You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
613 lines
23 KiB
613 lines
23 KiB
package lnd |
|
|
|
import ( |
|
"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/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") |
|
) |
|
|
|
// 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 |
|
|
|
// 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 |
|
} |
|
|
|
// 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 lnwallet.SatPerKWeight, negotiationHeight uint32, |
|
closeReq *htlcswitch.ChanClose) *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), |
|
} |
|
} |
|
|
|
// 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 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 |
|
} |
|
|
|
// 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)) |
|
} |
|
|
|
// Next, we'll note the other party's preference for their |
|
// 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)) |
|
} |
|
|
|
// Now that we know this is a valid shutdown message, 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 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) |
|
} |
|
|
|
// 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 |
|
} |
|
if err := c.cfg.channel.MarkCommitmentBroadcasted(); 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 |
|
} |
|
}
|
|
|