webrtc/p2p/base/transport.h - platform/external/webrtc - Git at Google

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */

 // A Transport manages a set of named channels of the same type.
 //
 // Subclasses choose the appropriate class to instantiate for each channel;
 // however, this base class keeps track of the channels by name, watches their
 // state changes (in order to update the manager's state), and forwards
 // requests to begin connecting or to reset to each of the channels.
 //
 // On Threading:  Transport performs work on both the signaling and worker
 // threads.  For subclasses, the rule is that all signaling related calls will
 // be made on the signaling thread and all channel related calls (including
 // signaling for a channel) will be made on the worker thread.  When
 // information needs to be sent between the two threads, this class should do
 // the work (e.g., OnRemoteCandidate).
 //
 // Note: Subclasses must call DestroyChannels() in their own constructors.
 // It is not possible to do so here because the subclass constructor will
 // already have run.

 #ifndef WEBRTC_P2P_BASE_TRANSPORT_H_
 #define WEBRTC_P2P_BASE_TRANSPORT_H_

 #include <map>
 #include <string>
 #include <vector>
 #include "webrtc/p2p/base/candidate.h"
 #include "webrtc/p2p/base/constants.h"
 #include "webrtc/p2p/base/sessiondescription.h"
 #include "webrtc/p2p/base/transportinfo.h"
 #include "webrtc/base/criticalsection.h"
 #include "webrtc/base/messagequeue.h"
 #include "webrtc/base/sigslot.h"
 #include "webrtc/base/sslstreamadapter.h"

 namespace rtc {
 class Thread;
 }

 namespace cricket {

 class PortAllocator;
 class TransportChannel;
 class TransportChannelImpl;

 typedef std::vector<Candidate> Candidates;

 // For "writable" and "readable", we need to differentiate between
 // none, all, and some.
 enum TransportState {
   TRANSPORT_STATE_NONE = 0,
   TRANSPORT_STATE_SOME,
   TRANSPORT_STATE_ALL
 };

 // Stats that we can return about the connections for a transport channel.
 // TODO(hta): Rename to ConnectionStats
 struct ConnectionInfo {
   ConnectionInfo()
       : best_connection(false),
         writable(false),
         readable(false),
         timeout(false),
         new_connection(false),
         rtt(0),
         sent_total_bytes(0),
         sent_bytes_second(0),
         sent_discarded_packets(0),
         sent_total_packets(0),
         recv_total_bytes(0),
         recv_bytes_second(0),
         key(NULL) {}

   bool best_connection;        // Is this the best connection we have?
   bool writable;               // Has this connection received a STUN response?
   bool readable;               // Has this connection received a STUN request?
   bool timeout;                // Has this connection timed out?
   bool new_connection;         // Is this a newly created connection?
   size_t rtt;                  // The STUN RTT for this connection.
   size_t sent_total_bytes;     // Total bytes sent on this connection.
   size_t sent_bytes_second;    // Bps over the last measurement interval.
   size_t sent_discarded_packets;  // Number of outgoing packets discarded due to
                                   // socket errors.
   size_t sent_total_packets;  // Number of total outgoing packets attempted for
                               // sending.

   size_t recv_total_bytes;     // Total bytes received on this connection.
   size_t recv_bytes_second;    // Bps over the last measurement interval.
   Candidate local_candidate;   // The local candidate for this connection.
   Candidate remote_candidate;  // The remote candidate for this connection.
   void* key;                   // A static value that identifies this conn.
 };

 // Information about all the connections of a channel.
 typedef std::vector<ConnectionInfo> ConnectionInfos;

 // Information about a specific channel
 struct TransportChannelStats {
   int component;
   ConnectionInfos connection_infos;
   std::string srtp_cipher;
   std::string ssl_cipher;
 };

 // Information about all the channels of a transport.
 // TODO(hta): Consider if a simple vector is as good as a map.
 typedef std::vector<TransportChannelStats> TransportChannelStatsList;

