sweepbatcher: add field SweepInfo.MinFeeRate

MinFeeRate is minimum fee rate that must be used by a batch of
the sweep. If it is specified, confTarget is ignored.

This is useful for external source of fees.

sweepbatcher/sweep_batch.go

@@ -97,6 +97,10 @@ type sweep struct {
 	// notifier is a collection of channels used to communicate the status
 	// of the sweep back to the swap that requested it.
 	notifier *SpendNotifier
+
+	// minFeeRate is minimum fee rate that must be used by a batch of
+	// the sweep. If it is specified, confTarget is ignored.
+	minFeeRate chainfee.SatPerKWeight
 }
 
 // batchState is the state of the batch.
@@ -399,9 +403,10 @@ func (b *batch) addSweep(ctx context.Context, sweep *sweep) (bool, error) {
 		b.sweeps[sweep.swapHash] = *sweep
 
 		// If this is the primary sweep, we also need to update the
-		// batch's confirmation target.
+		// batch's confirmation target and fee rate.
 		if b.primarySweepID == sweep.swapHash {
 			b.cfg.batchConfTarget = sweep.confTarget
+			b.rbfCache.FeeRate = sweep.minFeeRate
 		}
 
 		return true, nil
@@ -443,6 +448,7 @@ func (b *batch) addSweep(ctx context.Context, sweep *sweep) (bool, error) {
 	if b.primarySweepID == lntypes.ZeroHash {
 		b.primarySweepID = sweep.swapHash
 		b.cfg.batchConfTarget = sweep.confTarget
+		b.rbfCache.FeeRate = sweep.minFeeRate
 
 		// We also need to start the spend monitor for this new primary
 		// sweep.
@@ -456,6 +462,12 @@ func (b *batch) addSweep(ctx context.Context, sweep *sweep) (bool, error) {
 	b.log.Infof("adding sweep %x", sweep.swapHash[:6])
 	b.sweeps[sweep.swapHash] = *sweep
 
+	// Update FeeRate. Max(sweep.minFeeRate) for all the sweeps of
+	// the batch is the basis for fee bumps.
+	if b.rbfCache.FeeRate < sweep.minFeeRate {
+		b.rbfCache.FeeRate = sweep.minFeeRate
+	}
+
 	return true, b.persistSweep(ctx, *sweep, false)
 }
 

sweepbatcher/sweep_batcher.go

@@ -120,6 +120,10 @@ type SweepInfo struct {
 
 	// DestAddr is the destination address of the sweep.
 	DestAddr btcutil.Address
+
+	// MinFeeRate is minimum fee rate that must be used by a batch of
+	// the sweep. If it is specified, confTarget is ignored.
+	MinFeeRate chainfee.SatPerKWeight
 }
 
 // SweepFetcher is used to get details of a sweep.
@@ -523,6 +527,9 @@ func (b *Batcher) spinUpBatchFromDB(ctx context.Context, batch *batch) error {
 
 	sweeps := make(map[lntypes.Hash]sweep)
 
+	// Collect feeRate from sweeps and stored batch.
+	feeRate := batch.rbfCache.FeeRate
+
 	for _, dbSweep := range dbSweeps {
 		sweep, err := b.convertSweep(ctx, dbSweep)
 		if err != nil {
@@ -530,11 +537,16 @@ func (b *Batcher) spinUpBatchFromDB(ctx context.Context, batch *batch) error {
 		}
 
 		sweeps[sweep.swapHash] = *sweep
+
+		// Set minFeeRate to max(sweep.minFeeRate) for all sweeps.
+		if feeRate < sweep.minFeeRate {
+			feeRate = sweep.minFeeRate
+		}
 	}
 
 	rbfCache := rbfCache{
 		LastHeight: batch.rbfCache.LastHeight,
-		FeeRate:    batch.rbfCache.FeeRate,
+		FeeRate:    feeRate,
 	}
 
 	logger := batchPrefixLogger(fmt.Sprintf("%d", batch.id))
@@ -758,6 +770,7 @@ func (b *Batcher) convertSweep(ctx context.Context, dbSweep *dbSweep) (
 		protocolVersion:        s.ProtocolVersion,
 		isExternalAddr:         s.IsExternalAddr,
 		destAddr:               s.DestAddr,
+		minFeeRate:             s.MinFeeRate,
 	}, nil
 }
 
@@ -855,5 +868,6 @@ func (b *Batcher) fetchSweep(ctx context.Context,
 		protocolVersion:        s.ProtocolVersion,
 		isExternalAddr:         s.IsExternalAddr,
 		destAddr:               s.DestAddr,
+		minFeeRate:             s.MinFeeRate,
 	}, nil
 }

sweepbatcher/sweep_batcher_test.go

@@ -18,6 +18,7 @@ import (
 	"github.com/lightningnetwork/lnd/chainntnfs"
 	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lntypes"
+	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 	"github.com/stretchr/testify/require"
 )
 
@@ -1746,20 +1747,64 @@ func testSweepFetcher(t *testing.T, store testStore,
 	)
 	require.NoError(t, err)
 
