text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2019 The Bitcoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #ifndef BITCOIN_NET_H
  #define BITCOIN_NET_H
  
  #include <addrdb.h>
  #include <addrman.h>
  #include <amount.h>
  #include <bloom.h>
  #include <compat.h>
  #include <crypto/siphash.h>
  #include <hash.h>
  #include <limitedmap.h>
  #include <netaddress.h>
  #include <policy/feerate.h>
  #include <protocol.h>
  #include <random.h>
  #include <streams.h>
  #include <sync.h>
  #include <uint256.h>
  #include <threadinterrupt.h>
  
  #include <atomic>
  #include <deque>
  #include <stdint.h>
  #include <thread>
  #include <memory>
  #include <condition_variable>
  
  #ifndef WIN32
  #include <arpa/inet.h>
  #endif
  
  
  class CScheduler;
  class CNode;
  class BanMan;
  
  /** Time between pings automatically sent out for latency probing and keepalive (in seconds). */
  static const int PING_INTERVAL = 2 * 60;
  /** Time after which to disconnect, after waiting for a ping response (or inactivity). */
  static const int TIMEOUT_INTERVAL = 20 * 60;
  /** Run the feeler connection loop once every 2 minutes or 120 seconds. **/
  static const int FEELER_INTERVAL = 120;
  /** The maximum number of entries in an 'inv' protocol message */
  static const unsigned int MAX_INV_SZ = 50000;
  /** The maximum number of entries in a locator */
  static const unsigned int MAX_LOCATOR_SZ = 101;
  /** The maximum number of new addresses to accumulate before announcing. */
  static const unsigned int MAX_ADDR_TO_SEND = 1000;
  /** Maximum length of incoming protocol messages (no message over 4 MB is currently acceptable). */
  static const unsigned int MAX_PROTOCOL_MESSAGE_LENGTH = 4 * 1000 * 1000;
  /** Maximum length of strSubVer in `version` message */
  static const unsigned int MAX_SUBVERSION_LENGTH = 256;
  /** Maximum number of automatic outgoing nodes */
  static const int MAX_OUTBOUND_CONNECTIONS = 8;
  /** Maximum number of addnode outgoing nodes */
  static const int MAX_ADDNODE_CONNECTIONS = 8;
  /** -listen default */
  static const bool DEFAULT_LISTEN = true;
  /** -upnp default */
  #ifdef USE_UPNP
  static const bool DEFAULT_UPNP = USE_UPNP;
  #else
  static const bool DEFAULT_UPNP = false;
  #endif
  /** The maximum number of entries in mapAskFor */
  static const size_t MAPASKFOR_MAX_SZ = MAX_INV_SZ;
  /** The maximum number of entries in setAskFor (larger due to getdata latency)*/
  static const size_t SETASKFOR_MAX_SZ = 2 * MAX_INV_SZ;
  /** The maximum number of peer connections to maintain. */
  static const unsigned int DEFAULT_MAX_PEER_CONNECTIONS = 125;
  /** The default for -maxuploadtarget. 0 = Unlimited */
  static const uint64_t DEFAULT_MAX_UPLOAD_TARGET = 0;
  /** The default timeframe for -maxuploadtarget. 1 day. */
  static const uint64_t MAX_UPLOAD_TIMEFRAME = 60 * 60 * 24;
  /** Default for blocks only*/
  static const bool DEFAULT_BLOCKSONLY = false;
  /** -peertimeout default */
  static const int64_t DEFAULT_PEER_CONNECT_TIMEOUT = 60;
  
  static const bool DEFAULT_FORCEDNSSEED = false;
  static const size_t DEFAULT_MAXRECEIVEBUFFER = 5 * 1000;
  static const size_t DEFAULT_MAXSENDBUFFER    = 1 * 1000;
  
  typedef int64_t NodeId;
  
  struct AddedNodeInfo
  {
      std::string strAddedNode;
      CService resolvedAddress;
      bool fConnected;
      bool fInbound;
  };
  
  class CNodeStats;
  class CClientUIInterface;
  
  struct CSerializedNetMsg
  {
      CSerializedNetMsg() = default;
      CSerializedNetMsg(CSerializedNetMsg&&) = default;
      CSerializedNetMsg& operator=(CSerializedNetMsg&&) = default;
      // No copying, only moves.
      CSerializedNetMsg(const CSerializedNetMsg& msg) = delete;
      CSerializedNetMsg& operator=(const CSerializedNetMsg&) = delete;
  
