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* 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.
// P2PTransportChannel wraps up the state management of the connection between
// two P2P clients. Clients have candidate ports for connecting, and
// connections which are combinations of candidates from each end (Alice and
// Bob each have candidates, one candidate from Alice and one candidate from
// Bob are used to make a connection, repeat to make many connections).
// When all of the available connections become invalid (non-writable), we
// kick off a process of determining more candidates and more connections.
#include <stddef.h>
#include <stdint.h>
#include <algorithm>
#include <map>
#include <memory>
#include <set>
#include <string>
#include <utility>
#include <vector>
#include "absl/base/attributes.h"
#include "absl/strings/string_view.h"
#include "absl/types/optional.h"
#include "api/array_view.h"
#include "api/async_dns_resolver.h"
#include "api/candidate.h"
#include "api/ice_transport_interface.h"
#include "api/rtc_error.h"
#include "api/sequence_checker.h"
#include "api/task_queue/pending_task_safety_flag.h"
#include "api/transport/enums.h"
#include "api/transport/stun.h"
#include "logging/rtc_event_log/events/rtc_event_ice_candidate_pair_config.h"
#include "logging/rtc_event_log/ice_logger.h"
#include "p2p/base/active_ice_controller_factory_interface.h"
#include "p2p/base/candidate_pair_interface.h"
#include "p2p/base/connection.h"
#include "p2p/base/ice_agent_interface.h"
#include "p2p/base/ice_controller_factory_interface.h"
#include "p2p/base/ice_controller_interface.h"
#include "p2p/base/ice_switch_reason.h"
#include "p2p/base/ice_transport_internal.h"
#include "p2p/base/p2p_constants.h"
#include "p2p/base/p2p_transport_channel_ice_field_trials.h"
#include "p2p/base/port.h"
#include "p2p/base/port_allocator.h"
#include "p2p/base/port_interface.h"
#include "p2p/base/regathering_controller.h"
#include "p2p/base/stun_dictionary.h"
#include "p2p/base/transport_description.h"
#include "rtc_base/async_packet_socket.h"
#include "rtc_base/checks.h"
#include "rtc_base/dscp.h"
#include "rtc_base/network/sent_packet.h"
#include "rtc_base/network_route.h"
#include "rtc_base/socket.h"
#include "rtc_base/socket_address.h"
#include "rtc_base/strings/string_builder.h"
#include "rtc_base/system/rtc_export.h"
#include "rtc_base/thread.h"
#include "rtc_base/thread_annotations.h"
namespace webrtc {
class RtcEventLog;
} // namespace webrtc
namespace cricket {
bool IceCredentialsChanged(absl::string_view old_ufrag,
absl::string_view old_pwd,
absl::string_view new_ufrag,
absl::string_view new_pwd);
// Adds the port on which the candidate originated.
class RemoteCandidate : public Candidate {
RemoteCandidate(const Candidate& c, PortInterface* origin_port)
: Candidate(c), origin_port_(origin_port) {}
PortInterface* origin_port() { return origin_port_; }
PortInterface* origin_port_;
// P2PTransportChannel manages the candidates and connection process to keep
// two P2P clients connected to each other.
class RTC_EXPORT P2PTransportChannel : public IceTransportInternal,
public IceAgentInterface {
static std::unique_ptr<P2PTransportChannel> Create(
absl::string_view transport_name,
int component,
webrtc::IceTransportInit init);
// For testing only.
// TODO(zstein): Remove once AsyncDnsResolverFactory is required.
