1  // Copyright (c) 2009-2010 Satoshi Nakamoto
  2  // Copyright (c) 2009-2022 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 <node/miner.h>
  7  
  8  #include <chain.h>
  9  #include <chainparams.h>
 10  #include <coins.h>
 11  #include <common/args.h>
 12  #include <consensus/amount.h>
 13  #include <consensus/consensus.h>
 14  #include <consensus/merkle.h>
 15  #include <consensus/tx_verify.h>
 16  #include <consensus/validation.h>
 17  #include <deploymentstatus.h>
 18  #include <logging.h>
 19  #include <policy/feerate.h>
 20  #include <policy/policy.h>
 21  #include <pow.h>
 22  #include <primitives/transaction.h>
 23  #include <util/moneystr.h>
 24  #include <util/time.h>
 25  #include <validation.h>
 26  
 27  #include <algorithm>
 28  #include <utility>
 29  
 30  namespace node {
 31  
 32  int64_t GetMinimumTime(const CBlockIndex* pindexPrev, const int64_t difficulty_adjustment_interval)
 33  {
 34      int64_t min_time{pindexPrev->GetMedianTimePast() + 1};
 35      // Height of block to be mined.
 36      const int height{pindexPrev->nHeight + 1};
 37      // Account for BIP94 timewarp rule on all networks. This makes future
 38      // activation safer.
 39      if (height % difficulty_adjustment_interval == 0) {
 40          min_time = std::max<int64_t>(min_time, pindexPrev->GetBlockTime() - MAX_TIMEWARP);
 41      }
 42      return min_time;
 43  }
 44  
 45  int64_t UpdateTime(CBlockHeader* pblock, const Consensus::Params& consensusParams, const CBlockIndex* pindexPrev)
 46  {
 47      int64_t nOldTime = pblock->nTime;
 48      int64_t nNewTime{std::max<int64_t>(GetMinimumTime(pindexPrev, consensusParams.DifficultyAdjustmentInterval()),
 49                                         TicksSinceEpoch<std::chrono::seconds>(NodeClock::now()))};
 50  
 51      if (nOldTime < nNewTime) {
 52          pblock->nTime = nNewTime;
 53      }
 54  
 55      // Updating time can change work required on testnet:
 56      if (consensusParams.fPowAllowMinDifficultyBlocks) {
 57          pblock->nBits = GetNextWorkRequired(pindexPrev, pblock, consensusParams);
 58      }
 59  
 60      return nNewTime - nOldTime;
 61  }
 62  
 63  void RegenerateCommitments(CBlock& block, ChainstateManager& chainman)
 64  {
 65      CMutableTransaction tx{*block.vtx.at(0)};
 66      tx.vout.erase(tx.vout.begin() + GetWitnessCommitmentIndex(block));
 67      block.vtx.at(0) = MakeTransactionRef(tx);
 68  
 69      const CBlockIndex* prev_block = WITH_LOCK(::cs_main, return chainman.m_blockman.LookupBlockIndex(block.hashPrevBlock));
 70      chainman.GenerateCoinbaseCommitment(block, prev_block);
 71  
 72      block.hashMerkleRoot = BlockMerkleRoot(block);
 73  }
 74  
 75  static BlockAssembler::Options ClampOptions(BlockAssembler::Options options)
 76  {
 77      Assert(options.block_reserved_weight <= MAX_BLOCK_WEIGHT);
 78      Assert(options.block_reserved_weight >= MINIMUM_BLOCK_RESERVED_WEIGHT);
 79      Assert(options.coinbase_output_max_additional_sigops <= MAX_BLOCK_SIGOPS_COST);
 80      // Limit weight to between block_reserved_weight and MAX_BLOCK_WEIGHT for sanity:
 81      // block_reserved_weight can safely exceed -blockmaxweight, but the rest of the block template will be empty.
