Add a payments section to ChannelManager docs
[rust-lightning] / lightning / src / ln / channelmanager.rs
index 16ca44c34282f3b3ec68a7b4a153d605d8684e37..dc170b652b55bc953ee121d3109e5d2ecb77e8df 100644 (file)
@@ -200,6 +200,8 @@ pub enum PendingHTLCRouting {
                /// For HTLCs received by LDK, these will ultimately bubble back up as
                /// [`RecipientOnionFields::custom_tlvs`].
                custom_tlvs: Vec<(u64, Vec<u8>)>,
+               /// Set if this HTLC is the final hop in a multi-hop blinded path.
+               requires_blinded_error: bool,
        },
 }
 
@@ -221,6 +223,7 @@ impl PendingHTLCRouting {
                match self {
                        Self::Forward { blinded: Some(BlindedForward { failure, .. }), .. } => Some(*failure),
                        Self::Receive { requires_blinded_error: true, .. } => Some(BlindedFailure::FromBlindedNode),
+                       Self::ReceiveKeysend { requires_blinded_error: true, .. } => Some(BlindedFailure::FromBlindedNode),
                        _ => None,
                }
        }
@@ -1106,11 +1109,424 @@ where
        fn get_cm(&self) -> &ChannelManager<M, T, ES, NS, SP, F, R, L> { self }
 }
 
