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webrtc/net/dcsctp/socket/dcsctp_socket.cc
Victor Boivie 2bfb5db548 dcsctp: Update zero checksum option to v-06 draft 
https://datatracker.ietf.org/doc/draft-ietf-tsvwg-sctp-zero-checksum/06/

The previous implementation was for version 00, and since then changes
have been made. The chunk that is used to negotiate this capability has
now grown to include an additional property - the sender's alternate
error detection method.

Bug: webrtc:14997
Change-Id: I78043d187b79f40bbadbcba02eae6eedf54f30f9
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/336380
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#41759}
2024-02-19 10:25:17 +00:00

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/*
* Copyright (c) 2021 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 "net/dcsctp/socket/dcsctp_socket.h"
#include <algorithm>
#include <cstdint>
#include <limits>
#include <memory>
#include <string>
#include <utility>
#include <vector>
#include "absl/functional/bind_front.h"
#include "absl/memory/memory.h"
#include "absl/strings/string_view.h"
#include "absl/types/optional.h"
#include "api/array_view.h"
#include "net/dcsctp/packet/chunk/abort_chunk.h"
#include "net/dcsctp/packet/chunk/chunk.h"
#include "net/dcsctp/packet/chunk/cookie_ack_chunk.h"
#include "net/dcsctp/packet/chunk/cookie_echo_chunk.h"
#include "net/dcsctp/packet/chunk/data_chunk.h"
#include "net/dcsctp/packet/chunk/data_common.h"
#include "net/dcsctp/packet/chunk/error_chunk.h"
#include "net/dcsctp/packet/chunk/forward_tsn_chunk.h"
#include "net/dcsctp/packet/chunk/forward_tsn_common.h"
#include "net/dcsctp/packet/chunk/heartbeat_ack_chunk.h"
#include "net/dcsctp/packet/chunk/heartbeat_request_chunk.h"
#include "net/dcsctp/packet/chunk/idata_chunk.h"
#include "net/dcsctp/packet/chunk/iforward_tsn_chunk.h"
#include "net/dcsctp/packet/chunk/init_ack_chunk.h"
#include "net/dcsctp/packet/chunk/init_chunk.h"
#include "net/dcsctp/packet/chunk/reconfig_chunk.h"
#include "net/dcsctp/packet/chunk/sack_chunk.h"
#include "net/dcsctp/packet/chunk/shutdown_ack_chunk.h"
#include "net/dcsctp/packet/chunk/shutdown_chunk.h"
#include "net/dcsctp/packet/chunk/shutdown_complete_chunk.h"
#include "net/dcsctp/packet/chunk_validators.h"
#include "net/dcsctp/packet/data.h"
#include "net/dcsctp/packet/error_cause/cookie_received_while_shutting_down_cause.h"
#include "net/dcsctp/packet/error_cause/error_cause.h"
#include "net/dcsctp/packet/error_cause/no_user_data_cause.h"
#include "net/dcsctp/packet/error_cause/out_of_resource_error_cause.h"
#include "net/dcsctp/packet/error_cause/protocol_violation_cause.h"
#include "net/dcsctp/packet/error_cause/unrecognized_chunk_type_cause.h"
#include "net/dcsctp/packet/error_cause/user_initiated_abort_cause.h"
#include "net/dcsctp/packet/parameter/forward_tsn_supported_parameter.h"
#include "net/dcsctp/packet/parameter/parameter.h"
#include "net/dcsctp/packet/parameter/state_cookie_parameter.h"
#include "net/dcsctp/packet/parameter/supported_extensions_parameter.h"
#include "net/dcsctp/packet/parameter/zero_checksum_acceptable_chunk_parameter.h"
#include "net/dcsctp/packet/sctp_packet.h"
#include "net/dcsctp/packet/tlv_trait.h"
#include "net/dcsctp/public/dcsctp_message.h"
#include "net/dcsctp/public/dcsctp_options.h"
#include "net/dcsctp/public/dcsctp_socket.h"
#include "net/dcsctp/public/packet_observer.h"
#include "net/dcsctp/public/types.h"
#include "net/dcsctp/rx/data_tracker.h"
#include "net/dcsctp/rx/reassembly_queue.h"
#include "net/dcsctp/socket/callback_deferrer.h"
#include "net/dcsctp/socket/capabilities.h"
#include "net/dcsctp/socket/heartbeat_handler.h"
#include "net/dcsctp/socket/state_cookie.h"
#include "net/dcsctp/socket/stream_reset_handler.h"
#include "net/dcsctp/socket/transmission_control_block.h"
#include "net/dcsctp/timer/timer.h"
#include "net/dcsctp/tx/retransmission_queue.h"
#include "net/dcsctp/tx/send_queue.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
#include "rtc_base/strings/string_builder.h"
#include "rtc_base/strings/string_format.h"
namespace dcsctp {
namespace {
using ::webrtc::TimeDelta;
using ::webrtc::Timestamp;
// https://tools.ietf.org/html/rfc4960#section-5.1
constexpr uint32_t kMinVerificationTag = 1;
constexpr uint32_t kMaxVerificationTag = std::numeric_limits<uint32_t>::max();
// https://tools.ietf.org/html/rfc4960#section-3.3.2
constexpr uint32_t kMinInitialTsn = 0;
constexpr uint32_t kMaxInitialTsn = std::numeric_limits<uint32_t>::max();
Capabilities ComputeCapabilities(const DcSctpOptions& options,
uint16_t peer_nbr_outbound_streams,
uint16_t peer_nbr_inbound_streams,
const Parameters& parameters) {
Capabilities capabilities;
absl::optional<SupportedExtensionsParameter> supported_extensions =
parameters.get<SupportedExtensionsParameter>();
if (options.enable_partial_reliability) {
capabilities.partial_reliability =
parameters.get<ForwardTsnSupportedParameter>().has_value();
if (supported_extensions.has_value()) {
capabilities.partial_reliability |=
supported_extensions->supports(ForwardTsnChunk::kType);
}
}
if (options.enable_message_interleaving && supported_extensions.has_value()) {
capabilities.message_interleaving =
supported_extensions->supports(IDataChunk::kType) &&
supported_extensions->supports(IForwardTsnChunk::kType);
}
if (supported_extensions.has_value() &&
supported_extensions->supports(ReConfigChunk::kType)) {
capabilities.reconfig = true;
}
if (options.zero_checksum_alternate_error_detection_method !=
ZeroChecksumAlternateErrorDetectionMethod::None() &&
parameters.get<ZeroChecksumAcceptableChunkParameter>().has_value() &&
parameters.get<ZeroChecksumAcceptableChunkParameter>()
->error_detection_method() ==
options.zero_checksum_alternate_error_detection_method) {
capabilities.zero_checksum = true;
}
capabilities.negotiated_maximum_incoming_streams = std::min(
options.announced_maximum_incoming_streams, peer_nbr_outbound_streams);
capabilities.negotiated_maximum_outgoing_streams = std::min(
options.announced_maximum_outgoing_streams, peer_nbr_inbound_streams);
return capabilities;
}
void AddCapabilityParameters(const DcSctpOptions& options,
bool support_zero_checksum,
Parameters::Builder& builder) {
std::vector<uint8_t> chunk_types = {ReConfigChunk::kType};
if (options.enable_partial_reliability) {
builder.Add(ForwardTsnSupportedParameter());
chunk_types.push_back(ForwardTsnChunk::kType);
}
if (options.enable_message_interleaving) {
chunk_types.push_back(IDataChunk::kType);
chunk_types.push_back(IForwardTsnChunk::kType);
}
if (support_zero_checksum) {
RTC_DCHECK(options.zero_checksum_alternate_error_detection_method !=
ZeroChecksumAlternateErrorDetectionMethod::None());
builder.Add(ZeroChecksumAcceptableChunkParameter(
options.zero_checksum_alternate_error_detection_method));
}
builder.Add(SupportedExtensionsParameter(std::move(chunk_types)));
}
TieTag MakeTieTag(DcSctpSocketCallbacks& cb) {
uint32_t tie_tag_upper =
cb.GetRandomInt(0, std::numeric_limits<uint32_t>::max());
uint32_t tie_tag_lower =
cb.GetRandomInt(1, std::numeric_limits<uint32_t>::max());
return TieTag(static_cast<uint64_t>(tie_tag_upper) << 32 |
static_cast<uint64_t>(tie_tag_lower));
}
SctpImplementation DeterminePeerImplementation(
rtc::ArrayView<const uint8_t> cookie) {
if (cookie.size() > 8) {
absl::string_view magic(reinterpret_cast<const char*>(cookie.data()), 8);
if (magic == "dcSCTP00") {
return SctpImplementation::kDcsctp;
}
if (magic == "KAME-BSD") {
return SctpImplementation::kUsrSctp;
}
}
return SctpImplementation::kOther;
}
} // namespace
DcSctpSocket::DcSctpSocket(absl::string_view log_prefix,
DcSctpSocketCallbacks& callbacks,
std::unique_ptr<PacketObserver> packet_observer,
const DcSctpOptions& options)
: log_prefix_(std::string(log_prefix) + ": "),
