src/miner.cpp

   1 // Copyright (c) 2009-2010 Satoshi Nakamoto
   2 // Copyright (c) 2009-2016 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/tx_verify.h"
  14 #include "consensus/merkle.h"
  15 #include "consensus/validation.h"
  16 #include "hash.h"
  17 #include "validation.h"
  18 #include "net.h"
  19 #include "policy/feerate.h"
  20 #include "policy/policy.h"
  21 #include "pow.h"
  22 #include "primitives/transaction.h"
  23 #include "script/standard.h"
  24 #include "timedata.h"
  25 #include "txmempool.h"
  26 #include "util.h"
  27 #include "utilmoneystr.h"
  28 #include "validationinterface.h"
  29
  30 #include <algorithm>
  31 #include <queue>
  32 #include <utility>
  33
  34 //////////////////////////////////////////////////////////////////////////////
  35 //
  36 // BitcoinMiner
  37 //
  38
  39 //
  40 // Unconfirmed transactions in the memory pool often depend on other
  41 // transactions in the memory pool. When we select transactions from the
  42 // pool, we select by highest fee rate of a transaction combined with all
  43 // its ancestors.
  44
  45 uint64_t nLastBlockTx = 0;
  46 uint64_t nLastBlockWeight = 0;
  47
  48 int64_t UpdateTime(CBlockHeader* pblock, const Consensus::Params& consensusParams, const CBlockIndex* pindexPrev)
  49 {
  50     int64_t nOldTime = pblock->nTime;
  51     int64_t nNewTime = std::max(pindexPrev->GetMedianTimePast()+1, GetAdjustedTime());
  52
  53     if (nOldTime < nNewTime)
  54         pblock->nTime = nNewTime;
  55
  56     // Updating time can change work required on testnet:
  57     if (consensusParams.fPowAllowMinDifficultyBlocks)
  58         pblock->nBits = GetNextWorkRequired(pindexPrev, pblock, consensusParams);
  59
  60     return nNewTime - nOldTime;
  61 }
  62
  63 BlockAssembler::Options::Options() {
  64     blockMinFeeRate = CFeeRate(DEFAULT_BLOCK_MIN_TX_FEE);
  65     nBlockMaxWeight = DEFAULT_BLOCK_MAX_WEIGHT;
  66 }
  67
  68 BlockAssembler::BlockAssembler(const CChainParams& params, const Options& options) : chainparams(params)
  69 {
  70     blockMinFeeRate = options.blockMinFeeRate;
  71     // Limit weight to between 4K and MAX_BLOCK_WEIGHT-4K for sanity:
  72     nBlockMaxWeight = std::max<size_t>(4000, std::min<size_t>(MAX_BLOCK_WEIGHT - 4000, options.nBlockMaxWeight));
  73 }
  74
  75 static BlockAssembler::Options DefaultOptions(const CChainParams& params)
  76 {
  77     // Block resource limits
  78     // If neither -blockmaxsize or -blockmaxweight is given, limit to DEFAULT_BLOCK_MAX_*
  79     // If only one is given, only restrict the specified resource.
  80     // If both are given, restrict both.
