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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 <stddef.h>
#include <cstdint>
#include <memory>
#include <set>
#include <string>
#include <utility>
#include <vector>
#include "absl/functional/any_invocable.h"
#include "absl/strings/string_view.h"
#include "api/array_view.h"
#include "net/dcsctp/common/internal_types.h"
#include "net/dcsctp/common/sequence_numbers.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_handover_state.h"
#include "net/dcsctp/public/dcsctp_message.h"
#include "net/dcsctp/rx/reassembly_streams.h"
#include "rtc_base/containers/flat_set.h"
namespace dcsctp {
// Contains the received DATA chunks that haven't yet been reassembled, and
// reassembles chunks when possible.
// The actual assembly is handled by an implementation of the
// `ReassemblyStreams` interface.
// Except for reassembling fragmented messages, this class will also handle two
// less common operations; To handle the receiver-side of partial reliability
// (limited number of retransmissions or limited message lifetime) as well as
// stream resetting, which is used when a sender wishes to close a data channel.
// Partial reliability is handled when a FORWARD-TSN or I-FORWARD-TSN chunk is
// received, and it will simply delete any chunks matching the parameters in
// that chunk. This is mainly implemented in ReassemblyStreams.
// Resetting streams is handled when a RECONFIG chunks is received, with an
// "Outgoing SSN Reset Request" parameter. That parameter will contain a list of
// streams to reset, and a `sender_last_assigned_tsn`. If this TSN is not yet
// seen, the stream cannot be directly reset, and this class will respond that
// the reset is "deferred". But if this TSN provided is known, the stream can be
// immediately be reset.
// The ReassemblyQueue has a maximum size, as it would otherwise be an DoS
// attack vector where a peer could consume all memory of the other peer by
// sending a lot of ordered chunks, but carefully withholding an early one. It
// also has a watermark limit, which the caller can query is the number of bytes
// is above that limit. This is used by the caller to be selective in what to
// add to the reassembly queue, so that it's not exhausted. The caller is
// expected to call `is_full` prior to adding data to the queue and to act
// accordingly if the queue is full.
class ReassemblyQueue {
// When the queue is filled over this fraction (of its maximum size), the
// socket should restrict incoming data to avoid filling up the queue.
static constexpr float kHighWatermarkLimit = 0.9;
ReassemblyQueue(absl::string_view log_prefix,
TSN peer_initial_tsn,
size_t max_size_bytes,
bool use_message_interleaving = false);
// Adds a data chunk to the queue, with a `tsn` and other parameters in
// `data`.
void Add(TSN tsn, Data data);
// Indicates if the reassembly queue has any reassembled messages that can be
// retrieved by calling `FlushMessages`.
bool HasMessages() const { return !reassembled_messages_.empty(); }
// Returns any reassembled messages.
std::vector<DcSctpMessage> FlushMessages();
// Handle a ForwardTSN chunk, when the sender has indicated that the received
// (this class) should forget about some chunks. This is used to implement
// partial reliability.
void HandleForwardTsn(
TSN new_cumulative_tsn,
rtc::ArrayView<const AnyForwardTsnChunk::SkippedStream> skipped_streams);
// Resets the provided streams and leaves deferred reset processing, if
// enabled.
void ResetStreamsAndLeaveDeferredReset(
rtc::ArrayView<const StreamID> stream_ids);
// Enters deferred reset processing.
void EnterDeferredReset(TSN sender_last_assigned_tsn,
rtc::ArrayView<const StreamID> streams);
// The number of payload bytes that have been queued. Note that the actual
// memory usage is higher due to additional overhead of tracking received
// data.
size_t queued_bytes() const { return queued_bytes_; }
// The remaining bytes until the queue has reached the watermark limit.
size_t remaining_bytes() const { return watermark_bytes_ - queued_bytes_; }
// Indicates if the queue is full. Data should not be added to the queue when
// it's full.
bool is_full() const { return queued_bytes_ >= max_size_bytes_; }
// Indicates if the queue is above the watermark limit, which is a certain
// percentage of its size.
bool is_above_watermark() const { return queued_bytes_ >= watermark_bytes_; }
// Returns the watermark limit, in bytes.
size_t watermark_bytes() const { return watermark_bytes_; }
HandoverReadinessStatus GetHandoverReadiness() const;
void AddHandoverState(DcSctpSocketHandoverState& state);
void RestoreFromState(const DcSctpSocketHandoverState& state);
struct DeferredResetStreams {
DeferredResetStreams(UnwrappedTSN sender_last_assigned_tsn,
webrtc::flat_set<StreamID> streams)
: sender_last_assigned_tsn(sender_last_assigned_tsn),
streams(std::move(streams)) {}
UnwrappedTSN sender_last_assigned_tsn;
webrtc::flat_set<StreamID> streams;
std::vector<absl::AnyInvocable<void(void)>> deferred_actions;
bool IsConsistent() const;
void AddReassembledMessage(rtc::ArrayView<const UnwrappedTSN> tsns,
DcSctpMessage message);
const absl::string_view log_prefix_;
const size_t max_size_bytes_;
const size_t watermark_bytes_;
UnwrappedTSN::Unwrapper tsn_unwrapper_;
// Messages that have been reassembled, and will be returned by
// `FlushMessages`.
std::vector<DcSctpMessage> reassembled_messages_;
// If present, "deferred reset processing" mode is active.
absl::optional<DeferredResetStreams> deferred_reset_streams_;
// Contains the last request sequence number of the
// OutgoingSSNResetRequestParameter that was performed.
ReconfigRequestSN last_completed_reset_req_seq_nbr_;
// The number of "payload bytes" that are in this queue, in total.
size_t queued_bytes_ = 0;
// The actual implementation of ReassemblyStreams.
std::unique_ptr<ReassemblyStreams> streams_;
} // namespace dcsctp