lsquic_send_ctl.c revision 10c492f0 
1/* Copyright (c) 2017 - 2018 LiteSpeed Technologies Inc.  See LICENSE. */
2/*
3 * lsquic_send_ctl.c -- Logic for sending and sent packets
4 */
5
6#include <assert.h>
7#include <errno.h>
8#include <inttypes.h>
9#include <stdlib.h>
10#include <string.h>
11#include <sys/queue.h>
12
13#include "lsquic_types.h"
14#include "lsquic_int_types.h"
15#include "lsquic.h"
16#include "lsquic_mm.h"
17#include "lsquic_engine_public.h"
18#include "lsquic_alarmset.h"
19#include "lsquic_packet_common.h"
20#include "lsquic_parse.h"
21#include "lsquic_packet_out.h"
22#include "lsquic_senhist.h"
23#include "lsquic_rtt.h"
24#include "lsquic_cubic.h"
25#include "lsquic_pacer.h"
26#include "lsquic_send_ctl.h"
27#include "lsquic_util.h"
28#include "lsquic_sfcw.h"
29#include "lsquic_stream.h"
30#include "lsquic_ver_neg.h"
31#include "lsquic_ev_log.h"
32#include "lsquic_conn.h"
33#include "lsquic_conn_flow.h"
34#include "lsquic_conn_public.h"
35#include "lsquic_hash.h"
36
37#define LSQUIC_LOGGER_MODULE LSQLM_SENDCTL
38#define LSQUIC_LOG_CONN_ID ctl->sc_conn_pub->lconn->cn_cid
39#include "lsquic_logger.h"
40
41#define MAX_RESUBMITTED_ON_RTO  2
42#define MAX_RTO_BACKOFFS        10
43#define DEFAULT_RETX_DELAY      500000      /* Microseconds */
44#define MAX_RTO_DELAY           60000000    /* Microseconds */
45#define MIN_RTO_DELAY           1000000      /* Microseconds */
46#define N_NACKS_BEFORE_RETX     3
47
48
49enum retx_mode {
50    RETX_MODE_HANDSHAKE,
51    RETX_MODE_LOSS,
52    RETX_MODE_TLP,
53    RETX_MODE_RTO,
54};
55
56
57static const char *const retx2str[] = {
58    [RETX_MODE_HANDSHAKE] = "RETX_MODE_HANDSHAKE",
59    [RETX_MODE_LOSS]      = "RETX_MODE_LOSS",
60    [RETX_MODE_TLP]       = "RETX_MODE_TLP",
61    [RETX_MODE_RTO]       = "RETX_MODE_RTO",
62};
63
64
65static void
66update_for_resending (lsquic_send_ctl_t *ctl, lsquic_packet_out_t *packet_out);
67
68
69enum expire_filter { EXFI_ALL, EXFI_HSK, EXFI_LAST, };
70
71
72static void
73send_ctl_expire (lsquic_send_ctl_t *, enum expire_filter);
74
75static void
76set_retx_alarm (lsquic_send_ctl_t *ctl);
77
78static void
79send_ctl_detect_losses (lsquic_send_ctl_t *ctl, lsquic_time_t time);
80
81static unsigned
82send_ctl_retx_bytes_out (const struct lsquic_send_ctl *ctl);
83
84
85#ifdef NDEBUG
86static
87#elif __GNUC__
88__attribute__((weak))
89#endif
90int
91lsquic_send_ctl_schedule_stream_packets_immediately (lsquic_send_ctl_t *ctl)
92{
93    return !(ctl->sc_flags & SC_BUFFER_STREAM);
94}
95
96
97#ifdef NDEBUG
98static
99#elif __GNUC__
100__attribute__((weak))
101#endif
102enum lsquic_packno_bits
103lsquic_send_ctl_guess_packno_bits (lsquic_send_ctl_t *ctl)
104{
105    return PACKNO_LEN_2;
106}
107
108
109int
110lsquic_send_ctl_have_unacked_stream_frames (const lsquic_send_ctl_t *ctl)
111{
112    const lsquic_packet_out_t *packet_out;
113    TAILQ_FOREACH(packet_out, &ctl->sc_unacked_packets, po_next)
114        if (packet_out->po_frame_types &
115                    ((1 << QUIC_FRAME_STREAM) | (1 << QUIC_FRAME_RST_STREAM)))
116            return 1;
117    return 0;
118}
119
120
121static lsquic_packet_out_t *
122send_ctl_first_unacked_retx_packet (const lsquic_send_ctl_t *ctl)
123{
124    lsquic_packet_out_t *packet_out;
125    TAILQ_FOREACH(packet_out, &ctl->sc_unacked_packets, po_next)
126        if (packet_out->po_frame_types & QFRAME_RETRANSMITTABLE_MASK)
127            return packet_out;
128    return NULL;
129}
130
131
132static lsquic_packet_out_t *
133send_ctl_last_unacked_retx_packet (const lsquic_send_ctl_t *ctl)
134{
135    lsquic_packet_out_t *packet_out;
136    TAILQ_FOREACH_REVERSE(packet_out, &ctl->sc_unacked_packets,
137                                            lsquic_packets_tailq, po_next)
138        if (packet_out->po_frame_types & QFRAME_RETRANSMITTABLE_MASK)
139            return packet_out;
140    return NULL;
141}
142
143
144static int
145have_unacked_handshake_packets (const lsquic_send_ctl_t *ctl)
146{
147    const lsquic_packet_out_t *packet_out;
148    TAILQ_FOREACH(packet_out, &ctl->sc_unacked_packets, po_next)
149        if (packet_out->po_flags & PO_HELLO)
150            return 1;
151    return 0;
152}
153
154
155static enum retx_mode
156get_retx_mode (lsquic_send_ctl_t *ctl)
157{
158    if (!(ctl->sc_conn_pub->lconn->cn_flags & LSCONN_HANDSHAKE_DONE)
159                                    && have_unacked_handshake_packets(ctl))
160        return RETX_MODE_HANDSHAKE;
161    if (ctl->sc_loss_to)
162        return RETX_MODE_LOSS;
163    if (ctl->sc_n_tlp < 2)
164        return RETX_MODE_TLP;
165    return RETX_MODE_RTO;
166}
167
168
169static lsquic_time_t
170get_retx_delay (const struct lsquic_rtt_stats *rtt_stats)
171{
172    lsquic_time_t srtt, delay;
173
174    srtt = lsquic_rtt_stats_get_srtt(rtt_stats);
175    if (srtt)
176    {
177        delay = srtt + 4 * lsquic_rtt_stats_get_rttvar(rtt_stats);
178        if (delay < MIN_RTO_DELAY)
179            delay = MIN_RTO_DELAY;
180    }
181    else
182        delay = DEFAULT_RETX_DELAY;
183
184    return delay;
185}
186
187
188static void
189retx_alarm_rings (void *ctx, lsquic_time_t expiry, lsquic_time_t now)
190{
191    lsquic_send_ctl_t *ctl = ctx;
192    lsquic_packet_out_t *packet_out;
193    enum retx_mode rm;
194
195    /* This is a callback -- before it is called, the alarm is unset */
196    assert(!lsquic_alarmset_is_set(ctl->sc_alset, AL_RETX));
197
198    rm = get_retx_mode(ctl);
199    LSQ_INFO("retx timeout, mode %s", retx2str[rm]);
200
201    switch (rm)
202    {
203    case RETX_MODE_HANDSHAKE:
204        send_ctl_expire(ctl, EXFI_HSK);
205        /* Do not register cubic loss during handshake */
206        break;
207    case RETX_MODE_LOSS:
208        send_ctl_detect_losses(ctl, lsquic_time_now());
209        break;
210    case RETX_MODE_TLP:
211        ++ctl->sc_n_tlp;
212        send_ctl_expire(ctl, EXFI_LAST);
213        break;
214    case RETX_MODE_RTO:
215        ++ctl->sc_n_consec_rtos;
216        ctl->sc_next_limit = 2;
217        LSQ_DEBUG("packet RTO is %"PRIu64" usec", expiry);
218        send_ctl_expire(ctl, EXFI_ALL);
219        lsquic_cubic_timeout(&ctl->sc_cubic);
220        break;
221    }
222
223    packet_out = send_ctl_first_unacked_retx_packet(ctl);
224    if (packet_out)
225        set_retx_alarm(ctl);
226    lsquic_send_ctl_sanity_check(ctl);
227}
228
229
230void
231lsquic_send_ctl_init (lsquic_send_ctl_t *ctl, struct lsquic_alarmset *alset,
232          struct lsquic_engine_public *enpub, const struct ver_neg *ver_neg,
233          struct lsquic_conn_public *conn_pub, unsigned short pack_size)
234{
235    unsigned i;
236    memset(ctl, 0, sizeof(*ctl));
237    TAILQ_INIT(&ctl->sc_scheduled_packets);
238    TAILQ_INIT(&ctl->sc_unacked_packets);
239    TAILQ_INIT(&ctl->sc_lost_packets);
240    ctl->sc_enpub = enpub;
241    ctl->sc_alset = alset;
242    ctl->sc_ver_neg = ver_neg;
243    ctl->sc_pack_size = pack_size;
244    ctl->sc_conn_pub = conn_pub;
245    if (enpub->enp_settings.es_pace_packets)
246        ctl->sc_flags |= SC_PACE;
247    lsquic_alarmset_init_alarm(alset, AL_RETX, retx_alarm_rings, ctl);
248    lsquic_senhist_init(&ctl->sc_senhist);
249    lsquic_cubic_init(&ctl->sc_cubic, LSQUIC_LOG_CONN_ID);
250    if (ctl->sc_flags & SC_PACE)
251        pacer_init(&ctl->sc_pacer, LSQUIC_LOG_CONN_ID, 100000);
252    for (i = 0; i < sizeof(ctl->sc_buffered_packets) /
253                                sizeof(ctl->sc_buffered_packets[0]); ++i)
254        TAILQ_INIT(&ctl->sc_buffered_packets[i].bpq_packets);
