sweep: move tx generation to separate file
This commit is contained in:
Joost Jager
parent
e43e89514f
commit
067817f6d2
170
sweep/sweeper.go
170
sweep/sweeper.go
@ -1,11 +1,7 @@
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package sweep
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import (
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"fmt"
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"github.com/btcsuite/btcd/blockchain"
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"github.com/btcsuite/btcd/txscript"
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"github.com/btcsuite/btcd/wire"
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"github.com/btcsuite/btcutil"
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"github.com/lightningnetwork/lnd/lnwallet"
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)
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@ -69,169 +65,7 @@ func (s *UtxoSweeper) CreateSweepTx(inputs []Input, confTarget uint32,
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return nil, err
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}
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inputs, txWeight, csvCount, cltvCount := getWeightEstimate(inputs)
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log.Infof("Creating sweep transaction for %v inputs (%v CSV, %v CLTV) "+
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"using %v sat/kw", len(inputs), csvCount, cltvCount,
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int64(feePerKw))
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txFee := feePerKw.FeeForWeight(txWeight)
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// Sum up the total value contained in the inputs.
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var totalSum btcutil.Amount
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for _, o := range inputs {
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totalSum += btcutil.Amount(o.SignDesc().Output.Value)
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}
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// Sweep as much possible, after subtracting txn fees.
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sweepAmt := int64(totalSum - txFee)
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// Create the sweep transaction that we will be building. We use
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// version 2 as it is required for CSV. The txn will sweep the amount
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// after fees to the pkscript generated above.
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sweepTx := wire.NewMsgTx(2)
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sweepTx.AddTxOut(&wire.TxOut{
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PkScript: pkScript,
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Value: sweepAmt,
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})
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sweepTx.LockTime = currentBlockHeight
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// Add all inputs to the sweep transaction. Ensure that for each
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// csvInput, we set the sequence number properly.
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for _, input := range inputs {
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sweepTx.AddTxIn(&wire.TxIn{
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PreviousOutPoint: *input.OutPoint(),
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Sequence: input.BlocksToMaturity(),
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})
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}
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// Before signing the transaction, check to ensure that it meets some
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// basic validity requirements.
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//
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// TODO(conner): add more control to sanity checks, allowing us to
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// delay spending "problem" outputs, e.g. possibly batching with other
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// classes if fees are too low.
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btx := btcutil.NewTx(sweepTx)
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if err := blockchain.CheckTransactionSanity(btx); err != nil {
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return nil, err
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}
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hashCache := txscript.NewTxSigHashes(sweepTx)
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// With all the inputs in place, use each output's unique witness
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// function to generate the final witness required for spending.
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addWitness := func(idx int, tso Input) error {
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witness, err := tso.BuildWitness(
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s.cfg.Signer, sweepTx, hashCache, idx,
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)
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if err != nil {
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return err
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}
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sweepTx.TxIn[idx].Witness = witness
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return nil
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}
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// Finally we'll attach a valid witness to each csv and cltv input
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// within the sweeping transaction.
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for i, input := range inputs {
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if err := addWitness(i, input); err != nil {
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return nil, err
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}
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}
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return sweepTx, nil
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}
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// getInputWitnessSizeUpperBound returns the maximum length of the witness for
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// the given input if it would be included in a tx.
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func getInputWitnessSizeUpperBound(input Input) (int, error) {
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switch input.WitnessType() {
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// Outputs on a remote commitment transaction that pay directly
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// to us.
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case lnwallet.CommitmentNoDelay:
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return lnwallet.P2WKHWitnessSize, nil
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// Outputs on a past commitment transaction that pay directly
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// to us.
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case lnwallet.CommitmentTimeLock:
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return lnwallet.ToLocalTimeoutWitnessSize, nil
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// Outgoing second layer HTLC's that have confirmed within the
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// chain, and the output they produced is now mature enough to
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// sweep.
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case lnwallet.HtlcOfferedTimeoutSecondLevel:
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return lnwallet.ToLocalTimeoutWitnessSize, nil
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// Incoming second layer HTLC's that have confirmed within the
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// chain, and the output they produced is now mature enough to
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// sweep.
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case lnwallet.HtlcAcceptedSuccessSecondLevel:
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return lnwallet.ToLocalTimeoutWitnessSize, nil
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// An HTLC on the commitment transaction of the remote party,
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// that has had its absolute timelock expire.