packet_observer_(std::move(packet_observer)),
options_(options),
callbacks_(callbacks),
timer_manager_([this](webrtc::TaskQueueBase::DelayPrecision precision) {
return callbacks_.CreateTimeout(precision);
}),
t1_init_(timer_manager_.CreateTimer(
"t1-init",
absl::bind_front(&DcSctpSocket::OnInitTimerExpiry, this),
TimerOptions(options.t1_init_timeout.ToTimeDelta(),
TimerBackoffAlgorithm::kExponential,
options.max_init_retransmits))),
t1_cookie_(timer_manager_.CreateTimer(
"t1-cookie",
absl::bind_front(&DcSctpSocket::OnCookieTimerExpiry, this),
TimerOptions(options.t1_cookie_timeout.ToTimeDelta(),
TimerBackoffAlgorithm::kExponential,
options.max_init_retransmits))),
t2_shutdown_(timer_manager_.CreateTimer(
"t2-shutdown",
absl::bind_front(&DcSctpSocket::OnShutdownTimerExpiry, this),
TimerOptions(options.t2_shutdown_timeout.ToTimeDelta(),
TimerBackoffAlgorithm::kExponential,
options.max_retransmissions))),
packet_sender_(callbacks_,
absl::bind_front(&DcSctpSocket::OnSentPacket, this)),
send_queue_(log_prefix_,
&callbacks_,
options_.max_send_buffer_size,
options_.mtu,
options_.default_stream_priority,
options_.total_buffered_amount_low_threshold) {}
std::string DcSctpSocket::log_prefix() const {
return log_prefix_ + "[" + std::string(ToString(state_)) + "] ";
}
bool DcSctpSocket::IsConsistent() const {
if (tcb_ != nullptr && tcb_->reassembly_queue().HasMessages()) {
return false;
}
switch (state_) {
case State::kClosed:
return (tcb_ == nullptr && !t1_init_->is_running() &&
!t1_cookie_->is_running() && !t2_shutdown_->is_running());
case State::kCookieWait:
return (tcb_ == nullptr && t1_init_->is_running() &&
!t1_cookie_->is_running() && !t2_shutdown_->is_running());
case State::kCookieEchoed:
return (tcb_ != nullptr && !t1_init_->is_running() &&
t1_cookie_->is_running() && !t2_shutdown_->is_running() &&
tcb_->has_cookie_echo_chunk());
case State::kEstablished:
return (tcb_ != nullptr && !t1_init_->is_running() &&
!t1_cookie_->is_running() && !t2_shutdown_->is_running());
case State::kShutdownPending:
return (tcb_ != nullptr && !t1_init_->is_running() &&
!t1_cookie_->is_running() && !t2_shutdown_->is_running());
case State::kShutdownSent:
return (tcb_ != nullptr && !t1_init_->is_running() &&
!t1_cookie_->is_running() && t2_shutdown_->is_running());
case State::kShutdownReceived:
return (tcb_ != nullptr && !t1_init_->is_running() &&
!t1_cookie_->is_running() && !t2_shutdown_->is_running());
case State::kShutdownAckSent:
return (tcb_ != nullptr && !t1_init_->is_running() &&
!t1_cookie_->is_running() && t2_shutdown_->is_running());
}
}
constexpr absl::string_view DcSctpSocket::ToString(DcSctpSocket::State state) {
switch (state) {
case DcSctpSocket::State::kClosed:
return "CLOSED";
case DcSctpSocket::State::kCookieWait:
return "COOKIE_WAIT";
case DcSctpSocket::State::kCookieEchoed:
return "COOKIE_ECHOED";
case DcSctpSocket::State::kEstablished:
return "ESTABLISHED";
case DcSctpSocket::State::kShutdownPending:
return "SHUTDOWN_PENDING";
case DcSctpSocket::State::kShutdownSent:
return "SHUTDOWN_SENT";
case DcSctpSocket::State::kShutdownReceived:
return "SHUTDOWN_RECEIVED";
case DcSctpSocket::State::kShutdownAckSent:
return "SHUTDOWN_ACK_SENT";
}
}
void DcSctpSocket::SetState(State state, absl::string_view reason) {
if (state_ != state) {
RTC_DLOG(LS_VERBOSE) << log_prefix_ << "Socket state changed from "
<< ToString(state_) << " to " << ToString(state)
<< " due to " << reason;
state_ = state;
}
}
void DcSctpSocket::SendInit() {
Parameters::Builder params_builder;
AddCapabilityParameters(
options_, /*support_zero_checksum=*/
options_.zero_checksum_alternate_error_detection_method !=
ZeroChecksumAlternateErrorDetectionMethod::None(),
params_builder);
InitChunk init(/*initiate_tag=*/connect_params_.verification_tag,
/*a_rwnd=*/options_.max_receiver_window_buffer_size,
options_.announced_maximum_outgoing_streams,
options_.announced_maximum_incoming_streams,
connect_params_.initial_tsn, params_builder.Build());
SctpPacket::Builder b(VerificationTag(0), options_);
b.Add(init);
// https://www.ietf.org/archive/id/draft-tuexen-tsvwg-sctp-zero-checksum-01.html#section-4.2
// "When an end point sends a packet containing an INIT chunk, it MUST include
// a correct CRC32c checksum in the packet containing the INIT chunk."
packet_sender_.Send(b, /*write_checksum=*/true);
}
void DcSctpSocket::Connect() {
CallbackDeferrer::ScopedDeferrer deferrer(callbacks_);
if (state_ == State::kClosed) {
connect_params_.initial_tsn =
TSN(callbacks_.GetRandomInt(kMinInitialTsn, kMaxInitialTsn));
connect_params_.verification_tag = VerificationTag(
callbacks_.GetRandomInt(kMinVerificationTag, kMaxVerificationTag));
RTC_DLOG(LS_INFO)
<< log_prefix()
<< rtc::StringFormat(
"Connecting. my_verification_tag=%08x, my_initial_tsn=%u",
*connect_params_.verification_tag, *connect_params_.initial_tsn);
SendInit();
t1_init_->Start();
SetState(State::kCookieWait, "Connect called");
} else {
RTC_DLOG(LS_WARNING) << log_prefix()
<< "Called Connect on a socket that is not closed";
}
RTC_DCHECK(IsConsistent());
}
void DcSctpSocket::CreateTransmissionControlBlock(
const Capabilities& capabilities,
VerificationTag my_verification_tag,
TSN my_initial_tsn,
VerificationTag peer_verification_tag,
TSN peer_initial_tsn,
size_t a_rwnd,
TieTag tie_tag) {
metrics_.uses_message_interleaving = capabilities.message_interleaving;
metrics_.uses_zero_checksum = capabilities.zero_checksum;
metrics_.negotiated_maximum_incoming_streams =
capabilities.negotiated_maximum_incoming_streams;
metrics_.negotiated_maximum_outgoing_streams =
capabilities.negotiated_maximum_outgoing_streams;
tcb_ = std::make_unique<TransmissionControlBlock>(
timer_manager_, log_prefix_, options_, capabilities, callbacks_,
send_queue_, my_verification_tag, my_initial_tsn, peer_verification_tag,
peer_initial_tsn, a_rwnd, tie_tag, packet_sender_,
[this]() { return state_ == State::kEstablished; });
RTC_DLOG(LS_VERBOSE) << log_prefix() << "Created TCB: " << tcb_->ToString();
}
void DcSctpSocket::RestoreFromState(const DcSctpSocketHandoverState& state) {
CallbackDeferrer::ScopedDeferrer deferrer(callbacks_);
if (state_ != State::kClosed) {
callbacks_.OnError(ErrorKind::kUnsupportedOperation,
"Only closed socket can be restored from state");
} else {
if (state.socket_state ==
DcSctpSocketHandoverState::SocketState::kConnected) {
VerificationTag my_verification_tag =
VerificationTag(state.my_verification_tag);
connect_params_.verification_tag = my_verification_tag;
Capabilities capabilities;
capabilities.partial_reliability = state.capabilities.partial_reliability;
capabilities.message_interleaving =
state.capabilities.message_interleaving;
capabilities.reconfig = state.capabilities.reconfig;
capabilities.zero_checksum = state.capabilities.zero_checksum;
capabilities.negotiated_maximum_incoming_streams =
state.capabilities.negotiated_maximum_incoming_streams;
capabilities.negotiated_maximum_outgoing_streams =
state.capabilities.negotiated_maximum_outgoing_streams;
send_queue_.RestoreFromState(state);
CreateTransmissionControlBlock(
capabilities, my_verification_tag, TSN(state.my_initial_tsn),
VerificationTag(state.peer_verification_tag),
TSN(state.peer_initial_tsn), static_cast<size_t>(0),
TieTag(state.tie_tag));
tcb_->RestoreFromState(state);
SetState(State::kEstablished, "restored from handover state");
callbacks_.OnConnected();
}
}
RTC_DCHECK(IsConsistent());
}
void DcSctpSocket::Shutdown() {
CallbackDeferrer::ScopedDeferrer deferrer(callbacks_);
if (tcb_ != nullptr) {
// https://tools.ietf.org/html/rfc4960#section-9.2
// "Upon receipt of the SHUTDOWN primitive from its upper layer, the
// endpoint enters the SHUTDOWN-PENDING state and remains there until all
// outstanding data has been acknowledged by its peer."
