Add ReserveType to ChannelDetails

We expose the reserve type of each channel through
a new ReserveType enum on ChannelDetails. This tells
users whether a channel uses adaptive anchor reserves,
has no reserve due to a trusted peer, or is a legacy
pre-anchor channel.

The reserve type is derived at query time in list_channels
by checking the channel's type features against
trusted_peers_no_reserve.

Additionally, We replace the From<LdkChannelDetails>
impl with an explicit from_ldk method that takes the
anchor channels config.

Author: enigbe

src/lib.rs

@@ -177,7 +177,9 @@ use types::{
 	HRNResolver, KeysManager, OnionMessenger, PaymentStore, PeerManager, Router, Scorer, Sweeper,
 	Wallet,
 };
-pub use types::{ChannelDetails, CustomTlvRecord, PeerDetails, SyncAndAsyncKVStore, UserChannelId};
+pub use types::{
+	ChannelDetails, CustomTlvRecord, PeerDetails, ReserveType, SyncAndAsyncKVStore, UserChannelId,
+};
 pub use vss_client;
 
 use crate::scoring::setup_background_pathfinding_scores_sync;
@@ -1069,7 +1071,11 @@ impl Node {
 
 	/// Retrieve a list of known channels.
 	pub fn list_channels(&self) -> Vec<ChannelDetails> {
-		self.channel_manager.list_channels().into_iter().map(|c| c.into()).collect()
+		self.channel_manager
+			.list_channels()
+			.into_iter()
+			.map(|c| ChannelDetails::from_ldk(c, self.config.anchor_channels_config.as_ref()))
+			.collect()
 	}
 
 	/// Connect to a node on the peer-to-peer network.

src/types.rs

@@ -36,7 +36,7 @@ use lightning_net_tokio::SocketDescriptor;
 
 use crate::chain::bitcoind::UtxoSourceClient;
 use crate::chain::ChainSource;
-use crate::config::ChannelConfig;
+use crate::config::{AnchorChannelsConfig, ChannelConfig};
 use crate::data_store::DataStore;
 use crate::fee_estimator::OnchainFeeEstimator;
 use crate::logger::Logger;
@@ -399,6 +399,48 @@ pub struct ChannelCounterparty {
 	pub outbound_htlc_maximum_msat: Option<u64>,
 }
 
+/// Describes the reserve behavior of a channel based on its type and trust configuration.
+///
+/// This captures the combination of the channel's on-chain construction (anchor outputs vs legacy
+/// static_remote_key) and whether the counterparty is in our trusted peers list. It tells the
+/// user what reserve obligations exist for this channel without exposing internal protocol details.
+///
+/// See [`AnchorChannelsConfig`] for how reserve behavior is configured.
+///
+/// [`AnchorChannelsConfig`]: crate::config::AnchorChannelsConfig
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[cfg_attr(feature = "uniffi", derive(uniffi::Enum))]
+pub enum ReserveType {
+	/// An anchor outputs channel where we maintain a per-channel on-chain reserve for fee
+	/// bumping force-close transactions.
+	///
+	/// Anchor channels (using `option_anchors_zero_fee_htlc_tx` as defined in
+	/// [BOLT 3](https://github.com/lightning/bolts/03-transactions.md#to_local_anchor-and-to_remote_anchor-output-option_anchors))
+	/// allow either party to fee-bump commitment transactions via CPFP (Child-Pays-For-Parent)
+	/// at broadcast time. Because the pre-signed commitment fee may be insufficient under
+	/// current fee conditions, the broadcaster must supply additional funds (hence adaptive) through an
+	/// anchor output spend. The reserve ensures sufficient on-chain funds are available to cover this.
+	///
+	/// This is the default for anchor channels when the counterparty is not in
+	/// [`AnchorChannelsConfig::trusted_peers_no_reserve`].
+	///
+	/// [`AnchorChannelsConfig::trusted_peers_no_reserve`]: crate::config::AnchorChannelsConfig::trusted_peers_no_reserve
+	Adaptive,
+	/// An anchor outputs channel where we do not maintain any reserve, because the counterparty
+	/// is in our [`AnchorChannelsConfig::trusted_peers_no_reserve`] list.
+	///
+	/// In this mode, we trust the counterparty to broadcast a valid commitment transaction on
+	/// our behalf and do not set aside funds for fee bumping.
+	///
+	/// [`AnchorChannelsConfig::trusted_peers_no_reserve`]: crate::config::AnchorChannelsConfig::trusted_peers_no_reserve
+	TrustedPeersNoReserve,
+	/// A legacy (pre-anchor) channel using only `option_static_remotekey`.
+	///
+	/// These channels do not use anchor outputs and therefore do not require an on-chain reserve
+	/// for fee bumping. Commitment transaction fees are pre-committed at channel open time.
+	Legacy,
+}
+
 /// Details of a channel as returned by [`Node::list_channels`].
 ///
 /// When a channel is spliced, most fields continue to refer to the original pre-splice channel
@@ -559,10 +601,32 @@ pub struct ChannelDetails {
 	pub inbound_htlc_maximum_msat: Option<u64>,
 	/// Set of configurable parameters that affect channel operation.
 	pub config: ChannelConfig,
+	/// The type of on-chain reserve maintained for this channel.
+	///
+	/// See [`ReserveType`] for details on how reserves differ between anchor and legacy channels.
+	pub reserve_type: ReserveType,
 }
 
-impl From<LdkChannelDetails> for ChannelDetails {
-	fn from(value: LdkChannelDetails) -> Self {
+impl ChannelDetails {
+	pub(crate) fn from_ldk(
+		value: LdkChannelDetails, anchor_channels_config: Option<&AnchorChannelsConfig>,
+	) -> Self {
+		let is_anchor_channel =
+			value.channel_type.as_ref().map_or(false, |ct| ct.supports_anchors_zero_fee_htlc_tx());
+
+		let reserve_type = if is_anchor_channel {
+			let is_trusted = anchor_channels_config.map_or(false, |c| {
+				c.trusted_peers_no_reserve.contains(&value.counterparty.node_id)
+			});
+			if is_trusted {
+				ReserveType::TrustedPeersNoReserve
+			} else {
+				ReserveType::Adaptive
+			}
+		} else {
+			ReserveType::Legacy
+		};
+
 		ChannelDetails {
 			channel_id: value.channel_id,
 			counterparty: ChannelCounterparty {
@@ -601,6 +665,7 @@ impl From<LdkChannelDetails> for ChannelDetails {
 			inbound_htlc_maximum_msat: value.inbound_htlc_maximum_msat,
 			// unwrap safety: `config` is only `None` for LDK objects serialized prior to 0.0.109.
 			config: value.config.map(|c| c.into()).unwrap(),
+			reserve_type,
 		}
 	}
 }