lsquic_send_ctl.c revision 355db7c6 
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
888static unsigned
889send_ctl_all_bytes_out (const struct lsquic_send_ctl *ctl)
890{
891    return ctl->sc_bytes_scheduled
892         + ctl->sc_bytes_unacked_all
893         + ctl->sc_bytes_out;
894}
895
896
897int
898lsquic_send_ctl_pacer_blocked (struct lsquic_send_ctl *ctl)
899{
900    return (ctl->sc_flags & SC_PACE)
901        && !pacer_can_schedule(&ctl->sc_pacer,
902                               ctl->sc_n_scheduled + ctl->sc_n_in_flight_all);
903}
904
905
906#ifndef NDEBUG
907#if __GNUC__
908__attribute__((weak))
909#endif
910#endif
911int
912lsquic_send_ctl_can_send (lsquic_send_ctl_t *ctl)
913{
914    const unsigned n_out = send_ctl_all_bytes_out(ctl);
915    LSQ_DEBUG("%s: n_out: %u (unacked_all: %u, out: %u); cwnd: %lu", __func__,
916        n_out, ctl->sc_bytes_unacked_all, ctl->sc_bytes_out,
917        lsquic_cubic_get_cwnd(&ctl->sc_cubic));
918    if (ctl->sc_flags & SC_PACE)
919    {
920        if (n_out >= lsquic_cubic_get_cwnd(&ctl->sc_cubic))
921            return 0;
922        if (pacer_can_schedule(&ctl->sc_pacer,
923                               ctl->sc_n_scheduled + ctl->sc_n_in_flight_all))
924            return 1;
925        if (ctl->sc_flags & SC_SCHED_TICK)
926        {
927            ctl->sc_flags &= ~SC_SCHED_TICK;
928            lsquic_engine_add_conn_to_attq(ctl->sc_enpub,
929                    ctl->sc_conn_pub->lconn, pacer_next_sched(&ctl->sc_pacer));
930        }
931        return 0;
932    }
933    else
934        return n_out < lsquic_cubic_get_cwnd(&ctl->sc_cubic);
935}
936
937
938static void
939send_ctl_expire (lsquic_send_ctl_t *ctl, enum expire_filter filter)
940{
941    lsquic_packet_out_t *packet_out, *next;
942    int n_resubmitted;
943    static const char *const filter_type2str[] = {
944        [EXFI_ALL] = "all",
945        [EXFI_HSK] = "handshake",
946        [EXFI_LAST] = "last",
947    };
948
949    switch (filter)
950    {
951    case EXFI_ALL:
952        n_resubmitted = 0;
953        while ((packet_out = TAILQ_FIRST(&ctl->sc_unacked_packets)))
954            n_resubmitted += send_ctl_handle_lost_packet(ctl, packet_out);
955        break;
956    case EXFI_HSK:
957        n_resubmitted = 0;
958        for (packet_out = TAILQ_FIRST(&ctl->sc_unacked_packets); packet_out;
959                                                            packet_out = next)
960        {
961            next = TAILQ_NEXT(packet_out, po_next);
962            if (packet_out->po_flags & PO_HELLO)
963                n_resubmitted += send_ctl_handle_lost_packet(ctl, packet_out);
964        }
965        break;
966    case EXFI_LAST:
967        packet_out = send_ctl_last_unacked_retx_packet(ctl);
968        if (packet_out)
969            n_resubmitted = send_ctl_handle_lost_packet(ctl, packet_out);
970        else
971            n_resubmitted = 0;
972        break;
973#ifdef WIN32
974    default:
975        n_resubmitted = 0;
976#endif
977    }
978
979    LSQ_DEBUG("consider %s packets lost: %d resubmitted",
980                                    filter_type2str[filter], n_resubmitted);
981}
982
983
984void
985lsquic_send_ctl_expire_all (lsquic_send_ctl_t *ctl)
986{
987    lsquic_alarmset_unset(ctl->sc_alset, AL_RETX);
988    send_ctl_expire(ctl, EXFI_ALL);
989    lsquic_send_ctl_sanity_check(ctl);
990}
991
992
993#if LSQUIC_EXTRA_CHECKS
994void
995lsquic_send_ctl_sanity_check (const lsquic_send_ctl_t *ctl)
996{
997    const struct lsquic_packet_out *packet_out;
998    unsigned count, bytes;
999
1000    assert(!send_ctl_first_unacked_retx_packet(ctl) ||
1001                    lsquic_alarmset_is_set(ctl->sc_alset, AL_RETX));
1002    if (lsquic_alarmset_is_set(ctl->sc_alset, AL_RETX))
1003    {
1004        assert(send_ctl_first_unacked_retx_packet(ctl));
1005        assert(lsquic_time_now() < ctl->sc_alset->as_expiry[AL_RETX] + MAX_RTO_DELAY);
1006    }
1007
1008    count = 0, bytes = 0;
1009    TAILQ_FOREACH(packet_out, &ctl->sc_unacked_packets, po_next)
1010    {
1011        bytes += lsquic_packet_out_sent_sz(packet_out);
1012        ++count;
1013    }
1014    assert(count == ctl->sc_n_in_flight_all);
1015    assert(bytes == ctl->sc_bytes_unacked_all);
1016
1017    count = 0, bytes = 0;
1018    TAILQ_FOREACH(packet_out, &ctl->sc_scheduled_packets, po_next)
1019    {
1020        assert(packet_out->po_flags & PO_SCHED);
