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

   1 // This file is Copyright its original authors, visible in version control
   2 // history.
   3 //
   4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
   5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
   7 // You may not use this file except in accordance with one or both of these
   8 // licenses.
   9
  10 //! Feature flag definitions for the Lightning protocol according to [BOLT #9].
  11 //!
  12 //! Lightning nodes advertise a supported set of operation through feature flags. Features are
  13 //! applicable for a specific context as indicated in some [messages]. [`Features`] encapsulates
  14 //! behavior for specifying and checking feature flags for a particular context. Each feature is
  15 //! defined internally by a trait specifying the corresponding flags (i.e., even and odd bits). A
  16 //! [`Context`] is used to parameterize [`Features`] and defines which features it can support.
  17 //!
  18 //! Whether a feature is considered "known" or "unknown" is relative to the implementation, whereas
  19 //! the term "supports" is used in reference to a particular set of [`Features`]. That is, a node
  20 //! supports a feature if it advertises the feature (as either required or optional) to its peers.
  21 //! And the implementation can interpret a feature if the feature is known to it.
  22 //!
  23 //! [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
  24 //! [messages]: ../msgs/index.html
  25 //! [`Features`]: struct.Features.html
  26 //! [`Context`]: sealed/trait.Context.html
  27
  28 use std::{cmp, fmt};
  29 use std::marker::PhantomData;
  30
  31 use ln::msgs::DecodeError;
  32 use util::ser::{Readable, Writeable, Writer};
  33
  34 mod sealed {
  35         use ln::features::Features;
  36
  37         /// The context in which [`Features`] are applicable. Defines which features are required and
  38         /// which are optional for the context.
  39         ///
  40         /// [`Features`]: ../struct.Features.html
  41         pub trait Context {
  42                 /// Features that are known to the implementation, where a required feature is indicated by
  43                 /// its even bit and an optional feature is indicated by its odd bit.
  44                 const KNOWN_FEATURE_FLAGS: &'static [u8];
  45
  46                 /// Bitmask for selecting features that are known to the implementation, regardless of
  47                 /// whether each feature is required or optional.
  48                 const KNOWN_FEATURE_MASK: &'static [u8];
  49         }
  50
  51         /// Defines a [`Context`] by stating which features it requires and which are optional. Features
  52         /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
  53         /// feature identifiers.
  54         ///
  55         /// [`Context`]: trait.Context.html
  56         macro_rules! define_context {
  57                 ($context: ident {
  58                         required_features: [$( $( $required_feature: ident )|*, )*],
  59                         optional_features: [$( $( $optional_feature: ident )|*, )*],
  60                 }) => {
  61                         pub struct $context {}
  62
  63                         impl Context for $context {
  64                                 const KNOWN_FEATURE_FLAGS: &'static [u8] = &[
  65                                         // For each byte, use bitwise-OR to compute the applicable flags for known
  66                                         // required features `r_i` and optional features `o_j` for all `i` and `j` such
  67                                         // that the following slice is formed:
  68                                         //
  69                                         // [
  70                                         //  `r_0` | `r_1` | ... | `o_0` | `o_1` | ...,
  71                                         //  ...,
  72                                         // ]
  73                                         $(
  74                                                 0b00_00_00_00 $(|
  75                                                         <Self as $required_feature>::REQUIRED_MASK)*
  76                                                 $(|
  77                                                         <Self as $optional_feature>::OPTIONAL_MASK)*,
  78                                         )*
  79                                 ];
  80
  81                                 const KNOWN_FEATURE_MASK: &'static [u8] = &[
  82                                         // Similar as above, but set both flags for each feature regardless of whether
  83                                         // the feature is required or optional.
