git.bitcoin.ninja 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,
 141                         // Byte 3
 142                         ShutdownAnySegwit,
 143                         // Byte 4
 144                         ,
 145                         // Byte 5
 146                         ChannelType,
 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,
 173                         // Byte 3
 174                         ShutdownAnySegwit,
 175                         // Byte 4
 176                         ,
 177                         // Byte 5
 178                         ChannelType,
 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                         // Byte 3
 196                         ,
 197                         // Byte 4
 198                         ,
 199                         // Byte 5
 200                         ,
 201                         // Byte 6
 202                         ,
 203                 ],
 204                 // Note that the optional feature bits set here are used to check if a bit is "known", but
 205                 // the `InvoiceBuilder` in lightning-invoice starts with `empty()` and does not set these
 206                 // bits unless the relevant data is included in the invoice.
 207                 optional_features: [
 208                         // Byte 0
 209                         ,
 210                         // Byte 1
 211                         ,
 212                         // Byte 2
 213                         BasicMPP,
 214                         // Byte 3
 215                         ,
 216                         // Byte 4
 217                         ,
 218                         // Byte 5
 219                         ,
 220                         // Byte 6
 221                         PaymentMetadata,
 222                 ],
 223         });
 224         // This isn't a "real" feature context, and is only used in the channel_type field in an
 225         // `OpenChannel` message.
 226         define_context!(ChannelTypeContext {
 227                 required_features: [
 228                         // Byte 0
 229                         ,
 230                         // Byte 1
 231                         StaticRemoteKey,
 232                         // Byte 2
 233                         ,
 234                         // Byte 3
 235                         ,
 236                 ],
 237                 optional_features: [
 238                         // Byte 0
 239                         ,
 240                         // Byte 1
 241                         ,
 242                         // Byte 2
 243                         ,
 244                         // Byte 3
 245                         ,
 246                 ],
 247         });
 248
 249         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 250         /// useful for manipulating feature flags.
 251         macro_rules! define_feature {
 252                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 253                  $required_setter: ident, $supported_getter: ident) => {
 254                         #[doc = $doc]
 255                         ///
 256                         /// See [BOLT #9] for details.
 257                         ///
 258                         /// [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
 259                         pub trait $feature: Context {
 260                                 /// The bit used to signify that the feature is required.
 261                                 const EVEN_BIT: usize = $odd_bit - 1;
 262
 263                                 /// The bit used to signify that the feature is optional.
 264                                 const ODD_BIT: usize = $odd_bit;
 265
 266                                 /// Assertion that [`EVEN_BIT`] is actually even.
 267                                 ///
 268                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 269                                 const ASSERT_EVEN_BIT_PARITY: usize;
 270
 271                                 /// Assertion that [`ODD_BIT`] is actually odd.
 272                                 ///
 273                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 274                                 const ASSERT_ODD_BIT_PARITY: usize;
 275
 276                                 /// The byte where the feature is set.
 277                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 278
 279                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 280                                 ///
 281                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 282                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 283
 284                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 285                                 ///
 286                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 287                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 288
 289                                 /// Returns whether the feature is required by the given flags.
 290                                 #[inline]
 291                                 fn requires_feature(flags: &Vec<u8>) -> bool {
 292                                         flags.len() > Self::BYTE_OFFSET &&
 293                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
 294                                 }
 295
 296                                 /// Returns whether the feature is supported by the given flags.
 297                                 #[inline]
 298                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 299                                         flags.len() > Self::BYTE_OFFSET &&
 300                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 301                                 }
 302
 303                                 /// Sets the feature's required (even) bit in the given flags.
 304                                 #[inline]
 305                                 fn set_required_bit(flags: &mut Vec<u8>) {
 306                                         if flags.len() <= Self::BYTE_OFFSET {
 307                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 308                                         }
 309
 310                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
 311                                         flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 312                                 }
 313
 314                                 /// Sets the feature's optional (odd) bit in the given flags.
