From: Matt Corallo Date: Fri, 17 Sep 2021 16:59:09 +0000 (+0000) Subject: Add a ChannelTypeFeatures features object for the new channel_type X-Git-Tag: v0.0.104~44^2~2 X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=commitdiff_plain;h=e847c87dc2b54f4fb9092658ad7e48d585b00cad;p=rust-lightning Add a ChannelTypeFeatures features object for the new channel_type Its semantics are somewhat different from existing features, however not enough to merit a different struct entirely. Specifically, it only supports required features (if you send a channel_type, the counterparty has to accept it wholesale or try again, it cannot select only a subset of the flags) and it is serialized differently (only appearing in TLVs). --- diff --git a/lightning/src/ln/features.rs b/lightning/src/ln/features.rs index 8f251d847..46a296001 100644 --- a/lightning/src/ln/features.rs +++ b/lightning/src/ln/features.rs @@ -22,7 +22,7 @@ //! [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md //! [messages]: crate::ln::msgs -use io; +use {io, io_extras}; use prelude::*; use core::{cmp, fmt}; use core::hash::{Hash, Hasher}; @@ -194,6 +194,30 @@ mod sealed { BasicMPP, ], }); + // This isn't a "real" feature context, and is only used in the channel_type field in an + // `OpenChannel` message. + define_context!(ChannelTypeContext { + required_features: [ + // Byte 0 + , + // Byte 1 + StaticRemoteKey, + // Byte 2 + , + // Byte 3 + , + ], + optional_features: [ + // Byte 0 + , + // Byte 1 + , + // Byte 2 + , + // Byte 3 + , + ], + }); /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is /// useful for manipulating feature flags. @@ -325,7 +349,7 @@ mod sealed { define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext], "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional, set_variable_length_onion_required); - define_feature!(13, StaticRemoteKey, [InitContext, NodeContext], + define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext], "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional, set_static_remote_key_required); define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext], @@ -388,6 +412,18 @@ pub type ChannelFeatures = Features; /// Features used within an invoice. pub type InvoiceFeatures = Features; +/// Features used within the channel_type field in an OpenChannel message. +/// +/// A channel is always of some known "type", describing the transaction formats used and the exact +/// semantics of our interaction with our peer. +/// +/// Note that because a channel is a specific type which is proposed by the opener and accepted by +/// the counterparty, only required features are allowed here. +/// +/// This is serialized differently from other feature types - it is not prefixed by a length, and +/// thus must only appear inside a TLV where its length is known in advance. +pub type ChannelTypeFeatures = Features; + impl InitFeatures { /// Writes all features present up to, and including, 13. pub(crate) fn write_up_to_13(&self, w: &mut W) -> Result<(), io::Error> { @@ -442,6 +478,28 @@ impl InvoiceFeatures { } } +impl ChannelTypeFeatures { + /// Constructs the implicit channel type based on the common supported types between us and our + /// counterparty + pub(crate) fn from_counterparty_init(counterparty_init: &InitFeatures) -> Self { + let mut ret = counterparty_init.to_context_internal(); + // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all + // optional bits and then AND out the optional ones. + for byte in ret.flags.iter_mut() { + *byte |= (*byte & 0b10_10_10_10) >> 1; + *byte &= 0b01_01_01_01; + } + ret + } + + /// Constructs a ChannelTypeFeatures with only static_remotekey set + pub(crate) fn only_static_remote_key() -> Self { + let mut ret = Self::empty(); + ::set_required_bit(&mut ret.flags); + ret + } +} + impl ToBase32 for InvoiceFeatures { fn write_base32(&self, writer: &mut W) -> Result<(), ::Err> { // Explanation for the "4": the normal way to round up when dividing is to add the divisor @@ -553,6 +611,25 @@ impl Features { &self.flags } + fn write_be(&self, w: &mut W) -> Result<(), io::Error> { + for f in self.flags.iter().rev() { // Swap back to big-endian + f.write(w)?; + } + Ok(()) + } + + fn from_be_bytes(mut flags: Vec) -> Features { + flags.reverse(); // Swap to little-endian + Self { + flags, + mark: PhantomData, + } + } + + pub(crate) fn supports_any_optional_bits(&self) -> bool { + self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0) + } + /// Returns true if this `Features` object contains unknown feature flags which are set as /// "required". pub fn requires_unknown_bits(&self) -> bool { @@ -692,31 +769,44 @@ impl Features { self } } - -impl Writeable for Features { - fn write(&self, w: &mut W) -> Result<(), io::Error> { - (self.flags.len() as u16).write(w)?; - for f in self.flags.iter().rev() { // Swap back to big-endian - f.write(w)?; +macro_rules! impl_feature_len_prefixed_write { + ($features: ident) => { + impl Writeable for $features { + fn write(&self, w: &mut W) -> Result<(), io::Error> { + (self.flags.len() as u16).write(w)?; + self.write_be(w) + } + } + impl Readable for $features { + fn read(r: &mut R) -> Result { + Ok(Self::from_be_bytes(Vec::::read(r)?)) + } } - Ok(()) } } - -impl Readable for Features { +impl_feature_len_prefixed_write!(InitFeatures); +impl_feature_len_prefixed_write!(ChannelFeatures); +impl_feature_len_prefixed_write!(NodeFeatures); +impl_feature_len_prefixed_write!(InvoiceFeatures); + +// Because ChannelTypeFeatures only appears inside of TLVs, it doesn't have a length prefix when +// serialized. Thus, we can't use `impl_feature_len_prefixed_write`, above, and have to write our +// own serialization. +impl Writeable for ChannelTypeFeatures { + fn write(&self, w: &mut W) -> Result<(), io::Error> { + self.write_be(w) + } +} +impl Readable for ChannelTypeFeatures { fn read(r: &mut R) -> Result { - let mut flags: Vec = Readable::read(r)?; - flags.reverse(); // Swap to little-endian - Ok(Self { - flags, - mark: PhantomData, - }) + let v = io_extras::read_to_end(r)?; + Ok(Self::from_be_bytes(v)) } } #[cfg(test)] mod tests { - use super::{ChannelFeatures, InitFeatures, InvoiceFeatures, NodeFeatures}; + use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures}; use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5}; #[test] @@ -875,4 +965,15 @@ mod tests { let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap(); assert_eq!(features, features_deserialized); } + + #[test] + fn test_channel_type_mapping() { + // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a + // required-StaticRemoteKey ChannelTypeFeatures. + let init_features = InitFeatures::empty().set_static_remote_key_optional(); + let converted_features = ChannelTypeFeatures::from_counterparty_init(&init_features); + assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key()); + assert!(!converted_features.supports_any_optional_bits()); + assert!(converted_features.requires_static_remote_key()); + } }