_ 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                         // Byte 4
 130                         ,
 131                         // Byte 5
 132                         ,
 133                 ],
 134                 optional_features: [
 135                         // Byte 0
 136                         DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
 137                         // Byte 1
 138                         ,
 139                         // Byte 2
 140                         BasicMPP | Wumbo,
 141                         // Byte 3
 142                         ShutdownAnySegwit,
 143                         // Byte 4
 144                         ,
 145                         // Byte 5
 146                         ChannelType | SCIDPrivacy,
 147                 ],
 148         });
 149         define_context!(NodeContext {
 150                 required_features: [
 151                         // Byte 0
 152                         ,
 153                         // Byte 1
 154                         VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 155                         // Byte 2
 156                         ,
 157                         // Byte 3
 158                         ,
 159                         // Byte 4
 160                         ,
 161                         // Byte 5
 162                         ,
 163                         // Byte 6
 164                         ,
 165                 ],
 166                 optional_features: [
 167                         // Byte 0
 168                         DataLossProtect | UpfrontShutdownScript | GossipQueries,
 169                         // Byte 1
 170                         ,
 171                         // Byte 2
 172                         BasicMPP | Wumbo,
 173                         // Byte 3
 174                         ShutdownAnySegwit,
 175                         // Byte 4
 176                         ,
 177                         // Byte 5
 178                         ChannelType | SCIDPrivacy,
 179                         // Byte 6
 180                         Keysend,
 181                 ],
 182         });
 183         define_context!(ChannelContext {
 184                 required_features: [],
 185                 optional_features: [],
 186         });
 187         define_context!(InvoiceContext {
 188                 required_features: [
 189                         // Byte 0
 190                         ,
 191                         // Byte 1
 192                         VariableLengthOnion | PaymentSecret,
 193                         // Byte 2
 194                         ,
 195                 ],
 196                 optional_features: [
 197                         // Byte 0
 198                         ,
 199                         // Byte 1
 200                         ,
 201                         // Byte 2
 202                         BasicMPP,
 203                 ],
 204         });
 205         // This isn't a "real" feature context, and is only used in the channel_type field in an
 206         // `OpenChannel` message.
 207         define_context!(ChannelTypeContext {
 208                 required_features: [
 209                         // Byte 0
 210                         ,
 211                         // Byte 1
 212                         StaticRemoteKey,
 213                         // Byte 2
 214                         ,
 215                         // Byte 3
 216                         ,
 217                         // Byte 4
 218                         ,
 219                         // Byte 5
 220                         SCIDPrivacy,
 221                 ],
 222                 optional_features: [
 223                         // Byte 0
 224                         ,
 225                         // Byte 1
 226                         ,
 227                         // Byte 2
 228                         ,
 229                         // Byte 3
 230                         ,
 231                         // Byte 4
 232                         ,
 233                         // Byte 5
 234                         ,
 235                 ],
 236         });
 237
 238         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 239         /// useful for manipulating feature flags.
 240         macro_rules! define_feature {
 241                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 242                  $required_setter: ident, $supported_getter: ident) => {
 243                         #[doc = $doc]
 244                         ///
 245                         /// See [BOLT #9] for details.
 246                         ///
 247                         /// [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
 248                         pub trait $feature: Context {
 249                                 /// The bit used to signify that the feature is required.
 250                                 const EVEN_BIT: usize = $odd_bit - 1;
 251
 252                                 /// The bit used to signify that the feature is optional.
 253                                 const ODD_BIT: usize = $odd_bit;
 254
 255                                 /// Assertion that [`EVEN_BIT`] is actually even.
 256                                 ///
 257                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 258                                 const ASSERT_EVEN_BIT_PARITY: usize;
 259
 260                                 /// Assertion that [`ODD_BIT`] is actually odd.
 261                                 ///
 262                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 263                                 const ASSERT_ODD_BIT_PARITY: usize;
 264
 265                                 /// The byte where the feature is set.
 266                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 267
 268                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 269                                 ///
 270                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 271                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 272
 273                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 274                                 ///
 275                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 276                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 277
 278                                 /// Returns whether the feature is required by the given flags.
