diff options
| -rw-r--r-- | changelog.d/15080.bugfix | 1 | ||||
| -rw-r--r-- | synapse/handlers/federation.py | 16 |
2 files changed, 16 insertions, 1 deletions
diff --git a/changelog.d/15080.bugfix b/changelog.d/15080.bugfix new file mode 100644 index 0000000000..965d0b921e --- /dev/null +++ b/changelog.d/15080.bugfix @@ -0,0 +1 @@ +Reduce the likelihood of a rare race condition where rejoining a restricted room over federation would fail. diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py index 1d0f6bcd6f..5f2057269d 100644 --- a/synapse/handlers/federation.py +++ b/synapse/handlers/federation.py @@ -952,7 +952,20 @@ class FederationHandler: # # Note that this requires the /send_join request to come back to the # same server. + prev_event_ids = None if room_version.msc3083_join_rules: + # Note that the room's state can change out from under us and render our + # nice join rules-conformant event non-conformant by the time we build the + # event. When this happens, our validation at the end fails and we respond + # to the requesting server with a 403, which is misleading — it indicates + # that the user is not allowed to join the room and the joining server + # should not bother retrying via this homeserver or any others, when + # in fact we've just messed up with building the event. + # + # To reduce the likelihood of this race, we capture the forward extremities + # of the room (prev_event_ids) just before fetching the current state, and + # hope that the state we fetch corresponds to the prev events we chose. + prev_event_ids = await self.store.get_prev_events_for_room(room_id) state_ids = await self._state_storage_controller.get_current_state_ids( room_id ) @@ -994,7 +1007,8 @@ class FederationHandler: event, unpersisted_context, ) = await self.event_creation_handler.create_new_client_event( - builder=builder + builder=builder, + prev_event_ids=prev_event_ids, ) except SynapseError as e: logger.warning("Failed to create join to %s because %s", room_id, e) |