Add the option on path creator to specify the incoming channel on blinded path

cmd/commands/cmd_invoice.go

@@ -4,6 +4,7 @@ import (
 	"encoding/hex"
 	"fmt"
 	"strconv"
+	"strings"
 
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/urfave/cli"
@@ -116,6 +117,12 @@ var AddInvoiceCommand = cli.Command{
 				"use on a blinded path. The flag may be " +
 				"specified multiple times.",
 		},
+		cli.StringFlag{
+			Name: "blinded_path_incoming_channel_list",
+			Usage: "The chained channels specified via channel " +
+				"id (separated by commas), starting from a " +
+				"channel which points to the self node.",
+		},
 	},
 	Action: actionDecorator(addInvoice),
 }
@@ -202,7 +209,8 @@ func parseBlindedPathCfg(ctx *cli.Context) (*lnrpc.BlindedPathConfig, error) {
 		if ctx.IsSet("min_real_blinded_hops") ||
 			ctx.IsSet("num_blinded_hops") ||
 			ctx.IsSet("max_blinded_paths") ||
-			ctx.IsSet("blinded_path_omit_node") {
+			ctx.IsSet("blinded_path_omit_node") ||
+			ctx.IsSet("blinded_path_incoming_channel_list") {
 
 			return nil, fmt.Errorf("blinded path options are " +
 				"only used if the `--blind` options is set")
@@ -239,6 +247,21 @@ func parseBlindedPathCfg(ctx *cli.Context) (*lnrpc.BlindedPathConfig, error) {
 		)
 	}
 
+	if ctx.IsSet("blinded_path_incoming_channel_list") {
+		channels := strings.Split(
+			ctx.String("blinded_path_incoming_channel_list"), ",",
+		)
+		for _, channelID := range channels {
+			chanID, err := strconv.ParseUint(channelID, 10, 64)
+			if err != nil {
+				return nil, err
+			}
+			blindCfg.IncomingChannelList = append(
+				blindCfg.IncomingChannelList, chanID,
+			)
+		}
+	}
+
 	return &blindCfg, nil
 }
 

docs/release-notes/release-notes-0.20.0.md

@@ -26,6 +26,13 @@
 
 ## RPC Additions
 
+* The `lncli addinvoice --blind` command now has the option to include a
+  [chained channels](https://github.com/lightningnetwork/lnd/pull/9127)
+  incoming list `--blinded_path_incoming_channel_list` which gives users the 
+  control of specifying the channels they prefer to receive the payment on. With
+  the option to specify multiple channels this control can be extended to
+  multiple hops leading to the node.
+
 ## lncli Additions
 
 # Improvements
@@ -72,3 +79,5 @@
 ## Tooling and Documentation
 
 # Contributors (Alphabetical Order)
+
+Pins

itest/list_on_test.go

@@ -699,6 +699,10 @@ var allTestCases = []*lntest.TestCase{
 		Name:     "bump fee low budget",
 		TestFunc: testBumpFeeLowBudget,
 	},
+	{
+		Name:     "partially specified route blinded invoice",
+		TestFunc: testPartiallySpecifiedBlindedPath,
+	},
 }
 
