X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Fln%2Ffeatures.rs;h=613d2db14590b5115b9ae6c18461699141dd0c19;hb=b1c6499e1c50fc41c443883dde8e8248106089c3;hp=3440354ec54b6b5ab03bfa69867e61a0771a26e0;hpb=77b467c845792945a0caf19790e4aff883969258;p=rust-lightning diff --git a/lightning/src/ln/features.rs b/lightning/src/ln/features.rs index 3440354e..613d2db1 100644 --- a/lightning/src/ln/features.rs +++ b/lightning/src/ln/features.rs @@ -6,6 +6,11 @@ //! 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 @@ -18,17 +23,107 @@ use std::marker::PhantomData; 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]; + + /// 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]; + } - /// An internal trait capturing the various feature context types - pub trait Context {} - impl Context for InitContext {} - impl Context for NodeContext {} - impl Context for ChannelContext {} + /// 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 $(| + ::REQUIRED_MASK)* + $(| + ::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 $(| + ::REQUIRED_MASK | + ::OPTIONAL_MASK)* + $(| + ::REQUIRED_MASK | + ::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. @@ -78,6 +173,16 @@ mod sealed { // You should just use the type aliases instead. (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0 } + /// Sets the feature's required (even) bit in the given flags. + #[inline] + fn set_required_bit(flags: &mut Vec) { + if flags.len() <= Self::BYTE_OFFSET { + flags.resize(Self::BYTE_OFFSET + 1, 0u8); + } + + flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK; + } + /// Sets the feature's optional (odd) bit in the given flags. #[inline] fn set_optional_bit(flags: &mut Vec) { @@ -88,12 +193,18 @@ mod sealed { // You should just use the type aliases instead. 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) { + fn clear_bits(flags: &mut Vec) { if flags.len() > Self::BYTE_OFFSET { + flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK; flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK; } + + let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0); + let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 }; + flags.resize(size, 0u8); } } @@ -123,19 +234,29 @@ mod sealed { // You should just use the type aliases instead. 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 - )* - ) - } - } + #[cfg(test)] + define_context!(TestingContext { + required_features: [ + // Byte 0 + , + // Byte 1 + , + // Byte 2 + UnknownFeature, + ], + optional_features: [ + // Byte 0 + , + // Byte 1 + , + // Byte 2 + , + ], + }); + + #[cfg(test)] + define_feature!(23, UnknownFeature, [TestingContext], + "Feature flags for an unknown feature used in testing."); } /// Tracks the set of features which a node implements, templated by the context in which it @@ -173,18 +294,6 @@ pub type NodeFeatures = Features; pub type ChannelFeatures = Features; 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(&self, w: &mut W) -> Result<(), ::std::io::Error> { let len = cmp::min(2, self.flags.len()); @@ -211,95 +320,46 @@ 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`. Only known `InitFeatures` relevant to context `C` + /// are included in the result. + pub(crate) fn to_context(&self) -> Features { + 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 Features { + /// Create a blank Features with no features set + pub fn empty() -> Features { + 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 { + 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 - $( - | ::REQUIRED_MASK - | ::OPTIONAL_MASK - )* - ) - } - } - + /// Converts `Features` to `Features`. Only known `T` features relevant to context `C` are + /// included in the result. + fn to_context_internal(&self) -> Features { + let byte_count = C::KNOWN_FEATURE_MASK.len(); let mut flags = Vec::new(); - for (i, feature_byte)in init_ctx.flags.iter().enumerate() { - match i { - 0 => flags.push(feature_byte & features_including![DataLossProtect | UpfrontShutdownScript]), - 1 => flags.push(feature_byte & features_including![VariableLengthOnion | PaymentSecret]), - 2 => flags.push(feature_byte & features_including![BasicMPP]), - _ => (), + for (i, byte) in