text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2021 The DRiyal Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #ifndef DRIYAL_NET_H
  #define DRIYAL_NET_H
  
  #include <chainparams.h>
  #include <common/bloom.h>
  #include <compat.h>
  #include <consensus/amount.h>
  #include <crypto/siphash.h>
  #include <hash.h>
  #include <i2p.h>
  #include <net_permissions.h>
  #include <netaddress.h>
  #include <netbase.h>
  #include <policy/feerate.h>
  #include <protocol.h>
  #include <random.h>
  #include <span.h>
  #include <streams.h>
  #include <sync.h>
  #include <threadinterrupt.h>
  #include <uint256.h>
  #include <util/check.h>
  #include <util/sock.h>
  
  #include <atomic>
  #include <condition_variable>
  #include <cstdint>
  #include <deque>
  #include <map>
  #include <memory>
  #include <optional>
  #include <thread>
  #include <vector>
  
  class AddrMan;
  class BanMan;
  class CNode;
  class CScheduler;
  struct bilingual_str;
  
  /** Default for -whitelistrelay. */
  static const bool DEFAULT_WHITELISTRELAY = true;
  /** Default for -whitelistforcerelay. */
  static const bool DEFAULT_WHITELISTFORCERELAY = false;
  
  /** Time after which to disconnect, after waiting for a ping response (or inactivity). */
  static constexpr std::chrono::minutes TIMEOUT_INTERVAL{20};
  /** Run the feeler connection loop once every 2 minutes. **/
  static constexpr auto FEELER_INTERVAL = 2min;
  /** Run the extra block-relay-only connection loop once every 5 minutes. **/
  static constexpr auto EXTRA_BLOCK_RELAY_ONLY_PEER_INTERVAL = 5min;
  /** 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 the user agent string in `version` message */
  static const unsigned int MAX_SUBVERSION_LENGTH = 256;
  /** Maximum number of automatic outgoing nodes over which we'll relay everything (blocks, tx, addrs, etc) */
  static const int MAX_OUTBOUND_FULL_RELAY_CONNECTIONS = 8;
  /** Maximum number of addnode outgoing nodes */
  static const int MAX_ADDNODE_CONNECTIONS = 8;
  /** Maximum number of block-relay-only outgoing connections */
  static const int MAX_BLOCK_RELAY_ONLY_CONNECTIONS = 2;
  /** Maximum number of feeler connections */
  static const int MAX_FEELER_CONNECTIONS = 1;
  /** -listen default */
  static const bool DEFAULT_LISTEN = true;
  /** 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 std::string DEFAULT_MAX_UPLOAD_TARGET{"0M"};
  /** Default for blocks only*/
  static const bool DEFAULT_BLOCKSONLY = false;
  /** -peertimeout default */
  static const int64_t DEFAULT_PEER_CONNECT_TIMEOUT = 60;
  /** Number of file descriptors required for message capture **/
  static const int NUM_FDS_MESSAGE_CAPTURE = 1;
  
  static constexpr bool DEFAULT_FORCEDNSSEED{false};
  static constexpr bool DEFAULT_DNSSEED{true};
  static constexpr bool DEFAULT_FIXEDSEEDS{true};
  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 m_type;
  };
  
  /** Different types of connections to a peer. This enum encapsulates the
   * information we have available at the time of opening or accepting the
   * connection. Aside from INBOUND, all types are initiated by us.
   *
   * If adding or removing types, please update CONNECTION_TYPE_DOC in
   * src/rpc/net.cpp and src/qt/rpcconsole.cpp, as well as the descriptions in
   * src/qt/guiutil.cpp and src/driyal-cli.cpp::NetinfoRequestHandler. */
  enum class ConnectionType {
      /**
       * Inbound connections are those initiated by a peer. This is the only
       * property we know at the time of connection, until P2P messages are
       * exchanged.
       */
      INBOUND,
  
      /**
       * These are the default connections that we use to connect with the
       * network. There is no restriction on what is relayed; by default we relay
       * blocks, addresses & transactions. We automatically attempt to open
       * MAX_OUTBOUND_FULL_RELAY_CONNECTIONS using addresses from our AddrMan.
       */
      OUTBOUND_FULL_RELAY,
  
  
      /**
       * We open manual connections to addresses that users explicitly requested
       * via the addnode RPC or the -addnode/-connect configuration options. Even if a
       * manual connection is misbehaving, we do not automatically disconnect or
       * add it to our discouragement filter.
       */
      MANUAL,
  
      /**
       * Feeler connections are short-lived connections made to check that a node
       * is alive. They can be useful for:
       * - test-before-evict: if one of the peers is considered for eviction from
       *   our AddrMan because another peer is mapped to the same slot in the tried table,
       *   evict only if this longer-known peer is offline.
       * - move node addresses from New to Tried table, so that we have more
       *   connectable addresses in our AddrMan.
       * Note that in the literature ("Eclipse Attacks on DRiyal’s Peer-to-Peer Network")
       * only the latter feature is referred to as "feeler connections",
       * although in our codebase feeler connections encompass test-before-evict as well.
       * We make these connections approximately every FEELER_INTERVAL:
       * first we resolve previously found collisions if they exist (test-before-evict),
       * otherwise we connect to a node from the new table.
       */
      FEELER,
  
      /**
       * We use block-relay-only connections to help prevent against partition
       * attacks. By not relaying transactions or addresses, these connections
       * are harder to detect by a third party, thus helping obfuscate the
       * network topology. We automatically attempt to open
       * MAX_BLOCK_RELAY_ONLY_ANCHORS using addresses from our anchors.dat. Then
       * addresses from our AddrMan if MAX_BLOCK_RELAY_ONLY_CONNECTIONS
       * isn't reached yet.
       */
      BLOCK_RELAY,
  
