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view src/http/modules/ngx_http_headers_filter_module.c @ 7760:83c4622053b0

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Upstream: fixed zero size buf alerts on extra data (ticket #2117). After 7675:9afa45068b8f and 7678:bffcc5af1d72 (1.19.1), during non-buffered simple proxying, responses with extra data might result in zero size buffers being generated and "zero size buf" alerts in writer. This bug is similar to the one with FastCGI proxying fixed in 7689:da8d758aabeb. In non-buffered mode, normally the filter function is not called if u->length is already 0, since u->length is checked after each call of the filter function. There is a case when this can happen though: if the response length is 0, and there are pre-read response body data left after reading response headers. As such, a check for u->length is needed at the start of non-buffered filter functions, similar to the one for p->length present in buffered filter functions. Appropriate checks added to the existing non-buffered copy filters in the upstream (used by scgi and uwsgi proxying) and proxy modules.
author Maxim Dounin <mdounin@mdounin.ru>
date Tue, 12 Jan 2021 16:59:31 +0300
parents 6ba68ad8b24c
children ef6a3a99a81a
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>


typedef struct ngx_http_header_val_s  ngx_http_header_val_t;

typedef ngx_int_t (*ngx_http_set_header_pt)(ngx_http_request_t *r,
    ngx_http_header_val_t *hv, ngx_str_t *value);


typedef struct {
    ngx_str_t                  name;
    ngx_uint_t                 offset;
    ngx_http_set_header_pt     handler;
} ngx_http_set_header_t;


struct ngx_http_header_val_s {
    ngx_http_complex_value_t   value;
    ngx_str_t                  key;
    ngx_http_set_header_pt     handler;
    ngx_uint_t                 offset;
    ngx_uint_t                 always;  /* unsigned  always:1 */
};


typedef enum {
    NGX_HTTP_EXPIRES_OFF,
    NGX_HTTP_EXPIRES_EPOCH,
    NGX_HTTP_EXPIRES_MAX,
    NGX_HTTP_EXPIRES_ACCESS,
    NGX_HTTP_EXPIRES_MODIFIED,
    NGX_HTTP_EXPIRES_DAILY,
    NGX_HTTP_EXPIRES_UNSET
} ngx_http_expires_t;


typedef struct {
    ngx_http_expires_t         expires;
    time_t                     expires_time;
    ngx_http_complex_value_t  *expires_value;
    ngx_array_t               *headers;
    ngx_array_t               *trailers;
} ngx_http_headers_conf_t;


static ngx_int_t ngx_http_set_expires(ngx_http_request_t *r,
    ngx_http_headers_conf_t *conf);
static ngx_int_t ngx_http_parse_expires(ngx_str_t *value,
    ngx_http_expires_t *expires, time_t *expires_time, char **err);
static ngx_int_t ngx_http_add_multi_header_lines(ngx_http_request_t *r,
    ngx_http_header_val_t *hv, ngx_str_t *value);
static ngx_int_t ngx_http_add_header(ngx_http_request_t *r,
    ngx_http_header_val_t *hv, ngx_str_t *value);
static ngx_int_t ngx_http_set_last_modified(ngx_http_request_t *r,
    ngx_http_header_val_t *hv, ngx_str_t *value);
static ngx_int_t ngx_http_set_response_header(ngx_http_request_t *r,
    ngx_http_header_val_t *hv, ngx_str_t *value);

static void *ngx_http_headers_create_conf(ngx_conf_t *cf);
static char *ngx_http_headers_merge_conf(ngx_conf_t *cf,
    void *parent, void *child);
static ngx_int_t ngx_http_headers_filter_init(ngx_conf_t *cf);
static char *ngx_http_headers_expires(ngx_conf_t *cf, ngx_command_t *cmd,
    void *conf);
static char *ngx_http_headers_add(ngx_conf_t *cf, ngx_command_t *cmd,
    void *conf);


static ngx_http_set_header_t  ngx_http_set_headers[] = {

    { ngx_string("Cache-Control"),
                 offsetof(ngx_http_headers_out_t, cache_control),
                 ngx_http_add_multi_header_lines },

    { ngx_string("Link"),
                 offsetof(ngx_http_headers_out_t, link),
                 ngx_http_add_multi_header_lines },

