Add local DNS to dns list. shadowsocks#1281

mobile/src/main/java/com/github/shadowsocks/utils/Dns.java

@@ -0,0 +1,73 @@
+/* 
+ *  Copyright 2010 Brave New Software Project, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+package com.github.shadowsocks.utils;
+
+import android.annotation.SuppressLint;
+import android.app.PendingIntent;
+import android.content.Context;
+import android.content.Intent;
+import android.annotation.TargetApi;
+import android.util.Log;
+import android.net.ConnectivityManager;
+import android.net.LinkProperties;
+import android.os.Build;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.InvocationTargetException;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.net.InetAddress;
+
+public class Dns {
+
+    public static String getDnsResolver(Context context) throws Exception {
+        Collection<InetAddress> dnsResolvers = getDnsResolvers(context);
+        if (dnsResolvers.isEmpty()) {
+            throw new Exception("Couldn't find an active DNS resolver");
+        }
+        String dnsResolver = dnsResolvers.iterator().next().toString();
+        if (dnsResolver.startsWith("/")) {
+            dnsResolver = dnsResolver.substring(1);
+        }
+        return dnsResolver;
+    }
+
+    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
+    private static Collection<InetAddress> getDnsResolvers(Context context) throws Exception {
+        ArrayList<InetAddress> addresses = new ArrayList<InetAddress>();
+        ConnectivityManager connectivityManager =
+            (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
+        Class<?> LinkPropertiesClass = Class.forName("android.net.LinkProperties");
+        Method getActiveLinkPropertiesMethod = ConnectivityManager.class.getMethod("getActiveLinkProperties", new Class []{});
+        Object linkProperties = getActiveLinkPropertiesMethod.invoke(connectivityManager);
+        if (linkProperties != null) {
+            if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
+                Method getDnsesMethod = LinkPropertiesClass.getMethod("getDnses", new Class []{});
+                Collection<?> dnses = (Collection<?>)getDnsesMethod.invoke(linkProperties);
+                for (Object dns : dnses) {
+                    addresses.add((InetAddress)dns);
+                }
+            } else {
+                for (InetAddress dns : ((LinkProperties)linkProperties).getDnsServers()) {
+                    addresses.add(dns);
+                }
+            }
+        }
+
+        return addresses;
+    }
+}

mobile/src/main/scala/com/github/shadowsocks/BaseService.scala

@@ -341,12 +341,21 @@ trait BaseService extends Service {
     val remoteDns = new JSONArray(profile.remoteDns.split(",").zipWithIndex.map {
       case (dns, i) => makeDns("UserDef-" + i, dns.trim)
     })
+    val localDns = new JSONArray(Array(
+      makeDns("Primary-1", "119.29.29.29", edns = false),
+      makeDns("Primary-2", "114.114.114.114", edns = false)
+    ))
+
+    try {
+      val localLinkDns = com.github.shadowsocks.utils.Dns.getDnsResolver(this)
+      localDns.put(makeDns("Primary-3", localLinkDns, edns = false))
+    } catch {
+      case _: Exception => // Ignore
+    }
+
     profile.route match {
       case Acl.BYPASS_CHN | Acl.BYPASS_LAN_CHN | Acl.GFWLIST | Acl.CUSTOM_RULES => config
-        .put("PrimaryDNS", new JSONArray(Array(
-          makeDns("Primary-1", "119.29.29.29", edns = false),
-          makeDns("Primary-2", "114.114.114.114", edns = false)
-        )))
+        .put("PrimaryDNS", localDns)
         .put("AlternativeDNS", remoteDns)
         .put("IPNetworkFile", "china_ip_list.txt")
         .put("DomainFile", "gfwlist.txt")