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changeset 9143:48691bab4474

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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).
author Roman Arutyunyan <arut@nginx.com>
date Mon, 14 Aug 2023 08:28:30 +0400
parents 7e8ee4b7cbf4
children bba136612fe4
files src/event/quic/ngx_event_quic_ack.c src/event/quic/ngx_event_quic_output.c src/event/quic/ngx_event_quic_transport.h
diffstat 3 files changed, 12 insertions(+), 57 deletions(-) [+]
line wrap: on
line diff
--- 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);
 }
 
--- a/src/event/quic/ngx_event_quic_output.c
+++ b/src/event/quic/ngx_event_quic_output.c
@@ -631,10 +631,6 @@ ngx_quic_output_packet(ngx_connection_t 
         f->plen = 0;
 
         nframes++;
-
-        if (f->flush) {
-            break;
-        }
     }
 
     if (nframes == 0) {
--- 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 {