    { ngx_string("Last-Modified"),
                 offsetof(ngx_http_headers_out_t, last_modified),
                 ngx_http_set_last_modified },

    { ngx_string("ETag"),
                 offsetof(ngx_http_headers_out_t, etag),
                 ngx_http_set_response_header },

    { ngx_null_string, 0, NULL }
};


static ngx_command_t  ngx_http_headers_filter_commands[] = {

    { ngx_string("expires"),
      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_HTTP_LIF_CONF
                        |NGX_CONF_TAKE12,
      ngx_http_headers_expires,
      NGX_HTTP_LOC_CONF_OFFSET,
      0,
      NULL },

    { ngx_string("add_header"),
      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_HTTP_LIF_CONF
                        |NGX_CONF_TAKE23,
      ngx_http_headers_add,
      NGX_HTTP_LOC_CONF_OFFSET,
      offsetof(ngx_http_headers_conf_t, headers),
      NULL },

    { ngx_string("add_trailer"),
      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_HTTP_LIF_CONF
                        |NGX_CONF_TAKE23,
      ngx_http_headers_add,
      NGX_HTTP_LOC_CONF_OFFSET,
      offsetof(ngx_http_headers_conf_t, trailers),
      NULL },

      ngx_null_command
};


static ngx_http_module_t  ngx_http_headers_filter_module_ctx = {
    NULL,                                  /* preconfiguration */
    ngx_http_headers_filter_init,          /* postconfiguration */

    NULL,                                  /* create main configuration */
    NULL,                                  /* init main configuration */

    NULL,                                  /* create server configuration */
    NULL,                                  /* merge server configuration */

    ngx_http_headers_create_conf,          /* create location configuration */
    ngx_http_headers_merge_conf            /* merge location configuration */
};


ngx_module_t  ngx_http_headers_filter_module = {
    NGX_MODULE_V1,
    &ngx_http_headers_filter_module_ctx,   /* module context */
    ngx_http_headers_filter_commands,      /* module directives */
    NGX_HTTP_MODULE,                       /* module type */
    NULL,                                  /* init master */
    NULL,                                  /* init module */
    NULL,                                  /* init process */
    NULL,                                  /* init thread */
    NULL,                                  /* exit thread */
    NULL,                                  /* exit process */
    NULL,                                  /* exit master */
    NGX_MODULE_V1_PADDING
};


static ngx_http_output_header_filter_pt  ngx_http_next_header_filter;
static ngx_http_output_body_filter_pt    ngx_http_next_body_filter;


static ngx_int_t
ngx_http_headers_filter(ngx_http_request_t *r)
{
    ngx_str_t                 value;
    ngx_uint_t                i, safe_status;
    ngx_http_header_val_t    *h;
    ngx_http_headers_conf_t  *conf;

    if (r != r->main) {
        return ngx_http_next_header_filter(r);
    }

    conf = ngx_http_get_module_loc_conf(r, ngx_http_headers_filter_module);

    if (conf->expires == NGX_HTTP_EXPIRES_OFF
        && conf->headers == NULL
        && conf->trailers == NULL)
    {
        return ngx_http_next_header_filter(r);
    }

    switch (r->headers_out.status) {

    case NGX_HTTP_OK:
    case NGX_HTTP_CREATED:
    case NGX_HTTP_NO_CONTENT:
    case NGX_HTTP_PARTIAL_CONTENT:
    case NGX_HTTP_MOVED_PERMANENTLY:
    case NGX_HTTP_MOVED_TEMPORARILY:
    case NGX_HTTP_SEE_OTHER:
    case NGX_HTTP_NOT_MODIFIED:
    case NGX_HTTP_TEMPORARY_REDIRECT:
    case NGX_HTTP_PERMANENT_REDIRECT:
        safe_status = 1;
        break;

    default:
        safe_status = 0;
        break;
    }

    if (conf->expires != NGX_HTTP_EXPIRES_OFF && safe_status) {
        if (ngx_http_set_expires(r, conf) != NGX_OK) {
            return NGX_ERROR;
        }
    }

    if (conf->headers) {
        h = conf->headers->elts;
        for (i = 0; i < conf->headers->nelts; i++) {

