lnwallet: extract coin selection to distinct method
This is required since for single funder channels, we don’t contribute any funds so we don’t need to select any change or coins for input into the funding transaction.
This commit is contained in:
Olaoluwa Osuntokun
parent
e62fc414cb
commit
d52955b146
@ -452,104 +452,21 @@ func (l *LightningWallet) handleFundingReserveRequest(req *initFundingReserveMsg
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ourContribution.CsvDelay = req.csvDelay
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reservation.partialState.LocalCsvDelay = req.csvDelay
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// We hold the coin select mutex while querying for outputs, and
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// performing coin selection in order to avoid inadvertent double spends
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// accross funding transactions.
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// NOTE: We don't use defer her so we can properly release the lock
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// when we encounter an error condition.
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l.coinSelectMtx.Lock()
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// TODO(roasbeef): check if balance is insufficient, if so then select
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// on two channels, one is a time.After that will bail out with
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// insuffcient funds, the other is a notification that the balance has
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// been updated make(chan struct{}, 1).
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// Find all unlocked unspent witness outputs with greater than 6
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// confirmations.
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// TODO(roasbeef): make 6 a config paramter?
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unspentOutputs, err := l.ListUnspentWitness(6)
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if err != nil {
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l.coinSelectMtx.Unlock()
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req.err <- err
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req.resp <- nil
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return
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}
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// Convert the outputs to coins for coin selection below.
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coins, err := outputsToCoins(unspentOutputs)
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if err != nil {
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l.coinSelectMtx.Unlock()
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req.err <- err
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req.resp <- nil
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return
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}
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// Peform coin selection over our available, unlocked unspent outputs
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// in order to find enough coins to meet the funding amount requirements.
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//
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// TODO(roasbeef): Should extend coinset with optimal coin selection
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// heuristics for our use case.
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// TODO(roasbeef): factor in fees..
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// TODO(roasbeef): possibly integrate the fee prediction project? if
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// results hold up...
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// NOTE: this current selection assumes "priority" is still a thing.
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selector := &coinset.MaxValueAgeCoinSelector{
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MaxInputs: 10,
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MinChangeAmount: 10000,
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}
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selectedCoins, err := selector.CoinSelect(req.fundingAmount, coins)
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if err != nil {
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l.coinSelectMtx.Unlock()
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req.err <- err
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req.resp <- nil
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return
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}
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// Lock the selected coins. These coins are now "reserved", this
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// prevents concurrent funding requests from referring to and this
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// double-spending the same set of coins.
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ourContribution.Inputs = make([]*wire.TxIn, len(selectedCoins.Coins()))
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for i, coin := range selectedCoins.Coins() {
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txout := wire.NewOutPoint(coin.Hash(), coin.Index())
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l.LockOutpoint(*txout)
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// Empty sig script, we'll actually sign if this reservation is
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// queued up to be completed (the other side accepts).
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outPoint := wire.NewOutPoint(coin.Hash(), coin.Index())
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ourContribution.Inputs[i] = wire.NewTxIn(outPoint, nil, nil)
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}
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l.coinSelectMtx.Unlock()
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// Create some possibly neccessary change outputs.
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selectedTotalValue := coinset.NewCoinSet(selectedCoins.Coins()).TotalValue()
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if selectedTotalValue > req.fundingAmount {
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ourContribution.ChangeOutputs = make([]*wire.TxOut, 1)
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// Change is necessary. Query for an available change address to
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// send the remainder to.
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changeAddr, err := l.NewChangeAddress(waddrmgr.DefaultAccountNum,
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waddrmgr.WitnessPubKey)
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if err != nil {
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// If we're on the receiving end of a single funder channel then we
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// don't need to perform any coin selection. Otherwise, attempt to
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// obtain enough coins to meet the required funding amount.
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if req.fundingAmount != 0 {
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if err := l.selectCoinsAndChange(req.fundingAmount, ourContribution); err != nil {
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req.err <- err
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req.resp <- nil
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return
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}
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changeAddrScript, err := txscript.PayToAddrScript(changeAddr)
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if err != nil {
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req.err <- err
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req.resp <- nil
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return
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}
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changeAmount := selectedTotalValue - req.fundingAmount
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ourContribution.ChangeOutputs[0] = wire.NewTxOut(int64(changeAmount),
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changeAddrScript)
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}
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// TODO(roasbeef): re-calculate fees here to minFeePerKB, may need more inputs
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// Grab two fresh keys from out HD chain, one will be used for the
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// Grab two fresh keys from our HD chain, one will be used for the
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// multi-sig funding transaction, and the other for the commitment
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// transaction.