      /**
       * AddrFetch connections are short lived connections used to solicit
       * addresses from peers. These are initiated to addresses submitted via the
       * -seednode command line argument, or under certain conditions when the
       * AddrMan is empty.
       */
      ADDR_FETCH,
  };
  
  /** Convert ConnectionType enum to a string value */
  std::string ConnectionTypeAsString(ConnectionType conn_type);
  void Discover();
  uint16_t GetListenPort();
  
  enum
  {
      LOCAL_NONE,   // unknown
      LOCAL_IF,     // address a local interface listens on
      LOCAL_BIND,   // address explicit bound to
      LOCAL_MAPPED, // address reported by UPnP or NAT-PMP
      LOCAL_MANUAL, // address explicitly specified (-externalip=)
  
      LOCAL_MAX
  };
  
  bool IsPeerAddrLocalGood(CNode *pnode);
  /** Returns a local address that we should advertise to this peer */
  std::optional<CAddress> GetLocalAddrForPeer(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;
  
  /** Subversion as sent to the P2P network in `version` messages */
  extern std::string strSubVersion;
  
  struct LocalServiceInfo {
      int nScore;
      uint16_t nPort;
  };
  
  extern RecursiveMutex 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;
      std::chrono::seconds m_last_send;
      std::chrono::seconds m_last_recv;
      std::chrono::seconds m_last_tx_time;
      std::chrono::seconds m_last_block_time;
      std::chrono::seconds m_connected;
      int64_t nTimeOffset;
      std::string m_addr_name;
      int nVersion;
      std::string cleanSubVer;
      bool fInbound;
      bool m_bip152_highbandwidth_to;
      bool m_bip152_highbandwidth_from;
      int m_starting_height;
      uint64_t nSendBytes;
      mapMsgCmdSize mapSendBytesPerMsgCmd;
      uint64_t nRecvBytes;
      mapMsgCmdSize mapRecvBytesPerMsgCmd;
      NetPermissionFlags m_permissionFlags;
      std::chrono::microseconds m_last_ping_time;
      std::chrono::microseconds m_min_ping_time;
      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;
      // Network the peer connected through
      Network m_network;
      uint32_t m_mapped_as;
      ConnectionType m_conn_type;
  };
  
  
  /** Transport protocol agnostic message container.
   * Ideally it should only contain receive time, payload,
   * command and size.
   */
  class CNetMessage {
  public:
      CDataStream m_recv;                  //!< received message data
      std::chrono::microseconds m_time{0}; //!< time of message receipt
      uint32_t m_message_size{0};          //!< size of the payload
      uint32_t m_raw_message_size{0};      //!< used wire size of the message (including header/checksum)
      std::string m_command;
  
      CNetMessage(CDataStream&& recv_in) : m_recv(std::move(recv_in)) {}
  
      void SetVersion(int nVersionIn)
      {
          m_recv.SetVersion(nVersionIn);
      }
  };
  
  /** The TransportDeserializer takes care of holding and deserializing the
   * network receive buffer. It can deserialize the network buffer into a
   * transport protocol agnostic CNetMessage (command & payload)
   */
  class TransportDeserializer {
  public:
      // returns true if the current deserialization is complete
      virtual bool Complete() const = 0;
      // set the serialization context version
      virtual void SetVersion(int version) = 0;
      /** read and deserialize data, advances msg_bytes data pointer */
      virtual int Read(Span<const uint8_t>& msg_bytes) = 0;
      // decomposes a message from the context
      virtual CNetMessage GetMessage(std::chrono::microseconds time, bool& reject_message) = 0;
      virtual ~TransportDeserializer() {}
  };
  
  class V1TransportDeserializer final : public TransportDeserializer
  {
  private:
      const CChainParams& m_chain_params;
      const NodeId m_node_id; // Only for logging
      mutable CHash256 hasher;
      mutable uint256 data_hash;
      bool in_data;                   // parsing header (false) or data (true)
      CDataStream hdrbuf;             // partially received header
      CMessageHeader hdr;             // complete header
      CDataStream vRecv;              // received message data
      unsigned int nHdrPos;
      unsigned int nDataPos;
  
      const uint256& GetMessageHash() const;
      int readHeader(Span<const uint8_t> msg_bytes);
      int readData(Span<const uint8_t> msg_bytes);
  
      void Reset() {
          vRecv.clear();
          hdrbuf.clear();
          hdrbuf.resize(24);
          in_data = false;
          nHdrPos = 0;
          nDataPos = 0;
          data_hash.SetNull();
          hasher.Reset();
      }
  
  public:
      V1TransportDeserializer(const CChainParams& chain_params, const NodeId node_id, int nTypeIn, int nVersionIn)
          : m_chain_params(chain_params),
            m_node_id(node_id),
            hdrbuf(nTypeIn, nVersionIn),
            vRecv(nTypeIn, nVersionIn)
      {
          Reset();
      }
  
      bool Complete() const override
      {
          if (!in_data)
              return false;
          return (hdr.nMessageSize == nDataPos);
      }
      void SetVersion(int nVersionIn) override
      {
          hdrbuf.SetVersion(nVersionIn);
          vRecv.SetVersion(nVersionIn);
      }
      int Read(Span<const uint8_t>& msg_bytes) override
      {
          int ret = in_data ? readData(msg_bytes) : readHeader(msg_bytes);
          if (ret < 0) {
              Reset();
          } else {
              msg_bytes = msg_bytes.subspan(ret);
          }
          return ret;
      }
      CNetMessage GetMessage(std::chrono::microseconds time, bool& reject_message) override;
  };
  
  /** The TransportSerializer prepares messages for the network transport
   */
  class TransportSerializer {
  public:
      // prepare message for transport (header construction, error-correction computation, payload encryption, etc.)
      virtual void prepareForTransport(CSerializedNetMsg& msg, std::vector<unsigned char>& header) = 0;
      virtual ~TransportSerializer() {}
  };
  
  class V1TransportSerializer  : public TransportSerializer {
  public:
      void prepareForTransport(CSerializedNetMsg& msg, std::vector<unsigned char>& header) override;
  };
  