+	swapHash := lntypes.Hash{1, 1, 1}
+
+	// Provide min fee rate for the sweep.
+	feeRate := chainfee.SatPerKWeight(30000)
+	amt := btcutil.Amount(1_000_000)
+	weight := lntypes.WeightUnit(445) // Weight for 1-to-1 tx.
+	bumpedFee := feeRate + 100
+	expectedFee := bumpedFee.FeeForWeight(weight)
+
+	swap := &loopdb.LoopOutContract{
+		SwapContract: loopdb.SwapContract{
+			CltvExpiry:      222,
+			AmountRequested: amt,
+			ProtocolVersion: loopdb.ProtocolVersionMuSig2,
+			HtlcKeys: loopdb.HtlcKeys{
+				SenderScriptKey:        senderKey,
+				ReceiverScriptKey:      receiverKey,
+				SenderInternalPubKey:   senderKey,
+				ReceiverInternalPubKey: receiverKey,
+			},
+		},
+		DestAddr:        destAddr,
+		SwapInvoice:     swapInvoice,
+		SweepConfTarget: 321,
+	}
+
+	htlc, err := utils.GetHtlc(
+		swapHash, &swap.SwapContract, lnd.ChainParams,
+	)
+	require.NoError(t, err)
+
+	sweepInfo := &SweepInfo{
+		ConfTarget:             123,
+		Timeout:                111,
+		SwapInvoicePaymentAddr: *swapPaymentAddr,
+		MinFeeRate:             feeRate,
+		ProtocolVersion:        loopdb.ProtocolVersionMuSig2,
+		HTLCKeys: loopdb.HtlcKeys{
+			SenderScriptKey:        senderKey,
+			ReceiverScriptKey:      receiverKey,
+			SenderInternalPubKey:   senderKey,
+			ReceiverInternalPubKey: receiverKey,
+		},
+		HTLC:                 *htlc,
+		HTLCSuccessEstimator: htlc.AddSuccessToEstimator,
+		DestAddr:             destAddr,
+	}
+
 	sweepFetcher := &sweepFetcherMock{
 		store: map[lntypes.Hash]*SweepInfo{
-			{1, 1, 1}: {
-				ConfTarget:             123,
-				Timeout:                111,
-				SwapInvoicePaymentAddr: *swapPaymentAddr,
-			},
+			swapHash: sweepInfo,
 		},
 	}
 
 	// Create a sweep request.
 	sweepReq := SweepRequest{
-		SwapHash: lntypes.Hash{1, 1, 1},
-		Value:    111,
+		SwapHash: swapHash,
+		Value:    amt,
 		Outpoint: wire.OutPoint{
 			Hash:  chainhash.Hash{1, 1},
 			Index: 1,
@@ -1770,23 +1815,13 @@ func testSweepFetcher(t *testing.T, store testStore,
 	// Create a swap in the DB. It is needed to satisfy SQL constraints in
 	// case of SQL test. The data is not actually used, since we pass sweep
 	// fetcher, so put different conf target to make sure it is not used.
-	swap := &loopdb.LoopOutContract{
-		SwapContract: loopdb.SwapContract{
-			CltvExpiry:      222,
-			AmountRequested: 222,
-		},
-
-		DestAddr:        destAddr,
-		SwapInvoice:     swapInvoice,
-		SweepConfTarget: 321,
-	}
-	err = store.CreateLoopOut(ctx, sweepReq.SwapHash, swap)
+	err = store.CreateLoopOut(ctx, swapHash, swap)
 	require.NoError(t, err)
 	store.AssertLoopOutStored()
 
 	batcher := NewBatcher(lnd.WalletKit, lnd.ChainNotifier, lnd.Signer,
-		testMuSig2SignSweep, nil, lnd.ChainParams, batcherStore,
-		sweepFetcher)
+		testMuSig2SignSweep, testVerifySchnorrSig, lnd.ChainParams,
+		batcherStore, sweepFetcher)
 
 	var wg sync.WaitGroup
 	wg.Add(1)
@@ -1811,7 +1846,7 @@ func testSweepFetcher(t *testing.T, store testStore,
 	// batch.
 	require.Eventually(t, func() bool {
 		// Make sure that the sweep was stored
-		if !batcherStore.AssertSweepStored(sweepReq.SwapHash) {
+		if !batcherStore.AssertSweepStored(swapHash) {
 			return false
 		}
 
@@ -1832,6 +1867,12 @@ func testSweepFetcher(t *testing.T, store testStore,
 		return batch.cfg.batchConfTarget == 123
 	}, test.Timeout, eventuallyCheckFrequency)
 
+	// Get the published transaction and check the fee rate.
+	tx := <-lnd.TxPublishChannel
+	out := btcutil.Amount(tx.TxOut[0].Value)
+	gotFee := amt - out
+	require.Equal(t, expectedFee, gotFee, "fees don't match")
+
 	// Make sure we have stored the batch.
 	batches, err := batcherStore.FetchUnconfirmedSweepBatches(ctx)
 	require.NoError(t, err)