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1 /*
2  * ngtcp2
3  *
4  * Copyright (c) 2017 ngtcp2 contributors
5  *
6  * Permission is hereby granted, free of charge, to any person obtaining
7  * a copy of this software and associated documentation files (the
8  * "Software"), to deal in the Software without restriction, including
9  * without limitation the rights to use, copy, modify, merge, publish,
10  * distribute, sublicense, and/or sell copies of the Software, and to
11  * permit persons to whom the Software is furnished to do so, subject to
12  * the following conditions:
13  *
14  * The above copyright notice and this permission notice shall be
15  * included in all copies or substantial portions of the Software.
16  *
17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
18  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
19  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
20  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
21  * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
22  * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
23  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
24  */
25 #ifndef NGTCP2_CONN_H
26 #define NGTCP2_CONN_H
27 
28 #ifdef HAVE_CONFIG_H
29 #  include <config.h>
30 #endif /* HAVE_CONFIG_H */
31 
32 #include <ngtcp2/ngtcp2.h>
33 
34 #include "ngtcp2_mem.h"
35 #include "ngtcp2_crypto.h"
36 #include "ngtcp2_acktr.h"
37 #include "ngtcp2_rtb.h"
38 #include "ngtcp2_strm.h"
39 #include "ngtcp2_idtr.h"
40 #include "ngtcp2_str.h"
41 #include "ngtcp2_pkt.h"
42 #include "ngtcp2_log.h"
43 #include "ngtcp2_pq.h"
44 #include "ngtcp2_cc.h"
45 #include "ngtcp2_bbr.h"
46 #include "ngtcp2_bbr2.h"
47 #include "ngtcp2_pv.h"
48 #include "ngtcp2_pmtud.h"
49 #include "ngtcp2_cid.h"
50 #include "ngtcp2_buf.h"
51 #include "ngtcp2_ppe.h"
52 #include "ngtcp2_qlog.h"
53 #include "ngtcp2_rst.h"
54 
55 typedef enum {
56   /* Client specific handshake states */
57   NGTCP2_CS_CLIENT_INITIAL,
58   NGTCP2_CS_CLIENT_WAIT_HANDSHAKE,
59   NGTCP2_CS_CLIENT_TLS_HANDSHAKE_FAILED,
60   /* Server specific handshake states */
61   NGTCP2_CS_SERVER_INITIAL,
62   NGTCP2_CS_SERVER_WAIT_HANDSHAKE,
63   NGTCP2_CS_SERVER_TLS_HANDSHAKE_FAILED,
64   /* Shared by both client and server */
65   NGTCP2_CS_POST_HANDSHAKE,
66   NGTCP2_CS_CLOSING,
67   NGTCP2_CS_DRAINING,
68 } ngtcp2_conn_state;
69 
70 /* NGTCP2_MAX_STREAMS is the maximum number of streams. */
71 #define NGTCP2_MAX_STREAMS (1LL << 60)
72 
73 /* NGTCP2_MAX_NUM_BUFFED_RX_PKTS is the maximum number of buffered
74    reordered packets. */
75 #define NGTCP2_MAX_NUM_BUFFED_RX_PKTS 4
76 
77 /* NGTCP2_MAX_REORDERED_CRYPTO_DATA is the maximum offset of crypto
78    data which is not continuous.  In other words, there is a gap of
79    unreceived data. */
80 #define NGTCP2_MAX_REORDERED_CRYPTO_DATA 65536
81 
82 /* NGTCP2_MAX_RX_INITIAL_CRYPTO_DATA is the maximum offset of received
83    crypto stream in Initial packet.  We set this hard limit here
84    because crypto stream is unbounded. */
85 #define NGTCP2_MAX_RX_INITIAL_CRYPTO_DATA 65536
86 /* NGTCP2_MAX_RX_HANDSHAKE_CRYPTO_DATA is the maximum offset of
87    received crypto stream in Handshake packet.  We set this hard limit
88    here because crypto stream is unbounded. */
89 #define NGTCP2_MAX_RX_HANDSHAKE_CRYPTO_DATA 65536
90 
91 /* NGTCP2_MAX_RETRIES is the number of Retry packet which client can
92    accept. */
93 #define NGTCP2_MAX_RETRIES 3
94 
95 /* NGTCP2_MAX_BOUND_DCID_POOL_SIZE is the maximum number of
96    destination connection ID which have been bound to a particular
97    path, but not yet used as primary path and path validation is not
98    performed from the local endpoint. */
99 #define NGTCP2_MAX_BOUND_DCID_POOL_SIZE 4
100 /* NGTCP2_MAX_DCID_POOL_SIZE is the maximum number of destination
101    connection ID the remote endpoint provides to store.  It must be
102    the power of 2. */
103 #define NGTCP2_MAX_DCID_POOL_SIZE 8
104 /* NGTCP2_MAX_DCID_RETIRED_SIZE is the maximum number of retired DCID
105    kept to catch in-flight packet on retired path. */
106 #define NGTCP2_MAX_DCID_RETIRED_SIZE 2
107 /* NGTCP2_MAX_SCID_POOL_SIZE is the maximum number of source
108    connection ID the local endpoint provides to the remote endpoint.
109    The chosen value was described in old draft.  Now a remote endpoint
110    tells the maximum value.  The value can be quite large, and we have
111    to put the sane limit.*/
112 #define NGTCP2_MAX_SCID_POOL_SIZE 8
113 
114 /* NGTCP2_MAX_NON_ACK_TX_PKT is the maximum number of continuous non
115    ACK-eliciting packets. */
116 #define NGTCP2_MAX_NON_ACK_TX_PKT 3
117 
118 /* NGTCP2_ECN_MAX_NUM_VALIDATION_PKTS is the maximum number of ECN marked
119    packets sent in NGTCP2_ECN_STATE_TESTING period. */
120 #define NGTCP2_ECN_MAX_NUM_VALIDATION_PKTS 10
121 
122 /* NGTCP2_CONNECTION_CLOSE_ERROR_MAX_REASONLEN is the maximum length
123    of reason phrase to remember.  If the received reason phrase is
124    longer than this value, it is truncated. */
125 #define NGTCP2_CONNECTION_CLOSE_ERROR_MAX_REASONLEN 1024
126 
127 /* NGTCP2_WRITE_PKT_FLAG_NONE indicates that no flag is set. */
128 #define NGTCP2_WRITE_PKT_FLAG_NONE 0x00u
129 /* NGTCP2_WRITE_PKT_FLAG_REQUIRE_PADDING indicates that packet other
130    than Initial packet should be padded.  Initial packet might be
131    padded based on QUIC requirement regardless of this flag. */
132 #define NGTCP2_WRITE_PKT_FLAG_REQUIRE_PADDING 0x01u
133 /* NGTCP2_WRITE_PKT_FLAG_MORE indicates that more frames might come
134    and it should be encoded into the current packet. */
135 #define NGTCP2_WRITE_PKT_FLAG_MORE 0x02u
136 
137 /*
138  * ngtcp2_max_frame is defined so that it covers the largest ACK
139  * frame.