255}
256
257
258static lsquic_time_t
259calculate_packet_rto (lsquic_send_ctl_t *ctl)
260{
261    lsquic_time_t delay;
262
263    delay = get_retx_delay(&ctl->sc_conn_pub->rtt_stats);
264
265    unsigned exp = ctl->sc_n_consec_rtos;
266    if (exp > MAX_RTO_BACKOFFS)
267        exp = MAX_RTO_BACKOFFS;
268
269    delay = delay * (1 << exp);
270
271    return delay;
272}
273
274
275static lsquic_time_t
276calculate_tlp_delay (lsquic_send_ctl_t *ctl)
277{
278    lsquic_time_t srtt, delay;
279
280    srtt = lsquic_rtt_stats_get_srtt(&ctl->sc_conn_pub->rtt_stats);
281    if (ctl->sc_n_in_flight_all > 1)
282    {
283        delay = 10000;  /* 10 ms is the minimum tail loss probe delay */
284        if (delay < 2 * srtt)
285            delay = 2 * srtt;
286    }
287    else
288    {
289        delay = srtt + srtt / 2 + MIN_RTO_DELAY;
290        if (delay < 2 * srtt)
291            delay = 2 * srtt;
292    }
293
294    return delay;
295}
296
297
298static void
299set_retx_alarm (lsquic_send_ctl_t *ctl)
300{
301    enum retx_mode rm;
302    lsquic_time_t delay, now;
303
304    assert(!TAILQ_EMPTY(&ctl->sc_unacked_packets));
305
306    now = lsquic_time_now();
307
308    rm = get_retx_mode(ctl);
309    switch (rm)
310    {
311    case RETX_MODE_HANDSHAKE:
312    /* [draft-iyengar-quic-loss-recovery-01]:
313     *
314     *  if (handshake packets are outstanding):
315     *      alarm_duration = max(1.5 * smoothed_rtt, 10ms) << handshake_count;
316     *      handshake_count++;
317     */
318        delay = lsquic_rtt_stats_get_srtt(&ctl->sc_conn_pub->rtt_stats);
319        if (delay)
320        {
321            delay += delay / 2;
322            if (10000 > delay)
323                delay = 10000;
324        }
325        else
326            delay = 150000;
327        delay <<= ctl->sc_n_hsk;
328        ++ctl->sc_n_hsk;
329        break;
330    case RETX_MODE_LOSS:
331        delay = ctl->sc_loss_to;
332        break;
333    case RETX_MODE_TLP:
334        delay = calculate_tlp_delay(ctl);
335        break;
336    case RETX_MODE_RTO:
337        /* Base RTO on the first unacked packet, following reference
338         * implementation.
339         */
340        delay = calculate_packet_rto(ctl);
341        break;
342#ifdef WIN32
343    default:
344        delay = 0;
345#endif
346    }
347
348    if (delay > MAX_RTO_DELAY)
349        delay = MAX_RTO_DELAY;
350
351    LSQ_DEBUG("set retx alarm to %"PRIu64", which is %"PRIu64
352        " usec from now, mode %s", now + delay, delay, retx2str[rm]);
353    lsquic_alarmset_set(ctl->sc_alset, AL_RETX, now + delay);
354}
355
356
357static int
358send_ctl_in_recovery (lsquic_send_ctl_t *ctl)
359{
360    return ctl->sc_largest_acked_packno
361        && ctl->sc_largest_acked_packno <= ctl->sc_largest_sent_at_cutback;
362}
363
364
365static int
366send_ctl_in_slow_start (lsquic_send_ctl_t *ctl)
367{
368    return lsquic_cubic_in_slow_start(&ctl->sc_cubic);
369}
370
371
372static lsquic_time_t
373send_ctl_transfer_time (void *ctx)
374{
375    lsquic_send_ctl_t *const ctl = ctx;
376    uint64_t bandwidth, pacing_rate;
377    lsquic_time_t srtt, tx_time;
378    unsigned long cwnd;
379
380    srtt = lsquic_rtt_stats_get_srtt(&ctl->sc_conn_pub->rtt_stats);
381    if (srtt == 0)
382        srtt = 50000;
383    cwnd = lsquic_cubic_get_cwnd(&ctl->sc_cubic);
384    bandwidth = cwnd * 1000000 / srtt;
385    if (send_ctl_in_slow_start(ctl))
386        pacing_rate = bandwidth * 2;
387    else if (send_ctl_in_recovery(ctl))
388        pacing_rate = bandwidth;
389    else
390        pacing_rate = bandwidth + bandwidth / 4;
391
392    tx_time = (uint64_t) ctl->sc_pack_size * 1000000 / pacing_rate;
393    LSQ_DEBUG("srtt: %"PRIu64"; ss: %d; rec: %d; cwnd: %lu; bandwidth: "
394        "%"PRIu64"; tx_time: %"PRIu64, srtt, send_ctl_in_slow_start(ctl),
395        send_ctl_in_recovery(ctl), cwnd, bandwidth, tx_time);
396    return tx_time;
397}
398
399
400static void
401send_ctl_unacked_append (struct lsquic_send_ctl *ctl,
402                         struct lsquic_packet_out *packet_out)
403{
404    TAILQ_INSERT_TAIL(&ctl->sc_unacked_packets, packet_out, po_next);
405    ctl->sc_bytes_unacked_all += lsquic_packet_out_total_sz(packet_out);
406    ctl->sc_n_in_flight_all  += 1;
407    if (packet_out->po_frame_types & QFRAME_RETRANSMITTABLE_MASK)
408    {
409        ctl->sc_bytes_unacked_retx += lsquic_packet_out_total_sz(packet_out);
410        ++ctl->sc_n_in_flight_retx;
411    }
412}
413
414
415static void
416send_ctl_unacked_remove (struct lsquic_send_ctl *ctl,
417                     struct lsquic_packet_out *packet_out, unsigned packet_sz)
418{
419    TAILQ_REMOVE(&ctl->sc_unacked_packets, packet_out, po_next);
420    assert(ctl->sc_bytes_unacked_all >= packet_sz);
421    ctl->sc_bytes_unacked_all -= packet_sz;
422    ctl->sc_n_in_flight_all  -= 1;
423    if (packet_out->po_frame_types & QFRAME_RETRANSMITTABLE_MASK)
424    {
425        ctl->sc_bytes_unacked_retx -= packet_sz;
426        --ctl->sc_n_in_flight_retx;
427    }
428}
429
430
431static void
432send_ctl_sched_Xpend_common (struct lsquic_send_ctl *ctl,
433                      struct lsquic_packet_out *packet_out)
434{
435    packet_out->po_flags |= PO_SCHED;
436    ++ctl->sc_n_scheduled;
437    ctl->sc_bytes_scheduled += lsquic_packet_out_total_sz(packet_out);
438    lsquic_send_ctl_sanity_check(ctl);
439}
440
441
442static void
443send_ctl_sched_append (struct lsquic_send_ctl *ctl,
444                       struct lsquic_packet_out *packet_out)
445{
446    TAILQ_INSERT_TAIL(&ctl->sc_scheduled_packets, packet_out, po_next);
447    send_ctl_sched_Xpend_common(ctl, packet_out);
448}
449
450
451static void
452send_ctl_sched_prepend (struct lsquic_send_ctl *ctl,
453                       struct lsquic_packet_out *packet_out)
454{
455    TAILQ_INSERT_HEAD(&ctl->sc_scheduled_packets, packet_out, po_next);
456    send_ctl_sched_Xpend_common(ctl, packet_out);
457}
458
459
460static void
461send_ctl_sched_remove (struct lsquic_send_ctl *ctl,
462                       struct lsquic_packet_out *packet_out)
463{
464    TAILQ_REMOVE(&ctl->sc_scheduled_packets, packet_out, po_next);
465    packet_out->po_flags &= ~PO_SCHED;
466    assert(ctl->sc_n_scheduled);
467    --ctl->sc_n_scheduled;
468    ctl->sc_bytes_scheduled -= lsquic_packet_out_total_sz(packet_out);
469    lsquic_send_ctl_sanity_check(ctl);
470}
471
472
473int
474lsquic_send_ctl_sent_packet (lsquic_send_ctl_t *ctl,
475                             struct lsquic_packet_out *packet_out, int account)
476{
477    char frames[lsquic_frame_types_str_sz];
478    LSQ_DEBUG("packet %"PRIu64" has been sent (frame types: %s)",
479        packet_out->po_packno, lsquic_frame_types_to_str(frames,
480            sizeof(frames), packet_out->po_frame_types));
481    if (account)
482        ctl->sc_bytes_out -= lsquic_packet_out_total_sz(packet_out);
483    lsquic_senhist_add(&ctl->sc_senhist, packet_out->po_packno);
484    send_ctl_unacked_append(ctl, packet_out);
485    if (packet_out->po_frame_types & QFRAME_RETRANSMITTABLE_MASK)
486    {
487        if (!lsquic_alarmset_is_set(ctl->sc_alset, AL_RETX))
488            set_retx_alarm(ctl);
489        if (ctl->sc_n_in_flight_retx == 1)
490            ctl->sc_flags |= SC_WAS_QUIET;
491    }
492    /* TODO: Do we really want to use those for RTT info? Revisit this. */
493    /* Hold on to packets that are not retransmittable because we need them
494     * to sample RTT information.  They are released when ACK is received.
