lnd.xprv/lnwire/accept_channel.go

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package lnwire
import (
"fmt"
"io"
"github.com/btcsuite/btcd/btcec"
"github.com/btcsuite/btcutil"
)
// AcceptChannel is the message Bob sends to Alice after she initiates the
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// single funder channel workflow via an AcceptChannel message. Once Alice
// receives Bob's response, then she has all the items necessary to construct
// the funding transaction, and both commitment transactions.
type AcceptChannel struct {
// PendingChannelID serves to uniquely identify the future channel
// created by the initiated single funder workflow.
PendingChannelID [32]byte
// DustLimit is the specific dust limit the sender of this message
// would like enforced on their version of the commitment transaction.
// Any output below this value will be "trimmed" from the commitment
// transaction, with the amount of the HTLC going to dust.
DustLimit btcutil.Amount
// MaxValueInFlight represents the maximum amount of coins that can be
// pending within the channel at any given time. If the amount of funds
// in limbo exceeds this amount, then the channel will be failed.
MaxValueInFlight MilliSatoshi
// ChannelReserve is the amount of BTC that the receiving party MUST
// maintain a balance above at all times. This is a safety mechanism to
// ensure that both sides always have skin in the game during the
// channel's lifetime.
ChannelReserve btcutil.Amount
// HtlcMinimum is the smallest HTLC that the sender of this message
// will accept.
HtlcMinimum MilliSatoshi
// MinAcceptDepth is the minimum depth that the initiator of the
// channel should wait before considering the channel open.
MinAcceptDepth uint32
// CsvDelay is the number of blocks to use for the relative time lock
// in the pay-to-self output of both commitment transactions.
CsvDelay uint16
// MaxAcceptedHTLCs is the total number of incoming HTLC's that the
// sender of this channel will accept.
//
// TODO(roasbeef): acks the initiator's, same with max in flight?
MaxAcceptedHTLCs uint16
// FundingKey is the key that should be used on behalf of the sender
// within the 2-of-2 multi-sig output that it contained within the
// funding transaction.
FundingKey *btcec.PublicKey
// RevocationPoint is the base revocation point for the sending party.
// Any commitment transaction belonging to the receiver of this message
// should use this key and their per-commitment point to derive the
// revocation key for the commitment transaction.
RevocationPoint *btcec.PublicKey
// PaymentPoint is the base payment point for the sending party. This
// key should be combined with the per commitment point for a
// particular commitment state in order to create the key that should
// be used in any output that pays directly to the sending party, and
// also within the HTLC covenant transactions.
PaymentPoint *btcec.PublicKey
// DelayedPaymentPoint is the delay point for the sending party. This
// key should be combined with the per commitment point to derive the
// keys that are used in outputs of the sender's commitment transaction
// where they claim funds.
DelayedPaymentPoint *btcec.PublicKey
// HtlcPoint is the base point used to derive the set of keys for this
// party that will be used within the HTLC public key scripts. This
// value is combined with the receiver's revocation base point in order
// to derive the keys that are used within HTLC scripts.
HtlcPoint *btcec.PublicKey
// FirstCommitmentPoint is the first commitment point for the sending
// party. This value should be combined with the receiver's revocation
// base point in order to derive the revocation keys that are placed
// within the commitment transaction of the sender.
FirstCommitmentPoint *btcec.PublicKey
// UpfrontShutdownScript is the script to which the channel funds should
// be paid when mutually closing the channel. This field is optional, and
// and has a length prefix, so a zero will be written if it is not set
// and its length followed by the script will be written if it is set.
UpfrontShutdownScript DeliveryAddress
// ExtraData is the set of data that was appended to this message to
// fill out the full maximum transport message size. These fields can
// be used to specify optional data such as custom TLV fields.
//
// NOTE: Since the upfront shutdown script MUST be present (though can
// be zero-length) if any TLV data is available, the script will be
// extracted and removed from this blob when decoding. ExtraData will
// contain all TLV records _except_ the DeliveryAddress record in that
// case.
ExtraData ExtraOpaqueData
}
// A compile time check to ensure AcceptChannel implements the lnwire.Message
// interface.
var _ Message = (*AcceptChannel)(nil)
// Encode serializes the target AcceptChannel into the passed io.Writer
// implementation. Serialization will observe the rules defined by the passed
// protocol version.
