Adding upstream version 2.4.38.upstream/2.4.38upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1344 insertions, 0 deletions

diff --git a/modules/cache/cache_util.c b/modules/cache/cache_util.c
new file mode 100644
index 0000000..aa04913
--- /dev/null
+++ b/modules/cache/cache_util.c
@@ -0,0 +1,1344 @@
+/* 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.
+ */
+
+#include "mod_cache.h"
+
+#include "cache_util.h"
+#include <ap_provider.h>
+
+APLOG_USE_MODULE(cache);
+
+/* -------------------------------------------------------------- */
+
+extern APR_OPTIONAL_FN_TYPE(ap_cache_generate_key) *cache_generate_key;
+
+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(const apr_uri_t *filter, const int pathlen,
+                                const apr_uri_t *url, const char *path)
+{
+    /* Scheme, hostname port and local part. The filter URI and the
+     * URI we test may have the following shapes:
+     *   /<path>
+     *   <scheme>[:://<hostname>[:<port>][/<path>]]
+     * That is, if there is no scheme then there must be only the path,
+     * and we check only the path; if there is a scheme, we check the
+     * scheme for equality, and then if present we match the hostname,
+     * and then if present match the port, and finally the path if any.
+     *
+     * Note that this means that "/<path>" only matches local paths,
+     * and to match proxied paths one *must* specify the scheme.
+     */
+
+    /* Is the filter is just for a local path or a proxy URI? */
+    if (!filter->scheme) {
+        if (url->scheme || url->hostname) {
+            return 0;
+        }
+    }
+    else {
+        /* The URI scheme must be present and identical except for case. */
+        if (!url->scheme || ap_cstr_casecmp(filter->scheme, url->scheme)) {
+            return 0;
+        }
+
+        /* If the filter hostname is null or empty it matches any hostname,
+         * if it begins with a "*" it matches the _end_ of the URI hostname
+         * excluding the "*", if it begins with a "." it matches the _end_
+         * of the URI * hostname including the ".", otherwise it must match
+         * the URI hostname exactly. */
+
+        if (filter->hostname && filter->hostname[0]) {
+            if (filter->hostname[0] == '.') {
+                const size_t fhostlen = strlen(filter->hostname);
+                const size_t uhostlen = url->hostname ? strlen(url->hostname) : 0;
+
+                if (fhostlen > uhostlen
+                    || (url->hostname
+                        && strcasecmp(filter->hostname,
+                                      url->hostname + uhostlen - fhostlen))) {
+                    return 0;
+                }
+            }
+            else if (filter->hostname[0] == '*') {
+                const size_t fhostlen = strlen(filter->hostname + 1);
+                const size_t uhostlen = url->hostname ? strlen(url->hostname) : 0;
+
+                if (fhostlen > uhostlen
+                    || (url->hostname
+                        && strcasecmp(filter->hostname + 1,
+                                      url->hostname + uhostlen - fhostlen))) {
+                    return 0;
+                }
+            }
+            else if (!url->hostname || strcasecmp(filter->hostname, url->hostname)) {
+                return 0;
+            }
+        }
+
+        /* If the filter port is empty it matches any URL port.
+         * If the filter or URL port are missing, or the URL port is
+         * empty, they default to the port for their scheme. */
+
+        if (!(filter->port_str && !filter->port_str[0])) {
+            /* NOTE:  ap_port_of_scheme will return 0 if given NULL input */
+            const unsigned fport = filter->port_str ? filter->port
+                    : apr_uri_port_of_scheme(filter->scheme);
+            const unsigned uport = (url->port_str && url->port_str[0])
+                    ? url->port : apr_uri_port_of_scheme(url->scheme);
+
+            if (fport != uport) {
+                return 0;
+            }
+        }
+    }
+
+    /* For HTTP caching purposes, an empty (NULL) path is equivalent to
+     * a single "/" path. RFCs 3986/2396
+     */
+    if (!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, path, pathlen);
+}
+
+int cache_use_early_url(request_rec *r)
+{
+    cache_server_conf *conf;
+
+    if (r->proxyreq == PROXYREQ_PROXY) {
+        return 1;
+    }
+
+    conf = ap_get_module_config(r->server->module_config, &cache_module);
+    if (conf->quick) {
+        return 1;
+    }
+
+    return 0;
+}
+
+static cache_provider_list *get_provider(request_rec *r, struct cache_enable *ent,
+        cache_provider_list *providers)
+{
+    /* Fetch from global config and add to the list. */
+    cache_provider *provider;
+    provider = ap_lookup_provider(CACHE_PROVIDER_GROUP, ent->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->type;
+        newp->provider = provider;
+
+        if (!providers) {
+            providers = newp;
+        }
+        else {
+            cache_provider_list *last = providers;
+
+            while (last->next) {
+                if (last->provider == provider) {
+                    return providers;
+                }
+                last = last->next;
+            }
+            if (last->provider == provider) {
+                return providers;
+            }
+            last->next = newp;
+        }
+    }
+
+    return providers;
+}
+
+cache_provider_list *cache_get_providers(request_rec *r,
+                                         cache_server_conf *conf)
+{
+    cache_dir_conf *dconf = ap_get_module_config(r->per_dir_config, &cache_module);
+    cache_provider_list *providers = NULL;
+    const char *path;
+    int i;
+
+    /* per directory cache disable */
+    if (dconf->disable) {
+        return NULL;
+    }
+
+    path = cache_use_early_url(r) ? r->parsed_uri.path : r->uri;
+
+    /* global cache disable */
+    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,
+                                 &r->parsed_uri, path)) {
+            /* Stop searching now. */
+            return NULL;
+        }
+    }
+
+    /* loop through all the per directory cacheenable entries */
+    for (i = 0; i < dconf->cacheenable->nelts; i++) {
+        struct cache_enable *ent =
+                                (struct cache_enable *)dconf->cacheenable->elts;
+        providers = get_provider(r, &ent[i], providers);
+    }
+
+    /* loop through all the global 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,
+                                 &r->parsed_uri, path)) {
+            providers = get_provider(r, &ent[i], providers);
+        }
+    }
+
+    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;
+
+    if (current_age < 0) {
+        current_age = 0;
+    }
+
+    return apr_time_sec(current_age);
+}
+
+/**
+ * Try obtain a cache wide lock on the given cache key.
