quinn_proto/
endpoint.rs

1use std::{
2    collections::{HashMap, hash_map},
3    convert::TryFrom,
4    fmt, mem,
5    net::{IpAddr, SocketAddr},
6    ops::{Index, IndexMut},
7    sync::Arc,
8};
9
10use bytes::{BufMut, Bytes, BytesMut};
11use rand::{Rng, RngCore, SeedableRng, rngs::StdRng};
12use rustc_hash::FxHashMap;
13use slab::Slab;
14use thiserror::Error;
15use tracing::{debug, error, trace, warn};
16
17use crate::{
18    Duration, INITIAL_MTU, Instant, MAX_CID_SIZE, MIN_INITIAL_SIZE, RESET_TOKEN_SIZE, ResetToken,
19    Side, Transmit, TransportConfig, TransportError,
20    cid_generator::ConnectionIdGenerator,
21    coding::BufMutExt,
22    config::{ClientConfig, EndpointConfig, ServerConfig},
23    connection::{Connection, ConnectionError, SideArgs},
24    crypto::{self, Keys, UnsupportedVersion},
25    frame,
26    packet::{
27        FixedLengthConnectionIdParser, Header, InitialHeader, InitialPacket, PacketDecodeError,
28        PacketNumber, PartialDecode, ProtectedInitialHeader,
29    },
30    shared::{
31        ConnectionEvent, ConnectionEventInner, ConnectionId, DatagramConnectionEvent, EcnCodepoint,
32        EndpointEvent, EndpointEventInner, IssuedCid,
33    },
34    token::{IncomingToken, InvalidRetryTokenError, Token, TokenPayload},
35    transport_parameters::{PreferredAddress, TransportParameters},
36};
37
38/// The main entry point to the library
39///
40/// This object performs no I/O whatsoever. Instead, it consumes incoming packets and
41/// connection-generated events via `handle` and `handle_event`.
42pub struct Endpoint {
43    rng: StdRng,
44    index: ConnectionIndex,
45    connections: Slab<ConnectionMeta>,
46    local_cid_generator: Box<dyn ConnectionIdGenerator>,
47    config: Arc<EndpointConfig>,
48    server_config: Option<Arc<ServerConfig>>,
49    /// Whether the underlying UDP socket promises not to fragment packets
50    allow_mtud: bool,
51    /// Time at which a stateless reset was most recently sent
52    last_stateless_reset: Option<Instant>,
53    /// Buffered Initial and 0-RTT messages for pending incoming connections
54    incoming_buffers: Slab<IncomingBuffer>,
55    all_incoming_buffers_total_bytes: u64,
56}
57
58impl Endpoint {
59    /// Create a new endpoint
60    ///
61    /// `allow_mtud` enables path MTU detection when requested by `Connection` configuration for
62    /// better performance. This requires that outgoing packets are never fragmented, which can be
63    /// achieved via e.g. the `IPV6_DONTFRAG` socket option.
64    ///
65    /// If `rng_seed` is provided, it will be used to initialize the endpoint's rng (having priority
66    /// over the rng seed configured in [`EndpointConfig`]). Note that the `rng_seed` parameter will
67    /// be removed in a future release, so prefer setting it to `None` and configuring rng seeds
68    /// using [`EndpointConfig::rng_seed`].
69    pub fn new(
70        config: Arc<EndpointConfig>,
71        server_config: Option<Arc<ServerConfig>>,
72        allow_mtud: bool,
73        rng_seed: Option<[u8; 32]>,
74    ) -> Self {
75        let rng_seed = rng_seed.or(config.rng_seed);
76        Self {
77            rng: rng_seed.map_or(StdRng::from_os_rng(), StdRng::from_seed),
78            index: ConnectionIndex::default(),
79            connections: Slab::new(),
80            local_cid_generator: (config.connection_id_generator_factory.as_ref())(),
81            config,
82            server_config,
83            allow_mtud,
84            last_stateless_reset: None,
85            incoming_buffers: Slab::new(),
86            all_incoming_buffers_total_bytes: 0,
87        }
88    }
89
90    /// Replace the server configuration, affecting new incoming connections only
91    pub fn set_server_config(&mut self, server_config: Option<Arc<ServerConfig>>) {
92        self.server_config = server_config;
93    }
94
95    /// Process `EndpointEvent`s emitted from related `Connection`s
96    ///
97    /// In turn, processing this event may return a `ConnectionEvent` for the same `Connection`.
98    pub fn handle_event(
99        &mut self,
100        ch: ConnectionHandle,
101        event: EndpointEvent,
102    ) -> Option<ConnectionEvent> {
103        use EndpointEventInner::*;
104        match event.0 {
105            NeedIdentifiers(now, n) => {
106                return Some(self.send_new_identifiers(now, ch, n));
107            }
108            ResetToken(remote, token) => {
109                if let Some(old) = self.connections[ch].reset_token.replace((remote, token)) {
110                    self.index.connection_reset_tokens.remove(old.0, old.1);
111                }
112                if self.index.connection_reset_tokens.insert(remote, token, ch) {
113                    warn!("duplicate reset token");
114                }
115            }
116            RetireConnectionId(now, seq, allow_more_cids) => {
117                if let Some(cid) = self.connections[ch].loc_cids.remove(&seq) {
118                    trace!("peer retired CID {}: {}", seq, cid);
119                    self.index.retire(cid);
120                    if allow_more_cids {
121                        return Some(self.send_new_identifiers(now, ch, 1));
122                    }
123                }
124            }
125            Drained => {
126                if let Some(conn) = self.connections.try_remove(ch.0) {
127                    self.index.remove(&conn);
128                } else {
129                    // This indicates a bug in downstream code, which could cause spurious
130                    // connection loss instead of this error if the CID was (re)allocated prior to
131                    // the illegal call.
