Serialize blinded path forwards in Trampoline onions.

diff --git a/lightning/src/ln/msgs.rs b/lightning/src/ln/msgs.rs
index 9d1269c56d6752b089b086e8afa94d1e1b35d11f..4706793a681d0e86249aeff392b7acbbb63cad77 100644 (file)
--- a/lightning/src/ln/msgs.rs
+++ b/lightning/src/ln/msgs.rs
@@ -1746,9 +1746,9 @@ pub struct FinalOnionHopData {
 
 mod fuzzy_internal_msgs {
        use bitcoin::secp256k1::PublicKey;
-       use crate::blinded_path::payment::{PaymentConstraints, PaymentContext, PaymentRelay};
+       use crate::blinded_path::payment::{BlindedPaymentPath, PaymentConstraints, PaymentContext, PaymentRelay};
        use crate::types::payment::{PaymentPreimage, PaymentSecret};
-       use crate::types::features::BlindedHopFeatures;
+       use crate::types::features::{BlindedHopFeatures, Bolt12InvoiceFeatures};
        use super::{FinalOnionHopData, TrampolineOnionPacket};
 
        #[allow(unused_imports)]
@@ -1836,9 +1836,21 @@ mod fuzzy_internal_msgs {
                        /// The value, in msat, of the payment after this hop's fee is deducted.
                        amt_to_forward: u64,
                        outgoing_cltv_value: u32,
-                       /// The node id to which the trampoline node must find a route
+                       /// The node id to which the trampoline node must find a route.
                        outgoing_node_id: PublicKey,
-               }
+               },
+               #[allow(unused)]
+               /// This is the last Trampoline hop, whereupon the Trampoline forward mechanism is exited,
+               /// and payment data is relayed using non-Trampoline blinded hops
+               LegacyBlindedPathEntry {
+                       /// The value, in msat, of the payment after this hop's fee is deducted.
+                       amt_to_forward: u64,
+                       outgoing_cltv_value: u32,
+                       /// List of blinded path options the last trampoline hop may choose to route through.
+                       payment_paths: Vec<BlindedPaymentPath>,
+                       /// If applicable, features of the BOLT12 invoice being paid.
+                       invoice_features: Option<Bolt12InvoiceFeatures>,
+               },
        }
 
        pub struct DecodedOnionErrorPacket {
@@ -2763,7 +2775,26 @@ impl Writeable for OutboundTrampolinePayload {
                                        (4, HighZeroBytesDroppedBigSize(*outgoing_cltv_value), required),
                                        (14, outgoing_node_id, required)
                                });
-                       }
+                       },
+                       Self::LegacyBlindedPathEntry { amt_to_forward, outgoing_cltv_value, payment_paths, invoice_features } => {
+                               let mut blinded_path_serialization = [0u8; 2048]; // Fixed-length buffer on the stack
+                               let serialization_length = {
+                                       let buffer_size = blinded_path_serialization.len();
+                                       let mut blinded_path_slice = &mut blinded_path_serialization[..];
+                                       for current_payment_path in payment_paths {
+                                               current_payment_path.inner_blinded_path().write(&mut blinded_path_slice)?;
+                                               current_payment_path.payinfo.write(&mut blinded_path_slice)?;
+                                       }
+                                       buffer_size - blinded_path_slice.len()
+                               };
+                               let blinded_path_serialization = &blinded_path_serialization[..serialization_length];
+                               _encode_varint_length_prefixed_tlv!(w, {
+                                       (2, HighZeroBytesDroppedBigSize(*amt_to_forward), required),
+                                       (4, HighZeroBytesDroppedBigSize(*outgoing_cltv_value), required),
+                                       (21, invoice_features.as_ref().map(|m| WithoutLength(m)), option),
+                                       (22, WithoutLength(blinded_path_serialization), required)
+                               });
+                       },
                }
                Ok(())
        }