Implement ChannelMultiplexer.

ChannelMultiplexer allows multiple logical channels to share a 
single underlying transport channel.

BUG=137135

Review URL: https://chromiumcodereview.appspot.com/10830046

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@150484 0039d316-1c4b-4281-b951-d872f2087c98

11 files changed, 1001 insertions, 32 deletions

diff --git a/remoting/host/server_log_entry.cc b/remoting/host/server_log_entry.cc
index 98f39ee..dabcacf 100644
--- a/remoting/host/server_log_entry.cc
+++ b/remoting/host/server_log_entry.cc
@@ -4,6 +4,7 @@
 
 #include "remoting/host/server_log_entry.h"
 
+#include "base/logging.h"
 #include "base/sys_info.h"
 #include "remoting/base/constants.h"
 #include "remoting/protocol/session.h"
diff --git a/remoting/proto/chromotocol.gyp b/remoting/proto/chromotocol.gyp
index 98077ce..baf8c40 100644
--- a/remoting/proto/chromotocol.gyp
+++ b/remoting/proto/chromotocol.gyp
@@ -15,6 +15,7 @@
         'control.proto',
         'event.proto',
         'internal.proto',
+        'mux.proto',
         'video.proto',
       ],
       'variables': {
diff --git a/remoting/proto/mux.proto b/remoting/proto/mux.proto
new file mode 100644
index 0000000..ff0a8f6
--- /dev/null
+++ b/remoting/proto/mux.proto
@@ -0,0 +1,27 @@
+// 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.
+//
+// Protocol for the mux channel that multiplexes multiple channels.
+
+syntax = "proto2";
+
+option optimize_for = LITE_RUNTIME;
+
+package remoting.protocol;
+
+message MultiplexPacket {
+  // Channel ID. Each peer choses this value when it sends first packet to
+  // the other peer. It unique identified channel this packet belongs to.
+  // Channel ID is direction-specific, i.e. each channel has two IDs
+  // assigned to it: one for receiving and one for sending.
+  optional int32 channel_id = 1;
+
+  // Channel name. The name is used to identify channels before channel ID
+  // is assigned in the first message. This value must be included only
+  // in the first packet for a given channel. All other packets must be
+  // identified using channel ID.
+  optional string channel_name = 2;
+
+  optional bytes data = 3;
+}
diff --git a/remoting/protocol/buffered_socket_writer.cc b/remoting/protocol/buffered_socket_writer.cc
index 178f14a..de11356 100644
--- a/remoting/protocol/buffered_socket_writer.cc
+++ b/remoting/protocol/buffered_socket_writer.cc
@@ -55,7 +55,9 @@ bool BufferedSocketWriterBase::Write(
   buffer_size_ += data->size();
 
   DoWrite();
-  return true;
+
+  // DoWrite() may trigger OnWriteError() to be called.
+  return !closed_;
 }
 
