63 lines
2.0 KiB
C++
63 lines
2.0 KiB
C++
/*
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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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#include "net/dcsctp/tx/retransmission_timeout.h"
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#include <algorithm>
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#include <cstdint>
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#include "net/dcsctp/public/dcsctp_options.h"
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namespace dcsctp {
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RetransmissionTimeout::RetransmissionTimeout(const DcSctpOptions& options)
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: min_rto_(*options.rto_min),
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max_rto_(*options.rto_max),
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max_rtt_(*options.rtt_max),
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min_rtt_variance_(*options.min_rtt_variance),
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rto_(*options.rto_initial) {}
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void RetransmissionTimeout::ObserveRTT(DurationMs measured_rtt) {
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const int32_t rtt = *measured_rtt;
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// Unrealistic values will be skipped. If a wrongly measured (or otherwise
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// corrupt) value was processed, it could change the state in a way that would
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// take a very long time to recover.
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if (rtt < 0 || rtt > max_rtt_) {
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return;
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}
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// From https://tools.ietf.org/html/rfc4960#section-6.3.1, but avoiding
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// floating point math by implementing algorithm from "V. Jacobson: Congestion
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// avoidance and control", but adapted for SCTP.
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if (first_measurement_) {
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scaled_srtt_ = rtt << kRttShift;
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scaled_rtt_var_ = (rtt / 2) << kRttVarShift;
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first_measurement_ = false;
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} else {
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int32_t rtt_diff = rtt - (scaled_srtt_ >> kRttShift);
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scaled_srtt_ += rtt_diff;
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if (rtt_diff < 0) {
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rtt_diff = -rtt_diff;
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}
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rtt_diff -= (scaled_rtt_var_ >> kRttVarShift);
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scaled_rtt_var_ += rtt_diff;
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}
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if (scaled_rtt_var_ < min_rtt_variance_) {
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scaled_rtt_var_ = min_rtt_variance_;
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}
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rto_ = (scaled_srtt_ >> kRttShift) + scaled_rtt_var_;
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// Clamp RTO between min and max.
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rto_ = std::min(std::max(rto_, min_rto_), max_rto_);
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}
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} // namespace dcsctp
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