Fix backfill maybe

federationapi/routing/backfill.go

@@ -124,7 +124,7 @@ func Backfill(
 	}
 
 	txn := gomatrixserverlib.Transaction{
-		Origin:         cfg.Matrix.ServerName,
+		Origin:         request.Destination(),
 		PDUs:           eventJSONs,
 		OriginServerTS: gomatrixserverlib.AsTimestamp(time.Now()),
 	}

roomserver/internal/api.go

@@ -87,10 +87,10 @@ func NewRoomserverAPI(
 		Durable:                base.Cfg.Global.JetStream.Durable("RoomserverInputConsumer"),
 		ServerACLs:             serverACLs,
 		Queryer: &query.Queryer{
-			DB:         roomserverDB,
-			Cache:      base.Caches,
-			ServerName: base.Cfg.Global.ServerName,
-			ServerACLs: serverACLs,
+			DB:                roomserverDB,
+			Cache:             base.Caches,
+			IsLocalServerName: base.Cfg.Global.IsLocalServerName,
+			ServerACLs:        serverACLs,
 		},
 		// perform-er structs get initialised when we have a federation sender to use
 	}

roomserver/internal/perform/perform_backfill.go

@@ -55,7 +55,7 @@ func (r *Backfiller) PerformBackfill(
 	// if we are requesting the backfill then we need to do a federation hit
 	// TODO: we could be more sensible and fetch as many events we already have then request the rest
 	//       which is what the syncapi does already.
-	if !r.IsLocalServerName(request.ServerName) {
+	if r.IsLocalServerName(request.ServerName) {
 		return r.backfillViaFederation(ctx, request, response)
 	}
 	// someone else is requesting the backfill, try to service their request.
@@ -120,8 +120,10 @@ func (r *Backfiller) backfillViaFederation(ctx context.Context, req *api.Perform
 	// Specifically the test "Outbound federation can backfill events"
 	events, err := gomatrixserverlib.RequestBackfill(
 		ctx, req.VirtualHost, requester,
-		r.KeyRing, req.RoomID, info.RoomVersion, req.PrevEventIDs(), 100)
+		r.KeyRing, req.RoomID, info.RoomVersion, req.PrevEventIDs(), 100,
+	)
 	if err != nil {
+		logrus.WithError(err).Errorf("gomatrixserverlib.RequestBackfill failed")
 		return err
 	}
 	logrus.WithField("room_id", req.RoomID).Infof("backfilled %d events", len(events))

roomserver/internal/query/query.go

@@ -37,10 +37,10 @@ import (
 )
 
 type Queryer struct {
-	DB         storage.Database
-	Cache      caching.RoomServerCaches
-	ServerName gomatrixserverlib.ServerName
-	ServerACLs *acls.ServerACLs
+	DB                storage.Database
+	Cache             caching.RoomServerCaches
+	IsLocalServerName func(gomatrixserverlib.ServerName) bool
+	ServerACLs        *acls.ServerACLs
 }
 
 // QueryLatestEventsAndState implements api.RoomserverInternalAPI
@@ -392,7 +392,7 @@ func (r *Queryer) QueryServerJoinedToRoom(
 	}
 	response.RoomExists = true
 
-	if request.ServerName == r.ServerName || request.ServerName == "" {
+	if r.IsLocalServerName(request.ServerName) || request.ServerName == "" {
 		response.IsInRoom, err = r.DB.GetLocalServerInRoom(ctx, info.RoomNID)
 		if err != nil {
 			return fmt.Errorf("r.DB.GetLocalServerInRoom: %w", err)

syncapi/routing/messages.go

@@ -528,6 +528,7 @@ func (r *messagesReq) backfill(roomID string, backwardsExtremities map[string][]
 		BackwardsExtremities: backwardsExtremities,
 		Limit:                limit,
 		ServerName:           r.cfg.Matrix.ServerName,
+		VirtualHost:          r.device.UserDomain(),
 	}, &res)
 	if err != nil {
 		return nil, fmt.Errorf("PerformBackfill failed: %w", err)