arc-bridge: Add the ARC Bridge Service

components/arc/arc_bridge_service.h

+// Copyright 2015 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 COMPONENTS_ARC_ARC_BRIDGE_SERVICE_H_
+#define COMPONENTS_ARC_ARC_BRIDGE_SERVICE_H_
+
+#include "base/macros.h"
+#include "base/observer_list_threadsafe.h"
+#include "base/sequenced_task_runner.h"
+#include "chromeos/dbus/dbus_method_call_status.h"
+#include "components/keyed_service/core/keyed_service.h"
+#include "ipc/ipc_channel_proxy.h"
+#include "ipc/ipc_listener.h"
+#include "ipc/ipc_message.h"
+
+class PrefRegistrySimple;
+class PrefService;
+
+namespace arc {
+
+class ArcBridgeTest;
+
+// The Chrome-side service that handles ARC instances and ARC bridge creation.
+// This service handles the lifetime of ARC instances and sets up the
+// communication channel (the ARC bridge) used to send and receive messages.
+class ArcBridgeService : public KeyedService,
+                         public IPC::Listener {
+ public:
+  // The possible states of the bridge.  In the normal flow, the state changes
+  // in the following sequence:
+  //
+  // STOPPED
+  //   SetEnabled(true) + HandleStartup() -> SocketConnect() ->
+  // CONNECTING
+  //   Connect() ->
+  // CONNECTED
+  //   SocketConnectAfterSetsocketPermissions() ->

[hidehiko, 2015/11/05 18:08:50]

nit: SocketConnecetAfterSet*S*ocketPermissions.

[lhc(google), 2015/11/06 04:14:16]

Done.

[Luis Héctor Chávez, 2015/11/09 16:41:04]

Done.

+  // STARTING
+  //   StartInstance() -> OnInstanceReady() ->
+  // READY
+  //
+  // When Shutdown() is called, the state changes depending on the state it was
+  // at:
+  //
+  // CONNECTED/CONNECTING -> STOPPED
+  // STARTING/READY -> STOPPING -> StopInstance() -> STOPPED
+  enum State {
+    // ARC is not currently running.
+    STOPPED,
+
+    // The request to connect has been sent.
+    CONNECTING,
+
+    // The bridge has connected to the socket, but has not started the ARC
+    // instance.
+    CONNECTED,
+
+    // The ARC bridge has been set up and ARC is starting up.
+    STARTING,
+
+    // The ARC instance has been fully initialized and is now ready for user
+    // interaction.
+    READY,
+
+    // The ARC instance has started shutting down.
+    STOPPING,
+  };
+
+  class Observer {
+   public:
+    // Called whenever the state of the bridge has changed.
+    virtual void OnStateChanged(State state) {}
+
+    // Called whenever ARC's enabled status has changed for this session.
+    virtual void OnEnabledChanged(bool enabled) {}
+
+   protected:
+    virtual ~Observer() {}
+  };
+
+  explicit ArcBridgeService(
+      const scoped_refptr<base::SequencedTaskRunner>& file_task_runner);
+  virtual ~ArcBridgeService();
+
+  // Registers ARC preferences.
+  static void RegisterPrefs(PrefRegistrySimple* registry);
+
+  // Reads from the preference store if ARC has been enabled.
+  static bool GetEnabledPref(PrefService* pref_service);
+
+  // HandleStartup() should be called upon profile startup.  This will only
+  // launch an instance if the instance service is available and it is enabled.
+  void HandleStartup();
+
+  // Shuts down the running instance, if any.  This is safe to call even if
+  // there is no instance running.
+  void Shutdown();
+
+  // Adds or removes observers.
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
+  // Gets the current state of the bridge service.
+  State GetState() const { return state_; }
+
+  // Enables or disables the bridge for this session.
+  void SetEnabled(bool enabled);
+
+  // Gets if the bridge is enabled for this session.
+  bool IsEnabled() const { return enabled_; }
+
+  // Requests registration of an input device on the ARC instance.
+  // TODO(denniskempin): Make this interface more typesafe.
+  // |name| should be the displayable name of the emulated device (e.g. "Chrome
+  // OS Keyboard"), |device_type| the name of the device type (e.g. "keyboard")
+  // and |fd| a file descriptor that emulates the kernel events of the device.
+  bool RegisterInputDevice(const std::string& name,
+                           const std::string& device_type,
+                           base::ScopedFD fd);
+
+ private:
+  friend class arc::ArcBridgeTest;
+
+  // Binds to the socket specified by |socket_path|.
+  void SocketConnect(const base::FilePath& socket_path);
+
+  // Binds to the socket specified by |socket_path| after creating its parent
+  // directory is present.
+  void SocketConnectAfterEnsureParentDirectory(
+      const base::FilePath& socket_path, bool directory_present);
+
+  // Internal connection method. Separated to make testing easier.
+  bool Connect(const IPC::ChannelHandle& handle, IPC::Channel::Mode mode);
+
+  // Finishes connecting after setting socket permissions.
+  void SocketConnectAfterSetSocketPermissions(const base::FilePath& socket_path,
+                                              bool socket_permissions_success);
+
+  // Called when the ARC instance has finished setting up and is ready for user
+  // interaction.
+  void OnInstanceReady();
+
+  // Changes the current state and notify all observers.
+  void SetState(State state);
+
+  // IPC::Listener:
+  bool OnMessageReceived(const IPC::Message& message) override;
+
+  // DBus callbacks.
+  void OnInstanceStarted(bool success);
+  void OnInstanceStopped(bool success);
+
+  // Thread in which IPC messaging is performed.
+  base::Thread ipc_thread_;
+
+  // Task runner on which incoming messages are handled.
+  scoped_refptr<base::SequencedTaskRunner> origin_task_runner_;
+
+  // Task runner on which file operations are performed.
+  scoped_refptr<base::SequencedTaskRunner> file_task_runner_;
+
+  // The channel through which messages are sent.
+  scoped_ptr<IPC::ChannelProxy> ipc_channel_;

[hidehiko, 2015/11/05 18:08:50]

Design question.
ChannelProxy looks designed to be used from only one (in most cases Browser)
thread. If you're trying to send messages from various threads, probably using
IPC::Channel directly and communicating between threads manually would be an
option?

Or, alternatively, you may be able to PostMessage() to the BrowserThread once,
and SendMessage() on it, if the cost of the PostMessage is acceptable.
(IIUC, posting message between threads is a common way in Chrome).

WDYT?

[lhc(google), 2015/11/06 04:14:16]

Based on the number of comments about it, making this single-threaded, so
keeping the ChannelProxy.

+
+  // A Lock that guards the |ipc_channel_|.  Most of the methods are expected
+  // to be run in the same thread (the one in which the ArcBridgeService
+  // instance was created), but all the ones that send IPC messages can be
+  // called from any method.  This will prevent the |ipc_channel_| from being
+  // destroyed while a message is being sent.
+  base::Lock ipc_channel_lock_;
+
+  // List of observers to notify of state changes.
+  scoped_refptr<base::ObserverListThreadSafe<Observer>> observer_list_;
+
+  // If the ARC instance service is available.
+  bool available_;
+
+  // If ARC has been enabled by policy and user choice.
+  bool enabled_;
+
+  // The current state of the bridge.
+  ArcBridgeService::State state_;
+
+  // WeakPtrFactory to use callbacks.
+  base::WeakPtrFactory<ArcBridgeService> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ArcBridgeService);
+};
+
+}  // namespace arc
+
+#endif  // COMPONENTS_ARC_ARC_BRIDGE_SERVICE_H_