htlcswitch: expose custom records on intercepted packet

htlcswitch/interceptable_switch.go

@@ -127,6 +127,7 @@ func (f *interceptedForward) Packet() InterceptedPacket {
 		OutgoingAmount: f.htlc.Amount,
 		IncomingAmount: f.packet.incomingAmount,
 		IncomingExpiry: f.packet.incomingTimeout,
+		CustomRecords:  f.packet.customRecords,
 	}
 }
 

htlcswitch/interfaces.go

@@ -8,6 +8,7 @@ import (
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/lightningnetwork/lnd/record"
 )
 
 // InvoiceDatabase is an interface which represents the persistent subsystem
@@ -226,6 +227,10 @@ type InterceptedPacket struct {
 
 	// IncomingAmount is the amount of the accepted htlc.
 	IncomingAmount lnwire.MilliSatoshi
+
+	// CustomRecords are user-defined records in the custom type range that
+	// were included in the payload.
+	CustomRecords record.CustomSet
 }
 
 // InterceptedForward is passed to the ForwardInterceptor for every forwarded

htlcswitch/link.go

@@ -2731,6 +2731,7 @@ func (l *channelLink) processRemoteAdds(fwdPkg *channeldb.FwdPkg,
 					obfuscator:      obfuscator,
 					incomingTimeout: pd.Timeout,
 					outgoingTimeout: fwdInfo.OutgoingCTLV,
+					customRecords:   pld.CustomRecords(),
 				}
 				switchPackets = append(
 					switchPackets, updatePacket,
@@ -2794,6 +2795,7 @@ func (l *channelLink) processRemoteAdds(fwdPkg *channeldb.FwdPkg,
 					obfuscator:      obfuscator,
 					incomingTimeout: pd.Timeout,
 					outgoingTimeout: fwdInfo.OutgoingCTLV,
+					customRecords:   pld.CustomRecords(),
 				}
 
 				fwdPkg.FwdFilter.Set(idx)

htlcswitch/packet.go

@@ -4,6 +4,7 @@ import (
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/lightningnetwork/lnd/record"
 )
 
 // htlcPacket is a wrapper around htlc lnwire update, which adds additional
@@ -91,6 +92,10 @@ type htlcPacket struct {
 	// will be extraced from the hop payload recevived by the incoming
 	// link.
 	outgoingTimeout uint32
+
+	// customRecords are user-defined records in the custom type range that
+	// were included in the payload.
+	customRecords record.CustomSet
 }
 
 // inKey returns the circuit key used to identify the incoming htlc.

lnrpc/routerrpc/forward_interceptor.go

@@ -163,6 +163,7 @@ func (r *forwardInterceptor) holdAndForwardToClient(
 		OutgoingExpiry:          htlc.OutgoingExpiry,
 		IncomingAmountMsat:      uint64(htlc.IncomingAmount),
 		IncomingExpiry:          htlc.IncomingExpiry,
+		CustomRecords:           htlc.CustomRecords,
 	}
 
 	return r.stream.Send(interceptionRequest)

lnrpc/routerrpc/router.proto

@@ -628,6 +628,9 @@ message ForwardHtlcInterceptRequest {
 
     // The outgoing htlc expiry.
     uint32 outgoing_expiry = 4;
+
+    // Any custom records that were present in the payload.
+    map<uint64, bytes> custom_records = 8;
 }
 
 /**

lnrpc/routerrpc/router.swagger.json

@@ -936,6 +936,14 @@
           "type": "integer",
           "format": "int64",
           "description": "The outgoing htlc expiry."
+        },
+        "custom_records": {
+          "type": "object",
+          "additionalProperties": {
+            "type": "string",
+            "format": "byte"
+          },
+          "description": "Any custom records that were present in the payload."
         }
       }
     },

lntest/itest/lnd_forward_interceptor_test.go

@@ -21,6 +21,11 @@ import (
 	"google.golang.org/grpc/status"
 )
 
+var (
+	customTestKey   uint64 = 394829
+	customTestValue        = []byte{1, 3, 5}
+)
+
 type interceptorTestCase struct {
 	amountMsat        int64
 	invoice           *lnrpc.Invoice
@@ -149,6 +154,10 @@ func testForwardInterceptor(net *lntest.NetworkHarness, t *harnessTest) {
 				request.IncomingAmountMsat,
 			)
 
+			value, ok := request.CustomRecords[customTestKey]
+			require.True(t.t, ok, "expected custom record")
+			require.Equal(t.t, customTestValue, value)
+
 			testCase := testCases[i]
 
 			// For held packets we ignore, keeping them in hold status.
@@ -369,6 +378,11 @@ func (c *interceptorTestContext) sendAliceToCarolPayment(ctx context.Context,
 		Route:       route,
 	}
 
+	// Send a custom record to the forwarding node.
+	route.Hops[0].CustomRecords = map[uint64][]byte{
+		customTestKey: customTestValue,
+	}
+
 	// Send the payment.
 	return c.alice.RouterClient.SendToRouteV2(ctx, sendReq)
 }