LCOV - code coverage report
Current view: top level - src - blockencodings.cpp (source / functions) Hit Total Coverage
Test: fuzz_coverage.info Lines: 0 131 0.0 %
Date: 2024-01-03 14:57:27 Functions: 0 6 0.0 %
Branches: 0 206 0.0 %

           Branch data     Line data    Source code
       1                 :            : // Copyright (c) 2016-2022 The Bitcoin Core developers
       2                 :            : // Distributed under the MIT software license, see the accompanying
       3                 :            : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
       4                 :            : 
       5                 :            : #include <blockencodings.h>
       6                 :            : #include <chainparams.h>
       7                 :            : #include <common/system.h>
       8                 :            : #include <consensus/consensus.h>
       9                 :            : #include <consensus/validation.h>
      10                 :            : #include <crypto/sha256.h>
      11                 :            : #include <crypto/siphash.h>
      12                 :            : #include <logging.h>
      13                 :            : #include <random.h>
      14                 :            : #include <streams.h>
      15                 :            : #include <txmempool.h>
      16                 :            : #include <validation.h>
      17                 :            : 
      18                 :            : #include <unordered_map>
      19                 :            : 
      20                 :          0 : CBlockHeaderAndShortTxIDs::CBlockHeaderAndShortTxIDs(const CBlock& block) :
      21                 :          0 :         nonce(GetRand<uint64_t>()),
      22 [ #  # ][ #  # ]:          0 :         shorttxids(block.vtx.size() - 1), prefilledtxn(1), header(block) {
      23         [ #  # ]:          0 :     FillShortTxIDSelector();
      24                 :            :     //TODO: Use our mempool prior to block acceptance to predictively fill more than just the coinbase
      25                 :          0 :     prefilledtxn[0] = {0, block.vtx[0]};
      26         [ #  # ]:          0 :     for (size_t i = 1; i < block.vtx.size(); i++) {
      27                 :          0 :         const CTransaction& tx = *block.vtx[i];
      28 [ #  # ][ #  # ]:          0 :         shorttxids[i - 1] = GetShortID(tx.GetWitnessHash());
                 [ #  # ]
      29                 :          0 :     }
      30                 :          0 : }
      31                 :            : 
      32                 :          0 : void CBlockHeaderAndShortTxIDs::FillShortTxIDSelector() const {
      33                 :          0 :     DataStream stream{};
      34 [ #  # ][ #  # ]:          0 :     stream << header << nonce;
      35         [ #  # ]:          0 :     CSHA256 hasher;
      36 [ #  # ][ #  # ]:          0 :     hasher.Write((unsigned char*)&(*stream.begin()), stream.end() - stream.begin());
         [ #  # ][ #  # ]
      37         [ #  # ]:          0 :     uint256 shorttxidhash;
      38 [ #  # ][ #  # ]:          0 :     hasher.Finalize(shorttxidhash.begin());
      39         [ #  # ]:          0 :     shorttxidk0 = shorttxidhash.GetUint64(0);
      40         [ #  # ]:          0 :     shorttxidk1 = shorttxidhash.GetUint64(1);
      41                 :          0 : }
      42                 :            : 
      43                 :          0 : uint64_t CBlockHeaderAndShortTxIDs::GetShortID(const uint256& txhash) const {
      44                 :            :     static_assert(SHORTTXIDS_LENGTH == 6, "shorttxids calculation assumes 6-byte shorttxids");
      45                 :          0 :     return SipHashUint256(shorttxidk0, shorttxidk1, txhash) & 0xffffffffffffL;
      46                 :            : }
      47                 :            : 
      48                 :            : 
      49                 :            : 
      50                 :          0 : ReadStatus PartiallyDownloadedBlock::InitData(const CBlockHeaderAndShortTxIDs& cmpctblock, const std::vector<std::pair<uint256, CTransactionRef>>& extra_txn) {
      51 [ #  # ][ #  # ]:          0 :     if (cmpctblock.header.IsNull() || (cmpctblock.shorttxids.empty() && cmpctblock.prefilledtxn.empty()))
                 [ #  # ]
      52                 :          0 :         return READ_STATUS_INVALID;
      53         [ #  # ]:          0 :     if (cmpctblock.shorttxids.size() + cmpctblock.prefilledtxn.size() > MAX_BLOCK_WEIGHT / MIN_SERIALIZABLE_TRANSACTION_WEIGHT)
      54                 :          0 :         return READ_STATUS_INVALID;
      55                 :            : 
