Fix local joins & make /rooms/roomid/join endpoint work

clientapi/routing/routing.go

@@ -397,7 +397,6 @@ func Setup(
 			return GetJoinedRooms(req, device, rsAPI)
 		}, httputil.WithAllowGuests()),
 	).Methods(http.MethodGet, http.MethodOptions)
-	// TODO: update for cryptoIDs
 	v3mux.Handle("/rooms/{roomID}/join",
 		httputil.MakeAuthAPI(spec.Join, userAPI, func(req *http.Request, device *userapi.Device) util.JSONResponse {
 			if r := rateLimits.Limit(req, device); r != nil {
@@ -420,6 +419,28 @@ func Setup(
 			return resp.(util.JSONResponse)
 		}, httputil.WithAllowGuests()),
 	).Methods(http.MethodPost, http.MethodOptions)
+	unstableMux.Handle("/org.matrix.msc_cryptoids/rooms/{roomID}/join",
+		httputil.MakeAuthAPI(spec.Join, userAPI, func(req *http.Request, device *userapi.Device) util.JSONResponse {
+			if r := rateLimits.Limit(req, device); r != nil {
+				return *r
+			}
+			vars, err := httputil.URLDecodeMapValues(mux.Vars(req))
+			if err != nil {
+				return util.ErrorResponse(err)
+			}
+			// Only execute a join for roomID and UserID once. If there is a join in progress
+			// it waits for it to complete and returns that result for subsequent requests.
+			resp, _, _ := sf.Do(vars["roomID"]+device.UserID, func() (any, error) {
+				return JoinRoomByIDOrAliasCryptoIDs(
+					req, device, rsAPI, userAPI, vars["roomID"],
+				), nil
+			})
+			// once all joins are processed, drop them from the cache. Further requests
+			// will be processed as usual.
+			sf.Forget(vars["roomID"] + device.UserID)
+			return resp.(util.JSONResponse)
+		}, httputil.WithAllowGuests()),
+	).Methods(http.MethodPost, http.MethodOptions)
 	// TODO: update for cryptoIDs
 	v3mux.Handle("/rooms/{roomID}/leave",
 		httputil.MakeAuthAPI("membership", userAPI, func(req *http.Request, device *userapi.Device) util.JSONResponse {

clientapi/routing/send_pdus.go

@@ -125,6 +125,7 @@ func SendPDUs(
 						JSON: spec.Forbidden("userID doesn't have power level to change visibility"),
 					}
 				}
+				if !cfg.Matrix.IsLocalServerName(pdu.RoomID().Domain()) {
 					queryReq := roomserverAPI.QueryMembershipForUserRequest{
 						RoomID: pdu.RoomID().String(),
 						UserID: *deviceUserID,
@@ -155,6 +156,7 @@ func SendPDUs(
 					}
 				}
 			}
+		}
 
 		// TODO: cryptoIDs - does it matter which order these are added?
 		// yes - if the events are for room creation.