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Merge pull request #1618 from cfromknecht/resolver-subscribe-order

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contractcourt/contract_resolvers: fix subscribe preimage race
This commit is contained in:
Olaoluwa Osuntokun 2018-07-25 20:29:14 -07:00 committed by GitHub
commit b8c3987fd7
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1 changed files with 20 additions and 15 deletions
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35
contractcourt/contract_resolvers.go
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@ -8,12 +8,12 @@ import (
"io"
"io/ioutil"
"github.com/btcsuite/btcd/txscript"
"github.com/btcsuite/btcd/wire"
"github.com/davecgh/go-spew/spew"
"github.com/lightningnetwork/lnd/chainntnfs"
"github.com/lightningnetwork/lnd/lnwallet"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/btcsuite/btcd/txscript"
"github.com/btcsuite/btcd/wire"
)
var (
@ -1012,20 +1012,13 @@ func (h *htlcIncomingContestResolver) Resolve() (ContractResolver, error) {
copy(h.htlcResolution.Preimage[:], preimage[:])
}
// If the HTLC hasn't yet expired, then we'll query to see if we
// already know the preimage.
preimage, ok := h.PreimageDB.LookupPreimage(h.payHash[:])
if ok {
// If we do, then this means we can claim the HTLC! However,
// we don't know how to ourselves, so we'll return our inner
// resolver which has the knowledge to do so.
applyPreimage(preimage[:])
return &h.htlcSuccessResolver, nil
}
// If the HTLC hasn't expired yet, then we may still be able to claim
// it if we learn of the pre-image, so we'll wait and see if it pops
// up, or the HTLC times out.
// it if we learn of the pre-image, so we'll subscribe to the preimage
// database to see if it turns up, or the HTLC times out.
//
// NOTE: This is done BEFORE opportunistically querying the db, to
// ensure the preimage can't be delivered between querying and
// registering for the preimage subscription.
preimageSubscription := h.PreimageDB.SubscribeUpdates()
blockEpochs, err := h.Notifier.RegisterBlockEpochNtfn()
if err != nil {
@ -1035,6 +1028,18 @@ func (h *htlcIncomingContestResolver) Resolve() (ContractResolver, error) {
preimageSubscription.CancelSubscription()
blockEpochs.Cancel()
}()
// With the epochs and preimage subscriptions initialized, we'll query
// to see if we already know the preimage.
preimage, ok := h.PreimageDB.LookupPreimage(h.payHash[:])
if ok {
// If we do, then this means we can claim the HTLC! However,
// we don't know how to ourselves, so we'll return our inner
// resolver which has the knowledge to do so.
applyPreimage(preimage[:])
return &h.htlcSuccessResolver, nil
}
for {
select {