[PATCH] QUIC: use client dcid rather than odcid to receive packets

[Roman Arutyunyan]

# HG changeset patch
# User Roman Arutyunyan <arut at nginx.com>
# Date 1693292146 -14400
#      Tue Aug 29 10:55:46 2023 +0400
# Node ID 7f451ca6f449958011e29aee5231e70be4992374
# Parent  58afcd72446ff33811e773f1cabb7866a92a09a0
QUIC: use client dcid rather than odcid to receive packets.

Previously, odcid was used to receive initial client packets in case server
initial response was lost.  However, dcid should be used instead.  These two
are the same unless retry is used.  In case of retry, client resends initial
packets with the retry dcid.  If server response is lost, the client resends
this packet again with the same retry dcid, but not odcid.  This is shown in
RFC 9000, 7.3. Authenticating Connection IDs, Figure 8.

The issue manifested itself with creating multiple server sessions in response
to each post-retry client initial packet, if server response is lost.

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
@@ -1100,7 +1100,7 @@ ngx_quic_discard_ctx(ngx_connection_t *c
     }
 
     if (level == ssl_encryption_initial) {
-        /* close temporary listener with odcid */
+        /* close temporary listener with initial dcid */
         qsock = ngx_quic_find_socket(c, NGX_QUIC_UNSET_PN);
         if (qsock) {
             ngx_quic_close_socket(c, qsock);
diff --git a/src/event/quic/ngx_event_quic_socket.c b/src/event/quic/ngx_event_quic_socket.c
--- a/src/event/quic/ngx_event_quic_socket.c
+++ b/src/event/quic/ngx_event_quic_socket.c
@@ -93,8 +93,8 @@ ngx_quic_open_sockets(ngx_connection_t *
 
     tmp->sid.seqnum = NGX_QUIC_UNSET_PN; /* temporary socket */
 
-    ngx_memcpy(tmp->sid.id, pkt->odcid.data, pkt->odcid.len);
-    tmp->sid.len = pkt->odcid.len;
+    ngx_memcpy(tmp->sid.id, pkt->dcid.data, pkt->dcid.len);
+    tmp->sid.len = pkt->dcid.len;
 
     if (ngx_quic_listen(c, qc, tmp) != NGX_OK) {
         goto failed;