make "max_restarts" a configurable value

MAX_RESTARTS is no longer hard-coded; ns_server_setmaxrestarts()
and dns_client_setmaxrestarts() can now be used to modify the
max-restarts value at runtime. in both cases, the default is 11.

(cherry picked from commit c5588babaf)

bin/delv/delv.c

@@ -76,6 +76,12 @@
 
 #define MAXNAME (DNS_NAME_MAXTEXT + 1)
 
+/*
+ * Default maximum number of chained queries before we give up
+ * to prevent CNAME loops.
+ */
+#define MAX_RESTARTS 11
+
 /* Variables used internally by delv. */
 char *progname;
 static isc_mem_t *mctx = NULL;
@@ -1776,6 +1782,8 @@ main(int argc, char *argv[]) {
 		goto cleanup;
 	}
 
+	dns_client_setmaxrestarts(client, MAX_RESTARTS);
+
 	/* Set the nameserver */
 	if (server != NULL) {
 		addserver(client);

lib/dns/client.c

@@ -60,8 +60,6 @@
 #define UCTX_MAGIC    ISC_MAGIC('U', 'c', 't', 'x')
 #define UCTX_VALID(c) ISC_MAGIC_VALID(c, UCTX_MAGIC)
 
-#define MAX_RESTARTS 11
-
 #ifdef TUNE_LARGE
 #define RESOLVER_NTASKS 523
 #else /* ifdef TUNE_LARGE */
@@ -95,6 +93,7 @@ struct dns_client {
 
 	unsigned int find_timeout;
 	unsigned int find_udpretries;
+	uint8_t max_restarts;
 
 	isc_refcount_t references;
 
@@ -105,6 +104,7 @@ struct dns_client {
 
 #define DEF_FIND_TIMEOUT    5
 #define DEF_FIND_UDPRETRIES 3
+#define DEF_MAX_RESTARTS    11
 
 /*%
  * Internal state for a single name resolution procedure
@@ -281,7 +281,11 @@ dns_client_create(isc_mem_t *mctx, isc_appctx_t *actx, isc_taskmgr_t *taskmgr,
 
 	client = isc_mem_get(mctx, sizeof(*client));
 	*client = (dns_client_t){
-		.actx = actx, .taskmgr = taskmgr, .timermgr = timermgr, .nm = nm
+		.actx = actx,
+		.taskmgr = taskmgr,
+		.timermgr = timermgr,
+		.nm = nm,
+		.max_restarts = DEF_MAX_RESTARTS,
 	};
 
 	isc_mutex_init(&client->lock);
@@ -474,6 +478,14 @@ dns_client_clearservers(dns_client_t *client, dns_rdataclass_t rdclass,
 	return (result);
 }
 
+void
+dns_client_setmaxrestarts(dns_client_t *client, uint8_t max_restarts) {
+	REQUIRE(DNS_CLIENT_VALID(client));
+	REQUIRE(max_restarts > 0);
+
+	client->max_restarts = max_restarts;
+}
+
 static isc_result_t
 getrdataset(isc_mem_t *mctx, dns_rdataset_t **rdatasetp) {
 	dns_rdataset_t *rdataset;
@@ -886,7 +898,9 @@ client_resfind(resctx_t *rctx, dns_fetchevent_t *event) {
 		/*
 		 * Limit the number of restarts.
 		 */
-		if (want_restart && rctx->restarts == MAX_RESTARTS) {
+		if (want_restart &&
+		    rctx->restarts == rctx->client->max_restarts)
+		{
 			want_restart = false;
 			result = ISC_R_QUOTA;
 			send_event = true;

lib/dns/include/dns/client.h

@@ -189,6 +189,19 @@ dns_client_clearservers(dns_client_t *client, dns_rdataclass_t rdclass,
  *\li	Anything else				Failure.
  */
 
+void
+dns_client_setmaxrestarts(dns_client_t *client, uint8_t max_restarts);
+/*%<
+ * Set the number of permissible chained queries before we give up,
+ * to prevent CNAME loops. This defaults to 11.
+ *
+ * Requires:
+ *
+ *\li	'client' is a valid client.
+
+ *\li	'max_restarts' is greater than 0.
+ */
+
 isc_result_t
 dns_client_resolve(dns_client_t *client, const dns_name_t *name,
 		   dns_rdataclass_t rdclass, dns_rdatatype_t type,

lib/dns/include/dns/view.h

@@ -193,6 +193,7 @@ struct dns_view {
 	dns_badcache_t	 *failcache;
 	uint32_t	  maxrrperset;
 	uint32_t	  maxtypepername;
+	uint8_t		  max_restarts;
 
