Support ignoring penalty for bad wifi networks

This patch adds a way to configure devices so that a validated network
that becomes unvalidated is not penalized in the network scoring and
selection logic.

The intent is to prevent devices configured to do so from switching to a
lower scoring network such as cellular networks when a higher scoring
network such as wifi networks loses internet connectivity.

Bug: 31075769
Change-Id: Ie7e0f2607d214a178367fedfbef6c44768fa00a4

core/java/android/provider/Settings.java

@@ -7441,6 +7441,12 @@ public final class Settings {
        public static final String NETWORK_SWITCH_NOTIFICATION_RATE_LIMIT_MILLIS =
               "network_switch_notification_rate_limit_millis";
 
+       /**
+        * Whether to automatically switch away from wifi networks that lose Internet access.
+        * @hide
+        */
+       public static final String NETWORK_AVOID_BAD_WIFI = "network_avoid_bad_wifi";
+
        /**
         * Whether Wifi display is enabled/disabled
         * 0=disabled. 1=enabled.

core/res/res/values/config.xml

@@ -275,6 +275,11 @@
     <string-array translatable="false" name="config_networkNotifySwitches">
     </string-array>
 
+    <!-- Whether the device should automatically switch away from Wi-Fi networks that lose
+         Internet access. Actual device behaviour is controlled by
+         Settings.Global.NETWORK_AVOID_BAD_WIFI. This is the default value of that setting. -->
+    <integer translatable="false" name="config_networkAvoidBadWifi">1</integer>
+
     <!-- List of regexpressions describing the interface (if any) that represent tetherable
          USB interfaces.  If the device doesn't want to support tethering over USB this should
          be empty.  An example would be "usb.*" -->

core/res/res/values/symbols.xml

@@ -1746,6 +1746,7 @@
   <java-symbol type="integer" name="config_networkTransitionTimeout" />
   <java-symbol type="integer" name="config_networkNotifySwitchType" />
   <java-symbol type="array" name="config_networkNotifySwitches" />
+  <java-symbol type="integer" name="config_networkAvoidBadWifi" />
   <java-symbol type="integer" name="config_notificationsBatteryFullARGB" />
   <java-symbol type="integer" name="config_notificationsBatteryLedOff" />
   <java-symbol type="integer" name="config_notificationsBatteryLedOn" />

services/core/java/com/android/server/ConnectivityService.java

@@ -2704,6 +2704,15 @@ public class ConnectivityService extends IConnectivityManager.Stub
                 PROMPT_UNVALIDATED_DELAY_MS);
     }
 
+    @VisibleForTesting
+    public boolean avoidBadWifi() {
+        int defaultAvoidBadWifi =
+            mContext.getResources().getInteger(R.integer.config_networkAvoidBadWifi);
+        int avoid = Settings.Global.getInt(mContext.getContentResolver(),
+            Settings.Global.NETWORK_AVOID_BAD_WIFI, defaultAvoidBadWifi);
+        return avoid == 1;
+    }
+
     private void handlePromptUnvalidated(Network network) {
         if (VDBG) log("handlePromptUnvalidated " + network);
         NetworkAgentInfo nai = getNetworkAgentInfoForNetwork(network);

services/core/java/com/android/server/connectivity/NetworkAgentInfo.java

@@ -113,6 +113,7 @@ import java.util.TreeSet;
 // a NetworkRequest, ConnectivityService will cancel the future disconnection of the NetworkAgent's
 // AsyncChannel, and the network is no longer considered "lingering".
 public class NetworkAgentInfo implements Comparable<NetworkAgentInfo> {
+
     public NetworkInfo networkInfo;
     // This Network object should always be used if possible, so as to encourage reuse of the
     // enclosed socket factory and connection pool.  Avoid creating other Network objects.
@@ -354,13 +355,20 @@ public class NetworkAgentInfo implements Comparable<NetworkAgentInfo> {
         }
 
         int score = currentScore;
-        if (!lastValidated && !pretendValidated) {
+        if (!lastValidated && !pretendValidated && !ignoreWifiUnvalidationPenalty()) {
             score -= UNVALIDATED_SCORE_PENALTY;
         }
         if (score < 0) score = 0;
         return score;
     }
 
+    // Return true on devices configured to ignore score penalty for wifi networks
+    // that become unvalidated (b/31075769).
+    private boolean ignoreWifiUnvalidationPenalty() {
+        boolean isWifi = networkCapabilities.hasTransport(NetworkCapabilities.TRANSPORT_WIFI);
+        return isWifi && !mConnService.avoidBadWifi() && everValidated;
+    }
+
     // Get the current score for this Network.  This may be modified from what the
     // NetworkAgent sent, as it has modifiers applied to it.
     public int getCurrentScore() {