1021        bytes += lsquic_packet_out_total_sz(packet_out);
1022        ++count;
1023    }
1024    assert(count == ctl->sc_n_scheduled);
1025    assert(bytes == ctl->sc_bytes_scheduled);
1026}
1027
1028
1029#endif
1030
1031
1032void
1033lsquic_send_ctl_scheduled_one (lsquic_send_ctl_t *ctl,
1034                                            lsquic_packet_out_t *packet_out)
1035{
1036#ifndef NDEBUG
1037    const lsquic_packet_out_t *last;
1038    last = TAILQ_LAST(&ctl->sc_scheduled_packets, lsquic_packets_tailq);
1039    if (last)
1040        assert((last->po_flags & PO_REPACKNO) ||
1041                last->po_packno < packet_out->po_packno);
1042#endif
1043    if (ctl->sc_flags & SC_PACE)
1044    {
1045        unsigned n_out = ctl->sc_n_in_flight_retx + ctl->sc_n_scheduled;
1046        pacer_packet_scheduled(&ctl->sc_pacer, n_out,
1047            send_ctl_in_recovery(ctl), send_ctl_transfer_time, ctl);
1048    }
1049    send_ctl_sched_append(ctl, packet_out);
1050}
1051
1052
1053/* This mimics the logic in lsquic_send_ctl_next_packet_to_send(): we want
1054 * to check whether the first scheduled packet cannot be sent.
1055 */
1056int
1057lsquic_send_ctl_sched_is_blocked (const struct lsquic_send_ctl *ctl)
1058{
1059    const lsquic_packet_out_t *packet_out
1060                            = TAILQ_FIRST(&ctl->sc_scheduled_packets);
1061    return ctl->sc_n_consec_rtos
1062        && 0 == ctl->sc_next_limit
1063        && packet_out
1064        && !(packet_out->po_frame_types & (1 << QUIC_FRAME_ACK));
1065}
1066
1067
1068lsquic_packet_out_t *
1069lsquic_send_ctl_next_packet_to_send (lsquic_send_ctl_t *ctl)
1070{
1071    lsquic_packet_out_t *packet_out;
1072
1073    packet_out = TAILQ_FIRST(&ctl->sc_scheduled_packets);
1074    if (!packet_out)
1075        return NULL;
1076
1077    if (ctl->sc_n_consec_rtos &&
1078                    !(packet_out->po_frame_types & (1 << QUIC_FRAME_ACK)))
1079    {
1080        if (ctl->sc_next_limit)
1081            --ctl->sc_next_limit;
1082        else
1083            return NULL;
1084    }
1085
1086    if (packet_out->po_flags & PO_REPACKNO)
1087    {
1088        update_for_resending(ctl, packet_out);
1089        packet_out->po_flags &= ~PO_REPACKNO;
1090    }
1091
1092    send_ctl_sched_remove(ctl, packet_out);
1093    ctl->sc_bytes_out += lsquic_packet_out_total_sz(packet_out);
1094    return packet_out;
1095}
1096
1097
1098void
1099lsquic_send_ctl_delayed_one (lsquic_send_ctl_t *ctl,
1100                                            lsquic_packet_out_t *packet_out)
1101{
1102    send_ctl_sched_prepend(ctl, packet_out);
1103    ctl->sc_bytes_out -= lsquic_packet_out_total_sz(packet_out);
1104    LSQ_DEBUG("packet %"PRIu64" has been delayed", packet_out->po_packno);
1105#if LSQUIC_SEND_STATS
1106    ++ctl->sc_stats.n_delayed;
1107#endif
1108}
1109
1110
1111int
1112lsquic_send_ctl_have_outgoing_stream_frames (const lsquic_send_ctl_t *ctl)
1113{
1114    const lsquic_packet_out_t *packet_out;
1115    TAILQ_FOREACH(packet_out, &ctl->sc_scheduled_packets, po_next)
1116        if (packet_out->po_frame_types &
1117                    ((1 << QUIC_FRAME_STREAM) | (1 << QUIC_FRAME_RST_STREAM)))
1118            return 1;
1119    return 0;
1120}
1121
1122
1123int
1124lsquic_send_ctl_have_outgoing_retx_frames (const lsquic_send_ctl_t *ctl)
1125{
1126    const lsquic_packet_out_t *packet_out;
1127    TAILQ_FOREACH(packet_out, &ctl->sc_scheduled_packets, po_next)
1128        if (packet_out->po_frame_types & QFRAME_RETRANSMITTABLE_MASK)
1129            return 1;
1130    return 0;
1131}
1132
1133
1134static lsquic_packet_out_t *
1135send_ctl_allocate_packet (lsquic_send_ctl_t *ctl, enum lsquic_packno_bits bits,
1136                                                        unsigned need_at_least)
1137{
1138    lsquic_packet_out_t *packet_out;
1139
1140    packet_out = lsquic_packet_out_new(&ctl->sc_enpub->enp_mm,
1141                    ctl->sc_conn_pub->packet_out_malo,
1142                    !(ctl->sc_flags & SC_TCID0), ctl->sc_pack_size, bits,
1143                    ctl->sc_ver_neg->vn_tag, NULL);
1144    if (!packet_out)
1145        return NULL;
1146
1147    if (need_at_least && lsquic_packet_out_avail(packet_out) < need_at_least)
1148    {   /* This should never happen, this is why this check is performed at
1149         * this level and not lower, before the packet is actually allocated.
