12313002221

Committed 13 Dec 2024 09:25AM UTC coverage: 57.486% (+8.6%) from 48.92%

Build # 12313002221

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github

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web-flow

Commit Message

Merge pull request #9343 from ellemouton/contextGuard

fn: expand the ContextGuard and add tests

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39.37

/contractcourt/chain_arbitrator.go

package contractcourt

import (
        "errors"
        "fmt"
        "sync"
        "sync/atomic"
        "time"

        "github.com/btcsuite/btcd/btcutil"
        "github.com/btcsuite/btcd/chaincfg/chainhash"
        "github.com/btcsuite/btcd/wire"
        "github.com/btcsuite/btcwallet/walletdb"
        "github.com/lightningnetwork/lnd/chainntnfs"
        "github.com/lightningnetwork/lnd/channeldb"
        "github.com/lightningnetwork/lnd/clock"
        "github.com/lightningnetwork/lnd/fn/v2"
        "github.com/lightningnetwork/lnd/graph/db/models"
        "github.com/lightningnetwork/lnd/input"
        "github.com/lightningnetwork/lnd/kvdb"
        "github.com/lightningnetwork/lnd/labels"
        "github.com/lightningnetwork/lnd/lnwallet"
        "github.com/lightningnetwork/lnd/lnwallet/chainfee"
        "github.com/lightningnetwork/lnd/lnwire"
)

// ErrChainArbExiting signals that the chain arbitrator is shutting down.
var ErrChainArbExiting = errors.New("ChainArbitrator exiting")

// ResolutionMsg is a message sent by resolvers to outside sub-systems once an
// outgoing contract has been fully resolved. For multi-hop contracts, if we
// resolve the outgoing contract, we'll also need to ensure that the incoming
// contract is resolved as well. We package the items required to resolve the
// incoming contracts within this message.
type ResolutionMsg struct {
        // SourceChan identifies the channel that this message is being sent
        // from. This is the channel's short channel ID.
        SourceChan lnwire.ShortChannelID

        // HtlcIndex is the index of the contract within the original
        // commitment trace.
        HtlcIndex uint64

        // Failure will be non-nil if the incoming contract should be canceled
        // all together. This can happen if the outgoing contract was dust, if
        // if the outgoing HTLC timed out.
        Failure lnwire.FailureMessage

        // PreImage will be non-nil if the incoming contract can successfully
        // be redeemed. This can happen if we learn of the preimage from the
        // outgoing HTLC on-chain.
        PreImage *[32]byte
}

// ChainArbitratorConfig is a configuration struct that contains all the
// function closures and interface that required to arbitrate on-chain
// contracts for a particular chain.
type ChainArbitratorConfig struct {
        // ChainHash is the chain that this arbitrator is to operate within.
        ChainHash chainhash.Hash

        // IncomingBroadcastDelta is the delta that we'll use to decide when to
        // broadcast our commitment transaction if we have incoming htlcs. This
        // value should be set based on our current fee estimation of the
        // commitment transaction. We use this to determine when we should
        // broadcast instead of just the HTLC timeout, as we want to ensure
        // that the commitment transaction is already confirmed, by the time the
        // HTLC expires. Otherwise we may end up not settling the htlc on-chain
        // because the other party managed to time it out.
        IncomingBroadcastDelta uint32

        // OutgoingBroadcastDelta is the delta that we'll use to decide when to
        // broadcast our commitment transaction if there are active outgoing
        // htlcs. This value can be lower than the incoming broadcast delta.
        OutgoingBroadcastDelta uint32

        // NewSweepAddr is a function that returns a new address under control
        // by the wallet. We'll use this to sweep any no-delay outputs as a
        // result of unilateral channel closes.
        //
        // NOTE: This SHOULD return a p2wkh script.
        NewSweepAddr func() ([]byte, error)

        // PublishTx reliably broadcasts a transaction to the network. Once
        // this function exits without an error, then they transaction MUST
        // continually be rebroadcast if needed.
        PublishTx func(*wire.MsgTx, string) error

        // DeliverResolutionMsg is a function that will append an outgoing
        // message to the "out box" for a ChannelLink. This is used to cancel
        // backwards any HTLC's that are either dust, we're timing out, or
        // settling on-chain to the incoming link.
        DeliverResolutionMsg func(...ResolutionMsg) error

        // MarkLinkInactive is a function closure that the ChainArbitrator will
        // use to mark that active HTLC's shouldn't be attempted to be routed
        // over a particular channel. This function will be called in that a
        // ChannelArbitrator decides that it needs to go to chain in order to
        // resolve contracts.
        //
        // TODO(roasbeef): rename, routing based
        MarkLinkInactive func(wire.OutPoint) error

        // ContractBreach is a function closure that the ChainArbitrator will
        // use to notify the BreachArbitrator about a contract breach. It should
        // only return a non-nil error when the BreachArbitrator has preserved
        // the necessary breach info for this channel point. Once the breach
        // resolution is persisted in the ChannelArbitrator, it will be safe
        // to mark the channel closed.
        ContractBreach func(wire.OutPoint, *lnwallet.BreachRetribution) error

        // IsOurAddress is a function that returns true if the passed address
        // is known to the underlying wallet. Otherwise, false should be
        // returned.
        IsOurAddress func(btcutil.Address) bool

        // IncubateOutputs sends either an incoming HTLC, an outgoing HTLC, or
        // both to the utxo nursery. Once this function returns, the nursery
        // should have safely persisted the outputs to disk, and should start
        // the process of incubation. This is used when a resolver wishes to
        // pass off the output to the nursery as we're only waiting on an
        // absolute/relative item block.
        IncubateOutputs func(wire.OutPoint,
                fn.Option[lnwallet.OutgoingHtlcResolution],
                fn.Option[lnwallet.IncomingHtlcResolution],
                uint32, fn.Option[int32]) error

        // PreimageDB is a global store of all known pre-images. We'll use this
        // to decide if we should broadcast a commitment transaction to claim
        // an HTLC on-chain.
        PreimageDB WitnessBeacon

