generalize bumpfee to add inputs when needed

6 files changed, 153 insertions, 43 deletions

diff --git a/src/interfaces/wallet.cpp b/src/interfaces/wallet.cpp
index f98a49f9b1..ed73a71354 100644
--- a/src/interfaces/wallet.cpp
+++ b/src/interfaces/wallet.cpp
@@ -269,8 +269,13 @@ public:
         CAmount& new_fee,
         CMutableTransaction& mtx) override
     {
-        return feebumper::CreateTransaction(m_wallet.get(), txid, coin_control, total_fee, errors, old_fee, new_fee, mtx) ==
-               feebumper::Result::OK;
+        if (total_fee > 0) {
+            return feebumper::CreateTotalBumpTransaction(m_wallet.get(), txid, coin_control, total_fee, errors, old_fee, new_fee, mtx) ==
+                feebumper::Result::OK;
+        } else {
+            return feebumper::CreateRateBumpTransaction(m_wallet.get(), txid, coin_control, errors, old_fee, new_fee, mtx) ==
+                feebumper::Result::OK;
+        }
     }
     bool signBumpTransaction(CMutableTransaction& mtx) override { return feebumper::SignTransaction(m_wallet.get(), mtx); }
     bool commitBumpTransaction(const uint256& txid,
diff --git a/src/wallet/coincontrol.h b/src/wallet/coincontrol.h
index 48a924abfb..9257b272bc 100644
--- a/src/wallet/coincontrol.h
+++ b/src/wallet/coincontrol.h
@@ -36,6 +36,8 @@ public:
     bool m_avoid_partial_spends;
     //! Fee estimation mode to control arguments to estimateSmartFee
     FeeEstimateMode m_fee_mode;
+    //! Minimum chain depth value for coin availability
+    int m_min_depth{0};
 
     CCoinControl()
     {
diff --git a/src/wallet/feebumper.cpp b/src/wallet/feebumper.cpp
index b547ea21d9..4ec9dca420 100644
--- a/src/wallet/feebumper.cpp
+++ b/src/wallet/feebumper.cpp
@@ -75,9 +75,11 @@ bool TransactionCanBeBumped(const CWallet* wallet, const uint256& txid)
     return res == feebumper::Result::OK;
 }
 
-Result CreateTransaction(const CWallet* wallet, const uint256& txid, const CCoinControl& coin_control, CAmount total_fee, std::vector<std::string>& errors,
-                         CAmount& old_fee, CAmount& new_fee, CMutableTransaction& mtx)
+Result CreateTotalBumpTransaction(const CWallet* wallet, const uint256& txid, const CCoinControl& coin_control, CAmount total_fee, std::vector<std::string>& errors,
+                                  CAmount& old_fee, CAmount& new_fee, CMutableTransaction& mtx)
 {
+    new_fee = total_fee;
+
     auto locked_chain = wallet->chain().lock();
     LOCK(wallet->cs_wallet);
     errors.clear();
@@ -121,7 +123,6 @@ Result CreateTransaction(const CWallet* wallet, const uint256& txid, const CCoin
     // calculate the old fee and fee-rate
     old_fee = wtx.GetDebit(ISMINE_SPENDABLE) - wtx.tx->GetValueOut();
     CFeeRate nOldFeeRate(old_fee, txSize);
-    CFeeRate nNewFeeRate;
     // The wallet uses a conservative WALLET_INCREMENTAL_RELAY_FEE value to
     // future proof against changes to network wide policy for incremental relay
     // fee that our node may not be aware of.
@@ -131,34 +132,17 @@ Result CreateTransaction(const CWallet* wallet, const uint256& txid, const CCoin
         walletIncrementalRelayFee = nodeIncrementalRelayFee;
     }
 
