text: // Copyright (c) 2018-2019 The Bitcoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include <boost/test/unit_test.hpp>
  
  #include <auxpow.h>
  #include <chainparams.h>
  #include <consensus/merkle.h>
  #include <consensus/validation.h>
  #include <miner.h>
  #include <pow.h>
  #include <random.h>
  #include <script/standard.h>
  #include <test/util/setup_common.h>
  #include <util/time.h>
  #include <validation.h>
  #include <validationinterface.h>
  
  #include <thread>
  
  struct RegtestingSetup : public TestingSetup {
      RegtestingSetup() : TestingSetup(CBaseChainParams::REGTEST) {
          // SYSCOIN
          TurnOffSegwitForUnitTests();
      }
  };
  
  static const std::vector<unsigned char> V_OP_TRUE{OP_TRUE};
  
  namespace validation_block_tests {
  struct MinerTestingSetup : public RegtestingSetup {
      std::shared_ptr<CBlock> Block(const uint256& prev_hash);
      std::shared_ptr<const CBlock> GoodBlock(const uint256& prev_hash);
      std::shared_ptr<const CBlock> BadBlock(const uint256& prev_hash);
      std::shared_ptr<CBlock> FinalizeBlock(std::shared_ptr<CBlock> pblock);
      void BuildChain(const uint256& root, int height, const unsigned int invalid_rate, const unsigned int branch_rate, const unsigned int max_size, std::vector<std::shared_ptr<const CBlock>>& blocks);
  };
  } // namespace validation_block_tests
  
  BOOST_FIXTURE_TEST_SUITE(validation_block_tests, MinerTestingSetup)
  
  struct TestSubscriber : public CValidationInterface {
      uint256 m_expected_tip;
  
      explicit TestSubscriber(uint256 tip) : m_expected_tip(tip) {}
  
      void UpdatedBlockTip(const CBlockIndex* pindexNew, const CBlockIndex* pindexFork, bool fInitialDownload) override
      {
          BOOST_CHECK_EQUAL(m_expected_tip, pindexNew->GetBlockHash());
      }
  
      void BlockConnected(const std::shared_ptr<const CBlock>& block, const CBlockIndex* pindex, const std::vector<CTransactionRef>& txnConflicted) override
      {
          BOOST_CHECK_EQUAL(m_expected_tip, block->hashPrevBlock);
          BOOST_CHECK_EQUAL(m_expected_tip, pindex->pprev->GetBlockHash());
  
          m_expected_tip = block->GetHash();
      }
  
      void BlockDisconnected(const std::shared_ptr<const CBlock>& block, const CBlockIndex* pindex) override
      {
          BOOST_CHECK_EQUAL(m_expected_tip, block->GetHash());
          BOOST_CHECK_EQUAL(m_expected_tip, pindex->GetBlockHash());
  
          m_expected_tip = block->hashPrevBlock;
      }
  };
  
  std::shared_ptr<CBlock> MinerTestingSetup::Block(const uint256& prev_hash)
  {
      static int i = 0;
      static uint64_t time = Params().GenesisBlock().nTime;
  
      CScript pubKey;
      pubKey << i++ << OP_TRUE;
  
      auto ptemplate = BlockAssembler(*m_node.mempool, Params()).CreateNewBlock(pubKey);
      auto pblock = std::make_shared<CBlock>(ptemplate->block);
      pblock->hashPrevBlock = prev_hash;
      pblock->nTime = ++time;
  
      pubKey.clear();
      {
          WitnessV0ScriptHash witness_program;
          CSHA256().Write(&V_OP_TRUE[0], V_OP_TRUE.size()).Finalize(witness_program.begin());
          pubKey << OP_0 << ToByteVector(witness_program);
      }
  
      // Make the coinbase transaction with two outputs:
      // One zero-value one that has a unique pubkey to make sure that blocks at the same height can have a different hash
      // Another one that has the coinbase reward in a P2WSH with OP_TRUE as witness program to make it easy to spend
      CMutableTransaction txCoinbase(*pblock->vtx[0]);
      txCoinbase.vout.resize(2);
      txCoinbase.vout[1].scriptPubKey = pubKey;
      txCoinbase.vout[1].nValue = txCoinbase.vout[0].nValue;
      txCoinbase.vout[0].nValue = 0;
      txCoinbase.vin[0].scriptWitness.SetNull();
      pblock->vtx[0] = MakeTransactionRef(std::move(txCoinbase));
  
      return pblock;
  }
  
  std::shared_ptr<CBlock> MinerTestingSetup::FinalizeBlock(std::shared_ptr<CBlock> pblock)
  {
      LOCK(cs_main); // For LookupBlockIndex
      GenerateCoinbaseCommitment(*pblock, LookupBlockIndex(pblock->hashPrevBlock), Params().GetConsensus());
  
      pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);
  
      while (!CheckProofOfWork(pblock->GetHash(), pblock->nBits, Params().GetConsensus())) {
          ++(pblock->nNonce);
      }
  
      return pblock;
  }
  
  // construct a valid block
  std::shared_ptr<const CBlock> MinerTestingSetup::GoodBlock(const uint256& prev_hash)
  {
      return FinalizeBlock(Block(prev_hash));
  }
  
