validation.cpp

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2018 The Bitcoin Core developers
// Copyright (c) 2017-2020 The Bitcoin developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#include <validation.h>
 
#include <kernel/chainparams.h>
#include <kernel/coinstats.h>
#include <kernel/disconnected_transactions.h>
#include <kernel/mempool_entry.h>
#include <kernel/mempool_persist.h>
 
#include <arith_uint256.h>
#include <avalanche/avalanche.h>
#include <avalanche/processor.h>
#include <blockvalidity.h>
#include <chainparams.h>
#include <checkpoints.h>
#include <checkqueue.h>
#include <common/args.h>
#include <config.h>
#include <consensus/activation.h>
#include <consensus/amount.h>
#include <consensus/merkle.h>
#include <consensus/tx_check.h>
#include <consensus/tx_verify.h>
#include <consensus/validation.h>
#include <hash.h>
#include <kernel/notifications_interface.h>
#include <logging.h>
#include <logging/timer.h>
#include <minerfund.h>
#include <node/blockstorage.h>
#include <node/utxo_snapshot.h>
#include <policy/block/minerfund.h>
#include <policy/block/preconsensus.h>
#include <policy/block/rtt.h>
#include <policy/block/stakingrewards.h>
#include <policy/policy.h>
#include <policy/settings.h>
#include <pow/pow.h>
#include <primitives/block.h>
#include <primitives/transaction.h>
#include <random.h>
#include <reverse_iterator.h>
#include <script/script.h>
#include <script/scriptcache.h>
#include <script/sigcache.h>
#include <shutdown.h>
#include <tinyformat.h>
#include <txdb.h>
#include <txmempool.h>
#include <undo.h>
#include <util/check.h> // For NDEBUG compile time check
#include <util/fs.h>
#include <util/fs_helpers.h>
#include <util/strencodings.h>
#include <util/string.h>
#include <util/time.h>
#include <util/trace.h>
#include <util/translation.h>
#include <validationinterface.h>
#include <warnings.h>
 
#include <algorithm>
#include <atomic>
#include <cassert>
#include <chrono>
#include <deque>
#include <numeric>
#include <optional>
#include <string>
#include <thread>
 
using kernel::CCoinsStats;
using kernel::CoinStatsHashType;
using kernel::ComputeUTXOStats;
using kernel::LoadMempool;
using kernel::Notifications;
 
using fsbridge::FopenFn;
using node::BLOCKFILE_CHUNK_SIZE;
using node::BlockManager;
using node::BlockMap;
using node::fReindex;
using node::SnapshotMetadata;
using node::UNDOFILE_CHUNK_SIZE;
 
#define MICRO 0.000001
#define MILLI 0.001
 
static constexpr std::chrono::hours DATABASE_WRITE_INTERVAL{1};
static constexpr std::chrono::hours DATABASE_FLUSH_INTERVAL{24};
const std::vector<std::string> CHECKLEVEL_DOC{
    "level 0 reads the blocks from disk",
    "level 1 verifies block validity",
    "level 2 verifies undo data",
    "level 3 checks disconnection of tip blocks",
    "level 4 tries to reconnect the blocks",
    "each level includes the checks of the previous levels",
};
static constexpr int PRUNE_LOCK_BUFFER{10};
 
static constexpr uint64_t HEADERS_TIME_VERSION{1};
 
GlobalMutex g_best_block_mutex;
std::condition_variable g_best_block_cv;
const CBlockIndex *g_best_block;
 
BlockValidationOptions::BlockValidationOptions(const Config &config)
    : excessiveBlockSize(config.GetMaxBlockSize()), checkPoW(true),
      checkMerkleRoot(true) {}
 
const CBlockIndex *
Chainstate::FindForkInGlobalIndex(const CBlockLocator &locator) const {
    AssertLockHeld(cs_main);
 
    // Find the latest block common to locator and chain - we expect that
    // locator.vHave is sorted descending by height.
    for (const BlockHash &hash : locator.vHave) {
        const CBlockIndex *pindex{m_blockman.LookupBlockIndex(hash)};
        if (pindex) {
            if (m_chain.Contains(pindex)) {
                return pindex;
            }
            if (pindex->GetAncestor(m_chain.Height()) == m_chain.Tip()) {
                return m_chain.Tip();
            }
        }
    }
    return m_chain.Genesis();
}
 
static uint32_t GetNextBlockScriptFlags(const CBlockIndex *pindex,
                                        const ChainstateManager &chainman);
 
namespace {
std::optional<std::vector<int>> CalculatePrevHeights(const CBlockIndex &tip,
                                                     const CCoinsView &coins,
                                                     const CTransaction &tx) {
    std::vector<int> prev_heights;
    prev_heights.resize(tx.vin.size());
    for (size_t i = 0; i < tx.vin.size(); ++i) {
        const CTxIn &txin = tx.vin[i];
        Coin coin;
        if (!coins.GetCoin(txin.prevout, coin)) {
            LogPrintf("ERROR: %s: Missing input %d in transaction \'%s\'\n",
                      __func__, i, tx.GetId().GetHex());
            return std::nullopt;
        }
        if (coin.GetHeight() == MEMPOOL_HEIGHT) {
            // Assume all mempool transaction confirm in the next block.
            prev_heights[i] = tip.nHeight + 1;
        } else {
            prev_heights[i] = coin.GetHeight();
        }
    }
    return prev_heights;
}
} // namespace
 
std::optional<LockPoints> CalculateLockPointsAtTip(CBlockIndex *tip,
                                                   const CCoinsView &coins_view,
                                                   const CTransaction &tx) {
    assert(tip);
 
    auto prev_heights{CalculatePrevHeights(*tip, coins_view, tx)};
    if (!prev_heights.has_value()) {
        return std::nullopt;
    }
 
    CBlockIndex next_tip;
    next_tip.pprev = tip;
    // When SequenceLocks() is called within ConnectBlock(), the height
    // of the block *being* evaluated is what is used.
    // Thus if we want to know if a transaction can be part of the
    // *next* block, we need to use one more than
    // active_chainstate.m_chain.Height()
    next_tip.nHeight = tip->nHeight + 1;
    const auto [min_height, min_time] = CalculateSequenceLocks(
        tx, STANDARD_LOCKTIME_VERIFY_FLAGS, prev_heights.value(), next_tip);
 
    return LockPoints{min_height, min_time};
}
 
bool CheckSequenceLocksAtTip(CBlockIndex *tip, const LockPoints &lock_points) {
    assert(tip != nullptr);
 
    CBlockIndex index;
    index.pprev = tip;
    // CheckSequenceLocksAtTip() uses active_chainstate.m_chain.Height()+1 to
    // evaluate height based locks because when SequenceLocks() is called within
    // ConnectBlock(), the height of the block *being* evaluated is what is
    // used. Thus if we want to know if a transaction can be part of the *next*
    // block, we need to use one more than active_chainstate.m_chain.Height()
    index.nHeight = tip->nHeight + 1;
 
    return EvaluateSequenceLocks(index, {lock_points.height, lock_points.time});
}
 
// Command-line argument "-replayprotectionactivationtime=<timestamp>" will
// cause the node to switch to replay protected SigHash ForkID value when the
// median timestamp of the previous 11 blocks is greater than or equal to
// <timestamp>. Defaults to the pre-defined timestamp when not set.
static bool IsReplayProtectionEnabled(const Consensus::Params &params,
                                      int64_t nMedianTimePast) {
    return nMedianTimePast >= gArgs.GetIntArg("-replayprotectionactivationtime",
                                              params.schumpeterActivationTime);
}
 
static bool IsReplayProtectionEnabled(const Consensus::Params &params,
                                      const CBlockIndex *pindexPrev) {
    if (pindexPrev == nullptr) {
        return false;
    }
 
    return IsReplayProtectionEnabled(params, pindexPrev->GetMedianTimePast());
}
 
static bool CheckInputsFromMempoolAndCache(
    const CTransaction &tx, TxValidationState &state,
    const CCoinsViewCache &view, const CTxMemPool &pool, const uint32_t flags,
    PrecomputedTransactionData &txdata, int &nSigChecksOut,
    CCoinsViewCache &coins_tip) EXCLUSIVE_LOCKS_REQUIRED(cs_main, pool.cs) {
    AssertLockHeld(cs_main);
    AssertLockHeld(pool.cs);
 
    assert(!tx.IsCoinBase());
    for (const CTxIn &txin : tx.vin) {
        const Coin &coin = view.AccessCoin(txin.prevout);
 
        // This coin was checked in PreChecks and MemPoolAccept
        // has been holding cs_main since then.
        Assume(!coin.IsSpent());
        if (coin.IsSpent()) {
            return false;
        }
 
        // If the Coin is available, there are 2 possibilities:
        // it is available in our current ChainstateActive UTXO set,
        // or it's a UTXO provided by a transaction in our mempool.
        // Ensure the scriptPubKeys in Coins from CoinsView are correct.
        const CTransactionRef &txFrom = pool.get(txin.prevout.GetTxId());
        if (txFrom) {
            assert(txFrom->GetId() == txin.prevout.GetTxId());
            assert(txFrom->vout.size() > txin.prevout.GetN());
            assert(txFrom->vout[txin.prevout.GetN()] == coin.GetTxOut());
        } else {
            const Coin &coinFromUTXOSet = coins_tip.AccessCoin(txin.prevout);
            assert(!coinFromUTXOSet.IsSpent());
            assert(coinFromUTXOSet.GetTxOut() == coin.GetTxOut());
        }
    }
 
    // Call CheckInputScripts() to cache signature and script validity against
    // current tip consensus rules.
    return CheckInputScripts(tx, state, view, flags, /*sigCacheStore=*/true,
                             /*scriptCacheStore=*/true, txdata, nSigChecksOut);
}
 
namespace {
 
class MemPoolAccept {
public:
    MemPoolAccept(CTxMemPool &mempool, Chainstate &active_chainstate)
        : m_pool(mempool), m_view(&m_dummy),
          m_viewmempool(&active_chainstate.CoinsTip(), m_pool),
          m_active_chainstate(active_chainstate) {}
 
    // We put the arguments we're handed into a struct, so we can pass them
    // around easier.
    struct ATMPArgs {
        const Config &m_config;
        const int64_t m_accept_time;
        const bool m_bypass_limits;
        /*
         * Return any outpoints which were not previously present in the coins
         * cache, but were added as a result of validating the tx for mempool
         * acceptance. This allows the caller to optionally remove the cache
         * additions if the associated transaction ends up being rejected by
         * the mempool.
         */
        std::vector<COutPoint> &m_coins_to_uncache;
        const bool m_test_accept;
        const unsigned int m_heightOverride;
        const bool m_package_submission;
        const bool m_package_feerates;
 
        static ATMPArgs SingleAccept(const Config &config, int64_t accept_time,
                                     bool bypass_limits,
                                     std::vector<COutPoint> &coins_to_uncache,
                                     bool test_accept,
                                     unsigned int heightOverride) {
            return ATMPArgs{
                config,
                accept_time,
                bypass_limits,
                coins_to_uncache,
                test_accept,
                heightOverride,
                /*package_submission=*/false,
                /*package_feerates=*/false,
            };
        }
 
        static ATMPArgs
        PackageTestAccept(const Config &config, int64_t accept_time,
                          std::vector<COutPoint> &coins_to_uncache) {
            return ATMPArgs{
                config,
                accept_time,
                /*bypass_limits=*/false,
                coins_to_uncache,
                /*test_accept=*/true,
                /*height_override=*/0,
                // not submitting to mempool
                /*package_submission=*/false,
                /*package_feerates=*/false,
            };
        }
 
        static ATMPArgs
        PackageChildWithParents(const Config &config, int64_t accept_time,
                                std::vector<COutPoint> &coins_to_uncache) {
            return ATMPArgs{
                config,
                accept_time,
                /*bypass_limits=*/false,
                coins_to_uncache,
                /*test_accept=*/false,
                /*height_override=*/0,
                /*package_submission=*/true,
                /*package_feerates=*/true,
            };
        }
 
        static ATMPArgs SingleInPackageAccept(const ATMPArgs &package_args) {
            return ATMPArgs{
                /*config=*/package_args.m_config,
                /*accept_time=*/package_args.m_accept_time,
                /*bypass_limits=*/false,
                /*coins_to_uncache=*/package_args.m_coins_to_uncache,
                /*test_accept=*/package_args.m_test_accept,
                /*height_override=*/package_args.m_heightOverride,
                // do not LimitMempoolSize in Finalize()
                /*package_submission=*/true,
                // only 1 transaction
                /*package_feerates=*/false,
            };
        }
 
    private:
        // Private ctor to avoid exposing details to clients and allowing the
        // possibility of mixing up the order of the arguments. Use static
        // functions above instead.
        ATMPArgs(const Config &config, int64_t accept_time, bool bypass_limits,
                 std::vector<COutPoint> &coins_to_uncache, bool test_accept,
                 unsigned int height_override, bool package_submission,
                 bool package_feerates)
            : m_config{config}, m_accept_time{accept_time},
              m_bypass_limits{bypass_limits},
              m_coins_to_uncache{coins_to_uncache}, m_test_accept{test_accept},
              m_heightOverride{height_override},
              m_package_submission{package_submission},
              m_package_feerates(package_feerates) {}
    };
 
    // Single transaction acceptance
    MempoolAcceptResult AcceptSingleTransaction(const CTransactionRef &ptx,
                                                ATMPArgs &args)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
    PackageMempoolAcceptResult
    AcceptMultipleTransactions(const std::vector<CTransactionRef> &txns,
                               ATMPArgs &args)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
    PackageMempoolAcceptResult
    AcceptSubPackage(const std::vector<CTransactionRef> &subpackage,
                     ATMPArgs &args)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs);
 
    PackageMempoolAcceptResult AcceptPackage(const Package &package,
                                             ATMPArgs &args)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
private:
    // All the intermediate state that gets passed between the various levels
    // of checking a given transaction.
    struct Workspace {
        Workspace(const CTransactionRef &ptx,
                  const uint32_t next_block_script_verify_flags)
            : m_ptx(ptx),
              m_next_block_script_verify_flags(next_block_script_verify_flags) {
        }
        std::unique_ptr<CTxMemPoolEntry> m_entry;
 
        int64_t m_vsize;
        Amount m_base_fees;
 
        Amount m_modified_fees;
 
        CFeeRate m_package_feerate{Amount::zero()};
 
        const CTransactionRef &m_ptx;
        TxValidationState m_state;
        PrecomputedTransactionData m_precomputed_txdata;
 
        // ABC specific flags that are used in both PreChecks and
        // ConsensusScriptChecks
        const uint32_t m_next_block_script_verify_flags;
        int m_sig_checks_standard;
    };
 
    // Run the policy checks on a given transaction, excluding any script
    // checks. Looks up inputs, calculates feerate, considers replacement,
    // evaluates package limits, etc. As this function can be invoked for "free"
    // by a peer, only tests that are fast should be done here (to avoid CPU
    // DoS).
    bool PreChecks(ATMPArgs &args, Workspace &ws)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs);
 
    // Re-run the script checks, using consensus flags, and try to cache the
    // result in the scriptcache. This should be done after
    // PolicyScriptChecks(). This requires that all inputs either be in our
    // utxo set or in the mempool.
    bool ConsensusScriptChecks(const ATMPArgs &args, Workspace &ws)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs);
 
    // Try to add the transaction to the mempool, removing any conflicts first.
    // Returns true if the transaction is in the mempool after any size
    // limiting is performed, false otherwise.
    bool Finalize(const ATMPArgs &args, Workspace &ws)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs);
 
    // Submit all transactions to the mempool and call ConsensusScriptChecks to
    // add to the script cache - should only be called after successful
    // validation of all transactions in the package.
    // Does not call LimitMempoolSize(), so mempool max_size_bytes may be
    // temporarily exceeded.
    bool SubmitPackage(const ATMPArgs &args, std::vector<Workspace> &workspaces,
                       PackageValidationState &package_state,
                       std::map<TxId, MempoolAcceptResult> &results)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs);
 
    // Compare a package's feerate against minimum allowed.
    bool CheckFeeRate(size_t package_size, size_t package_vsize,
                      Amount package_fee, TxValidationState &state)
        EXCLUSIVE_LOCKS_REQUIRED(::cs_main, m_pool.cs) {
        AssertLockHeld(::cs_main);
        AssertLockHeld(m_pool.cs);
 
        const Amount mempoolRejectFee =
            m_pool.GetMinFee().GetFee(package_vsize);
 
        if (mempoolRejectFee > Amount::zero() &&
            package_fee < mempoolRejectFee) {
            return state.Invalid(
                TxValidationResult::TX_PACKAGE_RECONSIDERABLE,
                "mempool min fee not met",
                strprintf("%d < %d", package_fee, mempoolRejectFee));
        }
 
        // Do not change this to use virtualsize without coordinating a network
        // policy upgrade.
        if (package_fee < m_pool.m_min_relay_feerate.GetFee(package_size)) {
            return state.Invalid(
                TxValidationResult::TX_PACKAGE_RECONSIDERABLE,
                "min relay fee not met",
                strprintf("%d < %d", package_fee,
                          m_pool.m_min_relay_feerate.GetFee(package_size)));
        }
 
        return true;
    }
 
private:
    CTxMemPool &m_pool;
    CCoinsViewCache m_view;
    CCoinsViewMemPool m_viewmempool;
    CCoinsView m_dummy;
 
    Chainstate &m_active_chainstate;
};
 
bool MemPoolAccept::PreChecks(ATMPArgs &args, Workspace &ws) {
    AssertLockHeld(cs_main);
    AssertLockHeld(m_pool.cs);
    const CTransactionRef &ptx = ws.m_ptx;
    const CTransaction &tx = *ws.m_ptx;
    const TxId &txid = ws.m_ptx->GetId();
 
    // Copy/alias what we need out of args
    const int64_t nAcceptTime = args.m_accept_time;
    const bool bypass_limits = args.m_bypass_limits;
    std::vector<COutPoint> &coins_to_uncache = args.m_coins_to_uncache;
    const unsigned int heightOverride = args.m_heightOverride;
 
    // Alias what we need out of ws
    TxValidationState &state = ws.m_state;
    // Coinbase is only valid in a block, not as a loose transaction.
    if (!CheckRegularTransaction(tx, state)) {
        // state filled in by CheckRegularTransaction.
        return false;
    }
 
    // Rather not work on nonstandard transactions (unless -testnet)
    std::string reason;
    if (m_pool.m_require_standard &&
        !IsStandardTx(tx, m_pool.m_max_datacarrier_bytes,
                      m_pool.m_permit_bare_multisig,
                      m_pool.m_dust_relay_feerate, reason)) {
        return state.Invalid(TxValidationResult::TX_NOT_STANDARD, reason);
    }
 
    // Only accept nLockTime-using transactions that can be mined in the next
    // block; we don't want our mempool filled up with transactions that can't
    // be mined yet.
    TxValidationState ctxState;
    if (!ContextualCheckTransactionForCurrentBlock(
            *Assert(m_active_chainstate.m_chain.Tip()),
            args.m_config.GetChainParams().GetConsensus(), tx, ctxState)) {
        // We copy the state from a dummy to ensure we don't increase the
        // ban score of peer for transaction that could be valid in the future.
        return state.Invalid(TxValidationResult::TX_PREMATURE_SPEND,
                             ctxState.GetRejectReason(),
                             ctxState.GetDebugMessage());
    }
 
    // Is it already in the memory pool?
    if (m_pool.exists(txid)) {
        return state.Invalid(TxValidationResult::TX_DUPLICATE,
                             "txn-already-in-mempool");
    }
 
    // Check for conflicts with in-memory transactions
    for (const CTxIn &txin : tx.vin) {
        if (const auto ptxConflicting = m_pool.GetConflictTx(txin.prevout)) {
            if (m_pool.isAvalancheFinalized(ptxConflicting->GetId())) {
                return state.Invalid(TxValidationResult::TX_CONFLICT,
                                     "finalized-tx-conflict");
            }
 
            return state.Invalid(
                TxValidationResult::TX_AVALANCHE_RECONSIDERABLE,
                "txn-mempool-conflict");
        }
    }
 
    m_view.SetBackend(m_viewmempool);
 
    const CCoinsViewCache &coins_cache = m_active_chainstate.CoinsTip();
    // Do all inputs exist?
    for (const CTxIn &txin : tx.vin) {
        if (!coins_cache.HaveCoinInCache(txin.prevout)) {
            coins_to_uncache.push_back(txin.prevout);
        }
 
        // Note: this call may add txin.prevout to the coins cache
        // (coins_cache.cacheCoins) by way of FetchCoin(). It should be
        // removed later (via coins_to_uncache) if this tx turns out to be
        // invalid.
        if (!m_view.HaveCoin(txin.prevout)) {
            // Are inputs missing because we already have the tx?
            for (size_t out = 0; out < tx.vout.size(); out++) {
                // Optimistically just do efficient check of cache for
                // outputs.
                if (coins_cache.HaveCoinInCache(COutPoint(txid, out))) {
                    return state.Invalid(TxValidationResult::TX_DUPLICATE,
                                         "txn-already-known");
                }
            }
 
            // Otherwise assume this might be an orphan tx for which we just
            // haven't seen parents yet.
            return state.Invalid(TxValidationResult::TX_MISSING_INPUTS,
                                 "bad-txns-inputs-missingorspent");
        }
    }
 
    // Are the actual inputs available?
    if (!m_view.HaveInputs(tx)) {
        return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY,
                             "bad-txns-inputs-spent");
    }
 
    // Bring the best block into scope.
    m_view.GetBestBlock();
 
    // we have all inputs cached now, so switch back to dummy (to protect
    // against bugs where we pull more inputs from disk that miss being
    // added to coins_to_uncache)
    m_view.SetBackend(m_dummy);
 
    assert(m_active_chainstate.m_blockman.LookupBlockIndex(
               m_view.GetBestBlock()) == m_active_chainstate.m_chain.Tip());
 
    // Only accept BIP68 sequence locked transactions that can be mined in
    // the next block; we don't want our mempool filled up with transactions
    // that can't be mined yet.
    // Pass in m_view which has all of the relevant inputs cached. Note that,
    // since m_view's backend was removed, it no longer pulls coins from the
    // mempool.
    const std::optional<LockPoints> lock_points{CalculateLockPointsAtTip(
        m_active_chainstate.m_chain.Tip(), m_view, tx)};
    if (!lock_points.has_value() ||
        !CheckSequenceLocksAtTip(m_active_chainstate.m_chain.Tip(),
                                 *lock_points)) {
        return state.Invalid(TxValidationResult::TX_PREMATURE_SPEND,
                             "non-BIP68-final");
    }
 
