2 * Copyright 2022 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the Apache License 2.0 (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
10 #include "internal/quic_ackm.h"
11 #include "internal/uint_set.h"
12 #include "internal/common.h"
15 DEFINE_LIST_OF(tx_history, OSSL_ACKM_TX_PKT);
21 * The TX Packet History object tracks information about packets which have been
22 * sent for which we later expect to receive an ACK. It is essentially a simple
23 * database keeping a list of packet information structures in packet number
24 * order which can also be looked up directly by packet number.
26 * We currently only allow packets to be appended to the list (i.e. the packet
27 * numbers of the packets appended to the list must monotonically increase), as
28 * we should not currently need more general functionality such as a sorted list
31 struct tx_pkt_history_st {
32 /* A linked list of all our packets. */
33 OSSL_LIST(tx_history) packets;
36 * Mapping from packet numbers (uint64_t) to (OSSL_ACKM_TX_PKT *)
38 * Invariant: A packet is in this map if and only if it is in the linked
41 LHASH_OF(OSSL_ACKM_TX_PKT) *map;
44 * The lowest packet number which may currently be added to the history list
45 * (inclusive). We do not allow packet numbers to be added to the history
46 * list non-monotonically, so packet numbers must be greater than or equal
52 * Packet number of the highest packet info structure we have yet appended
53 * to the list. This is usually one less than watermark, except when we have
54 * not added any packet yet.
56 uint64_t highest_sent;
59 DEFINE_LHASH_OF_EX(OSSL_ACKM_TX_PKT);
61 static unsigned long tx_pkt_info_hash(const OSSL_ACKM_TX_PKT *pkt)
63 /* Using low bits of the packet number as the hash should be enough */
64 return (unsigned long)pkt->pkt_num;
67 static int tx_pkt_info_compare(const OSSL_ACKM_TX_PKT *a,
68 const OSSL_ACKM_TX_PKT *b)
70 if (a->pkt_num < b->pkt_num)
72 if (a->pkt_num > b->pkt_num)
78 tx_pkt_history_init(struct tx_pkt_history_st *h)
80 ossl_list_tx_history_init(&h->packets);
84 h->map = lh_OSSL_ACKM_TX_PKT_new(tx_pkt_info_hash, tx_pkt_info_compare);
92 tx_pkt_history_destroy(struct tx_pkt_history_st *h)
94 lh_OSSL_ACKM_TX_PKT_free(h->map);
96 ossl_list_tx_history_init(&h->packets);
100 tx_pkt_history_add_actual(struct tx_pkt_history_st *h,
101 OSSL_ACKM_TX_PKT *pkt)
103 OSSL_ACKM_TX_PKT *existing;
106 * There should not be any existing packet with this number
109 existing = lh_OSSL_ACKM_TX_PKT_retrieve(h->map, pkt);
110 if (!ossl_assert(existing == NULL))
113 /* Should not already be in a list. */
114 if (!ossl_assert(ossl_list_tx_history_next(pkt) == NULL
115 && ossl_list_tx_history_prev(pkt) == NULL))
118 lh_OSSL_ACKM_TX_PKT_insert(h->map, pkt);
120 ossl_list_tx_history_insert_tail(&h->packets, pkt);
124 /* Adds a packet information structure to the history list. */
126 tx_pkt_history_add(struct tx_pkt_history_st *h,
127 OSSL_ACKM_TX_PKT *pkt)
129 if (!ossl_assert(pkt->pkt_num >= h->watermark))
132 if (tx_pkt_history_add_actual(h, pkt) < 1)
135 h->watermark = pkt->pkt_num + 1;
136 h->highest_sent = pkt->pkt_num;
140 /* Retrieve a packet information structure by packet number. */
141 static OSSL_ACKM_TX_PKT *
142 tx_pkt_history_by_pkt_num(struct tx_pkt_history_st *h, uint64_t pkt_num)
144 OSSL_ACKM_TX_PKT key;
146 key.pkt_num = pkt_num;
148 return lh_OSSL_ACKM_TX_PKT_retrieve(h->map, &key);
151 /* Remove a packet information structure from the history log. */
153 tx_pkt_history_remove(struct tx_pkt_history_st *h, uint64_t pkt_num)
155 OSSL_ACKM_TX_PKT key, *pkt;
156 key.pkt_num = pkt_num;
158 pkt = tx_pkt_history_by_pkt_num(h, pkt_num);
162 ossl_list_tx_history_remove(&h->packets, pkt);
163 lh_OSSL_ACKM_TX_PKT_delete(h->map, &key);
168 * RX Packet Number Tracking
169 * *************************
171 * **Background.** The RX side of the ACK manager must track packets we have
172 * received for which we have to generate ACK frames. Broadly, this means we
173 * store a set of packet numbers which we have received but which we do not know
174 * for a fact that the transmitter knows we have received.
176 * This must handle various situations:
178 * 1. We receive a packet but have not sent an ACK yet, so the transmitter
179 * does not know whether we have received it or not yet.
181 * 2. We receive a packet and send an ACK which is lost. We do not
182 * immediately know that the ACK was lost and the transmitter does not know
183 * that we have received the packet.
185 * 3. We receive a packet and send an ACK which is received by the
186 * transmitter. The transmitter does not immediately respond with an ACK,
187 * or responds with an ACK which is lost. The transmitter knows that we
188 * have received the packet, but we do not know for sure that it knows,
189 * because the ACK we sent could have been lost.
191 * 4. We receive a packet and send an ACK which is received by the
192 * transmitter. The transmitter subsequently sends us an ACK which confirms
193 * its receipt of the ACK we sent, and we successfully receive that ACK, so
194 * we know that the transmitter knows, that we received the original
197 * Only when we reach case (4) are we relieved of any need to track a given
198 * packet number we have received, because only in this case do we know for sure
199 * that the peer knows we have received the packet. Having reached case (4) we
200 * will never again need to generate an ACK containing the PN in question, but
201 * until we reach that point, we must keep track of the PN as not having been
202 * provably ACKed, as we may have to keep generating ACKs for the given PN not
203 * just until the transmitter receives one, but until we know that it has
204 * received one. This will be referred to herein as "provably ACKed".
206 * **Duplicate handling.** The above discusses the case where we have received a
207 * packet with a given PN but are at best unsure whether the sender knows we
208 * have received it or not. However, we must also handle the case where we have
209 * yet to receive a packet with a given PN in the first place. The reason for
210 * this is because of the requirement expressed by RFC 9000 s. 12.3:
212 * "A receiver MUST discard a newly unprotected packet unless it is certain
213 * that it has not processed another packet with the same packet number from
214 * the same packet number space."
216 * We must ensure we never process a duplicate PN. As such, each possible PN we
217 * can receive must exist in one of the following logical states:
219 * - We have never processed this PN before
220 * (so if we receive such a PN, it can be processed)
222 * - We have processed this PN but it has not yet been provably ACKed
223 * (and should therefore be in any future ACK frame generated;
224 * if we receive such a PN again, it must be ignored)
226 * - We have processed this PN and it has been provably ACKed
227 * (if we receive such a PN again, it must be ignored)
229 * However, if we were to track this state for every PN ever used in the history
230 * of a connection, the amount of state required would increase unboundedly as
231 * the connection goes on (for example, we would have to store a set of every PN
234 * RFC 9000 s. 12.3 continues:
236 * "Endpoints that track all individual packets for the purposes of detecting
237 * duplicates are at risk of accumulating excessive state. The data required
238 * for detecting duplicates can be limited by maintaining a minimum packet
239 * number below which all packets are immediately dropped."
