text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2021 The Bitcoin Core 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 <banman.h>
  #include <blockencodings.h>
  #include <blockfilter.h>
  #include <chainparams.h>
  #include <consensus/amount.h>
  #include <consensus/validation.h>
  #include <deploymentstatus.h>
  #include <hash.h>
  #include <index/blockfilterindex.h>
  #include <merkleblock.h>
  #include <netbase.h>
  #include <netmessagemaker.h>
  #include <node/blockstorage.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 <streams.h>
  #include <sync.h>
  #include <tinyformat.h>
  #include <txmempool.h>
  #include <txorphanage.h>
  #include <txrequest.h>
  #include <util/check.h> // For NDEBUG compile time check
  #include <util/strencodings.h>
  #include <util/system.h>
  #include <util/trace.h>
  #include <validation.h>
  
  #include <algorithm>
  #include <atomic>
  #include <chrono>
  #include <memory>
  #include <optional>
  #include <typeinfo>
  
  using node::ReadBlockFromDisk;
  using node::ReadRawBlockFromDisk;
  using node::fImporting;
  using node::fPruneMode;
  using node::fReindex;
  
  /** How long to cache transactions in mapRelay for normal relay */
  static constexpr auto RELAY_TX_CACHE_TIME = 15min;
  /** How long a transaction has to be in the mempool before it can unconditionally be relayed (even when not in mapRelay). */
  static constexpr auto UNCONDITIONAL_RELAY_DELAY = 2min;
  /** Headers download timeout.
   *  Timeout = base + per_header * (expected number of headers) */
  static constexpr auto HEADERS_DOWNLOAD_TIMEOUT_BASE = 15min;
  static constexpr auto HEADERS_DOWNLOAD_TIMEOUT_PER_HEADER = 1ms;
  /** Protect at least this many outbound peers from disconnection due to slow/
   * behind headers chain.
   */
  static constexpr int32_t MAX_OUTBOUND_PEERS_TO_PROTECT_FROM_DISCONNECT = 4;
  /** Timeout for (unprotected) outbound peers to sync to our chainwork */
  static constexpr auto CHAIN_SYNC_TIMEOUT{20min};
  /** How frequently to check for stale tips */
  static constexpr auto STALE_CHECK_INTERVAL{10min};
  /** How frequently to check for extra outbound peers and disconnect */
  static constexpr auto EXTRA_PEER_CHECK_INTERVAL{45s};
  /** Minimum time an outbound-peer-eviction candidate must be connected for, in order to evict */
  static constexpr auto MINIMUM_CONNECT_TIME{30s};
  /** SHA256("main address relay")[0:8] */
  static constexpr uint64_t RANDOMIZER_ID_ADDRESS_RELAY = 0x3cac0035b5866b90ULL;
  /// Age after which a stale block will no longer be served if requested as
  /// protection against fingerprinting. Set to one month, denominated in seconds.
  static constexpr int STALE_RELAY_AGE_LIMIT = 30 * 24 * 60 * 60;
  /// Age after which a block is considered historical for purposes of rate
  /// limiting block relay. Set to one week, denominated in seconds.
  static constexpr int HISTORICAL_BLOCK_AGE = 7 * 24 * 60 * 60;
  /** Time between pings automatically sent out for latency probing and keepalive */
  static constexpr auto PING_INTERVAL{2min};
  /** The maximum number of entries in a locator */
  static const unsigned int MAX_LOCATOR_SZ = 101;
  /** The maximum number of entries in an 'inv' protocol message */
  static const unsigned int MAX_INV_SZ = 50000;
  /** Maximum number of in-flight transaction requests from a peer. It is not a hard limit, but the threshold at which
   *  point the OVERLOADED_PEER_TX_DELAY kicks in. */
  static constexpr int32_t MAX_PEER_TX_REQUEST_IN_FLIGHT = 100;
  /** Maximum number of transactions to consider for requesting, per peer. It provides a reasonable DoS limit to
   *  per-peer memory usage spent on announcements, while covering peers continuously sending INVs at the maximum
   *  rate (by our own policy, see INVENTORY_BROADCAST_PER_SECOND) for several minutes, while not receiving
   *  the actual transaction (from any peer) in response to requests for them. */
  static constexpr int32_t MAX_PEER_TX_ANNOUNCEMENTS = 5000;
  /** How long to delay requesting transactions via txids, if we have wtxid-relaying peers */
  static constexpr auto TXID_RELAY_DELAY{2s};
  /** How long to delay requesting transactions from non-preferred peers */
  static constexpr auto NONPREF_PEER_TX_DELAY{2s};
  /** How long to delay requesting transactions from overloaded peers (see MAX_PEER_TX_REQUEST_IN_FLIGHT). */
  static constexpr auto OVERLOADED_PEER_TX_DELAY{2s};
  /** How long to wait before downloading a transaction from an additional peer */
  static constexpr auto GETDATA_TX_INTERVAL{60s};
  /** Limit to avoid sending big packets. Not used in processing incoming GETDATA for compatibility */
  static const unsigned int MAX_GETDATA_SZ = 1000;
  /** Number of blocks that can be requested at any given time from a single peer. */
  static const int MAX_BLOCKS_IN_TRANSIT_PER_PEER = 16;
  /** Time during which a peer must stall block download progress before being disconnected. */
  static constexpr auto BLOCK_STALLING_TIMEOUT{2s};
  /** Number of headers sent in one getheaders result. We rely on the assumption that if a peer sends
   *  less than this number, we reached its tip. Changing this value is a protocol upgrade.
   *
   *  With a protocol upgrade, we now enforce an additional restriction on the
   *  total size of a "headers" message (see below).  The absolute limit
   *  on the number of headers still applies as well, so that we do not get
   *  overloaded both with small and large headers.
   */
  static const unsigned int MAX_HEADERS_RESULTS = 2000;
  /** Maximum size of a "headers" message.  This is enforced starting with
   *  SIZE_HEADERS_LIMIT_VERSION peers and prevents overloading if we have
   *  very large headers (due to auxpow).
   */
  static const unsigned int MAX_HEADERS_SIZE = (6 << 20); // 6 MiB
  /** Size of a headers message that is the threshold for assuming that the
   *  peer has more headers (even if we have less than MAX_HEADERS_RESULTS).
   *  This is used starting with SIZE_HEADERS_LIMIT_VERSION peers.
   */
  static const unsigned int THRESHOLD_HEADERS_SIZE = (4 << 20); // 4 MiB
  /** Maximum depth of blocks we're willing to serve as compact blocks to peers
   *  when requested. For older blocks, a regular BLOCK response will be sent. */
  static const int MAX_CMPCTBLOCK_DEPTH = 5;
  /** Maximum depth of blocks we're willing to respond to GETBLOCKTXN requests for. */
  static const int MAX_BLOCKTXN_DEPTH = 10;
  /** Size of the "block download window": how far ahead of our current height do we fetch?
   *  Larger windows tolerate larger download speed differences between peer, but increase the potential
   *  degree of disordering of blocks on disk (which make reindexing and pruning harder). We'll probably
   *  want to make this a per-peer adaptive value at some point. */
  static const unsigned int BLOCK_DOWNLOAD_WINDOW = 1024;
  /** Block download timeout base, expressed in multiples of the block interval (i.e. 10 min) */
  static constexpr double BLOCK_DOWNLOAD_TIMEOUT_BASE = 1;
  /** Additional block download timeout per parallel downloading peer (i.e. 5 min) */
  static constexpr double BLOCK_DOWNLOAD_TIMEOUT_PER_PEER = 0.5;
  /** Maximum number of headers to announce when relaying blocks with headers message.*/
  static const unsigned int MAX_BLOCKS_TO_ANNOUNCE = 8;
  /** Maximum number of unconnecting headers announcements before DoS score */
  static const int MAX_UNCONNECTING_HEADERS = 10;
  /** Minimum blocks required to signal NODE_NETWORK_LIMITED */
  static const unsigned int NODE_NETWORK_LIMITED_MIN_BLOCKS = 288;
  /** Average delay between local address broadcasts */
  static constexpr auto AVG_LOCAL_ADDRESS_BROADCAST_INTERVAL{24h};
  /** Average delay between peer address broadcasts */
  static constexpr auto AVG_ADDRESS_BROADCAST_INTERVAL{30s};
  /** Average delay between trickled inventory transmissions for inbound peers.
   *  Blocks and peers with NetPermissionFlags::NoBan permission bypass this. */
  static constexpr auto INBOUND_INVENTORY_BROADCAST_INTERVAL{5s};
  /** Average delay between trickled inventory transmissions for outbound peers.
   *  Use a smaller delay as there is less privacy concern for them.
   *  Blocks and peers with NetPermissionFlags::NoBan permission bypass this. */
  static constexpr auto OUTBOUND_INVENTORY_BROADCAST_INTERVAL{2s};
  /** Maximum rate of inventory items to send per second.
   *  Limits the impact of low-fee transaction floods. */
  static constexpr unsigned int INVENTORY_BROADCAST_PER_SECOND = 7;
  /** Maximum number of inventory items to send per transmission. */
  static constexpr unsigned int INVENTORY_BROADCAST_MAX = INVENTORY_BROADCAST_PER_SECOND * count_seconds(INBOUND_INVENTORY_BROADCAST_INTERVAL);
  /** The number of most recently announced transactions a peer can request. */
  static constexpr unsigned int INVENTORY_MAX_RECENT_RELAY = 3500;
  /** Verify that INVENTORY_MAX_RECENT_RELAY is enough to cache everything typically
   *  relayed before unconditional relay from the mempool kicks in. This is only a
   *  lower bound, and it should be larger to account for higher inv rate to outbound
   *  peers, and random variations in the broadcast mechanism. */
  static_assert(INVENTORY_MAX_RECENT_RELAY >= INVENTORY_BROADCAST_PER_SECOND * UNCONDITIONAL_RELAY_DELAY / std::chrono::seconds{1}, "INVENTORY_RELAY_MAX too low");
  /** Average delay between feefilter broadcasts in seconds. */
  static constexpr auto AVG_FEEFILTER_BROADCAST_INTERVAL{10min};
  /** Maximum feefilter broadcast delay after significant change. */
  static constexpr auto MAX_FEEFILTER_CHANGE_DELAY{5min};
  /** Maximum number of compact filters that may be requested with one getcfilters. See BIP 157. */
  static constexpr uint32_t MAX_GETCFILTERS_SIZE = 1000;
  /** Maximum number of cf hashes that may be requested with one getcfheaders. See BIP 157. */
  static constexpr uint32_t MAX_GETCFHEADERS_SIZE = 2000;
  /** the maximum percentage of addresses from our addrman to return in response to a getaddr message. */
  static constexpr size_t MAX_PCT_ADDR_TO_SEND = 23;
  /** The maximum number of address records permitted in an ADDR message. */
  static constexpr size_t MAX_ADDR_TO_SEND{1000};
  /** The maximum rate of address records we're willing to process on average. Can be bypassed using
   *  the NetPermissionFlags::Addr permission. */
  static constexpr double MAX_ADDR_RATE_PER_SECOND{0.1};
  /** The soft limit of the address processing token bucket (the regular MAX_ADDR_RATE_PER_SECOND
   *  based increments won't go above this, but the MAX_ADDR_TO_SEND increment following GETADDR
   *  is exempt from this limit). */
  static constexpr size_t MAX_ADDR_PROCESSING_TOKEN_BUCKET{MAX_ADDR_TO_SEND};
  
  // Internal stuff
  namespace {
  /** Blocks that are in flight, and that are in the queue to be downloaded. */
  struct QueuedBlock {
      /** BlockIndex. We must have this since we only request blocks when we've already validated the header. */
      const CBlockIndex* pindex;
      /** Optional, used for CMPCTBLOCK downloads */
      std::unique_ptr<PartiallyDownloadedBlock> partialBlock;
  };
  
  /**
   * Data structure for an individual peer. This struct is not protected by
   * cs_main since it does not contain validation-critical data.
   *
   * Memory is owned by shared pointers and this object is destructed when
   * the refcount drops to zero.
   *
   * Mutexes inside this struct must not be held when locking m_peer_mutex.
   *
   * TODO: move most members from CNodeState to this structure.
   * TODO: move remaining application-layer data members from CNode to this structure.
   */
  struct Peer {
      /** Same id as the CNode object for this peer */
      const NodeId m_id{0};
  
      /** Protects misbehavior data members */
      Mutex m_misbehavior_mutex;
      /** Accumulated misbehavior score for this peer */
      int m_misbehavior_score GUARDED_BY(m_misbehavior_mutex){0};
      /** Whether this peer should be disconnected and marked as discouraged (unless it has NetPermissionFlags::NoBan permission). */
      bool m_should_discourage GUARDED_BY(m_misbehavior_mutex){false};
  
      /** Protects block inventory data members */
      Mutex m_block_inv_mutex;
      /** List of blocks that we'll announce via an `inv` message.
       * There is no final sorting before sending, as they are always sent
       * immediately and in the order requested. */
      std::vector<uint256> m_blocks_for_inv_relay GUARDED_BY(m_block_inv_mutex);
      /** Unfiltered list of blocks that we'd like to announce via a `headers`
       * message. If we can't announce via a `headers` message, we'll fall back to
       * announcing via `inv`. */
      std::vector<uint256> m_blocks_for_headers_relay GUARDED_BY(m_block_inv_mutex);
      /** The final block hash that we sent in an `inv` message to this peer.
       * When the peer requests this block, we send an `inv` message to trigger
       * the peer to request the next sequence of block hashes.
       * Most peers use headers-first syncing, which doesn't use this mechanism */
      uint256 m_continuation_block GUARDED_BY(m_block_inv_mutex) {};
  
      /** This peer's reported block height when we connected */
      std::atomic<int> m_starting_height{-1};
  
      /** The pong reply we're expecting, or 0 if no pong expected. */
      std::atomic<uint64_t> m_ping_nonce_sent{0};
      /** When the last ping was sent, or 0 if no ping was ever sent */
      std::atomic<std::chrono::microseconds> m_ping_start{0us};
      /** Whether a ping has been requested by the user */
      std::atomic<bool> m_ping_queued{false};
  
      /** A vector of addresses to send to the peer, limited to MAX_ADDR_TO_SEND. */
      std::vector<CAddress> m_addrs_to_send;
      /** Probabilistic filter to track recent addr messages relayed with this
       *  peer. Used to avoid relaying redundant addresses to this peer.
       *
       *  We initialize this filter for outbound peers (other than
       *  block-relay-only connections) or when an inbound peer sends us an
       *  address related message (ADDR, ADDRV2, GETADDR).
       *
       *  Presence of this filter must correlate with m_addr_relay_enabled.
       **/
      std::unique_ptr<CRollingBloomFilter> m_addr_known;
      /** Whether we are participating in address relay with this connection.
       *
       *  We set this bool to true for outbound peers (other than
       *  block-relay-only connections), or when an inbound peer sends us an
       *  address related message (ADDR, ADDRV2, GETADDR).
       *
       *  We use this bool to decide whether a peer is eligible for gossiping
       *  addr messages. This avoids relaying to peers that are unlikely to
       *  forward them, effectively blackholing self announcements. Reasons
       *  peers might support addr relay on the link include that they connected
       *  to us as a block-relay-only peer or they are a light client.
       *
       *  This field must correlate with whether m_addr_known has been
       *  initialized.*/
      std::atomic_bool m_addr_relay_enabled{false};
      /** Whether a getaddr request to this peer is outstanding. */
      bool m_getaddr_sent{false};
      /** Guards address sending timers. */
      mutable Mutex m_addr_send_times_mutex;
      /** Time point to send the next ADDR message to this peer. */
      std::chrono::microseconds m_next_addr_send GUARDED_BY(m_addr_send_times_mutex){0};
      /** Time point to possibly re-announce our local address to this peer. */
      std::chrono::microseconds m_next_local_addr_send GUARDED_BY(m_addr_send_times_mutex){0};
      /** Whether the peer has signaled support for receiving ADDRv2 (BIP155)
       *  messages, indicating a preference to receive ADDRv2 instead of ADDR ones. */
      std::atomic_bool m_wants_addrv2{false};
      /** Whether this peer has already sent us a getaddr message. */
      bool m_getaddr_recvd{false};
      /** Number of addresses that can be processed from this peer. Start at 1 to
       *  permit self-announcement. */
      double m_addr_token_bucket{1.0};
      /** When m_addr_token_bucket was last updated */
      std::chrono::microseconds m_addr_token_timestamp{GetTime<std::chrono::microseconds>()};
      /** Total number of addresses that were dropped due to rate limiting. */
      std::atomic<uint64_t> m_addr_rate_limited{0};
      /** Total number of addresses that were processed (excludes rate-limited ones). */
      std::atomic<uint64_t> m_addr_processed{0};
  
      /** Set of txids to reconsider once their parent transactions have been accepted **/
      std::set<uint256> m_orphan_work_set GUARDED_BY(g_cs_orphans);
  
      /** Protects m_getdata_requests **/
      Mutex m_getdata_requests_mutex;
      /** Work queue of items requested by this peer **/
      std::deque<CInv> m_getdata_requests GUARDED_BY(m_getdata_requests_mutex);
  
      explicit Peer(NodeId id)
          : m_id(id)
      {}
  };
  
  using PeerRef = std::shared_ptr<Peer>;
  
  class PeerManagerImpl final : public PeerManager
  {
  public:
      PeerManagerImpl(const CChainParams& chainparams, CConnman& connman, AddrMan& addrman,
                      BanMan* banman, ChainstateManager& chainman,
                      CTxMemPool& pool, bool ignore_incoming_txs);
  
      /** Overridden from CValidationInterface. */
      void BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindexConnected) override;
      void BlockDisconnected(const std::shared_ptr<const CBlock> &block, const CBlockIndex* pindex) override;
      void UpdatedBlockTip(const CBlockIndex *pindexNew, const CBlockIndex *pindexFork, bool fInitialDownload) override;
      void BlockChecked(const CBlock& block, const BlockValidationState& state) override;
      void NewPoWValidBlock(const CBlockIndex *pindex, const std::shared_ptr<const CBlock>& pblock) override;
  
      /** Implement NetEventsInterface */
      void InitializeNode(CNode* pnode) override;
      void FinalizeNode(const CNode& node) override;
      bool ProcessMessages(CNode* pfrom, std::atomic<bool>& interrupt) override;
      bool SendMessages(CNode* pto) override EXCLUSIVE_LOCKS_REQUIRED(pto->cs_sendProcessing);
  
      /** Implement PeerManager */
      void StartScheduledTasks(CScheduler& scheduler) override;
      void CheckForStaleTipAndEvictPeers() override;
      std::optional<std::string> FetchBlock(NodeId peer_id, const CBlockIndex& block_index) override;
      bool GetNodeStateStats(NodeId nodeid, CNodeStateStats& stats) const override;
      bool IgnoresIncomingTxs() override { return m_ignore_incoming_txs; }
      void SendPings() override;
      void RelayTransaction(const uint256& txid, const uint256& wtxid) override;
      void SetBestHeight(int height) override { m_best_height = height; };
      void Misbehaving(const NodeId pnode, const int howmuch, const std::string& message) override;
      void ProcessMessage(CNode& pfrom, const std::string& msg_type, CDataStream& vRecv,
                          const std::chrono::microseconds time_received, const std::atomic<bool>& interruptMsgProc) override;
  
  private:
      void _RelayTransaction(const uint256& txid, const uint256& wtxid)
          EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
      /** Consider evicting an outbound peer based on the amount of time they've been behind our tip */
      void ConsiderEviction(CNode& pto, std::chrono::seconds time_in_seconds) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
      /** If we have extra outbound peers, try to disconnect the one with the oldest block announcement */
      void EvictExtraOutboundPeers(std::chrono::seconds now) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
      /** Retrieve unbroadcast transactions from the mempool and reattempt sending to peers */
      void ReattemptInitialBroadcast(CScheduler& scheduler);
  
      /** Get a shared pointer to the Peer object.
       *  May return an empty shared_ptr if the Peer object can't be found. */
      PeerRef GetPeerRef(NodeId id) const;
  
      /** Get a shared pointer to the Peer object and remove it from m_peer_map.
       *  May return an empty shared_ptr if the Peer object can't be found. */
      PeerRef RemovePeer(NodeId id);
  
      /**
       * Potentially mark a node discouraged based on the contents of a BlockValidationState object
       *
       * @param[in] via_compact_block this bool is passed in because net_processing should
       * punish peers differently depending on whether the data was provided in a compact
       * block message or not. If the compact block had a valid header, but contained invalid
       * txs, the peer should not be punished. See BIP 152.
       *
       * @return Returns true if the peer was punished (probably disconnected)
       */
      bool MaybePunishNodeForBlock(NodeId nodeid, const BlockValidationState& state,
                                   bool via_compact_block, const std::string& message = "");
  
      /**
       * Potentially disconnect and discourage a node based on the contents of a TxValidationState object
       *
       * @return Returns true if the peer was punished (probably disconnected)
       */
      bool MaybePunishNodeForTx(NodeId nodeid, const TxValidationState& state, const std::string& message = "");
  
      /** Maybe disconnect a peer and discourage future connections from its address.
       *
       * @param[in]   pnode     The node to check.
       * @param[in]   peer      The peer object to check.
       * @return                True if the peer was marked for disconnection in this function
       */
      bool MaybeDiscourageAndDisconnect(CNode& pnode, Peer& peer);
  
      void ProcessOrphanTx(std::set<uint256>& orphan_work_set) EXCLUSIVE_LOCKS_REQUIRED(cs_main, g_cs_orphans);
      /** Process a single headers message from a peer. */
      void ProcessHeadersMessage(CNode& pfrom, const Peer& peer,
                                 const std::vector<CBlockHeader>& headers,
                                 bool via_compact_block);
  
      void SendBlockTransactions(CNode& pfrom, const CBlock& block, const BlockTransactionsRequest& req);
  
      /** Register with TxRequestTracker that an INV has been received from a
       *  peer. The announcement parameters are decided in PeerManager and then
       *  passed to TxRequestTracker. */
      void AddTxAnnouncement(const CNode& node, const GenTxid& gtxid, std::chrono::microseconds current_time)
          EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
  
      /** Send a version message to a peer */
      void PushNodeVersion(CNode& pnode);
  
      /** Send a ping message every PING_INTERVAL or if requested via RPC. May
       *  mark the peer to be disconnected if a ping has timed out.
       *  We use mockable time for ping timeouts, so setmocktime may cause pings
       *  to time out. */
      void MaybeSendPing(CNode& node_to, Peer& peer, std::chrono::microseconds now);
  
      /** Send `addr` messages on a regular schedule. */
      void MaybeSendAddr(CNode& node, Peer& peer, std::chrono::microseconds current_time);
  
      /** Relay (gossip) an address to a few randomly chosen nodes.
       *
       * @param[in] originator   The id of the peer that sent us the address. We don't want to relay it back.
       * @param[in] addr         Address to relay.
       * @param[in] fReachable   Whether the address' network is reachable. We relay unreachable
       *                         addresses less.
       */
      void RelayAddress(NodeId originator, const CAddress& addr, bool fReachable);
  
