Remove now-unused ServeStaticInv::inv_slot from OM

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.

Now that the server includes the invoice_slot in the ServeStaticInvoice blinded
path context as added in the previous commit, there is no need for the
recipient to include it in the ServeStaticInvoice onion message itself.

Author: valentinewallace

lightning/src/offers/async_receive_offer_cache.rs

@@ -411,10 +411,10 @@ impl AsyncReceiveOfferCache {
 	/// the static invoice server.
 	pub(super) fn offers_needing_invoice_refresh(
 		&self, duration_since_epoch: Duration,
-	) -> impl Iterator<Item = (&Offer, Nonce, u16, &Responder)> {
+	) -> impl Iterator<Item = (&Offer, Nonce, &Responder)> {
 		// For any offers which are either in use or pending confirmation by the server, we should send
 		// them a fresh invoice on each timer tick.
-		self.offers_with_idx().filter_map(move |(idx, offer)| {
+		self.offers_with_idx().filter_map(move |(_, offer)| {
 			let needs_invoice_update = match offer.status {
 				OfferStatus::Used { invoice_created_at } => {
 					invoice_created_at.saturating_add(INVOICE_REFRESH_THRESHOLD)
@@ -426,13 +426,7 @@ impl AsyncReceiveOfferCache {
 				OfferStatus::Ready { .. } => false,
 			};
 			if needs_invoice_update {
-				let offer_slot = idx.try_into().unwrap_or(u16::MAX);
-				Some((
-					&offer.offer,
-					offer.offer_nonce,
-					offer_slot,
-					&offer.update_static_invoice_path,
-				))
+				Some((&offer.offer, offer.offer_nonce, &offer.update_static_invoice_path))
 			} else {
 				None
 			}

lightning/src/offers/flow.rs

@@ -1317,8 +1317,7 @@ where
 			let duration_since_epoch = self.duration_since_epoch();
 			let cache = self.async_receive_offer_cache.lock().unwrap();
 			for offer_and_metadata in cache.offers_needing_invoice_refresh(duration_since_epoch) {
-				let (offer, offer_nonce, slot_number, update_static_invoice_path) =
-					offer_and_metadata;
+				let (offer, offer_nonce, update_static_invoice_path) = offer_and_metadata;
 
 				let (invoice, forward_invreq_path) = match self.create_static_invoice_for_server(
 					offer,
@@ -1342,7 +1341,6 @@ where
 				let serve_invoice_message = ServeStaticInvoice {
 					invoice,
 					forward_invoice_request_path: forward_invreq_path,
-					invoice_slot: slot_number,
 				};
 				serve_static_invoice_msgs.push((
 					serve_invoice_message,
@@ -1517,8 +1515,7 @@ where
 			})
 		};
 
-		let serve_invoice_message =
-			ServeStaticInvoice { invoice, forward_invoice_request_path, invoice_slot };
+		let serve_invoice_message = ServeStaticInvoice { invoice, forward_invoice_request_path };
 		Some((serve_invoice_message, reply_path_context))
 	}
 

lightning/src/onion_message/async_payments.rs

@@ -172,11 +172,6 @@ pub struct ServeStaticInvoice {
 	/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 	/// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 	pub forward_invoice_request_path: BlindedMessagePath,
-	/// The "slot" in the static invoice server's database that this invoice should go into. This
-	/// allows recipients to replace a specific invoice that is stored by the server, which is useful
-	/// for limiting the number of invoices stored by the server while also keeping all the invoices
-	/// persisted with the server fresh.
-	pub invoice_slot: u16,
 }
 
 /// Confirmation from a static invoice server  that a [`StaticInvoice`] was persisted and the
@@ -251,7 +246,6 @@ impl_writeable_tlv_based!(OfferPaths, {
 impl_writeable_tlv_based!(ServeStaticInvoice, {
 	(0, invoice, required),
 	(2, forward_invoice_request_path, required),
-	(4, invoice_slot, required),
 });
 
 impl_writeable_tlv_based!(StaticInvoicePersisted, {});