 // Information about the stats of a transport.
 struct TransportStats {
   std::string content_name;
   TransportChannelStatsList channel_stats;
 };

 bool BadTransportDescription(const std::string& desc, std::string* err_desc);

 bool IceCredentialsChanged(const std::string& old_ufrag,
                            const std::string& old_pwd,
                            const std::string& new_ufrag,
                            const std::string& new_pwd);

 class Transport : public rtc::MessageHandler,
                   public sigslot::has_slots<> {
  public:
   Transport(rtc::Thread* signaling_thread,
             rtc::Thread* worker_thread,
             const std::string& content_name,
             const std::string& type,
             PortAllocator* allocator);
   virtual ~Transport();

   // Returns the signaling thread. The app talks to Transport on this thread.
   rtc::Thread* signaling_thread() { return signaling_thread_; }
   // Returns the worker thread. The actual networking is done on this thread.
   rtc::Thread* worker_thread() { return worker_thread_; }

   // Returns the content_name of this transport.
   const std::string& content_name() const { return content_name_; }
   // Returns the type of this transport.
   const std::string& type() const { return type_; }

   // Returns the port allocator object for this transport.
   PortAllocator* port_allocator() { return allocator_; }

   // Returns the readable and states of this manager.  These bits are the ORs
   // of the corresponding bits on the managed channels.  Each time one of these
   // states changes, a signal is raised.
   // TODO: Replace uses of readable() and writable() with
   // any_channels_readable() and any_channels_writable().
   bool readable() const { return any_channels_readable(); }
   bool writable() const { return any_channels_writable(); }
   bool was_writable() const { return was_writable_; }
   bool any_channels_readable() const {
     return (readable_ == TRANSPORT_STATE_SOME ||
             readable_ == TRANSPORT_STATE_ALL);
   }
   bool any_channels_writable() const {
     return (writable_ == TRANSPORT_STATE_SOME ||
             writable_ == TRANSPORT_STATE_ALL);
   }
   bool all_channels_readable() const {
     return (readable_ == TRANSPORT_STATE_ALL);
   }
   bool all_channels_writable() const {
     return (writable_ == TRANSPORT_STATE_ALL);
   }
   sigslot::signal1<Transport*> SignalReadableState;
   sigslot::signal1<Transport*> SignalWritableState;
   sigslot::signal1<Transport*> SignalCompleted;
   sigslot::signal1<Transport*> SignalFailed;

   // Returns whether the client has requested the channels to connect.
   bool connect_requested() const { return connect_requested_; }

   void SetIceRole(IceRole role);
   IceRole ice_role() const { return ice_role_; }

   void SetIceTiebreaker(uint64 IceTiebreaker) { tiebreaker_ = IceTiebreaker; }
   uint64 IceTiebreaker() { return tiebreaker_; }

   // Must be called before applying local session description.
   void SetIdentity(rtc::SSLIdentity* identity);

   // Get a copy of the local identity provided by SetIdentity.
   bool GetIdentity(rtc::SSLIdentity** identity);

   // Get a copy of the remote certificate in use by the specified channel.
   bool GetRemoteCertificate(rtc::SSLCertificate** cert);

   TransportProtocol protocol() const { return protocol_; }

   // Create, destroy, and lookup the channels of this type by their components.
   TransportChannelImpl* CreateChannel(int component);
   // Note: GetChannel may lead to race conditions, since the mutex is not held
   // after the pointer is returned.
   TransportChannelImpl* GetChannel(int component);
   // Note: HasChannel does not lead to race conditions, unlike GetChannel.
   bool HasChannel(int component) {
     return (NULL != GetChannel(component));
   }
   bool HasChannels();
   void DestroyChannel(int component);

   // Set the local TransportDescription to be used by TransportChannels.
   // This should be called before ConnectChannels().
   bool SetLocalTransportDescription(const TransportDescription& description,
                                     ContentAction action,
                                     std::string* error_desc);

   // Set the remote TransportDescription to be used by TransportChannels.
   bool SetRemoteTransportDescription(const TransportDescription& description,
                                      ContentAction action,
                                      std::string* error_desc);

   // Tells all current and future channels to start connecting.  When the first
   // channel begins connecting, the following signal is raised.
   void ConnectChannels();
   sigslot::signal1<Transport*> SignalConnecting;

   // Resets all of the channels back to their initial state.  They are no
   // longer connecting.
   void ResetChannels();

