From d155b0e18d7d8d4f6e6bcd904d29f23a68fc6f09 Mon Sep 17 00:00:00 2001
From: Duncan Dean <git@dunxen.dev>
Date: Mon, 22 May 2023 16:46:40 +0200
Subject: [PATCH] wip: Add channelmanager dual-funding support

---
 lightning/src/events/mod.rs        |  59 +++++
 lightning/src/ln/channel.rs        | 349 +++++++++++++++++------------
 lightning/src/ln/channelmanager.rs | 309 ++++++++++++++++++++++++-
 lightning/src/util/config.rs       |  16 ++
 4 files changed, 584 insertions(+), 149 deletions(-)

diff --git a/lightning/src/events/mod.rs b/lightning/src/events/mod.rs
index b9fb955a5a2..5f95d4f8104 100644
--- a/lightning/src/events/mod.rs
+++ b/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): Support zero-conf channels.
+		///
+		/// [`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.
 	///
@@ -1055,6 +1108,12 @@ 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`.
diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs
index 71b51f403d5..8cbaab47cb6 100644
--- a/lightning/src/ln/channel.rs
+++ b/lightning/src/ln/channel.rs
@@ -970,6 +970,143 @@ impl<Signer: ChannelSigner> ChannelContext<Signer> {
 		self.channel_transaction_parameters.funding_outpoint
 	}
 
+	fn do_accept_channel_checks(&mut self, default_limits: &ChannelHandshakeLimits,
+		their_features: &InitFeatures, msg_dust_limit_satoshis: u64, msg_channel_reserve_satoshis: u64,
+		msg_to_self_delay: u16, msg_max_accepted_htlcs: u16, msg_htlc_minimum_msat: u64,
+		msg_max_htlc_value_in_flight_msat: u64, msg_minimum_depth: u32, msg_channel_type: &Option<ChannelTypeFeatures>,
+		msg_shutdown_scriptpubkey: &Option<Script>, msg_funding_pubkey: PublicKey, msg_revocation_basepoint: PublicKey,
+		msg_payment_point: PublicKey, msg_delayed_payment_basepoint: PublicKey, msg_htlc_basepoint: PublicKey,
+		msg_first_per_commitment_point: PublicKey,
+	) -> Result<(), ChannelError> {
+		let peer_limits = if let Some(ref limits) = self.inbound_handshake_limits_override { limits } else { default_limits };
+
+		// Check sanity of message fields:
+		if !self.is_outbound() {
+			return Err(ChannelError::Close("Got an accept_channel message from an inbound peer".to_owned()));
+		}
+		if self.channel_state != ChannelState::OurInitSent as u32 {
+			return Err(ChannelError::Close("Got an accept_channel message at a strange time".to_owned()));
+		}
+		if msg_dust_limit_satoshis > 21000000 * 100000000 {
+			return Err(ChannelError::Close(format!("Peer never wants payout outputs? dust_limit_satoshis was {}", msg_dust_limit_satoshis)));
+		}
+		if msg_channel_reserve_satoshis > self.channel_value_satoshis {
+			return Err(ChannelError::Close(format!("Bogus channel_reserve_satoshis ({}). Must not be greater than ({})", msg_channel_reserve_satoshis, self.channel_value_satoshis)));
+		}
+		if msg_dust_limit_satoshis > self.holder_selected_channel_reserve_satoshis {
+			return Err(ChannelError::Close(format!("Dust limit ({}) is bigger than our channel reserve ({})", msg_dust_limit_satoshis, self.holder_selected_channel_reserve_satoshis)));
+		}
+		if msg_channel_reserve_satoshis > self.channel_value_satoshis - self.holder_selected_channel_reserve_satoshis {
+			return Err(ChannelError::Close(format!("Bogus channel_reserve_satoshis ({}). Must not be greater than channel value minus our reserve ({})",
+				msg_channel_reserve_satoshis, self.channel_value_satoshis - self.holder_selected_channel_reserve_satoshis)));
+		}
+		let full_channel_value_msat = (self.channel_value_satoshis - msg_channel_reserve_satoshis) * 1000;
+		if msg_htlc_minimum_msat >= full_channel_value_msat {
+			return Err(ChannelError::Close(format!("Minimum htlc value ({}) is full channel value ({})", msg_htlc_minimum_msat, full_channel_value_msat)));
+		}
+		let max_delay_acceptable = u16::min(peer_limits.their_to_self_delay, MAX_LOCAL_BREAKDOWN_TIMEOUT);
+		if msg_to_self_delay > max_delay_acceptable {
+			return Err(ChannelError::Close(format!("They wanted our payments to be delayed by a needlessly long period. Upper limit: {}. Actual: {}", max_delay_acceptable, msg_to_self_delay)));
+		}
+		if msg_max_accepted_htlcs < 1 {
+			return Err(ChannelError::Close("0 max_accepted_htlcs makes for a useless channel".to_owned()));
+		}
+		if msg_max_accepted_htlcs > MAX_HTLCS {
+			return Err(ChannelError::Close(format!("max_accepted_htlcs was {}. It must not be larger than {}", msg_max_accepted_htlcs, MAX_HTLCS)));
+		}
+
+		// Now check against optional parameters as set by config...
+		if msg_htlc_minimum_msat > peer_limits.max_htlc_minimum_msat {
+			return Err(ChannelError::Close(format!("htlc_minimum_msat ({}) is higher than the user specified limit ({})", msg_htlc_minimum_msat, peer_limits.max_htlc_minimum_msat)));
+		}
+		if msg_max_htlc_value_in_flight_msat < peer_limits.min_max_htlc_value_in_flight_msat {
+			return Err(ChannelError::Close(format!("max_htlc_value_in_flight_msat ({}) is less than the user specified limit ({})", msg_max_htlc_value_in_flight_msat, peer_limits.min_max_htlc_value_in_flight_msat)));
+		}