    // The mempool holds txs for the next block, so pass height+1 to
    // CheckTxInputs
    if (!Consensus::CheckTxInputs(tx, state, m_view,
                                  m_active_chainstate.m_chain.Height() + 1,
                                  ws.m_base_fees)) {
        // state filled in by CheckTxInputs
        return false;
    }
 
    // Check for non-standard pay-to-script-hash in inputs
    if (m_pool.m_require_standard &&
        !AreInputsStandard(tx, m_view, ws.m_next_block_script_verify_flags)) {
        return state.Invalid(TxValidationResult::TX_INPUTS_NOT_STANDARD,
                             "bad-txns-nonstandard-inputs");
    }
 
    // ws.m_modified_fess includes any fee deltas from PrioritiseTransaction
    ws.m_modified_fees = ws.m_base_fees;
    m_pool.ApplyDelta(txid, ws.m_modified_fees);
 
    unsigned int nSize = tx.GetTotalSize();
 
    // Validate input scripts against standard script flags.
    const uint32_t scriptVerifyFlags =
        ws.m_next_block_script_verify_flags | STANDARD_SCRIPT_VERIFY_FLAGS;
    ws.m_precomputed_txdata = PrecomputedTransactionData{tx};
    if (!CheckInputScripts(tx, state, m_view, scriptVerifyFlags, true, false,
                           ws.m_precomputed_txdata, ws.m_sig_checks_standard)) {
        // State filled in by CheckInputScripts
        return false;
    }
 
    ws.m_entry = std::make_unique<CTxMemPoolEntry>(
        ptx, ws.m_base_fees, nAcceptTime,
        heightOverride ? heightOverride : m_active_chainstate.m_chain.Height(),
        ws.m_sig_checks_standard, lock_points.value());
 
    ws.m_vsize = ws.m_entry->GetTxVirtualSize();
 
    // No individual transactions are allowed below the min relay feerate except
    // from disconnected blocks. This requirement, unlike CheckFeeRate, cannot
    // be bypassed using m_package_feerates because, while a tx could be package
    // CPFP'd when entering the mempool, we do not have a DoS-resistant method
    // of ensuring the tx remains bumped. For example, the fee-bumping child
    // could disappear due to a replacement.
    if (!bypass_limits &&
        ws.m_modified_fees <
            m_pool.m_min_relay_feerate.GetFee(ws.m_ptx->GetTotalSize())) {
        // Even though this is a fee-related failure, this result is
        // TX_MEMPOOL_POLICY, not TX_PACKAGE_RECONSIDERABLE, because it cannot
        // be bypassed using package validation.
        return state.Invalid(
            TxValidationResult::TX_MEMPOOL_POLICY, "min relay fee not met",
            strprintf("%d < %d", ws.m_modified_fees,
                      m_pool.m_min_relay_feerate.GetFee(nSize)));
    }
    // No individual transactions are allowed below the mempool min feerate
    // except from disconnected blocks and transactions in a package. Package
    // transactions will be checked using package feerate later.
    if (!bypass_limits && !args.m_package_feerates &&
        !CheckFeeRate(nSize, ws.m_vsize, ws.m_modified_fees, state)) {
        return false;
    }
 
    return true;
}
 
bool MemPoolAccept::ConsensusScriptChecks(const ATMPArgs &args, Workspace &ws) {
    AssertLockHeld(cs_main);
    AssertLockHeld(m_pool.cs);
    const CTransaction &tx = *ws.m_ptx;
    const TxId &txid = tx.GetId();
    TxValidationState &state = ws.m_state;
 
    // Check again against the next block's script verification flags
    // to cache our script execution flags.
    //
    // This is also useful in case of bugs in the standard flags that cause
    // transactions to pass as valid when they're actually invalid. For
    // instance the STRICTENC flag was incorrectly allowing certain CHECKSIG
    // NOT scripts to pass, even though they were invalid.
    //
    // There is a similar check in CreateNewBlock() to prevent creating
    // invalid blocks (using TestBlockValidity), however allowing such
    // transactions into the mempool can be exploited as a DoS attack.
    int nSigChecksConsensus;
    if (!CheckInputsFromMempoolAndCache(
            tx, state, m_view, m_pool, ws.m_next_block_script_verify_flags,
            ws.m_precomputed_txdata, nSigChecksConsensus,
            m_active_chainstate.CoinsTip())) {
        // This can occur under some circumstances, if the node receives an
        // unrequested tx which is invalid due to new consensus rules not
        // being activated yet (during IBD).
        LogPrintf("BUG! PLEASE REPORT THIS! CheckInputScripts failed against "
                  "latest-block but not STANDARD flags %s, %s\n",
                  txid.ToString(), state.ToString());
        return Assume(false);
    }
 
    if (ws.m_sig_checks_standard != nSigChecksConsensus) {
        // We can't accept this transaction as we've used the standard count
        // for the mempool/mining, but the consensus count will be enforced
        // in validation (we don't want to produce bad block templates).
        return error(
            "%s: BUG! PLEASE REPORT THIS! SigChecks count differed between "
            "standard and consensus flags in %s",
            __func__, txid.ToString());
    }
    return true;
}
 
// Get the coins spent by ptx from the coins_view. Assumes coins are present.
static std::vector<Coin> getSpentCoins(const CTransactionRef &ptx,
                                       const CCoinsViewCache &coins_view) {
    std::vector<Coin> spent_coins;
    spent_coins.reserve(ptx->vin.size());
    for (const CTxIn &input : ptx->vin) {
        Coin coin;
        const bool coinFound = coins_view.GetCoin(input.prevout, coin);
        Assume(coinFound);
        spent_coins.push_back(std::move(coin));
    }
    return spent_coins;
}
 
bool MemPoolAccept::Finalize(const ATMPArgs &args, Workspace &ws) {
    AssertLockHeld(cs_main);
    AssertLockHeld(m_pool.cs);
    const TxId &txid = ws.m_ptx->GetId();
    TxValidationState &state = ws.m_state;
    const bool bypass_limits = args.m_bypass_limits;
 
    // Store transaction in memory
    CTxMemPoolEntry *pentry = ws.m_entry.release();
    auto entry = CTxMemPoolEntryRef::acquire(pentry);
    m_pool.addUnchecked(entry);
 
    GetMainSignals().TransactionAddedToMempool(
        ws.m_ptx,
        std::make_shared<const std::vector<Coin>>(
            getSpentCoins(ws.m_ptx, m_view)),
        m_pool.GetAndIncrementSequence());
 
    // Trim mempool and check if tx was trimmed.
    // If we are validating a package, don't trim here because we could evict a
    // previous transaction in the package. LimitMempoolSize() should be called
    // at the very end to make sure the mempool is still within limits and
    // package submission happens atomically.
    if (!args.m_package_submission && !bypass_limits) {
        m_pool.LimitSize(m_active_chainstate.CoinsTip());
        if (!m_pool.exists(txid)) {
            // The tx no longer meets our (new) mempool minimum feerate but
            // could be reconsidered in a package.
            return state.Invalid(TxValidationResult::TX_PACKAGE_RECONSIDERABLE,
                                 "mempool full");
        }
    }
    return true;
}
 
bool MemPoolAccept::SubmitPackage(
    const ATMPArgs &args, std::vector<Workspace> &workspaces,
    PackageValidationState &package_state,
    std::map<TxId, MempoolAcceptResult> &results) {
    AssertLockHeld(cs_main);
    AssertLockHeld(m_pool.cs);
    // Sanity check: none of the transactions should be in the mempool.
    assert(std::all_of(
        workspaces.cbegin(), workspaces.cend(),
        [this](const auto &ws) { return !m_pool.exists(ws.m_ptx->GetId()); }));
 
    bool all_submitted = true;
    // ConsensusScriptChecks adds to the script cache and is therefore
    // consensus-critical; CheckInputsFromMempoolAndCache asserts that
    // transactions only spend coins available from the mempool or UTXO set.
    // Submit each transaction to the mempool immediately after calling
    // ConsensusScriptChecks to make the outputs available for subsequent
    // transactions.
    for (Workspace &ws : workspaces) {
        if (!ConsensusScriptChecks(args, ws)) {
            results.emplace(ws.m_ptx->GetId(),
                            MempoolAcceptResult::Failure(ws.m_state));
            // Since PreChecks() passed, this should never fail.
            all_submitted = false;
            package_state.Invalid(
                PackageValidationResult::PCKG_MEMPOOL_ERROR,
                strprintf("BUG! PolicyScriptChecks succeeded but "
                          "ConsensusScriptChecks failed: %s",
                          ws.m_ptx->GetId().ToString()));
        }
 
        // If we call LimitMempoolSize() for each individual Finalize(), the
        // mempool will not take the transaction's descendant feerate into
        // account because it hasn't seen them yet. Also, we risk evicting a
        // transaction that a subsequent package transaction depends on.
        // Instead, allow the mempool to temporarily bypass limits, the maximum
        // package size) while submitting transactions individually and then
        // trim at the very end.
        if (!Finalize(args, ws)) {
            results.emplace(ws.m_ptx->GetId(),
                            MempoolAcceptResult::Failure(ws.m_state));
            // Since LimitMempoolSize() won't be called, this should never fail.
            all_submitted = false;
            package_state.Invalid(PackageValidationResult::PCKG_MEMPOOL_ERROR,
                                  strprintf("BUG! Adding to mempool failed: %s",
                                            ws.m_ptx->GetId().ToString()));
        }
    }
 
    // It may or may not be the case that all the transactions made it into the
    // mempool. Regardless, make sure we haven't exceeded max mempool size.
    m_pool.LimitSize(m_active_chainstate.CoinsTip());
 
    std::vector<TxId> all_package_txids;
    all_package_txids.reserve(workspaces.size());
    std::transform(workspaces.cbegin(), workspaces.cend(),
                   std::back_inserter(all_package_txids),
                   [](const auto &ws) { return ws.m_ptx->GetId(); });
 
    // Add successful results. The returned results may change later if
    // LimitMempoolSize() evicts them.
    for (Workspace &ws : workspaces) {
        const auto effective_feerate =
            args.m_package_feerates
                ? ws.m_package_feerate
                : CFeeRate{ws.m_modified_fees,
                           static_cast<uint32_t>(ws.m_vsize)};
        const auto effective_feerate_txids =
            args.m_package_feerates ? all_package_txids
                                    : std::vector<TxId>({ws.m_ptx->GetId()});
        results.emplace(ws.m_ptx->GetId(),
                        MempoolAcceptResult::Success(ws.m_vsize, ws.m_base_fees,
                                                     effective_feerate,
                                                     effective_feerate_txids));
    }
    return all_submitted;
}
 
MempoolAcceptResult
MemPoolAccept::AcceptSingleTransaction(const CTransactionRef &ptx,
                                       ATMPArgs &args) {
    AssertLockHeld(cs_main);
    // mempool "read lock" (held through
    // GetMainSignals().TransactionAddedToMempool())
    LOCK(m_pool.cs);
 
    const CBlockIndex *tip = m_active_chainstate.m_chain.Tip();
 
    Workspace ws(ptx,
                 GetNextBlockScriptFlags(tip, m_active_chainstate.m_chainman));
 
    const std::vector<TxId> single_txid{ws.m_ptx->GetId()};
 
    // Perform the inexpensive checks first and avoid hashing and signature
    // verification unless those checks pass, to mitigate CPU exhaustion
    // denial-of-service attacks.
    if (!PreChecks(args, ws)) {
        if (ws.m_state.GetResult() ==
            TxValidationResult::TX_PACKAGE_RECONSIDERABLE) {
            // Failed for fee reasons. Provide the effective feerate and which
            // tx was included.
            return MempoolAcceptResult::FeeFailure(
                ws.m_state, CFeeRate(ws.m_modified_fees, ws.m_vsize),
                single_txid);
        }
        return MempoolAcceptResult::Failure(ws.m_state);
    }
 
    if (!ConsensusScriptChecks(args, ws)) {
        return MempoolAcceptResult::Failure(ws.m_state);
    }
 
    const TxId txid = ptx->GetId();
 
    // Mempool sanity check -- in our new mempool no tx can be added if its
    // outputs are already spent in the mempool (that is, no children before
    // parents allowed; the mempool must be consistent at all times).
    //
    // This means that on reorg, the disconnectpool *must* always import
    // the existing mempool tx's, clear the mempool, and then re-add
    // remaining tx's in topological order via this function. Our new mempool
    // has fast adds, so this is ok.
    if (auto it = m_pool.mapNextTx.lower_bound(COutPoint{txid, 0});
        it != m_pool.mapNextTx.end() && it->first->GetTxId() == txid) {
        LogPrintf("%s: BUG! PLEASE REPORT THIS! Attempt to add txid %s, but "
                  "its outputs are already spent in the "
                  "mempool\n",
                  __func__, txid.ToString());
        ws.m_state.Invalid(TxValidationResult::TX_CHILD_BEFORE_PARENT,
                           "txn-child-before-parent");
        return MempoolAcceptResult::Failure(ws.m_state);
    }
 
    const CFeeRate effective_feerate{ws.m_modified_fees,
                                     static_cast<uint32_t>(ws.m_vsize)};
    // Tx was accepted, but not added
    if (args.m_test_accept) {
        return MempoolAcceptResult::Success(ws.m_vsize, ws.m_base_fees,
                                            effective_feerate, single_txid);
    }
 
    if (!Finalize(args, ws)) {
        // The only possible failure reason is fee-related (mempool full).
        // Failed for fee reasons. Provide the effective feerate and which txns
        // were included.
        Assume(ws.m_state.GetResult() ==
               TxValidationResult::TX_PACKAGE_RECONSIDERABLE);
        return MempoolAcceptResult::FeeFailure(
            ws.m_state, CFeeRate(ws.m_modified_fees, ws.m_vsize), single_txid);
    }
 
    return MempoolAcceptResult::Success(ws.m_vsize, ws.m_base_fees,
                                        effective_feerate, single_txid);
}
 
PackageMempoolAcceptResult MemPoolAccept::AcceptMultipleTransactions(
    const std::vector<CTransactionRef> &txns, ATMPArgs &args) {
    AssertLockHeld(cs_main);
 
    // These context-free package limits can be done before taking the mempool
    // lock.
    PackageValidationState package_state;
    if (!CheckPackage(txns, package_state)) {
        return PackageMempoolAcceptResult(package_state, {});
    }
 
    std::vector<Workspace> workspaces{};
    workspaces.reserve(txns.size());
    std::transform(
        txns.cbegin(), txns.cend(), std::back_inserter(workspaces),
        [this](const auto &tx) {
            return Workspace(
                tx, GetNextBlockScriptFlags(m_active_chainstate.m_chain.Tip(),
                                            m_active_chainstate.m_chainman));
        });
    std::map<TxId, MempoolAcceptResult> results;
 
    LOCK(m_pool.cs);
 
    // Do all PreChecks first and fail fast to avoid running expensive script
    // checks when unnecessary.
    std::vector<TxId> valid_txids;
    for (Workspace &ws : workspaces) {
        if (!PreChecks(args, ws)) {
            package_state.Invalid(PackageValidationResult::PCKG_TX,
                                  "transaction failed");
            // Exit early to avoid doing pointless work. Update the failed tx
            // result; the rest are unfinished.
            results.emplace(ws.m_ptx->GetId(),
                            MempoolAcceptResult::Failure(ws.m_state));
            return PackageMempoolAcceptResult(package_state,
                                              std::move(results));
        }
        // Make the coins created by this transaction available for subsequent
        // transactions in the package to spend.
        m_viewmempool.PackageAddTransaction(ws.m_ptx);
        valid_txids.push_back(ws.m_ptx->GetId());
    }
 
    // Transactions must meet two minimum feerates: the mempool minimum fee and
    // min relay fee. For transactions consisting of exactly one child and its
    // parents, it suffices to use the package feerate
    // (total modified fees / total size or vsize) to check this requirement.
    // Note that this is an aggregate feerate; this function has not checked
    // that there are transactions too low feerate to pay for themselves, or
    // that the child transactions are higher feerate than their parents. Using
    // aggregate feerate may allow "parents pay for child" behavior and permit
    // a child that is below mempool minimum feerate. To avoid these behaviors,
    // callers of AcceptMultipleTransactions need to restrict txns topology
    // (e.g. to ancestor sets) and check the feerates of individuals and
    // subsets.
    const auto m_total_size = std::accumulate(
        workspaces.cbegin(), workspaces.cend(), int64_t{0},
        [](int64_t sum, auto &ws) { return sum + ws.m_ptx->GetTotalSize(); });
    const auto m_total_vsize =
        std::accumulate(workspaces.cbegin(), workspaces.cend(), int64_t{0},
                        [](int64_t sum, auto &ws) { return sum + ws.m_vsize; });
    const auto m_total_modified_fees = std::accumulate(
        workspaces.cbegin(), workspaces.cend(), Amount::zero(),
        [](Amount sum, auto &ws) { return sum + ws.m_modified_fees; });
    const CFeeRate package_feerate(m_total_modified_fees, m_total_vsize);
    std::vector<TxId> all_package_txids;
    all_package_txids.reserve(workspaces.size());
    std::transform(workspaces.cbegin(), workspaces.cend(),
                   std::back_inserter(all_package_txids),
                   [](const auto &ws) { return ws.m_ptx->GetId(); });
    TxValidationState placeholder_state;
    if (args.m_package_feerates &&
        !CheckFeeRate(m_total_size, m_total_vsize, m_total_modified_fees,
                      placeholder_state)) {
        package_state.Invalid(PackageValidationResult::PCKG_TX,
                              "transaction failed");
        return PackageMempoolAcceptResult(
            package_state, {{workspaces.back().m_ptx->GetId(),
                             MempoolAcceptResult::FeeFailure(
                                 placeholder_state,
                                 CFeeRate(m_total_modified_fees, m_total_vsize),
                                 all_package_txids)}});
    }
 
    for (Workspace &ws : workspaces) {
        ws.m_package_feerate = package_feerate;
        const TxId &ws_txid = ws.m_ptx->GetId();
        if (args.m_test_accept &&
            std::find(valid_txids.begin(), valid_txids.end(), ws_txid) !=
                valid_txids.end()) {
            const auto effective_feerate =
                args.m_package_feerates
                    ? ws.m_package_feerate
                    : CFeeRate{ws.m_modified_fees,
                               static_cast<uint32_t>(ws.m_vsize)};
            const auto effective_feerate_txids =
                args.m_package_feerates ? all_package_txids
                                        : std::vector<TxId>{ws.m_ptx->GetId()};
            // When test_accept=true, transactions that pass PreChecks
            // are valid because there are no further mempool checks (passing
            // PreChecks implies passing ConsensusScriptChecks).
            results.emplace(ws_txid,
                            MempoolAcceptResult::Success(
                                ws.m_vsize, ws.m_base_fees, effective_feerate,
                                effective_feerate_txids));
        }
    }
 
    if (args.m_test_accept) {
        return PackageMempoolAcceptResult(package_state, std::move(results));
    }
 
    if (!SubmitPackage(args, workspaces, package_state, results)) {
        // PackageValidationState filled in by SubmitPackage().
        return PackageMempoolAcceptResult(package_state, std::move(results));
    }
 
    return PackageMempoolAcceptResult(package_state, std::move(results));
}
 
PackageMempoolAcceptResult
MemPoolAccept::AcceptSubPackage(const std::vector<CTransactionRef> &subpackage,
                                ATMPArgs &args) {
    AssertLockHeld(::cs_main);
    AssertLockHeld(m_pool.cs);
 
    auto result = [&]() EXCLUSIVE_LOCKS_REQUIRED(::cs_main, m_pool.cs) {
        if (subpackage.size() > 1) {
            return AcceptMultipleTransactions(subpackage, args);
        }
        const auto &tx = subpackage.front();
        ATMPArgs single_args = ATMPArgs::SingleInPackageAccept(args);
        const auto single_res = AcceptSingleTransaction(tx, single_args);
        PackageValidationState package_state_wrapped;
        if (single_res.m_result_type !=
            MempoolAcceptResult::ResultType::VALID) {
            package_state_wrapped.Invalid(PackageValidationResult::PCKG_TX,
                                          "transaction failed");
        }
        return PackageMempoolAcceptResult(package_state_wrapped,
                                          {{tx->GetId(), single_res}});
    }();
 
    // Clean up m_view and m_viewmempool so that other subpackage evaluations
    // don't have access to coins they shouldn't. Keep some coins in order to
    // minimize re-fetching coins from the UTXO set.
    //
    // There are 3 kinds of coins in m_view:
    // (1) Temporary coins from the transactions in subpackage, constructed by
    //     m_viewmempool.
    // (2) Mempool coins from transactions in the mempool, constructed by
    //     m_viewmempool.
    // (3) Confirmed coins fetched from our current UTXO set.
    //
    // (1) Temporary coins need to be removed, regardless of whether the
    // transaction was submitted. If the transaction was submitted to the
    // mempool, m_viewmempool will be able to fetch them from there. If it
    // wasn't submitted to mempool, it is incorrect to keep them - future calls
    // may try to spend those coins that don't actually exist.
    // (2) Mempool coins also need to be removed. If the mempool contents have
    // changed as a result of submitting or replacing transactions, coins
    // previously fetched from mempool may now be spent or nonexistent. Those
    // coins need to be deleted from m_view.
    // (3) Confirmed coins don't need to be removed. The chainstate has not
    // changed (we are holding cs_main and no blocks have been processed) so the
    // confirmed tx cannot disappear like a mempool tx can. The coin may now be
    // spent after we submitted a tx to mempool, but we have already checked
    // that the package does not have 2 transactions spending the same coin.
    // Keeping them in m_view is an optimization to not re-fetch confirmed coins
    // if we later look up inputs for this transaction again.
    for (const auto &outpoint : m_viewmempool.GetNonBaseCoins()) {
        // In addition to resetting m_viewmempool, we also need to manually
        // delete these coins from m_view because it caches copies of the coins
        // it fetched from m_viewmempool previously.
        m_view.Uncache(outpoint);
    }
    // This deletes the temporary and mempool coins.
    m_viewmempool.Reset();
    return result;
}
 
PackageMempoolAcceptResult MemPoolAccept::AcceptPackage(const Package &package,
                                                        ATMPArgs &args) {
    AssertLockHeld(cs_main);
    // Used if returning a PackageMempoolAcceptResult directly from this
    // function.
    PackageValidationState package_state_quit_early;
 
    // Check that the package is well-formed. If it isn't, we won't try to
    // validate any of the transactions and thus won't return any
    // MempoolAcceptResults, just a package-wide error.
 
