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    /// When did we last send data.
156    pub(super) last_sent: Option<Instant>,
157    /// Total size of all UDP datagrams received on this path
158    pub(super) total_recvd: u64,
159    /// The state of the MTU discovery process
160    pub(super) mtud: MtuDiscovery,
161    /// Packet number of the first packet sent after an RTT sample was collected on this path
162    ///
163    /// Used in persistent congestion determination.
164    pub(super) first_packet_after_rtt_sample: Option<(SpaceId, u64)>,
165    /// The in-flight packets and bytes
166    ///
167    /// Note that this is across all spaces on this path
168    pub(super) in_flight: InFlight,
169    /// Whether this path has had it's remote address reported back to the peer. This only happens
170    /// if both peers agree to so based on their transport parameters.
171    pub(super) observed_addr_sent: bool,
172    /// Observed address frame with the largest sequence number received from the peer on this path.
173    pub(super) last_observed_addr_report: Option<ObservedAddr>,
174    /// The QUIC-MULTIPATH path status
175    pub(super) status: PathStatusState,
176    /// Number of the first packet sent on this path
177    ///
178    /// With RFC9000 §9 style migration (i.e. not multipath) the PathId does not change and
179    /// hence packet numbers continue. This is used to determine whether a packet was sent
180    /// on such an earlier path. Insufficient to determine if a packet was sent on a later
181    /// path.
182    first_packet: Option<u64>,
183    /// The number of times a PTO has been sent without receiving an ack.
184    pub(super) pto_count: u32,
185
186    //
187    // Per-path idle & keep alive
188    //
189    /// Idle timeout for the path
190    ///
191    /// If expired, the path will be abandoned.  This is different from the connection-wide
192    /// idle timeout which closes the connection if expired.
193    pub(super) idle_timeout: Option<Duration>,
194    /// Keep alives to send on this path
195    ///
196    /// There is also a connection-level keep alive configured in the
197    /// [`TransportParameters`].  This triggers activity on any path which can keep the
198    /// connection alive.
199    ///
200    /// [`TransportParameters`]: crate::transport_parameters::TransportParameters
201    pub(super) keep_alive: Option<Duration>,
202
203    /// Whether the path has already been considered opened from an application perspective
204    ///
205    /// This means, for paths other than the original [`PathId::ZERO`], a first path challenge has
206    /// been responded to, regardless of the initial validation status of the path. This state is
207    /// irreversible, since it's not affected by the path being closed.
208    pub(super) open: bool,
209
210    /// The time at which this path state should've received a PATH_ABANDON already.
211    ///
212    /// Receiving data on this path generates a transport error after that point in time.
213    /// This is checked in [`crate::Connection::on_packet_authenticated`].
214    ///
215    /// If set to `None`, then this path isn't abandoned yet and is allowed to receive data.
216    pub(super) last_allowed_receive: Option<Instant>,
217
218    /// Snapshot of the qlog recovery metrics
219    #[cfg(feature = "qlog")]
220    recovery_metrics: RecoveryMetrics,
221
222    /// Tag uniquely identifying a path in a connection
223    generation: u64,
224}
225
226impl PathData {
227    pub(super) fn new(
228        remote: SocketAddr,
229        allow_mtud: bool,
230        peer_max_udp_payload_size: Option<u16>,
231        generation: u64,
232        now: Instant,
233        config: &TransportConfig,
234    ) -> Self {
235        let congestion = config
236            .congestion_controller_factory
237            .clone()
238            .build(now, config.get_initial_mtu());
239        Self {
240            remote,
241            rtt: RttEstimator::new(config.initial_rtt),
242            sending_ecn: true,
243            pacing: Pacer::new(
244                config.initial_rtt,
245                congestion.initial_window(),
246                config.get_initial_mtu(),
247                now,
248            ),
249            congestion,
250            challenges_sent: Default::default(),
251            send_new_challenge: false,
252            path_responses: PathResponses::default(),
253            validated: false,
254            total_sent: 0,
255            last_sent: None,
256            total_recvd: 0,
257            mtud: config
258                .mtu_discovery_config
259                .as_ref()
260                .filter(|_| allow_mtud)
261                .map_or(
262                    MtuDiscovery::disabled(config.get_initial_mtu(), config.min_mtu),
263                    |mtud_config| {
264                        MtuDiscovery::new(
265                            config.get_initial_mtu(),
266                            config.min_mtu,
267                            peer_max_udp_payload_size,
268                            mtud_config.clone(),
269                        )
270                    },
271                ),
272            first_packet_after_rtt_sample: None,
273            in_flight: InFlight::new(),
274            observed_addr_sent: false,
275            last_observed_addr_report: None,
276            status: Default::default(),
277            first_packet: None,
278            pto_count: 0,
279            idle_timeout: None,
280            keep_alive: None,
281            open: false,
282            last_allowed_receive: None,
283            #[cfg(feature = "qlog")]
284            recovery_metrics: RecoveryMetrics::default(),
285            generation,
286        }
287    }
288
289    /// Create a new path from a previous one.
