Replace StaticInvoiceReq::invoice_id with ::inv_slot

In the initially-merged version of the static invoice server protocol, the
static invoice server would sometimes have to find a specific static invoice
based on (recipient_id, invoice_slot) and sometime based on (recipient_id,
invoice_id). This made the API harder to use in terms of how the server would
index into the KVStore.

We'd like to transition to the server always finding a specific invoice based on
(recipient_id, invoice_slot) and get rid of the invoice_id concept.

Previously, when an invoice request would come in for the server on behalf of
the often-offline recipient, they would need to find the static invoice based
on the recipient_id and invoice_id. However, previous commits have now led to
the server being able to use the invoice_slot in the initial offer paths that
they create, which we do here, obviating the need for them to create their own
randomly-generated invoice_id. The final dangling references to the invoice_id
will be removed in the next commit.

Author: valentinewallace

lightning/src/blinded_path/message.rs

@@ -353,7 +353,7 @@ pub enum OffersContext {
 	StaticInvoiceRequested {
 		/// An identifier for the async recipient for whom we as a static invoice server are serving
 		/// [`StaticInvoice`]s. Used paired with the
-		/// [`OffersContext::StaticInvoiceRequested::invoice_id`] when looking up a corresponding
+		/// [`OffersContext::StaticInvoiceRequested::invoice_slot`] when looking up a corresponding
 		/// [`StaticInvoice`] to return to the payer if the recipient is offline. This id was previously
 		/// provided via [`AsyncPaymentsContext::ServeStaticInvoice::recipient_id`].
 		///
@@ -364,15 +364,15 @@ pub enum OffersContext {
 		/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 		recipient_id: Vec<u8>,
 
-		/// A random unique identifier for a specific [`StaticInvoice`] that the recipient previously
+		/// The slot number for a specific [`StaticInvoice`] that the recipient previously
 		/// requested be served on their behalf. Useful when paired with the
 		/// [`OffersContext::StaticInvoiceRequested::recipient_id`] to pull that specific invoice from
 		/// the database when payers send an [`InvoiceRequest`]. This id was previously
-		/// provided via [`AsyncPaymentsContext::ServeStaticInvoice::invoice_id`].
+		/// provided via [`AsyncPaymentsContext::ServeStaticInvoice::invoice_slot`].
 		///
 		/// [`StaticInvoice`]: crate::offers::static_invoice::StaticInvoice
 		/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
-		invoice_id: u128,
+		invoice_slot: u16,
 
 		/// The time as duration since the Unix epoch at which this path expires and messages sent over
 		/// it should be ignored.
@@ -487,16 +487,16 @@ pub enum AsyncPaymentsContext {
 		recipient_id: Vec<u8>,
 		/// A random identifier for the specific [`StaticInvoice`] that the recipient is requesting be
 		/// served on their behalf. Useful when surfaced alongside the above `recipient_id` when payers
-		/// send an [`InvoiceRequest`], to pull the specific static invoice from the database. This id
-		/// will be provided back to us as the static invoice server via
-		/// [`OffersContext::StaticInvoiceRequested::invoice_id`].
+		/// send an [`InvoiceRequest`], to pull the specific static invoice from the database.
 		///
 		/// [`StaticInvoice`]: crate::offers::static_invoice::StaticInvoice
 		/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 		invoice_id: u128,
 		/// The slot number for the specific [`StaticInvoice`] that the recipient is requesting be
 		/// served on their behalf. Useful when surfaced alongside the above `recipient_id` when payers
-		/// send an [`InvoiceRequest`], to pull the specific static invoice from the database.
+		/// send an [`InvoiceRequest`], to pull the specific static invoice from the database. This id
+		/// will be provided back to us as the static invoice server via
+		/// [`OffersContext::StaticInvoiceRequested::invoice_slot`].
 		///
 		/// [`StaticInvoice`]: crate::offers::static_invoice::StaticInvoice
 		/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
@@ -574,7 +574,7 @@ impl_writeable_tlv_based_enum!(OffersContext,
 	},
 	(3, StaticInvoiceRequested) => {
 		(0, recipient_id, required),
-		(2, invoice_id, required),
+		(2, invoice_slot, required),
 		(4, path_absolute_expiry, required),
 	},
 );

