Open LN channel from incoming Payjoin tx

This commit allows users to schedule a channel that will opened
once a Payjoin request received. This can save users 1 extra onchain
transaction fees.

The Payjoin flow is normal with the following caveats:
1. We use `Payjoin::ProvisionalProposal::substitue_output_address` to
point to the multisig output script as retrived from
`LdkEvent::FundingGeneratingReady`.
2. We dont try to preserve privacy in Payjoin channel opening
transactions.
3. We wait with our response to the Payjoin sender until a
`Ldk::Event::FundingTxBroadcastSafe` event is received.

Author: jbesraa

Cargo.toml

@@ -28,23 +28,23 @@ panic = 'abort'     # Abort on panic
 default = []
 
 [dependencies]
-lightning = { version = "0.0.123", features = ["std"] }
-lightning-invoice = { version = "0.31.0" }
-lightning-net-tokio = { version = "0.0.123" }
-lightning-persister = { version = "0.0.123" }
-lightning-background-processor = { version = "0.0.123", features = ["futures"] }
-lightning-rapid-gossip-sync = { version = "0.0.123" }
-lightning-transaction-sync = { version = "0.0.123", features = ["esplora-async-https", "time"] }
-lightning-liquidity = { version = "0.1.0-alpha.4", features = ["std"] }
-
-#lightning = { git = "https://github.com/lightningdevkit/rust-lightning", branch="main", features = ["std"] }
-#lightning-invoice = { git = "https://github.com/lightningdevkit/rust-lightning", branch="main" }
-#lightning-net-tokio = { git = "https://github.com/lightningdevkit/rust-lightning", branch="main" }
-#lightning-persister = { git = "https://github.com/lightningdevkit/rust-lightning", branch="main" }
-#lightning-background-processor = { git = "https://github.com/lightningdevkit/rust-lightning", branch="main", features = ["futures"] }
-#lightning-rapid-gossip-sync = { git = "https://github.com/lightningdevkit/rust-lightning", branch="main" }
-#lightning-transaction-sync = { git = "https://github.com/lightningdevkit/rust-lightning", branch="main", features = ["esplora-async"] }
-#lightning-liquidity = { git = "https://github.com/lightningdevkit/lightning-liquidity", branch="main", features = ["std"] }
+# lightning = { version = "0.0.123", features = ["std"] }
+# lightning-invoice = { version = "0.31.0" }
+# lightning-net-tokio = { version = "0.0.123" }
+# lightning-persister = { version = "0.0.123" }
+# lightning-background-processor = { version = "0.0.123", features = ["futures"] }
+# lightning-rapid-gossip-sync = { version = "0.0.123" }
+# lightning-transaction-sync = { version = "0.0.123", features = ["esplora-async-https", "time"] }
+# lightning-liquidity = { version = "0.1.0-alpha.4", features = ["std"] }
+
+lightning = { git = "https://github.com/jbesraa/rust-lightning.git", branch="0.0.123-with-funding-brodsafe-event", features = ["std"] }
+lightning-invoice = { git = "https://github.com/jbesraa/rust-lightning.git", branch="0.0.123-with-funding-brodsafe-event" }
+lightning-net-tokio = { git = "https://github.com/jbesraa/rust-lightning.git", branch="0.0.123-with-funding-brodsafe-event" }
+lightning-persister = { git = "https://github.com/jbesraa/rust-lightning.git", branch="0.0.123-with-funding-brodsafe-event" }
+lightning-background-processor = { git = "https://github.com/jbesraa/rust-lightning.git", branch="0.0.123-with-funding-brodsafe-event", features = ["futures"] }
+lightning-rapid-gossip-sync = { git = "https://github.com/jbesraa/rust-lightning.git", branch="0.0.123-with-funding-brodsafe-event" }
+lightning-transaction-sync = { git = "https://github.com/jbesraa/rust-lightning.git", branch="0.0.123-with-funding-brodsafe-event", features = ["esplora-async"] }
+lightning-liquidity = { git = "https://github.com/jbesraa/lightning-liquidity", branch="pj-fixes", features = ["std"] }
 
 #lightning = { path = "../rust-lightning/lightning", features = ["std"] }
 #lightning-invoice = { path = "../rust-lightning/lightning-invoice" }
@@ -78,8 +78,8 @@ prost = { version = "0.11.6", default-features = false}
 winapi = { version = "0.3", features = ["winbase"] }
 
 [dev-dependencies]
-lightning = { version = "0.0.123", features = ["std", "_test_utils"] }
-#lightning = { git = "https://github.com/lightningdevkit/rust-lightning", branch="main", features = ["std", "_test_utils"] }
+# lightning = { version = "0.0.123", features = ["std", "_test_utils"] }
+lightning = { git = "https://github.com/jbesraa/rust-lightning.git", branch="0.0.123-with-funding-brodsafe-event", features = ["std", "_test_utils"] }
 electrum-client = { version = "0.15.1", default-features = true }
 bitcoincore-rpc = { version = "0.17.0", default-features = false }
 proptest = "1.0.0"

src/builder.rs

@@ -1070,6 +1070,7 @@ fn build_with_store_internal(
 				Some(Arc::new(PayjoinReceiver::new(
 					Arc::clone(&logger),
 					Arc::clone(&wallet),
+					Arc::clone(&channel_manager),
 					directory,
 					relay,
 					ohttp_keys,

