lnd.xprv/utxonursery.go

1200 lines
36 KiB
Go

package main
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"io"
"sync"
"sync/atomic"
"github.com/boltdb/bolt"
"github.com/davecgh/go-spew/spew"
"github.com/lightningnetwork/lnd/chainntnfs"
"github.com/lightningnetwork/lnd/channeldb"
"github.com/lightningnetwork/lnd/lnwallet"
"github.com/roasbeef/btcd/btcec"
"github.com/roasbeef/btcd/txscript"
"github.com/roasbeef/btcd/wire"
"github.com/roasbeef/btcutil"
)
var (
// preschoolBucket stores outputs from commitment transactions that
// have been broadcast, but not yet confirmed. This set of outputs is
// persisted in case the system is shut down between the time when the
// commitment has been broadcast and the time the transaction has been
// confirmed on the blockchain.
// TODO(roasbeef): modify schema later to be:
// * chanPoint ->
// {outpoint1} -> info
// {outpoint2} -> info
preschoolBucket = []byte("psc")
// preschoolIndex is an index that maps original chanPoint that created
// the channel to all the active time-locked outpoints for that
// channel.
preschoolIndex = []byte("preschool-index")
// kindergartenBucket stores outputs from commitment transactions that
// have received an initial confirmation, but which aren't yet
// spendable because they require additional confirmations enforced by
// CheckSequenceVerify. Once required additional confirmations have
// been reported, a sweep transaction will be created to move the funds
// out of these outputs. After a further six confirmations have been
// reported, the outputs will be deleted from this bucket. The purpose
// of this additional wait time is to ensure that a block
// reorganization doesn't result in the sweep transaction getting
// re-organized out of the chain.
// TODO(roasbeef): modify schema later to be:
// * height ->
// {chanPoint} -> info
kindergartenBucket = []byte("kdg")
// contractIndex is an index that maps a contract's channel point to
// the current information pertaining to the maturity of outputs within
// that contract. Items are inserted into this index once they've been
// accepted to pre-school and deleted after the output has been fully
// swept.
//
// mapping: chanPoint -> graduationHeight || byte-offset-in-kindergartenBucket
contractIndex = []byte("contract-index")
// lastGraduatedHeightKey is used to persist the last block height that
// has been checked for graduating outputs. When the nursery is
// restarted, lastGraduatedHeightKey is used to determine the point
// from which it's necessary to catch up.
lastGraduatedHeightKey = []byte("lgh")
byteOrder = binary.BigEndian
)
// witnessType determines how an output's witness will be generated. The
// default commitmentTimeLock type will generate a witness that will allow
// spending of a time-locked transaction enforced by CheckSequenceVerify.
type witnessType uint16
const (
commitmentTimeLock witnessType = 0
)
// witnessGenerator represents a function which is able to generate the final
// witness for a particular public key script. This function acts as an
// abstraction layer, hiding the details of the underlying script from the
// utxoNursery.
type witnessGenerator func(tx *wire.MsgTx, hc *txscript.TxSigHashes,
inputIndex int) ([][]byte, error)
// generateFunc will return the witnessGenerator function that a kidOutput uses
// to generate the witness for a sweep transaction. Currently there is only one
// witnessType but this will be expanded.
func (wt witnessType) generateFunc(signer *lnwallet.Signer,
descriptor *lnwallet.SignDescriptor) witnessGenerator {
switch wt {
case commitmentTimeLock:
return func(tx *wire.MsgTx, hc *txscript.TxSigHashes,
inputIndex int) ([][]byte, error) {
desc := descriptor
desc.SigHashes = hc
desc.InputIndex = inputIndex
return lnwallet.CommitSpendTimeout(*signer, desc, tx)
}
}
return nil
}
// utxoNursery is a system dedicated to incubating time-locked outputs created
// by the broadcast of a commitment transaction either by us, or the remote
// peer. The nursery accepts outputs and "incubates" them until they've reached
// maturity, then sweep the outputs into the source wallet. An output is
// considered mature after the relative time-lock within the pkScript has
// passed. As outputs reach their maturity age, they're swept in batches into
// the source wallet, returning the outputs so they can be used within future
// channels, or regular Bitcoin transactions.
type utxoNursery struct {
sync.RWMutex
notifier chainntnfs.ChainNotifier
wallet *lnwallet.LightningWallet
db *channeldb.DB
requests chan *incubationRequest
started uint32
stopped uint32
quit chan struct{}
wg sync.WaitGroup
}
// newUtxoNursery creates a new instance of the utxoNursery from a
// ChainNotifier and LightningWallet instance.
