Merge pull request #184 from bhandras/native-segwit

support for native segwit loop-in

client.go

@@ -194,17 +194,17 @@ func (s *Client) FetchSwaps() ([]*SwapInfo, error) {
 		}
 
 		swaps = append(swaps, &SwapInfo{
-			SwapType:      swap.TypeOut,
-			SwapContract:  swp.Contract.SwapContract,
-			SwapStateData: swp.State(),
-			SwapHash:      swp.Hash,
-			LastUpdate:    swp.LastUpdateTime(),
-			HtlcAddress:   htlc.Address,
+			SwapType:         swap.TypeOut,
+			SwapContract:     swp.Contract.SwapContract,
+			SwapStateData:    swp.State(),
+			SwapHash:         swp.Hash,
+			LastUpdate:       swp.LastUpdateTime(),
+			HtlcAddressP2WSH: htlc.Address,
 		})
 	}
 
 	for _, swp := range loopInSwaps {
-		htlc, err := swap.NewHtlc(
+		htlcNP2WSH, err := swap.NewHtlc(
 			swp.Contract.CltvExpiry, swp.Contract.SenderKey,
 			swp.Contract.ReceiverKey, swp.Hash, swap.HtlcNP2WSH,
 			s.lndServices.ChainParams,
@@ -213,13 +213,23 @@ func (s *Client) FetchSwaps() ([]*SwapInfo, error) {
 			return nil, err
 		}
 
+		htlcP2WSH, err := swap.NewHtlc(
+			swp.Contract.CltvExpiry, swp.Contract.SenderKey,
+			swp.Contract.ReceiverKey, swp.Hash, swap.HtlcP2WSH,
+			s.lndServices.ChainParams,
+		)
+		if err != nil {
+			return nil, err
+		}
+
 		swaps = append(swaps, &SwapInfo{
-			SwapType:      swap.TypeIn,
-			SwapContract:  swp.Contract.SwapContract,
-			SwapStateData: swp.State(),
-			SwapHash:      swp.Hash,
-			LastUpdate:    swp.LastUpdateTime(),
-			HtlcAddress:   htlc.Address,
+			SwapType:          swap.TypeIn,
+			SwapContract:      swp.Contract.SwapContract,
+			SwapStateData:     swp.State(),
+			SwapHash:          swp.Hash,
+			LastUpdate:        swp.LastUpdateTime(),
+			HtlcAddressP2WSH:  htlcP2WSH.Address,
+			HtlcAddressNP2WSH: htlcNP2WSH.Address,
 		})
 	}
 
@@ -464,7 +474,7 @@ func (s *Client) waitForInitialized(ctx context.Context) error {
 
 // LoopIn initiates a loop in swap.
 func (s *Client) LoopIn(globalCtx context.Context,
-	request *LoopInRequest) (*lntypes.Hash, btcutil.Address, error) {
+	request *LoopInRequest) (*LoopInSwapInfo, error) {
 
 	log.Infof("Loop in %v (last hop: %v)",
 		request.Amount,
@@ -472,7 +482,7 @@ func (s *Client) LoopIn(globalCtx context.Context,
 	)
 
 	if err := s.waitForInitialized(globalCtx); err != nil {
-		return nil, nil, err
+		return nil, err
 	}
 
 	// Create a new swap object for this swap.
@@ -486,7 +496,7 @@ func (s *Client) LoopIn(globalCtx context.Context,
 		globalCtx, &swapCfg, initiationHeight, request,
 	)
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
 
 	// Post swap to the main loop.
@@ -494,7 +504,12 @@ func (s *Client) LoopIn(globalCtx context.Context,
 
 	// Return hash so that the caller can identify this swap in the updates
 	// stream.
-	return &swap.hash, swap.htlc.Address, nil
+	swapInfo := &LoopInSwapInfo{
+		SwapHash:          swap.hash,
+		HtlcAddressP2WSH:  swap.htlcP2WSH.Address,
+		HtlcAddressNP2WSH: swap.htlcNP2WSH.Address,
+	}
+	return swapInfo, nil
 }
 
 // LoopInQuote takes an amount and returns a break down of estimated

cmd/loop/loopin.go

@@ -153,7 +153,10 @@ func loopIn(ctx *cli.Context) error {
 
 	fmt.Printf("Swap initiated\n")
 	fmt.Printf("ID:           %v\n", resp.Id)
-	fmt.Printf("HTLC address: %v\n", resp.HtlcAddress)
+	if external {
+		fmt.Printf("HTLC address (NP2WSH): %v\n", resp.HtlcAddressNp2Wsh)
+	}
+	fmt.Printf("HTLC address (P2WSH): %v\n", resp.HtlcAddressP2Wsh)
 	fmt.Println()
 	fmt.Printf("Run `loop monitor` to monitor progress.\n")
 