+ *
+ * If we return APR_SUCCESS, we obtained the lock, and we are clear to
+ * proceed to the backend. If we return APR_EEXIST, then the lock is
+ * already locked, someone else has gone to refresh the backend data
+ * already, so we must return stale data with a warning in the mean
+ * time. If we return anything else, then something has gone pear
+ * shaped, and we allow the request through to the backend regardless.
+ *
+ * This lock is created from the request pool, meaning that should
+ * something go wrong and the lock isn't deleted on return of the
+ * request headers from the backend for whatever reason, at worst the
+ * lock will be cleaned up when the request dies or finishes.
+ *
+ * If something goes truly bananas and the lock isn't deleted when the
+ * request dies, the lock will be trashed when its max-age is reached,
+ * or when a request arrives containing a Cache-Control: no-cache. At
+ * no point is it possible for this lock to permanently deny access to
+ * the backend.
+ */
+apr_status_t cache_try_lock(cache_server_conf *conf, cache_request_rec *cache,
+        request_rec *r)
+{
+    apr_status_t status;
+    const char *lockname;
+    const char *path;
+    char dir[5];
+    apr_time_t now = apr_time_now();
+    apr_finfo_t finfo;
+    apr_file_t *lockfile;
+    void *dummy;
+
+    finfo.mtime = 0;
+
+    if (!conf || !conf->lock || !conf->lockpath) {
+        /* no locks configured, leave */
+        return APR_SUCCESS;
+    }
+
+    /* lock already obtained earlier? if so, success */
+    apr_pool_userdata_get(&dummy, CACHE_LOCKFILE_KEY, r->pool);
+    if (dummy) {
+        return APR_SUCCESS;
+    }
+
+    /* create the key if it doesn't exist */
+    if (!cache->key) {
+        cache_handle_t *h;
+        /*
+         * Try to use the key of a possible open but stale cache
+         * entry if we have one.
+         */
+        if (cache->handle != NULL) {
+            h = cache->handle;
+        }
+        else {
+            h = cache->stale_handle;
+        }
+        if ((h != NULL) &&
+            (h->cache_obj != NULL) &&
+            (h->cache_obj->key != NULL)) {
+            cache->key = apr_pstrdup(r->pool, h->cache_obj->key);
+        }
+        else {
+            cache_generate_key(r, r->pool, &cache->key);
+        }
+    }
+
+    /* create a hashed filename from the key, and save it for later */
+    lockname = ap_cache_generate_name(r->pool, 0, 0, cache->key);
+
+    /* lock files represent discrete just-went-stale URLs "in flight", so
+     * we support a simple two level directory structure, more is overkill.
+     */
+    dir[0] = '/';
+    dir[1] = lockname[0];
+    dir[2] = '/';
+    dir[3] = lockname[1];
+    dir[4] = 0;
+
+    /* make the directories */
+    path = apr_pstrcat(r->pool, conf->lockpath, dir, NULL);
+    if (APR_SUCCESS != (status = apr_dir_make_recursive(path,
+            APR_UREAD|APR_UWRITE|APR_UEXECUTE, r->pool))) {
+        ap_log_rerror(APLOG_MARK, APLOG_ERR, status, r, APLOGNO(00778)
+                "Could not create a cache lock directory: %s",
+                path);
+        return status;
+    }
+    lockname = apr_pstrcat(r->pool, path, "/", lockname, NULL);
+    apr_pool_userdata_set(lockname, CACHE_LOCKNAME_KEY, NULL, r->pool);
+
+    /* is an existing lock file too old? */
+    status = apr_stat(&finfo, lockname,
+                APR_FINFO_MTIME | APR_FINFO_NLINK, r->pool);
+    if (!(APR_STATUS_IS_ENOENT(status)) && APR_SUCCESS != status) {
+        ap_log_rerror(APLOG_MARK, APLOG_ERR, status, r, APLOGNO(00779)
+                "Could not stat a cache lock file: %s",
+                lockname);
+        return status;
+    }
+    if ((status == APR_SUCCESS) && (((now - finfo.mtime) > conf->lockmaxage)
+                                  || (now < finfo.mtime))) {
+        ap_log_rerror(APLOG_MARK, APLOG_INFO, status, r, APLOGNO(00780)
+                "Cache lock file for '%s' too old, removing: %s",
+                r->uri, lockname);
+        apr_file_remove(lockname, r->pool);
+    }
+
+    /* try obtain a lock on the file */
+    if (APR_SUCCESS == (status = apr_file_open(&lockfile, lockname,
+            APR_WRITE | APR_CREATE | APR_EXCL | APR_DELONCLOSE,
+            APR_UREAD | APR_UWRITE, r->pool))) {
+        apr_pool_userdata_set(lockfile, CACHE_LOCKFILE_KEY, NULL, r->pool);
+    }
+    return status;
+
+}
+
+/**
+ * Remove the cache lock, if present.