132                    error!(id = ch.0, "unknown connection drained");
133                }
134            }
135        }
136        None
137    }
138
139    /// Process an incoming UDP datagram
140    pub fn handle(
141        &mut self,
142        now: Instant,
143        remote: SocketAddr,
144        local_ip: Option<IpAddr>,
145        ecn: Option<EcnCodepoint>,
146        data: BytesMut,
147        buf: &mut Vec<u8>,
148    ) -> Option<DatagramEvent> {
149        // Partially decode packet or short-circuit if unable
150        let datagram_len = data.len();
151        let event = match PartialDecode::new(
152            data,
153            &FixedLengthConnectionIdParser::new(self.local_cid_generator.cid_len()),
154            &self.config.supported_versions,
155            self.config.grease_quic_bit,
156        ) {
157            Ok((first_decode, remaining)) => DatagramConnectionEvent {
158                now,
159                remote,
160                ecn,
161                first_decode,
162                remaining,
163            },
164            Err(PacketDecodeError::UnsupportedVersion {
165                src_cid,
166                dst_cid,
167                version,
168            }) => {
169                if self.server_config.is_none() {
170                    debug!("dropping packet with unsupported version");
171                    return None;
172                }
173                trace!("sending version negotiation");
174                // Negotiate versions
175                Header::VersionNegotiate {
176                    random: self.rng.random::<u8>() | 0x40,
177                    src_cid: dst_cid,
178                    dst_cid: src_cid,
179                }
180                .encode(buf);
181                // Grease with a reserved version
182                buf.write::<u32>(match version {
183                    0x0a1a_2a3a => 0x0a1a_2a4a,
184                    _ => 0x0a1a_2a3a,
185                });
186                for &version in &self.config.supported_versions {
187                    buf.write(version);
188                }
189                return Some(DatagramEvent::Response(Transmit {
190                    destination: remote,
191                    ecn: None,
192                    size: buf.len(),
193                    segment_size: None,
194                    src_ip: local_ip,
195                }));
196            }
197            Err(e) => {
198                trace!("malformed header: {}", e);
199                return None;
200            }
201        };
202
203        let addresses = FourTuple { remote, local_ip };
204        let dst_cid = event.first_decode.dst_cid();
205
206        if let Some(route_to) = self.index.get(&addresses, &event.first_decode) {
207            // Handle packet on existing connection
208            match route_to {
209                RouteDatagramTo::Incoming(incoming_idx) => {
210                    let incoming_buffer = &mut self.incoming_buffers[incoming_idx];
211                    let config = &self.server_config.as_ref().unwrap();
212
213                    if incoming_buffer
214                        .total_bytes
215                        .checked_add(datagram_len as u64)
216                        .is_some_and(|n| n <= config.incoming_buffer_size)
217                        && self
218                            .all_incoming_buffers_total_bytes
219                            .checked_add(datagram_len as u64)
220                            .is_some_and(|n| n <= config.incoming_buffer_size_total)
221                    {
222                        incoming_buffer.datagrams.push(event);
223                        incoming_buffer.total_bytes += datagram_len as u64;
224                        self.all_incoming_buffers_total_bytes += datagram_len as u64;
225                    }
226
227                    None
228                }
229                RouteDatagramTo::Connection(ch) => Some(DatagramEvent::ConnectionEvent(
230                    ch,
231                    ConnectionEvent(ConnectionEventInner::Datagram(event)),
232                )),
233            }
234        } else if event.first_decode.initial_header().is_some() {
235            // Potentially create a new connection
236
237            self.handle_first_packet(datagram_len, event, addresses, buf)
238        } else if event.first_decode.has_long_header() {
239            debug!(
240                "ignoring non-initial packet for unknown connection {}",
241                dst_cid
242            );
243            None
244        } else if !event.first_decode.is_initial()
245            && self.local_cid_generator.validate(dst_cid).is_err()
246        {
247            // If we got this far, we're receiving a seemingly valid packet for an unknown
248            // connection. Send a stateless reset if possible.
249
250            debug!("dropping packet with invalid CID");
251            None
252        } else if dst_cid.is_empty() {
253            trace!("dropping unrecognized short packet without ID");
254            None
255        } else {
256            self.stateless_reset(now, datagram_len, addresses, *dst_cid, buf)
257                .map(DatagramEvent::Response)
258        }
259    }
260
261    fn stateless_reset(
262        &mut self,
263        now: Instant,
264        inciting_dgram_len: usize,
265        addresses: FourTuple,
266        dst_cid: ConnectionId,
267        buf: &mut Vec<u8>,
268    ) -> Option<Transmit> {
269        if self
270            .last_stateless_reset
271            .is_some_and(|last| last + self.config.min_reset_interval > now)
272        {
273            debug!("ignoring unexpected packet within minimum stateless reset interval");
274            return None;
275        }
276
277        /// Minimum amount of padding for the stateless reset to look like a short-header packet
278        const MIN_PADDING_LEN: usize = 5;
279
280        // Prevent amplification attacks and reset loops by ensuring we pad to at most 1 byte
281        // smaller than the inciting packet.
