Line data    Source code

       1             : // Copyright (c) 2009-2010 Satoshi Nakamoto
       2             : // Copyright (c) 2009-2020 The Bitcoin Core developers
       3             : // Distributed under the MIT software license, see the accompanying
       4             : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
       5             : 
       6             : #include <miner.h>
       7             : 
       8             : #include <amount.h>
       9             : #include <chain.h>
      10             : #include <chainparams.h>
      11             : #include <coins.h>
      12             : #include <consensus/consensus.h>
      13             : #include <consensus/merkle.h>
      14             : #include <consensus/tx_verify.h>
      15             : #include <consensus/validation.h>
      16             : #include <policy/feerate.h>
      17             : #include <policy/policy.h>
      18             : #include <pow.h>
      19             : #include <primitives/transaction.h>
      20             : #include <timedata.h>
      21             : #include <util/moneystr.h>
      22             : #include <util/system.h>
      23             : 
      24             : #include <algorithm>
      25             : #include <utility>
      26             : 
      27       21027 : int64_t UpdateTime(CBlockHeader* pblock, const Consensus::Params& consensusParams, const CBlockIndex* pindexPrev)
      28             : {
      29       21027 :     int64_t nOldTime = pblock->nTime;
      30       21027 :     int64_t nNewTime = std::max(pindexPrev->GetMedianTimePast()+1, GetAdjustedTime());
      31             : 
      32       21027 :     if (nOldTime < nNewTime)
      33       17647 :         pblock->nTime = nNewTime;
      34             : 
      35             :     // Updating time can change work required on testnet:
      36       21027 :     if (consensusParams.fPowAllowMinDifficultyBlocks)
      37       21008 :         pblock->nBits = GetNextWorkRequired(pindexPrev, pblock, consensusParams);
      38             : 
      39       21027 :     return nNewTime - nOldTime;
      40             : }
      41             : 
      42        2355 : void RegenerateCommitments(CBlock& block)
      43             : {
      44        2355 :     CMutableTransaction tx{*block.vtx.at(0)};
      45        2355 :     tx.vout.erase(tx.vout.begin() + GetWitnessCommitmentIndex(block));
      46        2355 :     block.vtx.at(0) = MakeTransactionRef(tx);
      47             : 
      48        4710 :     GenerateCoinbaseCommitment(block, WITH_LOCK(cs_main, return LookupBlockIndex(block.hashPrevBlock)), Params().GetConsensus());
      49             : 
      50        2355 :     block.hashMerkleRoot = BlockMerkleRoot(block);
      51        2355 : }
      52             : 
      53       42022 : BlockAssembler::Options::Options() {
      54       21011 :     blockMinFeeRate = CFeeRate(DEFAULT_BLOCK_MIN_TX_FEE);
      55       21011 :     nBlockMaxWeight = DEFAULT_BLOCK_MAX_WEIGHT;
      56       42022 : }
      57             : 
      58       42022 : BlockAssembler::BlockAssembler(const CTxMemPool& mempool, const CChainParams& params, const Options& options)
      59       21011 :     : chainparams(params),
      60       21011 :       m_mempool(mempool)
      61       21011 : {
      62       21011 :     blockMinFeeRate = options.blockMinFeeRate;
      63             :     // Limit weight to between 4K and MAX_BLOCK_WEIGHT-4K for sanity:
      64       21011 :     nBlockMaxWeight = std::max<size_t>(4000, std::min<size_t>(MAX_BLOCK_WEIGHT - 4000, options.nBlockMaxWeight));
      65       42022 : }
      66             : 
      67       20992 : static BlockAssembler::Options DefaultOptions()
      68             : {
      69             :     // Block resource limits
      70             :     // If -blockmaxweight is not given, limit to DEFAULT_BLOCK_MAX_WEIGHT
      71       20992 :     BlockAssembler::Options options;
      72       20992 :     options.nBlockMaxWeight = gArgs.GetArg("-blockmaxweight", DEFAULT_BLOCK_MAX_WEIGHT);
      73       20992 :     CAmount n = 0;
      74       20992 :     if (gArgs.IsArgSet("-blockmintxfee") && ParseMoney(gArgs.GetArg("-blockmintxfee", ""), n)) {
      75           0 :         options.blockMinFeeRate = CFeeRate(n);
      76           0 :     } else {
      77       20992 :         options.blockMinFeeRate = CFeeRate(DEFAULT_BLOCK_MIN_TX_FEE);
      78             :     }
      79             :     return options;
