_ 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, io_extras};
  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         // This isn't a "real" feature context, and is only used in the channel_type field in an
 198         // `OpenChannel` message.
 199         define_context!(ChannelTypeContext {
 200                 required_features: [
 201                         // Byte 0
 202                         ,
 203                         // Byte 1
 204                         StaticRemoteKey,
 205                         // Byte 2
 206                         ,
 207                         // Byte 3
 208                         ,
 209                 ],
 210                 optional_features: [
 211                         // Byte 0
 212                         ,
 213                         // Byte 1
 214                         ,
 215                         // Byte 2
 216                         ,
 217                         // Byte 3
 218                         ,
 219                 ],
 220         });
 221
 222         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 223         /// useful for manipulating feature flags.
 224         macro_rules! define_feature {
 225                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 226                  $required_setter: ident, $supported_getter: ident) => {
 227                         #[doc = $doc]
 228                         ///
 229                         /// See [BOLT #9] for details.
 230                         ///
 231                         /// [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
 232                         pub trait $feature: Context {
 233                                 /// The bit used to signify that the feature is required.
 234                                 const EVEN_BIT: usize = $odd_bit - 1;
 235
 236                                 /// The bit used to signify that the feature is optional.
 237                                 const ODD_BIT: usize = $odd_bit;
 238
 239                                 /// Assertion that [`EVEN_BIT`] is actually even.
 240                                 ///
 241                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 242                                 const ASSERT_EVEN_BIT_PARITY: usize;
 243
 244                                 /// Assertion that [`ODD_BIT`] is actually odd.
 245                                 ///
 246                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 247                                 const ASSERT_ODD_BIT_PARITY: usize;
 248
 249                                 /// The byte where the feature is set.
 250                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 251
 252                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 253                                 ///
 254                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 255                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 256
 257                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 258                                 ///
 259                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 260                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 261
 262                                 /// Returns whether the feature is required by the given flags.
 263                                 #[inline]
 264                                 fn requires_feature(flags: &Vec<u8>) -> bool {
 265                                         flags.len() > Self::BYTE_OFFSET &&
 266                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
 267                                 }
 268
 269                                 /// Returns whether the feature is supported by the given flags.
 270                                 #[inline]
 271                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 272                                         flags.len() > Self::BYTE_OFFSET &&
 273                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 274                                 }
 275
 276                                 /// Sets the feature's required (even) bit in the given flags.
 277                                 #[inline]
 278                                 fn set_required_bit(flags: &mut Vec<u8>) {
 279                                         if flags.len() <= Self::BYTE_OFFSET {
 280                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 281                                         }
 282
 283                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
 284                                 }
 285
 286                                 /// Sets the feature's optional (odd) bit in the given flags.
 287                                 #[inline]
 288                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 289                                         if flags.len() <= Self::BYTE_OFFSET {
 290                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 291                                         }
 292
 293                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 294                                 }
 295
 296                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 297                                 /// flags.
 298                                 #[inline]
 299                                 fn clear_bits(flags: &mut Vec<u8>) {
 300                                         if flags.len() > Self::BYTE_OFFSET {
 301                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 302                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 303                                         }
 304
 305                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 306                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 307                                         flags.resize(size, 0u8);
 308                                 }
 309                         }
 310
 311                         impl <T: $feature> Features<T> {
 312                                 /// Set this feature as optional.
 313                                 pub fn $optional_setter(mut self) -> Self {
 314                                         <T as $feature>::set_optional_bit(&mut self.flags);
 315                                         self
 316                                 }
 317
 318                                 /// Set this feature as required.
 319                                 pub fn $required_setter(mut self) -> Self {
 320                                         <T as $feature>::set_required_bit(&mut self.flags);
 321                                         self
 322                                 }
 323
 324                                 /// Checks if this feature is supported.
 325                                 pub fn $supported_getter(&self) -> bool {
 326                                         <T as $feature>::supports_feature(&self.flags)
 327                                 }
 328                         }
 329
 330                         $(
 331                                 impl $feature for $context {
 332                                         // EVEN_BIT % 2 == 0
 333                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 334
 335                                         // ODD_BIT % 2 == 1
 336                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 337                                 }
 338                         )*
 339                 };
 340                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 341                  $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
 342                         define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
 343                         impl <T: $feature> Features<T> {
 344                                 /// Checks if this feature is required.
