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QUIC: persistent congestion calculation.

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According to RFC 9002 (quic-recovery) 7.6.
This commit is contained in:
Vladimir Homutov 2021-06-09 15:11:43 +03:00
parent 64586eaa36
commit 0c77dc9c0b
3 changed files with 112 additions and 13 deletions
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1
src/event/quic/ngx_event_quic.c
View File

@ -271,6 +271,7 @@ ngx_quic_new_connection(ngx_connection_t *c, ngx_quic_conf_t *conf,
qc->avg_rtt = NGX_QUIC_INITIAL_RTT;
qc->rttvar = NGX_QUIC_INITIAL_RTT / 2;
qc->min_rtt = NGX_TIMER_INFINITE;
qc->first_rtt = NGX_TIMER_INFINITE;
/*
* qc->latest_rtt = 0

123
src/event/quic/ngx_event_quic_ack.c
View File

@ -18,19 +18,33 @@
#define NGX_QUIC_TIME_THR 1.125
#define NGX_QUIC_TIME_GRANULARITY 1 /* ms */
/* quic-recovery, section 7.6.1 Persistent congestion duration */
#define NGX_QUIC_PERSISTENT_CONGESTION_THR 3
#define ngx_quic_lost_threshold(qc) \
ngx_max(NGX_QUIC_TIME_THR * ngx_max((qc)->latest_rtt, (qc)->avg_rtt), \
NGX_QUIC_TIME_GRANULARITY)
/* send time of ACK'ed packets */
typedef struct {
ngx_msec_t max_pn;
ngx_msec_t oldest;
ngx_msec_t newest;
} ngx_quic_ack_stat_t;
static void ngx_quic_rtt_sample(ngx_connection_t *c, ngx_quic_ack_frame_t *ack,
enum ssl_encryption_level_t level, ngx_msec_t send_time);
static ngx_int_t ngx_quic_handle_ack_frame_range(ngx_connection_t *c,
ngx_quic_send_ctx_t *ctx, uint64_t min, uint64_t max,
ngx_msec_t *send_time);
ngx_quic_ack_stat_t *st);
static void ngx_quic_drop_ack_ranges(ngx_connection_t *c,
ngx_quic_send_ctx_t *ctx, uint64_t pn);
static ngx_int_t ngx_quic_detect_lost(ngx_connection_t *c);
static ngx_int_t ngx_quic_detect_lost(ngx_connection_t *c,
ngx_quic_ack_stat_t *st);
static ngx_msec_t ngx_quic_pcg_duration(ngx_connection_t *c);
static void ngx_quic_persistent_congestion(ngx_connection_t *c);
static void ngx_quic_congestion_lost(ngx_connection_t *c,
ngx_quic_frame_t *frame);
static void ngx_quic_lost_handler(ngx_event_t *ev);
@ -43,8 +57,8 @@ ngx_quic_handle_ack_frame(ngx_connection_t *c, ngx_quic_header_t *pkt,
ssize_t n;
u_char *pos, *end;
uint64_t min, max, gap, range;
ngx_msec_t send_time;
ngx_uint_t i;
ngx_quic_ack_stat_t send_time;
ngx_quic_send_ctx_t *ctx;
ngx_quic_ack_frame_t *ack;
ngx_quic_connection_t *qc;
@ -74,6 +88,9 @@ ngx_quic_handle_ack_frame(ngx_connection_t *c, ngx_quic_header_t *pkt,
min = ack->largest - ack->first_range;
max = ack->largest;
send_time.oldest = NGX_TIMER_INFINITE;
send_time.newest = NGX_TIMER_INFINITE;
if (ngx_quic_handle_ack_frame_range(c, ctx, min, max, &send_time)
!= NGX_OK)
{
@ -94,8 +111,8 @@ ngx_quic_handle_ack_frame(ngx_connection_t *c, ngx_quic_header_t *pkt,
* - at least one of the newly acknowledged packets was ack-eliciting.
*/
if (send_time != NGX_TIMER_INFINITE) {
ngx_quic_rtt_sample(c, ack, pkt->level, send_time);
if (send_time.max_pn != NGX_TIMER_INFINITE) {
ngx_quic_rtt_sample(c, ack, pkt->level, send_time.max_pn);
}
}
@ -141,7 +158,7 @@ ngx_quic_handle_ack_frame(ngx_connection_t *c, ngx_quic_header_t *pkt,
}
}
return ngx_quic_detect_lost(c);
return ngx_quic_detect_lost(c, &send_time);
}
@ -161,6 +178,7 @@ ngx_quic_rtt_sample(ngx_connection_t *c, ngx_quic_ack_frame_t *ack,
qc->min_rtt = latest_rtt;
qc->avg_rtt = latest_rtt;
qc->rttvar = latest_rtt / 2;
qc->first_rtt = ngx_current_msec;
} else {
qc->min_rtt = ngx_min(qc->min_rtt, latest_rtt);
@ -190,7 +208,7 @@ ngx_quic_rtt_sample(ngx_connection_t *c, ngx_quic_ack_frame_t *ack,
static ngx_int_t
ngx_quic_handle_ack_frame_range(ngx_connection_t *c, ngx_quic_send_ctx_t *ctx,
