lib/dns/cache.c

	cache.c revision b120e39deac3e9c323cdc7801ed2313f8ebbb744
/*
 * Copyright (C) 1999 Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 */

 /* $Id: cache.c,v 1.2 1999/12/02 22:35:29 gson Exp $ */

#include <config.h>
#include <limits.h>

#include <isc/assertions.h>
#include <isc/error.h>
#include <isc/mutex.h>

#include <dns/cache.h>
#include <dns/db.h>
#include <dns/dbiterator.h>
#include <dns/events.h>
#include <dns/log.h>
#include <dns/rdata.h>
#include <dns/types.h>

#define LOCK(lp) \
    RUNTIME_CHECK(isc_mutex_lock((lp)) == ISC_R_SUCCESS)
#define UNLOCK(lp) \
    RUNTIME_CHECK(isc_mutex_unlock((lp)) == ISC_R_SUCCESS)

#define CACHE_MAGIC 0x24242424U     /* $$$$. */
#define VALID_CACHE(cache) ((cache) != NULL && (cache)->magic == CACHE_MAGIC)

/***
 ***    Types
 ***/

/*
 * A cache_cleaner_t encapsulsates the state of the periodic
 * cache cleaning.
 */

typedef struct cache_cleaner cache_cleaner_t;

typedef enum {
    cleaner_s_idle, /* Waiting for cleaning-interval to expire. */
    cleaner_s_busy  /* Currently cleaning. */
} cleaner_state_t;

struct cache_cleaner {
    dns_cache_t *cache;
    isc_task_t  *task;
    int     cleaning_interval; /* The cleaning-interval from
                          named.conf, in seconds. */
    isc_timer_t     *cleaning_timer;
    isc_event_t *resched_event; /* Sent by cleaner task to
                       itself to reschedule */

    dns_dbiterator_t *iterator;
    int          increment; /* Number of names to
                       clean in one increment */
    cleaner_state_t  state;     /* Idle/Busy. */
};

/*
 * The actual cache object.
 */

struct dns_cache {
    /* Unlocked */
    unsigned int        magic;
    isc_mutex_t     lock;
    isc_mutex_t     filelock;
    isc_mem_t       *mctx;

    /* Locked by 'lock'. */
    unsigned int        references;
    unsigned int        live_tasks;
    dns_rdataclass_t    rdclass;
    dns_db_t        *db;
    cache_cleaner_t     cleaner;

    /* Locked by 'filelock'. */
    char *          filename;
    /* Access to the on-disk cache file is also locked by 'filelock'. */
};

/***
 ***    Functions
 ***/

static dns_result_t
cache_cleaner_init(dns_cache_t *cache,
           isc_taskmgr_t *taskmgr, isc_timermgr_t *timermgr,
           cache_cleaner_t *cleaner);

static void
cleaning_timer_action(isc_task_t *task, isc_event_t *event);

static void
incremental_cleaning_action(isc_task_t *task, isc_event_t *event);

static void
cleaner_shutdown_action(isc_task_t *task, isc_event_t *event);

dns_result_t
dns_cache_create(isc_mem_t *mctx, isc_taskmgr_t *taskmgr,
         isc_timermgr_t *timermgr, dns_rdataclass_t rdclass,
         char *db_type, unsigned int db_argc, char **db_argv,
         dns_cache_t **cachep)
{
    isc_result_t iresult;
    dns_result_t dresult;
    dns_cache_t *cache;

    REQUIRE(cachep != NULL);
    REQUIRE(*cachep == NULL);
    REQUIRE(mctx != NULL);

    cache = isc_mem_get(mctx, sizeof *cache);
    if (cache == NULL)
        return (ISC_R_NOMEMORY);

    cache->mctx = mctx;
    iresult = isc_mutex_init(&cache->lock);
    if (iresult != ISC_R_SUCCESS) {
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_mutex_init() failed: %s",
                 isc_result_totext(iresult));
        dresult = ISC_R_UNEXPECTED;
        goto fail;
    }

    cache->references = 1;
    cache->live_tasks = 0;
    cache->rdclass = rdclass;

    cache->db = NULL;
    dresult = dns_db_create(cache->mctx, db_type, dns_rootname, ISC_TRUE,
                rdclass, db_argc, db_argv, &cache->db);
    if (dresult != ISC_R_SUCCESS)
        goto fail;

    cache->filename = NULL;

    cache->magic = CACHE_MAGIC;

    dresult = cache_cleaner_init(cache, taskmgr, timermgr,
                     &cache->cleaner);
    RUNTIME_CHECK(dresult == ISC_R_SUCCESS);