+		if msg_channel_reserve_satoshis > peer_limits.max_channel_reserve_satoshis {
+			return Err(ChannelError::Close(format!("channel_reserve_satoshis ({}) is higher than the user specified limit ({})", msg_channel_reserve_satoshis, peer_limits.max_channel_reserve_satoshis)));
+		}
+		if msg_max_accepted_htlcs < peer_limits.min_max_accepted_htlcs {
+			return Err(ChannelError::Close(format!("max_accepted_htlcs ({}) is less than the user specified limit ({})", msg_max_accepted_htlcs, peer_limits.min_max_accepted_htlcs)));
+		}
+		if msg_dust_limit_satoshis < MIN_CHAN_DUST_LIMIT_SATOSHIS {
+			return Err(ChannelError::Close(format!("dust_limit_satoshis ({}) is less than the implementation limit ({})", msg_dust_limit_satoshis, MIN_CHAN_DUST_LIMIT_SATOSHIS)));
+		}
+		if msg_dust_limit_satoshis > MAX_CHAN_DUST_LIMIT_SATOSHIS {
+			return Err(ChannelError::Close(format!("dust_limit_satoshis ({}) is greater than the implementation limit ({})", msg_dust_limit_satoshis, MAX_CHAN_DUST_LIMIT_SATOSHIS)));
+		}
+		if msg_minimum_depth > peer_limits.max_minimum_depth {
+			return Err(ChannelError::Close(format!("We consider the minimum depth to be unreasonably large. Expected minimum: ({}). Actual: ({})", peer_limits.max_minimum_depth, msg_minimum_depth)));
+		}
+
+		if let Some(ty) = &msg_channel_type {
+			if *ty != self.channel_type {
+				return Err(ChannelError::Close("Channel Type in accept_channel didn't match the one sent in open_channel.".to_owned()));
+			}
+		} else if their_features.supports_channel_type() {
+			// Assume they've accepted the channel type as they said they understand it.
+		} else {
+			let channel_type = ChannelTypeFeatures::from_init(&their_features);
+			if channel_type != ChannelTypeFeatures::only_static_remote_key() {
+				return Err(ChannelError::Close("Only static_remote_key is supported for non-negotiated channel types".to_owned()));
+			}
+			self.channel_type = channel_type.clone();
+			self.channel_transaction_parameters.channel_type_features = channel_type;
+		}
+
+		let counterparty_shutdown_scriptpubkey = if their_features.supports_upfront_shutdown_script() {
+			match &msg_shutdown_scriptpubkey {
+				&Some(ref script) => {
+					// Peer is signaling upfront_shutdown and has opt-out with a 0-length script. We don't enforce anything
+					if script.len() == 0 {
+						None
+					} else {
+						if !script::is_bolt2_compliant(&script, their_features) {
+							return Err(ChannelError::Close(format!("Peer is signaling upfront_shutdown but has provided an unacceptable scriptpubkey format: {}", script)));
+						}
+						Some(script.clone())
+					}
+				},
+				// Peer is signaling upfront shutdown but don't opt-out with correct mechanism (a.k.a 0-length script). Peer looks buggy, we fail the channel
+				&None => {
+					return Err(ChannelError::Close("Peer is signaling upfront_shutdown but we don't get any script. Use 0-length script to opt-out".to_owned()));
+				}
+			}
+		} else { None };
+
+		self.counterparty_dust_limit_satoshis = msg_dust_limit_satoshis;
+		self.counterparty_max_htlc_value_in_flight_msat = cmp::min(msg_max_htlc_value_in_flight_msat, self.channel_value_satoshis * 1000);
+		self.counterparty_selected_channel_reserve_satoshis = Some(msg_channel_reserve_satoshis);
+		self.counterparty_htlc_minimum_msat = msg_htlc_minimum_msat;
+		self.counterparty_max_accepted_htlcs = msg_max_accepted_htlcs;
+
+		if peer_limits.trust_own_funding_0conf {
+			self.minimum_depth = Some(msg_minimum_depth);
+		} else {
+			self.minimum_depth = Some(cmp::max(1, msg_minimum_depth));
+		}
+
+		let counterparty_pubkeys = ChannelPublicKeys {
+			funding_pubkey: msg_funding_pubkey,
+			revocation_basepoint: msg_revocation_basepoint,
+			payment_point: msg_payment_point,
+			delayed_payment_basepoint: msg_delayed_payment_basepoint,
+			htlc_basepoint: msg_htlc_basepoint
+		};
+
+		self.channel_transaction_parameters.counterparty_parameters = Some(CounterpartyChannelTransactionParameters {
+			selected_contest_delay: msg_to_self_delay,
+			pubkeys: counterparty_pubkeys,
+		});
+
+		self.counterparty_cur_commitment_point = Some(msg_first_per_commitment_point);
+		self.counterparty_shutdown_scriptpubkey = counterparty_shutdown_scriptpubkey;
+
+		self.channel_state = ChannelState::OurInitSent as u32 | ChannelState::TheirInitSent as u32;
+		self.inbound_handshake_limits_override = None; // We're done enforcing limits on our peer's handshake now.
+
+		Ok(())
+	}
+
 	/// Returns the block hash in which our funding transaction was confirmed.
 	pub fn get_funding_tx_confirmed_in(&self) -> Option<BlockHash> {
 		self.funding_tx_confirmed_in
@@ -2008,23 +2145,23 @@ pub struct DualFundingUtxo {
 /// A wrapper for the common [`ChannelContext`] that includes dual-funding-specific fields.
 pub(super) struct DualFundingChannelContext<Signer: ChannelSigner> {
 	/// The common channel context, not specific to a particular channel establishment version.
-	common: ChannelContext<Signer>,
+	pub common: ChannelContext<Signer>,
 