-/// Manager which keeps track of a number of channels and sends messages to the appropriate
-/// channel, also tracking HTLC preimages and forwarding onion packets appropriately.
+/// A lightning node's channel state machine and payment management logic, which facilitates
+/// sending, forwarding, and receiving payments through lightning channels.
+///
+/// [`ChannelManager`] is parameterized by a number of components to achieve this.
+/// - [`chain::Watch`] (typically [`ChainMonitor`]) for on-chain monitoring and enforcement of each
+///   channel
+/// - [`BroadcasterInterface`] for broadcasting transactions related to opening, funding, and
+///   closing channels
+/// - [`EntropySource`] for providing random data needed for cryptographic operations
+/// - [`NodeSigner`] for cryptographic operations scoped to the node
+/// - [`SignerProvider`] for providing signers whose operations are scoped to individual channels
+/// - [`FeeEstimator`] to determine transaction fee rates needed to have a transaction mined in a
+///   timely manner
+/// - [`Router`] for finding payment paths when initiating and retrying payments
+/// - [`Logger`] for logging operational information of varying degrees
+///
+/// Additionally, it implements the following traits:
+/// - [`ChannelMessageHandler`] to handle off-chain channel activity from peers
+/// - [`MessageSendEventsProvider`] to similarly send such messages to peers
+/// - [`OffersMessageHandler`] for BOLT 12 message handling and sending
+/// - [`EventsProvider`] to generate user-actionable [`Event`]s
+/// - [`chain::Listen`] and [`chain::Confirm`] for notification of on-chain activity
+///
+/// Thus, [`ChannelManager`] is typically used to parameterize a [`MessageHandler`] and an
+/// [`OnionMessenger`]. The latter is required to support BOLT 12 functionality.
+///
+/// # `ChannelManager` vs `ChannelMonitor`
+///
+/// It's important to distinguish between the *off-chain* management and *on-chain* enforcement of
+/// lightning channels. [`ChannelManager`] exchanges messages with peers to manage the off-chain
+/// state of each channel. During this process, it generates a [`ChannelMonitor`] for each channel
+/// and a [`ChannelMonitorUpdate`] for each relevant change, notifying its parameterized
+/// [`chain::Watch`] of them.
+///
+/// An implementation of [`chain::Watch`], such as [`ChainMonitor`], is responsible for aggregating
+/// these [`ChannelMonitor`]s and applying any [`ChannelMonitorUpdate`]s to them. It then monitors
+/// for any pertinent on-chain activity, enforcing claims as needed.
+///
+/// This division of off-chain management and on-chain enforcement allows for interesting node
+/// setups. For instance, on-chain enforcement could be moved to a separate host or have added
+/// redundancy, possibly as a watchtower. See [`chain::Watch`] for the relevant interface.
+///
+/// # Initialization
+///
+/// Use [`ChannelManager::new`] with the most recent [`BlockHash`] when creating a fresh instance.
+/// Otherwise, if restarting, construct [`ChannelManagerReadArgs`] with the necessary parameters and
+/// references to any deserialized [`ChannelMonitor`]s that were previously persisted. Use this to
+/// deserialize the [`ChannelManager`] and feed it any new chain data since it was last online, as
+/// detailed in the [`ChannelManagerReadArgs`] documentation.
+///
+/// ```
+/// use bitcoin::BlockHash;
+/// use bitcoin::network::constants::Network;
+/// use lightning::chain::BestBlock;
+/// # use lightning::chain::channelmonitor::ChannelMonitor;
+/// use lightning::ln::channelmanager::{ChainParameters, ChannelManager, ChannelManagerReadArgs};
+/// # use lightning::routing::gossip::NetworkGraph;
+/// use lightning::util::config::UserConfig;
+/// use lightning::util::ser::ReadableArgs;
+///
+/// # fn read_channel_monitors() -> Vec<ChannelMonitor<lightning::sign::InMemorySigner>> { vec![] }
+/// # fn example<
+/// #     'a,
+/// #     L: lightning::util::logger::Logger,
+/// #     ES: lightning::sign::EntropySource,
+/// #     S: for <'b> lightning::routing::scoring::LockableScore<'b, ScoreLookUp = SL>,
+/// #     SL: lightning::routing::scoring::ScoreLookUp<ScoreParams = SP>,
+/// #     SP: Sized,
+/// #     R: lightning::io::Read,
+/// # >(
+/// #     fee_estimator: &dyn lightning::chain::chaininterface::FeeEstimator,
+/// #     chain_monitor: &dyn lightning::chain::Watch<lightning::sign::InMemorySigner>,
+/// #     tx_broadcaster: &dyn lightning::chain::chaininterface::BroadcasterInterface,
+/// #     router: &lightning::routing::router::DefaultRouter<&NetworkGraph<&'a L>, &'a L, &ES, &S, SP, SL>,
+/// #     logger: &L,
+/// #     entropy_source: &ES,
+/// #     node_signer: &dyn lightning::sign::NodeSigner,
+/// #     signer_provider: &lightning::sign::DynSignerProvider,
+/// #     best_block: lightning::chain::BestBlock,
+/// #     current_timestamp: u32,
+/// #     mut reader: R,
+/// # ) -> Result<(), lightning::ln::msgs::DecodeError> {
+/// // Fresh start with no channels
+/// let params = ChainParameters {
+///     network: Network::Bitcoin,
+///     best_block,
+/// };
+/// let default_config = UserConfig::default();
+/// let channel_manager = ChannelManager::new(
+///     fee_estimator, chain_monitor, tx_broadcaster, router, logger, entropy_source, node_signer,
+///     signer_provider, default_config, params, current_timestamp
+/// );
+///
+/// // Restart from deserialized data
+/// let mut channel_monitors = read_channel_monitors();
+/// let args = ChannelManagerReadArgs::new(
+///     entropy_source, node_signer, signer_provider, fee_estimator, chain_monitor, tx_broadcaster,
+///     router, logger, default_config, channel_monitors.iter_mut().collect()
+/// );
+/// let (block_hash, channel_manager) =
+///     <(BlockHash, ChannelManager<_, _, _, _, _, _, _, _>)>::read(&mut reader, args)?;
+///
+/// // Update the ChannelManager and ChannelMonitors with the latest chain data
+/// // ...
+///
+/// // Move the monitors to the ChannelManager's chain::Watch parameter
+/// for monitor in channel_monitors {
+///     chain_monitor.watch_channel(monitor.get_funding_txo().0, monitor);
+/// }
+/// # Ok(())
+/// # }
+/// ```
+///
+/// # Operation
+///
+/// The following is required for [`ChannelManager`] to function properly:
+/// - Handle messages from peers using its [`ChannelMessageHandler`] implementation (typically
+///   called by [`PeerManager::read_event`] when processing network I/O)
+/// - Send messages to peers obtained via its [`MessageSendEventsProvider`] implementation
+///   (typically initiated when [`PeerManager::process_events`] is called)
+/// - Feed on-chain activity using either its [`chain::Listen`] or [`chain::Confirm`] implementation
+///   as documented by those traits
+/// - Perform any periodic channel and payment checks by calling [`timer_tick_occurred`] roughly
+///   every minute
+/// - Persist to disk whenever [`get_and_clear_needs_persistence`] returns `true` using a
+///   [`Persister`] such as a [`KVStore`] implementation
+/// - Handle [`Event`]s obtained via its [`EventsProvider`] implementation
+///
+/// The [`Future`] returned by [`get_event_or_persistence_needed_future`] is useful in determining
+/// when the last two requirements need to be checked.
+///
+/// The [`lightning-block-sync`] and [`lightning-transaction-sync`] crates provide utilities that
+/// simplify feeding in on-chain activity using the [`chain::Listen`] and [`chain::Confirm`] traits,
+/// respectively. The remaining requirements can be met using the [`lightning-background-processor`]
+/// crate. For languages other than Rust, the availability of similar utilities may vary.
+///
+/// # Channels
+///
+/// [`ChannelManager`]'s primary function involves managing a channel state. Without channels,
+/// payments can't be sent. Use [`list_channels`] or [`list_usable_channels`] for a snapshot of the
+/// currently open channels.
+///
+/// ```
+/// # use lightning::ln::channelmanager::AChannelManager;
+/// #
+/// # fn example<T: AChannelManager>(channel_manager: T) {
+/// # let channel_manager = channel_manager.get_cm();
+/// let channels = channel_manager.list_usable_channels();
+/// for details in channels {
+///     println!("{:?}", details);
+/// }
+/// # }
+/// ```
+///
+/// Each channel is identified using a [`ChannelId`], which will change throughout the channel's
+/// life cycle. Additionally, channels are assigned a `user_channel_id`, which is given in
+/// [`Event`]s associated with the channel and serves as a fixed identifier but is otherwise unused
+/// by [`ChannelManager`].
+///
+/// ## Opening Channels
+///
+/// To an open a channel with a peer, call [`create_channel`]. This will initiate the process of
+/// opening an outbound channel, which requires self-funding when handling
+/// [`Event::FundingGenerationReady`].
+///
+/// ```
+/// # use bitcoin::{ScriptBuf, Transaction};
+/// # use bitcoin::secp256k1::PublicKey;
+/// # use lightning::ln::channelmanager::AChannelManager;
+/// # use lightning::events::{Event, EventsProvider};
+/// #
+/// # trait Wallet {
+/// #     fn create_funding_transaction(
+/// #         &self, _amount_sats: u64, _output_script: ScriptBuf
+/// #     ) -> Transaction;
+/// # }
+/// #
+/// # fn example<T: AChannelManager, W: Wallet>(channel_manager: T, wallet: W, peer_id: PublicKey) {
+/// # let channel_manager = channel_manager.get_cm();
+/// let value_sats = 1_000_000;
+/// let push_msats = 10_000_000;
+/// match channel_manager.create_channel(peer_id, value_sats, push_msats, 42, None, None) {
+///     Ok(channel_id) => println!("Opening channel {}", channel_id),
+///     Err(e) => println!("Error opening channel: {:?}", e),
+/// }
+///
+/// // On the event processing thread once the peer has responded
+/// channel_manager.process_pending_events(&|event| match event {
+///     Event::FundingGenerationReady {
+///         temporary_channel_id, counterparty_node_id, channel_value_satoshis, output_script,
+///         user_channel_id, ..
+///     } => {
+///         assert_eq!(user_channel_id, 42);
+///         let funding_transaction = wallet.create_funding_transaction(
+///             channel_value_satoshis, output_script
+///         );
+///         match channel_manager.funding_transaction_generated(
+///             &temporary_channel_id, &counterparty_node_id, funding_transaction
+///         ) {
+///             Ok(()) => println!("Funding channel {}", temporary_channel_id),
+///             Err(e) => println!("Error funding channel {}: {:?}", temporary_channel_id, e),
+///         }
+///     },
+///     Event::ChannelPending { channel_id, user_channel_id, former_temporary_channel_id, .. } => {
