noq_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::{Buf, 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, FourTuple, INITIAL_MTU, Instant, MAX_CID_SIZE, MIN_INITIAL_SIZE, PathId,
19    RESET_TOKEN_SIZE, ResetToken, Side, Transmit, TransportConfig, TransportError,
20    cid_generator::ConnectionIdGenerator,
21    coding::{BufMutExt, Decodable, Encodable, UnexpectedEnd},
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    pub fn new(
65        config: Arc<EndpointConfig>,
66        server_config: Option<Arc<ServerConfig>>,
67        allow_mtud: bool,
68    ) -> Self {
69        Self {
70            rng: config
71                .rng_seed
72                .map_or_else(StdRng::from_os_rng, StdRng::from_seed),
73            index: ConnectionIndex::default(),
74            connections: Slab::new(),
75            local_cid_generator: (config.connection_id_generator_factory.as_ref())(),
76            config,
77            server_config,
78            allow_mtud,
79            last_stateless_reset: None,
80            incoming_buffers: Slab::new(),
81            all_incoming_buffers_total_bytes: 0,
82        }
83    }
84
85    /// Replace the server configuration, affecting new incoming connections only
86    pub fn set_server_config(&mut self, server_config: Option<Arc<ServerConfig>>) {
87        self.server_config = server_config;
88    }
89
90    /// Process `EndpointEvent`s emitted from related `Connection`s
91    ///
92    /// In turn, processing this event may return a `ConnectionEvent` for the same `Connection`.
93    pub fn handle_event(
94        &mut self,
95        ch: ConnectionHandle,
96        event: EndpointEvent,
97    ) -> Option<ConnectionEvent> {
98        use EndpointEventInner::*;
99        match event.0 {
100            NeedIdentifiers(path_id, now, n) => {
101                return Some(self.send_new_identifiers(path_id, now, ch, n));
102            }
103            ResetToken(path_id, remote, token) => {
104                if let Some(old) = self.connections[ch]
105                    .reset_token
106                    .insert(path_id, (remote, token))
107                {
108                    self.index.connection_reset_tokens.remove(old.0, old.1);
109                }
110                if self.index.connection_reset_tokens.insert(remote, token, ch) {
111                    warn!("duplicate reset token");
112                }
113            }
114            RetireResetToken(path_id) => {
115                if let Some(old) = self.connections[ch].reset_token.remove(&path_id) {
116                    self.index.connection_reset_tokens.remove(old.0, old.1);
117                }
118            }
119            RetireConnectionId(now, path_id, seq, allow_more_cids) => {
120                if let Some(cid) = self.connections[ch]
121                    .local_cids
122                    .get_mut(&path_id)
123                    .and_then(|pcid| pcid.cids.remove(&seq))
124                {
125                    trace!(%path_id, "local CID retired {}: {}", seq, cid);
126                    self.index.retire(cid);
127                    if allow_more_cids {
128                        return Some(self.send_new_identifiers(path_id, now, ch, 1));
129                    }
130                }
131            }
132            Drained => {
133                if let Some(conn) = self.connections.try_remove(ch.0) {
134                    self.index.remove(&conn);
135                } else {
136                    // This indicates a bug in downstream code, which could cause spurious
137                    // connection loss instead of this error if the CID was (re)allocated prior to
138                    // the illegal call.
139                    error!(id = ch.0, "unknown connection drained");
140                }
141            }
142        }
143        None
144    }
145
146    /// Process an incoming UDP datagram
147    pub fn handle(
148        &mut self,
149        now: Instant,
150        network_path: FourTuple,
151        ecn: Option<EcnCodepoint>,
152        data: BytesMut,
153        buf: &mut Vec<u8>,
154    ) -> Option<DatagramEvent> {
155        // Partially decode packet or short-circuit if unable
156        let datagram_len = data.len();
157        let mut event = match PartialDecode::new(
158            data,
159            &FixedLengthConnectionIdParser::new(self.local_cid_generator.cid_len()),
160            &self.config.supported_versions,
161            self.config.grease_quic_bit,
162        ) {
163            Ok((first_decode, remaining)) => DatagramConnectionEvent {
164                now,
165                network_path,
166                path_id: PathId::ZERO, // Corrected later for existing paths
167                ecn,
168                first_decode,
169                remaining,
170            },
171            Err(PacketDecodeError::UnsupportedVersion {
172                src_cid,
173                dst_cid,
174                version,
175            }) => {
176                if self.server_config.is_none() {
177                    debug!("dropping packet with unsupported version");
178                    return None;
179                }
180                trace!("sending version negotiation");
181                // Negotiate versions
182                Header::VersionNegotiate {
183                    random: self.rng.random::<u8>() | 0x40,
184                    src_cid: dst_cid,
185                    dst_cid: src_cid,
186                }
187                .encode(buf);
188                // Grease with a reserved version
189                buf.write::<u32>(match version {
190                    0x0a1a_2a3a => 0x0a1a_2a4a,
191                    _ => 0x0a1a_2a3a,
192                });
193                for &version in &self.config.supported_versions {
194                    buf.write(version);
195                }
196                return Some(DatagramEvent::Response(Transmit {
197                    destination: network_path.remote,
198                    ecn: None,
199                    size: buf.len(),
200                    segment_size: None,
201                    src_ip: network_path.local_ip,
202                }));
203            }
204            Err(e) => {
205                trace!("malformed header: {}", e);
206                return None;
207            }
208        };
209
210        let dst_cid = event.first_decode.dst_cid();
211
212        if let Some(route_to) = self.index.get(&network_path, &event.first_decode) {
213            event.path_id = match route_to {
214                RouteDatagramTo::Incoming(_) => PathId::ZERO,
215                RouteDatagramTo::Connection(_, path_id) => path_id,
216            };
217            match route_to {
218                RouteDatagramTo::Incoming(incoming_idx) => {
219                    let incoming_buffer = &mut self.incoming_buffers[incoming_idx];
220                    let config = &self.server_config.as_ref().unwrap();
221
222                    if incoming_buffer
223                        .total_bytes
224                        .checked_add(datagram_len as u64)
225                        .is_some_and(|n| n <= config.incoming_buffer_size)
226                        && self
227                            .all_incoming_buffers_total_bytes
228                            .checked_add(datagram_len as u64)
229                            .is_some_and(|n| n <= config.incoming_buffer_size_total)
230                    {
231                        incoming_buffer.datagrams.push(event);
232                        incoming_buffer.total_bytes += datagram_len as u64;
233                        self.all_incoming_buffers_total_bytes += datagram_len as u64;
234                    }
235
236                    None
237                }
238                RouteDatagramTo::Connection(ch, _path_id) => Some(DatagramEvent::ConnectionEvent(
239                    ch,
240                    ConnectionEvent(ConnectionEventInner::Datagram(event)),
241                )),
242            }
243        } else if event.first_decode.initial_header().is_some() {
244            // Potentially create a new connection
245
246            self.handle_first_packet(datagram_len, event, network_path, buf)
247        } else if event.first_decode.has_long_header() {
248            debug!(
249                "ignoring non-initial packet for unknown connection {}",
250                dst_cid
251            );
252            None
253        } else if !event.first_decode.is_initial()
254            && self.local_cid_generator.validate(dst_cid).is_err()
255        {
256            debug!("dropping packet with invalid CID");
257            None
258        } else if dst_cid.is_empty() {
259            trace!("dropping unrecognized short packet without ID");
260            None
261        } else {
262            // If we got this far, we're receiving a seemingly valid packet for an unknown
263            // connection. Send a stateless reset if possible.
