Pocketmine-mp: Vertical movement more than 10 blocks triggers movement anti-cheat

[DarkWav]

Issue description

When a player climbs a high tower with ladders, its being dragged back. This also happens when anti flight is disabled, and in creative mode.

Steps to reproduce the issue

1. Build a really high tower with ladders (at least 30 blocks (for safety that it happens))
2. Climb the ladder. you´ll be dragged back on the ground (note that it will not instantly happen, you´ll have to climb some blocks.

OS and versions

• PocketMine-MP: github master (commit 2fba1073ddf4965eb5d2bbbbbfb4a5c5f9377db3)
• PHP: 7.0.11
• OS: Windows 10 Pro

Crashdump, backtrace or other files

none

[RocoWayne]

im having the same problem!

[dktapps]

This would appear to be a movement-check bug, but since I can't reproduce it, it's hard to say.

[TheUSBFlash]

Reason: Player's bounding box doesn't collide with Ladder's bounding box server side. Due to being in a free space/air part of the ladder, the server thinks you are flying.
If you make the AxisBB of the ladder bigger, it all works fine.
https://github.com/ClearSkyTeam/ClearSky/commit/c103fcb1ecf0a15492612d4e684e67a7912cc190

[dktapps]

:facepalm: if it thought you were flying, this wouldn't be the case:

This also happens when anti flight is disabled, and in creative mode.

[dktapps]

Found the _actual_ bug this time. Let's all take a moment to #blame @shoghicp.

Vertical movement less than 2.3 blocks at once is treated as zero. Of course, while you are climbing a ladder you are _continuously moving smaller amounts_ than this, so the server thinks you are not moving. Once you travel 10 blocks, the anti-cheat kicks in, thinking you have moved more than 10 blocks in a single tick.

[dktapps]

This is also the cause of the infamous pull-back bug in spectator mode when flying through blocks.

[dktapps]

Forget the 2.3 thing, this line is so badly wrong that it will affect _all_ heights. Unbelievable.

https://github.com/pmmp/PocketMine-MP/blame/mcpe-1.0/src/pocketmine/Player.php#L1377

[jojoe77777]

@dktapps Was https://github.com/pmmp/PocketMine-MP/commit/ef7a843fa3e0c0377ec0e8678da9f1b4e0484ddb heading in the right direction?

[dktapps]

@jojoe77777 no, that made related bugs worse.

[Sandertv]

I blame Shoghi.

[dktapps]

Fixed in #259