Update create_offer_builder to use create_blinded_paths

To simplify blinded path creation and uphold the principle of "One
`MessageRouter`, one `BlindedPath` type," this commit updates
`create_offer_builder` to use the `create_blinded_paths` method of the
`MessageRouter`.

Now, when `create_offer_builder` is called, the offer will be created using
the `MessageRouter` implementation that the `ChannelManager` or
`OffersMessageFlow` is parameterized with.

If a user wishes to create an offer with a different type of blinded path,
they can explicitly use `create_offer_builder_using_router`, which allows
passing a custom `MessageRouter`.

The reasoning behind this change is to give users clearer, more deterministic
control over the type of blinded path used in the offer. It also improves
user awareness, ensuring that creating a non-default blinded path becomes an
*intentional choice*.

Author: shaavan

lightning-dns-resolver/src/lib.rs

@@ -482,7 +482,7 @@ mod test {
 
 		let name = HumanReadableName::from_encoded("[email protected]").unwrap();
 
-		let bs_offer = nodes[1].node.create_offer_builder(None).unwrap().build().unwrap();
+		let bs_offer = nodes[1].node.create_offer_builder().unwrap().build().unwrap();
 		let resolvers = vec![Destination::Node(resolver_id)];
 		let retry = Retry::Attempts(0);
 		let amt = 42_000;

lightning/src/ln/channelmanager.rs

@@ -2212,9 +2212,8 @@ where
 /// #
 /// # fn example<T: AChannelManager>(channel_manager: T) -> Result<(), Bolt12SemanticError> {
 /// # let channel_manager = channel_manager.get_cm();
-/// # let absolute_expiry = None;
 /// let offer = channel_manager
-///     .create_offer_builder(absolute_expiry)?
+///     .create_offer_builder()?
 /// # ;
 /// # // Needed for compiling for c_bindings
 /// # let builder: lightning::offers::offer::OfferBuilder<_, _> = offer.into();
@@ -10852,9 +10851,8 @@ macro_rules! create_offer_builder { ($self: ident, $builder: ty) => {
 	///
 	/// # Privacy
 	///
-	/// Uses [`MessageRouter`] to construct a [`BlindedMessagePath`] for the offer based on the given
-	/// `absolute_expiry` according to [`MAX_SHORT_LIVED_RELATIVE_EXPIRY`]. See those docs for
-	/// privacy implications.
+	/// Uses the [`ChannelManager`]'s [`MessageRouter`] to construct a [`BlindedMessagePath`] for
+	/// the offer. See those docs for privacy implications.
 	///
 	/// Also, uses a derived signing pubkey in the offer for recipient privacy.
 	///
@@ -10869,12 +10867,46 @@ macro_rules! create_offer_builder { ($self: ident, $builder: ty) => {
 	/// [`BlindedMessagePath`]: crate::blinded_path::message::BlindedMessagePath
 	/// [`Offer`]: crate::offers::offer::Offer
 	/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
-	pub fn create_offer_builder(
-		&$self, absolute_expiry: Option<Duration>
-	) -> Result<$builder, Bolt12SemanticError> {
-		let entropy = &*$self.entropy_source;
+	pub fn create_offer_builder(&$self) -> Result<$builder, Bolt12SemanticError> {
+		let builder = $self.flow.create_offer_builder(
+			&*$self.entropy_source, $self.get_peers_for_blinded_path()
+		)?;
+
+		Ok(builder.into())
+	}
 
-		let builder = $self.flow.create_offer_builder(entropy, absolute_expiry, $self.get_peers_for_blinded_path())?;
+	/// Creates an [`OfferBuilder`] such that the [`Offer`] it builds is recognized by the
+	/// [`ChannelManager`] when handling [`InvoiceRequest`] messages for the offer.
+	///
+	/// # Privacy
+	///
+	/// Constructs a [`BlindedMessagePath`] for the offer using a custom [`MessageRouter`].
+	/// Users can implement a custom [`MessageRouter`] to define properties of the
+	/// [`BlindedMessagePath`] as required or opt not to create any `BlindedMessagePath`.
+	///
+	/// Also, uses a derived signing pubkey in the offer for recipient privacy.
+	///
+	/// # Limitations
+	///
+	/// See [`OffersMessageFlow::create_offer_builder`] for limitations on the offer builder.
+	///
+	/// # Errors
+	///
+	/// Errors if the provided [`MessageRouter`] is unable to create a blinded path for the offer.
+	///
+	/// [`BlindedMessagePath`]: crate::blinded_path::message::BlindedMessagePath
+	/// [`Offer`]: crate::offers::offer::Offer
+	/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
+	pub fn create_offer_builder_using_router<ME: Deref>(
+		&$self,
+		router: ME,
+	) -> Result<$builder, Bolt12SemanticError>
+	where
+		ME::Target: MessageRouter,
+	{
+		let builder = $self.flow.create_offer_builder_using_router(
+			router, &*$self.entropy_source, $self.get_peers_for_blinded_path()
+		)?;
 
