[PATCH 1 of 2] HTTP/3: eliminated v3_session field from ngx_http_connection_t

[Roman Arutyunyan]

# HG changeset patch
# User Roman Arutyunyan <arut at nginx.com>
# Date 1694088991 -14400
#      Thu Sep 07 16:16:31 2023 +0400
# Node ID 4e312ff4b6ba742a270864b9c6ad7d0484355a7b
# Parent  daf8f5ba23d8e9955b22782d945f9c065f4b6baa
HTTP/3: eliminated v3_session field from ngx_http_connection_t.

The field was under NGX_HTTP_V3 macro, which was a source of binary
compatibility problems when nginx/module is build with/without HTTP/3 support.

Now ngx_http_connection_t is copied to the first field of ngx_http_v3_session_t,
which is assigned to c->data.  A better solution would be to reference it
instead of copying, similar to the way ngx_http_v2_connection_t and
ngx_http_request_t do.  However, TLS handshake callbacks such as
ngx_http_ssl_servername() and ngx_http_ssl_alpn_select() expect c->data to
reference ngx_http_connection_t.

diff --git a/src/http/ngx_http_request.h b/src/http/ngx_http_request.h
--- a/src/http/ngx_http_request.h
+++ b/src/http/ngx_http_request.h
@@ -324,10 +324,6 @@ typedef struct {
 #endif
 #endif
 
-#if (NGX_HTTP_V3 || NGX_COMPAT)
-    ngx_http_v3_session_t            *v3_session;
-#endif
-
     ngx_chain_t                      *busy;
     ngx_int_t                         nbusy;
 
diff --git a/src/http/v3/ngx_http_v3.c b/src/http/v3/ngx_http_v3.c
--- a/src/http/v3/ngx_http_v3.c
+++ b/src/http/v3/ngx_http_v3.c
@@ -30,6 +30,8 @@ ngx_http_v3_init_session(ngx_connection_
         goto failed;
     }
 
+    h3c->http_connection = *hc;
+
     ngx_queue_init(&h3c->blocked);
 
     h3c->keepalive.log = c->log;
@@ -48,7 +50,7 @@ ngx_http_v3_init_session(ngx_connection_
     cln->handler = ngx_http_v3_cleanup_session;
     cln->data = h3c;
 
-    hc->v3_session = h3c;
+    c->data = h3c;
 
     return NGX_OK;
 
diff --git a/src/http/v3/ngx_http_v3.h b/src/http/v3/ngx_http_v3.h
--- a/src/http/v3/ngx_http_v3.h
+++ b/src/http/v3/ngx_http_v3.h
@@ -82,7 +82,8 @@
     ((ngx_http_connection_t *) ((c)->quic ? (c)->quic->parent->data           \
                                           : (c)->data))
 
-#define ngx_http_v3_get_session(c)  ngx_http_quic_get_connection(c)->v3_session
+#define ngx_http_v3_get_session(c)                                            \
+    ((ngx_http_v3_session_t *) ngx_http_quic_get_connection(c))
 
 #define ngx_http_v3_get_module_loc_conf(c, module)                            \
     ngx_http_get_module_loc_conf(ngx_http_quic_get_connection(c)->conf_ctx,   \
@@ -120,6 +121,8 @@ struct ngx_http_v3_parse_s {
 
 
 struct ngx_http_v3_session_s {
+    ngx_http_connection_t         http_connection;
+
     ngx_http_v3_dynamic_table_t   table;
 
     ngx_event_t                   keepalive;
diff --git a/src/http/v3/ngx_http_v3_request.c b/src/http/v3/ngx_http_v3_request.c
--- a/src/http/v3/ngx_http_v3_request.c
+++ b/src/http/v3/ngx_http_v3_request.c
@@ -78,7 +78,7 @@ ngx_http_v3_init_stream(ngx_connection_t
             return;
         }
 
-        h3c = hc->v3_session;
+        h3c = ngx_http_v3_get_session(c);
         ngx_add_timer(&h3c->keepalive, cscf->client_header_timeout);
 
         h3scf->quic.timeout = clcf->keepalive_timeout;