_ 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                         StaticRemoteKey,
  99                         // Byte 2
 100                         ,
 101                         // Byte 3
 102                         ,
 103                 ],
 104                 optional_features: [
 105                         // Byte 0
 106                         DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
 107                         // Byte 1
 108                         VariableLengthOnion | PaymentSecret,
 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                         StaticRemoteKey,
 121                         // Byte 2
 122                         ,
 123                         // Byte 3
 124                         ,
 125                 ],
 126                 optional_features: [
 127                         // Byte 0
 128                         DataLossProtect | UpfrontShutdownScript | GossipQueries,
 129                         // Byte 1
 130                         VariableLengthOnion | PaymentSecret,
 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                 optional_features: [
 144                         // Byte 0
 145                         ,
 146                         // Byte 1
 147                         VariableLengthOnion | PaymentSecret,
 148                         // Byte 2
 149                         BasicMPP,
 150                 ],
 151         });
 152
 153         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 154         /// useful for manipulating feature flags.
 155         macro_rules! define_feature {
 156                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 157                  $required_setter: ident) => {
 158                         #[doc = $doc]
 159                         ///
 160                         /// See [BOLT #9] for details.
 161                         ///
 162                         /// [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
 163                         pub trait $feature: Context {
 164                                 /// The bit used to signify that the feature is required.
 165                                 const EVEN_BIT: usize = $odd_bit - 1;
 166
 167                                 /// The bit used to signify that the feature is optional.
 168                                 const ODD_BIT: usize = $odd_bit;
 169
 170                                 /// Assertion that [`EVEN_BIT`] is actually even.
 171                                 ///
 172                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 173                                 const ASSERT_EVEN_BIT_PARITY: usize;
 174
 175                                 /// Assertion that [`ODD_BIT`] is actually odd.
 176                                 ///
 177                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 178                                 const ASSERT_ODD_BIT_PARITY: usize;
 179
 180                                 /// The byte where the feature is set.
 181                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 182
 183                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 184                                 ///
 185                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 186                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 187
 188                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 189                                 ///
 190                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 191                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 192
 193                                 /// Returns whether the feature is required by the given flags.
 194                                 #[inline]
 195                                 fn requires_feature(flags: &Vec<u8>) -> bool {
 196                                         flags.len() > Self::BYTE_OFFSET &&
 197                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
 198                                 }
 199
 200                                 /// Returns whether the feature is supported by the given flags.
 201                                 #[inline]
 202                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 203                                         flags.len() > Self::BYTE_OFFSET &&
 204                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 205                                 }
 206
 207                                 /// Sets the feature's required (even) bit in the given flags.
 208                                 #[inline]
 209                                 fn set_required_bit(flags: &mut Vec<u8>) {
 210                                         if flags.len() <= Self::BYTE_OFFSET {
 211                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 212                                         }
 213
 214                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
 215                                 }
 216
 217                                 /// Sets the feature's optional (odd) bit in the given flags.
 218                                 #[inline]
 219                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 220                                         if flags.len() <= Self::BYTE_OFFSET {
 221                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 222                                         }
 223
 224                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 225                                 }
 226
 227                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 228                                 /// flags.
 229                                 #[inline]
 230                                 fn clear_bits(flags: &mut Vec<u8>) {
 231                                         if flags.len() > Self::BYTE_OFFSET {
 232                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 233                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 234                                         }
 235
 236                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 237                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 238                                         flags.resize(size, 0u8);
 239                                 }
 240                         }
 241
 242                         impl <T: $feature> Features<T> {
 243                                 /// Set this feature as optional.
 244                                 pub fn $optional_setter(mut self) -> Self {
 245                                         <T as $feature>::set_optional_bit(&mut self.flags);
 246                                         self
 247                                 }
 248
 249                                 /// Set this feature as required.