495     */
496#if LSQUIC_SEND_STATS
497    ++ctl->sc_stats.n_total_sent;
498#endif
499    lsquic_send_ctl_sanity_check(ctl);
500    return 0;
501}
502
503
504static void
505take_rtt_sample (lsquic_send_ctl_t *ctl,
506                 lsquic_time_t now, lsquic_time_t lack_delta)
507{
508    const lsquic_packno_t packno = ctl->sc_largest_acked_packno;
509    const lsquic_time_t sent = ctl->sc_largest_acked_sent_time;
510    const lsquic_time_t measured_rtt = now - sent;
511    if (packno > ctl->sc_max_rtt_packno && lack_delta < measured_rtt)
512    {
513        ctl->sc_max_rtt_packno = packno;
514        lsquic_rtt_stats_update(&ctl->sc_conn_pub->rtt_stats, measured_rtt, lack_delta);
515        LSQ_DEBUG("packno %"PRIu64"; rtt: %"PRIu64"; delta: %"PRIu64"; "
516            "new srtt: %"PRIu64, packno, measured_rtt, lack_delta,
517            lsquic_rtt_stats_get_srtt(&ctl->sc_conn_pub->rtt_stats));
518    }
519}
520
521
522static void
523send_ctl_release_enc_data (struct lsquic_send_ctl *ctl,
524                                        struct lsquic_packet_out *packet_out)
525{
526    ctl->sc_enpub->enp_pmi->pmi_release(ctl->sc_enpub->enp_pmi_ctx,
527                                            packet_out->po_enc_data);
528    packet_out->po_flags &= ~PO_ENCRYPTED;
529    packet_out->po_enc_data = NULL;
530}
531
532
533/* Returns true if packet was rescheduled, false otherwise.  In the latter
534 * case, you should not dereference packet_out after the function returns.
535 */
536static int
537send_ctl_handle_lost_packet (lsquic_send_ctl_t *ctl,
538                                            lsquic_packet_out_t *packet_out)
539{
540    unsigned packet_sz;
541
542    assert(ctl->sc_n_in_flight_all);
543    packet_sz = lsquic_packet_out_sent_sz(packet_out);
544    send_ctl_unacked_remove(ctl, packet_out, packet_sz);
545    if (packet_out->po_flags & PO_ENCRYPTED)
546        send_ctl_release_enc_data(ctl, packet_out);
547    if (packet_out->po_frame_types & (1 << QUIC_FRAME_ACK))
548    {
549        ctl->sc_flags |= SC_LOST_ACK;
550        LSQ_DEBUG("lost ACK in packet %"PRIu64, packet_out->po_packno);
551    }
552    if (packet_out->po_frame_types & QFRAME_RETRANSMITTABLE_MASK)
553    {
554        LSQ_DEBUG("lost retransmittable packet %"PRIu64,
555                                                    packet_out->po_packno);
556        TAILQ_INSERT_TAIL(&ctl->sc_lost_packets, packet_out, po_next);
557        return 1;
558    }
559    else
560    {
561        LSQ_DEBUG("lost unretransmittable packet %"PRIu64,
562                                                    packet_out->po_packno);
563        lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
564        return 0;
565    }
566}
567
568
569static lsquic_packno_t
570largest_retx_packet_number (const lsquic_send_ctl_t *ctl)
571{
572    const lsquic_packet_out_t *packet_out;
573    TAILQ_FOREACH_REVERSE(packet_out, &ctl->sc_unacked_packets,
574                                                lsquic_packets_tailq, po_next)
575    {
576        if (packet_out->po_frame_types & QFRAME_RETRANSMITTABLE_MASK)
577            return packet_out->po_packno;
578    }
579    return 0;
580}
581
582
583static void
584send_ctl_detect_losses (lsquic_send_ctl_t *ctl, lsquic_time_t time)
585{
586    lsquic_packet_out_t *packet_out, *next;
587    lsquic_packno_t largest_retx_packno, largest_lost_packno;
588
589    largest_retx_packno = largest_retx_packet_number(ctl);
590    largest_lost_packno = 0;
591    ctl->sc_loss_to = 0;
592
593    for (packet_out = TAILQ_FIRST(&ctl->sc_unacked_packets);
594            packet_out && packet_out->po_packno <= ctl->sc_largest_acked_packno;
595                packet_out = next)
596    {
597        next = TAILQ_NEXT(packet_out, po_next);
598
599        if (packet_out->po_packno + N_NACKS_BEFORE_RETX <
600                                                ctl->sc_largest_acked_packno)
601        {
602            LSQ_DEBUG("loss by FACK detected, packet %"PRIu64,
603                                                    packet_out->po_packno);
604            largest_lost_packno = packet_out->po_packno;
605            (void) send_ctl_handle_lost_packet(ctl, packet_out);
606            continue;
607        }
608
609        if (largest_retx_packno
610            && (packet_out->po_frame_types & QFRAME_RETRANSMITTABLE_MASK)
611            && largest_retx_packno <= ctl->sc_largest_acked_packno)
612        {
613            LSQ_DEBUG("loss by early retransmit detected, packet %"PRIu64,
614                                                    packet_out->po_packno);
615            largest_lost_packno = packet_out->po_packno;
616            ctl->sc_loss_to =
617                lsquic_rtt_stats_get_srtt(&ctl->sc_conn_pub->rtt_stats) / 4;
618            LSQ_DEBUG("set sc_loss_to to %"PRIu64", packet %"PRIu64,
619                                    ctl->sc_loss_to, packet_out->po_packno);
620            (void) send_ctl_handle_lost_packet(ctl, packet_out);
621            continue;
622        }
623
624        if (ctl->sc_largest_acked_sent_time > packet_out->po_sent +
625                    lsquic_rtt_stats_get_srtt(&ctl->sc_conn_pub->rtt_stats))
626        {
627            LSQ_DEBUG("loss by sent time detected: packet %"PRIu64,
628                                                    packet_out->po_packno);
629            if (packet_out->po_frame_types & QFRAME_RETRANSMITTABLE_MASK)
630                largest_lost_packno = packet_out->po_packno;
631            else { /* don't count it as a loss */; }
632            (void) send_ctl_handle_lost_packet(ctl, packet_out);
633            continue;
634        }
635    }
636
637    if (largest_lost_packno > ctl->sc_largest_sent_at_cutback)
638    {
639        LSQ_DEBUG("detected new loss: packet %"PRIu64"; new lsac: "
640            "%"PRIu64, largest_lost_packno, ctl->sc_largest_sent_at_cutback);
641        lsquic_cubic_loss(&ctl->sc_cubic);
642        if (ctl->sc_flags & SC_PACE)
643            pacer_loss_event(&ctl->sc_pacer);
644        ctl->sc_largest_sent_at_cutback =
645                                lsquic_senhist_largest(&ctl->sc_senhist);
646    }
647    else if (largest_lost_packno)
648        /* Lost packets whose numbers are smaller than the largest packet
649         * number sent at the time of the last loss event indicate the same
650         * loss event.  This follows NewReno logic, see RFC 6582.
