resolver.c

bind 源码 最新实现 linux/unix/windows平台

			result = DNS_R_WAIT;
		} else if (pruned) {
			/*
			 * Some addresses were removed by lame pruning.
			 * Turn pruning off and try again.
			 */
			FCTXTRACE("restarting with returnlame");
			INSIST((stdoptions & DNS_ADBFIND_RETURNLAME) == 0);
			stdoptions |= DNS_ADBFIND_RETURNLAME;
			pruned = ISC_FALSE;
			fctx_cleanupaltfinds(fctx);
			fctx_cleanupfinds(fctx);
			goto restart;
		} else {
			/*
			 * We've lost completely.  We don't know any
			 * addresses, and the ADB has told us it can't get
			 * them.
			 */
			FCTXTRACE("no addresses");
			result = ISC_R_FAILURE;
		}
	} else {
		/*
		 * We've found some addresses.  We might still be looking
		 * for more addresses.
		 */
		sort_finds(fctx);
		result = ISC_R_SUCCESS;
	}

	return (result);
}

static inline void
possibly_mark(fetchctx_t *fctx, dns_adbaddrinfo_t *addr)
{
	isc_netaddr_t na;
	char buf[ISC_NETADDR_FORMATSIZE];
	isc_sockaddr_t *sa;
	isc_boolean_t aborted = ISC_FALSE;
	isc_boolean_t bogus;
	dns_acl_t *blackhole;
	isc_netaddr_t ipaddr;
	dns_peer_t *peer = NULL;
	dns_resolver_t *res;
	const char *msg = NULL;

	sa = &addr->sockaddr;

	res = fctx->res;
	isc_netaddr_fromsockaddr(&ipaddr, sa);
	blackhole = dns_dispatchmgr_getblackhole(res->dispatchmgr);
	(void) dns_peerlist_peerbyaddr(res->view->peers, &ipaddr, &peer);
	
	if (blackhole != NULL) {
		int match;

		if (dns_acl_match(&ipaddr, NULL, blackhole,
				  &res->view->aclenv,
				  &match, NULL) == ISC_R_SUCCESS &&
		    match > 0)
			aborted = ISC_TRUE;
	}

	if (peer != NULL &&
	    dns_peer_getbogus(peer, &bogus) == ISC_R_SUCCESS &&
	    bogus)
		aborted = ISC_TRUE;

	if (aborted) {
		addr->flags |= FCTX_ADDRINFO_MARK;
		msg = "ignoring blackholed / bogus server: ";
	} else if (isc_sockaddr_ismulticast(sa)) {
		addr->flags |= FCTX_ADDRINFO_MARK;
		msg = "ignoring multicast address: ";
	} else if (isc_sockaddr_isexperimental(sa)) {
		addr->flags |= FCTX_ADDRINFO_MARK;
		msg = "ignoring experimental address: ";
	} else if (sa->type.sa.sa_family != AF_INET6) {
		return;
	} else if (IN6_IS_ADDR_V4MAPPED(&sa->type.sin6.sin6_addr)) {
		addr->flags |= FCTX_ADDRINFO_MARK;
		msg = "ignoring IPv6 mapped IPV4 address: ";
	} else if (IN6_IS_ADDR_V4COMPAT(&sa->type.sin6.sin6_addr)) {
		addr->flags |= FCTX_ADDRINFO_MARK;
		msg = "ignoring IPv6 compatibility IPV4 address: ";
	} else
		return;

	if (!isc_log_wouldlog(dns_lctx, ISC_LOG_DEBUG(3)))
		return;

	isc_netaddr_fromsockaddr(&na, sa);
	isc_netaddr_format(&na, buf, sizeof(buf));
	FCTXTRACE2(msg, buf);
}

static inline dns_adbaddrinfo_t *
fctx_nextaddress(fetchctx_t *fctx) {
	dns_adbfind_t *find, *start;
	dns_adbaddrinfo_t *addrinfo;
	dns_adbaddrinfo_t *faddrinfo;