290    ///
291    /// This should only be called when migrating paths.
292    pub(super) fn from_previous(
293        remote: SocketAddr,
294        prev: &Self,
295        generation: u64,
296        now: Instant,
297    ) -> Self {
298        let congestion = prev.congestion.clone_box();
299        let smoothed_rtt = prev.rtt.get();
300        Self {
301            remote,
302            rtt: prev.rtt,
303            pacing: Pacer::new(smoothed_rtt, congestion.window(), prev.current_mtu(), now),
304            sending_ecn: true,
305            congestion,
306            challenges_sent: Default::default(),
307            send_new_challenge: false,
308            path_responses: PathResponses::default(),
309            validated: false,
310            total_sent: 0,
311            last_sent: None,
312            total_recvd: 0,
313            mtud: prev.mtud.clone(),
314            first_packet_after_rtt_sample: prev.first_packet_after_rtt_sample,
315            in_flight: InFlight::new(),
316            observed_addr_sent: false,
317            last_observed_addr_report: None,
318            status: prev.status.clone(),
319            first_packet: None,
320            pto_count: 0,
321            idle_timeout: prev.idle_timeout,
322            keep_alive: prev.keep_alive,
323            open: false,
324            last_allowed_receive: None,
325            #[cfg(feature = "qlog")]
326            recovery_metrics: prev.recovery_metrics.clone(),
327            generation,
328        }
329    }
330
331    /// Whether we're in the process of validating this path with PATH_CHALLENGEs
332    pub(super) fn is_validating_path(&self) -> bool {
333        !self.challenges_sent.is_empty() || self.send_new_challenge
334    }
335
336    /// Indicates whether we're a server that hasn't validated the peer's address and hasn't
337    /// received enough data from the peer to permit sending `bytes_to_send` additional bytes
338    pub(super) fn anti_amplification_blocked(&self, bytes_to_send: u64) -> bool {
339        !self.validated && self.total_recvd * 3 < self.total_sent + bytes_to_send
340    }
341
342    /// Returns the path's current MTU
343    pub(super) fn current_mtu(&self) -> u16 {
344        self.mtud.current_mtu()
345    }
346
347    /// Account for transmission of `packet` with number `pn` in `space`
348    pub(super) fn sent(
349        &mut self,
350        now: Instant,
351        pn: u64,
352        packet: SentPacket,
353        space: &mut PacketNumberSpace,
354    ) {
355        self.last_sent.replace(now);
356        self.in_flight.insert(&packet);
357        if self.first_packet.is_none() {
358            self.first_packet = Some(pn);
359        }
360        if let Some(forgotten) = space.sent(pn, packet) {
361            self.remove_in_flight(&forgotten);
362        }
363    }
364
365    pub(crate) fn timer_offset(&self, now: Instant, duration: Duration) -> Instant {
366        let start = self.last_sent.unwrap_or(now);
367        let end = start + duration;
368        if end > start {
369            return now;
370        }
371        end
372    }
373
374    /// Remove `packet` with number `pn` from this path's congestion control counters, or return
375    /// `false` if `pn` was sent before this path was established.
376    pub(super) fn remove_in_flight(&mut self, packet: &SentPacket) -> bool {
377        if packet.path_generation != self.generation {
378            return false;
379        }
380        self.in_flight.remove(packet);
381        true
382    }
383
384    /// Increment the total size of sent UDP datagrams
385    pub(super) fn inc_total_sent(&mut self, inc: u64) {
386        self.total_sent = self.total_sent.saturating_add(inc);
387        if !self.validated {
388            trace!(
389                remote = %self.remote,
390                anti_amplification_budget = %(self.total_recvd * 3).saturating_sub(self.total_sent),
391                "anti amplification budget decreased"
392            );
393        }
394    }
395
396    /// Increment the total size of received UDP datagrams
397    pub(super) fn inc_total_recvd(&mut self, inc: u64) {
398        self.total_recvd = self.total_recvd.saturating_add(inc);
399        if !self.validated {
400            trace!(
401                remote = %self.remote,
402                anti_amplification_budget = %(self.total_recvd * 3).saturating_sub(self.total_sent),
403                "anti amplification budget increased"
404            );
405        }
406    }
407
408    /// The earliest time at which a sent challenge is considered lost.