282        let max_padding_len = match inciting_dgram_len.checked_sub(RESET_TOKEN_SIZE) {
283            Some(headroom) if headroom > MIN_PADDING_LEN => headroom - 1,
284            _ => {
285                debug!(
286                    "ignoring unexpected {} byte packet: not larger than minimum stateless reset size",
287                    inciting_dgram_len
288                );
289                return None;
290            }
291        };
292
293        debug!(
294            "sending stateless reset for {} to {}",
295            dst_cid, addresses.remote
296        );
297        self.last_stateless_reset = Some(now);
298        // Resets with at least this much padding can't possibly be distinguished from real packets
299        const IDEAL_MIN_PADDING_LEN: usize = MIN_PADDING_LEN + MAX_CID_SIZE;
300        let padding_len = if max_padding_len <= IDEAL_MIN_PADDING_LEN {
301            max_padding_len
302        } else {
303            self.rng
304                .random_range(IDEAL_MIN_PADDING_LEN..max_padding_len)
305        };
306        buf.reserve(padding_len + RESET_TOKEN_SIZE);
307        buf.resize(padding_len, 0);
308        self.rng.fill_bytes(&mut buf[0..padding_len]);
309        buf[0] = 0b0100_0000 | (buf[0] >> 2);
310        buf.extend_from_slice(&ResetToken::new(&*self.config.reset_key, dst_cid));
311
312        debug_assert!(buf.len() < inciting_dgram_len);
313
314        Some(Transmit {
315            destination: addresses.remote,
316            ecn: None,
317            size: buf.len(),
318            segment_size: None,
319            src_ip: addresses.local_ip,
320        })
321    }
322
323    /// Initiate a connection
324    pub fn connect(
325        &mut self,
326        now: Instant,
327        config: ClientConfig,
328        remote: SocketAddr,
329        server_name: &str,
330    ) -> Result<(ConnectionHandle, Connection), ConnectError> {
331        if self.cids_exhausted() {
332            return Err(ConnectError::CidsExhausted);
333        }
334        if remote.port() == 0 || remote.ip().is_unspecified() {
335            return Err(ConnectError::InvalidRemoteAddress(remote));
336        }
337        if !self.config.supported_versions.contains(&config.version) {
338            return Err(ConnectError::UnsupportedVersion);
339        }
340
341        let remote_id = (config.initial_dst_cid_provider)();
342        trace!(initial_dcid = %remote_id);
343
344        let ch = ConnectionHandle(self.connections.vacant_key());
345        let loc_cid = self.new_cid(ch);
346        let params = TransportParameters::new(
347            &config.transport,
348            &self.config,
349            self.local_cid_generator.as_ref(),
350            loc_cid,
351            None,
352            &mut self.rng,
353        );
354        let tls = config
355            .crypto
356            .start_session(config.version, server_name, &params)?;
357
358        let conn = self.add_connection(
359            ch,
360            config.version,
361            remote_id,
362            loc_cid,
363            remote_id,
364            FourTuple {
365                remote,
366                local_ip: None,
367            },
368            now,
369            tls,
370            config.transport,
371            SideArgs::Client {
372                token_store: config.token_store,
373                server_name: server_name.into(),
374            },
375        );
376        Ok((ch, conn))
377    }
378
379    fn send_new_identifiers(
380        &mut self,
381        now: Instant,
382        ch: ConnectionHandle,
383        num: u64,
384    ) -> ConnectionEvent {
385        let mut ids = vec![];
386        for _ in 0..num {
387            let id = self.new_cid(ch);
388            let meta = &mut self.connections[ch];
389            let sequence = meta.cids_issued;
390            meta.cids_issued += 1;
391            meta.loc_cids.insert(sequence, id);
392            ids.push(IssuedCid {
393                sequence,
394                id,
395                reset_token: ResetToken::new(&*self.config.reset_key, id),
396            });
397        }
398        ConnectionEvent(ConnectionEventInner::NewIdentifiers(ids, now))
399    }
400
401    /// Generate a connection ID for `ch`
402    fn new_cid(&mut self, ch: ConnectionHandle) -> ConnectionId {
403        loop {
404            let cid = self.local_cid_generator.generate_cid();
405            if cid.is_empty() {
406                // Zero-length CID; nothing to track
407                debug_assert_eq!(self.local_cid_generator.cid_len(), 0);
408                return cid;
409            }
410            if let hash_map::Entry::Vacant(e) = self.index.connection_ids.entry(cid) {
411                e.insert(ch);
412                break cid;
413            }
414        }
415    }
416
417    fn handle_first_packet(
418        &mut self,
419        datagram_len: usize,
420        event: DatagramConnectionEvent,
421        addresses: FourTuple,
422        buf: &mut Vec<u8>,
423    ) -> Option<DatagramEvent> {
424        let dst_cid = event.first_decode.dst_cid();
425        let header = event.first_decode.initial_header().unwrap();
426
427        let Some(server_config) = &self.server_config else {
428            debug!("packet for unrecognized connection {}", dst_cid);
429            return self
430                .stateless_reset(event.now, datagram_len, addresses, *dst_cid, buf)
431                .map(DatagramEvent::Response);
432        };
433
434        if datagram_len < MIN_INITIAL_SIZE as usize {
435            debug!("ignoring short initial for connection {}", dst_cid);
436            return None;
437        }
438
439        let crypto = match server_config.crypto.initial_keys(header.version, dst_cid) {
440            Ok(keys) => keys,
441            Err(UnsupportedVersion) => {
442                // This probably indicates that the user set supported_versions incorrectly in
443                // `EndpointConfig`.
444                debug!(
445                    "ignoring initial packet version {:#x} unsupported by cryptographic layer",
446                    header.version
447                );
448                return None;
449            }
450        };
451
452        if let Err(reason) = self.early_validate_first_packet(header) {
453            return Some(DatagramEvent::Response(self.initial_close(
454                header.version,
455                addresses,
456                &crypto,
457                &header.src_cid,
458                reason,
459                buf,
460            )));
461        }
462
463        let packet = match event.first_decode.finish(Some(&*crypto.header.remote)) {
464            Ok(packet) => packet,
465            Err(e) => {
466                trace!("unable to decode initial packet: {}", e);
467                return None;
468            }
469        };
470
471        if !packet.reserved_bits_valid() {
472            debug!("dropping connection attempt with invalid reserved bits");
473            return None;
474        }
475
476        let Header::Initial(header) = packet.header else {
477            panic!("non-initial packet in handle_first_packet()");
478        };
479
480        let server_config = self.server_config.as_ref().unwrap().clone();
481
482        let token = match IncomingToken::from_header(&header, &server_config, addresses.remote) {
483            Ok(token) => token,
484            Err(InvalidRetryTokenError) => {
485                debug!("rejecting invalid retry token");
486                return Some(DatagramEvent::Response(self.initial_close(
487                    header.version,
488                    addresses,
489                    &crypto,
490                    &header.src_cid,
491                    TransportError::INVALID_TOKEN(""),
492                    buf,
493                )));
494            }
495        };
496
497        let incoming_idx = self.incoming_buffers.insert(IncomingBuffer::default());
498        self.index
499            .insert_initial_incoming(header.dst_cid, incoming_idx);
500
501        Some(DatagramEvent::NewConnection(Incoming {
502            received_at: event.now,
503            addresses,
504            ecn: event.ecn,
505            packet: InitialPacket {
506                header,
507                header_data: packet.header_data,
508                payload: packet.payload,
509            },
510            rest: event.remaining,
511            crypto,
512            token,
513            incoming_idx,
514            improper_drop_warner: IncomingImproperDropWarner,
515        }))
516    }
517
518    /// Attempt to accept this incoming connection (an error may still occur)
519    pub fn accept(
520        &mut self,
521        mut incoming: Incoming,
522        now: Instant,
523        buf: &mut Vec<u8>,
524        server_config: Option<Arc<ServerConfig>>,
525    ) -> Result<(ConnectionHandle, Connection), AcceptError> {
526        let remote_address_validated = incoming.remote_address_validated();
527        incoming.improper_drop_warner.dismiss();
528        let incoming_buffer = self.incoming_buffers.remove(incoming.incoming_idx);
529        self.all_incoming_buffers_total_bytes -= incoming_buffer.total_bytes;
530
531        let packet_number = incoming.packet.header.number.expand(0);
532        let InitialHeader {
533            src_cid,
534            dst_cid,
535            version,
536            ..