func newUtxoNursery(db *channeldb.DB, notifier chainntnfs.ChainNotifier,
wallet *lnwallet.LightningWallet) *utxoNursery {
return &utxoNursery{
notifier: notifier,
wallet: wallet,
requests: make(chan *incubationRequest),
db: db,
quit: make(chan struct{}),
}
}
// Start launches all goroutines the utxoNursery needs to properly carry out
// its duties.
func (u *utxoNursery) Start() error {
if !atomic.CompareAndSwapUint32(&u.started, 0, 1) {
return nil
}
utxnLog.Tracef("Starting UTXO nursery")
if err := u.reloadPreschool(); err != nil {
return err
}
// Register with the notifier to receive notifications for each newly
// connected block. We register during startup to ensure that no blocks
// are missed while we are handling blocks that were missed during the
// time the UTXO nursery was unavailable.
newBlockChan, err := u.notifier.RegisterBlockEpochNtfn()
if err != nil {
return err
}
if err := u.catchUpKindergarten(); err != nil {
return err
}
u.wg.Add(1)
go u.incubator(newBlockChan)
return nil
}
// reloadPreschool re-initializes the chain notifier with all of the outputs
// that had been saved to the "preschool" database bucket prior to shutdown.
func (u *utxoNursery) reloadPreschool() error {
return u.db.View(func(tx *bolt.Tx) error {
psclBucket := tx.Bucket(preschoolBucket)
if psclBucket == nil {
return nil
}
return psclBucket.ForEach(func(outputBytes, kidBytes []byte) error {
psclOutput, err := deserializeKidOutput(bytes.NewBuffer(kidBytes))
if err != nil {
return err
}
outpoint := psclOutput.outPoint
sourceTxid := outpoint.Hash
confChan, err := u.notifier.RegisterConfirmationsNtfn(&sourceTxid, 1)
if err != nil {
return err
}
utxnLog.Infof("Preschool outpoint %v re-registered for confirmation "+
"notification.", psclOutput.outPoint)
go psclOutput.waitForPromotion(u.db, confChan)
return nil
})
})
}
// catchUpKindergarten handles the graduation of kindergarten outputs from
// blocks that were missed while the UTXO Nursery was down or offline.
// graduateMissedBlocks is called during the startup of the UTXO Nursery.
func (u *utxoNursery) catchUpKindergarten() error {
var lastGraduatedHeight uint32
// Query the database for the most recently processed block
err := u.db.View(func(tx *bolt.Tx) error {
kgtnBucket := tx.Bucket(kindergartenBucket)
if kgtnBucket == nil {
return nil
}
heightBytes := kgtnBucket.Get(lastGraduatedHeightKey)
if heightBytes == nil {
return nil
}
lastGraduatedHeight = byteOrder.Uint32(heightBytes)
return nil
})
if err != nil {
return err
}
// Get the most recently mined block
_, bestHeight, err := u.wallet.ChainIO.GetBestBlock()
if err != nil {
return err
}
// If we haven't yet seen any registered force closes, or we're already
// caught up with the current best chain, then we can exit early.
if lastGraduatedHeight == 0 || uint32(bestHeight) == lastGraduatedHeight {
return nil
}
utxnLog.Infof("Processing outputs from missed blocks. Starting with "+
"blockHeight: %v, to current blockHeight: %v", lastGraduatedHeight,
bestHeight)
// Loop through and check for graduating outputs at each of the missed
// block heights.
for graduationHeight := lastGraduatedHeight + 1; graduationHeight <= uint32(bestHeight); graduationHeight++ {
utxnLog.Debugf("Attempting to graduate outputs at height=%v",
graduationHeight)
if err := u.graduateKindergarten(graduationHeight); err != nil {
return err
}
}
utxnLog.Infof("UTXO Nursery is now fully synced")
return nil
}
// Stop gracefully shuts down any lingering goroutines launched during normal
// operation of the utxoNursery.
func (u *utxoNursery) Stop() error {
if !atomic.CompareAndSwapUint32(&u.stopped, 0, 1) {
return nil
}
utxnLog.Infof("UTXO nursery shutting down")
close(u.quit)
u.wg.Wait()
return nil
}
// kidOutput represents an output that's waiting for a required blockheight
// before its funds will be available to be moved into the user's wallet. The
// struct includes a witnessGenerator closure which will be used to generate
// the witness required to sweep the output once it's mature.
