13157733617

Committed 05 Feb 2025 12:49PM UTC coverage: 57.712% (-1.1%) from 58.82%

Build # 13157733617

Build Type

Pull #9447

github

Committed by

yyforyongyu

Commit Message

sweep: rename methods for clarity

We now rename "third party" to "unknown" as the inputs can be spent via
an older sweeping tx, a third party (anchor), or a remote party (pin).
In fee bumper we don't have the info to distinguish the above cases, and
leave them to be further handled by the sweeper as it has more context.

Pull Request Pull Request #9447: sweep: start tracking input spending status in the fee bumper

Run Details

83 of 87 new or added lines in 2 files covered. (95.4%)

19472 existing lines in 252 files now uncovered.

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72.86

/lnwallet/chanfunding/wallet_assembler.go

package chanfunding

import (
        "fmt"
        "math"
        "time"

        "github.com/btcsuite/btcd/btcec/v2"
        "github.com/btcsuite/btcd/btcutil"
        "github.com/btcsuite/btcd/btcutil/txsort"
        "github.com/btcsuite/btcd/txscript"
        "github.com/btcsuite/btcd/wire"
        "github.com/btcsuite/btcwallet/wallet"
        "github.com/btcsuite/btcwallet/wtxmgr"
        "github.com/lightningnetwork/lnd/input"
        "github.com/lightningnetwork/lnd/keychain"
)

const (
        // DefaultReservationTimeout is the default time we wait until we remove
        // an unfinished (zombiestate) open channel flow from memory.
        DefaultReservationTimeout = 10 * time.Minute

        // DefaultLockDuration is the default duration used to lock outputs.
        DefaultLockDuration = 10 * time.Minute
)

var (
        // LndInternalLockID is the binary representation of the SHA256 hash of
        // the string "lnd-internal-lock-id" and is used for UTXO lock leases to
        // identify that we ourselves are locking an UTXO, for example when
        // giving out a funded PSBT. The ID corresponds to the hex value of
        // ede19a92ed321a4705f8a1cccc1d4f6182545d4bb4fae08bd5937831b7e38f98.
        LndInternalLockID = wtxmgr.LockID{
                0xed, 0xe1, 0x9a, 0x92, 0xed, 0x32, 0x1a, 0x47,
                0x05, 0xf8, 0xa1, 0xcc, 0xcc, 0x1d, 0x4f, 0x61,
                0x82, 0x54, 0x5d, 0x4b, 0xb4, 0xfa, 0xe0, 0x8b,
                0xd5, 0x93, 0x78, 0x31, 0xb7, 0xe3, 0x8f, 0x98,
        }
)

// FullIntent is an intent that is fully backed by the internal wallet. This
// intent differs from the ShimIntent, in that the funding transaction will be
// constructed internally, and will consist of only inputs we wholly control.
// This Intent implements a basic state machine that must be executed in order
// before CompileFundingTx can be called.
//
// Steps to final channel provisioning:
//  1. Call BindKeys to notify the intent which keys to use when constructing
//     the multi-sig output.
//  2. Call CompileFundingTx afterwards to obtain the funding transaction.
//
// If either of these steps fail, then the Cancel method MUST be called.
type FullIntent struct {
        ShimIntent

        // InputCoins are the set of coins selected as inputs to this funding
        // transaction.
        InputCoins []wallet.Coin

        // ChangeOutputs are the set of outputs that the Assembler will use as
        // change from the main funding transaction.
        ChangeOutputs []*wire.TxOut

        // coinLeaser is the Assembler's instance of the OutputLeaser
        // interface.
        coinLeaser OutputLeaser

        // coinSource is the Assembler's instance of the CoinSource interface.
        coinSource CoinSource

        // signer is the Assembler's instance of the Singer interface.
        signer input.Signer
}