 279                                 #[inline]
 280                                 fn requires_feature(flags: &Vec<u8>) -> bool {
 281                                         flags.len() > Self::BYTE_OFFSET &&
 282                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
 283                                 }
 284
 285                                 /// Returns whether the feature is supported by the given flags.
 286                                 #[inline]
 287                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 288                                         flags.len() > Self::BYTE_OFFSET &&
 289                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 290                                 }
 291
 292                                 /// Sets the feature's required (even) bit in the given flags.
 293                                 #[inline]
 294                                 fn set_required_bit(flags: &mut Vec<u8>) {
 295                                         if flags.len() <= Self::BYTE_OFFSET {
 296                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 297                                         }
 298
 299                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
 300                                 }
 301
 302                                 /// Sets the feature's optional (odd) bit in the given flags.
 303                                 #[inline]
 304                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 305                                         if flags.len() <= Self::BYTE_OFFSET {
 306                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 307                                         }
 308
 309                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 310                                 }
 311
 312                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 313                                 /// flags.
 314                                 #[inline]
 315                                 fn clear_bits(flags: &mut Vec<u8>) {
 316                                         if flags.len() > Self::BYTE_OFFSET {
 317                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 318                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 319                                         }
 320
 321                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 322                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 323                                         flags.resize(size, 0u8);
 324                                 }
 325                         }
 326
 327                         impl <T: $feature> Features<T> {
 328                                 /// Set this feature as optional.
 329                                 pub fn $optional_setter(&mut self) {
 330                                         <T as $feature>::set_optional_bit(&mut self.flags);
 331                                 }
 332
 333                                 /// Set this feature as required.
 334                                 pub fn $required_setter(&mut self) {
 335                                         <T as $feature>::set_required_bit(&mut self.flags);
 336                                 }
 337
 338                                 /// Checks if this feature is supported.
 339                                 pub fn $supported_getter(&self) -> bool {
 340                                         <T as $feature>::supports_feature(&self.flags)
 341                                 }
 342                         }
 343
 344                         $(
 345                                 impl $feature for $context {
 346                                         // EVEN_BIT % 2 == 0
 347                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 348
 349                                         // ODD_BIT % 2 == 1
 350                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 351                                 }
 352                         )*
 353                 };
 354                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 355                  $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
 356                         define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
 357                         impl <T: $feature> Features<T> {
 358                                 /// Checks if this feature is required.
 359                                 pub fn $required_getter(&self) -> bool {
 360                                         <T as $feature>::requires_feature(&self.flags)
 361                                 }
 362                         }
 363                 }
 364         }
 365
 366         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 367                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 368                 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
 369         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 370         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 371                 set_initial_routing_sync_optional, set_initial_routing_sync_required,
 372                 initial_routing_sync);
 373         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 374                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 375                 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
 376                 requires_upfront_shutdown_script);
 377         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 378                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
 379                 supports_gossip_queries, requires_gossip_queries);
 380         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
 381                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 382                 set_variable_length_onion_required, supports_variable_length_onion,
 383                 requires_variable_length_onion);
 384         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
 385                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 386                 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
 387         define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
 388                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
 389                 supports_payment_secret, requires_payment_secret);
 390         define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext],
 391                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
 392                 supports_basic_mpp, requires_basic_mpp);
 393         define_feature!(19, Wumbo, [InitContext, NodeContext],
 394                 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
 395                 supports_wumbo, requires_wumbo);
 396         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 397                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 398                 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
 399         define_feature!(45, ChannelType, [InitContext, NodeContext],
 400                 "Feature flags for `option_channel_type`.", set_channel_type_optional,
 401                 set_channel_type_required, supports_channel_type, requires_channel_type);
 402         define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
 403                 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
 404                 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
 405
 406         define_feature!(55, Keysend, [NodeContext],
 407                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
 408                 supports_keysend, requires_keysend);
 409
 410         #[cfg(test)]
 411         define_feature!(123456789, UnknownFeature, [NodeContext, ChannelContext, InvoiceContext],
 412                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 413                 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
 414 }
 415
 416 /// Tracks the set of features which a node implements, templated by the context in which it
 417 /// appears.