409    pub(super) fn earliest_expiring_challenge(&self) -> Option<Instant> {
410        if self.challenges_sent.is_empty() {
411            return None;
412        }
413        let pto = self.rtt.pto_base();
414        self.challenges_sent
415            .values()
416            .map(|info| info.sent_instant)
417            .min()
418            .map(|sent_instant| sent_instant + pto)
419    }
420
421    /// Handle receiving a PATH_RESPONSE.
422    pub(super) fn on_path_response_received(
423        &mut self,
424        now: Instant,
425        token: u64,
426        remote: SocketAddr,
427    ) -> OnPathResponseReceived {
428        match self.challenges_sent.get(&token) {
429            // Response to an on-path PathChallenge
430            Some(info) if info.remote == remote && self.remote == remote => {
431                let sent_instant = info.sent_instant;
432                if !std::mem::replace(&mut self.validated, true) {
433                    trace!("new path validated");
434                }
435                // Clear any other on-path sent challenge.
436                self.challenges_sent
437                    .retain(|_token, info| info.remote != remote);
438
439                self.send_new_challenge = false;
440
441                // This RTT can only be used for the initial RTT, not as a normal
442                // sample: https://www.rfc-editor.org/rfc/rfc9002#section-6.2.2-2.
443                let rtt = now.saturating_duration_since(sent_instant);
444                self.rtt.reset_initial_rtt(rtt);
445
446                let was_open = std::mem::replace(&mut self.open, true);
447                OnPathResponseReceived::OnPath { was_open }
448            }
449            // Response to an off-path PathChallenge
450            Some(info) if info.remote == remote => {
451                self.challenges_sent
452                    .retain(|_token, info| info.remote != remote);
453                OnPathResponseReceived::OffPath
454            }
455            // Response to a PathChallenge we recognize, but from an invalid remote
456            Some(info) => OnPathResponseReceived::Invalid {
457                expected: info.remote,
458            },
459            // Response to an unknown PathChallenge
460            None => OnPathResponseReceived::Unknown,
461        }
462    }
463
464    #[cfg(feature = "qlog")]
465    pub(super) fn qlog_recovery_metrics(
466        &mut self,
467        path_id: PathId,
468    ) -> Option<RecoveryMetricsUpdated> {
469        let controller_metrics = self.congestion.metrics();
470
471        let metrics = RecoveryMetrics {
472            min_rtt: Some(self.rtt.min),
473            smoothed_rtt: Some(self.rtt.get()),
474            latest_rtt: Some(self.rtt.latest),
475            rtt_variance: Some(self.rtt.var),
476            pto_count: Some(self.pto_count),
477            bytes_in_flight: Some(self.in_flight.bytes),
478            packets_in_flight: Some(self.in_flight.ack_eliciting),
479
480            congestion_window: Some(controller_metrics.congestion_window),
481            ssthresh: controller_metrics.ssthresh,
482            pacing_rate: controller_metrics.pacing_rate,
483        };
484
485        let event = metrics.to_qlog_event(path_id, &self.recovery_metrics);
486        self.recovery_metrics = metrics;
487        event
488    }
489
490    /// Return how long we need to wait before sending `bytes_to_send`
491    ///
492    /// See [`Pacer::delay`].
493    pub(super) fn pacing_delay(&mut self, bytes_to_send: u64, now: Instant) -> Option<Instant> {
494        let smoothed_rtt = self.rtt.get();
495        self.pacing.delay(
496            smoothed_rtt,
497            bytes_to_send,
498            self.current_mtu(),
499            self.congestion.window(),
500            now,
501        )
502    }
503
504    /// Updates the last observed address report received on this path.
505    ///
506    /// If the address was updated, it's returned to be informed to the application.
