Add experimental TLV fields for invoice requests: invreq_contact_secret, invreq_payer_offer, invreq_payer_bip_353_name

Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>

Author: vincenzopalazzo

lightning/src/offers/invoice.rs

@@ -1546,7 +1546,7 @@ type FullInvoiceTlvStreamRef<'a> = (
 	InvoiceTlvStreamRef<'a>,
 	SignatureTlvStreamRef<'a>,
 	ExperimentalOfferTlvStreamRef,
-	ExperimentalInvoiceRequestTlvStreamRef,
+	ExperimentalInvoiceRequestTlvStreamRef<'a>,
 	ExperimentalInvoiceTlvStreamRef,
 );
 
@@ -1590,7 +1590,7 @@ type PartialInvoiceTlvStreamRef<'a> = (
 	InvoiceRequestTlvStreamRef<'a>,
 	InvoiceTlvStreamRef<'a>,
 	ExperimentalOfferTlvStreamRef,
-	ExperimentalInvoiceRequestTlvStreamRef,
+	ExperimentalInvoiceRequestTlvStreamRef<'a>,
 	ExperimentalInvoiceTlvStreamRef,
 );
 
@@ -2013,7 +2013,12 @@ mod tests {
 				},
 				SignatureTlvStreamRef { signature: Some(&invoice.signature()) },
 				ExperimentalOfferTlvStreamRef { experimental_foo: None },
-				ExperimentalInvoiceRequestTlvStreamRef { experimental_bar: None },
+				ExperimentalInvoiceRequestTlvStreamRef {
+					experimental_bar: None,
+					invreq_contact_secret: None,
+					invreq_payer_offer: None,
+					invreq_payer_bip_353_name: None,
+				},
 				ExperimentalInvoiceTlvStreamRef { experimental_baz: None },
 			),
 		);
@@ -2116,7 +2121,12 @@ mod tests {
 				},
 				SignatureTlvStreamRef { signature: Some(&invoice.signature()) },
 				ExperimentalOfferTlvStreamRef { experimental_foo: None },
-				ExperimentalInvoiceRequestTlvStreamRef { experimental_bar: None },
+				ExperimentalInvoiceRequestTlvStreamRef {
+					experimental_bar: None,
+					invreq_contact_secret: None,
+					invreq_payer_offer: None,
+					invreq_payer_bip_353_name: None,
+				},
 				ExperimentalInvoiceTlvStreamRef { experimental_baz: None },
 			),
 		);

lightning/src/offers/invoice_request.rs

@@ -68,6 +68,7 @@
 use crate::blinded_path::message::BlindedMessagePath;
 use crate::blinded_path::payment::BlindedPaymentPath;
 use crate::io;
+use crate::io::Read;
 use crate::ln::channelmanager::PaymentId;
 use crate::ln::inbound_payment::{ExpandedKey, IV_LEN};
 use crate::ln::msgs::DecodeError;
@@ -499,7 +500,11 @@ impl UnsignedInvoiceRequest {
 
 		invoice_request_tlv_stream.write(&mut bytes).unwrap();
 
-		const EXPERIMENTAL_TLV_ALLOCATION_SIZE: usize = 0;
+		// Allocate sufficient capacity for experimental TLV fields to avoid reallocations.
+		// The new fields (invreq_contact_secret: ~48 bytes, invreq_payer_offer: ~116 bytes,
+		// invreq_payer_bip_353_name: ~116 bytes) total ~280 bytes, with 600 providing headroom
+		// for future experimental fields and variable-length data.
+		const EXPERIMENTAL_TLV_ALLOCATION_SIZE: usize = 600;
 		let mut experimental_bytes = Vec::with_capacity(EXPERIMENTAL_TLV_ALLOCATION_SIZE);
 
 		let experimental_tlv_stream =
@@ -1137,6 +1142,9 @@ impl InvoiceRequestContentsWithoutPayerSigningPubkey {
 		};
 
 		let experimental_invoice_request = ExperimentalInvoiceRequestTlvStreamRef {
+			invreq_contact_secret: None,
+			invreq_payer_offer: None,
+			invreq_payer_bip_353_name: None,
 			#[cfg(test)]
 			experimental_bar: self.experimental_bar,
 		};
@@ -1200,21 +1208,47 @@ tlv_stream!(InvoiceRequestTlvStream, InvoiceRequestTlvStreamRef<'a>, INVOICE_REQ
 pub(super) const EXPERIMENTAL_INVOICE_REQUEST_TYPES: core::ops::Range<u64> =
 	2_000_000_000..3_000_000_000;
 
+/// A contact secret used in experimental TLV fields.
+#[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
+pub struct ContactSecret {
+	contents: [u8; 32],
+}
+
+impl Readable for ContactSecret {
+	fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
+		let mut buf = [0u8; 32];
+		r.read_exact(&mut buf)?;
+		Ok(ContactSecret { contents: buf })
+	}
+}
+
+impl Writeable for ContactSecret {
+	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
+		w.write_all(&self.contents)
+	}
+}
+
 #[cfg(not(test))]
 tlv_stream!(
 	ExperimentalInvoiceRequestTlvStream,
-	ExperimentalInvoiceRequestTlvStreamRef,
+	ExperimentalInvoiceRequestTlvStreamRef<'a>,
 	EXPERIMENTAL_INVOICE_REQUEST_TYPES,
 	{
+		(2_000_001_729, invreq_contact_secret: (Vec<u8>, WithoutLength)),
+		(2_000_001_731, invreq_payer_offer: (Vec<u8>, WithoutLength)),
+		(2_000_001_733, invreq_payer_bip_353_name: (Vec<u8>, WithoutLength)),
 		// When adding experimental TLVs, update EXPERIMENTAL_TLV_ALLOCATION_SIZE accordingly in
 		// UnsignedInvoiceRequest::new to avoid unnecessary allocations.
 	}
 );
 