cmd/loop/main.go

@@ -225,11 +225,24 @@ func parseAmt(text string) (btcutil.Amount, error) {
 }
 
 func logSwap(swap *looprpc.SwapStatus) {
-	fmt.Printf("%v %v %v %v - %v",
-		time.Unix(0, swap.LastUpdateTime).Format(time.RFC3339),
-		swap.Type, swap.State, btcutil.Amount(swap.Amt),
-		swap.HtlcAddress,
-	)
+	if swap.Type == looprpc.SwapType_LOOP_OUT {
+		fmt.Printf("%v %v %v %v - %v",
+			time.Unix(0, swap.LastUpdateTime).Format(time.RFC3339),
+			swap.Type, swap.State, btcutil.Amount(swap.Amt),
+			swap.HtlcAddressP2Wsh,
+		)
+	} else {
+		fmt.Printf("%v %v %v %v -",
+			time.Unix(0, swap.LastUpdateTime).Format(time.RFC3339),
+			swap.Type, swap.State, btcutil.Amount(swap.Amt))
+		if swap.HtlcAddressP2Wsh != "" {
+			fmt.Printf(" P2WSH: %v", swap.HtlcAddressP2Wsh)
+		}
+
+		if swap.HtlcAddressNp2Wsh != "" {
+			fmt.Printf(" NP2WSH: %v", swap.HtlcAddressNp2Wsh)
+		}
+	}
 
 	if swap.State != looprpc.SwapState_INITIATED &&
 		swap.State != looprpc.SwapState_HTLC_PUBLISHED &&

interface.go

@@ -235,6 +235,21 @@ type LoopInQuote struct {
 	CltvDelta int32
 }
 
+// LoopInSwapInfo contains essential information of a loop-in swap after the
+// swap is initiated.
+type LoopInSwapInfo struct { // nolint
+	// SwapHash contains the sha256 hash of the swap preimage.
+	SwapHash lntypes.Hash
+
+	// HtlcAddressP2WSH contains the native segwit swap htlc address,
+	// where the loop-in funds may be paid.
+	HtlcAddressP2WSH btcutil.Address
+
+	// HtlcAddressNP2WSH contains the nested segwit swap htlc address,
+	// where the loop-in funds may be paid.
+	HtlcAddressNP2WSH btcutil.Address
+}
+
 // SwapInfoKit contains common swap info fields.
 type SwapInfoKit struct {
 	// Hash is the sha256 hash of the preimage that unlocks the htlcs. It
@@ -249,15 +264,27 @@ type SwapInfoKit struct {
 type SwapInfo struct {
 	loopdb.SwapStateData
 
+	loopdb.SwapContract
+
+	// LastUpdateTime is the time of the last state change.
 	LastUpdate time.Time
 
+	// SwapHash stores the swap preimage hash.
 	SwapHash lntypes.Hash
 
+	// SwapType describes whether this is a loop in or loop out swap.
 	SwapType swap.Type
 
-	loopdb.SwapContract
+	// HtlcAddressP2WSH stores the address of the P2WSH (native segwit)
+	// swap htlc. This is used for both loop-in and loop-out.
+	HtlcAddressP2WSH btcutil.Address
 
-	HtlcAddress btcutil.Address
+	// HtlcAddressNP2WSH stores the address of the NP2WSH (nested segwit)
+	// swap htlc. This is only used for external loop-in.
+	HtlcAddressNP2WSH btcutil.Address
+
+	// ExternalHtlc is set to true for external loop-in swaps.
+	ExternalHtlc bool
 }
 
 // LastUpdate returns the last update time of the swap

loopd/swapclient_server.go

@@ -126,27 +126,43 @@ func (s *swapClientServer) marshallSwap(loopSwap *loop.SwapInfo) (
 	}
 
 	var swapType looprpc.SwapType
+	var htlcAddress, htlcAddressP2WSH, htlcAddressNP2WSH string
+
 	switch loopSwap.SwapType {
 	case swap.TypeIn:
 		swapType = looprpc.SwapType_LOOP_IN
+		htlcAddressP2WSH = loopSwap.HtlcAddressP2WSH.EncodeAddress()
+
+		if loopSwap.ExternalHtlc {
+			htlcAddressNP2WSH = loopSwap.HtlcAddressNP2WSH.EncodeAddress()
+			htlcAddress = htlcAddressNP2WSH
+		} else {
+			htlcAddress = htlcAddressP2WSH
+		}
+
 	case swap.TypeOut:
 		swapType = looprpc.SwapType_LOOP_OUT
+		htlcAddressP2WSH = loopSwap.HtlcAddressP2WSH.EncodeAddress()
+		htlcAddress = htlcAddressP2WSH
+
 	default:
 		return nil, errors.New("unknown swap type")
 	}
 
 	return &looprpc.SwapStatus{
-		Amt:            int64(loopSwap.AmountRequested),
-		Id:             loopSwap.SwapHash.String(),
-		IdBytes:        loopSwap.SwapHash[:],
-		State:          state,
-		InitiationTime: loopSwap.InitiationTime.UnixNano(),
-		LastUpdateTime: loopSwap.LastUpdate.UnixNano(),
-		HtlcAddress:    loopSwap.HtlcAddress.EncodeAddress(),
-		Type:           swapType,
-		CostServer:     int64(loopSwap.Cost.Server),
-		CostOnchain:    int64(loopSwap.Cost.Onchain),
-		CostOffchain:   int64(loopSwap.Cost.Offchain),
+		Amt:               int64(loopSwap.AmountRequested),
+		Id:                loopSwap.SwapHash.String(),
+		IdBytes:           loopSwap.SwapHash[:],
+		State:             state,
+		InitiationTime:    loopSwap.InitiationTime.UnixNano(),
+		LastUpdateTime:    loopSwap.LastUpdate.UnixNano(),
+		HtlcAddress:       htlcAddress,
+		HtlcAddressP2Wsh:  htlcAddressP2WSH,
+		HtlcAddressNp2Wsh: htlcAddressNP2WSH,
+		Type:              swapType,
+		CostServer:        int64(loopSwap.Cost.Server),
+		CostOnchain:       int64(loopSwap.Cost.Onchain),
+		CostOffchain:      int64(loopSwap.Cost.Offchain),
 	}, nil
 }
 