      /** Send `feefilter` message. */
      void MaybeSendFeefilter(CNode& node, std::chrono::microseconds current_time) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
      const CChainParams& m_chainparams;
      CConnman& m_connman;
      AddrMan& m_addrman;
      /** Pointer to this node's banman. May be nullptr - check existence before dereferencing. */
      BanMan* const m_banman;
      ChainstateManager& m_chainman;
      CTxMemPool& m_mempool;
      TxRequestTracker m_txrequest GUARDED_BY(::cs_main);
  
      /** The height of the best chain */
      std::atomic<int> m_best_height{-1};
  
      /** Next time to check for stale tip */
      std::chrono::seconds m_stale_tip_check_time{0s};
  
      /** Whether this node is running in blocks only mode */
      const bool m_ignore_incoming_txs;
  
      /** Whether we've completed initial sync yet, for determining when to turn
        * on extra block-relay-only peers. */
      bool m_initial_sync_finished{false};
  
      /** Protects m_peer_map. This mutex must not be locked while holding a lock
       *  on any of the mutexes inside a Peer object. */
      mutable Mutex m_peer_mutex;
      /**
       * Map of all Peer objects, keyed by peer id. This map is protected
       * by the m_peer_mutex. Once a shared pointer reference is
       * taken, the lock may be released. Individual fields are protected by
       * their own locks.
       */
      std::map<NodeId, PeerRef> m_peer_map GUARDED_BY(m_peer_mutex);
  
      std::atomic<std::chrono::microseconds> m_next_inv_to_inbounds{0us};
  
      /** Number of nodes with fSyncStarted. */
      int nSyncStarted GUARDED_BY(cs_main) = 0;
  
      /**
       * Sources of received blocks, saved to be able punish them when processing
       * happens afterwards.
       * Set mapBlockSource[hash].second to false if the node should not be
       * punished if the block is invalid.
       */
      std::map<uint256, std::pair<NodeId, bool>> mapBlockSource GUARDED_BY(cs_main);
  
      /** Number of peers with wtxid relay. */
      int m_wtxid_relay_peers GUARDED_BY(cs_main) = 0;
  
      /** Number of outbound peers with m_chain_sync.m_protect. */
      int m_outbound_peers_with_protect_from_disconnect GUARDED_BY(cs_main) = 0;
  
      bool AlreadyHaveTx(const GenTxid& gtxid) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
      /**
       * Filter for transactions that were recently rejected by the mempool.
       * These are not rerequested until the chain tip changes, at which point
       * the entire filter is reset.
       *
       * Without this filter we'd be re-requesting txs from each of our peers,
       * increasing bandwidth consumption considerably. For instance, with 100
       * peers, half of which relay a tx we don't accept, that might be a 50x
       * bandwidth increase. A flooding attacker attempting to roll-over the
       * filter using minimum-sized, 60byte, transactions might manage to send
       * 1000/sec if we have fast peers, so we pick 120,000 to give our peers a
       * two minute window to send invs to us.
       *
       * Decreasing the false positive rate is fairly cheap, so we pick one in a
       * million to make it highly unlikely for users to have issues with this
       * filter.
       *
       * We typically only add wtxids to this filter. For non-segwit
       * transactions, the txid == wtxid, so this only prevents us from
       * re-downloading non-segwit transactions when communicating with
       * non-wtxidrelay peers -- which is important for avoiding malleation
       * attacks that could otherwise interfere with transaction relay from
       * non-wtxidrelay peers. For communicating with wtxidrelay peers, having
       * the reject filter store wtxids is exactly what we want to avoid
       * redownload of a rejected transaction.
       *
       * In cases where we can tell that a segwit transaction will fail
       * validation no matter the witness, we may add the txid of such
       * transaction to the filter as well. This can be helpful when
       * communicating with txid-relay peers or if we were to otherwise fetch a
       * transaction via txid (eg in our orphan handling).
       *
       * Memory used: 1.3 MB
       */
      CRollingBloomFilter m_recent_rejects GUARDED_BY(::cs_main){120'000, 0.000'001};
      uint256 hashRecentRejectsChainTip GUARDED_BY(cs_main);
  
      /*
       * Filter for transactions that have been recently confirmed.
       * We use this to avoid requesting transactions that have already been
       * confirnmed.
       *
       * Blocks don't typically have more than 4000 transactions, so this should
       * be at least six blocks (~1 hr) worth of transactions that we can store,
       * inserting both a txid and wtxid for every observed transaction.
       * If the number of transactions appearing in a block goes up, or if we are
       * seeing getdata requests more than an hour after initial announcement, we
       * can increase this number.
       * The false positive rate of 1/1M should come out to less than 1
       * transaction per day that would be inadvertently ignored (which is the
       * same probability that we have in the reject filter).
       */
      Mutex m_recent_confirmed_transactions_mutex;
      CRollingBloomFilter m_recent_confirmed_transactions GUARDED_BY(m_recent_confirmed_transactions_mutex){48'000, 0.000'001};
  
      /**
       * For sending `inv`s to inbound peers, we use a single (exponentially
       * distributed) timer for all peers. If we used a separate timer for each
       * peer, a spy node could make multiple inbound connections to us to
       * accurately determine when we received the transaction (and potentially
       * determine the transaction's origin). */
      std::chrono::microseconds NextInvToInbounds(std::chrono::microseconds now,
                                                  std::chrono::seconds average_interval);
  
      /** Have we requested this block from a peer */
      bool IsBlockRequested(const uint256& hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
      /** Remove this block from our tracked requested blocks. Called if:
       *  - the block has been received from a peer
       *  - the request for the block has timed out
       */
      void RemoveBlockRequest(const uint256& hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
      /* Mark a block as in flight
       * 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
       */
      bool BlockRequested(NodeId nodeid, const CBlockIndex& block, std::list<QueuedBlock>::iterator** pit = nullptr) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
      bool TipMayBeStale() EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
      /** Update pindexLastCommonBlock and add not-in-flight missing successors to vBlocks, until it has
       *  at most count entries.
       */
      void FindNextBlocksToDownload(NodeId nodeid, unsigned int count, std::vector<const CBlockIndex*>& vBlocks, NodeId& nodeStaller) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
      std::map<uint256, std::pair<NodeId, std::list<QueuedBlock>::iterator> > mapBlocksInFlight GUARDED_BY(cs_main);
  
      /** When our tip was last updated. */
      std::atomic<std::chrono::seconds> m_last_tip_update{0s};
  
      /** Determine whether or not a peer can request a transaction, and return it (or nullptr if not found or not allowed). */
      CTransactionRef FindTxForGetData(const CNode& peer, const GenTxid& gtxid, const std::chrono::seconds mempool_req, const std::chrono::seconds now) LOCKS_EXCLUDED(cs_main);
  
      void ProcessGetData(CNode& pfrom, Peer& peer, const std::atomic<bool>& interruptMsgProc) EXCLUSIVE_LOCKS_REQUIRED(peer.m_getdata_requests_mutex) LOCKS_EXCLUDED(::cs_main);
  
      /** Process a new block. Perform any post-processing housekeeping */
      void ProcessBlock(CNode& node, const std::shared_ptr<const CBlock>& block, bool force_processing);
  
      /** Relay map (txid or wtxid -> CTransactionRef) */
      typedef std::map<uint256, CTransactionRef> MapRelay;
      MapRelay mapRelay GUARDED_BY(cs_main);
      /** Expiration-time ordered list of (expire time, relay map entry) pairs. */
      std::deque<std::pair<std::chrono::microseconds, MapRelay::iterator>> g_relay_expiration GUARDED_BY(cs_main);
  
      /**
       * 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.
       */
      void MaybeSetPeerAsAnnouncingHeaderAndIDs(NodeId nodeid) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
      /** Stack of nodes which we have set to announce using compact blocks */
      std::list<NodeId> lNodesAnnouncingHeaderAndIDs GUARDED_BY(cs_main);
  
      /** Number of peers from which we're downloading blocks. */
      int m_peers_downloading_from GUARDED_BY(cs_main) = 0;
  
      /** Storage for orphan information */
      TxOrphanage m_orphanage;
  
      void AddToCompactExtraTransactions(const CTransactionRef& tx) EXCLUSIVE_LOCKS_REQUIRED(g_cs_orphans);
  
      /** Orphan/conflicted/etc transactions that are kept for compact block reconstruction.
       *  The last -blockreconstructionextratxn/DEFAULT_BLOCK_RECONSTRUCTION_EXTRA_TXN of
       *  these are kept in a ring buffer */
      std::vector<std::pair<uint256, CTransactionRef>> vExtraTxnForCompact GUARDED_BY(g_cs_orphans);
      /** Offset into vExtraTxnForCompact to insert the next tx */
      size_t vExtraTxnForCompactIt GUARDED_BY(g_cs_orphans) = 0;
  
      /** Check whether the last unknown block a peer advertised is not yet known. */
      void ProcessBlockAvailability(NodeId nodeid) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
      /** Update tracking information about which blocks a peer is assumed to have. */
      void UpdateBlockAvailability(NodeId nodeid, const uint256& hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
      bool CanDirectFetch() EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
      /**
       * 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.
       */
      bool BlockRequestAllowed(const CBlockIndex* pindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
      bool AlreadyHaveBlock(const uint256& block_hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
      void ProcessGetBlockData(CNode& pfrom, Peer& peer, const CInv& inv);
  
      /**
       * Validation logic for compact filters request handling.
       *
       * May disconnect from the peer in the case of a bad request.
       *
       * @param[in]   peer            The peer that we received the request from
       * @param[in]   filter_type     The filter type the request is for. Must be basic filters.
       * @param[in]   start_height    The start height for the request
       * @param[in]   stop_hash       The stop_hash for the request
       * @param[in]   max_height_diff The maximum number of items permitted to request, as specified in BIP 157
       * @param[out]  stop_index      The CBlockIndex for the stop_hash block, if the request can be serviced.
       * @param[out]  filter_index    The filter index, if the request can be serviced.
       * @return                      True if the request can be serviced.
       */
      bool PrepareBlockFilterRequest(CNode& peer,
                                     BlockFilterType filter_type, uint32_t start_height,
                                     const uint256& stop_hash, uint32_t max_height_diff,
                                     const CBlockIndex*& stop_index,
                                     BlockFilterIndex*& filter_index);
  
      /**
       * Handle a cfilters request.
       *
       * May disconnect from the peer in the case of a bad request.
       *
       * @param[in]   peer            The peer that we received the request from
       * @param[in]   vRecv           The raw message received
       */
      void ProcessGetCFilters(CNode& peer, CDataStream& vRecv);
  
      /**
       * Handle a cfheaders request.
       *
       * May disconnect from the peer in the case of a bad request.
       *
       * @param[in]   peer            The peer that we received the request from
       * @param[in]   vRecv           The raw message received
       */
      void ProcessGetCFHeaders(CNode& peer, CDataStream& vRecv);
  
      /**
       * Handle a getcfcheckpt request.
       *
       * May disconnect from the peer in the case of a bad request.
       *
       * @param[in]   peer            The peer that we received the request from
       * @param[in]   vRecv           The raw message received
       */
      void ProcessGetCFCheckPt(CNode& peer, CDataStream& vRecv);
  
      /** Checks if address relay is permitted with peer. If needed, initializes
       * the m_addr_known bloom filter and sets m_addr_relay_enabled to true.
       *
       *  @return   True if address relay is enabled with peer
       *            False if address relay is disallowed
       */
      bool SetupAddressRelay(const CNode& node, Peer& peer);
  };
  } // namespace
  
  namespace {
      /** Number of preferable block download peers. */
      int nPreferredDownload GUARDED_BY(cs_main) = 0;
  } // namespace
  
  namespace {
  /**
   * 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 best known block we know this peer has announced.
      const CBlockIndex* pindexBestKnownBlock{nullptr};
      //! The hash of the last unknown block this peer has announced.
      uint256 hashLastUnknownBlock{};
      //! The last full block we both have.
      const CBlockIndex* pindexLastCommonBlock{nullptr};
      //! The best header we have sent our peer.
      const CBlockIndex* pindexBestHeaderSent{nullptr};
      //! Length of current-streak of unconnecting headers announcements
      int nUnconnectingHeaders{0};
      //! Whether we've started headers synchronization with this peer.
      bool fSyncStarted{false};
      //! When to potentially disconnect peer for stalling headers download
      std::chrono::microseconds m_headers_sync_timeout{0us};
      //! Since when we're stalling block download progress (in microseconds), or 0.
      std::chrono::microseconds m_stalling_since{0us};
      std::list<QueuedBlock> vBlocksInFlight;
      //! When the first entry in vBlocksInFlight started downloading. Don't care when vBlocksInFlight is empty.
      std::chrono::microseconds m_downloading_since{0us};
      int nBlocksInFlight{0};
      //! Whether we consider this a preferred download peer.
      bool fPreferredDownload{false};
      //! Whether this peer wants invs or headers (when possible) for block announcements.
      bool fPreferHeaders{false};
      //! Whether this peer wants invs or cmpctblocks (when possible) for block announcements.
      bool fPreferHeaderAndIDs{false};
      /**
        * 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{false};
      //! Whether this peer can give us witnesses
      bool fHaveWitness{false};
      //! Whether this peer wants witnesses in cmpctblocks/blocktxns
      bool fWantsCmpctWitness{false};
      /**
       * 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{false};
  
      /** State used to enforce CHAIN_SYNC_TIMEOUT and EXTRA_PEER_CHECK_INTERVAL logic.
        *
        * Both are only in effect for outbound, non-manual, non-protected connections.
        * Any peer protected (m_protect = true) is not chosen for eviction. A peer is
        * marked as protected if all of these are true:
        *   - its connection type is IsBlockOnlyConn() == false
        *   - it gave us a valid connecting header
        *   - we haven't reached MAX_OUTBOUND_PEERS_TO_PROTECT_FROM_DISCONNECT yet
        *   - its chain tip has at least as much work as ours
        *
        * CHAIN_SYNC_TIMEOUT: if a peer's best known block has less work than our tip,
        * set a timeout CHAIN_SYNC_TIMEOUT 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.
        *
        * EXTRA_PEER_CHECK_INTERVAL: after each interval, if we have too many outbound peers,
        * drop the outbound one that least recently announced us a new block.
        */
      struct ChainSyncTimeoutState {
          //! A timeout used for checking whether our peer has sufficiently synced
          std::chrono::seconds m_timeout{0s};
          //! A header with the work we require on our peer's chain
          const CBlockIndex* m_work_header{nullptr};
          //! After timeout is reached, set to true after sending getheaders
          bool m_sent_getheaders{false};
          //! Whether this peer is protected from disconnection due to a bad/slow chain
          bool m_protect{false};
      };
  
      ChainSyncTimeoutState m_chain_sync;
  
      //! Time of last new block announcement
      int64_t m_last_block_announcement{0};
  
      //! Whether this peer is an inbound connection
      const bool m_is_inbound;
  
      //! A rolling bloom filter of all announced tx CInvs to this peer.
      CRollingBloomFilter m_recently_announced_invs = CRollingBloomFilter{INVENTORY_MAX_RECENT_RELAY, 0.000001};
  
      //! Whether this peer relays txs via wtxid
      bool m_wtxid_relay{false};
  
      CNodeState(bool is_inbound) : m_is_inbound(is_inbound) {}
  };
  
  /** Map maintaining per-node state. */
  static std::map<NodeId, CNodeState> mapNodeState GUARDED_BY(cs_main);
  
  static CNodeState *State(NodeId pnode) EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
      std::map<NodeId, CNodeState>::iterator it = mapNodeState.find(pnode);
      if (it == mapNodeState.end())
          return nullptr;
      return &it->second;
  }
  
  /**
   * Whether the peer supports the address. For example, a peer that does not
   * implement BIP155 cannot receive Tor v3 addresses because it requires
   * ADDRv2 (BIP155) encoding.
   */
  static bool IsAddrCompatible(const Peer& peer, const CAddress& addr)
  {
      return peer.m_wants_addrv2 || addr.IsAddrV1Compatible();
  }
  
  static void AddAddressKnown(Peer& peer, const CAddress& addr)
  {
      assert(peer.m_addr_known);
      peer.m_addr_known->insert(addr.GetKey());
  }
  
  static void PushAddress(Peer& peer, const CAddress& addr, FastRandomContext& insecure_rand)
  {
      // Known checking here is only to save space from duplicates.
      // Before sending, we'll filter it again for known addresses that were
      // added after addresses were pushed.
      assert(peer.m_addr_known);
      if (addr.IsValid() && !peer.m_addr_known->contains(addr.GetKey()) && IsAddrCompatible(peer, addr)) {
          if (peer.m_addrs_to_send.size() >= MAX_ADDR_TO_SEND) {
              peer.m_addrs_to_send[insecure_rand.randrange(peer.m_addrs_to_send.size())] = addr;
          } else {
              peer.m_addrs_to_send.push_back(addr);
          }
      }
  }
  
  static void UpdatePreferredDownload(const 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.IsInboundConn() || node.HasPermission(NetPermissionFlags::NoBan)) && !node.IsAddrFetchConn() && !node.fClient;
  
      nPreferredDownload += state->fPreferredDownload;
  }
  
  std::chrono::microseconds PeerManagerImpl::NextInvToInbounds(std::chrono::microseconds now,
                                                               std::chrono::seconds average_interval)
  {
      if (m_next_inv_to_inbounds.load() < now) {
          // If this function were called from multiple threads simultaneously
          // it would possible that both update the next send variable, and return a different result to their caller.
          // This is not possible in practice as only the net processing thread invokes this function.
          m_next_inv_to_inbounds = GetExponentialRand(now, average_interval);
      }
      return m_next_inv_to_inbounds;
  }
  
  bool PeerManagerImpl::IsBlockRequested(const uint256& hash)
  {
      return mapBlocksInFlight.find(hash) != mapBlocksInFlight.end();
  }
  
  void PeerManagerImpl::RemoveBlockRequest(const uint256& hash)
  {
      auto it = mapBlocksInFlight.find(hash);
      if (it == mapBlocksInFlight.end()) {
          // Block was not requested
          return;
      }
  
      auto [node_id, list_it] = it->second;
      CNodeState *state = State(node_id);
      assert(state != nullptr);
  
      if (state->vBlocksInFlight.begin() == list_it) {
          // First block on the queue was received, update the start download time for the next one
          state->m_downloading_since = std::max(state->m_downloading_since, GetTime<std::chrono::microseconds>());
      }
      state->vBlocksInFlight.erase(list_it);
  
      state->nBlocksInFlight--;
      if (state->nBlocksInFlight == 0) {
          // Last validated block on the queue was received.
          m_peers_downloading_from--;
      }
      state->m_stalling_since = 0us;
      mapBlocksInFlight.erase(it);
  }
  
  bool PeerManagerImpl::BlockRequested(NodeId nodeid, const CBlockIndex& block, std::list<QueuedBlock>::iterator** pit)
  {
      const uint256& hash{block.GetBlockHash()};
  
      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.
      RemoveBlockRequest(hash);
  
      std::list<QueuedBlock>::iterator it = state->vBlocksInFlight.insert(state->vBlocksInFlight.end(),
              {&block, std::unique_ptr<PartiallyDownloadedBlock>(pit ? new PartiallyDownloadedBlock(&m_mempool) : nullptr)});
      state->nBlocksInFlight++;
      if (state->nBlocksInFlight == 1) {
          // We're starting a block download (batch) from this peer.
          state->m_downloading_since = GetTime<std::chrono::microseconds>();
          m_peers_downloading_from++;
      }
      itInFlight = mapBlocksInFlight.insert(std::make_pair(hash, std::make_pair(nodeid, it))).first;
      if (pit) {
          *pit = &itInFlight->second.second;
      }
      return true;
  }
  
  void PeerManagerImpl::MaybeSetPeerAsAnnouncingHeaderAndIDs(NodeId nodeid)
  {
      AssertLockHeld(cs_main);
  
      // Never request high-bandwidth mode from peers if we're blocks-only. Our
      // mempool will not contain the transactions necessary to reconstruct the
      // compact block.
      if (m_ignore_incoming_txs) return;
  
      CNodeState* nodestate = State(nodeid);
      if (!nodestate || !nodestate->fSupportsDesiredCmpctVersion) {
          // Never ask from peers who can't provide witnesses.
          return;
      }
      if (nodestate->fProvidesHeaderAndIDs) {
          int num_outbound_hb_peers = 0;
          for (std::list<NodeId>::iterator it = lNodesAnnouncingHeaderAndIDs.begin(); it != lNodesAnnouncingHeaderAndIDs.end(); it++) {
              if (*it == nodeid) {
                  lNodesAnnouncingHeaderAndIDs.erase(it);
                  lNodesAnnouncingHeaderAndIDs.push_back(nodeid);
                  return;
              }
              CNodeState *state = State(*it);
              if (state != nullptr && !state->m_is_inbound) ++num_outbound_hb_peers;
          }
          if (nodestate->m_is_inbound) {
              // If we're adding an inbound HB peer, make sure we're not removing
              // our last outbound HB peer in the process.
              if (lNodesAnnouncingHeaderAndIDs.size() >= 3 && num_outbound_hb_peers == 1) {
                  CNodeState *remove_node = State(lNodesAnnouncingHeaderAndIDs.front());
                  if (remove_node != nullptr && !remove_node->m_is_inbound) {
                      // Put the HB outbound peer in the second slot, so that it
                      // doesn't get removed.
                      std::swap(lNodesAnnouncingHeaderAndIDs.front(), *std::next(lNodesAnnouncingHeaderAndIDs.begin()));
                  }
              }
          }
          m_connman.ForNode(nodeid, [this](CNode* pfrom) EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
              AssertLockHeld(::cs_main);
              uint64_t nCMPCTBLOCKVersion = 2;
              if (lNodesAnnouncingHeaderAndIDs.size() >= 3) {
                  // As per BIP152, we only get 3 of our peers to announce
                  // blocks using compact encodings.
                  m_connman.ForNode(lNodesAnnouncingHeaderAndIDs.front(), [this, nCMPCTBLOCKVersion](CNode* pnodeStop){
                      m_connman.PushMessage(pnodeStop, CNetMsgMaker(pnodeStop->GetCommonVersion()).Make(NetMsgType::SENDCMPCT, /*fAnnounceUsingCMPCTBLOCK=*/false, nCMPCTBLOCKVersion));
                      // save BIP152 bandwidth state: we select peer to be low-bandwidth
                      pnodeStop->m_bip152_highbandwidth_to = false;
                      return true;
                  });
                  lNodesAnnouncingHeaderAndIDs.pop_front();
              }
              m_connman.PushMessage(pfrom, CNetMsgMaker(pfrom->GetCommonVersion()).Make(NetMsgType::SENDCMPCT, /*fAnnounceUsingCMPCTBLOCK=*/true, nCMPCTBLOCKVersion));
              // save BIP152 bandwidth state: we select peer to be high-bandwidth
              pfrom->m_bip152_highbandwidth_to = true;
              lNodesAnnouncingHeaderAndIDs.push_back(pfrom->GetId());
              return true;
          });
      }
  }
  
  bool PeerManagerImpl::TipMayBeStale()
  {
      AssertLockHeld(cs_main);
      const Consensus::Params& consensusParams = m_chainparams.GetConsensus();
      if (m_last_tip_update.load() == 0s) {
          m_last_tip_update = GetTime<std::chrono::seconds>();
      }
      return m_last_tip_update.load() < GetTime<std::chrono::seconds>() - std::chrono::seconds{consensusParams.nPowTargetSpacing * 3} && mapBlocksInFlight.empty();
  }
  
  bool PeerManagerImpl::CanDirectFetch()
  {
      return m_chainman.ActiveChain().Tip()->GetBlockTime() > GetAdjustedTime() - m_chainparams.GetConsensus().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;
  }
  
  void PeerManagerImpl::ProcessBlockAvailability(NodeId nodeid) {
      CNodeState *state = State(nodeid);
      assert(state != nullptr);
  
      if (!state->hashLastUnknownBlock.IsNull()) {
          const CBlockIndex* pindex = m_chainman.m_blockman.LookupBlockIndex(state->hashLastUnknownBlock);
          if (pindex && pindex->nChainWork > 0) {
              if (state->pindexBestKnownBlock == nullptr || pindex->nChainWork >= state->pindexBestKnownBlock->nChainWork) {
                  state->pindexBestKnownBlock = pindex;
              }
              state->hashLastUnknownBlock.SetNull();
          }
      }
  }
  
  void PeerManagerImpl::UpdateBlockAvailability(NodeId nodeid, const uint256 &hash) {
      CNodeState *state = State(nodeid);
      assert(state != nullptr);
  
