fix a bypass issue

src/main/scala/com/github/shadowsocks/utils/ConfigUtils.scala

@@ -86,7 +86,7 @@ object ConfigUtils {
 	  |
       |server {
       | label = "china-servers";
-      | ip = %s, 114.114.114.114, 114.114.115.115;
+      | ip = %s, 114.114.114.114;
       | timeout = 5;
       |}
       |

src/main/scala/com/github/shadowsocks/utils/Utils.scala

@@ -53,7 +53,7 @@ import android.os.Build
 import android.provider.Settings
 import scala.Some
 import java.security.MessageDigest
-import com.github.shadowsocks.{BuildConfig}
+import com.github.shadowsocks.{BuildConfig, System}
 
 
 object Utils {
@@ -80,6 +80,15 @@ object Utils {
   var data_path: String = null
   var rootTries = 0
 
+  def getDNS(): String = {
+    val dns1 = System.getDNS1
+    if (dns1 != null && !dns1.isEmpty && InetAddressUtils.isIPv4Address(dns1)) {
+      dns1
+    } else {
+      "114.114.114.114"
+    }
+  }
+
   def getSignature(context: Context): String = {
     val info = context
       .getPackageManager