 	/// The amount in satoshis we will be contributing to the channel.
-	our_funding_satoshis: u64,
+	pub our_funding_satoshis: u64,
 	/// The UTXOs we will be adding in interactive transaction construction.
-	our_funding_inputs: Vec<DualFundingUtxo>,
+	pub our_funding_inputs: Vec<DualFundingUtxo>,
 	/// Flag indicating that we require our counterparty to use confirmed inputs for the construction
 	/// of the funding transaction.
-	we_require_confirmed_inputs: bool,
+	pub we_require_confirmed_inputs: bool,
 	/// Flag indicating that our counterparty requires us to use confirmed inputs for the construction
 	/// of the funding transaction.
-	counterparty_requires_confirmed_inputs: bool,
+	pub counterparty_requires_confirmed_inputs: bool,
 	/// The funding transaction locktime suggested by the initiator. If set by us, it is always set
 	/// to the current block height to align incentives against fee-sniping.
-	funding_tx_locktime: u32,
+	pub funding_tx_locktime: u32,
 	/// The destination for our change output, if one needs to be added.
-	our_change_script_pubkey: Script,
+	pub our_change_script_pubkey: Script,
 }
 
 // TODO: We should refactor this to be an Inbound/OutboundChannel until initial setup handshaking
@@ -2048,6 +2185,14 @@ struct CommitmentTxInfoCached {
 }
 
 impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
+	pub fn context(&self) -> &ChannelContext<Signer> {
+		&self.context
+	}
+
+	pub fn context_mut(&mut self) -> &mut ChannelContext<Signer> {
+		&mut self.context
+	}
+
 	fn check_remote_fee<F: Deref, L: Deref>(fee_estimator: &LowerBoundedFeeEstimator<F>,
 		feerate_per_kw: u32, cur_feerate_per_kw: Option<u32>, logger: &L)
 		-> Result<(), ChannelError> where F::Target: FeeEstimator, L::Target: Logger,
@@ -5636,6 +5781,14 @@ impl<Signer: WriteableEcdsaChannelSigner> OutboundV1Channel<Signer> {
 		})
 	}
 
+	pub fn context(&self) -> &ChannelContext<Signer> {
+		&self.context
+	}
+
+	pub fn context_mut(&mut self) -> &mut ChannelContext<Signer> {
+		&mut self.context
+	}
+
 	/// If an Err is returned, it is a ChannelError::Close (for get_outbound_funding_created)
 	fn get_outbound_funding_created_signature<L: Deref>(&mut self, logger: &L) -> Result<Signature, ChannelError> where L::Target: Logger {
 		let counterparty_keys = self.context.build_remote_transaction_keys();
@@ -5798,133 +5951,12 @@ impl<Signer: WriteableEcdsaChannelSigner> OutboundV1Channel<Signer> {
 
 	// Message handlers
 	pub fn accept_channel(&mut self, msg: &msgs::AcceptChannel, default_limits: &ChannelHandshakeLimits, their_features: &InitFeatures) -> Result<(), ChannelError> {
-		let peer_limits = if let Some(ref limits) = self.context.inbound_handshake_limits_override { limits } else { default_limits };
-
-		// Check sanity of message fields:
-		if !self.context.is_outbound() {
-			return Err(ChannelError::Close("Got an accept_channel message from an inbound peer".to_owned()));
-		}
-		if self.context.channel_state != ChannelState::OurInitSent as u32 {
-			return Err(ChannelError::Close("Got an accept_channel message at a strange time".to_owned()));
-		}
-		if msg.dust_limit_satoshis > 21000000 * 100000000 {
-			return Err(ChannelError::Close(format!("Peer never wants payout outputs? dust_limit_satoshis was {}", msg.dust_limit_satoshis)));
-		}
-		if msg.channel_reserve_satoshis > self.context.channel_value_satoshis {
-			return Err(ChannelError::Close(format!("Bogus channel_reserve_satoshis ({}). Must not be greater than ({})", msg.channel_reserve_satoshis, self.context.channel_value_satoshis)));
-		}
-		if msg.dust_limit_satoshis > self.context.holder_selected_channel_reserve_satoshis {
-			return Err(ChannelError::Close(format!("Dust limit ({}) is bigger than our channel reserve ({})", msg.dust_limit_satoshis, self.context.holder_selected_channel_reserve_satoshis)));
-		}
-		if msg.channel_reserve_satoshis > self.context.channel_value_satoshis - self.context.holder_selected_channel_reserve_satoshis {
-			return Err(ChannelError::Close(format!("Bogus channel_reserve_satoshis ({}). Must not be greater than channel value minus our reserve ({})",
-				msg.channel_reserve_satoshis, self.context.channel_value_satoshis - self.context.holder_selected_channel_reserve_satoshis)));
-		}
-		let full_channel_value_msat = (self.context.channel_value_satoshis - msg.channel_reserve_satoshis) * 1000;
-		if msg.htlc_minimum_msat >= full_channel_value_msat {
-			return Err(ChannelError::Close(format!("Minimum htlc value ({}) is full channel value ({})", msg.htlc_minimum_msat, full_channel_value_msat)));
-		}
-		let max_delay_acceptable = u16::min(peer_limits.their_to_self_delay, MAX_LOCAL_BREAKDOWN_TIMEOUT);
-		if msg.to_self_delay > max_delay_acceptable {
-			return Err(ChannelError::Close(format!("They wanted our payments to be delayed by a needlessly long period. Upper limit: {}. Actual: {}", max_delay_acceptable, msg.to_self_delay)));
-		}
-		if msg.max_accepted_htlcs < 1 {
-			return Err(ChannelError::Close("0 max_accepted_htlcs makes for a useless channel".to_owned()));
-		}
-		if msg.max_accepted_htlcs > MAX_HTLCS {
-			return Err(ChannelError::Close(format!("max_accepted_htlcs was {}. It must not be larger than {}", msg.max_accepted_htlcs, MAX_HTLCS)));
-		}
-
-		// Now check against optional parameters as set by config...
-		if msg.htlc_minimum_msat > peer_limits.max_htlc_minimum_msat {
