Merge #16521: rpc: Use the default maxfeerate value as BTC/kB

2dfd6834ef8737e16e4b96df0c459f30a0721d6c test: Add test for default maxfeerate in sendrawtransaction (Joonmo Yang)
261843e4bef96ab296a9775819a99bfa60cad743 wallet/rpc: Use the default maxfeerate value as BTC/kB (Joonmo Yang)

Pull request description:

  Fixes https://github.com/bitcoin/bitcoin/issues/16382

  This patch tries to treat `maxfeerate` in sendrawtransaction/testmempoolaccept RPC as a rate(BTC/kB) instead of an absolute value(BTC).
  The included test case checks if the new behavior works correctly, by using the transaction with an absolute fee of ~0.02BTC, where the fee rate is ~0.2BTC/kB.
  This test should be failing if the default `maxfeerate` is 0.1BTC, but pass if the default value is 0.1BTC/kB

ACKs for top commit:
  laanwj:
    ACK 2dfd6834ef8737e16e4b96df0c459f30a0721d6c (ACKs by Sjors and MarcoFalke above for trivially different code)

Tree-SHA512: a1795bffe8a182acef8844797955db1f60bb0c0ded97148f3572dc265234d5219271a3a7aa0b6418a43f73b2b2720ef7412ba169c99bb1cdcac52051f537d6af

1 files changed, 17 insertions, 20 deletions

diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 4003299662..461e8025da 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -14,6 +14,7 @@
 #include <node/coin.h>
 #include <node/psbt.h>
 #include <node/transaction.h>
+#include <policy/policy.h>
 #include <policy/rbf.h>
 #include <primitives/transaction.h>
 #include <psbt.h>
@@ -38,11 +39,11 @@
 
 #include <univalue.h>
 
-/** High fee for sendrawtransaction and testmempoolaccept.
- * By default, transaction with a fee higher than this will be rejected by the
- * RPCs. This can be overridden with the maxfeerate argument.
+/** High fee rate for sendrawtransaction and testmempoolaccept.
+ * By default, transaction with a fee rate higher than this will be rejected by
+ * the RPCs. This can be overridden with the maxfeerate argument.
  */
-constexpr static CAmount DEFAULT_MAX_RAW_TX_FEE{COIN / 10};
+static const CFeeRate DEFAULT_MAX_RAW_TX_FEE_RATE{COIN / 10};
 
 static void TxToJSON(const CTransaction& tx, const uint256 hashBlock, UniValue& entry)
 {
@@ -775,7 +776,7 @@ static UniValue sendrawtransaction(const JSONRPCRequest& request)
                 "\nAlso see createrawtransaction and signrawtransactionwithkey calls.\n",
                 {
                     {"hexstring", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The hex string of the raw transaction"},
-                    {"maxfeerate", RPCArg::Type::AMOUNT, /* default */ FormatMoney(DEFAULT_MAX_RAW_TX_FEE),
+                    {"maxfeerate", RPCArg::Type::AMOUNT, /* default */ FormatMoney(DEFAULT_MAX_RAW_TX_FEE_RATE.GetFeePerK()),
                         "Reject transactions whose fee rate is higher than the specified value, expressed in " + CURRENCY_UNIT +
                             "/kB.\nSet to 0 to accept any fee rate.\n"},
                 },
@@ -805,19 +806,17 @@ static UniValue sendrawtransaction(const JSONRPCRequest& request)
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
     CTransactionRef tx(MakeTransactionRef(std::move(mtx)));
 
-    CAmount max_raw_tx_fee = DEFAULT_MAX_RAW_TX_FEE;
+    CFeeRate max_raw_tx_fee_rate = DEFAULT_MAX_RAW_TX_FEE_RATE;
     // TODO: temporary migration code for old clients. Remove in v0.20
     if (request.params[1].isBool()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Second argument must be numeric (maxfeerate) and no longer supports a boolean. To allow a transaction with high fees, set maxfeerate to 0.");
     } else if (!request.params[1].isNull()) {
-        size_t weight = GetTransactionWeight(*tx);
-        CFeeRate fr(AmountFromValue(request.params[1]));
-        // the +3/4 part rounds the value up, and is the same formula used when
-        // calculating the fee for a transaction
-        // (see GetVirtualTransactionSize)
-        max_raw_tx_fee = fr.GetFee((weight+3)/4);
+        max_raw_tx_fee_rate = CFeeRate(AmountFromValue(request.params[1]));
     }
 
+    int64_t virtual_size = GetVirtualTransactionSize(*tx);
+    CAmount max_raw_tx_fee = max_raw_tx_fee_rate.GetFee(virtual_size);
+
     std::string err_string;
     AssertLockNotHeld(cs_main);
     const TransactionError err = BroadcastTransaction(tx, err_string, max_raw_tx_fee, /*relay*/ true, /*wait_callback*/ true);
@@ -841,7 +840,7 @@ static UniValue testmempoolaccept(const JSONRPCRequest& request)
                             {"rawtx", RPCArg::Type::STR_HEX, RPCArg::Optional::OMITTED, ""},
                         },
                         },
-                    {"maxfeerate", RPCArg::Type::AMOUNT, /* default */ FormatMoney(DEFAULT_MAX_RAW_TX_FEE), "Reject transactions whose fee rate is higher than the specified value, expressed in " + CURRENCY_UNIT + "/kB\n"},
+                    {"maxfeerate", RPCArg::Type::AMOUNT, /* default */ FormatMoney(DEFAULT_MAX_RAW_TX_FEE_RATE.GetFeePerK()), "Reject transactions whose fee rate is higher than the specified value, expressed in " + CURRENCY_UNIT + "/kB\n"},
                 },
                 RPCResult{
             "[                   (array) The result of the mempool acceptance test for each raw transaction in the input array.\n"
@@ -881,19 +880,17 @@ static UniValue testmempoolaccept(const JSONRPCRequest& request)
     CTransactionRef tx(MakeTransactionRef(std::move(mtx)));
     const uint256& tx_hash = tx->GetHash();
 
-    CAmount max_raw_tx_fee = DEFAULT_MAX_RAW_TX_FEE;
+    CFeeRate max_raw_tx_fee_rate = DEFAULT_MAX_RAW_TX_FEE_RATE;
     // TODO: temporary migration code for old clients. Remove in v0.20
     if (request.params[1].isBool()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Second argument must be numeric (maxfeerate) and no longer supports a boolean. To allow a transaction with high fees, set maxfeerate to 0.");
     } else if (!request.params[1].isNull()) {
-        size_t weight = GetTransactionWeight(*tx);
-        CFeeRate fr(AmountFromValue(request.params[1]));
-        // the +3/4 part rounds the value up, and is the same formula used when
-        // calculating the fee for a transaction
-        // (see GetVirtualTransactionSize)
-        max_raw_tx_fee = fr.GetFee((weight+3)/4);
+        max_raw_tx_fee_rate = CFeeRate(AmountFromValue(request.params[1]));
     }
 
+    int64_t virtual_size = GetVirtualTransactionSize(*tx);
+    CAmount max_raw_tx_fee = max_raw_tx_fee_rate.GetFee(virtual_size);
+
     UniValue result(UniValue::VARR);
     UniValue result_0(UniValue::VOBJ);
     result_0.pushKV("txid", tx_hash.GetHex());