-//! Lightning exposes sets of supported operations through "feature flags". This module includes
-//! types to store those feature flags and query for specific flags.
+//! Feature flag definitions for the Lightning protocol according to [BOLT #9].
+//!
+//! Lightning nodes advertise a supported set of operation through feature flags. Features are
+//! applicable for a specific context as indicated in some [messages]. [`Features`] encapsulates
+//! behavior for specifying and checking feature flags for a particular context. Each feature is
+//! defined internally by a trait specifying the corresponding flags (i.e., even and odd bits). A
+//! [`Context`] is used to parameterize [`Features`] and defines which features it can support.
+//!
+//! Whether a feature is considered "known" or "unknown" is relative to the implementation, whereas
+//! the term "supports" is used in reference to a particular set of [`Features`]. That is, a node
+//! supports a feature if it advertises the feature (as either required or optional) to its peers.
+//! And the implementation can interpret a feature if the feature is known to it.
+//!
+//! [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
+//! [messages]: ../msgs/index.html
+//! [`Features`]: struct.Features.html
+//! [`Context`]: sealed/trait.Context.html
use std::{cmp, fmt};
use std::result::Result;
use ln::msgs::DecodeError;
use util::ser::{Readable, Writeable, Writer};
-#[macro_use]
-mod sealed { // You should just use the type aliases instead.
- pub struct InitContext {}
- pub struct NodeContext {}
- pub struct ChannelContext {}
+mod sealed {
+ /// The context in which [`Features`] are applicable. Defines which features are required and
+ /// which are optional for the context.
+ ///
+ /// [`Features`]: ../struct.Features.html
+ pub trait Context {
+ /// Features that are known to the implementation, where a required feature is indicated by
+ /// its even bit and an optional feature is indicated by its odd bit.
+ const KNOWN_FEATURE_FLAGS: &'static [u8];
- /// An internal trait capturing the various feature context types
- pub trait Context {}
- impl Context for InitContext {}
- impl Context for NodeContext {}
- impl Context for ChannelContext {}
+ /// Bitmask for selecting features that are known to the implementation, regardless of
+ /// whether each feature is required or optional.
+ const KNOWN_FEATURE_MASK: &'static [u8];
+ }
+
+ /// Defines a [`Context`] by stating which features it requires and which are optional. Features
+ /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
+ /// feature identifiers.
+ ///
+ /// [`Context`]: trait.Context.html
+ macro_rules! define_context {
+ ($context: ident {
+ required_features: [$( $( $required_feature: ident )|*, )*],
+ optional_features: [$( $( $optional_feature: ident )|*, )*],
+ }) => {
+ pub struct $context {}
+
+ impl Context for $context {
+ const KNOWN_FEATURE_FLAGS: &'static [u8] = &[
+ // For each byte, use bitwise-OR to compute the applicable flags for known
+ // required features `r_i` and optional features `o_j` for all `i` and `j` such
+ // that the following slice is formed:
+ //
+ // [
+ // `r_0` | `r_1` | ... | `o_0` | `o_1` | ...,
+ // ...,
+ // ]
+ $(
+ 0b00_00_00_00 $(|
+ <Self as $required_feature>::REQUIRED_MASK)*
+ $(|
+ <Self as $optional_feature>::OPTIONAL_MASK)*,
+ )*
+ ];
+
+ const KNOWN_FEATURE_MASK: &'static [u8] = &[
+ // Similar as above, but set both flags for each feature regardless of whether
+ // the feature is required or optional.
