Rework linked_attributes module for the REPLACE case.

This moves to a smarter 'find the delta' based operation of the linked
attributes module, when the caller asks for a 'replace' of the link
source.  Previously we would spray operations all over the database,
even if the net result was just to modify one record.

This also means we need the transaction safety less, which may be
useful for some LDAP backends that don't provide this functionality on
the LDAP server.

Andrew Bartlett
(This used to be commit 8c88e4eb1c0a606e7899091525260e8d6558ffd0)

1 files changed, 86 insertions, 6 deletions

diff --git a/source4/dsdb/samdb/ldb_modules/linked_attributes.c b/source4/dsdb/samdb/ldb_modules/linked_attributes.c
index 803d24e34e..b3fdffe566 100644
--- a/source4/dsdb/samdb/ldb_modules/linked_attributes.c
+++ b/source4/dsdb/samdb/ldb_modules/linked_attributes.c
@@ -279,6 +279,27 @@ static int linked_attributes_add(struct ldb_module *module, struct ldb_request *
 	return setup_modifies(module->ldb, ac, ac, req->op.add.message, NULL, req->op.add.message->dn);
 }
 
+struct merge {
+	struct ldb_dn *dn;
+	bool add;
+	bool ignore;
+};
+
+static int merge_cmp(struct merge *merge1, struct merge *merge2) {
+	int ret;
+	ret = ldb_dn_compare(merge1->dn, merge2->dn);
+	if (ret == 0) {
+		if (merge1->add == merge2->add) {
+			return 0;
+		}
+		if (merge1->add == true) {
+			return 1;
+		}
+		return -1;
+	}
+	return ret;
+}
+
 static int linked_attributes_mod_replace_search_callback(struct ldb_context *ldb, void *context, struct ldb_reply *ares) 
 {
 	struct replace_context *ac2 = talloc_get_type(context, struct replace_context);
@@ -296,16 +317,63 @@ static int linked_attributes_mod_replace_search_callback(struct ldb_context *ldb
 		
 		/* See if this element already exists */
 		if (search_el) {
-			int ret;
+
+			struct merge *merged_list = NULL;
+
+			int ret, size = 0, i;
 			struct ldb_message *msg = ldb_msg_new(ac);
 			if (!msg) {
 				ldb_oom(ac->module->ldb);
 				return LDB_ERR_OPERATIONS_ERROR;
 			}
 
-			/* Lazy option:  Delete and add the elements on all members */
-			msg->num_elements = 1;
-			msg->elements = search_el;
+			/* Add all the existing elements, marking as 'proposed for delete' by setting .add = false */
+			for (i=0; i < search_el->num_values; i++) {
+				merged_list = talloc_realloc(ares, merged_list, struct merge, size + 1);
+				merged_list[size].dn = ldb_dn_new(merged_list, ldb, (char *)search_el->values[i].data);
+				merged_list[size].add = false;
+				merged_list[size].ignore = false;
+				size++;
+			}
+
+			/* Add all the new replacement elements, marking as 'proposed for add' by setting .add = true */
+			for (i=0; i < ac2->el->num_values; i++) {
+				merged_list = talloc_realloc(ares, merged_list, struct merge, size + 1);
+				merged_list[size].dn = ldb_dn_new(merged_list, ldb, (char *)ac2->el->values[i].data);
+				merged_list[size].add = true;
+				merged_list[size].ignore = false;
+				size++;
+			}
+
+			/* Sort the list, so we can pick out an add and delete for the same DN, and eliminate them */
+			qsort(merged_list, size,
+			      sizeof(*merged_list),
+			      (comparison_fn_t)merge_cmp);
+
+			/* Now things are sorted, it is trivial to mark pairs of DNs as 'ignore' */
+			for (i=0; i + 1 < size; i++) {
+				if (ldb_dn_compare(merged_list[i].dn, 
+						   merged_list[i+1].dn) == 0 
+				    /* Fortunetly the sort also sorts 'add == false' first */
+				    && merged_list[i].add == false
+				    && merged_list[i+1].add == true) {
+
+					/* Mark as ignore, so we include neither in the actual operations */
+					merged_list[i].ignore = true;
+					merged_list[i+1].ignore = true;
+				}
+			}
+
+			/* Arrange to delete anything the search found that we don't re-add */
+			for (i=0; i < size; i++) {
+				if (merged_list[i].ignore == false
+				    && merged_list[i].add == false) {
+					ldb_msg_add_steal_string(msg, search_el->name, 
+								 ldb_dn_get_linearized(merged_list[i].dn));
+				}
+			}
+
+			/* The DN to set on the linked attributes is the original DN of the modify message */
 			msg->dn = ac->orig_req->op.mod.message->dn;
 			
 			ret = setup_modifies(ac->module->ldb, ac2, ac, msg, ares->message->dn, NULL);
@@ -313,13 +381,21 @@ static int linked_attributes_mod_replace_search_callback(struct ldb_context *ldb
 				return ret;
 			}
 
-			msg->elements = ac2->el;
+			/* Now add links for all the actually new elements */
+			for (i=0; i < size; i++) {
+				if (merged_list[i].ignore == false && merged_list[i].add == true) {
+					ldb_msg_add_steal_string(msg, search_el->name, 
+								 ldb_dn_get_linearized(merged_list[i].dn));
+				}
+			}
 
 			ret = setup_modifies(ac->module->ldb, ac2, ac, msg, NULL, ares->message->dn);
 			if (ret != LDB_SUCCESS) {
 				return ret;
 			}
 			
+			talloc_free(merged_list);
+
 		} else {
 			/* Looks like it doesn't exist, process like an 'add' */
 			struct ldb_message *msg = ldb_msg_new(ac);
@@ -411,6 +487,7 @@ static int linked_attributes_modify(struct ldb_module *module, struct ldb_reques
 			return LDB_ERR_OBJECT_CLASS_VIOLATION;			
 		}
 
+		/* Replace with new set of values */
 		if (((el->flags & LDB_FLAG_MOD_MASK) == LDB_FLAG_MOD_REPLACE)
 		    && el->num_values > 0) {
 			struct replace_context *ac2 = talloc(ac, struct replace_context);
@@ -461,6 +538,8 @@ static int linked_attributes_modify(struct ldb_module *module, struct ldb_reques
 			}
 			
 			continue;
+
+			/* Delete all values case */
 		} else if (((el->flags & LDB_FLAG_MOD_MASK) & (LDB_FLAG_MOD_DELETE|LDB_FLAG_MOD_REPLACE)) 
 			   && el->num_values == 0) {
 			const char **attrs = talloc_array(ac, const char *, 2);
@@ -508,7 +587,8 @@ static int linked_attributes_modify(struct ldb_module *module, struct ldb_reques
 			
 			continue;
 		}
-		/* Prepare the modify (mod element) on the targets */
+
+		/* Prepare the modify (mod element) on the targets, for a normal modify request */
 
 		/* For each value being moded, we need to setup the modify */
 		for (j=0; j < el->num_values; j++) {