tor_circmgr/timeouts/
readonly.rs

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1//! Implement a timeout estimator that just uses another process's estimates.
2
3use crate::timeouts::{pareto::ParetoTimeoutState, Action, TimeoutEstimator};
4use std::time::Duration;
5
6/// A timeout estimator based on reading timeouts that another timeout estimator
7/// is computing, in another process.
8pub(crate) struct ReadonlyTimeoutEstimator {
9    /// Are we using the timeouts?
10    using_estimates: bool,
11    /// Latest estimate from the persistent state.
12    latest_timeout: Option<Duration>,
13    /// Timeout to use if we don't have a computed timeout.
14    default_timeout: Duration,
15}
16
17impl ReadonlyTimeoutEstimator {
18    /// Create a new ReadonlyTimeoutEstimator with default settings.
19    pub(crate) fn new() -> Self {
20        ReadonlyTimeoutEstimator {
21            using_estimates: true,
22            latest_timeout: None,
23            default_timeout: Duration::from_secs(60),
24        }
25    }
26
27    /// Create a new ReadonlyTimeoutEstimator, based on persistent state
28    pub(crate) fn from_state(s: &ParetoTimeoutState) -> Self {
29        let mut est = Self::new();
30        est.update_from_state(s);
31        est
32    }
33
34    /// Update this estimator based on a newly read state.
35    pub(crate) fn update_from_state(&mut self, s: &ParetoTimeoutState) {
36        self.latest_timeout = s.latest_estimate();
37    }
38}
39
40impl TimeoutEstimator for ReadonlyTimeoutEstimator {
41    fn note_hop_completed(&mut self, _hop: u8, _delay: Duration, _is_last: bool) {
42        // We don't record any timeouts with this estimator.
43    }
44
45    fn note_circ_timeout(&mut self, _hop: u8, _delay: Duration) {
46        // as above
47    }
48
49    fn timeouts(&mut self, action: &Action) -> (Duration, Duration) {
50        let base = match (self.using_estimates, self.latest_timeout) {
51            (true, Some(d)) => d,
52            (_, _) => self.default_timeout,
53        };
54
55        let reference_action = Action::BuildCircuit { length: 3 };
56        debug_assert!(reference_action.timeout_scale() > 0);
57
58        let multiplier =
59            (action.timeout_scale() as f64) / (reference_action.timeout_scale() as f64);
60
61        use super::mul_duration_f64_saturating as mul;
62        let timeout = mul(base, multiplier);
63
64        // We use the same timeout twice here, since we don't need
65        // separate abandon and timeout thresholds when we are not
66        // recording timeout info.
67        //
68        // TODO: decide whether it is a problem that this might let an
69        // observer know whether our stat is read-only.
70        (timeout, timeout)
71    }
72
73    fn learning_timeouts(&self) -> bool {
74        false
75    }
76
77    fn update_params(&mut self, params: &tor_netdir::params::NetParameters) {
78        self.using_estimates = !bool::from(params.cbt_learning_disabled);
79        self.default_timeout = params
80            .cbt_initial_timeout
81            .try_into()
82            .unwrap_or_else(|_| Duration::from_secs(60));
83    }
84
85    fn build_state(&mut self) -> Option<ParetoTimeoutState> {
86        None
87    }
88}
tor_circmgr/timeouts/readonly.rs

tor_circmgr/timeouts/
readonly.rs
