| /* |
| * 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/tx/retransmission_queue.h" |
| |
| #include <algorithm> |
| #include <cstdint> |
| #include <functional> |
| #include <iterator> |
| #include <map> |
| #include <set> |
| #include <string> |
| #include <utility> |
| #include <vector> |
| |
| #include "absl/algorithm/container.h" |
| #include "absl/strings/string_view.h" |
| #include "absl/types/optional.h" |
| #include "api/array_view.h" |
| #include "net/dcsctp/common/math.h" |
| #include "net/dcsctp/common/sequence_numbers.h" |
| #include "net/dcsctp/common/str_join.h" |
| #include "net/dcsctp/packet/chunk/data_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/idata_chunk.h" |
| #include "net/dcsctp/packet/chunk/iforward_tsn_chunk.h" |
| #include "net/dcsctp/packet/chunk/sack_chunk.h" |
| #include "net/dcsctp/packet/data.h" |
| #include "net/dcsctp/public/dcsctp_options.h" |
| #include "net/dcsctp/public/types.h" |
| #include "net/dcsctp/timer/timer.h" |
| #include "net/dcsctp/tx/outstanding_data.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" |
| |
| namespace dcsctp { |
| namespace { |
| |
| // Allow sending only slightly less than an MTU, to account for headers. |
| constexpr float kMinBytesRequiredToSendFactor = 0.9; |
| } // namespace |
| |
| RetransmissionQueue::RetransmissionQueue( |
| absl::string_view log_prefix, |
| TSN my_initial_tsn, |
| size_t a_rwnd, |
| SendQueue& send_queue, |
| std::function<void(DurationMs rtt)> on_new_rtt, |
| std::function<void()> on_clear_retransmission_counter, |
| Timer& t3_rtx, |
| const DcSctpOptions& options, |
| bool supports_partial_reliability, |
| bool use_message_interleaving, |
| const DcSctpSocketHandoverState* handover_state) |
| : options_(options), |
| min_bytes_required_to_send_(options.mtu * kMinBytesRequiredToSendFactor), |
| partial_reliability_(supports_partial_reliability), |
| log_prefix_(std::string(log_prefix) + "tx: "), |
| data_chunk_header_size_(use_message_interleaving |
| ? IDataChunk::kHeaderSize |
| : DataChunk::kHeaderSize), |
| on_new_rtt_(std::move(on_new_rtt)), |
| on_clear_retransmission_counter_( |
| std::move(on_clear_retransmission_counter)), |
| t3_rtx_(t3_rtx), |
| cwnd_(handover_state ? handover_state->tx.cwnd |
| : options_.cwnd_mtus_initial * options_.mtu), |
| rwnd_(handover_state ? handover_state->tx.rwnd : a_rwnd), |
| // https://tools.ietf.org/html/rfc4960#section-7.2.1 |
| // "The initial value of ssthresh MAY be arbitrarily high (for |
| // example, implementations MAY use the size of the receiver advertised |
| // window)."" |
| ssthresh_(handover_state ? handover_state->tx.ssthresh : rwnd_), |
| partial_bytes_acked_( |
| handover_state ? handover_state->tx.partial_bytes_acked : 0), |
| send_queue_(send_queue), |
| outstanding_data_( |
| data_chunk_header_size_, |
| tsn_unwrapper_.Unwrap(handover_state |
| ? TSN(handover_state->tx.next_tsn) |
| : my_initial_tsn), |
| tsn_unwrapper_.Unwrap(handover_state |
| ? TSN(handover_state->tx.next_tsn - 1) |
| : TSN(*my_initial_tsn - 1)), |
| [this](IsUnordered unordered, StreamID stream_id, MID message_id) { |
| return send_queue_.Discard(unordered, stream_id, message_id); |
| }) {} |
| |
| bool RetransmissionQueue::IsConsistent() const { |
| return true; |
| } |
| |
| // Returns how large a chunk will be, serialized, carrying the data |
| size_t RetransmissionQueue::GetSerializedChunkSize(const Data& data) const { |
| return RoundUpTo4(data_chunk_header_size_ + data.size()); |
| } |
| |
| void RetransmissionQueue::MaybeExitFastRecovery( |
| UnwrappedTSN cumulative_tsn_ack) { |
| // https://tools.ietf.org/html/rfc4960#section-7.2.4 |
