Introduce an overlay for actively preferring bad wifi.

This correctly updates when the mcc/mnc change.

Test: MultinetworkPolicyTrackerTest
Change-Id: I11c7ea7074a15975fb68d39eb3c728778d84a516
diff --git a/framework/src/android/net/util/MultinetworkPolicyTracker.java b/framework/src/android/net/util/MultinetworkPolicyTracker.java
index 2dcf932..4217921 100644
--- a/framework/src/android/net/util/MultinetworkPolicyTracker.java
+++ b/framework/src/android/net/util/MultinetworkPolicyTracker.java
@@ -39,6 +39,7 @@
 import android.util.Log;
 
 import com.android.internal.annotations.VisibleForTesting;
+import com.android.modules.utils.build.SdkLevel;
 
 import java.util.Arrays;
 import java.util.List;
@@ -79,6 +80,29 @@
     private int mActiveSubId = SubscriptionManager.INVALID_SUBSCRIPTION_ID;
     private volatile long mTestAllowBadWifiUntilMs = 0;
 
+    /**
+     * Whether to prefer bad wifi to a network that yields to bad wifis, even if it never validated
+     *
+     * This setting only makes sense if the system is configured not to avoid bad wifis, i.e.
+     * if mAvoidBadWifi is true. If it's not, then no network ever yields to bad wifis
+     * ({@see FullScore#POLICY_YIELD_TO_BAD_WIFI}) and this setting has therefore no effect.
+     *
+     * If this is false, when ranking a bad wifi that never validated against cell data (or any
+     * network that yields to bad wifis), the ranker will prefer cell data. It will prefer wifi
+     * if wifi loses validation later. This behavior avoids the device losing internet access when
+     * walking past a wifi network with no internet access.
+     * This is the default behavior up to Android T, but it can be overridden through an overlay
+     * to behave like below.
+     *
+     * If this is true, then in the same scenario, the ranker will prefer cell data until
+     * the wifi completes its first validation attempt (or the attempt times out after
+     * ConnectivityService#PROMPT_UNVALIDATED_DELAY_MS), then it will prefer the wifi even if it
+     * doesn't provide internet access, unless there is a captive portal on that wifi.
+     * This is the behavior in U and above.
+     */
+    // TODO : implement the behavior.
+    private boolean mActivelyPreferBadWifi;
+
     // Mainline module can't use internal HandlerExecutor, so add an identical executor here.
     private static class HandlerExecutor implements Executor {
         @NonNull
@@ -158,6 +182,10 @@
         return mAvoidBadWifi;
     }
 
+    public boolean getActivelyPreferBadWifi() {
+        return mActivelyPreferBadWifi;
+    }
+
     // TODO: move this to MultipathPolicyTracker.
     public int getMeteredMultipathPreference() {
         return mMeteredMultipathPreference;
@@ -180,6 +208,29 @@
     }
 
     /**
+     * Whether the device config prefers bad wifi actively, when it doesn't avoid them
+     *
+     * This is only relevant when the device is configured not to avoid bad wifis. In this
+     * case, "actively" preferring a bad wifi means that the device will switch to a bad
+     * wifi it just connected to, as long as it's not a captive portal.
+     *
+     * On U and above this always returns true. On T and below it reads a configuration option.
+     */
+    public boolean configActivelyPrefersBadWifi() {
+        // See the definition of config_activelyPreferBadWifi for a description of its meaning.
+        // On U and above, the config is ignored, and bad wifi is always actively preferred.
+        if (SdkLevel.isAtLeastU()) return true;
+        // TODO: use R.integer.config_activelyPreferBadWifi directly
+        final int id = mResources.get().getIdentifier("config_activelyPreferBadWifi",
+                "integer", mResources.getResourcesContext().getPackageName());
+        // On T and below, 1 means to actively prefer bad wifi, 0 means not to prefer
+        // bad wifi (only stay stuck on it if already on there). This implementation treats
+        // any non-0 value like 1, on the assumption that anybody setting it non-zero wants
+        // the newer behavior.
+        return 0 != getResourcesForActiveSubId().getInteger(id);
+    }
+
+    /**
      * Temporarily allow bad wifi to override {@code config_networkAvoidBadWifi} configuration.
      * The value works when the time set is more than {@link System.currentTimeMillis()}.
      */
@@ -224,9 +275,13 @@
 
