text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2018 The BIDX 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 <shutdown.h>
  #include <tinyformat.h>
  #include <txmempool.h>
  #include <ui_interface.h>
  #include <util.h>
  #include <utilmoneystr.h>
  #include <utilstrencodings.h>
  #include <spork.h>
  #include <map>
  #include <functional>
  #include <masternodeman.h>
  #include <masternode-sync.h>
  #include <masternode-payments.h>
  #include <governance/governance.h>
  #include <activemasternode.h>
  #include <instantx.h>
  #include <init.h>
  #include <boost/thread.hpp>
  
  #include <memory>
  
  #if defined(NDEBUG)
  # error "BIDX cannot be compiled without assertions."
  #endif
  
  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);
      }
  };
  
  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);
  std::map<COutPoint, std::set<std::map<uint256, COrphanTx>::iterator, IteratorComparator>> mapOrphanTransactionsByPrev GUARDED_BY(g_cs_orphans);
  void EraseOrphansFor(NodeId peer);
  
  static size_t vExtraTxnForCompactIt GUARDED_BY(g_cs_orphans) = 0;
  static std::vector<std::pair<uint256, CTransactionRef>> vExtraTxnForCompact GUARDED_BY(g_cs_orphans);
  
  static const uint64_t RANDOMIZER_ID_ADDRESS_RELAY = 0x3cac0035b5866b90ULL; // SHA256("main address relay")[0:8]
  
  /// 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 const 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 const int HISTORICAL_BLOCK_AGE = 7 * 24 * 60 * 60;
  
  // Internal stuff
  namespace {
  /** Number of nodes with fSyncStarted. */
  int nSyncStarted = 0;
  
  /**
       * Sources of received blocks, saved to be able to send them reject
       * messages or ban them when processing happens afterwards. Protected by
       * cs_main.
       * 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;
  
  /**
       * 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. Protected by
       * cs_main.
       *
       * 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;
  uint256 hashRecentRejectsChainTip;
  
  /** Blocks that are in flight, and that are in the queue to be downloaded. Protected by cs_main. */
  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;
  
  static std::map<uint256, std::shared_ptr<CBlock>> mapBlocksUnknownParent;
  
  /** Stack of nodes which we have set to announce using compact blocks */
  std::list<NodeId> lNodesAnnouncingHeaderAndIDs;
  
  /** Number of preferable block download peers. */
  int nPreferredDownload = 0;
  
  /** Number of peers from which we're downloading blocks. */
  int nPeersWithValidatedDownloads = 0;
  
  /** Number of outbound peers with m_chain_sync.m_protect. */
  int g_outbound_peers_with_protect_from_disconnect = 0;
  
  /** When our tip was last updated. */
  std::atomic<int64_t> g_last_tip_update(0);
  
  /** Relay map, protected by cs_main. */
  typedef std::map<uint256, CTransactionRef> MapRelay;
  MapRelay mapRelay;
  /** Expiration-time ordered list of (expire time, relay map entry) pairs, protected by cs_main). */
  std::deque<std::pair<int64_t, MapRelay::iterator>> vRelayExpiration;
  } // 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. Requires cs_main. */
  std::map<NodeId, CNodeState> mapNodeState;
  
  // Requires cs_main.
  CNodeState *State(NodeId pnode) {
      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;
  }
  
  // Requires cs_main.
  // 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) {
      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) {
      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) {
      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;
      }
  
  
      // process one of the extensions
      return net_processing_bitcoin::AlreadyHave(inv);
  }
  
  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 Consensus::Params& consensusParams, const CInv& inv, CConnman* connman, const std::atomic<bool>& interruptMsgProc)
  {
      bool send = false;
      std::shared_ptr<const CBlock> a_recent_block;
      std::shared_ptr<const CBlockHeaderAndShortTxIDs> a_recent_compact_block;
      bool fWitnessesPresentInARecentCompactBlock;
      {
          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 {
              // 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 (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 Consensus::Params& consensusParams, 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()) {
              if (interruptMsgProc)
                  return;
              // Don't bother if send buffer is too full to respond anyway
              if (pfrom->fPauseSend)
                  break;
  
