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