Add an IS_DESTROYED flag to FullScore.

This is being added as the lowest priority score factor, just
above the tie-breakers. It ensures that a network that has been
destroyed will lose to another identical network that has not
been destroyed, but will otherwise be scored identically.

The flag is a CS-managed flag that is stored in NetworkAgentInfo.
Currently it is always false, but it will be populated in
future CLs.

Bug: 216567577
Test: atest FrameworksNetTests
Change-Id: Ib1cd342ab7dfc4df45715da19b743d711fe8d605

service/src/com/android/server/connectivity/FullScore.java

@@ -98,9 +98,17 @@ public class FullScore {
     /** @hide */
     public static final int POLICY_EVER_VALIDATED_NOT_AVOIDED_WHEN_BAD = 57;
 
+    // The network agent has communicated that this network no longer functions, and the underlying
+    // native network has been destroyed. The network will still be reported to clients as connected
+    // until a timeout expires, the agent disconnects, or the network no longer satisfies requests.
+    // This network should lose to an identical network that has not been destroyed, but should
+    // otherwise be scored exactly the same.
+    /** @hide */
+    public static final int POLICY_IS_DESTROYED = 56;
+
     // To help iterate when printing
     @VisibleForTesting
-    static final int MIN_CS_MANAGED_POLICY = POLICY_EVER_VALIDATED_NOT_AVOIDED_WHEN_BAD;
+    static final int MIN_CS_MANAGED_POLICY = POLICY_IS_DESTROYED;
     @VisibleForTesting
     static final int MAX_CS_MANAGED_POLICY = POLICY_IS_VALIDATED;
 
@@ -142,6 +150,7 @@ public class FullScore {
      * @param config the NetworkAgentConfig of the network
      * @param everValidated whether this network has ever validated
      * @param yieldToBadWiFi whether this network yields to a previously validated wifi gone bad
+     * @param destroyed whether this network has been destroyed pending a replacement connecting
      * @return a FullScore that is appropriate to use for ranking.
      */
     // TODO : this shouldn't manage bad wifi avoidance – instead this should be done by the
@@ -149,7 +158,7 @@ public class FullScore {
     // connectivity for backward compatibility.
     public static FullScore fromNetworkScore(@NonNull final NetworkScore score,
             @NonNull final NetworkCapabilities caps, @NonNull final NetworkAgentConfig config,
-            final boolean everValidated, final boolean yieldToBadWiFi) {
+            final boolean everValidated, final boolean yieldToBadWiFi, final boolean destroyed) {
         return withPolicies(score.getLegacyInt(), score.getPolicies(),
                 score.getKeepConnectedReason(),
                 caps.hasCapability(NET_CAPABILITY_VALIDATED),
@@ -159,6 +168,7 @@ public class FullScore {
                 config.explicitlySelected,
                 config.acceptUnvalidated,
                 yieldToBadWiFi,
+                destroyed,
                 false /* invincible */); // only prospective scores can be invincible
     }
 
@@ -167,7 +177,7 @@ public class FullScore {
      *
      * NetworkOffers have score filters that are compared to the scores of actual networks
      * to see if they could possibly beat the current satisfier. Some things the agent can't
-     * know in advance ; a good example is the validation bit – some networks will validate,
+     * know in advance; a good example is the validation bit – some networks will validate,
      * others won't. For comparison purposes, assume the best, so all possibly beneficial
      * networks will be brought up.
      *
@@ -190,12 +200,14 @@ public class FullScore {
         final boolean everUserSelected = false;
         // Don't assume the user will accept unvalidated connectivity.
         final boolean acceptUnvalidated = false;
+        // A network can only be destroyed once it has connected.
+        final boolean destroyed = false;
         // A prospective score is invincible if the legacy int in the filter is over the maximum
         // score.
         final boolean invincible = score.getLegacyInt() > NetworkRanker.LEGACY_INT_MAX;
         return withPolicies(score.getLegacyInt(), score.getPolicies(), KEEP_CONNECTED_NONE,
                 mayValidate, vpn, unmetered, everValidated, everUserSelected, acceptUnvalidated,
-                yieldToBadWiFi, invincible);
+                yieldToBadWiFi, destroyed, invincible);
     }
 