P2PTransportChannel(absl::string_view transport_name,
int component,
PortAllocator* allocator,
const webrtc::FieldTrialsView* field_trials = nullptr);
~P2PTransportChannel() override;
P2PTransportChannel(const P2PTransportChannel&) = delete;
P2PTransportChannel& operator=(const P2PTransportChannel&) = delete;
// From TransportChannelImpl:
IceTransportState GetState() const override;
webrtc::IceTransportState GetIceTransportState() const override;
const std::string& transport_name() const override;
int component() const override;
bool writable() const override;
bool receiving() const override;
void SetIceRole(IceRole role) override;
IceRole GetIceRole() const override;
void SetIceTiebreaker(uint64_t tiebreaker) override;
void SetIceParameters(const IceParameters& ice_params) override;
void SetRemoteIceParameters(const IceParameters& ice_params) override;
void SetRemoteIceMode(IceMode mode) override;
// TODO(deadbeef): Deprecated. Remove when Chromium's
// IceTransportChannel does not depend on this.
void Connect() {}
void MaybeStartGathering() override;
IceGatheringState gathering_state() const override;
void ResolveHostnameCandidate(const Candidate& candidate);
void AddRemoteCandidate(const Candidate& candidate) override;
void RemoveRemoteCandidate(const Candidate& candidate) override;
void RemoveAllRemoteCandidates() override;
// Sets the parameters in IceConfig. We do not set them blindly. Instead, we
// only update the parameter if it is considered set in `config`. For example,
// a negative value of receiving_timeout will be considered "not set" and we
// will not use it to update the respective parameter in `config_`.
// TODO(deadbeef): Use absl::optional instead of negative values.
void SetIceConfig(const IceConfig& config) override;
const IceConfig& config() const;
static webrtc::RTCError ValidateIceConfig(const IceConfig& config);
// From TransportChannel:
int SendPacket(const char* data,
size_t len,
const rtc::PacketOptions& options,
int flags) override;
int SetOption(rtc::Socket::Option opt, int value) override;
bool GetOption(rtc::Socket::Option opt, int* value) override;
int GetError() override;
bool GetStats(IceTransportStats* ice_transport_stats) override;
absl::optional<int> GetRttEstimate() override;
const Connection* selected_connection() const override;
absl::optional<const CandidatePair> GetSelectedCandidatePair() const override;
// From IceAgentInterface
void OnStartedPinging() override;
int64_t GetLastPingSentMs() const override;
void UpdateConnectionStates() override;
void UpdateState() override;
void SendPingRequest(const Connection* connection) override;
void SwitchSelectedConnection(const Connection* connection,
IceSwitchReason reason) override;
void ForgetLearnedStateForConnections(
rtc::ArrayView<const Connection* const> connections) override;
bool PruneConnections(
rtc::ArrayView<const Connection* const> connections) override;
// TODO(honghaiz): Remove this method once the reference of it in
// Chromoting is removed.
const Connection* best_connection() const {
return selected_connection_;
void set_incoming_only(bool value) {
incoming_only_ = value;
// Note: These are only for testing purpose.
// `ports_` and `pruned_ports` should not be changed from outside.
const std::vector<PortInterface*>& ports() {
return ports_;
const std::vector<PortInterface*>& pruned_ports() {
return pruned_ports_;
IceMode remote_ice_mode() const {
return remote_ice_mode_;
void PruneAllPorts();
int check_receiving_interval() const;
absl::optional<rtc::NetworkRoute> network_route() const override;
void RemoveConnection(Connection* connection);
// Helper method used only in unittest.
rtc::DiffServCodePoint DefaultDscpValue() const;
// Public for unit tests.
Connection* FindNextPingableConnection();
void MarkConnectionPinged(Connection* conn);
// Public for unit tests.
rtc::ArrayView<Connection* const> connections() const;
void RemoveConnectionForTest(Connection* connection);
// Public for unit tests.
