1 // Copyright (c) 2011 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.
5 #ifndef IPC_IPC_CHANNEL_H_
6 #define IPC_IPC_CHANNEL_H_
9 #include "base/compiler_specific.h"
10 #include "ipc/ipc_channel_handle.h"
11 #include "ipc/ipc_message.h"
15 //------------------------------------------------------------------------------
17 // http://www.chromium.org/developers/design-documents/inter-process-communication
18 // for overview of IPC in Chromium.
20 // Channels are implemented using named pipes on Windows, and
21 // socket pairs (or in some special cases unix domain sockets) on POSIX.
22 // On Windows we access pipes in various processes by name.
23 // On POSIX we pass file descriptors to child processes and assign names to them
25 // In general on POSIX we do not use unix domain sockets due to security
26 // concerns and the fact that they can leave garbage around the file system
27 // (MacOS does not support abstract named unix domain sockets).
28 // You can use unix domain sockets if you like on POSIX by constructing the
29 // the channel with the mode set to one of the NAMED modes. NAMED modes are
30 // currently used by automation and service processes.
32 class IPC_EXPORT Channel : public Message::Sender {
33 // Security tests need access to the pipe handle.
34 friend class ChannelTest;
37 // Implemented by consumers of a Channel to receive messages.
38 class IPC_EXPORT Listener {
40 virtual ~Listener() {}
42 // Called when a message is received. Returns true iff the message was
44 virtual bool OnMessageReceived(const Message& message) = 0;
46 // Called when the channel is connected and we have received the internal
47 // Hello message from the peer.
48 virtual void OnChannelConnected(int32 peer_pid) {}
50 // Called when an error is detected that causes the channel to close.
51 // This method is not called when a channel is closed normally.
52 virtual void OnChannelError() {}
55 // Called on the server side when a channel that listens for connections
56 // denies an attempt to connect.
57 virtual void OnChannelDenied() {}
59 // Called on the server side when a channel that listens for connections
60 // has an error that causes the listening channel to close.
61 virtual void OnChannelListenError() {}
65 // Flags to test modes
68 MODE_SERVER_FLAG = 0x1,
69 MODE_CLIENT_FLAG = 0x2,
70 MODE_NAMED_FLAG = 0x4,
72 MODE_OPEN_ACCESS_FLAG = 0x8, // Don't restrict access based on client UID.
76 // Some Standard Modes
78 MODE_NONE = MODE_NO_FLAG,
79 MODE_SERVER = MODE_SERVER_FLAG,
80 MODE_CLIENT = MODE_CLIENT_FLAG,
81 // Channels on Windows are named by default and accessible from other
82 // processes. On POSIX channels are anonymous by default and not accessible
83 // from other processes. Named channels work via named unix domain sockets.
84 // On Windows MODE_NAMED_SERVER is equivalent to MODE_SERVER and
85 // MODE_NAMED_CLIENT is equivalent to MODE_CLIENT.
86 MODE_NAMED_SERVER = MODE_SERVER_FLAG | MODE_NAMED_FLAG,
87 MODE_NAMED_CLIENT = MODE_CLIENT_FLAG | MODE_NAMED_FLAG,
89 // An "open" named server accepts connections from ANY client.
90 // The caller must then implement their own access-control based on the
91 // client process' user Id.
92 MODE_OPEN_NAMED_SERVER = MODE_OPEN_ACCESS_FLAG | MODE_SERVER_FLAG |
98 // The maximum message size in bytes. Attempting to receive a
99 // message of this size or bigger results in a channel error.
100 kMaximumMessageSize = 128 * 1024 * 1024,
102 // Ammount of data to read at once from the pipe.
103 kReadBufferSize = 4 * 1024
106 // Initialize a Channel.
108 // |channel_handle| identifies the communication Channel. For POSIX, if
109 // the file descriptor in the channel handle is != -1, the channel takes
110 // ownership of the file descriptor and will close it appropriately, otherwise
111 // it will create a new descriptor internally.
112 // |mode| specifies whether this Channel is to operate in server mode or
113 // client mode. In server mode, the Channel is responsible for setting up the
114 // IPC object, whereas in client mode, the Channel merely connects to the
115 // already established IPC object.
116 // |listener| receives a callback on the current thread for each newly
119 Channel(const IPC::ChannelHandle &channel_handle, Mode mode,
124 // Connect the pipe. On the server side, this will initiate
125 // waiting for connections. On the client, it attempts to
126 // connect to a pre-existing pipe. Note, calling Connect()
127 // will not block the calling thread and may complete
129 bool Connect() WARN_UNUSED_RESULT;
131 // Close this Channel explicitly. May be called multiple times.
132 // On POSIX calling close on an IPC channel that listens for connections will
133 // cause it to close any accepted connections, and it will stop listening for
134 // new connections. If you just want to close the currently accepted
135 // connection and listen for new ones, use ResetToAcceptingConnectionState.
138 // Modify the Channel's listener.
139 void set_listener(Listener* listener);
141 // Send a message over the Channel to the listener on the other end.
143 // |message| must be allocated using operator new. This object will be
144 // deleted once the contents of the Message have been sent.
145 virtual bool Send(Message* message);
147 #if defined(OS_POSIX) && !defined(OS_NACL)
148 // On POSIX an IPC::Channel wraps a socketpair(), this method returns the
149 // FD # for the client end of the socket.
150 // This method may only be called on the server side of a channel.
151 int GetClientFileDescriptor() const;
153 // On POSIX an IPC::Channel can either wrap an established socket, or it
154 // can wrap a socket that is listening for connections. Currently an
155 // IPC::Channel that listens for connections can only accept one connection
158 // Returns true if the channel supports listening for connections.
159 bool AcceptsConnections() const;
161 // Returns true if the channel supports listening for connections and is
162 // currently connected.
163 bool HasAcceptedConnection() const;
165 // Returns true if the peer process' effective user id can be determined, in
166 // which case the supplied client_euid is updated with it.
167 bool GetClientEuid(uid_t* client_euid) const;
169 // Closes any currently connected socket, and returns to a listening state
170 // for more connections.
171 void ResetToAcceptingConnectionState();
172 #endif // defined(OS_POSIX) && !defined(OS_NACL)
174 // Returns true if a named server channel is initialized on the given channel
175 // ID. Even if true, the server may have already accepted a connection.
176 static bool IsNamedServerInitialized(const std::string& channel_id);
179 // Used in Chrome by the TestSink to provide a dummy channel implementation
180 // for testing. TestSink overrides the "interesting" functions in Channel so
181 // no actual implementation is needed. This will cause un-overridden calls to
182 // segfault. Do not use outside of test code!
183 Channel() : channel_impl_(0) { }
186 // PIMPL to which all channel calls are delegated.
188 ChannelImpl *channel_impl_;
190 // The Hello message is internal to the Channel class. It is sent
191 // by the peer when the channel is connected. The message contains
192 // just the process id (pid). The message has a special routing_id
193 // (MSG_ROUTING_NONE) and type (HELLO_MESSAGE_TYPE).
195 HELLO_MESSAGE_TYPE = kuint16max // Maximum value of message type (uint16),
196 // to avoid conflicting with normal
197 // message types, which are enumeration
198 // constants starting from 0.
204 #endif // IPC_IPC_CHANNEL_H_