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1938 lines
62 KiB
1938 lines
62 KiB
package contractcourt |
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|
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import ( |
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"bytes" |
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"errors" |
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"sync" |
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"sync/atomic" |
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|
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"github.com/btcsuite/btcd/wire" |
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"github.com/btcsuite/btcutil" |
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"github.com/davecgh/go-spew/spew" |
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"github.com/lightningnetwork/lnd/chainntnfs" |
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"github.com/lightningnetwork/lnd/channeldb" |
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"github.com/lightningnetwork/lnd/lntypes" |
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"github.com/lightningnetwork/lnd/lnwallet" |
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"github.com/lightningnetwork/lnd/lnwire" |
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) |
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var ( |
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// errAlreadyForceClosed is an error returned when we attempt to force |
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// close a channel that's already in the process of doing so. |
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errAlreadyForceClosed = errors.New("channel is already in the " + |
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"process of being force closed") |
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) |
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|
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// WitnessSubscription represents an intent to be notified once new witnesses |
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// are discovered by various active contract resolvers. A contract resolver may |
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// use this to be notified of when it can satisfy an incoming contract after we |
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// discover the witness for an outgoing contract. |
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type WitnessSubscription struct { |
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// WitnessUpdates is a channel that newly discovered witnesses will be |
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// sent over. |
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// |
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// TODO(roasbeef): couple with WitnessType? |
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WitnessUpdates <-chan lntypes.Preimage |
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|
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// CancelSubscription is a function closure that should be used by a |
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// client to cancel the subscription once they are no longer interested |
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// in receiving new updates. |
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CancelSubscription func() |
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} |
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// WitnessBeacon is a global beacon of witnesses. Contract resolvers will use |
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// this interface to lookup witnesses (preimages typically) of contracts |
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// they're trying to resolve, add new preimages they resolve, and finally |
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// receive new updates each new time a preimage is discovered. |
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// |
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// TODO(roasbeef): need to delete the pre-images once we've used them |
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// and have been sufficiently confirmed? |
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type WitnessBeacon interface { |
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// SubscribeUpdates returns a channel that will be sent upon *each* time |
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// a new preimage is discovered. |
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SubscribeUpdates() *WitnessSubscription |
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|
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// LookupPreImage attempts to lookup a preimage in the global cache. |
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// True is returned for the second argument if the preimage is found. |
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LookupPreimage(payhash lntypes.Hash) (lntypes.Preimage, bool) |
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// AddPreimages adds a batch of newly discovered preimages to the global |
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// cache, and also signals any subscribers of the newly discovered |
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// witness. |
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AddPreimages(preimages ...lntypes.Preimage) error |
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} |
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// ChannelArbitratorConfig contains all the functionality that the |
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// ChannelArbitrator needs in order to properly arbitrate any contract dispute |
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// on chain. |
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type ChannelArbitratorConfig struct { |
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// ChanPoint is the channel point that uniquely identifies this |
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// channel. |
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ChanPoint wire.OutPoint |
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// ShortChanID describes the exact location of the channel within the |
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// chain. We'll use this to address any messages that we need to send |
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// to the switch during contract resolution. |
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ShortChanID lnwire.ShortChannelID |
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|
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// BlockEpochs is an active block epoch event stream backed by an |
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// active ChainNotifier instance. We will use new block notifications |
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// sent over this channel to decide when we should go on chain to |
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// reclaim/redeem the funds in an HTLC sent to/from us. |
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BlockEpochs *chainntnfs.BlockEpochEvent |
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|
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// ChainEvents is an active subscription to the chain watcher for this |
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// channel to be notified of any on-chain activity related to this |
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// channel. |
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ChainEvents *ChainEventSubscription |
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|
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// ForceCloseChan should force close the contract that this attendant |
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// is watching over. We'll use this when we decide that we need to go |
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// to chain. It should in addition tell the switch to remove the |
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// corresponding link, such that we won't accept any new updates. The |
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// returned summary contains all items needed to eventually resolve all |
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// outputs on chain. |
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ForceCloseChan func() (*lnwallet.LocalForceCloseSummary, error) |
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// MarkCommitmentBroadcasted should mark the channel as the commitment |
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// being broadcast, and we are waiting for the commitment to confirm. |
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MarkCommitmentBroadcasted func() error |
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|
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// MarkChannelClosed marks the channel closed in the database, with the |
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// passed close summary. After this method successfully returns we can |
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// no longer expect to receive chain events for this channel, and must |
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// be able to recover from a failure without getting the close event |
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// again. |
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MarkChannelClosed func(*channeldb.ChannelCloseSummary) error |
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// IsPendingClose is a boolean indicating whether the channel is marked |
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// as pending close in the database. |
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IsPendingClose bool |
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// ClosingHeight is the height at which the channel was closed. Note |
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// that this value is only valid if IsPendingClose is true. |
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ClosingHeight uint32 |
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// CloseType is the type of the close event in case IsPendingClose is |
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// true. Otherwise this value is unset. |
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CloseType channeldb.ClosureType |
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// MarkChannelResolved is a function closure that serves to mark a |
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// channel as "fully resolved". A channel itself can be considered |
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// fully resolved once all active contracts have individually been |
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// fully resolved. |
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// |
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// TODO(roasbeef): need RPC's to combine for pendingchannels RPC |
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MarkChannelResolved func() error |
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ChainArbitratorConfig |
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} |
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// ContractReport provides a summary of a commitment tx output. |
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type ContractReport struct { |