+///         assert_eq!(user_channel_id, 42);
+///         println!(
+///             "Channel {} now {} pending (funding transaction has been broadcasted)", channel_id,
+///             former_temporary_channel_id.unwrap()
+///         );
+///     },
+///     Event::ChannelReady { channel_id, user_channel_id, .. } => {
+///         assert_eq!(user_channel_id, 42);
+///         println!("Channel {} ready", channel_id);
+///     },
+///     // ...
+/// #     _ => {},
+/// });
+/// # }
+/// ```
+///
+/// ## Accepting Channels
+///
+/// Inbound channels are initiated by peers and are automatically accepted unless [`ChannelManager`]
+/// has [`UserConfig::manually_accept_inbound_channels`] set. In that case, the channel may be
+/// either accepted or rejected when handling [`Event::OpenChannelRequest`].
+///
+/// ```
+/// # use bitcoin::secp256k1::PublicKey;
+/// # use lightning::ln::channelmanager::AChannelManager;
+/// # use lightning::events::{Event, EventsProvider};
+/// #
+/// # fn is_trusted(counterparty_node_id: PublicKey) -> bool {
+/// #     // ...
+/// #     unimplemented!()
+/// # }
+/// #
+/// # fn example<T: AChannelManager>(channel_manager: T) {
+/// # let channel_manager = channel_manager.get_cm();
+/// channel_manager.process_pending_events(&|event| match event {
+///     Event::OpenChannelRequest { temporary_channel_id, counterparty_node_id, ..  } => {
+///         if !is_trusted(counterparty_node_id) {
+///             match channel_manager.force_close_without_broadcasting_txn(
+///                 &temporary_channel_id, &counterparty_node_id
+///             ) {
+///                 Ok(()) => println!("Rejecting channel {}", temporary_channel_id),
+///                 Err(e) => println!("Error rejecting channel {}: {:?}", temporary_channel_id, e),
+///             }
+///             return;
+///         }
+///
+///         let user_channel_id = 43;
+///         match channel_manager.accept_inbound_channel(
+///             &temporary_channel_id, &counterparty_node_id, user_channel_id
+///         ) {
+///             Ok(()) => println!("Accepting channel {}", temporary_channel_id),
+///             Err(e) => println!("Error accepting channel {}: {:?}", temporary_channel_id, e),
+///         }
+///     },
+///     // ...
+/// #     _ => {},
+/// });
+/// # }
+/// ```
+///
+/// ## Closing Channels
 ///
-/// Implements [`ChannelMessageHandler`], handling the multi-channel parts and passing things through
-/// to individual Channels.
+/// There are two ways to close a channel: either cooperatively using [`close_channel`] or
+/// unilaterally using [`force_close_broadcasting_latest_txn`]. The former is ideal as it makes for
+/// lower fees and immediate access to funds. However, the latter may be necessary if the
+/// counterparty isn't behaving properly or has gone offline. [`Event::ChannelClosed`] is generated
+/// once the channel has been closed successfully.
+///
+/// ```
+/// # use bitcoin::secp256k1::PublicKey;
+/// # use lightning::ln::ChannelId;
+/// # use lightning::ln::channelmanager::AChannelManager;
+/// # use lightning::events::{Event, EventsProvider};
+/// #
+/// # fn example<T: AChannelManager>(
+/// #     channel_manager: T, channel_id: ChannelId, counterparty_node_id: PublicKey
+/// # ) {
+/// # let channel_manager = channel_manager.get_cm();
+/// match channel_manager.close_channel(&channel_id, &counterparty_node_id) {
+///     Ok(()) => println!("Closing channel {}", channel_id),
+///     Err(e) => println!("Error closing channel {}: {:?}", channel_id, e),
+/// }
+///
+/// // On the event processing thread
+/// channel_manager.process_pending_events(&|event| match event {
+///     Event::ChannelClosed { channel_id, user_channel_id, ..  } => {
+///         assert_eq!(user_channel_id, 42);
+///         println!("Channel {} closed", channel_id);
+///     },
+///     // ...
+/// #     _ => {},
+/// });
+/// # }
+/// ```
+///
+/// # Payments
+///
+/// [`ChannelManager`] is responsible for sending, forwarding, and receiving payments through its
+/// channels. A payment is typically initiated from a [BOLT 11] invoice or a [BOLT 12] offer, though
+/// spontaneous (i.e., keysend) payments are also possible. Incoming payments don't require
+/// maintaining any additional state as [`ChannelManager`] can reconstruct the [`PaymentPreimage`]
+/// from the [`PaymentSecret`]. Sending payments, however, require tracking in order to retry failed
+/// HTLCs.
+///
+/// After a payment is initiated, it will appear in [`list_recent_payments`] until a short time
+/// after either an [`Event::PaymentSent`] or [`Event::PaymentFailed`] is handled. Failed HTLCs
+/// for a payment will be retried according to the payment's [`Retry`] strategy or until
+/// [`abandon_payment`] is called.
+///
+/// ## BOLT 11 Invoices
+///
+/// The [`lightning-invoice`] crate is useful for creating BOLT 11 invoices. Specifically, use the
+/// functions in its `utils` module for constructing invoices that are compatible with
+/// [`ChannelManager`]. These functions serve as a convenience for building invoices with the
+/// [`PaymentHash`] and [`PaymentSecret`] returned from [`create_inbound_payment`]. To provide your
+/// own [`PaymentHash`], use [`create_inbound_payment_for_hash`] or the corresponding functions in
+/// the [`lightning-invoice`] `utils` module.
+///
+/// [`ChannelManager`] generates an [`Event::PaymentClaimable`] once the full payment has been
+/// received. Call [`claim_funds`] to release the [`PaymentPreimage`], which in turn will result in
+/// an [`Event::PaymentClaimed`].
+///
+/// ```
+/// # use lightning::events::{Event, EventsProvider, PaymentPurpose};
+/// # use lightning::ln::channelmanager::AChannelManager;
+/// #
+/// # fn example<T: AChannelManager>(channel_manager: T) {
+/// # let channel_manager = channel_manager.get_cm();
+/// // Or use utils::create_invoice_from_channelmanager
+/// let known_payment_hash = match channel_manager.create_inbound_payment(
+///     Some(10_000_000), 3600, None
+/// ) {
+///     Ok((payment_hash, _payment_secret)) => {
+///         println!("Creating inbound payment {}", payment_hash);
+///         payment_hash
+///     },
+///     Err(()) => panic!("Error creating inbound payment"),
+/// };
+///
+/// // On the event processing thread
+/// channel_manager.process_pending_events(&|event| match event {
+///     Event::PaymentClaimable { payment_hash, purpose, .. } => match purpose {
+///         PaymentPurpose::InvoicePayment { payment_preimage: Some(payment_preimage), .. } => {
+///             assert_eq!(payment_hash, known_payment_hash);
+///             println!("Claiming payment {}", payment_hash);
+///             channel_manager.claim_funds(payment_preimage);
+///         },
+///         PaymentPurpose::InvoicePayment { payment_preimage: None, .. } => {
+///             println!("Unknown payment hash: {}", payment_hash);
+///         },
+///         PaymentPurpose::SpontaneousPayment(payment_preimage) => {
+///             assert_ne!(payment_hash, known_payment_hash);
+///             println!("Claiming spontaneous payment {}", payment_hash);
+///             channel_manager.claim_funds(payment_preimage);
+///         },
+///     },
+///     Event::PaymentClaimed { payment_hash, amount_msat, .. } => {
+///         assert_eq!(payment_hash, known_payment_hash);
+///         println!("Claimed {} msats", amount_msat);
+///     },
+///     // ...
+/// #     _ => {},
+/// });
+/// # }
+/// ```
+///
+/// For paying an invoice, [`lightning-invoice`] provides a `payment` module with convenience
+/// functions for use with [`send_payment`].
+///
+/// ```
+/// # use lightning::events::{Event, EventsProvider};
+/// # use lightning::ln::PaymentHash;
+/// # use lightning::ln::channelmanager::{AChannelManager, PaymentId, RecentPaymentDetails, RecipientOnionFields, Retry};
+/// # use lightning::routing::router::RouteParameters;
+/// #
+/// # fn example<T: AChannelManager>(
+/// #     channel_manager: T, payment_hash: PaymentHash, recipient_onion: RecipientOnionFields,
+/// #     route_params: RouteParameters, retry: Retry
+/// # ) {
+/// # let channel_manager = channel_manager.get_cm();
+/// // let (payment_hash, recipient_onion, route_params) =
+/// //     payment::payment_parameters_from_invoice(&invoice);
+/// let payment_id = PaymentId([42; 32]);
+/// match channel_manager.send_payment(
+///     payment_hash, recipient_onion, payment_id, route_params, retry
+/// ) {
+///     Ok(()) => println!("Sending payment with hash {}", payment_hash),
+///     Err(e) => println!("Failed sending payment with hash {}: {:?}", payment_hash, e),
+/// }
+///
+/// let expected_payment_id = payment_id;
+/// let expected_payment_hash = payment_hash;
+/// assert!(
+///     channel_manager.list_recent_payments().iter().find(|details| matches!(
+///         details,
+///         RecentPaymentDetails::Pending {
+///             payment_id: expected_payment_id,
+///             payment_hash: expected_payment_hash,
+///             ..
+///         }
+///     )).is_some()
+/// );
+///
+/// // On the event processing thread
+/// channel_manager.process_pending_events(&|event| match event {
+///     Event::PaymentSent { payment_hash, .. } => println!("Paid {}", payment_hash),
+///     Event::PaymentFailed { payment_hash, .. } => println!("Failed paying {}", payment_hash),
+///     // ...
+/// #     _ => {},
+/// });
+/// # }
+/// ```
+///
+/// # Persistence
 ///
 /// Implements [`Writeable`] to write out all channel state to disk. Implies [`peer_disconnected`] for
 /// all peers during write/read (though does not modify this instance, only the instance being
@@ -1131,12 +1547,16 @@ where
 /// tells you the last block hash which was connected. You should get the best block tip before using the manager.
 /// See [`chain::Listen`] and [`chain::Confirm`] for more details.
 ///
+/// # `ChannelUpdate` Messages
+///
 /// Note that `ChannelManager` is responsible for tracking liveness of its channels and generating
 /// [`ChannelUpdate`] messages informing peers that the channel is temporarily disabled. To avoid
 /// spam due to quick disconnection/reconnection, updates are not sent until the channel has been
 /// offline for a full minute. In order to track this, you must call
 /// [`timer_tick_occurred`] roughly once per minute, though it doesn't have to be perfect.
 ///
+/// # DoS Mitigation
+///
 /// To avoid trivial DoS issues, `ChannelManager` limits the number of inbound connections and
 /// inbound channels without confirmed funding transactions. This may result in nodes which we do
