i2pd/transport/SSUData.h

#ifndef SSU_DATA_H__
#define SSU_DATA_H__

#include <inttypes.h>
#include <string.h>
#include <map>
#include <vector>
#include <set>
#include <memory>
#include <boost/asio.hpp>
#include "I2NPProtocol.h"
#include "Identity.h"
#include "RouterInfo.h"

namespace i2p
{
namespace transport
{

    const size_t SSU_MTU_V4 = 1484;
    const size_t SSU_MTU_V6 = 1472;
    const size_t IPV4_HEADER_SIZE = 20;
    const size_t IPV6_HEADER_SIZE = 40; 
    const size_t UDP_HEADER_SIZE = 8;
    const size_t SSU_V4_MAX_PACKET_SIZE = SSU_MTU_V4 - IPV4_HEADER_SIZE - UDP_HEADER_SIZE; // 1456
    const size_t SSU_V6_MAX_PACKET_SIZE = SSU_MTU_V6 - IPV6_HEADER_SIZE - UDP_HEADER_SIZE; // 1424
    const int RESEND_INTERVAL = 3; // in seconds
    const int MAX_NUM_RESENDS = 5;
    const int DECAY_INTERVAL = 20; // in seconds
    const int MAX_NUM_RECEIVED_MESSAGES = 1000; // how many msgID we store for duplicates check
    const int INCOMPLETE_MESSAGES_CLEANUP_TIMEOUT = 30; // in seconds
    // data flags
    const uint8_t DATA_FLAG_EXTENDED_DATA_INCLUDED = 0x02;
    const uint8_t DATA_FLAG_WANT_REPLY = 0x04;
    const uint8_t DATA_FLAG_REQUEST_PREVIOUS_ACKS = 0x08;
    const uint8_t DATA_FLAG_EXPLICIT_CONGESTION_NOTIFICATION = 0x10;
    const uint8_t DATA_FLAG_ACK_BITFIELDS_INCLUDED = 0x40;
    const uint8_t DATA_FLAG_EXPLICIT_ACKS_INCLUDED = 0x80;  

    struct Fragment
    {
        int fragmentNum;
        size_t len;
        bool isLast;
        uint8_t buf[SSU_V4_MAX_PACKET_SIZE + 18]; // use biggest

        Fragment () = default;
        Fragment (int n, const uint8_t * b, int l, bool last): 
            fragmentNum (n), len (l), isLast (last) { memcpy (buf, b, len); };      
    };  

    struct FragmentCmp
    {
        bool operator() (const std::unique_ptr<Fragment>& f1, const std::unique_ptr<Fragment>& f2) const
        {   
            return f1->fragmentNum < f2->fragmentNum; 
        };
    };  
    
    struct IncompleteMessage
    {
        std::shared_ptr<I2NPMessage> msg;
        int nextFragmentNum;    
        uint32_t lastFragmentInsertTime; // in seconds
        std::set<std::unique_ptr<Fragment>, FragmentCmp> savedFragments;
        
        IncompleteMessage (std::shared_ptr<I2NPMessage> m): msg (m), nextFragmentNum (0), lastFragmentInsertTime (0) {};
        void AttachNextFragment (const uint8_t * fragment, size_t fragmentSize);    
    };

    struct SentMessage
    {
        std::vector<std::unique_ptr<Fragment> > fragments;
        uint32_t nextResendTime; // in seconds
        int numResends;
    };  
    
    class SSUSession;
    class SSUData
    {
        public:

            SSUData (SSUSession& session);
            ~SSUData ();

            void Start ();
            void Stop ();   
            
            void ProcessMessage (uint8_t * buf, size_t len);
            void FlushReceivedMessage ();
            void Send (std::shared_ptr<i2p::I2NPMessage> msg);

            void UpdatePacketSize (const i2p::data::IdentHash& remoteIdent);

        private:

            void SendMsgAck (uint32_t msgID);
            void SendFragmentAck (uint32_t msgID, int fragmentNum);
            void ProcessAcks (uint8_t *& buf, uint8_t flag);
            void ProcessFragments (uint8_t * buf);
            void ProcessSentMessageAck (uint32_t msgID);    

            void ScheduleResend ();
            void HandleResendTimer (const boost::system::error_code& ecode);    

            void ScheduleDecay ();
            void HandleDecayTimer (const boost::system::error_code& ecode); 

            void ScheduleIncompleteMessagesCleanup ();
            void HandleIncompleteMessagesCleanupTimer (const boost::system::error_code& ecode); 
            
            void AdjustPacketSize (const i2p::data::RouterInfo& remoteRouter);  
            
        private:    

            SSUSession& m_Session;
            std::map<uint32_t, std::unique_ptr<IncompleteMessage> > m_IncompleteMessages;
            std::map<uint32_t, std::unique_ptr<SentMessage> > m_SentMessages;
            std::set<uint32_t> m_ReceivedMessages;
            boost::asio::deadline_timer m_ResendTimer, m_DecayTimer, m_IncompleteMessagesCleanupTimer;
            int m_MaxPacketSize, m_PacketSize;
            i2p::I2NPMessagesHandler m_Handler;
    };  
}
}

#endif