        // Notifier is an instance of a chain notifier we'll use to watch for
        // certain on-chain events.
        Notifier chainntnfs.ChainNotifier

        // Mempool is the a mempool watcher that allows us to watch for events
        // happened in mempool.
        Mempool chainntnfs.MempoolWatcher

        // Signer is a signer backed by the active lnd node. This should be
        // capable of producing a signature as specified by a valid
        // SignDescriptor.
        Signer input.Signer

        // FeeEstimator will be used to return fee estimates.
        FeeEstimator chainfee.Estimator

        // ChainIO allows us to query the state of the current main chain.
        ChainIO lnwallet.BlockChainIO

        // DisableChannel disables a channel, resulting in it not being able to
        // forward payments.
        DisableChannel func(wire.OutPoint) error

        // Sweeper allows resolvers to sweep their final outputs.
        Sweeper UtxoSweeper

        // Registry is the invoice database that is used by resolvers to lookup
        // preimages and settle invoices.
        Registry Registry

        // NotifyClosedChannel is a function closure that the ChainArbitrator
        // will use to notify the ChannelNotifier about a newly closed channel.
        NotifyClosedChannel func(wire.OutPoint)

        // NotifyFullyResolvedChannel is a function closure that the
        // ChainArbitrator will use to notify the ChannelNotifier about a newly
        // resolved channel. The main difference to NotifyClosedChannel is that
        // in case of a local force close the NotifyClosedChannel is called when
        // the published commitment transaction confirms while
        // NotifyFullyResolvedChannel is only called when the channel is fully
        // resolved (which includes sweeping any time locked funds).
        NotifyFullyResolvedChannel func(point wire.OutPoint)

        // OnionProcessor is used to decode onion payloads for on-chain
        // resolution.
        OnionProcessor OnionProcessor

        // PaymentsExpirationGracePeriod indicates a time window we let the
        // other node to cancel an outgoing htlc that our node has initiated and
        // has timed out.
        PaymentsExpirationGracePeriod time.Duration

        // IsForwardedHTLC checks for a given htlc, identified by channel id and
        // htlcIndex, if it is a forwarded one.
        IsForwardedHTLC func(chanID lnwire.ShortChannelID, htlcIndex uint64) bool

        // Clock is the clock implementation that ChannelArbitrator uses.
        // It is useful for testing.
        Clock clock.Clock

        // SubscribeBreachComplete is used by the breachResolver to register a
        // subscription that notifies when the breach resolution process is
        // complete.
        SubscribeBreachComplete func(op *wire.OutPoint, c chan struct{}) (
                bool, error)

        // PutFinalHtlcOutcome stores the final outcome of an htlc in the
        // database.
        PutFinalHtlcOutcome func(chanId lnwire.ShortChannelID,
                htlcId uint64, settled bool) error

        // HtlcNotifier is an interface that htlc events are sent to.
        HtlcNotifier HtlcNotifier

        // Budget is the configured budget for the arbitrator.
        Budget BudgetConfig

        // QueryIncomingCircuit is used to find the outgoing HTLC's
        // corresponding incoming HTLC circuit. It queries the circuit map for
        // a given outgoing circuit key and returns the incoming circuit key.
        //
        // TODO(yy): this is a hacky way to get around the cycling import issue
        // as we cannot import `htlcswitch` here. A proper way is to define an
        // interface here that asks for method `LookupOpenCircuit`,
        // meanwhile, turn `PaymentCircuit` into an interface or bring it to a
        // lower package.
        QueryIncomingCircuit func(circuit models.CircuitKey) *models.CircuitKey

        // AuxLeafStore is an optional store that can be used to store auxiliary
        // leaves for certain custom channel types.
        AuxLeafStore fn.Option[lnwallet.AuxLeafStore]

        // AuxSigner is an optional signer that can be used to sign auxiliary
        // leaves for certain custom channel types.
        AuxSigner fn.Option[lnwallet.AuxSigner]

        // AuxResolver is an optional interface that can be used to modify the
        // way contracts are resolved.
        AuxResolver fn.Option[lnwallet.AuxContractResolver]
}

// ChainArbitrator is a sub-system that oversees the on-chain resolution of all
// active, and channel that are in the "pending close" state. Within the
// contractcourt package, the ChainArbitrator manages a set of active
// ContractArbitrators. Each ContractArbitrators is responsible for watching
// the chain for any activity that affects the state of the channel, and also
// for monitoring each contract in order to determine if any on-chain activity is
// required. Outside sub-systems interact with the ChainArbitrator in order to
// forcibly exit a contract, update the set of live signals for each contract,
// and to receive reports on the state of contract resolution.
type ChainArbitrator struct {
        started int32 // To be used atomically.
        stopped int32 // To be used atomically.

        sync.Mutex

        // activeChannels is a map of all the active contracts that are still
        // open, and not fully resolved.
        activeChannels map[wire.OutPoint]*ChannelArbitrator

        // activeWatchers is a map of all the active chainWatchers for channels
        // that are still considered open.
        activeWatchers map[wire.OutPoint]*chainWatcher

        // cfg is the config struct for the arbitrator that contains all
        // methods and interface it needs to operate.
        cfg ChainArbitratorConfig

        // chanSource will be used by the ChainArbitrator to fetch all the
        // active channels that it must still watch over.
        chanSource *channeldb.DB

        quit chan struct{}

        wg sync.WaitGroup
}

// NewChainArbitrator returns a new instance of the ChainArbitrator using the
// passed config struct, and backing persistent database.
func NewChainArbitrator(cfg ChainArbitratorConfig,
        db *channeldb.DB) *ChainArbitrator {

        return &ChainArbitrator{
                cfg:            cfg,
                activeChannels: make(map[wire.OutPoint]*ChannelArbitrator),
                activeWatchers: make(map[wire.OutPoint]*chainWatcher),
                chanSource:     db,
                quit:           make(chan struct{}),
        }
}

// arbChannel is a wrapper around an open channel that channel arbitrators
// interact with.
type arbChannel struct {
        // channel is the in-memory channel state.
        channel *channeldb.OpenChannel