 345                                 pub fn $required_getter(&self) -> bool {
 346                                         <T as $feature>::requires_feature(&self.flags)
 347                                 }
 348                         }
 349                 }
 350         }
 351
 352         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 353                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 354                 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
 355         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 356         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 357                 set_initial_routing_sync_optional, set_initial_routing_sync_required,
 358                 initial_routing_sync);
 359         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 360                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 361                 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
 362                 requires_upfront_shutdown_script);
 363         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 364                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
 365                 supports_gossip_queries, requires_gossip_queries);
 366         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
 367                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 368                 set_variable_length_onion_required, supports_variable_length_onion,
 369                 requires_variable_length_onion);
 370         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
 371                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 372                 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
 373         define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
 374                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
 375                 supports_payment_secret, requires_payment_secret);
 376         define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext],
 377                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
 378                 supports_basic_mpp, requires_basic_mpp);
 379         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 380                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 381                 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
 382         define_feature!(55, Keysend, [NodeContext],
 383                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
 384                 supports_keysend, requires_keysend);
 385
 386         #[cfg(test)]
 387         define_feature!(123456789, UnknownFeature, [NodeContext, ChannelContext, InvoiceContext],
 388                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 389                 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
 390 }
 391
 392 /// Tracks the set of features which a node implements, templated by the context in which it
 393 /// appears.
 394 ///
 395 /// (C-not exported) as we map the concrete feature types below directly instead
 396 #[derive(Eq)]
 397 pub struct Features<T: sealed::Context> {
 398         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 399         flags: Vec<u8>,
 400         mark: PhantomData<T>,
 401 }
 402
 403 impl<T: sealed::Context> Clone for Features<T> {
 404         fn clone(&self) -> Self {
 405                 Self {
 406                         flags: self.flags.clone(),
 407                         mark: PhantomData,
 408                 }
 409         }
 410 }
 411 impl<T: sealed::Context> Hash for Features<T> {
 412         fn hash<H: Hasher>(&self, hasher: &mut H) {
 413                 self.flags.hash(hasher);
 414         }
 415 }
 416 impl<T: sealed::Context> PartialEq for Features<T> {
 417         fn eq(&self, o: &Self) -> bool {
 418                 self.flags.eq(&o.flags)
 419         }
 420 }
 421 impl<T: sealed::Context> fmt::Debug for Features<T> {
 422         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 423                 self.flags.fmt(fmt)
 424         }
 425 }
 426
 427 /// Features used within an `init` message.
 428 pub type InitFeatures = Features<sealed::InitContext>;
 429 /// Features used within a `node_announcement` message.
 430 pub type NodeFeatures = Features<sealed::NodeContext>;
 431 /// Features used within a `channel_announcement` message.
 432 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 433 /// Features used within an invoice.
 434 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
 435
 436 /// Features used within the channel_type field in an OpenChannel message.
 437 ///
 438 /// A channel is always of some known "type", describing the transaction formats used and the exact
 439 /// semantics of our interaction with our peer.
 440 ///
 441 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
 442 /// the counterparty, only required features are allowed here.
 443 ///
 444 /// This is serialized differently from other feature types - it is not prefixed by a length, and
 445 /// thus must only appear inside a TLV where its length is known in advance.
 446 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
 447
 448 impl InitFeatures {
 449         /// Writes all features present up to, and including, 13.
 450         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 451                 let len = cmp::min(2, self.flags.len());
 452                 (len as u16).write(w)?;
 453                 for i in (0..len).rev() {
 454                         if i == 0 {
 455                                 self.flags[i].write(w)?;
 456                         } else {
 457                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 458                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 459                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 460                         }
 461                 }
 462                 Ok(())
 463         }
 464
 465         /// or's another InitFeatures into this one.
 466         pub(crate) fn or(mut self, o: InitFeatures) -> InitFeatures {
 467                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
 468                 self.flags.resize(total_feature_len, 0u8);
 469                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
 470                         *byte |= *o_byte;
 471                 }
 472                 self
 473         }
 474
 475         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 476         /// are included in the result.
