multi: modify sweeper.CreateSweepTx to accept conf target, style changes

In this commit, we modify the newly introduced UtxoSweeper.CreateSweepTx
to accept the confirmation target as a param of the method rather than a
struct level variable. We do this as this allows each caller to decide
at sweep time, what the fee rate should be, rather than using a global
value that is meant to work in all scenarios. For example, anytime
we're sweeping an output with a CLTV lock that's has a dependant
transaction we need to sweep/cancel, we may require a higher fee rate
than a regular force close with a CSV output.

contractcourt/contract_resolvers.go

@@ -5,10 +5,11 @@ import (
 	"crypto/sha256"
 	"encoding/binary"
 	"fmt"
-	"github.com/lightningnetwork/lnd/sweep"
 	"io"
 	"io/ioutil"
 
+	"github.com/lightningnetwork/lnd/sweep"
+
 	"github.com/btcsuite/btcd/wire"
 	"github.com/davecgh/go-spew/spew"
 	"github.com/lightningnetwork/lnd/chainntnfs"
@@ -20,6 +21,12 @@ var (
 	endian = binary.BigEndian
 )
 
+const (
+	// sweepConfTarget is the default number of blocks that we'll use as a
+	// confirmation target when sweeping.
+	sweepConfTarget = 6
+)
+
 // ContractResolver is an interface which packages a state machine which is
 // able to carry out the necessary steps required to fully resolve a Bitcoin
 // contract on-chain. Resolvers are fully encodable to ensure callers are able
@@ -446,19 +453,27 @@ func (h *htlcSuccessResolver) Resolve() (ContractResolver, error) {
 				"incoming+remote htlc confirmed", h,
 				h.payHash[:])
 
+			// Before we can craft out sweeping transaction, we
+			// need to create an input which contains all the items
+			// required to add this input to a sweeping transaction,
+			// and generate a witness.
 			input := sweep.MakeHtlcSucceedInput(
 				&h.htlcResolution.ClaimOutpoint,
 				&h.htlcResolution.SweepSignDesc,
 				h.htlcResolution.Preimage[:],
 			)
 
+			// With the input created, we can now generate the full
+			// sweep transaction, that we'll use to move these
+			// coins back into the backing wallet.
+			//
+			// TODO: Set tx lock time to current block height
+			// instead of zero. Will be taken care of once sweeper
+			// implementation is complete.
 			var err error
-
-			// TODO: Set tx lock time to current block height instead of
-			// zero. Will be taken care of once sweeper implementation is
-			// complete.
 			h.sweepTx, err = h.Sweeper.CreateSweepTx(
-				[]sweep.Input{&input}, 0)
+				[]sweep.Input{&input}, sweepConfTarget, 0,
+			)
 			if err != nil {
 				return nil, err
 			}
@@ -1216,16 +1231,26 @@ func (c *commitSweepResolver) Resolve() (ContractResolver, error) {
 	// If the sweep transaction isn't already generated, and the remote
 	// party broadcast the commitment transaction then we'll create it now.
 	case c.sweepTx == nil && !isLocalCommitTx:
+		// As we haven't already generated the sweeping transaction,
+		// we'll now craft an input with all the information required
+		// to create a fully valid sweeping transaction to recover
+		// these coins.
 		input := sweep.MakeBaseInput(
 			&c.commitResolution.SelfOutPoint,
 			lnwallet.CommitmentNoDelay,
-			&c.commitResolution.SelfOutputSignDesc)
+			&c.commitResolution.SelfOutputSignDesc,
+		)
 
+		// With out input constructed, we'll now request that the
+		// sweeper construct a valid sweeping transaction for this
+		// input.
+		//
 		// TODO: Set tx lock time to current block height instead of
 		// zero. Will be taken care of once sweeper implementation is
 		// complete.
 		c.sweepTx, err = c.Sweeper.CreateSweepTx(
-			[]sweep.Input{&input}, 0)
+			[]sweep.Input{&input}, sweepConfTarget, 0,
+		)
 		if err != nil {
 			return nil, err
 		}

server.go

@@ -6,7 +6,6 @@ import (
 	"crypto/rand"
 	"encoding/hex"
 	"fmt"
-	"github.com/lightningnetwork/lnd/sweep"
 	"image/color"
 	"math/big"
 	"net"
@@ -16,6 +15,8 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/lightningnetwork/lnd/sweep"
+
 	"github.com/btcsuite/btcd/btcec"
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/connmgr"
@@ -59,10 +60,6 @@ const (
 	// durations exceeding this value will be eligible to have their
 	// backoffs reduced.
 	defaultStableConnDuration = 10 * time.Minute
-
-	// sweepTxConfirmationTarget assigns a confirmation target for sweep
-	// txes on which the fee calculation will be based.
-	sweepTxConfirmationTarget = 6
 )
 
