internal.h

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// Luanti
// SPDX-License-Identifier: LGPL-2.1-or-later
// Copyright (C) 2013 celeron55, Perttu Ahola <celeron55@gmail.com>
 
#pragma once
 
#include "network/mtp/impl.h"
 
#include "util/numeric.h"
 
// Constant that differentiates the protocol from random data and other protocols
#define PROTOCOL_ID 0x4f457403
 
#define MAX_UDP_PEERS 65535
 
/*
=== NOTES ===
 
A packet is sent through a channel to a peer with a basic header:
        Header (7 bytes):
        [0] u32 protocol_id
        [4] session_t sender_peer_id
        [6] u8 channel
sender_peer_id:
        Unique to each peer.
        value 0 (PEER_ID_INEXISTENT) is reserved for making new connections
        value 1 (PEER_ID_SERVER) is reserved for server
        these constants are defined in constants.h
channel:
        Channel numbers have no intrinsic meaning. Currently only 0, 1, 2 exist.
*/
#define BASE_HEADER_SIZE 7
#define CHANNEL_COUNT 3
 
/*
Packet types:
 
PACKET_TYPE_CONTROL: This is a packet used by the protocol.
- When this is processed, nothing is handed to the user.
        Header (2 byte):
        [0] u8 type
        [1] u8 controltype
controltype and data description:
        CONTROLTYPE_ACK
                [2] u16 seqnum
        CONTROLTYPE_SET_PEER_ID
                [2] session_t peer_id_new
        CONTROLTYPE_PING
        - There is no actual reply, but this can be sent in a reliable
          packet to get a reply
        CONTROLTYPE_DISCO
*/
 
/*
PACKET_TYPE_ORIGINAL: This is a plain packet with no control and no error
checking at all.
- When this is processed, it is directly handed to the user.
        Header (1 byte):
        [0] u8 type
*/
#define ORIGINAL_HEADER_SIZE 1
 
/*
PACKET_TYPE_SPLIT: These are sequences of packets forming one bigger piece of
data.
- When processed and all the packet_nums 0...packet_count-1 are
  present (this should be buffered), the resulting data shall be
  directly handed to the user.
- If the data fails to come up in a reasonable time, the buffer shall
  be silently discarded.
- These can be sent as-is or atop of a RELIABLE packet stream.
        Header (7 bytes):
        [0] u8 type
        [1] u16 seqnum
        [3] u16 chunk_count
        [5] u16 chunk_num
*/
 
/*
PACKET_TYPE_RELIABLE: Delivery of all RELIABLE packets shall be forced by ACKs,
and they shall be delivered in the same order as sent. This is done
with a buffer in the receiving and transmitting end.
- When this is processed, the contents of each packet is recursively
  processed as packets.
        Header (3 bytes):
        [0] u8 type
        [1] u16 seqnum
 
*/
#define RELIABLE_HEADER_SIZE 3
#define SEQNUM_INITIAL 65500
#define SEQNUM_MAX 65535
 
/****/
 
template<typename T>
class ConstSharedPtr {
public:
        ConstSharedPtr(T *ptr) : ptr(ptr) {}
        ConstSharedPtr(const std::shared_ptr<T> &ptr) : ptr(ptr) {}
 
        const T* get() const noexcept { return ptr.get(); }
        const T& operator*() const noexcept { return *ptr.get(); }
        const T* operator->() const noexcept { return ptr.get(); }
 
private:
        std::shared_ptr<T> ptr;
};
 
namespace con
{
 
enum PacketType : u8 {
        PACKET_TYPE_CONTROL = 0,
        PACKET_TYPE_ORIGINAL = 1,
        PACKET_TYPE_SPLIT = 2,
        PACKET_TYPE_RELIABLE = 3,
        PACKET_TYPE_MAX
};
 
enum ControlType : u8 {
        CONTROLTYPE_ACK = 0,
        CONTROLTYPE_SET_PEER_ID = 1,
        CONTROLTYPE_PING = 2,
        CONTROLTYPE_DISCO = 3,
};
 
inline bool seqnum_higher(u16 totest, u16 base)
{
        if (totest > base)
        {
                if ((totest - base) > (SEQNUM_MAX/2))
                        return false;
 
                return true;
        }
 
        if ((base - totest) > (SEQNUM_MAX/2))
                return true;
 
        return false;
}
 
inline bool seqnum_in_window(u16 seqnum, u16 next,u16 window_size)
{
        u16 window_start = next;
        u16 window_end   = ( next + window_size ) % (SEQNUM_MAX+1);
 
        if (window_start < window_end) {
                return ((seqnum >= window_start) && (seqnum < window_end));
        }
 
 
        return ((seqnum < window_end) || (seqnum >= window_start));
}
 
inline float CALC_DTIME(u64 lasttime, u64 curtime)
{
        float value = (curtime - lasttime) / 1000.0f;
        return MYMAX(MYMIN(value, 0.1f), 0.0f);
}
 