      ProcessBlockAvailability(nodeid);
  
      const CBlockIndex* pindex = m_chainman.m_blockman.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;
      }
  }
  
  void PeerManagerImpl::FindNextBlocksToDownload(NodeId nodeid, unsigned int count, std::vector<const CBlockIndex*>& vBlocks, NodeId& nodeStaller)
  {
      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 < m_chainman.ActiveChain().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 = m_chainman.ActiveChain()[std::min(state->pindexBestKnownBlock->nHeight, m_chainman.ActiveChain().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;
  
      const Consensus::Params& consensusParams = m_chainparams.GetConsensus();
      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 && DeploymentActiveAt(*pindex, consensusParams, Consensus::DEPLOYMENT_SEGWIT)) {
                  // We wouldn't download this block or its descendants from this peer.
                  return;
              }
              if (pindex->nStatus & BLOCK_HAVE_DATA || m_chainman.ActiveChain().Contains(pindex)) {
                  if (pindex->HaveTxsDownloaded())
                      state->pindexLastCommonBlock = pindex;
              } else if (!IsBlockRequested(pindex->GetBlockHash())) {
                  // 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
  
  void PeerManagerImpl::PushNodeVersion(CNode& pnode)
  {
      // Note that pnode->GetLocalServices() is a reflection of the local
      // services we were offering when the CNode object was created for this
      // peer.
      uint64_t my_services{pnode.GetLocalServices()};
      const int64_t nTime{count_seconds(GetTime<std::chrono::seconds>())};
      uint64_t nonce = pnode.GetLocalNonce();
      const int nNodeStartingHeight{m_best_height};
      NodeId nodeid = pnode.GetId();
      CAddress addr = pnode.addr;
  
      CService addr_you = addr.IsRoutable() && !IsProxy(addr) && addr.IsAddrV1Compatible() ? addr : CService();
      uint64_t your_services{addr.nServices};
  
      const bool tx_relay = !m_ignore_incoming_txs && pnode.m_tx_relay != nullptr && !pnode.IsFeelerConn();
      m_connman.PushMessage(&pnode, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::VERSION, PROTOCOL_VERSION, my_services, nTime,
              your_services, addr_you, // Together the pre-version-31402 serialization of CAddress "addrYou" (without nTime)
              my_services, CService(), // Together the pre-version-31402 serialization of CAddress "addrMe" (without nTime)
              nonce, strSubVersion, nNodeStartingHeight, tx_relay));
  
      if (fLogIPs) {
          LogPrint(BCLog::NET, "send version message: version %d, blocks=%d, them=%s, txrelay=%d, peer=%d\n", PROTOCOL_VERSION, nNodeStartingHeight, addr_you.ToString(), tx_relay, nodeid);
      } else {
          LogPrint(BCLog::NET, "send version message: version %d, blocks=%d, txrelay=%d, peer=%d\n", PROTOCOL_VERSION, nNodeStartingHeight, tx_relay, nodeid);
      }
  }
  
  void PeerManagerImpl::AddTxAnnouncement(const CNode& node, const GenTxid& gtxid, std::chrono::microseconds current_time)
  {
      AssertLockHeld(::cs_main); // For m_txrequest
      NodeId nodeid = node.GetId();
      if (!node.HasPermission(NetPermissionFlags::Relay) && m_txrequest.Count(nodeid) >= MAX_PEER_TX_ANNOUNCEMENTS) {
          // Too many queued announcements from this peer
          return;
      }
      const CNodeState* state = State(nodeid);
  
      // Decide the TxRequestTracker parameters for this announcement:
      // - "preferred": if fPreferredDownload is set (= outbound, or NetPermissionFlags::NoBan permission)
      // - "reqtime": current time plus delays for:
      //   - NONPREF_PEER_TX_DELAY for announcements from non-preferred connections
      //   - TXID_RELAY_DELAY for txid announcements while wtxid peers are available
      //   - OVERLOADED_PEER_TX_DELAY for announcements from peers which have at least
      //     MAX_PEER_TX_REQUEST_IN_FLIGHT requests in flight (and don't have NetPermissionFlags::Relay).
      auto delay{0us};
      const bool preferred = state->fPreferredDownload;
      if (!preferred) delay += NONPREF_PEER_TX_DELAY;
      if (!gtxid.IsWtxid() && m_wtxid_relay_peers > 0) delay += TXID_RELAY_DELAY;
      const bool overloaded = !node.HasPermission(NetPermissionFlags::Relay) &&
          m_txrequest.CountInFlight(nodeid) >= MAX_PEER_TX_REQUEST_IN_FLIGHT;
      if (overloaded) delay += OVERLOADED_PEER_TX_DELAY;
      m_txrequest.ReceivedInv(nodeid, gtxid, preferred, current_time + delay);
  }
  
  // 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;
  }
  
  void PeerManagerImpl::InitializeNode(CNode *pnode)
  {
      NodeId nodeid = pnode->GetId();
      {
          LOCK(cs_main);
          mapNodeState.emplace_hint(mapNodeState.end(), std::piecewise_construct, std::forward_as_tuple(nodeid), std::forward_as_tuple(pnode->IsInboundConn()));
          assert(m_txrequest.Count(nodeid) == 0);
      }
      {
          PeerRef peer = std::make_shared<Peer>(nodeid);
          LOCK(m_peer_mutex);
          m_peer_map.emplace_hint(m_peer_map.end(), nodeid, std::move(peer));
      }
      if (!pnode->IsInboundConn()) {
          PushNodeVersion(*pnode);
      }
  }
  
  void PeerManagerImpl::ReattemptInitialBroadcast(CScheduler& scheduler)
  {
      std::set<uint256> unbroadcast_txids = m_mempool.GetUnbroadcastTxs();
  
      for (const auto& txid : unbroadcast_txids) {
          CTransactionRef tx = m_mempool.get(txid);
  
          if (tx != nullptr) {
              LOCK(cs_main);
              _RelayTransaction(txid, tx->GetWitnessHash());
          } else {
              m_mempool.RemoveUnbroadcastTx(txid, true);
          }
      }
  
      // Schedule next run for 10-15 minutes in the future.
      // We add randomness on every cycle to avoid the possibility of P2P fingerprinting.
      const std::chrono::milliseconds delta = 10min + GetRandMillis(5min);
      scheduler.scheduleFromNow([&] { ReattemptInitialBroadcast(scheduler); }, delta);
  }
  
  void PeerManagerImpl::FinalizeNode(const CNode& node)
  {
      NodeId nodeid = node.GetId();
      int misbehavior{0};
      {
      LOCK(cs_main);
      {
          // We remove the PeerRef from g_peer_map here, but we don't always
          // destruct the Peer. Sometimes another thread is still holding a
          // PeerRef, so the refcount is >= 1. Be careful not to do any
          // processing here that assumes Peer won't be changed before it's
          // destructed.
          PeerRef peer = RemovePeer(nodeid);
          assert(peer != nullptr);
          misbehavior = WITH_LOCK(peer->m_misbehavior_mutex, return peer->m_misbehavior_score);
      }
      CNodeState *state = State(nodeid);
      assert(state != nullptr);
  
      if (state->fSyncStarted)
          nSyncStarted--;
  
      for (const QueuedBlock& entry : state->vBlocksInFlight) {
          mapBlocksInFlight.erase(entry.pindex->GetBlockHash());
      }
      WITH_LOCK(g_cs_orphans, m_orphanage.EraseForPeer(nodeid));
      m_txrequest.DisconnectedPeer(nodeid);
      nPreferredDownload -= state->fPreferredDownload;
      m_peers_downloading_from -= (state->nBlocksInFlight != 0);
      assert(m_peers_downloading_from >= 0);
      m_outbound_peers_with_protect_from_disconnect -= state->m_chain_sync.m_protect;
      assert(m_outbound_peers_with_protect_from_disconnect >= 0);
      m_wtxid_relay_peers -= state->m_wtxid_relay;
      assert(m_wtxid_relay_peers >= 0);
  
      mapNodeState.erase(nodeid);
  
      if (mapNodeState.empty()) {
          // Do a consistency check after the last peer is removed.
          assert(mapBlocksInFlight.empty());
          assert(nPreferredDownload == 0);
          assert(m_peers_downloading_from == 0);
          assert(m_outbound_peers_with_protect_from_disconnect == 0);
          assert(m_wtxid_relay_peers == 0);
          assert(m_txrequest.Size() == 0);
          assert(m_orphanage.Size() == 0);
      }
      } // cs_main
      if (node.fSuccessfullyConnected && misbehavior == 0 &&
          !node.IsBlockOnlyConn() && !node.IsInboundConn()) {
          // Only change visible addrman state for full outbound peers.  We don't
          // call Connected() for feeler connections since they don't have
          // fSuccessfullyConnected set.
          m_addrman.Connected(node.addr);
      }
      LogPrint(BCLog::NET, "Cleared nodestate for peer=%d\n", nodeid);
  }
  
  PeerRef PeerManagerImpl::GetPeerRef(NodeId id) const
  {
      LOCK(m_peer_mutex);
      auto it = m_peer_map.find(id);
      return it != m_peer_map.end() ? it->second : nullptr;
  }
  
  PeerRef PeerManagerImpl::RemovePeer(NodeId id)
  {
      PeerRef ret;
      LOCK(m_peer_mutex);
      auto it = m_peer_map.find(id);
      if (it != m_peer_map.end()) {
          ret = std::move(it->second);
          m_peer_map.erase(it);
      }
      return ret;
  }
  
  bool PeerManagerImpl::GetNodeStateStats(NodeId nodeid, CNodeStateStats& stats) const
  {
      {
          LOCK(cs_main);
          CNodeState* state = State(nodeid);
          if (state == nullptr)
              return false;
          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);
          }
      }
  
      PeerRef peer = GetPeerRef(nodeid);
      if (peer == nullptr) return false;
      stats.m_starting_height = peer->m_starting_height;
      // It is common for nodes with good ping times to suddenly become lagged,
      // due to a new block arriving or other large transfer.
      // Merely reporting pingtime might fool the caller into thinking the node was still responsive,
      // since pingtime does not update until the ping is complete, which might take a while.
      // So, if a ping is taking an unusually long time in flight,
      // the caller can immediately detect that this is happening.
      auto ping_wait{0us};
      if ((0 != peer->m_ping_nonce_sent) && (0 != peer->m_ping_start.load().count())) {
          ping_wait = GetTime<std::chrono::microseconds>() - peer->m_ping_start.load();
      }
  
      stats.m_ping_wait = ping_wait;
      stats.m_addr_processed = peer->m_addr_processed.load();
      stats.m_addr_rate_limited = peer->m_addr_rate_limited.load();
      stats.m_addr_relay_enabled = peer->m_addr_relay_enabled.load();
  
      return true;
  }
  
  void PeerManagerImpl::AddToCompactExtraTransactions(const CTransactionRef& tx)
  {
      size_t max_extra_txn = gArgs.GetIntArg("-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;
  }
  
  void PeerManagerImpl::Misbehaving(const NodeId pnode, const int howmuch, const std::string& message)
  {
      assert(howmuch > 0);
  
      PeerRef peer = GetPeerRef(pnode);
      if (peer == nullptr) return;
  
      LOCK(peer->m_misbehavior_mutex);
      const int score_before{peer->m_misbehavior_score};
      peer->m_misbehavior_score += howmuch;
      const int score_now{peer->m_misbehavior_score};
  
      const std::string message_prefixed = message.empty() ? "" : (": " + message);
      std::string warning;
  
      if (score_now >= DISCOURAGEMENT_THRESHOLD && score_before < DISCOURAGEMENT_THRESHOLD) {
          warning = " DISCOURAGE THRESHOLD EXCEEDED";
          peer->m_should_discourage = true;
      }
  
      LogPrint(BCLog::NET, "Misbehaving: peer=%d (%d -> %d)%s%s\n",
               pnode, score_before, score_now, warning, message_prefixed);
  }
  
  bool PeerManagerImpl::MaybePunishNodeForBlock(NodeId nodeid, const BlockValidationState& state,
                                                bool via_compact_block, const std::string& message)
  {
      switch (state.GetResult()) {
      case BlockValidationResult::BLOCK_RESULT_UNSET:
          break;
      // The node is providing invalid data:
      case BlockValidationResult::BLOCK_CONSENSUS:
      case BlockValidationResult::BLOCK_MUTATED:
          if (!via_compact_block) {
              Misbehaving(nodeid, 100, message);
              return true;
          }
          break;
      case BlockValidationResult::BLOCK_CACHED_INVALID:
          {
              LOCK(cs_main);
              CNodeState *node_state = State(nodeid);
              if (node_state == nullptr) {
                  break;
              }
  
              // Discourage outbound (but not inbound) peers if on an invalid chain.
              // Exempt HB compact block peers. Manual connections are always protected from discouragement.
              if (!via_compact_block && !node_state->m_is_inbound) {
                  Misbehaving(nodeid, 100, message);
                  return true;
              }
              break;
          }
      case BlockValidationResult::BLOCK_INVALID_HEADER:
      case BlockValidationResult::BLOCK_CHECKPOINT:
      case BlockValidationResult::BLOCK_INVALID_PREV:
          Misbehaving(nodeid, 100, message);
          return true;
      // Conflicting (but not necessarily invalid) data or different policy:
      case BlockValidationResult::BLOCK_MISSING_PREV:
          // TODO: Handle this much more gracefully (10 DoS points is super arbitrary)
          Misbehaving(nodeid, 10, message);
          return true;
      case BlockValidationResult::BLOCK_RECENT_CONSENSUS_CHANGE:
      case BlockValidationResult::BLOCK_TIME_FUTURE:
          break;
      }
      if (message != "") {
          LogPrint(BCLog::NET, "peer=%d: %s\n", nodeid, message);
      }
      return false;
  }
  
  bool PeerManagerImpl::MaybePunishNodeForTx(NodeId nodeid, const TxValidationState& state, const std::string& message)
  {
      switch (state.GetResult()) {
      case TxValidationResult::TX_RESULT_UNSET:
          break;
      // The node is providing invalid data:
      case TxValidationResult::TX_CONSENSUS:
          Misbehaving(nodeid, 100, message);
          return true;
      // Conflicting (but not necessarily invalid) data or different policy:
      case TxValidationResult::TX_RECENT_CONSENSUS_CHANGE:
      case TxValidationResult::TX_INPUTS_NOT_STANDARD:
      case TxValidationResult::TX_NOT_STANDARD:
      case TxValidationResult::TX_MISSING_INPUTS:
      case TxValidationResult::TX_PREMATURE_SPEND:
      case TxValidationResult::TX_WITNESS_MUTATED:
      case TxValidationResult::TX_WITNESS_STRIPPED:
      case TxValidationResult::TX_CONFLICT:
      case TxValidationResult::TX_MEMPOOL_POLICY:
      case TxValidationResult::TX_NO_MEMPOOL:
          break;
      }
      if (message != "") {
          LogPrint(BCLog::NET, "peer=%d: %s\n", nodeid, message);
      }
      return false;
  }
  
  bool PeerManagerImpl::BlockRequestAllowed(const CBlockIndex* pindex)
  {
      AssertLockHeld(cs_main);
      if (m_chainman.ActiveChain().Contains(pindex)) return true;
      return pindex->IsValid(BLOCK_VALID_SCRIPTS) && (pindexBestHeader != nullptr) &&
             (pindexBestHeader->GetBlockTime() - pindex->GetBlockTime() < STALE_RELAY_AGE_LIMIT) &&
             (GetBlockProofEquivalentTime(*pindexBestHeader, *pindex, *pindexBestHeader, m_chainparams.GetConsensus()) < STALE_RELAY_AGE_LIMIT);
  }
  
  std::optional<std::string> PeerManagerImpl::FetchBlock(NodeId peer_id, const CBlockIndex& block_index)
  {
      if (fImporting) return "Importing...";
      if (fReindex) return "Reindexing...";
  
      LOCK(cs_main);
      // Ensure this peer exists and hasn't been disconnected
      CNodeState* state = State(peer_id);
      if (state == nullptr) return "Peer does not exist";
      // Ignore pre-segwit peers
      if (!state->fHaveWitness) return "Pre-SegWit peer";
  
      // Mark block as in-flight unless it already is (for this peer).
      // If a block was already in-flight for a different peer, its BLOCKTXN
      // response will be dropped.
      if (!BlockRequested(peer_id, block_index)) return "Already requested from this peer";
  
      // Construct message to request the block
      const uint256& hash{block_index.GetBlockHash()};
      std::vector<CInv> invs{CInv(MSG_BLOCK | MSG_WITNESS_FLAG, hash)};
  
      // Send block request message to the peer
      bool success = m_connman.ForNode(peer_id, [this, &invs](CNode* node) {
          const CNetMsgMaker msgMaker(node->GetCommonVersion());
          this->m_connman.PushMessage(node, msgMaker.Make(NetMsgType::GETDATA, invs));
          return true;
      });
  
      if (!success) return "Peer not fully connected";
  
      LogPrint(BCLog::NET, "Requesting block %s from peer=%d\n",
                   hash.ToString(), peer_id);
      return std::nullopt;
  }
  
  std::unique_ptr<PeerManager> PeerManager::make(const CChainParams& chainparams, CConnman& connman, AddrMan& addrman,
                                                 BanMan* banman, ChainstateManager& chainman,
                                                 CTxMemPool& pool, bool ignore_incoming_txs)
  {
      return std::make_unique<PeerManagerImpl>(chainparams, connman, addrman, banman, chainman, pool, ignore_incoming_txs);
  }
  
  PeerManagerImpl::PeerManagerImpl(const CChainParams& chainparams, CConnman& connman, AddrMan& addrman,
                                   BanMan* banman, ChainstateManager& chainman,
                                   CTxMemPool& pool, bool ignore_incoming_txs)
      : m_chainparams(chainparams),
        m_connman(connman),
        m_addrman(addrman),
        m_banman(banman),
        m_chainman(chainman),
        m_mempool(pool),
        m_ignore_incoming_txs(ignore_incoming_txs)
  {
  }
  
  void PeerManagerImpl::StartScheduledTasks(CScheduler& scheduler)
  {
      // 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([this] { this->CheckForStaleTipAndEvictPeers(); }, std::chrono::seconds{EXTRA_PEER_CHECK_INTERVAL});
  
      // schedule next run for 10-15 minutes in the future
      const std::chrono::milliseconds delta = 10min + GetRandMillis(5min);
      scheduler.scheduleFromNow([&] { ReattemptInitialBroadcast(scheduler); }, delta);
  }
  
  /**
   * Evict orphan txn pool entries based on a newly connected
   * block, remember the recently confirmed transactions, and delete tracked
   * announcements for them. Also save the time of the last tip update.
   */
  void PeerManagerImpl::BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindex)
  {
      m_orphanage.EraseForBlock(*pblock);
      m_last_tip_update = GetTime<std::chrono::seconds>();
  
      {
          LOCK(m_recent_confirmed_transactions_mutex);
          for (const auto& ptx : pblock->vtx) {
              m_recent_confirmed_transactions.insert(ptx->GetHash());
              if (ptx->GetHash() != ptx->GetWitnessHash()) {
                  m_recent_confirmed_transactions.insert(ptx->GetWitnessHash());
              }
          }
      }
      {
          LOCK(cs_main);
          for (const auto& ptx : pblock->vtx) {
              m_txrequest.ForgetTxHash(ptx->GetHash());
              m_txrequest.ForgetTxHash(ptx->GetWitnessHash());
          }
      }
  }
  
  void PeerManagerImpl::BlockDisconnected(const std::shared_ptr<const CBlock> &block, const CBlockIndex* pindex)
  {
      // To avoid relay problems with transactions that were previously
      // confirmed, clear our filter of recently confirmed transactions whenever
      // there's a reorg.
      // This means that in a 1-block reorg (where 1 block is disconnected and
      // then another block reconnected), our filter will drop to having only one
      // block's worth of transactions in it, but that should be fine, since
      // presumably the most common case of relaying a confirmed transaction
      // should be just after a new block containing it is found.
      LOCK(m_recent_confirmed_transactions_mutex);
      m_recent_confirmed_transactions.reset();
  }
  
  // All of the following cache a recent block, and are protected by cs_most_recent_block
  static RecursiveMutex 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 PeerManagerImpl::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 = DeploymentActiveAt(*pindex, m_chainparams.GetConsensus(), Consensus::DEPLOYMENT_SEGWIT);
      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;
      }
  
      m_connman.ForEachNode([this, &pcmpctblock, pindex, &msgMaker, fWitnessEnabled, &hashBlock](CNode* pnode) EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
          AssertLockHeld(::cs_main);
  
          // TODO: Avoid the repeated-serialization here
          if (pnode->GetCommonVersion() < 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", "PeerManager::NewPoWValidBlock",
                      hashBlock.ToString(), pnode->GetId());
              m_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 m_chainman.ActiveChain() to our peers.
   */
  void PeerManagerImpl::UpdatedBlockTip(const CBlockIndex *pindexNew, const CBlockIndex *pindexFork, bool fInitialDownload)
  {
      SetBestHeight(pindexNew->nHeight);
      SetServiceFlagsIBDCache(!fInitialDownload);
  
      // Don't relay inventory during initial block download.
      if (fInitialDownload) return;
  
      // 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;
          }
      }
  
      {
          LOCK(m_peer_mutex);
          for (auto& it : m_peer_map) {
              Peer& peer = *it.second;
              LOCK(peer.m_block_inv_mutex);
              for (const uint256& hash : reverse_iterate(vHashes)) {
                  peer.m_blocks_for_headers_relay.push_back(hash);
              }
          }
      }
  
      m_connman.WakeMessageHandler();
  }
  
  /**
   * Handle invalid block rejection and consequent peer discouragement, maintain which
   * peers announce compact blocks.
   */
  void PeerManagerImpl::BlockChecked(const CBlock& block, const BlockValidationState& state)
  {
      LOCK(cs_main);
  
      const uint256 hash(block.GetHash());
      std::map<uint256, std::pair<NodeId, bool>>::iterator it = mapBlockSource.find(hash);
  