    // Context-free package checks.
    if (!CheckPackage(package, package_state_quit_early)) {
        return PackageMempoolAcceptResult(package_state_quit_early, {});
    }
 
    // All transactions in the package must be a parent of the last transaction.
    // This is just an opportunity for us to fail fast on a context-free check
    // without taking the mempool lock.
    if (!IsChildWithParents(package)) {
        package_state_quit_early.Invalid(PackageValidationResult::PCKG_POLICY,
                                         "package-not-child-with-parents");
        return PackageMempoolAcceptResult(package_state_quit_early, {});
    }
 
    // IsChildWithParents() guarantees the package is > 1 transactions.
    assert(package.size() > 1);
    // The package must be 1 child with all of its unconfirmed parents. The
    // package is expected to be sorted, so the last transaction is the child.
    const auto &child = package.back();
    std::unordered_set<TxId, SaltedTxIdHasher> unconfirmed_parent_txids;
    std::transform(
        package.cbegin(), package.cend() - 1,
        std::inserter(unconfirmed_parent_txids, unconfirmed_parent_txids.end()),
        [](const auto &tx) { return tx->GetId(); });
 
    // All child inputs must refer to a preceding package transaction or a
    // confirmed UTXO. The only way to verify this is to look up the child's
    // inputs in our current coins view (not including mempool), and enforce
    // that all parents not present in the package be available at chain tip.
    // Since this check can bring new coins into the coins cache, keep track of
    // these coins and uncache them if we don't end up submitting this package
    // to the mempool.
    const CCoinsViewCache &coins_tip_cache = m_active_chainstate.CoinsTip();
    for (const auto &input : child->vin) {
        if (!coins_tip_cache.HaveCoinInCache(input.prevout)) {
            args.m_coins_to_uncache.push_back(input.prevout);
        }
    }
    // Using the MemPoolAccept m_view cache allows us to look up these same
    // coins faster later. This should be connecting directly to CoinsTip, not
    // to m_viewmempool, because we specifically require inputs to be confirmed
    // if they aren't in the package.
    m_view.SetBackend(m_active_chainstate.CoinsTip());
    const auto package_or_confirmed = [this, &unconfirmed_parent_txids](
                                          const auto &input) {
        return unconfirmed_parent_txids.count(input.prevout.GetTxId()) > 0 ||
               m_view.HaveCoin(input.prevout);
    };
    if (!std::all_of(child->vin.cbegin(), child->vin.cend(),
                     package_or_confirmed)) {
        package_state_quit_early.Invalid(
            PackageValidationResult::PCKG_POLICY,
            "package-not-child-with-unconfirmed-parents");
        return PackageMempoolAcceptResult(package_state_quit_early, {});
    }
    // Protect against bugs where we pull more inputs from disk that miss being
    // added to coins_to_uncache. The backend will be connected again when
    // needed in PreChecks.
    m_view.SetBackend(m_dummy);
 
    LOCK(m_pool.cs);
    // Stores results from which we will create the returned
    // PackageMempoolAcceptResult. A result may be changed if a mempool
    // transaction is evicted later due to LimitMempoolSize().
    std::map<TxId, MempoolAcceptResult> results_final;
    // Results from individual validation which will be returned if no other
    // result is available for this transaction. "Nonfinal" because if a
    // transaction fails by itself but succeeds later (i.e. when evaluated with
    // a fee-bumping child), the result in this map may be discarded.
    std::map<TxId, MempoolAcceptResult> individual_results_nonfinal;
    bool quit_early{false};
    std::vector<CTransactionRef> txns_package_eval;
    for (const auto &tx : package) {
        const auto &txid = tx->GetId();
        // An already confirmed tx is treated as one not in mempool, because all
        // we know is that the inputs aren't available.
        if (m_pool.exists(txid)) {
            // Exact transaction already exists in the mempool.
            // Node operators are free to set their mempool policies however
            // they please, nodes may receive transactions in different orders,
            // and malicious counterparties may try to take advantage of policy
            // differences to pin or delay propagation of transactions. As such,
            // it's possible for some package transaction(s) to already be in
            // the mempool, and we don't want to reject the entire package in
            // that case (as that could be a censorship vector). De-duplicate
            // the transactions that are already in the mempool, and only call
            // AcceptMultipleTransactions() with the new transactions. This
            // ensures we don't double-count transaction counts and sizes when
            // checking ancestor/descendant limits, or double-count transaction
            // fees for fee-related policy.
            auto iter = m_pool.GetIter(txid);
            assert(iter != std::nullopt);
            results_final.emplace(txid, MempoolAcceptResult::MempoolTx(
                                            (*iter.value())->GetTxSize(),
                                            (*iter.value())->GetFee()));
        } else {
            // Transaction does not already exist in the mempool.
            // Try submitting the transaction on its own.
            const auto single_package_res = AcceptSubPackage({tx}, args);
            const auto &single_res = single_package_res.m_tx_results.at(txid);
            if (single_res.m_result_type ==
                MempoolAcceptResult::ResultType::VALID) {
                // The transaction succeeded on its own and is now in the
                // mempool. Don't include it in package validation, because its
                // fees should only be "used" once.
                assert(m_pool.exists(txid));
                results_final.emplace(txid, single_res);
            } else if (single_res.m_state.GetResult() !=
                           TxValidationResult::TX_PACKAGE_RECONSIDERABLE &&
                       single_res.m_state.GetResult() !=
                           TxValidationResult::TX_MISSING_INPUTS) {
                // Package validation policy only differs from individual policy
                // in its evaluation of feerate. For example, if a transaction
                // fails here due to violation of a consensus rule, the result
                // will not change when it is submitted as part of a package. To
                // minimize the amount of repeated work, unless the transaction
                // fails due to feerate or missing inputs (its parent is a
                // previous transaction in the package that failed due to
                // feerate), don't run package validation. Note that this
                // decision might not make sense if different types of packages
                // are allowed in the future.  Continue individually validating
                // the rest of the transactions, because some of them may still
                // be valid.
                quit_early = true;
                package_state_quit_early.Invalid(
                    PackageValidationResult::PCKG_TX, "transaction failed");
                individual_results_nonfinal.emplace(txid, single_res);
            } else {
                individual_results_nonfinal.emplace(txid, single_res);
                txns_package_eval.push_back(tx);
            }
        }
    }
 
    auto multi_submission_result =
        quit_early || txns_package_eval.empty()
            ? PackageMempoolAcceptResult(package_state_quit_early, {})
            : AcceptSubPackage(txns_package_eval, args);
    PackageValidationState &package_state_final =
        multi_submission_result.m_state;
 
    // Make sure we haven't exceeded max mempool size.
    // Package transactions that were submitted to mempool or already in mempool
    // may be evicted.
    m_pool.LimitSize(m_active_chainstate.CoinsTip());
 
    for (const auto &tx : package) {
        const auto &txid = tx->GetId();
        if (multi_submission_result.m_tx_results.count(txid) > 0) {
            // We shouldn't have re-submitted if the tx result was already in
            // results_final.
            Assume(results_final.count(txid) == 0);
            // If it was submitted, check to see if the tx is still in the
            // mempool. It could have been evicted due to LimitMempoolSize()
            // above.
            const auto &txresult =
                multi_submission_result.m_tx_results.at(txid);
            if (txresult.m_result_type ==
                    MempoolAcceptResult::ResultType::VALID &&
                !m_pool.exists(txid)) {
                package_state_final.Invalid(PackageValidationResult::PCKG_TX,
                                            "transaction failed");
                TxValidationState mempool_full_state;
                mempool_full_state.Invalid(
                    TxValidationResult::TX_MEMPOOL_POLICY, "mempool full");
                results_final.emplace(
                    txid, MempoolAcceptResult::Failure(mempool_full_state));
            } else {
                results_final.emplace(txid, txresult);
            }
        } else if (const auto final_it{results_final.find(txid)};
                   final_it != results_final.end()) {
            // Already-in-mempool transaction. Check to see if it's still there,
            // as it could have been evicted when LimitMempoolSize() was called.
            Assume(final_it->second.m_result_type !=
                   MempoolAcceptResult::ResultType::INVALID);
            Assume(individual_results_nonfinal.count(txid) == 0);
            if (!m_pool.exists(tx->GetId())) {
                package_state_final.Invalid(PackageValidationResult::PCKG_TX,
                                            "transaction failed");
                TxValidationState mempool_full_state;
                mempool_full_state.Invalid(
                    TxValidationResult::TX_MEMPOOL_POLICY, "mempool full");
                // Replace the previous result.
                results_final.erase(txid);
                results_final.emplace(
                    txid, MempoolAcceptResult::Failure(mempool_full_state));
            }
        } else if (const auto non_final_it{
                       individual_results_nonfinal.find(txid)};
                   non_final_it != individual_results_nonfinal.end()) {
            Assume(non_final_it->second.m_result_type ==
                   MempoolAcceptResult::ResultType::INVALID);
            // Interesting result from previous processing.
            results_final.emplace(txid, non_final_it->second);
        }
    }
    Assume(results_final.size() == package.size());
    return PackageMempoolAcceptResult(package_state_final,
                                      std::move(results_final));
}
} // namespace
 
MempoolAcceptResult AcceptToMemoryPool(Chainstate &active_chainstate,
                                       const CTransactionRef &tx,
                                       int64_t accept_time, bool bypass_limits,
                                       bool test_accept,
                                       unsigned int heightOverride) {
    AssertLockHeld(::cs_main);
    assert(active_chainstate.GetMempool() != nullptr);
    CTxMemPool &pool{*active_chainstate.GetMempool()};
 
    std::vector<COutPoint> coins_to_uncache;
    auto args = MemPoolAccept::ATMPArgs::SingleAccept(
        active_chainstate.m_chainman.GetConfig(), accept_time, bypass_limits,
        coins_to_uncache, test_accept, heightOverride);
    const MempoolAcceptResult result = MemPoolAccept(pool, active_chainstate)
                                           .AcceptSingleTransaction(tx, args);
    if (result.m_result_type != MempoolAcceptResult::ResultType::VALID) {
        // Remove coins that were not present in the coins cache before calling
        // ATMPW; this is to prevent memory DoS in case we receive a large
        // number of invalid transactions that attempt to overrun the in-memory
        // coins cache
        // (`CCoinsViewCache::cacheCoins`).
 
        for (const COutPoint &outpoint : coins_to_uncache) {
            active_chainstate.CoinsTip().Uncache(outpoint);
        }
    }
 
    // After we've (potentially) uncached entries, ensure our coins cache is
    // still within its size limits
    BlockValidationState stateDummy;
    active_chainstate.FlushStateToDisk(stateDummy, FlushStateMode::PERIODIC);
    return result;
}
 
PackageMempoolAcceptResult ProcessNewPackage(Chainstate &active_chainstate,
                                             CTxMemPool &pool,
                                             const Package &package,
                                             bool test_accept) {
    AssertLockHeld(cs_main);
    assert(!package.empty());
    assert(std::all_of(package.cbegin(), package.cend(),
                       [](const auto &tx) { return tx != nullptr; }));
 
    const Config &config = active_chainstate.m_chainman.GetConfig();
 
    std::vector<COutPoint> coins_to_uncache;
    const auto result = [&]() EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
        AssertLockHeld(cs_main);
        if (test_accept) {
            auto args = MemPoolAccept::ATMPArgs::PackageTestAccept(
                config, GetTime(), coins_to_uncache);
            return MemPoolAccept(pool, active_chainstate)
                .AcceptMultipleTransactions(package, args);
        } else {
            auto args = MemPoolAccept::ATMPArgs::PackageChildWithParents(
                config, GetTime(), coins_to_uncache);
            return MemPoolAccept(pool, active_chainstate)
                .AcceptPackage(package, args);
        }
    }();
 
    // Uncache coins pertaining to transactions that were not submitted to the
    // mempool.
    if (test_accept || result.m_state.IsInvalid()) {
        for (const COutPoint &hashTx : coins_to_uncache) {
            active_chainstate.CoinsTip().Uncache(hashTx);
        }
    }
    // Ensure the coins cache is still within limits.
    BlockValidationState state_dummy;
    active_chainstate.FlushStateToDisk(state_dummy, FlushStateMode::PERIODIC);
    return result;
}
 
Amount GetBlockSubsidy(int nHeight, const Consensus::Params &consensusParams) {
    int halvings = nHeight / consensusParams.nSubsidyHalvingInterval;
    // Force block reward to zero when right shift is undefined.
    if (halvings >= 64) {
        return Amount::zero();
    }
 
    Amount nSubsidy = 50 * COIN;
    // Subsidy is cut in half every 210,000 blocks which will occur
    // approximately every 4 years.
    return ((nSubsidy / SATOSHI) >> halvings) * SATOSHI;
}
 
CoinsViews::CoinsViews(DBParams db_params, CoinsViewOptions options)
    : m_dbview{std::move(db_params), std::move(options)},
      m_catcherview(&m_dbview) {}
 
void CoinsViews::InitCache() {
    AssertLockHeld(::cs_main);
    m_cacheview = std::make_unique<CCoinsViewCache>(&m_catcherview);
}
 
Chainstate::Chainstate(CTxMemPool *mempool, BlockManager &blockman,
                       ChainstateManager &chainman,
                       std::optional<BlockHash> from_snapshot_blockhash)
    : m_mempool(mempool), m_blockman(blockman), m_chainman(chainman),
      m_from_snapshot_blockhash(from_snapshot_blockhash) {}
 
void Chainstate::InitCoinsDB(size_t cache_size_bytes, bool in_memory,
                             bool should_wipe, std::string leveldb_name) {
    if (m_from_snapshot_blockhash) {
        leveldb_name += node::SNAPSHOT_CHAINSTATE_SUFFIX;
    }
 
    m_coins_views = std::make_unique<CoinsViews>(
        DBParams{.path = m_chainman.m_options.datadir / leveldb_name,
                 .cache_bytes = cache_size_bytes,
                 .memory_only = in_memory,
                 .wipe_data = should_wipe,
                 .obfuscate = true,
                 .options = m_chainman.m_options.coins_db},
        m_chainman.m_options.coins_view);
}
 
void Chainstate::InitCoinsCache(size_t cache_size_bytes) {
    AssertLockHeld(::cs_main);
    assert(m_coins_views != nullptr);
    m_coinstip_cache_size_bytes = cache_size_bytes;
    m_coins_views->InitCache();
}
 
// Note that though this is marked const, we may end up modifying
// `m_cached_finished_ibd`, which is a performance-related implementation
// detail. This function must be marked `const` so that `CValidationInterface`
// clients (which are given a `const Chainstate*`) can call it.
//
bool Chainstate::IsInitialBlockDownload() const {
    // Optimization: pre-test latch before taking the lock.
    if (m_cached_finished_ibd.load(std::memory_order_relaxed)) {
        return false;
    }
 
    LOCK(cs_main);
    if (m_cached_finished_ibd.load(std::memory_order_relaxed)) {
        return false;
    }
    if (m_chainman.m_blockman.LoadingBlocks()) {
        return true;
    }
    if (m_chain.Tip() == nullptr) {
        return true;
    }
    if (m_chain.Tip()->nChainWork < m_chainman.MinimumChainWork()) {
        return true;
    }
    if (m_chain.Tip()->Time() <
        Now<NodeSeconds>() - m_chainman.m_options.max_tip_age) {
        return true;
    }
    LogPrintf("Leaving InitialBlockDownload (latching to false)\n");
    m_cached_finished_ibd.store(true, std::memory_order_relaxed);
    return false;
}
 
void Chainstate::CheckForkWarningConditions() {
    AssertLockHeld(cs_main);
 
    // Before we get past initial download, we cannot reliably alert about forks
    // (we assume we don't get stuck on a fork before finishing our initial
    // sync)
    if (IsInitialBlockDownload()) {
        return;
    }
 
    // If our best fork is no longer within 72 blocks (+/- 12 hours if no one
    // mines it) of our head, or if it is back on the active chain, drop it
    if (m_best_fork_tip && (m_chain.Height() - m_best_fork_tip->nHeight >= 72 ||
                            m_chain.Contains(m_best_fork_tip))) {
        m_best_fork_tip = nullptr;
    }
 
    if (m_best_fork_tip ||
        (m_chainman.m_best_invalid &&
         m_chainman.m_best_invalid->nChainWork >
             m_chain.Tip()->nChainWork + (GetBlockProof(*m_chain.Tip()) * 6))) {
        if (!GetfLargeWorkForkFound() && m_best_fork_base) {
            std::string warning =
                std::string("'Warning: Large-work fork detected, forking after "
                            "block ") +
                m_best_fork_base->phashBlock->ToString() + std::string("'");
            m_chainman.GetNotifications().warning(warning);
        }
 
        if (m_best_fork_tip && m_best_fork_base) {
            LogPrintf("%s: Warning: Large fork found\n  forking the "
                      "chain at height %d (%s)\n  lasting to height %d "
                      "(%s).\nChain state database corruption likely.\n",
                      __func__, m_best_fork_base->nHeight,
                      m_best_fork_base->phashBlock->ToString(),
                      m_best_fork_tip->nHeight,
                      m_best_fork_tip->phashBlock->ToString());
            SetfLargeWorkForkFound(true);
        } else {
            LogPrintf("%s: Warning: Found invalid chain at least ~6 blocks "
                      "longer than our best chain.\nChain state database "
                      "corruption likely.\n",
                      __func__);
            SetfLargeWorkInvalidChainFound(true);
        }
    } else {
        SetfLargeWorkForkFound(false);
        SetfLargeWorkInvalidChainFound(false);
    }
}
 
void Chainstate::CheckForkWarningConditionsOnNewFork(
    CBlockIndex *pindexNewForkTip) {
    AssertLockHeld(cs_main);
 
    // If we are on a fork that is sufficiently large, set a warning flag.
    const CBlockIndex *pfork = m_chain.FindFork(pindexNewForkTip);
 
    // We define a condition where we should warn the user about as a fork of at
    // least 7 blocks with a tip within 72 blocks (+/- 12 hours if no one mines
    // it) of ours. We use 7 blocks rather arbitrarily as it represents just
    // under 10% of sustained network hash rate operating on the fork, or a
    // chain that is entirely longer than ours and invalid (note that this
    // should be detected by both). We define it this way because it allows us
    // to only store the highest fork tip (+ base) which meets the 7-block
    // condition and from this always have the most-likely-to-cause-warning fork
    if (pfork &&
        (!m_best_fork_tip ||
         pindexNewForkTip->nHeight > m_best_fork_tip->nHeight) &&
        pindexNewForkTip->nChainWork - pfork->nChainWork >
            (GetBlockProof(*pfork) * 7) &&
        m_chain.Height() - pindexNewForkTip->nHeight < 72) {
        m_best_fork_tip = pindexNewForkTip;
        m_best_fork_base = pfork;
    }
 
    CheckForkWarningConditions();
}
 
// Called both upon regular invalid block discovery *and* InvalidateBlock
void Chainstate::InvalidChainFound(CBlockIndex *pindexNew) {
    AssertLockHeld(cs_main);
    if (!m_chainman.m_best_invalid ||
        pindexNew->nChainWork > m_chainman.m_best_invalid->nChainWork) {
        m_chainman.m_best_invalid = pindexNew;
    }
    if (m_chainman.m_best_header != nullptr &&
        m_chainman.m_best_header->GetAncestor(pindexNew->nHeight) ==
            pindexNew) {
        m_chainman.m_best_header = m_chain.Tip();
    }
 
    // If the invalid chain found is supposed to be finalized, we need to move
    // back the finalization point.
    if (IsBlockAvalancheFinalized(pindexNew)) {
        LOCK(cs_avalancheFinalizedBlockIndex);
        m_avalancheFinalizedBlockIndex = pindexNew->pprev;
    }
 
    LogPrintf("%s: invalid block=%s  height=%d  log2_work=%f  date=%s\n",
              __func__, pindexNew->GetBlockHash().ToString(),
              pindexNew->nHeight,
              log(pindexNew->nChainWork.getdouble()) / log(2.0),
              FormatISO8601DateTime(pindexNew->GetBlockTime()));
    CBlockIndex *tip = m_chain.Tip();
    assert(tip);
    LogPrintf("%s:  current best=%s  height=%d  log2_work=%f  date=%s\n",
              __func__, tip->GetBlockHash().ToString(), m_chain.Height(),
              log(tip->nChainWork.getdouble()) / log(2.0),
              FormatISO8601DateTime(tip->GetBlockTime()));
}
 
// Same as InvalidChainFound, above, except not called directly from
// InvalidateBlock, which does its own setBlockIndexCandidates management.
void Chainstate::InvalidBlockFound(CBlockIndex *pindex,
                                   const BlockValidationState &state) {
    AssertLockHeld(cs_main);
    if (state.GetResult() != BlockValidationResult::BLOCK_MUTATED) {
        pindex->nStatus = pindex->nStatus.withFailed();
        m_chainman.m_failed_blocks.insert(pindex);
        m_blockman.m_dirty_blockindex.insert(pindex);
        InvalidChainFound(pindex);
    }
}
 
void SpendCoins(CCoinsViewCache &view, const CTransaction &tx, CTxUndo &txundo,
                int nHeight) {
    // Mark inputs spent.
    if (tx.IsCoinBase()) {
        return;
    }
 
    txundo.vprevout.reserve(tx.vin.size());
    for (const CTxIn &txin : tx.vin) {
        txundo.vprevout.emplace_back();
        bool is_spent = view.SpendCoin(txin.prevout, &txundo.vprevout.back());
        assert(is_spent);
    }
}
 
void UpdateCoins(CCoinsViewCache &view, const CTransaction &tx, CTxUndo &txundo,
                 int nHeight) {
    SpendCoins(view, tx, txundo, nHeight);
    AddCoins(view, tx, nHeight);
}
 
bool CScriptCheck::operator()() {
    const CScript &scriptSig = ptxTo->vin[nIn].scriptSig;
    if (!VerifyScript(scriptSig, m_tx_out.scriptPubKey, nFlags,
                      CachingTransactionSignatureChecker(
                          ptxTo, nIn, m_tx_out.nValue, cacheStore, txdata),
                      metrics, &error)) {
        return false;
    }
    if ((pTxLimitSigChecks &&
         !pTxLimitSigChecks->consume_and_check(metrics.nSigChecks)) ||
        (pBlockLimitSigChecks &&
         !pBlockLimitSigChecks->consume_and_check(metrics.nSigChecks))) {
        // we can't assign a meaningful script error (since the script
        // succeeded), but remove the ScriptError::OK which could be
        // misinterpreted.
        error = ScriptError::SIGCHECKS_LIMIT_EXCEEDED;
        return false;
    }
    return true;
}
 
bool CheckInputScripts(const CTransaction &tx, TxValidationState &state,
                       const CCoinsViewCache &inputs, const uint32_t flags,
                       bool sigCacheStore, bool scriptCacheStore,
                       const PrecomputedTransactionData &txdata,
                       int &nSigChecksOut, TxSigCheckLimiter &txLimitSigChecks,
                       CheckInputsLimiter *pBlockLimitSigChecks,
                       std::vector<CScriptCheck> *pvChecks) {
    AssertLockHeld(cs_main);
    assert(!tx.IsCoinBase());
 
    if (pvChecks) {
        pvChecks->reserve(tx.vin.size());
    }
 
    // First check if script executions have been cached with the same flags.
    // Note that this assumes that the inputs provided are correct (ie that the
    // transaction hash which is in tx's prevouts properly commits to the
    // scriptPubKey in the inputs view of that transaction).
    ScriptCacheKey hashCacheEntry(tx, flags);
    if (IsKeyInScriptCache(hashCacheEntry, !scriptCacheStore, nSigChecksOut)) {
        if (!txLimitSigChecks.consume_and_check(nSigChecksOut) ||
            (pBlockLimitSigChecks &&
             !pBlockLimitSigChecks->consume_and_check(nSigChecksOut))) {
            return state.Invalid(TxValidationResult::TX_CONSENSUS,
                                 "too-many-sigchecks");
        }
        return true;
    }
 
    int nSigChecksTotal = 0;
 
    for (size_t i = 0; i < tx.vin.size(); i++) {
        const COutPoint &prevout = tx.vin[i].prevout;
        const Coin &coin = inputs.AccessCoin(prevout);
        assert(!coin.IsSpent());
 
        // We very carefully only pass in things to CScriptCheck which are
        // clearly committed to by tx's hash. This provides a sanity
        // check that our caching is not introducing consensus failures through
        // additional data in, eg, the coins being spent being checked as a part
        // of CScriptCheck.
 