            if (!safe_status && !h[i].always) {
                continue;
            }

            if (ngx_http_complex_value(r, &h[i].value, &value) != NGX_OK) {
                return NGX_ERROR;
            }

            if (h[i].handler(r, &h[i], &value) != NGX_OK) {
                return NGX_ERROR;
            }
        }
    }

    if (conf->trailers) {
        h = conf->trailers->elts;
        for (i = 0; i < conf->trailers->nelts; i++) {

            if (!safe_status && !h[i].always) {
                continue;
            }

            r->expect_trailers = 1;
            break;
        }
    }

    return ngx_http_next_header_filter(r);
}


static ngx_int_t
ngx_http_trailers_filter(ngx_http_request_t *r, ngx_chain_t *in)
{
    ngx_str_t                 value;
    ngx_uint_t                i, safe_status;
    ngx_chain_t              *cl;
    ngx_table_elt_t          *t;
    ngx_http_header_val_t    *h;
    ngx_http_headers_conf_t  *conf;

    conf = ngx_http_get_module_loc_conf(r, ngx_http_headers_filter_module);

    if (in == NULL
        || conf->trailers == NULL
        || !r->expect_trailers
        || r->header_only)
    {
        return ngx_http_next_body_filter(r, in);
    }

    for (cl = in; cl; cl = cl->next) {
        if (cl->buf->last_buf) {
            break;
        }
    }

    if (cl == NULL) {
        return ngx_http_next_body_filter(r, in);
    }

    switch (r->headers_out.status) {

    case NGX_HTTP_OK:
    case NGX_HTTP_CREATED:
    case NGX_HTTP_NO_CONTENT:
    case NGX_HTTP_PARTIAL_CONTENT:
    case NGX_HTTP_MOVED_PERMANENTLY:
    case NGX_HTTP_MOVED_TEMPORARILY:
    case NGX_HTTP_SEE_OTHER:
    case NGX_HTTP_NOT_MODIFIED:
    case NGX_HTTP_TEMPORARY_REDIRECT:
    case NGX_HTTP_PERMANENT_REDIRECT:
        safe_status = 1;
        break;

    default:
        safe_status = 0;
        break;
    }

    h = conf->trailers->elts;
    for (i = 0; i < conf->trailers->nelts; i++) {

        if (!safe_status && !h[i].always) {
            continue;
        }

        if (ngx_http_complex_value(r, &h[i].value, &value) != NGX_OK) {
            return NGX_ERROR;
        }

        if (value.len) {
            t = ngx_list_push(&r->headers_out.trailers);
            if (t == NULL) {
                return NGX_ERROR;
            }

            t->key = h[i].key;
            t->value = value;
            t->hash = 1;
        }
    }

    return ngx_http_next_body_filter(r, in);
}


static ngx_int_t
ngx_http_set_expires(ngx_http_request_t *r, ngx_http_headers_conf_t *conf)
{
    char                *err;
    size_t               len;
    time_t               now, expires_time, max_age;
    ngx_str_t            value;
    ngx_int_t            rc;
    ngx_uint_t           i;
    ngx_table_elt_t     *e, *cc, **ccp;
    ngx_http_expires_t   expires;

    expires = conf->expires;
    expires_time = conf->expires_time;

    if (conf->expires_value != NULL) {

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

        rc = ngx_http_parse_expires(&value, &expires, &expires_time, &err);

        if (rc != NGX_OK) {
            return NGX_OK;
        }

        if (expires == NGX_HTTP_EXPIRES_OFF) {
            return NGX_OK;
        }
    }

    e = r->headers_out.expires;

    if (e == NULL) {

        e = ngx_list_push(&r->headers_out.headers);
        if (e == NULL) {
            return NGX_ERROR;
        }

        r->headers_out.expires = e;

        e->hash = 1;
        ngx_str_set(&e->key, "Expires");
    }

    len = sizeof("Mon, 28 Sep 1970 06:00:00 GMT");
    e->value.len = len - 1;

    ccp = r->headers_out.cache_control.elts;

    if (ccp == NULL) {

        if (ngx_array_init(&r->headers_out.cache_control, r->pool,
                           1, sizeof(ngx_table_elt_t *))
            != NGX_OK)
        {
            return NGX_ERROR;
        }

        cc = ngx_list_push(&r->headers_out.headers);
        if (cc == NULL) {
            return NGX_ERROR;
        }

        cc->hash = 1;
        ngx_str_set(&cc->key, "Cache-Control");

        ccp = ngx_array_push(&r->headers_out.cache_control);
        if (ccp == NULL) {
            return NGX_ERROR;
        }

