_ 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 prelude::*;
  26 use core::{cmp, fmt};
  27 use core::marker::PhantomData;
  28
  29 use bitcoin::bech32;
  30 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
  31 use ln::msgs::DecodeError;
  32 use util::ser::{Readable, Writeable, Writer};
  33
  34 mod sealed {
  35         use prelude::*;
  36         use ln::features::Features;
  37
  38         /// The context in which [`Features`] are applicable. Defines which features are required and
  39         /// which are optional for the context.
  40         pub trait Context {
  41                 /// Features that are known to the implementation, where a required feature is indicated by
  42                 /// its even bit and an optional feature is indicated by its odd bit.
  43                 const KNOWN_FEATURE_FLAGS: &'static [u8];
  44
  45                 /// Bitmask for selecting features that are known to the implementation, regardless of
  46                 /// whether each feature is required or optional.
  47                 const KNOWN_FEATURE_MASK: &'static [u8];
  48         }
  49
  50         /// Defines a [`Context`] by stating which features it requires and which are optional. Features
  51         /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
  52         /// feature identifiers.
  53         macro_rules! define_context {
  54                 ($context: ident {
  55                         required_features: [$( $( $required_feature: ident )|*, )*],
  56                         optional_features: [$( $( $optional_feature: ident )|*, )*],
  57                 }) => {
  58                         #[derive(Eq, PartialEq)]
  59                         pub struct $context {}
  60
  61                         impl Context for $context {
  62                                 const KNOWN_FEATURE_FLAGS: &'static [u8] = &[
  63                                         // For each byte, use bitwise-OR to compute the applicable flags for known
  64                                         // required features `r_i` and optional features `o_j` for all `i` and `j` such
  65                                         // that the following slice is formed:
  66                                         //
  67                                         // [
  68                                         //  `r_0` | `r_1` | ... | `o_0` | `o_1` | ...,
  69                                         //  ...,
  70                                         // ]
  71                                         $(
  72                                                 0b00_00_00_00 $(|
  73                                                         <Self as $required_feature>::REQUIRED_MASK)*
  74                                                 $(|
  75                                                         <Self as $optional_feature>::OPTIONAL_MASK)*,
  76                                         )*
  77                                 ];
  78
  79                                 const KNOWN_FEATURE_MASK: &'static [u8] = &[
  80                                         // Similar as above, but set both flags for each feature regardless of whether
  81                                         // the feature is required or optional.
  82                                         $(
  83                                                 0b00_00_00_00 $(|
  84                                                         <Self as $required_feature>::REQUIRED_MASK |
  85                                                         <Self as $required_feature>::OPTIONAL_MASK)*
  86                                                 $(|
  87                                                         <Self as $optional_feature>::REQUIRED_MASK |
  88                                                         <Self as $optional_feature>::OPTIONAL_MASK)*,
  89                                         )*
  90                                 ];
  91                         }
  92                 };
  93         }
  94
  95         define_context!(InitContext {
  96                 required_features: [
  97                         // Byte 0
  98                         ,
  99                         // Byte 1
 100                         VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 101                         // Byte 2
 102                         ,
 103                         // Byte 3
 104                         ,
 105                 ],
 106                 optional_features: [
 107                         // Byte 0
 108                         DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
 109                         // Byte 1
 110                         ,
 111                         // Byte 2
 112                         BasicMPP,
 113                         // Byte 3
 114                         ShutdownAnySegwit,
 115                 ],
 116         });
 117         define_context!(NodeContext {
 118                 required_features: [
 119                         // Byte 0
 120                         ,
 121                         // Byte 1
 122                         VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 123                         // Byte 2
 124                         ,
 125                         // Byte 3
 126                         ,
 127                 ],
 128                 optional_features: [
 129                         // Byte 0
 130                         DataLossProtect | UpfrontShutdownScript | GossipQueries,
 131                         // Byte 1
 132                         ,
 133                         // Byte 2
 134                         BasicMPP,
 135                         // Byte 3
 136                         ShutdownAnySegwit,
 137                 ],
 138         });
 139         define_context!(ChannelContext {
 140                 required_features: [],
 141                 optional_features: [],
 142         });
 143         define_context!(InvoiceContext {
 144                 required_features: [
 145                         // Byte 0
 146                         ,
 147                         // Byte 1
 148                         VariableLengthOnion | PaymentSecret,
 149                         // Byte 2
 150                         ,
 151                 ],
 152                 optional_features: [
 153                         // Byte 0
 154                         ,
 155                         // Byte 1
 156                         ,
 157                         // Byte 2
 158                         BasicMPP,
 159                 ],
 160         });
 161
 162         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 163         /// useful for manipulating feature flags.
