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TMessagesProj/jni/voip/webrtc/net/dcsctp/tx/outstanding_data.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_TX_OUTSTANDING_DATA_H_
+#define NET_DCSCTP_TX_OUTSTANDING_DATA_H_
+
+#include <deque>
+#include <map>
+#include <set>
+#include <utility>
+#include <vector>
+
+#include "absl/types/optional.h"
+#include "api/units/timestamp.h"
+#include "net/dcsctp/common/internal_types.h"
+#include "net/dcsctp/common/sequence_numbers.h"
+#include "net/dcsctp/packet/chunk/forward_tsn_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/types.h"
+#include "rtc_base/containers/flat_set.h"
+
+namespace dcsctp {
+
+// This class keeps track of outstanding data chunks (sent, not yet acked) and
+// handles acking, nacking, rescheduling and abandoning.
+//
+// Items are added to this queue as they are sent and will be removed when the
+// peer acks them using the cumulative TSN ack.
+class OutstandingData {
+ public:
+  // State for DATA chunks (message fragments) in the queue - used in tests.
+  enum class State {
+    // The chunk has been sent but not received yet (from the sender's point of
+    // view, as no SACK has been received yet that reference this chunk).
+    kInFlight,
+    // A SACK has been received which explicitly marked this chunk as missing -
+    // it's now NACKED and may be retransmitted if NACKED enough times.
+    kNacked,
+    // A chunk that will be retransmitted when possible.
+    kToBeRetransmitted,
+    // A SACK has been received which explicitly marked this chunk as received.
+    kAcked,
+    // A chunk whose message has expired or has been retransmitted too many
+    // times (RFC3758). It will not be retransmitted anymore.
+    kAbandoned,
+  };
+
+  // Contains variables scoped to a processing of an incoming SACK.
+  struct AckInfo {
+    explicit AckInfo(UnwrappedTSN cumulative_tsn_ack)
+        : highest_tsn_acked(cumulative_tsn_ack) {}
+
+    // Bytes acked by increasing cumulative_tsn_ack and gap_ack_blocks.
+    size_t bytes_acked = 0;
+
+    // Indicates if this SACK indicates that packet loss has occurred. Just
+    // because a packet is missing in the SACK doesn't necessarily mean that
+    // there is packet loss as that packet might be in-flight and received
+    // out-of-order. But when it has been reported missing consecutive times, it
+    // will eventually be considered "lost" and this will be set.
+    bool has_packet_loss = false;
+
+    // Highest TSN Newly Acknowledged, an SCTP variable.
+    UnwrappedTSN highest_tsn_acked;
+
+    // The set of lifecycle IDs that were acked using cumulative_tsn_ack.
+    std::vector<LifecycleId> acked_lifecycle_ids;
+    // The set of lifecycle IDs that were acked, but had been abandoned.
+    std::vector<LifecycleId> abandoned_lifecycle_ids;
+  };
+
+  OutstandingData(
+      size_t data_chunk_header_size,
+      UnwrappedTSN last_cumulative_tsn_ack,
+      std::function<bool(StreamID, OutgoingMessageId)> discard_from_send_queue)
+      : data_chunk_header_size_(data_chunk_header_size),
+        last_cumulative_tsn_ack_(last_cumulative_tsn_ack),
+        discard_from_send_queue_(std::move(discard_from_send_queue)) {}
+
+  AckInfo HandleSack(
+      UnwrappedTSN cumulative_tsn_ack,
+      rtc::ArrayView<const SackChunk::GapAckBlock> gap_ack_blocks,
+      bool is_in_fast_recovery);
+
+  // Returns as many of the chunks that are eligible for fast retransmissions
+  // and that would fit in a single packet of `max_size`. The eligible chunks
+  // that didn't fit will be marked for (normal) retransmission and will not be
+  // returned if this method is called again.
+  std::vector<std::pair<TSN, Data>> GetChunksToBeFastRetransmitted(
+      size_t max_size);
+
+  // Given `max_size` of space left in a packet, which chunks can be added to
+  // it?
