ipc/ipc_channel_proxy.h - chromium/src - Git at Google

 // Copyright (c) 2012 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 IPC_IPC_CHANNEL_PROXY_H_
 #define IPC_IPC_CHANNEL_PROXY_H_

 #include <stdint.h>

 #include <map>
 #include <memory>
 #include <string>
 #include <vector>

 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/component_export.h"
 #include "base/memory/ref_counted.h"
 #include "base/sequence_checker.h"
 #include "base/synchronization/lock.h"
 #include "build/build_config.h"
 #include "ipc/ipc.mojom.h"
 #include "ipc/ipc_channel.h"
 #include "ipc/ipc_channel_handle.h"
 #include "ipc/ipc_listener.h"
 #include "ipc/ipc_sender.h"
 #include "mojo/public/cpp/bindings/associated_interface_ptr.h"
 #include "mojo/public/cpp/bindings/associated_interface_request.h"
 #include "mojo/public/cpp/bindings/associated_remote.h"
 #include "mojo/public/cpp/bindings/scoped_interface_endpoint_handle.h"
 #include "mojo/public/cpp/bindings/thread_safe_interface_ptr.h"

 namespace base {
 class SingleThreadTaskRunner;
 }

 namespace IPC {

 class ChannelFactory;
 class MessageFilter;
 class MessageFilterRouter;

 //-----------------------------------------------------------------------------
 // IPC::ChannelProxy
 //
 // This class is a helper class that is useful when you wish to run an IPC
 // channel on a background thread.  It provides you with the option of either
 // handling IPC messages on that background thread or having them dispatched to
 // your main thread (the thread on which the IPC::ChannelProxy is created).
 //
 // The API for an IPC::ChannelProxy is very similar to that of an IPC::Channel.
 // When you send a message to an IPC::ChannelProxy, the message is routed to
 // the background thread, where it is then passed to the IPC::Channel's Send
 // method.  This means that you can send a message from your thread and your
 // message will be sent over the IPC channel when possible instead of being
 // delayed until your thread returns to its message loop.  (Often IPC messages
 // will queue up on the IPC::Channel when there is a lot of traffic, and the
 // channel will not get cycles to flush its message queue until the thread, on
 // which it is running, returns to its message loop.)
 //
 // An IPC::ChannelProxy can have a MessageFilter associated with it, which will
 // be notified of incoming messages on the IPC::Channel's thread.  This gives
 // the consumer of IPC::ChannelProxy the ability to respond to incoming
 // messages on this background thread instead of on their own thread, which may
 // be bogged down with other processing.  The result can be greatly improved
 // latency for messages that can be handled on a background thread.
 //
 // The consumer of IPC::ChannelProxy is responsible for allocating the Thread
 // instance where the IPC::Channel will be created and operated.
 //
 // Thread-safe send
 //
 // If a particular |Channel| implementation has a thread-safe |Send()| operation
 // then ChannelProxy skips the inter-thread hop and calls |Send()| directly. In
 // this case the |channel_| variable is touched by multiple threads so
 // |channel_lifetime_lock_| is used to protect it. The locking overhead is only
 // paid if the underlying channel supports thread-safe |Send|.
 //
 class COMPONENT_EXPORT(IPC) ChannelProxy : public Sender {
  public:
 #if defined(ENABLE_IPC_FUZZER)
   // Interface for a filter to be imposed on outgoing messages which can
   // re-write the message. Used for testing.
   class OutgoingMessageFilter {
    public:
     virtual Message* Rewrite(Message* message) = 0;
   };
 #endif

   // Initializes a channel proxy.  The channel_handle and mode parameters are
   // passed directly to the underlying IPC::Channel.  The listener is called on
   // the thread that creates the ChannelProxy.  The filter's OnMessageReceived
   // method is called on the thread where the IPC::Channel is running.  The
   // filter may be null if the consumer is not interested in handling messages
   // on the background thread.  Any message not handled by the filter will be
   // dispatched to the listener.  The given task runner correspond to a thread
   // on which IPC::Channel is created and used (e.g. IO thread).
   static std::unique_ptr<ChannelProxy> Create(
       const IPC::ChannelHandle& channel_handle,
       Channel::Mode mode,
       Listener* listener,
       const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
       const scoped_refptr<base::SingleThreadTaskRunner>& listener_task_runner);

   static std::unique_ptr<ChannelProxy> Create(
       std::unique_ptr<ChannelFactory> factory,
       Listener* listener,
       const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
       const scoped_refptr<base::SingleThreadTaskRunner>& listener_task_runner);