    *cachep = cache;
    return (ISC_R_SUCCESS);
 fail:
    isc_mem_put(cache->mctx, cache, sizeof *cache);
    return (dresult);
}

static void
cache_free(dns_cache_t *cache) {
    REQUIRE(VALID_CACHE(cache));
    REQUIRE(cache->references == 0);

    if (cache->cleaner.resched_event != NULL)
        isc_event_free(&cache->cleaner.resched_event);

    dns_dbiterator_destroy(&cache->cleaner.iterator);

    if (cache->filename) {
        isc_mem_free(cache->mctx, cache->filename);
        cache->filename = NULL;
    }

    if (cache->db) {
        dns_db_detach(&cache->db);
    }

    isc_mutex_destroy(&cache->lock);
    cache->magic = 0;
    isc_mem_put(cache->mctx, cache, sizeof *cache);
}


void
dns_cache_attach(dns_cache_t *cache, dns_cache_t **targetp) {

    REQUIRE(VALID_CACHE(cache));
    REQUIRE(targetp != NULL && *targetp == NULL);

    LOCK(&cache->lock);
    cache->references++;
    UNLOCK(&cache->lock);

    *targetp = cache;
}

void
dns_cache_detach(dns_cache_t **cachep) {
    dns_cache_t *cache;
    isc_boolean_t free_cache = ISC_FALSE;

    REQUIRE(cachep != NULL);
    cache = *cachep;
    REQUIRE(VALID_CACHE(cache));

    LOCK(&cache->lock);

    REQUIRE(cache->references > 0);
    cache->references--;
    if (cache->references == 0) {
        if (cache->live_tasks == 0)
            free_cache = ISC_TRUE;
        if (cache->cleaner.cleaning_timer != NULL)
            isc_timer_detach(&cache->cleaner.cleaning_timer);
        if (cache->cleaner.task != NULL)
            isc_task_destroy(&cache->cleaner.task);
    }
    UNLOCK(&cache->lock);

    if (free_cache)
        cache_free(cache);

    *cachep = NULL;
}

void
dns_cache_attachdb(dns_cache_t *cache, dns_db_t **dbp) {
    REQUIRE(VALID_CACHE(cache));
    REQUIRE(dbp != NULL && *dbp == NULL);
    REQUIRE(cache->db != NULL);
    LOCK(&cache->lock);
    dns_db_attach(cache->db, dbp);
    UNLOCK(&cache->lock);
}

#ifdef NOTYET

dns_result_t
dns_cache_setfilename(dns_cache_t *cahce, char *filename) /* ARGSUSED */
{
    char *newname = isc_mem_strdup(filename);
    if (newname == NULL)
        return (ISC_R_NOMEMORY);
    LOCK(&cache->filelock);
    if (cache->filename)
        isc_mem_free(cache->mctx, cache->filename);
    cache->filename = newname;
    UNLOCK(&cache->filelock);
    return (ISC_R_SUCCESS);
}

dns_result_t
dns_cache_load(dns_cache_t *cache) {
    dns_result_t dresult;
    if (cache->filename == NULL)
        return (ISC_R_SUCCESS);
    LOCK(&cache->filelock);
    /* XXX handle TTLs in a way appropriate for the cache */
    dresult = dns_db_load(cache->db, cache->filename);
    UNLOCK(&cache->filelock);
    return (dresult);
}

dns_result_t
dns_cache_dump(dns_cache_t *cache) {
    /* XXX to be written */
    return (ISC_R_NOTIMPLEMENTED);
}

#endif

/*
 * Initialize the cache cleaner object at *cleaner.
 * Space for the object must be allocated by the caller.
 */

static dns_result_t
cache_cleaner_init(dns_cache_t *cache, isc_taskmgr_t *taskmgr,
           isc_timermgr_t *timermgr, cache_cleaner_t *cleaner)
{
        isc_result_t iresult;
    dns_result_t dresult;

    cleaner->increment = 10; /* XXX debugging value; 100 realistic? */
    cleaner->state = cleaner_s_idle;
    cleaner->cache = cache;

    cleaner->iterator = NULL;
    dresult = dns_db_createiterator(cache->db,
                    ISC_FALSE, &cleaner->iterator);
    if (dresult != ISC_R_SUCCESS)
        goto fail;

    cleaner->task = NULL;
    cleaner->cleaning_timer = NULL;
    cleaner->resched_event = NULL;

