routing: use simple errors for path finding

routing/errors.go

@@ -7,18 +7,10 @@ import "github.com/go-errors/errors"
 type errorCode uint8
 
 const (
-	// ErrNoPathFound is returned when a path to the target destination
-	// does not exist in the graph.
-	ErrNoPathFound errorCode = iota
-
-	// ErrMaxHopsExceeded is returned when a candidate path is found, but
-	// the length of that path exceeds HopLimit.
-	ErrMaxHopsExceeded
-
 	// ErrTargetNotInNetwork is returned when the target of a path-finding
 	// or payment attempt isn't known to be within the current version of
 	// the channel graph.
-	ErrTargetNotInNetwork
+	ErrTargetNotInNetwork errorCode = iota
 
 	// ErrOutdated is returned when the routing update already have
 	// been applied, or a newer update is already known.

routing/pathfind.go

@@ -2,13 +2,13 @@ package routing
 
 import (
 	"container/heap"
+	"errors"
 	"fmt"
 	"math"
 	"time"
 
 	"github.com/btcsuite/btcd/btcec"
 	"github.com/coreos/bbolt"
-
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
@@ -63,6 +63,19 @@ var (
 	// DefaultAprioriHopProbability is the default a priori probability for
 	// a hop.
 	DefaultAprioriHopProbability = float64(0.6)
+
+	// errNoTlvPayload is returned when the destination hop does not support
+	// a tlv payload.
+	errNoTlvPayload = errors.New("destination hop doesn't " +
+		"understand new TLV payloads")
+
+	// errNoPathFound is returned when a path to the target destination does
+	// not exist in the graph.
+	errNoPathFound = errors.New("unable to find a path to destination")
+
+	// errMaxHopsExceeded is returned when a candidate path is found, but
+	// the length of that path exceeds HopLimit.
+	errMaxHopsExceeded = errors.New("potential path has too many hops")
 )
 
 // edgePolicyWithSource is a helper struct to keep track of the source node
@@ -347,8 +360,7 @@ func findPath(g *graphParams, r *RestrictParams, cfg *PathFindingConfig,
 				lnwire.TLVOnionPayloadOptional,
 			)
 			if !supportsTLV {
-				return nil, fmt.Errorf("destination hop doesn't " +
+				return nil, errNoTlvPayload
-					"understand new TLV paylods")
 			}
 		}
 	}
@@ -610,8 +622,7 @@ func findPath(g *graphParams, r *RestrictParams, cfg *PathFindingConfig,
 		currentNodeWithDist, ok := distance[currentNode]
 		if !ok {
 			// If the node doesnt have a next hop it means we didn't find a path.
-			return nil, newErrf(ErrNoPathFound, "unable to find a "+
+			return nil, errNoPathFound
-				"path to destination")
 		}
 
 		// Add the next hop to the list of path edges.
@@ -634,8 +645,7 @@ func findPath(g *graphParams, r *RestrictParams, cfg *PathFindingConfig,
 	// hops, then it's invalid.
 	numEdges := len(pathEdges)
 	if numEdges > HopLimit {
-		return nil, newErr(ErrMaxHopsExceeded, "potential path has "+
+		return nil, errMaxHopsExceeded
-			"too many hops")
 	}
 
 	log.Debugf("Found route: probability=%v, hops=%v, fee=%v\n",

routing/pathfind_test.go

@@ -1269,7 +1269,7 @@ func TestPathNotAvailable(t *testing.T) {
 		noRestrictions, testPathFindingConfig,
 		sourceNode.PubKeyBytes, unknownNode, 100,
 	)
-	if !IsError(err, ErrNoPathFound) {
+	if err != errNoPathFound {
 		t.Fatalf("path shouldn't have been found: %v", err)
 	}
 }
@@ -1306,7 +1306,7 @@ func TestPathInsufficientCapacity(t *testing.T) {
 		noRestrictions, testPathFindingConfig,
 		sourceNode.PubKeyBytes, target, payAmt,
 	)
-	if !IsError(err, ErrNoPathFound) {
+	if err != errNoPathFound {
 		t.Fatalf("graph shouldn't be able to support payment: %v", err)
 	}
 }
@@ -1339,7 +1339,7 @@ func TestRouteFailMinHTLC(t *testing.T) {
 		noRestrictions, testPathFindingConfig,
 		sourceNode.PubKeyBytes, target, payAmt,
 	)
-	if !IsError(err, ErrNoPathFound) {
+	if err != errNoPathFound {
 		t.Fatalf("graph shouldn't be able to support payment: %v", err)
 	}
 }
@@ -1403,7 +1403,7 @@ func TestRouteFailMaxHTLC(t *testing.T) {
 	// We'll now attempt to route through that edge with a payment above
 	// 100k msat, which should fail.
 	_, err = ctx.findPath(target, payAmt)
-	if !IsError(err, ErrNoPathFound) {
+	if err != errNoPathFound {
 		t.Fatalf("graph shouldn't be able to support payment: %v", err)
 	}
 }
@@ -1491,7 +1491,7 @@ func TestRouteFailDisabledEdge(t *testing.T) {
 		noRestrictions, testPathFindingConfig,
 		sourceNode.PubKeyBytes, target, payAmt,
 	)
-	if !IsError(err, ErrNoPathFound) {
+	if err != errNoPathFound {
 		t.Fatalf("graph shouldn't be able to support payment: %v", err)
 	}
 }
@@ -1549,7 +1549,7 @@ func TestPathSourceEdgesBandwidth(t *testing.T) {
 		noRestrictions, testPathFindingConfig,
 		sourceNode.PubKeyBytes, target, payAmt,
 	)
-	if !IsError(err, ErrNoPathFound) {
+	if err != errNoPathFound {
 		t.Fatalf("graph shouldn't be able to support payment: %v", err)
 	}
 
@@ -1971,7 +1971,7 @@ func testCltvLimit(t *testing.T, limit uint32, expectedChannel uint64) {
 	path, err := ctx.findPath(target, paymentAmt)
 	if expectedChannel == 0 {
 		// Finish test if we expect no route.
-		if IsError(err, ErrNoPathFound) {
+		if err == errNoPathFound {
 			return
 		}
 		t.Fatal("expected no path to be found")
@@ -2137,7 +2137,7 @@ func testProbabilityRouting(t *testing.T, p10, p11, p20, minProbability float64,
 
 	path, err := ctx.findPath(target, paymentAmt)
 	if expectedChan == 0 {
-		if err == nil || !IsError(err, ErrNoPathFound) {
+		if err != errNoPathFound {
 			t.Fatalf("expected no path found, but got %v", err)
 		}
 		return