 /// not have a channel with being unable to connect to us or open new channels with us if we have
@@ -1146,19 +1566,47 @@ where
 /// exempted from the count of unfunded channels. Similarly, outbound channels and connections are
 /// never limited. Please ensure you limit the count of such channels yourself.
 ///
+/// # Type Aliases
+///
 /// Rather than using a plain `ChannelManager`, it is preferable to use either a [`SimpleArcChannelManager`]
 /// a [`SimpleRefChannelManager`], for conciseness. See their documentation for more details, but
 /// essentially you should default to using a [`SimpleRefChannelManager`], and use a
 /// [`SimpleArcChannelManager`] when you require a `ChannelManager` with a static lifetime, such as when
 /// you're using lightning-net-tokio.
 ///
+/// [`ChainMonitor`]: crate::chain::chainmonitor::ChainMonitor
+/// [`MessageHandler`]: crate::ln::peer_handler::MessageHandler
+/// [`OnionMessenger`]: crate::onion_message::messenger::OnionMessenger
+/// [`PeerManager::read_event`]: crate::ln::peer_handler::PeerManager::read_event
+/// [`PeerManager::process_events`]: crate::ln::peer_handler::PeerManager::process_events
+/// [`timer_tick_occurred`]: Self::timer_tick_occurred
+/// [`get_and_clear_needs_persistence`]: Self::get_and_clear_needs_persistence
+/// [`Persister`]: crate::util::persist::Persister
+/// [`KVStore`]: crate::util::persist::KVStore
+/// [`get_event_or_persistence_needed_future`]: Self::get_event_or_persistence_needed_future
+/// [`lightning-block-sync`]: https://docs.rs/lightning_block_sync/latest/lightning_block_sync
+/// [`lightning-transaction-sync`]: https://docs.rs/lightning_transaction_sync/latest/lightning_transaction_sync
+/// [`lightning-background-processor`]: https://docs.rs/lightning_background_processor/lightning_background_processor
+/// [`list_channels`]: Self::list_channels
+/// [`list_usable_channels`]: Self::list_usable_channels
+/// [`create_channel`]: Self::create_channel
+/// [`close_channel`]: Self::force_close_broadcasting_latest_txn
+/// [`force_close_broadcasting_latest_txn`]: Self::force_close_broadcasting_latest_txn
+/// [BOLT 11]: https://github.com/lightning/bolts/blob/master/11-payment-encoding.md
+/// [BOLT 12]: https://github.com/rustyrussell/lightning-rfc/blob/guilt/offers/12-offer-encoding.md
+/// [`list_recent_payments`]: Self::list_recent_payments
+/// [`abandon_payment`]: Self::abandon_payment
+/// [`lightning-invoice`]: https://docs.rs/lightning_invoice/latest/lightning_invoice
+/// [`create_inbound_payment`]: Self::create_inbound_payment
+/// [`create_inbound_payment_for_hash`]: Self::create_inbound_payment_for_hash
+/// [`claim_funds`]: Self::claim_funds
+/// [`send_payment`]: Self::send_payment
 /// [`peer_disconnected`]: msgs::ChannelMessageHandler::peer_disconnected
 /// [`funding_created`]: msgs::FundingCreated
 /// [`funding_transaction_generated`]: Self::funding_transaction_generated
 /// [`BlockHash`]: bitcoin::hash_types::BlockHash
 /// [`update_channel`]: chain::Watch::update_channel
 /// [`ChannelUpdate`]: msgs::ChannelUpdate
-/// [`timer_tick_occurred`]: Self::timer_tick_occurred
 /// [`read`]: ReadableArgs::read
 //
 // Lock order:
@@ -4523,7 +4971,10 @@ where
                                                                                (incoming_cltv_expiry, OnionPayload::Invoice { _legacy_hop_data },
                                                                                        Some(payment_data), phantom_shared_secret, onion_fields)
                                                                        },
-                                                                       PendingHTLCRouting::ReceiveKeysend { payment_data, payment_preimage, payment_metadata, incoming_cltv_expiry, custom_tlvs } => {
+                                                                       PendingHTLCRouting::ReceiveKeysend {
+                                                                               payment_data, payment_preimage, payment_metadata,
+                                                                               incoming_cltv_expiry, custom_tlvs, requires_blinded_error: _
+                                                                       } => {
                                                                                let onion_fields = RecipientOnionFields {
                                                                                        payment_secret: payment_data.as_ref().map(|data| data.payment_secret),
                                                                                        payment_metadata,
@@ -5740,7 +6191,7 @@ where
        fn claim_funds_internal(&self, source: HTLCSource, payment_preimage: PaymentPreimage,
                forwarded_htlc_value_msat: Option<u64>, skimmed_fee_msat: Option<u64>, from_onchain: bool,
                startup_replay: bool, next_channel_counterparty_node_id: Option<PublicKey>,
-               next_channel_outpoint: OutPoint, next_channel_id: ChannelId,
+               next_channel_outpoint: OutPoint, next_channel_id: ChannelId, next_user_channel_id: Option<u128>,
        ) {
                match source {
                        HTLCSource::OutboundRoute { session_priv, payment_id, path, .. } => {
@@ -5759,11 +6210,10 @@ where
                        },
                        HTLCSource::PreviousHopData(hop_data) => {
                                let prev_channel_id = hop_data.channel_id;
+                               let prev_user_channel_id = hop_data.user_channel_id;
                                let completed_blocker = RAAMonitorUpdateBlockingAction::from_prev_hop_data(&hop_data);
                                #[cfg(debug_assertions)]
                                let claiming_chan_funding_outpoint = hop_data.outpoint;
-                               #[cfg(debug_assertions)]
-                               let claiming_channel_id = hop_data.channel_id;
                                let res = self.claim_funds_from_hop(hop_data, payment_preimage,
                                        |htlc_claim_value_msat, definitely_duplicate| {
                                                let chan_to_release =
@@ -5821,7 +6271,7 @@ where
                                                                                BackgroundEvent::MonitorUpdatesComplete {
                                                                                        channel_id, ..
                                                                                } =>
-                                                                                       *channel_id == claiming_channel_id,
+                                                                                       *channel_id == prev_channel_id,
                                                                        }
                                                                }), "{:?}", *background_events);
                                                        }
@@ -5845,12 +6295,14 @@ where
                                                                "skimmed_fee_msat must always be included in total_fee_earned_msat");
                                                        Some(MonitorUpdateCompletionAction::EmitEventAndFreeOtherChannel {
                                                                event: events::Event::PaymentForwarded {
-                                                                       total_fee_earned_msat,
-                                                                       claim_from_onchain_tx: from_onchain,
                                                                        prev_channel_id: Some(prev_channel_id),
                                                                        next_channel_id: Some(next_channel_id),
-                                                                       outbound_amount_forwarded_msat: forwarded_htlc_value_msat,
+                                                                       prev_user_channel_id,
+                                                                       next_user_channel_id,
+                                                                       total_fee_earned_msat,
                                                                        skimmed_fee_msat,
+                                                                       claim_from_onchain_tx: from_onchain,
+                                                                       outbound_amount_forwarded_msat: forwarded_htlc_value_msat,
                                                                },
                                                                downstream_counterparty_and_funding_outpoint: chan_to_release,
                                                        })
@@ -6105,73 +6557,82 @@ where
                // happening and return an error. N.B. that we create channel with an outbound SCID of zero so
                // that we can delay allocating the SCID until after we're sure that the checks below will
                // succeed.
-               let mut channel = match peer_state.inbound_channel_request_by_id.remove(temporary_channel_id) {
+               let res = match peer_state.inbound_channel_request_by_id.remove(temporary_channel_id) {
                        Some(unaccepted_channel) => {
                                let best_block_height = self.best_block.read().unwrap().height;
                                InboundV1Channel::new(&self.fee_estimator, &self.entropy_source, &self.signer_provider,
                                        counterparty_node_id.clone(), &self.channel_type_features(), &peer_state.latest_features,
                                        &unaccepted_channel.open_channel_msg, user_channel_id, &self.default_configuration, best_block_height,
-                                       &self.logger, accept_0conf).map_err(|e| {
-                                               let err_str = e.to_string();
-                                               log_error!(logger, "{}", err_str);
-
-                                               APIError::ChannelUnavailable { err: err_str }
-                                       })
-                               }
+                                       &self.logger, accept_0conf).map_err(|err| MsgHandleErrInternal::from_chan_no_close(err, *temporary_channel_id))
+                       },
                        _ => {
                                let err_str = "No such channel awaiting to be accepted.".to_owned();
                                log_error!(logger, "{}", err_str);
 
