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       1                 :            : // Copyright (c) 2021-2022 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 <policy/packages.h>
       6                 :            : #include <policy/policy.h>
       7                 :            : #include <primitives/transaction.h>
       8                 :            : #include <uint256.h>
       9                 :            : #include <util/hasher.h>
      10                 :            : 
      11                 :            : #include <algorithm>
      12                 :            : #include <cassert>
      13                 :            : #include <iterator>
      14                 :            : #include <memory>
      15                 :            : #include <numeric>
      16                 :            : #include <unordered_set>
      17                 :            : 
      18                 :          0 : bool CheckPackage(const Package& txns, PackageValidationState& state)
      19                 :            : {
      20                 :          0 :     const unsigned int package_count = txns.size();
      21                 :            : 
      22         [ #  # ]:          0 :     if (package_count > MAX_PACKAGE_COUNT) {
      23 [ #  # ][ #  # ]:          0 :         return state.Invalid(PackageValidationResult::PCKG_POLICY, "package-too-many-transactions");
                 [ #  # ]
      24                 :            :     }
      25                 :            : 
      26                 :          0 :     const int64_t total_weight = std::accumulate(txns.cbegin(), txns.cend(), 0,
      27                 :          0 :                                [](int64_t sum, const auto& tx) { return sum + GetTransactionWeight(*tx); });
      28                 :            :     // If the package only contains 1 tx, it's better to report the policy violation on individual tx weight.
      29 [ #  # ][ #  # ]:          0 :     if (package_count > 1 && total_weight > MAX_PACKAGE_WEIGHT) {
      30 [ #  # ][ #  # ]:          0 :         return state.Invalid(PackageValidationResult::PCKG_POLICY, "package-too-large");
                 [ #  # ]
      31                 :            :     }
      32                 :            : 
      33                 :            :     // Require the package to be sorted in order of dependency, i.e. parents appear before children.
      34                 :            :     // An unsorted package will fail anyway on missing-inputs, but it's better to quit earlier and
      35                 :            :     // fail on something less ambiguous (missing-inputs could also be an orphan or trying to
      36                 :            :     // spend nonexistent coins).
      37                 :          0 :     std::unordered_set<uint256, SaltedTxidHasher> later_txids;
      38 [ #  # ][ #  # ]:          0 :     std::transform(txns.cbegin(), txns.cend(), std::inserter(later_txids, later_txids.end()),
      39                 :          0 :                    [](const auto& tx) { return tx->GetHash(); });
      40                 :            : 
      41                 :            :     // Package must not contain any duplicate transactions, which is checked by txid. This also
      42                 :            :     // includes transactions with duplicate wtxids and same-txid-different-witness transactions.
      43         [ #  # ]:          0 :     if (later_txids.size() != txns.size()) {
      44 [ #  # ][ #  # ]:          0 :         return state.Invalid(PackageValidationResult::PCKG_POLICY, "package-contains-duplicates");
                 [ #  # ]
      45                 :            :     }
      46                 :            : 
      47         [ #  # ]:          0 :     for (const auto& tx : txns) {
      48         [ #  # ]:          0 :         for (const auto& input : tx->vin) {
      49 [ #  # ][ #  # ]:          0 :             if (later_txids.find(input.prevout.hash) != later_txids.end()) {
      50                 :            :                 // The parent is a subsequent transaction in the package.
      51 [ #  # ][ #  # ]:          0 :                 return state.Invalid(PackageValidationResult::PCKG_POLICY, "package-not-sorted");
                 [ #  # ]
      52                 :            :             }
      53                 :            :         }
      54 [ #  # ][ #  # ]:          0 :         later_txids.erase(tx->GetHash());
      55                 :            :     }
      56                 :            : 
      57                 :            :     // Don't allow any conflicting transactions, i.e. spending the same inputs, in a package.
      58         [ #  # ]:          0 :     std::unordered_set<COutPoint, SaltedOutpointHasher> inputs_seen;
      59         [ #  # ]:          0 :     for (const auto& tx : txns) {
      60         [ #  # ]:          0 :         for (const auto& input : tx->vin) {
      61 [ #  # ][ #  # ]:          0 :             if (inputs_seen.find(input.prevout) != inputs_seen.end()) {
      62                 :            :                 // This input is also present in another tx in the package.
      63 [ #  # ][ #  # ]:          0 :                 return state.Invalid(PackageValidationResult::PCKG_POLICY, "conflict-in-package");
                 [ #  # ]
      64                 :            :             }
      65                 :            :         }
      66                 :            :         // Batch-add all the inputs for a tx at a time. If we added them 1 at a time, we could
      67                 :            :         // catch duplicate inputs within a single tx.  This is a more severe, consensus error,
      68                 :            :         // and we want to report that from CheckTransaction instead.
      69 [ #  # ][ #  # ]:          0 :         std::transform(tx->vin.cbegin(), tx->vin.cend(), std::inserter(inputs_seen, inputs_seen.end()),
      70                 :          0 :                        [](const auto& input) { return input.prevout; });
      71                 :            :     }
      72                 :          0 :     return true;
      73                 :          0 : }
      74                 :            : 
      75                 :          0 : bool IsChildWithParents(const Package& package)
      76                 :            : {
      77         [ #  # ]:          0 :     assert(std::all_of(package.cbegin(), package.cend(), [](const auto& tx){return tx != nullptr;}));
      78         [ #  # ]:          0 :     if (package.size() < 2) return false;
      79                 :            : 
      80                 :            :     // The package is expected to be sorted, so the last transaction is the child.
      81                 :          0 :     const auto& child = package.back();
      82                 :          0 :     std::unordered_set<uint256, SaltedTxidHasher> input_txids;
      83         [ #  # ]:          0 :     std::transform(child->vin.cbegin(), child->vin.cend(),
      84         [ #  # ]:          0 :                    std::inserter(input_txids, input_txids.end()),
      85                 :          0 :                    [](const auto& input) { return input.prevout.hash; });
      86                 :            : 
      87                 :            :     // Every transaction must be a parent of the last transaction in the package.
      88 [ #  # ][ #  # ]:          0 :     return std::all_of(package.cbegin(), package.cend() - 1,
      89                 :          0 :                        [&input_txids](const auto& ptx) { return input_txids.count(ptx->GetHash()) > 0; });
      90                 :          0 : }
      91                 :            : 
      92                 :          0 : bool IsChildWithParentsTree(const Package& package)
      93                 :            : {
      94         [ #  # ]:          0 :     if (!IsChildWithParents(package)) return false;
      95                 :          0 :     std::unordered_set<uint256, SaltedTxidHasher> parent_txids;
      96 [ #  # ][ #  # ]:          0 :     std::transform(package.cbegin(), package.cend() - 1, std::inserter(parent_txids, parent_txids.end()),
      97                 :          0 :                    [](const auto& ptx) { return ptx->GetHash(); });
      98                 :            :     // Each parent must not have an input who is one of the other parents.
      99         [ #  # ]:          0 :     return std::all_of(package.cbegin(), package.cend() - 1, [&](const auto& ptx) {
     100         [ #  # ]:          0 :         for (const auto& input : ptx->vin) {
     101         [ #  # ]:          0 :             if (parent_txids.count(input.prevout.hash) > 0) return false;
     102                 :            :         }
     103                 :          0 :         return true;
     104                 :          0 :     });
     105                 :          0 : }