/**
* This feature attempts to prevent server crashes caused by someone
* quickly switching between being spectator and an active player.
*
* We do so by disconnecting players who start switching way too fast
* (more than twice in a short amount of time) and temporarily faking a large
* amount of players on the server, to prevent such spam from affecting the server.
* Copyright 2020 Anton Tarasenko
*------------------------------------------------------------------------------
* This file is part of Acedia.
*
* Acedia is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, version 3 of the License, or
* (at your option) any later version.
*
* Acedia is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Acedia. If not, see <https://www.gnu.org/licenses/>.
*/
class FixSpectatorCrash extends Feature
dependson(ConnectionService);
/**
* We use broadcast events to track when someone is switching
* to active player or spectator and remember such people
* for a short time (cooldown), defined by ('spectatorChangeTimeout').
* If one of the player we've remembered tries to switch again,
* before the defined cooldown ran out, - we kick him
* by destroying his controller.
* One possible problem arises from the fact that controllers aren't
* immediately destroyed and instead initiate player disconnection, -
* exploiter might have enough time to cause a lag or even crash the server.
* We address this issue by temporarily blocking anyone from
* becoming active player (we do this by setting 'numPlayers' variable in
* killing floor's game info to a large value).
* After all malicious players have successfully disconnected, -
* we remove the block.
*/
// This fix will try to kick any player that switches between active player
// and cooldown faster than time (in seconds) in this value.
// NOTE: raising this value past default value of '0.25'
// won't actually improve crash prevention.
var private config const float spectatorChangeTimeout;
// [ADVANCED] Don't change this setting unless you know what you're doing.
// Allows you to turn off server blocking.
// Players that don't respect timeout will still be kicked.
// This might be needed if this fix conflicts with another mutator
// that also changes 'numPlayers'.
// However, it is necessary to block aggressive enough server crash attempts,
// but can cause compatibility issues with some mutators.
// It's highly preferred to rewrite such a mutator to be compatible.
// NOTE: it should be compatible with most faked players-type mutators,
// since this fix remembers the difference between amount of
// real players and 'numPlayers'.
// After unblocking, it sets 'numPlayers' to
// the current amount of real players + that difference.
// So 4 players + 3 (=7 numPlayers) after kicking 1 player becomes
// 3 players + 3 (=6 numPlayers).
var private config const bool allowServerBlock;
// Stores remaining cooldown value before the next allowed
// spectator change per player.
struct CooldownRecord
{
var PlayerController player;
var float cooldown;
};
// Currently active cooldowns
var private array<CooldownRecord> currentCooldowns;
// Players who were decided to be violators and
// were marked for disconnecting.
// We'll be maintaining server block as long as even one
// of them hasn't yet disconnected.
var private array<PlayerController> violators;
// Is server currently blocked?
var private bool becomingActiveBlocked;
// This value introduced to accommodate mods such as faked player that can
// change 'numPlayers' to a value that isn't directly tied to the
// current number of active players.
// We remember the difference between active players and 'numPlayers'
/// variable in game type before server block and add it after block is over.
// If some mod introduces a more complicated relation between amount of
// active players and 'numPlayers', then it must take care of
// compatibility on it's own.
var private int recordedNumPlayersMod;
// If given 'PlayerController' is registered in our cooldown records, -
// returns it's index.
// If it doesn't exists (or 'none' value was passes), - returns '-1'.
private final function int GetCooldownIndex(PlayerController player)
{
local int i;
if (player == none) return -1;
for (i = 0; i < currentCooldowns.length; i += 1)
{
if (currentCooldowns[i].player == player)
{
return i;
}
}
return -1;
}
// Checks if given 'PlayerController' is registered as a violator.
// 'none' value isn't a violator.
public final function bool IsViolator(PlayerController player)
{
local int i;
if (player == none) return false;
for (i = 0; i < violators.length; i += 1)
{
if (violators[i] == player)
{
return true;
}
}
return false;
}
// This function is to notify our fix that some player just changed status
// of active player / spectator.