  /** Information about a peer */
  class CNode
  {
      friend class CConnman;
      friend struct ConnmanTestMsg;
  
  public:
      std::unique_ptr<TransportDeserializer> m_deserializer;
      std::unique_ptr<TransportSerializer> m_serializer;
  
      NetPermissionFlags m_permissionFlags{NetPermissionFlags::None};
      std::atomic<ServiceFlags> nServices{NODE_NONE};
      SOCKET hSocket GUARDED_BY(cs_hSocket);
      /** Total size of all vSendMsg entries */
      size_t nSendSize GUARDED_BY(cs_vSend){0};
      /** Offset inside the first vSendMsg already sent */
      size_t nSendOffset GUARDED_BY(cs_vSend){0};
      uint64_t nSendBytes GUARDED_BY(cs_vSend){0};
      std::deque<std::vector<unsigned char>> vSendMsg GUARDED_BY(cs_vSend);
      Mutex cs_vSend;
      Mutex cs_hSocket;
      Mutex cs_vRecv;
  
      RecursiveMutex cs_vProcessMsg;
      std::list<CNetMessage> vProcessMsg GUARDED_BY(cs_vProcessMsg);
      size_t nProcessQueueSize{0};
  
      RecursiveMutex cs_sendProcessing;
  
      uint64_t nRecvBytes GUARDED_BY(cs_vRecv){0};
  
      std::atomic<std::chrono::seconds> m_last_send{0s};
      std::atomic<std::chrono::seconds> m_last_recv{0s};
      //! Unix epoch time at peer connection
      const std::chrono::seconds m_connected;
      std::atomic<int64_t> nTimeOffset{0};
      // Address of this peer
      const CAddress addr;
      // Bind address of our side of the connection
      const CAddress addrBind;
      const std::string m_addr_name;
      //! Whether this peer is an inbound onion, i.e. connected via our Tor onion service.
      const bool m_inbound_onion;
      std::atomic<int> nVersion{0};
      RecursiveMutex cs_SubVer;
      /**
       * cleanSubVer is a sanitized string of the user agent byte array we read
       * from the wire. This cleaned string can safely be logged or displayed.
       */
      std::string cleanSubVer GUARDED_BY(cs_SubVer){};
      bool m_prefer_evict{false}; // This peer is preferred for eviction.
      bool HasPermission(NetPermissionFlags permission) const {
          return NetPermissions::HasFlag(m_permissionFlags, permission);
      }
      bool fClient{false}; // set by version message
      bool m_limited_node{false}; //after BIP159, set by version message
      /** fSuccessfullyConnected is set to true on receiving VERACK from the peer. */
      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};
      CSemaphoreGrant grantOutbound;
      std::atomic<int> nRefCount{0};
  
      const uint64_t nKeyedNetGroup;
      std::atomic_bool fPauseRecv{false};
      std::atomic_bool fPauseSend{false};
  
      bool IsOutboundOrBlockRelayConn() const {
          switch (m_conn_type) {
              case ConnectionType::OUTBOUND_FULL_RELAY:
              case ConnectionType::BLOCK_RELAY:
                  return true;
              case ConnectionType::INBOUND:
              case ConnectionType::MANUAL:
              case ConnectionType::ADDR_FETCH:
              case ConnectionType::FEELER:
                  return false;
          } // no default case, so the compiler can warn about missing cases
  
          assert(false);
      }
  
      bool IsFullOutboundConn() const {
          return m_conn_type == ConnectionType::OUTBOUND_FULL_RELAY;
      }
  
      bool IsManualConn() const {
          return m_conn_type == ConnectionType::MANUAL;
      }
  
      bool IsBlockOnlyConn() const {
          return m_conn_type == ConnectionType::BLOCK_RELAY;
      }
  
      bool IsFeelerConn() const {
          return m_conn_type == ConnectionType::FEELER;
      }
  
      bool IsAddrFetchConn() const {
          return m_conn_type == ConnectionType::ADDR_FETCH;
      }
  
      bool IsInboundConn() const {
          return m_conn_type == ConnectionType::INBOUND;
      }
  
      bool ExpectServicesFromConn() const {
          switch (m_conn_type) {
              case ConnectionType::INBOUND:
              case ConnectionType::MANUAL:
              case ConnectionType::FEELER:
                  return false;
              case ConnectionType::OUTBOUND_FULL_RELAY:
              case ConnectionType::BLOCK_RELAY:
              case ConnectionType::ADDR_FETCH:
                  return true;
          } // no default case, so the compiler can warn about missing cases
  
          assert(false);
      }
  
      /**
       * Get network the peer connected through.
       *
       * Returns Network::NET_ONION for *inbound* onion connections,
       * and CNetAddr::GetNetClass() otherwise. The latter cannot be used directly
       * because it doesn't detect the former, and it's not the responsibility of
       * the CNetAddr class to know the actual network a peer is connected through.
       *
       * @return network the peer connected through.
       */
      Network ConnectedThroughNetwork() const;
  
      // We selected peer as (compact blocks) high-bandwidth peer (BIP152)
      std::atomic<bool> m_bip152_highbandwidth_to{false};
      // Peer selected us as (compact blocks) high-bandwidth peer (BIP152)
      std::atomic<bool> m_bip152_highbandwidth_from{false};
  
      struct TxRelay {
          mutable RecursiveMutex cs_filter;
          // 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};
          std::unique_ptr<CBloomFilter> pfilter PT_GUARDED_BY(cs_filter) GUARDED_BY(cs_filter){nullptr};
  
          mutable RecursiveMutex cs_tx_inventory;
          CRollingBloomFilter filterInventoryKnown GUARDED_BY(cs_tx_inventory){50000, 0.000001};
          // 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;
          // Used for BIP35 mempool sending
          bool fSendMempool GUARDED_BY(cs_tx_inventory){false};
          // Last time a "MEMPOOL" request was serviced.
          std::atomic<std::chrono::seconds> m_last_mempool_req{0s};
          std::chrono::microseconds nNextInvSend{0};
  
