diff --git a/contractcourt/htlc_incoming_contest_resolver.go b/contractcourt/htlc_incoming_contest_resolver.go index 35765b653..3fc4400ad 100644 --- a/contractcourt/htlc_incoming_contest_resolver.go +++ b/contractcourt/htlc_incoming_contest_resolver.go @@ -78,6 +78,37 @@ func (h *htlcIncomingContestResolver) processFinalHtlcFail() error { return nil } +// Launch will call the inner resolver's launch method if the preimage can be +// found, otherwise it's a no-op. +func (h *htlcIncomingContestResolver) Launch() error { + // NOTE: we don't mark this resolver as launched as the inner resolver + // will set it when it's launched. + if h.launched { + h.log.Tracef("already launched") + return nil + } + + h.log.Debugf("launching contest resolver...") + + // Query the preimage and apply it if we already know it. + applied, err := h.findAndapplyPreimage() + if err != nil { + return err + } + + // No preimage found, leave it to be handled by the resolver. + if !applied { + return nil + } + + h.log.Debugf("found preimage for htlc=%x, launching success resolver", + h.htlc.RHash) + + // Once we've applied the preimage, we'll launch the inner resolver to + // attempt to claim the HTLC. + return h.htlcSuccessResolver.Launch() +} + // Resolve attempts to resolve this contract. As we don't yet know of the // preimage for the contract, we'll wait for one of two things to happen: // @@ -94,6 +125,7 @@ func (h *htlcIncomingContestResolver) Resolve() (ContractResolver, error) { // If we're already full resolved, then we don't have anything further // to do. if h.resolved { + h.log.Errorf("already resolved") return nil, nil } @@ -112,8 +144,7 @@ func (h *htlcIncomingContestResolver) Resolve() (ContractResolver, error) { // now. payload, nextHopOnionBlob, err := h.decodePayload() if err != nil { - log.Debugf("ChannelArbitrator(%v): cannot decode payload of "+ - "htlc %v", h.ChanPoint, h.HtlcPoint()) + h.log.Debugf("cannot decode payload of htlc %v", h.HtlcPoint()) // If we've locked in an htlc with an invalid payload on our // commitment tx, we don't need to resolve it. The other party @@ -188,65 +219,6 @@ func (h *htlcIncomingContestResolver) Resolve() (ContractResolver, error) { return nil, h.Checkpoint(h, report) } - // applyPreimage is a helper function that will populate our internal - // resolver with the preimage we learn of. This should be called once - // the preimage is revealed so the inner resolver can properly complete - // its duties. The error return value indicates whether the preimage - // was properly applied. - applyPreimage := func(preimage lntypes.Preimage) error { - // Sanity check to see if this preimage matches our htlc. At - // this point it should never happen that it does not match. - if !preimage.Matches(h.htlc.RHash) { - return errors.New("preimage does not match hash") - } - - // Update htlcResolution with the matching preimage. - h.htlcResolution.Preimage = preimage - - log.Infof("%T(%v): applied preimage=%v", h, - h.htlcResolution.ClaimOutpoint, preimage) - - isSecondLevel := h.htlcResolution.SignedSuccessTx != nil - - // If we didn't have to go to the second level to claim (this - // is the remote commitment transaction), then we don't need to - // modify our canned witness. - if !isSecondLevel { - return nil - } - - isTaproot := txscript.IsPayToTaproot( - h.htlcResolution.SignedSuccessTx.TxOut[0].PkScript, - ) - - // If this is our commitment transaction, then we'll need to - // populate the witness for the second-level HTLC transaction. - switch { - // For taproot channels, the witness for sweeping with success - // looks like: - // - - // - // - // So we'll insert it at the 3rd index of the witness. - case isTaproot: - //nolint:lll - h.htlcResolution.SignedSuccessTx.TxIn[0].Witness[2] = preimage[:] - - // Within the witness for the success transaction, the - // preimage is the 4th element as it looks like: - // - // * <0> - // - // We'll populate it within the witness, as since this - // was a "contest" resolver, we didn't yet know of the - // preimage. - case !isTaproot: - h.htlcResolution.SignedSuccessTx.TxIn[0].Witness[3] = preimage[:] - } - - return nil - } - // Define a closure to process htlc resolutions either directly or // triggered by future notifications. processHtlcResolution := func(e invoices.HtlcResolution) ( @@ -258,7 +230,7 @@ func (h *htlcIncomingContestResolver) Resolve() (ContractResolver, error) { // If the htlc resolution was a settle, apply the // preimage and return a success resolver. case *invoices.HtlcSettleResolution: - err := applyPreimage(resolution.Preimage) + err := h.applyPreimage(resolution.Preimage) if err != nil { return nil, err } @@ -380,7 +352,9 @@ func (h *htlcIncomingContestResolver) Resolve() (ContractResolver, error) { // However, we don't know how to ourselves, so we'll // return our inner resolver which has the knowledge to // do so. - if err := applyPreimage(preimage); err != nil { + h.log.Debugf("Found preimage for htlc=%x", h.htlc.RHash) + + if err := h.applyPreimage(preimage); err != nil { return nil, err } @@ -399,7 +373,10 @@ func (h *htlcIncomingContestResolver) Resolve() (ContractResolver, error) { continue } - if err := applyPreimage(preimage); err != nil { + h.log.Debugf("Received preimage for htlc=%x", + h.htlc.RHash) + + if err := h.applyPreimage(preimage); err != nil { return nil, err } @@ -446,6 +423,76 @@ func (h *htlcIncomingContestResolver) Resolve() (ContractResolver, error) { } } +// applyPreimage is a helper function that will populate our internal resolver +// with the preimage we learn of. This should be called once the preimage is +// revealed so the inner resolver can properly complete its duties. The error +// return value indicates whether the preimage was properly applied. +func (h *htlcIncomingContestResolver) applyPreimage( + preimage lntypes.Preimage) error { + + // Sanity check to see if this preimage matches our htlc. At this point + // it should never happen that it does not match. + if !preimage.Matches(h.htlc.RHash) { + return errors.New("preimage does not match hash") + } + + // We may already have the preimage since both the `Launch` and + // `Resolve` methods will look for it. + if h.htlcResolution.Preimage != lntypes.ZeroHash { + h.log.Debugf("already applied preimage for htlc=%x", + h.htlc.RHash) + + return nil + } + + // Update htlcResolution with the matching preimage. + h.htlcResolution.Preimage = preimage + + log.Infof("%T(%v): applied preimage=%v", h, + h.htlcResolution.ClaimOutpoint, preimage) + + isSecondLevel := h.htlcResolution.SignedSuccessTx != nil + + // If we didn't have to go to the second level to claim (this + // is the remote commitment transaction), then we don't need to + // modify our canned witness. + if !isSecondLevel { + return nil + } + + isTaproot := txscript.IsPayToTaproot( + h.htlcResolution.SignedSuccessTx.TxOut[0].PkScript, + ) + + // If this is our commitment transaction, then we'll need to + // populate the witness for the second-level HTLC transaction. + switch { + // For taproot channels, the witness for sweeping with success + // looks like: + // - + // + // + // So we'll insert it at the 3rd index of the witness. + case isTaproot: + //nolint:lll + h.htlcResolution.SignedSuccessTx.TxIn[0].Witness[2] = preimage[:] + + // Within the witness for the success transaction, the + // preimage is the 4th element as it looks like: + // + // * <0> + // + // We'll populate it within the witness, as since this + // was a "contest" resolver, we didn't yet know of the + // preimage. + case !isTaproot: + //nolint:lll + h.htlcResolution.SignedSuccessTx.TxIn[0].Witness[3] = preimage[:] + } + + return nil +} + // report returns a report on the resolution state of the contract. func (h *htlcIncomingContestResolver) report() *ContractReport { // No locking needed as these values are read-only. @@ -472,6 +519,7 @@ func (h *htlcIncomingContestResolver) report() *ContractReport { // // NOTE: Part of the ContractResolver interface. func (h *htlcIncomingContestResolver) Stop() { + h.log.Debugf("stopping...") close(h.quit) } @@ -571,3 +619,77 @@ func (h *htlcIncomingContestResolver) decodePayload() (*hop.Payload, // A compile time assertion to ensure htlcIncomingContestResolver meets the // ContractResolver interface. var _ htlcContractResolver = (*htlcIncomingContestResolver)(nil) + +// findAndapplyPreimage attempts to find the preimage for the incoming HTLC. If +// found, it will be applied. +func (h *htlcIncomingContestResolver) findAndapplyPreimage() (bool, error) { + // Query to see if we already know the preimage. + preimage, ok := h.PreimageDB.LookupPreimage(h.htlc.RHash) + + // If the preimage is known, we'll