htlcswitch: use fat errors as a sender

Author: joostjager

channeldb/payments.go

@@ -1176,6 +1176,12 @@ func serializeHop(w io.Writer, h *route.Hop) error {
 		records = append(records, record.NewMetadataRecord(&h.Metadata))
 	}
 
+	// Signal attributable errors.
+	if h.AttrError {
+		attrError := record.NewAttributableError()
+		records = append(records, attrError.Record())
+	}
+
 	// Final sanity check to absolutely rule out custom records that are not
 	// custom and write into the standard range.
 	if err := h.CustomRecords.Validate(); err != nil {
@@ -1297,6 +1303,13 @@ func deserializeHop(r io.Reader) (*route.Hop, error) {
 		h.Metadata = metadata
 	}
 
+	attributableErrorType := uint64(record.AttributableErrorOnionType)
+	if _, ok := tlvMap[attributableErrorType]; ok {
+		delete(tlvMap, attributableErrorType)
+
+		h.AttrError = true
+	}
+
 	h.CustomRecords = tlvMap
 
 	return h, nil

htlcswitch/failure.go

@@ -2,13 +2,17 @@ package htlcswitch
 
 import (
 	"bytes"
+	"encoding/binary"
 	"fmt"
+	"strings"
 
 	sphinx "github.com/lightningnetwork/lightning-onion"
 	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
+var byteOrder = binary.BigEndian
+
 // ClearTextError is an interface which is implemented by errors that occur
 // when we know the underlying wire failure message. These errors are the
 // opposite to opaque errors which are onion-encrypted blobs only understandable
@@ -166,7 +170,25 @@ type OnionErrorDecrypter interface {
 // SphinxErrorDecrypter wraps the sphinx data SphinxErrorDecrypter and maps the
 // returned errors to concrete lnwire.FailureMessage instances.
 type SphinxErrorDecrypter struct {
-	OnionErrorDecrypter
+	decrypter interface{}
+}
+
+// NewSphinxErrorDecrypter instantiates a new error decryptor.
+func NewSphinxErrorDecrypter(circuit *sphinx.Circuit,
+	attrError bool) *SphinxErrorDecrypter {
+
+	var decrypter interface{}
+	if !attrError {
+		decrypter = sphinx.NewOnionErrorDecrypter(circuit)
+	} else {
+		decrypter = sphinx.NewOnionAttrErrorDecrypter(
+			circuit, hop.AttrErrorStruct,
+		)
+	}
+
+	return &SphinxErrorDecrypter{
+		decrypter: decrypter,
+	}
 }
 
 // DecryptError peels off each layer of onion encryption from the first hop, to
@@ -177,9 +199,42 @@ type SphinxErrorDecrypter struct {
 func (s *SphinxErrorDecrypter) DecryptError(reason lnwire.OpaqueReason) (
 	*ForwardingError, error) {
 
-	failure, err := s.OnionErrorDecrypter.DecryptError(reason)
-	if err != nil {
-		return nil, err
+	var failure *sphinx.DecryptedError
+
+	switch decrypter := s.decrypter.(type) {
+	case OnionErrorDecrypter:
+		legacyError, err := decrypter.DecryptError(reason)
+		if err != nil {
+			return nil, err
+		}
+
+		failure = legacyError
+
+	case *sphinx.OnionAttrErrorDecrypter:
+		attributableError, err := decrypter.DecryptError(reason)
+		if err != nil {
+			return nil, err
+		}
+
+		// Log hold times.
+		//
+		// TODO: Use to penalize nodes.
+		var holdTimes []string
+		for _, payload := range attributableError.Payloads {
+			// Read hold time.
+			holdTimeMs := byteOrder.Uint32(payload)
+
+			holdTimes = append(
+				holdTimes,
+				fmt.Sprintf("%v", holdTimeMs),
+			)
+		}
+		log.Debugf("Hold times: %v", strings.Join(holdTimes, "/"))
+
+		failure = &attributableError.DecryptedError
+
+	default:
+		panic("unexpected decrypter type")
 	}
 
 	// Decode the failure. If an error occurs, we leave the failure message

htlcswitch/failure_test.go

@@ -52,7 +52,7 @@ func TestLongFailureMessage(t *testing.T) {
 	}
 
 	errorDecryptor := &SphinxErrorDecrypter{
-		OnionErrorDecrypter: sphinx.NewOnionErrorDecrypter(circuit),
+		decrypter: sphinx.NewOnionErrorDecrypter(circuit),
 	}
 
 	// Assert that the failure message can still be extracted.

