s4-drs: cope with dupliate linked attributes

With a w2k8-R2 DC, we sometimes get linked attribute updates via DRS
which are duplicates of entries that we already have. We need to cope
with this by using a remove/add pair in the ldb_modify() to avoid a
"entry already exists" error

diff --git a/source4/dsdb/samdb/ldb_modules/repl_meta_data.c b/source4/dsdb/samdb/ldb_modules/repl_meta_data.c
index 26703528a7f32c4ea355f15629cd6ee884aabcf8..283bdf7806359778b24993a28f42067a179cc6b2 100644 (file)
--- a/source4/dsdb/samdb/ldb_modules/repl_meta_data.c
+++ b/source4/dsdb/samdb/ldb_modules/repl_meta_data.c
@@ -2123,7 +2123,9 @@ linked_attributes[0]:
                talloc_free(tmp_ctx);
                return ret;
        }
-       ret_el->values = talloc_array(msg, struct ldb_val, 1);
+       /* we allocate two entries here, in case we need a remove/add
+          pair */
+       ret_el->values = talloc_array(msg, struct ldb_val, 2);
        if (!ret_el->values) {
                ldb_oom(ldb);
                talloc_free(tmp_ctx);
@@ -2168,10 +2170,48 @@ linked_attributes[0]:
                ret = ldb_wait(mod_req->handle, LDB_WAIT_ALL);
        }
 
+       if (ret == LDB_ERR_ATTRIBUTE_OR_VALUE_EXISTS) {
+               /* the link destination exists, we need to update it
+                * by deleting the old one for the same DN then adding
+                * the new one */
+               msg->elements = talloc_realloc(msg, msg->elements,
+                                              struct ldb_message_element,
+                                              msg->num_elements+1);
+               if (msg->elements == NULL) {
+                       ldb_oom(ldb);
+                       talloc_free(tmp_ctx);
+                       return LDB_ERR_OPERATIONS_ERROR;
+               }
+               /* this relies on the backend matching the old entry
+                  only by the DN portion of the extended DN */
+               msg->elements[1] = msg->elements[0];
+               msg->elements[0].flags = LDB_FLAG_MOD_DELETE;
+               msg->num_elements++;
+
+               ret = ldb_build_mod_req(&mod_req, ldb, tmp_ctx,
+                                       msg,
+                                       NULL,
+                                       NULL, 
+                                       ldb_op_default_callback,
+                                       NULL);
+               if (ret != LDB_SUCCESS) {
+                       talloc_free(tmp_ctx);
+                       return ret;
+               }
+
+               /* Run the new request */
+               ret = ldb_next_request(module, mod_req);
+               
+               if (ret == LDB_SUCCESS) {
+                       ret = ldb_wait(mod_req->handle, LDB_WAIT_ALL);
+               }
+       }
+
        if (ret != LDB_SUCCESS) {
                ldb_debug(ldb, LDB_DEBUG_WARNING, "Failed to apply linked attribute change '%s' %s\n",
                          ldb_errstring(ldb),
                          ldb_ldif_message_string(ldb, tmp_ctx, LDB_CHANGETYPE_MODIFY, msg));
+               ret = LDB_SUCCESS;
        }
        
        talloc_free(tmp_ctx);