Add a scan result cache to improve roaming speed if the driver gave us a background scan before losing the connection.

--- a/wpa_supplicant/config.h
+++ b/wpa_supplicant/config.h
@@ -97,6 +97,12 @@ struct wpa_config {
 	int ap_scan;
 
 	/**
+	 * scan_cache - controls the time in seconds after the last scan results
+	 * before a new scan may be initiated
+	 */
+	int scan_cache;
+
+	/**
 	 * ctrl_interface - Parameters for the control interface
 	 *
 	 * If this is specified, %wpa_supplicant will open a control interface
--- a/wpa_supplicant/config_file.c
+++ b/wpa_supplicant/config_file.c
@@ -306,6 +306,13 @@ static int wpa_config_parse_int(const st
 	return 0;
 }
 
+static int wpa_config_process_scan_cache(struct wpa_config *config, char *pos)
+{
+	config->scan_cache = atoi(pos);
+	wpa_printf(MSG_DEBUG, "scan_cache=%d", config->scan_cache);
+	return 0;
+}
+
 
 static int wpa_config_parse_str(const struct global_parse_data *data,
 				struct wpa_config *config, int line,
@@ -433,6 +440,7 @@ static const struct global_parse_data gl
 #endif /* CONFIG_CTRL_IFACE */
 	{ INT_RANGE(eapol_version, 1, 2) },
 	{ INT(ap_scan) },
+	{ INT(scan_cache) },
 	{ INT(fast_reauth) },
 #ifdef EAP_TLS_OPENSSL
 	{ STR(opensc_engine_path) },
@@ -834,6 +842,8 @@ static void wpa_config_write_global(FILE
 		fprintf(f, "eapol_version=%d\n", config->eapol_version);
 	if (config->ap_scan != DEFAULT_AP_SCAN)
 		fprintf(f, "ap_scan=%d\n", config->ap_scan);
+	if (config->scan_cache != 0)
+		fprintf(f, "scan_cache=%d\n", config->scan_cache);
 	if (config->fast_reauth != DEFAULT_FAST_REAUTH)
 		fprintf(f, "fast_reauth=%d\n", config->fast_reauth);
 #ifdef EAP_TLS_OPENSSL
--- a/wpa_supplicant/events.c
+++ b/wpa_supplicant/events.c
@@ -633,6 +633,9 @@ static void wpa_supplicant_event_scan_re
 	    wpa_s->disconnected)
 		return;
 
+	if (wpa_s->wpa_state > WPA_ASSOCIATED)
+		goto done;
+
 	while (selected == NULL) {
 		for (prio = 0; prio < wpa_s->conf->num_prio; prio++) {
 			selected = wpa_supplicant_select_bss(
@@ -645,6 +648,7 @@ static void wpa_supplicant_event_scan_re
 			wpa_printf(MSG_DEBUG, "No APs found - clear blacklist "
 				   "and try again");
 			wpa_blacklist_clear(wpa_s);
+			memset(&wpa_s->last_scan_results, 0, sizeof(wpa_s->last_scan_results));
 		} else if (selected == NULL) {
 			break;
 		}
@@ -679,10 +683,12 @@ static void wpa_supplicant_event_scan_re
 		rsn_preauth_scan_results(wpa_s->wpa, wpa_s->scan_res);
 	} else {
 		wpa_printf(MSG_DEBUG, "No suitable AP found.");
-		timeout = 5;
+		timeout = 0;
 		goto req_scan;
 	}
 
+done:
+	os_get_time(&wpa_s->last_scan_results);
 	return;
 
 req_scan:
@@ -886,6 +892,9 @@ static void wpa_supplicant_event_disasso
 	}
 	if (wpa_s->wpa_state >= WPA_ASSOCIATED)
 		wpa_supplicant_req_scan(wpa_s, 0, 100000);
+	else if (wpa_s->wpa_state == WPA_ASSOCIATING)
+		wpa_supplicant_req_auth_timeout(wpa_s, 0, 100000);
+
 	bssid = wpa_s->bssid;
 	if (is_zero_ether_addr(bssid))
 		bssid = wpa_s->pending_bssid;
--- a/wpa_supplicant/wpa_supplicant_i.h
+++ b/wpa_supplicant/wpa_supplicant_i.h
@@ -349,6 +349,7 @@ struct wpa_supplicant {
 	struct wpa_client_mlme mlme;
 	int use_client_mlme;
 	int driver_4way_handshake;
+	struct os_time last_scan_results;
 
 	int pending_mic_error_report;
 	int pending_mic_error_pairwise;
@@ -402,6 +403,7 @@ int wpa_supplicant_scard_init(struct wpa
 
 /* scan.c */
 void wpa_supplicant_req_scan(struct wpa_supplicant *wpa_s, int sec, int usec);
+int wpa_supplicant_may_scan(struct wpa_supplicant *wpa_s);
 void wpa_supplicant_cancel_scan(struct wpa_supplicant *wpa_s);
 
 /* events.c */
--- a/wpa_supplicant/scan.c
+++ b/wpa_supplicant/scan.c
@@ -40,6 +40,18 @@ static void wpa_supplicant_gen_assoc_eve
 	wpa_supplicant_event(wpa_s, EVENT_ASSOC, &data);
 }
 
+int wpa_supplicant_may_scan(struct wpa_supplicant *wpa_s)
+{
+	struct os_time time;
+
+	if (wpa_s->conf->scan_cache > 0) {
+		os_get_time(&time);
+		time.sec -= wpa_s->conf->scan_cache;
+		if (os_time_before(&time, &wpa_s->last_scan_results))
+			return 0;
+	}
+	return 1;
+}
 
 #ifdef CONFIG_WPS
 static int wpas_wps_in_use(struct wpa_config *conf,
@@ -183,8 +195,9 @@ static void wpa_supplicant_scan(void *el
 	wps = wpas_wps_in_use(wpa_s->conf, &req_type);
 #endif /* CONFIG_WPS */
 
-	if (wpa_s->scan_res_tried == 0 && wpa_s->conf->ap_scan == 1 &&
-	    !wpa_s->use_client_mlme && wps != 2) {
+	if (!wpa_supplicant_may_scan(wpa_s) ||
+	    (wpa_s->scan_res_tried == 0 && wpa_s->conf->ap_scan == 1 &&
+	    !wpa_s->use_client_mlme && wps != 2)) {
 		wpa_s->scan_res_tried++;
 		wpa_s->scan_req = scan_req;
 		wpa_printf(MSG_DEBUG, "Trying to get current scan results "
--- a/wpa_supplicant/wpa_supplicant.c
+++ b/wpa_supplicant/wpa_supplicant.c
@@ -1491,6 +1491,9 @@ void wpa_supplicant_rx_eapol(void *ctx, 
 {
 	struct wpa_supplicant *wpa_s = ctx;
 
+	if (wpa_s->wpa_state < WPA_ASSOCIATING)
+		return;
+
 	wpa_printf(MSG_DEBUG, "RX EAPOL from " MACSTR, MAC2STR(src_addr));
 	wpa_hexdump(MSG_MSGDUMP, "RX EAPOL", buf, len);