	/*
	 * Return the next untried address, if any.
	 */

	/*
	 * Find the first unmarked forwarder (if any).
	 */
	for (addrinfo = ISC_LIST_HEAD(fctx->forwaddrs);
	     addrinfo != NULL;
	     addrinfo = ISC_LIST_NEXT(addrinfo, publink)) {
		if (!UNMARKED(addrinfo))
			continue;
		possibly_mark(fctx, addrinfo);
		if (UNMARKED(addrinfo)) {
			addrinfo->flags |= FCTX_ADDRINFO_MARK;
			fctx->find = NULL;
			return (addrinfo);
		}
	}

	/*
	 * No forwarders.  Move to the next find.
	 */

	fctx->attributes |= FCTX_ATTR_TRIEDFIND;

	find = fctx->find;
	if (find == NULL)
		find = ISC_LIST_HEAD(fctx->finds);
	else {
		find = ISC_LIST_NEXT(find, publink);
		if (find == NULL)
			find = ISC_LIST_HEAD(fctx->finds);
	}

	/*
	 * Find the first unmarked addrinfo.
	 */
	addrinfo = NULL;
	if (find != NULL) {
		start = find;
		do {
			for (addrinfo = ISC_LIST_HEAD(find->list);
			     addrinfo != NULL;
			     addrinfo = ISC_LIST_NEXT(addrinfo, publink)) {
				if (!UNMARKED(addrinfo))
					continue;
				possibly_mark(fctx, addrinfo);
				if (UNMARKED(addrinfo)) {
					addrinfo->flags |= FCTX_ADDRINFO_MARK;
					break;
				}
			}
			if (addrinfo != NULL)
				break;
			find = ISC_LIST_NEXT(find, publink);
			if (find == NULL)
				find = ISC_LIST_HEAD(fctx->finds);
		} while (find != start);
	}

	fctx->find = find;
	if (addrinfo != NULL)
		return (addrinfo);

	/*
	 * No nameservers left.  Try alternates.
	 */

	fctx->attributes |= FCTX_ATTR_TRIEDALT;

	find = fctx->altfind;
	if (find == NULL)
		find = ISC_LIST_HEAD(fctx->altfinds);
	else {
		find = ISC_LIST_NEXT(find, publink);
		if (find == NULL)
			find = ISC_LIST_HEAD(fctx->altfinds);
	}

	/*
	 * Find the first unmarked addrinfo.
	 */
	addrinfo = NULL;
	if (find != NULL) {
		start = find;
		do {
			for (addrinfo = ISC_LIST_HEAD(find->list);
			     addrinfo != NULL;
			     addrinfo = ISC_LIST_NEXT(addrinfo, publink)) {
				if (!UNMARKED(addrinfo))
					continue;
				possibly_mark(fctx, addrinfo);
				if (UNMARKED(addrinfo)) {
					addrinfo->flags |= FCTX_ADDRINFO_MARK;
					break;
				}
			}
			if (addrinfo != NULL)
				break;
			find = ISC_LIST_NEXT(find, publink);
			if (find == NULL)
				find = ISC_LIST_HEAD(fctx->altfinds);
		} while (find != start);
	}

	faddrinfo = addrinfo;

	/*
	 * See if we have a better alternate server by address.
	 */

	for (addrinfo = ISC_LIST_HEAD(fctx->altaddrs);
	     addrinfo != NULL;
	     addrinfo = ISC_LIST_NEXT(addrinfo, publink)) {
		if (!UNMARKED(addrinfo))
			continue;
		possibly_mark(fctx, addrinfo);
		if (UNMARKED(addrinfo) &&
		    (faddrinfo == NULL ||
		     addrinfo->srtt < faddrinfo->srtt)) {
			if (faddrinfo != NULL)
				faddrinfo->flags &= ~FCTX_ADDRINFO_MARK;
			addrinfo->flags |= FCTX_ADDRINFO_MARK;
			break;
		}
	}

	if (addrinfo == NULL) {
		addrinfo = faddrinfo;
		fctx->altfind = find;
	}

	return (addrinfo);
}

static void
fctx_try(fetchctx_t *fctx) {
	isc_result_t result;
	dns_adbaddrinfo_t *addrinfo;

	FCTXTRACE("try");

