ipc/ipc_channel_posix.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef IPC_IPC_CHANNEL_POSIX_H_
   6 #define IPC_IPC_CHANNEL_POSIX_H_
   7
   8 #include "ipc/ipc_channel.h"
   9
  10 #include <sys/socket.h>  // for CMSG macros
  11
  12 #include <queue>
  13 #include <set>
  14 #include <string>
  15 #include <vector>
  16
  17 #include "base/message_loop/message_loop.h"
  18 #include "base/process/process.h"
  19 #include "ipc/file_descriptor_set_posix.h"
  20 #include "ipc/ipc_channel_reader.h"
  21
  22 #if !defined(OS_MACOSX)
  23 // On Linux, the seccomp sandbox makes it very expensive to call
  24 // recvmsg() and sendmsg(). The restriction on calling read() and write(), which
  25 // are cheap, is that we can't pass file descriptors over them.
  26 //
  27 // As we cannot anticipate when the sender will provide us with file
  28 // descriptors, we have to make the decision about whether we call read() or
  29 // recvmsg() before we actually make the call. The easiest option is to
  30 // create a dedicated socketpair() for exchanging file descriptors. Any file
  31 // descriptors are split out of a message, with the non-file-descriptor payload
  32 // going over the normal connection, and the file descriptors being sent
  33 // separately over the other channel. When read()ing from a channel, we'll
  34 // notice if the message was supposed to have come with file descriptors and
  35 // use recvmsg on the other socketpair to retrieve them and combine them
  36 // back with the rest of the message.
  37 //
  38 // Mac can also run in IPC_USES_READWRITE mode if necessary, but at this time
  39 // doesn't take a performance hit from recvmsg and sendmsg, so it doesn't
  40 // make sense to waste resources on having the separate dedicated socketpair.
  41 // It is however useful for debugging between Linux and Mac to be able to turn
  42 // this switch 'on' on the Mac as well.
  43 //
  44 // The HELLO message from the client to the server is always sent using
  45 // sendmsg because it will contain the file descriptor that the server
  46 // needs to send file descriptors in later messages.
  47 #define IPC_USES_READWRITE 1
  48 #endif
  49
  50 namespace IPC {
  51
  52 class ChannelPosix : public Channel,
  53                      public internal::ChannelReader,
  54                      public base::MessageLoopForIO::Watcher {
  55  public:
  56   // Mirror methods of Channel, see ipc_channel.h for description.
  57   ChannelPosix(const IPC::ChannelHandle& channel_handle, Mode mode,
  58                Listener* listener);
  59   virtual ~ChannelPosix();
  60
  61   // Channel implementation
  62   virtual bool Connect() OVERRIDE;
  63   virtual void Close() OVERRIDE;
  64   virtual bool Send(Message* message) OVERRIDE;
  65   virtual base::ProcessId GetPeerPID() const OVERRIDE;
  66   virtual int GetClientFileDescriptor() const OVERRIDE;
  67   virtual int TakeClientFileDescriptor() OVERRIDE;
  68   virtual bool AcceptsConnections() const OVERRIDE;
  69   virtual bool HasAcceptedConnection() const OVERRIDE;
  70   virtual bool GetPeerEuid(uid_t* peer_euid) const OVERRIDE;
  71   virtual void ResetToAcceptingConnectionState() OVERRIDE;
  72
  73   void CloseClientFileDescriptor();
  74
  75   static bool IsNamedServerInitialized(const std::string& channel_id);
  76 #if defined(OS_LINUX)
  77   static void SetGlobalPid(int pid);
  78 #endif  // OS_LINUX
  79
  80  private:
  81   bool CreatePipe(const IPC::ChannelHandle& channel_handle);
  82
  83   bool ProcessOutgoingMessages();
  84
  85   bool AcceptConnection();
  86   void ClosePipeOnError();
  87   int GetHelloMessageProcId();
  88   void QueueHelloMessage();
  89   void CloseFileDescriptors(Message* msg);
  90   void QueueCloseFDMessage(int fd, int hops);
  91
  92   // ChannelReader implementation.
  93   virtual ReadState ReadData(char* buffer,
  94                              int buffer_len,
  95                              int* bytes_read) OVERRIDE;
  96   virtual bool WillDispatchInputMessage(Message* msg) OVERRIDE;
  97   virtual bool DidEmptyInputBuffers() OVERRIDE;
  98   virtual void HandleInternalMessage(const Message& msg) OVERRIDE;
  99
 100 #if defined(IPC_USES_READWRITE)
 101   // Reads the next message from the fd_pipe_ and appends them to the
 102   // input_fds_ queue. Returns false if there was a message receiving error.
 103   // True means there was a message and it was processed properly, or there was
 104   // no messages.