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// Outpoint is the final output that will be swept back to the wallet. |
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Outpoint wire.OutPoint |
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// Incoming indicates whether the htlc was incoming to this channel. |
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Incoming bool |
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// Amount is the final value that will be swept in back to the wallet. |
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Amount btcutil.Amount |
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// MaturityHeight is the absolute block height that this output will |
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// mature at. |
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MaturityHeight uint32 |
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// Stage indicates whether the htlc is in the CLTV-timeout stage (1) or |
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// the CSV-delay stage (2). A stage 1 htlc's maturity height will be set |
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// to its expiry height, while a stage 2 htlc's maturity height will be |
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// set to its confirmation height plus the maturity requirement. |
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Stage uint32 |
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// LimboBalance is the total number of frozen coins within this |
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// contract. |
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LimboBalance btcutil.Amount |
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// RecoveredBalance is the total value that has been successfully swept |
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// back to the user's wallet. |
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RecoveredBalance btcutil.Amount |
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} |
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// htlcSet represents the set of active HTLCs on a given commitment |
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// transaction. |
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type htlcSet struct { |
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// incomingHTLCs is a map of all incoming HTLCs on our commitment |
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// transaction. We may potentially go onchain to claim the funds sent |
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// to us within this set. |
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incomingHTLCs map[uint64]channeldb.HTLC |
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|
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// outgoingHTLCs is a map of all outgoing HTLCs on our commitment |
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// transaction. We may potentially go onchain to reclaim the funds that |
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// are currently in limbo. |
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outgoingHTLCs map[uint64]channeldb.HTLC |
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} |
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// newHtlcSet constructs a new HTLC set from a slice of HTLC's. |
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func newHtlcSet(htlcs []channeldb.HTLC) htlcSet { |
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outHTLCs := make(map[uint64]channeldb.HTLC) |
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inHTLCs := make(map[uint64]channeldb.HTLC) |
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for _, htlc := range htlcs { |
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if htlc.Incoming { |
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inHTLCs[htlc.HtlcIndex] = htlc |
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continue |
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} |
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outHTLCs[htlc.HtlcIndex] = htlc |
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} |
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return htlcSet{ |
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incomingHTLCs: inHTLCs, |
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outgoingHTLCs: outHTLCs, |
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} |
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} |
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// ChannelArbitrator is the on-chain arbitrator for a particular channel. The |
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// struct will keep in sync with the current set of HTLCs on the commitment |
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// transaction. The job of the attendant is to go on-chain to either settle or |
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// cancel an HTLC as necessary iff: an HTLC times out, or we known the |
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// pre-image to an HTLC, but it wasn't settled by the link off-chain. The |
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// ChannelArbitrator will factor in an expected confirmation delta when |
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// broadcasting to ensure that we avoid any possibility of race conditions, and |
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// sweep the output(s) without contest. |
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type ChannelArbitrator struct { |
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started int32 // To be used atomically. |
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stopped int32 // To be used atomically. |
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|
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// log is a persistent log that the attendant will use to checkpoint |
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// its next action, and the state of any unresolved contracts. |
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log ArbitratorLog |
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// activeHTLCs is the set of active incoming/outgoing HTLC's on the |
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// commitment transaction. |
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activeHTLCs htlcSet |
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// cfg contains all the functionality that the ChannelArbitrator requires |
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// to do its duty. |
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cfg ChannelArbitratorConfig |
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// signalUpdates is a channel that any new live signals for the channel |
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// we're watching over will be sent. |
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signalUpdates chan *signalUpdateMsg |
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// htlcUpdates is a channel that is sent upon with new updates from the |
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// active channel. Each time a new commitment state is accepted, the |
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// set of HTLC's on the new state should be sent across this channel. |
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htlcUpdates <-chan []channeldb.HTLC |
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// activeResolvers is a slice of any active resolvers. This is used to |
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// be able to signal them for shutdown in the case that we shutdown. |
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activeResolvers []ContractResolver |
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|
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// activeResolversLock prevents simultaneous read and write to the |
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// resolvers slice. |
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activeResolversLock sync.RWMutex |
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// resolutionSignal is a channel that will be sent upon by contract |
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// resolvers once their contract has been fully resolved. With each |
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// send, we'll check to see if the contract is fully resolved. |
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resolutionSignal chan struct{} |
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// forceCloseReqs is a channel that requests to forcibly close the |
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// contract will be sent over. |
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forceCloseReqs chan *forceCloseReq |
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// state is the current state of the arbitrator. This state is examined |
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// upon start up to decide which actions to take. |
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state ArbitratorState |
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wg sync.WaitGroup |
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quit chan struct{} |
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} |
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// NewChannelArbitrator returns a new instance of a ChannelArbitrator backed by |
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// the passed config struct. |
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func NewChannelArbitrator(cfg ChannelArbitratorConfig, |
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startingHTLCs []channeldb.HTLC, log ArbitratorLog) *ChannelArbitrator { |
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return &ChannelArbitrator{ |
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log: log, |
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signalUpdates: make(chan *signalUpdateMsg), |
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htlcUpdates: make(<-chan []channeldb.HTLC), |
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resolutionSignal: make(chan struct{}), |
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forceCloseReqs: make(chan *forceCloseReq), |
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activeHTLCs: newHtlcSet(startingHTLCs), |
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cfg: cfg, |
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quit: make(chan struct{}), |
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} |
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} |
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// Start starts all the goroutines that the ChannelArbitrator needs to operate. |
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func (c *ChannelArbitrator) Start() error { |
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if !atomic.CompareAndSwapInt32(&c.started, 0, 1) { |
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return nil |
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} |
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var ( |
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err error |
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) |
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log.Debugf("Starting ChannelArbitrator(%v), htlc_set=%v", |
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c.cfg.ChanPoint, newLogClosure(func() string { |