	REQUIRE(!ADDRWAIT(fctx));

	addrinfo = fctx_nextaddress(fctx);
	if (addrinfo == NULL) {
		/*
		 * We have no more addresses.  Start over.
		 */
		fctx_cancelqueries(fctx, ISC_TRUE);
		fctx_cleanupfinds(fctx);
		fctx_cleanupaltfinds(fctx);
		fctx_cleanupforwaddrs(fctx);
		fctx_cleanupaltaddrs(fctx);
		result = fctx_getaddresses(fctx);
		if (result == DNS_R_WAIT) {
			/*
			 * Sleep waiting for addresses.
			 */
			FCTXTRACE("addrwait");
			fctx->attributes |= FCTX_ATTR_ADDRWAIT;
			return;
		} else if (result != ISC_R_SUCCESS) {
			/*
			 * Something bad happened.
			 */
			fctx_done(fctx, result);
			return;
		}

		addrinfo = fctx_nextaddress(fctx);
		/*
		 * While we may have addresses from the ADB, they
		 * might be bad ones.  In this case, return SERVFAIL.
		 */
		if (addrinfo == NULL) {
			fctx_done(fctx, DNS_R_SERVFAIL);
			return;
		}
	}

	result = fctx_query(fctx, addrinfo, fctx->options);
	if (result != ISC_R_SUCCESS)
		fctx_done(fctx, result);
}

static isc_boolean_t
fctx_destroy(fetchctx_t *fctx) {
	dns_resolver_t *res;
	unsigned int bucketnum;
	isc_sockaddr_t *sa, *next_sa;

	/*
	 * Caller must be holding the bucket lock.
	 */

	REQUIRE(VALID_FCTX(fctx));
	REQUIRE(fctx->state == fetchstate_done ||
		fctx->state == fetchstate_init);
	REQUIRE(ISC_LIST_EMPTY(fctx->events));
	REQUIRE(ISC_LIST_EMPTY(fctx->queries));
	REQUIRE(ISC_LIST_EMPTY(fctx->finds));
	REQUIRE(ISC_LIST_EMPTY(fctx->altfinds));
	REQUIRE(fctx->pending == 0);
	REQUIRE(ISC_LIST_EMPTY(fctx->validators));
	REQUIRE(fctx->references == 0);

	FCTXTRACE("destroy");

	res = fctx->res;
	bucketnum = fctx->bucketnum;

	ISC_LIST_UNLINK(res->buckets[bucketnum].fctxs, fctx, link);

	/*
	 * Free bad.
	 */
	for (sa = ISC_LIST_HEAD(fctx->bad);
	     sa != NULL;
	     sa = next_sa) {
		next_sa = ISC_LIST_NEXT(sa, link);
		ISC_LIST_UNLINK(fctx->bad, sa, link);
		isc_mem_put(res->mctx, sa, sizeof(*sa));
	}

	isc_timer_detach(&fctx->timer);
	dns_message_destroy(&fctx->rmessage);
	dns_message_destroy(&fctx->qmessage);
	if (dns_name_countlabels(&fctx->domain) > 0)
		dns_name_free(&fctx->domain, res->mctx);
	if (dns_rdataset_isassociated(&fctx->nameservers))
		dns_rdataset_disassociate(&fctx->nameservers);
	dns_name_free(&fctx->name, res->mctx);
	dns_db_detach(&fctx->cache);
	dns_adb_detach(&fctx->adb);
	isc_mem_free(res->mctx, fctx->info);
	isc_mem_put(res->mctx, fctx, sizeof(*fctx));

	LOCK(&res->nlock);
	res->nfctx--;
	UNLOCK(&res->nlock);

	if (res->buckets[bucketnum].exiting &&
	    ISC_LIST_EMPTY(res->buckets[bucketnum].fctxs))
		return (ISC_TRUE);

	return (ISC_FALSE);
}

/*
 * Fetch event handlers.
 */

static void
fctx_timeout(isc_task_t *task, isc_event_t *event) {
	fetchctx_t *fctx = event->ev_arg;

	REQUIRE(VALID_FCTX(fctx));

	UNUSED(task);

