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