| // "When a SACK acknowledges all TSNs up to and including this [fast |
| // recovery] exit point, Fast Recovery is exited." |
| if (fast_recovery_exit_tsn_.has_value() && |
| cumulative_tsn_ack >= *fast_recovery_exit_tsn_) { |
| RTC_DLOG(LS_VERBOSE) << log_prefix_ |
| << "exit_point=" << *fast_recovery_exit_tsn_->Wrap() |
| << " reached - exiting fast recovery"; |
| fast_recovery_exit_tsn_ = absl::nullopt; |
| } |
| } |
| |
| void RetransmissionQueue::HandleIncreasedCumulativeTsnAck( |
| size_t outstanding_bytes, |
| size_t total_bytes_acked) { |
| // Allow some margin for classifying as fully utilized, due to e.g. that too |
| // small packets (less than kMinimumFragmentedPayload) are not sent + |
| // overhead. |
| bool is_fully_utilized = outstanding_bytes + options_.mtu >= cwnd_; |
| size_t old_cwnd = cwnd_; |
| if (phase() == CongestionAlgorithmPhase::kSlowStart) { |
| if (is_fully_utilized && !is_in_fast_recovery()) { |
| // https://tools.ietf.org/html/rfc4960#section-7.2.1 |
| // "Only when these three conditions are met can the cwnd be |
| // increased; otherwise, the cwnd MUST not be increased. If these |
| // conditions are met, then cwnd MUST be increased by, at most, the |
| // lesser of 1) the total size of the previously outstanding DATA |
| // chunk(s) acknowledged, and 2) the destination's path MTU." |
| cwnd_ += std::min(total_bytes_acked, options_.mtu); |
| RTC_DLOG(LS_VERBOSE) << log_prefix_ << "SS increase cwnd=" << cwnd_ |
| << " (" << old_cwnd << ")"; |
| } |
| } else if (phase() == CongestionAlgorithmPhase::kCongestionAvoidance) { |
| // https://tools.ietf.org/html/rfc4960#section-7.2.2 |
| // "Whenever cwnd is greater than ssthresh, upon each SACK arrival |
| // that advances the Cumulative TSN Ack Point, increase |
| // partial_bytes_acked by the total number of bytes of all new chunks |
| // acknowledged in that SACK including chunks acknowledged by the new |
| // Cumulative TSN Ack and by Gap Ack Blocks." |
| size_t old_pba = partial_bytes_acked_; |
| partial_bytes_acked_ += total_bytes_acked; |
| |
| if (partial_bytes_acked_ >= cwnd_ && is_fully_utilized) { |
| // https://tools.ietf.org/html/rfc4960#section-7.2.2 |
| // "When partial_bytes_acked is equal to or greater than cwnd and |
| // before the arrival of the SACK the sender had cwnd or more bytes of |
| // data outstanding (i.e., before arrival of the SACK, flightsize was |
| // greater than or equal to cwnd), increase cwnd by MTU, and reset |
| // partial_bytes_acked to (partial_bytes_acked - cwnd)." |
| |
| // Errata: https://datatracker.ietf.org/doc/html/rfc8540#section-3.12 |
| partial_bytes_acked_ -= cwnd_; |
| cwnd_ += options_.mtu; |
| RTC_DLOG(LS_VERBOSE) << log_prefix_ << "CA increase cwnd=" << cwnd_ |
| << " (" << old_cwnd << ") ssthresh=" << ssthresh_ |
| << ", pba=" << partial_bytes_acked_ << " (" |
| << old_pba << ")"; |
| } else { |
| RTC_DLOG(LS_VERBOSE) << log_prefix_ << "CA unchanged cwnd=" << cwnd_ |
| << " (" << old_cwnd << ") ssthresh=" << ssthresh_ |
| << ", pba=" << partial_bytes_acked_ << " (" |
| << old_pba << ")"; |
| } |
| } |
| } |
| |
| void RetransmissionQueue::HandlePacketLoss(UnwrappedTSN highest_tsn_acked) { |
| if (!is_in_fast_recovery()) { |
| // https://tools.ietf.org/html/rfc4960#section-7.2.4 |
| // "If not in Fast Recovery, adjust the ssthresh and cwnd of the |
| // destination address(es) to which the missing DATA chunks were last |
| // sent, according to the formula described in Section 7.2.3." |
| size_t old_cwnd = cwnd_; |
| size_t old_pba = partial_bytes_acked_; |
| ssthresh_ = std::max(cwnd_ / 2, options_.cwnd_mtus_min * options_.mtu); |