        // c references the chain arbitrator and is used by arbChannel
        // internally.
        c *ChainArbitrator
}

// NewAnchorResolutions returns the anchor resolutions for currently valid
// commitment transactions.
//
// NOTE: Part of the ArbChannel interface.
func (a *arbChannel) NewAnchorResolutions() (*lnwallet.AnchorResolutions,
        error) {

        // Get a fresh copy of the database state to base the anchor resolutions
        // on. Unfortunately the channel instance that we have here isn't the
        // same instance that is used by the link.
        chanPoint := a.channel.FundingOutpoint

        channel, err := a.c.chanSource.ChannelStateDB().FetchChannel(chanPoint)
        if err != nil {
                return nil, err
        }

        var chanOpts []lnwallet.ChannelOpt
        a.c.cfg.AuxLeafStore.WhenSome(func(s lnwallet.AuxLeafStore) {
                chanOpts = append(chanOpts, lnwallet.WithLeafStore(s))
        })
        a.c.cfg.AuxSigner.WhenSome(func(s lnwallet.AuxSigner) {
                chanOpts = append(chanOpts, lnwallet.WithAuxSigner(s))
        })
        a.c.cfg.AuxResolver.WhenSome(func(s lnwallet.AuxContractResolver) {
                chanOpts = append(chanOpts, lnwallet.WithAuxResolver(s))
        })

        chanMachine, err := lnwallet.NewLightningChannel(
                a.c.cfg.Signer, channel, nil, chanOpts...,
        )
        if err != nil {
                return nil, err
        }

        return chanMachine.NewAnchorResolutions()
}

// ForceCloseChan should force close the contract that this attendant is
// watching over. We'll use this when we decide that we need to go to chain. It
// should in addition tell the switch to remove the corresponding link, such
// that we won't accept any new updates.
//
// NOTE: Part of the ArbChannel interface.
func (a *arbChannel) ForceCloseChan() (*wire.MsgTx, error) {
        // First, we mark the channel as borked, this ensure
        // that no new state transitions can happen, and also
        // that the link won't be loaded into the switch.
        if err := a.channel.MarkBorked(); err != nil {
                return nil, err
        }

        // With the channel marked as borked, we'll now remove
        // the link from the switch if its there. If the link
        // is active, then this method will block until it
        // exits.
        chanPoint := a.channel.FundingOutpoint

        if err := a.c.cfg.MarkLinkInactive(chanPoint); err != nil {
                log.Errorf("unable to mark link inactive: %v", err)
        }

        // Now that we know the link can't mutate the channel
        // state, we'll read the channel from disk the target
        // channel according to its channel point.
        channel, err := a.c.chanSource.ChannelStateDB().FetchChannel(chanPoint)
        if err != nil {
                return nil, err
        }

        var chanOpts []lnwallet.ChannelOpt
        a.c.cfg.AuxLeafStore.WhenSome(func(s lnwallet.AuxLeafStore) {
                chanOpts = append(chanOpts, lnwallet.WithLeafStore(s))
        })
        a.c.cfg.AuxSigner.WhenSome(func(s lnwallet.AuxSigner) {
                chanOpts = append(chanOpts, lnwallet.WithAuxSigner(s))
        })
        a.c.cfg.AuxResolver.WhenSome(func(s lnwallet.AuxContractResolver) {
                chanOpts = append(chanOpts, lnwallet.WithAuxResolver(s))
        })

        // Finally, we'll force close the channel completing
        // the force close workflow.
        chanMachine, err := lnwallet.NewLightningChannel(
                a.c.cfg.Signer, channel, nil, chanOpts...,
        )
        if err != nil {
                return nil, err
        }

        closeSummary, err := chanMachine.ForceClose(
                lnwallet.WithSkipContractResolutions(),
        )
        if err != nil {
                return nil, err
        }

        return closeSummary.CloseTx, nil
}

// newActiveChannelArbitrator creates a new instance of an active channel
// arbitrator given the state of the target channel.
func newActiveChannelArbitrator(channel *channeldb.OpenChannel,
        c *ChainArbitrator, chanEvents *ChainEventSubscription) (*ChannelArbitrator, error) {

        // TODO(roasbeef): fetch best height (or pass in) so can ensure block
        // epoch delivers all the notifications to

        chanPoint := channel.FundingOutpoint

        log.Tracef("Creating ChannelArbitrator for ChannelPoint(%v)", chanPoint)

        // Next we'll create the matching configuration struct that contains
        // all interfaces and methods the arbitrator needs to do its job.
        arbCfg := ChannelArbitratorConfig{
                ChanPoint:   chanPoint,
                Channel:     c.getArbChannel(channel),
                ShortChanID: channel.ShortChanID(),

                MarkCommitmentBroadcasted: channel.MarkCommitmentBroadcasted,
                MarkChannelClosed: func(summary *channeldb.ChannelCloseSummary,
                        statuses ...channeldb.ChannelStatus) error {

                        err := channel.CloseChannel(summary, statuses...)
                        if err != nil {
                                return err
                        }
                        c.cfg.NotifyClosedChannel(summary.ChanPoint)
                        return nil
                },
                IsPendingClose:        false,
                ChainArbitratorConfig: c.cfg,
                ChainEvents:           chanEvents,
                PutResolverReport: func(tx kvdb.RwTx,
                        report *channeldb.ResolverReport) error {

                        return c.chanSource.PutResolverReport(
                                tx, c.cfg.ChainHash, &chanPoint, report,
                        )
                },
                FetchHistoricalChannel: func() (*channeldb.OpenChannel, error) {
                        chanStateDB := c.chanSource.ChannelStateDB()
                        return chanStateDB.FetchHistoricalChannel(&chanPoint)
                },
                FindOutgoingHTLCDeadline: func(
                        htlc channeldb.HTLC) fn.Option[int32] {

                        return c.FindOutgoingHTLCDeadline(
                                channel.ShortChanID(), htlc,
                        )
                },
        }

