acache.c

非常好的dns解析软件

	INSIST(ISC_LIST_EMPTY(dbentry->originlist) &&
	       ISC_LIST_EMPTY(dbentry->referlist));

	bucket = isc_hash_calc((const unsigned char *)&db,
			       sizeof(db), ISC_TRUE) % DBBUCKETS;
	ISC_LIST_UNLINK(acache->dbbucket[bucket], dbentry, link);
	dns_db_detach(&dbentry->db);

	isc_mem_put(acache->mctx, dbentry, sizeof(*dbentry));

	acache->dbentries--;

	acache->stats.deleted++;

	UNLOCK(&acache->lock);

	return (ISC_R_SUCCESS);
}

isc_result_t
dns_acache_createentry(dns_acache_t *acache, dns_db_t *origdb,
		       void (*callback)(dns_acacheentry_t *, void **),
		       void *cbarg, dns_acacheentry_t **entryp)
{
	dns_acacheentry_t *newentry;
	isc_result_t result;
	isc_uint32_t r;

	REQUIRE(DNS_ACACHE_VALID(acache));
	REQUIRE(entryp != NULL && *entryp == NULL);
	REQUIRE(origdb != NULL);

	/* 
	 * Should we exceed our memory limit for some reason (for 
	 * example, if the cleaner does not run aggressively enough), 
	 * then we will not create additional entries.
	 *
	 * XXXSK: It might be better to lock the acache->cleaner->lock,
	 * but locking may be an expensive bottleneck. If we misread 
	 * the value, we will occasionally refuse to create a few 
	 * cache entries, or create a few that we should not. I do not
	 * expect this to happen often, and it will not have very bad
	 * effects when it does. So no lock for now.
	 */
	if (acache->cleaner.overmem) {
		acache->stats.overmem_nocreates++; /* XXXSK danger: unlocked! */
		return (ISC_R_NORESOURCES);
	}

	newentry = isc_mem_get(acache->mctx, sizeof(*newentry));
	if (newentry == NULL) {
		acache->stats.nomem++;  /* XXXMLG danger: unlocked! */
		return (ISC_R_NOMEMORY);
	}

	isc_random_get(&r);
	newentry->locknum = r % DEFAULT_ACACHE_ENTRY_LOCK_COUNT;
	
	result = isc_refcount_init(&newentry->references, 1);
	if (result != ISC_R_SUCCESS) {
		isc_mem_put(acache->mctx, newentry, sizeof(*newentry));
		return (result);
	};

	ISC_LINK_INIT(newentry, link);
	ISC_LINK_INIT(newentry, olink);
	ISC_LINK_INIT(newentry, rlink);

	newentry->acache = NULL;
	dns_acache_attach(acache, &newentry->acache);

	newentry->zone = NULL;
	newentry->db = NULL;
	newentry->version = NULL;
	newentry->node = NULL;
	newentry->foundname = NULL;

	newentry->callback = callback;
	newentry->cbarg = cbarg;
	newentry->origdb = NULL;
	dns_db_attach(origdb, &newentry->origdb);

	isc_stdtime_get(&newentry->lastused);

	newentry->magic = ACACHEENTRY_MAGIC;

	*entryp = newentry;

	return (ISC_R_SUCCESS);
}

isc_result_t
dns_acache_getentry(dns_acacheentry_t *entry, dns_zone_t **zonep,
		    dns_db_t **dbp, dns_dbversion_t **versionp,
		    dns_dbnode_t **nodep, dns_name_t *fname,
		    dns_message_t *msg, isc_stdtime_t now)
{
	isc_result_t result = ISC_R_SUCCESS;
	dns_rdataset_t *erdataset;
	isc_stdtime32_t	now32;
	dns_acache_t *acache;
	int locknum;

	REQUIRE(DNS_ACACHEENTRY_VALID(entry));
	REQUIRE(zonep == NULL || *zonep == NULL);
	REQUIRE(dbp != NULL && *dbp == NULL);
	REQUIRE(versionp != NULL && *versionp == NULL);
	REQUIRE(nodep != NULL && *nodep == NULL);
	REQUIRE(fname != NULL);
	REQUIRE(msg != NULL);
	acache = entry->acache;
	REQUIRE(DNS_ACACHE_VALID(acache));

	locknum = entry->locknum;
	ACACHE_LOCK(&acache->entrylocks[locknum], isc_rwlocktype_read);

	isc_stdtime_convert32(now, &now32);
	acache_storetime(entry, now32);

	if (entry->zone != NULL && zonep != NULL)
		dns_zone_attach(entry->zone, zonep);

	if (entry->db == NULL) {
		*dbp = NULL;
		*versionp = NULL;
	} else {
		dns_db_attach(entry->db, dbp);
		dns_db_attachversion(entry->db, entry->version, versionp);
	}
	if (entry->node == NULL)
		*nodep = NULL;
	else {
		dns_db_attachnode(entry->db, entry->node, nodep);

