lnd.xprv/lnwallet/channel.go
Olaoluwa Osuntokun e0c09a016b
lnwallet: use stored initiator bool to properly construct close tx
This commit modifies the channel closing logic to remove the hard coded
bools indicating which side is attempting the closure. With the recent
changes, the initiator must always pay the channel closure fees.

This information is recently stored on disk, therefore we can use the
boolean to ensure that the closure transaction is created properly no
matter who initiates the close.

This fixes a bug.
2016-12-07 22:39:33 -08:00

2143 lines
76 KiB
Go

package lnwallet
import (
"bytes"
"container/list"
"fmt"
"sync"
"github.com/btcsuite/fastsha256"
"github.com/davecgh/go-spew/spew"
"github.com/lightningnetwork/lnd/chainntnfs"
"github.com/lightningnetwork/lnd/channeldb"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/roasbeef/btcd/btcec"
"github.com/roasbeef/btcd/txscript"
"github.com/roasbeef/btcd/wire"
"github.com/roasbeef/btcutil"
"github.com/roasbeef/btcutil/txsort"
)
var zeroHash wire.ShaHash
var (
ErrChanClosing = fmt.Errorf("channel is being closed, operation disallowed")
ErrNoWindow = fmt.Errorf("unable to sign new commitment, the current" +
" revocation window is exhausted")
ErrMaxWeightCost = fmt.Errorf("commitment transaction exceed max " +
"available weight")
ErrMaxHTLCNumber = fmt.Errorf("commitment transaction exceed max " +
"htlc number")
)
const (
// MaxPendingPayments is the max number of pending HTLC's permitted on
// a channel.
// TODO(roasbeef): make not random value + enforce
// * should be tuned to account for max tx "cost"
MaxPendingPayments = 100
// InitialRevocationWindow is the number of revoked commitment
// transactions allowed within the commitment chain. This value allows
// a greater degree of de-synchronization by allowing either parties to
// extend the other's commitment chain non-interactively, and also
// serves as a flow control mechanism to a degree.
InitialRevocationWindow = 4
)
// channelState is an enum like type which represents the current state of a
// particular channel.
// TODO(roasbeef): actually update state
type channelState uint8
const (
// channelPending indicates this channel is still going through the
// funding workflow, and isn't yet open.
channelPending channelState = iota
// channelOpen represents an open, active channel capable of
// sending/receiving HTLCs.
channelOpen
// channelClosing represents a channel which is in the process of being
// closed.
channelClosing
// channelClosed represents a channel which has been fully closed. Note
// that before a channel can be closed, ALL pending HTLC's must be
// settled/removed.
channelClosed
// channelDispute indicates that an un-cooperative closure has been
// detected within the channel.
channelDispute
// channelPendingPayment indicates that there a currently outstanding
// HTLC's within the channel.
channelPendingPayment
)
// PaymentHash represents the sha256 of a random value. This hash is used to
// uniquely track incoming/outgoing payments within this channel, as well as
// payments requested by the wallet/daemon.
type PaymentHash [32]byte
// UpdateType is the exact type of an entry within the shared HTLC log.
type updateType uint8
const (
Add updateType = iota
Timeout
Settle
)
// PaymentDescriptor represents a commitment state update which either adds,
// settles, or removes an HTLC. PaymentDescriptors encapsulate all necessary
// meta-data w.r.t to an HTLC, and additional data pairing a settle message to
// the original added HTLC.
// TODO(roasbeef): LogEntry interface??
// * need to separate attrs for cancel/add/settle
type PaymentDescriptor struct {
sync.RWMutex
// RHash is the payment hash for this HTLC. The HTLC can be settled iff
// the preimage to this hash is presented.
RHash PaymentHash
// RPreimage is the preimage that settles the HTLC pointed to wthin the
// log by the ParentIndex.
RPreimage PaymentHash
// Timeout is the absolute timeout in blocks, after which this HTLC
// expires.
Timeout uint32
// Amount is the HTLC amount in satoshis.
Amount btcutil.Amount
// Index is the log entry number that his HTLC update has within the
// log. Depending on if IsIncoming is true, this is either an entry the
// remote party added, or one that we added locally.
Index uint32
// ParentIndex is the index of the log entry that this HTLC update
// settles or times out.
ParentIndex uint32
// Payload is an opaque blob which is used to complete multi-hop routing.
Payload []byte
// Type denotes the exact type of the PaymentDescriptor. In the case of
// a Timeout, or Settle type, then the Parent field will point into the
// log to the HTLC being modified.
EntryType updateType
// addCommitHeight[Remote|Local] encodes the height of the commitment
// which included this HTLC on either the remote or local commitment
// chain. This value is used to determine when an HTLC is fully
// "locked-in".
addCommitHeightRemote uint64
addCommitHeightLocal uint64
// removeCommitHeight[Remote|Local] encodes the height of the
//commitment which removed the parent pointer of this PaymentDescriptor
//either due to a timeout or a settle. Once both these heights are
//above the tail of both chains, the log entries can safely be removed.
removeCommitHeightRemote uint64
removeCommitHeightLocal uint64
// isForwarded denotes if an incoming HTLC has been forwarded to any
// possible upstream peers in the route.
isForwarded bool
settled bool
// pkScript is the raw public key script that encodes the redemption
// rules for this particular HTLC. This field will only be populated
// iff the EntryType of this PaymentDescriptor is Add.
pkScript []byte
}
// commitment represents a commitment to a new state within an active channel.
// New commitments can be initiated by either side. Commitments are ordered
// into a commitment chain, with one existing for both parties. Each side can
// independently extend the other side's commitment chain, up to a certain
// "revocation window", which once reached, disallows new commitments until
// the local nodes receives the revocation for the remote node's chain tail.
type commitment struct {
// height represents the commitment height of this commitment, or the
// update number of this commitment.
height uint64
// [our|their]MessageIndex are indexes into the HTLC log, up to which
// this commitment transaction includes. These indexes allow both sides
// to independently, and concurrent send create new commitments. Each
// new commitment sent to the remote party includes an index in the
// shared log which details which of their updates we're including in
// this new commitment.
// TODO(roasbeef): also make uint64?
ourMessageIndex uint32
theirMessageIndex uint32
// txn is the commitment transaction generated by including any HTLC
// updates whose index are below the two indexes listed above. If this
// commitment is being added to the remote chain, then this txn is
// their version of the commitment transactions. If the local commit
// chain is being modified, the opposite is true.
txn *wire.MsgTx
// sig is a signature for the above commitment transaction.
sig []byte
// [our|their]Balance represents the settled balances at this point
// within the commitment chain. This balance is computed by properly
// evaluating all the add/remove/settle log entries before the listed
// indexes.
ourBalance btcutil.Amount
theirBalance btcutil.Amount
// htlcs is the set of HTLC's which remain unsettled within this
// commitment.
outgoingHTLCs []*PaymentDescriptor
incomingHTLCs []*PaymentDescriptor
}
// toChannelDelta converts the target commitment into a format suitable to be
// written to disk after an accepted state transition.
// TODO(roasbeef): properly fill in refund timeouts
func (c *commitment) toChannelDelta() (*channeldb.ChannelDelta, error) {
numHtlcs := len(c.outgoingHTLCs) + len(c.incomingHTLCs)
delta := &channeldb.ChannelDelta{
LocalBalance: c.ourBalance,
RemoteBalance: c.theirBalance,
UpdateNum: uint32(c.height),
Htlcs: make([]*channeldb.HTLC, 0, numHtlcs),
}
// As we also store the output index of the HTLC for continence
// purposes, we create a small helper function to locate the output
// index of a particular HTLC within the current commitment
// transaction.
locateOutputIndex := func(p *PaymentDescriptor) uint16 {
var idx uint16
for i, txOut := range c.txn.TxOut {
// TODO(roasbeef): duplicated payment hashes...
if bytes.Equal(txOut.PkScript, p.pkScript) {
idx = uint16(i)
break
}
}
return idx
}
for _, htlc := range c.outgoingHTLCs {
h := &channeldb.HTLC{
Incoming: false,
Amt: htlc.Amount,
RHash: htlc.RHash,
RefundTimeout: htlc.Timeout,
RevocationDelay: 0,
OutputIndex: locateOutputIndex(htlc),
}
delta.Htlcs = append(delta.Htlcs, h)
}
for _, htlc := range c.incomingHTLCs {
h := &channeldb.HTLC{
Incoming: true,
Amt: htlc.Amount,
RHash: htlc.RHash,
RefundTimeout: htlc.Timeout,
RevocationDelay: 0,
OutputIndex: locateOutputIndex(htlc),
}
delta.Htlcs = append(delta.Htlcs, h)
}
return delta, nil
}
// commitmentChain represents a chain of unrevoked commitments. The tail of the
// chain is the latest fully signed, yet unrevoked commitment. Two chains are
// tracked, one for the local node, and another for the remote node. New
// commitments we create locally extend the remote node's chain, and vice
// versa. Commitment chains are allowed to grow to a bounded length, after
// which the tail needs to be "dropped" before new commitments can be received.
// The tail is "dropped" when the owner of the chain sends a revocation for the
// previous tail.
type commitmentChain struct {
// commitments is a linked list of commitments to new states. New
// commitments are added to the end of the chain with increase height.