 void BufferedSocketWriterBase::DoWrite() {
diff --git a/remoting/protocol/channel_factory.h b/remoting/protocol/channel_factory.h
new file mode 100644
index 0000000..7741e5d
--- /dev/null
+++ b/remoting/protocol/channel_factory.h
@@ -0,0 +1,59 @@
+// 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 REMOTING_PROTOCOL_CHANNEL_FACTORY_H_
+#define REMOTING_PROTOCOL_CHANNEL_FACTORY_H_
+
+#include "base/callback.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/threading/non_thread_safe.h"
+
+namespace net {
+class Socket;
+class StreamSocket;
+}  // namespace net
+
+namespace remoting {
+namespace protocol {
+
+class ChannelFactory : public base::NonThreadSafe {
+ public:
+  // TODO(sergeyu): Specify connection error code when channel
+  // connection fails.
+  typedef base::Callback<void(scoped_ptr<net::StreamSocket>)>
+      StreamChannelCallback;
+  typedef base::Callback<void(scoped_ptr<net::Socket>)>
+      DatagramChannelCallback;
+
+  ChannelFactory() {}
+
+  // Creates new channels for this connection. The specified callback is called
+  // when then new channel is created and connected. The callback is called with
+  // NULL if connection failed for any reason. Callback may be called
+  // synchronously, before the call returns. All channels must be destroyed
+  // before the factory is destroyed and CancelChannelCreation() must be called
+  // to cancel creation of channels for which the |callback| hasn't been called
+  // yet.
+  virtual void CreateStreamChannel(
+      const std::string& name, const StreamChannelCallback& callback) = 0;
+  virtual void CreateDatagramChannel(
+      const std::string& name, const DatagramChannelCallback& callback) = 0;
+
+  // Cancels a pending CreateStreamChannel() or CreateDatagramChannel()
+  // operation for the named channel. If the channel creation already
+  // completed then canceling it has no effect. When shutting down
+  // this method must be called for each channel pending creation.
+  virtual void CancelChannelCreation(const std::string& name) = 0;
+
+ protected:
+  virtual ~ChannelFactory() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ChannelFactory);
+};
+
+}  // namespace protocol
+}  // namespace remoting
+
+#endif  // REMOTING_PROTOCOL_CHANNEL_FACTORY_H_
diff --git a/remoting/protocol/channel_multiplexer.cc b/remoting/protocol/channel_multiplexer.cc
new file mode 100644
index 0000000..71647bf
--- /dev/null
+++ b/remoting/protocol/channel_multiplexer.cc
@@ -0,0 +1,513 @@
+// 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.
+
+#include "remoting/protocol/channel_multiplexer.h"
+
+#include <string.h>
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/location.h"
+#include "base/stl_util.h"
+#include "net/base/net_errors.h"
+#include "net/socket/stream_socket.h"
+#include "remoting/protocol/util.h"
+
+namespace remoting {
+namespace protocol {
+
+namespace {
+const int kChannelIdUnknown = -1;
+const int kMaxPacketSize = 1024;
+
+class PendingPacket {
+ public:
+  PendingPacket(scoped_ptr<MultiplexPacket> packet,
+                const base::Closure& done_task)
+      : packet(packet.Pass()),
+        done_task(done_task),
+        pos(0U) {
+  }
+  ~PendingPacket() {
+    done_task.Run();
+  }
+
+  bool is_empty() { return pos >= packet->data().size(); }
+
+  int Read(char* buffer, size_t size) {
+    size = std::min(size, packet->data().size() - pos);
+    memcpy(buffer, packet->data().data() + pos, size);
+    pos += size;
+    return size;
+  }
+
+ private:
+  scoped_ptr<MultiplexPacket> packet;
+  base::Closure done_task;
+  size_t pos;
+
+  DISALLOW_COPY_AND_ASSIGN(PendingPacket);
+};
+
+}  // namespace
+
+const char ChannelMultiplexer::kMuxChannelName[] = "mux";
+
+struct ChannelMultiplexer::PendingChannel {
+  PendingChannel(const std::string& name,
+                 const StreamChannelCallback& callback)
+      : name(name), callback(callback) {
+  }
+  std::string name;
+  StreamChannelCallback callback;
+};
+
+class ChannelMultiplexer::MuxChannel {
+ public:
+  MuxChannel(ChannelMultiplexer* multiplexer, const std::string& name,
+             int send_id);
+  ~MuxChannel();
+
+  const std::string& name() { return name_; }
+  int receive_id() { return receive_id_; }
+  void set_receive_id(int id) { receive_id_ = id; }
+
+  // Called by ChannelMultiplexer.
+  scoped_ptr<net::StreamSocket> CreateSocket();
+  void OnIncomingPacket(scoped_ptr<MultiplexPacket> packet,
+                        const base::Closure& done_task);
+  void OnWriteFailed();
+
+  // Called by MuxSocket.
+  void OnSocketDestroyed();
+  bool DoWrite(scoped_ptr<MultiplexPacket> packet,
+               const base::Closure& done_task);
+  int DoRead(net::IOBuffer* buffer, int buffer_len);
+
+ private:
+  ChannelMultiplexer* multiplexer_;
+  std::string name_;
+  int send_id_;
+  bool id_sent_;
+  int receive_id_;
+  MuxSocket* socket_;
+  std::list<PendingPacket*> pending_packets_;
+
+  DISALLOW_COPY_AND_ASSIGN(MuxChannel);
+};
+
+class ChannelMultiplexer::MuxSocket : public net::StreamSocket,
+                                      public base::NonThreadSafe,
+                                      public base::SupportsWeakPtr<MuxSocket> {
+ public:
+  MuxSocket(MuxChannel* channel);
+  ~MuxSocket();
+
+  void OnWriteComplete();
+  void OnWriteFailed();
+  void OnPacketReceived();
+
+  // net::StreamSocket interface.
+  virtual int Read(net::IOBuffer* buffer, int buffer_len,
+                   const net::CompletionCallback& callback) OVERRIDE;
+  virtual int Write(net::IOBuffer* buffer, int buffer_len,
+                    const net::CompletionCallback& callback) OVERRIDE;
+
+  virtual bool SetReceiveBufferSize(int32 size) OVERRIDE {
+    NOTIMPLEMENTED();
+    return false;
+  }
+  virtual bool SetSendBufferSize(int32 size) OVERRIDE {
+    NOTIMPLEMENTED();
+    return false;
+  }
+
+  virtual int Connect(const net::CompletionCallback& callback) OVERRIDE {
+    NOTIMPLEMENTED();
+    return net::ERR_FAILED;
+  }
+  virtual void Disconnect() OVERRIDE {
+    NOTIMPLEMENTED();
+  }
+  virtual bool IsConnected() const OVERRIDE {
+    NOTIMPLEMENTED();
+    return true;
+  }
+  virtual bool IsConnectedAndIdle() const OVERRIDE {
+    NOTIMPLEMENTED();
+    return false;
+  }
+  virtual int GetPeerAddress(net::IPEndPoint* address) const OVERRIDE {
+    NOTIMPLEMENTED();
+    return net::ERR_FAILED;
+  }
+  virtual int GetLocalAddress(net::IPEndPoint* address) const OVERRIDE {
+    NOTIMPLEMENTED();
+    return net::ERR_FAILED;
+  }
+  virtual const net::BoundNetLog& NetLog() const OVERRIDE {
+    NOTIMPLEMENTED();
+    return net_log_;
+  }
+  virtual void SetSubresourceSpeculation() OVERRIDE {
+    NOTIMPLEMENTED();
+  }
+  virtual void SetOmniboxSpeculation() OVERRIDE {
+    NOTIMPLEMENTED();
+  }
+  virtual bool WasEverUsed() const OVERRIDE {
+    return true;
+  }
+  virtual bool UsingTCPFastOpen() const OVERRIDE {
+    return false;
+  }
+  virtual int64 NumBytesRead() const OVERRIDE {
+    NOTIMPLEMENTED();
+    return 0;
+  }
+  virtual base::TimeDelta GetConnectTimeMicros() const OVERRIDE {
+    NOTIMPLEMENTED();
+    return base::TimeDelta();
+  }
+  virtual bool WasNpnNegotiated() const OVERRIDE {
+    return false;
+  }
+  virtual net::NextProto GetNegotiatedProtocol() const OVERRIDE {
+    return net::kProtoUnknown;
+  }
+  virtual bool GetSSLInfo(net::SSLInfo* ssl_info) OVERRIDE {
+    NOTIMPLEMENTED();
+    return false;
+  }
+
+ private:
+  MuxChannel* channel_;
+
+  net::CompletionCallback read_callback_;
+  scoped_refptr<net::IOBuffer> read_buffer_;
+  int read_buffer_size_;
+
+  bool write_pending_;
+  int write_result_;
+  net::CompletionCallback write_callback_;
+
+  net::BoundNetLog net_log_;
+
+  DISALLOW_COPY_AND_ASSIGN(MuxSocket);
+};
+
+
+ChannelMultiplexer::MuxChannel::MuxChannel(
+    ChannelMultiplexer* multiplexer,
+    const std::string& name,
+    int send_id)
+    : multiplexer_(multiplexer),
+      name_(name),
+      send_id_(send_id),
+      id_sent_(false),
+      receive_id_(kChannelIdUnknown),
+      socket_(NULL) {
+}
+
+ChannelMultiplexer::MuxChannel::~MuxChannel() {
+  // Socket must be destroyed before the channel.
+  DCHECK(!socket_);
+  STLDeleteElements(&pending_packets_);
+}
+
+scoped_ptr<net::StreamSocket> ChannelMultiplexer::MuxChannel::CreateSocket() {
+  DCHECK(!socket_);  // Can't create more than one socket per channel.
+  scoped_ptr<MuxSocket> result(new MuxSocket(this));
+  socket_ = result.get();
+  return result.PassAs<net::StreamSocket>();
+}
+
+void ChannelMultiplexer::MuxChannel::OnIncomingPacket(
+    scoped_ptr<MultiplexPacket> packet,
+    const base::Closure& done_task) {
+  DCHECK_EQ(packet->channel_id(), receive_id_);
+  if (packet->data().size() > 0) {
+    pending_packets_.push_back(new PendingPacket(packet.Pass(), done_task));
+    if (socket_) {
+      // Notify the socket that we have more data.
+      socket_->OnPacketReceived();
+    }
+  }
+}
+
+void ChannelMultiplexer::MuxChannel::OnWriteFailed() {
+  if (socket_)
+    socket_->OnWriteFailed();
+}
+
+void ChannelMultiplexer::MuxChannel::OnSocketDestroyed() {
+  DCHECK(socket_);
+  socket_ = NULL;
+}
+
+bool ChannelMultiplexer::MuxChannel::DoWrite(
+    scoped_ptr<MultiplexPacket> packet,
+    const base::Closure& done_task) {
+  packet->set_channel_id(send_id_);
+  if (!id_sent_) {
+    packet->set_channel_name(name_);
+    id_sent_ = true;
+  }
+  return multiplexer_->DoWrite(packet.Pass(), done_task);
+}
+
+int ChannelMultiplexer::MuxChannel::DoRead(net::IOBuffer* buffer,
+                                           int buffer_len) {
+  int pos = 0;
+  while (buffer_len > 0 && !pending_packets_.empty()) {
+    DCHECK(!pending_packets_.front()->is_empty());
+    int result = pending_packets_.front()->Read(
+        buffer->data() + pos, buffer_len);
+    DCHECK_LE(result, buffer_len);
+    pos += result;
+    buffer_len -= pos;
+    if (pending_packets_.front()->is_empty()) {
+      delete pending_packets_.front();
+      pending_packets_.erase(pending_packets_.begin());
+    }
+  }
+  return pos;
+}
+
+ChannelMultiplexer::MuxSocket::MuxSocket(MuxChannel* channel)
+    : channel_(channel),
+      read_buffer_size_(0),
+      write_pending_(false),
+      write_result_(0) {
+}
+
+ChannelMultiplexer::MuxSocket::~MuxSocket() {
+  channel_->OnSocketDestroyed();
+}
+
+int ChannelMultiplexer::MuxSocket::Read(