537        } = incoming.packet.header;
538        let server_config =
539            server_config.unwrap_or_else(|| self.server_config.as_ref().unwrap().clone());
540
541        if server_config
542            .transport
543            .max_idle_timeout
544            .is_some_and(|timeout| {
545                incoming.received_at + Duration::from_millis(timeout.into()) <= now
546            })
547        {
548            debug!("abandoning accept of stale initial");
549            self.index.remove_initial(dst_cid);
550            return Err(AcceptError {
551                cause: ConnectionError::TimedOut,
552                response: None,
553            });
554        }
555
556        if self.cids_exhausted() {
557            debug!("refusing connection");
558            self.index.remove_initial(dst_cid);
559            return Err(AcceptError {
560                cause: ConnectionError::CidsExhausted,
561                response: Some(self.initial_close(
562                    version,
563                    incoming.addresses,
564                    &incoming.crypto,
565                    &src_cid,
566                    TransportError::CONNECTION_REFUSED(""),
567                    buf,
568                )),
569            });
570        }
571
572        if incoming
573            .crypto
574            .packet
575            .remote
576            .decrypt(
577                packet_number,
578                &incoming.packet.header_data,
579                &mut incoming.packet.payload,
580            )
581            .is_err()
582        {
583            debug!(packet_number, "failed to authenticate initial packet");
584            self.index.remove_initial(dst_cid);
585            return Err(AcceptError {
586                cause: TransportError::PROTOCOL_VIOLATION("authentication failed").into(),
587                response: None,
588            });
589        };
590
591        let ch = ConnectionHandle(self.connections.vacant_key());
592        let loc_cid = self.new_cid(ch);
593        let mut params = TransportParameters::new(
594            &server_config.transport,
595            &self.config,
596            self.local_cid_generator.as_ref(),
597            loc_cid,
598            Some(&server_config),
599            &mut self.rng,
600        );
601        params.stateless_reset_token = Some(ResetToken::new(&*self.config.reset_key, loc_cid));
602        params.original_dst_cid = Some(incoming.token.orig_dst_cid);
603        params.retry_src_cid = incoming.token.retry_src_cid;
604        let mut pref_addr_cid = None;
605        if server_config.preferred_address_v4.is_some()
606            || server_config.preferred_address_v6.is_some()
607        {
608            let cid = self.new_cid(ch);
609            pref_addr_cid = Some(cid);
610            params.preferred_address = Some(PreferredAddress {
611                address_v4: server_config.preferred_address_v4,
612                address_v6: server_config.preferred_address_v6,
613                connection_id: cid,
614                stateless_reset_token: ResetToken::new(&*self.config.reset_key, cid),
615            });
616        }
617
618        let tls = server_config.crypto.clone().start_session(version, &params);
619        let transport_config = server_config.transport.clone();
620        let mut conn = self.add_connection(
621            ch,
622            version,
623            dst_cid,
624            loc_cid,
625            src_cid,
626            incoming.addresses,
627            incoming.received_at,
628            tls,
629            transport_config,
630            SideArgs::Server {
631                server_config,
632                pref_addr_cid,
633                path_validated: remote_address_validated,
634            },
635        );
636        self.index.insert_initial(dst_cid, ch);
637
638        match conn.handle_first_packet(
639            incoming.received_at,
640            incoming.addresses.remote,
641            incoming.ecn,
642            packet_number,
643            incoming.packet,
644            incoming.rest,
645        ) {
646            Ok(()) => {
647                trace!(id = ch.0, icid = %dst_cid, "new connection");
648
649                for event in incoming_buffer.datagrams {
650                    conn.handle_event(ConnectionEvent(ConnectionEventInner::Datagram(event)))
651                }
652
653                Ok((ch, conn))
654            }
655            Err(e) => {
656                debug!("handshake failed: {}", e);
657                self.handle_event(ch, EndpointEvent(EndpointEventInner::Drained));
658                let response = match e {
659                    ConnectionError::TransportError(ref e) => Some(self.initial_close(
660                        version,
661                        incoming.addresses,
662                        &incoming.crypto,
663                        &src_cid,
664                        e.clone(),
665                        buf,
666                    )),
667                    _ => None,
668                };
669                Err(AcceptError { cause: e, response })
670            }
671        }
672    }
673
674    /// Check if we should refuse a connection attempt regardless of the packet's contents
675    fn early_validate_first_packet(
676        &mut self,
677        header: &ProtectedInitialHeader,
678    ) -> Result<(), TransportError> {
679        let config = &self.server_config.as_ref().unwrap();
680        if self.cids_exhausted() || self.incoming_buffers.len() >= config.max_incoming {
681            return Err(TransportError::CONNECTION_REFUSED(""));
682        }
683
684        // RFC9000 §7.2 dictates that initial (client-chosen) destination CIDs must be at least 8
685        // bytes. If this is a Retry packet, then the length must instead match our usual CID
686        // length. If we ever issue non-Retry address validation tokens via `NEW_TOKEN`, then we'll
687        // also need to validate CID length for those after decoding the token.