        *ccp = cc;

    } else {
        for (i = 1; i < r->headers_out.cache_control.nelts; i++) {
            ccp[i]->hash = 0;
        }

        cc = ccp[0];
    }

    if (expires == NGX_HTTP_EXPIRES_EPOCH) {
        e->value.data = (u_char *) "Thu, 01 Jan 1970 00:00:01 GMT";
        ngx_str_set(&cc->value, "no-cache");
        return NGX_OK;
    }

    if (expires == NGX_HTTP_EXPIRES_MAX) {
        e->value.data = (u_char *) "Thu, 31 Dec 2037 23:55:55 GMT";
        /* 10 years */
        ngx_str_set(&cc->value, "max-age=315360000");
        return NGX_OK;
    }

    e->value.data = ngx_pnalloc(r->pool, len);
    if (e->value.data == NULL) {
        return NGX_ERROR;
    }

    if (expires_time == 0 && expires != NGX_HTTP_EXPIRES_DAILY) {
        ngx_memcpy(e->value.data, ngx_cached_http_time.data,
                   ngx_cached_http_time.len + 1);
        ngx_str_set(&cc->value, "max-age=0");
        return NGX_OK;
    }

    now = ngx_time();

    if (expires == NGX_HTTP_EXPIRES_DAILY) {
        expires_time = ngx_next_time(expires_time);
        max_age = expires_time - now;

    } else if (expires == NGX_HTTP_EXPIRES_ACCESS
               || r->headers_out.last_modified_time == -1)
    {
        max_age = expires_time;
        expires_time += now;

    } else {
        expires_time += r->headers_out.last_modified_time;
        max_age = expires_time - now;
    }

    ngx_http_time(e->value.data, expires_time);

    if (conf->expires_time < 0 || max_age < 0) {
        ngx_str_set(&cc->value, "no-cache");
        return NGX_OK;
    }

    cc->value.data = ngx_pnalloc(r->pool,
                                 sizeof("max-age=") + NGX_TIME_T_LEN + 1);
    if (cc->value.data == NULL) {
        return NGX_ERROR;
    }

    cc->value.len = ngx_sprintf(cc->value.data, "max-age=%T", max_age)
                    - cc->value.data;

    return NGX_OK;
}


static ngx_int_t
ngx_http_parse_expires(ngx_str_t *value, ngx_http_expires_t *expires,
    time_t *expires_time, char **err)
{
    ngx_uint_t  minus;

    if (*expires != NGX_HTTP_EXPIRES_MODIFIED) {

        if (value->len == 5 && ngx_strncmp(value->data, "epoch", 5) == 0) {
            *expires = NGX_HTTP_EXPIRES_EPOCH;
            return NGX_OK;
        }

        if (value->len == 3 && ngx_strncmp(value->data, "max", 3) == 0) {
            *expires = NGX_HTTP_EXPIRES_MAX;
            return NGX_OK;
        }

        if (value->len == 3 && ngx_strncmp(value->data, "off", 3) == 0) {
            *expires = NGX_HTTP_EXPIRES_OFF;
            return NGX_OK;
        }
    }

    if (value->len && value->data[0] == '@') {
        value->data++;
        value->len--;
        minus = 0;

        if (*expires == NGX_HTTP_EXPIRES_MODIFIED) {
            *err = "daily time cannot be used with \"modified\" parameter";
            return NGX_ERROR;
        }

        *expires = NGX_HTTP_EXPIRES_DAILY;

    } else if (value->len && value->data[0] == '+') {
        value->data++;
        value->len--;
        minus = 0;

    } else if (value->len && value->data[0] == '-') {
        value->data++;
        value->len--;
        minus = 1;

