multi: add TLV awareness to htlcswitch, pass extra EOB to the invoice registry

In this commit, we update the `HopIterator` to gain awareness of the new
TLV hop payload. The default `HopIterator` will now hide the details of
the TLV from the caller, and return the same `ForwardingInfo` struct in
a uniform manner. We also add a new method: `ExtraOnionBlob` to allow
the caller to obtain the raw EOB (the serialized TLV stream) to pass
around.

Within the link, we'll now pass the EOB information into the invoice
registry. This allows the registry to parse out any additional
information from the EOB that it needs to settle the payment, such as a
preimage shard in the AMP case.

contractcourt/htlc_incoming_contest_resolver.go

@@ -166,7 +166,7 @@ func (h *htlcIncomingContestResolver) Resolve() (ContractResolver, error) {
 	// identical to HTLC resolution in the link.
 	event, err := h.Registry.NotifyExitHopHtlc(
 		h.payHash, h.htlcAmt, h.htlcExpiry, currentHeight,
-		hodlChan,
+		hodlChan, nil,
 	)
 	switch err {
 	case channeldb.ErrInvoiceNotFound:

contractcourt/interfaces.go

@@ -22,7 +22,8 @@ type Registry interface {
 	// the resolution is sent on the passed in hodlChan later.
 	NotifyExitHopHtlc(payHash lntypes.Hash, paidAmount lnwire.MilliSatoshi,
 		expiry uint32, currentHeight int32,
-		hodlChan chan<- interface{}) (*invoices.HodlEvent, error)
+		hodlChan chan<- interface{},
+		eob []byte) (*invoices.HodlEvent, error)
 
 	// HodlUnsubscribeAll unsubscribes from all hodl events.
 	HodlUnsubscribeAll(subscriber chan<- interface{})

contractcourt/mock_registry_test.go

@@ -23,7 +23,7 @@ type mockRegistry struct {
 
 func (r *mockRegistry) NotifyExitHopHtlc(payHash lntypes.Hash,
 	paidAmount lnwire.MilliSatoshi, expiry uint32, currentHeight int32,
-	hodlChan chan<- interface{}) (*invoices.HodlEvent, error) {
+	hodlChan chan<- interface{}, eob []byte) (*invoices.HodlEvent, error) {
 
 	r.notifyChan <- notifyExitHopData{
 		hodlChan:      hodlChan,

htlcswitch/interfaces.go

@@ -23,10 +23,13 @@ type InvoiceDatabase interface {
 	// invoice is a debug invoice, then this method is a noop as debug
 	// invoices are never fully settled. The return value describes how the
 	// htlc should be resolved. If the htlc cannot be resolved immediately,
-	// the resolution is sent on the passed in hodlChan later.
+	// the resolution is sent on the passed in hodlChan later. The eob
+	// field passes the entire onion hop payload into the invoice registry
+	// for decoding purposes.
 	NotifyExitHopHtlc(payHash lntypes.Hash, paidAmount lnwire.MilliSatoshi,
 		expiry uint32, currentHeight int32,
-		hodlChan chan<- interface{}) (*invoices.HodlEvent, error)
+		hodlChan chan<- interface{},
+		eob []byte) (*invoices.HodlEvent, error)
 
 	// CancelInvoice attempts to cancel the invoice corresponding to the
 	// passed payment hash.

htlcswitch/iterator.go

@@ -1,12 +1,15 @@
 package htlcswitch
 
 import (
+	"bytes"
 	"encoding/binary"
+	"fmt"
 	"io"
 
 	"github.com/btcsuite/btcd/btcec"
 	"github.com/lightningnetwork/lightning-onion"
 	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/lightningnetwork/lnd/tlv"
 )
 
 // NetworkHop indicates the blockchain network that is intended to be the next
@@ -85,7 +88,10 @@ type HopIterator interface {
 	// Additionally, the information encoded within the returned
 	// ForwardingInfo is to be used by each hop to authenticate the
 	// information given to it by the prior hop.
-	ForwardingInstructions() ForwardingInfo
+	ForwardingInstructions() (ForwardingInfo, error)
+
+	// ExtraOnionBlob returns the additional EOB data (if available).
+	ExtraOnionBlob() []byte
 
