@ -8,30 +8,27 @@ import (
"github.com/lightningnetwork/lnd/lnwallet"
)
// UtxoSweeper provides the functionality to generate sweep txes. The plan is to
// extend UtxoSweeper in the future to also manage the actual sweeping process
// by itself.
// UtxoSweeper provides the functionality to generate sweep txes. The plan is
// to extend UtxoSweeper in the future to also manage the actual sweeping
// process by itself.
type UtxoSweeper struct {
cfg * UtxoSweeperConfig
}
// UtxoSweeperConfig contains dependencies of UtxoSweeper.
type UtxoSweeperConfig struct {
// GenSweepScript generates a P2WKH script belonging to the wallet where
// funds can be swept.
// GenSweepScript generates a P2WKH script belonging to the wallet
// where funds can be swept.
GenSweepScript func ( ) ( [ ] byte , error )
// Estimator is used when crafting sweep transactions to estimate the
// necessary fee relative to the expected size of the sweep transaction.
// necessary fee relative to the expected size of the sweep
// transaction.
Estimator lnwallet . FeeEstimator
// Signer is used by the sweeper to generate valid witnesses at the
// time the incubated outputs need to be spent.
Signer lnwallet . Signer
// ConfTarget specifies a target for the number of blocks until an
// initial confirmation.
ConfTarget uint32
}
// New returns a new UtxoSweeper instance.
@ -45,18 +42,18 @@ func New(cfg *UtxoSweeperConfig) *UtxoSweeper {
// spends from them. This method also makes an accurate fee estimate before
// generating the required witnesses.
//
// The created transaction has a single output sending all the funds back to the
// source wallet, after accounting for the fee estimate.
// The created transaction has a single output sending all the funds back to
// the source wallet, after accounting for the fee estimate.
//
// The value of currentBlockHeight argument will be set as the tx locktime. This
// function assumes that all CLTV inputs will be unlocked after
// The value of currentBlockHeight argument will be set as the tx locktime.
// This function assumes that all CLTV inputs will be unlocked after
// currentBlockHeight. Reasons not to use the maximum of all actual CLTV expiry
// values of the inputs:
//
// - Make handling re-orgs easier.
// - Thwart future possible fee sniping attempts.
// - Make us blend in with the bitcoind wallet.
func ( s * UtxoSweeper ) CreateSweepTx ( inputs [ ] Input ,
func ( s * UtxoSweeper ) CreateSweepTx ( inputs [ ] Input , confTarget uint32 ,
currentBlockHeight uint32 ) ( * wire . MsgTx , error ) {
// Generate the receiving script to which the funds will be swept.
@ -66,7 +63,7 @@ func (s *UtxoSweeper) CreateSweepTx(inputs []Input,
}
// Using the txn weight estimate, compute the required txn fee.
feePerKw , err := s . cfg . Estimator . EstimateFeePerKW ( s . cfg . C onfTarget)
feePerKw , err := s . cfg . Estimator . EstimateFeePerKW ( c onfTarget)
if err != nil {
return nil , err
}
@ -100,7 +97,6 @@ func (s *UtxoSweeper) CreateSweepTx(inputs []Input,
// Add all inputs to the sweep transaction. Ensure that for each
// csvInput, we set the sequence number properly.
for _ , input := range inputs {
sweepTx . AddTxIn ( & wire . TxIn {
PreviousOutPoint : * input . OutPoint ( ) ,
@ -110,9 +106,10 @@ func (s *UtxoSweeper) CreateSweepTx(inputs []Input,
// Before signing the transaction, check to ensure that it meets some
// basic validity requirements.
// TODO(conner): add more control to sanity checks, allowing us to delay
// spending "problem" outputs, e.g. possibly batching with other classes
// if fees are too low.
//
// TODO(conner): add more control to sanity checks, allowing us to
// delay spending "problem" outputs, e.g. possibly batching with other
// classes if fees are too low.
btx := btcutil . NewTx ( sweepTx )
if err := blockchain . CheckTransactionSanity ( btx ) ; err != nil {
return nil , err
@ -149,13 +146,11 @@ func (s *UtxoSweeper) CreateSweepTx(inputs []Input,
// getWeightEstimate returns a weight estimate for the given inputs.
// Additionally, it returns counts for the number of csv and cltv inputs.
func ( s * UtxoSweeper ) getWeightEstimate ( inputs [ ] Input ) ( [ ] Input , int64 , int , int ) {
// Create a transaction which sweeps all the newly mature outputs into
// an output controlled by the wallet.
// We initialize a weight estimator so we can accurately asses the
// amount of fees we need to pay for this sweep transaction.
//
// TODO(roasbeef): can be more intelligent about buffering outputs to
// be more efficient on-chain.
var weightEstimate lnwallet . TxWeightEstimator
// Our sweep transaction will pay to a single segwit p2wkh address,
@ -165,10 +160,10 @@ func (s *UtxoSweeper) getWeightEstimate(inputs []Input) ([]Input, int64, int, in
// For each output, use its witness type to determine the estimate
// weight of its witness, and add it to the proper set of spendable
// outputs.
csvCount := 0
cltvCount := 0
var sweepInputs [ ] Input
var (
sweepInputs [ ] Input
csvCount , cltvCount int
)
for i := range inputs {
input := inputs [ i ]
Olaoluwa Osuntokun
6 years ago