Add a queue system server-side for NetworkAgent

The intent is to remove the queue on the NetworkAgent side.
This queue is triggered with the same conditions as the
existing one.

Test: ConnectivityCoverageTests, CtsNetTests
Change-Id: I4bc29b10e48e13cdf3c3a8a15a7c8d15954d2457

service/src/com/android/server/ConnectivityService.java

@@ -526,6 +526,7 @@ public class ConnectivityService extends IConnectivityManager.Stub {
     private final boolean mBackgroundFirewallChainEnabled;
 
     private final boolean mUseDeclaredMethodsForCallbacksEnabled;
+    private final boolean mQueueNetworkAgentEventsInSystemServer;
 
     // Flag to delay callbacks for frozen apps, suppressing duplicate and stale callbacks.
     private final boolean mQueueCallbacksForFrozenApps;
@@ -1917,6 +1918,9 @@ public class ConnectivityService extends IConnectivityManager.Stub {
         mUseDeclaredMethodsForCallbacksEnabled =
                 mDeps.isFeatureNotChickenedOut(context,
                         ConnectivityFlags.USE_DECLARED_METHODS_FOR_CALLBACKS);
+        mQueueNetworkAgentEventsInSystemServer =
+                mDeps.isFeatureNotChickenedOut(context,
+                        ConnectivityFlags.QUEUE_NETWORK_AGENT_EVENTS_IN_SYSTEM_SERVER);
         // registerUidFrozenStateChangedCallback is only available on U+
         mQueueCallbacksForFrozenApps = mDeps.isAtLeastU()
                 && mDeps.isFeatureNotChickenedOut(context, QUEUE_CALLBACKS_FOR_FROZEN_APPS);
@@ -4677,18 +4681,30 @@ public class ConnectivityService extends IConnectivityManager.Stub {
         private void maybeHandleNetworkAgentMessage(Message msg) {
             final Pair<NetworkAgentInfo, Object> arg = (Pair<NetworkAgentInfo, Object>) msg.obj;
             final NetworkAgentInfo nai = arg.first;
-            if (!mNetworkAgentInfos.contains(nai)) {
-                if (VDBG) {
-                    log(String.format("%s from unknown NetworkAgent", eventName(msg.what)));
-                }
-                return;
-            }
 
             // If the network has been destroyed, the only thing that it can do is disconnect.
             if (nai.isDestroyed() && !isDisconnectRequest(msg)) {
                 return;
             }
 
+            if (mQueueNetworkAgentEventsInSystemServer && nai.maybeEnqueueMessage(msg)) {
+                // If the message is enqueued, the NAI will replay it immediately
+                // when registration is complete. It does this by sending all the
+                // messages in the order received immediately after the
+                // EVENT_AGENT_REGISTERED message.
+                return;
+            }
+
+            // If the nai has been registered (and doesn't enqueue), it should now be
+            // in the list of NAIs.
+            if (!mNetworkAgentInfos.contains(nai)) {
+                // TODO : this is supposed to be impossible
+                if (VDBG) {
+                    log(String.format("%s from unknown NetworkAgent", eventName(msg.what)));
+                }
+                return;
+            }
+
             switch (msg.what) {
                 case NetworkAgent.EVENT_NETWORK_CAPABILITIES_CHANGED: {
                     final NetworkCapabilities proposed = (NetworkCapabilities) arg.second;

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

@@ -62,6 +62,9 @@ public final class ConnectivityFlags {
     public static final String QUEUE_CALLBACKS_FOR_FROZEN_APPS =
             "queue_callbacks_for_frozen_apps";
 
+    public static final String QUEUE_NETWORK_AGENT_EVENTS_IN_SYSTEM_SERVER =
+            "queue_network_agent_events_in_system_server";
+
     private boolean mNoRematchAllRequestsOnRegister;
 
     /**

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

@@ -62,6 +62,7 @@ import android.net.QosSession;
 import android.net.TcpKeepalivePacketData;
 import android.os.Handler;
 import android.os.IBinder;
+import android.os.Message;
 import android.os.RemoteException;
 import android.os.ServiceSpecificException;
 import android.os.SystemClock;
@@ -630,6 +631,7 @@ public class NetworkAgentInfo implements NetworkRanker.Scoreable {
     // Used by ConnectivityService to keep track of 464xlat.
     public final Nat464Xlat clatd;
 
+    private final ArrayList<Message> mMessagesPendingRegistration = new ArrayList<>();
     // Set after asynchronous creation of the NetworkMonitor.
     private volatile NetworkMonitorManager mNetworkMonitor;
 
@@ -715,6 +717,29 @@ public class NetworkAgentInfo implements NetworkRanker.Scoreable {
         }
 
         mHandler.obtainMessage(EVENT_AGENT_REGISTERED, ARG_AGENT_SUCCESS, 0, this).sendToTarget();
+        for (final Message enqueued : mMessagesPendingRegistration) {
+            mHandler.sendMessage(enqueued);
+        }
+        mMessagesPendingRegistration.clear();
+    }
+
+    /**
+     * Enqueues a message if it needs to be enqueued, and returns whether it was enqueued.
+     *
+     * The message is enqueued iff it can't be sent just yet. If it can be sent
+     * immediately, this method returns false and doesn't enqueue.
+     *
+     * If it enqueues, this method will make a copy of the message for enqueuing since
+     * messages can't be reused or recycled before the end of their processing by the
+     * handler.
+     */
+    public boolean maybeEnqueueMessage(final Message msg) {
+        HandlerUtils.ensureRunningOnHandlerThread(mHandler);
+        if (null != mNetworkMonitor) return false;
+        final Message m = mHandler.obtainMessage();
+        m.copyFrom(msg);
+        mMessagesPendingRegistration.add(m);
+        return true;
     }
 
     /**

tests/unit/java/com/android/server/ConnectivityServiceTest.java

@@ -2199,6 +2199,7 @@ public class ConnectivityServiceTest {
                 case ConnectivityFlags.DELAY_DESTROY_SOCKETS:
                 case ConnectivityFlags.USE_DECLARED_METHODS_FOR_CALLBACKS:
                 case ConnectivityFlags.QUEUE_CALLBACKS_FOR_FROZEN_APPS:
+                case ConnectivityFlags.QUEUE_NETWORK_AGENT_EVENTS_IN_SYSTEM_SERVER:
                     return true;
                 default:
                     throw new UnsupportedOperationException("Unknown flag " + name

tests/unit/java/com/android/server/connectivityservice/base/CSTest.kt

@@ -168,6 +168,7 @@ open class CSTest {
         it[ConnectivityFlags.DELAY_DESTROY_SOCKETS] = true
         it[ConnectivityFlags.USE_DECLARED_METHODS_FOR_CALLBACKS] = true
         it[ConnectivityFlags.QUEUE_CALLBACKS_FOR_FROZEN_APPS] = true
+        it[ConnectivityFlags.QUEUE_NETWORK_AGENT_EVENTS_IN_SYSTEM_SERVER] = true
     }
     fun setFeatureEnabled(flag: String, enabled: Boolean) = enabledFeatures.set(flag, enabled)