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view src/http/ngx_http_special_response.c @ 6749:f88a145b093e stable-1.10

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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.
author Valentin Bartenev <vbart@nginx.com>
date Fri, 20 May 2016 18:41:17 +0300
parents 155871d773cc
children 6136a51f9c21
line wrap: on
line source


/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


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


static ngx_int_t ngx_http_send_error_page(ngx_http_request_t *r,
    ngx_http_err_page_t *err_page);
static ngx_int_t ngx_http_send_special_response(ngx_http_request_t *r,
    ngx_http_core_loc_conf_t *clcf, ngx_uint_t err);
static ngx_int_t ngx_http_send_refresh(ngx_http_request_t *r);


static u_char ngx_http_error_full_tail[] =
"<hr><center>" NGINX_VER "</center>" CRLF
"</body>" CRLF
"</html>" CRLF
;


static u_char ngx_http_error_tail[] =
"<hr><center>nginx</center>" CRLF
"</body>" CRLF
"</html>" CRLF
;


static u_char ngx_http_msie_padding[] =
"<!-- a padding to disable MSIE and Chrome friendly error page -->" CRLF
"<!-- a padding to disable MSIE and Chrome friendly error page -->" CRLF
"<!-- a padding to disable MSIE and Chrome friendly error page -->" CRLF
"<!-- a padding to disable MSIE and Chrome friendly error page -->" CRLF
"<!-- a padding to disable MSIE and Chrome friendly error page -->" CRLF
"<!-- a padding to disable MSIE and Chrome friendly error page -->" CRLF
;


static u_char ngx_http_msie_refresh_head[] =
"<html><head><meta http-equiv=\"Refresh\" content=\"0; URL=";


static u_char ngx_http_msie_refresh_tail[] =
"\"></head><body></body></html>" CRLF;


static char ngx_http_error_301_page[] =
"<html>" CRLF
"<head><title>301 Moved Permanently</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>301 Moved Permanently</h1></center>" CRLF
;


static char ngx_http_error_302_page[] =
"<html>" CRLF
"<head><title>302 Found</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>302 Found</h1></center>" CRLF
;


static char ngx_http_error_303_page[] =
"<html>" CRLF
"<head><title>303 See Other</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>303 See Other</h1></center>" CRLF
;


static char ngx_http_error_307_page[] =
"<html>" CRLF
"<head><title>307 Temporary Redirect</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>307 Temporary Redirect</h1></center>" CRLF
;


static char ngx_http_error_400_page[] =
"<html>" CRLF
"<head><title>400 Bad Request</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>400 Bad Request</h1></center>" CRLF
;


static char ngx_http_error_401_page[] =
"<html>" CRLF
"<head><title>401 Authorization Required</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>401 Authorization Required</h1></center>" CRLF
;


static char ngx_http_error_402_page[] =
"<html>" CRLF
"<head><title>402 Payment Required</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>402 Payment Required</h1></center>" CRLF
;


static char ngx_http_error_403_page[] =
"<html>" CRLF
"<head><title>403 Forbidden</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>403 Forbidden</h1></center>" CRLF
;


static char ngx_http_error_404_page[] =
"<html>" CRLF
"<head><title>404 Not Found</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>404 Not Found</h1></center>" CRLF
;


static char ngx_http_error_405_page[] =
"<html>" CRLF
"<head><title>405 Not Allowed</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>405 Not Allowed</h1></center>" CRLF
;


static char ngx_http_error_406_page[] =
"<html>" CRLF
"<head><title>406 Not Acceptable</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>406 Not Acceptable</h1></center>" CRLF
;


static char ngx_http_error_408_page[] =
"<html>" CRLF
"<head><title>408 Request Time-out</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>408 Request Time-out</h1></center>" CRLF
;


static char ngx_http_error_409_page[] =
"<html>" CRLF
"<head><title>409 Conflict</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>409 Conflict</h1></center>" CRLF
;


static char ngx_http_error_410_page[] =
"<html>" CRLF
"<head><title>410 Gone</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>410 Gone</h1></center>" CRLF
;


static char ngx_http_error_411_page[] =
"<html>" CRLF
"<head><title>411 Length Required</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>411 Length Required</h1></center>" CRLF
;


static char ngx_http_error_412_page[] =
"<html>" CRLF
"<head><title>412 Precondition Failed</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>412 Precondition Failed</h1></center>" CRLF
;


static char ngx_http_error_413_page[] =
"<html>" CRLF
"<head><title>413 Request Entity Too Large</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>413 Request Entity Too Large</h1></center>" CRLF
;