        // Verify signature
        CScriptCheck check(coin.GetTxOut(), tx, i, flags, sigCacheStore, txdata,
                           &txLimitSigChecks, pBlockLimitSigChecks);
 
        // If pvChecks is not null, defer the check execution to the caller.
        if (pvChecks) {
            pvChecks->push_back(std::move(check));
            continue;
        }
 
        if (!check()) {
            ScriptError scriptError = check.GetScriptError();
            // Compute flags without the optional standardness flags.
            // This differs from MANDATORY_SCRIPT_VERIFY_FLAGS as it contains
            // additional upgrade flags (see AcceptToMemoryPoolWorker variable
            // extraFlags).
            uint32_t mandatoryFlags =
                flags & ~STANDARD_NOT_MANDATORY_VERIFY_FLAGS;
            if (flags != mandatoryFlags) {
                // Check whether the failure was caused by a non-mandatory
                // script verification check. If so, ensure we return
                // NOT_STANDARD instead of CONSENSUS to avoid downstream users
                // splitting the network between upgraded and non-upgraded nodes
                // by banning CONSENSUS-failing data providers.
                CScriptCheck check2(coin.GetTxOut(), tx, i, mandatoryFlags,
                                    sigCacheStore, txdata);
                if (check2()) {
                    return state.Invalid(
                        TxValidationResult::TX_NOT_STANDARD,
                        strprintf("non-mandatory-script-verify-flag (%s)",
                                  ScriptErrorString(scriptError)));
                }
                // update the error message to reflect the mandatory violation.
                scriptError = check2.GetScriptError();
            }
 
            // MANDATORY flag failures correspond to
            // TxValidationResult::TX_CONSENSUS. Because CONSENSUS failures are
            // the most serious case of validation failures, we may need to
            // consider using RECENT_CONSENSUS_CHANGE for any script failure
            // that could be due to non-upgraded nodes which we may want to
            // support, to avoid splitting the network (but this depends on the
            // details of how net_processing handles such errors).
            return state.Invalid(
                TxValidationResult::TX_CONSENSUS,
                strprintf("mandatory-script-verify-flag-failed (%s)",
                          ScriptErrorString(scriptError)));
        }
 
        nSigChecksTotal += check.GetScriptExecutionMetrics().nSigChecks;
    }
 
    nSigChecksOut = nSigChecksTotal;
 
    if (scriptCacheStore && !pvChecks) {
        // We executed all of the provided scripts, and were told to cache the
        // result. Do so now.
        AddKeyInScriptCache(hashCacheEntry, nSigChecksTotal);
    }
 
    return true;
}
 
bool AbortNode(BlockValidationState &state, const std::string &strMessage,
               const bilingual_str &userMessage) {
    AbortNode(strMessage, userMessage);
    return state.Error(strMessage);
}
 
DisconnectResult UndoCoinSpend(Coin &&undo, CCoinsViewCache &view,
                               const COutPoint &out) {
    bool fClean = true;
 
    if (view.HaveCoin(out)) {
        // Overwriting transaction output.
        fClean = false;
    }
 
    if (undo.GetHeight() == 0) {
        // Missing undo metadata (height and coinbase). Older versions included
        // this information only in undo records for the last spend of a
        // transactions' outputs. This implies that it must be present for some
        // other output of the same tx.
        const Coin &alternate = AccessByTxid(view, out.GetTxId());
        if (alternate.IsSpent()) {
            // Adding output for transaction without known metadata
            return DisconnectResult::FAILED;
        }
 
        // This is somewhat ugly, but hopefully utility is limited. This is only
        // useful when working from legacy on disck data. In any case, putting
        // the correct information in there doesn't hurt.
        const_cast<Coin &>(undo) = Coin(undo.GetTxOut(), alternate.GetHeight(),
                                        alternate.IsCoinBase());
    }
 
    // If the coin already exists as an unspent coin in the cache, then the
    // possible_overwrite parameter to AddCoin must be set to true. We have
    // already checked whether an unspent coin exists above using HaveCoin, so
    // we don't need to guess. When fClean is false, an unspent coin already
    // existed and it is an overwrite.
    view.AddCoin(out, std::move(undo), !fClean);
 
    return fClean ? DisconnectResult::OK : DisconnectResult::UNCLEAN;
}
 
DisconnectResult Chainstate::DisconnectBlock(const CBlock &block,
                                             const CBlockIndex *pindex,
                                             CCoinsViewCache &view) {
    AssertLockHeld(::cs_main);
    CBlockUndo blockUndo;
    if (!m_blockman.UndoReadFromDisk(blockUndo, *pindex)) {
        error("DisconnectBlock(): failure reading undo data");
        return DisconnectResult::FAILED;
    }
 
    return ApplyBlockUndo(std::move(blockUndo), block, pindex, view);
}
 
DisconnectResult ApplyBlockUndo(CBlockUndo &&blockUndo, const CBlock &block,
                                const CBlockIndex *pindex,
                                CCoinsViewCache &view) {
    bool fClean = true;
 
    if (blockUndo.vtxundo.size() + 1 != block.vtx.size()) {
        error("DisconnectBlock(): block and undo data inconsistent");
        return DisconnectResult::FAILED;
    }
 
    // First, restore inputs.
    for (size_t i = 1; i < block.vtx.size(); i++) {
        const CTransaction &tx = *(block.vtx[i]);
        CTxUndo &txundo = blockUndo.vtxundo[i - 1];
        if (txundo.vprevout.size() != tx.vin.size()) {
            error("DisconnectBlock(): transaction and undo data inconsistent");
            return DisconnectResult::FAILED;
        }
 
        for (size_t j = 0; j < tx.vin.size(); j++) {
            const COutPoint &out = tx.vin[j].prevout;
            DisconnectResult res =
                UndoCoinSpend(std::move(txundo.vprevout[j]), view, out);
            if (res == DisconnectResult::FAILED) {
                return DisconnectResult::FAILED;
            }
            fClean = fClean && res != DisconnectResult::UNCLEAN;
        }
        // At this point, all of txundo.vprevout should have been moved out.
    }
 
    // Second, revert created outputs.
    for (const auto &ptx : block.vtx) {
        const CTransaction &tx = *ptx;
        const TxId &txid = tx.GetId();
        const bool is_coinbase = tx.IsCoinBase();
 
        // Check that all outputs are available and match the outputs in the
        // block itself exactly.
        for (size_t o = 0; o < tx.vout.size(); o++) {
            if (tx.vout[o].scriptPubKey.IsUnspendable()) {
                continue;
            }
 
            COutPoint out(txid, o);
            Coin coin;
            bool is_spent = view.SpendCoin(out, &coin);
            if (!is_spent || tx.vout[o] != coin.GetTxOut() ||
                uint32_t(pindex->nHeight) != coin.GetHeight() ||
                is_coinbase != coin.IsCoinBase()) {
                // transaction output mismatch
                fClean = false;
            }
        }
    }
 
    // Move best block pointer to previous block.
    view.SetBestBlock(block.hashPrevBlock);
 
    return fClean ? DisconnectResult::OK : DisconnectResult::UNCLEAN;
}
 
static CCheckQueue<CScriptCheck> scriptcheckqueue(128);
 
void StartScriptCheckWorkerThreads(int threads_num) {
    scriptcheckqueue.StartWorkerThreads(threads_num);
}
 
void StopScriptCheckWorkerThreads() {
    scriptcheckqueue.StopWorkerThreads();
}
 
// Returns the script flags which should be checked for the block after
// the given block.
static uint32_t GetNextBlockScriptFlags(const CBlockIndex *pindex,
                                        const ChainstateManager &chainman) {
    const Consensus::Params &consensusparams = chainman.GetConsensus();
 
    uint32_t flags = SCRIPT_VERIFY_NONE;
 
    // Enforce P2SH (BIP16)
    if (DeploymentActiveAfter(pindex, chainman, Consensus::DEPLOYMENT_P2SH)) {
        flags |= SCRIPT_VERIFY_P2SH;
    }
 
    // Enforce the DERSIG (BIP66) rule.
    if (DeploymentActiveAfter(pindex, chainman, Consensus::DEPLOYMENT_DERSIG)) {
        flags |= SCRIPT_VERIFY_DERSIG;
    }
 
    // Start enforcing CHECKLOCKTIMEVERIFY (BIP65) rule.
    if (DeploymentActiveAfter(pindex, chainman, Consensus::DEPLOYMENT_CLTV)) {
        flags |= SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY;
    }
 
    // Start enforcing CSV (BIP68, BIP112 and BIP113) rule.
    if (DeploymentActiveAfter(pindex, chainman, Consensus::DEPLOYMENT_CSV)) {
        flags |= SCRIPT_VERIFY_CHECKSEQUENCEVERIFY;
    }
 
    // If the UAHF is enabled, we start accepting replay protected txns
    if (IsUAHFenabled(consensusparams, pindex)) {
        flags |= SCRIPT_VERIFY_STRICTENC;
        flags |= SCRIPT_ENABLE_SIGHASH_FORKID;
    }
 
    // If the DAA HF is enabled, we start rejecting transaction that use a high
    // s in their signature. We also make sure that signature that are supposed
    // to fail (for instance in multisig or other forms of smart contracts) are
    // null.
    if (IsDAAEnabled(consensusparams, pindex)) {
        flags |= SCRIPT_VERIFY_LOW_S;
        flags |= SCRIPT_VERIFY_NULLFAIL;
    }
 
    // When the magnetic anomaly fork is enabled, we start accepting
    // transactions using the OP_CHECKDATASIG opcode and it's verify
    // alternative. We also start enforcing push only signatures and
    // clean stack.
    if (IsMagneticAnomalyEnabled(consensusparams, pindex)) {
        flags |= SCRIPT_VERIFY_SIGPUSHONLY;
        flags |= SCRIPT_VERIFY_CLEANSTACK;
    }
 
    if (IsGravitonEnabled(consensusparams, pindex)) {
        flags |= SCRIPT_ENABLE_SCHNORR_MULTISIG;
        flags |= SCRIPT_VERIFY_MINIMALDATA;
    }
 
    if (IsPhononEnabled(consensusparams, pindex)) {
        flags |= SCRIPT_ENFORCE_SIGCHECKS;
    }
 
    // We make sure this node will have replay protection during the next hard
    // fork.
    if (IsReplayProtectionEnabled(consensusparams, pindex)) {
        flags |= SCRIPT_ENABLE_REPLAY_PROTECTION;
    }
 
    return flags;
}
 
static int64_t nTimeCheck = 0;
static int64_t nTimeForks = 0;
static int64_t nTimeVerify = 0;
static int64_t nTimeConnect = 0;
static int64_t nTimeIndex = 0;
static int64_t nTimeTotal = 0;
static int64_t nBlocksTotal = 0;
 
bool Chainstate::ConnectBlock(const CBlock &block, BlockValidationState &state,
                              CBlockIndex *pindex, CCoinsViewCache &view,
                              BlockValidationOptions options, Amount *blockFees,
                              bool fJustCheck) {
    AssertLockHeld(cs_main);
    assert(pindex);
 
    const BlockHash block_hash{block.GetHash()};
    assert(*pindex->phashBlock == block_hash);
 
    int64_t nTimeStart = GetTimeMicros();
 
    const CChainParams &params{m_chainman.GetParams()};
    const Consensus::Params &consensusParams = params.GetConsensus();
 
    // Check it again in case a previous version let a bad block in
    // NOTE: We don't currently (re-)invoke ContextualCheckBlock() or
    // ContextualCheckBlockHeader() here. This means that if we add a new
    // consensus rule that is enforced in one of those two functions, then we
    // may have let in a block that violates the rule prior to updating the
    // software, and we would NOT be enforcing the rule here. Fully solving
    // upgrade from one software version to the next after a consensus rule
    // change is potentially tricky and issue-specific.
    // Also, currently the rule against blocks more than 2 hours in the future
    // is enforced in ContextualCheckBlockHeader(); we wouldn't want to
    // re-enforce that rule here (at least until we make it impossible for
    // m_adjusted_time_callback() to go backward).
    if (!CheckBlock(block, state, consensusParams,
                    options.withCheckPoW(!fJustCheck)
                        .withCheckMerkleRoot(!fJustCheck))) {
        if (state.GetResult() == BlockValidationResult::BLOCK_MUTATED) {
            // We don't write down blocks to disk if they may have been
            // corrupted, so this should be impossible unless we're having
            // hardware problems.
            return AbortNode(state, "Corrupt block found indicating potential "
                                    "hardware failure; shutting down");
        }
        return error("%s: Consensus::CheckBlock: %s", __func__,
                     state.ToString());
    }
 
    // Verify that the view's current state corresponds to the previous block
    BlockHash hashPrevBlock =
        pindex->pprev == nullptr ? BlockHash() : pindex->pprev->GetBlockHash();
    assert(hashPrevBlock == view.GetBestBlock());
 
    nBlocksTotal++;
 
    // Special case for the genesis block, skipping connection of its
    // transactions (its coinbase is unspendable)
    if (block_hash == consensusParams.hashGenesisBlock) {
        if (!fJustCheck) {
            view.SetBestBlock(pindex->GetBlockHash());
        }
 
        return true;
    }
 
    bool fScriptChecks = true;
    if (!m_chainman.AssumedValidBlock().IsNull()) {
        // We've been configured with the hash of a block which has been
        // externally verified to have a valid history. A suitable default value
        // is included with the software and updated from time to time. Because
        // validity relative to a piece of software is an objective fact these
        // defaults can be easily reviewed. This setting doesn't force the
        // selection of any particular chain but makes validating some faster by
        // effectively caching the result of part of the verification.
        BlockMap::const_iterator it{
            m_blockman.m_block_index.find(m_chainman.AssumedValidBlock())};
        if (it != m_blockman.m_block_index.end()) {
            if (it->second.GetAncestor(pindex->nHeight) == pindex &&
                m_chainman.m_best_header->GetAncestor(pindex->nHeight) ==
                    pindex &&
                m_chainman.m_best_header->nChainWork >=
                    m_chainman.MinimumChainWork()) {
                // This block is a member of the assumed verified chain and an
                // ancestor of the best header.
                // Script verification is skipped when connecting blocks under
                // the assumevalid block. Assuming the assumevalid block is
                // valid this is safe because block merkle hashes are still
                // computed and checked, Of course, if an assumed valid block is
                // invalid due to false scriptSigs this optimization would allow
                // an invalid chain to be accepted.
                // The equivalent time check discourages hash power from
                // extorting the network via DOS attack into accepting an
                // invalid block through telling users they must manually set
                // assumevalid. Requiring a software change or burying the
                // invalid block, regardless of the setting, makes it hard to
                // hide the implication of the demand. This also avoids having
                // release candidates that are hardly doing any signature
                // verification at all in testing without having to artificially
                // set the default assumed verified block further back. The test
                // against the minimum chain work prevents the skipping when
                // denied access to any chain at least as good as the expected
                // chain.
                fScriptChecks = (GetBlockProofEquivalentTime(
                                     *m_chainman.m_best_header, *pindex,
                                     *m_chainman.m_best_header,
                                     consensusParams) <= 60 * 60 * 24 * 7 * 2);
            }
        }
    }
 
    int64_t nTime1 = GetTimeMicros();
    nTimeCheck += nTime1 - nTimeStart;
    LogPrint(BCLog::BENCH, "    - Sanity checks: %.2fms [%.2fs (%.2fms/blk)]\n",
             MILLI * (nTime1 - nTimeStart), nTimeCheck * MICRO,
             nTimeCheck * MILLI / nBlocksTotal);
 
    // Do not allow blocks that contain transactions which 'overwrite' older
    // transactions, unless those are already completely spent. If such
    // overwrites are allowed, coinbases and transactions depending upon those
    // can be duplicated to remove the ability to spend the first instance --
    // even after being sent to another address.
    // See BIP30, CVE-2012-1909, and http://r6.ca/blog/20120206T005236Z.html
    // for more information. This rule was originally applied to all blocks
    // with a timestamp after March 15, 2012, 0:00 UTC. Now that the whole
    // chain is irreversibly beyond that time it is applied to all blocks
    // except the two in the chain that violate it. This prevents exploiting
    // the issue against nodes during their initial block download.
    bool fEnforceBIP30 = !((pindex->nHeight == 91842 &&
                            pindex->GetBlockHash() ==
                                uint256S("0x00000000000a4d0a398161ffc163c503763"
                                         "b1f4360639393e0e4c8e300e0caec")) ||
                           (pindex->nHeight == 91880 &&
                            pindex->GetBlockHash() ==
                                uint256S("0x00000000000743f190a18c5577a3c2d2a1f"
                                         "610ae9601ac046a38084ccb7cd721")));
 
    // Once BIP34 activated it was not possible to create new duplicate
    // coinbases and thus other than starting with the 2 existing duplicate
    // coinbase pairs, not possible to create overwriting txs. But by the time
    // BIP34 activated, in each of the existing pairs the duplicate coinbase had
    // overwritten the first before the first had been spent. Since those
    // coinbases are sufficiently buried it's no longer possible to create
    // further duplicate transactions descending from the known pairs either. If
    // we're on the known chain at height greater than where BIP34 activated, we
    // can save the db accesses needed for the BIP30 check.
 
    // BIP34 requires that a block at height X (block X) has its coinbase
    // scriptSig start with a CScriptNum of X (indicated height X).  The above
    // logic of no longer requiring BIP30 once BIP34 activates is flawed in the
    // case that there is a block X before the BIP34 height of 227,931 which has
    // an indicated height Y where Y is greater than X.  The coinbase for block
    // X would also be a valid coinbase for block Y, which could be a BIP30
    // violation.  An exhaustive search of all mainnet coinbases before the
    // BIP34 height which have an indicated height greater than the block height
    // reveals many occurrences. The 3 lowest indicated heights found are
    // 209,921, 490,897, and 1,983,702 and thus coinbases for blocks at these 3
    // heights would be the first opportunity for BIP30 to be violated.
 
    // The search reveals a great many blocks which have an indicated height
    // greater than 1,983,702, so we simply remove the optimization to skip
    // BIP30 checking for blocks at height 1,983,702 or higher.  Before we reach
    // that block in another 25 years or so, we should take advantage of a
    // future consensus change to do a new and improved version of BIP34 that
    // will actually prevent ever creating any duplicate coinbases in the
    // future.
    static constexpr int BIP34_IMPLIES_BIP30_LIMIT = 1983702;
 
    // There is no potential to create a duplicate coinbase at block 209,921
    // because this is still before the BIP34 height and so explicit BIP30
    // checking is still active.
 
    // The final case is block 176,684 which has an indicated height of
    // 490,897. Unfortunately, this issue was not discovered until about 2 weeks
    // before block 490,897 so there was not much opportunity to address this
    // case other than to carefully analyze it and determine it would not be a
    // problem. Block 490,897 was, in fact, mined with a different coinbase than
    // block 176,684, but it is important to note that even if it hadn't been or
    // is remined on an alternate fork with a duplicate coinbase, we would still
    // not run into a BIP30 violation.  This is because the coinbase for 176,684
    // is spent in block 185,956 in transaction
    // d4f7fbbf92f4a3014a230b2dc70b8058d02eb36ac06b4a0736d9d60eaa9e8781.  This
    // spending transaction can't be duplicated because it also spends coinbase
    // 0328dd85c331237f18e781d692c92de57649529bd5edf1d01036daea32ffde29.  This
    // coinbase has an indicated height of over 4.2 billion, and wouldn't be
    // duplicatable until that height, and it's currently impossible to create a
    // chain that long. Nevertheless we may wish to consider a future soft fork
    // which retroactively prevents block 490,897 from creating a duplicate
    // coinbase. The two historical BIP30 violations often provide a confusing
    // edge case when manipulating the UTXO and it would be simpler not to have
    // another edge case to deal with.
 
