From 90888948ed6b554e9afe5819f928d5c1ec2d386f 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/src/ln/channelmanager.rs |  2 ++
 lightning/src/ln/features.rs       | 10 ++++++++--
 lightning/src/ln/peer_handler.rs   |  1 +
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index 017ec99d5b3..68f1daf608e 100644
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -11354,6 +11354,8 @@ 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();
 	}
+	#[cfg(any(dual_funding, splicing))]
+	features.set_dual_fund_optional();
 	features
 }
 
diff --git a/lightning/src/ln/features.rs b/lightning/src/ln/features.rs
index 51c608c1a6b..59b4e186521 100644
--- a/lightning/src/ln/features.rs
+++ b/lightning/src/ln/features.rs
@@ -49,6 +49,9 @@
 //!     (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/pull/851/files) for more information).
+//     TODO: update link
 //! - `OnionMessages` - requires/supports forwarding onion messages
 //!     (see [BOLT-7](https://github.com/lightning/bolts/pull/759/files) for more information).
 //     TODO: update link
@@ -149,7 +152,7 @@ mod sealed {
 		// Byte 2
 		BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
 		// Byte 3
-		RouteBlinding | ShutdownAnySegwit | Taproot,
+		RouteBlinding | ShutdownAnySegwit | DualFund | Taproot,
 		// Byte 4
 		OnionMessages,
 		// Byte 5
@@ -167,7 +170,7 @@ mod sealed {
 		// Byte 2
 		BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
 		// Byte 3
-		RouteBlinding | ShutdownAnySegwit | Taproot,
+		RouteBlinding | ShutdownAnySegwit | DualFund | Taproot,
 		// Byte 4
 		OnionMessages,
 		// Byte 5
@@ -409,6 +412,9 @@ mod sealed {
 	define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 		"Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 		set_shutdown_any_segwit_required, 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, [InitContext, NodeContext, ChannelTypeContext],
 		"Feature flags for `option_taproot`.", set_taproot_optional,
 		set_taproot_required, supports_taproot, requires_taproot);
diff --git a/lightning/src/ln/peer_handler.rs b/lightning/src/ln/peer_handler.rs
index 448dd213dad..fc14a68d6c2 100644
--- a/lightning/src/ln/peer_handler.rs
+++ b/lightning/src/ln/peer_handler.rs
@@ -322,6 +322,7 @@ 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();