PortAllocatorSession* allocator_session() const {
if (allocator_sessions_.empty()) {
return nullptr;
return allocator_sessions_.back().get();
// Public for unit tests.
const std::vector<RemoteCandidate>& remote_candidates() const {
return remote_candidates_;
std::string ToString() const {
const std::string RECEIVING_ABBREV[2] = {"_", "R"};
const std::string WRITABLE_ABBREV[2] = {"_", "W"};
rtc::StringBuilder ss;
ss << "Channel[" << transport_name_ << "|" << component_ << "|"
<< RECEIVING_ABBREV[receiving_] << WRITABLE_ABBREV[writable_] << "]";
return ss.Release();
GetDictionaryWriter() override {
return stun_dict_writer_;
absl::string_view transport_name,
int component,
PortAllocator* allocator,
// DNS resolver factory
webrtc::AsyncDnsResolverFactoryInterface* async_dns_resolver_factory,
// If the P2PTransportChannel has to delete the DNS resolver factory
// on release, this pointer is set.
webrtc::RtcEventLog* event_log,
IceControllerFactoryInterface* ice_controller_factory,
ActiveIceControllerFactoryInterface* active_ice_controller_factory,
const webrtc::FieldTrialsView* field_trials);
bool IsGettingPorts() {
return allocator_session()->IsGettingPorts();
// Returns true if it's possible to send packets on `connection`.
bool ReadyToSend(const Connection* connection) const;
bool PresumedWritable(const Connection* conn) const;
void SendPingRequestInternal(Connection* connection);
rtc::NetworkRoute ConfigureNetworkRoute(const Connection* conn);
void SwitchSelectedConnectionInternal(Connection* conn,
IceSwitchReason reason);
void UpdateTransportState();
void HandleAllTimedOut();
void MaybeStopPortAllocatorSessions();
void OnSelectedConnectionDestroyed() RTC_RUN_ON(network_thread_);
// ComputeIceTransportState computes the RTCIceTransportState as described in
// ComputeState
// computes the value we currently export as RTCIceTransportState.
// TODO( Remove ComputeState once it's no longer used.
IceTransportState ComputeState() const;
webrtc::IceTransportState ComputeIceTransportState() const;
bool CreateConnections(const Candidate& remote_candidate,
PortInterface* origin_port);
bool CreateConnection(PortInterface* port,
const Candidate& remote_candidate,
PortInterface* origin_port);
bool FindConnection(const Connection* connection) const;
uint32_t GetRemoteCandidateGeneration(const Candidate& candidate);
bool IsDuplicateRemoteCandidate(const Candidate& candidate);
void RememberRemoteCandidate(const Candidate& remote_candidate,
PortInterface* origin_port);
void PingConnection(Connection* conn);
void AddAllocatorSession(std::unique_ptr<PortAllocatorSession> session);
void AddConnection(Connection* connection);
void OnPortReady(PortAllocatorSession* session, PortInterface* port);
void OnPortsPruned(PortAllocatorSession* session,
const std::vector<PortInterface*>& ports);
void OnCandidatesReady(PortAllocatorSession* session,
const std::vector<Candidate>& candidates);
void OnCandidateError(PortAllocatorSession* session,
const IceCandidateErrorEvent& event);
void OnCandidatesRemoved(PortAllocatorSession* session,
const std::vector<Candidate>& candidates);
void OnCandidatesAllocationDone(PortAllocatorSession* session);
void OnUnknownAddress(PortInterface* port,
const rtc::SocketAddress& addr,
ProtocolType proto,
IceMessage* stun_msg,
const std::string& remote_username,
bool port_muxed);
void OnCandidateFilterChanged(uint32_t prev_filter, uint32_t cur_filter);
// When a port is destroyed, remove it from both lists `ports_`
// and `pruned_ports_`.
void OnPortDestroyed(PortInterface* port);
// When pruning a port, move it from `ports_` to `pruned_ports_`.
// Returns true if the port is found and removed from `ports_`.
bool PrunePort(PortInterface* port);
void OnRoleConflict(PortInterface* port);
void OnConnectionStateChange(Connection* connection);
void OnReadPacket(Connection* connection, const rtc::ReceivedPacket& packet);
void OnSentPacket(const rtc::SentPacket& sent_packet);
void OnReadyToSend(Connection* connection);
void OnConnectionDestroyed(Connection* connection);
void OnNominated(Connection* conn);
void LogCandidatePairConfig(Connection* conn,
webrtc::IceCandidatePairConfigType type);
uint32_t GetNominationAttr(Connection* conn) const;
bool GetUseCandidateAttr(Connection* conn) const;
bool AllowedToPruneConnections() const;
// Returns the latest remote ICE parameters or nullptr if there are no remote
// ICE parameters yet.
