lnd.xprv/utxonursery.go

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package main
import (
"bytes"
"encoding/binary"
"fmt"
"io"
"sync"
"sync/atomic"
"github.com/lightningnetwork/lnd/sweep"
"github.com/btcsuite/btcd/txscript"
"github.com/btcsuite/btcd/wire"
"github.com/btcsuite/btcutil"
"github.com/davecgh/go-spew/spew"
"github.com/lightningnetwork/lnd/chainntnfs"
"github.com/lightningnetwork/lnd/channeldb"
"github.com/lightningnetwork/lnd/lnwallet"
)
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// SUMMARY OF OUTPUT STATES
//
// - CRIB
// - SerializedType: babyOutput
// - OriginalOutputType: HTLC
// - Awaiting: First-stage HTLC CLTV expiry
// - HeightIndexEntry: Absolute block height of CLTV expiry.
// - NextState: KNDR
// - PSCL
// - SerializedType: kidOutput
// - OriginalOutputType: Commitment
// - Awaiting: Confirmation of commitment txn
// - HeightIndexEntry: None.
// - NextState: KNDR
// - KNDR
// - SerializedType: kidOutput
// - OriginalOutputType: Commitment or HTLC
// - Awaiting: Commitment CSV expiry or second-stage HTLC CSV expiry.
// - HeightIndexEntry: Input confirmation height + relative CSV delay
// - NextState: GRAD
// - GRAD:
// - SerializedType: kidOutput
// - OriginalOutputType: Commitment or HTLC
// - Awaiting: All other outputs in channel to become GRAD.
// - NextState: Mark channel fully closed in channeldb and remove.
//
// DESCRIPTION OF OUTPUT STATES
//
// TODO(roasbeef): update comment with both new output types
//
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// - CRIB (babyOutput) outputs are two-stage htlc outputs that are initially
// locked using a CLTV delay, followed by a CSV delay. The first stage of a
// crib output requires broadcasting a presigned htlc timeout txn generated
// by the wallet after an absolute expiry height. Since the timeout txns are
// predetermined, they cannot be batched after-the-fact, meaning that all
// CRIB outputs are broadcast and confirmed independently. After the first
// stage is complete, a CRIB output is moved to the KNDR state, which will
// finishing sweeping the second-layer CSV delay.
//
// - PSCL (kidOutput) outputs are commitment outputs locked under a CSV delay.
// These outputs are stored temporarily in this state until the commitment
// transaction confirms, as this solidifies an absolute height that the
// relative time lock will expire. Once this maturity height is determined,
// the PSCL output is moved into KNDR.
//
// - KNDR (kidOutput) outputs are CSV delayed outputs for which the maturity
// height has been fully determined. This results from having received
// confirmation of the UTXO we are trying to spend, contained in either the
// commitment txn or htlc timeout txn. Once the maturity height is reached,
// the utxo nursery will sweep all KNDR outputs scheduled for that height
// using a single txn.
//
// - GRAD (kidOutput) outputs are KNDR outputs that have successfully been
// swept into the user's wallet. A channel is considered mature once all of
// its outputs, including two-stage htlcs, have entered the GRAD state,
// indicating that it safe to mark the channel as fully closed.
//
//
// OUTPUT STATE TRANSITIONS IN UTXO NURSERY
//
// ┌────────────────┐ ┌──────────────┐
// │ Commit Outputs │ │ HTLC Outputs │
// └────────────────┘ └──────────────┘
// │ │
// │ │
// │ │ UTXO NURSERY
// ┌───────────┼────────────────┬───────────┼───────────────────────────────┐
// │ │ │ │
// │ │ │ │ │
// │ │ │ CLTV-Delayed │
// │ │ │ V babyOutputs │
// │ │ ┌──────┐ │
// │ │ │ │ CRIB │ │
// │ │ └──────┘ │
// │ │ │ │ │
// │ │ │ │
// │ │ │ | │
// │ │ V Wait CLTV │
// │ │ │ [ ] + │
// │ │ | Publish Txn │
// │ │ │ │ │
// │ │ │ │
// │ │ │ V ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─┐ │
// │ │ ( ) waitForTimeoutConf │
// │ │ │ | └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─┘ │
// │ │ │ │
// │ │ │ │ │
// │ │ │ │
// │ V │ │ │
// │ ┌──────┐ │ │
// │ │ PSCL │ └ ── ── ─┼ ── ── ── ── ── ── ── ─┤
// │ └──────┘ │ │
// │ │ │ │
// │ │ │ │
// │ V ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─┐ │ CSV-Delayed │
// │ ( ) waitForCommitConf │ kidOutputs │
// │ | └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─┘ │ │
// │ │ │ │
// │ │ │ │
// │ │ V │
// │ │ ┌──────┐ │
// │ └─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─▶│ KNDR │ │
// │ └──────┘ │
// │ │ │
// │ │ │
// │ | │
// │ V Wait CSV │
// │ [ ] + │
// │ | Publish Txn │
// │ │ │
// │ │ │
// │ V ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ │
// │ ( ) waitForSweepConf │
// │ | └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ │
// │ │ │
// │ │ │
// │ V │
// │ ┌──────┐ │
// │ │ GRAD │ │
// │ └──────┘ │
// │ │ │
// │ │ │
// │ │ │
// └────────────────────────────────────────┼───────────────────────────────┘
// │
// │
// │
// │
// V
// ┌────────────────┐
// │ Wallet Outputs │
// └────────────────┘
var byteOrder = binary.BigEndian
var (
// ErrContractNotFound is returned when the nursery is unable to
// retrieve information about a queried contract.
ErrContractNotFound = fmt.Errorf("unable to locate contract")
)
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// NurseryConfig abstracts the required subsystems used by the utxo nursery. An
// instance of NurseryConfig is passed to newUtxoNursery during instantiation.
