Store keysend preimage in outbound payments

This sets us up for spontaneous payment retries in ChannelManager.

Currently, retrying spontaneous payments is broken in InvoicePayer because it
does not include the keysend preimage on retry.

Author: valentinewallace

lightning/src/ln/channelmanager.rs

@@ -7367,6 +7367,7 @@ where
 										session_privs: [session_priv_bytes].iter().map(|a| *a).collect(),
 										payment_hash: htlc.payment_hash,
 										payment_secret,
+										keysend_preimage: None, // only used for retries, and we'll never retry on startup
 										pending_amt_msat: path_amt,
 										pending_fee_msat: Some(path_fee),
 										total_msat: path_amt,

lightning/src/ln/outbound_payment.rs

@@ -48,6 +48,7 @@ pub(crate) enum PendingOutboundPayment {
 		session_privs: HashSet<[u8; 32]>,
 		payment_hash: PaymentHash,
 		payment_secret: Option<PaymentSecret>,
+		keysend_preimage: Option<PaymentPreimage>,
 		pending_amt_msat: u64,
 		/// Used to track the fee paid. Only present if the payment was serialized on 0.0.103+.
 		pending_fee_msat: Option<u64>,
@@ -432,7 +433,7 @@ impl OutboundPayments {
 		F: Fn(&Vec<RouteHop>, &Option<PaymentParameters>, &PaymentHash, &Option<PaymentSecret>, u64,
 		   u32, PaymentId, &Option<PaymentPreimage>, [u8; 32]) -> Result<(), APIError>
 	{
-		let onion_session_privs = self.add_new_pending_payment(payment_hash, *payment_secret, payment_id, route, None, None, entropy_source, best_block_height)?;
+		let onion_session_privs = self.add_new_pending_payment(payment_hash, *payment_secret, payment_id, None, route, None, None, entropy_source, best_block_height)?;
 		self.pay_route_internal(route, payment_hash, payment_secret, None, payment_id, None,
 			onion_session_privs, node_signer, best_block_height, &send_payment_along_path)
 			.map_err(|e| { self.remove_outbound_if_all_failed(payment_id, &e); e })
@@ -453,7 +454,7 @@ impl OutboundPayments {
 			None => PaymentPreimage(entropy_source.get_secure_random_bytes()),
 		};
 		let payment_hash = PaymentHash(Sha256::hash(&preimage.0).into_inner());
-		let onion_session_privs = self.add_new_pending_payment(payment_hash, None, payment_id, &route, None, None, entropy_source, best_block_height)?;
+		let onion_session_privs = self.add_new_pending_payment(payment_hash, None, payment_id, Some(preimage), &route, None, None, entropy_source, best_block_height)?;
 
 		match self.pay_route_internal(route, payment_hash, &None, Some(preimage), payment_id, None, onion_session_privs, node_signer, best_block_height, &send_payment_along_path) {
 			Ok(()) => Ok(payment_hash),
@@ -540,7 +541,7 @@ impl OutboundPayments {
 		}))?;
 
 		let res = if let Some((payment_hash, payment_secret, retry_strategy)) = initial_send_info {
-			let onion_session_privs = self.add_new_pending_payment(payment_hash, *payment_secret, payment_id, &route, Some(retry_strategy), Some(route_params.payment_params.clone()), entropy_source, best_block_height)?;
+			let onion_session_privs = self.add_new_pending_payment(payment_hash, *payment_secret, payment_id, None, &route, Some(retry_strategy), Some(route_params.payment_params.clone()), entropy_source, best_block_height)?;
 			self.pay_route_internal(&route, payment_hash, payment_secret, None, payment_id, None, onion_session_privs, node_signer, best_block_height, send_payment_along_path)
 		} else {
 			self.retry_payment_with_route(&route, payment_id, entropy_source, node_signer, best_block_height, send_payment_along_path)
@@ -669,7 +670,7 @@ impl OutboundPayments {
 		}
 
