_ 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 //! The following features are currently required in the LDK:
  23 //! - `VariableLengthOnion` - requires/supports variable-length routing onion payloads
  24 //!     (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md) for more information).
  25 //! - `StaticRemoteKey` - requires/supports static key for remote output
  26 //!     (see [BOLT-3](https://github.com/lightning/bolts/blob/master/03-transactions.md) for more information).
  27 //!
  28 //! The following features are currently supported in the LDK:
  29 //! - `DataLossProtect` - requires/supports that a node which has somehow fallen behind, e.g., has been restored from an old backup,
  30 //!     can detect that it has fallen behind
  31 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  32 //! - `InitialRoutingSync` - requires/supports that the sending node needs a complete routing information dump
  33 //!     (see [BOLT-7](https://github.com/lightning/bolts/blob/master/07-routing-gossip.md#initial-sync) for more information).
  34 //! - `UpfrontShutdownScript` - commits to a shutdown scriptpubkey when opening a channel
  35 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#the-open_channel-message) for more information).
  36 //! - `GossipQueries` - requires/supports more sophisticated gossip control
  37 //!     (see [BOLT-7](https://github.com/lightning/bolts/blob/master/07-routing-gossip.md) for more information).
  38 //! - `PaymentSecret` - requires/supports that a node supports payment_secret field
  39 //!     (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md) for more information).
  40 //! - `BasicMPP` - requires/supports that a node can receive basic multi-part payments
  41 //!     (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md#basic-multi-part-payments) for more information).
  42 //! - `ShutdownAnySegwit` - requires/supports that future segwit versions are allowed in `shutdown`
  43 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  44 //! - `ChannelType` - node supports the channel_type field in open/accept
  45 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  46 //! - `SCIDPrivacy` - supply channel aliases for routing
  47 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  48 //! - `Keysend` - send funds to a node without an invoice
  49 //!     (see the [`Keysend` feature assignment proposal](https://github.com/lightning/bolts/issues/605#issuecomment-606679798) for more information).
  50 //!
  51 //! [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
  52 //! [messages]: crate::ln::msgs
  53
  54 use {io, io_extras};
  55 use prelude::*;
  56 use core::{cmp, fmt};
  57 use core::hash::{Hash, Hasher};
  58 use core::marker::PhantomData;
  59
  60 use bitcoin::bech32;
  61 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
  62 use ln::msgs::DecodeError;
  63 use util::ser::{Readable, Writeable, Writer};
  64
  65 mod sealed {
  66         use prelude::*;
  67         use ln::features::Features;
  68
  69         /// The context in which [`Features`] are applicable. Defines which features are required and
  70         /// which are optional for the context.
  71         pub trait Context {
  72                 /// Features that are known to the implementation, where a required feature is indicated by
  73                 /// its even bit and an optional feature is indicated by its odd bit.
  74                 const KNOWN_FEATURE_FLAGS: &'static [u8];
  75
  76                 /// Bitmask for selecting features that are known to the implementation, regardless of
  77                 /// whether each feature is required or optional.
  78                 const KNOWN_FEATURE_MASK: &'static [u8];
  79         }
  80
  81         /// Defines a [`Context`] by stating which features it requires and which are optional. Features
  82         /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
  83         /// feature identifiers.
  84         macro_rules! define_context {
  85                 ($context: ident {
  86                         required_features: [$( $( $required_feature: ident )|*, )*],
  87                         optional_features: [$( $( $optional_feature: ident )|*, )*],
  88                 }) => {
  89                         #[derive(Eq, PartialEq)]
  90                         pub struct $context {}
  91
  92                         impl Context for $context {
  93                                 const KNOWN_FEATURE_FLAGS: &'static [u8] = &[
  94                                         // For each byte, use bitwise-OR to compute the applicable flags for known
  95                                         // required features `r_i` and optional features `o_j` for all `i` and `j` such
  96                                         // that the following slice is formed:
  97                                         //
  98                                         // [
  99                                         //  `r_0` | `r_1` | ... | `o_0` | `o_1` | ...,
 100                                         //  ...,
 101                                         // ]
 102                                         $(
 103                                                 0b00_00_00_00 $(|
 104                                                         <Self as $required_feature>::REQUIRED_MASK)*
 105                                                 $(|
 106                                                         <Self as $optional_feature>::OPTIONAL_MASK)*,
 107                                         )*
 108                                 ];
 109
 110                                 const KNOWN_FEATURE_MASK: &'static [u8] = &[
 111                                         // Similar as above, but set both flags for each feature regardless of whether
 112                                         // the feature is required or optional.