 164         macro_rules! define_feature {
 165                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 166                  $required_setter: ident) => {
 167                         #[doc = $doc]
 168                         ///
 169                         /// See [BOLT #9] for details.
 170                         ///
 171                         /// [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
 172                         pub trait $feature: Context {
 173                                 /// The bit used to signify that the feature is required.
 174                                 const EVEN_BIT: usize = $odd_bit - 1;
 175
 176                                 /// The bit used to signify that the feature is optional.
 177                                 const ODD_BIT: usize = $odd_bit;
 178
 179                                 /// Assertion that [`EVEN_BIT`] is actually even.
 180                                 ///
 181                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 182                                 const ASSERT_EVEN_BIT_PARITY: usize;
 183
 184                                 /// Assertion that [`ODD_BIT`] is actually odd.
 185                                 ///
 186                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 187                                 const ASSERT_ODD_BIT_PARITY: usize;
 188
 189                                 /// The byte where the feature is set.
 190                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 191
 192                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 193                                 ///
 194                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 195                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 196
 197                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 198                                 ///
 199                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 200                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 201
 202                                 /// Returns whether the feature is required by the given flags.
 203                                 #[inline]
 204                                 fn requires_feature(flags: &Vec<u8>) -> bool {
 205                                         flags.len() > Self::BYTE_OFFSET &&
 206                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
 207                                 }
 208
 209                                 /// Returns whether the feature is supported by the given flags.
 210                                 #[inline]
 211                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 212                                         flags.len() > Self::BYTE_OFFSET &&
 213                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 214                                 }
 215
 216                                 /// Sets the feature's required (even) bit in the given flags.
 217                                 #[inline]
 218                                 fn set_required_bit(flags: &mut Vec<u8>) {
 219                                         if flags.len() <= Self::BYTE_OFFSET {
 220                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 221                                         }
 222
 223                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
 224                                 }
 225
 226                                 /// Sets the feature's optional (odd) bit in the given flags.
 227                                 #[inline]
 228                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 229                                         if flags.len() <= Self::BYTE_OFFSET {
 230                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 231                                         }
 232
 233                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 234                                 }
 235
 236                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 237                                 /// flags.
 238                                 #[inline]
 239                                 fn clear_bits(flags: &mut Vec<u8>) {
 240                                         if flags.len() > Self::BYTE_OFFSET {
 241                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 242                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 243                                         }
 244
 245                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 246                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 247                                         flags.resize(size, 0u8);
 248                                 }
 249                         }
 250
 251                         impl <T: $feature> Features<T> {
 252                                 /// Set this feature as optional.
 253                                 pub fn $optional_setter(mut self) -> Self {
 254                                         <T as $feature>::set_optional_bit(&mut self.flags);
 255                                         self
 256                                 }
 257
 258                                 /// Set this feature as required.
 259                                 pub fn $required_setter(mut self) -> Self {
 260                                         <T as $feature>::set_required_bit(&mut self.flags);
 261                                         self
 262                                 }
 263                         }
 264
 265                         $(
 266                                 impl $feature for $context {
 267                                         // EVEN_BIT % 2 == 0
 268                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 269
 270                                         // ODD_BIT % 2 == 1
 271                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 272                                 }
 273                         )*
 274
 275                 }
 276         }
 277
 278         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 279                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 280                 set_data_loss_protect_required);
 281         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 282         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 283                 set_initial_routing_sync_optional, set_initial_routing_sync_required);
 284         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 285                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 286                 set_upfront_shutdown_script_required);
 287         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 288                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required);
 289         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
 290                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 291                 set_variable_length_onion_required);
 292         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext],
 293                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 294                 set_static_remote_key_required);
 295         define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
 296                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required);
 297         define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext],
 298                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required);
 299         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 300                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 301                 set_shutdown_any_segwit_required);
 302
 303         #[cfg(test)]
 304         define_context!(TestingContext {
 305                 required_features: [
 306                         // Byte 0
 307                         ,
 308                         // Byte 1
 309                         ,
 310                         // Byte 2
 311                         UnknownFeature,
 312                 ],
 313                 optional_features: [
 314                         // Byte 0
 315                         ,
 316                         // Byte 1
 317                         ,
 318                         // Byte 2
 319                         ,
 320                 ],
 321         });
 322
 323         #[cfg(test)]
 324         define_feature!(23, UnknownFeature, [TestingContext],
 325                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 326                 set_unknown_feature_required);
 327 }
 328
 329 /// Tracks the set of features which a node implements, templated by the context in which it
 330 /// appears.