              CInv &inv = *it;
              it++;
  
              net_processing_bitcoin::TransformInvForLegacyVersion(inv, pfrom, false);
  
              // Send stream from relay memory
              bool push = false;
              if(inv.type == MSG_TX || inv.type == MSG_WITNESS_TX) {
  
                  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;
                      }
                  }
              }
              else if (inv.type == MSG_BLOCK || inv.type == MSG_FILTERED_BLOCK || inv.type == MSG_CMPCT_BLOCK || inv.type == MSG_WITNESS_BLOCK) {
                  ProcessGetBlockData(pfrom, consensusParams, inv, connman, interruptMsgProc);
                  push = true;
              }
              else
              {
                  push = net_processing_bitcoin::ProcessGetData(pfrom, consensusParams, connman, inv);
              }
  
              if (!push) {
                  vNotFound.push_back(inv);
              }
  
              // Track requests for our stuff.
              GetMainSignals().Inventory(inv.hash);
          }
      } // release cs_main
  
      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) {
      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)
  {
  //    if(strCommand != "mnp" && strCommand != "inv")
      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");
              }
          }
      }
  
      else if (strCommand == NetMsgType::VERSION)
      {
          // Each connection can only send one version message
          if (pfrom->nVersion != 0)
          {
              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));
              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 (nServices & ((1 << 7) | (1 << 5))) {
              if (GetTime() < 1533096000) {
                  // Immediately disconnect peers that use service bits 6 or 8 until August 1st, 2018
                  // These bits have been used as a flag to indicate that a node is running incompatible
                  // consensus rules instead of changing the network magic, so we're stuck disconnecting
                  // based on these service bits, at least for a while.
                  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);
              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;
  
              net_processing_bitcoin::TransformInvForLegacyVersion(inv, pfrom, false);
  
              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);
                  }
              }
  
              // Track requests for our stuff
              GetMainSignals().Inventory(inv.hash);
          }
      }
  
  
      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.GetConsensus(), connman, interruptMsgProc);
      }
  
  
      else if (strCommand == NetMsgType::GETBLOCKS)
      {
          CBlockLocator locator;
          uint256 hashStop;
          vRecv >> locator >> hashStop;
  
          // 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;
  
          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/bitcoin/bitcoin/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/bitcoin/bitcoin/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 (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);
  
          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());
  
          auto it = mapBlockIndex.find(pblock->hashPrevBlock);
          if (it != mapBlockIndex.end() && ((it->second->nStatus & BLOCK_HAVE_DATA) == 0))
          {
              LogPrint(BCLog::NET, "Received block out of order: %s\n", pblock->GetHash().ToString());
              if (mapBlocksInFlight.count(pblock->hashPrevBlock))
              {
                  LOCK(cs_main);
                  mapBlocksUnknownParent.insert(std::make_pair(pblock->hashPrevBlock, pblock));
                  MarkBlockAsReceived(pblock->hashPrevBlock); // invalidate to send again.
              }
          }
          else
          {
              {
                  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();
  
                  std::deque<uint256> queue;
                  queue.push_back(hash);
                  while (!queue.empty())
                  {
                      uint256 head = queue.front();
                      queue.pop_front();
                      auto it = mapBlocksUnknownParent.find(head);
                      if (it != std::end(mapBlocksUnknownParent))
                      {
                          std::shared_ptr<CBlock> pblockrecursive = it->second;
                          auto recursiveHash = pblockrecursive->GetHash();
                          LogPrint(BCLog::NET, "%s: Processing out of order child %s of %s\n", __func__, recursiveHash.ToString(),
                                   head.ToString());
  
                          bool forceProcessing = false;
                          {
                              LOCK(cs_main);
                              mapBlocksUnknownParent.erase(it);
                              forceProcessing = MarkBlockAsReceived(recursiveHash);
                          }
                          ProcessNewBlock(chainparams, pblockrecursive, forceProcessing, &fNewBlock);
                          queue.push_back(recursiveHash);
                      }
                  }
              }
              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 {
          const auto &allMessages = getAllNetMessageTypes();
          if(std::find(std::begin(allMessages), std::end(allMessages), strCommand) != std::end(allMessages))
          {
              net_processing_bitcoin::ProcessExtension(pfrom, strCommand, vRecv, connman);
          }
          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)
  {
      AssertLockHeld(cs_main);
      CNodeState &state = *State(pnode->GetId());
  