//
// TODO(roasbeef): rename to immatureOutput?
type kidOutput struct {
originChanPoint wire.OutPoint
amt btcutil.Amount
outPoint wire.OutPoint
witnessFunc witnessGenerator
// TODO(roasbeef): using block timeouts everywhere currently, will need
// to modify logic later to account for MTP based timeouts.
blocksToMaturity uint32
confHeight uint32
signDescriptor *lnwallet.SignDescriptor
witnessType witnessType
}
// incubationRequest is a request to the utxoNursery to incubate a set of
// outputs until their mature, finally sweeping them into the wallet once
// available.
type incubationRequest struct {
outputs []*kidOutput
}
// incubateOutputs sends a request to utxoNursery to incubate the outputs
// defined within the summary of a closed channel. Individually, as all outputs
// reach maturity they'll be swept back into the wallet.
func (u *utxoNursery) IncubateOutputs(closeSummary *lnwallet.ForceCloseSummary) {
var incReq incubationRequest
// It could be that our to-self output was below the dust limit. In that
// case the SignDescriptor would be nil and we would not have that output
// to incubate.
if closeSummary.SelfOutputSignDesc != nil {
outputAmt := btcutil.Amount(closeSummary.SelfOutputSignDesc.Output.Value)
selfOutput := &kidOutput{
originChanPoint: closeSummary.ChanPoint,
amt: outputAmt,
outPoint: closeSummary.SelfOutpoint,
blocksToMaturity: closeSummary.SelfOutputMaturity,
signDescriptor: closeSummary.SelfOutputSignDesc,
witnessType: commitmentTimeLock,
}
incReq.outputs = append(incReq.outputs, selfOutput)
}
// If there are no outputs to incubate, there is nothing to send to the
// request channel.
if len(incReq.outputs) != 0 {
u.requests <- &incReq
}
}
// incubator is tasked with watching over all outputs from channel closes as
// they transition from being broadcast (at which point they move into the
// "preschool state"), then confirmed and waiting for the necessary number of
// blocks to be confirmed (as specified as kidOutput.blocksToMaturity and
// enforced by CheckSequenceVerify). When the necessary block height has been
// reached, the output has "matured" and the waitForGraduation function will
// generate a sweep transaction to move funds from the commitment transaction
// into the user's wallet.
func (u *utxoNursery) incubator(newBlockChan *chainntnfs.BlockEpochEvent) {
defer u.wg.Done()
out:
for {
select {
case preschoolRequest := <-u.requests:
utxnLog.Infof("Incubating %v new outputs",
len(preschoolRequest.outputs))
for _, output := range preschoolRequest.outputs {
// We'll skip any zero value'd outputs as this
// indicates we don't have a settled balance
// within the commitment transaction.
if output.amt == 0 {
continue
}
sourceTxid := output.outPoint.Hash
if err := output.enterPreschool(u.db); err != nil {
utxnLog.Errorf("unable to add kidOutput to preschool: %v, %v ",
output, err)
continue
}
// Register for a notification that will
// trigger graduation from preschool to
// kindergarten when the channel close
// transaction has been confirmed.
confChan, err := u.notifier.RegisterConfirmationsNtfn(&sourceTxid, 1)
if err != nil {
utxnLog.Errorf("unable to register output for confirmation: %v",
sourceTxid)
continue
}
// Launch a dedicated goroutine that will move
// the output from the preschool bucket to the
// kindergarten bucket once the channel close
// transaction has been confirmed.
go output.waitForPromotion(u.db, confChan)
}
case epoch, ok := <-newBlockChan.Epochs:
// If the epoch channel has been closed, then the
// ChainNotifier is exiting which means the daemon is
// as well. Therefore, we exit early also in order to
// ensure the daemon shuts down gracefully, yet
// swiftly.
if !ok {
return
}
// TODO(roasbeef): if the BlockChainIO is rescanning
// will give stale data
// A new block has just been connected to the main
// chain which means we might be able to graduate some
// outputs out of the kindergarten bucket. Graduation
// entails successfully sweeping a time-locked output.
height := uint32(epoch.Height)
if err := u.graduateKindergarten(height); err != nil {
utxnLog.Errorf("error while graduating "+
"kindergarten outputs: %v", err)
}
case <-u.quit:
break out
}
}
}
// contractMaturityReport is a report that details the maturity progress of a
// particular force closed contract.
type contractMaturityReport struct {
// chanPoint is the channel point of the original contract that is now
// awaiting maturity within the utxoNursery.
chanPoint wire.OutPoint
// limboBalance is the total number of frozen coins within this
// contract.
limboBalance btcutil.Amount
// confirmationHeight is the block height that this output originally
// confirmed at.
confirmationHeight uint32
// maturityHeight is the input age required for this output to reach
// maturity.
maturityRequirement uint32
// maturityHeight is the absolute block height that this output will mature
// at.
maturityHeight uint32
}
// NurseryReport attempts to return a nursery report stored for the target
// outpoint. A nursery report details the maturity/sweeping progress for a
// contract that was previously force closed. If a report entry for the target
// chanPoint is unable to be constructed, then an error will be returned.