+    net::IOBuffer* buffer, int buffer_len,
+    const net::CompletionCallback& callback) {
+  DCHECK(CalledOnValidThread());
+  DCHECK(read_callback_.is_null());
+
+  int result = channel_->DoRead(buffer, buffer_len);
+  if (result == 0) {
+    read_buffer_ = buffer;
+    read_buffer_size_ = buffer_len;
+    read_callback_ = callback;
+    return net::ERR_IO_PENDING;
+  }
+  return result;
+}
+
+int ChannelMultiplexer::MuxSocket::Write(
+    net::IOBuffer* buffer, int buffer_len,
+    const net::CompletionCallback& callback) {
+  DCHECK(CalledOnValidThread());
+
+  scoped_ptr<MultiplexPacket> packet(new MultiplexPacket());
+  size_t size = std::min(kMaxPacketSize, buffer_len);
+  packet->mutable_data()->assign(buffer->data(), size);
+
+  write_pending_ = true;
+  bool result = channel_->DoWrite(packet.Pass(), base::Bind(
+      &ChannelMultiplexer::MuxSocket::OnWriteComplete, AsWeakPtr()));
+
+  if (!result) {
+    // Cannot complete the write, e.g. if the connection has been terminated.
+    return net::ERR_FAILED;
+  }
+
+  // OnWriteComplete() might be called above synchronously.
+  if (write_pending_) {
+    DCHECK(write_callback_.is_null());
+    write_callback_ = callback;
+    write_result_ = size;
+    return net::ERR_IO_PENDING;
+  }
+
+  return size;
+}
+
+void ChannelMultiplexer::MuxSocket::OnWriteComplete() {
+  write_pending_ = false;
+  if (!write_callback_.is_null()) {
+    net::CompletionCallback cb;
+    std::swap(cb, write_callback_);
+    cb.Run(write_result_);
+  }
+}
+
+void ChannelMultiplexer::MuxSocket::OnWriteFailed() {
+  if (!write_callback_.is_null()) {
+    net::CompletionCallback cb;
+    std::swap(cb, write_callback_);
+    cb.Run(net::ERR_FAILED);
+  }
+}
+
+void ChannelMultiplexer::MuxSocket::OnPacketReceived() {
+  if (!read_callback_.is_null()) {
+    int result = channel_->DoRead(read_buffer_, read_buffer_size_);
+    read_buffer_ = NULL;
+    DCHECK_GT(result, 0);
+    net::CompletionCallback cb;
+    std::swap(cb, read_callback_);
+    cb.Run(result);
+  }
+}
+
+ChannelMultiplexer::ChannelMultiplexer(ChannelFactory* factory,
+                                       const std::string& base_channel_name)
+    : base_channel_factory_(factory),
+      base_channel_name_(base_channel_name),
+      next_channel_id_(0),
+      destroyed_flag_(NULL) {
+  factory->CreateStreamChannel(
+      base_channel_name,
+      base::Bind(&ChannelMultiplexer::OnBaseChannelReady,
+                 base::Unretained(this)));
+}
+
+ChannelMultiplexer::~ChannelMultiplexer() {
+  DCHECK(pending_channels_.empty());
+  STLDeleteValues(&channels_);
+
+  // Cancel creation of the base channel if it hasn't finished.
+  if (base_channel_factory_)
+    base_channel_factory_->CancelChannelCreation(base_channel_name_);
+
+  if (destroyed_flag_)
+    *destroyed_flag_ = true;
+}
+
+void ChannelMultiplexer::CreateStreamChannel(
+    const std::string& name,
+    const StreamChannelCallback& callback) {
+  if (base_channel_.get()) {
+    // Already have |base_channel_|. Create new multiplexed channel
+    // synchronously.
+    callback.Run(GetOrCreateChannel(name)->CreateSocket());
+  } else if (!base_channel_.get() && !base_channel_factory_) {
+    // Fail synchronously if we failed to create |base_channel_|.
+    callback.Run(scoped_ptr<net::StreamSocket>());
+  } else {
+    // Still waiting for the |base_channel_|.
+    pending_channels_.push_back(PendingChannel(name, callback));
+  }
+}
+
+void ChannelMultiplexer::CreateDatagramChannel(
+    const std::string& name,
+    const DatagramChannelCallback& callback) {
+  NOTIMPLEMENTED();
+  callback.Run(scoped_ptr<net::Socket>());
+}
+
+void ChannelMultiplexer::CancelChannelCreation(const std::string& name) {
+  for (std::list<PendingChannel>::iterator it = pending_channels_.begin();
+       it != pending_channels_.end(); ++it) {
+    if (it->name == name) {
+      pending_channels_.erase(it);
+      return;
+    }
+  }
+}
+
+void ChannelMultiplexer::OnBaseChannelReady(
+    scoped_ptr<net::StreamSocket> socket) {
+  base_channel_factory_ = NULL;
+  base_channel_ = socket.Pass();
+
+  if (!base_channel_.get()) {
+    // Notify all callers that we can't create any channels.
+    for (std::list<PendingChannel>::iterator it = pending_channels_.begin();
+         it != pending_channels_.end(); ++it) {
+      it->callback.Run(scoped_ptr<net::StreamSocket>());
+    }
+    pending_channels_.clear();
+    return;
+  }
+
+  // Initialize reader and writer.
+  reader_.Init(base_channel_.get(),
+               base::Bind(&ChannelMultiplexer::OnIncomingPacket,
+                          base::Unretained(this)));
+  writer_.Init(base_channel_.get(),
+               base::Bind(&ChannelMultiplexer::OnWriteFailed,
+                          base::Unretained(this)));
+
+  // Now create all pending channels.
+  for (std::list<PendingChannel>::iterator it = pending_channels_.begin();
+       it != pending_channels_.end(); ++it) {
+    it->callback.Run(GetOrCreateChannel(it->name)->CreateSocket());
+  }
+  pending_channels_.clear();
+}
+
+ChannelMultiplexer::MuxChannel* ChannelMultiplexer::GetOrCreateChannel(
+    const std::string& name) {
+  // Check if we already have a channel with the requested name.