      80       20992 : }
      81             : 
      82       20992 : BlockAssembler::BlockAssembler(const CTxMemPool& mempool, const CChainParams& params)
      83       20992 :     : BlockAssembler(mempool, params, DefaultOptions()) {}
      84             : 
      85       21011 : void BlockAssembler::resetBlock()
      86             : {
      87       21011 :     inBlock.clear();
      88             : 
      89             :     // Reserve space for coinbase tx
      90       21011 :     nBlockWeight = 4000;
      91       21011 :     nBlockSigOpsCost = 400;
      92       21011 :     fIncludeWitness = false;
      93             : 
      94             :     // These counters do not include coinbase tx
      95       21011 :     nBlockTx = 0;
      96       21011 :     nFees = 0;
      97       21011 : }
      98             : 
      99         640 : Optional<int64_t> BlockAssembler::m_last_block_num_txs{nullopt};
     100         640 : Optional<int64_t> BlockAssembler::m_last_block_weight{nullopt};
     101             : 
     102       21011 : std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn)
     103             : {
     104       21011 :     int64_t nTimeStart = GetTimeMicros();
     105             : 
     106       21011 :     resetBlock();
     107             : 
     108       21011 :     pblocktemplate.reset(new CBlockTemplate());
     109             : 
     110       21011 :     if(!pblocktemplate.get())
     111           0 :         return nullptr;
     112       21011 :     CBlock* const pblock = &pblocktemplate->block; // pointer for convenience
     113             : 
     114             :     // Add dummy coinbase tx as first transaction
     115       21011 :     pblock->vtx.emplace_back();
     116       21011 :     pblocktemplate->vTxFees.push_back(-1); // updated at end
     117       21011 :     pblocktemplate->vTxSigOpsCost.push_back(-1); // updated at end
     118             : 
     119       21011 :     LOCK2(cs_main, m_mempool.cs);
     120       21011 :     CBlockIndex* pindexPrev = ::ChainActive().Tip();
     121       21011 :     assert(pindexPrev != nullptr);
     122       21011 :     nHeight = pindexPrev->nHeight + 1;
     123             : 
     124       21011 :     pblock->nVersion = ComputeBlockVersion(pindexPrev, chainparams.GetConsensus());
     125             :     // -regtest only: allow overriding block.nVersion with
     126             :     // -blockversion=N to test forking scenarios
     127       21011 :     if (chainparams.MineBlocksOnDemand())
     128       20992 :         pblock->nVersion = gArgs.GetArg("-blockversion", pblock->nVersion);
     129             : 
     130       21011 :     pblock->nTime = GetAdjustedTime();
     131       21011 :     const int64_t nMedianTimePast = pindexPrev->GetMedianTimePast();
     132             : 
     133       21011 :     nLockTimeCutoff = (STANDARD_LOCKTIME_VERIFY_FLAGS & LOCKTIME_MEDIAN_TIME_PAST)
     134             :                        ? nMedianTimePast
     135             :                        : pblock->GetBlockTime();
     136             : 
     137             :     // Decide whether to include witness transactions
     138             :     // This is only needed in case the witness softfork activation is reverted
     139             :     // (which would require a very deep reorganization).
     140             :     // Note that the mempool would accept transactions with witness data before
     141             :     // IsWitnessEnabled, but we would only ever mine blocks after IsWitnessEnabled
     142             :     // unless there is a massive block reorganization with the witness softfork
     143             :     // not activated.
     144             :     // TODO: replace this with a call to main to assess validity of a mempool
     145             :     // transaction (which in most cases can be a no-op).
     146       21011 :     fIncludeWitness = IsWitnessEnabled(pindexPrev, chainparams.GetConsensus());
     147             : 
     148       21011 :     int nPackagesSelected = 0;
     149       21011 :     int nDescendantsUpdated = 0;
     150       21011 :     addPackageTxs(nPackagesSelected, nDescendantsUpdated);
     151             : 
     152       21011 :     int64_t nTime1 = GetTimeMicros();
     153             : 
     154       21011 :     m_last_block_num_txs = nBlockTx;
     155       21011 :     m_last_block_weight = nBlockWeight;
     156             : 
     157             :     // Create coinbase transaction.