    // testnet3 has no blocks before the BIP34 height with indicated heights
    // post BIP34 before approximately height 486,000,000 and presumably will
    // be reset before it reaches block 1,983,702 and starts doing unnecessary
    // BIP30 checking again.
    assert(pindex->pprev);
    CBlockIndex *pindexBIP34height =
        pindex->pprev->GetAncestor(consensusParams.BIP34Height);
    // Only continue to enforce if we're below BIP34 activation height or the
    // block hash at that height doesn't correspond.
    fEnforceBIP30 =
        fEnforceBIP30 &&
        (!pindexBIP34height ||
         !(pindexBIP34height->GetBlockHash() == consensusParams.BIP34Hash));
 
    // TODO: Remove BIP30 checking from block height 1,983,702 on, once we have
    // a consensus change that ensures coinbases at those heights can not
    // duplicate earlier coinbases.
    if (fEnforceBIP30 || pindex->nHeight >= BIP34_IMPLIES_BIP30_LIMIT) {
        for (const auto &tx : block.vtx) {
            for (size_t o = 0; o < tx->vout.size(); o++) {
                if (view.HaveCoin(COutPoint(tx->GetId(), o))) {
                    LogPrintf("ERROR: ConnectBlock(): tried to overwrite "
                              "transaction\n");
                    return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS,
                                         "bad-txns-BIP30");
                }
            }
        }
    }
 
    // Enforce BIP68 (sequence locks).
    int nLockTimeFlags = 0;
    if (DeploymentActiveAt(*pindex, consensusParams,
                           Consensus::DEPLOYMENT_CSV)) {
        nLockTimeFlags |= LOCKTIME_VERIFY_SEQUENCE;
    }
 
    const uint32_t flags = GetNextBlockScriptFlags(pindex->pprev, m_chainman);
 
    int64_t nTime2 = GetTimeMicros();
    nTimeForks += nTime2 - nTime1;
    LogPrint(BCLog::BENCH, "    - Fork checks: %.2fms [%.2fs (%.2fms/blk)]\n",
             MILLI * (nTime2 - nTime1), nTimeForks * MICRO,
             nTimeForks * MILLI / nBlocksTotal);
 
    std::vector<int> prevheights;
    Amount nFees = Amount::zero();
    int nInputs = 0;
 
    // Limit the total executed signature operations in the block, a consensus
    // rule. Tracking during the CPU-consuming part (validation of uncached
    // inputs) is per-input atomic and validation in each thread stops very
    // quickly after the limit is exceeded, so an adversary cannot cause us to
    // exceed the limit by much at all.
    CheckInputsLimiter nSigChecksBlockLimiter(
        GetMaxBlockSigChecksCount(options.getExcessiveBlockSize()));
 
    std::vector<TxSigCheckLimiter> nSigChecksTxLimiters;
    nSigChecksTxLimiters.resize(block.vtx.size() - 1);
 
    CBlockUndo blockundo;
    blockundo.vtxundo.resize(block.vtx.size() - 1);
 
    CCheckQueueControl<CScriptCheck> control(fScriptChecks ? &scriptcheckqueue
                                                           : nullptr);
 
    // Add all outputs
    try {
        for (const auto &ptx : block.vtx) {
            AddCoins(view, *ptx, pindex->nHeight);
        }
    } catch (const std::logic_error &e) {
        // This error will be thrown from AddCoin if we try to connect a block
        // containing duplicate transactions. Such a thing should normally be
        // caught early nowadays (due to ContextualCheckBlock's CTOR
        // enforcement) however some edge cases can escape that:
        // - ContextualCheckBlock does not get re-run after saving the block to
        // disk, and older versions may have saved a weird block.
        // - its checks are not applied to pre-CTOR chains, which we might visit
        // with checkpointing off.
        LogPrintf("ERROR: ConnectBlock(): tried to overwrite transaction\n");
        return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS,
                             "tx-duplicate");
    }
 
    size_t txIndex = 0;
    // nSigChecksRet may be accurate (found in cache) or 0 (checks were
    // deferred into vChecks).
    int nSigChecksRet;
    for (const auto &ptx : block.vtx) {
        const CTransaction &tx = *ptx;
        const bool isCoinBase = tx.IsCoinBase();
        nInputs += tx.vin.size();
 
        {
            Amount txfee = Amount::zero();
            TxValidationState tx_state;
            if (!isCoinBase &&
                !Consensus::CheckTxInputs(tx, tx_state, view, pindex->nHeight,
                                          txfee)) {
                // Any transaction validation failure in ConnectBlock is a block
                // consensus failure.
                state.Invalid(BlockValidationResult::BLOCK_CONSENSUS,
                              tx_state.GetRejectReason(),
                              tx_state.GetDebugMessage());
 
                return error("%s: Consensus::CheckTxInputs: %s, %s", __func__,
                             tx.GetId().ToString(), state.ToString());
            }
            nFees += txfee;
        }
 
        if (!MoneyRange(nFees)) {
            LogPrintf("ERROR: %s: accumulated fee in the block out of range.\n",
                      __func__);
            return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS,
                                 "bad-txns-accumulated-fee-outofrange");
        }
 
        // The following checks do not apply to the coinbase.
        if (isCoinBase) {
            continue;
        }
 
        // Check that transaction is BIP68 final BIP68 lock checks (as
        // opposed to nLockTime checks) must be in ConnectBlock because they
        // require the UTXO set.
        prevheights.resize(tx.vin.size());
        for (size_t j = 0; j < tx.vin.size(); j++) {
            prevheights[j] = view.AccessCoin(tx.vin[j].prevout).GetHeight();
        }
 
        if (!SequenceLocks(tx, nLockTimeFlags, prevheights, *pindex)) {
            LogPrintf("ERROR: %s: contains a non-BIP68-final transaction\n",
                      __func__);
            return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS,
                                 "bad-txns-nonfinal");
        }
 
        // Don't cache results if we're actually connecting blocks (still
        // consult the cache, though).
        bool fCacheResults = fJustCheck;
 
        const bool fEnforceSigCheck = flags & SCRIPT_ENFORCE_SIGCHECKS;
        if (!fEnforceSigCheck) {
            // Historically, there has been transactions with a very high
            // sigcheck count, so we need to disable this check for such
            // transactions.
            nSigChecksTxLimiters[txIndex] = TxSigCheckLimiter::getDisabled();
        }
 
        std::vector<CScriptCheck> vChecks;
        TxValidationState tx_state;
        if (fScriptChecks &&
            !CheckInputScripts(tx, tx_state, view, flags, fCacheResults,
                               fCacheResults, PrecomputedTransactionData(tx),
                               nSigChecksRet, nSigChecksTxLimiters[txIndex],
                               &nSigChecksBlockLimiter, &vChecks)) {
            // Any transaction validation failure in ConnectBlock is a block
            // consensus failure
            state.Invalid(BlockValidationResult::BLOCK_CONSENSUS,
                          tx_state.GetRejectReason(),
                          tx_state.GetDebugMessage());
            return error(
                "ConnectBlock(): CheckInputScripts on %s failed with %s",
                tx.GetId().ToString(), state.ToString());
        }
 
        control.Add(std::move(vChecks));
 
        // Note: this must execute in the same iteration as CheckTxInputs (not
        // in a separate loop) in order to detect double spends. However,
        // this does not prevent double-spending by duplicated transaction
        // inputs in the same transaction (cf. CVE-2018-17144) -- that check is
        // done in CheckBlock (CheckRegularTransaction).
        SpendCoins(view, tx, blockundo.vtxundo.at(txIndex), pindex->nHeight);
        txIndex++;
    }
 
    int64_t nTime3 = GetTimeMicros();
    nTimeConnect += nTime3 - nTime2;
    LogPrint(BCLog::BENCH,
             "      - Connect %u transactions: %.2fms (%.3fms/tx, %.3fms/txin) "
             "[%.2fs (%.2fms/blk)]\n",
             (unsigned)block.vtx.size(), MILLI * (nTime3 - nTime2),
             MILLI * (nTime3 - nTime2) / block.vtx.size(),
             nInputs <= 1 ? 0 : MILLI * (nTime3 - nTime2) / (nInputs - 1),
             nTimeConnect * MICRO, nTimeConnect * MILLI / nBlocksTotal);
 
    const Amount blockReward =
        nFees + GetBlockSubsidy(pindex->nHeight, consensusParams);
    if (block.vtx[0]->GetValueOut() > blockReward) {
        LogPrintf("ERROR: ConnectBlock(): coinbase pays too much (actual=%d vs "
                  "limit=%d)\n",
                  block.vtx[0]->GetValueOut(), blockReward);
        return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS,
                             "bad-cb-amount");
    }
 
    if (blockFees) {
        *blockFees = nFees;
    }
 
    if (!control.Wait()) {
        return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS,
                             "blk-bad-inputs", "parallel script check failed");
    }
 
    int64_t nTime4 = GetTimeMicros();
    nTimeVerify += nTime4 - nTime2;
    LogPrint(
        BCLog::BENCH,
        "    - Verify %u txins: %.2fms (%.3fms/txin) [%.2fs (%.2fms/blk)]\n",
        nInputs - 1, MILLI * (nTime4 - nTime2),
        nInputs <= 1 ? 0 : MILLI * (nTime4 - nTime2) / (nInputs - 1),
        nTimeVerify * MICRO, nTimeVerify * MILLI / nBlocksTotal);
 
    if (fJustCheck) {
        return true;
    }
 
    if (!m_blockman.WriteUndoDataForBlock(blockundo, state, *pindex)) {
        return false;
    }
 
    if (!pindex->IsValid(BlockValidity::SCRIPTS)) {
        pindex->RaiseValidity(BlockValidity::SCRIPTS);
        m_blockman.m_dirty_blockindex.insert(pindex);
    }
 
    // add this block to the view's block chain
    view.SetBestBlock(pindex->GetBlockHash());
 
    int64_t nTime5 = GetTimeMicros();
    nTimeIndex += nTime5 - nTime4;
    LogPrint(BCLog::BENCH, "    - Index writing: %.2fms [%.2fs (%.2fms/blk)]\n",
             MILLI * (nTime5 - nTime4), nTimeIndex * MICRO,
             nTimeIndex * MILLI / nBlocksTotal);
 
    TRACE6(validation, block_connected, block_hash.data(), pindex->nHeight,
           block.vtx.size(), nInputs, nSigChecksRet,
           // in microseconds (µs)
           nTime5 - nTimeStart);
 
    return true;
}
 
CoinsCacheSizeState Chainstate::GetCoinsCacheSizeState() {
    AssertLockHeld(::cs_main);
    return this->GetCoinsCacheSizeState(m_coinstip_cache_size_bytes,
                                        m_mempool ? m_mempool->m_max_size_bytes
                                                  : 0);
}
 
CoinsCacheSizeState
Chainstate::GetCoinsCacheSizeState(size_t max_coins_cache_size_bytes,
                                   size_t max_mempool_size_bytes) {
    AssertLockHeld(::cs_main);
    int64_t nMempoolUsage = m_mempool ? m_mempool->DynamicMemoryUsage() : 0;
    int64_t cacheSize = CoinsTip().DynamicMemoryUsage();
    int64_t nTotalSpace =
        max_coins_cache_size_bytes +
        std::max<int64_t>(int64_t(max_mempool_size_bytes) - nMempoolUsage, 0);
 
    static constexpr int64_t MAX_BLOCK_COINSDB_USAGE_BYTES =
        10 * 1024 * 1024; // 10MB
    int64_t large_threshold = std::max(
        (9 * nTotalSpace) / 10, nTotalSpace - MAX_BLOCK_COINSDB_USAGE_BYTES);
 
    if (cacheSize > nTotalSpace) {
        LogPrintf("Cache size (%s) exceeds total space (%s)\n", cacheSize,
                  nTotalSpace);
        return CoinsCacheSizeState::CRITICAL;
    } else if (cacheSize > large_threshold) {
        return CoinsCacheSizeState::LARGE;
    }
    return CoinsCacheSizeState::OK;
}
 
bool Chainstate::FlushStateToDisk(BlockValidationState &state,
                                  FlushStateMode mode, int nManualPruneHeight) {
    LOCK(cs_main);
    assert(this->CanFlushToDisk());
    std::set<int> setFilesToPrune;
    bool full_flush_completed = false;
 
    const size_t coins_count = CoinsTip().GetCacheSize();
    const size_t coins_mem_usage = CoinsTip().DynamicMemoryUsage();
 
    try {
        {
            bool fFlushForPrune = false;
            bool fDoFullFlush = false;
 
            CoinsCacheSizeState cache_state = GetCoinsCacheSizeState();
            LOCK(m_blockman.cs_LastBlockFile);
            if (m_blockman.IsPruneMode() &&
                (m_blockman.m_check_for_pruning || nManualPruneHeight > 0) &&
                !fReindex) {
                // Make sure we don't prune any of the prune locks bestblocks.
                // Pruning is height-based.
                int last_prune{m_chain.Height()};
                // prune lock that actually was the limiting factor, only used
                // for logging
                std::optional<std::string> limiting_lock;
 
                for (const auto &prune_lock : m_blockman.m_prune_locks) {
                    if (prune_lock.second.height_first ==
                        std::numeric_limits<int>::max()) {
                        continue;
                    }
                    // Remove the buffer and one additional block here to get
                    // actual height that is outside of the buffer
                    const int lock_height{prune_lock.second.height_first -
                                          PRUNE_LOCK_BUFFER - 1};
                    last_prune = std::max(1, std::min(last_prune, lock_height));
                    if (last_prune == lock_height) {
                        limiting_lock = prune_lock.first;
                    }
                }
 
                if (limiting_lock) {
                    LogPrint(BCLog::PRUNE, "%s limited pruning to height %d\n",
                             limiting_lock.value(), last_prune);
                }
 
                if (nManualPruneHeight > 0) {
                    LOG_TIME_MILLIS_WITH_CATEGORY(
                        "find files to prune (manual)", BCLog::BENCH);
                    m_blockman.FindFilesToPruneManual(
                        setFilesToPrune,
                        std::min(last_prune, nManualPruneHeight),
                        m_chain.Height());
                } else {
                    LOG_TIME_MILLIS_WITH_CATEGORY("find files to prune",
                                                  BCLog::BENCH);
                    m_blockman.FindFilesToPrune(
                        setFilesToPrune,
                        m_chainman.GetParams().PruneAfterHeight(),
                        m_chain.Height(), last_prune, IsInitialBlockDownload());
                    m_blockman.m_check_for_pruning = false;
                }
                if (!setFilesToPrune.empty()) {
                    fFlushForPrune = true;
                    if (!m_blockman.m_have_pruned) {
                        m_blockman.m_block_tree_db->WriteFlag(
                            "prunedblockfiles", true);
                        m_blockman.m_have_pruned = true;
                    }
                }
            }
            const auto nNow = GetTime<std::chrono::microseconds>();
            // Avoid writing/flushing immediately after startup.
            if (m_last_write.count() == 0) {
                m_last_write = nNow;
            }
            if (m_last_flush.count() == 0) {
                m_last_flush = nNow;
            }
            // The cache is large and we're within 10% and 10 MiB of the limit,
            // but we have time now (not in the middle of a block processing).
            bool fCacheLarge = mode == FlushStateMode::PERIODIC &&
                               cache_state >= CoinsCacheSizeState::LARGE;
            // The cache is over the limit, we have to write now.
            bool fCacheCritical = mode == FlushStateMode::IF_NEEDED &&
                                  cache_state >= CoinsCacheSizeState::CRITICAL;
            // It's been a while since we wrote the block index to disk. Do this
            // frequently, so we don't need to redownload after a crash.
            bool fPeriodicWrite = mode == FlushStateMode::PERIODIC &&
                                  nNow > m_last_write + DATABASE_WRITE_INTERVAL;
            // It's been very long since we flushed the cache. Do this
            // infrequently, to optimize cache usage.
            bool fPeriodicFlush = mode == FlushStateMode::PERIODIC &&
                                  nNow > m_last_flush + DATABASE_FLUSH_INTERVAL;
            // Combine all conditions that result in a full cache flush.
            fDoFullFlush = (mode == FlushStateMode::ALWAYS) || fCacheLarge ||
                           fCacheCritical || fPeriodicFlush || fFlushForPrune;
            // Write blocks and block index to disk.
            if (fDoFullFlush || fPeriodicWrite) {
                // Ensure we can write block index
                if (!CheckDiskSpace(gArgs.GetBlocksDirPath())) {
                    return AbortNode(state, "Disk space is too low!",
                                     _("Disk space is too low!"));
                }
 
                {
                    LOG_TIME_MILLIS_WITH_CATEGORY(
                        "write block and undo data to disk", BCLog::BENCH);
 
                    // First make sure all block and undo data is flushed to
                    // disk.
                    m_blockman.FlushBlockFile();
                }
                // Then update all block file information (which may refer to
                // block and undo files).
                {
                    LOG_TIME_MILLIS_WITH_CATEGORY("write block index to disk",
                                                  BCLog::BENCH);
 
                    if (!m_blockman.WriteBlockIndexDB()) {
                        return AbortNode(
                            state, "Failed to write to block index database");
                    }
                }
 
                // Finally remove any pruned files
                if (fFlushForPrune) {
                    LOG_TIME_MILLIS_WITH_CATEGORY("unlink pruned files",
                                                  BCLog::BENCH);
 
                    m_blockman.UnlinkPrunedFiles(setFilesToPrune);
                }
                m_last_write = nNow;
            }
            // Flush best chain related state. This can only be done if the
            // blocks / block index write was also done.
            if (fDoFullFlush && !CoinsTip().GetBestBlock().IsNull()) {
                LOG_TIME_MILLIS_WITH_CATEGORY(
                    strprintf("write coins cache to disk (%d coins, %.2fkB)",
                              coins_count, coins_mem_usage / 1000),
                    BCLog::BENCH);
 
                // Typical Coin structures on disk are around 48 bytes in size.
                // Pushing a new one to the database can cause it to be written
                // twice (once in the log, and once in the tables). This is
                // already an overestimation, as most will delete an existing
                // entry or overwrite one. Still, use a conservative safety
                // factor of 2.
                if (!CheckDiskSpace(gArgs.GetDataDirNet(),
                                    48 * 2 * 2 * CoinsTip().GetCacheSize())) {
                    return AbortNode(state, "Disk space is too low!",
                                     _("Disk space is too low!"));
                }
 
                // Flush the chainstate (which may refer to block index
                // entries).
                if (!CoinsTip().Flush()) {
                    return AbortNode(state, "Failed to write to coin database");
                }
                m_last_flush = nNow;
                full_flush_completed = true;
            }
 
            TRACE5(utxocache, flush,
                   // in microseconds (µs)
                   GetTimeMicros() - nNow.count(), uint32_t(mode), coins_count,
                   uint64_t(coins_mem_usage), fFlushForPrune);
        }
 
        if (full_flush_completed) {
            // Update best block in wallet (so we can detect restored wallets).
            GetMainSignals().ChainStateFlushed(m_chain.GetLocator());
        }
    } catch (const std::runtime_error &e) {
        return AbortNode(state, std::string("System error while flushing: ") +
                                    e.what());
    }
    return true;
}
 
void Chainstate::ForceFlushStateToDisk() {
    BlockValidationState state;
    if (!this->FlushStateToDisk(state, FlushStateMode::ALWAYS)) {
        LogPrintf("%s: failed to flush state (%s)\n", __func__,
                  state.ToString());
    }
}
 
void Chainstate::PruneAndFlush() {
    BlockValidationState state;
    m_blockman.m_check_for_pruning = true;
    if (!this->FlushStateToDisk(state, FlushStateMode::NONE)) {
        LogPrintf("%s: failed to flush state (%s)\n", __func__,
                  state.ToString());
    }
}
 
static void UpdateTipLog(const CCoinsViewCache &coins_tip,
                         const CBlockIndex *tip, const CChainParams &params,
                         const std::string &func_name,
                         const std::string &prefix)
    EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
    AssertLockHeld(::cs_main);
    LogPrintf("%s%s: new best=%s height=%d version=0x%08x log2_work=%f tx=%ld "
              "date='%s' progress=%f cache=%.1fMiB(%utxo)\n",
              prefix, func_name, tip->GetBlockHash().ToString(), tip->nHeight,
              tip->nVersion, log(tip->nChainWork.getdouble()) / log(2.0),
              tip->GetChainTxCount(),
              FormatISO8601DateTime(tip->GetBlockTime()),
              GuessVerificationProgress(params.TxData(), tip),
              coins_tip.DynamicMemoryUsage() * (1.0 / (1 << 20)),
              coins_tip.GetCacheSize());
}
 
void Chainstate::UpdateTip(const CBlockIndex *pindexNew) {
    AssertLockHeld(::cs_main);
    const auto &coins_tip = CoinsTip();
 
    const CChainParams &params{m_chainman.GetParams()};
 
    // The remainder of the function isn't relevant if we are not acting on
    // the active chainstate, so return if need be.
    if (this != &m_chainman.ActiveChainstate()) {
        // Only log every so often so that we don't bury log messages at the
        // tip.
        constexpr int BACKGROUND_LOG_INTERVAL = 2000;
        if (pindexNew->nHeight % BACKGROUND_LOG_INTERVAL == 0) {
            UpdateTipLog(coins_tip, pindexNew, params, __func__,
                         "[background validation] ");
        }
        return;
    }
 
    // New best block
    if (m_mempool) {
        m_mempool->AddTransactionsUpdated(1);
    }
 
    {
        LOCK(g_best_block_mutex);
        g_best_block = pindexNew;
        g_best_block_cv.notify_all();
    }
 
    UpdateTipLog(coins_tip, pindexNew, params, __func__, "");
}
 
bool Chainstate::DisconnectTip(BlockValidationState &state,
                               DisconnectedBlockTransactions *disconnectpool) {
    AssertLockHeld(cs_main);
    if (m_mempool) {
        AssertLockHeld(m_mempool->cs);
    }
 
    CBlockIndex *pindexDelete = m_chain.Tip();
 
    assert(pindexDelete);
    assert(pindexDelete->pprev);
 
    // Read block from disk.
    std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
    CBlock &block = *pblock;
    if (!m_blockman.ReadBlockFromDisk(block, *pindexDelete)) {
        return error("DisconnectTip(): Failed to read block");
    }
 
    // Apply the block atomically to the chain state.
    int64_t nStart = GetTimeMicros();
    {
        CCoinsViewCache view(&CoinsTip());
        assert(view.GetBestBlock() == pindexDelete->GetBlockHash());
        if (DisconnectBlock(block, pindexDelete, view) !=
            DisconnectResult::OK) {
            return error("DisconnectTip(): DisconnectBlock %s failed",
                         pindexDelete->GetBlockHash().ToString());
        }
 
        bool flushed = view.Flush();
        assert(flushed);
    }
 
    LogPrint(BCLog::BENCH, "- Disconnect block: %.2fms\n",
             (GetTimeMicros() - nStart) * MILLI);
 
