lnd.xprv/contractcourt/htlc_success_resolver.go

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package contractcourt
import (
"encoding/binary"
"io"
"github.com/btcsuite/btcd/wire"
"github.com/davecgh/go-spew/spew"
"github.com/lightningnetwork/lnd/input"
"github.com/lightningnetwork/lnd/lntypes"
"github.com/lightningnetwork/lnd/lnwallet"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/lightningnetwork/lnd/sweep"
)
// htlcSuccessResolver is a resolver that's capable of sweeping an incoming
// HTLC output on-chain. If this is the remote party's commitment, we'll sweep
// it directly from the commitment output *immediately*. If this is our
// commitment, we'll first broadcast the success transaction, then send it to
// the incubator for sweeping. That's it, no need to send any clean up
// messages.
//
// TODO(roasbeef): don't need to broadcast?
type htlcSuccessResolver struct {
// htlcResolution is the incoming HTLC resolution for this HTLC. It
// contains everything we need to properly resolve this HTLC.
htlcResolution lnwallet.IncomingHtlcResolution
// outputIncubating returns true if we've sent the output to the output
// incubator (utxo nursery).
outputIncubating bool
// resolved reflects if the contract has been fully resolved or not.
resolved bool
// broadcastHeight is the height that the original contract was
// broadcast to the main-chain at. We'll use this value to bound any
// historical queries to the chain for spends/confirmations.
broadcastHeight uint32
// payHash is the payment hash of the original HTLC extended to us.
payHash lntypes.Hash
// sweepTx will be non-nil if we've already crafted a transaction to
// sweep a direct HTLC output. This is only a concern if we're sweeping
// from the commitment transaction of the remote party.
//
// TODO(roasbeef): send off to utxobundler
sweepTx *wire.MsgTx
// htlcAmt is the original amount of the htlc, not taking into
// account any fees that may have to be paid if it goes on chain.
htlcAmt lnwire.MilliSatoshi
ResolverKit
}
// ResolverKey returns an identifier which should be globally unique for this
// particular resolver within the chain the original contract resides within.
//
// NOTE: Part of the ContractResolver interface.
func (h *htlcSuccessResolver) ResolverKey() []byte {
// The primary key for this resolver will be the outpoint of the HTLC
// on the commitment transaction itself. If this is our commitment,
// then the output can be found within the signed success tx,
// otherwise, it's just the ClaimOutpoint.
var op wire.OutPoint
if h.htlcResolution.SignedSuccessTx != nil {
op = h.htlcResolution.SignedSuccessTx.TxIn[0].PreviousOutPoint
} else {
op = h.htlcResolution.ClaimOutpoint
}
key := newResolverID(op)
return key[:]
}
// Resolve attempts to resolve an unresolved incoming HTLC that we know the
// preimage to. If the HTLC is on the commitment of the remote party, then we'll
// simply sweep it directly. Otherwise, we'll hand this off to the utxo nursery
// to do its duty. There is no need to make a call to the invoice registry
// anymore. Every HTLC has already passed through the incoming contest resolver
// and in there the invoice was already marked as settled.
//
// TODO(roasbeef): create multi to batch
//
// NOTE: Part of the ContractResolver interface.
func (h *htlcSuccessResolver) Resolve() (ContractResolver, error) {
// If we're already resolved, then we can exit early.
if h.resolved {
return nil, nil
}
// If we don't have a success transaction, then this means that this is
// an output on the remote party's commitment transaction.
if h.htlcResolution.SignedSuccessTx == nil {
// If we don't already have the sweep transaction constructed,
// we'll do so and broadcast it.
if h.sweepTx == nil {
log.Infof("%T(%x): crafting sweep tx for "+
"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.
inp := input.MakeHtlcSucceedInput(
&h.htlcResolution.ClaimOutpoint,
&h.htlcResolution.SweepSignDesc,
h.htlcResolution.Preimage[:],
h.broadcastHeight,
)
// 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.
//
// TODO: Use time-based sweeper and result chan.
var err error
h.sweepTx, err = h.Sweeper.CreateSweepTx(
[]input.Input{&inp},
sweep.FeePreference{
ConfTarget: sweepConfTarget,
}, 0,
)
if err != nil {
return nil, err
}
log.Infof("%T(%x): crafted sweep tx=%v", h,
h.payHash[:], spew.Sdump(h.sweepTx))
// With the sweep transaction signed, we'll now
// Checkpoint our state.
if err := h.Checkpoint(h); err != nil {
log.Errorf("unable to Checkpoint: %v", err)
return nil, err
}
}
// Regardless of whether an existing transaction was found or newly
// constructed, we'll broadcast the sweep transaction to the
// network.
err := h.PublishTx(h.sweepTx)
if err != nil {
log.Infof("%T(%x): unable to publish tx: %v",
h, h.payHash[:], err)
return nil, err
}
// With the sweep transaction broadcast, we'll wait for its
// confirmation.