          /** Minimum fee rate with which to filter inv's to this node */
          std::atomic<CAmount> minFeeFilter{0};
          CAmount lastSentFeeFilter{0};
          std::chrono::microseconds m_next_send_feefilter{0};
      };
  
      // m_tx_relay == nullptr if we're not relaying transactions with this peer
      std::unique_ptr<TxRelay> m_tx_relay;
  
      /** UNIX epoch time of the last block received from this peer that we had
       * not yet seen (e.g. not already received from another peer), that passed
       * preliminary validity checks and was saved to disk, even if we don't
       * connect the block or it eventually fails connection. Used as an inbound
       * peer eviction criterium in CConnman::AttemptToEvictConnection. */
      std::atomic<std::chrono::seconds> m_last_block_time{0s};
  
      /** UNIX epoch time of the last transaction received from this peer that we
       * had not yet seen (e.g. not already received from another peer) and that
       * was accepted into our mempool. Used as an inbound peer eviction criterium
       * in CConnman::AttemptToEvictConnection. */
      std::atomic<std::chrono::seconds> m_last_tx_time{0s};
  
      /** Last measured round-trip time. Used only for RPC/GUI stats/debugging.*/
      std::atomic<std::chrono::microseconds> m_last_ping_time{0us};
  
      /** Lowest measured round-trip time. Used as an inbound peer eviction
       * criterium in CConnman::AttemptToEvictConnection. */
      std::atomic<std::chrono::microseconds> m_min_ping_time{std::chrono::microseconds::max()};
  
      CNode(NodeId id, ServiceFlags nLocalServicesIn, SOCKET hSocketIn, const CAddress& addrIn, uint64_t nKeyedNetGroupIn, uint64_t nLocalHostNonceIn, const CAddress& addrBindIn, const std::string& addrNameIn, ConnectionType conn_type_in, bool inbound_onion);
      ~CNode();
      CNode(const CNode&) = delete;
      CNode& operator=(const CNode&) = delete;
  
      NodeId GetId() const {
          return id;
      }
  
      uint64_t GetLocalNonce() const {
          return nLocalHostNonce;
      }
  
      int GetRefCount() const
      {
          assert(nRefCount >= 0);
          return nRefCount;
      }
  
      /**
       * Receive bytes from the buffer and deserialize them into messages.
       *
       * @param[in]   msg_bytes   The raw data
       * @param[out]  complete    Set True if at least one message has been
       *                          deserialized and is ready to be processed
       * @return  True if the peer should stay connected,
       *          False if the peer should be disconnected from.
       */
      bool ReceiveMsgBytes(Span<const uint8_t> msg_bytes, bool& complete);
  
      void SetCommonVersion(int greatest_common_version)
      {
          Assume(m_greatest_common_version == INIT_PROTO_VERSION);
          m_greatest_common_version = greatest_common_version;
      }
      int GetCommonVersion() const
      {
          return m_greatest_common_version;
      }
  
      CService GetAddrLocal() const;
      //! May not be called more than once
      void SetAddrLocal(const CService& addrLocalIn);
  
      CNode* AddRef()
      {
          nRefCount++;
          return this;
      }
  
      void Release()
      {
          nRefCount--;
      }
  
      void AddKnownTx(const uint256& hash)
      {
          if (m_tx_relay != nullptr) {
              LOCK(m_tx_relay->cs_tx_inventory);
              m_tx_relay->filterInventoryKnown.insert(hash);
          }
      }
  
      void PushTxInventory(const uint256& hash)
      {
          if (m_tx_relay == nullptr) return;
          LOCK(m_tx_relay->cs_tx_inventory);
          if (!m_tx_relay->filterInventoryKnown.contains(hash)) {
              m_tx_relay->setInventoryTxToSend.insert(hash);
          }
      }
  
      void CloseSocketDisconnect();
  
      void CopyStats(CNodeStats& stats);
  
      ServiceFlags GetLocalServices() const
      {
          return nLocalServices;
      }
  
      std::string ConnectionTypeAsString() const { return ::ConnectionTypeAsString(m_conn_type); }
  
      /** A ping-pong round trip has completed successfully. Update latest and minimum ping times. */
      void PongReceived(std::chrono::microseconds ping_time) {
          m_last_ping_time = ping_time;
          m_min_ping_time = std::min(m_min_ping_time.load(), ping_time);
      }
  
  private:
      const NodeId id;
      const uint64_t nLocalHostNonce;
      const ConnectionType m_conn_type;
      std::atomic<int> m_greatest_common_version{INIT_PROTO_VERSION};
  
      //! Services offered to this peer.
      //!
      //! This is supplied by the parent CConnman during peer connection
      //! (CConnman::ConnectNode()) from its attribute of the same name.
      //!
      //! This is const because there is no protocol defined for renegotiating
      //! services initially offered to a peer. The set of local services we
      //! offer should not change after initialization.
      //!
      //! An interesting example of this is NODE_NETWORK and initial block
      //! download: a node which starts up from scratch doesn't have any blocks
      //! to serve, but still advertises NODE_NETWORK because it will eventually
      //! fulfill this role after IBD completes. P2P code is written in such a
      //! way that it can gracefully handle peers who don't make good on their
      //! service advertisements.
      const ServiceFlags nLocalServices;
  
      std::list<CNetMessage> vRecvMsg; // Used only by SocketHandler thread
  
      // Our address, as reported by the peer
      CService addrLocal GUARDED_BY(cs_addrLocal);
      mutable RecursiveMutex cs_addrLocal;
  
      mapMsgCmdSize mapSendBytesPerMsgCmd GUARDED_BY(cs_vSend);
      mapMsgCmdSize mapRecvBytesPerMsgCmd GUARDED_BY(cs_vRecv);
  };
  