    {
        // Prune locks that began at or after the tip should be moved backward
        // so they get a chance to reorg
        const int max_height_first{pindexDelete->nHeight - 1};
        for (auto &prune_lock : m_blockman.m_prune_locks) {
            if (prune_lock.second.height_first <= max_height_first) {
                continue;
            }
 
            prune_lock.second.height_first = max_height_first;
            LogPrint(BCLog::PRUNE, "%s prune lock moved back to %d\n",
                     prune_lock.first, max_height_first);
        }
    }
 
    // Write the chain state to disk, if necessary.
    if (!FlushStateToDisk(state, FlushStateMode::IF_NEEDED)) {
        return false;
    }
 
    if (m_mempool) {
        // If this block is deactivating a fork, we move all mempool
        // transactions in front of disconnectpool for reprocessing in a future
        // updateMempoolForReorg call
        if (pindexDelete->pprev != nullptr &&
            GetNextBlockScriptFlags(pindexDelete, m_chainman) !=
                GetNextBlockScriptFlags(pindexDelete->pprev, m_chainman)) {
            LogPrint(BCLog::MEMPOOL,
                     "Disconnecting mempool due to rewind of upgrade block\n");
            if (disconnectpool) {
                disconnectpool->importMempool(*m_mempool);
            }
            m_mempool->clear();
        }
 
        if (disconnectpool) {
            disconnectpool->addForBlock(block.vtx, *m_mempool);
        }
    }
 
    m_chain.SetTip(*pindexDelete->pprev);
 
    UpdateTip(pindexDelete->pprev);
    // Let wallets know transactions went from 1-confirmed to
    // 0-confirmed or conflicted:
    GetMainSignals().BlockDisconnected(pblock, pindexDelete);
    return true;
}
 
static int64_t nTimeReadFromDisk = 0;
static int64_t nTimeConnectTotal = 0;
static int64_t nTimeFlush = 0;
static int64_t nTimeChainState = 0;
static int64_t nTimePostConnect = 0;
 
bool Chainstate::ConnectTip(BlockValidationState &state,
                            BlockPolicyValidationState &blockPolicyState,
                            CBlockIndex *pindexNew,
                            const std::shared_ptr<const CBlock> &pblock,
                            DisconnectedBlockTransactions &disconnectpool,
                            const avalanche::Processor *const avalanche) {
    AssertLockHeld(cs_main);
    if (m_mempool) {
        AssertLockHeld(m_mempool->cs);
    }
 
    const Consensus::Params &consensusParams = m_chainman.GetConsensus();
 
    assert(pindexNew->pprev == m_chain.Tip());
    // Read block from disk.
    int64_t nTime1 = GetTimeMicros();
    std::shared_ptr<const CBlock> pthisBlock;
    if (!pblock) {
        std::shared_ptr<CBlock> pblockNew = std::make_shared<CBlock>();
        if (!m_blockman.ReadBlockFromDisk(*pblockNew, *pindexNew)) {
            return AbortNode(state, "Failed to read block");
        }
        pthisBlock = pblockNew;
    } else {
        pthisBlock = pblock;
    }
 
    const CBlock &blockConnecting = *pthisBlock;
 
    // Apply the block atomically to the chain state.
    int64_t nTime2 = GetTimeMicros();
    nTimeReadFromDisk += nTime2 - nTime1;
    int64_t nTime3;
    LogPrint(BCLog::BENCH, "  - Load block from disk: %.2fms [%.2fs]\n",
             (nTime2 - nTime1) * MILLI, nTimeReadFromDisk * MICRO);
    {
        Amount blockFees{Amount::zero()};
        CCoinsViewCache view(&CoinsTip());
        bool rv = ConnectBlock(blockConnecting, state, pindexNew, view,
                               BlockValidationOptions(m_chainman.GetConfig()),
                               &blockFees);
        GetMainSignals().BlockChecked(blockConnecting, state);
        if (!rv) {
            if (state.IsInvalid()) {
                InvalidBlockFound(pindexNew, state);
            }
 
            return error("%s: ConnectBlock %s failed, %s", __func__,
                         pindexNew->GetBlockHash().ToString(),
                         state.ToString());
        }
 
        const BlockHash blockhash = pindexNew->GetBlockHash();
        if (!IsInitialBlockDownload() &&
            !m_filterParkingPoliciesApplied.contains(blockhash)) {
            m_filterParkingPoliciesApplied.insert(blockhash);
 
            const Amount blockReward =
                blockFees +
                GetBlockSubsidy(pindexNew->nHeight, consensusParams);
 
            std::vector<std::unique_ptr<ParkingPolicy>> parkingPolicies;
            parkingPolicies.emplace_back(std::make_unique<MinerFundPolicy>(
                consensusParams, *pindexNew, blockConnecting, blockReward));
 
            if (avalanche) {
                // Only enable the RTT policy if the node already finalized a
                // block. This is because it's very possible that new blocks
                // will be parked after a node restart (but after IBD) if the
                // node is behind by a few blocks. We want to make sure that the
                // node will be able to switch back to the right tip in this
                // case.
                if (avalanche->hasFinalizedTip()) {
                    // Special case for testnet, don't reject blocks mined with
                    // the min difficulty
                    if (!consensusParams.fPowAllowMinDifficultyBlocks ||
                        (blockConnecting.GetBlockTime() <=
                         pindexNew->pprev->GetBlockTime() +
                             2 * consensusParams.nPowTargetSpacing)) {
                        parkingPolicies.emplace_back(
                            std::make_unique<RTTPolicy>(consensusParams,
                                                        *pindexNew));
                    }
                }
 
                parkingPolicies.emplace_back(
                    std::make_unique<StakingRewardsPolicy>(
                        *avalanche, consensusParams, *pindexNew,
                        blockConnecting, blockReward));
 
                if (m_mempool) {
                    parkingPolicies.emplace_back(
                        std::make_unique<PreConsensusPolicy>(
                            *pindexNew, blockConnecting, m_mempool));
                }
            }
 
            // If any block policy is violated, bail on the first one found
            if (std::find_if_not(parkingPolicies.begin(), parkingPolicies.end(),
                                 [&](const auto &policy) {
                                     bool ret = (*policy)(blockPolicyState);
                                     if (!ret) {
                                         LogPrintf(
                                             "Park block because it "
                                             "violated a block policy: %s\n",
                                             blockPolicyState.ToString());
                                     }
                                     return ret;
                                 }) != parkingPolicies.end()) {
                pindexNew->nStatus = pindexNew->nStatus.withParked();
                m_blockman.m_dirty_blockindex.insert(pindexNew);
                return false;
            }
        }
 
        nTime3 = GetTimeMicros();
        nTimeConnectTotal += nTime3 - nTime2;
        assert(nBlocksTotal > 0);
        LogPrint(BCLog::BENCH,
                 "  - Connect total: %.2fms [%.2fs (%.2fms/blk)]\n",
                 (nTime3 - nTime2) * MILLI, nTimeConnectTotal * MICRO,
                 nTimeConnectTotal * MILLI / nBlocksTotal);
        bool flushed = view.Flush();
        assert(flushed);
    }
 
    int64_t nTime4 = GetTimeMicros();
    nTimeFlush += nTime4 - nTime3;
    LogPrint(BCLog::BENCH, "  - Flush: %.2fms [%.2fs (%.2fms/blk)]\n",
             (nTime4 - nTime3) * MILLI, nTimeFlush * MICRO,
             nTimeFlush * MILLI / nBlocksTotal);
 
    // Write the chain state to disk, if necessary.
    if (!FlushStateToDisk(state, FlushStateMode::IF_NEEDED)) {
        return false;
    }
 
    int64_t nTime5 = GetTimeMicros();
    nTimeChainState += nTime5 - nTime4;
    LogPrint(BCLog::BENCH,
             "  - Writing chainstate: %.2fms [%.2fs (%.2fms/blk)]\n",
             (nTime5 - nTime4) * MILLI, nTimeChainState * MICRO,
             nTimeChainState * MILLI / nBlocksTotal);
 
    // Remove conflicting transactions from the mempool;
    if (m_mempool) {
        disconnectpool.removeForBlock(blockConnecting.vtx, *m_mempool);
 
        // If this block is activating a fork, we move all mempool transactions
        // in front of disconnectpool for reprocessing in a future
        // updateMempoolForReorg call
        if (pindexNew->pprev != nullptr &&
            GetNextBlockScriptFlags(pindexNew, m_chainman) !=
                GetNextBlockScriptFlags(pindexNew->pprev, m_chainman)) {
            LogPrint(
                BCLog::MEMPOOL,
                "Disconnecting mempool due to acceptance of upgrade block\n");
            disconnectpool.importMempool(*m_mempool);
        }
    }
 
    // Update m_chain & related variables.
    m_chain.SetTip(*pindexNew);
    UpdateTip(pindexNew);
 
    int64_t nTime6 = GetTimeMicros();
    nTimePostConnect += nTime6 - nTime5;
    nTimeTotal += nTime6 - nTime1;
    LogPrint(BCLog::BENCH,
             "  - Connect postprocess: %.2fms [%.2fs (%.2fms/blk)]\n",
             (nTime6 - nTime5) * MILLI, nTimePostConnect * MICRO,
             nTimePostConnect * MILLI / nBlocksTotal);
    LogPrint(BCLog::BENCH, "- Connect block: %.2fms [%.2fs (%.2fms/blk)]\n",
             (nTime6 - nTime1) * MILLI, nTimeTotal * MICRO,
             nTimeTotal * MILLI / nBlocksTotal);
 
    // If we are the background validation chainstate, check to see if we are
    // done validating the snapshot (i.e. our tip has reached the snapshot's
    // base block).
    if (this != &m_chainman.ActiveChainstate()) {
        // This call may set `m_disabled`, which is referenced immediately
        // afterwards in ActivateBestChain, so that we stop connecting blocks
        // past the snapshot base.
        m_chainman.MaybeCompleteSnapshotValidation();
    }
 
    GetMainSignals().BlockConnected(pthisBlock, pindexNew);
    return true;
}
 
CBlockIndex *Chainstate::FindMostWorkChain(
    std::vector<const CBlockIndex *> &blocksToReconcile, bool fAutoUnpark) {
    AssertLockHeld(::cs_main);
    do {
        CBlockIndex *pindexNew = nullptr;
 
        // Find the best candidate header.
        {
            std::set<CBlockIndex *, CBlockIndexWorkComparator>::reverse_iterator
                it = setBlockIndexCandidates.rbegin();
            if (it == setBlockIndexCandidates.rend()) {
                return nullptr;
            }
            pindexNew = *it;
        }
 
        // If this block will cause an avalanche finalized block to be reorged,
        // then we park it.
        {
            LOCK(cs_avalancheFinalizedBlockIndex);
            if (m_avalancheFinalizedBlockIndex &&
                !AreOnTheSameFork(pindexNew, m_avalancheFinalizedBlockIndex)) {
                LogPrintf("Park block %s because it forks prior to the "
                          "avalanche finalized chaintip.\n",
                          pindexNew->GetBlockHash().ToString());
                pindexNew->nStatus = pindexNew->nStatus.withParked();
                m_blockman.m_dirty_blockindex.insert(pindexNew);
            }
        }
 
        const CBlockIndex *pindexFork = m_chain.FindFork(pindexNew);
 
        // Check whether all blocks on the path between the currently active
        // chain and the candidate are valid. Just going until the active chain
        // is an optimization, as we know all blocks in it are valid already.
        CBlockIndex *pindexTest = pindexNew;
        bool hasValidAncestor = true;
        while (hasValidAncestor && pindexTest && pindexTest != pindexFork) {
            assert(pindexTest->HaveTxsDownloaded() || pindexTest->nHeight == 0);
 
            // If this is a parked chain, but it has enough PoW, clear the park
            // state.
            bool fParkedChain = pindexTest->nStatus.isOnParkedChain();
            if (fAutoUnpark && fParkedChain) {
                const CBlockIndex *pindexTip = m_chain.Tip();
 
                // During initialization, pindexTip and/or pindexFork may be
                // null. In this case, we just ignore the fact that the chain is
                // parked.
                if (!pindexTip || !pindexFork) {
                    UnparkBlock(pindexTest);
                    continue;
                }
 
                // A parked chain can be unparked if it has twice as much PoW
                // accumulated as the main chain has since the fork block.
                CBlockIndex const *pindexExtraPow = pindexTip;
                arith_uint256 requiredWork = pindexTip->nChainWork;
                switch (pindexTip->nHeight - pindexFork->nHeight) {
                    // Limit the penality for depth 1, 2 and 3 to half a block
                    // worth of work to ensure we don't fork accidentally.
                    case 3:
                    case 2:
                        pindexExtraPow = pindexExtraPow->pprev;
                    // FALLTHROUGH
                    case 1: {
                        const arith_uint256 deltaWork =
                            pindexExtraPow->nChainWork - pindexFork->nChainWork;
                        requiredWork += (deltaWork >> 1);
                        break;
                    }
                    default:
                        requiredWork +=
                            pindexExtraPow->nChainWork - pindexFork->nChainWork;
                        break;
                }
 
                if (pindexNew->nChainWork > requiredWork) {
                    // We have enough, clear the parked state.
                    LogPrintf("Unpark chain up to block %s as it has "
                              "accumulated enough PoW.\n",
                              pindexNew->GetBlockHash().ToString());
                    fParkedChain = false;
                    UnparkBlock(pindexTest);
                }
            }
 
            // Pruned nodes may have entries in setBlockIndexCandidates for
            // which block files have been deleted. Remove those as candidates
            // for the most work chain if we come across them; we can't switch
            // to a chain unless we have all the non-active-chain parent blocks.
            bool fInvalidChain = pindexTest->nStatus.isInvalid();
            bool fMissingData = !pindexTest->nStatus.hasData();
            if (!(fInvalidChain || fParkedChain || fMissingData)) {
                // The current block is acceptable, move to the parent, up to
                // the fork point.
                pindexTest = pindexTest->pprev;
                continue;
            }
 
            // Candidate chain is not usable (either invalid or parked or
            // missing data)
            hasValidAncestor = false;
            setBlockIndexCandidates.erase(pindexTest);
 
            if (fInvalidChain && (m_chainman.m_best_invalid == nullptr ||
                                  pindexNew->nChainWork >
                                      m_chainman.m_best_invalid->nChainWork)) {
                m_chainman.m_best_invalid = pindexNew;
            }
 
            if (fParkedChain && (m_chainman.m_best_parked == nullptr ||
                                 pindexNew->nChainWork >
                                     m_chainman.m_best_parked->nChainWork)) {
                m_chainman.m_best_parked = pindexNew;
            }
 
            LogPrintf("Considered switching to better tip %s but that chain "
                      "contains a%s%s%s block.\n",
                      pindexNew->GetBlockHash().ToString(),
                      fInvalidChain ? "n invalid" : "",
                      fParkedChain ? " parked" : "",
                      fMissingData ? " missing-data" : "");
 
            CBlockIndex *pindexFailed = pindexNew;
            // Remove the entire chain from the set.
            while (pindexTest != pindexFailed) {
                if (fInvalidChain || fParkedChain) {
                    pindexFailed->nStatus =
                        pindexFailed->nStatus.withFailedParent(fInvalidChain)
                            .withParkedParent(fParkedChain);
                } else if (fMissingData) {
                    // If we're missing data, then add back to
                    // m_blocks_unlinked, so that if the block arrives in the
                    // future we can try adding to setBlockIndexCandidates
                    // again.
                    m_blockman.m_blocks_unlinked.insert(
                        std::make_pair(pindexFailed->pprev, pindexFailed));
                }
                setBlockIndexCandidates.erase(pindexFailed);
                pindexFailed = pindexFailed->pprev;
            }
 
            if (fInvalidChain || fParkedChain) {
                // We discovered a new chain tip that is either parked or
                // invalid, we may want to warn.
                CheckForkWarningConditionsOnNewFork(pindexNew);
            }
        }
 
        blocksToReconcile.push_back(pindexNew);
 
        // We found a candidate that has valid ancestors. This is our guy.
        if (hasValidAncestor) {
            return pindexNew;
        }
    } while (true);
}
 
void Chainstate::PruneBlockIndexCandidates() {
    // Note that we can't delete the current block itself, as we may need to
    // return to it later in case a reorganization to a better block fails.
    auto it = setBlockIndexCandidates.begin();
    while (it != setBlockIndexCandidates.end() &&
           setBlockIndexCandidates.value_comp()(*it, m_chain.Tip())) {
        setBlockIndexCandidates.erase(it++);
    }
 
    // Either the current tip or a successor of it we're working towards is left
    // in setBlockIndexCandidates.
    assert(!setBlockIndexCandidates.empty());
}
 
bool Chainstate::ActivateBestChainStep(
    BlockValidationState &state, CBlockIndex *pindexMostWork,
    const std::shared_ptr<const CBlock> &pblock, bool &fInvalidFound,
    const avalanche::Processor *const avalanche) {
    AssertLockHeld(cs_main);
    if (m_mempool) {
        AssertLockHeld(m_mempool->cs);
    }
 
    const CBlockIndex *pindexOldTip = m_chain.Tip();
    const CBlockIndex *pindexFork = m_chain.FindFork(pindexMostWork);
 
    // Disconnect active blocks which are no longer in the best chain.
    bool fBlocksDisconnected = false;
    DisconnectedBlockTransactions disconnectpool;
    while (m_chain.Tip() && m_chain.Tip() != pindexFork) {
        if (!fBlocksDisconnected) {
            // Import and clear mempool; we must do this to preserve
            // topological ordering in the mempool index. This is ok since
            // inserts into the mempool are very fast now in our new
            // implementation.
            disconnectpool.importMempool(*m_mempool);
        }
 
        if (!DisconnectTip(state, &disconnectpool)) {
            // This is likely a fatal error, but keep the mempool consistent,
            // just in case. Only remove from the mempool in this case.
            if (m_mempool) {
                disconnectpool.updateMempoolForReorg(*this, false, *m_mempool);
            }
 
            // If we're unable to disconnect a block during normal operation,
            // then that is a failure of our local system -- we should abort
            // rather than stay on a less work chain.
            AbortNode(state,
                      "Failed to disconnect block; see debug.log for details");
            return false;
        }
 
        fBlocksDisconnected = true;
    }
 
    // Build list of new blocks to connect.
    std::vector<CBlockIndex *> vpindexToConnect;
    bool fContinue = true;
    int nHeight = pindexFork ? pindexFork->nHeight : -1;
    while (fContinue && nHeight != pindexMostWork->nHeight) {
        // Don't iterate the entire list of potential improvements toward the
        // best tip, as we likely only need a few blocks along the way.
        int nTargetHeight = std::min(nHeight + 32, pindexMostWork->nHeight);
        vpindexToConnect.clear();
        vpindexToConnect.reserve(nTargetHeight - nHeight);
        CBlockIndex *pindexIter = pindexMostWork->GetAncestor(nTargetHeight);
        while (pindexIter && pindexIter->nHeight != nHeight) {
            vpindexToConnect.push_back(pindexIter);
            pindexIter = pindexIter->pprev;
        }
 
        nHeight = nTargetHeight;
 
        // Connect new blocks.
        for (CBlockIndex *pindexConnect : reverse_iterate(vpindexToConnect)) {
            BlockPolicyValidationState blockPolicyState;
            if (!ConnectTip(state, blockPolicyState, pindexConnect,
                            pindexConnect == pindexMostWork
                                ? pblock
                                : std::shared_ptr<const CBlock>(),
                            disconnectpool, avalanche)) {
                if (state.IsInvalid()) {
                    // The block violates a consensus rule.
                    if (state.GetResult() !=
                        BlockValidationResult::BLOCK_MUTATED) {
                        InvalidChainFound(vpindexToConnect.back());
                    }
                    state = BlockValidationState();
                    fInvalidFound = true;
                    fContinue = false;
                    break;
                }
 
                if (blockPolicyState.IsInvalid()) {
                    // The block violates a policy rule.
                    fContinue = false;
                    break;
                }
 
                // A system error occurred (disk space, database error, ...).
                // Make the mempool consistent with the current tip, just in
                // case any observers try to use it before shutdown.
                if (m_mempool) {
                    disconnectpool.updateMempoolForReorg(*this, false,
                                                         *m_mempool);
                }
                return false;
            } else {
                PruneBlockIndexCandidates();
                if (!pindexOldTip ||
                    m_chain.Tip()->nChainWork > pindexOldTip->nChainWork) {
                    // We're in a better position than we were. Return
                    // temporarily to release the lock.
                    fContinue = false;
                    break;
                }
            }
        }
    }
 
    if (m_mempool) {
        if (fBlocksDisconnected || !disconnectpool.isEmpty()) {
            // If any blocks were disconnected, we need to update the mempool
            // even if disconnectpool is empty. The disconnectpool may also be
            // non-empty if the mempool was imported due to new validation rules
            // being in effect.
            LogPrint(BCLog::MEMPOOL,
                     "Updating mempool due to reorganization or "
                     "rules upgrade/downgrade\n");
            disconnectpool.updateMempoolForReorg(*this, true, *m_mempool);
        }
 
        m_mempool->check(this->CoinsTip(), this->m_chain.Height() + 1);
    }
 
    // Callbacks/notifications for a new best chain.
    if (fInvalidFound) {
        CheckForkWarningConditionsOnNewFork(pindexMostWork);
    } else {
        CheckForkWarningConditions();
    }
 
    return true;
}
 
static SynchronizationState GetSynchronizationState(bool init) {
    if (!init) {
        return SynchronizationState::POST_INIT;
    }
    if (::fReindex) {
        return SynchronizationState::INIT_REINDEX;
    }
    return SynchronizationState::INIT_DOWNLOAD;
}
 
static bool NotifyHeaderTip(Chainstate &chainstate) LOCKS_EXCLUDED(cs_main) {
    bool fNotify = false;
    bool fInitialBlockDownload = false;
    static CBlockIndex *pindexHeaderOld = nullptr;
    CBlockIndex *pindexHeader = nullptr;
    {
        LOCK(cs_main);
        pindexHeader = chainstate.m_chainman.m_best_header;
 
        if (pindexHeader != pindexHeaderOld) {
            fNotify = true;
            fInitialBlockDownload = chainstate.IsInitialBlockDownload();
            pindexHeaderOld = pindexHeader;
        }
    }
 