static char ngx_http_error_414_page[] =
"<html>" CRLF
"<head><title>414 Request-URI Too Large</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>414 Request-URI Too Large</h1></center>" CRLF
;


static char ngx_http_error_415_page[] =
"<html>" CRLF
"<head><title>415 Unsupported Media Type</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>415 Unsupported Media Type</h1></center>" CRLF
;


static char ngx_http_error_416_page[] =
"<html>" CRLF
"<head><title>416 Requested Range Not Satisfiable</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>416 Requested Range Not Satisfiable</h1></center>" CRLF
;


static char ngx_http_error_421_page[] =
"<html>" CRLF
"<head><title>421 Misdirected Request</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>421 Misdirected Request</h1></center>" CRLF
;


static char ngx_http_error_494_page[] =
"<html>" CRLF
"<head><title>400 Request Header Or Cookie Too Large</title></head>"
CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>400 Bad Request</h1></center>" CRLF
"<center>Request Header Or Cookie Too Large</center>" CRLF
;


static char ngx_http_error_495_page[] =
"<html>" CRLF
"<head><title>400 The SSL certificate error</title></head>"
CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>400 Bad Request</h1></center>" CRLF
"<center>The SSL certificate error</center>" CRLF
;


static char ngx_http_error_496_page[] =
"<html>" CRLF
"<head><title>400 No required SSL certificate was sent</title></head>"
CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>400 Bad Request</h1></center>" CRLF
"<center>No required SSL certificate was sent</center>" CRLF
;


static char ngx_http_error_497_page[] =
"<html>" CRLF
"<head><title>400 The plain HTTP request was sent to HTTPS port</title></head>"
CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>400 Bad Request</h1></center>" CRLF
"<center>The plain HTTP request was sent to HTTPS port</center>" CRLF
;


static char ngx_http_error_500_page[] =
"<html>" CRLF
"<head><title>500 Internal Server Error</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>500 Internal Server Error</h1></center>" CRLF
;


static char ngx_http_error_501_page[] =
"<html>" CRLF
"<head><title>501 Not Implemented</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>501 Not Implemented</h1></center>" CRLF
;


static char ngx_http_error_502_page[] =
"<html>" CRLF
"<head><title>502 Bad Gateway</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>502 Bad Gateway</h1></center>" CRLF
;


static char ngx_http_error_503_page[] =
"<html>" CRLF
"<head><title>503 Service Temporarily Unavailable</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>503 Service Temporarily Unavailable</h1></center>" CRLF
;


static char ngx_http_error_504_page[] =
"<html>" CRLF
"<head><title>504 Gateway Time-out</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>504 Gateway Time-out</h1></center>" CRLF
;


static char ngx_http_error_507_page[] =
"<html>" CRLF
"<head><title>507 Insufficient Storage</title></head>" CRLF
"<body bgcolor=\"white\">" CRLF
"<center><h1>507 Insufficient Storage</h1></center>" CRLF
;


static ngx_str_t ngx_http_error_pages[] = {

    ngx_null_string,                     /* 201, 204 */

#define NGX_HTTP_LAST_2XX  202
#define NGX_HTTP_OFF_3XX   (NGX_HTTP_LAST_2XX - 201)

    /* ngx_null_string, */               /* 300 */
    ngx_string(ngx_http_error_301_page),
    ngx_string(ngx_http_error_302_page),
    ngx_string(ngx_http_error_303_page),
    ngx_null_string,                     /* 304 */
    ngx_null_string,                     /* 305 */
    ngx_null_string,                     /* 306 */
    ngx_string(ngx_http_error_307_page),

#define NGX_HTTP_LAST_3XX  308
#define NGX_HTTP_OFF_4XX   (NGX_HTTP_LAST_3XX - 301 + NGX_HTTP_OFF_3XX)

    ngx_string(ngx_http_error_400_page),
    ngx_string(ngx_http_error_401_page),
    ngx_string(ngx_http_error_402_page),
    ngx_string(ngx_http_error_403_page),
    ngx_string(ngx_http_error_404_page),
    ngx_string(ngx_http_error_405_page),
    ngx_string(ngx_http_error_406_page),
    ngx_null_string,                     /* 407 */
    ngx_string(ngx_http_error_408_page),
    ngx_string(ngx_http_error_409_page),
    ngx_string(ngx_http_error_410_page),
    ngx_string(ngx_http_error_411_page),
    ngx_string(ngx_http_error_412_page),
    ngx_string(ngx_http_error_413_page),
    ngx_string(ngx_http_error_414_page),
    ngx_string(ngx_http_error_415_page),
    ngx_string(ngx_http_error_416_page),
    ngx_null_string,                     /* 417 */
    ngx_null_string,                     /* 418 */
    ngx_null_string,                     /* 419 */
    ngx_null_string,                     /* 420 */
    ngx_string(ngx_http_error_421_page),

