lnd.xprv/record/mpp.go
2019-12-20 11:00:01 +01:00

110 lines
3.0 KiB
Go

package record
import (
"fmt"
"io"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/lightningnetwork/lnd/tlv"
)
// MPPOnionType is the type used in the onion to reference the MPP fields:
// total_amt and payment_addr.
const MPPOnionType tlv.Type = 8
// MPP is a record that encodes the fields necessary for multi-path payments.
type MPP struct {
// paymentAddr is a random, receiver-generated value used to avoid
// collisions with concurrent payers.
paymentAddr [32]byte
// totalMsat is the total value of the payment, potentially spread
// across more than one HTLC.
totalMsat lnwire.MilliSatoshi
}
// NewMPP generates a new MPP record with the given total and payment address.
func NewMPP(total lnwire.MilliSatoshi, addr [32]byte) *MPP {
return &MPP{
paymentAddr: addr,
totalMsat: total,
}
}
// PaymentAddr returns the payment address contained in the MPP record.
func (r *MPP) PaymentAddr() [32]byte {
return r.paymentAddr
}
// TotalMsat returns the total value of an MPP payment in msats.
func (r *MPP) TotalMsat() lnwire.MilliSatoshi {
return r.totalMsat
}
// MPPEncoder writes the MPP record to the provided io.Writer.
func MPPEncoder(w io.Writer, val interface{}, buf *[8]byte) error {
if v, ok := val.(*MPP); ok {
err := tlv.EBytes32(w, &v.paymentAddr, buf)
if err != nil {
return err
}
return tlv.ETUint64T(w, uint64(v.totalMsat), buf)
}
return tlv.NewTypeForEncodingErr(val, "MPP")
}
const (
// minMPPLength is the minimum length of a serialized MPP TLV record,
// which occurs when the truncated encoding of total_amt_msat takes 0
// bytes, leaving only the payment_addr.
minMPPLength = 32
// maxMPPLength is the maximum length of a serialized MPP TLV record,
// which occurs when the truncated encoding of total_amt_msat takes 8
// bytes.
maxMPPLength = 40
)
// MPPDecoder reads the MPP record to the provided io.Reader.
func MPPDecoder(r io.Reader, val interface{}, buf *[8]byte, l uint64) error {
if v, ok := val.(*MPP); ok && minMPPLength <= l && l <= maxMPPLength {
if err := tlv.DBytes32(r, &v.paymentAddr, buf, 32); err != nil {
return err
}
var total uint64
if err := tlv.DTUint64(r, &total, buf, l-32); err != nil {
return err
}
v.totalMsat = lnwire.MilliSatoshi(total)
return nil
}
return tlv.NewTypeForDecodingErr(val, "MPP", l, maxMPPLength)
}
// Record returns a tlv.Record that can be used to encode or decode this record.
func (r *MPP) Record() tlv.Record {
// Fixed-size, 32 byte payment address followed by truncated 64-bit
// total msat.
size := func() uint64 {
return 32 + tlv.SizeTUint64(uint64(r.totalMsat))
}
return tlv.MakeDynamicRecord(
MPPOnionType, r, size, MPPEncoder, MPPDecoder,
)
}
// PayloadSize returns the size this record takes up in encoded form.
func (r *MPP) PayloadSize() uint64 {
return 32 + tlv.SizeTUint64(uint64(r.totalMsat))
}
// String returns a human-readable representation of the mpp payload field.
func (r *MPP) String() string {
return fmt.Sprintf("total=%v, addr=%x", r.totalMsat, r.paymentAddr)
}