Pipe received `payment_metadata` through the HTLC receipt pipeline

[rust-lightning] / lightning / src / ln / outbound_payment.rs

diff --git a/lightning/src/ln/outbound_payment.rs b/lightning/src/ln/outbound_payment.rs
index 738c1d1952f133fe46ad94be85378427e09e84d1..59efbcfa8c38e1740cad3fb507d0334c61f2e974 100644 (file)
--- a/lightning/src/ln/outbound_payment.rs
+++ b/lightning/src/ln/outbound_payment.rs
@@ -438,6 +438,11 @@ pub struct RecipientOnionFields {
        pub payment_metadata: Option<Vec<u8>>,
 }
 
+impl_writeable_tlv_based!(RecipientOnionFields, {
+       (0, payment_secret, option),
+       (2, payment_metadata, option),
+});
+
 impl RecipientOnionFields {
        /// Creates a [`RecipientOnionFields`] from only a [`PaymentSecret`]. This is the most common
        /// set of onion fields for today's BOLT11 invoices - most nodes require a [`PaymentSecret`]
@@ -454,6 +459,20 @@ impl RecipientOnionFields {
        pub fn spontaneous_empty() -> Self {
                Self { payment_secret: None, payment_metadata: None }
        }
+
+       /// When we have received some HTLC(s) towards an MPP payment, as we receive further HTLC(s) we
+       /// have to make sure that some fields match exactly across the parts. For those that aren't
+       /// required to match, if they don't match we should remove them so as to not expose data
+       /// that's dependent on the HTLC receive order to users.
+       ///
+       /// Here we implement this, first checking compatibility then mutating two objects and then
+       /// dropping any remaining non-matching fields from both.
+       pub(super) fn check_merge(&mut self, further_htlc_fields: &mut Self) -> Result<(), ()> {
+               if self.payment_secret != further_htlc_fields.payment_secret { return Err(()); }
+               if self.payment_metadata != further_htlc_fields.payment_metadata { return Err(()); }
+               // For custom TLVs we should just drop non-matching ones, but not reject the payment.
+               Ok(())
+       }
 }
 
 pub(super) struct OutboundPayments {