feat(android): detect network and dns changes and send them to connlib

kotlin/android/app/src/main/AndroidManifest.xml

@@ -3,6 +3,7 @@
 
     <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+    <uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />
     <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
     <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />

kotlin/android/app/src/main/java/dev/firezone/android/tunnel/ConnlibSession.kt

@@ -14,4 +14,11 @@ object ConnlibSession {
     ): Long
 
     external fun disconnect(connlibSession: Long): Boolean
+
+    external fun setDns(
+        connlibSession: Long,
+        dnsList: String,
+    ): Boolean
+
+    external fun reconnect(connlibSession: Long): Boolean
 }

kotlin/android/app/src/main/java/dev/firezone/android/tunnel/NetworkMonitor.kt

@@ -0,0 +1,17 @@
+/* Licensed under Apache 2.0 (C) 2024 Firezone, Inc. */
+import android.net.ConnectivityManager
+import android.net.LinkProperties
+import android.net.Network
+import com.google.gson.Gson
+import dev.firezone.android.tunnel.ConnlibSession
+
+class NetworkMonitor(private val connlibSessionPtr: Long) : ConnectivityManager.NetworkCallback() {
+    override fun onLinkPropertiesChanged(
+        network: Network,
+        linkProperties: LinkProperties,
+    ) {
+        ConnlibSession.setDns(connlibSessionPtr, Gson().toJson(linkProperties.dnsServers))
+        ConnlibSession.reconnect(connlibSessionPtr)
+        super.onLinkPropertiesChanged(network, linkProperties)
+    }
+}

kotlin/android/app/src/main/java/dev/firezone/android/tunnel/TunnelService.kt

@@ -1,13 +1,17 @@
 /* Licensed under Apache 2.0 (C) 2024 Firezone, Inc. */
 package dev.firezone.android.tunnel
 
+import NetworkMonitor
 import android.app.ActivityManager
 import android.app.Notification
 import android.app.NotificationChannel
 import android.app.NotificationManager
 import android.app.PendingIntent
 import android.content.Context
 import android.content.Intent
+import android.net.ConnectivityManager
+import android.net.NetworkCapabilities
+import android.net.NetworkRequest
 import android.net.VpnService
 import android.os.Binder
 import android.os.Build
@@ -27,7 +31,6 @@ import dev.firezone.android.core.presentation.MainActivity
 import dev.firezone.android.tunnel.callback.ConnlibCallback
 import dev.firezone.android.tunnel.model.Cidr
 import dev.firezone.android.tunnel.model.Resource
-import dev.firezone.android.tunnel.util.DnsServersDetector
 import java.nio.file.Files
 import java.nio.file.Paths
 import java.util.UUID
@@ -52,6 +55,7 @@ class TunnelService : VpnService() {
     private var connlibSessionPtr: Long? = null
     private var _tunnelResources: List<Resource> = emptyList()
     private var _tunnelState: State = State.DOWN
+    private var networkCallback: NetworkMonitor? = null
 
     var startedByUser: Boolean = false
 
@@ -136,16 +140,6 @@ class TunnelService : VpnService() {
                 return buildVpnService()
             }
 
-            override fun getSystemDefaultResolvers(): Array<ByteArray> {
-                val found = DnsServersDetector(this@TunnelService).servers
-                Log.d(TAG, "getSystemDefaultResolvers: $found")
-                Firebase.crashlytics.log("getSystemDefaultResolvers: $found")
-
-                return found.map {
-                    it.address
-                }.toTypedArray()
-            }
-
             // Unexpected disconnect, most likely a 401. Clear the token and initiate a stop of the
             // service.
             override fun onDisconnect(error: String): Boolean {
@@ -188,7 +182,7 @@ class TunnelService : VpnService() {
         Log.d(TAG, "disconnect")
 
         // Connlib should call onDisconnect() when it's done, with no error.
-        connlibSessionPtr!!.let {
+        connlibSessionPtr?.let {
             ConnlibSession.disconnect(it)
         }
 
@@ -198,6 +192,8 @@ class TunnelService : VpnService() {
     private fun shutdown() {
         Log.d(TAG, "shutdown")
 
+        stopNetworkMonitoring()
+
         connlibSessionPtr = null
         stopSelf()
         tunnelState = State.DOWN
@@ -223,6 +219,29 @@ class TunnelService : VpnService() {
                     logFilter = config.logFilter,
                     callback = callback,
                 )
+
+            startNetworkMonitoring()
+        }
+    }
+
+    private fun startNetworkMonitoring() {
+        networkCallback = NetworkMonitor(connlibSessionPtr!!)
+
+        val networkRequest =
+            NetworkRequest.Builder().addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_VPN)
+                .build()
+        val connectivityManager =
+            getSystemService(ConnectivityManager::class.java) as ConnectivityManager
+        connectivityManager.requestNetwork(networkRequest, networkCallback!!)
+    }
+
+    private fun stopNetworkMonitoring() {
+        networkCallback?.let {
+            val connectivityManager =
+                getSystemService(ConnectivityManager::class.java) as ConnectivityManager
+            connectivityManager.unregisterNetworkCallback(it)
+
+            networkCallback = null
         }
     }
 
@@ -312,7 +331,10 @@ class TunnelService : VpnService() {
             addAddress(tunnelIpv6Address!!, 128)
 
             updateAllowedDisallowedApplications("allowedApplications", ::addAllowedApplication)
-            updateAllowedDisallowedApplications("disallowedApplications", ::addDisallowedApplication)
+            updateAllowedDisallowedApplications(
+                "disallowedApplications",
+                ::addDisallowedApplication,
+            )
 
             setSession(SESSION_NAME)
             setMtu(MTU)
@@ -354,14 +376,10 @@ class TunnelService : VpnService() {
 
         val notificationBuilder = NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID)
         val notification =
-            notificationBuilder.setOngoing(true)
-                .setSmallIcon(R.drawable.ic_firezone_logo)
-                .setContentTitle(NOTIFICATION_TITLE)
-                .setContentText(message)
+            notificationBuilder.setOngoing(true).setSmallIcon(R.drawable.ic_firezone_logo)
+                .setContentTitle(NOTIFICATION_TITLE).setContentText(message)
                 .setPriority(NotificationManager.IMPORTANCE_MIN)
-                .setCategory(Notification.CATEGORY_SERVICE)
-                .setContentIntent(configIntent())
-                .build()
+                .setCategory(Notification.CATEGORY_SERVICE).setContentIntent(configIntent()).build()
 
         startForeground(STATUS_NOTIFICATION_ID, notification)
     }

kotlin/android/app/src/main/java/dev/firezone/android/tunnel/callback/ConnlibCallback.kt

@@ -20,7 +20,5 @@ interface ConnlibCallback {
     // The JNI doesn't support nullable types, so we need two method signatures
     fun onDisconnect(error: String): Boolean
 
-    fun getSystemDefaultResolvers(): Array<ByteArray>
-
     fun protectFileDescriptor(fileDescriptor: Int)
 }