dsdb:replmd: add compatible feature helper function

repl_meta_data.c uses the compatible features attribute of the
"@SAMBA_DSDB" special object to record that linked attributes are
being stored in the database in a sorted order. Soon the
linked_attributes module is going to want to know the same thing, and
in time other modules will want to know about other compatible
features, so we introduce a helper function.

Error checking is slightly improved.

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

2 files changed, 56 insertions, 22 deletions

diff --git a/source4/dsdb/samdb/ldb_modules/repl_meta_data.c b/source4/dsdb/samdb/ldb_modules/repl_meta_data.c
index 578ffe8a2b5..754f909467a 100644
--- a/source4/dsdb/samdb/ldb_modules/repl_meta_data.c
+++ b/source4/dsdb/samdb/ldb_modules/repl_meta_data.c
@@ -325,37 +325,24 @@ static int replmd_init(struct ldb_module *module)
 {
 	struct replmd_private *replmd_private;
 	struct ldb_context *ldb = ldb_module_get_ctx(module);
-	static const char *samba_dsdb_attrs[] = { SAMBA_COMPATIBLE_FEATURES_ATTR, NULL };
-	struct ldb_dn *samba_dsdb_dn;
-	struct ldb_result *res;
 	int ret;
-	TALLOC_CTX *frame = talloc_stackframe();
+
 	replmd_private = talloc_zero(module, struct replmd_private);
 	if (replmd_private == NULL) {
 		ldb_oom(ldb);
-		TALLOC_FREE(frame);
 		return LDB_ERR_OPERATIONS_ERROR;
 	}
-	ldb_module_set_private(module, replmd_private);
-
-	replmd_private->schema_dn = ldb_get_schema_basedn(ldb);
-
-	samba_dsdb_dn = ldb_dn_new(frame, ldb, "@SAMBA_DSDB");
-	if (!samba_dsdb_dn) {
-		TALLOC_FREE(frame);
-		return ldb_oom(ldb);
-	}
 
-	ret = dsdb_module_search_dn(module, frame, &res, samba_dsdb_dn,
-	                            samba_dsdb_attrs, DSDB_FLAG_NEXT_MODULE, NULL);
-	if (ret == LDB_SUCCESS) {
-		replmd_private->sorted_links
-			= ldb_msg_check_string_attribute(res->msgs[0],
-							 SAMBA_COMPATIBLE_FEATURES_ATTR,
-							 SAMBA_SORTED_LINKS_FEATURE);
+	ret = dsdb_check_samba_compatible_feature(module,
+						  SAMBA_SORTED_LINKS_FEATURE,
+						  &replmd_private->sorted_links);
+	if (ret != LDB_SUCCESS) {
+		talloc_free(replmd_private);
+		return ret;
 	}
-	TALLOC_FREE(frame);
 
+	replmd_private->schema_dn = ldb_get_schema_basedn(ldb);
+	ldb_module_set_private(module, replmd_private);
 	return ldb_next_init(module);
 }
 
diff --git a/source4/dsdb/samdb/ldb_modules/util.c b/source4/dsdb/samdb/ldb_modules/util.c
index ba1cfffe574..20c854f0b9a 100644
--- a/source4/dsdb/samdb/ldb_modules/util.c
+++ b/source4/dsdb/samdb/ldb_modules/util.c
@@ -681,6 +681,53 @@ int dsdb_check_single_valued_link(const struct dsdb_attribute *attr,
 	return LDB_SUCCESS;
 }
 
+
+int dsdb_check_samba_compatible_feature(struct ldb_module *module,
+					const char *feature,
+					bool *found)
+{
+	struct ldb_context *ldb = ldb_module_get_ctx(module);
+	struct ldb_result *res;
+	static const char *samba_dsdb_attrs[] = {
+		SAMBA_COMPATIBLE_FEATURES_ATTR,
+		NULL
+	};
+	int ret;
+	struct ldb_dn *samba_dsdb_dn = NULL;
+	TALLOC_CTX *tmp_ctx = talloc_new(ldb);
+	if (tmp_ctx == NULL) {
+		*found = false;
+		return ldb_oom(ldb);
+	}
+	*found = false;
+
+	samba_dsdb_dn = ldb_dn_new(tmp_ctx, ldb, "@SAMBA_DSDB");
+	if (samba_dsdb_dn == NULL) {
+		TALLOC_FREE(tmp_ctx);
+		return ldb_oom(ldb);
+	}
+
+	ret = dsdb_module_search_dn(module,
+				    tmp_ctx,
+				    &res,
+				    samba_dsdb_dn,
+				    samba_dsdb_attrs,
+				    DSDB_FLAG_NEXT_MODULE,
+				    NULL);
+	if (ret == LDB_SUCCESS) {
+		*found = ldb_msg_check_string_attribute(
+			res->msgs[0],
+			SAMBA_COMPATIBLE_FEATURES_ATTR,
+			feature);
+	} else if (ret == LDB_ERR_NO_SUCH_OBJECT) {
+		/* it is not an error not to find it */
+		ret = LDB_SUCCESS;
+	}
+	TALLOC_FREE(tmp_ctx);
+	return ret;
+}
+
+
 /*
   check if an optional feature is enabled on our own NTDS DN