 418 ///
 419 /// (C-not exported) as we map the concrete feature types below directly instead
 420 #[derive(Eq)]
 421 pub struct Features<T: sealed::Context> {
 422         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 423         flags: Vec<u8>,
 424         mark: PhantomData<T>,
 425 }
 426
 427 impl<T: sealed::Context> Clone for Features<T> {
 428         fn clone(&self) -> Self {
 429                 Self {
 430                         flags: self.flags.clone(),
 431                         mark: PhantomData,
 432                 }
 433         }
 434 }
 435 impl<T: sealed::Context> Hash for Features<T> {
 436         fn hash<H: Hasher>(&self, hasher: &mut H) {
 437                 self.flags.hash(hasher);
 438         }
 439 }
 440 impl<T: sealed::Context> PartialEq for Features<T> {
 441         fn eq(&self, o: &Self) -> bool {
 442                 self.flags.eq(&o.flags)
 443         }
 444 }
 445 impl<T: sealed::Context> fmt::Debug for Features<T> {
 446         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 447                 self.flags.fmt(fmt)
 448         }
 449 }
 450
 451 /// Features used within an `init` message.
 452 pub type InitFeatures = Features<sealed::InitContext>;
 453 /// Features used within a `node_announcement` message.
 454 pub type NodeFeatures = Features<sealed::NodeContext>;
 455 /// Features used within a `channel_announcement` message.
 456 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 457 /// Features used within an invoice.
 458 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
 459
 460 /// Features used within the channel_type field in an OpenChannel message.
 461 ///
 462 /// A channel is always of some known "type", describing the transaction formats used and the exact
 463 /// semantics of our interaction with our peer.
 464 ///
 465 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
 466 /// the counterparty, only required features are allowed here.
 467 ///
 468 /// This is serialized differently from other feature types - it is not prefixed by a length, and
 469 /// thus must only appear inside a TLV where its length is known in advance.
 470 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
 471
 472 impl InitFeatures {
 473         /// Writes all features present up to, and including, 13.
 474         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 475                 let len = cmp::min(2, self.flags.len());
 476                 (len as u16).write(w)?;
 477                 for i in (0..len).rev() {
 478                         if i == 0 {
 479                                 self.flags[i].write(w)?;
 480                         } else {
 481                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 482                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 483                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 484                         }
 485                 }
 486                 Ok(())
 487         }
 488
 489         /// or's another InitFeatures into this one.
 490         pub(crate) fn or(mut self, o: InitFeatures) -> InitFeatures {
 491                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
 492                 self.flags.resize(total_feature_len, 0u8);
 493                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
 494                         *byte |= *o_byte;
 495                 }
 496                 self
 497         }
 498
 499         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 500         /// are included in the result.
 501         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 502                 self.to_context_internal()
 503         }
 504 }
 505
 506 impl InvoiceFeatures {
 507         /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
 508         /// context `C` are included in the result.
 509         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 510                 self.to_context_internal()
 511         }
 512
 513         /// Getting a route for a keysend payment to a private node requires providing the payee's
 514         /// features (since they were not announced in a node announcement). However, keysend payments
 515         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 516         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
 517         /// `InvoiceFeatures` for [`find_route`].
 518         ///
 519         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
 520         /// [`find_route`]: crate::routing::router::find_route
 521         pub(crate) fn for_keysend() -> InvoiceFeatures {
 522                 let mut res = InvoiceFeatures::empty();
 523                 res.set_variable_length_onion_optional();
 524                 res
 525         }
 526 }
 527
 528 impl ChannelTypeFeatures {
 529         /// Constructs the implicit channel type based on the common supported types between us and our
 530         /// counterparty
 531         pub(crate) fn from_counterparty_init(counterparty_init: &InitFeatures) -> Self {
 532                 let mut ret = counterparty_init.to_context_internal();
 533                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
 534                 // optional bits and then AND out the optional ones.
