iroh_quinn_proto/connection/
paths.rs

1use std::{cmp, net::SocketAddr};
2
3use identity_hash::IntMap;
4use thiserror::Error;
5use tracing::{debug, trace};
6
7use super::{
8    PathError, PathStats,
9    mtud::MtuDiscovery,
10    pacing::Pacer,
11    spaces::{PacketNumberSpace, SentPacket},
12};
13use crate::{
14    ConnectionId, Duration, Instant, TIMER_GRANULARITY, TransportConfig, VarInt, coding,
15    congestion, frame::ObservedAddr, packet::SpaceId,
16};
17
18#[cfg(feature = "qlog")]
19use qlog::events::quic::RecoveryMetricsUpdated;
20
21/// Id representing different paths when using multipath extension
22#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Default)]
23pub struct PathId(pub(crate) u32);
24
25impl std::hash::Hash for PathId {
26    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
27        state.write_u32(self.0);
28    }
29}
30
31impl identity_hash::IdentityHashable for PathId {}
32
33impl coding::Codec for PathId {
34    fn decode<B: bytes::Buf>(r: &mut B) -> coding::Result<Self> {
35        let v = VarInt::decode(r)?;
36        let v = u32::try_from(v.0).map_err(|_| coding::UnexpectedEnd)?;
37        Ok(Self(v))
38    }
39
40    fn encode<B: bytes::BufMut>(&self, w: &mut B) {
41        VarInt(self.0.into()).encode(w)
42    }
43}
44
45impl PathId {
46    /// The maximum path ID allowed.
47    pub const MAX: Self = Self(u32::MAX);
48
49    /// The 0 path id.
50    pub const ZERO: Self = Self(0);
51
52    /// The number of bytes this [`PathId`] uses when encoded as a [`VarInt`]
53    pub(crate) const fn size(&self) -> usize {
54        VarInt(self.0 as u64).size()
55    }
56
57    /// Saturating integer addition. Computes self + rhs, saturating at the numeric bounds instead
58    /// of overflowing.
59    pub fn saturating_add(self, rhs: impl Into<Self>) -> Self {
60        let rhs = rhs.into();
61        let inner = self.0.saturating_add(rhs.0);
62        Self(inner)
63    }
64
65    /// Saturating integer subtraction. Computes self - rhs, saturating at the numeric bounds
66    /// instead of overflowing.
67    pub fn saturating_sub(self, rhs: impl Into<Self>) -> Self {
68        let rhs = rhs.into();
69        let inner = self.0.saturating_sub(rhs.0);
70        Self(inner)
71    }
72
73    /// Get the next [`PathId`]
74    pub(crate) fn next(&self) -> Self {
75        self.saturating_add(Self(1))
76    }
77
78    /// Get the underlying u32
79    pub(crate) fn as_u32(&self) -> u32 {
80        self.0
81    }
82}
83
84impl std::fmt::Display for PathId {
85    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
86        self.0.fmt(f)
87    }
88}
89
90impl<T: Into<u32>> From<T> for PathId {
91    fn from(source: T) -> Self {
92        Self(source.into())
93    }
94}
95
96/// State needed for a single path ID.
97///
98/// A single path ID can migrate according to the rules in RFC9000 §9, either voluntary or
99/// involuntary. We need to keep the [`PathData`] of the previously used such path available
100/// in order to defend against migration attacks (see RFC9000 §9.3.1, §9.3.2 and §9.3.3) as
101/// well as to support path probing (RFC9000 §9.1).
102#[derive(Debug)]
103pub(super) struct PathState {
104    pub(super) data: PathData,
105    pub(super) prev: Option<(ConnectionId, PathData)>,
106}
107
108impl PathState {
109    /// Update counters to account for a packet becoming acknowledged, lost, or abandoned
110    pub(super) fn remove_in_flight(&mut self, packet: &SentPacket) {
111        // Visit known paths from newest to oldest to find the one `pn` was sent on
112        for path_data in [&mut self.data]
113            .into_iter()
114            .chain(self.prev.as_mut().map(|(_, data)| data))
115        {
116            if path_data.remove_in_flight(packet) {
117                return;
118            }
119        }
120    }
121}
122
123#[derive(Debug)]
124pub(super) struct SentChallengeInfo {
125    /// When was the challenge sent on the wire.
126    pub(super) sent_instant: Instant,
127    /// The remote to which this path challenge was sent.