 477         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 478                 self.to_context_internal()
 479         }
 480 }
 481
 482 impl InvoiceFeatures {
 483         /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
 484         /// context `C` are included in the result.
 485         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 486                 self.to_context_internal()
 487         }
 488
 489         /// Getting a route for a keysend payment to a private node requires providing the payee's
 490         /// features (since they were not announced in a node announcement). However, keysend payments
 491         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 492         /// [`Payee::for_keysend`], thus omitting the need for payers to manually construct an
 493         /// `InvoiceFeatures` for [`find_route`].
 494         ///
 495         /// [`Payee::for_keysend`]: crate::routing::router::Payee::for_keysend
 496         /// [`find_route`]: crate::routing::router::find_route
 497         pub(crate) fn for_keysend() -> InvoiceFeatures {
 498                 InvoiceFeatures::empty().set_variable_length_onion_optional()
 499         }
 500 }
 501
 502 impl ChannelTypeFeatures {
 503         /// Constructs the implicit channel type based on the common supported types between us and our
 504         /// counterparty
 505         pub(crate) fn from_counterparty_init(counterparty_init: &InitFeatures) -> Self {
 506                 let mut ret = counterparty_init.to_context_internal();
 507                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
 508                 // optional bits and then AND out the optional ones.
 509                 for byte in ret.flags.iter_mut() {
 510                         *byte |= (*byte & 0b10_10_10_10) >> 1;
 511                         *byte &= 0b01_01_01_01;
 512                 }
 513                 ret
 514         }
 515
 516         /// Constructs a ChannelTypeFeatures with only static_remotekey set
 517         pub(crate) fn only_static_remote_key() -> Self {
 518                 let mut ret = Self::empty();
 519                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 520                 ret
 521         }
 522 }
 523
 524 impl ToBase32 for InvoiceFeatures {
 525         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 526                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 527                 // minus one before dividing
 528                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 529                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 530                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 531                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 532                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 533                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 534                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 535                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 536                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 537                         if new_u5_idx > 0 {
 538                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 539                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 540                         }
 541                         if new_u5_idx > 1 {
 542                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 543                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 544                         }
 545                 }
 546                 // Trim the highest feature bits.
 547                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 548                         res_u5s.remove(0);
 549                 }
 550                 writer.write(&res_u5s)
 551         }
 552 }
 553
 554 impl Base32Len for InvoiceFeatures {
 555         fn base32_len(&self) -> usize {
 556                 self.to_base32().len()
 557         }
 558 }
 559
 560 impl FromBase32 for InvoiceFeatures {
 561         type Err = bech32::Error;
 562
 563         fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
 564                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 565                 // minus one before dividing
 566                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 567                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 568                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 569                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 570                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 571                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 572                         let chunk_u16 = chunk.to_u8() as u16;
 573                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 574                         if new_byte_idx != length_bytes - 1 {
 575                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 576                         }
 577                 }
 578                 // Trim the highest feature bits.
 579                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 580                         res_bytes.pop();
 581                 }
 582                 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
 583         }
 584 }
 585
 586 impl<T: sealed::Context> Features<T> {
 587         /// Create a blank Features with no features set
 588         pub fn empty() -> Self {
 589                 Features {
 590                         flags: Vec::new(),
 591                         mark: PhantomData,
 592                 }
 593         }
 594
 595         /// Creates a Features with the bits set which are known by the implementation
 596         pub fn known() -> Self {
 597                 Self {
 598                         flags: T::KNOWN_FEATURE_FLAGS.to_vec(),
 599                         mark: PhantomData,
 600                 }
 601         }
 602
 603         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 604         /// included in the result.
 605         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 606                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 607                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 608                 let mut flags = Vec::new();
 609                 for (i, byte) in self.flags.iter().enumerate() {
 610                         if i < from_byte_count && i < to_byte_count {
 611                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 612                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 613                                 flags.push(byte & from_known_features & to_known_features);
 614                         }
 615                 }
 616                 Features::<C> { flags, mark: PhantomData, }
 617         }
 618
 619         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 620         /// most on-the-wire encodings.
 621         /// (C-not exported) as we don't support export across multiple T
 622         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 623                 Features {
 624                         flags,
 625                         mark: PhantomData,
 626                 }
 627         }
 628
 629         #[cfg(test)]
 630         /// Gets the underlying flags set, in LE.