      // If the block failed validation, we know where it came from and we're still connected
      // to that peer, maybe punish.
      if (state.IsInvalid() &&
          it != mapBlockSource.end() &&
          State(it->second.first)) {
              MaybePunishNodeForBlock(/*nodeid=*/ it->second.first, state, /*via_compact_block=*/ !it->second.second);
      }
      // 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() &&
               !m_chainman.ActiveChainstate().IsInitialBlockDownload() &&
               mapBlocksInFlight.count(hash) == mapBlocksInFlight.size()) {
          if (it != mapBlockSource.end()) {
              MaybeSetPeerAsAnnouncingHeaderAndIDs(it->second.first);
          }
      }
      if (it != mapBlockSource.end())
          mapBlockSource.erase(it);
  }
  
  //////////////////////////////////////////////////////////////////////////////
  //
  // Messages
  //
  
  
  bool PeerManagerImpl::AlreadyHaveTx(const GenTxid& gtxid)
  {
      if (m_chainman.ActiveChain().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 = m_chainman.ActiveChain().Tip()->GetBlockHash();
          m_recent_rejects.reset();
      }
  
      const uint256& hash = gtxid.GetHash();
  
      if (m_orphanage.HaveTx(gtxid)) return true;
  
      {
          LOCK(m_recent_confirmed_transactions_mutex);
          if (m_recent_confirmed_transactions.contains(hash)) return true;
      }
  
      return m_recent_rejects.contains(hash) || m_mempool.exists(gtxid);
  }
  
  bool PeerManagerImpl::AlreadyHaveBlock(const uint256& block_hash)
  {
      return m_chainman.m_blockman.LookupBlockIndex(block_hash) != nullptr;
  }
  
  void PeerManagerImpl::SendPings()
  {
      LOCK(m_peer_mutex);
      for(auto& it : m_peer_map) it.second->m_ping_queued = true;
  }
  
  void PeerManagerImpl::RelayTransaction(const uint256& txid, const uint256& wtxid)
  {
      WITH_LOCK(cs_main, _RelayTransaction(txid, wtxid););
  }
  
  void PeerManagerImpl::_RelayTransaction(const uint256& txid, const uint256& wtxid)
  {
      m_connman.ForEachNode([&txid, &wtxid](CNode* pnode) EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
          AssertLockHeld(::cs_main);
  
          CNodeState* state = State(pnode->GetId());
          if (state == nullptr) return;
          if (state->m_wtxid_relay) {
              pnode->PushTxInventory(wtxid);
          } else {
              pnode->PushTxInventory(txid);
          }
      });
  }
  
  void PeerManagerImpl::RelayAddress(NodeId originator,
                                     const CAddress& addr,
                                     bool fReachable)
  {
      // We choose the same nodes within a given 24h window (if the list of connected
      // nodes does not change) and we don't relay to nodes that already know an
      // address. So within 24h we will likely relay a given address once. This is to
      // prevent a peer from unjustly giving their address better propagation by sending
      // it to us repeatedly.
  
      if (!fReachable && !addr.IsRelayable()) return;
  
      // 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 m_addr_knowns of the chosen nodes prevent repeats
      const uint64_t hashAddr{addr.GetHash()};
      const CSipHasher hasher{m_connman.GetDeterministicRandomizer(RANDOMIZER_ID_ADDRESS_RELAY).Write(hashAddr).Write((GetTime() + hashAddr) / (24 * 60 * 60))};
      FastRandomContext insecure_rand;
  
      // Relay reachable addresses to 2 peers. Unreachable addresses are relayed randomly to 1 or 2 peers.
      unsigned int nRelayNodes = (fReachable || (hasher.Finalize() & 1)) ? 2 : 1;
  
      std::array<std::pair<uint64_t, Peer*>, 2> best{{{0, nullptr}, {0, nullptr}}};
      assert(nRelayNodes <= best.size());
  
      LOCK(m_peer_mutex);
  
      for (auto& [id, peer] : m_peer_map) {
          if (peer->m_addr_relay_enabled && id != originator && IsAddrCompatible(*peer, addr)) {
              uint64_t hashKey = CSipHasher(hasher).Write(id).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, peer.get());
                       break;
                   }
              }
          }
      };
  
      for (unsigned int i = 0; i < nRelayNodes && best[i].first != 0; i++) {
          PushAddress(*best[i].second, addr, insecure_rand);
      }
  }
  
  void PeerManagerImpl::ProcessGetBlockData(CNode& pfrom, Peer& peer, const CInv& inv)
  {
      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 = m_chainman.m_blockman.LookupBlockIndex(inv.hash);
          if (pindex) {
              if (pindex->HaveTxsDownloaded() && !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) {
          BlockValidationState state;
          if (!m_chainman.ActiveChainstate().ActivateBestChain(state, a_recent_block)) {
              LogPrint(BCLog::NET, "failed to activate chain (%s)\n", state.ToString());
          }
      }
  
      LOCK(cs_main);
      const CBlockIndex* pindex = m_chainman.m_blockman.LookupBlockIndex(inv.hash);
      if (!pindex) {
          return;
      }
      if (!BlockRequestAllowed(pindex)) {
          LogPrint(BCLog::NET, "%s: ignoring request from peer=%i for old block that isn't in the main chain\n", __func__, pfrom.GetId());
          return;
      }
      const CNetMsgMaker msgMaker(pfrom.GetCommonVersion());
      // disconnect node in case we have reached the outbound limit for serving historical blocks
      if (m_connman.OutboundTargetReached(true) &&
          (((pindexBestHeader != nullptr) && (pindexBestHeader->GetBlockTime() - pindex->GetBlockTime() > HISTORICAL_BLOCK_AGE)) || inv.IsMsgFilteredBlk()) &&
          !pfrom.HasPermission(NetPermissionFlags::Download) // nodes with the download permission may exceed target
      ) {
          LogPrint(BCLog::NET, "historical block serving limit reached, disconnect peer=%d\n", pfrom.GetId());
          pfrom.fDisconnect = true;
          return;
      }
      // Avoid leaking prune-height by never sending blocks below the NODE_NETWORK_LIMITED threshold
      if (!pfrom.HasPermission(NetPermissionFlags::NoBan) && (
              (((pfrom.GetLocalServices() & NODE_NETWORK_LIMITED) == NODE_NETWORK_LIMITED) && ((pfrom.GetLocalServices() & NODE_NETWORK) != NODE_NETWORK) && (m_chainman.ActiveChain().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, disconnect peer=%d\n", pfrom.GetId());
          //disconnect node and prevent it from stalling (would otherwise wait for the missing block)
          pfrom.fDisconnect = true;
          return;
      }
      // Pruned nodes may have deleted the block, so check whether
      // it's available before trying to send.
      if (!(pindex->nStatus & BLOCK_HAVE_DATA)) {
          return;
      }
      std::shared_ptr<const CBlock> pblock;
      if (a_recent_block && a_recent_block->GetHash() == pindex->GetBlockHash()) {
          pblock = a_recent_block;
      } else if (inv.IsMsgWitnessBlk()) {
          // Fast-path: in this case it is possible to serve the block directly from disk,
          // as the network format matches the format on disk
          std::vector<uint8_t> block_data;
          if (!ReadRawBlockFromDisk(block_data, pindex->GetBlockPos(), m_chainparams.MessageStart())) {
              assert(!"cannot load block from disk");
          }
          m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::BLOCK, Span{block_data}));
          // Don't set pblock as we've sent the block
      } else {
          // Send block from disk
          std::shared_ptr<CBlock> pblockRead = std::make_shared<CBlock>();
          if (!ReadBlockFromDisk(*pblockRead, pindex, m_chainparams.GetConsensus())) {
              assert(!"cannot load block from disk");
          }
          pblock = pblockRead;
      }
      if (pblock) {
          if (inv.IsMsgBlk()) {
              m_connman.PushMessage(&pfrom, msgMaker.Make(SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::BLOCK, *pblock));
          } else if (inv.IsMsgWitnessBlk()) {
              m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::BLOCK, *pblock));
          } else if (inv.IsMsgFilteredBlk()) {
              bool sendMerkleBlock = false;
              CMerkleBlock merkleBlock;
              if (pfrom.m_tx_relay != nullptr) {
                  LOCK(pfrom.m_tx_relay->cs_filter);
                  if (pfrom.m_tx_relay->pfilter) {
                      sendMerkleBlock = true;
                      merkleBlock = CMerkleBlock(*pblock, *pfrom.m_tx_relay->pfilter);
                  }
              }
              if (sendMerkleBlock) {
                  m_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)
                      m_connman.PushMessage(&pfrom, msgMaker.Make(SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::TX, *pblock->vtx[pair.first]));
              }
              // else
              // no response
          } else if (inv.IsMsgCmpctBlk()) {
              // 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() && pindex->nHeight >= m_chainman.ActiveChain().Height() - MAX_CMPCTBLOCK_DEPTH) {
                  if ((fPeerWantsWitness || !fWitnessesPresentInARecentCompactBlock) && a_recent_compact_block && a_recent_compact_block->header.GetHash() == pindex->GetBlockHash()) {
                      m_connman.PushMessage(&pfrom, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, *a_recent_compact_block));
                  } else {
                      CBlockHeaderAndShortTxIDs cmpctblock(*pblock, fPeerWantsWitness);
                      m_connman.PushMessage(&pfrom, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, cmpctblock));
                  }
              } else {
                  m_connman.PushMessage(&pfrom, msgMaker.Make(nSendFlags, NetMsgType::BLOCK, *pblock));
              }
          }
      }
  
      {
          LOCK(peer.m_block_inv_mutex);
          // Trigger the peer node to send a getblocks request for the next batch of inventory
          if (inv.hash == peer.m_continuation_block) {
              // Send immediately. 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, m_chainman.ActiveChain().Tip()->GetBlockHash()));
              m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::INV, vInv));
              peer.m_continuation_block.SetNull();
          }
      }
  }
  
  CTransactionRef PeerManagerImpl::FindTxForGetData(const CNode& peer, const GenTxid& gtxid, const std::chrono::seconds mempool_req, const std::chrono::seconds now)
  {
      auto txinfo = m_mempool.info(gtxid);
      if (txinfo.tx) {
          // If a TX could have been INVed in reply to a MEMPOOL request,
          // or is older than UNCONDITIONAL_RELAY_DELAY, permit the request
          // unconditionally.
          if ((mempool_req.count() && txinfo.m_time <= mempool_req) || txinfo.m_time <= now - UNCONDITIONAL_RELAY_DELAY) {
              return std::move(txinfo.tx);
          }
      }
  
      {
          LOCK(cs_main);
          // Otherwise, the transaction must have been announced recently.
          if (State(peer.GetId())->m_recently_announced_invs.contains(gtxid.GetHash())) {
              // If it was, it can be relayed from either the mempool...
              if (txinfo.tx) return std::move(txinfo.tx);
              // ... or the relay pool.
              auto mi = mapRelay.find(gtxid.GetHash());
              if (mi != mapRelay.end()) return mi->second;
          }
      }
  
      return {};
  }
  
  void PeerManagerImpl::ProcessGetData(CNode& pfrom, Peer& peer, const std::atomic<bool>& interruptMsgProc)
  {
      AssertLockNotHeld(cs_main);
  
      std::deque<CInv>::iterator it = peer.m_getdata_requests.begin();
      std::vector<CInv> vNotFound;
      const CNetMsgMaker msgMaker(pfrom.GetCommonVersion());
  
      const auto now{GetTime<std::chrono::seconds>()};
      // Get last mempool request time
      const auto mempool_req = pfrom.m_tx_relay != nullptr ? pfrom.m_tx_relay->m_last_mempool_req.load() : std::chrono::seconds::min();
  
      // Process as many TX items from the front of the getdata queue as
      // possible, since they're common and it's efficient to batch process
      // them.
      while (it != peer.m_getdata_requests.end() && it->IsGenTxMsg()) {
          if (interruptMsgProc) return;
          // The send buffer provides backpressure. If there's no space in
          // the buffer, pause processing until the next call.
          if (pfrom.fPauseSend) break;
  
          const CInv &inv = *it++;
  
          if (pfrom.m_tx_relay == nullptr) {
              // Ignore GETDATA requests for transactions from blocks-only peers.
              continue;
          }
  
          CTransactionRef tx = FindTxForGetData(pfrom, ToGenTxid(inv), mempool_req, now);
          if (tx) {
              // WTX and WITNESS_TX imply we serialize with witness
              int nSendFlags = (inv.IsMsgTx() ? SERIALIZE_TRANSACTION_NO_WITNESS : 0);
              m_connman.PushMessage(&pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *tx));
              m_mempool.RemoveUnbroadcastTx(tx->GetHash());
              // As we're going to send tx, make sure its unconfirmed parents are made requestable.
              std::vector<uint256> parent_ids_to_add;
              {
                  LOCK(m_mempool.cs);
                  auto txiter = m_mempool.GetIter(tx->GetHash());
                  if (txiter) {
                      const CTxMemPoolEntry::Parents& parents = (*txiter)->GetMemPoolParentsConst();
                      parent_ids_to_add.reserve(parents.size());
                      for (const CTxMemPoolEntry& parent : parents) {
                          if (parent.GetTime() > now - UNCONDITIONAL_RELAY_DELAY) {
                              parent_ids_to_add.push_back(parent.GetTx().GetHash());
                          }
                      }
                  }
              }
              for (const uint256& parent_txid : parent_ids_to_add) {
                  // Relaying a transaction with a recent but unconfirmed parent.
                  if (WITH_LOCK(pfrom.m_tx_relay->cs_tx_inventory, return !pfrom.m_tx_relay->filterInventoryKnown.contains(parent_txid))) {
                      LOCK(cs_main);
                      State(pfrom.GetId())->m_recently_announced_invs.insert(parent_txid);
                  }
              }
          } else {
              vNotFound.push_back(inv);
          }
      }
  
      // Only process one BLOCK item per call, since they're uncommon and can be
      // expensive to process.
      if (it != peer.m_getdata_requests.end() && !pfrom.fPauseSend) {
          const CInv &inv = *it++;
          if (inv.IsGenBlkMsg()) {
              ProcessGetBlockData(pfrom, peer, inv);
          }
          // else: If the first item on the queue is an unknown type, we erase it
          // and continue processing the queue on the next call.
      }
  
      peer.m_getdata_requests.erase(peer.m_getdata_requests.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.
          // SPV clients 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.
          // Also, other nodes can use these messages to automatically request a
          // transaction from some other peer that annnounced it, and stop
          // waiting for us to respond.
          // In normal operation, we often send NOTFOUND messages for parents of
          // transactions that we relay; if a peer is missing a parent, they may
          // assume we have them and request the parents from us.
          m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::NOTFOUND, vNotFound));
      }
  }
  
  static uint32_t GetFetchFlags(const CNode& pfrom) EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
      uint32_t nFetchFlags = 0;
      if (State(pfrom.GetId())->fHaveWitness) {
          nFetchFlags |= MSG_WITNESS_FLAG;
      }
      return nFetchFlags;
  }
  
  void PeerManagerImpl::SendBlockTransactions(CNode& pfrom, const CBlock& block, const BlockTransactionsRequest& req)
  {
      BlockTransactions resp(req);
      for (size_t i = 0; i < req.indexes.size(); i++) {
          if (req.indexes[i] >= block.vtx.size()) {
              Misbehaving(pfrom.GetId(), 100, "getblocktxn with out-of-bounds tx indices");
              return;
          }
          resp.txn[i] = block.vtx[req.indexes[i]];
      }
      LOCK(cs_main);
      const CNetMsgMaker msgMaker(pfrom.GetCommonVersion());
      int nSendFlags = State(pfrom.GetId())->fWantsCmpctWitness ? 0 : SERIALIZE_TRANSACTION_NO_WITNESS;
      m_connman.PushMessage(&pfrom, msgMaker.Make(nSendFlags, NetMsgType::BLOCKTXN, resp));
  }
  
  void PeerManagerImpl::ProcessHeadersMessage(CNode& pfrom, const Peer& peer,
                                              const std::vector<CBlockHeader>& headers,
                                              bool via_compact_block)
  {
      const CNetMsgMaker msgMaker(pfrom.GetCommonVersion());
      size_t nCount = headers.size();
  
      if (nCount == 0) {
          // Nothing interesting. Stop asking this peers for more headers.
          return;
      }
  
      size_t nSize = 0;
      for (const auto& header : headers) {
          nSize += GetSerializeSize(header, PROTOCOL_VERSION);
          if (pfrom.nVersion >= SIZE_HEADERS_LIMIT_VERSION
                && nSize > MAX_HEADERS_SIZE) {
              LOCK(cs_main);
              Misbehaving(pfrom.GetId(), 20, strprintf("headers message size = %u", nSize));
              return;
          }
      }
  
      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 (!m_chainman.m_blockman.LookupBlockIndex(headers[0].hashPrevBlock) && nCount < MAX_BLOCKS_TO_ANNOUNCE) {
              nodestate->nUnconnectingHeaders++;
              m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::GETHEADERS, m_chainman.ActiveChain().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, strprintf("%d non-connecting headers", nodestate->nUnconnectingHeaders));
              }
              return;
          }
  
          uint256 hashLastBlock;
          for (const CBlockHeader& header : headers) {
              if (!hashLastBlock.IsNull() && header.hashPrevBlock != hashLastBlock) {
                  Misbehaving(pfrom.GetId(), 20, "non-continuous headers sequence");
                  return;
              }
              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 (!m_chainman.m_blockman.LookupBlockIndex(hashLastBlock)) {
              received_new_header = true;
          }
      }
  
      BlockValidationState state;
      if (!m_chainman.ProcessNewBlockHeaders(headers, state, m_chainparams, &pindexLast)) {
          if (state.IsInvalid()) {
              MaybePunishNodeForBlock(pfrom.GetId(), state, via_compact_block, "invalid header received");
              return;
          }
      }
  
      {
          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 > m_chainman.ActiveChain().Tip()->nChainWork) {
              nodestate->m_last_block_announcement = GetTime();
          }
  
          bool maxSize = (nCount == MAX_HEADERS_RESULTS);
          if (pfrom.nVersion >= SIZE_HEADERS_LIMIT_VERSION
                && nSize >= THRESHOLD_HEADERS_SIZE)
              maxSize = true;
          // FIXME: This change (with hasNewHeaders) is rolled back in Bitcoin,
          // but I think it should stay here for merge-mined coins.  Try to get
          // it fixed again upstream and then update the fix.
          if (maxSize && received_new_header) {
              // Headers message had its maximum size; the peer may have more headers.
              // TODO: optimize: if pindexLast is an ancestor of m_chainman.ActiveChain().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(), peer.m_starting_height);
              m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::GETHEADERS, m_chainman.ActiveChain().GetLocator(pindexLast), uint256()));
          }
  
          // 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 (CanDirectFetch() && pindexLast->IsValid(BLOCK_VALID_TREE) && m_chainman.ActiveChain().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 && !m_chainman.ActiveChain().Contains(pindexWalk) && vToFetch.size() <= MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
                  if (!(pindexWalk->nStatus & BLOCK_HAVE_DATA) &&
                          !IsBlockRequested(pindexWalk->GetBlockHash()) &&
                          (!DeploymentActiveAt(*pindexWalk, m_chainparams.GetConsensus(), Consensus::DEPLOYMENT_SEGWIT) || 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 (!m_chainman.ActiveChain().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()));
                      BlockRequested(pfrom.GetId(), *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 (!m_ignore_incoming_txs &&
                          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);
                      }
                      m_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 (m_chainman.ActiveChainstate().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 it is an outbound disconnection
                  // candidate.
                  // Note: We compare their tip to nMinimumChainWork (rather than
                  // m_chainman.ActiveChain().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 (pfrom.IsOutboundOrBlockRelayConn()) {
                      LogPrintf("Disconnecting outbound peer %d -- headers chain has insufficient work\n", pfrom.GetId());
                      pfrom.fDisconnect = true;
                  }
              }
          }
  
          // If this is an outbound full-relay peer, check to see if we should protect
          // it from the bad/lagging chain logic.
          // Note that outbound block-relay peers are excluded from this protection, and
          // thus always subject to eviction under the bad/lagging chain logic.
          // See ChainSyncTimeoutState.
          if (!pfrom.fDisconnect && pfrom.IsFullOutboundConn() && nodestate->pindexBestKnownBlock != nullptr) {
              if (m_outbound_peers_with_protect_from_disconnect < MAX_OUTBOUND_PEERS_TO_PROTECT_FROM_DISCONNECT && nodestate->pindexBestKnownBlock->nChainWork >= m_chainman.ActiveChain().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;
                  ++m_outbound_peers_with_protect_from_disconnect;
              }
          }
      }
  
      return;
  }
  
  /**
   * Reconsider orphan transactions after a parent has been accepted to the mempool.
   *
   * @param[in,out]  orphan_work_set  The set of orphan transactions to reconsider. Generally only one
   *                                  orphan will be reconsidered on each call of this function. This set
   *                                  may be added to if accepting an orphan causes its children to be
   *                                  reconsidered.
   */
  void PeerManagerImpl::ProcessOrphanTx(std::set<uint256>& orphan_work_set)
  {
      AssertLockHeld(cs_main);
      AssertLockHeld(g_cs_orphans);
  
      while (!orphan_work_set.empty()) {
          const uint256 orphanHash = *orphan_work_set.begin();
          orphan_work_set.erase(orphan_work_set.begin());
  
          const auto [porphanTx, from_peer] = m_orphanage.GetTx(orphanHash);
          if (porphanTx == nullptr) continue;
  
          const MempoolAcceptResult result = m_chainman.ProcessTransaction(porphanTx);
          const TxValidationState& state = result.m_state;
  
          if (result.m_result_type == MempoolAcceptResult::ResultType::VALID) {
              LogPrint(BCLog::MEMPOOL, "   accepted orphan tx %s\n", orphanHash.ToString());
              _RelayTransaction(orphanHash, porphanTx->GetWitnessHash());
              m_orphanage.AddChildrenToWorkSet(*porphanTx, orphan_work_set);
              m_orphanage.EraseTx(orphanHash);
              for (const CTransactionRef& removedTx : result.m_replaced_transactions.value()) {
                  AddToCompactExtraTransactions(removedTx);
              }
              break;
          } else if (state.GetResult() != TxValidationResult::TX_MISSING_INPUTS) {
              if (state.IsInvalid()) {
                  LogPrint(BCLog::MEMPOOL, "   invalid orphan tx %s from peer=%d. %s\n",
                      orphanHash.ToString(),
                      from_peer,
                      state.ToString());
                  // Maybe punish peer that gave us an invalid orphan tx
                  MaybePunishNodeForTx(from_peer, state);
              }
              // Has inputs but not accepted to mempool
              // Probably non-standard or insufficient fee
              LogPrint(BCLog::MEMPOOL, "   removed orphan tx %s\n", orphanHash.ToString());
              if (state.GetResult() != TxValidationResult::TX_WITNESS_STRIPPED) {
                  // We can add the wtxid of this transaction to our reject filter.
                  // Do not add txids of witness transactions or witness-stripped
                  // transactions to the filter, as they can have been malleated;
                  // adding such txids to the reject filter would potentially
                  // interfere with relay of valid transactions from peers that
                  // do not support wtxid-based relay. See
                  // https://github.com/bitcoin/bitcoin/issues/8279 for details.
                  // We can remove this restriction (and always add wtxids to
                  // the filter even for witness stripped transactions) once
                  // wtxid-based relay is broadly deployed.
                  // See also comments in https://github.com/bitcoin/bitcoin/pull/18044#discussion_r443419034
                  // for concerns around weakening security of unupgraded nodes
                  // if we start doing this too early.
                  m_recent_rejects.insert(porphanTx->GetWitnessHash());
                  // If the transaction failed for TX_INPUTS_NOT_STANDARD,
                  // then we know that the witness was irrelevant to the policy
                  // failure, since this check depends only on the txid
                  // (the scriptPubKey being spent is covered by the txid).
                  // Add the txid to the reject filter to prevent repeated
                  // processing of this transaction in the event that child
                  // transactions are later received (resulting in
                  // parent-fetching by txid via the orphan-handling logic).
                  if (state.GetResult() == TxValidationResult::TX_INPUTS_NOT_STANDARD && porphanTx->GetWitnessHash() != porphanTx->GetHash()) {
                      // We only add the txid if it differs from the wtxid, to
                      // avoid wasting entries in the rolling bloom filter.
                      m_recent_rejects.insert(porphanTx->GetHash());
                  }
              }
              m_orphanage.EraseTx(orphanHash);
              break;
          }
      }
  }
  
  bool PeerManagerImpl::PrepareBlockFilterRequest(CNode& peer,
                                                  BlockFilterType filter_type, uint32_t start_height,
                                                  const uint256& stop_hash, uint32_t max_height_diff,
                                                  const CBlockIndex*& stop_index,
                                                  BlockFilterIndex*& filter_index)
  {
      const bool supported_filter_type =
          (filter_type == BlockFilterType::BASIC &&
           (peer.GetLocalServices() & NODE_COMPACT_FILTERS));
      if (!supported_filter_type) {
          LogPrint(BCLog::NET, "peer %d requested unsupported block filter type: %d\n",
                   peer.GetId(), static_cast<uint8_t>(filter_type));
          peer.fDisconnect = true;
          return false;
      }
  