507    #[must_use = "updated observed address must be reported to the application"]
508    pub(super) fn update_observed_addr_report(
509        &mut self,
510        observed: ObservedAddr,
511    ) -> Option<SocketAddr> {
512        match self.last_observed_addr_report.as_mut() {
513            Some(prev) => {
514                if prev.seq_no >= observed.seq_no {
515                    // frames that do not increase the sequence number on this path are ignored
516                    None
517                } else if prev.ip == observed.ip && prev.port == observed.port {
518                    // keep track of the last seq_no but do not report the address as updated
519                    prev.seq_no = observed.seq_no;
520                    None
521                } else {
522                    let addr = observed.socket_addr();
523                    self.last_observed_addr_report = Some(observed);
524                    Some(addr)
525                }
526            }
527            None => {
528                let addr = observed.socket_addr();
529                self.last_observed_addr_report = Some(observed);
530                Some(addr)
531            }
532        }
533    }
534
535    pub(crate) fn remote_status(&self) -> Option<PathStatus> {
536        self.status.remote_status.map(|(_seq, status)| status)
537    }
538
539    pub(crate) fn local_status(&self) -> PathStatus {
540        self.status.local_status
541    }
542
543    pub(super) fn generation(&self) -> u64 {
544        self.generation
545    }
546}
547
548pub(super) enum OnPathResponseReceived {
549    /// This response validates the path on its current remote address.
550    OnPath { was_open: bool },
551    /// This response is valid, but it's for a remote other than the path's current remote address.
552    OffPath,
553    /// The received token is unknown.
554    Unknown,
555    /// The response is invalid.
556    Invalid {
557        /// The remote that was expected for this token.
558        expected: SocketAddr,
559    },
560}
561
562/// Congestion metrics as described in [`recovery_metrics_updated`].
563///
564/// [`recovery_metrics_updated`]: https://datatracker.ietf.org/doc/html/draft-ietf-quic-qlog-quic-events.html#name-recovery_metrics_updated
565#[cfg(feature = "qlog")]
566#[derive(Default, Clone, PartialEq, Debug)]
567#[non_exhaustive]
568struct RecoveryMetrics {
569    pub min_rtt: Option<Duration>,
570    pub smoothed_rtt: Option<Duration>,
571    pub latest_rtt: Option<Duration>,
572    pub rtt_variance: Option<Duration>,
573    pub pto_count: Option<u32>,
574    pub bytes_in_flight: Option<u64>,
575    pub packets_in_flight: Option<u64>,
576    pub congestion_window: Option<u64>,
577    pub ssthresh: Option<u64>,
578    pub pacing_rate: Option<u64>,
579}
580
581#[cfg(feature = "qlog")]
582impl RecoveryMetrics {
583    /// Retain only values that have been updated since the last snapshot.
584    fn retain_updated(&self, previous: &Self) -> Self {
585        macro_rules! keep_if_changed {
586            ($name:ident) => {
587                if previous.$name == self.$name {
588                    None
589                } else {
590                    self.$name
591                }
592            };
593        }
594
595        Self {
596            min_rtt: keep_if_changed!(min_rtt),
597            smoothed_rtt: keep_if_changed!(smoothed_rtt),
598            latest_rtt: keep_if_changed!(latest_rtt),
599            rtt_variance: keep_if_changed!(rtt_variance),
600            pto_count: keep_if_changed!(pto_count),
601            bytes_in_flight: keep_if_changed!(bytes_in_flight),
602            packets_in_flight: keep_if_changed!(packets_in_flight),
603            congestion_window: keep_if_changed!(congestion_window),
604            ssthresh: keep_if_changed!(ssthresh),
605            pacing_rate: keep_if_changed!(pacing_rate),
606        }
607    }
608
609    /// Emit a `MetricsUpdated` event containing only updated values
610    fn to_qlog_event(&self, path_id: PathId, previous: &Self) -> Option<RecoveryMetricsUpdated> {
611        let updated = self.retain_updated(previous);
612
613        if updated == Self::default() {
614            return None;
615        }
616
617        Some(RecoveryMetricsUpdated {
618            min_rtt: updated.min_rtt.map(|rtt| rtt.as_secs_f32()),
619            smoothed_rtt: updated.smoothed_rtt.map(|rtt| rtt.as_secs_f32()),
620            latest_rtt: updated.latest_rtt.map(|rtt| rtt.as_secs_f32()),
621            rtt_variance: updated.rtt_variance.map(|rtt| rtt.as_secs_f32()),
622            pto_count: updated
623                .pto_count
624                .map(|count| count.try_into().unwrap_or(u16::MAX)),
625            bytes_in_flight: updated.bytes_in_flight,
626            packets_in_flight: updated.packets_in_flight,
627            congestion_window: updated.congestion_window,
628            ssthresh: updated.ssthresh,
629            pacing_rate: updated.pacing_rate,
630            path_id: Some(path_id.as_u32() as u64),
631        })
632    }
633}
634
635/// RTT estimation for a particular network path
636#[derive(Copy, Clone, Debug)]
637pub struct RttEstimator {
638    /// The most recent RTT measurement made when receiving an ack for a previously unacked packet
639    latest: Duration,
640    /// The smoothed RTT of the connection, computed as described in RFC6298
641    smoothed: Option<Duration>,
642    /// The RTT variance, computed as described in RFC6298
643    var: Duration,
644    /// The minimum RTT seen in the connection, ignoring ack delay.