#define NGX_HTTP_LAST_4XX  422
#define NGX_HTTP_OFF_5XX   (NGX_HTTP_LAST_4XX - 400 + NGX_HTTP_OFF_4XX)

    ngx_string(ngx_http_error_494_page), /* 494, request header too large */
    ngx_string(ngx_http_error_495_page), /* 495, https certificate error */
    ngx_string(ngx_http_error_496_page), /* 496, https no certificate */
    ngx_string(ngx_http_error_497_page), /* 497, http to https */
    ngx_string(ngx_http_error_404_page), /* 498, canceled */
    ngx_null_string,                     /* 499, client has closed connection */

    ngx_string(ngx_http_error_500_page),
    ngx_string(ngx_http_error_501_page),
    ngx_string(ngx_http_error_502_page),
    ngx_string(ngx_http_error_503_page),
    ngx_string(ngx_http_error_504_page),
    ngx_null_string,                     /* 505 */
    ngx_null_string,                     /* 506 */
    ngx_string(ngx_http_error_507_page)

#define NGX_HTTP_LAST_5XX  508

};


ngx_int_t
ngx_http_special_response_handler(ngx_http_request_t *r, ngx_int_t error)
{
    ngx_uint_t                 i, err;
    ngx_http_err_page_t       *err_page;
    ngx_http_core_loc_conf_t  *clcf;

    ngx_log_debug3(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "http special response: %i, \"%V?%V\"",
                   error, &r->uri, &r->args);

    r->err_status = error;

    if (r->keepalive) {
        switch (error) {
            case NGX_HTTP_BAD_REQUEST:
            case NGX_HTTP_REQUEST_ENTITY_TOO_LARGE:
            case NGX_HTTP_REQUEST_URI_TOO_LARGE:
            case NGX_HTTP_TO_HTTPS:
            case NGX_HTTPS_CERT_ERROR:
            case NGX_HTTPS_NO_CERT:
            case NGX_HTTP_INTERNAL_SERVER_ERROR:
            case NGX_HTTP_NOT_IMPLEMENTED:
                r->keepalive = 0;
        }
    }

    if (r->lingering_close) {
        switch (error) {
            case NGX_HTTP_BAD_REQUEST:
            case NGX_HTTP_TO_HTTPS:
            case NGX_HTTPS_CERT_ERROR:
            case NGX_HTTPS_NO_CERT:
                r->lingering_close = 0;
        }
    }

    r->headers_out.content_type.len = 0;

    clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);

    if (!r->error_page && clcf->error_pages && r->uri_changes != 0) {

        if (clcf->recursive_error_pages == 0) {
            r->error_page = 1;
        }

        err_page = clcf->error_pages->elts;

        for (i = 0; i < clcf->error_pages->nelts; i++) {
            if (err_page[i].status == error) {
                return ngx_http_send_error_page(r, &err_page[i]);
            }
        }
    }

    r->expect_tested = 1;

    if (ngx_http_discard_request_body(r) != NGX_OK) {
        r->keepalive = 0;
    }

    if (clcf->msie_refresh
        && r->headers_in.msie
        && (error == NGX_HTTP_MOVED_PERMANENTLY
            || error == NGX_HTTP_MOVED_TEMPORARILY))
    {
        return ngx_http_send_refresh(r);
    }

    if (error == NGX_HTTP_CREATED) {
        /* 201 */
        err = 0;

    } else if (error == NGX_HTTP_NO_CONTENT) {
        /* 204 */
        err = 0;

    } else if (error >= NGX_HTTP_MOVED_PERMANENTLY
               && error < NGX_HTTP_LAST_3XX)
    {
        /* 3XX */
        err = error - NGX_HTTP_MOVED_PERMANENTLY + NGX_HTTP_OFF_3XX;

    } else if (error >= NGX_HTTP_BAD_REQUEST
               && error < NGX_HTTP_LAST_4XX)
    {
        /* 4XX */
        err = error - NGX_HTTP_BAD_REQUEST + NGX_HTTP_OFF_4XX;

    } else if (error >= NGX_HTTP_NGINX_CODES
               && error < NGX_HTTP_LAST_5XX)
    {
        /* 49X, 5XX */
        err = error - NGX_HTTP_NGINX_CODES + NGX_HTTP_OFF_5XX;
        switch (error) {
            case NGX_HTTP_TO_HTTPS:
            case NGX_HTTPS_CERT_ERROR:
            case NGX_HTTPS_NO_CERT:
            case NGX_HTTP_REQUEST_HEADER_TOO_LARGE:
                r->err_status = NGX_HTTP_BAD_REQUEST;
                break;
        }

