_ 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 io;
  26 use prelude::*;
  27 use core::{cmp, fmt};
  28 use core::hash::{Hash, Hasher};
  29 use core::marker::PhantomData;
  30
  31 use bitcoin::bech32;
  32 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
  33 use ln::msgs::DecodeError;
  34 use util::ser::{Readable, Writeable, Writer};
  35
  36 mod sealed {
  37         use prelude::*;
  38         use ln::features::Features;
  39
  40         /// The context in which [`Features`] are applicable. Defines which features are required and
  41         /// which are optional for the context.
  42         pub trait Context {
  43                 /// Features that are known to the implementation, where a required feature is indicated by
  44                 /// its even bit and an optional feature is indicated by its odd bit.
  45                 const KNOWN_FEATURE_FLAGS: &'static [u8];
  46
  47                 /// Bitmask for selecting features that are known to the implementation, regardless of
  48                 /// whether each feature is required or optional.
  49                 const KNOWN_FEATURE_MASK: &'static [u8];
  50         }
  51
  52         /// Defines a [`Context`] by stating which features it requires and which are optional. Features
  53         /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
  54         /// feature identifiers.
  55         macro_rules! define_context {
  56                 ($context: ident {
  57                         required_features: [$( $( $required_feature: ident )|*, )*],
  58                         optional_features: [$( $( $optional_feature: ident )|*, )*],
  59                 }) => {
  60                         #[derive(Eq, PartialEq)]
  61                         pub struct $context {}
  62
  63                         impl Context for $context {
  64                                 const KNOWN_FEATURE_FLAGS: &'static [u8] = &[
  65                                         // For each byte, use bitwise-OR to compute the applicable flags for known
  66                                         // required features `r_i` and optional features `o_j` for all `i` and `j` such
  67                                         // that the following slice is formed:
  68                                         //
  69                                         // [
  70                                         //  `r_0` | `r_1` | ... | `o_0` | `o_1` | ...,
  71                                         //  ...,
  72                                         // ]
  73                                         $(
  74                                                 0b00_00_00_00 $(|
  75                                                         <Self as $required_feature>::REQUIRED_MASK)*
  76                                                 $(|
  77                                                         <Self as $optional_feature>::OPTIONAL_MASK)*,
  78                                         )*
  79                                 ];
  80
  81                                 const KNOWN_FEATURE_MASK: &'static [u8] = &[
  82                                         // Similar as above, but set both flags for each feature regardless of whether
  83                                         // the feature is required or optional.
  84                                         $(
  85                                                 0b00_00_00_00 $(|
  86                                                         <Self as $required_feature>::REQUIRED_MASK |
  87                                                         <Self as $required_feature>::OPTIONAL_MASK)*
  88                                                 $(|
  89                                                         <Self as $optional_feature>::REQUIRED_MASK |
  90                                                         <Self as $optional_feature>::OPTIONAL_MASK)*,
  91                                         )*
  92                                 ];
  93                         }
  94
  95                         impl alloc::fmt::Display for Features<$context> {
  96                                 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
  97                                         $(
  98                                                 $(
  99                                                         fmt.write_fmt(format_args!("{}: {}, ", stringify!($required_feature),
 100                                                                 if <$context as $required_feature>::requires_feature(&self.flags) { "required" }
 101                                                                 else if <$context as $required_feature>::supports_feature(&self.flags) { "supported" }
 102                                                                 else { "not supported" }))?;
 103                                                 )*
 104                                                 $(
 105                                                         fmt.write_fmt(format_args!("{}: {}, ", stringify!($optional_feature),
 106                                                                 if <$context as $optional_feature>::requires_feature(&self.flags) { "required" }
 107                                                                 else if <$context as $optional_feature>::supports_feature(&self.flags) { "supported" }
 108                                                                 else { "not supported" }))?;
 109                                                 )*
 110                                         )*
 111                                         fmt.write_fmt(format_args!("unknown flags: {}",
 112                                                 if self.requires_unknown_bits() { "required" }
 113                                                 else if self.supports_unknown_bits() { "supported" } else { "none" }))
 114                                 }
 115                         }
 116                 };
 117         }
 118
 119         define_context!(InitContext {
 120                 required_features: [
 121                         // Byte 0
 122                         ,
 123                         // Byte 1
 124                         VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 125                         // Byte 2
 126                         ,
 127                         // Byte 3
 128                         ,
 129                 ],
 130                 optional_features: [
 131                         // Byte 0
 132                         DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
 133                         // Byte 1
 134                         ,
 135                         // Byte 2
 136                         BasicMPP,
 137                         // Byte 3
 138                         ShutdownAnySegwit,
 139                 ],
 140         });
 141         define_context!(NodeContext {
 142                 required_features: [
 143                         // Byte 0