  /**
   * Interface for message handling
   */
  class NetEventsInterface
  {
  public:
      /** Initialize a peer (setup state, queue any initial messages) */
      virtual void InitializeNode(CNode* pnode) = 0;
  
      /** Handle removal of a peer (clear state) */
      virtual void FinalizeNode(const CNode& node) = 0;
  
      /**
      * Process protocol messages received from a given node
      *
      * @param[in]   pnode           The node which we have received messages from.
      * @param[in]   interrupt       Interrupt condition for processing threads
      * @return                      True if there is more work to be done
      */
      virtual bool ProcessMessages(CNode* pnode, std::atomic<bool>& interrupt) = 0;
  
      /**
      * Send queued protocol messages to a given node.
      *
      * @param[in]   pnode           The node which we are sending messages to.
      * @return                      True if there is more work to be done
      */
      virtual bool SendMessages(CNode* pnode) EXCLUSIVE_LOCKS_REQUIRED(pnode->cs_sendProcessing) = 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;
  };
  
  class CConnman
  {
  public:
  
      struct Options
      {
          ServiceFlags nLocalServices = NODE_NONE;
          int nMaxConnections = 0;
          int m_max_outbound_full_relay = 0;
          int m_max_outbound_block_relay = 0;
          int nMaxAddnode = 0;
          int nMaxFeeler = 0;
          CClientUIInterface* uiInterface = nullptr;
          NetEventsInterface* m_msgproc = nullptr;
          BanMan* m_banman = nullptr;
          unsigned int nSendBufferMaxSize = 0;
          unsigned int nReceiveFloodSize = 0;
          uint64_t nMaxOutboundLimit = 0;
          int64_t m_peer_connect_timeout = DEFAULT_PEER_CONNECT_TIMEOUT;
          std::vector<std::string> vSeedNodes;
          std::vector<NetWhitelistPermissions> vWhitelistedRange;
          std::vector<NetWhitebindPermissions> vWhiteBinds;
          std::vector<CService> vBinds;
          std::vector<CService> onion_binds;
          /// True if the user did not specify -bind= or -whitebind= and thus
          /// we should bind on `0.0.0.0` (IPv4) and `::` (IPv6).
          bool bind_on_any;
          bool m_use_addrman_outgoing = true;
          std::vector<std::string> m_specified_outgoing;
          std::vector<std::string> m_added_nodes;
          bool m_i2p_accept_incoming;
      };
  
      void Init(const Options& connOptions) {
          nLocalServices = connOptions.nLocalServices;
          nMaxConnections = connOptions.nMaxConnections;
          m_max_outbound_full_relay = std::min(connOptions.m_max_outbound_full_relay, connOptions.nMaxConnections);
          m_max_outbound_block_relay = connOptions.m_max_outbound_block_relay;
          m_use_addrman_outgoing = connOptions.m_use_addrman_outgoing;
          nMaxAddnode = connOptions.nMaxAddnode;
          nMaxFeeler = connOptions.nMaxFeeler;
          m_max_outbound = m_max_outbound_full_relay + m_max_outbound_block_relay + nMaxFeeler;
          m_client_interface = connOptions.uiInterface;
          m_banman = connOptions.m_banman;
          m_msgproc = connOptions.m_msgproc;
          nSendBufferMaxSize = connOptions.nSendBufferMaxSize;
          nReceiveFloodSize = connOptions.nReceiveFloodSize;
          m_peer_connect_timeout = std::chrono::seconds{connOptions.m_peer_connect_timeout};
          {
              LOCK(cs_totalBytesSent);
              nMaxOutboundLimit = connOptions.nMaxOutboundLimit;
          }
          vWhitelistedRange = connOptions.vWhitelistedRange;
          {
              LOCK(m_added_nodes_mutex);
              m_added_nodes = connOptions.m_added_nodes;
          }
          m_onion_binds = connOptions.onion_binds;
      }
  
      CConnman(uint64_t seed0, uint64_t seed1, AddrMan& addrman, bool network_active = true);
      ~CConnman();
      bool Start(CScheduler& scheduler, const Options& options);
  
      void StopThreads();
      void StopNodes();
      void Stop()
      {
          StopThreads();
          StopNodes();
      };
  
      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, const char* strDest, ConnectionType conn_type);
      bool CheckIncomingNonce(uint64_t nonce);
  
      bool ForNode(NodeId id, std::function<bool(CNode* pnode)> func);
  
      void PushMessage(CNode* pnode, CSerializedNetMsg&& msg);
  
      using NodeFn = std::function<void(CNode*)>;
      void ForEachNode(const NodeFn& func)
      {
          LOCK(m_nodes_mutex);
          for (auto&& node : m_nodes) {
              if (NodeFullyConnected(node))
                  func(node);
          }
      };
  
      void ForEachNode(const NodeFn& func) const
      {
          LOCK(m_nodes_mutex);
          for (auto&& node : m_nodes) {
              if (NodeFullyConnected(node))
                  func(node);
          }
      };
  
      // Addrman functions
      /**
       * Return all or many randomly selected addresses, optionally by network.
       *
       * @param[in] max_addresses  Maximum number of addresses to return (0 = all).
       * @param[in] max_pct        Maximum percentage of addresses to return (0 = all).
       * @param[in] network        Select only addresses of this network (nullopt = all).
       */
      std::vector<CAddress> GetAddresses(size_t max_addresses, size_t max_pct, std::optional<Network> network) const;
      /**
       * Cache is used to minimize topology leaks, so it should
       * be used for all non-trusted calls, for example, p2p.
       * A non-malicious call (from RPC or a peer with addr permission) should
       * call the function without a parameter to avoid using the cache.
       */
      std::vector<CAddress> GetAddresses(CNode& requestor, size_t max_addresses, size_t max_pct);
  