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type NurseryConfig struct {
// ChainIO is used by the utxo nursery to determine the current block
// height, which drives the incubation of the nursery's outputs.
ChainIO lnwallet.BlockChainIO
// ConfDepth is the number of blocks the nursery store waits before
// determining outputs in the chain as confirmed.
ConfDepth uint32
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// FetchClosedChannels provides access to a user's channels, such that
// they can be marked fully closed after incubation has concluded.
FetchClosedChannels func(pendingOnly bool) (
[]*channeldb.ChannelCloseSummary, error)
// FetchClosedChannel provides access to the close summary to extract a
// height hint from.
FetchClosedChannel func(chanID *wire.OutPoint) (
*channeldb.ChannelCloseSummary, error)
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// Notifier provides the utxo nursery the ability to subscribe to
// transaction confirmation events, which advance outputs through their
// persistence state transitions.
Notifier chainntnfs.ChainNotifier
// PublishTransaction facilitates the process of broadcasting a signed
// transaction to the appropriate network.
PublishTransaction func(*wire.MsgTx) error
// Store provides access to and modification of the persistent state
// maintained about the utxo nursery's incubating outputs.
Store NurseryStore
// Sweeper provides functionality to generate sweep transactions.
// Nursery uses this to sweep final outputs back into the wallet.
Sweeper *sweep.UtxoSweeper
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}
// 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 {
started uint32 // To be used atomically.
stopped uint32 // To be used atomically.
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cfg *NurseryConfig
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mu sync.Mutex
bestHeight uint32
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quit chan struct{}
wg sync.WaitGroup
}
// newUtxoNursery creates a new instance of the utxoNursery from a
// ChainNotifier and LightningWallet instance.
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func newUtxoNursery(cfg *NurseryConfig) *utxoNursery {
return &utxoNursery{
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cfg: cfg,
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")
// Retrieve the currently best known block. This is needed to have the
// state machine catch up with the blocks we missed when we were down.
bestHash, bestHeight, err := u.cfg.ChainIO.GetBestBlock()
if err != nil {
return err
}
// Set best known height to schedule late registrations properly.
atomic.StoreUint32(&u.bestHeight, uint32(bestHeight))
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// 2. Flush all fully-graduated channels from the pipeline.
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// Load any pending close channels, which represents the super set of
// all channels that may still be incubating.
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pendingCloseChans, err := u.cfg.FetchClosedChannels(true)
if err != nil {
return err
}
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// Ensure that all mature channels have been marked as fully closed in
// the channeldb.
for _, pendingClose := range pendingCloseChans {
err := u.closeAndRemoveIfMature(&pendingClose.ChanPoint)
if err != nil {
return err
}
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}
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// TODO(conner): check if any fully closed channels can be removed from
// utxn.
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// 2. Restart spend ntfns for any preschool outputs, which are waiting
// for the force closed commitment txn to confirm, or any second-layer
// HTLC success transactions.
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//
// NOTE: The next two steps *may* spawn go routines, thus from this
// point forward, we must close the nursery's quit channel if we detect
// any failures during startup to ensure they terminate.
if err := u.reloadPreschool(); err != nil {
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close(u.quit)
return err
}
// 3. Replay all crib and kindergarten outputs up to the current best
// height.
if err := u.reloadClasses(uint32(bestHeight)); err != nil {
close(u.quit)
return err
}
// Start watching for new blocks, as this will drive the nursery store's
// state machine.
newBlockChan, err := u.cfg.Notifier.RegisterBlockEpochNtfn(&chainntnfs.BlockEpoch{
Height: bestHeight,
Hash: bestHash,
})
if err != nil {
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close(u.quit)
return err
}
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u.wg.Add(1)
go u.incubator(newBlockChan)
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
}
// IncubateOutputs sends a request to the utxoNursery to incubate a set of
// outputs from an existing commitment transaction. Outputs need to incubate if
// they're CLTV absolute time locked, or if they're CSV relative time locked.
// Once all outputs reach maturity, they'll be swept back into the wallet.
func (u *utxoNursery) IncubateOutputs(chanPoint wire.OutPoint,
commitResolution *lnwallet.CommitOutputResolution,
outgoingHtlcs []lnwallet.OutgoingHtlcResolution,
incomingHtlcs []lnwallet.IncomingHtlcResolution,
broadcastHeight uint32) error {
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// Add to wait group because nursery might shut down during execution of
// this function. Otherwise it could happen that nursery thinks it is
// shut down, but in this function new goroutines were started and stay
// around.
u.wg.Add(1)
defer u.wg.Done()
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// Check quit channel for the case where the waitgroup wait was finished
// right before this function's add call was made.
select {
case <-u.quit:
return fmt.Errorf("nursery shutting down")
default:
}
numHtlcs := len(incomingHtlcs) + len(outgoingHtlcs)
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var (
hasCommit bool
// Kid outputs can be swept after an initial confirmation
// followed by a maturity period.Baby outputs are two stage and
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// will need to wait for an absolute time out to reach a
// confirmation, then require a relative confirmation delay.
kidOutputs = make([]kidOutput, 0, 1+len(incomingHtlcs))
babyOutputs = make([]babyOutput, 0, len(outgoingHtlcs))
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)
// 1. Build all the spendable outputs that we will try to incubate.
// It could be that our to-self output was below the dust limit. In
// that case the commit resolution would be nil and we would not have
// that output to incubate.
if commitResolution != nil {
hasCommit = true
selfOutput := makeKidOutput(
&commitResolution.SelfOutPoint,
&chanPoint,
commitResolution.MaturityDelay,
lnwallet.CommitmentTimeLock,
&commitResolution.SelfOutputSignDesc,
0,
)
// We'll skip any zero valued outputs as this indicates we
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// don't have a settled balance within the commitment
// transaction.
if selfOutput.Amount() > 0 {
kidOutputs = append(kidOutputs, selfOutput)
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}
}
// TODO(roasbeef): query and see if we already have, if so don't add?
