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* Copyright 2019 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.
#include <memory>
#include <string>
#include <vector>
#include "absl/types/optional.h"
#include "api/candidate.h"
#include "api/transport/stun.h"
#include "logging/rtc_event_log/ice_logger.h"
#include "p2p/base/candidate_pair_interface.h"
#include "p2p/base/connection_info.h"
#include "p2p/base/p2p_transport_channel_ice_field_trials.h"
#include "p2p/base/stun_request.h"
#include "p2p/base/transport_description.h"
#include "rtc_base/async_packet_socket.h"
#include "rtc_base/message_handler.h"
#include "rtc_base/network.h"
#include "rtc_base/numerics/event_based_exponential_moving_average.h"
#include "rtc_base/rate_tracker.h"
namespace cricket {
// Version number for GOOG_PING, this is added to have the option of
// adding other flavors in the future.
constexpr int kGoogPingVersion = 1;
// Connection and Port has circular dependencies.
// So we use forward declaration rather than include.
class Port;
// Forward declaration so that a ConnectionRequest can contain a Connection.
class Connection;
struct CandidatePair final : public CandidatePairInterface {
~CandidatePair() override = default;
const Candidate& local_candidate() const override { return local; }
const Candidate& remote_candidate() const override { return remote; }
Candidate local;
Candidate remote;
// A ConnectionRequest is a simple STUN ping used to determine writability.
class ConnectionRequest : public StunRequest {
explicit ConnectionRequest(Connection* connection);
void Prepare(StunMessage* request) override;
void OnResponse(StunMessage* response) override;
void OnErrorResponse(StunMessage* response) override;
void OnTimeout() override;
void OnSent() override;
int resend_delay() override;
Connection* const connection_;
// Represents a communication link between a port on the local client and a
// port on the remote client.
class Connection : public CandidatePairInterface,
public rtc::MessageHandlerAutoCleanup,
public sigslot::has_slots<> {
struct SentPing {
SentPing(const std::string id, int64_t sent_time, uint32_t nomination)
: id(id), sent_time(sent_time), nomination(nomination) {}
std::string id;
int64_t sent_time;
uint32_t nomination;
~Connection() override;
// A unique ID assigned when the connection is created.
uint32_t id() const { return id_; }
// Implementation of virtual methods in CandidatePairInterface.
// Returns the description of the local port
const Candidate& local_candidate() const override;
// Returns the description of the remote port to which we communicate.
const Candidate& remote_candidate() const override;
// Return local network for this connection.
virtual const rtc::Network* network() const;
// Return generation for this connection.
virtual int generation() const;
// Returns the pair priority.
virtual uint64_t priority() const;
enum WriteState {
STATE_WRITABLE = 0, // we have received ping responses recently
STATE_WRITE_UNRELIABLE = 1, // we have had a few ping failures
STATE_WRITE_INIT = 2, // we have yet to receive a ping response
STATE_WRITE_TIMEOUT = 3, // we have had a large number of ping failures
WriteState write_state() const { return write_state_; }
bool writable() const { return write_state_ == STATE_WRITABLE; }
bool receiving() const { return receiving_; }
// Determines whether the connection has finished connecting. This can only
// be false for TCP connections.
bool connected() const { return connected_; }
bool weak() const { return !(writable() && receiving() && connected()); }
bool active() const { return write_state_ != STATE_WRITE_TIMEOUT; }
// A connection is dead if it can be safely deleted.
bool dead(int64_t now) const;
// Estimate of the round-trip time over this connection.
int rtt() const { return rtt_; }
int unwritable_timeout() const;
void set_unwritable_timeout(const absl::optional<int>& value_ms) {
unwritable_timeout_ = value_ms;
int unwritable_min_checks() const;
void set_unwritable_min_checks(const absl::optional<int>& value) {
unwritable_min_checks_ = value;
int inactive_timeout() const;
void set_inactive_timeout(const absl::optional<int>& value) {
inactive_timeout_ = value;
// Gets the |ConnectionInfo| stats, where |best_connection| has not been
// populated (default value false).
