_ 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                         // Byte 4
 128                         ,
 129                         // Byte 5
 130                         ,
 131                         // Byte 6
 132                         ,
 133                 ],
 134                 optional_features: [
 135                         // Byte 0
 136                         DataLossProtect | UpfrontShutdownScript | GossipQueries,
 137                         // Byte 1
 138                         ,
 139                         // Byte 2
 140                         BasicMPP,
 141                         // Byte 3
 142                         ShutdownAnySegwit,
 143                         // Byte 4
 144                         ,
 145                         // Byte 5
 146                         ,
 147                         // Byte 6
 148                         Keysend,
 149                 ],
 150         });
 151         define_context!(ChannelContext {
 152                 required_features: [],
 153                 optional_features: [],
 154         });
 155         define_context!(InvoiceContext {
 156                 required_features: [
 157                         // Byte 0
 158                         ,
 159                         // Byte 1
 160                         VariableLengthOnion | PaymentSecret,
 161                         // Byte 2
 162                         ,
 163                 ],
 164                 optional_features: [
 165                         // Byte 0
 166                         ,
 167                         // Byte 1
 168                         ,
 169                         // Byte 2
 170                         BasicMPP,
 171                 ],
 172         });
 173
 174         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 175         /// useful for manipulating feature flags.
 176         macro_rules! define_feature {
 177                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 178                  $required_setter: ident) => {
 179                         #[doc = $doc]
 180                         ///
 181                         /// See [BOLT #9] for details.
 182                         ///
 183                         /// [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
 184                         pub trait $feature: Context {
 185                                 /// The bit used to signify that the feature is required.
 186                                 const EVEN_BIT: usize = $odd_bit - 1;
 187
 188                                 /// The bit used to signify that the feature is optional.
 189                                 const ODD_BIT: usize = $odd_bit;
 190
 191                                 /// Assertion that [`EVEN_BIT`] is actually even.
 192                                 ///
 193                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 194                                 const ASSERT_EVEN_BIT_PARITY: usize;
 195
 196                                 /// Assertion that [`ODD_BIT`] is actually odd.
 197                                 ///
 198                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 199                                 const ASSERT_ODD_BIT_PARITY: usize;
 200
 201                                 /// The byte where the feature is set.
 202                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 203
 204                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 205                                 ///
 206                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 207                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 208
 209                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 210                                 ///
 211                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 212                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 213
 214                                 /// Returns whether the feature is required by the given flags.
 215                                 #[inline]
 216                                 fn requires_feature(flags: &Vec<u8>) -> bool {
 217                                         flags.len() > Self::BYTE_OFFSET &&
 218                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
 219                                 }
 220
 221                                 /// Returns whether the feature is supported by the given flags.
 222                                 #[inline]
 223                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 224                                         flags.len() > Self::BYTE_OFFSET &&
 225                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 226                                 }
 227
 228                                 /// Sets the feature's required (even) bit in the given flags.
 229                                 #[inline]
 230                                 fn set_required_bit(flags: &mut Vec<u8>) {
 231                                         if flags.len() <= Self::BYTE_OFFSET {
 232                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 233                                         }
 234
 235                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
 236                                 }
 237
 238                                 /// Sets the feature's optional (odd) bit in the given flags.
 239                                 #[inline]
 240                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 241                                         if flags.len() <= Self::BYTE_OFFSET {
 242                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 243                                         }
 244
 245                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 246                                 }
 247
 248                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 249                                 /// flags.
 250                                 #[inline]
 251                                 fn clear_bits(flags: &mut Vec<u8>) {
 252                                         if flags.len() > Self::BYTE_OFFSET {
 253                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 254                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 255                                         }
 256
 257                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 258                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 259                                         flags.resize(size, 0u8);
 260                                 }
 261                         }
 262
 263                         impl <T: $feature> Features<T> {
 264                                 /// Set this feature as optional.
 265                                 pub fn $optional_setter(mut self) -> Self {
 266                                         <T as $feature>::set_optional_bit(&mut self.flags);
 267                                         self
 268                                 }
 269
 270                                 /// Set this feature as required.