     /**
@@ -211,7 +223,8 @@ public class FullScore {
     public FullScore mixInScore(@NonNull final NetworkCapabilities caps,
             @NonNull final NetworkAgentConfig config,
             final boolean everValidated,
-            final boolean yieldToBadWifi) {
+            final boolean yieldToBadWifi,
+            final boolean destroyed) {
         return withPolicies(mLegacyInt, mPolicies, mKeepConnectedReason,
                 caps.hasCapability(NET_CAPABILITY_VALIDATED),
                 caps.hasTransport(TRANSPORT_VPN),
@@ -220,6 +233,7 @@ public class FullScore {
                 config.explicitlySelected,
                 config.acceptUnvalidated,
                 yieldToBadWifi,
+                destroyed,
                 false /* invincible */); // only prospective scores can be invincible
     }
 
@@ -236,6 +250,7 @@ public class FullScore {
             final boolean everUserSelected,
             final boolean acceptUnvalidated,
             final boolean yieldToBadWiFi,
+            final boolean destroyed,
             final boolean invincible) {
         return new FullScore(legacyInt, (externalPolicies & EXTERNAL_POLICIES_MASK)
                 | (isValidated       ? 1L << POLICY_IS_VALIDATED : 0)
@@ -245,6 +260,7 @@ public class FullScore {
                 | (everUserSelected  ? 1L << POLICY_EVER_USER_SELECTED : 0)
                 | (acceptUnvalidated ? 1L << POLICY_ACCEPT_UNVALIDATED : 0)
                 | (yieldToBadWiFi    ? 1L << POLICY_YIELD_TO_BAD_WIFI : 0)
+                | (destroyed         ? 1L << POLICY_IS_DESTROYED : 0)
                 | (invincible        ? 1L << POLICY_IS_INVINCIBLE : 0),
                 keepConnectedReason);
     }

service/src/com/android/server/connectivity/NetworkAgentInfo.java

@@ -106,6 +106,12 @@ import java.util.TreeSet;
 //       or tunnel) but does not disconnect from the AP/cell tower, or
 //    d. a stand-alone device offering a WiFi AP without an uplink for configuration purposes.
 // 5. registered, created, connected, validated
+// 6. registered, created, connected, (validated or unvalidated), destroyed
+//    This is an optional state where the underlying native network is destroyed but the network is
+//    still connected for scoring purposes, so can satisfy requests, including the default request.
+//    It is used when the transport layer wants to replace a network with another network (e.g.,
+//    when Wi-Fi has roamed to a different BSSID that is part of a different L3 network) and does
+//    not want the device to switch to another network until the replacement connects and validates.
 //
 // The device's default network connection:
 // ----------------------------------------
@@ -184,6 +190,9 @@ public class NetworkAgentInfo implements Comparable<NetworkAgentInfo>, NetworkRa
     // shows up in API calls, is able to satisfy NetworkRequests and can become the default network.
     // This is a sticky bit; once set it is never cleared.
     public boolean everConnected;
+    // Whether this network has been destroyed and is being kept temporarily until it is replaced.
+    public boolean destroyed;
+
     // Set to true if this Network successfully passed validation or if it did not satisfy the
     // default NetworkRequest in which case validation will not be attempted.
     // This is a sticky bit; once set it is never cleared even if future validation attempts fail.
@@ -746,7 +755,7 @@ public class NetworkAgentInfo implements Comparable<NetworkAgentInfo>, NetworkRa
         final NetworkCapabilities oldNc = networkCapabilities;
         networkCapabilities = nc;
         mScore = mScore.mixInScore(networkCapabilities, networkAgentConfig, everValidatedForYield(),
-                yieldToBadWiFi());
+                yieldToBadWiFi(), destroyed);
         final NetworkMonitorManager nm = mNetworkMonitor;
         if (nm != null) {
             nm.notifyNetworkCapabilitiesChanged(nc);
@@ -961,7 +970,7 @@ public class NetworkAgentInfo implements Comparable<NetworkAgentInfo>, NetworkRa
      */
     public void setScore(final NetworkScore score) {
         mScore = FullScore.fromNetworkScore(score, networkCapabilities, networkAgentConfig,
-                everValidatedForYield(), yieldToBadWiFi());
+                everValidatedForYield(), yieldToBadWiFi(), destroyed);
     }
 