140  */
141 typedef union ngtcp2_max_frame {
142   ngtcp2_frame fr;
143   struct {
144     ngtcp2_ack ack;
145     /* ack includes 1 ngtcp2_ack_blk. */
146     ngtcp2_ack_blk blks[NGTCP2_MAX_ACK_BLKS - 1];
147   } ackfr;
148 } ngtcp2_max_frame;
149 
150 typedef struct ngtcp2_path_challenge_entry {
151   ngtcp2_path_storage ps;
152   uint8_t data[8];
153 } ngtcp2_path_challenge_entry;
154 
155 void ngtcp2_path_challenge_entry_init(ngtcp2_path_challenge_entry *pcent,
156                                       const ngtcp2_path *path,
157                                       const uint8_t *data);
158 
159 /* NGTCP2_CONN_FLAG_NONE indicates that no flag is set. */
160 #define NGTCP2_CONN_FLAG_NONE 0x00u
161 /* NGTCP2_CONN_FLAG_HANDSHAKE_COMPLETED is set when TLS stack declares
162    that TLS handshake has completed.  The condition of this
163    declaration varies between TLS implementations and this flag does
164    not indicate the completion of QUIC handshake.  Some
165    implementations declare TLS handshake completion as server when
166    they write off Server Finished and before deriving application rx
167    secret. */
168 #define NGTCP2_CONN_FLAG_HANDSHAKE_COMPLETED 0x01u
169 /* NGTCP2_CONN_FLAG_CONN_ID_NEGOTIATED is set if connection ID is
170    negotiated.  This is only used for client. */
171 #define NGTCP2_CONN_FLAG_CONN_ID_NEGOTIATED 0x02u
172 /* NGTCP2_CONN_FLAG_TRANSPORT_PARAM_RECVED is set if transport
173    parameters are received. */
174 #define NGTCP2_CONN_FLAG_TRANSPORT_PARAM_RECVED 0x04u
175 /* NGTCP2_CONN_FLAG_LOCAL_TRANSPORT_PARAMS_COMMITTED is set when a
176    local transport parameters are applied. */
177 #define NGTCP2_CONN_FLAG_LOCAL_TRANSPORT_PARAMS_COMMITTED 0x08u
178 /* NGTCP2_CONN_FLAG_RECV_RETRY is set when a client receives Retry
179    packet. */
180 #define NGTCP2_CONN_FLAG_RECV_RETRY 0x10u
181 /* NGTCP2_CONN_FLAG_EARLY_DATA_REJECTED is set when 0-RTT packet is
182    rejected by a peer. */
183 #define NGTCP2_CONN_FLAG_EARLY_DATA_REJECTED 0x20u
184 /* NGTCP2_CONN_FLAG_KEEP_ALIVE_CANCELLED is set when the expired
185    keep-alive timer has been cancelled. */
186 #define NGTCP2_CONN_FLAG_KEEP_ALIVE_CANCELLED 0x40u
187 /* NGTCP2_CONN_FLAG_HANDSHAKE_CONFIRMED is set when an endpoint
188    confirmed completion of handshake. */
189 #define NGTCP2_CONN_FLAG_HANDSHAKE_CONFIRMED 0x80u
190 /* NGTCP2_CONN_FLAG_HANDSHAKE_COMPLETED_HANDLED is set when the
191    library transitions its state to "post handshake". */
192 #define NGTCP2_CONN_FLAG_HANDSHAKE_COMPLETED_HANDLED 0x0100u
193 /* NGTCP2_CONN_FLAG_HANDSHAKE_EARLY_RETRANSMIT is set when the early
194    handshake retransmission has done when server receives overlapping
195    Initial crypto data. */
196 #define NGTCP2_CONN_FLAG_HANDSHAKE_EARLY_RETRANSMIT 0x0200u
197 /* NGTCP2_CONN_FLAG_CLEAR_FIXED_BIT indicates that the local endpoint
198    sends a QUIC packet without Fixed Bit set if a remote endpoint
199    supports Greasing QUIC Bit extension. */
200 #define NGTCP2_CONN_FLAG_CLEAR_FIXED_BIT 0x0400u
201 /* NGTCP2_CONN_FLAG_KEY_UPDATE_NOT_CONFIRMED is set when key update is
202    not confirmed by the local endpoint.  That is, it has not received
203    ACK frame which acknowledges packet which is encrypted with new
204    key. */
205 #define NGTCP2_CONN_FLAG_KEY_UPDATE_NOT_CONFIRMED 0x0800u
206 /* NGTCP2_CONN_FLAG_PPE_PENDING is set when
207    NGTCP2_WRITE_STREAM_FLAG_MORE is used and the intermediate state of
208    ngtcp2_ppe is stored in pkt struct of ngtcp2_conn. */
209 #define NGTCP2_CONN_FLAG_PPE_PENDING 0x1000u
210 /* NGTCP2_CONN_FLAG_RESTART_IDLE_TIMER_ON_WRITE is set when idle timer
211    should be restarted on next write. */
212 #define NGTCP2_CONN_FLAG_RESTART_IDLE_TIMER_ON_WRITE 0x2000u
213 /* NGTCP2_CONN_FLAG_SERVER_ADDR_VERIFIED indicates that server as peer
214    verified client address.  This flag is only used by client. */
215 #define NGTCP2_CONN_FLAG_SERVER_ADDR_VERIFIED 0x4000u
216 /* NGTCP2_CONN_FLAG_EARLY_KEY_INSTALLED indicates that an early key is
217    installed.  conn->early.ckm cannot be used for this purpose because
218    it might be discarded when a certain condition is met. */
219 #define NGTCP2_CONN_FLAG_EARLY_KEY_INSTALLED 0x8000u
220 /* NGTCP2_CONN_FLAG_KEY_UPDATE_INITIATOR is set when the local
221    endpoint has initiated key update. */
222 #define NGTCP2_CONN_FLAG_KEY_UPDATE_INITIATOR 0x10000u
223 
224 typedef struct ngtcp2_crypto_data {
225   ngtcp2_buf buf;
226   /* pkt_type is the type of packet to send data in buf.  If it is 0,
227      it must be sent in Short packet.  Otherwise, it is sent the long
228      packet type denoted by pkt_type. */
229   uint8_t pkt_type;
230 } ngtcp2_crypto_data;
231 
232 typedef struct ngtcp2_pktns {
233   struct {
234     /* last_pkt_num is the packet number which the local endpoint sent
235        last time.*/
236     int64_t last_pkt_num;
237     ngtcp2_frame_chain *frq;
238     /* num_non_ack_pkt is the number of continuous non ACK-eliciting
239        packets. */
240     size_t num_non_ack_pkt;
241 
242     struct {
243       /* ect0 is the number of QUIC packets, not UDP datagram, which
244          are sent in UDP datagram with ECT0 marking. */
245       size_t ect0;
246       /* start_pkt_num is the lowest packet number that are sent
247          during ECN validation period. */
248       int64_t start_pkt_num;
249       /* validation_pkt_sent is the number of QUIC packets sent during
250          validation period. */
251       size_t validation_pkt_sent;
252       /* validation_pkt_lost is the number of QUIC packets lost during
253          validation period. */
254       size_t validation_pkt_lost;
255     } ecn;
256   } tx;
257 
258   struct {
259     /* pngap tracks received packet number in order to suppress
260        duplicated packet number. */
261     ngtcp2_gaptr pngap;
262     /* max_pkt_num is the largest packet number received so far. */
263     int64_t max_pkt_num;
264     /* max_pkt_ts is the timestamp when max_pkt_num packet is
265        received. */
266     ngtcp2_tstamp max_pkt_ts;
267     /* max_ack_eliciting_pkt_num is the largest ack-eliciting packet
268        number received so far. */
269     int64_t max_ack_eliciting_pkt_num;
