Generalize with_known_relevant_init_flags
[rust-lightning] / lightning / src / ln / features.rs
index 5eb1bd909e80585408f6ce24853502e696cbc25f..381297703e882a08cce4577e01d5bd3f7a9a87af 100644 (file)
@@ -1,5 +1,20 @@
-//! 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;
@@ -8,45 +23,208 @@ use std::marker::PhantomData;
 use ln::msgs::DecodeError;
 use util::ser::{Readable, Writeable, Writer};
 
-mod sealed { // You should just use the type aliases instead.
-       pub struct InitContext {}
-       pub struct NodeContext {}
-       pub struct ChannelContext {}
-
-       /// An internal trait capturing the various feature context types
-       pub trait Context {}
-       impl Context for InitContext {}
-       impl Context for NodeContext {}
-       impl Context for ChannelContext {}
-
-       pub trait DataLossProtect: Context {}
-       impl DataLossProtect for InitContext {}
-       impl DataLossProtect for NodeContext {}
-
-       pub trait InitialRoutingSync: Context {}
-       impl InitialRoutingSync for InitContext {}
-
-       pub trait UpfrontShutdownScript: Context {}
-       impl UpfrontShutdownScript for InitContext {}
-       impl UpfrontShutdownScript for NodeContext {}
+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];
+
+               /// 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 $optional_feature>::OPTIONAL_MASK)*,
+                                       )*
+                               ];
+                       }
+               };
+       }
+
+       define_context!(InitContext {
+               required_features: [
+                       // Byte 0
+                       ,
+                       // Byte 1
+                       ,
+                       // Byte 2
+                       ,
+               ],
+               optional_features: [
+                       // Byte 0
+                       DataLossProtect | InitialRoutingSync | UpfrontShutdownScript,
+                       // Byte 1
+                       VariableLengthOnion | PaymentSecret,
+                       // Byte 2
+                       BasicMPP,
+               ],
+       });
+       define_context!(NodeContext {
+               required_features: [
+                       // Byte 0
+                       ,
+                       // Byte 1
+                       ,
+                       // Byte 2
+                       ,
+               ],
+               optional_features: [
+                       // Byte 0
+                       DataLossProtect | UpfrontShutdownScript,
+                       // Byte 1
+                       VariableLengthOnion | PaymentSecret,
+                       // Byte 2
+                       BasicMPP,
+               ],
+       });
+       define_context!(ChannelContext {
+               required_features: [],
+               optional_features: [],
+       });
+
+       /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
+       /// useful for manipulating feature flags.
+       ///
+       /// [`Context`]: trait.Context.html
+       macro_rules! define_feature {
+               ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr) => {
+                       #[doc = $doc]
+                       ///
+                       /// See [BOLT #9] for details.
+                       ///
+                       /// [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
+                       pub trait $feature: Context {
+                               /// The bit used to signify that the feature is required.
+                               const EVEN_BIT: usize = $odd_bit - 1;
+
+                               /// The bit used to signify that the feature is optional.
+                               const ODD_BIT: usize = $odd_bit;
+
+                               /// Assertion that [`EVEN_BIT`] is actually even.
+                               ///
+                               /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
+                               const ASSERT_EVEN_BIT_PARITY: usize;
+
+                               /// Assertion that [`ODD_BIT`] is actually odd.
+                               ///
+                               /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
+                               const ASSERT_ODD_BIT_PARITY: usize;
+
+                               /// The byte where the feature is set.
+                               const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
+
+                               /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
+                               ///
+                               /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
+                               const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
+
+                               /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
+                               ///
+                               /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
+                               const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
+
+                               /// Returns whether the feature is supported by the given flags.
+                               #[inline]
+                               fn supports_feature(flags: &Vec<u8>) -> bool {
+                                       flags.len() > Self::BYTE_OFFSET &&
+                                               (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
+                               }
+
+                               /// Sets the feature's optional (odd) bit in the given flags.
+                               #[inline]
+                               fn set_optional_bit(flags: &mut Vec<u8>) {
+                                       if flags.len() <= Self::BYTE_OFFSET {
+                                               flags.resize(Self::BYTE_OFFSET + 1, 0u8);
+                                       }
+
+                                       flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
+                               }
+
+                               /// Clears the feature's required (even) and optional (odd) bits from the given
+                               /// flags.
+                               #[inline]
+                               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;
+                                       }
+                               }
+                       }
 