264            self.stateless_reset(now, datagram_len, network_path, dst_cid, buf)
265                .map(DatagramEvent::Response)
266        }
267    }
268
269    /// Builds a stateless reset packet to respond with
270    fn stateless_reset(
271        &mut self,
272        now: Instant,
273        inciting_dgram_len: usize,
274        network_path: FourTuple,
275        dst_cid: ConnectionId,
276        buf: &mut Vec<u8>,
277    ) -> Option<Transmit> {
278        if self
279            .last_stateless_reset
280            .is_some_and(|last| last + self.config.min_reset_interval > now)
281        {
282            debug!("ignoring unexpected packet within minimum stateless reset interval");
283            return None;
284        }
285
286        /// Minimum amount of padding for the stateless reset to look like a short-header packet
287        const MIN_PADDING_LEN: usize = 5;
288
289        // Prevent amplification attacks and reset loops by ensuring we pad to at most 1 byte
290        // smaller than the inciting packet.
291        let max_padding_len = match inciting_dgram_len.checked_sub(RESET_TOKEN_SIZE) {
292            Some(headroom) if headroom > MIN_PADDING_LEN => headroom - 1,
293            _ => {
294                debug!(
295                    "ignoring unexpected {} byte packet: not larger than minimum stateless reset size",
296                    inciting_dgram_len
297                );
298                return None;
299            }
300        };
301
302        debug!(%dst_cid, %network_path.remote, "sending stateless reset");
303        self.last_stateless_reset = Some(now);
304        // Resets with at least this much padding can't possibly be distinguished from real packets
305        const IDEAL_MIN_PADDING_LEN: usize = MIN_PADDING_LEN + MAX_CID_SIZE;
306        let padding_len = if max_padding_len <= IDEAL_MIN_PADDING_LEN {
307            max_padding_len
308        } else {
309            self.rng
310                .random_range(IDEAL_MIN_PADDING_LEN..max_padding_len)
311        };
312        buf.reserve(padding_len + RESET_TOKEN_SIZE);
313        buf.resize(padding_len, 0);
314        self.rng.fill_bytes(&mut buf[0..padding_len]);
315        buf[0] = 0b0100_0000 | (buf[0] >> 2);
316        buf.extend_from_slice(&ResetToken::new(&*self.config.reset_key, dst_cid));
317
318        debug_assert!(buf.len() < inciting_dgram_len);
319
320        Some(Transmit {
321            destination: network_path.remote,
322            ecn: None,
323            size: buf.len(),
324            segment_size: None,
325            src_ip: network_path.local_ip,
326        })
327    }
328
329    /// Initiate a connection
330    pub fn connect(
331        &mut self,
332        now: Instant,
333        config: ClientConfig,
334        remote: SocketAddr,
335        server_name: &str,
336    ) -> Result<(ConnectionHandle, Connection), ConnectError> {
337        if self.cids_exhausted() {
338            return Err(ConnectError::CidsExhausted);
339        }
340        if remote.port() == 0 || remote.ip().is_unspecified() {
341            return Err(ConnectError::InvalidRemoteAddress(remote));
342        }
343        if !self.config.supported_versions.contains(&config.version) {
344            return Err(ConnectError::UnsupportedVersion);
345        }
346
347        let remote_id = (config.initial_dst_cid_provider)();
348        trace!(initial_dcid = %remote_id);
349
350        let ch = ConnectionHandle(self.connections.vacant_key());
351        let local_cid = self.new_cid(ch, PathId::ZERO);
352        let params = TransportParameters::new(
353            &config.transport,
354            &self.config,
355            self.local_cid_generator.as_ref(),
356            local_cid,
357            None,
358            &mut self.rng,
359        );
360        let tls = config
361            .crypto
362            .start_session(config.version, server_name, &params)?;
363
364        let conn = self.add_connection(
365            ch,
366            config.version,
367            remote_id,
368            local_cid,
369            remote_id,
370            FourTuple {
371                remote,
372                local_ip: None,
373            },
374            now,
375            tls,
376            config.transport,
377            SideArgs::Client {
378                token_store: config.token_store,
379                server_name: server_name.into(),
380            },
381            &params,
382        );
383        Ok((ch, conn))
384    }
385
386    /// Generates new CIDs and creates message to send to the connection state
387    fn send_new_identifiers(
388        &mut self,
389        path_id: PathId,
390        now: Instant,
391        ch: ConnectionHandle,
392        num: u64,
393    ) -> ConnectionEvent {
394        let mut ids = vec![];
395        for _ in 0..num {
396            let id = self.new_cid(ch, path_id);
397            let cid_meta = self.connections[ch].local_cids.entry(path_id).or_default();
398            let sequence = cid_meta.issued;
399            cid_meta.issued += 1;
400            cid_meta.cids.insert(sequence, id);
401            ids.push(IssuedCid {
402                path_id,
403                sequence,
404                id,
405                reset_token: ResetToken::new(&*self.config.reset_key, id),
406            });
407        }
408        ConnectionEvent(ConnectionEventInner::NewIdentifiers(
409            ids,
410            now,
411            self.local_cid_generator.cid_len(),
412            self.local_cid_generator.cid_lifetime(),
413        ))
414    }
415
416    /// Generate a connection ID for `ch`
417    fn new_cid(&mut self, ch: ConnectionHandle, path_id: PathId) -> ConnectionId {
418        loop {
419            let cid = self.local_cid_generator.generate_cid();
420            if cid.is_empty() {
421                // Zero-length CID; nothing to track
422                debug_assert_eq!(self.local_cid_generator.cid_len(), 0);
423                return cid;
424            }
425            if let hash_map::Entry::Vacant(e) = self.index.connection_ids.entry(cid) {
426                e.insert((ch, path_id));
427                break cid;
428            }
429        }
430    }
431
432    fn handle_first_packet(
433        &mut self,
434        datagram_len: usize,
435        event: DatagramConnectionEvent,
436        network_path: FourTuple,
437        buf: &mut Vec<u8>,
438    ) -> Option<DatagramEvent> {
439        let dst_cid = event.first_decode.dst_cid();
440        let header = event.first_decode.initial_header().unwrap();
441
442        let Some(server_config) = &self.server_config else {
443            debug!("packet for unrecognized connection {}", dst_cid);
444            return self
445                .stateless_reset(event.now, datagram_len, network_path, dst_cid, buf)
446                .map(DatagramEvent::Response);
447        };
448
449        if datagram_len < MIN_INITIAL_SIZE as usize {
450            debug!("ignoring short initial for connection {}", dst_cid);
451            return None;
452        }
453
454        let crypto = match server_config.crypto.initial_keys(header.version, dst_cid) {
455            Ok(keys) => keys,
456            Err(UnsupportedVersion) => {
457                // This probably indicates that the user set supported_versions incorrectly in
458                // `EndpointConfig`.