/* Exceptions */
 
class NotFoundException : public BaseException
{
public:
        NotFoundException(const char *s) : BaseException(s) {}
};
 
class ProcessedSilentlyException : public BaseException
{
public:
        ProcessedSilentlyException(const char *s) : BaseException(s) {}
};
 
class ProcessedQueued : public BaseException
{
public:
        ProcessedQueued(const char *s) : BaseException(s) {}
};
 
class IncomingDataCorruption : public BaseException
{
public:
        IncomingDataCorruption(const char *s) : BaseException(s) {}
};
 
 
/*
        Struct for all kinds of packets. Includes following data:
                BASE_HEADER
                u8[] packet data (usually copied from SharedBuffer<u8>)
*/
struct BufferedPacket {
        BufferedPacket(u32 a_size)
        {
                m_data.resize(a_size);
                data = &m_data[0];
        }
 
        DISABLE_CLASS_COPY(BufferedPacket)
 
        u16 getSeqnum() const;
        void setSenderPeerId(session_t id);
 
        inline size_t size() const { return m_data.size(); }
 
        u8 *data; // Direct memory access
        float time = 0.0f; // Seconds from buffering the packet or re-sending
        float totaltime = 0.0f; // Seconds from buffering the packet
        u64 absolute_send_time = -1;
        Address address; // Sender or destination
        unsigned int resend_count = 0;
 
private:
        std::vector<u8> m_data; // Data of the packet, including headers
};
 
 
// This adds the base headers to the data and makes a packet out of it
BufferedPacketPtr makePacket(const Address &address, const SharedBuffer<u8> &data,
                u32 protocol_id, session_t sender_peer_id, u8 channel);
 
// Depending on size, make a TYPE_ORIGINAL or TYPE_SPLIT packet
// Increments split_seqnum if a split packet is made
void makeAutoSplitPacket(const SharedBuffer<u8> &data, u32 chunksize_max,
                u16 &split_seqnum, std::list<SharedBuffer<u8>> *list);
 
// Add the TYPE_RELIABLE header to the data
SharedBuffer<u8> makeReliablePacket(const SharedBuffer<u8> &data, u16 seqnum);
 
struct IncomingSplitPacket
{
        IncomingSplitPacket(u32 cc, bool r):
                chunk_count(cc), reliable(r) {}
 
        IncomingSplitPacket() = delete;
 
        float time = 0.0f; // Seconds from adding
        u32 chunk_count;
        bool reliable; // If true, isn't deleted on timeout
 
        bool allReceived() const
        {
                return (chunks.size() == chunk_count);
        }
        bool insert(u32 chunk_num, SharedBuffer<u8> &chunkdata);
        SharedBuffer<u8> reassemble();
 
private:
        // Key is chunk number, value is data without headers
        std::map<u16, SharedBuffer<u8>> chunks;
};
 
/*
        A buffer which stores reliable packets and sorts them internally
        for fast access to the smallest one.
*/
 
class ReliablePacketBuffer
{
public:
        bool getFirstSeqnum(u16 &result);
 
        BufferedPacketPtr popFirst();
        BufferedPacketPtr popSeqnum(u16 seqnum);
        void insert(BufferedPacketPtr &p_ptr, u16 next_expected);
        void fixPeerId(session_t id);
 
        void incrementTimeouts(float dtime);
        u32 getTimedOuts(float timeout);
        // timeout relative to last resend
        std::vector<ConstSharedPtr<BufferedPacket>> getResend(float timeout, u32 max_packets);
 
        void print();
        bool empty();
        u32 size();
 
 
private:
        typedef std::list<BufferedPacketPtr>::iterator FindResult;
 
        FindResult findPacketNoLock(u16 seqnum);
 
        std::list<BufferedPacketPtr> m_list;
 
        u16 m_oldest_non_answered_ack;
 
        std::mutex m_list_mutex;
};
 