    } else {
        minus = 0;
    }

    *expires_time = ngx_parse_time(value, 1);

    if (*expires_time == (time_t) NGX_ERROR) {
        *err = "invalid value";
        return NGX_ERROR;
    }

    if (*expires == NGX_HTTP_EXPIRES_DAILY
        && *expires_time > 24 * 60 * 60)
    {
        *err = "daily time value must be less than 24 hours";
        return NGX_ERROR;
    }

    if (minus) {
        *expires_time = - *expires_time;
    }

    return NGX_OK;
}


static ngx_int_t
ngx_http_add_header(ngx_http_request_t *r, ngx_http_header_val_t *hv,
    ngx_str_t *value)
{
    ngx_table_elt_t  *h;

    if (value->len) {
        h = ngx_list_push(&r->headers_out.headers);
        if (h == NULL) {
            return NGX_ERROR;
        }

        h->hash = 1;
        h->key = hv->key;
        h->value = *value;
    }

    return NGX_OK;
}


static ngx_int_t
ngx_http_add_multi_header_lines(ngx_http_request_t *r,
    ngx_http_header_val_t *hv, ngx_str_t *value)
{
    ngx_array_t      *pa;
    ngx_table_elt_t  *h, **ph;

    if (value->len == 0) {
        return NGX_OK;
    }

    pa = (ngx_array_t *) ((char *) &r->headers_out + hv->offset);

    if (pa->elts == NULL) {
        if (ngx_array_init(pa, r->pool, 1, sizeof(ngx_table_elt_t *)) != NGX_OK)
        {
            return NGX_ERROR;
        }
    }

    h = ngx_list_push(&r->headers_out.headers);
    if (h == NULL) {
        return NGX_ERROR;
    }

    h->hash = 1;
    h->key = hv->key;
    h->value = *value;

    ph = ngx_array_push(pa);
    if (ph == NULL) {
        return NGX_ERROR;
    }

    *ph = h;

    return NGX_OK;
}


static ngx_int_t
ngx_http_set_last_modified(ngx_http_request_t *r, ngx_http_header_val_t *hv,
    ngx_str_t *value)
{
    if (ngx_http_set_response_header(r, hv, value) != NGX_OK) {
        return NGX_ERROR;
    }

    r->headers_out.last_modified_time =
        (value->len) ? ngx_parse_http_time(value->data, value->len) : -1;

    return NGX_OK;
}


static ngx_int_t
ngx_http_set_response_header(ngx_http_request_t *r, ngx_http_header_val_t *hv,
    ngx_str_t *value)
{
    ngx_table_elt_t  *h, **old;

    old = (ngx_table_elt_t **) ((char *) &r->headers_out + hv->offset);

    if (value->len == 0) {
        if (*old) {
            (*old)->hash = 0;
            *old = NULL;
        }

        return NGX_OK;
    }

    if (*old) {
        h = *old;

    } else {
        h = ngx_list_push(&r->headers_out.headers);
        if (h == NULL) {
            return NGX_ERROR;
        }

        *old = h;
    }

    h->hash = 1;
    h->key = hv->key;
    h->value = *value;

    return NGX_OK;
}


static void *
ngx_http_headers_create_conf(ngx_conf_t *cf)
{
    ngx_http_headers_conf_t  *conf;

    conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_headers_conf_t));
    if (conf == NULL) {
        return NULL;
    }

    /*
     * set by ngx_pcalloc():
     *
     *     conf->headers = NULL;
     *     conf->trailers = NULL;
     *     conf->expires_time = 0;
     *     conf->expires_value = NULL;
     */

    conf->expires = NGX_HTTP_EXPIRES_UNSET;

    return conf;
}


static char *
ngx_http_headers_merge_conf(ngx_conf_t *cf, void *parent, void *child)
{
    ngx_http_headers_conf_t *prev = parent;
    ngx_http_headers_conf_t *conf = child;

    if (conf->expires == NGX_HTTP_EXPIRES_UNSET) {
        conf->expires = prev->expires;
        conf->expires_time = prev->expires_time;
        conf->expires_value = prev->expires_value;

        if (conf->expires == NGX_HTTP_EXPIRES_UNSET) {
            conf->expires = NGX_HTTP_EXPIRES_OFF;
        }
    }