      56 [ #  # ][ #  # ]:          0 :     if (!header.IsNull() || !txn_available.empty()) return READ_STATUS_INVALID;
      57                 :            : 
      58                 :          0 :     header = cmpctblock.header;
      59                 :          0 :     txn_available.resize(cmpctblock.BlockTxCount());
      60                 :            : 
      61                 :          0 :     int32_t lastprefilledindex = -1;
      62         [ #  # ]:          0 :     for (size_t i = 0; i < cmpctblock.prefilledtxn.size(); i++) {
      63         [ #  # ]:          0 :         if (cmpctblock.prefilledtxn[i].tx->IsNull())
      64                 :          0 :             return READ_STATUS_INVALID;
      65                 :            : 
      66                 :          0 :         lastprefilledindex += cmpctblock.prefilledtxn[i].index + 1; //index is a uint16_t, so can't overflow here
      67         [ #  # ]:          0 :         if (lastprefilledindex > std::numeric_limits<uint16_t>::max())
      68                 :          0 :             return READ_STATUS_INVALID;
      69         [ #  # ]:          0 :         if ((uint32_t)lastprefilledindex > cmpctblock.shorttxids.size() + i) {
      70                 :            :             // If we are inserting a tx at an index greater than our full list of shorttxids
      71                 :            :             // plus the number of prefilled txn we've inserted, then we have txn for which we
      72                 :            :             // have neither a prefilled txn or a shorttxid!
      73                 :          0 :             return READ_STATUS_INVALID;
      74                 :            :         }
      75                 :          0 :         txn_available[lastprefilledindex] = cmpctblock.prefilledtxn[i].tx;
      76                 :          0 :     }
      77                 :          0 :     prefilled_count = cmpctblock.prefilledtxn.size();
      78                 :            : 
      79                 :            :     // Calculate map of txids -> positions and check mempool to see what we have (or don't)
      80                 :            :     // Because well-formed cmpctblock messages will have a (relatively) uniform distribution
      81                 :            :     // of short IDs, any highly-uneven distribution of elements can be safely treated as a
      82                 :            :     // READ_STATUS_FAILED.
      83         [ #  # ]:          0 :     std::unordered_map<uint64_t, uint16_t> shorttxids(cmpctblock.shorttxids.size());
      84                 :          0 :     uint16_t index_offset = 0;
      85         [ #  # ]:          0 :     for (size_t i = 0; i < cmpctblock.shorttxids.size(); i++) {
      86         [ #  # ]:          0 :         while (txn_available[i + index_offset])
      87                 :          0 :             index_offset++;
      88         [ #  # ]:          0 :         shorttxids[cmpctblock.shorttxids[i]] = i + index_offset;
      89                 :            :         // To determine the chance that the number of entries in a bucket exceeds N,
      90                 :            :         // we use the fact that the number of elements in a single bucket is
      91                 :            :         // binomially distributed (with n = the number of shorttxids S, and p =
      92                 :            :         // 1 / the number of buckets), that in the worst case the number of buckets is
      93                 :            :         // equal to S (due to std::unordered_map having a default load factor of 1.0),
      94                 :            :         // and that the chance for any bucket to exceed N elements is at most
      95                 :            :         // buckets * (the chance that any given bucket is above N elements).
      96                 :            :         // Thus: P(max_elements_per_bucket > N) <= S * (1 - cdf(binomial(n=S,p=1/S), N)).
      97                 :            :         // If we assume blocks of up to 16000, allowing 12 elements per bucket should
      98                 :            :         // only fail once per ~1 million block transfers (per peer and connection).
      99 [ #  # ][ #  # ]:          0 :         if (shorttxids.bucket_size(shorttxids.bucket(cmpctblock.shorttxids[i])) > 12)
                 [ #  # ]
     100                 :          0 :             return READ_STATUS_FAILED;
     101                 :          0 :     }
     102                 :            :     // TODO: in the shortid-collision case, we should instead request both transactions
     103                 :            :     // which collided. Falling back to full-block-request here is overkill.