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return spew.Sdump(c.activeHTLCs) |
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}), |
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) |
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// First, we'll read our last state from disk, so our internal state |
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// machine can act accordingly. |
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c.state, err = c.log.CurrentState() |
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if err != nil { |
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c.cfg.BlockEpochs.Cancel() |
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return err |
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} |
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log.Infof("ChannelArbitrator(%v): starting state=%v", c.cfg.ChanPoint, |
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c.state) |
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_, bestHeight, err := c.cfg.ChainIO.GetBestBlock() |
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if err != nil { |
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c.cfg.BlockEpochs.Cancel() |
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return err |
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} |
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|
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// If the channel has been marked pending close in the database, and we |
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// haven't transitioned the state machine to StateContractClosed (or a |
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// succeeding state), then a state transition most likely failed. We'll |
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// try to recover from this by manually advancing the state by setting |
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// the corresponding close trigger. |
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trigger := chainTrigger |
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triggerHeight := uint32(bestHeight) |
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if c.cfg.IsPendingClose { |
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switch c.state { |
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case StateDefault: |
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fallthrough |
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case StateBroadcastCommit: |
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fallthrough |
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case StateCommitmentBroadcasted: |
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switch c.cfg.CloseType { |
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|
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case channeldb.CooperativeClose: |
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trigger = coopCloseTrigger |
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case channeldb.LocalForceClose: |
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trigger = localCloseTrigger |
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case channeldb.RemoteForceClose: |
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trigger = remoteCloseTrigger |
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} |
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triggerHeight = c.cfg.ClosingHeight |
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log.Warnf("ChannelArbitrator(%v): detected stalled "+ |
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"state=%v for closed channel, using "+ |
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"trigger=%v", c.cfg.ChanPoint, c.state, trigger) |
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} |
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} |
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|
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// We'll now attempt to advance our state forward based on the current |
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// on-chain state, and our set of active contracts. |
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startingState := c.state |
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nextState, _, err := c.advanceState(triggerHeight, trigger) |
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if err != nil { |
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switch err { |
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|
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// If we detect that we tried to fetch resolutions, but failed, |
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// this channel was marked closed in the database before |
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// resolutions successfully written. In this case there is not |
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// much we can do, so we don't return the error. |
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case errScopeBucketNoExist: |
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fallthrough |
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case errNoResolutions: |
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log.Warnf("ChannelArbitrator(%v): detected closed"+ |
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"channel with no contract resolutions written.", |
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c.cfg.ChanPoint) |
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|
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default: |
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c.cfg.BlockEpochs.Cancel() |
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return err |
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} |
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} |
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|
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// If we start and ended at the awaiting full resolution state, then |
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// we'll relaunch our set of unresolved contracts. |
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if startingState == StateWaitingFullResolution && |
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nextState == StateWaitingFullResolution { |
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|
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if err := c.relaunchResolvers(); err != nil { |
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c.cfg.BlockEpochs.Cancel() |
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return err |
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} |
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} |
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// TODO(roasbeef): cancel if breached |
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c.wg.Add(1) |
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go c.channelAttendant(bestHeight) |
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return nil |
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} |
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// relauchResolvers relaunches the set of resolvers for unresolved contracts in |
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// order to provide them with information that's not immediately available upon |
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// starting the ChannelArbitrator. This information should ideally be stored in |
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// the database, so this only serves as a intermediate work-around to prevent a |
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// migration. |
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func (c *ChannelArbitrator) relaunchResolvers() error { |
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// We'll now query our log to see if there are any active |
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// unresolved contracts. If this is the case, then we'll |
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// relaunch all contract resolvers. |
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unresolvedContracts, err := c.log.FetchUnresolvedContracts() |
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if err != nil { |
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return err |
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} |
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|
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// Retrieve the commitment tx hash from the log. |
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contractResolutions, err := c.log.FetchContractResolutions() |
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if err != nil { |
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log.Errorf("unable to fetch contract resolutions: %v", |
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err) |
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return err |
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} |
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commitHash := contractResolutions.CommitHash |
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|
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// Reconstruct the htlc outpoints and data from the chain action log. |
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// The purpose of the constructed htlc map is to supplement to resolvers |
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// restored from database with extra data. Ideally this data is stored |
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// as part of the resolver in the log. This is a workaround to prevent a |
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// db migration. |
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htlcMap := make(map[wire.OutPoint]*channeldb.HTLC) |
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chainActions, err := c.log.FetchChainActions() |
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if err != nil { |
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log.Errorf("unable to fetch chain actions: %v", err) |
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return err |
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} |
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for _, htlcs := range chainActions { |
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for _, htlc := range htlcs { |
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outpoint := wire.OutPoint{ |
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Hash: commitHash, |
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Index: uint32(htlc.OutputIndex), |
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} |
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htlcMap[outpoint] = &htlc |
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} |
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} |
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log.Infof("ChannelArbitrator(%v): relaunching %v contract "+ |
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"resolvers", c.cfg.ChanPoint, len(unresolvedContracts)) |
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for _, resolver := range unresolvedContracts { |
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supplementResolver(resolver, htlcMap) |
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} |
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c.launchResolvers(unresolvedContracts) |