     158       21011 :     CMutableTransaction coinbaseTx;
     159       21011 :     coinbaseTx.vin.resize(1);
     160       21011 :     coinbaseTx.vin[0].prevout.SetNull();
     161       21011 :     coinbaseTx.vout.resize(1);
     162       21011 :     coinbaseTx.vout[0].scriptPubKey = scriptPubKeyIn;
     163       21011 :     coinbaseTx.vout[0].nValue = nFees + GetBlockSubsidy(nHeight, chainparams.GetConsensus());
     164       21011 :     coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
     165       21011 :     pblock->vtx[0] = MakeTransactionRef(std::move(coinbaseTx));
     166       21011 :     pblocktemplate->vchCoinbaseCommitment = GenerateCoinbaseCommitment(*pblock, pindexPrev, chainparams.GetConsensus());
     167       21011 :     pblocktemplate->vTxFees[0] = -nFees;
     168             : 
     169       21011 :     LogPrintf("CreateNewBlock(): block weight: %u txs: %u fees: %ld sigops %d\n", GetBlockWeight(*pblock), nBlockTx, nFees, nBlockSigOpsCost);
     170             : 
     171             :     // Fill in header
     172       21011 :     pblock->hashPrevBlock  = pindexPrev->GetBlockHash();
     173       21011 :     UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev);
     174       21011 :     pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());
     175       21011 :     pblock->nNonce         = 0;
     176       21011 :     pblocktemplate->vTxSigOpsCost[0] = WITNESS_SCALE_FACTOR * GetLegacySigOpCount(*pblock->vtx[0]);
     177             : 
     178       21011 :     BlockValidationState state;
     179       21011 :     if (!TestBlockValidity(state, chainparams, *pblock, pindexPrev, false, false)) {
     180           5 :         throw std::runtime_error(strprintf("%s: TestBlockValidity failed: %s", __func__, state.ToString()));
     181             :     }
     182       21006 :     int64_t nTime2 = GetTimeMicros();
     183             : 
     184       21006 :     LogPrint(BCLog::BENCH, "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));
     185             : 
     186       21006 :     return std::move(pblocktemplate);
     187       21011 : }
     188             : 
     189        9345 : void BlockAssembler::onlyUnconfirmed(CTxMemPool::setEntries& testSet)
     190             : {
     191       22604 :     for (CTxMemPool::setEntries::iterator iit = testSet.begin(); iit != testSet.end(); ) {
     192             :         // Only test txs not already in the block
     193       13259 :         if (inBlock.count(*iit)) {
     194       10950 :             testSet.erase(iit++);
     195       10950 :         }
     196             :         else {
     197        2309 :             iit++;
     198             :         }
     199             :     }
     200        9345 : }
     201             : 
     202       34267 : bool BlockAssembler::TestPackage(uint64_t packageSize, int64_t packageSigOpsCost) const
     203             : {
     204             :     // TODO: switch to weight-based accounting for packages instead of vsize-based accounting.
     205       34267 :     if (nBlockWeight + WITNESS_SCALE_FACTOR * packageSize >= nBlockMaxWeight)
     206       24909 :         return false;
     207        9358 :     if (nBlockSigOpsCost + packageSigOpsCost >= MAX_BLOCK_SIGOPS_COST)
     208          13 :         return false;
     209        9345 :     return true;
     210       34267 : }
     211             : 
     212             : // Perform transaction-level checks before adding to block:
     213             : // - transaction finality (locktime)
     214             : // - premature witness (in case segwit transactions are added to mempool before
     215             : //   segwit activation)
     216        9345 : bool BlockAssembler::TestPackageTransactions(const CTxMemPool::setEntries& package)
     217             : {
     218       20999 :     for (CTxMemPool::txiter it : package) {
     219       11654 :         if (!IsFinalTx(it->GetTx(), nHeight, nLockTimeCutoff))
     220           2 :             return false;
     221       11652 :         if (!fIncludeWitness && it->GetTx().HasWitness())
     222          26 :             return false;
     223       11654 :     }
     224        9317 :     return true;
     225        9345 : }
     226             : 
     227       11626 : void BlockAssembler::AddToBlock(CTxMemPool::txiter iter)
     228             : {
     229       11626 :     pblocktemplate->block.vtx.emplace_back(iter->GetSharedTx());
     230       11626 :     pblocktemplate->vTxFees.push_back(iter->GetFee());
     231       11626 :     pblocktemplate->vTxSigOpsCost.push_back(iter->GetSigOpCost());
     232       11626 :     nBlockWeight += iter->GetTxWeight();
