package main import ( "bytes" "encoding/binary" "fmt" "io" "sync" "sync/atomic" "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/input" "github.com/lightningnetwork/lnd/lnwallet" "github.com/lightningnetwork/lnd/sweep" ) // 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 // // - 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") ) // NurseryConfig abstracts the required subsystems used by the utxo nursery. An // instance of NurseryConfig is passed to newUtxoNursery during instantiation. 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 // 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) // 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 // Sweep sweeps an input back to the wallet. SweepInput func(input input.Input) (chan sweep.Result, error) } // 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. cfg *NurseryConfig mu sync.Mutex bestHeight uint32 quit chan struct{} wg sync.WaitGroup } // newUtxoNursery creates a new instance of the utxoNursery from a // ChainNotifier and LightningWallet instance. func newUtxoNursery(cfg *NurseryConfig) *utxoNursery { return &utxoNursery{ 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)) // 2. Flush all fully-graduated channels from the pipeline. // Load any pending close channels, which represents the super set of // all channels that may still be incubating. pendingCloseChans, err := u.cfg.FetchClosedChannels(true) if err != nil { return err } // 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 } } // TODO(conner): check if any fully closed channels can be removed from // utxn. // 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. // // 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 { 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 { close(u.quit) return err } 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 { // 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() // 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) var ( hasCommit bool // Kid outputs can be swept after an initial confirmation // followed by a maturity period.Baby outputs are two stage and // 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)) ) // 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, input.CommitmentTimeLock, &commitResolution.SelfOutputSignDesc, 0, ) // We'll skip any zero valued outputs as this indicates we // don't have a settled balance within the commitment // transaction. if selfOutput.Amount() > 0 { kidOutputs = append(kidOutputs, selfOutput) } } // 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, input.HtlcAcceptedSuccessSecondLevel, &htlcRes.SweepSignDesc, 0, ) if htlcOutput.Amount() > 0 { kidOutputs = append(kidOutputs, htlcOutput) } } // 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, input.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 utxnLog.Infof("Incubating Channel(%s) has-commit=%v, num-htlcs=%d", chanPoint, hasCommit, numHtlcs) u.mu.Lock() defer u.mu.Unlock() // 2. Persist the outputs we intended to sweep in the nursery store if err := u.cfg.Store.Incubate(kidOutputs, babyOutputs); err != nil { utxnLog.Errorf("unable to begin incubation of Channel(%s): %v", chanPoint, err) 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(babyOutput.expiry, &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 } } } 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. func (u *utxoNursery) NurseryReport( chanPoint *wire.OutPoint) (*contractMaturityReport, error) { u.mu.Lock() defer u.mu.Unlock() utxnLog.Infof("NurseryReport: building nursery report for channel %v", chanPoint) report := &contractMaturityReport{} 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 } // Each crib output represents a stage one htlc, and // will contribute towards the limbo balance. report.AddLimboStage1TimeoutHtlc(&baby) case bytes.HasPrefix(k, psclPrefix), bytes.HasPrefix(k, kndrPrefix), bytes.HasPrefix(k, gradPrefix): // 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. switch { case bytes.HasPrefix(k, psclPrefix): // Preschool outputs are awaiting the // confirmation of the commitment transaction. switch kid.WitnessType() { case input.CommitmentTimeLock: report.AddLimboCommitment(&kid) case input.HtlcAcceptedSuccessSecondLevel: // An HTLC output on our commitment transaction // where the second-layer transaction hasn't // yet confirmed. report.AddLimboStage1SuccessHtlc(&kid) case input.HtlcOfferedRemoteTimeout: // This is an HTLC output on the // commitment transaction of the remote // party. We are waiting for the CLTV // timelock expire. report.AddLimboDirectHtlc(&kid) } 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 input.CommitmentTimeLock: // The commitment transaction has been // confirmed, and we are waiting the CSV // delay to expire. report.AddLimboCommitment(&kid) case input.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 input.HtlcAcceptedSuccessSecondLevel: fallthrough case input.HtlcOfferedTimeoutSecondLevel: // The htlc timeout or success // transaction has confirmed, and the // CSV delay has begun ticking. report.AddLimboStage2Htlc(&kid) } 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 input.CommitmentTimeLock: // The commitment output was // successfully swept back into a // regular p2wkh output. report.AddRecoveredCommitment(&kid) case input.HtlcAcceptedSuccessSecondLevel: fallthrough case input.HtlcOfferedTimeoutSecondLevel: fallthrough case input.HtlcOfferedRemoteTimeout: // This htlc output successfully // resides in a p2wkh output belonging // to the user. report.AddRecoveredHtlc(&kid) } } default: } return nil }); err != nil { return nil, err } return report, 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 { 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. for i := range psclOutputs { kid := &psclOutputs[i] chanPoint := kid.OriginChanPoint() // Load the close summary for this output's channel point. 