      std::vector<unsigned char> data;
      std::string command;
  };
  
  
  class NetEventsInterface;
  class CConnman
  {
  public:
  
      enum NumConnections {
          CONNECTIONS_NONE = 0,
          CONNECTIONS_IN = (1U << 0),
          CONNECTIONS_OUT = (1U << 1),
          CONNECTIONS_ALL = (CONNECTIONS_IN | CONNECTIONS_OUT),
      };
  
      struct Options
      {
          ServiceFlags nLocalServices = NODE_NONE;
          int nMaxConnections = 0;
          int nMaxOutbound = 0;
          int nMaxAddnode = 0;
          int nMaxFeeler = 0;
          int nBestHeight = 0;
          CClientUIInterface* uiInterface = nullptr;
          NetEventsInterface* m_msgproc = nullptr;
          BanMan* m_banman = nullptr;
          unsigned int nSendBufferMaxSize = 0;
          unsigned int nReceiveFloodSize = 0;
          uint64_t nMaxOutboundTimeframe = 0;
          uint64_t nMaxOutboundLimit = 0;
          int64_t m_peer_connect_timeout = DEFAULT_PEER_CONNECT_TIMEOUT;
          std::vector<std::string> vSeedNodes;
          std::vector<CSubNet> vWhitelistedRange;
          std::vector<CService> vBinds, vWhiteBinds;
          bool m_use_addrman_outgoing = true;
          std::vector<std::string> m_specified_outgoing;
          std::vector<std::string> m_added_nodes;
      };
  
      void Init(const Options& connOptions) {
          nLocalServices = connOptions.nLocalServices;
          nMaxConnections = connOptions.nMaxConnections;
          nMaxOutbound = std::min(connOptions.nMaxOutbound, connOptions.nMaxConnections);
          m_use_addrman_outgoing = connOptions.m_use_addrman_outgoing;
          nMaxAddnode = connOptions.nMaxAddnode;
          nMaxFeeler = connOptions.nMaxFeeler;
          nBestHeight = connOptions.nBestHeight;
          clientInterface = connOptions.uiInterface;
          m_banman = connOptions.m_banman;
          m_msgproc = connOptions.m_msgproc;
          nSendBufferMaxSize = connOptions.nSendBufferMaxSize;
          nReceiveFloodSize = connOptions.nReceiveFloodSize;
          m_peer_connect_timeout = connOptions.m_peer_connect_timeout;
          {
              LOCK(cs_totalBytesSent);
              nMaxOutboundTimeframe = connOptions.nMaxOutboundTimeframe;
              nMaxOutboundLimit = connOptions.nMaxOutboundLimit;
          }
          vWhitelistedRange = connOptions.vWhitelistedRange;
          {
              LOCK(cs_vAddedNodes);
              vAddedNodes = connOptions.m_added_nodes;
          }
      }
  
      CConnman(uint64_t seed0, uint64_t seed1);
      ~CConnman();
      bool Start(CScheduler& scheduler, const Options& options);
  
      // TODO: Remove NO_THREAD_SAFETY_ANALYSIS. Lock cs_vNodes before reading the variable vNodes.
      //
      // When removing NO_THREAD_SAFETY_ANALYSIS be aware of the following lock order requirements:
      // * CheckForStaleTipAndEvictPeers locks cs_main before indirectly calling GetExtraOutboundCount
      //   which locks cs_vNodes.
      // * ProcessMessage locks cs_main and g_cs_orphans before indirectly calling ForEachNode which
      //   locks cs_vNodes.
      //
      // Thus the implicit locking order requirement is: (1) cs_main, (2) g_cs_orphans, (3) cs_vNodes.
      void Stop() NO_THREAD_SAFETY_ANALYSIS;
  
      void Interrupt();
      bool GetNetworkActive() const { return fNetworkActive; };
      bool GetUseAddrmanOutgoing() const { return m_use_addrman_outgoing; };
      void SetNetworkActive(bool active);
      void OpenNetworkConnection(const CAddress& addrConnect, bool fCountFailure, CSemaphoreGrant *grantOutbound = nullptr, const char *strDest = nullptr, bool fOneShot = false, bool fFeeler = false, bool manual_connection = false);
      bool CheckIncomingNonce(uint64_t nonce);
  