 	// EncodeNextHop encodes the onion packet destined for the next hop
 	// into the passed io.Writer.
@@ -139,10 +145,19 @@ func (r *sphinxHopIterator) EncodeNextHop(w io.Writer) error {
 // hop to authenticate the information given to it by the prior hop.
 //
 // NOTE: Part of the HopIterator interface.
-func (r *sphinxHopIterator) ForwardingInstructions() ForwardingInfo {
+func (r *sphinxHopIterator) ForwardingInstructions() (ForwardingInfo, error) {
+	var (
+		nextHop lnwire.ShortChannelID
+		amt     uint64
+		cltv    uint32
+	)
+
+	switch r.processedPacket.Payload.Type {
+	// If this is the legacy payload, then we'll extract the information
+	// directly from the pre-populated ForwardingInstructions field.
+	case sphinx.PayloadLegacy:
 		fwdInst := r.processedPacket.ForwardingInstructions
 
-	var nextHop lnwire.ShortChannelID
 		switch r.processedPacket.Action {
 		case sphinx.ExitNode:
 			nextHop = exitHop
@@ -151,12 +166,58 @@ func (r *sphinxHopIterator) ForwardingInstructions() ForwardingInfo {
 			nextHop = lnwire.NewShortChanIDFromInt(s)
 		}
 
+		amt = fwdInst.ForwardAmount
+		cltv = fwdInst.OutgoingCltv
+
+	// Otherwise, if this is the TLV payload, then we'll make a new stream
+	// to decode only what we need to make routing decisions.
+	case sphinx.PayloadTLV:
+		var cid uint64
+
+		tlvStream, err := tlv.NewStream(
+			tlv.MakeDynamicRecord(
+				tlv.AmtOnionType, &amt, nil,
+				tlv.ETUint64, tlv.DTUint64,
+			),
+			tlv.MakeDynamicRecord(
+				tlv.LockTimeOnionType, &cltv, nil,
+				tlv.ETUint32, tlv.DTUint32,
+			),
+			tlv.MakePrimitiveRecord(tlv.NextHopOnionType, &cid),
+		)
+		if err != nil {
+			return ForwardingInfo{}, err
+		}
+
+		err = tlvStream.Decode(bytes.NewReader(
+			r.processedPacket.Payload.Payload,
+		))
+		if err != nil {
+			return ForwardingInfo{}, err
+		}
+
+		nextHop = lnwire.NewShortChanIDFromInt(cid)
+
+	default:
+		return ForwardingInfo{}, fmt.Errorf("unknown sphinx payload "+
+			"type: %v", r.processedPacket.Payload.Type)
+	}
+
 	return ForwardingInfo{
 		Network:         BitcoinHop,
 		NextHop:         nextHop,
-		AmountToForward: lnwire.MilliSatoshi(fwdInst.ForwardAmount),
+		AmountToForward: lnwire.MilliSatoshi(amt),
-		OutgoingCTLV:    fwdInst.OutgoingCltv,
+		OutgoingCTLV:    cltv,
+	}, nil
 }
+
+// ExtraOnionBlob returns the additional EOB data (if available).
+func (r *sphinxHopIterator) ExtraOnionBlob() []byte {
+	if r.processedPacket.Payload.Type == sphinx.PayloadLegacy {
+		return nil
+	}
+
+	return r.processedPacket.Payload.Payload
 }
 
