cache_util.c

Apache官方在今天放出产品系列2.2的最新版本2.2.11的源码包 最流行的HTTP服务器软件之一

/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#define CORE_PRIVATE

#include "mod_cache.h"

#include <ap_provider.h>

/* -------------------------------------------------------------- */

extern module AP_MODULE_DECLARE_DATA cache_module;

/* Determine if "url" matches the hostname, scheme and port and path
 * in "filter". All but the path comparisons are case-insensitive.
 */
static int uri_meets_conditions(apr_uri_t filter, int pathlen, apr_uri_t url)
{
    /* Compare the hostnames */
    if(filter.hostname) {
        if (!url.hostname) {
            return 0;
        }
        else if (strcasecmp(filter.hostname, url.hostname)) {
            return 0;
        }
    }

    /* Compare the schemes */
    if(filter.scheme) {
        if (!url.scheme) {
            return 0;
        }
        else if (strcasecmp(filter.scheme, url.scheme)) {
            return 0;
        }
    }

    /* Compare the ports */
    if(filter.port_str) {
        if (url.port_str && filter.port != url.port) {
            return 0;
        }
        /* NOTE:  ap_port_of_scheme will return 0 if given NULL input */
        else if (filter.port != apr_uri_port_of_scheme(url.scheme)) {
            return 0;
        }
    }
    else if(url.port_str && filter.scheme) {
        if (apr_uri_port_of_scheme(filter.scheme) == url.port) {
            return 0;
        }
    }

    /* For HTTP caching purposes, an empty (NULL) path is equivalent to
     * a single "/" path. RFCs 3986/2396
     */
    if (!url.path) {
        if (*filter.path == '/' && pathlen == 1) {
            return 1;
        }
        else {
            return 0;
        }
    }

    /* Url has met all of the filter conditions so far, determine
     * if the paths match.
     */
    return !strncmp(filter.path, url.path, pathlen);
}

CACHE_DECLARE(cache_provider_list *)ap_cache_get_providers(request_rec *r,
                                                  cache_server_conf *conf,
                                                  apr_uri_t uri)
{
    cache_provider_list *providers = NULL;
    int i;

    /* loop through all the cacheenable entries */
    for (i = 0; i < conf->cacheenable->nelts; i++) {
        struct cache_enable *ent =
                                (struct cache_enable *)conf->cacheenable->elts;
        if (uri_meets_conditions(ent[i].url, ent[i].pathlen, uri)) {
            /* Fetch from global config and add to the list. */
            cache_provider *provider;
            provider = ap_lookup_provider(CACHE_PROVIDER_GROUP, ent[i].type,
                                          "0");
            if (!provider) {
                /* Log an error! */
            }
            else {
                cache_provider_list *newp;
                newp = apr_pcalloc(r->pool, sizeof(cache_provider_list));
                newp->provider_name = ent[i].type;
                newp->provider = provider;

                if (!providers) {
                    providers = newp;
                }
                else {
                    cache_provider_list *last = providers;

                    while (last->next) {
                        last = last->next;
                    }
                    last->next = newp;
                }
            }
        }
    }

    /* then loop through all the cachedisable entries
     * Looking for urls that contain the full cachedisable url and possibly
     * more.
     * This means we are disabling cachedisable url and below...
     */
    for (i = 0; i < conf->cachedisable->nelts; i++) {
        struct cache_disable *ent =
                               (struct cache_disable *)conf->cachedisable->elts;
        if (uri_meets_conditions(ent[i].url, ent[i].pathlen, uri)) {
            /* Stop searching now. */
            return NULL;
        }
    }

    return providers;
}


/* do a HTTP/1.1 age calculation */
CACHE_DECLARE(apr_int64_t) ap_cache_current_age(cache_info *info,
                                                const apr_time_t age_value,
                                                apr_time_t now)
{
    apr_time_t apparent_age, corrected_received_age, response_delay,
               corrected_initial_age, resident_time, current_age,
               age_value_usec;

    age_value_usec = apr_time_from_sec(age_value);