	FCTXTRACE("timeout");

	if (event->ev_type == ISC_TIMEREVENT_LIFE) {
		fctx_done(fctx, ISC_R_TIMEDOUT);
	} else {
		isc_result_t result;

		fctx->timeouts++;
		/*
		 * We could cancel the running queries here, or we could let
		 * them keep going.  Right now we choose the latter...
		 */
		fctx->attributes &= ~FCTX_ATTR_ADDRWAIT;
		/*
		 * Our timer has triggered.  Reestablish the fctx lifetime
		 * timer.
		 */
		result = fctx_starttimer(fctx);
		if (result != ISC_R_SUCCESS)
			fctx_done(fctx, result);
		else
			/*
			 * Keep trying.
			 */
			fctx_try(fctx);
	}

	isc_event_free(&event);
}

static void
fctx_shutdown(fetchctx_t *fctx) {
	isc_event_t *cevent;

	/*
	 * Start the shutdown process for fctx, if it isn't already underway.
	 */

	FCTXTRACE("shutdown");

	/*
	 * The caller must be holding the appropriate bucket lock.
	 */

	if (fctx->want_shutdown)
		return;

	fctx->want_shutdown = ISC_TRUE;

	/*
	 * Unless we're still initializing (in which case the
	 * control event is still outstanding), we need to post
	 * the control event to tell the fetch we want it to
	 * exit.
	 */
	if (fctx->state != fetchstate_init) {
		cevent = &fctx->control_event;
		isc_task_send(fctx->res->buckets[fctx->bucketnum].task,
			      &cevent);
	}
}

static void
fctx_doshutdown(isc_task_t *task, isc_event_t *event) {
	fetchctx_t *fctx = event->ev_arg;
	isc_boolean_t bucket_empty = ISC_FALSE;
	dns_resolver_t *res;
	unsigned int bucketnum;
	dns_validator_t *validator;

	REQUIRE(VALID_FCTX(fctx));

	UNUSED(task);

	res = fctx->res;
	bucketnum = fctx->bucketnum;

	FCTXTRACE("doshutdown");

	/*
	 * An fctx that is shutting down is no longer in ADDRWAIT mode.
	 */
	fctx->attributes &= ~FCTX_ATTR_ADDRWAIT;

	/*
	 * Cancel all pending validators.  Note that this must be done
	 * without the bucket lock held, since that could cause deadlock.
	 */
	validator = ISC_LIST_HEAD(fctx->validators);
	while (validator != NULL) {
		dns_validator_cancel(validator);
		validator = ISC_LIST_NEXT(validator, link);
	}
	
	if (fctx->nsfetch != NULL)
		dns_resolver_cancelfetch(fctx->nsfetch);

	/*
	 * Shut down anything that is still running on behalf of this
	 * fetch.  To avoid deadlock with the ADB, we must do this
	 * before we lock the bucket lock.
	 */
	fctx_stopeverything(fctx, ISC_FALSE);

	LOCK(&res->buckets[bucketnum].lock);

	fctx->attributes |= FCTX_ATTR_SHUTTINGDOWN;

	INSIST(fctx->state == fetchstate_active ||
	       fctx->state == fetchstate_done);
	INSIST(fctx->want_shutdown);

	if (fctx->state != fetchstate_done) {
		fctx->state = fetchstate_done;
		fctx_sendevents(fctx, ISC_R_CANCELED);
	}

	if (fctx->references == 0 && fctx->pending == 0 &&
	    ISC_LIST_EMPTY(fctx->validators))
		bucket_empty = fctx_destroy(fctx);

	UNLOCK(&res->buckets[bucketnum].lock);

	if (bucket_empty)
		empty_bucket(res);
}

static void
fctx_start(isc_task_t *task, isc_event_t *event) {
	fetchctx_t *fctx = event->ev_arg;
	isc_boolean_t done = ISC_FALSE, bucket_empty = ISC_FALSE;
	dns_resolver_t *res;
	unsigned int bucketnum;

	REQUIRE(VALID_FCTX(fctx));

	UNUSED(task);

	res = fctx->res;
	bucketnum = fctx->bucketnum;

	FCTXTRACE("start");

	LOCK(&res->buckets[bucketnum].lock);

	INSIST(fctx->state == fetchstate_init);
	if (fctx->want_shutdown) {
		/*
		 * We ha