        // The final component needed is an arbitrator log that the arbitrator
        // will use to keep track of its internal state using a backed
        // persistent log.
        //
        // TODO(roasbeef); abstraction leak...
        //  * rework: adaptor method to set log scope w/ factory func
        chanLog, err := newBoltArbitratorLog(
                c.chanSource.Backend, arbCfg, c.cfg.ChainHash, chanPoint,
        )
        if err != nil {
                return nil, err
        }

        arbCfg.MarkChannelResolved = func() error {
                if c.cfg.NotifyFullyResolvedChannel != nil {
                        c.cfg.NotifyFullyResolvedChannel(chanPoint)
                }

                return c.ResolveContract(chanPoint)
        }

        // Finally, we'll need to construct a series of htlc Sets based on all
        // currently known valid commitments.
        htlcSets := make(map[HtlcSetKey]htlcSet)
        htlcSets[LocalHtlcSet] = newHtlcSet(channel.LocalCommitment.Htlcs)
        htlcSets[RemoteHtlcSet] = newHtlcSet(channel.RemoteCommitment.Htlcs)

        pendingRemoteCommitment, err := channel.RemoteCommitChainTip()
        if err != nil && err != channeldb.ErrNoPendingCommit {
                return nil, err
        }
        if pendingRemoteCommitment != nil {
                htlcSets[RemotePendingHtlcSet] = newHtlcSet(
                        pendingRemoteCommitment.Commitment.Htlcs,
                )
        }

        return NewChannelArbitrator(
                arbCfg, htlcSets, chanLog,
        ), nil
}

// getArbChannel returns an open channel wrapper for use by channel arbitrators.
func (c *ChainArbitrator) getArbChannel(
        channel *channeldb.OpenChannel) *arbChannel {

        return &arbChannel{
                channel: channel,
                c:       c,
        }
}

// ResolveContract marks a contract as fully resolved within the database.
// This is only to be done once all contracts which were live on the channel
// before hitting the chain have been resolved.
func (c *ChainArbitrator) ResolveContract(chanPoint wire.OutPoint) error {
        log.Infof("Marking ChannelPoint(%v) fully resolved", chanPoint)

        // First, we'll we'll mark the channel as fully closed from the PoV of
        // the channel source.
        err := c.chanSource.ChannelStateDB().MarkChanFullyClosed(&chanPoint)
        if err != nil {
                log.Errorf("ChainArbitrator: unable to mark ChannelPoint(%v) "+
                        "fully closed: %v", chanPoint, err)
                return err
        }

        // Now that the channel has been marked as fully closed, we'll stop
        // both the channel arbitrator and chain watcher for this channel if
        // they're still active.
        var arbLog ArbitratorLog
        c.Lock()
        chainArb := c.activeChannels[chanPoint]
        delete(c.activeChannels, chanPoint)

        chainWatcher := c.activeWatchers[chanPoint]
        delete(c.activeWatchers, chanPoint)
        c.Unlock()

        if chainArb != nil {
                arbLog = chainArb.log

                if err := chainArb.Stop(); err != nil {
                        log.Warnf("unable to stop ChannelArbitrator(%v): %v",
                                chanPoint, err)
                }
        }
        if chainWatcher != nil {
                if err := chainWatcher.Stop(); err != nil {
                        log.Warnf("unable to stop ChainWatcher(%v): %v",
                                chanPoint, err)
                }
        }

        // Once this has been marked as resolved, we'll wipe the log that the
        // channel arbitrator was using to store its persistent state. We do
        // this after marking the channel resolved, as otherwise, the
        // arbitrator would be re-created, and think it was starting from the
        // default state.
        if arbLog != nil {
                if err := arbLog.WipeHistory(); err != nil {
                        return err
                }
        }

        return nil
}

// Start launches all goroutines that the ChainArbitrator needs to operate.
func (c *ChainArbitrator) Start() error {
        if !atomic.CompareAndSwapInt32(&c.started, 0, 1) {
                return nil
        }

        log.Infof("ChainArbitrator starting with config: budget=[%v]",
                &c.cfg.Budget)

        // First, we'll fetch all the channels that are still open, in order to
        // collect them within our set of active contracts.
        openChannels, err := c.chanSource.ChannelStateDB().FetchAllChannels()
        if err != nil {
                return err
        }

        if len(openChannels) > 0 {
                log.Infof("Creating ChannelArbitrators for %v active channels",
                        len(openChannels))
        }

        // For each open channel, we'll configure then launch a corresponding
        // ChannelArbitrator.
        for _, channel := range openChannels {
                chanPoint := channel.FundingOutpoint
                channel := channel

                // First, we'll create an active chainWatcher for this channel
                // to ensure that we detect any relevant on chain events.
                breachClosure := func(ret *lnwallet.BreachRetribution) error {
                        return c.cfg.ContractBreach(chanPoint, ret)
                }

                chainWatcher, err := newChainWatcher(
                        chainWatcherConfig{
                                chanState:           channel,
                                notifier:            c.cfg.Notifier,
                                signer:              c.cfg.Signer,
                                isOurAddr:           c.cfg.IsOurAddress,
                                contractBreach:      breachClosure,
                                extractStateNumHint: lnwallet.GetStateNumHint,
                                auxLeafStore:        c.cfg.AuxLeafStore,
                                auxResolver:         c.cfg.AuxResolver,
                        },
                )
                if err != nil {
                        return err
                }

                c.activeWatchers[chanPoint] = chainWatcher
                channelArb, err := newActiveChannelArbitrator(
                        channel, c, chainWatcher.SubscribeChannelEvents(),
                )
                if err != nil {
                        return err
                }

                c.activeChannels[chanPoint] = channelArb

                // Republish any closing transactions for this channel.
                err = c.republishClosingTxs(channel)
                if err != nil {
                        log.Errorf("Failed to republish closing txs for "+
                                "channel %v", chanPoint)
                }
        }