651         */
652        LSQ_DEBUG("ignore loss of packet %"PRIu64" smaller than lsac "
653            "%"PRIu64, largest_lost_packno, ctl->sc_largest_sent_at_cutback);
654}
655
656
657int
658lsquic_send_ctl_got_ack (lsquic_send_ctl_t *ctl,
659                         const struct ack_info *acki,
660                         lsquic_time_t ack_recv_time)
661{
662    struct lsquic_packets_tailq acked_acks =
663                                    TAILQ_HEAD_INITIALIZER(acked_acks);
664    const struct lsquic_packno_range *range =
665                                    &acki->ranges[ acki->n_ranges - 1 ];
666    lsquic_packet_out_t *packet_out, *next;
667    lsquic_time_t now = 0;
668    lsquic_packno_t smallest_unacked;
669    lsquic_packno_t ack2ed[2];
670    unsigned packet_sz;
671    int app_limited;
672    signed char do_rtt, skip_checks;
673
674    packet_out = TAILQ_FIRST(&ctl->sc_unacked_packets);
675#if __GNUC__
676    __builtin_prefetch(packet_out);
677#endif
678
679#if __GNUC__
680#   define UNLIKELY(cond) __builtin_expect(cond, 0)
681#else
682#   define UNLIKELY(cond) cond
683#endif
684
685#if __GNUC__
686    if (UNLIKELY(LSQ_LOG_ENABLED(LSQ_LOG_DEBUG)))
687#endif
688        LSQ_DEBUG("Got ACK frame, largest acked: %"PRIu64"; delta: %"PRIu64,
689                            largest_acked(acki), acki->lack_delta);
690
691    /* Validate ACK first: */
692    if (UNLIKELY(largest_acked(acki)
693                                > lsquic_senhist_largest(&ctl->sc_senhist)))
694    {
695        LSQ_INFO("at least one packet in ACK range [%"PRIu64" - %"PRIu64"] "
696            "was never sent", acki->ranges[0].low, acki->ranges[0].high);
697        return -1;
698    }
699
700    if (UNLIKELY(ctl->sc_flags & SC_WAS_QUIET))
701    {
702        ctl->sc_flags &= ~SC_WAS_QUIET;
703        LSQ_DEBUG("ACK comes after a period of quiescence");
704        if (!now)
705            now = lsquic_time_now();
706        lsquic_cubic_was_quiet(&ctl->sc_cubic, now);
707    }
708
709    if (UNLIKELY(!packet_out))
710        goto no_unacked_packets;
711
712    smallest_unacked = packet_out->po_packno;
713    ack2ed[1] = 0;
714
715    if (packet_out->po_packno > largest_acked(acki))
716        goto detect_losses;
717
718    do_rtt = 0, skip_checks = 0;
719    app_limited = -1;
720    do
721    {
722        next = TAILQ_NEXT(packet_out, po_next);
723#if __GNUC__
724        __builtin_prefetch(next);
725#endif
726        if (skip_checks)
727            goto after_checks;
728        /* This is faster than binary search in the normal case when the number
729         * of ranges is not much larger than the number of unacked packets.
730         */
731        while (UNLIKELY(range->high < packet_out->po_packno))
732            --range;
733        if (range->low <= packet_out->po_packno)
734        {
735            skip_checks = range == acki->ranges;
736            if (app_limited < 0)
737                app_limited = send_ctl_retx_bytes_out(ctl) + 3 * ctl->sc_pack_size /* This
738                    is the "maximum burst" parameter */
739                    < lsquic_cubic_get_cwnd(&ctl->sc_cubic);
740            if (!now)
741                now = lsquic_time_now();
742  after_checks:
743            packet_sz = lsquic_packet_out_sent_sz(packet_out);
744            ctl->sc_largest_acked_packno    = packet_out->po_packno;
745            ctl->sc_largest_acked_sent_time = packet_out->po_sent;
746            send_ctl_unacked_remove(ctl, packet_out, packet_sz);
747            ack2ed[!!(packet_out->po_frame_types & (1 << QUIC_FRAME_ACK))]
748                = packet_out->po_ack2ed;
749            do_rtt |= packet_out->po_packno == largest_acked(acki);
750            lsquic_cubic_ack(&ctl->sc_cubic, now, now - packet_out->po_sent,
751                             app_limited, packet_sz);
752            lsquic_packet_out_ack_streams(packet_out);
753            lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
754        }
755        packet_out = next;
756    }
757    while (packet_out && packet_out->po_packno <= largest_acked(acki));
758
759    if (do_rtt)
760    {
761        take_rtt_sample(ctl, ack_recv_time, acki->lack_delta);
762        ctl->sc_n_consec_rtos = 0;
763        ctl->sc_n_hsk = 0;
764        ctl->sc_n_tlp = 0;
765    }
766
767  detect_losses:
768    send_ctl_detect_losses(ctl, ack_recv_time);
769    if (send_ctl_first_unacked_retx_packet(ctl))
770        set_retx_alarm(ctl);
771    else
772    {
773        LSQ_DEBUG("No retransmittable packets: clear alarm");
774        lsquic_alarmset_unset(ctl->sc_alset, AL_RETX);
775    }
776    lsquic_send_ctl_sanity_check(ctl);
777
778    if ((ctl->sc_flags & SC_NSTP) && ack2ed[1] > ctl->sc_largest_ack2ed)
779        ctl->sc_largest_ack2ed = ack2ed[1];
780
781    if (ctl->sc_n_in_flight_retx == 0)
782        ctl->sc_flags |= SC_WAS_QUIET;
783
784  update_n_stop_waiting:
785    if (smallest_unacked > smallest_acked(acki))
786        /* Peer is acking packets that have been acked already.  Schedule ACK
787         * and STOP_WAITING frame to chop the range if we get two of these in
788         * a row.
789         */
790        ++ctl->sc_n_stop_waiting;
791    else
792        ctl->sc_n_stop_waiting = 0;
793    lsquic_send_ctl_sanity_check(ctl);
794    return 0;
795
796  no_unacked_packets:
797    smallest_unacked = lsquic_senhist_largest(&ctl->sc_senhist) + 1;
798    ctl->sc_flags |= SC_WAS_QUIET;
799    goto update_n_stop_waiting;
800}
801
802
803lsquic_packno_t
804lsquic_send_ctl_smallest_unacked (lsquic_send_ctl_t *ctl)
805{
806    const lsquic_packet_out_t *packet_out;
807
808    /* Packets are always sent out in order (unless we are reordering them
809     * on purpose).  Thus, the first packet on the unacked packets list has
810     * the smallest packet number of all packets on that list.
811     */
812    if ((packet_out = TAILQ_FIRST(&ctl->sc_unacked_packets)))
813        return packet_out->po_packno;
814    else
815        return lsquic_senhist_largest(&ctl->sc_senhist) + 1;
816}
817
818
819static struct lsquic_packet_out *
820send_ctl_next_lost (lsquic_send_ctl_t *ctl)
821{
822    lsquic_packet_out_t *lost_packet = TAILQ_FIRST(&ctl->sc_lost_packets);
823    if (lost_packet)
824    {
825        TAILQ_REMOVE(&ctl->sc_lost_packets, lost_packet, po_next);
826        if (lost_packet->po_frame_types & (1 << QUIC_FRAME_STREAM))
827        {
828                lsquic_packet_out_elide_reset_stream_frames(lost_packet, 0);
829        }
830        return lost_packet;
831    }
832    else
833        return NULL;
834}
835
836
837static lsquic_packno_t
838send_ctl_next_packno (lsquic_send_ctl_t *ctl)
839{
840    return ++ctl->sc_cur_packno;
841}
842
843
844void
845lsquic_send_ctl_cleanup (lsquic_send_ctl_t *ctl)
846{
847    lsquic_packet_out_t *packet_out;
848    lsquic_senhist_cleanup(&ctl->sc_senhist);
849    while ((packet_out = TAILQ_FIRST(&ctl->sc_scheduled_packets)))
850    {
851        send_ctl_sched_remove(ctl, packet_out);
852        lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
853    }
854    assert(0 == ctl->sc_n_scheduled);
855    assert(0 == ctl->sc_bytes_scheduled);
856    while ((packet_out = TAILQ_FIRST(&ctl->sc_unacked_packets)))
857    {
858        TAILQ_REMOVE(&ctl->sc_unacked_packets, packet_out, po_next);
859        ctl->sc_bytes_unacked_all -= lsquic_packet_out_total_sz(packet_out);
860        lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
861        --ctl->sc_n_in_flight_all;
862    }
863    assert(0 == ctl->sc_n_in_flight_all);
864    assert(0 == ctl->sc_bytes_unacked_all);
865    while ((packet_out = TAILQ_FIRST(&ctl->sc_lost_packets)))
866    {
867        TAILQ_REMOVE(&ctl->sc_lost_packets, packet_out, po_next);
868        lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
869    }
870    pacer_cleanup(&ctl->sc_pacer);
871#if LSQUIC_SEND_STATS
872    LSQ_NOTICE("stats: n_total_sent: %u; n_resent: %u; n_delayed: %u",
873        ctl->sc_stats.n_total_sent, ctl->sc_stats.n_resent,
874        ctl->sc_stats.n_delayed);
875#endif
876}
877
878
879static unsigned
