lnd.xprv/lnwallet/channel.go
2016-06-30 12:12:19 -07:00

791 lines
25 KiB
Go

package lnwallet
import (
"bytes"
"fmt"
"sync"
"github.com/lightningnetwork/lnd/chainntfs"
"github.com/lightningnetwork/lnd/channeldb"
"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 (
ErrChanClosing = fmt.Errorf("channel is being closed, operation disallowed")
)
const (
// TODO(roasbeef): make not random value
MaxPendingPayments = 10
)
// channelState is an enum like type which represents the current state of a
// particular channel.
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 presents the hash160 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
// LightningChannel...
// TODO(roasbeef): future peer struct should embed this struct
type LightningChannel struct {
lnwallet *LightningWallet
channelEvents chainntnfs.ChainNotifier
sync.RWMutex
status channelState
// TODO(roasbeef): Stores all previous R values + timeouts for each
// commitment update, plus some other meta-data...Or just use OP_RETURN
// to help out?
// currently going for: nSequence/nLockTime overloading
channelDB *channeldb.DB
// stateMtx protects concurrent access to the state struct.
stateMtx sync.RWMutex
channelState *channeldb.OpenChannel
updateTotem chan struct{}
// Uncleared HTLC's.
pendingPayments map[PaymentHash]*PaymentDescriptor
// Payment's which we've requested.
unfufilledPayments map[PaymentHash]*PaymentRequest
fundingTxIn *wire.TxIn
fundingP2SH []byte
// TODO(roasbeef): create and embed 'Service' interface w/ below?
started int32
shutdown int32
quit chan struct{}
wg sync.WaitGroup
}
// NewLightningChannel...
func NewLightningChannel(wallet *LightningWallet, events chainntnfs.ChainNotifier,
chanDB *channeldb.DB, state *channeldb.OpenChannel) (*LightningChannel, error) {
lc := &LightningChannel{
lnwallet: wallet,
channelEvents: events,
channelState: state,
channelDB: chanDB,
updateTotem: make(chan struct{}, 1),
pendingPayments: make(map[PaymentHash]*PaymentDescriptor),
unfufilledPayments: make(map[PaymentHash]*PaymentRequest),
}
// TODO(roasbeef): do a NotifySpent for the funding input, and
// NotifyReceived for all commitment outputs.
// Populate the totem.
lc.updateTotem <- struct{}{}
fundingPkScript, err := witnessScriptHash(state.FundingRedeemScript)
if err != nil {
return nil, err
}
lc.fundingTxIn = wire.NewTxIn(state.FundingOutpoint, nil, nil)
lc.fundingP2SH = fundingPkScript
return lc, nil
}
// PaymentDescriptor...
type PaymentDescriptor struct {
RHash [32]byte
Timeout uint32
Value btcutil.Amount
OurRevocation [32]byte // TODO(roasbeef): don't need these?
TheirRevocation [32]byte
PayToUs bool
}
// ChannelUpdate...
type ChannelUpdate struct {
pendingDesc *PaymentDescriptor
deletion bool
currentUpdateNum uint64
pendingUpdateNum uint64
ourPendingCommitTx *wire.MsgTx
theirPendingCommitTx *wire.MsgTx
pendingRevocation [32]byte
sigTheirNewCommit []byte
// TODO(roasbeef): some enum to track current state in lifetime?
// state UpdateStag
lnChannel *LightningChannel
}
// RevocationHash...
func (c *ChannelUpdate) RevocationHash() ([]byte, error) {
c.lnChannel.stateMtx.RLock()
defer c.lnChannel.stateMtx.RUnlock()
e := c.lnChannel.channelState.LocalElkrem
nextPreimage, err := e.AtIndex(c.pendingUpdateNum)
if err != nil {
return nil, err
}
return nextPreimage[:], nil
}
// SignCounterPartyCommitment...
func (c *ChannelUpdate) SignCounterPartyCommitment() ([]byte, error) {
c.lnChannel.stateMtx.RLock()
defer c.lnChannel.stateMtx.RUnlock()
if c.sigTheirNewCommit != nil {
return c.sigTheirNewCommit, nil
}
// Sign their version of the commitment transaction.
