dash/src/miner.cpp

// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2020 The Bitcoin Core developers
// Copyright (c) 2014-2022 The Dash Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <miner.h>

#include <amount.h>
#include <chain.h>
#include <chainparams.h>
#include <consensus/consensus.h>
#include <consensus/merkle.h>
#include <consensus/tx_verify.h>
#include <consensus/validation.h>
#include <deploymentstatus.h>
#include <policy/feerate.h>
#include <policy/policy.h>
#include <pow.h>
#include <primitives/transaction.h>
#include <timedata.h>
#include <util/moneystr.h>
#include <util/system.h>

#include <evo/specialtx.h>
#include <evo/cbtx.h>
#include <evo/creditpool.h>
#include <evo/mnhftx.h>
#include <evo/simplifiedmns.h>
#include <governance/governance.h>
#include <llmq/blockprocessor.h>
#include <llmq/chainlocks.h>
#include <llmq/context.h>
#include <llmq/instantsend.h>
#include <llmq/utils.h>
#include <masternode/payments.h>
#include <spork.h>
#include <validation.h>

#include <algorithm>
#include <utility>

int64_t UpdateTime(CBlockHeader* pblock, const Consensus::Params& consensusParams, const CBlockIndex* pindexPrev)
{
    int64_t nOldTime = pblock->nTime;
    int64_t nNewTime = std::max(pindexPrev->GetMedianTimePast()+1, GetAdjustedTime());

    if (nOldTime < nNewTime)
        pblock->nTime = nNewTime;

    // Updating time can change work required on testnet:
    if (consensusParams.fPowAllowMinDifficultyBlocks)
        pblock->nBits = GetNextWorkRequired(pindexPrev, pblock, consensusParams);

    return nNewTime - nOldTime;
}

BlockAssembler::Options::Options() {
    blockMinFeeRate = CFeeRate(DEFAULT_BLOCK_MIN_TX_FEE);
    nBlockMaxSize = DEFAULT_BLOCK_MAX_SIZE;
}

BlockAssembler::BlockAssembler(const CSporkManager& sporkManager, CGovernanceManager& governanceManager,
                               LLMQContext& llmq_ctx, CEvoDB& evoDb, CChainState& chainstate, const CTxMemPool& mempool, const CChainParams& params, const Options& options) :
      chainparams(params),
      m_mempool(mempool),
      m_chainstate(chainstate),
      spork_manager(sporkManager),
      governance_manager(governanceManager),
      quorum_block_processor(*llmq_ctx.quorum_block_processor),
      m_clhandler(*llmq_ctx.clhandler),
      m_isman(*llmq_ctx.isman),
      m_evoDb(evoDb)
{
    blockMinFeeRate = options.blockMinFeeRate;
    nBlockMaxSize = options.nBlockMaxSize;
}

static BlockAssembler::Options DefaultOptions()
{
    // Block resource limits
    BlockAssembler::Options options;
    options.nBlockMaxSize = DEFAULT_BLOCK_MAX_SIZE;
    if (gArgs.IsArgSet("-blockmaxsize")) {
        options.nBlockMaxSize = gArgs.GetArg("-blockmaxsize", DEFAULT_BLOCK_MAX_SIZE);
    }
    if (gArgs.IsArgSet("-blockmintxfee")) {
        std::optional<CAmount> parsed = ParseMoney(gArgs.GetArg("-blockmintxfee", ""));
        options.blockMinFeeRate = CFeeRate{parsed.value_or(DEFAULT_BLOCK_MIN_TX_FEE)};
    } else {
        options.blockMinFeeRate = CFeeRate{DEFAULT_BLOCK_MIN_TX_FEE};
    }
    return options;
}

BlockAssembler::BlockAssembler(const CSporkManager& sporkManager, CGovernanceManager& governanceManager,
                               LLMQContext& llmq_ctx, CEvoDB& evoDb, CChainState& chainstate, const CTxMemPool& mempool, const CChainParams& params)
    : BlockAssembler(sporkManager, governanceManager, llmq_ctx, evoDb, chainstate, mempool, params, DefaultOptions()) {}

void BlockAssembler::resetBlock()
{
    inBlock.clear();

    // Reserve space for coinbase tx
    nBlockSize = 1000;
    nBlockSigOps = 100;

    // These counters do not include coinbase tx
    nBlockTx = 0;
    nFees = 0;
}

std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn)
{
    int64_t nTimeStart = GetTimeMicros();

    resetBlock();

    pblocktemplate.reset(new CBlockTemplate());

    if(!pblocktemplate.get())
        return nullptr;
    CBlock* const pblock = &pblocktemplate->block; // pointer for convenience