      bool ForNode(NodeId id, std::function<bool(CNode* pnode)> func);
  
      void PushMessage(CNode* pnode, CSerializedNetMsg&& msg);
  
      template<typename Callable>
      void ForEachNode(Callable&& func)
      {
          LOCK(cs_vNodes);
          for (auto&& node : vNodes) {
              if (NodeFullyConnected(node))
                  func(node);
          }
      };
  
      template<typename Callable>
      void ForEachNode(Callable&& func) const
      {
          LOCK(cs_vNodes);
          for (auto&& node : vNodes) {
              if (NodeFullyConnected(node))
                  func(node);
          }
      };
  
      template<typename Callable, typename CallableAfter>
      void ForEachNodeThen(Callable&& pre, CallableAfter&& post)
      {
          LOCK(cs_vNodes);
          for (auto&& node : vNodes) {
              if (NodeFullyConnected(node))
                  pre(node);
          }
          post();
      };
  
      template<typename Callable, typename CallableAfter>
      void ForEachNodeThen(Callable&& pre, CallableAfter&& post) const
      {
          LOCK(cs_vNodes);
          for (auto&& node : vNodes) {
              if (NodeFullyConnected(node))
                  pre(node);
          }
          post();
      };
  
      // Addrman functions
      size_t GetAddressCount() const;
      void SetServices(const CService &addr, ServiceFlags nServices);
      void MarkAddressGood(const CAddress& addr);
      void AddNewAddresses(const std::vector<CAddress>& vAddr, const CAddress& addrFrom, int64_t nTimePenalty = 0);
      std::vector<CAddress> GetAddresses();
  
      // This allows temporarily exceeding nMaxOutbound, with the goal of finding
      // a peer that is better than all our current peers.
      void SetTryNewOutboundPeer(bool flag);
      bool GetTryNewOutboundPeer();
  
      // Return the number of outbound peers we have in excess of our target (eg,
      // if we previously called SetTryNewOutboundPeer(true), and have since set
      // to false, we may have extra peers that we wish to disconnect). This may
      // return a value less than (num_outbound_connections - num_outbound_slots)
      // in cases where some outbound connections are not yet fully connected, or
      // not yet fully disconnected.
      int GetExtraOutboundCount();
  
      bool AddNode(const std::string& node);
      bool RemoveAddedNode(const std::string& node);
      std::vector<AddedNodeInfo> GetAddedNodeInfo();
  
      size_t GetNodeCount(NumConnections num);
      void GetNodeStats(std::vector<CNodeStats>& vstats);
      bool DisconnectNode(const std::string& node);
      bool DisconnectNode(const CSubNet& subnet);
      bool DisconnectNode(const CNetAddr& addr);
      bool DisconnectNode(NodeId id);
  
      ServiceFlags GetLocalServices() const;
  
      //!set the max outbound target in bytes
      void SetMaxOutboundTarget(uint64_t limit);
      uint64_t GetMaxOutboundTarget();
  
      //!set the timeframe for the max outbound target
      void SetMaxOutboundTimeframe(uint64_t timeframe);
      uint64_t GetMaxOutboundTimeframe();
  
      //! check if the outbound target is reached
      //! if param historicalBlockServingLimit is set true, the function will
      //! response true if the limit for serving historical blocks has been reached
      bool OutboundTargetReached(bool historicalBlockServingLimit);
  
      //! response the bytes left in the current max outbound cycle
      //! in case of no limit, it will always response 0
      uint64_t GetOutboundTargetBytesLeft();
  
      //! response the time in second left in the current max outbound cycle
      //! in case of no limit, it will always response 0
      uint64_t GetMaxOutboundTimeLeftInCycle();
  
      uint64_t GetTotalBytesRecv();
      uint64_t GetTotalBytesSent();
  
      void SetBestHeight(int height);
      int GetBestHeight() const;
  
      /** Get a unique deterministic randomizer. */
      CSipHasher GetDeterministicRandomizer(uint64_t id) const;
  
      unsigned int GetReceiveFloodSize() const;
  
      void WakeMessageHandler();
  
      /** Attempts to obfuscate tx time through exponentially distributed emitting.
          Works assuming that a single interval is used.
          Variable intervals will result in privacy decrease.
      */
      int64_t PoissonNextSendInbound(int64_t now, int average_interval_seconds);
  
  private:
      struct ListenSocket {
          SOCKET socket;
          bool whitelisted;
  