    // Send block tip changed notifications without cs_main
    if (fNotify) {
        chainstate.m_chainman.GetNotifications().headerTip(
            GetSynchronizationState(fInitialBlockDownload),
            pindexHeader->nHeight, pindexHeader->nTime, false);
    }
    return fNotify;
}
 
static void LimitValidationInterfaceQueue() LOCKS_EXCLUDED(cs_main) {
    AssertLockNotHeld(cs_main);
 
    if (GetMainSignals().CallbacksPending() > 10) {
        SyncWithValidationInterfaceQueue();
    }
}
 
bool Chainstate::ActivateBestChain(BlockValidationState &state,
                                   std::shared_ptr<const CBlock> pblock,
                                   avalanche::Processor *const avalanche,
                                   bool skip_checkblockindex) {
    AssertLockNotHeld(m_chainstate_mutex);
 
    // Note that while we're often called here from ProcessNewBlock, this is
    // far from a guarantee. Things in the P2P/RPC will often end up calling
    // us in the middle of ProcessNewBlock - do not assume pblock is set
    // sanely for performance or correctness!
    AssertLockNotHeld(::cs_main);
 
    // ABC maintains a fair degree of expensive-to-calculate internal state
    // because this function periodically releases cs_main so that it does not
    // lock up other threads for too long during large connects - and to allow
    // for e.g. the callback queue to drain we use m_chainstate_mutex to enforce
    // mutual exclusion so that only one caller may execute this function at a
    // time
    LOCK(m_chainstate_mutex);
 
    // Belt-and-suspenders check that we aren't attempting to advance the
    // background chainstate past the snapshot base block.
    if (WITH_LOCK(::cs_main, return m_disabled)) {
        LogPrintf("m_disabled is set - this chainstate should not be in "
                  "operation. Please report this as a bug. %s\n",
                  PACKAGE_BUGREPORT);
        return false;
    }
 
    CBlockIndex *pindexMostWork = nullptr;
    CBlockIndex *pindexNewTip = nullptr;
    int nStopAtHeight = gArgs.GetIntArg("-stopatheight", DEFAULT_STOPATHEIGHT);
    do {
        // Block until the validation queue drains. This should largely
        // never happen in normal operation, however may happen during
        // reindex, causing memory blowup if we run too far ahead.
        // Note that if a validationinterface callback ends up calling
        // ActivateBestChain this may lead to a deadlock! We should
        // probably have a DEBUG_LOCKORDER test for this in the future.
        LimitValidationInterfaceQueue();
 
        std::vector<const CBlockIndex *> blocksToReconcile;
        bool blocks_connected = false;
 
        const bool fAutoUnpark =
            gArgs.GetBoolArg("-automaticunparking", !avalanche);
 
        {
            LOCK(cs_main);
            // Lock transaction pool for at least as long as it takes for
            // updateMempoolForReorg to be executed if needed
            LOCK(MempoolMutex());
            CBlockIndex *starting_tip = m_chain.Tip();
            do {
                // We absolutely may not unlock cs_main until we've made forward
                // progress (with the exception of shutdown due to hardware
                // issues, low disk space, etc).
 
                if (pindexMostWork == nullptr) {
                    pindexMostWork =
                        FindMostWorkChain(blocksToReconcile, fAutoUnpark);
                }
 
                // Whether we have anything to do at all.
                if (pindexMostWork == nullptr ||
                    pindexMostWork == m_chain.Tip()) {
                    break;
                }
 
                bool fInvalidFound = false;
                std::shared_ptr<const CBlock> nullBlockPtr;
                if (!ActivateBestChainStep(
                        state, pindexMostWork,
                        pblock && pblock->GetHash() ==
                                      pindexMostWork->GetBlockHash()
                            ? pblock
                            : nullBlockPtr,
                        fInvalidFound, avalanche)) {
                    // A system error occurred
                    return false;
                }
                blocks_connected = true;
 
                if (fInvalidFound ||
                    (pindexMostWork && pindexMostWork->nStatus.isParked())) {
                    // Wipe cache, we may need another branch now.
                    pindexMostWork = nullptr;
                }
 
                pindexNewTip = m_chain.Tip();
 
                // This will have been toggled in
                // ActivateBestChainStep -> ConnectTip ->
                // MaybeCompleteSnapshotValidation, if at all, so we should
                // catch it here.
                //
                // Break this do-while to ensure we don't advance past the base
                // snapshot.
                if (m_disabled) {
                    break;
                }
            } while (!m_chain.Tip() ||
                     (starting_tip && CBlockIndexWorkComparator()(
                                          m_chain.Tip(), starting_tip)));
 
            // Check the index once we're done with the above loop, since
            // we're going to release cs_main soon. If the index is in a bad
            // state now, then it's better to know immediately rather than
            // randomly have it cause a problem in a race.
            if (!skip_checkblockindex) {
                CheckBlockIndex();
            }
 
            if (blocks_connected) {
                const CBlockIndex *pindexFork = m_chain.FindFork(starting_tip);
                bool fInitialDownload = IsInitialBlockDownload();
 
                // Notify external listeners about the new tip.
                // Enqueue while holding cs_main to ensure that UpdatedBlockTip
                // is called in the order in which blocks are connected
                if (pindexFork != pindexNewTip) {
                    // Notify ValidationInterface subscribers
                    GetMainSignals().UpdatedBlockTip(pindexNewTip, pindexFork,
                                                     fInitialDownload);
 
                    // Always notify the UI if a new block tip was connected
                    m_chainman.GetNotifications().blockTip(
                        GetSynchronizationState(fInitialDownload),
                        *pindexNewTip);
                }
            }
        }
        // When we reach this point, we switched to a new tip (stored in
        // pindexNewTip).
        if (avalanche) {
            const CBlockIndex *pfinalized =
                WITH_LOCK(cs_avalancheFinalizedBlockIndex,
                          return m_avalancheFinalizedBlockIndex);
            for (const CBlockIndex *pindex : blocksToReconcile) {
                avalanche->addToReconcile(pindex);
 
                // Compute staking rewards for all blocks with more chainwork to
                // just after the finalized block. We could stop at the fork
                // point, but this is more robust.
                if (blocks_connected) {
                    const CBlockIndex *pindexTest = pindex;
                    while (pindexTest && pindexTest != pfinalized) {
                        if (pindexTest->nHeight < pindex->nHeight - 3) {
                            // Only compute up to some max depth
                            break;
                        }
                        avalanche->computeStakingReward(pindexTest);
                        pindexTest = pindexTest->pprev;
                    }
                }
            }
        }
 
        if (!blocks_connected) {
            return true;
        }
 
        if (nStopAtHeight && pindexNewTip &&
            pindexNewTip->nHeight >= nStopAtHeight) {
            StartShutdown();
        }
 
        if (WITH_LOCK(::cs_main, return m_disabled)) {
            // Background chainstate has reached the snapshot base block, so
            // exit.
            break;
        }
 
        // We check shutdown only after giving ActivateBestChainStep a chance to
        // run once so that we never shutdown before connecting the genesis
        // block during LoadChainTip(). Previously this caused an assert()
        // failure during shutdown in such cases as the UTXO DB flushing checks
        // that the best block hash is non-null.
        if (ShutdownRequested()) {
            break;
        }
    } while (pindexNewTip != pindexMostWork);
 
    // Write changes periodically to disk, after relay.
    if (!FlushStateToDisk(state, FlushStateMode::PERIODIC)) {
        return false;
    }
 
    return true;
}
 
bool Chainstate::PreciousBlock(BlockValidationState &state, CBlockIndex *pindex,
                               avalanche::Processor *const avalanche) {
    AssertLockNotHeld(m_chainstate_mutex);
    AssertLockNotHeld(::cs_main);
    {
        LOCK(cs_main);
        if (pindex->nChainWork < m_chain.Tip()->nChainWork) {
            // Nothing to do, this block is not at the tip.
            return true;
        }
 
        if (m_chain.Tip()->nChainWork > nLastPreciousChainwork) {
            // The chain has been extended since the last call, reset the
            // counter.
            nBlockReverseSequenceId = -1;
        }
 
        nLastPreciousChainwork = m_chain.Tip()->nChainWork;
        setBlockIndexCandidates.erase(pindex);
        pindex->nSequenceId = nBlockReverseSequenceId;
        if (nBlockReverseSequenceId > std::numeric_limits<int32_t>::min()) {
            // We can't keep reducing the counter if somebody really wants to
            // call preciousblock 2**31-1 times on the same set of tips...
            nBlockReverseSequenceId--;
        }
 
        // In case this was parked, unpark it.
        UnparkBlock(pindex);
 
        // Make sure it is added to the candidate list if appropriate.
        if (pindex->IsValid(BlockValidity::TRANSACTIONS) &&
            pindex->HaveTxsDownloaded()) {
            setBlockIndexCandidates.insert(pindex);
            PruneBlockIndexCandidates();
        }
    }
 
    return ActivateBestChain(state, /*pblock=*/nullptr, avalanche);
}
 
namespace {
// Leverage RAII to run a functor at scope end
template <typename Func> struct Defer {
    Func func;
    Defer(Func &&f) : func(std::move(f)) {}
    ~Defer() { func(); }
};
} // namespace
 
bool Chainstate::UnwindBlock(BlockValidationState &state, CBlockIndex *pindex,
                             bool invalidate) {
    // Genesis block can't be invalidated or parked
    assert(pindex);
    if (pindex->nHeight == 0) {
        return false;
    }
 
    CBlockIndex *to_mark_failed_or_parked = pindex;
    bool pindex_was_in_chain = false;
    int disconnected = 0;
 
    // We do not allow ActivateBestChain() to run while UnwindBlock() is
    // running, as that could cause the tip to change while we disconnect
    // blocks. (Note for backport of Core PR16849: we acquire
    // LOCK(m_chainstate_mutex) in the Park, Invalidate and FinalizeBlock
    // functions due to differences in our code)
    AssertLockHeld(m_chainstate_mutex);
 
    // We'll be acquiring and releasing cs_main below, to allow the validation
    // callbacks to run. However, we should keep the block index in a
    // consistent state as we disconnect blocks -- in particular we need to
    // add equal-work blocks to setBlockIndexCandidates as we disconnect.
    // To avoid walking the block index repeatedly in search of candidates,
    // build a map once so that we can look up candidate blocks by chain
    // work as we go.
    std::multimap<const arith_uint256, CBlockIndex *> candidate_blocks_by_work;
 
    {
        LOCK(cs_main);
        for (auto &entry : m_blockman.m_block_index) {
            CBlockIndex *candidate = &entry.second;
            // We don't need to put anything in our active chain into the
            // multimap, because those candidates will be found and considered
            // as we disconnect.
            // Instead, consider only non-active-chain blocks that have at
            // least as much work as where we expect the new tip to end up.
            if (!m_chain.Contains(candidate) &&
                !CBlockIndexWorkComparator()(candidate, pindex->pprev) &&
                candidate->IsValid(BlockValidity::TRANSACTIONS) &&
                candidate->HaveTxsDownloaded()) {
                candidate_blocks_by_work.insert(
                    std::make_pair(candidate->nChainWork, candidate));
            }
        }
    }
 
    {
        LOCK(cs_main);
        // Lock for as long as disconnectpool is in scope to make sure
        // UpdateMempoolForReorg is called after DisconnectTip without unlocking
        // in between
        LOCK(MempoolMutex());
 
        constexpr int maxDisconnectPoolBlocks = 10;
        bool ret = false;
        DisconnectedBlockTransactions disconnectpool;
        // After 10 blocks this becomes nullptr, so that DisconnectTip will
        // stop giving us unwound block txs if we are doing a deep unwind.
        DisconnectedBlockTransactions *optDisconnectPool = &disconnectpool;
 
        // Disable thread safety analysis because we can't require m_mempool->cs
        // as m_mempool can be null. We keep the runtime analysis though.
        Defer deferred([&]() NO_THREAD_SAFETY_ANALYSIS {
            AssertLockHeld(cs_main);
            if (m_mempool && !disconnectpool.isEmpty()) {
                AssertLockHeld(m_mempool->cs);
                // DisconnectTip will add transactions to disconnectpool.
                // When all unwinding is done and we are on a new tip, we must
                // add all transactions back to the mempool against the new tip.
                disconnectpool.updateMempoolForReorg(*this,
                                                     /* fAddToMempool = */ ret,
                                                     *m_mempool);
            }
        });
 
        // Disconnect (descendants of) pindex, and mark them invalid.
        while (true) {
            if (ShutdownRequested()) {
                break;
            }
 
            // Make sure the queue of validation callbacks doesn't grow
            // unboundedly.
            // FIXME this commented code is a regression and could cause OOM if
            // a very old block is invalidated via the invalidateblock RPC.
            // This can be uncommented if the main signals are moved away from
            // cs_main or this code is refactored so that cs_main can be
            // released at this point.
            //
            // LimitValidationInterfaceQueue();
 
            if (!m_chain.Contains(pindex)) {
                break;
            }
 
            if (m_mempool && disconnected == 0) {
                // On first iteration, we grab all the mempool txs to preserve
                // topological ordering. This has the side-effect of temporarily
                // clearing the mempool, but we will re-add later in
                // updateMempoolForReorg() (above). This technique guarantees
                // mempool consistency as well as ensures that our topological
                // entry_id index is always correct.
                disconnectpool.importMempool(*m_mempool);
            }
 
            pindex_was_in_chain = true;
            CBlockIndex *invalid_walk_tip = m_chain.Tip();
 
            // ActivateBestChain considers blocks already in m_chain
            // unconditionally valid already, so force disconnect away from it.
 
            ret = DisconnectTip(state, optDisconnectPool);
            ++disconnected;
 
            if (optDisconnectPool && disconnected > maxDisconnectPoolBlocks) {
                // Stop using the disconnect pool after 10 blocks. After 10
                // blocks we no longer add block tx's to the disconnectpool.
                // However, when this scope ends we will reconcile what's
                // in the pool with the new tip (in the deferred d'tor above).
                optDisconnectPool = nullptr;
            }
 
            if (!ret) {
                return false;
            }
 
            assert(invalid_walk_tip->pprev == m_chain.Tip());
 
            // We immediately mark the disconnected blocks as invalid.
            // This prevents a case where pruned nodes may fail to
            // invalidateblock and be left unable to start as they have no tip
            // candidates (as there are no blocks that meet the "have data and
            // are not invalid per nStatus" criteria for inclusion in
            // setBlockIndexCandidates).
 
            invalid_walk_tip->nStatus =
                invalidate ? invalid_walk_tip->nStatus.withFailed()
                           : invalid_walk_tip->nStatus.withParked();
 
            m_blockman.m_dirty_blockindex.insert(invalid_walk_tip);
            setBlockIndexCandidates.insert(invalid_walk_tip->pprev);
 
            if (invalid_walk_tip == to_mark_failed_or_parked->pprev &&
                (invalidate ? to_mark_failed_or_parked->nStatus.hasFailed()
                            : to_mark_failed_or_parked->nStatus.isParked())) {
                // We only want to mark the last disconnected block as
                // Failed (or Parked); its children need to be FailedParent (or
                // ParkedParent) instead.
                to_mark_failed_or_parked->nStatus =
                    (invalidate
                         ? to_mark_failed_or_parked->nStatus.withFailed(false)
                               .withFailedParent()
                         : to_mark_failed_or_parked->nStatus.withParked(false)
                               .withParkedParent());
 
                m_blockman.m_dirty_blockindex.insert(to_mark_failed_or_parked);
            }
 
            // Add any equal or more work headers to setBlockIndexCandidates
            auto candidate_it = candidate_blocks_by_work.lower_bound(
                invalid_walk_tip->pprev->nChainWork);
            while (candidate_it != candidate_blocks_by_work.end()) {
                if (!CBlockIndexWorkComparator()(candidate_it->second,
                                                 invalid_walk_tip->pprev)) {
                    setBlockIndexCandidates.insert(candidate_it->second);
                    candidate_it = candidate_blocks_by_work.erase(candidate_it);
                } else {
                    ++candidate_it;
                }
            }
 
            // Track the last disconnected block, so we can correct its
            // FailedParent (or ParkedParent) status in future iterations, or,
            // if it's the last one, call InvalidChainFound on it.
            to_mark_failed_or_parked = invalid_walk_tip;
        }
    }
 
    CheckBlockIndex();
 
    {
        LOCK(cs_main);
        if (m_chain.Contains(to_mark_failed_or_parked)) {
            // If the to-be-marked invalid block is in the active chain,
            // something is interfering and we can't proceed.
            return false;
        }
 
        // Mark pindex (or the last disconnected block) as invalid (or parked),
        // even when it never was in the main chain.
        to_mark_failed_or_parked->nStatus =
            invalidate ? to_mark_failed_or_parked->nStatus.withFailed()
                       : to_mark_failed_or_parked->nStatus.withParked();
        m_blockman.m_dirty_blockindex.insert(to_mark_failed_or_parked);
        if (invalidate) {
            m_chainman.m_failed_blocks.insert(to_mark_failed_or_parked);
        }
 
        // If any new blocks somehow arrived while we were disconnecting
        // (above), then the pre-calculation of what should go into
        // setBlockIndexCandidates may have missed entries. This would
        // technically be an inconsistency in the block index, but if we clean
        // it up here, this should be an essentially unobservable error.
        // Loop back over all block index entries and add any missing entries
        // to setBlockIndexCandidates.
        for (auto &[_, block_index] : m_blockman.m_block_index) {
            if (block_index.IsValid(BlockValidity::TRANSACTIONS) &&
                block_index.HaveTxsDownloaded() &&
                !setBlockIndexCandidates.value_comp()(&block_index,
                                                      m_chain.Tip())) {
                setBlockIndexCandidates.insert(&block_index);
            }
        }
 
        if (invalidate) {
            InvalidChainFound(to_mark_failed_or_parked);
        }
    }
 
    // Only notify about a new block tip if the active chain was modified.
    if (pindex_was_in_chain) {
        m_chainman.GetNotifications().blockTip(
            GetSynchronizationState(IsInitialBlockDownload()),
            *to_mark_failed_or_parked->pprev);
    }
    return true;
}
 
bool Chainstate::InvalidateBlock(BlockValidationState &state,
                                 CBlockIndex *pindex) {
    AssertLockNotHeld(m_chainstate_mutex);
    AssertLockNotHeld(::cs_main);
    // See 'Note for backport of Core PR16849' in Chainstate::UnwindBlock
    LOCK(m_chainstate_mutex);
 
    return UnwindBlock(state, pindex, true);
}
 
bool Chainstate::ParkBlock(BlockValidationState &state, CBlockIndex *pindex) {
    AssertLockNotHeld(m_chainstate_mutex);
    AssertLockNotHeld(::cs_main);
    // See 'Note for backport of Core PR16849' in Chainstate::UnwindBlock
    LOCK(m_chainstate_mutex);
 
    return UnwindBlock(state, pindex, false);
}
 
template <typename F>
bool Chainstate::UpdateFlagsForBlock(CBlockIndex *pindexBase,
                                     CBlockIndex *pindex, F f) {
    BlockStatus newStatus = f(pindex->nStatus);
    if (pindex->nStatus != newStatus &&
        (!pindexBase ||
         pindex->GetAncestor(pindexBase->nHeight) == pindexBase)) {
        pindex->nStatus = newStatus;
        m_blockman.m_dirty_blockindex.insert(pindex);
        if (newStatus.isValid()) {
            m_chainman.m_failed_blocks.erase(pindex);
        }
 
        if (pindex->IsValid(BlockValidity::TRANSACTIONS) &&
            pindex->HaveTxsDownloaded() &&
            setBlockIndexCandidates.value_comp()(m_chain.Tip(), pindex)) {
            setBlockIndexCandidates.insert(pindex);
        }
        return true;
    }
    return false;
}
 
template <typename F, typename C, typename AC>
void Chainstate::UpdateFlags(CBlockIndex *pindex, CBlockIndex *&pindexReset,
                             F f, C fChild, AC fAncestorWasChanged) {
    AssertLockHeld(cs_main);
 
    // Update the current block and ancestors; while we're doing this, identify
    // which was the deepest ancestor we changed.
    CBlockIndex *pindexDeepestChanged = pindex;
    for (auto pindexAncestor = pindex; pindexAncestor != nullptr;
         pindexAncestor = pindexAncestor->pprev) {
        if (UpdateFlagsForBlock(nullptr, pindexAncestor, f)) {
            pindexDeepestChanged = pindexAncestor;
        }
    }
 
    if (pindexReset &&
        pindexReset->GetAncestor(pindexDeepestChanged->nHeight) ==
            pindexDeepestChanged) {
        // reset pindexReset if it had a modified ancestor.
        pindexReset = nullptr;
    }
 
    // Update all blocks under modified blocks.
    for (auto &[_, block_index] : m_blockman.m_block_index) {
        UpdateFlagsForBlock(pindex, &block_index, fChild);
        UpdateFlagsForBlock(pindexDeepestChanged, &block_index,
                            fAncestorWasChanged);
    }
}
 
void Chainstate::ResetBlockFailureFlags(CBlockIndex *pindex) {
    AssertLockHeld(cs_main);
 
    UpdateFlags(
        pindex, m_chainman.m_best_invalid,
        [](const BlockStatus status) {
            return status.withClearedFailureFlags();
        },
        [](const BlockStatus status) {
            return status.withClearedFailureFlags();
        },
        [](const BlockStatus status) {
            return status.withFailedParent(false);
        });
}
 
void Chainstate::UnparkBlockImpl(CBlockIndex *pindex, bool fClearChildren) {
    AssertLockHeld(cs_main);
 
    UpdateFlags(
        pindex, m_chainman.m_best_parked,
        [](const BlockStatus status) {
            return status.withClearedParkedFlags();
        },
        [fClearChildren](const BlockStatus status) {
            return fClearChildren ? status.withClearedParkedFlags()
                                  : status.withParkedParent(false);
        },
        [](const BlockStatus status) {
            return status.withParkedParent(false);
        });
}
 
void Chainstate::UnparkBlockAndChildren(CBlockIndex *pindex) {
    return UnparkBlockImpl(pindex, true);
}
 
void Chainstate::UnparkBlock(CBlockIndex *pindex) {
    return UnparkBlockImpl(pindex, false);
}
 
bool Chainstate::AvalancheFinalizeBlock(CBlockIndex *pindex,
                                        avalanche::Processor &avalanche) {
    if (!pindex) {
        return false;
    }
 
    if (!m_chain.Contains(pindex)) {
        LogPrint(BCLog::AVALANCHE,
                 "The block to mark finalized by avalanche is not on the "
                 "active chain: %s\n",
                 pindex->GetBlockHash().ToString());
        return false;
    }
 
    avalanche.cleanupStakingRewards(pindex->nHeight);
 
    if (IsBlockAvalancheFinalized(pindex)) {
        return true;
    }
 
    {
        LOCK(cs_avalancheFinalizedBlockIndex);
        m_avalancheFinalizedBlockIndex = pindex;
    }
 
