lnd.xprv/chancloser.go
carla d3cb6ad869
channeldb: store close initiator status
This commit adds two new channel statuses which indicate the party that
initatited closing the channel. These statuses are set in conjunction
with the existing commit broadcast status so that we do not need to
migrate existing logic to handle multiple types of closes. This status
is set for locally initiated force closes in this commit because they
follow a similar pattern to cooparative closes, marking the commitment
broadcast then proceeding with tx broadcast. Remote force closes are
added in the following commit, as they are handled differently.
2020-02-21 13:33:49 +02:00

697 lines
26 KiB
Go

package lnd
import (
"bytes"
"fmt"
"github.com/btcsuite/btcd/txscript"
"github.com/btcsuite/btcd/wire"
"github.com/btcsuite/btcutil"
"github.com/davecgh/go-spew/spew"
"github.com/lightningnetwork/lnd/htlcswitch"
"github.com/lightningnetwork/lnd/lnwallet"
"github.com/lightningnetwork/lnd/lnwallet/chainfee"
"github.com/lightningnetwork/lnd/lnwire"
)
var (
// ErrChanAlreadyClosing is returned when a channel shutdown is
// attempted more than once.
ErrChanAlreadyClosing = fmt.Errorf("channel shutdown already initiated")
// ErrChanCloseNotFinished is returned when a caller attempts to access
// a field or function that is contingent on the channel closure
// negotiation already being completed.
ErrChanCloseNotFinished = fmt.Errorf("close negotiation not finished")
// ErrInvalidState is returned when the closing state machine receives
// a message while it is in an unknown state.
ErrInvalidState = fmt.Errorf("invalid state")
// errUpfrontShutdownScriptMismatch is returned when a peer or end user
// provides a script to cooperatively close out to which does not match
// the upfront shutdown script previously set for that party.
errUpfrontShutdownScriptMismatch = fmt.Errorf("shutdown " +
"script does not match upfront shutdown script")
)
// closeState represents all the possible states the channel closer state
// machine can be in. Each message will either advance to the next state, or
// remain at the current state. Once the state machine reaches a state of
// closeFinished, then negotiation is over.
type closeState uint8
const (
// closeIdle is the initial starting state. In this state, the state
// machine has been instantiated, but no state transitions have been
// attempted. If a state machine receives a message while in this
// state, then it is the responder to an initiated cooperative channel
// closure.
closeIdle closeState = iota
// closeShutdownInitiated is the state that's transitioned to once the
// initiator of a closing workflow sends the shutdown message. At this
// point, they're waiting for the remote party to respond with their
// own shutdown message. After which, they'll both enter the fee
// negotiation phase.
closeShutdownInitiated
// closeFeeNegotiation is the third, and most persistent state. Both
// parties enter this state after they've sent and received a shutdown
// message. During this phase, both sides will send monotonically
// increasing fee requests until one side accepts the last fee rate
// offered by the other party. In this case, the party will broadcast
// the closing transaction, and send the accepted fee to the remote
// party. This then causes a shift into the closeFinished state.
closeFeeNegotiation
// closeFinished is the final state of the state machine. In this,
// state a side has accepted a fee offer and has broadcast the valid
// closing transaction to the network. During this phase, the closing
// transaction becomes available for examination.
closeFinished
)
// chanCloseCfg holds all the items that a channelCloser requires to carry out
// its duties.
type chanCloseCfg struct {
// channel is the channel that should be closed.
channel *lnwallet.LightningChannel
// unregisterChannel is a function closure that allows the
// channelCloser to re-register a channel. Once this has been done, no
// further HTLC's should be routed through the channel.
unregisterChannel func(lnwire.ChannelID)
// broadcastTx broadcasts the passed transaction to the network.
broadcastTx func(*wire.MsgTx) error
// disableChannel disables a channel, resulting in it not being able to
// forward payments.
disableChannel func(wire.OutPoint) error
// disconnect will disconnect from the remote peer in this close.
disconnect func() error
// quit is a channel that should be sent upon in the occasion the state
// machine should cease all progress and shutdown.
quit chan struct{}
}
// channelCloser is a state machine that handles the cooperative channel
// closure procedure. This includes shutting down a channel, marking it
// ineligible for routing HTLC's, negotiating fees with the remote party, and
// finally broadcasting the fully signed closure transaction to the network.
