1  // Copyright (c) 2024-present 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 <consensus/validation.h>
 6  #include <policy/ephemeral_policy.h>
 7  #include <policy/feerate.h>
 8  #include <policy/packages.h>
 9  #include <policy/policy.h>
10  #include <primitives/transaction.h>
11  #include <txmempool.h>
12  #include <util/check.h>
13  #include <util/hasher.h>
14  
15  #include <algorithm>
16  #include <cstdint>
17  #include <map>
18  #include <memory>
19  #include <unordered_set>
20  #include <utility>
21  #include <vector>
22  
23  bool PreCheckEphemeralTx(const CTransaction& tx, CFeeRate dust_relay_rate, CAmount base_fee, CAmount mod_fee, TxValidationState& state)
24  {
25      // We never want to give incentives to mine this transaction alone
26      if ((base_fee != 0 || mod_fee != 0) && !GetDust(tx, dust_relay_rate).empty()) {
27          return state.Invalid(TxValidationResult::TX_NOT_STANDARD, "dust", "tx with dust output must be 0-fee");
28      }
29  
30      return true;
31  }
32  
33  bool CheckEphemeralSpends(const Package& package, CFeeRate dust_relay_rate, const CTxMemPool& tx_pool, TxValidationState& out_child_state, Wtxid& out_child_wtxid)
34  {
35      if (!Assume(std::ranges::all_of(package, [](const auto& tx){return tx != nullptr;}))) {
36          // Bail out of spend checks if caller gave us an invalid package
37          return true;
38      }
39  
40      std::map<Txid, CTransactionRef> map_txid_ref;
41      for (const auto& tx : package) {
42          map_txid_ref[tx->GetHash()] = tx;
43      }
44  
45      for (const auto& tx : package) {
46          std::unordered_set<Txid, SaltedTxidHasher> processed_parent_set;
47          std::unordered_set<COutPoint, SaltedOutpointHasher> unspent_parent_dust;
48  
49          for (const auto& tx_input : tx->vin) {
50              const Txid& parent_txid{tx_input.prevout.hash};
51              // Skip parents we've already checked dust for
52              if (processed_parent_set.contains(parent_txid)) continue;
53  
54              // We look for an in-package or in-mempool dependency
55              CTransactionRef parent_ref = nullptr;
56              if (auto it = map_txid_ref.find(parent_txid); it != map_txid_ref.end()) {
57                  parent_ref = it->second;
58              } else {
59                  parent_ref = tx_pool.get(parent_txid);
60              }
61  
62              // Check for dust on parents
63              if (parent_ref) {
64                  for (uint32_t out_index = 0; out_index < parent_ref->vout.size(); out_index++) {
65                      const auto& tx_output = parent_ref->vout[out_index];
66                      if (IsDust(tx_output, dust_relay_rate)) {
67                          unspent_parent_dust.insert(COutPoint(parent_txid, out_index));
68                      }
69                  }
70              }
71  
72              processed_parent_set.insert(parent_txid);
73          }
74  
75          if (unspent_parent_dust.empty()) {
76              continue;
77          }
78  
79          // Now that we have gathered parents' dust, make sure it's spent
80          // by the child
81          for (const auto& tx_input : tx->vin) {
82              unspent_parent_dust.erase(tx_input.prevout);
83          }
84  
85          if (!unspent_parent_dust.empty()) {
86              const Txid& out_child_txid = tx->GetHash();
87              out_child_wtxid = tx->GetWitnessHash();
88              out_child_state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "missing-ephemeral-spends",
89                                  strprintf("tx %s (wtxid=%s) did not spend parent's ephemeral dust", out_child_txid.ToString(), out_child_wtxid.ToString()));
90              return false;
91          }
92      }
93  
94      return true;
95  }