-                               Err(APIError::APIMisuseError { err: err_str })
+                               return Err(APIError::APIMisuseError { err: err_str });
                        }
-               }?;
+               };
 
-               if accept_0conf {
-                       // This should have been correctly configured by the call to InboundV1Channel::new.
-                       debug_assert!(channel.context.minimum_depth().unwrap() == 0);
-               } else if channel.context.get_channel_type().requires_zero_conf() {
-                       let send_msg_err_event = events::MessageSendEvent::HandleError {
-                               node_id: channel.context.get_counterparty_node_id(),
-                               action: msgs::ErrorAction::SendErrorMessage{
-                                       msg: msgs::ErrorMessage { channel_id: temporary_channel_id.clone(), data: "No zero confirmation channels accepted".to_owned(), }
+               match res {
+                       Err(err) => {
+                               mem::drop(peer_state_lock);
+                               mem::drop(per_peer_state);
+                               match handle_error!(self, Result::<(), MsgHandleErrInternal>::Err(err), *counterparty_node_id) {
+                                       Ok(_) => unreachable!("`handle_error` only returns Err as we've passed in an Err"),
+                                       Err(e) => {
+                                               return Err(APIError::ChannelUnavailable { err: e.err });
+                                       },
                                }
-                       };
-                       peer_state.pending_msg_events.push(send_msg_err_event);
-                       let err_str = "Please use accept_inbound_channel_from_trusted_peer_0conf to accept channels with zero confirmations.".to_owned();
-                       log_error!(logger, "{}", err_str);
+                       }
+                       Ok(mut channel) => {
+                               if accept_0conf {
+                                       // This should have been correctly configured by the call to InboundV1Channel::new.
+                                       debug_assert!(channel.context.minimum_depth().unwrap() == 0);
+                               } else if channel.context.get_channel_type().requires_zero_conf() {
+                                       let send_msg_err_event = events::MessageSendEvent::HandleError {
+                                               node_id: channel.context.get_counterparty_node_id(),
+                                               action: msgs::ErrorAction::SendErrorMessage{
+                                                       msg: msgs::ErrorMessage { channel_id: temporary_channel_id.clone(), data: "No zero confirmation channels accepted".to_owned(), }
+                                               }
+                                       };
+                                       peer_state.pending_msg_events.push(send_msg_err_event);
+                                       let err_str = "Please use accept_inbound_channel_from_trusted_peer_0conf to accept channels with zero confirmations.".to_owned();
+                                       log_error!(logger, "{}", err_str);
 