@@ -255,6 +271,9 @@ func (s *swapClientServer) ListSwaps(_ context.Context,
 		err      error
 	)
 
+	s.swapsLock.Lock()
+	defer s.swapsLock.Unlock()
+
 	// We can just use the server's in-memory cache as that contains the
 	// most up-to-date state including temporary failures which aren't
 	// persisted to disk. The swaps field is a map, that's why we need an
@@ -409,17 +428,25 @@ func (s *swapClientServer) LoopIn(ctx context.Context,
 		}
 		req.LastHop = &lastHop
 	}
-	hash, htlc, err := s.impl.LoopIn(ctx, req)
+	swapInfo, err := s.impl.LoopIn(ctx, req)
 	if err != nil {
 		log.Errorf("Loop in: %v", err)
 		return nil, err
 	}
 
-	return &looprpc.SwapResponse{
-		Id:          hash.String(),
-		IdBytes:     hash[:],
-		HtlcAddress: htlc.String(),
-	}, nil
+	np2wshAddress := swapInfo.HtlcAddressNP2WSH.String()
+	response := &looprpc.SwapResponse{
+		Id:                swapInfo.SwapHash.String(),
+		IdBytes:           swapInfo.SwapHash[:],
+		HtlcAddress:       np2wshAddress,
+		HtlcAddressNp2Wsh: np2wshAddress,
+	}
+
+	if req.ExternalHtlc {
+		response.HtlcAddressP2Wsh = swapInfo.HtlcAddressP2WSH.String()
+	}
+
+	return response, nil
 }
 
 // GetLsatTokens returns all tokens that are contained in the LSAT token store.

loopin.go

@@ -48,8 +48,16 @@ var (
 type loopInSwap struct {
 	swapKit
 
+	executeConfig
+
 	loopdb.LoopInContract
 
+	htlc *swap.Htlc
+
+	htlcP2WSH *swap.Htlc
+
+	htlcNP2WSH *swap.Htlc
+
 	timeoutAddr btcutil.Address
 }
 
@@ -148,13 +156,9 @@ func newLoopInSwap(globalCtx context.Context, cfg *swapConfig,
 		},
 	}
 
-	swapKit, err := newSwapKit(
+	swapKit := newSwapKit(
 		swapHash, swap.TypeIn, cfg, &contract.SwapContract,
-		swap.HtlcNP2WSH,
 	)
-	if err != nil {
-		return nil, err
-	}
 
 	swapKit.lastUpdateTime = initiationTime
 
@@ -163,6 +167,10 @@ func newLoopInSwap(globalCtx context.Context, cfg *swapConfig,
 		swapKit:        *swapKit,
 	}
 
+	if err := swap.initHtlcs(); err != nil {
+		return nil, err
+	}
+
 	// Persist the data before exiting this function, so that the caller can
 	// trust that this swap will be resumed on restart.
 	err = cfg.store.CreateLoopIn(swapHash, &swap.LoopInContract)
@@ -182,19 +190,19 @@ func resumeLoopInSwap(reqContext context.Context, cfg *swapConfig,
 
 	log.Infof("Resuming loop in swap %v", hash)
 
-	swapKit, err := newSwapKit(
+	swapKit := newSwapKit(
 		hash, swap.TypeIn, cfg, &pend.Contract.SwapContract,
-		swap.HtlcNP2WSH,
 	)
-	if err != nil {
-		return nil, err
-	}
 
 	swap := &loopInSwap{
 		LoopInContract: *pend.Contract,
 		swapKit:        *swapKit,
 	}
 
+	if err := swap.initHtlcs(); err != nil {
+		return nil, err
+	}
+
 	lastUpdate := pend.LastUpdate()
 	if lastUpdate == nil {
 		swap.lastUpdateTime = pend.Contract.InitiationTime
@@ -222,6 +230,47 @@ func validateLoopInContract(lnd *lndclient.LndServices,
 	return nil
 }
 
+// initHtlcs creates and updates the native and nested segwit htlcs
+// of the loopInSwap.
+func (s *loopInSwap) initHtlcs() error {
+	htlcP2WSH, err := s.swapKit.getHtlc(swap.HtlcP2WSH)
+	if err != nil {
+		return err
+	}
+
+	htlcNP2WSH, err := s.swapKit.getHtlc(swap.HtlcNP2WSH)
+	if err != nil {
+		return err
+	}
+
+	// Log htlc addresses for debugging.
+	s.swapKit.log.Infof("Htlc address (P2WSH): %v", htlcP2WSH.Address)
+	s.swapKit.log.Infof("Htlc address (NP2WSH): %v", htlcNP2WSH.Address)
+
+	s.htlcP2WSH = htlcP2WSH
+	s.htlcNP2WSH = htlcNP2WSH
+
+	return nil
+}
+
+// sendUpdate reports an update to the swap state.
+func (s *loopInSwap) sendUpdate(ctx context.Context) error {
+	info := s.swapInfo()
+	s.log.Infof("Loop in swap state: %v", info.State)
+
+	info.HtlcAddressP2WSH = s.htlcP2WSH.Address
+	info.HtlcAddressNP2WSH = s.htlcNP2WSH.Address
+	info.ExternalHtlc = s.ExternalHtlc
+
+	select {
+	case s.statusChan <- *info:
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+
+	return nil
+}
+
 // execute starts/resumes the swap. It is a thin wrapper around executeSwap to
 // conveniently handle the error case.
 func (s *loopInSwap) execute(mainCtx context.Context,
@@ -340,21 +389,44 @@ func (s *loopInSwap) waitForHtlcConf(globalCtx context.Context) (
 