lightning/src/events/mod.rs

@@ -1688,7 +1688,7 @@ pub enum Event {
 	/// them via [`ChannelManager::set_paths_to_static_invoice_server`].
 	///
 	/// If we previously persisted a [`StaticInvoice`] from an [`Event::PersistStaticInvoice`] that
-	/// matches the below `recipient_id` and `invoice_id`, that invoice should be retrieved now
+	/// matches the below `recipient_id` and `invoice_slot`, that invoice should be retrieved now
 	/// and forwarded to the payer via [`ChannelManager::send_static_invoice`].
 	///
 	/// [`ChannelManager::blinded_paths_for_async_recipient`]: crate::ln::channelmanager::ChannelManager::blinded_paths_for_async_recipient
@@ -1697,13 +1697,13 @@ pub enum Event {
 	/// [`ChannelManager::send_static_invoice`]: crate::ln::channelmanager::ChannelManager::send_static_invoice
 	StaticInvoiceRequested {
 		/// An identifier for the recipient previously surfaced in
-		/// [`Event::PersistStaticInvoice::recipient_id`]. Useful when paired with the `invoice_id` to
+		/// [`Event::PersistStaticInvoice::recipient_id`]. Useful when paired with the `invoice_slot` to
 		/// retrieve the [`StaticInvoice`] requested by the payer.
 		recipient_id: Vec<u8>,
-		/// A random identifier for the invoice being requested, previously surfaced in
-		/// [`Event::PersistStaticInvoice::invoice_id`]. Useful when paired with the `recipient_id` to
+		/// The slot number for the invoice being requested, previously surfaced in
+		/// [`Event::PersistStaticInvoice::invoice_slot`]. Useful when paired with the `recipient_id` to
 		/// retrieve the [`StaticInvoice`] requested by the payer.
-		invoice_id: u128,
+		invoice_slot: u16,
 		/// The path over which the [`StaticInvoice`] will be sent to the payer, which should be
 		/// provided to [`ChannelManager::send_static_invoice`] along with the invoice.
 		///

lightning/src/ln/async_payments_tests.rs

@@ -209,7 +209,7 @@ fn pass_async_payments_oms(
 	let mut events = always_online_recipient_counterparty.node.get_and_clear_pending_events();
 	assert_eq!(events.len(), 1);
 	let reply_path = match events.pop().unwrap() {
-		Event::StaticInvoiceRequested { recipient_id: ev_id, invoice_id: _, reply_path } => {
+		Event::StaticInvoiceRequested { recipient_id: ev_id, invoice_slot: _, reply_path } => {
 			assert_eq!(recipient_id, ev_id);
 			reply_path
 		},
@@ -573,7 +573,7 @@ fn ignore_unexpected_static_invoice() {
 	let mut events = nodes[1].node.get_and_clear_pending_events();
 	assert_eq!(events.len(), 1);
 	let reply_path = match events.pop().unwrap() {
-		Event::StaticInvoiceRequested { recipient_id: ev_id, invoice_id: _, reply_path } => {
+		Event::StaticInvoiceRequested { recipient_id: ev_id, invoice_slot: _, reply_path } => {
 			assert_eq!(recipient_id, ev_id);
 			reply_path
 		},

lightning/src/ln/channelmanager.rs

@@ -14317,9 +14317,9 @@ where
 
 				let invoice_request = match self.flow.verify_invoice_request(invoice_request, context) {
 					Ok(InvreqResponseInstructions::SendInvoice(invoice_request)) => invoice_request,
-					Ok(InvreqResponseInstructions::SendStaticInvoice { recipient_id, invoice_id }) => {
+					Ok(InvreqResponseInstructions::SendStaticInvoice { recipient_id, invoice_slot }) => {
 						self.pending_events.lock().unwrap().push_back((Event::StaticInvoiceRequested {
-							recipient_id, invoice_id, reply_path: responder
+							recipient_id, invoice_slot, reply_path: responder
 						}, None));
 
 						return None

lightning/src/offers/flow.rs

@@ -395,7 +395,7 @@ pub enum InvreqResponseInstructions {
 	/// the invoice request since it is now verified.
 	SendInvoice(VerifiedInvoiceRequest),
 	/// We are a static invoice server and should respond to this invoice request by retrieving the
-	/// [`StaticInvoice`] corresponding to the `recipient_id` and `invoice_id` and calling
+	/// [`StaticInvoice`] corresponding to the `recipient_id` and `invoice_slot` and calling
 	/// `OffersMessageFlow::enqueue_static_invoice`.
 	///
 	/// [`StaticInvoice`]: crate::offers::static_invoice::StaticInvoice
@@ -404,8 +404,8 @@ pub enum InvreqResponseInstructions {
 		///
 		/// [`StaticInvoice`]: crate::offers::static_invoice::StaticInvoice
 		recipient_id: Vec<u8>,
-		/// An identifier for the specific invoice being requested by the payer.
-		invoice_id: u128,
+		/// The slot number for the specific invoice being requested by the payer.
+		invoice_slot: u16,
 	},
 }
 
@@ -435,7 +435,7 @@ where
 			Some(OffersContext::InvoiceRequest { nonce }) => Some(nonce),
 			Some(OffersContext::StaticInvoiceRequested {
 				recipient_id,
-				invoice_id,
+				invoice_slot,
 				path_absolute_expiry,
 			}) => {
 				if path_absolute_expiry < self.duration_since_epoch() {
@@ -444,7 +444,7 @@ where
 
 				return Ok(InvreqResponseInstructions::SendStaticInvoice {
 					recipient_id,
-					invoice_id,
+					invoice_slot,
 				});
 			},
 			_ => return Err(()),
@@ -1401,7 +1401,7 @@ where
 			let context = MessageContext::Offers(OffersContext::StaticInvoiceRequested {
 				recipient_id: recipient_id.clone(),
 				path_absolute_expiry,
-				invoice_id,
+				invoice_slot: request.invoice_slot,
 			});
 
 			match self.create_blinded_paths(peers, context) {