		INSIST(entry->foundname != NULL);
		dns_name_copy(entry->foundname, fname, NULL);
		for (erdataset = ISC_LIST_HEAD(entry->foundname->list);
		     erdataset != NULL;
		     erdataset = ISC_LIST_NEXT(erdataset, link)) {
			dns_rdataset_t *ardataset;

			ardataset = NULL;
			result = dns_message_gettemprdataset(msg, &ardataset);
			if (result != ISC_R_SUCCESS) {
				ACACHE_UNLOCK(&acache->entrylocks[locknum],
					      isc_rwlocktype_read);
				goto fail;
			}

			/*
			 * XXXJT: if we simply clone the rdataset, we'll get
			 * lost wrt cyclic ordering.  We'll need an additional
			 * trick to get the latest counter from the original
			 * header.
			 */
			dns_rdataset_init(ardataset);
			dns_rdataset_clone(erdataset, ardataset);
			ISC_LIST_APPEND(fname->list, ardataset, link);
		}
	}

	entry->acache->stats.hits++; /* XXXMLG danger: unlocked! */
	entry->acache->stats.queries++;

	ACACHE_UNLOCK(&acache->entrylocks[locknum], isc_rwlocktype_read);

	return (result);

  fail:
	while ((erdataset = ISC_LIST_HEAD(fname->list)) != NULL) {
		ISC_LIST_UNLINK(fname->list, erdataset, link);
		dns_rdataset_disassociate(erdataset);
		dns_message_puttemprdataset(msg, &erdataset);
	}
	if (*nodep != NULL)
		dns_db_detachnode(*dbp, nodep);
	if (*versionp != NULL)
		dns_db_closeversion(*dbp, versionp, ISC_FALSE);
	if (*dbp != NULL)
		dns_db_detach(dbp);
	if (zonep != NULL && *zonep != NULL)
		dns_zone_detach(zonep);

	return (result);
}

isc_result_t
dns_acache_setentry(dns_acache_t *acache, dns_acacheentry_t *entry,
		    dns_zone_t *zone, dns_db_t *db, dns_dbversion_t *version,
		    dns_dbnode_t *node, dns_name_t *fname)
{
	isc_result_t result;
	dbentry_t *odbent;
	dbentry_t *rdbent = NULL;
	isc_boolean_t close_version = ISC_FALSE;
	dns_acacheentry_t *dummy_entry = NULL;

	REQUIRE(DNS_ACACHE_VALID(acache));
	REQUIRE(DNS_ACACHEENTRY_VALID(entry));

	LOCK(&acache->lock);	/* XXX: need to lock it here for ordering */
	ACACHE_LOCK(&acache->entrylocks[entry->locknum], isc_rwlocktype_write);

	/* Set zone */
	if (zone != NULL)
		dns_zone_attach(zone, &entry->zone);
	/* Set DB */
	if (db != NULL)
		dns_db_attach(db, &entry->db);
	/*
	 * Set DB version.  If the version is not given by the caller,
	 * which is the case for glue or cache DBs, use the current version.
	 */
	if (version == NULL) {
		if (db != NULL) {
			dns_db_currentversion(db, &version);
			close_version = ISC_TRUE;
		}
	}
	if (version != NULL) {
		INSIST(db != NULL);
		dns_db_attachversion(db, version, &entry->version);
	}
	if (close_version)
		dns_db_closeversion(db, &version, ISC_FALSE);
	/* Set DB node. */
	if (node != NULL) {
		INSIST(db != NULL);
		dns_db_attachnode(db, node, &entry->node);
	}

	/*
	 * Set list of the corresponding rdatasets, if given.
	 * To minimize the overhead and memory consumption, we'll do this for
	 * positive cache only, in which case the DB node is non NULL.
	 * We do not want to cache incomplete information, so give up the
	 * entire entry when a memory shortage happen during the process.
	 */
	if (node != NULL) {
		dns_rdataset_t *ardataset, *crdataset;

		entry->foundname = isc_mem_get(acache->mctx,
					       sizeof(*entry->foundname));

		if (entry->foundname == NULL) {
			result = ISC_R_NOMEMORY;
			goto fail;
		}
		dns_name_init(entry->foundname, NULL);
		result = dns_name_dup(fname, acache->mctx,
				      entry->foundname);
		if (result != ISC_R_SUCCESS)
			goto fail;

		for (ardataset = ISC_LIST_HEAD(fname->list);
		     ardataset != NULL;
		     ardataset = ISC_LIST_NEXT(ardataset, link)) {
			crdataset = isc_mem_get(acache->mctx,
						sizeof(*crdataset));
			if (crdataset == NULL) {
				result = ISC_R_NOMEMORY;
				goto fail;
			}

			dns_rdataset_init(crdataset);
			dns_rdataset_clone(ardataset, crdataset);
			ISC_LIST_APPEND(entry->foundname->list, crdataset,
					link);
		}
	}

	odbent = NULL;
	result = finddbent(acache, entry->origdb, &odbent);
	if (result != ISC_R_SUCCESS)
		goto fail;
	if (db != NULL) {
		rdbent = NULL;
		result = finddbent(acache, db, &rdbent);
		if (result != ISC_R_SUCCESS)
			goto fail;
	}

