rlm_cache_rbtree.c

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/*
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or (at
 *   your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/**
 * $Id: bb6fa3eb41f7f54926f74807f05be7ea3a4a51f2 $
 * @file rlm_cache_rbtree.c
 * @brief Simple rbtree based cache.
 *
 * @copyright 2014 The FreeRADIUS server project
 */
#include <freeradius-devel/server/base.h>
#include <freeradius-devel/util/debug.h>
#include "../../rlm_cache.h"
 
typedef struct {
        fr_rb_tree_t                    *cache;         //!< Tree for looking up cache keys.
        fr_heap_t                       *heap;          //!< For managing entry expiry.
 
        pthread_mutex_t                 mutex;          //!< Protect the tree from multiple readers/writers.
} rlm_cache_rbtree_mutable_t;
 
typedef struct {
        rlm_cache_rbtree_mutable_t      *mutable;       //!< Mutable instance data.
} rlm_cache_rbtree_t;
 
typedef struct {
        rlm_cache_entry_t               fields;         //!< Entry data.
 
        fr_rb_node_t                    node;           //!< Entry used for lookups.
        fr_heap_index_t                 heap_id;        //!< Offset used for expiry heap.
} rlm_cache_rb_entry_t;
 
/** Compare two entries by key
 *
 * There may only be one entry with the same key.
 */
static int8_t cache_entry_cmp(void const *one, void const *two)
{
        rlm_cache_entry_t const *a = one, *b = two;
 
        return MEMCMP_FIELDS(a, b, key.vb_strvalue, key.vb_length);
}
 
/** Compare two entries by expiry time
 *
 * There may be multiple entries with the same expiry time.
 */
static int8_t cache_heap_cmp(void const *one, void const *two)
{
        rlm_cache_entry_t const *a = one, *b = two;
 
        return fr_unix_time_cmp(a->expires, b->expires);
}
 
/** Custom allocation function for the driver
 *
 * Allows allocation of cache entry structures with additional fields.
 *
 * @copydetails cache_entry_alloc_t
 */
static rlm_cache_entry_t *cache_entry_alloc(UNUSED rlm_cache_config_t const *config, UNUSED void *instance,
                                            request_t *request)
{
        rlm_cache_rb_entry_t *c;
 
        c = talloc_zero(NULL, rlm_cache_rb_entry_t);
        if (!c) {
                RERROR("Failed allocating cache entry");
                return NULL;
        }
 
        return (rlm_cache_entry_t *)c;
}
 
/** Locate a cache entry
 *
 * @note handle not used except for sanity checks.
 *
 * @copydetails cache_entry_find_t
 */
static cache_status_t cache_entry_find(rlm_cache_entry_t **out,
                                       UNUSED rlm_cache_config_t const *config, void *instance,
                                       request_t *request, UNUSED void *handle, fr_value_box_t const *key)
{
        rlm_cache_rbtree_t *driver = talloc_get_type_abort(instance, rlm_cache_rbtree_t);
        rlm_cache_rbtree_mutable_t *mutable = driver->mutable;
        rlm_cache_entry_t find = {};
        int i;
        rlm_cache_entry_t *c;
 
        fr_assert(mutable->cache);
 
        /*
         *      Clear out old entries
         */
        for (i = 0; i < 3; i++) {
                c = fr_heap_peek(mutable->heap);
                if (!c) break;
 
                if (fr_unix_time_gt(c->expires, fr_time_to_unix_time(request->packet->timestamp))) break;
 
                fr_heap_extract(&mutable->heap, c);
                fr_rb_delete(mutable->cache, c);
                talloc_free(c);
        }
 
        fr_value_box_copy_shallow(NULL, &find.key, key);
 