 // ExtractErrorEncrypter decodes and returns the ErrorEncrypter for this hop,

htlcswitch/iterator_test.go

@@ -0,0 +1,109 @@
+package htlcswitch
+
+import (
+	"bytes"
+	"encoding/binary"
+	"testing"
+
+	"github.com/davecgh/go-spew/spew"
+	sphinx "github.com/lightningnetwork/lightning-onion"
+	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/lightningnetwork/lnd/tlv"
+)
+
+// TestSphinxHopIteratorForwardingInstructions tests that we're able to
+// properly decode an onion payload, no matter the payload type, into the
+// original set of forwarding instructions.
+func TestSphinxHopIteratorForwardingInstructions(t *testing.T) {
+	t.Parallel()
+
+	// First, we'll make the hop data that the sender would create to send
+	// an HTLC through our imaginary route.
+	hopData := sphinx.HopData{
+		ForwardAmount: 100000,
+		OutgoingCltv:  4343,
+	}
+	copy(hopData.NextAddress[:], bytes.Repeat([]byte("a"), 8))
+
+	// Next, we'll make the hop forwarding information that we should
+	// extract each type, no matter the payload type.
+	nextAddrInt := binary.BigEndian.Uint64(hopData.NextAddress[:])
+	expectedFwdInfo := ForwardingInfo{
+		NextHop:         lnwire.NewShortChanIDFromInt(nextAddrInt),
+		AmountToForward: lnwire.MilliSatoshi(hopData.ForwardAmount),
+		OutgoingCTLV:    hopData.OutgoingCltv,
+	}
+
+	// For our TLV payload, we'll serialize the hop into into a TLV stream
+	// as we would normally in the routing network.
+	var b bytes.Buffer
+	tlvRecords := []tlv.Record{
+		tlv.MakeDynamicRecord(
+			tlv.AmtOnionType, &hopData.ForwardAmount, func() uint64 {
+				return tlv.SizeTUint64(hopData.ForwardAmount)
+			},
+			tlv.ETUint64, tlv.DTUint64,
+		),
+		tlv.MakeDynamicRecord(
+			tlv.LockTimeOnionType, &hopData.OutgoingCltv, func() uint64 {
+				return tlv.SizeTUint32(hopData.OutgoingCltv)
+			},
+			tlv.ETUint32, tlv.DTUint32,
+		),
+		tlv.MakePrimitiveRecord(tlv.NextHopOnionType, &nextAddrInt),
+	}
+	tlvStream, err := tlv.NewStream(tlvRecords...)
+	if err != nil {
+		t.Fatalf("unable to create stream: %v", err)
+	}
+	if err := tlvStream.Encode(&b); err != nil {
+		t.Fatalf("unable to encode stream: %v", err)
+	}
+
+	var testCases = []struct {
+		sphinxPacket    *sphinx.ProcessedPacket
+		expectedFwdInfo ForwardingInfo
+	}{
+		// A regular legacy payload that signals more hops.
+		{
+			sphinxPacket: &sphinx.ProcessedPacket{
+				Payload: sphinx.HopPayload{
+					Type: sphinx.PayloadLegacy,
+				},
+				Action:                 sphinx.MoreHops,
+				ForwardingInstructions: &hopData,
+			},
+			expectedFwdInfo: expectedFwdInfo,
+		},
+		// A TLV payload, we can leave off the action as we'll always
+		// read the cid encoded.
+		{
+			sphinxPacket: &sphinx.ProcessedPacket{
+				Payload: sphinx.HopPayload{
+					Type:    sphinx.PayloadTLV,
+					Payload: b.Bytes(),
+				},
+			},
+			expectedFwdInfo: expectedFwdInfo,
+		},
+	}
+
+	// Finally, we'll test that we get the same set of
+	// ForwardingInstructions for each payload type.
+	iterator := sphinxHopIterator{}
+	for i, testCase := range testCases {
+		iterator.processedPacket = testCase.sphinxPacket
+
+		fwdInfo, err := iterator.ForwardingInstructions()
+		if err != nil {
+			t.Fatalf("#%v: unable to extract forwarding "+
+				"instructions: %v", i, err)
+		}
+
+		if fwdInfo != testCase.expectedFwdInfo {
+			t.Fatalf("#%v: wrong fwding info: expected %v, got %v",
+				i, spew.Sdump(testCase.expectedFwdInfo),
+				spew.Sdump(fwdInfo))
+		}
+	}
+}

htlcswitch/link.go

@@ -2627,8 +2627,9 @@ func (l *channelLink) processRemoteAdds(fwdPkg *channeldb.FwdPkg,
 			// If we're unable to process the onion blob than we
 			// should send the malformed htlc error to payment
 			// sender.
-			l.sendMalformedHTLCError(pd.HtlcIndex, failureCode,
+			l.sendMalformedHTLCError(
-				onionBlob[:], pd.SourceRef)
+				pd.HtlcIndex, failureCode, onionBlob[:], pd.SourceRef,
+			)
 			needUpdate = true
 
 			log.Errorf("unable to decode onion "+
@@ -2638,11 +2639,29 @@ func (l *channelLink) processRemoteAdds(fwdPkg *channeldb.FwdPkg,
 
 		heightNow := l.cfg.Switch.BestHeight()
 
