Add dns_db_subtractrdataset().

Add DNS_R_UNCHANGED results for dns_db_{add,delete}rdataset().
Add merge flag to dns_db_addrdataset().
The way add and delete work should now match the .h file comments.

lib/dns/db.c

@@ -420,7 +420,7 @@ dns_db_allrdatasets(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
 dns_result_t
 dns_db_addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
 		   isc_stdtime_t now, dns_rdataset_t *rdataset,
-		   dns_rdataset_t *addedrdataset)
+		   isc_boolean_t merge, dns_rdataset_t *addedrdataset)
 {
 	/*
 	 * Add 'rdataset' to 'node' in version 'version' of 'db'.
@@ -429,7 +429,8 @@ dns_db_addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
 	REQUIRE(DNS_DB_VALID(db));
 	REQUIRE(node != NULL);
 	REQUIRE(((db->attributes & DNS_DBATTR_CACHE) == 0 && version != NULL)||
-		((db->attributes & DNS_DBATTR_CACHE) != 0 && version == NULL));
+		((db->attributes & DNS_DBATTR_CACHE) != 0 &&
+		 version == NULL && !merge));
 	REQUIRE(DNS_RDATASET_VALID(rdataset));
 	REQUIRE(rdataset->methods != NULL);
 	REQUIRE(rdataset->rdclass == db->rdclass);
@@ -438,7 +439,31 @@ dns_db_addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
 		 addedrdataset->methods == NULL));
 
 	return ((db->methods->addrdataset)(db, node, version, now, rdataset,
-					   addedrdataset));
+					   merge, addedrdataset));
+}
+
+dns_result_t
+dns_db_subtractrdataset(dns_db_t *db, dns_dbnode_t *node,
+			dns_dbversion_t *version, dns_rdataset_t *rdataset,
+			dns_rdataset_t *newrdataset)
+{
+	/*
+	 * Remove any rdata in 'rdataset' from 'node' in version 'version' of
+	 * 'db'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE(node != NULL);
+	REQUIRE(((db->attributes & DNS_DBATTR_CACHE) == 0 && version != NULL));
+	REQUIRE(DNS_RDATASET_VALID(rdataset));
+	REQUIRE(rdataset->methods != NULL);
+	REQUIRE(rdataset->rdclass == db->rdclass);
+	REQUIRE(newrdataset == NULL ||
+		(DNS_RDATASET_VALID(newrdataset) &&
+		 newrdataset->methods == NULL));
+
+	return ((db->methods->subtractrdataset)(db, node, version, rdataset,
+						newrdataset));
 }
 