128    pub(super) remote: SocketAddr,
129}
130
131/// Description of a particular network path
132#[derive(Debug)]
133pub(super) struct PathData {
134    pub(super) remote: SocketAddr,
135    pub(super) rtt: RttEstimator,
136    /// Whether we're enabling ECN on outgoing packets
137    pub(super) sending_ecn: bool,
138    /// Congestion controller state
139    pub(super) congestion: Box<dyn congestion::Controller>,
140    /// Pacing state
141    pub(super) pacing: Pacer,
142    /// Actually sent challenges (on the wire).
143    pub(super) challenges_sent: IntMap<u64, SentChallengeInfo>,
144    /// Whether to *immediately* trigger another PATH_CHALLENGE (via [`super::Connection::can_send`])
145    pub(super) send_new_challenge: bool,
146    /// Pending responses to PATH_CHALLENGE frames
147    pub(super) path_responses: PathResponses,
148    /// Whether we're certain the peer can both send and receive on this address
149    ///
150    /// Initially equal to `use_stateless_retry` for servers, and becomes false again on every
151    /// migration. Always true for clients.
152    pub(super) validated: bool,
153    /// Total size of all UDP datagrams sent on this path
154    pub(super) total_sent: u64,
155    /// Total size of all UDP datagrams received on this path
156    pub(super) total_recvd: u64,
157    /// The state of the MTU discovery process
158    pub(super) mtud: MtuDiscovery,
159    /// Packet number of the first packet sent after an RTT sample was collected on this path
160    ///
161    /// Used in persistent congestion determination.
162    pub(super) first_packet_after_rtt_sample: Option<(SpaceId, u64)>,
163    /// The in-flight packets and bytes
164    ///
165    /// Note that this is across all spaces on this path
166    pub(super) in_flight: InFlight,
167    /// Whether this path has had it's remote address reported back to the peer. This only happens
168    /// if both peers agree to so based on their transport parameters.
169    pub(super) observed_addr_sent: bool,
170    /// Observed address frame with the largest sequence number received from the peer on this path.
171    pub(super) last_observed_addr_report: Option<ObservedAddr>,
172    /// The QUIC-MULTIPATH path status
173    pub(super) status: PathStatusState,
174    /// Number of the first packet sent on this path
175    ///
176    /// With RFC9000 §9 style migration (i.e. not multipath) the PathId does not change and
177    /// hence packet numbers continue. This is used to determine whether a packet was sent
178    /// on such an earlier path. Insufficient to determine if a packet was sent on a later
179    /// path.
180    first_packet: Option<u64>,
181    /// The number of times a PTO has been sent without receiving an ack.
182    pub(super) pto_count: u32,
183
184    //
185    // Per-path idle & keep alive
186    //
187    /// Idle timeout for the path
188    ///
189    /// If expired, the path will be abandoned.  This is different from the connection-wide
190    /// idle timeout which closes the connection if expired.
191    pub(super) idle_timeout: Option<Duration>,
192    /// Keep alives to send on this path
193    ///
194    /// There is also a connection-level keep alive configured in the
195    /// [`TransportParameters`].  This triggers activity on any path which can keep the
196    /// connection alive.
197    ///
198    /// [`TransportParameters`]: crate::transport_parameters::TransportParameters
199    pub(super) keep_alive: Option<Duration>,
200
201    /// Whether the path has already been considered opened from an application perspective
202    ///
203    /// This means, for paths other than the original [`PathId::ZERO`], a first path challenge has
204    /// been responded to, regardless of the initial validation status of the path. This state is
205    /// irreversible, since it's not affected by the path being closed.
206    pub(super) open: bool,
207
208    /// The time at which this path state should've received a PATH_ABANDON already.
209    ///
210    /// Receiving data on this path generates a transport error after that point in time.
211    /// This is checked in [`crate::Connection::on_packet_authenticated`].
212    ///
213    /// If set to `None`, then this path isn't abandoned yet and is allowed to receive data.