  81     BlockAssembler::Options options;
  82     options.nBlockMaxWeight = gArgs.GetArg("-blockmaxweight", DEFAULT_BLOCK_MAX_WEIGHT);
  83     if (gArgs.IsArgSet("-blockmintxfee")) {
  84         CAmount n = 0;
  85         ParseMoney(gArgs.GetArg("-blockmintxfee", ""), n);
  86         options.blockMinFeeRate = CFeeRate(n);
  87     } else {
  88         options.blockMinFeeRate = CFeeRate(DEFAULT_BLOCK_MIN_TX_FEE);
  89     }
  90     return options;
  91 }
  92
  93 BlockAssembler::BlockAssembler(const CChainParams& params) : BlockAssembler(params, DefaultOptions(params)) {}
  94
  95 void BlockAssembler::resetBlock()
  96 {
  97     inBlock.clear();
  98
  99     // Reserve space for coinbase tx
 100     nBlockWeight = 4000;
 101     nBlockSigOpsCost = 400;
 102     fIncludeWitness = false;
 103
 104     // These counters do not include coinbase tx
 105     nBlockTx = 0;
 106     nFees = 0;
 107 }
 108
 109 std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn, bool fMineWitnessTx)
 110 {
 111     int64_t nTimeStart = GetTimeMicros();
 112
 113     resetBlock();
 114
 115     pblocktemplate.reset(new CBlockTemplate());
 116
 117     if(!pblocktemplate.get())
 118         return nullptr;
 119     pblock = &pblocktemplate->block; // pointer for convenience
 120
 121     // Add dummy coinbase tx as first transaction
 122     pblock->vtx.emplace_back();
 123     pblocktemplate->vTxFees.push_back(-1); // updated at end
 124     pblocktemplate->vTxSigOpsCost.push_back(-1); // updated at end
 125
 126     LOCK2(cs_main, mempool.cs);
 127     CBlockIndex* pindexPrev = chainActive.Tip();
 128     assert(pindexPrev != nullptr);
 129     nHeight = pindexPrev->nHeight + 1;
 130
 131     pblock->nVersion = ComputeBlockVersion(pindexPrev, chainparams.GetConsensus());
 132     // -regtest only: allow overriding block.nVersion with
 133     // -blockversion=N to test forking scenarios
 134     if (chainparams.MineBlocksOnDemand())
 135         pblock->nVersion = gArgs.GetArg("-blockversion", pblock->nVersion);
 136
 137     pblock->nTime = GetAdjustedTime();
 138     const int64_t nMedianTimePast = pindexPrev->GetMedianTimePast();
 139
 140     nLockTimeCutoff = (STANDARD_LOCKTIME_VERIFY_FLAGS & LOCKTIME_MEDIAN_TIME_PAST)
 141                        ? nMedianTimePast
 142                        : pblock->GetBlockTime();
 143
 144     // Decide whether to include witness transactions
 145     // This is only needed in case the witness softfork activation is reverted
 146     // (which would require a very deep reorganization) or when
 147     // -promiscuousmempoolflags is used.
 148     // TODO: replace this with a call to main to assess validity of a mempool
 149     // transaction (which in most cases can be a no-op).
 150     fIncludeWitness = IsWitnessEnabled(pindexPrev, chainparams.GetConsensus()) && fMineWitnessTx;
 151
 152     int nPackagesSelected = 0;
 153     int nDescendantsUpdated = 0;
 154     addPackageTxs(nPackagesSelected, nDescendantsUpdated);
 155
 156     int64_t nTime1 = GetTimeMicros();
 157
 158     nLastBlockTx = nBlockTx;
 159     nLastBlockWeight = nBlockWeight;
 160
 161     // Create coinbase transaction.
 162     CMutableTransaction coinbaseTx;
 163     coinbaseTx.vin.resize(1);
 164     coinbaseTx.vin[0].prevout.SetNull();
 165     coinbaseTx.vout.resize(1);
 166     coinbaseTx.vout[0].scriptPubKey = scriptPubKeyIn;
 167     coinbaseTx.vout[0].nValue = nFees + GetBlockSubsidy(nHeight, chainparams.GetConsensus());
 168     coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
 169     pblock->vtx[0] = MakeTransactionRef(std::move(coinbaseTx));
 170     pblocktemplate->vchCoinbaseCommitment = GenerateCoinbaseCommitment(*pblock, pindexPrev, chainparams.GetConsensus());
 171     pblocktemplate->vTxFees[0] = -nFees;
 172
 173     LogPrintf("CreateNewBlock(): block weight: %u txs: %u fees: %ld sigops %d\n", GetBlockWeight(*pblock), nBlockTx, nFees, nBlockSigOpsCost);
 174
 175     // Fill in header
 176     pblock->hashPrevBlock  = pindexPrev->GetBlockHash();
 177     UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev);
 178     pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());
 179     pblock->nNonce         = 0;
 180     pblocktemplate->vTxSigOpsCost[0] = WITNESS_SCALE_FACTOR * GetLegacySigOpCount(*pblock->vtx[0]);
 181
 182     CValidationState state;
 183     if (!TestBlockValidity(state, chainparams, *pblock, pindexPrev, false, false)) {
 184         throw std::runtime_error(strprintf("%s: TestBlockValidity failed: %s", __func__, FormatStateMessage(state)));
 185     }
 186     int64_t nTime2 = GetTimeMicros();
 187
 188     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));
 189
 190     return std::move(pblocktemplate);
 191 }
 192
 193 void BlockAssembler::onlyUnconfirmed(CTxMemPool::setEntries& testSet)
 194 {
 195     for (CTxMemPool::setEntries::iterator iit = testSet.begin(); iit != testSet.end(); ) {
 196         // Only test txs not already in the block
 197         if (inBlock.count(*iit)) {
 198             testSet.erase(iit++);
 199         }
 200         else {
 201             iit++;
 202         }
 203     }
 204 }
 205
 206 bool BlockAssembler::TestPackage(uint64_t packageSize, int64_t packageSigOpsCost) const
 207 {
 208     // TODO: switch to weight-based accounting for packages instead of vsize-based accounting.