459                debug!(
460                    "ignoring initial packet version {:#x} unsupported by cryptographic layer",
461                    header.version
462                );
463                return None;
464            }
465        };
466
467        if let Err(reason) = self.early_validate_first_packet(header) {
468            return Some(DatagramEvent::Response(self.initial_close(
469                header.version,
470                network_path,
471                &crypto,
472                header.src_cid,
473                reason,
474                buf,
475            )));
476        }
477
478        let packet = match event.first_decode.finish(Some(&*crypto.header.remote)) {
479            Ok(packet) => packet,
480            Err(e) => {
481                trace!("unable to decode initial packet: {}", e);
482                return None;
483            }
484        };
485
486        if !packet.reserved_bits_valid() {
487            debug!("dropping connection attempt with invalid reserved bits");
488            return None;
489        }
490
491        let Header::Initial(header) = packet.header else {
492            panic!("non-initial packet in handle_first_packet()");
493        };
494
495        let server_config = self.server_config.as_ref().unwrap().clone();
496
497        let token = match IncomingToken::from_header(&header, &server_config, network_path.remote) {
498            Ok(token) => token,
499            Err(InvalidRetryTokenError) => {
500                debug!("rejecting invalid retry token");
501                return Some(DatagramEvent::Response(self.initial_close(
502                    header.version,
503                    network_path,
504                    &crypto,
505                    header.src_cid,
506                    TransportError::INVALID_TOKEN(""),
507                    buf,
508                )));
509            }
510        };
511
512        let incoming_idx = self.incoming_buffers.insert(IncomingBuffer::default());
513        self.index
514            .insert_initial_incoming(header.dst_cid, incoming_idx);
515
516        Some(DatagramEvent::NewConnection(Incoming {
517            received_at: event.now,
518            network_path,
519            ecn: event.ecn,
520            packet: InitialPacket {
521                header,
522                header_data: packet.header_data,
523                payload: packet.payload,
524            },
525            rest: event.remaining,
526            crypto,
527            token,
528            incoming_idx,
529            improper_drop_warner: IncomingImproperDropWarner,
530        }))
531    }
532
533    /// Attempt to accept this incoming connection (an error may still occur)
534    // box err to avoid clippy::result_large_err
535    pub fn accept(
536        &mut self,
537        mut incoming: Incoming,
538        now: Instant,
539        buf: &mut Vec<u8>,
540        server_config: Option<Arc<ServerConfig>>,
541    ) -> Result<(ConnectionHandle, Connection), Box<AcceptError>> {
542        let remote_address_validated = incoming.remote_address_validated();
543        incoming.improper_drop_warner.dismiss();
544        let incoming_buffer = self.incoming_buffers.remove(incoming.incoming_idx);
545        self.all_incoming_buffers_total_bytes -= incoming_buffer.total_bytes;
546
547        let packet_number = incoming.packet.header.number.expand(0);
548        let InitialHeader {
549            src_cid,
550            dst_cid,
551            version,
552            ..
553        } = incoming.packet.header;
554        let server_config =
555            server_config.unwrap_or_else(|| self.server_config.as_ref().unwrap().clone());
556
557        if server_config
558            .transport
559            .max_idle_timeout
560            .is_some_and(|timeout| {
561                incoming.received_at + Duration::from_millis(timeout.into()) <= now
562            })
563        {
564            debug!("abandoning accept of stale initial");
565            self.index.remove_initial(dst_cid);
566            return Err(Box::new(AcceptError {
567                cause: ConnectionError::TimedOut,
568                response: None,
569            }));
570        }
571
572        if self.cids_exhausted() {
573            debug!("refusing connection");
574            self.index.remove_initial(dst_cid);
575            return Err(Box::new(AcceptError {
576                cause: ConnectionError::CidsExhausted,
577                response: Some(self.initial_close(
578                    version,
579                    incoming.network_path,
580                    &incoming.crypto,
581                    src_cid,
582                    TransportError::CONNECTION_REFUSED(""),
583                    buf,
584                )),
585            }));
586        }
587
588        if incoming
589            .crypto
590            .packet
591            .remote
592            .decrypt(
593                PathId::ZERO,
594                packet_number,
595                &incoming.packet.header_data,
596                &mut incoming.packet.payload,
597            )
598            .is_err()
599        {
600            debug!(packet_number, "failed to authenticate initial packet");
601            self.index.remove_initial(dst_cid);
602            return Err(Box::new(AcceptError {
603                cause: TransportError::PROTOCOL_VIOLATION("authentication failed").into(),
604                response: None,
605            }));
606        };
607
608        let ch = ConnectionHandle(self.connections.vacant_key());
609        let local_cid = self.new_cid(ch, PathId::ZERO);
610        let mut params = TransportParameters::new(
611            &server_config.transport,
612            &self.config,
613            self.local_cid_generator.as_ref(),
614            local_cid,
615            Some(&server_config),
616            &mut self.rng,
617        );
618        params.stateless_reset_token = Some(ResetToken::new(&*self.config.reset_key, local_cid));
619        params.original_dst_cid = Some(incoming.token.orig_dst_cid);
620        params.retry_src_cid = incoming.token.retry_src_cid;
621        let mut pref_addr_cid = None;
622        if server_config.has_preferred_address() {
623            let cid = self.new_cid(ch, PathId::ZERO);
624            pref_addr_cid = Some(cid);
625            params.preferred_address = Some(PreferredAddress {
626                address_v4: server_config.preferred_address_v4,
627                address_v6: server_config.preferred_address_v6,
628                connection_id: cid,
629                stateless_reset_token: ResetToken::new(&*self.config.reset_key, cid),
630            });
631        }
632
633        let tls = server_config.crypto.clone().start_session(version, &params);
634        let transport_config = server_config.transport.clone();
635        let mut conn = self.add_connection(
636            ch,
637            version,
638            dst_cid,
639            local_cid,
640            src_cid,
641            incoming.network_path,
642            incoming.received_at,
643            tls,
644            transport_config,
645            SideArgs::Server {
646                server_config,
647                pref_addr_cid,
648                path_validated: remote_address_validated,
649            },
650            &params,
651        );
652        self.index.insert_initial(dst_cid, ch);
653
654        match conn.handle_first_packet(
655            incoming.received_at,
656            incoming.network_path,
657            incoming.ecn,
658            packet_number,
659            incoming.packet,
660            incoming.rest,
661        ) {
662            Ok(()) => {
663                trace!(id = ch.0, icid = %dst_cid, "new connection");
664
665                for event in incoming_buffer.datagrams {
666                    conn.handle_event(ConnectionEvent(ConnectionEventInner::Datagram(event)))
667                }
668
669                Ok((ch, conn))
670            }
671            Err(e) => {
672                debug!("handshake failed: {}", e);
673                self.handle_event(ch, EndpointEvent(EndpointEventInner::Drained));
674                let response = match e {
675                    ConnectionError::TransportError(ref e) => Some(self.initial_close(
676                        version,
677                        incoming.network_path,
678                        &incoming.crypto,
679                        src_cid,
680                        e.clone(),
681                        buf,
682                    )),
683                    _ => None,
684                };
685                Err(Box::new(AcceptError { cause: e, response }))
686            }
687        }
688    }
689
690    /// Check if we should refuse a connection attempt regardless of the packet's contents
691    fn early_validate_first_packet(
692        &mut self,
693        header: &ProtectedInitialHeader,
694    ) -> Result<(), TransportError> {
695        let config = &self.server_config.as_ref().unwrap();
696        if self.cids_exhausted() || self.incoming_buffers.len() >= config.max_incoming {
697            return Err(TransportError::CONNECTION_REFUSED(""));
698        }
699
700        // RFC9000 §7.2 dictates that initial (client-chosen) destination CIDs must be at least 8
701        // bytes. If this is a Retry packet, then the length must instead match our usual CID
702        // length. If we ever issue non-Retry address validation tokens via `NEW_TOKEN`, then we'll
703        // also need to validate CID length for those after decoding the token.
