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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/rx/reassembly_queue.h"
#include <stddef.h>
#include <algorithm>
#include <cstdint>
#include <memory>
#include <set>
#include <string>
#include <utility>
#include <vector>
#include "absl/strings/string_view.h"
#include "absl/types/optional.h"
#include "api/array_view.h"
#include "net/dcsctp/common/sequence_numbers.h"
#include "net/dcsctp/common/str_join.h"
#include "net/dcsctp/packet/chunk/forward_tsn_common.h"
#include "net/dcsctp/packet/data.h"
#include "net/dcsctp/packet/parameter/outgoing_ssn_reset_request_parameter.h"
#include "net/dcsctp/packet/parameter/reconfiguration_response_parameter.h"
#include "net/dcsctp/public/dcsctp_message.h"
#include "net/dcsctp/rx/interleaved_reassembly_streams.h"
#include "net/dcsctp/rx/reassembly_streams.h"
#include "net/dcsctp/rx/traditional_reassembly_streams.h"
#include "rtc_base/logging.h"
namespace dcsctp {
namespace {
std::unique_ptr<ReassemblyStreams> CreateStreams(
absl::string_view log_prefix,
ReassemblyStreams::OnAssembledMessage on_assembled_message,
bool use_message_interleaving,
const DcSctpSocketHandoverState* handover_state) {
if (use_message_interleaving) {
return std::make_unique<InterleavedReassemblyStreams>(
log_prefix, std::move(on_assembled_message), handover_state);
}
return std::make_unique<TraditionalReassemblyStreams>(
log_prefix, std::move(on_assembled_message), handover_state);
}
} // namespace
ReassemblyQueue::ReassemblyQueue(
absl::string_view log_prefix,
TSN peer_initial_tsn,
size_t max_size_bytes,
bool use_message_interleaving,
const DcSctpSocketHandoverState* handover_state)
: log_prefix_(std::string(log_prefix) + "reasm: "),
max_size_bytes_(max_size_bytes),
watermark_bytes_(max_size_bytes * kHighWatermarkLimit),
last_assembled_tsn_watermark_(tsn_unwrapper_.Unwrap(
handover_state ? TSN(handover_state->rx.last_assembled_tsn)
: TSN(*peer_initial_tsn - 1))),
last_completed_reset_req_seq_nbr_(
handover_state
? ReconfigRequestSN(
handover_state->rx.last_completed_deferred_reset_req_sn)
: ReconfigRequestSN(0)),
streams_(CreateStreams(
log_prefix_,
[this](rtc::ArrayView<const UnwrappedTSN> tsns,
DcSctpMessage message) {
AddReassembledMessage(tsns, std::move(message));
},
use_message_interleaving,
handover_state)) {}
void ReassemblyQueue::Add(TSN tsn, Data data) {
RTC_DCHECK(IsConsistent());
RTC_DLOG(LS_VERBOSE) << log_prefix_ << "added tsn=" << *tsn
<< ", stream=" << *data.stream_id << ":"
<< *data.message_id << ":" << *data.fsn << ", type="
<< (data.is_beginning && data.is_end
? "complete"
: data.is_beginning
? "first"
: data.is_end ? "last" : "middle");
UnwrappedTSN unwrapped_tsn = tsn_unwrapper_.Unwrap(tsn);
if (unwrapped_tsn <= last_assembled_tsn_watermark_ ||
delivered_tsns_.find(unwrapped_tsn) != delivered_tsns_.end()) {
RTC_DLOG(LS_VERBOSE) << log_prefix_
<< "Chunk has already been delivered - skipping";
return;
}
// If a stream reset has been received with a "sender's last assigned tsn" in
// the future, the socket is in "deferred reset processing" mode and must
// buffer chunks until it's exited.
if (deferred_reset_streams_.has_value() &&
unwrapped_tsn >
tsn_unwrapper_.Unwrap(
deferred_reset_streams_->req.sender_last_assigned_tsn())) {
RTC_DLOG(LS_VERBOSE)
<< log_prefix_ << "Deferring chunk with tsn=" << *tsn
<< " until cum_ack_tsn="
<< *deferred_reset_streams_->req.sender_last_assigned_tsn();
// https://tools.ietf.org/html/rfc6525#section-5.2.2
// "In this mode, any data arriving with a TSN larger than the
// Sender's Last Assigned TSN for the affected stream(s) MUST be queued
// locally and held until the cumulative acknowledgment point reaches the
// Sender's Last Assigned TSN."
queued_bytes_ += data.size();
deferred_reset_streams_->deferred_chunks.emplace_back(
std::make_pair(tsn, std::move(data)));
} else {
queued_bytes_ += streams_->Add(unwrapped_tsn, std::move(data));
}
// https://tools.ietf.org/html/rfc4960#section-6.9
// "Note: If the data receiver runs out of buffer space while still
// waiting for more fragments to complete the reassembly of the message, it
// should dispatch part of its inbound message through a partial delivery
// API (see Section 10), freeing some of its receive buffer space so that
// the rest of the message may be received."