 dns_result_t

lib/dns/include/dns/db.h

@@ -119,7 +119,12 @@ typedef struct dns_dbmethods {
 				       dns_dbversion_t *version,
 				       isc_stdtime_t now,
 				       dns_rdataset_t *rdataset,
+				       isc_boolean_t merge,
 				       dns_rdataset_t *addedrdataset);
+	dns_result_t	(*subtractrdataset)(dns_db_t *db, dns_dbnode_t *node,
+					    dns_dbversion_t *version,
+					    dns_rdataset_t *rdataset,
+					    dns_rdataset_t *newrdataset);
 	dns_result_t	(*deleterdataset)(dns_db_t *db, dns_dbnode_t *node,
 					  dns_dbversion_t *version,
 					  dns_rdatatype_t type);
@@ -794,12 +799,18 @@ dns_db_allrdatasets(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
 dns_result_t
 dns_db_addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
 		   isc_stdtime_t now, dns_rdataset_t *rdataset,
-		   dns_rdataset_t *addedrdataset);
+		   isc_boolean_t merge, dns_rdataset_t *addedrdataset);
 /*
  * Add 'rdataset' to 'node' in version 'version' of 'db'.
  *
  * Notes:
  *
+ *	If the database has zone semantics, 'merge' is ISC_TRUE, and an
+ *	rdataset of the same type as 'rdataset' already exists at 'node',
+ *	then the contents of 'rdataset' will be merged with the existing
+ *	rdataset.  If merge is ISC_FALSE, then rdataset will replace any
+ *	existing rdataset of the same type.
+ *
  *	The 'now' field is ignored if 'db' is a zone database.  If 'db' is
  *	a cache database, then the added rdataset will expire no later than
  *	now + rdataset->ttl.
@@ -822,13 +833,52 @@ dns_db_addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
  *	read-write version, or the database has cache semantics
  *	and version is NULL.
  *
+ *	If the database has cache semantics, 'merge' must be ISC_FALSE.
+ *
  * Returns:
  *
  *	DNS_R_SUCCESS
+ *	DNS_R_UNCHANGED			The operation did not change anything.
  *	DNS_R_NOMEMORY
- *	DNS_R_EXISTS			An rdataset with the specified
+ *	
- *					rdataset's type and version's serial
+ *	Other results are possible, depending upon the database
- *					number already exists.
+ *	implementation used.
+ */
+
+dns_result_t
+dns_db_subtractrdataset(dns_db_t *db, dns_dbnode_t *node,
+			dns_dbversion_t *version, dns_rdataset_t *rdataset,
+			dns_rdataset_t *newrdataset);
+/*
+ * Remove any rdata in 'rdataset' from 'node' in version 'version' of
+ * 'db'.
+ *
+ * Notes:
+ *
+ *	If 'newrdataset' is not NULL, then it will be attached to the
+ *	rdataset added to the database, unless the rdataset has become
+ *	nonexistent.
+ *
+ * Requires:
+ *
+ *	'db' is a valid database.
+ *
+ *	'node' is a valid node.
+ *
+ *	'rdataset' is a valid, associated rdataset with the same class
+ *	as 'db'.
+ *
+ *	'newrdataset' is NULL, or a valid, unassociated rdataset.
+ *
+ *	The database has zone semantics and 'version' is a valid
+ *	read-write version.
+ *
+ * Returns:
+ *
+ *	DNS_R_SUCCESS
+ *	DNS_R_UNCHANGED			The operation did not change anything.
+ *	DNS_R_NXRDATASET		All rdata of the same type as those
+ *					in 'rdataset' have been deleted.
  *	
  *	Other results are possible, depending upon the database
  *	implementation used.
@@ -867,7 +917,8 @@ dns_db_deleterdataset(dns_db_t *db, dns_dbnode_t *node,
  * Returns:
  *
  *	DNS_R_SUCCESS
- *	DNS_R_NOTFOUND
+ *	DNS_R_UNCHANGED			No rdatasets of 'type' existed before
+ *					the operation was attempted.
  *	
  *	Other results are possible, depending upon the database
  *	implementation used.

lib/dns/rbtdb.c

@@ -2274,6 +2274,9 @@ add(dns_rbtdb_t *rbtdb, dns_rbtnode_t *rbtnode, rbtdb_version_t *rbtversion,
 	rdatasetheader_t *header, *header_prev;
 	unsigned char *merged;
 	dns_result_t result;
+	isc_boolean_t force = ISC_FALSE;
+	isc_boolean_t header_nx;
+	isc_boolean_t newheader_nx;
 
 	/*
 	 * Add an rdatasetheader_t to a node.
@@ -2284,11 +2287,19 @@ add(dns_rbtdb_t *rbtdb, dns_rbtnode_t *rbtnode, rbtdb_version_t *rbtversion,
 	 */
 
 	if (rbtversion != NULL && !loading) {
+		/*
+		 * We always add a changed record, even if no changes end up
+		 * being made to this node, because it's harmless and
+		 * simplifies the code.
+		 */
 		changed = add_changed(rbtdb, rbtversion, rbtnode);
 		if (changed == NULL)
 			return (DNS_R_NOMEMORY);
 	}
 