// BindKeys is a method unique to the FullIntent variant. This allows the
// caller to decide precisely which keys are used in the final funding
// transaction. This is kept out of the main Assembler as these may may not
// necessarily be under full control of the wallet. Only after this method has
// been executed will CompileFundingTx succeed.
func (f *FullIntent) BindKeys(localKey *keychain.KeyDescriptor,
        remoteKey *btcec.PublicKey) {

        f.localKey = localKey
        f.remoteKey = remoteKey
}

// CompileFundingTx is to be called after BindKeys on the sub-intent has been
// called. This method will construct the final funding transaction, and fully
// sign all inputs that are known by the backing CoinSource. After this method
// returns, the Intent is assumed to be complete, as the output can be created
// at any point.
func (f *FullIntent) CompileFundingTx(extraInputs []*wire.TxIn,
        extraOutputs []*wire.TxOut) (*wire.MsgTx, error) {

        // Create a blank, fresh transaction. Soon to be a complete funding
        // transaction which will allow opening a lightning channel.
        fundingTx := wire.NewMsgTx(2)

        // Add all multi-party inputs and outputs to the transaction.
        for _, coin := range f.InputCoins {
                fundingTx.AddTxIn(&wire.TxIn{
                        PreviousOutPoint: coin.OutPoint,
                })
        }
        for _, theirInput := range extraInputs {
                fundingTx.AddTxIn(theirInput)
        }
        for _, ourChangeOutput := range f.ChangeOutputs {
                fundingTx.AddTxOut(ourChangeOutput)
        }
        for _, theirChangeOutput := range extraOutputs {
                fundingTx.AddTxOut(theirChangeOutput)
        }

        _, fundingOutput, err := f.FundingOutput()
        if err != nil {
                return nil, err
        }

        // Sort the transaction. Since both side agree to a canonical ordering,
        // by sorting we no longer need to send the entire transaction. Only
        // signatures will be exchanged.
        fundingTx.AddTxOut(fundingOutput)
        txsort.InPlaceSort(fundingTx)

        // Now that the funding tx has been fully assembled, we'll locate the
        // index of the funding output so we can create our final channel
        // point.
        _, multiSigIndex := input.FindScriptOutputIndex(
                fundingTx, fundingOutput.PkScript,
        )

        // Next, sign all inputs that are ours, collecting the signatures in
        // order of the inputs.
        prevOutFetcher := NewSegWitV0DualFundingPrevOutputFetcher(
                f.coinSource, extraInputs,
        )
        sigHashes := txscript.NewTxSigHashes(fundingTx, prevOutFetcher)
        for i, txIn := range fundingTx.TxIn {
                signDesc := input.SignDescriptor{
                        SigHashes:         sigHashes,
                        PrevOutputFetcher: prevOutFetcher,
                }
                // We can only sign this input if it's ours, so we'll ask the
                // coin source if it can map this outpoint into a coin we own.
                // If not, then we'll continue as it isn't our input.
                info, err := f.coinSource.CoinFromOutPoint(
                        txIn.PreviousOutPoint,
                )
                if err != nil {
                        continue
                }

                // Now that we know the input is ours, we'll populate the
                // signDesc with the per input unique information.
                signDesc.Output = &wire.TxOut{
                        Value:    info.Value,
                        PkScript: info.PkScript,
                }
                signDesc.InputIndex = i

                // We support spending a p2tr input ourselves. But not as part
                // of their inputs.
                signDesc.HashType = txscript.SigHashAll
                if txscript.IsPayToTaproot(info.PkScript) {
                        signDesc.HashType = txscript.SigHashDefault
                }

                // Finally, we'll sign the input as is, and populate the input
                // with the witness and sigScript (if needed).
                inputScript, err := f.signer.ComputeInputScript(
                        fundingTx, &signDesc,
                )
                if err != nil {
                        return nil, err
                }

                txIn.SignatureScript = inputScript.SigScript
                txIn.Witness = inputScript.Witness
        }

