src/miner.cpp

   1 // Copyright (c) 2009-2010 Satoshi Nakamoto
   2 // Copyright (c) 2009-2017 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 <util.h>
  26 #include <utilmoneystr.h>
  27 #include <validationinterface.h>
  28
  29 #include <algorithm>
  30 #include <queue>
  31 #include <utility>
  32
  33 //////////////////////////////////////////////////////////////////////////////
  34 //
  35 // BitcoinMiner
  36 //
  37
  38 //
  39 // Unconfirmed transactions in the memory pool often depend on other
  40 // transactions in the memory pool. When we select transactions from the
  41 // pool, we select by highest fee rate of a transaction combined with all
  42 // its ancestors.
  43
  44 uint64_t nLastBlockTx = 0;
  45 uint64_t nLastBlockWeight = 0;
  46
  47 int64_t UpdateTime(CBlockHeader* pblock, const Consensus::Params& consensusParams, const CBlockIndex* pindexPrev)
  48 {
  49     int64_t nOldTime = pblock->nTime;
  50     int64_t nNewTime = std::max(pindexPrev->GetMedianTimePast()+1, GetAdjustedTime());
  51
  52     if (nOldTime < nNewTime)
  53         pblock->nTime = nNewTime;
  54
  55     // Updating time can change work required on testnet:
  56     if (consensusParams.fPowAllowMinDifficultyBlocks)
  57         pblock->nBits = GetNextWorkRequired(pindexPrev, pblock, consensusParams);
  58
  59     return nNewTime - nOldTime;
  60 }
  61
  62 BlockAssembler::Options::Options() {
  63     blockMinFeeRate = CFeeRate(DEFAULT_BLOCK_MIN_TX_FEE);
  64     nBlockMaxWeight = DEFAULT_BLOCK_MAX_WEIGHT;
  65 }
  66
  67 BlockAssembler::BlockAssembler(const CChainParams& params, const Options& options) : chainparams(params)
  68 {
  69     blockMinFeeRate = options.blockMinFeeRate;
  70     // Limit weight to between 4K and MAX_BLOCK_WEIGHT-4K for sanity:
  71     nBlockMaxWeight = std::max<size_t>(4000, std::min<size_t>(MAX_BLOCK_WEIGHT - 4000, options.nBlockMaxWeight));
  72 }
  73
  74 static BlockAssembler::Options DefaultOptions(const CChainParams& params)
  75 {
  76     // Block resource limits
  77     // If neither -blockmaxsize or -blockmaxweight is given, limit to DEFAULT_BLOCK_MAX_*
  78     // If only one is given, only restrict the specified resource.
  79     // If both are given, restrict both.
  80     BlockAssembler::Options options;
  81     options.nBlockMaxWeight = gArgs.GetArg("-blockmaxweight", DEFAULT_BLOCK_MAX_WEIGHT);
  82     if (gArgs.IsArgSet("-blockmintxfee")) {
  83         CAmount n = 0;
  84         ParseMoney(gArgs.GetArg("-blockmintxfee", ""), n);
  85         options.blockMinFeeRate = CFeeRate(n);
  86     } else {
  87         options.blockMinFeeRate = CFeeRate(DEFAULT_BLOCK_MIN_TX_FEE);
  88     }
  89     return options;
  90 }
  91
  92 BlockAssembler::BlockAssembler(const CChainParams& params) : BlockAssembler(params, DefaultOptions(params)) {}
  93
  94 void BlockAssembler::resetBlock()
  95 {
  96     inBlock.clear();
  97
  98     // Reserve space for coinbase tx
  99     nBlockWeight = 4000;
 100     nBlockSigOpsCost = 400;
 101     fIncludeWitness = false;
 102
 103     // These counters do not include coinbase tx
 104     nBlockTx = 0;
 105     nFees = 0;
 106 }
 107
 108 std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn, bool fMineWitnessTx)
 109 {
 110     int64_t nTimeStart = GetTimeMicros();
 111
 112     resetBlock();
 113
 114     pblocktemplate.reset(new CBlockTemplate());
 115
 116     if(!pblocktemplate.get())
 117         return nullptr;
 118     pblock = &pblocktemplate->block; // pointer for convenience
 119
 120     // Add dummy coinbase tx as first transaction
 121     pblock->vtx.emplace_back();
 122     pblocktemplate->vTxFees.push_back(-1); // updated at end
 123     pblocktemplate->vTxSigOpsCost.push_back(-1); // updated at end
 124
 125     LOCK2(cs_main, mempool.cs);