        /*
         *      Is there an entry for this key?
         */
        c = fr_rb_find(mutable->cache, &find);
        if (!c) {
                *out = NULL;
                return CACHE_MISS;
        }
        *out = c;
 
        return CACHE_OK;
}
 
/** Free an entry and remove it from the data store
 *
 * @note handle not used except for sanity checks.
 *
 * @copydetails cache_entry_expire_t
 */
static cache_status_t cache_entry_expire(UNUSED rlm_cache_config_t const *config, void *instance,
                                         request_t *request, UNUSED void *handle,
                                         fr_value_box_t const *key)
{
        rlm_cache_rbtree_t *driver = talloc_get_type_abort(instance, rlm_cache_rbtree_t);
        rlm_cache_entry_t find = {};
        rlm_cache_entry_t *c;
 
        if (!request) return CACHE_ERROR;
 
        fr_value_box_copy_shallow(NULL, &find.key, key);
 
        c = fr_rb_find(driver->mutable->cache, &find);
        if (!c) return CACHE_MISS;
 
        fr_heap_extract(&driver->mutable->heap, c);
        fr_rb_delete(driver->mutable->cache, c);
        talloc_free(c);
 
        return CACHE_OK;
}
 
/** Insert a new entry into the data store
 *
 * @note handle not used except for sanity checks.
 *
 * @copydetails cache_entry_insert_t
 */
static cache_status_t cache_entry_insert(rlm_cache_config_t const *config, void *instance,
                                         request_t *request, void *handle,
                                         rlm_cache_entry_t const *c)
{
        cache_status_t status;
 
        rlm_cache_rbtree_t *driver = talloc_get_type_abort(instance, rlm_cache_rbtree_t);
 
        fr_assert(handle == request);
 
        if (!request) return CACHE_ERROR;
 
        /*
         *      Allow overwriting
         */
        if (!fr_rb_insert(driver->mutable->cache, c)) {
                status = cache_entry_expire(config, instance, request, handle, &c->key);
                if ((status != CACHE_OK) && !fr_cond_assert(0)) return CACHE_ERROR;
 
                if (!fr_rb_insert(driver->mutable->cache, c)) {
                        RERROR("Failed adding entry");
 
                        return CACHE_ERROR;
                }
        }
 
        if (fr_heap_insert(&driver->mutable->heap, UNCONST(rlm_cache_entry_t *, c)) < 0) {
                fr_rb_delete(driver->mutable->cache, c);
                RERROR("Failed adding entry to expiry heap");
 
                return CACHE_ERROR;
        }
 
        return CACHE_OK;
}
 
/** Update the TTL of an entry
 *
 * @note handle not used except for sanity checks.
 *
 * @copydetails cache_entry_set_ttl_t
 */
static cache_status_t cache_entry_set_ttl(UNUSED rlm_cache_config_t const *config, void *instance,
                                          request_t *request, UNUSED void *handle,
                                          rlm_cache_entry_t *c)
{
        rlm_cache_rbtree_t *driver = talloc_get_type_abort(instance, rlm_cache_rbtree_t);
 
#ifdef NDEBUG
        if (!request) return CACHE_ERROR;
#endif
 
        if (!fr_cond_assert(fr_heap_extract(&driver->mutable->heap, c) == 0)) {
                RERROR("Entry not in heap");
                return CACHE_ERROR;
        }
 
        if (fr_heap_insert(&driver->mutable->heap, c) < 0) {
                fr_rb_delete(driver->mutable->cache, c);        /* make sure we don't leak entries... */
                RERROR("Failed updating entry TTL.  Entry was forcefully expired");
                return CACHE_ERROR;
        }
        return CACHE_OK;
}
 
/** Return the number of entries in the cache
 *
 * @note handle not used except for sanity checks.
 *
 * @copydetails cache_entry_count_t
 */
static uint64_t cache_entry_count(UNUSED rlm_cache_config_t const *config, void *instance,
                                  request_t *request, UNUSED void *handle)
{
        rlm_cache_rbtree_t *driver = talloc_get_type_abort(instance, rlm_cache_rbtree_t);
 
        if (!request) return 0; /* can't return an error due to signed   */
 
        return fr_rb_num_elements(driver->mutable->cache);
}
 
/** Lock the rbtree
 *
 * @note handle not used except for sanity checks.
 *
 * @copydetails cache_acquire_t
 */
static int cache_acquire(void **handle, UNUSED rlm_cache_config_t const *config, void *instance,
                         request_t *request)
{
        rlm_cache_rbtree_t *driver = talloc_get_type_abort(instance, rlm_cache_rbtree_t);
 
        pthread_mutex_lock(&driver->mutable->mutex);
 