 315                                 #[inline]
 316                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 317                                         if flags.len() <= Self::BYTE_OFFSET {
 318                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 319                                         }
 320
 321                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 322                                 }
 323
 324                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 325                                 /// flags.
 326                                 #[inline]
 327                                 fn clear_bits(flags: &mut Vec<u8>) {
 328                                         if flags.len() > Self::BYTE_OFFSET {
 329                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 330                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 331                                         }
 332
 333                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 334                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 335                                         flags.resize(size, 0u8);
 336                                 }
 337                         }
 338
 339                         impl <T: $feature> Features<T> {
 340                                 /// Set this feature as optional.
 341                                 pub fn $optional_setter(mut self) -> Self {
 342                                         <T as $feature>::set_optional_bit(&mut self.flags);
 343                                         self
 344                                 }
 345
 346                                 /// Set this feature as required.
 347                                 pub fn $required_setter(mut self) -> Self {
 348                                         <T as $feature>::set_required_bit(&mut self.flags);
 349                                         self
 350                                 }
 351
 352                                 /// Checks if this feature is supported.
 353                                 pub fn $supported_getter(&self) -> bool {
 354                                         <T as $feature>::supports_feature(&self.flags)
 355                                 }
 356                         }
 357
 358                         $(
 359                                 impl $feature for $context {
 360                                         // EVEN_BIT % 2 == 0
 361                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 362
 363                                         // ODD_BIT % 2 == 1
 364                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 365                                 }
 366                         )*
 367                 };
 368                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 369                  $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
 370                         define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
 371                         impl <T: $feature> Features<T> {
 372                                 /// Checks if this feature is required.
 373                                 pub fn $required_getter(&self) -> bool {
 374                                         <T as $feature>::requires_feature(&self.flags)
 375                                 }
 376                         }
 377                 }
 378         }
 379
 380         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 381                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 382                 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
 383         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 384         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 385                 set_initial_routing_sync_optional, set_initial_routing_sync_required,
 386                 initial_routing_sync);
 387         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 388                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 389                 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
 390                 requires_upfront_shutdown_script);
 391         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 392                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
 393                 supports_gossip_queries, requires_gossip_queries);
 394         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
 395                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 396                 set_variable_length_onion_required, supports_variable_length_onion,
 397                 requires_variable_length_onion);
 398         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
 399                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 400                 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
 401         define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
 402                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
 403                 supports_payment_secret, requires_payment_secret);
 404         define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext],
 405                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
 406                 supports_basic_mpp, requires_basic_mpp);
 407         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 408                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 409                 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
 410         define_feature!(45, ChannelType, [InitContext, NodeContext],
 411                 "Feature flags for `option_channel_type`.", set_channel_type_optional,
 412                 set_channel_type_required, supports_channel_type, requires_channel_type);
 413         define_feature!(49, PaymentMetadata, [InvoiceContext],
 414                 "Feature flags for payment metadata in invoices.", set_payment_metadata_optional,
 415                 set_payment_metadata_required, supports_payment_metadata, requires_payment_metadata);
 416         define_feature!(55, Keysend, [NodeContext],
 417                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
 418                 supports_keysend, requires_keysend);
 419
 420         #[cfg(test)]
 421         define_feature!(123456789, UnknownFeature, [NodeContext, ChannelContext, InitContext],
 422                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 423                 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
 424 }
 425
 426 /// Tracks the set of features which a node implements, templated by the context in which it
 427 /// appears.