704        if header.dst_cid.len() < 8
705            && (header.token_pos.is_empty()
706                || header.dst_cid.len() != self.local_cid_generator.cid_len())
707        {
708            debug!(
709                "rejecting connection due to invalid DCID length {}",
710                header.dst_cid.len()
711            );
712            return Err(TransportError::PROTOCOL_VIOLATION(
713                "invalid destination CID length",
714            ));
715        }
716
717        Ok(())
718    }
719
720    /// Reject this incoming connection attempt
721    pub fn refuse(&mut self, incoming: Incoming, buf: &mut Vec<u8>) -> Transmit {
722        self.clean_up_incoming(&incoming);
723        incoming.improper_drop_warner.dismiss();
724
725        self.initial_close(
726            incoming.packet.header.version,
727            incoming.network_path,
728            &incoming.crypto,
729            incoming.packet.header.src_cid,
730            TransportError::CONNECTION_REFUSED(""),
731            buf,
732        )
733    }
734
735    /// Respond with a retry packet, requiring the client to retry with address validation
736    ///
737    /// Errors if `incoming.may_retry()` is false.
738    pub fn retry(&mut self, incoming: Incoming, buf: &mut Vec<u8>) -> Result<Transmit, RetryError> {
739        if !incoming.may_retry() {
740            return Err(RetryError(Box::new(incoming)));
741        }
742
743        self.clean_up_incoming(&incoming);
744        incoming.improper_drop_warner.dismiss();
745
746        let server_config = self.server_config.as_ref().unwrap();
747
748        // First Initial
749        // The peer will use this as the DCID of its following Initials. Initial DCIDs are
750        // looked up separately from Handshake/Data DCIDs, so there is no risk of collision
751        // with established connections. In the unlikely event that a collision occurs
752        // between two connections in the initial phase, both will fail fast and may be
753        // retried by the application layer.
754        let local_cid = self.local_cid_generator.generate_cid();
755
756        let payload = TokenPayload::Retry {
757            address: incoming.network_path.remote,
758            orig_dst_cid: incoming.packet.header.dst_cid,
759            issued: server_config.time_source.now(),
760        };
761        let token = Token::new(payload, &mut self.rng).encode(&*server_config.token_key);
762
763        let header = Header::Retry {
764            src_cid: local_cid,
765            dst_cid: incoming.packet.header.src_cid,
766            version: incoming.packet.header.version,
767        };
768
769        let encode = header.encode(buf);
770        buf.put_slice(&token);
771        buf.extend_from_slice(&server_config.crypto.retry_tag(
772            incoming.packet.header.version,
773            incoming.packet.header.dst_cid,
774            buf,
775        ));
776        encode.finish(buf, &*incoming.crypto.header.local, None);
777
778        Ok(Transmit {
779            destination: incoming.network_path.remote,
780            ecn: None,
781            size: buf.len(),
782            segment_size: None,
783            src_ip: incoming.network_path.local_ip,
784        })
785    }
786
787    /// Ignore this incoming connection attempt, not sending any packet in response
788    ///
789    /// Doing this actively, rather than merely dropping the [`Incoming`], is necessary to prevent
790    /// memory leaks due to state within [`Endpoint`] tracking the incoming connection.
791    pub fn ignore(&mut self, incoming: Incoming) {
792        self.clean_up_incoming(&incoming);
793        incoming.improper_drop_warner.dismiss();
794    }
795
796    /// Clean up endpoint data structures associated with an `Incoming`.
797    fn clean_up_incoming(&mut self, incoming: &Incoming) {
798        self.index.remove_initial(incoming.packet.header.dst_cid);
799        let incoming_buffer = self.incoming_buffers.remove(incoming.incoming_idx);
800        self.all_incoming_buffers_total_bytes -= incoming_buffer.total_bytes;
801    }
802
803    fn add_connection(
804        &mut self,
805        ch: ConnectionHandle,
806        version: u32,
807        init_cid: ConnectionId,
808        local_cid: ConnectionId,
809        remote_cid: ConnectionId,
810        network_path: FourTuple,
811        now: Instant,
812        tls: Box<dyn crypto::Session>,
813        transport_config: Arc<TransportConfig>,
814        side_args: SideArgs,
815        // Only used for qlog.
816        params: &TransportParameters,
817    ) -> Connection {
818        let mut rng_seed = [0; 32];
819        self.rng.fill_bytes(&mut rng_seed);
820        let side = side_args.side();
821        let pref_addr_cid = side_args.pref_addr_cid();
822
823        let qlog =
824            transport_config.create_qlog_sink(side_args.side(), network_path.remote, init_cid, now);
825
826        qlog.emit_connection_started(
827            now,
828            local_cid,
829            remote_cid,
830            network_path.remote,
831            network_path.local_ip,
832            params,
833        );
834
835        let conn = Connection::new(
836            self.config.clone(),
837            transport_config,
838            init_cid,
839            local_cid,
840            remote_cid,
841            network_path,
842            tls,
843            self.local_cid_generator.as_ref(),
844            now,
845            version,
846            self.allow_mtud,
847            rng_seed,
848            side_args,
849            qlog,
850        );
851
852        let mut path_cids = PathLocalCids::default();
853        path_cids.cids.insert(path_cids.issued, local_cid);
854        path_cids.issued += 1;
855
856        if let Some(cid) = pref_addr_cid {
857            debug_assert_eq!(path_cids.issued, 1, "preferred address cid seq must be 1");
858            path_cids.cids.insert(path_cids.issued, cid);
859            path_cids.issued += 1;
860        }
861
862        let id = self.connections.insert(ConnectionMeta {
863            init_cid,
864            local_cids: FxHashMap::from_iter([(PathId::ZERO, path_cids)]),
865            network_path,
866            side,
867            reset_token: Default::default(),
868        });
869        debug_assert_eq!(id, ch.0, "connection handle allocation out of sync");
870
871        self.index.insert_conn(network_path, local_cid, ch, side);
872
873        conn
874    }
875
876    fn initial_close(
877        &mut self,
878        version: u32,
879        network_path: FourTuple,
880        crypto: &Keys,
881        remote_id: ConnectionId,
882        reason: TransportError,
883        buf: &mut Vec<u8>,
884    ) -> Transmit {
885        // We don't need to worry about CID collisions in initial closes because the peer
886        // shouldn't respond, and if it does, and the CID collides, we'll just drop the
887        // unexpected response.