  84                                         $(
  85                                                 0b00_00_00_00 $(|
  86                                                         <Self as $required_feature>::REQUIRED_MASK |
  87                                                         <Self as $required_feature>::OPTIONAL_MASK)*
  88                                                 $(|
  89                                                         <Self as $optional_feature>::REQUIRED_MASK |
  90                                                         <Self as $optional_feature>::OPTIONAL_MASK)*,
  91                                         )*
  92                                 ];
  93                         }
  94                 };
  95         }
  96
  97         define_context!(InitContext {
  98                 required_features: [
  99                         // Byte 0
 100                         ,
 101                         // Byte 1
 102                         StaticRemoteKey,
 103                         // Byte 2
 104                         ,
 105                         // Byte 3
 106                         ,
 107                 ],
 108                 optional_features: [
 109                         // Byte 0
 110                         DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
 111                         // Byte 1
 112                         VariableLengthOnion | PaymentSecret,
 113                         // Byte 2
 114                         BasicMPP,
 115                         // Byte 3
 116                         ShutdownAnySegwit,
 117                 ],
 118         });
 119         define_context!(NodeContext {
 120                 required_features: [
 121                         // Byte 0
 122                         ,
 123                         // Byte 1
 124                         StaticRemoteKey,
 125                         // Byte 2
 126                         ,
 127                         // Byte 3
 128                         ,
 129                 ],
 130                 optional_features: [
 131                         // Byte 0
 132                         DataLossProtect | UpfrontShutdownScript | GossipQueries,
 133                         // Byte 1
 134                         VariableLengthOnion | PaymentSecret,
 135                         // Byte 2
 136                         BasicMPP,
 137                         // Byte 3
 138                         ShutdownAnySegwit,
 139                 ],
 140         });
 141         define_context!(ChannelContext {
 142                 required_features: [],
 143                 optional_features: [],
 144         });
 145         define_context!(InvoiceContext {
 146                 required_features: [,,,],
 147                 optional_features: [
 148                         // Byte 0
 149                         ,
 150                         // Byte 1
 151                         VariableLengthOnion | PaymentSecret,
 152                         // Byte 2
 153                         BasicMPP,
 154                 ],
 155         });
 156
 157         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 158         /// useful for manipulating feature flags.
 159         ///
 160         /// [`Context`]: trait.Context.html
 161         macro_rules! define_feature {
 162                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 163                  $required_setter: ident) => {
 164                         #[doc = $doc]
 165                         ///
 166                         /// See [BOLT #9] for details.
 167                         ///
 168                         /// [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
 169                         pub trait $feature: Context {
 170                                 /// The bit used to signify that the feature is required.
 171                                 const EVEN_BIT: usize = $odd_bit - 1;
 172
 173                                 /// The bit used to signify that the feature is optional.
 174                                 const ODD_BIT: usize = $odd_bit;
 175
 176                                 /// Assertion that [`EVEN_BIT`] is actually even.
 177                                 ///
 178                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 179                                 const ASSERT_EVEN_BIT_PARITY: usize;
 180
 181                                 /// Assertion that [`ODD_BIT`] is actually odd.
 182                                 ///
 183                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 184                                 const ASSERT_ODD_BIT_PARITY: usize;
 185
 186                                 /// The byte where the feature is set.
 187                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 188
 189                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 190                                 ///
 191                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 192                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 193
 194                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 195                                 ///
 196                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 197                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 198
 199                                 /// Returns whether the feature is required by the given flags.
 200                                 #[inline]
 201                                 fn requires_feature(flags: &Vec<u8>) -> bool {
 202                                         flags.len() > Self::BYTE_OFFSET &&
 203                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
 204                                 }
 205
 206                                 /// Returns whether the feature is supported by the given flags.
 207                                 #[inline]
 208                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 209                                         flags.len() > Self::BYTE_OFFSET &&
 210                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 211                                 }
 212
 213                                 /// Sets the feature's required (even) bit in the given flags.
 214                                 #[inline]
 215                                 fn set_required_bit(flags: &mut Vec<u8>) {
 216                                         if flags.len() <= Self::BYTE_OFFSET {
 217                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 218                                         }
 219
 220                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
 221                                 }
 222
 223                                 /// Sets the feature's optional (odd) bit in the given flags.
 224                                 #[inline]
 225                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 226                                         if flags.len() <= Self::BYTE_OFFSET {
 227                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 228                                         }
 229
 230                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 231                                 }
 232
 233                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 234                                 /// flags.
