[wallet] Move maxTxFee to wallet

This commit moves the maxtxfee setting to the wallet. There is only
one minor behavior change:

- an error message in feebumper now refers to -maxtxfee instead of
maxTxFee.

5 files changed, 37 insertions, 8 deletions

diff --git a/src/wallet/feebumper.cpp b/src/wallet/feebumper.cpp
index b547ea21d9..7ffea3867d 100644
--- a/src/wallet/feebumper.cpp
+++ b/src/wallet/feebumper.cpp
@@ -162,9 +162,9 @@ Result CreateTransaction(const CWallet* wallet, const uint256& txid, const CCoin
     }
 
     // Check that in all cases the new fee doesn't violate maxTxFee
-     const CAmount max_tx_fee = wallet->chain().maxTxFee();
+     const CAmount max_tx_fee = wallet->m_default_max_tx_fee;
      if (new_fee > max_tx_fee) {
-         errors.push_back(strprintf("Specified or calculated fee %s is too high (cannot be higher than maxTxFee %s)",
+         errors.push_back(strprintf("Specified or calculated fee %s is too high (cannot be higher than -maxtxfee %s)",
                                FormatMoney(new_fee), FormatMoney(max_tx_fee)));
          return Result::WALLET_ERROR;
      }
diff --git a/src/wallet/fees.cpp b/src/wallet/fees.cpp
index 560c86a70a..d9ae18ed60 100644
--- a/src/wallet/fees.cpp
+++ b/src/wallet/fees.cpp
@@ -22,7 +22,7 @@ CAmount GetMinimumFee(const CWallet& wallet, unsigned int nTxBytes, const CCoinC
 {
     CAmount fee_needed = GetMinimumFeeRate(wallet, coin_control, feeCalc).GetFee(nTxBytes);
     // Always obey the maximum
-    const CAmount max_tx_fee = wallet.chain().maxTxFee();
+    const CAmount max_tx_fee = wallet.m_default_max_tx_fee;
     if (fee_needed > max_tx_fee) {
         fee_needed = max_tx_fee;
         if (feeCalc) feeCalc->reason = FeeReason::MAXTXFEE;
diff --git a/src/wallet/init.cpp b/src/wallet/init.cpp
index e7eea94e06..47ef01bfd1 100644
--- a/src/wallet/init.cpp
+++ b/src/wallet/init.cpp
@@ -48,6 +48,8 @@ void WalletInit::AddWalletOptions() const
     gArgs.AddArg("-fallbackfee=<amt>", strprintf("A fee rate (in %s/kB) that will be used when fee estimation has insufficient data (default: %s)",
                                                                CURRENCY_UNIT, FormatMoney(DEFAULT_FALLBACK_FEE)), false, OptionsCategory::WALLET);
     gArgs.AddArg("-keypool=<n>", strprintf("Set key pool size to <n> (default: %u)", DEFAULT_KEYPOOL_SIZE), false, OptionsCategory::WALLET);
+    gArgs.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)), false, OptionsCategory::DEBUG_TEST);
     gArgs.AddArg("-mintxfee=<amt>", strprintf("Fees (in %s/kB) smaller than this are considered zero fee for transaction creation (default: %s)",
                                                             CURRENCY_UNIT, FormatMoney(DEFAULT_TRANSACTION_MINFEE)), false, OptionsCategory::WALLET);
     gArgs.AddArg("-paytxfee=<amt>", strprintf("Fee (in %s/kB) to add to transactions you send (default: %s)",
@@ -124,10 +126,6 @@ bool WalletInit::ParameterInteraction() const
     if (gArgs.GetArg("-prune", 0) && gArgs.GetBoolArg("-rescan", false))
         return InitError(_("Rescans are not possible in pruned mode. You will need to use -reindex which will download the whole blockchain again."));
 
-    if (::minRelayTxFee.GetFeePerK() > HIGH_TX_FEE_PER_KB)
-        InitWarning(AmountHighWarn("-minrelaytxfee") + " " +
-                    _("The wallet will avoid paying less than the minimum relay fee."));
-
     return true;
 }
 
