# HG changeset patch
# User Roman Arutyunyan <arut@nginx.com>
# Date 1690873324 -14400
# Tue Aug 01 11:02:04 2023 +0400
# Node ID cd0ef56b0f1afaa54d7d2756dad2182628445e04
# Parent 741deb8ff8257914312ab134f3a0b69256c661f4
QUIC: fixed probe-congestion deadlock.

When probe timeout expired while congestion window was exhausted, probe PINGs
could not be sent. As a result, lost packets could not be declared lost and
congestion window could not be freed for new packets. This deadlock
continued until connection idle timeout expiration.

Now PINGs are sent separately from the frame queue without congestion control.

diff --git a/src/event/quic/ngx_event_quic_ack.c b/src/event/quic/ngx_event_quic_ack.c
--- a/src/event/quic/ngx_event_quic_ack.c
+++ b/src/event/quic/ngx_event_quic_ack.c
@@ -820,9 +820,9 @@ ngx_quic_pto_handler(ngx_event_t *ev)
{
ngx_uint_t i;
ngx_msec_t now;
- ngx_queue_t *q, *next;
+ ngx_queue_t *q;
ngx_connection_t *c;
- ngx_quic_frame_t *f;
+ ngx_quic_frame_t *f, frame;
ngx_quic_send_ctx_t *ctx;
ngx_quic_connection_t *qc;

@@ -859,63 +859,23 @@ ngx_quic_pto_handler(ngx_event_t *ev)
"quic pto %s pto_count:%ui",
ngx_quic_level_name(ctx->level), qc->pto_count);

- for (q = ngx_queue_head(&ctx->frames);
- q != ngx_queue_sentinel(&ctx->frames);
- /* void */)
- {
- next = ngx_queue_next(q);
- f = ngx_queue_data(q, ngx_quic_frame_t, queue);
+ ngx_memzero(&frame, sizeof(ngx_quic_frame_t));

- if (f->type == NGX_QUIC_FT_PING) {
- ngx_queue_remove(q);
- ngx_quic_free_frame(c, f);
- }
-
- q = next;
- }
-
- for (q = ngx_queue_head(&ctx->sent);
- q != ngx_queue_sentinel(&ctx->sent);
- /* void */)
- {
- next = ngx_queue_next(q);
- f = ngx_queue_data(q, ngx_quic_frame_t, queue);
+ frame.level = ctx->level;
+ frame.type = NGX_QUIC_FT_PING;

- if (f->type == NGX_QUIC_FT_PING) {
- ngx_quic_congestion_lost(c, f);
- ngx_queue_remove(q);
- ngx_quic_free_frame(c, f);
- }
-
- q = next;
- }
-
- /* enforce 2 udp datagrams */
-
- f = ngx_quic_alloc_frame(c);
- if (f == NULL) {
- break;
+ if (ngx_quic_frame_sendto(c, &frame, 0, qc->path) != NGX_OK
+ || ngx_quic_frame_sendto(c, &frame, 0, qc->path) != NGX_OK)
+ {
+ ngx_quic_close_connection(c, NGX_ERROR);
+ return;
}
-
- f->level = ctx->level;
- f->type = NGX_QUIC_FT_PING;
- f->flush = 1;
-
- ngx_quic_queue_frame(qc, f);
-
- f = ngx_quic_alloc_frame(c);
- if (f == NULL) {
- break;
- }
-
- f->level = ctx->level;
- f->type = NGX_QUIC_FT_PING;
-
- ngx_quic_queue_frame(qc, f);
}

qc->pto_count++;

+ ngx_quic_set_lost_timer(c);
+
ngx_quic_connstate_dbg(c);
}

diff --git a/src/event/quic/ngx_event_quic_output.c b/src/event/quic/ngx_event_quic_output.c
--- a/src/event/quic/ngx_event_quic_output.c
+++ b/src/event/quic/ngx_event_quic_output.c
@@ -645,10 +645,6 @@ ngx_quic_output_packet(ngx_connection_t
f->plen = 0;

nframes++;
-
- if (f->flush) {
- break;
- }
}

if (nframes == 0) {
diff --git a/src/event/quic/ngx_event_quic_transport.h b/src/event/quic/ngx_event_quic_transport.h
--- a/src/event/quic/ngx_event_quic_transport.h
+++ b/src/event/quic/ngx_event_quic_transport.h
@@ -271,7 +271,6 @@ struct ngx_quic_frame_s {
ssize_t len;
unsigned need_ack:1;
unsigned pkt_need_ack:1;
- unsigned flush:1;

ngx_chain_t *data;
union {
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