1150         */
1151        LSQ_ERROR("wanted to allocate packet with at least %u bytes of "
1152            "payload, but only got %u bytes (mtu: %u bytes)", need_at_least,
1153            lsquic_packet_out_avail(packet_out), ctl->sc_pack_size);
1154        lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
1155        return NULL;
1156    }
1157
1158    return packet_out;
1159}
1160
1161
1162lsquic_packet_out_t *
1163lsquic_send_ctl_new_packet_out (lsquic_send_ctl_t *ctl, unsigned need_at_least)
1164{
1165    lsquic_packet_out_t *packet_out;
1166    enum lsquic_packno_bits bits;
1167
1168    bits = lsquic_send_ctl_packno_bits(ctl);
1169    packet_out = send_ctl_allocate_packet(ctl, bits, need_at_least);
1170    if (!packet_out)
1171        return NULL;
1172
1173    packet_out->po_packno = send_ctl_next_packno(ctl);
1174    LSQ_DEBUG("created packet %"PRIu64, packet_out->po_packno);
1175    EV_LOG_PACKET_CREATED(LSQUIC_LOG_CONN_ID, packet_out);
1176    return packet_out;
1177}
1178
1179
1180/* Do not use for STREAM frames
1181 */
1182lsquic_packet_out_t *
1183lsquic_send_ctl_get_writeable_packet (lsquic_send_ctl_t *ctl,
1184                                      unsigned need_at_least, int *is_err)
1185{
1186    lsquic_packet_out_t *packet_out;
1187
1188    assert(need_at_least > 0);
1189
1190    packet_out = lsquic_send_ctl_last_scheduled(ctl);
1191    if (packet_out
1192        && !(packet_out->po_flags & PO_STREAM_END)
1193        && lsquic_packet_out_avail(packet_out) >= need_at_least)
1194    {
1195        return packet_out;
1196    }
1197
1198    if (!lsquic_send_ctl_can_send(ctl))
1199    {
1200        *is_err = 0;
1201        return NULL;
1202    }
1203
1204    packet_out = lsquic_send_ctl_new_packet_out(ctl, need_at_least);
1205    if (packet_out)
1206        lsquic_send_ctl_scheduled_one(ctl, packet_out);
1207    else
1208        *is_err = 1;
1209    return packet_out;
1210}
1211
1212
1213static lsquic_packet_out_t *
1214send_ctl_get_packet_for_stream (lsquic_send_ctl_t *ctl,
1215                      unsigned need_at_least, const lsquic_stream_t *stream)
1216{
1217    lsquic_packet_out_t *packet_out;
1218
1219    assert(need_at_least > 0);
1220
1221    packet_out = lsquic_send_ctl_last_scheduled(ctl);
1222    if (packet_out
1223        && !(packet_out->po_flags & PO_STREAM_END)
1224        && lsquic_packet_out_avail(packet_out) >= need_at_least
1225        && !lsquic_packet_out_has_frame(packet_out, stream, QUIC_FRAME_STREAM))
1226    {
1227        return packet_out;
1228    }
1229
1230    if (!lsquic_send_ctl_can_send(ctl))
1231        return NULL;
1232
1233    packet_out = lsquic_send_ctl_new_packet_out(ctl, need_at_least);
1234    if (!packet_out)
1235        return NULL;
1236
1237    lsquic_send_ctl_scheduled_one(ctl, packet_out);
1238    return packet_out;
1239}
1240
1241
1242static void
1243update_for_resending (lsquic_send_ctl_t *ctl, lsquic_packet_out_t *packet_out)
1244{
1245
1246    lsquic_packno_t oldno, packno;
1247
1248    /* When the packet is resent, it uses the same number of bytes to encode
1249     * the packet number as the original packet.  This follows the reference
1250     * implementation.
