Pass back errors to the client when trying multiple federation destinations

synapse/federation/federation_client.py

@@ -821,28 +821,19 @@ async def _do_send_invite(
                 },
             )
         except HttpResponseException as e:
-            if e.code in [400, 404]:
-                err = e.to_synapse_error()
-
-                # If we receive an error response that isn't a generic error, we
-                # assume that the remote understands the v2 invite API and this
-                # is a legitimate error.
-                if err.errcode != Codes.UNKNOWN:
-                    raise err
-
-                # Otherwise, we assume that the remote server doesn't understand
-                # the v2 invite API. That's ok provided the room uses old-style event
-                # IDs.
+            # If an error is received that is due to an unrecognised endpoint,
+            # fallback to the v1 endpoint if the room uses old-style event IDs.
+            # Otherwise consider it a legitmate error and raise.
+            err = e.to_synapse_error()
+            if self._is_unknown_endpoint(e, err):
                 if room_version.event_format != EventFormatVersions.V1:
                     raise SynapseError(
                         400,
                         "User's homeserver does not support this room version",
                         Codes.UNSUPPORTED_ROOM_VERSION,
                     )
-            elif e.code in (403, 429):
-                raise e.to_synapse_error()
             else:
-                raise
+                raise err
 
         # Didn't work, try v1 API.
         # Note the v1 API returns a tuple of `(200, content)`