-    if (total_fee > 0) {
-        CAmount minTotalFee = nOldFeeRate.GetFee(maxNewTxSize) + nodeIncrementalRelayFee.GetFee(maxNewTxSize);
-        if (total_fee < minTotalFee) {
-            errors.push_back(strprintf("Insufficient totalFee, must be at least %s (oldFee %s + incrementalFee %s)",
-                                                                FormatMoney(minTotalFee), FormatMoney(nOldFeeRate.GetFee(maxNewTxSize)), FormatMoney(nodeIncrementalRelayFee.GetFee(maxNewTxSize))));
-            return Result::INVALID_PARAMETER;
-        }
-        CAmount requiredFee = GetRequiredFee(*wallet, maxNewTxSize);
-        if (total_fee < requiredFee) {
-            errors.push_back(strprintf("Insufficient totalFee (cannot be less than required fee %s)",
-                                                                FormatMoney(requiredFee)));
-            return Result::INVALID_PARAMETER;
-        }
-        new_fee = total_fee;
-        nNewFeeRate = CFeeRate(total_fee, maxNewTxSize);
-    } else {
-        new_fee = GetMinimumFee(*wallet, maxNewTxSize, coin_control, nullptr /* FeeCalculation */);
-        nNewFeeRate = CFeeRate(new_fee, maxNewTxSize);
-
-        // New fee rate must be at least old rate + minimum incremental relay rate
-        // walletIncrementalRelayFee.GetFeePerK() should be exact, because it's initialized
-        // in that unit (fee per kb).
-        // However, nOldFeeRate is a calculated value from the tx fee/size, so
-        // add 1 satoshi to the result, because it may have been rounded down.
-        if (nNewFeeRate.GetFeePerK() < nOldFeeRate.GetFeePerK() + 1 + walletIncrementalRelayFee.GetFeePerK()) {
-            nNewFeeRate = CFeeRate(nOldFeeRate.GetFeePerK() + 1 + walletIncrementalRelayFee.GetFeePerK());
-            new_fee = nNewFeeRate.GetFee(maxNewTxSize);
-        }
+    CAmount minTotalFee = nOldFeeRate.GetFee(maxNewTxSize) + nodeIncrementalRelayFee.GetFee(maxNewTxSize);
+    if (total_fee < minTotalFee) {
+        errors.push_back(strprintf("Insufficient totalFee, must be at least %s (oldFee %s + incrementalFee %s)",
+            FormatMoney(minTotalFee), FormatMoney(nOldFeeRate.GetFee(maxNewTxSize)), FormatMoney(nodeIncrementalRelayFee.GetFee(maxNewTxSize))));
+        return Result::INVALID_PARAMETER;
+    }
+    CAmount requiredFee = GetRequiredFee(*wallet, maxNewTxSize);
+    if (total_fee < requiredFee) {
+        errors.push_back(strprintf("Insufficient totalFee (cannot be less than required fee %s)",
+            FormatMoney(requiredFee)));
+        return Result::INVALID_PARAMETER;
     }
 
     // Check that in all cases the new fee doesn't violate maxTxFee
@@ -175,14 +159,14 @@ Result CreateTransaction(const CWallet* wallet, const uint256& txid, const CCoin
     // in a rare situation where the mempool minimum fee increased significantly since the fee estimation just a
     // moment earlier. In this case, we report an error to the user, who may use total_fee to make an adjustment.
     CFeeRate minMempoolFeeRate = wallet->chain().mempoolMinFee();
+    CFeeRate nNewFeeRate = CFeeRate(total_fee, maxNewTxSize);
     if (nNewFeeRate.GetFeePerK() < minMempoolFeeRate.GetFeePerK()) {
         errors.push_back(strprintf(
             "New fee rate (%s) is lower than the minimum fee rate (%s) to get into the mempool -- "
-            "the totalFee value should be at least %s or the settxfee value should be at least %s to add transaction",
+            "the totalFee value should be at least %s to add transaction",
             FormatMoney(nNewFeeRate.GetFeePerK()),
             FormatMoney(minMempoolFeeRate.GetFeePerK()),
-            FormatMoney(minMempoolFeeRate.GetFee(maxNewTxSize)),
-            FormatMoney(minMempoolFeeRate.GetFeePerK())));
+            FormatMoney(minMempoolFeeRate.GetFee(maxNewTxSize))));
         return Result::WALLET_ERROR;
     }
 
@@ -212,6 +196,109 @@ Result CreateTransaction(const CWallet* wallet, const uint256& txid, const CCoin
         }
     }
 
