From 75ce63e063cc12f8465c14c10f07ed2d28ad5fe7 Mon Sep 17 00:00:00 2001
From: Dmitry Lebed <dlebed@quantenna.com>
Date: Thu, 1 Mar 2018 14:49:28 +0300
Subject: [PATCH] ACS: Add supported channel bandwidth checking

While doing automatic channel selection we need to take into account
supported bandwidth for each channel provided via nl80211. Without this
modification hostapd might select an unsupported channel which would
fail during AP startup.

Signed-off-by: Dmitry Lebed <dlebed@quantenna.com>
---
 src/ap/acs.c | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/src/ap/acs.c b/src/ap/acs.c
index 129ee46ec..3b4507575 100644
--- a/src/ap/acs.c
+++ b/src/ap/acs.c
@@ -13,6 +13,7 @@
 #include "utils/common.h"
 #include "utils/list.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"
@@ -578,6 +579,7 @@ acs_find_ideal_chan(struct hostapd_iface *iface)
 	long double factor, ideal_factor = 0;
 	int i, j;
 	int n_chans = 1;
+	u32 bw;
 	unsigned int k;
 
 	/* TODO: HT40- support */
@@ -603,10 +605,12 @@ acs_find_ideal_chan(struct hostapd_iface *iface)
 		}
 	}
 
+	bw = num_chan_to_bw(n_chans);
+
 	/* TODO: VHT80+80. Update acs_adjust_vht_center_freq() too. */
 
-	wpa_printf(MSG_DEBUG, "ACS: Survey analysis for selected bandwidth %d MHz",
-		   n_chans * 20);
+	wpa_printf(MSG_DEBUG,
+		   "ACS: Survey analysis for selected bandwidth %d MHz", bw);
 
 	for (i = 0; i < iface->current_mode->num_channels; i++) {
 		double total_weight;
@@ -614,12 +618,23 @@ acs_find_ideal_chan(struct hostapd_iface *iface)
 
 		chan = &iface->current_mode->channels[i];
 
-		if (chan->flag & HOSTAPD_CHAN_DISABLED)
+		/* 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 (!chan_pri_allowed(chan))
 			continue;
 
 		if (!is_in_chanlist(iface, chan))
 			continue;
 
+		if (!chan_bw_allowed(chan, bw, 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 (iface->current_mode->mode == HOSTAPD_MODE_IEEE80211A &&
@@ -662,6 +677,13 @@ acs_find_ideal_chan(struct hostapd_iface *iface)
 			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)) {
 				factor += adj_chan->interference_factor;
 				total_weight += 1;