X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Fln%2Ffeatures.rs;h=9d865d15ec2bbc6f11e8ce39b2c970a0f48d4314;hb=7497ed2402aaf8b69b6d5c1a85dc99dba36a6ca3;hp=5eb1bd909e80585408f6ce24853502e696cbc25f;hpb=8ca6cb765eff80e656337c6fdf3a84bc81ee6240;p=rust-lightning

diff --git a/lightning/src/ln/features.rs b/lightning/src/ln/features.rs
index 5eb1bd90..9d865d15 100644
--- a/lightning/src/ln/features.rs
+++ b/lightning/src/ln/features.rs
@@ -1,52 +1,338 @@
-//! Lightning exposes sets of supported operations through "feature flags". This module includes
-//! types to store those feature flags and query for specific flags.
-
-use std::{cmp, fmt};
-use std::result::Result;
-use std::marker::PhantomData;
-
+// This file is Copyright its original authors, visible in version control
+// history.
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+
+//! 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).
+//!
+//! 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]: crate::ln::msgs
+
+use prelude::*;
+use core::{cmp, fmt};
+use core::marker::PhantomData;
+
+use bitcoin::bech32;
+use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
 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 {}
+mod sealed {
+	use prelude::*;
+	use ln::features::Features;
+
+	/// The context in which [`Features`] are applicable. Defines which features are required and
+	/// which are optional for the context.
+	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.
+	macro_rules! define_context {
+		($context: ident {
+			required_features: [$( $( $required_feature: ident )|*, )*],
+			optional_features: [$( $( $optional_feature: ident )|*, )*],
+		}) => {
+			#[derive(Eq, PartialEq)]
+			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 $optional_feature>::OPTIONAL_MASK)*,
+					)*
+				];
+			}
+		};
+	}
+
+	define_context!(InitContext {
+		required_features: [
+			// Byte 0
+			,
+			// Byte 1
+			VariableLengthOnion | StaticRemoteKey | PaymentSecret,
+			// Byte 2
+			,
+			// Byte 3
+			,
+		],
+		optional_features: [
+			// Byte 0
+			DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
+			// Byte 1
+			,
+			// Byte 2
+			BasicMPP,
+			// Byte 3
+			ShutdownAnySegwit,
+		],
+	});
+	define_context!(NodeContext {
+		required_features: [
+			// Byte 0
+			,
+			// Byte 1
+			VariableLengthOnion | StaticRemoteKey | PaymentSecret,
+			// Byte 2
+			,
+			// Byte 3
+			,
+		],
+		optional_features: [
+			// Byte 0
+			DataLossProtect | UpfrontShutdownScript | GossipQueries,
+			// Byte 1
+			,
+			// Byte 2
+			BasicMPP,
+			// Byte 3
+			ShutdownAnySegwit,
+		],
+	});
+	define_context!(ChannelContext {
+		required_features: [],
+		optional_features: [],
+	});
+	define_context!(InvoiceContext {
+		required_features: [
+			// Byte 0
+			,
+			// Byte 1
+			VariableLengthOnion | PaymentSecret,
+			// Byte 2
+			,
+		],
+		optional_features: [
+			// Byte 0
+			,
+			// Byte 1
+			,
+			// Byte 2
+			BasicMPP,
+		],
+	});
+
+	/// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
+	/// useful for manipulating feature flags.
+	macro_rules! define_feature {
+		($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
+		 $required_setter: ident) => {
+			#[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 required by the given flags.
+				#[inline]
+				fn requires_feature(flags: &Vec<u8>) -> bool {
+					flags.len() > Self::BYTE_OFFSET &&
+						(flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
+				}
+
+				/// 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 required (even) bit in the given flags.
+				#[inline]
+				fn set_required_bit(flags: &mut Vec<u8>) {
+					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<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;
+					}
+
+					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);
+				}
+			}
 
-	/// An internal trait capturing the various feature context types
-	pub trait Context {}
-	impl Context for InitContext {}
-	impl Context for NodeContext {}
-	impl Context for ChannelContext {}
+			impl <T: $feature> Features<T> {
+				/// Set this feature as optional.
+				pub fn $optional_setter(mut self) -> Self {
+					<T as $feature>::set_optional_bit(&mut self.flags);
+					self
+				}
+
+				/// Set this feature as required.
+				pub fn $required_setter(mut self) -> Self {
+					<T as $feature>::set_required_bit(&mut self.flags);
+					self
+				}
+			}
 