241 * Moreover, RFC 9000 s. 13.2.3 states that:
243 * "A receiver MUST retain an ACK Range unless it can ensure that it will not
244 * subsequently accept packets with numbers in that range. Maintaining a
245 * minimum packet number that increases as ranges are discarded is one way to
246 * achieve this with minimal state."
248 * This touches on a subtlety of the original requirement quoted above: the
249 * receiver MUST discard a packet unless it is certain that it has not processed
250 * another packet with the same PN. However, this does not forbid the receiver
251 * from also discarding some PNs even though it has not yet processed them. In
252 * other words, implementations must be conservative and err in the direction of
253 * assuming a packet is a duplicate, but it is acceptable for this to come at
254 * the cost of falsely identifying some packets as duplicates.
256 * This allows us to bound the amount of state we must keep, and we adopt the
257 * suggested strategy quoted above to do so. We define a watermark PN below
258 * which all PNs are in the same state. This watermark is only ever increased.
259 * Thus the PNs the state for which needs to be explicitly tracked is limited to
260 * only a small number of recent PNs, and all older PNs have an assumed state.
262 * Any given PN thus falls into one of the following states:
264 * - (A) The PN is above the watermark but we have not yet received it.
266 * If we receive such a PN, we should process it and record the PN as
269 * - (B) The PN is above the watermark and we have received it.
271 * The PN should be included in any future ACK frame we generate.
272 * If we receive such a PN again, we should ignore it.
274 * - (C) The PN is below the watermark.
276 * We do not know whether a packet with the given PN was received or
277 * not. To be safe, if we receive such a packet, it is not processed.
279 * Note that state (C) corresponds to both "we have processed this PN and it has
280 * been provably ACKed" logical state and a subset of the PNs in the "we have
281 * never processed this PN before" logical state (namely all PNs which were lost
282 * and never received, but which are not recent enough to be above the
283 * watermark). The reason we can merge these states and avoid tracking states
284 * for the PNs in this state is because the provably ACKed and never-received
285 * states are functionally identical in terms of how we need to handle them: we
286 * don't need to do anything for PNs in either of these states, so we don't have
287 * to care about PNs in this state nor do we have to care about distinguishing
288 * the two states for a given PN.
290 * Note that under this scheme provably ACKed PNs are by definition always below
291 * the watermark; therefore, it follows that when a PN becomes provably ACKed,
292 * the watermark must be immediately increased to exceed it (otherwise we would
293 * keep reporting it in future ACK frames).
295 * This is in line with RFC 9000 s. 13.2.4's suggested strategy on when
296 * to advance the watermark:
298 * "When a packet containing an ACK frame is sent, the Largest Acknowledged
299 * field in that frame can be saved. When a packet containing an ACK frame is
300 * acknowledged, the receiver can stop acknowledging packets less than or
301 * equal to the Largest Acknowledged field in the sent ACK frame."
303 * This is where our scheme's false positives arise. When a packet containing an
304 * ACK frame is itself ACK'd, PNs referenced in that ACK frame become provably
305 * acked, and the watermark is bumped accordingly. However, the Largest
306 * Acknowledged field does not imply that all lower PNs have been received,
307 * because there may be gaps expressed in the ranges of PNs expressed by that
308 * and previous ACK frames. Thus, some unreceived PNs may be moved below the
309 * watermark, and we may subsequently reject those PNs as possibly being
310 * duplicates even though we have not actually received those PNs. Since we bump
311 * the watermark when a PN becomes provably ACKed, it follows that an unreceived
312 * PN falls below the watermark (and thus becomes a false positive for the
313 * purposes of duplicate detection) when a higher-numbered PN becomes provably
316 * Thus, when PN n becomes provably acked, any unreceived PNs in the range [0,
317 * n) will no longer be processed. Although datagrams may be reordered in the
318 * network, a PN we receive can only become provably ACKed after our own
319 * subsequently generated ACK frame is sent in a future TX packet, and then we
320 * receive another RX PN acknowledging that TX packet. This means that a given RX
321 * PN can only become provably ACKed at least 1 RTT after it is received; it is
322 * unlikely that any reordered datagrams will still be "in the network" (and not
323 * lost) by this time. If this does occur for whatever reason and a late PN is
324 * received, the packet will be discarded unprocessed and the PN is simply
325 * handled as though lost (a "written off" PN).
327 * **Data structure.** Our state for the RX handling side of the ACK manager, as
328 * discussed above, mainly comprises:
330 * a) a logical set of PNs, and
331 * b) a monotonically increasing PN counter (the watermark).
333 * For (a), we define a data structure which stores a logical set of PNs, which
334 * we use to keep track of which PNs we have received but which have not yet
335 * been provably ACKed, and thus will later need to generate an ACK frame for.
337 * The correspondence with the logical states discussed above is as follows. A
338 * PN is in state (C) if it is below the watermark; otherwise it is in state (B)
339 * if it is in the logical set of PNs, and in state (A) otherwise.
341 * Note that PNs are only removed from the PN set (when they become provably
342 * ACKed or written off) by virtue of advancement of the watermark. Removing PNs
343 * from the PN set any other way would be ambiguous as it would be
344 * indistinguishable from a PN we have not yet received and risk us processing a
345 * duplicate packet. In other words, for a given PN:
347 * - State (A) can transition to state (B) or (C)
348 * - State (B) can transition to state (C) only
349 * - State (C) is the terminal state
351 * We can query the logical set data structure for PNs which have been received
352 * but which have not been provably ACKed when we want to generate ACK frames.
353 * Since ACK frames can be lost and/or we might not know that the peer has
354 * successfully received them, we might generate multiple ACK frames covering a
355 * given PN until that PN becomes provably ACKed and we finally remove it from
356 * our set (by bumping the watermark) as no longer being our concern.
358 * The data structure used is the UINT_SET structure defined in uint_set.h,
359 * which is used as a PN set. We use the following operations of the structure:
361 * Insert Range: Used when we receive a new PN.
363 * Remove Range: Used when bumping the watermark.
365 * Query: Used to determine if a PN is in the set.
367 * **Possible duplicates.** A PN is considered a possible duplicate when either:
369 * a) its PN is already in the PN set (i.e. has already been received), or
370 * b) its PN is below the watermark (i.e. was provably ACKed or written off).
372 * A packet with a given PN is considered 'processable' when that PN is not
373 * considered a possible duplicate (see ossl_ackm_is_rx_pn_processable).
375 * **TX/RX interaction.** The watermark is bumped whenever an RX packet becomes
376 * provably ACKed. This occurs when an ACK frame is received by the TX side of
377 * the ACK manager; thus, there is necessary interaction between the TX and RX
378 * sides of the ACK manager.
380 * This is implemented as follows. When a packet is queued as sent in the TX
381 * side of the ACK manager, it may optionally have a Largest Acked value set on
382 * it. The user of the ACK manager should do this if the packet being
383 * transmitted contains an ACK frame, by setting the field to the Largest Acked
384 * field of that frame. Otherwise, this field should be set to QUIC_PN_INVALID.
385 * When a TX packet is eventually acknowledged which has this field set, it is
386 * used to update the state of the RX side of the ACK manager by bumping the
387 * watermark accordingly.
389 struct rx_pkt_history_st {
393 * Invariant: PNs below this are not in the set.
394 * Invariant: This is monotonic and only ever increases.