apply it. + if ok { + if err := h.applyPreimage(preimage); err != nil { + return false, err + } + + // Successfully applied the preimage, we can now return. + return true, nil + } + + // First try to parse the payload. + payload, _, err := h.decodePayload() + if err != nil { + h.log.Errorf("Cannot decode payload of htlc %v", h.HtlcPoint()) + + // If we cannot decode the payload, we will return a nil error + // and let it to be handled in `Resolve`. + return false, nil + } + + // Exit early if this is not the exit hop, which means we are not the + // payment receiver and don't have preimage. + if payload.FwdInfo.NextHop != hop.Exit { + return false, nil + } + + // Notify registry that we are potentially resolving as an exit hop + // on-chain. If this HTLC indeed pays to an existing invoice, the + // invoice registry will tell us what to do with the HTLC. This is + // identical to HTLC resolution in the link. + circuitKey := models.CircuitKey{ + ChanID: h.ShortChanID, + HtlcID: h.htlc.HtlcIndex, + } + + // Try get the resolution - if it doesn't give us a resolution + // immediately, we'll assume we don't know it yet and let the `Resolve` + // handle the waiting. + // + // NOTE: we use a nil subscriber here and a zero current height as we + // are only interested in the settle resolution. + // + // TODO(yy): move this logic to link and let the preimage be accessed + // via the preimage beacon. + resolution, err := h.Registry.NotifyExitHopHtlc( + h.htlc.RHash, h.htlc.Amt, h.htlcExpiry, 0, + circuitKey, nil, nil, payload, + ) + if err != nil { + return false, err + } + + res, ok := resolution.(*invoices.HtlcSettleResolution) + + // Exit early if it's not a settle resolution. + if !ok { + return false, nil + } + + // Otherwise we have a settle resolution, apply the preimage. + err = h.applyPreimage(res.Preimage) + if err != nil { + return false, err + } + + return true, nil +} diff --git a/contractcourt/htlc_incoming_contest_resolver_test.go b/contractcourt/htlc_incoming_contest_resolver_test.go index 649f0adf3..9b3204f2e 100644 --- a/contractcourt/htlc_incoming_contest_resolver_test.go +++ b/contractcourt/htlc_incoming_contest_resolver_test.go @@ -5,11 +5,13 @@ import ( "io" "testing" + "github.com/btcsuite/btcd/wire" sphinx "github.com/lightningnetwork/lightning-onion" "github.com/lightningnetwork/lnd/chainntnfs" "github.com/lightningnetwork/lnd/channeldb" "github.com/lightningnetwork/lnd/channeldb/models" "github.com/lightningnetwork/lnd/htlcswitch/hop" + "github.com/lightningnetwork/lnd/input" "github.com/lightningnetwork/lnd/invoices" "github.com/lightningnetwork/lnd/kvdb" "github.com/lightningnetwork/lnd/lnmock" @@ -356,6 +358,7 @@ func newIncomingResolverTestContext(t *testing.T, isExit bool) *incomingResolver return nil }, + Sweeper: newMockSweeper(), }, PutResolverReport: func(_ kvdb.RwTx, _ *channeldb.ResolverReport) error { @@ -374,10 +377,16 @@ func newIncomingResolverTestContext(t *testing.T, isExit bool) *incomingResolver }, } + res := lnwallet.IncomingHtlcResolution{ + SweepSignDesc: input.SignDescriptor{ + Output: &wire.TxOut{}, + }, + } + c.resolver = &htlcIncomingContestResolver{ htlcSuccessResolver: &htlcSuccessResolver{ contractResolverKit: *newContractResolverKit(cfg), - htlcResolution: lnwallet.IncomingHtlcResolution{}, + htlcResolution: res, htlc: channeldb.HTLC{ Amt: lnwire.MilliSatoshi(testHtlcAmount), RHash: testResHash, @@ -386,6 +395,7 @@ func newIncomingResolverTestContext(t *testing.T, isExit bool) *incomingResolver }, htlcExpiry: testHtlcExpiry, } + c.resolver.initLogger("htlcIncomingContestResolver") return c } @@ -395,6 +405,10 @@ func (i *incomingResolverTestContext) resolve() { i.resolveErr = make(chan error, 1) go func() { var err error + + err = i.resolver.Launch() + require.NoError(i.t, err) + i.nextResolver, err = i.resolver.Resolve() i.resolveErr <- err }() diff --git a/invoices/invoiceregistry.go b/invoices/invoiceregistry.go index 9d54b6ad8..34e22fb3b 100644 --- a/invoices/invoiceregistry.go +++ b/invoices/invoiceregistry.go @@ -1806,6 +1806,10 @@ func (i *InvoiceRegistry) notifyHodlSubscribers(htlcResolution HtlcResolution) { func (i *InvoiceRegistry) hodlSubscribe(subscriber chan<- interface{}, circuitKey CircuitKey) { + if subscriber == nil { + return + } + i.hodlSubscriptionsMux.Lock() defer i.hodlSubscriptionsMux.Unlock()