// If passes value isn't 'none', it puts given player on cooldown or kicks him.
public final function NotifyStatusChange(PlayerController player)
{
local int index;
local CooldownRecord newRecord;
if (player == none) return;
index = GetCooldownIndex(player);
// Players already on cool down must be kicked and marked as violators
if (index >= 0)
{
player.Destroy();
currentCooldowns.Remove(index, 1);
violators[violators.length] = player;
if (allowServerBlock)
{
SetBlock(true);
}
}
// Players that aren't on cooldown are
// either violators (do nothing, just wait for their disconnect)
// or didn't recently change their status (put them on cooldown).
else if (!IsViolator(player))
{
newRecord.player = player;
newRecord.cooldown = spectatorChangeTimeout;
currentCooldowns[currentCooldowns.length] = newRecord;
}
}
// Pass 'true' to block server, 'false' to unblock.
// Only works if 'allowServerBlock' is set to 'true'.
private final function SetBlock(bool activateBlock)
{
local KFGameType kfGameType;
// Do we even need to do anything?
if (!allowServerBlock) return;
if (activateBlock == becomingActiveBlocked) return;
// Only works with 'KFGameType' and it's children.
if (level != none) kfGameType = KFGameType(level.game);
if (kfGameType == none) return;
// Actually block/unblock
becomingActiveBlocked = activateBlock;
if (activateBlock)
{
recordedNumPlayersMod = GetNumPlayersMod();
// This value both can't realistically fall below
// 'kfGameType.maxPlayer' and won't overflow from random increase
// in vanilla code.
kfGameType.numPlayers = maxInt / 2;
}
else
{
// Adding 'recordedNumPlayersMod' should prevent
// faked players from breaking.
kfGameType.numPlayers = GetRealPlayers() + recordedNumPlayersMod;
}
}
// Performs server blocking if violators have disconnected.
private final function TryUnblocking()
{
local int i;
if (!allowServerBlock) return;
if (!becomingActiveBlocked) return;
for (i = 0; i < violators.length; i += 1)
{
if (violators[i] != none)
{
return;
}
}
SetBlock(false);
}
// Counts current amount of "real" active players
// (connected to the server and not spectators).
// Need 'ConnectionService' to be running, otherwise return '-1'.
private final function int GetRealPlayers()
{
// Auxiliary variables
local int i;
local int realPlayersAmount;
local PlayerController player;
// Information extraction
local ConnectionService service;
local array<ConnectionService.Connection> connections;
service = ConnectionService(class'ConnectionService'.static.GetInstance());
if (service == none) return -1;
// Count non-spectators
connections = service.GetActiveConnections();
realPlayersAmount = 0;
for (i = 0; i < connections.length; i += 1)
{
player = connections[i].controllerReference;
if (player == none) continue;
if (player.playerReplicationInfo == none) continue;
if (!player.playerReplicationInfo.bOnlySpectator)
{
realPlayersAmount += 1;
}
}
return realPlayersAmount;
}
// Calculates difference between current amount of "real" active players
// and 'numPlayers' from 'KFGameType'.
// Most typically this difference will be non-zero when using
// faked players-type mutators
// (difference will be equal to the amount of faked players).
private final function int GetNumPlayersMod()
{
local KFGameType kfGameType;
if (level != none) kfGameType = KFGameType(level.game);
if (kfGameType == none) return 0;
return kfGameType.numPlayers - GetRealPlayers();
}
private final function ReduceCooldowns(float timePassed)
{
local int i;
i = 0;
while (i < currentCooldowns.length)
{
currentCooldowns[i].cooldown -= timePassed;
if ( currentCooldowns[i].player != none
&& currentCooldowns[i].cooldown > 0.0)
{
i += 1;
}
else
{
currentCooldowns.Remove(i, 1);
}
}
}
event Tick(float delta)
{
local float trueTimePassed;
trueTimePassed = delta * (1.1 / level.timeDilation);
TryUnblocking();
ReduceCooldowns(trueTimePassed);
}
defaultproperties
{
// Configurable variables
spectatorChangeTimeout = 0.25
allowServerBlock = true
// Inner variables
becomingActiveBlocked = false
// Listeners
requiredListeners(0) = class'BroadcastListener_FixSpectatorCrash'
}