        // Finally, we'll populate the chanPoint now that we've fully
        // constructed the funding transaction.
        f.chanPoint = &wire.OutPoint{
                Hash:  fundingTx.TxHash(),
                Index: multiSigIndex,
        }

        return fundingTx, nil
}

// Inputs returns all inputs to the final funding transaction that we
// know about. Since this funding transaction is created all from our wallet,
// it will be all inputs.
func (f *FullIntent) Inputs() []wire.OutPoint {
        var ins []wire.OutPoint
        for _, coin := range f.InputCoins {
                ins = append(ins, coin.OutPoint)
        }

        return ins
}

// Outputs returns all outputs of the final funding transaction that we
// know about. This will be the funding output and the change outputs going
// back to our wallet.
func (f *FullIntent) Outputs() []*wire.TxOut {
        outs := f.ShimIntent.Outputs()
        outs = append(outs, f.ChangeOutputs...)

        return outs
}

// Cancel allows the caller to cancel a funding Intent at any time.  This will
// return any resources such as coins back to the eligible pool to be used in
// order channel fundings.
//
// NOTE: Part of the chanfunding.Intent interface.
func (f *FullIntent) Cancel() {
        for _, coin := range f.InputCoins {
                err := f.coinLeaser.ReleaseOutput(
                        LndInternalLockID, coin.OutPoint,
                )
                if err != nil {
                        log.Warnf("Failed to release UTXO %s (%v))",
                                coin.OutPoint, err)
                }
        }

        f.ShimIntent.Cancel()
}

// A compile-time check to ensure FullIntent meets the Intent interface.
var _ Intent = (*FullIntent)(nil)

// WalletConfig is the main config of the WalletAssembler.
type WalletConfig struct {
        // CoinSource is what the WalletAssembler uses to list/locate coins.
        CoinSource CoinSource

        // CoinSelectionStrategy is the strategy that is used for selecting
        // coins when funding a transaction.
        CoinSelectionStrategy wallet.CoinSelectionStrategy

        // CoinSelectionLocker allows the WalletAssembler to gain exclusive
        // access to the current set of coins returned by the CoinSource.
        CoinSelectLocker CoinSelectionLocker

        // CoinLeaser is what the WalletAssembler uses to lease coins that may
        // be used as inputs for a new funding transaction.
        CoinLeaser OutputLeaser

        // Signer allows the WalletAssembler to sign inputs on any potential
        // funding transactions.
        Signer input.Signer

        // DustLimit is the current dust limit. We'll use this to ensure that
        // we don't make dust outputs on the funding transaction.
        DustLimit btcutil.Amount
}

// WalletAssembler is an instance of the Assembler interface that is backed by
// a full wallet. This variant of the Assembler interface will produce the
// entirety of the funding transaction within the wallet. This implements the
// typical funding flow that is initiated either on the p2p level or using the
// CLi.
type WalletAssembler struct {
        cfg WalletConfig
}

// NewWalletAssembler creates a new instance of the WalletAssembler from a
// fully populated wallet config.
func NewWalletAssembler(cfg WalletConfig) *WalletAssembler {
        return &WalletAssembler{
                cfg: cfg,
        }
}

// ProvisionChannel is the main entry point to begin a funding workflow given a
// fully populated request. The internal WalletAssembler will perform coin
// selection in a goroutine safe manner, returning an Intent that will allow
// the caller to finalize the funding process.
//
// NOTE: To cancel the funding flow the Cancel() method on the returned Intent,
// MUST be called.
//
// NOTE: This is a part of the chanfunding.Assembler interface.
func (w *WalletAssembler) ProvisionChannel(r *Request) (Intent, error) {
        var intent Intent

        // We hold the coin select mutex while querying for outputs, and
        // performing coin selection in order to avoid inadvertent double
        // spends across funding transactions.
        err := w.cfg.CoinSelectLocker.WithCoinSelectLock(func() error {
                log.Infof("Performing funding tx coin selection using %v "+
                        "sat/kw as fee rate", int64(r.FeeRate))

                var (
                        // allCoins refers to the entirety of coins in our
                        // wallet that are available for funding a channel.
                        allCoins []wallet.Coin

