content: /*
   * Copyright (C) 2019 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.os.ParcelFileDescriptor;
  import android.os.RemoteException;
  import android.util.Log;
  
  import java.io.FileDescriptor;
  import java.util.concurrent.Executor;
  
  /** @hide */
  final class TcpSocketKeepalive extends SocketKeepalive {
  
      TcpSocketKeepalive(@NonNull IConnectivityManager service,
              @NonNull Network network,
              @NonNull ParcelFileDescriptor pfd,
              @NonNull Executor executor,
              @NonNull Callback callback) {
          super(service, network, pfd, executor, callback);
      }
  
      /**
       * Starts keepalives. {@code mSocket} must be a connected TCP socket.
       *
       * - The application must not write to or read from the socket after calling this method, until
       *   onDataReceived, onStopped, or onError are called. If it does, the keepalive will fail
       *   with {@link #ERROR_SOCKET_NOT_IDLE}, or {@code #ERROR_INVALID_SOCKET} if the socket
       *   experienced an error (as in poll(2) returned POLLERR or POLLHUP); if this happens, the data
       *   received from the socket may be invalid, and the socket can't be recovered.
       * - If the socket has data in the send or receive buffer, then this call will fail with
       *   {@link #ERROR_SOCKET_NOT_IDLE} and can be retried after the data has been processed.
       *   An app could ensure this by using an application-layer protocol to receive acknowledgement
       *   that indicates all data has been delivered to server, e.g. HTTP 200 OK.
       *   Then the app could go into keepalive mode after reading all remaining data within the
       *   acknowledgement.
       */
      @Override
      void startImpl(int intervalSec) {
          mExecutor.execute(() -> {
              try {
                  final FileDescriptor fd = mPfd.getFileDescriptor();
                  mService.startTcpKeepalive(mNetwork, fd, intervalSec, mCallback);
              } catch (RemoteException e) {
                  Log.e(TAG, "Error starting packet keepalive: ", e);
                  throw e.rethrowFromSystemServer();
              }
          });
      }
  
      @Override
      void stopImpl() {
          mExecutor.execute(() -> {
              try {
                  if (mSlot != null) {
                      mService.stopKeepalive(mNetwork, mSlot);
                  }
              } catch (RemoteException e) {
                  Log.e(TAG, "Error stopping packet keepalive: ", e);
                  throw e.rethrowFromSystemServer();
              }
          });
      }
  }
  