 126     CBlockIndex* pindexPrev = chainActive.Tip();
 127     assert(pindexPrev != nullptr);
 128     nHeight = pindexPrev->nHeight + 1;
 129
 130     pblock->nVersion = ComputeBlockVersion(pindexPrev, chainparams.GetConsensus());
 131     // -regtest only: allow overriding block.nVersion with
 132     // -blockversion=N to test forking scenarios
 133     if (chainparams.MineBlocksOnDemand())
 134         pblock->nVersion = gArgs.GetArg("-blockversion", pblock->nVersion);
 135
 136     pblock->nTime = GetAdjustedTime();
 137     const int64_t nMedianTimePast = pindexPrev->GetMedianTimePast();
 138
 139     nLockTimeCutoff = (STANDARD_LOCKTIME_VERIFY_FLAGS & LOCKTIME_MEDIAN_TIME_PAST)
 140                        ? nMedianTimePast
 141                        : pblock->GetBlockTime();
 142
 143     // Decide whether to include witness transactions
 144     // This is only needed in case the witness softfork activation is reverted
 145     // (which would require a very deep reorganization) or when
 146     // -promiscuousmempoolflags is used.
 147     // TODO: replace this with a call to main to assess validity of a mempool
 148     // transaction (which in most cases can be a no-op).
 149     fIncludeWitness = IsWitnessEnabled(pindexPrev, chainparams.GetConsensus()) && fMineWitnessTx;
 150
 151     int nPackagesSelected = 0;
 152     int nDescendantsUpdated = 0;
 153     addPackageTxs(nPackagesSelected, nDescendantsUpdated);
 154
 155     int64_t nTime1 = GetTimeMicros();
 156
 157     nLastBlockTx = nBlockTx;
 158     nLastBlockWeight = nBlockWeight;
 159
 160     // Create coinbase transaction.
 161     CMutableTransaction coinbaseTx;
 162     coinbaseTx.vin.resize(1);
 163     coinbaseTx.vin[0].prevout.SetNull();
 164     coinbaseTx.vout.resize(1);
 165     coinbaseTx.vout[0].scriptPubKey = scriptPubKeyIn;
 166     coinbaseTx.vout[0].nValue = nFees + GetBlockSubsidy(nHeight, chainparams.GetConsensus());
 167     coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
 168     pblock->vtx[0] = MakeTransactionRef(std::move(coinbaseTx));
 169     pblocktemplate->vchCoinbaseCommitment = GenerateCoinbaseCommitment(*pblock, pindexPrev, chainparams.GetConsensus());
 170     pblocktemplate->vTxFees[0] = -nFees;
 171
 172     LogPrintf("CreateNewBlock(): block weight: %u txs: %u fees: %ld sigops %d\n", GetBlockWeight(*pblock), nBlockTx, nFees, nBlockSigOpsCost);
 173
 174     // Fill in header
 175     pblock->hashPrevBlock  = pindexPrev->GetBlockHash();
 176     UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev);
 177     pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());
 178     pblock->nNonce         = 0;
 179     pblocktemplate->vTxSigOpsCost[0] = WITNESS_SCALE_FACTOR * GetLegacySigOpCount(*pblock->vtx[0]);
 180
 181     CValidationState state;
 182     if (!TestBlockValidity(state, chainparams, *pblock, pindexPrev, false, false)) {
 183         throw std::runtime_error(strprintf("%s: TestBlockValidity failed: %s", __func__, FormatStateMessage(state)));
 184     }
 185     int64_t nTime2 = GetTimeMicros();
 186
 187     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));
 188
 189     return std::move(pblocktemplate);
 190 }
 191
 192 void BlockAssembler::onlyUnconfirmed(CTxMemPool::setEntries& testSet)
 193 {
 194     for (CTxMemPool::setEntries::iterator iit = testSet.begin(); iit != testSet.end(); ) {
 195         // Only test txs not already in the block
 196         if (inBlock.count(*iit)) {
 197             testSet.erase(iit++);
 198         }
 199         else {
 200             iit++;
 201         }
 202     }
 203 }
 204
 205 bool BlockAssembler::TestPackage(uint64_t packageSize, int64_t packageSigOpsCost) const
 206 {
 207     // TODO: switch to weight-based accounting for packages instead of vsize-based accounting.