 144                         ,
 145                         // Byte 1
 146                         VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 147                         // Byte 2
 148                         ,
 149                         // Byte 3
 150                         ,
 151                         // Byte 4
 152                         ,
 153                         // Byte 5
 154                         ,
 155                         // Byte 6
 156                         ,
 157                 ],
 158                 optional_features: [
 159                         // Byte 0
 160                         DataLossProtect | UpfrontShutdownScript | GossipQueries,
 161                         // Byte 1
 162                         ,
 163                         // Byte 2
 164                         BasicMPP,
 165                         // Byte 3
 166                         ShutdownAnySegwit,
 167                         // Byte 4
 168                         ,
 169                         // Byte 5
 170                         ,
 171                         // Byte 6
 172                         Keysend,
 173                 ],
 174         });
 175         define_context!(ChannelContext {
 176                 required_features: [],
 177                 optional_features: [],
 178         });
 179         define_context!(InvoiceContext {
 180                 required_features: [
 181                         // Byte 0
 182                         ,
 183                         // Byte 1
 184                         VariableLengthOnion | PaymentSecret,
 185                         // Byte 2
 186                         ,
 187                 ],
 188                 optional_features: [
 189                         // Byte 0
 190                         ,
 191                         // Byte 1
 192                         ,
 193                         // Byte 2
 194                         BasicMPP,
 195                 ],
 196         });
 197
 198         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 199         /// useful for manipulating feature flags.
 200         macro_rules! define_feature {
 201                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 202                  $required_setter: ident) => {
 203                         #[doc = $doc]
 204                         ///
 205                         /// See [BOLT #9] for details.
 206                         ///
 207                         /// [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
 208                         pub trait $feature: Context {
 209                                 /// The bit used to signify that the feature is required.
 210                                 const EVEN_BIT: usize = $odd_bit - 1;
 211
 212                                 /// The bit used to signify that the feature is optional.
 213                                 const ODD_BIT: usize = $odd_bit;
 214
 215                                 /// Assertion that [`EVEN_BIT`] is actually even.
 216                                 ///
 217                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 218                                 const ASSERT_EVEN_BIT_PARITY: usize;
 219
 220                                 /// Assertion that [`ODD_BIT`] is actually odd.
 221                                 ///
 222                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 223                                 const ASSERT_ODD_BIT_PARITY: usize;
 224
 225                                 /// The byte where the feature is set.
 226                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 227
 228                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 229                                 ///
 230                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 231                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 232
 233                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 234                                 ///
 235                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 236                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 237
 238                                 /// Returns whether the feature is required by the given flags.
 239                                 #[inline]
 240                                 fn requires_feature(flags: &Vec<u8>) -> bool {
 241                                         flags.len() > Self::BYTE_OFFSET &&
 242                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
 243                                 }
 244
 245                                 /// Returns whether the feature is supported by the given flags.
 246                                 #[inline]
 247                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 248                                         flags.len() > Self::BYTE_OFFSET &&
 249                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 250                                 }
 251
 252                                 /// Sets the feature's required (even) bit in the given flags.
 253                                 #[inline]
 254                                 fn set_required_bit(flags: &mut Vec<u8>) {
 255                                         if flags.len() <= Self::BYTE_OFFSET {
 256                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 257                                         }
 258
 259                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
 260                                 }
 261
 262                                 /// Sets the feature's optional (odd) bit in the given flags.
 263                                 #[inline]
 264                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 265                                         if flags.len() <= Self::BYTE_OFFSET {
 266                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 267                                         }
 268
 269                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 270                                 }
 271
 272                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 273                                 /// flags.
 274                                 #[inline]
 275                                 fn clear_bits(flags: &mut Vec<u8>) {
 276                                         if flags.len() > Self::BYTE_OFFSET {
 277                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 278                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 279                                         }
 280
 281                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 282                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 283                                         flags.resize(size, 0u8);
 284                                 }
 285                         }
 286
 287                         impl <T: $feature> Features<T> {
 288                                 /// Set this feature as optional.
