Add a protectFromVpn method that takes a FileDescriptor

Bug: 19704592
Change-Id: I9aeb29c2f6cf55fa010bc606c99b21a797ac5a19

core/java/android/net/NetworkUtils.java

@@ -177,6 +177,15 @@ public class NetworkUtils {
      */
     public native static int bindSocketToNetwork(int socketfd, int netId);
 
+    /**
+     * Protect {@code fd} from VPN connections.  After protecting, data sent through
+     * this socket will go directly to the underlying network, so its traffic will not be
+     * forwarded through the VPN.
+     */
+    public static boolean protectFromVpn(FileDescriptor fd) {
+        return protectFromVpn(fd.getInt$());
+    }
+
     /**
      * Protect {@code socketfd} from VPN connections.  After protecting, data sent through
      * this socket will go directly to the underlying network, so its traffic will not be