     /**
@@ -971,7 +980,7 @@ public class NetworkAgentInfo implements Comparable<NetworkAgentInfo>, NetworkRa
      */
     public void updateScoreForNetworkAgentUpdate() {
         mScore = mScore.mixInScore(networkCapabilities, networkAgentConfig,
-                everValidatedForYield(), yieldToBadWiFi());
+                everValidatedForYield(), yieldToBadWiFi(), destroyed);
     }
 
     private boolean everValidatedForYield() {

service/src/com/android/server/connectivity/NetworkRanker.java

@@ -28,6 +28,7 @@ import static com.android.net.module.util.CollectionUtils.filter;
 import static com.android.server.connectivity.FullScore.POLICY_ACCEPT_UNVALIDATED;
 import static com.android.server.connectivity.FullScore.POLICY_EVER_USER_SELECTED;
 import static com.android.server.connectivity.FullScore.POLICY_EVER_VALIDATED_NOT_AVOIDED_WHEN_BAD;
+import static com.android.server.connectivity.FullScore.POLICY_IS_DESTROYED;
 import static com.android.server.connectivity.FullScore.POLICY_IS_INVINCIBLE;
 import static com.android.server.connectivity.FullScore.POLICY_IS_VALIDATED;
 import static com.android.server.connectivity.FullScore.POLICY_IS_VPN;
@@ -263,6 +264,15 @@ public class NetworkRanker {
             }
         }
 
+        // If two networks are equivalent, and one has been destroyed pending replacement, keep the
+        // other one. This ensures that when the replacement connects, it's preferred.
+        partitionInto(candidates, nai -> !nai.getScore().hasPolicy(POLICY_IS_DESTROYED),
+                accepted, rejected);
+        if (accepted.size() == 1) return accepted.get(0);
+        if (accepted.size() > 0 && rejected.size() > 0) {
+            candidates = new ArrayList<>(accepted);
+        }
+
         // At this point there are still multiple networks passing all the tests above. If any
         // of them is the previous satisfier, keep it.
         if (candidates.contains(currentSatisfier)) return currentSatisfier;

tests/unit/java/com/android/server/connectivity/FullScoreTest.kt

@@ -26,6 +26,7 @@ import androidx.test.filters.SmallTest
 import com.android.server.connectivity.FullScore.MAX_CS_MANAGED_POLICY
 import com.android.server.connectivity.FullScore.POLICY_ACCEPT_UNVALIDATED
 import com.android.server.connectivity.FullScore.POLICY_EVER_USER_SELECTED
+import com.android.server.connectivity.FullScore.POLICY_IS_DESTROYED
 import com.android.server.connectivity.FullScore.POLICY_IS_UNMETERED
 import com.android.server.connectivity.FullScore.POLICY_IS_VALIDATED
 import com.android.server.connectivity.FullScore.POLICY_IS_VPN
@@ -48,7 +49,8 @@ class FullScoreTest {
         validated: Boolean = false,
         vpn: Boolean = false,
         onceChosen: Boolean = false,
-        acceptUnvalidated: Boolean = false
+        acceptUnvalidated: Boolean = false,
+        destroyed: Boolean = false
     ): FullScore {
         val nac = NetworkAgentConfig.Builder().apply {
             setUnvalidatedConnectivityAcceptable(acceptUnvalidated)
@@ -58,7 +60,7 @@ class FullScoreTest {
             if (vpn) addTransportType(NetworkCapabilities.TRANSPORT_VPN)
             if (validated) addCapability(NetworkCapabilities.NET_CAPABILITY_VALIDATED)
         }.build()
-        return mixInScore(nc, nac, validated, false /* yieldToBadWifi */)
+        return mixInScore(nc, nac, validated, false /* yieldToBadWifi */, destroyed)
     }
 
     @Test
@@ -120,6 +122,7 @@ class FullScoreTest {
         assertTrue(ns.withPolicies(vpn = true).hasPolicy(POLICY_IS_VPN))
         assertTrue(ns.withPolicies(onceChosen = true).hasPolicy(POLICY_EVER_USER_SELECTED))
         assertTrue(ns.withPolicies(acceptUnvalidated = true).hasPolicy(POLICY_ACCEPT_UNVALIDATED))
+        assertTrue(ns.withPolicies(destroyed = true).hasPolicy(POLICY_IS_DESTROYED))
     }
 
     @Test