 209     if (nBlockWeight + WITNESS_SCALE_FACTOR * packageSize >= nBlockMaxWeight)
 210         return false;
 211     if (nBlockSigOpsCost + packageSigOpsCost >= MAX_BLOCK_SIGOPS_COST)
 212         return false;
 213     return true;
 214 }
 215
 216 // Perform transaction-level checks before adding to block:
 217 // - transaction finality (locktime)
 218 // - premature witness (in case segwit transactions are added to mempool before
 219 //   segwit activation)
 220 bool BlockAssembler::TestPackageTransactions(const CTxMemPool::setEntries& package)
 221 {
 222     for (const CTxMemPool::txiter it : package) {
 223         if (!IsFinalTx(it->GetTx(), nHeight, nLockTimeCutoff))
 224             return false;
 225         if (!fIncludeWitness && it->GetTx().HasWitness())
 226             return false;
 227     }
 228     return true;
 229 }
 230
 231 void BlockAssembler::AddToBlock(CTxMemPool::txiter iter)
 232 {
 233     pblock->vtx.emplace_back(iter->GetSharedTx());
 234     pblocktemplate->vTxFees.push_back(iter->GetFee());
 235     pblocktemplate->vTxSigOpsCost.push_back(iter->GetSigOpCost());
 236     nBlockWeight += iter->GetTxWeight();
 237     ++nBlockTx;
 238     nBlockSigOpsCost += iter->GetSigOpCost();
 239     nFees += iter->GetFee();
 240     inBlock.insert(iter);
 241
 242     bool fPrintPriority = gArgs.GetBoolArg("-printpriority", DEFAULT_PRINTPRIORITY);
 243     if (fPrintPriority) {
 244         LogPrintf("fee %s txid %s\n",
 245                   CFeeRate(iter->GetModifiedFee(), iter->GetTxSize()).ToString(),
 246                   iter->GetTx().GetHash().ToString());
 247     }
 248 }
 249
 250 int BlockAssembler::UpdatePackagesForAdded(const CTxMemPool::setEntries& alreadyAdded,
 251         indexed_modified_transaction_set &mapModifiedTx)
 252 {
 253     int nDescendantsUpdated = 0;
 254     for (const CTxMemPool::txiter it : alreadyAdded) {
 255         CTxMemPool::setEntries descendants;
 256         mempool.CalculateDescendants(it, descendants);
 257         // Insert all descendants (not yet in block) into the modified set
 258         for (CTxMemPool::txiter desc : descendants) {
 259             if (alreadyAdded.count(desc))
 260                 continue;
 261             ++nDescendantsUpdated;
 262             modtxiter mit = mapModifiedTx.find(desc);
 263             if (mit == mapModifiedTx.end()) {
 264                 CTxMemPoolModifiedEntry modEntry(desc);
 265                 modEntry.nSizeWithAncestors -= it->GetTxSize();
 266                 modEntry.nModFeesWithAncestors -= it->GetModifiedFee();
 267                 modEntry.nSigOpCostWithAncestors -= it->GetSigOpCost();
 268                 mapModifiedTx.insert(modEntry);
 269             } else {
 270                 mapModifiedTx.modify(mit, update_for_parent_inclusion(it));
 271             }
 272         }
 273     }
 274     return nDescendantsUpdated;
 275 }
 276
 277 // Skip entries in mapTx that are already in a block or are present
 278 // in mapModifiedTx (which implies that the mapTx ancestor state is
 279 // stale due to ancestor inclusion in the block)
 280 // Also skip transactions that we've already failed to add. This can happen if
 281 // we consider a transaction in mapModifiedTx and it fails: we can then
 282 // potentially consider it again while walking mapTx.  It's currently
 283 // guaranteed to fail again, but as a belt-and-suspenders check we put it in
 284 // failedTx and avoid re-evaluation, since the re-evaluation would be using
 285 // cached size/sigops/fee values that are not actually correct.