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 9ee6329f8c..8a1cb83e74 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -4204,6 +4204,29 @@ std::shared_ptr<CWallet> CWallet::CreateWalletFromFile(interfaces::Chain& chain,
             return nullptr;
         }
     }
+
+    if (gArgs.IsArgSet("-maxtxfee"))
+    {
+        CAmount nMaxFee = 0;
+        if (!ParseMoney(gArgs.GetArg("-maxtxfee", ""), nMaxFee)) {
+            chain.initError(AmountErrMsg("maxtxfee", gArgs.GetArg("-maxtxfee", "")));
+            return nullptr;
+        }
+        if (nMaxFee > HIGH_MAX_TX_FEE) {
+            chain.initWarning(_("-maxtxfee is set very high! Fees this large could be paid on a single transaction."));
+        }
+        if (CFeeRate(nMaxFee, 1000) < chain.relayMinFee()) {
+            chain.initError(strprintf(_("Invalid amount for -maxtxfee=<amount>: '%s' (must be at least the minrelay fee of %s to prevent stuck transactions)"),
+                                       gArgs.GetArg("-maxtxfee", ""), chain.relayMinFee().ToString()));
+            return nullptr;
+        }
+        walletInstance->m_default_max_tx_fee = nMaxFee;
+    }
+
+    if (chain.relayMinFee().GetFeePerK() > HIGH_TX_FEE_PER_KB)
+        chain.initWarning(AmountHighWarn("-minrelaytxfee") + " " +
+                    _("The wallet will avoid paying less than the minimum relay fee."));
+
     walletInstance->m_confirm_target = gArgs.GetArg("-txconfirmtarget", DEFAULT_TX_CONFIRM_TARGET);
     walletInstance->m_spend_zero_conf_change = gArgs.GetBoolArg("-spendzeroconfchange", DEFAULT_SPEND_ZEROCONF_CHANGE);
     walletInstance->m_signal_rbf = gArgs.GetBoolArg("-walletrbf", DEFAULT_WALLET_RBF);
@@ -4394,7 +4417,7 @@ bool CWalletTx::AcceptToMemoryPool(interfaces::Chain::Lock& locked_chain, CValid
     // user could call sendmoney in a loop and hit spurious out of funds errors
     // because we think that this newly generated transaction's change is
     // unavailable as we're not yet aware that it is in the mempool.
-    bool ret = locked_chain.submitToMemoryPool(tx, pwallet->chain().maxTxFee(), state);
+    bool ret = locked_chain.submitToMemoryPool(tx, pwallet->m_default_max_tx_fee, state);
     fInMempool |= ret;
     return ret;
 }
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 4cc6973802..008765bccc 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -73,6 +73,12 @@ static const unsigned int DEFAULT_TX_CONFIRM_TARGET = 6;
 static const bool DEFAULT_WALLET_RBF = false;
 static const bool DEFAULT_WALLETBROADCAST = true;
 static const bool DEFAULT_DISABLE_WALLET = false;
+//! -maxtxfee default
+constexpr CAmount DEFAULT_TRANSACTION_MAXFEE{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)
+constexpr CAmount HIGH_MAX_TX_FEE{100 * HIGH_TX_FEE_PER_KB};
 
 //! Pre-calculated constants for input size estimation in *virtual size*
 static constexpr size_t DUMMY_NESTED_P2WPKH_INPUT_SIZE = 91;
@@ -983,6 +989,8 @@ public:
     CFeeRate m_discard_rate{DEFAULT_DISCARD_FEE};
     OutputType m_default_address_type{DEFAULT_ADDRESS_TYPE};
     OutputType m_default_change_type{DEFAULT_CHANGE_TYPE};
+    /** Absolute maximum transaction fee (in satoshis) used by default for the wallet */
+    CAmount m_default_max_tx_fee{DEFAULT_TRANSACTION_MAXFEE};
 
     bool NewKeyPool();
     size_t KeypoolCountExternalKeys() EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);