 82      options.nBlockMaxWeight = std::clamp<size_t>(options.nBlockMaxWeight, options.block_reserved_weight, MAX_BLOCK_WEIGHT);
 83      return options;
 84  }
 85  
 86  BlockAssembler::BlockAssembler(Chainstate& chainstate, const CTxMemPool* mempool, const Options& options)
 87      : chainparams{chainstate.m_chainman.GetParams()},
 88        m_mempool{options.use_mempool ? mempool : nullptr},
 89        m_chainstate{chainstate},
 90        m_options{ClampOptions(options)}
 91  {
 92  }
 93  
 94  void ApplyArgsManOptions(const ArgsManager& args, BlockAssembler::Options& options)
 95  {
 96      // Block resource limits
 97      options.nBlockMaxWeight = args.GetIntArg("-blockmaxweight", options.nBlockMaxWeight);
 98      if (const auto blockmintxfee{args.GetArg("-blockmintxfee")}) {
 99          if (const auto parsed{ParseMoney(*blockmintxfee)}) options.blockMinFeeRate = CFeeRate{*parsed};
100      }
101      options.print_modified_fee = args.GetBoolArg("-printpriority", options.print_modified_fee);
102      options.block_reserved_weight = args.GetIntArg("-blockreservedweight", options.block_reserved_weight);
103  }
104  
105  void BlockAssembler::resetBlock()
106  {
107      inBlock.clear();
108  
109      // Reserve space for fixed-size block header, txs count, and coinbase tx.
110      nBlockWeight = m_options.block_reserved_weight;
111      nBlockSigOpsCost = m_options.coinbase_output_max_additional_sigops;
112  
113      // These counters do not include coinbase tx
114      nBlockTx = 0;
115      nFees = 0;
116  }
117  
118  std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock()
119  {
120      const auto time_start{SteadyClock::now()};
121  
122      resetBlock();
123  
124      pblocktemplate.reset(new CBlockTemplate());
125      CBlock* const pblock = &pblocktemplate->block; // pointer for convenience
126  
127      // Add dummy coinbase tx as first transaction. It is skipped by the
128      // getblocktemplate RPC and mining interface consumers must not use it.
129      pblock->vtx.emplace_back();
130  
131      LOCK(::cs_main);
132      CBlockIndex* pindexPrev = m_chainstate.m_chain.Tip();
133      assert(pindexPrev != nullptr);
134      nHeight = pindexPrev->nHeight + 1;
135  
136      pblock->nVersion = m_chainstate.m_chainman.m_versionbitscache.ComputeBlockVersion(pindexPrev, chainparams.GetConsensus());
137      // -regtest only: allow overriding block.nVersion with
138      // -blockversion=N to test forking scenarios
139      if (chainparams.MineBlocksOnDemand()) {
140          pblock->nVersion = gArgs.GetIntArg("-blockversion", pblock->nVersion);
141      }
142  
143      pblock->nTime = TicksSinceEpoch<std::chrono::seconds>(NodeClock::now());
144      m_lock_time_cutoff = pindexPrev->GetMedianTimePast();
145  
146      int nPackagesSelected = 0;
147      int nDescendantsUpdated = 0;
148      if (m_mempool) {
149          addPackageTxs(nPackagesSelected, nDescendantsUpdated);
150      }
151  
152      const auto time_1{SteadyClock::now()};
153  
154      m_last_block_num_txs = nBlockTx;
155      m_last_block_weight = nBlockWeight;
156  
157      // Create coinbase transaction.
