[PATCH 1 of 8] QUIC: treat qc->error == -1 as a missing error

[Roman Arutyunyan]

# HG changeset patch
# User Roman Arutyunyan <arut at nginx.com>
# Date 1655889315 -14400
#      Wed Jun 22 13:15:15 2022 +0400
# Branch quic
# Node ID 951d7116f37dc39d9eba20ceae49434592ce4677
# Parent  5b1011b5702b5c5db2ba3d392a4da25596183cc2
QUIC: treat qc->error == -1 as a missing error.

Previously, zero was used for this purpose.  However, NGX_QUIC_ERR_NO_ERROR is
zero too.  As a result, NGX_QUIC_ERR_NO_ERROR was changed to
NGX_QUIC_ERR_INTERNAL_ERROR when closing a QUIC connection.

diff --git a/src/event/quic/ngx_event_quic.c b/src/event/quic/ngx_event_quic.c
--- a/src/event/quic/ngx_event_quic.c
+++ b/src/event/quic/ngx_event_quic.c
@@ -317,6 +317,8 @@ ngx_quic_new_connection(ngx_connection_t
     qc->congestion.ssthresh = (size_t) -1;
     qc->congestion.recovery_start = ngx_current_msec;
 
+    qc->error = (ngx_uint_t) -1;
+
     if (pkt->validated && pkt->retried) {
         qc->tp.retry_scid.len = pkt->dcid.len;
         qc->tp.retry_scid.data = ngx_pstrdup(c->pool, &pkt->dcid);
@@ -523,7 +525,7 @@ ngx_quic_close_connection(ngx_connection
                 qc->error = NGX_QUIC_ERR_NO_ERROR;
 
             } else {
-                if (qc->error == 0 && !qc->error_app) {
+                if (qc->error == (ngx_uint_t) -1 && !qc->error_app) {
                     qc->error = NGX_QUIC_ERR_INTERNAL_ERROR;
                 }