Fix addRoute replace default route unexpectedly

In aosp/1203789, if two routes are with the same destination,
it will be replaced instead of added when calling addRoute.
This breaks scenarios which rely on the ability to add multiple
default routes, such as multiple IPv6 default routes learned
via address autoconfiguration.

This change treats the route is an update if the destination
and nexthop are the same, but different in other properties.

Test: atest OffloadControllerTest#testSetUpstreamLinkPropertiesWorking
Test: atest LinkPropertiesUtilsTest#testLinkPropertiesIdenticalEqual
Test: atest ConnectivityServiceTest#testStackedLinkProperties
Test: atest ConnectivityServiceTest#testRouteAddDeleteUpdate
  (only directly related tests are listed)
Fix: 152170074
Fix: 151911339
Bug: 142892223

Change-Id: I7153ec9866f14a109ba8155c905e5d9e4f85eb64

2 files changed, 26 insertions, 21 deletions

diff --git a/core/java/android/net/LinkProperties.java b/core/java/android/net/LinkProperties.java
index 2c356e43d9fe..7ff954bdc1d2 100644
--- a/core/java/android/net/LinkProperties.java
+++ b/core/java/android/net/LinkProperties.java
@@ -690,9 +690,9 @@ public final class LinkProperties implements Parcelable {
             route.getMtu());
     }
 
-    private int findRouteIndexByDestination(RouteInfo route) {
+    private int findRouteIndexByRouteKey(RouteInfo route) {
         for (int i = 0; i < mRoutes.size(); i++) {
-            if (mRoutes.get(i).isSameDestinationAs(route)) {
+            if (mRoutes.get(i).getRouteKey().equals(route.getRouteKey())) {
                 return i;
             }
         }
@@ -701,11 +701,11 @@ public final class LinkProperties implements Parcelable {
 
     /**
      * Adds a {@link RouteInfo} to this {@code LinkProperties}, if a {@link RouteInfo}
-     * with the same destination exists with different properties (e.g., different MTU),
-     * it will be updated. 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}.
+     * with the same {@link RouteInfo.RouteKey} with different properties
+     * (e.g., different MTU), it will be updated. 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 true} was added or updated, false otherwise.
@@ -719,7 +719,7 @@ public final class LinkProperties implements Parcelable {
         }
         route = routeWithInterface(route);
 
-        int i = findRouteIndexByDestination(route);
+        int i = findRouteIndexByRouteKey(route);
         if (i == -1) {
             // Route was not present. Add it.
             mRoutes.add(route);
diff --git a/core/java/android/net/RouteInfo.java b/core/java/android/net/RouteInfo.java
index fec2df412adb..dbdaa4c2da67 100644
--- a/core/java/android/net/RouteInfo.java
+++ b/core/java/android/net/RouteInfo.java
@@ -26,6 +26,7 @@ import android.net.util.NetUtils;
 import android.os.Build;
 import android.os.Parcel;
 import android.os.Parcelable;
+import android.util.Pair;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -527,23 +528,27 @@ public final class RouteInfo implements Parcelable {
     }
 
     /**
-     * Compares this RouteInfo object against the specified object and indicates if the
-     * destinations of both routes are equal.
-     * @return {@code true} if the route destinations are equal, {@code false} otherwise.
+     * A helper class that contains the destination and the gateway in a {@code RouteInfo},
+     * used by {@link ConnectivityService#updateRoutes} or
+     * {@link LinkProperties#addRoute} to calculate the list to be updated.
      *
      * @hide
      */
-    public boolean isSameDestinationAs(@Nullable Object obj) {
-        if (this == obj) return true;
-
-        if (!(obj instanceof RouteInfo)) return false;
-
-        RouteInfo target = (RouteInfo) obj;
-
-        if (Objects.equals(mDestination, target.getDestination())) {
-            return true;
+    public static class RouteKey extends Pair<IpPrefix, InetAddress> {
+        RouteKey(@NonNull IpPrefix destination, @Nullable InetAddress gateway) {
+            super(destination, gateway);
         }
-        return false;
+    }
+
+    /**
+     * Get {@code RouteKey} of this {@code RouteInfo}.
+     * @return a {@code RouteKey} object.
+     *
+     * @hide
+     */
+    @NonNull
+    public RouteKey getRouteKey() {
+        return new RouteKey(mDestination, mGateway);
     }
 
     /**