By EZ in Releases — Oct 4, 2023

LDK v0.0.117: Improved Payment Success Rates, Bug Fixes & More

Lightning Development Kit (LDK) is a full and completely standalone Lightning implementation with supporting modules enabling greater flexibility.

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Highlights

Batch channel opens
Basic watchtower client support
Important fixes for anchor channel users
Custom HTLC TLVs
A new KVStore interface
Better payment success rates

What's new

API Updates

ProbabilisticScorer's internal models have been substantially improved,
including better decaying (#1789), a more granular historical channel
liquidity tracker (#2176) and a now-default option to make our estimate for a
channel's current liquidity nonlinear in the channel's capacity (#2547). In
total, these changes should result in improved payment success rates at the
cost of slightly worse routefinding performance.
Support for custom TLVs for recipients of HTLCs has been added (#2308).
Support for generating transactions for third-party watchtowers has been
added to ChannelMonitor/Updates (#2337).
KVStorePersister has been replaced with a more generic and featureful
KVStore interface (#2472).
A new MonitorUpdatingPersister is provided which wraps a KVStore and
implements Persist by writing differential updates rather than full
ChannelMonitors (#2359).
Batch funding of outbound channels is now supported using the new
ChannelManager::batch_funding_transaction_generated method (#2486).
ChannelManager::send_preflight_probes has been added to probe a payment's
potential paths while a user is providing approval for a payment (#2534).
Fully asynchronous ChannelMonitor updating is available as an alpha
preview. There remain a few known but incredibly rare race conditions which
may lead to loss of funds (#2112, #2169, #2562).
ChannelMonitorUpdateStatus::PermanentFailure has been removed in favor of a
new ChannelMonitorUpdateStatus::UnrecoverableError. The new variant panics
on use, rather than force-closing a channel in an unsafe manner, which the
previous variant did (#2562). Rather than panicking with the new variant,
users may wish to use the new asynchronous ChannelMonitor updating using
ChannelMonitorUpdateStatus::InProgress.
RouteParameters::max_total_routing_fee_msat was added to limit the fees
paid when routing, defaulting to 1% + 50sats when using the new
from_payment_params_and_value constructor (#2417, #2603, #2604).
Implementations of UtxoSource are now provided in lightning-block-sync.
Those running with a full node should use this to validate gossip (#2248).
LockableScore now supports read locking for parallel routefinding (#2197).
ChannelMonitor::get_spendable_outputs was added to allow for re-generation
of SpendableOutputDescriptors for a channel after they were provided via
Event::SpendableOutputs (#2609, #2624).
[u8; 32] has been replaced with a ChannelId newtype for chan ids (#2485).
NetAddress was renamed SocketAddress (#2549) and FromStr impl'd (#2134)
For no-std users, parse_onion_address was added which creates a
NetAddress from a "...onion" string and port (#2134, #2633).
HTLC information is now provided in Event::PaymentClaimed::htlcs (#2478).
The success probability used in historical penalties when scoring is now
available via historical_estimated_payment_success_probability (#2466).
RecentPaymentDetails::*::payment_id has been added (#2567).
Route now contains a RouteParameters rather than a PaymentParameters,
tracking the original arguments passed to routefinding (#2555).
Balance::*::claimable_amount_satoshis was renamed amount_satoshis (#2460)
*Features::set_*_feature_bit have been added for non-custom flags (#2522).
channel_id was added to SpendableOutputs events (#2511).
counterparty_node_id and channel_capacity_sats were added to
ChannelClosed events (#2387).
ChannelMonitor now implements Clone for Cloneable signers (#2448).
create_onion_message was added to build an onion message (#2583, #2595).
HTLCDescriptor now implements Writeable/Readable (#2571).
SpendableOutputDescriptor now implements Hash (#2602).
MonitorUpdateId now implements Debug (#2594).
Payment{Hash,Id,Preimage} now implement Display (#2492).
NodeSigner::sign_bolt12_invoice{,request} were added for future use (#2432)