399 static int rx_pkt_history_bump_watermark(struct rx_pkt_history_st *h,
402 static void rx_pkt_history_init(struct rx_pkt_history_st *h)
404 ossl_uint_set_init(&h->set);
408 static void rx_pkt_history_destroy(struct rx_pkt_history_st *h)
410 ossl_uint_set_destroy(&h->set);
414 * Limit the number of ACK ranges we store to prevent resource consumption DoS
417 #define MAX_RX_ACK_RANGES 32
419 static void rx_pkt_history_trim_range_count(struct rx_pkt_history_st *h)
421 QUIC_PN highest = QUIC_PN_INVALID;
423 while (ossl_list_uint_set_num(&h->set) > MAX_RX_ACK_RANGES) {
424 UINT_RANGE r = ossl_list_uint_set_head(&h->set)->range;
426 highest = (highest == QUIC_PN_INVALID)
427 ? r.end : ossl_quic_pn_max(highest, r.end);
429 ossl_uint_set_remove(&h->set, &r);
433 * Bump watermark to cover all PNs we removed to avoid accidental
434 * reprocessing of packets.
436 if (highest != QUIC_PN_INVALID)
437 rx_pkt_history_bump_watermark(h, highest + 1);
440 static int rx_pkt_history_add_pn(struct rx_pkt_history_st *h,
448 if (pn < h->watermark)
449 return 1; /* consider this a success case */
451 if (ossl_uint_set_insert(&h->set, &r) != 1)
454 rx_pkt_history_trim_range_count(h);
458 static int rx_pkt_history_bump_watermark(struct rx_pkt_history_st *h,
463 if (watermark <= h->watermark)
466 /* Remove existing PNs below the watermark. */
468 r.end = watermark - 1;
469 if (ossl_uint_set_remove(&h->set, &r) != 1)
472 h->watermark = watermark;
477 * ACK Manager Implementation
478 * **************************
479 * Implementation of the ACK manager proper.
482 /* Constants used by the ACK manager; see RFC 9002. */
483 #define K_GRANULARITY (1 * OSSL_TIME_MS)
484 #define K_PKT_THRESHOLD 3
485 #define K_TIME_THRESHOLD_NUM 9
486 #define K_TIME_THRESHOLD_DEN 8
488 /* The maximum number of times we allow PTO to be doubled. */
489 #define MAX_PTO_COUNT 16
491 /* Default maximum amount of time to leave an ACK-eliciting packet un-ACK'd. */
492 #define DEFAULT_TX_MAX_ACK_DELAY ossl_ms2time(QUIC_DEFAULT_MAX_ACK_DELAY)
494 struct ossl_ackm_st {
495 /* Our list of transmitted packets. Corresponds to RFC 9002 sent_packets. */
496 struct tx_pkt_history_st tx_history[QUIC_PN_SPACE_NUM];
498 /* Our list of received PNs which are not yet provably acked. */
499 struct rx_pkt_history_st rx_history[QUIC_PN_SPACE_NUM];
501 /* Polymorphic dependencies that we consume. */
502 OSSL_TIME (*now)(void *arg);
505 const OSSL_CC_METHOD *cc_method;
506 OSSL_CC_DATA *cc_data;
508 /* RFC 9002 variables. */
510 QUIC_PN largest_acked_pkt[QUIC_PN_SPACE_NUM];
511 OSSL_TIME time_of_last_ack_eliciting_pkt[QUIC_PN_SPACE_NUM];
512 OSSL_TIME loss_time[QUIC_PN_SPACE_NUM];
513 OSSL_TIME loss_detection_deadline;
515 /* Lowest PN which is still not known to be ACKed. */
516 QUIC_PN lowest_unacked_pkt[QUIC_PN_SPACE_NUM];
518 /* Time at which we got our first RTT sample, or 0. */
519 OSSL_TIME first_rtt_sample;
522 * A packet's num_bytes are added to this if it is inflight,
523 * and removed again once ack'd/lost/discarded.
525 uint64_t bytes_in_flight;
528 * A packet's num_bytes are added to this if it is both inflight and
529 * ack-eliciting, and removed again once ack'd/lost/discarded.
531 uint64_t ack_eliciting_bytes_in_flight[QUIC_PN_SPACE_NUM];
533 /* Count of ECN-CE events. */
534 uint64_t peer_ecnce[QUIC_PN_SPACE_NUM];
536 /* Set to 1 when the handshake is confirmed. */
537 char handshake_confirmed;
539 /* Set to 1 when the peer has completed address validation. */
540 char peer_completed_addr_validation;
542 /* Set to 1 when a PN space has been discarded. */
543 char discarded[QUIC_PN_SPACE_NUM];
545 /* Set to 1 when we think an ACK frame should be generated. */
546 char rx_ack_desired[QUIC_PN_SPACE_NUM];
548 /* Set to 1 if an ACK frame has ever been generated. */
549 char rx_ack_generated[QUIC_PN_SPACE_NUM];
551 /* Probe request counts for reporting to the user. */
552 OSSL_ACKM_PROBE_INFO pending_probe;
554 /* Generated ACK frames for each PN space. */
555 OSSL_QUIC_FRAME_ACK ack[QUIC_PN_SPACE_NUM];
556 OSSL_QUIC_ACK_RANGE ack_ranges[QUIC_PN_SPACE_NUM][MAX_RX_ACK_RANGES];
558 /* Other RX state. */
559 /* Largest PN we have RX'd. */
560 QUIC_PN rx_largest_pn[QUIC_PN_SPACE_NUM];
562 /* Time at which the PN in rx_largest_pn was RX'd. */
563 OSSL_TIME rx_largest_time[QUIC_PN_SPACE_NUM];
566 * ECN event counters. Each time we receive a packet with a given ECN label,
567 * the corresponding ECN counter here is incremented.
569 uint64_t rx_ect0[QUIC_PN_SPACE_NUM];
570 uint64_t rx_ect1[QUIC_PN_SPACE_NUM];
571 uint64_t rx_ecnce[QUIC_PN_SPACE_NUM];
574 * Number of ACK-eliciting packets since last ACK. We use this to defer
575 * emitting ACK frames until a threshold number of ACK-eliciting packets
576 * have been received.
578 uint32_t rx_ack_eliciting_pkts_since_last_ack[QUIC_PN_SPACE_NUM];
581 * The ACK frame coalescing deadline at which we should flush any unsent ACK
584 OSSL_TIME rx_ack_flush_deadline[QUIC_PN_SPACE_NUM];
587 * The RX maximum ACK delay (the maximum amount of time our peer might
588 * wait to send us an ACK after receiving an ACK-eliciting packet).
590 OSSL_TIME rx_max_ack_delay;
593 * The TX maximum ACK delay (the maximum amount of time we allow ourselves
594 * to wait before generating an ACK after receiving an ACK-eliciting
597 OSSL_TIME tx_max_ack_delay;
599 /* Callbacks for deadline updates. */
600 void (*loss_detection_deadline_cb)(OSSL_TIME deadline, void *arg);
601 void *loss_detection_deadline_cb_arg;
603 void (*ack_deadline_cb)(OSSL_TIME deadline, int pkt_space, void *arg);
604 void *ack_deadline_cb_arg;
607 static ossl_inline uint32_t min_u32(uint32_t x, uint32_t y)
609 return x < y ? x : y;
613 * Get TX history for a given packet number space. Must not have been
616 static struct tx_pkt_history_st *get_tx_history(OSSL_ACKM *ackm, int pkt_space)
618 assert(!ackm->discarded[pkt_space]);
620 return &ackm->tx_history[pkt_space];
624 * Get RX history for a given packet number space. Must not have been
627 static struct rx_pkt_history_st *get_rx_history(OSSL_ACKM *ackm, int pkt_space)
629 assert(!ackm->discarded[pkt_space]);
631 return &ackm->rx_history[pkt_space];
634 /* Does the newly-acknowledged list contain any ack-eliciting packet? */
635 static int ack_includes_ack_eliciting(OSSL_ACKM_TX_PKT *pkt)
637 for (; pkt != NULL; pkt = pkt->anext)
638 if (pkt->is_ack_eliciting)
644 /* Return number of ACK-eliciting bytes in flight across all PN spaces. */
645 static uint64_t ackm_ack_eliciting_bytes_in_flight(OSSL_ACKM *ackm)
650 for (i = 0; i < QUIC_PN_SPACE_NUM; ++i)
651 total += ackm->ack_eliciting_bytes_in_flight[i];
656 /* Return 1 if the range contains the given PN. */
657 static int range_contains(const OSSL_QUIC_ACK_RANGE *range, QUIC_PN pn)
659 return pn >= range->start && pn <= range->end;
663 * Given a logical representation of an ACK frame 'ack', create a singly-linked
664 * list of the newly ACK'd frames; that is, of frames which are matched by the
665 * list of PN ranges contained in the ACK frame. The packet structures in the
666 * list returned are removed from the TX history list. Returns a pointer to the
667 * list head (or NULL) if empty.