    if (taskmgr != NULL && timermgr != NULL) {
        isc_interval_t interval;

        iresult = isc_task_create(taskmgr, cache->mctx,
                      1, &cleaner->task);
        if (iresult != ISC_R_SUCCESS) {
            UNEXPECTED_ERROR(__FILE__, __LINE__,
                     "isc_task_create() failed: %s",
                     isc_result_totext(iresult));
            dresult = ISC_R_UNEXPECTED;
            goto cleanup_dbiterator;
        }
        cleaner->cache->live_tasks++;

        iresult = isc_task_onshutdown(cleaner->task,
                          cleaner_shutdown_action, cache);
        RUNTIME_CHECK(iresult == ISC_R_SUCCESS);

        /* XXX get this from the configuration file */
        cleaner->cleaning_interval = 30; /* seconds */
        isc_interval_set(&interval, cleaner->cleaning_interval, 0);
        iresult = isc_timer_create(timermgr, isc_timertype_ticker,
                       NULL, &interval,
                       cleaner->task,
                       cleaning_timer_action, cleaner,
                       &cleaner->cleaning_timer);
        if (iresult != ISC_R_SUCCESS) {
            UNEXPECTED_ERROR(__FILE__, __LINE__,
                     "isc_timer_create() failed: %s",
                     isc_result_totext(iresult));
            dresult = ISC_R_UNEXPECTED;
            goto cleanup_task;
        }

        cleaner->resched_event =
            isc_event_allocate(cache->mctx, cleaner,
                       DNS_EVENT_CACHECLEAN,
                       incremental_cleaning_action,
                       cleaner, sizeof(isc_event_t));
        if (cleaner->resched_event == NULL) {
            dresult = ISC_R_NOMEMORY;
            goto cleanup_timer;
        }
    }

    return (ISC_R_SUCCESS);

    cleanup_timer:
    isc_timer_detach(&cleaner->cleaning_timer);
    cleanup_task:
    isc_task_detach(&cleaner->task);
    cleanup_dbiterator:
    dns_dbiterator_destroy(&cleaner->iterator);
    fail:
    return (dresult);
}

/*
 * Try to clean the next n_names domain names.
 */
static dns_result_t
do_some_cleaning(cache_cleaner_t *cleaner, isc_stdtime_t now, int n_names) {
    dns_result_t dresult;
    dns_result_t return_result;

    REQUIRE(DNS_DBITERATOR_VALID(cleaner->iterator));

    /*
     * When starting or restarting from the idle state,
     * position the iterator at the beginning of the cache.
     */
    if (cleaner->state == cleaner_s_idle) {
        isc_log_write(dns_lctx, DNS_LOGCATEGORY_GENERAL,
                  DNS_LOGMODULE_CACHE, ISC_LOG_DEBUG(1),
                  "begin cache cleaning");
        dresult = dns_dbiterator_first(cleaner->iterator);
        if (dresult == ISC_R_NOMORE) {
            /*
             * We have an empty database, but that's OK.
             */
            return_result = ISC_R_SUCCESS;
            goto idle;
        }
        if (dresult != ISC_R_SUCCESS) {
            UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "cache cleaner: dns_dbiterator_first() "
                 "failed: %s", dns_result_totext(dresult));
            return_result = ISC_R_UNEXPECTED;
            goto idle;
        }
        cleaner->state = cleaner_s_busy;
    }

    while (n_names-- > 0) {
        dns_dbnode_t *node = NULL;
        dresult = dns_dbiterator_current(cleaner->iterator, &node,
                         (dns_name_t *) NULL);
        if (dresult != ISC_R_SUCCESS) {
            UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "cache cleaner: dns_dbiterator_current() "
                 "failed: %s", dns_result_totext(dresult));
            return_result = ISC_R_UNEXPECTED;
            goto idle;
        }
        INSIST(node != NULL);

        /* Check TTLs, mark expired rdatasets stale. */
        dresult = dns_db_expirenode(cleaner->cache->db, node, now);
        RUNTIME_CHECK(dresult == ISC_R_SUCCESS);

        /* This is where the actual freeing takes place. */
        dns_db_detachnode(cleaner->cache->db, &node);

        /* Step to the next node */
        dresult = dns_dbiterator_next(cleaner->iterator);
        if (dresult == ISC_R_NOMORE) {
            /* We have successfully cleaned the whole cache. */
            return_result = ISC_R_SUCCESS;
            goto idle;
        }
        if (dresult != ISC_R_SUCCESS) {
            UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "cache cleaner: dns_dbiterator_next() "
                 "failed: %s", dns_result_totext(dresult));
            return_result = ISC_R_UNEXPECTED;
            goto idle;
        }
    }

