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.

bin/delv/delv.c

@@ -88,6 +88,12 @@
 
 #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 = NULL;
 static isc_mem_t *mctx = NULL;
@@ -1898,6 +1904,7 @@ run_resolve(void *arg) {
 	/* Create client */
 	CHECK(dns_client_create(mctx, loopmgr, netmgr, 0, tlsctx_client_cache,
 				&client, srcaddr4, srcaddr6));
+	dns_client_setmaxrestarts(client, MAX_RESTARTS);
 
 	/* Set the nameserver */
 	if (server != NULL) {
@@ -2162,6 +2169,7 @@ run_server(void *arg) {
 	dns_view_setcache(view, cache, false);
 	dns_cache_detach(&cache);
 	dns_view_setdstport(view, destport);
+	dns_view_setmaxrestarts(view, MAX_RESTARTS);
 
 	CHECK(dns_rootns_create(mctx, dns_rdataclass_in, hintfile, &roothints));
 	dns_view_sethints(view, roothints);

lib/dns/client.c

@@ -57,8 +57,6 @@
 #define UCTX_MAGIC    ISC_MAGIC('U', 'c', 't', 'x')
 #define UCTX_VALID(c) ISC_MAGIC_VALID(c, UCTX_MAGIC)
 
-#define MAX_RESTARTS 11
-
 #define CHECK(r)                             \
 	do {                                 \
 		result = (r);                \
@@ -81,6 +79,7 @@ struct dns_client {
 
 	unsigned int find_timeout;
 	unsigned int find_udpretries;
+	uint8_t max_restarts;
 
 	isc_refcount_t references;
 
@@ -90,6 +89,7 @@ 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
@@ -250,6 +250,7 @@ dns_client_create(isc_mem_t *mctx, isc_loopmgr_t *loopmgr, isc_nm_t *nm,
 	*client = (dns_client_t){
 		.loop = isc_loop_get(loopmgr, 0),
 		.nm = nm,
+		.max_restarts = DEF_MAX_RESTARTS,
 	};
 
 	result = dns_dispatchmgr_create(mctx, loopmgr, nm,
@@ -384,6 +385,14 @@ dns_client_setservers(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;
@@ -778,7 +787,9 @@ client_resfind(resctx_t *rctx, dns_fetchresponse_t *resp) {
 		/*
 		 * 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

@@ -174,6 +174,19 @@ dns_client_setservers(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.
+ */
+
 typedef void (*dns_client_resolve_cb)(dns_client_t     *client,
 				      const dns_name_t *name,
 				      dns_namelist_t   *namelist,

lib/dns/include/dns/view.h

@@ -185,6 +185,7 @@ struct dns_view {
 	unsigned int	      udpsize;
 	uint32_t	      maxrrperset;
 	uint32_t	      maxtypepername;
+	uint8_t		      max_restarts;
 
 	/*
 	 * Configurable data for server use only,
@@ -1327,4 +1328,16 @@ dns_view_getadb(dns_view_t *view, dns_adb_t **adbp);
  *\li	'adbp' is non-NULL and '*adbp' is NULL.
  */
 
+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

@@ -74,6 +74,12 @@
 
 #define DNS_VIEW_DELONLYHASH 111
 
+/*%
+ * Default maximum number of chained queries before we give up
+ * to prevent CNAME loops.
+ */
+#define DEFAULT_MAX_RESTARTS 11
+
 /*%
  * Default EDNS0 buffer size
  */
@@ -116,6 +122,7 @@ dns_view_create(isc_mem_t *mctx, dns_dispatchmgr_t *dispatchmgr,
 		.trust_anchor_telemetry = true,
 		.root_key_sentinel = true,
 		.udpsize = DEFAULT_EDNS_BUFSIZE,
+		.max_restarts = DEFAULT_MAX_RESTARTS,
 	};
 
 	isc_refcount_init(&view->references, 1);
@@ -2455,3 +2462,11 @@ dns_view_getadb(dns_view_t *view, dns_adb_t **adbp) {
 	}
 	rcu_read_unlock();
 }
+
+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

@@ -103,6 +103,7 @@ 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

@@ -86,12 +86,6 @@
 #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;           \
@@ -2046,10 +2040,10 @@ 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);
 		}
@@ -11580,7 +11574,9 @@ 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)
+		{
 			query_ctx_t *saved_qctx = NULL;
 			qctx->client->query.restarts++;
 			saved_qctx = isc_mem_get(qctx->client->manager->mctx,

lib/ns/server.c

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