 250                                 pub fn $required_setter(mut self) -> Self {
 251                                         <T as $feature>::set_required_bit(&mut self.flags);
 252                                         self
 253                                 }
 254                         }
 255
 256                         $(
 257                                 impl $feature for $context {
 258                                         // EVEN_BIT % 2 == 0
 259                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 260
 261                                         // ODD_BIT % 2 == 1
 262                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 263                                 }
 264                         )*
 265
 266                 }
 267         }
 268
 269         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 270                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 271                 set_data_loss_protect_required);
 272         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 273         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 274                 set_initial_routing_sync_optional, set_initial_routing_sync_required);
 275         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 276                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 277                 set_upfront_shutdown_script_required);
 278         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 279                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required);
 280         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
 281                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 282                 set_variable_length_onion_required);
 283         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext],
 284                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 285                 set_static_remote_key_required);
 286         define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
 287                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required);
 288         define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext],
 289                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required);
 290         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 291                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 292                 set_shutdown_any_segwit_required);
 293
 294         #[cfg(test)]
 295         define_context!(TestingContext {
 296                 required_features: [
 297                         // Byte 0
 298                         ,
 299                         // Byte 1
 300                         ,
 301                         // Byte 2
 302                         UnknownFeature,
 303                 ],
 304                 optional_features: [
 305                         // Byte 0
 306                         ,
 307                         // Byte 1
 308                         ,
 309                         // Byte 2
 310                         ,
 311                 ],
 312         });
 313
 314         #[cfg(test)]
 315         define_feature!(23, UnknownFeature, [TestingContext],
 316                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 317                 set_unknown_feature_required);
 318 }
 319
 320 /// Tracks the set of features which a node implements, templated by the context in which it
 321 /// appears.
 322 ///
 323 /// (C-not exported) as we map the concrete feature types below directly instead
 324 #[derive(Eq)]
 325 pub struct Features<T: sealed::Context> {
 326         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 327         flags: Vec<u8>,
 328         mark: PhantomData<T>,
 329 }
 330
 331 impl<T: sealed::Context> Clone for Features<T> {
 332         fn clone(&self) -> Self {
 333                 Self {
 334                         flags: self.flags.clone(),
 335                         mark: PhantomData,
 336                 }
 337         }
 338 }
 339 impl<T: sealed::Context> PartialEq for Features<T> {
 340         fn eq(&self, o: &Self) -> bool {
 341                 self.flags.eq(&o.flags)
 342         }
 343 }
 344 impl<T: sealed::Context> fmt::Debug for Features<T> {
 345         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 346                 self.flags.fmt(fmt)
 347         }
 348 }
 349
 350 /// Features used within an `init` message.
 351 pub type InitFeatures = Features<sealed::InitContext>;
 352 /// Features used within a `node_announcement` message.
 353 pub type NodeFeatures = Features<sealed::NodeContext>;
 354 /// Features used within a `channel_announcement` message.
 355 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 356 /// Features used within an invoice.
 357 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
 358
 359 impl InitFeatures {
 360         /// Writes all features present up to, and including, 13.
 361         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
 362                 let len = cmp::min(2, self.flags.len());
 363                 w.size_hint(len + 2);
 364                 (len as u16).write(w)?;
 365                 for i in (0..len).rev() {
 366                         if i == 0 {
 367                                 self.flags[i].write(w)?;
 368                         } else {
 369                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 370                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 371                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 372                         }
 373                 }
 374                 Ok(())
 375         }
 376
 377         /// or's another InitFeatures into this one.
 378         pub(crate) fn or(mut self, o: InitFeatures) -> InitFeatures {
 379                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
 380                 self.flags.resize(total_feature_len, 0u8);
 381                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
 382                         *byte |= *o_byte;
 383                 }
 384                 self
 385         }
 386
 387         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 388         /// are included in the result.
 389         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 390                 self.to_context_internal()
 391         }
 392 }
 393
 394 impl InvoiceFeatures {
 395         /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
 396         /// context `C` are included in the result.
 397         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 398                 self.to_context_internal()
 399         }
 400 }
 401
 402 impl ToBase32 for InvoiceFeatures {
 403         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 404                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 405                 // minus one before dividing
 406                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 407                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 408                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 409                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 410                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 411                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 412                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 413                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 414                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 415                         if new_u5_idx > 0 {
 416                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 417                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 418                         }
 419                         if new_u5_idx > 1 {
 420                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 421                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 422                         }
 423                 }
 424                 // Trim the highest feature bits.