    } else {
        /* unknown code, zero body */
        err = 0;
    }

    return ngx_http_send_special_response(r, clcf, err);
}


ngx_int_t
ngx_http_filter_finalize_request(ngx_http_request_t *r, ngx_module_t *m,
    ngx_int_t error)
{
    void       *ctx;
    ngx_int_t   rc;

    ngx_http_clean_header(r);

    ctx = NULL;

    if (m) {
        ctx = r->ctx[m->ctx_index];
    }

    /* clear the modules contexts */
    ngx_memzero(r->ctx, sizeof(void *) * ngx_http_max_module);

    if (m) {
        r->ctx[m->ctx_index] = ctx;
    }

    r->filter_finalize = 1;

    rc = ngx_http_special_response_handler(r, error);

    /* NGX_ERROR resets any pending data */

    switch (rc) {

    case NGX_OK:
    case NGX_DONE:
        return NGX_ERROR;

    default:
        return rc;
    }
}


void
ngx_http_clean_header(ngx_http_request_t *r)
{
    ngx_memzero(&r->headers_out.status,
                sizeof(ngx_http_headers_out_t)
                    - offsetof(ngx_http_headers_out_t, status));

    r->headers_out.headers.part.nelts = 0;
    r->headers_out.headers.part.next = NULL;
    r->headers_out.headers.last = &r->headers_out.headers.part;

    r->headers_out.content_length_n = -1;
    r->headers_out.last_modified_time = -1;
}


static ngx_int_t
ngx_http_send_error_page(ngx_http_request_t *r, ngx_http_err_page_t *err_page)
{
    ngx_int_t                  overwrite;
    ngx_str_t                  uri, args;
    ngx_table_elt_t           *location;
    ngx_http_core_loc_conf_t  *clcf;

    overwrite = err_page->overwrite;

    if (overwrite && overwrite != NGX_HTTP_OK) {
        r->expect_tested = 1;
    }

    if (overwrite >= 0) {
        r->err_status = overwrite;
    }

    if (ngx_http_complex_value(r, &err_page->value, &uri) != NGX_OK) {
        return NGX_ERROR;
    }

    if (uri.len && uri.data[0] == '/') {

        if (err_page->value.lengths) {
            ngx_http_split_args(r, &uri, &args);

        } else {
            args = err_page->args;
        }

        if (r->method != NGX_HTTP_HEAD) {
            r->method = NGX_HTTP_GET;
            r->method_name = ngx_http_core_get_method;
        }

        return ngx_http_internal_redirect(r, &uri, &args);
    }

    if (uri.len && uri.data[0] == '@') {
        return ngx_http_named_location(r, &uri);
    }

    location = ngx_list_push(&r->headers_out.headers);

    if (location == NULL) {
        return NGX_ERROR;
    }

    if (overwrite != NGX_HTTP_MOVED_PERMANENTLY
        && overwrite != NGX_HTTP_MOVED_TEMPORARILY
        && overwrite != NGX_HTTP_SEE_OTHER
        && overwrite != NGX_HTTP_TEMPORARY_REDIRECT)
    {
        r->err_status = NGX_HTTP_MOVED_TEMPORARILY;
    }

    location->hash = 1;
    ngx_str_set(&location->key, "Location");
    location->value = uri;

    ngx_http_clear_location(r);

    r->headers_out.location = location;

    clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);

    if (clcf->msie_refresh && r->headers_in.msie) {
        return ngx_http_send_refresh(r);
    }

    return ngx_http_send_special_response(r, clcf, r->err_status
                                                   - NGX_HTTP_MOVED_PERMANENTLY
                                                   + NGX_HTTP_OFF_3XX);
}


static ngx_int_t
ngx_http_send_special_response(ngx_http_request_t *r,
    ngx_http_core_loc_conf_t *clcf, ngx_uint_t err)
{
    u_char       *tail;
    size_t        len;
    ngx_int_t     rc;
    ngx_buf_t    *b;
    ngx_uint_t    msie_padding;
    ngx_chain_t   out[3];

    if (clcf->server_tokens) {
        len = sizeof(ngx_http_error_full_tail) - 1;
        tail = ngx_http_error_full_tail;