     public boolean updateAvoidBadWifi() {
         final boolean settingAvoidBadWifi = "1".equals(getAvoidBadWifiSetting());
-        final boolean prev = mAvoidBadWifi;
+        final boolean prevAvoid = mAvoidBadWifi;
         mAvoidBadWifi = settingAvoidBadWifi || !configRestrictsAvoidBadWifi();
-        return mAvoidBadWifi != prev;
+
+        final boolean prevActive = mActivelyPreferBadWifi;
+        mActivelyPreferBadWifi = configActivelyPrefersBadWifi();
+
+        return mAvoidBadWifi != prevAvoid || mActivelyPreferBadWifi != prevActive;
     }
 
     /**
diff --git a/service/ServiceConnectivityResources/res/values/config.xml b/service/ServiceConnectivityResources/res/values/config.xml
index bff6953..7d777ec 100644
--- a/service/ServiceConnectivityResources/res/values/config.xml
+++ b/service/ServiceConnectivityResources/res/values/config.xml
@@ -78,6 +78,27 @@
          Settings.Global.NETWORK_AVOID_BAD_WIFI. This is the default value of that setting. -->
     <integer translatable="false" name="config_networkAvoidBadWifi">1</integer>
 
+    <!-- Whether the device should actively prefer bad wifi to good cell on Android 12/13.
+
+         This setting only makes sense if the system is configured not to avoid bad wifis
+         (config_networkAvoidBadWifi=0 and Settings.Global.NETWORK_AVOID_BAD_WIFI=IGNORE
+         or PROMPT), otherwise it's not used.
+
+         On Android 12 and 13, if this is 0, when ranking a bad wifi that never validated against
+         validated mobile data, the system will prefer mobile data. It will prefer wifi if wifi
+         loses validation later. This is the default behavior up to Android 13.
+         This behavior avoids the device losing internet access when walking past a wifi network
+         with no internet access.
+
+         If this is 1, then in the same scenario, the system will prefer mobile data until the wifi
+         completes its first validation attempt (or the attempt times out), and after that it
+         will prefer the wifi even if it doesn't provide internet access, unless there is a captive
+         portal on that wifi.
+
+         On Android 14 and above, the behavior is always like 1, regardless of the value of this
+         setting. -->
+    <integer translatable="false" name="config_activelyPreferBadWifi">1</integer>
+
     <!-- Array of ConnectivityManager.TYPE_xxxx constants for networks that may only
          be controlled by systemOrSignature apps.  -->
     <integer-array translatable="false" name="config_protectedNetworks">
diff --git a/service/ServiceConnectivityResources/res/values/overlayable.xml b/service/ServiceConnectivityResources/res/values/overlayable.xml
index 3389d63..4c85e8c 100644
--- a/service/ServiceConnectivityResources/res/values/overlayable.xml
+++ b/service/ServiceConnectivityResources/res/values/overlayable.xml
@@ -24,6 +24,7 @@
             <item type="integer" name="config_networkMeteredMultipathPreference"/>
             <item type="array" name="config_networkSupportedKeepaliveCount"/>
             <item type="integer" name="config_networkAvoidBadWifi"/>
+            <item type="integer" name="config_activelyPreferBadWifi"/>
             <item type="array" name="config_protectedNetworks"/>
             <item type="bool" name="config_vehicleInternalNetworkAlwaysRequested"/>
             <item type="integer" name="config_networkWakeupPacketMark"/>
diff --git a/service/src/com/android/server/ConnectivityService.java b/service/src/com/android/server/ConnectivityService.java
index 93265e5..cb209e8 100755
--- a/service/src/com/android/server/ConnectivityService.java
+++ b/service/src/com/android/server/ConnectivityService.java
@@ -783,7 +783,8 @@
     final ConnectivityDiagnosticsHandler mConnectivityDiagnosticsHandler;
 