// TODO(boivie): Support EOR flag and partial delivery?
RTC_DCHECK(IsConsistent());
}
ReconfigurationResponseParameter::Result ReassemblyQueue::ResetStreams(
const OutgoingSSNResetRequestParameter& req,
TSN cum_tsn_ack) {
RTC_DCHECK(IsConsistent());
if (deferred_reset_streams_.has_value()) {
// In deferred mode already.
return ReconfigurationResponseParameter::Result::kInProgress;
} else if (req.request_sequence_number() <=
last_completed_reset_req_seq_nbr_) {
// Already performed at some time previously.
return ReconfigurationResponseParameter::Result::kSuccessPerformed;
}
UnwrappedTSN sla_tsn = tsn_unwrapper_.Unwrap(req.sender_last_assigned_tsn());
UnwrappedTSN unwrapped_cum_tsn_ack = tsn_unwrapper_.Unwrap(cum_tsn_ack);
// https://tools.ietf.org/html/rfc6525#section-5.2.2
// "If the Sender's Last Assigned TSN is greater than the
// cumulative acknowledgment point, then the endpoint MUST enter "deferred
// reset processing"."
if (sla_tsn > unwrapped_cum_tsn_ack) {
RTC_DLOG(LS_VERBOSE)
<< log_prefix_
<< "Entering deferred reset processing mode until cum_tsn_ack="
<< *req.sender_last_assigned_tsn();
deferred_reset_streams_ = absl::make_optional<DeferredResetStreams>(req);
return ReconfigurationResponseParameter::Result::kInProgress;
}
// https://tools.ietf.org/html/rfc6525#section-5.2.2
// "... streams MUST be reset to 0 as the next expected SSN."
streams_->ResetStreams(req.stream_ids());
last_completed_reset_req_seq_nbr_ = req.request_sequence_number();
RTC_DCHECK(IsConsistent());
return ReconfigurationResponseParameter::Result::kSuccessPerformed;
}
bool ReassemblyQueue::MaybeResetStreamsDeferred(TSN cum_ack_tsn) {
RTC_DCHECK(IsConsistent());
if (deferred_reset_streams_.has_value()) {
UnwrappedTSN unwrapped_cum_ack_tsn = tsn_unwrapper_.Unwrap(cum_ack_tsn);
UnwrappedTSN unwrapped_sla_tsn = tsn_unwrapper_.Unwrap(
deferred_reset_streams_->req.sender_last_assigned_tsn());
if (unwrapped_cum_ack_tsn >= unwrapped_sla_tsn) {
RTC_DLOG(LS_VERBOSE) << log_prefix_
<< "Leaving deferred reset processing with tsn="
<< *cum_ack_tsn << ", feeding back "
<< deferred_reset_streams_->deferred_chunks.size()
<< " chunks";
// https://tools.ietf.org/html/rfc6525#section-5.2.2
// "... streams MUST be reset to 0 as the next expected SSN."
streams_->ResetStreams(deferred_reset_streams_->req.stream_ids());
std::vector<std::pair<TSN, Data>> deferred_chunks =
std::move(deferred_reset_streams_->deferred_chunks);
// The response will not be sent now, but as a reply to the retried
// request, which will come as "in progress" has been sent prior.
last_completed_reset_req_seq_nbr_ =
deferred_reset_streams_->req.request_sequence_number();
deferred_reset_streams_ = absl::nullopt;
// https://tools.ietf.org/html/rfc6525#section-5.2.2
// "Any queued TSNs (queued at step E2) MUST now be released and processed
// normally."