1251     */
1252    oldno = packet_out->po_packno;
1253    packno = send_ctl_next_packno(ctl);
1254
1255    packet_out->po_flags &= ~PO_SENT_SZ;
1256    packet_out->po_frame_types &= ~QFRAME_REGEN_MASK;
1257    assert(packet_out->po_frame_types);
1258    packet_out->po_packno = packno;
1259
1260    if (ctl->sc_ver_neg->vn_tag)
1261    {
1262        assert(packet_out->po_flags & PO_VERSION);  /* It can only disappear */
1263        packet_out->po_ver_tag = *ctl->sc_ver_neg->vn_tag;
1264    }
1265
1266    assert(packet_out->po_regen_sz < packet_out->po_data_sz);
1267    if (packet_out->po_regen_sz)
1268    {
1269        assert(!(packet_out->po_flags & PO_SCHED));
1270        lsquic_packet_out_chop_regen(packet_out);
1271    }
1272    LSQ_DEBUG("Packet %"PRIu64" repackaged for resending as packet %"PRIu64,
1273                                                            oldno, packno);
1274    EV_LOG_CONN_EVENT(LSQUIC_LOG_CONN_ID, "packet %"PRIu64" repackaged for "
1275        "resending as packet %"PRIu64, oldno, packno);
1276}
1277
1278
1279unsigned
1280lsquic_send_ctl_reschedule_packets (lsquic_send_ctl_t *ctl)
1281{
1282    lsquic_packet_out_t *packet_out;
1283    unsigned n = 0;
1284
1285    while (lsquic_send_ctl_can_send(ctl) &&
1286                                (packet_out = send_ctl_next_lost(ctl)))
1287    {
1288        if (packet_out->po_regen_sz < packet_out->po_data_sz)
1289        {
1290            ++n;
1291            update_for_resending(ctl, packet_out);
1292            lsquic_send_ctl_scheduled_one(ctl, packet_out);
1293        }
1294        else
1295        {
1296            LSQ_DEBUG("Dropping packet %"PRIu64" from unacked queue",
1297                packet_out->po_packno);
1298            lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
1299        }
1300    }
1301
1302    if (n)
1303        LSQ_DEBUG("rescheduled %u packets", n);
1304
1305    return n;
1306}
1307
1308
1309void
1310lsquic_send_ctl_set_tcid0 (lsquic_send_ctl_t *ctl, int tcid0)
1311{
1312    if (tcid0)
1313    {
1314        LSQ_INFO("set TCID flag");
1315        ctl->sc_flags |=  SC_TCID0;
1316    }
1317    else
1318    {
1319        LSQ_INFO("unset TCID flag");
1320        ctl->sc_flags &= ~SC_TCID0;
1321    }
1322}
1323
1324
1325/* Need to assign new packet numbers to all packets following the first
1326 * dropped packet to eliminate packet number gap.
1327 */
1328static void
1329send_ctl_repackno_sched_tail (struct lsquic_send_ctl *ctl,
1330                              struct lsquic_packet_out *pre_dropped)
1331{
1332    struct lsquic_packet_out *packet_out;
1333
1334    assert(pre_dropped);
1335
1336    ctl->sc_cur_packno = lsquic_senhist_largest(&ctl->sc_senhist);
1337    for (packet_out = TAILQ_NEXT(pre_dropped, po_next); packet_out;
1338                            packet_out = TAILQ_NEXT(packet_out, po_next))
1339    {
1340        packet_out->po_flags |= PO_REPACKNO;
1341        if (packet_out->po_flags & PO_ENCRYPTED)
1342            send_ctl_release_enc_data(ctl, packet_out);
1343    }
1344}
1345
1346
1347/* The controller elides this STREAM frames of stream `stream_id' from
1348 * scheduled and buffered packets.  If a packet becomes empty as a result,
1349 * it is dropped.
1350 *
1351 * Packets on other queues do not need to be processed: unacked packets
1352 * have already been sent, and lost packets' reset stream frames will be
1353 * elided in due time.
