lnd.xprv/contractcourt/chain_arbitrator.go

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package contractcourt
import (
"errors"
"fmt"
"sync"
"sync/atomic"
"github.com/btcsuite/btcd/chaincfg/chainhash"
"github.com/btcsuite/btcd/wire"
"github.com/btcsuite/btcutil"
"github.com/lightningnetwork/lnd/chainntnfs"
"github.com/lightningnetwork/lnd/channeldb"
"github.com/lightningnetwork/lnd/lnwallet"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/lightningnetwork/lnd/sweep"
)
// 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 cancelled
// 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
// BroadcastDelta is the delta that we'll use to decide when to
// broadcast our commitment transaction. 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 the
// just the HTLC timeout, as we want to ensure that the commitment
// transaction is already confirmed, by the time the HTLC expires.
BroadcastDelta 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) 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 attempt ted 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 breachArbiter about a contract breach. It should
// only return a non-nil error when the breachArbiter has preserved the
// necessary breach info for this channel point, and it is safe to mark
// the channel as pending close in the database.
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
2018-04-18 05:02:04 +03:00
// IncubateOutput 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, *lnwallet.CommitOutputResolution,
*lnwallet.OutgoingHtlcResolution,
*lnwallet.IncomingHtlcResolution, uint32) 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
// 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 lnwallet.Signer
// FeeEstimator will be used to return fee estimates.
FeeEstimator lnwallet.FeeEstimator
// 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 *sweep.UtxoSweeper
// SettleInvoice attempts to settle an existing invoice on-chain with
// the given payment hash. ErrInvoiceNotFound is returned if an invoice
// is not found.
SettleInvoice func(chainhash.Hash, lnwire.MilliSatoshi) error
}
// 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{}),
}
}
// 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) {
log.Tracef("Creating ChannelArbitrator for ChannelPoint(%v)",
channel.FundingOutpoint)
// We'll start by registering for a block epoch notifications so this
// channel can keep track of the current state of the main chain.
//
// TODO(roasbeef): fetch best height (or pass in) so can ensure block
// epoch delivers all the notifications to
//
// TODO(roasbeef): instead 1 block epoch that multi-plexes to the rest?
// * reduces the number of goroutines
blockEpoch, err := c.cfg.Notifier.RegisterBlockEpochNtfn(nil)
if err != nil {
return nil, err
}
chanPoint := channel.FundingOutpoint
// 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,
ShortChanID: channel.ShortChanID(),
BlockEpochs: blockEpoch,
ForceCloseChan: func() (*lnwallet.LocalForceCloseSummary, error) {
// With the channels fetched, attempt to locate
// the target channel according to its channel
// point.
channel, err := c.chanSource.FetchChannel(chanPoint)
if err != nil {
return nil, err
}
chanMachine, err := lnwallet.NewLightningChannel(
c.cfg.Signer, c.cfg.PreimageDB, channel, nil,
)
if err != nil {
return nil, err
}
if err := c.cfg.MarkLinkInactive(chanPoint); err != nil {
log.Errorf("unable to mark link inactive: %v", err)
}
return chanMachine.ForceClose()
},
MarkCommitmentBroadcasted: channel.MarkCommitmentBroadcasted,
MarkChannelClosed: channel.CloseChannel,
IsPendingClose: false,
ChainArbitratorConfig: c.cfg,
ChainEvents: chanEvents,
}
// 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.DB, arbCfg, c.cfg.ChainHash, chanPoint,
)
if err != nil {
blockEpoch.Cancel()
return nil, err
}
arbCfg.MarkChannelResolved = func() error {
return c.resolveContract(chanPoint, chanLog)
}
return NewChannelArbitrator(
arbCfg, channel.LocalCommitment.Htlcs, chanLog,
), nil
}
// 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,
arbLog ArbitratorLog) 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.MarkChanFullyClosed(&chanPoint)
if err != nil {
log.Errorf("ChainArbitrator: unable to mark ChannelPoint(%v) "+
"fully closed: %v", chanPoint, err)
return err
}
if arbLog != nil {
// 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 err := arbLog.WipeHistory(); err != nil {
return err
}
}
c.Lock()
delete(c.activeChannels, chanPoint)
chainWatcher, ok := c.activeWatchers[chanPoint]
if ok {
chainWatcher.Stop()
}
delete(c.activeWatchers, chanPoint)
c.Unlock()
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.Tracef("Starting ChainArbitrator")
// 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.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.