      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.GetConsensus(), 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);
          if (interruptMsgProc)
              return false;
          if (!pfrom->vRecvGetData.empty())
              fMoreWork = true;
      }
      catch (const std::ios_base::failure& e)
      {
          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);
  
      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) {
              // 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) {
                      // 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;
      }
  }
  
  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, std::atomic<bool>& interruptMsgProc)
  {
      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))
              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;
                  // Use half the delay for outbound peers, as there is less privacy concern for them.
                  pto->nNextInvSend = PoissonNextSend(nNow, INVENTORY_BROADCAST_INTERVAL >> !pto->fInbound);
              }
  
              // 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);
                  }
              }
  
              for(auto &&inv : pto->vInventoryToSend)
              {
                  net_processing_bitcoin::TransformInvForLegacyVersion(inv, pto, true);
                  vInv.push_back(inv);
                  if (vInv.size() == MAX_INV_SZ)
                  {
                      connman->PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
                      vInv.clear();
                  }
              }
  
              pto->vInventoryToSend.clear();
          }
          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)
          {
              CInv& inv = (*pto->mapAskFor.begin()).second;
              if (!AlreadyHave(inv))
              {
                  LogPrint(BCLog::NET, "Requesting %s peer=%d s:%d r:%d\n", inv.ToString(), pto->GetId(),
                           pto->GetSendVersion(),
                           pto->GetRecvVersion());
  
                  net_processing_bitcoin::TransformInvForLegacyVersion(inv, pto, true);
  
                  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;
  
  namespace LegacyInvMsg {
  enum {
      MSG_TX = 1,
      MSG_BLOCK,
      // Nodes may always request a MSG_FILTERED_BLOCK in a getdata, however,
      // MSG_FILTERED_BLOCK should not appear in any invs except as a part of getdata.
      MSG_FILTERED_BLOCK,
      // BIDX message types
      // NOTE: declare non-implmented here, we must keep this enum consistent and backwards compatible
      MSG_TXLOCK_REQUEST,
      MSG_TXLOCK_VOTE,
      MSG_SPORK,
      MSG_MASTERNODE_PAYMENT_VOTE,
      MSG_MASTERNODE_PAYMENT_BLOCK, // reusing, was MSG_MASTERNODE_SCANNING_ERROR previousely, was NOT used in 12.0
      MSG_BUDGET_VOTE, // depreciated since 12.1
      MSG_BUDGET_PROPOSAL, // depreciated since 12.1
      MSG_BUDGET_FINALIZED, // depreciated since 12.1
      MSG_BUDGET_FINALIZED_VOTE, // depreciated since 12.1
      MSG_MASTERNODE_QUORUM, // not implemented
      MSG_MASTERNODE_ANNOUNCE,
      MSG_MASTERNODE_PING,
      MSG_DSTX,
      MSG_GOVERNANCE_OBJECT,
      MSG_GOVERNANCE_OBJECT_VOTE,
      MSG_MASTERNODE_VERIFY
  };
  }
  
  using SporkHandler = std::function<CSerializedNetMsg(const CNetMsgMaker &, const uint256 &)>;
  using MapSporkHandlers = std::map<int, SporkHandler>;
  
