Mercurial > hg > nginx
changeset 8792:004172345bdc quic
QUIC: persistent congestion calculation.
According to RFC 9002 (quic-recovery) 7.6.
| author | Vladimir Homutov <vl@nginx.com> |
|---|---|
| date | Wed, 09 Jun 2021 15:11:43 +0300 |
| parents | af33d1ef1c3c |
| children | 80d396fd8ee8 |
| files | src/event/quic/ngx_event_quic.c src/event/quic/ngx_event_quic_ack.c src/event/quic/ngx_event_quic_connection.h |
| diffstat | 3 files changed, 112 insertions(+), 13 deletions(-) [+] |
line wrap: on
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--- a/src/event/quic/ngx_event_quic.c +++ b/src/event/quic/ngx_event_quic.c @@ -271,6 +271,7 @@ ngx_quic_new_connection(ngx_connection_t 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
--- a/src/event/quic/ngx_event_quic_ack.c +++ b/src/event/quic/ngx_event_quic_ack.c @@ -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 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 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 * - 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 } } - 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, 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, 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_conn 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_conn } 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_ 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 * 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); }