package contractcourt import ( "encoding/binary" "io" "github.com/btcsuite/btcd/chaincfg/chainhash" "github.com/btcsuite/btcd/wire" "github.com/btcsuite/btcutil" "github.com/davecgh/go-spew/spew" "github.com/lightningnetwork/lnd/channeldb" "github.com/lightningnetwork/lnd/input" "github.com/lightningnetwork/lnd/lnwallet" "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 // 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 // htlc contains information on the htlc that we are resolving on-chain. htlc channeldb.HTLC contractResolverKit } // newSuccessResolver instanties a new htlc success resolver. func newSuccessResolver(res lnwallet.IncomingHtlcResolution, broadcastHeight uint32, htlc channeldb.HTLC, resCfg ResolverConfig) *htlcSuccessResolver { return &htlcSuccessResolver{ contractResolverKit: *newContractResolverKit(resCfg), htlcResolution: res, broadcastHeight: broadcastHeight, htlc: htlc, } } // 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.htlc.RHash[:]) // 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, h.htlcResolution.CsvDelay, ) // 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.htlc.RHash[:], 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.htlc.RHash[:], 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.htlc.RHash[:], 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 // Checkpoint the resolver, and write the outcome to disk. return nil, h.checkpointClaim( &sweepTXID, channeldb.ResolverOutcomeClaimed, ) } log.Infof("%T(%x): broadcasting second-layer transition tx: %v", h, h.htlc.RHash[:], 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.htlc.RHash[:]) err := h.IncubateOutputs( h.ChanPoint, 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.htlc.RHash[:], h.htlcResolution.CsvDelay) var spendTxid *chainhash.Hash select { case spend, ok := <-spendNtfn.Spend: if !ok { return nil, errResolverShuttingDown } spendTxid = spend.SpenderTxHash case <-h.quit: return nil, errResolverShuttingDown } h.resolved = true return nil, h.checkpointClaim( spendTxid, channeldb.ResolverOutcomeClaimed, ) } // checkpointClaim checkpoints the success resolver with the reports it needs. // If this htlc was claimed two stages, it will write reports for both stages, // otherwise it will just write for the single htlc claim. func (h *htlcSuccessResolver) checkpointClaim(spendTx *chainhash.Hash, outcome channeldb.ResolverOutcome) error { // Create a resolver report for claiming of the htlc itself. amt := btcutil.Amount(h.htlcResolution.SweepSignDesc.Output.Value) reports := []*channeldb.ResolverReport{ { OutPoint: h.htlcResolution.ClaimOutpoint, Amount: amt, ResolverType: channeldb.ResolverTypeIncomingHtlc, ResolverOutcome: outcome, SpendTxID: spendTx, }, } // If we have a success tx, we append a report to represent our first // stage claim. if h.htlcResolution.SignedSuccessTx != nil { // If the SignedSuccessTx is not nil, we are claiming the htlc // in two stages, so we need to create a report for the first // stage transaction as well. spendTx := h.htlcResolution.SignedSuccessTx spendTxID := spendTx.TxHash() report := &channeldb.ResolverReport{ OutPoint: spendTx.TxIn[0].PreviousOutPoint, Amount: h.htlc.Amt.ToSatoshis(), ResolverType: channeldb.ResolverTypeIncomingHtlc, ResolverOutcome: channeldb.ResolverOutcomeFirstStage, SpendTxID: &spendTxID, } reports = append(reports, report) } // Finally, we checkpoint the resolver with our report(s). return h.Checkpoint(h, reports...) } // 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.htlc.RHash[:]); err != nil { return err } return nil } // newSuccessResolverFromReader attempts to decode an encoded ContractResolver // from the passed Reader instance, returning an active ContractResolver // instance. func newSuccessResolverFromReader(r io.Reader, resCfg ResolverConfig) ( *htlcSuccessResolver, error) { h := &htlcSuccessResolver{ contractResolverKit: *newContractResolverKit(resCfg), } // First we'll decode our inner HTLC resolution. if err := decodeIncomingResolution(r, &h.htlcResolution); err != nil { return nil, 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 nil, err } if err := binary.Read(r, endian, &h.resolved); err != nil { return nil, err } if err := binary.Read(r, endian, &h.broadcastHeight); err != nil { return nil, err } if _, err := io.ReadFull(r, h.htlc.RHash[:]); err != nil { return nil, err } return h, nil } // Supplement adds additional information to the resolver that is required // before Resolve() is called. // // NOTE: Part of the htlcContractResolver interface. func (h *htlcSuccessResolver) Supplement(htlc channeldb.HTLC) { h.htlc = htlc } // HtlcPoint returns the htlc's outpoint on the commitment tx. // // NOTE: Part of the htlcContractResolver interface. func (h *htlcSuccessResolver) HtlcPoint() wire.OutPoint { return h.htlcResolution.HtlcPoint() } // A compile time assertion to ensure htlcSuccessResolver meets the // ContractResolver interface. var _ htlcContractResolver = (*htlcSuccessResolver)(nil)