dsdb: Fix behaviour for when to update the USN when there is no change

This handles deletions and replacements with no value, or with an
exactly specified value, as well as modifies.

Pair-Programmed-With: Stefan Metzmacher <metze@samba.org>

Andrew Bartlett

Signed-off-by: Stefan Metzmacher <metze@samba.org>

1 files changed, 28 insertions, 6 deletions

diff --git a/source4/dsdb/samdb/ldb_modules/repl_meta_data.c b/source4/dsdb/samdb/ldb_modules/repl_meta_data.c
index 24dcc6f04dc..0f2aa58635c 100644
--- a/source4/dsdb/samdb/ldb_modules/repl_meta_data.c
+++ b/source4/dsdb/samdb/ldb_modules/repl_meta_data.c
@@ -1086,6 +1086,7 @@ static int replmd_update_rpmd_element(struct ldb_context *ldb,
 	uint32_t i;
 	const struct dsdb_attribute *a;
 	struct replPropertyMetaData1 *md1;
+	bool may_skip = false;
 
 	a = dsdb_attribute_by_lDAPDisplayName(schema, el->name);
 	if (a == NULL) {
@@ -1104,13 +1105,34 @@ static int replmd_update_rpmd_element(struct ldb_context *ldb,
 		return LDB_SUCCESS;
 	}
 
-	/* if the attribute's value haven't changed then return LDB_SUCCESS
-	 * Unless we have the provision control or if the attribute is
-	 * interSiteTopologyGenerator as this page explain: http://support.microsoft.com/kb/224815
-	 * this attribute is periodicaly written by the DC responsible for the intersite generation
-	 * in a given site
+	/*
+	 * if the attribute's value haven't changed, and this isn't
+	 * just a delete of everything then return LDB_SUCCESS Unless
+	 * we have the provision control or if the attribute is
+	 * interSiteTopologyGenerator as this page explain:
+	 * http://support.microsoft.com/kb/224815 this attribute is
+	 * periodicaly written by the DC responsible for the intersite
+	 * generation in a given site
+	 *
+	 * Unchanged could be deleting or replacing an already-gone
+	 * thing with an unconstrained delete/empty replace or a
+	 * replace with the same value, but not an add with the same
+	 * value because that could be about adding a duplicate (which
+	 * is for someone else to error out on).
 	 */
-	if (old_el != NULL && ldb_msg_element_compare(el, old_el) == 0) {
+	if (old_el != NULL && ldb_msg_element_equal_ordered(el, old_el)) {
+		if (LDB_FLAG_MOD_TYPE(el->flags) == LDB_FLAG_MOD_REPLACE) {
+			may_skip = true;
+		}
+	} else if (old_el == NULL && el->num_values == 0) {
+		if (LDB_FLAG_MOD_TYPE(el->flags) == LDB_FLAG_MOD_REPLACE) {
+			may_skip = true;
+		} else if (LDB_FLAG_MOD_TYPE(el->flags) == LDB_FLAG_MOD_DELETE) {
+			may_skip = true;
+		}
+	}
+
+	if (may_skip) {
 		if (strcmp(el->name, "interSiteTopologyGenerator") != 0 &&
 		    !ldb_request_get_control(req, LDB_CONTROL_PROVISION_OID)) {
 			/*