+ *
+ * First, try to close the file handle, whose delete-on-close should
+ * kill the file. Otherwise, just delete the file by name.
+ *
+ * If no lock name has yet been calculated, do the calculation of the
+ * lock name first before trying to delete the file.
+ *
+ * If an optional bucket brigade is passed, the lock will only be
+ * removed if the bucket brigade contains an EOS bucket.
+ */
+apr_status_t cache_remove_lock(cache_server_conf *conf,
+        cache_request_rec *cache, request_rec *r, apr_bucket_brigade *bb)
+{
+    void *dummy;
+    const char *lockname;
+
+    if (!conf || !conf->lock || !conf->lockpath) {
+        /* no locks configured, leave */
+        return APR_SUCCESS;
+    }
+    if (bb) {
+        apr_bucket *e;
+        int eos_found = 0;
+        for (e = APR_BRIGADE_FIRST(bb);
+             e != APR_BRIGADE_SENTINEL(bb);
+             e = APR_BUCKET_NEXT(e))
+        {
+            if (APR_BUCKET_IS_EOS(e)) {
+                eos_found = 1;
+                break;
+            }
+        }
+        if (!eos_found) {
+            /* no eos found in brigade, don't delete anything just yet,
+             * we are not done.
+             */
+            return APR_SUCCESS;
+        }
+    }
+    apr_pool_userdata_get(&dummy, CACHE_LOCKFILE_KEY, r->pool);
+    if (dummy) {
+        return apr_file_close((apr_file_t *)dummy);
+    }
+    apr_pool_userdata_get(&dummy, CACHE_LOCKNAME_KEY, r->pool);
+    lockname = (const char *)dummy;
+    if (!lockname) {
+        char dir[5];
+
+        /* create the key if it doesn't exist */
+        if (!cache->key) {
+            cache_generate_key(r, r->pool, &cache->key);
+        }
+
+        /* create a hashed filename from the key, and save it for later */
+        lockname = ap_cache_generate_name(r->pool, 0, 0, cache->key);
+
+        /* lock files represent discrete just-went-stale URLs "in flight", so
+         * we support a simple two level directory structure, more is overkill.
+         */
+        dir[0] = '/';
+        dir[1] = lockname[0];
+        dir[2] = '/';
+        dir[3] = lockname[1];
+        dir[4] = 0;
+
+        lockname = apr_pstrcat(r->pool, conf->lockpath, dir, "/", lockname, NULL);
+    }
+    return apr_file_remove(lockname, r->pool);
+}
+
+int ap_cache_check_no_cache(cache_request_rec *cache, request_rec *r)
+{
+
+    cache_server_conf *conf =
+      (cache_server_conf *)ap_get_module_config(r->server->module_config,
+                                                &cache_module);
+
+    /*
+     * At this point, we may have data cached, but the request may have
+     * specified that cached data may not be used in a response.
+     *
+     * This is covered under RFC2616 section 14.9.4 (Cache Revalidation and
+     * Reload Controls).
+     *
+     * - RFC2616 14.9.4 End to end reload, Cache-Control: no-cache, or Pragma:
+     * no-cache. The server MUST NOT use a cached copy when responding to such
+     * a request.
+     */
+
+    /* This value comes from the client's initial request. */
+    if (!cache->control_in.parsed) {
+        const char *cc_req = cache_table_getm(r->pool, r->headers_in,
+                "Cache-Control");
+        const char *pragma = cache_table_getm(r->pool, r->headers_in, "Pragma");
+        ap_cache_control(r, &cache->control_in, cc_req, pragma, r->headers_in);
+    }
+
+    if (cache->control_in.no_cache) {
+
+        if (!conf->ignorecachecontrol) {
+            return 0;
+        }
+        else {
+            ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, r, APLOGNO(02657)
+                    "Incoming request is asking for an uncached version of "
+                    "%s, but we have been configured to ignore it and serve "
+                    "cached content anyway", r->unparsed_uri);
+        }
+    }
+
+    return 1;
+}
+
+int ap_cache_check_no_store(cache_request_rec *cache, request_rec *r)
+{
+
+    cache_server_conf *conf =
+      (cache_server_conf *)ap_get_module_config(r->server->module_config,
+                                                &cache_module);
+
+    /*
+     * At this point, we may have data cached, but the request may have
+     * specified that cached data may not be used in a response.