      // This allows temporarily exceeding m_max_outbound_full_relay, with the goal of finding
      // a peer that is better than all our current peers.
      void SetTryNewOutboundPeer(bool flag);
      bool GetTryNewOutboundPeer() const;
  
      void StartExtraBlockRelayPeers() {
          LogPrint(BCLog::NET, "net: enabling extra block-relay-only peers\n");
          m_start_extra_block_relay_peers = true;
      }
  
      // 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 GetExtraFullOutboundCount() const;
      // Count the number of block-relay-only peers we have over our limit.
      int GetExtraBlockRelayCount() const;
  
      bool AddNode(const std::string& node);
      bool RemoveAddedNode(const std::string& node);
      std::vector<AddedNodeInfo> GetAddedNodeInfo() const;
  
      /**
       * Attempts to open a connection. Currently only used from tests.
       *
       * @param[in]   address     Address of node to try connecting to
       * @param[in]   conn_type   ConnectionType::OUTBOUND, ConnectionType::BLOCK_RELAY,
       *                          ConnectionType::ADDR_FETCH or ConnectionType::FEELER
       * @return      bool        Returns false if there are no available
       *                          slots for this connection:
       *                          - conn_type not a supported ConnectionType
       *                          - Max total outbound connection capacity filled
       *                          - Max connection capacity for type is filled
       */
      bool AddConnection(const std::string& address, ConnectionType conn_type);
  
      size_t GetNodeCount(ConnectionDirection) const;
      void GetNodeStats(std::vector<CNodeStats>& vstats) const;
      bool DisconnectNode(const std::string& node);
      bool DisconnectNode(const CSubNet& subnet);
      bool DisconnectNode(const CNetAddr& addr);
      bool DisconnectNode(NodeId id);
  
      //! Used to convey which local services we are offering peers during node
      //! connection.
      //!
      //! The data returned by this is used in CNode construction,
      //! which is used to advertise which services we are offering
      //! that peer during `net_processing.cpp:PushNodeVersion()`.
      ServiceFlags GetLocalServices() const;
  
      uint64_t GetMaxOutboundTarget() const;
      std::chrono::seconds GetMaxOutboundTimeframe() const;
  
      //! 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) const;
  
      //! response the bytes left in the current max outbound cycle
      //! in case of no limit, it will always response 0
      uint64_t GetOutboundTargetBytesLeft() const;
  
      //! returns the time left in the current max outbound cycle
      //! in case of no limit, it will always return 0
      std::chrono::seconds GetMaxOutboundTimeLeftInCycle() const;
  
      uint64_t GetTotalBytesRecv() const;
      uint64_t GetTotalBytesSent() 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.
      */
      std::chrono::microseconds PoissonNextSendInbound(std::chrono::microseconds now, std::chrono::seconds average_interval);
  
      /** Return true if we should disconnect the peer for failing an inactivity check. */
      bool ShouldRunInactivityChecks(const CNode& node, std::chrono::seconds now) const;
  
  private:
      struct ListenSocket {
      public:
          std::shared_ptr<Sock> sock;
          inline void AddSocketPermissionFlags(NetPermissionFlags& flags) const { NetPermissions::AddFlag(flags, m_permissions); }
          ListenSocket(std::shared_ptr<Sock> sock_, NetPermissionFlags permissions_)
              : sock{sock_}, m_permissions{permissions_}
          {
          }
  
      private:
          NetPermissionFlags m_permissions;
      };
  
      bool BindListenPort(const CService& bindAddr, bilingual_str& strError, NetPermissionFlags permissions);
      bool Bind(const CService& addr, unsigned int flags, NetPermissionFlags permissions);
      bool InitBinds(const Options& options);
  
      void ThreadOpenAddedConnections();
      void AddAddrFetch(const std::string& strDest);
      void ProcessAddrFetch();
      void ThreadOpenConnections(std::vector<std::string> connect);
      void ThreadMessageHandler();
      void ThreadI2PAcceptIncoming();
      void AcceptConnection(const ListenSocket& hListenSocket);
  
      /**
       * Create a `CNode` object from a socket that has just been accepted and add the node to
       * the `m_nodes` member.
       * @param[in] sock Connected socket to communicate with the peer.
       * @param[in] permissionFlags The peer's permissions.
       * @param[in] addr_bind The address and port at our side of the connection.
       * @param[in] addr The address and port at the peer's side of the connection.
       */
      void CreateNodeFromAcceptedSocket(std::unique_ptr<Sock>&& sock,
                                        NetPermissionFlags permissionFlags,
                                        const CAddress& addr_bind,
                                        const CAddress& addr);
  
      void DisconnectNodes();
      void NotifyNumConnectionsChanged();
      /** Return true if the peer is inactive and should be disconnected. */
      bool InactivityCheck(const CNode& node) const;
  
      /**
       * Generate a collection of sockets to check for IO readiness.
       * @param[in] nodes Select from these nodes' sockets.
       * @param[out] recv_set Sockets to check for read readiness.
       * @param[out] send_set Sockets to check for write readiness.
       * @param[out] error_set Sockets to check for errors.
       * @return true if at least one socket is to be checked (the returned set is not empty)
       */
      bool GenerateSelectSet(const std::vector<CNode*>& nodes,
                             std::set<SOCKET>& recv_set,
                             std::set<SOCKET>& send_set,
                             std::set<SOCKET>& error_set);
  
      /**
       * Check which sockets are ready for IO.
       * @param[in] nodes Select from these nodes' sockets.
       * @param[out] recv_set Sockets which are ready for read.
       * @param[out] send_set Sockets which are ready for write.
       * @param[out] error_set Sockets which have errors.
       * This calls `GenerateSelectSet()` to gather a list of sockets to check.
       */
      void SocketEvents(const std::vector<CNode*>& nodes,
                        std::set<SOCKET>& recv_set,
                        std::set<SOCKET>& send_set,
                        std::set<SOCKET>& error_set);
  