 425                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 426                         res_u5s.remove(0);
 427                 }
 428                 writer.write(&res_u5s)
 429         }
 430 }
 431
 432 impl Base32Len for InvoiceFeatures {
 433         fn base32_len(&self) -> usize {
 434                 self.to_base32().len()
 435         }
 436 }
 437
 438 impl FromBase32 for InvoiceFeatures {
 439         type Err = bech32::Error;
 440
 441         fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
 442                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 443                 // minus one before dividing
 444                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 445                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 446                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 447                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 448                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 449                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 450                         let chunk_u16 = chunk.to_u8() as u16;
 451                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 452                         if new_byte_idx != length_bytes - 1 {
 453                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 454                         }
 455                 }
 456                 // Trim the highest feature bits.
 457                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 458                         res_bytes.pop();
 459                 }
 460                 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
 461         }
 462 }
 463
 464 impl<T: sealed::Context> Features<T> {
 465         /// Create a blank Features with no features set
 466         pub fn empty() -> Self {
 467                 Features {
 468                         flags: Vec::new(),
 469                         mark: PhantomData,
 470                 }
 471         }
 472
 473         /// Creates a Features with the bits set which are known by the implementation
 474         pub fn known() -> Self {
 475                 Self {
 476                         flags: T::KNOWN_FEATURE_FLAGS.to_vec(),
 477                         mark: PhantomData,
 478                 }
 479         }
 480
 481         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 482         /// included in the result.
 483         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 484                 let byte_count = C::KNOWN_FEATURE_MASK.len();
 485                 let mut flags = Vec::new();
 486                 for (i, byte) in self.flags.iter().enumerate() {
 487                         if i < byte_count {
 488                                 let known_source_features = T::KNOWN_FEATURE_MASK[i];
 489                                 let known_target_features = C::KNOWN_FEATURE_MASK[i];
 490                                 flags.push(byte & known_source_features & known_target_features);
 491                         }
 492                 }
 493                 Features::<C> { flags, mark: PhantomData, }
 494         }
 495
 496         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 497         /// most on-the-wire encodings.
 498         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 499                 Features {
 500                         flags,
 501                         mark: PhantomData,
 502                 }
 503         }
 504
 505         #[cfg(test)]
 506         /// Gets the underlying flags set, in LE.
 507         pub fn le_flags(&self) -> &Vec<u8> {
 508                 &self.flags
 509         }
 510
 511         pub(crate) fn requires_unknown_bits(&self) -> bool {
 512                 // Bitwise AND-ing with all even bits set except for known features will select required
 513                 // unknown features.
 514                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 515                 self.flags.iter().enumerate().any(|(i, &byte)| {
 516                         let required_features = 0b01_01_01_01;
 517                         let unknown_features = if i < byte_count {
 518                                 !T::KNOWN_FEATURE_MASK[i]
 519                         } else {
 520                                 0b11_11_11_11
 521                         };
 522                         (byte & (required_features & unknown_features)) != 0
 523                 })
 524         }
 525
 526         pub(crate) fn supports_unknown_bits(&self) -> bool {
 527                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 528                 // both required and optional unknown features.
 529                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 530                 self.flags.iter().enumerate().any(|(i, &byte)| {
 531                         let unknown_features = if i < byte_count {
 532                                 !T::KNOWN_FEATURE_MASK[i]
 533                         } else {
 534                                 0b11_11_11_11
 535                         };
 536                         (byte & unknown_features) != 0
 537                 })
 538         }
 539
 540         /// The number of bytes required to represent the feature flags present. This does not include
 541         /// the length bytes which are included in the serialized form.