 271                                 pub fn $required_setter(mut self) -> Self {
 272                                         <T as $feature>::set_required_bit(&mut self.flags);
 273                                         self
 274                                 }
 275                         }
 276
 277                         $(
 278                                 impl $feature for $context {
 279                                         // EVEN_BIT % 2 == 0
 280                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 281
 282                                         // ODD_BIT % 2 == 1
 283                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 284                                 }
 285                         )*
 286
 287                 }
 288         }
 289
 290         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 291                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 292                 set_data_loss_protect_required);
 293         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 294         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 295                 set_initial_routing_sync_optional, set_initial_routing_sync_required);
 296         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 297                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 298                 set_upfront_shutdown_script_required);
 299         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 300                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required);
 301         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
 302                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 303                 set_variable_length_onion_required);
 304         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext],
 305                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 306                 set_static_remote_key_required);
 307         define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
 308                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required);
 309         define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext],
 310                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required);
 311         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 312                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 313                 set_shutdown_any_segwit_required);
 314         define_feature!(55, Keysend, [NodeContext],
 315                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required);
 316
 317         #[cfg(test)]
 318         define_feature!(123456789, UnknownFeature, [NodeContext, ChannelContext, InvoiceContext],
 319                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 320                 set_unknown_feature_required);
 321 }
 322
 323 /// Tracks the set of features which a node implements, templated by the context in which it
 324 /// appears.
 325 ///
 326 /// (C-not exported) as we map the concrete feature types below directly instead
 327 #[derive(Eq)]
 328 pub struct Features<T: sealed::Context> {
 329         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 330         flags: Vec<u8>,
 331         mark: PhantomData<T>,
 332 }
 333
 334 impl<T: sealed::Context> Clone for Features<T> {
 335         fn clone(&self) -> Self {
 336                 Self {
 337                         flags: self.flags.clone(),
 338                         mark: PhantomData,
 339                 }
 340         }
 341 }
 342 impl<T: sealed::Context> PartialEq for Features<T> {
 343         fn eq(&self, o: &Self) -> bool {
 344                 self.flags.eq(&o.flags)
 345         }
 346 }
 347 impl<T: sealed::Context> fmt::Debug for Features<T> {
 348         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 349                 self.flags.fmt(fmt)
 350         }
 351 }
 352
 353 /// Features used within an `init` message.
 354 pub type InitFeatures = Features<sealed::InitContext>;
 355 /// Features used within a `node_announcement` message.
 356 pub type NodeFeatures = Features<sealed::NodeContext>;
 357 /// Features used within a `channel_announcement` message.
 358 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 359 /// Features used within an invoice.
 360 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
 361
 362 impl InitFeatures {
 363         /// Writes all features present up to, and including, 13.
 364         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
 365                 let len = cmp::min(2, self.flags.len());
 366                 w.size_hint(len + 2);
 367                 (len as u16).write(w)?;
 368                 for i in (0..len).rev() {
 369                         if i == 0 {
 370                                 self.flags[i].write(w)?;
 371                         } else {
 372                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 373                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 374                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 375                         }
 376                 }
 377                 Ok(())
 378         }
 379
 380         /// or's another InitFeatures into this one.
 381         pub(crate) fn or(mut self, o: InitFeatures) -> InitFeatures {
 382                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
 383                 self.flags.resize(total_feature_len, 0u8);
 384                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
 385                         *byte |= *o_byte;
 386                 }
 387                 self
 388         }
 389
 390         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 391         /// are included in the result.
 392         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 393                 self.to_context_internal()
 394         }
 395 }
 396
 397 impl InvoiceFeatures {
 398         /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
 399         /// context `C` are included in the result.
 400         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 401                 self.to_context_internal()
 402         }
 403
 404         /// Getting a route for a keysend payment to a private node requires providing the payee's
 405         /// features (since they were not announced in a node announcement). However, keysend payments
 406         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 407         /// [`get_keysend_route`], thus omitting the need for payers to manually construct an
 408         /// `InvoiceFeatures` for [`get_route`].