ConnectionInfo stats();
sigslot::signal1<Connection*> SignalStateChange;
// Sent when the connection has decided that it is no longer of value. It
// will delete itself immediately after this call.
sigslot::signal1<Connection*> SignalDestroyed;
// The connection can send and receive packets asynchronously. This matches
// the interface of AsyncPacketSocket, which may use UDP or TCP under the
// covers.
virtual int Send(const void* data,
size_t size,
const rtc::PacketOptions& options) = 0;
// Error if Send() returns < 0
virtual int GetError() = 0;
sigslot::signal4<Connection*, const char*, size_t, int64_t> SignalReadPacket;
sigslot::signal1<Connection*> SignalReadyToSend;
// Called when a packet is received on this connection.
void OnReadPacket(const char* data, size_t size, int64_t packet_time_us);
// Called when the socket is currently able to send.
void OnReadyToSend();
// Called when a connection is determined to be no longer useful to us. We
// still keep it around in case the other side wants to use it. But we can
// safely stop pinging on it and we can allow it to time out if the other
// side stops using it as well.
bool pruned() const { return pruned_; }
void Prune();
bool use_candidate_attr() const { return use_candidate_attr_; }
void set_use_candidate_attr(bool enable);
void set_nomination(uint32_t value) { nomination_ = value; }
uint32_t remote_nomination() const { return remote_nomination_; }
// One or several pairs may be nominated based on if Regular or Aggressive
// Nomination is used.
// |nominated| is defined both for the controlling or controlled agent based
// on if a nomination has been pinged or acknowledged. The controlled agent
// gets its |remote_nomination_| set when pinged by the controlling agent with
// a nomination value. The controlling agent gets its |acked_nomination_| set
// when receiving a response to a nominating ping.
bool nominated() const { return acked_nomination_ || remote_nomination_; }
void set_remote_ice_mode(IceMode mode) { remote_ice_mode_ = mode; }
int receiving_timeout() const;
void set_receiving_timeout(absl::optional<int> receiving_timeout_ms) {
receiving_timeout_ = receiving_timeout_ms;
// Makes the connection go away.
void Destroy();
// Makes the connection go away, in a failed state.
void FailAndDestroy();
// Prunes the connection and sets its state to STATE_FAILED,
// It will not be used or send pings although it can still receive packets.
void FailAndPrune();
// Checks that the state of this connection is up-to-date. The argument is
// the current time, which is compared against various timeouts.
void UpdateState(int64_t now);
// Called when this connection should try checking writability again.
int64_t last_ping_sent() const { return last_ping_sent_; }
void Ping(int64_t now);
void ReceivedPingResponse(
int rtt,
const std::string& request_id,
const absl::optional<uint32_t>& nomination = absl::nullopt);
int64_t last_ping_response_received() const {
return last_ping_response_received_;
const absl::optional<std::string>& last_ping_id_received() const {
return last_ping_id_received_;
// Used to check if any STUN ping response has been received.
int rtt_samples() const { return rtt_samples_; }
// Called whenever a valid ping is received on this connection. This is
// public because the connection intercepts the first ping for us.
int64_t last_ping_received() const { return last_ping_received_; }
void ReceivedPing(
const absl::optional<std::string>& request_id = absl::nullopt);
// Handles the binding request; sends a response if this is a valid request.
void HandleStunBindingOrGoogPingRequest(IceMessage* msg);
// Handles the piggyback acknowledgement of the lastest connectivity check
// that the remote peer has received, if it is indicated in the incoming
// connectivity check from the peer.
void HandlePiggybackCheckAcknowledgementIfAny(StunMessage* msg);
// Timestamp when data was last sent (or attempted to be sent).
int64_t last_send_data() const { return last_send_data_; }
int64_t last_data_received() const { return last_data_received_; }
// Debugging description of this connection
std::string ToDebugId() const;
std::string ToString() const;
std::string ToSensitiveString() const;
// Structured description of this candidate pair.