 	ctx, cancel := context.WithCancel(globalCtx)
 	defer cancel()
-	confChan, confErr, err := s.lnd.ChainNotifier.RegisterConfirmationsNtfn(
-		ctx, nil, s.htlc.PkScript, 1, s.InitiationHeight,
+
+	notifier := s.lnd.ChainNotifier
+
+	confChanP2WSH, confErrP2WSH, err := notifier.RegisterConfirmationsNtfn(
+		ctx, nil, s.htlcP2WSH.PkScript, 1, s.InitiationHeight,
 	)
 	if err != nil {
 		return nil, err
 	}
+
+	confChanNP2WSH, confErrNP2WSH, err := notifier.RegisterConfirmationsNtfn(
+		ctx, nil, s.htlcNP2WSH.PkScript, 1, s.InitiationHeight,
+	)
+	if err != nil {
+		return nil, err
+	}
+
 	for {
 		select {
 
-		// Htlc confirmed.
-		case conf := <-confChan:
+		// P2WSH htlc confirmed.
+		case conf := <-confChanP2WSH:
+			s.htlc = s.htlcP2WSH
+			s.log.Infof("P2WSH htlc confirmed")
 			return conf, nil
 
+		// NP2WSH htlc confirmed.
+		case conf := <-confChanNP2WSH:
+			s.htlc = s.htlcNP2WSH
+			s.log.Infof("NP2WSH htlc confirmed")
+			return conf, nil
+
+		// Conf ntfn error.
+		case err := <-confErrP2WSH:
+			return nil, err
+
 		// Conf ntfn error.
-		case err := <-confErr:
+		case err := <-confErrNP2WSH:
 			return nil, err
 
 		// Keep up with block height.
@@ -399,9 +471,11 @@ func (s *loopInSwap) publishOnChainHtlc(ctx context.Context) (bool, error) {
 	}
 
 	s.log.Infof("Publishing on chain HTLC with fee rate %v", feeRate)
+
+	// Internal loop-in is always P2WSH.
 	tx, err := s.lnd.WalletKit.SendOutputs(ctx,
 		[]*wire.TxOut{{
-			PkScript: s.htlc.PkScript,
+			PkScript: s.htlcP2WSH.PkScript,
 			Value:    int64(s.LoopInContract.AmountRequested),
 		}},
 		feeRate,

loopin_test.go

@@ -67,6 +67,7 @@ func TestLoopInSuccess(t *testing.T) {
 
 	// Expect register for htlc conf.
 	<-ctx.lnd.RegisterConfChannel
+	<-ctx.lnd.RegisterConfChannel
 
 	// Confirm htlc.
 	ctx.lnd.ConfChannel <- &chainntnfs.TxConfirmation{
@@ -118,20 +119,32 @@ func TestLoopInSuccess(t *testing.T) {
 func TestLoopInTimeout(t *testing.T) {
 	testAmt := int64(testLoopInRequest.Amount)
 	t.Run("internal htlc", func(t *testing.T) {
-		testLoopInTimeout(t, 0)
-	})
-	t.Run("external htlc", func(t *testing.T) {
-		testLoopInTimeout(t, testAmt)
-	})
-	t.Run("external amount too high", func(t *testing.T) {
-		testLoopInTimeout(t, testAmt+1)
-	})
-	t.Run("external amount too low", func(t *testing.T) {
-		testLoopInTimeout(t, testAmt-1)
+		testLoopInTimeout(t, swap.HtlcP2WSH, 0)
 	})
+
+	outputTypes := []swap.HtlcOutputType{swap.HtlcP2WSH, swap.HtlcNP2WSH}
+
+	for _, outputType := range outputTypes {
+		outputType := outputType
+		t.Run(outputType.String(), func(t *testing.T) {
+			t.Run("external htlc", func(t *testing.T) {
+				testLoopInTimeout(t, outputType, testAmt)
+			})
+
+			t.Run("external amount too high", func(t *testing.T) {
+				testLoopInTimeout(t, outputType, testAmt+1)
+			})
+
+			t.Run("external amount too low", func(t *testing.T) {
+				testLoopInTimeout(t, outputType, testAmt-1)
+			})
+		})
+	}
 }
 
-func testLoopInTimeout(t *testing.T, externalValue int64) {
+func testLoopInTimeout(t *testing.T,
+	outputType swap.HtlcOutputType, externalValue int64) {
+
 	defer test.Guard(t)()
 
 	ctx := newLoopInTestContext(t)
@@ -149,7 +162,7 @@ func testLoopInTimeout(t *testing.T, externalValue int64) {
 		req.ExternalHtlc = true
 	}
 