uint64_t min, uint64_t max, ngx_msec_t *send_time)
uint64_t min, uint64_t max, ngx_quic_ack_stat_t *st)
{
ngx_uint_t found;
ngx_queue_t *q;
@ -199,7 +217,7 @@ ngx_quic_handle_ack_frame_range(ngx_connection_t *c, ngx_quic_send_ctx_t *ctx,
qc = ngx_quic_get_connection(c);
*send_time = NGX_TIMER_INFINITE;
st->max_pn = NGX_TIMER_INFINITE;
found = 0;
q = ngx_queue_last(&ctx->sent);
@ -231,7 +249,16 @@ ngx_quic_handle_ack_frame_range(ngx_connection_t *c, ngx_quic_send_ctx_t *ctx,
}
if (f->pnum == max) {
*send_time = f->last;
st->max_pn = f->last;
}
/* save earliest and latest send times of frames ack'ed */
if (st->oldest == NGX_TIMER_INFINITE || f->last < st->oldest) {
st->oldest = f->last;
}
if (st->newest == NGX_TIMER_INFINITE || f->last > st->newest) {
st->newest = f->last;
}
ngx_queue_remove(&f->queue);
@ -377,10 +404,10 @@ ngx_quic_drop_ack_ranges(ngx_connection_t *c, ngx_quic_send_ctx_t *ctx,
static ngx_int_t
ngx_quic_detect_lost(ngx_connection_t *c)
ngx_quic_detect_lost(ngx_connection_t *c, ngx_quic_ack_stat_t *st)
{
ngx_uint_t i;
ngx_msec_t now, wait, thr;
ngx_uint_t i, nlost;
ngx_msec_t now, wait, thr, oldest, newest;
ngx_queue_t *q;
ngx_quic_frame_t *start;
ngx_quic_send_ctx_t *ctx;
@ -390,6 +417,12 @@ ngx_quic_detect_lost(ngx_connection_t *c)
now = ngx_current_msec;
thr = ngx_quic_lost_threshold(qc);
/* send time of lost packets across all send contexts */
oldest = NGX_TIMER_INFINITE;
newest = NGX_TIMER_INFINITE;
nlost = 0;
for (i = 0; i < NGX_QUIC_SEND_CTX_LAST; i++) {
ctx = &qc->send_ctx[i];
@ -419,16 +452,80 @@ ngx_quic_detect_lost(ngx_connection_t *c)
break;
}
if (start->last > qc->first_rtt) {
if (oldest == NGX_TIMER_INFINITE || start->last < oldest) {
oldest = start->last;
}
if (newest == NGX_TIMER_INFINITE || start->last > newest) {
newest = start->last;
}
nlost++;
}
ngx_quic_resend_frames(c, ctx);
}
}
/* Establishing Persistent Congestion (7.6.2) */
/*
* Once acknowledged, packets are no longer tracked. Thus no send time
* information is available for such packets. This limits persistent
* congestion algorithm to packets mentioned within ACK ranges of the
* latest ACK frame.
*/
if (st && nlost >= 2 && (st->newest < oldest || st->oldest > newest)) {
if (newest - oldest > ngx_quic_pcg_duration(c)) {
ngx_quic_persistent_congestion(c);
}
}
ngx_quic_set_lost_timer(c);
return NGX_OK;
}
static ngx_msec_t
ngx_quic_pcg_duration(ngx_connection_t *c)
{
ngx_msec_t duration;
ngx_quic_connection_t *qc;
qc = ngx_quic_get_connection(c);
duration = qc->avg_rtt;
duration += ngx_max(4 * qc->rttvar, NGX_QUIC_TIME_GRANULARITY);
duration += qc->ctp.max_ack_delay;
duration *= NGX_QUIC_PERSISTENT_CONGESTION_THR;
return duration;
}
static void
ngx_quic_persistent_congestion(ngx_connection_t *c)
{
ngx_quic_congestion_t *cg;
ngx_quic_connection_t *qc;
qc = ngx_quic_get_connection(c);
cg = &qc->congestion;
cg->recovery_start = ngx_current_msec;
cg->window = qc->tp.max_udp_payload_size * 2;
ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0,
"quic persistent congestion win:%uz", cg->window);
}
void
ngx_quic_resend_frames(ngx_connection_t *c, ngx_quic_send_ctx_t *ctx)
{
@ -687,7 +784,7 @@ void ngx_quic_lost_handler(ngx_event_t *ev)
c = ev->data;
if (ngx_quic_detect_lost(c) != NGX_OK) {
if (ngx_quic_detect_lost(c, NULL) != NGX_OK) {
ngx_quic_close_connection(c, NGX_ERROR);
}

1
src/event/quic/ngx_event_quic_connection.h
View File

@ -211,6 +211,7 @@ struct ngx_quic_connection_s {
ngx_event_t path_validation;
ngx_msec_t last_cc;
ngx_msec_t first_rtt;
ngx_msec_t latest_rtt;
ngx_msec_t avg_rtt;
ngx_msec_t min_rtt;