_ Git - rust-lightning/blob - lightning/src/ln/features.rs

   1 //! Feature flag definitions for the Lightning protocol according to [BOLT #9].
   2 //!
   3 //! Lightning nodes advertise a supported set of operation through feature flags. Features are
   4 //! applicable for a specific context as indicated in some [messages]. [`Features`] encapsulates
   5 //! behavior for specifying and checking feature flags for a particular context. Each feature is
   6 //! defined internally by a trait specifying the corresponding flags (i.e., even and odd bits). A
   7 //! [`Context`] is used to parameterize [`Features`] and defines which features it can support.
   8 //!
   9 //! Whether a feature is considered "known" or "unknown" is relative to the implementation, whereas
  10 //! the term "supports" is used in reference to a particular set of [`Features`]. That is, a node
  11 //! supports a feature if it advertises the feature (as either required or optional) to its peers.
  12 //! And the implementation can interpret a feature if the feature is known to it.
  13 //!
  14 //! [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
  15 //! [messages]: ../msgs/index.html
  16 //! [`Features`]: struct.Features.html
  17 //! [`Context`]: sealed/trait.Context.html
  18
  19 use std::{cmp, fmt};
  20 use std::result::Result;
  21 use std::marker::PhantomData;
  22
  23 use ln::msgs::DecodeError;
  24 use util::ser::{Readable, Writeable, Writer};
  25
  26 mod sealed {
  27         /// The context in which [`Features`] are applicable. Defines which features are required and
  28         /// which are optional for the context.
  29         ///
  30         /// [`Features`]: ../struct.Features.html
  31         pub trait Context {
  32                 /// Features that are known to the implementation, where a required feature is indicated by
  33                 /// its even bit and an optional feature is indicated by its odd bit.
  34                 const KNOWN_FEATURE_FLAGS: &'static [u8];
  35
  36                 /// Bitmask for selecting features that are known to the implementation, regardless of
  37                 /// whether each feature is required or optional.
  38                 const KNOWN_FEATURE_MASK: &'static [u8];
  39         }
  40
  41         /// Defines a [`Context`] by stating which features it requires and which are optional. Features
  42         /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
  43         /// feature identifiers.
  44         ///
  45         /// [`Context`]: trait.Context.html
  46         macro_rules! define_context {
  47                 ($context: ident {
  48                         required_features: [$( $( $required_feature: ident )|*, )*],
  49                         optional_features: [$( $( $optional_feature: ident )|*, )*],
  50                 }) => {
  51                         pub struct $context {}
  52
  53                         impl Context for $context {
  54                                 const KNOWN_FEATURE_FLAGS: &'static [u8] = &[
  55                                         // For each byte, use bitwise-OR to compute the applicable flags for known
  56                                         // required features `r_i` and optional features `o_j` for all `i` and `j` such
  57                                         // that the following slice is formed:
  58                                         //
  59                                         // [
  60                                         //  `r_0` | `r_1` | ... | `o_0` | `o_1` | ...,
  61                                         //  ...,
  62                                         // ]
  63                                         $(
  64                                                 0b00_00_00_00 $(|
  65                                                         <Self as $required_feature>::REQUIRED_MASK)*
  66                                                 $(|
  67                                                         <Self as $optional_feature>::OPTIONAL_MASK)*,
  68                                         )*
  69                                 ];
  70
  71                                 const KNOWN_FEATURE_MASK: &'static [u8] = &[
  72                                         // Similar as above, but set both flags for each feature regardless of whether
  73                                         // the feature is required or optional.