 235                                 #[inline]
 236                                 fn clear_bits(flags: &mut Vec<u8>) {
 237                                         if flags.len() > Self::BYTE_OFFSET {
 238                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 239                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 240                                         }
 241
 242                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 243                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 244                                         flags.resize(size, 0u8);
 245                                 }
 246                         }
 247
 248                         impl <T: $feature> Features<T> {
 249                                 /// Set this feature as optional.
 250                                 pub fn $optional_setter(mut self) -> Self {
 251                                         <T as $feature>::set_optional_bit(&mut self.flags);
 252                                         self
 253                                 }
 254
 255                                 /// Set this feature as required.
 256                                 pub fn $required_setter(mut self) -> Self {
 257                                         <T as $feature>::set_required_bit(&mut self.flags);
 258                                         self
 259                                 }
 260                         }
 261
 262                         $(
 263                                 impl $feature for $context {
 264                                         // EVEN_BIT % 2 == 0
 265                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 266
 267                                         // ODD_BIT % 2 == 1
 268                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 269                                 }
 270                         )*
 271
 272                 }
 273         }
 274
 275         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 276                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 277                 set_data_loss_protect_required);
 278         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 279         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 280                 set_initial_routing_sync_optional, set_initial_routing_sync_required);
 281         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 282                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 283                 set_upfront_shutdown_script_required);
 284         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 285                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required);
 286         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
 287                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 288                 set_variable_length_onion_required);
 289         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext],
 290                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 291                 set_static_remote_key_required);
 292         define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
 293                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required);
 294         define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext],
 295                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required);
 296         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 297                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 298                 set_shutdown_any_segwit_required);
 299
 300         #[cfg(test)]
 301         define_context!(TestingContext {
 302                 required_features: [
 303                         // Byte 0
 304                         ,
 305                         // Byte 1
 306                         ,
 307                         // Byte 2
 308                         UnknownFeature,
 309                 ],
 310                 optional_features: [
 311                         // Byte 0
 312                         ,
 313                         // Byte 1
 314                         ,
 315                         // Byte 2
 316                         ,
 317                 ],
 318         });
 319
 320         #[cfg(test)]
 321         define_feature!(23, UnknownFeature, [TestingContext],
 322                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 323                 set_unknown_feature_required);
 324 }
 325
 326 /// Tracks the set of features which a node implements, templated by the context in which it
 327 /// appears.
 328 ///
 329 /// (C-not exported) as we map the concrete feature types below directly instead
 330 pub struct Features<T: sealed::Context> {
 331         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 332         flags: Vec<u8>,
 333         mark: PhantomData<T>,
 334 }
 335
 336 impl<T: sealed::Context> Clone for Features<T> {
 337         fn clone(&self) -> Self {
 338                 Self {
 339                         flags: self.flags.clone(),
 340                         mark: PhantomData,
 341                 }
 342         }
 343 }
 344 impl<T: sealed::Context> PartialEq for Features<T> {
 345         fn eq(&self, o: &Self) -> bool {
 346                 self.flags.eq(&o.flags)
 347         }
 348 }
 349 impl<T: sealed::Context> fmt::Debug for Features<T> {
 350         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 351                 self.flags.fmt(fmt)
 352         }
 353 }
 354
 355 /// Features used within an `init` message.
 356 pub type InitFeatures = Features<sealed::InitContext>;
 357 /// Features used within a `node_announcement` message.
 358 pub type NodeFeatures = Features<sealed::NodeContext>;
 359 /// Features used within a `channel_announcement` message.
 360 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 361 /// Features used within an invoice.
 362 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
 363
 364 impl InitFeatures {
 365         /// Writes all features present up to, and including, 13.
 366         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
 367                 let len = cmp::min(2, self.flags.len());
 368                 w.size_hint(len + 2);
 369                 (len as u16).write(w)?;
 370                 for i in (0..len).rev() {
 371                         if i == 0 {
 372                                 self.flags[i].write(w)?;
 373                         } else {
 374                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 375                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 376                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 377                         }
 378                 }
 379                 Ok(())
 380         }
 381
 382         /// or's another InitFeatures into this one.
