Give users who use get_payment_secret_preimage the PaymentPreimage

For users who get PaymentPreimages via
`get_payment_secret_preimage`, they need to provide the
PaymentPreimage back in `claim_funds` but they aren't actually
given the preimage anywhere.

This commit gives users the PaymentPreimage in the
`PaymentReceived` event.

Author: TheBlueMatt

lightning/src/ln/chanmon_update_fail_tests.rs

@@ -206,8 +206,9 @@ fn do_test_simple_monitor_temporary_update_fail(disconnect: bool, persister_fail
 	let events_3 = nodes[1].node.get_and_clear_pending_events();
 	assert_eq!(events_3.len(), 1);
 	match events_3[0] {
-		Event::PaymentReceived { ref payment_hash, ref payment_secret, amt, user_payment_id: _ } => {
+		Event::PaymentReceived { ref payment_hash, ref payment_preimage, ref payment_secret, amt, user_payment_id: _ } => {
 			assert_eq!(payment_hash_1, *payment_hash);
+			assert!(payment_preimage.is_none());
 			assert_eq!(payment_secret_1, *payment_secret);
 			assert_eq!(amt, 1000000);
 		},
@@ -574,8 +575,9 @@ fn do_test_monitor_temporary_update_fail(disconnect_count: usize) {
 	let events_5 = nodes[1].node.get_and_clear_pending_events();
 	assert_eq!(events_5.len(), 1);
 	match events_5[0] {
-		Event::PaymentReceived { ref payment_hash, ref payment_secret, amt, user_payment_id: _ } => {
+		Event::PaymentReceived { ref payment_hash, ref payment_preimage, ref payment_secret, amt, user_payment_id: _ } => {
 			assert_eq!(payment_hash_2, *payment_hash);
+			assert!(payment_preimage.is_none());
 			assert_eq!(payment_secret_2, *payment_secret);
 			assert_eq!(amt, 1000000);
 		},
@@ -688,8 +690,9 @@ fn test_monitor_update_fail_cs() {
 	let events = nodes[1].node.get_and_clear_pending_events();
 	assert_eq!(events.len(), 1);
 	match events[0] {
-		Event::PaymentReceived { payment_hash, payment_secret, amt, user_payment_id: _ } => {
+		Event::PaymentReceived { payment_hash, payment_preimage, payment_secret, amt, user_payment_id: _ } => {
 			assert_eq!(payment_hash, our_payment_hash);
+			assert!(payment_preimage.is_none());
 			assert_eq!(our_payment_secret, payment_secret);
 			assert_eq!(amt, 1000000);
 		},

lightning/src/ln/channelmanager.rs

@@ -2014,6 +2014,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 											} else if total_value == payment_data.total_msat {
 												new_events.push(events::Event::PaymentReceived {
 													payment_hash,
+													payment_preimage: inbound_payment.get().payment_preimage,
 													payment_secret: payment_data.payment_secret,
 													amt: total_value,
 													user_payment_id: inbound_payment.get().user_payment_id,
@@ -3371,6 +3372,9 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 	/// secret fetched via this method or [`get_payment_secret`], and which is at least the `value`
 	/// provided here, if one is provided.
 	///
+	/// The [`PaymentReceived`] event will have the [`PaymentReceived::payment_preimage`] field
+	/// filled in, allowing you to pass the preimage generated for you directly to [`claim_funds`].
+	///
 	/// `user_payment_id` will be provided back in [`PaymentReceived::user_payment_id`] events to
 	/// allow tracking of which events correspond with which get_payment_secret_preimage calls.
 	/// user_payment_id has no meaning inside of LDK, it is simply copied to events and otherwise
@@ -3388,8 +3392,10 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 	/// May panic if `invoice_expiry_delta_blocks` is greater than one year of blocks (52,560).
 	///
 	/// [`get_payment_secret`]: Self::get_payment_secret
+	/// [`claim_funds`]: Self::claim_funds
 	/// [`PaymentReceived`]: events::Event::PaymentReceived
 	/// [`PaymentReceived::user_payment_id`]: events::Event::PaymentReceived::user_payment_id
+	/// [`PaymentReceived::payment_preimage`]: events::Event::PaymentReceived::payment_preimage
 	pub fn get_payment_secret_preimage(&self, min_value_msat: Option<u64>, invoice_expiry_delta_blocks: u32, user_payment_id: u64) -> (PaymentHash, PaymentSecret) {
 		assert!(invoice_expiry_delta_blocks <= 6*24*365); // We may overflow later if this value is too large
 

lightning/src/ln/functional_test_utils.rs

@@ -941,8 +941,9 @@ macro_rules! expect_payment_received {
 		let events = $node.node.get_and_clear_pending_events();
 		assert_eq!(events.len(), 1);
 		match events[0] {
-			Event::PaymentReceived { ref payment_hash, ref payment_secret, amt, user_payment_id: _ } => {
+			Event::PaymentReceived { ref payment_hash, ref payment_preimage, ref payment_secret, amt, user_payment_id: _ } => {
 				assert_eq!($expected_payment_hash, *payment_hash);
+				assert!(payment_preimage.is_none());
 				assert_eq!($expected_payment_secret, *payment_secret);
 				assert_eq!($expected_recv_value, amt);
 			},
@@ -1009,8 +1010,9 @@ pub fn pass_along_path<'a, 'b, 'c>(origin_node: &Node<'a, 'b, 'c>, expected_path
 			if payment_received_expected {
 				assert_eq!(events_2.len(), 1);
 				match events_2[0] {
-					Event::PaymentReceived { ref payment_hash, ref payment_secret, amt, user_payment_id: _ } => {
+					Event::PaymentReceived { ref payment_hash, ref payment_preimage, ref payment_secret, amt, user_payment_id: _ } => {
 						assert_eq!(our_payment_hash, *payment_hash);
+						assert!(payment_preimage.is_none());
 						assert_eq!(our_payment_secret, *payment_secret);
 						assert_eq!(amt, recv_value);
 					},