1354 */
1355void
1356lsquic_send_ctl_elide_stream_frames (lsquic_send_ctl_t *ctl, uint32_t stream_id)
1357{
1358    struct lsquic_packet_out *packet_out, *next;
1359    struct lsquic_packet_out *pre_dropped;
1360    unsigned n, adj;
1361
1362    pre_dropped = NULL;
1363#ifdef WIN32
1364    next = NULL;
1365#endif
1366    for (packet_out = TAILQ_FIRST(&ctl->sc_scheduled_packets); packet_out;
1367                                                            packet_out = next)
1368    {
1369        next = TAILQ_NEXT(packet_out, po_next);
1370
1371        if ((packet_out->po_frame_types & (1 << QUIC_FRAME_STREAM))
1372                                                                   )
1373        {
1374            adj = lsquic_packet_out_elide_reset_stream_frames(packet_out,
1375                                                              stream_id);
1376            ctl->sc_bytes_scheduled -= adj;
1377            if (0 == packet_out->po_frame_types)
1378            {
1379                if (!pre_dropped)
1380                    pre_dropped = TAILQ_PREV(packet_out, lsquic_packets_tailq,
1381                                                                    po_next);
1382                LSQ_DEBUG("cancel packet %"PRIu64" after eliding frames for "
1383                    "stream %"PRIu32, packet_out->po_packno, stream_id);
1384                send_ctl_sched_remove(ctl, packet_out);
1385                lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
1386            }
1387        }
1388    }
1389
1390    if (pre_dropped)
1391        send_ctl_repackno_sched_tail(ctl, pre_dropped);
1392
1393    for (n = 0; n < sizeof(ctl->sc_buffered_packets) /
1394                                sizeof(ctl->sc_buffered_packets[0]); ++n)
1395    {
1396        for (packet_out = TAILQ_FIRST(&ctl->sc_buffered_packets[n].bpq_packets);
1397                                                packet_out; packet_out = next)
1398        {
1399            next = TAILQ_NEXT(packet_out, po_next);
1400            assert(packet_out->po_frame_types & (1 << QUIC_FRAME_STREAM));
1401            lsquic_packet_out_elide_reset_stream_frames(packet_out, stream_id);
1402            if (0 == packet_out->po_frame_types)
1403            {
1404                LSQ_DEBUG("cancel buffered packet in queue #%u after eliding "
1405                    "frames for stream %"PRIu32, n, stream_id);
1406                TAILQ_REMOVE(&ctl->sc_buffered_packets[n].bpq_packets,
1407                             packet_out, po_next);
1408                --ctl->sc_buffered_packets[n].bpq_count;
1409                lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
1410                LSQ_DEBUG("Elide packet from buffered queue #%u; count: %u",
1411                          n, ctl->sc_buffered_packets[n].bpq_count);
1412            }
1413        }
1414    }
1415}
1416
1417
1418/* Count how many packets will remain after the squeezing performed by
1419 * lsquic_send_ctl_squeeze_sched().  This is the number of delayed data
1420 * packets.
1421 */
1422#ifndef NDEBUG
1423#if __GNUC__
1424__attribute__((weak))
1425#endif
1426#endif
1427int
1428lsquic_send_ctl_have_delayed_packets (const lsquic_send_ctl_t *ctl)
1429{
1430    const struct lsquic_packet_out *packet_out;
1431    TAILQ_FOREACH(packet_out, &ctl->sc_scheduled_packets, po_next)
1432        if (packet_out->po_regen_sz < packet_out->po_data_sz)
1433            return 1;
1434    return 0;
1435}
1436
1437
1438#ifndef NDEBUG
1439static void
1440send_ctl_log_packet_q (const lsquic_send_ctl_t *ctl, const char *prefix,
1441                                const struct lsquic_packets_tailq *tailq)
1442{
1443    const lsquic_packet_out_t *packet_out;
1444    unsigned n_packets;
1445    char *buf;
1446    size_t bufsz;
1447    int off;
1448
1449    n_packets = 0;
1450    TAILQ_FOREACH(packet_out, tailq, po_next)
1451        ++n_packets;
1452
1453    if (n_packets == 0)
1454    {
1455        LSQ_DEBUG("%s: [<empty set>]", prefix);
1456        return;
1457    }
1458
1459    bufsz = n_packets * sizeof("18446744073709551615" /* UINT64_MAX */);
1460    buf = malloc(bufsz);
1461    if (!buf)
1462    {
1463        LSQ_ERROR("%s: malloc: %s", __func__, strerror(errno));
1464        return;
1465    }
1466
1467    off = 0;
1468    TAILQ_FOREACH(packet_out, tailq, po_next)
1469    {
1470        if (off)
1471            buf[off++] = ' ';
1472        off += sprintf(buf + off, "%"PRIu64, packet_out->po_packno);
1473    }
1474
1475    LSQ_DEBUG("%s: [%s]", prefix, buf);
1476    free(buf);
1477}
1478
1479