+  std::vector<std::pair<TSN, Data>> GetChunksToBeRetransmitted(size_t max_size);
+
+  size_t unacked_bytes() const { return unacked_bytes_; }
+
+  // Returns the number of DATA chunks that are in-flight (not acked or nacked).
+  size_t unacked_items() const { return unacked_items_; }
+
+  // Given the current time `now_ms`, expire and abandon outstanding (sent at
+  // least once) chunks that have a limited lifetime.
+  void ExpireOutstandingChunks(webrtc::Timestamp now);
+
+  bool empty() const { return outstanding_data_.empty(); }
+
+  bool has_data_to_be_fast_retransmitted() const {
+    return !to_be_fast_retransmitted_.empty();
+  }
+
+  bool has_data_to_be_retransmitted() const {
+    return !to_be_retransmitted_.empty() || !to_be_fast_retransmitted_.empty();
+  }
+
+  UnwrappedTSN last_cumulative_tsn_ack() const {
+    return last_cumulative_tsn_ack_;
+  }
+
+  UnwrappedTSN next_tsn() const {
+    return highest_outstanding_tsn().next_value();
+  }
+
+  UnwrappedTSN highest_outstanding_tsn() const;
+
+  // Schedules `data` to be sent, with the provided partial reliability
+  // parameters. Returns the TSN if the item was actually added and scheduled to
+  // be sent, and absl::nullopt if it shouldn't be sent.
+  absl::optional<UnwrappedTSN> Insert(
+      OutgoingMessageId message_id,
+      const Data& data,
+      webrtc::Timestamp time_sent,
+      MaxRetransmits max_retransmissions = MaxRetransmits::NoLimit(),
+      webrtc::Timestamp expires_at = webrtc::Timestamp::PlusInfinity(),
+      LifecycleId lifecycle_id = LifecycleId::NotSet());
+
+  // Nacks all outstanding data.
+  void NackAll();
+
+  // Creates a FORWARD-TSN chunk.
+  ForwardTsnChunk CreateForwardTsn() const;
+
+  // Creates an I-FORWARD-TSN chunk.
+  IForwardTsnChunk CreateIForwardTsn() const;
+
+  // Given the current time and a TSN, it returns the measured RTT between when
+  // the chunk was sent and now. It takes into acccount Karn's algorithm, so if
+  // the chunk has ever been retransmitted, it will return `PlusInfinity()`.
+  webrtc::TimeDelta MeasureRTT(webrtc::Timestamp now, UnwrappedTSN tsn) const;
+
+  // Returns the internal state of all queued chunks. This is only used in
+  // unit-tests.
+  std::vector<std::pair<TSN, State>> GetChunkStatesForTesting() const;
+
+  // Returns true if the next chunk that is not acked by the peer has been
+  // abandoned, which means that a FORWARD-TSN should be sent.
+  bool ShouldSendForwardTsn() const;
+
+  // Sets the next TSN to be used. This is used in handover.
+  void ResetSequenceNumbers(UnwrappedTSN last_cumulative_tsn);
+
+  // Called when an outgoing stream reset is sent, marking the last assigned TSN
+  // as a breakpoint that a FORWARD-TSN shouldn't cross.
+  void BeginResetStreams();
+
+ private:
+  // A fragmented message's DATA chunk while in the retransmission queue, and
+  // its associated metadata.
+  class Item {
+   public:
+    enum class NackAction {
+      kNothing,
+      kRetransmit,
+      kAbandon,
+    };
+
+    Item(OutgoingMessageId message_id,
+         Data data,
+         webrtc::Timestamp time_sent,
+         MaxRetransmits max_retransmissions,
+         webrtc::Timestamp expires_at,
+         LifecycleId lifecycle_id)
+        : message_id_(message_id),
+          time_sent_(time_sent),
+          max_retransmissions_(max_retransmissions),
+          expires_at_(expires_at),
+          lifecycle_id_(lifecycle_id),
+          data_(std::move(data)) {}
+
+    Item(const Item&) = delete;
+    Item& operator=(const Item&) = delete;
+
+    OutgoingMessageId message_id() const { return message_id_; }
+
+    webrtc::Timestamp time_sent() const { return time_sent_; }
+
+    const Data& data() const { return data_; }
+
+    // Acks an item.