 331 ///
 332 /// (C-not exported) as we map the concrete feature types below directly instead
 333 #[derive(Eq)]
 334 pub struct Features<T: sealed::Context> {
 335         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 336         flags: Vec<u8>,
 337         mark: PhantomData<T>,
 338 }
 339
 340 impl<T: sealed::Context> Clone for Features<T> {
 341         fn clone(&self) -> Self {
 342                 Self {
 343                         flags: self.flags.clone(),
 344                         mark: PhantomData,
 345                 }
 346         }
 347 }
 348 impl<T: sealed::Context> PartialEq for Features<T> {
 349         fn eq(&self, o: &Self) -> bool {
 350                 self.flags.eq(&o.flags)
 351         }
 352 }
 353 impl<T: sealed::Context> fmt::Debug for Features<T> {
 354         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 355                 self.flags.fmt(fmt)
 356         }
 357 }
 358
 359 /// Features used within an `init` message.
 360 pub type InitFeatures = Features<sealed::InitContext>;
 361 /// Features used within a `node_announcement` message.
 362 pub type NodeFeatures = Features<sealed::NodeContext>;
 363 /// Features used within a `channel_announcement` message.
 364 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 365 /// Features used within an invoice.
 366 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
 367
 368 impl InitFeatures {
 369         /// Writes all features present up to, and including, 13.
 370         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
 371                 let len = cmp::min(2, self.flags.len());
 372                 w.size_hint(len + 2);
 373                 (len as u16).write(w)?;
 374                 for i in (0..len).rev() {
 375                         if i == 0 {
 376                                 self.flags[i].write(w)?;
 377                         } else {
 378                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 379                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 380                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 381                         }
 382                 }
 383                 Ok(())
 384         }
 385
 386         /// or's another InitFeatures into this one.
 387         pub(crate) fn or(mut self, o: InitFeatures) -> InitFeatures {
 388                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
 389                 self.flags.resize(total_feature_len, 0u8);
 390                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
 391                         *byte |= *o_byte;
 392                 }
 393                 self
 394         }
 395
 396         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 397         /// are included in the result.
 398         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 399                 self.to_context_internal()
 400         }
 401 }
 402
 403 impl InvoiceFeatures {
 404         /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
 405         /// context `C` are included in the result.
 406         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 407                 self.to_context_internal()
 408         }
 409 }
 410
 411 impl ToBase32 for InvoiceFeatures {
 412         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 413                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 414                 // minus one before dividing
 415                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 416                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 417                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 418                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 419                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 420                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 421                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 422                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 423                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 424                         if new_u5_idx > 0 {
 425                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 426                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 427                         }
 428                         if new_u5_idx > 1 {
 429                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 430                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 431                         }
 432                 }
 433                 // Trim the highest feature bits.
 434                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 435                         res_u5s.remove(0);
 436                 }
 437                 writer.write(&res_u5s)
 438         }
 439 }
 440
 441 impl Base32Len for InvoiceFeatures {
 442         fn base32_len(&self) -> usize {
 443                 self.to_base32().len()
 444         }
 445 }
 446
 447 impl FromBase32 for InvoiceFeatures {
 448         type Err = bech32::Error;
 449
 450         fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
 451                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 452                 // minus one before dividing
 453                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 454                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 455                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 456                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 457                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 458                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 459                         let chunk_u16 = chunk.to_u8() as u16;
 460                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 461                         if new_byte_idx != length_bytes - 1 {
 462                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 463                         }
 464                 }
 465                 // Trim the highest feature bits.