| cwnd_ = ssthresh_; |
| partial_bytes_acked_ = 0; |
| |
| RTC_DLOG(LS_VERBOSE) << log_prefix_ |
| << "packet loss detected (not fast recovery). cwnd=" |
| << cwnd_ << " (" << old_cwnd |
| << "), ssthresh=" << ssthresh_ |
| << ", pba=" << partial_bytes_acked_ << " (" << old_pba |
| << ")"; |
| |
| // https://tools.ietf.org/html/rfc4960#section-7.2.4 |
| // "If not in Fast Recovery, enter Fast Recovery and mark the highest |
| // outstanding TSN as the Fast Recovery exit point." |
| fast_recovery_exit_tsn_ = outstanding_data_.highest_outstanding_tsn(); |
| RTC_DLOG(LS_VERBOSE) << log_prefix_ |
| << "fast recovery initiated with exit_point=" |
| << *fast_recovery_exit_tsn_->Wrap(); |
| } else { |
| // https://tools.ietf.org/html/rfc4960#section-7.2.4 |
| // "While in Fast Recovery, the ssthresh and cwnd SHOULD NOT change for |
| // any destinations due to a subsequent Fast Recovery event (i.e., one |
| // SHOULD NOT reduce the cwnd further due to a subsequent Fast Retransmit)." |
| RTC_DLOG(LS_VERBOSE) << log_prefix_ |
| << "packet loss detected (fast recovery). No changes."; |
| } |
| } |
| |
| void RetransmissionQueue::UpdateReceiverWindow(uint32_t a_rwnd) { |
| rwnd_ = outstanding_data_.outstanding_bytes() >= a_rwnd |
| ? 0 |
| : a_rwnd - outstanding_data_.outstanding_bytes(); |
| } |
| |
| void RetransmissionQueue::StartT3RtxTimerIfOutstandingData() { |
| // Note: Can't use `outstanding_bytes()` as that one doesn't count chunks to |
| // be retransmitted. |
| if (outstanding_data_.empty()) { |
| // https://tools.ietf.org/html/rfc4960#section-6.3.2 |
| // "Whenever all outstanding data sent to an address have been |
| // acknowledged, turn off the T3-rtx timer of that address. |
| // Note: Already stopped in `StopT3RtxTimerOnIncreasedCumulativeTsnAck`." |
| } else { |
| // https://tools.ietf.org/html/rfc4960#section-6.3.2 |
| // "Whenever a SACK is received that acknowledges the DATA chunk |
| // with the earliest outstanding TSN for that address, restart the T3-rtx |
| // timer for that address with its current RTO (if there is still |
| // outstanding data on that address)." |
| // "Whenever a SACK is received missing a TSN that was previously |
| // acknowledged via a Gap Ack Block, start the T3-rtx for the destination |
| // address to which the DATA chunk was originally transmitted if it is not |
| // already running." |
| if (!t3_rtx_.is_running()) { |
| t3_rtx_.Start(); |
| } |
| } |
| } |
| |
| bool RetransmissionQueue::IsSackValid(const SackChunk& sack) const { |
| // https://tools.ietf.org/html/rfc4960#section-6.2.1 |
| // "If Cumulative TSN Ack is less than the Cumulative TSN Ack Point, |
| // then drop the SACK. Since Cumulative TSN Ack is monotonically increasing, |
| // a SACK whose Cumulative TSN Ack is less than the Cumulative TSN Ack Point |
| // indicates an out-of- order SACK." |
| // |
| // Note: Important not to drop SACKs with identical TSN to that previously |
| // received, as the gap ack blocks or dup tsn fields may have changed. |
| UnwrappedTSN cumulative_tsn_ack = |
| tsn_unwrapper_.PeekUnwrap(sack.cumulative_tsn_ack()); |
| if (cumulative_tsn_ack < outstanding_data_.last_cumulative_tsn_ack()) { |
| // https://tools.ietf.org/html/rfc4960#section-6.2.1 |
| // "If Cumulative TSN Ack is less than the Cumulative TSN Ack Point, |
| // then drop the SACK. Since Cumulative TSN Ack is monotonically |
| // increasing, a SACK whose Cumulative TSN Ack is less than the Cumulative |
| // TSN Ack Point indicates an out-of- order SACK." |
| return false; |
| } else if (cumulative_tsn_ack > outstanding_data_.highest_outstanding_tsn()) { |
| return false; |
| } |
