lnd.xprv/lnwallet/reservation.go

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package lnwallet
import (
"sync"
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"github.com/lightningnetwork/lnd/channeldb"
"github.com/roasbeef/btcd/btcec"
"github.com/roasbeef/btcd/wire"
"github.com/roasbeef/btcutil"
)
// ChannelContribution is the primary constituent of the funding workflow within
// lnwallet. Each side first exchanges their respective contributions along with
// channel specific paramters like the min fee/KB. Once contributions have been
// exchanged, each side will then produce signatures for all their inputs to the
// funding transactions, and finally a signature for the other party's version
// of the commitment transaction.
type ChannelContribution struct {
// Amount of funds contributed to the funding transaction.
FundingAmount btcutil.Amount
// Inputs to the funding transaction.
Inputs []*wire.TxIn
// Outputs to be used in the case that the total value of the fund
// ing inputs is greather than the total potential channel capacity.
ChangeOutputs []*wire.TxOut
// The key to be used for the funding transaction's P2SH multi-sig
// 2-of-2 output.
MultiSigKey *btcec.PublicKey
// The key to be used for this party's version of the commitment
// transaction.
CommitKey *btcec.PublicKey
// Address to be used for delivery of cleared channel funds in the scenario
// of a cooperative channel closure.
DeliveryAddress btcutil.Address
// Hash to be used as the revocation for the initial version of this
// party's commitment transaction.
RevocationHash [20]byte
// The delay (in blocks) to be used for the pay-to-self output in this
// party's version of the commitment transaction.
CsvDelay uint32
}
// InputScripts represents any script inputs required to redeem a previous
// output. This struct is used rather than just a witness, or scripSig in
// order to accomdate nested p2sh which utilizes both types of input scripts.
type InputScript struct {
Witness [][]byte
ScriptSig []byte
}
// ChannelReservation represents an intent to open a lightning payment channel
// a counterpaty. The funding proceses from reservation to channel opening is a
// 3-step process. In order to allow for full concurrency during the reservation
// workflow, resources consumed by a contribution are "locked" themselves. This
// prevents a number of race conditions such as two funding transactions
// double-spending the same input. A reservation can also be cancelled, which
// removes the resources from limbo, allowing another reservation to claim them.
//
// The reservation workflow consists of the following three steps:
// 1. lnwallet.InitChannelReservation
// * One requests the wallet to allocate the neccessary resources for a
// channel reservation. These resources a put in limbo for the lifetime
// of a reservation.
// * Once completed the reservation will have the wallet's contribution
// accessible via the .OurContribution() method. This contribution
// contains the neccessary items to allow the remote party to build both
// the funding, and commitment transactions.
// 2. ChannelReservation.ProcessContribution
// * The counterparty presents their contribution to the payment channel.
// This allows us to build the funding, and commitment transactions
// ourselves.
// * We're now able to sign our inputs to the funding transactions, and
// the counterparty's version of the commitment transaction.
// * All signatures crafted by us, are now available via .OurSignatures().
// 3. ChannelReservation.CompleteReservation
// * The final step in the workflow. The counterparty presents the
// signatures for all their inputs to the funding transation, as well
// as a signature to our version of the commitment transaction.
// * We then verify the validity of all signatures before considering the
// channel "open".
type ChannelReservation struct {
// This mutex MUST be held when either reading or modifying any of the
// fields below.
sync.RWMutex
// For CLTV it is nLockTime, for CSV it's nSequence, for segwit it's
// not needed
fundingLockTime uint32
// In order of sorted inputs. Sorting is done in accordance
// to BIP-69: https://github.com/bitcoin/bips/blob/master/bip-0069.mediawiki.
ourFundingInputScripts []*InputScript
theirFundingInputScripts []*InputScript
// Our signature for their version of the commitment transaction.
ourCommitmentSig []byte
theirCommitmentSig []byte
ourContribution *ChannelContribution
theirContribution *ChannelContribution
partialState *channeldb.OpenChannel
// The ID of this reservation, used to uniquely track the reservation
// throughout its lifetime.
reservationID uint64
// A channel which will be sent on once the channel is considered
// 'open'. A channel is open once the funding transaction has reached
// a sufficient number of confirmations.
chanOpen chan *LightningChannel
wallet *LightningWallet
}
// newChannelReservation creates a new channel reservation. This function is
// used only internally by lnwallet. In order to concurrent safety, the creation
// of all channel reservations should be carried out via the
// lnwallet.InitChannelReservation interface.
func newChannelReservation(fundingAmt btcutil.Amount, minFeeRate btcutil.Amount,
wallet *LightningWallet, id uint64) *ChannelReservation {
// TODO(roasbeef): CSV here, or on delay?
return &ChannelReservation{
ourContribution: &ChannelContribution{
FundingAmount: fundingAmt,
},
theirContribution: &ChannelContribution{
FundingAmount: fundingAmt,
},
partialState: &channeldb.OpenChannel{
// TODO(roasbeef): assumes balanced symmetric channels.