645    min: Duration,
646}
647
648impl RttEstimator {
649    pub(super) fn new(initial_rtt: Duration) -> Self {
650        Self {
651            latest: initial_rtt,
652            smoothed: None,
653            var: initial_rtt / 2,
654            min: initial_rtt,
655        }
656    }
657
658    /// Resets the estimator using a new initial_rtt value.
659    ///
660    /// This only resets the initial_rtt **if** no samples have been recorded yet. If there
661    /// are any recorded samples the initial estimate can not be adjusted after the fact.
662    ///
663    /// This is useful when you receive a PATH_RESPONSE in the first packet received on a
664    /// new path. In this case you can use the delay of the PATH_CHALLENGE-PATH_RESPONSE as
665    /// the initial RTT to get a better expected estimation.
666    ///
667    /// A PATH_CHALLENGE-PATH_RESPONSE pair later in the connection should not be used
668    /// explicitly as an estimation since PATH_CHALLENGE is an ACK-eliciting packet itself
669    /// already.
670    pub(crate) fn reset_initial_rtt(&mut self, initial_rtt: Duration) {
671        if self.smoothed.is_none() {
672            self.latest = initial_rtt;
673            self.var = initial_rtt / 2;
674            self.min = initial_rtt;
675        }
676    }
677
678    /// The current best RTT estimation.
679    pub fn get(&self) -> Duration {
680        self.smoothed.unwrap_or(self.latest)
681    }
682
683    /// Conservative estimate of RTT
684    ///
685    /// Takes the maximum of smoothed and latest RTT, as recommended
686    /// in 6.1.2 of the recovery spec (draft 29).
687    pub fn conservative(&self) -> Duration {
688        self.get().max(self.latest)
689    }
690
691    /// Minimum RTT registered so far for this estimator.
692    pub fn min(&self) -> Duration {
693        self.min
694    }
695
696    /// PTO computed as described in RFC9002#6.2.1.
697    pub(crate) fn pto_base(&self) -> Duration {
698        self.get() + cmp::max(4 * self.var, TIMER_GRANULARITY)
699    }
700
701    /// Records an RTT sample.
702    pub(crate) fn update(&mut self, ack_delay: Duration, rtt: Duration) {
703        self.latest = rtt;
704        // https://www.rfc-editor.org/rfc/rfc9002.html#section-5.2-3:
705        // min_rtt does not adjust for ack_delay to avoid underestimating.
706        self.min = cmp::min(self.min, self.latest);
707        // Based on RFC6298.
708        if let Some(smoothed) = self.smoothed {
709            let adjusted_rtt = if self.min + ack_delay <= self.latest {
710                self.latest - ack_delay
711            } else {
712                self.latest
713            };
714            let var_sample = smoothed.abs_diff(adjusted_rtt);
715            self.var = (3 * self.var + var_sample) / 4;
716            self.smoothed = Some((7 * smoothed + adjusted_rtt) / 8);
717        } else {
718            self.smoothed = Some(self.latest);
719            self.var = self.latest / 2;
720            self.min = self.latest;
721        }
722    }
723}
724
725#[derive(Default, Debug)]
726pub(crate) struct PathResponses {
727    pending: Vec<PathResponse>,
728}
729
730impl PathResponses {
731    pub(crate) fn push(&mut self, packet: u64, token: u64, remote: SocketAddr) {
732        /// Arbitrary permissive limit to prevent abuse
733        const MAX_PATH_RESPONSES: usize = 16;
734        let response = PathResponse {
735            packet,
736            token,
737            remote,
738        };
739        let existing = self.pending.iter_mut().find(|x| x.remote == remote);
740        if let Some(existing) = existing {
741            // Update a queued response
742            if existing.packet <= packet {
743                *existing = response;
744            }
745            return;
746        }
747        if self.pending.len() < MAX_PATH_RESPONSES {
748            self.pending.push(response);
749        } else {
750            // We don't expect to ever hit this with well-behaved peers, so we don't bother dropping
751            // older challenges.