   // Destroys every channel created so far.
   void DestroyAllChannels();

   bool GetStats(TransportStats* stats);

   // Before any stanza is sent, the manager will request signaling.  Once
   // signaling is available, the client should call OnSignalingReady.  Once
   // this occurs, the transport (or its channels) can send any waiting stanzas.
   // OnSignalingReady invokes OnTransportSignalingReady and then forwards this
   // signal to each channel.
   sigslot::signal1<Transport*> SignalRequestSignaling;
   void OnSignalingReady();

   // Handles sending of ready candidates and receiving of remote candidates.
   sigslot::signal2<Transport*,
                    const std::vector<Candidate>&> SignalCandidatesReady;

   sigslot::signal1<Transport*> SignalCandidatesAllocationDone;
   void OnRemoteCandidates(const std::vector<Candidate>& candidates);

   // If candidate is not acceptable, returns false and sets error.
   // Call this before calling OnRemoteCandidates.
   virtual bool VerifyCandidate(const Candidate& candidate,
                                std::string* error);

   // Signals when the best connection for a channel changes.
   sigslot::signal3<Transport*,
                    int,  // component
                    const Candidate&> SignalRouteChange;

   // Forwards the signal from TransportChannel to BaseSession.
   sigslot::signal0<> SignalRoleConflict;

   virtual bool GetSslRole(rtc::SSLRole* ssl_role) const;

  protected:
   // These are called by Create/DestroyChannel above in order to create or
   // destroy the appropriate type of channel.
   virtual TransportChannelImpl* CreateTransportChannel(int component) = 0;
   virtual void DestroyTransportChannel(TransportChannelImpl* channel) = 0;

   // Informs the subclass that we received the signaling ready message.
   virtual void OnTransportSignalingReady() {}

   // The current local transport description, for use by derived classes
   // when performing transport description negotiation.
   const TransportDescription* local_description() const {
     return local_description_.get();
   }

   // The current remote transport description, for use by derived classes
   // when performing transport description negotiation.
   const TransportDescription* remote_description() const {
     return remote_description_.get();
   }

   virtual void SetIdentity_w(rtc::SSLIdentity* identity) {}

   virtual bool GetIdentity_w(rtc::SSLIdentity** identity) {
     return false;
   }

   // Pushes down the transport parameters from the local description, such
   // as the ICE ufrag and pwd.
   // Derived classes can override, but must call the base as well.
   virtual bool ApplyLocalTransportDescription_w(TransportChannelImpl* channel,
                                                 std::string* error_desc);

   // Pushes down remote ice credentials from the remote description to the
   // transport channel.
   virtual bool ApplyRemoteTransportDescription_w(TransportChannelImpl* ch,
                                                  std::string* error_desc);

   // Negotiates the transport parameters based on the current local and remote
   // transport description, such at the version of ICE to use, and whether DTLS
   // should be activated.
   // Derived classes can negotiate their specific parameters here, but must call
   // the base as well.
   virtual bool NegotiateTransportDescription_w(ContentAction local_role,
                                                std::string* error_desc);

   // Pushes down the transport parameters obtained via negotiation.
   // Derived classes can set their specific parameters here, but must call the
   // base as well.
   virtual bool ApplyNegotiatedTransportDescription_w(
       TransportChannelImpl* channel, std::string* error_desc);

   virtual bool GetSslRole_w(rtc::SSLRole* ssl_role) const {
     return false;
   }

  private:
   struct ChannelMapEntry {
     ChannelMapEntry() : impl_(NULL), candidates_allocated_(false), ref_(0) {}
     explicit ChannelMapEntry(TransportChannelImpl *impl)
         : impl_(impl),
           candidates_allocated_(false),
           ref_(0) {
     }

     void AddRef() { ++ref_; }
     void DecRef() {
       ASSERT(ref_ > 0);
       --ref_;
     }
     int ref() const { return ref_; }

     TransportChannelImpl* get() const { return impl_; }
     TransportChannelImpl* operator->() const  { return impl_; }
     void set_candidates_allocated(bool status) {
       candidates_allocated_ = status;
     }
     bool candidates_allocated() const { return candidates_allocated_; }

   private:
     TransportChannelImpl *impl_;
     bool candidates_allocated_;
     int ref_;
   };