214    pub(super) last_allowed_receive: Option<Instant>,
215
216    /// Snapshot of the qlog recovery metrics
217    #[cfg(feature = "qlog")]
218    recovery_metrics: RecoveryMetrics,
219
220    /// Tag uniquely identifying a path in a connection
221    generation: u64,
222}
223
224impl PathData {
225    pub(super) fn new(
226        remote: SocketAddr,
227        allow_mtud: bool,
228        peer_max_udp_payload_size: Option<u16>,
229        generation: u64,
230        now: Instant,
231        config: &TransportConfig,
232    ) -> Self {
233        let congestion = config
234            .congestion_controller_factory
235            .clone()
236            .build(now, config.get_initial_mtu());
237        Self {
238            remote,
239            rtt: RttEstimator::new(config.initial_rtt),
240            sending_ecn: true,
241            pacing: Pacer::new(
242                config.initial_rtt,
243                congestion.initial_window(),
244                config.get_initial_mtu(),
245                now,
246            ),
247            congestion,
248            challenges_sent: Default::default(),
249            send_new_challenge: false,
250            path_responses: PathResponses::default(),
251            validated: false,
252            total_sent: 0,
253            total_recvd: 0,
254            mtud: config
255                .mtu_discovery_config
256                .as_ref()
257                .filter(|_| allow_mtud)
258                .map_or(
259                    MtuDiscovery::disabled(config.get_initial_mtu(), config.min_mtu),
260                    |mtud_config| {
261                        MtuDiscovery::new(
262                            config.get_initial_mtu(),
263                            config.min_mtu,
264                            peer_max_udp_payload_size,
265                            mtud_config.clone(),
266                        )
267                    },
268                ),
269            first_packet_after_rtt_sample: None,
270            in_flight: InFlight::new(),
271            observed_addr_sent: false,
272            last_observed_addr_report: None,
273            status: Default::default(),
274            first_packet: None,
275            pto_count: 0,
276            idle_timeout: None,
277            keep_alive: None,
278            open: false,
279            last_allowed_receive: None,
280            #[cfg(feature = "qlog")]
281            recovery_metrics: RecoveryMetrics::default(),
282            generation,
283        }
284    }
285
286    /// Create a new path from a previous one.
287    ///
288    /// This should only be called when migrating paths.
289    pub(super) fn from_previous(
290        remote: SocketAddr,
291        prev: &Self,
292        generation: u64,
293        now: Instant,
294    ) -> Self {
295        let congestion = prev.congestion.clone_box();
296        let smoothed_rtt = prev.rtt.get();
297        Self {
298            remote,
299            rtt: prev.rtt,
300            pacing: Pacer::new(smoothed_rtt, congestion.window(), prev.current_mtu(), now),
301            sending_ecn: true,
302            congestion,
303            challenges_sent: Default::default(),
304            send_new_challenge: false,
305            path_responses: PathResponses::default(),
306            validated: false,
307            total_sent: 0,
308            total_recvd: 0,
309            mtud: prev.mtud.clone(),
310            first_packet_after_rtt_sample: prev.first_packet_after_rtt_sample,
311            in_flight: InFlight::new(),
312            observed_addr_sent: false,
313            last_observed_addr_report: None,
314            status: prev.status.clone(),
315            first_packet: None,
316            pto_count: 0,
317            idle_timeout: prev.idle_timeout,
318            keep_alive: prev.keep_alive,
319            open: false,
320            last_allowed_receive: None,
321            #[cfg(feature = "qlog")]
322            recovery_metrics: prev.recovery_metrics.clone(),
323            generation,
324        }
325    }
326
327    /// Whether we're in the process of validating this path with PATH_CHALLENGEs
328    pub(super) fn is_validating_path(&self) -> bool {
329        !self.challenges_sent.is_empty() || self.send_new_challenge
330    }
331
332    /// Indicates whether we're a server that hasn't validated the peer's address and hasn't
333    /// received enough data from the peer to permit sending `bytes_to_send` additional bytes
334    pub(super) fn anti_amplification_blocked(&self, bytes_to_send: u64) -> bool {
335        !self.validated && self.total_recvd * 3 < self.total_sent + bytes_to_send
336    }
337
338    /// Returns the path's current MTU
339    pub(super) fn current_mtu(&self) -> u16 {
340        self.mtud.current_mtu()
341    }
342
343    /// Account for transmission of `packet` with number `pn` in `space`
344    pub(super) fn sent(&mut self, pn: u64, packet: SentPacket, space: &mut PacketNumberSpace) {
345        self.in_flight.insert(&packet);
346        if self.first_packet.is_none() {
347            self.first_packet = Some(pn);
348        }
349        if let Some(forgotten) = space.sent(pn, packet) {
350            self.remove_in_flight(&forgotten);
351        }
352    }
353
354    /// Remove `packet` with number `pn` from this path's congestion control counters, or return
355    /// `false` if `pn` was sent before this path was established.