/*
        A buffer for reconstructing split packets
*/
 
class IncomingSplitBuffer
{
public:
        ~IncomingSplitBuffer();
 
        /*
                Returns a reference counted buffer of length != 0 when a full split
                packet is constructed. If not, returns one of length 0.
        */
        SharedBuffer<u8> insert(BufferedPacketPtr &p_ptr, bool reliable);
 
        void removeUnreliableTimedOuts(float dtime, float timeout);
 
private:
        // Key is seqnum
        std::map<u16, IncomingSplitPacket*> m_buf;
 
        std::mutex m_map_mutex;
};
 
enum ConnectionCommandType{
        CONNCMD_NONE,
        CONNCMD_SERVE,
        CONNCMD_CONNECT,
        CONNCMD_DISCONNECT,
        CONNCMD_DISCONNECT_PEER,
        CONNCMD_SEND,
        CONNCMD_SEND_TO_ALL,
        CONCMD_ACK,
        CONCMD_CREATE_PEER,
        CONNCMD_RESEND_ONE,
        CONNCMD_PEER_ID_SET
};
 
// This is very similar to ConnectionEvent
struct ConnectionCommand
{
        const ConnectionCommandType type;
        Address address;
        session_t peer_id = PEER_ID_INEXISTENT;
        u8 channelnum = 0;
        Buffer<u8> data;
        bool reliable = false;
        bool raw = false;
 
        DISABLE_CLASS_COPY(ConnectionCommand);
 
        static ConnectionCommandPtr serve(Address address);
        static ConnectionCommandPtr connect(Address address);
        static ConnectionCommandPtr disconnect();
        static ConnectionCommandPtr disconnect_peer(session_t peer_id);
        static ConnectionCommandPtr resend_one(session_t peer_id);
        static ConnectionCommandPtr peer_id_set(session_t own_peer_id);
        static ConnectionCommandPtr send(session_t peer_id, u8 channelnum, NetworkPacket *pkt, bool reliable);
        static ConnectionCommandPtr ack(session_t peer_id, u8 channelnum, const Buffer<u8> &data);
        static ConnectionCommandPtr createPeer(session_t peer_id, const Buffer<u8> &data);
 
private:
        ConnectionCommand(ConnectionCommandType type_) :
                type(type_) {}
 
        static ConnectionCommandPtr create(ConnectionCommandType type);
};
 
/*
 * Window sizes to use, in packets (not bytes!).
 * 0xFFFF is theoretical maximum. don't think about
 * touching it, the less you're away from it the more likely data corruption
 * will occur
 *
 * Note: window sizes directly translate to maximum possible throughput, e.g.
 *       (2048 * 512 bytes) / 33ms = 15 MiB/s
 */
 
// Due to backwards compatibility we have different window sizes for what we'll
// accept from peers vs. what we use for sending.
#define MAX_RELIABLE_WINDOW_SIZE 0x8000
#define MAX_RELIABLE_WINDOW_SIZE_SEND 2048
/* starting value for window size */
#define START_RELIABLE_WINDOW_SIZE 64
/* minimum value for window size */
#define MIN_RELIABLE_WINDOW_SIZE 32
 
class Channel
{
 
public:
        u16 readNextIncomingSeqNum();
        u16 incNextIncomingSeqNum();
 
        u16 getOutgoingSequenceNumber(bool& successful);
        u16 readOutgoingSequenceNumber();
        bool putBackSequenceNumber(u16);
 
        u16 readNextSplitSeqNum();
        void setNextSplitSeqNum(u16 seqnum);
 
        // This is for buffering the incoming packets that are coming in
        // the wrong order
        ReliablePacketBuffer incoming_reliables;
        // This is for buffering the sent packets so that the sender can
        // re-send them if no ACK is received
        ReliablePacketBuffer outgoing_reliables_sent;
 
        //queued reliable packets
        std::queue<BufferedPacketPtr> queued_reliables;
 
        //queue commands prior splitting to packets
        std::deque<ConnectionCommandPtr> queued_commands;
 
        IncomingSplitBuffer incoming_splits;
 
