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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 19:33:14 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 19:33:14 +0000
commit36d22d82aa202bb199967e9512281e9a53db42c9 (patch)
tree105e8c98ddea1c1e4784a60a5a6410fa416be2de /third_party/libwebrtc/net/dcsctp/rx/data_tracker.h
parentInitial commit. (diff)
downloadfirefox-esr-36d22d82aa202bb199967e9512281e9a53db42c9.tar.xz
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Adding upstream version 115.7.0esr.upstream/115.7.0esr
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'third_party/libwebrtc/net/dcsctp/rx/data_tracker.h')
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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.
+ */
+#ifndef NET_DCSCTP_RX_DATA_TRACKER_H_
+#define NET_DCSCTP_RX_DATA_TRACKER_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <cstdint>
+#include <set>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "absl/strings/string_view.h"
+#include "net/dcsctp/common/sequence_numbers.h"
+#include "net/dcsctp/packet/chunk/data_common.h"
+#include "net/dcsctp/packet/chunk/sack_chunk.h"
+#include "net/dcsctp/packet/data.h"
+#include "net/dcsctp/public/dcsctp_handover_state.h"
+#include "net/dcsctp/timer/timer.h"
+
+namespace dcsctp {
+
+// Keeps track of received DATA chunks and handles all logic for _when_ to
+// create SACKs and also _how_ to generate them.
+//
+// It only uses TSNs to track delivery and doesn't need to be aware of streams.
+//
+// SACKs are optimally sent every second packet on connections with no packet
+// loss. When packet loss is detected, it's sent for every packet. When SACKs
+// are not sent directly, a timer is used to send a SACK delayed (by RTO/2, or
+// 200ms, whatever is smallest).
+class DataTracker {
+ public:
+ // The maximum number of duplicate TSNs that will be reported in a SACK.
+ static constexpr size_t kMaxDuplicateTsnReported = 20;
+ // The maximum number of gap-ack-blocks that will be reported in a SACK.
+ static constexpr size_t kMaxGapAckBlocksReported = 20;
+
+ // The maximum number of accepted in-flight DATA chunks. This indicates the
+ // maximum difference from this buffer's last cumulative ack TSN, and any
+ // received data. Data received beyond this limit will be dropped, which will
+ // force the transmitter to send data that actually increases the last
+ // cumulative acked TSN.
+ static constexpr uint32_t kMaxAcceptedOutstandingFragments = 100000;
+
+ DataTracker(absl::string_view log_prefix,
+ Timer* delayed_ack_timer,
+ TSN peer_initial_tsn)
+ : log_prefix_(std::string(log_prefix) + "dtrack: "),
+ seen_packet_(false),
+ delayed_ack_timer_(*delayed_ack_timer),
+ last_cumulative_acked_tsn_(
+ tsn_unwrapper_.Unwrap(TSN(*peer_initial_tsn - 1))) {}
+
+ // Indicates if the provided TSN is valid. If this return false, the data
+ // should be dropped and not added to any other buffers, which essentially
+ // means that there is intentional packet loss.
+ bool IsTSNValid(TSN tsn) const;
+
+ // Call for every incoming data chunk. Returns `true` if `tsn` was seen for
+ // the first time, and `false` if it has been seen before (a duplicate `tsn`).
+ bool Observe(TSN tsn,
+ AnyDataChunk::ImmediateAckFlag immediate_ack =
+ AnyDataChunk::ImmediateAckFlag(false));
+ // Called at the end of processing an SCTP packet.
+ void ObservePacketEnd();
+
+ // Called for incoming FORWARD-TSN/I-FORWARD-TSN chunks
+ void HandleForwardTsn(TSN new_cumulative_ack);
+
+ // Indicates if a SACK should be sent. There may be other reasons to send a
+ // SACK, but if this function indicates so, it should be sent as soon as
+ // possible. Calling this function will make it clear a flag so that if it's
+ // called again, it will probably return false.
+ //
+ // If the delayed ack timer is running, this method will return false _unless_
+ // `also_if_delayed` is set to true. Then it will return true as well.