 428 ///
 429 /// (C-not exported) as we map the concrete feature types below directly instead
 430 #[derive(Eq)]
 431 pub struct Features<T: sealed::Context> {
 432         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 433         flags: Vec<u8>,
 434         mark: PhantomData<T>,
 435 }
 436
 437 impl<T: sealed::Context> Clone for Features<T> {
 438         fn clone(&self) -> Self {
 439                 Self {
 440                         flags: self.flags.clone(),
 441                         mark: PhantomData,
 442                 }
 443         }
 444 }
 445 impl<T: sealed::Context> Hash for Features<T> {
 446         fn hash<H: Hasher>(&self, hasher: &mut H) {
 447                 self.flags.hash(hasher);
 448         }
 449 }
 450 impl<T: sealed::Context> PartialEq for Features<T> {
 451         fn eq(&self, o: &Self) -> bool {
 452                 self.flags.eq(&o.flags)
 453         }
 454 }
 455 impl<T: sealed::Context> fmt::Debug for Features<T> {
 456         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 457                 self.flags.fmt(fmt)
 458         }
 459 }
 460
 461 /// Features used within an `init` message.
 462 pub type InitFeatures = Features<sealed::InitContext>;
 463 /// Features used within a `node_announcement` message.
 464 pub type NodeFeatures = Features<sealed::NodeContext>;
 465 /// Features used within a `channel_announcement` message.
 466 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 467 /// Features used within an invoice.
 468 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
 469
 470 /// Features used within the channel_type field in an OpenChannel message.
 471 ///
 472 /// A channel is always of some known "type", describing the transaction formats used and the exact
 473 /// semantics of our interaction with our peer.
 474 ///
 475 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
 476 /// the counterparty, only required features are allowed here.
 477 ///
 478 /// This is serialized differently from other feature types - it is not prefixed by a length, and
 479 /// thus must only appear inside a TLV where its length is known in advance.
 480 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
 481
 482 impl InitFeatures {
 483         /// Writes all features present up to, and including, 13.
 484         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 485                 let len = cmp::min(2, self.flags.len());
 486                 (len as u16).write(w)?;
 487                 for i in (0..len).rev() {
 488                         if i == 0 {
 489                                 self.flags[i].write(w)?;
 490                         } else {
 491                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 492                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 493                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 494                         }
 495                 }
 496                 Ok(())
 497         }
 498
 499         /// or's another InitFeatures into this one.
 500         pub(crate) fn or(mut self, o: InitFeatures) -> InitFeatures {
 501                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
 502                 self.flags.resize(total_feature_len, 0u8);
 503                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
 504                         *byte |= *o_byte;
 505                 }
 506                 self
 507         }
 508
 509         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 510         /// are included in the result.
 511         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 512                 self.to_context_internal()
 513         }
 514 }
 515
 516 impl InvoiceFeatures {
 517         /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
 518         /// context `C` are included in the result.
 519         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 520                 self.to_context_internal()
 521         }
 522
 523         /// Getting a route for a keysend payment to a private node requires providing the payee's
 524         /// features (since they were not announced in a node announcement). However, keysend payments
 525         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 526         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
 527         /// `InvoiceFeatures` for [`find_route`].
 528         ///
 529         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
 530         /// [`find_route`]: crate::routing::router::find_route
 531         pub(crate) fn for_keysend() -> InvoiceFeatures {
 532                 InvoiceFeatures::empty().set_variable_length_onion_optional()
 533         }
 534 }
 535
 536 impl ChannelTypeFeatures {
 537         /// Constructs the implicit channel type based on the common supported types between us and our
 538         /// counterparty
 539         pub(crate) fn from_counterparty_init(counterparty_init: &InitFeatures) -> Self {
 540                 let mut ret = counterparty_init.to_context_internal();
 541                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
 542                 // optional bits and then AND out the optional ones.
