diff options
Diffstat (limited to 'net/dcsctp/socket/dcsctp_socket.cc')
| -rw-r--r-- | net/dcsctp/socket/dcsctp_socket.cc | 1550 |
1 files changed, 1550 insertions, 0 deletions
diff --git a/net/dcsctp/socket/dcsctp_socket.cc b/net/dcsctp/socket/dcsctp_socket.cc new file mode 100644 index 0000000000..71bc98c70d --- /dev/null +++ b/net/dcsctp/socket/dcsctp_socket.cc @@ -0,0 +1,1550 @@ +/* + * 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/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/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/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 { + +// 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 GetCapabilities(const DcSctpOptions& options, + 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; + } + return capabilities; +} + +void AddCapabilityParameters(const DcSctpOptions& options, + 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); + } + 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)); +} + +} // 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]() { return callbacks_.CreateTimeout(); }), + t1_init_(timer_manager_.CreateTimer( + "t1-init", + [this]() { return OnInitTimerExpiry(); }, + TimerOptions(options.t1_init_timeout, + TimerBackoffAlgorithm::kExponential, + options.max_init_retransmits))), + t1_cookie_(timer_manager_.CreateTimer( + "t1-cookie", + [this]() { return OnCookieTimerExpiry(); }, + TimerOptions(options.t1_cookie_timeout, + TimerBackoffAlgorithm::kExponential, + options.max_init_retransmits))), + t2_shutdown_(timer_manager_.CreateTimer( + "t2-shutdown", + [this]() { return OnShutdownTimerExpiry(); }, + TimerOptions(options.t2_shutdown_timeout, + TimerBackoffAlgorithm::kExponential, + options.max_retransmissions))), + send_queue_( + log_prefix_, + options_.max_send_buffer_size, + [this](StreamID stream_id) { + callbacks_.OnBufferedAmountLow(stream_id); + }, + options_.total_buffered_amount_low_threshold, + [this]() { callbacks_.OnTotalBufferedAmountLow(); }) {} + +std::string DcSctpSocket::log_prefix() const { + return log_prefix_ + "[" + std::string(ToString(state_)) + "] "; +} + +bool DcSctpSocket::IsConsistent() const { + 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_, 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); + SendPacket(b); +} + +void DcSctpSocket::MakeConnectionParameters() { + VerificationTag new_verification_tag( + callbacks_.GetRandomInt(kMinVerificationTag, kMaxVerificationTag)); + TSN initial_tsn(callbacks_.GetRandomInt(kMinInitialTsn, kMaxInitialTsn)); + connect_params_.initial_tsn = initial_tsn; + connect_params_.verification_tag = new_verification_tag; +} + +void DcSctpSocket::Connect() { + if (state_ == State::kClosed) { + MakeConnectionParameters(); + 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()); + callbacks_.TriggerDeferred(); +} + +void DcSctpSocket::Shutdown() { + 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()); + callbacks_.TriggerDeferred(); +} + +void DcSctpSocket::Close() { + 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())); + SendPacket(b); + } + InternalClose(ErrorKind::kNoError, ""); + } else { + RTC_DLOG(LS_INFO) << log_prefix() << "Called Close on a closed socket"; + } + RTC_DCHECK(IsConsistent()); + callbacks_.TriggerDeferred(); +} + +void DcSctpSocket::CloseConnectionBecauseOfTooManyTransmissionErrors() { + SendPacket(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()); +} + +SendStatus DcSctpSocket::Send(DcSctpMessage message, + const SendOptions& send_options) { + if (message.payload().empty()) { + callbacks_.OnError(ErrorKind::kProtocolViolation, + "Unable to send empty message"); + return SendStatus::kErrorMessageEmpty; + } + if (message.payload().size() > options_.max_message_size) { + 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." + callbacks_.OnError(ErrorKind::kWrongSequence, + "Unable to send message as the socket is shutting down"); + return SendStatus::kErrorShuttingDown; + } + if (send_queue_.IsFull()) { + callbacks_.OnError(ErrorKind::kResourceExhaustion, + "Unable to send message as the send queue is full"); + return SendStatus::kErrorResourceExhaustion; + } + + TimeMs now = callbacks_.TimeMillis(); + send_queue_.Add(now, std::move(message), send_options); + if (tcb_ != nullptr) { + tcb_->SendBufferedPackets(now); + } + + RTC_DCHECK(IsConsistent()); + callbacks_.TriggerDeferred(); + return SendStatus::kSuccess; +} + +ResetStreamsStatus DcSctpSocket::ResetStreams( + rtc::ArrayView<const StreamID> outgoing_streams) { + 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); + absl::optional<ReConfigChunk> reconfig = + tcb_->stream_reset_handler().MakeStreamResetRequest(); + if (reconfig.has_value()) { + SctpPacket::Builder builder = tcb_->PacketBuilder(); + builder.Add(*reconfig); + SendPacket(builder); + } + + RTC_DCHECK(IsConsistent()); + callbacks_.TriggerDeferred(); + return ResetStreamsStatus::kPerformed; +} + +SocketState DcSctpSocket::state() const { + switch (state_) { + case State::kClosed: + return SocketState::kClosed; + case State::kCookieWait: + ABSL_FALLTHROUGH_INTENDED; + case State::kCookieEchoed: + return SocketState::kConnecting; + case State::kEstablished: + return SocketState::kConnected; + case State::kShutdownPending: + ABSL_FALLTHROUGH_INTENDED; + case State::kShutdownSent: + ABSL_FALLTHROUGH_INTENDED; + case State::kShutdownReceived: + ABSL_FALLTHROUGH_INTENDED; + 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); +} + +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(); + } + } +} + +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) { + 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()); + callbacks_.TriggerDeferred(); +} + +void DcSctpSocket::ReceivePacket(rtc::ArrayView<const uint8_t> data) { + if (packet_observer_ != nullptr) { + packet_observer_->OnReceivedPacket(callbacks_.TimeMillis(), data); + } + + absl::optional<SctpPacket> packet = + SctpPacket::Parse(data, options_.disable_checksum_verification); + 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()); + callbacks_.TriggerDeferred(); + 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()); + callbacks_.TriggerDeferred(); + 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()); + callbacks_.TriggerDeferred(); +} + +void DcSctpSocket::DebugPrintOutgoing(rtc::ArrayView<const uint8_t> payload) { + auto packet = SctpPacket::Parse(payload); + 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: + HandleForwardTsn(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. + SendPacket(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; +} + +absl::optional<DurationMs> DcSctpSocket::OnInitTimerExpiry() { + RTC_DLOG(LS_VERBOSE) << log_prefix() << "Timer " << t1_init_->name() + << " has expired: " << t1_init_->expiration_count() + << "/" << t1_init_->options().max_restarts; + RTC_DCHECK(state_ == State::kCookieWait); + + if (t1_init_->is_running()) { + SendInit(); + } else { + InternalClose(ErrorKind::kTooManyRetries, "No INIT_ACK received"); + } + RTC_DCHECK(IsConsistent()); + return absl::nullopt; +} + +absl::optional<DurationMs> 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; + + RTC_DCHECK(state_ == State::kCookieEchoed); + + if (t1_cookie_->is_running()) { + tcb_->SendBufferedPackets(callbacks_.TimeMillis()); + } else { + InternalClose(ErrorKind::kTooManyRetries, "No COOKIE_ACK received"); + } + + RTC_DCHECK(IsConsistent()); + return absl::nullopt; +} + +absl::optional<DurationMs> DcSctpSocket::OnShutdownTimerExpiry() { + RTC_DLOG(LS_VERBOSE) << log_prefix() << "Timer " << t2_shutdown_->name() + << " has expired: " << t2_shutdown_->expiration_count() + << "/" << t2_shutdown_->options().max_restarts; + + 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..." + + SendPacket(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 absl::nullopt; + } + + // 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::SendPacket(SctpPacket::Builder& builder) { + if (builder.empty()) { + return; + } + + std::vector<uint8_t> payload = builder.Build(); + + if (RTC_DLOG_IS_ON) { + DebugPrintOutgoing(payload); + } + + // 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(); + } + + if (packet_observer_ != nullptr) { + packet_observer_->OnSentPacket(callbacks_.TimeMillis(), payload); + } + callbacks_.SendPacket(payload); +} + +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. + SendPacket(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. + SendPacket(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; + } + + tcb_->data_tracker().Observe(tsn, immediate_ack); + tcb_->reassembly_queue().MaybeResetStreamsDeferred( + tcb_->data_tracker().last_cumulative_acked_tsn()); + tcb_->reassembly_queue().Add(tsn, std::move(data)); + DeliverReassembledMessages(); +} + +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." + + SendPacket(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); + if (state_ == State::kClosed) { + RTC_DLOG(LS_VERBOSE) << log_prefix() + << "Received Init in closed state (normal)"; + + MakeConnectionParameters(); + } 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"; + } 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) { + connect_params_.verification_tag = VerificationTag( + callbacks_.GetRandomInt(kMinVerificationTag, kMaxVerificationTag)); + if (connect_params_.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. + connect_params_.