// Copyright (c) 2006-2008 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 CHROME_COMMON_IPC_CHANNEL_H_
#define CHROME_COMMON_IPC_CHANNEL_H_

#include <cstdint>
#include <variant>
#include "base/basictypes.h"
#include "base/process.h"
#include "mozilla/EventTargetAndLockCapability.h"
#include "mozilla/Mutex.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/UniquePtrExtensions.h"
#include "chrome/common/ipc_message.h"

#include "nsISerialEventTarget.h"

#ifdef XP_WIN
#endif

namespace IPC {

class Message;
class MessageReader;
class MessageWriter;

//------------------------------------------------------------------------------

class Channel {
 public:
  NS_INLINE_DECL_THREADSAFE_REFCOUNTING_WITH_DELETE_ON_EVENT_TARGET(
      Channel, IOThread().GetEventTarget());

  // For channels which are created after initialization, handles to the pipe
  // endpoints may be passed around directly using IPC messages.
  using ChannelHandle =
      std::variant<std::monostate, mozilla::UniqueFileHandle
#if defined(XP_DARWIN)
                   ,
                   mozilla::UniqueMachSendRight, mozilla::UniqueMachReceiveRight
#endif
                   >;

  // Implemented by consumers of a Channel to receive messages.
  //
  // All listeners will only be called on the IO thread, and must be destroyed
  // on the IO thread.
  class Listener {
   public:
    virtual ~Listener() = default;

    // Called when a message is received.
    virtual void OnMessageReceived(mozilla::UniquePtr<Message> message) = 0;

    // Called when the channel is connected and we have received the internal
    // Hello message from the peer.
    virtual void OnChannelConnected(base::ProcessId peer_pid) {}

    // Called when an error is detected that causes the channel to close.
    // This method is not called when a channel is closed normally.
    virtual void OnChannelError() {}
  };

  enum Mode { MODE_BROKER_SERVER, MODE_BROKER_CLIENT, MODE_PEER };

  enum {

  // The maximum message size in bytes. Attempting to receive a
  // message of this size or bigger results in a channel error.
  // This is larger in fuzzing builds to allow the fuzzing of passing
  // large data structures into DOM methods without crashing.
#ifndef FUZZING
    kMaximumMessageSize = 256 * 1024 * 1024,
#else
    kMaximumMessageSize = 1792 * 1024 * 1024,  // 1.75GB
#endif

    // Amount of data to read at once from the pipe.
    kReadBufferSize = 4 * 1024,
  };

  // Each channel implementation has a static ChannelKind vtable which can be
  // used to access "static" methods, not associated with a Channel instance.
  struct ChannelKind {
    // Create a new pair of pipe endpoints which can be used to establish a
    // native IPC::Channel connection.
    bool (*create_raw_pipe)(ChannelHandle* server, ChannelHandle* client);

    // The number of attachments in |message| which will need to be relayed via.
    // the broker channel, rather than being sent directly to a non-broker peer.
    uint32_t (*num_relayed_attachments)(const IPC::Message& message);

    // Check if |handle| is a valid handle for creating a channel of this kind.
    bool (*is_valid_handle)(const ChannelHandle& handle);
  };

  // Initialize a Channel.
  //
  // |pipe| identifies the pipe which will be used. It should have been created
  // using CreateRawPipe().
  // |mode| specifies whether this channel is operating in server mode or client
  // mode. One side of the connection should be the client, and the other should
  // be the server.
  // |other_pid| specifies the pid of the other side of this channel. This will
  // be used for logging, and for transferring HANDLEs from a privileged process
  // on Windows (if enabled).
  //
  // The Channel must be created and destroyed on the IO thread, and all
  // methods, unless otherwise noted, are only safe to call on the I/O thread.
  //
  static already_AddRefed<Channel> Create(ChannelHandle pipe, Mode mode,
                                          base::ProcessId other_pid);

  Channel(const Channel&) = delete;
  Channel& operator=(const Channel&) = delete;

  // Connect the pipe.  On the server side, this will initiate
  // waiting for connections.  On the client, it attempts to
  // connect to a pre-existing pipe.  Note, calling Connect()
  // will not block the calling thread and may complete
  // asynchronously.
  //
  // |listener| will receive a callback on the current thread for each newly
  // received message.
  virtual bool Connect(Listener* listener) MOZ_EXCLUDES(SendMutex()) = 0;

  // Close this Channel explicitly.  May be called multiple times.
  virtual void Close() MOZ_EXCLUDES(SendMutex()) = 0;

  // Send a message over the Channel to the listener on the other end.
  //
  // This method may be called from any thread, so long as the `Channel` is not
  // destroyed before it returns.
  //
  // If you Send() a message on a Close()'d channel, we delete the message
  // immediately.
  virtual bool Send(mozilla::UniquePtr<Message> message)
      MOZ_EXCLUDES(SendMutex()) = 0;

  // Explicitly set the pid expected for the other side of this channel. This
  // will be used for logging, and on Windows may be used for transferring
  // handles between processes.
  //
  // If it is set this way, the "hello" message will be checked to ensure that
  // the same pid is reported.
  virtual void SetOtherPid(base::ProcessId other_pid)
      MOZ_EXCLUDES(SendMutex()) = 0;

#if defined(XP_DARWIN)
  // Configure the mach task_t for the peer task.
  virtual void SetOtherMachTask(task_t task) MOZ_EXCLUDES(SendMutex()) = 0;
#endif

  // Get the static ChannelKind vtable for this Channel's implementation.
  virtual const ChannelKind* GetKind() const = 0;

 protected:
  Channel();
  virtual ~Channel();

  // Capability for members which may only be used on the IO thread. Generally
  // used for state related to receiving IPC messages.
  const mozilla::EventTargetCapability<nsISerialEventTarget>& IOThread() const
      MOZ_RETURN_CAPABILITY(chan_cap_.Target()) {
    return chan_cap_.Target();
  }

  // Capability for members which may only be used with the send mutex held.
  // Generally used for state related to sending IPC messages.
  mozilla::Mutex& SendMutex() MOZ_RETURN_CAPABILITY(chan_cap_.Lock()) {
    return chan_cap_.Lock();
  }

  // Compound capability of the IO thread and a Mutex. This can be used for
  // members which may be used immutably either on the IO thread or with the
  // send mutex held, but may only be modified if both on the IO thread, and
  // holding the send mutex.
  mozilla::EventTargetAndLockCapability<nsISerialEventTarget, mozilla::Mutex>
      chan_cap_;

  enum {
#if defined(XP_DARWIN)
    // If the channel receives a message that contains file descriptors, then
    // it will reply back with this message, indicating that the message has
    // been received. The sending channel can then close any descriptors that
    // had been marked as auto_close. This works around a sendmsg() bug on BSD
    // where the kernel can eagerly close file descriptors that are in message
    // queues but not yet delivered.
    RECEIVED_FDS_MESSAGE_TYPE = kuint16max - 1,
#endif

    // The Hello message is internal to the Channel class.  It is sent
    // by the peer when the channel is connected.  The message contains
    // just the process id (pid).  The message has a special routing_id
    // (MSG_ROUTING_NONE) and type (HELLO_MESSAGE_TYPE).
    HELLO_MESSAGE_TYPE = kuint16max  // Maximum value of message type
                                     // (uint16_t), to avoid conflicting with
                                     // normal message types, which are
                                     // enumeration constants starting from 0.
  };
};

}  // namespace IPC

#endif  // CHROME_COMMON_IPC_CHANNEL_H_