   // Constructs a ChannelProxy without initializing it.
   ChannelProxy(
       Listener* listener,
       const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
       const scoped_refptr<base::SingleThreadTaskRunner>& listener_task_runner);

   ~ChannelProxy() override;

   // Initializes the channel proxy. Only call this once to initialize a channel
   // proxy that was not initialized in its constructor. If |create_pipe_now| is
   // true, the pipe is created synchronously. Otherwise it's created on the IO
   // thread.
   void Init(const IPC::ChannelHandle& channel_handle,
             Channel::Mode mode,
             bool create_pipe_now);
   void Init(std::unique_ptr<ChannelFactory> factory,
             bool create_pipe_now);

   // Pause the channel. Subsequent calls to Send() will be internally queued
   // until Unpause() is called. Queued messages will not be sent until the
   // channel is flushed.
   void Pause();

   // Unpause the channel. If |flush| is true the channel will be flushed as soon
   // as it's unpaused (see Flush() below.) Otherwise you must explicitly call
   // Flush() to flush messages which were queued while the channel was paused.
   void Unpause(bool flush);

   // Flush the channel. This sends any messages which were queued before calling
   // Connect. Only useful if Unpause(false) was called previously.
   void Flush();

   // Close the IPC::Channel.  This operation completes asynchronously, once the
   // background thread processes the command to close the channel.  It is ok to
   // call this method multiple times.  Redundant calls are ignored.
   //
   // WARNING: MessageFilter objects held by the ChannelProxy is also
   // released asynchronously, and it may in fact have its final reference
   // released on the background thread.  The caller should be careful to deal
   // with / allow for this possibility.
   void Close();

   // Send a message asynchronously.  The message is routed to the background
   // thread where it is passed to the IPC::Channel's Send method.
   bool Send(Message* message) override;

   // Used to intercept messages as they are received on the background thread.
   //
   // Ordinarily, messages sent to the ChannelProxy are routed to the matching
   // listener on the worker thread.  This API allows code to intercept messages
   // before they are sent to the worker thread.
   // If you call this before the target process is launched, then you're
   // guaranteed to not miss any messages.  But if you call this anytime after,
   // then some messages might be missed since the filter is added internally on
   // the IO thread.
   void AddFilter(MessageFilter* filter);
   void RemoveFilter(MessageFilter* filter);

   using GenericAssociatedInterfaceFactory =
       base::Callback<void(mojo::ScopedInterfaceEndpointHandle)>;

   // Adds a generic associated interface factory to bind incoming interface
   // requests directly on the IO thread. MUST be called either before Init() or
   // before the remote end of the Channel is able to send messages (e.g. before
   // its process is launched.)
   void AddGenericAssociatedInterfaceForIOThread(
       const std::string& name,
       const GenericAssociatedInterfaceFactory& factory);

   template <typename Interface>
   using AssociatedInterfaceFactory =
       base::Callback<void(mojo::AssociatedInterfaceRequest<Interface>)>;

   // Helper to bind an IO-thread associated interface factory, inferring the
   // interface name from the callback argument's type. MUST be called before
   // Init().
   template <typename Interface>
   void AddAssociatedInterfaceForIOThread(
       const AssociatedInterfaceFactory<Interface>& factory) {
     AddGenericAssociatedInterfaceForIOThread(
         Interface::Name_,
         base::Bind(&ChannelProxy::BindAssociatedInterfaceRequest<Interface>,
                    factory));
   }

   // Requests an associated interface from the remote endpoint.
   void GetGenericRemoteAssociatedInterface(
       const std::string& name,
       mojo::ScopedInterfaceEndpointHandle handle);

   // Template helper to request associated interfaces from the remote endpoint.
   template <typename Interface>
   void GetRemoteAssociatedInterface(
       mojo::AssociatedInterfacePtr<Interface>* proxy) {
     auto request = mojo::MakeRequest(proxy);
     GetGenericRemoteAssociatedInterface(Interface::Name_, request.PassHandle());
   }