 var (
@@ -591,13 +588,13 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB, cc *chainControl,
 		GenSweepScript: func() ([]byte, error) {
 			return newSweepPkScript(cc.wallet)
 		},
-		Signer:     cc.wallet.Cfg.Signer,
+		Signer: cc.wallet.Cfg.Signer,
-		ConfTarget: sweepTxConfirmationTarget,
 	})
 
 	s.utxoNursery = newUtxoNursery(&NurseryConfig{
 		ChainIO:             cc.chainIO,
 		ConfDepth:           1,
+		SweepTxConfTarget:   6,
 		FetchClosedChannels: chanDB.FetchClosedChannels,
 		FetchClosedChannel:  chanDB.FetchClosedChannel,
 		Notifier:            cc.chainNotifier,

sweep/input.go

@@ -16,9 +16,9 @@ type Input interface {
 	// be generated in order to spend this output.
 	WitnessType() lnwallet.WitnessType
 
-	// SignDesc returns a reference to a spendable output's sign descriptor,
+	// SignDesc returns a reference to a spendable output's sign
-	// which is used during signing to compute a valid witness that spends
+	// descriptor, which is used during signing to compute a valid witness
-	// this output.
+	// that spends this output.
 	SignDesc() *lnwallet.SignDescriptor
 
 	// BuildWitness returns a valid witness allowing this output to be
@@ -41,8 +41,8 @@ type inputKit struct {
 	signDesc    lnwallet.SignDescriptor
 }
 
-// OutPoint returns the breached output's identifier that is to be included as a
+// OutPoint returns the breached output's identifier that is to be included as
-// transaction input.
+// a transaction input.
 func (i *inputKit) OutPoint() *wire.OutPoint {
 	return &i.outpoint
 }
@@ -67,8 +67,7 @@ type BaseInput struct {
 
 // MakeBaseInput assembles a new BaseInput that can be used to construct a
 // sweep transaction.
-func MakeBaseInput(outpoint *wire.OutPoint,
+func MakeBaseInput(outpoint *wire.OutPoint, witnessType lnwallet.WitnessType,
-	witnessType lnwallet.WitnessType,
 	signDescriptor *lnwallet.SignDescriptor) BaseInput {
 
 	return BaseInput{
@@ -82,8 +81,8 @@ func MakeBaseInput(outpoint *wire.OutPoint,
 
 // BuildWitness computes a valid witness that allows us to spend from the
 // breached output. It does so by generating the witness generation function,
-// which is parameterized primarily by the witness type and sign descriptor. The
+// which is parameterized primarily by the witness type and sign descriptor.
-// method then returns the witness computed by invoking this function.
+// The method then returns the witness computed by invoking this function.
 func (bi *BaseInput) BuildWitness(signer lnwallet.Signer, txn *wire.MsgTx,
 	hashCache *txscript.TxSigHashes, txinIdx int) ([][]byte, error) {
 
@@ -102,8 +101,8 @@ func (bi *BaseInput) BlocksToMaturity() uint32 {
 }
 
 // HtlcSucceedInput constitutes a sweep input that needs a pre-image. The input
-// is expected to reside on the commitment tx of the remote party and should not
+// is expected to reside on the commitment tx of the remote party and should
-// be a second level tx output.
+// not be a second level tx output.
 type HtlcSucceedInput struct {
 	inputKit
 
@@ -127,8 +126,8 @@ func MakeHtlcSucceedInput(outpoint *wire.OutPoint,
 }
 
 // BuildWitness computes a valid witness that allows us to spend from the
-// breached output. For HtlcSpendInput it will need to make the preimage part of
+// breached output. For HtlcSpendInput it will need to make the preimage part
-// the witness.
+// of the witness.
 func (h *HtlcSucceedInput) BuildWitness(signer lnwallet.Signer, txn *wire.MsgTx,
 	hashCache *txscript.TxSigHashes, txinIdx int) ([][]byte, error) {
 
@@ -149,6 +148,7 @@ func (h *HtlcSucceedInput) BlocksToMaturity() uint32 {
 	return 0
 }
 
-// Add compile-time constraint ensuring input structs implement Input interface.
+// Compile-time constraints to ensure each input struct implement the Input
+// interface.
 var _ Input = (*BaseInput)(nil)
 var _ Input = (*HtlcSucceedInput)(nil)

sweep/log.go

@@ -5,9 +5,9 @@ import (
 	"github.com/lightningnetwork/lnd/build"
 )
 