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multiSigKey, err := l.getNextRawKey()
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@ -1094,6 +1011,103 @@ func (l *LightningWallet) ListUnspentWitness(minConfs int32) ([]*btcjson.ListUns
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return witnessOutputs, nil
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}
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// selectCoinsAndChange performs coin selection in order to obtain witness
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// outputs which sum to at least 'numCoins' amount of satoshis. If coin
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// selection is succesful/possible, then the selected coins are available within
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// the passed contribution's inputs. If necessary, a change address will also be
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// generated.
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// TODO(roasbeef): remove hardcoded fees and req'd confs for outputs.
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func (l *LightningWallet) selectCoinsAndChange(numCoins btcutil.Amount,
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contribution *ChannelContribution) error {
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// We hold the coin select mutex while querying for outputs, and
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// performing coin selection in order to avoid inadvertent double spends
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// accross funding transactions.
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// NOTE: We don't use defer her so we can properly release the lock
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// when we encounter an error condition.
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l.coinSelectMtx.Lock()
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// TODO(roasbeef): check if balance is insufficient, if so then select
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// on two channels, one is a time.After that will bail out with
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// insuffcient funds, the other is a notification that the balance has
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// been updated make(chan struct{}, 1).
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// Find all unlocked unspent witness outputs with greater than 1
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// confirmation.
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// TODO(roasbeef): make num confs a configuration paramter
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unspentOutputs, err := l.ListUnspentWitness(1)
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if err != nil {
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l.coinSelectMtx.Unlock()
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return err
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}
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// Convert the outputs to coins for coin selection below.
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coins, err := outputsToCoins(unspentOutputs)
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if err != nil {
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l.coinSelectMtx.Unlock()
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return err
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}
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// Peform coin selection over our available, unlocked unspent outputs
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// in order to find enough coins to meet the funding amount requirements.
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//
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// TODO(roasbeef): Should extend coinset with optimal coin selection
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// heuristics for our use case.
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// NOTE: this current selection assumes "priority" is still a thing.
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selector := &coinset.MaxValueAgeCoinSelector{
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MaxInputs: 10,
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MinChangeAmount: 10000,
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}
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// TODO(roasbeef): don't hardcode fee...
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totalWithFee := numCoins + 10000
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selectedCoins, err := selector.CoinSelect(totalWithFee, coins)
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if err != nil {
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l.coinSelectMtx.Unlock()
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return err
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}
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// Lock the selected coins. These coins are now "reserved", this
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// prevents concurrent funding requests from referring to and this
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// double-spending the same set of coins.
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contribution.Inputs = make([]*wire.TxIn, len(selectedCoins.Coins()))
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for i, coin := range selectedCoins.Coins() {
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txout := wire.NewOutPoint(coin.Hash(), coin.Index())
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l.LockOutpoint(*txout)
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// Empty sig script, we'll actually sign if this reservation is
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// queued up to be completed (the other side accepts).
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outPoint := wire.NewOutPoint(coin.Hash(), coin.Index())
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contribution.Inputs[i] = wire.NewTxIn(outPoint, nil, nil)
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}
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l.coinSelectMtx.Unlock()
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// Create some possibly neccessary change outputs.
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selectedTotalValue := coinset.NewCoinSet(selectedCoins.Coins()).TotalValue()
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if selectedTotalValue > totalWithFee {
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// Change is necessary. Query for an available change address to
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// send the remainder to.
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contribution.ChangeOutputs = make([]*wire.TxOut, 1)
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changeAddr, err := l.NewChangeAddress(waddrmgr.DefaultAccountNum,
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waddrmgr.WitnessPubKey)
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if err != nil {
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return err
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}
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changeAddrScript, err := txscript.PayToAddrScript(changeAddr)
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if err != nil {
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return err
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}
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changeAmount := selectedTotalValue - totalWithFee
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contribution.ChangeOutputs[0] = wire.NewTxOut(int64(changeAmount),
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changeAddrScript)
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}
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// TODO(roasbeef): re-calculate fees here to minFeePerKB, may need more inputs
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return nil
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}
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type WaddrmgrEncryptorDecryptor struct {
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M *waddrmgr.Manager
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}
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