 		let route = Route { paths: vec![hops], payment_params: None };
-		let onion_session_privs = self.add_new_pending_payment(payment_hash, None, payment_id, &route, None, None, entropy_source, best_block_height)?;
+		let onion_session_privs = self.add_new_pending_payment(payment_hash, None, payment_id, None, &route, None, None, entropy_source, best_block_height)?;
 
 		match self.pay_route_internal(&route, payment_hash, &None, None, payment_id, None, onion_session_privs, node_signer, best_block_height, &send_payment_along_path) {
 			Ok(()) => Ok((payment_hash, payment_id)),
@@ -685,13 +686,13 @@ impl OutboundPayments {
 		&self, payment_hash: PaymentHash, payment_secret: Option<PaymentSecret>, payment_id: PaymentId,
 		route: &Route, retry_strategy: Option<Retry>, entropy_source: &ES, best_block_height: u32
 	) -> Result<Vec<[u8; 32]>, PaymentSendFailure> where ES::Target: EntropySource {
-		self.add_new_pending_payment(payment_hash, payment_secret, payment_id, route, retry_strategy, None, entropy_source, best_block_height)
+		self.add_new_pending_payment(payment_hash, payment_secret, payment_id, None, route, retry_strategy, None, entropy_source, best_block_height)
 	}
 
 	pub(super) fn add_new_pending_payment<ES: Deref>(
 		&self, payment_hash: PaymentHash, payment_secret: Option<PaymentSecret>, payment_id: PaymentId,
-		route: &Route, retry_strategy: Option<Retry>, payment_params: Option<PaymentParameters>,
-		entropy_source: &ES, best_block_height: u32
+		keysend_preimage: Option<PaymentPreimage>, route: &Route, retry_strategy: Option<Retry>,
+		payment_params: Option<PaymentParameters>, entropy_source: &ES, best_block_height: u32
 	) -> Result<Vec<[u8; 32]>, PaymentSendFailure> where ES::Target: EntropySource {
 		let mut onion_session_privs = Vec::with_capacity(route.paths.len());
 		for _ in 0..route.paths.len() {
@@ -711,6 +712,7 @@ impl OutboundPayments {
 					pending_fee_msat: Some(0),
 					payment_hash,
 					payment_secret,
+					keysend_preimage,
 					starting_block_height: best_block_height,
 					total_msat: route.get_total_amount(),
 				});
@@ -1158,6 +1160,7 @@ impl_writeable_tlv_based_enum_upgradable!(PendingOutboundPayment,
 		(10, starting_block_height, required),
 		(not_written, retry_strategy, (static_value, None)),
 		(not_written, attempts, (static_value, PaymentAttempts::new())),
+		(not_written, keysend_preimage, (static_value, None)),
 	},
 	(3, Abandoned) => {
 		(0, session_privs, required),
@@ -1247,9 +1250,9 @@ mod tests {
 			Err(LightningError { err: String::new(), action: ErrorAction::IgnoreError }));
 
 		let err = if on_retry {
-			outbound_payments.add_new_pending_payment(PaymentHash([0; 32]), None, PaymentId([0; 32]),
-			&Route { paths: vec![], payment_params: None }, Some(Retry::Attempts(1)), Some(route_params.payment_params.clone()),
-			&&keys_manager, 0).unwrap();
+			outbound_payments.add_new_pending_payment(PaymentHash([0; 32]), None, PaymentId([0; 32]), None,
+				&Route { paths: vec![], payment_params: None }, Some(Retry::Attempts(1)),
+				Some(route_params.payment_params.clone()), &&keys_manager, 0).unwrap();
 			outbound_payments.pay_internal(
 				PaymentId([0; 32]), None, route_params, &&router, vec![], InFlightHtlcs::new(),
 				&&keys_manager, &&keys_manager, 0, &&logger, &|_, _, _, _, _, _, _, _, _| Ok(())).unwrap_err()