        // In addition to the channels that we know to be open, we'll also
        // launch arbitrators to finishing resolving any channels that are in
        // the pending close state.
        closingChannels, err := c.chanSource.ChannelStateDB().FetchClosedChannels(
                true,
        )
        if err != nil {
                return err
        }

        if len(closingChannels) > 0 {
                log.Infof("Creating ChannelArbitrators for %v closing channels",
                        len(closingChannels))
        }

        // Next, for each channel is the closing state, we'll launch a
        // corresponding more restricted resolver, as we don't have to watch
        // the chain any longer, only resolve the contracts on the confirmed
        // commitment.
        //nolint:ll
        for _, closeChanInfo := range closingChannels {
                // We can leave off the CloseContract and ForceCloseChan
                // methods as the channel is already closed at this point.
                chanPoint := closeChanInfo.ChanPoint
                arbCfg := ChannelArbitratorConfig{
                        ChanPoint:             chanPoint,
                        ShortChanID:           closeChanInfo.ShortChanID,
                        ChainArbitratorConfig: c.cfg,
                        ChainEvents:           &ChainEventSubscription{},
                        IsPendingClose:        true,
                        ClosingHeight:         closeChanInfo.CloseHeight,
                        CloseType:             closeChanInfo.CloseType,
                        PutResolverReport: func(tx kvdb.RwTx,
                                report *channeldb.ResolverReport) error {

                                return c.chanSource.PutResolverReport(
                                        tx, c.cfg.ChainHash, &chanPoint, report,
                                )
                        },
                        FetchHistoricalChannel: func() (*channeldb.OpenChannel, error) {
                                chanStateDB := c.chanSource.ChannelStateDB()
                                return chanStateDB.FetchHistoricalChannel(&chanPoint)
                        },
                        FindOutgoingHTLCDeadline: func(
                                htlc channeldb.HTLC) fn.Option[int32] {

                                return c.FindOutgoingHTLCDeadline(
                                        closeChanInfo.ShortChanID, htlc,
                                )
                        },
                }
                chanLog, err := newBoltArbitratorLog(
                        c.chanSource.Backend, arbCfg, c.cfg.ChainHash, chanPoint,
                )
                if err != nil {
                        return err
                }
                arbCfg.MarkChannelResolved = func() error {
                        if c.cfg.NotifyFullyResolvedChannel != nil {
                                c.cfg.NotifyFullyResolvedChannel(chanPoint)
                        }

                        return c.ResolveContract(chanPoint)
                }

                // We create an empty map of HTLC's here since it's possible
                // that the channel is in StateDefault and updateActiveHTLCs is
                // called. We want to avoid writing to an empty map. Since the
                // channel is already in the process of being resolved, no new
                // HTLCs will be added.
                c.activeChannels[chanPoint] = NewChannelArbitrator(
                        arbCfg, make(map[HtlcSetKey]htlcSet), chanLog,
                )
        }

        // Now, we'll start all chain watchers in parallel to shorten start up
        // duration. In neutrino mode, this allows spend registrations to take
        // advantage of batch spend reporting, instead of doing a single rescan
        // per chain watcher.
        //
        // NOTE: After this point, we Stop the chain arb to ensure that any
        // lingering goroutines are cleaned up before exiting.
        watcherErrs := make(chan error, len(c.activeWatchers))
        var wg sync.WaitGroup
        for _, watcher := range c.activeWatchers {
                wg.Add(1)
                go func(w *chainWatcher) {
                        defer wg.Done()
                        select {
                        case watcherErrs <- w.Start():
                        case <-c.quit:
                                watcherErrs <- ErrChainArbExiting
                        }
                }(watcher)
        }

        // Once all chain watchers have been started, seal the err chan to
        // signal the end of the err stream.
        go func() {
                wg.Wait()
                close(watcherErrs)
        }()

        // stopAndLog is a helper function which shuts down the chain arb and
        // logs errors if they occur.
        stopAndLog := func() {
                if err := c.Stop(); err != nil {
                        log.Errorf("ChainArbitrator could not shutdown: %v", err)
                }
        }

        // Handle all errors returned from spawning our chain watchers. If any
        // of them failed, we will stop the chain arb to shutdown any active
        // goroutines.
        for err := range watcherErrs {
                if err != nil {
                        stopAndLog()
                        return err
                }
        }

        // Before we start all of our arbitrators, we do a preliminary state
        // lookup so that we can combine all of these lookups in a single db
        // transaction.
        var startStates map[wire.OutPoint]*chanArbStartState

        err = kvdb.View(c.chanSource, func(tx walletdb.ReadTx) error {
                for _, arbitrator := range c.activeChannels {
                        startState, err := arbitrator.getStartState(tx)
                        if err != nil {
                                return err
                        }

                        startStates[arbitrator.cfg.ChanPoint] = startState
                }

                return nil
        }, func() {
                startStates = make(
                        map[wire.OutPoint]*chanArbStartState,
                        len(c.activeChannels),
                )
        })
        if err != nil {
                stopAndLog()
                return err
        }

        // Launch all the goroutines for each arbitrator so they can carry out
        // their duties.
        for _, arbitrator := range c.activeChannels {
                startState, ok := startStates[arbitrator.cfg.ChanPoint]
                if !ok {
                        stopAndLog()
                        return fmt.Errorf("arbitrator: %v has no start state",
                                arbitrator.cfg.ChanPoint)
                }

                if err := arbitrator.Start(startState); err != nil {
                        stopAndLog()
                        return err
                }
        }

        // Subscribe to a single stream of block epoch notifications that we
        // will dispatch to all active arbitrators.
        blockEpoch, err := c.cfg.Notifier.RegisterBlockEpochNtfn(nil)
        if err != nil {
                return err
        }

        // Start our goroutine which will dispatch blocks to each arbitrator.
        c.wg.Add(1)
        go func() {
                defer c.wg.Done()
                c.dispatchBlocks(blockEpoch)
        }()

        // TODO(roasbeef): eventually move all breach watching here

        return nil
}

// blockRecipient contains the information we need to dispatch a block to a
// channel arbitrator.
type blockRecipient struct {
        // chanPoint is the funding outpoint of the channel.
        chanPoint wire.OutPoint