    // Add dummy coinbase tx as first transaction
    pblock->vtx.emplace_back();
    pblocktemplate->vTxFees.push_back(-1); // updated at end
    pblocktemplate->vTxSigOps.push_back(-1); // updated at end

    LOCK2(cs_main, m_mempool.cs);
    assert(std::addressof(*::ChainActive().Tip()) == std::addressof(*m_chainstate.m_chain.Tip()));
    CBlockIndex* pindexPrev = m_chainstate.m_chain.Tip();
    assert(pindexPrev != nullptr);
    nHeight = pindexPrev->nHeight + 1;

    const bool fDIP0001Active_context{DeploymentActiveAfter(pindexPrev, chainparams.GetConsensus(), Consensus::DEPLOYMENT_DIP0001)};
    const bool fDIP0003Active_context{DeploymentActiveAfter(pindexPrev, chainparams.GetConsensus(), Consensus::DEPLOYMENT_DIP0003)};
    const bool fDIP0008Active_context{DeploymentActiveAfter(pindexPrev, chainparams.GetConsensus(), Consensus::DEPLOYMENT_DIP0008)};
    const bool fV20Active_context{DeploymentActiveAfter(pindexPrev, chainparams.GetConsensus(), Consensus::DEPLOYMENT_V20)};

    // Limit size to between 1K and MaxBlockSize()-1K for sanity:
    nBlockMaxSize = std::max<unsigned int>(1000, std::min<unsigned int>(MaxBlockSize(fDIP0001Active_context) - 1000, nBlockMaxSize));
    nBlockMaxSigOps = MaxBlockSigOps(fDIP0001Active_context);

    pblock->nVersion = g_versionbitscache.ComputeBlockVersion(pindexPrev, chainparams.GetConsensus());
    // Non-mainnet only: allow overriding block.nVersion with
    // -blockversion=N to test forking scenarios
    if (Params().NetworkIDString() != CBaseChainParams::MAIN)
        pblock->nVersion = gArgs.GetArg("-blockversion", pblock->nVersion);

    pblock->nTime = GetAdjustedTime();
    const int64_t nMedianTimePast = pindexPrev->GetMedianTimePast();

    nLockTimeCutoff = (STANDARD_LOCKTIME_VERIFY_FLAGS & LOCKTIME_MEDIAN_TIME_PAST)
                       ? nMedianTimePast
                       : pblock->GetBlockTime();

    if (fDIP0003Active_context) {
        for (const Consensus::LLMQParams& params : llmq::utils::GetEnabledQuorumParams(pindexPrev)) {
            std::vector<CTransactionRef> vqcTx;
            if (quorum_block_processor.GetMineableCommitmentsTx(params,
                                                                nHeight,
                                                                vqcTx)) {
                for (const auto& qcTx : vqcTx) {
                    pblock->vtx.emplace_back(qcTx);
                    pblocktemplate->vTxFees.emplace_back(0);
                    pblocktemplate->vTxSigOps.emplace_back(0);
                    nBlockSize += qcTx->GetTotalSize();
                    ++nBlockTx;
                }
            }
        }
    }

    int nPackagesSelected = 0;
    int nDescendantsUpdated = 0;

    addPackageTxs(nPackagesSelected, nDescendantsUpdated, pindexPrev);

    int64_t nTime1 = GetTimeMicros();

    m_last_block_num_txs = nBlockTx;
    m_last_block_size = nBlockSize;
    LogPrintf("CreateNewBlock(): total size %u txs: %u fees: %ld sigops %d\n", nBlockSize, nBlockTx, nFees, nBlockSigOps);

    // Create coinbase transaction.
    CMutableTransaction coinbaseTx;
    coinbaseTx.vin.resize(1);
    coinbaseTx.vin[0].prevout.SetNull();
    coinbaseTx.vout.resize(1);
    coinbaseTx.vout[0].scriptPubKey = scriptPubKeyIn;

    // NOTE: unlike in bitcoin, we need to pass PREVIOUS block height here
    CAmount blockSubsidy = GetBlockSubsidyInner(pindexPrev->nBits, pindexPrev->nHeight, Params().GetConsensus(), fV20Active_context);
    CAmount blockReward = blockSubsidy + nFees;

