// 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_H_
#define IPC_IPC_CHANNEL_H_
#include <string>
#if defined(OS_POSIX)
#include <sys/types.h>
#endif
#include "base/compiler_specific.h"
#include "base/process/process.h"
#include "ipc/ipc_channel_handle.h"
#include "ipc/ipc_message.h"
#include "ipc/ipc_sender.h"
namespace IPC {
class Listener;
//------------------------------------------------------------------------------
// See
// http://www.chromium.org/developers/design-documents/inter-process-communication
// for overview of IPC in Chromium.
// Channels are implemented using named pipes on Windows, and
// socket pairs (or in some special cases unix domain sockets) on POSIX.
// On Windows we access pipes in various processes by name.
// On POSIX we pass file descriptors to child processes and assign names to them
// in a lookup table.
// In general on POSIX we do not use unix domain sockets due to security
// concerns and the fact that they can leave garbage around the file system
// (MacOS does not support abstract named unix domain sockets).
// You can use unix domain sockets if you like on POSIX by constructing the
// the channel with the mode set to one of the NAMED modes. NAMED modes are
// currently used by automation and service processes.
class IPC_EXPORT Channel : public Sender {
// Security tests need access to the pipe handle.
friend class ChannelTest;
public:
// Flags to test modes
enum ModeFlags {
MODE_NO_FLAG = 0x0,
MODE_SERVER_FLAG = 0x1,
MODE_CLIENT_FLAG = 0x2,
MODE_NAMED_FLAG = 0x4,
#if defined(OS_POSIX)
MODE_OPEN_ACCESS_FLAG = 0x8, // Don't restrict access based on client UID.
#endif
};
// Some Standard Modes
enum Mode {
MODE_NONE = MODE_NO_FLAG,
MODE_SERVER = MODE_SERVER_FLAG,
MODE_CLIENT = MODE_CLIENT_FLAG,
// Channels on Windows are named by default and accessible from other
// processes. On POSIX channels are anonymous by default and not accessible
// from other processes. Named channels work via named unix domain sockets.
// On Windows MODE_NAMED_SERVER is equivalent to MODE_SERVER and
// MODE_NAMED_CLIENT is equivalent to MODE_CLIENT.
MODE_NAMED_SERVER = MODE_SERVER_FLAG | MODE_NAMED_FLAG,
MODE_NAMED_CLIENT = MODE_CLIENT_FLAG | MODE_NAMED_FLAG,
#if defined(OS_POSIX)
// An "open" named server accepts connections from ANY client.
// The caller must then implement their own access-control based on the
// client process' user Id.
MODE_OPEN_NAMED_SERVER = MODE_OPEN_ACCESS_FLAG | MODE_SERVER_FLAG |
MODE_NAMED_FLAG
#endif
};
// Messages internal to the IPC implementation are defined here.
// Uses Maximum value of message type (uint16), to avoid conflicting
// with normal message types, which are enumeration constants starting from 0.
enum {
// The Hello message is sent by the peer when the channel is connected.
// The message contains just the process id (pid).
// The message has a special routing_id (MSG_ROUTING_NONE)
// and type (HELLO_MESSAGE_TYPE).
HELLO_MESSAGE_TYPE = kuint16max,
// The CLOSE_FD_MESSAGE_TYPE is used in the IPC class to
// work around a bug in sendmsg() on Mac. When an FD is sent
// over the socket, a CLOSE_FD_MESSAGE is sent with hops = 2.
// The client will return the message with hops = 1, *after* it
// has received the message that contains the FD. When we
// receive it again on the sender side, we close the FD.
CLOSE_FD_MESSAGE_TYPE = HELLO_MESSAGE_TYPE - 1
};
// The maximum message size in bytes. Attempting to receive a message of this
// size or bigger results in a channel error.
static const size_t kMaximumMessageSize = 128 * 1024 * 1024;
// Amount of data to read at once from the pipe.
static const size_t kReadBufferSize = 4 * 1024;
// Initialize a Channel.
//
// |channel_handle| identifies the communication Channel. For POSIX, if
// the file descriptor in the channel handle is != -1, the channel takes
// ownership of the file descriptor and will close it appropriately, otherwise
// it will create a new descriptor internally.
// |mode| specifies whether this Channel is to operate in server mode or
// client mode. In server mode, the Channel is responsible for setting up the
// IPC object, whereas in client mode, the Channel merely connects to the
// already established IPC object.