 		Ok(builder.into())
 	}

lightning/src/ln/max_payment_path_len_tests.rs

@@ -517,7 +517,7 @@ fn bolt12_invoice_too_large_blinded_paths() {
 		),
 	]);
 
-	let offer = nodes[1].node.create_offer_builder(None).unwrap().build().unwrap();
+	let offer = nodes[1].node.create_offer_builder().unwrap().build().unwrap();
 	let payment_id = PaymentId([1; 32]);
 	let route_config = RouteParametersConfig::default();
 	nodes[0]

lightning/src/ln/offers_tests.rs

@@ -307,7 +307,7 @@ fn prefers_non_tor_nodes_in_blinded_paths() {
 	announce_node_address(charlie, &[alice, bob, david, &nodes[4], &nodes[5]], tor.clone());
 
 	let offer = bob.node
-		.create_offer_builder(None).unwrap()
+		.create_offer_builder().unwrap()
 		.amount_msats(10_000_000)
 		.build().unwrap();
 	assert_ne!(offer.issuer_signing_pubkey(), Some(bob_id));
@@ -323,7 +323,7 @@ fn prefers_non_tor_nodes_in_blinded_paths() {
 	announce_node_address(&nodes[5], &[alice, bob, charlie, david, &nodes[4]], tor.clone());
 
 	let offer = bob.node
-		.create_offer_builder(None).unwrap()
+		.create_offer_builder().unwrap()
 		.amount_msats(10_000_000)
 		.build().unwrap();
 	assert_ne!(offer.issuer_signing_pubkey(), Some(bob_id));
@@ -374,7 +374,7 @@ fn prefers_more_connected_nodes_in_blinded_paths() {
 	disconnect_peers(david, &[bob, &nodes[4], &nodes[5]]);
 
 	let offer = bob.node
-		.create_offer_builder(None).unwrap()
+		.create_offer_builder().unwrap()
 		.amount_msats(10_000_000)
 		.build().unwrap();
 	assert_ne!(offer.issuer_signing_pubkey(), Some(bob_id));
@@ -399,11 +399,9 @@ fn creates_short_lived_offer() {
 	let alice_id = alice.node.get_our_node_id();
 	let bob = &nodes[1];
 
-	let absolute_expiry = alice.node.duration_since_epoch() + MAX_SHORT_LIVED_RELATIVE_EXPIRY;
 	let offer = alice.node
-		.create_offer_builder(Some(absolute_expiry)).unwrap()
+		.create_offer_builder().unwrap()
 		.build().unwrap();
-	assert_eq!(offer.absolute_expiry(), Some(absolute_expiry));
 	assert!(!offer.paths().is_empty());
 	for path in offer.paths() {
 		let introduction_node_id = resolve_introduction_node(bob, &path);
@@ -425,20 +423,17 @@ fn creates_long_lived_offer() {
 	let alice = &nodes[0];
 	let alice_id = alice.node.get_our_node_id();
 