 383         pub(crate) fn or(mut self, o: InitFeatures) -> InitFeatures {
 384                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
 385                 self.flags.resize(total_feature_len, 0u8);
 386                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
 387                         *byte |= *o_byte;
 388                 }
 389                 self
 390         }
 391
 392         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 393         /// are included in the result.
 394         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 395                 self.to_context_internal()
 396         }
 397 }
 398
 399 impl InvoiceFeatures {
 400         /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
 401         /// context `C` are included in the result.
 402         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 403                 self.to_context_internal()
 404         }
 405 }
 406
 407 impl<T: sealed::Context> Features<T> {
 408         /// Create a blank Features with no features set
 409         pub fn empty() -> Self {
 410                 Features {
 411                         flags: Vec::new(),
 412                         mark: PhantomData,
 413                 }
 414         }
 415
 416         /// Creates features known by the implementation as defined by [`T::KNOWN_FEATURE_FLAGS`].
 417         ///
 418         /// [`T::KNOWN_FEATURE_FLAGS`]: sealed/trait.Context.html#associatedconstant.KNOWN_FEATURE_FLAGS
 419         pub fn known() -> Self {
 420                 Self {
 421                         flags: T::KNOWN_FEATURE_FLAGS.to_vec(),
 422                         mark: PhantomData,
 423                 }
 424         }
 425
 426         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 427         /// included in the result.
 428         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 429                 let byte_count = C::KNOWN_FEATURE_MASK.len();
 430                 let mut flags = Vec::new();
 431                 for (i, byte) in self.flags.iter().enumerate() {
 432                         if i < byte_count {
 433                                 let known_source_features = T::KNOWN_FEATURE_MASK[i];
 434                                 let known_target_features = C::KNOWN_FEATURE_MASK[i];
 435                                 flags.push(byte & known_source_features & known_target_features);
 436                         }
 437                 }
 438                 Features::<C> { flags, mark: PhantomData, }
 439         }
 440
 441         #[cfg(test)]
 442         /// Create a Features given a set of flags, in LE.
 443         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 444                 Features {
 445                         flags,
 446                         mark: PhantomData,
 447                 }
 448         }
 449
 450         #[cfg(test)]
 451         /// Gets the underlying flags set, in LE.
 452         pub fn le_flags(&self) -> &Vec<u8> {
 453                 &self.flags
 454         }
 455
 456         pub(crate) fn requires_unknown_bits(&self) -> bool {
 457                 // Bitwise AND-ing with all even bits set except for known features will select required
 458                 // unknown features.
 459                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 460                 self.flags.iter().enumerate().any(|(i, &byte)| {
 461                         let required_features = 0b01_01_01_01;
 462                         let unknown_features = if i < byte_count {
 463                                 !T::KNOWN_FEATURE_MASK[i]
 464                         } else {
 465                                 0b11_11_11_11
 466                         };
 467                         (byte & (required_features & unknown_features)) != 0
 468                 })
 469         }
 470
 471         pub(crate) fn supports_unknown_bits(&self) -> bool {
 472                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 473                 // both required and optional unknown features.
 474                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 475                 self.flags.iter().enumerate().any(|(i, &byte)| {
 476                         let unknown_features = if i < byte_count {
 477                                 !T::KNOWN_FEATURE_MASK[i]
 478                         } else {
 479                                 0b11_11_11_11
 480                         };
 481                         (byte & unknown_features) != 0
 482                 })
 483         }
 484
 485         /// The number of bytes required to represent the feature flags present. This does not include
 486         /// the length bytes which are included in the serialized form.
