MOVEONLY: fee checks (Rules 3 and 4) to policy/rbf

glozow · glozow · commit 781e100b6047 · 2021-08-24T16:01:54.000+01:00
diff --git a/src/policy/rbf.cpp b/src/policy/rbf.cpp
@@ -165,3 +165,29 @@ bool PaysMoreThanConflicts(const CTxMemPool::setEntries& setIterConflicting, CFe
     return true;
 }
 
+bool PaysForRBF(CAmount nConflictingFees, CAmount nModifiedFees, size_t nSize,
+                const uint256& hash, std::string& err_string)
+{
+    // The replacement must pay greater fees than the transactions it
+    // replaces - if we did the bandwidth used by those conflicting
+    // transactions would not be paid for.
+    if (nModifiedFees < nConflictingFees)
+    {
+        err_string = strprintf("rejecting replacement %s, less fees than conflicting txs; %s < %s",
+                    hash.ToString(), FormatMoney(nModifiedFees), FormatMoney(nConflictingFees));
+        return false;
+    }
+
+    // Finally in addition to paying more fees than the conflicts the
+    // new transaction must pay for its own bandwidth.
+    CAmount nDeltaFees = nModifiedFees - nConflictingFees;
+    if (nDeltaFees < ::incrementalRelayFee.GetFee(nSize))
+    {
+        err_string = strprintf("rejecting replacement %s, not enough additional fees to relay; %s < %s",
+                    hash.ToString(),
+                    FormatMoney(nDeltaFees),
+                    FormatMoney(::incrementalRelayFee.GetFee(nSize)));
+        return false;
+    }
+    return true;
+}
diff --git a/src/policy/rbf.h b/src/policy/rbf.h
@@ -76,4 +76,16 @@ bool EntriesAndTxidsDisjoint(const CTxMemPool::setEntries& setAncestors,
 bool PaysMoreThanConflicts(const CTxMemPool::setEntries& setIterConflicting, CFeeRate newFeeRate,
                            const uint256& hash, std::string& err_string);
 
+/** Enforce BIP125 Rule #3 "The replacement transaction pays an absolute fee of at least the sum
+ * paid by the original transactions." Enforce BIP125 Rule #4 "The replacement transaction must also
+ * pay for its own bandwidth at or above the rate set by the node's minimum relay fee setting."
+ * @param[in]   nConflictingFees    Total modified fees of original transaction(s).
+ * @param[in]   nModifiedFees       Total modified fees of replacement transaction(s).
+ * @param[in]   nSize               Total virtual size of replacement transaction(s).
+ * @param[in]   hash                Transaction ID, included in the error message if violation occurs.
+ * returns true if fees are sufficient, false if otherwise.
+ */
+bool PaysForRBF(CAmount nConflictingFees, CAmount nModifiedFees, size_t nSize,
+                const uint256& hash, std::string& err_string);
+
 #endif // BITCOIN_POLICY_RBF_H
diff --git a/src/validation.cpp b/src/validation.cpp
@@ -797,32 +797,13 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
         }
 
         // Check if it's economically rational to mine this transaction rather
-        // than the ones it replaces.
+        // than the ones it replaces. Enforce Rules #3 and #4.
         for (CTxMemPool::txiter it : allConflicting) {
             nConflictingFees += it->GetModifiedFee();
             nConflictingSize += it->GetTxSize();
         }
-
-        // The replacement must pay greater fees than the transactions it
-        // replaces - if we did the bandwidth used by those conflicting
-        // transactions would not be paid for.
-        if (nModifiedFees < nConflictingFees)
-        {
-            return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "insufficient fee",
-                    strprintf("rejecting replacement %s, less fees than conflicting txs; %s < %s",
-                        hash.ToString(), FormatMoney(nModifiedFees), FormatMoney(nConflictingFees)));
-        }
-
-        // Finally in addition to paying more fees than the conflicts the
-        // new transaction must pay for its own bandwidth.
-        CAmount nDeltaFees = nModifiedFees - nConflictingFees;
-        if (nDeltaFees < ::incrementalRelayFee.GetFee(nSize))
-        {
-            return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "insufficient fee",
-                    strprintf("rejecting replacement %s, not enough additional fees to relay; %s < %s",
-                        hash.ToString(),
-                        FormatMoney(nDeltaFees),
-                        FormatMoney(::incrementalRelayFee.GetFee(nSize))));
+        if (!PaysForRBF(nConflictingFees, nModifiedFees, nSize, hash, err_string)) {
+            return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "insufficient fee", err_string);
         }
     }
     return true;