   // Template helper to receive associated interfaces from the remote endpoint.
   template <typename Interface>
   void GetRemoteAssociatedInterface(mojo::AssociatedRemote<Interface>* proxy) {
     GetGenericRemoteAssociatedInterface(
         Interface::Name_, proxy->BindNewEndpointAndPassReceiver().PassHandle());
   }

 #if defined(ENABLE_IPC_FUZZER)
   void set_outgoing_message_filter(OutgoingMessageFilter* filter) {
     outgoing_message_filter_ = filter;
   }
 #endif

   // Creates a ThreadSafeAssociatedInterfacePtr for |Interface|. This object
   // may be used to send messages on the interface from any thread and those
   // messages will remain ordered with respect to other messages sent on the
   // same thread over other ThreadSafeAssociatedInterfacePtrs associated with
   // the same Channel.
   template <typename Interface>
   void GetThreadSafeRemoteAssociatedInterface(
       scoped_refptr<mojo::ThreadSafeAssociatedInterfacePtr<Interface>>*
           out_ptr) {
     mojo::AssociatedInterfacePtrInfo<Interface> ptr_info;
     auto request = mojo::MakeRequest(&ptr_info);
     GetGenericRemoteAssociatedInterface(Interface::Name_, request.PassHandle());
     *out_ptr = mojo::ThreadSafeAssociatedInterfacePtr<Interface>::Create(
         std::move(ptr_info), ipc_task_runner());
   }

   base::SingleThreadTaskRunner* ipc_task_runner() const {
     return context_->ipc_task_runner();
   }

   const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner_refptr()
       const {
     return context_->ipc_task_runner_refptr();
   }

   // Called to clear the pointer to the IPC task runner when it's going away.
   void ClearIPCTaskRunner();

  protected:
   class Context;
   // A subclass uses this constructor if it needs to add more information
   // to the internal state.
   explicit ChannelProxy(Context* context);

   // Used internally to hold state that is referenced on the IPC thread.
   class Context : public base::RefCountedThreadSafe<Context>,
                   public Listener {
    public:
     Context(Listener* listener,
             const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
             const scoped_refptr<base::SingleThreadTaskRunner>&
                 listener_task_runner);
     void ClearIPCTaskRunner();
     base::SingleThreadTaskRunner* ipc_task_runner() const {
       return ipc_task_runner_.get();
     }
     const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner_refptr()
         const {
       return ipc_task_runner_;
     }

     scoped_refptr<base::SingleThreadTaskRunner> listener_task_runner() {
       return default_listener_task_runner_;
     }

     // Dispatches a message on the listener thread.
     void OnDispatchMessage(const Message& message);

     // Sends |message| from appropriate thread.
     void Send(Message* message);

     // Adds |task_runner| for the task to be executed later.
     void AddListenerTaskRunner(
         int32_t routing_id,
         scoped_refptr<base::SingleThreadTaskRunner> task_runner);

     // Removes task runner for |routing_id|.
     void RemoveListenerTaskRunner(int32_t routing_id);

     // Called on the IPC::Channel thread.
     // Returns the task runner associated with |routing_id|.
     scoped_refptr<base::SingleThreadTaskRunner> GetTaskRunner(
         int32_t routing_id);

    protected:
     friend class base::RefCountedThreadSafe<Context>;
     ~Context() override;

     // IPC::Listener methods:
     bool OnMessageReceived(const Message& message) override;
     void OnChannelConnected(int32_t peer_pid) override;
     void OnChannelError() override;
     void OnAssociatedInterfaceRequest(
         const std::string& interface_name,
         mojo::ScopedInterfaceEndpointHandle handle) override;

     // Like OnMessageReceived but doesn't try the filters.
     bool OnMessageReceivedNoFilter(const Message& message);

     // Gives the filters a chance at processing |message|.
     // Returns true if the message was processed, false otherwise.
     bool TryFilters(const Message& message);

     void PauseChannel();
     void UnpauseChannel(bool flush);
     void FlushChannel();

     // Like Open and Close, but called on the IPC thread.
     virtual void OnChannelOpened();
     virtual void OnChannelClosed();

     // Called on the consumers thread when the ChannelProxy is closed.  At that
     // point the consumer is telling us that they don't want to receive any
     // more messages, so we honor that wish by forgetting them!
     virtual void Clear();

    private:
     friend class ChannelProxy;
     friend class IpcSecurityTestUtil;

     // Create the Channel
     void CreateChannel(std::unique_ptr<ChannelFactory> factory);