func (u *utxoNursery) NurseryReport(chanPoint *wire.OutPoint) (*contractMaturityReport, error) {
var report *contractMaturityReport
if err := u.db.View(func(tx *bolt.Tx) error {
// First we'll examine the preschool bucket as the target
// contract may not yet have been confirmed.
psclBucket := tx.Bucket(preschoolBucket)
if psclBucket == nil {
return nil
}
psclIndex := tx.Bucket(preschoolIndex)
if psclIndex == nil {
return nil
}
var b bytes.Buffer
if err := writeOutpoint(&b, chanPoint); err != nil {
return err
}
chanPointBytes := b.Bytes()
var outputReader *bytes.Reader
// If the target contract hasn't been confirmed yet, then we
// can just construct the report from this information.
if outPoint := psclIndex.Get(chanPointBytes); outPoint != nil {
// The channel entry hasn't yet been fully confirmed
// yet, so we'll dig into the preschool bucket to fetch
// the channel information.
outputBytes := psclBucket.Get(outPoint)
if outputBytes == nil {
return nil
}
outputReader = bytes.NewReader(outputBytes)
} else {
// Otherwise, we'll have to consult out contract index,
// so fetch that bucket as well as the kindergarten
// bucket.
indexBucket := tx.Bucket(contractIndex)
if indexBucket == nil {
return fmt.Errorf("contract not found, " +
"contract index not populated")
}
kgtnBucket := tx.Bucket(kindergartenBucket)
if kgtnBucket == nil {
return fmt.Errorf("contract not found, " +
"kindergarten bucket not populated")
}
// Attempt to query the index to see if we have an
// entry for this particular contract.
indexInfo := indexBucket.Get(chanPointBytes)
if indexInfo == nil {
return fmt.Errorf("contract not found in index")
}
// If an entry is found, then using the height store in
// the first 4 bytes, we'll fetch the height that this
// entry matures at.
height := indexInfo[:4]
heightRow := kgtnBucket.Get(height)
if heightRow == nil {
return fmt.Errorf("contract not found")
}
// Once we have the entry itself, we'll slice of the
// last for bytes so we can seek into this row to fetch
// the contract's information.
offset := byteOrder.Uint32(indexInfo[4:])
outputReader = bytes.NewReader(heightRow[offset:])
}
// With the proper set of bytes received, we'll deserialize the
// information for this immature output.
immatureOutput, err := deserializeKidOutput(outputReader)
if err != nil {
return err
}
// TODO(roasbeef): should actually be list of outputs
report = &contractMaturityReport{
chanPoint: *chanPoint,
limboBalance: immatureOutput.amt,
maturityRequirement: immatureOutput.blocksToMaturity,
}
// If the confirmation height is set, then this means the
// contract has been confirmed, and we know the final maturity
// height.
if immatureOutput.confHeight != 0 {
report.confirmationHeight = immatureOutput.confHeight
report.maturityHeight = (immatureOutput.blocksToMaturity +
immatureOutput.confHeight)
}
return nil
}); err != nil {
return nil, err
}
return report, nil
}
// enterPreschool is the first stage in the process of transferring funds from
// a force closed channel into the user's wallet. When an output is in the
// "preschool" stage, the daemon is waiting for the initial confirmation of the
// commitment transaction.
func (k *kidOutput) enterPreschool(db *channeldb.DB) error {
return db.Update(func(tx *bolt.Tx) error {
psclBucket, err := tx.CreateBucketIfNotExists(preschoolBucket)
if err != nil {
return err
}
psclIndex, err := tx.CreateBucketIfNotExists(preschoolIndex)
if err != nil {
return err
}
// Once we have the buckets we can insert the raw bytes of the
// immature outpoint into the preschool bucket.
var outpointBytes bytes.Buffer
if err := writeOutpoint(&outpointBytes, &k.outPoint); err != nil {
return err
}
var kidBytes bytes.Buffer
if err := serializeKidOutput(&kidBytes, k); err != nil {
return err
}
err = psclBucket.Put(outpointBytes.Bytes(), kidBytes.Bytes())
if err != nil {
return err
}
// Additionally, we'll populate the preschool index so we can
// track all the immature outpoints for a particular channel's
// chanPoint.
var b bytes.Buffer
err = writeOutpoint(&b, &k.originChanPoint)
if err != nil {
return err
}
err = psclIndex.Put(b.Bytes(), outpointBytes.Bytes())
if err != nil {
return err
}
utxnLog.Infof("Outpoint %v now in preschool, waiting for "+
"initial confirmation", k.outPoint)
return nil
})
}
// waitForPromotion is intended to be run as a goroutine that will wait until a
// channel force close commitment transaction has been included in a confirmed
// block. Once the transaction has been confirmed (as reported by the Chain
// Notifier), waitForPromotion will delete the output from the "preschool"
// database bucket and atomically add it to the "kindergarten" database bucket.
