lib/dns/dbtable.c

/*
 * Copyright (C) 1999-2001, 2004, 2005, 2007, 2013, 2016  Internet Systems Consortium, Inc. ("ISC")
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

/*
 * $Id: dbtable.c,v 1.33 2007/06/19 23:47:16 tbox Exp $
 */

/*! \file
 * \author
 * Principal Author: DCL
 */

#include <config.h>

#include <isc/mem.h>
#include <isc/rwlock.h>
#include <isc/util.h>

#include <dns/dbtable.h>
#include <dns/db.h>
#include <dns/rbt.h>
#include <dns/result.h>

struct dns_dbtable {
    /* Unlocked. */
    unsigned int        magic;
    isc_mem_t *     mctx;
    dns_rdataclass_t    rdclass;
    isc_mutex_t     lock;
    isc_rwlock_t        tree_lock;
    /* Locked by lock. */
    unsigned int        references;
    /* Locked by tree_lock. */
    dns_rbt_t *     rbt;
    dns_db_t *      default_db;
};

#define DBTABLE_MAGIC       ISC_MAGIC('D', 'B', '-', '-')
#define VALID_DBTABLE(dbtable)  ISC_MAGIC_VALID(dbtable, DBTABLE_MAGIC)

static void
dbdetach(void *data, void *arg) {
    dns_db_t *db = data;

    UNUSED(arg);

    dns_db_detach(&db);
}

isc_result_t
dns_dbtable_create(isc_mem_t *mctx, dns_rdataclass_t rdclass,
           dns_dbtable_t **dbtablep)
{
    dns_dbtable_t *dbtable;
    isc_result_t result;

    REQUIRE(mctx != NULL);
    REQUIRE(dbtablep != NULL && *dbtablep == NULL);

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

    dbtable->rbt = NULL;
    result = dns_rbt_create(mctx, dbdetach, NULL, &dbtable->rbt);
    if (result != ISC_R_SUCCESS)
        goto clean1;

    result = isc_mutex_init(&dbtable->lock);
    if (result != ISC_R_SUCCESS)
        goto clean2;

    result = isc_rwlock_init(&dbtable->tree_lock, 0, 0);
    if (result != ISC_R_SUCCESS)
        goto clean3;

    dbtable->default_db = NULL;
    dbtable->mctx = NULL;
    isc_mem_attach(mctx, &dbtable->mctx);
    dbtable->rdclass = rdclass;
    dbtable->magic = DBTABLE_MAGIC;
    dbtable->references = 1;

    *dbtablep = dbtable;

    return (ISC_R_SUCCESS);

 clean3:
    DESTROYLOCK(&dbtable->lock);

 clean2:
    dns_rbt_destroy(&dbtable->rbt);

 clean1:
    isc_mem_putanddetach(&mctx, dbtable, sizeof(*dbtable));

    return (result);
}

static inline void
dbtable_free(dns_dbtable_t *dbtable) {
    /*
     * Caller must ensure that it is safe to call.
     */

    RWLOCK(&dbtable->tree_lock, isc_rwlocktype_write);

    if (dbtable->default_db != NULL)
        dns_db_detach(&dbtable->default_db);

    dns_rbt_destroy(&dbtable->rbt);

    RWUNLOCK(&dbtable->tree_lock, isc_rwlocktype_write);

    isc_rwlock_destroy(&dbtable->tree_lock);

    dbtable->magic = 0;

    isc_mem_putanddetach(&dbtable->mctx, dbtable, sizeof(*dbtable));
}

void
dns_dbtable_attach(dns_dbtable_t *source, dns_dbtable_t **targetp) {
    REQUIRE(VALID_DBTABLE(source));
    REQUIRE(targetp != NULL && *targetp == NULL);

    LOCK(&source->lock);

    INSIST(source->references > 0);
    source->references++;
    INSIST(source->references != 0);

    UNLOCK(&source->lock);

    *targetp = source;
}

void
dns_dbtable_detach(dns_dbtable_t **dbtablep) {
    dns_dbtable_t *dbtable;
    isc_boolean_t free_dbtable = ISC_FALSE;

    REQUIRE(dbtablep != NULL);
    dbtable = *dbtablep;
    REQUIRE(VALID_DBTABLE(dbtable));

    LOCK(&dbtable->lock);

    INSIST(dbtable->references > 0);
    dbtable->references--;
    if (dbtable->references == 0)
        free_dbtable = ISC_TRUE;