-                       return Err(APIError::APIMisuseError { err: err_str });
-               } else {
-                       // If this peer already has some channels, a new channel won't increase our number of peers
-                       // with unfunded channels, so as long as we aren't over the maximum number of unfunded
-                       // channels per-peer we can accept channels from a peer with existing ones.
-                       if is_only_peer_channel && peers_without_funded_channels >= MAX_UNFUNDED_CHANNEL_PEERS {
-                               let send_msg_err_event = events::MessageSendEvent::HandleError {
-                                       node_id: channel.context.get_counterparty_node_id(),
-                                       action: msgs::ErrorAction::SendErrorMessage{
-                                               msg: msgs::ErrorMessage { channel_id: temporary_channel_id.clone(), data: "Have too many peers with unfunded channels, not accepting new ones".to_owned(), }
-                                       }
-                               };
-                               peer_state.pending_msg_events.push(send_msg_err_event);
-                               let err_str = "Too many peers with unfunded channels, refusing to accept new ones".to_owned();
-                               log_error!(logger, "{}", err_str);
+                                       return Err(APIError::APIMisuseError { err: err_str });
+                               } else {
+                                       // If this peer already has some channels, a new channel won't increase our number of peers
+                                       // with unfunded channels, so as long as we aren't over the maximum number of unfunded
+                                       // channels per-peer we can accept channels from a peer with existing ones.
+                                       if is_only_peer_channel && peers_without_funded_channels >= MAX_UNFUNDED_CHANNEL_PEERS {
+                                               let send_msg_err_event = events::MessageSendEvent::HandleError {
+                                                       node_id: channel.context.get_counterparty_node_id(),
+                                                       action: msgs::ErrorAction::SendErrorMessage{
+                                                               msg: msgs::ErrorMessage { channel_id: temporary_channel_id.clone(), data: "Have too many peers with unfunded channels, not accepting new ones".to_owned(), }
+                                                       }
+                                               };
+                                               peer_state.pending_msg_events.push(send_msg_err_event);
+                                               let err_str = "Too many peers with unfunded channels, refusing to accept new ones".to_owned();
+                                               log_error!(logger, "{}", err_str);
 