 543                 for byte in ret.flags.iter_mut() {
 544                         *byte |= (*byte & 0b10_10_10_10) >> 1;
 545                         *byte &= 0b01_01_01_01;
 546                 }
 547                 ret
 548         }
 549
 550         /// Constructs a ChannelTypeFeatures with only static_remotekey set
 551         pub(crate) fn only_static_remote_key() -> Self {
 552                 let mut ret = Self::empty();
 553                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 554                 ret
 555         }
 556 }
 557
 558 impl ToBase32 for InvoiceFeatures {
 559         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 560                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 561                 // minus one before dividing
 562                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 563                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 564                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 565                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 566                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 567                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 568                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 569                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 570                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 571                         if new_u5_idx > 0 {
 572                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 573                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 574                         }
 575                         if new_u5_idx > 1 {
 576                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 577                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 578                         }
 579                 }
 580                 // Trim the highest feature bits.
 581                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 582                         res_u5s.remove(0);
 583                 }
 584                 writer.write(&res_u5s)
 585         }
 586 }
 587
 588 impl Base32Len for InvoiceFeatures {
 589         fn base32_len(&self) -> usize {
 590                 self.to_base32().len()
 591         }
 592 }
 593
 594 impl FromBase32 for InvoiceFeatures {
 595         type Err = bech32::Error;
 596
 597         fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
 598                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 599                 // minus one before dividing
 600                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 601                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 602                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 603                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 604                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 605                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 606                         let chunk_u16 = chunk.to_u8() as u16;
 607                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 608                         if new_byte_idx != length_bytes - 1 {
 609                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 610                         }
 611                 }
 612                 // Trim the highest feature bits.
 613                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 614                         res_bytes.pop();
 615                 }
 616                 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
 617         }
 618 }
 619
 620 impl<T: sealed::Context> Features<T> {
 621         /// Create a blank Features with no features set
 622         pub fn empty() -> Self {
 623                 Features {
 624                         flags: Vec::new(),
 625                         mark: PhantomData,
 626                 }
 627         }
 628
 629         /// Creates a Features with the bits set which are known by the implementation
 630         pub fn known() -> Self {
 631                 Self {
 632                         flags: T::KNOWN_FEATURE_FLAGS.to_vec(),
 633                         mark: PhantomData,
 634                 }
 635         }
 636
 637         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 638         /// included in the result.
 639         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 640                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 641                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 642                 let mut flags = Vec::new();
 643                 for (i, byte) in self.flags.iter().enumerate() {
 644                         if i < from_byte_count && i < to_byte_count {
 645                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 646                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 647                                 flags.push(byte & from_known_features & to_known_features);
 648                         }
 649                 }
 650                 Features::<C> { flags, mark: PhantomData, }
 651         }
 652
 653         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 654         /// most on-the-wire encodings.
 655         /// (C-not exported) as we don't support export across multiple T
 656         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 657                 Features {
 658                         flags,
 659                         mark: PhantomData,
 660                 }
 661         }
 662
 663         #[cfg(test)]
 664         /// Gets the underlying flags set, in LE.
 665         pub fn le_flags(&self) -> &Vec<u8> {
 666                 &self.flags
 667         }
 668
 669         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 670                 for f in self.flags.iter().rev() { // Swap back to big-endian
 671                         f.write(w)?;
 672                 }
 673                 Ok(())
 674         }
 675
 676         fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
 677                 flags.reverse(); // Swap to little-endian
 678                 Self {
 679                         flags,
 680                         mark: PhantomData,
 681                 }
 682         }
 683
 684         pub(crate) fn supports_any_optional_bits(&self) -> bool {
 685                 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
 686         }
 687
 688         /// Returns true if this `Features` object contains unknown feature flags which are set as
 689         /// "required".
 690         pub fn requires_unknown_bits(&self) -> bool {
 691                 // Bitwise AND-ing with all even bits set except for known features will select required
 692                 // unknown features.
 693                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 694                 self.flags.iter().enumerate().any(|(i, &byte)| {
 695                         let required_features = 0b01_01_01_01;
 696                         let unknown_features = if i < byte_count {
 697                                 !T::KNOWN_FEATURE_MASK[i]
 698                         } else {
 699                                 0b11_11_11_11
 700                         };
 701                         (byte & (required_features & unknown_features)) != 0
 702                 })
 703         }
 704
 705         pub(crate) fn supports_unknown_bits(&self) -> bool {
 706                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 707                 // both required and optional unknown features.
