This commit moves the responsibility for closing local and remote force
closes in the database from the chain watcher to the channel arbitrator.
We do this because we previously would close the channel in the
database, before sending the event to the channel arbitrator. This could
lead to a situation where the channel was marked closed, but the channel
arbitrator didn't receive the event before shutdown. As we don't listen
for chain events for channels that are closed, those channels would be
stuck in the pending close state forever, as the channel arbitrator
state machine wouldn't progress.
We fix this by letting the ChannelArbitrator close the channel in the
database. After the contract resolutions are logged (in the state
callback before transitioning to StateContractClosed) we mark the
channel closed in the database. This way we make sure that it is marked
closed only if the resolutions have been successfully persisted.
This commit makes the chainwatcher attempt to dispatch a remote close
when it detects a remote state with a state number higher than our
known remote state. This can mean that we lost some state, and we check
the database for (hopefully) a data loss commit point retrieved during
channel sync with the remote peer. If this commit point is found in the
database we use it to try to recover our funds from the commitment.
In this commit, we alter cooperative channel closures to also use
MarkChannelResolved in order to unify the logic for the different types
of channel closures.
This commit makes the dispatchCooperativeClose method mark the channel
fully closed directly, without registering for confirmation
notifications first. We can do this as recent changes to the
contractcourt changed the definition of a closed channel in the database
to have had its closing tx confirmed, and we only dispatch the
cooperative close once the transaction has 1 confirmation.
We also rename the markChanClosed method to notifyChanClosed, to more
clearly indicate that the ChainArbitrator no longer has to mark the
channel fully closed in the database.
This commit changes how the ChainWatcher notifies the breachArbiter
about a channel breach. Instead of assuming the breachArbiter is among
the clients subscibing to channel events, it will call a new method
contractBreach(), and assume the breachArbiter has reliably gotten the
breach info when this method returns with a non-nil error.
Since the breachArbiter was the only sybsystem having a sync chain
subsciption, we also remove the (now) unused syncDispatch option.
This move the log message "channel marked pending-closed" to the point
where the channel actually has been marked pending closed, instead of
before the database transaction has been done.
This commit removes the for loop in the closeObserver, as it wasn't
serving any purpose. After receiving a spend notification we would
return, breaking out of the loop. When getting a quit signal we would
also return, making the loop only do one iteration in any case.
This commit makes clients subscribing to channel events that are marked
"sync dispatch" _not_ being deleted from the list of clients when they
call Cancel(). Instead a go routine will be launched that will send an
error on every read of the ProcessACK channel.
This fixes a race in handing off the breach info while lnd was shutting
down. The breach arbiter could end up being shut down (and calling
Cancel()) before while the ChainWatcher was in the process of
dispatching a breach. Since the breach arbiter no longer was among the
registered clients at this point, the ChainWatcher would assume the
breach was handed off successfully, and mark the channel as pending
closed. When lnd now was restarted, the breach arbiter would not know
about the breach, and the ChainWatcher wouldn't attempt to re-dispatch,
as it was already marked as pending closed.
This commit changes the ChainWatcher to only send a chain event in case
the various spends are _confirmed_ on-chain, not only seen on the
network.
A consequence of this is that we now give the ChainWatcher the
responsibility of marking the channel closed when the closing tx is
confirmed, instead of the ChannelArbitrator.
This commit adds a new method dispatchLocalClose, which will be called
in case our commitment is detected to spend the funding transaction. In
this case LocalUnilateralCloseInfo will be sent on the
LocalUnilateralClosure channel to all subscribers.
The UnilateralClosure channel is renamed to RemoteUnilateralClosure for
consistency.
In this commit, we fix a long standing bug where at times a co-op
channel closure wouldn't be properly marked as fully closed in the
database. The culprit was a re-occurring code flaw we've seen many times
in the codebase: a closure variable that closes over a loop iterator
variable. Before this instance, I assumed that this could only pop up
when goroutines bind to the loop iterator within a closure. However,
this instance is the exact same issue, but within a regular closure that
has _delayed_ execution. As the closure doesn't execute until long after
the loop has finished executing, it may still be holding onto the _last_
item the loop iterator variable was assigned to.
The fix for this issue is very simple: re-assign the channel point
before creating the closure. Without this fix, we would go to call
db.MarkChanFullyClosed on a channel that may not have yet actually be in
the pending close state, causing all executions to fail.
Fixes#1054.
Fixes#1056.
Fixes#1075.
In this commit, we modify the way that notifications are dispatched
within the chainWatcher. Before we would *always* wait for an ack back
before we started to clean up he database state. This would at times
lead to deadlocks. To remedy this, we now allow callers to decide if
they want notifications to be sync or not. The only current caller that
requires this is the breach arbiter.
In this commit, we modify the interaction between the chanCloser
sub-system and the chain notifier all together. This fixes a series of
bugs as before this commit, we wouldn’t be able to detect if the remote
party actually broadcasted *any* of the transactions that we signed off
upon. This would be rejected to the user by having a “zombie” channel
close that would never actually be resolved.
Rather than the chanCloser watching for on-chain closes, we’ll now open
up a co-op close context to the chainWatcher (via a layer of
indirection via the ChainArbitrator), and report to it all possible
closes that we’ve signed. The chainWatcher will then be able to launch
a goroutine to properly update the database state once any of the
possible closure transactions confirms.
In this commit, we extend the chainWatcher to be able to automatically
detect co-op closes of the channel. With this change, it’s now fully
encompassed so able to detect all types of closes on-chain. We detect a
co-op close due to the sequence number being finalized, as well as
paying to us directly in a regular p2wkh-like output.
In this commit, we add a new struct to the package, the chainWatcher.
The duty of this struct is to replace the functionality that was
previously implemented by the closeObserver of each channel. Rather
than the source of notification being tied to the lifetime of a
particular object, it’s now delegated to a persistent object that will
be around for the entire lifetime of the channel (until it’s closed).
This will serve to greatly simplify the code, and eliminate a large
class of bugs.