   // Candidate component => ChannelMapEntry
   typedef std::map<int, ChannelMapEntry> ChannelMap;

   // Called when the state of a channel changes.
   void OnChannelReadableState(TransportChannel* channel);
   void OnChannelWritableState(TransportChannel* channel);

   // Called when a channel requests signaling.
   void OnChannelRequestSignaling(TransportChannelImpl* channel);

   // Called when a candidate is ready from remote peer.
   void OnRemoteCandidate(const Candidate& candidate);
   // Called when a candidate is ready from channel.
   void OnChannelCandidateReady(TransportChannelImpl* channel,
                                const Candidate& candidate);
   void OnChannelRouteChange(TransportChannel* channel,
                             const Candidate& remote_candidate);
   void OnChannelCandidatesAllocationDone(TransportChannelImpl* channel);
   // Called when there is ICE role change.
   void OnRoleConflict(TransportChannelImpl* channel);
   // Called when the channel removes a connection.
   void OnChannelConnectionRemoved(TransportChannelImpl* channel);

   // Dispatches messages to the appropriate handler (below).
   void OnMessage(rtc::Message* msg);

   // These are versions of the above methods that are called only on a
   // particular thread (s = signaling, w = worker).  The above methods post or
   // send a message to invoke this version.
   TransportChannelImpl* CreateChannel_w(int component);
   void DestroyChannel_w(int component);
   void ConnectChannels_w();
   void ResetChannels_w();
   void DestroyAllChannels_w();
   void OnRemoteCandidate_w(const Candidate& candidate);
   void OnChannelReadableState_s();
   void OnChannelWritableState_s();
   void OnChannelRequestSignaling_s();
   void OnConnecting_s();
   void OnChannelRouteChange_s(const TransportChannel* channel,
                               const Candidate& remote_candidate);
   void OnChannelCandidatesAllocationDone_s();

   // Helper function that invokes the given function on every channel.
   typedef void (TransportChannelImpl::* TransportChannelFunc)();
   void CallChannels_w(TransportChannelFunc func);

   // Computes the OR of the channel's read or write state (argument picks).
   TransportState GetTransportState_s(bool read);

   void OnChannelCandidateReady_s();

   void SetIceRole_w(IceRole role);
   void SetRemoteIceMode_w(IceMode mode);
   bool SetLocalTransportDescription_w(const TransportDescription& desc,
                                       ContentAction action,
                                       std::string* error_desc);
   bool SetRemoteTransportDescription_w(const TransportDescription& desc,
                                        ContentAction action,
                                        std::string* error_desc);
   bool GetStats_w(TransportStats* infos);
   bool GetRemoteCertificate_w(rtc::SSLCertificate** cert);

   // Sends SignalCompleted if we are now in that state.
   void MaybeCompleted_w();

   rtc::Thread* const signaling_thread_;
   rtc::Thread* const worker_thread_;
   const std::string content_name_;
   const std::string type_;
   PortAllocator* const allocator_;
   bool destroyed_;
   TransportState readable_;
   TransportState writable_;
   bool was_writable_;
   bool connect_requested_;
   IceRole ice_role_;
   uint64 tiebreaker_;
   TransportProtocol protocol_;
   IceMode remote_ice_mode_;
   rtc::scoped_ptr<TransportDescription> local_description_;
   rtc::scoped_ptr<TransportDescription> remote_description_;

   // TODO(tommi): Make sure we only use this on the worker thread.
   ChannelMap channels_;
   // Buffers the ready_candidates so that SignalCanidatesReady can
   // provide them in multiples.
   std::vector<Candidate> ready_candidates_;
   // Protects changes to channels and messages
   rtc::CriticalSection crit_;

   DISALLOW_COPY_AND_ASSIGN(Transport);
 };

 // Extract a TransportProtocol from a TransportDescription.
 TransportProtocol TransportProtocolFromDescription(
     const TransportDescription* desc);

