Session.php

<?php
 
/*
 * This file is part of RakLib.
 * Copyright (C) 2014-2022 PocketMine Team <https://github.com/pmmp/RakLib>
 *
 * RakLib is not affiliated with Jenkins Software LLC nor RakNet.
 *
 * RakLib 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, either version 3 of the License, or
 * (at your option) any later version.
 */
 
declare(strict_types=1);
 
namespace raklib\generic;
 
use raklib\protocol\ACK;
use raklib\protocol\AcknowledgePacket;
use raklib\protocol\ConnectedPacket;
use raklib\protocol\ConnectedPing;
use raklib\protocol\ConnectedPong;
use raklib\protocol\Datagram;
use raklib\protocol\DisconnectionNotification;
use raklib\protocol\EncapsulatedPacket;
use raklib\protocol\MessageIdentifiers;
use raklib\protocol\NACK;
use raklib\protocol\Packet;
use raklib\protocol\PacketReliability;
use raklib\protocol\PacketSerializer;
use raklib\utils\InternetAddress;
use function hrtime;
use function intdiv;
use function microtime;
use function ord;
use const PHP_INT_MAX;
 
abstract class Session{
    public const STATE_CONNECTING = 0;
    public const STATE_CONNECTED = 1;
    public const STATE_DISCONNECT_PENDING = 2;
    public const STATE_DISCONNECT_NOTIFIED = 3;
    public const STATE_DISCONNECTED = 4;
 
    public const MIN_MTU_SIZE = 400;
 
    private \Logger $logger;
 
    protected InternetAddress $address;
 
    protected int $state = self::STATE_CONNECTING;
 
    private int $id;
 
    private float $lastUpdate;
    private float $disconnectionTime = 0;
 
    private bool $isActive = false;
 
    private float $lastPingTime = -1;
 
    private int $lastPingMeasure = 1;
 
    private ReceiveReliabilityLayer $recvLayer;
 
    private SendReliabilityLayer $sendLayer;
 
    public function __construct(
        \Logger $logger,
        InternetAddress $address,
        int $clientId,
        int $mtuSize,
        int $recvMaxSplitParts = PHP_INT_MAX,
        int $recvMaxConcurrentSplits = PHP_INT_MAX
    ){
        if($mtuSize < self::MIN_MTU_SIZE){
            throw new \InvalidArgumentException("MTU size must be at least " . self::MIN_MTU_SIZE . ", got $mtuSize");
        }
        $this->logger = new \PrefixedLogger($logger, "Session: " . $address->toString());
        $this->address = $address;
        $this->id = $clientId;
 
        $this->lastUpdate = microtime(true);
 
        $this->recvLayer = new ReceiveReliabilityLayer(
            $this->logger,
            function(EncapsulatedPacket $pk) : void{
                $this->handleEncapsulatedPacketRoute($pk);
            },
            function(AcknowledgePacket $pk) : void{
                $this->sendPacket($pk);
            },
            $recvMaxSplitParts,
            $recvMaxConcurrentSplits
        );
        $this->sendLayer = new SendReliabilityLayer(
            $mtuSize,
            function(Datagram $datagram) : void{
                $this->sendPacket($datagram);
            },
            function(int $identifierACK) : void{
                $this->onPacketAck($identifierACK);
            }
        );
    }
 
    abstract protected function sendPacket(Packet $packet) : void;
 
    abstract protected function onPacketAck(int $identifierACK) : void;
 
    abstract protected function onDisconnect(int $reason) : void;
 
    abstract protected function handleRakNetConnectionPacket(string $packet) : void;
 
    abstract protected function onPacketReceive(string $packet) : void;
 
    abstract protected function onPingMeasure(int $pingMS) : void;
 
    protected function getRakNetTimeMS() : int{
        return intdiv(hrtime(true), 1_000_000);
    }
 
    public function getLogger() : \Logger{
        return $this->logger;
    }
 
    public function getAddress() : InternetAddress{
        return $this->address;
    }
 
    public function getID() : int{
        return $this->id;
    }
 
    public function getState() : int{
        return $this->state;
    }
 
    public function isTemporary() : bool{
        return $this->state === self::STATE_CONNECTING;
    }
 
    public function isConnected() : bool{
        return
            $this->state !== self::STATE_DISCONNECT_PENDING and
            $this->state !== self::STATE_DISCONNECT_NOTIFIED and
            $this->state !== self::STATE_DISCONNECTED;
    }
 
    public function update(float $time) : void{
        if(!$this->isActive and ($this->lastUpdate + 10) < $time){
            $this->forciblyDisconnect(DisconnectReason::PEER_TIMEOUT);
 
            return;
        }
 
        if($this->state === self::STATE_DISCONNECT_PENDING || $this->state === self::STATE_DISCONNECT_NOTIFIED){
            //by this point we already told the event listener that the session is closing, so we don't need to do it again
            if(!$this->sendLayer->needsUpdate() and !$this->recvLayer->needsUpdate()){
                if($this->state === self::STATE_DISCONNECT_PENDING){
                    $this->queueConnectedPacket(new DisconnectionNotification(), PacketReliability::RELIABLE_ORDERED, 0, true);
                    $this->state = self::STATE_DISCONNECT_NOTIFIED;
                    $this->logger->debug("All pending traffic flushed, sent disconnect notification");
                }else{
                    $this->state = self::STATE_DISCONNECTED;
                    $this->logger->debug("Client cleanly disconnected, marking session for destruction");
                    return;
                }
            }elseif($this->disconnectionTime + 10 < $time){
                $this->state = self::STATE_DISCONNECTED;
                $this->logger->debug("Timeout during graceful disconnect, forcibly closing session");
                return;
            }
        }
 