 542         pub(crate) fn byte_count(&self) -> usize {
 543                 self.flags.len()
 544         }
 545
 546         #[cfg(test)]
 547         pub(crate) fn set_required_unknown_bits(&mut self) {
 548                 <sealed::TestingContext as sealed::UnknownFeature>::set_required_bit(&mut self.flags);
 549         }
 550
 551         #[cfg(test)]
 552         pub(crate) fn set_optional_unknown_bits(&mut self) {
 553                 <sealed::TestingContext as sealed::UnknownFeature>::set_optional_bit(&mut self.flags);
 554         }
 555
 556         #[cfg(test)]
 557         pub(crate) fn clear_unknown_bits(&mut self) {
 558                 <sealed::TestingContext as sealed::UnknownFeature>::clear_bits(&mut self.flags);
 559         }
 560 }
 561
 562 impl<T: sealed::DataLossProtect> Features<T> {
 563         #[cfg(test)]
 564         pub(crate) fn requires_data_loss_protect(&self) -> bool {
 565                 <T as sealed::DataLossProtect>::requires_feature(&self.flags)
 566         }
 567         pub(crate) fn supports_data_loss_protect(&self) -> bool {
 568                 <T as sealed::DataLossProtect>::supports_feature(&self.flags)
 569         }
 570 }
 571
 572 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 573         #[cfg(test)]
 574         pub(crate) fn requires_upfront_shutdown_script(&self) -> bool {
 575                 <T as sealed::UpfrontShutdownScript>::requires_feature(&self.flags)
 576         }
 577         pub(crate) fn supports_upfront_shutdown_script(&self) -> bool {
 578                 <T as sealed::UpfrontShutdownScript>::supports_feature(&self.flags)
 579         }
 580         #[cfg(test)]
 581         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 582                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 583                 self
 584         }
 585 }
 586
 587
 588 impl<T: sealed::GossipQueries> Features<T> {
 589         #[cfg(test)]
 590         pub(crate) fn requires_gossip_queries(&self) -> bool {
 591                 <T as sealed::GossipQueries>::requires_feature(&self.flags)
 592         }
 593         pub(crate) fn supports_gossip_queries(&self) -> bool {
 594                 <T as sealed::GossipQueries>::supports_feature(&self.flags)
 595         }
 596         #[cfg(test)]
 597         pub(crate) fn clear_gossip_queries(mut self) -> Self {
 598                 <T as sealed::GossipQueries>::clear_bits(&mut self.flags);
 599                 self
 600         }
 601 }
 602
 603 impl<T: sealed::VariableLengthOnion> Features<T> {
 604         #[cfg(test)]
 605         pub(crate) fn requires_variable_length_onion(&self) -> bool {
 606                 <T as sealed::VariableLengthOnion>::requires_feature(&self.flags)
 607         }
 608         pub(crate) fn supports_variable_length_onion(&self) -> bool {
 609                 <T as sealed::VariableLengthOnion>::supports_feature(&self.flags)
 610         }
 611 }
 612
 613 impl<T: sealed::StaticRemoteKey> Features<T> {
 614         pub(crate) fn supports_static_remote_key(&self) -> bool {
 615                 <T as sealed::StaticRemoteKey>::supports_feature(&self.flags)
 616         }
 617         #[cfg(test)]
 618         pub(crate) fn requires_static_remote_key(&self) -> bool {
 619                 <T as sealed::StaticRemoteKey>::requires_feature(&self.flags)
 620         }
 621 }
 622
 623 impl<T: sealed::InitialRoutingSync> Features<T> {
 624         pub(crate) fn initial_routing_sync(&self) -> bool {
 625                 <T as sealed::InitialRoutingSync>::supports_feature(&self.flags)
 626         }
 627         // We are no longer setting initial_routing_sync now that gossip_queries
 628         // is enabled. This feature is ignored by a peer when gossip_queries has
 629         // been negotiated.
 630         #[cfg(test)]
 631         pub(crate) fn clear_initial_routing_sync(&mut self) {
 632                 <T as sealed::InitialRoutingSync>::clear_bits(&mut self.flags)
 633         }
 634 }
 635
 636 impl<T: sealed::PaymentSecret> Features<T> {
 637         #[cfg(test)]
 638         pub(crate) fn requires_payment_secret(&self) -> bool {
 639                 <T as sealed::PaymentSecret>::requires_feature(&self.flags)
 640         }
 641         // Note that we never need to test this since what really matters is the invoice - iff the
 642         // invoice provides a payment_secret, we assume that we can use it (ie that the recipient
 643         // supports payment_secret).
 644         #[allow(dead_code)]
 645         pub(crate) fn supports_payment_secret(&self) -> bool {
 646                 <T as sealed::PaymentSecret>::supports_feature(&self.flags)
 647         }
 648 }
 649
 650 impl<T: sealed::BasicMPP> Features<T> {
 651         #[cfg(test)]
 652         pub(crate) fn requires_basic_mpp(&self) -> bool {
 653                 <T as sealed::BasicMPP>::requires_feature(&self.flags)
 654         }
 655         // We currently never test for this since we don't actually *generate* multipath routes.