356    pub(super) fn remove_in_flight(&mut self, packet: &SentPacket) -> bool {
357        if packet.path_generation != self.generation {
358            return false;
359        }
360        self.in_flight.remove(packet);
361        true
362    }
363
364    /// Increment the total size of sent UDP datagrams
365    pub(super) fn inc_total_sent(&mut self, inc: u64) {
366        self.total_sent = self.total_sent.saturating_add(inc);
367        if !self.validated {
368            trace!(
369                remote = %self.remote,
370                anti_amplification_budget = %(self.total_recvd * 3).saturating_sub(self.total_sent),
371                "anti amplification budget decreased"
372            );
373        }
374    }
375
376    /// Increment the total size of received UDP datagrams
377    pub(super) fn inc_total_recvd(&mut self, inc: u64) {
378        self.total_recvd = self.total_recvd.saturating_add(inc);
379        if !self.validated {
380            trace!(
381                remote = %self.remote,
382                anti_amplification_budget = %(self.total_recvd * 3).saturating_sub(self.total_sent),
383                "anti amplification budget increased"
384            );
385        }
386    }
387
388    /// Handle receiving a PATH_RESPONSE.
389    pub(super) fn on_path_response_received(
390        &mut self,
391        now: Instant,
392        token: u64,
393        remote: SocketAddr,
394    ) -> OnPathResponseReceived {
395        match self.challenges_sent.get(&token) {
396            // Response to an on-path PathChallenge
397            Some(info) if info.remote == remote && self.remote == remote => {
398                let sent_instant = info.sent_instant;
399                if !std::mem::replace(&mut self.validated, true) {
400                    trace!("new path validated");
401                }
402                // Clear any other on-path sent challenge.
403                self.challenges_sent
404                    .retain(|_token, info| info.remote != remote);
405
406                self.send_new_challenge = false;
407
408                // This RTT can only be used for the initial RTT, not as a normal
409                // sample: https://www.rfc-editor.org/rfc/rfc9002#section-6.2.2-2.
410                let rtt = now.saturating_duration_since(sent_instant);
411                self.rtt.reset_initial_rtt(rtt);
412
413                let was_open = std::mem::replace(&mut self.open, true);
414                OnPathResponseReceived::OnPath { was_open }
415            }
416            // Response to an off-path PathChallenge
417            Some(info) if info.remote == remote => {
418                self.challenges_sent
419                    .retain(|_token, info| info.remote != remote);
420                OnPathResponseReceived::OffPath
421            }
422            // Response to a PathChallenge we recognize, but from an invalid remote
423            Some(info) => OnPathResponseReceived::Invalid {
424                expected: info.remote,
425            },
426            // Response to an unknown PathChallenge
427            None => OnPathResponseReceived::Unknown,
428        }
429    }
430
431    #[cfg(feature = "qlog")]
432    pub(super) fn qlog_recovery_metrics(
433        &mut self,
434        path_id: PathId,
435    ) -> Option<RecoveryMetricsUpdated> {
436        let controller_metrics = self.congestion.metrics();
437
438        let metrics = RecoveryMetrics {
439            min_rtt: Some(self.rtt.min),
440            smoothed_rtt: Some(self.rtt.get()),
441            latest_rtt: Some(self.rtt.latest),
442            rtt_variance: Some(self.rtt.var),
443            pto_count: Some(self.pto_count),
444            bytes_in_flight: Some(self.in_flight.bytes),
445            packets_in_flight: Some(self.in_flight.ack_eliciting),
446
447            congestion_window: Some(controller_metrics.congestion_window),
448            ssthresh: controller_metrics.ssthresh,
449            pacing_rate: controller_metrics.pacing_rate,
450        };
451
452        let event = metrics.to_qlog_event(path_id, &self.recovery_metrics);
453        self.recovery_metrics = metrics;
454        event
455    }
456
457    /// Return how long we need to wait before sending `bytes_to_send`
458    ///
459    /// See [`Pacer::delay`].
460    pub(super) fn pacing_delay(&mut self, bytes_to_send: u64, now: Instant) -> Option<Instant> {
461        let smoothed_rtt = self.rtt.get();
462        self.pacing.delay(
463            smoothed_rtt,
464            bytes_to_send,
465            self.current_mtu(),
466            self.congestion.window(),
467            now,
468        )
469    }
470
471    /// Updates the last observed address report received on this path.
472    ///
473    /// If the address was updated, it's returned to be informed to the application.
