routing+htlcswitch: fix stuck inflight payments

channeldb/mp_payment.go

@@ -10,7 +10,10 @@ import (
 
 	"github.com/btcsuite/btcd/btcec/v2"
 	"github.com/btcsuite/btcd/wire"
+	"github.com/davecgh/go-spew/spew"
+	sphinx "github.com/lightningnetwork/lightning-onion"
 	"github.com/lightningnetwork/lnd/lntypes"
+	"github.com/lightningnetwork/lnd/lnutils"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
 )
@@ -45,12 +48,19 @@ type HTLCAttemptInfo struct {
 	// in which the payment's PaymentHash in the PaymentCreationInfo should
 	// be used.
 	Hash *lntypes.Hash
+
+	// onionBlob is the cached value for onion blob created from the sphinx
+	// construction.
+	onionBlob [lnwire.OnionPacketSize]byte
+
+	// circuit is the cached value for sphinx circuit.
+	circuit *sphinx.Circuit
 }
 
 // NewHtlcAttempt creates a htlc attempt.
 func NewHtlcAttempt(attemptID uint64, sessionKey *btcec.PrivateKey,
 	route route.Route, attemptTime time.Time,
-	hash *lntypes.Hash) *HTLCAttempt {
+	hash *lntypes.Hash) (*HTLCAttempt, error) {
 
 	var scratch [btcec.PrivKeyBytesLen]byte
 	copy(scratch[:], sessionKey.Serialize())
@@ -64,7 +74,11 @@ func NewHtlcAttempt(attemptID uint64, sessionKey *btcec.PrivateKey,
 		Hash:             hash,
 	}
 
-	return &HTLCAttempt{HTLCAttemptInfo: info}
+	if err := info.attachOnionBlobAndCircuit(); err != nil {
+		return nil, err
+	}
+
+	return &HTLCAttempt{HTLCAttemptInfo: info}, nil
 }
 
 // SessionKey returns the ephemeral key used for a htlc attempt. This function
@@ -79,6 +93,45 @@ func (h *HTLCAttemptInfo) SessionKey() *btcec.PrivateKey {
 	return h.cachedSessionKey
 }
 
+// OnionBlob returns the onion blob created from the sphinx construction.
+func (h *HTLCAttemptInfo) OnionBlob() ([lnwire.OnionPacketSize]byte, error) {
+	var zeroBytes [lnwire.OnionPacketSize]byte
+	if h.onionBlob == zeroBytes {
+		if err := h.attachOnionBlobAndCircuit(); err != nil {
+			return zeroBytes, err
+		}
+	}
+
+	return h.onionBlob, nil
+}
+
+// Circuit returns the sphinx circuit for this attempt.
+func (h *HTLCAttemptInfo) Circuit() (*sphinx.Circuit, error) {
+	if h.circuit == nil {
+		if err := h.attachOnionBlobAndCircuit(); err != nil {
+			return nil, err
+		}
+	}
+
+	return h.circuit, nil
+}
+
+// attachOnionBlobAndCircuit creates a sphinx packet and caches the onion blob
+// and circuit for this attempt.
+func (h *HTLCAttemptInfo) attachOnionBlobAndCircuit() error {
+	onionBlob, circuit, err := generateSphinxPacket(
+		&h.Route, h.Hash[:], h.SessionKey(),
+	)
+	if err != nil {
+		return err
+	}
+
+	copy(h.onionBlob[:], onionBlob)
+	h.circuit = circuit
+
+	return nil
+}
+
 // HTLCAttempt contains information about a specific HTLC attempt for a given
 // payment. It contains the HTLCAttemptInfo used to send the HTLC, as well
 // as a timestamp and any known outcome of the attempt.
@@ -629,3 +682,69 @@ func serializeTime(w io.Writer, t time.Time) error {
 	_, err := w.Write(scratch[:])
 	return err
 }
+
+// generateSphinxPacket generates then encodes a sphinx packet which encodes
+// the onion route specified by the passed layer 3 route. The blob returned
+// from this function can immediately be included within an HTLC add packet to
+// be sent to the first hop within the route.
+func generateSphinxPacket(rt *route.Route, paymentHash []byte,
+	sessionKey *btcec.PrivateKey) ([]byte, *sphinx.Circuit, error) {
+
+	// Now that we know we have an actual route, we'll map the route into a
+	// sphinx payment path which includes per-hop payloads for each hop
+	// that give each node within the route the necessary information
+	// (fees, CLTV value, etc.) to properly forward the payment.
+	sphinxPath, err := rt.ToSphinxPath()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	log.Tracef("Constructed per-hop payloads for payment_hash=%x: %v",
+		paymentHash, lnutils.NewLogClosure(func() string {
+			path := make(
+				[]sphinx.OnionHop, sphinxPath.TrueRouteLength(),
+			)
+			for i := range path {
+				hopCopy := sphinxPath[i]
+				path[i] = hopCopy
+			}
+
+			return spew.Sdump(path)
+		}),
+	)
+
+	// Next generate the onion routing packet which allows us to perform
+	// privacy preserving source routing across the network.
+	sphinxPacket, err := sphinx.NewOnionPacket(
+		sphinxPath, sessionKey, paymentHash,
+		sphinx.DeterministicPacketFiller,
+	)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// Finally, encode Sphinx packet using its wire representation to be
+	// included within the HTLC add packet.
+	var onionBlob bytes.Buffer
+	if err := sphinxPacket.Encode(&onionBlob); err != nil {
+		return nil, nil, err
+	}
+
+	log.Tracef("Generated sphinx packet: %v",
+		lnutils.NewLogClosure(func() string {
+			// We make a copy of the ephemeral key and unset the
+			// internal curve here in order to keep the logs from
+			// getting noisy.
+			key := *sphinxPacket.EphemeralKey
+			packetCopy := *sphinxPacket
+			packetCopy.EphemeralKey = &key
+
+			return spew.Sdump(packetCopy)
+		}),
+	)
+
+	return onionBlob.Bytes(), &sphinx.Circuit{
+		SessionKey:  sessionKey,
+		PaymentPath: sphinxPath.NodeKeys(),
+	}, nil
+}

