lncli+lnrpc: add payment address to sendpayment

cmd/lncli/cmd_pay.go

@@ -147,14 +147,17 @@ var sendPaymentCommand = cli.Command{
 	If payment isn't manually specified, then only a payment request needs
 	to be passed using the --pay_req argument.
 
-	If the payment *is* manually specified, then all four alternative
-	arguments need to be specified in order to complete the payment:
-	    * --dest=N
-	    * --amt=A
-	    * --final_cltv_delta=T
-	    * --payment_hash=H
+	If the payment *is* manually specified, then the following arguments
+	need to be specified in order to complete the payment:
+
+	For invoice with keysend,
+	    --dest=N --amt=A --final_cltv_delta=T --keysend
+	For invoice without payment address:
+	    --dest=N --amt=A --payment_hash=H --final_cltv_delta=T
+	For invoice with payment address:
+	    --dest=N --amt=A --payment_hash=H --final_cltv_delta=T --pay_addr=H
 	`,
-	ArgsUsage: "dest amt payment_hash final_cltv_delta | --pay_req=[payment request]",
+	ArgsUsage: "dest amt payment_hash final_cltv_delta pay_addr | --pay_req=[payment request]",
 	Flags: append(paymentFlags(),
 		cli.StringFlag{
 			Name: "dest, d",
@@ -173,6 +176,10 @@ var sendPaymentCommand = cli.Command{
 			Name:  "final_cltv_delta",
 			Usage: "the number of blocks the last hop has to reveal the preimage",
 		},
+		cli.StringFlag{
+			Name:  "pay_addr",
+			Usage: "the payment address of the generated invoice",
+		},
 		cli.BoolFlag{
 			Name:  "keysend",
 			Usage: "will generate a pre-image and encode it in the sphinx packet, a dest must be set [experimental]",
@@ -330,9 +337,28 @@ func sendPayment(ctx *cli.Context) error {
 		if err != nil {
 			return err
 		}
+		args = args.Tail()
 		req.FinalCltvDelta = int32(delta)
 	}
 
+	var payAddr []byte
+	switch {
+	case ctx.IsSet("pay_addr"):
+		payAddr, err = hex.DecodeString(ctx.String("pay_addr"))
+	case args.Present():
+		payAddr, err = hex.DecodeString(args.First())
+	}
+
+	if err != nil {
+		return err
+	}
+	// payAddr may be not required if it's a legacy invoice.
+	if len(payAddr) != 0 && len(payAddr) != 32 {
+		return fmt.Errorf("payment addr must be exactly 32 "+
+			"bytes, is instead %v", len(payAddr))
+	}
+	req.PaymentAddr = payAddr
+
 	return sendPaymentRequest(ctx, req)
 }
 

lnrpc/rpc.proto

@@ -708,6 +708,11 @@ message SendRequest {
     fallback.
     */
     repeated FeatureBit dest_features = 15;
+
+    /*
+    The payment address of the generated invoice.
+    */
+    bytes payment_addr = 16;
 }
 
 message SendResponse {

lnrpc/rpc.swagger.json

@@ -5503,6 +5503,11 @@
             "$ref": "#/definitions/lnrpcFeatureBit"
           },
           "description": "Features assumed to be supported by the final node. All transitive feature\ndependencies must also be set properly. For a given feature bit pair, either\noptional or remote may be set, but not both. If this field is nil or empty,\nthe router will try to load destination features from the graph as a\nfallback."
+        },
+        "payment_addr": {
+          "type": "string",
+          "format": "byte",
+          "description": "The payment address of the generated invoice."
         }
       }
     },

rpcserver.go

@@ -4216,6 +4216,12 @@ func (r *rpcServer) extractPaymentIntent(rpcPayReq *rpcPaymentRequest) (rpcPayme
 		return payIntent, err
 	}
 
+	// Payment address may not be needed by legacy invoices.
+	if len(rpcPayReq.PaymentAddr) != 0 && len(rpcPayReq.PaymentAddr) != 32 {
+		return payIntent, errors.New("invalid payment address length")
+	}
+	copy(payIntent.paymentAddr[:], rpcPayReq.PaymentAddr)
+
 	// Otherwise, If the payment request field was not specified
 	// (and a custom route wasn't specified), construct the payment
 	// from the other fields.