158      CMutableTransaction coinbaseTx;
159      coinbaseTx.vin.resize(1);
160      coinbaseTx.vin[0].prevout.SetNull();
161      coinbaseTx.vout.resize(1);
162      coinbaseTx.vout[0].scriptPubKey = m_options.coinbase_output_script;
163      coinbaseTx.vout[0].nValue = nFees + GetBlockSubsidy(nHeight, chainparams.GetConsensus());
164      coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
165      pblock->vtx[0] = MakeTransactionRef(std::move(coinbaseTx));
166      pblocktemplate->vchCoinbaseCommitment = m_chainstate.m_chainman.GenerateCoinbaseCommitment(*pblock, pindexPrev);
167  
168      LogPrintf("CreateNewBlock(): block weight: %u txs: %u fees: %ld sigops %d\n", GetBlockWeight(*pblock), nBlockTx, nFees, nBlockSigOpsCost);
169  
170      // Fill in header
171      pblock->hashPrevBlock  = pindexPrev->GetBlockHash();
172      UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev);
173      pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());
174      pblock->nNonce         = 0;
175  
176      BlockValidationState state;
177      if (m_options.test_block_validity && !TestBlockValidity(state, chainparams, m_chainstate, *pblock, pindexPrev,
178                                                              /*fCheckPOW=*/false, /*fCheckMerkleRoot=*/false)) {
179          throw std::runtime_error(strprintf("%s: TestBlockValidity failed: %s", __func__, state.ToString()));
180      }
181      const auto time_2{SteadyClock::now()};
182  
183      LogDebug(BCLog::BENCH, "CreateNewBlock() packages: %.2fms (%d packages, %d updated descendants), validity: %.2fms (total %.2fms)\n",
184               Ticks<MillisecondsDouble>(time_1 - time_start), nPackagesSelected, nDescendantsUpdated,
185               Ticks<MillisecondsDouble>(time_2 - time_1),
186               Ticks<MillisecondsDouble>(time_2 - time_start));
187  
188      return std::move(pblocktemplate);
189  }
190  
191  void BlockAssembler::onlyUnconfirmed(CTxMemPool::setEntries& testSet)
192  {
193      for (CTxMemPool::setEntries::iterator iit = testSet.begin(); iit != testSet.end(); ) {
194          // Only test txs not already in the block
195          if (inBlock.count((*iit)->GetSharedTx()->GetHash())) {
196              testSet.erase(iit++);
197          } else {
198              iit++;
199          }
200      }
201  }
202  
203  bool BlockAssembler::TestPackage(uint64_t packageSize, int64_t packageSigOpsCost) const
204  {
205      // TODO: switch to weight-based accounting for packages instead of vsize-based accounting.
206      if (nBlockWeight + WITNESS_SCALE_FACTOR * packageSize >= m_options.nBlockMaxWeight) {
207          return false;
208      }
209      if (nBlockSigOpsCost + packageSigOpsCost >= MAX_BLOCK_SIGOPS_COST) {
210          return false;
211      }
212      return true;
213  }
214  
215  // Perform transaction-level checks before adding to block:
216  // - transaction finality (locktime)
217  bool BlockAssembler::TestPackageTransactions(const CTxMemPool::setEntries& package) const
218  {
219      for (CTxMemPool::txiter it : package) {
220          if (!IsFinalTx(it->GetTx(), nHeight, m_lock_time_cutoff)) {
221              return false;
222          }
223      }
224      return true;
225  }
226  
227  void BlockAssembler::AddToBlock(CTxMemPool::txiter iter)
228  {
229      pblocktemplate->block.vtx.emplace_back(iter->GetSharedTx());
230      pblocktemplate->vTxFees.push_back(iter->GetFee());
231      pblocktemplate->vTxSigOpsCost.push_back(iter->GetSigOpCost());
232      nBlockWeight += iter->GetTxWeight();
233      ++nBlockTx;
234      nBlockSigOpsCost += iter->GetSigOpCost();
235      nFees += iter->GetFee();
236      inBlock.insert(iter->GetSharedTx()->GetHash());
237  
238      if (m_options.print_modified_fee) {
239          LogPrintf("fee rate %s txid %s\n",
240                    CFeeRate(iter->GetModifiedFee(), iter->GetTxSize()).ToString(),
241                    iter->GetTx().GetHash().ToString());
242      }
243  }
244  
245  /** Add descendants of given transactions to mapModifiedTx with ancestor
246   * state updated assuming given transactions are inBlock. Returns number
247   * of updated descendants. */
248  static int UpdatePackagesForAdded(const CTxMemPool& mempool,
249                                    const CTxMemPool::setEntries& alreadyAdded,
250                                    indexed_modified_transaction_set& mapModifiedTx) EXCLUSIVE_LOCKS_REQUIRED(mempool.cs)
251  {
252      AssertLockHeld(mempool.cs);
253  
254      int nDescendantsUpdated = 0;
255      for (CTxMemPool::txiter it : alreadyAdded) {
256          CTxMemPool::setEntries descendants;
257          mempool.CalculateDescendants(it, descendants);
258          // Insert all descendants (not yet in block) into the modified set
259          for (CTxMemPool::txiter desc : descendants) {
260              if (alreadyAdded.count(desc)) {
261                  continue;
262              }
263              ++nDescendantsUpdated;
264              modtxiter mit = mapModifiedTx.find(desc);
265              if (mit == mapModifiedTx.end()) {
266                  CTxMemPoolModifiedEntry modEntry(desc);
267                  mit = mapModifiedTx.insert(modEntry).first;
268              }
269              mapModifiedTx.modify(mit, update_for_parent_inclusion(it));
270          }
271      }
272      return nDescendantsUpdated;
273  }
274  
275  void BlockAssembler::SortForBlock(const CTxMemPool::setEntries& package, std::vector<CTxMemPool::txiter>& sortedEntries)
276  {
277      // Sort package by ancestor count
278      // If a transaction A depends on transaction B, then A's ancestor count
279      // must be greater than B's.  So this is sufficient to validly order the
280      // transactions for block inclusion.