 289                                 pub fn $optional_setter(mut self) -> Self {
 290                                         <T as $feature>::set_optional_bit(&mut self.flags);
 291                                         self
 292                                 }
 293
 294                                 /// Set this feature as required.
 295                                 pub fn $required_setter(mut self) -> Self {
 296                                         <T as $feature>::set_required_bit(&mut self.flags);
 297                                         self
 298                                 }
 299                         }
 300
 301                         $(
 302                                 impl $feature for $context {
 303                                         // EVEN_BIT % 2 == 0
 304                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 305
 306                                         // ODD_BIT % 2 == 1
 307                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 308                                 }
 309                         )*
 310
 311                 }
 312         }
 313
 314         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 315                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 316                 set_data_loss_protect_required);
 317         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 318         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 319                 set_initial_routing_sync_optional, set_initial_routing_sync_required);
 320         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 321                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 322                 set_upfront_shutdown_script_required);
 323         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 324                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required);
 325         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
 326                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 327                 set_variable_length_onion_required);
 328         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext],
 329                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 330                 set_static_remote_key_required);
 331         define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
 332                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required);
 333         define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext],
 334                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required);
 335         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 336                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 337                 set_shutdown_any_segwit_required);
 338         define_feature!(55, Keysend, [NodeContext],
 339                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required);
 340
 341         #[cfg(test)]
 342         define_feature!(123456789, UnknownFeature, [NodeContext, ChannelContext, InvoiceContext],
 343                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 344                 set_unknown_feature_required);
 345 }
 346
 347 /// Tracks the set of features which a node implements, templated by the context in which it
 348 /// appears.
 349 ///
 350 /// (C-not exported) as we map the concrete feature types below directly instead
 351 #[derive(Eq)]
 352 pub struct Features<T: sealed::Context> {
 353         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 354         flags: Vec<u8>,
 355         mark: PhantomData<T>,
 356 }
 357
 358 impl<T: sealed::Context> Clone for Features<T> {
 359         fn clone(&self) -> Self {
 360                 Self {
 361                         flags: self.flags.clone(),
 362                         mark: PhantomData,
 363                 }
 364         }
 365 }
 366 impl<T: sealed::Context> Hash for Features<T> {
 367         fn hash<H: Hasher>(&self, hasher: &mut H) {
 368                 self.flags.hash(hasher);
 369         }
 370 }
 371 impl<T: sealed::Context> PartialEq for Features<T> {
 372         fn eq(&self, o: &Self) -> bool {
 373                 self.flags.eq(&o.flags)
 374         }
 375 }
 376 impl<T: sealed::Context> fmt::Debug for Features<T> {
 377         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 378                 self.flags.fmt(fmt)
 379         }
 380 }
 381
 382 /// Features used within an `init` message.
 383 pub type InitFeatures = Features<sealed::InitContext>;
 384 /// Features used within a `node_announcement` message.
 385 pub type NodeFeatures = Features<sealed::NodeContext>;
 386 /// Features used within a `channel_announcement` message.
 387 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 388 /// Features used within an invoice.
 389 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
 390
 391 impl InitFeatures {
 392         /// Writes all features present up to, and including, 13.
 393         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 394                 let len = cmp::min(2, self.flags.len());
 395                 (len as u16).write(w)?;
 396                 for i in (0..len).rev() {
 397                         if i == 0 {
 398                                 self.flags[i].write(w)?;
 399                         } else {
 400                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 401                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 402                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 403                         }
 404                 }
 405                 Ok(())
 406         }
 407
 408         /// or's another InitFeatures into this one.
 409         pub(crate) fn or(mut self, o: InitFeatures) -> InitFeatures {
 410                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
 411                 self.flags.resize(total_feature_len, 0u8);
 412                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
 413                         *byte |= *o_byte;
 414                 }
 415                 self
 416         }
 417
 418         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 419         /// are included in the result.
 420         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 421                 self.to_context_internal()
 422         }
 423 }
 424
 425 impl InvoiceFeatures {
 426         /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
 427         /// context `C` are included in the result.
 428         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 429                 self.to_context_internal()
 430         }
 431
 432         /// Getting a route for a keysend payment to a private node requires providing the payee's
 433         /// features (since they were not announced in a node announcement). However, keysend payments
 434         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 435         /// [`get_keysend_route`], thus omitting the need for payers to manually construct an
 436         /// `InvoiceFeatures` for [`get_route`].
