Packet/NBT Tag Size issue caused by Velocity
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- Java
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Description
Steps to reproduce packet size issue:
Run a 1.19.2 Fabric server with the Dogcraft modpack under a Velocity server. Attempt to connect. Be met with the following (server side): https://mclo.gs/IHaC5YP
Steps to reproduce NBT tag size issue:
Run a 1.19.2 Fabric server with the mods Chipped, Consistency+, Continuity, Create, and Create Deco (all of which are in the aforementioned modpack) under a Velocity server. Attempt to connect. Be met with the following (client-side): https://mclo.gs/IUUz5pu
My best guess as to the cause: Velocity probably shares/uses the same built-in, hard-coded values for packet sizes and NBT tags as vanilla, and as soon as it sees something go over these limits, it throws up an error and disconnects the player, even if the player would have not been kicked by the Minecraft server itself.
Note: This is also pure speculation, so feel free to look for other explanations if this is not the case.
Additional Info: These errors do not occur when running the server bare, without Velocity. The root cause would seem to be Velocity somehow mishandling data that is too large, which tends to happen with the listed mods for some reason (which is strange, considering they basically all just add blocks). I also would use the Connectivity mod and call it a day, but it seems to have some sort of conflict with at least one of the other mods in the above pack (the reason I am reporting this in the first place), so that solution is out the window for the time being.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reproducing both connection failures with the listed 1.19.2 Fabric setups under Velocity, then compare them with a bare server using the linked server- and client-side logs. Done means identifying the cause and preventing the packet or NBT size failures without relying on the incompatible Connectivity mod.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- java
- Domain
- networking
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 32/100