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", + *connect_params_.verification_tag, *connect_params_.initial_tsn, + *chunk->initiate_tag(), *chunk->initial_tsn()); + + Capabilities capabilities = GetCapabilities(options_, chunk->parameters()); + + SctpPacket::Builder b(chunk->initiate_tag(), options_); + Parameters::Builder params_builder = + Parameters::Builder().Add(StateCookieParameter( + StateCookie(chunk->initiate_tag(), chunk->initial_tsn(), + chunk->a_rwnd(), tie_tag, capabilities) + .Serialize())); + AddCapabilityParameters(options_, params_builder); + + InitAckChunk init_ack(/*initiate_tag=*/connect_params_.verification_tag, + options_.max_receiver_window_buffer_size, + options_.announced_maximum_outgoing_streams, + options_.announced_maximum_incoming_streams, + connect_params_.initial_tsn, params_builder.Build()); + b.Add(init_ack); + SendPacket(b); +} + +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()) { + SendPacket(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 = GetCapabilities(options_, chunk->parameters()); + t1_init_->Stop(); + + tcb_ = std::make_unique<TransmissionControlBlock>( + timer_manager_, log_prefix_, options_, capabilities, callbacks_, + send_queue_, connect_params_.verification_tag, + connect_params_.initial_tsn, chunk->initiate_tag(), chunk->initial_tsn(), + chunk->a_rwnd(), MakeTieTag(callbacks_), + [this]() { return state_ == State::kEstablished; }, + [this](SctpPacket::Builder& builder) { return SendPacket(builder); }); + RTC_DLOG(LS_VERBOSE) << log_prefix() + << "Created peer TCB: " << tcb_->ToString(); + + SetState(State::kCookieEchoed, "INIT_ACK received"); + + // The connection isn't fully established just yet. + tcb_->SetCookieEchoChunk(CookieEchoChunk(cookie->data())); + tcb_->SendBufferedPackets(callbacks_.TimeMillis()); + 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 != connect_params_.verification_tag) { + callbacks_.OnError( + ErrorKind::kParseFailed, + rtc::StringFormat( + "Received CookieEcho with invalid verification tag: %08x, " + "expected %08x", + *header.verification_tag, *connect_params_.verification_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) { + tcb_ = std::make_unique<TransmissionControlBlock>( + timer_manager_, log_prefix_, options_, cookie->capabilities(), + callbacks_, send_queue_, connect_params_.verification_tag, + connect_params_.initial_tsn, cookie->initiate_tag(), + cookie->initial_tsn(), cookie->a_rwnd(), MakeTieTag(callbacks_), + [this]() { return state_ == State::kEstablished; }, + [this](SctpPacket::Builder& builder) { return SendPacket(builder); }); + RTC_DLOG(LS_VERBOSE) << log_prefix() + << "Created peer TCB: " << tcb_->ToString(); + } + + 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_.TimeMillis()); +} + +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() + << ", cookie_tag=" << *cookie.initiate_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.initiate_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.initiate_tag(), options_); + b.Add(ShutdownAckChunk()); + b.Add(ErrorChunk(Parameters::Builder() + .Add(CookieReceivedWhileShuttingDownCause()) + .Build())); + SendPacket(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"; + + // If a message was partly sent, and the peer restarted, resend it in + // full by resetting the send queue. + send_queue_.Reset(); + tcb_ = nullptr; + callbacks_.OnConnectionRestarted(); + } else if (header.verification_tag == tcb_->my_verification_tag() && + tcb_->peer_verification_tag() != cookie.initiate_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.initiate_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.initiate_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_.TimeMillis()); + callbacks_.OnConnected(); +} + +void DcSctpSocket::DeliverReassembledMessages() { + if (tcb_->reassembly_queue().HasMessages()) { + for (auto& message : tcb_->reassembly_queue().FlushMessages()) { + 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()) { + TimeMs now = callbacks_.TimeMillis(); + SackChunk sack = ChunkValidators::Clean(*std::move(chunk)); + + if (tcb_->retransmission_queue().HandleSack(now, sack)) { + MaybeSendShutdownOrAck(); + // 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) { + absl::optional<ReConfigChunk> chunk = ReConfigChunk::Parse(descriptor.data); + if (ValidateParseSuccess(chunk) && ValidateHasTCB()) { + tcb_->stream_reset_handler().HandleReConfig(*std::move(chunk)); + } +} + +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)); + SendPacket(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)); + SendPacket(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())); + SendPacket(b); + + callbacks_.OnError(ErrorKind::kProtocolViolation, + "Received a FORWARD_TSN without announced peer support"); + return; + } + tcb_->data_tracker().HandleForwardTsn(chunk.new_cumulative_tsn()); + tcb_->reassembly_queue().Handle(chunk); + // A forward TSN - for ordered streams - may allow messages to be + // delivered. + DeliverReassembledMessages(); + + // Processing a FORWARD_TSN might result in sending a SACK. + tcb_->MaybeSendSack(); +} + +void DcSctpSocket::MaybeSendShutdownOrAck() { + if (tcb_->retransmission_queue().outstanding_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())); + SendPacket(b); +} + +void DcSctpSocket::SendShutdownAck() { + SendPacket(tcb_->PacketBuilder().Add(ShutdownAckChunk())); + t2_shutdown_->set_duration(tcb_->current_rto()); + t2_shutdown_->Start(); +} + +} // namespace dcsctp |