 437         ///
 438         /// [`get_keysend_route`]: crate::routing::router::get_keysend_route
 439         /// [`get_route`]: crate::routing::router::get_route
 440         pub(crate) fn for_keysend() -> InvoiceFeatures {
 441                 InvoiceFeatures::empty().set_variable_length_onion_optional()
 442         }
 443 }
 444
 445 impl ToBase32 for InvoiceFeatures {
 446         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 447                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 448                 // minus one before dividing
 449                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 450                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 451                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 452                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 453                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 454                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 455                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 456                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 457                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 458                         if new_u5_idx > 0 {
 459                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 460                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 461                         }
 462                         if new_u5_idx > 1 {
 463                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 464                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 465                         }
 466                 }
 467                 // Trim the highest feature bits.
 468                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 469                         res_u5s.remove(0);
 470                 }
 471                 writer.write(&res_u5s)
 472         }
 473 }
 474
 475 impl Base32Len for InvoiceFeatures {
 476         fn base32_len(&self) -> usize {
 477                 self.to_base32().len()
 478         }
 479 }
 480
 481 impl FromBase32 for InvoiceFeatures {
 482         type Err = bech32::Error;
 483
 484         fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
 485                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 486                 // minus one before dividing
 487                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 488                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 489                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 490                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 491                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 492                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 493                         let chunk_u16 = chunk.to_u8() as u16;
 494                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 495                         if new_byte_idx != length_bytes - 1 {
 496                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 497                         }
 498                 }
 499                 // Trim the highest feature bits.
 500                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 501                         res_bytes.pop();
 502                 }
 503                 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
 504         }
 505 }
 506
 507 impl<T: sealed::Context> Features<T> {
 508         /// Create a blank Features with no features set
 509         pub fn empty() -> Self {
 510                 Features {
 511                         flags: Vec::new(),
 512                         mark: PhantomData,
 513                 }
 514         }
 515
 516         /// Creates a Features with the bits set which are known by the implementation
 517         pub fn known() -> Self {
 518                 Self {
 519                         flags: T::KNOWN_FEATURE_FLAGS.to_vec(),
 520                         mark: PhantomData,
 521                 }
 522         }
 523
 524         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 525         /// included in the result.
 526         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 527                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 528                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 529                 let mut flags = Vec::new();
 530                 for (i, byte) in self.flags.iter().enumerate() {
 531                         if i < from_byte_count && i < to_byte_count {
 532                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 533                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 534                                 flags.push(byte & from_known_features & to_known_features);
 535                         }
 536                 }
 537                 Features::<C> { flags, mark: PhantomData, }
 538         }
 539
 540         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 541         /// most on-the-wire encodings.
 542         /// (C-not exported) as we don't support export across multiple T
 543         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 544                 Features {
 545                         flags,
 546                         mark: PhantomData,
 547                 }
 548         }
 549
 550         #[cfg(test)]
 551         /// Gets the underlying flags set, in LE.
 552         pub fn le_flags(&self) -> &Vec<u8> {
 553                 &self.flags
 554         }
 555
 556         /// Returns true if this `Features` object contains unknown feature flags which are set as
 557         /// "required".
 558         pub fn requires_unknown_bits(&self) -> bool {
 559                 // Bitwise AND-ing with all even bits set except for known features will select required
 560                 // unknown features.
 561                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 562                 self.flags.iter().enumerate().any(|(i, &byte)| {
 563                         let required_features = 0b01_01_01_01;
 564                         let unknown_features = if i < byte_count {
 565                                 !T::KNOWN_FEATURE_MASK[i]
 566                         } else {
 567                                 0b11_11_11_11
 568                         };
 569                         (byte & (required_features & unknown_features)) != 0
 570                 })
 571         }
 572
 573         pub(crate) fn supports_unknown_bits(&self) -> bool {
 574                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 575                 // both required and optional unknown features.