// TODO(webrtc:12739): Remove this check, as it just hides the problem that
// the socket can transition from ShutdownSent to ShutdownPending, or
// ShutdownAckSent to ShutdownPending which is illegal.
if (state_ != State::kShutdownSent && state_ != State::kShutdownAckSent) {
SetState(State::kShutdownPending, "Shutdown called");
t1_init_->Stop();
t1_cookie_->Stop();
MaybeSendShutdownOrAck();
}
} else {
// Connection closed before even starting to connect, or during the initial
// connection phase. There is no outstanding data, so the socket can just
// be closed (stopping any connection timers, if any), as this is the
// client's intention, by calling Shutdown.
InternalClose(ErrorKind::kNoError, "");
}
RTC_DCHECK(IsConsistent());
}
void DcSctpSocket::Close() {
CallbackDeferrer::ScopedDeferrer deferrer(callbacks_);
if (state_ != State::kClosed) {
if (tcb_ != nullptr) {
SctpPacket::Builder b = tcb_->PacketBuilder();
b.Add(AbortChunk(/*filled_in_verification_tag=*/true,
Parameters::Builder()
.Add(UserInitiatedAbortCause("Close called"))
.Build()));
packet_sender_.Send(b);
}
InternalClose(ErrorKind::kNoError, "");
} else {
RTC_DLOG(LS_INFO) << log_prefix() << "Called Close on a closed socket";
}
RTC_DCHECK(IsConsistent());
}
void DcSctpSocket::CloseConnectionBecauseOfTooManyTransmissionErrors() {
packet_sender_.Send(tcb_->PacketBuilder().Add(AbortChunk(
true, Parameters::Builder()
.Add(UserInitiatedAbortCause("Too many retransmissions"))
.Build())));
InternalClose(ErrorKind::kTooManyRetries, "Too many retransmissions");
}
void DcSctpSocket::InternalClose(ErrorKind error, absl::string_view message) {
if (state_ != State::kClosed) {
t1_init_->Stop();
t1_cookie_->Stop();
t2_shutdown_->Stop();
tcb_ = nullptr;
if (error == ErrorKind::kNoError) {
callbacks_.OnClosed();
} else {
callbacks_.OnAborted(error, message);
}
SetState(State::kClosed, message);
}
// This method's purpose is to abort/close and make it consistent by ensuring
// that e.g. all timers really are stopped.
RTC_DCHECK(IsConsistent());
}
void DcSctpSocket::SetStreamPriority(StreamID stream_id,
StreamPriority priority) {
send_queue_.SetStreamPriority(stream_id, priority);
}
StreamPriority DcSctpSocket::GetStreamPriority(StreamID stream_id) const {
return send_queue_.GetStreamPriority(stream_id);
}
SendStatus DcSctpSocket::Send(DcSctpMessage message,
const SendOptions& send_options) {
CallbackDeferrer::ScopedDeferrer deferrer(callbacks_);
SendStatus send_status = InternalSend(message, send_options);
if (send_status != SendStatus::kSuccess)
return send_status;
Timestamp now = callbacks_.Now();
++metrics_.tx_messages_count;
send_queue_.Add(now, std::move(message), send_options);
if (tcb_ != nullptr)
tcb_->SendBufferedPackets(now);
RTC_DCHECK(IsConsistent());
return SendStatus::kSuccess;
}
std::vector<SendStatus> DcSctpSocket::SendMany(
rtc::ArrayView<DcSctpMessage> messages,
const SendOptions& send_options) {
CallbackDeferrer::ScopedDeferrer deferrer(callbacks_);
Timestamp now = callbacks_.Now();
std::vector<SendStatus> send_statuses;
send_statuses.reserve(messages.size());
for (DcSctpMessage& message : messages) {
SendStatus send_status = InternalSend(message, send_options);
send_statuses.push_back(send_status);
if (send_status != SendStatus::kSuccess)
continue;
++metrics_.tx_messages_count;
send_queue_.Add(now, std::move(message), send_options);
}
if (tcb_ != nullptr)
tcb_->SendBufferedPackets(now);
RTC_DCHECK(IsConsistent());
return send_statuses;
}
SendStatus DcSctpSocket::InternalSend(const DcSctpMessage& message,
const SendOptions& send_options) {
LifecycleId lifecycle_id = send_options.lifecycle_id;
if (message.payload().empty()) {
if (lifecycle_id.IsSet()) {
callbacks_.OnLifecycleEnd(lifecycle_id);
}
callbacks_.OnError(ErrorKind::kProtocolViolation,
"Unable to send empty message");
return SendStatus::kErrorMessageEmpty;
}
if (message.payload().size() > options_.max_message_size) {
if (lifecycle_id.IsSet()) {
callbacks_.OnLifecycleEnd(lifecycle_id);
}
callbacks_.OnError(ErrorKind::kProtocolViolation,
"Unable to send too large message");
return SendStatus::kErrorMessageTooLarge;
}
if (state_ == State::kShutdownPending || state_ == State::kShutdownSent ||
state_ == State::kShutdownReceived || state_ == State::kShutdownAckSent) {
// https://tools.ietf.org/html/rfc4960#section-9.2
// "An endpoint should reject any new data request from its upper layer
// if it is in the SHUTDOWN-PENDING, SHUTDOWN-SENT, SHUTDOWN-RECEIVED, or
// SHUTDOWN-ACK-SENT state."
if (lifecycle_id.IsSet()) {
callbacks_.OnLifecycleEnd(lifecycle_id);
}
callbacks_.OnError(ErrorKind::kWrongSequence,
"Unable to send message as the socket is shutting down");
return SendStatus::kErrorShuttingDown;
}
if (send_queue_.IsFull()) {
if (lifecycle_id.IsSet()) {
callbacks_.OnLifecycleEnd(lifecycle_id);
}
callbacks_.OnError(ErrorKind::kResourceExhaustion,
"Unable to send message as the send queue is full");
return SendStatus::kErrorResourceExhaustion;
}
return SendStatus::kSuccess;
}
ResetStreamsStatus DcSctpSocket::ResetStreams(
rtc::ArrayView<const StreamID> outgoing_streams) {
CallbackDeferrer::ScopedDeferrer deferrer(callbacks_);
if (tcb_ == nullptr) {
callbacks_.OnError(ErrorKind::kWrongSequence,
"Can't reset streams as the socket is not connected");
return ResetStreamsStatus::kNotConnected;
}
if (!tcb_->capabilities().reconfig) {
callbacks_.OnError(ErrorKind::kUnsupportedOperation,
"Can't reset streams as the peer doesn't support it");
return ResetStreamsStatus::kNotSupported;
}
tcb_->stream_reset_handler().ResetStreams(outgoing_streams);
MaybeSendResetStreamsRequest();
RTC_DCHECK(IsConsistent());
return ResetStreamsStatus::kPerformed;
}
SocketState DcSctpSocket::state() const {
switch (state_) {
case State::kClosed:
return SocketState::kClosed;
case State::kCookieWait:
case State::kCookieEchoed:
return SocketState::kConnecting;
case State::kEstablished:
return SocketState::kConnected;
case State::kShutdownPending:
case State::kShutdownSent:
case State::kShutdownReceived:
case State::kShutdownAckSent:
return SocketState::kShuttingDown;
}
}
void DcSctpSocket::SetMaxMessageSize(size_t max_message_size) {
options_.max_message_size = max_message_size;
}
size_t DcSctpSocket::buffered_amount(StreamID stream_id) const {
return send_queue_.buffered_amount(stream_id);
}
size_t DcSctpSocket::buffered_amount_low_threshold(StreamID stream_id) const {
return send_queue_.buffered_amount_low_threshold(stream_id);
}
void DcSctpSocket::SetBufferedAmountLowThreshold(StreamID stream_id,
size_t bytes) {
send_queue_.SetBufferedAmountLowThreshold(stream_id, bytes);
}
absl::optional<Metrics> DcSctpSocket::GetMetrics() const {
if (tcb_ == nullptr) {
return absl::nullopt;
}
Metrics metrics = metrics_;
metrics.cwnd_bytes = tcb_->cwnd();
metrics.srtt_ms = tcb_->current_srtt().ms();
size_t packet_payload_size =
options_.mtu - SctpPacket::kHeaderSize - DataChunk::kHeaderSize;
metrics.unack_data_count =
tcb_->retransmission_queue().unacked_items() +
(send_queue_.total_buffered_amount() + packet_payload_size - 1) /
packet_payload_size;
metrics.peer_rwnd_bytes = tcb_->retransmission_queue().rwnd();
metrics.negotiated_maximum_incoming_streams =
tcb_->capabilities().negotiated_maximum_incoming_streams;
metrics.negotiated_maximum_incoming_streams =
tcb_->capabilities().negotiated_maximum_incoming_streams;
metrics.rtx_packets_count = tcb_->retransmission_queue().rtx_packets_count();
metrics.rtx_bytes_count = tcb_->retransmission_queue().rtx_bytes_count();
return metrics;
}
void DcSctpSocket::MaybeSendShutdownOnPacketReceived(const SctpPacket& packet) {
if (state_ == State::kShutdownSent) {
bool has_data_chunk =
std::find_if(packet.descriptors().begin(), packet.descriptors().end(),
[](const SctpPacket::ChunkDescriptor& descriptor) {
return descriptor.type == DataChunk::kType;
}) != packet.descriptors().end();
if (has_data_chunk) {
// https://tools.ietf.org/html/rfc4960#section-9.2
// "While in the SHUTDOWN-SENT state, the SHUTDOWN sender MUST immediately
// respond to each received packet containing one or more DATA chunks with
// a SHUTDOWN chunk and restart the T2-shutdown timer.""
