Function cache_check_freshness

modules/cache/cache_util.c:533–806

}

int cache_check_freshness(cache_handle_t *h, cache_request_rec *cache,
        request_rec *r)
{
    apr_status_t status;
    apr_int64_t age, maxage_req, maxage_cresp, maxage, smaxage, maxstale;
    apr_int64_t minfresh;
    const char *cc_req;
    const char *pragma;
    const char *agestr = NULL;
    apr_time_t age_c = 0;
    cache_info *info = &(h->cache_obj->info);
    const char *warn_head;
    cache_server_conf *conf =
      (cache_server_conf *)ap_get_module_config(r->server->module_config,
                                                &cache_module);

    /*
     * We now want to check if our cached data is still fresh. This depends
     * on a few things, in this order:
     *
     * - RFC2616 14.9.4 End to end reload, Cache-Control: no-cache. no-cache
     * in either the request or the cached response means that we must
     * perform the request unconditionally, and ignore cached content. We
     * should never reach here, but if we do, mark the content as stale,
     * as this is the best we can do.
     *
     * - RFC2616 14.32 Pragma: no-cache This is treated the same as
     * Cache-Control: no-cache.
     *
     * - RFC2616 14.9.3 Cache-Control: max-stale, must-revalidate,
     * proxy-revalidate if the max-stale request header exists, modify the
     * stale calculations below so that an object can be at most <max-stale>
     * seconds stale before we request a revalidation, _UNLESS_ a
     * must-revalidate or proxy-revalidate cached response header exists to
     * stop us doing this.
     *
     * - RFC2616 14.9.3 Cache-Control: s-maxage the origin server specifies the
     * maximum age an object can be before it is considered stale. This
     * directive has the effect of proxy|must revalidate, which in turn means
     * simple ignore any max-stale setting.
     *
     * - RFC2616 14.9.4 Cache-Control: max-age this header can appear in both
     * requests and responses. If both are specified, the smaller of the two
     * takes priority.
     *
     * - RFC2616 14.21 Expires: if this request header exists in the cached
     * entity, and it's value is in the past, it has expired.
     *
     */

    /* This value comes from the client's initial request. */
    cc_req = apr_table_get(r->headers_in, "Cache-Control");
    pragma = apr_table_get(r->headers_in, "Pragma");

    ap_cache_control(r, &cache->control_in, cc_req, pragma, r->headers_in);

    if (cache->control_in.no_cache) {