270     /*
271      * buffed_pkts is buffered packets which cannot be decrypted with
272      * the current encryption level.
273      *
274      * In server Initial encryption level, 0-RTT packet may be buffered.
275      * In server Handshake encryption level, Short packet may be buffered.
276      *
277      * In client Initial encryption level, Handshake or Short packet may
278      * be buffered.  In client Handshake encryption level, Short packet
279      * may be buffered.
280      *
281      * - 0-RTT packet is only buffered in server Initial encryption
282      *   level ngtcp2_pktns.
283      *
284      * - Handshake packet is only buffered in client Handshake
285      *   encryption level ngtcp2_pktns.
286      *
287      * - Short packet is only buffered in Short encryption level
288      *   ngtcp2_pktns.
289      */
290     ngtcp2_pkt_chain *buffed_pkts;
291 
292     struct {
293       /* ect0, ect1, and ce are the number of QUIC packets received
294          with those markings. */
295       size_t ect0;
296       size_t ect1;
297       size_t ce;
298       struct {
299         /* ect0, ect1, ce are the ECN counts received in the latest
300            ACK frame. */
301         uint64_t ect0;
302         uint64_t ect1;
303         uint64_t ce;
304       } ack;
305     } ecn;
306   } rx;
307 
308   struct {
309     struct {
310       /* frq contains crypto data sorted by their offset. */
311       ngtcp2_ksl frq;
312       /* offset is the offset of crypto stream in this packet number
313          space. */
314       uint64_t offset;
315       /* ckm is a cryptographic key, and iv to encrypt outgoing
316          packets. */
317       ngtcp2_crypto_km *ckm;
318       /* hp_ctx is cipher context for packet header protection. */
319       ngtcp2_crypto_cipher_ctx hp_ctx;
320       /* data is the submitted crypto data. */
321       ngtcp2_buf_chain *data;
322     } tx;
323 
324     struct {
325       /* ckm is a cryptographic key, and iv to decrypt incoming
326          packets. */
327       ngtcp2_crypto_km *ckm;
328       /* hp_ctx is cipher context for packet header protection. */
329       ngtcp2_crypto_cipher_ctx hp_ctx;
330     } rx;
331 
332     ngtcp2_strm strm;
333     ngtcp2_crypto_ctx ctx;
334   } crypto;
335 
336   ngtcp2_acktr acktr;
337   ngtcp2_rtb rtb;
338 } ngtcp2_pktns;
339 
340 typedef enum ngtcp2_ecn_state {
341   NGTCP2_ECN_STATE_TESTING,
342   NGTCP2_ECN_STATE_UNKNOWN,
343   NGTCP2_ECN_STATE_FAILED,
344   NGTCP2_ECN_STATE_CAPABLE,
345 } ngtcp2_ecn_state;
346 
347 ngtcp2_static_ringbuf_def(dcid_bound, NGTCP2_MAX_BOUND_DCID_POOL_SIZE,
348                           sizeof(ngtcp2_dcid));
349 ngtcp2_static_ringbuf_def(dcid_unused, NGTCP2_MAX_DCID_POOL_SIZE,
350                           sizeof(ngtcp2_dcid));
351 ngtcp2_static_ringbuf_def(dcid_retired, NGTCP2_MAX_DCID_RETIRED_SIZE,
352                           sizeof(ngtcp2_dcid));
353 ngtcp2_static_ringbuf_def(path_challenge, 4,
354                           sizeof(ngtcp2_path_challenge_entry));
355 
356 ngtcp2_objalloc_def(strm, ngtcp2_strm, oplent);
357 
358 struct ngtcp2_conn {
359   ngtcp2_objalloc frc_objalloc;
360   ngtcp2_objalloc rtb_entry_objalloc;
361   ngtcp2_objalloc strm_objalloc;
362   ngtcp2_conn_state state;
363   ngtcp2_callbacks callbacks;
364   /* rcid is a connection ID present in Initial or 0-RTT packet from
365      client as destination connection ID.  Server uses this field to
366      check that duplicated Initial or 0-RTT packet are indeed sent to
367      this connection.  Client uses this field to validate
368      original_destination_connection_id transport parameter. */
369   ngtcp2_cid rcid;
370   /* oscid is the source connection ID initially used by the local
371      endpoint. */
372   ngtcp2_cid oscid;
373   /* retry_scid is the source connection ID from Retry packet.  Client
374      records it in order to verify retry_source_connection_id
375      transport parameter.  Server does not use this field. */
376   ngtcp2_cid retry_scid;
377   ngtcp2_pktns *in_pktns;
378   ngtcp2_pktns *hs_pktns;
379   ngtcp2_pktns pktns;
380 
381   struct {
382     /* current is the current destination connection ID. */
383     ngtcp2_dcid current;
384     /* bound is a set of destination connection IDs which are bound to
385        particular paths.  These paths are not validated yet. */
386     ngtcp2_static_ringbuf_dcid_bound bound;
387     /* unused is a set of unused CID received from peer. */
388     ngtcp2_static_ringbuf_dcid_unused unused;
389     /* retired is a set of CID retired by local endpoint.  Keep them
390        in 3*PTO to catch packets in flight along the old path. */
391     ngtcp2_static_ringbuf_dcid_retired retired;
392     /* seqgap tracks received sequence numbers in order to ignore
393        retransmitted duplicated NEW_CONNECTION_ID frame. */
394     ngtcp2_gaptr seqgap;
395     /* retire_prior_to is the largest retire_prior_to received so
396        far. */
397     uint64_t retire_prior_to;
398     struct {
399       /* seqs contains sequence number of Connection ID whose
400          retirement is not acknowledged by the remote endpoint yet. */
401       uint64_t seqs[NGTCP2_MAX_DCID_POOL_SIZE * 2];
402       /* len is the number of sequence numbers that seq contains. */
403       size_t len;
404     } retire_unacked;
405     /* zerolen_seq is a pseudo sequence number of zero-length
406        Destination Connection ID in order to distinguish between
407        them. */
408     uint64_t zerolen_seq;
409   } dcid;
410 
411   struct {
412     /* set is a set of CID sent to peer.  The peer can use any CIDs in
413        this set.  This includes used CID as well as unused ones. */
414     ngtcp2_ksl set;
415     /* used is a set of CID used by peer.  The sort function of this
416        priority queue takes timestamp when CID is retired and sorts
417        them in ascending order. */
418     ngtcp2_pq used;
419     /* last_seq is the last sequence number of connection ID. */
420     uint64_t last_seq;
421     /* num_retired is the number of retired Connection ID still
422        included in set. */
423     size_t num_retired;
424   } scid;
425 
426   struct {
