sweep: add fee info for published inputs

This commit attaches RBFInfo to an input before it's been published or
it's already been published.

sweep/sweeper.go

@@ -14,6 +14,7 @@ import (
 	"github.com/btcsuite/btcd/wire"
 	"github.com/davecgh/go-spew/spew"
 	"github.com/lightningnetwork/lnd/chainntnfs"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/labels"
 	"github.com/lightningnetwork/lnd/lnwallet"
@@ -157,6 +158,19 @@ func (s SweepState) String() string {
 	}
 }
 
+// RBFInfo stores the information required to perform a RBF bump on a pending
+// sweeping tx.
+type RBFInfo struct {
+	// Txid is the txid of the sweeping tx.
+	Txid chainhash.Hash
+
+	// FeeRate is the fee rate of the sweeping tx.
+	FeeRate chainfee.SatPerKWeight
+
+	// Fee is the total fee of the sweeping tx.
+	Fee btcutil.Amount
+}
+
 // pendingInput is created when an input reaches the main loop for the first
 // time. It wraps the input and tracks all relevant state that is needed for
 // sweeping.
@@ -188,6 +202,9 @@ type pendingInput struct {
 	// lastFeeRate is the most recent fee rate used for this input within a
 	// transaction broadcast to the network.
 	lastFeeRate chainfee.SatPerKWeight
+
+	// rbf records the RBF constraints.
+	rbf fn.Option[RBFInfo]
 }
 
 // parameters returns the sweep parameters for this input.
@@ -1012,11 +1029,16 @@ func (s *UtxoSweeper) markInputsPendingPublish(tr *TxRecord,
 		}
 
 		// Update the input's state.
-		//
-		// TODO: also calculate the fees and fee rate of this tx to
-		// prepare possible RBF.
 		pi.state = StatePendingPublish
 
+		// Record the fees and fee rate of this tx to prepare possible
+		// RBF.
+		pi.rbf = fn.Some(RBFInfo{
+			Txid:    tx.TxHash(),
+			FeeRate: chainfee.SatPerKWeight(tr.FeeRate),
+			Fee:     btcutil.Amount(tr.Fee),
+		})
+
 		// Record another publish attempt.
 		pi.publishAttempts++
 
@@ -1440,12 +1462,9 @@ func (s *UtxoSweeper) handleNewInput(input *sweepInputMessage) {
 		params:           input.params,
 	}
 
-	// If the input is already spent in the mempool, update its state to
-	// StatePublished.
-	_, spent := s.mempoolLookup(outpoint)
-	if spent {
-		pi.state = StatePublished
-	}
+	// Try to find fee info for possible RBF if this input has already been
+	// spent.
+	pi = s.attachAvailableRBFInfo(pi)
 
 	s.pendingInputs[outpoint] = pi
 	log.Tracef("input %v added to pendingInputs", outpoint)
@@ -1466,6 +1485,60 @@ func (s *UtxoSweeper) handleNewInput(input *sweepInputMessage) {
 	pi.ntfnRegCancel = cancel
 }
 
+// attachAvailableRBFInfo queries the mempool to see whether the given input
+// has already been spent. If so, it will query the sweeper store to fetch the
+// fee info of the spending transction, hence preparing for possible RBF.
+func (s *UtxoSweeper) attachAvailableRBFInfo(pi *pendingInput) *pendingInput {
+	// Check if we can find the spending tx of this input in mempool.
+	tx, spent := s.mempoolLookup(*pi.OutPoint())
+
+	// Exit early if it's not found.
+	//
+	// NOTE: this is not accurate for backends that don't support mempool
+	// lookup:
+	// - for neutrino we don't have a mempool.
+	// - for btcd below v0.24.1 we don't have `gettxspendingprevout`.
+	if !spent {
+		return pi
+	}
+
+	// Otherwise the input is already spent in the mempool, update its
+	// state to StatePublished.
+	pi.state = StatePublished
+
+	// We also need to update the RBF info for this input. If the sweeping
+	// transaction is broadcast by us, we can find the fee info in the
+	// sweeper store.
+	txid := tx.TxHash()
+	tr, err := s.cfg.Store.GetTx(txid)
+
+	// If the tx is not found in the store, it means it's not broadcast by
+	// us, hence we can't find the fee info. This is fine as, later on when
+	// this tx is confirmed, we will remove the input from our
+	// pendingInputs.
+	if errors.Is(err, ErrTxNotFound) {
+		log.Warnf("Spending tx %v not found in sweeper store", txid)
+		return pi
+	}
+
+	// Exit if we get an db error.
+	if err != nil {
+		log.Errorf("Unable to get tx %v from sweeper store: %v",
+			txid, err)
+
+		return pi
+	}
+
+	// Attach the fee info and return it.
+	pi.rbf = fn.Some(RBFInfo{
+		Txid:    txid,
+		Fee:     btcutil.Amount(tr.Fee),
+		FeeRate: chainfee.SatPerKWeight(tr.FeeRate),
+	})
+
+	return pi
+}
+
 // handleExistingInput processes an input that is already known to the sweeper.
 // It will overwrite the params of the old input with the new ones.
 func (s *UtxoSweeper) handleExistingInput(input *sweepInputMessage,

sweep/sweeper_test.go

@@ -15,11 +15,13 @@ import (
 	"github.com/lightningnetwork/lnd/build"
 	"github.com/lightningnetwork/lnd/chainntnfs"
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/keychain"
-	"github.com/lightningnetwork/lnd/lntest/mock"
+	lnmock "github.com/lightningnetwork/lnd/lntest/mock"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
+	"github.com/stretchr/testify/mock"
 	"github.com/stretchr/testify/require"
 )
 
