s4:dsdb - enhance "get_last_structural_class()" for optimisations

If the objectclass entry has been sorted before we are able to determine
the (last) structural or 88 object class in constant time.

Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Signed-off-by: Andrew Bartlett <abartlet@samba.org>

3 files changed, 29 insertions, 10 deletions

diff --git a/source4/dsdb/samdb/ldb_modules/descriptor.c b/source4/dsdb/samdb/ldb_modules/descriptor.c
index 409d08dea9..47207db201 100644
--- a/source4/dsdb/samdb/ldb_modules/descriptor.c
+++ b/source4/dsdb/samdb/ldb_modules/descriptor.c
@@ -542,7 +542,8 @@ static int descriptor_add(struct ldb_module *module, struct ldb_request *req)
 		return ldb_operr(ldb);
 	}
 
-	objectclass = get_last_structural_class(schema, objectclass_element, req);
+	objectclass = get_last_structural_class(schema, objectclass_element,
+						false);
 	if (objectclass == NULL) {
 		return ldb_operr(ldb);
 	}
@@ -660,7 +661,8 @@ static int descriptor_modify(struct ldb_module *module, struct ldb_request *req)
 		return ldb_operr(ldb);
 	}
 
-	objectclass = get_last_structural_class(schema, objectclass_element, req);
+	objectclass = get_last_structural_class(schema, objectclass_element,
+						false);
 	if (objectclass == NULL) {
 		return ldb_operr(ldb);
 	}
diff --git a/source4/dsdb/samdb/ldb_modules/objectclass.c b/source4/dsdb/samdb/ldb_modules/objectclass.c
index b66b4d7a5f..0d75e5ff89 100644
--- a/source4/dsdb/samdb/ldb_modules/objectclass.c
+++ b/source4/dsdb/samdb/ldb_modules/objectclass.c
@@ -637,7 +637,8 @@ static int objectclass_do_add(struct oc_context *ac)
 
 		/* Make sure its valid to add an object of this type */
 		objectclass = get_last_structural_class(ac->schema,
-							objectclass_element, ac->req);
+							objectclass_element,
+							true);
 		if(objectclass == NULL) {
 			ldb_asprintf_errstring(ldb,
 					       "Failed to find a structural class for %s",
@@ -1112,7 +1113,7 @@ static int objectclass_do_mod(struct oc_context *ac)
 
 		/* Get the new top-most structural object class */
 		objectclass = get_last_structural_class(ac->schema, oc_el_entry,
-							ac->req);
+							false);
 		if (objectclass == NULL) {
 			ldb_set_errstring(ldb,
 					  "objectclass: cannot delete all structural objectclasses!");
@@ -1312,7 +1313,8 @@ static int objectclass_do_rename2(struct oc_context *ac)
 			/* existing entry without a valid object class? */
 			return ldb_operr(ldb);
 		}
-		objectclass = get_last_structural_class(ac->schema, oc_el_entry, ac->req);
+		objectclass = get_last_structural_class(ac->schema, oc_el_entry,
+							false);
 		if (objectclass == NULL) {
 			/* existing entry without a valid object class? */
 			return ldb_operr(ldb);
diff --git a/source4/dsdb/samdb/ldb_modules/schema.c b/source4/dsdb/samdb/ldb_modules/schema.c
index 51c6a658d6..f483fd386e 100644
--- a/source4/dsdb/samdb/ldb_modules/schema.c
+++ b/source4/dsdb/samdb/ldb_modules/schema.c
@@ -29,14 +29,29 @@
 #include "libcli/security/security.h"
 #include "dsdb/samdb/ldb_modules/schema.h"
 
-
-const struct dsdb_class * get_last_structural_class(const struct dsdb_schema *schema,const struct ldb_message_element *element,
-						    struct ldb_request *parent)
+/*
+ * This function determines the (last) structural or 88 object class of a passed
+ * "objectClass" attribute.
+ * Without schema this does not work and hence NULL is returned. If the
+ * "objectClass" attribute has already been sorted then only a check on the
+ * last value is necessary (MS-ADTS 3.1.1.1.4)
+ */
+const struct dsdb_class *get_last_structural_class(const struct dsdb_schema *schema,
+						   const struct ldb_message_element *element,
+						   bool sorted)
 {
 	const struct dsdb_class *last_class = NULL;
-	unsigned int i;
+	unsigned int i = 0;
+
+	if (schema == NULL) {
+		return NULL;
+	}
+
+	if (sorted && (element->num_values > 1)) {
+		i = element->num_values - 1;
+	}
 
-	for (i = 0; i < element->num_values; i++){
+	for (; i < element->num_values; i++){
 		const struct dsdb_class *tmp_class = dsdb_class_by_lDAPDisplayName_ldb_val(schema, &element->values[i]);
 
 		if(tmp_class == NULL) {