 // appendPrefixed is used to add a prefix to each test name in the subtests

itest/lnd_route_blinding_test.go

@@ -1420,3 +1420,179 @@ func testBlindedPaymentHTLCReForward(ht *lntest.HarnessTest) {
 		require.Fail(ht, "timeout waiting for sending payment")
 	}
 }
+
+// testPartiallySpecifiedBlindedPath tests lnd's ability to:
+//   - Assert the error when attempting to create a blinded payment with an
+//     invalid partially specified path.
+//   - Create a blinded payment path when the blinded path is partially
+//     pre-specified.
+func testPartiallySpecifiedBlindedPath(ht *lntest.HarnessTest) {
+	// Create a six hop network:
+	// Alice -> Bob -> Carol -> Dave -> Eve -> Frank.
+	chanAmt := btcutil.Amount(100000)
+	cfgs := [][]string{nil, nil, nil, nil, nil, nil}
+	chanPoints, nodes := ht.CreateSimpleNetwork(
+		cfgs, lntest.OpenChannelParams{Amt: chanAmt},
+	)
+
+	alice, bob, carol, dave, eve := nodes[0], nodes[1], nodes[2], nodes[3],
+		nodes[4]
+
+	chanPointAliceBob, chanPointBobCarol, chanPointCarolDave :=
+		chanPoints[0], chanPoints[1], chanPoints[2]
+
+	// Lookup full channel info so that we have channel ids for our route.
+	aliceBobChan := ht.GetChannelByChanPoint(alice, chanPointAliceBob)
+	bobCarolChan := ht.GetChannelByChanPoint(bob, chanPointBobCarol)
+	carolDaveChan := ht.GetChannelByChanPoint(carol, chanPointCarolDave)
+
+	// Let carol set no incoming channel restrictions.
+	var (
+		minNumRealHops uint32 = 1
+		numHops        uint32 = 1
+	)
+	invoice := carol.RPC.AddInvoice(&lnrpc.Invoice{
+		Memo:      "test",
+		ValueMsat: 10_000_000,
+		IsBlinded: true,
+		BlindedPathConfig: &lnrpc.BlindedPathConfig{
+			MinNumRealHops: &minNumRealHops,
+			NumHops:        &numHops,
+		},
+	})
+
+	introNodesFound := make([][]byte, 0)
+	introNodesExpected := [][]byte{bob.PubKey[:], dave.PubKey[:]}
+
+	// Assert that it contains two blinded path with only 2 hops each one.
+	payReq := carol.RPC.DecodePayReq(invoice.PaymentRequest)
+	require.Len(ht, payReq.BlindedPaths, 2)
+	path := payReq.BlindedPaths[0].BlindedPath
+	require.Len(ht, path.BlindedHops, 2)
+	introNodesFound = append(introNodesFound, path.IntroductionNode)
+	path = payReq.BlindedPaths[1].BlindedPath
+	require.Len(ht, path.BlindedHops, 2)
+	introNodesFound = append(introNodesFound, path.IntroductionNode)
+
+	// Assert the introduction nodes without caring about the routes order.
+	require.ElementsMatch(ht, introNodesExpected, introNodesFound)
+
+	// Let carol choose the wrong incoming channel.
+	var (
+		incomingChannelList = []uint64{aliceBobChan.ChanId}
+	)
+
+	err := fmt.Sprintf("incoming channel %v is not seen as owned by node",
+		aliceBobChan.ChanId)
+
+	carol.RPC.AddInvoiceAssertErr(
+		&lnrpc.Invoice{
+			Memo:      "test",
+			ValueMsat: 10_000_000,
+			IsBlinded: true,
+			BlindedPathConfig: &lnrpc.BlindedPathConfig{
+				MinNumRealHops:      &minNumRealHops,
+				NumHops:             &numHops,
+				IncomingChannelList: incomingChannelList,
+			},
+		},
+		err,
+	)
+
+	// Let Carol set the incoming channel list greater than minimum number
+	// of real hops.
+	incomingChannelList = []uint64{aliceBobChan.ChanId, bobCarolChan.ChanId}
+	err = fmt.Sprintf("minimum number of blinded path hops (%d) must be "+
+		"greater than or equal to the number of hops specified on "+
+		"the chained channels (%d)", minNumRealHops,
+		len(incomingChannelList),
+	)
+
+	carol.RPC.AddInvoiceAssertErr(
+		&lnrpc.Invoice{
+			Memo:      "test",
+			ValueMsat: 10_000_000,
+			IsBlinded: true,
+			BlindedPathConfig: &lnrpc.BlindedPathConfig{
+				MinNumRealHops:      &minNumRealHops,