+     *
+     * - RFC2616 14.9.2 What May be Stored by Caches. If Cache-Control:
+     * no-store arrives, do not serve from or store to the cache.
+     */
+
+    /* This value comes from the client's initial request. */
+    if (!cache->control_in.parsed) {
+        const char *cc_req = cache_table_getm(r->pool, r->headers_in,
+                "Cache-Control");
+        const char *pragma = cache_table_getm(r->pool, r->headers_in, "Pragma");
+        ap_cache_control(r, &cache->control_in, cc_req, pragma, r->headers_in);
+    }
+
+    if (cache->control_in.no_store) {
+
+        if (!conf->ignorecachecontrol) {
+            /* We're not allowed to serve a cached copy */
+            return 0;
+        }
+        else {
+            ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, r, APLOGNO(02658)
+                    "Incoming request is asking for a no-store version of "
+                    "%s, but we have been configured to ignore it and serve "
+                    "cached content anyway", r->unparsed_uri);
+        }
+    }
+
+    return 1;
+}
+
+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) {
+
+        if (!conf->ignorecachecontrol) {
+            /* Treat as stale, causing revalidation */
+            return 0;
+        }
+
+        ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, r, APLOGNO(00781)
+                "Incoming request is asking for a uncached version of "
+                "%s, but we have been configured to ignore it and "
+                "serve a cached response anyway",
+                r->unparsed_uri);
+    }
+
+    /* These come from the cached entity. */
+    if (h->cache_obj->info.control.no_cache
+            || h->cache_obj->info.control.invalidated) {
+        /*
+         * The cached entity contained Cache-Control: no-cache, or a
+         * no-cache with a header present, or a private with a header
+         * present, or the cached entity has been invalidated in the
+         * past, so treat as stale causing revalidation.
+         */
+        return 0;
+    }
+
+    if ((agestr = apr_table_get(h->resp_hdrs, "Age"))) {
+        char *endp;
+        apr_off_t offt;
+        if (!apr_strtoff(&offt, agestr, &endp, 10)
+                && endp > agestr && !*endp) {
+            age_c = offt;
+        }
+    }
+
+    /* calculate age of object */
+    age = ap_cache_current_age(info, age_c, r->request_time);
+
+    /* extract s-maxage */
+    smaxage = h->cache_obj->info.control.s_maxage_value;
+
+    /* extract max-age from request */
+    maxage_req = -1;
+    if (!conf->ignorecachecontrol) {
+        maxage_req = cache->control_in.max_age_value;
+    }
+
+    /*
+     * extract max-age from response, if both s-maxage and max-age, s-maxage
+     * takes priority
+     */
+    if (smaxage != -1) {
+        maxage_cresp = smaxage;
+    }
+    else {
+        maxage_cresp = h->cache_obj->info.control.max_age_value;
+    }
+
+    /*
+     * 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 (cache->control_in.max_stale) {
+        if (cache->control_in.max_stale_value != -1) {
+            maxstale = cache->control_in.max_stale_value;
+        }
+        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);
+        }
+    }
+    else {
+        maxstale = 0;
+    }
+
+    /* extract min-fresh */
+    if (!conf->ignorecachecontrol && cache->control_in.min_fresh) {
+        minfresh = cache->control_in.min_fresh_value;
+    }
+    else {
+        minfresh = 0;
+    }
+
+    /* override maxstale if must-revalidate, proxy-revalidate or s-maxage */
+    if (maxstale && (h->cache_obj->info.control.must_revalidate
+            || h->cache_obj->info.control.proxy_revalidate || smaxage != -1)) {
+        maxstale = 0;
+    }
+
+    /* handle expiration */
+    if (((maxage != -1) && (age < (maxage + maxstale - minfresh))) ||
+        ((smaxage == -1) && (maxage == -1) &&
+         (info->expire != APR_DATE_BAD) &&
+         (age < (apr_time_sec(info->expire - info->date) + maxstale - minfresh)))) {
+
+        warn_head = apr_table_get(h->resp_hdrs, "Warning");
+
+        /* it's fresh darlings... */
+        /* set age header on response */
+        apr_table_set(h->resp_hdrs, "Age",
+                      apr_psprintf(r->pool, "%lu", (unsigned long)age));
+
+        /* add warning if maxstale overrode freshness calculation */
+        if (!(((maxage != -1) && age < maxage) ||
+              (info->expire != APR_DATE_BAD &&
+               (apr_time_sec(info->expire - info->date)) > age))) {
+            /* make sure we don't stomp on a previous warning */
+            if ((warn_head == NULL) ||
+                ((warn_head != NULL) && (ap_strstr_c(warn_head, "110") == NULL))) {
+                apr_table_mergen(h->resp_hdrs, "Warning",
+                                 "110 Response is stale");
+            }
+        }
+
+        /*
+         * If none of Expires, Cache-Control: max-age, or Cache-Control:
+         * s-maxage appears in the response, and the response header age
+         * calculated is more than 24 hours add the warning 113
+         */
+        if ((maxage_cresp == -1) && (smaxage == -1) && (apr_table_get(
+                h->resp_hdrs, "Expires") == NULL) && (age > 86400)) {
+
+            /* Make sure we don't stomp on a previous warning, and don't dup
+             * a 113 marning that is already present. Also, make sure to add
+             * the new warning to the correct *headers_out location.