// This is the second step in the output incubation process.
func (k *kidOutput) waitForPromotion(db *channeldb.DB, confChan *chainntnfs.ConfirmationEvent) {
txConfirmation, ok := <-confChan.Confirmed
if !ok {
utxnLog.Errorf("notification chan "+
"closed, can't advance output %v", k.outPoint)
return
}
utxnLog.Infof("Outpoint %v confirmed in block %v moving to kindergarten",
k.outPoint, txConfirmation.BlockHeight)
k.confHeight = txConfirmation.BlockHeight
// The following block deletes a kidOutput from the preschool database
// bucket and adds it to the kindergarten database bucket which is
// keyed by block height. Keys and values are serialized into byte
// array form prior to database insertion.
err := db.Update(func(tx *bolt.Tx) error {
var originPoint bytes.Buffer
if err := writeOutpoint(&originPoint, &k.originChanPoint); err != nil {
return err
}
psclBucket := tx.Bucket(preschoolBucket)
if psclBucket == nil {
return errors.New("unable to open preschool bucket")
}
psclIndex := tx.Bucket(preschoolIndex)
if psclIndex == nil {
return errors.New("unable to open preschool index")
}
// Now that the entry has been confirmed, in order to move it
// along in the maturity pipeline we first delete the entry
// from the preschool bucket, as well as the secondary index.
var outpointBytes bytes.Buffer
if err := writeOutpoint(&outpointBytes, &k.outPoint); err != nil {
return err
}
if err := psclBucket.Delete(outpointBytes.Bytes()); err != nil {
utxnLog.Errorf("unable to delete kindergarten output from "+
"preschool bucket: %v", k.outPoint)
return err
}
if err := psclIndex.Delete(originPoint.Bytes()); err != nil {
utxnLog.Errorf("unable to delete kindergarten output from "+
"preschool index: %v", k.outPoint)
return err
}
// Next, fetch the kindergarten bucket. This output will remain
// in this bucket until it's fully mature.
kgtnBucket, err := tx.CreateBucketIfNotExists(kindergartenBucket)
if err != nil {
return err
}
maturityHeight := k.confHeight + k.blocksToMaturity
heightBytes := make([]byte, 4)
byteOrder.PutUint32(heightBytes, maturityHeight)
// If there're any existing outputs for this particular block
// height target, then we'll append this new output to the
// serialized list of outputs.
var existingOutputs []byte
if results := kgtnBucket.Get(heightBytes); results != nil {
existingOutputs = results
}
// We'll grab the output's offset in the value for its maturity
// height so we can add this to the contract index.
outputOffset := len(existingOutputs)
b := bytes.NewBuffer(existingOutputs)
if err := serializeKidOutput(b, k); err != nil {
return err
}
if err := kgtnBucket.Put(heightBytes, b.Bytes()); err != nil {
return err
}
// Finally, we'll insert a new entry into the contract index.
// The entry itself consists of 4 bytes for the height, and 4
// bytes for the offset within the value for the height.
var indexEntry [4 + 4]byte
copy(indexEntry[:4], heightBytes)
byteOrder.PutUint32(indexEntry[4:], uint32(outputOffset))
indexBucket, err := tx.CreateBucketIfNotExists(contractIndex)
if err != nil {
return err
}
err = indexBucket.Put(originPoint.Bytes(), indexEntry[:])
if err != nil {
return err
}
utxnLog.Infof("Outpoint %v now in kindergarten, will mature "+
"at height %v (delay of %v)", k.outPoint,
maturityHeight, k.blocksToMaturity)
return nil
})
if err != nil {
utxnLog.Errorf("unable to move kid output from preschool bucket "+
"to kindergarten bucket: %v", err)
}
}
// graduateKindergarten handles the steps invoked with moving funds from a
// force close commitment transaction into a user's wallet after the output
// from the commitment transaction has become spendable. graduateKindergarten
// is called both when a new block notification has been received and also at
// startup in order to process graduations from blocks missed while the UTXO
// nursery was offline.