type channelCloser struct {
// state is the current state of the state machine.
state closeState
// cfg holds the configuration for this channelCloser instance.
cfg chanCloseCfg
// chanPoint is the full channel point of the target channel.
chanPoint wire.OutPoint
// cid is the full channel ID of the target channel.
cid lnwire.ChannelID
// negotiationHeight is the height that the fee negotiation begun at.
negotiationHeight uint32
// closingTx is the final, fully signed closing transaction. This will
// only be populated once the state machine shifts to the closeFinished
// state.
closingTx *wire.MsgTx
// idealFeeSat is the ideal fee that the state machine should initially
// offer when starting negotiation. This will be used as a baseline.
idealFeeSat btcutil.Amount
// lastFeeProposal is the last fee that we proposed to the remote
// party. We'll use this as a pivot point to rachet our next offer up,
// or down, or simply accept the remote party's prior offer.
lastFeeProposal btcutil.Amount
// priorFeeOffers is a map that keeps track of all the proposed fees
// that we've offered during the fee negotiation. We use this map to
// cut the negotiation early if the remote party ever sends an offer
// that we've sent in the past. Once negotiation terminates, we can
// extract the prior signature of our accepted offer from this map.
//
// TODO(roasbeef): need to ensure if they broadcast w/ any of our prior
// sigs, we are aware of
priorFeeOffers map[btcutil.Amount]*lnwire.ClosingSigned
// closeReq is the initial closing request. This will only be populated
// if we're the initiator of this closing negotiation.
//
// TODO(roasbeef): abstract away
closeReq *htlcswitch.ChanClose
// localDeliveryScript is the script that we'll send our settled
// channel funds to.
localDeliveryScript []byte
// remoteDeliveryScript is the script that we'll send the remote
// party's settled channel funds to.
remoteDeliveryScript []byte
// locallyInitiated is true if we initiated the channel close.
locallyInitiated bool
}
// newChannelCloser creates a new instance of the channel closure given the
// passed configuration, and delivery+fee preference. The final argument should
// only be populated iff, we're the initiator of this closing request.
func newChannelCloser(cfg chanCloseCfg, deliveryScript []byte,
idealFeePerKw chainfee.SatPerKWeight, negotiationHeight uint32,
closeReq *htlcswitch.ChanClose, locallyInitiated bool) *channelCloser {
// Given the target fee-per-kw, we'll compute what our ideal _total_
// fee will be starting at for this fee negotiation.
//
// TODO(roasbeef): should factor in minimal commit
idealFeeSat := cfg.channel.CalcFee(idealFeePerKw)
// If this fee is greater than the fee currently present within the
// commitment transaction, then we'll clamp it down to be within the
// proper range.
//
// TODO(roasbeef): clamp fee func?
channelCommitFee := cfg.channel.StateSnapshot().CommitFee
if idealFeeSat > channelCommitFee {
peerLog.Infof("Ideal starting fee of %v is greater than "+
"commit fee of %v, clamping", int64(idealFeeSat),
int64(channelCommitFee))
idealFeeSat = channelCommitFee
}
peerLog.Infof("Ideal fee for closure of ChannelPoint(%v) is: %v sat",
cfg.channel.ChannelPoint(), int64(idealFeeSat))
cid := lnwire.NewChanIDFromOutPoint(cfg.channel.ChannelPoint())
return &channelCloser{
closeReq: closeReq,
state: closeIdle,
chanPoint: *cfg.channel.ChannelPoint(),
cid: cid,
cfg: cfg,
negotiationHeight: negotiationHeight,
idealFeeSat: idealFeeSat,
localDeliveryScript: deliveryScript,
priorFeeOffers: make(map[btcutil.Amount]*lnwire.ClosingSigned),
locallyInitiated: locallyInitiated,
}
}
// initChanShutdown begins the shutdown process by un-registering the channel,
// and creating a valid shutdown message to our target delivery address.
func (c *channelCloser) initChanShutdown() (*lnwire.Shutdown, error) {
// With both items constructed we'll now send the shutdown message for
// this particular channel, advertising a shutdown request to our
// desired closing script.
shutdown := lnwire.NewShutdown(c.cid, c.localDeliveryScript)
// TODO(roasbeef): err if channel has htlc's?