669 static OSSL_ACKM_TX_PKT *ackm_detect_and_remove_newly_acked_pkts(OSSL_ACKM *ackm,
670 const OSSL_QUIC_FRAME_ACK *ack,
673 OSSL_ACKM_TX_PKT *acked_pkts = NULL, **fixup = &acked_pkts, *pkt, *pprev;
674 struct tx_pkt_history_st *h;
677 assert(ack->num_ack_ranges > 0);
680 * Our history list is a list of packets sorted in ascending order
683 * ack->ack_ranges is a list of packet number ranges in descending order.
685 * Walk through our history list from the end in order to efficiently detect
686 * membership in the specified ack ranges. As an optimization, we use our
687 * hashtable to try and skip to the first matching packet. This may fail if
688 * the ACK ranges given include nonexistent packets.
690 h = get_tx_history(ackm, pkt_space);
692 pkt = tx_pkt_history_by_pkt_num(h, ack->ack_ranges[0].end);
694 pkt = ossl_list_tx_history_tail(&h->packets);
696 for (; pkt != NULL; pkt = pprev) {
698 * Save prev value as it will be zeroed if we remove the packet from the
699 * history list below.
701 pprev = ossl_list_tx_history_prev(pkt);
704 if (ridx >= ack->num_ack_ranges) {
706 * We have exhausted all ranges so stop here, even if there are
707 * more packets to look at.
712 if (range_contains(&ack->ack_ranges[ridx], pkt->pkt_num)) {
713 /* We have matched this range. */
714 tx_pkt_history_remove(h, pkt->pkt_num);
720 } else if (pkt->pkt_num > ack->ack_ranges[ridx].end) {
722 * We have not reached this range yet in our list, so do not
728 * We have moved beyond this range, so advance to the next range
729 * and try matching again.
731 assert(pkt->pkt_num < ack->ack_ranges[ridx].start);
742 * Create a singly-linked list of newly detected-lost packets in the given
743 * packet number space. Returns the head of the list or NULL if no packets were
744 * detected lost. The packets in the list are removed from the TX history list.
746 static OSSL_ACKM_TX_PKT *ackm_detect_and_remove_lost_pkts(OSSL_ACKM *ackm,
749 OSSL_ACKM_TX_PKT *lost_pkts = NULL, **fixup = &lost_pkts, *pkt, *pnext;
750 OSSL_TIME loss_delay, lost_send_time, now;
752 struct tx_pkt_history_st *h;
754 assert(ackm->largest_acked_pkt[pkt_space] != QUIC_PN_INVALID);
756 ossl_statm_get_rtt_info(ackm->statm, &rtt);
758 ackm->loss_time[pkt_space] = ossl_time_zero();
760 loss_delay = ossl_time_multiply(ossl_time_max(rtt.latest_rtt,
762 K_TIME_THRESHOLD_NUM);
763 loss_delay = ossl_time_divide(loss_delay, K_TIME_THRESHOLD_DEN);
765 /* Minimum time of K_GRANULARITY before packets are deemed lost. */
766 loss_delay = ossl_time_max(loss_delay, ossl_ticks2time(K_GRANULARITY));
768 /* Packets sent before this time are deemed lost. */
769 now = ackm->now(ackm->now_arg);
770 lost_send_time = ossl_time_subtract(now, loss_delay);
772 h = get_tx_history(ackm, pkt_space);
773 pkt = ossl_list_tx_history_head(&h->packets);
775 for (; pkt != NULL; pkt = pnext) {
776 assert(pkt_space == pkt->pkt_space);
779 * Save prev value as it will be zeroed if we remove the packet from the
780 * history list below.
782 pnext = ossl_list_tx_history_next(pkt);
784 if (pkt->pkt_num > ackm->largest_acked_pkt[pkt_space])
788 * Mark packet as lost, or set time when it should be marked.
790 if (ossl_time_compare(pkt->time, lost_send_time) <= 0
791 || ackm->largest_acked_pkt[pkt_space]
792 >= pkt->pkt_num + K_PKT_THRESHOLD) {
793 tx_pkt_history_remove(h, pkt->pkt_num);
799 if (ossl_time_is_zero(ackm->loss_time[pkt_space]))
800 ackm->loss_time[pkt_space] =
801 ossl_time_add(pkt->time, loss_delay);
803 ackm->loss_time[pkt_space] =
804 ossl_time_min(ackm->loss_time[pkt_space],
805 ossl_time_add(pkt->time, loss_delay));
812 static OSSL_TIME ackm_get_loss_time_and_space(OSSL_ACKM *ackm, int *pspace)
814 OSSL_TIME time = ackm->loss_time[QUIC_PN_SPACE_INITIAL];
815 int i, space = QUIC_PN_SPACE_INITIAL;
817 for (i = space + 1; i < QUIC_PN_SPACE_NUM; ++i)
818 if (ossl_time_is_zero(time)
819 || ossl_time_compare(ackm->loss_time[i], time) == -1) {
820 time = ackm->loss_time[i];
828 static OSSL_TIME ackm_get_pto_time_and_space(OSSL_ACKM *ackm, int *space)
832 OSSL_TIME pto_timeout = ossl_time_infinite(), t;
833 int pto_space = QUIC_PN_SPACE_INITIAL, i;
835 ossl_statm_get_rtt_info(ackm->statm, &rtt);
838 = ossl_time_add(rtt.smoothed_rtt,
839 ossl_time_max(ossl_time_multiply(rtt.rtt_variance, 4),
840 ossl_ticks2time(K_GRANULARITY)));
843 = ossl_time_multiply(duration,
844 (uint64_t)1 << min_u32(ackm->pto_count,
847 /* Anti-deadlock PTO starts from the current time. */
848 if (ackm_ack_eliciting_bytes_in_flight(ackm) == 0) {
849 assert(!ackm->peer_completed_addr_validation);
851 *space = ackm->discarded[QUIC_PN_SPACE_INITIAL]
852 ? QUIC_PN_SPACE_HANDSHAKE
853 : QUIC_PN_SPACE_INITIAL;
854 return ossl_time_add(ackm->now(ackm->now_arg), duration);
857 for (i = QUIC_PN_SPACE_INITIAL; i < QUIC_PN_SPACE_NUM; ++i) {
858 if (ackm->ack_eliciting_bytes_in_flight[i] == 0)
861 if (i == QUIC_PN_SPACE_APP) {
862 /* Skip application data until handshake confirmed. */
863 if (!ackm->handshake_confirmed)
866 /* Include max_ack_delay and backoff for app data. */
867 if (!ossl_time_is_infinite(ackm->rx_max_ack_delay)) {
869 = (uint64_t)1 << min_u32(ackm->pto_count, MAX_PTO_COUNT);
872 = ossl_time_add(duration,
873 ossl_time_multiply(ackm->rx_max_ack_delay,
878 t = ossl_time_add(ackm->time_of_last_ack_eliciting_pkt[i], duration);
879 if (ossl_time_compare(t, pto_timeout) < 0) {
889 static void ackm_set_loss_detection_timer_actual(OSSL_ACKM *ackm,
892 ackm->loss_detection_deadline = deadline;
894 if (ackm->loss_detection_deadline_cb != NULL)
895 ackm->loss_detection_deadline_cb(deadline,
896 ackm->loss_detection_deadline_cb_arg);
899 static int ackm_set_loss_detection_timer(OSSL_ACKM *ackm)
902 OSSL_TIME earliest_loss_time, timeout;
904 earliest_loss_time = ackm_get_loss_time_and_space(ackm, &space);
905 if (!ossl_time_is_zero(earliest_loss_time)) {
906 /* Time threshold loss detection. */
907 ackm_set_loss_detection_timer_actual(ackm, earliest_loss_time);
911 if (ackm_ack_eliciting_bytes_in_flight(ackm) == 0
912 && ackm->peer_completed_addr_validation) {
914 * Nothing to detect lost, so no timer is set. However, the client
915 * needs to arm the timer if the server might be blocked by the
916 * anti-amplification limit.