427     /* strmq contains ngtcp2_strm which has frames to send. */
428     ngtcp2_pq strmq;
429     /* strmq_nretrans is the number of entries in strmq which has
430        stream data to resent. */
431     size_t strmq_nretrans;
432     /* ack is ACK frame.  The underlying buffer is reused. */
433     ngtcp2_frame *ack;
434     /* max_ack_blks is the number of additional ngtcp2_ack_blk which
435        ack can contain. */
436     size_t max_ack_blks;
437     /* offset is the offset the local endpoint has sent to the remote
438        endpoint. */
439     uint64_t offset;
440     /* max_offset is the maximum offset that local endpoint can
441        send. */
442     uint64_t max_offset;
443     /* last_max_data_ts is the timestamp when last MAX_DATA frame is
444        sent. */
445     ngtcp2_tstamp last_max_data_ts;
446 
447     struct {
448       /* state is the state of ECN validation */
449       ngtcp2_ecn_state state;
450       /* validation_start_ts is the timestamp when ECN validation is
451          started.  It is UINT64_MAX if it has not started yet. */
452       ngtcp2_tstamp validation_start_ts;
453       /* dgram_sent is the number of UDP datagram sent during ECN
454          validation period. */
455       size_t dgram_sent;
456     } ecn;
457 
458     struct {
459       /* pktlen is the number of bytes written before calling
460          ngtcp2_conn_update_pkt_tx_time which resets this field to
461          0. */
462       size_t pktlen;
463       /* next_ts is the time to send next packet.  It is UINT64_MAX if
464          packet pacing is disabled or expired.*/
465       ngtcp2_tstamp next_ts;
466     } pacing;
467   } tx;
468 
469   struct {
470     /* unsent_max_offset is the maximum offset that remote endpoint
471        can send without extending MAX_DATA.  This limit is not yet
472        notified to the remote endpoint. */
473     uint64_t unsent_max_offset;
474     /* offset is the cumulative sum of stream data received for this
475        connection. */
476     uint64_t offset;
477     /* max_offset is the maximum offset that remote endpoint can
478        send. */
479     uint64_t max_offset;
480     /* window is the connection-level flow control window size. */
481     uint64_t window;
482     /* path_challenge stores received PATH_CHALLENGE data. */
483     ngtcp2_static_ringbuf_path_challenge path_challenge;
484     /* ccerr is the received connection close error. */
485     ngtcp2_connection_close_error ccerr;
486   } rx;
487 
488   struct {
489     ngtcp2_crypto_km *ckm;
490     ngtcp2_crypto_cipher_ctx hp_ctx;
491     ngtcp2_crypto_ctx ctx;
492     /* discard_started_ts is the timestamp when the timer to discard
493        early key has started.  Used by server only. */
494     ngtcp2_tstamp discard_started_ts;
495     /* transport_params is the values remembered by client from the
496        previous session.  These are set by
497        ngtcp2_conn_set_early_remote_transport_params().  Server does
498        not use this field.  Server must not set values for these
499        parameters that are smaller than the remembered values. */
500     struct {
501       uint64_t initial_max_streams_bidi;
502       uint64_t initial_max_streams_uni;
503       uint64_t initial_max_stream_data_bidi_local;
504       uint64_t initial_max_stream_data_bidi_remote;
505       uint64_t initial_max_stream_data_uni;
506       uint64_t initial_max_data;
507       uint64_t active_connection_id_limit;
508       uint64_t max_datagram_frame_size;
509     } transport_params;
510   } early;
511 
512   struct {
513     ngtcp2_settings settings;
514     /* transport_params is the local transport parameters.  It is used
515        for Short packet only. */
516     ngtcp2_transport_params transport_params;
517     struct {
518       /* max_streams is the maximum number of bidirectional streams which
519          the local endpoint can open. */
520       uint64_t max_streams;
521       /* next_stream_id is the bidirectional stream ID which the local
522          endpoint opens next. */
523       int64_t next_stream_id;
524     } bidi;
525 
526     struct {
527       /* max_streams is the maximum number of unidirectional streams
528          which the local endpoint can open. */
529       uint64_t max_streams;
530       /* next_stream_id is the unidirectional stream ID which the
531          local endpoint opens next. */
532       int64_t next_stream_id;
533     } uni;
534   } local;
535 
536   struct {
537     /* transport_params is the received transport parameters during
538        handshake.  It is used for Short packet only. */
539     ngtcp2_transport_params *transport_params;
540     /* pending_transport_params is received transport parameters
541        during handshake.  It is copied to transport_params when 1RTT
542        key is available. */
543     ngtcp2_transport_params *pending_transport_params;
544     struct {
545       ngtcp2_idtr idtr;
546       /* unsent_max_streams is the maximum number of streams of peer
547          initiated bidirectional stream which the local endpoint can
548          accept.  This limit is not yet notified to the remote
549          endpoint. */
550       uint64_t unsent_max_streams;
551       /* max_streams is the maximum number of streams of peer
552          initiated bidirectional stream which the local endpoint can
553          accept. */
554       uint64_t max_streams;
555     } bidi;
556 
557     struct {
558       ngtcp2_idtr idtr;
559       /* unsent_max_streams is the maximum number of streams of peer
560          initiated unidirectional stream which the local endpoint can
561          accept.  This limit is not yet notified to the remote
562          endpoint. */
563       uint64_t unsent_max_streams;
564       /* max_streams is the maximum number of streams of peer
565          initiated unidirectional stream which the local endpoint can
566          accept. */
567       uint64_t max_streams;
568     } uni;
569   } remote;
570 
571   struct {
572     struct {
573       /* new_tx_ckm is a new sender 1RTT key which has not been
574          used. */
575       ngtcp2_crypto_km *new_tx_ckm;
576       /* new_rx_ckm is a new receiver 1RTT key which has not
577          successfully decrypted incoming packet yet. */