+  std::map<std::string, MuxChannel*>::iterator it = channels_.find(name);
+  if (it != channels_.end())
+    return it->second;
+
+  // Create a new channel if we haven't found existing one.
+  MuxChannel* channel = new MuxChannel(this, name, next_channel_id_);
+  ++next_channel_id_;
+  channels_[channel->name()] = channel;
+  return channel;
+}
+
+
+void ChannelMultiplexer::OnWriteFailed(int error) {
+  bool destroyed = false;
+  destroyed_flag_ = &destroyed;
+  for (std::map<std::string, MuxChannel*>::iterator it = channels_.begin();
+       it != channels_.end(); ++it) {
+    it->second->OnWriteFailed();
+    if (destroyed)
+      return;
+  }
+  destroyed_flag_ = NULL;
+}
+
+void ChannelMultiplexer::OnIncomingPacket(scoped_ptr<MultiplexPacket> packet,
+                                          const base::Closure& done_task) {
+  if (!packet->has_channel_id()) {
+    LOG(ERROR) << "Received packet without channel_id.";
+    done_task.Run();
+    return;
+  }
+
+  int receive_id = packet->channel_id();
+  MuxChannel* channel = NULL;
+  std::map<int, MuxChannel*>::iterator it =
+      channels_by_receive_id_.find(receive_id);
+  if (it != channels_by_receive_id_.end()) {
+    channel = it->second;
+  } else {
+    // This is a new |channel_id| we haven't seen before. Look it up by name.
+    if (!packet->has_channel_name()) {
+      LOG(ERROR) << "Received packet with unknown channel_id and "
+          "without channel_name.";
+      done_task.Run();
+      return;
+    }
+    channel = GetOrCreateChannel(packet->channel_name());
+    channel->set_receive_id(receive_id);
+    channels_by_receive_id_[receive_id] = channel;
+  }
+
+  channel->OnIncomingPacket(packet.Pass(), done_task);
+}
+
+bool ChannelMultiplexer::DoWrite(scoped_ptr<MultiplexPacket> packet,
+                                 const base::Closure& done_task) {
+  return writer_.Write(SerializeAndFrameMessage(*packet), done_task);
+}
+
+}  // namespace protocol
+}  // namespace remoting
diff --git a/remoting/protocol/channel_multiplexer.h b/remoting/protocol/channel_multiplexer.h
new file mode 100644
index 0000000..0f16fb1
--- /dev/null
+++ b/remoting/protocol/channel_multiplexer.h
@@ -0,0 +1,88 @@
+// 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 REMOTING_PROTOCOL_CHANNEL_MULTIPLEXER_H_
+#define REMOTING_PROTOCOL_CHANNEL_MULTIPLEXER_H_
+
+#include "remoting/proto/mux.pb.h"
+#include "remoting/protocol/buffered_socket_writer.h"
+#include "remoting/protocol/channel_factory.h"
+#include "remoting/protocol/message_reader.h"
+
+namespace remoting {
+namespace protocol {
+
+class ChannelMultiplexer : public ChannelFactory {
+ public:
+  static const char kMuxChannelName[];
+
+  // |factory| is used to create the channel upon which to multiplex.
+  ChannelMultiplexer(ChannelFactory* factory,
+                     const std::string& base_channel_name);
+  virtual ~ChannelMultiplexer();
+
+  // ChannelFactory interface.
+  virtual void CreateStreamChannel(
+      const std::string& name,
+      const StreamChannelCallback& callback) OVERRIDE;
+  virtual void CreateDatagramChannel(
+      const std::string& name,
+      const DatagramChannelCallback& callback) OVERRIDE;
+  virtual void CancelChannelCreation(const std::string& name) OVERRIDE;
+
+ private:
+  struct PendingChannel;
+  class MuxChannel;
+  class MuxSocket;
+  friend class MuxChannel;
+
+  // Callback for |base_channel_| creation.
+  void OnBaseChannelReady(scoped_ptr<net::StreamSocket> socket);
+
+  // Helper method used to create channels.
+  MuxChannel* GetOrCreateChannel(const std::string& name);
+
+  // Callbacks for |writer_| and |reader_|.
+  void OnWriteFailed(int error);
+  void OnIncomingPacket(scoped_ptr<MultiplexPacket> packet,
+                        const base::Closure& done_task);
+
+  // Called by MuxChannel.
+  bool DoWrite(scoped_ptr<MultiplexPacket> packet,
+               const base::Closure& done_task);
+
+  // Factory used to create |base_channel_|. Set to NULL once creation is
+  // finished or failed.
+  ChannelFactory* base_channel_factory_;
+
+  // Name of the underlying channel.
+  std::string base_channel_name_;
+
+  // The channel over which to multiplex.
+  scoped_ptr<net::StreamSocket> base_channel_;
+
+  // List of requested channels while we are waiting for |base_channel_|.
+  std::list<PendingChannel> pending_channels_;
+
+  int next_channel_id_;
+  std::map<std::string, MuxChannel*> channels_;
+
+  // Channels are added to |channels_by_receive_id_| only after we receive
+  // receive_id from the remote peer.
+  std::map<int, MuxChannel*> channels_by_receive_id_;
+
+  BufferedSocketWriter writer_;
+  ProtobufMessageReader<MultiplexPacket> reader_;
+
+  // Flag used by OnWriteFailed() to detect when the multiplexer is destroyed.
+  bool* destroyed_flag_;
+
+  DISALLOW_COPY_AND_ASSIGN(ChannelMultiplexer);
+};
+
+}  // namespace protocol
+}  // namespace remoting
+
+
+#endif  // REMOTING_PROTOCOL_CHANNEL_MULTIPLEXER_H_
diff --git a/remoting/protocol/channel_multiplexer_unittest.cc b/remoting/protocol/channel_multiplexer_unittest.cc
new file mode 100644
index 0000000..11a459b
--- /dev/null
+++ b/remoting/protocol/channel_multiplexer_unittest.cc