    UNLOCK(&dbtable->lock);

    if (free_dbtable)
        dbtable_free(dbtable);

    *dbtablep = NULL;
}

isc_result_t
dns_dbtable_add(dns_dbtable_t *dbtable, dns_db_t *db) {
    isc_result_t result;
    dns_db_t *dbclone;

    REQUIRE(VALID_DBTABLE(dbtable));
    REQUIRE(dns_db_class(db) == dbtable->rdclass);

    dbclone = NULL;
    dns_db_attach(db, &dbclone);

    RWLOCK(&dbtable->tree_lock, isc_rwlocktype_write);
    result = dns_rbt_addname(dbtable->rbt, dns_db_origin(dbclone), dbclone);
    RWUNLOCK(&dbtable->tree_lock, isc_rwlocktype_write);

    return (result);
}

void
dns_dbtable_remove(dns_dbtable_t *dbtable, dns_db_t *db) {
    dns_db_t *stored_data = NULL;
    isc_result_t result;
    dns_name_t *name;

    REQUIRE(VALID_DBTABLE(dbtable));

    name = dns_db_origin(db);

    /*
     * There is a requirement that the association of name with db
     * be verified.  With the current rbt.c this is expensive to do,
     * because effectively two find operations are being done, but
     * deletion is relatively infrequent.
     * XXXDCL ... this could be cheaper now with dns_rbt_deletenode.
     */

    RWLOCK(&dbtable->tree_lock, isc_rwlocktype_write);

    result = dns_rbt_findname(dbtable->rbt, name, 0, NULL,
                  (void **) (void *)&stored_data);

    if (result == ISC_R_SUCCESS) {
        INSIST(stored_data == db);

        (void)dns_rbt_deletename(dbtable->rbt, name, ISC_FALSE);
    }

    RWUNLOCK(&dbtable->tree_lock, isc_rwlocktype_write);
}

void
dns_dbtable_adddefault(dns_dbtable_t *dbtable, dns_db_t *db) {
    REQUIRE(VALID_DBTABLE(dbtable));
    REQUIRE(dbtable->default_db == NULL);
    REQUIRE(dns_name_compare(dns_db_origin(db), dns_rootname) == 0);

    RWLOCK(&dbtable->tree_lock, isc_rwlocktype_write);

    dbtable->default_db = NULL;
    dns_db_attach(db, &dbtable->default_db);

    RWUNLOCK(&dbtable->tree_lock, isc_rwlocktype_write);
}

void
dns_dbtable_getdefault(dns_dbtable_t *dbtable, dns_db_t **dbp) {
    REQUIRE(VALID_DBTABLE(dbtable));
    REQUIRE(dbp != NULL && *dbp == NULL);

    RWLOCK(&dbtable->tree_lock, isc_rwlocktype_read);

    dns_db_attach(dbtable->default_db, dbp);

    RWUNLOCK(&dbtable->tree_lock, isc_rwlocktype_read);
}

void
dns_dbtable_removedefault(dns_dbtable_t *dbtable) {
    REQUIRE(VALID_DBTABLE(dbtable));

    RWLOCK(&dbtable->tree_lock, isc_rwlocktype_write);

    dns_db_detach(&dbtable->default_db);

    RWUNLOCK(&dbtable->tree_lock, isc_rwlocktype_write);
}

isc_result_t
dns_dbtable_find(dns_dbtable_t *dbtable, dns_name_t *name,
         unsigned int options, dns_db_t **dbp)
{
    dns_db_t *stored_data = NULL;
    isc_result_t result;
    unsigned int rbtoptions = 0;

    REQUIRE(dbp != NULL && *dbp == NULL);

    if ((options & DNS_DBTABLEFIND_NOEXACT) != 0)
        rbtoptions |= DNS_RBTFIND_NOEXACT;

    RWLOCK(&dbtable->tree_lock, isc_rwlocktype_read);

    result = dns_rbt_findname(dbtable->rbt, name, rbtoptions, NULL,
                  (void **) (void *)&stored_data);

    if (result == ISC_R_SUCCESS || result == DNS_R_PARTIALMATCH)
        dns_db_attach(stored_data, dbp);
    else if (dbtable->default_db != NULL) {
        dns_db_attach(dbtable->default_db, dbp);
        result = DNS_R_PARTIALMATCH;
    } else
        result = ISC_R_NOTFOUND;

    RWUNLOCK(&dbtable->tree_lock, isc_rwlocktype_read);

    return (result);
}