-	swap, err := newLoopInSwap(
+	s, err := newLoopInSwap(
 		context.Background(), cfg,
 		height, &req,
 	)
@@ -161,7 +174,7 @@ func testLoopInTimeout(t *testing.T, externalValue int64) {
 
 	errChan := make(chan error)
 	go func() {
-		err := swap.execute(context.Background(), ctx.cfg, height)
+		err := s.execute(context.Background(), ctx.cfg, height)
 		if err != nil {
 			log.Error(err)
 		}
@@ -179,10 +192,16 @@ func testLoopInTimeout(t *testing.T, externalValue int64) {
 		htlcTx = <-ctx.lnd.SendOutputsChannel
 	} else {
 		// Create an external htlc publish tx.
+		var pkScript []byte
+		if outputType == swap.HtlcNP2WSH {
+			pkScript = s.htlcNP2WSH.PkScript
+		} else {
+			pkScript = s.htlcP2WSH.PkScript
+		}
 		htlcTx = wire.MsgTx{
 			TxOut: []*wire.TxOut{
 				{
-					PkScript: swap.htlc.PkScript,
+					PkScript: pkScript,
 					Value:    externalValue,
 				},
 			},
@@ -191,6 +210,7 @@ func testLoopInTimeout(t *testing.T, externalValue int64) {
 
 	// Expect register for htlc conf.
 	<-ctx.lnd.RegisterConfChannel
+	<-ctx.lnd.RegisterConfChannel
 
 	// Confirm htlc.
 	ctx.lnd.ConfChannel <- &chainntnfs.TxConfirmation{
@@ -207,7 +227,7 @@ func testLoopInTimeout(t *testing.T, externalValue int64) {
 	}
 
 	// Let htlc expire.
-	ctx.blockEpochChan <- swap.LoopInContract.CltvExpiry
+	ctx.blockEpochChan <- s.LoopInContract.CltvExpiry
 
 	// Expect a signing request for the htlc tx output value.
 	signReq := <-ctx.lnd.SignOutputRawChannel
@@ -378,6 +398,7 @@ func testLoopInResume(t *testing.T, state loopdb.SwapState, expired bool) {
 
 	// Expect register for htlc conf.
 	<-ctx.lnd.RegisterConfChannel
+	<-ctx.lnd.RegisterConfChannel
 
 	// Confirm htlc.
 	ctx.lnd.ConfChannel <- &chainntnfs.TxConfirmation{

loopout.go

@@ -52,6 +52,10 @@ type loopOutSwap struct {
 
 	loopdb.LoopOutContract
 
+	executeConfig
+
+	htlc *swap.Htlc
+
 	swapPaymentChan chan lndclient.PaymentResult
 	prePaymentChan  chan lndclient.PaymentResult
 }
@@ -134,19 +138,25 @@ func newLoopOutSwap(globalCtx context.Context, cfg *swapConfig,
 		},
 	}
 
-	swapKit, err := newSwapKit(
+	swapKit := newSwapKit(
 		swapHash, swap.TypeOut, cfg, &contract.SwapContract,
-		swap.HtlcP2WSH,
 	)
+
+	swapKit.lastUpdateTime = initiationTime
+
+	// Create the htlc.
+	htlc, err := swapKit.getHtlc(swap.HtlcP2WSH)
 	if err != nil {
 		return nil, err
 	}
 
-	swapKit.lastUpdateTime = initiationTime
+	// Log htlc address for debugging.
+	swapKit.log.Infof("Htlc address: %v", htlc.Address)
 
 	swap := &loopOutSwap{
 		LoopOutContract: contract,
 		swapKit:         *swapKit,
+		htlc:            htlc,
 	}
 
 	// Persist the data before exiting this function, so that the caller
@@ -168,17 +178,24 @@ func resumeLoopOutSwap(reqContext context.Context, cfg *swapConfig,
 
 	log.Infof("Resuming loop out swap %v", hash)
 
-	swapKit, err := newSwapKit(
+	swapKit := newSwapKit(
 		hash, swap.TypeOut, cfg, &pend.Contract.SwapContract,
-		swap.HtlcP2WSH,
 	)
+
+	// Create the htlc.
+	htlc, err := swapKit.getHtlc(swap.HtlcP2WSH)
 	if err != nil {
 		return nil, err
 	}
 
+	// Log htlc address for debugging.
+	swapKit.log.Infof("Htlc address: %v", htlc.Address)
+
+	// Create the swap.
 	swap := &loopOutSwap{
 		LoopOutContract: *pend.Contract,
 		swapKit:         *swapKit,
+		htlc:            htlc,
 	}
 
 	lastUpdate := pend.LastUpdate()
@@ -192,6 +209,22 @@ func resumeLoopOutSwap(reqContext context.Context, cfg *swapConfig,
 	return swap, nil
 }
 
+// sendUpdate reports an update to the swap state.
+func (s *loopOutSwap) sendUpdate(ctx context.Context) error {
+	info := s.swapInfo()
+	s.log.Infof("Loop out swap state: %v", info.State)
+
+	info.HtlcAddressP2WSH = s.htlc.Address
+
+	select {
+	case s.statusChan <- *info:
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+
+	return nil
+}
+
 // execute starts/resumes the swap. It is a thin wrapper around
 // executeAndFinalize to conveniently handle the error case.
 func (s *loopOutSwap) execute(mainCtx context.Context,