281      sortedEntries.clear();
282      sortedEntries.insert(sortedEntries.begin(), package.begin(), package.end());
283      std::sort(sortedEntries.begin(), sortedEntries.end(), CompareTxIterByAncestorCount());
284  }
285  
286  // This transaction selection algorithm orders the mempool based
287  // on feerate of a transaction including all unconfirmed ancestors.
288  // Since we don't remove transactions from the mempool as we select them
289  // for block inclusion, we need an alternate method of updating the feerate
290  // of a transaction with its not-yet-selected ancestors as we go.
291  // This is accomplished by walking the in-mempool descendants of selected
292  // transactions and storing a temporary modified state in mapModifiedTxs.
293  // Each time through the loop, we compare the best transaction in
294  // mapModifiedTxs with the next transaction in the mempool to decide what
295  // transaction package to work on next.
296  void BlockAssembler::addPackageTxs(int& nPackagesSelected, int& nDescendantsUpdated)
297  {
298      const auto& mempool{*Assert(m_mempool)};
299      LOCK(mempool.cs);
300  
301      // mapModifiedTx will store sorted packages after they are modified
302      // because some of their txs are already in the block
303      indexed_modified_transaction_set mapModifiedTx;
304      // Keep track of entries that failed inclusion, to avoid duplicate work
305      std::set<Txid> failedTx;
306  
307      CTxMemPool::indexed_transaction_set::index<ancestor_score>::type::iterator mi = mempool.mapTx.get<ancestor_score>().begin();
308      CTxMemPool::txiter iter;
309  
310      // Limit the number of attempts to add transactions to the block when it is
311      // close to full; this is just a simple heuristic to finish quickly if the
312      // mempool has a lot of entries.
313      const int64_t MAX_CONSECUTIVE_FAILURES = 1000;
314      constexpr int32_t BLOCK_FULL_ENOUGH_WEIGHT_DELTA = 4000;
315      int64_t nConsecutiveFailed = 0;
316  
317      while (mi != mempool.mapTx.get<ancestor_score>().end() || !mapModifiedTx.empty()) {
318          // First try to find a new transaction in mapTx to evaluate.
319          //
320          // Skip entries in mapTx that are already in a block or are present
321          // in mapModifiedTx (which implies that the mapTx ancestor state is
322          // stale due to ancestor inclusion in the block)
323          // Also skip transactions that we've already failed to add. This can happen if
324          // we consider a transaction in mapModifiedTx and it fails: we can then
325          // potentially consider it again while walking mapTx.  It's currently
326          // guaranteed to fail again, but as a belt-and-suspenders check we put it in
327          // failedTx and avoid re-evaluation, since the re-evaluation would be using
328          // cached size/sigops/fee values that are not actually correct.
329          /** Return true if given transaction from mapTx has already been evaluated,
330           * or if the transaction's cached data in mapTx is incorrect. */
331          if (mi != mempool.mapTx.get<ancestor_score>().end()) {
332              auto it = mempool.mapTx.project<0>(mi);
333              assert(it != mempool.mapTx.end());
334              if (mapModifiedTx.count(it) || inBlock.count(it->GetSharedTx()->GetHash()) || failedTx.count(it->GetSharedTx()->GetHash())) {
335                  ++mi;
336                  continue;
337              }
338          }
339  
340          // Now that mi is not stale, determine which transaction to evaluate:
341          // the next entry from mapTx, or the best from mapModifiedTx?
