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lnwallet: state transition from correct node during test, remove panic

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The unit test TestNewBreachRetributionSkipsDustHtlcs triggered a state
transition from Bob, even though it was Alice that had added the HTLCs.
This is wrong since it will lead to Bob still owing Alice a commitment,
which is not accounted for in the unit tests.

We add a sanity check that the add heights has been set for all entries
found in the logs, and return an error otherwise. This won't happen
during normal operation, but it does reveal the mistake in the unit
test, which is fixed by making Alice trigger the transition.

In addition we resolve a long standing TODO by removing a (purposeful)
panic in the channel state machine. Old version of lnd had a bug that
could lead to the parent entries being lost during channel restore. A
panic was added to get to the bottom of if.

This is now fixed, so new nodes shouldn't encounter it. However, to be
on the safe side, instead of panicking we return an error back to
gracefully exit the channel state machine.
This commit is contained in:
Johan T. Halseth 2020-02-12 11:10:19 +01:00
parent e114f58b5e
commit 5943e5d8b1
No known key found for this signature in database
GPG Key ID: 15BAADA29DA20D26
2 changed files with 52 additions and 22 deletions
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70
lnwallet/channel.go
View File

@ -2374,9 +2374,12 @@ func (lc *LightningChannel) fetchCommitmentView(remoteChain bool,
// these balances will be *before* taking a commitment fee from the
// initiator.
htlcView := lc.fetchHTLCView(theirLogIndex, ourLogIndex)
ourBalance, theirBalance, _, filteredHTLCView := lc.computeView(
ourBalance, theirBalance, _, filteredHTLCView, err := lc.computeView(
htlcView, remoteChain, true,
)
if err != nil {
return nil, err
}
feePerKw := filteredHTLCView.feePerKw
// Actually generate unsigned commitment transaction for this view.
@ -2444,7 +2447,7 @@ func fundingTxIn(chanState *channeldb.OpenChannel) wire.TxIn {
// method.
func (lc *LightningChannel) evaluateHTLCView(view *htlcView, ourBalance,
theirBalance *lnwire.MilliSatoshi, nextHeight uint64,
remoteChain, mutateState bool) *htlcView {
remoteChain, mutateState bool) (*htlcView, error) {
// We initialize the view's fee rate to the fee rate of the unfiltered
// view. If any fee updates are found when evaluating the view, it will
@ -2463,7 +2466,7 @@ func (lc *LightningChannel) evaluateHTLCView(view *htlcView, ourBalance,
// fetchParentEntry is a helper method that will fetch the parent of
// entry from the corresponding update log.
fetchParentEntry := func(entry *PaymentDescriptor,
remoteLog bool) *PaymentDescriptor {
remoteLog bool) (*PaymentDescriptor, error) {
var (
updateLog *updateLog
@ -2481,23 +2484,34 @@ func (lc *LightningChannel) evaluateHTLCView(view *htlcView, ourBalance,
addEntry := updateLog.lookupHtlc(entry.ParentIndex)
switch {
// We check if the parent entry is not found at this point. We
// have seen this happening a few times and panic with some
// addtitional info to figure out why.
// TODO(halseth): remove when bug is fixed.
// We check if the parent entry is not found at this point.
// This could happen for old versions of lnd, and we return an
// error to gracefully shut down the state machine if such an
// entry is still in the logs.
case addEntry == nil:
panic(fmt.Sprintf("unable to find parent entry %d "+
"in %v update log: %v\nUpdatelog: %v",
return nil, fmt.Errorf("unable to find parent entry "+
"%d in %v update log: %v\nUpdatelog: %v",
entry.ParentIndex, logName,
newLogClosure(func() string {
return spew.Sdump(entry)
}), newLogClosure(func() string {
return spew.Sdump(updateLog)
}),
))
)
// The parent add height should never be zero at this point. If
// that's the case we probably forgot to send a new commitment.
case remoteChain && addEntry.addCommitHeightRemote == 0:
return nil, fmt.Errorf("parent entry %d for update %d "+
"had zero remote add height", entry.ParentIndex,
entry.LogIndex)
case !remoteChain && addEntry.addCommitHeightLocal == 0:
return nil, fmt.Errorf("parent entry %d for update %d "+
"had zero local add height", entry.ParentIndex,
entry.LogIndex)
}
return addEntry
return addEntry, nil
}
