Rename `starting_htlc_offset` `cur_block_height` in onion building
What the developer wrote
Authored by Matt Corallo
Rename `starting_htlc_offset` `cur_block_height` in onion building
Now that we are consistently using the
`RouteHop::cltv_expiry_delta` as the last hop's starting CLTV
rather than summing trampoline hops, `starting_htlc_offset` is a
bit confusing - its actually always the current block height. Thus,
here we rename it.
What changed, and why it matters
This commit is a simple variable rename in the code that builds Lightning payment onion payloads. The old name `starting_htlc_offset` was misleading because the value is actually the current block height, so it was renamed to `cur_block_height`. No behavior changed.
No action needed; this is a cosmetic rename with no security or functional impact.
Security signals we found
No strong security signals were identified.
Evidence from the diff
The patch renames the parameter starting_htlc_offset to cur_block_height in build_trampoline_onion_payloads, test_build_onion_payloads, build_onion_payloads, and build_onion_payloads_callback in lightning/src/ln/onion_utils.rs. All call sites and internal uses are updated consistently. The logic remains identical: cur_cltv is still initialized from this value, and the final blinded receive CLTV is still computed as the same value plus excess_final_cltv_expiry_delta. This is a non-functional refactor.
Changed components
lightning/src/ln/onion_utils.rsInspect captured patch +9 / −9
diff --git a/lightning/src/ln/onion_utils.rs b/lightning/src/ln/onion_utils.rs
index 099690e..9b1b009 100644
--- a/lightning/src/ln/onion_utils.rs
+++ b/lightning/src/ln/onion_utils.rs
@@ -415,7 +415,7 @@ pub(super) fn construct_trampoline_onion_keys<T: secp256k1::Signing>(
pub(super) fn build_trampoline_onion_payloads<'a>(
blinded_tail: &'a BlindedTail, recipient_onion: &'a RecipientOnionFields,
- starting_htlc_offset: u32, keysend_preimage: &Option<PaymentPreimage>,
+ cur_block_height: u32, keysend_preimage: &Option<PaymentPreimage>,
) -> Result<(Vec<msgs::OutboundTrampolinePayload<'a>>, u64), APIError> {
let mut res: Vec<msgs::OutboundTrampolinePayload> =
Vec::with_capacity(blinded_tail.trampoline_hops.len() + blinded_tail.hops.len());
@@ -430,7 +430,7 @@ pub(super) fn build_trampoline_onion_payloads<'a>(
blinded_tail.trampoline_hops.iter(),
Some(blinded_tail_with_hop_iter),
recipient_onion,
- starting_htlc_offset,
+ cur_block_height,
keysend_preimage,
None,
|action, payload| match action {
@@ -444,14 +444,14 @@ pub(super) fn build_trampoline_onion_payloads<'a>(
/// returns the hop data, as well as the first-hop value_msat and CLTV value we should send.
#[cfg(any(test, feature = "_externalize_tests"))]
pub(crate) fn test_build_onion_payloads<'a>(
- path: &'a Path, recipient_onion: &'a RecipientOnionFields, starting_htlc_offset: u32,
+ path: &'a Path, recipient_onion: &'a RecipientOnionFields, cur_block_height: u32,
keysend_preimage: &Option<PaymentPreimage>, invoice_request: Option<&'a InvoiceRequest>,
trampoline_packet: Option<msgs::TrampolineOnionPacket>,
) -> Result<(Vec<msgs::OutboundOnionPayload<'a>>, u64, u32), APIError> {
build_onion_payloads(
path,
recipient_onion,
- starting_htlc_offset,
+ cur_block_height,
keysend_preimage,
invoice_request,
trampoline_packet,
@@ -460,7 +460,7 @@ pub(crate) fn test_build_onion_payloads<'a>(
/// returns the hop data, as well as the first-hop value_msat and CLTV value we should send.
fn build_onion_payloads<'a>(
- path: &'a Path, recipient_onion: &'a RecipientOnionFields, starting_htlc_offset: u32,
+ path: &'a Path, recipient_onion: &'a RecipientOnionFields, cur_block_height: u32,
keysend_preimage: &Option<PaymentPreimage>, invoice_request: Option<&'a InvoiceRequest>,
trampoline_packet: Option<msgs::TrampolineOnionPacket>,
) -> Result<(Vec<msgs::OutboundOnionPayload<'a>>, u64, u32), APIError> {
@@ -490,7 +490,7 @@ fn build_onion_payloads<'a>(
path.hops.iter(),
blinded_tail_with_hop_iter,
recipient_onion,
- starting_htlc_offset,
+ cur_block_height,
keysend_preimage,
invoice_request,
|action, payload| match action {
@@ -520,7 +520,7 @@ enum PayloadCallbackAction {
}
fn build_onion_payloads_callback<'a, 'b, H, B, F, OP>(
hops: H, mut blinded_tail: Option<BlindedTailDetails<'a, B>>,
- recipient_onion: &'a RecipientOnionFields, starting_htlc_offset: u32,
+ recipient_onion: &'a RecipientOnionFields, cur_block_height: u32,
keysend_preimage: &Option<PaymentPreimage>, invoice_request: Option<&'a InvoiceRequest>,
mut callback: F,
) -> Result<(u64, u32), APIError>
@@ -531,7 +531,7 @@ where
OP: OnionPayload<'a, 'b, ReceiveType = OP>,
{
let mut cur_value_msat = 0u64;
- let mut cur_cltv = starting_htlc_offset;
+ let mut cur_cltv = cur_block_height;
let mut last_hop_id = None;
for (idx, hop) in hops.rev().enumerate() {
@@ -559,7 +559,7 @@ where
OP::new_blinded_receive(
final_value_msat,
recipient_onion.total_mpp_amount_msat,
- starting_htlc_offset + excess_final_cltv_expiry_delta,
+ cur_block_height + excess_final_cltv_expiry_delta,
&blinded_hop.encrypted_payload,
blinding_point.take(),
*keysend_preimage,
Why this scored 15/100
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