     104         [ #  # ]:          0 :     if (shorttxids.size() != cmpctblock.shorttxids.size())
     105                 :          0 :         return READ_STATUS_FAILED; // Short ID collision
     106                 :            : 
     107         [ #  # ]:          0 :     std::vector<bool> have_txn(txn_available.size());
     108                 :            :     {
     109 [ #  # ][ #  # ]:          0 :     LOCK(pool->cs);
     110         [ #  # ]:          0 :     for (const auto& tx : pool->txns_randomized) {
     111 [ #  # ][ #  # ]:          0 :         uint64_t shortid = cmpctblock.GetShortID(tx->GetWitnessHash());
                 [ #  # ]
     112         [ #  # ]:          0 :         std::unordered_map<uint64_t, uint16_t>::iterator idit = shorttxids.find(shortid);
     113         [ #  # ]:          0 :         if (idit != shorttxids.end()) {
     114 [ #  # ][ #  # ]:          0 :             if (!have_txn[idit->second]) {
     115                 :          0 :                 txn_available[idit->second] = tx;
     116         [ #  # ]:          0 :                 have_txn[idit->second]  = true;
     117                 :          0 :                 mempool_count++;
     118                 :          0 :             } else {
     119                 :            :                 // If we find two mempool txn that match the short id, just request it.
     120                 :            :                 // This should be rare enough that the extra bandwidth doesn't matter,
     121                 :            :                 // but eating a round-trip due to FillBlock failure would be annoying
     122         [ #  # ]:          0 :                 if (txn_available[idit->second]) {
     123                 :          0 :                     txn_available[idit->second].reset();
     124                 :          0 :                     mempool_count--;
     125                 :          0 :                 }
     126                 :            :             }
     127                 :          0 :         }
     128                 :            :         // Though ideally we'd continue scanning for the two-txn-match-shortid case,
     129                 :            :         // the performance win of an early exit here is too good to pass up and worth
     130                 :            :         // the extra risk.
     131         [ #  # ]:          0 :         if (mempool_count == shorttxids.size())
     132                 :          0 :             break;
     133                 :            :     }
     134                 :          0 :     }
     135                 :            : 
     136         [ #  # ]:          0 :     for (size_t i = 0; i < extra_txn.size(); i++) {
     137         [ #  # ]:          0 :         uint64_t shortid = cmpctblock.GetShortID(extra_txn[i].first);
     138         [ #  # ]:          0 :         std::unordered_map<uint64_t, uint16_t>::iterator idit = shorttxids.find(shortid);
     139         [ #  # ]:          0 :         if (idit != shorttxids.end()) {
     140 [ #  # ][ #  # ]:          0 :             if (!have_txn[idit->second]) {
     141                 :          0 :                 txn_available[idit->second] = extra_txn[i].second;
     142         [ #  # ]:          0 :                 have_txn[idit->second]  = true;
     143                 :          0 :                 mempool_count++;
     144                 :          0 :                 extra_count++;
     145                 :          0 :             } else {
     146                 :            :                 // If we find two mempool/extra txn that match the short id, just
     147                 :            :                 // request it.
     148                 :            :                 // This should be rare enough that the extra bandwidth doesn't matter,
     149                 :            :                 // but eating a round-trip due to FillBlock failure would be annoying
     150                 :            :                 // Note that we don't want duplication between extra_txn and mempool to
     151                 :            :                 // trigger this case, so we compare witness hashes first
     152 [ #  # ][ #  # ]:          0 :                 if (txn_available[idit->second] &&
     153 [ #  # ][ #  # ]:          0 :                         txn_available[idit->second]->GetWitnessHash() != extra_txn[i].second->GetWitnessHash()) {
                 [ #  # ]
     154                 :          0 :                     txn_available[idit->second].reset();
     155                 :          0 :                     mempool_count--;
     156                 :          0 :                     extra_count--;
     157                 :          0 :                 }
     158                 :            :             }
     159                 :          0 :         }
     160                 :            :         // Though ideally we'd continue scanning for the two-txn-match-shortid case,
     161                 :            :         // the performance win of an early exit here is too good to pass up and worth
     162                 :            :         // the extra risk.