+             */
+            if ((warn_head == NULL) ||
+                ((warn_head != NULL) && (ap_strstr_c(warn_head, "113") == NULL))) {
+                apr_table_mergen(h->resp_hdrs, "Warning",
+                                 "113 Heuristic expiration");
+            }
+        }
+        return 1;    /* Cache object is fresh (enough) */
+    }
+
+    /*
+     * At this point we are stale, but: if we are under load, we may let
+     * a significant number of stale requests through before the first
+     * stale request successfully revalidates itself, causing a sudden
+     * unexpected thundering herd which in turn brings angst and drama.
+     *
+     * So.
+     *
+     * We want the first stale request to go through as normal. But the
+     * second and subsequent request, we must pretend to be fresh until
+     * the first request comes back with either new content or confirmation
+     * that the stale content is still fresh.
+     *
+     * To achieve this, we create a very simple file based lock based on
+     * the key of the cached object. We attempt to open the lock file with
+     * exclusive write access. If we succeed, woohoo! we're first, and we
+     * follow the stale path to the backend server. If we fail, oh well,
+     * we follow the fresh path, and avoid being a thundering herd.
+     *
+     * The lock lives only as long as the stale request that went on ahead.
+     * If the request succeeds, the lock is deleted. If the request fails,
+     * the lock is deleted, and another request gets to make a new lock
+     * and try again.
+     *
+     * At any time, a request marked "no-cache" will force a refresh,
+     * ignoring the lock, ensuring an extended lockout is impossible.
+     *
+     * A lock that exceeds a maximum age will be deleted, and another
+     * request gets to make a new lock and try again.
+     */
+    status = cache_try_lock(conf, cache, r);
+    if (APR_SUCCESS == status) {
+        /* we obtained a lock, follow the stale path */
+        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(00782)
+                "Cache lock obtained for stale cached URL, "
+                "revalidating entry: %s",
+                r->unparsed_uri);
+        return 0;
+    }
+    else if (APR_STATUS_IS_EEXIST(status)) {
+        /* lock already exists, return stale data anyway, with a warning */
+        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, status, r, APLOGNO(00783)
+                "Cache already locked for stale cached URL, "
+                "pretend it is fresh: %s",
+                r->unparsed_uri);
+
+        /* make sure we don't stomp on a previous warning */
+        warn_head = apr_table_get(h->resp_hdrs, "Warning");
+        if ((warn_head == NULL) ||
+            ((warn_head != NULL) && (ap_strstr_c(warn_head, "110") == NULL))) {
+            apr_table_mergen(h->resp_hdrs, "Warning",
+                             "110 Response is stale");
+        }
+
+        return 1;
+    }
+    else {
+        /* some other error occurred, just treat the object as stale */
+        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, status, r, APLOGNO(00784)
+                "Attempt to obtain a cache lock for stale "
+                "cached URL failed, revalidating entry anyway: %s",
+                r->unparsed_uri);
+        return 0;
+    }
+
+}
+
+/* return each comma separated token, one at a time */
+CACHE_DECLARE(const char *)ap_cache_tokstr(apr_pool_t *p, const char *list,
+                                           const char **str)
+{
+    apr_size_t i;
+    const char *s;
+
+    s = ap_strchr_c(list, ',');
+    if (s != NULL) {
+        i = s - list;
+        do
+            s++;
+        while (apr_isspace(*s))
+            ; /* noop */
+    }
+    else
+        i = strlen(list);
+
+    while (i > 0 && apr_isspace(list[i - 1]))
+        i--;
+
+    *str = s;
+    if (i)
+        return apr_pstrmemdup(p, list, i);
+    else
+        return NULL;
+}
+
+/*
+ * Converts apr_time_t expressed as hex digits to
+ * a true apr_time_t.
+ */
+CACHE_DECLARE(apr_time_t) ap_cache_hex2usec(const char *x)
+{
+    int i, ch;
+    apr_time_t j;
+    for (i = 0, j = 0; i < sizeof(j) * 2; i++) {
+        ch = x[i];
+        j <<= 4;
+        if (apr_isdigit(ch))
+            j |= ch - '0';
+        else if (apr_isupper(ch))
+            j |= ch - ('A' - 10);
+        else
+            j |= ch - ('a' - 10);
+    }
+    return j;
+}
+
+/*
+ * Converts apr_time_t to apr_time_t expressed as hex digits.
