Introduce -incrementalrelayfee

1 files changed, 16 insertions, 1 deletions

diff --git a/src/init.cpp b/src/init.cpp
index b0c045da15..f3a3a1d276 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -465,8 +465,10 @@ std::string HelpMessage(HelpMessageMode mode)
     AppendParamsHelpMessages(strUsage, showDebug);
 
     strUsage += HelpMessageGroup(_("Node relay options:"));
-    if (showDebug)
+    if (showDebug) {
         strUsage += HelpMessageOpt("-acceptnonstdtxn", strprintf("Relay and mine \"non-standard\" transactions (%sdefault: %u)", "testnet/regtest only; ", !Params(CBaseChainParams::TESTNET).RequireStandard()));
+        strUsage += HelpMessageOpt("-incrementalrelayfee=<amt>", strprintf("Fee rate (in %s/kB) used to define cost of relay, used for mempool limiting and BIP 125 replacement. (default: %s)", CURRENCY_UNIT, FormatMoney(DEFAULT_INCREMENTAL_RELAY_FEE)));
+    }
     strUsage += HelpMessageOpt("-bytespersigop", strprintf(_("Equivalent bytes per sigop in transactions for relay and mining (default: %u)"), DEFAULT_BYTES_PER_SIGOP));
     strUsage += HelpMessageOpt("-datacarrier", strprintf(_("Relay and mine data carrier transactions (default: %u)"), DEFAULT_ACCEPT_DATACARRIER));
     strUsage += HelpMessageOpt("-datacarriersize", strprintf(_("Maximum size of data in data carrier transactions we relay and mine (default: %u)"), MAX_OP_RETURN_RELAY));
@@ -923,6 +925,15 @@ bool AppInitParameterInteraction()
     int64_t nMempoolSizeMin = GetArg("-limitdescendantsize", DEFAULT_DESCENDANT_SIZE_LIMIT) * 1000 * 40;
     if (nMempoolSizeMax < 0 || nMempoolSizeMax < nMempoolSizeMin)
         return InitError(strprintf(_("-maxmempool must be at least %d MB"), std::ceil(nMempoolSizeMin / 1000000.0)));
+    // incremental relay fee sets the minimimum feerate increase necessary for BIP 125 replacement in the mempool
+    // and the amount the mempool min fee increases above the feerate of txs evicted due to mempool limiting.
+    if (IsArgSet("-incrementalrelayfee"))
+    {
+        CAmount n = 0;
+        if (!ParseMoney(GetArg("-incrementalrelayfee", ""), n))
+            return InitError(AmountErrMsg("incrementalrelayfee", GetArg("-incrementalrelayfee", "")));
+        incrementalRelayFee = CFeeRate(n);
+    }
 
     // -par=0 means autodetect, but nScriptCheckThreads==0 means no concurrency
     nScriptCheckThreads = GetArg("-par", DEFAULT_SCRIPTCHECK_THREADS);
@@ -969,6 +980,10 @@ bool AppInitParameterInteraction()
             return InitError(AmountErrMsg("minrelaytxfee", GetArg("-minrelaytxfee", "")));
         // High fee check is done afterward in CWallet::ParameterInteraction()
         ::minRelayTxFee = CFeeRate(n);
+    } else if (incrementalRelayFee > ::minRelayTxFee) {
+        // Allow only setting incrementalRelayFee to control both
+        ::minRelayTxFee = incrementalRelayFee;
+        LogPrintf("Increasing minrelaytxfee to %s to match incrementalrelayfee\n",::minRelayTxFee.ToString());
     }
 
     // Sanity check argument for min fee for including tx in block