// For each incoming HTLC, we'll register a kid output marked as a
// second-layer HTLC output. We effectively skip the baby stage (as the
// timelock is zero), and enter the kid stage.
for _, htlcRes := range incomingHtlcs {
htlcOutput := makeKidOutput(
&htlcRes.ClaimOutpoint, &chanPoint, htlcRes.CsvDelay,
lnwallet.HtlcAcceptedSuccessSecondLevel,
&htlcRes.SweepSignDesc, 0,
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)
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if htlcOutput.Amount() > 0 {
kidOutputs = append(kidOutputs, htlcOutput)
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}
}
// For each outgoing HTLC, we'll create a baby output. If this is our
// commitment transaction, then we'll broadcast a second-layer
// transaction to transition to a kid output. Otherwise, we'll directly
// spend once the CLTV delay us up.
for _, htlcRes := range outgoingHtlcs {
// If this HTLC is on our commitment transaction, then it'll be
// a baby output as we need to go to the second level to sweep
// it.
if htlcRes.SignedTimeoutTx != nil {
htlcOutput := makeBabyOutput(&chanPoint, &htlcRes)
if htlcOutput.Amount() > 0 {
babyOutputs = append(babyOutputs, htlcOutput)
}
continue
}
// Otherwise, this is actually a kid output as we can sweep it
// once the commitment transaction confirms, and the absolute
// CLTV lock has expired. We set the CSV delay to zero to
// indicate this is actually a CLTV output.
htlcOutput := makeKidOutput(
&htlcRes.ClaimOutpoint, &chanPoint, 0,
lnwallet.HtlcOfferedRemoteTimeout,
&htlcRes.SweepSignDesc, htlcRes.Expiry,
)
kidOutputs = append(kidOutputs, htlcOutput)
}
// TODO(roasbeef): if want to handle outgoing on remote commit
// * need ability to cancel in the case that we learn of pre-image or
// remote party pulls
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utxnLog.Infof("Incubating Channel(%s) has-commit=%v, num-htlcs=%d",
chanPoint, hasCommit, numHtlcs)
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u.mu.Lock()
defer u.mu.Unlock()
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// 2. Persist the outputs we intended to sweep in the nursery store
if err := u.cfg.Store.Incubate(kidOutputs, babyOutputs); err != nil {
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utxnLog.Errorf("unable to begin incubation of Channel(%s): %v",
chanPoint, err)
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return err
}
// As an intermediate step, we'll now check to see if any of the baby
// outputs has actually _already_ expired. This may be the case if
// blocks were mined while we processed this message.
_, bestHeight, err := u.cfg.ChainIO.GetBestBlock()
if err != nil {
return err
}
// We'll examine all the baby outputs just inserted into the database,
// if the output has already expired, then we'll *immediately* sweep
// it. This may happen if the caller raced a block to call this method.
for _, babyOutput := range babyOutputs {
if uint32(bestHeight) >= babyOutput.expiry {
err = u.sweepCribOutput(uint32(bestHeight), &babyOutput)
if err != nil {
return err
}
}
}
// 3. If we are incubating any preschool outputs, register for a
// confirmation notification that will transition it to the
// kindergarten bucket.
if len(kidOutputs) != 0 {
for _, kidOutput := range kidOutputs {
err := u.registerPreschoolConf(
&kidOutput, broadcastHeight,
)
if err != nil {
return err
}
}
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}
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return nil
}
// 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.
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func (u *utxoNursery) NurseryReport(
chanPoint *wire.OutPoint) (*contractMaturityReport, error) {
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u.mu.Lock()
defer u.mu.Unlock()
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utxnLog.Infof("NurseryReport: building nursery report for channel %v",
chanPoint)
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report := &contractMaturityReport{
chanPoint: *chanPoint,
}
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if err := u.cfg.Store.ForChanOutputs(chanPoint, func(k, v []byte) error {
switch {
case bytes.HasPrefix(k, cribPrefix):
// Cribs outputs are the only kind currently stored as
// baby outputs.
var baby babyOutput
err := baby.Decode(bytes.NewReader(v))
if err != nil {
return err
}
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// Each crib output represents a stage one htlc, and
// will contribute towards the limbo balance.
report.AddLimboStage1TimeoutHtlc(&baby)
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case bytes.HasPrefix(k, psclPrefix),
bytes.HasPrefix(k, kndrPrefix),
bytes.HasPrefix(k, gradPrefix):
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// All others states can be deserialized as kid outputs.
var kid kidOutput
err := kid.Decode(bytes.NewReader(v))
if err != nil {
return err
}
// Now, use the state prefixes to determine how the
// this output should be represented in the nursery
// report. An output's funds are always in limbo until
// reaching the graduate state.
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switch {
case bytes.HasPrefix(k, psclPrefix):
// Preschool outputs are awaiting the
// confirmation of the commitment transaction.
switch kid.WitnessType() {
case lnwallet.CommitmentTimeLock:
report.AddLimboCommitment(&kid)
// An HTLC output on our commitment transaction
// where the second-layer transaction hasn't
// yet confirmed.
case lnwallet.HtlcAcceptedSuccessSecondLevel:
report.AddLimboStage1SuccessHtlc(&kid)
}
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case bytes.HasPrefix(k, kndrPrefix):
// Kindergarten outputs may originate from
// either the commitment transaction or an htlc.