        // blocks is the channel that new block heights are sent into. This
        // channel should be sufficiently buffered as to not block the sender.
        blocks chan<- int32

        // quit is closed if the receiving entity is shutting down.
        quit chan struct{}
}

// dispatchBlocks consumes a block epoch notification stream and dispatches
// blocks to each of the chain arb's active channel arbitrators. This function
// must be run in a goroutine.
func (c *ChainArbitrator) dispatchBlocks(
        blockEpoch *chainntnfs.BlockEpochEvent) {

        // getRecipients is a helper function which acquires the chain arb
        // lock and returns a set of block recipients which can be used to
        // dispatch blocks.
        getRecipients := func() []blockRecipient {
                c.Lock()
                blocks := make([]blockRecipient, 0, len(c.activeChannels))
                for _, channel := range c.activeChannels {
                        blocks = append(blocks, blockRecipient{
                                chanPoint: channel.cfg.ChanPoint,
                                blocks:    channel.blocks,
                                quit:      channel.quit,
                        })
                }
                c.Unlock()

                return blocks
        }

        // On exit, cancel our blocks subscription and close each block channel
        // so that the arbitrators know they will no longer be receiving blocks.
        defer func() {
                blockEpoch.Cancel()

                recipients := getRecipients()
                for _, recipient := range recipients {
                        close(recipient.blocks)
                }
        }()

        // Consume block epochs until we receive the instruction to shutdown.
        for {
                select {
                // Consume block epochs, exiting if our subscription is
                // terminated.
                case block, ok := <-blockEpoch.Epochs:
                        if !ok {
                                log.Trace("dispatchBlocks block epoch " +
                                        "cancelled")
                                return
                        }

                        // Get the set of currently active channels block
                        // subscription channels and dispatch the block to
                        // each.
                        for _, recipient := range getRecipients() {
                                select {
                                // Deliver the block to the arbitrator.
                                case recipient.blocks <- block.Height:

                                // If the recipient is shutting down, exit
                                // without delivering the block. This may be
                                // the case when two blocks are mined in quick
                                // succession, and the arbitrator resolves
                                // after the first block, and does not need to
                                // consume the second block.
                                case <-recipient.quit:
                                        log.Debugf("channel: %v exit without "+
                                                "receiving block: %v",
                                                recipient.chanPoint,
                                                block.Height)

                                // If the chain arb is shutting down, we don't
                                // need to deliver any more blocks (everything
                                // will be shutting down).
                                case <-c.quit:
                                        return
                                }
                        }

                // Exit if the chain arbitrator is shutting down.
                case <-c.quit:
                        return
                }
        }
}

// republishClosingTxs will load any stored cooperative or unilateral closing
// transactions and republish them. This helps ensure propagation of the
// transactions in the event that prior publications failed.
func (c *ChainArbitrator) republishClosingTxs(
        channel *channeldb.OpenChannel) error {

        // If the channel has had its unilateral close broadcasted already,
        // republish it in case it didn't propagate.
        if channel.HasChanStatus(channeldb.ChanStatusCommitBroadcasted) {
                err := c.rebroadcast(
                        channel, channeldb.ChanStatusCommitBroadcasted,
                )
                if err != nil {
                        return err
                }
        }

        // If the channel has had its cooperative close broadcasted
        // already, republish it in case it didn't propagate.
        if channel.HasChanStatus(channeldb.ChanStatusCoopBroadcasted) {
                err := c.rebroadcast(
                        channel, channeldb.ChanStatusCoopBroadcasted,
                )
                if err != nil {
                        return err
                }
        }

        return nil
}

// rebroadcast is a helper method which will republish the unilateral or
// cooperative close transaction or a channel in a particular state.
//
// NOTE: There is no risk to calling this method if the channel isn't in either
// CommitmentBroadcasted or CoopBroadcasted, but the logs will be misleading.
func (c *ChainArbitrator) rebroadcast(channel *channeldb.OpenChannel,
        state channeldb.ChannelStatus) error {

        chanPoint := channel.FundingOutpoint

        var (
                closeTx *wire.MsgTx
                kind    string
                err     error
        )
        switch state {
        case channeldb.ChanStatusCommitBroadcasted:
                kind = "force"
                closeTx, err = channel.BroadcastedCommitment()

        case channeldb.ChanStatusCoopBroadcasted:
                kind = "coop"
                closeTx, err = channel.BroadcastedCooperative()

        default:
                return fmt.Errorf("unknown closing state: %v", state)
        }

        switch {
        // This can happen for channels that had their closing tx published
        // before we started storing it to disk.
        case err == channeldb.ErrNoCloseTx:
                log.Warnf("Channel %v is in state %v, but no %s closing tx "+
                        "to re-publish...", chanPoint, state, kind)
                return nil

        case err != nil:
                return err
        }

        log.Infof("Re-publishing %s close tx(%v) for channel %v",
                kind, closeTx.TxHash(), chanPoint)

        label := labels.MakeLabel(
                labels.LabelTypeChannelClose, &channel.ShortChannelID,
        )
        err = c.cfg.PublishTx(closeTx, label)
        if err != nil && err != lnwallet.ErrDoubleSpend {
                log.Warnf("Unable to broadcast %s close tx(%v): %v",
                        kind, closeTx.TxHash(), err)
        }

        return nil
}

// Stop signals the ChainArbitrator to trigger a graceful shutdown. Any active
// channel arbitrators will be signalled to exit, and this method will block
// until they've all exited.
func (c *ChainArbitrator) Stop() error {
        if !atomic.CompareAndSwapInt32(&c.stopped, 0, 1) {
                return nil
        }

        log.Info("ChainArbitrator shutting down...")
        defer log.Debug("ChainArbitrator shutdown complete")

        close(c.quit)

        var (
                activeWatchers = make(map[wire.OutPoint]*chainWatcher)
                activeChannels = make(map[wire.OutPoint]*ChannelArbitrator)
        )