578       ngtcp2_crypto_km *new_rx_ckm;
579       /* old_rx_ckm is an old receiver 1RTT key. */
580       ngtcp2_crypto_km *old_rx_ckm;
581       /* confirmed_ts is the time instant when the key update is
582          confirmed by the local endpoint last time.  UINT64_MAX means
583          undefined value. */
584       ngtcp2_tstamp confirmed_ts;
585     } key_update;
586 
587     /* tls_native_handle is a native handle to TLS session object. */
588     void *tls_native_handle;
589     /* decrypt_hp_buf is a buffer which is used to write unprotected
590        packet header. */
591     ngtcp2_vec decrypt_hp_buf;
592     /* decrypt_buf is a buffer which is used to write decrypted data. */
593     ngtcp2_vec decrypt_buf;
594     /* retry_aead is AEAD to verify Retry packet integrity.  It is
595        used by client only. */
596     ngtcp2_crypto_aead retry_aead;
597     /* retry_aead_ctx is AEAD cipher context to verify Retry packet
598        integrity.  It is used by client only. */
599     ngtcp2_crypto_aead_ctx retry_aead_ctx;
600     /* tls_error is TLS related error. */
601     int tls_error;
602     /* tls_alert is TLS alert generated by the local endpoint. */
603     uint8_t tls_alert;
604     /* decryption_failure_count is the number of received packets that
605        fail authentication. */
606     uint64_t decryption_failure_count;
607   } crypto;
608 
609   /* pkt contains the packet intermediate construction data to support
610      NGTCP2_WRITE_STREAM_FLAG_MORE */
611   struct {
612     ngtcp2_crypto_cc cc;
613     ngtcp2_pkt_hd hd;
614     ngtcp2_ppe ppe;
615     ngtcp2_frame_chain **pfrc;
616     int pkt_empty;
617     int hd_logged;
618     /* flags is bitwise OR of zero or more of
619        NGTCP2_RTB_ENTRY_FLAG_*. */
620     uint16_t rtb_entry_flags;
621     ngtcp2_ssize hs_spktlen;
622     int require_padding;
623   } pkt;
624 
625   struct {
626     /* last_ts is a timestamp when a last packet is sent or received
627        on a current path. */
628     ngtcp2_tstamp last_ts;
629     /* timeout is keep-alive timeout.  When it expires, a packet
630        should be sent to a current path to keep connection alive.  It
631        might be used to keep NAT binding intact.  If 0 is set,
632        keep-alive timer is disabled. */
633     ngtcp2_duration timeout;
634   } keep_alive;
635 
636   struct {
637     /* Initial keys for negotiated version.  If original version ==
638        negotiated version, these fields are not used. */
639     struct {
640       ngtcp2_crypto_km *ckm;
641       ngtcp2_crypto_cipher_ctx hp_ctx;
642     } rx;
643     struct {
644       ngtcp2_crypto_km *ckm;
645       ngtcp2_crypto_cipher_ctx hp_ctx;
646     } tx;
647     /* version is QUIC version that the above Initial keys are created
648        for. */
649     uint32_t version;
650     /* preferred_versions is the array of versions that are preferred
651        by the local endpoint.  Server negotiates one of those versions
652        in this array if a client initially selects a less preferred
653        version.  Client uses this field and original_version field to
654        prevent version downgrade attack if it reacted upon Version
655        Negotiation packet. */
656     uint32_t *preferred_versions;
657     /* preferred_versionslen is the number of versions stored in the
658        array pointed by preferred_versions.  This field is only used
659        by server. */
660     size_t preferred_versionslen;
661     /* other_versions is the versions that the local endpoint sends in
662        version_information transport parameter.  This is the wire
663        image of other_versions field of version_information transport
664        parameter. */
665     uint8_t *other_versions;
666     /* other_versionslen is the length of data pointed by
667        other_versions field. */
668     size_t other_versionslen;
669   } vneg;
670 
671   ngtcp2_map strms;
672   ngtcp2_conn_stat cstat;
673   ngtcp2_pv *pv;
674   ngtcp2_pmtud *pmtud;
675   ngtcp2_log log;
676   ngtcp2_qlog qlog;
677   ngtcp2_rst rst;
678   ngtcp2_cc_algo cc_algo;
679   ngtcp2_cc cc;
680   const ngtcp2_mem *mem;
681   /* idle_ts is the time instant when idle timer started. */
682   ngtcp2_tstamp idle_ts;
683   void *user_data;
684   uint32_t client_chosen_version;
685   uint32_t negotiated_version;
686   /* flags is bitwise OR of zero or more of NGTCP2_CONN_FLAG_*. */
687   uint32_t flags;
688   int server;
689 };
690 
691 typedef enum ngtcp2_vmsg_type {
692   NGTCP2_VMSG_TYPE_STREAM,
693   NGTCP2_VMSG_TYPE_DATAGRAM,
694 } ngtcp2_vmsg_type;
695 
696 typedef struct ngtcp2_vmsg_stream {
697   /* strm is a stream that data is sent to. */
698   ngtcp2_strm *strm;
699   /* flags is bitwise OR of zero or more of
700      NGTCP2_WRITE_STREAM_FLAG_*. */
701   uint32_t flags;
702   /* data is the pointer to ngtcp2_vec array which contains the stream
703      data to send. */
704   const ngtcp2_vec *data;
705   /* datacnt is the number of ngtcp2_vec pointed by data. */
706   size_t datacnt;
707   /* pdatalen is the pointer to the variable which the number of bytes
708      written is assigned to if pdatalen is not NULL. */
709   ngtcp2_ssize *pdatalen;
710 } ngtcp2_vmsg_stream;
711 
712 typedef struct ngtcp2_vmsg_datagram {
713   /* data is the pointer to ngtcp2_vec array which contains the data
714      to send. */
715   const ngtcp2_vec *data;
716   /* datacnt is the number of ngtcp2_vec pointed by data. */
717   size_t datacnt;
718   /* dgram_id is an opaque identifier chosen by an application. */
719   uint64_t dgram_id;
720   /* flags is bitwise OR of zero or more of
721      NGTCP2_WRITE_DATAGRAM_FLAG_*. */
722   uint32_t flags;
723   /* paccepted is the pointer to the variable which, if it is not
724      NULL, is assigned nonzero if data is written to a packet. */
725   int *paccepted;
726 } ngtcp2_vmsg_datagram;
727 
728 typedef struct ngtcp2_vmsg {
729   ngtcp2_vmsg_type type;
730   union {
731     ngtcp2_vmsg_stream stream;
732     ngtcp2_vmsg_datagram datagram;
733   };
734 } ngtcp2_vmsg;
735 
736 /*
737  * ngtcp2_conn_sched_ack stores packet number |pkt_num| and its
738  * reception timestamp |ts| in order to send its ACK.
