Add ignore_old_scan_res configuration parameter

This can be used to configure wpa_supplicant to ignore old scan results
from the driver cache in cases where such results were not updated after
the scan trigger from wpa_supplicant. This can be useful in some cases
where the driver may cache information for a significant time and the AP
configuration is changing. Many such cases are for testing scripts, but
this could potentially be useful for some WPS use cases, too.

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

wpa_supplicant/bss.c

@@ -224,11 +224,27 @@ struct wpa_bss * wpa_bss_get(struct wpa_supplicant *wpa_s, const u8 *bssid,
 }
 
 
-static void wpa_bss_copy_res(struct wpa_bss *dst, struct wpa_scan_res *src,
+static void calculate_update_time(const struct os_time *fetch_time,
-			     struct os_time *fetch_time)
+				  unsigned int age_ms,
+				  struct os_time *update_time)
 {
 	os_time_t usec;
 
+	update_time->sec = fetch_time->sec;
+	update_time->usec = fetch_time->usec;
+	update_time->sec -= age_ms / 1000;
+	usec = (age_ms % 1000) * 1000;
+	if (update_time->usec < usec) {
+		update_time->sec--;
+		update_time->usec += 1000000;
+	}
+	update_time->usec -= usec;
+}
+
+
+static void wpa_bss_copy_res(struct wpa_bss *dst, struct wpa_scan_res *src,
+			     struct os_time *fetch_time)
+{
 	dst->flags = src->flags;
 	os_memcpy(dst->bssid, src->bssid, ETH_ALEN);
 	dst->freq = src->freq;
@@ -239,15 +255,7 @@ static void wpa_bss_copy_res(struct wpa_bss *dst, struct wpa_scan_res *src,
 	dst->level = src->level;
 	dst->tsf = src->tsf;
 
-	dst->last_update.sec = fetch_time->sec;
+	calculate_update_time(fetch_time, src->age, &dst->last_update);
-	dst->last_update.usec = fetch_time->usec;
-	dst->last_update.sec -= src->age / 1000;
-	usec = (src->age % 1000) * 1000;
-	if (dst->last_update.usec < usec) {
-		dst->last_update.sec--;
-		dst->last_update.usec += 1000000;
-	}
-	dst->last_update.usec -= usec;
 }
 
 
@@ -567,6 +575,21 @@ void wpa_bss_update_scan_res(struct wpa_supplicant *wpa_s,
 	const u8 *ssid, *p2p;
 	struct wpa_bss *bss;
 
+	if (wpa_s->conf->ignore_old_scan_res) {
+		struct os_time update;
+		calculate_update_time(fetch_time, res->age, &update);
+		if (os_time_before(&update, &wpa_s->scan_trigger_time)) {
+			struct os_time age;
+			os_time_sub(&wpa_s->scan_trigger_time, &update, &age);
+			wpa_dbg(wpa_s, MSG_DEBUG, "BSS: Ignore driver BSS "
+				"table entry that is %u.%06u seconds older "
+				"than our scan trigger",
+				(unsigned int) age.sec,
+				(unsigned int) age.usec);
+			return;
+		}
+	}
+
 	ssid = wpa_scan_get_ie(res, WLAN_EID_SSID);
 	if (ssid == NULL) {
 		wpa_dbg(wpa_s, MSG_DEBUG, "BSS: No SSID IE included for "

wpa_supplicant/config.c

@@ -3089,6 +3089,7 @@ static const struct global_parse_data global_fields[] = {
 	{ INT(dtim_period), 0 },
 	{ INT(beacon_int), 0 },
 	{ FUNC(ap_vendor_elements), 0 },
+	{ INT_RANGE(ignore_old_scan_res, 0, 1), 0 },
 };
 
 #undef FUNC

wpa_supplicant/config.h

@@ -844,6 +844,16 @@ struct wpa_config {
 	 * elements (id+len+payload for one or more elements).
 	 */
 	struct wpabuf *ap_vendor_elements;
+
+	/**
+	 * ignore_old_scan_res - Ignore scan results older than request
+	 *
+	 * The driver may have a cache of scan results that makes it return
+	 * information that is older than our scan trigger. This parameter can
+	 * be used to configure such old information to be ignored instead of
+	 * allowing it to update the internal BSS table.
+	 */
+	int ignore_old_scan_res;
 };
 
 

wpa_supplicant/config_file.c

@@ -1004,6 +1004,10 @@ static void wpa_config_write_global(FILE *f, struct wpa_config *config)
 			fprintf(f, "\n");
 		}
 	}
+
+	if (config->ignore_old_scan_res)
+		fprintf(f, "ignore_old_scan_res=%d\n",
+			config->ignore_old_scan_res);
 }
 
 #endif /* CONFIG_NO_CONFIG_WRITE */

wpa_supplicant/p2p_supplicant.c

@@ -216,8 +216,10 @@ static int wpas_p2p_scan(void *ctx, enum p2p_scan_type type, int freq,
 				break;
 			}
 		}
-	} else
+	} else {
+		os_get_time(&wpa_s->scan_trigger_time);
 		wpa_s->scan_res_handler = wpas_p2p_scan_res_handler;
+	}
 
 	return ret;
 }
@@ -970,6 +972,7 @@ static void wpas_p2p_clone_config(struct wpa_supplicant *dst,
 	d->persistent_reconnect = s->persistent_reconnect;
 	d->max_num_sta = s->max_num_sta;
 	d->pbc_in_m1 = s->pbc_in_m1;
+	d->ignore_old_scan_res = s->ignore_old_scan_res;
 }
 
 
@@ -3550,8 +3553,10 @@ static void wpas_p2p_join_scan_req(struct wpa_supplicant *wpa_s, int freq)
 	 * the new scan results become available.
 	 */
 	ret = wpa_drv_scan(wpa_s, &params);
-	if (!ret)
+	if (!ret) {
+		os_get_time(&wpa_s->scan_trigger_time);
 		wpa_s->scan_res_handler = wpas_p2p_scan_res_join;
+	}
 
 	wpabuf_free(ies);
 

wpa_supplicant/scan.c

@@ -227,6 +227,7 @@ int wpa_supplicant_trigger_scan(struct wpa_supplicant *wpa_s,
 		wpa_supplicant_notify_scanning(wpa_s, 0);
 		wpas_notify_scan_done(wpa_s, 0);
 	} else {
+		os_get_time(&wpa_s->scan_trigger_time);
 		wpa_s->scan_runs++;
 		wpa_s->normal_scans++;
 	}

wpa_supplicant/wpa_supplicant.conf

@@ -302,6 +302,15 @@ fast_reauth=1
 # one or more elements). This is used in AP and P2P GO modes.
 #ap_vendor_elements=dd0411223301
 
+# Ignore scan results older than request
+#
+# The driver may have a cache of scan results that makes it return
+# information that is older than our scan trigger. This parameter can
+# be used to configure such old information to be ignored instead of
+# allowing it to update the internal BSS table.
+#ignore_old_scan_res=0
+
+
 # Interworking (IEEE 802.11u)
 
 # Enable Interworking

wpa_supplicant/wpa_supplicant_i.h

@@ -444,6 +444,7 @@ struct wpa_supplicant {
 		 */
 		MANUAL_SCAN_REQ
 	} scan_req;
+	struct os_time scan_trigger_time;
 	int scan_runs; /* number of scan runs since WPS was started */
 	int *next_scan_freqs;
 	int scan_interval; /* time in sec between scans to find suitable AP */