 }  // namespace cricket

 #endif  // WEBRTC_P2P_BASE_TRANSPORT_H_
	/*
	* Copyright 2004 The WebRTC Project Authors. All rights reserved.
	*
	* Use of this source code is governed by a BSD-style license
	* that can be found in the LICENSE file in the root of the source
	* tree. An additional intellectual property rights grant can be found
	* in the file PATENTS. All contributing project authors may
	* be found in the AUTHORS file in the root of the source tree.
	*/

	// A Transport manages a set of named channels of the same type.
	//
	// Subclasses choose the appropriate class to instantiate for each channel;
	// however, this base class keeps track of the channels by name, watches their
	// state changes (in order to update the manager's state), and forwards
	// requests to begin connecting or to reset to each of the channels.
	//
	// On Threading: Transport performs work on both the signaling and worker
	// threads. For subclasses, the rule is that all signaling related calls will
	// be made on the signaling thread and all channel related calls (including
	// signaling for a channel) will be made on the worker thread. When
	// information needs to be sent between the two threads, this class should do
	// the work (e.g., OnRemoteCandidate).
	//
	// Note: Subclasses must call DestroyChannels() in their own constructors.
	// It is not possible to do so here because the subclass constructor will
	// already have run.

	#ifndef WEBRTC_P2P_BASE_TRANSPORT_H_
	#define WEBRTC_P2P_BASE_TRANSPORT_H_

	#include <map>
	#include <string>
	#include <vector>
	#include "webrtc/p2p/base/candidate.h"
	#include "webrtc/p2p/base/constants.h"
	#include "webrtc/p2p/base/sessiondescription.h"
	#include "webrtc/p2p/base/transportinfo.h"
	#include "webrtc/base/criticalsection.h"
	#include "webrtc/base/messagequeue.h"
	#include "webrtc/base/sigslot.h"
	#include "webrtc/base/sslstreamadapter.h"

	namespace rtc {
	class Thread;
	}

	namespace cricket {

	class PortAllocator;
	class TransportChannel;
	class TransportChannelImpl;

	typedef std::vector<Candidate> Candidates;

	// For "writable" and "readable", we need to differentiate between
	// none, all, and some.
	enum TransportState {
	TRANSPORT_STATE_NONE = 0,
	TRANSPORT_STATE_SOME,
	TRANSPORT_STATE_ALL
	};

	// Stats that we can return about the connections for a transport channel.
	// TODO(hta): Rename to ConnectionStats
	struct ConnectionInfo {
	ConnectionInfo()
	: best_connection(false),
	writable(false),
	readable(false),
	timeout(false),
	new_connection(false),
	rtt(0),
	sent_total_bytes(0),
	sent_bytes_second(0),
	sent_discarded_packets(0),
	sent_total_packets(0),
	recv_total_bytes(0),
	recv_bytes_second(0),
	key(NULL) {}

	bool best_connection; // Is this the best connection we have?
	bool writable; // Has this connection received a STUN response?
	bool readable; // Has this connection received a STUN request?
	bool timeout; // Has this connection timed out?
	bool new_connection; // Is this a newly created connection?
	size_t rtt; // The STUN RTT for this connection.
	size_t sent_total_bytes; // Total bytes sent on this connection.
	size_t sent_bytes_second; // Bps over the last measurement interval.
	size_t sent_discarded_packets; // Number of outgoing packets discarded due to
	// socket errors.
	size_t sent_total_packets; // Number of total outgoing packets attempted for
	// sending.

	size_t recv_total_bytes; // Total bytes received on this connection.
	size_t recv_bytes_second; // Bps over the last measurement interval.
	Candidate local_candidate; // The local candidate for this connection.
	Candidate remote_candidate; // The remote candidate for this connection.
	void* key; // A static value that identifies this conn.
	};

	// Information about all the connections of a channel.
	typedef std::vector<ConnectionInfo> ConnectionInfos;

	// Information about a specific channel
	struct TransportChannelStats {
	int component;
	ConnectionInfos connection_infos;
	std::string srtp_cipher;
	std::string ssl_cipher;
	};

	// Information about all the channels of a transport.
	// TODO(hta): Consider if a simple vector is as good as a map.
	typedef std::vector<TransportChannelStats> TransportChannelStatsList;

