update entity_teleport packet on 1.21.3+

[TheSharkyOfficial]

Updated teleport_entity packet according to https://minecraft.wiki/w/Java_Edition_protocol/Packets#Synchronize_Vehicle_Position
Should fix partial packet errors for this packet.

[extremeheat]

Do you have link to relevant vanilla source code for this?

[atiweb]

Re: the vanilla source — here's the relevant code, decompiled from the server jar (ClientboundTeleportEntityPacket):

public record ClientboundTeleportEntityPacket(int id, PositionMoveRotation change, Set<Relative> relatives, boolean onGround) {
    public static final StreamCodec<FriendlyByteBuf, ClientboundTeleportEntityPacket> STREAM_CODEC = StreamCodec.composite(
        ByteBufCodecs.VAR_INT,             ClientboundTeleportEntityPacket::id,
        PositionMoveRotation.STREAM_CODEC, ClientboundTeleportEntityPacket::change,
        Relative.SET_STREAM_CODEC,         ClientboundTeleportEntityPacket::relatives,
        ByteBufCodecs.BOOL,                ClientboundTeleportEntityPacket::onGround,
        ClientboundTeleportEntityPacket::new);
}
public record PositionMoveRotation(Vec3 position, Vec3 deltaMovement, float yRot, float xRot) { /* Vec3, Vec3, FLOAT, FLOAT */ }

So the wire layout is id(varint), position x/y/z (f64), deltaMovement x/y/z (f64), yRot/xRot (f32), relatives, onGround(bool). The position / velocity / f32-rotation / onGround part of this PR matches. I checked the codec is byte-for-byte the same in 1.21.3, 1.21.11 and 26.2, so it's been stable since the 1.21.2 rework.

Two things worth fixing:

1. flags is a 4-byte int, not a 9-bit bitfield. Relative.SET_STREAM_CODEC is:

public enum Relative { X(0), Y(1), Z(2), Y_ROT(3), X_ROT(4), DELTA_X(5), DELTA_Y(6), DELTA_Z(7), ROTATE_DELTA(8); }
public static final StreamCodec<ByteBuf, Set<Relative>> SET_STREAM_CODEC = ByteBufCodecs.INT.map(Relative::unpack, Relative::pack);

— a 4-byte int with bits 0–8. The inline bitfield of 9×1 bits here only consumes 2 bytes (and reads MSB-first), so it would still desync. minecraft-data already has the right type for this exact Set<Relative> — PositionUpdateRelatives (bitflags over u32), used by packet_position:

"PositionUpdateRelatives": ["bitflags", { "type": "u32", "flags": ["x","y","z","yaw","pitch","dx","dy","dz","yawDelta"] }]

So "type": "PositionUpdateRelatives" is a drop-in fix (correct width + reuses the existing type instead of a new inline bitfield).

2. This affects every 1.21.2+ version, not only 1.21.3. entity_teleport is still the old yaw/pitch: i8 form in 1.21.3, 1.21.6, 1.21.9 and 1.21.11 (and in the generated 26.2 data in #1198), and the jar structure is identical across all of them — so the same fix is needed everywhere from 1.21.2 onward.

[DatArnoGuy]

Is this ready to be merged? My console is again full of this spam :D

Chunk size is 64 but only 30 was read ; partial packet : {"name":"entity_teleport","params":{"entityId":791,"x":48.97947009945363,"y":60,"z":133.125,"yaw":21,"pitch":-72,"onGround":true}}; buffer :7b970640487d5f46b64817404e0000000000004060a4000000000015b82325d210bf270000000000000000000000000000000040f3e0ee000000000000000001

[extremeheat]

@copilot Please correct the changes made per atiweb comment with PositionUpdateRelatives and also apply this to all subsequent versions