474    #[must_use = "updated observed address must be reported to the application"]
475    pub(super) fn update_observed_addr_report(
476        &mut self,
477        observed: ObservedAddr,
478    ) -> Option<SocketAddr> {
479        match self.last_observed_addr_report.as_mut() {
480            Some(prev) => {
481                if prev.seq_no >= observed.seq_no {
482                    // frames that do not increase the sequence number on this path are ignored
483                    None
484                } else if prev.ip == observed.ip && prev.port == observed.port {
485                    // keep track of the last seq_no but do not report the address as updated
486                    prev.seq_no = observed.seq_no;
487                    None
488                } else {
489                    let addr = observed.socket_addr();
490                    self.last_observed_addr_report = Some(observed);
491                    Some(addr)
492                }
493            }
494            None => {
495                let addr = observed.socket_addr();
496                self.last_observed_addr_report = Some(observed);
497                Some(addr)
498            }
499        }
500    }
501
502    pub(crate) fn remote_status(&self) -> Option<PathStatus> {
503        self.status.remote_status.map(|(_seq, status)| status)
504    }
505
506    pub(crate) fn local_status(&self) -> PathStatus {
507        self.status.local_status
508    }
509
510    pub(super) fn generation(&self) -> u64 {
511        self.generation
512    }
513}
514
515pub(super) enum OnPathResponseReceived {
516    /// This response validates the path on its current remote address.
517    OnPath { was_open: bool },
518    /// This response is valid, but it's for a remote other than the path's current remote address.
519    OffPath,
520    /// The received token is unknown.
521    Unknown,
522    /// The response is invalid.
523    Invalid {
524        /// The remote that was expected for this token.
525        expected: SocketAddr,
526    },
527}
528
529/// Congestion metrics as described in [`recovery_metrics_updated`].
530///
531/// [`recovery_metrics_updated`]: https://datatracker.ietf.org/doc/html/draft-ietf-quic-qlog-quic-events.html#name-recovery_metrics_updated
532#[cfg(feature = "qlog")]
533#[derive(Default, Clone, PartialEq, Debug)]
534#[non_exhaustive]
535struct RecoveryMetrics {
536    pub min_rtt: Option<Duration>,
537    pub smoothed_rtt: Option<Duration>,
538    pub latest_rtt: Option<Duration>,
539    pub rtt_variance: Option<Duration>,
540    pub pto_count: Option<u32>,
541    pub bytes_in_flight: Option<u64>,
542    pub packets_in_flight: Option<u64>,
543    pub congestion_window: Option<u64>,
544    pub ssthresh: Option<u64>,
545    pub pacing_rate: Option<u64>,
546}
547
548#[cfg(feature = "qlog")]
549impl RecoveryMetrics {
550    /// Retain only values that have been updated since the last snapshot.
551    fn retain_updated(&self, previous: &Self) -> Self {
552        macro_rules! keep_if_changed {
553            ($name:ident) => {
554                if previous.$name == self.$name {
555                    None
556                } else {
557                    self.$name
558                }
559            };
560        }
561
562        Self {
563            min_rtt: keep_if_changed!(min_rtt),
564            smoothed_rtt: keep_if_changed!(smoothed_rtt),
565            latest_rtt: keep_if_changed!(latest_rtt),
566            rtt_variance: keep_if_changed!(rtt_variance),
567            pto_count: keep_if_changed!(pto_count),
568            bytes_in_flight: keep_if_changed!(bytes_in_flight),
569            packets_in_flight: keep_if_changed!(packets_in_flight),
570            congestion_window: keep_if_changed!(congestion_window),
571            ssthresh: keep_if_changed!(ssthresh),
572            pacing_rate: keep_if_changed!(pacing_rate),
573        }
574    }
575
576    /// Emit a `MetricsUpdated` event containing only updated values
577    fn to_qlog_event(&self, path_id: PathId, previous: &Self) -> Option<RecoveryMetricsUpdated> {
578        let updated = self.retain_updated(previous);
579
580        if updated == Self::default() {
581            return None;
582        }
583
584        Some(RecoveryMetricsUpdated {
585            min_rtt: updated.min_rtt.map(|rtt| rtt.as_secs_f32()),
586            smoothed_rtt: updated.smoothed_rtt.map(|rtt| rtt.as_secs_f32()),
587            latest_rtt: updated.latest_rtt.map(|rtt| rtt.as_secs_f32()),
588            rtt_variance: updated.rtt_variance.map(|rtt| rtt.as_secs_f32()),
589            pto_count: updated
590                .pto_count
591                .map(|count| count.try_into().unwrap_or(u16::MAX)),
592            bytes_in_flight: updated.bytes_in_flight,
593            packets_in_flight: updated.packets_in_flight,
594            congestion_window: updated.congestion_window,
595            ssthresh: updated.ssthresh,
596            pacing_rate: updated.pacing_rate,
597            path_id: Some(path_id.as_u32() as u64),
598        })
599    }
600}
601
602/// RTT estimation for a particular network path
603#[derive(Copy, Clone, Debug)]
604pub struct RttEstimator {
605    /// The most recent RTT measurement made when receiving an ack for a previously unacked packet
606    latest: Duration,
607    /// The smoothed RTT of the connection, computed as described in RFC6298
608    smoothed: Option<Duration>,
609    /// The RTT variance, computed as described in RFC6298
610    var: Duration,
611    /// The minimum RTT seen in the connection, ignoring ack delay.