@@ -0,0 +1,301 @@
+// 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.
+
+#include "remoting/protocol/channel_multiplexer.h"
+
+#include "base/bind.h"
+#include "base/message_loop.h"
+#include "net/base/net_errors.h"
+#include "net/socket/socket.h"
+#include "net/socket/stream_socket.h"
+#include "remoting/base/constants.h"
+#include "remoting/protocol/connection_tester.h"
+#include "remoting/protocol/fake_session.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using testing::_;
+using testing::AtMost;
+using testing::InvokeWithoutArgs;
+
+namespace remoting {
+namespace protocol {
+
+namespace {
+
+const int kMessageSize = 1024;
+const int kMessages = 100;
+const char kMuxChannelName[] = "mux";
+
+void QuitCurrentThread() {
+  MessageLoop::current()->PostTask(FROM_HERE, MessageLoop::QuitClosure());
+}
+
+class MockSocketCallback {
+ public:
+  MOCK_METHOD1(OnDone, void(int result));
+};
+
+}  // namespace
+
+class ChannelMultiplexerTest : public testing::Test {
+ public:
+  void DeleteAll() {
+    host_socket1_.reset();
+    host_socket2_.reset();
+    client_socket1_.reset();
+    client_socket2_.reset();
+    host_mux_.reset();
+    client_mux_.reset();
+  }
+
+ protected:
+  virtual void SetUp() OVERRIDE {
+    // Create pair of multiplexers and connect them to each other.
+    host_mux_.reset(new ChannelMultiplexer(&host_session_, kMuxChannelName));
+    client_mux_.reset(new ChannelMultiplexer(&client_session_,
+                                             kMuxChannelName));
+    FakeSocket* host_socket =
+        host_session_.GetStreamChannel(ChannelMultiplexer::kMuxChannelName);
+    FakeSocket* client_socket =
+        client_session_.GetStreamChannel(ChannelMultiplexer::kMuxChannelName);
+    host_socket->PairWith(client_socket);
+
+    // Make writes asynchronous in one direction.
+    host_socket->set_async_write(true);
+  }
+
+  void CreateChannel(const std::string& name,
+                     scoped_ptr<net::StreamSocket>* host_socket,
+                     scoped_ptr<net::StreamSocket>* client_socket) {
+    int counter = 2;
+    host_mux_->CreateStreamChannel(name, base::Bind(
+        &ChannelMultiplexerTest::OnChannelConnected, base::Unretained(this),
+        host_socket, &counter));
+    client_mux_->CreateStreamChannel(name, base::Bind(
+        &ChannelMultiplexerTest::OnChannelConnected, base::Unretained(this),
+        client_socket, &counter));
+
+    message_loop_.Run();
+
+    EXPECT_TRUE(host_socket->get());
+    EXPECT_TRUE(client_socket->get());
+  }
+
+  void OnChannelConnected(
+      scoped_ptr<net::StreamSocket>* storage,
+      int* counter,
+      scoped_ptr<net::StreamSocket> socket) {
+    *storage = socket.Pass();
+    --(*counter);
+    EXPECT_GE(*counter, 0);
+    if (*counter == 0)
+      QuitCurrentThread();
+  }
+
+  scoped_refptr<net::IOBufferWithSize> CreateTestBuffer(int size) {
+    scoped_refptr<net::IOBufferWithSize> result =
+        new net::IOBufferWithSize(size);
+    for (int i = 0; i< size; ++i) {
+      result->data()[i] = rand() % 256;
+    }
+    return result;
+  }
+
+  MessageLoop message_loop_;
+
+  FakeSession host_session_;
+  FakeSession client_session_;
+
+  scoped_ptr<ChannelMultiplexer> host_mux_;
+  scoped_ptr<ChannelMultiplexer> client_mux_;
+
+  scoped_ptr<net::StreamSocket> host_socket1_;
+  scoped_ptr<net::StreamSocket> client_socket1_;
+  scoped_ptr<net::StreamSocket> host_socket2_;
+  scoped_ptr<net::StreamSocket> client_socket2_;
+};
+
+
+TEST_F(ChannelMultiplexerTest, OneChannel) {
+  scoped_ptr<net::StreamSocket> host_socket;
+  scoped_ptr<net::StreamSocket> client_socket;
+  ASSERT_NO_FATAL_FAILURE(CreateChannel("test", &host_socket, &client_socket));
+
+  StreamConnectionTester tester(host_socket.get(), client_socket.get(),
+                                kMessageSize, kMessages);
+  tester.Start();
+  message_loop_.Run();
+  tester.CheckResults();
+}
+
+TEST_F(ChannelMultiplexerTest, TwoChannels) {
+  scoped_ptr<net::StreamSocket> host_socket1_;
+  scoped_ptr<net::StreamSocket> client_socket1_;
+  ASSERT_NO_FATAL_FAILURE(
+      CreateChannel("test", &host_socket1_, &client_socket1_));
+
+  scoped_ptr<net::StreamSocket> host_socket2_;
+  scoped_ptr<net::StreamSocket> client_socket2_;
+  ASSERT_NO_FATAL_FAILURE(
+      CreateChannel("ch2", &host_socket2_, &client_socket2_));
+
+  StreamConnectionTester tester1(host_socket1_.get(), client_socket1_.get(),
+                                kMessageSize, kMessages);
+  StreamConnectionTester tester2(host_socket2_.get(), client_socket2_.get(),
+                                 kMessageSize, kMessages);
+  tester1.Start();
+  tester2.Start();
+  while (!tester1.done() || !tester2.done()) {
+    message_loop_.Run();
+  }
+  tester1.CheckResults();
+  tester2.CheckResults();
+}
+
+// Four channels, two in each direction
+TEST_F(ChannelMultiplexerTest, FourChannels) {
+  scoped_ptr<net::StreamSocket> host_socket1_;
+  scoped_ptr<net::StreamSocket> client_socket1_;
+  ASSERT_NO_FATAL_FAILURE(
+      CreateChannel("test", &host_socket1_, &client_socket1_));
+
+  scoped_ptr<net::StreamSocket> host_socket2_;
+  scoped_ptr<net::StreamSocket> client_socket2_;