-	let absolute_expiry = alice.node.duration_since_epoch() + MAX_SHORT_LIVED_RELATIVE_EXPIRY
-		+ Duration::from_secs(1);
 	let offer = alice.node
-		.create_offer_builder(Some(absolute_expiry))
+		.create_offer_builder()
 		.unwrap()
 		.build().unwrap();
-	assert_eq!(offer.absolute_expiry(), Some(absolute_expiry));
 	assert!(!offer.paths().is_empty());
 	for path in offer.paths() {
 		assert_eq!(path.introduction_node(), &IntroductionNode::NodeId(alice_id));
 	}
 
 	let offer = alice.node
-		.create_offer_builder(None).unwrap()
+		.create_offer_builder().unwrap()
 		.build().unwrap();
 	assert_eq!(offer.absolute_expiry(), None);
 	assert!(!offer.paths().is_empty());
@@ -542,7 +537,7 @@ fn creates_and_pays_for_offer_using_two_hop_blinded_path() {
 	disconnect_peers(david, &[bob, &nodes[4], &nodes[5]]);
 
 	let offer = alice.node
-		.create_offer_builder(None)
+		.create_offer_builder()
 		.unwrap()
 		.amount_msats(10_000_000)
 		.build().unwrap();
@@ -709,7 +704,7 @@ fn creates_and_pays_for_offer_using_one_hop_blinded_path() {
 	let bob_id = bob.node.get_our_node_id();
 
 	let offer = alice.node
-		.create_offer_builder(None).unwrap()
+		.create_offer_builder().unwrap()
 		.amount_msats(10_000_000)
 		.build().unwrap();
 	assert_ne!(offer.issuer_signing_pubkey(), Some(alice_id));
@@ -832,7 +827,7 @@ fn pays_for_offer_without_blinded_paths() {
 	let bob_id = bob.node.get_our_node_id();
 
 	let offer = alice.node
-		.create_offer_builder(None).unwrap()
+		.create_offer_builder().unwrap()
 		.clear_paths()
 		.amount_msats(10_000_000)
 		.build().unwrap();
@@ -956,7 +951,7 @@ fn send_invoice_requests_with_distinct_reply_path() {
 	disconnect_peers(david, &[bob, &nodes[4], &nodes[5]]);
 
 	let offer = alice.node
-		.create_offer_builder(None)
+		.create_offer_builder()
 		.unwrap()
 		.amount_msats(10_000_000)
 		.build().unwrap();
@@ -1092,7 +1087,7 @@ fn creates_and_pays_for_offer_with_retry() {
 	let bob_id = bob.node.get_our_node_id();
 
 	let offer = alice.node
-		.create_offer_builder(None).unwrap()
+		.create_offer_builder().unwrap()
 		.amount_msats(10_000_000)
 		.build().unwrap();
 	assert_ne!(offer.issuer_signing_pubkey(), Some(alice_id));
@@ -1168,7 +1163,7 @@ fn pays_bolt12_invoice_asynchronously() {
 	let bob_id = bob.node.get_our_node_id();
 
 	let offer = alice.node
-		.create_offer_builder(None).unwrap()
+		.create_offer_builder().unwrap()
 		.amount_msats(10_000_000)
 		.build().unwrap();
 
@@ -1260,7 +1255,7 @@ fn creates_offer_with_blinded_path_using_unannounced_introduction_node() {
 	let bob_id = bob.node.get_our_node_id();
 
 	let offer = alice.node
-		.create_offer_builder(None).unwrap()
+		.create_offer_builder().unwrap()
 		.amount_msats(10_000_000)
 		.build().unwrap();
 	assert_ne!(offer.issuer_signing_pubkey(), Some(alice_id));
@@ -1390,7 +1385,7 @@ fn fails_authentication_when_handling_invoice_request() {
 	disconnect_peers(david, &[bob, &nodes[4], &nodes[5]]);
 
 	let offer = alice.node
-		.create_offer_builder(None)
+		.create_offer_builder()
 		.unwrap()
 		.amount_msats(10_000_000)
 		.build().unwrap();
@@ -1402,7 +1397,7 @@ fn fails_authentication_when_handling_invoice_request() {
 	}
 
 	let invalid_path = alice.node
-		.create_offer_builder(None)
+		.create_offer_builder()
 		.unwrap()
 		.build().unwrap()
 		.paths().first().unwrap()
@@ -1502,7 +1497,7 @@ fn fails_authentication_when_handling_invoice_for_offer() {
 	disconnect_peers(david, &[bob, &nodes[4], &nodes[5]]);
 
 	let offer = alice.node
-		.create_offer_builder(None)
+		.create_offer_builder()
 		.unwrap()
 		.amount_msats(10_000_000)
 		.build().unwrap();
@@ -1698,8 +1693,7 @@ fn fails_creating_or_paying_for_offer_without_connected_peers() {
 	disconnect_peers(alice, &[bob, charlie, david, &nodes[4], &nodes[5]]);
 	disconnect_peers(david, &[bob, charlie, &nodes[4], &nodes[5]]);
 