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return nil |
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} |
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// supplementResolver takes a resolver as it is restored from the log and fills |
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// in missing data from the htlcMap. |
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func supplementResolver(resolver ContractResolver, |
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htlcMap map[wire.OutPoint]*channeldb.HTLC) error { |
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|
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switch r := resolver.(type) { |
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|
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case *htlcSuccessResolver: |
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return supplementSuccessResolver(r, htlcMap) |
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|
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case *htlcIncomingContestResolver: |
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return supplementSuccessResolver( |
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&r.htlcSuccessResolver, htlcMap, |
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) |
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|
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case *htlcTimeoutResolver: |
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return supplementTimeoutResolver(r, htlcMap) |
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|
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case *htlcOutgoingContestResolver: |
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return supplementTimeoutResolver( |
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&r.htlcTimeoutResolver, htlcMap, |
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) |
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} |
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return nil |
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} |
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|
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// supplementSuccessResolver takes a htlcSuccessResolver as it is restored from |
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// the log and fills in missing data from the htlcMap. |
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func supplementSuccessResolver(r *htlcSuccessResolver, |
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htlcMap map[wire.OutPoint]*channeldb.HTLC) error { |
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|
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res := r.htlcResolution |
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htlcPoint := res.HtlcPoint() |
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htlc, ok := htlcMap[htlcPoint] |
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if !ok { |
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return errors.New( |
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"htlc for success resolver unavailable", |
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) |
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} |
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r.htlcAmt = htlc.Amt |
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return nil |
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} |
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|
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// supplementTimeoutResolver takes a htlcSuccessResolver as it is restored from |
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// the log and fills in missing data from the htlcMap. |
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func supplementTimeoutResolver(r *htlcTimeoutResolver, |
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htlcMap map[wire.OutPoint]*channeldb.HTLC) error { |
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|
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res := r.htlcResolution |
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htlcPoint := res.HtlcPoint() |
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htlc, ok := htlcMap[htlcPoint] |
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if !ok { |
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return errors.New( |
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"htlc for timeout resolver unavailable", |
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) |
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} |
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r.htlcAmt = htlc.Amt |
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return nil |
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} |
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|
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// Report returns htlc reports for the active resolvers. |
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func (c *ChannelArbitrator) Report() []*ContractReport { |
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c.activeResolversLock.RLock() |
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defer c.activeResolversLock.RUnlock() |
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|
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var reports []*ContractReport |
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for _, resolver := range c.activeResolvers { |
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r, ok := resolver.(reportingContractResolver) |
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if !ok { |
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continue |
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} |
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|
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if r.IsResolved() { |
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continue |
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} |
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|
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report := r.report() |
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if report == nil { |
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continue |
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} |
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|
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reports = append(reports, report) |
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} |
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|
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return reports |
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} |
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|
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// Stop signals the ChannelArbitrator for a graceful shutdown. |
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func (c *ChannelArbitrator) Stop() error { |
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if !atomic.CompareAndSwapInt32(&c.stopped, 0, 1) { |
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return nil |
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} |
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|
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log.Debugf("Stopping ChannelArbitrator(%v)", c.cfg.ChanPoint) |
|
|
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if c.cfg.ChainEvents.Cancel != nil { |
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go c.cfg.ChainEvents.Cancel() |
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} |
|
|
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c.activeResolversLock.RLock() |
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for _, activeResolver := range c.activeResolvers { |
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activeResolver.Stop() |
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} |
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c.activeResolversLock.RUnlock() |
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|
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close(c.quit) |
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c.wg.Wait() |
|
|
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return nil |
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} |
|
|
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// transitionTrigger is an enum that denotes exactly *why* a state transition |
|
// was initiated. This is useful as depending on the initial trigger, we may |
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// skip certain states as those actions are expected to have already taken |
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// place as a result of the external trigger. |
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type transitionTrigger uint8 |
|
|
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const ( |
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// chainTrigger is a transition trigger that has been attempted due to |
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// changing on-chain conditions such as a block which times out HTLC's |
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// being attached. |
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chainTrigger transitionTrigger = iota |
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|
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// userTrigger is a transition trigger driven by user action. Examples |
|
// of such a trigger include a user requesting a force closure of the |
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// channel. |
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userTrigger |
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|
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// remoteCloseTrigger is a transition trigger driven by the remote |
|
// peer's commitment being confirmed. |
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remoteCloseTrigger |
|
|
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// localCloseTrigger is a transition trigger driven by our commitment |
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// being confirmed. |
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localCloseTrigger |
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|
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// coopCloseTrigger is a transition trigger driven by a cooperative |
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// close transaction being confirmed. |
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coopCloseTrigger |
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) |
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|
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// String returns a human readable string describing the passed |
|
// transitionTrigger. |
|
func (t transitionTrigger) String() string { |
|
switch t { |
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case chainTrigger: |
|
return "chainTrigger" |
|
|
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case remoteCloseTrigger: |
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return "remoteCloseTrigger" |
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|
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case userTrigger: |
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return "userTrigger" |
|
|
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case localCloseTrigger: |
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return "localCloseTrigger" |
