CastExtension Impl for Chromoting Host

remoting/host/cast_extension_session.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef REMOTING_HOST_CAST_EXTENSION_SESSION_H_
+#define REMOTING_HOST_CAST_EXTENSION_SESSION_H_
+
+#include <string>
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/threading/thread.h"
+#include "base/timer/timer.h"
+#include "base/values.h"
+#include "jingle/glue/thread_wrapper.h"
+#include "remoting/host/host_extension_session.h"
+#include "third_party/libjingle/source/talk/app/webrtc/peerconnectioninterface.h"
+#include "third_party/webrtc/base/scoped_ref_ptr.h"
+#include "third_party/webrtc/modules/desktop_capture/desktop_capturer.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+class WaitableEvent;
+}  // namespace base
+
+namespace net {
+class URLRequestContextGetter;
+}  // namespace net
+
+namespace webrtc {
+class MediaStreamInterface;
+}  // namespace webrtc
+
+namespace remoting {
+
+namespace protocol {
+struct NetworkSettings;
+}  // namespace protocol
+
+// A HostExtensionSession implementation that enables WebRTC support using
+// the PeerConnection native API.
+class CastExtensionSession : public HostExtensionSession,
+                             public webrtc::PeerConnectionObserver {
+ public:
+  virtual ~CastExtensionSession();
+
+  // Creates and returns a CastExtensionSession object, after performing
+  // initialization steps on it. The caller must take ownership of the returned
+  // object.
+  static scoped_ptr<CastExtensionSession> Create(
+      scoped_refptr<base::SingleThreadTaskRunner> caller_task_runner,
+      scoped_refptr<net::URLRequestContextGetter> url_request_context_getter,
+      const protocol::NetworkSettings& network_settings,
+      ClientSessionControl* client_session_control,
+      protocol::ClientStub* client_stub);
+
+  // Called by webrtc::CreateSessionDescriptionObserver implementation.
+  void OnCreateSessionDescription(webrtc::SessionDescriptionInterface* desc);
+  void OnCreateSessionDescriptionFailure(const std::string& error);
+
+  // HostExtensionSession interface.
+  virtual scoped_ptr<webrtc::DesktopCapturer> OnCreateVideoCapturer(
+      scoped_ptr<webrtc::DesktopCapturer> capturer) OVERRIDE;
+  virtual bool ModifiesVideoPipeline() const OVERRIDE;
+  virtual bool OnExtensionMessage(
+      ClientSessionControl* client_session_control,
+      protocol::ClientStub* client_stub,
+      const protocol::ExtensionMessage& message) OVERRIDE;
+
+  // webrtc::PeerConnectionObserver interface.
+  virtual void OnError() OVERRIDE;
+  virtual void OnSignalingChange(
+      webrtc::PeerConnectionInterface::SignalingState new_state) OVERRIDE;
+  virtual void OnStateChange(
+      webrtc::PeerConnectionObserver::StateType state_changed) OVERRIDE;
+  virtual void OnAddStream(webrtc::MediaStreamInterface* stream) OVERRIDE;
+  virtual void OnRemoveStream(webrtc::MediaStreamInterface* stream) OVERRIDE;
+  virtual void OnDataChannel(
+      webrtc::DataChannelInterface* data_channel) OVERRIDE;
+  virtual void OnRenegotiationNeeded() OVERRIDE;
+  virtual void OnIceConnectionChange(
+      webrtc::PeerConnectionInterface::IceConnectionState new_state) OVERRIDE;
+  virtual void OnIceGatheringChange(
+      webrtc::PeerConnectionInterface::IceGatheringState new_state) OVERRIDE;
+  virtual void OnIceCandidate(
+      const webrtc::IceCandidateInterface* candidate) OVERRIDE;
+  virtual void OnIceComplete() OVERRIDE;
+
+ private:
+  CastExtensionSession(
+      scoped_refptr<base::SingleThreadTaskRunner> caller_task_runner,
+      scoped_refptr<net::URLRequestContextGetter> url_request_context_getter,
+      const protocol::NetworkSettings& network_settings,
+      ClientSessionControl* client_session_control,
+      protocol::ClientStub* client_stub);
+
+  // Parses |message| for a Session Description and sets the remote
+  // description, returning true if successful.
+  bool ParseAndSetRemoteDescription(base::DictionaryValue* message);
+
+  // Parses |message| for a PeerConnection ICE candidate and adds it to the
+  // Peer Connection, returning true if successful.
+  bool ParseAndAddICECandidate(base::DictionaryValue* message);
+
+  // Sends a message to the client through |client_stub_|. This method must be
+  // called on the network thread.
+  //
+  // A protocol::ExtensionMessage consists of two string fields: type and data.
+  //
+  // The specifications for Cast Extension Messages are as follows:

[Wez, 2014/08/14 19:22:03]

nit: This line adds nothing.

[aiguha, 2014/08/15 04:11:39]

Done.

+  // The type field must be |kExtensionMessageType|.
+  // The data field must be a JSON formatted string with two compulsory
+  // top level keys: |kTopLevelSubject| and |kTopLevelData|.
+  // Thus, the data field of any properly formed Cast Extension Message should
+  // look like:
+  //  {subject: '...', chromoting_data: '...'}

[Wez, 2014/08/14 19:22:03]

nit: Suggest just documenting what 'subject' and 'data' mean; the example
doesn't really add anything. An example of possible 'subject' values, to
illustrate that it's effectively identifying the command the peer wants to
perform, may help.

