android: updates - honour the charging constraint, real metered check

- drop the in-process 12 h loop: the VPN keeps the process alive, so it
  checked and pre-downloaded on battery, defeating the worker constraint
- the worker now waits for the check and a silent download it starts
- metered is judged by the physical network: the VPN reports itself
  unmetered, so pre-downloads ran over cellular while connected

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/frontends/android/app/src/main/java/org/strongswan/android/logic/updates/UpdateCheckWorker.kt

@@ -29,7 +29,12 @@ class UpdateCheckWorker(context: Context, params: WorkerParameters) : CoroutineW
 {
 	override suspend fun doWork(): Result
 	{
-		UpdateManager.getInstance(applicationContext).checkIfDue()
+		/* wait for the check (and a silent pre-download it starts): returning
+		 * early lets the system reclaim the process mid-request, outside the
+		 * worker's charging/network constraints */
+		val manager = UpdateManager.getInstance(applicationContext)
+		manager.checkIfDue()?.join()
+		manager.awaitDownload()
 		return Result.success()
 	}
 

src/frontends/android/app/src/main/java/org/strongswan/android/logic/updates/UpdateManager.kt

@@ -26,6 +26,7 @@ import android.content.SharedPreferences
 import android.content.pm.PackageInfo
 import android.content.pm.PackageManager
 import android.net.ConnectivityManager
+import android.net.NetworkCapabilities
 import android.os.Build
 import android.os.IBinder
 import android.util.Log
@@ -41,7 +42,6 @@ import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.SupervisorJob
-import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.launch
@@ -51,6 +51,7 @@ import org.strongswan.android.R
 import org.strongswan.android.logic.DiagLog
 import org.strongswan.android.logic.StrongSwanApplication
 import org.strongswan.android.logic.VpnStateService
+import org.strongswan.android.logic.connectivity.UnderlyingNetwork
 import org.strongswan.android.ui.MainActivity
 import org.strongswan.android.utils.Constants
 import java.io.File
@@ -198,13 +199,16 @@ class UpdateManager private constructor(private val context: Context)
 			.build()
 		WorkManager.getInstance(context).enqueueUniquePeriodicWork(
 			UpdateCheckWorker.WORK_NAME, ExistingPeriodicWorkPolicy.UPDATE, request)
-		mScope.launch {
-			while (true)
-			{
-				checkIfDue()
-				delay(Constants.UPDATE_CHECK_INTERVAL_MS)
-			}
-		}
+		/* no in-process timer: the VPN service keeps the process alive, so a
+		 * loop here would check (and pre-download) on battery every 12 h and
+		 * defeat the worker's charging constraint.  The worker and the check
+		 * on app resume cover it. */
+	}
+
+	/** Waits for a running silent download (used by the worker). */
+	suspend fun awaitDownload()
+	{
+		mDownloadJob?.join()
 	}
 
 	/**
@@ -212,17 +216,18 @@ class UpdateManager private constructor(private val context: Context)
 	 * last-check timestamp). Called by the periodic worker, the in-process
 	 * loop and on app resume.
 	 */
-	fun checkIfDue()
+	fun checkIfDue(): Job?
 	{
 		if (!isAutoCheckEnabled() || mCheckJob?.isActive == true || mDownloadJob?.isActive == true)
 		{
-			return
+			return null
 		}
 		val last = mPrefs.getLong(Constants.PREF_LAST_UPDATE_CHECK, 0L)
 		if (System.currentTimeMillis() - last >= Constants.UPDATE_CHECK_INTERVAL_MS)
 		{
-			check()
+			return check()
 		}
+		return null
 	}
 
 	fun isAutoCheckEnabled(): Boolean
@@ -239,13 +244,13 @@ class UpdateManager private constructor(private val context: Context)
 	}
 
 	@Synchronized
-	private fun check()
+	private fun check(): Job?
 	{
 		if (mCheckJob?.isActive == true || mDownloadJob?.isActive == true)
 		{
-			return
+			return mCheckJob?.takeIf { it.isActive }
 		}
-		mCheckJob = mScope.launch {
+		val job = mScope.launch {
 			mState.value = UpdateState.Checking
 			val info = fetchManifest() ?: run {
 				mInstallPending = false
@@ -274,6 +279,8 @@ class UpdateManager private constructor(private val context: Context)
 				mState.value = UpdateState.UpToDate
 			}
 		}
+		mCheckJob = job
+		return job
 	}
 
 	/**
@@ -348,8 +355,20 @@ class UpdateManager private constructor(private val context: Context)
 
 	private fun isNetworkMetered(): Boolean
 	{
-		val cm = context.getSystemService(Context.CONNECTIVITY_SERVICE) as? ConnectivityManager
-		return cm?.isActiveNetworkMetered ?: true
+		val cm = context.getSystemService(Context.CONNECTIVITY_SERVICE) as? ConnectivityManager ?: return true
+		/* the VPN marks itself unmetered (setMetered(false)), so with the tunnel
+		 * up the active network always looks unmetered - judge by the physical
+		 * network below it instead */
+		val underlying = UnderlyingNetwork.resolve(context) ?: return cm.isActiveNetworkMetered
+		val caps = try
+		{
+			cm.getNetworkCapabilities(underlying)
+		}
+		catch (_: Exception)
+		{
+			null
+		} ?: return true
+		return !caps.hasCapability(NetworkCapabilities.NET_CAPABILITY_NOT_METERED)
 	}
 
 	private fun isVpnDown(): Boolean