 #[cfg(test)]
 tlv_stream!(
-	ExperimentalInvoiceRequestTlvStream, ExperimentalInvoiceRequestTlvStreamRef,
+	ExperimentalInvoiceRequestTlvStream, ExperimentalInvoiceRequestTlvStreamRef<'a>,
 	EXPERIMENTAL_INVOICE_REQUEST_TYPES, {
+		(2_000_001_729, invreq_contact_secret: (Vec<u8>, WithoutLength)),
+		(2_000_001_731, invreq_payer_offer: (Vec<u8>, WithoutLength)),
+		(2_000_001_733, invreq_payer_bip_353_name: (Vec<u8>, WithoutLength)),
 		(2_999_999_999, experimental_bar: (u64, HighZeroBytesDroppedBigSize)),
 	}
 );
@@ -1234,7 +1268,7 @@ type FullInvoiceRequestTlvStreamRef<'a> = (
 	InvoiceRequestTlvStreamRef<'a>,
 	SignatureTlvStreamRef<'a>,
 	ExperimentalOfferTlvStreamRef,
-	ExperimentalInvoiceRequestTlvStreamRef,
+	ExperimentalInvoiceRequestTlvStreamRef<'a>,
 );
 
 impl CursorReadable for FullInvoiceRequestTlvStream {
@@ -1270,7 +1304,7 @@ type PartialInvoiceRequestTlvStreamRef<'a> = (
 	OfferTlvStreamRef<'a>,
 	InvoiceRequestTlvStreamRef<'a>,
 	ExperimentalOfferTlvStreamRef,
-	ExperimentalInvoiceRequestTlvStreamRef,
+	ExperimentalInvoiceRequestTlvStreamRef<'a>,
 );
 
 impl TryFrom<Vec<u8>> for UnsignedInvoiceRequest {
@@ -1349,6 +1383,9 @@ impl TryFrom<PartialInvoiceRequestTlvStream> for InvoiceRequestContents {
 			},
 			experimental_offer_tlv_stream,
 			ExperimentalInvoiceRequestTlvStream {
+				invreq_contact_secret: _,
+				invreq_payer_offer: _,
+				invreq_payer_bip_353_name: _,
 				#[cfg(test)]
 				experimental_bar,
 			},
@@ -1572,7 +1609,12 @@ mod tests {
 				},
 				SignatureTlvStreamRef { signature: Some(&invoice_request.signature()) },
 				ExperimentalOfferTlvStreamRef { experimental_foo: None },
-				ExperimentalInvoiceRequestTlvStreamRef { experimental_bar: None },
+				ExperimentalInvoiceRequestTlvStreamRef {
+					invreq_contact_secret: None,
+					invreq_payer_offer: None,
+					invreq_payer_bip_353_name: None,
+					experimental_bar: None,
+				},
 			),
 		);
 

lightning/src/offers/refund.rs

@@ -816,6 +816,9 @@ impl RefundContents {
 		};
 
 		let experimental_invoice_request = ExperimentalInvoiceRequestTlvStreamRef {
+			invreq_contact_secret: None,
+			invreq_payer_offer: None,
+			invreq_payer_bip_353_name: None,
 			#[cfg(test)]
 			experimental_bar: self.experimental_bar,
 		};
@@ -861,7 +864,7 @@ type RefundTlvStreamRef<'a> = (
 	OfferTlvStreamRef<'a>,
 	InvoiceRequestTlvStreamRef<'a>,
 	ExperimentalOfferTlvStreamRef,
-	ExperimentalInvoiceRequestTlvStreamRef,
+	ExperimentalInvoiceRequestTlvStreamRef<'a>,
 );
 
 impl CursorReadable for RefundTlvStream {
@@ -934,6 +937,9 @@ impl TryFrom<RefundTlvStream> for RefundContents {
 				experimental_foo,
 			},
 			ExperimentalInvoiceRequestTlvStream {
+				invreq_contact_secret: _,
+				invreq_payer_offer: _,
+				invreq_payer_bip_353_name: _,
 				#[cfg(test)]
 				experimental_bar,
 			},
@@ -1120,7 +1126,12 @@ mod tests {
 					offer_from_hrn: None,
 				},
 				ExperimentalOfferTlvStreamRef { experimental_foo: None },
-				ExperimentalInvoiceRequestTlvStreamRef { experimental_bar: None },
+				ExperimentalInvoiceRequestTlvStreamRef {
+					invreq_contact_secret: None,
+					invreq_payer_offer: None,
+					invreq_payer_bip_353_name: None,
+					experimental_bar: None,
+				},
 			),
 		);