 656         pub(crate) fn supports_basic_mpp(&self) -> bool {
 657                 <T as sealed::BasicMPP>::supports_feature(&self.flags)
 658         }
 659 }
 660
 661 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 662         pub(crate) fn supports_shutdown_anysegwit(&self) -> bool {
 663                 <T as sealed::ShutdownAnySegwit>::supports_feature(&self.flags)
 664         }
 665         #[cfg(test)]
 666         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 667                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 668                 self
 669         }
 670 }
 671
 672 impl<T: sealed::Context> Writeable for Features<T> {
 673         fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
 674                 w.size_hint(self.flags.len() + 2);
 675                 (self.flags.len() as u16).write(w)?;
 676                 for f in self.flags.iter().rev() { // Swap back to big-endian
 677                         f.write(w)?;
 678                 }
 679                 Ok(())
 680         }
 681 }
 682
 683 impl<T: sealed::Context> Readable for Features<T> {
 684         fn read<R: ::std::io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 685                 let mut flags: Vec<u8> = Readable::read(r)?;
 686                 flags.reverse(); // Swap to little-endian
 687                 Ok(Self {
 688                         flags,
 689                         mark: PhantomData,
 690                 })
 691         }
 692 }
 693
 694 #[cfg(test)]
 695 mod tests {
 696         use super::{ChannelFeatures, InitFeatures, InvoiceFeatures, NodeFeatures};
 697         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
 698
 699         #[test]
 700         fn sanity_test_known_features() {
 701                 assert!(!ChannelFeatures::known().requires_unknown_bits());
 702                 assert!(!ChannelFeatures::known().supports_unknown_bits());
 703                 assert!(!InitFeatures::known().requires_unknown_bits());
 704                 assert!(!InitFeatures::known().supports_unknown_bits());
 705                 assert!(!NodeFeatures::known().requires_unknown_bits());
 706                 assert!(!NodeFeatures::known().supports_unknown_bits());
 707
 708                 assert!(InitFeatures::known().supports_upfront_shutdown_script());
 709                 assert!(NodeFeatures::known().supports_upfront_shutdown_script());
 710                 assert!(!InitFeatures::known().requires_upfront_shutdown_script());
 711                 assert!(!NodeFeatures::known().requires_upfront_shutdown_script());
 712
 713                 assert!(InitFeatures::known().supports_gossip_queries());
 714                 assert!(NodeFeatures::known().supports_gossip_queries());
 715                 assert!(!InitFeatures::known().requires_gossip_queries());
 716                 assert!(!NodeFeatures::known().requires_gossip_queries());
 717
 718                 assert!(InitFeatures::known().supports_data_loss_protect());
 719                 assert!(NodeFeatures::known().supports_data_loss_protect());
 720                 assert!(!InitFeatures::known().requires_data_loss_protect());
 721                 assert!(!NodeFeatures::known().requires_data_loss_protect());
 722
 723                 assert!(InitFeatures::known().supports_variable_length_onion());
 724                 assert!(NodeFeatures::known().supports_variable_length_onion());
 725                 assert!(!InitFeatures::known().requires_variable_length_onion());
 726                 assert!(!NodeFeatures::known().requires_variable_length_onion());
 727
 728                 assert!(InitFeatures::known().supports_static_remote_key());
 729                 assert!(NodeFeatures::known().supports_static_remote_key());
 730                 assert!(InitFeatures::known().requires_static_remote_key());
 731                 assert!(NodeFeatures::known().requires_static_remote_key());
 732
 733                 assert!(InitFeatures::known().supports_payment_secret());
 734                 assert!(NodeFeatures::known().supports_payment_secret());
 735                 assert!(!InitFeatures::known().requires_payment_secret());
 736                 assert!(!NodeFeatures::known().requires_payment_secret());
 737
 738                 assert!(InitFeatures::known().supports_basic_mpp());
 739                 assert!(NodeFeatures::known().supports_basic_mpp());
 740                 assert!(!InitFeatures::known().requires_basic_mpp());
 741                 assert!(!NodeFeatures::known().requires_basic_mpp());
 742
 743                 assert!(InitFeatures::known().supports_shutdown_anysegwit());
 744                 assert!(NodeFeatures::known().supports_shutdown_anysegwit());
 745
 746                 let mut init_features = InitFeatures::known();
 747                 assert!(init_features.initial_routing_sync());
