[wallet]: add maxfeerate wallet startup option

- The commits adds a new wallet startup option `-maxfeerate`

- The value will be used as the upper limit of wallet transaction fee rate.

- The commit updates all instances where `-maxtxfee` value is utilized to check
  wallet transactions fee rate upper limit to now use `-maxfeerate` value.

- `settxfee` RPC now only check if the fee rate user set is less `minrelaytxfee`,
   less than wallet min fee, or whether it exceed `maxfeerate`.
   We should not check whether `settxfee` RPC respects `maxtxfee` limit in
   in the functional test because its not enforced.
   We now only check if `settxfee` respects `maxfeerate` limit.

src/dummywallet.cpp

@@ -37,6 +37,7 @@ void DummyWalletInit::AddWalletOptions(ArgsManager& argsman) const
         "-keypool=<n>",
         "-maxapsfee=<n>",
         "-maxtxfee=<amt>",
+        "-maxfeerate=<amt>",
         "-mintxfee=<amt>",
         "-paytxfee=<amt>",
         "-signer=<cmd>",

src/wallet/init.cpp

@@ -64,6 +64,7 @@ void WalletInit::AddWalletOptions(ArgsManager& argsman) const
     argsman.AddArg("-maxapsfee=<n>", strprintf("Spend up to this amount in additional (absolute) fees (in %s) if it allows the use of partial spend avoidance (default: %s)", CURRENCY_UNIT, FormatMoney(DEFAULT_MAX_AVOIDPARTIALSPEND_FEE)), ArgsManager::ALLOW_ANY, OptionsCategory::WALLET);
     argsman.AddArg("-maxtxfee=<amt>", strprintf("Maximum total fees (in %s) to use in a single wallet transaction; setting this too low may abort large transactions (default: %s)",
         CURRENCY_UNIT, FormatMoney(DEFAULT_TRANSACTION_MAXFEE)), ArgsManager::ALLOW_ANY, OptionsCategory::DEBUG_TEST);
+    argsman.AddArg("-maxfeerate=<amt>", strprintf("Maximum fee rate (in %s/kvB) for a wallet transactions (default: %s %s/kvB)", CURRENCY_UNIT, FormatMoney(DEFAULT_MAX_TRANSACTION_FEERATE.GetFeePerK()), CURRENCY_UNIT), ArgsManager::ALLOW_ANY, OptionsCategory::WALLET);
     argsman.AddArg("-mintxfee=<amt>", strprintf("Fee rates (in %s/kvB) smaller than this are considered zero fee for transaction creation (default: %s)",
                                                             CURRENCY_UNIT, FormatMoney(DEFAULT_TRANSACTION_MINFEE)), ArgsManager::ALLOW_ANY, OptionsCategory::WALLET);
     argsman.AddArg("-paytxfee=<amt>", strprintf("Fee rate (in %s/kvB) to add to transactions you send (default: %s)",

src/wallet/rpc/spend.cpp

@@ -439,15 +439,14 @@ RPCHelpMan settxfee()
 
     CAmount nAmount = AmountFromValue(request.params[0]);
     CFeeRate tx_fee_rate(nAmount, 1000);
-    CFeeRate max_tx_fee_rate(pwallet->m_max_tx_fee, 1000);
     if (tx_fee_rate == CFeeRate(0)) {
         // automatic selection
     } else if (tx_fee_rate < pwallet->chain().relayMinFee()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("txfee cannot be less than min relay tx fee (%s)", pwallet->chain().relayMinFee().ToString()));
     } else if (tx_fee_rate < pwallet->m_min_fee) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("txfee cannot be less than wallet min fee (%s)", pwallet->m_min_fee.ToString()));
-    } else if (tx_fee_rate > max_tx_fee_rate) {
-        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("txfee cannot be more than wallet max tx fee (%s)", max_tx_fee_rate.ToString()));
+    } else if (tx_fee_rate > pwallet->m_max_tx_fee_rate) {
+        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("fee rate cannot be more than wallet max tx fee rate (%s)", pwallet->m_max_tx_fee_rate.ToString()));
     }
 
     pwallet->m_pay_tx_fee = tx_fee_rate;

src/wallet/wallet.cpp

@@ -3194,13 +3194,22 @@ std::shared_ptr<CWallet> CWallet::Create(WalletContext& context, const std::stri
             warnings.push_back(strprintf(_("%s is set very high! Fees this large could be paid on a single transaction."), "-maxtxfee"));
         }
 