SendShutdown();
t2_shutdown_->set_duration(tcb_->current_rto());
t2_shutdown_->Start();
}
}
}
void DcSctpSocket::MaybeSendResetStreamsRequest() {
absl::optional<ReConfigChunk> reconfig =
tcb_->stream_reset_handler().MakeStreamResetRequest();
if (reconfig.has_value()) {
SctpPacket::Builder builder = tcb_->PacketBuilder();
builder.Add(*reconfig);
packet_sender_.Send(builder);
}
}
bool DcSctpSocket::ValidatePacket(const SctpPacket& packet) {
const CommonHeader& header = packet.common_header();
VerificationTag my_verification_tag =
tcb_ != nullptr ? tcb_->my_verification_tag() : VerificationTag(0);
if (header.verification_tag == VerificationTag(0)) {
if (packet.descriptors().size() == 1 &&
packet.descriptors()[0].type == InitChunk::kType) {
// https://tools.ietf.org/html/rfc4960#section-8.5.1
// "When an endpoint receives an SCTP packet with the Verification Tag
// set to 0, it should verify that the packet contains only an INIT chunk.
// Otherwise, the receiver MUST silently discard the packet.""
return true;
}
callbacks_.OnError(
ErrorKind::kParseFailed,
"Only a single INIT chunk can be present in packets sent on "
"verification_tag = 0");
return false;
}
if (packet.descriptors().size() == 1 &&
packet.descriptors()[0].type == AbortChunk::kType) {
// https://tools.ietf.org/html/rfc4960#section-8.5.1
// "The receiver of an ABORT MUST accept the packet if the Verification
// Tag field of the packet matches its own tag and the T bit is not set OR
// if it is set to its peer's tag and the T bit is set in the Chunk Flags.
// Otherwise, the receiver MUST silently discard the packet and take no
// further action."
bool t_bit = (packet.descriptors()[0].flags & 0x01) != 0;
if (t_bit && tcb_ == nullptr) {
// Can't verify the tag - assume it's okey.
return true;
}
if ((!t_bit && header.verification_tag == my_verification_tag) ||
(t_bit && header.verification_tag == tcb_->peer_verification_tag())) {
return true;
}
callbacks_.OnError(ErrorKind::kParseFailed,
"ABORT chunk verification tag was wrong");
return false;
}
if (packet.descriptors()[0].type == InitAckChunk::kType) {
if (header.verification_tag == connect_params_.verification_tag) {
return true;
}
callbacks_.OnError(
ErrorKind::kParseFailed,
rtc::StringFormat(
"Packet has invalid verification tag: %08x, expected %08x",
*header.verification_tag, *connect_params_.verification_tag));
return false;
}
if (packet.descriptors()[0].type == CookieEchoChunk::kType) {
// Handled in chunk handler (due to RFC 4960, section 5.2.4).
return true;
}
if (packet.descriptors().size() == 1 &&
packet.descriptors()[0].type == ShutdownCompleteChunk::kType) {
// https://tools.ietf.org/html/rfc4960#section-8.5.1
// "The receiver of a SHUTDOWN COMPLETE shall accept the packet if the
// Verification Tag field of the packet matches its own tag and the T bit is
// not set OR if it is set to its peer's tag and the T bit is set in the
// Chunk Flags. Otherwise, the receiver MUST silently discard the packet
// and take no further action."
bool t_bit = (packet.descriptors()[0].flags & 0x01) != 0;
if (t_bit && tcb_ == nullptr) {
// Can't verify the tag - assume it's okey.
return true;
}
if ((!t_bit && header.verification_tag == my_verification_tag) ||
(t_bit && header.verification_tag == tcb_->peer_verification_tag())) {
return true;
}
callbacks_.OnError(ErrorKind::kParseFailed,
"SHUTDOWN_COMPLETE chunk verification tag was wrong");
return false;
}
// https://tools.ietf.org/html/rfc4960#section-8.5
// "When receiving an SCTP packet, the endpoint MUST ensure that the value
// in the Verification Tag field of the received SCTP packet matches its own
// tag. If the received Verification Tag value does not match the receiver's
// own tag value, the receiver shall silently discard the packet and shall not
// process it any further..."
if (header.verification_tag == my_verification_tag) {
return true;
}
callbacks_.OnError(
ErrorKind::kParseFailed,
rtc::StringFormat(
"Packet has invalid verification tag: %08x, expected %08x",
*header.verification_tag, *my_verification_tag));
return false;
}
void DcSctpSocket::HandleTimeout(TimeoutID timeout_id) {
CallbackDeferrer::ScopedDeferrer deferrer(callbacks_);
timer_manager_.HandleTimeout(timeout_id);
if (tcb_ != nullptr && tcb_->HasTooManyTxErrors()) {
// Tearing down the TCB has to be done outside the handlers.
CloseConnectionBecauseOfTooManyTransmissionErrors();
}
RTC_DCHECK(IsConsistent());
}
void DcSctpSocket::ReceivePacket(rtc::ArrayView<const uint8_t> data) {
CallbackDeferrer::ScopedDeferrer deferrer(callbacks_);
++metrics_.rx_packets_count;
if (packet_observer_ != nullptr) {
packet_observer_->OnReceivedPacket(TimeMs(callbacks_.Now().ms()), data);
}
absl::optional<SctpPacket> packet = SctpPacket::Parse(data, options_);
if (!packet.has_value()) {
// https://tools.ietf.org/html/rfc4960#section-6.8
// "The default procedure for handling invalid SCTP packets is to
// silently discard them."
callbacks_.OnError(ErrorKind::kParseFailed,
"Failed to parse received SCTP packet");
RTC_DCHECK(IsConsistent());
return;
}
if (RTC_DLOG_IS_ON) {
for (const auto& descriptor : packet->descriptors()) {
RTC_DLOG(LS_VERBOSE) << log_prefix() << "Received "
<< DebugConvertChunkToString(descriptor.data);
}
}
if (!ValidatePacket(*packet)) {
RTC_DLOG(LS_VERBOSE) << log_prefix()
<< "Packet failed verification tag check - dropping";
RTC_DCHECK(IsConsistent());
return;
}
MaybeSendShutdownOnPacketReceived(*packet);
for (const auto& descriptor : packet->descriptors()) {
if (!Dispatch(packet->common_header(), descriptor)) {
break;
}
}
if (tcb_ != nullptr) {
tcb_->data_tracker().ObservePacketEnd();
tcb_->MaybeSendSack();
}
RTC_DCHECK(IsConsistent());
}
void DcSctpSocket::DebugPrintOutgoing(rtc::ArrayView<const uint8_t> payload) {
auto packet = SctpPacket::Parse(payload, options_);
RTC_DCHECK(packet.has_value());
for (const auto& desc : packet->descriptors()) {
RTC_DLOG(LS_VERBOSE) << log_prefix() << "Sent "
<< DebugConvertChunkToString(desc.data);
}
}
bool DcSctpSocket::Dispatch(const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
switch (descriptor.type) {
case DataChunk::kType:
HandleData(header, descriptor);
break;
case InitChunk::kType:
HandleInit(header, descriptor);
break;
case InitAckChunk::kType:
HandleInitAck(header, descriptor);
break;
case SackChunk::kType:
HandleSack(header, descriptor);
break;
case HeartbeatRequestChunk::kType:
HandleHeartbeatRequest(header, descriptor);
break;
case HeartbeatAckChunk::kType:
HandleHeartbeatAck(header, descriptor);
break;
case AbortChunk::kType:
HandleAbort(header, descriptor);
break;
case ErrorChunk::kType:
HandleError(header, descriptor);
break;
case CookieEchoChunk::kType:
HandleCookieEcho(header, descriptor);
break;
case CookieAckChunk::kType:
HandleCookieAck(header, descriptor);
break;
case ShutdownChunk::kType:
HandleShutdown(header, descriptor);
break;
case ShutdownAckChunk::kType:
HandleShutdownAck(header, descriptor);
break;
case ShutdownCompleteChunk::kType:
HandleShutdownComplete(header, descriptor);
break;
case ReConfigChunk::kType:
HandleReconfig(header, descriptor);
break;
case ForwardTsnChunk::kType:
HandleForwardTsn(header, descriptor);
break;
case IDataChunk::kType:
HandleIData(header, descriptor);
break;
case IForwardTsnChunk::kType:
HandleIForwardTsn(header, descriptor);
break;
default:
return HandleUnrecognizedChunk(descriptor);
}
return true;
}
bool DcSctpSocket::HandleUnrecognizedChunk(
const SctpPacket::ChunkDescriptor& descriptor) {
bool report_as_error = (descriptor.type & 0x40) != 0;
bool continue_processing = (descriptor.type & 0x80) != 0;
RTC_DLOG(LS_VERBOSE) << log_prefix() << "Received unknown chunk: "
<< static_cast<int>(descriptor.type);
if (report_as_error) {
rtc::StringBuilder sb;
sb << "Received unknown chunk of type: "
<< static_cast<int>(descriptor.type) << " with report-error bit set";
callbacks_.OnError(ErrorKind::kParseFailed, sb.str());
RTC_DLOG(LS_VERBOSE)
<< log_prefix()
<< "Unknown chunk, with type indicating it should be reported.";
// https://tools.ietf.org/html/rfc4960#section-3.2
// "... report in an ERROR chunk using the 'Unrecognized Chunk Type'
// cause."
if (tcb_ != nullptr) {
// Need TCB - this chunk must be sent with a correct verification tag.
packet_sender_.Send(tcb_->PacketBuilder().Add(
ErrorChunk(Parameters::Builder()
.Add(UnrecognizedChunkTypeCause(std::vector<uint8_t>(
descriptor.data.begin(), descriptor.data.end())))
.Build())));
}
}
if (!continue_processing) {
// https://tools.ietf.org/html/rfc4960#section-3.2
// "Stop processing this SCTP packet and discard it, do not process any
// further chunks within it."