 576                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 577                 self.flags.iter().enumerate().any(|(i, &byte)| {
 578                         let unknown_features = if i < byte_count {
 579                                 !T::KNOWN_FEATURE_MASK[i]
 580                         } else {
 581                                 0b11_11_11_11
 582                         };
 583                         (byte & unknown_features) != 0
 584                 })
 585         }
 586 }
 587
 588 impl<T: sealed::DataLossProtect> Features<T> {
 589         #[cfg(test)]
 590         pub(crate) fn requires_data_loss_protect(&self) -> bool {
 591                 <T as sealed::DataLossProtect>::requires_feature(&self.flags)
 592         }
 593         #[cfg(test)]
 594         pub(crate) fn supports_data_loss_protect(&self) -> bool {
 595                 <T as sealed::DataLossProtect>::supports_feature(&self.flags)
 596         }
 597 }
 598
 599 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 600         #[cfg(test)]
 601         pub(crate) fn requires_upfront_shutdown_script(&self) -> bool {
 602                 <T as sealed::UpfrontShutdownScript>::requires_feature(&self.flags)
 603         }
 604         pub(crate) fn supports_upfront_shutdown_script(&self) -> bool {
 605                 <T as sealed::UpfrontShutdownScript>::supports_feature(&self.flags)
 606         }
 607         #[cfg(test)]
 608         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 609                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 610                 self
 611         }
 612 }
 613
 614
 615 impl<T: sealed::GossipQueries> Features<T> {
 616         #[cfg(test)]
 617         pub(crate) fn requires_gossip_queries(&self) -> bool {
 618                 <T as sealed::GossipQueries>::requires_feature(&self.flags)
 619         }
 620         pub(crate) fn supports_gossip_queries(&self) -> bool {
 621                 <T as sealed::GossipQueries>::supports_feature(&self.flags)
 622         }
 623         #[cfg(test)]
 624         pub(crate) fn clear_gossip_queries(mut self) -> Self {
 625                 <T as sealed::GossipQueries>::clear_bits(&mut self.flags);
 626                 self
 627         }
 628 }
 629
 630 impl<T: sealed::VariableLengthOnion> Features<T> {
 631         #[cfg(test)]
 632         pub(crate) fn requires_variable_length_onion(&self) -> bool {
 633                 <T as sealed::VariableLengthOnion>::requires_feature(&self.flags)
 634         }
 635         pub(crate) fn supports_variable_length_onion(&self) -> bool {
 636                 <T as sealed::VariableLengthOnion>::supports_feature(&self.flags)
 637         }
 638 }
 639
 640 impl<T: sealed::StaticRemoteKey> Features<T> {
 641         pub(crate) fn supports_static_remote_key(&self) -> bool {
 642                 <T as sealed::StaticRemoteKey>::supports_feature(&self.flags)
 643         }
 644         #[cfg(test)]
 645         pub(crate) fn requires_static_remote_key(&self) -> bool {
 646                 <T as sealed::StaticRemoteKey>::requires_feature(&self.flags)
 647         }
 648 }
 649
 650 impl<T: sealed::InitialRoutingSync> Features<T> {
 651         pub(crate) fn initial_routing_sync(&self) -> bool {
 652                 <T as sealed::InitialRoutingSync>::supports_feature(&self.flags)
 653         }
 654         // We are no longer setting initial_routing_sync now that gossip_queries
 655         // is enabled. This feature is ignored by a peer when gossip_queries has
 656         // been negotiated.
 657         #[cfg(test)]
 658         pub(crate) fn clear_initial_routing_sync(&mut self) {
 659                 <T as sealed::InitialRoutingSync>::clear_bits(&mut self.flags)
 660         }
 661 }
 662
 663 impl<T: sealed::PaymentSecret> Features<T> {
 664         #[cfg(test)]
 665         pub(crate) fn requires_payment_secret(&self) -> bool {
 666                 <T as sealed::PaymentSecret>::requires_feature(&self.flags)
 667         }
 668         /// Returns whether the `payment_secret` feature is supported.
 669         pub fn supports_payment_secret(&self) -> bool {
 670                 <T as sealed::PaymentSecret>::supports_feature(&self.flags)
 671         }
 672 }
 673
 674 impl<T: sealed::BasicMPP> Features<T> {
 675         #[cfg(test)]
 676         pub(crate) fn requires_basic_mpp(&self) -> bool {
 677                 <T as sealed::BasicMPP>::requires_feature(&self.flags)
 678         }
 679         // We currently never test for this since we don't actually *generate* multipath routes.