880send_ctl_retx_bytes_out (const struct lsquic_send_ctl *ctl)
881{
882    return ctl->sc_bytes_scheduled
883         + ctl->sc_bytes_unacked_retx
884         + ctl->sc_bytes_out;
885}
886
887
888int
889lsquic_send_ctl_pacer_blocked (struct lsquic_send_ctl *ctl)
890{
891    return (ctl->sc_flags & SC_PACE)
892        && !pacer_can_schedule(&ctl->sc_pacer,
893                               ctl->sc_n_scheduled + ctl->sc_n_in_flight_all);
894}
895
896
897#ifndef NDEBUG
898#if __GNUC__
899__attribute__((weak))
900#endif
901#endif
902int
903lsquic_send_ctl_can_send (lsquic_send_ctl_t *ctl)
904{
905    const unsigned n_out = send_ctl_retx_bytes_out(ctl);
906    LSQ_DEBUG("%s: n_out: %u (unacked_retx: %u, out: %u); cwnd: %lu", __func__,
907        n_out, ctl->sc_bytes_unacked_retx, ctl->sc_bytes_out,
908        lsquic_cubic_get_cwnd(&ctl->sc_cubic));
909    if (ctl->sc_flags & SC_PACE)
910    {
911        if (n_out >= lsquic_cubic_get_cwnd(&ctl->sc_cubic))
912            return 0;
913        if (pacer_can_schedule(&ctl->sc_pacer,
914                               ctl->sc_n_scheduled + ctl->sc_n_in_flight_all))
915            return 1;
916        if (ctl->sc_flags & SC_SCHED_TICK)
917        {
918            ctl->sc_flags &= ~SC_SCHED_TICK;
919            lsquic_engine_add_conn_to_attq(ctl->sc_enpub,
920                    ctl->sc_conn_pub->lconn, pacer_next_sched(&ctl->sc_pacer));
921        }
922        return 0;
923    }
924    else
925        return n_out < lsquic_cubic_get_cwnd(&ctl->sc_cubic);
926}
927
928
929static void
930send_ctl_expire (lsquic_send_ctl_t *ctl, enum expire_filter filter)
931{
932    lsquic_packet_out_t *packet_out, *next;
933    int n_resubmitted;
934    static const char *const filter_type2str[] = {
935        [EXFI_ALL] = "all",
936        [EXFI_HSK] = "handshake",
937        [EXFI_LAST] = "last",
938    };
939
940    switch (filter)
941    {
942    case EXFI_ALL:
943        n_resubmitted = 0;
944        while ((packet_out = TAILQ_FIRST(&ctl->sc_unacked_packets)))
945            n_resubmitted += send_ctl_handle_lost_packet(ctl, packet_out);
946        break;
947    case EXFI_HSK:
948        n_resubmitted = 0;
949        for (packet_out = TAILQ_FIRST(&ctl->sc_unacked_packets); packet_out;
950                                                            packet_out = next)
951        {
952            next = TAILQ_NEXT(packet_out, po_next);
953            if (packet_out->po_flags & PO_HELLO)
954                n_resubmitted += send_ctl_handle_lost_packet(ctl, packet_out);
955        }
956        break;
957    case EXFI_LAST:
958        packet_out = send_ctl_last_unacked_retx_packet(ctl);
959        if (packet_out)
960            n_resubmitted = send_ctl_handle_lost_packet(ctl, packet_out);
961        else
962            n_resubmitted = 0;
963        break;
964#ifdef WIN32
965    default:
966        n_resubmitted = 0;
967#endif
968    }
969
970    LSQ_DEBUG("consider %s packets lost: %d resubmitted",
971                                    filter_type2str[filter], n_resubmitted);
972}
973
974
975void
976lsquic_send_ctl_expire_all (lsquic_send_ctl_t *ctl)
977{
978    lsquic_alarmset_unset(ctl->sc_alset, AL_RETX);
979    send_ctl_expire(ctl, EXFI_ALL);
980    lsquic_send_ctl_sanity_check(ctl);
981}
982
983
984#if LSQUIC_EXTRA_CHECKS
985void
986lsquic_send_ctl_sanity_check (const lsquic_send_ctl_t *ctl)
987{
988    const struct lsquic_packet_out *packet_out;
989    unsigned count, bytes;
990
991    assert(!send_ctl_first_unacked_retx_packet(ctl) ||
992                    lsquic_alarmset_is_set(ctl->sc_alset, AL_RETX));
993    if (lsquic_alarmset_is_set(ctl->sc_alset, AL_RETX))
994    {
995        assert(send_ctl_first_unacked_retx_packet(ctl));
996        assert(lsquic_time_now() < ctl->sc_alset->as_expiry[AL_RETX] + MAX_RTO_DELAY);
997    }
998
999    count = 0, bytes = 0;
1000    TAILQ_FOREACH(packet_out, &ctl->sc_unacked_packets, po_next)
1001    {
1002        bytes += lsquic_packet_out_sent_sz(packet_out);
1003        ++count;
1004    }
1005    assert(count == ctl->sc_n_in_flight_all);
1006    assert(bytes == ctl->sc_bytes_unacked_all);
1007
1008    count = 0, bytes = 0;
1009    TAILQ_FOREACH(packet_out, &ctl->sc_scheduled_packets, po_next)
1010    {
1011        assert(packet_out->po_flags & PO_SCHED);
1012        bytes += lsquic_packet_out_total_sz(packet_out);
1013        ++count;
1014    }
1015    assert(count == ctl->sc_n_scheduled);
1016    assert(bytes == ctl->sc_bytes_scheduled);
1017}
1018
1019
1020#endif
1021
1022
1023void
1024lsquic_send_ctl_scheduled_one (lsquic_send_ctl_t *ctl,
1025                                            lsquic_packet_out_t *packet_out)
1026{
1027#ifndef NDEBUG
1028    const lsquic_packet_out_t *last;
1029    last = TAILQ_LAST(&ctl->sc_scheduled_packets, lsquic_packets_tailq);
1030    if (last)
1031        assert((last->po_flags & PO_REPACKNO) ||
1032                last->po_packno < packet_out->po_packno);
1033#endif
1034    if (ctl->sc_flags & SC_PACE)
1035    {
1036        unsigned n_out = ctl->sc_n_in_flight_retx + ctl->sc_n_scheduled;
1037        pacer_packet_scheduled(&ctl->sc_pacer, n_out,
1038            send_ctl_in_recovery(ctl), send_ctl_transfer_time, ctl);
1039    }
1040    send_ctl_sched_append(ctl, packet_out);
1041}
1042
1043
1044lsquic_packet_out_t *
1045lsquic_send_ctl_next_packet_to_send (lsquic_send_ctl_t *ctl)
1046{
1047    lsquic_packet_out_t *packet_out;
1048
1049    packet_out = TAILQ_FIRST(&ctl->sc_scheduled_packets);
1050    if (!packet_out)
1051        return NULL;
1052
1053    if (ctl->sc_n_consec_rtos &&
1054                    !(packet_out->po_frame_types & (1 << QUIC_FRAME_ACK)))
1055    {
1056        if (ctl->sc_next_limit)
1057            --ctl->sc_next_limit;
1058        else
1059            return NULL;
1060    }
1061
1062    if (packet_out->po_flags & PO_REPACKNO)
1063    {
1064        update_for_resending(ctl, packet_out);
1065        packet_out->po_flags &= ~PO_REPACKNO;
1066    }
1067
1068    send_ctl_sched_remove(ctl, packet_out);
1069    ctl->sc_bytes_out += lsquic_packet_out_total_sz(packet_out);
1070    return packet_out;
1071}
1072
1073
1074void
1075lsquic_send_ctl_delayed_one (lsquic_send_ctl_t *ctl,
1076                                            lsquic_packet_out_t *packet_out)
1077{
1078    send_ctl_sched_prepend(ctl, packet_out);
1079    ctl->sc_bytes_out -= lsquic_packet_out_total_sz(packet_out);
1080    LSQ_DEBUG("packet %"PRIu64" has been delayed", packet_out->po_packno);
1081#if LSQUIC_SEND_STATS
1082    ++ctl->sc_stats.n_delayed;
1083#endif
1084}
1085
1086
1087int
1088lsquic_send_ctl_have_outgoing_stream_frames (const lsquic_send_ctl_t *ctl)
1089{
1090    const lsquic_packet_out_t *packet_out;
1091    TAILQ_FOREACH(packet_out, &ctl->sc_scheduled_packets, po_next)
1092        if (packet_out->po_frame_types &
1093                    ((1 << QUIC_FRAME_STREAM) | (1 << QUIC_FRAME_RST_STREAM)))
1094            return 1;
1095    return 0;
1096}
1097
1098
1099int
1100lsquic_send_ctl_have_outgoing_retx_frames (const lsquic_send_ctl_t *ctl)
1101{
1102    const lsquic_packet_out_t *packet_out;
1103    TAILQ_FOREACH(packet_out, &ctl->sc_scheduled_packets, po_next)
1104        if (packet_out->po_frame_types & QFRAME_RETRANSMITTABLE_MASK)
1105            return 1;
1106    return 0;
1107}
1108
1109
1110static lsquic_packet_out_t *
1111send_ctl_allocate_packet (lsquic_send_ctl_t *ctl, enum lsquic_packno_bits bits,
1112                                                        unsigned need_at_least)
1113{
1114    lsquic_packet_out_t *packet_out;
1115
1116    packet_out = lsquic_packet_out_new(&ctl->sc_enpub->enp_mm,
1117                    ctl->sc_conn_pub->packet_out_malo,
1118                    !(ctl->sc_flags & SC_TCID0), ctl->sc_pack_size, bits,
1119                    ctl->sc_ver_neg->vn_tag, NULL);
1120    if (!packet_out)
1121        return NULL;
1122
1123    if (need_at_least && lsquic_packet_out_avail(packet_out) < need_at_least)
1124    {   /* This should never happen, this is why this check is performed at
1125         * this level and not lower, before the packet is actually allocated.