 487         pub(crate) fn byte_count(&self) -> usize {
 488                 self.flags.len()
 489         }
 490
 491         #[cfg(test)]
 492         pub(crate) fn set_required_unknown_bits(&mut self) {
 493                 <sealed::TestingContext as sealed::UnknownFeature>::set_required_bit(&mut self.flags);
 494         }
 495
 496         #[cfg(test)]
 497         pub(crate) fn set_optional_unknown_bits(&mut self) {
 498                 <sealed::TestingContext as sealed::UnknownFeature>::set_optional_bit(&mut self.flags);
 499         }
 500
 501         #[cfg(test)]
 502         pub(crate) fn clear_unknown_bits(&mut self) {
 503                 <sealed::TestingContext as sealed::UnknownFeature>::clear_bits(&mut self.flags);
 504         }
 505 }
 506
 507 impl<T: sealed::DataLossProtect> Features<T> {
 508         #[cfg(test)]
 509         pub(crate) fn requires_data_loss_protect(&self) -> bool {
 510                 <T as sealed::DataLossProtect>::requires_feature(&self.flags)
 511         }
 512         pub(crate) fn supports_data_loss_protect(&self) -> bool {
 513                 <T as sealed::DataLossProtect>::supports_feature(&self.flags)
 514         }
 515 }
 516
 517 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 518         #[cfg(test)]
 519         pub(crate) fn requires_upfront_shutdown_script(&self) -> bool {
 520                 <T as sealed::UpfrontShutdownScript>::requires_feature(&self.flags)
 521         }
 522         pub(crate) fn supports_upfront_shutdown_script(&self) -> bool {
 523                 <T as sealed::UpfrontShutdownScript>::supports_feature(&self.flags)
 524         }
 525         #[cfg(test)]
 526         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 527                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 528                 self
 529         }
 530 }
 531
 532
 533 impl<T: sealed::GossipQueries> Features<T> {
 534         #[cfg(test)]
 535         pub(crate) fn requires_gossip_queries(&self) -> bool {
 536                 <T as sealed::GossipQueries>::requires_feature(&self.flags)
 537         }
 538         pub(crate) fn supports_gossip_queries(&self) -> bool {
 539                 <T as sealed::GossipQueries>::supports_feature(&self.flags)
 540         }
 541         #[cfg(test)]
 542         pub(crate) fn clear_gossip_queries(mut self) -> Self {
 543                 <T as sealed::GossipQueries>::clear_bits(&mut self.flags);
 544                 self
 545         }
 546 }
 547
 548 impl<T: sealed::VariableLengthOnion> Features<T> {
 549         #[cfg(test)]
 550         pub(crate) fn requires_variable_length_onion(&self) -> bool {
 551                 <T as sealed::VariableLengthOnion>::requires_feature(&self.flags)
 552         }
 553         pub(crate) fn supports_variable_length_onion(&self) -> bool {
 554                 <T as sealed::VariableLengthOnion>::supports_feature(&self.flags)
 555         }
 556 }
 557
 558 impl<T: sealed::StaticRemoteKey> Features<T> {
 559         pub(crate) fn supports_static_remote_key(&self) -> bool {
 560                 <T as sealed::StaticRemoteKey>::supports_feature(&self.flags)
 561         }
 562         #[cfg(test)]
 563         pub(crate) fn requires_static_remote_key(&self) -> bool {
 564                 <T as sealed::StaticRemoteKey>::requires_feature(&self.flags)
 565         }
 566 }
 567
 568 impl<T: sealed::InitialRoutingSync> Features<T> {
 569         pub(crate) fn initial_routing_sync(&self) -> bool {
 570                 <T as sealed::InitialRoutingSync>::supports_feature(&self.flags)
 571         }
 572         // We are no longer setting initial_routing_sync now that gossip_queries
 573         // is enabled. This feature is ignored by a peer when gossip_queries has
 574         // been negotiated.
 575         #[cfg(test)]
 576         pub(crate) fn clear_initial_routing_sync(&mut self) {
 577                 <T as sealed::InitialRoutingSync>::clear_bits(&mut self.flags)
 578         }
 579 }
 580
 581 impl<T: sealed::PaymentSecret> Features<T> {
 582         #[cfg(test)]
 583         pub(crate) fn requires_payment_secret(&self) -> bool {
 584                 <T as sealed::PaymentSecret>::requires_feature(&self.flags)
 585         }
 586         // Note that we never need to test this since what really matters is the invoice - iff the
 587         // invoice provides a payment_secret, we assume that we can use it (ie that the recipient
 588         // supports payment_secret).