+    return Result::OK;
+}
+
+
+Result CreateRateBumpTransaction(CWallet* wallet, const uint256& txid, const CCoinControl& coin_control, std::vector<std::string>& errors,
+                                 CAmount& old_fee, CAmount& new_fee, CMutableTransaction& mtx)
+{
+    // We are going to modify coin control later, copy to re-use
+    CCoinControl new_coin_control(coin_control);
+
+    auto locked_chain = wallet->chain().lock();
+    LOCK(wallet->cs_wallet);
+    errors.clear();
+    auto it = wallet->mapWallet.find(txid);
+    if (it == wallet->mapWallet.end()) {
+        errors.push_back("Invalid or non-wallet transaction id");
+        return Result::INVALID_ADDRESS_OR_KEY;
+    }
+    const CWalletTx& wtx = it->second;
+
+    Result result = PreconditionChecks(*locked_chain, wallet, wtx, errors);
+    if (result != Result::OK) {
+        return result;
+    }
+
+    // Fill in recipients(and preserve a single change key if there is one)
+    std::vector<CRecipient> recipients;
+    for (const auto& output : wtx.tx->vout) {
+        if (!wallet->IsChange(output)) {
+            CRecipient recipient = {output.scriptPubKey, output.nValue, false};
+            recipients.push_back(recipient);
+        } else {
+            CTxDestination change_dest;
+            ExtractDestination(output.scriptPubKey, change_dest);
+            new_coin_control.destChange = change_dest;
+        }
+    }
+
+    // Get the fee rate of the original transaction. This is calculated from
+    // the tx fee/vsize, so it may have been rounded down. Add 1 satoshi to the
+    // result.
+    old_fee = wtx.GetDebit(ISMINE_SPENDABLE) - wtx.tx->GetValueOut();
+    int64_t txSize = GetVirtualTransactionSize(*(wtx.tx));
+    // Feerate of thing we are bumping
+    CFeeRate feerate(old_fee, txSize);
+    feerate += CFeeRate(1);
+
+    // The node has a configurable incremental relay fee. Increment the fee by
+    // the minimum of that and the wallet's conservative
+    // WALLET_INCREMENTAL_RELAY_FEE value to future proof against changes to
+    // network wide policy for incremental relay fee that our node may not be
+    // aware of. This ensures we're over the over the required relay fee rate
+    // (BIP 125 rule 4).  The replacement tx will be at least as large as the
+    // original tx, so the total fee will be greater (BIP 125 rule 3)
+    CFeeRate node_incremental_relay_fee = wallet->chain().relayIncrementalFee();
+    CFeeRate wallet_incremental_relay_fee = CFeeRate(WALLET_INCREMENTAL_RELAY_FEE);
+    feerate += std::max(node_incremental_relay_fee, wallet_incremental_relay_fee);
+
+    // Fee rate must also be at least the wallet's GetMinimumFeeRate
+    CFeeRate min_feerate(GetMinimumFeeRate(*wallet, new_coin_control, /* feeCalc */ nullptr));
+
+    // Set the required fee rate for the replacement transaction in coin control.
+    new_coin_control.m_feerate = std::max(feerate, min_feerate);
+
+    // Fill in required inputs we are double-spending(all of them)
+    // N.B.: bip125 doesn't require all the inputs in the replaced transaction to be
+    // used in the replacement transaction, but it's very important for wallets to make
+    // sure that happens. If not, it would be possible to bump a transaction A twice to
+    // A2 and A3 where A2 and A3 don't conflict (or alternatively bump A to A2 and A2
+    // to A3 where A and A3 don't conflict). If both later get confirmed then the sender
+    // has accidentally double paid.
+    for (const auto& inputs : wtx.tx->vin) {
+        new_coin_control.Select(COutPoint(inputs.prevout));
+    }
+    new_coin_control.fAllowOtherInputs = true;
+
+    // We cannot source new unconfirmed inputs(bip125 rule 2)
+    new_coin_control.m_min_depth = 1;
+
+    CTransactionRef tx_new = MakeTransactionRef();
+    CReserveKey reservekey(wallet);
+    CAmount fee_ret;
+    int change_pos_in_out = -1; // No requested location for change
+    std::string fail_reason;
+    if (!wallet->CreateTransaction(*locked_chain, recipients, tx_new, reservekey, fee_ret, change_pos_in_out, fail_reason, new_coin_control, false)) {
+        errors.push_back("Unable to create transaction: " + fail_reason);
+        return Result::WALLET_ERROR;
+    }
+
+    // If change key hasn't been ReturnKey'ed by this point, we take it out of keypool
+    reservekey.KeepKey();
+
+    // Write back new fee if successful
+    new_fee = fee_ret;
+
+    // Write back transaction
+    mtx = CMutableTransaction(*tx_new);
+    // Mark new tx not replaceable, if requested.
+    if (!coin_control.m_signal_bip125_rbf.get_value_or(wallet->m_signal_rbf)) {
+        for (auto& input : mtx.vin) {
+            if (input.nSequence < 0xfffffffe) input.nSequence = 0xfffffffe;
+        }
+    }
 
     return Result::OK;
 }
diff --git a/src/wallet/feebumper.h b/src/wallet/feebumper.h
index a1eb5d0e0d..f9cbfc5f68 100644
--- a/src/wallet/feebumper.h
+++ b/src/wallet/feebumper.h
@@ -28,8 +28,8 @@ enum class Result
 //! Return whether transaction can be bumped.
 bool TransactionCanBeBumped(const CWallet* wallet, const uint256& txid);
 