+				NumHops:             &numHops,
+				IncomingChannelList: incomingChannelList,
+			},
+		},
+		err,
+	)
+
+	// Let Carol choose an incoming channel that points to a node in the
+	// omission set.
+	incomingChannelList = []uint64{bobCarolChan.ChanId}
+	var nodeOmissionList [][]byte
+	nodeOmissionList = append(nodeOmissionList, bob.PubKey[:])
+
+	err = fmt.Sprintf("cannot simultaneously be included in the omission " +
+		"set and in the partially specified path",
+	)
+
+	carol.RPC.AddInvoiceAssertErr(
+		&lnrpc.Invoice{
+			Memo:      "test",
+			ValueMsat: 10_000_000,
+			IsBlinded: true,
+			BlindedPathConfig: &lnrpc.BlindedPathConfig{
+				MinNumRealHops:      &minNumRealHops,
+				NumHops:             &numHops,
+				IncomingChannelList: incomingChannelList,
+				NodeOmissionList:    nodeOmissionList,
+			},
+		},
+		err,
+	)
+
+	// Let carol restrict bob as incoming channel.
+	incomingChannelList = []uint64{bobCarolChan.ChanId}
+
+	invoice = carol.RPC.AddInvoice(&lnrpc.Invoice{
+		Memo:      "test",
+		ValueMsat: 10_000_000,
+		IsBlinded: true,
+		BlindedPathConfig: &lnrpc.BlindedPathConfig{
+			MinNumRealHops:      &minNumRealHops,
+			NumHops:             &numHops,
+			IncomingChannelList: incomingChannelList,
+		},
+	})
+
+	// Assert that it contains a single blinded path with only
+	// 2 hops, with bob as the introduction node.
+	payReq = carol.RPC.DecodePayReq(invoice.PaymentRequest)
+	require.Len(ht, payReq.BlindedPaths, 1)
+	path = payReq.BlindedPaths[0].BlindedPath
+	require.Len(ht, path.BlindedHops, 2)
+	require.EqualValues(ht, path.IntroductionNode, bob.PubKey[:])
+
+	// Now let alice pay the invoice.
+	ht.CompletePaymentRequests(alice, []string{invoice.PaymentRequest})
+
+	// Let carol restrict dave as incoming channel and max Hops as 2
+	numHops = 2
+	incomingChannelList = []uint64{carolDaveChan.ChanId}
+
+	invoice = carol.RPC.AddInvoice(&lnrpc.Invoice{
+		Memo:      "test",
+		ValueMsat: 10_000_000,
+		IsBlinded: true,
+		BlindedPathConfig: &lnrpc.BlindedPathConfig{
+			MinNumRealHops:      &minNumRealHops,
+			NumHops:             &numHops,
+			IncomingChannelList: incomingChannelList,
+		},
+	})
+
+	// Assert that it contains one path with 3 hops, with dave as the
+	// introduction node. The path alice -> bob -> carol is discarded
+	// because alice is a dead-end.
+	payReq = carol.RPC.DecodePayReq(invoice.PaymentRequest)
+	require.Len(ht, payReq.BlindedPaths, 1)
+	path = payReq.BlindedPaths[0].BlindedPath
+	require.Len(ht, path.BlindedHops, 3)
+	require.EqualValues(ht, path.IntroductionNode, eve.PubKey[:])
+}

lncfg/routing.go

@@ -34,6 +34,10 @@ func (r *Routing) Validate() error {
 			"number of hops expected to be included in each path")
 	}
 
+	if r.BlindedPaths.MaxNumPaths == 0 {
+		return fmt.Errorf("blinded max num paths cannot be 0")
+	}
+
 	if r.BlindedPaths.PolicyIncreaseMultiplier < 1 {
 		return fmt.Errorf("the blinded route policy increase " +
 			"multiplier must be greater than or equal to 1")

lnrpc/invoicesrpc/invoices.swagger.json

@@ -534,6 +534,14 @@
             "format": "byte"
           },
           "description": "A list of node IDs of nodes that should not be used in any of our generated\nblinded paths."
+        },
+        "incoming_channel_list": {
+          "type": "array",
+          "items": {
+            "type": "string",
+            "format": "uint64"
+          },
+          "description": "The chained channels list specified via channel id (separated by commas),\nstarting from a channel owned by the receiver node."
         }
       }
     },