// TODO(roasbeef): single db transaction for the below
func (u *utxoNursery) graduateKindergarten(blockHeight uint32) error {
// First fetch the set of outputs that we can "graduate" at this
// particular block height. We can graduate an output once we've
// reached its height maturity.
kgtnOutputs, err := fetchGraduatingOutputs(u.db, u.wallet, blockHeight)
if err != nil {
return err
}
// If we're able to graduate any outputs, then create a single
// transaction which sweeps them all into the wallet.
if len(kgtnOutputs) > 0 {
err := sweepGraduatingOutputs(u.wallet, kgtnOutputs)
if err != nil {
return err
}
// Now that the sweeping transaction has been broadcast, for
// each of the immature outputs, we'll mark them as being fully
// closed within the database.
for _, closedChan := range kgtnOutputs {
err := u.db.MarkChanFullyClosed(&closedChan.originChanPoint)
if err != nil {
return err
}
}
}
// Using a re-org safety margin of 6-blocks, delete any outputs which
// have graduated 6 blocks ago.
deleteHeight := blockHeight - 6
if err := deleteGraduatedOutputs(u.db, deleteHeight); err != nil {
return err
}
// Finally, record the last height at which we graduated outputs so we
// can reconcile our state with that of the main-chain during restarts.
return putLastHeightGraduated(u.db, blockHeight)
}
// fetchGraduatingOutputs checks the "kindergarten" database bucket whenever a
// new block is received in order to determine if commitment transaction
// outputs have become newly spendable. If fetchGraduatingOutputs finds outputs
// that are ready for "graduation," it passes them on to be swept. This is the
// third step in the output incubation process.
func fetchGraduatingOutputs(db *channeldb.DB, wallet *lnwallet.LightningWallet,
blockHeight uint32) ([]*kidOutput, error) {
var results []byte
if err := db.View(func(tx *bolt.Tx) error {
// A new block has just been connected, check to see if we have
// any new outputs that can be swept into the wallet.
kgtnBucket := tx.Bucket(kindergartenBucket)
if kgtnBucket == nil {
return nil
}
heightBytes := make([]byte, 4)
byteOrder.PutUint32(heightBytes, blockHeight)
results = kgtnBucket.Get(heightBytes)
return nil
}); err != nil {
return nil, err
}
// If no time-locked outputs can be swept at this point, ten we can
// exit early.
if len(results) == 0 {
return nil, nil
}
// Otherwise, we deserialize the list of kid outputs into their full
// forms.
kgtnOutputs, err := deserializeKidList(bytes.NewReader(results))
if err != nil {
utxnLog.Errorf("error while deserializing list of kidOutputs: %v", err)
}
// For each of the outputs, we also generate its proper witness
// function based on its witness type. This varies if the output is on
// our commitment transaction or theirs, and also if it's an HTLC
// output or not.
for _, kgtnOutput := range kgtnOutputs {
kgtnOutput.witnessFunc = kgtnOutput.witnessType.generateFunc(
&wallet.Signer, kgtnOutput.signDescriptor,
)
}
utxnLog.Infof("New block: height=%v, sweeping %v mature outputs",
blockHeight, len(kgtnOutputs))
return kgtnOutputs, nil
}
// sweepGraduatingOutputs generates and broadcasts the transaction that
// transfers control of funds from a channel commitment transaction to the
// user's wallet.
func sweepGraduatingOutputs(wallet *lnwallet.LightningWallet, kgtnOutputs []*kidOutput) error {
// Create a transaction which sweeps all the newly mature outputs into
// a output controlled by the wallet.
// TODO(roasbeef): can be more intelligent about buffering outputs to
// be more efficient on-chain.
sweepTx, err := createSweepTx(wallet, kgtnOutputs)
if err != nil {
// TODO(roasbeef): retry logic?
utxnLog.Errorf("unable to create sweep tx: %v", err)
return err
}
utxnLog.Infof("Sweeping %v time-locked outputs "+
"with sweep tx (txid=%v): %v", len(kgtnOutputs),
sweepTx.TxHash(),
newLogClosure(func() string {
return spew.Sdump(sweepTx)
}))
// With the sweep transaction fully signed, broadcast the transaction
// to the network. Additionally, we can stop tracking these outputs as
// they've just been swept.
if err := wallet.PublishTransaction(sweepTx); err != nil {
utxnLog.Errorf("unable to broadcast sweep tx: %v, %v",
err, spew.Sdump(sweepTx))
return err
}
return nil
}
// createSweepTx creates a final sweeping transaction with all witnesses in
// place for all inputs. The created transaction has a single output sending
// all the funds back to the source wallet.
func createSweepTx(wallet *lnwallet.LightningWallet,
matureOutputs []*kidOutput) (*wire.MsgTx, error) {
pkScript, err := newSweepPkScript(wallet)
if err != nil {
return nil, err
}
var totalSum btcutil.Amount
for _, o := range matureOutputs {
totalSum += o.amt
}
sweepTx := wire.NewMsgTx(2)
sweepTx.AddTxOut(&wire.TxOut{
PkScript: pkScript,
Value: int64(totalSum - 5000),
})
for _, utxo := range matureOutputs {
sweepTx.AddTxIn(&wire.TxIn{
PreviousOutPoint: utxo.outPoint,
// TODO(roasbeef): assumes pure block delays
Sequence: utxo.blocksToMaturity,
})
}
// TODO(roasbeef): insert fee calculation
// * remove hardcoded fee above
// With all the inputs in place, use each output's unique witness
// function to generate the final witness required for spending.
hashCache := txscript.NewTxSigHashes(sweepTx)
for i, txIn := range sweepTx.TxIn {
witness, err := matureOutputs[i].witnessFunc(sweepTx, hashCache, i)
if err != nil {
return nil, err
}
txIn.Witness = witness
}
return sweepTx, nil
}
// deleteGraduatedOutputs removes outputs from the kindergarten database bucket
// when six blockchain confirmations have passed since the outputs were swept.