 466                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 467                         res_bytes.pop();
 468                 }
 469                 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
 470         }
 471 }
 472
 473 impl<T: sealed::Context> Features<T> {
 474         /// Create a blank Features with no features set
 475         pub fn empty() -> Self {
 476                 Features {
 477                         flags: Vec::new(),
 478                         mark: PhantomData,
 479                 }
 480         }
 481
 482         /// Creates a Features with the bits set which are known by the implementation
 483         pub fn known() -> Self {
 484                 Self {
 485                         flags: T::KNOWN_FEATURE_FLAGS.to_vec(),
 486                         mark: PhantomData,
 487                 }
 488         }
 489
 490         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 491         /// included in the result.
 492         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 493                 let byte_count = C::KNOWN_FEATURE_MASK.len();
 494                 let mut flags = Vec::new();
 495                 for (i, byte) in self.flags.iter().enumerate() {
 496                         if i < byte_count {
 497                                 let known_source_features = T::KNOWN_FEATURE_MASK[i];
 498                                 let known_target_features = C::KNOWN_FEATURE_MASK[i];
 499                                 flags.push(byte & known_source_features & known_target_features);
 500                         }
 501                 }
 502                 Features::<C> { flags, mark: PhantomData, }
 503         }
 504
 505         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 506         /// most on-the-wire encodings.
 507         /// (C-not exported) as we don't support export across multiple T
 508         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 509                 Features {
 510                         flags,
 511                         mark: PhantomData,
 512                 }
 513         }
 514
 515         #[cfg(test)]
 516         /// Gets the underlying flags set, in LE.
 517         pub fn le_flags(&self) -> &Vec<u8> {
 518                 &self.flags
 519         }
 520
 521         pub(crate) fn requires_unknown_bits(&self) -> bool {
 522                 // Bitwise AND-ing with all even bits set except for known features will select required
 523                 // unknown features.
 524                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 525                 self.flags.iter().enumerate().any(|(i, &byte)| {
 526                         let required_features = 0b01_01_01_01;
 527                         let unknown_features = if i < byte_count {
 528                                 !T::KNOWN_FEATURE_MASK[i]
 529                         } else {
 530                                 0b11_11_11_11
 531                         };
 532                         (byte & (required_features & unknown_features)) != 0
 533                 })
 534         }
 535
 536         pub(crate) fn supports_unknown_bits(&self) -> bool {
 537                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 538                 // both required and optional unknown features.
 539                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 540                 self.flags.iter().enumerate().any(|(i, &byte)| {
 541                         let unknown_features = if i < byte_count {
 542                                 !T::KNOWN_FEATURE_MASK[i]
 543                         } else {
 544                                 0b11_11_11_11
 545                         };
 546                         (byte & unknown_features) != 0
 547                 })
 548         }
 549
 550         /// The number of bytes required to represent the feature flags present. This does not include
 551         /// the length bytes which are included in the serialized form.