1126         */
1127        LSQ_ERROR("wanted to allocate packet with at least %u bytes of "
1128            "payload, but only got %u bytes (mtu: %u bytes)", need_at_least,
1129            lsquic_packet_out_avail(packet_out), ctl->sc_pack_size);
1130        lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
1131        return NULL;
1132    }
1133
1134    return packet_out;
1135}
1136
1137
1138lsquic_packet_out_t *
1139lsquic_send_ctl_new_packet_out (lsquic_send_ctl_t *ctl, unsigned need_at_least)
1140{
1141    lsquic_packet_out_t *packet_out;
1142    enum lsquic_packno_bits bits;
1143
1144    bits = lsquic_send_ctl_packno_bits(ctl);
1145    packet_out = send_ctl_allocate_packet(ctl, bits, need_at_least);
1146    if (!packet_out)
1147        return NULL;
1148
1149    packet_out->po_packno = send_ctl_next_packno(ctl);
1150    LSQ_DEBUG("created packet %"PRIu64, packet_out->po_packno);
1151    EV_LOG_PACKET_CREATED(LSQUIC_LOG_CONN_ID, packet_out);
1152    return packet_out;
1153}
1154
1155
1156/* Do not use for STREAM frames
1157 */
1158lsquic_packet_out_t *
1159lsquic_send_ctl_get_writeable_packet (lsquic_send_ctl_t *ctl,
1160                                      unsigned need_at_least, int *is_err)
1161{
1162    lsquic_packet_out_t *packet_out;
1163
1164    assert(need_at_least > 0);
1165
1166    packet_out = lsquic_send_ctl_last_scheduled(ctl);
1167    if (packet_out
1168        && !(packet_out->po_flags & PO_STREAM_END)
1169        && lsquic_packet_out_avail(packet_out) >= need_at_least)
1170    {
1171        return packet_out;
1172    }
1173
1174    if (!lsquic_send_ctl_can_send(ctl))
1175    {
1176        *is_err = 0;
1177        return NULL;
1178    }
1179
1180    packet_out = lsquic_send_ctl_new_packet_out(ctl, need_at_least);
1181    if (packet_out)
1182        lsquic_send_ctl_scheduled_one(ctl, packet_out);
1183    else
1184        *is_err = 1;
1185    return packet_out;
1186}
1187
1188
1189static lsquic_packet_out_t *
1190send_ctl_get_packet_for_stream (lsquic_send_ctl_t *ctl,
1191                      unsigned need_at_least, const lsquic_stream_t *stream)
1192{
1193    lsquic_packet_out_t *packet_out;
1194
1195    assert(need_at_least > 0);
1196
1197    packet_out = lsquic_send_ctl_last_scheduled(ctl);
1198    if (packet_out
1199        && !(packet_out->po_flags & PO_STREAM_END)
1200        && lsquic_packet_out_avail(packet_out) >= need_at_least
1201        && !lsquic_packet_out_has_frame(packet_out, stream, QUIC_FRAME_STREAM))
1202    {
1203        return packet_out;
1204    }
1205
1206    if (!lsquic_send_ctl_can_send(ctl))
1207        return NULL;
1208
1209    packet_out = lsquic_send_ctl_new_packet_out(ctl, need_at_least);
1210    if (!packet_out)
1211        return NULL;
1212
1213    lsquic_send_ctl_scheduled_one(ctl, packet_out);
1214    return packet_out;
1215}
1216
1217
1218static void
1219update_for_resending (lsquic_send_ctl_t *ctl, lsquic_packet_out_t *packet_out)
1220{
1221
1222    lsquic_packno_t oldno, packno;
1223
1224    /* When the packet is resent, it uses the same number of bytes to encode
1225     * the packet number as the original packet.  This follows the reference
1226     * implementation.
1227     */
1228    oldno = packet_out->po_packno;
1229    packno = send_ctl_next_packno(ctl);
1230
1231    packet_out->po_flags &= ~PO_SENT_SZ;
1232    packet_out->po_frame_types &= ~QFRAME_REGEN_MASK;
1233    assert(packet_out->po_frame_types);
1234    packet_out->po_packno = packno;
1235
1236    if (ctl->sc_ver_neg->vn_tag)
1237    {
1238        assert(packet_out->po_flags & PO_VERSION);  /* It can only disappear */
1239        packet_out->po_ver_tag = *ctl->sc_ver_neg->vn_tag;
1240    }
1241
1242    assert(packet_out->po_regen_sz < packet_out->po_data_sz);
1243    if (packet_out->po_regen_sz)
1244    {
1245        assert(!(packet_out->po_flags & PO_SCHED));
1246        lsquic_packet_out_chop_regen(packet_out);
1247    }
1248    LSQ_DEBUG("Packet %"PRIu64" repackaged for resending as packet %"PRIu64,
1249                                                            oldno, packno);
1250    EV_LOG_CONN_EVENT(LSQUIC_LOG_CONN_ID, "packet %"PRIu64" repackaged for "
1251        "resending as packet %"PRIu64, oldno, packno);
1252}
1253
1254
1255unsigned
1256lsquic_send_ctl_reschedule_packets (lsquic_send_ctl_t *ctl)
1257{
1258    lsquic_packet_out_t *packet_out;
1259    unsigned n = 0;
1260
1261    while (lsquic_send_ctl_can_send(ctl) &&
1262                                (packet_out = send_ctl_next_lost(ctl)))
1263    {
1264        if (packet_out->po_regen_sz < packet_out->po_data_sz)
1265        {
1266            ++n;
1267            update_for_resending(ctl, packet_out);
1268            lsquic_send_ctl_scheduled_one(ctl, packet_out);
1269        }
1270        else
1271        {
1272            LSQ_DEBUG("Dropping packet %"PRIu64" from unacked queue",
1273                packet_out->po_packno);
1274            lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
1275        }
1276    }
1277
1278    if (n)
1279        LSQ_DEBUG("rescheduled %u packets", n);
1280
1281    return n;
1282}
1283
1284
1285void
1286lsquic_send_ctl_set_tcid0 (lsquic_send_ctl_t *ctl, int tcid0)
1287{
1288    if (tcid0)
1289    {
1290        LSQ_INFO("set TCID flag");
1291        ctl->sc_flags |=  SC_TCID0;
1292    }
1293    else
1294    {
1295        LSQ_INFO("unset TCID flag");
1296        ctl->sc_flags &= ~SC_TCID0;
1297    }
1298}
1299
1300
1301/* The controller elides this STREAM frames of stream `stream_id' from
1302 * scheduled and buffered packets.  If a packet becomes empty as a result,
1303 * it is dropped.
1304 *
1305 * Packets on other queues do not need to be processed: unacked packets
1306 * have already been sent, and lost packets' reset stream frames will be
1307 * elided in due time.
1308 */
1309void
1310lsquic_send_ctl_elide_stream_frames (lsquic_send_ctl_t *ctl, uint32_t stream_id)
1311{
1312    struct lsquic_packet_out *packet_out, *next;
1313    struct lsquic_packet_out *pre_dropped;
1314    unsigned n, adj;
1315
1316    pre_dropped = NULL;
1317#ifdef WIN32
1318    next = NULL;
1319#endif
1320    for (packet_out = TAILQ_FIRST(&ctl->sc_scheduled_packets); packet_out;
1321                                                            packet_out = next)
1322    {
1323        next = TAILQ_NEXT(packet_out, po_next);
1324
1325        if ((packet_out->po_frame_types & (1 << QUIC_FRAME_STREAM))
1326                                                                   )
1327        {
1328            adj = lsquic_packet_out_elide_reset_stream_frames(packet_out,
1329                                                              stream_id);
1330            ctl->sc_bytes_scheduled -= adj;
1331            if (0 == packet_out->po_frame_types)
1332            {
1333                if (!pre_dropped)
1334                    pre_dropped = TAILQ_PREV(packet_out, lsquic_packets_tailq,
1335                                                                    po_next);
1336                LSQ_DEBUG("cancel packet %"PRIu64" after eliding frames for "
1337                    "stream %"PRIu32, packet_out->po_packno, stream_id);
1338                send_ctl_sched_remove(ctl, packet_out);
1339                lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
1340            }
1341        }
1342    }
1343
1344    /* Need to assign new packet numbers to all packets following the first
1345     * dropped packet to eliminate packet number gap.
1346     */
1347    if (pre_dropped)
1348    {
1349        ctl->sc_cur_packno = lsquic_senhist_largest(&ctl->sc_senhist);
1350        for (packet_out = TAILQ_NEXT(pre_dropped, po_next); packet_out;
1351                                packet_out = TAILQ_NEXT(packet_out, po_next))
1352        {
1353            packet_out->po_flags |= PO_REPACKNO;
1354            if (packet_out->po_flags & PO_ENCRYPTED)
1355                send_ctl_release_enc_data(ctl, packet_out);
1356        }
1357    }
1358
1359    for (n = 0; n < sizeof(ctl->sc_buffered_packets) /
1360                                sizeof(ctl->sc_buffered_packets[0]); ++n)
1361    {
1362        for (packet_out = TAILQ_FIRST(&ctl->sc_buffered_packets[n].bpq_packets);
1363                                                packet_out; packet_out = next)
1364        {
1365            next = TAILQ_NEXT(packet_out, po_next);
1366            assert(packet_out->po_frame_types & (1 << QUIC_FRAME_STREAM));
1367            lsquic_packet_out_elide_reset_stream_frames(packet_out, stream_id);
1368            if (0 == packet_out->po_frame_types)
1369            {
1370                LSQ_DEBUG("cancel buffered packet in queue #%u after eliding "
1371                    "frames for stream %"PRIu32, n, stream_id);
1372                TAILQ_REMOVE(&ctl->sc_buffered_packets[n].bpq_packets,
1373                             packet_out, po_next);
1374                --ctl->sc_buffered_packets[n].bpq_count;
1375                lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
1376                LSQ_DEBUG("Elide packet from buffered queue #%u; count: %u",
1377                          n, ctl->sc_buffered_packets[n].bpq_count);
1378            }
1379        }
1380    }
1381}
1382
1383
1384/* Count how many packets will remain after the squeezing performed by
1385 * lsquic_send_ctl_squeeze_sched().  This is the number of delayed data
1386 * packets.
