Fix ClientMovementPredictionSync packet

legacyver/legacypacket/client_movement_prediction_sync.go

@@ -48,19 +48,7 @@ func (*ClientMovementPredictionSync) ID() uint32 {
 }
 
 func (pk *ClientMovementPredictionSync) Marshal(io protocol.IO) {
-	var bitsetSize int
-	if proto.IsProtoGTE(io, proto.ID898) {
-		bitsetSize = 127
-	} else if proto.IsProtoGTE(io, proto.ID844) {
-		bitsetSize = 126
-	} else if proto.IsProtoGTE(io, proto.ID818) {
-		bitsetSize = 125
-	} else if proto.IsProtoGTE(io, proto.ID786) {
-		bitsetSize = 123
-	} else {
-		bitsetSize = 120
-	}
-	io.Bitset(&pk.ActorFlags, bitsetSize)
+	io.Bitset(&pk.ActorFlags, proto.EntityDataFlagsLength(proto.FetchProtoID(io)))
 	io.Float32(&pk.BoundingBoxScale)
 	io.Float32(&pk.BoundingBoxWidth)
 	io.Float32(&pk.BoundingBoxHeight)

legacyver/proto/entity_metadata.go

@@ -0,0 +1,17 @@
+package proto
+
+func EntityDataFlagsLength(protoID int32) int {
+	if protoID >= ID898 {
+		return 127
+	}
+	if protoID >= ID844 {
+		return 126
+	}
+	if protoID >= ID818 {
+		return 125
+	}
+	if protoID >= ID786 {
+		return 123
+	}
+	return 120
+}

legacyver/protocol.go

@@ -702,10 +702,7 @@ func (p *Protocol) downgradePackets(pks []packet.Packet, conn *minecraft.Conn) [
 		case *packet.PlayerSkin:
 			pk.Skin.GeometryDataEngineVersion = []byte(p.Ver())
 		case *packet.ClientMovementPredictionSync:
-			actorFlags := pk.ActorFlags
-			if p.ID() < proto.ID786 {
-				actorFlags = fitBitset(actorFlags, 120)
-			}
+			actorFlags := fitBitset(pk.ActorFlags, proto.EntityDataFlagsLength(p.ID()))
 			pks[pkIndex] = &legacypacket.ClientMovementPredictionSync{
 				ActorFlags:              actorFlags,
 				BoundingBoxScale:        pk.BoundingBoxScale,
@@ -1308,7 +1305,7 @@ func (p *Protocol) upgradePackets(pks []packet.Packet, conn *minecraft.Conn) []p
 			pks[pkIndex] = &packet.UpdateAbilities{AbilityData: pk.AbilityData.ToLatest()}
 		case *legacypacket.ClientMovementPredictionSync:
 			pks[pkIndex] = &packet.ClientMovementPredictionSync{
-				ActorFlags:              fitBitset(pk.ActorFlags, protocol.EntityDataFlagCount),
+				ActorFlags:              fitBitset(pk.ActorFlags, proto.EntityDataFlagsLength(p.ID())),
 				BoundingBoxScale:        pk.BoundingBoxScale,
 				BoundingBoxWidth:        pk.BoundingBoxWidth,
 				BoundingBoxHeight:       pk.BoundingBoxHeight,