 409         ///
 410         /// [`get_keysend_route`]: crate::routing::router::get_keysend_route
 411         /// [`get_route`]: crate::routing::router::get_route
 412         pub(crate) fn for_keysend() -> InvoiceFeatures {
 413                 InvoiceFeatures::empty().set_variable_length_onion_optional()
 414         }
 415 }
 416
 417 impl ToBase32 for InvoiceFeatures {
 418         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 419                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 420                 // minus one before dividing
 421                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 422                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 423                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 424                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 425                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 426                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 427                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 428                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 429                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 430                         if new_u5_idx > 0 {
 431                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 432                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 433                         }
 434                         if new_u5_idx > 1 {
 435                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 436                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 437                         }
 438                 }
 439                 // Trim the highest feature bits.
 440                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 441                         res_u5s.remove(0);
 442                 }
 443                 writer.write(&res_u5s)
 444         }
 445 }
 446
 447 impl Base32Len for InvoiceFeatures {
 448         fn base32_len(&self) -> usize {
 449                 self.to_base32().len()
 450         }
 451 }
 452
 453 impl FromBase32 for InvoiceFeatures {
 454         type Err = bech32::Error;
 455
 456         fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
 457                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 458                 // minus one before dividing
 459                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 460                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 461                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 462                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 463                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 464                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 465                         let chunk_u16 = chunk.to_u8() as u16;
 466                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 467                         if new_byte_idx != length_bytes - 1 {
 468                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 469                         }
 470                 }
 471                 // Trim the highest feature bits.
 472                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 473                         res_bytes.pop();
 474                 }
 475                 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
 476         }
 477 }
 478
 479 impl<T: sealed::Context> Features<T> {
 480         /// Create a blank Features with no features set
 481         pub fn empty() -> Self {
 482                 Features {
 483                         flags: Vec::new(),
 484                         mark: PhantomData,
 485                 }
 486         }
 487
 488         /// Creates a Features with the bits set which are known by the implementation
 489         pub fn known() -> Self {
 490                 Self {
 491                         flags: T::KNOWN_FEATURE_FLAGS.to_vec(),
 492                         mark: PhantomData,
 493                 }
 494         }
 495
 496         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 497         /// included in the result.
 498         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 499                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 500                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 501                 let mut flags = Vec::new();
 502                 for (i, byte) in self.flags.iter().enumerate() {
 503                         if i < from_byte_count && i < to_byte_count {
 504                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 505                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 506                                 flags.push(byte & from_known_features & to_known_features);
 507                         }
 508                 }
 509                 Features::<C> { flags, mark: PhantomData, }
 510         }
 511
 512         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 513         /// most on-the-wire encodings.
 514         /// (C-not exported) as we don't support export across multiple T
 515         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 516                 Features {
 517                         flags,
 518                         mark: PhantomData,
 519                 }
 520         }
 521
 522         #[cfg(test)]
 523         /// Gets the underlying flags set, in LE.
 524         pub fn le_flags(&self) -> &Vec<u8> {
 525                 &self.flags
 526         }
 527
 528         pub(crate) fn requires_unknown_bits(&self) -> bool {
 529                 // Bitwise AND-ing with all even bits set except for known features will select required
 530                 // unknown features.
 531                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 532                 self.flags.iter().enumerate().any(|(i, &byte)| {
 533                         let required_features = 0b01_01_01_01;
 534                         let unknown_features = if i < byte_count {
 535                                 !T::KNOWN_FEATURE_MASK[i]
 536                         } else {
 537                                 0b11_11_11_11
 538                         };
 539                         (byte & (required_features & unknown_features)) != 0
 540                 })
 541         }
 542
 543         pub(crate) fn supports_unknown_bits(&self) -> bool {
 544                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 545                 // both required and optional unknown features.