    // Compute regular coinbase transaction.
    coinbaseTx.vout[0].nValue = blockReward;

    if (!fDIP0003Active_context) {
        coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
    } else {
        coinbaseTx.vin[0].scriptSig = CScript() << OP_RETURN;

        coinbaseTx.nVersion = 3;
        coinbaseTx.nType = TRANSACTION_COINBASE;

        CCbTx cbTx;

        if (fV20Active_context) {
            cbTx.nVersion = CCbTx::Version::CLSIG_AND_BALANCE;
        } else if (fDIP0008Active_context) {
            cbTx.nVersion = CCbTx::Version::MERKLE_ROOT_QUORUMS;
        } else {
            cbTx.nVersion = CCbTx::Version::MERKLE_ROOT_MNLIST;
        }

        cbTx.nHeight = nHeight;

        BlockValidationState state;
        if (!CalcCbTxMerkleRootMNList(*pblock, pindexPrev, cbTx.merkleRootMNList, state, ::ChainstateActive().CoinsTip())) {
            throw std::runtime_error(strprintf("%s: CalcCbTxMerkleRootMNList failed: %s", __func__, state.ToString()));
        }
        if (fDIP0008Active_context) {
            if (!CalcCbTxMerkleRootQuorums(*pblock, pindexPrev, quorum_block_processor, cbTx.merkleRootQuorums, state)) {
                throw std::runtime_error(strprintf("%s: CalcCbTxMerkleRootQuorums failed: %s", __func__, state.ToString()));
            }
            if (fV20Active_context) {
                if (CalcCbTxBestChainlock(m_clhandler, pindexPrev, cbTx.bestCLHeightDiff, cbTx.bestCLSignature)) {
                    LogPrintf("CreateNewBlock() h[%d] CbTx bestCLHeightDiff[%d] CLSig[%s]\n", nHeight, cbTx.bestCLHeightDiff, cbTx.bestCLSignature.ToString());
                } else {
                    // not an error
                    LogPrintf("CreateNewBlock() h[%d] CbTx failed to find best CL. Inserting null CL\n", nHeight);
                }
                BlockValidationState state;
                const auto creditPoolDiff = GetCreditPoolDiffForBlock(*pblock, pindexPrev, chainparams.GetConsensus(), blockSubsidy, state);
                if (creditPoolDiff == std::nullopt) {
                    throw std::runtime_error(strprintf("%s: GetCreditPoolDiffForBlock failed: %s", __func__, state.ToString()));
                }

                cbTx.creditPoolBalance = creditPoolDiff->GetTotalLocked();
            }
        }

        SetTxPayload(coinbaseTx, cbTx);
    }

    // Update coinbase transaction with additional info about masternode and governance payments,
    // get some info back to pass to getblocktemplate
    MasternodePayments::FillBlockPayments(spork_manager, governance_manager, coinbaseTx, pindexPrev, blockSubsidy, nFees, pblocktemplate->voutMasternodePayments, pblocktemplate->voutSuperblockPayments);

    pblock->vtx[0] = MakeTransactionRef(std::move(coinbaseTx));
    pblocktemplate->vTxFees[0] = -nFees;

    // Fill in header
    pblock->hashPrevBlock  = pindexPrev->GetBlockHash();
    UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev);
    pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());
    pblock->nNonce         = 0;
    pblocktemplate->nPrevBits = pindexPrev->nBits;
    pblocktemplate->vTxSigOps[0] = GetLegacySigOpCount(*pblock->vtx[0]);

    BlockValidationState state;
    assert(std::addressof(::ChainstateActive()) == std::addressof(m_chainstate));
    if (!TestBlockValidity(state, m_clhandler, m_evoDb, chainparams, m_chainstate, *pblock, pindexPrev, false, false)) {
        throw std::runtime_error(strprintf("%s: TestBlockValidity failed: %s", __func__, state.ToString()));
    }
    int64_t nTime2 = GetTimeMicros();

    LogPrint(BCLog::BENCHMARK, "CreateNewBlock() packages: %.2fms (%d packages, %d updated descendants), validity: %.2fms (total %.2fms)\n", 0.001 * (nTime1 - nTimeStart), nPackagesSelected, nDescendantsUpdated, 0.001 * (nTime2 - nTime1), 0.001 * (nTime2 - nTimeStart));

    return std::move(pblocktemplate);
}

void BlockAssembler::onlyUnconfirmed(CTxMemPool::setEntries& testSet)
{
    for (CTxMemPool::setEntries::iterator iit = testSet.begin(); iit != testSet.end(); ) {
        // Only test txs not already in the block
        if (inBlock.count(*iit)) {
            testSet.erase(iit++);
        }
        else {
            iit++;
        }
    }
}

bool BlockAssembler::TestPackage(uint64_t packageSize, unsigned int packageSigOps) const
{
    if (nBlockSize + packageSize >= nBlockMaxSize)
        return false;
    if (nBlockSigOps + packageSigOps >= nBlockMaxSigOps)
        return false;
    return true;
}

