Use all valid routes during blinded path construction

lnrpc/invoicesrpc/addinvoice.go

@@ -179,6 +179,9 @@ type BlindedPathConfig struct {
 	// less than this.
 	MinNumPathHops uint8
 
+	// MaxNumPaths is the maximum number of blinded paths to select.
+	MaxNumPaths uint8
+
 	// DefaultDummyHopPolicy holds the default policy values to use for
 	// dummy hops in a blinded path in the case where they cant be derived
 	// through other means.
@@ -542,6 +545,7 @@ func AddInvoice(ctx context.Context, cfg *AddInvoiceConfig,
 				},
 				MinNumHops:            blindCfg.MinNumPathHops,
 				DefaultDummyHopPolicy: blindCfg.DefaultDummyHopPolicy,
+				MaxNumPaths:           blindCfg.MaxNumPaths,
 			},
 		)
 		if err != nil {

routing/blindedpath/blinded_path.go

@@ -100,6 +100,9 @@ type BuildBlindedPathCfg struct {
 	// route.
 	MinNumHops uint8
 
+	// MaxNumPaths is the maximum number of blinded paths to select.
+	MaxNumPaths uint8
+
 	// DefaultDummyHopPolicy holds the policy values that should be used for
 	// dummy hops in the cases where it cannot be derived via other means
 	// such as averaging the policy values of other hops on the path. This
@@ -132,8 +135,11 @@ func BuildBlindedPaymentPaths(cfg *BuildBlindedPathCfg) (
 	paths := make([]*zpay32.BlindedPaymentPath, 0, len(routes))
 
 	// For each route returned, we will construct the associated blinded
-	// payment path.
+	// payment path, until the maximum number of allowed paths.
 	for _, route := range routes {
+		if len(paths) >= int(cfg.MaxNumPaths) {
+			break
+		}
 		// Extract the information we need from the route.
 		candidatePath := extractCandidatePath(route)
 

routing/router.go

@@ -698,18 +698,13 @@ func (r *ChannelRouter) FindBlindedPaths(destination route.Vertex,
 		return routes[i].probability > routes[j].probability
 	})
 
-	// Now just choose the best paths up until the maximum number of allowed
-	// paths.
-	bestRoutes := make([]*route.Route, 0, restrictions.MaxNumPaths)
+	// Return all routes.
+	allRoutes := make([]*route.Route, 0, len(routes))
 	for _, route := range routes {
-		if len(bestRoutes) >= int(restrictions.MaxNumPaths) {
-			break
-		}
-
-		bestRoutes = append(bestRoutes, route.route)
+		allRoutes = append(allRoutes, route.route)
 	}
 
-	return bestRoutes, nil
+	return allRoutes, nil
 }
 
 // generateNewSessionKey generates a new ephemeral private key to be used for a

routing/router_test.go

@@ -3167,7 +3167,6 @@ func TestFindBlindedPathsWithMC(t *testing.T) {
 		dave, 1000, probabilitySrc, &BlindedPathRestrictions{
 			MinDistanceFromIntroNode: 2,
 			NumHops:                  2,
-			MaxNumPaths:              3,
 		},
 	)
 	require.NoError(t, err)
@@ -3201,8 +3200,7 @@ func TestFindBlindedPathsWithMC(t *testing.T) {
 	}
 
 	// Now, let's lower the MC probability of the B-D to 0.5 and F-D link to
-	// 0.25. We will leave the MaxNumPaths as 3 and so all paths should
-	// still be returned but the order should be:
+	// 0.25:
 	// 1) A -> C -> D
 	// 2) A -> B -> D
 	// 3) A -> F -> D
@@ -3212,7 +3210,6 @@ func TestFindBlindedPathsWithMC(t *testing.T) {
 		dave, 1000, probabilitySrc, &BlindedPathRestrictions{
 			MinDistanceFromIntroNode: 2,
 			NumHops:                  2,
-			MaxNumPaths:              3,
 		},
 	)
 	require.NoError(t, err)
@@ -3229,7 +3226,6 @@ func TestFindBlindedPathsWithMC(t *testing.T) {
 		dave, 1000, probabilitySrc, &BlindedPathRestrictions{
 			MinDistanceFromIntroNode: 2,
 			NumHops:                  2,
-			MaxNumPaths:              3,
 		},
 	)
 	require.NoError(t, err)
@@ -3239,27 +3235,12 @@ func TestFindBlindedPathsWithMC(t *testing.T) {
 		"alice,charlie,dave",
 	})
 
-	// Change the MaxNumPaths to 1 to assert that only the best route is
-	// returned.
-	routes, err = ctx.router.FindBlindedPaths(
-		dave, 1000, probabilitySrc, &BlindedPathRestrictions{
-			MinDistanceFromIntroNode: 2,
-			NumHops:                  2,
-			MaxNumPaths:              1,
-		},
-	)
-	require.NoError(t, err)
-	assertPaths(routes, []string{
-		"alice,bob,dave",
-	})
-
 	// Test the edge case where Dave, the recipient, is also the
 	// introduction node.
 	routes, err = ctx.router.FindBlindedPaths(
 		dave, 1000, probabilitySrc, &BlindedPathRestrictions{
 			MinDistanceFromIntroNode: 0,
 			NumHops:                  0,
-			MaxNumPaths:              1,
 		},
 	)
 	require.NoError(t, err)
@@ -3274,7 +3255,6 @@ func TestFindBlindedPathsWithMC(t *testing.T) {
 		dave, 1000, probabilitySrc, &BlindedPathRestrictions{
 			MinDistanceFromIntroNode: 2,
 			NumHops:                  2,
-			MaxNumPaths:              3,
 		},
 	)
 	require.NoError(t, err)
@@ -3289,7 +3269,6 @@ func TestFindBlindedPathsWithMC(t *testing.T) {
 		dave, 1000, probabilitySrc, &BlindedPathRestrictions{
 			MinDistanceFromIntroNode: 2,
 			NumHops:                  2,
-			MaxNumPaths:              3,
 			NodeOmissionSet:          fn.NewSet(frank),
 		},
 	)

rpcserver.go

@@ -6168,6 +6168,7 @@ func (r *rpcServer) AddInvoice(ctx context.Context,
 				MaxHTLCMsat: 0,
 			},
 			MinNumPathHops: blindingRestrictions.NumHops,
+			MaxNumPaths:    blindingRestrictions.MaxNumPaths,
 		}
 	}