Add OpenChannelV2Request & dual-funded channel contribute config

lightning/src/events/mod.rs

@@ -812,6 +812,59 @@ pub enum Event {
 		/// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
 		channel_type: ChannelTypeFeatures,
 	},
+	/// Indicates a request to open a new dual-funded channel by a peer.
+	///
+	/// To accept the request, call [`ChannelManager::accept_inbound_dual_funded_channel`].
+	/// To reject the request, call [`ChannelManager::force_close_without_broadcasting_txn`].
+	///
+	/// The event is always triggered when a new open channel request is received for a dual-funded
+	/// channel, regardless of the value of the [`UserConfig::manually_accept_inbound_channels`]
+	/// config flag. This is so that funding inputs can be manually provided to contribute to the
+	/// overall channel capacity on the acceptor side.
+	///
+	/// [`ChannelManager::accept_inbound_dual_funded_channel`]: crate::ln::channelmanager::ChannelManager::accept_inbound_dual_funded_channel
+	/// [`ChannelManager::force_close_without_broadcasting_txn`]: crate::ln::channelmanager::ChannelManager::force_close_without_broadcasting_txn
+	/// [`UserConfig::manually_accept_inbound_channels`]: crate::util::config::UserConfig::manually_accept_inbound_channels
+	OpenChannelV2Request {
+		/// The temporary channel ID of the channel requested to be opened.
+		///
+		/// When responding to the request, the `temporary_channel_id` should be passed
+		/// back to the ChannelManager through [`ChannelManager::accept_inbound_dual_funded_channel`] to
+		/// accept, or through [`ChannelManager::force_close_without_broadcasting_txn`] to reject.
+		///
+		/// [`ChannelManager::accept_inbound_dual_funded_channel`]: crate::ln::channelmanager::ChannelManager::accept_inbound_dual_funded_channel
+		/// [`ChannelManager::force_close_without_broadcasting_txn`]: crate::ln::channelmanager::ChannelManager::force_close_without_broadcasting_txn
+		temporary_channel_id: [u8; 32],
+		/// The node_id of the counterparty requesting to open the channel.
+		///
+		/// When responding to the request, the `counterparty_node_id` should be passed
+		/// back to the `ChannelManager` through [`ChannelManager::accept_inbound_dual_funded_channel`] to
+		/// accept the request, or through [`ChannelManager::force_close_without_broadcasting_txn`] to reject the
+		/// request.
+		///
+		/// [`ChannelManager::accept_inbound_dual_funded_channel`]: crate::ln::channelmanager::ChannelManager::accept_inbound_dual_funded_channel
+		/// [`ChannelManager::force_close_without_broadcasting_txn`]: crate::ln::channelmanager::ChannelManager::force_close_without_broadcasting_txn
+		counterparty_node_id: PublicKey,
+		/// The counterparty's contribution to the channel value in satoshis.
+		funding_satoshis: u64,
+		/// The features that this channel will operate with. If you reject the channel, a
+		/// well-behaved counterparty may automatically re-attempt the channel with a new set of
+		/// feature flags.
+		///
+		/// Note that if [`ChannelTypeFeatures::supports_scid_privacy`] returns true on this type,
+		/// the resulting [`ChannelManager`] will not be readable by versions of LDK prior to
+		/// 0.0.106.
+		///
+		/// Furthermore, note that if [`ChannelTypeFeatures::supports_zero_conf`] returns true on this type,
+		/// the resulting [`ChannelManager`] will not be readable by versions of LDK prior to
+		/// 0.0.107.
+		///
+		/// NOTE: Zero-conf dual-funded channels are not currently accepted.
+		// TODO(dual_funding): Maybe support opportunistic zero-conf channels like Eclair?
+		///
+		/// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
+		channel_type: ChannelTypeFeatures,
+	},
 	/// Indicates that the HTLC was accepted, but could not be processed when or after attempting to
 	/// forward it.
 	///
@@ -1058,6 +1111,12 @@ impl Writeable for Event {
 					(8, funding_txo, required),
 				});
 			},
+			&Event::OpenChannelV2Request { .. } => {
+				33u8.write(writer)?;
+				// We never write the OpenChannelV2Request events as, upon disconnection, peers
+				// drop any channels which have not yet completed any interactive funding transaction
+				// construction.
+			},
 			// Note that, going forward, all new events must only write data inside of
 			// `write_tlv_fields`. Versions 0.0.101+ will ignore odd-numbered events that write
 			// data via `write_tlv_fields`.

lightning/src/util/config.rs

@@ -764,6 +764,21 @@ pub struct UserConfig {
 	///
 	/// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
 	pub accept_mpp_keysend: bool,
+	/// If this is set to true, regardless of `accept_inbound_channels`, the user needs to manually
+	/// accept inbound requests to open a new dual-funded channel and provide any UTXOs they'd like
+	/// to contribute to the funding transaction.
+	///
+	/// When set to true, [`Event::OpenChannelV2Request`] will be triggered once a request to open a
+	/// new inbound dual-funded channel is received through a [`msgs::OpenChannelV2`] message. In that
+	/// case, a [`msgs::AcceptChannelV2`] message will not be sent back to the counterparty node unless
+	/// the user explicitly chooses to accept the request.
+	///
+	/// Default value: false.
+	///
+	/// [`Event::OpenChannelV2Request`]: crate::events::Event::OpenChannelV2Request
+	/// [`msgs::OpenChannelV2`]: crate::ln::msgs::OpenChannelV2
+	/// [`msgs::AcceptChannelV2`]: crate::ln::msgs::AcceptChannelV2
+	pub contribute_to_dual_funded_channels: bool,
 }
 
 impl Default for UserConfig {
@@ -777,6 +792,7 @@ impl Default for UserConfig {
 			manually_accept_inbound_channels: false,
 			accept_intercept_htlcs: false,
 			accept_mpp_keysend: false,
+			contribute_to_dual_funded_channels: false,
 		}
 	}
 }