        // Copy the current set of active watchers and arbitrators to shutdown.
        // We don't want to hold the lock when shutting down each watcher or
        // arbitrator individually, as they may need to acquire this mutex.
        c.Lock()
        for chanPoint, watcher := range c.activeWatchers {
                activeWatchers[chanPoint] = watcher
        }
        for chanPoint, arbitrator := range c.activeChannels {
                activeChannels[chanPoint] = arbitrator
        }
        c.Unlock()

        for chanPoint, watcher := range activeWatchers {
                log.Tracef("Attempting to stop ChainWatcher(%v)",
                        chanPoint)

                if err := watcher.Stop(); err != nil {
                        log.Errorf("unable to stop watcher for "+
                                "ChannelPoint(%v): %v", chanPoint, err)
                }
        }
        for chanPoint, arbitrator := range activeChannels {
                log.Tracef("Attempting to stop ChannelArbitrator(%v)",
                        chanPoint)

                if err := arbitrator.Stop(); err != nil {
                        log.Errorf("unable to stop arbitrator for "+
                                "ChannelPoint(%v): %v", chanPoint, err)
                }
        }

        c.wg.Wait()

        return nil
}

// ContractUpdate is a message packages the latest set of active HTLCs on a
// commitment, and also identifies which commitment received a new set of
// HTLCs.
type ContractUpdate struct {
        // HtlcKey identifies which commitment the HTLCs below are present on.
        HtlcKey HtlcSetKey

        // Htlcs are the of active HTLCs on the commitment identified by the
        // above HtlcKey.
        Htlcs []channeldb.HTLC
}

// ContractSignals is used by outside subsystems to notify a channel arbitrator
// of its ShortChannelID.
type ContractSignals struct {
        // ShortChanID is the up to date short channel ID for a contract. This
        // can change either if when the contract was added it didn't yet have
        // a stable identifier, or in the case of a reorg.
        ShortChanID lnwire.ShortChannelID
}

// UpdateContractSignals sends a set of active, up to date contract signals to
// the ChannelArbitrator which is has been assigned to the channel infield by
// the passed channel point.
func (c *ChainArbitrator) UpdateContractSignals(chanPoint wire.OutPoint,
        signals *ContractSignals) error {

        log.Infof("Attempting to update ContractSignals for ChannelPoint(%v)",
                chanPoint)

        c.Lock()
        arbitrator, ok := c.activeChannels[chanPoint]
        c.Unlock()
        if !ok {
                return fmt.Errorf("unable to find arbitrator")
        }

        arbitrator.UpdateContractSignals(signals)

        return nil
}

// NotifyContractUpdate lets a channel arbitrator know that a new
// ContractUpdate is available. This calls the ChannelArbitrator's internal
// method NotifyContractUpdate which waits for a response on a done chan before
// returning. This method will return an error if the ChannelArbitrator is not
// in the activeChannels map. However, this only happens if the arbitrator is
// resolved and the related link would already be shut down.
func (c *ChainArbitrator) NotifyContractUpdate(chanPoint wire.OutPoint,
        update *ContractUpdate) error {

        c.Lock()
        arbitrator, ok := c.activeChannels[chanPoint]
        c.Unlock()
        if !ok {
                return fmt.Errorf("can't find arbitrator for %v", chanPoint)
        }

        arbitrator.notifyContractUpdate(update)
        return nil
}

// GetChannelArbitrator safely returns the channel arbitrator for a given
// channel outpoint.
func (c *ChainArbitrator) GetChannelArbitrator(chanPoint wire.OutPoint) (
        *ChannelArbitrator, error) {

        c.Lock()
        arbitrator, ok := c.activeChannels[chanPoint]
        c.Unlock()
        if !ok {
                return nil, fmt.Errorf("unable to find arbitrator")
        }

        return arbitrator, nil
}

// forceCloseReq is a request sent from an outside sub-system to the arbitrator
// that watches a particular channel to broadcast the commitment transaction,
// and enter the resolution phase of the channel.
type forceCloseReq struct {
        // errResp is a channel that will be sent upon either in the case of
        // force close success (nil error), or in the case on an error.
        //
        // NOTE; This channel MUST be buffered.
        errResp chan error

        // closeTx is a channel that carries the transaction which ultimately
        // closed out the channel.
        closeTx chan *wire.MsgTx
}

// ForceCloseContract attempts to force close the channel infield by the passed
// channel point. A force close will immediately terminate the contract,
// causing it to enter the resolution phase. If the force close was successful,
// then the force close transaction itself will be returned.
//
// TODO(roasbeef): just return the summary itself?
func (c *ChainArbitrator) ForceCloseContract(chanPoint wire.OutPoint) (*wire.MsgTx, error) {
        c.Lock()
        arbitrator, ok := c.activeChannels[chanPoint]
        c.Unlock()
        if !ok {
                return nil, fmt.Errorf("unable to find arbitrator")
        }

        log.Infof("Attempting to force close ChannelPoint(%v)", chanPoint)

        // Before closing, we'll attempt to send a disable update for the
        // channel. We do so before closing the channel as otherwise the current
        // edge policy won't be retrievable from the graph.
        if err := c.cfg.DisableChannel(chanPoint); err != nil {
                log.Warnf("Unable to disable channel %v on "+
                        "close: %v", chanPoint, err)
        }

        errChan := make(chan error, 1)
        respChan := make(chan *wire.MsgTx, 1)

        // With the channel found, and the request crafted, we'll send over a
        // force close request to the arbitrator that watches this channel.
        select {
        case arbitrator.forceCloseReqs <- &forceCloseReq{
                errResp: errChan,
                closeTx: respChan,
        }:
        case <-c.quit:
                return nil, ErrChainArbExiting
        }

