Allow users to accept skimmed fees in calling `peel_payment_onion`

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

diff --git a/lightning/src/ln/onion_payment.rs b/lightning/src/ln/onion_payment.rs
index ca15a37c072d89625a0a235fb226d170f758cdb4..06a9ae07e1e0024c075082711d9064278227cf5a 100644 (file)
--- a/lightning/src/ln/onion_payment.rs
+++ b/lightning/src/ln/onion_payment.rs
@@ -1,6 +1,7 @@
-//! Utilities for channelmanager.rs
+//! Utilities to decode payment onions and do contextless validation of incoming payments.
 //!
-//! Includes a public [`peel_payment_onion`] function for use by external projects or libraries.
+//! Primarily features [`peel_payment_onion`], which allows the decoding of an onion statelessly
+//! and can be used to predict whether we'd accept a payment.
 
 use bitcoin::hashes::Hash;
 use bitcoin::hashes::sha256::Hash as Sha256;
@@ -225,7 +226,9 @@ pub(super) fn create_recv_pending_htlc_info(
        })
 }
 
-/// Peel one layer off an incoming onion, returning [`PendingHTLCInfo`] (either Forward or Receive).
+/// Peel one layer off an incoming onion, returning a [`PendingHTLCInfo`] that contains information
+/// about the intended next-hop for the HTLC.
+///
 /// This does all the relevant context-free checks that LDK requires for payment relay or
 /// acceptance. If the payment is to be received, and the amount matches the expected amount for
 /// a given invoice, this indicates the [`msgs::UpdateAddHTLC`], once fully committed in the
@@ -234,7 +237,7 @@ pub(super) fn create_recv_pending_htlc_info(
 /// [`Event::PaymentClaimable`]: crate::events::Event::PaymentClaimable
 pub fn peel_payment_onion<NS: Deref, L: Deref, T: secp256k1::Verification>(
        msg: &msgs::UpdateAddHTLC, node_signer: &NS, logger: &L, secp_ctx: &Secp256k1<T>,
-       cur_height: u32, accept_mpp_keysend: bool,
+       cur_height: u32, accept_mpp_keysend: bool, allow_skimmed_fees: bool,
 ) -> Result<PendingHTLCInfo, InboundOnionErr>
 where
        NS::Target: NodeSigner,
@@ -273,6 +276,10 @@ where
                                        err_data: Vec::new(),
                                });
                        }
+
+                       // TODO: If this is potentially a phantom payment we should decode the phantom payment
+                       // onion here and check it.
+
                        create_fwd_pending_htlc_info(
                                msg, next_hop_data, next_hop_hmac, new_packet_bytes, shared_secret,
                                Some(next_packet_pubkey)
@@ -281,7 +288,7 @@ where
                onion_utils::Hop::Receive(received_data) => {
                        create_recv_pending_htlc_info(
                                received_data, shared_secret, msg.payment_hash, msg.amount_msat, msg.cltv_expiry,
-                               None, false, msg.skimmed_fee_msat, cur_height, accept_mpp_keysend,
+                               None, allow_skimmed_fees, msg.skimmed_fee_msat, cur_height, accept_mpp_keysend,
                        )?
                }
        })
@@ -477,7 +484,7 @@ mod tests {
                let msg = make_update_add_msg(amount_msat, cltv_expiry, payment_hash, onion);
                let logger = test_utils::TestLogger::with_id("bob".to_string());
 
-               let peeled = peel_payment_onion(&msg, &&bob, &&logger, &secp_ctx, cur_height, true)
+               let peeled = peel_payment_onion(&msg, &&bob, &&logger, &secp_ctx, cur_height, true, false)
                        .map_err(|e| e.msg).unwrap();
 
                let next_onion = match peeled.routing {
@@ -488,7 +495,7 @@ mod tests {
                };
 
                let msg2 = make_update_add_msg(amount_msat, cltv_expiry, payment_hash, next_onion);
-               let peeled2 = peel_payment_onion(&msg2, &&charlie, &&logger, &secp_ctx, cur_height, true)
+               let peeled2 = peel_payment_onion(&msg2, &&charlie, &&logger, &secp_ctx, cur_height, true, false)
                        .map_err(|e| e.msg).unwrap();
 
                match peeled2.routing {