WNM: Use recent scan results on BSS transition request

If the last scans are recent (for now, less than ten seconds old), use
them instead of triggering a new scan when a BSS Transition Management
Request frame is received. As a fallback, allow a new scan to be
triggered if no matches were found.

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

wpa_supplicant/events.c

@@ -1314,7 +1314,7 @@ static int _wpa_supplicant_event_scan_results(struct wpa_supplicant *wpa_s,
 		return 0;
 	}
 
-	if (wnm_scan_process(wpa_s) > 0)
+	if (wnm_scan_process(wpa_s, 1) > 0)
 		goto scan_work_done;
 
 	if (sme_proc_obss_scan(wpa_s) > 0)

wpa_supplicant/wnm_sta.c

@@ -576,7 +576,7 @@ static void wnm_send_bss_transition_mgmt_resp(
 }
 
 
-int wnm_scan_process(struct wpa_supplicant *wpa_s)
+int wnm_scan_process(struct wpa_supplicant *wpa_s, int reply_on_fail)
 {
 	struct wpa_bss *bss;
 	struct wpa_ssid *ssid = wpa_s->current_ssid;
@@ -628,8 +628,12 @@ int wnm_scan_process(struct wpa_supplicant *wpa_s)
 	wnm_deallocate_memory(wpa_s);
 	return 1;
 
-	/* Send reject response for all the failures */
 send_bss_resp_fail:
+	if (!reply_on_fail)
+		return 0;
+
+	/* Send reject response for all the failures */
+
 	if (wpa_s->wnm_reply) {
 		wpa_s->wnm_reply = 0;
 		wnm_send_bss_transition_mgmt_resp(wpa_s,
@@ -874,6 +878,20 @@ static void ieee802_11_rx_bss_trans_mgmt_req(struct wpa_supplicant *wpa_s,
 		wpa_s->wnm_cand_valid_until.usec %= 1000000;
 		os_memcpy(wpa_s->wnm_cand_from_bss, wpa_s->bssid, ETH_ALEN);
 
+		if (wpa_s->last_scan_res_used > 0) {
+			struct os_reltime now;
+
+			os_get_reltime(&now);
+			if (!os_reltime_expired(&now, &wpa_s->last_scan, 10)) {
+				wpa_printf(MSG_DEBUG,
+					   "WNM: Try to use recent scan results");
+				if (wnm_scan_process(wpa_s, 0) > 0)
+					return;
+				wpa_printf(MSG_DEBUG,
+					   "WNM: No match in previous scan results - try a new scan");
+			}
+		}
+
 		wnm_set_scan_freqs(wpa_s);
 		wpa_supplicant_req_scan(wpa_s, 0, 0);
 	} else if (reply) {

wpa_supplicant/wnm_sta.h

@@ -62,11 +62,12 @@ void wnm_deallocate_memory(struct wpa_supplicant *wpa_s);
 
 #ifdef CONFIG_WNM
 
-int wnm_scan_process(struct wpa_supplicant *wpa_s);
+int wnm_scan_process(struct wpa_supplicant *wpa_s, int reply_on_fail);
 
 #else /* CONFIG_WNM */
 
-static inline int wnm_scan_process(struct wpa_supplicant *wpa_s)
+static inline int wnm_scan_process(struct wpa_supplicant *wpa_s,
+				   int reply_on_fail)
 {
 	return 0;
 }