     233       11626 :     ++nBlockTx;
     234       11626 :     nBlockSigOpsCost += iter->GetSigOpCost();
     235       11626 :     nFees += iter->GetFee();
     236       11626 :     inBlock.insert(iter);
     237             : 
     238       11626 :     bool fPrintPriority = gArgs.GetBoolArg("-printpriority", DEFAULT_PRINTPRIORITY);
     239       11626 :     if (fPrintPriority) {
     240         129 :         LogPrintf("fee %s txid %s\n",
     241         129 :                   CFeeRate(iter->GetModifiedFee(), iter->GetTxSize()).ToString(),
     242         129 :                   iter->GetTx().GetHash().ToString());
     243         129 :     }
     244       11626 : }
     245             : 
     246       30328 : int BlockAssembler::UpdatePackagesForAdded(const CTxMemPool::setEntries& alreadyAdded,
     247             :         indexed_modified_transaction_set &mapModifiedTx)
     248             : {
     249     1077865 :     int nDescendantsUpdated = 0;
     250       41954 :     for (CTxMemPool::txiter it : alreadyAdded) {
     251       11626 :         CTxMemPool::setEntries descendants;
     252       11626 :         m_mempool.CalculateDescendants(it, descendants);
     253             :         // Insert all descendants (not yet in block) into the modified set
     254     1035911 :         for (CTxMemPool::txiter desc : descendants) {
     255     1024285 :             if (alreadyAdded.count(desc))
     256      241098 :                 continue;
     257      783187 :             ++nDescendantsUpdated;
     258      783187 :             modtxiter mit = mapModifiedTx.find(desc);
     259      783187 :             if (mit == mapModifiedTx.end()) {
     260        2511 :                 CTxMemPoolModifiedEntry modEntry(desc);
     261        2511 :                 modEntry.nSizeWithAncestors -= it->GetTxSize();
     262        2511 :                 modEntry.nModFeesWithAncestors -= it->GetModifiedFee();
     263        2511 :                 modEntry.nSigOpCostWithAncestors -= it->GetSigOpCost();
     264        2511 :                 mapModifiedTx.insert(modEntry);
     265        2511 :             } else {
     266      780676 :                 mapModifiedTx.modify(mit, update_for_parent_inclusion(it));
     267             :             }
     268     1024285 :         }
     269       11626 :     }
     270       30328 :     return nDescendantsUpdated;
     271           0 : }
     272             : 
     273             : // Skip entries in mapTx that are already in a block or are present
     274             : // in mapModifiedTx (which implies that the mapTx ancestor state is
     275             : // stale due to ancestor inclusion in the block)
     276             : // Also skip transactions that we've already failed to add. This can happen if
     277             : // we consider a transaction in mapModifiedTx and it fails: we can then
     278             : // potentially consider it again while walking mapTx.  It's currently
     279             : // guaranteed to fail again, but as a belt-and-suspenders check we put it in
     280             : // failedTx and avoid re-evaluation, since the re-evaluation would be using
     281             : // cached size/sigops/fee values that are not actually correct.
     282       36605 : bool BlockAssembler::SkipMapTxEntry(CTxMemPool::txiter it, indexed_modified_transaction_set &mapModifiedTx, CTxMemPool::setEntries &failedTx)
     283             : {
     284       36605 :     assert(it != m_mempool.mapTx.end());
     285       36605 :     return mapModifiedTx.count(it) || inBlock.count(it) || failedTx.count(it);
     286             : }
     287             : 
     288        9317 : void BlockAssembler::SortForBlock(const CTxMemPool::setEntries& package, std::vector<CTxMemPool::txiter>& sortedEntries)
     289             : {
     290             :     // Sort package by ancestor count
     291             :     // If a transaction A depends on transaction B, then A's ancestor count
     292             :     // must be greater than B's.  So this is sufficient to validly order the
     293             :     // transactions for block inclusion.
     294        9317 :     sortedEntries.clear();
     295        9317 :     sortedEntries.insert(sortedEntries.begin(), package.begin(), package.end());
     296        9317 :     std::sort(sortedEntries.begin(), sortedEntries.end(), CompareTxIterByAncestorCount());
     297        9317 : }
     298             : 
     299             : // This transaction selection algorithm orders the mempool based
     300             : // on feerate of a transaction including all unconfirmed ancestors.