    /* We have successfully performed a cleaning increment. */
    return_result = ISC_R_SUCCESS;
    goto done;

 idle:
    isc_log_write(dns_lctx, DNS_LOGCATEGORY_GENERAL,
              DNS_LOGMODULE_CACHE, ISC_LOG_DEBUG(1),
              "end cache cleaning");
    cleaner->state = cleaner_s_idle;

 done:
    dresult = dns_dbiterator_pause(cleaner->iterator);
    if (dresult != ISC_R_SUCCESS && dresult != ISC_R_NOMORE) {
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "cache cleaner: dns_dbiterator_pause() "
                 "failed: %s", dns_result_totext(dresult));
        return (ISC_R_UNEXPECTED);
    }
    return (return_result);
}

/*
 * This is run once for every cache-cleaning-interval as defined in named.conf.
 */
static void
cleaning_timer_action(isc_task_t *task, isc_event_t *event) {
    cache_cleaner_t *cleaner = event->arg;
    INSIST(event->type == ISC_TIMEREVENT_TICK);
    if (cleaner->state == cleaner_s_idle) {
        INSIST(cleaner->resched_event != NULL);
        isc_task_send(task, &cleaner->resched_event);
    } else {
        INSIST(cleaner->resched_event == NULL);
        isc_log_write(dns_lctx, DNS_LOGCATEGORY_GENERAL,
                  DNS_LOGMODULE_CACHE, ISC_LOG_WARNING,
                  "cache cleaner did not finish "
                  "in one cleaning-interval");
    }
    isc_event_free(&event);
}

/*
 * Do incremental cleaning.
 */
static void
incremental_cleaning_action(isc_task_t *task, isc_event_t *event) {
    cache_cleaner_t *cleaner = event->arg;
    isc_stdtime_t now;
    INSIST(event->type == DNS_EVENT_CACHECLEAN);
    RUNTIME_CHECK(isc_stdtime_get(&now) == ISC_R_SUCCESS);
    /*
     * The return value from do_some_cleaning() is ignored because it
     * does its own error reporting.
     */
    (void) do_some_cleaning(cleaner, now, cleaner->increment);
    if (cleaner->state == cleaner_s_idle) {
        /* Went idle.  Save the event for later reuse. */
        INSIST(cleaner->resched_event == NULL);
        cleaner->resched_event = event;
        event = NULL;
    } else {
        /* Still busy.  Reschedule. */
        isc_task_send(task, &event);
    }
}

/*
 * Do immediate cleaning.
 */
dns_result_t
dns_cache_clean(dns_cache_t *cache, isc_stdtime_t now) {
    dns_result_t dresult;
    dns_dbiterator_t *iterator = NULL;

    dresult = dns_db_createiterator(cache->db, ISC_FALSE, &iterator);
    if (dresult != ISC_R_SUCCESS)
        return dresult;

    dresult = dns_dbiterator_first(iterator);

    while (dresult == ISC_R_SUCCESS) {
        dns_dbnode_t *node = NULL;
        dresult = dns_dbiterator_current(iterator, &node,
                         (dns_name_t *) NULL);
        if (dresult != ISC_R_SUCCESS)
            break;

        /* Check TTLs, mark expired rdatasets stale. */
        dresult = dns_db_expirenode(cache->db, node, now);
        RUNTIME_CHECK(dresult == ISC_R_SUCCESS);

        /* This is where the actual freeing takes place. */
        dns_db_detachnode(cache->db, &node);

        dresult = dns_dbiterator_next(iterator);
    }

    dns_dbiterator_destroy(&iterator);

    if (dresult == ISC_R_NOMORE)
        dresult = ISC_R_SUCCESS;

    return dresult;
}

/*
 * The cleaner task is shutting down; do the necessary cleanup.
 */
static void
cleaner_shutdown_action(isc_task_t *task, isc_event_t *event) {
    dns_cache_t *cache = event->arg;
    isc_boolean_t should_free = ISC_FALSE;
    INSIST(event->type == ISC_TASKEVENT_SHUTDOWN);
    task = task; /* Unused. */
    LOCK(&cache->lock);
    cache->live_tasks--;
    if (cache->references == 0 && cache->live_tasks == 0)
        should_free = ISC_TRUE;
    UNLOCK(&cache->lock);
    if (should_free)
        cache_free(cache);
    isc_event_free(&event);
}