Capacity: fundingAmt * 2,
OurBalance: fundingAmt,
TheirBalance: fundingAmt,
MinFeePerKb: minFeeRate,
Db: wallet.channelDB,
},
reservationID: id,
wallet: wallet,
}
}
// OurContribution returns the wallet's fully populated contribution to the
// pending payment channel. See 'ChannelContribution' for further details
// regarding the contents of a contribution.
// NOTE: This SHOULD NOT be modified.
// TODO(roasbeef): make copy?
func (r *ChannelReservation) OurContribution() *ChannelContribution {
r.RLock()
defer r.RUnlock()
return r.ourContribution
}
// ProcesContribution verifies the counterparty's contribution to the pending
// payment channel. As a result of this incoming message, lnwallet is able to
// build the funding transaction, and both commitment transactions. Once this
// message has been processed, all signatures to inputs to the funding
// transaction belonging to the wallet are available. Additionally, the wallet
// will generate a signature to the counterparty's version of the commitment
// transaction.
func (r *ChannelReservation) ProcessContribution(theirContribution *ChannelContribution) error {
errChan := make(chan error, 1)
r.wallet.msgChan <- &addContributionMsg{
pendingFundingID: r.reservationID,
contribution: theirContribution,
err: errChan,
}
return <-errChan
}
// TheirContribution returns the counterparty's pending contribution to the
// payment channel. See 'ChannelContribution' for further details regarding
// the contents of a contribution. This attribute will ONLY be available
// after a call to .ProcesContribution().
// NOTE: This SHOULD NOT be modified.
func (r *ChannelReservation) TheirContribution() *ChannelContribution {
r.RLock()
defer r.RUnlock()
return r.theirContribution
}
// OurSignatures retrieves the wallet's signatures to all inputs to the funding
// transaction belonging to itself, and also a signature for the counterparty's
// version of the commitment transaction. The signatures for the wallet's
// inputs to the funding transaction are returned in sorted order according to
// BIP-69: https://github.com/bitcoin/bips/blob/master/bip-0069.mediawiki.
// NOTE: These signatures will only be populated after a call to
// .ProcesContribution()
func (r *ChannelReservation) OurSignatures() ([]*InputScript, []byte) {
r.RLock()
defer r.RUnlock()
return r.ourFundingInputScripts, r.ourCommitmentSig
}
// CompleteFundingReservation finalizes the pending channel reservation,
// transitioning from a pending payment channel, to an open payment
// channel. All passed signatures to the counterparty's inputs to the funding
// transaction will be fully verified. Signatures are expected to be passed in
// sorted order according to BIP-69:
// https://github.com/bitcoin/bips/blob/master/bip-0069.mediawiki. Additionally,
// verification is performed in order to ensure that the counterparty supplied
// a valid signature to our version of the commitment transaction.
// Once this method returns, caller's should then call .WaitForChannelOpen()
// which will block until the funding transaction obtains the configured number
// of confirmations. Once the method unblocks, a LightningChannel instance is
// returned, marking the channel available for updates.
func (r *ChannelReservation) CompleteReservation(fundingInputScripts []*InputScript,
commitmentSig []byte) error {
errChan := make(chan error, 1)
r.wallet.msgChan <- &addCounterPartySigsMsg{
pendingFundingID: r.reservationID,
theirFundingInputScripts: fundingInputScripts,
theirCommitmentSig: commitmentSig,
err: errChan,
}
return <-errChan
}
// OurSignatures returns the counterparty's signatures to all inputs to the
// funding transaction belonging to them, as well as their signature for the
// wallet's version of the commitment transaction. This methods is provided for
// additional verification, such as needed by tests.
// NOTE: These attributes will be unpopulated before a call to
// .CompleteReservation().
func (r *ChannelReservation) TheirSignatures() ([]*InputScript, []byte) {
r.RLock()
defer r.RUnlock()
return r.theirFundingInputScripts, r.theirCommitmentSig
}
// FinalFundingTx returns the finalized, fully signed funding transaction for
// this reservation.
func (r *ChannelReservation) FinalFundingTx() *wire.MsgTx {
r.RLock()
defer r.RUnlock()
return r.partialState.FundingTx
}
// Cancel abandons this channel reservation. This method should be called in
// the scenario that communications with the counterparty break down. Upon
// cancellation, all resources previously reserved for this pending payment
// channel are returned to the free pool, allowing subsequent reservations to
// utilize the now freed resources.
func (r *ChannelReservation) Cancel() error {
errChan := make(chan error, 1)
r.wallet.msgChan <- &fundingReserveCancelMsg{
pendingFundingID: r.reservationID,
err: errChan,
}
return <-errChan
}
// WaitForChannelOpen blocks until the funding transaction for this pending
// payment channel obtains the configured number of confirmations. Once
// confirmations have been obtained, a fully initialized LightningChannel
// instance is returned, allowing for channel updates.
// NOTE: If this method is called before .CompleteReservation(), it will block
// indefinitely.
func (r *ChannelReservation) WaitForChannelOpen() *LightningChannel {
return <-r.chanOpen
}
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// * finish reset of tests
// * start on commitment side
// * channel should have active namespace to it's bucket, query at that point fo past commits etc