-       pub trait VariableLengthOnion: Context {}
-       impl VariableLengthOnion for InitContext {}
-       impl VariableLengthOnion for NodeContext {}
+                       $(
+                               impl $feature for $context {
+                                       // EVEN_BIT % 2 == 0
+                                       const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 
-       pub trait PaymentSecret: Context {}
-       impl PaymentSecret for InitContext {}
-       impl PaymentSecret for NodeContext {}
+                                       // ODD_BIT % 2 == 1
+                                       const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
+                               }
+                       )*
+               }
+       }
 
-       pub trait BasicMPP: Context {}
-       impl BasicMPP for InitContext {}
-       impl BasicMPP for NodeContext {}
+       define_feature!(1, DataLossProtect, [InitContext, NodeContext],
+               "Feature flags for `option_data_loss_protect`.");
+       // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
+       define_feature!(3, InitialRoutingSync, [InitContext],
+               "Feature flags for `initial_routing_sync`.");
+       define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
+               "Feature flags for `option_upfront_shutdown_script`.");
+       define_feature!(9, VariableLengthOnion, [InitContext, NodeContext],
+               "Feature flags for `var_onion_optin`.");
+       define_feature!(15, PaymentSecret, [InitContext, NodeContext],
+               "Feature flags for `payment_secret`.");
+       define_feature!(17, BasicMPP, [InitContext, NodeContext],
+               "Feature flags for `basic_mpp`.");
 }
 
 /// 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>,
 }
@@ -70,22 +248,14 @@ impl<T: sealed::Context> fmt::Debug for Features<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![2 | 1 << 5, 1 << (9-8) | 1 << (15 - 8), 1 << (17 - 8*2)],
-                       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());
@@ -112,77 +282,46 @@ impl InitFeatures {
                }
                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![2 | 1 << 5, 1 << (9 - 8) | 1 << (15 - 8), 1 << (17 - 8*2)],
+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![2 | 1 << 5, 1 << (9 - 8) | 1 << (15 - 8), 1 << (17 - 8*2)],
+
+       /// 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 {
+       /// 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 {
-                               // Blank out initial_routing_sync (feature bits 2/3), gossip_queries (6/7),
-                               // gossip_queries_ex (10/11), option_static_remotekey (12/13), and
-                               // option_support_large_channel (16/17)
-                               0 => flags.push(feature_byte & 0b00110011),
-                               1 => flags.push(feature_byte & 0b11000011),
-                               2 => flags.push(feature_byte & 0b00000011),
-                               _ => (),
+               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)]
@@ -201,35 +340,31 @@ impl<T: sealed::Context> Features<T> {
        }
 
        pub(crate) fn requires_unknown_bits(&self) -> bool {
-               self.flags.iter().enumerate().any(|(idx, &byte)| {
-                       (match idx {
-                               // Unknown bits are even bits which we don't understand, we list ones which we do
-                               // here:
-                               // unknown, upfront_shutdown_script, unknown (actually initial_routing_sync, but it
-                               // is only valid as an optional feature), and data_loss_protect:
-                               0 => (byte & 0b01000100),
-                               // payment_secret, unknown, unknown, var_onion_optin:
-                               1 => (byte & 0b00010100),
-                               // unknown, unknown, unknown, basic_mpp:
-                               2 => (byte & 0b01010100),
-                               // fallback, all even bits set:
-                               _ => (byte & 0b01010101),
-                       }) != 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 {
-               self.flags.iter().enumerate().any(|(idx, &byte)| {
-                       (match idx {
-                               // unknown, upfront_shutdown_script, initial_routing_sync (is only valid as an
-                               // optional feature), and data_loss_protect:
-                               0 => (byte & 0b11000100),
-                               // payment_secret, unknown, unknown, var_onion_optin:
-                               1 => (byte & 0b00111100),
-                               // unknown, unknown, unknown, basic_mpp:
-                               2 => (byte & 0b11111100),
-                               _ => 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
                })
        }
 