+ $(
+ 0b00_00_00_00 $(|
+ <Self as $required_feature>::REQUIRED_MASK |
+ <Self as $required_feature>::OPTIONAL_MASK)*
+ $(|
+ <Self as $optional_feature>::REQUIRED_MASK |
+ <Self as $optional_feature>::OPTIONAL_MASK)*,
+ )*
+ ];
+ }
+ };
+ }
+
+ define_context!(InitContext {
+ required_features: [
+ // Byte 0
+ ,
+ // Byte 1
+ ,
+ // Byte 2
+ ,
+ ],
+ optional_features: [
+ // Byte 0
+ DataLossProtect | InitialRoutingSync | UpfrontShutdownScript,
+ // Byte 1
+ VariableLengthOnion | PaymentSecret,
+ // Byte 2
+ BasicMPP,
+ ],
+ });
+ define_context!(NodeContext {
+ required_features: [
+ // Byte 0
+ ,
+ // Byte 1
+ ,
+ // Byte 2
+ ,
+ ],
+ optional_features: [
+ // Byte 0
+ DataLossProtect | UpfrontShutdownScript,
+ // Byte 1
+ VariableLengthOnion | PaymentSecret,
+ // Byte 2
+ BasicMPP,
+ ],
+ });
+ define_context!(ChannelContext {
+ required_features: [],
+ optional_features: [],
+ });
/// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
/// useful for manipulating feature flags.
flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
}
- /// Clears the feature's optional (odd) bit from the given flags.
+ /// Clears the feature's required (even) and optional (odd) bits from the given
+ /// flags.
#[inline]
- fn clear_optional_bit(flags: &mut Vec<u8>) {
+ fn clear_bits(flags: &mut Vec<u8>) {
if flags.len() > Self::BYTE_OFFSET {
+ flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
}
}
"Feature flags for `payment_secret`.");
define_feature!(17, BasicMPP, [InitContext, NodeContext],
"Feature flags for `basic_mpp`.");
-
- /// Generates a feature flag byte with the given features set as optional. Useful for initializing
- /// the flags within [`Features`].
- ///
- /// [`Features`]: struct.Features.html
- macro_rules! feature_flags {
- ($context: ty; $($feature: ident)|*) => {
- (0b00_00_00_00
- $(
- | <$context as sealed::$feature>::OPTIONAL_MASK
- )*
- )
- }
- }
}
/// Tracks the set of features which a node implements, templated by the context in which it
/// appears.
pub struct Features<T: sealed::Context> {
- /// Note that, for convinience, flags is LITTLE endian (despite being big-endian on the wire)
+ /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
flags: Vec<u8>,
mark: PhantomData<T>,
}
}
}
-/// A feature message as it appears in an init message
+/// Features used within an `init` message.
pub type InitFeatures = Features<sealed::InitContext>;
-/// A feature message as it appears in a node_announcement message
+/// Features used within a `node_announcement` message.
pub type NodeFeatures = Features<sealed::NodeContext>;
-/// A feature message as it appears in a channel_announcement message
+/// Features used within a `channel_announcement` message.
pub type ChannelFeatures = Features<sealed::ChannelContext>;
impl InitFeatures {
- /// Create a Features with the features we support
- pub fn supported() -> InitFeatures {
- InitFeatures {
- flags: vec![
- feature_flags![sealed::InitContext; DataLossProtect | InitialRoutingSync | UpfrontShutdownScript],
- feature_flags![sealed::InitContext; VariableLengthOnion | PaymentSecret],
- feature_flags![sealed::InitContext; BasicMPP],
- ],
- mark: PhantomData,
- }
- }
-
/// Writes all features present up to, and including, 13.
pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
let len = cmp::min(2, self.flags.len());
}
self
}
-}
-
-impl ChannelFeatures {
- /// Create a Features with the features we support
- #[cfg(not(feature = "fuzztarget"))]
- pub(crate) fn supported() -> ChannelFeatures {
- ChannelFeatures {
- flags: Vec::new(),
- mark: PhantomData,
- }
- }
- #[cfg(feature = "fuzztarget")]
- pub fn supported() -> ChannelFeatures {
- ChannelFeatures {
- flags: Vec::new(),
- mark: PhantomData,
- }
- }
- /// Takes the flags that we know how to interpret in an init-context features that are also
- /// relevant in a channel-context features and creates a channel-context features from them.
- pub(crate) fn with_known_relevant_init_flags(_init_ctx: &InitFeatures) -> Self {
- // There are currently no channel flags defined that we understand.