htlcswitch/switch_test.go

@@ -3253,7 +3253,7 @@ func TestInvalidFailure(t *testing.T) {
 	// Get payment result from switch. We expect an unreadable failure
 	// message error.
 	deobfuscator := SphinxErrorDecrypter{
-		OnionErrorDecrypter: &mockOnionErrorDecryptor{
+		decrypter: &mockOnionErrorDecryptor{
 			err: ErrUnreadableFailureMessage,
 		},
 	}
@@ -3278,7 +3278,7 @@ func TestInvalidFailure(t *testing.T) {
 	// Modify the decryption to simulate that decryption went alright, but
 	// the failure cannot be decoded.
 	deobfuscator = SphinxErrorDecrypter{
-		OnionErrorDecrypter: &mockOnionErrorDecryptor{
+		decrypter: &mockOnionErrorDecryptor{
 			sourceIdx: 2,
 			message:   []byte{200},
 		},

itest/lnd_multi-hop-error-propagation_test.go

@@ -2,23 +2,53 @@ package itest
 
 import (
 	"math"
+	"testing"
 
+	"github.com/btcsuite/btcd/btcutil"
 	"github.com/lightningnetwork/lnd/funding"
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/routerrpc"
 	"github.com/lightningnetwork/lnd/lntest"
+	"github.com/lightningnetwork/lnd/lntest/node"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/stretchr/testify/require"
 )
 
 func testHtlcErrorPropagation(ht *lntest.HarnessTest) {
+	ht.Run("legacy error", func(tt *testing.T) {
+		st := ht.Subtest(tt)
+		st.EnsureConnected(st.Alice, st.Bob)
+
+		// Test legacy errors using the standby node.
+		testHtlcErrorPropagationWithNode(st, st.Alice)
+	})
+
+	ht.Run("attr error", func(tt *testing.T) {
+		st := ht.Subtest(tt)
+
+		// Create a different Alice node with attributable
+		// errors enabled. Alice will signal to Bob and Carol to
+		// return attributable errors to her.
+		alice := st.NewNode("Alice", []string{"--routerrpc.attrerrors"})
+		st.FundCoins(btcutil.SatoshiPerBitcoin, alice)
+
+		st.ConnectNodes(alice, st.Bob)
+
+		testHtlcErrorPropagationWithNode(st, alice)
+
+		st.Shutdown(alice)
+	})
+}
+
+func testHtlcErrorPropagationWithNode(ht *lntest.HarnessTest,
+	alice *node.HarnessNode) {
+
 	// In this test we wish to exercise the daemon's correct parsing,
 	// handling, and propagation of errors that occur while processing a
 	// multi-hop payment.
 	const chanAmt = funding.MaxBtcFundingAmount
 
-	alice, bob := ht.Alice, ht.Bob
-
+	bob := ht.Bob
 	// Since we'd like to test some multi-hop failure scenarios, we'll
 	// introduce another node into our test network: Carol.
 	carol := ht.NewNode("Carol", nil)

lnrpc/routerrpc/config.go

@@ -87,5 +87,6 @@ func GetRoutingConfig(cfg *Config) *RoutingConfig {
 			NodeWeight: cfg.BimodalConfig.NodeWeight,
 			DecayTime:  cfg.BimodalConfig.DecayTime,
 		},
+		AttrErrors: cfg.AttrErrors,
 	}
 }

lnrpc/routerrpc/routing_config.go

@@ -41,6 +41,10 @@ type RoutingConfig struct {
 
 	// BimodalConfig defines parameters for the bimodal probability.
 	BimodalConfig *BimodalConfig `group:"bimodal" namespace:"bimodal" description:"configuration for the bimodal pathfinding probability estimator"`
+
+	// AttrErrors indicates whether attributable errors should be requested
+	// if the whole route supports it.
+	AttrErrors bool `long:"attrerrors" description:"request attributable errors if the whole route supports it"`
 }
 
 // AprioriConfig defines parameters for the apriori probability.

routing/pathfind.go

@@ -11,6 +11,7 @@ import (
 	sphinx "github.com/lightningnetwork/lightning-onion"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/feature"
+	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/record"
 	"github.com/lightningnetwork/lnd/routing/route"
@@ -105,6 +106,36 @@ type finalHopParams struct {
 	metadata []byte
 }
 
+// useAttrErrors returns true if the path can use attributable errors.
+func useAttrErrors(pathEdges []*channeldb.CachedEdgePolicy) bool {
+	// Use legacy errors if the route length exceeds the maximum number of
+	// hops for attributable errors.
+	if len(pathEdges) > hop.AttrErrorStruct.HopCount() {
+		return false
+	}
+
+	// Every node along the path must signal support for attributable
+	// errors.
+	for _, edge := range pathEdges {
+		// Get the node features.
+		toFeat := edge.ToNodeFeatures
+
+		// If there are no features known, assume the node cannot handle
+		// attributable errors.
+		if toFeat == nil {
+			return false
+		}
+
+		// If the node does not signal support for attributable errors,
+		// do not use them.
+		if !toFeat.HasFeature(lnwire.AttributableErrorsOptional) {
+			return false
+		}
+	}
+
+	return true
+}
+
 // newRoute constructs a route using the provided path and final hop constraints.
 // Any destination specific fields from the final hop params  will be attached
 // assuming the destination's feature vector signals support, otherwise this
@@ -117,7 +148,7 @@ type finalHopParams struct {
 // dependencies.
 func newRoute(sourceVertex route.Vertex,
 	pathEdges []*channeldb.CachedEdgePolicy, currentHeight uint32,
-	finalHop finalHopParams) (*route.Route, error) {
+	finalHop finalHopParams, attrErrors bool) (*route.Route, error) {
 