RTC_DLOG(LS_VERBOSE) << log_prefix()
<< "Unknown chunk, with type indicating not to "
"process any further chunks";
}
return continue_processing;
}
TimeDelta DcSctpSocket::OnInitTimerExpiry() {
RTC_DLOG(LS_VERBOSE) << log_prefix() << "Timer " << t1_init_->name()
<< " has expired: " << t1_init_->expiration_count()
<< "/" << t1_init_->options().max_restarts.value_or(-1);
RTC_DCHECK(state_ == State::kCookieWait);
if (t1_init_->is_running()) {
SendInit();
} else {
InternalClose(ErrorKind::kTooManyRetries, "No INIT_ACK received");
}
RTC_DCHECK(IsConsistent());
return TimeDelta::Zero();
}
TimeDelta DcSctpSocket::OnCookieTimerExpiry() {
// https://tools.ietf.org/html/rfc4960#section-4
// "If the T1-cookie timer expires, the endpoint MUST retransmit COOKIE
// ECHO and restart the T1-cookie timer without changing state. This MUST
// be repeated up to 'Max.Init.Retransmits' times. After that, the endpoint
// MUST abort the initialization process and report the error to the SCTP
// user."
RTC_DLOG(LS_VERBOSE) << log_prefix() << "Timer " << t1_cookie_->name()
<< " has expired: " << t1_cookie_->expiration_count()
<< "/"
<< t1_cookie_->options().max_restarts.value_or(-1);
RTC_DCHECK(state_ == State::kCookieEchoed);
if (t1_cookie_->is_running()) {
tcb_->SendBufferedPackets(callbacks_.Now());
} else {
InternalClose(ErrorKind::kTooManyRetries, "No COOKIE_ACK received");
}
RTC_DCHECK(IsConsistent());
return TimeDelta::Zero();
}
TimeDelta DcSctpSocket::OnShutdownTimerExpiry() {
RTC_DLOG(LS_VERBOSE) << log_prefix() << "Timer " << t2_shutdown_->name()
<< " has expired: " << t2_shutdown_->expiration_count()
<< "/"
<< t2_shutdown_->options().max_restarts.value_or(-1);
if (!t2_shutdown_->is_running()) {
// https://tools.ietf.org/html/rfc4960#section-9.2
// "An endpoint should limit the number of retransmissions of the SHUTDOWN
// chunk to the protocol parameter 'Association.Max.Retrans'. If this
// threshold is exceeded, the endpoint should destroy the TCB..."
packet_sender_.Send(tcb_->PacketBuilder().Add(
AbortChunk(true, Parameters::Builder()
.Add(UserInitiatedAbortCause(
"Too many retransmissions of SHUTDOWN"))
.Build())));
InternalClose(ErrorKind::kTooManyRetries, "No SHUTDOWN_ACK received");
RTC_DCHECK(IsConsistent());
return TimeDelta::Zero();
}
// https://tools.ietf.org/html/rfc4960#section-9.2
// "If the timer expires, the endpoint must resend the SHUTDOWN with the
// updated last sequential TSN received from its peer."
SendShutdown();
RTC_DCHECK(IsConsistent());
return tcb_->current_rto();
}
void DcSctpSocket::OnSentPacket(rtc::ArrayView<const uint8_t> packet,
SendPacketStatus status) {
// The packet observer is invoked even if the packet was failed to be sent, to
// indicate an attempt was made.
if (packet_observer_ != nullptr) {
packet_observer_->OnSentPacket(TimeMs(callbacks_.Now().ms()), packet);
}
if (status == SendPacketStatus::kSuccess) {
if (RTC_DLOG_IS_ON) {
DebugPrintOutgoing(packet);
}
// The heartbeat interval timer is restarted for every sent packet, to
// fire when the outgoing channel is inactive.
if (tcb_ != nullptr) {
tcb_->heartbeat_handler().RestartTimer();
}
++metrics_.tx_packets_count;
}
}
bool DcSctpSocket::ValidateHasTCB() {
if (tcb_ != nullptr) {
return true;
}
callbacks_.OnError(
ErrorKind::kNotConnected,
"Received unexpected commands on socket that is not connected");
return false;
}
void DcSctpSocket::ReportFailedToParseChunk(int chunk_type) {
rtc::StringBuilder sb;
sb << "Failed to parse chunk of type: " << chunk_type;
callbacks_.OnError(ErrorKind::kParseFailed, sb.str());
}
void DcSctpSocket::HandleData(const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
absl::optional<DataChunk> chunk = DataChunk::Parse(descriptor.data);
if (ValidateParseSuccess(chunk) && ValidateHasTCB()) {
HandleDataCommon(*chunk);
}
}
void DcSctpSocket::HandleIData(const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
absl::optional<IDataChunk> chunk = IDataChunk::Parse(descriptor.data);
if (ValidateParseSuccess(chunk) && ValidateHasTCB()) {
HandleDataCommon(*chunk);
}
}
void DcSctpSocket::HandleDataCommon(AnyDataChunk& chunk) {
TSN tsn = chunk.tsn();
AnyDataChunk::ImmediateAckFlag immediate_ack = chunk.options().immediate_ack;
Data data = std::move(chunk).extract();
if (data.payload.empty()) {
// Empty DATA chunks are illegal.
packet_sender_.Send(tcb_->PacketBuilder().Add(
ErrorChunk(Parameters::Builder().Add(NoUserDataCause(tsn)).Build())));
callbacks_.OnError(ErrorKind::kProtocolViolation,
"Received DATA chunk with no user data");
return;
}
RTC_DLOG(LS_VERBOSE) << log_prefix() << "Handle DATA, queue_size="
<< tcb_->reassembly_queue().queued_bytes()
<< ", water_mark="
<< tcb_->reassembly_queue().watermark_bytes()
<< ", full=" << tcb_->reassembly_queue().is_full()
<< ", above="
<< tcb_->reassembly_queue().is_above_watermark();
if (tcb_->reassembly_queue().is_full()) {
// If the reassembly queue is full, there is nothing that can be done. The
// specification only allows dropping gap-ack-blocks, and that's not
// likely to help as the socket has been trying to fill gaps since the
// watermark was reached.
packet_sender_.Send(tcb_->PacketBuilder().Add(AbortChunk(
true, Parameters::Builder().Add(OutOfResourceErrorCause()).Build())));
InternalClose(ErrorKind::kResourceExhaustion,
"Reassembly Queue is exhausted");
return;
}
if (tcb_->reassembly_queue().is_above_watermark()) {
RTC_DLOG(LS_VERBOSE) << log_prefix() << "Is above high watermark";
// If the reassembly queue is above its high watermark, only accept data
// chunks that increase its cumulative ack tsn in an attempt to fill gaps
// to deliver messages.
if (!tcb_->data_tracker().will_increase_cum_ack_tsn(tsn)) {
RTC_DLOG(LS_VERBOSE) << log_prefix()
<< "Rejected data because of exceeding watermark";
tcb_->data_tracker().ForceImmediateSack();
return;
}
}
if (!tcb_->data_tracker().IsTSNValid(tsn)) {
RTC_DLOG(LS_VERBOSE) << log_prefix()
<< "Rejected data because of failing TSN validity";
return;
}
if (tcb_->data_tracker().Observe(tsn, immediate_ack)) {
tcb_->reassembly_queue().Add(tsn, std::move(data));
MaybeDeliverMessages();
}
}
void DcSctpSocket::HandleInit(const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
absl::optional<InitChunk> chunk = InitChunk::Parse(descriptor.data);
if (!ValidateParseSuccess(chunk)) {
return;
}
if (chunk->initiate_tag() == VerificationTag(0) ||
chunk->nbr_outbound_streams() == 0 || chunk->nbr_inbound_streams() == 0) {
// https://tools.ietf.org/html/rfc4960#section-3.3.2
// "If the value of the Initiate Tag in a received INIT chunk is found
// to be 0, the receiver MUST treat it as an error and close the
// association by transmitting an ABORT."
// "A receiver of an INIT with the OS value set to 0 SHOULD abort the
// association."