      {
          LOCK(cs_main);
          stop_index = m_chainman.m_blockman.LookupBlockIndex(stop_hash);
  
          // Check that the stop block exists and the peer would be allowed to fetch it.
          if (!stop_index || !BlockRequestAllowed(stop_index)) {
              LogPrint(BCLog::NET, "peer %d requested invalid block hash: %s\n",
                       peer.GetId(), stop_hash.ToString());
              peer.fDisconnect = true;
              return false;
          }
      }
  
      uint32_t stop_height = stop_index->nHeight;
      if (start_height > stop_height) {
          LogPrint(BCLog::NET, "peer %d sent invalid getcfilters/getcfheaders with " /* Continued */
                   "start height %d and stop height %d\n",
                   peer.GetId(), start_height, stop_height);
          peer.fDisconnect = true;
          return false;
      }
      if (stop_height - start_height >= max_height_diff) {
          LogPrint(BCLog::NET, "peer %d requested too many cfilters/cfheaders: %d / %d\n",
                   peer.GetId(), stop_height - start_height + 1, max_height_diff);
          peer.fDisconnect = true;
          return false;
      }
  
      filter_index = GetBlockFilterIndex(filter_type);
      if (!filter_index) {
          LogPrint(BCLog::NET, "Filter index for supported type %s not found\n", BlockFilterTypeName(filter_type));
          return false;
      }
  
      return true;
  }
  
  void PeerManagerImpl::ProcessGetCFilters(CNode& peer, CDataStream& vRecv)
  {
      uint8_t filter_type_ser;
      uint32_t start_height;
      uint256 stop_hash;
  
      vRecv >> filter_type_ser >> start_height >> stop_hash;
  
      const BlockFilterType filter_type = static_cast<BlockFilterType>(filter_type_ser);
  
      const CBlockIndex* stop_index;
      BlockFilterIndex* filter_index;
      if (!PrepareBlockFilterRequest(peer, filter_type, start_height, stop_hash,
                                     MAX_GETCFILTERS_SIZE, stop_index, filter_index)) {
          return;
      }
  
      std::vector<BlockFilter> filters;
      if (!filter_index->LookupFilterRange(start_height, stop_index, filters)) {
          LogPrint(BCLog::NET, "Failed to find block filter in index: filter_type=%s, start_height=%d, stop_hash=%s\n",
                       BlockFilterTypeName(filter_type), start_height, stop_hash.ToString());
          return;
      }
  
      for (const auto& filter : filters) {
          CSerializedNetMsg msg = CNetMsgMaker(peer.GetCommonVersion())
              .Make(NetMsgType::CFILTER, filter);
          m_connman.PushMessage(&peer, std::move(msg));
      }
  }
  
  void PeerManagerImpl::ProcessGetCFHeaders(CNode& peer, CDataStream& vRecv)
  {
      uint8_t filter_type_ser;
      uint32_t start_height;
      uint256 stop_hash;
  
      vRecv >> filter_type_ser >> start_height >> stop_hash;
  
      const BlockFilterType filter_type = static_cast<BlockFilterType>(filter_type_ser);
  
      const CBlockIndex* stop_index;
      BlockFilterIndex* filter_index;
      if (!PrepareBlockFilterRequest(peer, filter_type, start_height, stop_hash,
                                     MAX_GETCFHEADERS_SIZE, stop_index, filter_index)) {
          return;
      }
  
      uint256 prev_header;
      if (start_height > 0) {
          const CBlockIndex* const prev_block =
              stop_index->GetAncestor(static_cast<int>(start_height - 1));
          if (!filter_index->LookupFilterHeader(prev_block, prev_header)) {
              LogPrint(BCLog::NET, "Failed to find block filter header in index: filter_type=%s, block_hash=%s\n",
                           BlockFilterTypeName(filter_type), prev_block->GetBlockHash().ToString());
              return;
          }
      }
  
      std::vector<uint256> filter_hashes;
      if (!filter_index->LookupFilterHashRange(start_height, stop_index, filter_hashes)) {
          LogPrint(BCLog::NET, "Failed to find block filter hashes in index: filter_type=%s, start_height=%d, stop_hash=%s\n",
                       BlockFilterTypeName(filter_type), start_height, stop_hash.ToString());
          return;
      }
  
      CSerializedNetMsg msg = CNetMsgMaker(peer.GetCommonVersion())
          .Make(NetMsgType::CFHEADERS,
                filter_type_ser,
                stop_index->GetBlockHash(),
                prev_header,
                filter_hashes);
      m_connman.PushMessage(&peer, std::move(msg));
  }
  
  void PeerManagerImpl::ProcessGetCFCheckPt(CNode& peer, CDataStream& vRecv)
  {
      uint8_t filter_type_ser;
      uint256 stop_hash;
  
      vRecv >> filter_type_ser >> stop_hash;
  
      const BlockFilterType filter_type = static_cast<BlockFilterType>(filter_type_ser);
  
      const CBlockIndex* stop_index;
      BlockFilterIndex* filter_index;
      if (!PrepareBlockFilterRequest(peer, filter_type, /*start_height=*/0, stop_hash,
                                     /*max_height_diff=*/std::numeric_limits<uint32_t>::max(),
                                     stop_index, filter_index)) {
          return;
      }
  
      std::vector<uint256> headers(stop_index->nHeight / CFCHECKPT_INTERVAL);
  
      // Populate headers.
      const CBlockIndex* block_index = stop_index;
      for (int i = headers.size() - 1; i >= 0; i--) {
          int height = (i + 1) * CFCHECKPT_INTERVAL;
          block_index = block_index->GetAncestor(height);
  
          if (!filter_index->LookupFilterHeader(block_index, headers[i])) {
              LogPrint(BCLog::NET, "Failed to find block filter header in index: filter_type=%s, block_hash=%s\n",
                           BlockFilterTypeName(filter_type), block_index->GetBlockHash().ToString());
              return;
          }
      }
  
      CSerializedNetMsg msg = CNetMsgMaker(peer.GetCommonVersion())
          .Make(NetMsgType::CFCHECKPT,
                filter_type_ser,
                stop_index->GetBlockHash(),
                headers);
      m_connman.PushMessage(&peer, std::move(msg));
  }
  
  void PeerManagerImpl::ProcessBlock(CNode& node, const std::shared_ptr<const CBlock>& block, bool force_processing)
  {
      bool new_block{false};
      m_chainman.ProcessNewBlock(m_chainparams, block, force_processing, &new_block);
      if (new_block) {
          node.m_last_block_time = GetTime<std::chrono::seconds>();
      } else {
          LOCK(cs_main);
          mapBlockSource.erase(block->GetHash());
      }
  }
  
  void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type, CDataStream& vRecv,
                                       const std::chrono::microseconds time_received,
                                       const std::atomic<bool>& interruptMsgProc)
  {
      LogPrint(BCLog::NET, "received: %s (%u bytes) peer=%d\n", SanitizeString(msg_type), vRecv.size(), pfrom.GetId());
  
      PeerRef peer = GetPeerRef(pfrom.GetId());
      if (peer == nullptr) return;
  
      if (msg_type == NetMsgType::VERSION) {
          if (pfrom.nVersion != 0) {
              LogPrint(BCLog::NET, "redundant version message from peer=%d\n", pfrom.GetId());
              return;
          }
  
          int64_t nTime;
          CService addrMe;
          uint64_t nNonce = 1;
          ServiceFlags nServices;
          int nVersion;
          std::string cleanSubVer;
          int starting_height = -1;
          bool fRelay = true;
  
          vRecv >> nVersion >> Using<CustomUintFormatter<8>>(nServices) >> nTime;
          if (nTime < 0) {
              nTime = 0;
          }
          vRecv.ignore(8); // Ignore the addrMe service bits sent by the peer
          vRecv >> addrMe;
          if (!pfrom.IsInboundConn())
          {
              m_addrman.SetServices(pfrom.addr, nServices);
          }
          if (pfrom.ExpectServicesFromConn() && !HasAllDesirableServiceFlags(nServices))
          {
              LogPrint(BCLog::NET, "peer=%d does not offer the expected services (%08x offered, %08x expected); disconnecting\n", pfrom.GetId(), nServices, GetDesirableServiceFlags(nServices));
              pfrom.fDisconnect = true;
              return;
          }
  
          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);
              pfrom.fDisconnect = true;
              return;
          }
  
          if (!vRecv.empty()) {
              // The version message includes information about the sending node which we don't use:
              //   - 8 bytes (service bits)
              //   - 16 bytes (ipv6 address)
              //   - 2 bytes (port)
              vRecv.ignore(26);
              vRecv >> nNonce;
          }
          if (!vRecv.empty()) {
              std::string strSubVer;
              vRecv >> LIMITED_STRING(strSubVer, MAX_SUBVERSION_LENGTH);
              cleanSubVer = SanitizeString(strSubVer);
          }
          if (!vRecv.empty()) {
              vRecv >> starting_height;
          }
          if (!vRecv.empty())
              vRecv >> fRelay;
          // Disconnect if we connected to ourself
          if (pfrom.IsInboundConn() && !m_connman.CheckIncomingNonce(nNonce))
          {
              LogPrintf("connected to self at %s, disconnecting\n", pfrom.addr.ToString());
              pfrom.fDisconnect = true;
              return;
          }
  
          if (pfrom.IsInboundConn() && addrMe.IsRoutable())
          {
              SeenLocal(addrMe);
          }
  
          // Inbound peers send us their version message when they connect.
          // We send our version message in response.
          if (pfrom.IsInboundConn()) {
              PushNodeVersion(pfrom);
          }
  
          // Change version
          const int greatest_common_version = std::min(nVersion, PROTOCOL_VERSION);
          pfrom.SetCommonVersion(greatest_common_version);
          pfrom.nVersion = nVersion;
  
          const CNetMsgMaker msg_maker(greatest_common_version);
  
          if (greatest_common_version >= WTXID_RELAY_VERSION) {
              m_connman.PushMessage(&pfrom, msg_maker.Make(NetMsgType::WTXIDRELAY));
          }
  
          // Signal ADDRv2 support (BIP155).
          if (greatest_common_version >= 70016) {
              // BIP155 defines addrv2 and sendaddrv2 for all protocol versions, but some
              // implementations reject messages they don't know. As a courtesy, don't send
              // it to nodes with a version before 70016, as no software is known to support
              // BIP155 that doesn't announce at least that protocol version number.
              m_connman.PushMessage(&pfrom, msg_maker.Make(NetMsgType::SENDADDRV2));
          }
  
          m_connman.PushMessage(&pfrom, msg_maker.Make(NetMsgType::VERACK));
  
          pfrom.nServices = nServices;
          pfrom.SetAddrLocal(addrMe);
          {
              LOCK(pfrom.m_subver_mutex);
              pfrom.cleanSubVer = cleanSubVer;
          }
          peer->m_starting_height = starting_height;
  
          // 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));
  
          if (pfrom.m_tx_relay != nullptr) {
              LOCK(pfrom.m_tx_relay->cs_filter);
              pfrom.m_tx_relay->fRelayTxes = fRelay; // set to true after we get the first filter* message
          }
  
          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()));
          }
  
          // Self advertisement & GETADDR logic
          if (!pfrom.IsInboundConn() && SetupAddressRelay(pfrom, *peer)) {
              // For outbound peers, we try to relay our address (so that other
              // nodes can try to find us more quickly, as we have no guarantee
              // that an outbound peer is even aware of how to reach us) and do a
              // one-time address fetch (to help populate/update our addrman). If
              // we're starting up for the first time, our addrman may be pretty
              // empty and no one will know who we are, so these mechanisms are
              // important to help us connect to the network.
              //
              // We skip this for block-relay-only peers. We want to avoid
              // potentially leaking addr information and we do not want to
              // indicate to the peer that we will participate in addr relay.
              if (fListen && !m_chainman.ActiveChainstate().IsInitialBlockDownload())
              {
                  CAddress addr = GetLocalAddress(&pfrom.addr, pfrom.GetLocalServices());
                  FastRandomContext insecure_rand;
                  if (addr.IsRoutable())
                  {
                      LogPrint(BCLog::NET, "ProcessMessages: advertising address %s\n", addr.ToString());
                      PushAddress(*peer, addr, insecure_rand);
                  } else if (IsPeerAddrLocalGood(&pfrom)) {
                      addr.SetIP(addrMe);
                      LogPrint(BCLog::NET, "ProcessMessages: advertising address %s\n", addr.ToString());
                      PushAddress(*peer, addr, insecure_rand);
                  }
              }
  
              // Get recent addresses
              m_connman.PushMessage(&pfrom, CNetMsgMaker(greatest_common_version).Make(NetMsgType::GETADDR));
              peer->m_getaddr_sent = true;
              // When requesting a getaddr, accept an additional MAX_ADDR_TO_SEND addresses in response
              // (bypassing the MAX_ADDR_PROCESSING_TOKEN_BUCKET limit).
              peer->m_addr_token_bucket += MAX_ADDR_TO_SEND;
          }
  
          if (!pfrom.IsInboundConn()) {
              // For non-inbound connections, we update the addrman to record
              // connection success so that addrman will have an up-to-date
              // notion of which peers are online and available.
              //
              // While we strive to not leak information about block-relay-only
              // connections via the addrman, not moving an address to the tried
              // table is also potentially detrimental because new-table entries
              // are subject to eviction in the event of addrman collisions.  We
              // mitigate the information-leak by never calling
              // AddrMan::Connected() on block-relay-only peers; see
              // FinalizeNode().
              //
              // This moves an address from New to Tried table in Addrman,
              // resolves tried-table collisions, etc.
              m_addrman.Good(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, txrelay=%d, peer=%d%s\n",
                    cleanSubVer, pfrom.nVersion,
                    peer->m_starting_height, addrMe.ToString(), fRelay, pfrom.GetId(),
                    remoteAddr);
  
          int64_t nTimeOffset = nTime - GetTime();
          pfrom.nTimeOffset = nTimeOffset;
          if (!pfrom.IsInboundConn()) {
              // Don't use timedata samples from inbound peers to make it
              // harder for others to tamper with our adjusted time.
              AddTimeData(pfrom.addr, nTimeOffset);
          }
  
          // If the peer is old enough to have the old alert system, send it the final alert.
          if (greatest_common_version <= 70012) {
              CDataStream finalAlert(ParseHex("60010000000000000000000000ffffff7f00000000ffffff7ffeffff7f01ffffff7f00000000ffffff7f00ffffff7f002f555247454e543a20416c657274206b657920636f6d70726f6d697365642c2075706772616465207265717569726564004630440220653febd6410f470f6bae11cad19c48413becb1ac2c17f908fd0fd53bdc3abd5202206d0e9c96fe88d4a0f01ed9dedae2b6f9e00da94cad0fecaae66ecf689bf71b50"), SER_NETWORK, PROTOCOL_VERSION);
              m_connman.PushMessage(&pfrom, CNetMsgMaker(greatest_common_version).Make("alert", finalAlert));
          }
  
          // Feeler connections exist only to verify if address is online.
          if (pfrom.IsFeelerConn()) {
              LogPrint(BCLog::NET, "feeler connection completed peer=%d; disconnecting\n", pfrom.GetId());
              pfrom.fDisconnect = true;
          }
          return;
      }
  
      if (pfrom.nVersion == 0) {
          // Must have a version message before anything else
          LogPrint(BCLog::NET, "non-version message before version handshake. Message \"%s\" from peer=%d\n", SanitizeString(msg_type), pfrom.GetId());
          return;
      }
  
      // At this point, the outgoing message serialization version can't change.
      const CNetMsgMaker msgMaker(pfrom.GetCommonVersion());
  
      if (msg_type == NetMsgType::VERACK) {
          if (pfrom.fSuccessfullyConnected) {
              LogPrint(BCLog::NET, "ignoring redundant verack message from peer=%d\n", pfrom.GetId());
              return;
          }
  
          if (!pfrom.IsInboundConn()) {
              LogPrintf("New outbound peer connected: version: %d, blocks=%d, peer=%d%s (%s)\n",
                        pfrom.nVersion.load(), peer->m_starting_height,
                        pfrom.GetId(), (fLogIPs ? strprintf(", peeraddr=%s", pfrom.addr.ToString()) : ""),
                        pfrom.ConnectionTypeAsString());
          }
  
          if (pfrom.GetCommonVersion() >= 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)
              m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::SENDHEADERS));
          }
          if (pfrom.GetCommonVersion() >= 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;
              m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
              nCMPCTBLOCKVersion = 1;
              m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
          }
          pfrom.fSuccessfullyConnected = true;
          return;
      }
  
      if (msg_type == NetMsgType::SENDHEADERS) {
          LOCK(cs_main);
          State(pfrom.GetId())->fPreferHeaders = true;
          return;
      }
  
      if (msg_type == NetMsgType::SENDCMPCT) {
          bool fAnnounceUsingCMPCTBLOCK = false;
          uint64_t nCMPCTBLOCKVersion = 0;
          vRecv >> fAnnounceUsingCMPCTBLOCK >> nCMPCTBLOCKVersion;
          if (nCMPCTBLOCKVersion == 1 || 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;
                  // save whether peer selects us as BIP152 high-bandwidth peer
                  // (receiving sendcmpct(1) signals high-bandwidth, sendcmpct(0) low-bandwidth)
                  pfrom.m_bip152_highbandwidth_from = fAnnounceUsingCMPCTBLOCK;
              }
              if (!State(pfrom.GetId())->fSupportsDesiredCmpctVersion) {
                  State(pfrom.GetId())->fSupportsDesiredCmpctVersion = (nCMPCTBLOCKVersion == 2);
              }
          }
          return;
      }
  
      // BIP339 defines feature negotiation of wtxidrelay, which must happen between
      // VERSION and VERACK to avoid relay problems from switching after a connection is up.
      if (msg_type == NetMsgType::WTXIDRELAY) {
          if (pfrom.fSuccessfullyConnected) {
              // Disconnect peers that send a wtxidrelay message after VERACK.
              LogPrint(BCLog::NET, "wtxidrelay received after verack from peer=%d; disconnecting\n", pfrom.GetId());
              pfrom.fDisconnect = true;
              return;
          }
          if (pfrom.GetCommonVersion() >= WTXID_RELAY_VERSION) {
              LOCK(cs_main);
              if (!State(pfrom.GetId())->m_wtxid_relay) {
                  State(pfrom.GetId())->m_wtxid_relay = true;
                  m_wtxid_relay_peers++;
              } else {
                  LogPrint(BCLog::NET, "ignoring duplicate wtxidrelay from peer=%d\n", pfrom.GetId());
              }
          } else {
              LogPrint(BCLog::NET, "ignoring wtxidrelay due to old common version=%d from peer=%d\n", pfrom.GetCommonVersion(), pfrom.GetId());
          }
          return;
      }
  
      // BIP155 defines feature negotiation of addrv2 and sendaddrv2, which must happen
      // between VERSION and VERACK.
      if (msg_type == NetMsgType::SENDADDRV2) {
          if (pfrom.fSuccessfullyConnected) {
              // Disconnect peers that send a SENDADDRV2 message after VERACK.
              LogPrint(BCLog::NET, "sendaddrv2 received after verack from peer=%d; disconnecting\n", pfrom.GetId());
              pfrom.fDisconnect = true;
              return;
          }
          peer->m_wants_addrv2 = true;
          return;
      }
  
      if (!pfrom.fSuccessfullyConnected) {
          LogPrint(BCLog::NET, "Unsupported message \"%s\" prior to verack from peer=%d\n", SanitizeString(msg_type), pfrom.GetId());
          return;
      }
  
      if (msg_type == NetMsgType::ADDR || msg_type == NetMsgType::ADDRV2) {
          int stream_version = vRecv.GetVersion();
          if (msg_type == NetMsgType::ADDRV2) {
              // Add ADDRV2_FORMAT to the version so that the CNetAddr and CAddress
              // unserialize methods know that an address in v2 format is coming.
              stream_version |= ADDRV2_FORMAT;
          }
  
          OverrideStream<CDataStream> s(&vRecv, vRecv.GetType(), stream_version);
          std::vector<CAddress> vAddr;
  
          s >> vAddr;
  
          if (!SetupAddressRelay(pfrom, *peer)) {
              LogPrint(BCLog::NET, "ignoring %s message from %s peer=%d\n", msg_type, pfrom.ConnectionTypeAsString(), pfrom.GetId());
              return;
          }
  
          if (vAddr.size() > MAX_ADDR_TO_SEND)
          {
              Misbehaving(pfrom.GetId(), 20, strprintf("%s message size = %u", msg_type, vAddr.size()));
              return;
          }
  
          // Store the new addresses
          std::vector<CAddress> vAddrOk;
          int64_t nNow = GetAdjustedTime();
          int64_t nSince = nNow - 10 * 60;
  