688        if header.dst_cid.len() < 8
689            && (header.token_pos.is_empty()
690                || header.dst_cid.len() != self.local_cid_generator.cid_len())
691        {
692            debug!(
693                "rejecting connection due to invalid DCID length {}",
694                header.dst_cid.len()
695            );
696            return Err(TransportError::PROTOCOL_VIOLATION(
697                "invalid destination CID length",
698            ));
699        }
700
701        Ok(())
702    }
703
704    /// Reject this incoming connection attempt
705    pub fn refuse(&mut self, incoming: Incoming, buf: &mut Vec<u8>) -> Transmit {
706        self.clean_up_incoming(&incoming);
707        incoming.improper_drop_warner.dismiss();
708
709        self.initial_close(
710            incoming.packet.header.version,
711            incoming.addresses,
712            &incoming.crypto,
713            &incoming.packet.header.src_cid,
714            TransportError::CONNECTION_REFUSED(""),
715            buf,
716        )
717    }
718
719    /// Respond with a retry packet, requiring the client to retry with address validation
720    ///
721    /// Errors if `incoming.may_retry()` is false.
722    pub fn retry(&mut self, incoming: Incoming, buf: &mut Vec<u8>) -> Result<Transmit, RetryError> {
723        if !incoming.may_retry() {
724            return Err(RetryError(incoming));
725        }
726
727        self.clean_up_incoming(&incoming);
728        incoming.improper_drop_warner.dismiss();
729
730        let server_config = self.server_config.as_ref().unwrap();
731
732        // First Initial
733        // The peer will use this as the DCID of its following Initials. Initial DCIDs are
734        // looked up separately from Handshake/Data DCIDs, so there is no risk of collision
735        // with established connections. In the unlikely event that a collision occurs
736        // between two connections in the initial phase, both will fail fast and may be
737        // retried by the application layer.
738        let loc_cid = self.local_cid_generator.generate_cid();
739
740        let payload = TokenPayload::Retry {
741            address: incoming.addresses.remote,
742            orig_dst_cid: incoming.packet.header.dst_cid,
743            issued: server_config.time_source.now(),
744        };
745        let token = Token::new(payload, &mut self.rng).encode(&*server_config.token_key);
746
747        let header = Header::Retry {
748            src_cid: loc_cid,
749            dst_cid: incoming.packet.header.src_cid,
750            version: incoming.packet.header.version,
751        };
752
753        let encode = header.encode(buf);
754        buf.put_slice(&token);
755        buf.extend_from_slice(&server_config.crypto.retry_tag(
756            incoming.packet.header.version,
757            &incoming.packet.header.dst_cid,
758            buf,
759        ));
760        encode.finish(buf, &*incoming.crypto.header.local, None);
761
762        Ok(Transmit {
763            destination: incoming.addresses.remote,
764            ecn: None,
765            size: buf.len(),
766            segment_size: None,
767            src_ip: incoming.addresses.local_ip,
768        })
769    }
770
771    /// Ignore this incoming connection attempt, not sending any packet in response
772    ///
773    /// Doing this actively, rather than merely dropping the [`Incoming`], is necessary to prevent
774    /// memory leaks due to state within [`Endpoint`] tracking the incoming connection.
775    pub fn ignore(&mut self, incoming: Incoming) {
776        self.clean_up_incoming(&incoming);
777        incoming.improper_drop_warner.dismiss();
778    }
779
780    /// Clean up endpoint data structures associated with an `Incoming`.
781    fn clean_up_incoming(&mut self, incoming: &Incoming) {
782        self.index.remove_initial(incoming.packet.header.dst_cid);
783        let incoming_buffer = self.incoming_buffers.remove(incoming.incoming_idx);
784        self.all_incoming_buffers_total_bytes -= incoming_buffer.total_bytes;
785    }
786
787    fn add_connection(
788        &mut self,
789        ch: ConnectionHandle,
790        version: u32,
791        init_cid: ConnectionId,
792        loc_cid: ConnectionId,
793        rem_cid: ConnectionId,
794        addresses: FourTuple,
795        now: Instant,
796        tls: Box<dyn crypto::Session>,
797        transport_config: Arc<TransportConfig>,
798        side_args: SideArgs,
799    ) -> Connection {
800        let mut rng_seed = [0; 32];
801        self.rng.fill_bytes(&mut rng_seed);
802        let side = side_args.side();
803        let pref_addr_cid = side_args.pref_addr_cid();
804        let conn = Connection::new(
805            self.config.clone(),
806            transport_config,
807            init_cid,
808            loc_cid,
809            rem_cid,
810            addresses.remote,
811            addresses.local_ip,
812            tls,
813            self.local_cid_generator.as_ref(),
814            now,
815            version,
816            self.allow_mtud,
817            rng_seed,
818            side_args,
819        );
820
821        let mut cids_issued = 0;
822        let mut loc_cids = FxHashMap::default();
823
824        loc_cids.insert(cids_issued, loc_cid);
825        cids_issued += 1;
826
827        if let Some(cid) = pref_addr_cid {
828            debug_assert_eq!(cids_issued, 1, "preferred address cid seq must be 1");
829            loc_cids.insert(cids_issued, cid);
830            cids_issued += 1;
831        }
832
833        let id = self.connections.insert(ConnectionMeta {
834            init_cid,
835            cids_issued,
836            loc_cids,
837            addresses,
838            side,
839            reset_token: None,
840        });
841        debug_assert_eq!(id, ch.0, "connection handle allocation out of sync");
842
843        self.index.insert_conn(addresses, loc_cid, ch, side);
844
845        conn
846    }
847
848    fn initial_close(
849        &mut self,
850        version: u32,
851        addresses: FourTuple,
852        crypto: &Keys,
853        remote_id: &ConnectionId,
854        reason: TransportError,
855        buf: &mut Vec<u8>,
856    ) -> Transmit {
857        // We don't need to worry about CID collisions in initial closes because the peer
858        // shouldn't respond, and if it does, and the CID collides, we'll just drop the
859        // unexpected response.
