lncli: Add --route_hints flag support

Adds --route_hints flag to sendpayment.
Hints should be JSON encoded (see usage for example).

Adds --route_hints flag to queryroutes.
Errors if blinded paths are set.

cmd/commands/cmd_payments.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"crypto/rand"
 	"encoding/hex"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -254,6 +255,15 @@ var SendPaymentCommand = cli.Command{
 			Name:  "keysend",
 			Usage: "will generate a pre-image and encode it in the sphinx packet, a dest must be set [experimental]",
 		},
+		cli.StringFlag{
+			Name: "route_hints",
+			Usage: `route hints for sending through private ` +
+				`channels. eg: ` +
+				`'[{"hop_hints":[{"node_id":"A","chan_id":1,` +
+				`"fee_base_msat":2,` +
+				`"fee_proportional_millionths":3,` +
+				`"cltv_expiry_delta":4}]}]'`,
+		},
 	),
 	Action: SendPayment,
 }
@@ -473,6 +483,20 @@ func SendPayment(ctx *cli.Context) error {
 
 	req.PaymentAddr = payAddr
 
+	if ctx.IsSet("route_hints") {
+		// Parse the route hints JSON.
+		routeHintsJSON := ctx.String("route_hints")
+		var routeHints []*lnrpc.RouteHint
+
+		err := json.Unmarshal([]byte(routeHintsJSON), &routeHints)
+		if err != nil {
+			return fmt.Errorf("error unmarshaling route_hints "+
+				"json: %w", err)
+		}
+
+		req.RouteHints = routeHints
+	}
+
 	return SendPaymentRequest(ctx, req, conn, conn, routerRPCSendPayment)
 }
 
@@ -1154,6 +1178,15 @@ var queryRoutesCommand = cli.Command{
 		blindedBaseFlag,
 		blindedPPMFlag,
 		blindedCLTVFlag,
+		cli.StringFlag{
+			Name: "route_hints",
+			Usage: `route hints for searching through private ` +
+				`channels (and no blinded paths set). eg: ` +
+				`'[{"hop_hints":[{"node_id":"A","chan_id":1,` +
+				`"fee_base_msat":2,` +
+				`"fee_proportional_millionths":3,` +
+				`"cltv_expiry_delta":4}]}]'`,
+		},
 	},
 	Action: actionDecorator(queryRoutes),
 }
@@ -1248,6 +1281,23 @@ func queryRoutes(ctx *cli.Context) error {
 		BlindedPaymentPaths: blindedRoutes,
 	}
 
+	if ctx.IsSet("route_hints") {
+		if len(blindedRoutes) > 0 {
+			return fmt.Errorf("--route_hints should not be used " +
+				"if blinded paths are set")
+		}
+		routeHintsJSON := ctx.String("route_hints")
+		var routeHints []*lnrpc.RouteHint
+
+		err := json.Unmarshal([]byte(routeHintsJSON), &routeHints)
+		if err != nil {
+			return fmt.Errorf("error unmarshaling route_hints "+
+				"json: %w", err)
+		}
+
+		req.RouteHints = routeHints
+	}
+
 	route, err := client.QueryRoutes(ctxc, req)
 	if err != nil {
 		return err