        $this->isActive = false;
 
        $this->recvLayer->update();
        $this->sendLayer->update();
 
        if($this->lastPingTime + 5 < $time){
            $this->sendPing();
            $this->lastPingTime = $time;
        }
    }
 
    protected function queueConnectedPacket(ConnectedPacket $packet, int $reliability, int $orderChannel, bool $immediate = false) : void{
        $out = new PacketSerializer();  //TODO: reuse streams to reduce allocations
        $packet->encode($out);
 
        $encapsulated = new EncapsulatedPacket();
        $encapsulated->reliability = $reliability;
        $encapsulated->orderChannel = $orderChannel;
        $encapsulated->buffer = $out->getBuffer();
 
        $this->sendLayer->addEncapsulatedToQueue($encapsulated, $immediate);
    }
 
    public function addEncapsulatedToQueue(EncapsulatedPacket $packet, bool $immediate) : void{
        $this->sendLayer->addEncapsulatedToQueue($packet, $immediate);
    }
 
    protected function sendPing(int $reliability = PacketReliability::UNRELIABLE) : void{
        $this->queueConnectedPacket(ConnectedPing::create($this->getRakNetTimeMS()), $reliability, 0, true);
    }
 
    private function handleEncapsulatedPacketRoute(EncapsulatedPacket $packet) : void{
        $id = ord($packet->buffer[0]);
        if($id < MessageIdentifiers::ID_USER_PACKET_ENUM){ //internal data packet
            if($this->state === self::STATE_CONNECTING){
                $this->handleRakNetConnectionPacket($packet->buffer);
            }elseif($id === MessageIdentifiers::ID_DISCONNECTION_NOTIFICATION){
                $this->handleRemoteDisconnect();
            }elseif($id === MessageIdentifiers::ID_CONNECTED_PING){
                $dataPacket = new ConnectedPing();
                $dataPacket->decode(new PacketSerializer($packet->buffer));
                $this->queueConnectedPacket(ConnectedPong::create(
                    $dataPacket->sendPingTime,
                    $this->getRakNetTimeMS()
                ), PacketReliability::UNRELIABLE, 0);
            }elseif($id === MessageIdentifiers::ID_CONNECTED_PONG){
                $dataPacket = new ConnectedPong();
                $dataPacket->decode(new PacketSerializer($packet->buffer));
 
                $this->handlePong($dataPacket->sendPingTime, $dataPacket->sendPongTime);
            }
        }elseif($this->state === self::STATE_CONNECTED){
            $this->onPacketReceive($packet->buffer);
        }else{
            //$this->logger->notice("Received packet before connection: " . bin2hex($packet->buffer));
        }
    }
 
    private function handlePong(int $sendPingTime, int $sendPongTime) : void{
        if($sendPingTime < 0){
            $this->logger->debug("Received invalid pong: timestamp overflow");
        }else{
            $currentTime = $this->getRakNetTimeMS();
            if($currentTime < $sendPingTime){
                $this->logger->debug("Received invalid pong: timestamp is in the future by " . ($sendPingTime - $currentTime) . " ms");
            }else{
                $this->lastPingMeasure = $currentTime - $sendPingTime;
                $this->onPingMeasure($this->lastPingMeasure);
            }
        }
    }
 
    public function handlePacket(Packet $packet) : void{
        $this->isActive = true;
        $this->lastUpdate = microtime(true);
 
        if($packet instanceof Datagram){ //In reality, ALL of these packets are datagrams.
            $this->recvLayer->onDatagram($packet);
        }elseif($packet instanceof ACK){
            $this->sendLayer->onACK($packet);
        }elseif($packet instanceof NACK){
            $this->sendLayer->onNACK($packet);
        }
    }
 
    public function initiateDisconnect(int $reason) : void{
        if($this->isConnected()){
            $this->state = self::STATE_DISCONNECT_PENDING;
            $this->disconnectionTime = microtime(true);
            $this->onDisconnect($reason);
            $this->logger->debug("Requesting graceful disconnect because \"" . DisconnectReason::toString($reason) . "\"");
        }
    }
 
    public function forciblyDisconnect(int $reason) : void{
        $this->state = self::STATE_DISCONNECTED;
        $this->onDisconnect($reason);
        $this->logger->debug("Forcibly disconnecting session due to " . DisconnectReason::toString($reason));
    }
 
    private function handleRemoteDisconnect() : void{
        //the client will expect an ACK for this; make sure it gets sent, because after forcible termination
        //there won't be any session ticks to update it
        $this->recvLayer->update();
 
        if($this->isConnected()){
            //the client might have disconnected after the server sent a disconnect notification, but before the client
            //received it - in this case, we don't want to notify the event handler twice
            $this->onDisconnect(DisconnectReason::CLIENT_DISCONNECT);
        }
        $this->state = self::STATE_DISCONNECTED;
        $this->logger->debug("Terminating session due to client disconnect");
    }
 
    public function isFullyDisconnected() : bool{
        return $this->state === self::STATE_DISCONNECTED;
    }
}