Cache package names and Fix stats update loop continuing every 10s when screen is off (#549)

* Fix stats update loop continuing every 10s when screen is off

The recent battery optimization (9f15d42) introduced a race condition:
when screen turns off, stopStats() removes pending MSG_STATS_UPDATE
messages and sets stats=false. However, if an already-delayed update
fires after stopStats(), updateStats() would reschedule itself every
10 seconds indefinitely since it never checked the stats flag.

This caused ~360 unnecessary handler wakeups per hour while screen off.

Fix: check the stats flag at the start of updateStats() and bail out
without rescheduling if stats have been stopped.

https://claude.ai/code/session_01XpUzMgtH7S4K72UX2DQ1cC

* Cache getPackagesForUid() result in shouldTrackApp() to avoid per-packet Binder IPC

shouldTrackApp() is called twice per packet (from blockKnownTracker
and from log) and each call made an uncached getPackagesForUid()
Binder IPC. Cache uid→packageName in a ConcurrentHashMap, invalidated
on package removal and cleared during 12-hour housekeeping.

https://claude.ai/code/session_01XpUzMgtH7S4K72UX2DQ1cC

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: kasnder

app/src/main/java/eu/faircode/netguard/ServiceSinkhole.java

@@ -731,6 +731,7 @@ private void householding(Intent intent) {
             ipToHost.clear();
             ipToTracker.clear();
             uidToApp.clear();
+            uidToPackage.clear();
 
             // Check for update
             if (!Util.isPlayStoreInstall(ServiceSinkhole.this)
@@ -1091,9 +1092,13 @@ private void stopStats() {
         }
 
         private void updateStats() {
+            // Stop the stats loop if stats were stopped (e.g. screen turned off)
+            if (!stats) {
+                return;
+            }
+
             // Skip stats updates when screen is off to save battery
             if (!last_interactive) {
-                this.sendEmptyMessageDelayed(MSG_STATS_UPDATE, 10000);
                 return;
             }
 
@@ -2144,6 +2149,7 @@ private boolean isSupported(int protocol) {
     }
 
     static ConcurrentHashMap<Integer, String> uidToApp = new ConcurrentHashMap<>();
+    private static final ConcurrentHashMap<Integer, String> uidToPackage = new ConcurrentHashMap<>();
     static ConcurrentHashMap<String, Expiring<String>> ipToHost = new ConcurrentHashMap<>();
     static ConcurrentHashMap<String, Expiring<Tracker>> ipToTracker = new ConcurrentHashMap<>();
     static String NO_DNAME = "null"; // use a String, unequal the real null
@@ -2236,20 +2242,24 @@ private Allowed isAddressAllowed(Packet packet) {
      * - It's a system app and manage_system is disabled
      */
     private boolean shouldTrackApp(int uid) {
-        String[] packages;
-        try {
-            packages = getPackageManager().getPackagesForUid(uid);
-        } catch (SecurityException ex) {
-            // In work profiles, getPackagesForUid throws SecurityException for
-            // cross-user UIDs (requires INTERACT_ACROSS_USERS_FULL permission).
-            // Default to tracking so blocking/logging still works.
-            Log.w(TAG, "SecurityException in shouldTrackApp for uid " + uid + ": " + ex.getMessage());
-            return true;
-        }
-        if (packages == null || packages.length == 0) {
-            return true; // Unknown UID, default to tracking
+        String packageName = uidToPackage.get(uid);
+        if (packageName == null) {
+            String[] packages;
+            try {
+                packages = getPackageManager().getPackagesForUid(uid);
+            } catch (SecurityException ex) {
+                // In work profiles, getPackagesForUid throws SecurityException for
+                // cross-user UIDs (requires INTERACT_ACROSS_USERS_FULL permission).
+                // Default to tracking so blocking/logging still works.
+                Log.w(TAG, "SecurityException in shouldTrackApp for uid " + uid + ": " + ex.getMessage());
+                return true;
+            }
+            if (packages == null || packages.length == 0) {
+                return true; // Unknown UID, default to tracking
+            }
+            packageName = packages[0];
+            uidToPackage.put(uid, packageName);
         }
-        String packageName = packages[0];
 
         // Check if tracker protection is enabled for this app
         SharedPreferences trackerProtectPrefs = cachedTrackerProtectPrefs;
@@ -2686,6 +2696,7 @@ public void onReceive(Context context, Intent intent) {
                             dh.clearLog(uid);
                             dh.clearAccess(uid, false);
                             uidToApp.remove(uid);
+                            uidToPackage.remove(uid);
 
                             NotificationManagerCompat.from(context).cancel(uid); // installed notification
                             NotificationManagerCompat.from(context).cancel(uid + 10000); // access notification