| return true; |
| } |
| |
| bool RetransmissionQueue::HandleSack(TimeMs now, const SackChunk& sack) { |
| if (!IsSackValid(sack)) { |
| return false; |
| } |
| |
| UnwrappedTSN old_last_cumulative_tsn_ack = |
| outstanding_data_.last_cumulative_tsn_ack(); |
| size_t old_outstanding_bytes = outstanding_data_.outstanding_bytes(); |
| size_t old_rwnd = rwnd_; |
| UnwrappedTSN cumulative_tsn_ack = |
| tsn_unwrapper_.Unwrap(sack.cumulative_tsn_ack()); |
| |
| if (sack.gap_ack_blocks().empty()) { |
| UpdateRTT(now, cumulative_tsn_ack); |
| } |
| |
| OutstandingData::AckInfo ack_info = outstanding_data_.HandleSack( |
| cumulative_tsn_ack, sack.gap_ack_blocks(), is_in_fast_retransmit_); |
| |
| // Update of outstanding_data_ is now done. Congestion control remains. |
| UpdateReceiverWindow(sack.a_rwnd()); |
| |
| RTC_DLOG(LS_VERBOSE) << log_prefix_ << "Received SACK, cum_tsn_ack=" |
| << *cumulative_tsn_ack.Wrap() << " (" |
| << *old_last_cumulative_tsn_ack.Wrap() |
| << "), outstanding_bytes=" |
| << outstanding_data_.outstanding_bytes() << " (" |
| << old_outstanding_bytes << "), rwnd=" << rwnd_ << " (" |
| << old_rwnd << ")"; |
| |
| MaybeExitFastRecovery(cumulative_tsn_ack); |
| |
| if (cumulative_tsn_ack > old_last_cumulative_tsn_ack) { |
| // https://tools.ietf.org/html/rfc4960#section-6.3.2 |
| // "Whenever a SACK is received that acknowledges the DATA chunk |
| // with the earliest outstanding TSN for that address, restart the T3-rtx |
| // timer for that address with its current RTO (if there is still |
| // outstanding data on that address)." |
| // Note: It may be started again in a bit further down. |
| t3_rtx_.Stop(); |
| |
| HandleIncreasedCumulativeTsnAck(old_outstanding_bytes, |
| ack_info.bytes_acked); |
| } |
| |
| if (ack_info.has_packet_loss) { |
| is_in_fast_retransmit_ = true; |
| HandlePacketLoss(ack_info.highest_tsn_acked); |
| } |
| |
| // https://tools.ietf.org/html/rfc4960#section-8.2 |
| // "When an outstanding TSN is acknowledged [...] the endpoint shall clear |
| // the error counter ..." |
| if (ack_info.bytes_acked > 0) { |
| on_clear_retransmission_counter_(); |
| } |
| |
| StartT3RtxTimerIfOutstandingData(); |
| RTC_DCHECK(IsConsistent()); |
| return true; |
| } |
| |
| void RetransmissionQueue::UpdateRTT(TimeMs now, |
| UnwrappedTSN cumulative_tsn_ack) { |
| // RTT updating is flawed in SCTP, as explained in e.g. Pedersen J, Griwodz C, |
| // Halvorsen P (2006) Considerations of SCTP retransmission delays for thin |
| // streams. |
| // Due to delayed acknowledgement, the SACK may be sent much later which |
| // increases the calculated RTT. |
| // TODO(boivie): Consider occasionally sending DATA chunks with I-bit set and |
| // use only those packets for measurement. |
| |
| absl::optional<DurationMs> rtt = |
| outstanding_data_.MeasureRTT(now, cumulative_tsn_ack); |
| |
| if (rtt.has_value()) { |
| on_new_rtt_(*rtt); |
| } |
| } |
| |
| void RetransmissionQueue::HandleT3RtxTimerExpiry() { |
| size_t old_cwnd = cwnd_; |
| size_t old_outstanding_bytes = outstanding_bytes(); |
| // https://tools.ietf.org/html/rfc4960#section-6.3.3 |
| // "For the destination address for which the timer expires, adjust |
| // its ssthresh with rules defined in Section 7.2.3 and set the cwnd <- MTU." |
| ssthresh_ = std::max(cwnd_ / 2, 4 * options_.mtu); |
| cwnd_ = 1 * options_.mtu; |
| // Errata: https://datatracker.ietf.org/doc/html/rfc8540#section-3.11 |
| partial_bytes_acked_ = 0; |
| |
| // https://tools.ietf.org/html/rfc4960#section-6.3.3 |
| // "For the destination address for which the timer expires, set RTO |
| // <- RTO * 2 ("back off the timer"). The maximum value discussed in rule C7 |