 	/*
 	 * Configurable data for server use only,
@@ -1427,4 +1428,16 @@ dns_view_setmaxtypepername(dns_view_t *view, uint32_t value);
  * Set the maximum resource record types per owner name that can be cached.
  */
 
+void
+dns_view_setmaxrestarts(dns_view_t *view, uint8_t max_restarts);
+/*%<
+ * Set the number of permissible chained queries before we give up,
+ * to prevent CNAME loops. This defaults to 11.
+ *
+ * Requires:
+ *
+ *\li	'view' is valid;
+ *\li	'max_restarts' is greater than 0.
+ */
+
 ISC_LANG_ENDDECLS

lib/dns/view.c

@@ -88,6 +88,12 @@ adb_shutdown(isc_task_t *task, isc_event_t *event);
 static void
 req_shutdown(isc_task_t *task, isc_event_t *event);
 
+/*%
+ * Default maximum number of chained queries before we give up
+ * to prevent CNAME loops.
+ */
+#define DEFAULT_MAX_RESTARTS 11
+
 isc_result_t
 dns_view_create(isc_mem_t *mctx, dns_rdataclass_t rdclass, const char *name,
 		dns_view_t **viewp) {
@@ -266,6 +272,8 @@ dns_view_create(isc_mem_t *mctx, dns_rdataclass_t rdclass, const char *name,
 	view->hooktable = NULL;
 	view->hooktable_free = NULL;
 
+	view->max_restarts = DEFAULT_MAX_RESTARTS;
+
 	isc_mutex_init(&view->new_zone_lock);
 
 	result = dns_order_create(view->mctx, &view->order);
@@ -2780,3 +2788,11 @@ dns_view_setmaxtypepername(dns_view_t *view, uint32_t value) {
 		dns_cache_setmaxtypepername(view->cache, value);
 	}
 }
+
+void
+dns_view_setmaxrestarts(dns_view_t *view, uint8_t max_restarts) {
+	REQUIRE(DNS_VIEW_VALID(view));
+	REQUIRE(max_restarts > 0);
+
+	view->max_restarts = max_restarts;
+}

lib/ns/include/ns/server.h

@@ -100,6 +100,7 @@ struct ns_server {
 	uint16_t       transfer_tcp_message_size;
 	bool	       interface_auto;
 	dns_tkeyctx_t *tkeyctx;
+	uint8_t	       max_restarts;
 
 	/*% Server id for NSID */
 	char *server_id;

lib/ns/query.c

@@ -85,12 +85,6 @@
 #define dns64_bis_return_excluded_addresses 1
 #endif /* if 0 */
 
-/*%
- * Maximum number of chained queries before we give up
- * to prevent CNAME loops.
- */
-#define MAX_RESTARTS 11
-
 #define QUERY_ERROR(qctx, r)                  \
 	do {                                  \
 		(qctx)->result = r;           \
@@ -2095,10 +2089,10 @@ addname:
 	/*
 	 * In some cases, a record that has been added as additional
 	 * data may *also* trigger the addition of additional data.
-	 * This cannot go more than MAX_RESTARTS levels deep.
+	 * This cannot go more than 'max-restarts' levels deep.
 	 */
 	if (trdataset != NULL && dns_rdatatype_followadditional(type)) {
-		if (client->additionaldepth++ < MAX_RESTARTS) {
+		if (client->additionaldepth++ < client->view->max_restarts) {
 			eresult = dns_rdataset_additionaldata(
 				trdataset, fname, query_additional_cb, qctx);
 		}
@@ -11945,7 +11939,9 @@ ns_query_done(query_ctx_t *qctx) {
 	 * Do we need to restart the query (e.g. for CNAME chaining)?
 	 */
 	if (qctx->want_restart) {
-		if (qctx->client->query.restarts < MAX_RESTARTS) {
+		if (qctx->client->query.restarts <
+		    qctx->client->view->max_restarts)
+		{
 			qctx->client->query.restarts++;
 			return (ns__query_start(qctx));
 		} else {

lib/ns/server.c

@@ -38,7 +38,7 @@
 isc_result_t
 ns_server_create(isc_mem_t *mctx, ns_matchview_t matchingview,
 		 ns_server_t **sctxp) {
-	ns_server_t *sctx;
+	ns_server_t *sctx = NULL;
 	isc_result_t result;
 
 	REQUIRE(sctxp != NULL && *sctxp == NULL);