- Self { flags: Vec::new(), mark: PhantomData, }
+ /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
+ /// are included in the result.
+ pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
+ self.to_context_internal()
}
}
-impl NodeFeatures {
- /// Create a Features with the features we support
- #[cfg(not(feature = "fuzztarget"))]
- pub(crate) fn supported() -> NodeFeatures {
- NodeFeatures {
- flags: vec![
- feature_flags![sealed::NodeContext; DataLossProtect | UpfrontShutdownScript],
- feature_flags![sealed::NodeContext; VariableLengthOnion | PaymentSecret],
- feature_flags![sealed::NodeContext; BasicMPP],
- ],
+impl<T: sealed::Context> Features<T> {
+ /// Create a blank Features with no features set
+ pub fn empty() -> Features<T> {
+ Features {
+ flags: Vec::new(),
mark: PhantomData,
}
}
- #[cfg(feature = "fuzztarget")]
- pub fn supported() -> NodeFeatures {
- NodeFeatures {
- flags: vec![
- feature_flags![sealed::NodeContext; DataLossProtect | UpfrontShutdownScript],
- feature_flags![sealed::NodeContext; VariableLengthOnion | PaymentSecret],
- feature_flags![sealed::NodeContext; BasicMPP],
- ],
+
+ /// Creates features known by the implementation as defined by [`T::KNOWN_FEATURE_FLAGS`].
+ ///
+ /// [`T::KNOWN_FEATURE_FLAGS`]: sealed/trait.Context.html#associatedconstant.KNOWN_FEATURE_FLAGS
+ pub fn known() -> Features<T> {
+ Self {
+ flags: T::KNOWN_FEATURE_FLAGS.to_vec(),
mark: PhantomData,
}
}
- /// Takes the flags that we know how to interpret in an init-context features that are also
- /// relevant in a node-context features and creates a node-context features from them.
- /// Be sure to blank out features that are unknown to us.
- pub(crate) fn with_known_relevant_init_flags(init_ctx: &InitFeatures) -> Self {
- // Generates a bitmask with both even and odd bits set for the given features. Bitwise
- // AND-ing it with a byte will select only common features.
- macro_rules! features_including {
- ($($feature: ident)|*) => {
- (0b00_00_00_00
- $(
- | <sealed::NodeContext as sealed::$feature>::REQUIRED_MASK
- | <sealed::NodeContext as sealed::$feature>::OPTIONAL_MASK
- )*
- )
- }
- }
-
+ /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
+ /// included in the result.
+ fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
+ let byte_count = C::KNOWN_FEATURE_MASK.len();
let mut flags = Vec::new();
- for (i, feature_byte)in init_ctx.flags.iter().enumerate() {
- match i {
- 0 => flags.push(feature_byte & features_including![DataLossProtect | UpfrontShutdownScript]),
- 1 => flags.push(feature_byte & features_including![VariableLengthOnion | PaymentSecret]),
- 2 => flags.push(feature_byte & features_including![BasicMPP]),
- _ => (),
+ for (i, byte) in self.flags.iter().enumerate() {
+ if i < byte_count {
+ let known_source_features = T::KNOWN_FEATURE_MASK[i];
+ let known_target_features = C::KNOWN_FEATURE_MASK[i];
+ flags.push(byte & known_source_features & known_target_features);
}
}
- Self { flags, mark: PhantomData, }
- }
-}
-
-impl<T: sealed::Context> Features<T> {
- /// Create a blank Features with no features set
- pub fn empty() -> Features<T> {
- Features {
- flags: Vec::new(),
- mark: PhantomData,
- }
+ Features::<C> { flags, mark: PhantomData, }
}
#[cfg(test)]
}
pub(crate) fn requires_unknown_bits(&self) -> bool {
- // Generates a bitmask with all even bits set except for the given features. Bitwise
- // AND-ing it with a byte will select unknown required features.