hashCache := txscript.NewTxSigHashes(c.theirPendingCommitTx)
sig, err := txscript.RawTxInWitnessSignature(c.theirPendingCommitTx,
hashCache, 0, int64(c.lnChannel.channelState.Capacity),
c.lnChannel.channelState.FundingRedeemScript, txscript.SigHashAll,
c.lnChannel.channelState.OurMultiSigKey)
if err != nil {
return nil, err
}
c.sigTheirNewCommit = sig
return sig, nil
}
// PreviousRevocationPreImage...
func (c *ChannelUpdate) PreviousRevocationPreImage() ([]byte, error) {
c.lnChannel.stateMtx.RLock()
defer c.lnChannel.stateMtx.RUnlock()
// Retrieve the pre-image to the revocation hash our current commitment
// transaction.
e := c.lnChannel.channelState.LocalElkrem
revokePreImage, err := e.AtIndex(c.currentUpdateNum)
if err != nil {
return nil, err
}
return revokePreImage[:], nil
}
// VerifyNewCommitmentSigs...
func (c *ChannelUpdate) VerifyNewCommitmentSigs(ourSig, theirSig []byte) error {
c.lnChannel.stateMtx.RLock()
defer c.lnChannel.stateMtx.RUnlock()
channelState := c.lnChannel.channelState
// TODO(roasbeef): replace with sighash calc and regular sig check
// after merge
// When initially generating the redeemScript, we sorted the serialized
// public keys in descending order. So we do a quick comparison in order
// ensure the signatures appear on the Script Virual Machine stack in
// the correct order.
redeemScript := channelState.FundingRedeemScript
ourKey := channelState.OurCommitKey.PubKey().SerializeCompressed()
theirKey := channelState.TheirCommitKey.SerializeCompressed()
witness := spendMultiSig(redeemScript, ourKey, ourSig, theirKey, theirSig)
// Attach the scriptSig to our commitment transaction's only input,
// then validate that the scriptSig executes correctly.
commitTx := c.ourPendingCommitTx
commitTx.TxIn[0].Witness = witness
// TODO(roasbeef): need hashcache and value here
vm, err := txscript.NewEngine(c.lnChannel.fundingP2SH, commitTx, 0,
txscript.StandardVerifyFlags, nil, nil, 0)
if err != nil {
return err
}
return vm.Execute()
}
// Commit...
func (c *ChannelUpdate) Commit(pastRevokePreimage []byte) error {
c.lnChannel.stateMtx.Lock()
defer c.lnChannel.stateMtx.Unlock()
// First, ensure that the pre-image properly links into the shachain.
//theirShaChain := c.lnChannel.channelState.TheirShaChain
//var preImage [32]byte
//copy(preImage[:], pastRevokePreimage)
//if err := theirShaChain.AddNextHash(preImage); err != nil {
// return err
//}
channelState := c.lnChannel.channelState
// Finally, verify that that this is indeed the pre-image to the
// revocation hash we were given earlier.
if !bytes.Equal(btcutil.Hash160(pastRevokePreimage),
channelState.TheirCurrentRevocation[:]) {
return fmt.Errorf("pre-image hash does not match revocation")
}
// Store this current revocation in the channel state so we can
// verify future channel updates.
channelState.TheirCurrentRevocation = c.pendingRevocation
// The channel update is now complete, roll over to the newest commitment
// transaction.
channelState.OurCommitTx = c.ourPendingCommitTx
channelState.TheirCommitTx = c.theirPendingCommitTx
channelState.NumUpdates = c.pendingUpdateNum
// If this channel update involved deleting an HTLC, remove it from the
// set of pending payments.
if c.deletion {
delete(c.lnChannel.pendingPayments, c.pendingDesc.RHash)
}
// TODO(roasbeef): db writes, checkpoints, and such
// Return the updateTotem, allowing another update to be created now
// that this pending update has been commited, and finalized.
c.lnChannel.updateTotem <- struct{}{}
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...