1387 */
1388#ifndef NDEBUG
1389#if __GNUC__
1390__attribute__((weak))
1391#endif
1392#endif
1393int
1394lsquic_send_ctl_have_delayed_packets (const lsquic_send_ctl_t *ctl)
1395{
1396    const struct lsquic_packet_out *packet_out;
1397    TAILQ_FOREACH(packet_out, &ctl->sc_scheduled_packets, po_next)
1398        if (packet_out->po_regen_sz < packet_out->po_data_sz)
1399            return 1;
1400    return 0;
1401}
1402
1403
1404#ifndef NDEBUG
1405static void
1406send_ctl_log_packet_q (const lsquic_send_ctl_t *ctl, const char *prefix,
1407                                const struct lsquic_packets_tailq *tailq)
1408{
1409    const lsquic_packet_out_t *packet_out;
1410    unsigned n_packets;
1411    char *buf;
1412    size_t bufsz;
1413    int off;
1414
1415    n_packets = 0;
1416    TAILQ_FOREACH(packet_out, tailq, po_next)
1417        ++n_packets;
1418
1419    if (n_packets == 0)
1420    {
1421        LSQ_DEBUG("%s: [<empty set>]", prefix);
1422        return;
1423    }
1424
1425    bufsz = n_packets * sizeof("18446744073709551615" /* UINT64_MAX */);
1426    buf = malloc(bufsz);
1427    if (!buf)
1428    {
1429        LSQ_ERROR("%s: malloc: %s", __func__, strerror(errno));
1430        return;
1431    }
1432
1433    off = 0;
1434    TAILQ_FOREACH(packet_out, tailq, po_next)
1435    {
1436        if (off)
1437            buf[off++] = ' ';
1438        off += sprintf(buf + off, "%"PRIu64, packet_out->po_packno);
1439    }
1440
1441    LSQ_DEBUG("%s: [%s]", prefix, buf);
1442    free(buf);
1443}
1444
1445
1446#define LOG_PACKET_Q(prefix, queue) do {                                    \
1447    if (LSQ_LOG_ENABLED(LSQ_LOG_DEBUG))                                     \
1448        send_ctl_log_packet_q(ctl, queue, prefix);                          \
1449} while (0)
1450#else
1451#define LOG_PACKET_Q(p, q)
1452#endif
1453
1454
1455int
1456lsquic_send_ctl_squeeze_sched (lsquic_send_ctl_t *ctl)
1457{
1458    struct lsquic_packet_out *packet_out, *next;
1459#ifndef NDEBUG
1460    int pre_squeeze_logged = 0;
1461#endif
1462
1463    for (packet_out = TAILQ_FIRST(&ctl->sc_scheduled_packets); packet_out;
1464                                                            packet_out = next)
1465    {
1466        next = TAILQ_NEXT(packet_out, po_next);
1467        if (packet_out->po_regen_sz < packet_out->po_data_sz)
1468        {
1469            if (packet_out->po_flags & PO_ENCRYPTED)
1470                send_ctl_release_enc_data(ctl, packet_out);
1471        }
1472        else
1473        {
1474#ifndef NDEBUG
1475            /* Log the whole list before we squeeze for the first time */
1476            if (!pre_squeeze_logged++)
1477                LOG_PACKET_Q(&ctl->sc_scheduled_packets,
1478                                        "unacked packets before squeezing");
1479#endif
1480            send_ctl_sched_remove(ctl, packet_out);
1481            LSQ_DEBUG("Dropping packet %"PRIu64" from scheduled queue",
1482                packet_out->po_packno);
1483            lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
1484        }
1485    }
1486
1487#ifndef NDEBUG
1488    if (pre_squeeze_logged)
1489        LOG_PACKET_Q(&ctl->sc_scheduled_packets,
1490                                        "unacked packets after squeezing");
1491    else if (ctl->sc_n_scheduled > 0)
1492        LOG_PACKET_Q(&ctl->sc_scheduled_packets, "delayed packets");
1493#endif
1494
1495    return ctl->sc_n_scheduled > 0;
1496}
1497
1498
1499void
1500lsquic_send_ctl_reset_packnos (lsquic_send_ctl_t *ctl)
1501{
1502    struct lsquic_packet_out *packet_out;
1503
1504    assert(ctl->sc_n_scheduled > 0);    /* Otherwise, why is this called? */
1505    ctl->sc_cur_packno = lsquic_senhist_largest(&ctl->sc_senhist);
1506    TAILQ_FOREACH(packet_out, &ctl->sc_scheduled_packets, po_next)
1507        packet_out->po_flags |= PO_REPACKNO;
1508}
1509
1510
1511void
1512lsquic_send_ctl_ack_to_front (lsquic_send_ctl_t *ctl)
1513{
1514    struct lsquic_packet_out *ack_packet;
1515
1516    assert(ctl->sc_n_scheduled > 1);    /* Otherwise, why is this called? */
1517    ack_packet = TAILQ_LAST(&ctl->sc_scheduled_packets, lsquic_packets_tailq);
1518    assert(ack_packet->po_frame_types & (1 << QUIC_FRAME_ACK));
1519    TAILQ_REMOVE(&ctl->sc_scheduled_packets, ack_packet, po_next);
1520    TAILQ_INSERT_HEAD(&ctl->sc_scheduled_packets, ack_packet, po_next);
1521}
1522
1523
1524void
1525lsquic_send_ctl_drop_scheduled (lsquic_send_ctl_t *ctl)
1526{
1527    lsquic_packet_out_t *packet_out;
1528    const unsigned n = ctl->sc_n_scheduled;
1529    while ((packet_out = TAILQ_FIRST(&ctl->sc_scheduled_packets)))
1530    {
1531        send_ctl_sched_remove(ctl, packet_out);
1532        lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
1533    }
1534    assert(0 == ctl->sc_n_scheduled);
1535    ctl->sc_cur_packno = lsquic_senhist_largest(&ctl->sc_senhist);
1536    LSQ_DEBUG("dropped %u scheduled packet%s", n, n != 0 ? "s" : "");
1537}
1538
1539
1540#ifdef NDEBUG
1541static
1542#elif __GNUC__
1543__attribute__((weak))
1544#endif
1545enum buf_packet_type
1546lsquic_send_ctl_determine_bpt (lsquic_send_ctl_t *ctl,
1547                                            const lsquic_stream_t *stream)
1548{
1549    const lsquic_stream_t *other_stream;
1550    struct lsquic_hash_elem *el;
1551    struct lsquic_hash *all_streams;
1552
1553    all_streams = ctl->sc_conn_pub->all_streams;
1554    for (el = lsquic_hash_first(all_streams); el;
1555                                     el = lsquic_hash_next(all_streams))
1556    {
1557        other_stream = lsquic_hashelem_getdata(el);
1558        if (other_stream != stream
1559              && (!(other_stream->stream_flags & STREAM_U_WRITE_DONE))
1560                && !lsquic_stream_is_critical(other_stream)
1561                  && other_stream->sm_priority < stream->sm_priority)
1562            return BPT_OTHER_PRIO;
1563    }
1564    return BPT_HIGHEST_PRIO;
1565}
1566
1567
1568static enum buf_packet_type
1569send_ctl_lookup_bpt (lsquic_send_ctl_t *ctl,
1570                                        const struct lsquic_stream *stream)
1571{
1572    if (ctl->sc_cached_bpt.stream_id != stream->id)
1573    {
1574        ctl->sc_cached_bpt.stream_id = stream->id;
1575        ctl->sc_cached_bpt.packet_type =
1576                                lsquic_send_ctl_determine_bpt(ctl, stream);
1577    }
1578    return ctl->sc_cached_bpt.packet_type;
1579}
1580
1581
1582static unsigned
1583send_ctl_max_bpq_count (const lsquic_send_ctl_t *ctl,
1584                                        enum buf_packet_type packet_type)
1585{
1586    unsigned count;
1587
1588    switch (packet_type)
1589    {
1590    case BPT_OTHER_PRIO:
1591        return MAX_BPQ_COUNT;
1592    case BPT_HIGHEST_PRIO:
1593    default: /* clang does not complain about absence of `default'... */
1594        count = ctl->sc_n_scheduled + ctl->sc_n_in_flight_retx;
1595        if (count < lsquic_cubic_get_cwnd(&ctl->sc_cubic) / ctl->sc_pack_size)
1596        {
1597            count -= lsquic_cubic_get_cwnd(&ctl->sc_cubic) / ctl->sc_pack_size;
1598            if (count > MAX_BPQ_COUNT)
1599                return count;
1600        }
1601        return MAX_BPQ_COUNT;
1602    }
1603}
1604
1605
1606static lsquic_packet_out_t *
1607send_ctl_get_buffered_packet (lsquic_send_ctl_t *ctl,
1608                enum buf_packet_type packet_type, unsigned need_at_least,
1609                                        const struct lsquic_stream *stream)