	// Information about the stats of a transport.
	struct TransportStats {
	std::string content_name;
	TransportChannelStatsList channel_stats;
	};

	bool BadTransportDescription(const std::string& desc, std::string* err_desc);

	bool IceCredentialsChanged(const std::string& old_ufrag,
	const std::string& old_pwd,
	const std::string& new_ufrag,
	const std::string& new_pwd);

	class Transport : public rtc::MessageHandler,
	public sigslot::has_slots<> {
	public:
	Transport(rtc::Thread* signaling_thread,
	rtc::Thread* worker_thread,
	const std::string& content_name,
	const std::string& type,
	PortAllocator* allocator);
	virtual ~Transport();

	// Returns the signaling thread. The app talks to Transport on this thread.
	rtc::Thread* signaling_thread() { return signaling_thread_; }
	// Returns the worker thread. The actual networking is done on this thread.
	rtc::Thread* worker_thread() { return worker_thread_; }

	// Returns the content_name of this transport.
	const std::string& content_name() const { return content_name_; }
	// Returns the type of this transport.
	const std::string& type() const { return type_; }

	// Returns the port allocator object for this transport.
	PortAllocator* port_allocator() { return allocator_; }

	// Returns the readable and states of this manager. These bits are the ORs
	// of the corresponding bits on the managed channels. Each time one of these
	// states changes, a signal is raised.
	// TODO: Replace uses of readable() and writable() with
	// any_channels_readable() and any_channels_writable().
	bool readable() const { return any_channels_readable(); }
	bool writable() const { return any_channels_writable(); }
	bool was_writable() const { return was_writable_; }
	bool any_channels_readable() const {
	return (readable_ == TRANSPORT_STATE_SOME \|\|
	readable_ == TRANSPORT_STATE_ALL);
	}
	bool any_channels_writable() const {
	return (writable_ == TRANSPORT_STATE_SOME \|\|
	writable_ == TRANSPORT_STATE_ALL);
	}
	bool all_channels_readable() const {
	return (readable_ == TRANSPORT_STATE_ALL);
	}
	bool all_channels_writable() const {
	return (writable_ == TRANSPORT_STATE_ALL);
	}
	sigslot::signal1<Transport*> SignalReadableState;
	sigslot::signal1<Transport*> SignalWritableState;
	sigslot::signal1<Transport*> SignalCompleted;
	sigslot::signal1<Transport*> SignalFailed;

	// Returns whether the client has requested the channels to connect.
	bool connect_requested() const { return connect_requested_; }

	void SetIceRole(IceRole role);
	IceRole ice_role() const { return ice_role_; }

	void SetIceTiebreaker(uint64 IceTiebreaker) { tiebreaker_ = IceTiebreaker; }
	uint64 IceTiebreaker() { return tiebreaker_; }

	// Must be called before applying local session description.
	void SetIdentity(rtc::SSLIdentity* identity);

	// Get a copy of the local identity provided by SetIdentity.
	bool GetIdentity(rtc::SSLIdentity** identity);

	// Get a copy of the remote certificate in use by the specified channel.
	bool GetRemoteCertificate(rtc::SSLCertificate** cert);

	TransportProtocol protocol() const { return protocol_; }

	// Create, destroy, and lookup the channels of this type by their components.
	TransportChannelImpl* CreateChannel(int component);
	// Note: GetChannel may lead to race conditions, since the mutex is not held
	// after the pointer is returned.
	TransportChannelImpl* GetChannel(int component);
	// Note: HasChannel does not lead to race conditions, unlike GetChannel.
	bool HasChannel(int component) {
	return (NULL != GetChannel(component));
	}
	bool HasChannels();
	void DestroyChannel(int component);

	// Set the local TransportDescription to be used by TransportChannels.
	// This should be called before ConnectChannels().
	bool SetLocalTransportDescription(const TransportDescription& description,
	ContentAction action,
	std::string* error_desc);

	// Set the remote TransportDescription to be used by TransportChannels.
	bool SetRemoteTransportDescription(const TransportDescription& description,
	ContentAction action,
	std::string* error_desc);

	// Tells all current and future channels to start connecting. When the first
	// channel begins connecting, the following signal is raised.
	void ConnectChannels();
	sigslot::signal1<Transport*> SignalConnecting;