// We can distinguish them via their witness
// types.
switch kid.WitnessType() {
case lnwallet.CommitmentTimeLock:
// The commitment transaction has been
// confirmed, and we are waiting the CSV
// delay to expire.
report.AddLimboCommitment(&kid)
case lnwallet.HtlcOfferedRemoteTimeout:
// This is an HTLC output on the
// commitment transaction of the remote
// party. The CLTV timelock has
// expired, and we only need to sweep
// it.
report.AddLimboDirectHtlc(&kid)
case lnwallet.HtlcAcceptedSuccessSecondLevel:
fallthrough
case lnwallet.HtlcOfferedTimeoutSecondLevel:
// The htlc timeout or success
// transaction has confirmed, and the
// CSV delay has begun ticking.
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report.AddLimboStage2Htlc(&kid)
}
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case bytes.HasPrefix(k, gradPrefix):
// Graduate outputs are those whose funds have
// been swept back into the wallet. Each output
// will contribute towards the recovered
// balance.
switch kid.WitnessType() {
case lnwallet.CommitmentTimeLock:
// The commitment output was
// successfully swept back into a
// regular p2wkh output.
report.AddRecoveredCommitment(&kid)
case lnwallet.HtlcAcceptedSuccessSecondLevel:
fallthrough
case lnwallet.HtlcOfferedTimeoutSecondLevel:
fallthrough
case lnwallet.HtlcOfferedRemoteTimeout:
// This htlc output successfully
// resides in a p2wkh output belonging
// to the user.
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report.AddRecoveredHtlc(&kid)
}
}
default:
}
return nil
}); err != nil {
return nil, err
}
return report, nil
}
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// 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 {
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psclOutputs, err := u.cfg.Store.FetchPreschools()
if err != nil {
return err
}
// For each of the preschool outputs stored in the nursery store, load
// its close summary from disk so that we can get an accurate height
// hint from which to start our range for spend notifications.
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for i := range psclOutputs {
kid := &psclOutputs[i]
chanPoint := kid.OriginChanPoint()
// Load the close summary for this output's channel point.
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closeSummary, err := u.cfg.FetchClosedChannel(chanPoint)
if err == channeldb.ErrClosedChannelNotFound {
// This should never happen since the close summary
// should only be removed after the channel has been
// swept completely.
utxnLog.Warnf("Close summary not found for "+
"chan_point=%v, can't determine height hint"+
"to sweep commit txn", chanPoint)
continue
} else if err != nil {
return err
}
// Use the close height from the channel summary as our height
// hint to drive our spend notifications, with our confirmation
// depth as a buffer for reorgs.
heightHint := closeSummary.CloseHeight - u.cfg.ConfDepth
err = u.registerPreschoolConf(kid, heightHint)
if err != nil {
return err
}
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}
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return nil
}
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// reloadClasses reinitializes any height-dependent state transitions for which
// the utxonursery has not received confirmation, and replays the graduation of
// all kindergarten and crib outputs for all heights up to the current block.
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// This allows the nursery to reinitialize all state to continue sweeping
// outputs, even in the event that we missed blocks while offline. reloadClasses
// is called during the startup of the UTXO Nursery.
func (u *utxoNursery) reloadClasses(bestHeight uint32) error {
// Loading all active heights up to and including the current block.
activeHeights, err := u.cfg.Store.HeightsBelowOrEqual(
uint32(bestHeight))
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if err != nil {
return err
}
// Return early if nothing to sweep.
if len(activeHeights) == 0 {
return nil
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}
utxnLog.Infof("(Re)-sweeping %d heights below height=%d",
len(activeHeights), bestHeight)
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// Attempt to re-register notifications for any outputs still at these
// heights.
for _, classHeight := range activeHeights {
utxnLog.Debugf("Attempting to sweep outputs at height=%v",
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classHeight)
if err = u.graduateClass(classHeight); err != nil {
utxnLog.Errorf("Failed to sweep outputs at "+
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"height=%v: %v", classHeight, err)
return err
}
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}
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utxnLog.Infof("UTXO Nursery is now fully synced")
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return nil
}
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// incubator is tasked with driving all state transitions that are dependent on
// the current height of the blockchain. As new blocks arrive, the incubator
// will attempt spend outputs at the latest height. The asynchronous
// confirmation of these spends will either 1) move a crib output into the
// kindergarten bucket or 2) move a kindergarten output into the graduated
// bucket.
func (u *utxoNursery) incubator(newBlockChan *chainntnfs.BlockEpochEvent) {
defer u.wg.Done()
defer newBlockChan.Cancel()
for {
select {
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 crib
// or kindergarten outputs at this height. This involves
// broadcasting any presigned htlc timeout txns, as well
// as signing and broadcasting a sweep txn that spends
// from all kindergarten outputs at this height.
height := uint32(epoch.Height)
// Update best known block height for late registrations
// to be scheduled properly.
atomic.StoreUint32(&u.bestHeight, height)
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if err := u.graduateClass(height); err != nil {
utxnLog.Errorf("error while graduating "+
"class at height=%d: %v", height, err)
// TODO(conner): signal fatal error to daemon
}
case <-u.quit:
return
}
}
}
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// graduateClass handles the steps involved in spending outputs whose CSV or
// CLTV delay expires at the nursery's current height. This method is called
// each time a new block arrives, or during startup to catch up on heights we
// may have missed while the nursery was offline.
func (u *utxoNursery) graduateClass(classHeight uint32) error {
// Record this height as the nursery's current best height.
u.mu.Lock()
defer u.mu.Unlock()
// Fetch all information about the crib and kindergarten outputs at
// this height.
kgtnOutputs, cribOutputs, err := u.cfg.Store.FetchClass(
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classHeight)
if err != nil {
return err
}
utxnLog.Infof("Attempting to graduate height=%v: num_kids=%v, "+
"num_babies=%v", classHeight, len(kgtnOutputs), len(cribOutputs))
// Offer the outputs to the sweeper and set up notifications that will
// transition the swept kindergarten outputs and cltvCrib into graduated
// outputs.
if len(kgtnOutputs) > 0 {
if err := u.sweepMatureOutputs(classHeight, kgtnOutputs); err != nil {
utxnLog.Errorf("Failed to sweep %d kindergarten "+
"outputs at height=%d: %v",
len(kgtnOutputs), classHeight, err)
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return err
}
}
// Now, we broadcast all pre-signed htlc txns from the csv crib outputs
// at this height.