  74                                         $(
  75                                                 0b00_00_00_00 $(|
  76                                                         <Self as $required_feature>::REQUIRED_MASK |
  77                                                         <Self as $required_feature>::OPTIONAL_MASK)*
  78                                                 $(|
  79                                                         <Self as $optional_feature>::REQUIRED_MASK |
  80                                                         <Self as $optional_feature>::OPTIONAL_MASK)*,
  81                                         )*
  82                                 ];
  83                         }
  84                 };
  85         }
  86
  87         define_context!(InitContext {
  88                 required_features: [
  89                         // Byte 0
  90                         ,
  91                         // Byte 1
  92                         ,
  93                         // Byte 2
  94                         ,
  95                 ],
  96                 optional_features: [
  97                         // Byte 0
  98                         DataLossProtect | InitialRoutingSync | UpfrontShutdownScript,
  99                         // Byte 1
 100                         VariableLengthOnion | PaymentSecret,
 101                         // Byte 2
 102                         BasicMPP,
 103                 ],
 104         });
 105         define_context!(NodeContext {
 106                 required_features: [
 107                         // Byte 0
 108                         ,
 109                         // Byte 1
 110                         ,
 111                         // Byte 2
 112                         ,
 113                 ],
 114                 optional_features: [
 115                         // Byte 0
 116                         DataLossProtect | UpfrontShutdownScript,
 117                         // Byte 1
 118                         VariableLengthOnion | PaymentSecret,
 119                         // Byte 2
 120                         BasicMPP,
 121                 ],
 122         });
 123         define_context!(ChannelContext {
 124                 required_features: [],
 125                 optional_features: [],
 126         });
 127
 128         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 129         /// useful for manipulating feature flags.
 130         ///
 131         /// [`Context`]: trait.Context.html
 132         macro_rules! define_feature {
 133                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr) => {
 134                         #[doc = $doc]
 135                         ///
 136                         /// See [BOLT #9] for details.
 137                         ///
 138                         /// [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
 139                         pub trait $feature: Context {
 140                                 /// The bit used to signify that the feature is required.
 141                                 const EVEN_BIT: usize = $odd_bit - 1;
 142
 143                                 /// The bit used to signify that the feature is optional.
 144                                 const ODD_BIT: usize = $odd_bit;
 145
 146                                 /// Assertion that [`EVEN_BIT`] is actually even.
 147                                 ///
 148                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 149                                 const ASSERT_EVEN_BIT_PARITY: usize;
 150
 151                                 /// Assertion that [`ODD_BIT`] is actually odd.
 152                                 ///
 153                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 154                                 const ASSERT_ODD_BIT_PARITY: usize;
 155
 156                                 /// The byte where the feature is set.
 157                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 158
 159                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 160                                 ///
 161                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 162                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 163
 164                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 165                                 ///
 166                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 167                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 168
 169                                 /// Returns whether the feature is supported by the given flags.
 170                                 #[inline]
 171                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 172                                         flags.len() > Self::BYTE_OFFSET &&
 173                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 174                                 }
 175
 176                                 /// Sets the feature's required (even) bit in the given flags.
 177                                 #[inline]
 178                                 fn set_required_bit(flags: &mut Vec<u8>) {
 179                                         if flags.len() <= Self::BYTE_OFFSET {
 180                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 181                                         }
 182
 183                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
 184                                 }
 185
 186                                 /// Sets the feature's optional (odd) bit in the given flags.
 187                                 #[inline]
 188                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 189                                         if flags.len() <= Self::BYTE_OFFSET {
 190                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 191                                         }
 192
 193                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 194                                 }
 195
 196                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 197                                 /// flags.
 198                                 #[inline]
 199                                 fn clear_bits(flags: &mut Vec<u8>) {
 200                                         if flags.len() > Self::BYTE_OFFSET {
 201                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 202                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 203                                         }
 204
 205                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 206                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 207                                         flags.resize(size, 0u8);
 208                                 }
 209                         }
 210
 211                         $(
 212                                 impl $feature for $context {
 213                                         // EVEN_BIT % 2 == 0
 214                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 215
 216                                         // ODD_BIT % 2 == 1
 217                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 218                                 }
 219                         )*
 220                 }
 221         }
 222
 223         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 224                 "Feature flags for `option_data_loss_protect`.");
 225         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 226         define_feature!(3, InitialRoutingSync, [InitContext],
 227                 "Feature flags for `initial_routing_sync`.");
 228         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 229                 "Feature flags for `option_upfront_shutdown_script`.");
 230         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext],
 231                 "Feature flags for `var_onion_optin`.");
 232         define_feature!(15, PaymentSecret, [InitContext, NodeContext],
 233                 "Feature flags for `payment_secret`.");
 234         define_feature!(17, BasicMPP, [InitContext, NodeContext],
 235                 "Feature flags for `basic_mpp`.");
 236
 237         #[cfg(test)]
 238         define_context!(TestingContext {
 239                 required_features: [
 240                         // Byte 0
 241                         ,
 242                         // Byte 1
 243                         ,
 244                         // Byte 2
 245                         UnknownFeature,
 246                 ],
 247                 optional_features: [
 248                         // Byte 0
 249                         ,
 250                         // Byte 1
 251                         ,
 252                         // Byte 2
 253                         ,
 254                 ],
 255         });
 256
 257         #[cfg(test)]
 258         define_feature!(23, UnknownFeature, [TestingContext],
 259                 "Feature flags for an unknown feature used in testing.");
 260 }
 261
 262 /// Tracks the set of features which a node implements, templated by the context in which it
 263 /// appears.
