62 lines
2.2 KiB
C
62 lines
2.2 KiB
C
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/*
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* Copyright (c) 2021 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef NET_DCSCTP_TX_RETRANSMISSION_TIMEOUT_H_
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#define NET_DCSCTP_TX_RETRANSMISSION_TIMEOUT_H_
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#include <cstdint>
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#include <functional>
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#include "net/dcsctp/public/dcsctp_options.h"
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namespace dcsctp {
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// Manages updating of the Retransmission Timeout (RTO) SCTP variable, which is
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// used directly as the base timeout for T3-RTX and for other timers, such as
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// delayed ack.
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//
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// When a round-trip-time (RTT) is calculated (outside this class), `Observe`
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// is called, which calculates the retransmission timeout (RTO) value. The RTO
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// value will become larger if the RTT is high and/or the RTT values are varying
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// a lot, which is an indicator of a bad connection.
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class RetransmissionTimeout {
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public:
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static constexpr int kRttShift = 3;
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static constexpr int kRttVarShift = 2;
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explicit RetransmissionTimeout(const DcSctpOptions& options);
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// To be called when a RTT has been measured, to update the RTO value.
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void ObserveRTT(webrtc::TimeDelta measured_rtt);
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// Returns the Retransmission Timeout (RTO) value, in milliseconds.
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webrtc::TimeDelta rto() const { return webrtc::TimeDelta::Millis(rto_); }
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// Returns the smoothed RTT value, in milliseconds.
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webrtc::TimeDelta srtt() const {
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return webrtc::TimeDelta::Millis(scaled_srtt_ >> kRttShift);
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}
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private:
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const webrtc::TimeDelta min_rto_;
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const webrtc::TimeDelta max_rto_;
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const webrtc::TimeDelta max_rtt_;
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const int64_t min_rtt_variance_;
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// If this is the first measurement
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bool first_measurement_ = true;
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// Smoothed Round-Trip Time, shifted by kRttShift
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int64_t scaled_srtt_;
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// Round-Trip Time Variation, shifted by kRttVarShift
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int64_t scaled_rtt_var_ = 0;
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// Retransmission Timeout
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int64_t rto_;
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};
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} // namespace dcsctp
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#endif // NET_DCSCTP_TX_RETRANSMISSION_TIMEOUT_H_
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