X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Fln%2Ffeatures.rs;h=381297703e882a08cce4577e01d5bd3f7a9a87af;hb=4bd2c974a2c96a2ce98a4055a72b2b3c687e78bc;hp=9ab53b4ae82c808745fec6b9d6e71a4cc9502650;hpb=d39f25839ad9ff5e2a0e1dd8919e991828d1bf35;p=rust-lightning diff --git a/lightning/src/ln/features.rs b/lightning/src/ln/features.rs index 9ab53b4a..38129770 100644 --- a/lightning/src/ln/features.rs +++ b/lightning/src/ln/features.rs @@ -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 $(| + ::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)* + $(| + ::REQUIRED_MASK | + ::OPTIONAL_MASK)*, + )* + ]; + } + }; + } + + define_context!(InitContext { + required_features: [ + // Byte 0 + , + // Byte 1 + , + // Byte 2 + , + ], + optional_features: [ + // Byte 0 + DataLossProtect | InitialRoutingSync | UpfrontShutdownScript, + // Byte 1 + VariableLengthOnion | PaymentSecret, + // Byte 2 + BasicMPP, + ], + }); + define_context!(NodeContext { + required_features: [ + // Byte 0 + , + // Byte 1 + , + // Byte 2 + , + ], + optional_features: [ + // Byte 0 + DataLossProtect | UpfrontShutdownScript, + // Byte 1 + VariableLengthOnion | PaymentSecret, + // Byte 2 + BasicMPP, + ], + }); + define_context!(ChannelContext { + required_features: [], + optional_features: [], + }); + + /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is + /// useful for manipulating feature flags. + /// + /// [`Context`]: trait.Context.html + macro_rules! define_feature { + ($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) -> 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) { + 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) { + 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 - (::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 = (::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 { - /// 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, mark: PhantomData, } @@ -70,22 +248,14 @@ impl fmt::Debug for Features { } } -/// A feature message as it appears in an init message +/// Features used within an `init` message. pub type InitFeatures = Features; -/// A feature message as it appears in a node_announcement message +/// Features used within a `node_announcement` message. pub type NodeFeatures = Features; -/// A feature message as it appears in a channel_announcement message +/// Features used within a `channel_announcement` message. pub type ChannelFeatures = Features; 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(&self, w: &mut W) -> Result<(), ::std::io::Error> { let len = cmp::min(2, self.flags.len()); @@ -112,76 +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`. 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![2 | 1 << 5, 1 << (9 - 8) | 1 << (15 - 8), 1 << (17 - 8*2)], +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![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 { + 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` 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 { - // Blank out initial_routing_sync (feature bits 2/3), gossip_queries (6/7), - // gossip_queries_ex (10/11), option_static_remotekey (12/13), and - // payment_secret (14/15) - 0 => flags.push(feature_byte & 0b00110011), - 1 => 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 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)] @@ -200,35 +340,31 @@ impl Features { } 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 }) } @@ -261,36 +397,33 @@ impl Features { impl Features { pub(crate) fn supports_data_loss_protect(&self) -> bool { - self.flags.len() > 0 && (self.flags[0] & 3) != 0 + ::supports_feature(&self.flags) } } impl Features { pub(crate) fn supports_upfront_shutdown_script(&self) -> bool { - self.flags.len() > 0 && (self.flags[0] & (3 << 4)) != 0 + ::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 { + ::clear_bits(&mut self.flags); + self } } impl Features { pub(crate) fn supports_variable_length_onion(&self) -> bool { - self.flags.len() > 1 && (self.flags[1] & 3) != 0 + ::supports_feature(&self.flags) } } impl Features { pub(crate) fn initial_routing_sync(&self) -> bool { - self.flags.len() > 0 && (self.flags[0] & (1 << 3)) != 0 + ::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) { + ::clear_bits(&mut self.flags) } } @@ -299,16 +432,16 @@ impl Features { // Note that we never need to test this since what really matters is the invoice - iff the // invoice provides a payment_secret, we assume that we can use it (ie that the recipient // supports payment_secret). - pub(crate) fn payment_secret(&self) -> bool { - self.flags.len() > 1 && (self.flags[1] & (3 << (14-8))) != 0 + pub(crate) fn supports_payment_secret(&self) -> bool { + ::supports_feature(&self.flags) } } impl Features { // We currently never test for this since we don't actually *generate* multipath routes. #[allow(dead_code)] - pub(crate) fn basic_mpp(&self) -> bool { - self.flags.len() > 2 && (self.flags[2] & (3 << (16-8*2))) != 0 + pub(crate) fn supports_basic_mpp(&self) -> bool { + ::supports_feature(&self.flags) } } @@ -336,35 +469,41 @@ 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::known().supports_upfront_shutdown_script()); + assert!(NodeFeatures::known().supports_upfront_shutdown_script()); - assert!(InitFeatures::supported().supports_upfront_shutdown_script()); - assert!(NodeFeatures::supported().supports_upfront_shutdown_script()); + assert!(InitFeatures::known().supports_data_loss_protect()); + assert!(NodeFeatures::known().supports_data_loss_protect()); - assert!(InitFeatures::supported().supports_data_loss_protect()); - assert!(NodeFeatures::supported().supports_data_loss_protect()); + assert!(InitFeatures::known().supports_variable_length_onion()); + assert!(NodeFeatures::known().supports_variable_length_onion()); - assert!(InitFeatures::supported().supports_variable_length_onion()); - assert!(NodeFeatures::supported().supports_variable_length_onion()); + assert!(InitFeatures::known().supports_payment_secret()); + assert!(NodeFeatures::known().supports_payment_secret()); - let mut init_features = InitFeatures::supported(); - init_features.set_initial_routing_sync(); - assert!(!init_features.requires_unknown_bits()); - assert!(!init_features.supports_unknown_bits()); + assert!(InitFeatures::known().supports_basic_mpp()); + assert!(NodeFeatures::known().supports_basic_mpp()); + + 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(); @@ -372,24 +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, and var_onion_optin set. - assert_eq!(res.flags[0], 0b00100010); - assert_eq!(res.flags[1], 0b00000010); - assert_eq!(res.flags.len(), 2); + // 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()); } }