[core] server.feature-flags to enable h2

server.feature-flags = ("server.h2proto" => "enable") to enable h2

src/base.h

@@ -90,6 +90,7 @@ typedef struct {
 	unsigned char http_host_normalize;
 	unsigned char http_method_get_body;
 	unsigned char high_precision_timestamps;
+	unsigned char h2proto;
 	unsigned short http_url_normalize;
 
 	unsigned short max_worker;

src/configfile.c

@@ -784,6 +784,10 @@ static int config_insert_srvconf(server *srv) {
                 break;
               case 33:/* server.feature-flags */
                 srv->srvconf.feature_flags = cpv->v.a;
+                srv->srvconf.h2proto =
+                  config_plugin_value_tobool(
+                    array_get_element_klen(cpv->v.a,
+                                           CONST_STR_LEN("server.h2proto")), 0);
                 break;
               default:/* should not happen */
                 break;
@@ -1033,6 +1037,7 @@ static int config_insert(server *srv) {
       | (srv->srvconf.http_method_get_body ?  HTTP_PARSEOPT_METHOD_GET_BODY :0);
     p->defaults.http_parseopts |= srv->srvconf.http_url_normalize;
     p->defaults.mimetypes = &srv->srvconf.empty_array; /*(must not be NULL)*/
+    p->defaults.h2proto = srv->srvconf.h2proto;
 
     /* initialize p->defaults from global config context */
     if (p->nconfig > 0 && p->cvlist->v.u2[1]) {

src/request.h

@@ -41,6 +41,8 @@ typedef struct {
     unsigned char range_requests;
     unsigned char error_intercept;
 
+    unsigned char h2proto; /*(global setting copied for convenient access)*/
+
     /* debug */
     unsigned char log_file_not_found;
     unsigned char log_request_header;

src/response.c

@@ -305,8 +305,8 @@ static handler_t http_response_config (request_st * const r) {
     config_cond_cache_reset(r);
     config_patch_config(r);
 
-    /* do we have to downgrade to 1.0 ? */
-    if (!r->conf.allow_http11)
+    /* do we have to downgrade from 1.1 to 1.0 ? (ignore for HTTP/2) */
+    if (!r->conf.allow_http11 && r->http_version == HTTP_VERSION_1_1)
         r->http_version = HTTP_VERSION_1_0;
 
     /* r->conf.max_request_size is in kBytes */