- macro_rules! features_excluding {
- ($($feature: ident)|*) => {
- (0b01_01_01_01
- $(
- & !(<sealed::InitContext as sealed::$feature>::REQUIRED_MASK)
- )*
- )
- }
- }
-
- self.flags.iter().enumerate().any(|(idx, &byte)| {
- (match idx {
- 0 => (byte & features_excluding![DataLossProtect | InitialRoutingSync | UpfrontShutdownScript]),
- 1 => (byte & features_excluding![VariableLengthOnion | PaymentSecret]),
- 2 => (byte & features_excluding![BasicMPP]),
- _ => (byte & features_excluding![]),
- }) != 0
+ // Bitwise AND-ing with all even bits set except for known features will select required
+ // unknown features.
+ let byte_count = T::KNOWN_FEATURE_MASK.len();
+ self.flags.iter().enumerate().any(|(i, &byte)| {
+ let required_features = 0b01_01_01_01;
+ let unknown_features = if i < byte_count {
+ !T::KNOWN_FEATURE_MASK[i]
+ } else {
+ 0b11_11_11_11
+ };
+ (byte & (required_features & unknown_features)) != 0
})
}
pub(crate) fn supports_unknown_bits(&self) -> bool {
- // Generates a bitmask with all even and odd bits set except for the given features. Bitwise
- // AND-ing it with a byte will select unknown supported features.
- macro_rules! features_excluding {
- ($($feature: ident)|*) => {
- (0b11_11_11_11
- $(
- & !(<sealed::InitContext as sealed::$feature>::REQUIRED_MASK)
- & !(<sealed::InitContext as sealed::$feature>::OPTIONAL_MASK)
- )*
- )
- }
- }
-
- self.flags.iter().enumerate().any(|(idx, &byte)| {
- (match idx {
- 0 => (byte & features_excluding![DataLossProtect | InitialRoutingSync | UpfrontShutdownScript]),
- 1 => (byte & features_excluding![VariableLengthOnion | PaymentSecret]),
- 2 => (byte & features_excluding![BasicMPP]),
- _ => byte,
- }) != 0
+ // Bitwise AND-ing with all even and odd bits set except for known features will select
+ // both required and optional unknown features.
+ let byte_count = T::KNOWN_FEATURE_MASK.len();
+ self.flags.iter().enumerate().any(|(i, &byte)| {
+ let unknown_features = if i < byte_count {
+ !T::KNOWN_FEATURE_MASK[i]
+ } else {
+ 0b11_11_11_11
+ };
+ (byte & unknown_features) != 0
})
}
<T as sealed::UpfrontShutdownScript>::supports_feature(&self.flags)
}
#[cfg(test)]
- pub(crate) fn unset_upfront_shutdown_script(&mut self) {
- <T as sealed::UpfrontShutdownScript>::clear_optional_bit(&mut self.flags)
+ pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
+ <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
+ self
}
}
<T as sealed::InitialRoutingSync>::supports_feature(&self.flags)
}
pub(crate) fn clear_initial_routing_sync(&mut self) {
- <T as sealed::InitialRoutingSync>::clear_optional_bit(&mut self.flags)
+ <T as sealed::InitialRoutingSync>::clear_bits(&mut self.flags)
}
}
#[cfg(test)]
mod tests {
- use super::{ChannelFeatures, InitFeatures, NodeFeatures, Features};
+ use super::{ChannelFeatures, InitFeatures, NodeFeatures};
#[test]
fn sanity_test_our_features() {
- assert!(!ChannelFeatures::supported().requires_unknown_bits());
- assert!(!ChannelFeatures::supported().supports_unknown_bits());
- assert!(!InitFeatures::supported().requires_unknown_bits());
- assert!(!InitFeatures::supported().supports_unknown_bits());
- assert!(!NodeFeatures::supported().requires_unknown_bits());
- assert!(!NodeFeatures::supported().supports_unknown_bits());
+ assert!(!ChannelFeatures::known().requires_unknown_bits());
+ assert!(!ChannelFeatures::known().supports_unknown_bits());
+ assert!(!InitFeatures::known().requires_unknown_bits());
+ assert!(!InitFeatures::known().supports_unknown_bits());
+ assert!(!NodeFeatures::known().requires_unknown_bits());
+ assert!(!NodeFeatures::known().supports_unknown_bits());