IceParameters* remote_ice() {
return remote_ice_parameters_.empty() ? nullptr
: &remote_ice_parameters_.back();
// Returns the remote IceParameters and generation that match `ufrag`
// if found, and returns nullptr otherwise.
const IceParameters* FindRemoteIceFromUfrag(absl::string_view ufrag,
uint32_t* generation);
// Returns the index of the latest remote ICE parameters, or 0 if no remote
// ICE parameters have been received.
uint32_t remote_ice_generation() {
return remote_ice_parameters_.empty()
? 0
: static_cast<uint32_t>(remote_ice_parameters_.size() - 1);
// Indicates if the given local port has been pruned.
bool IsPortPruned(const PortInterface* port) const;
// Indicates if the given remote candidate has been pruned.
bool IsRemoteCandidatePruned(const Candidate& cand) const;
// Sets the writable state, signaling if necessary.
void SetWritable(bool writable);
// Sets the receiving state, signaling if necessary.
void SetReceiving(bool receiving);
// Clears the address and the related address fields of a local candidate to
// avoid IP leakage. This is applicable in several scenarios as commented in
// `PortAllocator::SanitizeCandidate`.
Candidate SanitizeLocalCandidate(const Candidate& c) const;
// Clears the address field of a remote candidate to avoid IP leakage. This is
// applicable in the following scenarios:
// 1. mDNS candidates are received.
// 2. Peer-reflexive remote candidates.
Candidate SanitizeRemoteCandidate(const Candidate& c) const;
// Cast a Connection returned from IceController and verify that it exists.
// (P2P owns all Connections, and only gives const pointers to IceController,
// see IceControllerInterface).
Connection* FromIceController(const Connection* conn) {
// Verify that IceController does not return a connection
// that we have destroyed.
return const_cast<Connection*>(conn);
int64_t ComputeEstimatedDisconnectedTimeMs(int64_t now,
Connection* old_connection);
void ParseFieldTrials(const webrtc::FieldTrialsView* field_trials);
std::string transport_name_ RTC_GUARDED_BY(network_thread_);
int component_ RTC_GUARDED_BY(network_thread_);
PortAllocator* allocator_ RTC_GUARDED_BY(network_thread_);
webrtc::AsyncDnsResolverFactoryInterface* const async_dns_resolver_factory_
const std::unique_ptr<webrtc::AsyncDnsResolverFactoryInterface>
rtc::Thread* const network_thread_;
bool incoming_only_ RTC_GUARDED_BY(network_thread_);
int error_ RTC_GUARDED_BY(network_thread_);
std::vector<std::unique_ptr<PortAllocatorSession>> allocator_sessions_
// `ports_` contains ports that are used to form new connections when
// new remote candidates are added.
std::vector<PortInterface*> ports_ RTC_GUARDED_BY(network_thread_);
// `pruned_ports_` contains ports that have been removed from `ports_` and
// are not being used to form new connections, but that aren't yet destroyed.