looprpc/client.pb.go

@@ -379,8 +379,23 @@ type SwapResponse struct {
 	//the Start() call. Currently this is the hash that locks the htlcs.
 	IdBytes []byte `protobuf:"bytes,3,opt,name=id_bytes,json=idBytes,proto3" json:"id_bytes,omitempty"`
 	//*
-	//The address of the on-chain htlc.
-	HtlcAddress          string   `protobuf:"bytes,2,opt,name=htlc_address,json=htlcAddress,proto3" json:"htlc_address,omitempty"`
+	//DEPRECATED. This field stores the address of the onchain htlc, but
+	//depending on the request, the semantics are different.
+	//- For internal loop-in htlc_address contains the address of the
+	//native segwit (P2WSH) htlc.
+	//- For external loop-in htlc_address contains the address of the
+	//nested segwit (NP2WSH) htlc.
+	//- For loop-out htlc_address always contains the native segwit (P2WSH)
+	//htlc address.
+	HtlcAddress string `protobuf:"bytes,2,opt,name=htlc_address,json=htlcAddress,proto3" json:"htlc_address,omitempty"` // Deprecated: Do not use.
+	//*
+	//The nested segwit address of the on-chain htlc.
+	//This field remains empty for loop-out.
+	HtlcAddressNp2Wsh string `protobuf:"bytes,4,opt,name=htlc_address_np2wsh,json=htlcAddressNp2wsh,proto3" json:"htlc_address_np2wsh,omitempty"`
+	//*
+	//The native segwit address of the on-chain htlc.
+	//Used for both loop-in and loop-out.
+	HtlcAddressP2Wsh     string   `protobuf:"bytes,5,opt,name=htlc_address_p2wsh,json=htlcAddressP2wsh,proto3" json:"htlc_address_p2wsh,omitempty"`
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
 	XXX_unrecognized     []byte   `json:"-"`
 	XXX_sizecache        int32    `json:"-"`
@@ -426,6 +441,7 @@ func (m *SwapResponse) GetIdBytes() []byte {
 	return nil
 }
 
+// Deprecated: Do not use.
 func (m *SwapResponse) GetHtlcAddress() string {
 	if m != nil {
 		return m.HtlcAddress
@@ -433,6 +449,20 @@ func (m *SwapResponse) GetHtlcAddress() string {
 	return ""
 }
 
+func (m *SwapResponse) GetHtlcAddressNp2Wsh() string {
+	if m != nil {
+		return m.HtlcAddressNp2Wsh
+	}
+	return ""
+}
+
+func (m *SwapResponse) GetHtlcAddressP2Wsh() string {
+	if m != nil {
+		return m.HtlcAddressP2Wsh
+	}
+	return ""
+}
+
 type MonitorRequest struct {
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
 	XXX_unrecognized     []byte   `json:"-"`
@@ -492,8 +522,18 @@ type SwapStatus struct {
 	//Initiation time of the swap.
 	LastUpdateTime int64 `protobuf:"varint,6,opt,name=last_update_time,json=lastUpdateTime,proto3" json:"last_update_time,omitempty"`
 	//*
-	//Htlc address.
-	HtlcAddress string `protobuf:"bytes,7,opt,name=htlc_address,json=htlcAddress,proto3" json:"htlc_address,omitempty"`
+	//DEPRECATED:  This field stores the address of the onchain htlc.
+	//- For internal loop-in htlc_address contains the address of the
+	//native segwit (P2WSH) htlc.
+	//- For external loop-in htlc_address contains the nested segwit (NP2WSH)
+	//address.
+	//- For loop-out htlc_address always contains the native segwit (P2WSH)
+	//htlc address.
+	HtlcAddress string `protobuf:"bytes,7,opt,name=htlc_address,json=htlcAddress,proto3" json:"htlc_address,omitempty"` // Deprecated: Do not use.
+	// HTLC address (native segwit), used in loop-in and loop-out swaps.
+	HtlcAddressP2Wsh string `protobuf:"bytes,12,opt,name=htlc_address_p2wsh,json=htlcAddressP2wsh,proto3" json:"htlc_address_p2wsh,omitempty"`
+	// HTLC address (nested segwit), used in loop-in swaps only.
+	HtlcAddressNp2Wsh string `protobuf:"bytes,13,opt,name=htlc_address_np2wsh,json=htlcAddressNp2wsh,proto3" json:"htlc_address_np2wsh,omitempty"`
 	/// Swap server cost
 	CostServer int64 `protobuf:"varint,8,opt,name=cost_server,json=costServer,proto3" json:"cost_server,omitempty"`
 	// On-chain transaction cost
@@ -580,6 +620,7 @@ func (m *SwapStatus) GetLastUpdateTime() int64 {
 	return 0
 }
 
+// Deprecated: Do not use.
 func (m *SwapStatus) GetHtlcAddress() string {
 	if m != nil {
 		return m.HtlcAddress
@@ -587,6 +628,20 @@ func (m *SwapStatus) GetHtlcAddress() string {
 	return ""
 }
 