// Before closing, we'll attempt to send a disable update for the
// channel. We do so before closing the channel as otherwise the current
// edge policy won't be retrievable from the graph.
if err := c.cfg.disableChannel(c.chanPoint); err != nil {
peerLog.Warnf("Unable to disable channel %v on "+
"close: %v", c.chanPoint, err)
}
// Before continuing, mark the channel as cooperatively closed with a
// nil txn. Even though we haven't negotiated the final txn, this
// guarantees that our listchannels rpc will be externally consistent,
// and reflect that the channel is being shutdown by the time the
// closing request returns.
err := c.cfg.channel.MarkCoopBroadcasted(nil, c.locallyInitiated)
if err != nil {
return nil, err
}
// Before returning the shutdown message, we'll unregister the channel
// to ensure that it isn't seen as usable within the system.
//
// TODO(roasbeef): fail if err?
c.cfg.unregisterChannel(c.cid)
peerLog.Infof("ChannelPoint(%v): sending shutdown message", c.chanPoint)
return shutdown, nil
}
// ShutdownChan is the first method that's to be called by the initiator of the
// cooperative channel closure. This message returns the shutdown message to
// send to the remote party. Upon completion, we enter the
// closeShutdownInitiated phase as we await a response.
func (c *channelCloser) ShutdownChan() (*lnwire.Shutdown, error) {
// If we attempt to shutdown the channel for the first time, and we're
// not in the closeIdle state, then the caller made an error.
if c.state != closeIdle {
return nil, ErrChanAlreadyClosing
}
peerLog.Infof("ChannelPoint(%v): initiating shutdown of", c.chanPoint)
shutdownMsg, err := c.initChanShutdown()
if err != nil {
return nil, err
}
// With the opening steps complete, we'll transition into the
// closeShutdownInitiated state. In this state, we'll wait until the
// other party sends their version of the shutdown message.
c.state = closeShutdownInitiated
// Finally, we'll return the shutdown message to the caller so it can
// send it to the remote peer.
return shutdownMsg, nil
}
// ClosingTx returns the fully signed, final closing transaction.
//
// NOTE: This transaction is only available if the state machine is in the
// closeFinished state.
func (c *channelCloser) ClosingTx() (*wire.MsgTx, error) {
// If the state machine hasn't finished closing the channel then we'll
// return an error as we haven't yet computed the closing tx.
if c.state != closeFinished {
return nil, ErrChanCloseNotFinished
}
return c.closingTx, nil
}
// CloseRequest returns the original close request that prompted the creation
// of the state machine.
//
// NOTE: This will only return a non-nil pointer if we were the initiator of
// the cooperative closure workflow.
func (c *channelCloser) CloseRequest() *htlcswitch.ChanClose {
return c.closeReq
}
// maybeMatchScript attempts to match the script provided in our peer's
// shutdown message with the upfront shutdown script we have on record.
// If no upfront shutdown script was set, we do not need to enforce option
// upfront shutdown, so the function returns early. If an upfront script is
// set, we check whether it matches the script provided by our peer. If they
// do not match, we use the disconnect function provided to disconnect from
// the peer.
func maybeMatchScript(disconnect func() error,
upfrontScript, peerScript lnwire.DeliveryAddress) error {
// If no upfront shutdown script was set, return early because we do not
// need to enforce closure to a specific script.
if len(upfrontScript) == 0 {
return nil
}
// If an upfront shutdown script was provided, disconnect from the peer, as
// per BOLT 2, and return an error.
if !bytes.Equal(upfrontScript, peerScript) {
peerLog.Warnf("peer's script: %x does not match upfront "+
"shutdown script: %x", peerScript, upfrontScript)
// Disconnect from the peer because they have violated option upfront
// shutdown.
if err := disconnect(); err != nil {
return err
}
return errUpfrontShutdownScriptMismatch
}
return nil
}
// ProcessCloseMsg attempts to process the next message in the closing series.