+ */
+CACHE_DECLARE(void) ap_cache_usec2hex(apr_time_t j, char *y)
+{
+    int i, ch;
+
+    for (i = (sizeof(j) * 2)-1; i >= 0; i--) {
+        ch = (int)(j & 0xF);
+        j >>= 4;
+        if (ch >= 10)
+            y[i] = ch + ('A' - 10);
+        else
+            y[i] = ch + '0';
+    }
+    y[sizeof(j) * 2] = '\0';
+}
+
+static void cache_hash(const char *it, char *val, int ndepth, int nlength)
+{
+    apr_md5_ctx_t context;
+    unsigned char digest[16];
+    char tmp[22];
+    int i, k, d;
+    unsigned int x;
+    static const char enc_table[64] =
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_@";
+
+    apr_md5_init(&context);
+    apr_md5_update(&context, (const unsigned char *) it, strlen(it));
+    apr_md5_final(digest, &context);
+
+    /* encode 128 bits as 22 characters, using a modified uuencoding
+     * the encoding is 3 bytes -> 4 characters* i.e. 128 bits is
+     * 5 x 3 bytes + 1 byte -> 5 * 4 characters + 2 characters
+     */
+    for (i = 0, k = 0; i < 15; i += 3) {
+        x = (digest[i] << 16) | (digest[i + 1] << 8) | digest[i + 2];
+        tmp[k++] = enc_table[x >> 18];
+        tmp[k++] = enc_table[(x >> 12) & 0x3f];
+        tmp[k++] = enc_table[(x >> 6) & 0x3f];
+        tmp[k++] = enc_table[x & 0x3f];
+    }
+
+    /* one byte left */
+    x = digest[15];
+    tmp[k++] = enc_table[x >> 2];    /* use up 6 bits */
+    tmp[k++] = enc_table[(x << 4) & 0x3f];
+
+    /* now split into directory levels */
+    for (i = k = d = 0; d < ndepth; ++d) {
+        memcpy(&val[i], &tmp[k], nlength);
+        k += nlength;
+        val[i + nlength] = '/';
+        i += nlength + 1;
+    }
+    memcpy(&val[i], &tmp[k], 22 - k);
+    val[i + 22 - k] = '\0';
+}
+
+CACHE_DECLARE(char *)ap_cache_generate_name(apr_pool_t *p, int dirlevels,
+                                            int dirlength, const char *name)
+{
+    char hashfile[66];
+    cache_hash(name, hashfile, dirlevels, dirlength);
+    return apr_pstrdup(p, hashfile);
+}
+
+/**
+ * String tokenizer that ignores separator characters within quoted strings
+ * and escaped characters, as per RFC2616 section 2.2.
+ */
+char *cache_strqtok(char *str, const char *sep, char **last)
+{
+    char *token;
+    int quoted = 0;
+
+    if (!str) {         /* subsequent call */
+        str = *last;    /* start where we left off */
+    }
+
+    if (!str) {         /* no more tokens */
+        return NULL;
+    }
+
+    /* skip characters in sep (will terminate at '\0') */
+    while (*str && ap_strchr_c(sep, *str)) {
+        ++str;
+    }
+
+    if (!*str) {        /* no more tokens */
+        return NULL;
+    }
+
+    token = str;
+
+    /* skip valid token characters to terminate token and
+     * prepare for the next call (will terminate at '\0)
+     * on the way, ignore all quoted strings, and within
+     * quoted strings, escaped characters.
+     */
+    *last = token;
+    while (**last) {
+        if (!quoted) {
+            if (**last == '\"' && !ap_strchr_c(sep, '\"')) {
+                quoted = 1;
+                ++*last;
+            }
+            else if (!ap_strchr_c(sep, **last)) {
+                ++*last;
+            }
+            else {
+                break;
+            }
+        }
+        else {
+            if (**last == '\"') {
+                quoted = 0;
+                ++*last;
+            }
+            else if (**last == '\\') {
+                ++*last;
+                if (**last) {
+                    ++*last;
+                }
+            }
+            else {
+                ++*last;
+            }
+        }
+    }
+
+    if (**last) {
+        **last = '\0';
+        ++*last;
+    }
+
+    return token;
+}
+
+/**
+ * Parse the Cache-Control and Pragma headers in one go, marking
+ * which tokens appear within the header. Populate the structure
+ * passed in.