1610{
1611    struct buf_packet_q *const packet_q =
1612                                    &ctl->sc_buffered_packets[packet_type];
1613    lsquic_packet_out_t *packet_out;
1614    enum lsquic_packno_bits bits;
1615
1616    packet_out = TAILQ_LAST(&packet_q->bpq_packets, lsquic_packets_tailq);
1617    if (packet_out
1618        && !(packet_out->po_flags & PO_STREAM_END)
1619        && lsquic_packet_out_avail(packet_out) >= need_at_least
1620        && !lsquic_packet_out_has_frame(packet_out, stream, QUIC_FRAME_STREAM))
1621    {
1622        return packet_out;
1623    }
1624
1625    if (packet_q->bpq_count >= send_ctl_max_bpq_count(ctl, packet_type))
1626        return NULL;
1627
1628    bits = lsquic_send_ctl_guess_packno_bits(ctl);
1629    packet_out = send_ctl_allocate_packet(ctl, bits, need_at_least);
1630    if (!packet_out)
1631        return NULL;
1632
1633    TAILQ_INSERT_TAIL(&packet_q->bpq_packets, packet_out, po_next);
1634    ++packet_q->bpq_count;
1635    LSQ_DEBUG("Add new packet to buffered queue #%u; count: %u",
1636              packet_type, packet_q->bpq_count);
1637    return packet_out;
1638}
1639
1640
1641lsquic_packet_out_t *
1642lsquic_send_ctl_get_packet_for_stream (lsquic_send_ctl_t *ctl,
1643                unsigned need_at_least, const struct lsquic_stream *stream)
1644{
1645    enum buf_packet_type packet_type;
1646
1647    if (lsquic_send_ctl_schedule_stream_packets_immediately(ctl))
1648        return send_ctl_get_packet_for_stream(ctl, need_at_least, stream);
1649    else
1650    {
1651        packet_type = send_ctl_lookup_bpt(ctl, stream);
1652        return send_ctl_get_buffered_packet(ctl, packet_type, need_at_least,
1653                                            stream);
1654    }
1655}
1656
1657
1658#ifdef NDEBUG
1659static
1660#elif __GNUC__
1661__attribute__((weak))
1662#endif
1663enum lsquic_packno_bits
1664lsquic_send_ctl_calc_packno_bits (lsquic_send_ctl_t *ctl)
1665{
1666    lsquic_packno_t smallest_unacked;
1667    unsigned n_in_flight;
1668
1669    smallest_unacked = lsquic_send_ctl_smallest_unacked(ctl);
1670    n_in_flight = lsquic_cubic_get_cwnd(&ctl->sc_cubic) / ctl->sc_pack_size;
1671    return calc_packno_bits(ctl->sc_cur_packno + 1, smallest_unacked,
1672                                                            n_in_flight);
1673}
1674
1675
1676enum lsquic_packno_bits
1677lsquic_send_ctl_packno_bits (lsquic_send_ctl_t *ctl)
1678{
1679
1680    if (lsquic_send_ctl_schedule_stream_packets_immediately(ctl))
1681        return lsquic_send_ctl_calc_packno_bits(ctl);
1682    else
1683        return lsquic_send_ctl_guess_packno_bits(ctl);
1684}
1685
1686
1687static int
1688split_buffered_packet (lsquic_send_ctl_t *ctl,
1689        enum buf_packet_type packet_type, lsquic_packet_out_t *packet_out,
1690        enum lsquic_packno_bits bits, unsigned excess_bytes)
1691{
1692    struct buf_packet_q *const packet_q =
1693                                    &ctl->sc_buffered_packets[packet_type];
1694    lsquic_packet_out_t *new_packet_out;
1695
1696    assert(TAILQ_FIRST(&packet_q->bpq_packets) == packet_out);
1697
1698    new_packet_out = send_ctl_allocate_packet(ctl, bits, 0);
1699    if (!packet_out)
1700        return -1;
1701
1702    if (0 == lsquic_packet_out_split_in_two(&ctl->sc_enpub->enp_mm, packet_out,
1703                  new_packet_out, ctl->sc_conn_pub->lconn->cn_pf, excess_bytes))
1704    {
1705        lsquic_packet_out_set_packno_bits(packet_out, bits);
1706        TAILQ_INSERT_AFTER(&packet_q->bpq_packets, packet_out, new_packet_out,
1707                           po_next);
1708        ++packet_q->bpq_count;
1709        LSQ_DEBUG("Add split packet to buffered queue #%u; count: %u",
1710                  packet_type, packet_q->bpq_count);
1711        return 0;
1712    }
1713    else
1714    {
1715        lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
1716        return -1;
1717    }
1718}
1719
1720
1721int
1722lsquic_send_ctl_schedule_buffered (lsquic_send_ctl_t *ctl,
1723                                            enum buf_packet_type packet_type)
1724{
1725    struct buf_packet_q *const packet_q =
1726                                    &ctl->sc_buffered_packets[packet_type];
1727    lsquic_packet_out_t *packet_out;
1728    unsigned used, excess;
1729
1730    assert(lsquic_send_ctl_schedule_stream_packets_immediately(ctl));
1731    const enum lsquic_packno_bits bits = lsquic_send_ctl_calc_packno_bits(ctl);
1732    const unsigned need = packno_bits2len(bits);
1733
1734    while ((packet_out = TAILQ_FIRST(&packet_q->bpq_packets)) &&
1735                                            lsquic_send_ctl_can_send(ctl))
1736    {
1737        if (bits != lsquic_packet_out_packno_bits(packet_out))
1738        {
1739            used = packno_bits2len(lsquic_packet_out_packno_bits(packet_out));
1740            if (need > used
1741                && need - used > lsquic_packet_out_avail(packet_out))
1742            {
1743                excess = need - used - lsquic_packet_out_avail(packet_out);
1744                if (0 != split_buffered_packet(ctl, packet_type,
1745                                               packet_out, bits, excess))
1746                {
1747                    return -1;
1748                }
1749            }
1750        }
1751        TAILQ_REMOVE(&packet_q->bpq_packets, packet_out, po_next);
1752        --packet_q->bpq_count;
1753        LSQ_DEBUG("Remove packet from buffered queue #%u; count: %u",
1754                  packet_type, packet_q->bpq_count);
1755        packet_out->po_packno = send_ctl_next_packno(ctl);
1756        lsquic_send_ctl_scheduled_one(ctl, packet_out);
1757    }
1758
1759    return 0;
1760}
1761
1762
1763int
1764lsquic_send_ctl_turn_on_fin (struct lsquic_send_ctl *ctl,
1765                             const struct lsquic_stream *stream)
1766{
1767    enum buf_packet_type packet_type;
1768    struct buf_packet_q *packet_q;
1769    lsquic_packet_out_t *packet_out;
1770    const struct parse_funcs *pf;
1771
1772    pf = ctl->sc_conn_pub->lconn->cn_pf;
1773    packet_type = send_ctl_lookup_bpt(ctl, stream);
1774    packet_q = &ctl->sc_buffered_packets[packet_type];
1775
1776    TAILQ_FOREACH_REVERSE(packet_out, &packet_q->bpq_packets,
1777                          lsquic_packets_tailq, po_next)
1778        if (0 == lsquic_packet_out_turn_on_fin(packet_out, pf, stream))
1779            return 0;
1780
1781    TAILQ_FOREACH(packet_out, &ctl->sc_scheduled_packets, po_next)
1782        if (0 == packet_out->po_sent
1783            && 0 == lsquic_packet_out_turn_on_fin(packet_out, pf, stream))
1784        {
1785            return 0;
1786        }
1787
1788    return -1;
1789}
1790
1791
1792size_t
1793lsquic_send_ctl_mem_used (const struct lsquic_send_ctl *ctl)
1794{
1795    const lsquic_packet_out_t *packet_out;
1796    unsigned n;
1797    size_t size;
1798    const struct lsquic_packets_tailq queues[] = {
1799        ctl->sc_scheduled_packets,
1800        ctl->sc_unacked_packets,
1801        ctl->sc_lost_packets,
1802        ctl->sc_buffered_packets[0].bpq_packets,
1803        ctl->sc_buffered_packets[1].bpq_packets,
1804    };
1805
1806    size = sizeof(*ctl);
1807
1808    for (n = 0; n < sizeof(queues) / sizeof(queues[0]); ++n)
1809        TAILQ_FOREACH(packet_out, &queues[n], po_next)
1810            size += lsquic_packet_out_mem_used(packet_out);
1811
1812    return size;
1813}
1814
1815
1816