-	pub trait DataLossProtect: Context {}
-	impl DataLossProtect for InitContext {}
-	impl DataLossProtect 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 InitialRoutingSync: Context {}
-	impl InitialRoutingSync for InitContext {}
+					// ODD_BIT % 2 == 1
+					const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
+				}
+			)*
 
-	pub trait UpfrontShutdownScript: Context {}
-	impl UpfrontShutdownScript for InitContext {}
-	impl UpfrontShutdownScript for NodeContext {}
+		}
+	}
 
-	pub trait VariableLengthOnion: Context {}
-	impl VariableLengthOnion for InitContext {}
-	impl VariableLengthOnion for NodeContext {}
+	define_feature!(1, DataLossProtect, [InitContext, NodeContext],
+		"Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
+		set_data_loss_protect_required);
+	// NOTE: Per Bolt #9, initial_routing_sync has no even bit.
+	define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
+		set_initial_routing_sync_optional, set_initial_routing_sync_required);
+	define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
+		"Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
+		set_upfront_shutdown_script_required);
+	define_feature!(7, GossipQueries, [InitContext, NodeContext],
+		"Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required);
+	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],
+		"Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
+		set_static_remote_key_required);
+	define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
+		"Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required);
+	define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext],
+		"Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required);
+	define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
+		"Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
+		set_shutdown_any_segwit_required);
 
-	pub trait PaymentSecret: Context {}
-	impl PaymentSecret for InitContext {}
-	impl PaymentSecret for NodeContext {}
+	#[cfg(test)]
+	define_context!(TestingContext {
+		required_features: [
+			// Byte 0
+			,
+			// Byte 1
+			,
+			// Byte 2
+			UnknownFeature,
+		],
+		optional_features: [
+			// Byte 0
+			,
+			// Byte 1
+			,
+			// Byte 2
+			,
+		],
+	});
 
-	pub trait BasicMPP: Context {}
-	impl BasicMPP for InitContext {}
-	impl BasicMPP for NodeContext {}
+	#[cfg(test)]
+	define_feature!(23, UnknownFeature, [TestingContext],
+		"Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
+		set_unknown_feature_required);
 }
 
 /// Tracks the set of features which a node implements, templated by the context in which it
 /// appears.
+///
+/// (C-not exported) as we map the concrete feature types below directly instead
+#[derive(Eq)]
 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 +356,16 @@ 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>;
+/// Features used within an invoice.
+pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
 
 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());
@@ -112,81 +392,120 @@ 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,
-		}
+	/// 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()
 	}
+}
 
-	/// 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, }
+impl InvoiceFeatures {
+	/// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` 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)],
-			mark: PhantomData,
+impl ToBase32 for InvoiceFeatures {
+	fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
+		// Explanation for the "4": the normal way to round up when dividing is to add the divisor
+		// minus one before dividing
+		let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
+		let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
+		for (byte_idx, byte) in self.flags.iter().enumerate() {
+			let bit_pos_from_left_0_indexed = byte_idx * 8;
+			let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
+			let new_bit_pos = bit_pos_from_left_0_indexed % 5;
+			let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
+			let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
+			res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
+			if new_u5_idx > 0 {
+				let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
+				res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
+			}
+			if new_u5_idx > 1 {
+				let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
+				res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
+			}
 		}
-	}
-	#[cfg(feature = "fuzztarget")]
-	pub fn supported() -> NodeFeatures {
-		NodeFeatures {
-			flags: vec![2 | 1 << 5, 1 << (9 - 8) | 1 << (15 - 8), 1 << (17 - 8*2)],
-			mark: PhantomData,
+		// Trim the highest feature bits.
+		while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
+			res_u5s.remove(0);
 		}
+		writer.write(&res_u5s)
 	}
+}
 