1480#define LOG_PACKET_Q(prefix, queue) do {                                    \
1481    if (LSQ_LOG_ENABLED(LSQ_LOG_DEBUG))                                     \
1482        send_ctl_log_packet_q(ctl, queue, prefix);                          \
1483} while (0)
1484#else
1485#define LOG_PACKET_Q(p, q)
1486#endif
1487
1488
1489int
1490lsquic_send_ctl_squeeze_sched (lsquic_send_ctl_t *ctl)
1491{
1492    struct lsquic_packet_out *packet_out, *next;
1493    struct lsquic_packet_out *pre_dropped;
1494#ifndef NDEBUG
1495    int pre_squeeze_logged = 0;
1496#endif
1497
1498    pre_dropped = NULL;
1499    for (packet_out = TAILQ_FIRST(&ctl->sc_scheduled_packets); packet_out;
1500                                                            packet_out = next)
1501    {
1502        next = TAILQ_NEXT(packet_out, po_next);
1503        if (packet_out->po_regen_sz < packet_out->po_data_sz)
1504        {
1505            if (packet_out->po_flags & PO_ENCRYPTED)
1506                send_ctl_release_enc_data(ctl, packet_out);
1507        }
1508        else
1509        {
1510#ifndef NDEBUG
1511            /* Log the whole list before we squeeze for the first time */
1512            if (!pre_squeeze_logged++)
1513                LOG_PACKET_Q(&ctl->sc_scheduled_packets,
1514                                        "unacked packets before squeezing");
1515#endif
1516            if (!pre_dropped)
1517                pre_dropped = TAILQ_PREV(packet_out, lsquic_packets_tailq,
1518                                                                    po_next);
1519            send_ctl_sched_remove(ctl, packet_out);
1520            LSQ_DEBUG("Dropping packet %"PRIu64" from scheduled queue",
1521                packet_out->po_packno);
1522            lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
1523        }
1524    }
1525
1526    if (pre_dropped)
1527        send_ctl_repackno_sched_tail(ctl, pre_dropped);
1528
1529#ifndef NDEBUG
1530    if (pre_squeeze_logged)
1531        LOG_PACKET_Q(&ctl->sc_scheduled_packets,
1532                                        "unacked packets after squeezing");
1533    else if (ctl->sc_n_scheduled > 0)
1534        LOG_PACKET_Q(&ctl->sc_scheduled_packets, "delayed packets");
1535#endif
1536
1537    return ctl->sc_n_scheduled > 0;
1538}
1539
1540
1541void
1542lsquic_send_ctl_reset_packnos (lsquic_send_ctl_t *ctl)
1543{
1544    struct lsquic_packet_out *packet_out;
1545
1546    assert(ctl->sc_n_scheduled > 0);    /* Otherwise, why is this called? */
1547    ctl->sc_cur_packno = lsquic_senhist_largest(&ctl->sc_senhist);
1548    TAILQ_FOREACH(packet_out, &ctl->sc_scheduled_packets, po_next)
1549        packet_out->po_flags |= PO_REPACKNO;
1550}
1551
1552
1553void
1554lsquic_send_ctl_ack_to_front (lsquic_send_ctl_t *ctl)
1555{
1556    struct lsquic_packet_out *ack_packet;
1557
1558    assert(ctl->sc_n_scheduled > 1);    /* Otherwise, why is this called? */
1559    ack_packet = TAILQ_LAST(&ctl->sc_scheduled_packets, lsquic_packets_tailq);
1560    assert(ack_packet->po_frame_types & (1 << QUIC_FRAME_ACK));
1561    TAILQ_REMOVE(&ctl->sc_scheduled_packets, ack_packet, po_next);
1562    TAILQ_INSERT_HEAD(&ctl->sc_scheduled_packets, ack_packet, po_next);
1563}
1564
1565
1566void
1567lsquic_send_ctl_drop_scheduled (lsquic_send_ctl_t *ctl)
1568{
1569    lsquic_packet_out_t *packet_out;
1570    const unsigned n = ctl->sc_n_scheduled;
1571    while ((packet_out = TAILQ_FIRST(&ctl->sc_scheduled_packets)))
1572    {
1573        send_ctl_sched_remove(ctl, packet_out);
1574        lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
1575    }
1576    assert(0 == ctl->sc_n_scheduled);
1577    ctl->sc_cur_packno = lsquic_senhist_largest(&ctl->sc_senhist);
1578    LSQ_DEBUG("dropped %u scheduled packet%s", n, n != 0 ? "s" : "");
1579}
1580
1581
1582#ifdef NDEBUG
1583static
1584#elif __GNUC__
1585__attribute__((weak))
1586#endif
1587enum buf_packet_type
1588lsquic_send_ctl_determine_bpt (lsquic_send_ctl_t *ctl,
1589                                            const lsquic_stream_t *stream)
1590{
1591    const lsquic_stream_t *other_stream;
1592    struct lsquic_hash_elem *el;
1593    struct lsquic_hash *all_streams;
1594
1595    all_streams = ctl->sc_conn_pub->all_streams;
1596    for (el = lsquic_hash_first(all_streams); el;
1597                                     el = lsquic_hash_next(all_streams))
1598    {
1599        other_stream = lsquic_hashelem_getdata(el);
1600        if (other_stream != stream
1601              && (!(other_stream->stream_flags & STREAM_U_WRITE_DONE))
1602                && !lsquic_stream_is_critical(other_stream)