// They may have existing connections, and they still fire signals such as
// SignalUnknownAddress.
std::vector<PortInterface*> pruned_ports_ RTC_GUARDED_BY(network_thread_);
Connection* selected_connection_ RTC_GUARDED_BY(network_thread_) = nullptr;
std::vector<Connection*> connections_ RTC_GUARDED_BY(network_thread_);
std::vector<RemoteCandidate> remote_candidates_
bool had_connection_ RTC_GUARDED_BY(network_thread_) =
false; // if connections_ has ever been nonempty
typedef std::map<rtc::Socket::Option, int> OptionMap;
OptionMap options_ RTC_GUARDED_BY(network_thread_);
IceParameters ice_parameters_ RTC_GUARDED_BY(network_thread_);
std::vector<IceParameters> remote_ice_parameters_
IceMode remote_ice_mode_ RTC_GUARDED_BY(network_thread_);
IceRole ice_role_ RTC_GUARDED_BY(network_thread_);
uint64_t ice_tiebreaker_ RTC_GUARDED_BY(network_thread_);
IceGatheringState gathering_state_ RTC_GUARDED_BY(network_thread_);
std::unique_ptr<webrtc::BasicRegatheringController> regathering_controller_
int64_t last_ping_sent_ms_ RTC_GUARDED_BY(network_thread_) = 0;
int weak_ping_interval_ RTC_GUARDED_BY(network_thread_) = WEAK_PING_INTERVAL;
// TODO(jonasolsson): Remove state_ and rename standardized_state_ once state_
// is no longer used to compute the ICE connection state.
IceTransportState state_ RTC_GUARDED_BY(network_thread_) =
webrtc::IceTransportState standardized_state_
RTC_GUARDED_BY(network_thread_) = webrtc::IceTransportState::kNew;
IceConfig config_ RTC_GUARDED_BY(network_thread_);
int last_sent_packet_id_ RTC_GUARDED_BY(network_thread_) =
-1; // -1 indicates no packet was sent before.
// The value put in the "nomination" attribute for the next nominated
// connection. A zero-value indicates the connection will not be nominated.
uint32_t nomination_ RTC_GUARDED_BY(network_thread_) = 0;
bool receiving_ RTC_GUARDED_BY(network_thread_) = false;
bool writable_ RTC_GUARDED_BY(network_thread_) = false;
bool has_been_writable_ RTC_GUARDED_BY(network_thread_) =
false; // if writable_ has ever been true
absl::optional<rtc::NetworkRoute> network_route_
webrtc::IceEventLog ice_event_log_ RTC_GUARDED_BY(network_thread_);
std::unique_ptr<ActiveIceControllerInterface> ice_controller_
struct CandidateAndResolver final {
const Candidate& candidate,
std::unique_ptr<webrtc::AsyncDnsResolverInterface>&& resolver);
// Moveable, but not copyable.
CandidateAndResolver(CandidateAndResolver&&) = default;
CandidateAndResolver& operator=(CandidateAndResolver&&) = default;
Candidate candidate_;
std::unique_ptr<webrtc::AsyncDnsResolverInterface> resolver_;
std::vector<CandidateAndResolver> resolvers_ RTC_GUARDED_BY(network_thread_);
void FinishAddingRemoteCandidate(const Candidate& new_remote_candidate);
void OnCandidateResolved(webrtc::AsyncDnsResolverInterface* resolver);
void AddRemoteCandidateWithResult(
Candidate candidate,
const webrtc::AsyncDnsResolverResult& result);
std::unique_ptr<StunAttribute> GoogDeltaReceived(
const StunByteStringAttribute*);
void GoogDeltaAckReceived(webrtc::RTCErrorOr<const StunUInt64Attribute*>);
// Bytes/packets sent/received on this channel.
uint64_t bytes_sent_ = 0;
uint64_t bytes_received_ = 0;
uint64_t packets_sent_ = 0;
uint64_t packets_received_ = 0;
// Number of times the selected_connection_ has been modified.
uint32_t selected_candidate_pair_changes_ = 0;
// When was last data received on a existing connection,
// from connection->last_data_received() that uses rtc::TimeMillis().
int64_t last_data_received_ms_ = 0;
// Parsed field trials.
IceFieldTrials ice_field_trials_;
// A dictionary of attributes that will be reflected to peer.
StunDictionaryWriter stun_dict_writer_;
// A dictionary that tracks attributes from peer.
StunDictionaryView stun_dict_view_;
} // namespace cricket