  // construct an invalid block (but with a valid header)
  std::shared_ptr<const CBlock> MinerTestingSetup::BadBlock(const uint256& prev_hash)
  {
      auto pblock = Block(prev_hash);
  
      CMutableTransaction coinbase_spend;
      coinbase_spend.vin.push_back(CTxIn(COutPoint(pblock->vtx[0]->GetHash(), 0), CScript(), 0));
      coinbase_spend.vout.push_back(pblock->vtx[0]->vout[0]);
  
      CTransactionRef tx = MakeTransactionRef(coinbase_spend);
      pblock->vtx.push_back(tx);
  
      auto ret = FinalizeBlock(pblock);
      return ret;
  }
  
  void MinerTestingSetup::BuildChain(const uint256& root, int height, const unsigned int invalid_rate, const unsigned int branch_rate, const unsigned int max_size, std::vector<std::shared_ptr<const CBlock>>& blocks)
  {
      if (height <= 0 || blocks.size() >= max_size) return;
  
      bool gen_invalid = InsecureRandRange(100) < invalid_rate;
      bool gen_fork = InsecureRandRange(100) < branch_rate;
  
      const std::shared_ptr<const CBlock> pblock = gen_invalid ? BadBlock(root) : GoodBlock(root);
      blocks.push_back(pblock);
      if (!gen_invalid) {
          BuildChain(pblock->GetHash(), height - 1, invalid_rate, branch_rate, max_size, blocks);
      }
  
      if (gen_fork) {
          blocks.push_back(GoodBlock(root));
          BuildChain(blocks.back()->GetHash(), height - 1, invalid_rate, branch_rate, max_size, blocks);
      }
  }
  
  BOOST_AUTO_TEST_CASE(processnewblock_signals_ordering)
  {
      // build a large-ish chain that's likely to have some forks
      std::vector<std::shared_ptr<const CBlock>> blocks;
      while (blocks.size() < 50) {
          blocks.clear();
          BuildChain(Params().GenesisBlock().GetHash(), 100, 15, 10, 500, blocks);
      }
  
      bool ignored;
      BlockValidationState state;
      std::vector<CBlockHeader> headers;
      std::transform(blocks.begin(), blocks.end(), std::back_inserter(headers), [](std::shared_ptr<const CBlock> b) { return b->GetBlockHeader(); });
  
      // Process all the headers so we understand the toplogy of the chain
      BOOST_CHECK(ProcessNewBlockHeaders(headers, state, Params()));
  
      // Connect the genesis block and drain any outstanding events
      BOOST_CHECK(ProcessNewBlock(Params(), std::make_shared<CBlock>(Params().GenesisBlock()), true, &ignored));
      SyncWithValidationInterfaceQueue();
  
      // subscribe to events (this subscriber will validate event ordering)
      const CBlockIndex* initial_tip = nullptr;
      {
          LOCK(cs_main);
          initial_tip = ::ChainActive().Tip();
      }
      TestSubscriber sub(initial_tip->GetBlockHash());
      RegisterValidationInterface(&sub);
  
      // create a bunch of threads that repeatedly process a block generated above at random
      // this will create parallelism and randomness inside validation - the ValidationInterface
      // will subscribe to events generated during block validation and assert on ordering invariance
      std::vector<std::thread> threads;
      for (int i = 0; i < 10; i++) {
          threads.emplace_back([&blocks]() {
              bool ignored;
              FastRandomContext insecure;
              for (int i = 0; i < 1000; i++) {
                  auto block = blocks[insecure.randrange(blocks.size() - 1)];
                  ProcessNewBlock(Params(), block, true, &ignored);
              }
  
              // to make sure that eventually we process the full chain - do it here
  
              for (auto block : blocks) {
                  if (block->vtx.size() == 1) {
                      bool processed = ProcessNewBlock(Params(), block, true, &ignored);
                      assert(processed);
                  }
              }
          });
      }
  
      for (auto& t : threads) {
          t.join();
      }
      while (GetMainSignals().CallbacksPending() > 0) {
          MilliSleep(100);
      }
  
      UnregisterValidationInterface(&sub);
  
      LOCK(cs_main);
      BOOST_CHECK_EQUAL(sub.m_expected_tip, ::ChainActive().Tip()->GetBlockHash());
  }
  