+    void Ack();
+
+    // Nacks an item. If it has been nacked enough times, or if `retransmit_now`
+    // is set, it might be marked for retransmission. If the item has reached
+    // its max retransmission value, it will instead be abandoned. The action
+    // performed is indicated as return value.
+    NackAction Nack(bool retransmit_now);
+
+    // Prepares the item to be retransmitted. Sets it as outstanding and
+    // clears all nack counters.
+    void MarkAsRetransmitted();
+
+    // Marks this item as abandoned.
+    void Abandon();
+
+    bool is_outstanding() const { return ack_state_ == AckState::kUnacked; }
+    bool is_acked() const { return ack_state_ == AckState::kAcked; }
+    bool is_nacked() const { return ack_state_ == AckState::kNacked; }
+    bool is_abandoned() const { return lifecycle_ == Lifecycle::kAbandoned; }
+
+    // Indicates if this chunk should be retransmitted.
+    bool should_be_retransmitted() const {
+      return lifecycle_ == Lifecycle::kToBeRetransmitted;
+    }
+    // Indicates if this chunk has ever been retransmitted.
+    bool has_been_retransmitted() const { return num_retransmissions_ > 0; }
+
+    // Given the current time, and the current state of this DATA chunk, it will
+    // indicate if it has expired (SCTP Partial Reliability Extension).
+    bool has_expired(webrtc::Timestamp now) const;
+
+    LifecycleId lifecycle_id() const { return lifecycle_id_; }
+
+   private:
+    enum class Lifecycle : uint8_t {
+      // The chunk is alive (sent, received, etc)
+      kActive,
+      // The chunk is scheduled to be retransmitted, and will then transition to
+      // become active.
+      kToBeRetransmitted,
+      // The chunk has been abandoned. This is a terminal state.
+      kAbandoned
+    };
+    enum class AckState : uint8_t {
+      // The chunk is in-flight.
+      kUnacked,
+      // The chunk has been received and acknowledged.
+      kAcked,
+      // The chunk has been nacked and is possibly lost.
+      kNacked
+    };
+
+    // NOTE: This data structure has been optimized for size, by ordering fields
+    // to avoid unnecessary padding.
+
+    const OutgoingMessageId message_id_;
+
+    // When the packet was sent, and placed in this queue.
+    const webrtc::Timestamp time_sent_;
+    // If the message was sent with a maximum number of retransmissions, this is
+    // set to that number. The value zero (0) means that it will never be
+    // retransmitted.
+    const MaxRetransmits max_retransmissions_;
+
+    // Indicates the life cycle status of this chunk.
+    Lifecycle lifecycle_ = Lifecycle::kActive;
+    // Indicates the presence of this chunk, if it's in flight (Unacked), has
+    // been received (Acked) or is possibly lost (Nacked).
+    AckState ack_state_ = AckState::kUnacked;
+
+    // The number of times the DATA chunk has been nacked (by having received a
+    // SACK which doesn't include it). Will be cleared on retransmissions.
+    uint8_t nack_count_ = 0;
+    // The number of times the DATA chunk has been retransmitted.
+    uint16_t num_retransmissions_ = 0;
+
+    // At this exact millisecond, the item is considered expired. If the message
+    // is not to be expired, this is set to the infinite future.
+    const webrtc::Timestamp expires_at_;
+
+    // An optional lifecycle id, which may only be set for the last fragment.
+    const LifecycleId lifecycle_id_;
+
+    // The actual data to send/retransmit.
+    const Data data_;
+  };
+
+  // Returns how large a chunk will be, serialized, carrying the data
+  size_t GetSerializedChunkSize(const Data& data) const;
+
+  Item& GetItem(UnwrappedTSN tsn);
+  const Item& GetItem(UnwrappedTSN tsn) const;
+
+  // Given a `cumulative_tsn_ack` from an incoming SACK, will remove those items
+  // in the retransmission queue up until this value and will update `ack_info`
+  // by setting `bytes_acked_by_cumulative_tsn_ack`.