 631         pub fn le_flags(&self) -> &Vec<u8> {
 632                 &self.flags
 633         }
 634
 635         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 636                 for f in self.flags.iter().rev() { // Swap back to big-endian
 637                         f.write(w)?;
 638                 }
 639                 Ok(())
 640         }
 641
 642         fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
 643                 flags.reverse(); // Swap to little-endian
 644                 Self {
 645                         flags,
 646                         mark: PhantomData,
 647                 }
 648         }
 649
 650         pub(crate) fn supports_any_optional_bits(&self) -> bool {
 651                 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
 652         }
 653
 654         /// Returns true if this `Features` object contains unknown feature flags which are set as
 655         /// "required".
 656         pub fn requires_unknown_bits(&self) -> bool {
 657                 // Bitwise AND-ing with all even bits set except for known features will select required
 658                 // unknown features.
 659                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 660                 self.flags.iter().enumerate().any(|(i, &byte)| {
 661                         let required_features = 0b01_01_01_01;
 662                         let unknown_features = if i < byte_count {
 663                                 !T::KNOWN_FEATURE_MASK[i]
 664                         } else {
 665                                 0b11_11_11_11
 666                         };
 667                         (byte & (required_features & unknown_features)) != 0
 668                 })
 669         }
 670
 671         pub(crate) fn supports_unknown_bits(&self) -> bool {
 672                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 673                 // both required and optional unknown features.
 674                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 675                 self.flags.iter().enumerate().any(|(i, &byte)| {
 676                         let unknown_features = if i < byte_count {
 677                                 !T::KNOWN_FEATURE_MASK[i]
 678                         } else {
 679                                 0b11_11_11_11
 680                         };
 681                         (byte & unknown_features) != 0
 682                 })
 683         }
 684 }
 685
 686 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 687         #[cfg(test)]
 688         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 689                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 690                 self
 691         }
 692 }
 693
 694
 695 impl<T: sealed::GossipQueries> Features<T> {
 696         #[cfg(test)]
 697         pub(crate) fn clear_gossip_queries(mut self) -> Self {
 698                 <T as sealed::GossipQueries>::clear_bits(&mut self.flags);
 699                 self
 700         }
 701 }
 702
 703 impl<T: sealed::InitialRoutingSync> Features<T> {
 704         // We are no longer setting initial_routing_sync now that gossip_queries
 705         // is enabled. This feature is ignored by a peer when gossip_queries has
 706         // been negotiated.
 707         #[cfg(test)]
 708         pub(crate) fn clear_initial_routing_sync(&mut self) {
 709                 <T as sealed::InitialRoutingSync>::clear_bits(&mut self.flags)
 710         }
 711 }
 712
 713 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 714         #[cfg(test)]
 715         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 716                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 717                 self
 718         }
 719 }
 720 macro_rules! impl_feature_len_prefixed_write {
 721         ($features: ident) => {
 722                 impl Writeable for $features {
 723                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 724                                 (self.flags.len() as u16).write(w)?;
 725                                 self.write_be(w)
 726                         }
 727                 }
 728                 impl Readable for $features {
 729                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 730                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
 731                         }
 732                 }
 733         }
 734 }
 735 impl_feature_len_prefixed_write!(InitFeatures);
 736 impl_feature_len_prefixed_write!(ChannelFeatures);
 737 impl_feature_len_prefixed_write!(NodeFeatures);
 738 impl_feature_len_prefixed_write!(InvoiceFeatures);
 739
 740 // Because ChannelTypeFeatures only appears inside of TLVs, it doesn't have a length prefix when
 741 // serialized. Thus, we can't use `impl_feature_len_prefixed_write`, above, and have to write our
 742 // own serialization.