// 1. request R_Hash from receiver (only if single hop, would be out of band)
// 2. propose HTLC
// * timeout
// * value
// * r_hash
// * next revocation hash
// 3. they accept
// * their next revocation hash
// * their sig for our new commitment tx (verify correctness)
// Can buld both new commitment txns at this point
// 4. we give sigs
// * our sigs for their new commitment tx
// * the pre-image to our old commitment tx
// 5. they complete
// * the pre-image to their old commitment tx (verify is part of their chain, is pre-image)
func (lc *LightningChannel) AddHTLC(timeout uint32, value btcutil.Amount,
rHash, revocation PaymentHash, payToUs bool) (*ChannelUpdate, error) {
// Grab the updateTotem, this acts as a barrier upholding the invariant
// that only one channel update transaction should exist at any moment.
// This aides in ensuring the channel updates are atomic, and consistent.
<-lc.updateTotem
chanUpdate := &ChannelUpdate{
pendingDesc: &PaymentDescriptor{
RHash: rHash,
TheirRevocation: revocation,
Timeout: timeout,
Value: value,
PayToUs: payToUs,
},
pendingRevocation: revocation,
lnChannel: lc,
}
// Get next revocation hash, updating the number of updates in the
// channel as a result.
chanUpdate.currentUpdateNum = lc.channelState.NumUpdates
chanUpdate.pendingUpdateNum = lc.channelState.NumUpdates + 1
nextPreimage, err := lc.channelState.LocalElkrem.AtIndex(chanUpdate.pendingUpdateNum)
if err != nil {
return nil, err
}
copy(chanUpdate.pendingDesc.OurRevocation[:], btcutil.Hash160(nextPreimage[:]))
// Re-calculate the amount of cleared funds for each side.
var amountToUs, amountToThem btcutil.Amount
if payToUs {
amountToUs = lc.channelState.OurBalance
amountToThem = lc.channelState.TheirBalance - value
} else {
amountToUs = lc.channelState.OurBalance - value
amountToThem = lc.channelState.TheirBalance
}
// Re-create copies of the current commitment transactions to be updated.
ourNewCommitTx, theirNewCommitTx, err := createNewCommitmentTxns(
lc.fundingTxIn, lc.channelState, chanUpdate, amountToUs, amountToThem,
)
if err != nil {
return nil, err
}
// First, re-add all the old HTLCs.
for _, paymentDesc := range lc.pendingPayments {
if err := lc.addHTLC(ourNewCommitTx, theirNewCommitTx, paymentDesc); err != nil {
return nil, err
}
}
// Then add this new HTLC.
if err := lc.addHTLC(ourNewCommitTx, theirNewCommitTx, chanUpdate.pendingDesc); err != nil {
return nil, err
}
lc.pendingPayments[rHash] = chanUpdate.pendingDesc // TODO(roasbeef): check for dups?
// Sort both transactions according to the agreed upon cannonical
// ordering. This lets us skip sending the entire transaction over,
// instead we'll just send signatures.
txsort.InPlaceSort(ourNewCommitTx)
txsort.InPlaceSort(theirNewCommitTx)
// TODO(roasbeef): locktimes/sequence set
// TODO(roasbeef): write checkpoint here...
chanUpdate.ourPendingCommitTx = ourNewCommitTx
chanUpdate.theirPendingCommitTx = theirNewCommitTx
return chanUpdate, nil
}
// addHTLC...
// NOTE: This MUST be called with stateMtx held.
func (lc *LightningChannel) addHTLC(ourCommitTx, theirCommitTx *wire.MsgTx,
paymentDesc *PaymentDescriptor) error {
// If the HTLC is going to us, then we're the sender, otherwise they
// are.
var senderKey, receiverKey *btcec.PublicKey
var senderRevocation, receiverRevocation []byte
if paymentDesc.PayToUs {
receiverKey = lc.channelState.OurCommitKey.PubKey()
receiverRevocation = paymentDesc.OurRevocation[:]
senderKey = lc.channelState.TheirCommitKey
senderRevocation = paymentDesc.TheirRevocation[:]
} else {
senderKey = lc.channelState.OurCommitKey.PubKey()
senderRevocation = paymentDesc.OurRevocation[:]
receiverKey = lc.channelState.TheirCommitKey
receiverRevocation = paymentDesc.TheirRevocation[:]
}
// Generate the proper redeem scripts for the HTLC output for both the
// sender and the receiver.