// "A receiver of an INIT with the MIS value of 0 SHOULD abort the
// association."
packet_sender_.Send(
SctpPacket::Builder(VerificationTag(0), options_)
.Add(AbortChunk(
/*filled_in_verification_tag=*/false,
Parameters::Builder()
.Add(ProtocolViolationCause("INIT malformed"))
.Build())));
InternalClose(ErrorKind::kProtocolViolation, "Received invalid INIT");
return;
}
if (state_ == State::kShutdownAckSent) {
// https://tools.ietf.org/html/rfc4960#section-9.2
// "If an endpoint is in the SHUTDOWN-ACK-SENT state and receives an
// INIT chunk (e.g., if the SHUTDOWN COMPLETE was lost) with source and
// destination transport addresses (either in the IP addresses or in the
// INIT chunk) that belong to this association, it should discard the INIT
// chunk and retransmit the SHUTDOWN ACK chunk."
RTC_DLOG(LS_VERBOSE) << log_prefix()
<< "Received Init indicating lost ShutdownComplete";
SendShutdownAck();
return;
}
TieTag tie_tag(0);
VerificationTag my_verification_tag;
TSN my_initial_tsn;
if (state_ == State::kClosed) {
RTC_DLOG(LS_VERBOSE) << log_prefix()
<< "Received Init in closed state (normal)";
my_verification_tag = VerificationTag(
callbacks_.GetRandomInt(kMinVerificationTag, kMaxVerificationTag));
my_initial_tsn =
TSN(callbacks_.GetRandomInt(kMinInitialTsn, kMaxInitialTsn));
} else if (state_ == State::kCookieWait || state_ == State::kCookieEchoed) {
// https://tools.ietf.org/html/rfc4960#section-5.2.1
// "This usually indicates an initialization collision, i.e., each
// endpoint is attempting, at about the same time, to establish an
// association with the other endpoint. Upon receipt of an INIT in the
// COOKIE-WAIT state, an endpoint MUST respond with an INIT ACK using the
// same parameters it sent in its original INIT chunk (including its
// Initiate Tag, unchanged). When responding, the endpoint MUST send the
// INIT ACK back to the same address that the original INIT (sent by this
// endpoint) was sent."
RTC_DLOG(LS_VERBOSE) << log_prefix()
<< "Received Init indicating simultaneous connections";
my_verification_tag = connect_params_.verification_tag;
my_initial_tsn = connect_params_.initial_tsn;
} else {
RTC_DCHECK(tcb_ != nullptr);
// https://tools.ietf.org/html/rfc4960#section-5.2.2
// "The outbound SCTP packet containing this INIT ACK MUST carry a
// Verification Tag value equal to the Initiate Tag found in the
// unexpected INIT. And the INIT ACK MUST contain a new Initiate Tag
// (randomly generated; see Section 5.3.1). Other parameters for the
// endpoint SHOULD be copied from the existing parameters of the
// association (e.g., number of outbound streams) into the INIT ACK and
// cookie."
RTC_DLOG(LS_VERBOSE) << log_prefix()
<< "Received Init indicating restarted connection";
// Create a new verification tag - different from the previous one.
for (int tries = 0; tries < 10; ++tries) {
my_verification_tag = VerificationTag(
callbacks_.GetRandomInt(kMinVerificationTag, kMaxVerificationTag));
if (my_verification_tag != tcb_->my_verification_tag()) {
break;
}
}
// Make the initial TSN make a large jump, so that there is no overlap
// with the old and new association.
my_initial_tsn = TSN(*tcb_->retransmission_queue().next_tsn() + 1000000);
tie_tag = tcb_->tie_tag();
}
RTC_DLOG(LS_VERBOSE)
<< log_prefix()
<< rtc::StringFormat(
"Proceeding with connection. my_verification_tag=%08x, "
"my_initial_tsn=%u, peer_verification_tag=%08x, "
"peer_initial_tsn=%u",
*my_verification_tag, *my_initial_tsn, *chunk->initiate_tag(),
*chunk->initial_tsn());
Capabilities capabilities =
ComputeCapabilities(options_, chunk->nbr_outbound_streams(),
chunk->nbr_inbound_streams(), chunk->parameters());
SctpPacket::Builder b(chunk->initiate_tag(), options_);
Parameters::Builder params_builder =
Parameters::Builder().Add(StateCookieParameter(
StateCookie(chunk->initiate_tag(), my_verification_tag,
chunk->initial_tsn(), my_initial_tsn, chunk->a_rwnd(),
tie_tag, capabilities)
.Serialize()));
AddCapabilityParameters(options_, capabilities.zero_checksum, params_builder);
InitAckChunk init_ack(/*initiate_tag=*/my_verification_tag,
options_.max_receiver_window_buffer_size,
options_.announced_maximum_outgoing_streams,
options_.announced_maximum_incoming_streams,
my_initial_tsn, params_builder.Build());
b.Add(init_ack);
// If the peer has signaled that it supports zero checksum, INIT-ACK can then
// have its checksum as zero.
packet_sender_.Send(b, /*write_checksum=*/!capabilities.zero_checksum);
}
void DcSctpSocket::HandleInitAck(
const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
absl::optional<InitAckChunk> chunk = InitAckChunk::Parse(descriptor.data);
if (!ValidateParseSuccess(chunk)) {
return;
}
if (state_ != State::kCookieWait) {
// https://tools.ietf.org/html/rfc4960#section-5.2.3
// "If an INIT ACK is received by an endpoint in any state other than
// the COOKIE-WAIT state, the endpoint should discard the INIT ACK chunk."
RTC_DLOG(LS_VERBOSE) << log_prefix()
<< "Received INIT_ACK in unexpected state";
return;
}
auto cookie = chunk->parameters().get<StateCookieParameter>();
if (!cookie.has_value()) {
packet_sender_.Send(
SctpPacket::Builder(connect_params_.verification_tag, options_)
.Add(AbortChunk(
/*filled_in_verification_tag=*/false,
Parameters::Builder()
.Add(ProtocolViolationCause("INIT-ACK malformed"))
.Build())));
InternalClose(ErrorKind::kProtocolViolation,
"InitAck chunk doesn't contain a cookie");
return;
}
Capabilities capabilities =
ComputeCapabilities(options_, chunk->nbr_outbound_streams(),
chunk->nbr_inbound_streams(), chunk->parameters());
t1_init_->Stop();
metrics_.peer_implementation = DeterminePeerImplementation(cookie->data());
// If the connection is re-established (peer restarted, but re-used old
// connection), make sure that all message identifiers are reset and any
// partly sent message is re-sent in full. The same is true when the socket
// is closed and later re-opened, which never happens in WebRTC, but is a
// valid operation on the SCTP level. Note that in case of handover, the
// send queue is already re-configured, and shouldn't be reset.
send_queue_.Reset();
CreateTransmissionControlBlock(capabilities, connect_params_.verification_tag,
connect_params_.initial_tsn,
chunk->initiate_tag(), chunk->initial_tsn(),
chunk->a_rwnd(), MakeTieTag(callbacks_));
SetState(State::kCookieEchoed, "INIT_ACK received");
// The connection isn't fully established just yet.
tcb_->SetCookieEchoChunk(CookieEchoChunk(cookie->data()));
tcb_->SendBufferedPackets(callbacks_.Now());
t1_cookie_->Start();
}
void DcSctpSocket::HandleCookieEcho(
const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
absl::optional<CookieEchoChunk> chunk =
CookieEchoChunk::Parse(descriptor.data);
if (!ValidateParseSuccess(chunk)) {
return;
}
absl::optional<StateCookie> cookie =
StateCookie::Deserialize(chunk->cookie());
if (!cookie.has_value()) {
callbacks_.OnError(ErrorKind::kParseFailed, "Failed to parse state cookie");
return;
}
if (tcb_ != nullptr) {
if (!HandleCookieEchoWithTCB(header, *cookie)) {
return;
}
} else {
if (header.verification_tag != cookie->my_tag()) {
callbacks_.OnError(
ErrorKind::kParseFailed,
rtc::StringFormat(
"Received CookieEcho with invalid verification tag: %08x, "
"expected %08x",
*header.verification_tag, *cookie->my_tag()));
return;
}
}
// The init timer can be running on simultaneous connections.
t1_init_->Stop();
t1_cookie_->Stop();
if (state_ != State::kEstablished) {
if (tcb_ != nullptr) {
tcb_->ClearCookieEchoChunk();
}
SetState(State::kEstablished, "COOKIE_ECHO received");
callbacks_.OnConnected();
}
if (tcb_ == nullptr) {
// If the connection is re-established (peer restarted, but re-used old
// connection), make sure that all message identifiers are reset and any
// partly sent message is re-sent in full. The same is true when the socket
// is closed and later re-opened, which never happens in WebRTC, but is a
// valid operation on the SCTP level. Note that in case of handover, the
// send queue is already re-configured, and shouldn't be reset.
send_queue_.Reset();
CreateTransmissionControlBlock(cookie->capabilities(), cookie->my_tag(),
cookie->my_initial_tsn(), cookie->peer_tag(),
cookie->peer_initial_tsn(), cookie->a_rwnd(),
MakeTieTag(callbacks_));
}
SctpPacket::Builder b = tcb_->PacketBuilder();
b.Add(CookieAckChunk());
// https://tools.ietf.org/html/rfc4960#section-5.1
// "A COOKIE ACK chunk may be bundled with any pending DATA chunks (and/or
// SACK chunks), but the COOKIE ACK chunk MUST be the first chunk in the
// packet."
tcb_->SendBufferedPackets(b, callbacks_.Now());
}
bool DcSctpSocket::HandleCookieEchoWithTCB(const CommonHeader& header,
const StateCookie& cookie) {
RTC_DLOG(LS_VERBOSE) << log_prefix()
<< "Handling CookieEchoChunk with TCB. local_tag="
<< *tcb_->my_verification_tag()
<< ", peer_tag=" << *header.verification_tag
<< ", tcb_tag=" << *tcb_->peer_verification_tag()
<< ", peer_tag=" << *cookie.peer_tag()
<< ", local_tie_tag=" << *tcb_->tie_tag()
<< ", peer_tie_tag=" << *cookie.tie_tag();
// https://tools.ietf.org/html/rfc4960#section-5.2.4
// "Handle a COOKIE ECHO when a TCB Exists"
if (header.verification_tag != tcb_->my_verification_tag() &&
tcb_->peer_verification_tag() != cookie.peer_tag() &&
cookie.tie_tag() == tcb_->tie_tag()) {
// "A) In this case, the peer may have restarted."
if (state_ == State::kShutdownAckSent) {
// "If the endpoint is in the SHUTDOWN-ACK-SENT state and recognizes
// that the peer has restarted ... it MUST NOT set up a new association
// but instead resend the SHUTDOWN ACK and send an ERROR chunk with a
// "Cookie Received While Shutting Down" error cause to its peer."