// Perform transaction-level checks before adding to block:
// - transaction finality (locktime)
// - safe TXs in regard to ChainLocks
bool BlockAssembler::TestPackageTransactions(const CTxMemPool::setEntries& package) const
{
    for (CTxMemPool::txiter it : package) {
        if (!IsFinalTx(it->GetTx(), nHeight, nLockTimeCutoff))
            return false;

        const auto& txid = it->GetTx().GetHash();
        if (!m_isman.RejectConflictingBlocks() || !m_isman.IsInstantSendEnabled() || m_isman.IsLocked(txid)) continue;

        if (!it->GetTx().vin.empty() && !m_clhandler.IsTxSafeForMining(txid)) {
            return false;
        }
    }
    return true;
}

void BlockAssembler::AddToBlock(CTxMemPool::txiter iter)
{
    pblocktemplate->block.vtx.emplace_back(iter->GetSharedTx());
    pblocktemplate->vTxFees.push_back(iter->GetFee());
    pblocktemplate->vTxSigOps.push_back(iter->GetSigOpCount());
    nBlockSize += iter->GetTxSize();
    ++nBlockTx;
    nBlockSigOps += iter->GetSigOpCount();
    nFees += iter->GetFee();
    inBlock.insert(iter);

    bool fPrintPriority = gArgs.GetBoolArg("-printpriority", DEFAULT_PRINTPRIORITY);
    if (fPrintPriority) {
        LogPrintf("fee %s txid %s\n",
                  CFeeRate(iter->GetModifiedFee(), iter->GetTxSize()).ToString(),
                  iter->GetTx().GetHash().ToString());
    }
}

int BlockAssembler::UpdatePackagesForAdded(const CTxMemPool::setEntries& alreadyAdded,
        indexed_modified_transaction_set &mapModifiedTx)
{
    AssertLockHeld(m_mempool.cs);

    int nDescendantsUpdated = 0;
    for (CTxMemPool::txiter it : alreadyAdded) {
        CTxMemPool::setEntries descendants;
        m_mempool.CalculateDescendants(it, descendants);
        // Insert all descendants (not yet in block) into the modified set
        for (CTxMemPool::txiter desc : descendants) {
            if (alreadyAdded.count(desc))
                continue;
            ++nDescendantsUpdated;
            modtxiter mit = mapModifiedTx.find(desc);
            if (mit == mapModifiedTx.end()) {
                CTxMemPoolModifiedEntry modEntry(desc);
                modEntry.nSizeWithAncestors -= it->GetTxSize();
                modEntry.nModFeesWithAncestors -= it->GetModifiedFee();
                modEntry.nSigOpCountWithAncestors -= it->GetSigOpCount();
                mapModifiedTx.insert(modEntry);
            } else {
                mapModifiedTx.modify(mit, update_for_parent_inclusion(it));
            }
        }
    }
    return nDescendantsUpdated;
}

// Skip entries in mapTx that are already in a block or are present
// in mapModifiedTx (which implies that the mapTx ancestor state is
// stale due to ancestor inclusion in the block)
// Also skip transactions that we've already failed to add. This can happen if
// we consider a transaction in mapModifiedTx and it fails: we can then
// potentially consider it again while walking mapTx.  It's currently
// guaranteed to fail again, but as a belt-and-suspenders check we put it in
// failedTx and avoid re-evaluation, since the re-evaluation would be using
// cached size/sigops/fee values that are not actually correct.
bool BlockAssembler::SkipMapTxEntry(CTxMemPool::txiter it, indexed_modified_transaction_set &mapModifiedTx, CTxMemPool::setEntries &failedTx)
{
    AssertLockHeld(m_mempool.cs);

    assert(it != m_mempool.mapTx.end());
    return mapModifiedTx.count(it) || inBlock.count(it) || failedTx.count(it);
}

void BlockAssembler::SortForBlock(const CTxMemPool::setEntries& package, std::vector<CTxMemPool::txiter>& sortedEntries)
{
    // Sort package by ancestor count
    // If a transaction A depends on transaction B, then A's ancestor count
    // must be greater than B's.  So this is sufficient to validly order the
    // transactions for block inclusion.
    sortedEntries.clear();
    sortedEntries.insert(sortedEntries.begin(), package.begin(), package.end());
    std::sort(sortedEntries.begin(), sortedEntries.end(), CompareTxIterByAncestorCount());
}