 743 impl Writeable for ChannelTypeFeatures {
 744         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 745                 self.write_be(w)
 746         }
 747 }
 748 impl Readable for ChannelTypeFeatures {
 749         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 750                 let v = io_extras::read_to_end(r)?;
 751                 Ok(Self::from_be_bytes(v))
 752         }
 753 }
 754
 755 #[cfg(test)]
 756 mod tests {
 757         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures};
 758         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
 759
 760         #[test]
 761         fn sanity_test_known_features() {
 762                 assert!(!ChannelFeatures::known().requires_unknown_bits());
 763                 assert!(!ChannelFeatures::known().supports_unknown_bits());
 764                 assert!(!InitFeatures::known().requires_unknown_bits());
 765                 assert!(!InitFeatures::known().supports_unknown_bits());
 766                 assert!(!NodeFeatures::known().requires_unknown_bits());
 767                 assert!(!NodeFeatures::known().supports_unknown_bits());
 768
 769                 assert!(InitFeatures::known().supports_upfront_shutdown_script());
 770                 assert!(NodeFeatures::known().supports_upfront_shutdown_script());
 771                 assert!(!InitFeatures::known().requires_upfront_shutdown_script());
 772                 assert!(!NodeFeatures::known().requires_upfront_shutdown_script());
 773
 774                 assert!(InitFeatures::known().supports_gossip_queries());
 775                 assert!(NodeFeatures::known().supports_gossip_queries());
 776                 assert!(!InitFeatures::known().requires_gossip_queries());
 777                 assert!(!NodeFeatures::known().requires_gossip_queries());
 778
 779                 assert!(InitFeatures::known().supports_data_loss_protect());
 780                 assert!(NodeFeatures::known().supports_data_loss_protect());
 781                 assert!(!InitFeatures::known().requires_data_loss_protect());
 782                 assert!(!NodeFeatures::known().requires_data_loss_protect());
 783
 784                 assert!(InitFeatures::known().supports_variable_length_onion());
 785                 assert!(NodeFeatures::known().supports_variable_length_onion());
 786                 assert!(InvoiceFeatures::known().supports_variable_length_onion());
 787                 assert!(InitFeatures::known().requires_variable_length_onion());
 788                 assert!(NodeFeatures::known().requires_variable_length_onion());
 789                 assert!(InvoiceFeatures::known().requires_variable_length_onion());
 790
 791                 assert!(InitFeatures::known().supports_static_remote_key());
 792                 assert!(NodeFeatures::known().supports_static_remote_key());
 793                 assert!(InitFeatures::known().requires_static_remote_key());
 794                 assert!(NodeFeatures::known().requires_static_remote_key());
 795
 796                 assert!(InitFeatures::known().supports_payment_secret());
 797                 assert!(NodeFeatures::known().supports_payment_secret());
 798                 assert!(InvoiceFeatures::known().supports_payment_secret());
 799                 assert!(InitFeatures::known().requires_payment_secret());
 800                 assert!(NodeFeatures::known().requires_payment_secret());
 801                 assert!(InvoiceFeatures::known().requires_payment_secret());
 802
 803                 assert!(InitFeatures::known().supports_basic_mpp());
 804                 assert!(NodeFeatures::known().supports_basic_mpp());
 805                 assert!(InvoiceFeatures::known().supports_basic_mpp());
 806                 assert!(!InitFeatures::known().requires_basic_mpp());
 807                 assert!(!NodeFeatures::known().requires_basic_mpp());
 808                 assert!(!InvoiceFeatures::known().requires_basic_mpp());
 809
 810                 assert!(InitFeatures::known().supports_shutdown_anysegwit());
 811                 assert!(NodeFeatures::known().supports_shutdown_anysegwit());
 812
 813                 let mut init_features = InitFeatures::known();
 814                 assert!(init_features.initial_routing_sync());
 815                 init_features.clear_initial_routing_sync();
 816                 assert!(!init_features.initial_routing_sync());
 817         }
 818
 819         #[test]
 820         fn sanity_test_unknown_bits() {
 821                 let features = ChannelFeatures::empty();
 822                 assert!(!features.requires_unknown_bits());
 823                 assert!(!features.supports_unknown_bits());
 824
 825                 let features = ChannelFeatures::empty().set_unknown_feature_required();
 826                 assert!(features.requires_unknown_bits());
 827                 assert!(features.supports_unknown_bits());
 828
 829                 let features = ChannelFeatures::empty().set_unknown_feature_optional();
 830                 assert!(!features.requires_unknown_bits());
 831                 assert!(features.supports_unknown_bits());
 832         }
 833