        // We'll await two responses: the error response, and the transaction
        // that closed out the channel.
        select {
        case err := <-errChan:
                if err != nil {
                        return nil, err
                }
        case <-c.quit:
                return nil, ErrChainArbExiting
        }

        var closeTx *wire.MsgTx
        select {
        case closeTx = <-respChan:
        case <-c.quit:
                return nil, ErrChainArbExiting
        }

        return closeTx, nil
}

// WatchNewChannel sends the ChainArbitrator a message to create a
// ChannelArbitrator tasked with watching over a new channel. Once a new
// channel has finished its final funding flow, it should be registered with
// the ChainArbitrator so we can properly react to any on-chain events.
func (c *ChainArbitrator) WatchNewChannel(newChan *channeldb.OpenChannel) error {
        c.Lock()
        defer c.Unlock()

        chanPoint := newChan.FundingOutpoint

        log.Infof("Creating new ChannelArbitrator for ChannelPoint(%v)",
                chanPoint)

        // If we're already watching this channel, then we'll ignore this
        // request.
        if _, ok := c.activeChannels[chanPoint]; ok {
                return nil
        }

        // First, also create an active chainWatcher for this channel to ensure
        // that we detect any relevant on chain events.
        chainWatcher, err := newChainWatcher(
                chainWatcherConfig{
                        chanState: newChan,
                        notifier:  c.cfg.Notifier,
                        signer:    c.cfg.Signer,
                        isOurAddr: c.cfg.IsOurAddress,
                        contractBreach: func(
                                retInfo *lnwallet.BreachRetribution) error {

                                return c.cfg.ContractBreach(
                                        chanPoint, retInfo,
                                )
                        },
                        extractStateNumHint: lnwallet.GetStateNumHint,
                        auxLeafStore:        c.cfg.AuxLeafStore,
                        auxResolver:         c.cfg.AuxResolver,
                },
        )
        if err != nil {
                return err
        }

        c.activeWatchers[chanPoint] = chainWatcher

        // We'll also create a new channel arbitrator instance using this new
        // channel, and our internal state.
        channelArb, err := newActiveChannelArbitrator(
                newChan, c, chainWatcher.SubscribeChannelEvents(),
        )
        if err != nil {
                return err
        }

        // With the arbitrator created, we'll add it to our set of active
        // arbitrators, then launch it.
        c.activeChannels[chanPoint] = channelArb

        if err := channelArb.Start(nil); err != nil {
                return err
        }

        return chainWatcher.Start()
}

// SubscribeChannelEvents returns a new active subscription for the set of
// possible on-chain events for a particular channel. The struct can be used by
// callers to be notified whenever an event that changes the state of the
// channel on-chain occurs.
func (c *ChainArbitrator) SubscribeChannelEvents(
        chanPoint wire.OutPoint) (*ChainEventSubscription, error) {

        // First, we'll attempt to look up the active watcher for this channel.
        // If we can't find it, then we'll return an error back to the caller.
        c.Lock()
        watcher, ok := c.activeWatchers[chanPoint]
        c.Unlock()

        if !ok {
                return nil, fmt.Errorf("unable to find watcher for: %v",
                        chanPoint)
        }

        // With the watcher located, we'll request for it to create a new chain
        // event subscription client.
        return watcher.SubscribeChannelEvents(), nil
}

// FindOutgoingHTLCDeadline returns the deadline in absolute block height for
// the specified outgoing HTLC. For an outgoing HTLC, its deadline is defined
// by the timeout height of its corresponding incoming HTLC - this is the
// expiry height the that remote peer can spend his/her outgoing HTLC via the
// timeout path.
func (c *ChainArbitrator) FindOutgoingHTLCDeadline(scid lnwire.ShortChannelID,
        outgoingHTLC channeldb.HTLC) fn.Option[int32] {

        // Find the outgoing HTLC's corresponding incoming HTLC in the circuit
        // map.
        rHash := outgoingHTLC.RHash
        circuit := models.CircuitKey{
                ChanID: scid,
                HtlcID: outgoingHTLC.HtlcIndex,
        }
        incomingCircuit := c.cfg.QueryIncomingCircuit(circuit)

        // If there's no incoming circuit found, we will use the default
        // deadline.
        if incomingCircuit == nil {
                log.Warnf("ChannelArbitrator(%v): incoming circuit key not "+
                        "found for rHash=%x, using default deadline instead",
                        scid, rHash)

                return fn.None[int32]()
        }

        // If this is a locally initiated HTLC, it means we are the first hop.
        // In this case, we can relax the deadline.
        if incomingCircuit.ChanID.IsDefault() {
                log.Infof("ChannelArbitrator(%v): using default deadline for "+
                        "locally initiated HTLC for rHash=%x", scid, rHash)

                return fn.None[int32]()
        }

        log.Debugf("Found incoming circuit %v for rHash=%x using outgoing "+
                "circuit %v", incomingCircuit, rHash, circuit)

        c.Lock()
        defer c.Unlock()

        // Iterate over all active channels to find the incoming HTLC specified
        // by its circuit key.
        for cp, channelArb := range c.activeChannels {
                // Skip if the SCID doesn't match.
                if channelArb.cfg.ShortChanID != incomingCircuit.ChanID {
                        continue
                }

                // Make sure the channel arbitrator has the latest view of its
                // active HTLCs.
                channelArb.updateActiveHTLCs()

                // Iterate all the known HTLCs to find the targeted incoming
                // HTLC.
                for _, htlcs := range channelArb.activeHTLCs {
                        for _, htlc := range htlcs.incomingHTLCs {
                                // Skip if the index doesn't match.
                                if htlc.HtlcIndex != incomingCircuit.HtlcID {
                                        continue
                                }

                                log.Debugf("ChannelArbitrator(%v): found "+
                                        "incoming HTLC in channel=%v using "+
                                        "rHash=%x, refundTimeout=%v", scid,
                                        cp, rHash, htlc.RefundTimeout)

                                return fn.Some(int32(htlc.RefundTimeout))
                        }
                }
        }

        // If there's no incoming HTLC found, yet we have the incoming circuit,
        // something is wrong - in this case, we return the none deadline.
        log.Errorf("ChannelArbitrator(%v): incoming HTLC not found for "+
                "rHash=%x, using default deadline instead", scid, rHash)

        return fn.None[int32]()
}

// TODO(roasbeef): arbitration reports
//  * types: contested, waiting for success conf, etc

lightningnetwork / lnd / 12313002221

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