          ListenSocket(SOCKET socket_, bool whitelisted_) : socket(socket_), whitelisted(whitelisted_) {}
      };
  
      bool BindListenPort(const CService &bindAddr, std::string& strError, bool fWhitelisted = false);
      bool Bind(const CService &addr, unsigned int flags);
      bool InitBinds(const std::vector<CService>& binds, const std::vector<CService>& whiteBinds);
      void ThreadOpenAddedConnections();
      void AddOneShot(const std::string& strDest);
      void ProcessOneShot();
      void ThreadOpenConnections(std::vector<std::string> connect);
      void ThreadMessageHandler();
      void AcceptConnection(const ListenSocket& hListenSocket);
      void DisconnectNodes();
      void NotifyNumConnectionsChanged();
      void InactivityCheck(CNode *pnode);
      bool GenerateSelectSet(std::set<SOCKET> &recv_set, std::set<SOCKET> &send_set, std::set<SOCKET> &error_set);
      void SocketEvents(std::set<SOCKET> &recv_set, std::set<SOCKET> &send_set, std::set<SOCKET> &error_set);
      void SocketHandler();
      void ThreadSocketHandler();
      void ThreadDNSAddressSeed();
  
      uint64_t CalculateKeyedNetGroup(const CAddress& ad) const;
  
      CNode* FindNode(const CNetAddr& ip);
      CNode* FindNode(const CSubNet& subNet);
      CNode* FindNode(const std::string& addrName);
      CNode* FindNode(const CService& addr);
  
      bool AttemptToEvictConnection();
      CNode* ConnectNode(CAddress addrConnect, const char *pszDest, bool fCountFailure, bool manual_connection);
      bool IsWhitelistedRange(const CNetAddr &addr);
  
      void DeleteNode(CNode* pnode);
  
      NodeId GetNewNodeId();
  
      size_t SocketSendData(CNode *pnode) const;
      void DumpAddresses();
  
      // Network stats
      void RecordBytesRecv(uint64_t bytes);
      void RecordBytesSent(uint64_t bytes);
  
      // Whether the node should be passed out in ForEach* callbacks
      static bool NodeFullyConnected(const CNode* pnode);
  
      // Network usage totals
      CCriticalSection cs_totalBytesRecv;
      CCriticalSection cs_totalBytesSent;
      uint64_t nTotalBytesRecv GUARDED_BY(cs_totalBytesRecv);
      uint64_t nTotalBytesSent GUARDED_BY(cs_totalBytesSent);
  
      // outbound limit & stats
      uint64_t nMaxOutboundTotalBytesSentInCycle GUARDED_BY(cs_totalBytesSent);
      uint64_t nMaxOutboundCycleStartTime GUARDED_BY(cs_totalBytesSent);
      uint64_t nMaxOutboundLimit GUARDED_BY(cs_totalBytesSent);
      uint64_t nMaxOutboundTimeframe GUARDED_BY(cs_totalBytesSent);
  
      // P2P timeout in seconds
      int64_t m_peer_connect_timeout;
  
      // Whitelisted ranges. Any node connecting from these is automatically
      // whitelisted (as well as those connecting to whitelisted binds).
      std::vector<CSubNet> vWhitelistedRange;
  
      unsigned int nSendBufferMaxSize{0};
      unsigned int nReceiveFloodSize{0};
  
      std::vector<ListenSocket> vhListenSocket;
      std::atomic<bool> fNetworkActive{true};
      bool fAddressesInitialized{false};
      CAddrMan addrman;
      std::deque<std::string> vOneShots GUARDED_BY(cs_vOneShots);
      CCriticalSection cs_vOneShots;
      std::vector<std::string> vAddedNodes GUARDED_BY(cs_vAddedNodes);
      CCriticalSection cs_vAddedNodes;
      std::vector<CNode*> vNodes GUARDED_BY(cs_vNodes);
      std::list<CNode*> vNodesDisconnected;
      mutable CCriticalSection cs_vNodes;
      std::atomic<NodeId> nLastNodeId{0};
      unsigned int nPrevNodeCount{0};
  