-			return Err(ChannelError::Close(format!("htlc_minimum_msat ({}) is higher than the user specified limit ({})", msg.htlc_minimum_msat, peer_limits.max_htlc_minimum_msat)));
-		}
-		if msg.max_htlc_value_in_flight_msat < peer_limits.min_max_htlc_value_in_flight_msat {
-			return Err(ChannelError::Close(format!("max_htlc_value_in_flight_msat ({}) is less than the user specified limit ({})", msg.max_htlc_value_in_flight_msat, peer_limits.min_max_htlc_value_in_flight_msat)));
-		}
-		if msg.channel_reserve_satoshis > peer_limits.max_channel_reserve_satoshis {
-			return Err(ChannelError::Close(format!("channel_reserve_satoshis ({}) is higher than the user specified limit ({})", msg.channel_reserve_satoshis, peer_limits.max_channel_reserve_satoshis)));
-		}
-		if msg.max_accepted_htlcs < peer_limits.min_max_accepted_htlcs {
-			return Err(ChannelError::Close(format!("max_accepted_htlcs ({}) is less than the user specified limit ({})", msg.max_accepted_htlcs, peer_limits.min_max_accepted_htlcs)));
-		}
-		if msg.dust_limit_satoshis < MIN_CHAN_DUST_LIMIT_SATOSHIS {
-			return Err(ChannelError::Close(format!("dust_limit_satoshis ({}) is less than the implementation limit ({})", msg.dust_limit_satoshis, MIN_CHAN_DUST_LIMIT_SATOSHIS)));
-		}
-		if msg.dust_limit_satoshis > MAX_CHAN_DUST_LIMIT_SATOSHIS {
-			return Err(ChannelError::Close(format!("dust_limit_satoshis ({}) is greater than the implementation limit ({})", msg.dust_limit_satoshis, MAX_CHAN_DUST_LIMIT_SATOSHIS)));
-		}
-		if msg.minimum_depth > peer_limits.max_minimum_depth {
-			return Err(ChannelError::Close(format!("We consider the minimum depth to be unreasonably large. Expected minimum: ({}). Actual: ({})", peer_limits.max_minimum_depth, msg.minimum_depth)));
-		}
-
-		if let Some(ty) = &msg.channel_type {
-			if *ty != self.context.channel_type {
-				return Err(ChannelError::Close("Channel Type in accept_channel didn't match the one sent in open_channel.".to_owned()));
-			}
-		} else if their_features.supports_channel_type() {
-			// Assume they've accepted the channel type as they said they understand it.
-		} else {
-			let channel_type = ChannelTypeFeatures::from_init(&their_features);
-			if channel_type != ChannelTypeFeatures::only_static_remote_key() {
-				return Err(ChannelError::Close("Only static_remote_key is supported for non-negotiated channel types".to_owned()));
-			}
-			self.context.channel_type = channel_type.clone();
-			self.context.channel_transaction_parameters.channel_type_features = channel_type;
-		}
-
-		let counterparty_shutdown_scriptpubkey = if their_features.supports_upfront_shutdown_script() {
-			match &msg.shutdown_scriptpubkey {
-				&Some(ref script) => {
-					// Peer is signaling upfront_shutdown and has opt-out with a 0-length script. We don't enforce anything
-					if script.len() == 0 {
-						None
-					} else {
-						if !script::is_bolt2_compliant(&script, their_features) {
-							return Err(ChannelError::Close(format!("Peer is signaling upfront_shutdown but has provided an unacceptable scriptpubkey format: {}", script)));
-						}
-						Some(script.clone())
-					}
-				},
-				// Peer is signaling upfront shutdown but don't opt-out with correct mechanism (a.k.a 0-length script). Peer looks buggy, we fail the channel
-				&None => {
-					return Err(ChannelError::Close("Peer is signaling upfront_shutdown but we don't get any script. Use 0-length script to opt-out".to_owned()));
-				}
-			}
-		} else { None };
-
-		self.context.counterparty_dust_limit_satoshis = msg.dust_limit_satoshis;
-		self.context.counterparty_max_htlc_value_in_flight_msat = cmp::min(msg.max_htlc_value_in_flight_msat, self.context.channel_value_satoshis * 1000);
-		self.context.counterparty_selected_channel_reserve_satoshis = Some(msg.channel_reserve_satoshis);
-		self.context.counterparty_htlc_minimum_msat = msg.htlc_minimum_msat;
-		self.context.counterparty_max_accepted_htlcs = msg.max_accepted_htlcs;
-
-		if peer_limits.trust_own_funding_0conf {
-			self.context.minimum_depth = Some(msg.minimum_depth);
-		} else {
-			self.context.minimum_depth = Some(cmp::max(1, msg.minimum_depth));
-		}
-
-		let counterparty_pubkeys = ChannelPublicKeys {
-			funding_pubkey: msg.funding_pubkey,
-			revocation_basepoint: msg.revocation_basepoint,
-			payment_point: msg.payment_point,
-			delayed_payment_basepoint: msg.delayed_payment_basepoint,
-			htlc_basepoint: msg.htlc_basepoint
-		};
-
-		self.context.channel_transaction_parameters.counterparty_parameters = Some(CounterpartyChannelTransactionParameters {
-			selected_contest_delay: msg.to_self_delay,
-			pubkeys: counterparty_pubkeys,
-		});
-
-		self.context.counterparty_cur_commitment_point = Some(msg.first_per_commitment_point);
-		self.context.counterparty_shutdown_scriptpubkey = counterparty_shutdown_scriptpubkey;
-
-		self.context.channel_state = ChannelState::OurInitSent as u32 | ChannelState::TheirInitSent as u32;
-		self.context.inbound_handshake_limits_override = None; // We're done enforcing limits on our peer's handshake now.
-
-		Ok(())
+		self.context.do_accept_channel_checks(
+			default_limits, their_features, msg.dust_limit_satoshis, msg.channel_reserve_satoshis,
+			msg.to_self_delay, msg.max_accepted_htlcs, msg.htlc_minimum_msat,
+			msg.max_htlc_value_in_flight_msat, msg.minimum_depth, &msg.channel_type,
+			&msg.shutdown_scriptpubkey, msg.funding_pubkey, msg.revocation_basepoint, msg.payment_point,
+			msg.delayed_payment_basepoint, msg.htlc_basepoint, msg.first_per_commitment_point)
 	}
 }
 
