text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2018 The Bitcoin Core developers
  // Copyright (c) 2018 The Deftchain developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include <net_processing.h>
  
  #include <addrman.h>
  #include <arith_uint256.h>
  #include <blockencodings.h>
  #include <chainparams.h>
  #include <consensus/validation.h>
  #include <hash.h>
  #include <validation.h>
  #include <merkleblock.h>
  #include <netmessagemaker.h>
  #include <netbase.h>
  #include <policy/fees.h>
  #include <policy/policy.h>
  #include <primitives/block.h>
  #include <primitives/transaction.h>
  #include <random.h>
  #include <reverse_iterator.h>
  #include <scheduler.h>
  #include <tinyformat.h>
  #include <txmempool.h>
  #include <ui_interface.h>
  #include <util.h>
  #include <utilmoneystr.h>
  #include <utilstrencodings.h>
  
  #include <memory>
  
  #if defined(NDEBUG)
  # error "Bitcoin cannot be compiled without assertions."
  #endif
  
  /** Expiration time for orphan transactions in seconds */
  static constexpr int64_t ORPHAN_TX_EXPIRE_TIME = 20 * 60;
  /** Minimum time between orphan transactions expire time checks in seconds */
  static constexpr int64_t ORPHAN_TX_EXPIRE_INTERVAL = 5 * 60;
  /** Headers download timeout expressed in microseconds
   *  Timeout = base + per_header * (expected number of headers) */
  static constexpr int64_t HEADERS_DOWNLOAD_TIMEOUT_BASE = 15 * 60 * 1000000; // 15 minutes
  static constexpr int64_t HEADERS_DOWNLOAD_TIMEOUT_PER_HEADER = 1000; // 1ms/header
  /** Protect at least this many outbound peers from disconnection due to slow/
   * behind headers chain.
   */
  static constexpr int32_t MAX_OUTBOUND_PEERS_TO_PROTECT_FROM_DISCONNECT = 4;
  /** Timeout for (unprotected) outbound peers to sync to our chainwork, in seconds */
  static constexpr int64_t CHAIN_SYNC_TIMEOUT = 20 * 60; // 20 minutes
  /** How frequently to check for stale tips, in seconds */
  static constexpr int64_t STALE_CHECK_INTERVAL = 10 * 60; // 10 minutes
  /** How frequently to check for extra outbound peers and disconnect, in seconds */
  static constexpr int64_t EXTRA_PEER_CHECK_INTERVAL = 45;
  /** Minimum time an outbound-peer-eviction candidate must be connected for, in order to evict, in seconds */
  static constexpr int64_t MINIMUM_CONNECT_TIME = 30;
  /** SHA256("main address relay")[0:8] */
  static constexpr uint64_t RANDOMIZER_ID_ADDRESS_RELAY = 0x3cac0035b5866b90ULL;
  /// Age after which a stale block will no longer be served if requested as
  /// protection against fingerprinting. Set to one month, denominated in seconds.
  static constexpr int STALE_RELAY_AGE_LIMIT = 30 * 24 * 60 * 60;
  /// Age after which a block is considered historical for purposes of rate
  /// limiting block relay. Set to one week, denominated in seconds.
  static constexpr int HISTORICAL_BLOCK_AGE = 7 * 24 * 60 * 60;
  
  struct COrphanTx {
      // When modifying, adapt the copy of this definition in tests/DoS_tests.
      CTransactionRef tx;
      NodeId fromPeer;
      int64_t nTimeExpire;
  };
  static CCriticalSection g_cs_orphans;
  std::map<uint256, COrphanTx> mapOrphanTransactions GUARDED_BY(g_cs_orphans);
  
  void EraseOrphansFor(NodeId peer);
  
  /** Increase a node's misbehavior score. */
  void Misbehaving(NodeId nodeid, int howmuch, const std::string& message="") EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
  /** Average delay between local address broadcasts in seconds. */
  static constexpr unsigned int AVG_LOCAL_ADDRESS_BROADCAST_INTERVAL = 24 * 60 * 60;
  /** Average delay between peer address broadcasts in seconds. */
  static const unsigned int AVG_ADDRESS_BROADCAST_INTERVAL = 30;
  /** Average delay between trickled inventory transmissions in seconds.
   *  Blocks and whitelisted receivers bypass this, outbound peers get half this delay. */
  static const unsigned int INVENTORY_BROADCAST_INTERVAL = 5;
  /** Maximum number of inventory items to send per transmission.
   *  Limits the impact of low-fee transaction floods. */
  static constexpr unsigned int INVENTORY_BROADCAST_MAX = 7 * INVENTORY_BROADCAST_INTERVAL;
  /** Average delay between feefilter broadcasts in seconds. */
  static constexpr unsigned int AVG_FEEFILTER_BROADCAST_INTERVAL = 10 * 60;
  /** Maximum feefilter broadcast delay after significant change. */
  static constexpr unsigned int MAX_FEEFILTER_CHANGE_DELAY = 5 * 60;
  
  // Internal stuff
  namespace {
      /** Number of nodes with fSyncStarted. */
      int nSyncStarted GUARDED_BY(cs_main) = 0;
  
      /**
       * Sources of received blocks, saved to be able to send them reject
       * messages or ban them when processing happens afterwards.
       * Set mapBlockSource[hash].second to false if the node should not be
       * punished if the block is invalid.
       */
      std::map<uint256, std::pair<NodeId, bool>> mapBlockSource GUARDED_BY(cs_main);
  
      /**
       * Filter for transactions that were recently rejected by
       * AcceptToMemoryPool. These are not rerequested until the chain tip
       * changes, at which point the entire filter is reset.
       *
       * Without this filter we'd be re-requesting txs from each of our peers,
       * increasing bandwidth consumption considerably. For instance, with 100
       * peers, half of which relay a tx we don't accept, that might be a 50x
       * bandwidth increase. A flooding attacker attempting to roll-over the
       * filter using minimum-sized, 60byte, transactions might manage to send
       * 1000/sec if we have fast peers, so we pick 120,000 to give our peers a
       * two minute window to send invs to us.
       *
       * Decreasing the false positive rate is fairly cheap, so we pick one in a
       * million to make it highly unlikely for users to have issues with this
       * filter.
       *
       * Memory used: 1.3 MB
       */
      std::unique_ptr<CRollingBloomFilter> recentRejects GUARDED_BY(cs_main);
      uint256 hashRecentRejectsChainTip GUARDED_BY(cs_main);
  
      /** Blocks that are in flight, and that are in the queue to be downloaded. */
      struct QueuedBlock {
          uint256 hash;
          const CBlockIndex* pindex;                               //!< Optional.
          bool fValidatedHeaders;                                  //!< Whether this block has validated headers at the time of request.
          std::unique_ptr<PartiallyDownloadedBlock> partialBlock;  //!< Optional, used for CMPCTBLOCK downloads
      };
      std::map<uint256, std::pair<NodeId, std::list<QueuedBlock>::iterator> > mapBlocksInFlight GUARDED_BY(cs_main);
  
      /** Stack of nodes which we have set to announce using compact blocks */
      std::list<NodeId> lNodesAnnouncingHeaderAndIDs GUARDED_BY(cs_main);
  
      /** Number of preferable block download peers. */
      int nPreferredDownload GUARDED_BY(cs_main) = 0;
  
      /** Number of peers from which we're downloading blocks. */
      int nPeersWithValidatedDownloads GUARDED_BY(cs_main) = 0;
  
      /** Number of outbound peers with m_chain_sync.m_protect. */
      int g_outbound_peers_with_protect_from_disconnect GUARDED_BY(cs_main) = 0;
  
      /** When our tip was last updated. */
      std::atomic<int64_t> g_last_tip_update(0);
  
      /** Relay map */
      typedef std::map<uint256, CTransactionRef> MapRelay;
      MapRelay mapRelay GUARDED_BY(cs_main);
      /** Expiration-time ordered list of (expire time, relay map entry) pairs. */
      std::deque<std::pair<int64_t, MapRelay::iterator>> vRelayExpiration GUARDED_BY(cs_main);
  
      std::atomic<int64_t> nTimeBestReceived(0); // Used only to inform the wallet of when we last received a block
  
      struct IteratorComparator
      {
          template<typename I>
          bool operator()(const I& a, const I& b) const
          {
              return &(*a) < &(*b);
          }
      };
      std::map<COutPoint, std::set<std::map<uint256, COrphanTx>::iterator, IteratorComparator>> mapOrphanTransactionsByPrev GUARDED_BY(g_cs_orphans);
  
      static size_t vExtraTxnForCompactIt GUARDED_BY(g_cs_orphans) = 0;
      static std::vector<std::pair<uint256, CTransactionRef>> vExtraTxnForCompact GUARDED_BY(g_cs_orphans);
  } // namespace
  
  namespace {
  struct CBlockReject {
      unsigned char chRejectCode;
      std::string strRejectReason;
      uint256 hashBlock;
  };
  
  /**
   * Maintain validation-specific state about nodes, protected by cs_main, instead
   * by CNode's own locks. This simplifies asynchronous operation, where
   * processing of incoming data is done after the ProcessMessage call returns,
   * and we're no longer holding the node's locks.
   */
  struct CNodeState {
      //! The peer's address
      const CService address;
      //! Whether we have a fully established connection.
      bool fCurrentlyConnected;
      //! Accumulated misbehaviour score for this peer.
      int nMisbehavior;
      //! Whether this peer should be disconnected and banned (unless whitelisted).
      bool fShouldBan;
      //! String name of this peer (debugging/logging purposes).
      const std::string name;
      //! List of asynchronously-determined block rejections to notify this peer about.
      std::vector<CBlockReject> rejects;
      //! The best known block we know this peer has announced.
      const CBlockIndex *pindexBestKnownBlock;
      //! The hash of the last unknown block this peer has announced.
      uint256 hashLastUnknownBlock;
      //! The last full block we both have.
      const CBlockIndex *pindexLastCommonBlock;
      //! The best header we have sent our peer.
      const CBlockIndex *pindexBestHeaderSent;
      //! Length of current-streak of unconnecting headers announcements
      int nUnconnectingHeaders;
      //! Whether we've started headers synchronization with this peer.
      bool fSyncStarted;
      //! When to potentially disconnect peer for stalling headers download
      int64_t nHeadersSyncTimeout;
      //! Since when we're stalling block download progress (in microseconds), or 0.
      int64_t nStallingSince;
      std::list<QueuedBlock> vBlocksInFlight;
      //! When the first entry in vBlocksInFlight started downloading. Don't care when vBlocksInFlight is empty.
      int64_t nDownloadingSince;
      int nBlocksInFlight;
      int nBlocksInFlightValidHeaders;
      //! Whether we consider this a preferred download peer.
      bool fPreferredDownload;
      //! Whether this peer wants invs or headers (when possible) for block announcements.
      bool fPreferHeaders;
      //! Whether this peer wants invs or cmpctblocks (when possible) for block announcements.
      bool fPreferHeaderAndIDs;
      /**
        * Whether this peer will send us cmpctblocks if we request them.
        * This is not used to gate request logic, as we really only care about fSupportsDesiredCmpctVersion,
        * but is used as a flag to "lock in" the version of compact blocks (fWantsCmpctWitness) we send.
        */
      bool fProvidesHeaderAndIDs;
      //! Whether this peer can give us witnesses
      bool fHaveWitness;
      //! Whether this peer wants witnesses in cmpctblocks/blocktxns
      bool fWantsCmpctWitness;
      /**
       * If we've announced NODE_WITNESS to this peer: whether the peer sends witnesses in cmpctblocks/blocktxns,
       * otherwise: whether this peer sends non-witnesses in cmpctblocks/blocktxns.
       */
      bool fSupportsDesiredCmpctVersion;
  
      /** State used to enforce CHAIN_SYNC_TIMEOUT
        * Only in effect for outbound, non-manual connections, with
        * m_protect == false
        * Algorithm: if a peer's best known block has less work than our tip,
        * set a timeout CHAIN_SYNC_TIMEOUT seconds in the future:
        *   - If at timeout their best known block now has more work than our tip
        *     when the timeout was set, then either reset the timeout or clear it
        *     (after comparing against our current tip's work)
        *   - If at timeout their best known block still has less work than our
        *     tip did when the timeout was set, then send a getheaders message,
        *     and set a shorter timeout, HEADERS_RESPONSE_TIME seconds in future.
        *     If their best known block is still behind when that new timeout is
        *     reached, disconnect.
        */
      struct ChainSyncTimeoutState {
          //! A timeout used for checking whether our peer has sufficiently synced
          int64_t m_timeout;
          //! A header with the work we require on our peer's chain
          const CBlockIndex * m_work_header;
          //! After timeout is reached, set to true after sending getheaders
          bool m_sent_getheaders;
          //! Whether this peer is protected from disconnection due to a bad/slow chain
          bool m_protect;
      };
  
      ChainSyncTimeoutState m_chain_sync;
  
      //! Time of last new block announcement
      int64_t m_last_block_announcement;
  
      CNodeState(CAddress addrIn, std::string addrNameIn) : address(addrIn), name(addrNameIn) {
          fCurrentlyConnected = false;
          nMisbehavior = 0;
          fShouldBan = false;
          pindexBestKnownBlock = nullptr;
          hashLastUnknownBlock.SetNull();
          pindexLastCommonBlock = nullptr;
          pindexBestHeaderSent = nullptr;
          nUnconnectingHeaders = 0;
          fSyncStarted = false;
          nHeadersSyncTimeout = 0;
          nStallingSince = 0;
          nDownloadingSince = 0;
          nBlocksInFlight = 0;
          nBlocksInFlightValidHeaders = 0;
          fPreferredDownload = false;
          fPreferHeaders = false;
          fPreferHeaderAndIDs = false;
          fProvidesHeaderAndIDs = false;
          fHaveWitness = false;
          fWantsCmpctWitness = false;
          fSupportsDesiredCmpctVersion = false;
          m_chain_sync = { 0, nullptr, false, false };
          m_last_block_announcement = 0;
      }
  };
  
  /** Map maintaining per-node state. */
  static std::map<NodeId, CNodeState> mapNodeState GUARDED_BY(cs_main);
  
  static CNodeState *State(NodeId pnode) EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
      std::map<NodeId, CNodeState>::iterator it = mapNodeState.find(pnode);
      if (it == mapNodeState.end())
          return nullptr;
      return &it->second;
  }
  
  static void UpdatePreferredDownload(CNode* node, CNodeState* state) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
  {
      nPreferredDownload -= state->fPreferredDownload;
  
      // Whether this node should be marked as a preferred download node.
      state->fPreferredDownload = (!node->fInbound || node->fWhitelisted) && !node->fOneShot && !node->fClient;
  
      nPreferredDownload += state->fPreferredDownload;
  }
  
  static void PushNodeVersion(CNode *pnode, CConnman* connman, int64_t nTime)
  {
      ServiceFlags nLocalNodeServices = pnode->GetLocalServices();
      uint64_t nonce = pnode->GetLocalNonce();
      int nNodeStartingHeight = pnode->GetMyStartingHeight();
      NodeId nodeid = pnode->GetId();
      CAddress addr = pnode->addr;
  
      CAddress addrYou = (addr.IsRoutable() && !IsProxy(addr) ? addr : CAddress(CService(), addr.nServices));
      CAddress addrMe = CAddress(CService(), nLocalNodeServices);
  
      connman->PushMessage(pnode, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::VERSION, PROTOCOL_VERSION, (uint64_t)nLocalNodeServices, nTime, addrYou, addrMe,
              nonce, strSubVersion, nNodeStartingHeight, ::fRelayTxes));
  
      if (fLogIPs) {
          LogPrint(BCLog::NET, "send version message: version %d, blocks=%d, us=%s, them=%s, peer=%d\n", PROTOCOL_VERSION, nNodeStartingHeight, addrMe.ToString(), addrYou.ToString(), nodeid);
      } else {
          LogPrint(BCLog::NET, "send version message: version %d, blocks=%d, us=%s, peer=%d\n", PROTOCOL_VERSION, nNodeStartingHeight, addrMe.ToString(), nodeid);
      }
  }
  
  // Returns a bool indicating whether we requested this block.
  // Also used if a block was /not/ received and timed out or started with another peer
  static bool MarkBlockAsReceived(const uint256& hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
      std::map<uint256, std::pair<NodeId, std::list<QueuedBlock>::iterator> >::iterator itInFlight = mapBlocksInFlight.find(hash);
      if (itInFlight != mapBlocksInFlight.end()) {
          CNodeState *state = State(itInFlight->second.first);
          assert(state != nullptr);
          state->nBlocksInFlightValidHeaders -= itInFlight->second.second->fValidatedHeaders;
          if (state->nBlocksInFlightValidHeaders == 0 && itInFlight->second.second->fValidatedHeaders) {
              // Last validated block on the queue was received.
              nPeersWithValidatedDownloads--;
          }
          if (state->vBlocksInFlight.begin() == itInFlight->second.second) {
              // First block on the queue was received, update the start download time for the next one
              state->nDownloadingSince = std::max(state->nDownloadingSince, GetTimeMicros());
          }
          state->vBlocksInFlight.erase(itInFlight->second.second);
          state->nBlocksInFlight--;
          state->nStallingSince = 0;
          mapBlocksInFlight.erase(itInFlight);
          return true;
      }
      return false;
  }
  
  // returns false, still setting pit, if the block was already in flight from the same peer
  // pit will only be valid as long as the same cs_main lock is being held
  static bool MarkBlockAsInFlight(NodeId nodeid, const uint256& hash, const CBlockIndex* pindex = nullptr, std::list<QueuedBlock>::iterator** pit = nullptr) EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
      CNodeState *state = State(nodeid);
      assert(state != nullptr);
  
      // Short-circuit most stuff in case it is from the same node
      std::map<uint256, std::pair<NodeId, std::list<QueuedBlock>::iterator> >::iterator itInFlight = mapBlocksInFlight.find(hash);
      if (itInFlight != mapBlocksInFlight.end() && itInFlight->second.first == nodeid) {
          if (pit) {
              *pit = &itInFlight->second.second;
          }
          return false;
      }
  
      // Make sure it's not listed somewhere already.
      MarkBlockAsReceived(hash);
  
      std::list<QueuedBlock>::iterator it = state->vBlocksInFlight.insert(state->vBlocksInFlight.end(),
              {hash, pindex, pindex != nullptr, std::unique_ptr<PartiallyDownloadedBlock>(pit ? new PartiallyDownloadedBlock(&mempool) : nullptr)});
      state->nBlocksInFlight++;
      state->nBlocksInFlightValidHeaders += it->fValidatedHeaders;
      if (state->nBlocksInFlight == 1) {
          // We're starting a block download (batch) from this peer.
          state->nDownloadingSince = GetTimeMicros();
      }
      if (state->nBlocksInFlightValidHeaders == 1 && pindex != nullptr) {
          nPeersWithValidatedDownloads++;
      }
      itInFlight = mapBlocksInFlight.insert(std::make_pair(hash, std::make_pair(nodeid, it))).first;
      if (pit)
          *pit = &itInFlight->second.second;
      return true;
  }
  
  /** Check whether the last unknown block a peer advertised is not yet known. */
  static void ProcessBlockAvailability(NodeId nodeid) EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
      CNodeState *state = State(nodeid);
      assert(state != nullptr);
  
      if (!state->hashLastUnknownBlock.IsNull()) {
          const CBlockIndex* pindex = LookupBlockIndex(state->hashLastUnknownBlock);
          if (pindex && pindex->nChainWork > 0) {
              if (state->pindexBestKnownBlock == nullptr || pindex->nChainWork >= state->pindexBestKnownBlock->nChainWork) {
                  state->pindexBestKnownBlock = pindex;
              }
              state->hashLastUnknownBlock.SetNull();
          }
      }
  }
  
  /** Update tracking information about which blocks a peer is assumed to have. */
  static void UpdateBlockAvailability(NodeId nodeid, const uint256 &hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
      CNodeState *state = State(nodeid);
      assert(state != nullptr);
  
      ProcessBlockAvailability(nodeid);
  
      const CBlockIndex* pindex = LookupBlockIndex(hash);
      if (pindex && pindex->nChainWork > 0) {
          // An actually better block was announced.
          if (state->pindexBestKnownBlock == nullptr || pindex->nChainWork >= state->pindexBestKnownBlock->nChainWork) {
              state->pindexBestKnownBlock = pindex;
          }
      } else {
          // An unknown block was announced; just assume that the latest one is the best one.
          state->hashLastUnknownBlock = hash;
      }
  }
  