-		fwdInfo := chanIterator.ForwardingInstructions()
+		fwdInfo, err := chanIterator.ForwardingInstructions()
+		if err != nil {
+			// If we're unable to process the onion payload, or we
+			// we received malformed TLV stream, then we should
+			// send an error back to the caller so the HTLC can be
+			// cancelled.
+			l.sendHTLCError(
+				pd.HtlcIndex,
+				lnwire.NewInvalidOnionVersion(onionBlob[:]),
+				obfuscator, pd.SourceRef,
+			)
+			needUpdate = true
+
+			log.Errorf("Unable to decode forwarding "+
+				"instructions: %v", err)
+			continue
+		}
+
 		switch fwdInfo.NextHop {
 		case exitHop:
 			updated, err := l.processExitHop(
 				pd, obfuscator, fwdInfo, heightNow,
+				chanIterator.ExtraOnionBlob(),
 			)
 			if err != nil {
 				l.fail(LinkFailureError{code: ErrInternalError},
@@ -2814,8 +2833,8 @@ func (l *channelLink) processRemoteAdds(fwdPkg *channeldb.FwdPkg,
 // processExitHop handles an htlc for which this link is the exit hop. It
 // returns a boolean indicating whether the commitment tx needs an update.
 func (l *channelLink) processExitHop(pd *lnwallet.PaymentDescriptor,
-	obfuscator ErrorEncrypter, fwdInfo ForwardingInfo, heightNow uint32) (
+	obfuscator ErrorEncrypter, fwdInfo ForwardingInfo,
-	bool, error) {
+	heightNow uint32, eob []byte) (bool, error) {
 
 	// If hodl.ExitSettle is requested, we will not validate the final hop's
 	// ADD, nor will we settle the corresponding invoice or respond with the
@@ -2861,7 +2880,7 @@ func (l *channelLink) processExitHop(pd *lnwallet.PaymentDescriptor,
 
 	event, err := l.cfg.Registry.NotifyExitHopHtlc(
 		invoiceHash, pd.Amount, pd.Timeout, int32(heightNow),
-		l.hodlQueue.ChanIn(),
+		l.hodlQueue.ChanIn(), eob,
 	)
 
 	switch err {

htlcswitch/mock.go

@@ -275,10 +275,14 @@ func newMockHopIterator(hops ...ForwardingInfo) HopIterator {
 	return &mockHopIterator{hops: hops}
 }
 
-func (r *mockHopIterator) ForwardingInstructions() ForwardingInfo {
+func (r *mockHopIterator) ForwardingInstructions() (ForwardingInfo, error) {
 	h := r.hops[0]
 	r.hops = r.hops[1:]
-	return h
+	return h, nil
+}
+
+func (r *mockHopIterator) ExtraOnionBlob() []byte {
+	return nil
 }
 
 func (r *mockHopIterator) ExtractErrorEncrypter(
@@ -789,10 +793,10 @@ func (i *mockInvoiceRegistry) SettleHodlInvoice(preimage lntypes.Preimage) error
 
 func (i *mockInvoiceRegistry) NotifyExitHopHtlc(rhash lntypes.Hash,
 	amt lnwire.MilliSatoshi, expiry uint32, currentHeight int32,
-	hodlChan chan<- interface{}) (*invoices.HodlEvent, error) {
+	hodlChan chan<- interface{}, eob []byte) (*invoices.HodlEvent, error) {
 
 	event, err := i.registry.NotifyExitHopHtlc(
-		rhash, amt, expiry, currentHeight, hodlChan,
+		rhash, amt, expiry, currentHeight, hodlChan, eob,
 	)
 	if err != nil {
 		return nil, err