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|
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case coopCloseTrigger: |
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return "coopCloseTrigger" |
|
|
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default: |
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return "unknown trigger" |
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} |
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} |
|
|
|
// stateStep is a help method that examines our internal state, and attempts |
|
// the appropriate state transition if necessary. The next state we transition |
|
// to is returned, Additionally, if the next transition results in a commitment |
|
// broadcast, the commitment transaction itself is returned. |
|
func (c *ChannelArbitrator) stateStep(triggerHeight uint32, |
|
trigger transitionTrigger) (ArbitratorState, *wire.MsgTx, error) { |
|
|
|
var ( |
|
nextState ArbitratorState |
|
closeTx *wire.MsgTx |
|
) |
|
switch c.state { |
|
|
|
// If we're in the default state, then we'll check our set of actions |
|
// to see if while we were down, conditions have changed. |
|
case StateDefault: |
|
log.Debugf("ChannelArbitrator(%v): new block (height=%v) "+ |
|
"examining active HTLC's", c.cfg.ChanPoint, |
|
triggerHeight) |
|
|
|
// As a new block has been connected to the end of the main |
|
// chain, we'll check to see if we need to make any on-chain |
|
// claims on behalf of the channel contract that we're |
|
// arbitrating for. |
|
chainActions, err := c.checkChainActions(triggerHeight, trigger) |
|
if err != nil { |
|
return StateError, closeTx, err |
|
} |
|
|
|
// If there are no actions to be made, then we'll remain in the |
|
// default state. If this isn't a self initiated event (we're |
|
// checking due to a chain update), then we'll exit now. |
|
if len(chainActions) == 0 && trigger == chainTrigger { |
|
log.Tracef("ChannelArbitrator(%v): no actions for "+ |
|
"chain trigger, terminating", c.cfg.ChanPoint) |
|
|
|
return StateDefault, closeTx, nil |
|
} |
|
|
|
// Otherwise, we'll log that we checked the HTLC actions as the |
|
// commitment transaction has already been broadcast. |
|
log.Tracef("ChannelArbitrator(%v): logging chain_actions=%v", |
|
c.cfg.ChanPoint, |
|
newLogClosure(func() string { |
|
return spew.Sdump(chainActions) |
|
})) |
|
if err := c.log.LogChainActions(chainActions); err != nil { |
|
return StateError, closeTx, err |
|
} |
|
|
|
// Depending on the type of trigger, we'll either "tunnel" |
|
// through to a farther state, or just proceed linearly to the |
|
// next state. |
|
switch trigger { |
|
|
|
// If this is a chain trigger, then we'll go straight to the |
|
// next state, as we still need to broadcast the commitment |
|
// transaction. |
|
case chainTrigger: |
|
fallthrough |
|
case userTrigger: |
|
nextState = StateBroadcastCommit |
|
|
|
// If the trigger is a cooperative close being confirmed, then |
|
// we can go straight to StateFullyResolved, as there won't be |
|
// any contracts to resolve. |
|
case coopCloseTrigger: |
|
nextState = StateFullyResolved |
|
|
|
// Otherwise, if this state advance was triggered by a |
|
// commitment being confirmed on chain, then we'll jump |
|
// straight to the state where the contract has already been |
|
// closed, and we will inspect the set of unresolved contracts. |
|
case localCloseTrigger: |
|
log.Errorf("ChannelArbitrator(%v): unexpected local "+ |
|
"commitment confirmed while in StateDefault", |
|
c.cfg.ChanPoint) |
|
fallthrough |
|
case remoteCloseTrigger: |
|
nextState = StateContractClosed |
|
} |
|
|
|
// If we're in this state, then we've decided to broadcast the |
|
// commitment transaction. We enter this state either due to an outside |
|
// sub-system, or because an on-chain action has been triggered. |
|
case StateBroadcastCommit: |
|
// Under normal operation, we can only enter |
|
// StateBroadcastCommit via a user or chain trigger. On restart, |
|
// this state may be reexecuted after closing the channel, but |
|
// failing to commit to StateContractClosed or |
|
// StateFullyResolved. In that case, one of the three close |
|
// triggers will be presented, signifying that we should skip |
|
// rebroadcasting, and go straight to resolving the on-chain |
|
// contract or marking the channel resolved. |
|
switch trigger { |
|
case localCloseTrigger, remoteCloseTrigger: |
|
log.Infof("ChannelArbitrator(%v): detected %s "+ |
|
"close after closing channel, fast-forwarding "+ |
|
"to %s to resolve contract", |
|
c.cfg.ChanPoint, trigger, StateContractClosed) |
|
return StateContractClosed, closeTx, nil |
|
|
|
case coopCloseTrigger: |
|
log.Infof("ChannelArbitrator(%v): detected %s "+ |
|
"close after closing channel, fast-forwarding "+ |
|
"to %s to resolve contract", |
|
c.cfg.ChanPoint, trigger, StateFullyResolved) |
|
return StateFullyResolved, closeTx, nil |
|
} |
|
|
|
log.Infof("ChannelArbitrator(%v): force closing "+ |
|
"chan", c.cfg.ChanPoint) |
|
|
|
// Now that we have all the actions decided for the set of |
|
// HTLC's, we'll broadcast the commitment transaction, and |
|
// signal the link to exit. |
|
|
|
// We'll tell the switch that it should remove the link for |
|
// this channel, in addition to fetching the force close |
|
// summary needed to close this channel on chain. |
|
closeSummary, err := c.cfg.ForceCloseChan() |
|
if err != nil { |
|
log.Errorf("ChannelArbitrator(%v): unable to "+ |
|
"force close: %v", c.cfg.ChanPoint, err) |
|
return StateError, closeTx, err |
|
} |
|
closeTx = closeSummary.CloseTx |
|
|
|
// With the close transaction in hand, broadcast the |
|
// transaction to the network, thereby entering the post |
|
// channel resolution state. |
|
log.Infof("Broadcasting force close transaction, "+ |
|
"ChannelPoint(%v): %v", c.cfg.ChanPoint, |
|
newLogClosure(func() string { |
|
return spew.Sdump(closeTx) |
|
})) |
|
|
|
// At this point, we'll now broadcast the commitment |
|
// transaction itself. |
|
if err := c.cfg.PublishTx(closeTx); err != nil { |
|
log.Errorf("ChannelArbitrator(%v): unable to broadcast "+ |
|
"close tx: %v", c.cfg.ChanPoint, err) |
|
if err != lnwallet.ErrDoubleSpend { |
|
return StateError, closeTx, err |
|
} |
|
} |
|
|
|
if err := c.cfg.MarkCommitmentBroadcasted(); err != nil { |
|
log.Errorf("ChannelArbitrator(%v): unable to "+ |
|
"mark commitment broadcasted: %v", |
|
c.cfg.ChanPoint, err) |
|
} |
|
|
|
// We go to the StateCommitmentBroadcasted state, where we'll |
|
// be waiting for the commitment to be confirmed. |
|
nextState = StateCommitmentBroadcasted |
|
|
|
// In this state we have broadcasted our own commitment, and will need |
|
// to wait for a commitment (not necessarily the one we broadcasted!) |
|
// to be confirmed. |
|
case StateCommitmentBroadcasted: |
|
switch trigger { |
|
// We are waiting for a commitment to be confirmed, so any |
|
// other trigger will be ignored. |
|
case chainTrigger, userTrigger: |
|
log.Infof("ChannelArbitrator(%v): noop trigger %v", |
|
c.cfg.ChanPoint, trigger) |
|
nextState = StateCommitmentBroadcasted |
|
|
|
// If this state advance was triggered by any of the |
|
// commitments being confirmed, then we'll jump to the state |
|
// where the contract has been closed. |
|
case localCloseTrigger, remoteCloseTrigger: |
|
log.Infof("ChannelArbitrator(%v): trigger %v, "+ |
|
" going to StateContractClosed", |
|
c.cfg.ChanPoint, trigger) |
|
nextState = StateContractClosed |
|
|
|
case coopCloseTrigger: |
|
log.Infof("ChannelArbitrator(%v): trigger %v, "+ |
|
" going to StateFullyResolved", |
|
c.cfg.ChanPoint, trigger) |
|
nextState = StateFullyResolved |
|
} |
|
|
|
// If we're in this state, then the contract has been fully closed to |
|
// outside sub-systems, so we'll process the prior set of on-chain |
|
// contract actions and launch a set of resolvers. |
|
case StateContractClosed: |
|
// First, we'll fetch our chain actions, and both sets of |
|
// resolutions so we can process them. |
|
chainActions, err := c.log.FetchChainActions() |
|
if err != nil { |
|
log.Errorf("unable to fetch chain actions: %v", err) |
|
return StateError, closeTx, err |
|
} |
|
contractResolutions, err := c.log.FetchContractResolutions() |
|
if err != nil { |
|
log.Errorf("unable to fetch contract resolutions: %v", |
|
err) |
|
return StateError, closeTx, err |
|
} |
|
|
|
// If the resolution is empty, then we're done here. We don't |
|
// need to launch any resolvers, and can go straight to our |
|
// final state. |
|
if contractResolutions.IsEmpty() { |
|
log.Infof("ChannelArbitrator(%v): contract "+ |
|
"resolutions empty, marking channel as fully resolved!", |
|
c.cfg.ChanPoint) |
|
nextState = StateFullyResolved |
|
break |
|
} |
|
|
|
// If we've have broadcast the commitment transaction, we send |
|
// our commitment output for incubation, but only if it wasn't |
|
// trimmed. We'll need to wait for a CSV timeout before we can |
|
// reclaim the funds. |
|
commitRes := contractResolutions.CommitResolution |
|
if commitRes != nil && commitRes.MaturityDelay > 0 { |
|
log.Infof("ChannelArbitrator(%v): sending commit "+ |
|
"output for incubation", c.cfg.ChanPoint) |
|
|
|
err = c.cfg.IncubateOutputs( |
|
c.cfg.ChanPoint, commitRes, |
|
nil, nil, triggerHeight, |
|
) |
|
if err != nil { |
|
// TODO(roasbeef): check for AlreadyExists errors |
|
log.Errorf("unable to incubate commitment "+ |
|
"output: %v", err) |
|
return StateError, closeTx, err |
|
} |
|
} |
|
|
|
// Now that we know we'll need to act, we'll process the htlc |
|
// actions, wen create the structures we need to resolve all |
|
// outstanding contracts. |
|
htlcResolvers, pktsToSend, err := c.prepContractResolutions( |
|
chainActions, contractResolutions, triggerHeight, |
|
) |
|
if err != nil { |
|
log.Errorf("ChannelArbitrator(%v): unable to "+ |
|
"resolve contracts: %v", c.cfg.ChanPoint, err) |
|
return StateError, closeTx, err |
|
} |
|
|
|
log.Debugf("ChannelArbitrator(%v): sending resolution message=%v", |
|
c.cfg.ChanPoint, |
|
newLogClosure(func() string { |
|
return spew.Sdump(pktsToSend) |
|
})) |
|
|
|
// With the commitment broadcast, we'll then send over all |
|
// messages we can send immediately. |
|
err = c.cfg.DeliverResolutionMsg(pktsToSend...) |
|
if err != nil { |
|
// TODO(roasbeef): make sure packet sends are idempotent |
|
log.Errorf("unable to send pkts: %v", err) |
|
return StateError, closeTx, err |
|
} |
|
|
|
log.Debugf("ChannelArbitrator(%v): inserting %v contract "+ |
|
"resolvers", c.cfg.ChanPoint, len(htlcResolvers)) |
|
|
|
err = c.log.InsertUnresolvedContracts(htlcResolvers...) |
|
if err != nil { |
|
return StateError, closeTx, err |
|
} |
|
|
|
// Finally, we'll launch all the required contract resolvers. |
|
// Once they're all resolved, we're no longer needed. |
|
c.launchResolvers(htlcResolvers) |
|
|
|
nextState = StateWaitingFullResolution |
|
|
|
// This is our terminal state. We'll keep returning this state until |
|
// all contracts are fully resolved. |
|
case StateWaitingFullResolution: |
|
log.Infof("ChannelArbitrator(%v): still awaiting contract "+ |
|
"resolution", c.cfg.ChanPoint) |
|
|
|
numUnresolved, err := c.log.FetchUnresolvedContracts() |
|
if err != nil { |
|
return StateError, closeTx, err |
|
} |
|
|
|
// If we still have unresolved contracts, then we'll stay alive |
|
// to oversee their resolution. |
|
if len(numUnresolved) != 0 { |
|
nextState = StateWaitingFullResolution |
|
break |
|
} |
|
|
|
nextState = StateFullyResolved |
|
|
|
// If we start as fully resolved, then we'll end as fully resolved. |
|
case StateFullyResolved: |
|
// To ensure that the state of the contract in persistent |
