This should prevent bouncing higher and higher (cheat).
Missing:
* The bounce effect should be set considering the last yDistance, in
order to allow negative vertical velocity to work.
* Add workaorunds for gravity with exiting cobweb.
* Allow multiple times zero y-distance (cobweb several times, slime 2).
Cobweb may need adjusting the bounding box to check with, instead.
* The server might reset the fall distance with preceding micro-moves,
so use NoFall data already on checking pre-conditions for bounce.
* Cap the bounce effect slightly smaller.
* Renew the bounce effect under certain conditions.
* Gravity, odds.
Remaining:
* Two consecutive times yDist = 0 at the maximum of a jump.
MISSING:
* Micro move onto ground, fall distance resets before sf check is run.
Done:
* Split PlayerMoveEvent processing to from -> loc + from -> to. Just if
from isn't the same coordinates as player.getLocation. This
reduces the complexity of workarounds.
* You do take fall damage falling onto slime blocks while sneaking.
* Queue bounce effect, only if the move is valid. Skip NoFall then.
* Apply bounce effect once moving up, to allow overriding.
* Cover more odd cases.
Unrelated:
* Use data.debug instead of cc.debug.
Adjust workarounds, confine velocity activation to next tick.
Cases missing:
* Lost ground cases (yOnGround has been reduced, strikes here).
* Two consecutive yDist = 0.
This will preserve the order of debug messages sent from multiple
threads. As a side effect, this might be better for performance, given
that on constant input the logging task will stay registered, so there
is little overhead and the file-io is taken off the asynchronous packet
and chat handler threads.Hopefully the thread switching is less
expensive than the gain by not delaying chat/packet threads, in case of
servers with few cores. We might adapt the used policy later, based on
cores and/or config.
* Queue outgoing positions in order to detect ACK on incoming.
* Since we can't detect relative teleports, positions are only queued,
if they match an absolute location from a teleport event (Bukkit).
* The queue is kept simple: only store the latest position.
* Cancel incoming flying/pos/look until ACK is received.
Missing:
* Are yaw/pitch are ever sent back changed.
* Configuration to turn it off.
* Might use this to just skip all violation handling until ACK.
This is a quick go with little testing, roughly up to level 60. Above
that there may be more false positives, also "no jumping" is not
enforced there.
A suggestion for the future could be to just use/part-calculate an array
for all the typical effects.
Used to be 0.0625 for a while, but intentions are to cover ground-loss
as lostground workarounds. Later switch to calculate the distance to
ground (with a given max-distance).
For efficiency (several?) other cases will be removable, once we model
the per-move ground/medium properties more accurately also for the past
move(s). At least lostground_pyramid should be removed then.
Splits CoordMap into interface, abstract hash map, implementations.
Sketch Linked version, hinting at access order, e.g. with
tracking piston effects with timeouts.
Missing:
* Implementation of a linked version.
Cancelling redundant packets has to big problems:
* The normal case is to not run in the primary thread.
* For legit players a missed micro move could mean that survivalfly can
not detect ground properly.
Better approaches could be:
* Cancel asynchronous packets if they match the last sent one (only
simple hacks).
* Check for moves passing block borders, request block shapes and such
from the main thread.
* Detect actual cheating or unusual patterns instead.
* Queue packets for processing in the main thread.
Missing:
* Actually detect ACK packets for previous outgoing teleports.
* Do something upon detecting illegal coordinates (asynchronous
disconnect? queue kicking, config).
* In addition to the "distance from set-back" check, we have a check of
the per-move distance for in-air checks, taking account of friction.
* In-air and liquid checks should consume vertical velocity once needed.
* Model vertical velocity "exact", i.e. positive and negative, use an
entry once a sub-check fails, quite strict invalidation of not matching
values, matching against the y-distance directly.
* Vertical accounting has been sharpened for the moment. The new
per-move checking might make it superfluous.
* Remove MediumLiftOff in favor of a LiftOffEnvelope carrying basic
lift-off max-gain/max-height/max-phase, enabling to distinguish between
normal lift-off and liquid near ground.