 264 pub struct Features<T: sealed::Context> {
 265         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 266         flags: Vec<u8>,
 267         mark: PhantomData<T>,
 268 }
 269
 270 impl<T: sealed::Context> Clone for Features<T> {
 271         fn clone(&self) -> Self {
 272                 Self {
 273                         flags: self.flags.clone(),
 274                         mark: PhantomData,
 275                 }
 276         }
 277 }
 278 impl<T: sealed::Context> PartialEq for Features<T> {
 279         fn eq(&self, o: &Self) -> bool {
 280                 self.flags.eq(&o.flags)
 281         }
 282 }
 283 impl<T: sealed::Context> fmt::Debug for Features<T> {
 284         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 285                 self.flags.fmt(fmt)
 286         }
 287 }
 288
 289 /// Features used within an `init` message.
 290 pub type InitFeatures = Features<sealed::InitContext>;
 291 /// Features used within a `node_announcement` message.
 292 pub type NodeFeatures = Features<sealed::NodeContext>;
 293 /// Features used within a `channel_announcement` message.
 294 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 295
 296 impl InitFeatures {
 297         /// Writes all features present up to, and including, 13.
 298         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
 299                 let len = cmp::min(2, self.flags.len());
 300                 w.size_hint(len + 2);
 301                 (len as u16).write(w)?;
 302                 for i in (0..len).rev() {
 303                         if i == 0 {
 304                                 self.flags[i].write(w)?;
 305                         } else {
 306                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 307                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 308                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 309                         }
 310                 }
 311                 Ok(())
 312         }
 313
 314         /// or's another InitFeatures into this one.
 315         pub(crate) fn or(mut self, o: InitFeatures) -> InitFeatures {
 316                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
 317                 self.flags.resize(total_feature_len, 0u8);
 318                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
 319                         *byte |= *o_byte;
 320                 }
 321                 self
 322         }
 323
 324         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 325         /// are included in the result.
 326         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 327                 self.to_context_internal()
 328         }
 329 }
 330
 331 impl<T: sealed::Context> Features<T> {
 332         /// Create a blank Features with no features set
 333         pub fn empty() -> Features<T> {
 334                 Features {
 335                         flags: Vec::new(),
 336                         mark: PhantomData,
 337                 }
 338         }
 339
 340         /// Creates features known by the implementation as defined by [`T::KNOWN_FEATURE_FLAGS`].
 341         ///
 342         /// [`T::KNOWN_FEATURE_FLAGS`]: sealed/trait.Context.html#associatedconstant.KNOWN_FEATURE_FLAGS
 343         pub fn known() -> Features<T> {
 344                 Self {
 345                         flags: T::KNOWN_FEATURE_FLAGS.to_vec(),
 346                         mark: PhantomData,
 347                 }
 348         }
 349
 350         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 351         /// included in the result.
 352         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 353                 let byte_count = C::KNOWN_FEATURE_MASK.len();
 354                 let mut flags = Vec::new();
 355                 for (i, byte) in self.flags.iter().enumerate() {
 356                         if i < byte_count {
 357                                 let known_source_features = T::KNOWN_FEATURE_MASK[i];
 358                                 let known_target_features = C::KNOWN_FEATURE_MASK[i];
 359                                 flags.push(byte & known_source_features & known_target_features);
 360                         }
 361                 }
 362                 Features::<C> { flags, mark: PhantomData, }
 363         }
 364
 365         #[cfg(test)]
 366         /// Create a Features given a set of flags, in LE.
 367         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 368                 Features {
 369                         flags,
 370                         mark: PhantomData,
 371                 }
 372         }
 373
 374         #[cfg(test)]
 375         /// Gets the underlying flags set, in LE.