888        let local_id = self.local_cid_generator.generate_cid();
889        let number = PacketNumber::U8(0);
890        let header = Header::Initial(InitialHeader {
891            dst_cid: remote_id,
892            src_cid: local_id,
893            number,
894            token: Bytes::new(),
895            version,
896        });
897
898        let partial_encode = header.encode(buf);
899        let max_len =
900            INITIAL_MTU as usize - partial_encode.header_len - crypto.packet.local.tag_len();
901        frame::Close::from(reason).encoder(max_len).encode(buf);
902        buf.resize(buf.len() + crypto.packet.local.tag_len(), 0);
903        partial_encode.finish(
904            buf,
905            &*crypto.header.local,
906            Some((0, Default::default(), &*crypto.packet.local)),
907        );
908        Transmit {
909            destination: network_path.remote,
910            ecn: None,
911            size: buf.len(),
912            segment_size: None,
913            src_ip: network_path.local_ip,
914        }
915    }
916
917    /// Access the configuration used by this endpoint
918    pub fn config(&self) -> &EndpointConfig {
919        &self.config
920    }
921
922    /// Number of connections that are currently open
923    pub fn open_connections(&self) -> usize {
924        self.connections.len()
925    }
926
927    /// Counter for the number of bytes currently used
928    /// in the buffers for Initial and 0-RTT messages for pending incoming connections
929    pub fn incoming_buffer_bytes(&self) -> u64 {
930        self.all_incoming_buffers_total_bytes
931    }
932
933    #[cfg(test)]
934    pub(crate) fn known_connections(&self) -> usize {
935        let x = self.connections.len();
936        debug_assert_eq!(x, self.index.connection_ids_initial.len());
937        // Not all connections have known reset tokens
938        debug_assert!(x >= self.index.connection_reset_tokens.0.len());
939        // Not all connections have unique remotes, and 0-length CIDs might not be in use.
940        debug_assert!(x >= self.index.incoming_connection_remotes.len());
941        debug_assert!(x >= self.index.outgoing_connection_remotes.len());
942        x
943    }
944
945    #[cfg(test)]
946    pub(crate) fn known_cids(&self) -> usize {
947        self.index.connection_ids.len()
948    }
949
950    /// Whether we've used up 3/4 of the available CID space
951    ///
952    /// We leave some space unused so that `new_cid` can be relied upon to finish quickly. We don't
953    /// bother to check when CID longer than 4 bytes are used because 2^40 connections is a lot.
954    fn cids_exhausted(&self) -> bool {
955        self.local_cid_generator.cid_len() <= 4
956            && self.local_cid_generator.cid_len() != 0
957            && (2usize.pow(self.local_cid_generator.cid_len() as u32 * 8)
958                - self.index.connection_ids.len())
959                < 2usize.pow(self.local_cid_generator.cid_len() as u32 * 8 - 2)
960    }
961}
962
963impl fmt::Debug for Endpoint {
964    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
965        fmt.debug_struct("Endpoint")
966            .field("rng", &self.rng)
967            .field("index", &self.index)
968            .field("connections", &self.connections)
969            .field("config", &self.config)
970            .field("server_config", &self.server_config)
971            // incoming_buffers too large
972            .field("incoming_buffers.len", &self.incoming_buffers.len())
973            .field(
974                "all_incoming_buffers_total_bytes",
975                &self.all_incoming_buffers_total_bytes,
976            )
977            .finish()
978    }
979}
980
981/// Buffered Initial and 0-RTT messages for a pending incoming connection
982#[derive(Default)]
983struct IncomingBuffer {
984    datagrams: Vec<DatagramConnectionEvent>,
985    total_bytes: u64,
986}
987
988/// Part of protocol state incoming datagrams can be routed to
989#[derive(Copy, Clone, Debug)]
990enum RouteDatagramTo {
991    Incoming(usize),
992    Connection(ConnectionHandle, PathId),
993}
994
995/// Maps packets to existing connections
996#[derive(Default, Debug)]
997struct ConnectionIndex {
998    /// Identifies connections based on the initial DCID the peer utilized
999    ///
1000    /// Uses a standard `HashMap` to protect against hash collision attacks.
1001    ///
1002    /// Used by the server, not the client.
1003    connection_ids_initial: HashMap<ConnectionId, RouteDatagramTo>,
1004    /// Identifies connections based on locally created CIDs
1005    ///
1006    /// Uses a cheaper hash function since keys are locally created
1007    connection_ids: FxHashMap<ConnectionId, (ConnectionHandle, PathId)>,
1008    /// Identifies incoming connections with zero-length CIDs
1009    ///
1010    /// Uses a standard `HashMap` to protect against hash collision attacks.
1011    incoming_connection_remotes: HashMap<FourTuple, ConnectionHandle>,
1012    /// Identifies outgoing connections with zero-length CIDs
1013    ///
1014    /// We don't yet support explicit source addresses for client connections, and zero-length CIDs
1015    /// require a unique 4-tuple, so at most one client connection with zero-length local CIDs
1016    /// may be established per remote. We must omit the local address from the key because we don't
1017    /// necessarily know what address we're sending from, and hence receiving at.
1018    ///
1019    /// Uses a standard `HashMap` to protect against hash collision attacks.
1020    // TODO(matheus23): It's possible this could be changed now that we track the full 4-tuple on the client side, too.
1021    outgoing_connection_remotes: HashMap<SocketAddr, ConnectionHandle>,
1022    /// Reset tokens provided by the peer for the CID each connection is currently sending to
1023    ///
1024    /// Incoming stateless resets do not have correct CIDs, so we need this to identify the correct
1025    /// recipient, if any.
1026    connection_reset_tokens: ResetTokenTable,
1027}
1028
1029impl ConnectionIndex {
1030    /// Associate an incoming connection with its initial destination CID
1031    fn insert_initial_incoming(&mut self, dst_cid: ConnectionId, incoming_key: usize) {
1032        if dst_cid.is_empty() {
1033            return;
1034        }
1035        self.connection_ids_initial
1036            .insert(dst_cid, RouteDatagramTo::Incoming(incoming_key));
1037    }
1038
1039    /// Remove an association with an initial destination CID
1040    fn remove_initial(&mut self, dst_cid: ConnectionId) {
1041        if dst_cid.is_empty() {
1042            return;
1043        }
1044        let removed = self.connection_ids_initial.remove(&dst_cid);
1045        debug_assert!(removed.is_some());
1046    }
1047
1048    /// Associate a connection with its initial destination CID
1049    fn insert_initial(&mut self, dst_cid: ConnectionId, connection: ConnectionHandle) {
1050        if dst_cid.is_empty() {
1051            return;
1052        }
1053        self.connection_ids_initial.insert(
1054            dst_cid,
1055            RouteDatagramTo::Connection(connection, PathId::ZERO),
1056        );
1057    }
1058
1059    /// Associate a connection with its first locally-chosen destination CID if used, or otherwise
1060    /// its current 4-tuple
1061    fn insert_conn(
1062        &mut self,
1063        network_path: FourTuple,
1064        dst_cid: ConnectionId,
1065        connection: ConnectionHandle,
1066        side: Side,
1067    ) {
1068        match dst_cid.len() {
1069            0 => match side {
1070                Side::Server => {
1071                    self.incoming_connection_remotes
1072                        .insert(network_path, connection);
1073                }
1074                Side::Client => {
1075                    self.outgoing_connection_remotes
1076                        .insert(network_path.remote, connection);
1077                }
1078            },
1079            _ => {
1080                self.connection_ids
1081                    .insert(dst_cid, (connection, PathId::ZERO));
1082            }
1083        }
1084    }
1085
1086    /// Discard a connection ID
1087    fn retire(&mut self, dst_cid: ConnectionId) {
1088        self.connection_ids.remove(&dst_cid);
1089    }
1090
1091    /// Remove all references to a connection
1092    fn remove(&mut self, conn: &ConnectionMeta) {
1093        if conn.side.is_server() {
1094            self.remove_initial(conn.init_cid);
1095        }
1096        for cid in conn
1097            .local_cids
1098            .values()
1099            .flat_map(|pcids| pcids.cids.values())
1100        {
1101            self.connection_ids.remove(cid);
1102        }
1103        self.incoming_connection_remotes.remove(&conn.network_path);
1104        self.outgoing_connection_remotes
1105            .remove(&conn.network_path.remote);
1106        for (remote, token) in conn.reset_token.values() {
1107            self.connection_reset_tokens.remove(*remote, *token);
1108        }
1109    }
1110
1111    /// Find the existing connection that `datagram` should be routed to, if any
1112    fn get(&self, network_path: &FourTuple, datagram: &PartialDecode) -> Option<RouteDatagramTo> {
1113        if !datagram.dst_cid().is_empty()
1114            && let Some(&(ch, path_id)) = self.connection_ids.get(&datagram.dst_cid())
1115        {
1116            return Some(RouteDatagramTo::Connection(ch, path_id));
1117        }
1118        if (datagram.is_initial() || datagram.is_0rtt())
1119            && let Some(&ch) = self.connection_ids_initial.get(&datagram.dst_cid())
1120        {
1121            return Some(ch);
1122        }
1123        if datagram.dst_cid().is_empty() {
1124            if let Some(&ch) = self.incoming_connection_remotes.get(network_path) {
1125                // Never multipath because QUIC-MULTIPATH 1.1 mandates the use of non-zero
1126                // length CIDs.  So this is always PathId::ZERO.