// Once a commitment transaction is revoked, the tail is incremented,
// freeing up the revocation window for new commitments.
commitments *list.List
// startingHeight is the starting height of this commitment chain on a
// session basis.
startingHeight uint64
}
// newCommitmentChain creates a new commitment chain from an initial height.
func newCommitmentChain(initialHeight uint64) *commitmentChain {
return &commitmentChain{
commitments: list.New(),
startingHeight: initialHeight,
}
}
// addCommitment extends the commitment chain by a single commitment. This
// added commitment represents a state update propsed by either party. Once the
// commitment prior to this commitment is revoked, the commitment becomes the
// new defacto state within the channel.
func (s *commitmentChain) addCommitment(c *commitment) {
s.commitments.PushBack(c)
}
// advanceTail reduces the length of the commitment chain by one. The tail of
// the chain should be advanced once a revocation for the lowest unrevoked
// commitment in the chain is received.
func (s *commitmentChain) advanceTail() {
s.commitments.Remove(s.commitments.Front())
}
// tip returns the latest commitment added to the chain.
func (s *commitmentChain) tip() *commitment {
return s.commitments.Back().Value.(*commitment)
}
// tail returns the lowest unrevoked commitment transaction in the chain.
func (s *commitmentChain) tail() *commitment {
return s.commitments.Front().Value.(*commitment)
}
// LightningChannel implements the state machine which corresponds to the
// current commitment protocol wire spec. The state machine implemented allows
// for asynchronous fully desynchronized, batched+pipelined updates to
// commitment transactions allowing for a high degree of non-blocking
// bi-directional payment throughput.
//
// In order to allow updates to be fully non-blocking, either side is able to
// create multiple new commitment states up to a pre-determined window size.
// This window size is encoded within InitialRevocationWindow. Before the start
// of a session, both side should send out revocation messages with nil
// preimages in order to populate their revocation window for the remote party.
// Ths method .ExtendRevocationWindow() is used to extend the revocation window
// by a single revocation.
//
// The state machine has for main methods:
// * .SignNextCommitment()
// * Called one one wishes to sign the next commitment, either initiating a
// new state update, or responding to a received commitment.
// * .ReceiveNewCommitment()
// * Called upon receipt of a new commitment from the remote party. If the
// new commitment is valid, then a revocation should immediately be
// generated and sent.
// * .RevokeCurrentCommitment()
// * Revokes the current commitment. Should be called directly after
// receiving a new commitment.
// * .ReceiveRevocation()
// * Processes a revocation from the remote party. If successful creates a
// new defacto broadcastable state.
//
// See the individual comments within the above methods for further details.
type LightningChannel struct {
signer Signer
signDesc *SignDescriptor
bio BlockChainIO
channelEvents chainntnfs.ChainNotifier
sync.RWMutex
ourLogCounter uint32
theirLogCounter uint32
status channelState
Capacity btcutil.Amount
// currentHeight is the current height of our local commitment chain.
// This is also the same as the number of updates to the channel we've
// accepted.
currentHeight uint64
// revocationWindowEdge is the edge of the current revocation window.
// New revocations for prior states created by this channel extend the
// edge of this revocation window. The existence of a revocation window
// allows the remote party to initiate new state updates independently
// until the window is exhausted.
revocationWindowEdge uint64
// usedRevocations is a slice of revocations given to us by the remote
// party that we've used. This slice is extended each time we create a
// new commitment. The front of the slice is popped off once we receive
// a revocation for a prior state. This head element then becomes the
// next set of keys/hashes we expect to be revoked.
usedRevocations []*lnwire.CommitRevocation
// revocationWindow is a window of revocations sent to use by the
// remote party, allowing us to create new commitment transactions
// until depleted. The revocations don't contain a valid pre-image,
// only an additional key/hash allowing us to create a new commitment
// transaction for the remote node that they are able to revoke. If
// this slice is empty, then we cannot make any new updates to their
// commitment chain.
revocationWindow []*lnwire.CommitRevocation
// remoteCommitChain is the remote node's commitment chain. Any new
// commitments we initiate are added to the tip of this chain.
remoteCommitChain *commitmentChain
// localCommitChain is our local commitment chain. Any new commitments
// received are added to the tip of this chain. The tail (or lowest
// height) in this chain is our current accepted state, which we are
// able to broadcast safely.
localCommitChain *commitmentChain
// stateMtx protects concurrent access to the state struct.
stateMtx sync.RWMutex
channelState *channeldb.OpenChannel
// stateUpdateLog is a (mostly) append-only log storing all the HTLC
// updates to this channel. The log is walked backwards as HTLC updates
// are applied in order to re-construct a commitment transaction from a
// commitment. The log is compacted once a revocation is received.
ourUpdateLog *list.List
theirUpdateLog *list.List
// logIndex is an index into the above log. This index is used to
// remove Add state updates, once a timeout/settle is received.
ourLogIndex map[uint32]*list.Element
theirLogIndex map[uint32]*list.Element
LocalDeliveryScript []byte
RemoteDeliveryScript []byte
FundingWitnessScript []byte
fundingTxIn *wire.TxIn
fundingP2WSH []byte
// ForceCloseSignal is a channel that is closed to indicate that a
// local system has initiated a force close by broadcasting the current
// commitment transaction directly on-chain.
ForceCloseSignal chan struct{}
// UnilateralCloseSignal is a channel that is closed to indicate that
// the remote party has performed a unilateral close by broadcasting
// their version of the commitment transaction on-chain.
UnilateralCloseSignal chan struct{}
// ContractBreach is a channel that is used to communicate the data
// necessary to fully resolve the channel in the case that a contract
// breach is detected. A contract breach occurs it is detected that the
// counter party has broadcast a prior *revoked* state.
ContractBreach chan *BreachRetribution
started int32
shutdown int32
quit chan struct{}
wg sync.WaitGroup
}
// NewLightningChannel creates a new, active payment channel given an
// implementation of the chain notifier, channel database, and the current
// settled channel state. Throughout state transitions, then channel will
// automatically persist pertinent state to the database in an efficient
// manner.
func NewLightningChannel(signer Signer, bio BlockChainIO,
events chainntnfs.ChainNotifier,
state *channeldb.OpenChannel) (*LightningChannel, error) {
lc := &LightningChannel{
signer: signer,
bio: bio,
channelEvents: events,
currentHeight: state.NumUpdates,
remoteCommitChain: newCommitmentChain(state.NumUpdates),
localCommitChain: newCommitmentChain(state.NumUpdates),
channelState: state,
revocationWindowEdge: state.NumUpdates,
ourUpdateLog: list.New(),
theirUpdateLog: list.New(),
ourLogIndex: make(map[uint32]*list.Element),
theirLogIndex: make(map[uint32]*list.Element),
Capacity: state.Capacity,
LocalDeliveryScript: state.OurDeliveryScript,
RemoteDeliveryScript: state.TheirDeliveryScript,
FundingWitnessScript: state.FundingWitnessScript,
ForceCloseSignal: make(chan struct{}),
UnilateralCloseSignal: make(chan struct{}),
ContractBreach: make(chan *BreachRetribution, 1),
}
// Initialize both of our chains the current un-revoked commitment for
// each side.
// TODO(roasbeef): add chnneldb.RevocationLogTail method, then init
// their commitment from that as we may be de-synced
initialCommitment := &commitment{
height: lc.currentHeight,
ourBalance: state.OurBalance,
ourMessageIndex: 0,
theirBalance: state.TheirBalance,
theirMessageIndex: 0,
}
lc.localCommitChain.addCommitment(initialCommitment)
lc.remoteCommitChain.addCommitment(initialCommitment)
// If we're restarting from a channel with history, then restore the
// update in-memory update logs to that of the prior state.
if lc.currentHeight != 0 {
lc.restoreStateLogs()
}
// Create the sign descriptor which we'll be using very frequently to
// request a signature for the 2-of-2 multi-sig from the signer in
// order to complete channel state transitions.
fundingPkScript, err := witnessScriptHash(state.FundingWitnessScript)
if err != nil {
return nil, err
}
lc.fundingTxIn = wire.NewTxIn(state.FundingOutpoint, nil, nil)
lc.fundingP2WSH = fundingPkScript
lc.signDesc = &SignDescriptor{
PubKey: lc.channelState.OurMultiSigKey,
WitnessScript: lc.channelState.FundingWitnessScript,
Output: &wire.TxOut{
PkScript: lc.fundingP2WSH,
Value: int64(lc.channelState.Capacity),
},
HashType: txscript.SigHashAll,
InputIndex: 0,
}
// Register for a notification to be dispatched if the funding outpoint
// has been spent. This indicates that either us or the remote party
// has broadcasted a commitment transaction on-chain.
fundingOut := &lc.fundingTxIn.PreviousOutPoint
channelCloseNtfn, err := lc.channelEvents.RegisterSpendNtfn(fundingOut)
if err != nil {
return nil, err
}
// Launch the close observer which will vigilantly watch the network
// for any broadcasts the current or prior commitment transactions,
// taking action accordingly.
go lc.closeObserver(channelCloseNtfn)
return lc, nil
}
// BreachRetribution contains all the data necessary to bring a channel
// counter-party to justice claiming ALL lingering funds within the channel in
// the scenario that they broadcast a revoked commitment transaction. A
// BreachRetribution is created by the closeObserver if it detects an
// uncooperative close of the channel which uses a revoked commitment
// transaction. The BreachRetribution is then sent over the ContractBreach
// channel in order to allow the subscriber of the channel to dispatch justice.
type BreachRetribution struct {
// BreachTransaction is the transaction which breached the channel
// contract by spending from the funding multi-sig with a revoked
// commitment transaction.
BreachTransaction *wire.MsgTx
// RevokedStateNum is the revoked state number which was broadcast.
RevokedStateNum uint64
// PendingHTLCs is a slice of the HTLC's which were pending at this
// point within the channel's history transcript.
