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QUIC: reworked retransmission mechanism.

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Instead of timer-based retransmissions with constant packet lifetime,
this patch implements ack-based loss detection and probe timeout
for the cases, when no ack is received, according to the quic-recovery
draft 29.
This commit is contained in:
Vladimir Homutov 2020-07-13 17:31:29 +03:00
parent 230882ba50
commit 782a634e38
2 changed files with 77 additions and 65 deletions
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136
src/event/ngx_event_quic.c
View File

@ -247,8 +247,7 @@ static ngx_int_t ngx_quic_send_frames(ngx_connection_t *c,
static void ngx_quic_set_packet_number(ngx_quic_header_t *pkt,
ngx_quic_send_ctx_t *ctx);
static void ngx_quic_pto_handler(ngx_event_t *ev);
static ngx_int_t ngx_quic_detect_lost(ngx_connection_t *c,
ngx_quic_send_ctx_t *ctx, ngx_msec_t *waitp);
static ngx_int_t ngx_quic_detect_lost(ngx_connection_t *c, ngx_uint_t ack);
static void ngx_quic_push_handler(ngx_event_t *ev);
static void ngx_quic_rbtree_insert_stream(ngx_rbtree_node_t *temp,
@ -2341,7 +2340,7 @@ ngx_quic_handle_ack_frame(ngx_connection_t *c, ngx_quic_header_t *pkt,
}
}
return NGX_OK;
return ngx_quic_detect_lost(c, 1);
}
@ -3535,34 +3534,15 @@ ngx_quic_set_packet_number(ngx_quic_header_t *pkt, ngx_quic_send_ctx_t *ctx)
static void
ngx_quic_pto_handler(ngx_event_t *ev)
{
ngx_uint_t i;
ngx_msec_t wait, nswait;
ngx_connection_t *c;
ngx_quic_connection_t *qc;
ngx_connection_t *c;
ngx_log_debug0(NGX_LOG_DEBUG_EVENT, ev->log, 0, "quic pto timer");
c = ev->data;
qc = c->quic;
wait = 0;
for (i = 0; i < NGX_QUIC_SEND_CTX_LAST; i++) {
if (ngx_quic_detect_lost(c, &qc->send_ctx[i], &nswait) != NGX_OK) {
ngx_quic_close_connection(c, NGX_ERROR);
return;
}
if (i == 0) {
wait = nswait;
} else if (nswait > 0 && (wait == 0 || wait > nswait)) {
wait = nswait;
}
}
if (wait > 0) {
ngx_add_timer(&qc->pto, wait);
if (ngx_quic_detect_lost(c, 0) != NGX_OK) {
ngx_quic_close_connection(c, NGX_ERROR);
return;
}
}
@ -3584,70 +3564,96 @@ ngx_quic_push_handler(ngx_event_t *ev)
static ngx_int_t
ngx_quic_detect_lost(ngx_connection_t *c, ngx_quic_send_ctx_t *ctx,
ngx_msec_t *waitp)
ngx_quic_detect_lost(ngx_connection_t *c, ngx_uint_t ack)
{
uint64_t pn;
ngx_msec_t now, wait;
ngx_uint_t i;
ngx_msec_t now, wait, min_wait, thr;
ngx_queue_t *q, range;
ngx_quic_frame_t *f, *start;
ngx_quic_send_ctx_t *ctx;
ngx_quic_connection_t *qc;
qc = c->quic;
now = ngx_current_msec;
if (ngx_queue_empty(&ctx->sent)) {
*waitp = 0;
return NGX_OK;
min_wait = 0;
if (ack) {
thr = NGX_QUIC_TIME_THR * ngx_max(qc->latest_rtt, qc->avg_rtt);
thr = ngx_max(thr, NGX_QUIC_TIME_GRANULARITY);
} else {
thr = NGX_QUIC_HARDCODED_PTO;
}
q = ngx_queue_head(&ctx->sent);
for (i = 0; i < NGX_QUIC_SEND_CTX_LAST; i++) {
do {
start = ngx_queue_data(q, ngx_quic_frame_t, queue);
ctx = &qc->send_ctx[i];
wait = start->last + qc->ctp.max_ack_delay
+ NGX_QUIC_HARDCODED_PTO - now;
if ((ngx_msec_int_t) wait > 0) {
break;
if (ngx_queue_empty(&ctx->sent)) {
continue;
}
pn = start->pnum;
q = ngx_queue_head(&ctx->sent);
ngx_queue_init(&range);
/* send frames with same packet number to the wire */
do {
f = ngx_queue_data(q, ngx_quic_frame_t, queue);
start = ngx_queue_data(q, ngx_quic_frame_t, queue);
if (now - start->first > qc->tp.max_idle_timeout) {
ngx_log_error(NGX_LOG_ERR, c->log, 0,
"quic retransmission timeout");
return NGX_DECLINED;
wait = start->last + thr - now;
if ((ngx_msec_int_t) wait >= 0) {
if (min_wait == 0 || wait < min_wait) {
min_wait = wait;
}
if (!ack) {
break;
}
if ((start->pnum > ctx->largest_ack)
|| ((ctx->largest_ack - start->pnum) < NGX_QUIC_PKT_THR))
{
break;
}
}
if (f->pnum != pn) {
break;
pn = start->pnum;
ngx_queue_init(&range);
/* send frames with same packet number to the wire */
do {
f = ngx_queue_data(q, ngx_quic_frame_t, queue);
if (f->pnum != pn) {
break;
}
q = ngx_queue_next(q);
ngx_queue_remove(&f->queue);
ngx_queue_insert_tail(&range, &f->queue);
} while (q != ngx_queue_sentinel(&ctx->sent));
ngx_quic_congestion_lost(c, start->last);
if (ngx_quic_send_frames(c, ctx, &range) != NGX_OK) {
return NGX_ERROR;
}
q = ngx_queue_next(q);
ngx_queue_remove(&f->queue);
ngx_queue_insert_tail(&range, &f->queue);
} while (q != ngx_queue_sentinel(&ctx->sent));
}
ngx_quic_congestion_lost(c, start->last);
if (qc->pto.timer_set) {
ngx_del_timer(&qc->pto);
}
if (ngx_quic_send_frames(c, ctx, &range) != NGX_OK) {
return NGX_ERROR;
}
} while (q != ngx_queue_sentinel(&ctx->sent));
*waitp = wait;
if (min_wait > 0) {
ngx_add_timer(&qc->pto, min_wait);
}
return NGX_OK;
}

6
src/event/ngx_event_quic.h
View File

@ -45,6 +45,12 @@
#define NGX_QUIC_INITIAL_RTT 333 /* ms */
#define NGX_QUIC_HARDCODED_PTO 1000 /* 1s, TODO: collect */
/* quic-recovery, section 6.1.1, Packet Threshold */
#define NGX_QUIC_PKT_THR 3 /* packets */
/* quic-recovery, section 6.1.2, Time Threshold */
#define NGX_QUIC_TIME_THR 1.125
#define NGX_QUIC_TIME_GRANULARITY 1 /* ms */
#define NGX_QUIC_CC_MIN_INTERVAL 1000 /* 1s */
#define NGX_QUIC_MIN_INITIAL_SIZE 1200