1603                  && other_stream->sm_priority < stream->sm_priority)
1604            return BPT_OTHER_PRIO;
1605    }
1606    return BPT_HIGHEST_PRIO;
1607}
1608
1609
1610static enum buf_packet_type
1611send_ctl_lookup_bpt (lsquic_send_ctl_t *ctl,
1612                                        const struct lsquic_stream *stream)
1613{
1614    if (ctl->sc_cached_bpt.stream_id != stream->id)
1615    {
1616        ctl->sc_cached_bpt.stream_id = stream->id;
1617        ctl->sc_cached_bpt.packet_type =
1618                                lsquic_send_ctl_determine_bpt(ctl, stream);
1619    }
1620    return ctl->sc_cached_bpt.packet_type;
1621}
1622
1623
1624static unsigned
1625send_ctl_max_bpq_count (const lsquic_send_ctl_t *ctl,
1626                                        enum buf_packet_type packet_type)
1627{
1628    unsigned count;
1629
1630    switch (packet_type)
1631    {
1632    case BPT_OTHER_PRIO:
1633        return MAX_BPQ_COUNT;
1634    case BPT_HIGHEST_PRIO:
1635    default: /* clang does not complain about absence of `default'... */
1636        count = ctl->sc_n_scheduled + ctl->sc_n_in_flight_retx;
1637        if (count < lsquic_cubic_get_cwnd(&ctl->sc_cubic) / ctl->sc_pack_size)
1638        {
1639            count -= lsquic_cubic_get_cwnd(&ctl->sc_cubic) / ctl->sc_pack_size;
1640            if (count > MAX_BPQ_COUNT)
1641                return count;
1642        }
1643        return MAX_BPQ_COUNT;
1644    }
1645}
1646
1647
1648static lsquic_packet_out_t *
1649send_ctl_get_buffered_packet (lsquic_send_ctl_t *ctl,
1650                enum buf_packet_type packet_type, unsigned need_at_least,
1651                                        const struct lsquic_stream *stream)
1652{
1653    struct buf_packet_q *const packet_q =
1654                                    &ctl->sc_buffered_packets[packet_type];
1655    lsquic_packet_out_t *packet_out;
1656    enum lsquic_packno_bits bits;
1657
1658    packet_out = TAILQ_LAST(&packet_q->bpq_packets, lsquic_packets_tailq);
1659    if (packet_out
1660        && !(packet_out->po_flags & PO_STREAM_END)
1661        && lsquic_packet_out_avail(packet_out) >= need_at_least
1662        && !lsquic_packet_out_has_frame(packet_out, stream, QUIC_FRAME_STREAM))
1663    {
1664        return packet_out;
1665    }
1666
1667    if (packet_q->bpq_count >= send_ctl_max_bpq_count(ctl, packet_type))
1668        return NULL;
1669
1670    bits = lsquic_send_ctl_guess_packno_bits(ctl);
1671    packet_out = send_ctl_allocate_packet(ctl, bits, need_at_least);
1672    if (!packet_out)
1673        return NULL;
1674
1675    TAILQ_INSERT_TAIL(&packet_q->bpq_packets, packet_out, po_next);
1676    ++packet_q->bpq_count;
1677    LSQ_DEBUG("Add new packet to buffered queue #%u; count: %u",
1678              packet_type, packet_q->bpq_count);
1679    return packet_out;
1680}
1681
1682
1683lsquic_packet_out_t *
1684lsquic_send_ctl_get_packet_for_stream (lsquic_send_ctl_t *ctl,
1685                unsigned need_at_least, const struct lsquic_stream *stream)
1686{
1687    enum buf_packet_type packet_type;
1688
1689    if (lsquic_send_ctl_schedule_stream_packets_immediately(ctl))
1690        return send_ctl_get_packet_for_stream(ctl, need_at_least, stream);
1691    else
1692    {
1693        packet_type = send_ctl_lookup_bpt(ctl, stream);
1694        return send_ctl_get_buffered_packet(ctl, packet_type, need_at_least,
1695                                            stream);
1696    }
1697}
1698
1699
1700#ifdef NDEBUG
1701static
1702#elif __GNUC__
1703__attribute__((weak))
1704#endif
1705enum lsquic_packno_bits
1706lsquic_send_ctl_calc_packno_bits (lsquic_send_ctl_t *ctl)
1707{
1708    lsquic_packno_t smallest_unacked;
1709    unsigned n_in_flight;
1710
1711    smallest_unacked = lsquic_send_ctl_smallest_unacked(ctl);
1712    n_in_flight = lsquic_cubic_get_cwnd(&ctl->sc_cubic) / ctl->sc_pack_size;
1713    return calc_packno_bits(ctl->sc_cur_packno + 1, smallest_unacked,
1714                                                            n_in_flight);
1715}
1716
1717
1718enum lsquic_packno_bits
1719lsquic_send_ctl_packno_bits (lsquic_send_ctl_t *ctl)
1720{
1721
1722    if (lsquic_send_ctl_schedule_stream_packets_immediately(ctl))
1723        return lsquic_send_ctl_calc_packno_bits(ctl);
1724    else
1725        return lsquic_send_ctl_guess_packno_bits(ctl);
1726}
1727
1728
1729static int
1730split_buffered_packet (lsquic_send_ctl_t *ctl,
1731        enum buf_packet_type packet_type, lsquic_packet_out_t *packet_out,
1732        enum lsquic_packno_bits bits, unsigned excess_bytes)
