records/mpp: add MPP struct to create corresponding tlv.Record

Used to encode/decode MPP tlv records
This commit is contained in:
Conner Fromknecht 2019-11-04 14:11:02 -08:00
parent b3b51923dc
commit b1b7ff8006
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3 changed files with 179 additions and 0 deletions

98
record/mpp.go Normal file

@ -0,0 +1,98 @@
package record
import (
"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,
)
}

73
record/record_test.go Normal file

@ -0,0 +1,73 @@
package record_test
import (
"bytes"
"testing"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/lightningnetwork/lnd/record"
"github.com/lightningnetwork/lnd/tlv"
)
type recordEncDecTest struct {
name string
encRecord func() tlv.RecordProducer
decRecord func() tlv.RecordProducer
assert func(*testing.T, interface{})
}
var (
testTotal = lnwire.MilliSatoshi(45)
testAddr = [32]byte{0x01, 0x02}
)
var recordEncDecTests = []recordEncDecTest{
{
name: "mpp",
encRecord: func() tlv.RecordProducer {
return record.NewMPP(testTotal, testAddr)
},
decRecord: func() tlv.RecordProducer {
return new(record.MPP)
},
assert: func(t *testing.T, r interface{}) {
mpp := r.(*record.MPP)
if mpp.TotalMsat() != testTotal {
t.Fatal("incorrect total msat")
}
if mpp.PaymentAddr() != testAddr {
t.Fatal("incorrect payment addr")
}
},
},
}
// TestRecordEncodeDecode is a generic test framework for custom TLV records. It
// asserts that records can encode and decode themselves, and that the value of
// the original record matches the decoded record.
func TestRecordEncodeDecode(t *testing.T) {
for _, test := range recordEncDecTests {
test := test
t.Run(test.name, func(t *testing.T) {
r := test.encRecord()
r2 := test.decRecord()
encStream := tlv.MustNewStream(r.Record())
decStream := tlv.MustNewStream(r2.Record())
test.assert(t, r)
var b bytes.Buffer
err := encStream.Encode(&b)
if err != nil {
t.Fatalf("unable to encode record: %v", err)
}
err = decStream.Decode(bytes.NewReader(b.Bytes()))
if err != nil {
t.Fatalf("unable to decode record: %v", err)
}
test.assert(t, r2)
})
}
}

@ -43,6 +43,14 @@ func SizeVarBytes(e *[]byte) SizeFunc {
}
}
// RecorderProducer is an interface for objects that can produce a Record object
// capable of encoding and/or decoding the RecordProducer as a Record.
type RecordProducer interface {
// Record returns a Record that can be used to encode or decode the
// backing object.
Record() Record
}
// Record holds the required information to encode or decode a TLV record.
type Record struct {
value interface{}