iroh_quinn_proto/
endpoint.rs

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

iroh_quinn_proto/
endpoint.rs