 680         pub(crate) fn supports_basic_mpp(&self) -> bool {
 681                 <T as sealed::BasicMPP>::supports_feature(&self.flags)
 682         }
 683 }
 684
 685 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 686         pub(crate) fn supports_shutdown_anysegwit(&self) -> bool {
 687                 <T as sealed::ShutdownAnySegwit>::supports_feature(&self.flags)
 688         }
 689         #[cfg(test)]
 690         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 691                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 692                 self
 693         }
 694 }
 695
 696 impl<T: sealed::Context> Writeable for Features<T> {
 697         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 698                 (self.flags.len() as u16).write(w)?;
 699                 for f in self.flags.iter().rev() { // Swap back to big-endian
 700                         f.write(w)?;
 701                 }
 702                 Ok(())
 703         }
 704 }
 705
 706 impl<T: sealed::Context> Readable for Features<T> {
 707         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 708                 let mut flags: Vec<u8> = Readable::read(r)?;
 709                 flags.reverse(); // Swap to little-endian
 710                 Ok(Self {
 711                         flags,
 712                         mark: PhantomData,
 713                 })
 714         }
 715 }
 716
 717 #[cfg(test)]
 718 mod tests {
 719         use super::{ChannelFeatures, InitFeatures, InvoiceFeatures, NodeFeatures};
 720         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
 721
 722         #[test]
 723         fn sanity_test_known_features() {
 724                 assert!(!ChannelFeatures::known().requires_unknown_bits());
 725                 assert!(!ChannelFeatures::known().supports_unknown_bits());
 726                 assert!(!InitFeatures::known().requires_unknown_bits());
 727                 assert!(!InitFeatures::known().supports_unknown_bits());
 728                 assert!(!NodeFeatures::known().requires_unknown_bits());
 729                 assert!(!NodeFeatures::known().supports_unknown_bits());
 730
 731                 assert!(InitFeatures::known().supports_upfront_shutdown_script());
 732                 assert!(NodeFeatures::known().supports_upfront_shutdown_script());
 733                 assert!(!InitFeatures::known().requires_upfront_shutdown_script());
 734                 assert!(!NodeFeatures::known().requires_upfront_shutdown_script());
 735
 736                 assert!(InitFeatures::known().supports_gossip_queries());
 737                 assert!(NodeFeatures::known().supports_gossip_queries());
 738                 assert!(!InitFeatures::known().requires_gossip_queries());
 739                 assert!(!NodeFeatures::known().requires_gossip_queries());
 740
 741                 assert!(InitFeatures::known().supports_data_loss_protect());
 742                 assert!(NodeFeatures::known().supports_data_loss_protect());
 743                 assert!(!InitFeatures::known().requires_data_loss_protect());
 744                 assert!(!NodeFeatures::known().requires_data_loss_protect());
 745
 746                 assert!(InitFeatures::known().supports_variable_length_onion());
 747                 assert!(NodeFeatures::known().supports_variable_length_onion());
 748                 assert!(InvoiceFeatures::known().supports_variable_length_onion());
 749                 assert!(InitFeatures::known().requires_variable_length_onion());
 750                 assert!(NodeFeatures::known().requires_variable_length_onion());
 751                 assert!(InvoiceFeatures::known().requires_variable_length_onion());
 752
 753                 assert!(InitFeatures::known().supports_static_remote_key());
 754                 assert!(NodeFeatures::known().supports_static_remote_key());
 755                 assert!(InitFeatures::known().requires_static_remote_key());
 756                 assert!(NodeFeatures::known().requires_static_remote_key());
 757
 758                 assert!(InitFeatures::known().supports_payment_secret());
 759                 assert!(NodeFeatures::known().supports_payment_secret());
 760                 assert!(InvoiceFeatures::known().supports_payment_secret());
 761                 assert!(InitFeatures::known().requires_payment_secret());
 762                 assert!(NodeFeatures::known().requires_payment_secret());
 763                 assert!(InvoiceFeatures::known().requires_payment_secret());
 764
 765                 assert!(InitFeatures::known().supports_basic_mpp());
 766                 assert!(NodeFeatures::known().supports_basic_mpp());
 767                 assert!(InvoiceFeatures::known().supports_basic_mpp());
 768                 assert!(!InitFeatures::known().requires_basic_mpp());
 769                 assert!(!NodeFeatures::known().requires_basic_mpp());
 770                 assert!(!InvoiceFeatures::known().requires_basic_mpp());
 771
 772                 assert!(InitFeatures::known().supports_shutdown_anysegwit());
 773                 assert!(NodeFeatures::known().supports_shutdown_anysegwit());
 774
 775                 let mut init_features = InitFeatures::known();
 776                 assert!(init_features.initial_routing_sync());
 777                 init_features.clear_initial_routing_sync();