 708                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 709                 self.flags.iter().enumerate().any(|(i, &byte)| {
 710                         let unknown_features = if i < byte_count {
 711                                 !T::KNOWN_FEATURE_MASK[i]
 712                         } else {
 713                                 0b11_11_11_11
 714                         };
 715                         (byte & unknown_features) != 0
 716                 })
 717         }
 718 }
 719
 720 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 721         #[cfg(test)]
 722         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 723                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 724                 self
 725         }
 726 }
 727
 728
 729 impl<T: sealed::GossipQueries> Features<T> {
 730         #[cfg(test)]
 731         pub(crate) fn clear_gossip_queries(mut self) -> Self {
 732                 <T as sealed::GossipQueries>::clear_bits(&mut self.flags);
 733                 self
 734         }
 735 }
 736
 737 impl<T: sealed::InitialRoutingSync> Features<T> {
 738         // We are no longer setting initial_routing_sync now that gossip_queries
 739         // is enabled. This feature is ignored by a peer when gossip_queries has
 740         // been negotiated.
 741         #[cfg(test)]
 742         pub(crate) fn clear_initial_routing_sync(&mut self) {
 743                 <T as sealed::InitialRoutingSync>::clear_bits(&mut self.flags)
 744         }
 745 }
 746
 747 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 748         #[cfg(test)]
 749         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 750                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 751                 self
 752         }
 753 }
 754 macro_rules! impl_feature_len_prefixed_write {
 755         ($features: ident) => {
 756                 impl Writeable for $features {
 757                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 758                                 (self.flags.len() as u16).write(w)?;
 759                                 self.write_be(w)
 760                         }
 761                 }
 762                 impl Readable for $features {
 763                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 764                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
 765                         }
 766                 }
 767         }
 768 }
 769 impl_feature_len_prefixed_write!(InitFeatures);
 770 impl_feature_len_prefixed_write!(ChannelFeatures);
 771 impl_feature_len_prefixed_write!(NodeFeatures);
 772 impl_feature_len_prefixed_write!(InvoiceFeatures);
 773
 774 // Because ChannelTypeFeatures only appears inside of TLVs, it doesn't have a length prefix when
 775 // serialized. Thus, we can't use `impl_feature_len_prefixed_write`, above, and have to write our
 776 // own serialization.
 777 impl Writeable for ChannelTypeFeatures {
 778         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 779                 self.write_be(w)
 780         }
 781 }
 782 impl Readable for ChannelTypeFeatures {
 783         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 784                 let v = io_extras::read_to_end(r)?;
 785                 Ok(Self::from_be_bytes(v))
 786         }
 787 }
 788
 789 #[cfg(test)]
 790 mod tests {
 791         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures};
 792         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
 793
 794         #[test]
 795         fn sanity_test_known_features() {
 796                 assert!(!ChannelFeatures::known().requires_unknown_bits());
 797                 assert!(!ChannelFeatures::known().supports_unknown_bits());
 798                 assert!(!InitFeatures::known().requires_unknown_bits());
 799                 assert!(!InitFeatures::known().supports_unknown_bits());
 800                 assert!(!NodeFeatures::known().requires_unknown_bits());
 801                 assert!(!NodeFeatures::known().supports_unknown_bits());
 802
 803                 assert!(InitFeatures::known().supports_upfront_shutdown_script());
 804                 assert!(NodeFeatures::known().supports_upfront_shutdown_script());
 805                 assert!(!InitFeatures::known().requires_upfront_shutdown_script());
 806                 assert!(!NodeFeatures::known().requires_upfront_shutdown_script());
 807
 808                 assert!(InitFeatures::known().supports_gossip_queries());
 809                 assert!(NodeFeatures::known().supports_gossip_queries());