 208     if (nBlockWeight + WITNESS_SCALE_FACTOR * packageSize >= nBlockMaxWeight)
 209         return false;
 210     if (nBlockSigOpsCost + packageSigOpsCost >= MAX_BLOCK_SIGOPS_COST)
 211         return false;
 212     return true;
 213 }
 214
 215 // Perform transaction-level checks before adding to block:
 216 // - transaction finality (locktime)
 217 // - premature witness (in case segwit transactions are added to mempool before
 218 //   segwit activation)
 219 bool BlockAssembler::TestPackageTransactions(const CTxMemPool::setEntries& package)
 220 {
 221     for (const CTxMemPool::txiter it : package) {
 222         if (!IsFinalTx(it->GetTx(), nHeight, nLockTimeCutoff))
 223             return false;
 224         if (!fIncludeWitness && it->GetTx().HasWitness())
 225             return false;
 226     }
 227     return true;
 228 }
 229
 230 void BlockAssembler::AddToBlock(CTxMemPool::txiter iter)
 231 {
 232     pblock->vtx.emplace_back(iter->GetSharedTx());
 233     pblocktemplate->vTxFees.push_back(iter->GetFee());
 234     pblocktemplate->vTxSigOpsCost.push_back(iter->GetSigOpCost());
 235     nBlockWeight += iter->GetTxWeight();
 236     ++nBlockTx;
 237     nBlockSigOpsCost += iter->GetSigOpCost();
 238     nFees += iter->GetFee();
 239     inBlock.insert(iter);
 240
 241     bool fPrintPriority = gArgs.GetBoolArg("-printpriority", DEFAULT_PRINTPRIORITY);
 242     if (fPrintPriority) {
 243         LogPrintf("fee %s txid %s\n",
 244                   CFeeRate(iter->GetModifiedFee(), iter->GetTxSize()).ToString(),
 245                   iter->GetTx().GetHash().ToString());
 246     }
 247 }
 248
 249 int BlockAssembler::UpdatePackagesForAdded(const CTxMemPool::setEntries& alreadyAdded,
 250         indexed_modified_transaction_set &mapModifiedTx)
 251 {
 252     int nDescendantsUpdated = 0;
 253     for (const CTxMemPool::txiter it : alreadyAdded) {
 254         CTxMemPool::setEntries descendants;
 255         mempool.CalculateDescendants(it, descendants);
 256         // Insert all descendants (not yet in block) into the modified set
 257         for (CTxMemPool::txiter desc : descendants) {
 258             if (alreadyAdded.count(desc))
 259                 continue;
 260             ++nDescendantsUpdated;
 261             modtxiter mit = mapModifiedTx.find(desc);
 262             if (mit == mapModifiedTx.end()) {
 263                 CTxMemPoolModifiedEntry modEntry(desc);
 264                 modEntry.nSizeWithAncestors -= it->GetTxSize();
 265                 modEntry.nModFeesWithAncestors -= it->GetModifiedFee();
 266                 modEntry.nSigOpCostWithAncestors -= it->GetSigOpCost();
 267                 mapModifiedTx.insert(modEntry);
 268             } else {
 269                 mapModifiedTx.modify(mit, update_for_parent_inclusion(it));
 270             }
 271         }
 272     }
 273     return nDescendantsUpdated;
 274 }
 275
 276 // Skip entries in mapTx that are already in a block or are present
 277 // in mapModifiedTx (which implies that the mapTx ancestor state is
 278 // stale due to ancestor inclusion in the block)
 279 // Also skip transactions that we've already failed to add. This can happen if
 280 // we consider a transaction in mapModifiedTx and it fails: we can then
 281 // potentially consider it again while walking mapTx.  It's currently
 282 // guaranteed to fail again, but as a belt-and-suspenders check we put it in
 283 // failedTx and avoid re-evaluation, since the re-evaluation would be using
 284 // cached size/sigops/fee values that are not actually correct.