+func (m *SwapStatus) GetHtlcAddressP2Wsh() string {
+	if m != nil {
+		return m.HtlcAddressP2Wsh
+	}
+	return ""
+}
+
+func (m *SwapStatus) GetHtlcAddressNp2Wsh() string {
+	if m != nil {
+		return m.HtlcAddressNp2Wsh
+	}
+	return ""
+}
+
 func (m *SwapStatus) GetCostServer() int64 {
 	if m != nil {
 		return m.CostServer
@@ -1180,98 +1235,101 @@ func init() {
 func init() { proto.RegisterFile("client.proto", fileDescriptor_014de31d7ac8c57c) }
 
 var fileDescriptor_014de31d7ac8c57c = []byte{
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+	// 1504 bytes of a gzipped FileDescriptorProto
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+	0x8e, 0xfe, 0x2d, 0xd4, 0xf9, 0x0a, 0x73, 0xdf, 0xa3, 0xa9, 0xfe, 0xcd, 0x98, 0x6b, 0x7b, 0xed,
+	0x16, 0x9e, 0x3d, 0x13, 0xa8, 0x21, 0x96, 0xa0, 0x98, 0x75, 0xa4, 0xa1, 0x9e, 0x95, 0xc4, 0xff,
+	0xa5, 0xe7, 0x7f, 0x05, 0x00, 0x00, 0xff, 0xff, 0x46, 0x6c, 0x13, 0xa0, 0x66, 0x0d, 0x00, 0x00,
 }
 
 // Reference imports to suppress errors if they are not otherwise used.

looprpc/client.proto

@@ -242,9 +242,28 @@ message SwapResponse {
     bytes id_bytes = 3;
 
     /**
-    The address of the on-chain htlc.
+    DEPRECATED. This field stores the address of the onchain htlc, but
+    depending on the request, the semantics are different.
+    - For internal loop-in htlc_address contains the address of the
+    native segwit (P2WSH) htlc.
+    - For external loop-in htlc_address contains the address of the
+    nested segwit (NP2WSH) htlc.
+    - For loop-out htlc_address always contains the native segwit (P2WSH)
+    htlc address.
     */
-    string htlc_address = 2;
+    string htlc_address = 2 [deprecated = true];
+
+    /**
+    The nested segwit address of the on-chain htlc.
+    This field remains empty for loop-out.
+    */
+    string htlc_address_np2wsh = 4;
+
+    /**
+    The native segwit address of the on-chain htlc.
+    Used for both loop-in and loop-out.
+    */
+    string htlc_address_p2wsh = 5;
 }
 
 message MonitorRequest {
@@ -292,9 +311,21 @@ message SwapStatus {
     int64 last_update_time = 6;
 
     /**
-    Htlc address.
+    DEPRECATED:  This field stores the address of the onchain htlc.
+    - For internal loop-in htlc_address contains the address of the
+    native segwit (P2WSH) htlc.
+    - For external loop-in htlc_address contains the nested segwit (NP2WSH)
+    address.
+    - For loop-out htlc_address always contains the native segwit (P2WSH)
+    htlc address.
     */
-    string htlc_address = 7;
+    string htlc_address = 7 [deprecated = true];
+
+    // HTLC address (native segwit), used in loop-in and loop-out swaps.
+    string htlc_address_p2wsh = 12;
+
+    // HTLC address (nested segwit), used in loop-in swaps only.
+    string htlc_address_np2wsh = 13;
 
     /// Swap server cost
     int64 cost_server = 8;

looprpc/client.swagger.json

@@ -457,7 +457,15 @@
         },
         "htlc_address": {
           "type": "string",
-          "description": "*\nThe address of the on-chain htlc."
+          "description": "*\nDEPRECATED. This field stores the address of the onchain htlc, but\ndepending on the request, the semantics are different.\n- For internal loop-in htlc_address contains the address of the\nnative segwit (P2WSH) htlc.\n- For external loop-in htlc_address contains the address of the\nnested segwit (NP2WSH) htlc.\n- For loop-out htlc_address always contains the native segwit (P2WSH)\nhtlc address."
+        },
+        "htlc_address_np2wsh": {
+          "type": "string",
+          "description": "*\nThe nested segwit address of the on-chain htlc.\nThis field remains empty for loop-out."
+        },
+        "htlc_address_p2wsh": {
+          "type": "string",
+          "description": "*\nThe native segwit address of the on-chain htlc.\nUsed for both loop-in and loop-out."
         }
       }
     },
@@ -511,7 +519,15 @@
         },
         "htlc_address": {
           "type": "string",
-          "description": "*\nHtlc address."
+          "description": "*\nDEPRECATED:  This field stores the address of the onchain htlc.\n- For internal loop-in htlc_address contains the address of the\nnative segwit (P2WSH) htlc.\n- For external loop-in htlc_address contains the nested segwit (NP2WSH)\naddress.\n- For loop-out htlc_address always contains the native segwit (P2WSH)\nhtlc address."
+        },
+        "htlc_address_p2wsh": {
+          "type": "string",
+          "description": "HTLC address (native segwit), used in loop-in and loop-out swaps."
+        },
+        "htlc_address_np2wsh": {
+          "type": "string",
+          "description": "HTLC address (nested segwit), used in loop-in swaps only."
         },
         "cost_server": {
           "type": "string",

looprpc/server.pb.go

@@ -35,16 +35,22 @@ const (
 	ProtocolVersion_LEGACY ProtocolVersion = 0
 	/// Client may attempt to send the loop out payment in multiple parts.
 	ProtocolVersion_MULTI_LOOP_OUT ProtocolVersion = 1
+	//*
+	//Loop will use native segwit (P2WSH) htlcs by default, while externally
+	//published htlcs may use native (P2WSH) or nested (NP2WSH) segwit as well.
+	ProtocolVersion_NATIVE_SEGWIT_LOOP_IN ProtocolVersion = 2
 )
 
 var ProtocolVersion_name = map[int32]string{
 	0: "LEGACY",
 	1: "MULTI_LOOP_OUT",
+	2: "NATIVE_SEGWIT_LOOP_IN",
 }
 
 var ProtocolVersion_value = map[string]int32{
-	"LEGACY":         0,
-	"MULTI_LOOP_OUT": 1,
+	"LEGACY":                0,
+	"MULTI_LOOP_OUT":        1,
+	"NATIVE_SEGWIT_LOOP_IN": 2,
 }
 
 func (x ProtocolVersion) String() string {
@@ -784,57 +790,58 @@ func init() {
 func init() { proto.RegisterFile("server.proto", fileDescriptor_ad098daeda4239f7) }
 
 var fileDescriptor_ad098daeda4239f7 = []byte{
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+	0xff, 0xff, 0xd3, 0x5d, 0x9c, 0x31, 0xe8, 0x09, 0x00, 0x00,
 }
 
