1 files changed, 23 insertions, 0 deletions
diff --git a/src/policy/rbf.cpp b/src/policy/rbf.cpp
index f0830d8f22..a2c6990657 100644
--- a/src/policy/rbf.cpp
+++ b/src/policy/rbf.cpp
@@ -19,6 +19,8 @@
 #include <limits>
 #include <vector>
 
+#include <compare>
+
 RBFTransactionState IsRBFOptIn(const CTransaction& tx, const CTxMemPool& pool)
 {
     AssertLockHeld(pool.cs);
@@ -181,3 +183,24 @@ std::optional<std::string> PaysForRBF(CAmount original_fees,
     }
     return std::nullopt;
 }
+
+std::optional<std::pair<DiagramCheckError, std::string>> ImprovesFeerateDiagram(CTxMemPool& pool,
+                                                const CTxMemPool::setEntries& direct_conflicts,
+                                                const CTxMemPool::setEntries& all_conflicts,
+                                                CAmount replacement_fees,
+                                                int64_t replacement_vsize)
+{
+    // Require that the replacement strictly improve the mempool's feerate diagram.
+    std::vector<FeeFrac> old_diagram, new_diagram;
+
+    const auto diagram_results{pool.CalculateFeerateDiagramsForRBF(replacement_fees, replacement_vsize, direct_conflicts, all_conflicts)};
+
+    if (!diagram_results.has_value()) {
+        return std::make_pair(DiagramCheckError::UNCALCULABLE, util::ErrorString(diagram_results).original);
+    }
+
+    if (!std::is_gt(CompareFeerateDiagram(diagram_results.value().second, diagram_results.value().first))) {
+        return std::make_pair(DiagramCheckError::FAILURE, "insufficient feerate: does not improve feerate diagram");
+    }
+    return std::nullopt;
+}