        *handle = request;              /* handle is unused, this is just for sanity checking */
 
        RDEBUG3("Mutex acquired");
 
        return 0;
}
 
/** Release an entry unlocking any mutexes
 *
 * @note handle not used except for sanity checks.
 *
 * @copydetails cache_release_t
 */
static void cache_release(UNUSED rlm_cache_config_t const *config, void *instance, request_t *request,
                          UNUSED rlm_cache_handle_t *handle)
{
        rlm_cache_rbtree_t *driver = talloc_get_type_abort(instance, rlm_cache_rbtree_t);
 
        pthread_mutex_unlock(&driver->mutable->mutex);
 
        RDEBUG3("Mutex released");
}
 
/** Cleanup a cache_rbtree instance
 *
 */
static int mod_detach(module_detach_ctx_t const *mctx)
{
        rlm_cache_rbtree_t              *driver = talloc_get_type_abort(mctx->mi->data, rlm_cache_rbtree_t);
        rlm_cache_rbtree_mutable_t      *mutable = driver->mutable;
 
        if (mutable->cache) {
                fr_rb_iter_inorder_t    iter;
                void                    *data;
 
                for (data = fr_rb_iter_init_inorder(mutable->cache, &iter);
                     data;
                     data = fr_rb_iter_next_inorder(mutable->cache, &iter)) {
                        fr_rb_iter_delete_inorder(mutable->cache, &iter);
                        talloc_free(data);
                }
        }
 
        pthread_mutex_destroy(&mutable->mutex);
 
        TALLOC_FREE(driver->mutable);
 
        return 0;
}
 
/** Create a new cache_rbtree instance
 *
 * @param[in] mctx              Data required for instantiation.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
static int mod_instantiate(module_inst_ctx_t const *mctx)
{
        rlm_cache_rbtree_t              *driver = talloc_get_type_abort(mctx->mi->data, rlm_cache_rbtree_t);
        rlm_cache_rbtree_mutable_t      *mutable;
        int ret;
 
        MEM(mutable = talloc_zero(NULL, rlm_cache_rbtree_mutable_t));
 
        /*
         *      The cache.
         */
        mutable->cache = fr_rb_inline_talloc_alloc(mutable, rlm_cache_rb_entry_t, node, cache_entry_cmp, NULL);
        if (!mutable->cache) {
                ERROR("Failed to create cache");
        error:
                talloc_free(mutable);
                return -1;
        }
 
        /*
         *      The heap of entries to expire.
         */
        mutable->heap = fr_heap_talloc_alloc(mutable, cache_heap_cmp, rlm_cache_rb_entry_t, heap_id, 0);
        if (!mutable->heap) {
                ERROR("Failed to create heap for the cache");
                goto error;
        }
 
        if ((ret = pthread_mutex_init(&mutable->mutex, NULL)) < 0) {
                ERROR("Failed initializing mutex: %s", fr_syserror(ret));
                goto error;
        }
 
        driver->mutable = mutable;
 
        return 0;
}
 
extern rlm_cache_driver_t rlm_cache_rbtree;
rlm_cache_driver_t rlm_cache_rbtree = {
        .common = {
                .magic          = MODULE_MAGIC_INIT,
                .name           = "cache_rbtree",
                .instantiate    = mod_instantiate,
                .detach         = mod_detach,
                .inst_size      = sizeof(rlm_cache_rbtree_t),
                .inst_type      = "rlm_cache_rbtree_t",
        },
        .alloc          = cache_entry_alloc,
 
        .find           = cache_entry_find,
        .insert         = cache_entry_insert,
        .expire         = cache_entry_expire,
        .set_ttl        = cache_entry_set_ttl,
        .count          = cache_entry_count,
 
        .acquire        = cache_acquire,
        .release        = cache_release,
};