PendingHTLCs []*channeldb.HTLC
// LocalOutputSignDesc is a SignDescriptor which is capable of
// generating the signature necessary to sweep the output within the
// BreachTransaction that pays directly us.
LocalOutputSignDesc *SignDescriptor
// LocalOutpoint is the outpoint of the output paying to us (the local
// party) within the breach transaction.
LocalOutpoint wire.OutPoint
// RemoteOutputSignDesc is a SignDescriptor which is capable of
// generating the signature required to claim the funds as described
// within the revocation clause of the remote party's commitment
// output.
RemoteOutputSignDesc *SignDescriptor
// RemoteOutpoint is the output of the output paying to the remote
// party within the breach transaction.
RemoteOutpoint wire.OutPoint
}
// newBreachRetribution creates a new fully populated BreachRetribution for the
// passed channel, at a particular revoked state number, and one which targets
// the passed commitment transaction.
func newBreachRetribution(chanState *channeldb.OpenChannel, stateNum uint64,
broadcastCommitment *wire.MsgTx) (*BreachRetribution, error) {
commitHash := broadcastCommitment.TxSha()
// Query the on-disk revocation log for the snapshot which was recorded
// at this particular state num.
revokedSnapshot, err := chanState.FindPreviousState(stateNum)
if err != nil {
return nil, err
}
// With the state number broadcast known, we can now derive the proper
// leaf from our revocation tree necessary to sweep the remote party's
// output.
revocationPreimage, err := chanState.RemoteElkrem.AtIndex(stateNum)
if err != nil {
return nil, err
}
// Once we derive the revocation leaf, we can then re-create the
// revocation public key used within this state. This is needed in
// order to create the proper script below.
localCommitKey := chanState.OurCommitKey
revocationKey := DeriveRevocationPubkey(localCommitKey, revocationPreimage[:])
remoteCommitkey := chanState.TheirCommitKey
remoteDelay := chanState.RemoteCsvDelay
// Next, reconstruct the scripts as they were present at this state
// number so we can have the proper witness script to sign and include
// within the final witness.
remotePkScript, err := commitScriptToSelf(remoteDelay,
remoteCommitkey, revocationKey)
if err != nil {
return nil, err
}
remoteWitnessHash, err := witnessScriptHash(remotePkScript)
if err != nil {
return nil, err
}
localPkScript, err := commitScriptUnencumbered(localCommitKey)
if err != nil {
return nil, err
}
// In order to fully populate the breach retribution struct, we'll need
// to find the exact index of the local+remote commitment outputs.
localOutpoint := wire.OutPoint{
Hash: commitHash,
}
remoteOutpoint := wire.OutPoint{
Hash: commitHash,
}
for i, txOut := range broadcastCommitment.TxOut {
switch {
case bytes.Equal(txOut.PkScript, localPkScript):
localOutpoint.Index = uint32(i)
case bytes.Equal(txOut.PkScript, remoteWitnessHash):
remoteOutpoint.Index = uint32(i)
}
}
// Finally, with all the necessary data constructed, we can create the
// BreachRetribution struct which houses all the data necessary to
// swiftly bring justice to the cheating remote party.
return &BreachRetribution{
BreachTransaction: broadcastCommitment,
RevokedStateNum: stateNum,
PendingHTLCs: revokedSnapshot.Htlcs,
LocalOutpoint: localOutpoint,
LocalOutputSignDesc: &SignDescriptor{
PubKey: localCommitKey,
Output: &wire.TxOut{
PkScript: localPkScript,
Value: int64(revokedSnapshot.LocalBalance),
},
HashType: txscript.SigHashAll,
},
RemoteOutpoint: remoteOutpoint,
RemoteOutputSignDesc: &SignDescriptor{
PubKey: localCommitKey,
PrivateTweak: revocationPreimage[:],
WitnessScript: remotePkScript,
Output: &wire.TxOut{
PkScript: remoteWitnessHash,
Value: int64(revokedSnapshot.RemoteBalance),
},
HashType: txscript.SigHashAll,
},
}, nil
}
// closeObserver is a goroutine which watches the network for any spends of the
// multi-sig funding output. A spend from the multi-sig output may occur under
// the following three scenarios: a cooperative close, a unilateral close, and
// a uncooperative contract breaching close. In the case of the last scenario a
// BreachRetribution struct is created and sent over the ContractBreach channel
// notifying subscribers that the counter-party has violated the condition of
// the channel by broadcasting a revoked prior state.
//
// NOTE: This MUST be run as a goroutine.
func (lc *LightningChannel) closeObserver(channelCloseNtfn *chainntnfs.SpendEvent) {
// If the daemon is shutting down, then this notification channel will
// be closed, so check the second read-value to avoid a false positive.
commitSpend, ok := <-channelCloseNtfn.Spend
if !ok {
return
}
// If we've already initiated a local cooperative or unilateral close
// locally, then we have nothing more to do.
lc.RLock()
if lc.status == channelClosed || lc.status == channelDispute {
lc.RUnlock()
return
}
lc.RUnlock()
lc.Lock()
defer lc.Unlock()
// TODO(roasbeef): logs duplicated due to breachArbiter...
walletLog.Warnf("Unprompted commitment broadcast for ChannelPoint(%v) "+
"detected!", lc.channelState.ChanID)
// Otherwise, the remote party might have broadcast a prior revoked
// state...!!!
commitTxBroadcast := commitSpend.SpendingTx
// Decode the state hint encoded within the commitment transaction to
// determine if this is a revoked state or not.
obsfucator := lc.channelState.StateHintObsfucator
broadcastStateNum := uint64(GetStateNumHint(commitTxBroadcast, obsfucator))
currentStateNum, err := lc.channelState.CommitmentHeight()
if err != nil {
walletLog.Errorf("unable to obtain commitment height: %v", err)
return
}
switch {
// If state number spending transaction matches the current latest
// state, then they've initiated a unilateral close. So we'll trigger
// the unilateral close signal so subscribers can clean up the state as
// necessary.
case broadcastStateNum == currentStateNum:
walletLog.Infof("Unilateral close of ChannelPoint(%v) "+
"detected", lc.channelState.ChanID)
close(lc.UnilateralCloseSignal)
// If the state number broadcast is lower than the remote node's
// current un-revoked height, then THEY'RE ATTEMPTING TO VIOLATE THE
// CONTRACT LAID OUT WITHIN THE PAYMENT CHANNEL. Therefore we close
// the signal indicating a revoked broadcast to allow subscribers to
// swiftly dispatch justice!!!
case broadcastStateNum < currentStateNum:
walletLog.Warnf("Remote peer has breached the channel "+
"contract for ChannelPoint(%v). Revoked state #%v was "+
"broadcast!!!", lc.channelState.ChanID,
broadcastStateNum)
// Create a new reach retribution struct which contains all the
// data needed to swiftly bring the cheating peer to justice.
retribution, err := newBreachRetribution(lc.channelState,
broadcastStateNum, commitTxBroadcast)
if err != nil {
walletLog.Errorf("unable to create breach retribution: %v", err)
return
}
walletLog.Debugf("Punishment breach retribution created: %#v",
retribution)
// Finally, send the retribution struct over the contract beach
// channel to allow the observer the use the breach retribution
// to sweep ALL funds.
lc.ContractBreach <- retribution
case broadcastStateNum > currentStateNum:
}
}
// restoreStateLogs runs through the current locked-in HTLC's from the point of
// view of the channel and insert corresponding log entries (both local and
// remote) for each HTLC read from disk. This method is required sync the
// in-memory state of the state machine with that read from persistent storage.
func (lc *LightningChannel) restoreStateLogs() error {
var pastHeight uint64
if lc.currentHeight > 0 {
pastHeight = lc.currentHeight - 1
}
var ourCounter, theirCounter uint32
for _, htlc := range lc.channelState.Htlcs {
// TODO(roasbeef): set isForwarded to false for all? need to
// persist state w.r.t to if forwarded or not, or can
// inadvertently trigger replays
pd := &PaymentDescriptor{
RHash: htlc.RHash,
Timeout: htlc.RefundTimeout,
Amount: htlc.Amt,
EntryType: Add,
addCommitHeightRemote: pastHeight,
addCommitHeightLocal: pastHeight,
}
if !htlc.Incoming {
pd.Index = ourCounter
lc.ourLogIndex[pd.Index] = lc.ourUpdateLog.PushBack(pd)
ourCounter++
} else {
pd.Index = theirCounter
lc.theirLogIndex[pd.Index] = lc.theirUpdateLog.PushBack(pd)
theirCounter++
}
}
lc.ourLogCounter = ourCounter
lc.theirLogCounter = theirCounter
lc.localCommitChain.tail().ourMessageIndex = ourCounter
lc.localCommitChain.tail().theirMessageIndex = theirCounter
lc.remoteCommitChain.tail().ourMessageIndex = ourCounter
lc.remoteCommitChain.tail().theirMessageIndex = theirCounter
return nil
}
// htlcView represents the "active" HTLC's at a particular point within the
// history of the HTLC update log.
type htlcView struct {
ourUpdates []*PaymentDescriptor
theirUpdates []*PaymentDescriptor
}
// fetchHTLCView returns all the candidate HTLC updates which should be
// considered for inclusion within a commitment based on the passed HTLC log
// indexes.
func (lc *LightningChannel) fetchHTLCView(theirLogIndex, ourLogIndex uint32) *htlcView {
var ourHTLCs []*PaymentDescriptor
for e := lc.ourUpdateLog.Front(); e != nil; e = e.Next() {
htlc := e.Value.(*PaymentDescriptor)
// This HTLC is active from this point-of-view iff the log
// index of the state update is below the specified index in
// our update log.