timeout := paymentDesc.Timeout
rHash := paymentDesc.RHash
delay := lc.channelState.LocalCsvDelay
senderPKScript, err := senderHTLCScript(timeout, delay, senderKey,
receiverKey, senderRevocation[:], rHash[:])
if err != nil {
return nil
}
receiverPKScript, err := receiverHTLCScript(timeout, delay, senderKey,
receiverKey, receiverRevocation[:], rHash[:])
if err != nil {
return nil
}
// Now that we have the redeem scripts, create the P2WSH public key
// script for each.
senderP2SH, err := witnessScriptHash(senderPKScript)
if err != nil {
return nil
}
receiverP2SH, err := witnessScriptHash(receiverPKScript)
if err != nil {
return nil
}
// Add the new HTLC outputs to the respective commitment transactions.
amountPending := int64(paymentDesc.Value)
if paymentDesc.PayToUs {
ourCommitTx.AddTxOut(wire.NewTxOut(amountPending, receiverP2SH))
theirCommitTx.AddTxOut(wire.NewTxOut(amountPending, senderP2SH))
} else {
ourCommitTx.AddTxOut(wire.NewTxOut(amountPending, senderP2SH))
theirCommitTx.AddTxOut(wire.NewTxOut(amountPending, receiverP2SH))
}
return nil
}
// SettleHTLC...
// R-VALUE, NEW REVOKE HASH
// accept, sig
func (lc *LightningChannel) SettleHTLC(rValue [32]byte, newRevocation [32]byte) (*ChannelUpdate, error) {
// Grab the updateTotem, this acts as a barrier upholding the invariant
// that only one channel update transaction should exist at any moment.
// This aides in ensuring the channel updates are atomic, and consistent.
<-lc.updateTotem
// Find the matching payment descriptor, bailing out early if it
// doesn't exist.
var rHash PaymentHash
copy(rHash[:], btcutil.Hash160(rValue[:]))
payDesc, ok := lc.pendingPayments[rHash]
if !ok {
return nil, fmt.Errorf("r-hash for preimage not found")
}
chanUpdate := &ChannelUpdate{
pendingDesc: payDesc,
deletion: true,
pendingRevocation: newRevocation,
lnChannel: lc,
}
// TODO(roasbeef): such copy pasta, make into func...
// Get next revocation hash, updating the number of updates in the
// channel as a result.
chanUpdate.currentUpdateNum = lc.channelState.NumUpdates
chanUpdate.pendingUpdateNum = lc.channelState.NumUpdates + 1
nextPreimage, err := lc.channelState.LocalElkrem.AtIndex(chanUpdate.pendingUpdateNum)
if err != nil {
return nil, err
}
copy(chanUpdate.pendingDesc.OurRevocation[:], btcutil.Hash160(nextPreimage[:]))
// Re-calculate the amount of cleared funds for each side.
var amountToUs, amountToThem btcutil.Amount
if payDesc.PayToUs {
amountToUs = lc.channelState.OurBalance + payDesc.Value
amountToThem = lc.channelState.TheirBalance
} else {
amountToUs = lc.channelState.OurBalance
amountToThem = lc.channelState.TheirBalance + payDesc.Value
}
// Create new commitment transactions that reflect the settlement of
// this pending HTLC.
ourNewCommitTx, theirNewCommitTx, err := createNewCommitmentTxns(
lc.fundingTxIn, lc.channelState, chanUpdate, amountToUs, amountToThem,
)
if err != nil {
return nil, err
}
// Re-add all the HTLC's skipping over this newly settled payment.
for paymentHash, paymentDesc := range lc.pendingPayments {
if bytes.Equal(paymentHash[:], rHash[:]) {
continue
}
if err := lc.addHTLC(ourNewCommitTx, theirNewCommitTx, paymentDesc); err != nil {
return nil, err
}
}
// Sort both transactions according to the agreed upon cannonical
// ordering. This lets us skip sending the entire transaction over,
// instead we'll just send signatures.