chainWatcher, err := newChainWatcher(
chainWatcherConfig{
chanState: channel,
notifier: c.cfg.Notifier,
pCache: c.cfg.PreimageDB,
signer: c.cfg.Signer,
isOurAddr: c.cfg.IsOurAddress,
contractBreach: func(retInfo *lnwallet.BreachRetribution) error {
return c.cfg.ContractBreach(chanPoint, retInfo)
},
},
)
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
}
// 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.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.
for _, closeChanInfo := range closingChannels {
blockEpoch, err := c.cfg.Notifier.RegisterBlockEpochNtfn(nil)
if err != nil {
return err
}
// 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,
BlockEpochs: blockEpoch,
ChainArbitratorConfig: c.cfg,
ChainEvents: &ChainEventSubscription{},
IsPendingClose: true,
ClosingHeight: closeChanInfo.CloseHeight,
CloseType: closeChanInfo.CloseType,
}
chanLog, err := newBoltArbitratorLog(
c.chanSource.DB, arbCfg, c.cfg.ChainHash, chanPoint,
)
if err != nil {
blockEpoch.Cancel()
return err
}
arbCfg.MarkChannelResolved = func() error {
return c.resolveContract(chanPoint, chanLog)
}
// We can also leave off the set of HTLC's here as since the
// channel is already in the process of being full resolved, no
// new HTLC's we be added.
c.activeChannels[chanPoint] = NewChannelArbitrator(
arbCfg, nil, 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)
}()
// 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 {
c.Stop()
return err
}
}
// Finally, we'll launch all the goroutines for each arbitrator so they
// can carry out their duties.
for _, arbitrator := range c.activeChannels {
if err := arbitrator.Start(); err != nil {
c.Stop()
return err
}
}
// TODO(roasbeef): eventually move all breach watching here
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.Infof("Stopping ChainArbitrator")
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
}
// ContractSignals wraps the two signals that affect the state of a channel
// being watched by an arbitrator. The two signals we care about are: the
// channel has a new set of HTLC's, and the remote party has just broadcast
// their version of the commitment transaction.
type ContractSignals struct {
// HtlcUpdates is a channel that once we new commitment updates takes
// place, the later set of HTLC's on the commitment transaction should
// be sent over.
HtlcUpdates chan []channeldb.HTLC
// 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
}
// 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)
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
}
// We'll attempt to disable the channel in the background to
// avoid blocking due to sending the update message to all
// active peers.
go func() {
if err := c.cfg.DisableChannel(chanPoint); err != nil {
log.Errorf("Unable to disable channel %v on "+
"close: %v", chanPoint, err)
}
}()
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()
log.Infof("Creating new ChannelArbitrator for ChannelPoint(%v)",
newChan.FundingOutpoint)
// If we're already watching this channel, then we'll ignore this
// request.
chanPoint := newChan.FundingOutpoint
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,
pCache: c.cfg.PreimageDB,
signer: c.cfg.Signer,
isOurAddr: c.cfg.IsOurAddress,
contractBreach: func(retInfo *lnwallet.BreachRetribution) error {
return c.cfg.ContractBreach(chanPoint, retInfo)
},
},
)
if err != nil {
return err
}
c.activeWatchers[newChan.FundingOutpoint] = 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(); 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. If syncDispatch is true, then the sender of the
// notification will wait until an error is sent over the ProcessACK before
// modifying any database state. This allows callers to request a reliable hand
// off.
//
// TODO(roasbeef): can be used later to provide RPC hook for all channel
// lifetimes
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.
watcher, ok := c.activeWatchers[chanPoint]
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
}
// TODO(roasbeef): arbitration reports
// * types: contested, waiting for success conf, etc