	// Resets all of the channels back to their initial state. They are no
	// longer connecting.
	void ResetChannels();

	// Destroys every channel created so far.
	void DestroyAllChannels();

	bool GetStats(TransportStats* stats);

	// Before any stanza is sent, the manager will request signaling. Once
	// signaling is available, the client should call OnSignalingReady. Once
	// this occurs, the transport (or its channels) can send any waiting stanzas.
	// OnSignalingReady invokes OnTransportSignalingReady and then forwards this
	// signal to each channel.
	sigslot::signal1<Transport*> SignalRequestSignaling;
	void OnSignalingReady();

	// Handles sending of ready candidates and receiving of remote candidates.
	sigslot::signal2<Transport*,
	const std::vector<Candidate>&> SignalCandidatesReady;

	sigslot::signal1<Transport*> SignalCandidatesAllocationDone;
	void OnRemoteCandidates(const std::vector<Candidate>& candidates);

	// If candidate is not acceptable, returns false and sets error.
	// Call this before calling OnRemoteCandidates.
	virtual bool VerifyCandidate(const Candidate& candidate,
	std::string* error);

	// Signals when the best connection for a channel changes.
	sigslot::signal3<Transport*,
	int, // component
	const Candidate&> SignalRouteChange;

	// Forwards the signal from TransportChannel to BaseSession.
	sigslot::signal0<> SignalRoleConflict;

	virtual bool GetSslRole(rtc::SSLRole* ssl_role) const;

	protected:
	// These are called by Create/DestroyChannel above in order to create or
	// destroy the appropriate type of channel.
	virtual TransportChannelImpl* CreateTransportChannel(int component) = 0;
	virtual void DestroyTransportChannel(TransportChannelImpl* channel) = 0;

	// Informs the subclass that we received the signaling ready message.
	virtual void OnTransportSignalingReady() {}

	// The current local transport description, for use by derived classes
	// when performing transport description negotiation.
	const TransportDescription* local_description() const {
	return local_description_.get();
	}

	// The current remote transport description, for use by derived classes
	// when performing transport description negotiation.
	const TransportDescription* remote_description() const {
	return remote_description_.get();
	}

	virtual void SetIdentity_w(rtc::SSLIdentity* identity) {}

	virtual bool GetIdentity_w(rtc::SSLIdentity** identity) {
	return false;
	}

	// Pushes down the transport parameters from the local description, such
	// as the ICE ufrag and pwd.
	// Derived classes can override, but must call the base as well.
	virtual bool ApplyLocalTransportDescription_w(TransportChannelImpl* channel,
	std::string* error_desc);

	// Pushes down remote ice credentials from the remote description to the
	// transport channel.
	virtual bool ApplyRemoteTransportDescription_w(TransportChannelImpl* ch,
	std::string* error_desc);

	// Negotiates the transport parameters based on the current local and remote
	// transport description, such at the version of ICE to use, and whether DTLS
	// should be activated.
	// Derived classes can negotiate their specific parameters here, but must call
	// the base as well.
	virtual bool NegotiateTransportDescription_w(ContentAction local_role,
	std::string* error_desc);

	// Pushes down the transport parameters obtained via negotiation.
	// Derived classes can set their specific parameters here, but must call the
	// base as well.
	virtual bool ApplyNegotiatedTransportDescription_w(
	TransportChannelImpl* channel, std::string* error_desc);

	virtual bool GetSslRole_w(rtc::SSLRole* ssl_role) const {
	return false;
	}

	private:
	struct ChannelMapEntry {
	ChannelMapEntry() : impl_(NULL), candidates_allocated_(false), ref_(0) {}
	explicit ChannelMapEntry(TransportChannelImpl *impl)
	: impl_(impl),
	candidates_allocated_(false),
	ref_(0) {
	}

	void AddRef() { ++ref_; }
	void DecRef() {
	ASSERT(ref_ > 0);
	--ref_;
	}
	int ref() const { return ref_; }