+  ASSERT_NO_FATAL_FAILURE(
+      CreateChannel("ch2", &host_socket2_, &client_socket2_));
+
+  scoped_ptr<net::StreamSocket> host_socket3;
+  scoped_ptr<net::StreamSocket> client_socket3;
+  ASSERT_NO_FATAL_FAILURE(
+      CreateChannel("test3", &host_socket3, &client_socket3));
+
+  scoped_ptr<net::StreamSocket> host_socket4;
+  scoped_ptr<net::StreamSocket> client_socket4;
+  ASSERT_NO_FATAL_FAILURE(
+      CreateChannel("ch4", &host_socket4, &client_socket4));
+
+  StreamConnectionTester tester1(host_socket1_.get(), client_socket1_.get(),
+                                kMessageSize, kMessages);
+  StreamConnectionTester tester2(host_socket2_.get(), client_socket2_.get(),
+                                 kMessageSize, kMessages);
+  StreamConnectionTester tester3(client_socket3.get(), host_socket3.get(),
+                                 kMessageSize, kMessages);
+  StreamConnectionTester tester4(client_socket4.get(), host_socket4.get(),
+                                 kMessageSize, kMessages);
+  tester1.Start();
+  tester2.Start();
+  tester3.Start();
+  tester4.Start();
+  while (!tester1.done() || !tester2.done() ||
+         !tester3.done() || !tester4.done()) {
+    message_loop_.Run();
+  }
+  tester1.CheckResults();
+  tester2.CheckResults();
+  tester3.CheckResults();
+  tester4.CheckResults();
+}
+
+TEST_F(ChannelMultiplexerTest, SyncFail) {
+  scoped_ptr<net::StreamSocket> host_socket1_;
+  scoped_ptr<net::StreamSocket> client_socket1_;
+  ASSERT_NO_FATAL_FAILURE(
+      CreateChannel("test", &host_socket1_, &client_socket1_));
+
+  scoped_ptr<net::StreamSocket> host_socket2_;
+  scoped_ptr<net::StreamSocket> client_socket2_;
+  ASSERT_NO_FATAL_FAILURE(
+      CreateChannel("ch2", &host_socket2_, &client_socket2_));
+
+  host_session_.GetStreamChannel(kMuxChannelName)->
+      set_next_write_error(net::ERR_FAILED);
+  host_session_.GetStreamChannel(kMuxChannelName)->
+      set_async_write(false);
+
+  scoped_refptr<net::IOBufferWithSize> buf = CreateTestBuffer(100);
+
+  MockSocketCallback cb1;
+  MockSocketCallback cb2;
+
+  EXPECT_CALL(cb1, OnDone(_))
+      .Times(0);
+  EXPECT_CALL(cb2, OnDone(_))
+      .Times(0);
+
+  EXPECT_EQ(net::ERR_FAILED, host_socket1_->Write(buf, buf->size(), base::Bind(
+      &MockSocketCallback::OnDone, base::Unretained(&cb1))));
+  EXPECT_EQ(net::ERR_FAILED, host_socket2_->Write(buf, buf->size(), base::Bind(
+        &MockSocketCallback::OnDone, base::Unretained(&cb2))));
+
+  message_loop_.RunAllPending();
+}
+
+TEST_F(ChannelMultiplexerTest, AsyncFail) {
+  ASSERT_NO_FATAL_FAILURE(
+      CreateChannel("test", &host_socket1_, &client_socket1_));
+
+  ASSERT_NO_FATAL_FAILURE(
+      CreateChannel("ch2", &host_socket2_, &client_socket2_));
+
+  host_session_.GetStreamChannel(kMuxChannelName)->
+      set_next_write_error(net::ERR_FAILED);
+  host_session_.GetStreamChannel(kMuxChannelName)->
+      set_async_write(true);
+
+  scoped_refptr<net::IOBufferWithSize> buf = CreateTestBuffer(100);
+
+  MockSocketCallback cb1;
+  MockSocketCallback cb2;
+  EXPECT_CALL(cb1, OnDone(net::ERR_FAILED));
+  EXPECT_CALL(cb2, OnDone(net::ERR_FAILED));
+
+  EXPECT_EQ(net::ERR_IO_PENDING,
+            host_socket1_->Write(buf, buf->size(), base::Bind(
+                &MockSocketCallback::OnDone, base::Unretained(&cb1))));
+  EXPECT_EQ(net::ERR_IO_PENDING,
+            host_socket2_->Write(buf, buf->size(), base::Bind(
+                &MockSocketCallback::OnDone, base::Unretained(&cb2))));
+
+  message_loop_.RunAllPending();
+}
+
+TEST_F(ChannelMultiplexerTest, DeleteWhenFailed) {
+  ASSERT_NO_FATAL_FAILURE(
+      CreateChannel("test", &host_socket1_, &client_socket1_));
+  ASSERT_NO_FATAL_FAILURE(
+      CreateChannel("ch2", &host_socket2_, &client_socket2_));
+
+  host_session_.GetStreamChannel(kMuxChannelName)->
+      set_next_write_error(net::ERR_FAILED);
+  host_session_.GetStreamChannel(kMuxChannelName)->
+      set_async_write(true);
+
+  scoped_refptr<net::IOBufferWithSize> buf = CreateTestBuffer(100);
+
+  MockSocketCallback cb1;
+  MockSocketCallback cb2;
+
+  EXPECT_CALL(cb1, OnDone(net::ERR_FAILED))
+      .Times(AtMost(1))
+      .WillOnce(InvokeWithoutArgs(this, &ChannelMultiplexerTest::DeleteAll));
+  EXPECT_CALL(cb2, OnDone(net::ERR_FAILED))
+      .Times(AtMost(1))
+      .WillOnce(InvokeWithoutArgs(this, &ChannelMultiplexerTest::DeleteAll));
+
+  EXPECT_EQ(net::ERR_IO_PENDING,
+            host_socket1_->Write(buf, buf->size(), base::Bind(
+                &MockSocketCallback::OnDone, base::Unretained(&cb1))));
+  EXPECT_EQ(net::ERR_IO_PENDING,
+            host_socket2_->Write(buf, buf->size(), base::Bind(
+                &MockSocketCallback::OnDone, base::Unretained(&cb2))));
+
+  message_loop_.RunAllPending();
+
+  // Check that the sockets were destroyed.
+  EXPECT_FALSE(host_mux_.get());
+}
+
+}  // namespace protocol
+}  // namespace remoting
diff --git a/remoting/protocol/connection_tester.h b/remoting/protocol/connection_tester.h
index b32cf62..f89cd7a 100644
--- a/remoting/protocol/connection_tester.h
+++ b/remoting/protocol/connection_tester.h
@@ -34,6 +34,7 @@ class StreamConnectionTester {
   ~StreamConnectionTester();
 