 552         pub(crate) fn byte_count(&self) -> usize {
 553                 self.flags.len()
 554         }
 555
 556         #[cfg(test)]
 557         pub(crate) fn set_required_unknown_bits(&mut self) {
 558                 <sealed::TestingContext as sealed::UnknownFeature>::set_required_bit(&mut self.flags);
 559         }
 560
 561         #[cfg(test)]
 562         pub(crate) fn set_optional_unknown_bits(&mut self) {
 563                 <sealed::TestingContext as sealed::UnknownFeature>::set_optional_bit(&mut self.flags);
 564         }
 565
 566         #[cfg(test)]
 567         pub(crate) fn clear_unknown_bits(&mut self) {
 568                 <sealed::TestingContext as sealed::UnknownFeature>::clear_bits(&mut self.flags);
 569         }
 570 }
 571
 572 impl<T: sealed::DataLossProtect> Features<T> {
 573         #[cfg(test)]
 574         pub(crate) fn requires_data_loss_protect(&self) -> bool {
 575                 <T as sealed::DataLossProtect>::requires_feature(&self.flags)
 576         }
 577         pub(crate) fn supports_data_loss_protect(&self) -> bool {
 578                 <T as sealed::DataLossProtect>::supports_feature(&self.flags)
 579         }
 580 }
 581
 582 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 583         #[cfg(test)]
 584         pub(crate) fn requires_upfront_shutdown_script(&self) -> bool {
 585                 <T as sealed::UpfrontShutdownScript>::requires_feature(&self.flags)
 586         }
 587         pub(crate) fn supports_upfront_shutdown_script(&self) -> bool {
 588                 <T as sealed::UpfrontShutdownScript>::supports_feature(&self.flags)
 589         }
 590         #[cfg(test)]
 591         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 592                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 593                 self
 594         }
 595 }
 596
 597
 598 impl<T: sealed::GossipQueries> Features<T> {
 599         #[cfg(test)]
 600         pub(crate) fn requires_gossip_queries(&self) -> bool {
 601                 <T as sealed::GossipQueries>::requires_feature(&self.flags)
 602         }
 603         pub(crate) fn supports_gossip_queries(&self) -> bool {
 604                 <T as sealed::GossipQueries>::supports_feature(&self.flags)
 605         }
 606         #[cfg(test)]
 607         pub(crate) fn clear_gossip_queries(mut self) -> Self {
 608                 <T as sealed::GossipQueries>::clear_bits(&mut self.flags);
 609                 self
 610         }
 611 }
 612
 613 impl<T: sealed::VariableLengthOnion> Features<T> {
 614         #[cfg(test)]
 615         pub(crate) fn requires_variable_length_onion(&self) -> bool {
 616                 <T as sealed::VariableLengthOnion>::requires_feature(&self.flags)
 617         }
 618         pub(crate) fn supports_variable_length_onion(&self) -> bool {
 619                 <T as sealed::VariableLengthOnion>::supports_feature(&self.flags)
 620         }
 621 }
 622
 623 impl<T: sealed::StaticRemoteKey> Features<T> {
 624         pub(crate) fn supports_static_remote_key(&self) -> bool {
 625                 <T as sealed::StaticRemoteKey>::supports_feature(&self.flags)
 626         }
 627         #[cfg(test)]
 628         pub(crate) fn requires_static_remote_key(&self) -> bool {
 629                 <T as sealed::StaticRemoteKey>::requires_feature(&self.flags)
 630         }
 631 }
 632
 633 impl<T: sealed::InitialRoutingSync> Features<T> {
 634         pub(crate) fn initial_routing_sync(&self) -> bool {
 635                 <T as sealed::InitialRoutingSync>::supports_feature(&self.flags)
 636         }
 637         // We are no longer setting initial_routing_sync now that gossip_queries
 638         // is enabled. This feature is ignored by a peer when gossip_queries has
 639         // been negotiated.
 640         #[cfg(test)]
 641         pub(crate) fn clear_initial_routing_sync(&mut self) {
 642                 <T as sealed::InitialRoutingSync>::clear_bits(&mut self.flags)
 643         }
 644 }
 645
 646 impl<T: sealed::PaymentSecret> Features<T> {
 647         #[cfg(test)]
 648         pub(crate) fn requires_payment_secret(&self) -> bool {
 649                 <T as sealed::PaymentSecret>::requires_feature(&self.flags)
 650         }
 651         /// Returns whether the `payment_secret` feature is supported.
 652         pub fn supports_payment_secret(&self) -> bool {
 653                 <T as sealed::PaymentSecret>::supports_feature(&self.flags)
 654         }
 655 }
 656
 657 impl<T: sealed::BasicMPP> Features<T> {
 658         #[cfg(test)]
 659         pub(crate) fn requires_basic_mpp(&self) -> bool {
 660                 <T as sealed::BasicMPP>::requires_feature(&self.flags)
 661         }
 662         // We currently never test for this since we don't actually *generate* multipath routes.