	TransportChannelImpl* get() const { return impl_; }
	TransportChannelImpl* operator->() const { return impl_; }
	void set_candidates_allocated(bool status) {
	candidates_allocated_ = status;
	}
	bool candidates_allocated() const { return candidates_allocated_; }

	private:
	TransportChannelImpl *impl_;
	bool candidates_allocated_;
	int ref_;
	};

	// Candidate component => ChannelMapEntry
	typedef std::map<int, ChannelMapEntry> ChannelMap;

	// Called when the state of a channel changes.
	void OnChannelReadableState(TransportChannel* channel);
	void OnChannelWritableState(TransportChannel* channel);

	// Called when a channel requests signaling.
	void OnChannelRequestSignaling(TransportChannelImpl* channel);

	// Called when a candidate is ready from remote peer.
	void OnRemoteCandidate(const Candidate& candidate);
	// Called when a candidate is ready from channel.
	void OnChannelCandidateReady(TransportChannelImpl* channel,
	const Candidate& candidate);
	void OnChannelRouteChange(TransportChannel* channel,
	const Candidate& remote_candidate);
	void OnChannelCandidatesAllocationDone(TransportChannelImpl* channel);
	// Called when there is ICE role change.
	void OnRoleConflict(TransportChannelImpl* channel);
	// Called when the channel removes a connection.
	void OnChannelConnectionRemoved(TransportChannelImpl* channel);

	// Dispatches messages to the appropriate handler (below).
	void OnMessage(rtc::Message* msg);

	// These are versions of the above methods that are called only on a
	// particular thread (s = signaling, w = worker). The above methods post or
	// send a message to invoke this version.
	TransportChannelImpl* CreateChannel_w(int component);
	void DestroyChannel_w(int component);
	void ConnectChannels_w();
	void ResetChannels_w();
	void DestroyAllChannels_w();
	void OnRemoteCandidate_w(const Candidate& candidate);
	void OnChannelReadableState_s();
	void OnChannelWritableState_s();
	void OnChannelRequestSignaling_s();
	void OnConnecting_s();
	void OnChannelRouteChange_s(const TransportChannel* channel,
	const Candidate& remote_candidate);
	void OnChannelCandidatesAllocationDone_s();

	// Helper function that invokes the given function on every channel.
	typedef void (TransportChannelImpl::* TransportChannelFunc)();
	void CallChannels_w(TransportChannelFunc func);

	// Computes the OR of the channel's read or write state (argument picks).
	TransportState GetTransportState_s(bool read);

	void OnChannelCandidateReady_s();

	void SetIceRole_w(IceRole role);
	void SetRemoteIceMode_w(IceMode mode);
	bool SetLocalTransportDescription_w(const TransportDescription& desc,
	ContentAction action,
	std::string* error_desc);
	bool SetRemoteTransportDescription_w(const TransportDescription& desc,
	ContentAction action,
	std::string* error_desc);
	bool GetStats_w(TransportStats* infos);
	bool GetRemoteCertificate_w(rtc::SSLCertificate** cert);

	// Sends SignalCompleted if we are now in that state.
	void MaybeCompleted_w();

	rtc::Thread* const signaling_thread_;
	rtc::Thread* const worker_thread_;
	const std::string content_name_;
	const std::string type_;
	PortAllocator* const allocator_;
	bool destroyed_;
	TransportState readable_;
	TransportState writable_;
	bool was_writable_;
	bool connect_requested_;
	IceRole ice_role_;
	uint64 tiebreaker_;
	TransportProtocol protocol_;
	IceMode remote_ice_mode_;
	rtc::scoped_ptr<TransportDescription> local_description_;
	rtc::scoped_ptr<TransportDescription> remote_description_;

	// TODO(tommi): Make sure we only use this on the worker thread.
	ChannelMap channels_;
	// Buffers the ready_candidates so that SignalCanidatesReady can
	// provide them in multiples.
	std::vector<Candidate> ready_candidates_;
	// Protects changes to channels and messages
	rtc::CriticalSection crit_;

	DISALLOW_COPY_AND_ASSIGN(Transport);
	};

	// Extract a TransportProtocol from a TransportDescription.
	TransportProtocol TransportProtocolFromDescription(
	const TransportDescription* desc);

	} // namespace cricket

	#endif // WEBRTC_P2P_BASE_TRANSPORT_H_