     301             : // Since we don't remove transactions from the mempool as we select them
     302             : // for block inclusion, we need an alternate method of updating the feerate
     303             : // of a transaction with its not-yet-selected ancestors as we go.
     304             : // This is accomplished by walking the in-mempool descendants of selected
     305             : // transactions and storing a temporary modified state in mapModifiedTxs.
     306             : // Each time through the loop, we compare the best transaction in
     307             : // mapModifiedTxs with the next transaction in the mempool to decide what
     308             : // transaction package to work on next.
     309       21011 : void BlockAssembler::addPackageTxs(int &nPackagesSelected, int &nDescendantsUpdated)
     310             : {
     311             :     // mapModifiedTx will store sorted packages after they are modified
     312             :     // because some of their txs are already in the block
     313       21011 :     indexed_modified_transaction_set mapModifiedTx;
     314             :     // Keep track of entries that failed inclusion, to avoid duplicate work
     315       21011 :     CTxMemPool::setEntries failedTx;
     316             : 
     317             :     // Start by adding all descendants of previously added txs to mapModifiedTx
     318             :     // and modifying them for their already included ancestors
     319       21011 :     UpdatePackagesForAdded(inBlock, mapModifiedTx);
     320             : 
     321       21011 :     CTxMemPool::indexed_transaction_set::index<ancestor_score>::type::iterator mi = m_mempool.mapTx.get<ancestor_score>().begin();
     322       21011 :     CTxMemPool::txiter iter;
     323             : 
     324             :     // Limit the number of attempts to add transactions to the block when it is
     325             :     // close to full; this is just a simple heuristic to finish quickly if the
     326             :     // mempool has a lot of entries.
     327             :     const int64_t MAX_CONSECUTIVE_FAILURES = 1000;
     328       58020 :     int64_t nConsecutiveFailed = 0;
     329             : 
     330       58020 :     while (mi != m_mempool.mapTx.get<ancestor_score>().end() || !mapModifiedTx.empty()) {
     331             :         // First try to find a new transaction in mapTx to evaluate.
     332       73627 :         if (mi != m_mempool.mapTx.get<ancestor_score>().end() &&
     333       36605 :             SkipMapTxEntry(m_mempool.mapTx.project<0>(mi), mapModifiedTx, failedTx)) {
     334        2742 :             ++mi;
     335             :             continue;
     336             :         }
     337             : 
     338             :         // Now that mi is not stale, determine which transaction to evaluate:
     339             :         // the next entry from mapTx, or the best from mapModifiedTx?
     340             :         bool fUsingModified = false;
     341             : 
     342       34280 :         modtxscoreiter modit = mapModifiedTx.get<ancestor_score>().begin();
     343       34280 :         if (mi == m_mempool.mapTx.get<ancestor_score>().end()) {
     344             :             // We're out of entries in mapTx; use the entry from mapModifiedTx
     345         417 :             iter = modit->iter;
     346             :             fUsingModified = true;
     347         417 :         } else {
     348             :             // Try to compare the mapTx entry to the mapModifiedTx entry
     349       33863 :             iter = m_mempool.mapTx.project<0>(mi);
     350       33956 :             if (modit != mapModifiedTx.get<ancestor_score>().end() &&
     351          93 :                     CompareTxMemPoolEntryByAncestorFee()(*modit, CTxMemPoolModifiedEntry(iter))) {
     352             :                 // The best entry in mapModifiedTx has higher score
     353             :                 // than the one from mapTx.
     354             :                 // Switch which transaction (package) to consider
     355          22 :                 iter = modit->iter;
     356             :                 fUsingModified = true;
     357          22 :             } else {
     358             :                 // Either no entry in mapModifiedTx, or it's worse than mapTx.
     359             :                 // Increment mi for the next loop iteration.
     360       33841 :                 ++mi;
     361             :             }
     362             :         }
     363             : 
     364             :         // We skip mapTx entries that are inBlock, and mapModifiedTx shouldn't
     365             :         // contain anything that is inBlock.