|
// storage is properly reflected, we'll mark the contract as |
|
// fully resolved now. |
|
nextState = StateFullyResolved |
|
|
|
log.Infof("ChannelPoint(%v) has been fully resolved "+ |
|
"on-chain at height=%v", c.cfg.ChanPoint, triggerHeight) |
|
|
|
if err := c.cfg.MarkChannelResolved(); err != nil { |
|
log.Errorf("unable to mark channel resolved: %v", err) |
|
return StateError, closeTx, err |
|
} |
|
} |
|
|
|
log.Tracef("ChannelArbitrator(%v): next_state=%v", c.cfg.ChanPoint, |
|
nextState) |
|
|
|
return nextState, closeTx, nil |
|
} |
|
|
|
// launchResolvers updates the activeResolvers list and starts the resolvers. |
|
func (c *ChannelArbitrator) launchResolvers(resolvers []ContractResolver) { |
|
c.activeResolversLock.Lock() |
|
defer c.activeResolversLock.Unlock() |
|
|
|
c.activeResolvers = resolvers |
|
for _, contract := range resolvers { |
|
c.wg.Add(1) |
|
go c.resolveContract(contract) |
|
} |
|
} |
|
|
|
// advanceState is the main driver of our state machine. This method is an |
|
// iterative function which repeatedly attempts to advance the internal state |
|
// of the channel arbitrator. The state will be advanced until we reach a |
|
// redundant transition, meaning that the state transition is a noop. The final |
|
// param is a callback that allows the caller to execute an arbitrary action |
|
// after each state transition. |
|
func (c *ChannelArbitrator) advanceState(triggerHeight uint32, |
|
trigger transitionTrigger) (ArbitratorState, *wire.MsgTx, error) { |
|
|
|
var ( |
|
priorState ArbitratorState |
|
forceCloseTx *wire.MsgTx |
|
) |
|
|
|
// We'll continue to advance our state forward until the state we |
|
// transition to is that same state that we started at. |
|
for { |
|
priorState = c.state |
|
log.Tracef("ChannelArbitrator(%v): attempting state step with "+ |
|
"trigger=%v from state=%v", c.cfg.ChanPoint, trigger, |
|
priorState) |
|
|
|
nextState, closeTx, err := c.stateStep( |
|
triggerHeight, trigger, |
|
) |
|
if err != nil { |
|
log.Errorf("ChannelArbitrator(%v): unable to advance "+ |
|
"state: %v", c.cfg.ChanPoint, err) |
|
return priorState, nil, err |
|
} |
|
|
|
if forceCloseTx == nil && closeTx != nil { |
|
forceCloseTx = closeTx |
|
} |
|
|
|
// Our termination transition is a noop transition. If we get |
|
// our prior state back as the next state, then we'll |
|
// terminate. |
|
if nextState == priorState { |
|
log.Tracef("ChannelArbitrator(%v): terminating at "+ |
|
"state=%v", c.cfg.ChanPoint, nextState) |
|
return nextState, forceCloseTx, nil |
|
} |
|
|
|
// As the prior state was successfully executed, we can now |
|
// commit the next state. This ensures that we will re-execute |
|
// the prior state if anything fails. |
|
if err := c.log.CommitState(nextState); err != nil { |
|
log.Errorf("ChannelArbitrator(%v): unable to commit "+ |
|
"next state(%v): %v", c.cfg.ChanPoint, |
|
nextState, err) |
|
return priorState, nil, err |
|
} |
|
c.state = nextState |
|
} |
|
} |
|
|
|
// ChainAction is an enum that encompasses all possible on-chain actions |
|
// we'll take for a set of HTLC's. |
|
type ChainAction uint8 |
|
|
|
const ( |
|
// NoAction is the min chainAction type, indicating that no action |
|
// needs to be taken for a given HTLC. |
|
NoAction ChainAction = 0 |
|
|
|
// HtlcTimeoutAction indicates that the HTLC will timeout soon. As a |
|
// result, we should get ready to sweep it on chain after the timeout. |
|
HtlcTimeoutAction = 1 |
|
|
|
// HtlcClaimAction indicates that we should claim the HTLC on chain |
|
// before its timeout period. |
|
HtlcClaimAction = 2 |
|
|
|
// HtlcFailNowAction indicates that we should fail an outgoing HTLC |
|
// immediately by cancelling it backwards as it has no corresponding |
|
// output in our commitment transaction. |
|
HtlcFailNowAction = 3 |
|
|
|
// HtlcOutgoingWatchAction indicates that we can't yet timeout this |
|
// HTLC, but we had to go to chain on order to resolve an existing |
|
// HTLC. In this case, we'll either: time it out once it expires, or |
|
// will learn the pre-image if the remote party claims the output. In |
|
// this case, well add the pre-image to our global store. |
|
HtlcOutgoingWatchAction = 4 |
|
|
|
// HtlcIncomingWatchAction indicates that we don't yet have the |
|
// pre-image to claim incoming HTLC, but we had to go to chain in order |
|
// to resolve and existing HTLC. In this case, we'll either: let the |
|
// other party time it out, or eventually learn of the pre-image, in |
|
// which case we'll claim on chain. |
|
HtlcIncomingWatchAction = 5 |
|
) |
|
|
|
// String returns a human readable string describing a chain action. |
|
func (c ChainAction) String() string { |
|
switch c { |
|
case NoAction: |
|
return "NoAction" |
|
|
|
case HtlcTimeoutAction: |
|
return "HtlcTimeoutAction" |
|
|
|
case HtlcClaimAction: |
|
return "HtlcClaimAction" |
|
|
|
case HtlcFailNowAction: |
|
return "HtlcFailNowAction" |
|
|
|
case HtlcOutgoingWatchAction: |
|
return "HtlcOutgoingWatchAction" |
|
|
|
case HtlcIncomingWatchAction: |
|
return "HtlcIncomingWatchAction" |
|
|
|
default: |
|
return "<unknown action>" |
|
} |
|
} |
|
|
|
// ChainActionMap is a map of a chain action, to the set of HTLC's that need to |
|
// be acted upon for a given action type. The channel |
|
type ChainActionMap map[ChainAction][]channeldb.HTLC |
|
|
|
// shouldGoOnChain takes into account the absolute timeout of the HTLC, if the |
|
// confirmation delta that we need is close, and returns a bool indicating if |
|
// we should go on chain to claim. We do this rather than waiting up until the |
|
// last minute as we want to ensure that when we *need* (HTLC is timed out) to |
|
// sweep, the commitment is already confirmed. |
|
func (c *ChannelArbitrator) shouldGoOnChain(htlcExpiry, broadcastDelta, |
|
currentHeight uint32) bool { |
|
|
|
// We'll calculate the broadcast cut off for this HTLC. This is the |
|
// height that (based on our current fee estimation) we should |
|
// broadcast in order to ensure the commitment transaction is confirmed |
|
// before the HTLC fully expires. |
|
broadcastCutOff := htlcExpiry - broadcastDelta |
|
|
|
log.Tracef("ChannelArbitrator(%v): examining outgoing contract: "+ |
|
"expiry=%v, cutoff=%v, height=%v", c.cfg.ChanPoint, htlcExpiry, |
|
broadcastCutOff, currentHeight) |
|
|
|
// TODO(roasbeef): take into account default HTLC delta, don't need to |
|
// broadcast immediately |
|
// * can then batch with SINGLE | ANYONECANPAY |
|
|
|
// We should on-chain for this HTLC, iff we're within out broadcast |
|
// cutoff window. |
|
return currentHeight >= broadcastCutOff |
|
} |
|
|
|
// checkChainActions is called for each new block connected to the end of the |
|
// main chain. Given the new block height, this new method will examine all |
|
// active HTLC's, and determine if we need to go on-chain to claim any of them. |
|
// A map of action -> []htlc is returned, detailing what action (if any) should |
|
// be performed for each HTLC. For timed out HTLC's, once the commitment has |
|
// been sufficiently confirmed, the HTLC's should be canceled backwards. For |
|
// redeemed HTLC's, we should send the pre-image back to the incoming link. |
|
func (c *ChannelArbitrator) checkChainActions(height uint32, |
|
trigger transitionTrigger) (ChainActionMap, error) { |
|
|
|
// TODO(roasbeef): would need to lock channel? channel totem? |
|
// * race condition if adding and we broadcast, etc |
|
// * or would make each instance sync? |
|
|
|
log.Debugf("ChannelArbitrator(%v): checking chain actions at "+ |
|
"height=%v", c.cfg.ChanPoint, height) |
|
|
|
actionMap := make(ChainActionMap) |
|
|
|
// First, we'll make an initial pass over the set of incoming and |
|
// outgoing HTLC's to decide if we need to go on chain at all. |
|
haveChainActions := false |
|
for _, htlc := range c.activeHTLCs.outgoingHTLCs { |
|
// We'll need to go on-chain for an outgoing HTLC if it was |
|
// never resolved downstream, and it's "close" to timing out. |
|
toChain := c.shouldGoOnChain( |
|
htlc.RefundTimeout, c.cfg.OutgoingBroadcastDelta, |
|
height, |
|
) |
|
|
|
if toChain { |
|
log.Debugf("ChannelArbitrator(%v): go to chain for "+ |
|
"outgoing htlc %x: timeout=%v, "+ |
|
"blocks_until_expiry=%v, broadcast_delta=%v", |
|
c.cfg.ChanPoint, htlc.RHash[:], |
|
htlc.RefundTimeout, htlc.RefundTimeout-height, |
|
c.cfg.OutgoingBroadcastDelta, |
|
) |
|
} |
|
|
|
haveChainActions = haveChainActions || toChain |
|
} |
|
|
|
for _, htlc := range c.activeHTLCs.incomingHTLCs { |
|
// We'll need to go on-chain to pull an incoming HTLC iff we |
|
// know the pre-image and it's close to timing out. We need to |
|
// ensure that we claim the funds that our rightfully ours |
|
// on-chain. |
|
preimageAvailable, err := c.isPreimageAvailable(htlc.RHash) |
|
if err != nil { |
|
return nil, err |
|
} |
|
|
|
if !preimageAvailable { |
|
continue |
|
} |
|
|
|
toChain := c.shouldGoOnChain( |
|
htlc.RefundTimeout, c.cfg.IncomingBroadcastDelta, |
|
height, |
|
) |
|
|
|
if toChain { |
|
log.Debugf("ChannelArbitrator(%v): go to chain for "+ |
|
"incoming htlc %x: timeout=%v, "+ |
|
"blocks_until_expiry=%v, broadcast_delta=%v", |
|
c.cfg.ChanPoint, htlc.RHash[:], |
|
htlc.RefundTimeout, htlc.RefundTimeout-height, |
|
c.cfg.IncomingBroadcastDelta, |
|
) |
|
} |
|
|
|
haveChainActions = haveChainActions || toChain |
|
} |
|
|
|
// If we don't have any actions to make, then we'll return an empty |
|
// action map. We only do this if this was a chain trigger though, as |
|
// if we're going to broadcast the commitment (or the remote party) did |
|
// we're *forced* to act on each HTLC. |
|
if !haveChainActions && trigger == chainTrigger { |
|
log.Tracef("ChannelArbitrator(%v): no actions to take at "+ |
|
"height=%v", c.cfg.ChanPoint, height) |
|
return actionMap, nil |
|
} |
|
|
|
// Now that we know we'll need to go on-chain, we'll examine all of our |
|
// active outgoing HTLC's to see if we either need to: sweep them after |
|
// a timeout (then cancel backwards), cancel them backwards |
|
// immediately, or watch them as they're still active contracts. |
|
for _, htlc := range c.activeHTLCs.outgoingHTLCs { |
|
switch { |
|
// If the HTLC is dust, then we can cancel it backwards |
|
// immediately as there's no matching contract to arbitrate |
|
// on-chain. We know the HTLC is dust, if the OutputIndex |
|
// negative. |
|
case htlc.OutputIndex < 0: |
|
log.Tracef("ChannelArbitrator(%v): immediately "+ |
|
"failing dust htlc=%x", c.cfg.ChanPoint, |
|
htlc.RHash[:]) |
|
|
|
actionMap[HtlcFailNowAction] = append( |
|
actionMap[HtlcFailNowAction], htlc, |
|
) |
|
|
|
// If we don't need to immediately act on this HTLC, then we'll |
|
// mark it still "live". After we broadcast, we'll monitor it |
|
// until the HTLC times out to see if we can also redeem it |
|
// on-chain. |
|
case !c.shouldGoOnChain( |
|
htlc.RefundTimeout, c.cfg.OutgoingBroadcastDelta, |
|
height, |
|
): |
|
// TODO(roasbeef): also need to be able to query |
|
// circuit map to see if HTLC hasn't been fully |
|
// resolved |
|
// |
|
// * can't fail incoming until if outgoing not yet |
|
// failed |
|
|
|
log.Tracef("ChannelArbitrator(%v): watching chain to "+ |
|
"decide action for outgoing htlc=%x", |
|
c.cfg.ChanPoint, htlc.RHash[:]) |
|
|
|
actionMap[HtlcOutgoingWatchAction] = append( |
|
actionMap[HtlcOutgoingWatchAction], htlc, |
|
) |
|
|
|
// Otherwise, we'll update our actionMap to mark that we need |
|
// to sweep this HTLC on-chain |
|
default: |
|
log.Tracef("ChannelArbitrator(%v): going on-chain to "+ |
|
"timeout htlc=%x", c.cfg.ChanPoint, htlc.RHash[:]) |
|
|
|
actionMap[HtlcTimeoutAction] = append( |
|