 286 bool BlockAssembler::SkipMapTxEntry(CTxMemPool::txiter it, indexed_modified_transaction_set &mapModifiedTx, CTxMemPool::setEntries &failedTx)
 287 {
 288     assert (it != mempool.mapTx.end());
 289     return mapModifiedTx.count(it) || inBlock.count(it) || failedTx.count(it);
 290 }
 291
 292 void BlockAssembler::SortForBlock(const CTxMemPool::setEntries& package, CTxMemPool::txiter entry, std::vector<CTxMemPool::txiter>& sortedEntries)
 293 {
 294     // Sort package by ancestor count
 295     // If a transaction A depends on transaction B, then A's ancestor count
 296     // must be greater than B's.  So this is sufficient to validly order the
 297     // transactions for block inclusion.
 298     sortedEntries.clear();
 299     sortedEntries.insert(sortedEntries.begin(), package.begin(), package.end());
 300     std::sort(sortedEntries.begin(), sortedEntries.end(), CompareTxIterByAncestorCount());
 301 }
 302
 303 // This transaction selection algorithm orders the mempool based
 304 // on feerate of a transaction including all unconfirmed ancestors.
 305 // Since we don't remove transactions from the mempool as we select them
 306 // for block inclusion, we need an alternate method of updating the feerate
 307 // of a transaction with its not-yet-selected ancestors as we go.
 308 // This is accomplished by walking the in-mempool descendants of selected
 309 // transactions and storing a temporary modified state in mapModifiedTxs.
 310 // Each time through the loop, we compare the best transaction in
 311 // mapModifiedTxs with the next transaction in the mempool to decide what
 312 // transaction package to work on next.
 313 void BlockAssembler::addPackageTxs(int &nPackagesSelected, int &nDescendantsUpdated)
 314 {
 315     // mapModifiedTx will store sorted packages after they are modified
 316     // because some of their txs are already in the block
 317     indexed_modified_transaction_set mapModifiedTx;
 318     // Keep track of entries that failed inclusion, to avoid duplicate work
 319     CTxMemPool::setEntries failedTx;
 320
 321     // Start by adding all descendants of previously added txs to mapModifiedTx
 322     // and modifying them for their already included ancestors
 323     UpdatePackagesForAdded(inBlock, mapModifiedTx);
 324
 325     CTxMemPool::indexed_transaction_set::index<ancestor_score>::type::iterator mi = mempool.mapTx.get<ancestor_score>().begin();
 326     CTxMemPool::txiter iter;
 327
 328     // Limit the number of attempts to add transactions to the block when it is
 329     // close to full; this is just a simple heuristic to finish quickly if the
 330     // mempool has a lot of entries.
 331     const int64_t MAX_CONSECUTIVE_FAILURES = 1000;
 332     int64_t nConsecutiveFailed = 0;
 333
 334     while (mi != mempool.mapTx.get<ancestor_score>().end() || !mapModifiedTx.empty())
 335     {
 336         // First try to find a new transaction in mapTx to evaluate.
 337         if (mi != mempool.mapTx.get<ancestor_score>().end() &&
 338                 SkipMapTxEntry(mempool.mapTx.project<0>(mi), mapModifiedTx, failedTx)) {
 339             ++mi;
 340             continue;
 341         }
 342
 343         // Now that mi is not stale, determine which transaction to evaluate:
 344         // the next entry from mapTx, or the best from mapModifiedTx?
 345         bool fUsingModified = false;
 346
 347         modtxscoreiter modit = mapModifiedTx.get<ancestor_score>().begin();
 348         if (mi == mempool.mapTx.get<ancestor_score>().end()) {
 349             // We're out of entries in mapTx; use the entry from mapModifiedTx
 350             iter = modit->iter;
 351             fUsingModified = true;
 352         } else {
 353             // Try to compare the mapTx entry to the mapModifiedTx entry
 354             iter = mempool.mapTx.project<0>(mi);
 355             if (modit != mapModifiedTx.get<ancestor_score>().end() &&
 356                     CompareModifiedEntry()(*modit, CTxMemPoolModifiedEntry(iter))) {
 357                 // The best entry in mapModifiedTx has higher score
 358                 // than the one from mapTx.