if htlc.Index < ourLogIndex {
ourHTLCs = append(ourHTLCs, htlc)
}
}
var theirHTLCs []*PaymentDescriptor
for e := lc.theirUpdateLog.Front(); e != nil; e = e.Next() {
htlc := e.Value.(*PaymentDescriptor)
// If this is an incoming HTLC, then it is only active from
// this point-of-view if the index of the HTLC addition in
// their log is below the specified view index.
if htlc.Index < theirLogIndex {
theirHTLCs = append(theirHTLCs, htlc)
}
}
return &htlcView{
ourUpdates: ourHTLCs,
theirUpdates: theirHTLCs,
}
}
// fetchCommitmentView returns a populated commitment which expresses the state
// of the channel from the point of view of a local or remote chain, evaluating
// the HTLC log up to the passed indexes. This function is used to construct
// both local and remote commitment transactions in order to sign or verify new
// commitment updates. A fully populated commitment is returned which reflects
// the proper balances for both sides at this point in the commitment chain.
func (lc *LightningChannel) fetchCommitmentView(remoteChain bool,
ourLogIndex, theirLogIndex uint32, revocationKey *btcec.PublicKey,
revocationHash [32]byte) (*commitment, error) {
var commitChain *commitmentChain
if remoteChain {
commitChain = lc.remoteCommitChain
} else {
commitChain = lc.localCommitChain
}
// TODO(roasbeef): don't assume view is always fetched from tip?
var ourBalance, theirBalance btcutil.Amount
if commitChain.tip() == nil {
ourBalance = lc.channelState.OurBalance
theirBalance = lc.channelState.TheirBalance
} else {
ourBalance = commitChain.tip().ourBalance
theirBalance = commitChain.tip().theirBalance
}
nextHeight := commitChain.tip().height + 1
// Run through all the HTLC's that will be covered by this transaction
// in order to update their commitment addition height, and to adjust
// the balances on the commitment transaction accordingly.
// TODO(roasbeef): error if log empty?
htlcView := lc.fetchHTLCView(theirLogIndex, ourLogIndex)
filteredHTLCView := lc.evaluateHTLCView(htlcView, &ourBalance, &theirBalance,
nextHeight, remoteChain)
var selfKey *btcec.PublicKey
var remoteKey *btcec.PublicKey
var delay uint32
var delayBalance, p2wkhBalance btcutil.Amount
if remoteChain {
selfKey = lc.channelState.TheirCommitKey
remoteKey = lc.channelState.OurCommitKey
delay = lc.channelState.RemoteCsvDelay
delayBalance = theirBalance
p2wkhBalance = ourBalance
} else {
selfKey = lc.channelState.OurCommitKey
remoteKey = lc.channelState.TheirCommitKey
delay = lc.channelState.LocalCsvDelay
delayBalance = ourBalance
p2wkhBalance = theirBalance
}
// Generate a new commitment transaction with all the latest
// unsettled/un-timed out HTLC's.
ourCommitTx := !remoteChain
commitTx, err := CreateCommitTx(lc.fundingTxIn, selfKey, remoteKey,
revocationKey, delay, delayBalance, p2wkhBalance)
if err != nil {
return nil, err
}
for _, htlc := range filteredHTLCView.ourUpdates {
err := lc.addHTLC(commitTx, ourCommitTx, htlc,
revocationHash, delay, false)
if err != nil {
return nil, err
}
}
for _, htlc := range filteredHTLCView.theirUpdates {
err := lc.addHTLC(commitTx, ourCommitTx, htlc,
revocationHash, delay, true)
if err != nil {
return nil, err
}
}
// Set the state hint of the commitment transaction to facilitate
// quickly recovering the necessary penalty state in the case of an
// uncooperative broadcast.
obsfucator := lc.channelState.StateHintObsfucator
stateNum := uint32(nextHeight)
if err := SetStateNumHint(commitTx, stateNum, obsfucator); err != nil {
return nil, err
}
// Sort the transactions according to the agreed upon canonical
// ordering. This lets us skip sending the entire transaction over,
// instead we'll just send signatures.
txsort.InPlaceSort(commitTx)
return &commitment{
txn: commitTx,
height: nextHeight,
ourBalance: ourBalance,
ourMessageIndex: ourLogIndex,
theirMessageIndex: theirLogIndex,
theirBalance: theirBalance,
outgoingHTLCs: filteredHTLCView.ourUpdates,
incomingHTLCs: filteredHTLCView.theirUpdates,
}, nil
}
// evaluateHTLCView processes all update entries in both HTLC update logs,
// producing a final view which is the result of properly applying all adds,
// settles, and timeouts found in both logs. The resulting view returned
// reflects the current state of htlc's within the remote or local commitment
// chain.
func (lc *LightningChannel) evaluateHTLCView(view *htlcView, ourBalance,
theirBalance *btcutil.Amount, nextHeight uint64, remoteChain bool) *htlcView {
newView := &htlcView{}
// We use two maps, one for the local log and one for the remote log to
// keep track of which entries we need to skip when creating the final
// htlc view. We skip an entry whenever we find a settle or a timeout
// modifying an entry.
skipUs := make(map[uint32]struct{})
skipThem := make(map[uint32]struct{})
// First we run through non-add entries in both logs, populating the
// skip sets and mutating the current chain state (crediting balances, etc) to
// reflect the settle/timeout entry encountered.
for _, entry := range view.ourUpdates {
if entry.EntryType == Add {
continue
}
if entry.EntryType == Settle && !remoteChain {
lc.channelState.TotalSatoshisReceived += uint64(entry.Amount)
}
addEntry := lc.theirLogIndex[entry.ParentIndex].Value.(*PaymentDescriptor)
skipThem[addEntry.Index] = struct{}{}
processRemoveEntry(entry, ourBalance, theirBalance,
nextHeight, remoteChain, true)
}
for _, entry := range view.theirUpdates {
if entry.EntryType == Add {
continue
}
if entry.EntryType == Settle && !remoteChain {
lc.channelState.TotalSatoshisSent += uint64(entry.Amount)
}
addEntry := lc.ourLogIndex[entry.ParentIndex].Value.(*PaymentDescriptor)
skipUs[addEntry.Index] = struct{}{}
processRemoveEntry(entry, ourBalance, theirBalance,
nextHeight, remoteChain, false)
}
// Next we take a second pass through all the log entries, skipping any
// settled HTLC's, and debiting the chain state balance due to any
// newly added HTLC's.
for _, entry := range view.ourUpdates {
isAdd := entry.EntryType == Add
if _, ok := skipUs[entry.Index]; !isAdd || ok {
continue
}
processAddEntry(entry, ourBalance, theirBalance, nextHeight,
remoteChain, false)
newView.ourUpdates = append(newView.ourUpdates, entry)
}
for _, entry := range view.theirUpdates {
isAdd := entry.EntryType == Add
if _, ok := skipThem[entry.Index]; !isAdd || ok {
continue
}
processAddEntry(entry, ourBalance, theirBalance, nextHeight,
remoteChain, true)
newView.theirUpdates = append(newView.theirUpdates, entry)
}
return newView
}
// processAddEntry evaluates the effect of an add entry within the HTLC log.
// If the HTLC hasn't yet been committed in either chain, then the height it
// was committed is updated. Keeping track of this inclusion height allows us to
// later compact the log once the change is fully committed in both chains.
func processAddEntry(htlc *PaymentDescriptor, ourBalance, theirBalance *btcutil.Amount,
nextHeight uint64, remoteChain bool, isIncoming bool) {
// If we're evaluating this entry for the remote chain (to create/view
// a new commitment), then we'll may be updating the height this entry
// was added to the chain. Otherwise, we may be updating the entry's
// height w.r.t the local chain.
var addHeight *uint64
if remoteChain {
addHeight = &htlc.addCommitHeightRemote
} else {
addHeight = &htlc.addCommitHeightLocal
}
if *addHeight != 0 {
return
}
if isIncoming {
// If this is a new incoming (un-committed) HTLC, then we need
// to update their balance accordingly by subtracting the
// amount of the HTLC that are funds pending.
*theirBalance -= htlc.Amount
} else {
// Similarly, we need to debit our balance if this is an out
// going HTLC to reflect the pending balance.