918 ackm_set_loss_detection_timer_actual(ackm, ossl_time_zero());
922 timeout = ackm_get_pto_time_and_space(ackm, &space);
923 ackm_set_loss_detection_timer_actual(ackm, timeout);
927 static int ackm_in_persistent_congestion(OSSL_ACKM *ackm,
928 const OSSL_ACKM_TX_PKT *lpkt)
930 /* TODO(QUIC FUTURE): Persistent congestion not currently implemented. */
934 static void ackm_on_pkts_lost(OSSL_ACKM *ackm, int pkt_space,
935 const OSSL_ACKM_TX_PKT *lpkt, int pseudo)
937 const OSSL_ACKM_TX_PKT *p, *pnext;
939 QUIC_PN largest_pn_lost = 0;
940 OSSL_CC_LOSS_INFO loss_info = {0};
943 for (p = lpkt; p != NULL; p = pnext) {
946 if (p->is_inflight) {
947 ackm->bytes_in_flight -= p->num_bytes;
948 if (p->is_ack_eliciting)
949 ackm->ack_eliciting_bytes_in_flight[p->pkt_space]
952 if (p->pkt_num > largest_pn_lost)
953 largest_pn_lost = p->pkt_num;
957 * If this is pseudo-loss (e.g. during connection retry) we do not
958 * inform the CC as it is not a real loss and not reflective of
959 * network conditions.
961 loss_info.tx_time = p->time;
962 loss_info.tx_size = p->num_bytes;
964 ackm->cc_method->on_data_lost(ackm->cc_data, &loss_info);
968 p->on_lost(p->cb_arg);
972 * Persistent congestion can only be considered if we have gotten at least
975 ossl_statm_get_rtt_info(ackm->statm, &rtt);
976 if (!ossl_time_is_zero(ackm->first_rtt_sample)
977 && ackm_in_persistent_congestion(ackm, lpkt))
978 flags |= OSSL_CC_LOST_FLAG_PERSISTENT_CONGESTION;
980 ackm->cc_method->on_data_lost_finished(ackm->cc_data, flags);
983 static void ackm_on_pkts_acked(OSSL_ACKM *ackm, const OSSL_ACKM_TX_PKT *apkt)
985 const OSSL_ACKM_TX_PKT *anext;
986 QUIC_PN last_pn_acked = 0;
987 OSSL_CC_ACK_INFO ainfo = {0};
989 for (; apkt != NULL; apkt = anext) {
990 if (apkt->is_inflight) {
991 ackm->bytes_in_flight -= apkt->num_bytes;
992 if (apkt->is_ack_eliciting)
993 ackm->ack_eliciting_bytes_in_flight[apkt->pkt_space]
996 if (apkt->pkt_num > last_pn_acked)
997 last_pn_acked = apkt->pkt_num;
999 if (apkt->largest_acked != QUIC_PN_INVALID)
1001 * This can fail, but it is monotonic; worst case we try again
1004 rx_pkt_history_bump_watermark(get_rx_history(ackm,
1006 apkt->largest_acked + 1);
1009 ainfo.tx_time = apkt->time;
1010 ainfo.tx_size = apkt->num_bytes;
1012 anext = apkt->anext;
1013 apkt->on_acked(apkt->cb_arg); /* may free apkt */
1015 if (apkt->is_inflight)
1016 ackm->cc_method->on_data_acked(ackm->cc_data, &ainfo);
1020 OSSL_ACKM *ossl_ackm_new(OSSL_TIME (*now)(void *arg),
1023 const OSSL_CC_METHOD *cc_method,
1024 OSSL_CC_DATA *cc_data)
1029 ackm = OPENSSL_zalloc(sizeof(OSSL_ACKM));
1033 for (i = 0; i < (int)OSSL_NELEM(ackm->tx_history); ++i) {
1034 ackm->largest_acked_pkt[i] = QUIC_PN_INVALID;
1035 ackm->rx_ack_flush_deadline[i] = ossl_time_infinite();
1036 if (tx_pkt_history_init(&ackm->tx_history[i]) < 1)
1040 for (i = 0; i < (int)OSSL_NELEM(ackm->rx_history); ++i)
1041 rx_pkt_history_init(&ackm->rx_history[i]);
1044 ackm->now_arg = now_arg;
1045 ackm->statm = statm;
1046 ackm->cc_method = cc_method;
1047 ackm->cc_data = cc_data;
1049 ackm->rx_max_ack_delay = ossl_ms2time(QUIC_DEFAULT_MAX_ACK_DELAY);
1050 ackm->tx_max_ack_delay = DEFAULT_TX_MAX_ACK_DELAY;
1056 tx_pkt_history_destroy(&ackm->tx_history[i]);
1062 void ossl_ackm_free(OSSL_ACKM *ackm)
1069 for (i = 0; i < OSSL_NELEM(ackm->tx_history); ++i)
1070 if (!ackm->discarded[i]) {
1071 tx_pkt_history_destroy(&ackm->tx_history[i]);
1072 rx_pkt_history_destroy(&ackm->rx_history[i]);
1078 int ossl_ackm_on_tx_packet(OSSL_ACKM *ackm, OSSL_ACKM_TX_PKT *pkt)
1080 struct tx_pkt_history_st *h = get_tx_history(ackm, pkt->pkt_space);
1082 /* Time must be set and not move backwards. */
1083 if (ossl_time_is_zero(pkt->time)
1084 || ossl_time_compare(ackm->time_of_last_ack_eliciting_pkt[pkt->pkt_space],
1088 /* Must have non-zero number of bytes. */
1089 if (pkt->num_bytes == 0)
1092 /* Does not make any sense for a non-in-flight packet to be ACK-eliciting. */
1093 if (!pkt->is_inflight && pkt->is_ack_eliciting)
1096 if (tx_pkt_history_add(h, pkt) == 0)
1099 if (pkt->is_inflight) {
1100 if (pkt->is_ack_eliciting) {
1101 ackm->time_of_last_ack_eliciting_pkt[pkt->pkt_space] = pkt->time;
1102 ackm->ack_eliciting_bytes_in_flight[pkt->pkt_space]
1106 ackm->bytes_in_flight += pkt->num_bytes;
1107 ackm_set_loss_detection_timer(ackm);
1109 ackm->cc_method->on_data_sent(ackm->cc_data, pkt->num_bytes);
1115 int ossl_ackm_on_rx_datagram(OSSL_ACKM *ackm, size_t num_bytes)
1117 /* No-op on the client. */
1121 static void ackm_process_ecn(OSSL_ACKM *ackm, const OSSL_QUIC_FRAME_ACK *ack,
1124 struct tx_pkt_history_st *h;
1125 OSSL_ACKM_TX_PKT *pkt;
1126 OSSL_CC_ECN_INFO ecn_info = {0};
1129 * If the ECN-CE counter reported by the peer has increased, this could
1130 * be a new congestion event.