 376         pub fn le_flags(&self) -> &Vec<u8> {
 377                 &self.flags
 378         }
 379
 380         pub(crate) fn requires_unknown_bits(&self) -> bool {
 381                 // Bitwise AND-ing with all even bits set except for known features will select required
 382                 // unknown features.
 383                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 384                 self.flags.iter().enumerate().any(|(i, &byte)| {
 385                         let required_features = 0b01_01_01_01;
 386                         let unknown_features = if i < byte_count {
 387                                 !T::KNOWN_FEATURE_MASK[i]
 388                         } else {
 389                                 0b11_11_11_11
 390                         };
 391                         (byte & (required_features & unknown_features)) != 0
 392                 })
 393         }
 394
 395         pub(crate) fn supports_unknown_bits(&self) -> bool {
 396                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 397                 // both required and optional unknown features.
 398                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 399                 self.flags.iter().enumerate().any(|(i, &byte)| {
 400                         let unknown_features = if i < byte_count {
 401                                 !T::KNOWN_FEATURE_MASK[i]
 402                         } else {
 403                                 0b11_11_11_11
 404                         };
 405                         (byte & unknown_features) != 0
 406                 })
 407         }
 408
 409         /// The number of bytes required to represent the feature flags present. This does not include
 410         /// the length bytes which are included in the serialized form.
 411         pub(crate) fn byte_count(&self) -> usize {
 412                 self.flags.len()
 413         }
 414
 415         #[cfg(test)]
 416         pub(crate) fn set_required_unknown_bits(&mut self) {
 417                 <sealed::TestingContext as sealed::UnknownFeature>::set_required_bit(&mut self.flags);
 418         }
 419
 420         #[cfg(test)]
 421         pub(crate) fn set_optional_unknown_bits(&mut self) {
 422                 <sealed::TestingContext as sealed::UnknownFeature>::set_optional_bit(&mut self.flags);
 423         }
 424
 425         #[cfg(test)]
 426         pub(crate) fn clear_unknown_bits(&mut self) {
 427                 <sealed::TestingContext as sealed::UnknownFeature>::clear_bits(&mut self.flags);
 428         }
 429 }
 430
 431 impl<T: sealed::DataLossProtect> Features<T> {
 432         pub(crate) fn supports_data_loss_protect(&self) -> bool {
 433                 <T as sealed::DataLossProtect>::supports_feature(&self.flags)
 434         }
 435 }
 436
 437 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 438         pub(crate) fn supports_upfront_shutdown_script(&self) -> bool {
 439                 <T as sealed::UpfrontShutdownScript>::supports_feature(&self.flags)
 440         }
 441         #[cfg(test)]
 442         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 443                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 444                 self
 445         }
 446 }
 447
 448 impl<T: sealed::VariableLengthOnion> Features<T> {
 449         pub(crate) fn supports_variable_length_onion(&self) -> bool {
 450                 <T as sealed::VariableLengthOnion>::supports_feature(&self.flags)
 451         }
 452 }
 453
 454 impl<T: sealed::InitialRoutingSync> Features<T> {
 455         pub(crate) fn initial_routing_sync(&self) -> bool {
 456                 <T as sealed::InitialRoutingSync>::supports_feature(&self.flags)
 457         }
 458         pub(crate) fn clear_initial_routing_sync(&mut self) {
 459                 <T as sealed::InitialRoutingSync>::clear_bits(&mut self.flags)
 460         }
 461 }
 462
 463 impl<T: sealed::PaymentSecret> Features<T> {
 464         #[allow(dead_code)]
 465         // Note that we never need to test this since what really matters is the invoice - iff the
 466         // invoice provides a payment_secret, we assume that we can use it (ie that the recipient
 467         // supports payment_secret).
 468         pub(crate) fn supports_payment_secret(&self) -> bool {
 469                 <T as sealed::PaymentSecret>::supports_feature(&self.flags)
 470         }
 471 }
 472
 473 impl<T: sealed::BasicMPP> Features<T> {
 474         // We currently never test for this since we don't actually *generate* multipath routes.
