Update scan interval gracefully

When the scan interval is changed the new interval is effective
after the old interval timer fires off one last time. This can cause
an unacceptable long delay when updating the interval.

Change this behaviour to use MIN(left of old interval, new interval)
for the scan interval following the interval change.

Signed-hostap: Pontus Fuchs <pontus.fuchs@gmail.com>

wpa_supplicant/scan.c

@@ -816,6 +816,27 @@ scan:
 }
 
 
+void wpa_supplicant_update_scan_int(struct wpa_supplicant *wpa_s, int sec)
+{
+	struct os_time remaining, new_int;
+	int cancelled;
+
+	cancelled = eloop_cancel_timeout_one(wpa_supplicant_scan, wpa_s, NULL,
+					     &remaining);
+
+	new_int.sec = sec;
+	new_int.usec = 0;
+	if (cancelled && os_time_before(&remaining, &new_int)) {
+		new_int.sec = remaining.sec;
+		new_int.usec = remaining.usec;
+	}
+
+	eloop_register_timeout(new_int.sec, new_int.usec, wpa_supplicant_scan,
+			       wpa_s, NULL);
+	wpa_s->scan_interval = sec;
+}
+
+
 /**
  * wpa_supplicant_req_scan - Schedule a scan for neighboring access points
  * @wpa_s: Pointer to wpa_supplicant data

wpa_supplicant/scan.h

@@ -32,5 +32,6 @@ struct wpabuf * wpa_scan_get_vendor_ie_multi(const struct wpa_scan_res *res,
 					     u32 vendor_type);
 int wpa_supplicant_filter_bssid_match(struct wpa_supplicant *wpa_s,
 				      const u8 *bssid);
+void wpa_supplicant_update_scan_int(struct wpa_supplicant *wpa_s, int sec);
 
 #endif /* SCAN_H */

wpa_supplicant/wpa_supplicant.c

@@ -1980,7 +1980,7 @@ int wpa_supplicant_set_scan_interval(struct wpa_supplicant *wpa_s,
 	}
 	wpa_msg(wpa_s, MSG_DEBUG, "Setting scan interval: %d sec",
 		scan_interval);
-	wpa_s->scan_interval = scan_interval;
+	wpa_supplicant_update_scan_int(wpa_s, scan_interval);
 
 	return 0;
 }