// This method will update the state accordingly and return two primary values:
// the next set of messages to be sent, and a bool indicating if the fee
// negotiation process has completed. If the second value is true, then this
// means the channelCloser can be garbage collected.
func (c *channelCloser) ProcessCloseMsg(msg lnwire.Message) ([]lnwire.Message, bool, error) {
switch c.state {
// If we're in the close idle state, and we're receiving a channel
// closure related message, then this indicates that we're on the
// receiving side of an initiated channel closure.
case closeIdle:
// First, we'll assert that we have a channel shutdown message,
// otherwise, this is an attempted invalid state transition.
shutDownMsg, ok := msg.(*lnwire.Shutdown)
if !ok {
return nil, false, fmt.Errorf("expected lnwire.Shutdown, "+
"instead have %v", spew.Sdump(msg))
}
// If the remote node opened the channel with option upfront shutdown
// script, check that the script they provided matches.
if err := maybeMatchScript(
c.cfg.disconnect, c.cfg.channel.RemoteUpfrontShutdownScript(),
shutDownMsg.Address,
); err != nil {
return nil, false, err
}
// Once we have checked that the other party has not violated option
// upfront shutdown we set their preference for delivery address. We'll
// use this when we craft the closure transaction.
c.remoteDeliveryScript = shutDownMsg.Address
// We'll generate a shutdown message of our own to send across
// the wire.
localShutdown, err := c.initChanShutdown()
if err != nil {
return nil, false, err
}
peerLog.Infof("ChannelPoint(%v): Responding to shutdown",
c.chanPoint)
msgsToSend := make([]lnwire.Message, 0, 2)
msgsToSend = append(msgsToSend, localShutdown)
// After the other party receives this message, we'll actually
// start the final stage of the closure process: fee
// negotiation. So we'll update our internal state to reflect
// this, so we can handle the next message sent.
c.state = closeFeeNegotiation
// We'll also craft our initial close proposal in order to keep
// the negotiation moving, but only if we're the negotiator.
if c.cfg.channel.IsInitiator() {
closeSigned, err := c.proposeCloseSigned(c.idealFeeSat)
if err != nil {
return nil, false, err
}
msgsToSend = append(msgsToSend, closeSigned)
}
// We'll return both sets of messages to send to the remote
// party to kick off the fee negotiation process.
return msgsToSend, false, nil
// If we just initiated a channel shutdown, and we receive a new
// message, then this indicates the other party is ready to shutdown as
// well. In this state we'll send our first signature.
case closeShutdownInitiated:
// First, we'll assert that we have a channel shutdown message,
// otherwise, this is an attempted invalid state transition.
shutDownMsg, ok := msg.(*lnwire.Shutdown)
if !ok {
return nil, false, fmt.Errorf("expected lnwire.Shutdown, "+
"instead have %v", spew.Sdump(msg))
}
// If the remote node opened the channel with option upfront shutdown
// script, check that the script they provided matches.
if err := maybeMatchScript(
c.cfg.disconnect, c.cfg.channel.RemoteUpfrontShutdownScript(),
shutDownMsg.Address,
); err != nil {
return nil, false, err
}
// Now that we know this is a valid shutdown message and address, we'll
// record their preferred delivery closing script.
c.remoteDeliveryScript = shutDownMsg.Address
// At this point, we can now start the fee negotiation state,
// by constructing and sending our initial signature for what
// we think the closing transaction should look like.
c.state = closeFeeNegotiation
peerLog.Infof("ChannelPoint(%v): shutdown response received, "+
"entering fee negotiation", c.chanPoint)
// Starting with our ideal fee rate, we'll create an initial
// closing proposal, but only if we're the initiator, as
// otherwise, the other party will send their first proposal
// first.
if c.cfg.channel.IsInitiator() {
closeSigned, err := c.proposeCloseSigned(c.idealFeeSat)
if err != nil {
return nil, false, err
}
return []lnwire.Message{closeSigned}, false, nil
}
return nil, false, nil
// If we're receiving a message while we're in the fee negotiation
// phase, then this indicates the remote party is responding to a closed
// signed message we sent, or kicking off the process with their own.
case closeFeeNegotiation:
// First, we'll assert that we're actually getting a
// CloseSigned message, otherwise an invalid state transition
// was attempted.
closeSignedMsg, ok := msg.(*lnwire.ClosingSigned)
if !ok {
return nil, false, fmt.Errorf("expected lnwire.ClosingSigned, "+
"instead have %v", spew.Sdump(msg))
}
// We'll compare the proposed total fee, to what we've proposed
// during the negotiations, if it doesn't match any of our
// prior offers, then we'll attempt to rachet the fee closer to
remoteProposedFee := closeSignedMsg.FeeSatoshis
if _, ok := c.priorFeeOffers[remoteProposedFee]; !ok {
// We'll now attempt to rachet towards a fee deemed
// acceptable by both parties, factoring in our ideal
// fee rate, and the last proposed fee by both sides.