     private final DnsManager mDnsManager;
-    private final NetworkRanker mNetworkRanker;
+    @VisibleForTesting
+    final NetworkRanker mNetworkRanker;
 
     private boolean mSystemReady;
     private Intent mInitialBroadcast;
@@ -1417,7 +1418,6 @@
                 new RequestInfoPerUidCounter(MAX_NETWORK_REQUESTS_PER_SYSTEM_UID - 1);
 
         mMetricsLog = logger;
-        mNetworkRanker = new NetworkRanker();
         final NetworkRequest defaultInternetRequest = createDefaultRequest();
         mDefaultRequest = new NetworkRequestInfo(
                 Process.myUid(), defaultInternetRequest, null,
@@ -1538,6 +1538,9 @@
 
         mMultinetworkPolicyTracker = mDeps.makeMultinetworkPolicyTracker(
                 mContext, mHandler, () -> updateAvoidBadWifi());
+        mNetworkRanker =
+                new NetworkRanker(new NetworkRanker.Configuration(activelyPreferBadWifi()));
+
         mMultinetworkPolicyTracker.start();
 
         mDnsManager = new DnsManager(mContext, mDnsResolver);
@@ -5050,6 +5053,10 @@
         return mMultinetworkPolicyTracker.getAvoidBadWifi();
     }
 
+    private boolean activelyPreferBadWifi() {
+        return mMultinetworkPolicyTracker.getActivelyPreferBadWifi();
+    }
+
     /**
      * Return whether the device should maintain continuous, working connectivity by switching away
      * from WiFi networks having no connectivity.
@@ -5073,6 +5080,7 @@
         for (final NetworkOfferInfo noi : offersToUpdate) {
             updateOfferScore(noi.offer);
         }
+        mNetworkRanker.setConfiguration(new NetworkRanker.Configuration(activelyPreferBadWifi()));
         rematchAllNetworksAndRequests();
     }
 
@@ -5088,6 +5096,7 @@
         pw.println("Bad Wi-Fi avoidance: " + avoidBadWifi());
         pw.increaseIndent();
         pw.println("Config restrict:   " + configRestrict);
+        pw.println("Actively prefer:   " + activelyPreferBadWifi());
 
         final String value = mMultinetworkPolicyTracker.getAvoidBadWifiSetting();
         String description;
diff --git a/service/src/com/android/server/connectivity/NetworkRanker.java b/service/src/com/android/server/connectivity/NetworkRanker.java
index f2c6aa1..d56e171 100644
--- a/service/src/com/android/server/connectivity/NetworkRanker.java
+++ b/service/src/com/android/server/connectivity/NetworkRanker.java
@@ -38,19 +38,42 @@
 import android.annotation.Nullable;
 import android.net.NetworkCapabilities;
 import android.net.NetworkRequest;
+import android.net.util.MultinetworkPolicyTracker;
 
+import com.android.internal.annotations.VisibleForTesting;
 import com.android.net.module.util.CollectionUtils;
 
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
+import java.util.Objects;
 import java.util.function.Predicate;
 
 /**
  * A class that knows how to find the best network matching a request out of a list of networks.
  */
 public class NetworkRanker {
+    /**
+     * Home for all configurations of NetworkRanker
+     */
+    public static final class Configuration {
+        private final boolean mActivelyPreferBadWifi;
+
+        public Configuration(final boolean activelyPreferBadWifi) {
+            this.mActivelyPreferBadWifi = activelyPreferBadWifi;
+        }
+
+        /**
+         * @see MultinetworkPolicyTracker#getActivelyPreferBadWifi()
+         */
+        // TODO : implement the behavior.
+        public boolean activelyPreferBadWifi() {
+            return mActivelyPreferBadWifi;
+        }
+    }
+    @NonNull private volatile Configuration mConf;
+
     // Historically the legacy ints have been 0~100 in principle (though the highest score in
     // AOSP has always been 90). This is relied on by VPNs that send a legacy score of 101.
     public static final int LEGACY_INT_MAX = 100;
@@ -65,7 +88,22 @@
         NetworkCapabilities getCapsNoCopy();
     }
 