-// log is a logger that is initialized with no output filters.  This
+// log is a logger that is initialized with no output filters.  This means the
-// means the package will not perform any logging by default until the caller
+// package will not perform any logging by default until the caller requests
-// requests it.
+// it.
 var log btclog.Logger
 
 // The default amount of logging is none.
@@ -15,15 +15,15 @@ func init() {
 	UseLogger(build.NewSubLogger("SWPR", nil))
 }
 
-// DisableLog disables all library log output.  Logging output is disabled
+// DisableLog disables all library log output.  Logging output is disabled by
-// by default until UseLogger is called.
+// default until UseLogger is called.
 func DisableLog() {
 	UseLogger(btclog.Disabled)
 }
 
-// UseLogger uses a specified Logger to output package logging info.
+// UseLogger uses a specified Logger to output package logging info.  This
-// This should be used in preference to SetLogWriter if the caller is also
+// should be used in preference to SetLogWriter if the caller is also using
-// using btclog.
+// btclog.
 func UseLogger(logger btclog.Logger) {
 	log = logger
 }

sweep/sweeper.go

@@ -8,30 +8,27 @@ import (
 	"github.com/lightningnetwork/lnd/lnwallet"
 )
 
-// UtxoSweeper provides the functionality to generate sweep txes. The plan is to
+// UtxoSweeper provides the functionality to generate sweep txes. The plan is
-// extend UtxoSweeper in the future to also manage the actual sweeping process
+// to extend UtxoSweeper in the future to also manage the actual sweeping
-// by itself.
+// 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
+	// GenSweepScript generates a P2WKH script belonging to the wallet
-	// funds can be swept.
+	// 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
+// The created transaction has a single output sending all the funds back to
-// source wallet, after accounting for the fee estimate.
+// the source wallet, after accounting for the fee estimate.
 //
-// The value of currentBlockHeight argument will be set as the tx locktime. This
+// The value of currentBlockHeight argument will be set as the tx locktime.
-// function assumes that all CLTV inputs will be unlocked after
+// 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.ConfTarget)
+	feePerKw, err := s.cfg.Estimator.EstimateFeePerKW(confTarget)
 	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
+	// TODO(conner): add more control to sanity checks, allowing us to
-	// if fees are too low.
+	// 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) {
-
+	// We initialize a weight estimator so we can accurately asses the
-	// Create a transaction which sweeps all the newly mature outputs into
+	// amount of fees we need to pay for this sweep transaction.
-	// an output controlled by the wallet.
+	//
-
 	// 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
+	var (
-	cltvCount := 0
+		sweepInputs         []Input
-
+		csvCount, cltvCount int
-	var sweepInputs []Input
+	)
 	for i := range inputs {
 		input := inputs[i]
 

utxonursery.go

@@ -4,11 +4,12 @@ import (
 	"bytes"
 	"encoding/binary"
 	"fmt"
-	"github.com/lightningnetwork/lnd/sweep"
 	"io"
 	"sync"
 	"sync/atomic"
 
+	"github.com/lightningnetwork/lnd/sweep"
+
 	"github.com/btcsuite/btcd/txscript"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcutil"
@@ -182,6 +183,10 @@ type NurseryConfig struct {
 	// determining outputs in the chain as confirmed.
 	ConfDepth uint32
 
+	// SweepTxConfTarget assigns a confirmation target for sweep txes on
+	// which the fee calculation will be based.
+	SweepTxConfTarget uint32
+
 	// FetchClosedChannels provides access to a user's channels, such that
 	// they can be marked fully closed after incubation has concluded.
 	FetchClosedChannels func(pendingOnly bool) (
@@ -871,15 +876,15 @@ func (u *utxoNursery) graduateClass(classHeight uint32) error {
 		// generated a sweep txn for this height. Generate one if there
 		// are kindergarten outputs or cltv crib outputs to be spent.
 		if len(kgtnOutputs) > 0 {
-			sweepInputs := make([]sweep.Input,
+			sweepInputs := make([]sweep.Input, len(kgtnOutputs))
-				len(kgtnOutputs))
 			for i := range kgtnOutputs {
 				sweepInputs[i] = &kgtnOutputs[i]
 			}
 
 			finalTx, err = u.cfg.Sweeper.CreateSweepTx(
-				sweepInputs, classHeight)
+				sweepInputs, u.cfg.SweepTxConfTarget,
-
+				classHeight,
+			)
 			if err != nil {
 				utxnLog.Errorf("Failed to create sweep txn at "+
 					"height=%d", classHeight)