for (auto& [tsn, data] : deferred_chunks) {
queued_bytes_ -= data.size();
Add(tsn, std::move(data));
}
RTC_DCHECK(IsConsistent());
return true;
} else {
RTC_DLOG(LS_VERBOSE) << "Staying in deferred reset processing. tsn="
<< *cum_ack_tsn;
}
}
return false;
}
std::vector<DcSctpMessage> ReassemblyQueue::FlushMessages() {
std::vector<DcSctpMessage> ret;
reassembled_messages_.swap(ret);
return ret;
}
void ReassemblyQueue::AddReassembledMessage(
rtc::ArrayView<const UnwrappedTSN> tsns,
DcSctpMessage message) {
RTC_DLOG(LS_VERBOSE) << log_prefix_ << "Assembled message from TSN=["
<< StrJoin(tsns, ",",
[](rtc::StringBuilder& sb, UnwrappedTSN tsn) {
sb << *tsn.Wrap();
})
<< "], message; stream_id=" << *message.stream_id()
<< ", ppid=" << *message.ppid()
<< ", payload=" << message.payload().size() << " bytes";
for (const UnwrappedTSN tsn : tsns) {
if (tsn <= last_assembled_tsn_watermark_) {
// This can be provoked by a misbehaving peer by sending FORWARD-TSN with
// invalid SSNs, allowing ordered messages to stay in the queue that
// should've been discarded.
RTC_DLOG(LS_VERBOSE)
<< log_prefix_
<< "Message is built from fragments already seen - skipping";
return;
} else if (tsn == last_assembled_tsn_watermark_.next_value()) {
// Update watermark, or insert into delivered_tsns_
last_assembled_tsn_watermark_.Increment();
} else {
delivered_tsns_.insert(tsn);
}
}
// With new TSNs in delivered_tsns, gaps might be filled.
MaybeMoveLastAssembledWatermarkFurther();
reassembled_messages_.emplace_back(std::move(message));
}
void ReassemblyQueue::MaybeMoveLastAssembledWatermarkFurther() {
// `delivered_tsns_` contain TSNS when there is a gap between ranges of
// assembled TSNs. `last_assembled_tsn_watermark_` should not be adjacent to
// that list, because if so, it can be moved.
while (!delivered_tsns_.empty() &&
*delivered_tsns_.begin() ==
last_assembled_tsn_watermark_.next_value()) {
last_assembled_tsn_watermark_.Increment();
delivered_tsns_.erase(delivered_tsns_.begin());
}
}
void ReassemblyQueue::Handle(const AnyForwardTsnChunk& forward_tsn) {
RTC_DCHECK(IsConsistent());
UnwrappedTSN tsn = tsn_unwrapper_.Unwrap(forward_tsn.new_cumulative_tsn());
last_assembled_tsn_watermark_ = std::max(last_assembled_tsn_watermark_, tsn);
delivered_tsns_.erase(delivered_tsns_.begin(),
delivered_tsns_.upper_bound(tsn));
MaybeMoveLastAssembledWatermarkFurther();
queued_bytes_ -=
streams_->HandleForwardTsn(tsn, forward_tsn.skipped_streams());
RTC_DCHECK(IsConsistent());
}
bool ReassemblyQueue::IsConsistent() const {
// `delivered_tsns_` and `last_assembled_tsn_watermark_` mustn't overlap or be
// adjacent.
if (!delivered_tsns_.empty() &&
last_assembled_tsn_watermark_.next_value() >= *delivered_tsns_.begin()) {
return false;
}
// Allow queued_bytes_ to be larger than max_size_bytes, as it's not actively
// enforced in this class. This comparison will still trigger if queued_bytes_
// became "negative".
return (queued_bytes_ >= 0 && queued_bytes_ <= 2 * max_size_bytes_);
}
HandoverReadinessStatus ReassemblyQueue::GetHandoverReadiness() const {
HandoverReadinessStatus status = streams_->GetHandoverReadiness();
if (!delivered_tsns_.empty()) {
status.Add(HandoverUnreadinessReason::kReassemblyQueueDeliveredTSNsGap);
}
if (deferred_reset_streams_.has_value()) {
status.Add(HandoverUnreadinessReason::kStreamResetDeferred);
}
return status;
}
void ReassemblyQueue::AddHandoverState(DcSctpSocketHandoverState& state) {
state.rx.last_assembled_tsn = last_assembled_tsn_watermark_.Wrap().value();
state.rx.last_completed_deferred_reset_req_sn =
last_completed_reset_req_seq_nbr_.value();
streams_->AddHandoverState(state);
}
} // namespace dcsctp