-	/// 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 {
-		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),
-				_ => (),
+impl Base32Len for InvoiceFeatures {
+	fn base32_len(&self) -> usize {
+		self.to_base32().len()
+	}
+}
+
+impl FromBase32 for InvoiceFeatures {
+	type Err = bech32::Error;
+
+	fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
+		// Explanation for the "7": the normal way to round up when dividing is to add the divisor
+		// minus one before dividing
+		let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
+		let mut res_bytes: Vec<u8> = vec![0; length_bytes];
+		for (u5_idx, chunk) in field_data.iter().enumerate() {
+			let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
+			let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
+			let new_bit_pos = bit_pos_from_right_0_indexed % 8;
+			let chunk_u16 = chunk.to_u8() as u16;
+			res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
+			if new_byte_idx != length_bytes - 1 {
+				res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 			}
 		}
-		Self { flags, mark: PhantomData, }
+		// Trim the highest feature bits.
+		while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
+			res_bytes.pop();
+		}
+		Ok(InvoiceFeatures::from_le_bytes(res_bytes))
 	}
 }
 
 impl<T: sealed::Context> Features<T> {
 	/// Create a blank Features with no features set
-	pub fn empty() -> Features<T> {
+	pub fn empty() -> Self {
 		Features {
 			flags: Vec::new(),
 			mark: PhantomData,
 		}
 	}
 
-	#[cfg(test)]
-	/// Create a Features given a set of flags, in LE.
+	/// Creates a Features with the bits set which are known by the implementation
+	pub fn known() -> Self {
+		Self {
+			flags: T::KNOWN_FEATURE_FLAGS.to_vec(),
+			mark: PhantomData,
+		}
+	}
+
+	/// 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 from_byte_count = T::KNOWN_FEATURE_MASK.len();
+		let to_byte_count = C::KNOWN_FEATURE_MASK.len();
+		let mut flags = Vec::new();
+		for (i, byte) in self.flags.iter().enumerate() {
+			if i < from_byte_count && i < to_byte_count {
+				let from_known_features = T::KNOWN_FEATURE_MASK[i];
+				let to_known_features = C::KNOWN_FEATURE_MASK[i];
+				flags.push(byte & from_known_features & to_known_features);
+			}
+		}
+		Features::<C> { flags, mark: PhantomData, }
+	}
+
+	/// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
+	/// most on-the-wire encodings.
+	/// (C-not exported) as we don't support export across multiple T
 	pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 		Features {
 			flags,
@@ -201,35 +520,31 @@ 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
 		})
 	}
 
@@ -240,76 +555,125 @@ impl<T: sealed::Context> Features<T> {
 	}
 
 	#[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) {
+		<sealed::TestingContext as sealed::UnknownFeature>::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) {
+		<sealed::TestingContext as sealed::UnknownFeature>::set_optional_bit(&mut self.flags);
+	}
+
+	#[cfg(test)]
+	pub(crate) fn clear_unknown_bits(&mut self) {
+		<sealed::TestingContext as sealed::UnknownFeature>::clear_bits(&mut self.flags);
 	}
 }
 
 impl<T: sealed::DataLossProtect> Features<T> {
+	#[cfg(test)]
+	pub(crate) fn requires_data_loss_protect(&self) -> bool {
+		<T as sealed::DataLossProtect>::requires_feature(&self.flags)
+	}
 	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> {
+	#[cfg(test)]
+	pub(crate) fn requires_upfront_shutdown_script(&self) -> bool {
+		<T as sealed::UpfrontShutdownScript>::requires_feature(&self.flags)
+	}
 	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 clear_upfront_shutdown_script(mut self) -> Self {
+		<T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
+		self
+	}
+}
+
+
+impl<T: sealed::GossipQueries> Features<T> {
+	#[cfg(test)]
+	pub(crate) fn requires_gossip_queries(&self) -> bool {
+		<T as sealed::GossipQueries>::requires_feature(&self.flags)
+	}
+	pub(crate) fn supports_gossip_queries(&self) -> bool {
+		<T as sealed::GossipQueries>::supports_feature(&self.flags)
 	}
 	#[cfg(test)]
-	pub(crate) fn unset_upfront_shutdown_script(&mut self) {
-		self.flags[0] ^= 1 << 5;
+	pub(crate) fn clear_gossip_queries(mut self) -> Self {
+		<T as sealed::GossipQueries>::clear_bits(&mut self.flags);
+		self
 	}
 }
 