sweepTXID := h.sweepTx.TxHash()
sweepScript := h.sweepTx.TxOut[0].PkScript
confNtfn, err := h.Notifier.RegisterConfirmationsNtfn(
&sweepTXID, sweepScript, 1, h.broadcastHeight,
)
if err != nil {
return nil, err
}
log.Infof("%T(%x): waiting for sweep tx (txid=%v) to be "+
"confirmed", h, h.payHash[:], sweepTXID)
select {
case _, ok := <-confNtfn.Confirmed:
if !ok {
return nil, errResolverShuttingDown
}
case <-h.Quit:
return nil, errResolverShuttingDown
}
// Once the transaction has received a sufficient number of
// confirmations, we'll mark ourselves as fully resolved and exit.
h.resolved = true
return nil, h.Checkpoint(h)
}
log.Infof("%T(%x): broadcasting second-layer transition tx: %v",
h, h.payHash[:], spew.Sdump(h.htlcResolution.SignedSuccessTx))
// We'll now broadcast the second layer transaction so we can kick off
// the claiming process.
//
// TODO(roasbeef): after changing sighashes send to tx bundler
err := h.PublishTx(h.htlcResolution.SignedSuccessTx)
if err != nil {
return nil, err
}
// Otherwise, this is an output on our commitment transaction. In this
// case, we'll send it to the incubator, but only if we haven't already
// done so.
if !h.outputIncubating {
log.Infof("%T(%x): incubating incoming htlc output",
h, h.payHash[:])
err := h.IncubateOutputs(
h.ChanPoint, nil, nil, &h.htlcResolution,
h.broadcastHeight,
)
if err != nil {
return nil, err
}
h.outputIncubating = true
if err := h.Checkpoint(h); err != nil {
log.Errorf("unable to Checkpoint: %v", err)
return nil, err
}
}
// To wrap this up, we'll wait until the second-level transaction has
// been spent, then fully resolve the contract.
spendNtfn, err := h.Notifier.RegisterSpendNtfn(
&h.htlcResolution.ClaimOutpoint,
h.htlcResolution.SweepSignDesc.Output.PkScript,
h.broadcastHeight,
)
if err != nil {
return nil, err
}
log.Infof("%T(%x): waiting for second-level HTLC output to be spent "+
"after csv_delay=%v", h, h.payHash[:], h.htlcResolution.CsvDelay)
select {
case _, ok := <-spendNtfn.Spend:
if !ok {
return nil, errResolverShuttingDown
}
case <-h.Quit:
return nil, errResolverShuttingDown
}
h.resolved = true
return nil, h.Checkpoint(h)
}
// Stop signals the resolver to cancel any current resolution processes, and
// suspend.
//
// NOTE: Part of the ContractResolver interface.
func (h *htlcSuccessResolver) Stop() {
close(h.Quit)
}
// IsResolved returns true if the stored state in the resolve is fully
// resolved. In this case the target output can be forgotten.
//
// NOTE: Part of the ContractResolver interface.
func (h *htlcSuccessResolver) IsResolved() bool {
return h.resolved
}
// Encode writes an encoded version of the ContractResolver into the passed
// Writer.
//
// NOTE: Part of the ContractResolver interface.
func (h *htlcSuccessResolver) Encode(w io.Writer) error {
// First we'll encode our inner HTLC resolution.
if err := encodeIncomingResolution(w, &h.htlcResolution); err != nil {
return err
}
// Next, we'll write out the fields that are specified to the contract
// resolver.
if err := binary.Write(w, endian, h.outputIncubating); err != nil {
return err
}
if err := binary.Write(w, endian, h.resolved); err != nil {
return err
}
if err := binary.Write(w, endian, h.broadcastHeight); err != nil {
return err
}
if _, err := w.Write(h.payHash[:]); err != nil {
return err
}
return nil
}
// Decode attempts to decode an encoded ContractResolver from the passed Reader
// instance, returning an active ContractResolver instance.
//
// NOTE: Part of the ContractResolver interface.
func (h *htlcSuccessResolver) Decode(r io.Reader) error {
// First we'll decode our inner HTLC resolution.
if err := decodeIncomingResolution(r, &h.htlcResolution); err != nil {
return err
}
// Next, we'll read all the fields that are specified to the contract
// resolver.
if err := binary.Read(r, endian, &h.outputIncubating); err != nil {
return err
}
if err := binary.Read(r, endian, &h.resolved); err != nil {
return err
}
if err := binary.Read(r, endian, &h.broadcastHeight); err != nil {
return err
}
if _, err := io.ReadFull(r, h.payHash[:]); err != nil {
return err
}
return nil
}
// AttachResolverKit should be called once a resolved is successfully decoded
// from its stored format. This struct delivers a generic tool kit that
// resolvers need to complete their duty.
//
// NOTE: Part of the ContractResolver interface.
func (h *htlcSuccessResolver) AttachResolverKit(r ResolverKit) {
h.ResolverKit = r
}
// A compile time assertion to ensure htlcSuccessResolver meets the
// ContractResolver interface.
var _ ContractResolver = (*htlcSuccessResolver)(nil)