// We wait for six confirmations to ensure that the outputs will be swept if a
// chain reorganization occurs. This is the final step in the output incubation
// process.
func deleteGraduatedOutputs(db *channeldb.DB, deleteHeight uint32) error {
return db.Update(func(tx *bolt.Tx) error {
kgtnBucket := tx.Bucket(kindergartenBucket)
if kgtnBucket == nil {
return nil
}
heightBytes := make([]byte, 4)
byteOrder.PutUint32(heightBytes, deleteHeight)
results := kgtnBucket.Get(heightBytes)
if results == nil {
return nil
}
// Delete the row for this height within the kindergarten bucket.k
if err := kgtnBucket.Delete(heightBytes); err != nil {
return err
}
sweptOutputs, err := deserializeKidList(bytes.NewBuffer(results))
if err != nil {
return err
}
utxnLog.Infof("Deleting %v swept outputs from kindergarten bucket "+
"at block height: %v", len(sweptOutputs), deleteHeight)
// Additionally, for each output that has now been fully swept,
// we'll also remove the index entry for that output.
indexBucket := tx.Bucket(contractIndex)
if indexBucket == nil {
return nil
}
for _, sweptOutput := range sweptOutputs {
var chanPoint bytes.Buffer
err := writeOutpoint(&chanPoint, &sweptOutput.originChanPoint)
if err != nil {
return err
}
if err := indexBucket.Delete(chanPoint.Bytes()); err != nil {
return err
}
}
return nil
})
}
// putLastHeightGraduated persists the most recently processed blockheight
// to the database. This blockheight is used during restarts to determine if
// blocks were missed while the UTXO Nursery was offline.
func putLastHeightGraduated(db *channeldb.DB, blockheight uint32) error {
return db.Update(func(tx *bolt.Tx) error {
kgtnBucket, err := tx.CreateBucketIfNotExists(kindergartenBucket)
if err != nil {
return nil
}
heightBytes := make([]byte, 4)
byteOrder.PutUint32(heightBytes, blockheight)
return kgtnBucket.Put(lastGraduatedHeightKey, heightBytes)
})
}
// newSweepPkScript creates a new public key script which should be used to
// sweep any time-locked, or contested channel funds into the wallet.
// Specifically, the script generated is a version 0,
// pay-to-witness-pubkey-hash (p2wkh) output.
func newSweepPkScript(wallet lnwallet.WalletController) ([]byte, error) {
sweepAddr, err := wallet.NewAddress(lnwallet.WitnessPubKey, false)
if err != nil {
return nil, err
}
return txscript.PayToAddrScript(sweepAddr)
}
// deserializedKidList takes a sequence of serialized kid outputs and returns a
// slice of kidOutput structs.
func deserializeKidList(r io.Reader) ([]*kidOutput, error) {
var kidOutputs []*kidOutput
for {
kidOutput, err := deserializeKidOutput(r)
if err != nil {
if err == io.EOF {
break
} else {
return nil, err
}
}
kidOutputs = append(kidOutputs, kidOutput)
}
return kidOutputs, nil
}
// serializeKidOutput converts a KidOutput struct into a form
// suitable for on-disk database storage. Note that the signDescriptor
// struct field is included so that the output's witness can be generated
// by createSweepTx() when the output becomes spendable.
func serializeKidOutput(w io.Writer, kid *kidOutput) error {
var scratch [8]byte
byteOrder.PutUint64(scratch[:], uint64(kid.amt))
if _, err := w.Write(scratch[:]); err != nil {
return err
}
if err := writeOutpoint(w, &kid.outPoint); err != nil {
return err
}
if err := writeOutpoint(w, &kid.originChanPoint); err != nil {
return err
}
byteOrder.PutUint32(scratch[:4], kid.blocksToMaturity)
if _, err := w.Write(scratch[:4]); err != nil {
return err
}
byteOrder.PutUint32(scratch[:4], kid.confHeight)
if _, err := w.Write(scratch[:4]); err != nil {
return err
}
byteOrder.PutUint16(scratch[:2], uint16(kid.witnessType))
if _, err := w.Write(scratch[:2]); err != nil {
return err
}
serializedPubKey := kid.signDescriptor.PubKey.SerializeCompressed()
if err := wire.WriteVarBytes(w, 0, serializedPubKey); err != nil {
return err
}
if err := wire.WriteVarBytes(w, 0, kid.signDescriptor.PrivateTweak); err != nil {
return err
}
if err := wire.WriteVarBytes(w, 0, kid.signDescriptor.WitnessScript); err != nil {
return err
}
if err := writeTxOut(w, kid.signDescriptor.Output); err != nil {
return err
}
byteOrder.PutUint32(scratch[:4], uint32(kid.signDescriptor.HashType))
_, err := w.Write(scratch[:4])
return err
}
// deserializeKidOutput takes a byte array representation of a kidOutput
// and converts it to an struct. Note that the witnessFunc method isn't added
// during deserialization and must be added later based on the value of the
// witnessType field.