  /**
   * When a peer sends us a valid block, instruct it to announce blocks to us
   * using CMPCTBLOCK if possible by adding its nodeid to the end of
   * lNodesAnnouncingHeaderAndIDs, and keeping that list under a certain size by
   * removing the first element if necessary.
   */
  static void MaybeSetPeerAsAnnouncingHeaderAndIDs(NodeId nodeid, CConnman* connman)
  {
      AssertLockHeld(cs_main);
      CNodeState* nodestate = State(nodeid);
      if (!nodestate || !nodestate->fSupportsDesiredCmpctVersion) {
          // Never ask from peers who can't provide witnesses.
          return;
      }
      if (nodestate->fProvidesHeaderAndIDs) {
          for (std::list<NodeId>::iterator it = lNodesAnnouncingHeaderAndIDs.begin(); it != lNodesAnnouncingHeaderAndIDs.end(); it++) {
              if (*it == nodeid) {
                  lNodesAnnouncingHeaderAndIDs.erase(it);
                  lNodesAnnouncingHeaderAndIDs.push_back(nodeid);
                  return;
              }
          }
          connman->ForNode(nodeid, [connman](CNode* pfrom){
              AssertLockHeld(cs_main);
              uint64_t nCMPCTBLOCKVersion = (pfrom->GetLocalServices() & NODE_WITNESS) ? 2 : 1;
              if (lNodesAnnouncingHeaderAndIDs.size() >= 3) {
                  // As per BIP152, we only get 3 of our peers to announce
                  // blocks using compact encodings.
                  connman->ForNode(lNodesAnnouncingHeaderAndIDs.front(), [connman, nCMPCTBLOCKVersion](CNode* pnodeStop){
                      AssertLockHeld(cs_main);
                      connman->PushMessage(pnodeStop, CNetMsgMaker(pnodeStop->GetSendVersion()).Make(NetMsgType::SENDCMPCT, /*fAnnounceUsingCMPCTBLOCK=*/false, nCMPCTBLOCKVersion));
                      return true;
                  });
                  lNodesAnnouncingHeaderAndIDs.pop_front();
              }
              connman->PushMessage(pfrom, CNetMsgMaker(pfrom->GetSendVersion()).Make(NetMsgType::SENDCMPCT, /*fAnnounceUsingCMPCTBLOCK=*/true, nCMPCTBLOCKVersion));
              lNodesAnnouncingHeaderAndIDs.push_back(pfrom->GetId());
              return true;
          });
      }
  }
  
  static bool TipMayBeStale(const Consensus::Params &consensusParams) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
  {
      AssertLockHeld(cs_main);
      if (g_last_tip_update == 0) {
          g_last_tip_update = GetTime();
      }
      return g_last_tip_update < GetTime() - consensusParams.nPowTargetSpacing * 3 && mapBlocksInFlight.empty();
  }
  
  static bool CanDirectFetch(const Consensus::Params &consensusParams) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
  {
      return chainActive.Tip()->GetBlockTime() > GetAdjustedTime() - consensusParams.nPowTargetSpacing * 20;
  }
  
  static bool PeerHasHeader(CNodeState *state, const CBlockIndex *pindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
  {
      if (state->pindexBestKnownBlock && pindex == state->pindexBestKnownBlock->GetAncestor(pindex->nHeight))
          return true;
      if (state->pindexBestHeaderSent && pindex == state->pindexBestHeaderSent->GetAncestor(pindex->nHeight))
          return true;
      return false;
  }
  
  /** Update pindexLastCommonBlock and add not-in-flight missing successors to vBlocks, until it has
   *  at most count entries. */
  static void FindNextBlocksToDownload(NodeId nodeid, unsigned int count, std::vector<const CBlockIndex*>& vBlocks, NodeId& nodeStaller, const Consensus::Params& consensusParams) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
  {
      if (count == 0)
          return;
  
      vBlocks.reserve(vBlocks.size() + count);
      CNodeState *state = State(nodeid);
      assert(state != nullptr);
  
      // Make sure pindexBestKnownBlock is up to date, we'll need it.
      ProcessBlockAvailability(nodeid);
  
      if (state->pindexBestKnownBlock == nullptr || state->pindexBestKnownBlock->nChainWork < chainActive.Tip()->nChainWork || state->pindexBestKnownBlock->nChainWork < nMinimumChainWork) {
          // This peer has nothing interesting.
          return;
      }
  
      if (state->pindexLastCommonBlock == nullptr) {
          // Bootstrap quickly by guessing a parent of our best tip is the forking point.
          // Guessing wrong in either direction is not a problem.
          state->pindexLastCommonBlock = chainActive[std::min(state->pindexBestKnownBlock->nHeight, chainActive.Height())];
      }
  
      // If the peer reorganized, our previous pindexLastCommonBlock may not be an ancestor
      // of its current tip anymore. Go back enough to fix that.
      state->pindexLastCommonBlock = LastCommonAncestor(state->pindexLastCommonBlock, state->pindexBestKnownBlock);
      if (state->pindexLastCommonBlock == state->pindexBestKnownBlock)
          return;
  
      std::vector<const CBlockIndex*> vToFetch;
      const CBlockIndex *pindexWalk = state->pindexLastCommonBlock;
      // Never fetch further than the best block we know the peer has, or more than BLOCK_DOWNLOAD_WINDOW + 1 beyond the last
      // linked block we have in common with this peer. The +1 is so we can detect stalling, namely if we would be able to
      // download that next block if the window were 1 larger.
      int nWindowEnd = state->pindexLastCommonBlock->nHeight + BLOCK_DOWNLOAD_WINDOW;
      int nMaxHeight = std::min<int>(state->pindexBestKnownBlock->nHeight, nWindowEnd + 1);
      NodeId waitingfor = -1;
      while (pindexWalk->nHeight < nMaxHeight) {
          // Read up to 128 (or more, if more blocks than that are needed) successors of pindexWalk (towards
          // pindexBestKnownBlock) into vToFetch. We fetch 128, because CBlockIndex::GetAncestor may be as expensive
          // as iterating over ~100 CBlockIndex* entries anyway.
          int nToFetch = std::min(nMaxHeight - pindexWalk->nHeight, std::max<int>(count - vBlocks.size(), 128));
          vToFetch.resize(nToFetch);
          pindexWalk = state->pindexBestKnownBlock->GetAncestor(pindexWalk->nHeight + nToFetch);
          vToFetch[nToFetch - 1] = pindexWalk;
          for (unsigned int i = nToFetch - 1; i > 0; i--) {
              vToFetch[i - 1] = vToFetch[i]->pprev;
          }
  
          // Iterate over those blocks in vToFetch (in forward direction), adding the ones that
          // are not yet downloaded and not in flight to vBlocks. In the meantime, update
          // pindexLastCommonBlock as long as all ancestors are already downloaded, or if it's
          // already part of our chain (and therefore don't need it even if pruned).
          for (const CBlockIndex* pindex : vToFetch) {
              if (!pindex->IsValid(BLOCK_VALID_TREE)) {
                  // We consider the chain that this peer is on invalid.
                  return;
              }
              if (!State(nodeid)->fHaveWitness && IsWitnessEnabled(pindex->pprev, consensusParams)) {
                  // We wouldn't download this block or its descendants from this peer.
                  return;
              }
              if (pindex->nStatus & BLOCK_HAVE_DATA || chainActive.Contains(pindex)) {
                  if (pindex->nChainTx)
                      state->pindexLastCommonBlock = pindex;
              } else if (mapBlocksInFlight.count(pindex->GetBlockHash()) == 0) {
                  // The block is not already downloaded, and not yet in flight.
                  if (pindex->nHeight > nWindowEnd) {
                      // We reached the end of the window.
                      if (vBlocks.size() == 0 && waitingfor != nodeid) {
                          // We aren't able to fetch anything, but we would be if the download window was one larger.
                          nodeStaller = waitingfor;
                      }
                      return;
                  }
                  vBlocks.push_back(pindex);
                  if (vBlocks.size() == count) {
                      return;
                  }
              } else if (waitingfor == -1) {
                  // This is the first already-in-flight block.
                  waitingfor = mapBlocksInFlight[pindex->GetBlockHash()].first;
              }
          }
      }
  }
  
  } // namespace
  
  // This function is used for testing the stale tip eviction logic, see
  // denialofservice_tests.cpp
  void UpdateLastBlockAnnounceTime(NodeId node, int64_t time_in_seconds)
  {
      LOCK(cs_main);
      CNodeState *state = State(node);
      if (state) state->m_last_block_announcement = time_in_seconds;
  }
  
  // Returns true for outbound peers, excluding manual connections, feelers, and
  // one-shots
  static bool IsOutboundDisconnectionCandidate(const CNode *node)
  {
      return !(node->fInbound || node->m_manual_connection || node->fFeeler || node->fOneShot);
  }
  
  void PeerLogicValidation::InitializeNode(CNode *pnode) {
      CAddress addr = pnode->addr;
      std::string addrName = pnode->GetAddrName();
      NodeId nodeid = pnode->GetId();
      {
          LOCK(cs_main);
          mapNodeState.emplace_hint(mapNodeState.end(), std::piecewise_construct, std::forward_as_tuple(nodeid), std::forward_as_tuple(addr, std::move(addrName)));
      }
      if(!pnode->fInbound)
          PushNodeVersion(pnode, connman, GetTime());
  }
  
  void PeerLogicValidation::FinalizeNode(NodeId nodeid, bool& fUpdateConnectionTime) {
      fUpdateConnectionTime = false;
      LOCK(cs_main);
      CNodeState *state = State(nodeid);
      assert(state != nullptr);
  
      if (state->fSyncStarted)
          nSyncStarted--;
  
      if (state->nMisbehavior == 0 && state->fCurrentlyConnected) {
          fUpdateConnectionTime = true;
      }
  
      for (const QueuedBlock& entry : state->vBlocksInFlight) {
          mapBlocksInFlight.erase(entry.hash);
      }
      EraseOrphansFor(nodeid);
      nPreferredDownload -= state->fPreferredDownload;
      nPeersWithValidatedDownloads -= (state->nBlocksInFlightValidHeaders != 0);
      assert(nPeersWithValidatedDownloads >= 0);
      g_outbound_peers_with_protect_from_disconnect -= state->m_chain_sync.m_protect;
      assert(g_outbound_peers_with_protect_from_disconnect >= 0);
  
      mapNodeState.erase(nodeid);
  
      if (mapNodeState.empty()) {
          // Do a consistency check after the last peer is removed.
          assert(mapBlocksInFlight.empty());
          assert(nPreferredDownload == 0);
          assert(nPeersWithValidatedDownloads == 0);
          assert(g_outbound_peers_with_protect_from_disconnect == 0);
      }
      LogPrint(BCLog::NET, "Cleared nodestate for peer=%d\n", nodeid);
  }
  
  bool GetNodeStateStats(NodeId nodeid, CNodeStateStats &stats) {
      LOCK(cs_main);
      CNodeState *state = State(nodeid);
      if (state == nullptr)
          return false;
      stats.nMisbehavior = state->nMisbehavior;
      stats.nSyncHeight = state->pindexBestKnownBlock ? state->pindexBestKnownBlock->nHeight : -1;
      stats.nCommonHeight = state->pindexLastCommonBlock ? state->pindexLastCommonBlock->nHeight : -1;
      for (const QueuedBlock& queue : state->vBlocksInFlight) {
          if (queue.pindex)
              stats.vHeightInFlight.push_back(queue.pindex->nHeight);
      }
      return true;
  }
  
  //////////////////////////////////////////////////////////////////////////////
  //
  // mapOrphanTransactions
  //
  
  static void AddToCompactExtraTransactions(const CTransactionRef& tx) EXCLUSIVE_LOCKS_REQUIRED(g_cs_orphans)
  {
      size_t max_extra_txn = gArgs.GetArg("-blockreconstructionextratxn", DEFAULT_BLOCK_RECONSTRUCTION_EXTRA_TXN);
      if (max_extra_txn <= 0)
          return;
      if (!vExtraTxnForCompact.size())
          vExtraTxnForCompact.resize(max_extra_txn);
      vExtraTxnForCompact[vExtraTxnForCompactIt] = std::make_pair(tx->GetWitnessHash(), tx);
      vExtraTxnForCompactIt = (vExtraTxnForCompactIt + 1) % max_extra_txn;
  }
  
  bool AddOrphanTx(const CTransactionRef& tx, NodeId peer) EXCLUSIVE_LOCKS_REQUIRED(g_cs_orphans)
  {
      const uint256& hash = tx->GetHash();
      if (mapOrphanTransactions.count(hash))
          return false;
  
      // Ignore big transactions, to avoid a
      // send-big-orphans memory exhaustion attack. If a peer has a legitimate
      // large transaction with a missing parent then we assume
      // it will rebroadcast it later, after the parent transaction(s)
      // have been mined or received.
      // 100 orphans, each of which is at most 100,000 bytes big is
      // at most 10 megabytes of orphans and somewhat more byprev index (in the worst case):
      unsigned int sz = GetTransactionWeight(*tx);
      if (sz > MAX_STANDARD_TX_WEIGHT)
      {
          LogPrint(BCLog::MEMPOOL, "ignoring large orphan tx (size: %u, hash: %s)\n", sz, hash.ToString());
          return false;
      }
  
      auto ret = mapOrphanTransactions.emplace(hash, COrphanTx{tx, peer, GetTime() + ORPHAN_TX_EXPIRE_TIME});
      assert(ret.second);
      for (const CTxIn& txin : tx->vin) {
          mapOrphanTransactionsByPrev[txin.prevout].insert(ret.first);
      }
  
      AddToCompactExtraTransactions(tx);
  
      LogPrint(BCLog::MEMPOOL, "stored orphan tx %s (mapsz %u outsz %u)\n", hash.ToString(),
               mapOrphanTransactions.size(), mapOrphanTransactionsByPrev.size());
      return true;
  }
  
  int static EraseOrphanTx(uint256 hash) EXCLUSIVE_LOCKS_REQUIRED(g_cs_orphans)
  {
      std::map<uint256, COrphanTx>::iterator it = mapOrphanTransactions.find(hash);
      if (it == mapOrphanTransactions.end())
          return 0;
      for (const CTxIn& txin : it->second.tx->vin)
      {
          auto itPrev = mapOrphanTransactionsByPrev.find(txin.prevout);
          if (itPrev == mapOrphanTransactionsByPrev.end())
              continue;
          itPrev->second.erase(it);
          if (itPrev->second.empty())
              mapOrphanTransactionsByPrev.erase(itPrev);
      }
      mapOrphanTransactions.erase(it);
      return 1;
  }
  
  void EraseOrphansFor(NodeId peer)
  {
      LOCK(g_cs_orphans);
      int nErased = 0;
      std::map<uint256, COrphanTx>::iterator iter = mapOrphanTransactions.begin();
      while (iter != mapOrphanTransactions.end())
      {
          std::map<uint256, COrphanTx>::iterator maybeErase = iter++; // increment to avoid iterator becoming invalid
          if (maybeErase->second.fromPeer == peer)
          {
              nErased += EraseOrphanTx(maybeErase->second.tx->GetHash());
          }
      }
      if (nErased > 0) LogPrint(BCLog::MEMPOOL, "Erased %d orphan tx from peer=%d\n", nErased, peer);
  }
  
  
  unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans)
  {
      LOCK(g_cs_orphans);
  
      unsigned int nEvicted = 0;
      static int64_t nNextSweep;
      int64_t nNow = GetTime();
      if (nNextSweep <= nNow) {
          // Sweep out expired orphan pool entries:
          int nErased = 0;
          int64_t nMinExpTime = nNow + ORPHAN_TX_EXPIRE_TIME - ORPHAN_TX_EXPIRE_INTERVAL;
          std::map<uint256, COrphanTx>::iterator iter = mapOrphanTransactions.begin();
          while (iter != mapOrphanTransactions.end())
          {
              std::map<uint256, COrphanTx>::iterator maybeErase = iter++;
              if (maybeErase->second.nTimeExpire <= nNow) {
                  nErased += EraseOrphanTx(maybeErase->second.tx->GetHash());
              } else {
                  nMinExpTime = std::min(maybeErase->second.nTimeExpire, nMinExpTime);
              }
          }
          // Sweep again 5 minutes after the next entry that expires in order to batch the linear scan.
          nNextSweep = nMinExpTime + ORPHAN_TX_EXPIRE_INTERVAL;
          if (nErased > 0) LogPrint(BCLog::MEMPOOL, "Erased %d orphan tx due to expiration\n", nErased);
      }
      while (mapOrphanTransactions.size() > nMaxOrphans)
      {
          // Evict a random orphan:
          uint256 randomhash = GetRandHash();
          std::map<uint256, COrphanTx>::iterator it = mapOrphanTransactions.lower_bound(randomhash);
          if (it == mapOrphanTransactions.end())
              it = mapOrphanTransactions.begin();
          EraseOrphanTx(it->first);
          ++nEvicted;
      }
      return nEvicted;
  }
  
  /**
   * Mark a misbehaving peer to be banned depending upon the value of `-banscore`.
   */
  void Misbehaving(NodeId pnode, int howmuch, const std::string& message) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
  {
      if (howmuch == 0)
          return;
  
      CNodeState *state = State(pnode);
      if (state == nullptr)
          return;
  
      state->nMisbehavior += howmuch;
      int banscore = gArgs.GetArg("-banscore", DEFAULT_BANSCORE_THRESHOLD);
      std::string message_prefixed = message.empty() ? "" : (": " + message);
      if (state->nMisbehavior >= banscore && state->nMisbehavior - howmuch < banscore)
      {
          LogPrint(BCLog::NET, "%s: %s peer=%d (%d -> %d) BAN THRESHOLD EXCEEDED%s\n", __func__, state->name, pnode, state->nMisbehavior-howmuch, state->nMisbehavior, message_prefixed);
          state->fShouldBan = true;
      } else
          LogPrint(BCLog::NET, "%s: %s peer=%d (%d -> %d)%s\n", __func__, state->name, pnode, state->nMisbehavior-howmuch, state->nMisbehavior, message_prefixed);
  }
  
  
  
  
  
  
  
  
  //////////////////////////////////////////////////////////////////////////////
  //
  // blockchain -> download logic notification
  //
  
  // To prevent fingerprinting attacks, only send blocks/headers outside of the
  // active chain if they are no more than a month older (both in time, and in
  // best equivalent proof of work) than the best header chain we know about and
  // we fully-validated them at some point.
  static bool BlockRequestAllowed(const CBlockIndex* pindex, const Consensus::Params& consensusParams)
  {
      AssertLockHeld(cs_main);
      if (chainActive.Contains(pindex)) return true;
      return pindex->IsValid(BLOCK_VALID_SCRIPTS) && (pindexBestHeader != nullptr) &&
          (pindexBestHeader->GetBlockTime() - pindex->GetBlockTime() < STALE_RELAY_AGE_LIMIT) &&
          (GetBlockProofEquivalentTime(*pindexBestHeader, *pindex, *pindexBestHeader, consensusParams) < STALE_RELAY_AGE_LIMIT);
  }
  
  PeerLogicValidation::PeerLogicValidation(CConnman* connmanIn, CScheduler &scheduler, bool enable_bip61)
      : connman(connmanIn), m_stale_tip_check_time(0), m_enable_bip61(enable_bip61) {
  
      // Initialize global variables that cannot be constructed at startup.
      recentRejects.reset(new CRollingBloomFilter(120000, 0.000001));
  
      const Consensus::Params& consensusParams = Params().GetConsensus();
      // Stale tip checking and peer eviction are on two different timers, but we
      // don't want them to get out of sync due to drift in the scheduler, so we
      // combine them in one function and schedule at the quicker (peer-eviction)
      // timer.
      static_assert(EXTRA_PEER_CHECK_INTERVAL < STALE_CHECK_INTERVAL, "peer eviction timer should be less than stale tip check timer");
      scheduler.scheduleEvery(std::bind(&PeerLogicValidation::CheckForStaleTipAndEvictPeers, this, consensusParams), EXTRA_PEER_CHECK_INTERVAL * 1000);
  }
  
  /**
   * Evict orphan txn pool entries (EraseOrphanTx) based on a newly connected
   * block. Also save the time of the last tip update.
   */
  void PeerLogicValidation::BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindex, const std::vector<CTransactionRef>& vtxConflicted) {
      LOCK(g_cs_orphans);
  
      std::vector<uint256> vOrphanErase;
  
      for (const CTransactionRef& ptx : pblock->vtx) {
          const CTransaction& tx = *ptx;
  
          // Which orphan pool entries must we evict?
          for (const auto& txin : tx.vin) {
              auto itByPrev = mapOrphanTransactionsByPrev.find(txin.prevout);
              if (itByPrev == mapOrphanTransactionsByPrev.end()) continue;
              for (auto mi = itByPrev->second.begin(); mi != itByPrev->second.end(); ++mi) {
                  const CTransaction& orphanTx = *(*mi)->second.tx;
                  const uint256& orphanHash = orphanTx.GetHash();
                  vOrphanErase.push_back(orphanHash);
              }
          }
      }
  
      // Erase orphan transactions included or precluded by this block
      if (vOrphanErase.size()) {
          int nErased = 0;
          for (uint256 &orphanHash : vOrphanErase) {
              nErased += EraseOrphanTx(orphanHash);
          }
          LogPrint(BCLog::MEMPOOL, "Erased %d orphan tx included or conflicted by block\n", nErased);
      }
  
      g_last_tip_update = GetTime();
  }
  
  // All of the following cache a recent block, and are protected by cs_most_recent_block
  static CCriticalSection cs_most_recent_block;
  static std::shared_ptr<const CBlock> most_recent_block GUARDED_BY(cs_most_recent_block);
  static std::shared_ptr<const CBlockHeaderAndShortTxIDs> most_recent_compact_block GUARDED_BY(cs_most_recent_block);
  static uint256 most_recent_block_hash GUARDED_BY(cs_most_recent_block);
  static bool fWitnessesPresentInMostRecentCompactBlock GUARDED_BY(cs_most_recent_block);
  
  /**
   * Maintain state about the best-seen block and fast-announce a compact block
   * to compatible peers.
   */
  void PeerLogicValidation::NewPoWValidBlock(const CBlockIndex *pindex, const std::shared_ptr<const CBlock>& pblock) {
      std::shared_ptr<const CBlockHeaderAndShortTxIDs> pcmpctblock = std::make_shared<const CBlockHeaderAndShortTxIDs> (*pblock, true);
      const CNetMsgMaker msgMaker(PROTOCOL_VERSION);
  
