1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
|
// 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_POSIX_H_
#define IPC_IPC_CHANNEL_POSIX_H_
#include "ipc/ipc_channel.h"
#include <sys/socket.h> // for CMSG macros
#include <queue>
#include <string>
#include <vector>
#include "base/message_loop.h"
#include "base/process.h"
#include "ipc/file_descriptor_set_posix.h"
#include "ipc/ipc_channel_reader.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 internal::ChannelReader,
public base::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();
bool Send(Message* message);
int GetClientFileDescriptor();
int TakeClientFileDescriptor();
void CloseClientFileDescriptor();
bool AcceptsConnections() const;
bool HasAcceptedConnection() const;
bool GetPeerEuid(uid_t* peer_euid) const;
void ResetToAcceptingConnectionState();
base::ProcessId peer_pid() const { return peer_pid_; }
static bool IsNamedServerInitialized(const std::string& channel_id);
#if defined(OS_LINUX)
static void SetGlobalPid(int pid);
#endif // OS_LINUX
private:
bool CreatePipe(const IPC::ChannelHandle& channel_handle);
bool ProcessOutgoingMessages();
bool AcceptConnection();
void ClosePipeOnError();
int GetHelloMessageProcId();
void QueueHelloMessage();
// ChannelReader implementation.
virtual ReadState ReadData(char* buffer,
int buffer_len,
int* bytes_read) OVERRIDE;
virtual bool WillDispatchInputMessage(Message* msg) OVERRIDE;
virtual bool DidEmptyInputBuffers() OVERRIDE;
virtual void HandleHelloMessage(const Message& msg) OVERRIDE;
#if defined(IPC_USES_READWRITE)
// Reads the next message from the fd_pipe_ and appends them to the
// input_fds_ queue. Returns false if there was a message receiving error.
// True means there was a message and it was processed properly, or there was
// no messages.
bool ReadFileDescriptorsFromFDPipe();
#endif
// Finds the set of file descriptors in the given message. On success,
// appends the descriptors to the input_fds_ member and returns true
//
// Returns false if the message was truncated. In this case, any handles that
// were sent will be closed.
bool ExtractFileDescriptorsFromMsghdr(msghdr* msg);
// Closes all handles in the input_fds_ list and clears the list. This is
// used to clean up handles in error conditions to avoid leaking the handles.
void ClearInputFDs();
// MessageLoopForIO::Watcher implementation.
virtual void OnFileCanReadWithoutBlocking(int fd) OVERRIDE;
virtual void OnFileCanWriteWithoutBlocking(int fd) OVERRIDE;
Mode mode_;
base::ProcessId peer_pid_;
// After accepting one client connection on our server socket we want to
// stop listening.
base::MessageLoopForIO::FileDescriptorWatcher
server_listen_connection_watcher_;
base::MessageLoopForIO::FileDescriptorWatcher read_watcher_;
base::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_;
base::Lock client_pipe_lock_; // Lock that protects |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_;
// Messages to be sent are queued here.
std::queue<Message*> output_queue_;
// We assume a worst case: kReadBufferSize bytes of messages, where each
// message has no payload and a full complement of descriptors.
static const size_t kMaxReadFDs =
(Channel::kReadBufferSize / sizeof(IPC::Message::Header)) *
FileDescriptorSet::kMaxDescriptorsPerMessage;
// Buffer size for file descriptors used for recvmsg. On Mac the CMSG macros
// don't seem to be constant so we have to pick a "large enough" value.
#if defined(OS_MACOSX)
static const size_t kMaxReadFDBuffer = 1024;
#else
static const size_t kMaxReadFDBuffer = CMSG_SPACE(sizeof(int) * kMaxReadFDs);
#endif
// Temporary buffer used to receive the file descriptors from recvmsg.
// Code that writes into this should immediately read them out and save
// them to input_fds_, since this buffer will be re-used anytime we call
// recvmsg.
char input_cmsg_buf_[kMaxReadFDBuffer];
// File descriptors extracted from messages coming off of the channel. The
// handles may span messages and come off different channels from the message
// data (in the case of READWRITE), and are processed in FIFO here.
// NOTE: The implementation assumes underlying storage here is contiguous, so
// don't change to something like std::deque<> without changing the
// implementation!
std::vector<int> input_fds_;
// True if we are responsible for unlinking the unix domain socket file.
bool must_unlink_;
#if defined(OS_LINUX)
// If non-zero, overrides the process ID sent in the hello message.
static int global_pid_;
#endif // OS_LINUX
DISALLOW_IMPLICIT_CONSTRUCTORS(ChannelImpl);
};
} // namespace IPC
#endif // IPC_IPC_CHANNEL_POSIX_H_
|