                        // manuallySelectedCoins refers to the client-side
                        // selected coins that should be considered available
                        // for funding a channel.
                        manuallySelectedCoins []wallet.Coin
                        err                   error
                )

                // Convert manually selected outpoints to coins.
                manuallySelectedCoins, err = outpointsToCoins(
                        r.Outpoints, w.cfg.CoinSource.CoinFromOutPoint,
                )
                if err != nil {
                        return err
                }

                // Find all unlocked unspent witness outputs that satisfy the
                // minimum number of confirmations required. Coin selection in
                // this function currently ignores the configured coin selection
                // strategy.
                allCoins, err = w.cfg.CoinSource.ListCoins(
                        r.MinConfs, math.MaxInt32,
                )
                if err != nil {
                        return err
                }

                // Ensure that all manually selected coins remain unspent.
                unspent := make(map[wire.OutPoint]struct{})
                for _, coin := range allCoins {
                        unspent[coin.OutPoint] = struct{}{}
                }
                for _, coin := range manuallySelectedCoins {
                        if _, ok := unspent[coin.OutPoint]; !ok {
                                return fmt.Errorf("outpoint already spent or "+
                                        "locked by another subsystem: %v",
                                        coin.OutPoint)
                        }
                }

                // The coin selection algorithm requires to know what
                // inputs/outputs are already present in the funding
                // transaction and what a change output would look like. Since
                // a channel funding is always either a P2WSH or P2TR output,
                // we can use just P2WSH here (both of these output types have
                // the same length). And we currently don't support specifying a
                // change output type, so we always use P2TR.
                var fundingOutputWeight input.TxWeightEstimator
                fundingOutputWeight.AddP2WSHOutput()
                changeType := P2TRChangeAddress

                var (
                        coins                []wallet.Coin
                        selectedCoins        []wallet.Coin
                        localContributionAmt btcutil.Amount
                        changeAmt            btcutil.Amount
                )

                // If outputs were specified manually then we'll take the
                // corresponding coins as basis for coin selection. Otherwise,
                // all available coins from our wallet are used.
                coins = allCoins
                if len(manuallySelectedCoins) > 0 {
                        coins = manuallySelectedCoins
                }

                // Perform coin selection over our available, unlocked unspent
                // outputs in order to find enough coins to meet the funding
                // amount requirements.
                switch {
                // If there's no funding amount at all (receiving an inbound
                // single funder request), then we don't need to perform any
                // coin selection at all.
                case r.LocalAmt == 0 && r.FundUpToMaxAmt == 0:
                        break

                // The local funding amount cannot be used in combination with
                // the funding up to some maximum amount. If that is the case
                // we return an error.
                case r.LocalAmt != 0 && r.FundUpToMaxAmt != 0:
                        return fmt.Errorf("cannot use a local funding amount " +
                                "and fundmax parameters")

                // We cannot use the subtract fees flag while using the funding
                // up to some maximum amount. If that is the case we return an
                // error.
                case r.SubtractFees && r.FundUpToMaxAmt != 0:
                        return fmt.Errorf("cannot subtract fees from local " +
                                "amount while using fundmax parameters")

                // In case this request uses funding up to some maximum amount,
                // we will call the specialized coin selection function for
                // that.
                case r.FundUpToMaxAmt != 0 && r.MinFundAmt != 0:
                        // We need to ensure that manually selected coins, which
                        // are spent entirely on the channel funding, leave
                        // enough funds in the wallet to cover for a reserve.
                        reserve := r.WalletReserve
                        if len(manuallySelectedCoins) > 0 {
                                sumCoins := func(
                                        coins []wallet.Coin) btcutil.Amount {

                                        var sum btcutil.Amount
                                        for _, coin := range coins {
                                                sum += btcutil.Amount(
                                                        coin.Value,
                                                )
                                        }

                                        return sum
                                }

                                sumManual := sumCoins(manuallySelectedCoins)
                                sumAll := sumCoins(allCoins)