 589         #[allow(dead_code)]
 590         pub(crate) fn supports_payment_secret(&self) -> bool {
 591                 <T as sealed::PaymentSecret>::supports_feature(&self.flags)
 592         }
 593 }
 594
 595 impl<T: sealed::BasicMPP> Features<T> {
 596         #[cfg(test)]
 597         pub(crate) fn requires_basic_mpp(&self) -> bool {
 598                 <T as sealed::BasicMPP>::requires_feature(&self.flags)
 599         }
 600         // We currently never test for this since we don't actually *generate* multipath routes.
 601         pub(crate) fn supports_basic_mpp(&self) -> bool {
 602                 <T as sealed::BasicMPP>::supports_feature(&self.flags)
 603         }
 604 }
 605
 606 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 607         pub(crate) fn supports_shutdown_anysegwit(&self) -> bool {
 608                 <T as sealed::ShutdownAnySegwit>::supports_feature(&self.flags)
 609         }
 610         #[cfg(test)]
 611         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 612                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 613                 self
 614         }
 615 }
 616
 617 impl<T: sealed::Context> Writeable for Features<T> {
 618         fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
 619                 w.size_hint(self.flags.len() + 2);
 620                 (self.flags.len() as u16).write(w)?;
 621                 for f in self.flags.iter().rev() { // Swap back to big-endian
 622                         f.write(w)?;
 623                 }
 624                 Ok(())
 625         }
 626 }
 627
 628 impl<T: sealed::Context> Readable for Features<T> {
 629         fn read<R: ::std::io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 630                 let mut flags: Vec<u8> = Readable::read(r)?;
 631                 flags.reverse(); // Swap to little-endian
 632                 Ok(Self {
 633                         flags,
 634                         mark: PhantomData,
 635                 })
 636         }
 637 }
 638
 639 #[cfg(test)]
 640 mod tests {
 641         use super::{ChannelFeatures, InitFeatures, InvoiceFeatures, NodeFeatures};
 642
 643         #[test]
 644         fn sanity_test_known_features() {
 645                 assert!(!ChannelFeatures::known().requires_unknown_bits());
 646                 assert!(!ChannelFeatures::known().supports_unknown_bits());
 647                 assert!(!InitFeatures::known().requires_unknown_bits());
 648                 assert!(!InitFeatures::known().supports_unknown_bits());
 649                 assert!(!NodeFeatures::known().requires_unknown_bits());
 650                 assert!(!NodeFeatures::known().supports_unknown_bits());
 651
 652                 assert!(InitFeatures::known().supports_upfront_shutdown_script());
 653                 assert!(NodeFeatures::known().supports_upfront_shutdown_script());
 654                 assert!(!InitFeatures::known().requires_upfront_shutdown_script());
 655                 assert!(!NodeFeatures::known().requires_upfront_shutdown_script());
 656
 657                 assert!(InitFeatures::known().supports_gossip_queries());
 658                 assert!(NodeFeatures::known().supports_gossip_queries());
 659                 assert!(!InitFeatures::known().requires_gossip_queries());
 660                 assert!(!NodeFeatures::known().requires_gossip_queries());
 661
 662                 assert!(InitFeatures::known().supports_data_loss_protect());
 663                 assert!(NodeFeatures::known().supports_data_loss_protect());
 664                 assert!(!InitFeatures::known().requires_data_loss_protect());
 665                 assert!(!NodeFeatures::known().requires_data_loss_protect());
 666
 667                 assert!(InitFeatures::known().supports_variable_length_onion());
 668                 assert!(NodeFeatures::known().supports_variable_length_onion());
 669                 assert!(!InitFeatures::known().requires_variable_length_onion());
 670                 assert!(!NodeFeatures::known().requires_variable_length_onion());
 671
 672                 assert!(InitFeatures::known().supports_static_remote_key());
 673                 assert!(NodeFeatures::known().supports_static_remote_key());
 674                 assert!(InitFeatures::known().requires_static_remote_key());
 675                 assert!(NodeFeatures::known().requires_static_remote_key());
