Make it clearer that ap_scan=2 mode should not be used with nl80211

Add more details into configuration comments and a runtime info message
if ap_scan=2 is used with the nl80211 driver interface.

Signed-off-by: Jouni Malinen <j@w1.fi>

wpa_supplicant/config.h

@@ -406,6 +406,11 @@ struct wpa_config {
 	 * one by one until the driver reports successful association; each
 	 * network block should have explicit security policy (i.e., only one
 	 * option in the lists) for key_mgmt, pairwise, group, proto variables.
+	 *
+	 * Note: ap_scan=2 should not be used with the nl80211 driver interface
+	 * (the current Linux interface). ap_scan=1 is optimized work working
+	 * with nl80211. For finding networks using hidden SSID, scan_ssid=1 in
+	 * the network block can be used with nl80211.
 	 */
 	int ap_scan;
 

wpa_supplicant/config_ssid.h

@@ -225,7 +225,9 @@ struct wpa_ssid {
 	 *
 	 * scan_ssid can be used to scan for APs using hidden SSIDs.
 	 * Note: Many drivers do not support this. ap_mode=2 can be used with
-	 * such drivers to use hidden SSIDs.
+	 * such drivers to use hidden SSIDs. Note2: Most nl80211-based drivers
+	 * do support scan_ssid=1 and that should be used with them instead of
+	 * ap_scan=2.
 	 */
 	int scan_ssid;
 

wpa_supplicant/wpa_supplicant.c

@@ -2790,6 +2790,11 @@ int wpa_supplicant_set_ap_scan(struct wpa_supplicant *wpa_s, int ap_scan)
 	if (ap_scan < 0 || ap_scan > 2)
 		return -1;
 
+	if (ap_scan == 2 && os_strcmp(wpa_s->driver->name, "nl80211") == 0) {
+		wpa_printf(MSG_INFO,
+			   "Note: nl80211 driver interface is not designed to be used with ap_scan=2; this can result in connection failures");
+	}
+
 #ifdef ANDROID
 	if (ap_scan == 2 && ap_scan != wpa_s->conf->ap_scan &&
 	    wpa_s->wpa_state >= WPA_ASSOCIATING &&
@@ -3295,6 +3300,12 @@ int wpa_supplicant_driver_init(struct wpa_supplicant *wpa_s)
 		}
 	}
 
+	if (wpa_s->conf->ap_scan == 2 &&
+	    os_strcmp(wpa_s->driver->name, "nl80211") == 0) {
+		wpa_printf(MSG_INFO,
+			   "Note: nl80211 driver interface is not designed to be used with ap_scan=2; this can result in connection failures");
+	}
+
 	wpa_clear_keys(wpa_s, NULL);
 
 	/* Make sure that TKIP countermeasures are not left enabled (could

wpa_supplicant/wpa_supplicant.conf

@@ -108,6 +108,10 @@ eapol_version=1
 #    the driver reports successful association; each network block should have
 #    explicit security policy (i.e., only one option in the lists) for
 #    key_mgmt, pairwise, group, proto variables
+# Note: ap_scan=2 should not be used with the nl80211 driver interface (the
+# current Linux interface). ap_scan=1 is optimized work working with nl80211.
+# For finding networks using hidden SSID, scan_ssid=1 in the network block can
+# be used with nl80211.
 # When using IBSS or AP mode, ap_scan=2 mode can force the new network to be
 # created immediately regardless of scan results. ap_scan=1 mode will first try
 # to scan for existing networks and only if no matches with the enabled