    WITH_LOCK(cs_main, GetMainSignals().BlockFinalized(pindex));
 
    return true;
}
 
void Chainstate::ClearAvalancheFinalizedBlock() {
    LOCK(cs_avalancheFinalizedBlockIndex);
    m_avalancheFinalizedBlockIndex = nullptr;
}
 
bool Chainstate::IsBlockAvalancheFinalized(const CBlockIndex *pindex) const {
    LOCK(cs_avalancheFinalizedBlockIndex);
    return pindex && m_avalancheFinalizedBlockIndex &&
           m_avalancheFinalizedBlockIndex->GetAncestor(pindex->nHeight) ==
               pindex;
}
 
void Chainstate::ReceivedBlockTransactions(const CBlock &block,
                                           CBlockIndex *pindexNew,
                                           const FlatFilePos &pos) {
    pindexNew->nTx = block.vtx.size();
    pindexNew->nSize = ::GetSerializeSize(block, PROTOCOL_VERSION);
    pindexNew->nFile = pos.nFile;
    pindexNew->nDataPos = pos.nPos;
    pindexNew->nUndoPos = 0;
    pindexNew->nStatus = pindexNew->nStatus.withData();
    pindexNew->RaiseValidity(BlockValidity::TRANSACTIONS);
    m_blockman.m_dirty_blockindex.insert(pindexNew);
 
    if (pindexNew->UpdateChainStats()) {
        // If pindexNew is the genesis block or all parents are
        // BLOCK_VALID_TRANSACTIONS.
        std::deque<CBlockIndex *> queue;
        queue.push_back(pindexNew);
 
        // Recursively process any descendant blocks that now may be eligible to
        // be connected.
        while (!queue.empty()) {
            CBlockIndex *pindex = queue.front();
            queue.pop_front();
            pindex->UpdateChainStats();
            if (pindex->nSequenceId == 0) {
                // We assign a sequence is when transaction are received to
                // prevent a miner from being able to broadcast a block but not
                // its content. However, a sequence id may have been set
                // manually, for instance via PreciousBlock, in which case, we
                // don't need to assign one.
                pindex->nSequenceId = nBlockSequenceId++;
            }
 
            if (m_chain.Tip() == nullptr ||
                !setBlockIndexCandidates.value_comp()(pindex, m_chain.Tip())) {
                setBlockIndexCandidates.insert(pindex);
            }
 
            std::pair<std::multimap<CBlockIndex *, CBlockIndex *>::iterator,
                      std::multimap<CBlockIndex *, CBlockIndex *>::iterator>
                range = m_blockman.m_blocks_unlinked.equal_range(pindex);
            while (range.first != range.second) {
                std::multimap<CBlockIndex *, CBlockIndex *>::iterator it =
                    range.first;
                queue.push_back(it->second);
                range.first++;
                m_blockman.m_blocks_unlinked.erase(it);
            }
        }
    } else if (pindexNew->pprev &&
               pindexNew->pprev->IsValid(BlockValidity::TREE)) {
        m_blockman.m_blocks_unlinked.insert(
            std::make_pair(pindexNew->pprev, pindexNew));
    }
}
 
static bool CheckBlockHeader(const CBlockHeader &block,
                             BlockValidationState &state,
                             const Consensus::Params &params,
                             BlockValidationOptions validationOptions) {
    // Check proof of work matches claimed amount
    if (validationOptions.shouldValidatePoW() &&
        !CheckProofOfWork(block.GetHash(), block.nBits, params)) {
        return state.Invalid(BlockValidationResult::BLOCK_INVALID_HEADER,
                             "high-hash", "proof of work failed");
    }
 
    return true;
}
 
bool CheckBlock(const CBlock &block, BlockValidationState &state,
                const Consensus::Params &params,
                BlockValidationOptions validationOptions) {
    // These are checks that are independent of context.
    if (block.fChecked) {
        return true;
    }
 
    // Check that the header is valid (particularly PoW).  This is mostly
    // redundant with the call in AcceptBlockHeader.
    if (!CheckBlockHeader(block, state, params, validationOptions)) {
        return false;
    }
 
    // Check the merkle root.
    if (validationOptions.shouldValidateMerkleRoot()) {
        bool mutated;
        uint256 hashMerkleRoot2 = BlockMerkleRoot(block, &mutated);
        if (block.hashMerkleRoot != hashMerkleRoot2) {
            return state.Invalid(BlockValidationResult::BLOCK_MUTATED,
                                 "bad-txnmrklroot", "hashMerkleRoot mismatch");
        }
 
        // Check for merkle tree malleability (CVE-2012-2459): repeating
        // sequences of transactions in a block without affecting the merkle
        // root of a block, while still invalidating it.
        if (mutated) {
            return state.Invalid(BlockValidationResult::BLOCK_MUTATED,
                                 "bad-txns-duplicate", "duplicate transaction");
        }
    }
 
    // All potential-corruption validation must be done before we do any
    // transaction validation, as otherwise we may mark the header as invalid
    // because we receive the wrong transactions for it.
 
    // First transaction must be coinbase.
    if (block.vtx.empty()) {
        return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS,
                             "bad-cb-missing", "first tx is not coinbase");
    }
 
    // Size limits.
    auto nMaxBlockSize = validationOptions.getExcessiveBlockSize();
 
    // Bail early if there is no way this block is of reasonable size.
    if ((block.vtx.size() * MIN_TRANSACTION_SIZE) > nMaxBlockSize) {
        return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS,
                             "bad-blk-length", "size limits failed");
    }
 
    auto currentBlockSize = ::GetSerializeSize(block, PROTOCOL_VERSION);
    if (currentBlockSize > nMaxBlockSize) {
        return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS,
                             "bad-blk-length", "size limits failed");
    }
 
    // And a valid coinbase.
    TxValidationState tx_state;
    if (!CheckCoinbase(*block.vtx[0], tx_state)) {
        return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS,
                             tx_state.GetRejectReason(),
                             strprintf("Coinbase check failed (txid %s) %s",
                                       block.vtx[0]->GetId().ToString(),
                                       tx_state.GetDebugMessage()));
    }
 
    // Check transactions for regularity, skipping the first. Note that this
    // is the first time we check that all after the first are !IsCoinBase.
    for (size_t i = 1; i < block.vtx.size(); i++) {
        auto *tx = block.vtx[i].get();
        if (!CheckRegularTransaction(*tx, tx_state)) {
            return state.Invalid(
                BlockValidationResult::BLOCK_CONSENSUS,
                tx_state.GetRejectReason(),
                strprintf("Transaction check failed (txid %s) %s",
                          tx->GetId().ToString(), tx_state.GetDebugMessage()));
        }
    }
 
    if (validationOptions.shouldValidatePoW() &&
        validationOptions.shouldValidateMerkleRoot()) {
        block.fChecked = true;
    }
 
    return true;
}
 
bool HasValidProofOfWork(const std::vector<CBlockHeader> &headers,
                         const Consensus::Params &consensusParams) {
    return std::all_of(headers.cbegin(), headers.cend(),
                       [&](const auto &header) {
                           return CheckProofOfWork(
                               header.GetHash(), header.nBits, consensusParams);
                       });
}
 
arith_uint256 CalculateHeadersWork(const std::vector<CBlockHeader> &headers) {
    arith_uint256 total_work{0};
    for (const CBlockHeader &header : headers) {
        CBlockIndex dummy(header);
        total_work += GetBlockProof(dummy);
    }
    return total_work;
}
 
static bool ContextualCheckBlockHeader(
    const CBlockHeader &block, BlockValidationState &state,
    BlockManager &blockman, ChainstateManager &chainman,
    const CBlockIndex *pindexPrev, NodeClock::time_point now,
    const std::optional<CCheckpointData> &test_checkpoints = std::nullopt)
    EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
    AssertLockHeld(::cs_main);
    assert(pindexPrev != nullptr);
    const int nHeight = pindexPrev->nHeight + 1;
 
    const CChainParams &params = chainman.GetParams();
 
    // Check proof of work
    if (block.nBits != GetNextWorkRequired(pindexPrev, &block, params)) {
        LogPrintf("bad bits after height: %d\n", pindexPrev->nHeight);
        return state.Invalid(BlockValidationResult::BLOCK_INVALID_HEADER,
                             "bad-diffbits", "incorrect proof of work");
    }
 
    // Check against checkpoints
    if (chainman.m_options.checkpoints_enabled) {
        const CCheckpointData &checkpoints =
            test_checkpoints ? test_checkpoints.value() : params.Checkpoints();
 
        // Check that the block chain matches the known block chain up to a
        // checkpoint.
        if (!Checkpoints::CheckBlock(checkpoints, nHeight, block.GetHash())) {
            LogPrint(BCLog::VALIDATION,
                     "ERROR: %s: rejected by checkpoint lock-in at %d\n",
                     __func__, nHeight);
            return state.Invalid(BlockValidationResult::BLOCK_CHECKPOINT,
                                 "checkpoint mismatch");
        }
 
        // Don't accept any forks from the main chain prior to last checkpoint.
        // GetLastCheckpoint finds the last checkpoint in MapCheckpoints that's
        // in our BlockIndex().
 
        const CBlockIndex *pcheckpoint =
            blockman.GetLastCheckpoint(checkpoints);
        if (pcheckpoint && nHeight < pcheckpoint->nHeight) {
            LogPrint(BCLog::VALIDATION,
                     "ERROR: %s: forked chain older than last checkpoint "
                     "(height %d)\n",
                     __func__, nHeight);
            return state.Invalid(BlockValidationResult::BLOCK_CHECKPOINT,
                                 "bad-fork-prior-to-checkpoint");
        }
    }
 
    // Check timestamp against prev
    if (block.GetBlockTime() <= pindexPrev->GetMedianTimePast()) {
        return state.Invalid(BlockValidationResult::BLOCK_INVALID_HEADER,
                             "time-too-old", "block's timestamp is too early");
    }
 
    // Check timestamp
    if (block.Time() > now + std::chrono::seconds{MAX_FUTURE_BLOCK_TIME}) {
        return state.Invalid(BlockValidationResult::BLOCK_TIME_FUTURE,
                             "time-too-new",
                             "block timestamp too far in the future");
    }
 
    // Reject blocks with outdated version
    if ((block.nVersion < 2 &&
         DeploymentActiveAfter(pindexPrev, chainman,
                               Consensus::DEPLOYMENT_HEIGHTINCB)) ||
        (block.nVersion < 3 &&
         DeploymentActiveAfter(pindexPrev, chainman,
                               Consensus::DEPLOYMENT_DERSIG)) ||
        (block.nVersion < 4 &&
         DeploymentActiveAfter(pindexPrev, chainman,
                               Consensus::DEPLOYMENT_CLTV))) {
        return state.Invalid(
            BlockValidationResult::BLOCK_INVALID_HEADER,
            strprintf("bad-version(0x%08x)", block.nVersion),
            strprintf("rejected nVersion=0x%08x block", block.nVersion));
    }
 
    return true;
}
 
bool ContextualCheckTransactionForCurrentBlock(
    const CBlockIndex &active_chain_tip, const Consensus::Params &params,
    const CTransaction &tx, TxValidationState &state) {
    AssertLockHeld(cs_main);
 
    // ContextualCheckTransactionForCurrentBlock() uses
    // active_chain_tip.Height()+1 to evaluate nLockTime because when
    // IsFinalTx() is called within AcceptBlock(), the height of the
    // block *being* evaluated is what is used. Thus if we want to know if a
    // transaction can be part of the *next* block, we need to call
    // ContextualCheckTransaction() with one more than
    // active_chain_tip.Height().
    const int nBlockHeight = active_chain_tip.nHeight + 1;
 
    // BIP113 will require that time-locked transactions have nLockTime set to
    // less than the median time of the previous block they're contained in.
    // When the next block is created its previous block will be the current
    // chain tip, so we use that to calculate the median time passed to
    // ContextualCheckTransaction().
    // This time can also be used for consensus upgrades.
    const int64_t nMedianTimePast{active_chain_tip.GetMedianTimePast()};
 
    return ContextualCheckTransaction(params, tx, state, nBlockHeight,
                                      nMedianTimePast);
}
 
static bool ContextualCheckBlock(const CBlock &block,
                                 BlockValidationState &state,
                                 const ChainstateManager &chainman,
                                 const CBlockIndex *pindexPrev) {
    const int nHeight = pindexPrev == nullptr ? 0 : pindexPrev->nHeight + 1;
 
    // Enforce BIP113 (Median Time Past).
    bool enforce_locktime_median_time_past{false};
    if (DeploymentActiveAfter(pindexPrev, chainman,
                              Consensus::DEPLOYMENT_CSV)) {
        assert(pindexPrev != nullptr);
        enforce_locktime_median_time_past = true;
    }
 
    const int64_t nMedianTimePast =
        pindexPrev == nullptr ? 0 : pindexPrev->GetMedianTimePast();
 
    const int64_t nLockTimeCutoff{enforce_locktime_median_time_past
                                      ? nMedianTimePast
                                      : block.GetBlockTime()};
 
    const Consensus::Params params = chainman.GetConsensus();
    const bool fIsMagneticAnomalyEnabled =
        IsMagneticAnomalyEnabled(params, pindexPrev);
 
    // Check transactions:
    // - canonical ordering
    // - ensure they are finalized
    // - check they have the minimum size
    const CTransaction *prevTx = nullptr;
    for (const auto &ptx : block.vtx) {
        const CTransaction &tx = *ptx;
        if (fIsMagneticAnomalyEnabled) {
            if (prevTx && (tx.GetId() <= prevTx->GetId())) {
                if (tx.GetId() == prevTx->GetId()) {
                    return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS,
                                         "tx-duplicate",
                                         strprintf("Duplicated transaction %s",
                                                   tx.GetId().ToString()));
                }
 
                return state.Invalid(
                    BlockValidationResult::BLOCK_CONSENSUS, "tx-ordering",
                    strprintf("Transaction order is invalid (%s < %s)",
                              tx.GetId().ToString(),
                              prevTx->GetId().ToString()));
            }
 
            if (prevTx || !tx.IsCoinBase()) {
                prevTx = &tx;
            }
        }
 
        TxValidationState tx_state;
        if (!ContextualCheckTransaction(params, tx, tx_state, nHeight,
                                        nLockTimeCutoff)) {
            return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS,
                                 tx_state.GetRejectReason(),
                                 tx_state.GetDebugMessage());
        }
    }
 
    // Enforce rule that the coinbase starts with serialized block height
    if (DeploymentActiveAfter(pindexPrev, chainman,
                              Consensus::DEPLOYMENT_HEIGHTINCB)) {
        CScript expect = CScript() << nHeight;
        if (block.vtx[0]->vin[0].scriptSig.size() < expect.size() ||
            !std::equal(expect.begin(), expect.end(),
                        block.vtx[0]->vin[0].scriptSig.begin())) {
            return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS,
                                 "bad-cb-height",
                                 "block height mismatch in coinbase");
        }
    }
 
    return true;
}
 
bool ChainstateManager::AcceptBlockHeader(
    const CBlockHeader &block, BlockValidationState &state,
    CBlockIndex **ppindex, bool min_pow_checked,
    const std::optional<CCheckpointData> &test_checkpoints) {
    AssertLockHeld(cs_main);
    const Config &config = this->GetConfig();
    const CChainParams &chainparams = config.GetChainParams();
 
    // Check for duplicate
    BlockHash hash = block.GetHash();
    BlockMap::iterator miSelf{m_blockman.m_block_index.find(hash)};
    if (hash != chainparams.GetConsensus().hashGenesisBlock) {
        if (miSelf != m_blockman.m_block_index.end()) {
            // Block header is already known.
            CBlockIndex *pindex = &(miSelf->second);
            if (ppindex) {
                *ppindex = pindex;
            }
 
            if (pindex->nStatus.isInvalid()) {
                LogPrint(BCLog::VALIDATION, "%s: block %s is marked invalid\n",
                         __func__, hash.ToString());
                return state.Invalid(
                    BlockValidationResult::BLOCK_CACHED_INVALID, "duplicate");
            }
 
            return true;
        }
 
        if (!CheckBlockHeader(block, state, chainparams.GetConsensus(),
                              BlockValidationOptions(config))) {
            LogPrint(BCLog::VALIDATION,
                     "%s: Consensus::CheckBlockHeader: %s, %s\n", __func__,
                     hash.ToString(), state.ToString());
            return false;
        }
 
        // Get prev block index
        BlockMap::iterator mi{
            m_blockman.m_block_index.find(block.hashPrevBlock)};
        if (mi == m_blockman.m_block_index.end()) {
            LogPrint(BCLog::VALIDATION,
                     "header %s has prev block not found: %s\n",
                     hash.ToString(), block.hashPrevBlock.ToString());
            return state.Invalid(BlockValidationResult::BLOCK_MISSING_PREV,
                                 "prev-blk-not-found");
        }
 
        CBlockIndex *pindexPrev = &((*mi).second);
        assert(pindexPrev);
        if (pindexPrev->nStatus.isInvalid()) {
            LogPrint(BCLog::VALIDATION,
                     "header %s has prev block invalid: %s\n", hash.ToString(),
                     block.hashPrevBlock.ToString());
            return state.Invalid(BlockValidationResult::BLOCK_INVALID_PREV,
                                 "bad-prevblk");
        }
 
        if (!ContextualCheckBlockHeader(
                block, state, m_blockman, *this, pindexPrev,
                m_options.adjusted_time_callback(), test_checkpoints)) {
            LogPrint(BCLog::VALIDATION,
                     "%s: Consensus::ContextualCheckBlockHeader: %s, %s\n",
                     __func__, hash.ToString(), state.ToString());
            return false;
        }
 
        /* Determine if this block descends from any block which has been found
         * invalid (m_failed_blocks), then mark pindexPrev and any blocks
         * between them as failed. For example:
         *
         *                D3
         *              /
         *      B2 - C2
         *    /         \
         *  A             D2 - E2 - F2
         *    \
         *      B1 - C1 - D1 - E1
         *
         * In the case that we attempted to reorg from E1 to F2, only to find
         * C2 to be invalid, we would mark D2, E2, and F2 as BLOCK_FAILED_CHILD
         * but NOT D3 (it was not in any of our candidate sets at the time).
         *
         * In any case D3 will also be marked as BLOCK_FAILED_CHILD at restart
         * in LoadBlockIndex.
         */
        if (!pindexPrev->IsValid(BlockValidity::SCRIPTS)) {
            // The above does not mean "invalid": it checks if the previous
            // block hasn't been validated up to BlockValidity::SCRIPTS. This is
            // a performance optimization, in the common case of adding a new
            // block to the tip, we don't need to iterate over the failed blocks
            // list.
            for (const CBlockIndex *failedit : m_failed_blocks) {
                if (pindexPrev->GetAncestor(failedit->nHeight) == failedit) {
                    assert(failedit->nStatus.hasFailed());
                    CBlockIndex *invalid_walk = pindexPrev;
                    while (invalid_walk != failedit) {
                        invalid_walk->nStatus =
                            invalid_walk->nStatus.withFailedParent();
                        m_blockman.m_dirty_blockindex.insert(invalid_walk);
                        invalid_walk = invalid_walk->pprev;
                    }
                    LogPrint(BCLog::VALIDATION,
                             "header %s has prev block invalid: %s\n",
                             hash.ToString(), block.hashPrevBlock.ToString());
                    return state.Invalid(
                        BlockValidationResult::BLOCK_INVALID_PREV,
                        "bad-prevblk");
                }
            }
        }
    }
    if (!min_pow_checked) {
        LogPrint(BCLog::VALIDATION,
                 "%s: not adding new block header %s, missing anti-dos "
                 "proof-of-work validation\n",
                 __func__, hash.ToString());
        return state.Invalid(BlockValidationResult::BLOCK_HEADER_LOW_WORK,
                             "too-little-chainwork");
    }
    CBlockIndex *pindex{m_blockman.AddToBlockIndex(block, m_best_header)};
 
    if (ppindex) {
        *ppindex = pindex;
    }
 
    // Since this is the earliest point at which we have determined that a
    // header is both new and valid, log here.
    //
    // These messages are valuable for detecting potential selfish mining
    // behavior; if multiple displacing headers are seen near simultaneously
    // across many nodes in the network, this might be an indication of selfish
    // mining. Having this log by default when not in IBD ensures broad
    // availability of this data in case investigation is merited.
    const auto msg = strprintf("Saw new header hash=%s height=%d",
                               hash.ToString(), pindex->nHeight);
 
    if (ActiveChainstate().IsInitialBlockDownload()) {
        LogPrintLevel(BCLog::VALIDATION, BCLog::Level::Debug, "%s\n", msg);
    } else {
        LogPrintf("%s\n", msg);
    }
 
    return true;
}
 
// Exposed wrapper for AcceptBlockHeader
bool ChainstateManager::ProcessNewBlockHeaders(
    const std::vector<CBlockHeader> &headers, bool min_pow_checked,
    BlockValidationState &state, const CBlockIndex **ppindex,
    const std::optional<CCheckpointData> &test_checkpoints) {
    AssertLockNotHeld(cs_main);
    {
        LOCK(cs_main);
        for (const CBlockHeader &header : headers) {
            // Use a temp pindex instead of ppindex to avoid a const_cast
            CBlockIndex *pindex = nullptr;
            bool accepted = AcceptBlockHeader(
                header, state, &pindex, min_pow_checked, test_checkpoints);
            ActiveChainstate().CheckBlockIndex();
 
            if (!accepted) {
                return false;
            }
 
            if (ppindex) {
                *ppindex = pindex;
            }
        }
    }
 
    if (NotifyHeaderTip(ActiveChainstate())) {
        if (ActiveChainstate().IsInitialBlockDownload() && ppindex &&
            *ppindex) {
            const CBlockIndex &last_accepted{**ppindex};
            const int64_t blocks_left{
                (GetTime() - last_accepted.GetBlockTime()) /
                this->GetConsensus().nPowTargetSpacing};
            const double progress{100.0 * last_accepted.nHeight /
                                  (last_accepted.nHeight + blocks_left)};
            LogPrintf("Synchronizing blockheaders, height: %d (~%.2f%%)\n",
                      last_accepted.nHeight, progress);
        }