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NetworkSession: extract rate limiting functionality into its own unit, and apply a separate rate limit to game packets

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Dylan K. Taylor 2023-04-10 13:53:15 +01:00
parent 7b55c984bf
commit 24374297e7
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GPG Key ID: 8927471A91CAFD3D
2 changed files with 91 additions and 37 deletions
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48
src/network/mcpe/NetworkSession.php
View File

@ -128,19 +128,14 @@ use function ucfirst;
use const JSON_THROW_ON_ERROR;
class NetworkSession{
private const INCOMING_PACKET_BATCH_PER_TICK = 2; //usually max 1 per tick, but transactions may arrive separately
private const INCOMING_PACKET_BATCH_MAX_BUDGET = 100 * self::INCOMING_PACKET_BATCH_PER_TICK; //enough to account for a 5-second lag spike
private const INCOMING_PACKET_BATCH_PER_TICK = 2; //usually max 1 per tick, but transactions arrive separately
private const INCOMING_PACKET_BATCH_BUFFER_TICKS = 100; //enough to account for a 5-second lag spike
/**
* At most this many more packets can be received. If this reaches zero, any additional packets received will cause
* the player to be kicked from the server.
* This number is increased every tick up to a maximum limit.
*
* @see self::INCOMING_PACKET_BATCH_PER_TICK
* @see self::INCOMING_PACKET_BATCH_MAX_BUDGET
*/
private int $incomingPacketBatchBudget = self::INCOMING_PACKET_BATCH_MAX_BUDGET;
private int $lastPacketBudgetUpdateTimeNs;
private const INCOMING_GAME_PACKETS_PER_TICK = 2;
private const INCOMING_GAME_PACKETS_BUFFER_TICKS = 100;
private PacketRateLimiter $packetBatchLimiter;
private PacketRateLimiter $gamePacketLimiter;
private \PrefixedLogger $logger;
private ?Player $player = null;
@ -196,7 +191,8 @@ class NetworkSession{
$this->disposeHooks = new ObjectSet();
$this->connectTime = time();
$this->lastPacketBudgetUpdateTimeNs = hrtime(true);
$this->packetBatchLimiter = new PacketRateLimiter("Packet Batches", self::INCOMING_PACKET_BATCH_PER_TICK, self::INCOMING_PACKET_BATCH_BUFFER_TICKS);
$this->gamePacketLimiter = new PacketRateLimiter("Game Packets", self::INCOMING_GAME_PACKETS_PER_TICK, self::INCOMING_GAME_PACKETS_BUFFER_TICKS);
$this->setHandler(new SessionStartPacketHandler(
$this->server,
@ -339,13 +335,7 @@ class NetworkSession{
Timings::$playerNetworkReceive->startTiming();
try{
if($this->incomingPacketBatchBudget <= 0){
$this->updatePacketBudget();
if($this->incomingPacketBatchBudget <= 0){
throw new PacketHandlingException("Receiving packets too fast");
}
}
$this->incomingPacketBatchBudget--;
$this->packetBatchLimiter->decrement();
if($this->cipher !== null){
Timings::$playerNetworkReceiveDecrypt->startTiming();
@ -377,6 +367,7 @@ class NetworkSession{
$stream = new BinaryStream($decompressed);
$count = 0;
foreach(PacketBatch::decodeRaw($stream) as $buffer){
$this->gamePacketLimiter->decrement();
if(++$count > 100){
throw new PacketHandlingException("Too many packets in batch");
}
@ -1105,23 +1096,6 @@ class NetworkSession{
$this->sendDataPacket(ToastRequestPacket::create($title, $body));
}
private function updatePacketBudget() : void{
$nowNs = hrtime(true);
$timeSinceLastUpdateNs = $nowNs - $this->lastPacketBudgetUpdateTimeNs;
if($timeSinceLastUpdateNs > 50_000_000){
$ticksSinceLastUpdate = intdiv($timeSinceLastUpdateNs, 50_000_000);
/*
* If the server takes an abnormally long time to process a tick, add the budget for time difference to
* compensate. This extra budget may be very large, but it will disappear the next time a normal update
* occurs. This ensures that backlogs during a large lag spike don't cause everyone to get kicked.
* As long as all the backlogged packets are processed before the next tick, everything should be OK for
* clients behaving normally.
*/
$this->incomingPacketBatchBudget = min($this->incomingPacketBatchBudget, self::INCOMING_PACKET_BATCH_MAX_BUDGET) + (self::INCOMING_PACKET_BATCH_PER_TICK * 2 * $ticksSinceLastUpdate);
$this->lastPacketBudgetUpdateTimeNs = $nowNs;
}
}
public function tick() : void{
if(!$this->isConnected()){
$this->dispose();

80
src/network/mcpe/PacketRateLimiter.php Normal file
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@ -0,0 +1,80 @@
<?php
/*
*
* ____ _ _ __ __ _ __ __ ____
* | _ \ ___ ___| | _____| |_| \/ (_)_ __ ___ | \/ | _ \
* | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
* | __/ (_) | (__| < __/ |_| | | | | | | | __/_____| | | | __/
* |_| \___/ \___|_|\_\___|\__|_| |_|_|_| |_|\___| |_| |_|_|
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* @author PocketMine Team
* @link http://www.pocketmine.net/
*
*
*/
declare(strict_types=1);
namespace pocketmine\network\mcpe;
use pocketmine\network\PacketHandlingException;
use function intdiv;
use function min;
final class PacketRateLimiter{
/**
* At most this many more packets can be received. If this reaches zero, any additional packets received will cause
* the player to be kicked from the server.
* This number is increased every tick up to a maximum limit, and decreased by one every time a packet is received.
*/
private int $budget;
private int $lastUpdateTimeNs;
private int $maxBudget;
public function __construct(
private string $name,
private int $averagePerTick,
int $maxBufferTicks,
private int $updateFrequencyNs = 50_000_000,
){
$this->maxBudget = $this->averagePerTick * $maxBufferTicks;
$this->budget = $this->maxBudget;
$this->lastUpdateTimeNs = hrtime(true);
}
/**
* @throws PacketHandlingException if the rate limit has been exceeded
*/
public function decrement(int $amount = 1) : void{
if($this->budget <= 0){
$this->update();
if($this->budget <= 0){
throw new PacketHandlingException("Exceeded rate limit for \"$this->name\"");
}
}
$this->budget -= $amount;
}
public function update() : void{
$nowNs = hrtime(true);
$timeSinceLastUpdateNs = $nowNs - $this->lastUpdateTimeNs;
if($timeSinceLastUpdateNs > $this->updateFrequencyNs){
$ticksSinceLastUpdate = intdiv($timeSinceLastUpdateNs, $this->updateFrequencyNs);
/*
* If the server takes an abnormally long time to process a tick, add the budget for time difference to
* compensate. This extra budget may be very large, but it will disappear the next time a normal update
* occurs. This ensures that backlogs during a large lag spike don't cause everyone to get kicked.
* As long as all the backlogged packets are processed before the next tick, everything should be OK for
* clients behaving normally.
*/
$this->budget = min($this->budget, $this->maxBudget) + ($this->averagePerTick * 2 * $ticksSinceLastUpdate);
$this->lastUpdateTimeNs = $nowNs;
}
}
}