actionMap[HtlcTimeoutAction], htlc, |
|
) |
|
} |
|
} |
|
|
|
// Similarly, for each incoming HTLC, now that we need to go on-chain, |
|
// we'll either: sweep it immediately if we know the pre-image, or |
|
// observe the output on-chain if we don't In this last, case we'll |
|
// either learn of it eventually from the outgoing HTLC, or the sender |
|
// will timeout the HTLC. |
|
for _, htlc := range c.activeHTLCs.incomingHTLCs { |
|
log.Tracef("ChannelArbitrator(%v): watching chain to decide "+ |
|
"action for incoming htlc=%x", c.cfg.ChanPoint, |
|
htlc.RHash[:]) |
|
|
|
actionMap[HtlcIncomingWatchAction] = append( |
|
actionMap[HtlcIncomingWatchAction], htlc, |
|
) |
|
} |
|
|
|
return actionMap, nil |
|
} |
|
|
|
// isPreimageAvailable returns whether the hash preimage is available in either |
|
// the preimage cache or the invoice database. |
|
func (c *ChannelArbitrator) isPreimageAvailable(hash lntypes.Hash) (bool, |
|
error) { |
|
|
|
// Start by checking the preimage cache for preimages of |
|
// forwarded HTLCs. |
|
_, preimageAvailable := c.cfg.PreimageDB.LookupPreimage( |
|
hash, |
|
) |
|
if preimageAvailable { |
|
return true, nil |
|
} |
|
|
|
// Then check if we have an invoice that can be settled by this HTLC. |
|
// |
|
// TODO(joostjager): Check that there are still more blocks remaining |
|
// than the invoice cltv delta. We don't want to go to chain only to |
|
// have the incoming contest resolver decide that we don't want to |
|
// settle this invoice. |
|
invoice, _, err := c.cfg.Registry.LookupInvoice(hash) |
|
switch err { |
|
case nil: |
|
case channeldb.ErrInvoiceNotFound, channeldb.ErrNoInvoicesCreated: |
|
return false, nil |
|
default: |
|
return false, err |
|
} |
|
|
|
preimageAvailable = invoice.Terms.PaymentPreimage != |
|
channeldb.UnknownPreimage |
|
|
|
return preimageAvailable, nil |
|
} |
|
|
|
// prepContractResolutions is called either int he case that we decide we need |
|
// to go to chain, or the remote party goes to chain. Given a set of actions we |
|
// need to take for each HTLC, this method will return a set of contract |
|
// resolvers that will resolve the contracts on-chain if needed, and also a set |
|
// of packets to send to the htlcswitch in order to ensure all incoming HTLC's |
|
// are properly resolved. |
|
func (c *ChannelArbitrator) prepContractResolutions(htlcActions ChainActionMap, |
|
contractResolutions *ContractResolutions, height uint32, |
|
) ([]ContractResolver, []ResolutionMsg, error) { |
|
|
|
// There may be a class of HTLC's which we can fail back immediately, |
|
// for those we'll prepare a slice of packets to add to our outbox. Any |
|
// packets we need to send, will be cancels. |
|
var ( |
|
msgsToSend []ResolutionMsg |
|
) |
|
|
|
incomingResolutions := contractResolutions.HtlcResolutions.IncomingHTLCs |
|
outgoingResolutions := contractResolutions.HtlcResolutions.OutgoingHTLCs |
|
|
|
// We'll use these two maps to quickly look up an active HTLC with its |
|
// matching HTLC resolution. |
|
outResolutionMap := make(map[wire.OutPoint]lnwallet.OutgoingHtlcResolution) |
|
inResolutionMap := make(map[wire.OutPoint]lnwallet.IncomingHtlcResolution) |
|
for i := 0; i < len(incomingResolutions); i++ { |
|
inRes := incomingResolutions[i] |
|
inResolutionMap[inRes.HtlcPoint()] = inRes |
|
} |
|
for i := 0; i < len(outgoingResolutions); i++ { |
|
outRes := outgoingResolutions[i] |
|
outResolutionMap[outRes.HtlcPoint()] = outRes |
|
} |
|
|
|
// We'll create the resolver kit that we'll be cloning for each |
|
// resolver so they each can do their duty. |
|
resKit := ResolverKit{ |
|
ChannelArbitratorConfig: c.cfg, |
|
Checkpoint: func(res ContractResolver) error { |
|
return c.log.InsertUnresolvedContracts(res) |
|
}, |
|
} |
|
|
|
commitHash := contractResolutions.CommitHash |
|
failureMsg := &lnwire.FailPermanentChannelFailure{} |
|
|
|
// For each HTLC, we'll either act immediately, meaning we'll instantly |
|
// fail the HTLC, or we'll act only once the transaction has been |
|
// confirmed, in which case we'll need an HTLC resolver. |
|
var htlcResolvers []ContractResolver |
|
for htlcAction, htlcs := range htlcActions { |
|
switch htlcAction { |
|
|
|
// If we can fail an HTLC immediately (an outgoing HTLC with no |
|
// contract), then we'll assemble an HTLC fail packet to send. |
|
case HtlcFailNowAction: |
|
for _, htlc := range htlcs { |
|
failMsg := ResolutionMsg{ |
|
SourceChan: c.cfg.ShortChanID, |
|
HtlcIndex: htlc.HtlcIndex, |
|
Failure: failureMsg, |
|
} |
|
|
|
msgsToSend = append(msgsToSend, failMsg) |
|
} |
|
|
|
// If we can claim this HTLC, we'll create an HTLC resolver to |
|
// claim the HTLC (second-level or directly), then add the pre |
|
case HtlcClaimAction: |
|
for _, htlc := range htlcs { |
|
htlcOp := wire.OutPoint{ |
|
Hash: commitHash, |
|
Index: uint32(htlc.OutputIndex), |
|
} |
|
|
|
resolution, ok := inResolutionMap[htlcOp] |
|
if !ok { |
|
// TODO(roasbeef): panic? |
|
log.Errorf("ChannelArbitrator(%v) unable to find "+ |
|
"incoming resolution: %v", |
|
c.cfg.ChanPoint, htlcOp) |
|
continue |
|
} |
|
|
|
resKit.Quit = make(chan struct{}) |
|
resolver := &htlcSuccessResolver{ |
|
htlcResolution: resolution, |
|
broadcastHeight: height, |
|
payHash: htlc.RHash, |
|
htlcAmt: htlc.Amt, |
|
ResolverKit: resKit, |
|
} |
|
htlcResolvers = append(htlcResolvers, resolver) |
|
} |
|
|
|
// If we can timeout the HTLC directly, then we'll create the |
|
// proper resolver to do so, who will then cancel the packet |
|
// backwards. |
|
case HtlcTimeoutAction: |
|
for _, htlc := range htlcs { |
|
htlcOp := wire.OutPoint{ |
|
Hash: commitHash, |
|
Index: uint32(htlc.OutputIndex), |
|
} |
|
|
|
resolution, ok := outResolutionMap[htlcOp] |
|
if !ok { |
|
log.Errorf("ChannelArbitrator(%v) unable to find "+ |
|
"outgoing resolution: %v", c.cfg.ChanPoint, htlcOp) |
|
continue |
|
} |
|
|
|
resKit.Quit = make(chan struct{}) |
|
resolver := &htlcTimeoutResolver{ |
|
htlcResolution: resolution, |
|
broadcastHeight: height, |
|
htlcIndex: htlc.HtlcIndex, |
|
htlcAmt: htlc.Amt, |
|
ResolverKit: resKit, |
|
} |
|
htlcResolvers = append(htlcResolvers, resolver) |
|
} |
|
|
|
// If this is an incoming HTLC, but we can't act yet, then |
|
// we'll create an incoming resolver to redeem the HTLC if we |
|
// learn of the pre-image, or let the remote party time out. |
|
case HtlcIncomingWatchAction: |
|
for _, htlc := range htlcs { |
|
htlcOp := wire.OutPoint{ |
|
Hash: commitHash, |
|
Index: uint32(htlc.OutputIndex), |
|
} |
|
|
|
// TODO(roasbeef): need to handle incoming dust... |
|
|
|
// TODO(roasbeef): can't be negative!!! |
|
resolution, ok := inResolutionMap[htlcOp] |
|
if !ok { |
|
log.Errorf("ChannelArbitrator(%v) unable to find "+ |
|
"incoming resolution: %v", |
|
c.cfg.ChanPoint, htlcOp) |
|
continue |
|
} |
|
|
|
resKit.Quit = make(chan struct{}) |
|
resolver := &htlcIncomingContestResolver{ |
|
htlcExpiry: htlc.RefundTimeout, |
|
htlcSuccessResolver: htlcSuccessResolver{ |
|
htlcResolution: resolution, |
|
broadcastHeight: height, |
|
payHash: htlc.RHash, |
|
htlcAmt: htlc.Amt, |
|
ResolverKit: resKit, |
|
}, |
|
} |
|
htlcResolvers = append(htlcResolvers, resolver) |
|
} |
|
|
|
// Finally, if this is an outgoing HTLC we've sent, then we'll |
|
// launch a resolver to watch for the pre-image (and settle |
|
// backwards), or just timeout. |
|
case HtlcOutgoingWatchAction: |
|
for _, htlc := range htlcs { |
|
htlcOp := wire.OutPoint{ |
|
Hash: commitHash, |
|
Index: uint32(htlc.OutputIndex), |
|
} |
|
|
|
resolution, ok := outResolutionMap[htlcOp] |
|
if !ok { |
|
log.Errorf("ChannelArbitrator(%v) unable to find "+ |
|
"outgoing resolution: %v", |
|
c.cfg.ChanPoint, htlcOp) |
|
continue |
|
} |
|
|
|
resKit.Quit = make(chan struct{}) |
|
resolver := &htlcOutgoingContestResolver{ |
|
htlcTimeoutResolver: htlcTimeoutResolver{ |
|
htlcResolution: resolution, |
|
broadcastHeight: height, |
|
htlcIndex: htlc.HtlcIndex, |
|
htlcAmt: htlc.Amt, |
|
ResolverKit: resKit, |
|
}, |
|
} |
|
htlcResolvers = append(htlcResolvers, resolver) |
|
} |
|
} |
|
} |
|
|
|
// Finally, if this is was a unilateral closure, then we'll also create |
|
// a resolver to sweep our commitment output (but only if it wasn't |
|
// trimmed). |
|
if contractResolutions.CommitResolution != nil { |
|
resKit.Quit = make(chan struct{}) |
|
resolver := &commitSweepResolver{ |
|
commitResolution: *contractResolutions.CommitResolution, |
|
broadcastHeight: height, |
|
chanPoint: c.cfg.ChanPoint, |
|
ResolverKit: resKit, |
|
} |
|
|
|
htlcResolvers = append(htlcResolvers, resolver) |
|
} |
|
|
|
return htlcResolvers, msgsToSend, nil |
|
} |
|
|
|
// replaceResolver replaces a in the list of active resolvers. If the resolver |
|
// to be replaced is not found, it returns an error. |
|
func (c *ChannelArbitrator) replaceResolver(oldResolver, |
|
newResolver ContractResolver) error { |
|
|
|
c.activeResolversLock.Lock() |
|
defer c.activeResolversLock.Unlock() |
|
|
|
oldKey := oldResolver.ResolverKey() |
|
for i, r := range c.activeResolvers { |
|
if bytes.Equal(r.ResolverKey(), oldKey) { |
|
c.activeResolvers[i] = newResolver |
|
return nil |
|
} |
|
} |
|
|
|
return errors.New("resolver to be replaced not found") |
|
} |
|
|
|
// resolveContract is a goroutine tasked with fully resolving an unresolved |
|
// contract. Either the initial contract will be resolved after a single step, |
|
// or the contract will itself create another contract to be resolved. In |
|
// either case, one the contract has been fully resolved, we'll signal back to |
|
// the main goroutine so it can properly keep track of the set of unresolved |
|
// contracts. |
|
// |
|
// NOTE: This MUST be run as a goroutine. |
|
func (c *ChannelArbitrator) resolveContract(currentContract ContractResolver) { |
|
defer c.wg.Done() |
|
|
|
log.Debugf("ChannelArbitrator(%v): attempting to resolve %T", |
|
c.cfg.ChanPoint, currentContract) |
|
|
|
// Until the contract is fully resolved, we'll continue to iteratively |
|
// resolve the contract one step at a time. |
|
for !currentContract.IsResolved() { |
|
log.Debugf("ChannelArbitrator(%v): contract %T not yet resolved", |
|
c.cfg.ChanPoint, currentContract) |
|
|
|
select { |
|
|
|
// If we've been signalled to quit, then we'll exit early. |
|
case <-c.quit: |
|
return |
|
|
|
default: |
|
// Otherwise, we'll attempt to resolve the current |
|
// contract. |
|
nextContract, err := currentContract.Resolve() |
|
if err != nil { |
|
log.Errorf("ChannelArbitrator(%v): unable to "+ |
|
"progress resolver: %v", |
|
c.cfg.ChanPoint, err) |
|
return |
|
} |
|
|
|
switch { |
|
// If this contract produced another, then this means |
|
// the current contract was only able to be partially |
|
// resolved in this step. So we'll not a contract swap |
|
// within our logs: the new contract will take the |
|
// place of the old one. |
|
case nextContract != nil: |
|
log.Debugf("ChannelArbitrator(%v): swapping "+ |
|
"out contract %T for %T ", |
|
c.cfg.ChanPoint, currentContract, |
|
nextContract) |
|
|
|
// Swap contract in log. |
|
err := c.log.SwapContract( |
|
currentContract, nextContract, |
|
) |
|
if err != nil { |
|
log.Errorf("unable to add recurse "+ |
|
"contract: %v", err) |
|
} |
|
|
|
// Swap contract in resolvers list. This is to |
|
// make sure that reports are queried from the |
|
// new resolver. |
|
err = c.replaceResolver( |
|
currentContract, nextContract, |
|
) |
|
if err != nil { |
|
log.Errorf("unable to replace "+ |
|
"contract: %v", err) |
|
} |
|
|
|
// As this contract produced another, we'll |
|
// re-assign, so we can continue our resolution |
|
// loop. |
|
currentContract = nextContract |
|
|
|
// If this contract is actually fully resolved, then |
