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sweep: allow specified outputs to sweep tx

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We'll use this to attach an output for the value reserved for anchor
commitments fee bumping if the user requests a send_all transaction.
This commit is contained in:
Johan T. Halseth
2021-01-14 11:49:27 +01:00
parent eaf97418be
commit 185ba77f8e
7 changed files with 80 additions and 33 deletions
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48
sweep/txgenerator.go
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@@ -131,12 +131,14 @@ func generateInputPartitionings(sweepableInputs []txInput,
return sets, nil
}
// createSweepTx builds a signed tx spending the inputs to a the output script.
func createSweepTx(inputs []input.Input, outputPkScript []byte,
currentBlockHeight uint32, feePerKw chainfee.SatPerKWeight,
dustLimit btcutil.Amount, signer input.Signer) (*wire.MsgTx, error) {
// createSweepTx builds a signed tx spending the inputs to the given outputs,
// sending any leftover change to the change script.
func createSweepTx(inputs []input.Input, outputs []*wire.TxOut,
changePkScript []byte, currentBlockHeight uint32,
feePerKw chainfee.SatPerKWeight, dustLimit btcutil.Amount,
signer input.Signer) (*wire.MsgTx, error) {
inputs, estimator := getWeightEstimate(inputs, feePerKw)
inputs, estimator := getWeightEstimate(inputs, outputs, feePerKw)
txFee := estimator.fee()
var (
@@ -210,6 +212,16 @@ func createSweepTx(inputs []input.Input, outputPkScript []byte,
totalInput += btcutil.Amount(o.SignDesc().Output.Value)
}
// Add the outputs given, if any.
for _, o := range outputs {
sweepTx.AddTxOut(o)
requiredOutput += btcutil.Amount(o.Value)
}
if requiredOutput+txFee > totalInput {
return nil, fmt.Errorf("insufficient input to create sweep tx")
}
// The value remaining after the required output and fees, go to
// change. Not that this fee is what we would have to pay in case the
// sweep tx has a change output.
@@ -219,7 +231,7 @@ func createSweepTx(inputs []input.Input, outputPkScript []byte,
// above.
if changeAmt >= dustLimit {
sweepTx.AddTxOut(&wire.TxOut{
PkScript: outputPkScript,
PkScript: changePkScript,
Value: int64(changeAmt),
})
} else {
@@ -287,8 +299,8 @@ func createSweepTx(inputs []input.Input, outputPkScript []byte,
// getWeightEstimate returns a weight estimate for the given inputs.
// Additionally, it returns counts for the number of csv and cltv inputs.
func getWeightEstimate(inputs []input.Input, feeRate chainfee.SatPerKWeight) (
[]input.Input, *weightEstimator) {
func getWeightEstimate(inputs []input.Input, outputs []*wire.TxOut,
feeRate chainfee.SatPerKWeight) ([]input.Input, *weightEstimator) {
// We initialize a weight estimator so we can accurately asses the
// amount of fees we need to pay for this sweep transaction.
@@ -297,13 +309,19 @@ func getWeightEstimate(inputs []input.Input, feeRate chainfee.SatPerKWeight) (
// be more efficient on-chain.
weightEstimate := newWeightEstimator(feeRate)
// Our sweep transaction will pay to a single segwit p2wkh address,
// ensure it contributes to our weight estimate. If the inputs we add
// have required TxOuts, then this will be our change address. Note
// that if we have required TxOuts, we might end up creating a sweep tx
// without a change output. It is okay to add the change output to the
// weight estimate regardless, since the estimated fee will just be
// subtracted from this already dust output, and trimmed.
// Our sweep transaction will always pay to the given set of outputs.
for _, o := range outputs {
weightEstimate.addOutput(o)
}
// If there is any leftover change after paying to the given outputs
// and required outputs, it will go to a single segwit p2wkh address.
// This will be our change address, so ensure it contributes to our
// weight estimate. Note that if we have other outputs, we might end up
// creating a sweep tx without a change output. It is okay to add the
// change output to the weight estimate regardless, since the estimated
// fee will just be subtracted from this already dust output, and
// trimmed.
weightEstimate.addP2WKHOutput()
// For each output, use its witness type to determine the estimate