    if (conf->headers == NULL) {
        conf->headers = prev->headers;
    }

    if (conf->trailers == NULL) {
        conf->trailers = prev->trailers;
    }

    return NGX_CONF_OK;
}


static ngx_int_t
ngx_http_headers_filter_init(ngx_conf_t *cf)
{
    ngx_http_next_header_filter = ngx_http_top_header_filter;
    ngx_http_top_header_filter = ngx_http_headers_filter;

    ngx_http_next_body_filter = ngx_http_top_body_filter;
    ngx_http_top_body_filter = ngx_http_trailers_filter;

    return NGX_OK;
}


static char *
ngx_http_headers_expires(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    ngx_http_headers_conf_t *hcf = conf;

    char                              *err;
    ngx_str_t                         *value;
    ngx_int_t                          rc;
    ngx_uint_t                         n;
    ngx_http_complex_value_t           cv;
    ngx_http_compile_complex_value_t   ccv;

    if (hcf->expires != NGX_HTTP_EXPIRES_UNSET) {
        return "is duplicate";
    }

    value = cf->args->elts;

    if (cf->args->nelts == 2) {

        hcf->expires = NGX_HTTP_EXPIRES_ACCESS;

        n = 1;

    } else { /* cf->args->nelts == 3 */

        if (ngx_strcmp(value[1].data, "modified") != 0) {
            return "invalid value";
        }

        hcf->expires = NGX_HTTP_EXPIRES_MODIFIED;

        n = 2;
    }

    ngx_memzero(&ccv, sizeof(ngx_http_compile_complex_value_t));

    ccv.cf = cf;
    ccv.value = &value[n];
    ccv.complex_value = &cv;

    if (ngx_http_compile_complex_value(&ccv) != NGX_OK) {
        return NGX_CONF_ERROR;
    }

    if (cv.lengths != NULL) {

        hcf->expires_value = ngx_palloc(cf->pool,
                                        sizeof(ngx_http_complex_value_t));
        if (hcf->expires_value == NULL) {
            return NGX_CONF_ERROR;
        }

        *hcf->expires_value = cv;

        return NGX_CONF_OK;
    }

    rc = ngx_http_parse_expires(&value[n], &hcf->expires, &hcf->expires_time,
                                &err);
    if (rc != NGX_OK) {
        return err;
    }

    return NGX_CONF_OK;
}


static char *
ngx_http_headers_add(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    ngx_http_headers_conf_t *hcf = conf;

    ngx_str_t                          *value;
    ngx_uint_t                          i;
    ngx_array_t                       **headers;
    ngx_http_header_val_t              *hv;
    ngx_http_set_header_t              *set;
    ngx_http_compile_complex_value_t    ccv;

    value = cf->args->elts;

    headers = (ngx_array_t **) ((char *) hcf + cmd->offset);

    if (*headers == NULL) {
        *headers = ngx_array_create(cf->pool, 1,
                                    sizeof(ngx_http_header_val_t));
        if (*headers == NULL) {
            return NGX_CONF_ERROR;
        }
    }

    hv = ngx_array_push(*headers);
    if (hv == NULL) {
        return NGX_CONF_ERROR;
    }

    hv->key = value[1];
    hv->handler = NULL;
    hv->offset = 0;
    hv->always = 0;

    if (headers == &hcf->headers) {
        hv->handler = ngx_http_add_header;

        set = ngx_http_set_headers;
        for (i = 0; set[i].name.len; i++) {
            if (ngx_strcasecmp(value[1].data, set[i].name.data) != 0) {
                continue;
            }

            hv->offset = set[i].offset;
            hv->handler = set[i].handler;

            break;
        }
    }

    if (value[2].len == 0) {
        ngx_memzero(&hv->value, sizeof(ngx_http_complex_value_t));

    } else {
        ngx_memzero(&ccv, sizeof(ngx_http_compile_complex_value_t));

        ccv.cf = cf;
        ccv.value = &value[2];
        ccv.complex_value = &hv->value;

        if (ngx_http_compile_complex_value(&ccv) != NGX_OK) {
            return NGX_CONF_ERROR;
        }
    }

    if (cf->args->nelts == 3) {
        return NGX_CONF_OK;
    }

    if (ngx_strcmp(value[3].data, "always") != 0) {
        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                           "invalid parameter \"%V\"", &value[3]);
        return NGX_CONF_ERROR;
    }

    hv->always = 1;

    return NGX_CONF_OK;
}