1132 if (ack->ecnce > ackm->peer_ecnce[pkt_space]) {
1133 ackm->peer_ecnce[pkt_space] = ack->ecnce;
1135 h = get_tx_history(ackm, pkt_space);
1136 pkt = tx_pkt_history_by_pkt_num(h, ack->ack_ranges[0].end);
1140 ecn_info.largest_acked_time = pkt->time;
1141 ackm->cc_method->on_ecn(ackm->cc_data, &ecn_info);
1145 int ossl_ackm_on_rx_ack_frame(OSSL_ACKM *ackm, const OSSL_QUIC_FRAME_ACK *ack,
1146 int pkt_space, OSSL_TIME rx_time)
1148 OSSL_ACKM_TX_PKT *na_pkts, *lost_pkts;
1149 int must_set_timer = 0;
1151 if (ackm->largest_acked_pkt[pkt_space] == QUIC_PN_INVALID)
1152 ackm->largest_acked_pkt[pkt_space] = ack->ack_ranges[0].end;
1154 ackm->largest_acked_pkt[pkt_space]
1155 = ossl_quic_pn_max(ackm->largest_acked_pkt[pkt_space],
1156 ack->ack_ranges[0].end);
1159 * If we get an ACK in the handshake space, address validation is completed.
1160 * Make sure we update the timer, even if no packets were ACK'd.
1162 if (!ackm->peer_completed_addr_validation
1163 && pkt_space == QUIC_PN_SPACE_HANDSHAKE) {
1164 ackm->peer_completed_addr_validation = 1;
1169 * Find packets that are newly acknowledged and remove them from the list.
1171 na_pkts = ackm_detect_and_remove_newly_acked_pkts(ackm, ack, pkt_space);
1172 if (na_pkts == NULL) {
1174 ackm_set_loss_detection_timer(ackm);
1180 * Update the RTT if the largest acknowledged is newly acked and at least
1181 * one ACK-eliciting packet was newly acked.
1183 * First packet in the list is always the one with the largest PN.
1185 if (na_pkts->pkt_num == ack->ack_ranges[0].end &&
1186 ack_includes_ack_eliciting(na_pkts)) {
1187 OSSL_TIME now = ackm->now(ackm->now_arg), ack_delay;
1188 if (ossl_time_is_zero(ackm->first_rtt_sample))
1189 ackm->first_rtt_sample = now;
1191 /* Enforce maximum ACK delay. */
1192 ack_delay = ack->delay_time;
1193 if (ackm->handshake_confirmed)
1194 ack_delay = ossl_time_min(ack_delay, ackm->rx_max_ack_delay);
1196 ossl_statm_update_rtt(ackm->statm, ack_delay,
1197 ossl_time_subtract(now, na_pkts->time));
1201 * Process ECN information if present.
1203 * We deliberately do most ECN processing in the ACKM rather than the
1204 * congestion controller to avoid having to give the congestion controller
1205 * access to ACKM internal state.
1207 if (ack->ecn_present)
1208 ackm_process_ecn(ackm, ack, pkt_space);
1210 /* Handle inferred loss. */
1211 lost_pkts = ackm_detect_and_remove_lost_pkts(ackm, pkt_space);
1212 if (lost_pkts != NULL)
1213 ackm_on_pkts_lost(ackm, pkt_space, lost_pkts, /*pseudo=*/0);
1215 ackm_on_pkts_acked(ackm, na_pkts);
1218 * Reset pto_count unless the client is unsure if the server validated the
1221 if (ackm->peer_completed_addr_validation)
1222 ackm->pto_count = 0;
1224 ackm_set_loss_detection_timer(ackm);
1228 int ossl_ackm_on_pkt_space_discarded(OSSL_ACKM *ackm, int pkt_space)
1230 OSSL_ACKM_TX_PKT *pkt, *pnext;
1231 uint64_t num_bytes_invalidated = 0;
1233 if (ackm->discarded[pkt_space])
1236 if (pkt_space == QUIC_PN_SPACE_HANDSHAKE)
1237 ackm->peer_completed_addr_validation = 1;
1239 for (pkt = ossl_list_tx_history_head(&get_tx_history(ackm, pkt_space)->packets);
1240 pkt != NULL; pkt = pnext) {
1241 pnext = ossl_list_tx_history_next(pkt);
1242 if (pkt->is_inflight) {
1243 ackm->bytes_in_flight -= pkt->num_bytes;
1244 num_bytes_invalidated += pkt->num_bytes;
1247 pkt->on_discarded(pkt->cb_arg); /* may free pkt */
1250 tx_pkt_history_destroy(&ackm->tx_history[pkt_space]);
1251 rx_pkt_history_destroy(&ackm->rx_history[pkt_space]);
1253 if (num_bytes_invalidated > 0)
1254 ackm->cc_method->on_data_invalidated(ackm->cc_data,
1255 num_bytes_invalidated);
1257 ackm->time_of_last_ack_eliciting_pkt[pkt_space] = ossl_time_zero();
1258 ackm->loss_time[pkt_space] = ossl_time_zero();
1259 ackm->pto_count = 0;
1260 ackm->discarded[pkt_space] = 1;
1261 ackm->ack_eliciting_bytes_in_flight[pkt_space] = 0;
1262 ackm_set_loss_detection_timer(ackm);
1266 int ossl_ackm_on_handshake_confirmed(OSSL_ACKM *ackm)
1268 ackm->handshake_confirmed = 1;
1269 ackm->peer_completed_addr_validation = 1;
1270 ackm_set_loss_detection_timer(ackm);
1274 static void ackm_queue_probe_anti_deadlock_handshake(OSSL_ACKM *ackm)
1276 ++ackm->pending_probe.anti_deadlock_handshake;
1279 static void ackm_queue_probe_anti_deadlock_initial(OSSL_ACKM *ackm)
1281 ++ackm->pending_probe.anti_deadlock_initial;
1284 static void ackm_queue_probe(OSSL_ACKM *ackm, int pkt_space)
1287 * TODO(QUIC FUTURE): We are allowed to send either one or two probe
1289 * Determine a strategy for when we should send two probe packets.
