Make Channel::commit_tx_fee_msat static and take fee explicitly

[rust-lightning] / lightning / src / chain / keysinterface.rs

diff --git a/lightning/src/chain/keysinterface.rs b/lightning/src/chain/keysinterface.rs
index 2da9e575047f68ec805fe0089642cdd90169ce92..b36694eb126cded8b5048dd1a2f28461eb5c25f6 100644 (file)
--- a/lightning/src/chain/keysinterface.rs
+++ b/lightning/src/chain/keysinterface.rs
@@ -960,7 +960,8 @@ impl KeysManager {
                        input,
                        output: outputs,
                };
-               transaction_utils::maybe_add_change_output(&mut spend_tx, input_value, witness_weight, feerate_sat_per_1000_weight, change_destination_script)?;
+               let expected_max_weight =
+                       transaction_utils::maybe_add_change_output(&mut spend_tx, input_value, witness_weight, feerate_sat_per_1000_weight, change_destination_script)?;
 
                let mut keys_cache: Option<(InMemorySigner, [u8; 32])> = None;
                let mut input_idx = 0;
@@ -1014,6 +1015,12 @@ impl KeysManager {
                        }
                        input_idx += 1;
                }
+
+               debug_assert!(expected_max_weight >= spend_tx.get_weight());
+               // Note that witnesses with a signature vary somewhat in size, so allow
+               // `expected_max_weight` to overshoot by up to 3 bytes per input.
+               debug_assert!(expected_max_weight <= spend_tx.get_weight() + descriptors.len() * 3);
+
                Ok(spend_tx)
        }
 }