[Tether03] Migrate IpServer into module

Add IpServer which is used to serve ip configuration, dhcp, dns proxy
and nat for downstream interface.

Bug: 136040414
Test: -build, flash, boot
      -atest TetheringTests
      -atest FrameworksNetTests

Change-Id: I23652ae0b9509abe7d38da96d523eb22ab00a343
diff --git a/Tethering/src/android/net/dhcp/DhcpServerCallbacks.java b/Tethering/src/android/net/dhcp/DhcpServerCallbacks.java
new file mode 100644
index 0000000..7c41377
--- /dev/null
+++ b/Tethering/src/android/net/dhcp/DhcpServerCallbacks.java
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * 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 android.net.dhcp;
+
+/**
+ * Convenience wrapper around IDhcpServerCallbacks.Stub that implements getInterfaceVersion().
+ * @hide
+ */
+public abstract class DhcpServerCallbacks extends IDhcpServerCallbacks.Stub {
+    /**
+     * Get the version of the aidl interface implemented by the callbacks.
+     */
+    @Override
+    public int getInterfaceVersion() {
+        return IDhcpServerCallbacks.VERSION;
+    }
+}