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for i := range cribOutputs {
err := u.sweepCribOutput(classHeight, &cribOutputs[i])
if err != nil {
utxnLog.Errorf("Failed to sweep first-stage HTLC "+
"(CLTV-delayed) output %v",
cribOutputs[i].OutPoint())
return err
}
}
return nil
}
// sweepMatureOutputs generates and broadcasts the transaction that transfers
// control of funds from a prior channel commitment transaction to the user's
// wallet. The outputs swept were previously time locked (either absolute or
// relative), but are not mature enough to sweep into the wallet.
func (u *utxoNursery) sweepMatureOutputs(classHeight uint32,
kgtnOutputs []kidOutput) error {
utxnLog.Infof("Sweeping %v CSV-delayed outputs with sweep tx for "+
"height %v", len(kgtnOutputs), classHeight)
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for _, output := range kgtnOutputs {
// Create local copy to prevent pointer to loop variable to be
// passed in with disastruous consequences.
local := output
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resultChan, err := u.cfg.Sweeper.SweepInput(&local)
if err != nil {
return err
}
u.wg.Add(1)
go u.waitForSweepConf(classHeight, &output, resultChan)
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}
return nil
}
// waitForSweepConf watches for the confirmation of a sweep transaction
// containing a batch of kindergarten outputs. Once confirmation has been
// received, the nursery will mark those outputs as fully graduated, and proceed
// to mark any mature channels as fully closed in channeldb.
// NOTE(conner): this method MUST be called as a go routine.
func (u *utxoNursery) waitForSweepConf(classHeight uint32,
output *kidOutput, resultChan chan sweep.Result) {
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defer u.wg.Done()
select {
case result, ok := <-resultChan:
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if !ok {
utxnLog.Errorf("Notification chan closed, can't" +
" advance graduating output")
return
}
// In case of a remote spend, still graduate the output. There
// is no way to sweep it anymore.
if result.Err == sweep.ErrRemoteSpend {
utxnLog.Infof("Output %v was spend by remote party",
output.OutPoint())
break
}
if result.Err != nil {
utxnLog.Errorf("Failed to sweep %v at "+
"height=%d", output.OutPoint(),
classHeight)
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return
}
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case <-u.quit:
return
}
u.mu.Lock()
defer u.mu.Unlock()
// TODO(conner): add retry logic?
// Mark the confirmed kindergarten output as graduated.
if err := u.cfg.Store.GraduateKinder(classHeight, output); err != nil {
utxnLog.Errorf("Unable to graduate kindergarten output %v: %v",
output.OutPoint(), err)
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return
}
utxnLog.Infof("Graduated kindergarten output from height=%d",
classHeight)
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// Attempt to close the channel, only doing so if all of the channel's
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// outputs have been graduated.
chanPoint := output.OriginChanPoint()
if err := u.closeAndRemoveIfMature(chanPoint); err != nil {
utxnLog.Errorf("Failed to close and remove channel %v",
*chanPoint)
return
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}
}
// sweepCribOutput broadcasts the crib output's htlc timeout txn, and sets up a
// notification that will advance it to the kindergarten bucket upon
// confirmation.
func (u *utxoNursery) sweepCribOutput(classHeight uint32, baby *babyOutput) error {
utxnLog.Infof("Publishing CLTV-delayed HTLC output using timeout tx "+
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"(txid=%v): %v", baby.timeoutTx.TxHash(),
newLogClosure(func() string {
return spew.Sdump(baby.timeoutTx)
}),
)
// We'll now broadcast the HTLC transaction, then wait for it to be
// confirmed before transitioning it to kindergarten.
err := u.cfg.PublishTransaction(baby.timeoutTx)
if err != nil && err != lnwallet.ErrDoubleSpend {
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utxnLog.Errorf("Unable to broadcast baby tx: "+
"%v, %v", err, spew.Sdump(baby.timeoutTx))
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return err
}
return u.registerTimeoutConf(baby, classHeight)
}
// registerTimeoutConf is responsible for subscribing to confirmation
// notification for an htlc timeout transaction. If successful, a goroutine
// will be spawned that will transition the provided baby output into the
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// kindergarten state within the nursery store.
func (u *utxoNursery) registerTimeoutConf(baby *babyOutput, heightHint uint32) error {
birthTxID := baby.timeoutTx.TxHash()
// Register for the confirmation of presigned htlc txn.
confChan, err := u.cfg.Notifier.RegisterConfirmationsNtfn(
&birthTxID, baby.timeoutTx.TxOut[0].PkScript, u.cfg.ConfDepth,
heightHint,
)
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if err != nil {
return err
}
utxnLog.Infof("Htlc output %v registered for promotion "+
"notification.", baby.OutPoint())
u.wg.Add(1)
go u.waitForTimeoutConf(baby, confChan)
return nil
}
// waitForTimeoutConf watches for the confirmation of an htlc timeout
// transaction, and attempts to move the htlc output from the crib bucket to the
// kindergarten bucket upon success.