@@ -6264,6 +6296,14 @@ impl<Signer: WriteableEcdsaChannelSigner> InboundV1Channel<Signer> {
 		Ok(chan)
 	}
 
+	pub fn context(&self) -> &ChannelContext<Signer> {
+		&self.context
+	}
+
+	pub fn context_mut(&mut self) -> &mut ChannelContext<Signer> {
+		&mut self.context
+	}
+
 	pub fn is_awaiting_accept(&self) -> bool {
 		self.context.inbound_awaiting_accept
 	}
@@ -6474,9 +6514,6 @@ impl<Signer: WriteableEcdsaChannelSigner> InboundV1Channel<Signer> {
 
 // A not-yet-funded outbound (from holder) channel using V2 channel establishment.
 pub(super) struct OutboundV2Channel<Signer: ChannelSigner> {
-	#[cfg(not(test))]
-	context: DualFundingChannelContext<Signer>,
-	#[cfg(test)]
 	pub context: DualFundingChannelContext<Signer>,
 }
 
@@ -6693,6 +6730,14 @@ impl<Signer: WriteableEcdsaChannelSigner> OutboundV2Channel<Signer> {
 		})
 	}
 
+	pub fn context(&self) -> &ChannelContext<Signer> {
+		&self.context.common
+	}
+
+	pub fn context_mut(&mut self) -> &mut ChannelContext<Signer> {
+		&mut self.context.common
+	}
+
 	pub fn get_open_channel_v2(&self, chain_hash: BlockHash) -> msgs::OpenChannelV2 {
 		if self.context.common.channel_state != ChannelState::OurInitSent as u32 {
 			panic!("Cannot generate an open_channel2 after we've moved forward");
@@ -6736,13 +6781,25 @@ impl<Signer: WriteableEcdsaChannelSigner> OutboundV2Channel<Signer> {
 			require_confirmed_inputs: if self.context.we_require_confirmed_inputs { Some(()) } else { None },
 		}
 	}
+
+	pub fn accept_channel_v2(&mut self, msg: &msgs::AcceptChannelV2, default_limits: &ChannelHandshakeLimits,
+		their_features: &InitFeatures) -> Result<(), ChannelError> {
+		self.context.common.do_accept_channel_checks(
+			default_limits, their_features, msg.dust_limit_satoshis, get_v2_channel_reserve_satoshis(
+				msg.funding_satoshis + self.context.our_funding_satoshis, msg.dust_limit_satoshis),
+			msg.to_self_delay, msg.max_accepted_htlcs, msg.htlc_minimum_msat,
+			msg.max_htlc_value_in_flight_msat, msg.minimum_depth, &msg.channel_type,
+			&msg.shutdown_scriptpubkey, msg.funding_pubkey, msg.revocation_basepoint, msg.payment_basepoint,
+			msg.delayed_payment_basepoint, msg.htlc_basepoint, msg.first_per_commitment_point)?;
+
+		// TODO(dual_funding): V2 Establishment Checks
+
+		Ok(())
+	}
 }
 
 // A not-yet-funded inbound (from counterparty) channel using V2 channel establishment.
 pub(super) struct InboundV2Channel<Signer: ChannelSigner> {
-	#[cfg(not(test))]
-	context: DualFundingChannelContext<Signer>,
-	#[cfg(test)]
 	pub context: DualFundingChannelContext<Signer>,
 }
 
@@ -7107,6 +7164,18 @@ impl<Signer: WriteableEcdsaChannelSigner> InboundV2Channel<Signer> {
 		Ok(chan)
 	}
 
+	pub fn context(&self) -> &ChannelContext<Signer> {
+		&self.context.common
+	}
+
+	pub fn context_mut(&mut self) -> &mut ChannelContext<Signer> {
+		&mut self.context.common
+	}
+
+	pub fn is_awaiting_accept(&self) -> bool {
+		self.context.common.inbound_awaiting_accept
+	}
+
 	/// Marks an inbound channel as accepted and generates a [`msgs::AcceptChannelV2`] message which
 	/// should be sent back to the counterparty node.
 	///
diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index 65f442f1c09..bdb94ad520a 100644
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -28,7 +28,7 @@ use bitcoin::hash_types::{BlockHash, Txid};
 
 use bitcoin::secp256k1::{SecretKey,PublicKey};
 use bitcoin::secp256k1::Secp256k1;
-use bitcoin::{LockTime, secp256k1, Sequence};
+use bitcoin::{LockTime, secp256k1, Sequence, Script};
 
 use crate::chain;
 use crate::chain::{Confirm, ChannelMonitorUpdateStatus, Watch, BestBlock};
@@ -40,7 +40,7 @@ use crate::events::{Event, EventHandler, EventsProvider, MessageSendEvent, Messa
 // Since this struct is returned in `list_channels` methods, expose it here in case users want to
 // construct one themselves.
 use crate::ln::{inbound_payment, PaymentHash, PaymentPreimage, PaymentSecret};
-use crate::ln::channel::{Channel, ChannelContext, ChannelError, ChannelUpdateStatus, ShutdownResult, UpdateFulfillCommitFetch, OutboundV1Channel, InboundV1Channel};
+use crate::ln::channel::{Channel, ChannelContext, OutboundV1Channel, InboundV1Channel, OutboundV2Channel, InboundV2Channel, ChannelError, ChannelUpdateStatus, UpdateFulfillCommitFetch, ShutdownResult};
 use crate::ln::features::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, NodeFeatures};
 #[cfg(any(feature = "_test_utils", test))]
 use crate::ln::features::InvoiceFeatures;
@@ -80,6 +80,9 @@ use core::ops::Deref;
 pub use crate::ln::outbound_payment::{PaymentSendFailure, Retry, RetryableSendFailure, RecipientOnionFields};
 use crate::ln::script::ShutdownScript;
 
+// Re-export this for use in the public API.
+pub use super::channel::DualFundingUtxo;
+
 // We hold various information about HTLC relay in the HTLC objects in Channel itself:
 //
 // Upon receipt of an HTLC from a peer, we'll give it a PendingHTLCStatus indicating if it should
@@ -628,6 +631,27 @@ pub(super) struct PeerState<Signer: ChannelSigner> {
 	/// been assigned a `channel_id`, the entry in this map is removed and one is created in
 	/// `channel_by_id`.
 	pub(super) inbound_v1_channel_by_id: HashMap<[u8; 32], InboundV1Channel<Signer>>,
+	/// `(temporary_)channel_id` -> `OutboundV2Channel`.
+	///
+	/// Holds all outbound V2 channels where the peer is the counterparty. V2 channels are assigned
+	/// a `channel_id` before a funding transaction is created interactively as it's derived from
+	/// both parties' revocation basepoints once these are known. Hence, this map's keys are either
+	/// temporary channel IDs or channel IDs.
+	///
+	/// The entries in this map are only moved to `channel_by_id` once interactive transaction
+	/// construction completes successfully.
+	pub(super) outbound_v2_channel_by_id: HashMap<[u8; 32], OutboundV2Channel<Signer>>,
+	/// `channel_id` -> `InboundV2Channel`.
+	///
+	/// Holds all inbound V2 channels where the peer is the counterparty. V2 channels are assigned
+	/// a `channel_id` before a funding transaction is created interactively as it's derived from
+	/// both parties' revocation basepoints once these are known. At the stage of receiving an
+	/// `open_channel2` request, we have enough information to derive the `channel_id`. Hence, this
+	/// map's keys are always `channel_id`s.
+	///
+	/// The entries in this map are only moved to `channel_by_id` once interactive transaction
+	/// construction completes successfully.
+	pub(super) inbound_v2_channel_by_id: HashMap<[u8; 32], InboundV2Channel<Signer>>,
 	/// The latest `InitFeatures` we heard from the peer.
 	latest_features: InitFeatures,
 	/// Messages to send to the peer - pushed to in the same lock that they are generated in (except
@@ -1691,8 +1715,8 @@ macro_rules! convert_chan_err {
 			},
 			ChannelError::Close(msg) => {
 				log_error!($self.logger, "Closing channel {} due to close-required error: {}", log_bytes!($channel_id[..]), msg);
-				update_maps_on_chan_removal!($self, &$channel.context);
-				let shutdown_res = $channel.context.force_shutdown(true);
+				update_maps_on_chan_removal!($self, &$channel.context());
+				let shutdown_res = $channel.context_mut().force_shutdown(true);
 				(true, MsgHandleErrInternal::from_finish_shutdown(msg, *$channel_id, $channel.context.get_user_id(),
 					shutdown_res, $self.get_channel_update_for_broadcast(&$channel).ok()))
 			},
@@ -1762,7 +1786,7 @@ macro_rules! remove_channel {
 	($self: expr, $entry: expr) => {
 		{
 			let channel = $entry.remove_entry().1;
-			update_maps_on_chan_removal!($self, &channel.context);
+			update_maps_on_chan_removal!($self, &channel.context());
 			channel
 		}
 	}
@@ -1884,7 +1908,7 @@ macro_rules! handle_new_monitor_update {
 			ChannelMonitorUpdateStatus::PermanentFailure => {
 				log_error!($self.logger, "Closing channel {} due to monitor update ChannelMonitorUpdateStatus::PermanentFailure",
 					log_bytes!($chan.context.channel_id()[..]));
-				update_maps_on_chan_removal!($self, &$chan.context);
+				update_maps_on_chan_removal!($self, &$chan.context());
 				let res = Err(MsgHandleErrInternal::from_finish_shutdown(
 					"ChannelMonitor storage failure".to_owned(), $chan.context.channel_id(),
 					$chan.context.get_user_id(), $chan.context.force_shutdown(false),
@@ -2182,6 +2206,106 @@ where
 		Ok(temporary_channel_id)
 	}
 