-    public NetworkRanker() { }
+    public NetworkRanker(@NonNull final Configuration conf) {
+        // Because mConf is volatile, the only way it could be seen null would be an access to it
+        // on some other thread during this constructor. But this is not possible because mConf is
+        // private and `this` doesn't escape this constructor.
+        setConfiguration(conf);
+    }
+
+    public void setConfiguration(@NonNull final Configuration conf) {
+        mConf = Objects.requireNonNull(conf);
+    }
+
+    // There shouldn't be a use case outside of testing
+    @VisibleForTesting
+    public Configuration getConfiguration() {
+        return mConf;
+    }
 
     /**
      * Find the best network satisfying this request among the list of passed networks.
diff --git a/tests/unit/java/android/net/util/MultinetworkPolicyTrackerTest.kt b/tests/unit/java/android/net/util/MultinetworkPolicyTrackerTest.kt
index 0dbee5d..f317863 100644
--- a/tests/unit/java/android/net/util/MultinetworkPolicyTrackerTest.kt
+++ b/tests/unit/java/android/net/util/MultinetworkPolicyTrackerTest.kt
@@ -35,6 +35,7 @@
 import androidx.test.filters.SmallTest
 import com.android.connectivity.resources.R
 import com.android.internal.util.test.FakeSettingsProvider
+import com.android.modules.utils.build.SdkLevel
 import com.android.testutils.DevSdkIgnoreRule
 import com.android.testutils.DevSdkIgnoreRunner
 import org.junit.After
@@ -50,7 +51,6 @@
 import org.mockito.ArgumentMatchers.eq
 import org.mockito.Mockito.any
 import org.mockito.Mockito.doCallRealMethod
-import org.mockito.Mockito.doNothing
 import org.mockito.Mockito.doReturn
 import org.mockito.Mockito.mock
 import org.mockito.Mockito.times
@@ -69,7 +69,10 @@
     private val resources = mock(Resources::class.java).also {
         doReturn(R.integer.config_networkAvoidBadWifi).`when`(it).getIdentifier(
                 eq("config_networkAvoidBadWifi"), eq("integer"), any())
+        doReturn(R.integer.config_activelyPreferBadWifi).`when`(it).getIdentifier(
+                eq("config_activelyPreferBadWifi"), eq("integer"), any())
         doReturn(0).`when`(it).getInteger(R.integer.config_networkAvoidBadWifi)
+        doReturn(0).`when`(it).getInteger(R.integer.config_activelyPreferBadWifi)
     }
     private val telephonyManager = mock(TelephonyManager::class.java)
     private val subscriptionManager = mock(SubscriptionManager::class.java).also {
@@ -122,6 +125,7 @@
 
     @Test
     fun testUpdateAvoidBadWifi() {
+        doReturn(0).`when`(resources).getInteger(R.integer.config_activelyPreferBadWifi)
         Settings.Global.putString(resolver, NETWORK_AVOID_BAD_WIFI, "0")
         assertTrue(tracker.updateAvoidBadWifi())
         assertFalse(tracker.avoidBadWifi)
@@ -129,6 +133,24 @@
         doReturn(1).`when`(resources).getInteger(R.integer.config_networkAvoidBadWifi)
         assertTrue(tracker.updateAvoidBadWifi())
         assertTrue(tracker.avoidBadWifi)
+
+        if (SdkLevel.isAtLeastU()) {
+            // On U+, the system always prefers bad wifi.
+            assertTrue(tracker.activelyPreferBadWifi)
+        } else {
+            assertFalse(tracker.activelyPreferBadWifi)
+        }
+
+        doReturn(1).`when`(resources).getInteger(R.integer.config_activelyPreferBadWifi)
+        if (SdkLevel.isAtLeastU()) {
+            // On U+, this didn't change the setting
+            assertFalse(tracker.updateAvoidBadWifi())
+        } else {
+            // On T-, this must have changed the setting
+            assertTrue(tracker.updateAvoidBadWifi())
+        }
+        // In all cases, now the system actively prefers bad wifi
+        assertTrue(tracker.activelyPreferBadWifi)
     }
 