 676
 677                 assert!(InitFeatures::known().supports_payment_secret());
 678                 assert!(NodeFeatures::known().supports_payment_secret());
 679                 assert!(!InitFeatures::known().requires_payment_secret());
 680                 assert!(!NodeFeatures::known().requires_payment_secret());
 681
 682                 assert!(InitFeatures::known().supports_basic_mpp());
 683                 assert!(NodeFeatures::known().supports_basic_mpp());
 684                 assert!(!InitFeatures::known().requires_basic_mpp());
 685                 assert!(!NodeFeatures::known().requires_basic_mpp());
 686
 687                 assert!(InitFeatures::known().supports_shutdown_anysegwit());
 688                 assert!(NodeFeatures::known().supports_shutdown_anysegwit());
 689
 690                 let mut init_features = InitFeatures::known();
 691                 assert!(init_features.initial_routing_sync());
 692                 init_features.clear_initial_routing_sync();
 693                 assert!(!init_features.initial_routing_sync());
 694         }
 695
 696         #[test]
 697         fn sanity_test_unknown_bits() {
 698                 let mut features = ChannelFeatures::empty();
 699                 assert!(!features.requires_unknown_bits());
 700                 assert!(!features.supports_unknown_bits());
 701
 702                 features.set_required_unknown_bits();
 703                 assert!(features.requires_unknown_bits());
 704                 assert!(features.supports_unknown_bits());
 705
 706                 features.clear_unknown_bits();
 707                 assert!(!features.requires_unknown_bits());
 708                 assert!(!features.supports_unknown_bits());
 709
 710                 features.set_optional_unknown_bits();
 711                 assert!(!features.requires_unknown_bits());
 712                 assert!(features.supports_unknown_bits());
 713         }
 714
 715         #[test]
 716         fn convert_to_context_with_relevant_flags() {
 717                 let init_features = InitFeatures::known().clear_upfront_shutdown_script().clear_gossip_queries();
 718                 assert!(init_features.initial_routing_sync());
 719                 assert!(!init_features.supports_upfront_shutdown_script());
 720                 assert!(!init_features.supports_gossip_queries());
 721
 722                 let node_features: NodeFeatures = init_features.to_context();
 723                 {
 724                         // Check that the flags are as expected:
 725                         // - option_data_loss_protect
 726                         // - var_onion_optin | static_remote_key (req) | payment_secret
 727                         // - basic_mpp
 728                         // - opt_shutdown_anysegwit
 729                         assert_eq!(node_features.flags.len(), 4);
 730                         assert_eq!(node_features.flags[0], 0b00000010);
 731                         assert_eq!(node_features.flags[1], 0b10010010);
 732                         assert_eq!(node_features.flags[2], 0b00000010);
 733                         assert_eq!(node_features.flags[3], 0b00001000);
 734                 }
 735
 736                 // Check that cleared flags are kept blank when converting back:
 737                 // - initial_routing_sync was not applicable to NodeContext
 738                 // - upfront_shutdown_script was cleared before converting
 739                 // - gossip_queries was cleared before converting
 740                 let features: InitFeatures = node_features.to_context_internal();
 741                 assert!(!features.initial_routing_sync());
 742                 assert!(!features.supports_upfront_shutdown_script());
 743                 assert!(!init_features.supports_gossip_queries());
 744         }
 745
 746         #[test]
 747         fn set_feature_bits() {
 748                 let features = InvoiceFeatures::empty()
 749                         .set_basic_mpp_optional()
 750                         .set_payment_secret_required();
 751                 assert!(features.supports_basic_mpp());
 752                 assert!(!features.requires_basic_mpp());
 753                 assert!(features.requires_payment_secret());
 754                 assert!(features.supports_payment_secret());
 755         }
 756 }