-                               return Err(APIError::APIMisuseError { err: err_str });
-                       }
-               }
+                                               return Err(APIError::APIMisuseError { err: err_str });
+                                       }
+                               }
 
-               // Now that we know we have a channel, assign an outbound SCID alias.
-               let outbound_scid_alias = self.create_and_insert_outbound_scid_alias();
-               channel.context.set_outbound_scid_alias(outbound_scid_alias);
+                               // Now that we know we have a channel, assign an outbound SCID alias.
+                               let outbound_scid_alias = self.create_and_insert_outbound_scid_alias();
+                               channel.context.set_outbound_scid_alias(outbound_scid_alias);
 
-               peer_state.pending_msg_events.push(events::MessageSendEvent::SendAcceptChannel {
-                       node_id: channel.context.get_counterparty_node_id(),
-                       msg: channel.accept_inbound_channel(),
-               });
+                               peer_state.pending_msg_events.push(events::MessageSendEvent::SendAcceptChannel {
+                                       node_id: channel.context.get_counterparty_node_id(),
+                                       msg: channel.accept_inbound_channel(),
+                               });
 
-               peer_state.channel_by_id.insert(temporary_channel_id.clone(), ChannelPhase::UnfundedInboundV1(channel));
+                               peer_state.channel_by_id.insert(temporary_channel_id.clone(), ChannelPhase::UnfundedInboundV1(channel));
 
-               Ok(())
+                               Ok(())
+                       },
+               }
        }
 
        /// Gets the number of peers which match the given filter and do not have any funded, outbound,
@@ -6824,6 +7285,7 @@ where
 
        fn internal_update_fulfill_htlc(&self, counterparty_node_id: &PublicKey, msg: &msgs::UpdateFulfillHTLC) -> Result<(), MsgHandleErrInternal> {
                let funding_txo;
+               let next_user_channel_id;
                let (htlc_source, forwarded_htlc_value, skimmed_fee_msat) = {
                        let per_peer_state = self.per_peer_state.read().unwrap();
                        let peer_state_mutex = per_peer_state.get(counterparty_node_id)
@@ -6853,6 +7315,7 @@ where
                                                // outbound HTLC is claimed. This is guaranteed to all complete before we
                                                // process the RAA as messages are processed from single peers serially.
                                                funding_txo = chan.context.get_funding_txo().expect("We won't accept a fulfill until funded");
+                                               next_user_channel_id = chan.context.get_user_id();
                                                res
                                        } else {
                                                return try_chan_phase_entry!(self, Err(ChannelError::Close(
@@ -6864,7 +7327,7 @@ where
                };
                self.claim_funds_internal(htlc_source, msg.payment_preimage.clone(),
                        Some(forwarded_htlc_value), skimmed_fee_msat, false, false, Some(*counterparty_node_id),
-                       funding_txo, msg.channel_id
+                       funding_txo, msg.channel_id, Some(next_user_channel_id),
                );
 
                Ok(())
@@ -7366,7 +7829,7 @@ where
                                                        log_trace!(logger, "Claiming HTLC with preimage {} from our monitor", preimage);
                                                        self.claim_funds_internal(htlc_update.source, preimage,
                                                                htlc_update.htlc_value_satoshis.map(|v| v * 1000), None, true,
-                                                               false, counterparty_node_id, funding_outpoint, channel_id);
+                                                               false, counterparty_node_id, funding_outpoint, channel_id, None);
                                                } else {
                                                        log_trace!(logger, "Failing HTLC with hash {} from our monitor", &htlc_update.payment_hash);
                                                        let receiver = HTLCDestination::NextHopChannel { node_id: counterparty_node_id, channel_id };
@@ -7374,7 +7837,7 @@ where
                                                        self.fail_htlc_backwards_internal(&htlc_update.source, &htlc_update.payment_hash, &reason, receiver);
                                                }
                                        },
-                                       MonitorEvent::HolderForceClosed(_funding_outpoint) => {
+                                       MonitorEvent::HolderForceClosed(_) | MonitorEvent::HolderForceClosedWithInfo { .. } => {
                                                let counterparty_node_id_opt = match counterparty_node_id {
                                                        Some(cp_id) => Some(cp_id),
                                                        None => {
@@ -7392,7 +7855,12 @@ where
                                                                let pending_msg_events = &mut peer_state.pending_msg_events;
                                                                if let hash_map::Entry::Occupied(chan_phase_entry) = peer_state.channel_by_id.entry(channel_id) {
                                                                        if let ChannelPhase::Funded(mut chan) = remove_channel_phase!(self, chan_phase_entry) {
-                                                                               failed_channels.push(chan.context.force_shutdown(false, ClosureReason::HolderForceClosed));
+                                                                               let reason = if let MonitorEvent::HolderForceClosedWithInfo { reason, .. } = monitor_event {
+                                                                                       reason
+                                                                               } else {
+                                                                                       ClosureReason::HolderForceClosed
+                                                                               };
+                                                                               failed_channels.push(chan.context.force_shutdown(false, reason.clone()));
                                                                                if let Ok(update) = self.get_channel_update_for_broadcast(&chan) {
                                                                                        pending_msg_events.push(events::MessageSendEvent::BroadcastChannelUpdate {
                                                                                                msg: update
@@ -7401,7 +7869,7 @@ where
                                                                                pending_msg_events.push(events::MessageSendEvent::HandleError {
                                                                                        node_id: chan.context.get_counterparty_node_id(),
                                                                                        action: msgs::ErrorAction::DisconnectPeer {
-                                                                                               msg: Some(msgs::ErrorMessage { channel_id: chan.context.channel_id(), data: "Channel force-closed".to_owned() })
+                                                                                               msg: Some(msgs::ErrorMessage { channel_id: chan.context.channel_id(), data: reason.to_string() })
                                                                                        },
                                                                                });
                                                                        }
@@ -8738,6 +9206,9 @@ where
        }
 