 359                 // Switch which transaction (package) to consider
 360                 iter = modit->iter;
 361                 fUsingModified = true;
 362             } else {
 363                 // Either no entry in mapModifiedTx, or it's worse than mapTx.
 364                 // Increment mi for the next loop iteration.
 365                 ++mi;
 366             }
 367         }
 368
 369         // We skip mapTx entries that are inBlock, and mapModifiedTx shouldn't
 370         // contain anything that is inBlock.
 371         assert(!inBlock.count(iter));
 372
 373         uint64_t packageSize = iter->GetSizeWithAncestors();
 374         CAmount packageFees = iter->GetModFeesWithAncestors();
 375         int64_t packageSigOpsCost = iter->GetSigOpCostWithAncestors();
 376         if (fUsingModified) {
 377             packageSize = modit->nSizeWithAncestors;
 378             packageFees = modit->nModFeesWithAncestors;
 379             packageSigOpsCost = modit->nSigOpCostWithAncestors;
 380         }
 381
 382         if (packageFees < blockMinFeeRate.GetFee(packageSize)) {
 383             // Everything else we might consider has a lower fee rate
 384             return;
 385         }
 386
 387         if (!TestPackage(packageSize, packageSigOpsCost)) {
 388             if (fUsingModified) {
 389                 // Since we always look at the best entry in mapModifiedTx,
 390                 // we must erase failed entries so that we can consider the
 391                 // next best entry on the next loop iteration
 392                 mapModifiedTx.get<ancestor_score>().erase(modit);
 393                 failedTx.insert(iter);
 394             }
 395
 396             ++nConsecutiveFailed;
 397
 398             if (nConsecutiveFailed > MAX_CONSECUTIVE_FAILURES && nBlockWeight >
 399                     nBlockMaxWeight - 4000) {
 400                 // Give up if we're close to full and haven't succeeded in a while
 401                 break;
 402             }
 403             continue;
 404         }
 405
 406         CTxMemPool::setEntries ancestors;
 407         uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
 408         std::string dummy;
 409         mempool.CalculateMemPoolAncestors(*iter, ancestors, nNoLimit, nNoLimit, nNoLimit, nNoLimit, dummy, false);
 410
 411         onlyUnconfirmed(ancestors);
 412         ancestors.insert(iter);
 413
 414         // Test if all tx's are Final
 415         if (!TestPackageTransactions(ancestors)) {
 416             if (fUsingModified) {
 417                 mapModifiedTx.get<ancestor_score>().erase(modit);
 418                 failedTx.insert(iter);
 419             }
 420             continue;
 421         }
 422
 423         // This transaction will make it in; reset the failed counter.
 424         nConsecutiveFailed = 0;
 425
 426         // Package can be added. Sort the entries in a valid order.
 427         std::vector<CTxMemPool::txiter> sortedEntries;
 428         SortForBlock(ancestors, iter, sortedEntries);
 429
 430         for (size_t i=0; i<sortedEntries.size(); ++i) {
 431             AddToBlock(sortedEntries[i]);
 432             // Erase from the modified set, if present
 433             mapModifiedTx.erase(sortedEntries[i]);
 434         }
 435
 436         ++nPackagesSelected;
 437
 438         // Update transactions that depend on each of these
 439         nDescendantsUpdated += UpdatePackagesForAdded(ancestors, mapModifiedTx);
 440     }
 441 }
 442
 443 void IncrementExtraNonce(CBlock* pblock, const CBlockIndex* pindexPrev, unsigned int& nExtraNonce)
 444 {
 445     // Update nExtraNonce
 446     static uint256 hashPrevBlock;
 447     if (hashPrevBlock != pblock->hashPrevBlock)
 448     {
 449         nExtraNonce = 0;
 450         hashPrevBlock = pblock->hashPrevBlock;
 451     }
 452     ++nExtraNonce;
 453     unsigned int nHeight = pindexPrev->nHeight+1; // Height first in coinbase required for block.version=2
 454     CMutableTransaction txCoinbase(*pblock->vtx[0]);
 455     txCoinbase.vin[0].scriptSig = (CScript() << nHeight << CScriptNum(nExtraNonce)) + COINBASE_FLAGS;
 456     assert(txCoinbase.vin[0].scriptSig.size() <= 100);
 457
 458     pblock->vtx[0] = MakeTransactionRef(std::move(txCoinbase));
 459     pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);
 460 }