From b815910fab85153f820564354c3d2d83f8d8fbb4 Mon Sep 17 00:00:00 2001
From: Duncan Dean <git@dunxen.dev>
Date: Wed, 13 Sep 2023 23:42:05 +0200
Subject: [PATCH] Add `option_dual_fund` feature

---
 lightning-types/src/features.rs    | 16 ++++++++++++++--
 lightning/src/ln/channelmanager.rs |  1 +
 lightning/src/ln/peer_handler.rs   |  1 +
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/lightning-types/src/features.rs b/lightning-types/src/features.rs
index 7ce87e0263e..65b829deacd 100644
--- a/lightning-types/src/features.rs
+++ b/lightning-types/src/features.rs
@@ -49,6 +49,8 @@
 //!     (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md#route-blinding) for more information).
 //! - `ShutdownAnySegwit` - requires/supports that future segwit versions are allowed in `shutdown`
 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
+//! - `DualFund` - requires/supports V2 channel establishment
+//!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#channel-establishment-v2) for more information).
 //! - `OnionMessages` - requires/supports forwarding onion messages
 //!     (see [BOLT-7](https://github.com/lightning/bolts/pull/759/files) for more information).
 //     TODO: update link
@@ -147,7 +149,7 @@ mod sealed {
 			// Byte 2
 			BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
 			// Byte 3
-			RouteBlinding | ShutdownAnySegwit | Taproot,
+			RouteBlinding | ShutdownAnySegwit | DualFund | Taproot,
 			// Byte 4
 			OnionMessages,
 			// Byte 5
@@ -168,7 +170,7 @@ mod sealed {
 			// Byte 2
 			BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
 			// Byte 3
-			RouteBlinding | ShutdownAnySegwit | Taproot,
+			RouteBlinding | ShutdownAnySegwit | DualFund | Taproot,
 			// Byte 4
 			OnionMessages,
 			// Byte 5
@@ -499,6 +501,16 @@ mod sealed {
 		supports_shutdown_anysegwit,
 		requires_shutdown_anysegwit
 	);
+	define_feature!(
+		29,
+		DualFund,
+		[InitContext, NodeContext],
+		"Feature flags for `option_dual_fund`.",
+		set_dual_fund_optional,
+		set_dual_fund_required,
+		supports_dual_fund,
+		requires_dual_fund
+	);
 	define_feature!(
 		31,
 		Taproot,
diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index b2e658b8c98..494e2094a17 100644
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -11779,6 +11779,7 @@ 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();
 	features
 }
 
diff --git a/lightning/src/ln/peer_handler.rs b/lightning/src/ln/peer_handler.rs
index 5293906f91c..fe2f3668634 100644
--- a/lightning/src/ln/peer_handler.rs
+++ b/lightning/src/ln/peer_handler.rs
@@ -331,6 +331,7 @@ impl ChannelMessageHandler for ErroringMessageHandler {
 		features.set_basic_mpp_optional();
 		features.set_wumbo_optional();
 		features.set_shutdown_any_segwit_optional();
+		features.set_dual_fund_optional();
 		features.set_channel_type_optional();
 		features.set_scid_privacy_optional();
 		features.set_zero_conf_optional();