      /**
       * Check connected and listening sockets for IO readiness and process them accordingly.
       */
      void SocketHandler();
  
      /**
       * Do the read/write for connected sockets that are ready for IO.
       * @param[in] nodes Nodes to process. The socket of each node is checked against
       * `recv_set`, `send_set` and `error_set`.
       * @param[in] recv_set Sockets that are ready for read.
       * @param[in] send_set Sockets that are ready for send.
       * @param[in] error_set Sockets that have an exceptional condition (error).
       */
      void SocketHandlerConnected(const std::vector<CNode*>& nodes,
                                  const std::set<SOCKET>& recv_set,
                                  const std::set<SOCKET>& send_set,
                                  const std::set<SOCKET>& error_set);
  
      /**
       * Accept incoming connections, one from each read-ready listening socket.
       * @param[in] recv_set Sockets that are ready for read.
       */
      void SocketHandlerListening(const std::set<SOCKET>& recv_set);
  
      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);
  
      /**
       * Determine whether we're already connected to a given address, in order to
       * avoid initiating duplicate connections.
       */
      bool AlreadyConnectedToAddress(const CAddress& addr);
  
      bool AttemptToEvictConnection();
      CNode* ConnectNode(CAddress addrConnect, const char *pszDest, bool fCountFailure, ConnectionType conn_type);
      void AddWhitelistPermissionFlags(NetPermissionFlags& flags, const CNetAddr &addr) const;
  
      void DeleteNode(CNode* pnode);
  
      NodeId GetNewNodeId();
  
      size_t SocketSendData(CNode& node) const EXCLUSIVE_LOCKS_REQUIRED(node.cs_vSend);
      void DumpAddresses();
  
      // Network stats
      void RecordBytesRecv(uint64_t bytes);
      void RecordBytesSent(uint64_t bytes);
  
      /**
       * Return vector of current BLOCK_RELAY peers.
       */
      std::vector<CAddress> GetCurrentBlockRelayOnlyConns() const;
  
      // Whether the node should be passed out in ForEach* callbacks
      static bool NodeFullyConnected(const CNode* pnode);
  
      // Network usage totals
      mutable RecursiveMutex cs_totalBytesSent;
      std::atomic<uint64_t> nTotalBytesRecv{0};
      uint64_t nTotalBytesSent GUARDED_BY(cs_totalBytesSent) {0};
  
      // outbound limit & stats
      uint64_t nMaxOutboundTotalBytesSentInCycle GUARDED_BY(cs_totalBytesSent) {0};
      std::chrono::seconds nMaxOutboundCycleStartTime GUARDED_BY(cs_totalBytesSent) {0};
      uint64_t nMaxOutboundLimit GUARDED_BY(cs_totalBytesSent);
  
      // P2P timeout in seconds
      std::chrono::seconds m_peer_connect_timeout;
  
      // Whitelisted ranges. Any node connecting from these is automatically
      // whitelisted (as well as those connecting to whitelisted binds).
      std::vector<NetWhitelistPermissions> vWhitelistedRange;
  
      unsigned int nSendBufferMaxSize{0};
      unsigned int nReceiveFloodSize{0};
  
      std::vector<ListenSocket> vhListenSocket;
      std::atomic<bool> fNetworkActive{true};
      bool fAddressesInitialized{false};
      AddrMan& addrman;
      std::deque<std::string> m_addr_fetches GUARDED_BY(m_addr_fetches_mutex);
      Mutex m_addr_fetches_mutex;
      std::vector<std::string> m_added_nodes GUARDED_BY(m_added_nodes_mutex);
      mutable Mutex m_added_nodes_mutex;
      std::vector<CNode*> m_nodes GUARDED_BY(m_nodes_mutex);
      std::list<CNode*> m_nodes_disconnected;
      mutable RecursiveMutex m_nodes_mutex;
      std::atomic<NodeId> nLastNodeId{0};
      unsigned int nPrevNodeCount{0};
  
      /**
       * Cache responses to addr requests to minimize privacy leak.
       * Attack example: scraping addrs in real-time may allow an attacker
       * to infer new connections of the victim by detecting new records
       * with fresh timestamps (per self-announcement).
       */
      struct CachedAddrResponse {
          std::vector<CAddress> m_addrs_response_cache;
          std::chrono::microseconds m_cache_entry_expiration{0};
      };
  
      /**
       * Addr responses stored in different caches
       * per (network, local socket) prevent cross-network node identification.
       * If a node for example is multi-homed under Tor and IPv6,
       * a single cache (or no cache at all) would let an attacker
       * to easily detect that it is the same node by comparing responses.
       * Indexing by local socket prevents leakage when a node has multiple
       * listening addresses on the same network.
       *
       * The used memory equals to 1000 CAddress records (or around 40 bytes) per
       * distinct Network (up to 5) we have/had an inbound peer from,
       * resulting in at most ~196 KB. Every separate local socket may
       * add up to ~196 KB extra.
       */
      std::map<uint64_t, CachedAddrResponse> m_addr_response_caches;
  
      /**
       * Services this instance offers.
       *
       * This data is replicated in each CNode instance we create during peer
       * connection (in ConnectNode()) under a member also called
       * nLocalServices.
       *
       * This data is not marked const, but after being set it should not
       * change. See the note in CNode::nLocalServices documentation.
       *
       * \sa CNode::nLocalServices
       */
      ServiceFlags nLocalServices;
  
      std::unique_ptr<CSemaphore> semOutbound;
      std::unique_ptr<CSemaphore> semAddnode;
      int nMaxConnections;
  
      // How many full-relay (tx, block, addr) outbound peers we want
      int m_max_outbound_full_relay;
  