   void Start();
+  bool done() { return done_; }
   void CheckResults();
 
  protected:
diff --git a/remoting/protocol/session.h b/remoting/protocol/session.h
index 9148318..7041486 100644
--- a/remoting/protocol/session.h
+++ b/remoting/protocol/session.h
@@ -7,16 +7,12 @@
 
 #include <string>
 
-#include "base/callback.h"
-#include "base/threading/non_thread_safe.h"
-#include "remoting/protocol/buffered_socket_writer.h"
+#include "remoting/protocol/channel_factory.h"
 #include "remoting/protocol/errors.h"
 #include "remoting/protocol/session_config.h"
 
 namespace net {
 class IPEndPoint;
-class Socket;
-class StreamSocket;
 }  // namespace net
 
 namespace remoting {
@@ -27,7 +23,7 @@ struct TransportRoute;
 // Generic interface for Chromotocol connection used by both client and host.
 // Provides access to the connection channels, but doesn't depend on the
 // protocol used for each channel.
-class Session : public base::NonThreadSafe {
+class Session : public ChannelFactory {
  public:
   enum State {
     // Created, but not connecting yet.
@@ -74,12 +70,6 @@ class Session : public base::NonThreadSafe {
                                        bool ready) {}
   };
 
-  // TODO(sergeyu): Specify connection error code when channel
-  // connection fails.
-  typedef base::Callback<void(scoped_ptr<net::StreamSocket>)>
-      StreamChannelCallback;
-  typedef base::Callback<void(scoped_ptr<net::Socket>)>
-      DatagramChannelCallback;
 
   Session() {}
   virtual ~Session() {}
@@ -91,23 +81,6 @@ class Session : public base::NonThreadSafe {
   // Returns error code for a failed session.
   virtual ErrorCode error() = 0;
 
-  // Creates new channels for this connection. The specified callback
-  // is called when then new channel is created and connected. The
-  // callback is called with NULL if connection failed for any reason.
-  // All channels must be destroyed before the session is
-  // destroyed. Can be called only when in CONNECTING, CONNECTED or
-  // AUTHENTICATED states.
-  virtual void CreateStreamChannel(
-      const std::string& name, const StreamChannelCallback& callback) = 0;
-  virtual void CreateDatagramChannel(
-      const std::string& name, const DatagramChannelCallback& callback) = 0;
-
-  // Cancels a pending CreateStreamChannel() or CreateDatagramChannel()
-  // operation for the named channel. If the channel creation already
-  // completed then cancelling it has no effect. When shutting down
-  // this method must be called for each channel pending creation.
-  virtual void CancelChannelCreation(const std::string& name) = 0;
-
   // JID of the other side.
   virtual const std::string& jid() = 0;
 
diff --git a/remoting/remoting.gyp b/remoting/remoting.gyp
index fc8f683..48725f9 100644
--- a/remoting/remoting.gyp
+++ b/remoting/remoting.gyp
@@ -1616,6 +1616,8 @@
         'protocol/channel_authenticator.h',
         'protocol/channel_dispatcher_base.cc',
         'protocol/channel_dispatcher_base.h',
+        'protocol/channel_multiplexer.cc',
+        'protocol/channel_multiplexer.h',
         'protocol/client_control_dispatcher.cc',
         'protocol/client_control_dispatcher.h',
         'protocol/client_event_dispatcher.cc',
@@ -1623,11 +1625,11 @@
         'protocol/client_stub.h',
         'protocol/clipboard_echo_filter.cc',
         'protocol/clipboard_echo_filter.h',
-        'protocol/clipboard_filter.h',
         'protocol/clipboard_filter.cc',
+        'protocol/clipboard_filter.h',
+        'protocol/clipboard_stub.h',
         'protocol/clipboard_thread_proxy.cc',
         'protocol/clipboard_thread_proxy.h',
-        'protocol/clipboard_stub.h',
         'protocol/connection_to_client.cc',
         'protocol/connection_to_client.h',
         'protocol/connection_to_host.cc',
@@ -1802,6 +1804,7 @@
         'protocol/authenticator_test_base.cc',
         'protocol/authenticator_test_base.h',
         'protocol/buffered_socket_writer_unittest.cc',
+        'protocol/channel_multiplexer_unittest.cc',
         'protocol/clipboard_echo_filter_unittest.cc',
         'protocol/connection_tester.cc',
         'protocol/connection_tester.h',