quiche/recovery/gcongestion/bbr2/
drain.rs

1// Copyright (c) 2015 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5// Copyright (C) 2023, Cloudflare, Inc.
6// All rights reserved.
7//
8// Redistribution and use in source and binary forms, with or without
9// modification, are permitted provided that the following conditions are
10// met:
11//
12//     * Redistributions of source code must retain the above copyright notice,
13//       this list of conditions and the following disclaimer.
14//
15//     * Redistributions in binary form must reproduce the above copyright
16//       notice, this list of conditions and the following disclaimer in the
17//       documentation and/or other materials provided with the distribution.
18//
19// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
20// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
21// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
23// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
24// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
25// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
26// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
27// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
28// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
29// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30
31use std::time::Instant;
32
33use crate::recovery::gcongestion::Acked;
34use crate::recovery::gcongestion::Lost;
35
36use super::mode::Cycle;
37use super::mode::Mode;
38use super::mode::ModeImpl;
39use super::network_model::BBRv2NetworkModel;
40use super::BBRv2CongestionEvent;
41use super::Limits;
42use super::PARAMS;
43
44#[derive(Debug)]
45pub(super) struct Drain {
46    pub(super) model: BBRv2NetworkModel,
47    pub(super) cycle: Cycle,
48}
49
50impl ModeImpl for Drain {
51    fn is_probing_for_bandwidth(&self) -> bool {
52        false
53    }
54
55    fn on_congestion_event(
56        mut self, _prior_in_flight: usize, event_time: Instant,
57        _acked_packets: &[Acked], _lost_packets: &[Lost],
58        congestion_event: &mut BBRv2CongestionEvent,
59        _target_bytes_inflight: usize,
60    ) -> Mode {
61        self.model.set_pacing_gain(PARAMS.drain_pacing_gain);
62        // Only STARTUP can transition to DRAIN, both of them use the same cwnd
63        // gain.
64        self.model.set_cwnd_gain(PARAMS.drain_cwnd_gain);
65
66        let drain_target = self.drain_target();
67        if congestion_event.bytes_in_flight <= drain_target {
68            return self.into_probe_bw(event_time, Some(congestion_event));
69        }
70
71        Mode::Drain(self)
72    }
73
74    fn get_cwnd_limits(&self) -> Limits<usize> {
75        Limits {
76            lo: 0,
77            hi: self.model.inflight_lo(),
78        }
79    }
80
81    fn on_exit_quiescence(
82        self, _now: Instant, _quiescence_start_time: Instant,
83    ) -> Mode {
84        Mode::Drain(self)
85    }
86
87    fn enter(&mut self, _: Instant, _: Option<&BBRv2CongestionEvent>) {}
88
89    fn leave(&mut self, _: Instant, _: Option<&BBRv2CongestionEvent>) {}
90}
91
92impl Drain {
93    fn into_probe_bw(
94        mut self, now: Instant, congestion_event: Option<&BBRv2CongestionEvent>,
95    ) -> Mode {
96        self.leave(now, congestion_event);
97        let mut next_mode = Mode::probe_bw(self.model, self.cycle);
98        next_mode.enter(now, congestion_event);
99        next_mode
100    }
101
102    fn drain_target(&self) -> usize {
103        self.model.bdp0()
104    }
105}
quiche/recovery/gcongestion/bbr2/drain.rs

quiche/recovery/gcongestion/bbr2/
drain.rs