-	let absolute_expiry = alice.node.duration_since_epoch() + MAX_SHORT_LIVED_RELATIVE_EXPIRY;
-	match alice.node.create_offer_builder(Some(absolute_expiry)) {
+	match alice.node.create_offer_builder() {
 		Ok(_) => panic!("Expected error"),
 		Err(e) => assert_eq!(e, Bolt12SemanticError::MissingPaths),
 	}
@@ -1708,9 +1702,11 @@ fn fails_creating_or_paying_for_offer_without_connected_peers() {
 	args.send_channel_ready = (true, true);
 	reconnect_nodes(args);
 
+	let absolute_expiry = alice.node.duration_since_epoch() + MAX_SHORT_LIVED_RELATIVE_EXPIRY;
 	let offer = alice.node
-		.create_offer_builder(Some(absolute_expiry)).unwrap()
+		.create_offer_builder().unwrap()
 		.amount_msats(10_000_000)
+		.absolute_expiry(absolute_expiry)
 		.build().unwrap();
 
 	let payment_id = PaymentId([1; 32]);
@@ -1813,7 +1809,7 @@ fn fails_creating_invoice_request_for_unsupported_chain() {
 	let bob = &nodes[1];
 
 	let offer = alice.node
-		.create_offer_builder(None).unwrap()
+		.create_offer_builder().unwrap()
 		.clear_chains()
 		.chain(Network::Signet)
 		.build().unwrap();
@@ -1872,7 +1868,7 @@ fn fails_creating_invoice_request_without_blinded_reply_path() {
 	disconnect_peers(david, &[bob, charlie, &nodes[4], &nodes[5]]);
 
 	let offer = alice.node
-		.create_offer_builder(None).unwrap()
+		.create_offer_builder().unwrap()
 		.amount_msats(10_000_000)
 		.build().unwrap();
 
@@ -1906,7 +1902,7 @@ fn fails_creating_invoice_request_with_duplicate_payment_id() {
 	disconnect_peers(alice, &[charlie, david, &nodes[4], &nodes[5]]);
 
 	let offer = alice.node
-		.create_offer_builder(None).unwrap()
+		.create_offer_builder().unwrap()
 		.amount_msats(10_000_000)
 		.build().unwrap();
 
@@ -1992,7 +1988,7 @@ fn fails_sending_invoice_without_blinded_payment_paths_for_offer() {
 	disconnect_peers(david, &[bob, &nodes[4], &nodes[5]]);
 
 	let offer = alice.node
-		.create_offer_builder(None).unwrap()
+		.create_offer_builder().unwrap()
 		.amount_msats(10_000_000)
 		.build().unwrap();
 
@@ -2201,7 +2197,7 @@ fn fails_paying_invoice_with_unknown_required_features() {
 	disconnect_peers(david, &[bob, &nodes[4], &nodes[5]]);
 
 	let offer = alice.node
-		.create_offer_builder(None).unwrap()
+		.create_offer_builder().unwrap()
 		.amount_msats(10_000_000)
 		.build().unwrap();
 
@@ -2280,7 +2276,7 @@ fn rejects_keysend_to_non_static_invoice_path() {
 	create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 1_000_000, 0);
 
 	// First pay the offer and save the payment preimage and invoice.
-	let offer = nodes[1].node.create_offer_builder(None).unwrap().build().unwrap();
+	let offer = nodes[1].node.create_offer_builder().unwrap().build().unwrap();
 	let amt_msat = 5000;
 	let payment_id = PaymentId([1; 32]);
 	nodes[0].node.pay_for_offer(&offer, None, Some(amt_msat), None, payment_id, Retry::Attempts(1), RouteParametersConfig::default()).unwrap();
@@ -2360,7 +2356,7 @@ fn no_double_pay_with_stale_channelmanager() {
 
 	let amt_msat = nodes[0].node.list_usable_channels()[0].next_outbound_htlc_limit_msat + 1; // Force MPP
 	let offer = nodes[1].node
-		.create_offer_builder(None).unwrap()
+		.create_offer_builder().unwrap()
 		.clear_paths()
 		.amount_msats(amt_msat)
 		.build().unwrap();