hostapd: Allow ACS to deal with partial survey data

Previously ACS required valid survey data on all available channels.
This can however not be guaranteed. Instead of just failing, fall back
to the subset of channels that have valid ACS data.

Signed-hostap: Helmut Schaa <helmut.schaa@googlemail.com>

src/ap/acs.c

@@ -352,16 +352,6 @@ acs_survey_chan_interference_factor(struct hostapd_iface *iface,
 }
 
 
-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;
-	return 1;
-}
-
-
 static int acs_usable_ht40_chan(struct hostapd_channel_data *chan)
 {
 	const int allowed[] = { 36, 44, 52, 60, 100, 108, 116, 124, 132, 149,
@@ -398,28 +388,54 @@ static int acs_survey_is_sufficient(struct freq_survey *survey)
 }
 
 
+static int acs_survey_list_is_sufficient(struct hostapd_channel_data *chan)
+{
+	struct freq_survey *survey;
+
+	dl_list_for_each(survey, &chan->survey_list, struct freq_survey, list)
+	{
+		if (!acs_survey_is_sufficient(survey)) {
+			wpa_printf(MSG_ERROR, "ACS: Channel %d has insufficient survey data",
+				   chan->chan);
+			return 0;
+		}
+	}
+
+	return 1;
+
+}
+
+
 static int acs_surveys_are_sufficient(struct hostapd_iface *iface)
 {
 	int i;
 	struct hostapd_channel_data *chan;
-	struct freq_survey *survey;
+	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;
 
-		dl_list_for_each(survey, &chan->survey_list,
-				 struct freq_survey, list)
-		{
-			if (!acs_survey_is_sufficient(survey)) {
-				wpa_printf(MSG_ERROR, "ACS: Channel %d has insufficient survey data",
-					   chan->chan);
-				return 0;
-			}
-		}
+		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;
 }