860        let local_id = self.local_cid_generator.generate_cid();
861        let number = PacketNumber::U8(0);
862        let header = Header::Initial(InitialHeader {
863            dst_cid: *remote_id,
864            src_cid: local_id,
865            number,
866            token: Bytes::new(),
867            version,
868        });
869
870        let partial_encode = header.encode(buf);
871        let max_len =
872            INITIAL_MTU as usize - partial_encode.header_len - crypto.packet.local.tag_len();
873        frame::Close::from(reason).encode(buf, max_len);
874        buf.resize(buf.len() + crypto.packet.local.tag_len(), 0);
875        partial_encode.finish(buf, &*crypto.header.local, Some((0, &*crypto.packet.local)));
876        Transmit {
877            destination: addresses.remote,
878            ecn: None,
879            size: buf.len(),
880            segment_size: None,
881            src_ip: addresses.local_ip,
882        }
883    }
884
885    /// Access the configuration used by this endpoint
886    pub fn config(&self) -> &EndpointConfig {
887        &self.config
888    }
889
890    /// Number of connections that are currently open
891    pub fn open_connections(&self) -> usize {
892        self.connections.len()
893    }
894
895    /// Counter for the number of bytes currently used
896    /// in the buffers for Initial and 0-RTT messages for pending incoming connections
897    pub fn incoming_buffer_bytes(&self) -> u64 {
898        self.all_incoming_buffers_total_bytes
899    }
900
901    #[cfg(test)]
902    pub(crate) fn known_connections(&self) -> usize {
903        let x = self.connections.len();
904        debug_assert_eq!(x, self.index.connection_ids_initial.len());
905        // Not all connections have known reset tokens
906        debug_assert!(x >= self.index.connection_reset_tokens.0.len());
907        // Not all connections have unique remotes, and 0-length CIDs might not be in use.
908        debug_assert!(x >= self.index.incoming_connection_remotes.len());
909        debug_assert!(x >= self.index.outgoing_connection_remotes.len());
910        x
911    }
912
913    #[cfg(test)]
914    pub(crate) fn known_cids(&self) -> usize {
915        self.index.connection_ids.len()
916    }
917
918    /// Whether we've used up 3/4 of the available CID space
919    ///
920    /// We leave some space unused so that `new_cid` can be relied upon to finish quickly. We don't
921    /// bother to check when CID longer than 4 bytes are used because 2^40 connections is a lot.
922    fn cids_exhausted(&self) -> bool {
923        self.local_cid_generator.cid_len() <= 4
924            && self.local_cid_generator.cid_len() != 0
925            && (2usize.pow(self.local_cid_generator.cid_len() as u32 * 8)
926                - self.index.connection_ids.len())
927                < 2usize.pow(self.local_cid_generator.cid_len() as u32 * 8 - 2)
928    }
929}
930
931impl fmt::Debug for Endpoint {
932    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
933        fmt.debug_struct("Endpoint")
934            .field("rng", &self.rng)
935            .field("index", &self.index)
936            .field("connections", &self.connections)
937            .field("config", &self.config)
938            .field("server_config", &self.server_config)
939            // incoming_buffers too large
940            .field("incoming_buffers.len", &self.incoming_buffers.len())
941            .field(
942                "all_incoming_buffers_total_bytes",
943                &self.all_incoming_buffers_total_bytes,
944            )
945            .finish()
946    }
947}
948
949/// Buffered Initial and 0-RTT messages for a pending incoming connection
950#[derive(Default)]
951struct IncomingBuffer {
952    datagrams: Vec<DatagramConnectionEvent>,
953    total_bytes: u64,
954}
955
956/// Part of protocol state incoming datagrams can be routed to
957#[derive(Copy, Clone, Debug)]
958enum RouteDatagramTo {
959    Incoming(usize),
960    Connection(ConnectionHandle),
961}
962
963/// Maps packets to existing connections
964#[derive(Default, Debug)]
965struct ConnectionIndex {
966    /// Identifies connections based on the initial DCID the peer utilized
967    ///
968    /// Uses a standard `HashMap` to protect against hash collision attacks.
969    ///
970    /// Used by the server, not the client.
971    connection_ids_initial: HashMap<ConnectionId, RouteDatagramTo>,
972    /// Identifies connections based on locally created CIDs
973    ///
974    /// Uses a cheaper hash function since keys are locally created
975    connection_ids: FxHashMap<ConnectionId, ConnectionHandle>,
976    /// Identifies incoming connections with zero-length CIDs
977    ///
978    /// Uses a standard `HashMap` to protect against hash collision attacks.
979    incoming_connection_remotes: HashMap<FourTuple, ConnectionHandle>,
980    /// Identifies outgoing connections with zero-length CIDs
981    ///
982    /// We don't yet support explicit source addresses for client connections, and zero-length CIDs
983    /// require a unique four-tuple, so at most one client connection with zero-length local CIDs
984    /// may be established per remote. We must omit the local address from the key because we don't
985    /// necessarily know what address we're sending from, and hence receiving at.
986    ///
987    /// Uses a standard `HashMap` to protect against hash collision attacks.
988    outgoing_connection_remotes: HashMap<SocketAddr, ConnectionHandle>,
989    /// Reset tokens provided by the peer for the CID each connection is currently sending to
990    ///
991    /// Incoming stateless resets do not have correct CIDs, so we need this to identify the correct
992    /// recipient, if any.