-        if (chain && CFeeRate{max_tx_fee.value(), 1000} < chain->relayMinFee()) {
+        walletInstance->m_max_tx_fee = max_tx_fee.value();
+    }
+
+    if (args.IsArgSet("-maxfeerate")) {
+        std::optional<CAmount> max_tx_fee_rate = ParseMoney(args.GetArg("-maxfeerate", ""));
+        if (!max_tx_fee_rate) {
+            error = AmountErrMsg("maxfeerate", args.GetArg("-maxfeerate", ""));
+            return nullptr;
+        }
+        if (chain && CFeeRate(max_tx_fee_rate.value()) < chain->relayMinFee()) {
             error = strprintf(_("Invalid amount for %s=<amount>: '%s' (must be at least the minrelay fee of %s to prevent stuck transactions)"),
-                "-maxtxfee", args.GetArg("-maxtxfee", ""), chain->relayMinFee().ToString());
+                "-maxfeerate", args.GetArg("-maxfeerate", ""), chain->relayMinFee().ToString());
             return nullptr;
         }
 
-        walletInstance->m_max_tx_fee = max_tx_fee.value();
+        walletInstance->m_max_tx_fee_rate = CFeeRate(max_tx_fee_rate.value());
     }
 
     if (args.IsArgSet("-consolidatefeerate")) {

src/wallet/wallet.h

@@ -135,6 +135,8 @@ static const bool DEFAULT_DISABLE_WALLET = false;
 static const bool DEFAULT_WALLETCROSSCHAIN = false;
 //! -maxtxfee default
 constexpr CAmount DEFAULT_TRANSACTION_MAXFEE{COIN / 10};
+//! maxfeerate default
+const CFeeRate DEFAULT_MAX_TRANSACTION_FEERATE(CFeeRate(COIN / 10));
 //! Discourage users to set fees higher than this amount (in satoshis) per kB
 constexpr CAmount HIGH_TX_FEE_PER_KB{COIN / 100};
 //! -maxtxfee will warn if called with a higher fee than this amount (in satoshis)
@@ -730,6 +732,8 @@ public:
     /** Absolute maximum transaction fee (in satoshis) used by default for the wallet */
     CAmount m_max_tx_fee{DEFAULT_TRANSACTION_MAXFEE};
 
+    /** Maximum transaction fee rate used for the wallet */
+    CFeeRate m_max_tx_fee_rate{DEFAULT_MAX_TRANSACTION_FEERATE};
     /** Number of pre-generated keys/scripts by each spkm (part of the look-ahead process, used to detect payments) */
     int64_t m_keypool_size{DEFAULT_KEYPOOL_SIZE};
 

test/functional/wallet_bumpfee.py

@@ -547,9 +547,9 @@ def test_settxfee(self, rbf_node, dest_address):
     assert_greater_than(Decimal("0.00001000"), abs(requested_feerate - actual_feerate))
     rbf_node.settxfee(Decimal("0.00000000"))  # unset paytxfee
 
-    # check that settxfee respects -maxtxfee
-    self.restart_node(1, ['-maxtxfee=0.000025'] + self.extra_args[1])
-    assert_raises_rpc_error(-8, "txfee cannot be more than wallet max tx fee", rbf_node.settxfee, Decimal('0.00003'))
+    # check that settxfee respects -maxfeerate
+    self.restart_node(1, ['-maxfeerate=0.000025'] + self.extra_args[1])
+    assert_raises_rpc_error(-8, "fee rate cannot be more than wallet max tx fee rate", rbf_node.settxfee, Decimal('0.00003'))
     self.restart_node(1, self.extra_args[1])
     rbf_node.walletpassphrase(WALLET_PASSPHRASE, WALLET_PASSPHRASE_TIMEOUT)
     self.connect_nodes(1, 0)