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Merged
merged 1 commit into from
Oct 9, 2025
+92 −28
Merged

Allow stale ChannelMonitors if we are sure they don't have funds #4146

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57 changes: 44 additions & 13 deletions lightning/src/chain/channelmonitor.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1059,11 +1059,21 @@ impl Readable for IrrevocablyResolvedHTLC {
/// You MUST ensure that no ChannelMonitors for a given channel anywhere contain out-of-date
/// information and are actively monitoring the chain.
///
/// Note that the deserializer is only implemented for (BlockHash, ChannelMonitor), which
/// tells you the last block hash which was block_connect()ed. You MUST rescan any blocks along
/// the "reorg path" (ie disconnecting blocks until you find a common ancestor from both the
/// returned block hash and the the current chain and then reconnecting blocks to get to the
/// best chain) upon deserializing the object!
/// Like the [`ChannelManager`], deserialization is implemented for `(BlockHash, ChannelMonitor)`,
/// providing you with the last block hash which was connected before shutting down. You must begin
/// syncing the chain from that point, disconnecting and connecting blocks as required to get to
/// the best chain on startup. Note that all [`ChannelMonitor`]s passed to a [`ChainMonitor`] must
/// by synced as of the same block, so syncing must happen prior to [`ChainMonitor`]
/// initialization.
///
/// For those loading potentially-ancient [`ChannelMonitor`]s, deserialization is also implemented
/// for `Option<(BlockHash, ChannelMonitor)>`. LDK can no longer deserialize a [`ChannelMonitor`]
/// that was first created in LDK prior to 0.0.110 and last updated prior to LDK 0.0.119. In such
/// cases, the `Option<(..)>` deserialization option may return `Ok(None)` rather than failing to
/// deserialize, allowing you to differentiate between the two cases.
///
/// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
/// [`ChainMonitor`]: crate::chain::chainmonitor::ChainMonitor
pub struct ChannelMonitor<Signer: EcdsaChannelSigner> {
pub(crate) inner: Mutex<ChannelMonitorImpl<Signer>>,
}
Expand Down Expand Up @@ -6251,6 +6261,18 @@ const MAX_ALLOC_SIZE: usize = 64 * 1024;

impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP)>
for (BlockHash, ChannelMonitor<SP::EcdsaSigner>)
{
fn read<R: io::Read>(reader: &mut R, args: (&'a ES, &'b SP)) -> Result<Self, DecodeError> {
match <Option<Self>>::read(reader, args) {
Ok(Some(res)) => Ok(res),
Ok(None) => Err(DecodeError::UnknownRequiredFeature),
Err(e) => Err(e),
}
}
}

impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP)>
for Option<(BlockHash, ChannelMonitor<SP::EcdsaSigner>)>
{
#[rustfmt::skip]
fn read<R: io::Read>(reader: &mut R, args: (&'a ES, &'b SP)) -> Result<Self, DecodeError> {
Expand Down Expand Up @@ -6528,11 +6550,6 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
}

let channel_id = channel_id.unwrap_or(ChannelId::v1_from_funding_outpoint(outpoint));
if counterparty_node_id.is_none() {
panic!("Found monitor for channel {} with no updates since v0.0.118.\
These monitors are no longer supported.\
To continue, run a v0.1 release, send/route a payment over the channel or close it.", channel_id);
}

let (current_holder_commitment_tx, current_holder_htlc_data) = {
let holder_commitment_tx = onchain_tx_handler.current_holder_commitment_tx();
Expand Down Expand Up @@ -6586,7 +6603,8 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
(None, None)
};

Ok((best_block.block_hash, ChannelMonitor::from_impl(ChannelMonitorImpl {
let dummy_node_id = PublicKey::from_slice(&[2; 33]).unwrap();
let monitor = ChannelMonitor::from_impl(ChannelMonitorImpl {
funding: FundingScope {
channel_parameters,