  #define ADD_HANDLER(sporkID, handler) sporkHandlers.emplace(sporkID, [](const CNetMsgMaker &msgMaker, const uint256 &hash) -> CSerializedNetMsg handler)
  
  static const MapSporkHandlers &GetMapGetDataHandlers()
  {
      static MapSporkHandlers sporkHandlers;
      if(sporkHandlers.empty())
      {
          ADD_HANDLER(MSG_SPORK, {
                          if(mapSporks.count(hash)) {
                              return msgMaker.Make(NetMsgType::SPORK, mapSporks[hash]);
                          }
                          return {};
                      });
          ADD_HANDLER(MSG_TXLOCK_REQUEST, {
                          CTxLockRequestRef txLockRequest;
                          if(instantsend.GetTxLockRequest(hash, txLockRequest)) {
                              return msgMaker.Make(NetMsgType::TXLOCKREQUEST, *txLockRequest);
                          }
                          return {};
                      });
          ADD_HANDLER(MSG_TXLOCK_VOTE, {
                          CTxLockVote vote;
                          if(instantsend.GetTxLockVote(hash, vote)) {
                              return msgMaker.Make(NetMsgType::TXLOCKVOTE, vote);
                          }
                          return {};
                      });
          ADD_HANDLER(MSG_MASTERNODE_PAYMENT_BLOCK, {
                          BlockMap::iterator mi = mapBlockIndex.find(hash);
                          LOCK(cs_mapMasternodeBlocks);
                          if (mi != mapBlockIndex.end() && mnpayments.mapMasternodeBlocks.count(mi->second->nHeight)) {
                              for(const CMasternodePayee& payee : mnpayments.mapMasternodeBlocks[mi->second->nHeight].vecPayees) {
                                  std::vector<uint256> vecVoteHashes = payee.GetVoteHashes();
                                  for(const uint256& hash : vecVoteHashes) {
                                      if(mnpayments.HasVerifiedPaymentVote(hash)) {
                                          return msgMaker.Make(NetMsgType::MASTERNODEPAYMENTVOTE, mnpayments.mapMasternodePaymentVotes[hash]);
                                      }
                                  }
                              }
                          }
                          return {};
                      });
          ADD_HANDLER(MSG_MASTERNODE_PAYMENT_VOTE, {
                          if(mnpayments.HasVerifiedPaymentVote(hash)) {
                              return msgMaker.Make(NetMsgType::MASTERNODEPAYMENTVOTE, mnpayments.mapMasternodePaymentVotes[hash]);
                          }
                          return {};
                      });
          ADD_HANDLER(MSG_MASTERNODE_ANNOUNCE, {
                          if(mnodeman.mapSeenMasternodeBroadcast.count(hash)) {
                              return msgMaker.Make(NetMsgType::MNANNOUNCE, mnodeman.mapSeenMasternodeBroadcast[hash].second);
                          }
                          return {};
                      });
          ADD_HANDLER(MSG_MASTERNODE_PING, {
                          if(mnodeman.mapSeenMasternodePing.count(hash)) {
                              return msgMaker.Make(NetMsgType::MNPING, mnodeman.mapSeenMasternodePing[hash]);
                          }
                          return {};
                      });
          ADD_HANDLER(MSG_GOVERNANCE_OBJECT, {
                          if(governance.HaveObjectForHash(hash)) {
                              CGovernanceObject obj;
                              if(governance.SerializeObjectForHash(hash, obj)) {
                                  return msgMaker.Make(NetMsgType::MNGOVERNANCEOBJECT, obj);
                              }
                          }
                          return {};
                      });
          ADD_HANDLER(MSG_GOVERNANCE_OBJECT_VOTE, {
                          if(governance.HaveVoteForHash(hash)) {
                              CGovernanceVote vote;
                              if(governance.SerializeVoteForHash(hash, vote)) {
                                  return msgMaker.Make(NetMsgType::MNGOVERNANCEOBJECTVOTE, vote);
  
                              }
                          }
                          return {};
                      });
          ADD_HANDLER(MSG_MASTERNODE_VERIFY, {
                          if(mnodeman.mapSeenMasternodeVerification.count(hash)) {
                              return msgMaker.Make(NetMsgType::MNVERIFY, mnodeman.mapSeenMasternodeVerification[hash]);
  