 285 bool BlockAssembler::SkipMapTxEntry(CTxMemPool::txiter it, indexed_modified_transaction_set &mapModifiedTx, CTxMemPool::setEntries &failedTx)
 286 {
 287     assert (it != mempool.mapTx.end());
 288     return mapModifiedTx.count(it) || inBlock.count(it) || failedTx.count(it);
 289 }
 290
 291 void BlockAssembler::SortForBlock(const CTxMemPool::setEntries& package, CTxMemPool::txiter entry, std::vector<CTxMemPool::txiter>& sortedEntries)
 292 {
 293     // Sort package by ancestor count
 294     // If a transaction A depends on transaction B, then A's ancestor count
 295     // must be greater than B's.  So this is sufficient to validly order the
 296     // transactions for block inclusion.
 297     sortedEntries.clear();
 298     sortedEntries.insert(sortedEntries.begin(), package.begin(), package.end());
 299     std::sort(sortedEntries.begin(), sortedEntries.end(), CompareTxIterByAncestorCount());
 300 }
 301
 302 // This transaction selection algorithm orders the mempool based
 303 // on feerate of a transaction including all unconfirmed ancestors.
 304 // Since we don't remove transactions from the mempool as we select them
 305 // for block inclusion, we need an alternate method of updating the feerate
 306 // of a transaction with its not-yet-selected ancestors as we go.
 307 // This is accomplished by walking the in-mempool descendants of selected
 308 // transactions and storing a temporary modified state in mapModifiedTxs.
 309 // Each time through the loop, we compare the best transaction in
 310 // mapModifiedTxs with the next transaction in the mempool to decide what
 311 // transaction package to work on next.
 312 void BlockAssembler::addPackageTxs(int &nPackagesSelected, int &nDescendantsUpdated)
 313 {
 314     // mapModifiedTx will store sorted packages after they are modified
 315     // because some of their txs are already in the block
 316     indexed_modified_transaction_set mapModifiedTx;
 317     // Keep track of entries that failed inclusion, to avoid duplicate work
 318     CTxMemPool::setEntries failedTx;
 319
 320     // Start by adding all descendants of previously added txs to mapModifiedTx
 321     // and modifying them for their already included ancestors
 322     UpdatePackagesForAdded(inBlock, mapModifiedTx);
 323
 324     CTxMemPool::indexed_transaction_set::index<ancestor_score>::type::iterator mi = mempool.mapTx.get<ancestor_score>().begin();
 325     CTxMemPool::txiter iter;
 326
 327     // Limit the number of attempts to add transactions to the block when it is
 328     // close to full; this is just a simple heuristic to finish quickly if the
 329     // mempool has a lot of entries.
 330     const int64_t MAX_CONSECUTIVE_FAILURES = 1000;
 331     int64_t nConsecutiveFailed = 0;
 332
 333     while (mi != mempool.mapTx.get<ancestor_score>().end() || !mapModifiedTx.empty())
 334     {
 335         // First try to find a new transaction in mapTx to evaluate.
 336         if (mi != mempool.mapTx.get<ancestor_score>().end() &&
 337                 SkipMapTxEntry(mempool.mapTx.project<0>(mi), mapModifiedTx, failedTx)) {
 338             ++mi;
 339             continue;
 340         }
 341
 342         // Now that mi is not stale, determine which transaction to evaluate:
 343         // the next entry from mapTx, or the best from mapModifiedTx?
 344         bool fUsingModified = false;
 345
 346         modtxscoreiter modit = mapModifiedTx.get<ancestor_score>().begin();
 347         if (mi == mempool.mapTx.get<ancestor_score>().end()) {
 348             // We're out of entries in mapTx; use the entry from mapModifiedTx
 349             iter = modit->iter;
 350             fUsingModified = true;
 351         } else {
 352             // Try to compare the mapTx entry to the mapModifiedTx entry
 353             iter = mempool.mapTx.project<0>(mi);
 354             if (modit != mapModifiedTx.get<ancestor_score>().end() &&
 355                     CompareModifiedEntry()(*modit, CTxMemPoolModifiedEntry(iter))) {
 356                 // The best entry in mapModifiedTx has higher score
 357                 // than the one from mapTx.
 358                 // Switch which transaction (package) to consider
 359                 iter = modit->iter;
 360                 fUsingModified = true;
 361             } else {
 362                 // Either no entry in mapModifiedTx, or it's worse than mapTx.