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case lnwallet.HtlcOfferedRemoteTimeout:
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return lnwallet.AcceptedHtlcTimeoutWitnessSize, nil
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// An HTLC on the commitment transaction of the remote party,
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// that can be swept with the preimage.
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case lnwallet.HtlcAcceptedRemoteSuccess:
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return lnwallet.OfferedHtlcSuccessWitnessSize, nil
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}
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return 0, fmt.Errorf("unexpected witness type: %v", input.WitnessType())
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}
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// getWeightEstimate returns a weight estimate for the given inputs.
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// Additionally, it returns counts for the number of csv and cltv inputs.
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func getWeightEstimate(inputs []Input) ([]Input, int64, int, int) {
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// We initialize a weight estimator so we can accurately asses the
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// amount of fees we need to pay for this sweep transaction.
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//
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// TODO(roasbeef): can be more intelligent about buffering outputs to
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// be more efficient on-chain.
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var weightEstimate lnwallet.TxWeightEstimator
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// Our sweep transaction will pay to a single segwit p2wkh address,
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// ensure it contributes to our weight estimate.
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weightEstimate.AddP2WKHOutput()
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// For each output, use its witness type to determine the estimate
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// weight of its witness, and add it to the proper set of spendable
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// outputs.
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var (
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sweepInputs []Input
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csvCount, cltvCount int
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return createSweepTx(
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inputs, pkScript, currentBlockHeight, feePerKw, s.cfg.Signer,
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)
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for i := range inputs {
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input := inputs[i]
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size, err := getInputWitnessSizeUpperBound(input)
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if err != nil {
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log.Warn(err)
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// Skip inputs for which no weight estimate can be
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// given.
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continue
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}
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weightEstimate.AddWitnessInput(size)
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switch input.WitnessType() {
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case lnwallet.CommitmentTimeLock,
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lnwallet.HtlcOfferedTimeoutSecondLevel,
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lnwallet.HtlcAcceptedSuccessSecondLevel:
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csvCount++
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case lnwallet.HtlcOfferedRemoteTimeout:
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cltvCount++
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}
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sweepInputs = append(sweepInputs, input)
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}
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txWeight := int64(weightEstimate.Weight())
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return sweepInputs, txWeight, csvCount, cltvCount
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}
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183
sweep/txgenerator.go
Normal file
183
sweep/txgenerator.go
Normal file
@ -0,0 +1,183 @@
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package sweep
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import (
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"fmt"
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"github.com/btcsuite/btcd/blockchain"
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"github.com/btcsuite/btcd/txscript"
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"github.com/btcsuite/btcd/wire"
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"github.com/btcsuite/btcutil"
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"github.com/lightningnetwork/lnd/lnwallet"
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)
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// createSweepTx builds a signed tx spending the inputs to a the output script.
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func createSweepTx(inputs []Input, outputPkScript []byte,
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currentBlockHeight uint32, feePerKw lnwallet.SatPerKWeight,
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signer lnwallet.Signer) (*wire.MsgTx, error) {
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inputs, txWeight, csvCount, cltvCount := getWeightEstimate(inputs)
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log.Infof("Creating sweep transaction for %v inputs (%v CSV, %v CLTV) "+
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"using %v sat/kw", len(inputs), csvCount, cltvCount,
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int64(feePerKw))
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txFee := feePerKw.FeeForWeight(txWeight)
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// Sum up the total value contained in the inputs.
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var totalSum btcutil.Amount
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for _, o := range inputs {
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totalSum += btcutil.Amount(o.SignDesc().Output.Value)
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}
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// Sweep as much possible, after subtracting txn fees.
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sweepAmt := int64(totalSum - txFee)
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// Create the sweep transaction that we will be building. We use
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// version 2 as it is required for CSV. The txn will sweep the amount
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// after fees to the pkscript generated above.
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sweepTx := wire.NewMsgTx(2)
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sweepTx.AddTxOut(&wire.TxOut{
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PkScript: outputPkScript,
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Value: sweepAmt,
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})
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sweepTx.LockTime = currentBlockHeight
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// Add all inputs to the sweep transaction. Ensure that for each
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// csvInput, we set the sequence number properly.
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for _, input := range inputs {
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sweepTx.AddTxIn(&wire.TxIn{
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PreviousOutPoint: *input.OutPoint(),
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Sequence: input.BlocksToMaturity(),
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})
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}
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// Before signing the transaction, check to ensure that it meets some
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// basic validity requirements.