        /// Returns true if this [`ChannelManager`] needs to be persisted.
+       ///
+       /// See [`Self::get_event_or_persistence_needed_future`] for retrieving a [`Future`] that
+       /// indicates this should be checked.
        pub fn get_and_clear_needs_persistence(&self) -> bool {
                self.needs_persist_flag.swap(false, Ordering::AcqRel)
        }
@@ -9242,8 +9713,6 @@ where
        }
 
        fn handle_error(&self, counterparty_node_id: &PublicKey, msg: &msgs::ErrorMessage) {
-               let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(self);
-
                match &msg.data as &str {
                        "cannot co-op close channel w/ active htlcs"|
                        "link failed to shutdown" =>
@@ -9256,34 +9725,45 @@ where
                                // We're not going to bother handling this in a sensible way, instead simply
                                // repeating the Shutdown message on repeat until morale improves.
                                if !msg.channel_id.is_zero() {
-                                       let per_peer_state = self.per_peer_state.read().unwrap();
-                                       let peer_state_mutex_opt = per_peer_state.get(counterparty_node_id);
-                                       if peer_state_mutex_opt.is_none() { return; }
-                                       let mut peer_state = peer_state_mutex_opt.unwrap().lock().unwrap();
-                                       if let Some(ChannelPhase::Funded(chan)) = peer_state.channel_by_id.get(&msg.channel_id) {
-                                               if let Some(msg) = chan.get_outbound_shutdown() {
-                                                       peer_state.pending_msg_events.push(events::MessageSendEvent::SendShutdown {
-                                                               node_id: *counterparty_node_id,
-                                                               msg,
-                                                       });
-                                               }
-                                               peer_state.pending_msg_events.push(events::MessageSendEvent::HandleError {
-                                                       node_id: *counterparty_node_id,
-                                                       action: msgs::ErrorAction::SendWarningMessage {
-                                                               msg: msgs::WarningMessage {
-                                                                       channel_id: msg.channel_id,
-                                                                       data: "You appear to be exhibiting LND bug 6039, we'll keep sending you shutdown messages until you handle them correctly".to_owned()
-                                                               },
-                                                               log_level: Level::Trace,
+                                       PersistenceNotifierGuard::optionally_notify(
+                                               self,
+                                               || -> NotifyOption {
+                                                       let per_peer_state = self.per_peer_state.read().unwrap();
+                                                       let peer_state_mutex_opt = per_peer_state.get(counterparty_node_id);
+                                                       if peer_state_mutex_opt.is_none() { return NotifyOption::SkipPersistNoEvents; }
+                                                       let mut peer_state = peer_state_mutex_opt.unwrap().lock().unwrap();
+                                                       if let Some(ChannelPhase::Funded(chan)) = peer_state.channel_by_id.get(&msg.channel_id) {
+                                                               if let Some(msg) = chan.get_outbound_shutdown() {
+                                                                       peer_state.pending_msg_events.push(events::MessageSendEvent::SendShutdown {
+                                                                               node_id: *counterparty_node_id,
+                                                                               msg,
+                                                                       });
+                                                               }
+                                                               peer_state.pending_msg_events.push(events::MessageSendEvent::HandleError {
+                                                                       node_id: *counterparty_node_id,
+                                                                       action: msgs::ErrorAction::SendWarningMessage {
+                                                                               msg: msgs::WarningMessage {
+                                                                                       channel_id: msg.channel_id,
+                                                                                       data: "You appear to be exhibiting LND bug 6039, we'll keep sending you shutdown messages until you handle them correctly".to_owned()
+                                                                               },
+                                                                               log_level: Level::Trace,
+                                                                       }
+                                                               });
+                                                               // This can happen in a fairly tight loop, so we absolutely cannot trigger
+                                                               // a `ChannelManager` write here.
+                                                               return NotifyOption::SkipPersistHandleEvents;
                                                        }
-                                               });
-                                       }
+                                                       NotifyOption::SkipPersistNoEvents
+                                               }
+                                       );
                                }
                                return;
                        }
                        _ => {}
                }
 
+               let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(self);
+
                if msg.channel_id.is_zero() {
                        let channel_ids: Vec<ChannelId> = {
                                let per_peer_state = self.per_peer_state.read().unwrap();
@@ -9766,6 +10246,7 @@ impl_writeable_tlv_based_enum!(PendingHTLCRouting,
        },
        (2, ReceiveKeysend) => {
                (0, payment_preimage, required),
+               (1, requires_blinded_error, (default_value, false)),
                (2, incoming_cltv_expiry, required),
                (3, payment_metadata, option),
                (4, payment_data, option), // Added in 0.0.116
@@ -11377,7 +11858,9 @@ where
                        // don't remember in the `ChannelMonitor` where we got a preimage from, but if the
                        // channel is closed we just assume that it probably came from an on-chain claim.
                        channel_manager.claim_funds_internal(source, preimage, Some(downstream_value), None,
-                               downstream_closed, true, downstream_node_id, downstream_funding, downstream_channel_id);
+                               downstream_closed, true, downstream_node_id, downstream_funding,
+                               downstream_channel_id, None
+                       );
                }
 
                //TODO: Broadcast channel update for closed channels, but only after we've made a