  /**
   * Test that mempool updates happen atomically with reorgs.
   *
   * This prevents RPC clients, among others, from retrieving immediately-out-of-date mempool data
   * during large reorgs.
   *
   * The test verifies this by creating a chain of `num_txs` blocks, matures their coinbases, and then
   * submits txns spending from their coinbase to the mempool. A fork chain is then processed,
   * invalidating the txns and evicting them from the mempool.
   *
   * We verify that the mempool updates atomically by polling it continuously
   * from another thread during the reorg and checking that its size only changes
   * once. The size changing exactly once indicates that the polling thread's
   * view of the mempool is either consistent with the chain state before reorg,
   * or consistent with the chain state after the reorg, and not just consistent
   * with some intermediate state during the reorg.
   */
  BOOST_AUTO_TEST_CASE(mempool_locks_reorg)
  {
      bool ignored;
      auto ProcessBlock = [&ignored](std::shared_ptr<const CBlock> block) -> bool {
          return ProcessNewBlock(Params(), block, /* fForceProcessing */ true, /* fNewBlock */ &ignored);
      };
  
      // Process all mined blocks
      BOOST_REQUIRE(ProcessBlock(std::make_shared<CBlock>(Params().GenesisBlock())));
      auto last_mined = GoodBlock(Params().GenesisBlock().GetHash());
      BOOST_REQUIRE(ProcessBlock(last_mined));
  
      // Run the test multiple times
      for (int test_runs = 3; test_runs > 0; --test_runs) {
          BOOST_CHECK_EQUAL(last_mined->GetHash(), ::ChainActive().Tip()->GetBlockHash());
  
          // Later on split from here
          const uint256 split_hash{last_mined->hashPrevBlock};
  
          // Create a bunch of transactions to spend the miner rewards of the
          // most recent blocks
          std::vector<CTransactionRef> txs;
          for (int num_txs = 22; num_txs > 0; --num_txs) {
              CMutableTransaction mtx;
              mtx.vin.push_back(CTxIn{COutPoint{last_mined->vtx[0]->GetHash(), 1}, CScript{}});
              mtx.vin[0].scriptWitness.stack.push_back(V_OP_TRUE);
              mtx.vout.push_back(last_mined->vtx[0]->vout[1]);
              mtx.vout[0].nValue -= 1000;
              txs.push_back(MakeTransactionRef(mtx));
  
              last_mined = GoodBlock(last_mined->GetHash());
              BOOST_REQUIRE(ProcessBlock(last_mined));
          }
  
          // Mature the inputs of the txs
          for (int j = COINBASE_MATURITY; j > 0; --j) {
              last_mined = GoodBlock(last_mined->GetHash());
              BOOST_REQUIRE(ProcessBlock(last_mined));
          }
  
          // Mine a reorg (and hold it back) before adding the txs to the mempool
          const uint256 tip_init{last_mined->GetHash()};
  
          std::vector<std::shared_ptr<const CBlock>> reorg;
          last_mined = GoodBlock(split_hash);
          reorg.push_back(last_mined);
          for (size_t j = COINBASE_MATURITY + txs.size() + 1; j > 0; --j) {
              last_mined = GoodBlock(last_mined->GetHash());
              reorg.push_back(last_mined);
          }
  
          // Add the txs to the tx pool
          {
              LOCK(cs_main);
              TxValidationState state;
              std::list<CTransactionRef> plTxnReplaced;
              for (const auto& tx : txs) {
                  BOOST_REQUIRE(AcceptToMemoryPool(
                      *m_node.mempool,
                      state,
                      tx,
                      &plTxnReplaced,
                      /* bypass_limits */ false,
                      /* nAbsurdFee */ 0));
              }
          }
  
          // Check that all txs are in the pool
          {
              LOCK(m_node.mempool->cs);
              BOOST_CHECK_EQUAL(m_node.mempool->mapTx.size(), txs.size());
          }
  
          // Run a thread that simulates an RPC caller that is polling while
          // validation is doing a reorg
          std::thread rpc_thread{[&]() {
              // This thread is checking that the mempool either contains all of
              // the transactions invalidated by the reorg, or none of them, and
              // not some intermediate amount.
              while (true) {
                  LOCK(m_node.mempool->cs);
                  if (m_node.mempool->mapTx.size() == 0) {
                      // We are done with the reorg
                      break;
                  }
                  // Internally, we might be in the middle of the reorg, but
                  // externally the reorg to the most-proof-of-work chain should
                  // be atomic. So the caller assumes that the returned mempool
                  // is consistent. That is, it has all txs that were there
                  // before the reorg.
                  assert(m_node.mempool->mapTx.size() == txs.size());
                  continue;
              }
              LOCK(cs_main);
              // We are done with the reorg, so the tip must have changed
              assert(tip_init != ::ChainActive().Tip()->GetBlockHash());
          }};
  
          // Submit the reorg in this thread to invalidate and remove the txs from the tx pool
          for (const auto& b : reorg) {
              ProcessBlock(b);
          }
          // Check that the reorg was eventually successful
          BOOST_CHECK_EQUAL(last_mined->GetHash(), ::ChainActive().Tip()->GetBlockHash());
  
          // We can join the other thread, which returns when the reorg was successful
          rpc_thread.join();
      }
  }
  BOOST_AUTO_TEST_SUITE_END()
  