612    min: Duration,
613}
614
615impl RttEstimator {
616    pub(super) fn new(initial_rtt: Duration) -> Self {
617        Self {
618            latest: initial_rtt,
619            smoothed: None,
620            var: initial_rtt / 2,
621            min: initial_rtt,
622        }
623    }
624
625    /// Resets the estimator using a new initial_rtt value.
626    ///
627    /// This only resets the initial_rtt **if** no samples have been recorded yet. If there
628    /// are any recorded samples the initial estimate can not be adjusted after the fact.
629    ///
630    /// This is useful when you receive a PATH_RESPONSE in the first packet received on a
631    /// new path. In this case you can use the delay of the PATH_CHALLENGE-PATH_RESPONSE as
632    /// the initial RTT to get a better expected estimation.
633    ///
634    /// A PATH_CHALLENGE-PATH_RESPONSE pair later in the connection should not be used
635    /// explicitly as an estimation since PATH_CHALLENGE is an ACK-eliciting packet itself
636    /// already.
637    pub(crate) fn reset_initial_rtt(&mut self, initial_rtt: Duration) {
638        if self.smoothed.is_none() {
639            self.latest = initial_rtt;
640            self.var = initial_rtt / 2;
641            self.min = initial_rtt;
642        }
643    }
644
645    /// The current best RTT estimation.
646    pub fn get(&self) -> Duration {
647        self.smoothed.unwrap_or(self.latest)
648    }
649
650    /// Conservative estimate of RTT
651    ///
652    /// Takes the maximum of smoothed and latest RTT, as recommended
653    /// in 6.1.2 of the recovery spec (draft 29).
654    pub fn conservative(&self) -> Duration {
655        self.get().max(self.latest)
656    }
657
658    /// Minimum RTT registered so far for this estimator.
659    pub fn min(&self) -> Duration {
660        self.min
661    }
662
663    /// PTO computed as described in RFC9002#6.2.1.
664    pub(crate) fn pto_base(&self) -> Duration {
665        self.get() + cmp::max(4 * self.var, TIMER_GRANULARITY)
666    }
667
668    /// Records an RTT sample.
669    pub(crate) fn update(&mut self, ack_delay: Duration, rtt: Duration) {
670        self.latest = rtt;
671        // https://www.rfc-editor.org/rfc/rfc9002.html#section-5.2-3:
672        // min_rtt does not adjust for ack_delay to avoid underestimating.
673        self.min = cmp::min(self.min, self.latest);
674        // Based on RFC6298.
675        if let Some(smoothed) = self.smoothed {
676            let adjusted_rtt = if self.min + ack_delay <= self.latest {
677                self.latest - ack_delay
678            } else {
679                self.latest
680            };
681            let var_sample = smoothed.abs_diff(adjusted_rtt);
682            self.var = (3 * self.var + var_sample) / 4;
683            self.smoothed = Some((7 * smoothed + adjusted_rtt) / 8);
684        } else {
685            self.smoothed = Some(self.latest);
686            self.var = self.latest / 2;
687            self.min = self.latest;
688        }
689    }
690}
691
692#[derive(Default, Debug)]
693pub(crate) struct PathResponses {
694    pending: Vec<PathResponse>,
695}
696
697impl PathResponses {
698    pub(crate) fn push(&mut self, packet: u64, token: u64, remote: SocketAddr) {
699        /// Arbitrary permissive limit to prevent abuse
700        const MAX_PATH_RESPONSES: usize = 16;
701        let response = PathResponse {
702            packet,
703            token,
704            remote,
705        };
706        let existing = self.pending.iter_mut().find(|x| x.remote == remote);
707        if let Some(existing) = existing {
708            // Update a queued response
709            if existing.packet <= packet {
710                *existing = response;
711            }
712            return;
713        }
714        if self.pending.len() < MAX_PATH_RESPONSES {
715            self.pending.push(response);
716        } else {
717            // We don't expect to ever hit this with well-behaved peers, so we don't bother dropping
718            // older challenges.