 impl<T: sealed::VariableLengthOnion> Features<T> {
+	#[cfg(test)]
+	pub(crate) fn requires_variable_length_onion(&self) -> bool {
+		<T as sealed::VariableLengthOnion>::requires_feature(&self.flags)
+	}
 	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::StaticRemoteKey> Features<T> {
+	pub(crate) fn supports_static_remote_key(&self) -> bool {
+		<T as sealed::StaticRemoteKey>::supports_feature(&self.flags)
+	}
+	#[cfg(test)]
+	pub(crate) fn requires_static_remote_key(&self) -> bool {
+		<T as sealed::StaticRemoteKey>::requires_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;
-		}
+	// We are no longer setting initial_routing_sync now that gossip_queries
+	// is enabled. This feature is ignored by a peer when gossip_queries has 
+	// been negotiated.
+	#[cfg(test)]
+	pub(crate) fn clear_initial_routing_sync(&mut self) {
+		<T as sealed::InitialRoutingSync>::clear_bits(&mut self.flags)
 	}
 }
 
 impl<T: sealed::PaymentSecret> Features<T> {
-	#[allow(dead_code)]
-	// 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 supports_payment_secret(&self) -> bool {
-		self.flags.len() > 1 && (self.flags[1] & (3 << (14-8))) != 0
+	#[cfg(test)]
+	pub(crate) fn requires_payment_secret(&self) -> bool {
+		<T as sealed::PaymentSecret>::requires_feature(&self.flags)
+	}
+	/// Returns whether the `payment_secret` feature is supported.
+	pub fn supports_payment_secret(&self) -> bool {
+		<T as sealed::PaymentSecret>::supports_feature(&self.flags)
 	}
 }
 
 impl<T: sealed::BasicMPP> Features<T> {
+	#[cfg(test)]
+	pub(crate) fn requires_basic_mpp(&self) -> bool {
+		<T as sealed::BasicMPP>::requires_feature(&self.flags)
+	}
 	// 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)
+	}
+}
+
+impl<T: sealed::ShutdownAnySegwit> Features<T> {
+	pub(crate) fn supports_shutdown_anysegwit(&self) -> bool {
+		<T as sealed::ShutdownAnySegwit>::supports_feature(&self.flags)
+	}
+	#[cfg(test)]
+	pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
+		<T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
+		self
 	}
 }
 
@@ -337,68 +701,157 @@ impl<T: sealed::Context> Readable for Features<T> {
 
 #[cfg(test)]
 mod tests {
-	use super::{ChannelFeatures, InitFeatures, NodeFeatures, Features};
+	use super::{ChannelFeatures, InitFeatures, InvoiceFeatures, NodeFeatures};
+	use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
 