1127                return Some(RouteDatagramTo::Connection(ch, PathId::ZERO));
1128            }
1129            if let Some(&ch) = self.outgoing_connection_remotes.get(&network_path.remote) {
1130                // Like above, QUIC-MULTIPATH 1.1 mandates the use of non-zero length CIDs.
1131                return Some(RouteDatagramTo::Connection(ch, PathId::ZERO));
1132            }
1133        }
1134        let data = datagram.data();
1135        if data.len() < RESET_TOKEN_SIZE {
1136            return None;
1137        }
1138        // For stateless resets the PathId is meaningless since it closes the entire
1139        // connection regardless of path.  So use PathId::ZERO.
1140        self.connection_reset_tokens
1141            .get(network_path.remote, &data[data.len() - RESET_TOKEN_SIZE..])
1142            .cloned()
1143            .map(|ch| RouteDatagramTo::Connection(ch, PathId::ZERO))
1144    }
1145}
1146
1147#[derive(Debug)]
1148pub(crate) struct ConnectionMeta {
1149    init_cid: ConnectionId,
1150    /// Locally issues CIDs for each path
1151    local_cids: FxHashMap<PathId, PathLocalCids>,
1152    /// Remote/local addresses the connection began with
1153    ///
1154    /// Only needed to support connections with zero-length CIDs, which cannot migrate, so we don't
1155    /// bother keeping it up to date.
1156    network_path: FourTuple,
1157    side: Side,
1158    /// Reset tokens provided by the peer for CIDs we're currently sending to
1159    ///
1160    /// Since each reset token is for a CID, it is also for a fixed remote address which is
1161    /// also stored. This allows us to look up which reset tokens we might expect from a
1162    /// given remote address, see [`ResetTokenTable`].
1163    ///
1164    /// Each path has its own active CID. We use the [`PathId`] as a unique index, allowing
1165    /// us to retire the reset token when a path is abandoned.
1166    // TODO(matheus23): Should be migrated to make reset tokens per 4-tuple instead of per remote addr
1167    reset_token: FxHashMap<PathId, (SocketAddr, ResetToken)>,
1168}
1169
1170/// Local connection IDs for a single path
1171#[derive(Debug, Default)]
1172struct PathLocalCids {
1173    /// Number of connection IDs that have been issued in (PATH_)NEW_CONNECTION_ID frames
1174    ///
1175    /// Another way of saying this is that this is the next sequence number to be issued.
1176    issued: u64,
1177    /// Issues CIDs indexed by their sequence number.
1178    cids: FxHashMap<u64, ConnectionId>,
1179}
1180
1181/// Internal identifier for a `Connection` currently associated with an endpoint
1182#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash, Ord, PartialOrd)]
1183pub struct ConnectionHandle(pub usize);
1184
1185impl From<ConnectionHandle> for usize {
1186    fn from(x: ConnectionHandle) -> Self {
1187        x.0
1188    }
1189}
1190
1191impl Index<ConnectionHandle> for Slab<ConnectionMeta> {
1192    type Output = ConnectionMeta;
1193    fn index(&self, ch: ConnectionHandle) -> &ConnectionMeta {
1194        &self[ch.0]
1195    }
1196}
1197
1198impl IndexMut<ConnectionHandle> for Slab<ConnectionMeta> {
1199    fn index_mut(&mut self, ch: ConnectionHandle) -> &mut ConnectionMeta {
1200        &mut self[ch.0]
1201    }
1202}
1203
1204/// Event resulting from processing a single datagram
1205pub enum DatagramEvent {
1206    /// The datagram is redirected to its `Connection`
1207    ConnectionEvent(ConnectionHandle, ConnectionEvent),
1208    /// The datagram may result in starting a new `Connection`
1209    NewConnection(Incoming),
1210    /// Response generated directly by the endpoint
1211    Response(Transmit),
1212}
1213
1214/// An incoming connection for which the server has not yet begun its part of the handshake.
1215#[derive(derive_more::Debug)]
1216pub struct Incoming {
1217    #[debug(skip)]
1218    received_at: Instant,
1219    network_path: FourTuple,
1220    ecn: Option<EcnCodepoint>,
1221    #[debug(skip)]
1222    packet: InitialPacket,
1223    #[debug(skip)]
1224    rest: Option<BytesMut>,
1225    #[debug(skip)]
1226    crypto: Keys,
1227    token: IncomingToken,
1228    incoming_idx: usize,
1229    #[debug(skip)]
1230    improper_drop_warner: IncomingImproperDropWarner,
1231}
1232
1233impl Incoming {
1234    /// The local IP address which was used when the peer established the connection
1235    pub fn local_ip(&self) -> Option<IpAddr> {
1236        self.network_path.local_ip
1237    }
1238
1239    /// The peer's UDP address
1240    pub fn remote_address(&self) -> SocketAddr {
1241        self.network_path.remote
1242    }
1243
1244    /// Whether the socket address that is initiating this connection has been validated
1245    ///
1246    /// This means that the sender of the initial packet has proved that they can receive traffic
1247    /// sent to `self.remote_address()`.
1248    ///
1249    /// If `self.remote_address_validated()` is false, `self.may_retry()` is guaranteed to be true.
1250    /// The inverse is not guaranteed.
1251    pub fn remote_address_validated(&self) -> bool {
1252        self.token.validated
1253    }
1254
1255    /// Whether it is legal to respond with a retry packet
1256    ///
1257    /// If `self.remote_address_validated()` is false, `self.may_retry()` is guaranteed to be true.
1258    /// The inverse is not guaranteed.