const webrtc::IceCandidatePairDescription& ToLogDescription();
void set_ice_event_log(webrtc::IceEventLog* ice_event_log) {
ice_event_log_ = ice_event_log;
// Prints pings_since_last_response_ into a string.
void PrintPingsSinceLastResponse(std::string* pings, size_t max);
bool reported() const { return reported_; }
void set_reported(bool reported) { reported_ = reported; }
// The following two methods are only used for logging in ToString above, and
// this flag is set true by P2PTransportChannel for its selected candidate
// pair.
bool selected() const { return selected_; }
void set_selected(bool selected) { selected_ = selected; }
// This signal will be fired if this connection is nominated by the
// controlling side.
sigslot::signal1<Connection*> SignalNominated;
// Invoked when Connection receives STUN error response with 487 code.
void HandleRoleConflictFromPeer();
IceCandidatePairState state() const { return state_; }
int num_pings_sent() const { return num_pings_sent_; }
IceMode remote_ice_mode() const { return remote_ice_mode_; }
uint32_t ComputeNetworkCost() const;
// Update the ICE password and/or generation of the remote candidate if the
// ufrag in |params| matches the candidate's ufrag, and the
// candidate's password and/or ufrag has not been set.
void MaybeSetRemoteIceParametersAndGeneration(const IceParameters& params,
int generation);
// If |remote_candidate_| is peer reflexive and is equivalent to
// |new_candidate| except the type, update |remote_candidate_| to
// |new_candidate|.
void MaybeUpdatePeerReflexiveCandidate(const Candidate& new_candidate);
// Returns the last received time of any data, stun request, or stun
// response in milliseconds
int64_t last_received() const;
// Returns the last time when the connection changed its receiving state.
int64_t receiving_unchanged_since() const {
return receiving_unchanged_since_;
bool stable(int64_t now) const;
// Check if we sent |val| pings without receving a response.
bool TooManyOutstandingPings(const absl::optional<int>& val) const;
void SetIceFieldTrials(const IceFieldTrials* field_trials);
const rtc::EventBasedExponentialMovingAverage& GetRttEstimate() const {
return rtt_estimate_;
// Reset the connection to a state of a newly connected.
// - receving = false
// - throw away all pending request
// - reset RttEstimate
// Keep the following unchanged:
// - connected
// - remote_candidate
// - statistics
// Does not trigger SignalStateChange
void ForgetLearnedState();
void SendStunBindingResponse(const StunMessage* request);
void SendGoogPingResponse(const StunMessage* request);
void SendResponseMessage(const StunMessage& response);
// An accessor for unit tests.
Port* PortForTest() { return port_; }
const Port* PortForTest() const { return port_; }
// Public for unit tests.
uint32_t acked_nomination() const { return acked_nomination_; }
// Public for unit tests.
void set_remote_nomination(uint32_t remote_nomination) {
remote_nomination_ = remote_nomination;
// Constructs a new connection to the given remote port.
Connection(Port* port, size_t index, const Candidate& candidate);
// Called back when StunRequestManager has a stun packet to send
void OnSendStunPacket(const void* data, size_t size, StunRequest* req);
// Callbacks from ConnectionRequest
virtual void OnConnectionRequestResponse(ConnectionRequest* req,
StunMessage* response);
void OnConnectionRequestErrorResponse(ConnectionRequest* req,
StunMessage* response);
void OnConnectionRequestTimeout(ConnectionRequest* req);
void OnConnectionRequestSent(ConnectionRequest* req);
bool rtt_converged() const;
// If the response is not received within 2 * RTT, the response is assumed to
// be missing.
bool missing_responses(int64_t now) const;
// Changes the state and signals if necessary.
void set_write_state(WriteState value);
void UpdateReceiving(int64_t now);
void set_state(IceCandidatePairState state);
void set_connected(bool value);
uint32_t nomination() const { return nomination_; }
void OnMessage(rtc::Message* pmsg) override;
// The local port where this connection sends and receives packets.