      /** Services this instance offers */
      ServiceFlags nLocalServices;
  
      std::unique_ptr<CSemaphore> semOutbound;
      std::unique_ptr<CSemaphore> semAddnode;
      int nMaxConnections;
      int nMaxOutbound;
      int nMaxAddnode;
      int nMaxFeeler;
      bool m_use_addrman_outgoing;
      std::atomic<int> nBestHeight;
      CClientUIInterface* clientInterface;
      NetEventsInterface* m_msgproc;
      BanMan* m_banman;
  
      /** SipHasher seeds for deterministic randomness */
      const uint64_t nSeed0, nSeed1;
  
      /** flag for waking the message processor. */
      bool fMsgProcWake;
  
      std::condition_variable condMsgProc;
      Mutex mutexMsgProc;
      std::atomic<bool> flagInterruptMsgProc{false};
  
      CThreadInterrupt interruptNet;
  
      std::thread threadDNSAddressSeed;
      std::thread threadSocketHandler;
      std::thread threadOpenAddedConnections;
      std::thread threadOpenConnections;
      std::thread threadMessageHandler;
  
      /** flag for deciding to connect to an extra outbound peer,
       *  in excess of nMaxOutbound
       *  This takes the place of a feeler connection */
      std::atomic_bool m_try_another_outbound_peer;
  
      std::atomic<int64_t> m_next_send_inv_to_incoming{0};
  
      friend struct CConnmanTest;
  };
  extern std::unique_ptr<CConnman> g_connman;
  extern std::unique_ptr<BanMan> g_banman;
  void Discover();
  void StartMapPort();
  void InterruptMapPort();
  void StopMapPort();
  unsigned short GetListenPort();
  bool BindListenPort(const CService &bindAddr, std::string& strError, bool fWhitelisted = false);
  
  struct CombinerAll
  {
      typedef bool result_type;
  
      template<typename I>
      bool operator()(I first, I last) const
      {
          while (first != last) {
              if (!(*first)) return false;
              ++first;
          }
          return true;
      }
  };
  
  /**
   * Interface for message handling
   */
  class NetEventsInterface
  {
  public:
      virtual bool ProcessMessages(CNode* pnode, std::atomic<bool>& interrupt) = 0;
      virtual bool SendMessages(CNode* pnode) = 0;
      virtual void InitializeNode(CNode* pnode) = 0;
      virtual void FinalizeNode(NodeId id, bool& update_connection_time) = 0;
  
  protected:
      /**
       * Protected destructor so that instances can only be deleted by derived classes.
       * If that restriction is no longer desired, this should be made public and virtual.
       */
      ~NetEventsInterface() = default;
  };
  
  enum
  {
      LOCAL_NONE,   // unknown
      LOCAL_IF,     // address a local interface listens on
      LOCAL_BIND,   // address explicit bound to
      LOCAL_UPNP,   // address reported by UPnP
      LOCAL_MANUAL, // address explicitly specified (-externalip=)
  
      LOCAL_MAX
  };
  
  bool IsPeerAddrLocalGood(CNode *pnode);
  void AdvertiseLocal(CNode *pnode);
  
  /**
   * Mark a network as reachable or unreachable (no automatic connects to it)
   * @note Networks are reachable by default
   */
  void SetReachable(enum Network net, bool reachable);
  /** @returns true if the network is reachable, false otherwise */
  bool IsReachable(enum Network net);
  /** @returns true if the address is in a reachable network, false otherwise */
  bool IsReachable(const CNetAddr& addr);
  
  bool AddLocal(const CService& addr, int nScore = LOCAL_NONE);
  bool AddLocal(const CNetAddr& addr, int nScore = LOCAL_NONE);
  void RemoveLocal(const CService& addr);
  bool SeenLocal(const CService& addr);
  bool IsLocal(const CService& addr);
  bool GetLocal(CService &addr, const CNetAddr *paddrPeer = nullptr);
  CAddress GetLocalAddress(const CNetAddr *paddrPeer, ServiceFlags nLocalServices);
  
  
  extern bool fDiscover;
  extern bool fListen;
  extern bool g_relay_txes;
  
  extern limitedmap<uint256, int64_t> mapAlreadyAskedFor;
  
