lnd.xprv/lnwire/channel_update.go
Olaoluwa Osuntokun 941a123ab0 lnwire: add new ExtraOpaqueData field to gossip messages
In this commit, we add a new field to all the existing gossip messages:
ExtraOpqueData. We do this, as before this commit, if we came across a
ChannelUpdate message with a set of optional fields, then we wouldn't be
able to properly parse the signatures related to the message. If we
never corrected this behavior, then we would violate the forwards
compatible principle we use when parsing existing messages.

As these messages can now be padded out to the max message size, we've
increased the MaxPayloadLength value for all of these messages.

Fixes #1814.
2018-09-04 20:52:39 -07:00

184 lines
5.4 KiB
Go

package lnwire
import (
"bytes"
"io"
"io/ioutil"
"github.com/btcsuite/btcd/chaincfg/chainhash"
)
// ChanUpdateFlag is a bitfield that signals various options concerning a
// particular channel edge. Each bit is to be examined in order to determine
// how the ChannelUpdate message is to be interpreted.
type ChanUpdateFlag uint16
const (
// ChanUpdateDirection indicates the direction of a channel update. If
// this bit is set to 0 if Node1 (the node with the "smaller" Node ID)
// is updating the channel, and to 1 otherwise.
ChanUpdateDirection ChanUpdateFlag = 1 << iota
// ChanUpdateDisabled is a bit that indicates if the channel edge
// selected by the ChanUpdateDirection bit is to be treated as being
// disabled.
ChanUpdateDisabled
)
// ChannelUpdate message is used after channel has been initially announced.
// Each side independently announces its fees and minimum expiry for HTLCs and
// other parameters. Also this message is used to redeclare initially set
// channel parameters.
type ChannelUpdate struct {
// Signature is used to validate the announced data and prove the
// ownership of node id.
Signature Sig
// ChainHash denotes the target chain that this channel was opened
// within. This value should be the genesis hash of the target chain.
// Along with the short channel ID, this uniquely identifies the
// channel globally in a blockchain.
ChainHash chainhash.Hash
// ShortChannelID is the unique description of the funding transaction.
ShortChannelID ShortChannelID
// Timestamp allows ordering in the case of multiple announcements. We
// should ignore the message if timestamp is not greater than
// the last-received.
Timestamp uint32
// Flags is a bitfield that describes additional meta-data concerning
// how the update is to be interpreted. Currently, the
// least-significant bit must be set to 0 if the creating node
// corresponds to the first node in the previously sent channel
// announcement and 1 otherwise. If the second bit is set, then the
// channel is set to be disabled.
Flags ChanUpdateFlag
// TimeLockDelta is the minimum number of blocks this node requires to
// be added to the expiry of HTLCs. This is a security parameter
// determined by the node operator. This value represents the required
// gap between the time locks of the incoming and outgoing HTLC's set
// to this node.
TimeLockDelta uint16
// HtlcMinimumMsat is the minimum HTLC value which will be accepted.
HtlcMinimumMsat MilliSatoshi
// BaseFee is the base fee that must be used for incoming HTLC's to
// this particular channel. This value will be tacked onto the required
// for a payment independent of the size of the payment.
BaseFee uint32
// FeeRate is the fee rate that will be charged per millionth of a
// satoshi.
FeeRate uint32
// ExtraOpaqueData is the set of data that was appended to this
// message, some of which we may not actually know how to iterate or
// parse. By holding onto this data, we ensure that we're able to
// properly validate the set of signatures that cover these new fields,
// and ensure we're able to make upgrades to the network in a forwards
// compatible manner.
ExtraOpaqueData []byte
}
// A compile time check to ensure ChannelUpdate implements the lnwire.Message
// interface.
var _ Message = (*ChannelUpdate)(nil)
// Decode deserializes a serialized ChannelUpdate stored in the passed
// io.Reader observing the specified protocol version.
//
// This is part of the lnwire.Message interface.
func (a *ChannelUpdate) Decode(r io.Reader, pver uint32) error {
err := readElements(r,
&a.Signature,
a.ChainHash[:],
&a.ShortChannelID,
&a.Timestamp,
&a.Flags,
&a.TimeLockDelta,
&a.HtlcMinimumMsat,
&a.BaseFee,
&a.FeeRate,
)
if err != nil {
return err
}
// Now that we've read out all the fields that we explicitly know of,
// we'll collect the remainder into the ExtraOpaqueData field. If there
// aren't any bytes, then we'll snip off the slice to avoid carrying
// around excess capacity.
a.ExtraOpaqueData, err = ioutil.ReadAll(r)
if err != nil {
return err
}
if len(a.ExtraOpaqueData) == 0 {
a.ExtraOpaqueData = nil
}
return nil
}
// Encode serializes the target ChannelUpdate into the passed io.Writer
// observing the protocol version specified.
//
// This is part of the lnwire.Message interface.
func (a *ChannelUpdate) Encode(w io.Writer, pver uint32) error {
return writeElements(w,
a.Signature,
a.ChainHash[:],
a.ShortChannelID,
a.Timestamp,
a.Flags,
a.TimeLockDelta,
a.HtlcMinimumMsat,
a.BaseFee,
a.FeeRate,
a.ExtraOpaqueData,
)
}
// MsgType returns the integer uniquely identifying this message type on the
// wire.
//
// This is part of the lnwire.Message interface.
func (a *ChannelUpdate) MsgType() MessageType {
return MsgChannelUpdate
}
// MaxPayloadLength returns the maximum allowed payload size for this message
// observing the specified protocol version.
//
// This is part of the lnwire.Message interface.
func (a *ChannelUpdate) MaxPayloadLength(pver uint32) uint32 {
return 65533
}
// DataToSign is used to retrieve part of the announcement message which should
// be signed.
func (a *ChannelUpdate) DataToSign() ([]byte, error) {
// We should not include the signatures itself.
var w bytes.Buffer
err := writeElements(&w,
a.ChainHash[:],
a.ShortChannelID,
a.Timestamp,
a.Flags,
a.TimeLockDelta,
a.HtlcMinimumMsat,
a.BaseFee,
a.FeeRate,
a.ExtraOpaqueData,
)
if err != nil {
return nil, err
}
return w.Bytes(), nil
}