993    connection_reset_tokens: ResetTokenTable,
994}
995
996impl ConnectionIndex {
997    /// Associate an incoming connection with its initial destination CID
998    fn insert_initial_incoming(&mut self, dst_cid: ConnectionId, incoming_key: usize) {
999        if dst_cid.is_empty() {
1000            return;
1001        }
1002        self.connection_ids_initial
1003            .insert(dst_cid, RouteDatagramTo::Incoming(incoming_key));
1004    }
1005
1006    /// Remove an association with an initial destination CID
1007    fn remove_initial(&mut self, dst_cid: ConnectionId) {
1008        if dst_cid.is_empty() {
1009            return;
1010        }
1011        let removed = self.connection_ids_initial.remove(&dst_cid);
1012        debug_assert!(removed.is_some());
1013    }
1014
1015    /// Associate a connection with its initial destination CID
1016    fn insert_initial(&mut self, dst_cid: ConnectionId, connection: ConnectionHandle) {
1017        if dst_cid.is_empty() {
1018            return;
1019        }
1020        self.connection_ids_initial
1021            .insert(dst_cid, RouteDatagramTo::Connection(connection));
1022    }
1023
1024    /// Associate a connection with its first locally-chosen destination CID if used, or otherwise
1025    /// its current 4-tuple
1026    fn insert_conn(
1027        &mut self,
1028        addresses: FourTuple,
1029        dst_cid: ConnectionId,
1030        connection: ConnectionHandle,
1031        side: Side,
1032    ) {
1033        match dst_cid.len() {
1034            0 => match side {
1035                Side::Server => {
1036                    self.incoming_connection_remotes
1037                        .insert(addresses, connection);
1038                }
1039                Side::Client => {
1040                    self.outgoing_connection_remotes
1041                        .insert(addresses.remote, connection);
1042                }
1043            },
1044            _ => {
1045                self.connection_ids.insert(dst_cid, connection);
1046            }
1047        }
1048    }
1049
1050    /// Discard a connection ID
1051    fn retire(&mut self, dst_cid: ConnectionId) {
1052        self.connection_ids.remove(&dst_cid);
1053    }
1054
1055    /// Remove all references to a connection
1056    fn remove(&mut self, conn: &ConnectionMeta) {
1057        if conn.side.is_server() {
1058            self.remove_initial(conn.init_cid);
1059        }
1060        for cid in conn.loc_cids.values() {
1061            self.connection_ids.remove(cid);
1062        }
1063        self.incoming_connection_remotes.remove(&conn.addresses);
1064        self.outgoing_connection_remotes
1065            .remove(&conn.addresses.remote);
1066        if let Some((remote, token)) = conn.reset_token {
1067            self.connection_reset_tokens.remove(remote, token);
1068        }
1069    }
1070
1071    /// Find the existing connection that `datagram` should be routed to, if any
1072    fn get(&self, addresses: &FourTuple, datagram: &PartialDecode) -> Option<RouteDatagramTo> {
1073        if !datagram.dst_cid().is_empty() {
1074            if let Some(&ch) = self.connection_ids.get(datagram.dst_cid()) {
1075                return Some(RouteDatagramTo::Connection(ch));
1076            }
1077        }
1078        if datagram.is_initial() || datagram.is_0rtt() {
1079            if let Some(&ch) = self.connection_ids_initial.get(datagram.dst_cid()) {
1080                return Some(ch);
1081            }
1082        }
1083        if datagram.dst_cid().is_empty() {
1084            if let Some(&ch) = self.incoming_connection_remotes.get(addresses) {
1085                return Some(RouteDatagramTo::Connection(ch));
1086            }
1087            if let Some(&ch) = self.outgoing_connection_remotes.get(&addresses.remote) {
1088                return Some(RouteDatagramTo::Connection(ch));
1089            }
1090        }
1091        let data = datagram.data();
1092        if data.len() < RESET_TOKEN_SIZE {
1093            return None;
1094        }
1095        self.connection_reset_tokens
1096            .get(addresses.remote, &data[data.len() - RESET_TOKEN_SIZE..])
1097            .cloned()
1098            .map(RouteDatagramTo::Connection)
1099    }
1100}
1101
1102#[derive(Debug)]
1103pub(crate) struct ConnectionMeta {
1104    init_cid: ConnectionId,
1105    /// Number of local connection IDs that have been issued in NEW_CONNECTION_ID frames.
1106    cids_issued: u64,
1107    loc_cids: FxHashMap<u64, ConnectionId>,
1108    /// Remote/local addresses the connection began with
1109    ///
1110    /// Only needed to support connections with zero-length CIDs, which cannot migrate, so we don't
1111    /// bother keeping it up to date.
1112    addresses: FourTuple,
1113    side: Side,
1114    /// Reset token provided by the peer for the CID we're currently sending to, and the address
1115    /// being sent to
1116    reset_token: Option<(SocketAddr, ResetToken)>,
1117}
1118
1119/// Internal identifier for a `Connection` currently associated with an endpoint
1120#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash, Ord, PartialOrd)]
1121pub struct ConnectionHandle(pub usize);
1122
1123impl From<ConnectionHandle> for usize {
1124    fn from(x: ConnectionHandle) -> Self {
1125        x.0
1126    }
1127}
1128
1129impl Index<ConnectionHandle> for Slab<ConnectionMeta> {
1130    type Output = ConnectionMeta;
1131    fn index(&self, ch: ConnectionHandle) -> &ConnectionMeta {
1132        &self[ch.0]
1133    }
1134}
1135
1136impl IndexMut<ConnectionHandle> for Slab<ConnectionMeta> {
1137    fn index_mut(&mut self, ch: ConnectionHandle) -> &mut ConnectionMeta {
1138        &mut self[ch.0]
1139    }
1140}
1141
1142/// Event resulting from processing a single datagram
1143pub enum DatagramEvent {
1144    /// The datagram is redirected to its `Connection`
1145    ConnectionEvent(ConnectionHandle, ConnectionEvent),
1146    /// The datagram may result in starting a new `Connection`
1147    NewConnection(Incoming),
1148    /// Response generated directly by the endpoint
1149    Response(Transmit),
1150}
1151
1152/// An incoming connection for which the server has not yet begun its part of the handshake.
1153pub struct Incoming {
1154    received_at: Instant,
1155    addresses: FourTuple,
1156    ecn: Option<EcnCodepoint>,
1157    packet: InitialPacket,
1158    rest: Option<BytesMut>,
1159    crypto: Keys,
1160    token: IncomingToken,
1161    incoming_idx: usize,
1162    improper_drop_warner: IncomingImproperDropWarner,
1163}
1164
1165impl Incoming {
1166    /// The local IP address which was used when the peer established the connection
1167    ///
1168    /// This has the same behavior as [`Connection::local_ip`].