+ */
+int ap_cache_control(request_rec *r, cache_control_t *cc,
+        const char *cc_header, const char *pragma_header, apr_table_t *headers)
+{
+    char *last;
+
+    if (cc->parsed) {
+        return cc->cache_control || cc->pragma;
+    }
+
+    cc->parsed = 1;
+    cc->max_age_value = -1;
+    cc->max_stale_value = -1;
+    cc->min_fresh_value = -1;
+    cc->s_maxage_value = -1;
+
+    if (pragma_header) {
+        char *header = apr_pstrdup(r->pool, pragma_header);
+        const char *token = cache_strqtok(header, CACHE_SEPARATOR, &last);
+        while (token) {
+            if (!ap_cstr_casecmp(token, "no-cache")) {
+                cc->no_cache = 1;
+            }
+            token = cache_strqtok(NULL, CACHE_SEPARATOR, &last);
+        }
+        cc->pragma = 1;
+    }
+
+    if (cc_header) {
+        char *endp;
+        apr_off_t offt;
+        char *header = apr_pstrdup(r->pool, cc_header);
+        const char *token = cache_strqtok(header, CACHE_SEPARATOR, &last);
+        while (token) {
+            switch (token[0]) {
+            case 'n':
+            case 'N': {
+                if (!ap_cstr_casecmpn(token, "no-cache", 8)) {
+                    if (token[8] == '=') {
+                        cc->no_cache_header = 1;
+                    }
+                    else if (!token[8]) {
+                        cc->no_cache = 1;
+                    }
+                }
+                else if (!ap_cstr_casecmp(token, "no-store")) {
+                    cc->no_store = 1;
+                }
+                else if (!ap_cstr_casecmp(token, "no-transform")) {
+                    cc->no_transform = 1;
+                }
+                break;
+            }
+            case 'm':
+            case 'M': {
+                if (!ap_cstr_casecmpn(token, "max-age", 7)) {
+                    if (token[7] == '='
+                            && !apr_strtoff(&offt, token + 8, &endp, 10)
+                            && endp > token + 8 && !*endp) {
+                        cc->max_age = 1;
+                        cc->max_age_value = offt;
+                    }
+                }
+                else if (!ap_cstr_casecmp(token, "must-revalidate")) {
+                    cc->must_revalidate = 1;
+                }
+                else if (!ap_cstr_casecmpn(token, "max-stale", 9)) {
+                    if (token[9] == '='
+                            && !apr_strtoff(&offt, token + 10, &endp, 10)
+                            && endp > token + 10 && !*endp) {
+                        cc->max_stale = 1;
+                        cc->max_stale_value = offt;
+                    }
+                    else if (!token[9]) {
+                        cc->max_stale = 1;
+                        cc->max_stale_value = -1;
+                    }
+                }
+                else if (!ap_cstr_casecmpn(token, "min-fresh", 9)) {
+                    if (token[9] == '='
+                            && !apr_strtoff(&offt, token + 10, &endp, 10)
+                            && endp > token + 10 && !*endp) {
+                        cc->min_fresh = 1;
+                        cc->min_fresh_value = offt;
+                    }
+                }
+                break;
+            }
+            case 'o':
+            case 'O': {
+                if (!ap_cstr_casecmp(token, "only-if-cached")) {
+                    cc->only_if_cached = 1;
+                }
+                break;
+            }
+            case 'p':
+            case 'P': {
+                if (!ap_cstr_casecmp(token, "public")) {
+                    cc->public = 1;
+                }
+                else if (!ap_cstr_casecmpn(token, "private", 7)) {
+                    if (token[7] == '=') {
+                        cc->private_header = 1;
+                    }
+                    else if (!token[7]) {
+                        cc->private = 1;
+                    }
+                }
+                else if (!ap_cstr_casecmp(token, "proxy-revalidate")) {
+                    cc->proxy_revalidate = 1;
+                }
+                break;
+            }
+            case 's':
+            case 'S': {
+                if (!ap_cstr_casecmpn(token, "s-maxage", 8)) {
+                    if (token[8] == '='
+                            && !apr_strtoff(&offt, token + 9, &endp, 10)
+                            && endp > token + 9 && !*endp) {
+                        cc->s_maxage = 1;
+                        cc->s_maxage_value = offt;
+                    }
+                }
+                break;
+            }
+            }
+            token = cache_strqtok(NULL, CACHE_SEPARATOR, &last);
+        }
+        cc->cache_control = 1;
+    }
+
+    return (cc_header != NULL || pragma_header != NULL);
+}
+
+/**
+ * Parse the Cache-Control, identifying and removing headers that
+ * exist as tokens after the no-cache and private tokens.
+ */
+static int cache_control_remove(request_rec *r, const char *cc_header,
+        apr_table_t *headers)
+{
+    char *last, *slast;
+    int found = 0;
+
+    if (cc_header) {
+        char *header = apr_pstrdup(r->pool, cc_header);
+        char *token = cache_strqtok(header, CACHE_SEPARATOR, &last);
+        while (token) {
+            switch (token[0]) {
+            case 'n':
+            case 'N': {
+                if (!ap_cstr_casecmpn(token, "no-cache", 8)) {
+                    if (token[8] == '=') {
+                        const char *header = cache_strqtok(token + 9,
+                                CACHE_SEPARATOR "\"", &slast);
+                        while (header) {
+                            apr_table_unset(headers, header);
+                            header = cache_strqtok(NULL, CACHE_SEPARATOR "\"",
+                                    &slast);
+                        }
+                        found = 1;
+                    }
+                }
+                break;
+            }
+            case 'p':
+            case 'P': {
+                if (!ap_cstr_casecmpn(token, "private", 7)) {
+                    if (token[7] == '=') {
+                        const char *header = cache_strqtok(token + 8,
+                                CACHE_SEPARATOR "\"", &slast);
+                        while (header) {
+                            apr_table_unset(headers, header);
+                            header = cache_strqtok(NULL, CACHE_SEPARATOR "\"",
+                                    &slast);
+                        }
+                        found = 1;
+                    }
+                }
+                break;
+            }
+            }
+            token = cache_strqtok(NULL, CACHE_SEPARATOR, &last);
+        }
+    }
+
+    return found;
+}
+
+/*
+ * Create a new table consisting of those elements from an
+ * headers table that are allowed to be stored in a cache.