        Channel() = default;
        ~Channel() = default;
 
        void UpdatePacketLossCounter(unsigned int count);
        void UpdatePacketTooLateCounter();
        void UpdateBytesSent(unsigned int bytes,unsigned int packages=1);
        void UpdateBytesLost(unsigned int bytes);
        void UpdateBytesReceived(unsigned int bytes);
 
        void UpdateTimers(float dtime);
 
        float getCurrentDownloadRateKB()
                { MutexAutoLock lock(m_internal_mutex); return cur_kbps; };
        float getMaxDownloadRateKB()
                { MutexAutoLock lock(m_internal_mutex); return max_kbps; };
 
        float getCurrentLossRateKB()
                { MutexAutoLock lock(m_internal_mutex); return cur_kbps_lost; };
        float getMaxLossRateKB()
                { MutexAutoLock lock(m_internal_mutex); return max_kbps_lost; };
 
        float getCurrentIncomingRateKB()
                { MutexAutoLock lock(m_internal_mutex); return cur_incoming_kbps; };
        float getMaxIncomingRateKB()
                { MutexAutoLock lock(m_internal_mutex); return max_incoming_kbps; };
 
        float getAvgDownloadRateKB()
                { MutexAutoLock lock(m_internal_mutex); return avg_kbps; };
        float getAvgLossRateKB()
                { MutexAutoLock lock(m_internal_mutex); return avg_kbps_lost; };
        float getAvgIncomingRateKB()
                { MutexAutoLock lock(m_internal_mutex); return avg_incoming_kbps; };
 
        u16 getWindowSize() const { return m_window_size; };
 
        void setWindowSize(long size)
        {
                m_window_size = (u16)rangelim(size, MIN_RELIABLE_WINDOW_SIZE, MAX_RELIABLE_WINDOW_SIZE_SEND);
        }
 
private:
        std::mutex m_internal_mutex;
        u16 m_window_size = MIN_RELIABLE_WINDOW_SIZE;
 
        u16 next_incoming_seqnum = SEQNUM_INITIAL;
 
        u16 next_outgoing_seqnum = SEQNUM_INITIAL;
        u16 next_outgoing_split_seqnum = SEQNUM_INITIAL;
 
        unsigned int current_packet_loss = 0;
        unsigned int current_packet_too_late = 0;
        unsigned int current_packet_successful = 0;
        float packet_loss_counter = 0.0f;
 
        unsigned int current_bytes_transfered = 0;
        unsigned int current_bytes_received = 0;
        unsigned int current_bytes_lost = 0;
        float max_kbps = 0.0f;
        float cur_kbps = 0.0f;
        float avg_kbps = 0.0f;
        float max_incoming_kbps = 0.0f;
        float cur_incoming_kbps = 0.0f;
        float avg_incoming_kbps = 0.0f;
        float max_kbps_lost = 0.0f;
        float cur_kbps_lost = 0.0f;
        float avg_kbps_lost = 0.0f;
        float bpm_counter = 0.0f;
 
        unsigned int rate_samples = 0;
};
 
 
class UDPPeer final : public Peer
{
public:
 
        friend class PeerHelper;
        friend class ConnectionReceiveThread;
        friend class ConnectionSendThread;
        friend class Connection;
 
        UDPPeer(session_t id, const Address &address, Connection *connection);
        virtual ~UDPPeer() = default;
 
        void PutReliableSendCommand(ConnectionCommandPtr &c,
                                                        unsigned int max_packet_size) override;
 
        virtual const Address &getAddress() const override {
                return address;
        }
 
        u16 getNextSplitSequenceNumber(u8 channel) override;
        void setNextSplitSequenceNumber(u8 channel, u16 seqnum) override;
 
        SharedBuffer<u8> addSplitPacket(u8 channel, BufferedPacketPtr &toadd,
                bool reliable) override;
 
        bool isTimedOut(float timeout, std::string &reason) override;
 
protected:
        /*
                Calculates avg_rtt and resend_timeout.
                rtt=-1 only recalculates resend_timeout
        */
        void reportRTT(float rtt) override;
 
        void RunCommandQueues(
                                        unsigned int max_packet_size,
                                        unsigned int maxtransfer);
 
        float getResendTimeout()
                { MutexAutoLock lock(m_exclusive_access_mutex); return resend_timeout; }
 
        void setResendTimeout(float timeout)
                { MutexAutoLock lock(m_exclusive_access_mutex); resend_timeout = timeout; }
 
        bool Ping(float dtime, SharedBuffer<u8>& data) override;
 
        Channel channels[CHANNEL_COUNT];
        bool m_pending_disconnect = false;
private:
        // This is changed dynamically
        float resend_timeout = 0.5;
 
        bool processReliableSendCommand(
                                        ConnectionCommandPtr &c_ptr,
                                        unsigned int max_packet_size);
};
 
}