Modify LinkProperties add/remove route functions.

This will allow us to dynamically track routes being added and
removed, similar to what we do for IP addresses.

1. Support removing routes. Since this is a new function, we
   don't need to jump through hoops to support callers passing
   in routes that have no interface, we just fail to match them.
2. Make the addRoute method return a boolean value indicating
   whether anything changed. This is consistent with what we do
   for addresses and is used to decide whether to update the
   rest of the system when an update comes in.

Bug: 9180552
Change-Id: I50648b5f81ec55c88501a7640e119cda2bb540f2

core/java/android/net/LinkProperties.java

@@ -31,6 +31,7 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.Hashtable;
 import java.util.List;
+import java.util.Objects;
 
 /**
  * Describes the properties of a network link.
@@ -334,15 +335,17 @@ public final class LinkProperties implements Parcelable {
     }
 
     /**
-     * Adds a {@link RouteInfo} to this {@code LinkProperties}.  If the {@link RouteInfo}
-     * had an interface name set and that differs from the interface set for this
-     * {@code LinkProperties} an {@link IllegalArgumentException} will be thrown.  The
-     * proper course is to add either un-named or properly named {@link RouteInfo}.
+     * Adds a {@link RouteInfo} to this {@code LinkProperties}, if not present. If the
+     * {@link RouteInfo} had an interface name set and that differs from the interface set for this
+     * {@code LinkProperties} an {@link IllegalArgumentException} will be thrown.  The proper
+     * course is to add either un-named or properly named {@link RouteInfo}.
      *
      * @param route A {@link RouteInfo} to add to this object.
+     * @return {@code false} if the route was already present, {@code true} if it was added.
+     *
      * @hide
      */
-    public void addRoute(RouteInfo route) {
+    public boolean addRoute(RouteInfo route) {
         if (route != null) {
             String routeIface = route.getInterface();
             if (routeIface != null && !routeIface.equals(mIfaceName)) {
@@ -350,8 +353,28 @@ public final class LinkProperties implements Parcelable {
                    "Route added with non-matching interface: " + routeIface +
                    " vs. " + mIfaceName);
             }
-            mRoutes.add(routeWithInterface(route));
+            route = routeWithInterface(route);
+            if (!mRoutes.contains(route)) {
+                mRoutes.add(route);
+                return true;
+            }
         }
+        return false;
+    }
+
+    /**
+     * Removes a {@link RouteInfo} from this {@code LinkProperties}, if present. The route must
+     * specify an interface and the interface must match the interface of this
+     * {@code LinkProperties}, or it will not be removed.
+     *
+     * @return {@code true} if the route was removed, {@code false} if it was not present.
+     *
+     * @hide
+     */
+    public boolean removeRoute(RouteInfo route) {
+        return route != null &&
+                Objects.equals(mIfaceName, route.getInterface()) &&
+                mRoutes.remove(route);
     }
 
     /**