1291 ++ackm->pending_probe.pto[pkt_space];
1294 int ossl_ackm_on_timeout(OSSL_ACKM *ackm)
1297 OSSL_TIME earliest_loss_time;
1298 OSSL_ACKM_TX_PKT *lost_pkts;
1300 earliest_loss_time = ackm_get_loss_time_and_space(ackm, &pkt_space);
1301 if (!ossl_time_is_zero(earliest_loss_time)) {
1302 /* Time threshold loss detection. */
1303 lost_pkts = ackm_detect_and_remove_lost_pkts(ackm, pkt_space);
1304 assert(lost_pkts != NULL);
1305 ackm_on_pkts_lost(ackm, pkt_space, lost_pkts, /*pseudo=*/0);
1306 ackm_set_loss_detection_timer(ackm);
1310 if (ackm_ack_eliciting_bytes_in_flight(ackm) == 0) {
1311 assert(!ackm->peer_completed_addr_validation);
1313 * Client sends an anti-deadlock packet: Initial is padded to earn more
1314 * anti-amplification credit. A handshake packet proves address
1317 if (ackm->discarded[QUIC_PN_SPACE_INITIAL])
1318 ackm_queue_probe_anti_deadlock_handshake(ackm);
1320 ackm_queue_probe_anti_deadlock_initial(ackm);
1323 * PTO. The user of the ACKM should send new data if available, else
1324 * retransmit old data, or if neither is available, send a single PING
1327 ackm_get_pto_time_and_space(ackm, &pkt_space);
1328 ackm_queue_probe(ackm, pkt_space);
1332 ackm_set_loss_detection_timer(ackm);
1336 OSSL_TIME ossl_ackm_get_loss_detection_deadline(OSSL_ACKM *ackm)
1338 return ackm->loss_detection_deadline;
1341 OSSL_ACKM_PROBE_INFO *ossl_ackm_get0_probe_request(OSSL_ACKM *ackm)
1343 return &ackm->pending_probe;
1346 int ossl_ackm_get_largest_unacked(OSSL_ACKM *ackm, int pkt_space, QUIC_PN *pn)
1348 struct tx_pkt_history_st *h;
1349 OSSL_ACKM_TX_PKT *p;
1351 h = get_tx_history(ackm, pkt_space);
1352 p = ossl_list_tx_history_tail(&h->packets);
1361 /* Number of ACK-eliciting packets RX'd before we always emit an ACK. */
1362 #define PKTS_BEFORE_ACK 2
1365 * Return 1 if emission of an ACK frame is currently desired.
1367 * This occurs when one or more of the following conditions occurs:
1369 * - We have flagged that we want to send an ACK frame
1370 * (for example, due to the packet threshold count being exceeded), or
1372 * - We have exceeded the ACK flush deadline, meaning that
1373 * we have received at least one ACK-eliciting packet, but held off on
1374 * sending an ACK frame immediately in the hope that more ACK-eliciting
1375 * packets might come in, but not enough did and we are now requesting
1376 * transmission of an ACK frame anyway.
1379 int ossl_ackm_is_ack_desired(OSSL_ACKM *ackm, int pkt_space)
1381 return ackm->rx_ack_desired[pkt_space]
1382 || (!ossl_time_is_infinite(ackm->rx_ack_flush_deadline[pkt_space])
1383 && ossl_time_compare(ackm->now(ackm->now_arg),
1384 ackm->rx_ack_flush_deadline[pkt_space]) >= 0);
1388 * Returns 1 if an ACK frame matches a given packet number.
1390 static int ack_contains(const OSSL_QUIC_FRAME_ACK *ack, QUIC_PN pkt_num)
1394 for (i = 0; i < ack->num_ack_ranges; ++i)
1395 if (range_contains(&ack->ack_ranges[i], pkt_num))
1402 * Returns 1 iff a PN (which we have just received) was previously reported as
1403 * implied missing (by us, in an ACK frame we previously generated).
1405 static int ackm_is_missing(OSSL_ACKM *ackm, int pkt_space, QUIC_PN pkt_num)
1408 * A PN is implied missing if it is not greater than the highest PN in our
1409 * generated ACK frame, but is not matched by the frame.
1411 return ackm->ack[pkt_space].num_ack_ranges > 0
1412 && pkt_num <= ackm->ack[pkt_space].ack_ranges[0].end
1413 && !ack_contains(&ackm->ack[pkt_space], pkt_num);
1417 * Returns 1 iff our RX of a PN newly establishes the implication of missing
1420 static int ackm_has_newly_missing(OSSL_ACKM *ackm, int pkt_space)
1422 struct rx_pkt_history_st *h;
1424 h = get_rx_history(ackm, pkt_space);
1426 if (ossl_list_uint_set_is_empty(&h->set))
1430 * The second condition here establishes that the highest PN range in our RX
1431 * history comprises only a single PN. If there is more than one, then this
1432 * function will have returned 1 during a previous call to
1433 * ossl_ackm_on_rx_packet assuming the third condition below was met. Thus
1434 * we only return 1 when the missing PN condition is newly established.
1436 * The third condition here establishes that the highest PN range in our RX
1437 * history is beyond (and does not border) the highest PN we have yet
1438 * reported in any ACK frame. Thus there is a gap of at least one PN between
1439 * the PNs we have ACK'd previously and the PN we have just received.
1441 return ackm->ack[pkt_space].num_ack_ranges > 0
1442 && ossl_list_uint_set_tail(&h->set)->range.start
1443 == ossl_list_uint_set_tail(&h->set)->range.end
1444 && ossl_list_uint_set_tail(&h->set)->range.start
1445 > ackm->ack[pkt_space].ack_ranges[0].end + 1;
1448 static void ackm_set_flush_deadline(OSSL_ACKM *ackm, int pkt_space,
1451 ackm->rx_ack_flush_deadline[pkt_space] = deadline;
1453 if (ackm->ack_deadline_cb != NULL)
1454 ackm->ack_deadline_cb(ossl_ackm_get_ack_deadline(ackm, pkt_space),
1455 pkt_space, ackm->ack_deadline_cb_arg);
1458 /* Explicitly flags that we want to generate an ACK frame. */
1459 static void ackm_queue_ack(OSSL_ACKM *ackm, int pkt_space)
1461 ackm->rx_ack_desired[pkt_space] = 1;
1463 /* Cancel deadline. */
1464 ackm_set_flush_deadline(ackm, pkt_space, ossl_time_infinite());
1467 static void ackm_on_rx_ack_eliciting(OSSL_ACKM *ackm,
1468 OSSL_TIME rx_time, int pkt_space,
1471 OSSL_TIME tx_max_ack_delay;
1473 if (ackm->rx_ack_desired[pkt_space])
1474 /* ACK generation already requested so nothing to do. */
1477 ++ackm->rx_ack_eliciting_pkts_since_last_ack[pkt_space];
1479 if (!ackm->rx_ack_generated[pkt_space]
1481 || ackm->rx_ack_eliciting_pkts_since_last_ack[pkt_space]
1483 || ackm_has_newly_missing(ackm, pkt_space)) {
1487 * - We have never yet generated an ACK frame, meaning that this
1488 * is the first ever packet received, which we should always
1489 * acknowledge immediately, or
1491 * - We previously reported the PN that we have just received as
1492 * missing in a previous ACK frame (meaning that we should report
1493 * the fact that we now have it to the peer immediately), or
1495 * - We have exceeded the ACK-eliciting packet threshold count
1496 * for the purposes of ACK coalescing, so request transmission
1497 * of an ACK frame, or
1499 * - The PN we just received and added to our PN RX history
1500 * newly implies one or more missing PNs, in which case we should
1501 * inform the peer by sending an ACK frame immediately.
1503 * We do not test the ACK flush deadline here because it is tested
1504 * separately in ossl_ackm_is_ack_desired.
1506 ackm_queue_ack(ackm, pkt_space);
1511 * Not emitting an ACK yet.
1513 * Update the ACK flush deadline.
1515 * RFC 9000 s. 13.2.1: "An endpoint MUST acknowledge all ack-eliciting
1516 * Initial and Handshake packets immediately"; don't delay ACK generation if
1517 * we are using the Initial or Handshake PN spaces.