*ourBalance -= htlc.Amount
}
*addHeight = nextHeight
}
// processRemoveEntry processes a log entry which settles or timesout a
// previously added HTLC. If the removal entry has already been processed, it
// is skipped.
func processRemoveEntry(htlc *PaymentDescriptor, ourBalance,
theirBalance *btcutil.Amount, nextHeight uint64,
remoteChain bool, isIncoming bool) {
var removeHeight *uint64
if remoteChain {
removeHeight = &htlc.removeCommitHeightRemote
} else {
removeHeight = &htlc.removeCommitHeightLocal
}
// Ignore any removal entries which have already been processed.
if *removeHeight != 0 {
return
}
switch {
// If an incoming HTLC is being settled, then this means that we've
// received the preimage either from another sub-system, or the
// upstream peer in the route. Therefore, we increase our balance by
// the HTLC amount.
case isIncoming && htlc.EntryType == Settle:
*ourBalance += htlc.Amount
// Otherwise, this HTLC is being timed out, therefore the value of the
// HTLC should return to the remote party.
case isIncoming && htlc.EntryType == Timeout:
*theirBalance += htlc.Amount
// If an outgoing HTLC is being settled, then this means that the
// downstream party resented the preimage or learned of it via a
// downstream peer. In either case, we credit their settled value with
// the value of the HTLC.
case !isIncoming && htlc.EntryType == Settle:
*theirBalance += htlc.Amount
// Otherwise, one of our outgoing HTLC's has timed out, so the value of
// the HTLC should be returned to our settled balance.
case !isIncoming && htlc.EntryType == Timeout:
*ourBalance += htlc.Amount
}
*removeHeight = nextHeight
}
// SignNextCommitment signs a new commitment which includes any previous
// unsettled HTLCs, any new HTLCs, and any modifications to prior HTLCs
// committed in previous commitment updates. Signing a new commitment
// decrements the available revocation window by 1. After a successful method
// call, the remote party's commitment chain is extended by a new commitment
// which includes all updates to the HTLC log prior to this method invocation.
func (lc *LightningChannel) SignNextCommitment() ([]byte, uint32, error) {
lc.Lock()
defer lc.Unlock()
err := lc.validateCommitmentSanity(lc.theirLogCounter, lc.ourLogCounter, false)
if err != nil {
return nil, 0, err
}
// Ensure that we have enough unused revocation hashes given to us by the
// remote party. If the set is empty, then we're unable to create a new
// state unless they first revoke a prior commitment transaction.
if len(lc.revocationWindow) == 0 ||
len(lc.usedRevocations) == InitialRevocationWindow {
return nil, 0, ErrNoWindow
}
// Grab the next revocation hash and key to use for this new commitment
// transaction, if no errors occur then this revocation tuple will be
// moved to the used set.
nextRevocation := lc.revocationWindow[0]
remoteRevocationKey := nextRevocation.NextRevocationKey
remoteRevocationHash := nextRevocation.NextRevocationHash
// Create a new commitment view which will calculate the evaluated
// state of the remote node's new commitment including our latest added
// HTLC's. The view includes the latest balances for both sides on the
// remote node's chain, and also update the addition height of any new
// HTLC log entries.
newCommitView, err := lc.fetchCommitmentView(true, lc.ourLogCounter,
lc.theirLogCounter, remoteRevocationKey, remoteRevocationHash)
if err != nil {
return nil, 0, err
}
walletLog.Tracef("ChannelPoint(%v): extending remote chain to height %v",
lc.channelState.ChanID, newCommitView.height)
walletLog.Tracef("ChannelPoint(%v): remote chain: our_balance=%v, "+
"their_balance=%v, commit_tx: %v", lc.channelState.ChanID,
newCommitView.ourBalance, newCommitView.theirBalance,
newLogClosure(func() string {
return spew.Sdump(newCommitView.txn)
}))
// Sign their version of the new commitment transaction.
lc.signDesc.SigHashes = txscript.NewTxSigHashes(newCommitView.txn)
sig, err := lc.signer.SignOutputRaw(newCommitView.txn, lc.signDesc)
if err != nil {
return nil, 0, err
}
// Extend the remote commitment chain by one with the addition of our
// latest commitment update.
lc.remoteCommitChain.addCommitment(newCommitView)
// Move the now used revocation hash from the unused set to the used set.
// We only do this at the end, as we know at this point the procedure will
// succeed without any errors.
lc.usedRevocations = append(lc.usedRevocations, nextRevocation)
lc.revocationWindow[0] = nil // Avoid a GC leak.
lc.revocationWindow = lc.revocationWindow[1:]
// Strip off the sighash flag on the signature in order to send it over
// the wire.
return sig, lc.theirLogCounter, nil
}
// validateCommitmentSanity is used to validate that on current state the commitment
// transaction is valid in terms of propagating it over Bitcoin network, and
// also that all outputs are meet Bitcoin spec requirements and they are
// spendable.
func (lc *LightningChannel) validateCommitmentSanity(theirLogCounter,
ourLogCounter uint32, prediction bool) error {
htlcCount := 0
if prediction {
htlcCount++
}
// Run through all the HTLC's that will be covered by this transaction
// in order to calculate theirs count.
htlcView := lc.fetchHTLCView(theirLogCounter, ourLogCounter)
for _, entry := range htlcView.ourUpdates {
if entry.EntryType == Add {
htlcCount++
} else {
htlcCount--
}
}
for _, entry := range htlcView.theirUpdates {
if entry.EntryType == Add {
htlcCount++
} else {
htlcCount--
}
}
if htlcCount > MaxHTLCNumber {
return ErrMaxHTLCNumber
}
return nil
}
// ReceiveNewCommitment process a signature for a new commitment state sent by
// the remote party. This method will should be called in response to the
// remote party initiating a new change, or when the remote party sends a
// signature fully accepting a new state we've initiated. If we are able to
// successfully validate the signature, then the generated commitment is added
// to our local commitment chain. Once we send a revocation for our prior
// state, then this newly added commitment becomes our current accepted channel
// state.
func (lc *LightningChannel) ReceiveNewCommitment(rawSig []byte,
ourLogIndex uint32) error {
lc.Lock()
defer lc.Unlock()
err := lc.validateCommitmentSanity(lc.theirLogCounter, ourLogIndex, false)
if err != nil {
return err
}
theirCommitKey := lc.channelState.TheirCommitKey
theirMultiSigKey := lc.channelState.TheirMultiSigKey
// We're receiving a new commitment which attempts to extend our local
// commitment chain height by one, so fetch the proper revocation to
// derive the key+hash needed to construct the new commitment view and
// state.
nextHeight := lc.currentHeight + 1
revocation, err := lc.channelState.LocalElkrem.AtIndex(nextHeight)
if err != nil {
return err
}
revocationKey := DeriveRevocationPubkey(theirCommitKey, revocation[:])
revocationHash := fastsha256.Sum256(revocation[:])
// With the revocation information calculated, construct the new
// commitment view which includes all the entries we know of in their
// HTLC log, and up to ourLogIndex in our HTLC log.
localCommitmentView, err := lc.fetchCommitmentView(false, ourLogIndex,
lc.theirLogCounter, revocationKey, revocationHash)
if err != nil {
return err
}
walletLog.Tracef("ChannelPoint(%v): extending local chain to height %v",
lc.channelState.ChanID, localCommitmentView.height)
walletLog.Tracef("ChannelPoint(%v): local chain: our_balance=%v, "+
"their_balance=%v, commit_tx: %v", lc.channelState.ChanID,
localCommitmentView.ourBalance, localCommitmentView.theirBalance,
newLogClosure(func() string {
return spew.Sdump(localCommitmentView.txn)
}))
// Construct the sighash of the commitment transaction corresponding to
// this newly proposed state update.
localCommitTx := localCommitmentView.txn
multiSigScript := lc.channelState.FundingWitnessScript
hashCache := txscript.NewTxSigHashes(localCommitTx)
sigHash, err := txscript.CalcWitnessSigHash(multiSigScript, hashCache,
txscript.SigHashAll, localCommitTx, 0, int64(lc.channelState.Capacity))
if err != nil {
// TODO(roasbeef): fetchview has already mutated the htlc's...
// * need to either roll-back, or make pure
return err
}
// Ensure that the newly constructed commitment state has a valid
// signature.
sig, err := btcec.ParseSignature(rawSig, btcec.S256())
if err != nil {
return err
} else if !sig.Verify(sigHash, theirMultiSigKey) {
return fmt.Errorf("invalid commitment signature")
}
// The signature checks out, so we can now add the new commitment to
// our local commitment chain.
localCommitmentView.sig = rawSig
lc.localCommitChain.addCommitment(localCommitmentView)
return nil
}
// PendingUpdates returns a boolean value reflecting if there are any pending
// updates which need to be committed. The state machine has pending updates if
// the local log index on the local and remote chain tip aren't identical. This
// indicates that either we have pending updates they need to commit, or vice
// versa.
func (lc *LightningChannel) PendingUpdates() bool {
lc.RLock()
defer lc.RUnlock()
fullySynced := (lc.localCommitChain.tip().ourMessageIndex ==
lc.remoteCommitChain.tip().ourMessageIndex)
return !fullySynced
}
// RevokeCurrentCommitment revokes the next lowest unrevoked commitment
// transaction in the local commitment chain. As a result the edge of our
// revocation window is extended by one, and the tail of our local commitment
// chain is advanced by a single commitment. This now lowest unrevoked
// commitment becomes our currently accepted state within the channel.
func (lc *LightningChannel) RevokeCurrentCommitment() (*lnwire.CommitRevocation, error) {
lc.Lock()
defer lc.Unlock()
theirCommitKey := lc.channelState.TheirCommitKey
// Now that we've accept a new state transition, we send the remote
// party the revocation for our current commitment state.
revocationMsg := &lnwire.CommitRevocation{}
currentRevocation, err := lc.channelState.LocalElkrem.AtIndex(lc.currentHeight)
if err != nil {
return nil, err
}
copy(revocationMsg.Revocation[:], currentRevocation[:])
// Along with this revocation, we'll also send an additional extension
// to our revocation window to the remote party.
lc.revocationWindowEdge++
revocationEdge, err := lc.channelState.LocalElkrem.AtIndex(lc.revocationWindowEdge)
if err != nil {
return nil, err
}
revocationMsg.NextRevocationKey = DeriveRevocationPubkey(theirCommitKey,
revocationEdge[:])
revocationMsg.NextRevocationHash = fastsha256.Sum256(revocationEdge[:])
walletLog.Tracef("ChannelPoint(%v): revoking height=%v, now at height=%v, window_edge=%v",
lc.channelState.ChanID, lc.localCommitChain.tail().height,
lc.currentHeight+1, lc.revocationWindowEdge)
// Advance our tail, as we've revoked our previous state.
lc.localCommitChain.advanceTail()
lc.currentHeight++
// Additionally, generate a channel delta for this state transition for
// persistent storage.