Port* port() { return port_; }
const Port* port() const { return port_; }
uint32_t id_;
Port* port_;
size_t local_candidate_index_;
Candidate remote_candidate_;
ConnectionInfo stats_;
rtc::RateTracker recv_rate_tracker_;
rtc::RateTracker send_rate_tracker_;
int64_t last_send_data_ = 0;
// Update the local candidate based on the mapped address attribute.
// If the local candidate changed, fires SignalStateChange.
void MaybeUpdateLocalCandidate(ConnectionRequest* request,
StunMessage* response);
void LogCandidatePairConfig(webrtc::IceCandidatePairConfigType type);
void LogCandidatePairEvent(webrtc::IceCandidatePairEventType type,
uint32_t transaction_id);
// Check if this IceMessage is identical
// to last message ack:ed STUN_BINDING_REQUEST.
bool ShouldSendGoogPing(const StunMessage* message);
WriteState write_state_;
bool receiving_;
bool connected_;
bool pruned_;
bool selected_ = false;
// By default |use_candidate_attr_| flag will be true,
// as we will be using aggressive nomination.
// But when peer is ice-lite, this flag "must" be initialized to false and
// turn on when connection becomes "best connection".
bool use_candidate_attr_;
// Used by the controlling side to indicate that this connection will be
// selected for transmission if the peer supports ICE-renomination when this
// value is positive. A larger-value indicates that a connection is nominated
// later and should be selected by the controlled side with higher precedence.
// A zero-value indicates not nominating this connection.
uint32_t nomination_ = 0;
// The last nomination that has been acknowledged.
uint32_t acked_nomination_ = 0;
// Used by the controlled side to remember the nomination value received from
// the controlling side. When the peer does not support ICE re-nomination, its
// value will be 1 if the connection has been nominated.
uint32_t remote_nomination_ = 0;
IceMode remote_ice_mode_;
StunRequestManager requests_;
int rtt_;
int rtt_samples_ = 0;
uint64_t total_round_trip_time_ms_ = 0;
absl::optional<uint32_t> current_round_trip_time_ms_;
int64_t last_ping_sent_; // last time we sent a ping to the other side
int64_t last_ping_received_; // last time we received a ping from the other
// side
int64_t last_data_received_;
int64_t last_ping_response_received_;
int64_t receiving_unchanged_since_ = 0;
std::vector<SentPing> pings_since_last_response_;
// Transaction ID of the last connectivity check received. Null if having not
// received a ping yet.
absl::optional<std::string> last_ping_id_received_;
absl::optional<int> unwritable_timeout_;
absl::optional<int> unwritable_min_checks_;
absl::optional<int> inactive_timeout_;
bool reported_;
IceCandidatePairState state_;
// Time duration to switch from receiving to not receiving.
absl::optional<int> receiving_timeout_;
int64_t time_created_ms_;
int num_pings_sent_ = 0;
absl::optional<webrtc::IceCandidatePairDescription> log_description_;
webrtc::IceEventLog* ice_event_log_ = nullptr;
// if configured via field trial, the remote peer supports it (signaled
// in STUN_BINDING) and if the last STUN BINDING is identical to the one
// that is about to be sent.
absl::optional<bool> remote_support_goog_ping_;
std::unique_ptr<StunMessage> cached_stun_binding_;
const IceFieldTrials* field_trials_;
rtc::EventBasedExponentialMovingAverage rtt_estimate_;
friend class Port;
friend class ConnectionRequest;
friend class P2PTransportChannel;
// ProxyConnection defers all the interesting work to the port.
class ProxyConnection : public Connection {
ProxyConnection(Port* port, size_t index, const Candidate& remote_candidate);
int Send(const void* data,
size_t size,
const rtc::PacketOptions& options) override;
int GetError() override;
int error_ = 0;
} // namespace cricket