1259    pub fn may_retry(&self) -> bool {
1260        self.token.retry_src_cid.is_none()
1261    }
1262
1263    /// The original destination connection ID sent by the client
1264    pub fn orig_dst_cid(&self) -> ConnectionId {
1265        self.token.orig_dst_cid
1266    }
1267
1268    /// Decrypt the Initial packet payload
1269    ///
1270    /// This clones and decrypts the packet payload (~1200 bytes).
1271    /// Can be used to extract information from the TLS ClientHello without completing the handshake.
1272    pub fn decrypt(&self) -> Option<DecryptedInitial> {
1273        let packet_number = self.packet.header.number.expand(0);
1274        let mut payload = self.packet.payload.clone();
1275        self.crypto
1276            .packet
1277            .remote
1278            .decrypt(
1279                PathId::ZERO,
1280                packet_number,
1281                &self.packet.header_data,
1282                &mut payload,
1283            )
1284            .ok()?;
1285        Some(DecryptedInitial(payload.freeze()))
1286    }
1287}
1288
1289/// Decrypted payload of a QUIC Initial packet
1290///
1291/// Obtained via [`Incoming::decrypt`]. Can be used to extract information from
1292/// the TLS ClientHello without completing the handshake.
1293pub struct DecryptedInitial(Bytes);
1294
1295impl DecryptedInitial {
1296    /// Best-effort extraction of the ALPN protocols from the TLS ClientHello
1297    ///
1298    /// Parses the CRYPTO frames to extract the ALPN extension. This is intended
1299    /// for routing and filtering; it is not guaranteed to succeed if the
1300    /// ClientHello spans multiple packets. Returns `None` if parsing fails.
1301    pub fn alpns(&self) -> Option<IncomingAlpns> {
1302        let frames = frame::Iter::new(self.0.clone()).ok()?;
1303        let mut first = None;
1304        let mut rest = Vec::new();
1305        for frame in frames {
1306            match frame {
1307                Ok(frame::Frame::Crypto(crypto)) => match first {
1308                    None => first = Some(crypto),
1309                    Some(_) => rest.push(crypto),
1310                },
1311                Err(_) => return None,
1312                _ => {}
1313            }
1314        }
1315        let first = first?;
1316
1317        // Fast path: single CRYPTO frame at offset 0 (no extra allocation)
1318        if rest.is_empty() && first.offset == 0 {
1319            let data = find_alpn_data(&first.data).ok()?;
1320            return Some(IncomingAlpns { data, pos: 0 });
1321        }
1322
1323        // Slow path: reassemble multiple CRYPTO frames
1324        rest.push(first);
1325        let source = assemble_crypto_frames(&mut rest)?;
1326        let data = find_alpn_data(&source).ok()?;
1327        Some(IncomingAlpns { data, pos: 0 })
1328    }
1329}
1330
1331/// TLS handshake type for ClientHello messages
1332/// <https://www.rfc-editor.org/rfc/rfc8446#section-4.1.2>
1333const TLS_HANDSHAKE_TYPE_CLIENT_HELLO: u8 = 0x01;
1334/// TLS extension type for Application-Layer Protocol Negotiation
1335/// <https://www.rfc-editor.org/rfc/rfc7301#section-3.1>
1336const TLS_EXTENSION_TYPE_ALPN: u16 = 0x0010;
1337/// Size of the fixed-length fields in a ClientHello (client_version + random)
1338/// <https://www.rfc-editor.org/rfc/rfc8446#section-4.1.2>
1339const TLS_CLIENT_HELLO_FIXED_LEN: usize = 2 + 32;
1340
1341/// Iterator over ALPN protocol names from a TLS ClientHello
1342///
1343/// Yields protocol names as [`Bytes`] slices. On the common fast path (single
1344/// CRYPTO frame), the only allocation is the payload clone for decryption.
1345pub struct IncomingAlpns {
1346    data: Bytes,
1347    pos: usize,
1348}
1349
1350impl Iterator for IncomingAlpns {
1351    type Item = Result<Bytes, UnexpectedEnd>;
1352
1353    fn next(&mut self) -> Option<Self::Item> {
1354        if self.pos >= self.data.len() {
1355            return None;
1356        }
1357        let len = self.data[self.pos] as usize;
1358        self.pos += 1;
1359        if self.pos + len > self.data.len() {
1360            return Some(Err(UnexpectedEnd));
1361        }
1362        let proto = self.data.slice(self.pos..self.pos + len);
1363        self.pos += len;
1364        Some(Ok(proto))
1365    }
1366}
1367
1368/// Sort CRYPTO frames by offset and concatenate into a contiguous `Bytes`
1369///
1370/// Returns `None` if there are gaps in the stream.
1371fn assemble_crypto_frames(frames: &mut [frame::Crypto]) -> Option<Bytes> {
1372    frames.sort_by_key(|f| f.offset);
1373    let capacity = frames.iter().map(|f| f.data.len()).sum();
1374    let mut buf = Vec::with_capacity(capacity);
1375    for f in frames.iter() {
1376        let start = f.offset as usize;
1377        if start > buf.len() {
1378            return None;
1379        }
1380        let end = start + f.data.len();
1381        if end > buf.len() {
1382            buf.extend_from_slice(&f.data[buf.len() - start..]);
1383        }
1384    }
1385    Some(Bytes::from(buf))
1386}
1387
1388/// Locate the raw ALPN protocol list data within a TLS ClientHello message
1389///
1390/// Parses the ClientHello in `source` and returns a [`Bytes`] containing the
1391/// u8-length-prefixed protocol names (after the outer ProtocolNameList u16
1392/// length prefix). The returned `Bytes` is a zero-copy slice of `source`.