 810                 assert!(!InitFeatures::known().requires_gossip_queries());
 811                 assert!(!NodeFeatures::known().requires_gossip_queries());
 812
 813                 assert!(InitFeatures::known().supports_data_loss_protect());
 814                 assert!(NodeFeatures::known().supports_data_loss_protect());
 815                 assert!(!InitFeatures::known().requires_data_loss_protect());
 816                 assert!(!NodeFeatures::known().requires_data_loss_protect());
 817
 818                 assert!(InitFeatures::known().supports_variable_length_onion());
 819                 assert!(NodeFeatures::known().supports_variable_length_onion());
 820                 assert!(InvoiceFeatures::known().supports_variable_length_onion());
 821                 assert!(InitFeatures::known().requires_variable_length_onion());
 822                 assert!(NodeFeatures::known().requires_variable_length_onion());
 823                 assert!(InvoiceFeatures::known().requires_variable_length_onion());
 824
 825                 assert!(InitFeatures::known().supports_static_remote_key());
 826                 assert!(NodeFeatures::known().supports_static_remote_key());
 827                 assert!(InitFeatures::known().requires_static_remote_key());
 828                 assert!(NodeFeatures::known().requires_static_remote_key());
 829
 830                 assert!(InitFeatures::known().supports_payment_secret());
 831                 assert!(NodeFeatures::known().supports_payment_secret());
 832                 assert!(InvoiceFeatures::known().supports_payment_secret());
 833                 assert!(InitFeatures::known().requires_payment_secret());
 834                 assert!(NodeFeatures::known().requires_payment_secret());
 835                 assert!(InvoiceFeatures::known().requires_payment_secret());
 836
 837                 assert!(InitFeatures::known().supports_basic_mpp());
 838                 assert!(NodeFeatures::known().supports_basic_mpp());
 839                 assert!(InvoiceFeatures::known().supports_basic_mpp());
 840                 assert!(!InitFeatures::known().requires_basic_mpp());
 841                 assert!(!NodeFeatures::known().requires_basic_mpp());
 842                 assert!(!InvoiceFeatures::known().requires_basic_mpp());
 843
 844                 assert!(InitFeatures::known().supports_channel_type());
 845                 assert!(NodeFeatures::known().supports_channel_type());
 846                 assert!(!InitFeatures::known().requires_channel_type());
 847                 assert!(!NodeFeatures::known().requires_channel_type());
 848
 849                 assert!(InitFeatures::known().supports_shutdown_anysegwit());
 850                 assert!(NodeFeatures::known().supports_shutdown_anysegwit());
 851
 852                 let mut init_features = InitFeatures::known();
 853                 assert!(init_features.initial_routing_sync());
 854                 init_features.clear_initial_routing_sync();
 855                 assert!(!init_features.initial_routing_sync());
 856         }
 857
 858         #[test]
 859         fn sanity_test_unknown_bits() {
 860                 let features = ChannelFeatures::empty();
 861                 assert!(!features.requires_unknown_bits());
 862                 assert!(!features.supports_unknown_bits());
 863
 864                 let features = ChannelFeatures::empty().set_unknown_feature_required();
 865                 assert!(features.requires_unknown_bits());
 866                 assert!(features.supports_unknown_bits());
 867
 868                 let features = ChannelFeatures::empty().set_unknown_feature_optional();
 869                 assert!(!features.requires_unknown_bits());
 870                 assert!(features.supports_unknown_bits());
 871         }
 872
 873         #[test]
 874         fn convert_to_context_with_relevant_flags() {
 875                 let init_features = InitFeatures::known().clear_upfront_shutdown_script().clear_gossip_queries();
 876                 assert!(init_features.initial_routing_sync());
 877                 assert!(!init_features.supports_upfront_shutdown_script());
 878                 assert!(!init_features.supports_gossip_queries());
 879
 880                 let node_features: NodeFeatures = init_features.to_context();
 881                 {
 882                         // Check that the flags are as expected:
 883                         // - option_data_loss_protect
 884                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
 885                         // - basic_mpp
