Introduce -blockmintxfee

src/init.cpp

@@ -476,6 +476,7 @@ std::string HelpMessage(HelpMessageMode mode)
     strUsage += HelpMessageOpt("-blockmaxweight=<n>", strprintf(_("Set maximum BIP141 block weight (default: %d)"), DEFAULT_BLOCK_MAX_WEIGHT));
     strUsage += HelpMessageOpt("-blockmaxsize=<n>", strprintf(_("Set maximum block size in bytes (default: %d)"), DEFAULT_BLOCK_MAX_SIZE));
     strUsage += HelpMessageOpt("-blockprioritysize=<n>", strprintf(_("Set maximum size of high-priority/low-fee transactions in bytes (default: %d)"), DEFAULT_BLOCK_PRIORITY_SIZE));
+    strUsage += HelpMessageOpt("-blockmintxfee=<amt>", strprintf(_("Set lowest fee rate (in %s/kB) for transactions to be included in block creation. (default: %s)"), CURRENCY_UNIT, FormatMoney(DEFAULT_BLOCK_MIN_TX_FEE)));
     if (showDebug)
         strUsage += HelpMessageOpt("-blockversion=<n>", "Override block version to test forking scenarios");
 
@@ -970,6 +971,15 @@ bool AppInitParameterInteraction()
         ::minRelayTxFee = CFeeRate(n);
     }
 
+    // Sanity check argument for min fee for including tx in block
+    // TODO: Harmonize which arguments need sanity checking and where that happens
+    if (IsArgSet("-blockmintxfee"))
+    {
+        CAmount n = 0;
+        if (!ParseMoney(GetArg("-blockmintxfee", ""), n))
+            return InitError(AmountErrMsg("blockmintxfee", GetArg("-blockmintxfee", "")));
+    }
+
     fRequireStandard = !GetBoolArg("-acceptnonstdtxn", !chainparams.RequireStandard());
     if (chainparams.RequireStandard() && !fRequireStandard)
         return InitError(strprintf("acceptnonstdtxn is not currently supported for %s chain", chainparams.NetworkIDString()));

src/miner.cpp

@@ -95,12 +95,18 @@ BlockAssembler::BlockAssembler(const CChainParams& _chainparams)
             nBlockMaxWeight = nBlockMaxSize * WITNESS_SCALE_FACTOR;
         }
     }
+    if (IsArgSet("-blockmintxfee")) {
+        CAmount n = 0;
+        ParseMoney(GetArg("-blockmintxfee", ""), n);
+        blockMinFeeRate = CFeeRate(n);
+    } else {
+        blockMinFeeRate = CFeeRate(DEFAULT_BLOCK_MIN_TX_FEE);
+    }
 
     // Limit weight to between 4K and MAX_BLOCK_WEIGHT-4K for sanity:
     nBlockMaxWeight = std::max((unsigned int)4000, std::min((unsigned int)(MAX_BLOCK_WEIGHT-4000), nBlockMaxWeight));
     // Limit size to between 1K and MAX_BLOCK_SERIALIZED_SIZE-1K for sanity:
     nBlockMaxSize = std::max((unsigned int)1000, std::min((unsigned int)(MAX_BLOCK_SERIALIZED_SIZE-1000), nBlockMaxSize));
-
     // Whether we need to account for byte usage (in addition to weight usage)
     fNeedSizeAccounting = (nBlockMaxSize < MAX_BLOCK_SERIALIZED_SIZE-1000);
 }
@@ -460,7 +466,7 @@ void BlockAssembler::addPackageTxs()
             packageSigOpsCost = modit->nSigOpCostWithAncestors;
         }
 
-        if (packageFees < ::minRelayTxFee.GetFee(packageSize)) {
+        if (packageFees < blockMinFeeRate.GetFee(packageSize)) {
             // Everything else we might consider has a lower fee rate
             return;
         }

src/miner.h

@@ -143,6 +143,7 @@ private:
     bool fIncludeWitness;
     unsigned int nBlockMaxWeight, nBlockMaxSize;
     bool fNeedSizeAccounting;
+    CFeeRate blockMinFeeRate;
 
     // Information on the current status of the block
     uint64_t nBlockWeight;

src/policy/policy.h

@@ -20,6 +20,8 @@ static const unsigned int DEFAULT_BLOCK_MAX_SIZE = 750000;
 static const unsigned int DEFAULT_BLOCK_PRIORITY_SIZE = 0;
 /** Default for -blockmaxweight, which controls the range of block weights the mining code will create **/
 static const unsigned int DEFAULT_BLOCK_MAX_WEIGHT = 3000000;
+/** Default for -blockmintxfee, which sets the minimum feerate for a transaction in blocks created by mining code **/
+static const unsigned int DEFAULT_BLOCK_MIN_TX_FEE = 1000;
 /** The maximum weight for transactions we're willing to relay/mine */
 static const unsigned int MAX_STANDARD_TX_WEIGHT = 400000;
 /** Maximum number of signature check operations in an IsStandard() P2SH script */