// |listener| receives a callback on the current thread for each newly
// received message.
//
Channel(const IPC::ChannelHandle &channel_handle, Mode mode,
Listener* listener);
virtual ~Channel();
// Connect the pipe. On the server side, this will initiate
// waiting for connections. On the client, it attempts to
// connect to a pre-existing pipe. Note, calling Connect()
// will not block the calling thread and may complete
// asynchronously.
bool Connect() WARN_UNUSED_RESULT;
// Close this Channel explicitly. May be called multiple times.
// On POSIX calling close on an IPC channel that listens for connections will
// cause it to close any accepted connections, and it will stop listening for
// new connections. If you just want to close the currently accepted
// connection and listen for new ones, use ResetToAcceptingConnectionState.
void Close();
// Get the process ID for the connected peer.
//
// Returns base::kNullProcessId if the peer is not connected yet. Watch out
// for race conditions. You can easily get a channel to another process, but
// if your process has not yet processed the "hello" message from the remote
// side, this will fail. You should either make sure calling this is either
// in response to a message from the remote side (which guarantees that it's
// been connected), or you wait for the "connected" notification on the
// listener.
base::ProcessId peer_pid() const;
// Send a message over the Channel to the listener on the other end.
//
// |message| must be allocated using operator new. This object will be
// deleted once the contents of the Message have been sent.
virtual bool Send(Message* message) OVERRIDE;
#if defined(OS_POSIX)
// On POSIX an IPC::Channel wraps a socketpair(), this method returns the
// FD # for the client end of the socket.
// This method may only be called on the server side of a channel.
// This method can be called on any thread.
int GetClientFileDescriptor() const;
// Same as GetClientFileDescriptor, but transfers the ownership of the
// file descriptor to the caller.
// This method can be called on any thread.
int TakeClientFileDescriptor();
// On POSIX an IPC::Channel can either wrap an established socket, or it
// can wrap a socket that is listening for connections. Currently an
// IPC::Channel that listens for connections can only accept one connection
// at a time.
// Returns true if the channel supports listening for connections.
bool AcceptsConnections() const;
// Returns true if the channel supports listening for connections and is
// currently connected.
bool HasAcceptedConnection() const;
// Returns true if the peer process' effective user id can be determined, in
// which case the supplied peer_euid is updated with it.
bool GetPeerEuid(uid_t* peer_euid) const;
// Closes any currently connected socket, and returns to a listening state
// for more connections.
void ResetToAcceptingConnectionState();
#endif // defined(OS_POSIX) && !defined(OS_NACL)
// Returns true if a named server channel is initialized on the given channel
// ID. Even if true, the server may have already accepted a connection.
static bool IsNamedServerInitialized(const std::string& channel_id);
#if !defined(OS_NACL)
// Generates a channel ID that's non-predictable and unique.
static std::string GenerateUniqueRandomChannelID();
// Generates a channel ID that, if passed to the client as a shared secret,
// will validate that the client's authenticity. On platforms that do not
// require additional this is simply calls GenerateUniqueRandomChannelID().
// For portability the prefix should not include the \ character.
static std::string GenerateVerifiedChannelID(const std::string& prefix);
#endif
#if defined(OS_LINUX)
// Sandboxed processes live in a PID namespace, so when sending the IPC hello
// message from client to server we need to send the PID from the global
// PID namespace.
static void SetGlobalPid(int pid);
#endif
#if defined(OS_ANDROID)
// Most tests are single process and work the same on all platforms. However
// in some cases we want to test multi-process, and Android differs in that it
// can't 'exec' after forking. This callback resets any data in the forked
// process such that it acts similar to if it was exec'd, for tests.
static void NotifyProcessForkedForTesting();
#endif
protected:
// Used in Chrome by the TestSink to provide a dummy channel implementation
// for testing. TestSink overrides the "interesting" functions in Channel so
// no actual implementation is needed. This will cause un-overridden calls to
// segfault. Do not use outside of test code!
Channel() : channel_impl_(0) { }
private:
// PIMPL to which all channel calls are delegated.
class ChannelImpl;
ChannelImpl *channel_impl_;
};
#if defined(OS_POSIX)
// SocketPair() creates a pair of socket FDs suitable for using with
// IPC::Channel.
IPC_EXPORT bool SocketPair(int* fd1, int* fd2);
#endif
} // namespace IPC
#endif // IPC_IPC_CHANNEL_H_