channeldb/mp_payment_test.go

@@ -5,12 +5,22 @@ import (
 	"fmt"
 	"testing"
 
+	"github.com/btcsuite/btcd/btcec/v2"
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
 	"github.com/stretchr/testify/require"
 )
 
+var (
+	testHash = [32]byte{
+		0xb7, 0x94, 0x38, 0x5f, 0x2d, 0x1e, 0xf7, 0xab,
+		0x4d, 0x92, 0x73, 0xd1, 0x90, 0x63, 0x81, 0xb4,
+		0x4f, 0x2f, 0x6f, 0x25, 0x88, 0xa3, 0xef, 0xb9,
+		0x6a, 0x49, 0x18, 0x83, 0x31, 0x98, 0x47, 0x53,
+	}
+)
+
 // TestLazySessionKeyDeserialize tests that we can read htlc attempt session
 // keys that were previously serialized as a private key as raw bytes.
 func TestLazySessionKeyDeserialize(t *testing.T) {
@@ -578,3 +588,15 @@ func makeAttemptInfo(total, amtForwarded int) HTLCAttemptInfo {
 		},
 	}
 }
+
+// TestEmptyRoutesGenerateSphinxPacket tests that the generateSphinxPacket
+// function is able to gracefully handle being passed a nil set of hops for the
+// route by the caller.
+func TestEmptyRoutesGenerateSphinxPacket(t *testing.T) {
+	t.Parallel()
+
+	sessionKey, _ := btcec.NewPrivateKey()
+	emptyRoute := &route.Route{}
+	_, _, err := generateSphinxPacket(emptyRoute, testHash[:], sessionKey)
+	require.ErrorIs(t, err, route.ErrNoRouteHopsProvided)
+}

channeldb/payment_control.go

@@ -115,6 +115,10 @@ var (
 	// amount exceed the total amount.
 	ErrSentExceedsTotal = errors.New("total sent exceeds total amount")
 
+	// ErrRegisterAttempt is returned when a new htlc attempt cannot be
+	// registered.
+	ErrRegisterAttempt = errors.New("cannot register htlc attempt")
+
 	// errNoAttemptInfo is returned when no attempt info is stored yet.
 	errNoAttemptInfo = errors.New("unable to find attempt info for " +
 		"inflight payment")
@@ -342,7 +346,8 @@ func (p *PaymentControl) RegisterAttempt(paymentHash lntypes.Hash,
 
 		// Check if registering a new attempt is allowed.
 		if err := payment.Registrable(); err != nil {
-			return err
+			return fmt.Errorf("%w: %v", ErrRegisterAttempt,
+				err.Error())
 		}
 
 		// If the final hop has encrypted data, then we know this is a

channeldb/payment_control_test.go

@@ -28,7 +28,7 @@ func genPreimage() ([32]byte, error) {
 	return preimage, nil
 }
 