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//
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// TODO(conner): add more control to sanity checks, allowing us to
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// delay spending "problem" outputs, e.g. possibly batching with other
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// classes if fees are too low.
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btx := btcutil.NewTx(sweepTx)
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if err := blockchain.CheckTransactionSanity(btx); err != nil {
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return nil, err
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}
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hashCache := txscript.NewTxSigHashes(sweepTx)
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// With all the inputs in place, use each output's unique witness
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// function to generate the final witness required for spending.
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addWitness := func(idx int, tso Input) error {
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witness, err := tso.BuildWitness(
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signer, sweepTx, hashCache, idx,
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)
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if err != nil {
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return err
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}
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sweepTx.TxIn[idx].Witness = witness
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return nil
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}
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// Finally we'll attach a valid witness to each csv and cltv input
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// within the sweeping transaction.
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for i, input := range inputs {
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if err := addWitness(i, input); err != nil {
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return nil, err
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}
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}
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return sweepTx, nil
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}
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// getInputWitnessSizeUpperBound returns the maximum length of the witness for
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// the given input if it would be included in a tx.
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func getInputWitnessSizeUpperBound(input Input) (int, error) {
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switch input.WitnessType() {
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// Outputs on a remote commitment transaction that pay directly
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// to us.
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case lnwallet.CommitmentNoDelay:
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return lnwallet.P2WKHWitnessSize, nil
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// Outputs on a past commitment transaction that pay directly
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// to us.
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case lnwallet.CommitmentTimeLock:
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return lnwallet.ToLocalTimeoutWitnessSize, nil
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// Outgoing second layer HTLC's that have confirmed within the
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// chain, and the output they produced is now mature enough to
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// sweep.
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case lnwallet.HtlcOfferedTimeoutSecondLevel:
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return lnwallet.ToLocalTimeoutWitnessSize, nil
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// Incoming second layer HTLC's that have confirmed within the
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// chain, and the output they produced is now mature enough to
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// sweep.
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case lnwallet.HtlcAcceptedSuccessSecondLevel:
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return lnwallet.ToLocalTimeoutWitnessSize, nil
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// An HTLC on the commitment transaction of the remote party,
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// that has had its absolute timelock expire.
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case lnwallet.HtlcOfferedRemoteTimeout:
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return lnwallet.AcceptedHtlcTimeoutWitnessSize, nil
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// An HTLC on the commitment transaction of the remote party,
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// that can be swept with the preimage.
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case lnwallet.HtlcAcceptedRemoteSuccess:
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return lnwallet.OfferedHtlcSuccessWitnessSize, nil
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}
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return 0, fmt.Errorf("unexpected witness type: %v", input.WitnessType())
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}
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// getWeightEstimate returns a weight estimate for the given inputs.
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// Additionally, it returns counts for the number of csv and cltv inputs.
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func getWeightEstimate(inputs []Input) ([]Input, int64, int, int) {
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// We initialize a weight estimator so we can accurately asses the
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// amount of fees we need to pay for this sweep transaction.
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//
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// TODO(roasbeef): can be more intelligent about buffering outputs to
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// be more efficient on-chain.
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var weightEstimate lnwallet.TxWeightEstimator
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// Our sweep transaction will pay to a single segwit p2wkh address,
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// ensure it contributes to our weight estimate.
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weightEstimate.AddP2WKHOutput()
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// For each output, use its witness type to determine the estimate
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// weight of its witness, and add it to the proper set of spendable
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// outputs.
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var (
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sweepInputs []Input
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csvCount, cltvCount int
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)
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for i := range inputs {
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input := inputs[i]
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size, err := getInputWitnessSizeUpperBound(input)
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if err != nil {
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log.Warn(err)
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// Skip inputs for which no weight estimate can be
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// given.
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continue
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}
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weightEstimate.AddWitnessInput(size)
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switch input.WitnessType() {
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case lnwallet.CommitmentTimeLock,
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lnwallet.HtlcOfferedTimeoutSecondLevel,
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lnwallet.HtlcAcceptedSuccessSecondLevel:
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csvCount++
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case lnwallet.HtlcOfferedRemoteTimeout:
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cltvCount++
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}
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sweepInputs = append(sweepInputs, input)
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}
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txWeight := int64(weightEstimate.Weight())
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return sweepInputs, txWeight, csvCount, cltvCount
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}
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