* Rename others (e.g. sfLastYDist -> lastYDist). Thus breaking internal
naming, adding velocity via MovingData still works, but should behave
slightly differently.
* Fixes (waterwalk with head obstructed, resetting of sfDirty, possibly
others).
Issues.
* Edge cases with velocity, water.
* Lava needs friction, at least with velocity.
* Lostground_edge(ydist < 0.0) ->
bunny with yDistance > 0.0. Need more flags or better model for keeping
past moves information.
* Plain ground misses (layered snow).
* lostground with yDist == 0.0, then seemingly in-air yDist== 0.0, then
bunny/lifft-off (similar to above). Needs better modeling of past moves,
because several lostgorund cases mean "the move has been on ground".
Also includes geting the distance to ground for hack-proof set-back-y.
* Vertical velocity is now matched with a margin, because the client
seems to add randomly.
* Possibly new loopholes/exploits (extreme large moves?).
* Cleanup pending.
* Group selected classes into sub-packages of moving.
* Rename classes.
* Must use LinkedList for velocity entries.
* Prepare SimpleAxisVelocity + entry for use-once accounting.
(Might not be the final naming.)
* Use BlockProperties.collides to use the actual bounds of blocks.
* Don't test for sfLowJump to set allowHop.
* Set head bump margin to match 2-high spots and to prevent lowjump fps.
* Tighten conditions for actual hop.
* Don't x > 1.314 * x.
* Add height, eyeHeight, isHeadObstructed to PlayerLocation.
* lowjump detection: from is higher than to, test both locations.
* Remove bunny reset within lowjump detection (defeated flying bunny).
* Check isHeadObstructed directly in the bunnyHop method.
Issues remaining:
* Moderate acceleration ground to ground, after having landed (+1st).
* Possibly transitions between 2-high and other.
* More edge cases with slowness potion.
This seems to be the same value on ground as with slowness potion and
2-step acceleration. Not possible to squeeze into the ordinary bunny
envelope.
On the fly: add PlayerLocation.isOnGroundOrResetCond.
Slowness+bunny will still not fully work, because we need to model
closer to the client here, i.e. acceleration and friction. Remaining
issues in rough order of naughtiness:
* On-ground friction based speed decrease.
* Increasing of speed, above slowness sprinting speed but below normal
sprinting speed.
* Two-step bunnyhop, having h-speed increase to bunny with two packets.
Similarly acceleration effects when touching ground, not modeled right
by bunny.
* Possibly more.
* Remove early return, as we prefer to know what NCP would allow, at
least until sf changes have stabilized.
* Only count in speed effects for normal running/jumping, not
water/web/blocking/sneaking. Either check potion effects or attributes.
Mainly catches the instant ladder and too large moves, generalize step
to have general "reset" as condition instead of "ground", don't limit by
a distance.
* Not actually a fix for anything we encountered.
* Nailed down blockinteract.visible raytracing issues to bad end-points
for raytracing.
* Also test/prepare logging test-cases for raytracing in general. Not
enabled, because we should have some flag/permission/command to check
before logging ~ 5KB per interact event.
This makes logging all violations potentially useful to use alongside
with the "ncp debug player" command in production environments. The flag
debugonly must be set with at least one backend being activated.
Similar to TestNCP but reduced/different features:
* Config: trace for the log file and notify to send to notify channel.
* It's not possible to confine whose messages you receive (yet).
Meant for better local/quick testing in the first place.
* Make attribute methods consistent (remove the sprint boost modifier
from the generic speed multiplier, because it's inconsistent).
* Add missing implementations.
* Adjust default sprinting speed modifier.
* Add more guards for the latest compat module (1.8_R3).
* Add a reflection based compat module for CB, to cover minor updates.
* Possibly other minor fixes/changes.
[Hail "insufficient data written"!]
When the respawn/login location is obstructed, the respawn event shows
that location, but the first move will start at several blocks above,
without having a teleport event to rely on, thus this workaround.
Vertical velocity handling can be much simplified (and possibly extended
to including downwards velocity) with using a friction-based modeling.
Absolute envelopes can still be checked extra, where appropriate.