719            trace!("ignoring excessive PATH_CHALLENGE");
720        }
721    }
722
723    pub(crate) fn pop_off_path(&mut self, remote: SocketAddr) -> Option<(u64, SocketAddr)> {
724        let response = *self.pending.last()?;
725        if response.remote == remote {
726            // We don't bother searching further because we expect that the on-path response will
727            // get drained in the immediate future by a call to `pop_on_path`
728            return None;
729        }
730        self.pending.pop();
731        Some((response.token, response.remote))
732    }
733
734    pub(crate) fn pop_on_path(&mut self, remote: SocketAddr) -> Option<u64> {
735        let response = *self.pending.last()?;
736        if response.remote != remote {
737            // We don't bother searching further because we expect that the off-path response will
738            // get drained in the immediate future by a call to `pop_off_path`
739            return None;
740        }
741        self.pending.pop();
742        Some(response.token)
743    }
744
745    pub(crate) fn is_empty(&self) -> bool {
746        self.pending.is_empty()
747    }
748}
749
750#[derive(Copy, Clone, Debug)]
751struct PathResponse {
752    /// The packet number the corresponding PATH_CHALLENGE was received in
753    packet: u64,
754    /// The token of the PATH_CHALLENGE
755    token: u64,
756    /// The address the corresponding PATH_CHALLENGE was received from
757    remote: SocketAddr,
758}
759
760/// Summary statistics of packets that have been sent on a particular path, but which have not yet
761/// been acked or deemed lost
762#[derive(Debug)]
763pub(super) struct InFlight {
764    /// Sum of the sizes of all sent packets considered "in flight" by congestion control
765    ///
766    /// The size does not include IP or UDP overhead. Packets only containing ACK frames do not
767    /// count towards this to ensure congestion control does not impede congestion feedback.
768    pub(super) bytes: u64,
769    /// Number of packets in flight containing frames other than ACK and PADDING
770    ///
771    /// This can be 0 even when bytes is not 0 because PADDING frames cause a packet to be
772    /// considered "in flight" by congestion control. However, if this is nonzero, bytes will always
773    /// also be nonzero.
774    pub(super) ack_eliciting: u64,
775}
776
777impl InFlight {
778    fn new() -> Self {
779        Self {
780            bytes: 0,
781            ack_eliciting: 0,
782        }
783    }
784
785    fn insert(&mut self, packet: &SentPacket) {
786        self.bytes += u64::from(packet.size);
787        self.ack_eliciting += u64::from(packet.ack_eliciting);
788    }
789
790    /// Update counters to account for a packet becoming acknowledged, lost, or abandoned
791    fn remove(&mut self, packet: &SentPacket) {
792        self.bytes -= u64::from(packet.size);
793        self.ack_eliciting -= u64::from(packet.ack_eliciting);
794    }
795}
796
797/// State for QUIC-MULTIPATH PATH_STATUS_AVAILABLE and PATH_STATUS_BACKUP frames
798#[derive(Debug, Clone, Default)]
799pub(super) struct PathStatusState {
800    /// The local status
801    local_status: PathStatus,
802    /// Local sequence number, for both PATH_STATUS_AVAILABLE and PATH_STATUS_BACKUP
803    ///
804    /// This is the number of the *next* path status frame to be sent.
