Show a notification when the VPN seems to have disconnected

app/src/main/java/com/frostnerd/smokescreen/service/DnsVpnService.kt

@@ -95,6 +95,7 @@ class DnsVpnService : VpnService(), Runnable, CoroutineScope {
     private var localResolver:LocalResolver? = null
     private var runInNonVpnMode:Boolean = getPreferences().runWithoutVpn
     private var connectionWatchDog:ConnectionWatchdog? = null
+    private var vpnWatchdog:VpnWatchDog? = null
     private var watchdogDisabledForSession = false
     private val coroutineSupervisor = SupervisorJob()
     @Suppress("EXPERIMENTAL_API_USAGE")
@@ -912,6 +913,7 @@ class DnsVpnService : VpnService(), Runnable, CoroutineScope {
             vpnProxy?.stop()
             dnsServerProxy?.stop()
             connectionWatchDog?.stop()
+            vpnWatchdog?.stop()
             if(ipTablesRedirector == null || ipTablesRedirector?.endForward() == IpTablesPacketRedirector.IpTablesMode.SUCCEEDED) {
                 getPreferences().lastIptablesRedirectAddress = null
                 getPreferences().lastIptablesRedirectAddressIPv6 = null
@@ -973,16 +975,20 @@ class DnsVpnService : VpnService(), Runnable, CoroutineScope {
                 BackgroundVpnConfigureActivity.prepareVpn(this, userServerConfig)
             }, 250)
         } else if(getPreferences().showNotificationOnRevoked){
-            NotificationCompat.Builder(this, Notifications.getHighPriorityChannelId(this)).apply {
-                setSmallIcon(R.drawable.ic_cloud_warn)
-                setContentTitle(getString(R.string.notification_service_revoked_title))
-                setContentText(getString(R.string.notification_service_revoked_message))
-                setContentIntent(PendingIntent.getActivity(this@DnsVpnService, RequestCodes.RESTART_AFTER_REVOKE, Intent(this@DnsVpnService, BackgroundVpnConfigureActivity::class.java), PendingIntent.FLAG_CANCEL_CURRENT))
-                setAutoCancel(true)
-                priority = NotificationCompat.PRIORITY_HIGH
-            }.build().also {
-                (getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager).notify(Notifications.ID_SERVICE_REVOKED, it)
-            }
+            showVpnRevokedNotification()
+        }
+    }
+
+    private fun showVpnRevokedNotification() {
+        NotificationCompat.Builder(this, Notifications.getHighPriorityChannelId(this)).apply {
+            setSmallIcon(R.drawable.ic_cloud_warn)
+            setContentTitle(getString(R.string.notification_service_revoked_title))
+            setContentText(getString(R.string.notification_service_revoked_message))
+            setContentIntent(PendingIntent.getActivity(this@DnsVpnService, RequestCodes.RESTART_AFTER_REVOKE, Intent(this@DnsVpnService, BackgroundVpnConfigureActivity::class.java), PendingIntent.FLAG_CANCEL_CURRENT))
+            setAutoCancel(true)
+            priority = NotificationCompat.PRIORITY_HIGH
+        }.build().also {
+            (getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager).notify(Notifications.ID_SERVICE_REVOKED, it)
         }
     }
 
@@ -1383,7 +1389,6 @@ class DnsVpnService : VpnService(), Runnable, CoroutineScope {
                 val usedAddress = if(bindAddress == defaultBindAddress) "localhost" else bindAddress.hostAddress
                 showDnsServerModeNotification(usedAddress, actualPort, preferredPort, iptablesMode)
                 currentTrafficStats = vpnProxy?.trafficStats
-                createConnectionWatchdog()
                 log("Non-VPN proxy started.")
             }
         } else {
@@ -1427,6 +1432,9 @@ class DnsVpnService : VpnService(), Runnable, CoroutineScope {
                     hideBadConnectionNotification()
                 }, logger = this@DnsVpnService.logger, advancedLogging = getPreferences().advancedLogging)
             }
+        vpnWatchdog = VpnWatchDog({
+            showVpnRevokedNotification()
+        }, this)
     }
 
     private fun createQueryLogger(): QueryListener? {

app/src/main/java/com/frostnerd/smokescreen/service/VpnWatchDog.kt

+package com.frostnerd.smokescreen.service
+
+import android.content.Context
+import android.net.ConnectivityManager
+import com.frostnerd.smokescreen.Logger
+import com.frostnerd.smokescreen.isVpnNetwork
+import com.frostnerd.smokescreen.logger
+import kotlinx.coroutines.*
+
+/*
+ * Copyright (C) 2020 Daniel Wolf (Ch4t4r)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * You can contact the developer at daniel.wolf@frostnerd.com.
+ */
+class VpnWatchDog(private val onVpnDisconnected:() -> Unit,
+                  private val context: Context) {
+    private val supervisor = SupervisorJob()
+    private val scope = CoroutineScope(supervisor + Dispatchers.IO)
+    private var running = true
+    private var vpnRunning:Boolean = true
+    private val logger:Logger? = context.logger
+    private val connectivityManager = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
+
+    init {
+        scope.launch {
+            checkConnection()
+        }
+    }
+
+    private fun log(text:String) {
+        logger?.log(text, "ConnectionWatchdog")
+    }
+
+    private suspend fun checkConnection() {
+        delay(3000)
+        log("Beginning VPN-check")
+        val networks = connectivityManager.allNetworks.toList().filterNotNull()
+        val isStillRunning = networks.any { connectivityManager.isVpnNetwork(it) } || networks.isEmpty()
+
+        if(!isStillRunning && vpnRunning) {
+            callCallback()
+        }
+        vpnRunning = isStillRunning
+
+        if(running) {
+            log("Connection check done.")
+            scope.launch {
+                checkConnection()
+            }
+        }
+    }
+
+    private fun callCallback() {
+        if(!running) return
+        log("Calling callback.")
+        onVpnDisconnected()
+    }
+
+    fun stop() {
+        supervisor.cancel()
+        running = false
+    }
+}
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