 535                 for byte in ret.flags.iter_mut() {
 536                         *byte |= (*byte & 0b10_10_10_10) >> 1;
 537                         *byte &= 0b01_01_01_01;
 538                 }
 539                 ret
 540         }
 541
 542         /// Constructs a ChannelTypeFeatures with only static_remotekey set
 543         pub(crate) fn only_static_remote_key() -> Self {
 544                 let mut ret = Self::empty();
 545                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 546                 ret
 547         }
 548 }
 549
 550 impl ToBase32 for InvoiceFeatures {
 551         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 552                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 553                 // minus one before dividing
 554                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 555                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 556                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 557                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 558                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 559                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 560                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 561                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 562                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 563                         if new_u5_idx > 0 {
 564                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 565                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 566                         }
 567                         if new_u5_idx > 1 {
 568                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 569                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 570                         }
 571                 }
 572                 // Trim the highest feature bits.
 573                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 574                         res_u5s.remove(0);
 575                 }
 576                 writer.write(&res_u5s)
 577         }
 578 }
 579
 580 impl Base32Len for InvoiceFeatures {
 581         fn base32_len(&self) -> usize {
 582                 self.to_base32().len()
 583         }
 584 }
 585
 586 impl FromBase32 for InvoiceFeatures {
 587         type Err = bech32::Error;
 588
 589         fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
 590                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 591                 // minus one before dividing
 592                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 593                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 594                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 595                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 596                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 597                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 598                         let chunk_u16 = chunk.to_u8() as u16;
 599                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 600                         if new_byte_idx != length_bytes - 1 {
 601                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 602                         }
 603                 }
 604                 // Trim the highest feature bits.
 605                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 606                         res_bytes.pop();
 607                 }
 608                 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
 609         }
 610 }
 611
 612 impl<T: sealed::Context> Features<T> {
 613         /// Create a blank Features with no features set
 614         pub fn empty() -> Self {
 615                 Features {
 616                         flags: Vec::new(),
 617                         mark: PhantomData,
 618                 }
 619         }
 620
 621         /// Creates a Features with the bits set which are known by the implementation
 622         pub fn known() -> Self {
 623                 Self {
 624                         flags: T::KNOWN_FEATURE_FLAGS.to_vec(),
 625                         mark: PhantomData,
 626                 }
 627         }
 628
 629         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 630         /// included in the result.
 631         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 632                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 633                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 634                 let mut flags = Vec::new();
 635                 for (i, byte) in self.flags.iter().enumerate() {
 636                         if i < from_byte_count && i < to_byte_count {
 637                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 638                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 639                                 flags.push(byte & from_known_features & to_known_features);
 640                         }
 641                 }
 642                 Features::<C> { flags, mark: PhantomData, }
 643         }
 644
 645         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 646         /// most on-the-wire encodings.
 647         /// (C-not exported) as we don't support export across multiple T
 648         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 649                 Features {
 650                         flags,
 651                         mark: PhantomData,
 652                 }
 653         }
 654
 655         #[cfg(test)]
 656         /// Gets the underlying flags set, in LE.
 657         pub fn le_flags(&self) -> &Vec<u8> {
 658                 &self.flags
 659         }
 660
 661         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 662                 for f in self.flags.iter().rev() { // Swap back to big-endian
 663                         f.write(w)?;
 664                 }
 665                 Ok(())
 666         }
 667
 668         fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
 669                 flags.reverse(); // Swap to little-endian
 670                 Self {
 671                         flags,
 672                         mark: PhantomData,
 673                 }
 674         }
 675
 676         pub(crate) fn supports_any_optional_bits(&self) -> bool {
 677                 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
 678         }
 679
 680         /// Returns true if this `Features` object contains unknown feature flags which are set as
 681         /// "required".
 682         pub fn requires_unknown_bits(&self) -> bool {
 683                 // Bitwise AND-ing with all even bits set except for known features will select required
 684                 // unknown features.
 685                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 686                 self.flags.iter().enumerate().any(|(i, &byte)| {
 687                         let required_features = 0b01_01_01_01;
 688                         let unknown_features = if i < byte_count {
 689                                 !T::KNOWN_FEATURE_MASK[i]
 690                         } else {
 691                                 0b11_11_11_11
 692                         };
 693                         (byte & (required_features & unknown_features)) != 0
 694                 })
 695         }
 696
 697         pub(crate) fn supports_unknown_bits(&self) -> bool {
 698                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 699                 // both required and optional unknown features.
