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