SctpPacket::Builder b(cookie.peer_tag(), options_);
b.Add(ShutdownAckChunk());
b.Add(ErrorChunk(Parameters::Builder()
.Add(CookieReceivedWhileShuttingDownCause())
.Build()));
packet_sender_.Send(b);
callbacks_.OnError(ErrorKind::kWrongSequence,
"Received COOKIE-ECHO while shutting down");
return false;
}
RTC_DLOG(LS_VERBOSE) << log_prefix()
<< "Received COOKIE-ECHO indicating a restarted peer";
tcb_ = nullptr;
callbacks_.OnConnectionRestarted();
} else if (header.verification_tag == tcb_->my_verification_tag() &&
tcb_->peer_verification_tag() != cookie.peer_tag()) {
// TODO(boivie): Handle the peer_tag == 0?
// "B) In this case, both sides may be attempting to start an
// association at about the same time, but the peer endpoint started its
// INIT after responding to the local endpoint's INIT."
RTC_DLOG(LS_VERBOSE)
<< log_prefix()
<< "Received COOKIE-ECHO indicating simultaneous connections";
tcb_ = nullptr;
} else if (header.verification_tag != tcb_->my_verification_tag() &&
tcb_->peer_verification_tag() == cookie.peer_tag() &&
cookie.tie_tag() == TieTag(0)) {
// "C) In this case, the local endpoint's cookie has arrived late.
// Before it arrived, the local endpoint sent an INIT and received an
// INIT ACK and finally sent a COOKIE ECHO with the peer's same tag but
// a new tag of its own. The cookie should be silently discarded. The
// endpoint SHOULD NOT change states and should leave any timers
// running."
RTC_DLOG(LS_VERBOSE)
<< log_prefix()
<< "Received COOKIE-ECHO indicating a late COOKIE-ECHO. Discarding";
return false;
} else if (header.verification_tag == tcb_->my_verification_tag() &&
tcb_->peer_verification_tag() == cookie.peer_tag()) {
// "D) When both local and remote tags match, the endpoint should enter
// the ESTABLISHED state, if it is in the COOKIE-ECHOED state. It
// should stop any cookie timer that may be running and send a COOKIE
// ACK."
RTC_DLOG(LS_VERBOSE)
<< log_prefix()
<< "Received duplicate COOKIE-ECHO, probably because of peer not "
"receiving COOKIE-ACK and retransmitting COOKIE-ECHO. Continuing.";
}
return true;
}
void DcSctpSocket::HandleCookieAck(
const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
absl::optional<CookieAckChunk> chunk = CookieAckChunk::Parse(descriptor.data);
if (!ValidateParseSuccess(chunk)) {
return;
}
if (state_ != State::kCookieEchoed) {
// https://tools.ietf.org/html/rfc4960#section-5.2.5
// "At any state other than COOKIE-ECHOED, an endpoint should silently
// discard a received COOKIE ACK chunk."
RTC_DLOG(LS_VERBOSE) << log_prefix()
<< "Received COOKIE_ACK not in COOKIE_ECHOED state";
return;
}
// RFC 4960, Errata ID: 4400
t1_cookie_->Stop();
tcb_->ClearCookieEchoChunk();
SetState(State::kEstablished, "COOKIE_ACK received");
tcb_->SendBufferedPackets(callbacks_.Now());
callbacks_.OnConnected();
}
void DcSctpSocket::MaybeDeliverMessages() {
for (auto& message : tcb_->reassembly_queue().FlushMessages()) {
++metrics_.rx_messages_count;
callbacks_.OnMessageReceived(std::move(message));
}
}
void DcSctpSocket::HandleSack(const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
absl::optional<SackChunk> chunk = SackChunk::Parse(descriptor.data);
if (ValidateParseSuccess(chunk) && ValidateHasTCB()) {
Timestamp now = callbacks_.Now();
SackChunk sack = ChunkValidators::Clean(*std::move(chunk));
if (tcb_->retransmission_queue().HandleSack(now, sack)) {
MaybeSendShutdownOrAck();
// Receiving an ACK may make the socket go into fast recovery mode.
// https://datatracker.ietf.org/doc/html/rfc4960#section-7.2.4
// "Determine how many of the earliest (i.e., lowest TSN) DATA chunks
// marked for retransmission will fit into a single packet, subject to
// constraint of the path MTU of the destination transport address to
// which the packet is being sent. Call this value K. Retransmit those K
// DATA chunks in a single packet. When a Fast Retransmit is being
// performed, the sender SHOULD ignore the value of cwnd and SHOULD NOT
// delay retransmission for this single packet."
tcb_->MaybeSendFastRetransmit();
// Receiving an ACK will decrease outstanding bytes (maybe now below
// cwnd?) or indicate packet loss that may result in sending FORWARD-TSN.
tcb_->SendBufferedPackets(now);
} else {
RTC_DLOG(LS_VERBOSE) << log_prefix()
<< "Dropping out-of-order SACK with TSN "
<< *sack.cumulative_tsn_ack();
}
}
}
void DcSctpSocket::HandleHeartbeatRequest(
const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
absl::optional<HeartbeatRequestChunk> chunk =
HeartbeatRequestChunk::Parse(descriptor.data);
if (ValidateParseSuccess(chunk) && ValidateHasTCB()) {
tcb_->heartbeat_handler().HandleHeartbeatRequest(*std::move(chunk));
}
}
void DcSctpSocket::HandleHeartbeatAck(
const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
absl::optional<HeartbeatAckChunk> chunk =
HeartbeatAckChunk::Parse(descriptor.data);
if (ValidateParseSuccess(chunk) && ValidateHasTCB()) {
tcb_->heartbeat_handler().HandleHeartbeatAck(*std::move(chunk));
}
}
void DcSctpSocket::HandleAbort(const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
absl::optional<AbortChunk> chunk = AbortChunk::Parse(descriptor.data);
if (ValidateParseSuccess(chunk)) {
std::string error_string = ErrorCausesToString(chunk->error_causes());
if (tcb_ == nullptr) {
// https://tools.ietf.org/html/rfc4960#section-3.3.7
// "If an endpoint receives an ABORT with a format error or no TCB is
// found, it MUST silently discard it."
RTC_DLOG(LS_VERBOSE) << log_prefix() << "Received ABORT (" << error_string
<< ") on a connection with no TCB. Ignoring";
return;
}
RTC_DLOG(LS_WARNING) << log_prefix() << "Received ABORT (" << error_string
<< ") - closing connection.";
InternalClose(ErrorKind::kPeerReported, error_string);
}
}
void DcSctpSocket::HandleError(const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
absl::optional<ErrorChunk> chunk = ErrorChunk::Parse(descriptor.data);
if (ValidateParseSuccess(chunk)) {
std::string error_string = ErrorCausesToString(chunk->error_causes());
if (tcb_ == nullptr) {
RTC_DLOG(LS_VERBOSE) << log_prefix() << "Received ERROR (" << error_string
<< ") on a connection with no TCB. Ignoring";
return;
}
RTC_DLOG(LS_WARNING) << log_prefix() << "Received ERROR: " << error_string;
callbacks_.OnError(ErrorKind::kPeerReported,
"Peer reported error: " + error_string);
}
}
void DcSctpSocket::HandleReconfig(
const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
Timestamp now = callbacks_.Now();
absl::optional<ReConfigChunk> chunk = ReConfigChunk::Parse(descriptor.data);
if (ValidateParseSuccess(chunk) && ValidateHasTCB()) {
tcb_->stream_reset_handler().HandleReConfig(*std::move(chunk));
// Handling this response may result in outgoing stream resets finishing
// (either successfully or with failure). If there still are pending streams
// that were waiting for this request to finish, continue resetting them.
MaybeSendResetStreamsRequest();
// If a response was processed, pending to-be-reset streams may now have
// become unpaused. Try to send more DATA chunks.
tcb_->SendBufferedPackets(now);
// If it leaves "deferred reset processing", there may be chunks to deliver
// that were queued while waiting for the stream to reset.