Backwards Compatibility

Users migrating to the new KVStore can use a concatentation of
[{primary_namespace}/[{secondary_namespace}/]]{key} to build a key
compatible with the previous KVStorePersister interface (#2472).
Downgrading after receipt of a payment with custom HTLC TLVs may result in
unintentionally accepting payments with TLVs you do not understand (#2308).
Route objects (including pending payments) written by LDK versions prior
to 0.0.117 won't be retryable after being deserialized by LDK 0.0.117 or
above (#2555).
Users of the MonitorUpdatingPersister can upgrade seamlessly from the
default KVStore Persist implementation, however the stored
ChannelMonitors are deliberately unreadable by the default Persist. This
ensures the correct downgrade procedure is followed, which is: (#2359)

- First, make a backup copy of all channel state,
- then ensure all ChannelMonitorUpdates stored are fully applied to the
relevant ChannelMonitor,
- finally, write each full ChannelMonitor using your new Persist impl.

Bug Fixes

Anchor channels which were closed by a counterparty broadcasting its
commitment transaction (i.e. force-closing) would previously not generate a
SpendableOutputs event for our to_remote (i.e. non-HTLC-encumbered)
balance. Those with such balances available should fetch the missing
SpendableOutputDescriptors using the new
ChannelMonitor::get_spendable_outputs method (#2605).
Anchor channels may result in spurious or missing Balance entries for HTLC
balances (#2610).
ChannelManager::send_spontaneous_payment_with_retry spuriously did not
provide the recipient with enough information to claim the payment, leading
to all spontaneous payments failing (#2475).
send_spontaneous_payment_with_route was unaffected.
The keysend feature on node announcements was spuriously un-set in 0.0.112
and has been re-enabled (#2465).
Fixed several races which could lead to deadlock when force-closing a channel
(#2597). These races have not been seen in production.
The ChannelManager is persisted substantially less when it has not changed,
leading to substantially less I/O traffic for it (#2521, #2617).
Passing new block data to ChainMonitor no longer results in all other
monitor operations being blocked until it completes (#2528).
When retrying payments, any excess amount sent to the recipient in order to
meet an htlc_minimum constraint on the path is now no longer included in
the amount we send in the retry (#2575).
Several edge cases in route-finding around HTLC minimums were fixed which
could have caused invalid routes or panics when built with debug assertions
(#2570, #2575).
Several edge cases in route-finding around HTLC minimums and route hints
were fixed which would spuriously result in no route found (#2575, #2604).
The user_channel_id passed to SignerProvider::generate_channel_keys_id
for inbound channels is now correctly using the one passed to
ChannelManager::accept_inbound_channel rather than a default value (#2428).
Users of impl_writeable_tlv_based! no longer have use requirements (#2506).
No longer force-close channels when counterparties send a channel_update
with a bogus htlc_minimum_msat, which LND users can manually build (#2611).

Node Compatibility

LDK now ignores error messages generated by LND in response to a
shutdown message, avoiding force-closes due to LND bug 6039. This may
lead to non-trivial bandwidth usage with LND peers exhibiting this bug
during the cooperative shutdown process (#2507).

Security

0.0.117 fixes several loss-of-funds vulnerabilities in anchor output channels,
support for which was added in 0.0.116, in reorg handling, and when accepting
channel(s) from counterparties which are miners.

When a counterparty broadcasts their latest commitment transaction for a
channel with anchor outputs, we'd previously fail to build claiming
transactions against any HTLC outputs in that transaction. This could lead
to loss of funds if the counterparty is able to eventually claim the HTLC
after a timeout (#2606).
Anchor channels HTLC claims on-chain previously spent the entire value of any
HTLCs as fee, which has now been fixed (#2587).
If a channel is closed via an on-chain commitment transaction confirmation
with a pending outbound HTLC in the commitment transaction, followed by a
reorg which replaces the confirmed commitment transaction with a different
(but non-revoked) commitment transaction, all before we learn the payment
preimage for this HTLC, we may previously have not generated a proper
claiming transaction for the HTLC's value (#2623).
0.0.117 now correctly handles channels for which our counterparty funded the
channel with a coinbase transaction. As such transactions are not spendable
until they've reached 100 confirmations, this could have resulted in
accepting HTLC(s) which are not enforcible on-chain (#1924).