QUIC: optimized immediate close. Previously, before sending CONNECTION_CLOSE to client, all pending frames were sent. This is redundant and could prevent CONNECTION_CLOSE from being sent due to congestion control. Now pending frames are freed and CONNECTION_CLOSE is sent without congestion control, as advised by RFC 9002: Packets containing frames besides ACK or CONNECTION_CLOSE frames count toward congestion control limits and are considered to be in flight.

--- a/src/event/quic/ngx_event_quic.c
+++ b/src/event/quic/ngx_event_quic.c
@@ -482,6 +482,7 @@ ngx_quic_close_connection(ngx_connection
 
         /* drop packets from retransmit queues, no ack is expected */
         for (i = 0; i < NGX_QUIC_SEND_CTX_LAST; i++) {
+            ngx_quic_free_frames(c, &qc->send_ctx[i].frames);
             ngx_quic_free_frames(c, &qc->send_ctx[i].sent);
         }