     // Methods called on the IO thread.
     void OnSendMessage(std::unique_ptr<Message> message_ptr);
     void OnAddFilter();
     void OnRemoveFilter(MessageFilter* filter);

     // Methods called on the listener thread.
     void AddFilter(MessageFilter* filter);
     void OnDispatchConnected();
     void OnDispatchError();
     void OnDispatchBadMessage(const Message& message);
     void OnDispatchAssociatedInterfaceRequest(
         const std::string& interface_name,
         mojo::ScopedInterfaceEndpointHandle handle);

     void ClearChannel();

     mojom::Channel& thread_safe_channel() {
       return thread_safe_channel_->proxy();
     }

     void AddGenericAssociatedInterfaceForIOThread(
         const std::string& name,
         const GenericAssociatedInterfaceFactory& factory);

     base::Lock listener_thread_task_runners_lock_;
     // Map of routing_id and listener's thread task runner.
     std::map<int32_t, scoped_refptr<base::SingleThreadTaskRunner>>
         listener_thread_task_runners_
             GUARDED_BY(listener_thread_task_runners_lock_);

     scoped_refptr<base::SingleThreadTaskRunner> default_listener_task_runner_;
     Listener* listener_;

     // List of filters.  This is only accessed on the IPC thread.
     std::vector<scoped_refptr<MessageFilter> > filters_;
     scoped_refptr<base::SingleThreadTaskRunner> ipc_task_runner_;

     // Note, channel_ may be set on the Listener thread or the IPC thread.
     // But once it has been set, it must only be read or cleared on the IPC
     // thread.
     // One exception is the thread-safe send. See the class comment.
     std::unique_ptr<Channel> channel_;
     bool channel_connected_called_;

     // Lock for |channel_| value. This is only relevant in the context of
     // thread-safe send.
     base::Lock channel_lifetime_lock_;

     // Routes a given message to a proper subset of |filters_|, depending
     // on which message classes a filter might support.
     std::unique_ptr<MessageFilterRouter> message_filter_router_;

     // Holds filters between the AddFilter call on the listerner thread and the
     // IPC thread when they're added to filters_.
     std::vector<scoped_refptr<MessageFilter> > pending_filters_;
     // Lock for pending_filters_.
     base::Lock pending_filters_lock_;

     // Cached copy of the peer process ID. Set on IPC but read on both IPC and
     // listener threads.
     base::ProcessId peer_pid_;
     base::Lock peer_pid_lock_;

     // A thread-safe mojom::Channel interface we use to make remote interface
     // requests from the proxy thread.
     std::unique_ptr<mojo::ThreadSafeForwarder<mojom::Channel>>
         thread_safe_channel_;

     // Holds associated interface binders added by
     // AddGenericAssociatedInterfaceForIOThread until the underlying channel has
     // been initialized.
     base::Lock pending_io_thread_interfaces_lock_;
     std::vector<std::pair<std::string, GenericAssociatedInterfaceFactory>>
         pending_io_thread_interfaces_;
   };

   Context* context() { return context_.get(); }

 #if defined(ENABLE_IPC_FUZZER)
   OutgoingMessageFilter* outgoing_message_filter() const {
     return outgoing_message_filter_;
   }
 #endif

   bool did_init() const { return did_init_; }

   // A Send() which doesn't DCHECK if the message is synchronous.
   void SendInternal(Message* message);

  private:
   friend class IpcSecurityTestUtil;

   template <typename Interface>
   static void BindAssociatedInterfaceRequest(
       const AssociatedInterfaceFactory<Interface>& factory,
       mojo::ScopedInterfaceEndpointHandle handle) {
     factory.Run(mojo::AssociatedInterfaceRequest<Interface>(std::move(handle)));
   }

   // Always called once immediately after Init.
   virtual void OnChannelInit();

   // By maintaining this indirection (ref-counted) to our internal state, we
   // can safely be destroyed while the background thread continues to do stuff
   // that involves this data.
   scoped_refptr<Context> context_;

   // Whether the channel has been initialized.
   bool did_init_;

 #if defined(ENABLE_IPC_FUZZER)
   OutgoingMessageFilter* outgoing_message_filter_;
 #endif

   SEQUENCE_CHECKER(sequence_checker_);
 };