 546                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 547                 self.flags.iter().enumerate().any(|(i, &byte)| {
 548                         let unknown_features = if i < byte_count {
 549                                 !T::KNOWN_FEATURE_MASK[i]
 550                         } else {
 551                                 0b11_11_11_11
 552                         };
 553                         (byte & unknown_features) != 0
 554                 })
 555         }
 556
 557         /// The number of bytes required to represent the feature flags present. This does not include
 558         /// the length bytes which are included in the serialized form.
 559         pub(crate) fn byte_count(&self) -> usize {
 560                 self.flags.len()
 561         }
 562 }
 563
 564 impl<T: sealed::DataLossProtect> Features<T> {
 565         #[cfg(test)]
 566         pub(crate) fn requires_data_loss_protect(&self) -> bool {
 567                 <T as sealed::DataLossProtect>::requires_feature(&self.flags)
 568         }
 569         pub(crate) fn supports_data_loss_protect(&self) -> bool {
 570                 <T as sealed::DataLossProtect>::supports_feature(&self.flags)
 571         }
 572 }
 573
 574 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 575         #[cfg(test)]
 576         pub(crate) fn requires_upfront_shutdown_script(&self) -> bool {
 577                 <T as sealed::UpfrontShutdownScript>::requires_feature(&self.flags)
 578         }
 579         pub(crate) fn supports_upfront_shutdown_script(&self) -> bool {
 580                 <T as sealed::UpfrontShutdownScript>::supports_feature(&self.flags)
 581         }
 582         #[cfg(test)]
 583         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 584                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 585                 self
 586         }
 587 }
 588
 589
 590 impl<T: sealed::GossipQueries> Features<T> {
 591         #[cfg(test)]
 592         pub(crate) fn requires_gossip_queries(&self) -> bool {
 593                 <T as sealed::GossipQueries>::requires_feature(&self.flags)
 594         }
 595         pub(crate) fn supports_gossip_queries(&self) -> bool {
 596                 <T as sealed::GossipQueries>::supports_feature(&self.flags)
 597         }
 598         #[cfg(test)]
 599         pub(crate) fn clear_gossip_queries(mut self) -> Self {
 600                 <T as sealed::GossipQueries>::clear_bits(&mut self.flags);
 601                 self
 602         }
 603 }
 604
 605 impl<T: sealed::VariableLengthOnion> Features<T> {
 606         #[cfg(test)]
 607         pub(crate) fn requires_variable_length_onion(&self) -> bool {
 608                 <T as sealed::VariableLengthOnion>::requires_feature(&self.flags)
 609         }
 610         pub(crate) fn supports_variable_length_onion(&self) -> bool {
 611                 <T as sealed::VariableLengthOnion>::supports_feature(&self.flags)
 612         }
 613 }
 614
 615 impl<T: sealed::StaticRemoteKey> Features<T> {
 616         pub(crate) fn supports_static_remote_key(&self) -> bool {
 617                 <T as sealed::StaticRemoteKey>::supports_feature(&self.flags)
 618         }
 619         #[cfg(test)]
 620         pub(crate) fn requires_static_remote_key(&self) -> bool {
 621                 <T as sealed::StaticRemoteKey>::requires_feature(&self.flags)
 622         }
 623 }
 624
 625 impl<T: sealed::InitialRoutingSync> Features<T> {
 626         pub(crate) fn initial_routing_sync(&self) -> bool {
 627                 <T as sealed::InitialRoutingSync>::supports_feature(&self.flags)
 628         }
 629         // We are no longer setting initial_routing_sync now that gossip_queries
 630         // is enabled. This feature is ignored by a peer when gossip_queries has
 631         // been negotiated.
 632         #[cfg(test)]
 633         pub(crate) fn clear_initial_routing_sync(&mut self) {
 634                 <T as sealed::InitialRoutingSync>::clear_bits(&mut self.flags)
 635         }
 636 }
 637
 638 impl<T: sealed::PaymentSecret> Features<T> {
 639         #[cfg(test)]
 640         pub(crate) fn requires_payment_secret(&self) -> bool {
 641                 <T as sealed::PaymentSecret>::requires_feature(&self.flags)
 642         }
 643         /// Returns whether the `payment_secret` feature is supported.