// This transaction selection algorithm orders the mempool based
// on feerate of a transaction including all unconfirmed ancestors.
// Since we don't remove transactions from the mempool as we select them
// for block inclusion, we need an alternate method of updating the feerate
// of a transaction with its not-yet-selected ancestors as we go.
// This is accomplished by walking the in-mempool descendants of selected
// transactions and storing a temporary modified state in mapModifiedTxs.
// Each time through the loop, we compare the best transaction in
// mapModifiedTxs with the next transaction in the mempool to decide what
// transaction package to work on next.
void BlockAssembler::addPackageTxs(int &nPackagesSelected, int &nDescendantsUpdated, const CBlockIndex* const pindexPrev)
{
    AssertLockHeld(m_mempool.cs);

    // This credit pool is used only to check withdrawal limits and to find
    // duplicates of indexes. There's used `BlockSubsidy` equaled to 0
    std::optional<CCreditPoolDiff> creditPoolDiff;
    if (DeploymentActiveAfter(pindexPrev, chainparams.GetConsensus(), Consensus::DEPLOYMENT_V20)) {
        CCreditPool creditPool = creditPoolManager->GetCreditPool(pindexPrev, chainparams.GetConsensus());
        creditPoolDiff.emplace(std::move(creditPool), pindexPrev, chainparams.GetConsensus(), 0);
    }

    // This map with signals is used only to find duplicates
    std::unordered_map<uint8_t, int> signals = m_chainstate.GetMNHFSignalsStage(pindexPrev);

    // mapModifiedTx will store sorted packages after they are modified
    // because some of their txs are already in the block
    indexed_modified_transaction_set mapModifiedTx;
    // Keep track of entries that failed inclusion, to avoid duplicate work
    CTxMemPool::setEntries failedTx;

    // Start by adding all descendants of previously added txs to mapModifiedTx
    // and modifying them for their already included ancestors
    UpdatePackagesForAdded(inBlock, mapModifiedTx);

    CTxMemPool::indexed_transaction_set::index<ancestor_score>::type::iterator mi = m_mempool.mapTx.get<ancestor_score>().begin();
    CTxMemPool::txiter iter;

    // Limit the number of attempts to add transactions to the block when it is
    // close to full; this is just a simple heuristic to finish quickly if the
    // mempool has a lot of entries.
    const int64_t MAX_CONSECUTIVE_FAILURES = 1000;
    int64_t nConsecutiveFailed = 0;

    while (mi != m_mempool.mapTx.get<ancestor_score>().end() || !mapModifiedTx.empty()) {
        // First try to find a new transaction in mapTx to evaluate.
        if (mi != m_mempool.mapTx.get<ancestor_score>().end() &&
            SkipMapTxEntry(m_mempool.mapTx.project<0>(mi), mapModifiedTx, failedTx)) {
            ++mi;
            continue;
        }

        // Now that mi is not stale, determine which transaction to evaluate:
        // the next entry from mapTx, or the best from mapModifiedTx?
        bool fUsingModified = false;

        modtxscoreiter modit = mapModifiedTx.get<ancestor_score>().begin();
        if (mi == m_mempool.mapTx.get<ancestor_score>().end()) {
            // We're out of entries in mapTx; use the entry from mapModifiedTx
            iter = modit->iter;
            fUsingModified = true;
        } else {
            // Try to compare the mapTx entry to the mapModifiedTx entry
            iter = m_mempool.mapTx.project<0>(mi);
            if (modit != mapModifiedTx.get<ancestor_score>().end() &&
                    CompareTxMemPoolEntryByAncestorFee()(*modit, CTxMemPoolModifiedEntry(iter))) {
                // The best entry in mapModifiedTx has higher score
                // than the one from mapTx.
                // Switch which transaction (package) to consider
                iter = modit->iter;
                fUsingModified = true;
            } else {
                // Either no entry in mapModifiedTx, or it's worse than mapTx.
                // Increment mi for the next loop iteration.
                ++mi;
            }
        }

        if (creditPoolDiff != std::nullopt) {
            // If one transaction is skipped due to limits, it is not a reason to interrupt
            // whole process of adding transactions.
            // `state` is local here because used only to log info about this specific tx
            TxValidationState state;

