[feat] add nack module

src/qos/nack_requester.h

@@ -0,0 +1,73 @@
+/*
+ * @Author: DI JUNKUN
+ * @Date: 2025-02-12
+ * Copyright (c) 2025 by DI JUNKUN, All Rights Reserved.
+ */
+
+#ifndef _NACK_REQUESTER_H_
+#define _NACK_REQUESTER_H_
+
+#include <cstddef>
+#include <cstdint>
+#include <map>
+#include <set>
+#include <vector>
+
+#include "api/units/timestamp.h"
+#include "clock.h"
+#include "histogram.h"
+#include "module_common_types.h"
+#include "rtc_base/numerics/sequence_number_util.h"
+
+using namespace webrtc;
+
+class NackRequester {
+ private:
+  // Which fields to consider when deciding which packet to nack in
+  // GetNackBatch.
+  enum NackFilterOptions { kSeqNumOnly, kTimeOnly, kSeqNumAndTime };
+
+  struct NackInfo {
+    NackInfo();
+    NackInfo(uint16_t seq_num, uint16_t send_at_seq_num,
+             Timestamp created_at_time);
+
+    uint16_t seq_num;
+    uint16_t send_at_seq_num;
+    Timestamp created_at_time;
+    Timestamp sent_at_time;
+    int retries;
+  };
+
+ public:
+  NackRequester(Clock* clock, NackSender* nack_sender,
+                KeyFrameRequestSender* keyframe_request_sender);
+  ~NackRequester();
+
+ public:
+  int OnReceivedPacket(uint16_t seq_num);
+  int OnReceivedPacket(uint16_t seq_num, bool is_recovered);
+
+ private:
+  void ClearUpTo(uint16_t seq_num);
+  void UpdateRtt(int64_t rtt_ms);
+  void AddPacketsToNack(uint16_t seq_num_start, uint16_t seq_num_end);
+  std::vector<uint16_t> GetNackBatch(NackFilterOptions options);
+  void UpdateReorderingStatistics(uint16_t seq_num);
+  int WaitNumberOfPackets(float probability) const;
+
+ private:
+  Clock* const clock_;
+  NackSender* const nack_sender_;
+  KeyFrameRequestSender* const keyframe_request_sender_;
+
+  std::map<uint16_t, NackInfo, DescendingSeqNumComp<uint16_t>> nack_list_;
+  std::set<uint16_t, DescendingSeqNumComp<uint16_t>> recovered_list_;
+  Histogram reordering_histogram_;
+  bool initialized_;
+  TimeDelta rtt_;
+  uint16_t newest_seq_num_;
+  const TimeDelta send_nack_delay_;
+};
+
+#endif