Add -allowpackagebelowminrelayfeerate option

src/init.cpp

@@ -603,6 +603,7 @@ void SetupServerArgs(ArgsManager& argsman)
                    OptionsCategory::NODE_RELAY);
     argsman.AddArg("-minrelaytxfee=<amt>", strprintf("Fees (in %s/kvB) smaller than this are considered zero fee for relaying, mining and transaction creation (default: %s)",
         CURRENCY_UNIT, FormatMoney(DEFAULT_MIN_RELAY_TX_FEE)), ArgsManager::ALLOW_ANY, OptionsCategory::NODE_RELAY);
+    argsman.AddArg("-allowpackagebelowminrelayfeerate", strprintf("Allow indivual transactions below -minrelaytxfee for packages (default: %u)", DEFAULT_ALLOW_PACKAGE_BELOW_MIN_RELAY_FEE_RATE), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::NODE_RELAY);
     argsman.AddArg("-whitelistforcerelay", strprintf("Add 'forcerelay' permission to whitelisted inbound peers with default permissions. This will relay transactions even if the transactions were already in the mempool. (default: %d)", DEFAULT_WHITELISTFORCERELAY), ArgsManager::ALLOW_ANY, OptionsCategory::NODE_RELAY);
     argsman.AddArg("-whitelistrelay", strprintf("Add 'relay' permission to whitelisted inbound peers with default permissions. This will accept relayed transactions even when not relaying transactions (default: %d)", DEFAULT_WHITELISTRELAY), ArgsManager::ALLOW_ANY, OptionsCategory::NODE_RELAY);
 

src/kernel/mempool_options.h

@@ -25,6 +25,8 @@ static constexpr unsigned int DEFAULT_MEMPOOL_EXPIRY_HOURS{336};
 static constexpr bool DEFAULT_MEMPOOL_FULL_RBF{false};
 /** Default for -acceptnonstdtxn */
 static constexpr bool DEFAULT_ACCEPT_NON_STD_TXN{false};
+/** Default for -allowpackagebelowminrelayfeerate */
+static constexpr bool DEFAULT_ALLOW_PACKAGE_BELOW_MIN_RELAY_FEE_RATE{false};
 
 namespace kernel {
 /**
@@ -44,6 +46,7 @@ struct MemPoolOptions {
     CFeeRate incremental_relay_feerate{DEFAULT_INCREMENTAL_RELAY_FEE};
     /** A fee rate smaller than this is considered zero fee (for relaying, mining and transaction creation) */
     CFeeRate min_relay_feerate{DEFAULT_MIN_RELAY_TX_FEE};
+    bool allow_package_below_min_relay_feerate{DEFAULT_ALLOW_PACKAGE_BELOW_MIN_RELAY_FEE_RATE};
     CFeeRate dust_relay_feerate{DUST_RELAY_TX_FEE};
     /**
      * A data carrying output is an unspendable output containing data. The script

src/node/mempool_args.cpp

@@ -68,6 +68,8 @@ util::Result<void> ApplyArgsManOptions(const ArgsManager& argsman, const CChainP
         LogPrintf("Increasing minrelaytxfee to %s to match incrementalrelayfee\n", mempool_opts.min_relay_feerate.ToString());
     }
 
+    mempool_opts.allow_package_below_min_relay_feerate = argsman.GetBoolArg("-allowpackagebelowminrelayfeerate", DEFAULT_ALLOW_PACKAGE_BELOW_MIN_RELAY_FEE_RATE);
+
     // Feerate used to define dust.  Shouldn't be changed lightly as old
     // implementations may inadvertently create non-standard transactions
     if (argsman.IsArgSet("-dustrelayfee")) {

src/txmempool.cpp

@@ -407,6 +407,7 @@ CTxMemPool::CTxMemPool(const Options& opts)
       m_expiry{opts.expiry},
       m_incremental_relay_feerate{opts.incremental_relay_feerate},
       m_min_relay_feerate{opts.min_relay_feerate},
+      m_allow_package_below_min_relay_feerate{opts.allow_package_below_min_relay_feerate},
       m_dust_relay_feerate{opts.dust_relay_feerate},
       m_permit_bare_multisig{opts.permit_bare_multisig},
       m_max_datacarrier_bytes{opts.max_datacarrier_bytes},

src/txmempool.h

@@ -441,6 +441,7 @@ class CTxMemPool
     const std::chrono::seconds m_expiry;
     const CFeeRate m_incremental_relay_feerate;
     const CFeeRate m_min_relay_feerate;
+    const bool m_allow_package_below_min_relay_feerate;
     const CFeeRate m_dust_relay_feerate;
     const bool m_permit_bare_multisig;
     const std::optional<unsigned> m_max_datacarrier_bytes;

src/validation.cpp

@@ -670,11 +670,11 @@ class MemPoolAccept
         AssertLockHeld(m_pool.cs);
         CAmount mempoolRejectFee = m_pool.GetMinFee().GetFee(package_size);
         if (mempoolRejectFee > 0 && package_fee < mempoolRejectFee) {
-            return state.Invalid(TxValidationResult::TX_RECONSIDERABLE, "mempool min fee not met", strprintf("%d < %d", package_fee, mempoolRejectFee));
+            return state.Invalid(TxValidationResult::TX_RECONSIDERABLE, "mempool min fee not met for package", strprintf("%d < %d", package_fee, mempoolRejectFee));
         }
 
         if (package_fee < m_pool.m_min_relay_feerate.GetFee(package_size)) {
-            return state.Invalid(TxValidationResult::TX_RECONSIDERABLE, "min relay fee not met",
+            return state.Invalid(TxValidationResult::TX_RECONSIDERABLE, "min relay fee not met for pacage",
                                  strprintf("%d < %d", package_fee, m_pool.m_min_relay_feerate.GetFee(package_size)));
         }
         return true;
@@ -866,7 +866,7 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
     // while a tx could be package CPFP'd when entering the mempool, we do not have a DoS-resistant
     // method of ensuring the tx remains bumped. For example, the fee-bumping child could disappear
     // due to a replacement.
-    if (!bypass_limits && ws.m_modified_fees < m_pool.m_min_relay_feerate.GetFee(ws.m_vsize)) {
+    if (!bypass_limits && !m_pool.m_allow_package_below_min_relay_feerate && ws.m_modified_fees < m_pool.m_min_relay_feerate.GetFee(ws.m_vsize)) {
         // Even though this is a fee-related failure, this result is TX_MEMPOOL_POLICY, not
         // TX_RECONSIDERABLE, because it cannot be bypassed using package validation.
         return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "min relay fee not met",

test/functional/mempool_limit.py

@@ -170,7 +170,7 @@ def test_mid_package_eviction(self):
             confirmed_only=True)
         package_hex.append(cpfp_parent["hex"])
         parent_utxos.append(cpfp_parent["new_utxo"])
-        assert_equal(node.testmempoolaccept([cpfp_parent["hex"]])[0]["reject-reason"], "mempool min fee not met")
+        assert_equal(node.testmempoolaccept([cpfp_parent["hex"]])[0]["reject-reason"], "mempool min fee not met for package")
 
         self.wallet.rescan_utxos()