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QUIC: optimized acknowledgement generation.

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For application level packets, only every second packet is now acknowledged,
respecting max ack delay.

13.2.1 Sending ACK Frames

   In order to assist loss detection at the sender, an endpoint SHOULD
   generate and send an ACK frame without delay when it receives an ack-
   eliciting packet either:

   *  when the received packet has a packet number less than another
      ack-eliciting packet that has been received, or

   *  when the packet has a packet number larger than the highest-
      numbered ack-eliciting packet that has been received and there are
      missing packets between that packet and this packet.


13.2.2.  Acknowledgement Frequency

    A receiver SHOULD send an ACK frame after receiving at least two
    ack-eliciting packets.
This commit is contained in:
Vladimir Homutov 2020-10-23 17:08:50 +03:00
parent b92e596918
commit 83d7a949e8
2 changed files with 55 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

89
src/event/ngx_event_quic.c
View File

@ -48,6 +48,8 @@
#define NGX_QUIC_MIN_SR_PACKET 43 /* 5 random + 16 srt + 22 padding */
#define NGX_QUIC_MAX_SR_PACKET 1200
#define NGX_QUIC_MAX_ACK_GAP 2
#define ngx_quic_level_name(lvl) \
(lvl == ssl_encryption_application) ? "application" \
: (lvl == ssl_encryption_initial) ? "initial" \
@ -107,10 +109,11 @@ typedef struct {
uint64_t pending_ack; /* non sent ack-eliciting */
uint64_t largest_range;
uint64_t first_range;
ngx_msec_t largest_received;
ngx_msec_t ack_delay_start;
ngx_uint_t nranges;
ngx_quic_ack_range_t ranges[NGX_QUIC_MAX_RANGES];
struct timeval ack_received;
ngx_uint_t send_ack; /* unsigned send_ack:1 */
ngx_uint_t send_ack;
} ngx_quic_send_ctx_t;
@ -250,8 +253,6 @@ 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_send_ack(ngx_connection_t *c,
ngx_quic_send_ctx_t *ctx);
static ngx_int_t ngx_quic_ack_delay(ngx_connection_t *c,
struct timeval *received, enum ssl_encryption_level_t level);
static ngx_int_t ngx_quic_send_cc(ngx_connection_t *c);
static ngx_int_t ngx_quic_send_new_token(ngx_connection_t *c);
@ -1911,11 +1912,7 @@ ngx_quic_process_packet(ngx_connection_t *c, ngx_quic_conf_t *conf,
qc->validated = 1;
}
if (pkt->level == ssl_encryption_early_data
|| pkt->level == ssl_encryption_application)
{
ngx_gettimeofday(&pkt->received);
}
pkt->received = ngx_current_msec;
c->log->action = "handling payload";
@ -2320,7 +2317,11 @@ ngx_quic_ack_packet(ngx_connection_t *c, ngx_quic_header_t *pkt)
ngx_post_event(&c->quic->push, &ngx_posted_events);
ctx->send_ack = 1;
if (ctx->send_ack == 0) {
ctx->ack_delay_start = ngx_current_msec;
}
ctx->send_ack++;
if (ctx->pending_ack == NGX_QUIC_UNSET_PN
|| ctx->pending_ack < pkt->pn)
@ -2334,7 +2335,7 @@ ngx_quic_ack_packet(ngx_connection_t *c, ngx_quic_header_t *pkt)
if (base == NGX_QUIC_UNSET_PN) {
ctx->largest_range = pn;
ctx->ack_received = pkt->received;
ctx->largest_received = pkt->received;
return NGX_OK;
}
@ -2350,7 +2351,7 @@ ngx_quic_ack_packet(ngx_connection_t *c, ngx_quic_header_t *pkt)
if (pn - base == 1) {