 105   bool ReadFileDescriptorsFromFDPipe();
 106 #endif
 107
 108   // Finds the set of file descriptors in the given message.  On success,
 109   // appends the descriptors to the input_fds_ member and returns true
 110   //
 111   // Returns false if the message was truncated. In this case, any handles that
 112   // were sent will be closed.
 113   bool ExtractFileDescriptorsFromMsghdr(msghdr* msg);
 114
 115   // Closes all handles in the input_fds_ list and clears the list. This is
 116   // used to clean up handles in error conditions to avoid leaking the handles.
 117   void ClearInputFDs();
 118
 119   // MessageLoopForIO::Watcher implementation.
 120   virtual void OnFileCanReadWithoutBlocking(int fd) OVERRIDE;
 121   virtual void OnFileCanWriteWithoutBlocking(int fd) OVERRIDE;
 122
 123   Mode mode_;
 124
 125   base::ProcessId peer_pid_;
 126
 127   // After accepting one client connection on our server socket we want to
 128   // stop listening.
 129   base::MessageLoopForIO::FileDescriptorWatcher
 130   server_listen_connection_watcher_;
 131   base::MessageLoopForIO::FileDescriptorWatcher read_watcher_;
 132   base::MessageLoopForIO::FileDescriptorWatcher write_watcher_;
 133
 134   // Indicates whether we're currently blocked waiting for a write to complete.
 135   bool is_blocked_on_write_;
 136   bool waiting_connect_;
 137
 138   // If sending a message blocks then we use this variable
 139   // to keep track of where we are.
 140   size_t message_send_bytes_written_;
 141
 142   // File descriptor we're listening on for new connections if we listen
 143   // for connections.
 144   int server_listen_pipe_;
 145
 146   // The pipe used for communication.
 147   int pipe_;
 148
 149   // For a server, the client end of our socketpair() -- the other end of our
 150   // pipe_ that is passed to the client.
 151   int client_pipe_;
 152   mutable base::Lock client_pipe_lock_;  // Lock that protects |client_pipe_|.
 153
 154 #if defined(IPC_USES_READWRITE)
 155   // Linux/BSD use a dedicated socketpair() for passing file descriptors.
 156   int fd_pipe_;
 157   int remote_fd_pipe_;
 158 #endif
 159
 160   // The "name" of our pipe.  On Windows this is the global identifier for
 161   // the pipe.  On POSIX it's used as a key in a local map of file descriptors.
 162   std::string pipe_name_;
 163
 164   // Messages to be sent are queued here.
 165   std::queue<Message*> output_queue_;
 166
 167   // We assume a worst case: kReadBufferSize bytes of messages, where each
 168   // message has no payload and a full complement of descriptors.
 169   static const size_t kMaxReadFDs =
 170       (Channel::kReadBufferSize / sizeof(IPC::Message::Header)) *
 171       FileDescriptorSet::kMaxDescriptorsPerMessage;
 172
 173   // Buffer size for file descriptors used for recvmsg. On Mac the CMSG macros
 174   // don't seem to be constant so we have to pick a "large enough" value.
 175 #if defined(OS_MACOSX)
 176   static const size_t kMaxReadFDBuffer = 1024;
 177 #else
 178   static const size_t kMaxReadFDBuffer = CMSG_SPACE(sizeof(int) * kMaxReadFDs);
 179 #endif
 180
 181   // Temporary buffer used to receive the file descriptors from recvmsg.
 182   // Code that writes into this should immediately read them out and save
 183   // them to input_fds_, since this buffer will be re-used anytime we call
 184   // recvmsg.
 185   char input_cmsg_buf_[kMaxReadFDBuffer];
 186
 187   // File descriptors extracted from messages coming off of the channel. The
 188   // handles may span messages and come off different channels from the message
 189   // data (in the case of READWRITE), and are processed in FIFO here.
 190   // NOTE: The implementation assumes underlying storage here is contiguous, so
 191   // don't change to something like std::deque<> without changing the
 192   // implementation!
 193   std::vector<int> input_fds_;
 194
 195 #if defined(OS_MACOSX)
 196   // On OSX, sent FDs must not be closed until we get an ack.
 197   // Keep track of sent FDs here to make sure the remote is not
 198   // trying to bamboozle us.
 199   std::set<int> fds_to_close_;
 200 #endif
 201
 202   // True if we are responsible for unlinking the unix domain socket file.
 203   bool must_unlink_;
 204
 205 #if defined(OS_LINUX)
 206   // If non-zero, overrides the process ID sent in the hello message.
 207   static int global_pid_;
 208 #endif  // OS_LINUX
 209
 210   DISALLOW_IMPLICIT_CONSTRUCTORS(ChannelPosix);
 211 };
 212
 213 }  // namespace IPC
 214
 215 #endif  // IPC_IPC_CHANNEL_POSIX_H_