+
+	/// Creates a new outbound dual-funded channel to the given remote node and with the given value
+	/// contributed by us.
+	///
+	/// `user_channel_id` will be provided back as in
+	/// [`Event::FundingGenerationReady::user_channel_id`] to allow tracking of which events
+	/// correspond with which `create_channel` call. Note that the `user_channel_id` defaults to a
+	/// randomized value for inbound channels. `user_channel_id` has no meaning inside of LDK, it
+	/// is simply copied to events and otherwise ignored.
+	///
+	/// `funnding_satoshis` is the amount we are contributing to the channel.
+	/// Raises [`APIError::APIMisuseError`] when `funding_satoshis` > 2**24.
+	///
+	/// The `funding_inputs` parameter accepts UTXOs in the form of [`DualFundingUtxo`] which will
+	/// be used to contribute `funding_satoshis` towards the channel (minus any mining fees due).
+	/// Raises [`APIError::APIMisuseError`] if the total value of the provided `funding_inputs` is
+	/// less than `funding_satoshis`.
+	//  TODO(dual_funding): Describe error relating to inputs not being able to cover fees payable by us.
+	///
+	/// The `change_script_pubkey` parameter provides a destination for the change output if any value
+	/// is remaining (greater than dust) after `funding_satoshis` and fees payable are satisfied by
+	/// `funding_inputs`
+	//  TODO(dual_funding): We could allow a list of such outputs to be provided so that the user may
+	/// be able to do some more interesting things at the same time as funding a channel, like making
+	/// some low priority on-chain payment.
+	///
+	/// The `funding_conf_target` parameter sets the priority of the funding transaction for appropriate
+	/// fee estimation. If `None`, then [`ConfirmationTarget::Normal`] is used.
+	///
+	/// Raises [`APIError::ChannelUnavailable`] if the channel cannot be opened due to failing to
+	/// generate a shutdown scriptpubkey or destination script set by
+	/// [`SignerProvider::get_shutdown_scriptpubkey`] or [`SignerProvider::get_destination_script`].
+	///
+	/// Note that we do not check if you are currently connected to the given peer. If no
+	/// connection is available, the outbound `open_channel` message may fail to send, resulting in
+	/// the channel eventually being silently forgotten (dropped on reload).
+	///
+	/// Returns the new Channel's temporary `channel_id`. This ID will appear as
+	/// [`Event::FundingGenerationReady::temporary_channel_id`] and in
+	/// [`ChannelDetails::channel_id`] until after
+	/// [`ChannelManager::funding_transaction_generated`] is called, swapping the Channel's ID for
+	/// one derived from the funding transaction's TXID. If the counterparty rejects the channel
+	/// immediately, this temporary ID will appear in [`Event::ChannelClosed::channel_id`].
+	///
+	/// [`Event::FundingGenerationReady::user_channel_id`]: events::Event::FundingGenerationReady::user_channel_id
+	/// [`Event::FundingGenerationReady::temporary_channel_id`]: events::Event::FundingGenerationReady::temporary_channel_id
+	/// [`Event::ChannelClosed::channel_id`]: events::Event::ChannelClosed::channel_id
+	/// [`ConfirmationTarget::Normal`]: chain::chaininterface::ConfirmationTarget
+	pub fn create_dual_funded_channel(&self, their_network_key: PublicKey, funding_satoshis: u64,
+		funding_inputs: Vec<DualFundingUtxo>, change_script_pubkey: Script, funding_conf_target: Option<ConfirmationTarget>,
+		user_channel_id: u128, override_config: Option<UserConfig>) -> Result<[u8; 32], APIError>
+	{
+		Self::dual_funding_amount_checks(funding_satoshis, &funding_inputs)?;
+
+		let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(self);
+		// We want to make sure the lock is actually acquired by PersistenceNotifierGuard.
+		debug_assert!(&self.total_consistency_lock.try_write().is_err());
+
+		let per_peer_state = self.per_peer_state.read().unwrap();
+
+		let peer_state_mutex = per_peer_state.get(&their_network_key)
+			.ok_or_else(|| APIError::APIMisuseError{ err: format!("Not connected to node: {}", their_network_key) })?;
+
+		let mut peer_state = peer_state_mutex.lock().unwrap();
+		let channel = {
+			let outbound_scid_alias = self.create_and_insert_outbound_scid_alias();
+			let their_features = &peer_state.latest_features;
+			let config = if override_config.is_some() { override_config.as_ref().unwrap() } else { &self.default_configuration };
+			match OutboundV2Channel::new(&self.fee_estimator, &self.entropy_source, &self.signer_provider, their_network_key,
+				their_features, funding_satoshis, funding_inputs, change_script_pubkey, user_channel_id, config,
+				self.best_block.read().unwrap().height(), outbound_scid_alias, true, funding_conf_target)
+			{
+				Ok(res) => res,
+				Err(e) => {
+					self.outbound_scid_aliases.lock().unwrap().remove(&outbound_scid_alias);
+					return Err(e);
+				},
+			}
+		};
+		let res = channel.get_open_channel_v2(self.genesis_hash.clone());
+
+		let temporary_channel_id = channel.context.common.channel_id();
+		match peer_state.outbound_v2_channel_by_id.entry(temporary_channel_id) {
+			hash_map::Entry::Occupied(_) => {
+				if cfg!(fuzzing) {
+					return Err(APIError::APIMisuseError { err: "Fuzzy bad RNG".to_owned() });
+				} else {
+					panic!("RNG is bad???");
+				}
+			},
+			hash_map::Entry::Vacant(entry) => { entry.insert(channel); }
+		}
+
+		peer_state.pending_msg_events.push(events::MessageSendEvent::SendOpenChannelV2 {
+			node_id: their_network_key,
+			msg: res,
+		});
+		Ok(temporary_channel_id)
+	}
+
 	fn list_funded_channels_with_filter<Fn: FnMut(&(&[u8; 32], &Channel<<SP::Target as SignerProvider>::Signer>)) -> bool + Copy>(&self, f: Fn) -> Vec<ChannelDetails> {
 		// Allocate our best estimate of the number of channels we have in the `res`
 		// Vec. Sadly the `short_to_chan_info` map doesn't cover channels without
@@ -5041,6 +5165,130 @@ where
 		Ok(())
 	}
 