                          }
                          return {};
                      });
      }
      return sporkHandlers;
  }
  
  bool net_processing_bitcoin::ProcessGetData(CNode *pfrom, const Consensus::Params &consensusParams, CConnman *connman, const CInv &inv)
  {
      const auto &handlersMap = GetMapGetDataHandlers();
      auto it = handlersMap.find(inv.type);
      if(it != std::end(handlersMap))
      {
          const CNetMsgMaker msgMaker(pfrom->GetSendVersion());
          auto &&msg = it->second(msgMaker, inv.hash);
          if(!msg.command.empty())
          {
              connman->PushMessage(pfrom, std::move(msg));
              return true;
          }
      }
      return false;
  }
  
  void net_processing_bitcoin::ProcessExtension(CNode *pfrom, const std::string &strCommand, CDataStream &vRecv, CConnman *connman)
  {
      mnodeman.ProcessMessage(pfrom, strCommand, vRecv, *connman);
      mnpayments.ProcessMessage(pfrom, strCommand, vRecv, *connman);
      instantsend.ProcessMessage(pfrom, strCommand, vRecv, *connman);
      sporkManager.ProcessSpork(pfrom, strCommand, vRecv, connman);
      masternodeSync.ProcessMessage(pfrom, strCommand, vRecv);
      governance.ProcessMessage(pfrom, strCommand, vRecv, *connman);
  }
  
  void net_processing_bitcoin::ThreadProcessExtensions(CConnman *pConnman)
  {
      if(fLiteMode) return; // disable all BIDX specific functionality
  
      static bool fOneThread;
      if(fOneThread) return;
      fOneThread = true;
  
      // Make this thread recognisable as the PrivateSend thread
      RenameThread("bitcoin-ps");
  
      unsigned int nTick = 0;
  
      auto &connman = *pConnman;
      while (!ShutdownRequested())
      {
          boost::this_thread::interruption_point();
          MilliSleep(1000);
  
          // try to sync from all available nodes, one step at a time
          masternodeSync.ProcessTick(connman);
  
          if(!ShutdownRequested()) {
  
              nTick++;
  
              if(masternodeSync.IsBlockchainSynced()) {
                  // make sure to check all masternodes first
                  mnodeman.Check();
  
                  // check if we should activate or ping every few minutes,
                  // slightly postpone first run to give net thread a chance to connect to some peers
                  if(nTick % MASTERNODE_MIN_MNP_SECONDS == 15)
                      activeMasternode.ManageState(connman);
  
                  if(nTick % 60 == 0) {
                      mnodeman.ProcessMasternodeConnections(connman);
                      mnodeman.CheckAndRemove(connman);
                      mnpayments.CheckAndRemove();
                      instantsend.CheckAndRemove();
                  }
                  if(fMasterNode && (nTick % (60 * 5) == 0)) {
                      mnodeman.DoFullVerificationStep(connman);
                  }
  
                  if(nTick % (60 * 5) == 0) {
                      governance.DoMaintenance(connman);
                  }
              }
  
          }
      }
  }
  
  bool net_processing_bitcoin::AlreadyHave(const CInv &inv)
  {
      switch(inv.type)
      {
      /*
      BIDX Related Inventory Messages
  
      --
  
      We shouldn't update the sync times for each of the messages when we already have it.
      We're going to be asking many nodes upfront for the full inventory list, so we'll get duplicates of these.
      We want to only update the time on new hits, so that we can time out appropriately if needed.
      */
      case MSG_TXLOCK_REQUEST:
          return instantsend.AlreadyHave(inv.hash);
  
      case MSG_TXLOCK_VOTE:
          return instantsend.AlreadyHave(inv.hash);
  
      case MSG_SPORK:
          return mapSporks.count(inv.hash);
  
      case MSG_MASTERNODE_PAYMENT_VOTE:
          return mnpayments.mapMasternodePaymentVotes.count(inv.hash);
  
      case MSG_MASTERNODE_PAYMENT_BLOCK:
      {
          BlockMap::iterator mi = mapBlockIndex.find(inv.hash);
          return mi != mapBlockIndex.end() && mnpayments.mapMasternodeBlocks.find(mi->second->nHeight) != mnpayments.mapMasternodeBlocks.end();
      }
  
      case MSG_MASTERNODE_ANNOUNCE:
          return mnodeman.mapSeenMasternodeBroadcast.count(inv.hash) && !mnodeman.IsMnbRecoveryRequested(inv.hash);
  