1393fn find_alpn_data(source: &Bytes) -> Result<Bytes, UnexpectedEnd> {
1394    let mut r = &**source;
1395
1396    if u8::decode(&mut r)? != TLS_HANDSHAKE_TYPE_CLIENT_HELLO {
1397        return Err(UnexpectedEnd);
1398    }
1399
1400    // Handshake message length (u24), scopes the remainder
1401    let len = decode_u24(&mut r)?;
1402    let mut body = take(&mut r, len)?;
1403
1404    // Client version + random
1405    skip(&mut body, TLS_CLIENT_HELLO_FIXED_LEN)?;
1406
1407    // Session ID, cipher suites, compression methods
1408    skip_u8_prefixed(&mut body)?;
1409    skip_u16_prefixed(&mut body)?;
1410    skip_u8_prefixed(&mut body)?;
1411
1412    // Extensions
1413    let mut exts = take_u16_prefixed(&mut body)?;
1414    while exts.has_remaining() {
1415        let ext_type = u16::decode(&mut exts)?;
1416        let ext_data = take_u16_prefixed(&mut exts)?;
1417        if ext_type == TLS_EXTENSION_TYPE_ALPN {
1418            let list = take_u16_prefixed(&mut &*ext_data)?;
1419            return Ok(source.slice_ref(list));
1420        }
1421    }
1422    Err(UnexpectedEnd)
1423}
1424
1425/// Decode a big-endian u24 as usize
1426fn decode_u24(r: &mut &[u8]) -> Result<usize, UnexpectedEnd> {
1427    let a = u8::decode(r)?;
1428    let b = u8::decode(r)?;
1429    let c = u8::decode(r)?;
1430    Ok(u32::from_be_bytes([0, a, b, c]) as usize)
1431}
1432
1433/// Take `len` bytes from the front and return them as a sub-slice
1434fn take<'a>(r: &mut &'a [u8], len: usize) -> Result<&'a [u8], UnexpectedEnd> {
1435    if r.remaining() < len {
1436        return Err(UnexpectedEnd);
1437    }
1438    let data = &r[..len];
1439    r.advance(len);
1440    Ok(data)
1441}
1442
1443/// Read a u16 length prefix and return the sub-slice it covers
1444fn take_u16_prefixed<'a>(r: &mut &'a [u8]) -> Result<&'a [u8], UnexpectedEnd> {
1445    let len = u16::decode(r)? as usize;
1446    take(r, len)
1447}
1448
1449/// Advance past `n` bytes
1450fn skip(r: &mut &[u8], len: usize) -> Result<(), UnexpectedEnd> {
1451    take(r, len)?;
1452    Ok(())
1453}
1454
1455/// Skip a u8-length-prefixed field
1456fn skip_u8_prefixed(r: &mut &[u8]) -> Result<(), UnexpectedEnd> {
1457    let len = u8::decode(r)? as usize;
1458    skip(r, len)
1459}
1460
1461/// Skip a u16-length-prefixed field
1462fn skip_u16_prefixed(r: &mut &[u8]) -> Result<(), UnexpectedEnd> {
1463    let len = u16::decode(r)? as usize;
1464    skip(r, len)
1465}
1466
1467struct IncomingImproperDropWarner;
1468
1469impl IncomingImproperDropWarner {
1470    fn dismiss(self) {
1471        mem::forget(self);
1472    }
1473}
1474
1475impl Drop for IncomingImproperDropWarner {
1476    fn drop(&mut self) {
1477        warn!(
1478            "noq_proto::Incoming dropped without passing to Endpoint::accept/refuse/retry/ignore \
1479               (may cause memory leak and eventual inability to accept new connections)"
1480        );
1481    }
1482}
1483
1484/// Errors in the parameters being used to create a new connection
1485///
1486/// These arise before any I/O has been performed.
1487#[derive(Debug, Error, Clone, PartialEq, Eq)]
1488pub enum ConnectError {
1489    /// The endpoint can no longer create new connections
1490    ///
1491    /// Indicates that a necessary component of the endpoint has been dropped or otherwise disabled.
1492    #[error("endpoint stopping")]
1493    EndpointStopping,
1494    /// The connection could not be created because not enough of the CID space is available
1495    ///
1496    /// Try using longer connection IDs
1497    #[error("CIDs exhausted")]
1498    CidsExhausted,
1499    /// The given server name was malformed
1500    #[error("invalid server name: {0}")]
1501    InvalidServerName(String),
1502    /// The remote [`SocketAddr`] supplied was malformed
1503    ///
1504    /// Examples include attempting to connect to port 0, or using an inappropriate address family.
1505    #[error("invalid remote address: {0}")]
1506    InvalidRemoteAddress(SocketAddr),
1507    /// No default client configuration was set up
1508    ///
1509    /// Use `Endpoint::connect_with` to specify a client configuration.
1510    #[error("no default client config")]
1511    NoDefaultClientConfig,
1512    /// The local endpoint does not support the QUIC version specified in the client configuration
1513    #[error("unsupported QUIC version")]
1514    UnsupportedVersion,
1515}
1516
1517/// Error type for attempting to accept an [`Incoming`]
1518#[derive(Debug)]
1519pub struct AcceptError {
1520    /// Underlying error describing reason for failure
1521    pub cause: ConnectionError,
1522    /// Optional response to transmit back
1523    pub response: Option<Transmit>,
1524}
1525
1526/// Error for attempting to retry an [`Incoming`] which already bears a token from a previous retry
1527#[derive(Debug, Error)]
1528#[error("retry() with validated Incoming")]
1529pub struct RetryError(Box<Incoming>);
1530
1531impl RetryError {
1532    /// Get the [`Incoming`]
1533    pub fn into_incoming(self) -> Incoming {
1534        *self.0
1535    }
1536}
1537
1538/// Reset Tokens which are associated with peer socket addresses
1539///
1540/// The standard `HashMap` is used since both `SocketAddr` and `ResetToken` are
1541/// peer generated and might be usable for hash collision attacks.
1542#[derive(Default, Debug)]
1543struct ResetTokenTable(HashMap<SocketAddr, HashMap<ResetToken, ConnectionHandle>>);
1544
1545impl ResetTokenTable {
1546    fn insert(&mut self, remote: SocketAddr, token: ResetToken, ch: ConnectionHandle) -> bool {
1547        self.0
1548            .entry(remote)
1549            .or_default()
1550            .insert(token, ch)
1551            .is_some()
1552    }
1553
1554    fn remove(&mut self, remote: SocketAddr, token: ResetToken) {
1555        use std::collections::hash_map::Entry;
1556        match self.0.entry(remote) {
1557            Entry::Vacant(_) => {}
1558            Entry::Occupied(mut e) => {
1559                e.get_mut().remove(&token);
1560                if e.get().is_empty() {
1561                    e.remove_entry();
1562                }
1563            }
1564        }
1565    }
1566
1567    fn get(&self, remote: SocketAddr, token: &[u8]) -> Option<&ConnectionHandle> {
1568        let token = ResetToken::from(<[u8; RESET_TOKEN_SIZE]>::try_from(token).ok()?);
1569        self.0.get(&remote)?.get(&token)
1570    }
1571}
1572
1573#[cfg(test)]
1574mod tests {
1575    use super::*;
1576
1577    #[test]
1578    fn assemble_contiguous() {
1579        let data = b"hello world";
1580        let mut frames = vec![
1581            frame::Crypto {
1582                offset: 0,
1583                data: Bytes::from_static(&data[..5]),
1584            },
1585            frame::Crypto {
1586                offset: 5,
1587                data: Bytes::from_static(&data[5..]),
1588            },
1589        ];
1590        assert_eq!(&assemble_crypto_frames(&mut frames).unwrap()[..], &data[..]);
1591    }
1592
1593    #[test]
1594    fn assemble_out_of_order() {
1595        let data = b"hello world";
1596        let mut frames = vec![
1597            frame::Crypto {
1598                offset: 5,
1599                data: Bytes::from_static(&data[5..]),
1600            },
1601            frame::Crypto {
1602                offset: 0,
1603                data: Bytes::from_static(&data[..5]),
1604            },
1605        ];
1606        assert_eq!(&assemble_crypto_frames(&mut frames).unwrap()[..], &data[..]);
1607    }
1608
1609    #[test]
1610    fn assemble_with_overlap() {
1611        let data = b"hello world";
1612        let mut frames = vec![
1613            frame::Crypto {
1614                offset: 0,
1615                data: Bytes::from_static(&data[..7]),
1616            },
1617            frame::Crypto {
1618                offset: 5,
1619                data: Bytes::from_static(&data[5..]),
1620            },
1621        ];
1622        assert_eq!(&assemble_crypto_frames(&mut frames).unwrap()[..], &data[..]);
1623    }
1624
1625    #[test]
1626    fn assemble_with_gap() {
1627        let mut frames = vec![frame::Crypto {
1628            offset: 10,
1629            data: Bytes::from_static(b"world"),
1630        }];
1631        assert!(assemble_crypto_frames(&mut frames).is_none());
1632    }
1633}
noq_proto/endpoint.rs

noq_proto/
endpoint.rs
