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// Copyright (c) 2011 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.
#pragma once
#include "ipc/ipc_channel.h"
#include <sys/socket.h> // for CMSG macros
#include <queue>
#include <string>
#include <vector>
#include "base/message_loop.h"
#include "ipc/file_descriptor_set_posix.h"
#if !defined(OS_MACOSX)
// On Linux, the seccomp sandbox makes it very expensive to call
// recvmsg() and sendmsg(). The restriction on calling read() and write(), which
// are cheap, is that we can't pass file descriptors over them.
// As we cannot anticipate when the sender will provide us with file
// descriptors, we have to make the decision about whether we call read() or
// recvmsg() before we actually make the call. The easiest option is to
// create a dedicated socketpair() for exchanging file descriptors. Any file
// descriptors are split out of a message, with the non-file-descriptor payload
// going over the normal connection, and the file descriptors being sent
// separately over the other channel. When read()ing from a channel, we'll
// notice if the message was supposed to have come with file descriptors and
// use recvmsg on the other socketpair to retrieve them and combine them
// back with the rest of the message.
// Mac can also run in IPC_USES_READWRITE mode if necessary, but at this time
// doesn't take a performance hit from recvmsg and sendmsg, so it doesn't
// make sense to waste resources on having the separate dedicated socketpair.
// It is however useful for debugging between Linux and Mac to be able to turn
// this switch 'on' on the Mac as well.
// The HELLO message from the client to the server is always sent using
// sendmsg because it will contain the file descriptor that the server
// needs to send file descriptors in later messages.
namespace IPC {
class Channel::ChannelImpl : public MessageLoopForIO::Watcher {
// Mirror methods of Channel, see ipc_channel.h for description.
ChannelImpl(const IPC::ChannelHandle& channel_handle, Mode mode,
Listener* listener);
virtual ~ChannelImpl();
bool Connect();
void Close();
void set_listener(Listener* listener) { listener_ = listener; }
bool Send(Message* message);
int GetClientFileDescriptor() const;
bool AcceptsConnections() const;
bool HasAcceptedConnection() const;
bool GetClientEuid(uid_t* client_euid) const;
void ResetToAcceptingConnectionState();
bool CreatePipe(const IPC::ChannelHandle& channel_handle);
bool ProcessIncomingMessages();
bool ProcessOutgoingMessages();
bool AcceptConnection();
void ClosePipeOnError();
void QueueHelloMessage();
bool IsHelloMessage(const Message* m) const;
// MessageLoopForIO::Watcher implementation.
virtual void OnFileCanReadWithoutBlocking(int fd);
virtual void OnFileCanWriteWithoutBlocking(int fd);
Mode mode_;
// After accepting one client connection on our server socket we want to
// stop listening.
MessageLoopForIO::FileDescriptorWatcher server_listen_connection_watcher_;
MessageLoopForIO::FileDescriptorWatcher read_watcher_;
MessageLoopForIO::FileDescriptorWatcher write_watcher_;
// Indicates whether we're currently blocked waiting for a write to complete.
bool is_blocked_on_write_;
bool waiting_connect_;
// If sending a message blocks then we use this variable
// to keep track of where we are.
size_t message_send_bytes_written_;
// File descriptor we're listening on for new connections if we listen
// for connections.
int server_listen_pipe_;
// The pipe used for communication.
int pipe_;
// For a server, the client end of our socketpair() -- the other end of our
// pipe_ that is passed to the client.
int client_pipe_;
// Linux/BSD use a dedicated socketpair() for passing file descriptors.
int fd_pipe_;
int remote_fd_pipe_;
// The "name" of our pipe. On Windows this is the global identifier for
// the pipe. On POSIX it's used as a key in a local map of file descriptors.
std::string pipe_name_;
Listener* listener_;
// Messages to be sent are queued here.
std::queue<Message*> output_queue_;
// We read from the pipe into this buffer
char input_buf_[Channel::kReadBufferSize];
enum {
// We assume a worst case: kReadBufferSize bytes of messages, where each
// message has no payload and a full complement of descriptors.
MAX_READ_FDS = (Channel::kReadBufferSize / sizeof(IPC::Message::Header)) *
// This is a control message buffer large enough to hold kMaxReadFDs
#if defined(OS_MACOSX)
// TODO(agl): OSX appears to have non-constant CMSG macros!
char input_cmsg_buf_[1024];
char input_cmsg_buf_[CMSG_SPACE(sizeof(int) * MAX_READ_FDS)];
// Large messages that span multiple pipe buffers, get built-up using
// this buffer.
std::string input_overflow_buf_;
std::vector<int> input_overflow_fds_;
// True if we are responsible for unlinking the unix domain socket file.
bool must_unlink_;
// The maximum length of the name of a pipe for MODE_NAMED_SERVER or
// MODE_NAMED_CLIENT if you want to pass in your own socket.
// The standard size on linux is 108, mac is 104. To maintain consistency
// across platforms we standardize on the smaller value.
static const size_t kMaxPipeNameLength = 104;
} // namespace IPC