invoices/invoiceregistry.go

@@ -489,7 +489,7 @@ func (i *InvoiceRegistry) checkHtlcParameters(invoice *channeldb.Invoice,
 // prevent deadlock.
 func (i *InvoiceRegistry) NotifyExitHopHtlc(rHash lntypes.Hash,
 	amtPaid lnwire.MilliSatoshi, expiry uint32, currentHeight int32,
-	hodlChan chan<- interface{}) (*HodlEvent, error) {
+	hodlChan chan<- interface{}, eob []byte) (*HodlEvent, error) {
 
 	i.Lock()
 	defer i.Unlock()

invoices/invoiceregistry_test.go

@@ -119,7 +119,7 @@ func TestSettleInvoice(t *testing.T) {
 	// Settle invoice with a slightly higher amount.
 	amtPaid := lnwire.MilliSatoshi(100500)
 	_, err = registry.NotifyExitHopHtlc(
-		hash, amtPaid, testInvoiceExpiry, 0, hodlChan,
+		hash, amtPaid, testInvoiceExpiry, 0, hodlChan, nil,
 	)
 	if err != nil {
 		t.Fatal(err)
@@ -155,6 +155,7 @@ func TestSettleInvoice(t *testing.T) {
 	// restart.
 	event, err := registry.NotifyExitHopHtlc(
 		hash, amtPaid, testInvoiceExpiry, testCurrentHeight, hodlChan,
+		nil,
 	)
 	if err != nil {
 		t.Fatalf("unexpected NotifyExitHopHtlc error: %v", err)
@@ -168,7 +169,7 @@ func TestSettleInvoice(t *testing.T) {
 	// same. New HTLCs with a different amount should be rejected.
 	event, err = registry.NotifyExitHopHtlc(
 		hash, amtPaid+600, testInvoiceExpiry, testCurrentHeight,
-		hodlChan,
+		hodlChan, nil,
 	)
 	if err != nil {
 		t.Fatalf("unexpected NotifyExitHopHtlc error: %v", err)
@@ -181,7 +182,7 @@ func TestSettleInvoice(t *testing.T) {
 	// behaviour as settling with a higher amount.
 	event, err = registry.NotifyExitHopHtlc(
 		hash, amtPaid-600, testInvoiceExpiry, testCurrentHeight,
-		hodlChan,
+		hodlChan, nil,
 	)
 	if err != nil {
 		t.Fatalf("unexpected NotifyExitHopHtlc error: %v", err)
@@ -304,7 +305,7 @@ func TestCancelInvoice(t *testing.T) {
 	// succeed.
 	hodlChan := make(chan interface{})
 	event, err := registry.NotifyExitHopHtlc(
-		hash, amt, testInvoiceExpiry, testCurrentHeight, hodlChan,
+		hash, amt, testInvoiceExpiry, testCurrentHeight, hodlChan, nil,
 	)
 	if err != nil {
 		t.Fatal("expected settlement of a canceled invoice to succeed")
@@ -381,6 +382,7 @@ func TestHoldInvoice(t *testing.T) {
 	// should be possible.
 	event, err := registry.NotifyExitHopHtlc(
 		hash, amtPaid, testInvoiceExpiry, testCurrentHeight, hodlChan,
+		nil,
 	)
 	if err != nil {
 		t.Fatalf("expected settle to succeed but got %v", err)
@@ -392,6 +394,7 @@ func TestHoldInvoice(t *testing.T) {
 	// Test idempotency.
 	event, err = registry.NotifyExitHopHtlc(
 		hash, amtPaid, testInvoiceExpiry, testCurrentHeight, hodlChan,
+		nil,
 	)
 	if err != nil {
 		t.Fatalf("expected settle to succeed but got %v", err)
@@ -487,7 +490,7 @@ func TestUnknownInvoice(t *testing.T) {
 	hodlChan := make(chan interface{})
 	amt := lnwire.MilliSatoshi(100000)
 	_, err := registry.NotifyExitHopHtlc(
-		hash, amt, testInvoiceExpiry, testCurrentHeight, hodlChan,
+		hash, amt, testInvoiceExpiry, testCurrentHeight, hodlChan, nil,
 	)
 	if err != channeldb.ErrInvoiceNotFound {
 		t.Fatal("expected invoice not found error")