	ISC_LIST_APPEND(acache->entries, entry, link);
	ISC_LIST_APPEND(odbent->originlist, entry, olink);
	if (rdbent != NULL)
		ISC_LIST_APPEND(rdbent->referlist, entry, rlink);

	/*
	 * The additional cache needs an implicit reference to entries in its
	 * link.
	 */
	dns_acache_attachentry(entry, &dummy_entry);

	ACACHE_UNLOCK(&acache->entrylocks[entry->locknum],
		      isc_rwlocktype_write);

	acache->stats.adds++;
	UNLOCK(&acache->lock);

	return (ISC_R_SUCCESS);

 fail:
	clear_entry(acache, entry);

	ACACHE_UNLOCK(&acache->entrylocks[entry->locknum],
		      isc_rwlocktype_write);
	UNLOCK(&acache->lock);

	return (result);
}

void
dns_acache_cancelentry(dns_acacheentry_t *entry) {
	dns_acache_t *acache = entry->acache;

	REQUIRE(DNS_ACACHEENTRY_VALID(entry));
	INSIST(DNS_ACACHE_VALID(acache));

	LOCK(&acache->lock);
	ACACHE_LOCK(&acache->entrylocks[entry->locknum], isc_rwlocktype_write);

	/*
	 * Release dependencies stored in this entry as much as possible.
	 * The main link cannot be released, since the acache object has
	 * a reference to this entry; the empty entry will be released in
	 * the next cleaning action.
	 */
	unlink_dbentries(acache, entry);
	clear_entry(entry->acache, entry);

	entry->callback = NULL;
	entry->cbarg = NULL;

	ACACHE_UNLOCK(&acache->entrylocks[entry->locknum],
		      isc_rwlocktype_write);
	UNLOCK(&acache->lock);
}

void
dns_acache_attachentry(dns_acacheentry_t *source,
		       dns_acacheentry_t **targetp)
{
	REQUIRE(DNS_ACACHEENTRY_VALID(source));
	REQUIRE(targetp != NULL && *targetp == NULL);

	isc_refcount_increment(&source->references, NULL);

	*targetp = source;
}

void
dns_acache_detachentry(dns_acacheentry_t **entryp) {
	dns_acacheentry_t *entry;
	unsigned int refs;

	REQUIRE(entryp != NULL && DNS_ACACHEENTRY_VALID(*entryp));
	entry = *entryp;

	isc_refcount_decrement(&entry->references, &refs);

	/*
	 * If there are no references to the entry, the entry must have been
	 * unlinked and can be destroyed safely.
	 */
	if (refs == 0) {
		INSIST(!ISC_LINK_LINKED(entry, link));
		(*entryp)->acache->stats.deleted++;
		destroy_entry(entry);
	}

	*entryp = NULL;
}

void
dns_acache_setcleaninginterval(dns_acache_t *acache, unsigned int t) {
	isc_interval_t interval;
	isc_result_t result;

	REQUIRE(DNS_ACACHE_VALID(acache));

	ATRACE("dns_acache_setcleaninginterval");

	LOCK(&acache->lock);

	/*
	 * It may be the case that the acache has already shut down.
	 * If so, it has no timer.  (Not sure if this can really happen.)
	 */
	if (acache->cleaner.cleaning_timer == NULL)
		goto unlock;

	acache->cleaner.cleaning_interval = t;

	if (t == 0) {
		result = isc_timer_reset(acache->cleaner.cleaning_timer,
					 isc_timertype_inactive,
					 NULL, NULL, ISC_TRUE);
	} else {
		isc_interval_set(&interval, acache->cleaner.cleaning_interval,
				 0);
		result = isc_timer_reset(acache->cleaner.cleaning_timer,
					 isc_timertype_ticker,
					 NULL, &interval, ISC_FALSE);
	}
	if (result != ISC_R_SUCCESS)	
		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
			      DNS_LOGMODULE_ACACHE, ISC_LOG_WARNING,
			      "could not set acache cleaning interval: %s",
			      isc_result_totext(result));
	else
		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
			      DNS_LOGMODULE_ACACHE, ISC_LOG_NOTICE,
			      "acache %p cleaning interval set to %d.",
			      acache, t);

 unlock:
	UNLOCK(&acache->lock);
}

/*
 * This function was derived from cache.c:dns_cache_setcachesize().  See the
 * function for more details about the logic.
 */
void
dns_acache_setcachesize(dns_acache_t *acache, isc_uint32_t size) {
	isc_uint32_t lowater;
	isc_uint32_t hiwater;

	REQUIRE(DNS_ACACHE_VALID(acache));

	if (size != 0 && size < DNS_ACACHE_MINSIZE)
		size = DNS_ACACHE_MINSIZE;

	hiwater = size - (size >> 3);
	lowater = size - (size >> 2);

	if (size == 0 || hiwater == 0 || lowater == 0)
		isc_mem_setwater(acache->mctx, water, acache, 0, 0);
	else
		isc_mem_setwater(acache->mctx, water, acache,
				 hiwater, lowater);
}