     366       34280 :         assert(!inBlock.count(iter));
     367             : 
     368       34280 :         uint64_t packageSize = iter->GetSizeWithAncestors();
     369       34280 :         CAmount packageFees = iter->GetModFeesWithAncestors();
     370       34280 :         int64_t packageSigOpsCost = iter->GetSigOpCostWithAncestors();
     371       34280 :         if (fUsingModified) {
     372         439 :             packageSize = modit->nSizeWithAncestors;
     373         439 :             packageFees = modit->nModFeesWithAncestors;
     374         439 :             packageSigOpsCost = modit->nSigOpCostWithAncestors;
     375         439 :         }
     376             : 
     377       34280 :         if (packageFees < blockMinFeeRate.GetFee(packageSize)) {
     378             :             // Everything else we might consider has a lower fee rate
     379          13 :             return;
     380             :         }
     381             : 
     382       34267 :         if (!TestPackage(packageSize, packageSigOpsCost)) {
     383       24922 :             if (fUsingModified) {
     384             :                 // Since we always look at the best entry in mapModifiedTx,
     385             :                 // we must erase failed entries so that we can consider the
     386             :                 // next best entry on the next loop iteration
     387          36 :                 mapModifiedTx.get<ancestor_score>().erase(modit);
     388          36 :                 failedTx.insert(iter);
     389          36 :             }
     390             : 
     391       24922 :             ++nConsecutiveFailed;
     392             : 
     393       24922 :             if (nConsecutiveFailed > MAX_CONSECUTIVE_FAILURES && nBlockWeight >
     394           0 :                     nBlockMaxWeight - 4000) {
     395             :                 // Give up if we're close to full and haven't succeeded in a while
     396           0 :                 break;
     397             :             }
     398       24922 :             continue;
     399             :         }
     400             : 
     401        9345 :         CTxMemPool::setEntries ancestors;
     402        9345 :         uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
     403        9345 :         std::string dummy;
     404        9345 :         m_mempool.CalculateMemPoolAncestors(*iter, ancestors, nNoLimit, nNoLimit, nNoLimit, nNoLimit, dummy, false);
     405             : 
     406        9345 :         onlyUnconfirmed(ancestors);
     407        9345 :         ancestors.insert(iter);
     408             : 
     409             :         // Test if all tx's are Final
     410        9345 :         if (!TestPackageTransactions(ancestors)) {
     411          28 :             if (fUsingModified) {
     412           0 :                 mapModifiedTx.get<ancestor_score>().erase(modit);
     413           0 :                 failedTx.insert(iter);
     414           0 :             }
     415          28 :             continue;
     416             :         }
     417             : 
     418             :         // This transaction will make it in; reset the failed counter.
     419             :         nConsecutiveFailed = 0;
     420             : 
     421             :         // Package can be added. Sort the entries in a valid order.
     422        9317 :         std::vector<CTxMemPool::txiter> sortedEntries;
     423        9317 :         SortForBlock(ancestors, sortedEntries);
     424             : 
     425       20943 :         for (size_t i=0; i<sortedEntries.size(); ++i) {
     426       11626 :             AddToBlock(sortedEntries[i]);
     427             :             // Erase from the modified set, if present
     428       11626 :             mapModifiedTx.erase(sortedEntries[i]);
     429             :         }
     430             : 
     431        9317 :         ++nPackagesSelected;
     432             : 
     433             :         // Update transactions that depend on each of these
     434        9317 :         nDescendantsUpdated += UpdatePackagesForAdded(ancestors, mapModifiedTx);
     435       34280 :     }
     436       21011 : }
     437             : 
     438       16687 : void IncrementExtraNonce(CBlock* pblock, const CBlockIndex* pindexPrev, unsigned int& nExtraNonce)
     439             : {
     440             :     // Update nExtraNonce
     441       16687 :     static uint256 hashPrevBlock;
     442       16687 :     if (hashPrevBlock != pblock->hashPrevBlock)
     443             :     {
     444       16685 :         nExtraNonce = 0;
     445       16685 :         hashPrevBlock = pblock->hashPrevBlock;
     446       16685 :     }
     447       16687 :     ++nExtraNonce;
     448       16687 :     unsigned int nHeight = pindexPrev->nHeight+1; // Height first in coinbase required for block.version=2
     449       16687 :     CMutableTransaction txCoinbase(*pblock->vtx[0]);
     450       16687 :     txCoinbase.vin[0].scriptSig = (CScript() << nHeight << CScriptNum(nExtraNonce));
     451       16687 :     assert(txCoinbase.vin[0].scriptSig.size() <= 100);
     452             : 
     453       16687 :     pblock->vtx[0] = MakeTransactionRef(std::move(txCoinbase));
     454       16687 :     pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);
     455       16687 : }