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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.
+
+#ifndef IPC_IPC_CHANNEL_POSIX_H_
+#define IPC_IPC_CHANNEL_POSIX_H_
+#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.
+#define IPC_USES_READWRITE 1
+#endif
+
+namespace IPC {
+
+class Channel::ChannelImpl : public MessageLoopForIO::Watcher {
+ public:
+ // 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();
+ static bool IsNamedServerInitialized(const std::string& channel_id);
+
+ private:
+ 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_;
+
+#if defined(IPC_USES_READWRITE)
+ // Linux/BSD use a dedicated socketpair() for passing file descriptors.
+ int fd_pipe_;
+ int remote_fd_pipe_;
+#endif
+
+ // 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)) *
+ FileDescriptorSet::MAX_DESCRIPTORS_PER_MESSAGE,
+ };
+
+ // 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];
+#else
+ char input_cmsg_buf_[CMSG_SPACE(sizeof(int) * MAX_READ_FDS)];
+#endif
+
+ // 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_;
+
+ DISALLOW_IMPLICIT_CONSTRUCTORS(ChannelImpl);
+};
+
+// 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
+
+#endif // IPC_IPC_CHANNEL_POSIX_H_