+	newheader_nx = ((newheader->attributes & RDATASET_ATTR_NONEXISTENT)
+			!= 0 ? ISC_TRUE : ISC_FALSE);
+
 	header_prev = NULL;
 	for (header = rbtnode->data; header != NULL; header = header->next) {
 		if (header->type == newheader->type)
@@ -2296,13 +2307,28 @@ add(dns_rbtdb_t *rbtdb, dns_rbtnode_t *rbtnode, rbtdb_version_t *rbtversion,
 		header_prev = header;
 	}
 	if (header != NULL) {
+		header_nx = ((header->attributes & RDATASET_ATTR_NONEXISTENT)
+			     != 0 ? ISC_TRUE : ISC_FALSE);
+
+		/*
+		 * Deleting an already non-existent rdataset has no effect.
+		 */
+		if (header_nx && newheader_nx) {
+			free_rdataset(rbtdb->common.mctx, newheader);
+			return (DNS_R_UNCHANGED);
+		}
+			
 		/*
 		 * Don't merge if a nonexistent rdataset is involved.
 		 */
-		if (merge &&
+		if (merge && (header_nx || newheader_nx))
-		    ((newheader->attributes & RDATASET_ATTR_NONEXISTENT) != 0
-		     || (header->attributes & RDATASET_ATTR_NONEXISTENT) != 0))
 			merge = ISC_FALSE;
+
+		/*
+		 * XXXRTH  We should turn off merging for rdata types that
+		 * cannot be merged, e.g. SOA, CNAME, WKS.
+		 */
+
 		/*
 		 * If 'merge' is ISC_TRUE, we'll try to create a new rdataset
 		 * that is the union of 'newheader' and 'header'.
@@ -2310,6 +2336,12 @@ add(dns_rbtdb_t *rbtdb, dns_rbtnode_t *rbtnode, rbtdb_version_t *rbtversion,
 		if (merge) {
 			INSIST(rbtversion->serial >= header->serial);
 			merged = NULL;
+			if (newheader->ttl != header->ttl)
+				force = ISC_TRUE;
+			/*
+			 * XXXRTH we're going to have to deal with signatures
+			 * somehow here...
+			 */
 			result = dns_rdataslab_merge(
 					     (unsigned char *)header,
 					     (unsigned char *)newheader,
@@ -2317,6 +2349,7 @@ add(dns_rbtdb_t *rbtdb, dns_rbtnode_t *rbtnode, rbtdb_version_t *rbtversion,
 					     rbtdb->common.mctx,
 					     rbtdb->common.rdclass,
 					     header->type,
+					     force,
 					     &merged);
 			if (result == DNS_R_SUCCESS) {
 				/*
@@ -2331,13 +2364,6 @@ add(dns_rbtdb_t *rbtdb, dns_rbtnode_t *rbtnode, rbtdb_version_t *rbtversion,
 				newheader = (rdatasetheader_t *)merged;
 			} else {
 				free_rdataset(rbtdb->common.mctx, newheader);
-				if (result == DNS_R_UNCHANGED) {
-					if (addedrdataset != NULL)
-						bind_rdataset(rbtdb, rbtnode,
-							      header, now,
-							      addedrdataset);
-					return (DNS_R_SUCCESS);
-				}
 				return (result);
 			}
 		}
@@ -2368,6 +2394,15 @@ add(dns_rbtdb_t *rbtdb, dns_rbtnode_t *rbtnode, rbtdb_version_t *rbtversion,
 		/*
 		 * The rdataset type doesn't exist at this node.
 		 */
+
+		/*
+		 * If we're trying to delete it, don't bother.
+		 */
+		if (newheader_nx) {
+			free_rdataset(rbtdb->common.mctx, newheader);
+			return (DNS_R_UNCHANGED);
+		}
+	
 		newheader->next = rbtnode->data;
 		newheader->down = NULL;
 		rbtnode->data = newheader;
@@ -2394,7 +2429,7 @@ delegating_type(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
 
 static dns_result_t
 addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
-	    isc_stdtime_t now, dns_rdataset_t *rdataset,
+	    isc_stdtime_t now, dns_rdataset_t *rdataset, isc_boolean_t merge,
 	    dns_rdataset_t *addedrdataset)
 {
 	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
@@ -2403,7 +2438,7 @@ addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
 	isc_region_t region;
 	rdatasetheader_t *newheader;
 	dns_result_t result;
-	isc_boolean_t merge, delegating;
+	isc_boolean_t delegating;
 
 	REQUIRE(VALID_RBTDB(rbtdb));
 
@@ -2459,6 +2494,18 @@ addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
 	return (result);
 }
 
+static dns_result_t
+subtractrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
+		 dns_rdataset_t *rdataset, dns_rdataset_t *newrdataset) {
+	(void)db;
+	(void)node;
+	(void)version;
+	(void)rdataset;
+	(void)newrdataset;
+
+	return (DNS_R_NOTIMPLEMENTED);
+}
+
 static dns_result_t
 deleterdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
 	       dns_rdatatype_t type)
@@ -2659,6 +2706,7 @@ static dns_dbmethods_t zone_methods = {
 	zone_findrdataset,
 	allrdatasets,
 	addrdataset,
+	subtractrdataset,
 	deleterdataset
 };
 
@@ -2681,6 +2729,7 @@ static dns_dbmethods_t cache_methods = {
 	cache_findrdataset,
 	allrdatasets,
 	addrdataset,
+	subtractrdataset,
 	deleterdataset
 };