 644         pub fn supports_payment_secret(&self) -> bool {
 645                 <T as sealed::PaymentSecret>::supports_feature(&self.flags)
 646         }
 647 }
 648
 649 impl<T: sealed::BasicMPP> Features<T> {
 650         #[cfg(test)]
 651         pub(crate) fn requires_basic_mpp(&self) -> bool {
 652                 <T as sealed::BasicMPP>::requires_feature(&self.flags)
 653         }
 654         // We currently never test for this since we don't actually *generate* multipath routes.
 655         pub(crate) fn supports_basic_mpp(&self) -> bool {
 656                 <T as sealed::BasicMPP>::supports_feature(&self.flags)
 657         }
 658 }
 659
 660 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 661         pub(crate) fn supports_shutdown_anysegwit(&self) -> bool {
 662                 <T as sealed::ShutdownAnySegwit>::supports_feature(&self.flags)
 663         }
 664         #[cfg(test)]
 665         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 666                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 667                 self
 668         }
 669 }
 670
 671 impl<T: sealed::Context> Writeable for Features<T> {
 672         fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
 673                 w.size_hint(self.flags.len() + 2);
 674                 (self.flags.len() as u16).write(w)?;
 675                 for f in self.flags.iter().rev() { // Swap back to big-endian
 676                         f.write(w)?;
 677                 }
 678                 Ok(())
 679         }
 680 }
 681
 682 impl<T: sealed::Context> Readable for Features<T> {
 683         fn read<R: ::std::io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 684                 let mut flags: Vec<u8> = Readable::read(r)?;
 685                 flags.reverse(); // Swap to little-endian
 686                 Ok(Self {
 687                         flags,
 688                         mark: PhantomData,
 689                 })
 690         }
 691 }
 692
 693 #[cfg(test)]
 694 mod tests {
 695         use super::{ChannelFeatures, InitFeatures, InvoiceFeatures, NodeFeatures};
 696         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
 697
 698         #[test]
 699         fn sanity_test_known_features() {
 700                 assert!(!ChannelFeatures::known().requires_unknown_bits());
 701                 assert!(!ChannelFeatures::known().supports_unknown_bits());
 702                 assert!(!InitFeatures::known().requires_unknown_bits());
 703                 assert!(!InitFeatures::known().supports_unknown_bits());
 704                 assert!(!NodeFeatures::known().requires_unknown_bits());
 705                 assert!(!NodeFeatures::known().supports_unknown_bits());
 706
 707                 assert!(InitFeatures::known().supports_upfront_shutdown_script());
 708                 assert!(NodeFeatures::known().supports_upfront_shutdown_script());
 709                 assert!(!InitFeatures::known().requires_upfront_shutdown_script());
 710                 assert!(!NodeFeatures::known().requires_upfront_shutdown_script());
 711
 712                 assert!(InitFeatures::known().supports_gossip_queries());
 713                 assert!(NodeFeatures::known().supports_gossip_queries());
 714                 assert!(!InitFeatures::known().requires_gossip_queries());
 715                 assert!(!NodeFeatures::known().requires_gossip_queries());
 716
 717                 assert!(InitFeatures::known().supports_data_loss_protect());
 718                 assert!(NodeFeatures::known().supports_data_loss_protect());
 719                 assert!(!InitFeatures::known().requires_data_loss_protect());
 720                 assert!(!NodeFeatures::known().requires_data_loss_protect());
 721
 722                 assert!(InitFeatures::known().supports_variable_length_onion());
 723                 assert!(NodeFeatures::known().supports_variable_length_onion());
 724                 assert!(InvoiceFeatures::known().supports_variable_length_onion());
 725                 assert!(InitFeatures::known().requires_variable_length_onion());
 726                 assert!(NodeFeatures::known().requires_variable_length_onion());
 727                 assert!(InvoiceFeatures::known().requires_variable_length_onion());
 728
 729                 assert!(InitFeatures::known().supports_static_remote_key());
 730                 assert!(NodeFeatures::known().supports_static_remote_key());
 731                 assert!(InitFeatures::known().requires_static_remote_key());
 732                 assert!(NodeFeatures::known().requires_static_remote_key());
 733
