Use stable API to detect system nameservers

Motivation:
__system_get_property is a hidden api and has already been removed from the ndk once

5 files changed, 53 insertions, 2 deletions

diff --git a/build.gradle b/build.gradle
index 779e8e3..25b4423 100644
--- a/build.gradle
+++ b/build.gradle
@@ -11,7 +11,7 @@ buildscript {
 apply plugin: 'com.android.application'
 
 android {
-    compileSdkVersion 15
+    compileSdkVersion 21
     buildToolsVersion "21.1.2"
 
     sourceSets.main {
diff --git a/src/main/AndroidManifest.xml b/src/main/AndroidManifest.xml
index 0bea991..5325d7f 100644
--- a/src/main/AndroidManifest.xml
+++ b/src/main/AndroidManifest.xml
@@ -9,6 +9,7 @@
             android:targetSdkVersion="16"/>
 
     <uses-permission android:name="android.permission.INTERNET"/>
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
 
     <application
             android:allowBackup="false"
diff --git a/src/main/java/org/xapek/andiodine/IodineVpnService.java b/src/main/java/org/xapek/andiodine/IodineVpnService.java
index 8d5afe9..ac0f45c 100644
--- a/src/main/java/org/xapek/andiodine/IodineVpnService.java
+++ b/src/main/java/org/xapek/andiodine/IodineVpnService.java
@@ -1,10 +1,16 @@
 package org.xapek.andiodine;
 
+import android.annotation.TargetApi;
 import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
+import android.net.ConnectivityManager;
+import android.net.LinkProperties;
+import android.net.Network;
+import android.net.NetworkInfo;
 import android.net.VpnService;
+import android.os.Build;
 import android.os.ParcelFileDescriptor;
 import android.util.Log;
 
@@ -12,8 +18,10 @@ import org.xapek.andiodine.config.ConfigDatabase;
 import org.xapek.andiodine.config.IodineConfiguration;
 
 import java.io.IOException;
+import java.net.Inet4Address;
 import java.net.InetAddress;
 import java.net.UnknownHostException;
+import java.util.List;
 
 public class IodineVpnService extends VpnService implements Runnable {
     private class IodineVpnException extends Exception {
@@ -203,13 +211,53 @@ public class IodineVpnService extends VpnService implements Runnable {
         }
     }
 
+    @TargetApi(21)
+    private Network getActiveNetwork() {
+        ConnectivityManager cm =
+                (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
+        NetworkInfo defaultNetworkInfo = cm.getActiveNetworkInfo();
+        for (Network n : cm.getAllNetworks()) {
+            NetworkInfo info = cm.getNetworkInfo(n);
+            if (info.getType() == defaultNetworkInfo.getType() &&
+                    info.getSubtype() == defaultNetworkInfo.getSubtype() &&
+                    info.isConnected()) {
+                return n;
+            }
+        }
+        return null;
+    }
+
     @Override
     public void run() {
         try {
             Log.d(TAG, "VPN Thread enter");
             setStatus(ACTION_STATUS_CONNECT, mConfiguration.getId(), null);
 
-            String tunnelNameserver = IodineClient.getPropertyNetDns1();
+            String tunnelNameserver = "";
+
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+                ConnectivityManager cm =
+                        (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
+                Network activeNetwork = getActiveNetwork();
+                if (activeNetwork == null) {
+                    String errorMessage = getString(R.string.vpnservice_error_no_active_network);
+                    setStatus(ACTION_STATUS_ERROR, mConfiguration.getId(), errorMessage);
+                    Log.e(TAG, "No active network. Aborting...");
+                    return;
+                }
+                LinkProperties prop = cm.getLinkProperties(activeNetwork);
+                List<InetAddress> servers = prop.getDnsServers();
+                for (InetAddress candidate : servers) {
+                    Log.d(TAG, "detected dns server: " + candidate);
+                    if (candidate instanceof Inet4Address) {
+                        tunnelNameserver = candidate.getHostAddress();
+                        break;
+                    }
+                }
+            } else {
+                tunnelNameserver = IodineClient.getPropertyNetDns1();
+            }
+
             if (tunnelNameserver.isEmpty()) {
                 String errorMessage = getString(R.string.vpnservice_error_dns_detect_failed);
                 setStatus(ACTION_STATUS_ERROR, mConfiguration.getId(), errorMessage);
diff --git a/src/main/res/values-de/strings.xml b/src/main/res/values-de/strings.xml
index 9ad840b..b39b207 100644
--- a/src/main/res/values-de/strings.xml
+++ b/src/main/res/values-de/strings.xml
@@ -51,6 +51,7 @@
     <string name="vpnservice_error_unknown_error_string">Unbekannter Fehler. Grund: %s</string>
     <string name="vpnservice_error_dns_detect_failed">Es wurden keine gültigen IPv4-Nameserver erkannt</string>
     <string name="vpnservice_error_create_interface_string">Das Tunnel-Netzwerkgerät konnte nicht erstellt werden</string>
+    <string name="vpnservice_error_no_active_network">Kein aktives Netzwerk</string>
     <string name="idle">Leerlauf</string>
     <string name="warning">Warnung</string>
     <string name="error">Fehler</string>
diff --git a/src/main/res/values/strings.xml b/src/main/res/values/strings.xml
index bd9709b..95b2250 100644
--- a/src/main/res/values/strings.xml
+++ b/src/main/res/values/strings.xml
@@ -76,6 +76,7 @@
     <string name="vpnservice_error_unknown_error_string">Unknown Error. Reason: %s</string>
     <string name="vpnservice_error_dns_detect_failed">No valid IPv4 name servers detected</string>
     <string name="vpnservice_error_create_interface_string">Failed to create tunnel network device</string>
+    <string name="vpnservice_error_no_active_network">No active network</string>
     <string name="idle">Idle</string>
     <string name="warning">Warning</string>
     <string name="error">Error</string>