      LOCK(cs_main);
  
      static int nHighestFastAnnounce = 0;
      if (pindex->nHeight <= nHighestFastAnnounce)
          return;
      nHighestFastAnnounce = pindex->nHeight;
  
      bool fWitnessEnabled = IsWitnessEnabled(pindex->pprev, Params().GetConsensus());
      uint256 hashBlock(pblock->GetHash());
  
      {
          LOCK(cs_most_recent_block);
          most_recent_block_hash = hashBlock;
          most_recent_block = pblock;
          most_recent_compact_block = pcmpctblock;
          fWitnessesPresentInMostRecentCompactBlock = fWitnessEnabled;
      }
  
      connman->ForEachNode([this, &pcmpctblock, pindex, &msgMaker, fWitnessEnabled, &hashBlock](CNode* pnode) {
          AssertLockHeld(cs_main);
  
          // TODO: Avoid the repeated-serialization here
          if (pnode->nVersion < INVALID_CB_NO_BAN_VERSION || pnode->fDisconnect)
              return;
          ProcessBlockAvailability(pnode->GetId());
          CNodeState &state = *State(pnode->GetId());
          // If the peer has, or we announced to them the previous block already,
          // but we don't think they have this one, go ahead and announce it
          if (state.fPreferHeaderAndIDs && (!fWitnessEnabled || state.fWantsCmpctWitness) &&
                  !PeerHasHeader(&state, pindex) && PeerHasHeader(&state, pindex->pprev)) {
  
              LogPrint(BCLog::NET, "%s sending header-and-ids %s to peer=%d\n", "PeerLogicValidation::NewPoWValidBlock",
                      hashBlock.ToString(), pnode->GetId());
              connman->PushMessage(pnode, msgMaker.Make(NetMsgType::CMPCTBLOCK, *pcmpctblock));
              state.pindexBestHeaderSent = pindex;
          }
      });
  }
  
  /**
   * Update our best height and announce any block hashes which weren't previously
   * in chainActive to our peers.
   */
  void PeerLogicValidation::UpdatedBlockTip(const CBlockIndex *pindexNew, const CBlockIndex *pindexFork, bool fInitialDownload) {
      const int nNewHeight = pindexNew->nHeight;
      connman->SetBestHeight(nNewHeight);
  
      SetServiceFlagsIBDCache(!fInitialDownload);
      if (!fInitialDownload) {
          // Find the hashes of all blocks that weren't previously in the best chain.
          std::vector<uint256> vHashes;
          const CBlockIndex *pindexToAnnounce = pindexNew;
          while (pindexToAnnounce != pindexFork) {
              vHashes.push_back(pindexToAnnounce->GetBlockHash());
              pindexToAnnounce = pindexToAnnounce->pprev;
              if (vHashes.size() == MAX_BLOCKS_TO_ANNOUNCE) {
                  // Limit announcements in case of a huge reorganization.
                  // Rely on the peer's synchronization mechanism in that case.
                  break;
              }
          }
          // Relay inventory, but don't relay old inventory during initial block download.
          connman->ForEachNode([nNewHeight, &vHashes](CNode* pnode) {
              if (nNewHeight > (pnode->nStartingHeight != -1 ? pnode->nStartingHeight - 2000 : 0)) {
                  for (const uint256& hash : reverse_iterate(vHashes)) {
                      pnode->PushBlockHash(hash);
                  }
              }
          });
          connman->WakeMessageHandler();
      }
  
      nTimeBestReceived = GetTime();
  }
  
  /**
   * Handle invalid block rejection and consequent peer banning, maintain which
   * peers announce compact blocks.
   */
  void PeerLogicValidation::BlockChecked(const CBlock& block, const CValidationState& state) {
      LOCK(cs_main);
  
      const uint256 hash(block.GetHash());
      std::map<uint256, std::pair<NodeId, bool>>::iterator it = mapBlockSource.find(hash);
  
      int nDoS = 0;
      if (state.IsInvalid(nDoS)) {
          // Don't send reject message with code 0 or an internal reject code.
          if (it != mapBlockSource.end() && State(it->second.first) && state.GetRejectCode() > 0 && state.GetRejectCode() < REJECT_INTERNAL) {
              CBlockReject reject = {(unsigned char)state.GetRejectCode(), state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), hash};
              State(it->second.first)->rejects.push_back(reject);
              if (nDoS > 0 && it->second.second)
                  Misbehaving(it->second.first, nDoS);
          }
      }
      // Check that:
      // 1. The block is valid
      // 2. We're not in initial block download
      // 3. This is currently the best block we're aware of. We haven't updated
      //    the tip yet so we have no way to check this directly here. Instead we
      //    just check that there are currently no other blocks in flight.
      else if (state.IsValid() &&
               !IsInitialBlockDownload() &&
               mapBlocksInFlight.count(hash) == mapBlocksInFlight.size()) {
          if (it != mapBlockSource.end()) {
              MaybeSetPeerAsAnnouncingHeaderAndIDs(it->second.first, connman);
          }
      }
      if (it != mapBlockSource.end())
          mapBlockSource.erase(it);
  }
  
  //////////////////////////////////////////////////////////////////////////////
  //
  // Messages
  //
  
  
  bool static AlreadyHave(const CInv& inv) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
  {
      switch (inv.type)
      {
      case MSG_TX:
      case MSG_WITNESS_TX:
          {
              assert(recentRejects);
              if (chainActive.Tip()->GetBlockHash() != hashRecentRejectsChainTip)
              {
                  // If the chain tip has changed previously rejected transactions
                  // might be now valid, e.g. due to a nLockTime'd tx becoming valid,
                  // or a double-spend. Reset the rejects filter and give those
                  // txs a second chance.
                  hashRecentRejectsChainTip = chainActive.Tip()->GetBlockHash();
                  recentRejects->reset();
              }
  
              {
                  LOCK(g_cs_orphans);
                  if (mapOrphanTransactions.count(inv.hash)) return true;
              }
  
              return recentRejects->contains(inv.hash) ||
                     mempool.exists(inv.hash) ||
                     pcoinsTip->HaveCoinInCache(COutPoint(inv.hash, 0)) || // Best effort: only try output 0 and 1
                     pcoinsTip->HaveCoinInCache(COutPoint(inv.hash, 1));
          }
      case MSG_BLOCK:
      case MSG_WITNESS_BLOCK:
          return LookupBlockIndex(inv.hash) != nullptr;
      }
      // Don't know what it is, just say we already got one
      return true;
  }
  
  static void RelayTransaction(const CTransaction& tx, CConnman* connman)
  {
      CInv inv(MSG_TX, tx.GetHash());
      connman->ForEachNode([&inv](CNode* pnode)
      {
          pnode->PushInventory(inv);
      });
  }
  
  static void RelayAddress(const CAddress& addr, bool fReachable, CConnman* connman)
  {
      unsigned int nRelayNodes = fReachable ? 2 : 1; // limited relaying of addresses outside our network(s)
  
      // Relay to a limited number of other nodes
      // Use deterministic randomness to send to the same nodes for 24 hours
      // at a time so the addrKnowns of the chosen nodes prevent repeats
      uint64_t hashAddr = addr.GetHash();
      const CSipHasher hasher = connman->GetDeterministicRandomizer(RANDOMIZER_ID_ADDRESS_RELAY).Write(hashAddr << 32).Write((GetTime() + hashAddr) / (24*60*60));
      FastRandomContext insecure_rand;
  
      std::array<std::pair<uint64_t, CNode*>,2> best{{{0, nullptr}, {0, nullptr}}};
      assert(nRelayNodes <= best.size());
  
      auto sortfunc = [&best, &hasher, nRelayNodes](CNode* pnode) {
          if (pnode->nVersion >= CADDR_TIME_VERSION) {
              uint64_t hashKey = CSipHasher(hasher).Write(pnode->GetId()).Finalize();
              for (unsigned int i = 0; i < nRelayNodes; i++) {
                   if (hashKey > best[i].first) {
                       std::copy(best.begin() + i, best.begin() + nRelayNodes - 1, best.begin() + i + 1);
                       best[i] = std::make_pair(hashKey, pnode);
                       break;
                   }
              }
          }
      };
  
      auto pushfunc = [&addr, &best, nRelayNodes, &insecure_rand] {
          for (unsigned int i = 0; i < nRelayNodes && best[i].first != 0; i++) {
              best[i].second->PushAddress(addr, insecure_rand);
          }
      };
  
      connman->ForEachNodeThen(std::move(sortfunc), std::move(pushfunc));
  }
  
  void static ProcessGetBlockData(CNode* pfrom, const CChainParams& chainparams, const CInv& inv, CConnman* connman)
  {
      bool send = false;
      std::shared_ptr<const CBlock> a_recent_block;
      std::shared_ptr<const CBlockHeaderAndShortTxIDs> a_recent_compact_block;
      bool fWitnessesPresentInARecentCompactBlock;
      const Consensus::Params& consensusParams = chainparams.GetConsensus();
      {
          LOCK(cs_most_recent_block);
          a_recent_block = most_recent_block;
          a_recent_compact_block = most_recent_compact_block;
          fWitnessesPresentInARecentCompactBlock = fWitnessesPresentInMostRecentCompactBlock;
      }
  
      bool need_activate_chain = false;
      {
          LOCK(cs_main);
          const CBlockIndex* pindex = LookupBlockIndex(inv.hash);
          if (pindex) {
              if (pindex->nChainTx && !pindex->IsValid(BLOCK_VALID_SCRIPTS) &&
                      pindex->IsValid(BLOCK_VALID_TREE)) {
                  // If we have the block and all of its parents, but have not yet validated it,
                  // we might be in the middle of connecting it (ie in the unlock of cs_main
                  // before ActivateBestChain but after AcceptBlock).
                  // In this case, we need to run ActivateBestChain prior to checking the relay
                  // conditions below.
                  need_activate_chain = true;
              }
          }
      } // release cs_main before calling ActivateBestChain
      if (need_activate_chain) {
          CValidationState state;
          if (!ActivateBestChain(state, Params(), a_recent_block)) {
              LogPrint(BCLog::NET, "failed to activate chain (%s)\n", FormatStateMessage(state));
          }
      }
  
      LOCK(cs_main);
      const CBlockIndex* pindex = LookupBlockIndex(inv.hash);
      if (pindex) {
          send = BlockRequestAllowed(pindex, consensusParams);
          if (!send) {
              LogPrint(BCLog::NET, "%s: ignoring request from peer=%i for old block that isn't in the main chain\n", __func__, pfrom->GetId());
          }
      }
      const CNetMsgMaker msgMaker(pfrom->GetSendVersion());
      // disconnect node in case we have reached the outbound limit for serving historical blocks
      // never disconnect whitelisted nodes
      if (send && connman->OutboundTargetReached(true) && ( ((pindexBestHeader != nullptr) && (pindexBestHeader->GetBlockTime() - pindex->GetBlockTime() > HISTORICAL_BLOCK_AGE)) || inv.type == MSG_FILTERED_BLOCK) && !pfrom->fWhitelisted)
      {
          LogPrint(BCLog::NET, "historical block serving limit reached, disconnect peer=%d\n", pfrom->GetId());
  
          //disconnect node
          pfrom->fDisconnect = true;
          send = false;
      }
      // Avoid leaking prune-height by never sending blocks below the NODE_NETWORK_LIMITED threshold
      if (send && !pfrom->fWhitelisted && (
              (((pfrom->GetLocalServices() & NODE_NETWORK_LIMITED) == NODE_NETWORK_LIMITED) && ((pfrom->GetLocalServices() & NODE_NETWORK) != NODE_NETWORK) && (chainActive.Tip()->nHeight - pindex->nHeight > (int)NODE_NETWORK_LIMITED_MIN_BLOCKS + 2 /* add two blocks buffer extension for possible races */) )
         )) {
          LogPrint(BCLog::NET, "Ignore block request below NODE_NETWORK_LIMITED threshold from peer=%d\n", pfrom->GetId());
  
          //disconnect node and prevent it from stalling (would otherwise wait for the missing block)
          pfrom->fDisconnect = true;
          send = false;
      }
      // Pruned nodes may have deleted the block, so check whether
      // it's available before trying to send.
      if (send && (pindex->nStatus & BLOCK_HAVE_DATA))
      {
          std::shared_ptr<const CBlock> pblock;
          if (a_recent_block && a_recent_block->GetHash() == pindex->GetBlockHash()) {
              pblock = a_recent_block;
          } else if (inv.type == MSG_WITNESS_BLOCK) {
              // Fast-path: in this case it is possible to serve the block directly from disk,
              // as the network format matches the format on disk
              std::vector<uint8_t> block_data;
              if (!ReadRawBlockFromDisk(block_data, pindex, chainparams.MessageStart())) {
                  assert(!"cannot load block from disk");
              }
              connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::BLOCK, MakeSpan(block_data)));
              // Don't set pblock as we've sent the block
          } else {
              // Send block from disk
              std::shared_ptr<CBlock> pblockRead = std::make_shared<CBlock>();
              if (!ReadBlockFromDisk(*pblockRead, pindex, consensusParams))
                  assert(!"cannot load block from disk");
              pblock = pblockRead;
          }
          if (pblock) {
              if (inv.type == MSG_BLOCK)
                  connman->PushMessage(pfrom, msgMaker.Make(SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::BLOCK, *pblock));
              else if (inv.type == MSG_WITNESS_BLOCK)
                  connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::BLOCK, *pblock));
              else if (inv.type == MSG_FILTERED_BLOCK)
              {
                  bool sendMerkleBlock = false;
                  CMerkleBlock merkleBlock;
                  {
                      LOCK(pfrom->cs_filter);
                      if (pfrom->pfilter) {
                          sendMerkleBlock = true;
                          merkleBlock = CMerkleBlock(*pblock, *pfrom->pfilter);
                      }
                  }
                  if (sendMerkleBlock) {
                      connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::MERKLEBLOCK, merkleBlock));
                      // CMerkleBlock just contains hashes, so also push any transactions in the block the client did not see
                      // This avoids hurting performance by pointlessly requiring a round-trip
                      // Note that there is currently no way for a node to request any single transactions we didn't send here -
                      // they must either disconnect and retry or request the full block.
                      // Thus, the protocol spec specified allows for us to provide duplicate txn here,
                      // however we MUST always provide at least what the remote peer needs
                      typedef std::pair<unsigned int, uint256> PairType;
                      for (PairType& pair : merkleBlock.vMatchedTxn)
                          connman->PushMessage(pfrom, msgMaker.Make(SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::TX, *pblock->vtx[pair.first]));
                  }
                  // else
                      // no response
              }
              else if (inv.type == MSG_CMPCT_BLOCK)
              {
                  // If a peer is asking for old blocks, we're almost guaranteed
                  // they won't have a useful mempool to match against a compact block,
                  // and we don't feel like constructing the object for them, so
                  // instead we respond with the full, non-compact block.
                  bool fPeerWantsWitness = State(pfrom->GetId())->fWantsCmpctWitness;
                  int nSendFlags = fPeerWantsWitness ? 0 : SERIALIZE_TRANSACTION_NO_WITNESS;
                  if (CanDirectFetch(consensusParams) && pindex->nHeight >= chainActive.Height() - MAX_CMPCTBLOCK_DEPTH) {
                      if ((fPeerWantsWitness || !fWitnessesPresentInARecentCompactBlock) && a_recent_compact_block && a_recent_compact_block->header.GetHash() == pindex->GetBlockHash()) {
                          connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, *a_recent_compact_block));
                      } else {
                          CBlockHeaderAndShortTxIDs cmpctblock(*pblock, fPeerWantsWitness);
                          connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, cmpctblock));
                      }
                  } else {
                      connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::BLOCK, *pblock));
                  }
              }
          }
  
          // Trigger the peer node to send a getblocks request for the next batch of inventory
          if (inv.hash == pfrom->hashContinue)
          {
              // Bypass PushInventory, this must send even if redundant,
              // and we want it right after the last block so they don't
              // wait for other stuff first.
              std::vector<CInv> vInv;
              vInv.push_back(CInv(MSG_BLOCK, chainActive.Tip()->GetBlockHash()));
              connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::INV, vInv));
              pfrom->hashContinue.SetNull();
          }
      }
  }
  
  void static ProcessGetData(CNode* pfrom, const CChainParams& chainparams, CConnman* connman, const std::atomic<bool>& interruptMsgProc)
  {
      AssertLockNotHeld(cs_main);
  
      std::deque<CInv>::iterator it = pfrom->vRecvGetData.begin();
      std::vector<CInv> vNotFound;
      const CNetMsgMaker msgMaker(pfrom->GetSendVersion());
      {
          LOCK(cs_main);
  
          while (it != pfrom->vRecvGetData.end() && (it->type == MSG_TX || it->type == MSG_WITNESS_TX)) {
              if (interruptMsgProc)
                  return;
              // Don't bother if send buffer is too full to respond anyway
              if (pfrom->fPauseSend)
                  break;
  
              const CInv &inv = *it;
              it++;
  
              // Send stream from relay memory
              bool push = false;
              auto mi = mapRelay.find(inv.hash);
              int nSendFlags = (inv.type == MSG_TX ? SERIALIZE_TRANSACTION_NO_WITNESS : 0);
              if (mi != mapRelay.end()) {
                  connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *mi->second));
                  push = true;
              } else if (pfrom->timeLastMempoolReq) {
                  auto txinfo = mempool.info(inv.hash);
                  // To protect privacy, do not answer getdata using the mempool when
                  // that TX couldn't have been INVed in reply to a MEMPOOL request.
                  if (txinfo.tx && txinfo.nTime <= pfrom->timeLastMempoolReq) {
                      connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *txinfo.tx));
                      push = true;
                  }
              }
              if (!push) {
                  vNotFound.push_back(inv);
              }
          }
      } // release cs_main
  
      if (it != pfrom->vRecvGetData.end() && !pfrom->fPauseSend) {
          const CInv &inv = *it;
          if (inv.type == MSG_BLOCK || inv.type == MSG_FILTERED_BLOCK || inv.type == MSG_CMPCT_BLOCK || inv.type == MSG_WITNESS_BLOCK) {
              it++;
              ProcessGetBlockData(pfrom, chainparams, inv, connman);
          }
      }
  
      pfrom->vRecvGetData.erase(pfrom->vRecvGetData.begin(), it);
  
      if (!vNotFound.empty()) {
          // Let the peer know that we didn't find what it asked for, so it doesn't
          // have to wait around forever. Currently only SPV clients actually care
          // about this message: it's needed when they are recursively walking the
          // dependencies of relevant unconfirmed transactions. SPV clients want to
          // do that because they want to know about (and store and rebroadcast and
          // risk analyze) the dependencies of transactions relevant to them, without
          // having to download the entire memory pool.
          connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::NOTFOUND, vNotFound));
      }
  }
  
  static uint32_t GetFetchFlags(CNode* pfrom) EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
      uint32_t nFetchFlags = 0;
      if ((pfrom->GetLocalServices() & NODE_WITNESS) && State(pfrom->GetId())->fHaveWitness) {
          nFetchFlags |= MSG_WITNESS_FLAG;
      }
      return nFetchFlags;
  }
  
  inline void static SendBlockTransactions(const CBlock& block, const BlockTransactionsRequest& req, CNode* pfrom, CConnman* connman) {
      BlockTransactions resp(req);
      for (size_t i = 0; i < req.indexes.size(); i++) {
          if (req.indexes[i] >= block.vtx.size()) {
              LOCK(cs_main);
              Misbehaving(pfrom->GetId(), 100, strprintf("Peer %d sent us a getblocktxn with out-of-bounds tx indices", pfrom->GetId()));
              return;
          }
          resp.txn[i] = block.vtx[req.indexes[i]];
      }
      LOCK(cs_main);
      const CNetMsgMaker msgMaker(pfrom->GetSendVersion());
      int nSendFlags = State(pfrom->GetId())->fWantsCmpctWitness ? 0 : SERIALIZE_TRANSACTION_NO_WITNESS;
      connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::BLOCKTXN, resp));
  }
  
  bool static ProcessHeadersMessage(CNode *pfrom, CConnman *connman, const std::vector<CBlockHeader>& headers, const CChainParams& chainparams, bool punish_duplicate_invalid)
  {
      const CNetMsgMaker msgMaker(pfrom->GetSendVersion());
      size_t nCount = headers.size();
  
      if (nCount == 0) {
          // Nothing interesting. Stop asking this peers for more headers.
          return true;
      }
  
      bool received_new_header = false;
      const CBlockIndex *pindexLast = nullptr;
      {
          LOCK(cs_main);
          CNodeState *nodestate = State(pfrom->GetId());
  