lightning/src/ln/functional_tests.rs

@@ -2070,16 +2070,18 @@ fn test_channel_reserve_holding_cell_htlcs() {
 	let events = nodes[2].node.get_and_clear_pending_events();
 	assert_eq!(events.len(), 2);
 	match events[0] {
-		Event::PaymentReceived { ref payment_hash, ref payment_secret, amt, user_payment_id: _ } => {
+		Event::PaymentReceived { ref payment_hash, ref payment_preimage, ref payment_secret, amt, user_payment_id: _ } => {
 			assert_eq!(our_payment_hash_21, *payment_hash);
+			assert!(payment_preimage.is_none());
 			assert_eq!(our_payment_secret_21, *payment_secret);
 			assert_eq!(recv_value_21, amt);
 		},
 		_ => panic!("Unexpected event"),
 	}
 	match events[1] {
-		Event::PaymentReceived { ref payment_hash, ref payment_secret, amt, user_payment_id: _ } => {
+		Event::PaymentReceived { ref payment_hash, ref payment_preimage, ref payment_secret, amt, user_payment_id: _ } => {
 			assert_eq!(our_payment_hash_22, *payment_hash);
+			assert!(payment_preimage.is_none());
 			assert_eq!(our_payment_secret_22, *payment_secret);
 			assert_eq!(recv_value_22, amt);
 		},
@@ -3646,8 +3648,9 @@ fn do_test_drop_messages_peer_disconnect(messages_delivered: u8) {
 	let events_2 = nodes[1].node.get_and_clear_pending_events();
 	assert_eq!(events_2.len(), 1);
 	match events_2[0] {
-		Event::PaymentReceived { ref payment_hash, ref payment_secret, amt, user_payment_id: _ } => {
+		Event::PaymentReceived { ref payment_hash, ref payment_preimage, ref payment_secret, amt, user_payment_id: _ } => {
 			assert_eq!(payment_hash_1, *payment_hash);
+			assert!(payment_preimage.is_none());
 			assert_eq!(payment_secret_1, *payment_secret);
 			assert_eq!(amt, 1000000);
 		},
@@ -3983,8 +3986,9 @@ fn test_drop_messages_peer_disconnect_dual_htlc() {
 	let events_5 = nodes[1].node.get_and_clear_pending_events();
 	assert_eq!(events_5.len(), 1);
 	match events_5[0] {
-		Event::PaymentReceived { ref payment_hash, ref payment_secret, amt: _, user_payment_id: _ } => {
+		Event::PaymentReceived { ref payment_hash, ref payment_preimage, ref payment_secret, amt: _, user_payment_id: _ } => {
 			assert_eq!(payment_hash_2, *payment_hash);
+			assert!(payment_preimage.is_none());
 			assert_eq!(payment_secret_2, *payment_secret);
 		},
 		_ => panic!("Unexpected event"),

lightning/src/util/events.rs

@@ -61,6 +61,13 @@ pub enum Event {
 	PaymentReceived {
 		/// The hash for which the preimage should be handed to the ChannelManager.
 		payment_hash: PaymentHash,
+		/// The preimage to the payment_hash, if the payment hash (and secret) were fetched via
+		/// [`ChannelManager::get_payment_secret_preimage`]. If provided, this can be handed
+		/// directly to [`ChannelManager::claim_funds`].
+		///
+		/// [`ChannelManager::get_payment_secret_preimage`]: crate::ln::channelmanager::ChannelManager::get_payment_secret_preimage
+		/// [`ChannelManager::claim_funds`]: crate::ln::channelmanager::ChannelManager::claim_funds
+		payment_preimage: Option<PaymentPreimage>,
 		/// The "payment secret". This authenticates the sender to the recipient, preventing a
 		/// number of deanonymization attacks during the routing process.
 		/// It is provided here for your reference, however its accuracy is enforced directly by
@@ -139,9 +146,10 @@ impl Writeable for Event {
 				// We never write out FundingGenerationReady events as, upon disconnection, peers
 				// drop any channels which have not yet exchanged funding_signed.
 			},
-			&Event::PaymentReceived { ref payment_hash, ref payment_secret, ref amt, ref user_payment_id } => {
+			&Event::PaymentReceived { ref payment_hash, ref payment_preimage, ref payment_secret, ref amt, ref user_payment_id } => {
 				1u8.write(writer)?;
 				payment_hash.write(writer)?;
+				payment_preimage.write(writer)?;
 				payment_secret.write(writer)?;
 				amt.write(writer)?;
 				user_payment_id.write(writer)?;
@@ -186,6 +194,7 @@ impl MaybeReadable for Event {
 			0u8 => Ok(None),
 			1u8 => Ok(Some(Event::PaymentReceived {
 					payment_hash: Readable::read(reader)?,
+					payment_preimage: Readable::read(reader)?,
 					payment_secret: Readable::read(reader)?,
 					amt: Readable::read(reader)?,
 					user_payment_id: Readable::read(reader)?,