 }  // namespace IPC

 #endif  // IPC_IPC_CHANNEL_PROXY_H_
	// Copyright (c) 2012 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 IPC_IPC_CHANNEL_PROXY_H_
	#define IPC_IPC_CHANNEL_PROXY_H_

	#include <stdint.h>

	#include <map>
	#include <memory>
	#include <string>
	#include <vector>

	#include "base/bind.h"
	#include "base/callback.h"
	#include "base/component_export.h"
	#include "base/memory/ref_counted.h"
	#include "base/sequence_checker.h"
	#include "base/synchronization/lock.h"
	#include "build/build_config.h"
	#include "ipc/ipc.mojom.h"
	#include "ipc/ipc_channel.h"
	#include "ipc/ipc_channel_handle.h"
	#include "ipc/ipc_listener.h"
	#include "ipc/ipc_sender.h"
	#include "mojo/public/cpp/bindings/associated_interface_ptr.h"
	#include "mojo/public/cpp/bindings/associated_interface_request.h"
	#include "mojo/public/cpp/bindings/associated_remote.h"
	#include "mojo/public/cpp/bindings/scoped_interface_endpoint_handle.h"
	#include "mojo/public/cpp/bindings/thread_safe_interface_ptr.h"

	namespace base {
	class SingleThreadTaskRunner;
	}

	namespace IPC {

	class ChannelFactory;
	class MessageFilter;
	class MessageFilterRouter;

	//-----------------------------------------------------------------------------
	// IPC::ChannelProxy
	//
	// This class is a helper class that is useful when you wish to run an IPC
	// channel on a background thread. It provides you with the option of either
	// handling IPC messages on that background thread or having them dispatched to
	// your main thread (the thread on which the IPC::ChannelProxy is created).
	//
	// The API for an IPC::ChannelProxy is very similar to that of an IPC::Channel.
	// When you send a message to an IPC::ChannelProxy, the message is routed to
	// the background thread, where it is then passed to the IPC::Channel's Send
	// method. This means that you can send a message from your thread and your
	// message will be sent over the IPC channel when possible instead of being
	// delayed until your thread returns to its message loop. (Often IPC messages
	// will queue up on the IPC::Channel when there is a lot of traffic, and the
	// channel will not get cycles to flush its message queue until the thread, on
	// which it is running, returns to its message loop.)
	//
	// An IPC::ChannelProxy can have a MessageFilter associated with it, which will
	// be notified of incoming messages on the IPC::Channel's thread. This gives
	// the consumer of IPC::ChannelProxy the ability to respond to incoming
	// messages on this background thread instead of on their own thread, which may
	// be bogged down with other processing. The result can be greatly improved
	// latency for messages that can be handled on a background thread.
	//
	// The consumer of IPC::ChannelProxy is responsible for allocating the Thread
	// instance where the IPC::Channel will be created and operated.
	//
	// Thread-safe send
	//
	// If a particular \|Channel\| implementation has a thread-safe \|Send()\| operation
	// then ChannelProxy skips the inter-thread hop and calls \|Send()\| directly. In
	// this case the \|channel_\| variable is touched by multiple threads so
	// \|channel_lifetime_lock_\| is used to protect it. The locking overhead is only
	// paid if the underlying channel supports thread-safe \|Send\|.
	//
	class COMPONENT_EXPORT(IPC) ChannelProxy : public Sender {
	public:
	#if defined(ENABLE_IPC_FUZZER)
	// Interface for a filter to be imposed on outgoing messages which can
	// re-write the message. Used for testing.
	class OutgoingMessageFilter {
	public:
	virtual Message* Rewrite(Message* message) = 0;
	};
	#endif

	// Initializes a channel proxy. The channel_handle and mode parameters are
	// passed directly to the underlying IPC::Channel. The listener is called on
	// the thread that creates the ChannelProxy. The filter's OnMessageReceived
	// method is called on the thread where the IPC::Channel is running. The
	// filter may be null if the consumer is not interested in handling messages
	// on the background thread. Any message not handled by the filter will be
	// dispatched to the listener. The given task runner correspond to a thread
	// on which IPC::Channel is created and used (e.g. IO thread).
	static std::unique_ptr<ChannelProxy> Create(
	const IPC::ChannelHandle& channel_handle,
	Channel::Mode mode,
	Listener* listener,
	const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
	const scoped_refptr<base::SingleThreadTaskRunner>& listener_task_runner);

	static std::unique_ptr<ChannelProxy> Create(
	std::unique_ptr<ChannelFactory> factory,
	Listener* listener,
	const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
	const scoped_refptr<base::SingleThreadTaskRunner>& listener_task_runner);

