Add manually_broadcast_outbound_channels

  Add a new flag to `UserConfig` and `ChannelContext`
  to allow users to broadcast an outbound channel funding transaction
  manually and halt the automatic broadcasting from LDK.

Author: jbesraa

lightning/src/ln/channel.rs

@@ -1541,6 +1541,16 @@ pub(super) struct ChannelContext<SP: Deref> where SP::Target: SignerProvider {
 	/// If we can't release a [`ChannelMonitorUpdate`] until some external action completes, we
 	/// store it here and only release it to the `ChannelManager` once it asks for it.
 	blocked_monitor_updates: Vec<PendingChannelMonitorUpdate>,
+
+	/// Upon receving a `FundingSigned` message, if the channel is
+	/// outbound and we are ready to broadcast the funding
+	/// transaction, LDK will broadcast it and set the channel state
+	/// to `ChannelPending`. 
+	///
+	/// Using this flag will allow you to halt the broadcast of the
+	/// funding transaction and the channel state will be set to
+	/// `FundingSigned`.
+	manually_broadcast_outbound_channels: Option<()>,
 }
 
 impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider  {
@@ -1872,6 +1882,8 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider  {
 			local_initiated_shutdown: None,
 
 			blocked_monitor_updates: Vec::new(),
+
+			manually_broadcast_outbound_channels: None,
 		};
 
 		Ok(channel_context)
@@ -2092,6 +2104,7 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider  {
 
 			blocked_monitor_updates: Vec::new(),
 			local_initiated_shutdown: None,
+			manually_broadcast_outbound_channels: if config.manually_broadcast_outbound_channels { Some(()) } else { None }
 		})
 	}
 
@@ -2333,6 +2346,10 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider  {
 		self.config.options.forwarding_fee_proportional_millionths
 	}
 
+	pub fn get_manually_broadcast_outbound_channels(&self) -> Option<()> {
+		self.manually_broadcast_outbound_channels
+	}
+
 	pub fn get_cltv_expiry_delta(&self) -> u16 {
 		cmp::max(self.config.options.cltv_expiry_delta, MIN_CLTV_EXPIRY_DELTA)
 	}
@@ -9047,6 +9064,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 		let mut holding_cell_skimmed_fees_opt: Option<Vec<Option<u64>>> = None;
 
 		let mut is_batch_funding: Option<()> = None;
+		let mut manually_broadcast_outbound_channels: Option<()> = None;
 
 		let mut local_initiated_shutdown: Option<()> = None;
 
@@ -9088,6 +9106,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 			(43, malformed_htlcs, optional_vec), // Added in 0.0.119
 			// 45 and 47 are reserved for async signing
 			(49, local_initiated_shutdown, option),
+			(51, manually_broadcast_outbound_channels, option),
 		});
 
 		let (channel_keys_id, holder_signer) = if let Some(channel_keys_id) = channel_keys_id {
@@ -9322,6 +9341,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 				local_initiated_shutdown,
 
 				blocked_monitor_updates: blocked_monitor_updates.unwrap(),
+				manually_broadcast_outbound_channels,
 			},
 			#[cfg(any(dual_funding, splicing))]
 			dual_funding_channel_context: None,

lightning/src/util/config.rs

@@ -810,6 +810,8 @@ pub struct UserConfig {
 	///
 	/// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
 	pub accept_mpp_keysend: bool,
+	/// broadcast funding transaction manually
+	pub manually_broadcast_outbound_channels: bool,
 }
 
 impl Default for UserConfig {
@@ -823,6 +825,7 @@ impl Default for UserConfig {
 			manually_accept_inbound_channels: false,
 			accept_intercept_htlcs: false,
 			accept_mpp_keysend: false,
+			manually_broadcast_outbound_channels: false,
 		}
 	}
 }
@@ -842,6 +845,7 @@ impl Readable for UserConfig {
 			manually_accept_inbound_channels: Readable::read(reader)?,
 			accept_intercept_htlcs: Readable::read(reader)?,
 			accept_mpp_keysend: Readable::read(reader)?,
+			manually_broadcast_outbound_channels: Readable::read(reader)?,
 		})
 	}
 }