WEIGHT *
 						adj_chan->interference_factor;
@@ -850,7 +875,7 @@ acs_find_ideal_chan_mode(struct hostapd_iface *iface,
 				}
 
 				adj_chan = acs_find_chan(iface, chan->freq +
-							 (j * 20) - 10);
+							  (j * sec_ch_factor * 20) - 10);
 				if (adj_chan && acs_usable_chan(adj_chan)) {
 					factor += ACS_NEXT_ADJ_WEIGHT *
 						adj_chan->interference_factor;
@@ -858,7 +883,7 @@ acs_find_ideal_chan_mode(struct hostapd_iface *iface,
 				}
 
 				adj_chan = acs_find_chan(iface, chan->freq +
-							 (j * 20) + 5);
+							 (j * sec_ch_factor * 20) + 5);
 				if (adj_chan && acs_usable_chan(adj_chan)) {
 					factor += ACS_ADJ_WEIGHT *
 						adj_chan->interference_factor;
@@ -866,7 +891,7 @@ acs_find_ideal_chan_mode(struct hostapd_iface *iface,
 				}
 
 				adj_chan = acs_find_chan(iface, chan->freq +
-							 (j * 20) + 10);
+							 (j * sec_ch_factor * 20) + 10);
 				if (adj_chan && acs_usable_chan(adj_chan)) {
 					factor += ACS_NEXT_ADJ_WEIGHT *
 						adj_chan->interference_factor;
@@ -875,7 +900,8 @@ acs_find_ideal_chan_mode(struct hostapd_iface *iface,
 			}
 		}
 
-		factor /= total_weight;
+		if (total_weight)
+			factor /= total_weight;
 
 		bias = NULL;
 		if (iface->conf->acs_chan_bias) {
@@ -894,11 +920,11 @@ acs_find_ideal_chan_mode(struct hostapd_iface *iface,
 
 		if (bias) {
 			factor *= bias->bias;
-			wpa_printf(MSG_DEBUG,
+			wpa_printf(MSG_INFO,
 				   "ACS:  * channel %d: total interference = %Lg (%f bias)",
 				   chan->chan, factor, bias->bias);
 		} else {
-			wpa_printf(MSG_DEBUG,
+			wpa_printf(MSG_INFO,
 				   "ACS:  * channel %d: total interference = %Lg",
 				   chan->chan, factor);
 		}
@@ -939,14 +965,6 @@ acs_find_ideal_chan(struct hostapd_iface *iface)
 		goto bw_selected;
 	}
 
-	/* 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;
@@ -981,7 +999,7 @@ bw_selected:
 	}
 
 	if (ideal_chan) {
-		wpa_printf(MSG_DEBUG, "ACS: Ideal channel is %d (%d MHz) with total interference factor of %Lg",
+		wpa_printf(MSG_INFO, "ACS: Ideal channel is %d (%d MHz) with total interference factor of %Lg",
 			   ideal_chan->chan, ideal_chan->freq, ideal_factor);
 		return ideal_chan;
 	}
diff --git a/src/ap/hostapd.c b/src/ap/hostapd.c
index f2eb638..250c168 100644
--- a/src/ap/hostapd.c
+++ b/src/ap/hostapd.c
@@ -3895,6 +3895,9 @@ hostapd_switch_channel_fallback(struct hostapd_iface *iface,
 
 	iface->freq = freq_params->freq;
 	iface->conf->channel = freq_params->channel;
+	if (iface->conf->channel != 0) /* If channel not zero, will disable acs. */
+		iface->conf->acs = 0;
+
 	iface->conf->secondary_channel = freq_params->sec_channel_offset;
 	hostapd_set_oper_centr_freq_seg0_idx(iface->conf, seg0_idx);
 	hostapd_set_oper_centr_freq_seg1_idx(iface->conf, seg1_idx);
-- 
2.18.0