//
// This is part of the lnwire.Message interface.
func (a *AcceptChannel) Encode(w io.Writer, pver uint32) error {
// Since the upfront script is encoded as a TLV record, concatenate it
// with the ExtraData, and write them as one.
tlvRecords, err := packShutdownScript(
a.UpfrontShutdownScript, a.ExtraData,
)
if err != nil {
return err
}
return WriteElements(w,
a.PendingChannelID[:],
a.DustLimit,
a.MaxValueInFlight,
a.ChannelReserve,
a.HtlcMinimum,
a.MinAcceptDepth,
a.CsvDelay,
a.MaxAcceptedHTLCs,
a.FundingKey,
a.RevocationPoint,
a.PaymentPoint,
a.DelayedPaymentPoint,
a.HtlcPoint,
a.FirstCommitmentPoint,
tlvRecords,
)
}
// Decode deserializes the serialized AcceptChannel stored in the passed
// io.Reader into the target AcceptChannel using the deserialization rules
// defined by the passed protocol version.
//
// This is part of the lnwire.Message interface.
func (a *AcceptChannel) Decode(r io.Reader, pver uint32) error {
// Read all the mandatory fields in the accept message.
err := ReadElements(r,
a.PendingChannelID[:],
&a.DustLimit,
&a.MaxValueInFlight,
&a.ChannelReserve,
&a.HtlcMinimum,
&a.MinAcceptDepth,
&a.CsvDelay,
&a.MaxAcceptedHTLCs,
&a.FundingKey,
&a.RevocationPoint,
&a.PaymentPoint,
&a.DelayedPaymentPoint,
&a.HtlcPoint,
&a.FirstCommitmentPoint,
)
if err != nil {
return err
}
// For backwards compatibility, the optional extra data blob for
// AcceptChannel must contain an entry for the upfront shutdown script.
// We'll read it out and attempt to parse it.
var tlvRecords ExtraOpaqueData
if err := ReadElements(r, &tlvRecords); err != nil {
return err
}
a.UpfrontShutdownScript, a.ExtraData, err = parseShutdownScript(
tlvRecords,
)
if err != nil {
return err
}
return nil
}
// packShutdownScript takes an upfront shutdown script and an opaque data blob
// and concatenates them.
func packShutdownScript(addr DeliveryAddress, extraData ExtraOpaqueData) (
ExtraOpaqueData, error) {
// We'll always write the upfront shutdown script record, regardless of
// the script being empty.
var tlvRecords ExtraOpaqueData
// Pack it into a data blob as a TLV record.
err := tlvRecords.PackRecords(addr.NewRecord())
if err != nil {
return nil, fmt.Errorf("unable to pack upfront shutdown "+
"script as TLV record: %v", err)
}
// Concatenate the remaining blob with the shutdown script record.
tlvRecords = append(tlvRecords, extraData...)
return tlvRecords, nil
}
// parseShutdownScript reads and extract the upfront shutdown script from the
// passe data blob. It returns the script, if any, and the remainder of the
// data blob.
//
// This can be used to parse extra data for the OpenChannel and AcceptChannel
// messages, where the shutdown script is mandatory if extra TLV data is
// present.
func parseShutdownScript(tlvRecords ExtraOpaqueData) (DeliveryAddress,
ExtraOpaqueData, error) {
// If no TLV data is present there can't be any script available.
if len(tlvRecords) == 0 {
return nil, tlvRecords, nil
}
// Otherwise the shutdown script MUST be present.
var addr DeliveryAddress
tlvs, err := tlvRecords.ExtractRecords(addr.NewRecord())
if err != nil {
return nil, nil, err
}
// Not among TLV records, this means the data was invalid.
if _, ok := tlvs[DeliveryAddrType]; !ok {
return nil, nil, fmt.Errorf("no shutdown script in non-empty " +
"data blob")
}
// Now that we have retrieved the address (which can be zero-length),
// we'll remove the bytes encoding it from the TLV data before
// returning it.
addrLen := len(addr)
tlvRecords = tlvRecords[addrLen+2:]
return addr, tlvRecords, nil
}
// MsgType returns the MessageType code which uniquely identifies this message
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// as an AcceptChannel on the wire.
//
// This is part of the lnwire.Message interface.
func (a *AcceptChannel) MsgType() MessageType {
return MsgAcceptChannel
}