1733{
1734    struct buf_packet_q *const packet_q =
1735                                    &ctl->sc_buffered_packets[packet_type];
1736    lsquic_packet_out_t *new_packet_out;
1737
1738    assert(TAILQ_FIRST(&packet_q->bpq_packets) == packet_out);
1739
1740    new_packet_out = send_ctl_allocate_packet(ctl, bits, 0);
1741    if (!packet_out)
1742        return -1;
1743
1744    if (0 == lsquic_packet_out_split_in_two(&ctl->sc_enpub->enp_mm, packet_out,
1745                  new_packet_out, ctl->sc_conn_pub->lconn->cn_pf, excess_bytes))
1746    {
1747        lsquic_packet_out_set_packno_bits(packet_out, bits);
1748        TAILQ_INSERT_AFTER(&packet_q->bpq_packets, packet_out, new_packet_out,
1749                           po_next);
1750        ++packet_q->bpq_count;
1751        LSQ_DEBUG("Add split packet to buffered queue #%u; count: %u",
1752                  packet_type, packet_q->bpq_count);
1753        return 0;
1754    }
1755    else
1756    {
1757        lsquic_packet_out_destroy(packet_out, ctl->sc_enpub);
1758        return -1;
1759    }
1760}
1761
1762
1763int
1764lsquic_send_ctl_schedule_buffered (lsquic_send_ctl_t *ctl,
1765                                            enum buf_packet_type packet_type)
1766{
1767    struct buf_packet_q *const packet_q =
1768                                    &ctl->sc_buffered_packets[packet_type];
1769    lsquic_packet_out_t *packet_out;
1770    unsigned used, excess;
1771
1772    assert(lsquic_send_ctl_schedule_stream_packets_immediately(ctl));
1773    const enum lsquic_packno_bits bits = lsquic_send_ctl_calc_packno_bits(ctl);
1774    const unsigned need = packno_bits2len(bits);
1775
1776    while ((packet_out = TAILQ_FIRST(&packet_q->bpq_packets)) &&
1777                                            lsquic_send_ctl_can_send(ctl))
1778    {
1779        if (bits != lsquic_packet_out_packno_bits(packet_out))
1780        {
1781            used = packno_bits2len(lsquic_packet_out_packno_bits(packet_out));
1782            if (need > used
1783                && need - used > lsquic_packet_out_avail(packet_out))
1784            {
1785                excess = need - used - lsquic_packet_out_avail(packet_out);
1786                if (0 != split_buffered_packet(ctl, packet_type,
1787                                               packet_out, bits, excess))
1788                {
1789                    return -1;
1790                }
1791            }
1792        }
1793        TAILQ_REMOVE(&packet_q->bpq_packets, packet_out, po_next);
1794        --packet_q->bpq_count;
1795        LSQ_DEBUG("Remove packet from buffered queue #%u; count: %u",
1796                  packet_type, packet_q->bpq_count);
1797        packet_out->po_packno = send_ctl_next_packno(ctl);
1798        lsquic_send_ctl_scheduled_one(ctl, packet_out);
1799    }
1800
1801    return 0;
1802}
1803
1804
1805int
1806lsquic_send_ctl_turn_on_fin (struct lsquic_send_ctl *ctl,
1807                             const struct lsquic_stream *stream)
1808{
1809    enum buf_packet_type packet_type;
1810    struct buf_packet_q *packet_q;
1811    lsquic_packet_out_t *packet_out;
1812    const struct parse_funcs *pf;
1813
1814    pf = ctl->sc_conn_pub->lconn->cn_pf;
1815    packet_type = send_ctl_lookup_bpt(ctl, stream);
1816    packet_q = &ctl->sc_buffered_packets[packet_type];
1817
1818    TAILQ_FOREACH_REVERSE(packet_out, &packet_q->bpq_packets,
1819                          lsquic_packets_tailq, po_next)
1820        if (0 == lsquic_packet_out_turn_on_fin(packet_out, pf, stream))
1821            return 0;
1822
1823    TAILQ_FOREACH(packet_out, &ctl->sc_scheduled_packets, po_next)
1824        if (0 == packet_out->po_sent
1825            && 0 == lsquic_packet_out_turn_on_fin(packet_out, pf, stream))
1826        {
1827            return 0;
1828        }
1829
1830    return -1;
1831}
1832
1833
1834size_t
1835lsquic_send_ctl_mem_used (const struct lsquic_send_ctl *ctl)
1836{
1837    const lsquic_packet_out_t *packet_out;
1838    unsigned n;
1839    size_t size;
1840    const struct lsquic_packets_tailq queues[] = {
1841        ctl->sc_scheduled_packets,
1842        ctl->sc_unacked_packets,
1843        ctl->sc_lost_packets,
1844        ctl->sc_buffered_packets[0].bpq_packets,
1845        ctl->sc_buffered_packets[1].bpq_packets,
1846    };
1847
1848    size = sizeof(*ctl);
1849
1850    for (n = 0; n < sizeof(queues) / sizeof(queues[0]); ++n)
1851        TAILQ_FOREACH(packet_out, &queues[n], po_next)
1852            size += lsquic_packet_out_mem_used(packet_out);
1853
1854    return size;
1855}
1856