      // How many block-relay only outbound peers we want
      // We do not relay tx or addr messages with these peers
      int m_max_outbound_block_relay;
  
      int nMaxAddnode;
      int nMaxFeeler;
      int m_max_outbound;
      bool m_use_addrman_outgoing;
      CClientUIInterface* m_client_interface;
      NetEventsInterface* m_msgproc;
      /** Pointer to this node's banman. May be nullptr - check existence before dereferencing. */
      BanMan* m_banman;
  
      /**
       * Addresses that were saved during the previous clean shutdown. We'll
       * attempt to make block-relay-only connections to them.
       */
      std::vector<CAddress> m_anchors;
  
      /** SipHasher seeds for deterministic randomness */
      const uint64_t nSeed0, nSeed1;
  
      /** flag for waking the message processor. */
      bool fMsgProcWake GUARDED_BY(mutexMsgProc);
  
      std::condition_variable condMsgProc;
      Mutex mutexMsgProc;
      std::atomic<bool> flagInterruptMsgProc{false};
  
      /**
       * This is signaled when network activity should cease.
       * A pointer to it is saved in `m_i2p_sam_session`, so make sure that
       * the lifetime of `interruptNet` is not shorter than
       * the lifetime of `m_i2p_sam_session`.
       */
      CThreadInterrupt interruptNet;
  
      /**
       * I2P SAM session.
       * Used to accept incoming and make outgoing I2P connections.
       */
      std::unique_ptr<i2p::sam::Session> m_i2p_sam_session;
  
      std::thread threadDNSAddressSeed;
      std::thread threadSocketHandler;
      std::thread threadOpenAddedConnections;
      std::thread threadOpenConnections;
      std::thread threadMessageHandler;
      std::thread threadI2PAcceptIncoming;
  
      /** flag for deciding to connect to an extra outbound peer,
       *  in excess of m_max_outbound_full_relay
       *  This takes the place of a feeler connection */
      std::atomic_bool m_try_another_outbound_peer;
  
      /** flag for initiating extra block-relay-only peer connections.
       *  this should only be enabled after initial chain sync has occurred,
       *  as these connections are intended to be short-lived and low-bandwidth.
       */
      std::atomic_bool m_start_extra_block_relay_peers{false};
  
      std::atomic<std::chrono::microseconds> m_next_send_inv_to_incoming{0us};
  
      /**
       * A vector of -bind=<address>:<port>=onion arguments each of which is
       * an address and port that are designated for incoming Tor connections.
       */
      std::vector<CService> m_onion_binds;
  
      /**
       * RAII helper to atomically create a copy of `m_nodes` and add a reference
       * to each of the nodes. The nodes are released when this object is destroyed.
       */
      class NodesSnapshot
      {
      public:
          explicit NodesSnapshot(const CConnman& connman, bool shuffle)
          {
              {
                  LOCK(connman.m_nodes_mutex);
                  m_nodes_copy = connman.m_nodes;
                  for (auto& node : m_nodes_copy) {
                      node->AddRef();
                  }
              }
              if (shuffle) {
                  Shuffle(m_nodes_copy.begin(), m_nodes_copy.end(), FastRandomContext{});
              }
          }
  
          ~NodesSnapshot()
          {
              for (auto& node : m_nodes_copy) {
                  node->Release();
              }
          }
  
          const std::vector<CNode*>& Nodes() const
          {
              return m_nodes_copy;
          }
  
      private:
          std::vector<CNode*> m_nodes_copy;
      };
  
      friend struct CConnmanTest;
      friend struct ConnmanTestMsg;
  };
  
  /** Return a timestamp in the future (in microseconds) for exponentially distributed events. */
  std::chrono::microseconds PoissonNextSend(std::chrono::microseconds now, std::chrono::seconds average_interval);
  
  /** Dump binary message to file, with timestamp */
  void CaptureMessage(const CAddress& addr, const std::string& msg_type, const Span<const unsigned char>& data, bool is_incoming);
  
  struct NodeEvictionCandidate
  {
      NodeId id;
      std::chrono::seconds m_connected;
      std::chrono::microseconds m_min_ping_time;
      std::chrono::seconds m_last_block_time;
      std::chrono::seconds m_last_tx_time;
      bool fRelevantServices;
      bool fRelayTxes;
      bool fBloomFilter;
      uint64_t nKeyedNetGroup;
      bool prefer_evict;
      bool m_is_local;
      Network m_network;
  };
  
  /**
   * Select an inbound peer to evict after filtering out (protecting) peers having
   * distinct, difficult-to-forge characteristics. The protection logic picks out
   * fixed numbers of desirable peers per various criteria, followed by (mostly)
   * ratios of desirable or disadvantaged peers. If any eviction candidates
   * remain, the selection logic chooses a peer to evict.
   */
  [[nodiscard]] std::optional<NodeId> SelectNodeToEvict(std::vector<NodeEvictionCandidate>&& vEvictionCandidates);
  
  /** Protect desirable or disadvantaged inbound peers from eviction by ratio.
   *
   * This function protects half of the peers which have been connected the
   * longest, to replicate the non-eviction implicit behavior and preclude attacks
   * that start later.
   *
   * Half of these protected spots (1/4 of the total) are reserved for the
   * following categories of peers, sorted by longest uptime, even if they're not
   * longest uptime overall:
   *
   * - onion peers connected via our tor control service
   *
   * - localhost peers, as manually configured hidden services not using
   *   `-bind=addr[:port]=onion` will not be detected as inbound onion connections
   *
   * - I2P peers
   *
   * This helps protect these privacy network peers, which tend to be otherwise
   * disadvantaged under our eviction criteria for their higher min ping times
   * relative to IPv4/IPv6 peers, and favorise the diversity of peer connections.
   */
  void ProtectEvictionCandidatesByRatio(std::vector<NodeEvictionCandidate>& vEvictionCandidates);
  
  #endif // DRIYAL_NET_H
  