          // If this looks like it could be a block announcement (nCount <
          // MAX_BLOCKS_TO_ANNOUNCE), use special logic for handling headers that
          // don't connect:
          // - Send a getheaders message in response to try to connect the chain.
          // - The peer can send up to MAX_UNCONNECTING_HEADERS in a row that
          //   don't connect before giving DoS points
          // - Once a headers message is received that is valid and does connect,
          //   nUnconnectingHeaders gets reset back to 0.
          if (!LookupBlockIndex(headers[0].hashPrevBlock) && nCount < MAX_BLOCKS_TO_ANNOUNCE) {
              nodestate->nUnconnectingHeaders++;
              connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), uint256()));
              LogPrint(BCLog::NET, "received header %s: missing prev block %s, sending getheaders (%d) to end (peer=%d, nUnconnectingHeaders=%d)\n",
                      headers[0].GetHash().ToString(),
                      headers[0].hashPrevBlock.ToString(),
                      pindexBestHeader->nHeight,
                      pfrom->GetId(), nodestate->nUnconnectingHeaders);
              // Set hashLastUnknownBlock for this peer, so that if we
              // eventually get the headers - even from a different peer -
              // we can use this peer to download.
              UpdateBlockAvailability(pfrom->GetId(), headers.back().GetHash());
  
              if (nodestate->nUnconnectingHeaders % MAX_UNCONNECTING_HEADERS == 0) {
                  Misbehaving(pfrom->GetId(), 20);
              }
              return true;
          }
  
          uint256 hashLastBlock;
          for (const CBlockHeader& header : headers) {
              if (!hashLastBlock.IsNull() && header.hashPrevBlock != hashLastBlock) {
                  Misbehaving(pfrom->GetId(), 20, "non-continuous headers sequence");
                  return false;
              }
              hashLastBlock = header.GetHash();
          }
  
          // If we don't have the last header, then they'll have given us
          // something new (if these headers are valid).
          if (!LookupBlockIndex(hashLastBlock)) {
              received_new_header = true;
          }
      }
  
      CValidationState state;
      CBlockHeader first_invalid_header;
      if (!ProcessNewBlockHeaders(headers, state, chainparams, &pindexLast, &first_invalid_header)) {
          int nDoS;
          if (state.IsInvalid(nDoS)) {
              LOCK(cs_main);
              if (nDoS > 0) {
                  Misbehaving(pfrom->GetId(), nDoS, "invalid header received");
              } else {
                  LogPrint(BCLog::NET, "peer=%d: invalid header received\n", pfrom->GetId());
              }
              if (punish_duplicate_invalid && LookupBlockIndex(first_invalid_header.GetHash())) {
                  // Goal: don't allow outbound peers to use up our outbound
                  // connection slots if they are on incompatible chains.
                  //
                  // We ask the caller to set punish_invalid appropriately based
                  // on the peer and the method of header delivery (compact
                  // blocks are allowed to be invalid in some circumstances,
                  // under BIP 152).
                  // Here, we try to detect the narrow situation that we have a
                  // valid block header (ie it was valid at the time the header
                  // was received, and hence stored in mapBlockIndex) but know the
                  // block is invalid, and that a peer has announced that same
                  // block as being on its active chain.
                  // Disconnect the peer in such a situation.
                  //
                  // Note: if the header that is invalid was not accepted to our
                  // mapBlockIndex at all, that may also be grounds for
                  // disconnecting the peer, as the chain they are on is likely
                  // to be incompatible. However, there is a circumstance where
                  // that does not hold: if the header's timestamp is more than
                  // 2 hours ahead of our current time. In that case, the header
                  // may become valid in the future, and we don't want to
                  // disconnect a peer merely for serving us one too-far-ahead
                  // block header, to prevent an attacker from splitting the
                  // network by mining a block right at the 2 hour boundary.
                  //
                  // TODO: update the DoS logic (or, rather, rewrite the
                  // DoS-interface between validation and net_processing) so that
                  // the interface is cleaner, and so that we disconnect on all the
                  // reasons that a peer's headers chain is incompatible
                  // with ours (eg block->nVersion softforks, MTP violations,
                  // etc), and not just the duplicate-invalid case.
                  pfrom->fDisconnect = true;
              }
              return false;
          }
      }
  
      {
          LOCK(cs_main);
          CNodeState *nodestate = State(pfrom->GetId());
          if (nodestate->nUnconnectingHeaders > 0) {
              LogPrint(BCLog::NET, "peer=%d: resetting nUnconnectingHeaders (%d -> 0)\n", pfrom->GetId(), nodestate->nUnconnectingHeaders);
          }
          nodestate->nUnconnectingHeaders = 0;
  
          assert(pindexLast);
          UpdateBlockAvailability(pfrom->GetId(), pindexLast->GetBlockHash());
  
          // From here, pindexBestKnownBlock should be guaranteed to be non-null,
          // because it is set in UpdateBlockAvailability. Some nullptr checks
          // are still present, however, as belt-and-suspenders.
  
          if (received_new_header && pindexLast->nChainWork > chainActive.Tip()->nChainWork) {
              nodestate->m_last_block_announcement = GetTime();
          }
  
          if (nCount == MAX_HEADERS_RESULTS) {
              // Headers message had its maximum size; the peer may have more headers.
              // TODO: optimize: if pindexLast is an ancestor of chainActive.Tip or pindexBestHeader, continue
              // from there instead.
              LogPrint(BCLog::NET, "more getheaders (%d) to end to peer=%d (startheight:%d)\n", pindexLast->nHeight, pfrom->GetId(), pfrom->nStartingHeight);
              connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexLast), uint256()));
          }
  
          bool fCanDirectFetch = CanDirectFetch(chainparams.GetConsensus());
          // If this set of headers is valid and ends in a block with at least as
          // much work as our tip, download as much as possible.
          if (fCanDirectFetch && pindexLast->IsValid(BLOCK_VALID_TREE) && chainActive.Tip()->nChainWork <= pindexLast->nChainWork) {
              std::vector<const CBlockIndex*> vToFetch;
              const CBlockIndex *pindexWalk = pindexLast;
              // Calculate all the blocks we'd need to switch to pindexLast, up to a limit.
              while (pindexWalk && !chainActive.Contains(pindexWalk) && vToFetch.size() <= MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
                  if (!(pindexWalk->nStatus & BLOCK_HAVE_DATA) &&
                          !mapBlocksInFlight.count(pindexWalk->GetBlockHash()) &&
                          (!IsWitnessEnabled(pindexWalk->pprev, chainparams.GetConsensus()) || State(pfrom->GetId())->fHaveWitness)) {
                      // We don't have this block, and it's not yet in flight.
                      vToFetch.push_back(pindexWalk);
                  }
                  pindexWalk = pindexWalk->pprev;
              }
              // If pindexWalk still isn't on our main chain, we're looking at a
              // very large reorg at a time we think we're close to caught up to
              // the main chain -- this shouldn't really happen.  Bail out on the
              // direct fetch and rely on parallel download instead.
              if (!chainActive.Contains(pindexWalk)) {
                  LogPrint(BCLog::NET, "Large reorg, won't direct fetch to %s (%d)\n",
                          pindexLast->GetBlockHash().ToString(),
                          pindexLast->nHeight);
              } else {
                  std::vector<CInv> vGetData;
                  // Download as much as possible, from earliest to latest.
                  for (const CBlockIndex *pindex : reverse_iterate(vToFetch)) {
                      if (nodestate->nBlocksInFlight >= MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
                          // Can't download any more from this peer
                          break;
                      }
                      uint32_t nFetchFlags = GetFetchFlags(pfrom);
                      vGetData.push_back(CInv(MSG_BLOCK | nFetchFlags, pindex->GetBlockHash()));
                      MarkBlockAsInFlight(pfrom->GetId(), pindex->GetBlockHash(), pindex);
                      LogPrint(BCLog::NET, "Requesting block %s from  peer=%d\n",
                              pindex->GetBlockHash().ToString(), pfrom->GetId());
                  }
                  if (vGetData.size() > 1) {
                      LogPrint(BCLog::NET, "Downloading blocks toward %s (%d) via headers direct fetch\n",
                              pindexLast->GetBlockHash().ToString(), pindexLast->nHeight);
                  }
                  if (vGetData.size() > 0) {
                      if (nodestate->fSupportsDesiredCmpctVersion && vGetData.size() == 1 && mapBlocksInFlight.size() == 1 && pindexLast->pprev->IsValid(BLOCK_VALID_CHAIN)) {
                          // In any case, we want to download using a compact block, not a regular one
                          vGetData[0] = CInv(MSG_CMPCT_BLOCK, vGetData[0].hash);
                      }
                      connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vGetData));
                  }
              }
          }
          // If we're in IBD, we want outbound peers that will serve us a useful
          // chain. Disconnect peers that are on chains with insufficient work.
          if (IsInitialBlockDownload() && nCount != MAX_HEADERS_RESULTS) {
              // When nCount < MAX_HEADERS_RESULTS, we know we have no more
              // headers to fetch from this peer.
              if (nodestate->pindexBestKnownBlock && nodestate->pindexBestKnownBlock->nChainWork < nMinimumChainWork) {
                  // This peer has too little work on their headers chain to help
                  // us sync -- disconnect if using an outbound slot (unless
                  // whitelisted or addnode).
                  // Note: We compare their tip to nMinimumChainWork (rather than
                  // chainActive.Tip()) because we won't start block download
                  // until we have a headers chain that has at least
                  // nMinimumChainWork, even if a peer has a chain past our tip,
                  // as an anti-DoS measure.
                  if (IsOutboundDisconnectionCandidate(pfrom)) {
                      LogPrintf("Disconnecting outbound peer %d -- headers chain has insufficient work\n", pfrom->GetId());
                      pfrom->fDisconnect = true;
                  }
              }
          }
  
          if (!pfrom->fDisconnect && IsOutboundDisconnectionCandidate(pfrom) && nodestate->pindexBestKnownBlock != nullptr) {
              // If this is an outbound peer, check to see if we should protect
              // it from the bad/lagging chain logic.
              if (g_outbound_peers_with_protect_from_disconnect < MAX_OUTBOUND_PEERS_TO_PROTECT_FROM_DISCONNECT && nodestate->pindexBestKnownBlock->nChainWork >= chainActive.Tip()->nChainWork && !nodestate->m_chain_sync.m_protect) {
                  LogPrint(BCLog::NET, "Protecting outbound peer=%d from eviction\n", pfrom->GetId());
                  nodestate->m_chain_sync.m_protect = true;
                  ++g_outbound_peers_with_protect_from_disconnect;
              }
          }
      }
  
      return true;
  }
  
  bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStream& vRecv, int64_t nTimeReceived, const CChainParams& chainparams, CConnman* connman, const std::atomic<bool>& interruptMsgProc, bool enable_bip61)
  {
      LogPrint(BCLog::NET, "received: %s (%u bytes) peer=%d\n", SanitizeString(strCommand), vRecv.size(), pfrom->GetId());
      if (gArgs.IsArgSet("-dropmessagestest") && GetRand(gArgs.GetArg("-dropmessagestest", 0)) == 0)
      {
          LogPrintf("dropmessagestest DROPPING RECV MESSAGE\n");
          return true;
      }
  
  
      if (!(pfrom->GetLocalServices() & NODE_BLOOM) &&
                (strCommand == NetMsgType::FILTERLOAD ||
                 strCommand == NetMsgType::FILTERADD))
      {
          if (pfrom->nVersion >= NO_BLOOM_VERSION) {
              LOCK(cs_main);
              Misbehaving(pfrom->GetId(), 100);
              return false;
          } else {
              pfrom->fDisconnect = true;
              return false;
          }
      }
  
      if (strCommand == NetMsgType::REJECT)
      {
          if (LogAcceptCategory(BCLog::NET)) {
              try {
                  std::string strMsg; unsigned char ccode; std::string strReason;
                  vRecv >> LIMITED_STRING(strMsg, CMessageHeader::COMMAND_SIZE) >> ccode >> LIMITED_STRING(strReason, MAX_REJECT_MESSAGE_LENGTH);
  
                  std::ostringstream ss;
                  ss << strMsg << " code " << itostr(ccode) << ": " << strReason;
  
                  if (strMsg == NetMsgType::BLOCK || strMsg == NetMsgType::TX)
                  {
                      uint256 hash;
                      vRecv >> hash;
                      ss << ": hash " << hash.ToString();
                  }
                  LogPrint(BCLog::NET, "Reject %s\n", SanitizeString(ss.str()));
              } catch (const std::ios_base::failure&) {
                  // Avoid feedback loops by preventing reject messages from triggering a new reject message.
                  LogPrint(BCLog::NET, "Unparseable reject message received\n");
              }
          }
          return true;
      }
  
      else if (strCommand == NetMsgType::VERSION)
      {
          // Each connection can only send one version message
          if (pfrom->nVersion != 0)
          {
              if (enable_bip61) {
                  connman->PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_DUPLICATE, std::string("Duplicate version message")));
              }
              LOCK(cs_main);
              Misbehaving(pfrom->GetId(), 1);
              return false;
          }
  
          int64_t nTime;
          CAddress addrMe;
          CAddress addrFrom;
          uint64_t nNonce = 1;
          uint64_t nServiceInt;
          ServiceFlags nServices;
          int nVersion;
          int nSendVersion;
          std::string strSubVer;
          std::string cleanSubVer;
          int nStartingHeight = -1;
          bool fRelay = true;
  
          vRecv >> nVersion >> nServiceInt >> nTime >> addrMe;
          nSendVersion = std::min(nVersion, PROTOCOL_VERSION);
          nServices = ServiceFlags(nServiceInt);
          if (!pfrom->fInbound)
          {
              connman->SetServices(pfrom->addr, nServices);
          }
          if (!pfrom->fInbound && !pfrom->fFeeler && !pfrom->m_manual_connection && !HasAllDesirableServiceFlags(nServices))
          {
              LogPrint(BCLog::NET, "peer=%d does not offer the expected services (%08x offered, %08x expected); disconnecting\n", pfrom->GetId(), nServices, GetDesirableServiceFlags(nServices));
              if (enable_bip61) {
                  connman->PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_NONSTANDARD,
                                     strprintf("Expected to offer services %08x", GetDesirableServiceFlags(nServices))));
              }
              pfrom->fDisconnect = true;
              return false;
          }
  
          if (nVersion < MIN_PEER_PROTO_VERSION)
          {
              // disconnect from peers older than this proto version
              LogPrint(BCLog::NET, "peer=%d using obsolete version %i; disconnecting\n", pfrom->GetId(), nVersion);
              if (enable_bip61) {
                  connman->PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_OBSOLETE,
                                     strprintf("Version must be %d or greater", MIN_PEER_PROTO_VERSION)));
              }
              pfrom->fDisconnect = true;
              return false;
          }
  
          if (nVersion == 10300)
              nVersion = 300;
          if (!vRecv.empty())
              vRecv >> addrFrom >> nNonce;
          if (!vRecv.empty()) {
              vRecv >> LIMITED_STRING(strSubVer, MAX_SUBVERSION_LENGTH);
              cleanSubVer = SanitizeString(strSubVer);
          }
          if (!vRecv.empty()) {
              vRecv >> nStartingHeight;
          }
          if (!vRecv.empty())
              vRecv >> fRelay;
          // Disconnect if we connected to ourself
          if (pfrom->fInbound && !connman->CheckIncomingNonce(nNonce))
          {
              LogPrintf("connected to self at %s, disconnecting\n", pfrom->addr.ToString());
              pfrom->fDisconnect = true;
              return true;
          }
  
          if (pfrom->fInbound && addrMe.IsRoutable())
          {
              SeenLocal(addrMe);
          }
  
          // Be shy and don't send version until we hear
          if (pfrom->fInbound)
              PushNodeVersion(pfrom, connman, GetAdjustedTime());
  
          connman->PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::VERACK));
  
          pfrom->nServices = nServices;
          pfrom->SetAddrLocal(addrMe);
          {
              LOCK(pfrom->cs_SubVer);
              pfrom->strSubVer = strSubVer;
              pfrom->cleanSubVer = cleanSubVer;
          }
          pfrom->nStartingHeight = nStartingHeight;
  
          // set nodes not relaying blocks and tx and not serving (parts) of the historical blockchain as "clients"
          pfrom->fClient = (!(nServices & NODE_NETWORK) && !(nServices & NODE_NETWORK_LIMITED));
  
          // set nodes not capable of serving the complete blockchain history as "limited nodes"
          pfrom->m_limited_node = (!(nServices & NODE_NETWORK) && (nServices & NODE_NETWORK_LIMITED));
  
          {
              LOCK(pfrom->cs_filter);
              pfrom->fRelayTxes = fRelay; // set to true after we get the first filter* message
          }
  
          // Change version
          pfrom->SetSendVersion(nSendVersion);
          pfrom->nVersion = nVersion;
  
          if((nServices & NODE_WITNESS))
          {
              LOCK(cs_main);
              State(pfrom->GetId())->fHaveWitness = true;
          }
  
          // Potentially mark this peer as a preferred download peer.
          {
          LOCK(cs_main);
          UpdatePreferredDownload(pfrom, State(pfrom->GetId()));
          }
  
          if (!pfrom->fInbound)
          {
              // Advertise our address
              if (fListen && !IsInitialBlockDownload())
              {
                  CAddress addr = GetLocalAddress(&pfrom->addr, pfrom->GetLocalServices());
                  FastRandomContext insecure_rand;
                  if (addr.IsRoutable())
                  {
                      LogPrint(BCLog::NET, "ProcessMessages: advertising address %s\n", addr.ToString());
                      pfrom->PushAddress(addr, insecure_rand);
                  } else if (IsPeerAddrLocalGood(pfrom)) {
                      addr.SetIP(addrMe);
                      LogPrint(BCLog::NET, "ProcessMessages: advertising address %s\n", addr.ToString());
                      pfrom->PushAddress(addr, insecure_rand);
                  }
              }
  
              // Get recent addresses
              if (pfrom->fOneShot || pfrom->nVersion >= CADDR_TIME_VERSION || connman->GetAddressCount() < 1000)
              {
                  connman->PushMessage(pfrom, CNetMsgMaker(nSendVersion).Make(NetMsgType::GETADDR));
                  pfrom->fGetAddr = true;
              }
              connman->MarkAddressGood(pfrom->addr);
          }
  
          std::string remoteAddr;
          if (fLogIPs)
              remoteAddr = ", peeraddr=" + pfrom->addr.ToString();
  
          LogPrint(BCLog::NET, "receive version message: %s: version %d, blocks=%d, us=%s, peer=%d%s\n",
                    cleanSubVer, pfrom->nVersion,
                    pfrom->nStartingHeight, addrMe.ToString(), pfrom->GetId(),
                    remoteAddr);
  
          int64_t nTimeOffset = nTime - GetTime();
          pfrom->nTimeOffset = nTimeOffset;
          AddTimeData(pfrom->addr, nTimeOffset);
  
          // If the peer is old enough to have the old alert system, send it the final alert.
          if (pfrom->nVersion <= 70012) {
              CDataStream finalAlert(ParseHex("60010000000000000000000000ffffff7f00000000ffffff7ffeffff7f01ffffff7f00000000ffffff7f00ffffff7f002f555247454e543a20416c657274206b657920636f6d70726f6d697365642c2075706772616465207265717569726564004630440220653febd6410f470f6bae11cad19c48413becb1ac2c17f908fd0fd53bdc3abd5202206d0e9c96fe88d4a0f01ed9dedae2b6f9e00da94cad0fecaae66ecf689bf71b50"), SER_NETWORK, PROTOCOL_VERSION);
              connman->PushMessage(pfrom, CNetMsgMaker(nSendVersion).Make("alert", finalAlert));
          }
  
          // Feeler connections exist only to verify if address is online.
          if (pfrom->fFeeler) {
              assert(pfrom->fInbound == false);
              pfrom->fDisconnect = true;
          }
          return true;
      }
  
  
      else if (pfrom->nVersion == 0)
      {
          // Must have a version message before anything else
          LOCK(cs_main);
          Misbehaving(pfrom->GetId(), 1);
          return false;
      }
  
      // At this point, the outgoing message serialization version can't change.
      const CNetMsgMaker msgMaker(pfrom->GetSendVersion());
  
      if (strCommand == NetMsgType::VERACK)
      {
          pfrom->SetRecvVersion(std::min(pfrom->nVersion.load(), PROTOCOL_VERSION));
  
          if (!pfrom->fInbound) {
              // Mark this node as currently connected, so we update its timestamp later.
              LOCK(cs_main);
              State(pfrom->GetId())->fCurrentlyConnected = true;
              LogPrintf("New outbound peer connected: version: %d, blocks=%d, peer=%d%s\n",
                        pfrom->nVersion.load(), pfrom->nStartingHeight, pfrom->GetId(),
                        (fLogIPs ? strprintf(", peeraddr=%s", pfrom->addr.ToString()) : ""));
          }
  
          if (pfrom->nVersion >= SENDHEADERS_VERSION) {
              // Tell our peer we prefer to receive headers rather than inv's
              // We send this to non-NODE NETWORK peers as well, because even
              // non-NODE NETWORK peers can announce blocks (such as pruning
              // nodes)
              connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::SENDHEADERS));
          }
          if (pfrom->nVersion >= SHORT_IDS_BLOCKS_VERSION) {
              // Tell our peer we are willing to provide version 1 or 2 cmpctblocks
              // However, we do not request new block announcements using
              // cmpctblock messages.
              // We send this to non-NODE NETWORK peers as well, because
              // they may wish to request compact blocks from us
              bool fAnnounceUsingCMPCTBLOCK = false;
              uint64_t nCMPCTBLOCKVersion = 2;
              if (pfrom->GetLocalServices() & NODE_WITNESS)
                  connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
              nCMPCTBLOCKVersion = 1;
              connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
          }
          pfrom->fSuccessfullyConnected = true;
      }
  
      else if (!pfrom->fSuccessfullyConnected)
      {
          // Must have a verack message before anything else
          LOCK(cs_main);
          Misbehaving(pfrom->GetId(), 1);
          return false;
      }
  
      else if (strCommand == NetMsgType::ADDR)
      {
          std::vector<CAddress> vAddr;
          vRecv >> vAddr;
  