	// Constructs a ChannelProxy without initializing it.
	ChannelProxy(
	Listener* listener,
	const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
	const scoped_refptr<base::SingleThreadTaskRunner>& listener_task_runner);

	~ChannelProxy() override;

	// Initializes the channel proxy. Only call this once to initialize a channel
	// proxy that was not initialized in its constructor. If \|create_pipe_now\| is
	// true, the pipe is created synchronously. Otherwise it's created on the IO
	// thread.
	void Init(const IPC::ChannelHandle& channel_handle,
	Channel::Mode mode,
	bool create_pipe_now);
	void Init(std::unique_ptr<ChannelFactory> factory,
	bool create_pipe_now);

	// Pause the channel. Subsequent calls to Send() will be internally queued
	// until Unpause() is called. Queued messages will not be sent until the
	// channel is flushed.
	void Pause();

	// Unpause the channel. If \|flush\| is true the channel will be flushed as soon
	// as it's unpaused (see Flush() below.) Otherwise you must explicitly call
	// Flush() to flush messages which were queued while the channel was paused.
	void Unpause(bool flush);

	// Flush the channel. This sends any messages which were queued before calling
	// Connect. Only useful if Unpause(false) was called previously.
	void Flush();

	// Close the IPC::Channel. This operation completes asynchronously, once the
	// background thread processes the command to close the channel. It is ok to
	// call this method multiple times. Redundant calls are ignored.
	//
	// WARNING: MessageFilter objects held by the ChannelProxy is also
	// released asynchronously, and it may in fact have its final reference
	// released on the background thread. The caller should be careful to deal
	// with / allow for this possibility.
	void Close();

	// Send a message asynchronously. The message is routed to the background
	// thread where it is passed to the IPC::Channel's Send method.
	bool Send(Message* message) override;

	// Used to intercept messages as they are received on the background thread.
	//
	// Ordinarily, messages sent to the ChannelProxy are routed to the matching
	// listener on the worker thread. This API allows code to intercept messages
	// before they are sent to the worker thread.
	// If you call this before the target process is launched, then you're
	// guaranteed to not miss any messages. But if you call this anytime after,
	// then some messages might be missed since the filter is added internally on
	// the IO thread.
	void AddFilter(MessageFilter* filter);
	void RemoveFilter(MessageFilter* filter);

	using GenericAssociatedInterfaceFactory =
	base::Callback<void(mojo::ScopedInterfaceEndpointHandle)>;

	// Adds a generic associated interface factory to bind incoming interface
	// requests directly on the IO thread. MUST be called either before Init() or
	// before the remote end of the Channel is able to send messages (e.g. before
	// its process is launched.)
	void AddGenericAssociatedInterfaceForIOThread(
	const std::string& name,
	const GenericAssociatedInterfaceFactory& factory);

	template <typename Interface>
	using AssociatedInterfaceFactory =
	base::Callback<void(mojo::AssociatedInterfaceRequest<Interface>)>;

	// Helper to bind an IO-thread associated interface factory, inferring the
	// interface name from the callback argument's type. MUST be called before
	// Init().
	template <typename Interface>
	void AddAssociatedInterfaceForIOThread(
	const AssociatedInterfaceFactory<Interface>& factory) {
	AddGenericAssociatedInterfaceForIOThread(
	Interface::Name_,
	base::Bind(&ChannelProxy::BindAssociatedInterfaceRequest<Interface>,
	factory));
	}

	// Requests an associated interface from the remote endpoint.
	void GetGenericRemoteAssociatedInterface(
	const std::string& name,
	mojo::ScopedInterfaceEndpointHandle handle);

	// Template helper to request associated interfaces from the remote endpoint.
	template <typename Interface>
	void GetRemoteAssociatedInterface(
	mojo::AssociatedInterfacePtr<Interface>* proxy) {
	auto request = mojo::MakeRequest(proxy);
	GetGenericRemoteAssociatedInterface(Interface::Name_, request.PassHandle());
	}

	// Template helper to receive associated interfaces from the remote endpoint.
	template <typename Interface>
	void GetRemoteAssociatedInterface(mojo::AssociatedRemote<Interface>* proxy) {
	GetGenericRemoteAssociatedInterface(
	Interface::Name_, proxy->BindNewEndpointAndPassReceiver().PassHandle());
	}