| // above (RTO.max) may be used to provide an upper bound to this doubling |
| // operation." |
| |
| // Already done by the Timer implementation. |
| |
| // https://tools.ietf.org/html/rfc4960#section-6.3.3 |
| // "Determine how many of the earliest (i.e., lowest TSN) outstanding |
| // DATA chunks for the address for which the T3-rtx has expired will fit into |
| // a single packet" |
| |
| // https://tools.ietf.org/html/rfc4960#section-6.3.3 |
| // "Note: Any DATA chunks that were sent to the address for which the |
| // T3-rtx timer expired but did not fit in one MTU (rule E3 above) should be |
| // marked for retransmission and sent as soon as cwnd allows (normally, when a |
| // SACK arrives)." |
| outstanding_data_.NackAll(); |
| |
| // https://tools.ietf.org/html/rfc4960#section-6.3.3 |
| // "Start the retransmission timer T3-rtx on the destination address |
| // to which the retransmission is sent, if rule R1 above indicates to do so." |
| |
| // Already done by the Timer implementation. |
| |
| RTC_DLOG(LS_INFO) << log_prefix_ << "t3-rtx expired. new cwnd=" << cwnd_ |
| << " (" << old_cwnd << "), ssthresh=" << ssthresh_ |
| << ", outstanding_bytes " << outstanding_bytes() << " (" |
| << old_outstanding_bytes << ")"; |
| RTC_DCHECK(IsConsistent()); |
| } |
| |
| std::vector<std::pair<TSN, Data>> RetransmissionQueue::GetChunksToSend( |
| TimeMs now, |
| size_t bytes_remaining_in_packet) { |
| // Chunks are always padded to even divisible by four. |
| RTC_DCHECK(IsDivisibleBy4(bytes_remaining_in_packet)); |
| |
| std::vector<std::pair<TSN, Data>> to_be_sent; |
| size_t old_outstanding_bytes = outstanding_bytes(); |
| size_t old_rwnd = rwnd_; |
| if (is_in_fast_retransmit_) { |
| // https://tools.ietf.org/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 ... 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." |
| is_in_fast_retransmit_ = false; |
| to_be_sent = |
| outstanding_data_.GetChunksToBeRetransmitted(bytes_remaining_in_packet); |
| size_t to_be_sent_bytes = absl::c_accumulate( |
| to_be_sent, 0, [&](size_t r, const std::pair<TSN, Data>& d) { |
| return r + GetSerializedChunkSize(d.second); |
| }); |
| RTC_DLOG(LS_VERBOSE) << log_prefix_ << "fast-retransmit: sending " |
| << to_be_sent.size() << " chunks, " << to_be_sent_bytes |
| << " bytes"; |
| } else { |
| // Normal sending. Calculate the bandwidth budget (how many bytes that is |
| // allowed to be sent), and fill that up first with chunks that are |
| // scheduled to be retransmitted. If there is still budget, send new chunks |
| // (which will have their TSN assigned here.) |
| size_t max_bytes = |
| RoundDownTo4(std::min(max_bytes_to_send(), bytes_remaining_in_packet)); |
| |
| to_be_sent = outstanding_data_.GetChunksToBeRetransmitted(max_bytes); |
| max_bytes -= absl::c_accumulate( |
| to_be_sent, 0, [&](size_t r, const std::pair<TSN, Data>& d) { |
| return r + GetSerializedChunkSize(d.second); |
| }); |
| |
| while (max_bytes > data_chunk_header_size_) { |
| RTC_DCHECK(IsDivisibleBy4(max_bytes)); |
| absl::optional<SendQueue::DataToSend> chunk_opt = |
| send_queue_.Produce(now, max_bytes - data_chunk_header_size_); |
| if (!chunk_opt.has_value()) { |
| break; |
| } |
| |
| size_t chunk_size = GetSerializedChunkSize(chunk_opt->data); |
| max_bytes -= chunk_size; |
| rwnd_ -= chunk_size; |
| |
| absl::optional<UnwrappedTSN> tsn = outstanding_data_.Insert( |
| chunk_opt->data, |
| partial_reliability_ ? chunk_opt->max_retransmissions : absl::nullopt, |
| now, partial_reliability_ ? chunk_opt->expires_at : absl::nullopt); |
| |
| if (tsn.has_value()) { |