- assert!(InitFeatures::supported().supports_upfront_shutdown_script());
- assert!(NodeFeatures::supported().supports_upfront_shutdown_script());
+ assert!(InitFeatures::known().supports_upfront_shutdown_script());
+ assert!(NodeFeatures::known().supports_upfront_shutdown_script());
- assert!(InitFeatures::supported().supports_data_loss_protect());
- assert!(NodeFeatures::supported().supports_data_loss_protect());
+ assert!(InitFeatures::known().supports_data_loss_protect());
+ assert!(NodeFeatures::known().supports_data_loss_protect());
- assert!(InitFeatures::supported().supports_variable_length_onion());
- assert!(NodeFeatures::supported().supports_variable_length_onion());
+ assert!(InitFeatures::known().supports_variable_length_onion());
+ assert!(NodeFeatures::known().supports_variable_length_onion());
- assert!(InitFeatures::supported().supports_payment_secret());
- assert!(NodeFeatures::supported().supports_payment_secret());
+ assert!(InitFeatures::known().supports_payment_secret());
+ assert!(NodeFeatures::known().supports_payment_secret());
- assert!(InitFeatures::supported().supports_basic_mpp());
- assert!(NodeFeatures::supported().supports_basic_mpp());
+ assert!(InitFeatures::known().supports_basic_mpp());
+ assert!(NodeFeatures::known().supports_basic_mpp());
- let mut init_features = InitFeatures::supported();
+ let mut init_features = InitFeatures::known();
assert!(init_features.initial_routing_sync());
init_features.clear_initial_routing_sync();
assert!(!init_features.initial_routing_sync());
#[test]
fn sanity_test_unkown_bits_testing() {
- let mut features = ChannelFeatures::supported();
+ let mut features = ChannelFeatures::known();
features.set_require_unknown_bits();
assert!(features.requires_unknown_bits());
features.clear_require_unknown_bits();
}
#[test]
- fn test_node_with_known_relevant_init_flags() {
- // Create an InitFeatures with initial_routing_sync supported.
- let init_features = InitFeatures::supported();
+ fn convert_to_context_with_relevant_flags() {
+ let init_features = InitFeatures::known().clear_upfront_shutdown_script();
assert!(init_features.initial_routing_sync());
+ assert!(!init_features.supports_upfront_shutdown_script());
- // Attempt to pull out non-node-context feature flags from these InitFeatures.
- let res = NodeFeatures::with_known_relevant_init_flags(&init_features);
-
+ let node_features: NodeFeatures = init_features.to_context();
{
- // Check that the flags are as expected: optional_data_loss_protect,
- // option_upfront_shutdown_script, var_onion_optin, payment_secret, and
- // basic_mpp.
- assert_eq!(res.flags.len(), 3);
- assert_eq!(res.flags[0], 0b00100010);
- assert_eq!(res.flags[1], 0b10000010);
- assert_eq!(res.flags[2], 0b00000010);
+ // Check that the flags are as expected:
+ // - option_data_loss_protect
+ // - var_onion_optin | payment_secret
+ // - basic_mpp
+ assert_eq!(node_features.flags.len(), 3);
+ assert_eq!(node_features.flags[0], 0b00000010);
+ assert_eq!(node_features.flags[1], 0b10000010);
+ assert_eq!(node_features.flags[2], 0b00000010);
}
- // Check that the initial_routing_sync feature was correctly blanked out.
- let new_features: InitFeatures = Features::from_le_bytes(res.flags);
- assert!(!new_features.initial_routing_sync());
+ // Check that cleared flags are kept blank when converting back:
+ // - initial_routing_sync was not applicable to NodeContext
+ // - upfront_shutdown_script was cleared before converting
+ let features: InitFeatures = node_features.to_context_internal();
+ assert!(!features.initial_routing_sync());
+ assert!(!features.supports_upfront_shutdown_script());
}
}
projects / rust-lightning / blobdiff