Track the amount spent on fees as payments are retried

[rust-lightning] / lightning / src / util / events.rs

diff --git a/lightning/src/util/events.rs b/lightning/src/util/events.rs
index bcd84ba42a6a069989523123290c384e594740b8..e0f0a63dbb341d8507a80ecd07b4a94f3cb91699 100644 (file)
--- a/lightning/src/util/events.rs
+++ b/lightning/src/util/events.rs
@@ -194,6 +194,16 @@ pub enum Event {
                ///
                /// [`ChannelManager::send_payment`]: crate::ln::channelmanager::ChannelManager::send_payment
                payment_hash: PaymentHash,
+               /// The total fee which was spent at intermediate hops in this payment, across all paths.
+               ///
+               /// Note that, like [`Route::get_total_fees`] this does *not* include any potential
+               /// overpayment to the recipient node.
+               ///
+               /// If the recipient or an intermediate node misbehaves and gives us free money, this may
+               /// overstate the amount paid, though this is unlikely.
+               ///
+               /// [`Route::get_total_fees`]: crate::routing::router::Route::get_total_fees
+               fee_paid_msat: Option<u64>,
        },
        /// Indicates an outbound payment we made failed. Probably some intermediary node dropped
        /// something. You may wish to retry with a different route.
@@ -336,12 +346,13 @@ impl Writeable for Event {
                                        (8, payment_preimage, option),
                                });
                        },
-                       &Event::PaymentSent { ref payment_id, ref payment_preimage, ref payment_hash} => {
+                       &Event::PaymentSent { ref payment_id, ref payment_preimage, ref payment_hash, ref fee_paid_msat } => {
                                2u8.write(writer)?;
                                write_tlv_fields!(writer, {
                                        (0, payment_preimage, required),
                                        (1, payment_hash, required),
                                        (3, payment_id, option),
+                                       (5, fee_paid_msat, option),
                                });
                        },
                        &Event::PaymentPathFailed {
@@ -452,10 +463,12 @@ impl MaybeReadable for Event {
                                        let mut payment_preimage = PaymentPreimage([0; 32]);
                                        let mut payment_hash = None;
                                        let mut payment_id = None;
+                                       let mut fee_paid_msat = None;
                                        read_tlv_fields!(reader, {
                                                (0, payment_preimage, required),
                                                (1, payment_hash, option),
                                                (3, payment_id, option),
+                                               (5, fee_paid_msat, option),
                                        });
                                        if payment_hash.is_none() {
                                                payment_hash = Some(PaymentHash(Sha256::hash(&payment_preimage.0[..]).into_inner()));
@@ -464,6 +477,7 @@ impl MaybeReadable for Event {
                                                payment_id,
                                                payment_preimage,
                                                payment_hash: payment_hash.unwrap(),
+                                               fee_paid_msat,
                                        }))
                                };
                                f()