In multiplayer, a player picking up a Paradox Machine can ban that player from the server until their NBT is edited.

[James103]

Just Dire Things version

1.4.4

Minecraft Version

1.21(.1)

(Neo)Forge Version

21.1.66

Modpack & Version

Craftoria 1.5.0 (Craftoria EU Server)

Do you have optifine or Rubidium installed?

None

Describe the issue

Picking up a Paradox Machine can ban someone from a multiplayer server due to excessive NBT data.
This occurs because a Paradox Machine can save as many blocks and entities as possible, limited only by the size of their NBT data. With enough saved blocks and entities, the NBT data of the machine block item becomes too large to fit inside the packets being sent, causing the player to be disconnected on pick up and when re-joining.

Steps to reproduce

1. Start a dedicated server and join it.
2. Craft and place a Paradox Machine.
3. Set the Paradox Machine to capture a large but confined area.
4. Spawn over a hundred entities in the area
5. Capture the area, which will save it to the machine's NBT data.
6. In survival mode, break the machine with a silk touch pickaxe and pick it up.
7. Depending on the number and arrangement of blocks and entities saved, the player picking up the machine may be disconnected and unable to rejoin.

Expected behaviour

A single Paradox Machine should not be able to kick or ban a player from a multiplayer server.
This can be done by adding a limit on the amount of blocks, entities, and/or NBT data that can be captured at once.

Alternatively, the Paradox Machine can hold a UUID which references an entry in a data file or spatial storage-like dimension containing the actual captured area. This is the approach taken by mods like Refined Storage and Sophisticated Backpacks.

Screenshots

No response

Log files

No response

Additional information

Originally reported in https://discord.com/channels/570630340075454474/1297364070579835043, re-posted here as this still looks like a problem.

See also:

JustDireThings/src/main/java/com/direwolf20/justdirethings/common/blockentities/ParadoxMachineBE.java

Lines 585 to 621 in b72e69d

	public void snapshotArea() {
	if (level == null) return;
	BlockPos machinePos = getBlockEntity().getBlockPos(); // Get the machine's position
	AABB area = getAABB(machinePos); // Get the affected area
	List<CompoundTag> blockDataList = new ArrayList<>();
	List<CompoundTag> entityDataList = new ArrayList<>();
	// Capture blocks in the area
	for (BlockPos pos : findBlocksToSave()) {
	BlockState blockState = level.getBlockState(pos);
	if (!blockState.isAir()) {
	CompoundTag blockTag = new CompoundTag();
	blockTag.put("pos", NbtUtils.writeBlockPos(pos.subtract(machinePos))); // Relative position
	blockTag.put("state", NbtUtils.writeBlockState(blockState)); // Block state
	blockDataList.add(blockTag);
	}
	}
	// Capture entities in the area
	List<LivingEntity> entities = findEntitiesToSave(area);
	for (LivingEntity entity : entities) {
	CompoundTag entityTag = new CompoundTag();
	CompoundTag entityData = new CompoundTag();
	entity.save(entityData);
	Vec3 entityRelativePos = entity.position().subtract(Vec3.atCenterOf(machinePos)); // Relative position as Vec3
	entityTag.put("relativePos", NBTHelpers.vec3ToNBT(entityRelativePos)); // Save Vec3 position
	entityTag.put("data", entityData);
	entityDataList.add(entityTag);
	}
	snapshotData = new CompoundTag();
	snapshotData.put("blocks", writeBlockDataList(blockDataList)); // Store blocks
	snapshotData.put("entities", writeEntityDataList(entityDataList)); // Store entities
	clearSnapshotCache();
	markDirtyClient();
	}