    /* Perform an HTTP/1.1 age calculation. (RFC2616 13.2.3) */

    apparent_age = MAX(0, info->response_time - info->date);
    corrected_received_age = MAX(apparent_age, age_value_usec);
    response_delay = info->response_time - info->request_time;
    corrected_initial_age = corrected_received_age + response_delay;
    resident_time = now - info->response_time;
    current_age = corrected_initial_age + resident_time;

    return apr_time_sec(current_age);
}

CACHE_DECLARE(int) ap_cache_check_freshness(cache_handle_t *h,
                                            request_rec *r)
{
    apr_int64_t age, maxage_req, maxage_cresp, maxage, smaxage, maxstale;
    apr_int64_t minfresh;
    const char *cc_cresp, *cc_req;
    const char *pragma;
    const char *agestr = NULL;
    const char *expstr = NULL;
    char *val;
    apr_time_t age_c = 0;
    cache_info *info = &(h->cache_obj->info);
    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
     * revalidate the request unconditionally, overriding any expiration
     * mechanism. It's equivalent to max-age=0,must-revalidate.
     *
     * - 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");

    if (ap_cache_liststr(NULL, pragma, "no-cache", NULL)
        || ap_cache_liststr(NULL, cc_req, "no-cache", NULL)) {

        if (!conf->ignorecachecontrol) {
            /* Treat as stale, causing revalidation */
            return 0;
        }

        ap_log_error(APLOG_MARK, APLOG_INFO, 0, r->server,
                     "Incoming request is asking for a uncached version of "
                     "%s, but we know better and are ignoring it",
                     r->unparsed_uri);
    }

    /* These come from the cached entity. */
    cc_cresp = apr_table_get(h->resp_hdrs, "Cache-Control");
    expstr = apr_table_get(h->resp_hdrs, "Expires");

    if (ap_cache_liststr(NULL, cc_cresp, "no-cache", NULL)) {
        /*
         * The cached entity contained Cache-Control: no-cache, so treat as
         * stale causing revalidation
         */
        return 0;
    }

    if ((agestr = apr_table_get(h->resp_hdrs, "Age"))) {
        age_c = apr_atoi64(agestr);
    }

    /* calculate age of object */
    age = ap_cache_current_age(info, age_c, r->request_time);

    /* extract s-maxage */
    if (cc_cresp && ap_cache_liststr(r->pool, cc_cresp, "s-maxage", &val)
        && val != NULL) {
        smaxage = apr_atoi64(val);
    }
    else {
        smaxage = -1;
    }

    /* extract max-age from request */
    if (!conf->ignorecachecontrol
        && cc_req && ap_cache_liststr(r->pool, cc_req, "max-age", &val)
        && val != NULL) {
        maxage_req = apr_atoi64(val);
    }
    else {
        maxage_req = -1;
    }

    /* extract max-age from response */
    if (cc_cresp && ap_cache_liststr(r->pool, cc_cresp, "max-age", &val)
        && val != NULL) {
        maxage_cresp = apr_atoi64(val);
    }
    else {
        maxage_cresp = -1;
    }

    /*
     * if both maxage request and response, the smaller one takes priority
     */
    if (maxage_req == -1) {
        maxage = maxage_cresp;
    }
    else if (maxage_cresp == -1) {
        maxage = maxage_req;
    }
    else {
        maxage = MIN(maxage_req, maxage_cresp);
    }

    /* extract max-stale */
    if (cc_req && ap_cache_liststr(r->pool, cc_req, "max-stale", &val)) {
        if(val != NULL) {
            maxstale = apr_atoi64(val);
        }
        else {
            /*
             * If no value is assigned to max-stale, then the client is willing
             * to accept a stale response of any age (RFC2616 14.9.3). We will
             * set it to one year in this case as this situation is somewhat
             * similar to a "never expires" Expires header (RFC2616 14.21)
             * which is set to a date one year from the time the response is
             * sent in this case.
             */
            maxstale = APR_INT64_C(86400*365);
        }
    }