 778                 assert!(!init_features.initial_routing_sync());
 779         }
 780
 781         #[test]
 782         fn sanity_test_unknown_bits() {
 783                 let features = ChannelFeatures::empty();
 784                 assert!(!features.requires_unknown_bits());
 785                 assert!(!features.supports_unknown_bits());
 786
 787                 let features = ChannelFeatures::empty().set_unknown_feature_required();
 788                 assert!(features.requires_unknown_bits());
 789                 assert!(features.supports_unknown_bits());
 790
 791                 let features = ChannelFeatures::empty().set_unknown_feature_optional();
 792                 assert!(!features.requires_unknown_bits());
 793                 assert!(features.supports_unknown_bits());
 794         }
 795
 796         #[test]
 797         fn convert_to_context_with_relevant_flags() {
 798                 let init_features = InitFeatures::known().clear_upfront_shutdown_script().clear_gossip_queries();
 799                 assert!(init_features.initial_routing_sync());
 800                 assert!(!init_features.supports_upfront_shutdown_script());
 801                 assert!(!init_features.supports_gossip_queries());
 802
 803                 let node_features: NodeFeatures = init_features.to_context();
 804                 {
 805                         // Check that the flags are as expected:
 806                         // - option_data_loss_protect
 807                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
 808                         // - basic_mpp
 809                         // - opt_shutdown_anysegwit
 810                         assert_eq!(node_features.flags.len(), 4);
 811                         assert_eq!(node_features.flags[0], 0b00000010);
 812                         assert_eq!(node_features.flags[1], 0b01010001);
 813                         assert_eq!(node_features.flags[2], 0b00000010);
 814                         assert_eq!(node_features.flags[3], 0b00001000);
 815                 }
 816
 817                 // Check that cleared flags are kept blank when converting back:
 818                 // - initial_routing_sync was not applicable to NodeContext
 819                 // - upfront_shutdown_script was cleared before converting
 820                 // - gossip_queries was cleared before converting
 821                 let features: InitFeatures = node_features.to_context_internal();
 822                 assert!(!features.initial_routing_sync());
 823                 assert!(!features.supports_upfront_shutdown_script());
 824                 assert!(!init_features.supports_gossip_queries());
 825         }
 826
 827         #[test]
 828         fn convert_to_context_with_unknown_flags() {
 829                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
 830                 assert!(InvoiceFeatures::known().flags.len() < NodeFeatures::known().flags.len());
 831                 let invoice_features = InvoiceFeatures::known().set_unknown_feature_optional();
 832                 assert!(invoice_features.supports_unknown_bits());
 833                 let node_features: NodeFeatures = invoice_features.to_context();
 834                 assert!(!node_features.supports_unknown_bits());
 835         }
 836
 837         #[test]
 838         fn set_feature_bits() {
 839                 let features = InvoiceFeatures::empty()
 840                         .set_basic_mpp_optional()
 841                         .set_payment_secret_required();
 842                 assert!(features.supports_basic_mpp());
 843                 assert!(!features.requires_basic_mpp());
 844                 assert!(features.requires_payment_secret());
 845                 assert!(features.supports_payment_secret());
 846         }
 847
 848         #[test]
 849         fn invoice_features_encoding() {
 850                 let features_as_u5s = vec![
 851                         u5::try_from_u8(6).unwrap(),
 852                         u5::try_from_u8(10).unwrap(),
 853                         u5::try_from_u8(25).unwrap(),
 854                         u5::try_from_u8(1).unwrap(),
 855                         u5::try_from_u8(10).unwrap(),
 856                         u5::try_from_u8(0).unwrap(),
 857                         u5::try_from_u8(20).unwrap(),
 858                         u5::try_from_u8(2).unwrap(),
 859                         u5::try_from_u8(0).unwrap(),
 860                         u5::try_from_u8(6).unwrap(),
 861                         u5::try_from_u8(0).unwrap(),
 862                         u5::try_from_u8(16).unwrap(),
 863                         u5::try_from_u8(1).unwrap(),
 864                 ];
 865                 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
 866
 867                 // Test length calculation.
 868                 assert_eq!(features.base32_len(), 13);
 869
 870                 // Test serialization.
 871                 let features_serialized = features.to_base32();
 872                 assert_eq!(features_as_u5s, features_serialized);
 873
 874                 // Test deserialization.
 875                 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
 876                 assert_eq!(features, features_deserialized);
 877         }
 878 }