 	#[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!(InitFeatures::supported().supports_upfront_shutdown_script());
-		assert!(NodeFeatures::supported().supports_upfront_shutdown_script());
-
-		assert!(InitFeatures::supported().supports_data_loss_protect());
-		assert!(NodeFeatures::supported().supports_data_loss_protect());
-
-		assert!(InitFeatures::supported().supports_variable_length_onion());
-		assert!(NodeFeatures::supported().supports_variable_length_onion());
-
-		assert!(InitFeatures::supported().supports_payment_secret());
-		assert!(NodeFeatures::supported().supports_payment_secret());
-
-		assert!(InitFeatures::supported().supports_basic_mpp());
-		assert!(NodeFeatures::supported().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());
+	fn sanity_test_known_features() {
+		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::known().requires_upfront_shutdown_script());
+		assert!(!NodeFeatures::known().requires_upfront_shutdown_script());
+
+		assert!(InitFeatures::known().supports_gossip_queries());
+		assert!(NodeFeatures::known().supports_gossip_queries());
+		assert!(!InitFeatures::known().requires_gossip_queries());
+		assert!(!NodeFeatures::known().requires_gossip_queries());
+
+		assert!(InitFeatures::known().supports_data_loss_protect());
+		assert!(NodeFeatures::known().supports_data_loss_protect());
+		assert!(!InitFeatures::known().requires_data_loss_protect());
+		assert!(!NodeFeatures::known().requires_data_loss_protect());
+
+		assert!(InitFeatures::known().supports_variable_length_onion());
+		assert!(NodeFeatures::known().supports_variable_length_onion());
+		assert!(InvoiceFeatures::known().supports_variable_length_onion());
+		assert!(InitFeatures::known().requires_variable_length_onion());
+		assert!(NodeFeatures::known().requires_variable_length_onion());
+		assert!(InvoiceFeatures::known().requires_variable_length_onion());
+
+		assert!(InitFeatures::known().supports_static_remote_key());
+		assert!(NodeFeatures::known().supports_static_remote_key());
+		assert!(InitFeatures::known().requires_static_remote_key());
+		assert!(NodeFeatures::known().requires_static_remote_key());
+
+		assert!(InitFeatures::known().supports_payment_secret());
+		assert!(NodeFeatures::known().supports_payment_secret());
+		assert!(InvoiceFeatures::known().supports_payment_secret());
+		assert!(InitFeatures::known().requires_payment_secret());
+		assert!(NodeFeatures::known().requires_payment_secret());
+		assert!(InvoiceFeatures::known().requires_payment_secret());
+
+		assert!(InitFeatures::known().supports_basic_mpp());
+		assert!(NodeFeatures::known().supports_basic_mpp());
+		assert!(InvoiceFeatures::known().supports_basic_mpp());
+		assert!(!InitFeatures::known().requires_basic_mpp());
+		assert!(!NodeFeatures::known().requires_basic_mpp());
+		assert!(!InvoiceFeatures::known().requires_basic_mpp());
+
+		assert!(InitFeatures::known().supports_shutdown_anysegwit());
+		assert!(NodeFeatures::known().supports_shutdown_anysegwit());
+
+		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 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().clear_gossip_queries();
+		assert!(init_features.initial_routing_sync());
+		assert!(!init_features.supports_upfront_shutdown_script());
+		assert!(!init_features.supports_gossip_queries());
 
+		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 (req) | static_remote_key (req) | payment_secret(req)
+			// - basic_mpp
+			// - opt_shutdown_anysegwit
+			assert_eq!(node_features.flags.len(), 4);
+			assert_eq!(node_features.flags[0], 0b00000010);
+			assert_eq!(node_features.flags[1], 0b01010001);
+			assert_eq!(node_features.flags[2], 0b00000010);
+			assert_eq!(node_features.flags[3], 0b00001000);
 		}
 
-		// 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
+		// - gossip_queries was cleared before converting
+		let features: InitFeatures = node_features.to_context_internal();
+		assert!(!features.initial_routing_sync());
+		assert!(!features.supports_upfront_shutdown_script());
+		assert!(!init_features.supports_gossip_queries());
+	}
+
+	#[test]
+	fn set_feature_bits() {
+		let features = InvoiceFeatures::empty()
+			.set_basic_mpp_optional()
+			.set_payment_secret_required();
+		assert!(features.supports_basic_mpp());
+		assert!(!features.requires_basic_mpp());
+		assert!(features.requires_payment_secret());
+		assert!(features.supports_payment_secret());
+	}
+
+	#[test]
+	fn invoice_features_encoding() {
+		let features_as_u5s = vec![
+			u5::try_from_u8(6).unwrap(),
+			u5::try_from_u8(10).unwrap(),
+			u5::try_from_u8(25).unwrap(),
+			u5::try_from_u8(1).unwrap(),
+			u5::try_from_u8(10).unwrap(),
+			u5::try_from_u8(0).unwrap(),
+			u5::try_from_u8(20).unwrap(),
+			u5::try_from_u8(2).unwrap(),
+			u5::try_from_u8(0).unwrap(),
+			u5::try_from_u8(6).unwrap(),
+			u5::try_from_u8(0).unwrap(),
+			u5::try_from_u8(16).unwrap(),
+			u5::try_from_u8(1).unwrap(),
+		];
+		let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
+
+		// Test length calculation.
+		assert_eq!(features.base32_len(), 13);
+
+		// Test serialization.
+		let features_serialized = features.to_base32();
+		assert_eq!(features_as_u5s, features_serialized);
+
+		// Test deserialization.
+		let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
+		assert_eq!(features, features_deserialized);
 	}
 }