What the developer wrote
Authored by Jeffrey Czyz
Add features for splicing
While splicing is not yet fully supported, checking if the feature has
been negotiated is needed for changes to the channel_reestablish logic.
What changed, and why it matters
This commit adds support for advertising a new Lightning protocol feature called 'Splicing' in the feature-bit flags that nodes exchange when connecting. It does not implement splicing itself and does not change any security-sensitive logic. It is a routine protocol-compatibility change.
No security action required. Review the follow-up `channel_reestablish` changes when they land, as the commit message flags that as the place where splicing negotiation will actually be used.
Security signals we found
No strong security signals were identified.
Evidence from the diff
The patch registers the Splice feature bit (bit 63) in LDK’s feature flags module, adding it to InitContext and NodeContext, exposing the usual optional/required getter/setter helpers, and updating the default feature allocation size and tests accordingly. The commit message explicitly states splicing is not yet fully supported and this is groundwork for later channel_reestablish changes.
Changed components
lightning-types/src/features.rsInspect captured patch +20 / −6
diff --git a/lightning-types/src/features.rs b/lightning-types/src/features.rs
index aca4bb6..148242e 100644
--- a/lightning-types/src/features.rs
+++ b/lightning-types/src/features.rs
@@ -80,6 +80,8 @@
//! (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#channel-quiescence) for more information).
//! - `ZeroFeeCommitments` - A channel type which always uses zero transaction fee on commitment transactions.
//! (see [BOLT PR #1228](https://github.com/lightning/bolts/pull/1228) for more info).
+//! - `Splice` - Allows replacing the currently-locked funding transaction with a new one
+//! (see [BOLT PR #1160](https://github.com/lightning/bolts/pull/1160) for more information).
//!
//! LDK knows about the following features, but does not support them:
//! - `AnchorsNonzeroFeeHtlcTx` - the initial version of anchor outputs, which was later found to be
@@ -163,7 +165,7 @@ mod sealed {
// Byte 6
ZeroConf,
// Byte 7
- Trampoline | SimpleClose,
+ Trampoline | SimpleClose | Splice,
]
);
define_context!(
@@ -184,7 +186,7 @@ mod sealed {
// Byte 6
ZeroConf | Keysend,
// Byte 7
- Trampoline | SimpleClose,
+ Trampoline | SimpleClose | Splice,
// Byte 8 - 31
,,,,,,,,,,,,,,,,,,,,,,,,
// Byte 32
@@ -673,9 +675,20 @@ mod sealed {
supports_simple_close,
requires_simple_close
);
- // By default, allocate enough bytes to cover up to SimpleClose. Update this as new features are
+ define_feature!(
+ 63,
+ Splice,
+ [InitContext, NodeContext],
+ "Feature flags for channel splicing.",
+ set_splicing_optional,
+ set_splicing_required,
+ clear_splicing,
+ supports_splicing,
+ requires_splicing
+ );
+ // By default, allocate enough bytes to cover up to Splice. Update this as new features are
// added which we expect to appear commonly across contexts.
- pub(super) const MIN_FEATURES_ALLOCATION_BYTES: usize = (61 + 7) / 8;
+ pub(super) const MIN_FEATURES_ALLOCATION_BYTES: usize = (63 + 7) / 8;
define_feature!(
259,
DnsResolver,
@@ -1369,6 +1382,7 @@ mod tests {
init_features.set_zero_conf_optional();
init_features.set_quiescence_optional();
init_features.set_simple_close_optional();
+ init_features.set_splicing_optional();
assert!(init_features.initial_routing_sync());
assert!(!init_features.supports_upfront_shutdown_script());
@@ -1384,7 +1398,7 @@ mod tests {
// - onion_messages
// - option_channel_type | option_scid_alias
// - option_zeroconf
- // - option_simple_close
+ // - option_simple_close | option_splice
assert_eq!(node_features.flags.len(), 8);
assert_eq!(node_features.flags[0], 0b00000001);
assert_eq!(node_features.flags[1], 0b01010001);
@@ -1393,7 +1407,7 @@ mod tests {
assert_eq!(node_features.flags[4], 0b10001000);
assert_eq!(node_features.flags[5], 0b10100000);
assert_eq!(node_features.flags[6], 0b00001000);
- assert_eq!(node_features.flags[7], 0b00100000);
+ assert_eq!(node_features.flags[7], 0b10100000);
}
// Check that cleared flags are kept blank when converting back:
Why this scored 18/100
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