src/event.rs

@@ -1,3 +1,4 @@
+use crate::payjoin_receiver::PayjoinReceiver;
 use crate::types::{DynStore, Sweeper, Wallet};
 
 use crate::{
@@ -323,6 +324,7 @@ where
 	network_graph: Arc<NetworkGraph>,
 	payment_store: Arc<PaymentStore<L>>,
 	peer_store: Arc<PeerStore<L>>,
+	payjoin_receiver: Option<Arc<PayjoinReceiver>>,
 	runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>,
 	logger: L,
 	config: Arc<Config>,
@@ -336,8 +338,8 @@ where
 		event_queue: Arc<EventQueue<L>>, wallet: Arc<Wallet>, channel_manager: Arc<ChannelManager>,
 		connection_manager: Arc<ConnectionManager<L>>, output_sweeper: Arc<Sweeper>,
 		network_graph: Arc<NetworkGraph>, payment_store: Arc<PaymentStore<L>>,
-		peer_store: Arc<PeerStore<L>>, runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>,
-		logger: L, config: Arc<Config>,
+		payjoin_receiver: Option<Arc<PayjoinReceiver>>, peer_store: Arc<PeerStore<L>>,
+		runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>, logger: L, config: Arc<Config>,
 	) -> Self {
 		Self {
 			event_queue,
@@ -347,6 +349,7 @@ where
 			output_sweeper,
 			network_graph,
 			payment_store,
+			payjoin_receiver,
 			peer_store,
 			logger,
 			runtime,
@@ -361,6 +364,7 @@ where
 				counterparty_node_id,
 				channel_value_satoshis,
 				output_script,
+				user_channel_id,
 				..
 			} => {
 				// Construct the raw transaction with the output that is paid the amount of the
@@ -371,6 +375,18 @@ where
 				let cur_height = self.channel_manager.current_best_block().height;
 				let locktime = LockTime::from_height(cur_height).unwrap_or(LockTime::ZERO);
 
+				if let Some(payjoin_receiver) = self.payjoin_receiver.clone() {
+					if payjoin_receiver
+						.set_channel_accepted(
+							user_channel_id,
+							&output_script,
+							temporary_channel_id.0,
+						)
+						.await
+					{
+						return;
+					}
+				}
 				// Sign the final funding transaction and broadcast it.
 				match self.wallet.create_funding_transaction(
 					output_script,
@@ -918,6 +934,45 @@ where
 					);
 				}
 			},
+			LdkEvent::FundingTxBroadcastSafe { funding_tx, .. } => {
+				use crate::io::utils::ohttp_headers;
+				if let Some(payjoin_receiver) = self.payjoin_receiver.clone() {
+					let is_payjoin_channel =
+						payjoin_receiver.set_funding_tx_signed(funding_tx.clone()).await;
+					if let Some((url, body)) = is_payjoin_channel {
+						log_info!(
+							self.logger,
+							"Detected payjoin channel transaction. Sending payjoin sender request for transaction {}",
+							funding_tx.txid()
+						);
+						let headers = ohttp_headers();
+						let client = reqwest::Client::builder().build().unwrap();
+						match client.post(url).body(body).headers(headers).send().await {
+							Ok(response) => {
+								if response.status().is_success() {
+									log_info!(
+										self.logger,
+										"Responded to 'Payjoin Sender' successfuly"
+									);
+								} else {
+									log_info!(
+										self.logger,
+										"Got unsuccessful response from 'Payjoin Sender': {}",
+										response.status()
+									);
+								}
+							},
+							Err(e) => {
+								log_error!(
+									self.logger,
+									"Failed to send a response to 'Payjoin Sender': {}",
+									e
+								);
+							},
+						};
+					}
+				}
+			},
 			LdkEvent::ChannelPending {
 				channel_id,
 				user_channel_id,

src/lib.rs

@@ -88,6 +88,7 @@ pub mod io;
 mod liquidity;
 mod logger;
 mod message_handler;
+mod payjoin_channel_scheduler;
 mod payjoin_receiver;
 mod payjoin_sender;
 pub mod payment;
@@ -661,6 +662,7 @@ impl Node {
 			Arc::clone(&self.output_sweeper),
 			Arc::clone(&self.network_graph),
 			Arc::clone(&self.payment_store),
+			self.payjoin_receiver.clone(),
 			Arc::clone(&self.peer_store),
 			Arc::clone(&self.runtime),
 			Arc::clone(&self.logger),
@@ -977,6 +979,9 @@ impl Node {
 			payjoin_sender.map(Arc::clone),
 			payjoin_receiver.map(Arc::clone),
 			Arc::clone(&self.config),
+			Arc::clone(&self.peer_store),
+			Arc::clone(&self.channel_manager),
+			Arc::clone(&self.connection_manager),
 		)
 	}
 
@@ -1003,6 +1008,9 @@ impl Node {
 			payjoin_sender.map(Arc::clone),
 			payjoin_receiver.map(Arc::clone),
 			Arc::clone(&self.config),
+			Arc::clone(&self.peer_store),
+			Arc::clone(&self.channel_manager),
+			Arc::clone(&self.connection_manager),
 		)
 	}