Add build target for NetworkStack on API 29

NetworkStack will need at least two different build targets: one for the
in-progress SDK for testing before release, and one for the latest
released SDK for releasing to production.

The difference in available APIs is abstracted from the core code by
using shims, with one shim for the released SDK that uses fallback code,
and one shim for the in-progress SDK that calls the actual new API.
The shim included in the built code depends on the build target.

AOSP does not yet have prebuilts for API 29, so the build rule still
references system_current for now.

Test: atest NetworkStackTests
Test: flashed, WiFi working
Test: aapt dump xmltree NetworkStack.apk AndroidManifest.xml: no change
Test: m NetworkStackApiStable (on a branch that has the prebuilt SDK)
Change-Id: I9cf8e712b56a8aad8656eb5095ac8a32f4a05037

1 files changed, 49 insertions, 0 deletions

diff --git a/src/com/android/networkstack/apishim/SocketUtilsShim.java b/src/com/android/networkstack/apishim/SocketUtilsShim.java
new file mode 100644
index 0000000..34b5f40
--- /dev/null
+++ b/src/com/android/networkstack/apishim/SocketUtilsShim.java
@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 2019 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 com.android.networkstack.apishim;
+
+import androidx.annotation.NonNull;
+
+import java.net.SocketAddress;
+
+/**
+ * Interface used to access API methods in {@link android.net.util.SocketUtils}, with appropriate
+ * fallbacks if the methods are not yet part of the released API.
+ *
+ * <p>This interface makes it easier for callers to use SocketUtilsShimImpl, as it's more obvious
+ * what methods must be implemented on each API level, and it abstracts from callers the need to
+ * reference classes that have different implementations (which also does not work well with IDEs).
+ */
+public interface SocketUtilsShim {
+    /**
+     * Create a new instance of SocketUtilsShim.
+     */
+    @NonNull
+    static SocketUtilsShim newInstance() {
+        // TODO: when the R API is finalized, rename the API 29 shim to SocketUtilsCompat, and
+        // return it here instead of SocketUtilsShimImpl for devices with Build.VERSION <= 29.
+        // For now, the switch between implementations is done at build time (swapping the java file
+        // with another), since production modules should not be built with a non-finalized API.
+        return new SocketUtilsShimImpl();
+    }
+
+    /**
+     * @see android.net.util.SocketUtils#makePacketSocketAddress(int, int, byte[])
+     */
+    @NonNull
+    SocketAddress makePacketSocketAddress(int protocol, int ifIndex, @NonNull byte[] hwAddr);
+}