 834         #[test]
 835         fn convert_to_context_with_relevant_flags() {
 836                 let init_features = InitFeatures::known().clear_upfront_shutdown_script().clear_gossip_queries();
 837                 assert!(init_features.initial_routing_sync());
 838                 assert!(!init_features.supports_upfront_shutdown_script());
 839                 assert!(!init_features.supports_gossip_queries());
 840
 841                 let node_features: NodeFeatures = init_features.to_context();
 842                 {
 843                         // Check that the flags are as expected:
 844                         // - option_data_loss_protect
 845                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
 846                         // - basic_mpp
 847                         // - opt_shutdown_anysegwit
 848                         assert_eq!(node_features.flags.len(), 4);
 849                         assert_eq!(node_features.flags[0], 0b00000010);
 850                         assert_eq!(node_features.flags[1], 0b01010001);
 851                         assert_eq!(node_features.flags[2], 0b00000010);
 852                         assert_eq!(node_features.flags[3], 0b00001000);
 853                 }
 854
 855                 // Check that cleared flags are kept blank when converting back:
 856                 // - initial_routing_sync was not applicable to NodeContext
 857                 // - upfront_shutdown_script was cleared before converting
 858                 // - gossip_queries was cleared before converting
 859                 let features: InitFeatures = node_features.to_context_internal();
 860                 assert!(!features.initial_routing_sync());
 861                 assert!(!features.supports_upfront_shutdown_script());
 862                 assert!(!init_features.supports_gossip_queries());
 863         }
 864
 865         #[test]
 866         fn convert_to_context_with_unknown_flags() {
 867                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
 868                 assert!(InvoiceFeatures::known().flags.len() < NodeFeatures::known().flags.len());
 869                 let invoice_features = InvoiceFeatures::known().set_unknown_feature_optional();
 870                 assert!(invoice_features.supports_unknown_bits());
 871                 let node_features: NodeFeatures = invoice_features.to_context();
 872                 assert!(!node_features.supports_unknown_bits());
 873         }
 874
 875         #[test]
 876         fn set_feature_bits() {
 877                 let features = InvoiceFeatures::empty()
 878                         .set_basic_mpp_optional()
 879                         .set_payment_secret_required();
 880                 assert!(features.supports_basic_mpp());
 881                 assert!(!features.requires_basic_mpp());
 882                 assert!(features.requires_payment_secret());
 883                 assert!(features.supports_payment_secret());
 884         }
 885
 886         #[test]
 887         fn invoice_features_encoding() {
 888                 let features_as_u5s = vec![
 889                         u5::try_from_u8(6).unwrap(),
 890                         u5::try_from_u8(10).unwrap(),
 891                         u5::try_from_u8(25).unwrap(),
 892                         u5::try_from_u8(1).unwrap(),
 893                         u5::try_from_u8(10).unwrap(),
 894                         u5::try_from_u8(0).unwrap(),
 895                         u5::try_from_u8(20).unwrap(),
 896                         u5::try_from_u8(2).unwrap(),
 897                         u5::try_from_u8(0).unwrap(),
 898                         u5::try_from_u8(6).unwrap(),
 899                         u5::try_from_u8(0).unwrap(),
 900                         u5::try_from_u8(16).unwrap(),
 901                         u5::try_from_u8(1).unwrap(),
 902                 ];
 903                 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
 904
 905                 // Test length calculation.
 906                 assert_eq!(features.base32_len(), 13);
 907
 908                 // Test serialization.
 909                 let features_serialized = features.to_base32();
 910                 assert_eq!(features_as_u5s, features_serialized);
 911
 912                 // Test deserialization.
 913                 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
 914                 assert_eq!(features, features_deserialized);
 915         }
 916
 917         #[test]
 918         fn test_channel_type_mapping() {
 919                 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
 920                 // required-StaticRemoteKey ChannelTypeFeatures.
 921                 let init_features = InitFeatures::empty().set_static_remote_key_optional();
 922                 let converted_features = ChannelTypeFeatures::from_counterparty_init(&init_features);
 923                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
 924                 assert!(!converted_features.supports_any_optional_bits());
 925                 assert!(converted_features.requires_static_remote_key());
 926         }
 927 }