 113                                         $(
 114                                                 0b00_00_00_00 $(|
 115                                                         <Self as $required_feature>::REQUIRED_MASK |
 116                                                         <Self as $required_feature>::OPTIONAL_MASK)*
 117                                                 $(|
 118                                                         <Self as $optional_feature>::REQUIRED_MASK |
 119                                                         <Self as $optional_feature>::OPTIONAL_MASK)*,
 120                                         )*
 121                                 ];
 122                         }
 123
 124                         impl alloc::fmt::Display for Features<$context> {
 125                                 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
 126                                         $(
 127                                                 $(
 128                                                         fmt.write_fmt(format_args!("{}: {}, ", stringify!($required_feature),
 129                                                                 if <$context as $required_feature>::requires_feature(&self.flags) { "required" }
 130                                                                 else if <$context as $required_feature>::supports_feature(&self.flags) { "supported" }
 131                                                                 else { "not supported" }))?;
 132                                                 )*
 133                                                 $(
 134                                                         fmt.write_fmt(format_args!("{}: {}, ", stringify!($optional_feature),
 135                                                                 if <$context as $optional_feature>::requires_feature(&self.flags) { "required" }
 136                                                                 else if <$context as $optional_feature>::supports_feature(&self.flags) { "supported" }
 137                                                                 else { "not supported" }))?;
 138                                                 )*
 139                                         )*
 140                                         fmt.write_fmt(format_args!("unknown flags: {}",
 141                                                 if self.requires_unknown_bits() { "required" }
 142                                                 else if self.supports_unknown_bits() { "supported" } else { "none" }))
 143                                 }
 144                         }
 145                 };
 146         }
 147
 148         define_context!(InitContext {
 149                 required_features: [
 150                         // Byte 0
 151                         ,
 152                         // Byte 1
 153                         VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 154                         // Byte 2
 155                         ,
 156                         // Byte 3
 157                         ,
 158                         // Byte 4
 159                         ,
 160                         // Byte 5
 161                         ,
 162                         // Byte 6
 163                         ,
 164                 ],
 165                 optional_features: [
 166                         // Byte 0
 167                         DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
 168                         // Byte 1
 169                         ,
 170                         // Byte 2
 171                         BasicMPP | Wumbo,
 172                         // Byte 3
 173                         ShutdownAnySegwit,
 174                         // Byte 4
 175                         ,
 176                         // Byte 5
 177                         ChannelType | SCIDPrivacy,
 178                         // Byte 6
 179                         ZeroConf,
 180                 ],
 181         });
 182         define_context!(NodeContext {
 183                 required_features: [
 184                         // Byte 0
 185                         ,
 186                         // Byte 1
 187                         VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 188                         // Byte 2
 189                         ,
 190                         // Byte 3
 191                         ,
 192                         // Byte 4
 193                         ,
 194                         // Byte 5
 195                         ,
 196                         // Byte 6
 197                         ,
 198                 ],
 199                 optional_features: [
 200                         // Byte 0
 201                         DataLossProtect | UpfrontShutdownScript | GossipQueries,
 202                         // Byte 1
 203                         ,
 204                         // Byte 2
 205                         BasicMPP | Wumbo,
 206                         // Byte 3
 207                         ShutdownAnySegwit,
 208                         // Byte 4
 209                         ,
 210                         // Byte 5
 211                         ChannelType | SCIDPrivacy,
 212                         // Byte 6
 213                         ZeroConf | Keysend,
 214                 ],
 215         });
 216         define_context!(ChannelContext {
 217                 required_features: [],
 218                 optional_features: [],
 219         });
 220         define_context!(InvoiceContext {
 221                 required_features: [
 222                         // Byte 0
 223                         ,
 224                         // Byte 1
 225                         VariableLengthOnion | PaymentSecret,
 226                         // Byte 2
 227                         ,
 228                 ],
 229                 optional_features: [
 230                         // Byte 0
 231                         ,
 232                         // Byte 1
 233                         ,
 234                         // Byte 2
 235                         BasicMPP,
 236                 ],
 237         });
 238         // This isn't a "real" feature context, and is only used in the channel_type field in an
 239         // `OpenChannel` message.