          // Don't want addr from older versions unless seeding
          if (pfrom->nVersion < CADDR_TIME_VERSION && connman->GetAddressCount() > 1000)
              return true;
          if (vAddr.size() > 1000)
          {
              LOCK(cs_main);
              Misbehaving(pfrom->GetId(), 20, strprintf("message addr size() = %u", vAddr.size()));
              return false;
          }
  
          // Store the new addresses
          std::vector<CAddress> vAddrOk;
          int64_t nNow = GetAdjustedTime();
          int64_t nSince = nNow - 10 * 60;
          for (CAddress& addr : vAddr)
          {
              if (interruptMsgProc)
                  return true;
  
              // We only bother storing full nodes, though this may include
              // things which we would not make an outbound connection to, in
              // part because we may make feeler connections to them.
              if (!MayHaveUsefulAddressDB(addr.nServices) && !HasAllDesirableServiceFlags(addr.nServices))
                  continue;
  
              if (addr.nTime <= 100000000 || addr.nTime > nNow + 10 * 60)
                  addr.nTime = nNow - 5 * 24 * 60 * 60;
              pfrom->AddAddressKnown(addr);
              bool fReachable = IsReachable(addr);
              if (addr.nTime > nSince && !pfrom->fGetAddr && vAddr.size() <= 10 && addr.IsRoutable())
              {
                  // Relay to a limited number of other nodes
                  RelayAddress(addr, fReachable, connman);
              }
              // Do not store addresses outside our network
              if (fReachable)
                  vAddrOk.push_back(addr);
          }
          connman->AddNewAddresses(vAddrOk, pfrom->addr, 2 * 60 * 60);
          if (vAddr.size() < 1000)
              pfrom->fGetAddr = false;
          if (pfrom->fOneShot)
              pfrom->fDisconnect = true;
      }
  
      else if (strCommand == NetMsgType::SENDHEADERS)
      {
          LOCK(cs_main);
          State(pfrom->GetId())->fPreferHeaders = true;
      }
  
      else if (strCommand == NetMsgType::SENDCMPCT)
      {
          bool fAnnounceUsingCMPCTBLOCK = false;
          uint64_t nCMPCTBLOCKVersion = 0;
          vRecv >> fAnnounceUsingCMPCTBLOCK >> nCMPCTBLOCKVersion;
          if (nCMPCTBLOCKVersion == 1 || ((pfrom->GetLocalServices() & NODE_WITNESS) && nCMPCTBLOCKVersion == 2)) {
              LOCK(cs_main);
              // fProvidesHeaderAndIDs is used to "lock in" version of compact blocks we send (fWantsCmpctWitness)
              if (!State(pfrom->GetId())->fProvidesHeaderAndIDs) {
                  State(pfrom->GetId())->fProvidesHeaderAndIDs = true;
                  State(pfrom->GetId())->fWantsCmpctWitness = nCMPCTBLOCKVersion == 2;
              }
              if (State(pfrom->GetId())->fWantsCmpctWitness == (nCMPCTBLOCKVersion == 2)) // ignore later version announces
                  State(pfrom->GetId())->fPreferHeaderAndIDs = fAnnounceUsingCMPCTBLOCK;
              if (!State(pfrom->GetId())->fSupportsDesiredCmpctVersion) {
                  if (pfrom->GetLocalServices() & NODE_WITNESS)
                      State(pfrom->GetId())->fSupportsDesiredCmpctVersion = (nCMPCTBLOCKVersion == 2);
                  else
                      State(pfrom->GetId())->fSupportsDesiredCmpctVersion = (nCMPCTBLOCKVersion == 1);
              }
          }
      }
  
  
      else if (strCommand == NetMsgType::INV)
      {
          std::vector<CInv> vInv;
          vRecv >> vInv;
          if (vInv.size() > MAX_INV_SZ)
          {
              LOCK(cs_main);
              Misbehaving(pfrom->GetId(), 20, strprintf("message inv size() = %u", vInv.size()));
              return false;
          }
  
          bool fBlocksOnly = !fRelayTxes;
  
          // Allow whitelisted peers to send data other than blocks in blocks only mode if whitelistrelay is true
          if (pfrom->fWhitelisted && gArgs.GetBoolArg("-whitelistrelay", DEFAULT_WHITELISTRELAY))
              fBlocksOnly = false;
  
          LOCK(cs_main);
  
          uint32_t nFetchFlags = GetFetchFlags(pfrom);
  
          for (CInv &inv : vInv)
          {
              if (interruptMsgProc)
                  return true;
  
              bool fAlreadyHave = AlreadyHave(inv);
              LogPrint(BCLog::NET, "got inv: %s  %s peer=%d\n", inv.ToString(), fAlreadyHave ? "have" : "new", pfrom->GetId());
  
              if (inv.type == MSG_TX) {
                  inv.type |= nFetchFlags;
              }
  
              if (inv.type == MSG_BLOCK) {
                  UpdateBlockAvailability(pfrom->GetId(), inv.hash);
                  if (!fAlreadyHave && !fImporting && !fReindex && !mapBlocksInFlight.count(inv.hash)) {
                      // We used to request the full block here, but since headers-announcements are now the
                      // primary method of announcement on the network, and since, in the case that a node
                      // fell back to inv we probably have a reorg which we should get the headers for first,
                      // we now only provide a getheaders response here. When we receive the headers, we will
                      // then ask for the blocks we need.
                      connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), inv.hash));
                      LogPrint(BCLog::NET, "getheaders (%d) %s to peer=%d\n", pindexBestHeader->nHeight, inv.hash.ToString(), pfrom->GetId());
                  }
              }
              else
              {
                  pfrom->AddInventoryKnown(inv);
                  if (fBlocksOnly) {
                      LogPrint(BCLog::NET, "transaction (%s) inv sent in violation of protocol peer=%d\n", inv.hash.ToString(), pfrom->GetId());
                  } else if (!fAlreadyHave && !fImporting && !fReindex && !IsInitialBlockDownload()) {
                      pfrom->AskFor(inv);
                  }
              }
          }
      }
  
  
      else if (strCommand == NetMsgType::GETDATA)
      {
          std::vector<CInv> vInv;
          vRecv >> vInv;
          if (vInv.size() > MAX_INV_SZ)
          {
              LOCK(cs_main);
              Misbehaving(pfrom->GetId(), 20, strprintf("message getdata size() = %u", vInv.size()));
              return false;
          }
  
          LogPrint(BCLog::NET, "received getdata (%u invsz) peer=%d\n", vInv.size(), pfrom->GetId());
  
          if (vInv.size() > 0) {
              LogPrint(BCLog::NET, "received getdata for: %s peer=%d\n", vInv[0].ToString(), pfrom->GetId());
          }
  
          pfrom->vRecvGetData.insert(pfrom->vRecvGetData.end(), vInv.begin(), vInv.end());
          ProcessGetData(pfrom, chainparams, connman, interruptMsgProc);
      }
  
  
      else if (strCommand == NetMsgType::GETBLOCKS)
      {
          CBlockLocator locator;
          uint256 hashStop;
          vRecv >> locator >> hashStop;
  
          if (locator.vHave.size() > MAX_LOCATOR_SZ) {
              LogPrint(BCLog::NET, "getblocks locator size %lld > %d, disconnect peer=%d\n", locator.vHave.size(), MAX_LOCATOR_SZ, pfrom->GetId());
              pfrom->fDisconnect = true;
              return true;
          }
  
          // We might have announced the currently-being-connected tip using a
          // compact block, which resulted in the peer sending a getblocks
          // request, which we would otherwise respond to without the new block.
          // To avoid this situation we simply verify that we are on our best
          // known chain now. This is super overkill, but we handle it better
          // for getheaders requests, and there are no known nodes which support
          // compact blocks but still use getblocks to request blocks.
          {
              std::shared_ptr<const CBlock> a_recent_block;
              {
                  LOCK(cs_most_recent_block);
                  a_recent_block = most_recent_block;
              }
              CValidationState state;
              if (!ActivateBestChain(state, Params(), a_recent_block)) {
                  LogPrint(BCLog::NET, "failed to activate chain (%s)\n", FormatStateMessage(state));
              }
          }
  
          LOCK(cs_main);
  
          // Find the last block the caller has in the main chain
          const CBlockIndex* pindex = FindForkInGlobalIndex(chainActive, locator);
  
          // Send the rest of the chain
          if (pindex)
              pindex = chainActive.Next(pindex);
          int nLimit = 500;
          LogPrint(BCLog::NET, "getblocks %d to %s limit %d from peer=%d\n", (pindex ? pindex->nHeight : -1), hashStop.IsNull() ? "end" : hashStop.ToString(), nLimit, pfrom->GetId());
          for (; pindex; pindex = chainActive.Next(pindex))
          {
              if (pindex->GetBlockHash() == hashStop)
              {
                  LogPrint(BCLog::NET, "  getblocks stopping at %d %s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
                  break;
              }
              // If pruning, don't inv blocks unless we have on disk and are likely to still have
              // for some reasonable time window (1 hour) that block relay might require.
              const int nPrunedBlocksLikelyToHave = MIN_BLOCKS_TO_KEEP - 3600 / chainparams.GetConsensus().nPowTargetSpacing;
              if (fPruneMode && (!(pindex->nStatus & BLOCK_HAVE_DATA) || pindex->nHeight <= chainActive.Tip()->nHeight - nPrunedBlocksLikelyToHave))
              {
                  LogPrint(BCLog::NET, " getblocks stopping, pruned or too old block at %d %s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
                  break;
              }
              pfrom->PushInventory(CInv(MSG_BLOCK, pindex->GetBlockHash()));
              if (--nLimit <= 0)
              {
                  // When this block is requested, we'll send an inv that'll
                  // trigger the peer to getblocks the next batch of inventory.
                  LogPrint(BCLog::NET, "  getblocks stopping at limit %d %s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
                  pfrom->hashContinue = pindex->GetBlockHash();
                  break;
              }
          }
      }
  
  
      else if (strCommand == NetMsgType::GETBLOCKTXN)
      {
          BlockTransactionsRequest req;
          vRecv >> req;
  
          std::shared_ptr<const CBlock> recent_block;
          {
              LOCK(cs_most_recent_block);
              if (most_recent_block_hash == req.blockhash)
                  recent_block = most_recent_block;
              // Unlock cs_most_recent_block to avoid cs_main lock inversion
          }
          if (recent_block) {
              SendBlockTransactions(*recent_block, req, pfrom, connman);
              return true;
          }
  
          LOCK(cs_main);
  
          const CBlockIndex* pindex = LookupBlockIndex(req.blockhash);
          if (!pindex || !(pindex->nStatus & BLOCK_HAVE_DATA)) {
              LogPrint(BCLog::NET, "Peer %d sent us a getblocktxn for a block we don't have\n", pfrom->GetId());
              return true;
          }
  
          if (pindex->nHeight < chainActive.Height() - MAX_BLOCKTXN_DEPTH) {
              // If an older block is requested (should never happen in practice,
              // but can happen in tests) send a block response instead of a
              // blocktxn response. Sending a full block response instead of a
              // small blocktxn response is preferable in the case where a peer
              // might maliciously send lots of getblocktxn requests to trigger
              // expensive disk reads, because it will require the peer to
              // actually receive all the data read from disk over the network.
              LogPrint(BCLog::NET, "Peer %d sent us a getblocktxn for a block > %i deep\n", pfrom->GetId(), MAX_BLOCKTXN_DEPTH);
              CInv inv;
              inv.type = State(pfrom->GetId())->fWantsCmpctWitness ? MSG_WITNESS_BLOCK : MSG_BLOCK;
              inv.hash = req.blockhash;
              pfrom->vRecvGetData.push_back(inv);
              // The message processing loop will go around again (without pausing) and we'll respond then (without cs_main)
              return true;
          }
  
          CBlock block;
          bool ret = ReadBlockFromDisk(block, pindex, chainparams.GetConsensus());
          assert(ret);
  
          SendBlockTransactions(block, req, pfrom, connman);
      }
  
  
      else if (strCommand == NetMsgType::GETHEADERS)
      {
          CBlockLocator locator;
          uint256 hashStop;
          vRecv >> locator >> hashStop;
  
          if (locator.vHave.size() > MAX_LOCATOR_SZ) {
              LogPrint(BCLog::NET, "getheaders locator size %lld > %d, disconnect peer=%d\n", locator.vHave.size(), MAX_LOCATOR_SZ, pfrom->GetId());
              pfrom->fDisconnect = true;
              return true;
          }
  
          LOCK(cs_main);
          if (IsInitialBlockDownload() && !pfrom->fWhitelisted) {
              LogPrint(BCLog::NET, "Ignoring getheaders from peer=%d because node is in initial block download\n", pfrom->GetId());
              return true;
          }
  
          CNodeState *nodestate = State(pfrom->GetId());
          const CBlockIndex* pindex = nullptr;
          if (locator.IsNull())
          {
              // If locator is null, return the hashStop block
              pindex = LookupBlockIndex(hashStop);
              if (!pindex) {
                  return true;
              }
  
              if (!BlockRequestAllowed(pindex, chainparams.GetConsensus())) {
                  LogPrint(BCLog::NET, "%s: ignoring request from peer=%i for old block header that isn't in the main chain\n", __func__, pfrom->GetId());
                  return true;
              }
          }
          else
          {
              // Find the last block the caller has in the main chain
              pindex = FindForkInGlobalIndex(chainActive, locator);
              if (pindex)
                  pindex = chainActive.Next(pindex);
          }
  
          // we must use CBlocks, as CBlockHeaders won't include the 0x00 nTx count at the end
          std::vector<CBlock> vHeaders;
          int nLimit = MAX_HEADERS_RESULTS;
          LogPrint(BCLog::NET, "getheaders %d to %s from peer=%d\n", (pindex ? pindex->nHeight : -1), hashStop.IsNull() ? "end" : hashStop.ToString(), pfrom->GetId());
          for (; pindex; pindex = chainActive.Next(pindex))
          {
              vHeaders.push_back(pindex->GetBlockHeader());
              if (--nLimit <= 0 || pindex->GetBlockHash() == hashStop)
                  break;
          }
          // pindex can be nullptr either if we sent chainActive.Tip() OR
          // if our peer has chainActive.Tip() (and thus we are sending an empty
          // headers message). In both cases it's safe to update
          // pindexBestHeaderSent to be our tip.
          //
          // It is important that we simply reset the BestHeaderSent value here,
          // and not max(BestHeaderSent, newHeaderSent). We might have announced
          // the currently-being-connected tip using a compact block, which
          // resulted in the peer sending a headers request, which we respond to
          // without the new block. By resetting the BestHeaderSent, we ensure we
          // will re-announce the new block via headers (or compact blocks again)
          // in the SendMessages logic.
          nodestate->pindexBestHeaderSent = pindex ? pindex : chainActive.Tip();
          connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::HEADERS, vHeaders));
      }
  
  
      else if (strCommand == NetMsgType::TX)
      {
          // Stop processing the transaction early if
          // We are in blocks only mode and peer is either not whitelisted or whitelistrelay is off
          if (!fRelayTxes && (!pfrom->fWhitelisted || !gArgs.GetBoolArg("-whitelistrelay", DEFAULT_WHITELISTRELAY)))
          {
              LogPrint(BCLog::NET, "transaction sent in violation of protocol peer=%d\n", pfrom->GetId());
              return true;
          }
  
          std::deque<COutPoint> vWorkQueue;
          std::vector<uint256> vEraseQueue;
          CTransactionRef ptx;
          vRecv >> ptx;
          const CTransaction& tx = *ptx;
  
          CInv inv(MSG_TX, tx.GetHash());
          pfrom->AddInventoryKnown(inv);
  
          LOCK2(cs_main, g_cs_orphans);
  
          bool fMissingInputs = false;
          CValidationState state;
  
          pfrom->setAskFor.erase(inv.hash);
          mapAlreadyAskedFor.erase(inv.hash);
  
          std::list<CTransactionRef> lRemovedTxn;
  
          if (!AlreadyHave(inv) &&
              AcceptToMemoryPool(mempool, state, ptx, &fMissingInputs, &lRemovedTxn, false /* bypass_limits */, 0 /* nAbsurdFee */)) {
              mempool.check(pcoinsTip.get());
              RelayTransaction(tx, connman);
              for (unsigned int i = 0; i < tx.vout.size(); i++) {
                  vWorkQueue.emplace_back(inv.hash, i);
              }
  
              pfrom->nLastTXTime = GetTime();
  
              LogPrint(BCLog::MEMPOOL, "AcceptToMemoryPool: peer=%d: accepted %s (poolsz %u txn, %u kB)\n",
                  pfrom->GetId(),
                  tx.GetHash().ToString(),
                  mempool.size(), mempool.DynamicMemoryUsage() / 1000);
  
              // Recursively process any orphan transactions that depended on this one
              std::set<NodeId> setMisbehaving;
              while (!vWorkQueue.empty()) {
                  auto itByPrev = mapOrphanTransactionsByPrev.find(vWorkQueue.front());
                  vWorkQueue.pop_front();
                  if (itByPrev == mapOrphanTransactionsByPrev.end())
                      continue;
                  for (auto mi = itByPrev->second.begin();
                       mi != itByPrev->second.end();
                       ++mi)
                  {
                      const CTransactionRef& porphanTx = (*mi)->second.tx;
                      const CTransaction& orphanTx = *porphanTx;
                      const uint256& orphanHash = orphanTx.GetHash();
                      NodeId fromPeer = (*mi)->second.fromPeer;
                      bool fMissingInputs2 = false;
                      // Use a dummy CValidationState so someone can't setup nodes to counter-DoS based on orphan
                      // resolution (that is, feeding people an invalid transaction based on LegitTxX in order to get
                      // anyone relaying LegitTxX banned)
                      CValidationState stateDummy;
  
  
                      if (setMisbehaving.count(fromPeer))
                          continue;
                      if (AcceptToMemoryPool(mempool, stateDummy, porphanTx, &fMissingInputs2, &lRemovedTxn, false /* bypass_limits */, 0 /* nAbsurdFee */)) {
                          LogPrint(BCLog::MEMPOOL, "   accepted orphan tx %s\n", orphanHash.ToString());
                          RelayTransaction(orphanTx, connman);
                          for (unsigned int i = 0; i < orphanTx.vout.size(); i++) {
                              vWorkQueue.emplace_back(orphanHash, i);
                          }
                          vEraseQueue.push_back(orphanHash);
                      }
                      else if (!fMissingInputs2)
                      {
                          int nDos = 0;
                          if (stateDummy.IsInvalid(nDos) && nDos > 0)
                          {
                              // Punish peer that gave us an invalid orphan tx
                              Misbehaving(fromPeer, nDos);
                              setMisbehaving.insert(fromPeer);
                              LogPrint(BCLog::MEMPOOL, "   invalid orphan tx %s\n", orphanHash.ToString());
                          }
                          // Has inputs but not accepted to mempool
                          // Probably non-standard or insufficient fee
                          LogPrint(BCLog::MEMPOOL, "   removed orphan tx %s\n", orphanHash.ToString());
                          vEraseQueue.push_back(orphanHash);
                          if (!orphanTx.HasWitness() && !stateDummy.CorruptionPossible()) {
                              // Do not use rejection cache for witness transactions or
                              // witness-stripped transactions, as they can have been malleated.
                              // See https://github.com/deftchain/deftchain/issues/8279 for details.
                              assert(recentRejects);
                              recentRejects->insert(orphanHash);
                          }
                      }
                      mempool.check(pcoinsTip.get());
                  }
              }
  
              for (uint256 hash : vEraseQueue)
                  EraseOrphanTx(hash);
          }
          else if (fMissingInputs)
          {
              bool fRejectedParents = false; // It may be the case that the orphans parents have all been rejected
              for (const CTxIn& txin : tx.vin) {
                  if (recentRejects->contains(txin.prevout.hash)) {
                      fRejectedParents = true;
                      break;
                  }
              }
              if (!fRejectedParents) {
                  uint32_t nFetchFlags = GetFetchFlags(pfrom);
                  for (const CTxIn& txin : tx.vin) {
                      CInv _inv(MSG_TX | nFetchFlags, txin.prevout.hash);
                      pfrom->AddInventoryKnown(_inv);
                      if (!AlreadyHave(_inv)) pfrom->AskFor(_inv);
                  }
                  AddOrphanTx(ptx, pfrom->GetId());
  
