lnwallet: add TLV blob to PaymentDescriptor + htlc add

In this commit, we add a TLV blob to the PaymentDescriptor struct. We also now thread through this value from the UpdateAddHTLC message to the PaymentDescriptor mapping, and the other way around.

channeldb/channel.go

@@ -2580,6 +2580,12 @@ type HTLC struct {
 	// HTLC. It is stored in the ExtraData field, which is used to store
 	// a TLV stream of additional information associated with the HTLC.
 	BlindingPoint lnwire.BlindingPointRecord
+
+	// CustomRecords is a set of custom TLV records that are associated with
+	// this HTLC. These records are used to store additional information
+	// about the HTLC that is not part of the standard HTLC fields. This
+	// field is encoded within the ExtraData field.
+	CustomRecords lnwire.CustomRecords
 }
 
 // serializeExtraData encodes a TLV stream of extra data to be stored with a
@@ -2598,6 +2604,11 @@ func (h *HTLC) serializeExtraData() error {
 		records = append(records, &b)
 	})
 
+	records, err := h.CustomRecords.ExtendRecordProducers(records)
+	if err != nil {
+		return err
+	}
+
 	return h.ExtraData.PackRecords(records...)
 }
 
@@ -2619,8 +2630,19 @@ func (h *HTLC) deserializeExtraData() error {
 
 	if val, ok := tlvMap[h.BlindingPoint.TlvType()]; ok && val == nil {
 		h.BlindingPoint = tlv.SomeRecordT(blindingPoint)
+
+		// Remove the entry from the TLV map. Anything left in the map
+		// will be included in the custom records field.
+		delete(tlvMap, h.BlindingPoint.TlvType())
 	}
 
+	// Set the custom records field to the remaining TLV records.
+	customRecords, err := lnwire.NewCustomRecords(tlvMap)
+	if err != nil {
+		return err
+	}
+	h.CustomRecords = customRecords
+
 	return nil
 }
 
@@ -2758,6 +2780,8 @@ func (h *HTLC) Copy() HTLC {
 	copy(clone.Signature[:], h.Signature)
 	copy(clone.RHash[:], h.RHash[:])
 	copy(clone.ExtraData, h.ExtraData)
+	clone.BlindingPoint = h.BlindingPoint
+	clone.CustomRecords = h.CustomRecords.Copy()
 
 	return clone
 }

channeldb/channel_test.go

@@ -1657,6 +1657,24 @@ func TestHTLCsExtraData(t *testing.T) {
 		),
 	}
 
+	// Custom channel data htlc with a blinding point.
+	customDataHTLC := HTLC{
+		Signature:     testSig.Serialize(),
+		Incoming:      false,
+		Amt:           10,
+		RHash:         key,
+		RefundTimeout: 1,
+		OnionBlob:     lnmock.MockOnion(),
+		BlindingPoint: tlv.SomeRecordT(
+			tlv.NewPrimitiveRecord[lnwire.BlindingPointTlvType](
+				pubKey,
+			),
+		),
+		CustomRecords: map[uint64][]byte{
+			uint64(lnwire.MinCustomRecordsTlvType + 3): {1, 2, 3},
+		},
+	}
+
 	testCases := []struct {
 		name        string
 		htlcs       []HTLC
@@ -1678,6 +1696,7 @@ func TestHTLCsExtraData(t *testing.T) {
 				mockHtlc,
 				blindingPointHTLC,
 				mockHtlc,
+				customDataHTLC,
 			},
 		},
 	}