 240         define_context!(ChannelTypeContext {
 241                 required_features: [
 242                         // Byte 0
 243                         ,
 244                         // Byte 1
 245                         StaticRemoteKey,
 246                         // Byte 2
 247                         ,
 248                         // Byte 3
 249                         ,
 250                         // Byte 4
 251                         ,
 252                         // Byte 5
 253                         SCIDPrivacy,
 254                         // Byte 6
 255                         ZeroConf,
 256                 ],
 257                 optional_features: [
 258                         // Byte 0
 259                         ,
 260                         // Byte 1
 261                         ,
 262                         // Byte 2
 263                         ,
 264                         // Byte 3
 265                         ,
 266                         // Byte 4
 267                         ,
 268                         // Byte 5
 269                         ,
 270                         // Byte 6
 271                         ,
 272                 ],
 273         });
 274
 275         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 276         /// useful for manipulating feature flags.
 277         macro_rules! define_feature {
 278                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 279                  $required_setter: ident, $supported_getter: ident) => {
 280                         #[doc = $doc]
 281                         ///
 282                         /// See [BOLT #9] for details.
 283                         ///
 284                         /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
 285                         pub trait $feature: Context {
 286                                 /// The bit used to signify that the feature is required.
 287                                 const EVEN_BIT: usize = $odd_bit - 1;
 288
 289                                 /// The bit used to signify that the feature is optional.
 290                                 const ODD_BIT: usize = $odd_bit;
 291
 292                                 /// Assertion that [`EVEN_BIT`] is actually even.
 293                                 ///
 294                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 295                                 const ASSERT_EVEN_BIT_PARITY: usize;
 296
 297                                 /// Assertion that [`ODD_BIT`] is actually odd.
 298                                 ///
 299                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 300                                 const ASSERT_ODD_BIT_PARITY: usize;
 301
 302                                 /// The byte where the feature is set.
 303                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 304
 305                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 306                                 ///
 307                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 308                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 309
 310                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 311                                 ///
 312                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 313                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 314
 315                                 /// Returns whether the feature is required by the given flags.
 316                                 #[inline]
 317                                 fn requires_feature(flags: &Vec<u8>) -> bool {
 318                                         flags.len() > Self::BYTE_OFFSET &&
 319                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
 320                                 }
 321
 322                                 /// Returns whether the feature is supported by the given flags.
 323                                 #[inline]
 324                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 325                                         flags.len() > Self::BYTE_OFFSET &&
 326                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 327                                 }
 328
 329                                 /// Sets the feature's required (even) bit in the given flags.
 330                                 #[inline]
 331                                 fn set_required_bit(flags: &mut Vec<u8>) {
 332                                         if flags.len() <= Self::BYTE_OFFSET {
 333                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 334                                         }
 335
 336                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
 337                                 }
 338
 339                                 /// Sets the feature's optional (odd) bit in the given flags.
 340                                 #[inline]
 341                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 342                                         if flags.len() <= Self::BYTE_OFFSET {
 343                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 344                                         }
 345
 346                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 347                                 }
 348
 349                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 350                                 /// flags.
 351                                 #[inline]
 352                                 fn clear_bits(flags: &mut Vec<u8>) {
 353                                         if flags.len() > Self::BYTE_OFFSET {
 354                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 355                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 356                                         }
 357
 358                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 359                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 360                                         flags.resize(size, 0u8);
 361                                 }
 362                         }
 363
 364                         impl <T: $feature> Features<T> {
 365                                 /// Set this feature as optional.