@@ -262,36 +397,33 @@ impl<T: sealed::Context> Features<T> {
 
 impl<T: sealed::DataLossProtect> Features<T> {
        pub(crate) fn supports_data_loss_protect(&self) -> bool {
-               self.flags.len() > 0 && (self.flags[0] & 3) != 0
+               <T as sealed::DataLossProtect>::supports_feature(&self.flags)
        }
 }
 
 impl<T: sealed::UpfrontShutdownScript> Features<T> {
        pub(crate) fn supports_upfront_shutdown_script(&self) -> bool {
-               self.flags.len() > 0 && (self.flags[0] & (3 << 4)) != 0
+               <T as sealed::UpfrontShutdownScript>::supports_feature(&self.flags)
        }
        #[cfg(test)]
-       pub(crate) fn unset_upfront_shutdown_script(&mut self) {
-               self.flags[0] ^= 1 << 5;
+       pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
+               <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
+               self
        }
 }
 
 impl<T: sealed::VariableLengthOnion> Features<T> {
        pub(crate) fn supports_variable_length_onion(&self) -> bool {
-               self.flags.len() > 1 && (self.flags[1] & 3) != 0
+               <T as sealed::VariableLengthOnion>::supports_feature(&self.flags)
        }
 }
 
 impl<T: sealed::InitialRoutingSync> Features<T> {
        pub(crate) fn initial_routing_sync(&self) -> bool {
-               self.flags.len() > 0 && (self.flags[0] & (1 << 3)) != 0
+               <T as sealed::InitialRoutingSync>::supports_feature(&self.flags)
        }
-       pub(crate) fn set_initial_routing_sync(&mut self) {
-               if self.flags.len() == 0 {
-                       self.flags.resize(1, 1 << 3);
-               } else {
-                       self.flags[0] |= 1 << 3;
-               }
+       pub(crate) fn clear_initial_routing_sync(&mut self) {
+               <T as sealed::InitialRoutingSync>::clear_bits(&mut self.flags)
        }
 }
 
@@ -301,7 +433,7 @@ impl<T: sealed::PaymentSecret> Features<T> {
        // invoice provides a payment_secret, we assume that we can use it (ie that the recipient
        // supports payment_secret).
        pub(crate) fn supports_payment_secret(&self) -> bool {
-               self.flags.len() > 1 && (self.flags[1] & (3 << (14-8))) != 0
+               <T as sealed::PaymentSecret>::supports_feature(&self.flags)
        }
 }
 
@@ -309,7 +441,7 @@ impl<T: sealed::BasicMPP> Features<T> {
        // We currently never test for this since we don't actually *generate* multipath routes.
        #[allow(dead_code)]
        pub(crate) fn supports_basic_mpp(&self) -> bool {
-               self.flags.len() > 2 && (self.flags[2] & (3 << (16-8*2))) != 0
+               <T as sealed::BasicMPP>::supports_feature(&self.flags)
        }
 }
 
@@ -337,41 +469,41 @@ impl<T: sealed::Context> Readable for Features<T> {
 
 #[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();
-               init_features.set_initial_routing_sync();
-               assert!(!init_features.requires_unknown_bits());
-               assert!(!init_features.supports_unknown_bits());
+               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();
@@ -379,26 +511,28 @@ mod tests {
        }
 
        #[test]
-       fn test_node_with_known_relevant_init_flags() {
-               // Create an InitFeatures with initial_routing_sync supported.
-               let mut init_features = InitFeatures::supported();
-               init_features.set_initial_routing_sync();
-
-               // Attempt to pull out non-node-context feature flags from these InitFeatures.
-               let res = NodeFeatures::with_known_relevant_init_flags(&init_features);
+       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());
 
+               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());
        }
 }