feeProposal := calcCompromiseFee(c.chanPoint,
c.idealFeeSat, c.lastFeeProposal,
remoteProposedFee,
)
// With our new fee proposal calculated, we'll craft a
// new close signed signature to send to the other
// party so we can continue the fee negotiation
// process.
closeSigned, err := c.proposeCloseSigned(feeProposal)
if err != nil {
return nil, false, err
}
// If the compromise fee doesn't match what the peer
// proposed, then we'll return this latest close signed
// message so we continue negotiation.
if feeProposal != remoteProposedFee {
peerLog.Debugf("ChannelPoint(%v): close tx "+
"fee disagreement, continuing negotiation",
c.chanPoint)
return []lnwire.Message{closeSigned}, false, nil
}
}
peerLog.Infof("ChannelPoint(%v) fee of %v accepted, ending "+
"negotiation", c.chanPoint, remoteProposedFee)
// Otherwise, we've agreed on a fee for the closing
// transaction! We'll craft the final closing transaction so
// we can broadcast it to the network.
matchingSig := c.priorFeeOffers[remoteProposedFee].Signature
localSigBytes := matchingSig.ToSignatureBytes()
localSig := append(localSigBytes, byte(txscript.SigHashAll))
remoteSigBytes := closeSignedMsg.Signature.ToSignatureBytes()
remoteSig := append(remoteSigBytes, byte(txscript.SigHashAll))
closeTx, _, err := c.cfg.channel.CompleteCooperativeClose(
localSig, remoteSig, c.localDeliveryScript,
c.remoteDeliveryScript, remoteProposedFee,
)
if err != nil {
return nil, false, err
}
c.closingTx = closeTx
// Before publishing the closing tx, we persist it to the
// database, such that it can be republished if something goes
// wrong.
err = c.cfg.channel.MarkCoopBroadcasted(
closeTx, c.locallyInitiated,
)
if err != nil {
return nil, false, err
}
// With the closing transaction crafted, we'll now broadcast it
// to the network.
peerLog.Infof("Broadcasting cooperative close tx: %v",
newLogClosure(func() string {
return spew.Sdump(closeTx)
}))
if err := c.cfg.broadcastTx(closeTx); err != nil {
return nil, false, err
}
// Finally, we'll transition to the closeFinished state, and
// also return the final close signed message we sent.
// Additionally, we return true for the second argument to
// indicate we're finished with the channel closing
// negotiation.
c.state = closeFinished
matchingOffer := c.priorFeeOffers[remoteProposedFee]
return []lnwire.Message{matchingOffer}, true, nil
// If we receive a message while in the closeFinished state, then this
// should only be the remote party echoing the last ClosingSigned
// message that we agreed on.
case closeFinished:
if _, ok := msg.(*lnwire.ClosingSigned); !ok {
return nil, false, fmt.Errorf("expected "+
"lnwire.ClosingSigned, instead have %v",
spew.Sdump(msg))
}
// There's no more to do as both sides should have already
// broadcast the closing transaction at this state.
return nil, true, nil
// Otherwise, we're in an unknown state, and can't proceed.
default:
return nil, false, ErrInvalidState
}
}
// proposeCloseSigned attempts to propose a new signature for the closing
// transaction for a channel based on the prior fee negotiations and our
// current compromise fee.
func (c *channelCloser) proposeCloseSigned(fee btcutil.Amount) (*lnwire.ClosingSigned, error) {
rawSig, _, _, err := c.cfg.channel.CreateCloseProposal(
fee, c.localDeliveryScript, c.remoteDeliveryScript,
)
if err != nil {
return nil, err
}
// We'll note our last signature and proposed fee so when the remote
// party responds we'll be able to decide if we've agreed on fees or
// not.
c.lastFeeProposal = fee
parsedSig, err := lnwire.NewSigFromRawSignature(rawSig)
if err != nil {
return nil, err
}
peerLog.Infof("ChannelPoint(%v): proposing fee of %v sat to close "+
"chan", c.chanPoint, int64(fee))
// We'll assemble a ClosingSigned message using this information and
// return it to the caller so we can kick off the final stage of the
// channel closure project.