  /** Subversion as sent to the P2P network in `version` messages */
  extern std::string strSubVersion;
  
  struct LocalServiceInfo {
      int nScore;
      int nPort;
  };
  
  extern CCriticalSection cs_mapLocalHost;
  extern std::map<CNetAddr, LocalServiceInfo> mapLocalHost GUARDED_BY(cs_mapLocalHost);
  
  extern const std::string NET_MESSAGE_COMMAND_OTHER;
  typedef std::map<std::string, uint64_t> mapMsgCmdSize; //command, total bytes
  
  class CNodeStats
  {
  public:
      NodeId nodeid;
      ServiceFlags nServices;
      bool fRelayTxes;
      int64_t nLastSend;
      int64_t nLastRecv;
      int64_t nTimeConnected;
      int64_t nTimeOffset;
      std::string addrName;
      int nVersion;
      std::string cleanSubVer;
      bool fInbound;
      bool m_manual_connection;
      int nStartingHeight;
      uint64_t nSendBytes;
      mapMsgCmdSize mapSendBytesPerMsgCmd;
      uint64_t nRecvBytes;
      mapMsgCmdSize mapRecvBytesPerMsgCmd;
      bool fWhitelisted;
      double dPingTime;
      double dPingWait;
      double dMinPing;
      CAmount minFeeFilter;
      // Our address, as reported by the peer
      std::string addrLocal;
      // Address of this peer
      CAddress addr;
      // Bind address of our side of the connection
      CAddress addrBind;
  };
  
  
  
  
  class CNetMessage {
  private:
      mutable CHash256 hasher;
      mutable uint256 data_hash;
  public:
      bool in_data;                   // parsing header (false) or data (true)
  
      CDataStream hdrbuf;             // partially received header
      CMessageHeader hdr;             // complete header
      unsigned int nHdrPos;
  
      CDataStream vRecv;              // received message data
      unsigned int nDataPos;
  
      int64_t nTime;                  // time (in microseconds) of message receipt.
  
      CNetMessage(const CMessageHeader::MessageStartChars& pchMessageStartIn, int nTypeIn, int nVersionIn) : hdrbuf(nTypeIn, nVersionIn), hdr(pchMessageStartIn), vRecv(nTypeIn, nVersionIn) {
          hdrbuf.resize(24);
          in_data = false;
          nHdrPos = 0;
          nDataPos = 0;
          nTime = 0;
      }
  
      bool complete() const
      {
          if (!in_data)
              return false;
          return (hdr.nMessageSize == nDataPos);
      }
  
      const uint256& GetMessageHash() const;
  
      void SetVersion(int nVersionIn)
      {
          hdrbuf.SetVersion(nVersionIn);
          vRecv.SetVersion(nVersionIn);
      }
  
      int readHeader(const char *pch, unsigned int nBytes);
      int readData(const char *pch, unsigned int nBytes);
  };
  
  
  /** Information about a peer */
  class CNode
  {
      friend class CConnman;
  public:
      // socket
      std::atomic<ServiceFlags> nServices{NODE_NONE};
      SOCKET hSocket GUARDED_BY(cs_hSocket);
      size_t nSendSize{0}; // total size of all vSendMsg entries
      size_t nSendOffset{0}; // offset inside the first vSendMsg already sent
      uint64_t nSendBytes GUARDED_BY(cs_vSend){0};
      std::deque<std::vector<unsigned char>> vSendMsg GUARDED_BY(cs_vSend);
      CCriticalSection cs_vSend;
      CCriticalSection cs_hSocket;
      CCriticalSection cs_vRecv;
  
      CCriticalSection cs_vProcessMsg;
      std::list<CNetMessage> vProcessMsg GUARDED_BY(cs_vProcessMsg);
      size_t nProcessQueueSize{0};
  
      CCriticalSection cs_sendProcessing;
  
      std::deque<CInv> vRecvGetData;
      uint64_t nRecvBytes GUARDED_BY(cs_vRecv){0};
      std::atomic<int> nRecvVersion{INIT_PROTO_VERSION};
  