          // Update/increment addr rate limiting bucket.
          const auto current_time{GetTime<std::chrono::microseconds>()};
          if (peer->m_addr_token_bucket < MAX_ADDR_PROCESSING_TOKEN_BUCKET) {
              // Don't increment bucket if it's already full
              const auto time_diff = std::max(current_time - peer->m_addr_token_timestamp, 0us);
              const double increment = CountSecondsDouble(time_diff) * MAX_ADDR_RATE_PER_SECOND;
              peer->m_addr_token_bucket = std::min<double>(peer->m_addr_token_bucket + increment, MAX_ADDR_PROCESSING_TOKEN_BUCKET);
          }
          peer->m_addr_token_timestamp = current_time;
  
          const bool rate_limited = !pfrom.HasPermission(NetPermissionFlags::Addr);
          uint64_t num_proc = 0;
          uint64_t num_rate_limit = 0;
          Shuffle(vAddr.begin(), vAddr.end(), FastRandomContext());
          for (CAddress& addr : vAddr)
          {
              if (interruptMsgProc)
                  return;
  
              // Apply rate limiting.
              if (peer->m_addr_token_bucket < 1.0) {
                  if (rate_limited) {
                      ++num_rate_limit;
                      continue;
                  }
              } else {
                  peer->m_addr_token_bucket -= 1.0;
              }
              // 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;
              AddAddressKnown(*peer, addr);
              if (m_banman && (m_banman->IsDiscouraged(addr) || m_banman->IsBanned(addr))) {
                  // Do not process banned/discouraged addresses beyond remembering we received them
                  continue;
              }
              ++num_proc;
              bool fReachable = IsReachable(addr);
              if (addr.nTime > nSince && !peer->m_getaddr_sent && vAddr.size() <= 10 && addr.IsRoutable()) {
                  // Relay to a limited number of other nodes
                  RelayAddress(pfrom.GetId(), addr, fReachable);
              }
              // Do not store addresses outside our network
              if (fReachable)
                  vAddrOk.push_back(addr);
          }
          peer->m_addr_processed += num_proc;
          peer->m_addr_rate_limited += num_rate_limit;
          LogPrint(BCLog::NET, "Received addr: %u addresses (%u processed, %u rate-limited) from peer=%d\n",
                   vAddr.size(), num_proc, num_rate_limit, pfrom.GetId());
  
          m_addrman.Add(vAddrOk, pfrom.addr, 2 * 60 * 60);
          if (vAddr.size() < 1000) peer->m_getaddr_sent = false;
  
          // AddrFetch: Require multiple addresses to avoid disconnecting on self-announcements
          if (pfrom.IsAddrFetchConn() && vAddr.size() > 1) {
              LogPrint(BCLog::NET, "addrfetch connection completed peer=%d; disconnecting\n", pfrom.GetId());
              pfrom.fDisconnect = true;
          }
          return;
      }
  
      if (msg_type == NetMsgType::INV) {
          std::vector<CInv> vInv;
          vRecv >> vInv;
          if (vInv.size() > MAX_INV_SZ)
          {
              Misbehaving(pfrom.GetId(), 20, strprintf("inv message size = %u", vInv.size()));
              return;
          }
  
          // Reject tx INVs when the -blocksonly setting is enabled, or this is a
          // block-relay-only peer
          bool reject_tx_invs{m_ignore_incoming_txs || (pfrom.m_tx_relay == nullptr)};
  
          // Allow peers with relay permission to send data other than blocks in blocks only mode
          if (pfrom.HasPermission(NetPermissionFlags::Relay)) {
              reject_tx_invs = false;
          }
  
          LOCK(cs_main);
  
          const auto current_time{GetTime<std::chrono::microseconds>()};
          uint256* best_block{nullptr};
  
          for (CInv& inv : vInv) {
              if (interruptMsgProc) return;
  
              // Ignore INVs that don't match wtxidrelay setting.
              // Note that orphan parent fetching always uses MSG_TX GETDATAs regardless of the wtxidrelay setting.
              // This is fine as no INV messages are involved in that process.
              if (State(pfrom.GetId())->m_wtxid_relay) {
                  if (inv.IsMsgTx()) continue;
              } else {
                  if (inv.IsMsgWtx()) continue;
              }
  
              if (inv.IsMsgBlk()) {
                  const bool fAlreadyHave = AlreadyHaveBlock(inv.hash);
                  LogPrint(BCLog::NET, "got inv: %s  %s peer=%d\n", inv.ToString(), fAlreadyHave ? "have" : "new", pfrom.GetId());
  
                  UpdateBlockAvailability(pfrom.GetId(), inv.hash);
                  if (!fAlreadyHave && !fImporting && !fReindex && !IsBlockRequested(inv.hash)) {
                      // Headers-first is the primary method of announcement on
                      // the network. If a node fell back to sending blocks by inv,
                      // it's probably for a re-org. The final block hash
                      // provided should be the highest, so send a getheaders and
                      // then fetch the blocks we need to catch up.
                      best_block = &inv.hash;
                  }
              } else if (inv.IsGenTxMsg()) {
                  if (reject_tx_invs) {
                      LogPrint(BCLog::NET, "transaction (%s) inv sent in violation of protocol, disconnecting peer=%d\n", inv.hash.ToString(), pfrom.GetId());
                      pfrom.fDisconnect = true;
                      return;
                  }
                  const GenTxid gtxid = ToGenTxid(inv);
                  const bool fAlreadyHave = AlreadyHaveTx(gtxid);
                  LogPrint(BCLog::NET, "got inv: %s  %s peer=%d\n", inv.ToString(), fAlreadyHave ? "have" : "new", pfrom.GetId());
  
                  pfrom.AddKnownTx(inv.hash);
                  if (!fAlreadyHave && !m_chainman.ActiveChainstate().IsInitialBlockDownload()) {
                      AddTxAnnouncement(pfrom, gtxid, current_time);
                  }
              } else {
                  LogPrint(BCLog::NET, "Unknown inv type \"%s\" received from peer=%d\n", inv.ToString(), pfrom.GetId());
              }
          }
  
          if (best_block != nullptr) {
              m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::GETHEADERS, m_chainman.ActiveChain().GetLocator(pindexBestHeader), *best_block));
              LogPrint(BCLog::NET, "getheaders (%d) %s to peer=%d\n", pindexBestHeader->nHeight, best_block->ToString(), pfrom.GetId());
          }
  
          return;
      }
  
      if (msg_type == NetMsgType::GETDATA) {
          std::vector<CInv> vInv;
          vRecv >> vInv;
          if (vInv.size() > MAX_INV_SZ)
          {
              Misbehaving(pfrom.GetId(), 20, strprintf("getdata message size = %u", vInv.size()));
              return;
          }
  
          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());
          }
  
          {
              LOCK(peer->m_getdata_requests_mutex);
              peer->m_getdata_requests.insert(peer->m_getdata_requests.end(), vInv.begin(), vInv.end());
              ProcessGetData(pfrom, *peer, interruptMsgProc);
          }
  
          return;
      }
  
      if (msg_type == NetMsgType::GETBLOCKS) {
          CBlockLocator locator;
          uint256 hashStop;
          vRecv >> locator >> hashStop;
  
          if (locator.vHave.size() > MAX_LOCATOR_SZ) {
              LogPrint(BCLog::NET, "getblocks locator size %lld > %d, disconnect peer=%d\n", locator.vHave.size(), MAX_LOCATOR_SZ, pfrom.GetId());
              pfrom.fDisconnect = true;
              return;
          }
  
          // 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;
              }
              BlockValidationState state;
              if (!m_chainman.ActiveChainstate().ActivateBestChain(state, a_recent_block)) {
                  LogPrint(BCLog::NET, "failed to activate chain (%s)\n", state.ToString());
              }
          }
  
          LOCK(cs_main);
  
          // Find the last block the caller has in the main chain
          const CBlockIndex* pindex = m_chainman.ActiveChainstate().FindForkInGlobalIndex(locator);
  
          // Send the rest of the chain
          if (pindex)
              pindex = m_chainman.ActiveChain().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 = m_chainman.ActiveChain().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 / m_chainparams.GetConsensus().nPowTargetSpacing;
              if (fPruneMode && (!(pindex->nStatus & BLOCK_HAVE_DATA) || pindex->nHeight <= m_chainman.ActiveChain().Tip()->nHeight - nPrunedBlocksLikelyToHave))
              {
                  LogPrint(BCLog::NET, " getblocks stopping, pruned or too old block at %d %s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
                  break;
              }
              WITH_LOCK(peer->m_block_inv_mutex, peer->m_blocks_for_inv_relay.push_back(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());
                  WITH_LOCK(peer->m_block_inv_mutex, {peer->m_continuation_block = pindex->GetBlockHash();});
                  break;
              }
          }
          return;
      }
  
      if (msg_type == 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(pfrom, *recent_block, req);
              return;
          }
  
          {
              LOCK(cs_main);
  
              const CBlockIndex* pindex = m_chainman.m_blockman.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;
              }
  
              if (pindex->nHeight >= m_chainman.ActiveChain().Height() - MAX_BLOCKTXN_DEPTH) {
                  CBlock block;
                  bool ret = ReadBlockFromDisk(block, pindex, m_chainparams.GetConsensus());
                  assert(ret);
  
                  SendBlockTransactions(pfrom, block, req);
                  return;
              }
          }
  
          // 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;
          WITH_LOCK(cs_main, inv.type = State(pfrom.GetId())->fWantsCmpctWitness ? MSG_WITNESS_BLOCK : MSG_BLOCK);
          inv.hash = req.blockhash;
          WITH_LOCK(peer->m_getdata_requests_mutex, peer->m_getdata_requests.push_back(inv));
          // The message processing loop will go around again (without pausing) and we'll respond then
          return;
      }
  
      if (msg_type == NetMsgType::GETHEADERS) {
          CBlockLocator locator;
          uint256 hashStop;
          vRecv >> locator >> hashStop;
  
          if (locator.vHave.size() > MAX_LOCATOR_SZ) {
              LogPrint(BCLog::NET, "getheaders locator size %lld > %d, disconnect peer=%d\n", locator.vHave.size(), MAX_LOCATOR_SZ, pfrom.GetId());
              pfrom.fDisconnect = true;
              return;
          }
  
          LOCK(cs_main);
          if (m_chainman.ActiveChainstate().IsInitialBlockDownload() && !pfrom.HasPermission(NetPermissionFlags::Download)) {
              LogPrint(BCLog::NET, "Ignoring getheaders from peer=%d because node is in initial block download\n", pfrom.GetId());
              return;
          }
  
          CNodeState *nodestate = State(pfrom.GetId());
          const CBlockIndex* pindex = nullptr;
          if (locator.IsNull())
          {
              // If locator is null, return the hashStop block
              pindex = m_chainman.m_blockman.LookupBlockIndex(hashStop);
              if (!pindex) {
                  return;
              }
  
              if (!BlockRequestAllowed(pindex)) {
                  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;
              }
          }
          else
          {
              // Find the last block the caller has in the main chain
              pindex = m_chainman.ActiveChainstate().FindForkInGlobalIndex(locator);
              if (pindex)
                  pindex = m_chainman.ActiveChain().Next(pindex);
          }
  
          // we must use CBlocks, as CBlockHeaders won't include the 0x00 nTx count at the end
          std::vector<CBlock> vHeaders;
          unsigned nCount = 0;
          unsigned nSize = 0;
          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 = m_chainman.ActiveChain().Next(pindex))
          {
              const CBlockHeader header = pindex->GetBlockHeader(m_chainparams.GetConsensus());
              ++nCount;
              nSize += GetSerializeSize(header, PROTOCOL_VERSION);
              vHeaders.push_back(header);
              if (nCount >= MAX_HEADERS_RESULTS
                    || pindex->GetBlockHash() == hashStop)
                  break;
              if (pfrom.nVersion >= SIZE_HEADERS_LIMIT_VERSION
                    && nSize >= THRESHOLD_HEADERS_SIZE)
                  break;
          }
  
          /* Check maximum headers size before pushing the message
             if the peer enforces it.  This should not fail since we
             break above in the loop at the threshold and the threshold
             should be small enough in comparison to the hard max size.
             Do it nevertheless to be sure.  */
          if (pfrom.nVersion >= SIZE_HEADERS_LIMIT_VERSION
                && nSize > MAX_HEADERS_SIZE)
              LogPrintf("ERROR: not pushing 'headers', too large\n");
          else
          {
              LogPrint(BCLog::NET, "pushing %u headers, %u bytes\n", nCount, nSize);
              // 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 : m_chainman.ActiveChain().Tip();
              m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::HEADERS, vHeaders));
          }
  
          return;
      }
  
      if (msg_type == NetMsgType::TX) {
          // Stop processing the transaction early if
          // 1) We are in blocks only mode and peer has no relay permission
          // 2) This peer is a block-relay-only peer
          if ((m_ignore_incoming_txs && !pfrom.HasPermission(NetPermissionFlags::Relay)) || (pfrom.m_tx_relay == nullptr))
          {
              LogPrint(BCLog::NET, "transaction sent in violation of protocol peer=%d\n", pfrom.GetId());
              pfrom.fDisconnect = true;
              return;
          }
  
          // Stop processing the transaction early if we are still in IBD since we don't
          // have enough information to validate it yet. Sending unsolicited transactions
          // is not considered a protocol violation, so don't punish the peer.
          if (m_chainman.ActiveChainstate().IsInitialBlockDownload()) return;
  
          CTransactionRef ptx;
          vRecv >> ptx;
          const CTransaction& tx = *ptx;
  
          const uint256& txid = ptx->GetHash();
          const uint256& wtxid = ptx->GetWitnessHash();
  
          LOCK2(cs_main, g_cs_orphans);
  
          CNodeState* nodestate = State(pfrom.GetId());
  
          const uint256& hash = nodestate->m_wtxid_relay ? wtxid : txid;
          pfrom.AddKnownTx(hash);
          if (nodestate->m_wtxid_relay && txid != wtxid) {
              // Insert txid into filterInventoryKnown, even for
              // wtxidrelay peers. This prevents re-adding of
              // unconfirmed parents to the recently_announced
              // filter, when a child tx is requested. See
              // ProcessGetData().
              pfrom.AddKnownTx(txid);
          }
  
          m_txrequest.ReceivedResponse(pfrom.GetId(), txid);
          if (tx.HasWitness()) m_txrequest.ReceivedResponse(pfrom.GetId(), wtxid);
  
          // We do the AlreadyHaveTx() check using wtxid, rather than txid - in the
          // absence of witness malleation, this is strictly better, because the
          // recent rejects filter may contain the wtxid but rarely contains
          // the txid of a segwit transaction that has been rejected.
          // In the presence of witness malleation, it's possible that by only
          // doing the check with wtxid, we could overlook a transaction which
          // was confirmed with a different witness, or exists in our mempool
          // with a different witness, but this has limited downside:
          // mempool validation does its own lookup of whether we have the txid
          // already; and an adversary can already relay us old transactions
          // (older than our recency filter) if trying to DoS us, without any need
          // for witness malleation.
          if (AlreadyHaveTx(GenTxid::Wtxid(wtxid))) {
              if (pfrom.HasPermission(NetPermissionFlags::ForceRelay)) {
                  // Always relay transactions received from peers with forcerelay
                  // permission, even if they were already in the mempool, allowing
                  // the node to function as a gateway for nodes hidden behind it.
                  if (!m_mempool.exists(GenTxid::Txid(tx.GetHash()))) {
                      LogPrintf("Not relaying non-mempool transaction %s from forcerelay peer=%d\n", tx.GetHash().ToString(), pfrom.GetId());
                  } else {
                      LogPrintf("Force relaying tx %s from peer=%d\n", tx.GetHash().ToString(), pfrom.GetId());
                      _RelayTransaction(tx.GetHash(), tx.GetWitnessHash());
                  }
              }
              return;
          }
  
          const MempoolAcceptResult result = m_chainman.ProcessTransaction(ptx);
          const TxValidationState& state = result.m_state;
  
          if (result.m_result_type == MempoolAcceptResult::ResultType::VALID) {
              // As this version of the transaction was acceptable, we can forget about any
              // requests for it.
              m_txrequest.ForgetTxHash(tx.GetHash());
              m_txrequest.ForgetTxHash(tx.GetWitnessHash());
              _RelayTransaction(tx.GetHash(), tx.GetWitnessHash());
              m_orphanage.AddChildrenToWorkSet(tx, peer->m_orphan_work_set);
  
              pfrom.m_last_tx_time = GetTime<std::chrono::seconds>();
  
              LogPrint(BCLog::MEMPOOL, "AcceptToMemoryPool: peer=%d: accepted %s (poolsz %u txn, %u kB)\n",
                  pfrom.GetId(),
                  tx.GetHash().ToString(),
                  m_mempool.size(), m_mempool.DynamicMemoryUsage() / 1000);
  
              for (const CTransactionRef& removedTx : result.m_replaced_transactions.value()) {
                  AddToCompactExtraTransactions(removedTx);
              }
  
              // Recursively process any orphan transactions that depended on this one
              ProcessOrphanTx(peer->m_orphan_work_set);
          }
          else if (state.GetResult() == TxValidationResult::TX_MISSING_INPUTS)
          {
              bool fRejectedParents = false; // It may be the case that the orphans parents have all been rejected
  
              // Deduplicate parent txids, so that we don't have to loop over
              // the same parent txid more than once down below.
              std::vector<uint256> unique_parents;
              unique_parents.reserve(tx.vin.size());
              for (const CTxIn& txin : tx.vin) {
                  // We start with all parents, and then remove duplicates below.
                  unique_parents.push_back(txin.prevout.hash);
              }
              std::sort(unique_parents.begin(), unique_parents.end());
              unique_parents.erase(std::unique(unique_parents.begin(), unique_parents.end()), unique_parents.end());
              for (const uint256& parent_txid : unique_parents) {
                  if (m_recent_rejects.contains(parent_txid)) {
                      fRejectedParents = true;
                      break;
                  }
              }
              if (!fRejectedParents) {
                  const auto current_time{GetTime<std::chrono::microseconds>()};
  
                  for (const uint256& parent_txid : unique_parents) {
                      // Here, we only have the txid (and not wtxid) of the
                      // inputs, so we only request in txid mode, even for
                      // wtxidrelay peers.
                      // Eventually we should replace this with an improved
                      // protocol for getting all unconfirmed parents.
                      const auto gtxid{GenTxid::Txid(parent_txid)};
                      pfrom.AddKnownTx(parent_txid);
                      if (!AlreadyHaveTx(gtxid)) AddTxAnnouncement(pfrom, gtxid, current_time);
                  }
  
                  if (m_orphanage.AddTx(ptx, pfrom.GetId())) {
                      AddToCompactExtraTransactions(ptx);
                  }
  
                  // Once added to the orphan pool, a tx is considered AlreadyHave, and we shouldn't request it anymore.
                  m_txrequest.ForgetTxHash(tx.GetHash());
                  m_txrequest.ForgetTxHash(tx.GetWitnessHash());
  
                  // DoS prevention: do not allow m_orphanage to grow unbounded (see CVE-2012-3789)
                  unsigned int nMaxOrphanTx = (unsigned int)std::max((int64_t)0, gArgs.GetIntArg("-maxorphantx", DEFAULT_MAX_ORPHAN_TRANSACTIONS));
                  unsigned int nEvicted = m_orphanage.LimitOrphans(nMaxOrphanTx);
                  if (nEvicted > 0) {
                      LogPrint(BCLog::MEMPOOL, "orphanage 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.
                  // Here we add both the txid and the wtxid, as we know that
                  // regardless of what witness is provided, we will not accept
                  // this, so we don't need to allow for redownload of this txid
                  // from any of our non-wtxidrelay peers.
                  m_recent_rejects.insert(tx.GetHash());
                  m_recent_rejects.insert(tx.GetWitnessHash());
                  m_txrequest.ForgetTxHash(tx.GetHash());
                  m_txrequest.ForgetTxHash(tx.GetWitnessHash());
              }
          } else {
              if (state.GetResult() != TxValidationResult::TX_WITNESS_STRIPPED) {
                  // We can add the wtxid of this transaction to our reject filter.
                  // Do not add txids of witness transactions or witness-stripped
                  // transactions to the filter, as they can have been malleated;
                  // adding such txids to the reject filter would potentially
                  // interfere with relay of valid transactions from peers that
                  // do not support wtxid-based relay. See
                  // https://github.com/bitcoin/bitcoin/issues/8279 for details.
                  // We can remove this restriction (and always add wtxids to
                  // the filter even for witness stripped transactions) once
                  // wtxid-based relay is broadly deployed.
                  // See also comments in https://github.com/bitcoin/bitcoin/pull/18044#discussion_r443419034
                  // for concerns around weakening security of unupgraded nodes
                  // if we start doing this too early.
                  m_recent_rejects.insert(tx.GetWitnessHash());
                  m_txrequest.ForgetTxHash(tx.GetWitnessHash());
                  // If the transaction failed for TX_INPUTS_NOT_STANDARD,
                  // then we know that the witness was irrelevant to the policy
                  // failure, since this check depends only on the txid
                  // (the scriptPubKey being spent is covered by the txid).
                  // Add the txid to the reject filter to prevent repeated
                  // processing of this transaction in the event that child
                  // transactions are later received (resulting in
                  // parent-fetching by txid via the orphan-handling logic).
                  if (state.GetResult() == TxValidationResult::TX_INPUTS_NOT_STANDARD && tx.GetWitnessHash() != tx.GetHash()) {
                      m_recent_rejects.insert(tx.GetHash());
                      m_txrequest.ForgetTxHash(tx.GetHash());
                  }
                  if (RecursiveDynamicUsage(*ptx) < 100000) {
                      AddToCompactExtraTransactions(ptx);
                  }
              }
          }
  
          // If a tx has been detected by m_recent_rejects, we will have reached
          // this point and the tx will have been ignored. Because we haven't
          // submitted the tx to our mempool, we won't have computed a DoS
          // score for it or determined exactly why we consider it invalid.
          //
          // This means we won't penalize any peer subsequently relaying a DoSy
          // tx (even if we penalized the first peer who gave it to us) because
          // we have to account for m_recent_rejects showing false positives. In
          // other words, we shouldn't penalize a peer if we aren't *sure* they
          // submitted a DoSy tx.
          //
          // Note that m_recent_rejects doesn't just record DoSy or invalid
          // transactions, but any tx not accepted by the mempool, which may be
          // due to node policy (vs. consensus). So we can't blanket penalize a
          // peer simply for relaying a tx that our m_recent_rejects has caught,
          // regardless of false positives.
  
          if (state.IsInvalid()) {
              LogPrint(BCLog::MEMPOOLREJ, "%s from peer=%d was not accepted: %s\n", tx.GetHash().ToString(),
                  pfrom.GetId(),
                  state.ToString());
              MaybePunishNodeForTx(pfrom.GetId(), state);
          }
          return;
      }
  
      if (msg_type == NetMsgType::CMPCTBLOCK)
      {
          // Ignore cmpctblock received while importing
          if (fImporting || fReindex) {
              LogPrint(BCLog::NET, "Unexpected cmpctblock message received from peer %d\n", pfrom.GetId());
              return;
          }
  
          CBlockHeaderAndShortTxIDs cmpctblock;
          vRecv >> cmpctblock;
  
          bool received_new_header = false;
  