txsort.InPlaceSort(ourNewCommitTx)
txsort.InPlaceSort(theirNewCommitTx)
// TODO(roasbeef): locktimes/sequence set
// TODO(roasbeef): write checkpoint here...
chanUpdate.ourPendingCommitTx = ourNewCommitTx
chanUpdate.theirPendingCommitTx = theirNewCommitTx
return chanUpdate, nil
}
// CancelHTLC...
func (lc *LightningChannel) CancelHTLC() error {
return nil
}
// ForceClose...
func (lc *LightningChannel) ForceClose() error {
return 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() // TODO(roasbeef): coarser graiend locking
// 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
// TODO(roasbeef): assumes initiator pays fees
closeTx := createCooperativeCloseTx(lc.fundingTxIn,
lc.channelState.OurBalance, lc.channelState.TheirBalance,
lc.channelState.OurDeliveryScript, lc.channelState.TheirDeliveryScript,
true)
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.
hashCache := txscript.NewTxSigHashes(closeTx)
closeSig, err := txscript.RawTxInWitnessSignature(closeTx,
hashCache, 0, int64(lc.channelState.Capacity),
lc.channelState.FundingRedeemScript, txscript.SigHashAll,
lc.channelState.OurMultiSigKey)
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 initating 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.
func (lc *LightningChannel) CompleteCooperativeClose(remoteSig []byte) (*wire.MsgTx, error) {
lc.Lock()
defer lc.Unlock() // TODO(roasbeef): coarser graiend locking
// 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,
false)
// With the transaction created, we can finally generate our half of
// the 2-of-2 multi-sig needed to redeem the funding output.
redeemScript := lc.channelState.FundingRedeemScript
hashCache := txscript.NewTxSigHashes(closeTx)
closeSig, err := txscript.RawTxInWitnessSignature(closeTx,
hashCache, 0, int64(lc.channelState.Capacity),
redeemScript, txscript.SigHashAll,
lc.channelState.OurMultiSigKey)
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.PubKey().SerializeCompressed()
theirKey := lc.channelState.TheirMultiSigKey.SerializeCompressed()
witness := spendMultiSig(redeemScript, ourKey, closeSig,
theirKey, remoteSig)
closeTx.TxIn[0].Witness = witness
// TODO(roasbeef): VALIDATE
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 b
func (lc *LightningChannel) StateSnapshot() *channeldb.ChannelSnapshot {
lc.stateMtx.RLock()
defer lc.stateMtx.RUnlock()
return lc.channelState.Snapshot()
}
// RequestPayment...
func (lc *LightningChannel) RequestPayment(amount btcutil.Amount) error {
// Validate amount
return nil
}
// PaymentRequest...
// TODO(roasbeef): serialization (bip 70, QR code, etc)
// * routing handled by upper layer
type PaymentRequest struct {
PaymentPreImage [20]byte
Value btcutil.Amount
}
// createNewCommitmentTxns....
// NOTE: This MUST be called with stateMtx held.
func createNewCommitmentTxns(fundingTxIn *wire.TxIn, state *channeldb.OpenChannel,
chanUpdate *ChannelUpdate, amountToUs, amountToThem btcutil.Amount) (*wire.MsgTx, *wire.MsgTx, error) {
ourNewCommitTx, err := createCommitTx(fundingTxIn,
state.OurCommitKey.PubKey(), state.TheirCommitKey,
chanUpdate.pendingDesc.OurRevocation[:], state.LocalCsvDelay,
amountToUs, amountToThem)
if err != nil {
return nil, nil, err
}
theirNewCommitTx, err := createCommitTx(fundingTxIn,
state.TheirCommitKey, state.OurCommitKey.PubKey(),
chanUpdate.pendingDesc.TheirRevocation[:], state.RemoteCsvDelay,
amountToThem, amountToUs)
if err != nil {
return nil, nil, err
}
return ourNewCommitTx, theirNewCommitTx, nil
}
// 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
// P2WKH 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)
commitTx.AddTxOut(wire.NewTxOut(int64(amountToSelf), payToUsScriptHash))
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
}