     @Test
diff --git a/tests/unit/java/com/android/server/ConnectivityServiceTest.java b/tests/unit/java/com/android/server/ConnectivityServiceTest.java
index d2a7135..5e681b6 100755
--- a/tests/unit/java/com/android/server/ConnectivityServiceTest.java
+++ b/tests/unit/java/com/android/server/ConnectivityServiceTest.java
@@ -1838,7 +1838,10 @@
                 .getIdentifier(eq("network_switch_type_name"), eq("array"), any());
         doReturn(R.integer.config_networkAvoidBadWifi).when(mResources)
                 .getIdentifier(eq("config_networkAvoidBadWifi"), eq("integer"), any());
+        doReturn(R.integer.config_activelyPreferBadWifi).when(mResources)
+                .getIdentifier(eq("config_activelyPreferBadWifi"), eq("integer"), any());
         doReturn(1).when(mResources).getInteger(R.integer.config_networkAvoidBadWifi);
+        doReturn(0).when(mResources).getInteger(R.integer.config_activelyPreferBadWifi);
         doReturn(true).when(mResources)
                 .getBoolean(R.bool.config_cellular_radio_timesharing_capable);
     }
@@ -5621,6 +5624,24 @@
     }
 
     @Test
+    public void testActivelyPreferBadWifiSetting() throws Exception {
+        doReturn(1).when(mResources).getInteger(R.integer.config_activelyPreferBadWifi);
+        mPolicyTracker.reevaluate();
+        waitForIdle();
+        assertTrue(mService.mNetworkRanker.getConfiguration().activelyPreferBadWifi());
+
+        doReturn(0).when(mResources).getInteger(R.integer.config_activelyPreferBadWifi);
+        mPolicyTracker.reevaluate();
+        waitForIdle();
+        if (SdkLevel.isAtLeastU()) {
+            // U+ ignore the setting and always actively prefers bad wifi
+            assertTrue(mService.mNetworkRanker.getConfiguration().activelyPreferBadWifi());
+        } else {
+            assertFalse(mService.mNetworkRanker.getConfiguration().activelyPreferBadWifi());
+        }
+    }
+
+    @Test
     public void testOffersAvoidsBadWifi() throws Exception {
         // Normal mode : the carrier doesn't restrict moving away from bad wifi.
         // This has getAvoidBadWifi return true.
diff --git a/tests/unit/java/com/android/server/connectivity/NetworkRankerTest.kt b/tests/unit/java/com/android/server/connectivity/NetworkRankerTest.kt
index 8b1c510..05c648d 100644
--- a/tests/unit/java/com/android/server/connectivity/NetworkRankerTest.kt
+++ b/tests/unit/java/com/android/server/connectivity/NetworkRankerTest.kt
@@ -42,7 +42,8 @@
 @RunWith(DevSdkIgnoreRunner::class)
 @DevSdkIgnoreRule.IgnoreUpTo(Build.VERSION_CODES.R)
 class NetworkRankerTest {
-    private val mRanker = NetworkRanker()
+    private val mRanker = NetworkRanker(NetworkRanker.Configuration(
+            false /* activelyPreferBadWifi */))
 
     private class TestScore(private val sc: FullScore, private val nc: NetworkCapabilities)
             : NetworkRanker.Scoreable {