 	var (
 		hops []*route.Hop
@@ -134,6 +165,9 @@ func newRoute(sourceVertex route.Vertex,
 		nextIncomingAmount lnwire.MilliSatoshi
 	)
 
+	// Use attributable errors if enabled and supported by the route.
+	attributableErrors := attrErrors && useAttrErrors(pathEdges)
+
 	pathLength := len(pathEdges)
 	for i := pathLength - 1; i >= 0; i-- {
 		// Now we'll start to calculate the items within the per-hop
@@ -250,6 +284,7 @@ func newRoute(sourceVertex route.Vertex,
 			CustomRecords:    customRecords,
 			MPP:              mpp,
 			Metadata:         metadata,
+			AttrError:        attributableErrors,
 		}
 
 		hops = append([]*route.Hop{currentHop}, hops...)
@@ -371,6 +406,10 @@ type PathFindingConfig struct {
 	// MinProbability defines the minimum success probability of the
 	// returned route.
 	MinProbability float64
+
+	// AttrErrors indicates whether we should use the new attributable
+	// errors if the nodes on the route allow it.
+	AttrErrors bool
 }
 
 // getOutgoingBalance returns the maximum available balance in any of the

routing/pathfind_test.go

@@ -959,6 +959,7 @@ func runFindLowestFeePath(t *testing.T, useCache bool) {
 			cltvDelta: finalHopCLTV,
 			records:   nil,
 		},
+		false,
 	)
 	require.NoError(t, err, "unable to create path")
 
@@ -1101,6 +1102,7 @@ func testBasicGraphPathFindingCase(t *testing.T, graphInstance *testGraphInstanc
 			cltvDelta: finalHopCLTV,
 			records:   nil,
 		},
+		false,
 	)
 	require.NoError(t, err, "unable to create path")
 
@@ -1639,6 +1641,7 @@ func TestNewRoute(t *testing.T) {
 					paymentAddr: testCase.paymentAddr,
 					metadata:    testCase.metadata,
 				},
+				false,
 			)
 
 			if testCase.expectError {
@@ -2641,6 +2644,7 @@ func testCltvLimit(t *testing.T, useCache bool, limit uint32,
 			cltvDelta: finalHopCLTV,
 			records:   nil,
 		},
+		false,
 	)
 	require.NoError(t, err, "unable to create path")
 
@@ -2964,6 +2968,7 @@ func runNoCycle(t *testing.T, useCache bool) {
 			cltvDelta: finalHopCLTV,
 			records:   nil,
 		},
+		false,
 	)
 	require.NoError(t, err, "unable to create path")
 

routing/payment_lifecycle.go

@@ -7,7 +7,6 @@ import (
 
 	"github.com/btcsuite/btcd/btcec/v2"
 	"github.com/davecgh/go-spew/spew"
-	sphinx "github.com/lightningnetwork/lightning-onion"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/htlcswitch"
 	"github.com/lightningnetwork/lnd/lntypes"
@@ -556,11 +555,14 @@ func (p *shardHandler) collectResult(attempt *channeldb.HTLCAttemptInfo) (
 	}
 
 	// Using the created circuit, initialize the error decrypter so we can
-	// parse+decode any failures incurred by this payment within the
-	// switch.
-	errorDecryptor := &htlcswitch.SphinxErrorDecrypter{
-		OnionErrorDecrypter: sphinx.NewOnionErrorDecrypter(circuit),
-	}
+	// parse+decode any failures incurred by this payment within the switch.
+	//
+	// The resolution format to use for the decryption is based on the
+	// instruction that we gave to the first hop.
+	attrError := attempt.Route.Hops[0].AttrError
+	errorDecryptor := htlcswitch.NewSphinxErrorDecrypter(
+		circuit, attrError,
+	)
 
 	// Now ask the switch to return the result of the payment when
 	// available.

routing/payment_session.go

@@ -391,6 +391,7 @@ func (p *paymentSession) RequestRoute(maxAmt, feeLimit lnwire.MilliSatoshi,
 				paymentAddr: p.payment.PaymentAddr,
 				metadata:    p.payment.Metadata,
 			},
+			p.pathFindingConfig.AttrErrors,
 		)
 		if err != nil {
 			return nil, err