| to_be_sent.emplace_back(tsn->Wrap(), std::move(chunk_opt->data)); |
| } |
| } |
| } |
| |
| if (!to_be_sent.empty()) { |
| // https://tools.ietf.org/html/rfc4960#section-6.3.2 |
| // "Every time a DATA chunk is sent to any address (including a |
| // retransmission), if the T3-rtx timer of that address is not running, |
| // start it running so that it will expire after the RTO of that address." |
| if (!t3_rtx_.is_running()) { |
| t3_rtx_.Start(); |
| } |
| RTC_DLOG(LS_VERBOSE) << log_prefix_ << "Sending TSN " |
| << StrJoin(to_be_sent, ",", |
| [&](rtc::StringBuilder& sb, |
| const std::pair<TSN, Data>& c) { |
| sb << *c.first; |
| }) |
| << " - " |
| << absl::c_accumulate( |
| to_be_sent, 0, |
| [&](size_t r, const std::pair<TSN, Data>& d) { |
| return r + GetSerializedChunkSize(d.second); |
| }) |
| << " bytes. outstanding_bytes=" << outstanding_bytes() |
| << " (" << old_outstanding_bytes << "), cwnd=" << cwnd_ |
| << ", rwnd=" << rwnd_ << " (" << old_rwnd << ")"; |
| } |
| RTC_DCHECK(IsConsistent()); |
| return to_be_sent; |
| } |
| |
| bool RetransmissionQueue::can_send_data() const { |
| return cwnd_ < options_.avoid_fragmentation_cwnd_mtus * options_.mtu || |
| max_bytes_to_send() >= min_bytes_required_to_send_; |
| } |
| |
| bool RetransmissionQueue::ShouldSendForwardTsn(TimeMs now) { |
| if (!partial_reliability_) { |
| return false; |
| } |
| outstanding_data_.ExpireOutstandingChunks(now); |
| bool ret = outstanding_data_.ShouldSendForwardTsn(); |
| RTC_DCHECK(IsConsistent()); |
| return ret; |
| } |
| |
| size_t RetransmissionQueue::max_bytes_to_send() const { |
| size_t left = outstanding_bytes() >= cwnd_ ? 0 : cwnd_ - outstanding_bytes(); |
| |
| if (outstanding_bytes() == 0) { |
| // https://datatracker.ietf.org/doc/html/rfc4960#section-6.1 |
| // ... However, regardless of the value of rwnd (including if it is 0), the |
| // data sender can always have one DATA chunk in flight to the receiver if |
| // allowed by cwnd (see rule B, below). |
| return left; |
| } |
| |
| return std::min(rwnd(), left); |
| } |
| |
| void RetransmissionQueue::PrepareResetStreams( |
| rtc::ArrayView<const StreamID> streams) { |
| // TODO(boivie): These calls are now only affecting the send queue. The |
| // packet buffer can also change behavior - for example draining the chunk |
| // producer and eagerly assign TSNs so that an "Outgoing SSN Reset Request" |
| // can be sent quickly, with a known `sender_last_assigned_tsn`. |
| send_queue_.PrepareResetStreams(streams); |
| } |
| bool RetransmissionQueue::CanResetStreams() const { |
| return send_queue_.CanResetStreams(); |
| } |
| void RetransmissionQueue::CommitResetStreams() { |
| send_queue_.CommitResetStreams(); |
| } |
| void RetransmissionQueue::RollbackResetStreams() { |
| send_queue_.RollbackResetStreams(); |
| } |
| |
| HandoverReadinessStatus RetransmissionQueue::GetHandoverReadiness() const { |
| HandoverReadinessStatus status; |
| if (!outstanding_data_.empty()) { |
| status.Add(HandoverUnreadinessReason::kRetransmissionQueueOutstandingData); |
| } |
| if (fast_recovery_exit_tsn_.has_value()) { |
| status.Add(HandoverUnreadinessReason::kRetransmissionQueueFastRecovery); |
| } |
| if (outstanding_data_.has_data_to_be_retransmitted()) { |
| status.Add(HandoverUnreadinessReason::kRetransmissionQueueNotEmpty); |
| } |
| return status; |
| } |
| |
| void RetransmissionQueue::AddHandoverState(DcSctpSocketHandoverState& state) { |
| state.tx.next_tsn = next_tsn().value(); |
| state.tx.rwnd = rwnd_; |
| state.tx.cwnd = cwnd_; |
| state.tx.ssthresh = ssthresh_; |
| state.tx.partial_bytes_acked = partial_bytes_acked_; |
| } |
| } // namespace dcsctp |