// First we run through non-add entries in both logs, populating the
@ -2526,7 +2540,10 @@ func (lc *LightningChannel) evaluateHTLCView(view *htlcView, ourBalance,
lc.channelState.TotalMSatReceived += entry.Amount
}
addEntry := fetchParentEntry(entry, true)
addEntry, err := fetchParentEntry(entry, true)
if err != nil {
return nil, err
}
skipThem[addEntry.HtlcIndex] = struct{}{}
processRemoveEntry(entry, ourBalance, theirBalance,
@ -2556,7 +2573,10 @@ func (lc *LightningChannel) evaluateHTLCView(view *htlcView, ourBalance,
lc.channelState.TotalMSatSent += entry.Amount
}
addEntry := fetchParentEntry(entry, false)
addEntry, err := fetchParentEntry(entry, false)
if err != nil {
return nil, err
}
skipUs[addEntry.HtlcIndex] = struct{}{}
processRemoveEntry(entry, ourBalance, theirBalance,
@ -2587,7 +2607,7 @@ func (lc *LightningChannel) evaluateHTLCView(view *htlcView, ourBalance,
newView.theirUpdates = append(newView.theirUpdates, entry)
}
return newView
return newView, nil
}
// processAddEntry evaluates the effect of an add entry within the HTLC log.
@ -3109,9 +3129,12 @@ func (lc *LightningChannel) validateCommitmentSanity(theirLogCounter,
ourInitialBalance := commitChain.tip().ourBalance
theirInitialBalance := commitChain.tip().theirBalance
ourBalance, theirBalance, commitWeight, filteredView := lc.computeView(
ourBalance, theirBalance, commitWeight, filteredView, err := lc.computeView(
view, remoteChain, false,
)
if err != nil {
return err
}
feePerKw := filteredView.feePerKw
// Calculate the commitment fee, and subtract it from the initiator's
@ -3202,7 +3225,7 @@ func (lc *LightningChannel) validateCommitmentSanity(theirLogCounter,
// First check that the remote updates won't violate it's channel
// constraints.
err := validateUpdates(
err = validateUpdates(
filteredView.theirUpdates, &lc.channelState.RemoteChanCfg,
)
if err != nil {
@ -3698,7 +3721,7 @@ func (lc *LightningChannel) ProcessChanSyncMsg(
// HTLCs will be set to the next commitment height.
func (lc *LightningChannel) computeView(view *htlcView, remoteChain bool,
updateState bool) (lnwire.MilliSatoshi, lnwire.MilliSatoshi, int64,
*htlcView) {
*htlcView, error) {
commitChain := lc.localCommitChain
dustLimit := lc.channelState.LocalChanCfg.DustLimit
@ -3737,8 +3760,11 @@ func (lc *LightningChannel) computeView(view *htlcView, remoteChain bool,
// channel constraints to the final commitment state. If any fee
// updates are found in the logs, the commitment fee rate should be
// changed, so we'll also set the feePerKw to this new value.
filteredHTLCView := lc.evaluateHTLCView(view, &ourBalance,
filteredHTLCView, err := lc.evaluateHTLCView(view, &ourBalance,
&theirBalance, nextHeight, remoteChain, updateState)
if err != nil {
return 0, 0, 0, nil, err
}
feePerKw := filteredHTLCView.feePerKw
// Now go through all HTLCs at this stage, to calculate the total
@ -3762,7 +3788,7 @@ func (lc *LightningChannel) computeView(view *htlcView, remoteChain bool,
}
totalCommitWeight := input.CommitWeight + totalHtlcWeight
return ourBalance, theirBalance, totalCommitWeight, filteredHTLCView
return ourBalance, theirBalance, totalCommitWeight, filteredHTLCView, nil
}
// genHtlcSigValidationJobs generates a series of signatures verification jobs
@ -5967,8 +5993,12 @@ func (lc *LightningChannel) availableBalance() (lnwire.MilliSatoshi, int64) {
lc.localUpdateLog.logIndex)
// Then compute our current balance for that view.
ourBalance, _, commitWeight, filteredView :=
ourBalance, _, commitWeight, filteredView, err :=
lc.computeView(htlcView, false, false)
if err != nil {
lc.log.Errorf("Unable to fetch available balance: %v", err)
return 0, 0
}
// If we are the channel initiator, we must remember to subtract the
// commitment fee from our available balance.

4
lnwallet/channel_test.go
View File

@ -5922,8 +5922,8 @@ func TestNewBreachRetributionSkipsDustHtlcs(t *testing.T) {
// With the HTLC's applied to both update logs, we'll initiate a state
// transition from Alice.
if err := ForceStateTransition(bobChannel, aliceChannel); err != nil {
t.Fatalf("unable to complete bob's state transition: %v", err)
if err := ForceStateTransition(aliceChannel, bobChannel); err != nil {
t.Fatalf("unable to complete alice's state transition: %v", err)
}
// At this point, we'll capture the current state number, as well as