          {
          LOCK(cs_main);
  
          if (!m_chainman.m_blockman.LookupBlockIndex(cmpctblock.header.hashPrevBlock)) {
              // Doesn't connect (or is genesis), instead of DoSing in AcceptBlockHeader, request deeper headers
              if (!m_chainman.ActiveChainstate().IsInitialBlockDownload())
                  m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::GETHEADERS, m_chainman.ActiveChain().GetLocator(pindexBestHeader), uint256()));
              return;
          }
  
          if (!m_chainman.m_blockman.LookupBlockIndex(cmpctblock.header.GetHash())) {
              received_new_header = true;
          }
          }
  
          const CBlockIndex *pindex = nullptr;
          BlockValidationState state;
          if (!m_chainman.ProcessNewBlockHeaders({cmpctblock.header}, state, m_chainparams, &pindex)) {
              if (state.IsInvalid()) {
                  MaybePunishNodeForBlock(pfrom.GetId(), state, /*via_compact_block*/ true, "invalid header via cmpctblock");
                  return;
              }
          }
  
          // 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 > m_chainman.ActiveChain().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;
  
          if (pindex->nChainWork <= m_chainman.ActiveChain().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());
                  m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::GETDATA, vInv));
              }
              return;
          }
  
          // If we're not close to tip yet, give up and let parallel block fetch work its magic
          if (!fAlreadyInFlight && !CanDirectFetch()) {
              return;
          }
  
          if (DeploymentActiveAt(*pindex, m_chainparams.GetConsensus(), Consensus::DEPLOYMENT_SEGWIT) && !nodestate->fSupportsDesiredCmpctVersion) {
              // Don't bother trying to process compact blocks from v1 peers
              // after segwit activates.
              return;
          }
  
          // We want to be a bit conservative just to be extra careful about DoS
          // possibilities in compact block processing...
          if (pindex->nHeight <= m_chainman.ActiveChain().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 (!BlockRequested(pfrom.GetId(), *pindex, &queuedBlockIt)) {
                      if (!(*queuedBlockIt)->partialBlock)
                          (*queuedBlockIt)->partialBlock.reset(new PartiallyDownloadedBlock(&m_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;
                      }
                  }
  
                  PartiallyDownloadedBlock& partialBlock = *(*queuedBlockIt)->partialBlock;
                  ReadStatus status = partialBlock.InitData(cmpctblock, vExtraTxnForCompact);
                  if (status == READ_STATUS_INVALID) {
                      RemoveBlockRequest(pindex->GetBlockHash()); // Reset in-flight state in case Misbehaving does not result in a disconnect
                      Misbehaving(pfrom.GetId(), 100, "invalid compact block");
                      return;
                  } 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());
                      m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::GETDATA, vInv));
                      return;
                  }
  
                  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();
                      m_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(&m_mempool);
                  ReadStatus status = tempBlock.InitData(cmpctblock, vExtraTxnForCompact);
                  if (status != READ_STATUS_OK) {
                      // TODO: don't ignore failures
                      return;
                  }
                  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());
                  m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::GETDATA, vInv));
                  return;
              } 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, time_received, 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 disconnected/discouraged.
              return ProcessHeadersMessage(pfrom, *peer, {cmpctblock.header}, /*via_compact_block=*/true);
          }
  
          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));
              }
              // Setting force_processing 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.
              ProcessBlock(pfrom, pblock, /*force_processing=*/true);
              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.
                  RemoveBlockRequest(pblock->GetHash());
              }
          }
          return;
      }
  
      if (msg_type == NetMsgType::BLOCKTXN)
      {
          // Ignore blocktxn received while importing
          if (fImporting || fReindex) {
              LogPrint(BCLog::NET, "Unexpected blocktxn message received from peer %d\n", pfrom.GetId());
              return;
          }
  
          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;
              }
  
              PartiallyDownloadedBlock& partialBlock = *it->second.second->partialBlock;
              ReadStatus status = partialBlock.FillBlock(*pblock, resp.txn);
              if (status == READ_STATUS_INVALID) {
                  RemoveBlockRequest(resp.blockhash); // Reset in-flight state in case Misbehaving does not result in a disconnect
                  Misbehaving(pfrom.GetId(), 100, "invalid compact block/non-matching block transactions");
                  return;
              } 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));
                  m_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 discourage the peer 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, etc.
                  RemoveBlockRequest(resp.blockhash); // it is now an empty pointer
                  fBlockRead = true;
                  // mapBlockSource is used for potentially punishing peers and
                  // updating which peers send us compact blocks, 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) {
              // 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.
              ProcessBlock(pfrom, pblock, /*force_processing=*/true);
          }
          return;
      }
  
      if (msg_type == NetMsgType::HEADERS)
      {
          // Ignore headers received while importing
          if (fImporting || fReindex) {
              LogPrint(BCLog::NET, "Unexpected headers message received from peer %d\n", pfrom.GetId());
              return;
          }
  
          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) {
              Misbehaving(pfrom.GetId(), 20, strprintf("headers message size = %u", nCount));
              return;
          }
          headers.resize(nCount);
          for (unsigned int n = 0; n < nCount; n++) {
              vRecv >> headers[n];
              ReadCompactSize(vRecv); // ignore tx count; assume it is 0.
          }
  
          return ProcessHeadersMessage(pfrom, *peer, headers, /*via_compact_block=*/false);
      }
  
      if (msg_type == NetMsgType::BLOCK)
      {
          // Ignore block received while importing
          if (fImporting || fReindex) {
              LogPrint(BCLog::NET, "Unexpected block message received from peer %d\n", pfrom.GetId());
              return;
          }
  
          std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
          vRecv >> *pblock;
  
          LogPrint(BCLog::NET, "received block %s peer=%d\n", pblock->GetHash().ToString(), pfrom.GetId());
  
          bool forceProcessing = false;
          const uint256 hash(pblock->GetHash());
          {
              LOCK(cs_main);
              // Always process the block if we requested it, since we may
              // need it even when it's not a candidate for a new best tip.
              forceProcessing = IsBlockRequested(hash);
              RemoveBlockRequest(hash);
              // mapBlockSource is only used for punishing peers and setting
              // which peers send us compact blocks, so the race between here and
              // cs_main in ProcessNewBlock is fine.
              mapBlockSource.emplace(hash, std::make_pair(pfrom.GetId(), true));
          }
          ProcessBlock(pfrom, pblock, forceProcessing);
          return;
      }
  
      if (msg_type == 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.IsInboundConn()) {
              LogPrint(BCLog::NET, "Ignoring \"getaddr\" from %s connection. peer=%d\n", pfrom.ConnectionTypeAsString(), pfrom.GetId());
              return;
          }
  
          // Since this must be an inbound connection, SetupAddressRelay will
          // never fail.
          Assume(SetupAddressRelay(pfrom, *peer));
  
          // Only send one GetAddr response per connection to reduce resource waste
          // and discourage addr stamping of INV announcements.
          if (peer->m_getaddr_recvd) {
              LogPrint(BCLog::NET, "Ignoring repeated \"getaddr\". peer=%d\n", pfrom.GetId());
              return;
          }
          peer->m_getaddr_recvd = true;
  
          peer->m_addrs_to_send.clear();
          std::vector<CAddress> vAddr;
          if (pfrom.HasPermission(NetPermissionFlags::Addr)) {
              vAddr = m_connman.GetAddresses(MAX_ADDR_TO_SEND, MAX_PCT_ADDR_TO_SEND, /* network */ std::nullopt);
          } else {
              vAddr = m_connman.GetAddresses(pfrom, MAX_ADDR_TO_SEND, MAX_PCT_ADDR_TO_SEND);
          }
          FastRandomContext insecure_rand;
          for (const CAddress &addr : vAddr) {
              PushAddress(*peer, addr, insecure_rand);
          }
          return;
      }
  
      if (msg_type == NetMsgType::MEMPOOL) {
          if (!(pfrom.GetLocalServices() & NODE_BLOOM) && !pfrom.HasPermission(NetPermissionFlags::Mempool))
          {
              if (!pfrom.HasPermission(NetPermissionFlags::NoBan))
              {
                  LogPrint(BCLog::NET, "mempool request with bloom filters disabled, disconnect peer=%d\n", pfrom.GetId());
                  pfrom.fDisconnect = true;
              }
              return;
          }
  
          if (m_connman.OutboundTargetReached(false) && !pfrom.HasPermission(NetPermissionFlags::Mempool))
          {
              if (!pfrom.HasPermission(NetPermissionFlags::NoBan))
              {
                  LogPrint(BCLog::NET, "mempool request with bandwidth limit reached, disconnect peer=%d\n", pfrom.GetId());
                  pfrom.fDisconnect = true;
              }
              return;
          }
  
          if (pfrom.m_tx_relay != nullptr) {
              LOCK(pfrom.m_tx_relay->cs_tx_inventory);
              pfrom.m_tx_relay->fSendMempool = true;
          }
          return;
      }
  
      if (msg_type == NetMsgType::PING) {
          if (pfrom.GetCommonVersion() > 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.
              m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::PONG, nonce));
          }
          return;
      }
  
      if (msg_type == NetMsgType::PONG) {
          const auto ping_end = time_received;
          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 (peer->m_ping_nonce_sent != 0) {
                  if (nonce == peer->m_ping_nonce_sent) {
                      // Matching pong received, this ping is no longer outstanding
                      bPingFinished = true;
                      const auto ping_time = ping_end - peer->m_ping_start.load();
                      if (ping_time.count() >= 0) {
                          // Let connman know about this successful ping-pong
                          pfrom.PongReceived(ping_time);
                      } 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,
                  peer->m_ping_nonce_sent,
                  nonce,
                  nAvail);
          }
          if (bPingFinished) {
              peer->m_ping_nonce_sent = 0;
          }
          return;
      }
  
      if (msg_type == NetMsgType::FILTERLOAD) {
          if (!(pfrom.GetLocalServices() & NODE_BLOOM)) {
              LogPrint(BCLog::NET, "filterload received despite not offering bloom services from peer=%d; disconnecting\n", pfrom.GetId());
              pfrom.fDisconnect = true;
              return;
          }
          CBloomFilter filter;
          vRecv >> filter;
  
          if (!filter.IsWithinSizeConstraints())
          {
              // There is no excuse for sending a too-large filter
              Misbehaving(pfrom.GetId(), 100, "too-large bloom filter");
          }
          else if (pfrom.m_tx_relay != nullptr)
          {
              LOCK(pfrom.m_tx_relay->cs_filter);
              pfrom.m_tx_relay->pfilter.reset(new CBloomFilter(filter));
              pfrom.m_tx_relay->fRelayTxes = true;
          }
          return;
      }
  
      if (msg_type == NetMsgType::FILTERADD) {
          if (!(pfrom.GetLocalServices() & NODE_BLOOM)) {
              LogPrint(BCLog::NET, "filteradd received despite not offering bloom services from peer=%d; disconnecting\n", pfrom.GetId());
              pfrom.fDisconnect = true;
              return;
          }
          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 if (pfrom.m_tx_relay != nullptr) {
              LOCK(pfrom.m_tx_relay->cs_filter);
              if (pfrom.m_tx_relay->pfilter) {
                  pfrom.m_tx_relay->pfilter->insert(vData);
              } else {
                  bad = true;
              }
          }
          if (bad) {
              Misbehaving(pfrom.GetId(), 100, "bad filteradd message");
          }
          return;
      }
  
      if (msg_type == NetMsgType::FILTERCLEAR) {
          if (!(pfrom.GetLocalServices() & NODE_BLOOM)) {
              LogPrint(BCLog::NET, "filterclear received despite not offering bloom services from peer=%d; disconnecting\n", pfrom.GetId());
              pfrom.fDisconnect = true;
              return;
          }
          if (pfrom.m_tx_relay == nullptr) {
              return;
          }
          LOCK(pfrom.m_tx_relay->cs_filter);
          pfrom.m_tx_relay->pfilter = nullptr;
          pfrom.m_tx_relay->fRelayTxes = true;
          return;
      }
  
      if (msg_type == NetMsgType::FEEFILTER) {
          CAmount newFeeFilter = 0;
          vRecv >> newFeeFilter;
          if (MoneyRange(newFeeFilter)) {
              if (pfrom.m_tx_relay != nullptr) {
                  pfrom.m_tx_relay->minFeeFilter = newFeeFilter;
              }
              LogPrint(BCLog::NET, "received: feefilter of %s from peer=%d\n", CFeeRate(newFeeFilter).ToString(), pfrom.GetId());
          }
          return;
      }
  
      if (msg_type == NetMsgType::GETCFILTERS) {
          ProcessGetCFilters(pfrom, vRecv);
          return;
      }
  
      if (msg_type == NetMsgType::GETCFHEADERS) {
          ProcessGetCFHeaders(pfrom, vRecv);
          return;
      }
  
      if (msg_type == NetMsgType::GETCFCHECKPT) {
          ProcessGetCFCheckPt(pfrom, vRecv);
          return;
      }
  
      if (msg_type == NetMsgType::NOTFOUND) {
          std::vector<CInv> vInv;
          vRecv >> vInv;
          if (vInv.size() <= MAX_PEER_TX_ANNOUNCEMENTS + MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
              LOCK(::cs_main);
              for (CInv &inv : vInv) {
                  if (inv.IsGenTxMsg()) {
                      // If we receive a NOTFOUND message for a tx we requested, mark the announcement for it as
                      // completed in TxRequestTracker.
                      m_txrequest.ReceivedResponse(pfrom.GetId(), inv.hash);
                  }
              }
          }
          return;
      }
  
      // Ignore unknown commands for extensibility
      LogPrint(BCLog::NET, "Unknown command \"%s\" from peer=%d\n", SanitizeString(msg_type), pfrom.GetId());
      return;
  }
  
  bool PeerManagerImpl::MaybeDiscourageAndDisconnect(CNode& pnode, Peer& peer)
  {
      {
          LOCK(peer.m_misbehavior_mutex);
  
          // There's nothing to do if the m_should_discourage flag isn't set
          if (!peer.m_should_discourage) return false;
  
          peer.m_should_discourage = false;
      } // peer.m_misbehavior_mutex
  
      if (pnode.HasPermission(NetPermissionFlags::NoBan)) {
          // We never disconnect or discourage peers for bad behavior if they have NetPermissionFlags::NoBan permission
          LogPrintf("Warning: not punishing noban peer %d!\n", peer.m_id);
          return false;
      }
  
      if (pnode.IsManualConn()) {
          // We never disconnect or discourage manual peers for bad behavior
          LogPrintf("Warning: not punishing manually connected peer %d!\n", peer.m_id);
          return false;
      }
  
      if (pnode.addr.IsLocal()) {
          // We disconnect local peers for bad behavior but don't discourage (since that would discourage
          // all peers on the same local address)
          LogPrint(BCLog::NET, "Warning: disconnecting but not discouraging %s peer %d!\n",
                   pnode.m_inbound_onion ? "inbound onion" : "local", peer.m_id);
          pnode.fDisconnect = true;
          return true;
      }
  
      // Normal case: Disconnect the peer and discourage all nodes sharing the address
      LogPrint(BCLog::NET, "Disconnecting and discouraging peer %d!\n", peer.m_id);
      if (m_banman) m_banman->Discourage(pnode.addr);
      m_connman.DisconnectNode(pnode.addr);
      return true;
  }
  
  bool PeerManagerImpl::ProcessMessages(CNode* pfrom, std::atomic<bool>& interruptMsgProc)
  {
      bool fMoreWork = false;
  
      PeerRef peer = GetPeerRef(pfrom->GetId());
      if (peer == nullptr) return false;
  
      {
          LOCK(peer->m_getdata_requests_mutex);
          if (!peer->m_getdata_requests.empty()) {
              ProcessGetData(*pfrom, *peer, interruptMsgProc);
          }
      }
  
      {
          LOCK2(cs_main, g_cs_orphans);
          if (!peer->m_orphan_work_set.empty()) {
              ProcessOrphanTx(peer->m_orphan_work_set);
          }
      }
  
      if (pfrom->fDisconnect)
          return false;
  
      // this maintains the order of responses
      // and prevents m_getdata_requests to grow unbounded
      {
          LOCK(peer->m_getdata_requests_mutex);
          if (!peer->m_getdata_requests.empty()) return true;
      }
  
      {
          LOCK(g_cs_orphans);
          if (!peer->m_orphan_work_set.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().m_raw_message_size;
          pfrom->fPauseRecv = pfrom->nProcessQueueSize > m_connman.GetReceiveFloodSize();
          fMoreWork = !pfrom->vProcessMsg.empty();
      }
      CNetMessage& msg(msgs.front());
  
      TRACE6(net, inbound_message,
          pfrom->GetId(),
          pfrom->m_addr_name.c_str(),
          pfrom->ConnectionTypeAsString().c_str(),
          msg.m_type.c_str(),
          msg.m_recv.size(),
          msg.m_recv.data()
      );
  
      if (gArgs.GetBoolArg("-capturemessages", false)) {
          CaptureMessage(pfrom->addr, msg.m_type, MakeUCharSpan(msg.m_recv), /*is_incoming=*/true);
      }
  
      msg.SetVersion(pfrom->GetCommonVersion());
  
      try {
          ProcessMessage(*pfrom, msg.m_type, msg.m_recv, msg.m_time, interruptMsgProc);
          if (interruptMsgProc) return false;
          {
              LOCK(peer->m_getdata_requests_mutex);
              if (!peer->m_getdata_requests.empty()) fMoreWork = true;
          }
      } catch (const std::exception& e) {
          LogPrint(BCLog::NET, "%s(%s, %u bytes): Exception '%s' (%s) caught\n", __func__, SanitizeString(msg.m_type), msg.m_message_size, e.what(), typeid(e).name());
      } catch (...) {
          LogPrint(BCLog::NET, "%s(%s, %u bytes): Unknown exception caught\n", __func__, SanitizeString(msg.m_type), msg.m_message_size);
      }
  
      return fMoreWork;
  }
  
  void PeerManagerImpl::ConsiderEviction(CNode& pto, std::chrono::seconds time_in_seconds)
  {
      AssertLockHeld(cs_main);
  
      CNodeState &state = *State(pto.GetId());
      const CNetMsgMaker msgMaker(pto.GetCommonVersion());
  
      if (!state.m_chain_sync.m_protect && pto.IsOutboundOrBlockRelayConn() && 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 >= m_chainman.ActiveChain().Tip()->nChainWork) {
              if (state.m_chain_sync.m_timeout != 0s) {
                  state.m_chain_sync.m_timeout = 0s;
                  state.m_chain_sync.m_work_header = nullptr;
                  state.m_chain_sync.m_sent_getheaders = false;
              }
          } else if (state.m_chain_sync.m_timeout == 0s || (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 = m_chainman.ActiveChain().Tip();
              state.m_chain_sync.m_sent_getheaders = false;
          } else if (state.m_chain_sync.m_timeout > 0s && 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());
                  m_connman.PushMessage(&pto, msgMaker.Make(NetMsgType::GETHEADERS, m_chainman.ActiveChain().GetLocator(state.m_chain_sync.m_work_header->pprev), uint256()));
                  state.m_chain_sync.m_sent_getheaders = true;
                  constexpr auto HEADERS_RESPONSE_TIME{2min};
                  // 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 PeerManagerImpl::EvictExtraOutboundPeers(std::chrono::seconds now)
  {
      // If we have any extra block-relay-only peers, disconnect the youngest unless
      // it's given us a block -- in which case, compare with the second-youngest, and
      // out of those two, disconnect the peer who least recently gave us a block.
      // The youngest block-relay-only peer would be the extra peer we connected
      // to temporarily in order to sync our tip; see net.cpp.
      // Note that we use higher nodeid as a measure for most recent connection.
      if (m_connman.GetExtraBlockRelayCount() > 0) {
          std::pair<NodeId, std::chrono::seconds> youngest_peer{-1, 0}, next_youngest_peer{-1, 0};
  
          m_connman.ForEachNode([&](CNode* pnode) {
              if (!pnode->IsBlockOnlyConn() || pnode->fDisconnect) return;
              if (pnode->GetId() > youngest_peer.first) {
                  next_youngest_peer = youngest_peer;
                  youngest_peer.first = pnode->GetId();
                  youngest_peer.second = pnode->m_last_block_time;
              }
          });
          NodeId to_disconnect = youngest_peer.first;
          if (youngest_peer.second > next_youngest_peer.second) {
              // Our newest block-relay-only peer gave us a block more recently;
              // disconnect our second youngest.
              to_disconnect = next_youngest_peer.first;
          }
          m_connman.ForNode(to_disconnect, [&](CNode* pnode) EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
              AssertLockHeld(::cs_main);
              // Make sure we're not getting a block right now, and that
              // we've been connected long enough for this eviction to happen
              // at all.
              // Note that we only request blocks from a peer if we learn of a
              // valid headers chain with at least as much work as our tip.
              CNodeState *node_state = State(pnode->GetId());
              if (node_state == nullptr ||
                  (now - pnode->m_connected >= MINIMUM_CONNECT_TIME && node_state->nBlocksInFlight == 0)) {
                  pnode->fDisconnect = true;
                  LogPrint(BCLog::NET, "disconnecting extra block-relay-only peer=%d (last block received at time %d)\n",
                           pnode->GetId(), count_seconds(pnode->m_last_block_time));
                  return true;
              } else {
                  LogPrint(BCLog::NET, "keeping block-relay-only peer=%d chosen for eviction (connect time: %d, blocks_in_flight: %d)\n",
                           pnode->GetId(), count_seconds(pnode->m_connected), node_state->nBlocksInFlight);
              }
              return false;
          });
      }
  
      // Check whether we have too many outbound-full-relay peers
      if (m_connman.GetExtraFullOutboundCount() > 0) {
          // If we have more outbound-full-relay peers than we target, disconnect one.
          // Pick the outbound-full-relay 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();
  
          m_connman.ForEachNode([&](CNode* pnode) EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
              AssertLockHeld(::cs_main);
  
              // Only consider outbound-full-relay peers that are not already
              // marked for disconnection
              if (!pnode->IsFullOutboundConn() || 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 = m_connman.ForNode(worst_peer, [&](CNode* pnode) EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
                  AssertLockHeld(::cs_main);
  
                  // Only disconnect a peer that has been connected to us for
                  // some reasonable fraction of our check-frequency, to give
                  // it time for new information to have arrived.
                  // Also don't disconnect any peer we're trying to download a
                  // block from.
                  CNodeState &state = *State(pnode->GetId());
                  if (now - pnode->m_connected > 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(), count_seconds(pnode->m_connected), 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.
                  m_connman.SetTryNewOutboundPeer(false);
              }
          }
      }
  }
  
  void PeerManagerImpl::CheckForStaleTipAndEvictPeers()
  {
      LOCK(cs_main);
  
      auto now{GetTime<std::chrono::seconds>()};
  