closeSignedMsg := lnwire.NewClosingSigned(c.cid, fee, parsedSig)
// We'll also save this close signed, in the case that the remote party
// accepts our offer. This way, we don't have to re-sign.
c.priorFeeOffers[fee] = closeSignedMsg
return closeSignedMsg, nil
}
// feeInAcceptableRange returns true if the passed remote fee is deemed to be
// in an "acceptable" range to our local fee. This is an attempt at a
// compromise and to ensure that the fee negotiation has a stopping point. We
// consider their fee acceptable if it's within 30% of our fee.
func feeInAcceptableRange(localFee, remoteFee btcutil.Amount) bool {
// If our offer is lower than theirs, then we'll accept their
// offer if it's no more than 30% *greater* than our current
// offer.
if localFee < remoteFee {
acceptableRange := localFee + ((localFee * 3) / 10)
return remoteFee <= acceptableRange
}
// If our offer is greater than theirs, then we'll accept their offer
// if it's no more than 30% *less* than our current offer.
acceptableRange := localFee - ((localFee * 3) / 10)
return remoteFee >= acceptableRange
}
// rachetFee is our step function used to inch our fee closer to something that
// both sides can agree on. If up is true, then we'll attempt to increase our
// offered fee. Otherwise, if up is false, then we'll attempt to decrease our
// offered fee.
func rachetFee(fee btcutil.Amount, up bool) btcutil.Amount {
// If we need to rachet up, then we'll increase our fee by 10%.
if up {
return fee + ((fee * 1) / 10)
}
// Otherwise, we'll *decrease* our fee by 10%.
return fee - ((fee * 1) / 10)
}
// calcCompromiseFee performs the current fee negotiation algorithm, taking
// into consideration our ideal fee based on current fee environment, the fee
// we last proposed (if any), and the fee proposed by the peer.
func calcCompromiseFee(chanPoint wire.OutPoint,
ourIdealFee, lastSentFee, remoteFee btcutil.Amount) btcutil.Amount {
// TODO(roasbeef): take in number of rounds as well?
peerLog.Infof("ChannelPoint(%v): computing fee compromise, ideal=%v, "+
"last_sent=%v, remote_offer=%v", chanPoint, int64(ourIdealFee),
int64(lastSentFee), int64(remoteFee))
// Otherwise, we'll need to attempt to make a fee compromise if this is
// the second round, and neither side has agreed on fees.
switch {
// If their proposed fee is identical to our ideal fee, then we'll go
// with that as we can short circuit the fee negotiation. Similarly, if
// we haven't sent an offer yet, we'll default to our ideal fee.
case ourIdealFee == remoteFee || lastSentFee == 0:
return ourIdealFee
// If the last fee we sent, is equal to the fee the remote party is
// offering, then we can simply return this fee as the negotiation is
// over.
case remoteFee == lastSentFee:
return lastSentFee
// If the fee the remote party is offering is less than the last one we
// sent, then we'll need to rachet down in order to move our offer
// closer to theirs.
case remoteFee < lastSentFee:
// If the fee is lower, but still acceptable, then we'll just
// return this fee and end the negotiation.
if feeInAcceptableRange(lastSentFee, remoteFee) {
peerLog.Infof("ChannelPoint(%v): proposed remote fee "+
"is close enough, capitulating", chanPoint)
return remoteFee
}
// Otherwise, we'll rachet the fee *down* using our current
// algorithm.
return rachetFee(lastSentFee, false)
// If the fee the remote party is offering is greater than the last one
// we sent, then we'll rachet up in order to ensure we terminate
// eventually.
case remoteFee > lastSentFee:
// If the fee is greater, but still acceptable, then we'll just
// return this fee in order to put an end to the negotiation.
if feeInAcceptableRange(lastSentFee, remoteFee) {
peerLog.Infof("ChannelPoint(%v): proposed remote fee "+
"is close enough, capitulating", chanPoint)
return remoteFee
}
// Otherwise, we'll rachet the fee up using our current
// algorithm.
return rachetFee(lastSentFee, true)
default:
// TODO(roasbeef): fail if their fee isn't in expected range
return remoteFee
}
}