     163         [ #  # ]:          0 :         if (mempool_count == shorttxids.size())
     164                 :          0 :             break;
     165                 :          0 :     }
     166                 :            : 
     167 [ #  # ][ #  # ]:          0 :     LogPrint(BCLog::CMPCTBLOCK, "Initialized PartiallyDownloadedBlock for block %s using a cmpctblock of size %lu\n", cmpctblock.header.GetHash().ToString(), GetSerializeSize(cmpctblock));
         [ #  # ][ #  # ]
         [ #  # ][ #  # ]
         [ #  # ][ #  # ]
     168                 :            : 
     169                 :          0 :     return READ_STATUS_OK;
     170                 :          0 : }
     171                 :            : 
     172                 :          0 : bool PartiallyDownloadedBlock::IsTxAvailable(size_t index) const
     173                 :            : {
     174         [ #  # ]:          0 :     if (header.IsNull()) return false;
     175                 :            : 
     176         [ #  # ]:          0 :     assert(index < txn_available.size());
     177                 :          0 :     return txn_available[index] != nullptr;
     178                 :          0 : }
     179                 :            : 
     180                 :          0 : ReadStatus PartiallyDownloadedBlock::FillBlock(CBlock& block, const std::vector<CTransactionRef>& vtx_missing)
     181                 :            : {
     182         [ #  # ]:          0 :     if (header.IsNull()) return READ_STATUS_INVALID;
     183                 :            : 
     184                 :          0 :     uint256 hash = header.GetHash();
     185                 :          0 :     block = header;
     186                 :          0 :     block.vtx.resize(txn_available.size());
     187                 :            : 
     188                 :          0 :     size_t tx_missing_offset = 0;
     189         [ #  # ]:          0 :     for (size_t i = 0; i < txn_available.size(); i++) {
     190         [ #  # ]:          0 :         if (!txn_available[i]) {
     191         [ #  # ]:          0 :             if (vtx_missing.size() <= tx_missing_offset)
     192                 :          0 :                 return READ_STATUS_INVALID;
     193                 :          0 :             block.vtx[i] = vtx_missing[tx_missing_offset++];
     194                 :          0 :         } else
     195                 :          0 :             block.vtx[i] = std::move(txn_available[i]);
     196                 :          0 :     }
     197                 :            : 
     198                 :            :     // Make sure we can't call FillBlock again.
     199                 :          0 :     header.SetNull();
     200                 :          0 :     txn_available.clear();
     201                 :            : 
     202         [ #  # ]:          0 :     if (vtx_missing.size() != tx_missing_offset)
     203                 :          0 :         return READ_STATUS_INVALID;
     204                 :            : 
     205                 :          0 :     BlockValidationState state;
     206 [ #  # ][ #  # ]:          0 :     CheckBlockFn check_block = m_check_block_mock ? m_check_block_mock : CheckBlock;
     207 [ #  # ][ #  # ]:          0 :     if (!check_block(block, state, Params().GetConsensus(), /*fCheckPoW=*/true, /*fCheckMerkleRoot=*/true)) {
         [ #  # ][ #  # ]
     208                 :            :         // TODO: We really want to just check merkle tree manually here,
     209                 :            :         // but that is expensive, and CheckBlock caches a block's
     210                 :            :         // "checked-status" (in the CBlock?). CBlock should be able to
     211                 :            :         // check its own merkle root and cache that check.
     212 [ #  # ][ #  # ]:          0 :         if (state.GetResult() == BlockValidationResult::BLOCK_MUTATED)
     213                 :          0 :             return READ_STATUS_FAILED; // Possible Short ID collision
     214                 :          0 :         return READ_STATUS_CHECKBLOCK_FAILED;
     215                 :            :     }
     216                 :            : 
     217 [ #  # ][ #  # ]:          0 :     LogPrint(BCLog::CMPCTBLOCK, "Successfully reconstructed block %s with %lu txn prefilled, %lu txn from mempool (incl at least %lu from extra pool) and %lu txn requested\n", hash.ToString(), prefilled_count, mempool_count, extra_count, vtx_missing.size());
         [ #  # ][ #  # ]
         [ #  # ][ #  # ]
     218         [ #  # ]:          0 :     if (vtx_missing.size() < 5) {
     219         [ #  # ]:          0 :         for (const auto& tx : vtx_missing) {
     220 [ #  # ][ #  # ]:          0 :             LogPrint(BCLog::CMPCTBLOCK, "Reconstructed block %s required tx %s\n", hash.ToString(), tx->GetHash().ToString());
         [ #  # ][ #  # ]
         [ #  # ][ #  # ]
         [ #  # ][ #  # ]
     221                 :            :         }
     222                 :          0 :     }
     223                 :            : 
     224                 :          0 :     return READ_STATUS_OK;
     225                 :          0 : }

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