342          bool fUsingModified = false;
343  
344          modtxscoreiter modit = mapModifiedTx.get<ancestor_score>().begin();
345          if (mi == mempool.mapTx.get<ancestor_score>().end()) {
346              // We're out of entries in mapTx; use the entry from mapModifiedTx
347              iter = modit->iter;
348              fUsingModified = true;
349          } else {
350              // Try to compare the mapTx entry to the mapModifiedTx entry
351              iter = mempool.mapTx.project<0>(mi);
352              if (modit != mapModifiedTx.get<ancestor_score>().end() &&
353                      CompareTxMemPoolEntryByAncestorFee()(*modit, CTxMemPoolModifiedEntry(iter))) {
354                  // The best entry in mapModifiedTx has higher score
355                  // than the one from mapTx.
356                  // Switch which transaction (package) to consider
357                  iter = modit->iter;
358                  fUsingModified = true;
359              } else {
360                  // Either no entry in mapModifiedTx, or it's worse than mapTx.
361                  // Increment mi for the next loop iteration.
362                  ++mi;
363              }
364          }
365  
366          // We skip mapTx entries that are inBlock, and mapModifiedTx shouldn't
367          // contain anything that is inBlock.
368          assert(!inBlock.count(iter->GetSharedTx()->GetHash()));
369  
370          uint64_t packageSize = iter->GetSizeWithAncestors();
371          CAmount packageFees = iter->GetModFeesWithAncestors();
372          int64_t packageSigOpsCost = iter->GetSigOpCostWithAncestors();
373          if (fUsingModified) {
374              packageSize = modit->nSizeWithAncestors;
375              packageFees = modit->nModFeesWithAncestors;
376              packageSigOpsCost = modit->nSigOpCostWithAncestors;
377          }
378  
379          if (packageFees < m_options.blockMinFeeRate.GetFee(packageSize)) {
380              // Everything else we might consider has a lower fee rate
381              return;
382          }
383  
384          if (!TestPackage(packageSize, packageSigOpsCost)) {
385              if (fUsingModified) {
386                  // Since we always look at the best entry in mapModifiedTx,
387                  // we must erase failed entries so that we can consider the
388                  // next best entry on the next loop iteration
389                  mapModifiedTx.get<ancestor_score>().erase(modit);
390                  failedTx.insert(iter->GetSharedTx()->GetHash());
391              }
392  
393              ++nConsecutiveFailed;
394  
395              if (nConsecutiveFailed > MAX_CONSECUTIVE_FAILURES && nBlockWeight >
396                      m_options.nBlockMaxWeight - BLOCK_FULL_ENOUGH_WEIGHT_DELTA) {
397                  // Give up if we're close to full and haven't succeeded in a while
398                  break;
399              }
400              continue;
401          }
402  
403          auto ancestors{mempool.AssumeCalculateMemPoolAncestors(__func__, *iter, CTxMemPool::Limits::NoLimits(), /*fSearchForParents=*/false)};
404  
405          onlyUnconfirmed(ancestors);
406          ancestors.insert(iter);
407  
408          // Test if all tx's are Final
409          if (!TestPackageTransactions(ancestors)) {
410              if (fUsingModified) {
411                  mapModifiedTx.get<ancestor_score>().erase(modit);
412                  failedTx.insert(iter->GetSharedTx()->GetHash());
413              }
414              continue;
415          }
416  
417          // This transaction will make it in; reset the failed counter.
418          nConsecutiveFailed = 0;
419  
420          // Package can be added. Sort the entries in a valid order.
421          std::vector<CTxMemPool::txiter> sortedEntries;
422          SortForBlock(ancestors, sortedEntries);
423  
424          for (size_t i = 0; i < sortedEntries.size(); ++i) {
425              AddToBlock(sortedEntries[i]);
426              // Erase from the modified set, if present
427              mapModifiedTx.erase(sortedEntries[i]);
428          }
429  
430          ++nPackagesSelected;
431          pblocktemplate->m_package_feerates.emplace_back(packageFees, static_cast<int32_t>(packageSize));
432  
433          // Update transactions that depend on each of these
434          nDescendantsUpdated += UpdatePackagesForAdded(mempool, ancestors, mapModifiedTx);
435      }
436  }
437  } // namespace node