	#if defined(ENABLE_IPC_FUZZER)
	void set_outgoing_message_filter(OutgoingMessageFilter* filter) {
	outgoing_message_filter_ = filter;
	}
	#endif

	// Creates a ThreadSafeAssociatedInterfacePtr for \|Interface\|. This object
	// may be used to send messages on the interface from any thread and those
	// messages will remain ordered with respect to other messages sent on the
	// same thread over other ThreadSafeAssociatedInterfacePtrs associated with
	// the same Channel.
	template <typename Interface>
	void GetThreadSafeRemoteAssociatedInterface(
	scoped_refptr<mojo::ThreadSafeAssociatedInterfacePtr<Interface>>*
	out_ptr) {
	mojo::AssociatedInterfacePtrInfo<Interface> ptr_info;
	auto request = mojo::MakeRequest(&ptr_info);
	GetGenericRemoteAssociatedInterface(Interface::Name_, request.PassHandle());
	*out_ptr = mojo::ThreadSafeAssociatedInterfacePtr<Interface>::Create(
	std::move(ptr_info), ipc_task_runner());
	}

	base::SingleThreadTaskRunner* ipc_task_runner() const {
	return context_->ipc_task_runner();
	}

	const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner_refptr()
	const {
	return context_->ipc_task_runner_refptr();
	}

	// Called to clear the pointer to the IPC task runner when it's going away.
	void ClearIPCTaskRunner();

	protected:
	class Context;
	// A subclass uses this constructor if it needs to add more information
	// to the internal state.
	explicit ChannelProxy(Context* context);

	// Used internally to hold state that is referenced on the IPC thread.
	class Context : public base::RefCountedThreadSafe<Context>,
	public Listener {
	public:
	Context(Listener* listener,
	const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
	const scoped_refptr<base::SingleThreadTaskRunner>&
	listener_task_runner);
	void ClearIPCTaskRunner();
	base::SingleThreadTaskRunner* ipc_task_runner() const {
	return ipc_task_runner_.get();
	}
	const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner_refptr()
	const {
	return ipc_task_runner_;
	}

	scoped_refptr<base::SingleThreadTaskRunner> listener_task_runner() {
	return default_listener_task_runner_;
	}

	// Dispatches a message on the listener thread.
	void OnDispatchMessage(const Message& message);

	// Sends \|message\| from appropriate thread.
	void Send(Message* message);

	// Adds \|task_runner\| for the task to be executed later.
	void AddListenerTaskRunner(
	int32_t routing_id,
	scoped_refptr<base::SingleThreadTaskRunner> task_runner);

	// Removes task runner for \|routing_id\|.
	void RemoveListenerTaskRunner(int32_t routing_id);

	// Called on the IPC::Channel thread.
	// Returns the task runner associated with \|routing_id\|.
	scoped_refptr<base::SingleThreadTaskRunner> GetTaskRunner(
	int32_t routing_id);

	protected:
	friend class base::RefCountedThreadSafe<Context>;
	~Context() override;

	// IPC::Listener methods:
	bool OnMessageReceived(const Message& message) override;
	void OnChannelConnected(int32_t peer_pid) override;
	void OnChannelError() override;
	void OnAssociatedInterfaceRequest(
	const std::string& interface_name,
	mojo::ScopedInterfaceEndpointHandle handle) override;

	// Like OnMessageReceived but doesn't try the filters.
	bool OnMessageReceivedNoFilter(const Message& message);

	// Gives the filters a chance at processing \|message\|.
	// Returns true if the message was processed, false otherwise.
	bool TryFilters(const Message& message);

	void PauseChannel();
	void UnpauseChannel(bool flush);
	void FlushChannel();

	// Like Open and Close, but called on the IPC thread.
	virtual void OnChannelOpened();
	virtual void OnChannelClosed();

	// Called on the consumers thread when the ChannelProxy is closed. At that
	// point the consumer is telling us that they don't want to receive any
	// more messages, so we honor that wish by forgetting them!
	virtual void Clear();

	private:
	friend class ChannelProxy;
	friend class IpcSecurityTestUtil;

	// Create the Channel
	void CreateChannel(std::unique_ptr<ChannelFactory> factory);