                                // If sufficient reserve funds are available we
                                // don't have to provide for it during coin
                                // selection. The manually selected coins can be
                                // spent entirely on the channel funding. If
                                // the excess of coins cover the reserve
                                // partially then we have to provide for the
                                // rest during coin selection.
                                excess := sumAll - sumManual
                                if excess >= reserve {
                                        reserve = 0
                                } else {
                                        reserve -= excess
                                }
                        }

                        selectedCoins, localContributionAmt, changeAmt,
                                err = CoinSelectUpToAmount(
                                r.FeeRate, r.MinFundAmt, r.FundUpToMaxAmt,
                                reserve, w.cfg.DustLimit, coins,
                                w.cfg.CoinSelectionStrategy,
                                fundingOutputWeight, changeType,
                                DefaultMaxFeeRatio,
                        )
                        if err != nil {
                                return err
                        }

                        // Now where the actual channel capacity is determined
                        // we can check for local contribution constraints.
                        //
                        // Ensure that the remote channel reserve does not
                        // exceed 20% of the channel capacity.
                        if r.RemoteChanReserve >= localContributionAmt/5 {
                                return fmt.Errorf("remote channel reserve " +
                                        "must be less than the %%20 of the " +
                                        "channel capacity")
                        }
                        // Ensure that the initial remote balance does not
                        // exceed our local contribution as that would leave a
                        // negative balance on our side.
                        if r.PushAmt >= localContributionAmt {
                                return fmt.Errorf("amount pushed to remote " +
                                        "peer for initial state must be " +
                                        "below the local funding amount")
                        }

                // In case this request want the fees subtracted from the local
                // amount, we'll call the specialized method for that. This
                // ensures that we won't deduct more that the specified balance
                // from our wallet.
                case r.SubtractFees:
                        dustLimit := w.cfg.DustLimit
                        selectedCoins, localContributionAmt, changeAmt,
                                err = CoinSelectSubtractFees(
                                r.FeeRate, r.LocalAmt, dustLimit, coins,
                                w.cfg.CoinSelectionStrategy,
                                fundingOutputWeight, changeType,
                                DefaultMaxFeeRatio,
                        )
                        if err != nil {
                                return err
                        }

                // Otherwise do a normal coin selection where we target a given
                // funding amount.
                default:
                        dustLimit := w.cfg.DustLimit
                        localContributionAmt = r.LocalAmt
                        selectedCoins, changeAmt, err = CoinSelect(
                                r.FeeRate, r.LocalAmt, dustLimit, coins,
                                w.cfg.CoinSelectionStrategy,
                                fundingOutputWeight, changeType,
                                DefaultMaxFeeRatio,
                        )
                        if err != nil {
                                return err
                        }
                }

                // Sanity check: The addition of the outputs should not lead to the
                // creation of dust.
                if changeAmt != 0 && changeAmt < w.cfg.DustLimit {
                        return fmt.Errorf("change amount(%v) after coin "+
                                "select is below dust limit(%v)", changeAmt,
                                w.cfg.DustLimit)
                }

                // Record any change output(s) generated as a result of the
                // coin selection.
                var changeOutput *wire.TxOut
                if changeAmt != 0 {
                        changeAddr, err := r.ChangeAddr()
                        if err != nil {
                                return err
                        }
                        changeScript, err := txscript.PayToAddrScript(changeAddr)
                        if err != nil {
                                return err
                        }

                        changeOutput = &wire.TxOut{
                                Value:    int64(changeAmt),
                                PkScript: changeScript,
                        }
                }

                // Lock the selected coins. These coins are now "reserved",
                // this prevents concurrent funding requests from referring to
                // and this double-spending the same set of coins.
                for _, coin := range selectedCoins {
                        outpoint := coin.OutPoint