 663         pub(crate) fn supports_basic_mpp(&self) -> bool {
 664                 <T as sealed::BasicMPP>::supports_feature(&self.flags)
 665         }
 666 }
 667
 668 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 669         pub(crate) fn supports_shutdown_anysegwit(&self) -> bool {
 670                 <T as sealed::ShutdownAnySegwit>::supports_feature(&self.flags)
 671         }
 672         #[cfg(test)]
 673         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 674                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 675                 self
 676         }
 677 }
 678
 679 impl<T: sealed::Context> Writeable for Features<T> {
 680         fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
 681                 w.size_hint(self.flags.len() + 2);
 682                 (self.flags.len() as u16).write(w)?;
 683                 for f in self.flags.iter().rev() { // Swap back to big-endian
 684                         f.write(w)?;
 685                 }
 686                 Ok(())
 687         }
 688 }
 689
 690 impl<T: sealed::Context> Readable for Features<T> {
 691         fn read<R: ::std::io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 692                 let mut flags: Vec<u8> = Readable::read(r)?;
 693                 flags.reverse(); // Swap to little-endian
 694                 Ok(Self {
 695                         flags,
 696                         mark: PhantomData,
 697                 })
 698         }
 699 }
 700
 701 #[cfg(test)]
 702 mod tests {
 703         use super::{ChannelFeatures, InitFeatures, InvoiceFeatures, NodeFeatures};
 704         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
 705
 706         #[test]
 707         fn sanity_test_known_features() {
 708                 assert!(!ChannelFeatures::known().requires_unknown_bits());
 709                 assert!(!ChannelFeatures::known().supports_unknown_bits());
 710                 assert!(!InitFeatures::known().requires_unknown_bits());
 711                 assert!(!InitFeatures::known().supports_unknown_bits());
 712                 assert!(!NodeFeatures::known().requires_unknown_bits());
 713                 assert!(!NodeFeatures::known().supports_unknown_bits());
 714
 715                 assert!(InitFeatures::known().supports_upfront_shutdown_script());
 716                 assert!(NodeFeatures::known().supports_upfront_shutdown_script());
 717                 assert!(!InitFeatures::known().requires_upfront_shutdown_script());
 718                 assert!(!NodeFeatures::known().requires_upfront_shutdown_script());
 719
 720                 assert!(InitFeatures::known().supports_gossip_queries());
 721                 assert!(NodeFeatures::known().supports_gossip_queries());
 722                 assert!(!InitFeatures::known().requires_gossip_queries());
 723                 assert!(!NodeFeatures::known().requires_gossip_queries());
 724
 725                 assert!(InitFeatures::known().supports_data_loss_protect());
 726                 assert!(NodeFeatures::known().supports_data_loss_protect());
 727                 assert!(!InitFeatures::known().requires_data_loss_protect());
 728                 assert!(!NodeFeatures::known().requires_data_loss_protect());
 729
 730                 assert!(InitFeatures::known().supports_variable_length_onion());
 731                 assert!(NodeFeatures::known().supports_variable_length_onion());
 732                 assert!(InvoiceFeatures::known().supports_variable_length_onion());
 733                 assert!(InitFeatures::known().requires_variable_length_onion());
 734                 assert!(NodeFeatures::known().requires_variable_length_onion());
 735                 assert!(InvoiceFeatures::known().requires_variable_length_onion());
 736
 737                 assert!(InitFeatures::known().supports_static_remote_key());
 738                 assert!(NodeFeatures::known().supports_static_remote_key());
 739                 assert!(InitFeatures::known().requires_static_remote_key());
 740                 assert!(NodeFeatures::known().requires_static_remote_key());
 741
 742                 assert!(InitFeatures::known().supports_payment_secret());
 743                 assert!(NodeFeatures::known().supports_payment_secret());
 744                 assert!(InvoiceFeatures::known().supports_payment_secret());
 745                 assert!(InitFeatures::known().requires_payment_secret());
 746                 assert!(NodeFeatures::known().requires_payment_secret());
 747                 assert!(InvoiceFeatures::known().requires_payment_secret());
 748
 749                 assert!(InitFeatures::known().supports_basic_mpp());
 750                 assert!(NodeFeatures::known().supports_basic_mpp());
 751                 assert!(InvoiceFeatures::known().supports_basic_mpp());
 752                 assert!(!InitFeatures::known().requires_basic_mpp());
 753                 assert!(!NodeFeatures::known().requires_basic_mpp());
 754                 assert!(!InvoiceFeatures::known().requires_basic_mpp());
 755
 756                 assert!(InitFeatures::known().supports_shutdown_anysegwit());