 886                         // - opt_shutdown_anysegwit
 887                         // -
 888                         // - option_channel_type
 889                         assert_eq!(node_features.flags.len(), 6);
 890                         assert_eq!(node_features.flags[0], 0b00000010);
 891                         assert_eq!(node_features.flags[1], 0b01010001);
 892                         assert_eq!(node_features.flags[2], 0b00000010);
 893                         assert_eq!(node_features.flags[3], 0b00001000);
 894                         assert_eq!(node_features.flags[4], 0b00000000);
 895                         assert_eq!(node_features.flags[5], 0b00100000);
 896                 }
 897
 898                 // Check that cleared flags are kept blank when converting back:
 899                 // - initial_routing_sync was not applicable to NodeContext
 900                 // - upfront_shutdown_script was cleared before converting
 901                 // - gossip_queries was cleared before converting
 902                 let features: InitFeatures = node_features.to_context_internal();
 903                 assert!(!features.initial_routing_sync());
 904                 assert!(!features.supports_upfront_shutdown_script());
 905                 assert!(!init_features.supports_gossip_queries());
 906         }
 907
 908         #[test]
 909         fn convert_to_context_with_unknown_flags() {
 910                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
 911                 assert!(InitFeatures::known().flags.len() < NodeFeatures::known().flags.len());
 912                 let init_features = InitFeatures::known().set_unknown_feature_optional();
 913                 assert!(init_features.supports_unknown_bits());
 914                 let node_features: NodeFeatures = init_features.to_context();
 915                 assert!(!node_features.supports_unknown_bits());
 916         }
 917
 918         #[test]
 919         fn set_feature_bits() {
 920                 let features = InvoiceFeatures::empty()
 921                         .set_basic_mpp_optional()
 922                         .set_payment_secret_required();
 923                 assert!(features.supports_basic_mpp());
 924                 assert!(!features.requires_basic_mpp());
 925                 assert!(features.requires_payment_secret());
 926                 assert!(features.supports_payment_secret());
 927         }
 928
 929         #[test]
 930         fn invoice_features_encoding() {
 931                 let features_as_u5s = vec![
 932                         u5::try_from_u8(6).unwrap(),
 933                         u5::try_from_u8(10).unwrap(),
 934                         u5::try_from_u8(25).unwrap(),
 935                         u5::try_from_u8(1).unwrap(),
 936                         u5::try_from_u8(10).unwrap(),
 937                         u5::try_from_u8(0).unwrap(),
 938                         u5::try_from_u8(20).unwrap(),
 939                         u5::try_from_u8(2).unwrap(),
 940                         u5::try_from_u8(0).unwrap(),
 941                         u5::try_from_u8(6).unwrap(),
 942                         u5::try_from_u8(0).unwrap(),
 943                         u5::try_from_u8(16).unwrap(),
 944                         u5::try_from_u8(1).unwrap(),
 945                 ];
 946                 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
 947
 948                 // Test length calculation.
 949                 assert_eq!(features.base32_len(), 13);
 950
 951                 // Test serialization.
 952                 let features_serialized = features.to_base32();
 953                 assert_eq!(features_as_u5s, features_serialized);
 954
 955                 // Test deserialization.
 956                 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
 957                 assert_eq!(features, features_deserialized);
 958         }
 959
 960         #[test]
 961         fn test_channel_type_mapping() {
 962                 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
 963                 // required-StaticRemoteKey ChannelTypeFeatures.
 964                 let init_features = InitFeatures::empty().set_static_remote_key_optional();
 965                 let converted_features = ChannelTypeFeatures::from_counterparty_init(&init_features);
 966                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
 967                 assert!(!converted_features.supports_any_optional_bits());
 968                 assert!(converted_features.requires_static_remote_key());
 969         }
 970 }