1169    pub fn local_ip(&self) -> Option<IpAddr> {
1170        self.addresses.local_ip
1171    }
1172
1173    /// The peer's UDP address
1174    pub fn remote_address(&self) -> SocketAddr {
1175        self.addresses.remote
1176    }
1177
1178    /// Whether the socket address that is initiating this connection has been validated
1179    ///
1180    /// This means that the sender of the initial packet has proved that they can receive traffic
1181    /// sent to `self.remote_address()`.
1182    ///
1183    /// If `self.remote_address_validated()` is false, `self.may_retry()` is guaranteed to be true.
1184    /// The inverse is not guaranteed.
1185    pub fn remote_address_validated(&self) -> bool {
1186        self.token.validated
1187    }
1188
1189    /// Whether it is legal to respond with a retry packet
1190    ///
1191    /// If `self.remote_address_validated()` is false, `self.may_retry()` is guaranteed to be true.
1192    /// The inverse is not guaranteed.
1193    pub fn may_retry(&self) -> bool {
1194        self.token.retry_src_cid.is_none()
1195    }
1196
1197    /// The original destination connection ID sent by the client
1198    pub fn orig_dst_cid(&self) -> &ConnectionId {
1199        &self.token.orig_dst_cid
1200    }
1201}
1202
1203impl fmt::Debug for Incoming {
1204    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1205        f.debug_struct("Incoming")
1206            .field("addresses", &self.addresses)
1207            .field("ecn", &self.ecn)
1208            // packet doesn't implement debug
1209            // rest is too big and not meaningful enough
1210            .field("token", &self.token)
1211            .field("incoming_idx", &self.incoming_idx)
1212            // improper drop warner contains no information
1213            .finish_non_exhaustive()
1214    }
1215}
1216
1217struct IncomingImproperDropWarner;
1218
1219impl IncomingImproperDropWarner {
1220    fn dismiss(self) {
1221        mem::forget(self);
1222    }
1223}
1224
1225impl Drop for IncomingImproperDropWarner {
1226    fn drop(&mut self) {
1227        warn!(
1228            "quinn_proto::Incoming dropped without passing to Endpoint::accept/refuse/retry/ignore \
1229               (may cause memory leak and eventual inability to accept new connections)"
1230        );
1231    }
1232}
1233
1234/// Errors in the parameters being used to create a new connection
1235///
1236/// These arise before any I/O has been performed.
1237#[derive(Debug, Error, Clone, PartialEq, Eq)]
1238pub enum ConnectError {
1239    /// The endpoint can no longer create new connections
1240    ///
1241    /// Indicates that a necessary component of the endpoint has been dropped or otherwise disabled.
1242    #[error("endpoint stopping")]
1243    EndpointStopping,
1244    /// The connection could not be created because not enough of the CID space is available
1245    ///
1246    /// Try using longer connection IDs
1247    #[error("CIDs exhausted")]
1248    CidsExhausted,
1249    /// The given server name was malformed
1250    #[error("invalid server name: {0}")]
1251    InvalidServerName(String),
1252    /// The remote [`SocketAddr`] supplied was malformed
1253    ///
1254    /// Examples include attempting to connect to port 0, or using an inappropriate address family.
1255    #[error("invalid remote address: {0}")]
1256    InvalidRemoteAddress(SocketAddr),
1257    /// No default client configuration was set up
1258    ///
1259    /// Use `Endpoint::connect_with` to specify a client configuration.
1260    #[error("no default client config")]
1261    NoDefaultClientConfig,
1262    /// The local endpoint does not support the QUIC version specified in the client configuration
1263    #[error("unsupported QUIC version")]
1264    UnsupportedVersion,
1265}
1266
1267/// Error type for attempting to accept an [`Incoming`]
1268#[derive(Debug)]
1269pub struct AcceptError {
1270    /// Underlying error describing reason for failure
1271    pub cause: ConnectionError,
1272    /// Optional response to transmit back
1273    pub response: Option<Transmit>,
1274}
1275
1276/// Error for attempting to retry an [`Incoming`] which already bears a token from a previous retry
1277#[derive(Debug, Error)]
1278#[error("retry() with validated Incoming")]
1279pub struct RetryError(Incoming);
1280
1281impl RetryError {
1282    /// Get the [`Incoming`]
1283    pub fn into_incoming(self) -> Incoming {
1284        self.0
1285    }
1286}
1287
1288/// Reset Tokens which are associated with peer socket addresses
1289///
1290/// The standard `HashMap` is used since both `SocketAddr` and `ResetToken` are
1291/// peer generated and might be usable for hash collision attacks.
1292#[derive(Default, Debug)]
1293struct ResetTokenTable(HashMap<SocketAddr, HashMap<ResetToken, ConnectionHandle>>);
1294
1295impl ResetTokenTable {
1296    fn insert(&mut self, remote: SocketAddr, token: ResetToken, ch: ConnectionHandle) -> bool {
1297        self.0
1298            .entry(remote)
1299            .or_default()
1300            .insert(token, ch)
1301            .is_some()
1302    }
1303
1304    fn remove(&mut self, remote: SocketAddr, token: ResetToken) {
1305        use std::collections::hash_map::Entry;
1306        match self.0.entry(remote) {
1307            Entry::Vacant(_) => {}
1308            Entry::Occupied(mut e) => {
1309                e.get_mut().remove(&token);
1310                if e.get().is_empty() {
1311                    e.remove_entry();
1312                }
1313            }
1314        }
1315    }
1316
1317    fn get(&self, remote: SocketAddr, token: &[u8]) -> Option<&ConnectionHandle> {
1318        let token = ResetToken::from(<[u8; RESET_TOKEN_SIZE]>::try_from(token).ok()?);
1319        self.0.get(&remote)?.get(&token)
1320    }
1321}
1322
1323/// Identifies a connection by the combination of remote and local addresses
1324///
1325/// Including the local ensures good behavior when the host has multiple IP addresses on the same
1326/// subnet and zero-length connection IDs are in use.
1327#[derive(Hash, Eq, PartialEq, Debug, Copy, Clone)]
1328struct FourTuple {
1329    remote: SocketAddr,
1330    // A single socket can only listen on a single port, so no need to store it explicitly
1331    local_ip: Option<IpAddr>,
1332}
quinn_proto/endpoint.rs

quinn_proto/
endpoint.rs