    } else {
        len = sizeof(ngx_http_error_tail) - 1;
        tail = ngx_http_error_tail;
    }

    msie_padding = 0;

    if (ngx_http_error_pages[err].len) {
        r->headers_out.content_length_n = ngx_http_error_pages[err].len + len;
        if (clcf->msie_padding
            && (r->headers_in.msie || r->headers_in.chrome)
            && r->http_version >= NGX_HTTP_VERSION_10
            && err >= NGX_HTTP_OFF_4XX)
        {
            r->headers_out.content_length_n +=
                                         sizeof(ngx_http_msie_padding) - 1;
            msie_padding = 1;
        }

        r->headers_out.content_type_len = sizeof("text/html") - 1;
        ngx_str_set(&r->headers_out.content_type, "text/html");
        r->headers_out.content_type_lowcase = NULL;

    } else {
        r->headers_out.content_length_n = 0;
    }

    if (r->headers_out.content_length) {
        r->headers_out.content_length->hash = 0;
        r->headers_out.content_length = NULL;
    }

    ngx_http_clear_accept_ranges(r);
    ngx_http_clear_last_modified(r);
    ngx_http_clear_etag(r);

    rc = ngx_http_send_header(r);

    if (rc == NGX_ERROR || r->header_only) {
        return rc;
    }

    if (ngx_http_error_pages[err].len == 0) {
        return ngx_http_send_special(r, NGX_HTTP_LAST);
    }

    b = ngx_calloc_buf(r->pool);
    if (b == NULL) {
        return NGX_ERROR;
    }

    b->memory = 1;
    b->pos = ngx_http_error_pages[err].data;
    b->last = ngx_http_error_pages[err].data + ngx_http_error_pages[err].len;

    out[0].buf = b;
    out[0].next = &out[1];

    b = ngx_calloc_buf(r->pool);
    if (b == NULL) {
        return NGX_ERROR;
    }

    b->memory = 1;

    b->pos = tail;
    b->last = tail + len;

    out[1].buf = b;
    out[1].next = NULL;

    if (msie_padding) {
        b = ngx_calloc_buf(r->pool);
        if (b == NULL) {
            return NGX_ERROR;
        }

        b->memory = 1;
        b->pos = ngx_http_msie_padding;
        b->last = ngx_http_msie_padding + sizeof(ngx_http_msie_padding) - 1;

        out[1].next = &out[2];
        out[2].buf = b;
        out[2].next = NULL;
    }

    if (r == r->main) {
        b->last_buf = 1;
    }

    b->last_in_chain = 1;

    return ngx_http_output_filter(r, &out[0]);
}


static ngx_int_t
ngx_http_send_refresh(ngx_http_request_t *r)
{
    u_char       *p, *location;
    size_t        len, size;
    uintptr_t     escape;
    ngx_int_t     rc;
    ngx_buf_t    *b;
    ngx_chain_t   out;

    len = r->headers_out.location->value.len;
    location = r->headers_out.location->value.data;

    escape = 2 * ngx_escape_uri(NULL, location, len, NGX_ESCAPE_REFRESH);

    size = sizeof(ngx_http_msie_refresh_head) - 1
           + escape + len
           + sizeof(ngx_http_msie_refresh_tail) - 1;

    r->err_status = NGX_HTTP_OK;

    r->headers_out.content_type_len = sizeof("text/html") - 1;
    ngx_str_set(&r->headers_out.content_type, "text/html");
    r->headers_out.content_type_lowcase = NULL;

    r->headers_out.location->hash = 0;
    r->headers_out.location = NULL;

    r->headers_out.content_length_n = size;

    if (r->headers_out.content_length) {
        r->headers_out.content_length->hash = 0;
        r->headers_out.content_length = NULL;
    }

    ngx_http_clear_accept_ranges(r);
    ngx_http_clear_last_modified(r);
    ngx_http_clear_etag(r);

    rc = ngx_http_send_header(r);

    if (rc == NGX_ERROR || r->header_only) {
        return rc;
    }

    b = ngx_create_temp_buf(r->pool, size);
    if (b == NULL) {
        return NGX_ERROR;
    }

    p = ngx_cpymem(b->pos, ngx_http_msie_refresh_head,
                   sizeof(ngx_http_msie_refresh_head) - 1);

    if (escape == 0) {
        p = ngx_cpymem(p, location, len);

    } else {
        p = (u_char *) ngx_escape_uri(p, location, len, NGX_ESCAPE_REFRESH);
    }

    b->last = ngx_cpymem(p, ngx_http_msie_refresh_tail,
                         sizeof(ngx_http_msie_refresh_tail) - 1);

    b->last_buf = 1;
    b->last_in_chain = 1;

    out.buf = b;
    out.next = NULL;

    return ngx_http_output_filter(r, &out);
}