                  // DoS prevention: do not allow mapOrphanTransactions to grow unbounded
                  unsigned int nMaxOrphanTx = (unsigned int)std::max((int64_t)0, gArgs.GetArg("-maxorphantx", DEFAULT_MAX_ORPHAN_TRANSACTIONS));
                  unsigned int nEvicted = LimitOrphanTxSize(nMaxOrphanTx);
                  if (nEvicted > 0) {
                      LogPrint(BCLog::MEMPOOL, "mapOrphan overflow, removed %u tx\n", nEvicted);
                  }
              } else {
                  LogPrint(BCLog::MEMPOOL, "not keeping orphan with rejected parents %s\n",tx.GetHash().ToString());
                  // We will continue to reject this tx since it has rejected
                  // parents so avoid re-requesting it from other peers.
                  recentRejects->insert(tx.GetHash());
              }
          } else {
              if (!tx.HasWitness() && !state.CorruptionPossible()) {
                  // Do not use rejection cache for witness transactions or
                  // witness-stripped transactions, as they can have been malleated.
                  // See https://github.com/deftchain/deftchain/issues/8279 for details.
                  assert(recentRejects);
                  recentRejects->insert(tx.GetHash());
                  if (RecursiveDynamicUsage(*ptx) < 100000) {
                      AddToCompactExtraTransactions(ptx);
                  }
              } else if (tx.HasWitness() && RecursiveDynamicUsage(*ptx) < 100000) {
                  AddToCompactExtraTransactions(ptx);
              }
  
              if (pfrom->fWhitelisted && gArgs.GetBoolArg("-whitelistforcerelay", DEFAULT_WHITELISTFORCERELAY)) {
                  // Always relay transactions received from whitelisted peers, even
                  // if they were already in the mempool or rejected from it due
                  // to policy, allowing the node to function as a gateway for
                  // nodes hidden behind it.
                  //
                  // Never relay transactions that we would assign a non-zero DoS
                  // score for, as we expect peers to do the same with us in that
                  // case.
                  int nDoS = 0;
                  if (!state.IsInvalid(nDoS) || nDoS == 0) {
                      LogPrintf("Force relaying tx %s from whitelisted peer=%d\n", tx.GetHash().ToString(), pfrom->GetId());
                      RelayTransaction(tx, connman);
                  } else {
                      LogPrintf("Not relaying invalid transaction %s from whitelisted peer=%d (%s)\n", tx.GetHash().ToString(), pfrom->GetId(), FormatStateMessage(state));
                  }
              }
          }
  
          for (const CTransactionRef& removedTx : lRemovedTxn)
              AddToCompactExtraTransactions(removedTx);
  
          int nDoS = 0;
          if (state.IsInvalid(nDoS))
          {
              LogPrint(BCLog::MEMPOOLREJ, "%s from peer=%d was not accepted: %s\n", tx.GetHash().ToString(),
                  pfrom->GetId(),
                  FormatStateMessage(state));
              if (enable_bip61 && state.GetRejectCode() > 0 && state.GetRejectCode() < REJECT_INTERNAL) { // Never send AcceptToMemoryPool's internal codes over P2P
                  connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::REJECT, strCommand, (unsigned char)state.GetRejectCode(),
                                     state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), inv.hash));
              }
              if (nDoS > 0) {
                  Misbehaving(pfrom->GetId(), nDoS);
              }
          }
      }
  
  
      else if (strCommand == NetMsgType::CMPCTBLOCK && !fImporting && !fReindex) // Ignore blocks received while importing
      {
          CBlockHeaderAndShortTxIDs cmpctblock;
          vRecv >> cmpctblock;
  
          bool received_new_header = false;
  
          {
          LOCK(cs_main);
  
          if (!LookupBlockIndex(cmpctblock.header.hashPrevBlock)) {
              // Doesn't connect (or is genesis), instead of DoSing in AcceptBlockHeader, request deeper headers
              if (!IsInitialBlockDownload())
                  connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), uint256()));
              return true;
          }
  
          if (!LookupBlockIndex(cmpctblock.header.GetHash())) {
              received_new_header = true;
          }
          }
  
          const CBlockIndex *pindex = nullptr;
          CValidationState state;
          if (!ProcessNewBlockHeaders({cmpctblock.header}, state, chainparams, &pindex)) {
              int nDoS;
              if (state.IsInvalid(nDoS)) {
                  if (nDoS > 0) {
                      LOCK(cs_main);
                      Misbehaving(pfrom->GetId(), nDoS, strprintf("Peer %d sent us invalid header via cmpctblock\n", pfrom->GetId()));
                  } else {
                      LogPrint(BCLog::NET, "Peer %d sent us invalid header via cmpctblock\n", pfrom->GetId());
                  }
                  return true;
              }
          }
  
          // When we succeed in decoding a block's txids from a cmpctblock
          // message we typically jump to the BLOCKTXN handling code, with a
          // dummy (empty) BLOCKTXN message, to re-use the logic there in
          // completing processing of the putative block (without cs_main).
          bool fProcessBLOCKTXN = false;
          CDataStream blockTxnMsg(SER_NETWORK, PROTOCOL_VERSION);
  
          // If we end up treating this as a plain headers message, call that as well
          // without cs_main.
          bool fRevertToHeaderProcessing = false;
  
          // Keep a CBlock for "optimistic" compactblock reconstructions (see
          // below)
          std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
          bool fBlockReconstructed = false;
  
          {
          LOCK2(cs_main, g_cs_orphans);
          // If AcceptBlockHeader returned true, it set pindex
          assert(pindex);
          UpdateBlockAvailability(pfrom->GetId(), pindex->GetBlockHash());
  
          CNodeState *nodestate = State(pfrom->GetId());
  
          // If this was a new header with more work than our tip, update the
          // peer's last block announcement time
          if (received_new_header && pindex->nChainWork > chainActive.Tip()->nChainWork) {
              nodestate->m_last_block_announcement = GetTime();
          }
  
          std::map<uint256, std::pair<NodeId, std::list<QueuedBlock>::iterator> >::iterator blockInFlightIt = mapBlocksInFlight.find(pindex->GetBlockHash());
          bool fAlreadyInFlight = blockInFlightIt != mapBlocksInFlight.end();
  
          if (pindex->nStatus & BLOCK_HAVE_DATA) // Nothing to do here
              return true;
  
          if (pindex->nChainWork <= chainActive.Tip()->nChainWork || // We know something better
                  pindex->nTx != 0) { // We had this block at some point, but pruned it
              if (fAlreadyInFlight) {
                  // We requested this block for some reason, but our mempool will probably be useless
                  // so we just grab the block via normal getdata
                  std::vector<CInv> vInv(1);
                  vInv[0] = CInv(MSG_BLOCK | GetFetchFlags(pfrom), cmpctblock.header.GetHash());
                  connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vInv));
              }
              return true;
          }
  
          // If we're not close to tip yet, give up and let parallel block fetch work its magic
          if (!fAlreadyInFlight && !CanDirectFetch(chainparams.GetConsensus()))
              return true;
  
          if (IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) && !nodestate->fSupportsDesiredCmpctVersion) {
              // Don't bother trying to process compact blocks from v1 peers
              // after segwit activates.
              return true;
          }
  
          // We want to be a bit conservative just to be extra careful about DoS
          // possibilities in compact block processing...
          if (pindex->nHeight <= chainActive.Height() + 2) {
              if ((!fAlreadyInFlight && nodestate->nBlocksInFlight < MAX_BLOCKS_IN_TRANSIT_PER_PEER) ||
                   (fAlreadyInFlight && blockInFlightIt->second.first == pfrom->GetId())) {
                  std::list<QueuedBlock>::iterator* queuedBlockIt = nullptr;
                  if (!MarkBlockAsInFlight(pfrom->GetId(), pindex->GetBlockHash(), pindex, &queuedBlockIt)) {
                      if (!(*queuedBlockIt)->partialBlock)
                          (*queuedBlockIt)->partialBlock.reset(new PartiallyDownloadedBlock(&mempool));
                      else {
                          // The block was already in flight using compact blocks from the same peer
                          LogPrint(BCLog::NET, "Peer sent us compact block we were already syncing!\n");
                          return true;
                      }
                  }
  
                  PartiallyDownloadedBlock& partialBlock = *(*queuedBlockIt)->partialBlock;
                  ReadStatus status = partialBlock.InitData(cmpctblock, vExtraTxnForCompact);
                  if (status == READ_STATUS_INVALID) {
                      MarkBlockAsReceived(pindex->GetBlockHash()); // Reset in-flight state in case of whitelist
                      Misbehaving(pfrom->GetId(), 100, strprintf("Peer %d sent us invalid compact block\n", pfrom->GetId()));
                      return true;
                  } else if (status == READ_STATUS_FAILED) {
                      // Duplicate txindexes, the block is now in-flight, so just request it
                      std::vector<CInv> vInv(1);
                      vInv[0] = CInv(MSG_BLOCK | GetFetchFlags(pfrom), cmpctblock.header.GetHash());
                      connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vInv));
                      return true;
                  }
  
                  BlockTransactionsRequest req;
                  for (size_t i = 0; i < cmpctblock.BlockTxCount(); i++) {
                      if (!partialBlock.IsTxAvailable(i))
                          req.indexes.push_back(i);
                  }
                  if (req.indexes.empty()) {
                      // Dirty hack to jump to BLOCKTXN code (TODO: move message handling into their own functions)
                      BlockTransactions txn;
                      txn.blockhash = cmpctblock.header.GetHash();
                      blockTxnMsg << txn;
                      fProcessBLOCKTXN = true;
                  } else {
                      req.blockhash = pindex->GetBlockHash();
                      connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETBLOCKTXN, req));
                  }
              } else {
                  // This block is either already in flight from a different
                  // peer, or this peer has too many blocks outstanding to
                  // download from.
                  // Optimistically try to reconstruct anyway since we might be
                  // able to without any round trips.
                  PartiallyDownloadedBlock tempBlock(&mempool);
                  ReadStatus status = tempBlock.InitData(cmpctblock, vExtraTxnForCompact);
                  if (status != READ_STATUS_OK) {
                      // TODO: don't ignore failures
                      return true;
                  }
                  std::vector<CTransactionRef> dummy;
                  status = tempBlock.FillBlock(*pblock, dummy);
                  if (status == READ_STATUS_OK) {
                      fBlockReconstructed = true;
                  }
              }
          } else {
              if (fAlreadyInFlight) {
                  // We requested this block, but its far into the future, so our
                  // mempool will probably be useless - request the block normally
                  std::vector<CInv> vInv(1);
                  vInv[0] = CInv(MSG_BLOCK | GetFetchFlags(pfrom), cmpctblock.header.GetHash());
                  connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vInv));
                  return true;
              } else {
                  // If this was an announce-cmpctblock, we want the same treatment as a header message
                  fRevertToHeaderProcessing = true;
              }
          }
          } // cs_main
  
          if (fProcessBLOCKTXN)
              return ProcessMessage(pfrom, NetMsgType::BLOCKTXN, blockTxnMsg, nTimeReceived, chainparams, connman, interruptMsgProc, enable_bip61);
  
          if (fRevertToHeaderProcessing) {
              // Headers received from HB compact block peers are permitted to be
              // relayed before full validation (see BIP 152), so we don't want to disconnect
              // the peer if the header turns out to be for an invalid block.
              // Note that if a peer tries to build on an invalid chain, that
              // will be detected and the peer will be banned.
              return ProcessHeadersMessage(pfrom, connman, {cmpctblock.header}, chainparams, /*punish_duplicate_invalid=*/false);
          }
  
          if (fBlockReconstructed) {
              // If we got here, we were able to optimistically reconstruct a
              // block that is in flight from some other peer.
              {
                  LOCK(cs_main);
                  mapBlockSource.emplace(pblock->GetHash(), std::make_pair(pfrom->GetId(), false));
              }
              bool fNewBlock = false;
              // Setting fForceProcessing to true means that we bypass some of
              // our anti-DoS protections in AcceptBlock, which filters
              // unrequested blocks that might be trying to waste our resources
              // (eg disk space). Because we only try to reconstruct blocks when
              // we're close to caught up (via the CanDirectFetch() requirement
              // above, combined with the behavior of not requesting blocks until
              // we have a chain with at least nMinimumChainWork), and we ignore
              // compact blocks with less work than our tip, it is safe to treat
              // reconstructed compact blocks as having been requested.
              ProcessNewBlock(chainparams, pblock, /*fForceProcessing=*/true, &fNewBlock);
              if (fNewBlock) {
                  pfrom->nLastBlockTime = GetTime();
              } else {
                  LOCK(cs_main);
                  mapBlockSource.erase(pblock->GetHash());
              }
              LOCK(cs_main); // hold cs_main for CBlockIndex::IsValid()
              if (pindex->IsValid(BLOCK_VALID_TRANSACTIONS)) {
                  // Clear download state for this block, which is in
                  // process from some other peer.  We do this after calling
                  // ProcessNewBlock so that a malleated cmpctblock announcement
                  // can't be used to interfere with block relay.
                  MarkBlockAsReceived(pblock->GetHash());
              }
          }
  
      }
  
      else if (strCommand == NetMsgType::BLOCKTXN && !fImporting && !fReindex) // Ignore blocks received while importing
      {
          BlockTransactions resp;
          vRecv >> resp;
  
          std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
          bool fBlockRead = false;
          {
              LOCK(cs_main);
  
              std::map<uint256, std::pair<NodeId, std::list<QueuedBlock>::iterator> >::iterator it = mapBlocksInFlight.find(resp.blockhash);
              if (it == mapBlocksInFlight.end() || !it->second.second->partialBlock ||
                      it->second.first != pfrom->GetId()) {
                  LogPrint(BCLog::NET, "Peer %d sent us block transactions for block we weren't expecting\n", pfrom->GetId());
                  return true;
              }
  
              PartiallyDownloadedBlock& partialBlock = *it->second.second->partialBlock;
              ReadStatus status = partialBlock.FillBlock(*pblock, resp.txn);
              if (status == READ_STATUS_INVALID) {
                  MarkBlockAsReceived(resp.blockhash); // Reset in-flight state in case of whitelist
                  Misbehaving(pfrom->GetId(), 100, strprintf("Peer %d sent us invalid compact block/non-matching block transactions\n", pfrom->GetId()));
                  return true;
              } else if (status == READ_STATUS_FAILED) {
                  // Might have collided, fall back to getdata now :(
                  std::vector<CInv> invs;
                  invs.push_back(CInv(MSG_BLOCK | GetFetchFlags(pfrom), resp.blockhash));
                  connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, invs));
              } else {
                  // Block is either okay, or possibly we received
                  // READ_STATUS_CHECKBLOCK_FAILED.
                  // Note that CheckBlock can only fail for one of a few reasons:
                  // 1. bad-proof-of-work (impossible here, because we've already
                  //    accepted the header)
                  // 2. merkleroot doesn't match the transactions given (already
                  //    caught in FillBlock with READ_STATUS_FAILED, so
                  //    impossible here)
                  // 3. the block is otherwise invalid (eg invalid coinbase,
                  //    block is too big, too many legacy sigops, etc).
                  // So if CheckBlock failed, #3 is the only possibility.
                  // Under BIP 152, we don't DoS-ban unless proof of work is
                  // invalid (we don't require all the stateless checks to have
                  // been run).  This is handled below, so just treat this as
                  // though the block was successfully read, and rely on the
                  // handling in ProcessNewBlock to ensure the block index is
                  // updated, reject messages go out, etc.
                  MarkBlockAsReceived(resp.blockhash); // it is now an empty pointer
                  fBlockRead = true;
                  // mapBlockSource is only used for sending reject messages and DoS scores,
                  // so the race between here and cs_main in ProcessNewBlock is fine.
                  // BIP 152 permits peers to relay compact blocks after validating
                  // the header only; we should not punish peers if the block turns
                  // out to be invalid.
                  mapBlockSource.emplace(resp.blockhash, std::make_pair(pfrom->GetId(), false));
              }
          } // Don't hold cs_main when we call into ProcessNewBlock
          if (fBlockRead) {
              bool fNewBlock = false;
              // Since we requested this block (it was in mapBlocksInFlight), force it to be processed,
              // even if it would not be a candidate for new tip (missing previous block, chain not long enough, etc)
              // This bypasses some anti-DoS logic in AcceptBlock (eg to prevent
              // disk-space attacks), but this should be safe due to the
              // protections in the compact block handler -- see related comment
              // in compact block optimistic reconstruction handling.
              ProcessNewBlock(chainparams, pblock, /*fForceProcessing=*/true, &fNewBlock);
              if (fNewBlock) {
                  pfrom->nLastBlockTime = GetTime();
              } else {
                  LOCK(cs_main);
                  mapBlockSource.erase(pblock->GetHash());
              }
          }
      }
  
  
      else if (strCommand == NetMsgType::HEADERS && !fImporting && !fReindex) // Ignore headers received while importing
      {
          std::vector<CBlockHeader> headers;
  
          // Bypass the normal CBlock deserialization, as we don't want to risk deserializing 2000 full blocks.
          unsigned int nCount = ReadCompactSize(vRecv);
          if (nCount > MAX_HEADERS_RESULTS) {
              LOCK(cs_main);
              Misbehaving(pfrom->GetId(), 20, strprintf("headers message size = %u", nCount));
              return false;
          }
          headers.resize(nCount);
          for (unsigned int n = 0; n < nCount; n++) {
              vRecv >> headers[n];
              ReadCompactSize(vRecv); // ignore tx count; assume it is 0.
          }
  
          // Headers received via a HEADERS message should be valid, and reflect
          // the chain the peer is on. If we receive a known-invalid header,
          // disconnect the peer if it is using one of our outbound connection
          // slots.
          bool should_punish = !pfrom->fInbound && !pfrom->m_manual_connection;
          return ProcessHeadersMessage(pfrom, connman, headers, chainparams, should_punish);
      }
  
      else if (strCommand == NetMsgType::BLOCK && !fImporting && !fReindex) // Ignore blocks received while importing
      {
          std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
          vRecv >> *pblock;
  
          LogPrint(BCLog::NET, "received block %s peer=%d\n", pblock->GetHash().ToString(), pfrom->GetId());
  
          bool forceProcessing = false;
          const uint256 hash(pblock->GetHash());
          {
              LOCK(cs_main);
              // Also always process if we requested the block explicitly, as we may
              // need it even though it is not a candidate for a new best tip.
              forceProcessing |= MarkBlockAsReceived(hash);
              // mapBlockSource is only used for sending reject messages and DoS scores,
              // so the race between here and cs_main in ProcessNewBlock is fine.
              mapBlockSource.emplace(hash, std::make_pair(pfrom->GetId(), true));
          }
          bool fNewBlock = false;
          ProcessNewBlock(chainparams, pblock, forceProcessing, &fNewBlock);
          if (fNewBlock) {
              pfrom->nLastBlockTime = GetTime();
          } else {
              LOCK(cs_main);
              mapBlockSource.erase(pblock->GetHash());
          }
      }
  
  
      else if (strCommand == NetMsgType::GETADDR)
      {
          // This asymmetric behavior for inbound and outbound connections was introduced
          // to prevent a fingerprinting attack: an attacker can send specific fake addresses
          // to users' AddrMan and later request them by sending getaddr messages.
          // Making nodes which are behind NAT and can only make outgoing connections ignore
          // the getaddr message mitigates the attack.
          if (!pfrom->fInbound) {
              LogPrint(BCLog::NET, "Ignoring \"getaddr\" from outbound connection. peer=%d\n", pfrom->GetId());
              return true;
          }
  
          // Only send one GetAddr response per connection to reduce resource waste
          //  and discourage addr stamping of INV announcements.
          if (pfrom->fSentAddr) {
              LogPrint(BCLog::NET, "Ignoring repeated \"getaddr\". peer=%d\n", pfrom->GetId());
              return true;
          }
          pfrom->fSentAddr = true;
  
          pfrom->vAddrToSend.clear();
          std::vector<CAddress> vAddr = connman->GetAddresses();
          FastRandomContext insecure_rand;
          for (const CAddress &addr : vAddr)
              pfrom->PushAddress(addr, insecure_rand);
      }
  
  
      else if (strCommand == NetMsgType::MEMPOOL)
      {
          if (!(pfrom->GetLocalServices() & NODE_BLOOM) && !pfrom->fWhitelisted)
          {
              LogPrint(BCLog::NET, "mempool request with bloom filters disabled, disconnect peer=%d\n", pfrom->GetId());
              pfrom->fDisconnect = true;
              return true;
          }
  
          if (connman->OutboundTargetReached(false) && !pfrom->fWhitelisted)
          {
              LogPrint(BCLog::NET, "mempool request with bandwidth limit reached, disconnect peer=%d\n", pfrom->GetId());
              pfrom->fDisconnect = true;
              return true;
          }
  
          LOCK(pfrom->cs_inventory);
          pfrom->fSendMempool = true;
      }
  
  
      else if (strCommand == NetMsgType::PING)
      {
          if (pfrom->nVersion > BIP0031_VERSION)
          {
              uint64_t nonce = 0;
              vRecv >> nonce;
              // Echo the message back with the nonce. This allows for two useful features:
              //
              // 1) A remote node can quickly check if the connection is operational
              // 2) Remote nodes can measure the latency of the network thread. If this node
              //    is overloaded it won't respond to pings quickly and the remote node can
              //    avoid sending us more work, like chain download requests.
              //
              // The nonce stops the remote getting confused between different pings: without
              // it, if the remote node sends a ping once per second and this node takes 5
              // seconds to respond to each, the 5th ping the remote sends would appear to
              // return very quickly.
              connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::PONG, nonce));
          }
      }
  
  
      else if (strCommand == NetMsgType::PONG)
      {
          int64_t pingUsecEnd = nTimeReceived;
          uint64_t nonce = 0;
          size_t nAvail = vRecv.in_avail();
          bool bPingFinished = false;
          std::string sProblem;
  
          if (nAvail >= sizeof(nonce)) {
              vRecv >> nonce;
  