// TODO(roasbeef): update sent/received.
tail := lc.localCommitChain.tail()
delta, err := tail.toChannelDelta()
if err != nil {
return nil, err
}
err = lc.channelState.UpdateCommitment(tail.txn, tail.sig, delta)
if err != nil {
return nil, err
}
walletLog.Tracef("ChannelPoint(%v): state transition accepted: "+
"our_balance=%v, their_balance=%v", lc.channelState.ChanID,
tail.ourBalance, tail.theirBalance)
revocationMsg.ChannelPoint = lc.channelState.ChanID
return revocationMsg, nil
}
// ReceiveRevocation processes a revocation sent by the remote party for the
// lowest unrevoked commitment within their commitment chain. We receive a
// revocation either during the initial session negotiation wherein revocation
// windows are extended, or in response to a state update that we initiate. If
// successful, then the remote commitment chain is advanced by a single
// commitment, and a log compaction is attempted. In addition, a slice of
// HTLC's which can be forwarded upstream are returned.
func (lc *LightningChannel) ReceiveRevocation(revMsg *lnwire.CommitRevocation) ([]*PaymentDescriptor, error) {
lc.Lock()
defer lc.Unlock()
// The revocation has a nil (zero) pre-image, then this should simply be
// added to the end of the revocation window for the remote node.
if bytes.Equal(zeroHash[:], revMsg.Revocation[:]) {
lc.revocationWindow = append(lc.revocationWindow, revMsg)
return nil, nil
}
ourCommitKey := lc.channelState.OurCommitKey
currentRevocationKey := lc.channelState.TheirCurrentRevocation
pendingRevocation := wire.ShaHash(revMsg.Revocation)
// Ensure the new pre-image fits in properly within the elkrem receiver
// tree. If this fails, then all other checks are skipped.
// TODO(rosbeef): abstract into func
remoteElkrem := lc.channelState.RemoteElkrem
if err := remoteElkrem.AddNext(&pendingRevocation); err != nil {
return nil, err
}
// Verify that the revocation public key we can derive using this
// pre-image and our private key is identical to the revocation key we
// were given for their current (prior) commitment transaction.
revocationPub := DeriveRevocationPubkey(ourCommitKey, pendingRevocation[:])
if !revocationPub.IsEqual(currentRevocationKey) {
return nil, fmt.Errorf("revocation key mismatch")
}
// Additionally, we need to ensure we were given the proper pre-image
// to the revocation hash used within any current HTLC's.
if !bytes.Equal(lc.channelState.TheirCurrentRevocationHash[:], zeroHash[:]) {
revokeHash := fastsha256.Sum256(pendingRevocation[:])
// TODO(roasbeef): rename to drop the "Their"
if !bytes.Equal(lc.channelState.TheirCurrentRevocationHash[:], revokeHash[:]) {
return nil, fmt.Errorf("revocation hash mismatch")
}
}
// Advance the head of the revocation queue now that this revocation has
// been verified. Additionally, extend the end of our unused revocation
// queue with the newly extended revocation window update.
nextRevocation := lc.usedRevocations[0]
lc.channelState.TheirCurrentRevocation = nextRevocation.NextRevocationKey
lc.channelState.TheirCurrentRevocationHash = nextRevocation.NextRevocationHash
lc.usedRevocations[0] = nil // Prevent GC leak.
lc.usedRevocations = lc.usedRevocations[1:]
lc.revocationWindow = append(lc.revocationWindow, revMsg)
walletLog.Tracef("ChannelPoint(%v): remote party accepted state transition, "+
"revoked height %v, now at %v", lc.channelState.ChanID,
lc.remoteCommitChain.tail().height,
lc.remoteCommitChain.tail().height+1)
// At this point, the revocation has been accepted, and we've rotated
// the current revocation key+hash for the remote party. Therefore we
// sync now to ensure the elkrem receiver state is consistent with the
// current commitment height.
tail := lc.remoteCommitChain.tail()
delta, err := tail.toChannelDelta()
if err != nil {
return nil, err
}
if err := lc.channelState.AppendToRevocationLog(delta); err != nil {
return nil, err
}
// Since they revoked the current lowest height in their commitment
// chain, we can advance their chain by a single commitment.
lc.remoteCommitChain.advanceTail()
remoteChainTail := lc.remoteCommitChain.tail().height
localChainTail := lc.localCommitChain.tail().height
// Now that we've verified the revocation update the state of the HTLC
// log as we may be able to prune portions of it now, and update their
// balance.
var htlcsToForward []*PaymentDescriptor
for e := lc.theirUpdateLog.Front(); e != nil; e = e.Next() {
htlc := e.Value.(*PaymentDescriptor)
if htlc.isForwarded {
continue
}
// TODO(roasbeef): re-visit after adding persistence to HTLC's
// * either record add height, or set to N - 1
uncomitted := (htlc.addCommitHeightRemote == 0 ||
htlc.addCommitHeightLocal == 0)
if htlc.EntryType == Add && uncomitted {
continue
}
if htlc.EntryType == Add &&
remoteChainTail >= htlc.addCommitHeightRemote &&
localChainTail >= htlc.addCommitHeightLocal {
htlc.isForwarded = true
htlcsToForward = append(htlcsToForward, htlc)
} else if htlc.EntryType != Add &&
remoteChainTail >= htlc.removeCommitHeightRemote &&
localChainTail >= htlc.removeCommitHeightLocal {
htlc.isForwarded = true
htlcsToForward = append(htlcsToForward, htlc)
}
}
lc.compactLogs(lc.ourUpdateLog, lc.theirUpdateLog,
localChainTail, remoteChainTail)
return htlcsToForward, nil
}
// compactLogs performs garbage collection within the log removing HTLC's which
// have been removed from the point-of-view of the tail of both chains. The
// entries which timeout/settle HTLC's are also removed.
func (lc *LightningChannel) compactLogs(ourLog, theirLog *list.List,
localChainTail, remoteChainTail uint64) {
compactLog := func(logA, logB *list.List, indexB, indexA map[uint32]*list.Element) {
var nextA *list.Element
for e := logA.Front(); e != nil; e = nextA {
nextA = e.Next()
htlc := e.Value.(*PaymentDescriptor)
if htlc.EntryType == Add {
continue
}
// If the HTLC hasn't yet been removed from either
// chain, the skip it.
if htlc.removeCommitHeightRemote == 0 ||
htlc.removeCommitHeightLocal == 0 {
continue
}
// Otherwise if the height of the tail of both chains
// is at least the height in which the HTLC was
// removed, then evict the settle/timeout entry along
// with the original add entry.
if remoteChainTail >= htlc.removeCommitHeightRemote &&
localChainTail >= htlc.removeCommitHeightLocal {
parentLink := indexB[htlc.ParentIndex]
parentIndex := parentLink.Value.(*PaymentDescriptor).Index
logB.Remove(parentLink)
logA.Remove(e)
delete(indexB, parentIndex)
delete(indexA, htlc.Index)
}
}
}
compactLog(ourLog, theirLog, lc.theirLogIndex, lc.ourLogIndex)
compactLog(theirLog, ourLog, lc.ourLogIndex, lc.theirLogIndex)
}
// ExtendRevocationWindow extends our revocation window by a single revocation,
// increasing the number of new commitment updates the remote party can
// initiate without our cooperation.
func (lc *LightningChannel) ExtendRevocationWindow() (*lnwire.CommitRevocation, error) {
lc.Lock()
defer lc.Unlock()
/// TODO(roasbeef): error if window edge differs from tail by more than
// InitialRevocationWindow
revMsg := &lnwire.CommitRevocation{}
revMsg.ChannelPoint = lc.channelState.ChanID
nextHeight := lc.revocationWindowEdge + 1
revocation, err := lc.channelState.LocalElkrem.AtIndex(nextHeight)
if err != nil {
return nil, err
}
theirCommitKey := lc.channelState.TheirCommitKey
revMsg.NextRevocationKey = DeriveRevocationPubkey(theirCommitKey,
revocation[:])
revMsg.NextRevocationHash = fastsha256.Sum256(revocation[:])
lc.revocationWindowEdge++
return revMsg, nil
}
// AddHTLC adds an HTLC to the state machine's local update log. This method
// should be called when preparing to send an outgoing HTLC.