 363                 // Increment mi for the next loop iteration.
 364                 ++mi;
 365             }
 366         }
 367
 368         // We skip mapTx entries that are inBlock, and mapModifiedTx shouldn't
 369         // contain anything that is inBlock.
 370         assert(!inBlock.count(iter));
 371
 372         uint64_t packageSize = iter->GetSizeWithAncestors();
 373         CAmount packageFees = iter->GetModFeesWithAncestors();
 374         int64_t packageSigOpsCost = iter->GetSigOpCostWithAncestors();
 375         if (fUsingModified) {
 376             packageSize = modit->nSizeWithAncestors;
 377             packageFees = modit->nModFeesWithAncestors;
 378             packageSigOpsCost = modit->nSigOpCostWithAncestors;
 379         }
 380
 381         if (packageFees < blockMinFeeRate.GetFee(packageSize)) {
 382             // Everything else we might consider has a lower fee rate
 383             return;
 384         }
 385
 386         if (!TestPackage(packageSize, packageSigOpsCost)) {
 387             if (fUsingModified) {
 388                 // Since we always look at the best entry in mapModifiedTx,
 389                 // we must erase failed entries so that we can consider the
 390                 // next best entry on the next loop iteration
 391                 mapModifiedTx.get<ancestor_score>().erase(modit);
 392                 failedTx.insert(iter);
 393             }
 394
 395             ++nConsecutiveFailed;
 396
 397             if (nConsecutiveFailed > MAX_CONSECUTIVE_FAILURES && nBlockWeight >
 398                     nBlockMaxWeight - 4000) {
 399                 // Give up if we're close to full and haven't succeeded in a while
 400                 break;
 401             }
 402             continue;
 403         }
 404
 405         CTxMemPool::setEntries ancestors;
 406         uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
 407         std::string dummy;
 408         mempool.CalculateMemPoolAncestors(*iter, ancestors, nNoLimit, nNoLimit, nNoLimit, nNoLimit, dummy, false);
 409
 410         onlyUnconfirmed(ancestors);
 411         ancestors.insert(iter);
 412
 413         // Test if all tx's are Final
 414         if (!TestPackageTransactions(ancestors)) {
 415             if (fUsingModified) {
 416                 mapModifiedTx.get<ancestor_score>().erase(modit);
 417                 failedTx.insert(iter);
 418             }
 419             continue;
 420         }
 421
 422         // This transaction will make it in; reset the failed counter.
 423         nConsecutiveFailed = 0;
 424
 425         // Package can be added. Sort the entries in a valid order.
 426         std::vector<CTxMemPool::txiter> sortedEntries;
 427         SortForBlock(ancestors, iter, sortedEntries);
 428
 429         for (size_t i=0; i<sortedEntries.size(); ++i) {
 430             AddToBlock(sortedEntries[i]);
 431             // Erase from the modified set, if present
 432             mapModifiedTx.erase(sortedEntries[i]);
 433         }
 434
 435         ++nPackagesSelected;
 436
 437         // Update transactions that depend on each of these
 438         nDescendantsUpdated += UpdatePackagesForAdded(ancestors, mapModifiedTx);
 439     }
 440 }
 441
 442 void IncrementExtraNonce(CBlock* pblock, const CBlockIndex* pindexPrev, unsigned int& nExtraNonce)
 443 {
 444     // Update nExtraNonce
 445     static uint256 hashPrevBlock;
 446     if (hashPrevBlock != pblock->hashPrevBlock)
 447     {
 448         nExtraNonce = 0;
 449         hashPrevBlock = pblock->hashPrevBlock;
 450     }
 451     ++nExtraNonce;
 452     unsigned int nHeight = pindexPrev->nHeight+1; // Height first in coinbase required for block.version=2
 453     CMutableTransaction txCoinbase(*pblock->vtx[0]);
 454     txCoinbase.vin[0].scriptSig = (CScript() << nHeight << CScriptNum(nExtraNonce)) + COINBASE_FLAGS;
 455     assert(txCoinbase.vin[0].scriptSig.size() <= 100);
 456
 457     pblock->vtx[0] = MakeTransactionRef(std::move(txCoinbase));
 458     pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);
 459 }