      EvictExtraOutboundPeers(now);
  
      if (now > m_stale_tip_check_time) {
          // Check whether our tip is stale, and if so, allow using an extra
          // outbound peer
          if (!fImporting && !fReindex && m_connman.GetNetworkActive() && m_connman.GetUseAddrmanOutgoing() && TipMayBeStale()) {
              LogPrintf("Potential stale tip detected, will try using extra outbound peer (last tip update: %d seconds ago)\n",
                        count_seconds(now - m_last_tip_update.load()));
              m_connman.SetTryNewOutboundPeer(true);
          } else if (m_connman.GetTryNewOutboundPeer()) {
              m_connman.SetTryNewOutboundPeer(false);
          }
          m_stale_tip_check_time = now + STALE_CHECK_INTERVAL;
      }
  
      if (!m_initial_sync_finished && CanDirectFetch()) {
          m_connman.StartExtraBlockRelayPeers();
          m_initial_sync_finished = true;
      }
  }
  
  void PeerManagerImpl::MaybeSendPing(CNode& node_to, Peer& peer, std::chrono::microseconds now)
  {
      if (m_connman.ShouldRunInactivityChecks(node_to, std::chrono::duration_cast<std::chrono::seconds>(now)) &&
          peer.m_ping_nonce_sent &&
          now > peer.m_ping_start.load() + TIMEOUT_INTERVAL)
      {
          // The ping timeout is using mocktime. To disable the check during
          // testing, increase -peertimeout.
          LogPrint(BCLog::NET, "ping timeout: %fs peer=%d\n", 0.000001 * count_microseconds(now - peer.m_ping_start.load()), peer.m_id);
          node_to.fDisconnect = true;
          return;
      }
  
      const CNetMsgMaker msgMaker(node_to.GetCommonVersion());
      bool pingSend = false;
  
      if (peer.m_ping_queued) {
          // RPC ping request by user
          pingSend = true;
      }
  
      if (peer.m_ping_nonce_sent == 0 && now > peer.m_ping_start.load() + PING_INTERVAL) {
          // 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));
          }
          peer.m_ping_queued = false;
          peer.m_ping_start = now;
          if (node_to.GetCommonVersion() > BIP0031_VERSION) {
              peer.m_ping_nonce_sent = nonce;
              m_connman.PushMessage(&node_to, msgMaker.Make(NetMsgType::PING, nonce));
          } else {
              // Peer is too old to support ping command with nonce, pong will never arrive.
              peer.m_ping_nonce_sent = 0;
              m_connman.PushMessage(&node_to, msgMaker.Make(NetMsgType::PING));
          }
      }
  }
  
  void PeerManagerImpl::MaybeSendAddr(CNode& node, Peer& peer, std::chrono::microseconds current_time)
  {
      // Nothing to do for non-address-relay peers
      if (!peer.m_addr_relay_enabled) return;
  
      LOCK(peer.m_addr_send_times_mutex);
      // Periodically advertise our local address to the peer.
      if (fListen && !m_chainman.ActiveChainstate().IsInitialBlockDownload() &&
          peer.m_next_local_addr_send < current_time) {
          // If we've sent before, clear the bloom filter for the peer, so that our
          // self-announcement will actually go out.
          // This might be unnecessary if the bloom filter has already rolled
          // over since our last self-announcement, but there is only a small
          // bandwidth cost that we can incur by doing this (which happens
          // once a day on average).
          if (peer.m_next_local_addr_send != 0us) {
              peer.m_addr_known->reset();
          }
          if (std::optional<CAddress> local_addr = GetLocalAddrForPeer(&node)) {
              FastRandomContext insecure_rand;
              PushAddress(peer, *local_addr, insecure_rand);
          }
          peer.m_next_local_addr_send = GetExponentialRand(current_time, AVG_LOCAL_ADDRESS_BROADCAST_INTERVAL);
      }
  
      // We sent an `addr` message to this peer recently. Nothing more to do.
      if (current_time <= peer.m_next_addr_send) return;
  
      peer.m_next_addr_send = GetExponentialRand(current_time, AVG_ADDRESS_BROADCAST_INTERVAL);
  
      if (!Assume(peer.m_addrs_to_send.size() <= MAX_ADDR_TO_SEND)) {
          // Should be impossible since we always check size before adding to
          // m_addrs_to_send. Recover by trimming the vector.
          peer.m_addrs_to_send.resize(MAX_ADDR_TO_SEND);
      }
  
      // Remove addr records that the peer already knows about, and add new
      // addrs to the m_addr_known filter on the same pass.
      auto addr_already_known = [&peer](const CAddress& addr) {
          bool ret = peer.m_addr_known->contains(addr.GetKey());
          if (!ret) peer.m_addr_known->insert(addr.GetKey());
          return ret;
      };
      peer.m_addrs_to_send.erase(std::remove_if(peer.m_addrs_to_send.begin(), peer.m_addrs_to_send.end(), addr_already_known),
                             peer.m_addrs_to_send.end());
  
      // No addr messages to send
      if (peer.m_addrs_to_send.empty()) return;
  
      const char* msg_type;
      int make_flags;
      if (peer.m_wants_addrv2) {
          msg_type = NetMsgType::ADDRV2;
          make_flags = ADDRV2_FORMAT;
      } else {
          msg_type = NetMsgType::ADDR;
          make_flags = 0;
      }
      m_connman.PushMessage(&node, CNetMsgMaker(node.GetCommonVersion()).Make(make_flags, msg_type, peer.m_addrs_to_send));
      peer.m_addrs_to_send.clear();
  
      // we only send the big addr message once
      if (peer.m_addrs_to_send.capacity() > 40) {
          peer.m_addrs_to_send.shrink_to_fit();
      }
  }
  
  void PeerManagerImpl::MaybeSendFeefilter(CNode& pto, std::chrono::microseconds current_time)
  {
      AssertLockHeld(cs_main);
  
      if (m_ignore_incoming_txs) return;
      if (!pto.m_tx_relay) return;
      if (pto.GetCommonVersion() < FEEFILTER_VERSION) return;
      // peers with the forcerelay permission should not filter txs to us
      if (pto.HasPermission(NetPermissionFlags::ForceRelay)) return;
  
      CAmount currentFilter = m_mempool.GetMinFee(gArgs.GetIntArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000).GetFeePerK();
      static FeeFilterRounder g_filter_rounder{CFeeRate{DEFAULT_MIN_RELAY_TX_FEE}};
  
      if (m_chainman.ActiveChainstate().IsInitialBlockDownload()) {
          // Received tx-inv messages are discarded when the active
          // chainstate is in IBD, so tell the peer to not send them.
          currentFilter = MAX_MONEY;
      } else {
          static const CAmount MAX_FILTER{g_filter_rounder.round(MAX_MONEY)};
          if (pto.m_tx_relay->lastSentFeeFilter == MAX_FILTER) {
              // Send the current filter if we sent MAX_FILTER previously
              // and made it out of IBD.
              pto.m_tx_relay->m_next_send_feefilter = 0us;
          }
      }
      if (current_time > pto.m_tx_relay->m_next_send_feefilter) {
          CAmount filterToSend = g_filter_rounder.round(currentFilter);
          // We always have a fee filter of at least minRelayTxFee
          filterToSend = std::max(filterToSend, ::minRelayTxFee.GetFeePerK());
          if (filterToSend != pto.m_tx_relay->lastSentFeeFilter) {
              m_connman.PushMessage(&pto, CNetMsgMaker(pto.GetCommonVersion()).Make(NetMsgType::FEEFILTER, filterToSend));
              pto.m_tx_relay->lastSentFeeFilter = filterToSend;
          }
          pto.m_tx_relay->m_next_send_feefilter = GetExponentialRand(current_time, 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 (current_time + MAX_FEEFILTER_CHANGE_DELAY < pto.m_tx_relay->m_next_send_feefilter &&
                  (currentFilter < 3 * pto.m_tx_relay->lastSentFeeFilter / 4 || currentFilter > 4 * pto.m_tx_relay->lastSentFeeFilter / 3)) {
          pto.m_tx_relay->m_next_send_feefilter = current_time + GetRandomDuration<std::chrono::microseconds>(MAX_FEEFILTER_CHANGE_DELAY);
      }
  }
  
  namespace {
  class CompareInvMempoolOrder
  {
      CTxMemPool *mp;
      bool m_wtxid_relay;
  public:
      explicit CompareInvMempoolOrder(CTxMemPool *_mempool, bool use_wtxid)
      {
          mp = _mempool;
          m_wtxid_relay = use_wtxid;
      }
  
      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, m_wtxid_relay);
      }
  };
  }
  
  bool PeerManagerImpl::SetupAddressRelay(const CNode& node, Peer& peer)
  {
      // We don't participate in addr relay with outbound block-relay-only
      // connections to prevent providing adversaries with the additional
      // information of addr traffic to infer the link.
      if (node.IsBlockOnlyConn()) return false;
  
      if (!peer.m_addr_relay_enabled.exchange(true)) {
          // First addr message we have received from the peer, initialize
          // m_addr_known
          peer.m_addr_known = std::make_unique<CRollingBloomFilter>(5000, 0.001);
      }
  
      return true;
  }
  
  bool PeerManagerImpl::SendMessages(CNode* pto)
  {
      PeerRef peer = GetPeerRef(pto->GetId());
      if (!peer) return false;
      const Consensus::Params& consensusParams = m_chainparams.GetConsensus();
  
      // We must call MaybeDiscourageAndDisconnect first, to ensure that we'll
      // disconnect misbehaving peers even before the version handshake is complete.
      if (MaybeDiscourageAndDisconnect(*pto, *peer)) return true;
  
      // 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->GetCommonVersion());
  
      const auto current_time{GetTime<std::chrono::microseconds>()};
  
      if (pto->IsAddrFetchConn() && current_time - pto->m_connected > 10 * AVG_ADDRESS_BROADCAST_INTERVAL) {
          LogPrint(BCLog::NET, "addrfetch connection timeout; disconnecting peer=%d\n", pto->GetId());
          pto->fDisconnect = true;
          return true;
      }
  
      MaybeSendPing(*pto, *peer, current_time);
  
      // MaybeSendPing may have marked peer for disconnection
      if (pto->fDisconnect) return true;
  
      MaybeSendAddr(*pto, *peer, current_time);
  
      {
          LOCK(cs_main);
  
          CNodeState &state = *State(pto->GetId());
  
          // Start block sync
          if (pindexBestHeader == nullptr)
              pindexBestHeader = m_chainman.ActiveChain().Tip();
          bool fFetch = state.fPreferredDownload || (nPreferredDownload == 0 && !pto->fClient && !pto->IsAddrFetchConn()); // 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.m_headers_sync_timeout = current_time + HEADERS_DOWNLOAD_TIMEOUT_BASE +
                      (
                          // Convert HEADERS_DOWNLOAD_TIMEOUT_PER_HEADER to microseconds before scaling
                          // to maintain precision
                          std::chrono::microseconds{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(), peer->m_starting_height);
                  m_connman.PushMessage(pto, msgMaker.Make(NetMsgType::GETHEADERS, m_chainman.ActiveChain().GetLocator(pindexStart), uint256()));
              }
          }
  
          //
          // 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(peer->m_block_inv_mutex);
              std::vector<CBlock> vHeaders;
              bool fRevertToInv = ((!state.fPreferHeaders &&
                                   (!state.fPreferHeaderAndIDs || peer->m_blocks_for_headers_relay.size() > 1)) ||
                                   peer->m_blocks_for_headers_relay.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 m_chainman.ActiveChain(), give up.
                  for (const uint256& hash : peer->m_blocks_for_headers_relay) {
                      const CBlockIndex* pindex = m_chainman.m_blockman.LookupBlockIndex(hash);
                      assert(pindex);
                      if (m_chainman.ActiveChain()[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 m_blocks_for_headers_relay.
                          // 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(consensusParams));
                      } 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(consensusParams));
                      } 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)
                                  m_connman.PushMessage(pto, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, *most_recent_compact_block));
                              else {
                                  CBlockHeaderAndShortTxIDs cmpctblock(*most_recent_block, state.fWantsCmpctWitness);
                                  m_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);
                          m_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());
                      }
                      m_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 m_blocks_for_headers_relay was our tip at some point
                  // in the past.
                  if (!peer->m_blocks_for_headers_relay.empty()) {
                      const uint256& hashToAnnounce = peer->m_blocks_for_headers_relay.back();
                      const CBlockIndex* pindex = m_chainman.m_blockman.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 (m_chainman.ActiveChain()[pindex->nHeight] != pindex) {
                          LogPrint(BCLog::NET, "Announcing block %s not on main chain (tip=%s)\n",
                              hashToAnnounce.ToString(), m_chainman.ActiveChain().Tip()->GetBlockHash().ToString());
                      }
  
                      // If the peer's chain has this block, don't inv it back.
                      if (!PeerHasHeader(&state, pindex)) {
                          peer->m_blocks_for_inv_relay.push_back(hashToAnnounce);
                          LogPrint(BCLog::NET, "%s: sending inv peer=%d hash=%s\n", __func__,
                              pto->GetId(), hashToAnnounce.ToString());
                      }
                  }
              }
              peer->m_blocks_for_headers_relay.clear();
          }
  
          //
          // Message: inventory
          //
          std::vector<CInv> vInv;
          {
              LOCK(peer->m_block_inv_mutex);
              vInv.reserve(std::max<size_t>(peer->m_blocks_for_inv_relay.size(), INVENTORY_BROADCAST_MAX));
  
              // Add blocks
              for (const uint256& hash : peer->m_blocks_for_inv_relay) {
                  vInv.push_back(CInv(MSG_BLOCK, hash));
                  if (vInv.size() == MAX_INV_SZ) {
                      m_connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
                      vInv.clear();
                  }
              }
              peer->m_blocks_for_inv_relay.clear();
          }
  
          if (pto->m_tx_relay != nullptr) {
                  LOCK(pto->m_tx_relay->cs_tx_inventory);
                  // Check whether periodic sends should happen
                  bool fSendTrickle = pto->HasPermission(NetPermissionFlags::NoBan);
                  if (pto->m_tx_relay->nNextInvSend < current_time) {
                      fSendTrickle = true;
                      if (pto->IsInboundConn()) {
                          pto->m_tx_relay->nNextInvSend = NextInvToInbounds(current_time, INBOUND_INVENTORY_BROADCAST_INTERVAL);
                      } else {
                          pto->m_tx_relay->nNextInvSend = GetExponentialRand(current_time, OUTBOUND_INVENTORY_BROADCAST_INTERVAL);
                      }
                  }
  
                  // Time to send but the peer has requested we not relay transactions.
                  if (fSendTrickle) {
                      LOCK(pto->m_tx_relay->cs_filter);
                      if (!pto->m_tx_relay->fRelayTxes) pto->m_tx_relay->setInventoryTxToSend.clear();
                  }
  
                  // Respond to BIP35 mempool requests
                  if (fSendTrickle && pto->m_tx_relay->fSendMempool) {
                      auto vtxinfo = m_mempool.infoAll();
                      pto->m_tx_relay->fSendMempool = false;
                      const CFeeRate filterrate{pto->m_tx_relay->minFeeFilter.load()};
  
                      LOCK(pto->m_tx_relay->cs_filter);
  
                      for (const auto& txinfo : vtxinfo) {
                          const uint256& hash = state.m_wtxid_relay ? txinfo.tx->GetWitnessHash() : txinfo.tx->GetHash();
                          CInv inv(state.m_wtxid_relay ? MSG_WTX : MSG_TX, hash);
                          pto->m_tx_relay->setInventoryTxToSend.erase(hash);
                          // Don't send transactions that peers will not put into their mempool
                          if (txinfo.fee < filterrate.GetFee(txinfo.vsize)) {
                              continue;
                          }
                          if (pto->m_tx_relay->pfilter) {
                              if (!pto->m_tx_relay->pfilter->IsRelevantAndUpdate(*txinfo.tx)) continue;
                          }
                          pto->m_tx_relay->filterInventoryKnown.insert(hash);
                          // Responses to MEMPOOL requests bypass the m_recently_announced_invs filter.
                          vInv.push_back(inv);
                          if (vInv.size() == MAX_INV_SZ) {
                              m_connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
                              vInv.clear();
                          }
                      }
                      pto->m_tx_relay->m_last_mempool_req = std::chrono::duration_cast<std::chrono::seconds>(current_time);
                  }
  
                  // Determine transactions to relay
                  if (fSendTrickle) {
                      // Produce a vector with all candidates for sending
                      std::vector<std::set<uint256>::iterator> vInvTx;
                      vInvTx.reserve(pto->m_tx_relay->setInventoryTxToSend.size());
                      for (std::set<uint256>::iterator it = pto->m_tx_relay->setInventoryTxToSend.begin(); it != pto->m_tx_relay->setInventoryTxToSend.end(); it++) {
                          vInvTx.push_back(it);
                      }
                      const CFeeRate filterrate{pto->m_tx_relay->minFeeFilter.load()};
                      // 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(&m_mempool, state.m_wtxid_relay);
                      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->m_tx_relay->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;
                          CInv inv(state.m_wtxid_relay ? MSG_WTX : MSG_TX, hash);
                          // Remove it from the to-be-sent set
                          pto->m_tx_relay->setInventoryTxToSend.erase(it);
                          // Check if not in the filter already
                          if (pto->m_tx_relay->filterInventoryKnown.contains(hash)) {
                              continue;
                          }
                          // Not in the mempool anymore? don't bother sending it.
                          auto txinfo = m_mempool.info(ToGenTxid(inv));
                          if (!txinfo.tx) {
                              continue;
                          }
                          auto txid = txinfo.tx->GetHash();
                          auto wtxid = txinfo.tx->GetWitnessHash();
                          // Peer told you to not send transactions at that feerate? Don't bother sending it.
                          if (txinfo.fee < filterrate.GetFee(txinfo.vsize)) {
                              continue;
                          }
                          if (pto->m_tx_relay->pfilter && !pto->m_tx_relay->pfilter->IsRelevantAndUpdate(*txinfo.tx)) continue;
                          // Send
                          State(pto->GetId())->m_recently_announced_invs.insert(hash);
                          vInv.push_back(inv);
                          nRelayedTransactions++;
                          {
                              // Expire old relay messages
                              while (!g_relay_expiration.empty() && g_relay_expiration.front().first < current_time)
                              {
                                  mapRelay.erase(g_relay_expiration.front().second);
                                  g_relay_expiration.pop_front();
                              }
  
                              auto ret = mapRelay.emplace(txid, std::move(txinfo.tx));
                              if (ret.second) {
                                  g_relay_expiration.emplace_back(current_time + RELAY_TX_CACHE_TIME, ret.first);
                              }
                              // Add wtxid-based lookup into mapRelay as well, so that peers can request by wtxid
                              auto ret2 = mapRelay.emplace(wtxid, ret.first->second);
                              if (ret2.second) {
                                  g_relay_expiration.emplace_back(current_time + RELAY_TX_CACHE_TIME, ret2.first);
                              }
                          }
                          if (vInv.size() == MAX_INV_SZ) {
                              m_connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
                              vInv.clear();
                          }
                          pto->m_tx_relay->filterInventoryKnown.insert(hash);
                          if (hash != txid) {
                              // Insert txid into filterInventoryKnown, even for
                              // wtxidrelay peers. This prevents re-adding of
                              // unconfirmed parents to the recently_announced
                              // filter, when a child tx is requested. See
                              // ProcessGetData().
                              pto->m_tx_relay->filterInventoryKnown.insert(txid);
                          }
                      }
                  }
          }
          if (!vInv.empty())
              m_connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
  
          // Detect whether we're stalling
          if (state.m_stalling_since.count() && state.m_stalling_since < current_time - 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 block_interval * (1 + 0.5 * N)
          // (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 = m_peers_downloading_from - 1;
              if (current_time > state.m_downloading_since + std::chrono::seconds{consensusParams.nPowTargetSpacing} * (BLOCK_DOWNLOAD_TIMEOUT_BASE + BLOCK_DOWNLOAD_TIMEOUT_PER_PEER * nOtherPeersWithValidatedDownloads)) {
                  LogPrintf("Timeout downloading block %s from peer=%d, disconnecting\n", queuedBlock.pindex->GetBlockHash().ToString(), pto->GetId());
                  pto->fDisconnect = true;
                  return true;
              }
          }
          // Check for headers sync timeouts
          if (state.fSyncStarted && state.m_headers_sync_timeout < std::chrono::microseconds::max()) {
              // Detect whether this is a stalling initial-headers-sync peer
              if (pindexBestHeader->GetBlockTime() <= GetAdjustedTime() - 24 * 60 * 60) {
                  if (current_time > state.m_headers_sync_timeout && nSyncStarted == 1 && (nPreferredDownload - state.fPreferredDownload >= 1)) {
                      // Disconnect a peer (without NetPermissionFlags::NoBan permission) 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->HasPermission(NetPermissionFlags::NoBan)) {
                          LogPrintf("Timeout downloading headers from peer=%d, disconnecting\n", pto->GetId());
                          pto->fDisconnect = true;
                          return true;
                      } else {
                          LogPrintf("Timeout downloading headers from noban 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.m_headers_sync_timeout = 0us;
                      }
                  }
              } else {
                  // After we've caught up once, reset the timeout so we can't trigger
                  // disconnect later.
                  state.m_headers_sync_timeout = std::chrono::microseconds::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<std::chrono::seconds>());
  
          //
          // Message: getdata (blocks)
          //
          std::vector<CInv> vGetData;
          if (!pto->fClient && ((fFetch && !pto->m_limited_node) || !m_chainman.ActiveChainstate().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);
              for (const CBlockIndex *pindex : vToDownload) {
                  uint32_t nFetchFlags = GetFetchFlags(*pto);
                  vGetData.push_back(CInv(MSG_BLOCK | nFetchFlags, pindex->GetBlockHash()));
                  BlockRequested(pto->GetId(), *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)->m_stalling_since == 0us) {
                      State(staller)->m_stalling_since = current_time;
                      LogPrint(BCLog::NET, "Stall started peer=%d\n", staller);
                  }
              }
          }
  
          //
          // Message: getdata (transactions)
          //
          std::vector<std::pair<NodeId, GenTxid>> expired;
          auto requestable = m_txrequest.GetRequestable(pto->GetId(), current_time, &expired);
          for (const auto& entry : expired) {
              LogPrint(BCLog::NET, "timeout of inflight %s %s from peer=%d\n", entry.second.IsWtxid() ? "wtx" : "tx",
                  entry.second.GetHash().ToString(), entry.first);
          }
          for (const GenTxid& gtxid : requestable) {
              if (!AlreadyHaveTx(gtxid)) {
                  LogPrint(BCLog::NET, "Requesting %s %s peer=%d\n", gtxid.IsWtxid() ? "wtx" : "tx",
                      gtxid.GetHash().ToString(), pto->GetId());
                  vGetData.emplace_back(gtxid.IsWtxid() ? MSG_WTX : (MSG_TX | GetFetchFlags(*pto)), gtxid.GetHash());
                  if (vGetData.size() >= MAX_GETDATA_SZ) {
                      m_connman.PushMessage(pto, msgMaker.Make(NetMsgType::GETDATA, vGetData));
                      vGetData.clear();
                  }
                  m_txrequest.RequestedTx(pto->GetId(), gtxid.GetHash(), current_time + GETDATA_TX_INTERVAL);
              } else {
                  // We have already seen this transaction, no need to download. This is just a belt-and-suspenders, as
                  // this should already be called whenever a transaction becomes AlreadyHaveTx().
                  m_txrequest.ForgetTxHash(gtxid.GetHash());
              }
          }
  
  
          if (!vGetData.empty())
              m_connman.PushMessage(pto, msgMaker.Make(NetMsgType::GETDATA, vGetData));
  
          MaybeSendFeefilter(*pto, current_time);
      } // release cs_main
      return true;
  }
  