Program offload-exempt local prefixes into the HAL

Additionally:
    - move mOffloadController into MasterTetherSM

Test: as follows
    - built
    - flashed
    - booted
    - "runtest frameworks-net" passes
    - observed calls to the HAL setLocalPrefixes in tethering log
Bug: 29337859
Bug: 32163131
Change-Id: Ifaf23c6179ead9de6ccfcf41e0c203025153167b

services/net/java/android/net/util/PrefixUtils.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2017 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.net.IpPrefix;
+import android.net.LinkAddress;
+import android.net.LinkProperties;
+
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Set;
+
+
+/**
+ * @hide
+ */
+public class PrefixUtils {
+    private static final IpPrefix[] MIN_NON_FORWARDABLE_PREFIXES = {
+            pfx("127.0.0.0/8"),     // IPv4 loopback
+            pfx("169.254.0.0/16"),  // IPv4 link-local, RFC3927#section-8
+            pfx("::/3"),
+            pfx("fe80::/64"),       // IPv6 link-local
+            pfx("fc00::/7"),        // IPv6 ULA
+            pfx("ff02::/8"),        // IPv6 link-local multicast
+    };
+
+    public static final IpPrefix DEFAULT_WIFI_P2P_PREFIX = pfx("192.168.49.0/24");
+
+    public static Set<IpPrefix> getNonForwardablePrefixes() {
+        final HashSet<IpPrefix> prefixes = new HashSet<>();
+        addNonForwardablePrefixes(prefixes);
+        return prefixes;
+    }
+
+    public static void addNonForwardablePrefixes(Set<IpPrefix> prefixes) {
+        Collections.addAll(prefixes, MIN_NON_FORWARDABLE_PREFIXES);
+    }
+
+    public static Set<IpPrefix> localPrefixesFrom(LinkProperties lp) {
+        final HashSet<IpPrefix> localPrefixes = new HashSet<>();
+        if (lp == null) return localPrefixes;
+
+        for (LinkAddress addr : lp.getAllLinkAddresses()) {
+            if (addr.getAddress().isLinkLocalAddress()) continue;
+            localPrefixes.add(asIpPrefix(addr));
+        }
+        // TODO: Add directly-connected routes as well (ones from which we did
+        // not also form a LinkAddress)?
+
+        return localPrefixes;
+    }
+
+    public static IpPrefix asIpPrefix(LinkAddress addr) {
+        return new IpPrefix(addr.getAddress(), addr.getPrefixLength());
+    }
+
+    private static IpPrefix pfx(String prefixStr) {
+        return new IpPrefix(prefixStr);
+    }
+}