func (u *utxoNursery) waitForTimeoutConf(baby *babyOutput,
confChan *chainntnfs.ConfirmationEvent) {
defer u.wg.Done()
select {
case txConfirmation, ok := <-confChan.Confirmed:
if !ok {
utxnLog.Errorf("Notification chan "+
"closed, can't advance baby output %v",
baby.OutPoint())
return
}
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baby.SetConfHeight(txConfirmation.BlockHeight)
case <-u.quit:
return
}
u.mu.Lock()
defer u.mu.Unlock()
// TODO(conner): add retry logic?
err := u.cfg.Store.CribToKinder(baby)
if err != nil {
utxnLog.Errorf("Unable to move htlc output from "+
"crib to kindergarten bucket: %v", err)
return
}
utxnLog.Infof("Htlc output %v promoted to "+
"kindergarten", baby.OutPoint())
}
// registerPreschoolConf is responsible for subscribing to the confirmation of
// a commitment transaction, or an htlc success transaction for an incoming
// HTLC on our commitment transaction.. If successful, the provided preschool
// output will be moved persistently into the kindergarten state within the
// nursery store.
func (u *utxoNursery) registerPreschoolConf(kid *kidOutput, heightHint uint32) error {
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txID := kid.OutPoint().Hash
// TODO(roasbeef): ensure we don't already have one waiting, need to
// de-duplicate
// * need to do above?
pkScript := kid.signDesc.Output.PkScript
confChan, err := u.cfg.Notifier.RegisterConfirmationsNtfn(
&txID, pkScript, u.cfg.ConfDepth, heightHint,
)
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if err != nil {
return err
}
var outputType string
if kid.isHtlc {
outputType = "HTLC"
} else {
outputType = "Commitment"
}
utxnLog.Infof("%v outpoint %v registered for "+
"confirmation notification.", outputType, kid.OutPoint())
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u.wg.Add(1)
go u.waitForPreschoolConf(kid, confChan)
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return nil
}
// waitForPreschoolConf is intended to be run as a goroutine that will wait until
// a channel force close commitment transaction, or a second layer HTLC success
// transaction has been included in a confirmed block. Once the transaction has
// been confirmed (as reported by the Chain Notifier), waitForPreschoolConf
// 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 (u *utxoNursery) waitForPreschoolConf(kid *kidOutput,
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confChan *chainntnfs.ConfirmationEvent) {
defer u.wg.Done()
select {
case txConfirmation, ok := <-confChan.Confirmed:
if !ok {
utxnLog.Errorf("Notification chan "+
"closed, can't advance output %v",
kid.OutPoint())
return
}
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kid.SetConfHeight(txConfirmation.BlockHeight)
case <-u.quit:
return
}
u.mu.Lock()
defer u.mu.Unlock()
// TODO(conner): add retry logic?
var outputType string
if kid.isHtlc {
outputType = "HTLC"
} else {
outputType = "Commitment"
}
bestHeight := atomic.LoadUint32(&u.bestHeight)
err := u.cfg.Store.PreschoolToKinder(kid, bestHeight)
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if err != nil {
utxnLog.Errorf("Unable to move %v output "+
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"from preschool to kindergarten bucket: %v",
outputType, err)
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return
}
}
// 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
// recoveredBalance is the total value that has been successfully swept
// back to the user's wallet.
recoveredBalance btcutil.Amount
// localAmount is the local value of the commitment output.
localAmount btcutil.Amount
// confHeight is the block height that this output originally confirmed.
confHeight uint32
// maturityRequirement 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
// htlcs records a maturity report for each htlc output in this channel.
htlcs []htlcMaturityReport
}
// htlcMaturityReport provides a summary of a single htlc output, and is
// embedded as party of the overarching contractMaturityReport
type htlcMaturityReport struct {
// outpoint is the final output that will be swept back to the wallet.
outpoint wire.OutPoint
// amount is the final value that will be swept in back to the wallet.
amount btcutil.Amount
// confHeight is the block height that this output originally confirmed.
confHeight uint32
// maturityRequirement 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
// stage indicates whether the htlc is in the CLTV-timeout stage (1) or
// the CSV-delay stage (2). A stage 1 htlc's maturity height will be set
// to its expiry height, while a stage 2 htlc's maturity height will be
// set to its confirmation height plus the maturity requirement.
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stage uint32
}
// AddLimboCommitment adds an incubating commitment output to maturity
// report's htlcs, and contributes its amount to the limbo balance.
func (c *contractMaturityReport) AddLimboCommitment(kid *kidOutput) {
c.limboBalance += kid.Amount()
c.localAmount += kid.Amount()
c.confHeight = kid.ConfHeight()
c.maturityRequirement = kid.BlocksToMaturity()
// If the confirmation height is set, then this means the contract has
// been confirmed, and we know the final maturity height.
if kid.ConfHeight() != 0 {
c.maturityHeight = kid.BlocksToMaturity() + kid.ConfHeight()
}
}
// AddRecoveredCommitment adds a graduated commitment output to maturity
// report's htlcs, and contributes its amount to the recovered balance.
func (c *contractMaturityReport) AddRecoveredCommitment(kid *kidOutput) {
c.recoveredBalance += kid.Amount()
c.localAmount += kid.Amount()
c.confHeight = kid.ConfHeight()
c.maturityRequirement = kid.BlocksToMaturity()
c.maturityHeight = kid.BlocksToMaturity() + kid.ConfHeight()
}
// AddLimboStage1TimeoutHtlc adds an htlc crib output to the maturity report's
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// htlcs, and contributes its amount to the limbo balance.
func (c *contractMaturityReport) AddLimboStage1TimeoutHtlc(baby *babyOutput) {
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c.limboBalance += baby.Amount()
// TODO(roasbeef): bool to indicate stage 1 vs stage 2?