            if (!creditPoolDiff->ProcessLockUnlockTransaction(iter->GetTx(), state)) {
                if (fUsingModified) {
                    mapModifiedTx.get<ancestor_score>().erase(modit);
                    failedTx.insert(iter);
                }
                LogPrintf("%s: asset-locks tx %s skipped due %s\n",
                          __func__, iter->GetTx().GetHash().ToString(), state.ToString());
                continue;
            }
        }
        if (std::optional<uint8_t> signal = extractEHFSignal(iter->GetTx()); signal != std::nullopt) {
            if (signals.find(*signal) != signals.end()) {
                if (fUsingModified) {
                    mapModifiedTx.get<ancestor_score>().erase(modit);
                    failedTx.insert(iter);
                }
                LogPrintf("%s: ehf signal tx %s skipped due to duplicate %d\n",
                          __func__, iter->GetTx().GetHash().ToString(), *signal);
                continue;
            }
            signals.insert({*signal, 0});
        }

        // We skip mapTx entries that are inBlock, and mapModifiedTx shouldn't
        // contain anything that is inBlock.
        assert(!inBlock.count(iter));

        uint64_t packageSize = iter->GetSizeWithAncestors();
        CAmount packageFees = iter->GetModFeesWithAncestors();
        unsigned int packageSigOps = iter->GetSigOpCountWithAncestors();
        if (fUsingModified) {
            packageSize = modit->nSizeWithAncestors;
            packageFees = modit->nModFeesWithAncestors;
            packageSigOps = modit->nSigOpCountWithAncestors;
        }

        if (packageFees < blockMinFeeRate.GetFee(packageSize)) {
            // Everything else we might consider has a lower fee rate
            return;
        }

        if (!TestPackage(packageSize, packageSigOps)) {
            if (fUsingModified) {
                // Since we always look at the best entry in mapModifiedTx,
                // we must erase failed entries so that we can consider the
                // next best entry on the next loop iteration
                mapModifiedTx.get<ancestor_score>().erase(modit);
                failedTx.insert(iter);
            }

            ++nConsecutiveFailed;

            if (nConsecutiveFailed > MAX_CONSECUTIVE_FAILURES && nBlockSize > nBlockMaxSize - 1000) {
                // Give up if we're close to full and haven't succeeded in a while
                break;
            }
            continue;
        }

        CTxMemPool::setEntries ancestors;
        uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
        std::string dummy;
        m_mempool.CalculateMemPoolAncestors(*iter, ancestors, nNoLimit, nNoLimit, nNoLimit, nNoLimit, dummy, false);

        onlyUnconfirmed(ancestors);
        ancestors.insert(iter);

        // Test if all tx's are Final and safe
        if (!TestPackageTransactions(ancestors)) {
            if (fUsingModified) {
                mapModifiedTx.get<ancestor_score>().erase(modit);
                failedTx.insert(iter);
            }
            continue;
        }

        // This transaction will make it in; reset the failed counter.
        nConsecutiveFailed = 0;

        // Package can be added. Sort the entries in a valid order.
        std::vector<CTxMemPool::txiter> sortedEntries;
        SortForBlock(ancestors, sortedEntries);

        for (size_t i=0; i<sortedEntries.size(); ++i) {
            AddToBlock(sortedEntries[i]);
            // Erase from the modified set, if present
            mapModifiedTx.erase(sortedEntries[i]);
        }

        ++nPackagesSelected;

        // Update transactions that depend on each of these
        nDescendantsUpdated += UpdatePackagesForAdded(ancestors, mapModifiedTx);
    }
}

void IncrementExtraNonce(CBlock* pblock, const CBlockIndex* pindexPrev, unsigned int& nExtraNonce)
{
    // Update nExtraNonce
    static uint256 hashPrevBlock;
    if (hashPrevBlock != pblock->hashPrevBlock)
    {
        nExtraNonce = 0;
        hashPrevBlock = pblock->hashPrevBlock;
    }
    ++nExtraNonce;
    unsigned int nHeight = pindexPrev->nHeight+1; // Height first in coinbase required for block.version=2
    CMutableTransaction txCoinbase(*pblock->vtx[0]);
    txCoinbase.vin[0].scriptSig = (CScript() << nHeight << CScriptNum(nExtraNonce));
    assert(txCoinbase.vin[0].scriptSig.size() <= 100);

    pblock->vtx[0] = MakeTransactionRef(std::move(txCoinbase));
    pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);
}