805    local_seq: VarInt,
806    /// The status set by the remote
807    remote_status: Option<(VarInt, PathStatus)>,
808}
809
810impl PathStatusState {
811    /// To be called on received PATH_STATUS_AVAILABLE/PATH_STATUS_BACKUP frames
812    pub(super) fn remote_update(&mut self, status: PathStatus, seq: VarInt) {
813        if self.remote_status.is_some_and(|(curr, _)| curr >= seq) {
814            return trace!(%seq, "ignoring path status update");
815        }
816
817        let prev = self.remote_status.replace((seq, status)).map(|(_, s)| s);
818        if prev != Some(status) {
819            debug!(?status, ?seq, "remote changed path status");
820        }
821    }
822
823    /// Updates the local status
824    ///
825    /// If the local status changed, the previous value is returned
826    pub(super) fn local_update(&mut self, status: PathStatus) -> Option<PathStatus> {
827        if self.local_status == status {
828            return None;
829        }
830
831        self.local_seq = self.local_seq.saturating_add(1u8);
832        Some(std::mem::replace(&mut self.local_status, status))
833    }
834
835    pub(crate) fn seq(&self) -> VarInt {
836        self.local_seq
837    }
838}
839
840/// The QUIC-MULTIPATH path status
841///
842/// See section "3.3 Path Status Management":
843/// <https://quicwg.org/multipath/draft-ietf-quic-multipath.html#name-path-status-management>
844#[derive(Debug, Copy, Clone, Default, PartialEq, Eq)]
845pub enum PathStatus {
846    /// Paths marked with as available will be used when scheduling packets
847    ///
848    /// If multiple paths are available, packets will be scheduled on whichever has
849    /// capacity.
850    #[default]
851    Available,
852    /// Paths marked as backup will only be used if there are no available paths
853    ///
854    /// If the max_idle_timeout is specified the path will be kept alive so that it does not
855    /// expire.
856    Backup,
857}
858
859/// Application events about paths
860#[derive(Debug, Clone, PartialEq, Eq)]
861pub enum PathEvent {
862    /// A new path has been opened
863    Opened {
864        /// Which path is now open
865        id: PathId,
866    },
867    /// A path has been closed
868    Closed {
869        /// Which path has been closed
870        id: PathId,
871        /// Error code supplied by the peer
872        /// See <https://www.ietf.org/archive/id/draft-ietf-quic-multipath-14.html#name-error-codes>
873        /// for a list of known errors.
874        error_code: VarInt,
875    },
876    /// All remaining state for a path has been removed
877    ///
878    /// The [`PathEvent::Closed`] would have been emitted for this path earlier.
879    Abandoned {
880        /// Which path had its state dropped
881        id: PathId,
882        /// The final path stats, they are no longer available via [`Connection::stats`]
883        ///
884        /// [`Connection::stats`]: super::Connection::stats
885        path_stats: PathStats,
886    },
887    /// Path was closed locally
888    LocallyClosed {
889        /// Path for which the error occurred
890        id: PathId,
891        /// The error that occurred
892        error: PathError,
893    },
894    /// The remote changed the status of the path
895    ///
896    /// The local status is not changed because of this event. It is up to the application
897    /// to update the local status, which is used for packet scheduling, when the remote
898    /// changes the status.
899    RemoteStatus {
900        /// Path which has changed status
901        id: PathId,
902        /// The new status set by the remote
903        status: PathStatus,
904    },
905    /// Received an observation of our external address from the peer.
906    ObservedAddr {
907        /// Path over which the observed address was reported, [`PathId::ZERO`] when multipath is
908        /// not negotiated
909        id: PathId,
910        /// The address observed by the remote over this path
911        addr: SocketAddr,
912    },
913}
914
915/// Error from setting path status
916#[derive(Debug, Error, Clone, PartialEq, Eq)]
917pub enum SetPathStatusError {
918    /// Error indicating that a path has not been opened or has already been abandoned
919    #[error("closed path")]
920    ClosedPath,
921    /// Error indicating that this operation requires multipath to be negotiated whereas it hasn't been
922    #[error("multipath not negotiated")]
923    MultipathNotNegotiated,
924}
925
926/// Error indicating that a path has not been opened or has already been abandoned
927#[derive(Debug, Default, Error, Clone, PartialEq, Eq)]
928#[error("closed path")]
929pub struct ClosedPath {
930    pub(super) _private: (),
931}
932
933#[cfg(test)]
934mod tests {
935    use super::*;
936
937    #[test]
938    fn test_path_id_saturating_add() {
939        // add within range behaves normally
940        let large: PathId = u16::MAX.into();
941        let next = u32::from(u16::MAX) + 1;
942        assert_eq!(large.saturating_add(1u8), PathId::from(next));
943
944        // outside range saturates
945        assert_eq!(PathId::MAX.saturating_add(1u8), PathId::MAX)
946    }
947}
iroh_quinn_proto/connection/paths.rs

iroh_quinn_proto/connection/
paths.rs