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c.htlcs = append(c.htlcs, htlcMaturityReport{
outpoint: *baby.OutPoint(),
amount: baby.Amount(),
confHeight: baby.ConfHeight(),
maturityHeight: baby.expiry,
stage: 1,
})
}
// AddLimboDirectHtlc adds a direct HTLC on the commitment transaction of the
// remote party to the maturity report. This a CLTV time-locked output that
// hasn't yet expired.
func (c *contractMaturityReport) AddLimboDirectHtlc(kid *kidOutput) {
c.limboBalance += kid.Amount()
htlcReport := htlcMaturityReport{
outpoint: *kid.OutPoint(),
amount: kid.Amount(),
confHeight: kid.ConfHeight(),
maturityHeight: kid.absoluteMaturity,
stage: 2,
}
c.htlcs = append(c.htlcs, htlcReport)
}
// AddLimboStage1SuccessHtlcHtlc adds an htlc crib output to the maturity
// report's set of HTLC's. We'll use this to report any incoming HTLC sweeps
// where the second level transaction hasn't yet confirmed.
func (c *contractMaturityReport) AddLimboStage1SuccessHtlc(kid *kidOutput) {
c.limboBalance += kid.Amount()
c.htlcs = append(c.htlcs, htlcMaturityReport{
outpoint: *kid.OutPoint(),
amount: kid.Amount(),
confHeight: kid.ConfHeight(),
maturityRequirement: kid.BlocksToMaturity(),
stage: 1,
})
}
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// AddLimboStage2Htlc adds an htlc kindergarten output to the maturity report's
// htlcs, and contributes its amount to the limbo balance.
func (c *contractMaturityReport) AddLimboStage2Htlc(kid *kidOutput) {
c.limboBalance += kid.Amount()
htlcReport := htlcMaturityReport{
outpoint: *kid.OutPoint(),
amount: kid.Amount(),
confHeight: kid.ConfHeight(),
maturityRequirement: kid.BlocksToMaturity(),
stage: 2,
}
// If the confirmation height is set, then this means the first stage
// has been confirmed, and we know the final maturity height of the CSV
// delay.
if kid.ConfHeight() != 0 {
htlcReport.maturityHeight = kid.ConfHeight() + kid.BlocksToMaturity()
}
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c.htlcs = append(c.htlcs, htlcReport)
}
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// AddRecoveredHtlc adds a graduate output to the maturity report's htlcs, and
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// contributes its amount to the recovered balance.
func (c *contractMaturityReport) AddRecoveredHtlc(kid *kidOutput) {
c.recoveredBalance += kid.Amount()
c.htlcs = append(c.htlcs, htlcMaturityReport{
outpoint: *kid.OutPoint(),
amount: kid.Amount(),
confHeight: kid.ConfHeight(),
maturityRequirement: kid.BlocksToMaturity(),
maturityHeight: kid.ConfHeight() + kid.BlocksToMaturity(),
})
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}
// closeAndRemoveIfMature removes a particular channel from the channel index
// if and only if all of its outputs have been marked graduated. If the channel
// still has ungraduated outputs, the method will succeed without altering the
// database state.
func (u *utxoNursery) closeAndRemoveIfMature(chanPoint *wire.OutPoint) error {
isMature, err := u.cfg.Store.IsMatureChannel(chanPoint)
if err == ErrContractNotFound {
return nil
} else if err != nil {
utxnLog.Errorf("Unable to determine maturity of "+
"channel=%s", chanPoint)
return err
}
// Nothing to do if we are still incubating.
if !isMature {
return nil
}
// Now that the channel is fully closed, we remove the channel from the
// nursery store here. This preserves the invariant that we never remove
// a channel unless it is mature, as this is the only place the utxo
// nursery removes a channel.
if err := u.cfg.Store.RemoveChannel(chanPoint); err != nil {
utxnLog.Errorf("Unable to remove channel=%s from "+
"nursery store: %v", chanPoint, err)
return err
}
utxnLog.Infof("Removed channel %v from nursery store", chanPoint)
return nil
}
// newSweepPkScript creates a new public key script which should be used to
// sweep any time-locked, or contested channel funds into the wallet.
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// 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)
}
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// babyOutput represents a two-stage CSV locked output, and is used to track
// htlc outputs through incubation. The first stage requires broadcasting a
// presigned timeout txn that spends from the CLTV locked output on the
// commitment txn. A babyOutput is treated as a subset of CsvSpendableOutputs,
// with the additional constraint that a transaction must be broadcast before
// it can be spent. Each baby transaction embeds the kidOutput that can later
// be used to spend the CSV output contained in the timeout txn.
//
// TODO(roasbeef): re-rename to timeout tx
// * create CltvCsvSpendableOutput
type babyOutput struct {
// expiry is the absolute block height at which the secondLevelTx
// should be broadcast to the network.
//
// NOTE: This value will be zero if this is a baby output for a prior
// incoming HTLC.
expiry uint32
// timeoutTx is a fully-signed transaction that, upon confirmation,
// transitions the htlc into the delay+claim stage.
timeoutTx *wire.MsgTx
// kidOutput represents the CSV output to be swept from the
// secondLevelTx after it has been broadcast and confirmed.
kidOutput
}
// makeBabyOutput constructs a baby output that wraps a future kidOutput. The
// provided sign descriptors and witness types will be used once the output
// reaches the delay and claim stage.
func makeBabyOutput(chanPoint *wire.OutPoint,
htlcResolution *lnwallet.OutgoingHtlcResolution) babyOutput {
htlcOutpoint := htlcResolution.ClaimOutpoint
blocksToMaturity := htlcResolution.CsvDelay
witnessType := lnwallet.HtlcOfferedTimeoutSecondLevel
kid := makeKidOutput(
&htlcOutpoint, chanPoint, blocksToMaturity, witnessType,
&htlcResolution.SweepSignDesc, 0,
)
return babyOutput{
kidOutput: kid,
expiry: htlcResolution.Expiry,
timeoutTx: htlcResolution.SignedTimeoutTx,
}
}
// Encode writes the baby output to the given io.Writer.