739  *
740  * It returns 0 if it succeeds, or one of the following negative error
741  * codes:
742  *
743  * NGTCP2_ERR_NOMEM
744  *     Out of memory
745  * NGTCP2_ERR_PROTO
746  *     Same packet number has already been added.
747  */
748 int ngtcp2_conn_sched_ack(ngtcp2_conn *conn, ngtcp2_acktr *acktr,
749                           int64_t pkt_num, int active_ack, ngtcp2_tstamp ts);
750 
751 /*
752  * ngtcp2_conn_find_stream returns a stream whose stream ID is
753  * |stream_id|.  If no such stream is found, it returns NULL.
754  */
755 ngtcp2_strm *ngtcp2_conn_find_stream(ngtcp2_conn *conn, int64_t stream_id);
756 
757 /*
758  * conn_init_stream initializes |strm|.  Its stream ID is |stream_id|.
759  * This function adds |strm| to conn->strms.  |strm| must be allocated
760  * by the caller.
761  *
762  * This function returns 0 if it succeeds, or one of the following
763  * negative error codes:
764  *
765  * NGTCP2_ERR_NOMEM
766  *     Out of memory
767  * NGTCP2_ERR_CALLBACK_FAILURE
768  *     User-callback function failed.
769  */
770 int ngtcp2_conn_init_stream(ngtcp2_conn *conn, ngtcp2_strm *strm,
771                             int64_t stream_id, void *stream_user_data);
772 
773 /*
774  * ngtcp2_conn_close_stream closes stream |strm|.
775  *
776  * This function returns 0 if it succeeds, or one of the following
777  * negative error codes:
778  *
779  * NGTCP2_ERR_INVALID_ARGUMENT
780  *     Stream is not found.
781  * NGTCP2_ERR_CALLBACK_FAILURE
782  *     User-defined callback function failed.
783  */
784 int ngtcp2_conn_close_stream(ngtcp2_conn *conn, ngtcp2_strm *strm);
785 
786 /*
787  * ngtcp2_conn_close_stream closes stream |strm| if no further
788  * transmission and reception are allowed, and all reordered incoming
789  * data are emitted to the application, and the transmitted data are
790  * acked.
791  *
792  * This function returns 0 if it succeeds, or one of the following
793  * negative error codes:
794  *
795  * NGTCP2_ERR_INVALID_ARGUMENT
796  *     Stream is not found.
797  * NGTCP2_ERR_CALLBACK_FAILURE
798  *     User-defined callback function failed.
799  */
800 int ngtcp2_conn_close_stream_if_shut_rdwr(ngtcp2_conn *conn, ngtcp2_strm *strm);
801 
802 /*
803  * ngtcp2_conn_update_rtt updates RTT measurements.  |rtt| is a latest
804  * RTT which is not adjusted by ack delay.  |ack_delay| is unscaled
805  * ack_delay included in ACK frame.  |ack_delay| is actually tainted
806  * (sent by peer), so don't assume that |ack_delay| is always smaller
807  * than, or equals to |rtt|.
808  *
809  * This function returns 0 if it succeeds, or one of the following
810  * negative error codes:
811  *
812  * NGTCP2_ERR_INVALID_ARGUMENT
813  *     RTT sample is ignored.
814  */
815 int ngtcp2_conn_update_rtt(ngtcp2_conn *conn, ngtcp2_duration rtt,
816                            ngtcp2_duration ack_delay, ngtcp2_tstamp ts);
817 
818 void ngtcp2_conn_set_loss_detection_timer(ngtcp2_conn *conn, ngtcp2_tstamp ts);
819 
820 int ngtcp2_conn_on_loss_detection_timer(ngtcp2_conn *conn, ngtcp2_tstamp ts);
821 
822 /*
823  * ngtcp2_conn_detect_lost_pkt detects lost packets.
824  *
825  * This function returns 0 if it succeeds, or one of the following
826  * negative error codes:
827  *
828  * NGTCP2_ERR_NOMEM
829  *     Out of memory.
830  */
831 int ngtcp2_conn_detect_lost_pkt(ngtcp2_conn *conn, ngtcp2_pktns *pktns,
832                                 ngtcp2_conn_stat *cstat, ngtcp2_tstamp ts);
833 
834 /*
835  * ngtcp2_conn_tx_strmq_top returns the ngtcp2_strm which sits on the
836  * top of queue.  tx_strmq must not be empty.
837  */
838 ngtcp2_strm *ngtcp2_conn_tx_strmq_top(ngtcp2_conn *conn);
839 
840 /*
841  * ngtcp2_conn_tx_strmq_pop pops the ngtcp2_strm from the queue.
842  * tx_strmq must not be empty.