+	/// Accepts a request to open a dual-funded channel after an [`Event::OpenChannelV2Request`].
+	///
+	/// The `temporary_channel_id` parameter indicates which inbound channel should be accepted,
+	/// and the `counterparty_node_id` parameter is the id of the peer which has requested to open
+	/// the channel.
+	///
+	/// The `user_channel_id` parameter will be provided back in
+	/// [`Event::ChannelClosed::user_channel_id`] to allow tracking of which events correspond
+	/// with which `accept_inbound_dual_funded_channel`/`accept_inbound_dual_funded_channel_from_trusted_peer_0conf` call.
+	///
+	/// `funnding_satoshis` is the amount we are contributing to the channel.
+	/// Raises [`APIError::APIMisuseError`] when `funding_satoshis` > 2**24.
+	///
+	/// The `funding_inputs` parameter accepts UTXOs in the form of [`DualFundingUtxo`] which will
+	/// be used to contribute `funding_satoshis` towards the channel (minus any mining fees due).
+	/// Raises [`APIError::APIMisuseError`] if the total value of the provided `funding_inputs` is
+	/// less than `funding_satoshis`.
+	//  TODO(dual_funding): Describe error relating to inputs not being able to cover fees payable by us.
+	///
+	/// The `change_script_pubkey` parameter provides a destination for the change output if any value
+	/// is remaining (greater than dust) after `funding_satoshis` and fees payable are satisfied by
+	/// `funding_inputs`
+	//  TODO(dual_funding): We could allow a list of such outputs to be provided so that the user may
+	/// be able to do some more interesting things at the same time as funding.
+
+	/// Note that this method will return an error and reject the channel, if it requires support
+	/// for zero confirmations.
+	// TODO(dual_funding): Discussion on complications with 0conf dual-funded channels where "locking"
+	// of UTXOs used for funding would be required and other issues.
+	// See: https://lists.linuxfoundation.org/pipermail/lightning-dev/2023-May/003920.html
+	/// 
+	///
+	/// [`Event::OpenChannelV2Request`]: events::Event::OpenChannelV2Request
+	/// [`Event::ChannelClosed::user_channel_id`]: events::Event::ChannelClosed::user_channel_id
+	pub fn accept_inbound_dual_funded_channel(&self, temporary_channel_id: &[u8; 32],
+		counterparty_node_id: &PublicKey, user_channel_id: u128, funding_satoshis: u64,
+		funding_inputs: Vec<DualFundingUtxo>, change_script_pubkey: Script) -> Result<(), APIError> {
+		self.do_accept_inbound_dual_funded_channel(temporary_channel_id, counterparty_node_id,
+			user_channel_id, funding_satoshis, funding_inputs, change_script_pubkey)
+	}
+
+	fn do_accept_inbound_dual_funded_channel(&self, temporary_channel_id: &[u8; 32],
+		counterparty_node_id: &PublicKey, user_channel_id: u128, funding_satoshis: u64,
+		funding_inputs: Vec<DualFundingUtxo>, change_script_pubkey: Script,
+	) -> Result<(), APIError> {
+		Self::dual_funding_amount_checks(funding_satoshis, &funding_inputs)?;
+
+		let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(self);
+
+		let peers_without_funded_channels =
+			self.peers_without_funded_channels(|peer| { peer.total_channel_count() > 0 });
+		let per_peer_state = self.per_peer_state.read().unwrap();
+		let peer_state_mutex = per_peer_state.get(counterparty_node_id)
+			.ok_or_else(|| APIError::ChannelUnavailable { err: format!("Can't find a peer matching the passed counterparty node_id {}", counterparty_node_id) })?;
+		let mut peer_state_lock = peer_state_mutex.lock().unwrap();
+		let peer_state = &mut *peer_state_lock;
+		let is_only_peer_channel = peer_state.total_channel_count() == 1;
+		match peer_state.inbound_v2_channel_by_id.entry(temporary_channel_id.clone()) {
+			hash_map::Entry::Occupied(mut channel) => {
+				if !channel.get().is_awaiting_accept() {
+					return Err(APIError::APIMisuseError { err: "The channel isn't currently awaiting to be accepted.".to_owned() });
+				}
+				// TODO(dual_funding): Accept zero-conf dual-funded channels.
+				// See: https://lists.linuxfoundation.org/pipermail/lightning-dev/2023-May/003920.html
+				if channel.get().context.common.get_channel_type().requires_zero_conf() {
+					let send_msg_err_event = events::MessageSendEvent::HandleError {
+						node_id: channel.get().context.common.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 _ = remove_channel!(self, channel);
+					return Err(APIError::APIMisuseError { err: "Zero-conf dual-funded channels are not yet accepted.".to_owned() });
+				} 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.get().context.common.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 _ = remove_channel!(self, channel);
+						return Err(APIError::APIMisuseError { err: "Too many peers with unfunded channels, refusing to accept new ones".to_owned() });
+					}
+				}
+
+				channel.get_mut().context.our_change_script_pubkey = change_script_pubkey;
+
+				peer_state.pending_msg_events.push(events::MessageSendEvent::SendAcceptChannelV2 {
+					node_id: channel.get().context.common.get_counterparty_node_id(),
+					msg: channel.get_mut().accept_inbound_dual_funded_channel(user_channel_id),
+				});
+			}
+			hash_map::Entry::Vacant(_) => {
+				return Err(APIError::ChannelUnavailable { err: format!("Channel with id {} not found for the passed counterparty node_id {}", log_bytes!(*temporary_channel_id), counterparty_node_id) });
+			}
+		}
+		Ok(())
+	}
+
+	/// Checks related to inputs and their amounts related to establishing dual-funded channels.
+	fn dual_funding_amount_checks(funding_satoshis: u64, funding_inputs: &Vec<DualFundingUtxo>)
+	-> Result<(), APIError> {
+		if funding_satoshis < 1000 {
+			return Err(APIError::APIMisuseError {
+				err: format!("Funding amount must be at least 1000 satoshis. It was {} sats", funding_satoshis),
+			});
+		}
+
+		let total_input_satoshis: u64 = funding_inputs.iter().map(|input| input.output.value).sum();
+		if total_input_satoshis < funding_satoshis {
+			Err(APIError::APIMisuseError {
+				err: format!("Total value of funding inputs must be at least funding amount. It was {} sats",
+					total_input_satoshis) })
+		} else {
+			Ok(())
+		}
+	}
+
 	/// Gets the number of peers which match the given filter and do not have any funded, outbound,
 	/// or 0-conf channels.
 	///
@@ -5082,6 +5330,11 @@ where
 				num_unfunded_channels += 1;
 			}
 		}
+		for (_, chan) in peer.inbound_v2_channel_by_id.iter() {
+			if chan.context.common.minimum_depth().unwrap_or(1) != 0 {
+				num_unfunded_channels += 1;
+			}
+		}
 		num_unfunded_channels
 	}
 
