From 82ddc2e2e659c03a0c66148cc87d87f4411569c1 Mon Sep 17 00:00:00 2001
From: Justin Moeller <jumoell@protonmail.com>
Date: Thu, 7 Nov 2024 17:13:03 -0600
Subject: [PATCH] fix: LNv1 add min_cltv_delta to timelock constant

---
 devimint/src/external.rs              | 11 ++++++++++-
 modules/fedimint-ln-client/src/lib.rs |  7 ++++++-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/devimint/src/external.rs b/devimint/src/external.rs
index 00fc955fef0..984c0e3cead 100644
--- a/devimint/src/external.rs
+++ b/devimint/src/external.rs
@@ -36,7 +36,7 @@ use crate::util::{
     poll, poll_with_timeout, ClnLightningCli, GatewayClnExtension, ProcessHandle, ProcessManager,
 };
 use crate::vars::utf8;
-use crate::version_constants::VERSION_0_4_0_ALPHA;
+use crate::version_constants::{VERSION_0_4_0_ALPHA, VERSION_0_5_0_ALPHA};
 use crate::{cmd, poll_eq, Gatewayd};
 
 #[derive(Clone)]
@@ -776,12 +776,21 @@ impl Lnd {
             bitcoin::hashes::HashEngine::input(&mut engine, &preimage);
             bitcoin::hashes::sha256::Hash::from_engine(engine)
         };
+        // TODO(support:v0.5): LNv1 cannot pay HOLD invoices with a CLTV expiry greater
+        // than 500 before v0.5
+        let fedimint_cli_version = crate::util::FedimintCli::version_or_default().await;
+        let cltv_expiry = if fedimint_cli_version >= *VERSION_0_5_0_ALPHA {
+            650
+        } else {
+            100
+        };
         let hold_request = self
             .invoices_client_lock()
             .await?
             .add_hold_invoice(tonic_lnd::invoicesrpc::AddHoldInvoiceRequest {
                 value_msat: amount as i64,
                 hash: hash.to_byte_array().to_vec(),
+                cltv_expiry,
                 ..Default::default()
             })
             .await?
diff --git a/modules/fedimint-ln-client/src/lib.rs b/modules/fedimint-ln-client/src/lib.rs
index 173c832603f..9f4e9681a69 100644
--- a/modules/fedimint-ln-client/src/lib.rs
+++ b/modules/fedimint-ln-client/src/lib.rs
@@ -711,7 +711,12 @@ impl LightningClientModule {
             .fetch_consensus_block_count()
             .await?
             .ok_or(format_err!("Cannot get consensus block count"))?;
-        let absolute_timelock = consensus_count + OUTGOING_LN_CONTRACT_TIMELOCK - 1;
+
+        // Add the timelock to the current block count and the invoice's
+        // `min_cltv_delta`
+        let min_final_cltv = invoice.min_final_cltv_expiry_delta();
+        let absolute_timelock =
+            consensus_count + min_final_cltv + OUTGOING_LN_CONTRACT_TIMELOCK - 1;
 
         // Compute amount to lock in the outgoing contract
         let invoice_amount = Amount::from_msats(