              // Only process pong message if there is an outstanding ping (old ping without nonce should never pong)
              if (pfrom->nPingNonceSent != 0) {
                  if (nonce == pfrom->nPingNonceSent) {
                      // Matching pong received, this ping is no longer outstanding
                      bPingFinished = true;
                      int64_t pingUsecTime = pingUsecEnd - pfrom->nPingUsecStart;
                      if (pingUsecTime > 0) {
                          // Successful ping time measurement, replace previous
                          pfrom->nPingUsecTime = pingUsecTime;
                          pfrom->nMinPingUsecTime = std::min(pfrom->nMinPingUsecTime.load(), pingUsecTime);
                      } else {
                          // This should never happen
                          sProblem = "Timing mishap";
                      }
                  } else {
                      // Nonce mismatches are normal when pings are overlapping
                      sProblem = "Nonce mismatch";
                      if (nonce == 0) {
                          // This is most likely a bug in another implementation somewhere; cancel this ping
                          bPingFinished = true;
                          sProblem = "Nonce zero";
                      }
                  }
              } else {
                  sProblem = "Unsolicited pong without ping";
              }
          } else {
              // This is most likely a bug in another implementation somewhere; cancel this ping
              bPingFinished = true;
              sProblem = "Short payload";
          }
  
          if (!(sProblem.empty())) {
              LogPrint(BCLog::NET, "pong peer=%d: %s, %x expected, %x received, %u bytes\n",
                  pfrom->GetId(),
                  sProblem,
                  pfrom->nPingNonceSent,
                  nonce,
                  nAvail);
          }
          if (bPingFinished) {
              pfrom->nPingNonceSent = 0;
          }
      }
  
  
      else if (strCommand == NetMsgType::FILTERLOAD)
      {
          CBloomFilter filter;
          vRecv >> filter;
  
          if (!filter.IsWithinSizeConstraints())
          {
              // There is no excuse for sending a too-large filter
              LOCK(cs_main);
              Misbehaving(pfrom->GetId(), 100);
          }
          else
          {
              LOCK(pfrom->cs_filter);
              pfrom->pfilter.reset(new CBloomFilter(filter));
              pfrom->pfilter->UpdateEmptyFull();
              pfrom->fRelayTxes = true;
          }
      }
  
  
      else if (strCommand == NetMsgType::FILTERADD)
      {
          std::vector<unsigned char> vData;
          vRecv >> vData;
  
          // Nodes must NEVER send a data item > 520 bytes (the max size for a script data object,
          // and thus, the maximum size any matched object can have) in a filteradd message
          bool bad = false;
          if (vData.size() > MAX_SCRIPT_ELEMENT_SIZE) {
              bad = true;
          } else {
              LOCK(pfrom->cs_filter);
              if (pfrom->pfilter) {
                  pfrom->pfilter->insert(vData);
              } else {
                  bad = true;
              }
          }
          if (bad) {
              LOCK(cs_main);
              Misbehaving(pfrom->GetId(), 100);
          }
      }
  
  
      else if (strCommand == NetMsgType::FILTERCLEAR)
      {
          LOCK(pfrom->cs_filter);
          if (pfrom->GetLocalServices() & NODE_BLOOM) {
              pfrom->pfilter.reset(new CBloomFilter());
          }
          pfrom->fRelayTxes = true;
      }
  
      else if (strCommand == NetMsgType::FEEFILTER) {
          CAmount newFeeFilter = 0;
          vRecv >> newFeeFilter;
          if (MoneyRange(newFeeFilter)) {
              {
                  LOCK(pfrom->cs_feeFilter);
                  pfrom->minFeeFilter = newFeeFilter;
              }
              LogPrint(BCLog::NET, "received: feefilter of %s from peer=%d\n", CFeeRate(newFeeFilter).ToString(), pfrom->GetId());
          }
      }
  
      else if (strCommand == NetMsgType::NOTFOUND) {
          // We do not care about the NOTFOUND message, but logging an Unknown Command
          // message would be undesirable as we transmit it ourselves.
      }
  
      else {
          // Ignore unknown commands for extensibility
          LogPrint(BCLog::NET, "Unknown command \"%s\" from peer=%d\n", SanitizeString(strCommand), pfrom->GetId());
      }
  
  
  
      return true;
  }
  
  static bool SendRejectsAndCheckIfBanned(CNode* pnode, CConnman* connman, bool enable_bip61)
  {
      AssertLockHeld(cs_main);
      CNodeState &state = *State(pnode->GetId());
  
      if (enable_bip61) {
          for (const CBlockReject& reject : state.rejects) {
              connman->PushMessage(pnode, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, std::string(NetMsgType::BLOCK), reject.chRejectCode, reject.strRejectReason, reject.hashBlock));
          }
      }
      state.rejects.clear();
  
      if (state.fShouldBan) {
          state.fShouldBan = false;
          if (pnode->fWhitelisted)
              LogPrintf("Warning: not punishing whitelisted peer %s!\n", pnode->addr.ToString());
          else if (pnode->m_manual_connection)
              LogPrintf("Warning: not punishing manually-connected peer %s!\n", pnode->addr.ToString());
          else {
              pnode->fDisconnect = true;
              if (pnode->addr.IsLocal())
                  LogPrintf("Warning: not banning local peer %s!\n", pnode->addr.ToString());
              else
              {
                  connman->Ban(pnode->addr, BanReasonNodeMisbehaving);
              }
          }
          return true;
      }
      return false;
  }
  
  bool PeerLogicValidation::ProcessMessages(CNode* pfrom, std::atomic<bool>& interruptMsgProc)
  {
      const CChainParams& chainparams = Params();
      //
      // Message format
      //  (4) message start
      //  (12) command
      //  (4) size
      //  (4) checksum
      //  (x) data
      //
      bool fMoreWork = false;
  
      if (!pfrom->vRecvGetData.empty())
          ProcessGetData(pfrom, chainparams, connman, interruptMsgProc);
  
      if (pfrom->fDisconnect)
          return false;
  
      // this maintains the order of responses
      if (!pfrom->vRecvGetData.empty()) return true;
  
      // Don't bother if send buffer is too full to respond anyway
      if (pfrom->fPauseSend)
          return false;
  
      std::list<CNetMessage> msgs;
      {
          LOCK(pfrom->cs_vProcessMsg);
          if (pfrom->vProcessMsg.empty())
              return false;
          // Just take one message
          msgs.splice(msgs.begin(), pfrom->vProcessMsg, pfrom->vProcessMsg.begin());
          pfrom->nProcessQueueSize -= msgs.front().vRecv.size() + CMessageHeader::HEADER_SIZE;
          pfrom->fPauseRecv = pfrom->nProcessQueueSize > connman->GetReceiveFloodSize();
          fMoreWork = !pfrom->vProcessMsg.empty();
      }
      CNetMessage& msg(msgs.front());
  
      msg.SetVersion(pfrom->GetRecvVersion());
      // Scan for message start
      if (memcmp(msg.hdr.pchMessageStart, chainparams.MessageStart(), CMessageHeader::MESSAGE_START_SIZE) != 0) {
          LogPrint(BCLog::NET, "PROCESSMESSAGE: INVALID MESSAGESTART %s peer=%d\n", SanitizeString(msg.hdr.GetCommand()), pfrom->GetId());
          pfrom->fDisconnect = true;
          return false;
      }
  
      // Read header
      CMessageHeader& hdr = msg.hdr;
      if (!hdr.IsValid(chainparams.MessageStart()))
      {
          LogPrint(BCLog::NET, "PROCESSMESSAGE: ERRORS IN HEADER %s peer=%d\n", SanitizeString(hdr.GetCommand()), pfrom->GetId());
          return fMoreWork;
      }
      std::string strCommand = hdr.GetCommand();
  
      // Message size
      unsigned int nMessageSize = hdr.nMessageSize;
  
      // Checksum
      CDataStream& vRecv = msg.vRecv;
      const uint256& hash = msg.GetMessageHash();
      if (memcmp(hash.begin(), hdr.pchChecksum, CMessageHeader::CHECKSUM_SIZE) != 0)
      {
          LogPrint(BCLog::NET, "%s(%s, %u bytes): CHECKSUM ERROR expected %s was %s\n", __func__,
             SanitizeString(strCommand), nMessageSize,
             HexStr(hash.begin(), hash.begin()+CMessageHeader::CHECKSUM_SIZE),
             HexStr(hdr.pchChecksum, hdr.pchChecksum+CMessageHeader::CHECKSUM_SIZE));
          return fMoreWork;
      }
  
      // Process message
      bool fRet = false;
      try
      {
          fRet = ProcessMessage(pfrom, strCommand, vRecv, msg.nTime, chainparams, connman, interruptMsgProc, m_enable_bip61);
          if (interruptMsgProc)
              return false;
          if (!pfrom->vRecvGetData.empty())
              fMoreWork = true;
      }
      catch (const std::ios_base::failure& e)
      {
          if (m_enable_bip61) {
              connman->PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_MALFORMED, std::string("error parsing message")));
          }
          if (strstr(e.what(), "end of data"))
          {
              // Allow exceptions from under-length message on vRecv
              LogPrint(BCLog::NET, "%s(%s, %u bytes): Exception '%s' caught, normally caused by a message being shorter than its stated length\n", __func__, SanitizeString(strCommand), nMessageSize, e.what());
          }
          else if (strstr(e.what(), "size too large"))
          {
              // Allow exceptions from over-long size
              LogPrint(BCLog::NET, "%s(%s, %u bytes): Exception '%s' caught\n", __func__, SanitizeString(strCommand), nMessageSize, e.what());
          }
          else if (strstr(e.what(), "non-canonical ReadCompactSize()"))
          {
              // Allow exceptions from non-canonical encoding
              LogPrint(BCLog::NET, "%s(%s, %u bytes): Exception '%s' caught\n", __func__, SanitizeString(strCommand), nMessageSize, e.what());
          }
          else
          {
              PrintExceptionContinue(&e, "ProcessMessages()");
          }
      }
      catch (const std::exception& e) {
          PrintExceptionContinue(&e, "ProcessMessages()");
      } catch (...) {
          PrintExceptionContinue(nullptr, "ProcessMessages()");
      }
  
      if (!fRet) {
          LogPrint(BCLog::NET, "%s(%s, %u bytes) FAILED peer=%d\n", __func__, SanitizeString(strCommand), nMessageSize, pfrom->GetId());
      }
  
      LOCK(cs_main);
      SendRejectsAndCheckIfBanned(pfrom, connman, m_enable_bip61);
  
      return fMoreWork;
  }
  
  void PeerLogicValidation::ConsiderEviction(CNode *pto, int64_t time_in_seconds)
  {
      AssertLockHeld(cs_main);
  
      CNodeState &state = *State(pto->GetId());
      const CNetMsgMaker msgMaker(pto->GetSendVersion());
  
      if (!state.m_chain_sync.m_protect && IsOutboundDisconnectionCandidate(pto) && state.fSyncStarted) {
          // This is an outbound peer subject to disconnection if they don't
          // announce a block with as much work as the current tip within
          // CHAIN_SYNC_TIMEOUT + HEADERS_RESPONSE_TIME seconds (note: if
          // their chain has more work than ours, we should sync to it,
          // unless it's invalid, in which case we should find that out and
          // disconnect from them elsewhere).
          if (state.pindexBestKnownBlock != nullptr && state.pindexBestKnownBlock->nChainWork >= chainActive.Tip()->nChainWork) {
              if (state.m_chain_sync.m_timeout != 0) {
                  state.m_chain_sync.m_timeout = 0;
                  state.m_chain_sync.m_work_header = nullptr;
                  state.m_chain_sync.m_sent_getheaders = false;
              }
          } else if (state.m_chain_sync.m_timeout == 0 || (state.m_chain_sync.m_work_header != nullptr && state.pindexBestKnownBlock != nullptr && state.pindexBestKnownBlock->nChainWork >= state.m_chain_sync.m_work_header->nChainWork)) {
              // Our best block known by this peer is behind our tip, and we're either noticing
              // that for the first time, OR this peer was able to catch up to some earlier point
              // where we checked against our tip.
              // Either way, set a new timeout based on current tip.
              state.m_chain_sync.m_timeout = time_in_seconds + CHAIN_SYNC_TIMEOUT;
              state.m_chain_sync.m_work_header = chainActive.Tip();
              state.m_chain_sync.m_sent_getheaders = false;
          } else if (state.m_chain_sync.m_timeout > 0 && time_in_seconds > state.m_chain_sync.m_timeout) {
              // No evidence yet that our peer has synced to a chain with work equal to that
              // of our tip, when we first detected it was behind. Send a single getheaders
              // message to give the peer a chance to update us.
              if (state.m_chain_sync.m_sent_getheaders) {
                  // They've run out of time to catch up!
                  LogPrintf("Disconnecting outbound peer %d for old chain, best known block = %s\n", pto->GetId(), state.pindexBestKnownBlock != nullptr ? state.pindexBestKnownBlock->GetBlockHash().ToString() : "<none>");
                  pto->fDisconnect = true;
              } else {
                  assert(state.m_chain_sync.m_work_header);
                  LogPrint(BCLog::NET, "sending getheaders to outbound peer=%d to verify chain work (current best known block:%s, benchmark blockhash: %s)\n", pto->GetId(), state.pindexBestKnownBlock != nullptr ? state.pindexBestKnownBlock->GetBlockHash().ToString() : "<none>", state.m_chain_sync.m_work_header->GetBlockHash().ToString());
                  connman->PushMessage(pto, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(state.m_chain_sync.m_work_header->pprev), uint256()));
                  state.m_chain_sync.m_sent_getheaders = true;
                  constexpr int64_t HEADERS_RESPONSE_TIME = 120; // 2 minutes
                  // Bump the timeout to allow a response, which could clear the timeout
                  // (if the response shows the peer has synced), reset the timeout (if
                  // the peer syncs to the required work but not to our tip), or result
                  // in disconnect (if we advance to the timeout and pindexBestKnownBlock
                  // has not sufficiently progressed)
                  state.m_chain_sync.m_timeout = time_in_seconds + HEADERS_RESPONSE_TIME;
              }
          }
      }
  }
  
  void PeerLogicValidation::EvictExtraOutboundPeers(int64_t time_in_seconds)
  {
      // Check whether we have too many outbound peers
      int extra_peers = connman->GetExtraOutboundCount();
      if (extra_peers > 0) {
          // If we have more outbound peers than we target, disconnect one.
          // Pick the outbound peer that least recently announced
          // us a new block, with ties broken by choosing the more recent
          // connection (higher node id)
          NodeId worst_peer = -1;
          int64_t oldest_block_announcement = std::numeric_limits<int64_t>::max();
  
          LOCK(cs_main);
  
          connman->ForEachNode([&](CNode* pnode) {
              AssertLockHeld(cs_main);
  
              // Ignore non-outbound peers, or nodes marked for disconnect already
              if (!IsOutboundDisconnectionCandidate(pnode) || pnode->fDisconnect) return;
              CNodeState *state = State(pnode->GetId());
              if (state == nullptr) return; // shouldn't be possible, but just in case
              // Don't evict our protected peers
              if (state->m_chain_sync.m_protect) return;
              if (state->m_last_block_announcement < oldest_block_announcement || (state->m_last_block_announcement == oldest_block_announcement && pnode->GetId() > worst_peer)) {
                  worst_peer = pnode->GetId();
                  oldest_block_announcement = state->m_last_block_announcement;
              }
          });
          if (worst_peer != -1) {
              bool disconnected = connman->ForNode(worst_peer, [&](CNode *pnode) {
                  AssertLockHeld(cs_main);
  
                  // Only disconnect a peer that has been connected to us for
                  // some reasonable fraction of our check-frequency, to give
                  // it time for new information to have arrived.
                  // Also don't disconnect any peer we're trying to download a
                  // block from.
                  CNodeState &state = *State(pnode->GetId());
                  if (time_in_seconds - pnode->nTimeConnected > MINIMUM_CONNECT_TIME && state.nBlocksInFlight == 0) {
                      LogPrint(BCLog::NET, "disconnecting extra outbound peer=%d (last block announcement received at time %d)\n", pnode->GetId(), oldest_block_announcement);
                      pnode->fDisconnect = true;
                      return true;
                  } else {
                      LogPrint(BCLog::NET, "keeping outbound peer=%d chosen for eviction (connect time: %d, blocks_in_flight: %d)\n", pnode->GetId(), pnode->nTimeConnected, state.nBlocksInFlight);
                      return false;
                  }
              });
              if (disconnected) {
                  // If we disconnected an extra peer, that means we successfully
                  // connected to at least one peer after the last time we
                  // detected a stale tip. Don't try any more extra peers until
                  // we next detect a stale tip, to limit the load we put on the
                  // network from these extra connections.
                  connman->SetTryNewOutboundPeer(false);
              }
          }
      }
  }
  
  void PeerLogicValidation::CheckForStaleTipAndEvictPeers(const Consensus::Params &consensusParams)
  {
      if (connman == nullptr) return;
  
      int64_t time_in_seconds = GetTime();
  
      EvictExtraOutboundPeers(time_in_seconds);
  
      if (time_in_seconds > m_stale_tip_check_time) {
          LOCK(cs_main);
          // Check whether our tip is stale, and if so, allow using an extra
          // outbound peer
          if (TipMayBeStale(consensusParams)) {
              LogPrintf("Potential stale tip detected, will try using extra outbound peer (last tip update: %d seconds ago)\n", time_in_seconds - g_last_tip_update);
              connman->SetTryNewOutboundPeer(true);
          } else if (connman->GetTryNewOutboundPeer()) {
              connman->SetTryNewOutboundPeer(false);
          }
          m_stale_tip_check_time = time_in_seconds + STALE_CHECK_INTERVAL;
      }
  }
  
  namespace {
  class CompareInvMempoolOrder
  {
      CTxMemPool *mp;
  public:
      explicit CompareInvMempoolOrder(CTxMemPool *_mempool)
      {
          mp = _mempool;
      }
  
      bool operator()(std::set<uint256>::iterator a, std::set<uint256>::iterator b)
      {
          /* As std::make_heap produces a max-heap, we want the entries with the
           * fewest ancestors/highest fee to sort later. */
          return mp->CompareDepthAndScore(*b, *a);
      }
  };
  }
  
  bool PeerLogicValidation::SendMessages(CNode* pto)
  {
      const Consensus::Params& consensusParams = Params().GetConsensus();
      {
          // Don't send anything until the version handshake is complete
          if (!pto->fSuccessfullyConnected || pto->fDisconnect)
              return true;
  
          // If we get here, the outgoing message serialization version is set and can't change.
          const CNetMsgMaker msgMaker(pto->GetSendVersion());
  
          //
          // Message: ping
          //
          bool pingSend = false;
          if (pto->fPingQueued) {
              // RPC ping request by user
              pingSend = true;
          }
          if (pto->nPingNonceSent == 0 && pto->nPingUsecStart + PING_INTERVAL * 1000000 < GetTimeMicros()) {
              // Ping automatically sent as a latency probe & keepalive.
              pingSend = true;
          }
          if (pingSend) {
              uint64_t nonce = 0;
              while (nonce == 0) {
                  GetRandBytes((unsigned char*)&nonce, sizeof(nonce));
              }
              pto->fPingQueued = false;
              pto->nPingUsecStart = GetTimeMicros();
              if (pto->nVersion > BIP0031_VERSION) {
                  pto->nPingNonceSent = nonce;
                  connman->PushMessage(pto, msgMaker.Make(NetMsgType::PING, nonce));
              } else {
                  // Peer is too old to support ping command with nonce, pong will never arrive.
                  pto->nPingNonceSent = 0;
                  connman->PushMessage(pto, msgMaker.Make(NetMsgType::PING));
              }
          }
  
          TRY_LOCK(cs_main, lockMain); // Acquire cs_main for IsInitialBlockDownload() and CNodeState()
          if (!lockMain)
              return true;
  
          if (SendRejectsAndCheckIfBanned(pto, connman, m_enable_bip61))
              return true;
          CNodeState &state = *State(pto->GetId());
  
          // Address refresh broadcast
          int64_t nNow = GetTimeMicros();
          if (!IsInitialBlockDownload() && pto->nNextLocalAddrSend < nNow) {
              AdvertiseLocal(pto);
              pto->nNextLocalAddrSend = PoissonNextSend(nNow, AVG_LOCAL_ADDRESS_BROADCAST_INTERVAL);
          }
  
          //
          // Message: addr
          //
          if (pto->nNextAddrSend < nNow) {
              pto->nNextAddrSend = PoissonNextSend(nNow, AVG_ADDRESS_BROADCAST_INTERVAL);
              std::vector<CAddress> vAddr;
              vAddr.reserve(pto->vAddrToSend.size());
              for (const CAddress& addr : pto->vAddrToSend)
              {
                  if (!pto->addrKnown.contains(addr.GetKey()))
                  {
                      pto->addrKnown.insert(addr.GetKey());
                      vAddr.push_back(addr);
                      // receiver rejects addr messages larger than 1000
                      if (vAddr.size() >= 1000)
                      {
                          connman->PushMessage(pto, msgMaker.Make(NetMsgType::ADDR, vAddr));
                          vAddr.clear();
                      }
                  }
              }
              pto->vAddrToSend.clear();
              if (!vAddr.empty())
                  connman->PushMessage(pto, msgMaker.Make(NetMsgType::ADDR, vAddr));
              // we only send the big addr message once
              if (pto->vAddrToSend.capacity() > 40)
                  pto->vAddrToSend.shrink_to_fit();
          }
  
