Add NetUtils to net static library

This class includes network common utilities.

Bug: 139268426
Bug: 135998869
Bug: 138306002
Bug: 143925787
Test: build lib pass
      atest NetworkStaticLibTests
Change-Id: I1ffe723aa4ff2ed7bc46f34106701c91fe93032a
diff --git a/staticlibs/src_frameworkcommon/android/net/util/NetUtils.java b/staticlibs/src_frameworkcommon/android/net/util/NetUtils.java
new file mode 100644
index 0000000..e006590
--- /dev/null
+++ b/staticlibs/src_frameworkcommon/android/net/util/NetUtils.java
@@ -0,0 +1,69 @@
+/*
+ * Copyright 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 android.net.util;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.net.RouteInfo;
+
+import java.net.Inet4Address;
+import java.net.Inet6Address;
+import java.net.InetAddress;
+import java.util.Collection;
+
+/**
+ * Collection of network common utilities.
+ */
+public final class NetUtils {
+
+    /**
+     * Check if IP address type is consistent between two InetAddress.
+     * @return true if both are the same type. False otherwise.
+     */
+    public static boolean addressTypeMatches(@NonNull InetAddress left,
+            @NonNull InetAddress right) {
+        return (((left instanceof Inet4Address) && (right instanceof Inet4Address))
+                || ((left instanceof Inet6Address) && (right instanceof Inet6Address)));
+    }
+
+    /**
+     * Find the route from a Collection of routes that best matches a given address.
+     * May return null if no routes are applicable.
+     * @param routes a Collection of RouteInfos to chose from
+     * @param dest the InetAddress your trying to get to
+     * @return the RouteInfo from the Collection that best fits the given address
+     */
+    @Nullable
+    public static RouteInfo selectBestRoute(@Nullable Collection<RouteInfo> routes,
+            @Nullable InetAddress dest) {
+        if ((routes == null) || (dest == null)) return null;
+
+        RouteInfo bestRoute = null;
+        // pick a longest prefix match under same address type
+        for (RouteInfo route : routes) {
+            if (addressTypeMatches(route.getDestination().getAddress(), dest)) {
+                if ((bestRoute != null)
+                        && (bestRoute.getDestination().getPrefixLength()
+                        >= route.getDestination().getPrefixLength())) {
+                    continue;
+                }
+                if (route.matches(dest)) bestRoute = route;
+            }
+        }
+        return bestRoute;
+    }
+}
diff --git a/staticlibs/tests/unit/src/android/net/util/NetUtilsTest.java b/staticlibs/tests/unit/src/android/net/util/NetUtilsTest.java
new file mode 100644
index 0000000..903e80d
--- /dev/null
+++ b/staticlibs/tests/unit/src/android/net/util/NetUtilsTest.java
@@ -0,0 +1,105 @@
+/*
+ * 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 android.net.util;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertTrue;
+
+import android.net.InetAddresses;
+import android.net.IpPrefix;
+import android.net.RouteInfo;
+
+import androidx.test.runner.AndroidJUnit4;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import java.net.InetAddress;
+import java.util.ArrayList;
+import java.util.List;
+
+@RunWith(AndroidJUnit4.class)
+public final class NetUtilsTest {
+    private static final InetAddress V4_ADDR1 = toInetAddress("75.208.7.1");
+    private static final InetAddress V4_ADDR2 = toInetAddress("75.208.7.2");
+    private static final InetAddress V6_ADDR1 = toInetAddress("2001:0db8:85a3::8a2e:0370:7334");
+    private static final InetAddress V6_ADDR2 = toInetAddress("2001:0db8:85a3::8a2e:0370:7335");
+
+    private static final InetAddress V4_GATEWAY = toInetAddress("75.208.8.1");
+    private static final InetAddress V6_GATEWAY = toInetAddress("fe80::6:0000:613");
+
+    private static InetAddress toInetAddress(String addr) {
+        return InetAddresses.parseNumericAddress(addr);
+    }
+    @Test
+    public void testAddressTypeMatches() {
+        assertTrue(NetUtils.addressTypeMatches(V4_ADDR1, V4_ADDR2));
+        assertTrue(NetUtils.addressTypeMatches(V6_ADDR1, V6_ADDR2));
+        assertFalse(NetUtils.addressTypeMatches(V4_ADDR1, V6_ADDR1));
+        assertFalse(NetUtils.addressTypeMatches(V6_ADDR1, V4_ADDR1));
+    }
+
+    @Test
+    public void testSelectBestRoute() {
+        final List<RouteInfo> routes = new ArrayList<>();
+        final InetAddress v4_dest = InetAddresses.parseNumericAddress("75.208.8.15");
+        final InetAddress v6_dest = InetAddresses.parseNumericAddress("2001:db8:cafe::123");
+
+        RouteInfo route = NetUtils.selectBestRoute(null, v4_dest);
+        assertEquals(null, route);
+        route = NetUtils.selectBestRoute(routes, null);
+        assertEquals(null, route);
+
+        route = NetUtils.selectBestRoute(routes, v4_dest);
+        assertEquals(null, route);
+
+        final RouteInfo v4_expected = new RouteInfo(new IpPrefix("75.208.8.10/24"),
+                V4_GATEWAY, "wlan0");
+        routes.add(v4_expected);
+        // "75.208.8.10/16" is not an expected result since it is not the longest prefix.
+        routes.add(new RouteInfo(new IpPrefix("75.208.8.10/16"), V4_GATEWAY, "wlan0"));
+        routes.add(new RouteInfo(new IpPrefix("75.208.7.32/24"), V4_GATEWAY, "wlan0"));
+
+        final RouteInfo v6_expected = new RouteInfo(new IpPrefix("2001:db8:cafe::/64"),
+                V6_GATEWAY, "wlan0");
+        routes.add(v6_expected);
+        // "2001:db8:cafe::123/32" is not an expected result since it is not the longest prefix.
+        routes.add(new RouteInfo(new IpPrefix("2001:db8:cafe::123/32"), V6_GATEWAY, "wlan0"));
+        routes.add(new RouteInfo(new IpPrefix("2001:db8:beef::/64"), V6_GATEWAY, "wlan0"));
+
+        // Verify expected v4 route is selected
+        route = NetUtils.selectBestRoute(routes, v4_dest);
+        assertEquals(v4_expected, route);
+
+        // Verify expected v6 route is selected
+        route = NetUtils.selectBestRoute(routes, v6_dest);
+        assertEquals(v6_expected, route);
+
+        // Remove expected v4 route
+        routes.remove(v4_expected);
+        route = NetUtils.selectBestRoute(routes, v4_dest);
+        assertNotEquals(v4_expected, route);
+
+        // Remove expected v6 route
+        routes.remove(v6_expected);
+        route = NetUtils.selectBestRoute(routes, v4_dest);
+        assertNotEquals(v6_expected, route);
+    }
+}
+