MaybeDeliverMessages();
}
}
void DcSctpSocket::HandleShutdown(
const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
if (!ValidateParseSuccess(ShutdownChunk::Parse(descriptor.data))) {
return;
}
if (state_ == State::kClosed) {
return;
} else if (state_ == State::kCookieWait || state_ == State::kCookieEchoed) {
// https://tools.ietf.org/html/rfc4960#section-9.2
// "If a SHUTDOWN is received in the COOKIE-WAIT or COOKIE ECHOED state,
// the SHUTDOWN chunk SHOULD be silently discarded."
} else if (state_ == State::kShutdownSent) {
// https://tools.ietf.org/html/rfc4960#section-9.2
// "If an endpoint is in the SHUTDOWN-SENT state and receives a
// SHUTDOWN chunk from its peer, the endpoint shall respond immediately
// with a SHUTDOWN ACK to its peer, and move into the SHUTDOWN-ACK-SENT
// state restarting its T2-shutdown timer."
SendShutdownAck();
SetState(State::kShutdownAckSent, "SHUTDOWN received");
} else if (state_ == State::kShutdownAckSent) {
// TODO(webrtc:12739): This condition should be removed and handled by the
// next (state_ != State::kShutdownReceived).
return;
} else if (state_ != State::kShutdownReceived) {
RTC_DLOG(LS_VERBOSE) << log_prefix()
<< "Received SHUTDOWN - shutting down the socket";
// https://tools.ietf.org/html/rfc4960#section-9.2
// "Upon reception of the SHUTDOWN, the peer endpoint shall enter the
// SHUTDOWN-RECEIVED state, stop accepting new data from its SCTP user,
// and verify, by checking the Cumulative TSN Ack field of the chunk, that
// all its outstanding DATA chunks have been received by the SHUTDOWN
// sender."
SetState(State::kShutdownReceived, "SHUTDOWN received");
MaybeSendShutdownOrAck();
}
}
void DcSctpSocket::HandleShutdownAck(
const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
if (!ValidateParseSuccess(ShutdownAckChunk::Parse(descriptor.data))) {
return;
}
if (state_ == State::kShutdownSent || state_ == State::kShutdownAckSent) {
// https://tools.ietf.org/html/rfc4960#section-9.2
// "Upon the receipt of the SHUTDOWN ACK, the SHUTDOWN sender shall stop
// the T2-shutdown timer, send a SHUTDOWN COMPLETE chunk to its peer, and
// remove all record of the association."
// "If an endpoint is in the SHUTDOWN-ACK-SENT state and receives a
// SHUTDOWN ACK, it shall stop the T2-shutdown timer, send a SHUTDOWN
// COMPLETE chunk to its peer, and remove all record of the association."
SctpPacket::Builder b = tcb_->PacketBuilder();
b.Add(ShutdownCompleteChunk(/*tag_reflected=*/false));
packet_sender_.Send(b);
InternalClose(ErrorKind::kNoError, "");
} else {
// https://tools.ietf.org/html/rfc4960#section-8.5.1
// "If the receiver is in COOKIE-ECHOED or COOKIE-WAIT state
// the procedures in Section 8.4 SHOULD be followed; in other words, it
// should be treated as an Out Of The Blue packet."
// https://tools.ietf.org/html/rfc4960#section-8.4
// "If the packet contains a SHUTDOWN ACK chunk, the receiver
// should respond to the sender of the OOTB packet with a SHUTDOWN
// COMPLETE. When sending the SHUTDOWN COMPLETE, the receiver of the OOTB
// packet must fill in the Verification Tag field of the outbound packet
// with the Verification Tag received in the SHUTDOWN ACK and set the T
// bit in the Chunk Flags to indicate that the Verification Tag is
// reflected."
SctpPacket::Builder b(header.verification_tag, options_);
b.Add(ShutdownCompleteChunk(/*tag_reflected=*/true));
packet_sender_.Send(b);
}
}
void DcSctpSocket::HandleShutdownComplete(
const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
if (!ValidateParseSuccess(ShutdownCompleteChunk::Parse(descriptor.data))) {
return;
}
if (state_ == State::kShutdownAckSent) {
// https://tools.ietf.org/html/rfc4960#section-9.2
// "Upon reception of the SHUTDOWN COMPLETE chunk, the endpoint will
// verify that it is in the SHUTDOWN-ACK-SENT state; if it is not, the
// chunk should be discarded. If the endpoint is in the SHUTDOWN-ACK-SENT
// state, the endpoint should stop the T2-shutdown timer and remove all
// knowledge of the association (and thus the association enters the
// CLOSED state)."
InternalClose(ErrorKind::kNoError, "");
}
}
void DcSctpSocket::HandleForwardTsn(
const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
absl::optional<ForwardTsnChunk> chunk =
ForwardTsnChunk::Parse(descriptor.data);
if (ValidateParseSuccess(chunk) && ValidateHasTCB()) {
HandleForwardTsnCommon(*chunk);
}
}
void DcSctpSocket::HandleIForwardTsn(
const CommonHeader& header,
const SctpPacket::ChunkDescriptor& descriptor) {
absl::optional<IForwardTsnChunk> chunk =
IForwardTsnChunk::Parse(descriptor.data);
if (ValidateParseSuccess(chunk) && ValidateHasTCB()) {
HandleForwardTsnCommon(*chunk);
}
}
void DcSctpSocket::HandleForwardTsnCommon(const AnyForwardTsnChunk& chunk) {
if (!tcb_->capabilities().partial_reliability) {
SctpPacket::Builder b = tcb_->PacketBuilder();
b.Add(AbortChunk(/*filled_in_verification_tag=*/true,
Parameters::Builder()
.Add(ProtocolViolationCause(
"I-FORWARD-TSN received, but not indicated "
"during connection establishment"))
.Build()));
packet_sender_.Send(b);
callbacks_.OnError(ErrorKind::kProtocolViolation,
"Received a FORWARD_TSN without announced peer support");
return;
}
if (tcb_->data_tracker().HandleForwardTsn(chunk.new_cumulative_tsn())) {
tcb_->reassembly_queue().HandleForwardTsn(chunk.new_cumulative_tsn(),
chunk.skipped_streams());
}
// A forward TSN - for ordered streams - may allow messages to be delivered.
MaybeDeliverMessages();
}
void DcSctpSocket::MaybeSendShutdownOrAck() {
if (tcb_->retransmission_queue().unacked_bytes() != 0) {
return;
}
if (state_ == State::kShutdownPending) {
// https://tools.ietf.org/html/rfc4960#section-9.2
// "Once all its outstanding data has been acknowledged, the endpoint
// shall send a SHUTDOWN chunk to its peer including in the Cumulative TSN
// Ack field the last sequential TSN it has received from the peer. It
// shall then start the T2-shutdown timer and enter the SHUTDOWN-SENT
// state.""
SendShutdown();
t2_shutdown_->set_duration(tcb_->current_rto());
t2_shutdown_->Start();
SetState(State::kShutdownSent, "No more outstanding data");
} else if (state_ == State::kShutdownReceived) {
// https://tools.ietf.org/html/rfc4960#section-9.2
// "If the receiver of the SHUTDOWN has no more outstanding DATA
// chunks, the SHUTDOWN receiver MUST send a SHUTDOWN ACK and start a
// T2-shutdown timer of its own, entering the SHUTDOWN-ACK-SENT state. If
// the timer expires, the endpoint must resend the SHUTDOWN ACK."
SendShutdownAck();
SetState(State::kShutdownAckSent, "No more outstanding data");
}
}
void DcSctpSocket::SendShutdown() {
SctpPacket::Builder b = tcb_->PacketBuilder();
b.Add(ShutdownChunk(tcb_->data_tracker().last_cumulative_acked_tsn()));
packet_sender_.Send(b);
}
void DcSctpSocket::SendShutdownAck() {
packet_sender_.Send(tcb_->PacketBuilder().Add(ShutdownAckChunk()));
t2_shutdown_->set_duration(tcb_->current_rto());
t2_shutdown_->Start();
}
HandoverReadinessStatus DcSctpSocket::GetHandoverReadiness() const {
HandoverReadinessStatus status;
if (state_ != State::kClosed && state_ != State::kEstablished) {
status.Add(HandoverUnreadinessReason::kWrongConnectionState);
}
status.Add(send_queue_.GetHandoverReadiness());
if (tcb_) {
status.Add(tcb_->GetHandoverReadiness());
}
return status;
}
absl::optional<DcSctpSocketHandoverState>
DcSctpSocket::GetHandoverStateAndClose() {
CallbackDeferrer::ScopedDeferrer deferrer(callbacks_);
if (!GetHandoverReadiness().IsReady()) {
return absl::nullopt;
}
DcSctpSocketHandoverState state;
if (state_ == State::kClosed) {
state.socket_state = DcSctpSocketHandoverState::SocketState::kClosed;
} else if (state_ == State::kEstablished) {
state.socket_state = DcSctpSocketHandoverState::SocketState::kConnected;
tcb_->AddHandoverState(state);
send_queue_.AddHandoverState(state);
InternalClose(ErrorKind::kNoError, "handover");
}
return std::move(state);
}
} // namespace dcsctp
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