# HG changeset patch
# User Roman Arutyunyan <arut@nginx.com>
# Date 1691987310 -14400
# Node ID 48691bab447419174229ebb7d2d9cac4ddc573ce
# Parent  7e8ee4b7cbf4e053c4125f6334c02becf7766632
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,
as specified by RFC 9002, Section 7:

  An endpoint MUST NOT send a packet if it would cause bytes_in_flight
  (see Appendix B.2) to be larger than the congestion window, unless the
  packet is sent on a PTO timer expiration (see Section 6.2) or when entering
  recovery (see Section 7.3.2).

diff -r 7e8ee4b7cbf4 -r 48691bab4474 src/event/quic/ngx_event_quic_ack.c
--- a/src/event/quic/ngx_event_quic_ack.c	Tue Aug 01 11:21:59 2023 +0400
+++ b/src/event/quic/ngx_event_quic_ack.c	Mon Aug 14 08:28:30 2023 +0400
@@ -820,9 +820,9 @@
 {
     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 @@
                        "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 -r 7e8ee4b7cbf4 -r 48691bab4474 src/event/quic/ngx_event_quic_output.c
--- a/src/event/quic/ngx_event_quic_output.c	Tue Aug 01 11:21:59 2023 +0400
+++ b/src/event/quic/ngx_event_quic_output.c	Mon Aug 14 08:28:30 2023 +0400
@@ -631,10 +631,6 @@
         f->plen = 0;
 
         nframes++;
-
-        if (f->flush) {
-            break;
-        }
     }
 
     if (nframes == 0) {
diff -r 7e8ee4b7cbf4 -r 48691bab4474 src/event/quic/ngx_event_quic_transport.h
--- a/src/event/quic/ngx_event_quic_transport.h	Tue Aug 01 11:21:59 2023 +0400
+++ b/src/event/quic/ngx_event_quic_transport.h	Mon Aug 14 08:28:30 2023 +0400
@@ -271,7 +271,6 @@
     ssize_t                                     len;
     unsigned                                    need_ack:1;
     unsigned                                    pkt_need_ack:1;
-    unsigned                                    flush:1;
 
     ngx_chain_t                                *data;
     union {