tethering: DAD Proxy Daemon

DAD proxy daemon responsible for forwarding NS/NA between
tethered iface and upstream iface.

Change-Id: I2e58e10e7fa7dba6a6f63ad03b000549f3afc37e

Tethering/src/android/net/util/TetheringUtils.java

@@ -17,11 +17,15 @@ package android.net.util;
 
 import android.net.TetherStatsParcel;
 import android.net.TetheringRequestParcel;
+import android.util.Log;
 
 import androidx.annotation.NonNull;
 
 import java.io.FileDescriptor;
+import java.net.Inet6Address;
 import java.net.SocketException;
+import java.net.UnknownHostException;
+import java.util.Arrays;
 import java.util.Objects;
 
 /**
@@ -30,6 +34,24 @@ import java.util.Objects;
  * {@hide}
  */
 public class TetheringUtils {
+    public static final byte[] ALL_NODES = new byte[] {
+        (byte) 0xff, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1
+    };
+
+    /**
+     * Configures a socket for receiving and sending ICMPv6 neighbor advertisments.
+     * @param fd the socket's {@link FileDescriptor}.
+     */
+    public static native void setupNaSocket(FileDescriptor fd)
+            throws SocketException;
+
+    /**
+     * Configures a socket for receiving and sending ICMPv6 neighbor solicitations.
+     * @param fd the socket's {@link FileDescriptor}.
+     */
+    public static native void setupNsSocket(FileDescriptor fd)
+            throws SocketException;
+
     /**
      *  The object which records offload Tx/Rx forwarded bytes/packets.
      *  TODO: Replace the inner class ForwardedStats of class OffloadHardwareInterface with
@@ -129,4 +151,15 @@ public class TetheringUtils {
                 && request.exemptFromEntitlementCheck == otherRequest.exemptFromEntitlementCheck
                 && request.showProvisioningUi == otherRequest.showProvisioningUi;
     }
+
+    /** Get inet6 address for all nodes given scope ID. */
+    public static Inet6Address getAllNodesForScopeId(int scopeId) {
+        try {
+            return Inet6Address.getByAddress("ff02::1", ALL_NODES, scopeId);
+        } catch (UnknownHostException uhe) {
+            Log.wtf("TetheringUtils", "Failed to construct Inet6Address from "
+                    + Arrays.toString(ALL_NODES) + " and scopedId " + scopeId);
+            return null;
+        }
+    }
 }