 366                                 pub fn $optional_setter(&mut self) {
 367                                         <T as $feature>::set_optional_bit(&mut self.flags);
 368                                 }
 369
 370                                 /// Set this feature as required.
 371                                 pub fn $required_setter(&mut self) {
 372                                         <T as $feature>::set_required_bit(&mut self.flags);
 373                                 }
 374
 375                                 /// Checks if this feature is supported.
 376                                 pub fn $supported_getter(&self) -> bool {
 377                                         <T as $feature>::supports_feature(&self.flags)
 378                                 }
 379                         }
 380
 381                         $(
 382                                 impl $feature for $context {
 383                                         // EVEN_BIT % 2 == 0
 384                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 385
 386                                         // ODD_BIT % 2 == 1
 387                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 388                                 }
 389                         )*
 390                 };
 391                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 392                  $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
 393                         define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
 394                         impl <T: $feature> Features<T> {
 395                                 /// Checks if this feature is required.
 396                                 pub fn $required_getter(&self) -> bool {
 397                                         <T as $feature>::requires_feature(&self.flags)
 398                                 }
 399                         }
 400                 }
 401         }
 402
 403         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 404                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 405                 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
 406         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 407         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 408                 set_initial_routing_sync_optional, set_initial_routing_sync_required,
 409                 initial_routing_sync);
 410         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 411                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 412                 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
 413                 requires_upfront_shutdown_script);
 414         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 415                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
 416                 supports_gossip_queries, requires_gossip_queries);
 417         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
 418                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 419                 set_variable_length_onion_required, supports_variable_length_onion,
 420                 requires_variable_length_onion);
 421         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
 422                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 423                 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
 424         define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
 425                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
 426                 supports_payment_secret, requires_payment_secret);
 427         define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext],
 428                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
 429                 supports_basic_mpp, requires_basic_mpp);
 430         define_feature!(19, Wumbo, [InitContext, NodeContext],
 431                 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
 432                 supports_wumbo, requires_wumbo);
 433         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 434                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 435                 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
 436         define_feature!(45, ChannelType, [InitContext, NodeContext],
 437                 "Feature flags for `option_channel_type`.", set_channel_type_optional,
 438                 set_channel_type_required, supports_channel_type, requires_channel_type);
 439         define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
 440                 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
 441                 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
 442         define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
 443                 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
 444                 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
 445         define_feature!(55, Keysend, [NodeContext],
 446                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
 447                 supports_keysend, requires_keysend);
 448
 449         #[cfg(test)]
 450         define_feature!(123456789, UnknownFeature, [NodeContext, ChannelContext, InvoiceContext],
 451                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 452                 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
 453 }
 454
 455 /// Tracks the set of features which a node implements, templated by the context in which it
 456 /// appears.
 457 ///
 458 /// (C-not exported) as we map the concrete feature types below directly instead
 459 #[derive(Eq)]
 460 pub struct Features<T: sealed::Context> {
 461         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 462         flags: Vec<u8>,
 463         mark: PhantomData<T>,
 464 }
 465
 466 impl<T: sealed::Context> Clone for Features<T> {
 467         fn clone(&self) -> Self {
 468                 Self {
 469                         flags: self.flags.clone(),
 470                         mark: PhantomData,
 471                 }
 472         }
 473 }
 474 impl<T: sealed::Context> Hash for Features<T> {
 475         fn hash<H: Hasher>(&self, hasher: &mut H) {
 476                 self.flags.hash(hasher);
 477         }
 478 }
 479 impl<T: sealed::Context> PartialEq for Features<T> {
 480         fn eq(&self, o: &Self) -> bool {
 481                 self.flags.eq(&o.flags)
 482         }
 483 }
 484 impl<T: sealed::Context> fmt::Debug for Features<T> {
 485         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 486                 self.flags.fmt(fmt)
 487         }
 488 }
 489
 490 /// Features used within an `init` message.
