htlcswitch+invoices: record payment metadata [TO BE REMOVED]

channeldb/invoices.go

@@ -193,6 +193,7 @@ const (
 	htlcAMPType      tlv.Type = 19
 	htlcHashType     tlv.Type = 21
 	htlcPreimageType tlv.Type = 23
+	metadataType     tlv.Type = 25
 
 	// A set of tlv type definitions used to serialize invoice bodiees.
 	//
@@ -701,6 +702,10 @@ type InvoiceHTLC struct {
 	//
 	// NOTE: This value will only be set for AMP HTLCs.
 	AMP *InvoiceHtlcAMPData
+
+	// Metadata is additional data that is sent along with the payment to
+	// the payee.
+	Metadata []byte
 }
 
 // Copy makes a deep copy of the target InvoiceHTLC.
@@ -810,6 +815,10 @@ type HtlcAcceptDesc struct {
 	//
 	// NOTE: This value will only be set for AMP HTLCs.
 	AMP *InvoiceHtlcAMPData
+
+	// Metadata is additional data that is sent along with the payment to
+	// the payee.
+	Metadata []byte
 }
 
 // InvoiceUpdateDesc describes the changes that should be applied to the
@@ -1724,6 +1733,13 @@ func serializeHtlcs(w io.Writer, htlcs map[CircuitKey]*InvoiceHTLC) error {
 			}
 		}
 
+		if len(htlc.Metadata) > 0 {
+			records = append(
+				records,
+				tlv.MakePrimitiveRecord(metadataType, &htlc.Metadata),
+			)
+		}
+
 		// Convert the custom records to tlv.Record types that are ready
 		// for serialization.
 		customRecords := tlv.MapToRecords(htlc.CustomRecords)
@@ -2341,6 +2357,7 @@ func deserializeHtlcs(r io.Reader) (map[CircuitKey]*InvoiceHTLC, error) {
 			amp                     = &record.AMP{}
 			hash32                  = &[32]byte{}
 			preimage32              = &[32]byte{}
+			metadata                = &[]byte{}
 		)
 		tlvStream, err := tlv.NewStream(
 			tlv.MakePrimitiveRecord(chanIDType, &chanID),
@@ -2360,6 +2377,7 @@ func deserializeHtlcs(r io.Reader) (map[CircuitKey]*InvoiceHTLC, error) {
 			),
 			tlv.MakePrimitiveRecord(htlcHashType, hash32),
 			tlv.MakePrimitiveRecord(htlcPreimageType, preimage32),
+			tlv.MakePrimitiveRecord(metadataType, metadata),
 		)
 		if err != nil {
 			return nil, err
@@ -2404,6 +2422,10 @@ func deserializeHtlcs(r io.Reader) (map[CircuitKey]*InvoiceHTLC, error) {
 		// map return from the tlv parser.
 		htlc.CustomRecords = hop.NewCustomRecords(parsedTypes)
 
+		if len(*metadata) > 0 {
+			htlc.Metadata = *metadata
+		}
+
 		htlcs[key] = &htlc
 	}
 
@@ -2704,6 +2726,7 @@ func (d *DB) updateInvoice(hash *lntypes.Hash, refSetID *SetID, invoices,
 			State:         HtlcStateAccepted,
 			CustomRecords: htlcUpdate.CustomRecords,
 			AMP:           htlcUpdate.AMP.Copy(),
+			Metadata:      htlcUpdate.Metadata,
 		}
 
 		invoice.Htlcs[key] = htlc

invoices/update.go

@@ -158,6 +158,7 @@ func updateMpp(ctx *invoiceUpdateCtx,
 		AcceptHeight:  ctx.currentHeight,
 		MppTotalAmt:   ctx.mpp.TotalMsat(),
 		CustomRecords: ctx.customRecords,
+		Metadata:      ctx.metadata,
 	}
 
 	if ctx.amp != nil {

lnrpc/invoicesrpc/invoices.swagger.json

@@ -643,6 +643,11 @@
         "amp": {
           "$ref": "#/definitions/lnrpcAMP",
           "description": "Details relevant to AMP HTLCs, only populated if this is an AMP HTLC."
+        },
+        "metadata": {
+          "type": "string",
+          "format": "byte",
+          "description": "The payment metadata to send along with the payment to the payee."
         }
       },
       "title": "Details of an HTLC that paid to an invoice"

lnrpc/invoicesrpc/utils.go

@@ -118,6 +118,7 @@ func CreateRPCInvoice(invoice *channeldb.Invoice,
 			State:           state,
 			CustomRecords:   htlc.CustomRecords,
 			MppTotalAmtMsat: uint64(htlc.MppTotalAmt),
+			Metadata:        htlc.Metadata,
 		}
 
 		// Populate any fields relevant to AMP payments.