[Wez, 2014/08/14 19:22:03]

Since the data portion is specific to this extension (via the type), why not
call this just 'data'?

[aiguha, 2014/08/15 04:11:39]

It's "chromoting_data" not just "data" because:
1. ExtensionMessages already have a data field
2. Worse, the Cast SDK, when sending messages as JSON, wraps them all in a
"data" header

It's "subject" not "type" because:
1. ExtensionMessage already have a type field
2. Similarly, WebRTC uses the type header within its offer/answer messages

Having distinct names made things easier for me to work with, as well as for
readers/maintainers I think :)

[aiguha, 2014/08/15 04:11:39]

I've made the comment clearer. Also added better examples with descriptions :)

+  //
+  // The |subject| of a message describes the message to the receiving peer, so
+  // the peer can easily decide what to do next. The |subject| MUST be one of

[Wez, 2014/08/14 19:22:03]

So the Subject is essentially the extension-specific message type? In the
VideoFrameRecorderHostExtension we just called that "type".

[aiguha, 2014/08/15 04:11:39]

responded above

+  // constants formatted as kSubject* defined in the .cc file. This set of
+  // subjects is identical between host and client, thus standardizing how they
+  // communicate WebRTC signaling and other control messages.
+  // The |data| of a message could be a simple string or another JSON-formatted
+  // string.

[Wez, 2014/08/14 19:22:03]

Better to say that the type of 'data' depends on the Subject.

[aiguha, 2014/08/15 04:11:39]

Done.

+  bool SendMessageToClient(const std::string& subject, const std::string& data);
+
+  // Creates the jingle wrapper for the current thread, sets send to allowed,
+  // and saves a pointer to the relevant thread pointer in ptr. If |event|
+  // is not NULL, signals the event on completion.
+  void EnsureTaskAndSetSend(rtc::Thread** ptr,
+                            base::WaitableEvent* event = NULL);
+
+  // Wraps each task runner in JingleThreadWrapper using EnsureTaskAndSetSend(),
+  // returning true if successful. Wrapping the task runners allows them to be
+  // shared with and used by the (about to be created) PeerConnectionFactory.
+  bool WrapTasksAndSave();
+
+  // Initializes PeerConnectionFactory and PeerConnection and sends a "ready"
+  // message to client. Returns true if these steps are performed successfully.
+  bool InitializePeerConnection();
+
+  // Constructs a CastVideoCapturerAdapter, a VideoSource, a VideoTrack and a
+  // MediaStream |stream_|, which it adds to the |peer_connection_|. Returns
+  // true if these steps are performed successfully. This method is called only
+  // when a PeerConnection offer is received from the client.
+  bool SetupVideoStream(scoped_ptr<webrtc::DesktopCapturer> desktop_capturer);
+
+  // Polls a single stats report from the PeerConnection immediately. Called
+  // periodically using |stats_polling_timer_| after a PeerConnection has been
+  // established.
+  void PollPeerConnectionStats();
+
+  // Closes |peer_connection_|, releases |peer_connection_|, |stream_| and
+  // |peer_conn_factory_| and stops the worker thread.
+  void CleanupPeerConnection();
+
+  // Check if the connection is active.
+  bool connection_active() const;
+
+  // TaskRunners that will be used to setup the PeerConnectionFactory's
+  // signalling thread and worker thread respectively.
+  scoped_refptr<base::SingleThreadTaskRunner> caller_task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner_;
+
+  // Objects related to the WebRTC PeerConnection.
+  rtc::scoped_refptr<webrtc::PeerConnectionInterface> peer_connection_;
+  rtc::scoped_refptr<webrtc::PeerConnectionFactoryInterface> peer_conn_factory_;
+  rtc::scoped_refptr<webrtc::MediaStreamInterface> stream_;
+
+  // Parameters passed to ChromiumPortAllocatorFactory on creation.
+  scoped_refptr<net::URLRequestContextGetter> url_request_context_getter_;
+  const protocol::NetworkSettings& network_settings_;
+
+  // Interface to interact with ClientSession.
+  ClientSessionControl* client_session_control_;
+
+  // Interface through which messages can be sent to the client.
+  protocol::ClientStub* client_stub_;
+
+  // Used to track webrtc connection statistics.
+  rtc::scoped_refptr<webrtc::StatsObserver> stats_observer_;
+
+  // Used to repeatedly poll stats from the |peer_connection_|.
+  base::RepeatingTimer<CastExtensionSession> stats_polling_timer_;
+
+  // True if a PeerConnection offer from the client has been received. This
+  // necessarily means that the host is not the caller in this attempted
+  // peer connection.
+  bool received_offer_;
+
+  // True if the webrtc::ScreenCapturer has been grabbed through the
+  // OnCreateVideoCapturer() callback.
+  bool has_grabbed_capturer_;
+
+  // PeerConnection signaling and worker threads created from
+  // JingleThreadWrappers. Each is created by calling
+  // jingle_glue::EnsureForCurrentMessageLoop() and thus deletes itself
+  // automatically when the associated MessageLoop is destroyed.
+  rtc::Thread* signaling_thread_wrapper_;
+  rtc::Thread* worker_thread_wrapper_;
+
+  // Worker thread that is wrapped to create |worker_thread_wrapper_|.
+  base::Thread worker_thread_;
+
+  DISALLOW_COPY_AND_ASSIGN(CastExtensionSession);
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_CAST_EXTENSION_SESSION_H_
+