 475         #[allow(dead_code)]
 476         pub(crate) fn supports_basic_mpp(&self) -> bool {
 477                 <T as sealed::BasicMPP>::supports_feature(&self.flags)
 478         }
 479 }
 480
 481 impl<T: sealed::Context> Writeable for Features<T> {
 482         fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
 483                 w.size_hint(self.flags.len() + 2);
 484                 (self.flags.len() as u16).write(w)?;
 485                 for f in self.flags.iter().rev() { // Swap back to big-endian
 486                         f.write(w)?;
 487                 }
 488                 Ok(())
 489         }
 490 }
 491
 492 impl<T: sealed::Context> Readable for Features<T> {
 493         fn read<R: ::std::io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 494                 let mut flags: Vec<u8> = Readable::read(r)?;
 495                 flags.reverse(); // Swap to little-endian
 496                 Ok(Self {
 497                         flags,
 498                         mark: PhantomData,
 499                 })
 500         }
 501 }
 502
 503 #[cfg(test)]
 504 mod tests {
 505         use super::{ChannelFeatures, InitFeatures, NodeFeatures};
 506
 507         #[test]
 508         fn sanity_test_our_features() {
 509                 assert!(!ChannelFeatures::known().requires_unknown_bits());
 510                 assert!(!ChannelFeatures::known().supports_unknown_bits());
 511                 assert!(!InitFeatures::known().requires_unknown_bits());
 512                 assert!(!InitFeatures::known().supports_unknown_bits());
 513                 assert!(!NodeFeatures::known().requires_unknown_bits());
 514                 assert!(!NodeFeatures::known().supports_unknown_bits());
 515
 516                 assert!(InitFeatures::known().supports_upfront_shutdown_script());
 517                 assert!(NodeFeatures::known().supports_upfront_shutdown_script());
 518
 519                 assert!(InitFeatures::known().supports_data_loss_protect());
 520                 assert!(NodeFeatures::known().supports_data_loss_protect());
 521
 522                 assert!(InitFeatures::known().supports_variable_length_onion());
 523                 assert!(NodeFeatures::known().supports_variable_length_onion());
 524
 525                 assert!(InitFeatures::known().supports_payment_secret());
 526                 assert!(NodeFeatures::known().supports_payment_secret());
 527
 528                 assert!(InitFeatures::known().supports_basic_mpp());
 529                 assert!(NodeFeatures::known().supports_basic_mpp());
 530
 531                 let mut init_features = InitFeatures::known();
 532                 assert!(init_features.initial_routing_sync());
 533                 init_features.clear_initial_routing_sync();
 534                 assert!(!init_features.initial_routing_sync());
 535         }
 536
 537         #[test]
 538         fn sanity_test_unknown_bits() {
 539                 let mut features = ChannelFeatures::empty();
 540                 assert!(!features.requires_unknown_bits());
 541                 assert!(!features.supports_unknown_bits());
 542
 543                 features.set_required_unknown_bits();
 544                 assert!(features.requires_unknown_bits());
 545                 assert!(features.supports_unknown_bits());
 546
 547                 features.clear_unknown_bits();
 548                 assert!(!features.requires_unknown_bits());
 549                 assert!(!features.supports_unknown_bits());
 550
 551                 features.set_optional_unknown_bits();
 552                 assert!(!features.requires_unknown_bits());
 553                 assert!(features.supports_unknown_bits());
 554         }
 555
 556         #[test]
 557         fn convert_to_context_with_relevant_flags() {
 558                 let init_features = InitFeatures::known().clear_upfront_shutdown_script();
 559                 assert!(init_features.initial_routing_sync());
 560                 assert!(!init_features.supports_upfront_shutdown_script());
 561
 562                 let node_features: NodeFeatures = init_features.to_context();
 563                 {
 564                         // Check that the flags are as expected:
 565                         // - option_data_loss_protect
 566                         // - var_onion_optin | payment_secret
 567                         // - basic_mpp
 568                         assert_eq!(node_features.flags.len(), 3);
 569                         assert_eq!(node_features.flags[0], 0b00000010);
 570                         assert_eq!(node_features.flags[1], 0b10000010);
 571                         assert_eq!(node_features.flags[2], 0b00000010);
 572                 }
 573
 574                 // Check that cleared flags are kept blank when converting back:
 575                 // - initial_routing_sync was not applicable to NodeContext
 576                 // - upfront_shutdown_script was cleared before converting
 577                 let features: InitFeatures = node_features.to_context_internal();
 578                 assert!(!features.initial_routing_sync());
 579                 assert!(!features.supports_upfront_shutdown_script());
 580         }
 581 }