@@ -5205,6 +5458,38 @@ where
 		Ok(())
 	}
 
+	fn internal_accept_channel_v2(&self, counterparty_node_id: &PublicKey, msg: &msgs::AcceptChannelV2) -> Result<(), MsgHandleErrInternal> {
+		let per_peer_state = self.per_peer_state.read().unwrap();
+		let peer_state_mutex = per_peer_state.get(counterparty_node_id)
+			.ok_or_else(|| {
+				debug_assert!(false);
+				MsgHandleErrInternal::send_err_msg_no_close(format!("Can't find a peer matching the passed counterparty node_id {}", counterparty_node_id), msg.temporary_channel_id)
+			})?;
+		let mut peer_state_lock = peer_state_mutex.lock().unwrap();
+		let peer_state = &mut *peer_state_lock;
+		match peer_state.outbound_v2_channel_by_id.entry(msg.temporary_channel_id) {
+			hash_map::Entry::Occupied(mut chan) => {
+				let res = chan.get_mut().accept_channel_v2(&msg, &self.default_configuration.channel_handshake_limits, &peer_state.latest_features);
+				if let Err(err) = res {
+					// If we get an error at this point, the outbound channel should just be discarded and
+					// removed from maps as it's safe to do so.
+					update_maps_on_chan_removal!(self, &chan.get().context());
+					let user_id = chan.get().context.common.get_user_id();
+					let shutdown_res = chan.get_mut().context.common.force_shutdown(false);
+					chan.remove_entry();
+					return Err(MsgHandleErrInternal::from_finish_shutdown(format!("{}", err),
+						msg.temporary_channel_id, user_id, shutdown_res, None));
+				};
+				// TODO(dual_funding): Begin Interactive Transaction Construction
+				// Here we will initialize the `InteractiveTxConstructor` and delegate
+				// the actual message handling for the interactive transaction protocol
+				// to its state machine.
+				Ok(())
+			},
+			hash_map::Entry::Vacant(_) => Err(MsgHandleErrInternal::send_err_msg_no_close(format!("Got a message for a channel from the wrong node! No such channel for the passed counterparty_node_id {}", counterparty_node_id), msg.temporary_channel_id)),
+		}
+	}
+
 	fn internal_funding_created(&self, counterparty_node_id: &PublicKey, msg: &msgs::FundingCreated) -> Result<(), MsgHandleErrInternal> {
 		let best_block = *self.best_block.read().unwrap();
 
@@ -6871,9 +7156,8 @@ where
 	}
 
 	fn handle_accept_channel_v2(&self, counterparty_node_id: &PublicKey, msg: &msgs::AcceptChannelV2) {
-		let _: Result<(), _> = handle_error!(self, Err(MsgHandleErrInternal::send_err_msg_no_close(
-			"Dual-funded channels not supported".to_owned(),
-			 msg.temporary_channel_id.clone())), *counterparty_node_id);
+		let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(self);
+		let _ = handle_error!(self, self.internal_accept_channel_v2(counterparty_node_id, msg), *counterparty_node_id);
 	}
 
 	fn handle_funding_created(&self, counterparty_node_id: &PublicKey, msg: &msgs::FundingCreated) {
@@ -7070,6 +7354,8 @@ where
 						channel_by_id: HashMap::new(),
 						outbound_v1_channel_by_id: HashMap::new(),
 						inbound_v1_channel_by_id: HashMap::new(),
+						outbound_v2_channel_by_id: HashMap::new(),
+						inbound_v2_channel_by_id: HashMap::new(),
 						latest_features: init_msg.features.clone(),
 						pending_msg_events: Vec::new(),
 						in_flight_monitor_updates: BTreeMap::new(),
@@ -8270,6 +8556,8 @@ where
 				channel_by_id,
 				outbound_v1_channel_by_id: HashMap::new(),
 				inbound_v1_channel_by_id: HashMap::new(),
+				outbound_v2_channel_by_id: HashMap::new(),
+				inbound_v2_channel_by_id: HashMap::new(),
 				latest_features: InitFeatures::empty(),
 				pending_msg_events: Vec::new(),
 				in_flight_monitor_updates: BTreeMap::new(),
@@ -9993,6 +10281,9 @@ mod tests {
 			_ => panic!("expected BroadcastChannelUpdate event"),
 		}
 	}
+
+	// Dual-funding: V2 Channel Establishment Tests
+	// TODO(dual_funding): Complete these.
 }
 
 #[cfg(ldk_bench)]
diff --git a/lightning/src/util/config.rs b/lightning/src/util/config.rs
index 5c8d5b6c554..c6795957657 100644
--- a/lightning/src/util/config.rs
+++ b/lightning/src/util/config.rs
@@ -660,6 +660,21 @@ 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 {
@@ -673,6 +688,7 @@ impl Default for UserConfig {
 			manually_accept_inbound_channels: false,
 			accept_intercept_htlcs: false,
 			accept_mpp_keysend: false,
+			contribute_to_dual_funded_channels: false,
 		}
 	}
 }