self.flags.iter().enumerate() { + if i < byte_count { + let known_source_features = T::KNOWN_FEATURE_MASK[i]; + let known_target_features = C::KNOWN_FEATURE_MASK[i]; + flags.push(byte & known_source_features & known_target_features); } } - Self { flags, mark: PhantomData, } - } -} - -impl Features { - /// Create a blank Features with no features set - pub fn empty() -> Features { - Features { - flags: Vec::new(), - mark: PhantomData, - } + Features:: { flags, mark: PhantomData, } } #[cfg(test)] @@ -318,49 +378,31 @@ impl Features { } pub(crate) fn requires_unknown_bits(&self) -> bool { - // Generates a bitmask with all even bits set except for the given features. Bitwise - // AND-ing it with a byte will select unknown required features. - macro_rules! features_excluding { - ($($feature: ident)|*) => { - (0b01_01_01_01 - $( - & !(::REQUIRED_MASK) - )* - ) - } - } - - self.flags.iter().enumerate().any(|(idx, &byte)| { - (match idx { - 0 => (byte & features_excluding![DataLossProtect | InitialRoutingSync | UpfrontShutdownScript]), - 1 => (byte & features_excluding![VariableLengthOnion | PaymentSecret]), - 2 => (byte & features_excluding![BasicMPP]), - _ => (byte & features_excluding![]), - }) != 0 + // Bitwise AND-ing with all even bits set except for known features will select required + // unknown features. + let byte_count = T::KNOWN_FEATURE_MASK.len(); + self.flags.iter().enumerate().any(|(i, &byte)| { + let required_features = 0b01_01_01_01; + let unknown_features = if i < byte_count { + !T::KNOWN_FEATURE_MASK[i] + } else { + 0b11_11_11_11 + }; + (byte & (required_features & unknown_features)) != 0 }) } pub(crate) fn supports_unknown_bits(&self) -> bool { - // Generates a bitmask with all even and odd bits set except for the given features. Bitwise - // AND-ing it with a byte will select unknown supported features. - macro_rules! features_excluding { - ($($feature: ident)|*) => { - (0b11_11_11_11 - $( - & !(::REQUIRED_MASK) - & !(::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 }) } @@ -371,23 +413,18 @@ impl Features { } #[cfg(test)] - pub(crate) fn set_require_unknown_bits(&mut self) { - let newlen = cmp::max(3, self.flags.len()); - self.flags.resize(newlen, 0u8); - self.flags[2] |= 0x40; + pub(crate) fn set_required_unknown_bits(&mut self) { + ::set_required_bit(&mut self.flags); } #[cfg(test)] - pub(crate) fn clear_require_unknown_bits(&mut self) { - let newlen = cmp::max(3, self.flags.len()); - self.flags.resize(newlen, 0u8); - self.flags[2] &= !0x40; - if self.flags.len() == 3 && self.flags[2] == 0 { - self.flags.resize(2, 0u8); - } - if self.flags.len() == 2 && self.flags[1] == 0 { - self.flags.resize(1, 0u8); - } + pub(crate) fn set_optional_unknown_bits(&mut self) { + ::set_optional_bit(&mut self.flags); + } + + #[cfg(test)] + pub(crate) fn clear_unknown_bits(&mut self) { + ::clear_bits(&mut self.flags); } } @@ -402,8 +439,9 @@ impl Features { ::supports_feature(&self.flags) } #[cfg(test)] - pub(crate) fn unset_upfront_shutdown_script(&mut self) { - ::clear_optional_bit(&mut self.flags) + pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self { + ::clear_bits(&mut self.flags); + self } } @@ -418,7 +456,7 @@ impl Features { ::supports_feature(&self.flags) } pub(crate) fn clear_initial_routing_sync(&mut self) { - ::clear_optional_bit(&mut self.flags) + ::clear_bits(&mut self.flags) } } @@ -464,68 +502,80 @@ impl Readable for Features { #[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(); - features.set_require_unknown_bits(); + fn sanity_test_unknown_bits() { + let mut features = ChannelFeatures::empty(); + assert!(!features.requires_unknown_bits()); + assert!(!features.supports_unknown_bits()); + + features.set_required_unknown_bits(); assert!(features.requires_unknown_bits()); - features.clear_require_unknown_bits(); + assert!(features.supports_unknown_bits()); + + features.clear_unknown_bits(); assert!(!features.requires_unknown_bits()); + assert!(!features.supports_unknown_bits()); + + features.set_optional_unknown_bits(); + assert!(!features.requires_unknown_bits()); + assert!(features.supports_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()); } }