ctx->first_range++;
ctx->largest_range = pn;
ctx->ack_received = pkt->received;
ctx->largest_received = pkt->received;
return NGX_OK;
@ -2376,7 +2377,12 @@ ngx_quic_ack_packet(ngx_connection_t *c, ngx_quic_header_t *pkt)
ctx->first_range = 0;
ctx->largest_range = pn;
ctx->ack_received = pkt->received;
ctx->largest_received = pkt->received;
/* packet is out of order, force send */
if (pkt->need_ack) {
ctx->send_ack = NGX_QUIC_MAX_ACK_GAP;
}
i = 0;
@ -2386,6 +2392,11 @@ ngx_quic_ack_packet(ngx_connection_t *c, ngx_quic_header_t *pkt)
/* pn < base, perform lookup in existing ranges */
/* packet is out of order */
if (pkt->need_ack) {
ctx->send_ack = NGX_QUIC_MAX_ACK_GAP;
}
if (pn >= smallest && pn <= largest) {
return NGX_OK;
}
@ -2604,8 +2615,18 @@ static ngx_int_t
ngx_quic_send_ack(ngx_connection_t *c, ngx_quic_send_ctx_t *ctx)
{
size_t ranges_len;
uint64_t ack_delay;
ngx_quic_frame_t *frame;
if (ctx->level == ssl_encryption_application) {
ack_delay = ngx_current_msec - ctx->largest_received;
ack_delay *= 1000;
ack_delay >>= c->quic->ctp.ack_delay_exponent;
} else {
ack_delay = 0;
}
ranges_len = sizeof(ngx_quic_ack_range_t) * ctx->nranges;
frame = ngx_quic_alloc_frame(c, ranges_len);
@ -2618,7 +2639,7 @@ ngx_quic_send_ack(ngx_connection_t *c, ngx_quic_send_ctx_t *ctx)
frame->level = ctx->level;
frame->type = NGX_QUIC_FT_ACK;
frame->u.ack.largest = ctx->largest_range;
frame->u.ack.delay = ngx_quic_ack_delay(c, &ctx->ack_received, ctx->level);
frame->u.ack.delay = ack_delay;
frame->u.ack.range_count = ctx->nranges;
frame->u.ack.first_range = ctx->first_range;
frame->u.ack.ranges_start = frame->data;
@ -2633,27 +2654,6 @@ ngx_quic_send_ack(ngx_connection_t *c, ngx_quic_send_ctx_t *ctx)
}
static ngx_int_t
ngx_quic_ack_delay(ngx_connection_t *c, struct timeval *received,
enum ssl_encryption_level_t level)
{
ngx_int_t ack_delay;
struct timeval tv;
ack_delay = 0;
if (level == ssl_encryption_application) {
ngx_gettimeofday(&tv);
ack_delay = (tv.tv_sec - received->tv_sec) * 1000000
+ tv.tv_usec - received->tv_usec;
ack_delay = ngx_max(ack_delay, 0);
ack_delay >>= c->quic->ctp.ack_delay_exponent;
}
return ack_delay;
}
static ngx_int_t
ngx_quic_send_cc(ngx_connection_t *c)
{
@ -4054,6 +4054,7 @@ static ngx_int_t
ngx_quic_output(ngx_connection_t *c)
{
ngx_uint_t i;
ngx_msec_t delay;
ngx_quic_send_ctx_t *ctx;
ngx_quic_connection_t *qc;
@ -4066,12 +4067,30 @@ ngx_quic_output(ngx_connection_t *c)
ctx = &qc->send_ctx[i];
if (ctx->send_ack) {
if (ctx->level == ssl_encryption_application) {
delay = ngx_current_msec - ctx->ack_delay_start;
if (ctx->send_ack < NGX_QUIC_MAX_ACK_GAP
&& delay < qc->tp.max_ack_delay)
{
if (!qc->push.timer_set && !qc->closing) {
ngx_add_timer(&qc->push, qc->tp.max_ack_delay - delay);
}
goto output;
}
}
if (ngx_quic_send_ack(c, ctx) != NGX_OK) {
return NGX_ERROR;
}
ctx->send_ack = 0;
}
output:
if (ngx_quic_output_frames(c, ctx) != NGX_OK) {
return NGX_ERROR;
}

2
src/event/ngx_event_quic_transport.h
View File

@ -293,7 +293,7 @@ typedef struct {
struct ngx_quic_secret_s *secret;
struct ngx_quic_secret_s *next;
struct timeval received;
ngx_msec_t received;
uint64_t number;
uint8_t num_len;
uint32_t trunc;