843  */
844 void ngtcp2_conn_tx_strmq_pop(ngtcp2_conn *conn);
845 
846 /*
847  * ngtcp2_conn_tx_strmq_push pushes |strm| into tx_strmq.
848  *
849  *  This function returns 0 if it succeeds, or one of the following
850  * negative error codes:
851  *
852  * NGTCP2_ERR_NOMEM
853  *     Out of memory.
854  */
855 int ngtcp2_conn_tx_strmq_push(ngtcp2_conn *conn, ngtcp2_strm *strm);
856 
857 /*
858  * ngtcp2_conn_internal_expiry returns the minimum expiry time among
859  * all timers in |conn|.
860  */
861 ngtcp2_tstamp ngtcp2_conn_internal_expiry(ngtcp2_conn *conn);
862 
863 ngtcp2_ssize ngtcp2_conn_write_vmsg(ngtcp2_conn *conn, ngtcp2_path *path,
864                                     int pkt_info_version, ngtcp2_pkt_info *pi,
865                                     uint8_t *dest, size_t destlen,
866                                     ngtcp2_vmsg *vmsg, ngtcp2_tstamp ts);
867 
868 /*
869  * ngtcp2_conn_write_single_frame_pkt writes a packet which contains
870  * |fr| frame only in the buffer pointed by |dest| whose length if
871  * |destlen|.  |type| is a long packet type to send.  If |type| is 0,
872  * Short packet is used.  |dcid| is used as a destination connection
873  * ID.  |flags| is zero or more of NGTCP2_WRITE_PKT_FLAG_*.  Only
874  * NGTCP2_WRITE_PKT_FLAG_REQUIRE_PADDING is recognized.
875  *
876  * The packet written by this function will not be retransmitted.
877  *
878  * This function returns the number of bytes written in |dest| if it
879  * succeeds, or one of the following negative error codes:
880  *
881  * NGTCP2_ERR_CALLBACK_FAILURE
882  *     User-defined callback function failed.
883  */
884 ngtcp2_ssize ngtcp2_conn_write_single_frame_pkt(
885     ngtcp2_conn *conn, ngtcp2_pkt_info *pi, uint8_t *dest, size_t destlen,
886     uint8_t type, uint8_t flags, const ngtcp2_cid *dcid, ngtcp2_frame *fr,
887     uint16_t rtb_entry_flags, const ngtcp2_path *path, ngtcp2_tstamp ts);
888 
889 /*
890  * ngtcp2_conn_commit_local_transport_params commits the local
891  * transport parameters, which is currently set to
892  * conn->local.settings.transport_params.  This function will do some
893  * amends on transport parameters for adjusting default values.
894  *
895  * This function returns 0 if it succeeds, or one of the following
896  * negative error codes:
897  *
898  * NGTCP2_ERR_NOMEM
899  *     Out of memory.
900  * NGTCP2_ERR_INVALID_ARGUMENT
901  *     CID in preferred address equals to the original SCID.
902  */
903 int ngtcp2_conn_commit_local_transport_params(ngtcp2_conn *conn);
904 
905 /*
906  * ngtcp2_conn_lost_pkt_expiry returns the earliest expiry time of
907  * lost packet.
908  */
909 ngtcp2_tstamp ngtcp2_conn_lost_pkt_expiry(ngtcp2_conn *conn);
910 
911 /*
912  * ngtcp2_conn_remove_lost_pkt removes the expired lost packet.
913  */
914 void ngtcp2_conn_remove_lost_pkt(ngtcp2_conn *conn, ngtcp2_tstamp ts);
915 
916 /*
917  * ngtcp2_conn_resched_frames reschedules frames linked from |*pfrc|
918  * for retransmission.
919  *
920  * This function returns 0 if it succeeds, or one of the following
921  * negative error codes:
922  *
923  * NGTCP2_ERR_NOMEM
924  *     Out of memory.
925  */
926 int ngtcp2_conn_resched_frames(ngtcp2_conn *conn, ngtcp2_pktns *pktns,
927                                ngtcp2_frame_chain **pfrc);
928 
929 uint64_t ngtcp2_conn_tx_strmq_first_cycle(ngtcp2_conn *conn);
930 
931 /**
932  * @function
933  *
934  * `ngtcp2_conn_ack_delay_expiry` returns the expiry time point of
935  * delayed protected ACK.  One should call
936  * `ngtcp2_conn_cancel_expired_ack_delay_timer` and
937  * `ngtcp2_conn_write_pkt` (or `ngtcp2_conn_writev_stream`) when it
938  * expires.  It returns UINT64_MAX if there is no expiry.
939  */
940 ngtcp2_tstamp ngtcp2_conn_ack_delay_expiry(ngtcp2_conn *conn);
941 
942 /**
943  * @function
944  *
945  * `ngtcp2_conn_cancel_expired_ack_delay_timer` stops expired ACK
946  * delay timer.  |ts| is the current time.  This function must be
947  * called when `ngtcp2_conn_ack_delay_expiry` <= ts.
948  */
949 void ngtcp2_conn_cancel_expired_ack_delay_timer(ngtcp2_conn *conn,
950                                                 ngtcp2_tstamp ts);
951 
952 /**
953  * @function
954  *
955  * `ngtcp2_conn_loss_detection_expiry` returns the expiry time point
956  * of loss detection timer.  One should call
957  * `ngtcp2_conn_on_loss_detection_timer` and `ngtcp2_conn_write_pkt`
958  * (or `ngtcp2_conn_writev_stream`) when it expires.  It returns
959  * UINT64_MAX if loss detection timer is not armed.
960  */
961 ngtcp2_tstamp ngtcp2_conn_loss_detection_expiry(ngtcp2_conn *conn);
962 
963 /**
964  * @function
965  *
966  * `ngtcp2_conn_get_idle_expiry` returns the time when a connection
967  * should be closed if it continues to be idle.  If idle timeout is
968  * disabled, this function returns ``UINT64_MAX``.
969  */
970 ngtcp2_tstamp ngtcp2_conn_get_idle_expiry(ngtcp2_conn *conn);
971 
972 ngtcp2_duration ngtcp2_conn_compute_pto(ngtcp2_conn *conn, ngtcp2_pktns *pktns);
973 
974 /*
975  * ngtcp2_conn_track_retired_dcid_seq tracks the sequence number |seq|
976  * of unacknowledged retiring Destination Connection ID.
977  *
978  * This function returns 0 if it succeeds, or one of the following
979  * negative error codes:
980  *
981  * NGTCP2_ERR_CONNECTION_ID_LIMIT
982  *     The number of unacknowledged retirement exceeds the limit.
