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// 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.
#include <stddef.h>
#include <stdint.h>
#include <memory>
#include <string>
#include "base/compiler_specific.h"
#include "base/component_export.h"
#include "base/files/scoped_file.h"
#include "base/memory/ref_counted.h"
#include "base/process/process.h"
#include "base/single_thread_task_runner.h"
#include "base/threading/thread_task_runner_handle.h"
#include "build/build_config.h"
#include "ipc/ipc.mojom.h"
#include "ipc/ipc_channel_handle.h"
#include "ipc/ipc_message.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/scoped_interface_endpoint_handle.h"
#include "mojo/public/cpp/bindings/thread_safe_interface_ptr.h"
#if defined(OS_POSIX)
#include <sys/types.h>
namespace IPC {
class Listener;
// See
// for overview of IPC in Chromium.
// Channels are implemented using mojo message pipes on all platforms other
// than NaCl.
class COMPONENT_EXPORT(IPC) Channel : public Sender {
// Security tests need access to the pipe handle.
friend class ChannelTest;
// Flags to test modes
enum ModeFlags {
// Some Standard Modes
// TODO(morrita): These are under deprecation work. You should use Create*()
// functions instead.
enum Mode {
// Messages internal to the IPC implementation are defined here.
// Uses Maximum value of message type (uint16_t), to avoid conflicting
// with normal message types, which are enumeration constants starting from 0.
enum {
// The Hello message 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).
// The CLOSE_FD_MESSAGE_TYPE is used in the IPC class to
// work around a bug in sendmsg() on Mac. When an FD is sent
// over the socket, a CLOSE_FD_MESSAGE is sent with hops = 2.
// The client will return the message with hops = 1, *after* it
// has received the message that contains the FD. When we
// receive it again on the sender side, we close the FD.
// Helper interface a Channel may implement to expose support for associated
// Mojo interfaces.
class COMPONENT_EXPORT(IPC) AssociatedInterfaceSupport {
using GenericAssociatedInterfaceFactory =
virtual ~AssociatedInterfaceSupport() {}
// Returns a ThreadSafeForwarded for this channel which can be used to
// safely send mojom::Channel requests from arbitrary threads.
virtual std::unique_ptr<mojo::ThreadSafeForwarder<mojom::Channel>>
CreateThreadSafeChannel() = 0;
// Adds an interface factory to this channel for interface |name|. Must be
// safe to call from any thread.
virtual void AddGenericAssociatedInterface(
const std::string& name,
const GenericAssociatedInterfaceFactory& factory) = 0;
// Requests an associated interface from the remote endpoint.
virtual void GetGenericRemoteAssociatedInterface(
const std::string& name,
mojo::ScopedInterfaceEndpointHandle handle) = 0;
// Template helper to add an interface factory to this channel.
template <typename Interface>
using AssociatedInterfaceFactory =
template <typename Interface>
void AddAssociatedInterface(
const AssociatedInterfaceFactory<Interface>& factory) {
base::Bind(&BindAssociatedInterfaceRequest<Interface>, factory));
// Template helper to request a remote associated interface.
template <typename Interface>
void GetRemoteAssociatedInterface(
mojo::AssociatedInterfacePtr<Interface>* proxy) {
auto request = mojo::MakeRequest(proxy);
Interface::Name_, request.PassHandle());
template <typename Interface>
static void BindAssociatedInterfaceRequest(
const AssociatedInterfaceFactory<Interface>& factory,
mojo::ScopedInterfaceEndpointHandle handle) {
// The maximum message size in bytes. Attempting to receive a message of this
// size or bigger results in a channel error.
static constexpr size_t kMaximumMessageSize = 128 * 1024 * 1024;
// Amount of data to read at once from the pipe.
static const size_t kReadBufferSize = 4 * 1024;
// Maximum persistent read buffer size. Read buffer can grow larger to
// accommodate large messages, but it's recommended to shrink back to this
// value because it fits 99.9% of all messages (see issue 529940 for data).
static const size_t kMaximumReadBufferSize = 64 * 1024;
// Initialize a Channel.
// |channel_handle| identifies the communication Channel. For POSIX, if
// the file descriptor in the channel handle is != -1, the channel takes
// ownership of the file descriptor and will close it appropriately, otherwise
// it will create a new descriptor internally.
// |listener| receives a callback on the current thread for each newly
// received message.
// There are four type of modes how channels operate:
// - Server and named server: In these modes, the Channel is
// responsible for settingb up the IPC object
// - An "open" named server: It accepts connections from ANY client.
// The caller must then implement their own access-control based on the
// client process' user Id.
// - Client and named client: In these mode, the Channel merely
// connects to the already established IPC object.
// Each mode has its own Create*() API to create the Channel object.
static std::unique_ptr<Channel> Create(
const IPC::ChannelHandle& channel_handle,
Mode mode,
Listener* listener);
static std::unique_ptr<Channel> CreateClient(
const IPC::ChannelHandle& channel_handle,
Listener* listener,
const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner);
static std::unique_ptr<Channel> CreateServer(
const IPC::ChannelHandle& channel_handle,
Listener* listener,
const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner);
~Channel() override;
// 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.
// The subclass implementation must call WillConnect() at the beginning of its
// implementation.
virtual bool Connect() WARN_UNUSED_RESULT = 0;
// Pause the channel. Subsequent sends will be queued internally until
// Unpause() is called and the channel is flushed either by Unpause() or a
// subsequent call to Flush().
virtual void Pause();
// Unpause the channel. This allows subsequent Send() calls to transmit
// messages immediately, without queueing. If |flush| is true, any messages
// queued while paused will be flushed immediately upon unpausing. Otherwise
// you must call Flush() explicitly.
// Not all implementations support Unpause(). See ConnectPaused() above for
// details.
virtual void Unpause(bool flush);
// Manually flush the pipe. This is only useful exactly once, and only after
// a call to Unpause(false), in order to explicitly flush out any
// messages which were queued prior to unpausing.
// Not all implementations support Flush(). See ConnectPaused() above for
// details.
virtual void Flush();
// Close this Channel explicitly. May be called multiple times.
// On POSIX calling close on an IPC channel that listens for connections will
// cause it to close any accepted connections, and it will stop listening for
// new connections. If you just want to close the currently accepted
// connection and listen for new ones, use ResetToAcceptingConnectionState.
virtual void Close() = 0;
// Gets a helper for associating Mojo interfaces with this Channel.
// NOTE: Not all implementations support this.
virtual AssociatedInterfaceSupport* GetAssociatedInterfaceSupport();
// Overridden from ipc::Sender.
// Send a message over the Channel to the listener on the other end.
// |message| must be allocated using operator new. This object will be
// deleted once the contents of the Message have been sent.
bool Send(Message* message) override = 0;
#if !defined(OS_NACL_SFI)
// Generates a channel ID that's non-predictable and unique.
static std::string GenerateUniqueRandomChannelID();
#if defined(OS_LINUX)
// Sandboxed processes live in a PID namespace, so when sending the IPC hello
// message from client to server we need to send the PID from the global
// PID namespace.
static void SetGlobalPid(int pid);
static int GetGlobalPid();
// Subclasses must call this method at the beginning of their implementation
// of Connect().
void WillConnect();
bool did_start_connect_ = false;
} // namespace IPC
#endif // IPC_IPC_CHANNEL_H_