 700                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 701                 self.flags.iter().enumerate().any(|(i, &byte)| {
 702                         let unknown_features = if i < byte_count {
 703                                 !T::KNOWN_FEATURE_MASK[i]
 704                         } else {
 705                                 0b11_11_11_11
 706                         };
 707                         (byte & unknown_features) != 0
 708                 })
 709         }
 710 }
 711
 712 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 713         #[cfg(test)]
 714         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 715                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 716                 self
 717         }
 718 }
 719
 720
 721 impl<T: sealed::GossipQueries> Features<T> {
 722         #[cfg(test)]
 723         pub(crate) fn clear_gossip_queries(mut self) -> Self {
 724                 <T as sealed::GossipQueries>::clear_bits(&mut self.flags);
 725                 self
 726         }
 727 }
 728
 729 impl<T: sealed::InitialRoutingSync> Features<T> {
 730         // We are no longer setting initial_routing_sync now that gossip_queries
 731         // is enabled. This feature is ignored by a peer when gossip_queries has
 732         // been negotiated.
 733         #[cfg(test)]
 734         pub(crate) fn clear_initial_routing_sync(&mut self) {
 735                 <T as sealed::InitialRoutingSync>::clear_bits(&mut self.flags)
 736         }
 737 }
 738
 739 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 740         #[cfg(test)]
 741         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 742                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 743                 self
 744         }
 745 }
 746 macro_rules! impl_feature_len_prefixed_write {
 747         ($features: ident) => {
 748                 impl Writeable for $features {
 749                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 750                                 (self.flags.len() as u16).write(w)?;
 751                                 self.write_be(w)
 752                         }
 753                 }
 754                 impl Readable for $features {
 755                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 756                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
 757                         }
 758                 }
 759         }
 760 }
 761 impl_feature_len_prefixed_write!(InitFeatures);
 762 impl_feature_len_prefixed_write!(ChannelFeatures);
 763 impl_feature_len_prefixed_write!(NodeFeatures);
 764 impl_feature_len_prefixed_write!(InvoiceFeatures);
 765
 766 // Because ChannelTypeFeatures only appears inside of TLVs, it doesn't have a length prefix when
 767 // serialized. Thus, we can't use `impl_feature_len_prefixed_write`, above, and have to write our
 768 // own serialization.
 769 impl Writeable for ChannelTypeFeatures {
 770         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 771                 self.write_be(w)
 772         }
 773 }
 774 impl Readable for ChannelTypeFeatures {
 775         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 776                 let v = io_extras::read_to_end(r)?;
 777                 Ok(Self::from_be_bytes(v))
 778         }
 779 }
 780
 781 #[cfg(test)]
 782 mod tests {
 783         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures};
 784         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
 785
 786         #[test]
 787         fn sanity_test_known_features() {
 788                 assert!(!ChannelFeatures::known().requires_unknown_bits());
 789                 assert!(!ChannelFeatures::known().supports_unknown_bits());
 790                 assert!(!InitFeatures::known().requires_unknown_bits());
 791                 assert!(!InitFeatures::known().supports_unknown_bits());
 792                 assert!(!NodeFeatures::known().requires_unknown_bits());
 793                 assert!(!NodeFeatures::known().supports_unknown_bits());
 794
 795                 assert!(InitFeatures::known().supports_upfront_shutdown_script());
 796                 assert!(NodeFeatures::known().supports_upfront_shutdown_script());
 797                 assert!(!InitFeatures::known().requires_upfront_shutdown_script());
 798                 assert!(!NodeFeatures::known().requires_upfront_shutdown_script());
 799
 800                 assert!(InitFeatures::known().supports_gossip_queries());
 801                 assert!(NodeFeatures::known().supports_gossip_queries());
 802                 assert!(!InitFeatures::known().requires_gossip_queries());
 803                 assert!(!NodeFeatures::known().requires_gossip_queries());
 804
 805                 assert!(InitFeatures::known().supports_data_loss_protect());