-//! Create bumpfee transaction.
-Result CreateTransaction(const CWallet* wallet,
+//! Create bumpfee transaction based on total amount.
+Result CreateTotalBumpTransaction(const CWallet* wallet,
                          const uint256& txid,
                          const CCoinControl& coin_control,
                          CAmount total_fee,
@@ -38,6 +38,15 @@ Result CreateTransaction(const CWallet* wallet,
                          CAmount& new_fee,
                          CMutableTransaction& mtx);
 
+//! Create bumpfee transaction based on feerate estimates.
+Result CreateRateBumpTransaction(CWallet* wallet,
+                         const uint256& txid,
+                         const CCoinControl& coin_control,
+                         std::vector<std::string>& errors,
+                         CAmount& old_fee,
+                         CAmount& new_fee,
+                         CMutableTransaction& mtx);
+
 //! Sign the new transaction,
 //! @return false if the tx couldn't be found or if it was
 //! impossible to create the signature(s)
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index cb6f7637ad..c0c9345bd7 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -3167,9 +3167,9 @@ static UniValue bumpfee(const JSONRPCRequest& request)
             RPCHelpMan{"bumpfee",
                 "\nBumps the fee of an opt-in-RBF transaction T, replacing it with a new transaction B.\n"
                 "An opt-in RBF transaction with the given txid must be in the wallet.\n"
-                "The command will pay the additional fee by decreasing (or perhaps removing) its change output.\n"
-                "If the change output is not big enough to cover the increased fee, the command will currently fail\n"
-                "instead of adding new inputs to compensate. (A future implementation could improve this.)\n"
+                "The command will pay the additional fee by reducing change outputs or adding inputs when necessary. It may add a new change output if one does not already exist.\n"
+                "If `totalFee` is given, adding inputs is not supported, so there must be a single change output that is big enough or it will fail.\n"
+                "All inputs in the original transaction will be included in the replacement transaction.\n"
                 "The command will fail if the wallet or mempool contains a transaction that spends one of T's outputs.\n"
                 "By default, the new fee will be calculated automatically using estimatesmartfee.\n"
                 "The user can specify a confirmation target for estimatesmartfee.\n"
@@ -3266,7 +3266,14 @@ static UniValue bumpfee(const JSONRPCRequest& request)
     CAmount old_fee;
     CAmount new_fee;
     CMutableTransaction mtx;
-    feebumper::Result res = feebumper::CreateTransaction(pwallet, hash, coin_control, totalFee, errors, old_fee, new_fee, mtx);
+    feebumper::Result res;
+    if (totalFee > 0) {
+        // Targeting total fee bump. Requires a change output of sufficient size.
+        res = feebumper::CreateTotalBumpTransaction(pwallet, hash, coin_control, totalFee, errors, old_fee, new_fee, mtx);
+    } else {
+        // Targeting feerate bump.
+        res = feebumper::CreateRateBumpTransaction(pwallet, hash, coin_control, errors, old_fee, new_fee, mtx);
+    }
     if (res != feebumper::Result::OK) {
         switch(res) {
             case feebumper::Result::INVALID_ADDRESS_OR_KEY:
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 9ee6329f8c..98ba489729 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -2736,7 +2736,7 @@ bool CWallet::CreateTransaction(interfaces::Chain::Lock& locked_chain, const std
         LOCK(cs_wallet);
         {
             std::vector<COutput> vAvailableCoins;
-            AvailableCoins(*locked_chain, vAvailableCoins, true, &coin_control);
+            AvailableCoins(*locked_chain, vAvailableCoins, true, &coin_control, 1, MAX_MONEY, MAX_MONEY, 0, coin_control.m_min_depth);
             CoinSelectionParams coin_selection_params; // Parameters for coin selection, init with dummy
 
             // Create change script that will be used if we need change