loopd: recover confirmed htlcs with direct sweep

Author: starius

loopd/daemon.go

@@ -571,6 +571,27 @@ func (d *Daemon) initialize(withMacaroonService bool) error {
 		}
 	})
 
+	// Start the HTLC recovery worker that handles HTLC-confirmed
+	// notifications with a direct sweep attempt.
+	htlcConfirmedRecovery := &htlcConfirmedRecoveryManager{
+		notificationSource: notificationManager,
+		swapStore:          swapDb,
+		chainParams:        d.lnd.ChainParams,
+		notifier:           d.lnd.ChainNotifier,
+		wallet:             d.lnd.WalletKit,
+		signer:             d.lnd.Signer,
+	}
+
+	d.wg.Go(func() {
+		debugf("Starting htlc confirmed recovery worker")
+		defer debugf("Htlc confirmed recovery worker stopped")
+
+		err := htlcConfirmedRecovery.run(d.mainCtx)
+		if shouldReportManagerErr(err) {
+			debugf("htlc confirmed recovery worker failed: %v", err)
+		}
+	})
+
 	var (
 		staticAddressManager *address.Manager
 		depositManager       *deposit.Manager

loopd/htlc_confirmed_recovery.go

@@ -0,0 +1,118 @@
+package loopd
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/btcsuite/btcd/chaincfg"
+	"github.com/btcsuite/btcd/wire"
+	"github.com/lightninglabs/loop/looprpc"
+	"github.com/lightninglabs/loop/swapserverrpc"
+)
+
+const (
+	// htlcConfirmedRecoverySatPerVByte is the fixed fee rate used by the
+	// HTLC recovery worker.
+	htlcConfirmedRecoverySatPerVByte = 10
+)
+
+// htlcConfirmedSubscriber exposes the HTLC-confirmed notification stream used
+// by the recovery worker.
+type htlcConfirmedSubscriber interface {
+	SubscribeHtlcConfirmed(ctx context.Context,
+	) <-chan *swapserverrpc.ServerHtlcConfirmedNotification
+}
+
+// htlcConfirmedRecoveryManager consumes HTLC-confirmed notifications and
+// reuses sweepHtlc to recover the notified loop-out HTLC.
+type htlcConfirmedRecoveryManager struct {
+	notificationSource htlcConfirmedSubscriber
+	swapStore          loopOutStore
+	chainParams        *chaincfg.Params
+	notifier           htlcChainNotifier
+	wallet             htlcWallet
+	signer             htlcSigner
+}
+
+// run starts the HTLC recovery worker.
+func (m *htlcConfirmedRecoveryManager) run(ctx context.Context) error {
+	if m.notificationSource == nil {
+		return nil
+	}
+
+	ntfnChan := m.notificationSource.SubscribeHtlcConfirmed(ctx)
+
+	for {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+
+		case ntfn, ok := <-ntfnChan:
+			if !ok {
+				return nil
+			}
+
+			m.handleNotification(ctx, ntfn)
+		}
+	}
+}
+
+// handleNotification validates a notification and triggers a direct sweep
+// attempt for the notified HTLC.
+func (m *htlcConfirmedRecoveryManager) handleNotification(ctx context.Context,
+	ntfn *swapserverrpc.ServerHtlcConfirmedNotification) {
+
+	if ntfn == nil {
+		debugf("Ignoring nil HTLC recovery notification")
+
+		return
+	}
+
+	// Require all dependencies up front so the optional recovery path
+	// exits quietly when the daemon is not wired for sweeping.
+	if m.swapStore == nil || m.chainParams == nil || m.notifier == nil ||
+		m.wallet == nil || m.signer == nil {
+
+		debugf("HTLC recovery dependencies unavailable")
+
+		return
+	}
+
+	outpoint, htlcAddress, err := m.parseNotification(ntfn)
+	if err != nil {
+		debugf("Ignoring HTLC recovery notification: %v", err)
+
+		return
+	}
+
+	// Reuse sweepHtlc so the worker follows the same success-path spend
+	// construction and destination selection as the manual sweep path.
+	_, err = sweepHtlc(
+		ctx, &looprpc.SweepHtlcRequest{
+			Outpoint:    outpoint.String(),
+			HtlcAddress: htlcAddress,
+			SatPerVbyte: htlcConfirmedRecoverySatPerVByte,
+			Publish:     true,
+		}, m.chainParams, m.swapStore, m.notifier, m.wallet, m.signer,
+	)
+	if err != nil {
+		debugf("Unable to recover HTLC outpoint %s: %v", outpoint, err)
+	}
+}
+
+// parseNotification parses the swap hash and outpoint from a notification.
+func (m *htlcConfirmedRecoveryManager) parseNotification(
+	ntfn *swapserverrpc.ServerHtlcConfirmedNotification) (*wire.OutPoint,
+	string, error) {
+
+	outpoint, err := wire.NewOutPointFromString(ntfn.HtlcOutpoint)
+	if err != nil {
+		return nil, "", fmt.Errorf("bad outpoint: %w", err)
+	}
+
+	if ntfn.HtlcAddress == "" {
+		return nil, "", fmt.Errorf("missing HTLC address")
+	}
+
+	return outpoint, ntfn.HtlcAddress, nil
+}