mac80211: do not actively scan DFS channels

DFS channels should not be actively scanned as we can't be sure
if we are allowed or not.

If the current channel is in the DFS band, active scan might be
performed after CSA, but we have no guarantee about other channels,
therefore it is safer to prevent active scanning at all.

Cc: [e-mail]
Signed-off-by: Antonio Quartulli <[e-mail]>
Signed-off-by: Johannes Berg <[e-mail]>

net/mac80211/scan.c

···
 		/* We need to ensure power level is at max for scanning. */
 		ieee80211_hw_config(local, 0);
 
-		if ((req->channels[0]->flags &
-		     IEEE80211_CHAN_NO_IR) ||
+		if ((req->channels[0]->flags & (IEEE80211_CHAN_NO_IR |
+						IEEE80211_CHAN_RADAR)) ||
 		    !req->n_ssids) {
 			next_delay = IEEE80211_PASSIVE_CHANNEL_TIME;
 		} else {
···
 	 * TODO: channel switching also consumes quite some time,
 	 * add that delay as well to get a better estimation
 	 */
-	if (chan->flags & IEEE80211_CHAN_NO_IR)
+	if (chan->flags & (IEEE80211_CHAN_NO_IR | IEEE80211_CHAN_RADAR))
 		return IEEE80211_PASSIVE_CHANNEL_TIME;
 	return IEEE80211_PROBE_DELAY + IEEE80211_CHANNEL_TIME;
 }
···
 	 *
 	 * In any case, it is not necessary for a passive scan.
 	 */
-	if (chan->flags & IEEE80211_CHAN_NO_IR || !scan_req->n_ssids) {
+	if ((chan->flags & (IEEE80211_CHAN_NO_IR | IEEE80211_CHAN_RADAR)) ||
+	    !scan_req->n_ssids) {
 		*next_delay = IEEE80211_PASSIVE_CHANNEL_TIME;
 		local->next_scan_state = SCAN_DECISION;
 		return;