Expand Down Expand Up @@ -6646,7 +6664,7 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
spendable_txids_confirmed: spendable_txids_confirmed.unwrap(),

best_block,
counterparty_node_id: counterparty_node_id.unwrap(),
counterparty_node_id: counterparty_node_id.unwrap_or(dummy_node_id),
initial_counterparty_commitment_info,
initial_counterparty_commitment_tx,
balances_empty_height,
Expand All @@ -6658,7 +6676,20 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
alternative_funding_confirmed,

written_by_0_1_or_later,
})))
});

if counterparty_node_id.is_none() {
if (holder_tx_signed || lockdown_from_offchain) && monitor.get_claimable_balances().is_empty() {
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Do we actually need to bother checking for (holder_tx_signed || lockdown_from_offchain)?

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Probably not but it seemed like a nice additional check to include cause I'm not at all confident in the balance set for really old monitors.

// If the monitor is no longer readable, but it is a candidate for archiving,
// return Ok(None) to allow it to be skipped and not loaded.
return Ok(None);
} else {
panic!("Found monitor for channel {channel_id} with no updates since v0.0.118. \
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This mentions 0.0.118 but the commit mentions 0.0.116

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Oh, that is from 601bf4b. I'll fix but looks like it was actually in 0.0.119

These monitors are no longer supported. \
To continue, run a v0.1 release, send/route a payment over the channel or close it.");
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Hm, so what if the monitor is already closed and you still have balances to claim? Is there any way you can realistically start up? I guess this would be pretty unlikely, unless you have an outbound payment you still need to time out on chain.

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No, you can't without manually deleting the monitor from your store. It really sucks and I'm not really happy with the state of things but it seems a bit late to walk this back :/

}
}
Ok(Some((best_block.block_hash, monitor)))
}
}

Expand Down
63 changes: 48 additions & 15 deletions lightning/src/util/persist.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -372,15 +372,15 @@ where
CHANNEL_MONITOR_PERSISTENCE_PRIMARY_NAMESPACE,
CHANNEL_MONITOR_PERSISTENCE_SECONDARY_NAMESPACE,
)? {
match <(BlockHash, ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>)>::read(
match <Option<(BlockHash, ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>)>>::read(
&mut io::Cursor::new(kv_store.read(
CHANNEL_MONITOR_PERSISTENCE_PRIMARY_NAMESPACE,
CHANNEL_MONITOR_PERSISTENCE_SECONDARY_NAMESPACE,
&stored_key,
)?),
(&*entropy_source, &*signer_provider),
) {
Ok((block_hash, channel_monitor)) => {
Ok(Some((block_hash, channel_monitor))) => {
let monitor_name = MonitorName::from_str(&stored_key)?;
if channel_monitor.persistence_key() != monitor_name {
return Err(io::Error::new(
Expand All @@ -391,6 +391,7 @@ where

res.push((block_hash, channel_monitor));
},
Ok(None) => {},
Err(_) => {
return Err(io::Error::new(
io::ErrorKind::InvalidData,
Expand Down Expand Up @@ -783,9 +784,12 @@ where
let secondary = CHANNEL_MONITOR_PERSISTENCE_SECONDARY_NAMESPACE;
let monitor_list = self.0.kv_store.list(primary, secondary).await?;
let mut res = Vec::with_capacity(monitor_list.len());
// TODO: Parallelize this loop
for monitor_key in monitor_list {
res.push(self.read_channel_monitor_with_updates(monitor_key.as_str()).await?)
let result =
self.0.maybe_read_channel_monitor_with_updates(monitor_key.as_str()).await?;
if let Some(read_res) = result {
res.push(read_res);
}
}
Ok(res)
}
Expand Down Expand Up @@ -923,8 +927,29 @@ where
&self, monitor_key: &str,
) -> Result<(BlockHash, ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>), io::Error>
{
match self.maybe_read_channel_monitor_with_updates(monitor_key).await? {
Some(res) => Ok(res),
None => Err(io::Error::new(
io::ErrorKind::InvalidData,
"ChannelMonitor was stale, with no updates since LDK 0.0.118. \
It cannot be read by modern versions of LDK, though also does not contain any funds left to sweep. \
You should manually delete it instead",
Comment on lines +934 to +936
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Might be worth including the monitor_key given this is called indirectly from read_all_channel_monitors_with_updates.