func deserializeKidOutput(r io.Reader) (*kidOutput, error) {
scratch := make([]byte, 8)
kid := &kidOutput{}
if _, err := r.Read(scratch[:]); err != nil {
return nil, err
}
kid.amt = btcutil.Amount(byteOrder.Uint64(scratch[:]))
if err := readOutpoint(io.LimitReader(r, 40), &kid.outPoint); err != nil {
return nil, err
}
if err := readOutpoint(io.LimitReader(r, 40), &kid.originChanPoint); err != nil {
return nil, err
}
if _, err := r.Read(scratch[:4]); err != nil {
return nil, err
}
kid.blocksToMaturity = byteOrder.Uint32(scratch[:4])
if _, err := r.Read(scratch[:4]); err != nil {
return nil, err
}
kid.confHeight = byteOrder.Uint32(scratch[:4])
if _, err := r.Read(scratch[:2]); err != nil {
return nil, err
}
kid.witnessType = witnessType(byteOrder.Uint16(scratch[:2]))
kid.signDescriptor = &lnwallet.SignDescriptor{}
descKeyBytes, err := wire.ReadVarBytes(r, 0, 34, "descKeyBytes")
if err != nil {
return nil, err
}
descKey, err := btcec.ParsePubKey(descKeyBytes, btcec.S256())
if err != nil {
return nil, err
}
kid.signDescriptor.PubKey = descKey
descPrivateTweak, err := wire.ReadVarBytes(r, 0, 32, "privateTweak")
if err != nil {
return nil, err
}
kid.signDescriptor.PrivateTweak = descPrivateTweak
descWitnessScript, err := wire.ReadVarBytes(r, 0, 100, "witnessScript")
if err != nil {
return nil, err
}
kid.signDescriptor.WitnessScript = descWitnessScript
descTxOut := &wire.TxOut{}
if err := readTxOut(r, descTxOut); err != nil {
return nil, err
}
kid.signDescriptor.Output = descTxOut
if _, err := r.Read(scratch[:4]); err != nil {
return nil, err
}
kid.signDescriptor.HashType = txscript.SigHashType(byteOrder.Uint32(scratch[:4]))
return kid, nil
}
// TODO(bvu): copied from channeldb, remove repetition
func writeOutpoint(w io.Writer, o *wire.OutPoint) error {
// TODO(roasbeef): make all scratch buffers on the stack
scratch := make([]byte, 4)
// TODO(roasbeef): write raw 32 bytes instead of wasting the extra
// byte.
if err := wire.WriteVarBytes(w, 0, o.Hash[:]); err != nil {
return err
}
byteOrder.PutUint32(scratch, o.Index)
_, err := w.Write(scratch)
return err
}
// TODO(bvu): copied from channeldb, remove repetition
func readOutpoint(r io.Reader, o *wire.OutPoint) error {
scratch := make([]byte, 4)
txid, err := wire.ReadVarBytes(r, 0, 32, "prevout")
if err != nil {
return err
}
copy(o.Hash[:], txid)
if _, err := r.Read(scratch); err != nil {
return err
}
o.Index = byteOrder.Uint32(scratch)
return nil
}
func writeTxOut(w io.Writer, txo *wire.TxOut) error {
scratch := make([]byte, 8)
byteOrder.PutUint64(scratch, uint64(txo.Value))
if _, err := w.Write(scratch); err != nil {
return err
}
if err := wire.WriteVarBytes(w, 0, txo.PkScript); err != nil {
return err
}
return nil
}
func readTxOut(r io.Reader, txo *wire.TxOut) error {
scratch := make([]byte, 8)
if _, err := r.Read(scratch); err != nil {
return err
}
txo.Value = int64(byteOrder.Uint64(scratch))
pkScript, err := wire.ReadVarBytes(r, 0, 80, "pkScript")
if err != nil {
return err
}
txo.PkScript = pkScript
return nil
}