          // Start block sync
          if (pindexBestHeader == nullptr)
              pindexBestHeader = chainActive.Tip();
          bool fFetch = state.fPreferredDownload || (nPreferredDownload == 0 && !pto->fClient && !pto->fOneShot); // Download if this is a nice peer, or we have no nice peers and this one might do.
          if (!state.fSyncStarted && !pto->fClient && !fImporting && !fReindex) {
              // Only actively request headers from a single peer, unless we're close to today.
              if ((nSyncStarted == 0 && fFetch) || pindexBestHeader->GetBlockTime() > GetAdjustedTime() - 24 * 60 * 60) {
                  state.fSyncStarted = true;
                  state.nHeadersSyncTimeout = GetTimeMicros() + HEADERS_DOWNLOAD_TIMEOUT_BASE + HEADERS_DOWNLOAD_TIMEOUT_PER_HEADER * (GetAdjustedTime() - pindexBestHeader->GetBlockTime())/(consensusParams.nPowTargetSpacing);
                  nSyncStarted++;
                  const CBlockIndex *pindexStart = pindexBestHeader;
                  /* If possible, start at the block preceding the currently
                     best known header.  This ensures that we always get a
                     non-empty list of headers back as long as the peer
                     is up-to-date.  With a non-empty response, we can initialise
                     the peer's known best block.  This wouldn't be possible
                     if we requested starting at pindexBestHeader and
                     got back an empty response.  */
                  if (pindexStart->pprev)
                      pindexStart = pindexStart->pprev;
                  LogPrint(BCLog::NET, "initial getheaders (%d) to peer=%d (startheight:%d)\n", pindexStart->nHeight, pto->GetId(), pto->nStartingHeight);
                  connman->PushMessage(pto, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexStart), uint256()));
              }
          }
  
          // Resend wallet transactions that haven't gotten in a block yet
          // Except during reindex, importing and IBD, when old wallet
          // transactions become unconfirmed and spams other nodes.
          if (!fReindex && !fImporting && !IsInitialBlockDownload())
          {
              GetMainSignals().Broadcast(nTimeBestReceived, connman);
          }
  
          //
          // Try sending block announcements via headers
          //
          {
              // If we have less than MAX_BLOCKS_TO_ANNOUNCE in our
              // list of block hashes we're relaying, and our peer wants
              // headers announcements, then find the first header
              // not yet known to our peer but would connect, and send.
              // If no header would connect, or if we have too many
              // blocks, or if the peer doesn't want headers, just
              // add all to the inv queue.
              LOCK(pto->cs_inventory);
              std::vector<CBlock> vHeaders;
              bool fRevertToInv = ((!state.fPreferHeaders &&
                                   (!state.fPreferHeaderAndIDs || pto->vBlockHashesToAnnounce.size() > 1)) ||
                                  pto->vBlockHashesToAnnounce.size() > MAX_BLOCKS_TO_ANNOUNCE);
              const CBlockIndex *pBestIndex = nullptr; // last header queued for delivery
              ProcessBlockAvailability(pto->GetId()); // ensure pindexBestKnownBlock is up-to-date
  
              if (!fRevertToInv) {
                  bool fFoundStartingHeader = false;
                  // Try to find first header that our peer doesn't have, and
                  // then send all headers past that one.  If we come across any
                  // headers that aren't on chainActive, give up.
                  for (const uint256 &hash : pto->vBlockHashesToAnnounce) {
                      const CBlockIndex* pindex = LookupBlockIndex(hash);
                      assert(pindex);
                      if (chainActive[pindex->nHeight] != pindex) {
                          // Bail out if we reorged away from this block
                          fRevertToInv = true;
                          break;
                      }
                      if (pBestIndex != nullptr && pindex->pprev != pBestIndex) {
                          // This means that the list of blocks to announce don't
                          // connect to each other.
                          // This shouldn't really be possible to hit during
                          // regular operation (because reorgs should take us to
                          // a chain that has some block not on the prior chain,
                          // which should be caught by the prior check), but one
                          // way this could happen is by using invalidateblock /
                          // reconsiderblock repeatedly on the tip, causing it to
                          // be added multiple times to vBlockHashesToAnnounce.
                          // Robustly deal with this rare situation by reverting
                          // to an inv.
                          fRevertToInv = true;
                          break;
                      }
                      pBestIndex = pindex;
                      if (fFoundStartingHeader) {
                          // add this to the headers message
                          vHeaders.push_back(pindex->GetBlockHeader());
                      } else if (PeerHasHeader(&state, pindex)) {
                          continue; // keep looking for the first new block
                      } else if (pindex->pprev == nullptr || PeerHasHeader(&state, pindex->pprev)) {
                          // Peer doesn't have this header but they do have the prior one.
                          // Start sending headers.
                          fFoundStartingHeader = true;
                          vHeaders.push_back(pindex->GetBlockHeader());
                      } else {
                          // Peer doesn't have this header or the prior one -- nothing will
                          // connect, so bail out.
                          fRevertToInv = true;
                          break;
                      }
                  }
              }
              if (!fRevertToInv && !vHeaders.empty()) {
                  if (vHeaders.size() == 1 && state.fPreferHeaderAndIDs) {
                      // We only send up to 1 block as header-and-ids, as otherwise
                      // probably means we're doing an initial-ish-sync or they're slow
                      LogPrint(BCLog::NET, "%s sending header-and-ids %s to peer=%d\n", __func__,
                              vHeaders.front().GetHash().ToString(), pto->GetId());
  
                      int nSendFlags = state.fWantsCmpctWitness ? 0 : SERIALIZE_TRANSACTION_NO_WITNESS;
  
                      bool fGotBlockFromCache = false;
                      {
                          LOCK(cs_most_recent_block);
                          if (most_recent_block_hash == pBestIndex->GetBlockHash()) {
                              if (state.fWantsCmpctWitness || !fWitnessesPresentInMostRecentCompactBlock)
                                  connman->PushMessage(pto, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, *most_recent_compact_block));
                              else {
                                  CBlockHeaderAndShortTxIDs cmpctblock(*most_recent_block, state.fWantsCmpctWitness);
                                  connman->PushMessage(pto, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, cmpctblock));
                              }
                              fGotBlockFromCache = true;
                          }
                      }
                      if (!fGotBlockFromCache) {
                          CBlock block;
                          bool ret = ReadBlockFromDisk(block, pBestIndex, consensusParams);
                          assert(ret);
                          CBlockHeaderAndShortTxIDs cmpctblock(block, state.fWantsCmpctWitness);
                          connman->PushMessage(pto, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, cmpctblock));
                      }
                      state.pindexBestHeaderSent = pBestIndex;
                  } else if (state.fPreferHeaders) {
                      if (vHeaders.size() > 1) {
                          LogPrint(BCLog::NET, "%s: %u headers, range (%s, %s), to peer=%d\n", __func__,
                                  vHeaders.size(),
                                  vHeaders.front().GetHash().ToString(),
                                  vHeaders.back().GetHash().ToString(), pto->GetId());
                      } else {
                          LogPrint(BCLog::NET, "%s: sending header %s to peer=%d\n", __func__,
                                  vHeaders.front().GetHash().ToString(), pto->GetId());
                      }
                      connman->PushMessage(pto, msgMaker.Make(NetMsgType::HEADERS, vHeaders));
                      state.pindexBestHeaderSent = pBestIndex;
                  } else
                      fRevertToInv = true;
              }
              if (fRevertToInv) {
                  // If falling back to using an inv, just try to inv the tip.
                  // The last entry in vBlockHashesToAnnounce was our tip at some point
                  // in the past.
                  if (!pto->vBlockHashesToAnnounce.empty()) {
                      const uint256 &hashToAnnounce = pto->vBlockHashesToAnnounce.back();
                      const CBlockIndex* pindex = LookupBlockIndex(hashToAnnounce);
                      assert(pindex);
  
                      // Warn if we're announcing a block that is not on the main chain.
                      // This should be very rare and could be optimized out.
                      // Just log for now.
                      if (chainActive[pindex->nHeight] != pindex) {
                          LogPrint(BCLog::NET, "Announcing block %s not on main chain (tip=%s)\n",
                              hashToAnnounce.ToString(), chainActive.Tip()->GetBlockHash().ToString());
                      }
  
                      // If the peer's chain has this block, don't inv it back.
                      if (!PeerHasHeader(&state, pindex)) {
                          pto->PushInventory(CInv(MSG_BLOCK, hashToAnnounce));
                          LogPrint(BCLog::NET, "%s: sending inv peer=%d hash=%s\n", __func__,
                              pto->GetId(), hashToAnnounce.ToString());
                      }
                  }
              }
              pto->vBlockHashesToAnnounce.clear();
          }
  
          //
          // Message: inventory
          //
          std::vector<CInv> vInv;
          {
              LOCK(pto->cs_inventory);
              vInv.reserve(std::max<size_t>(pto->vInventoryBlockToSend.size(), INVENTORY_BROADCAST_MAX));
  
              // Add blocks
              for (const uint256& hash : pto->vInventoryBlockToSend) {
                  vInv.push_back(CInv(MSG_BLOCK, hash));
                  if (vInv.size() == MAX_INV_SZ) {
                      connman->PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
                      vInv.clear();
                  }
              }
              pto->vInventoryBlockToSend.clear();
  
              // Check whether periodic sends should happen
              bool fSendTrickle = pto->fWhitelisted;
              if (pto->nNextInvSend < nNow) {
                  fSendTrickle = true;
                  if (pto->fInbound) {
                      pto->nNextInvSend = connman->PoissonNextSendInbound(nNow, INVENTORY_BROADCAST_INTERVAL);
                  } else {
                      // Use half the delay for outbound peers, as there is less privacy concern for them.
                      pto->nNextInvSend = PoissonNextSend(nNow, INVENTORY_BROADCAST_INTERVAL >> 1);
                  }
              }
  
              // Time to send but the peer has requested we not relay transactions.
              if (fSendTrickle) {
                  LOCK(pto->cs_filter);
                  if (!pto->fRelayTxes) pto->setInventoryTxToSend.clear();
              }
  
              // Respond to BIP35 mempool requests
              if (fSendTrickle && pto->fSendMempool) {
                  auto vtxinfo = mempool.infoAll();
                  pto->fSendMempool = false;
                  CAmount filterrate = 0;
                  {
                      LOCK(pto->cs_feeFilter);
                      filterrate = pto->minFeeFilter;
                  }
  
                  LOCK(pto->cs_filter);
  
                  for (const auto& txinfo : vtxinfo) {
                      const uint256& hash = txinfo.tx->GetHash();
                      CInv inv(MSG_TX, hash);
                      pto->setInventoryTxToSend.erase(hash);
                      if (filterrate) {
                          if (txinfo.feeRate.GetFeePerK() < filterrate)
                              continue;
                      }
                      if (pto->pfilter) {
                          if (!pto->pfilter->IsRelevantAndUpdate(*txinfo.tx)) continue;
                      }
                      pto->filterInventoryKnown.insert(hash);
                      vInv.push_back(inv);
                      if (vInv.size() == MAX_INV_SZ) {
                          connman->PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
                          vInv.clear();
                      }
                  }
                  pto->timeLastMempoolReq = GetTime();
              }
  
              // Determine transactions to relay
              if (fSendTrickle) {
                  // Produce a vector with all candidates for sending
                  std::vector<std::set<uint256>::iterator> vInvTx;
                  vInvTx.reserve(pto->setInventoryTxToSend.size());
                  for (std::set<uint256>::iterator it = pto->setInventoryTxToSend.begin(); it != pto->setInventoryTxToSend.end(); it++) {
                      vInvTx.push_back(it);
                  }
                  CAmount filterrate = 0;
                  {
                      LOCK(pto->cs_feeFilter);
                      filterrate = pto->minFeeFilter;
                  }
                  // Topologically and fee-rate sort the inventory we send for privacy and priority reasons.
                  // A heap is used so that not all items need sorting if only a few are being sent.
                  CompareInvMempoolOrder compareInvMempoolOrder(&mempool);
                  std::make_heap(vInvTx.begin(), vInvTx.end(), compareInvMempoolOrder);
                  // No reason to drain out at many times the network's capacity,
                  // especially since we have many peers and some will draw much shorter delays.
                  unsigned int nRelayedTransactions = 0;
                  LOCK(pto->cs_filter);
                  while (!vInvTx.empty() && nRelayedTransactions < INVENTORY_BROADCAST_MAX) {
                      // Fetch the top element from the heap
                      std::pop_heap(vInvTx.begin(), vInvTx.end(), compareInvMempoolOrder);
                      std::set<uint256>::iterator it = vInvTx.back();
                      vInvTx.pop_back();
                      uint256 hash = *it;
                      // Remove it from the to-be-sent set
                      pto->setInventoryTxToSend.erase(it);
                      // Check if not in the filter already
                      if (pto->filterInventoryKnown.contains(hash)) {
                          continue;
                      }
                      // Not in the mempool anymore? don't bother sending it.
                      auto txinfo = mempool.info(hash);
                      if (!txinfo.tx) {
                          continue;
                      }
                      if (filterrate && txinfo.feeRate.GetFeePerK() < filterrate) {
                          continue;
                      }
                      if (pto->pfilter && !pto->pfilter->IsRelevantAndUpdate(*txinfo.tx)) continue;
                      // Send
                      vInv.push_back(CInv(MSG_TX, hash));
                      nRelayedTransactions++;
                      {
                          // Expire old relay messages
                          while (!vRelayExpiration.empty() && vRelayExpiration.front().first < nNow)
                          {
                              mapRelay.erase(vRelayExpiration.front().second);
                              vRelayExpiration.pop_front();
                          }
  
                          auto ret = mapRelay.insert(std::make_pair(hash, std::move(txinfo.tx)));
                          if (ret.second) {
                              vRelayExpiration.push_back(std::make_pair(nNow + 15 * 60 * 1000000, ret.first));
                          }
                      }
                      if (vInv.size() == MAX_INV_SZ) {
                          connman->PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
                          vInv.clear();
                      }
                      pto->filterInventoryKnown.insert(hash);
                  }
              }
          }
          if (!vInv.empty())
              connman->PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
  
          // Detect whether we're stalling
          nNow = GetTimeMicros();
          if (state.nStallingSince && state.nStallingSince < nNow - 1000000 * BLOCK_STALLING_TIMEOUT) {
              // Stalling only triggers when the block download window cannot move. During normal steady state,
              // the download window should be much larger than the to-be-downloaded set of blocks, so disconnection
              // should only happen during initial block download.
              LogPrintf("Peer=%d is stalling block download, disconnecting\n", pto->GetId());
              pto->fDisconnect = true;
              return true;
          }
          // In case there is a block that has been in flight from this peer for 2 + 0.5 * N times the block interval
          // (with N the number of peers from which we're downloading validated blocks), disconnect due to timeout.
          // We compensate for other peers to prevent killing off peers due to our own downstream link
          // being saturated. We only count validated in-flight blocks so peers can't advertise non-existing block hashes
          // to unreasonably increase our timeout.
          if (state.vBlocksInFlight.size() > 0) {
              QueuedBlock &queuedBlock = state.vBlocksInFlight.front();
              int nOtherPeersWithValidatedDownloads = nPeersWithValidatedDownloads - (state.nBlocksInFlightValidHeaders > 0);
              if (nNow > state.nDownloadingSince + consensusParams.nPowTargetSpacing * (BLOCK_DOWNLOAD_TIMEOUT_BASE + BLOCK_DOWNLOAD_TIMEOUT_PER_PEER * nOtherPeersWithValidatedDownloads)) {
                  LogPrintf("Timeout downloading block %s from peer=%d, disconnecting\n", queuedBlock.hash.ToString(), pto->GetId());
                  pto->fDisconnect = true;
                  return true;
              }
          }
          // Check for headers sync timeouts
          if (state.fSyncStarted && state.nHeadersSyncTimeout < std::numeric_limits<int64_t>::max()) {
              // Detect whether this is a stalling initial-headers-sync peer
              if (pindexBestHeader->GetBlockTime() <= GetAdjustedTime() - 24*60*60) {
                  if (nNow > state.nHeadersSyncTimeout && nSyncStarted == 1 && (nPreferredDownload - state.fPreferredDownload >= 1)) {
                      // Disconnect a (non-whitelisted) peer if it is our only sync peer,
                      // and we have others we could be using instead.
                      // Note: If all our peers are inbound, then we won't
                      // disconnect our sync peer for stalling; we have bigger
                      // problems if we can't get any outbound peers.
                      if (!pto->fWhitelisted) {
                          LogPrintf("Timeout downloading headers from peer=%d, disconnecting\n", pto->GetId());
                          pto->fDisconnect = true;
                          return true;
                      } else {
                          LogPrintf("Timeout downloading headers from whitelisted peer=%d, not disconnecting\n", pto->GetId());
                          // Reset the headers sync state so that we have a
                          // chance to try downloading from a different peer.
                          // Note: this will also result in at least one more
                          // getheaders message to be sent to
                          // this peer (eventually).
                          state.fSyncStarted = false;
                          nSyncStarted--;
                          state.nHeadersSyncTimeout = 0;
                      }
                  }
              } else {
                  // After we've caught up once, reset the timeout so we can't trigger
                  // disconnect later.
                  state.nHeadersSyncTimeout = std::numeric_limits<int64_t>::max();
              }
          }
  
          // Check that outbound peers have reasonable chains
          // GetTime() is used by this anti-DoS logic so we can test this using mocktime
          ConsiderEviction(pto, GetTime());
  
          //
          // Message: getdata (blocks)
          //
          std::vector<CInv> vGetData;
          if (!pto->fClient && ((fFetch && !pto->m_limited_node) || !IsInitialBlockDownload()) && state.nBlocksInFlight < MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
              std::vector<const CBlockIndex*> vToDownload;
              NodeId staller = -1;
              FindNextBlocksToDownload(pto->GetId(), MAX_BLOCKS_IN_TRANSIT_PER_PEER - state.nBlocksInFlight, vToDownload, staller, consensusParams);
              for (const CBlockIndex *pindex : vToDownload) {
                  uint32_t nFetchFlags = GetFetchFlags(pto);
                  vGetData.push_back(CInv(MSG_BLOCK | nFetchFlags, pindex->GetBlockHash()));
                  MarkBlockAsInFlight(pto->GetId(), pindex->GetBlockHash(), pindex);
                  LogPrint(BCLog::NET, "Requesting block %s (%d) peer=%d\n", pindex->GetBlockHash().ToString(),
                      pindex->nHeight, pto->GetId());
              }
              if (state.nBlocksInFlight == 0 && staller != -1) {
                  if (State(staller)->nStallingSince == 0) {
                      State(staller)->nStallingSince = nNow;
                      LogPrint(BCLog::NET, "Stall started peer=%d\n", staller);
                  }
              }
          }
  
          //
          // Message: getdata (non-blocks)
          //
          while (!pto->mapAskFor.empty() && (*pto->mapAskFor.begin()).first <= nNow)
          {
              const CInv& inv = (*pto->mapAskFor.begin()).second;
              if (!AlreadyHave(inv))
              {
                  LogPrint(BCLog::NET, "Requesting %s peer=%d\n", inv.ToString(), pto->GetId());
                  vGetData.push_back(inv);
                  if (vGetData.size() >= 1000)
                  {
                      connman->PushMessage(pto, msgMaker.Make(NetMsgType::GETDATA, vGetData));
                      vGetData.clear();
                  }
              } else {
                  //If we're not going to ask, don't expect a response.
                  pto->setAskFor.erase(inv.hash);
              }
              pto->mapAskFor.erase(pto->mapAskFor.begin());
          }
          if (!vGetData.empty())
              connman->PushMessage(pto, msgMaker.Make(NetMsgType::GETDATA, vGetData));
  
          //
          // Message: feefilter
          //
          // We don't want white listed peers to filter txs to us if we have -whitelistforcerelay
          if (pto->nVersion >= FEEFILTER_VERSION && gArgs.GetBoolArg("-feefilter", DEFAULT_FEEFILTER) &&
              !(pto->fWhitelisted && gArgs.GetBoolArg("-whitelistforcerelay", DEFAULT_WHITELISTFORCERELAY))) {
              CAmount currentFilter = mempool.GetMinFee(gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000).GetFeePerK();
              int64_t timeNow = GetTimeMicros();
              if (timeNow > pto->nextSendTimeFeeFilter) {
                  static CFeeRate default_feerate(DEFAULT_MIN_RELAY_TX_FEE);
                  static FeeFilterRounder filterRounder(default_feerate);
                  CAmount filterToSend = filterRounder.round(currentFilter);
                  // We always have a fee filter of at least minRelayTxFee
                  filterToSend = std::max(filterToSend, ::minRelayTxFee.GetFeePerK());
                  if (filterToSend != pto->lastSentFeeFilter) {
                      connman->PushMessage(pto, msgMaker.Make(NetMsgType::FEEFILTER, filterToSend));
                      pto->lastSentFeeFilter = filterToSend;
                  }
                  pto->nextSendTimeFeeFilter = PoissonNextSend(timeNow, AVG_FEEFILTER_BROADCAST_INTERVAL);
              }
              // If the fee filter has changed substantially and it's still more than MAX_FEEFILTER_CHANGE_DELAY
              // until scheduled broadcast, then move the broadcast to within MAX_FEEFILTER_CHANGE_DELAY.
              else if (timeNow + MAX_FEEFILTER_CHANGE_DELAY * 1000000 < pto->nextSendTimeFeeFilter &&
                       (currentFilter < 3 * pto->lastSentFeeFilter / 4 || currentFilter > 4 * pto->lastSentFeeFilter / 3)) {
                  pto->nextSendTimeFeeFilter = timeNow + GetRandInt(MAX_FEEFILTER_CHANGE_DELAY) * 1000000;
              }
          }
      }
      return true;
  }
  
  class CNetProcessingCleanup
  {
  public:
      CNetProcessingCleanup() {}
      ~CNetProcessingCleanup() {
          // orphan transactions
          mapOrphanTransactions.clear();
          mapOrphanTransactionsByPrev.clear();
      }
  } instance_of_cnetprocessingcleanup;
  
  