	// Methods called on the IO thread.
	void OnSendMessage(std::unique_ptr<Message> message_ptr);
	void OnAddFilter();
	void OnRemoveFilter(MessageFilter* filter);

	// Methods called on the listener thread.
	void AddFilter(MessageFilter* filter);
	void OnDispatchConnected();
	void OnDispatchError();
	void OnDispatchBadMessage(const Message& message);
	void OnDispatchAssociatedInterfaceRequest(
	const std::string& interface_name,
	mojo::ScopedInterfaceEndpointHandle handle);

	void ClearChannel();

	mojom::Channel& thread_safe_channel() {
	return thread_safe_channel_->proxy();
	}

	void AddGenericAssociatedInterfaceForIOThread(
	const std::string& name,
	const GenericAssociatedInterfaceFactory& factory);

	base::Lock listener_thread_task_runners_lock_;
	// Map of routing_id and listener's thread task runner.
	std::map<int32_t, scoped_refptr<base::SingleThreadTaskRunner>>
	listener_thread_task_runners_
	GUARDED_BY(listener_thread_task_runners_lock_);

	scoped_refptr<base::SingleThreadTaskRunner> default_listener_task_runner_;
	Listener* listener_;

	// List of filters. This is only accessed on the IPC thread.
	std::vector<scoped_refptr<MessageFilter> > filters_;
	scoped_refptr<base::SingleThreadTaskRunner> ipc_task_runner_;

	// Note, channel_ may be set on the Listener thread or the IPC thread.
	// But once it has been set, it must only be read or cleared on the IPC
	// thread.
	// One exception is the thread-safe send. See the class comment.
	std::unique_ptr<Channel> channel_;
	bool channel_connected_called_;

	// Lock for \|channel_\| value. This is only relevant in the context of
	// thread-safe send.
	base::Lock channel_lifetime_lock_;

	// Routes a given message to a proper subset of \|filters_\|, depending
	// on which message classes a filter might support.
	std::unique_ptr<MessageFilterRouter> message_filter_router_;

	// Holds filters between the AddFilter call on the listerner thread and the
	// IPC thread when they're added to filters_.
	std::vector<scoped_refptr<MessageFilter> > pending_filters_;
	// Lock for pending_filters_.
	base::Lock pending_filters_lock_;

	// Cached copy of the peer process ID. Set on IPC but read on both IPC and
	// listener threads.
	base::ProcessId peer_pid_;
	base::Lock peer_pid_lock_;

	// A thread-safe mojom::Channel interface we use to make remote interface
	// requests from the proxy thread.
	std::unique_ptr<mojo::ThreadSafeForwarder<mojom::Channel>>
	thread_safe_channel_;

	// Holds associated interface binders added by
	// AddGenericAssociatedInterfaceForIOThread until the underlying channel has
	// been initialized.
	base::Lock pending_io_thread_interfaces_lock_;
	std::vector<std::pair<std::string, GenericAssociatedInterfaceFactory>>
	pending_io_thread_interfaces_;
	};

	Context* context() { return context_.get(); }

	#if defined(ENABLE_IPC_FUZZER)
	OutgoingMessageFilter* outgoing_message_filter() const {
	return outgoing_message_filter_;
	}
	#endif

	bool did_init() const { return did_init_; }

	// A Send() which doesn't DCHECK if the message is synchronous.
	void SendInternal(Message* message);

	private:
	friend class IpcSecurityTestUtil;

	template <typename Interface>
	static void BindAssociatedInterfaceRequest(
	const AssociatedInterfaceFactory<Interface>& factory,
	mojo::ScopedInterfaceEndpointHandle handle) {
	factory.Run(mojo::AssociatedInterfaceRequest<Interface>(std::move(handle)));
	}

	// Always called once immediately after Init.
	virtual void OnChannelInit();

	// By maintaining this indirection (ref-counted) to our internal state, we
	// can safely be destroyed while the background thread continues to do stuff
	// that involves this data.
	scoped_refptr<Context> context_;

	// Whether the channel has been initialized.
	bool did_init_;

	#if defined(ENABLE_IPC_FUZZER)
	OutgoingMessageFilter* outgoing_message_filter_;
	#endif

	SEQUENCE_CHECKER(sequence_checker_);
	};

	} // namespace IPC

	#endif // IPC_IPC_CHANNEL_PROXY_H_