|
// we'll mark it as such within the database. |
|
case currentContract.IsResolved(): |
|
log.Debugf("ChannelArbitrator(%v): marking "+ |
|
"contract %T fully resolved", |
|
c.cfg.ChanPoint, currentContract) |
|
|
|
err := c.log.ResolveContract(currentContract) |
|
if err != nil { |
|
log.Errorf("unable to resolve contract: %v", |
|
err) |
|
} |
|
|
|
// Now that the contract has been resolved, |
|
// well signal to the main goroutine. |
|
select { |
|
case c.resolutionSignal <- struct{}{}: |
|
case <-c.quit: |
|
return |
|
} |
|
} |
|
|
|
} |
|
} |
|
} |
|
|
|
// signalUpdateMsg is a struct that carries fresh signals to the |
|
// ChannelArbitrator. We need to receive a message like this each time the |
|
// channel becomes active, as it's internal state may change. |
|
type signalUpdateMsg struct { |
|
// newSignals is the set of new active signals to be sent to the |
|
// arbitrator. |
|
newSignals *ContractSignals |
|
|
|
// doneChan is a channel that will be closed on the arbitrator has |
|
// attached the new signals. |
|
doneChan chan struct{} |
|
} |
|
|
|
// UpdateContractSignals updates the set of signals the ChannelArbitrator needs |
|
// to receive from a channel in real-time in order to keep in sync with the |
|
// latest state of the contract. |
|
func (c *ChannelArbitrator) UpdateContractSignals(newSignals *ContractSignals) { |
|
done := make(chan struct{}) |
|
|
|
select { |
|
case c.signalUpdates <- &signalUpdateMsg{ |
|
newSignals: newSignals, |
|
doneChan: done, |
|
}: |
|
case <-c.quit: |
|
} |
|
|
|
select { |
|
case <-done: |
|
case <-c.quit: |
|
} |
|
} |
|
|
|
// channelAttendant is the primary goroutine that acts at the judicial |
|
// arbitrator between our channel state, the remote channel peer, and the |
|
// blockchain Our judge). This goroutine will ensure that we faithfully execute |
|
// all clauses of our contract in the case that we need to go on-chain for a |
|
// dispute. Currently, two such conditions warrant our intervention: when an |
|
// outgoing HTLC is about to timeout, and when we know the pre-image for an |
|
// incoming HTLC, but it hasn't yet been settled off-chain. In these cases, |
|
// we'll: broadcast our commitment, cancel/settle any HTLC's backwards after |
|
// sufficient confirmation, and finally send our set of outputs to the UTXO |
|
// Nursery for incubation, and ultimate sweeping. |
|
// |
|
// NOTE: This MUST be run as a goroutine. |
|
func (c *ChannelArbitrator) channelAttendant(bestHeight int32) { |
|
|
|
// TODO(roasbeef): tell top chain arb we're done |
|
defer func() { |
|
c.cfg.BlockEpochs.Cancel() |
|
c.wg.Done() |
|
}() |
|
|
|
for { |
|
select { |
|
|
|
// A new block has arrived, we'll examine all the active HTLC's |
|
// to see if any of them have expired, and also update our |
|
// track of the best current height. |
|
case blockEpoch, ok := <-c.cfg.BlockEpochs.Epochs: |
|
if !ok { |
|
return |
|
} |
|
bestHeight = blockEpoch.Height |
|
|
|
// If we're not in the default state, then we can |
|
// ignore this signal as we're waiting for contract |
|
// resolution. |
|
if c.state != StateDefault { |
|
continue |
|
} |
|
|
|
// Now that a new block has arrived, we'll attempt to |
|
// advance our state forward. |
|
nextState, _, err := c.advanceState( |
|
uint32(bestHeight), chainTrigger, |
|
) |
|
if err != nil { |
|
log.Errorf("unable to advance state: %v", err) |
|
} |
|
|
|
// If as a result of this trigger, the contract is |
|
// fully resolved, then well exit. |
|
if nextState == StateFullyResolved { |
|
return |
|
} |
|
|
|
// A new signal update was just sent. This indicates that the |
|
// channel under watch is now live, and may modify its internal |
|
// state, so we'll get the most up to date signals to we can |
|
// properly do our job. |
|
case signalUpdate := <-c.signalUpdates: |
|
log.Tracef("ChannelArbitrator(%v) got new signal "+ |
|
"update!", c.cfg.ChanPoint) |
|
|
|
// First, we'll update our set of signals. |
|
c.htlcUpdates = signalUpdate.newSignals.HtlcUpdates |
|
c.cfg.ShortChanID = signalUpdate.newSignals.ShortChanID |
|
|
|
// Now that the signals have been updated, we'll now |
|
// close the done channel to signal to the caller we've |
|
// registered the new contracts. |
|
close(signalUpdate.doneChan) |
|
|
|
// A new set of HTLC's has been added or removed from the |
|
// commitment transaction. So we'll update our activeHTLCs map |
|
// accordingly. |
|
case newStateHTLCs := <-c.htlcUpdates: |
|
// We'll wipe out our old set of HTLC's and instead |
|
// monitor only the HTLC's that are still active on the |
|
// current commitment state. |
|
c.activeHTLCs = newHtlcSet(newStateHTLCs) |
|
|
|
log.Tracef("ChannelArbitrator(%v): fresh set of "+ |
|
"htlcs=%v", c.cfg.ChanPoint, |
|
newLogClosure(func() string { |
|
return spew.Sdump(c.activeHTLCs) |
|
}), |
|
) |
|
|
|
// We've cooperatively closed the channel, so we're no longer |
|
// needed. We'll mark the channel as resolved and exit. |
|
case closeInfo := <-c.cfg.ChainEvents.CooperativeClosure: |
|
log.Infof("ChannelArbitrator(%v) marking channel "+ |
|
"cooperatively closed", c.cfg.ChanPoint) |
|
|
|
err := c.cfg.MarkChannelClosed( |
|
closeInfo.ChannelCloseSummary, |
|
) |
|
if err != nil { |
|
log.Errorf("unable to mark channel closed: "+ |
|
"%v", err) |
|
return |
|
} |
|
|
|
// We'll now advance our state machine until it reaches |
|
// a terminal state, and the channel is marked resolved. |
|
_, _, err = c.advanceState( |
|
closeInfo.CloseHeight, coopCloseTrigger, |
|
) |
|
if err != nil { |
|
log.Errorf("unable to advance state: %v", err) |
|
return |
|
} |
|
|
|
// We have broadcasted our commitment, and it is now confirmed |
|
// on-chain. |
|
case closeInfo := <-c.cfg.ChainEvents.LocalUnilateralClosure: |
|
log.Infof("ChannelArbitrator(%v): local on-chain "+ |
|
"channel close", c.cfg.ChanPoint) |
|
|
|
if c.state != StateCommitmentBroadcasted { |
|
log.Errorf("ChannelArbitrator(%v): unexpected "+ |
|
"local on-chain channel close", |
|
c.cfg.ChanPoint) |
|
} |
|
closeTx := closeInfo.CloseTx |
|
|
|
contractRes := &ContractResolutions{ |
|
CommitHash: closeTx.TxHash(), |
|
CommitResolution: closeInfo.CommitResolution, |
|
HtlcResolutions: *closeInfo.HtlcResolutions, |
|
} |
|
|
|
// When processing a unilateral close event, we'll |
|
// transition to the ContractClosed state. We'll log |
|
// out the set of resolutions such that they are |
|
// available to fetch in that state. |
|
err := c.log.LogContractResolutions(contractRes) |
|
if err != nil { |
|
log.Errorf("unable to write resolutions: %v", |
|
err) |
|
return |
|
} |
|
|
|
// After the set of resolutions are successfully |
|
// logged, we can safely close the channel. After this |
|
// succeeds we won't be getting chain events anymore, |
|
// so we must make sure we can recover on restart after |
|
// it is marked closed. If the next state transition |
|
// fails, we'll start up in the prior state again, and |
|
// we won't be longer getting chain events. In this |
|
// case we must manually re-trigger the state |
|
// transition into StateContractClosed based on the |
|
// close status of the channel. |
|
err = c.cfg.MarkChannelClosed( |
|
closeInfo.ChannelCloseSummary, |
|
) |
|
if err != nil { |
|
log.Errorf("unable to mark "+ |
|
"channel closed: %v", err) |
|
return |
|
} |
|
|
|
// We'll now advance our state machine until it reaches |
|
// a terminal state. |
|
_, _, err = c.advanceState( |
|
uint32(closeInfo.SpendingHeight), |
|
localCloseTrigger, |
|
) |
|
if err != nil { |
|
log.Errorf("unable to advance state: %v", err) |
|
} |
|
|
|
// The remote party has broadcast the commitment on-chain. |
|
// We'll examine our state to determine if we need to act at |
|
// all. |
|
case uniClosure := <-c.cfg.ChainEvents.RemoteUnilateralClosure: |
|
|
|
log.Infof("ChannelArbitrator(%v): remote party has "+ |
|
"closed channel out on-chain", c.cfg.ChanPoint) |
|
|
|
// If we don't have a self output, and there are no |
|
// active HTLC's, then we can immediately mark the |
|
// contract as fully resolved and exit. |
|
contractRes := &ContractResolutions{ |
|
CommitHash: *uniClosure.SpenderTxHash, |
|
CommitResolution: uniClosure.CommitResolution, |
|
HtlcResolutions: *uniClosure.HtlcResolutions, |
|
} |
|
|
|
// As we're now acting upon an event triggered by the |
|
// broadcast of the remote commitment transaction, |
|
// we'll swap out our active HTLC set with the set |
|
// present on their commitment. |
|
c.activeHTLCs = newHtlcSet(uniClosure.RemoteCommit.Htlcs) |
|
|
|
// When processing a unilateral close event, we'll |
|
// transition to the ContractClosed state. We'll log |
|
// out the set of resolutions such that they are |
|
// available to fetch in that state. |
|
err := c.log.LogContractResolutions(contractRes) |
|
if err != nil { |
|
log.Errorf("unable to write resolutions: %v", |
|
err) |
|
return |
|
} |
|
|
|
// After the set of resolutions are successfully |
|
// logged, we can safely close the channel. After this |
|
// succeeds we won't be getting chain events anymore, |
|
// so we must make sure we can recover on restart after |
|
// it is marked closed. If the next state transition |
|
// fails, we'll start up in the prior state again, and |
|
// we won't be longer getting chain events. In this |
|
// case we must manually re-trigger the state |
|
// transition into StateContractClosed based on the |
|
// close status of the channel. |
|
closeSummary := &uniClosure.ChannelCloseSummary |
|
err = c.cfg.MarkChannelClosed(closeSummary) |
|
if err != nil { |
|
log.Errorf("unable to mark channel closed: %v", |
|
err) |
|
return |
|
} |
|
|
|
// We'll now advance our state machine until it reaches |
|
// a terminal state. |
|
_, _, err = c.advanceState( |
|
uint32(uniClosure.SpendingHeight), |
|
remoteCloseTrigger, |
|
) |
|
if err != nil { |
|
log.Errorf("unable to advance state: %v", err) |
|
} |
|
|
|
// A new contract has just been resolved, we'll now check our |
|
// log to see if all contracts have been resolved. If so, then |
|
// we can exit as the contract is fully resolved. |
|
case <-c.resolutionSignal: |
|
log.Infof("ChannelArbitrator(%v): a contract has been "+ |
|
"fully resolved!", c.cfg.ChanPoint) |
|
|
|
nextState, _, err := c.advanceState( |
|
uint32(bestHeight), chainTrigger, |
|
) |
|
if err != nil { |
|
log.Errorf("unable to advance state: %v", err) |
|
} |
|
|
|
// If we don't have anything further to do after |
|
// advancing our state, then we'll exit. |
|
if nextState == StateFullyResolved { |
|
log.Infof("ChannelArbitrator(%v): all "+ |
|
"contracts fully resolved, exiting", |
|
c.cfg.ChanPoint) |
|
|
|
return |
|
} |
|
|
|
// We've just received a request to forcibly close out the |
|
// channel. We'll |
|
case closeReq := <-c.forceCloseReqs: |
|
if c.state != StateDefault { |
|
select { |
|
case closeReq.closeTx <- nil: |
|
case <-c.quit: |
|
} |
|
|
|
select { |
|
case closeReq.errResp <- errAlreadyForceClosed: |
|
case <-c.quit: |
|
} |
|
|
|
continue |
|
} |
|
|
|
nextState, closeTx, err := c.advanceState( |
|
uint32(bestHeight), userTrigger, |
|
) |
|
if err != nil { |
|
log.Errorf("unable to advance state: %v", err) |
|
} |
|
|
|
select { |
|
case closeReq.closeTx <- closeTx: |
|
case <-c.quit: |
|
return |
|
} |
|
|
|
select { |
|
case closeReq.errResp <- err: |
|
case <-c.quit: |
|
return |
|
} |
|
|
|
// If we don't have anything further to do after |
|
// advancing our state, then we'll exit. |
|
if nextState == StateFullyResolved { |
|
log.Infof("ChannelArbitrator(%v): all "+ |
|
"contracts resolved, exiting", |
|
c.cfg.ChanPoint) |
|
return |
|
} |
|
|
|
case <-c.quit: |
|
return |
|
} |
|
} |
|
}
|
|
|