983  */
984 int ngtcp2_conn_track_retired_dcid_seq(ngtcp2_conn *conn, uint64_t seq);
985 
986 /*
987  * ngtcp2_conn_untrack_retired_dcid_seq deletes the sequence number
988  * |seq| of unacknowledged retiring Destination Connection ID.  It is
989  * fine if such sequence number is not found.
990  */
991 void ngtcp2_conn_untrack_retired_dcid_seq(ngtcp2_conn *conn, uint64_t seq);
992 
993 /*
994  * ngtcp2_conn_server_negotiate_version negotiates QUIC version.  It
995  * is compatible version negotiation.  It returns the negotiated QUIC
996  * version.  This function must not be called by client.
997  */
998 uint32_t
999 ngtcp2_conn_server_negotiate_version(ngtcp2_conn *conn,
1000                                      const ngtcp2_version_info *version_info);
1001 
1002 /**
1003  * @function
1004  *
1005  * `ngtcp2_conn_write_connection_close_pkt` writes a packet which
1006  * contains a CONNECTION_CLOSE frame (type 0x1c) in the buffer pointed
1007  * by |dest| whose capacity is |datalen|.
1008  *
1009  * If |path| is not ``NULL``, this function stores the network path
1010  * with which the packet should be sent.  Each addr field must point
1011  * to the buffer which should be at least ``sizeof(struct
1012  * sockaddr_storage)`` bytes long.  The assignment might not be done
1013  * if nothing is written to |dest|.
1014  *
1015  * If |pi| is not ``NULL``, this function stores packet metadata in it
1016  * if it succeeds.  The metadata includes ECN markings.
1017  *
1018  * This function must not be called from inside the callback
1019  * functions.
1020  *
1021  * At the moment, successful call to this function makes connection
1022  * close.  We may change this behaviour in the future to allow
1023  * graceful shutdown.
1024  *
1025  * This function returns the number of bytes written in |dest| if it
1026  * succeeds, or one of the following negative error codes:
1027  *
1028  * :macro:`NGTCP2_ERR_NOMEM`
1029  *     Out of memory
1030  * :macro:`NGTCP2_ERR_NOBUF`
1031  *     Buffer is too small
1032  * :macro:`NGTCP2_ERR_INVALID_STATE`
1033  *     The current state does not allow sending CONNECTION_CLOSE.
1034  * :macro:`NGTCP2_ERR_PKT_NUM_EXHAUSTED`
1035  *     Packet number is exhausted, and cannot send any more packet.
1036  * :macro:`NGTCP2_ERR_CALLBACK_FAILURE`
1037  *     User callback failed
1038  */
1039 ngtcp2_ssize ngtcp2_conn_write_connection_close_pkt(
1040     ngtcp2_conn *conn, ngtcp2_path *path, ngtcp2_pkt_info *pi, uint8_t *dest,
1041     size_t destlen, uint64_t error_code, const uint8_t *reason,
1042     size_t reasonlen, ngtcp2_tstamp ts);
1043 
1044 /**
1045  * @function
1046  *
1047  * `ngtcp2_conn_write_application_close_pkt` writes a packet which
1048  * contains a CONNECTION_CLOSE frame (type 0x1d) in the buffer pointed
1049  * by |dest| whose capacity is |datalen|.
1050  *
1051  * If |path| is not ``NULL``, this function stores the network path
1052  * with which the packet should be sent.  Each addr field must point
1053  * to the buffer which should be at least ``sizeof(struct
1054  * sockaddr_storage)`` bytes long.  The assignment might not be done
1055  * if nothing is written to |dest|.
1056  *
1057  * If |pi| is not ``NULL``, this function stores packet metadata in it
1058  * if it succeeds.  The metadata includes ECN markings.
1059  *
1060  * If handshake has not been confirmed yet, CONNECTION_CLOSE (type
1061  * 0x1c) with error code :macro:`NGTCP2_APPLICATION_ERROR` is written
1062  * instead.
1063  *
1064  * This function must not be called from inside the callback
1065  * functions.
1066  *
1067  * At the moment, successful call to this function makes connection
1068  * close.  We may change this behaviour in the future to allow
1069  * graceful shutdown.
1070  *
1071  * This function returns the number of bytes written in |dest| if it
1072  * succeeds, or one of the following negative error codes:
1073  *
1074  * :macro:`NGTCP2_ERR_NOMEM`
1075  *     Out of memory
1076  * :macro:`NGTCP2_ERR_NOBUF`
1077  *     Buffer is too small
1078  * :macro:`NGTCP2_ERR_INVALID_STATE`
1079  *     The current state does not allow sending CONNECTION_CLOSE.
1080  * :macro:`NGTCP2_ERR_PKT_NUM_EXHAUSTED`
1081  *     Packet number is exhausted, and cannot send any more packet.
1082  * :macro:`NGTCP2_ERR_CALLBACK_FAILURE`
1083  *     User callback failed
1084  */
1085 ngtcp2_ssize ngtcp2_conn_write_application_close_pkt(
1086     ngtcp2_conn *conn, ngtcp2_path *path, ngtcp2_pkt_info *pi, uint8_t *dest,
1087     size_t destlen, uint64_t app_error_code, const uint8_t *reason,
1088     size_t reasonlen, ngtcp2_tstamp ts);
1089 
1090 int ngtcp2_conn_start_pmtud(ngtcp2_conn *conn);
1091 
1092 void ngtcp2_conn_stop_pmtud(ngtcp2_conn *conn);
1093 
1094 /**
1095  * @function
1096  *
1097  * `ngtcp2_conn_set_remote_transport_params` sets transport parameter
1098  * |params| from a remote endpoint to |conn|.
1099  *
1100  * This function returns 0 if it succeeds, or one of the following
1101  * negative error codes:
1102  *
1103  * :macro:`NGTCP2_ERR_TRANSPORT_PARAM`
1104  *     Failed to validate a remote transport parameters.
1105  * :macro:`NGTCP2_ERR_VERSION_NEGOTIATION_FAILURE`
1106  *     Version negotiation failure.
1107  * :macro:`NGTCP2_ERR_CALLBACK_FAILURE`
1108  *     User callback failed
1109  * :macro:`NGTCP2_ERR_NOMEM`
1110  *     Out of memory.
1111  */
1112 int ngtcp2_conn_set_remote_transport_params(
1113     ngtcp2_conn *conn, const ngtcp2_transport_params *params);
1114 
1115 #endif /* NGTCP2_CONN_H */
1116