      case MSG_MASTERNODE_PING:
          return mnodeman.mapSeenMasternodePing.count(inv.hash);
  
      case MSG_DSTX: {
          //        return static_cast<bool>(CPrivateSend::GetDSTX(inv.hash));
          return true;
      }
      case MSG_GOVERNANCE_OBJECT:
      case MSG_GOVERNANCE_OBJECT_VOTE:
          return !governance.ConfirmInventoryRequest(inv);
  
      case MSG_MASTERNODE_VERIFY:
          return mnodeman.mapSeenMasternodeVerification.count(inv.hash);
      }
      return true;
  }
  
  static int MapLegacyToCurrent(int nLegacyType)
  {
      switch(nLegacyType)
      {
      case LegacyInvMsg::MSG_TXLOCK_REQUEST: return MSG_TXLOCK_REQUEST;
      case LegacyInvMsg::MSG_TXLOCK_VOTE: return MSG_TXLOCK_VOTE;
      case LegacyInvMsg::MSG_SPORK: return MSG_SPORK;
      case LegacyInvMsg::MSG_MASTERNODE_PAYMENT_VOTE: return MSG_MASTERNODE_PAYMENT_VOTE;
      case LegacyInvMsg::MSG_MASTERNODE_PAYMENT_BLOCK: return MSG_MASTERNODE_PAYMENT_BLOCK;
      case LegacyInvMsg::MSG_MASTERNODE_ANNOUNCE: return MSG_MASTERNODE_ANNOUNCE;
      case LegacyInvMsg::MSG_MASTERNODE_PING: return MSG_MASTERNODE_PING;
      case LegacyInvMsg::MSG_DSTX: return MSG_DSTX;
      case LegacyInvMsg::MSG_GOVERNANCE_OBJECT: return MSG_GOVERNANCE_OBJECT;
      case LegacyInvMsg::MSG_GOVERNANCE_OBJECT_VOTE: return MSG_GOVERNANCE_OBJECT_VOTE;
      case LegacyInvMsg::MSG_MASTERNODE_VERIFY: return MSG_MASTERNODE_VERIFY;
      }
      return nLegacyType;
  }
  
  static int MapCurrentToLegacy(int nCurrentType)
  {
      switch(nCurrentType)
      {
      case MSG_TXLOCK_REQUEST: return LegacyInvMsg::MSG_TXLOCK_REQUEST;
      case MSG_TXLOCK_VOTE: return LegacyInvMsg::MSG_TXLOCK_VOTE;
      case MSG_SPORK: return LegacyInvMsg::MSG_SPORK;
      case MSG_MASTERNODE_PAYMENT_VOTE: return LegacyInvMsg::MSG_MASTERNODE_PAYMENT_VOTE;
      case MSG_MASTERNODE_PAYMENT_BLOCK: return LegacyInvMsg::MSG_MASTERNODE_PAYMENT_BLOCK;
      case MSG_MASTERNODE_ANNOUNCE: return LegacyInvMsg::MSG_MASTERNODE_ANNOUNCE;
      case MSG_MASTERNODE_PING: return LegacyInvMsg::MSG_MASTERNODE_PING;
      case MSG_DSTX: return LegacyInvMsg::MSG_DSTX;
      case MSG_GOVERNANCE_OBJECT: return LegacyInvMsg::MSG_GOVERNANCE_OBJECT;
      case MSG_GOVERNANCE_OBJECT_VOTE: return LegacyInvMsg::MSG_GOVERNANCE_OBJECT_VOTE;
      case MSG_MASTERNODE_VERIFY: return LegacyInvMsg::MSG_MASTERNODE_VERIFY;
      }
      return nCurrentType;
  }
  
  bool net_processing_bitcoin::TransformInvForLegacyVersion(CInv &inv, CNode *pfrom, bool fForSending)
  {
      if(pfrom->GetSendVersion() == PRESEGWIT_PROTO_VERSION)
      {
          if(fForSending)
              inv.type = MapCurrentToLegacy(inv.type);
          else
              inv.type = MapLegacyToCurrent(inv.type);
      }
      return true;
  }
  