+ bool ShouldSendAck(bool also_if_delayed = false);
+
+ // Returns the last cumulative ack TSN - the last seen data chunk's TSN
+ // value before any packet loss was detected.
+ TSN last_cumulative_acked_tsn() const {
+ return TSN(last_cumulative_acked_tsn_.Wrap());
+ }
+
+ // Returns true if the received `tsn` would increase the cumulative ack TSN.
+ bool will_increase_cum_ack_tsn(TSN tsn) const;
+
+ // Forces `ShouldSendSack` to return true.
+ void ForceImmediateSack();
+
+ // Note that this will clear `duplicates_`, so every SackChunk that is
+ // consumed must be sent.
+ SackChunk CreateSelectiveAck(size_t a_rwnd);
+
+ void HandleDelayedAckTimerExpiry();
+
+ HandoverReadinessStatus GetHandoverReadiness() const;
+
+ void AddHandoverState(DcSctpSocketHandoverState& state);
+ void RestoreFromState(const DcSctpSocketHandoverState& state);
+
+ private:
+ enum class AckState {
+ // No need to send an ACK.
+ kIdle,
+
+ // Has received data chunks (but not yet end of packet).
+ kBecomingDelayed,
+
+ // Has received data chunks and the end of a packet. Delayed ack timer is
+ // running and a SACK will be sent on expiry, or if DATA is sent, or after
+ // next packet with data.
+ kDelayed,
+
+ // Send a SACK immediately after handling this packet.
+ kImmediate,
+ };
+
+ // Represents ranges of TSNs that have been received that are not directly
+ // following the last cumulative acked TSN. This information is returned to
+ // the sender in the "gap ack blocks" in the SACK chunk. The blocks are always
+ // non-overlapping and non-adjacent.
+ class AdditionalTsnBlocks {
+ public:
+ // Represents an inclusive range of received TSNs, i.e. [first, last].
+ struct TsnRange {
+ TsnRange(UnwrappedTSN first, UnwrappedTSN last)
+ : first(first), last(last) {}
+ UnwrappedTSN first;
+ UnwrappedTSN last;
+ };
+
+ // Adds a TSN to the set. This will try to expand any existing block and
+ // might merge blocks to ensure that all blocks are non-adjacent. If a
+ // current block can't be expanded, a new block is created.
+ //
+ // The return value indicates if `tsn` was added. If false is returned, the
+ // `tsn` was already represented in one of the blocks.
+ bool Add(UnwrappedTSN tsn);
+
+ // Erases all TSNs up to, and including `tsn`. This will remove all blocks
+ // that are completely below `tsn` and may truncate a block where `tsn` is
+ // within that block. In that case, the frontmost block's start TSN will be
+ // the next following tsn after `tsn`.
+ void EraseTo(UnwrappedTSN tsn);
+
+ // Removes the first block. Must not be called on an empty set.
+ void PopFront();
+
+ const std::vector<TsnRange>& blocks() const { return blocks_; }
+
+ bool empty() const { return blocks_.empty(); }
+
+ const TsnRange& front() const { return blocks_.front(); }
+
+ private:
+ // A sorted vector of non-overlapping and non-adjacent blocks.
+ std::vector<TsnRange> blocks_;
+ };
+
+ std::vector<SackChunk::GapAckBlock> CreateGapAckBlocks() const;
+ void UpdateAckState(AckState new_state, absl::string_view reason);
+ static absl::string_view ToString(AckState ack_state);
+
+ const std::string log_prefix_;
+ // If a packet has ever been seen.
+ bool seen_packet_;
+ Timer& delayed_ack_timer_;
+ AckState ack_state_ = AckState::kIdle;
+ UnwrappedTSN::Unwrapper tsn_unwrapper_;
+
+ // All TSNs up until (and including) this value have been seen.
+ UnwrappedTSN last_cumulative_acked_tsn_;
+ // Received TSNs that are not directly following `last_cumulative_acked_tsn_`.
+ AdditionalTsnBlocks additional_tsn_blocks_;
+ std::set<TSN> duplicate_tsns_;
+};
+} // namespace dcsctp
+
+#endif // NET_DCSCTP_RX_DATA_TRACKER_H_