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 } } return nil } // 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. // 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)) if err != nil { return err } // Return early if nothing to sweep. if len(activeHeights) == 0 { return nil } utxnLog.Infof("(Re)-sweeping %d heights below height=%d", len(activeHeights), bestHeight) // 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", classHeight) if err = u.graduateClass(classHeight); err != nil { utxnLog.Errorf("Failed to sweep outputs at "+ "height=%v: %v", classHeight, err) return err } } utxnLog.Infof("UTXO Nursery is now fully synced") return nil } // 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) 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 } } } // 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( 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) return err } } // Now, we broadcast all pre-signed htlc txns from the csv crib outputs // at this height. 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) for _, output := range kgtnOutputs { // Create local copy to prevent pointer to loop variable to be // passed in with disastruous consequences. local := output resultChan, err := u.cfg.SweepInput(&local) if err != nil { return err } u.wg.Add(1) go u.waitForSweepConf(classHeight, &local, resultChan) } 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) { defer u.wg.Done() select { case result, ok := <-resultChan: 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) return } 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) return } utxnLog.Infof("Graduated kindergarten output from height=%d", classHeight) // Attempt to close the channel, only doing so if all of the channel's // 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 } } // 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 "+ "(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 { utxnLog.Errorf("Unable to broadcast baby tx: "+ "%v, %v", err, spew.Sdump(baby.timeoutTx)) 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 // 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, ) 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 } 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 { 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, ) 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()) u.wg.Add(1) go u.waitForPreschoolConf(kid, confChan) 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, 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 } 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) if err != nil { utxnLog.Errorf("Unable to move %v output "+ "from preschool to kindergarten bucket: %v", outputType, err) return } } // contractMaturityReport is a report that details the maturity progress of a // particular force closed contract. type contractMaturityReport struct { // 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 // 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 // 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. 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() // 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.maturityHeight = kid.BlocksToMaturity() + kid.ConfHeight() } // AddLimboStage1TimeoutHtlc adds an htlc crib output to the maturity report's // htlcs, and contributes its amount to the limbo balance. func (c *contractMaturityReport) AddLimboStage1TimeoutHtlc(baby *babyOutput) { c.limboBalance += baby.Amount() // TODO(roasbeef): bool to indicate stage 1 vs stage 2? c.htlcs = append(c.htlcs, htlcMaturityReport{ outpoint: *baby.OutPoint(), amount: baby.Amount(), 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 // has or hasn't expired yet. func (c *contractMaturityReport) AddLimboDirectHtlc(kid *kidOutput) { c.limboBalance += kid.Amount() htlcReport := htlcMaturityReport{ outpoint: *kid.OutPoint(), amount: kid.Amount(), 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(), stage: 1, }) } // 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(), 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() } c.htlcs = append(c.htlcs, htlcReport) } // AddRecoveredHtlc adds a graduate output to the maturity report's htlcs, and // 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(), maturityHeight: kid.ConfHeight() + kid.BlocksToMaturity(), }) } // 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. // 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) } // 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 := input.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 input.WitnessType, signDescriptor *input.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 == input.HtlcAcceptedSuccessSecondLevel || witnessType == input.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 input.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 = input.WitnessType(byteOrder.Uint16(scratch[:2])) return input.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 _ input.Input = (*kidOutput)(nil)