Add Qos Callback support

* Provide App Developers Qos related info associated to
  a bound socket through ConnectivityManager
* Qos sessions are generated and filtered by Network Agents
  and sent back through the Connectivity Service to the
  API consumer.
* The structure of the code within com.android.server
  is designed to support different types of filters in the
  the future.
* The first type of Qos Attributes are related to EPS
  Bearers in order support RCS.

Bug: 155176305
Test: Added to cts/NetworkAgentTest
Test: Added to ConnectivityServiceTest
Change-Id: I145dd065d9deeee449eb9695ab3f6c8556ee7c09

core/java/android/net/QosCallbackConnection.java

@@ -0,0 +1,128 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.net;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.telephony.data.EpsBearerQosSessionAttributes;
+
+import com.android.internal.annotations.VisibleForTesting;
+
+import java.util.Objects;
+import java.util.concurrent.Executor;
+
+/**
+ * Sends messages from {@link com.android.server.ConnectivityService} to the registered
+ * {@link QosCallback}.
+ * <p/>
+ * This is a satellite class of {@link ConnectivityManager} and not meant
+ * to be used in other contexts.
+ *
+ * @hide
+ */
+class QosCallbackConnection extends android.net.IQosCallback.Stub {
+
+    @NonNull private final ConnectivityManager mConnectivityManager;
+    @Nullable private volatile QosCallback mCallback;
+    @NonNull private final Executor mExecutor;
+
+    @VisibleForTesting
+    @Nullable
+    public QosCallback getCallback() {
+        return mCallback;
+    }
+
+    /**
+     * The constructor for the connection
+     *
+     * @param connectivityManager the mgr that created this connection
+     * @param callback the callback to send messages back to
+     * @param executor The executor on which the callback will be invoked. The provided
+     *                 {@link Executor} must run callback sequentially, otherwise the order of
+     *                 callbacks cannot be guaranteed.
+     */
+    QosCallbackConnection(@NonNull final ConnectivityManager connectivityManager,
+            @NonNull final QosCallback callback,
+            @NonNull final Executor executor) {
+        mConnectivityManager = Objects.requireNonNull(connectivityManager,
+                "connectivityManager must be non-null");
+        mCallback = Objects.requireNonNull(callback, "callback must be non-null");
+        mExecutor = Objects.requireNonNull(executor, "executor must be non-null");
+    }
+
+    /**
+     * Called when either the {@link EpsBearerQosSessionAttributes} has changed or on the first time
+     * the attributes have become available.
+     *
+     * @param session the session that is now available
+     * @param attributes the corresponding attributes of session
+     */
+    @Override
+    public void onQosEpsBearerSessionAvailable(@NonNull final QosSession session,
+            @NonNull final EpsBearerQosSessionAttributes attributes) {
+
+        mExecutor.execute(() -> {
+            final QosCallback callback = mCallback;
+            if (callback != null) {
+                callback.onQosSessionAvailable(session, attributes);
+            }
+        });
+    }
+
+    /**
+     * Called when the session is lost.
+     *
+     * @param session the session that was lost
+     */
+    @Override
+    public void onQosSessionLost(@NonNull final QosSession session) {
+        mExecutor.execute(() -> {
+            final QosCallback callback = mCallback;
+            if (callback != null) {
+                callback.onQosSessionLost(session);
+            }
+        });
+    }
+
+    /**
+     * Called when there is an error on the registered callback.
+     *
+     *  @param errorType the type of error
+     */
+    @Override
+    public void onError(@QosCallbackException.ExceptionType final int errorType) {
+        mExecutor.execute(() -> {
+            final QosCallback callback = mCallback;
+            if (callback != null) {
+                // Messages no longer need to be received since there was an error.
+                stopReceivingMessages();
+                mConnectivityManager.unregisterQosCallback(callback);
+                callback.onError(QosCallbackException.createException(errorType));
+            }
+        });
+    }
+
+    /**
+     * The callback will stop receiving messages.
+     * <p/>
+     * There are no synchronization guarantees on exactly when the callback will stop receiving
+     * messages.
+     */
+    void stopReceivingMessages() {
+        mCallback = null;
+    }
+}