 748                 init_features.clear_initial_routing_sync();
 749                 assert!(!init_features.initial_routing_sync());
 750         }
 751
 752         #[test]
 753         fn sanity_test_unknown_bits() {
 754                 let mut features = ChannelFeatures::empty();
 755                 assert!(!features.requires_unknown_bits());
 756                 assert!(!features.supports_unknown_bits());
 757
 758                 features.set_required_unknown_bits();
 759                 assert!(features.requires_unknown_bits());
 760                 assert!(features.supports_unknown_bits());
 761
 762                 features.clear_unknown_bits();
 763                 assert!(!features.requires_unknown_bits());
 764                 assert!(!features.supports_unknown_bits());
 765
 766                 features.set_optional_unknown_bits();
 767                 assert!(!features.requires_unknown_bits());
 768                 assert!(features.supports_unknown_bits());
 769         }
 770
 771         #[test]
 772         fn convert_to_context_with_relevant_flags() {
 773                 let init_features = InitFeatures::known().clear_upfront_shutdown_script().clear_gossip_queries();
 774                 assert!(init_features.initial_routing_sync());
 775                 assert!(!init_features.supports_upfront_shutdown_script());
 776                 assert!(!init_features.supports_gossip_queries());
 777
 778                 let node_features: NodeFeatures = init_features.to_context();
 779                 {
 780                         // Check that the flags are as expected:
 781                         // - option_data_loss_protect
 782                         // - var_onion_optin | static_remote_key (req) | payment_secret
 783                         // - basic_mpp
 784                         // - opt_shutdown_anysegwit
 785                         assert_eq!(node_features.flags.len(), 4);
 786                         assert_eq!(node_features.flags[0], 0b00000010);
 787                         assert_eq!(node_features.flags[1], 0b10010010);
 788                         assert_eq!(node_features.flags[2], 0b00000010);
 789                         assert_eq!(node_features.flags[3], 0b00001000);
 790                 }
 791
 792                 // Check that cleared flags are kept blank when converting back:
 793                 // - initial_routing_sync was not applicable to NodeContext
 794                 // - upfront_shutdown_script was cleared before converting
 795                 // - gossip_queries was cleared before converting
 796                 let features: InitFeatures = node_features.to_context_internal();
 797                 assert!(!features.initial_routing_sync());
 798                 assert!(!features.supports_upfront_shutdown_script());
 799                 assert!(!init_features.supports_gossip_queries());
 800         }
 801
 802         #[test]
 803         fn set_feature_bits() {
 804                 let features = InvoiceFeatures::empty()
 805                         .set_basic_mpp_optional()
 806                         .set_payment_secret_required();
 807                 assert!(features.supports_basic_mpp());
 808                 assert!(!features.requires_basic_mpp());
 809                 assert!(features.requires_payment_secret());
 810                 assert!(features.supports_payment_secret());
 811         }
 812
 813         #[test]
 814         fn invoice_features_encoding() {
 815                 let features_as_u5s = vec![
 816                         u5::try_from_u8(6).unwrap(),
 817                         u5::try_from_u8(10).unwrap(),
 818                         u5::try_from_u8(25).unwrap(),
 819                         u5::try_from_u8(1).unwrap(),
 820                         u5::try_from_u8(10).unwrap(),
 821                         u5::try_from_u8(0).unwrap(),
 822                         u5::try_from_u8(20).unwrap(),
 823                         u5::try_from_u8(2).unwrap(),
 824                         u5::try_from_u8(0).unwrap(),
 825                         u5::try_from_u8(6).unwrap(),
 826                         u5::try_from_u8(0).unwrap(),
 827                         u5::try_from_u8(16).unwrap(),
 828                         u5::try_from_u8(1).unwrap(),
 829                 ];
 830                 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
 831
 832                 // Test length calculation.
 833                 assert_eq!(features.base32_len(), 13);
 834
 835                 // Test serialization.
 836                 let features_serialized = features.to_base32();
 837                 assert_eq!(features_as_u5s, features_serialized);
 838
 839                 // Test deserialization.
 840                 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
 841                 assert_eq!(features, features_deserialized);
 842         }
 843 }