752            trace!("ignoring excessive PATH_CHALLENGE");
753        }
754    }
755
756    pub(crate) fn pop_off_path(&mut self, remote: SocketAddr) -> Option<(u64, SocketAddr)> {
757        let response = *self.pending.last()?;
758        if response.remote == remote {
759            // We don't bother searching further because we expect that the on-path response will
760            // get drained in the immediate future by a call to `pop_on_path`
761            return None;
762        }
763        self.pending.pop();
764        Some((response.token, response.remote))
765    }
766
767    pub(crate) fn pop_on_path(&mut self, remote: SocketAddr) -> Option<u64> {
768        let response = *self.pending.last()?;
769        if response.remote != remote {
770            // We don't bother searching further because we expect that the off-path response will
771            // get drained in the immediate future by a call to `pop_off_path`
772            return None;
773        }
774        self.pending.pop();
775        Some(response.token)
776    }
777
778    pub(crate) fn is_empty(&self) -> bool {
779        self.pending.is_empty()
780    }
781}
782
783#[derive(Copy, Clone, Debug)]
784struct PathResponse {
785    /// The packet number the corresponding PATH_CHALLENGE was received in
786    packet: u64,
787    /// The token of the PATH_CHALLENGE
788    token: u64,
789    /// The address the corresponding PATH_CHALLENGE was received from
790    remote: SocketAddr,
791}
792
793/// Summary statistics of packets that have been sent on a particular path, but which have not yet
794/// been acked or deemed lost
795#[derive(Debug)]
796pub(super) struct InFlight {
797    /// Sum of the sizes of all sent packets considered "in flight" by congestion control
798    ///
799    /// The size does not include IP or UDP overhead. Packets only containing ACK frames do not
800    /// count towards this to ensure congestion control does not impede congestion feedback.
801    pub(super) bytes: u64,
802    /// Number of packets in flight containing frames other than ACK and PADDING
803    ///
804    /// This can be 0 even when bytes is not 0 because PADDING frames cause a packet to be
805    /// considered "in flight" by congestion control. However, if this is nonzero, bytes will always
806    /// also be nonzero.
807    pub(super) ack_eliciting: u64,
808}
809
810impl InFlight {
811    fn new() -> Self {
812        Self {
813            bytes: 0,
814            ack_eliciting: 0,
815        }
816    }
817
818    fn insert(&mut self, packet: &SentPacket) {
819        self.bytes += u64::from(packet.size);
820        self.ack_eliciting += u64::from(packet.ack_eliciting);
821    }
822
823    /// Update counters to account for a packet becoming acknowledged, lost, or abandoned
824    fn remove(&mut self, packet: &SentPacket) {
825        self.bytes -= u64::from(packet.size);
826        self.ack_eliciting -= u64::from(packet.ack_eliciting);
827    }
828}
829
830/// State for QUIC-MULTIPATH PATH_STATUS_AVAILABLE and PATH_STATUS_BACKUP frames
831#[derive(Debug, Clone, Default)]
832pub(super) struct PathStatusState {
833    /// The local status
834    local_status: PathStatus,
835    /// Local sequence number, for both PATH_STATUS_AVAILABLE and PATH_STATUS_BACKUP
836    ///
837    /// This is the number of the *next* path status frame to be sent.