func (bo *babyOutput) Encode(w io.Writer) error {
var scratch [4]byte
byteOrder.PutUint32(scratch[:], bo.expiry)
if _, err := w.Write(scratch[:]); err != nil {
return err
}
if err := bo.timeoutTx.Serialize(w); err != nil {
return err
}
return bo.kidOutput.Encode(w)
}
// Decode reconstructs a baby output using the provided io.Reader.
func (bo *babyOutput) Decode(r io.Reader) error {
var scratch [4]byte
if _, err := r.Read(scratch[:]); err != nil {
return err
}
bo.expiry = byteOrder.Uint32(scratch[:])
bo.timeoutTx = new(wire.MsgTx)
if err := bo.timeoutTx.Deserialize(r); err != nil {
return err
}
return bo.kidOutput.Decode(r)
}
// 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 {
breachedOutput
originChanPoint wire.OutPoint
// isHtlc denotes if this kid output is an HTLC output or not. This
// value will be used to determine how to report this output within the
// nursery report.
isHtlc bool
// blocksToMaturity is the relative CSV delay required after initial
// confirmation of the commitment transaction before we can sweep this
// output.
//
// NOTE: This will be set for: commitment outputs, and incoming HTLC's.
// Otherwise, this will be zero.
blocksToMaturity uint32
// absoluteMaturity is the absolute height that this output will be
// mature at. In order to sweep the output after this height, the
// locktime of sweep transaction will need to be set to this value.
//
// NOTE: This will only be set for: outgoing HTLC's on the commitment
// transaction of the remote party.
absoluteMaturity uint32
}
func makeKidOutput(outpoint, originChanPoint *wire.OutPoint,
blocksToMaturity uint32, witnessType lnwallet.WitnessType,
signDescriptor *lnwallet.SignDescriptor,
absoluteMaturity uint32) kidOutput {
// This is an HTLC either if it's an incoming HTLC on our commitment
// transaction, or is an outgoing HTLC on the commitment transaction of
// the remote peer.
isHtlc := (witnessType == lnwallet.HtlcAcceptedSuccessSecondLevel ||
witnessType == lnwallet.HtlcOfferedRemoteTimeout)
// heightHint can be safely set to zero here, because after this
// function returns, nursery will set a proper confirmation height in
// waitForTimeoutConf or waitForPreschoolConf.
heightHint := uint32(0)
return kidOutput{
breachedOutput: makeBreachedOutput(
outpoint, witnessType, nil, signDescriptor, heightHint,
),
isHtlc: isHtlc,
originChanPoint: *originChanPoint,
blocksToMaturity: blocksToMaturity,
absoluteMaturity: absoluteMaturity,
}
}
func (k *kidOutput) OriginChanPoint() *wire.OutPoint {
return &k.originChanPoint
}
func (k *kidOutput) BlocksToMaturity() uint32 {
return k.blocksToMaturity
}
func (k *kidOutput) SetConfHeight(height uint32) {
k.confHeight = height
}
func (k *kidOutput) ConfHeight() uint32 {
return k.confHeight
}
// Encode 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 (k *kidOutput) Encode(w io.Writer) error {
var scratch [8]byte
byteOrder.PutUint64(scratch[:], uint64(k.Amount()))
if _, err := w.Write(scratch[:]); err != nil {
return err
}
if err := writeOutpoint(w, k.OutPoint()); err != nil {
return err
}
if err := writeOutpoint(w, k.OriginChanPoint()); err != nil {
return err
}
if err := binary.Write(w, byteOrder, k.isHtlc); err != nil {
return err
}
byteOrder.PutUint32(scratch[:4], k.BlocksToMaturity())
if _, err := w.Write(scratch[:4]); err != nil {
return err
}
byteOrder.PutUint32(scratch[:4], k.absoluteMaturity)
if _, err := w.Write(scratch[:4]); err != nil {
return err
}
byteOrder.PutUint32(scratch[:4], k.ConfHeight())
if _, err := w.Write(scratch[:4]); err != nil {
return err
}
byteOrder.PutUint16(scratch[:2], uint16(k.WitnessType()))
if _, err := w.Write(scratch[:2]); err != nil {
return err
}
return lnwallet.WriteSignDescriptor(w, k.SignDesc())
}
// Decode 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 (k *kidOutput) Decode(r io.Reader) error {
var scratch [8]byte
if _, err := r.Read(scratch[:]); err != nil {
return err
}
k.amt = btcutil.Amount(byteOrder.Uint64(scratch[:]))
if err := readOutpoint(io.LimitReader(r, 40), &k.outpoint); err != nil {
return err
}
err := readOutpoint(io.LimitReader(r, 40), &k.originChanPoint)
if err != nil {
return err
}
if err := binary.Read(r, byteOrder, &k.isHtlc); err != nil {
return err
}
if _, err := r.Read(scratch[:4]); err != nil {
return err
}
k.blocksToMaturity = byteOrder.Uint32(scratch[:4])
if _, err := r.Read(scratch[:4]); err != nil {
return err
}
k.absoluteMaturity = byteOrder.Uint32(scratch[:4])
if _, err := r.Read(scratch[:4]); err != nil {
return err
}
k.confHeight = byteOrder.Uint32(scratch[:4])
if _, err := r.Read(scratch[:2]); err != nil {
return err
}
k.witnessType = lnwallet.WitnessType(byteOrder.Uint16(scratch[:2]))
return lnwallet.ReadSignDescriptor(r, &k.signDesc)
}
// 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
}
// Compile-time constraint to ensure kidOutput implements the
// Input interface.
var _ sweep.Input = (*kidOutput)(nil)