      std::atomic<int64_t> nLastSend{0};
      std::atomic<int64_t> nLastRecv{0};
      const int64_t nTimeConnected;
      std::atomic<int64_t> nTimeOffset{0};
      // Address of this peer
      const CAddress addr;
      // Bind address of our side of the connection
      const CAddress addrBind;
      std::atomic<int> nVersion{0};
      // strSubVer is whatever byte array we read from the wire. However, this field is intended
      // to be printed out, displayed to humans in various forms and so on. So we sanitize it and
      // store the sanitized version in cleanSubVer. The original should be used when dealing with
      // the network or wire types and the cleaned string used when displayed or logged.
      std::string strSubVer GUARDED_BY(cs_SubVer), cleanSubVer GUARDED_BY(cs_SubVer);
      CCriticalSection cs_SubVer; // used for both cleanSubVer and strSubVer
      bool m_prefer_evict{false}; // This peer is preferred for eviction.
      bool fWhitelisted{false}; // This peer can bypass DoS banning.
      bool fFeeler{false}; // If true this node is being used as a short lived feeler.
      bool fOneShot{false};
      bool m_manual_connection{false};
      bool fClient{false}; // set by version message
      bool m_limited_node{false}; //after BIP159, set by version message
      const bool fInbound;
      std::atomic_bool fSuccessfullyConnected{false};
      // Setting fDisconnect to true will cause the node to be disconnected the
      // next time DisconnectNodes() runs
      std::atomic_bool fDisconnect{false};
      // We use fRelayTxes for two purposes -
      // a) it allows us to not relay tx invs before receiving the peer's version message
      // b) the peer may tell us in its version message that we should not relay tx invs
      //    unless it loads a bloom filter.
      bool fRelayTxes GUARDED_BY(cs_filter){false};
      bool fSentAddr{false};
      CSemaphoreGrant grantOutbound;
      mutable CCriticalSection cs_filter;
      std::unique_ptr<CBloomFilter> pfilter PT_GUARDED_BY(cs_filter);
      std::atomic<int> nRefCount{0};
  
      const uint64_t nKeyedNetGroup;
      std::atomic_bool fPauseRecv{false};
      std::atomic_bool fPauseSend{false};
  
  protected:
      mapMsgCmdSize mapSendBytesPerMsgCmd;
      mapMsgCmdSize mapRecvBytesPerMsgCmd GUARDED_BY(cs_vRecv);
  
  public:
      uint256 hashContinue;
      std::atomic<int> nStartingHeight{-1};
  
      // flood relay
      std::vector<CAddress> vAddrToSend;
      CRollingBloomFilter addrKnown;
      bool fGetAddr{false};
      std::set<uint256> setKnown;
      int64_t nNextAddrSend GUARDED_BY(cs_sendProcessing){0};
      int64_t nNextLocalAddrSend GUARDED_BY(cs_sendProcessing){0};
      uint256 hashCheckpointKnown;
      bool supportACPMessages{false};
  
      // inventory based relay
      CRollingBloomFilter filterInventoryKnown GUARDED_BY(cs_inventory);
      // Set of transaction ids we still have to announce.
      // They are sorted by the mempool before relay, so the order is not important.
      std::set<uint256> setInventoryTxToSend;
      // List of block ids we still have announce.
      // There is no final sorting before sending, as they are always sent immediately
      // and in the order requested.
      std::vector<uint256> vInventoryBlockToSend GUARDED_BY(cs_inventory);
      CCriticalSection cs_inventory;
      std::set<uint256> setAskFor;
      std::multimap<int64_t, CInv> mapAskFor;
      int64_t nNextInvSend{0};
      // Used for headers announcements - unfiltered blocks to relay
      std::vector<uint256> vBlockHashesToAnnounce GUARDED_BY(cs_inventory);
      // Used for BIP35 mempool sending
      bool fSendMempool GUARDED_BY(cs_inventory){false};
  
      // Last time a "MEMPOOL" request was serviced.
      std::atomic<int64_t> timeLastMempoolReq{0};
  
      // Block and TXN accept times
      std::atomic<int64_t> nLastBlockTime{0};
      std::atomic<int64_t> nLastTXTime{0};
  
      // Ping time measurement:
      // The pong reply we're expecting, or 0 if no pong expected.
      std::atomic<uint64_t> nPingNonceSent{0};
      // Time (in usec) the last ping was sent, or 0 if no ping was ever sent.
      std::atomic<int64_t> nPingUsecStart{0};
      // Last measured round-trip time.
      std::atomic<int64_t> nPingUsecTime{0};
      // Best measured round-trip time.
      std::atomic<int64_t> nMinPingUsecTime{std::numeric_limits<int64_t>::max()};
      // Whether a ping is requested.
      std::atomic<bool> fPingQueued{false};
      // Minimum fee rate with which to filter inv's to this node
      CAmount minFeeFilter GUARDED_BY(cs_feeFilter){0};
      CCriticalSection cs_feeFilter;
      CAmount lastSentFeeFilter{0};
      int64_t nextSendTimeFeeFilter{0};
  
      std::set<uint256> orphan_work_set;
  