1519 tx_max_ack_delay = ackm->tx_max_ack_delay;
1520 if (pkt_space == QUIC_PN_SPACE_INITIAL
1521 || pkt_space == QUIC_PN_SPACE_HANDSHAKE)
1522 tx_max_ack_delay = ossl_time_zero();
1524 if (ossl_time_is_infinite(ackm->rx_ack_flush_deadline[pkt_space]))
1525 ackm_set_flush_deadline(ackm, pkt_space,
1526 ossl_time_add(rx_time, tx_max_ack_delay));
1528 ackm_set_flush_deadline(ackm, pkt_space,
1529 ossl_time_min(ackm->rx_ack_flush_deadline[pkt_space],
1530 ossl_time_add(rx_time,
1531 tx_max_ack_delay)));
1534 int ossl_ackm_on_rx_packet(OSSL_ACKM *ackm, const OSSL_ACKM_RX_PKT *pkt)
1536 struct rx_pkt_history_st *h = get_rx_history(ackm, pkt->pkt_space);
1539 if (ossl_ackm_is_rx_pn_processable(ackm, pkt->pkt_num, pkt->pkt_space) != 1)
1540 /* PN has already been processed or written off, no-op. */
1544 * Record the largest PN we have RX'd and the time we received it.
1545 * We use this to calculate the ACK delay field of ACK frames.
1547 if (pkt->pkt_num > ackm->rx_largest_pn[pkt->pkt_space]) {
1548 ackm->rx_largest_pn[pkt->pkt_space] = pkt->pkt_num;
1549 ackm->rx_largest_time[pkt->pkt_space] = pkt->time;
1553 * If the PN we just received was previously implied missing by virtue of
1554 * being omitted from a previous ACK frame generated, we skip any packet
1555 * count thresholds or coalescing delays and emit a new ACK frame
1558 was_missing = ackm_is_missing(ackm, pkt->pkt_space, pkt->pkt_num);
1561 * Add the packet number to our history list of PNs we have not yet provably
1564 if (rx_pkt_history_add_pn(h, pkt->pkt_num) != 1)
1568 * Receiving this packet may or may not cause us to emit an ACK frame.
1569 * We may not emit an ACK frame yet if we have not yet received a threshold
1570 * number of packets.
1572 if (pkt->is_ack_eliciting)
1573 ackm_on_rx_ack_eliciting(ackm, pkt->time, pkt->pkt_space, was_missing);
1575 /* Update the ECN counters according to which ECN signal we got, if any. */
1577 case OSSL_ACKM_ECN_ECT0:
1578 ++ackm->rx_ect0[pkt->pkt_space];
1580 case OSSL_ACKM_ECN_ECT1:
1581 ++ackm->rx_ect1[pkt->pkt_space];
1583 case OSSL_ACKM_ECN_ECNCE:
1584 ++ackm->rx_ecnce[pkt->pkt_space];
1593 static void ackm_fill_rx_ack_ranges(OSSL_ACKM *ackm, int pkt_space,
1594 OSSL_QUIC_FRAME_ACK *ack)
1596 struct rx_pkt_history_st *h = get_rx_history(ackm, pkt_space);
1601 * Copy out ranges from the PN set, starting at the end, until we reach our
1602 * maximum number of ranges.
1604 for (x = ossl_list_uint_set_tail(&h->set);
1605 x != NULL && i < OSSL_NELEM(ackm->ack_ranges);
1606 x = ossl_list_uint_set_prev(x), ++i) {
1607 ackm->ack_ranges[pkt_space][i].start = x->range.start;
1608 ackm->ack_ranges[pkt_space][i].end = x->range.end;
1611 ack->ack_ranges = ackm->ack_ranges[pkt_space];
1612 ack->num_ack_ranges = i;
1615 const OSSL_QUIC_FRAME_ACK *ossl_ackm_get_ack_frame(OSSL_ACKM *ackm,
1618 OSSL_QUIC_FRAME_ACK *ack = &ackm->ack[pkt_space];
1619 OSSL_TIME now = ackm->now(ackm->now_arg);
1621 ackm_fill_rx_ack_ranges(ackm, pkt_space, ack);
1623 if (!ossl_time_is_zero(ackm->rx_largest_time[pkt_space])
1624 && ossl_time_compare(now, ackm->rx_largest_time[pkt_space]) > 0
1625 && pkt_space == QUIC_PN_SPACE_APP)
1627 ossl_time_subtract(now, ackm->rx_largest_time[pkt_space]);
1629 ack->delay_time = ossl_time_zero();
1631 ack->ect0 = ackm->rx_ect0[pkt_space];
1632 ack->ect1 = ackm->rx_ect1[pkt_space];
1633 ack->ecnce = ackm->rx_ecnce[pkt_space];
1634 ack->ecn_present = 1;
1636 ackm->rx_ack_eliciting_pkts_since_last_ack[pkt_space] = 0;
1638 ackm->rx_ack_generated[pkt_space] = 1;
1639 ackm->rx_ack_desired[pkt_space] = 0;
1640 ackm_set_flush_deadline(ackm, pkt_space, ossl_time_infinite());
1645 OSSL_TIME ossl_ackm_get_ack_deadline(OSSL_ACKM *ackm, int pkt_space)
1647 if (ackm->rx_ack_desired[pkt_space])
1648 /* Already desired, deadline is now. */
1649 return ossl_time_zero();
1651 return ackm->rx_ack_flush_deadline[pkt_space];
1654 int ossl_ackm_is_rx_pn_processable(OSSL_ACKM *ackm, QUIC_PN pn, int pkt_space)
1656 struct rx_pkt_history_st *h = get_rx_history(ackm, pkt_space);
1658 return pn >= h->watermark && ossl_uint_set_query(&h->set, pn) == 0;
1661 void ossl_ackm_set_loss_detection_deadline_callback(OSSL_ACKM *ackm,
1662 void (*fn)(OSSL_TIME deadline,
1666 ackm->loss_detection_deadline_cb = fn;
1667 ackm->loss_detection_deadline_cb_arg = arg;
1670 void ossl_ackm_set_ack_deadline_callback(OSSL_ACKM *ackm,
1671 void (*fn)(OSSL_TIME deadline,
1676 ackm->ack_deadline_cb = fn;
1677 ackm->ack_deadline_cb_arg = arg;
1680 int ossl_ackm_mark_packet_pseudo_lost(OSSL_ACKM *ackm,
1681 int pkt_space, QUIC_PN pn)
1683 struct tx_pkt_history_st *h = get_tx_history(ackm, pkt_space);
1684 OSSL_ACKM_TX_PKT *pkt;
1686 pkt = tx_pkt_history_by_pkt_num(h, pn);
1690 tx_pkt_history_remove(h, pkt->pkt_num);
1692 ackm_on_pkts_lost(ackm, pkt_space, pkt, /*pseudo=*/1);
1696 OSSL_TIME ossl_ackm_get_pto_duration(OSSL_ACKM *ackm)
1701 ossl_statm_get_rtt_info(ackm->statm, &rtt);
1703 duration = ossl_time_add(rtt.smoothed_rtt,
1704 ossl_time_max(ossl_time_multiply(rtt.rtt_variance, 4),
1705 ossl_ticks2time(K_GRANULARITY)));
1706 if (!ossl_time_is_infinite(ackm->rx_max_ack_delay))
1707 duration = ossl_time_add(duration, ackm->rx_max_ack_delay);
1712 QUIC_PN ossl_ackm_get_largest_acked(OSSL_ACKM *ackm, int pkt_space)
1714 return ackm->largest_acked_pkt[pkt_space];
1717 void ossl_ackm_set_rx_max_ack_delay(OSSL_ACKM *ackm, OSSL_TIME rx_max_ack_delay)
1719 ackm->rx_max_ack_delay = rx_max_ack_delay;
1722 void ossl_ackm_set_tx_max_ack_delay(OSSL_ACKM *ackm, OSSL_TIME tx_max_ack_delay)
1724 ackm->tx_max_ack_delay = tx_max_ack_delay;