// TODO(roasbeef): check for duplicates below? edge case during restart w/ HTLC
// persistence
func (lc *LightningChannel) AddHTLC(htlc *lnwire.HTLCAddRequest) (uint32, error) {
lc.Lock()
defer lc.Unlock()
err := lc.validateCommitmentSanity(lc.theirLogCounter, lc.ourLogCounter, true)
if err != nil {
return 0, err
}
pd := &PaymentDescriptor{
EntryType: Add,
RHash: PaymentHash(htlc.RedemptionHashes[0]),
Timeout: htlc.Expiry,
Amount: btcutil.Amount(htlc.Amount),
Index: lc.ourLogCounter,
}
lc.ourLogIndex[pd.Index] = lc.ourUpdateLog.PushBack(pd)
lc.ourLogCounter++
return pd.Index, nil
}
// ReceiveHTLC adds an HTLC to the state machine's remote update log. This
// method should be called in response to receiving a new HTLC from the remote
// party.
func (lc *LightningChannel) ReceiveHTLC(htlc *lnwire.HTLCAddRequest) (uint32, error) {
lc.Lock()
defer lc.Unlock()
err := lc.validateCommitmentSanity(lc.theirLogCounter, lc.ourLogCounter, true)
if err != nil {
return 0, err
}
pd := &PaymentDescriptor{
EntryType: Add,
RHash: PaymentHash(htlc.RedemptionHashes[0]),
Timeout: htlc.Expiry,
Amount: btcutil.Amount(htlc.Amount),
Index: lc.theirLogCounter,
}
lc.theirLogIndex[pd.Index] = lc.theirUpdateLog.PushBack(pd)
lc.theirLogCounter++
return pd.Index, nil
}
// SettleHTLC attempts to settle an existing outstanding received HTLC. The
// remote log index of the HTLC settled is returned in order to facilitate
// creating the corresponding wire message. In the case the supplied pre-image
// is invalid, an error is returned.
func (lc *LightningChannel) SettleHTLC(preimage [32]byte) (uint32, error) {
lc.Lock()
defer lc.Unlock()
var targetHTLC *list.Element
// TODO(roasbeef): optimize
paymentHash := fastsha256.Sum256(preimage[:])
for e := lc.theirUpdateLog.Front(); e != nil; e = e.Next() {
htlc := e.Value.(*PaymentDescriptor)
if htlc.EntryType != Add {
continue
}
if !htlc.settled && bytes.Equal(htlc.RHash[:], paymentHash[:]) {
htlc.settled = true
targetHTLC = e
break
}
}
if targetHTLC == nil {
return 0, fmt.Errorf("invalid payment hash")
}
parentPd := targetHTLC.Value.(*PaymentDescriptor)
pd := &PaymentDescriptor{
Amount: parentPd.Amount,
RPreimage: preimage,
Index: lc.ourLogCounter,
ParentIndex: parentPd.Index,
EntryType: Settle,
}
lc.ourUpdateLog.PushBack(pd)
lc.ourLogCounter++
return targetHTLC.Value.(*PaymentDescriptor).Index, nil
}
// ReceiveHTLCSettle attempts to settle an existing outgoing HTLC indexed by an
// index into the local log. If the specified index doesn't exist within the
// log, and error is returned. Similarly if the preimage is invalid w.r.t to
// the referenced of then a distinct error is returned.
func (lc *LightningChannel) ReceiveHTLCSettle(preimage [32]byte, logIndex uint32) error {
lc.Lock()
defer lc.Unlock()
paymentHash := fastsha256.Sum256(preimage[:])
addEntry, ok := lc.ourLogIndex[logIndex]
if !ok {
return fmt.Errorf("non existant log entry")
}
htlc := addEntry.Value.(*PaymentDescriptor)
if !bytes.Equal(htlc.RHash[:], paymentHash[:]) {
return fmt.Errorf("invalid payment hash")
}
pd := &PaymentDescriptor{
Amount: htlc.Amount,
RPreimage: preimage,
ParentIndex: htlc.Index,
Index: lc.theirLogCounter,
EntryType: Settle,
}
lc.theirUpdateLog.PushBack(pd)
lc.theirLogCounter++
return nil
}
// TimeoutHTLC...
func (lc *LightningChannel) TimeoutHTLC() error {
return nil
}
// ChannelPoint returns the outpoint of the original funding transaction which
// created this active channel. This outpoint is used throughout various
// sub-systems to uniquely identify an open channel.
func (lc *LightningChannel) ChannelPoint() *wire.OutPoint {
return lc.channelState.ChanID
}
// addHTLC adds a new HTLC to the passed commitment transaction. One of four
// full scripts will be generated for the HTLC output depending on if the HTLC
// is incoming and if it's being applied to our commitment transaction or that
// of the remote node's. Additionally, in order to be able to efficiently
// locate the added HTLC on the commitment transaction from the
// PaymentDescriptor that generated it, the generated script is stored within
// the descriptor itself.
func (lc *LightningChannel) addHTLC(commitTx *wire.MsgTx, ourCommit bool,
paymentDesc *PaymentDescriptor, revocation [32]byte, delay uint32,
isIncoming bool) error {
localKey := lc.channelState.OurCommitKey
remoteKey := lc.channelState.TheirCommitKey
timeout := paymentDesc.Timeout
rHash := paymentDesc.RHash
// Generate the proper redeem scripts for the HTLC output modified by
// two-bits denoting if this is an incoming HTLC, and if the HTLC is
// being applied to their commitment transaction or ours.
var pkScript []byte
var err error
switch {
// The HTLC is paying to us, and being applied to our commitment
// transaction. So we need to use the receiver's version of HTLC the
// script.
case isIncoming && ourCommit:
pkScript, err = receiverHTLCScript(timeout, delay, remoteKey,
localKey, revocation[:], rHash[:])
// We're being paid via an HTLC by the remote party, and the HTLC is
// being added to their commitment transaction, so we use the sender's
// version of the HTLC script.
case isIncoming && !ourCommit:
pkScript, err = senderHTLCScript(timeout, delay, remoteKey,
localKey, revocation[:], rHash[:])
// We're sending an HTLC which is being added to our commitment
// transaction. Therefore, we need to use the sender's version of the
// HTLC script.
case !isIncoming && ourCommit:
pkScript, err = senderHTLCScript(timeout, delay, localKey,
remoteKey, revocation[:], rHash[:])
// Finally, we're paying the remote party via an HTLC, which is being
// added to their commitment transaction. Therefore, we use the
// receiver's version of the HTLC script.
case !isIncoming && !ourCommit:
pkScript, err = receiverHTLCScript(timeout, delay, localKey,
remoteKey, revocation[:], rHash[:])
}
if err != nil {
return err
}
// Now that we have the redeem scripts, create the P2WSH public key
// script for the output itself.
htlcP2WSH, err := witnessScriptHash(pkScript)
if err != nil {
return err
}
// Add the new HTLC outputs to the respective commitment transactions.
amountPending := int64(paymentDesc.Amount)
commitTx.AddTxOut(wire.NewTxOut(amountPending, htlcP2WSH))
// Store the pkScript of this particular PaymentDescriptor so we can
// quickly locate it within the commitment transaction later.
paymentDesc.pkScript = htlcP2WSH
return nil
}
// ForceCloseSummary describes the final commitment state before the channel is
// locked-down to initiate a force closure by broadcasting the latest state
// on-chain. The summary includes all the information required to claim all
// rightfully owned outputs.
// TODO(roasbeef): generalize, add HTLC info, etc.
type ForceCloseSummary struct {
// CloseTx is the transaction which closed the channel on-chain. If we
// initiate the force close, then this'll be our latest commitment
// state. Otherwise, this'll be the state that the remote peer
// broadcasted on-chain.
CloseTx *wire.MsgTx
// SelfOutpoint is the output created by the above close tx which is
// spendable by us after a relative time delay.
SelfOutpoint wire.OutPoint
// SelfOutputMaturity is the relative maturity period before the above
// output can be claimed.
SelfOutputMaturity uint32
// SelfOutputSignDesc is a fully populated sign descriptor capable of
// generating a valid signature to sweep the self output.
SelfOutputSignDesc *SignDescriptor
}
// getSignedCommitTx function take the latest commitment transaction and populate
// it with witness data.
func (lc *LightningChannel) getSignedCommitTx() (*wire.MsgTx, error) {
// Fetch the current commitment transaction, along with their signature
// for the transaction.
commitTx := lc.channelState.OurCommitTx
theirSig := append(lc.channelState.OurCommitSig, byte(txscript.SigHashAll))
// With this, we then generate the full witness so the caller can
// broadcast a fully signed transaction.
lc.signDesc.SigHashes = txscript.NewTxSigHashes(commitTx)
ourSigRaw, err := lc.signer.SignOutputRaw(commitTx, lc.signDesc)
if err != nil {
return nil, err
}
ourSig := append(ourSigRaw, byte(txscript.SigHashAll))
// With the final signature generated, create the witness stack
// required to spend from the multi-sig output.
ourKey := lc.channelState.OurMultiSigKey.SerializeCompressed()
theirKey := lc.channelState.TheirMultiSigKey.SerializeCompressed()
commitTx.TxIn[0].Witness = SpendMultiSig(lc.FundingWitnessScript, ourKey,
ourSig, theirKey, theirSig)
return commitTx, nil
}
// ForceClose executes a unilateral closure of the transaction at the current
// lowest commitment height of the channel. Following a force closure, all
// state transitions, or modifications to the state update logs will be
// rejected. Additionally, this function also returns a ForceCloseSummary which
// includes the necessary details required to sweep all the time-locked within
// the commitment transaction.
//
// TODO(roasbeef): all methods need to abort if in dispute state
// TODO(roasbeef): method to generate CloseSummaries for when the remote peer
// does a unilateral close
func (lc *LightningChannel) ForceClose() (*ForceCloseSummary, error) {
lc.Lock()
defer lc.Unlock()
// Set the channel state to indicate that the channel is now in a
// contested state.
lc.status = channelDispute
commitTx, err := lc.getSignedCommitTx()
if err != nil {
return nil, err
}
// Locate the output index of the delayed commitment output back to us.
// We'll return the details of this output to the caller so they can
// sweep it once it's mature.
