HTTP/2: the "421 Misdirected Request" response (closes #848). Since 4fbef397c753 nginx rejects with the 400 error any attempts of requesting different host over the same connection, if the relevant virtual server requires verification of a client certificate. While requesting hosts other than negotiated isn't something legal in HTTP/1.x, the HTTP/2 specification explicitly permits such requests for connection reuse and has introduced a special response code 421. According to RFC 7540 Section 9.1.2 this code can be sent by a server that is not configured to produce responses for the combination of scheme and authority that are included in the request URI. And the client may retry the request over a different connection. Now this code is used for requests that aren't authorized in current connection. After receiving the 421 response a client will be able to open a new connection, provide the required certificate and retry the request. Unfortunately, not all clients currently are able to handle it well. Notably Chrome just shows an error, while at least the latest version of Firefox retries the request over a new connection.

/*
 * Copyright (C) Nginx, Inc.
 * Copyright (C) Valentin V. Bartenev
 */


#ifndef _NGX_HTTP_V2_MODULE_H_INCLUDED_
#define _NGX_HTTP_V2_MODULE_H_INCLUDED_


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>


typedef struct {
    size_t                          recv_buffer_size;
    u_char                         *recv_buffer;
} ngx_http_v2_main_conf_t;


typedef struct {
    size_t                          pool_size;
    ngx_uint_t                      concurrent_streams;
    size_t                          max_field_size;
    size_t                          max_header_size;
    ngx_uint_t                      streams_index_mask;
    ngx_msec_t                      recv_timeout;
    ngx_msec_t                      idle_timeout;
} ngx_http_v2_srv_conf_t;


typedef struct {
    size_t                          chunk_size;
} ngx_http_v2_loc_conf_t;


extern ngx_module_t  ngx_http_v2_module;


#endif /* _NGX_HTTP_V2_MODULE_H_INCLUDED_ */