                        _, err = w.cfg.CoinLeaser.LeaseOutput(
                                LndInternalLockID, outpoint,
                                DefaultReservationTimeout,
                        )
                        if err != nil {
                                return err
                        }
                }

                newIntent := &FullIntent{
                        ShimIntent: ShimIntent{
                                localFundingAmt:  localContributionAmt,
                                remoteFundingAmt: r.RemoteAmt,
                                musig2:           r.Musig2,
                                tapscriptRoot:    r.TapscriptRoot,
                        },
                        InputCoins: selectedCoins,
                        coinLeaser: w.cfg.CoinLeaser,
                        coinSource: w.cfg.CoinSource,
                        signer:     w.cfg.Signer,
                }

                if changeOutput != nil {
                        newIntent.ChangeOutputs = []*wire.TxOut{changeOutput}
                }

                intent = newIntent

                return nil
        })
        if err != nil {
                return nil, err
        }

        return intent, nil
}

// outpointsToCoins maps outpoints to coins in our wallet iff these coins are
// existent and returns an error otherwise.
func outpointsToCoins(outpoints []wire.OutPoint,
        coinFromOutPoint func(wire.OutPoint) (*wallet.Coin, error)) (
        []wallet.Coin, error) {

        var selectedCoins []wallet.Coin
        for _, outpoint := range outpoints {
                coin, err := coinFromOutPoint(
                        outpoint,
                )
                if err != nil {
                        return nil, err
                }
                selectedCoins = append(
                        selectedCoins, *coin,
                )
        }

        return selectedCoins, nil
}

// FundingTxAvailable is an empty method that an assembler can implement to
// signal to callers that its able to provide the funding transaction for the
// channel via the intent it returns.
//
// NOTE: This method is a part of the FundingTxAssembler interface.
func (w *WalletAssembler) FundingTxAvailable() {}

// A compile-time assertion to ensure the WalletAssembler meets the
// FundingTxAssembler interface.
var _ FundingTxAssembler = (*WalletAssembler)(nil)

// SegWitV0DualFundingPrevOutputFetcher is a txscript.PrevOutputFetcher that
// knows about local and remote funding inputs.
//
// TODO(guggero): Support dual funding with p2tr inputs, currently only segwit
// v0 inputs are supported.
type SegWitV0DualFundingPrevOutputFetcher struct {
        local  CoinSource
        remote *txscript.MultiPrevOutFetcher
}

var _ txscript.PrevOutputFetcher = (*SegWitV0DualFundingPrevOutputFetcher)(nil)

// NewSegWitV0DualFundingPrevOutputFetcher creates a new
// txscript.PrevOutputFetcher from the given local and remote inputs.
//
// NOTE: Since the actual pkScript and amounts aren't passed in, this will just
// make sure that nothing will panic when creating a SegWit v0 sighash. But this
// code will NOT WORK for transactions that spend any _remote_ Taproot inputs!
// So basically dual-funding won't work with Taproot inputs unless the UTXO info
// is exchanged between the peers.
func NewSegWitV0DualFundingPrevOutputFetcher(localSource CoinSource,
        remoteInputs []*wire.TxIn) txscript.PrevOutputFetcher {

        remote := txscript.NewMultiPrevOutFetcher(nil)
        for _, inp := range remoteInputs {
                // We add an empty output to prevent the sighash calculation
                // from panicking. But this will always detect the inputs as
                // SegWig v0!
                remote.AddPrevOut(inp.PreviousOutPoint, &wire.TxOut{})
        }
        return &SegWitV0DualFundingPrevOutputFetcher{
                local:  localSource,
                remote: remote,
        }
}

// FetchPrevOutput attempts to fetch the previous output referenced by the
// passed outpoint.
//
// NOTE: This is a part of the txscript.PrevOutputFetcher interface.
func (d *SegWitV0DualFundingPrevOutputFetcher) FetchPrevOutput(
        op wire.OutPoint) *wire.TxOut {

        // Try the local source first. This will return nil if our internal
        // wallet doesn't know the outpoint.
        coin, err := d.local.CoinFromOutPoint(op)
        if err == nil && coin != nil {
                return &coin.TxOut
        }

        // Fall back to the remote
        return d.remote.FetchPrevOutput(op)
}

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