 806                 assert!(NodeFeatures::known().supports_data_loss_protect());
 807                 assert!(!InitFeatures::known().requires_data_loss_protect());
 808                 assert!(!NodeFeatures::known().requires_data_loss_protect());
 809
 810                 assert!(InitFeatures::known().supports_variable_length_onion());
 811                 assert!(NodeFeatures::known().supports_variable_length_onion());
 812                 assert!(InvoiceFeatures::known().supports_variable_length_onion());
 813                 assert!(InitFeatures::known().requires_variable_length_onion());
 814                 assert!(NodeFeatures::known().requires_variable_length_onion());
 815                 assert!(InvoiceFeatures::known().requires_variable_length_onion());
 816
 817                 assert!(InitFeatures::known().supports_static_remote_key());
 818                 assert!(NodeFeatures::known().supports_static_remote_key());
 819                 assert!(InitFeatures::known().requires_static_remote_key());
 820                 assert!(NodeFeatures::known().requires_static_remote_key());
 821
 822                 assert!(InitFeatures::known().supports_payment_secret());
 823                 assert!(NodeFeatures::known().supports_payment_secret());
 824                 assert!(InvoiceFeatures::known().supports_payment_secret());
 825                 assert!(InitFeatures::known().requires_payment_secret());
 826                 assert!(NodeFeatures::known().requires_payment_secret());
 827                 assert!(InvoiceFeatures::known().requires_payment_secret());
 828
 829                 assert!(InitFeatures::known().supports_basic_mpp());
 830                 assert!(NodeFeatures::known().supports_basic_mpp());
 831                 assert!(InvoiceFeatures::known().supports_basic_mpp());
 832                 assert!(!InitFeatures::known().requires_basic_mpp());
 833                 assert!(!NodeFeatures::known().requires_basic_mpp());
 834                 assert!(!InvoiceFeatures::known().requires_basic_mpp());
 835
 836                 assert!(InitFeatures::known().supports_channel_type());
 837                 assert!(NodeFeatures::known().supports_channel_type());
 838                 assert!(!InitFeatures::known().requires_channel_type());
 839                 assert!(!NodeFeatures::known().requires_channel_type());
 840
 841                 assert!(InitFeatures::known().supports_shutdown_anysegwit());
 842                 assert!(NodeFeatures::known().supports_shutdown_anysegwit());
 843
 844                 assert!(InitFeatures::known().supports_scid_privacy());
 845                 assert!(NodeFeatures::known().supports_scid_privacy());
 846                 assert!(!InitFeatures::known().requires_scid_privacy());
 847                 assert!(!NodeFeatures::known().requires_scid_privacy());
 848
 849                 assert!(InitFeatures::known().supports_wumbo());
 850                 assert!(NodeFeatures::known().supports_wumbo());
 851                 assert!(!InitFeatures::known().requires_wumbo());
 852                 assert!(!NodeFeatures::known().requires_wumbo());
 853
 854                 let mut init_features = InitFeatures::known();
 855                 assert!(init_features.initial_routing_sync());
 856                 init_features.clear_initial_routing_sync();
 857                 assert!(!init_features.initial_routing_sync());
 858         }
 859
 860         #[test]
 861         fn sanity_test_unknown_bits() {
 862                 let features = ChannelFeatures::empty();
 863                 assert!(!features.requires_unknown_bits());
 864                 assert!(!features.supports_unknown_bits());
 865
 866                 let mut features = ChannelFeatures::empty();
 867                 features.set_unknown_feature_required();
 868                 assert!(features.requires_unknown_bits());
 869                 assert!(features.supports_unknown_bits());
 870
 871                 let mut features = ChannelFeatures::empty();
 872                 features.set_unknown_feature_optional();
 873                 assert!(!features.requires_unknown_bits());
 874                 assert!(features.supports_unknown_bits());
 875         }
 876
 877         #[test]
 878         fn convert_to_context_with_relevant_flags() {
 879                 let init_features = InitFeatures::known().clear_upfront_shutdown_script().clear_gossip_queries();
 880                 assert!(init_features.initial_routing_sync());
 881                 assert!(!init_features.supports_upfront_shutdown_script());
 882                 assert!(!init_features.supports_gossip_queries());
 883
 884                 let node_features: NodeFeatures = init_features.to_context();
 885                 {
 886                         // Check that the flags are as expected:
 887                         // - option_data_loss_protect