 734                 assert!(InitFeatures::known().supports_payment_secret());
 735                 assert!(NodeFeatures::known().supports_payment_secret());
 736                 assert!(InvoiceFeatures::known().supports_payment_secret());
 737                 assert!(InitFeatures::known().requires_payment_secret());
 738                 assert!(NodeFeatures::known().requires_payment_secret());
 739                 assert!(InvoiceFeatures::known().requires_payment_secret());
 740
 741                 assert!(InitFeatures::known().supports_basic_mpp());
 742                 assert!(NodeFeatures::known().supports_basic_mpp());
 743                 assert!(InvoiceFeatures::known().supports_basic_mpp());
 744                 assert!(!InitFeatures::known().requires_basic_mpp());
 745                 assert!(!NodeFeatures::known().requires_basic_mpp());
 746                 assert!(!InvoiceFeatures::known().requires_basic_mpp());
 747
 748                 assert!(InitFeatures::known().supports_shutdown_anysegwit());
 749                 assert!(NodeFeatures::known().supports_shutdown_anysegwit());
 750
 751                 let mut init_features = InitFeatures::known();
 752                 assert!(init_features.initial_routing_sync());
 753                 init_features.clear_initial_routing_sync();
 754                 assert!(!init_features.initial_routing_sync());
 755         }
 756
 757         #[test]
 758         fn sanity_test_unknown_bits() {
 759                 let features = ChannelFeatures::empty();
 760                 assert!(!features.requires_unknown_bits());
 761                 assert!(!features.supports_unknown_bits());
 762
 763                 let features = ChannelFeatures::empty().set_unknown_feature_required();
 764                 assert!(features.requires_unknown_bits());
 765                 assert!(features.supports_unknown_bits());
 766
 767                 let features = ChannelFeatures::empty().set_unknown_feature_optional();
 768                 assert!(!features.requires_unknown_bits());
 769                 assert!(features.supports_unknown_bits());
 770         }
 771
 772         #[test]
 773         fn convert_to_context_with_relevant_flags() {
 774                 let init_features = InitFeatures::known().clear_upfront_shutdown_script().clear_gossip_queries();
 775                 assert!(init_features.initial_routing_sync());
 776                 assert!(!init_features.supports_upfront_shutdown_script());
 777                 assert!(!init_features.supports_gossip_queries());
 778
 779                 let node_features: NodeFeatures = init_features.to_context();
 780                 {
 781                         // Check that the flags are as expected:
 782                         // - option_data_loss_protect
 783                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
 784                         // - basic_mpp
 785                         // - opt_shutdown_anysegwit
 786                         assert_eq!(node_features.flags.len(), 4);
 787                         assert_eq!(node_features.flags[0], 0b00000010);
 788                         assert_eq!(node_features.flags[1], 0b01010001);
 789                         assert_eq!(node_features.flags[2], 0b00000010);
 790                         assert_eq!(node_features.flags[3], 0b00001000);
 791                 }
 792
 793                 // Check that cleared flags are kept blank when converting back:
 794                 // - initial_routing_sync was not applicable to NodeContext
 795                 // - upfront_shutdown_script was cleared before converting
 796                 // - gossip_queries was cleared before converting
 797                 let features: InitFeatures = node_features.to_context_internal();
 798                 assert!(!features.initial_routing_sync());
 799                 assert!(!features.supports_upfront_shutdown_script());
 800                 assert!(!init_features.supports_gossip_queries());
 801         }
 802
 803         #[test]
 804         fn convert_to_context_with_unknown_flags() {
 805                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
 806                 assert!(InvoiceFeatures::known().byte_count() < NodeFeatures::known().byte_count());
 807                 let invoice_features = InvoiceFeatures::known().set_unknown_feature_optional();
 808                 assert!(invoice_features.supports_unknown_bits());
 809                 let node_features: NodeFeatures = invoice_features.to_context();
 810                 assert!(!node_features.supports_unknown_bits());
 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 }