+ */
+CACHE_DECLARE(apr_table_t *)ap_cache_cacheable_headers(apr_pool_t *pool,
+                                                        apr_table_t *t,
+                                                        server_rec *s)
+{
+    cache_server_conf *conf;
+    char **header;
+    int i;
+    apr_table_t *headers_out;
+
+    /* Short circuit the common case that there are not
+     * (yet) any headers populated.
+     */
+    if (t == NULL) {
+        return apr_table_make(pool, 10);
+    };
+
+    /* Make a copy of the headers, and remove from
+     * the copy any hop-by-hop headers, as defined in Section
+     * 13.5.1 of RFC 2616
+     */
+    headers_out = apr_table_copy(pool, t);
+
+    apr_table_unset(headers_out, "Connection");
+    apr_table_unset(headers_out, "Keep-Alive");
+    apr_table_unset(headers_out, "Proxy-Authenticate");
+    apr_table_unset(headers_out, "Proxy-Authorization");
+    apr_table_unset(headers_out, "TE");
+    apr_table_unset(headers_out, "Trailers");
+    apr_table_unset(headers_out, "Transfer-Encoding");
+    apr_table_unset(headers_out, "Upgrade");
+
+    conf = (cache_server_conf *)ap_get_module_config(s->module_config,
+                                                     &cache_module);
+
+    /* Remove the user defined headers set with CacheIgnoreHeaders.
+     * This may break RFC 2616 compliance on behalf of the administrator.
+     */
+    header = (char **)conf->ignore_headers->elts;
+    for (i = 0; i < conf->ignore_headers->nelts; i++) {
+        apr_table_unset(headers_out, header[i]);
+    }
+    return headers_out;
+}
+
+/*
+ * Create a new table consisting of those elements from an input
+ * headers table that are allowed to be stored in a cache.
+ */
+CACHE_DECLARE(apr_table_t *)ap_cache_cacheable_headers_in(request_rec *r)
+{
+    return ap_cache_cacheable_headers(r->pool, r->headers_in, r->server);
+}
+
+/*
+ * Create a new table consisting of those elements from an output
+ * headers table that are allowed to be stored in a cache;
+ * ensure there is a content type and capture any errors.
+ */
+CACHE_DECLARE(apr_table_t *)ap_cache_cacheable_headers_out(request_rec *r)
+{
+    apr_table_t *headers_out;
+
+    headers_out = ap_cache_cacheable_headers(r->pool,
+                                             cache_merge_headers_out(r),
+                                             r->server);
+
+    cache_control_remove(r,
+            cache_table_getm(r->pool, headers_out, "Cache-Control"),
+            headers_out);
+
+    return headers_out;
+}
+
+apr_table_t *cache_merge_headers_out(request_rec *r)
+{
+    apr_table_t *headers_out;
+
+    headers_out = apr_table_overlay(r->pool, r->headers_out,
+                                    r->err_headers_out);
+
+    if (r->content_type
+            && !apr_table_get(headers_out, "Content-Type")) {
+        const char *ctype = ap_make_content_type(r, r->content_type);
+        if (ctype) {
+            apr_table_setn(headers_out, "Content-Type", ctype);
+        }
+    }
+
+    if (r->content_encoding
+            && !apr_table_get(headers_out, "Content-Encoding")) {
+        apr_table_setn(headers_out, "Content-Encoding",
+                       r->content_encoding);
+    }
+
+    return headers_out;
+}
+
+typedef struct
+{
+    apr_pool_t *p;
+    const char *first;
+    apr_array_header_t *merged;
+} cache_table_getm_t;
+
+static int cache_table_getm_do(void *v, const char *key, const char *val)
+{
+    cache_table_getm_t *state = (cache_table_getm_t *) v;
+
+    if (!state->first) {
+        /**
+         * The most common case is a single header, and this is covered by
+         * a fast path that doesn't allocate any memory. On the second and
+         * subsequent header, an array is created and the array concatenated
+         * together to form the final value.
+         */
+        state->first = val;
+    }
+    else {
+        const char **elt;
+        if (!state->merged) {
+            state->merged = apr_array_make(state->p, 10, sizeof(const char *));
+            elt = apr_array_push(state->merged);
+            *elt = state->first;
+        }
+        elt = apr_array_push(state->merged);
+        *elt = val;
+    }
+    return 1;
+}
+
+const char *cache_table_getm(apr_pool_t *p, const apr_table_t *t,
+        const char *key)
+{
+    cache_table_getm_t state;
+
+    state.p = p;
+    state.first = NULL;
+    state.merged = NULL;
+
+    apr_table_do(cache_table_getm_do, &state, t, key, NULL);
+
+    if (!state.first) {
+        return NULL;
+    }
+    else if (!state.merged) {
+        return state.first;
+    }
+    else {
+        return apr_array_pstrcat(p, state.merged, ',');
+    }
+}