838    local_seq: VarInt,
839    /// The status set by the remote
840    remote_status: Option<(VarInt, PathStatus)>,
841}
842
843impl PathStatusState {
844    /// To be called on received PATH_STATUS_AVAILABLE/PATH_STATUS_BACKUP frames
845    pub(super) fn remote_update(&mut self, status: PathStatus, seq: VarInt) {
846        if self.remote_status.is_some_and(|(curr, _)| curr >= seq) {
847            return trace!(%seq, "ignoring path status update");
848        }
849
850        let prev = self.remote_status.replace((seq, status)).map(|(_, s)| s);
851        if prev != Some(status) {
852            debug!(?status, ?seq, "remote changed path status");
853        }
854    }
855
856    /// Updates the local status
857    ///
858    /// If the local status changed, the previous value is returned
859    pub(super) fn local_update(&mut self, status: PathStatus) -> Option<PathStatus> {
860        if self.local_status == status {
861            return None;
862        }
863
864        self.local_seq = self.local_seq.saturating_add(1u8);
865        Some(std::mem::replace(&mut self.local_status, status))
866    }
867
868    pub(crate) fn seq(&self) -> VarInt {
869        self.local_seq
870    }
871}
872
873/// The QUIC-MULTIPATH path status
874///
875/// See section "3.3 Path Status Management":
876/// <https://quicwg.org/multipath/draft-ietf-quic-multipath.html#name-path-status-management>
877#[derive(Debug, Copy, Clone, Default, PartialEq, Eq)]
878pub enum PathStatus {
879    /// Paths marked with as available will be used when scheduling packets
880    ///
881    /// If multiple paths are available, packets will be scheduled on whichever has
882    /// capacity.
883    #[default]
884    Available,
885    /// Paths marked as backup will only be used if there are no available paths
886    ///
887    /// If the max_idle_timeout is specified the path will be kept alive so that it does not
888    /// expire.
889    Backup,
890}
891
892/// Application events about paths
893#[derive(Debug, Clone, PartialEq, Eq)]
894pub enum PathEvent {
895    /// A new path has been opened
896    Opened {
897        /// Which path is now open
898        id: PathId,
899    },
900    /// A path has been closed
901    Closed {
902        /// Which path has been closed
903        id: PathId,
904        /// Error code supplied by the peer
905        /// See <https://www.ietf.org/archive/id/draft-ietf-quic-multipath-14.html#name-error-codes>
906        /// for a list of known errors.
907        error_code: VarInt,
908    },
909    /// All remaining state for a path has been removed
910    ///
911    /// The [`PathEvent::Closed`] would have been emitted for this path earlier.
912    Abandoned {
913        /// Which path had its state dropped
914        id: PathId,
915        /// The final path stats, they are no longer available via [`Connection::stats`]
916        ///
917        /// [`Connection::stats`]: super::Connection::stats
918        path_stats: PathStats,
919    },
920    /// Path was closed locally
921    LocallyClosed {
922        /// Path for which the error occurred
923        id: PathId,
924        /// The error that occurred
925        error: PathError,
926    },
927    /// The remote changed the status of the path
928    ///
929    /// The local status is not changed because of this event. It is up to the application
930    /// to update the local status, which is used for packet scheduling, when the remote
931    /// changes the status.
932    RemoteStatus {
933        /// Path which has changed status
934        id: PathId,
935        /// The new status set by the remote
936        status: PathStatus,
937    },
938    /// Received an observation of our external address from the peer.
939    ObservedAddr {
940        /// Path over which the observed address was reported, [`PathId::ZERO`] when multipath is
941        /// not negotiated
942        id: PathId,
943        /// The address observed by the remote over this path
944        addr: SocketAddr,
945    },
946}
947
948/// Error from setting path status
949#[derive(Debug, Error, Clone, PartialEq, Eq)]
950pub enum SetPathStatusError {
951    /// Error indicating that a path has not been opened or has already been abandoned
952    #[error("closed path")]
953    ClosedPath,
954    /// Error indicating that this operation requires multipath to be negotiated whereas it hasn't been
955    #[error("multipath not negotiated")]
956    MultipathNotNegotiated,
957}
958
959/// Error indicating that a path has not been opened or has already been abandoned
960#[derive(Debug, Default, Error, Clone, PartialEq, Eq)]
961#[error("closed path")]
962pub struct ClosedPath {
963    pub(super) _private: (),
964}
965
966#[cfg(test)]
967mod tests {
968    use super::*;
969
970    #[test]
971    fn test_path_id_saturating_add() {
972        // add within range behaves normally
973        let large: PathId = u16::MAX.into();
974        let next = u32::from(u16::MAX) + 1;
975        assert_eq!(large.saturating_add(1u8), PathId::from(next));
976
977        // outside range saturates
978        assert_eq!(PathId::MAX.saturating_add(1u8), PathId::MAX)
979    }
980}
iroh_quinn_proto/connection/paths.rs

iroh_quinn_proto/connection/
paths.rs