// TODO(roasbeef): also return HTLC info, assumes only p2wsh is commit
// tx
var delayIndex uint32
var delayScript []byte
for i, txOut := range commitTx.TxOut {
if !txscript.IsPayToWitnessScriptHash(txOut.PkScript) {
continue
}
delayIndex = uint32(i)
delayScript = txOut.PkScript
}
csvTimeout := lc.channelState.LocalCsvDelay
selfKey := lc.channelState.OurCommitKey
// Re-derive the original pkScript for out to-self output within the
// commitment transaction. We'll need this for the created sign
// descriptor.
elkrem := lc.channelState.LocalElkrem
unusedRevocation, err := elkrem.AtIndex(lc.currentHeight)
if err != nil {
return nil, err
}
revokeKey := DeriveRevocationPubkey(lc.channelState.TheirCommitKey,
unusedRevocation[:])
selfScript, err := commitScriptToSelf(csvTimeout, selfKey, revokeKey)
if err != nil {
return nil, err
}
// With the necessary information gathered above, create a new sign
// descriptor which is capable of generating the signature the caller
// needs to sweep this output. The hash cache, and input index are not
// set as the caller will decide these values once sweeping the output.
selfSignDesc := &SignDescriptor{
PubKey: selfKey,
WitnessScript: selfScript,
Output: &wire.TxOut{
PkScript: delayScript,
Value: int64(lc.channelState.OurBalance),
},
HashType: txscript.SigHashAll,
}
// Finally, close the channel force close signal which notifies any
// subscribers that the channel has now been forcibly closed. This
// allows callers to begin to carry out any post channel closure
// activities.
close(lc.ForceCloseSignal)
return &ForceCloseSummary{
CloseTx: commitTx,
SelfOutpoint: wire.OutPoint{
Hash: commitTx.TxSha(),
Index: delayIndex,
},
SelfOutputMaturity: csvTimeout,
SelfOutputSignDesc: selfSignDesc,
}, nil
}
// InitCooperativeClose initiates a cooperative closure of an active lightning
// channel. This method should only be executed once all pending HTLCs (if any)
// on the channel have been cleared/removed. Upon completion, the source
// channel will shift into the "closing" state, which indicates that all
// incoming/outgoing HTLC requests should be rejected. A signature for the
// closing transaction, and the txid of the closing transaction are returned.
// The initiator of the channel closure should then watch the blockchain for a
// confirmation of the closing transaction before considering the channel
// terminated. In the case of an unresponsive remote party, the initiator can
// either choose to execute a force closure, or backoff for a period of time,
// and retry the cooperative closure.
//
// TODO(roasbeef): caller should initiate signal to reject all incoming HTLCs,
// settle any inflight.
func (lc *LightningChannel) InitCooperativeClose() ([]byte, *wire.ShaHash, error) {
lc.Lock()
defer lc.Unlock()
// If we're already closing the channel, then ignore this request.
if lc.status == channelClosing || lc.status == channelClosed {
// TODO(roasbeef): check to ensure no pending payments
return nil, nil, ErrChanClosing
}
// Otherwise, indicate in the channel status that a channel closure has
// been initiated.
lc.status = channelClosing
closeTx := CreateCooperativeCloseTx(lc.fundingTxIn,
lc.channelState.OurBalance, lc.channelState.TheirBalance,
lc.channelState.OurDeliveryScript, lc.channelState.TheirDeliveryScript,
lc.channelState.IsInitiator)
closeTxSha := closeTx.TxSha()
// Finally, sign the completed cooperative closure transaction. As the
// initiator we'll simply send our signature over the the remote party,
// using the generated txid to be notified once the closure transaction
// has been confirmed.
lc.signDesc.SigHashes = txscript.NewTxSigHashes(closeTx)
closeSig, err := lc.signer.SignOutputRaw(closeTx, lc.signDesc)
if err != nil {
return nil, nil, err
}
return closeSig, &closeTxSha, nil
}
// CompleteCooperativeClose completes the cooperative closure of the target
// active lightning channel. This method should be called in response to the
// remote node initiating a cooperative channel closure. A fully signed closure
// transaction is returned. It is the duty of the responding node to broadcast
// a signed+valid closure transaction to the network.
//
// NOTE: The passed remote sig is expected to be a fully complete signature
// including the proper sighash byte.
func (lc *LightningChannel) CompleteCooperativeClose(remoteSig []byte) (*wire.MsgTx, error) {
lc.Lock()
defer lc.Unlock()
// If we're already closing the channel, then ignore this request.
if lc.status == channelClosing || lc.status == channelClosed {
// TODO(roasbeef): check to ensure no pending payments
return nil, ErrChanClosing
}
lc.status = channelClosed
// Create the transaction used to return the current settled balance
// on this active channel back to both parties. In this current model,
// the initiator pays full fees for the cooperative close transaction.
closeTx := CreateCooperativeCloseTx(lc.fundingTxIn,
lc.channelState.OurBalance, lc.channelState.TheirBalance,
lc.channelState.OurDeliveryScript, lc.channelState.TheirDeliveryScript,
lc.channelState.IsInitiator)
// With the transaction created, we can finally generate our half of
// the 2-of-2 multi-sig needed to redeem the funding output.
hashCache := txscript.NewTxSigHashes(closeTx)
lc.signDesc.SigHashes = hashCache
closeSig, err := lc.signer.SignOutputRaw(closeTx, lc.signDesc)
if err != nil {
return nil, err
}
// Finally, construct the witness stack minding the order of the
// pubkeys+sigs on the stack.
ourKey := lc.channelState.OurMultiSigKey.SerializeCompressed()
theirKey := lc.channelState.TheirMultiSigKey.SerializeCompressed()
ourSig := append(closeSig, byte(txscript.SigHashAll))
witness := SpendMultiSig(lc.signDesc.WitnessScript, ourKey, ourSig,
theirKey, remoteSig)
closeTx.TxIn[0].Witness = witness
// Validate the finalized transaction to ensure the output script is
// properly met, and that the remote peer supplied a valid signature.
vm, err := txscript.NewEngine(lc.fundingP2WSH, closeTx, 0,
txscript.StandardVerifyFlags, nil, hashCache,
int64(lc.channelState.Capacity))
if err != nil {
return nil, err
}
if err := vm.Execute(); err != nil {
return nil, err
}
return closeTx, nil
}
// DeleteState deletes all state concerning the channel from the underlying
// database, only leaving a small summary describing meta-data of the
// channel's lifetime.
func (lc *LightningChannel) DeleteState() error {
return lc.channelState.CloseChannel()
}
// StateSnapshot returns a snapshot of the current fully committed state within
// the channel.
func (lc *LightningChannel) StateSnapshot() *channeldb.ChannelSnapshot {
lc.stateMtx.RLock()
defer lc.stateMtx.RUnlock()
return lc.channelState.Snapshot()
}
// CreateCommitTx creates a commitment transaction, spending from specified
// funding output. The commitment transaction contains two outputs: one paying
// to the "owner" of the commitment transaction which can be spent after a
// relative block delay or revocation event, and the other paying the the
// counter-party within the channel, which can be spent immediately.
func CreateCommitTx(fundingOutput *wire.TxIn, selfKey, theirKey *btcec.PublicKey,
revokeKey *btcec.PublicKey, csvTimeout uint32, amountToSelf,
amountToThem btcutil.Amount) (*wire.MsgTx, error) {
// First, we create the script for the delayed "pay-to-self" output.
// This output has 2 main redemption clauses: either we can redeem the
// output after a relative block delay, or the remote node can claim
// the funds with the revocation key if we broadcast a revoked
// commitment transaction.
ourRedeemScript, err := commitScriptToSelf(csvTimeout, selfKey,
revokeKey)
if err != nil {
return nil, err
}
payToUsScriptHash, err := witnessScriptHash(ourRedeemScript)
if err != nil {
return nil, err
}
// Next, we create the script paying to them. This is just a regular
// P2WPKH output, without any added CSV delay.
theirWitnessKeyHash, err := commitScriptUnencumbered(theirKey)
if err != nil {
return nil, err
}
// Now that both output scripts have been created, we can finally create
// the transaction itself. We use a transaction version of 2 since CSV
// will fail unless the tx version is >= 2.
commitTx := wire.NewMsgTx()
commitTx.Version = 2
commitTx.AddTxIn(fundingOutput)
// Avoid creating zero value outputs within the commitment transaction.
if amountToSelf != 0 {
commitTx.AddTxOut(wire.NewTxOut(int64(amountToSelf), payToUsScriptHash))
}
if amountToThem != 0 {
commitTx.AddTxOut(wire.NewTxOut(int64(amountToThem), theirWitnessKeyHash))
}
return commitTx, nil
}
// CreateCooperativeCloseTx creates a transaction which if signed by both
// parties, then broadcast cooperatively closes an active channel. The creation
// of the closure transaction is modified by a boolean indicating if the party
// constructing the channel is the initiator of the closure. Currently it is
// expected that the initiator pays the transaction fees for the closing
// transaction in full.
func CreateCooperativeCloseTx(fundingTxIn *wire.TxIn,
ourBalance, theirBalance btcutil.Amount,
ourDeliveryScript, theirDeliveryScript []byte,
initiator bool) *wire.MsgTx {
// Construct the transaction to perform a cooperative closure of the
// channel. In the event that one side doesn't have any settled funds
// within the channel then a refund output for that particular side can
// be omitted.
closeTx := wire.NewMsgTx()
closeTx.AddTxIn(fundingTxIn)
// The initiator the a cooperative closure pays the fee in entirety.
// Determine if we're the initiator so we can compute fees properly.
if initiator {
// TODO(roasbeef): take sat/byte here instead of properly calc
ourBalance -= 5000
} else {
theirBalance -= 5000
}
// TODO(roasbeef): dust check...
// * although upper layers should prevent
if ourBalance != 0 {
closeTx.AddTxOut(&wire.TxOut{
PkScript: ourDeliveryScript,
Value: int64(ourBalance),
})
}
if theirBalance != 0 {
closeTx.AddTxOut(&wire.TxOut{
PkScript: theirDeliveryScript,
Value: int64(theirBalance),
})
}
txsort.InPlaceSort(closeTx)
return closeTx
}