)),
}
}

async fn maybe_read_channel_monitor_with_updates(
&self, monitor_key: &str,
) -> Result<
Option<(BlockHash, ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>)>,
io::Error,
> {
let monitor_name = MonitorName::from_str(monitor_key)?;
let (block_hash, monitor) = self.read_monitor(&monitor_name, monitor_key).await?;
let read_res = self.maybe_read_monitor(&monitor_name, monitor_key).await?;
let (block_hash, monitor) = match read_res {
Some(res) => res,
None => return Ok(None),
};
let mut current_update_id = monitor.get_latest_update_id();
// TODO: Parallelize this loop by speculatively reading a batch of updates
loop {
Expand Down Expand Up @@ -955,14 +980,16 @@ where
io::Error::new(io::ErrorKind::Other, "Monitor update failed")
})?;
}
Ok((block_hash, monitor))
Ok(Some((block_hash, monitor)))
}

/// Read a channel monitor.
async fn read_monitor(
async fn maybe_read_monitor(
&self, monitor_name: &MonitorName, monitor_key: &str,
) -> Result<(BlockHash, ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>), io::Error>
{
) -> Result<
Option<(BlockHash, ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>)>,
io::Error,
> {
let primary = CHANNEL_MONITOR_PERSISTENCE_PRIMARY_NAMESPACE;
let secondary = CHANNEL_MONITOR_PERSISTENCE_SECONDARY_NAMESPACE;
let monitor_bytes = self.kv_store.read(primary, secondary, monitor_key).await?;
Expand All @@ -971,11 +998,12 @@ where
if monitor_cursor.get_ref().starts_with(MONITOR_UPDATING_PERSISTER_PREPEND_SENTINEL) {
monitor_cursor.set_position(MONITOR_UPDATING_PERSISTER_PREPEND_SENTINEL.len() as u64);
}
match <(BlockHash, ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>)>::read(
match <Option<(BlockHash, ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>)>>::read(
&mut monitor_cursor,
(&*self.entropy_source, &*self.signer_provider),
) {
Ok((blockhash, channel_monitor)) => {
Ok(None) => Ok(None),
Ok(Some((blockhash, channel_monitor))) => {
if channel_monitor.persistence_key() != *monitor_name {
log_error!(
self.logger,
Expand All @@ -987,7 +1015,7 @@ where
"ChannelMonitor was stored under the wrong key",
))
} else {
Ok((blockhash, channel_monitor))
Ok(Some((blockhash, channel_monitor)))
}
},
Err(e) => {
Expand Down Expand Up @@ -1027,9 +1055,14 @@ where
let monitor_keys = self.kv_store.list(primary, secondary).await?;
for monitor_key in monitor_keys {
let monitor_name = MonitorName::from_str(&monitor_key)?;
let (_, current_monitor) = self.read_monitor(&monitor_name, &monitor_key).await?;
let latest_update_id = current_monitor.get_latest_update_id();
self.cleanup_stale_updates_for_monitor_to(&monitor_key, latest_update_id).await?;
let maybe_monitor = self.maybe_read_monitor(&monitor_name, &monitor_key).await?;
if let Some((_, current_monitor)) = maybe_monitor {
let latest_update_id = current_monitor.get_latest_update_id();
self.cleanup_stale_updates_for_monitor_to(&monitor_key, latest_update_id).await?;
} else {
// TODO: Also clean up super stale monitors (created pre-0.0.110 and last updated
// pre-0.0.119).
}
}
Ok(())
}
Expand Down