      CNode(NodeId id, ServiceFlags nLocalServicesIn, int nMyStartingHeightIn, SOCKET hSocketIn, const CAddress &addrIn, uint64_t nKeyedNetGroupIn, uint64_t nLocalHostNonceIn, const CAddress &addrBindIn, const std::string &addrNameIn = "", bool fInboundIn = false);
      ~CNode();
      CNode(const CNode&) = delete;
      CNode& operator=(const CNode&) = delete;
  
  private:
      const NodeId id;
      const uint64_t nLocalHostNonce;
      // Services offered to this peer
      const ServiceFlags nLocalServices;
      const int nMyStartingHeight;
      int nSendVersion{0};
      std::list<CNetMessage> vRecvMsg;  // Used only by SocketHandler thread
  
      mutable CCriticalSection cs_addrName;
      std::string addrName GUARDED_BY(cs_addrName);
  
      // Our address, as reported by the peer
      CService addrLocal GUARDED_BY(cs_addrLocal);
      mutable CCriticalSection cs_addrLocal;
  public:
  
      NodeId GetId() const {
          return id;
      }
  
      uint64_t GetLocalNonce() const {
          return nLocalHostNonce;
      }
  
      int GetMyStartingHeight() const {
          return nMyStartingHeight;
      }
  
      int GetRefCount() const
      {
          assert(nRefCount >= 0);
          return nRefCount;
      }
  
      bool ReceiveMsgBytes(const char *pch, unsigned int nBytes, bool& complete);
  
      void SetRecvVersion(int nVersionIn)
      {
          nRecvVersion = nVersionIn;
      }
      int GetRecvVersion() const
      {
          return nRecvVersion;
      }
      void SetSendVersion(int nVersionIn);
      int GetSendVersion() const;
  
      CService GetAddrLocal() const;
      //! May not be called more than once
      void SetAddrLocal(const CService& addrLocalIn);
  
      CNode* AddRef()
      {
          nRefCount++;
          return this;
      }
  
      void Release()
      {
          nRefCount--;
      }
  
  
  
      void AddAddressKnown(const CAddress& _addr)
      {
          addrKnown.insert(_addr.GetKey());
      }
  
      void PushAddress(const CAddress& _addr, FastRandomContext &insecure_rand)
      {
          // Known checking here is only to save space from duplicates.
          // SendMessages will filter it again for knowns that were added
          // after addresses were pushed.
          if (_addr.IsValid() && !addrKnown.contains(_addr.GetKey())) {
              if (vAddrToSend.size() >= MAX_ADDR_TO_SEND) {
                  vAddrToSend[insecure_rand.randrange(vAddrToSend.size())] = _addr;
              } else {
                  vAddrToSend.push_back(_addr);
              }
          }
      }
  
  
      void AddInventoryKnown(const CInv& inv)
      {
          {
              LOCK(cs_inventory);
              filterInventoryKnown.insert(inv.hash);
          }
      }
  
      void PushInventory(const CInv& inv)
      {
          LOCK(cs_inventory);
          if (inv.type == MSG_TX) {
              if (!filterInventoryKnown.contains(inv.hash)) {
                  setInventoryTxToSend.insert(inv.hash);
              }
          } else if (inv.type == MSG_BLOCK) {
              vInventoryBlockToSend.push_back(inv.hash);
          }
      }
  
      void PushBlockHash(const uint256 &hash)
      {
          LOCK(cs_inventory);
          vBlockHashesToAnnounce.push_back(hash);
      }
  
      void AskFor(const CInv& inv);
  
      void CloseSocketDisconnect();
  
      void copyStats(CNodeStats &stats);
  
      ServiceFlags GetLocalServices() const
      {
          return nLocalServices;
      }
  
      std::string GetAddrName() const;
      //! Sets the addrName only if it was not previously set
      void MaybeSetAddrName(const std::string& addrNameIn);
  };
  
  
  
  
  
  /** Return a timestamp in the future (in microseconds) for exponentially distributed events. */
  int64_t PoissonNextSend(int64_t now, int average_interval_seconds);
  
  #endif // BITCOIN_NET_H
  