+  void RemoveAcked(UnwrappedTSN cumulative_tsn_ack, AckInfo& ack_info);
+
+  // Will mark the chunks covered by the `gap_ack_blocks` from an incoming SACK
+  // as "acked" and update `ack_info` by adding new TSNs to `added_tsns`.
+  void AckGapBlocks(UnwrappedTSN cumulative_tsn_ack,
+                    rtc::ArrayView<const SackChunk::GapAckBlock> gap_ack_blocks,
+                    AckInfo& ack_info);
+
+  // Mark chunks reported as "missing", as "nacked" or "to be retransmitted"
+  // depending how many times this has happened. Only packets up until
+  // `ack_info.highest_tsn_acked` (highest TSN newly acknowledged) are
+  // nacked/retransmitted. The method will set `ack_info.has_packet_loss`.
+  void NackBetweenAckBlocks(
+      UnwrappedTSN cumulative_tsn_ack,
+      rtc::ArrayView<const SackChunk::GapAckBlock> gap_ack_blocks,
+      bool is_in_fast_recovery,
+      OutstandingData::AckInfo& ack_info);
+
+  // Process the acknowledgement of the chunk referenced by `iter` and updates
+  // state in `ack_info` and the object's state.
+  void AckChunk(AckInfo& ack_info, UnwrappedTSN tsn, Item& item);
+
+  // Helper method to process an incoming nack of an item and perform the
+  // correct operations given the action indicated when nacking an item (e.g.
+  // retransmitting or abandoning). The return value indicate if an action was
+  // performed, meaning that packet loss was detected and acted upon. If
+  // `do_fast_retransmit` is set and if the item has been nacked sufficiently
+  // many times so that it should be retransmitted, this will schedule it to be
+  // "fast retransmitted". This is only done just before going into fast
+  // recovery.
+  //
+  // Note that since nacking an item may result in it becoming abandoned, which
+  // in turn could alter `outstanding_data_`, any iterators are invalidated
+  // after having called this method.
+  bool NackItem(UnwrappedTSN tsn, bool retransmit_now, bool do_fast_retransmit);
+
+  // Given that a message fragment, `item` has been abandoned, abandon all other
+  // fragments that share the same message - both never-before-sent fragments
+  // that are still in the SendQueue and outstanding chunks.
+  void AbandonAllFor(const OutstandingData::Item& item);
+
+  std::vector<std::pair<TSN, Data>> ExtractChunksThatCanFit(
+      std::set<UnwrappedTSN>& chunks,
+      size_t max_size);
+
+  bool IsConsistent() const;
+
+  // The size of the data chunk (DATA/I-DATA) header that is used.
+  const size_t data_chunk_header_size_;
+  // The last cumulative TSN ack number.
+  UnwrappedTSN last_cumulative_tsn_ack_;
+  // Callback when to discard items from the send queue.
+  std::function<bool(StreamID, OutgoingMessageId)> discard_from_send_queue_;
+
+  // Outstanding items. If non-empty, the first element has
+  // `TSN=last_cumulative_tsn_ack_ + 1` and the following items are in strict
+  // increasing TSN order. The last item has `TSN=highest_outstanding_tsn()`.
+  std::deque<Item> outstanding_data_;
+  // The number of bytes that are in-flight (sent but not yet acked or nacked).
+  size_t unacked_bytes_ = 0;
+  // The number of DATA chunks that are in-flight (sent but not yet acked or
+  // nacked).
+  size_t unacked_items_ = 0;
+  // Data chunks that are eligible for fast retransmission.
+  std::set<UnwrappedTSN> to_be_fast_retransmitted_;
+  // Data chunks that are to be retransmitted.
+  std::set<UnwrappedTSN> to_be_retransmitted_;
+  // Wben a stream reset has begun, the "next TSN to assign" is added to this
+  // set, and removed when the cum-ack TSN reaches it. This is used to limit a
+  // FORWARD-TSN to reset streams past a "stream reset last assigned TSN".
+  webrtc::flat_set<UnwrappedTSN> stream_reset_breakpoint_tsns_;
+};
+}  // namespace dcsctp
+#endif  // NET_DCSCTP_TX_OUTSTANDING_DATA_H_