 888                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
 889                         // - basic_mpp | wumbo
 890                         // - opt_shutdown_anysegwit
 891                         // -
 892                         // - option_channel_type | option_scid_alias
 893                         assert_eq!(node_features.flags.len(), 6);
 894                         assert_eq!(node_features.flags[0], 0b00000010);
 895                         assert_eq!(node_features.flags[1], 0b01010001);
 896                         assert_eq!(node_features.flags[2], 0b00001010);
 897                         assert_eq!(node_features.flags[3], 0b00001000);
 898                         assert_eq!(node_features.flags[4], 0b00000000);
 899                         assert_eq!(node_features.flags[5], 0b10100000);
 900                 }
 901
 902                 // Check that cleared flags are kept blank when converting back:
 903                 // - initial_routing_sync was not applicable to NodeContext
 904                 // - upfront_shutdown_script was cleared before converting
 905                 // - gossip_queries was cleared before converting
 906                 let features: InitFeatures = node_features.to_context_internal();
 907                 assert!(!features.initial_routing_sync());
 908                 assert!(!features.supports_upfront_shutdown_script());
 909                 assert!(!init_features.supports_gossip_queries());
 910         }
 911
 912         #[test]
 913         fn convert_to_context_with_unknown_flags() {
 914                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
 915                 assert!(InvoiceFeatures::known().flags.len() < NodeFeatures::known().flags.len());
 916                 let mut invoice_features = InvoiceFeatures::known();
 917                 invoice_features.set_unknown_feature_optional();
 918                 assert!(invoice_features.supports_unknown_bits());
 919                 let node_features: NodeFeatures = invoice_features.to_context();
 920                 assert!(!node_features.supports_unknown_bits());
 921         }
 922
 923         #[test]
 924         fn set_feature_bits() {
 925                 let mut features = InvoiceFeatures::empty();
 926                 features.set_basic_mpp_optional();
 927                 features.set_payment_secret_required();
 928                 assert!(features.supports_basic_mpp());
 929                 assert!(!features.requires_basic_mpp());
 930                 assert!(features.requires_payment_secret());
 931                 assert!(features.supports_payment_secret());
 932         }
 933
 934         #[test]
 935         fn invoice_features_encoding() {
 936                 let features_as_u5s = vec![
 937                         u5::try_from_u8(6).unwrap(),
 938                         u5::try_from_u8(10).unwrap(),
 939                         u5::try_from_u8(25).unwrap(),
 940                         u5::try_from_u8(1).unwrap(),
 941                         u5::try_from_u8(10).unwrap(),
 942                         u5::try_from_u8(0).unwrap(),
 943                         u5::try_from_u8(20).unwrap(),
 944                         u5::try_from_u8(2).unwrap(),
 945                         u5::try_from_u8(0).unwrap(),
 946                         u5::try_from_u8(6).unwrap(),
 947                         u5::try_from_u8(0).unwrap(),
 948                         u5::try_from_u8(16).unwrap(),
 949                         u5::try_from_u8(1).unwrap(),
 950                 ];
 951                 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
 952
 953                 // Test length calculation.
 954                 assert_eq!(features.base32_len(), 13);
 955
 956                 // Test serialization.
 957                 let features_serialized = features.to_base32();
 958                 assert_eq!(features_as_u5s, features_serialized);
 959
 960                 // Test deserialization.
 961                 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
 962                 assert_eq!(features, features_deserialized);
 963         }
 964
 965         #[test]
 966         fn test_channel_type_mapping() {
 967                 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
 968                 // required-StaticRemoteKey ChannelTypeFeatures.
 969                 let mut init_features = InitFeatures::empty();
 970                 init_features.set_static_remote_key_optional();
 971                 let converted_features = ChannelTypeFeatures::from_counterparty_init(&init_features);
 972                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
 973                 assert!(!converted_features.supports_any_optional_bits());
 974                 assert!(converted_features.requires_static_remote_key());
 975         }
 976 }