 // Reference imports to suppress errors if they are not otherwise used.

looprpc/server.proto

@@ -31,6 +31,12 @@ enum ProtocolVersion {
 
     /// Client may attempt to send the loop out payment in multiple parts.
     MULTI_LOOP_OUT = 1;
+
+    /**
+    Loop will use native segwit (P2WSH) htlcs by default, while externally
+    published htlcs may use native (P2WSH) or nested (NP2WSH) segwit as well.
+    */
+    NATIVE_SEGWIT_LOOP_IN = 2;
 }
 
 message ServerLoopOutRequest {

swap.go

@@ -11,7 +11,6 @@ import (
 )
 
 type swapKit struct {
-	htlc *swap.Htlc
 	hash lntypes.Hash
 
 	height int32
@@ -19,51 +18,49 @@ type swapKit struct {
 	log *swap.PrefixLog
 
 	lastUpdateTime time.Time
-	cost           loopdb.SwapCost
-	state          loopdb.SwapState
-	executeConfig
-	swapConfig
+
+	cost loopdb.SwapCost
+
+	state loopdb.SwapState
 
 	contract *loopdb.SwapContract
+
 	swapType swap.Type
+
+	swapConfig
 }
 
 func newSwapKit(hash lntypes.Hash, swapType swap.Type, cfg *swapConfig,
-	contract *loopdb.SwapContract, outputType swap.HtlcOutputType) (
-	*swapKit, error) {
-
-	// Compose expected on-chain swap script
-	htlc, err := swap.NewHtlc(
-		contract.CltvExpiry, contract.SenderKey,
-		contract.ReceiverKey, hash, outputType,
-		cfg.lnd.ChainParams,
-	)
-	if err != nil {
-		return nil, err
-	}
+	contract *loopdb.SwapContract) *swapKit {
 
 	log := &swap.PrefixLog{
 		Hash:   hash,
 		Logger: log,
 	}
 
-	// Log htlc address for debugging.
-	log.Infof("Htlc address: %v", htlc.Address)
-
 	return &swapKit{
 		swapConfig: *cfg,
 		hash:       hash,
 		log:        log,
-		htlc:       htlc,
 		state:      loopdb.StateInitiated,
 		contract:   contract,
 		swapType:   swapType,
-	}, nil
+	}
+}
+
+// getHtlc composes and returns the on-chain swap script.
+func (s *swapKit) getHtlc(outputType swap.HtlcOutputType) (*swap.Htlc, error) {
+	return swap.NewHtlc(
+		s.contract.CltvExpiry, s.contract.SenderKey,
+		s.contract.ReceiverKey, s.hash, outputType,
+		s.swapConfig.lnd.ChainParams,
+	)
 }
 
-// sendUpdate reports an update to the swap state.
-func (s *swapKit) sendUpdate(ctx context.Context) error {
-	info := &SwapInfo{
+// swapInfo constructs and returns a filled SwapInfo from
+// the swapKit.
+func (s *swapKit) swapInfo() *SwapInfo {
+	return &SwapInfo{
 		SwapContract: *s.contract,
 		SwapHash:     s.hash,
 		SwapType:     s.swapType,
@@ -72,18 +69,7 @@ func (s *swapKit) sendUpdate(ctx context.Context) error {
 			State: s.state,
 			Cost:  s.cost,
 		},
-		HtlcAddress: s.htlc.Address,
 	}
-
-	s.log.Infof("state %v", info.State)
-
-	select {
-	case s.statusChan <- *info:
-	case <-ctx.Done():
-		return ctx.Err()
-	}
-
-	return nil
 }
 
 type genericSwap interface {

swap/htlc.go

@@ -50,6 +50,20 @@ var (
 	)
 )
 
+// String returns the string value of HtlcOutputType.
+func (h HtlcOutputType) String() string {
+	switch h {
+	case HtlcP2WSH:
+		return "P2WSH"
+
+	case HtlcNP2WSH:
+		return "NP2WSH"
+
+	default:
+		return "unknown"
+	}
+}
+
 // NewHtlc returns a new instance.
 func NewHtlc(cltvExpiry int32, senderKey, receiverKey [33]byte,
 	hash lntypes.Hash, outputType HtlcOutputType,

swap_server_client.go

@@ -22,7 +22,7 @@ import (
 
 // protocolVersion defines the version of the protocol that is currently
 // supported by the loop client.
-const protocolVersion = looprpc.ProtocolVersion_MULTI_LOOP_OUT
+const protocolVersion = looprpc.ProtocolVersion_NATIVE_SEGWIT_LOOP_IN
 
 type swapServerClient interface {
 	GetLoopOutTerms(ctx context.Context) (