@@ -137,7 +139,7 @@ func createSweeperTestContext(t *testing.T) *sweeperTestContext {
 		Wallet:         backend,
 		TickerDuration: 100 * time.Millisecond,
 		Store:          store,
-		Signer:         &mock.DummySigner{},
+		Signer:         &lnmock.DummySigner{},
 		GenSweepScript: func() ([]byte, error) {
 			script := make([]byte, input.P2WPKHSize)
 			script[0] = 0
@@ -2308,3 +2310,107 @@ func TestUpdateSweeperInputs(t *testing.T) {
 	// Assert the sweeper inputs are as expected.
 	require.Equal(expectedInputs, s.pendingInputs)
 }
+
+// TestAttachAvailableRBFInfo checks that the RBF info is attached to the
+// pending input, along with the state being marked as published, when this
+// input can be found both in mempool and the sweeper store.
+func TestAttachAvailableRBFInfo(t *testing.T) {
+	t.Parallel()
+
+	require := require.New(t)
+
+	// Create a test outpoint.
+	op := wire.OutPoint{Index: 1}
+
+	// Create a mock input.
+	testInput := &input.MockInput{}
+	testInput.On("OutPoint").Return(&op)
+	pi := &pendingInput{
+		Input: testInput,
+		state: StateInit,
+	}
+
+	// Create a mock mempool watcher and a mock sweeper store.
+	mockMempool := chainntnfs.NewMockMempoolWatcher()
+	mockStore := NewMockSweeperStore()
+
+	// Create a mempool spend event to be returned by the mempool watcher.
+	spendChan := make(chan *chainntnfs.SpendDetail, 1)
+	spendEvent := &chainntnfs.MempoolSpendEvent{
+		Spend: spendChan,
+	}
+
+	// Mock the cancel subscription calls.
+	mockMempool.On("CancelMempoolSpendEvent", spendEvent)
+
+	// Create a test sweeper.
+	s := New(&UtxoSweeperConfig{
+		Store:   mockStore,
+		Mempool: mockMempool,
+	})
+
+	// First, mock the mempool to return an error.
+	dummyErr := errors.New("dummy err")
+	mockMempool.On("SubscribeMempoolSpent", op).Return(nil, dummyErr).Once()
+
+	// Since the mempool lookup failed, we exepect the original pending
+	// input to stay unchanged.
+	result := s.attachAvailableRBFInfo(pi)
+	require.True(result.rbf.IsNone())
+	require.Equal(StateInit, result.state)
+
+	// Mock the mempool lookup to return a tx three times.
+	tx := &wire.MsgTx{}
+	mockMempool.On("SubscribeMempoolSpent", op).Return(
+		spendEvent, nil).Times(3).Run(func(_ mock.Arguments) {
+		// Eeac time the method is called, we send a tx to the spend
+		// channel.
+		spendChan <- &chainntnfs.SpendDetail{
+			SpendingTx: tx,
+		}
+	})
+
+	// Mock the store to return an error saying the tx cannot be found.
+	mockStore.On("GetTx", tx.TxHash()).Return(nil, ErrTxNotFound).Once()
+
+	// Although the db lookup failed, the pending input should have been
+	// marked as published without attaching any RBF info.
+	result = s.attachAvailableRBFInfo(pi)
+	require.True(result.rbf.IsNone())
+	require.Equal(StatePublished, result.state)
+
+	// Mock the store to return a db error.
+	mockStore.On("GetTx", tx.TxHash()).Return(nil, dummyErr).Once()
+
+	// Although the db lookup failed, the pending input should have been
+	// marked as published without attaching any RBF info.
+	result = s.attachAvailableRBFInfo(pi)
+	require.True(result.rbf.IsNone())
+	require.Equal(StatePublished, result.state)
+
+	// Mock the store to return a record.
+	tr := &TxRecord{
+		Fee:     100,
+		FeeRate: 100,
+	}
+	mockStore.On("GetTx", tx.TxHash()).Return(tr, nil).Once()
+
+	// Call the method again.
+	result = s.attachAvailableRBFInfo(pi)
+
+	// Assert that the RBF info is attached to the pending input.
+	rbfInfo := fn.Some(RBFInfo{
+		Txid:    tx.TxHash(),
+		Fee:     btcutil.Amount(tr.Fee),
+		FeeRate: chainfee.SatPerKWeight(tr.FeeRate),
+	})
+	require.Equal(rbfInfo, result.rbf)
+
+	// Assert the state is updated.
+	require.Equal(StatePublished, result.state)
+
+	// Assert mocked statements.
+	testInput.AssertExpectations(t)
+	mockMempool.AssertExpectations(t)
+	mockStore.AssertExpectations(t)
+}