-func genInfo() (*PaymentCreationInfo, *HTLCAttemptInfo,
+func genInfo(t *testing.T) (*PaymentCreationInfo, *HTLCAttemptInfo,
 	lntypes.Preimage, error) {
 
 	preimage, err := genPreimage()
@@ -38,9 +38,14 @@ func genInfo() (*PaymentCreationInfo, *HTLCAttemptInfo,
 	}
 
 	rhash := sha256.Sum256(preimage[:])
-	attempt := NewHtlcAttempt(
-		0, priv, *testRoute.Copy(), time.Time{}, nil,
+	var hash lntypes.Hash
+	copy(hash[:], rhash[:])
+
+	attempt, err := NewHtlcAttempt(
+		0, priv, *testRoute.Copy(), time.Time{}, &hash,
 	)
+	require.NoError(t, err)
+
 	return &PaymentCreationInfo{
 		PaymentIdentifier: rhash,
 		Value:             testRoute.ReceiverAmt(),
@@ -60,7 +65,7 @@ func TestPaymentControlSwitchFail(t *testing.T) {
 
 	pControl := NewPaymentControl(db)
 
-	info, attempt, preimg, err := genInfo()
+	info, attempt, preimg, err := genInfo(t)
 	require.NoError(t, err, "unable to generate htlc message")
 
 	// Sends base htlc message which initiate StatusInFlight.
@@ -196,7 +201,7 @@ func TestPaymentControlSwitchDoubleSend(t *testing.T) {
 
 	pControl := NewPaymentControl(db)
 
-	info, attempt, preimg, err := genInfo()
+	info, attempt, preimg, err := genInfo(t)
 	require.NoError(t, err, "unable to generate htlc message")
 
 	// Sends base htlc message which initiate base status and move it to
@@ -266,7 +271,7 @@ func TestPaymentControlSuccessesWithoutInFlight(t *testing.T) {
 
 	pControl := NewPaymentControl(db)
 
-	info, _, preimg, err := genInfo()
+	info, _, preimg, err := genInfo(t)
 	require.NoError(t, err, "unable to generate htlc message")
 
 	// Attempt to complete the payment should fail.
@@ -291,7 +296,7 @@ func TestPaymentControlFailsWithoutInFlight(t *testing.T) {
 
 	pControl := NewPaymentControl(db)
 
-	info, _, _, err := genInfo()
+	info, _, _, err := genInfo(t)
 	require.NoError(t, err, "unable to generate htlc message")
 
 	// Calling Fail should return an error.
@@ -346,7 +351,7 @@ func TestPaymentControlDeleteNonInFlight(t *testing.T) {
 	var numSuccess, numInflight int
 
 	for _, p := range payments {
-		info, attempt, preimg, err := genInfo()
+		info, attempt, preimg, err := genInfo(t)
 		if err != nil {
 			t.Fatalf("unable to generate htlc message: %v", err)
 		}
@@ -684,7 +689,7 @@ func TestPaymentControlMultiShard(t *testing.T) {
 
 		pControl := NewPaymentControl(db)
 
-		info, attempt, preimg, err := genInfo()
+		info, attempt, preimg, err := genInfo(t)
 		if err != nil {
 			t.Fatalf("unable to generate htlc message: %v", err)
 		}
@@ -948,7 +953,7 @@ func TestPaymentControlMPPRecordValidation(t *testing.T) {
 
 	pControl := NewPaymentControl(db)
 
-	info, attempt, _, err := genInfo()
+	info, attempt, _, err := genInfo(t)
 	require.NoError(t, err, "unable to generate htlc message")
 
 	// Init the payment.
@@ -997,7 +1002,7 @@ func TestPaymentControlMPPRecordValidation(t *testing.T) {
 
 	// Create and init a new payment. This time we'll check that we cannot
 	// register an MPP attempt if we already registered a non-MPP one.
-	info, attempt, _, err = genInfo()
+	info, attempt, _, err = genInfo(t)
 	require.NoError(t, err, "unable to generate htlc message")
 
 	err = pControl.InitPayment(info.PaymentIdentifier, info)
@@ -1271,7 +1276,7 @@ func createTestPayments(t *testing.T, p *PaymentControl, payments []*payment) {
 	attemptID := uint64(0)
 
 	for i := 0; i < len(payments); i++ {
-		info, attempt, preimg, err := genInfo()
+		info, attempt, preimg, err := genInfo(t)
 		require.NoError(t, err, "unable to generate htlc message")
 
 		// Set the payment id accordingly in the payments slice.