Clarify the invite flows

synapse/events/__init__.py

@@ -41,8 +41,12 @@ class _EventInternalMetadata(object):
     def is_outlier(self):
         return getattr(self, "outlier", False)
 
-    def is_invite_from_remote(self):
-        return getattr(self, "invite_from_remote", False)
+    def is_new_remote_event(self):
+        """Whether this is a new remote event, like an invite or an invite
+        rejection. This is needed as those events are marked as outliers, but
+        they still need to be processed.
+        """
+        return getattr(self, "new_remote_event", False)
 
     def get_send_on_behalf_of(self):
         """Whether this server should send the event on behalf of another server.

synapse/handlers/federation.py

@@ -43,6 +43,7 @@ from synapse.api.errors import (
     StoreError,
     SynapseError,
 )
+from synapse.crypto.event_signing import compute_event_signature
 from synapse.events.validator import EventValidator
 from synapse.replication.http.federation import (
     ReplicationCleanRoomRestServlet,
@@ -1283,7 +1284,15 @@ class FederationHandler(BaseHandler):
             )
 
         event.internal_metadata.outlier = True
-        event.internal_metadata.invite_from_remote = True
+        event.internal_metadata.new_remote_event = True
+
+        event.signatures.update(
+            compute_event_signature(
+                event,
+                self.hs.hostname,
+                self.hs.config.signing_key[0]
+            )
+        )
 
         context = yield self.state_handler.compute_event_context(event)
         yield self.persist_events_and_notify([(event, context)])
@@ -1301,6 +1310,7 @@ class FederationHandler(BaseHandler):
         # Mark as outlier as we don't have any state for this event; we're not
         # even in the room.
         event.internal_metadata.outlier = True
+        event.internal_metadata.new_remote_event = True
 
         # Try the host that we succesfully called /make_leave/ on first for
         # the /send_leave/ request.

synapse/storage/roommember.py

@@ -588,10 +588,13 @@ class RoomMemberStore(RoomMemberWorkerStore):
             )
 
             # We update the local_invites table only if the event is "current",
-            # i.e., its something that has just happened.
-            # The only current event that can also be an outlier is if its an
-            # invite that has come in across federation.
-            is_new_state = not backfilled
+            # i.e., its something that has just happened. If the event is an
+            # outlier it is only current if its a "new remote event", like a
+            # remote invite or a rejection of a remote invite.
+            is_new_state = not backfilled and (
+                not event.internal_metadata.is_outlier()
+                or event.internal_metadata.is_new_remote_event()
+            )
             is_mine = self.hs.is_mine_id(event.state_key)
             if is_new_state and is_mine:
                 if event.membership == Membership.INVITE: