add rdataset cloning

lib/dns/include/dns/rdataset.h

@@ -65,6 +65,8 @@ typedef struct dns_rdatasetmethods {
 	dns_result_t		(*next)(dns_rdataset_t *rdataset);
 	void			(*current)(dns_rdataset_t *rdataset,
 					   dns_rdata_t *rdata);
+	void			(*clone)(dns_rdataset_t *source,
+					 dns_rdataset_t *target);
 } dns_rdatasetmethods_t;
 
 #define DNS_RDATASET_MAGIC		0x444E5352U	/* DNSR. */
@@ -167,6 +169,20 @@ dns_rdataset_makequestion(dns_rdataset_t *rdataset, dns_rdataclass_t rdclass,
  *	'rdataset' is a valid, associated, question rdataset.
  */
 
+void
+dns_rdataset_clone(dns_rdataset_t *source, dns_rdataset_t *target);
+/*
+ * Make 'target' refer to the same rdataset as 'source'.
+ *
+ * Requires:
+ *	'source' is a valid, associated rdataset.
+ *
+ *	'target' is a valid, dissociated rdataset.
+ *
+ * Ensures:
+ *	'target' references the same rdataset as 'source.
+ */
+
 dns_result_t
 dns_rdataset_first(dns_rdataset_t *rdataset);
 /*

lib/dns/rbtdb.c

@@ -171,16 +171,18 @@ typedef struct {
 	isc_stdtime_t		now;
 } rbtdb_load_t;
 
-static void rdataset_disassociate(dns_rdataset_t *rdatasetp);
+static void rdataset_disassociate(dns_rdataset_t *rdataset);
 static dns_result_t rdataset_first(dns_rdataset_t *rdataset);
 static dns_result_t rdataset_next(dns_rdataset_t *rdataset);
 static void rdataset_current(dns_rdataset_t *rdataset, dns_rdata_t *rdata);
+static void rdataset_clone(dns_rdataset_t *source, dns_rdataset_t *target);
 
 static dns_rdatasetmethods_t rdataset_methods = {
 	rdataset_disassociate,
 	rdataset_first,
 	rdataset_next,
-	rdataset_current
+	rdataset_current,
+	rdataset_clone
 };
 
 static void rdatasetiter_destroy(dns_rdatasetiter_t **iteratorp);
@@ -3105,6 +3107,22 @@ rdataset_current(dns_rdataset_t *rdataset, dns_rdata_t *rdata) {
 	dns_rdata_fromregion(rdata, rdataset->rdclass, rdataset->type, &r);
 }
 
+static void
+rdataset_clone(dns_rdataset_t *source, dns_rdataset_t *target) {
+	dns_db_t *db = source->private1;
+	dns_dbnode_t *node = source->private2;
+	dns_dbnode_t *cloned_node;
+
+	attachnode(db, &node, &cloned_node);
+	*target = *source;
+
+	/*
+	 * Reset iterator state.
+	 */
+	target->private4 = NULL;
+	target->private5 = NULL;
+}
+
 
 /*
  * Rdataset Iterator Methods

lib/dns/rdatalist.c

@@ -27,12 +27,14 @@ static void disassociate(dns_rdataset_t *rdatasetp);
 static dns_result_t first(dns_rdataset_t *rdataset);
 static dns_result_t next(dns_rdataset_t *rdataset);
 static void current(dns_rdataset_t *rdataset, dns_rdata_t *rdata);
+static void clone(dns_rdataset_t *source, dns_rdataset_t *target);
 
 static dns_rdatasetmethods_t methods = {
 	disassociate,
 	first,
 	next,
-	current
+	current,
+	clone
 };
 
 dns_result_t
@@ -104,3 +106,13 @@ current(dns_rdataset_t *rdataset, dns_rdata_t *rdata) {
 	*rdata = *list_rdata;
 	ISC_LINK_INIT(rdata, link);
 }
+
+static void
+clone(dns_rdataset_t *source, dns_rdataset_t *target) {
+	*target = *source;
+
+	/*
+	 * Reset iterator state.
+	 */
+	target->private2 = NULL;
+}

lib/dns/rdataset.c

@@ -122,11 +122,17 @@ question_current(dns_rdataset_t *rdataset, dns_rdata_t *rdata) {
 	REQUIRE(0);
 }
 
+static void
+question_clone(dns_rdataset_t *source, dns_rdataset_t *target) {
+	*target = *source;
+}
+
 static dns_rdatasetmethods_t question_methods = {
 	question_disassociate,
 	question_cursor,
 	question_cursor,
-	question_current
+	question_current,
+	question_clone
 };
 
 void
@@ -148,6 +154,21 @@ dns_rdataset_makequestion(dns_rdataset_t *rdataset, dns_rdataclass_t rdclass,
 	rdataset->attributes |= DNS_RDATASETATTR_QUESTION;
 }
 
+void
+dns_rdataset_clone(dns_rdataset_t *source, dns_rdataset_t *target) {
+
+	/*
+	 * Make 'target' refer to the same rdataset as 'source'.
+	 */
+
+	REQUIRE(DNS_RDATASET_VALID(source));
+	REQUIRE(source->methods != NULL);
+	REQUIRE(DNS_RDATASET_VALID(target));
+	REQUIRE(target->methods == NULL);
+	
+	(source->methods->clone)(source, target);
+}
+
 dns_result_t
 dns_rdataset_first(dns_rdataset_t *rdataset) {