 757                 assert!(NodeFeatures::known().supports_shutdown_anysegwit());
 758
 759                 let mut init_features = InitFeatures::known();
 760                 assert!(init_features.initial_routing_sync());
 761                 init_features.clear_initial_routing_sync();
 762                 assert!(!init_features.initial_routing_sync());
 763         }
 764
 765         #[test]
 766         fn sanity_test_unknown_bits() {
 767                 let mut features = ChannelFeatures::empty();
 768                 assert!(!features.requires_unknown_bits());
 769                 assert!(!features.supports_unknown_bits());
 770
 771                 features.set_required_unknown_bits();
 772                 assert!(features.requires_unknown_bits());
 773                 assert!(features.supports_unknown_bits());
 774
 775                 features.clear_unknown_bits();
 776                 assert!(!features.requires_unknown_bits());
 777                 assert!(!features.supports_unknown_bits());
 778
 779                 features.set_optional_unknown_bits();
 780                 assert!(!features.requires_unknown_bits());
 781                 assert!(features.supports_unknown_bits());
 782         }
 783
 784         #[test]
 785         fn convert_to_context_with_relevant_flags() {
 786                 let init_features = InitFeatures::known().clear_upfront_shutdown_script().clear_gossip_queries();
 787                 assert!(init_features.initial_routing_sync());
 788                 assert!(!init_features.supports_upfront_shutdown_script());
 789                 assert!(!init_features.supports_gossip_queries());
 790
 791                 let node_features: NodeFeatures = init_features.to_context();
 792                 {
 793                         // Check that the flags are as expected:
 794                         // - option_data_loss_protect
 795                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
 796                         // - basic_mpp
 797                         // - opt_shutdown_anysegwit
 798                         assert_eq!(node_features.flags.len(), 4);
 799                         assert_eq!(node_features.flags[0], 0b00000010);
 800                         assert_eq!(node_features.flags[1], 0b01010001);
 801                         assert_eq!(node_features.flags[2], 0b00000010);
 802                         assert_eq!(node_features.flags[3], 0b00001000);
 803                 }
 804
 805                 // Check that cleared flags are kept blank when converting back:
 806                 // - initial_routing_sync was not applicable to NodeContext
 807                 // - upfront_shutdown_script was cleared before converting
 808                 // - gossip_queries was cleared before converting
 809                 let features: InitFeatures = node_features.to_context_internal();
 810                 assert!(!features.initial_routing_sync());
 811                 assert!(!features.supports_upfront_shutdown_script());
 812                 assert!(!init_features.supports_gossip_queries());
 813         }
 814
 815         #[test]
 816         fn set_feature_bits() {
 817                 let features = InvoiceFeatures::empty()
 818                         .set_basic_mpp_optional()
 819                         .set_payment_secret_required();
 820                 assert!(features.supports_basic_mpp());
 821                 assert!(!features.requires_basic_mpp());
 822                 assert!(features.requires_payment_secret());
 823                 assert!(features.supports_payment_secret());
 824         }
 825
 826         #[test]
 827         fn invoice_features_encoding() {
 828                 let features_as_u5s = vec![
 829                         u5::try_from_u8(6).unwrap(),
 830                         u5::try_from_u8(10).unwrap(),
 831                         u5::try_from_u8(25).unwrap(),
 832                         u5::try_from_u8(1).unwrap(),
 833                         u5::try_from_u8(10).unwrap(),
 834                         u5::try_from_u8(0).unwrap(),
 835                         u5::try_from_u8(20).unwrap(),
 836                         u5::try_from_u8(2).unwrap(),
 837                         u5::try_from_u8(0).unwrap(),
 838                         u5::try_from_u8(6).unwrap(),
 839                         u5::try_from_u8(0).unwrap(),
 840                         u5::try_from_u8(16).unwrap(),
 841                         u5::try_from_u8(1).unwrap(),
 842                 ];
 843                 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
 844
 845                 // Test length calculation.
 846                 assert_eq!(features.base32_len(), 13);
 847
 848                 // Test serialization.
 849                 let features_serialized = features.to_base32();
 850                 assert_eq!(features_as_u5s, features_serialized);
 851
 852                 // Test deserialization.
 853                 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
 854                 assert_eq!(features, features_deserialized);
 855         }
 856 }