Add enable_dual_funded_channels to UserConfig

When this config field is enabled, the dual_fund feature bit will be
set which determines support when receiving `open_channel2` messages.

Author: dunxen

lightning/src/ln/channelmanager.rs

@@ -11984,6 +11984,12 @@ where
 	}
 
 	fn handle_open_channel_v2(&self, counterparty_node_id: PublicKey, msg: &msgs::OpenChannelV2) {
+		if !self.node_features().supports_dual_fund() {
+			let _: Result<(), _> = handle_error!(self, Err(MsgHandleErrInternal::send_err_msg_no_close(
+				"Dual-funded channels not supported".to_owned(),
+				msg.common_fields.temporary_channel_id.clone())), counterparty_node_id);
+			return;
+		}
 		// Note that we never need to persist the updated ChannelManager for an inbound
 		// open_channel message - pre-funded channels are never written so there should be no
 		// change to the contents.
@@ -12873,7 +12879,9 @@ pub fn provided_init_features(config: &UserConfig) -> InitFeatures {
 	if config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx {
 		features.set_anchors_zero_fee_htlc_tx_optional();
 	}
-	features.set_dual_fund_optional();
+	if config.enable_dual_funded_channels {
+		features.set_dual_fund_optional();
+	}
 	// Only signal quiescence support in tests for now, as we don't yet support any
 	// quiescent-dependent protocols (e.g., splicing).
 	#[cfg(any(test, fuzzing))]

lightning/src/ln/dual_funding_tests.rs

@@ -39,7 +39,9 @@ struct V2ChannelEstablishmentTestSession {
 fn do_test_v2_channel_establishment(session: V2ChannelEstablishmentTestSession) {
 	let chanmon_cfgs = create_chanmon_cfgs(2);
 	let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
-	let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
+	let mut node_1_user_config = test_default_channel_config();
+	node_1_user_config.enable_dual_funded_channels = true;
+	let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, Some(node_1_user_config)]);
 	let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
 	let logger_a = test_utils::TestLogger::with_id("node a".to_owned());
 

lightning/src/util/config.rs

@@ -875,6 +875,10 @@ pub struct UserConfig {
 	/// [`ChannelManager::send_payment_for_bolt12_invoice`]: crate::ln::channelmanager::ChannelManager::send_payment_for_bolt12_invoice
 	/// [`ChannelManager::abandon_payment`]: crate::ln::channelmanager::ChannelManager::abandon_payment
 	pub manually_handle_bolt12_invoices: bool,
+	/// If this is set to `true`, dual-funded channels will be enabled.
+	///
+	/// Default value: `false`
+	pub enable_dual_funded_channels: bool,
 }
 
 impl Default for UserConfig {
@@ -888,6 +892,7 @@ impl Default for UserConfig {
 			manually_accept_inbound_channels: false,
 			accept_intercept_htlcs: false,
 			manually_handle_bolt12_invoices: false,
+			enable_dual_funded_channels: false,
 		}
 	}
 }
@@ -907,6 +912,7 @@ impl Readable for UserConfig {
 			manually_accept_inbound_channels: Readable::read(reader)?,
 			accept_intercept_htlcs: Readable::read(reader)?,
 			manually_handle_bolt12_invoices: Readable::read(reader)?,
+			enable_dual_funded_channels: Readable::read(reader)?,
 		})
 	}
 }