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