 491 pub type InitFeatures = Features<sealed::InitContext>;
 492 /// Features used within a `node_announcement` message.
 493 pub type NodeFeatures = Features<sealed::NodeContext>;
 494 /// Features used within a `channel_announcement` message.
 495 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 496 /// Features used within an invoice.
 497 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
 498
 499 /// Features used within the channel_type field in an OpenChannel message.
 500 ///
 501 /// A channel is always of some known "type", describing the transaction formats used and the exact
 502 /// semantics of our interaction with our peer.
 503 ///
 504 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
 505 /// the counterparty, only required features are allowed here.
 506 ///
 507 /// This is serialized differently from other feature types - it is not prefixed by a length, and
 508 /// thus must only appear inside a TLV where its length is known in advance.
 509 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
 510
 511 impl InitFeatures {
 512         /// Writes all features present up to, and including, 13.
 513         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 514                 let len = cmp::min(2, self.flags.len());
 515                 (len as u16).write(w)?;
 516                 for i in (0..len).rev() {
 517                         if i == 0 {
 518                                 self.flags[i].write(w)?;
 519                         } else {
 520                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 521                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 522                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 523                         }
 524                 }
 525                 Ok(())
 526         }
 527
 528         /// or's another InitFeatures into this one.
 529         pub(crate) fn or(mut self, o: InitFeatures) -> InitFeatures {
 530                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
 531                 self.flags.resize(total_feature_len, 0u8);
 532                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
 533                         *byte |= *o_byte;
 534                 }
 535                 self
 536         }
 537
 538         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 539         /// are included in the result.
 540         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 541                 self.to_context_internal()
 542         }
 543 }
 544
 545 impl InvoiceFeatures {
 546         /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
 547         /// context `C` are included in the result.
 548         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 549                 self.to_context_internal()
 550         }
 551
 552         /// Getting a route for a keysend payment to a private node requires providing the payee's
 553         /// features (since they were not announced in a node announcement). However, keysend payments
 554         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 555         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
 556         /// `InvoiceFeatures` for [`find_route`].
 557         ///
 558         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
 559         /// [`find_route`]: crate::routing::router::find_route
 560         pub(crate) fn for_keysend() -> InvoiceFeatures {
 561                 let mut res = InvoiceFeatures::empty();
 562                 res.set_variable_length_onion_optional();
 563                 res
 564         }
 565 }
 566
 567 impl ChannelTypeFeatures {
 568         /// Constructs the implicit channel type based on the common supported types between us and our
 569         /// counterparty
 570         pub(crate) fn from_counterparty_init(counterparty_init: &InitFeatures) -> Self {
 571                 let mut ret = counterparty_init.to_context_internal();
 572                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
 573                 // optional bits and then AND out the optional ones.
 574                 for byte in ret.flags.iter_mut() {
 575                         *byte |= (*byte & 0b10_10_10_10) >> 1;
 576                         *byte &= 0b01_01_01_01;
 577                 }
 578                 ret
 579         }
 580
 581         /// Constructs a ChannelTypeFeatures with only static_remotekey set
 582         pub(crate) fn only_static_remote_key() -> Self {
 583                 let mut ret = Self::empty();
 584                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 585                 ret
 586         }
 587 }
 588
 589 impl ToBase32 for InvoiceFeatures {
 590         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 591                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 592                 // minus one before dividing
 593                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 594                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 595                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 596                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 597                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 598                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 599                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 600                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 601                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 602                         if new_u5_idx > 0 {
 603                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 604                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 605                         }
 606                         if new_u5_idx > 1 {
 607                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 608                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 609                         }
 610                 }
 611                 // Trim the highest feature bits.
 612                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 613                         res_u5s.remove(0);
 614                 }
 615                 writer.write(&res_u5s)
 616         }
 617 }
 618
 619 impl Base32Len for InvoiceFeatures {
 620         fn base32_len(&self) -> usize {
 621                 self.to_base32().len()
 622         }
 623 }
 624
 625 impl FromBase32 for InvoiceFeatures {
 626         type Err = bech32::Error;
 627
 628         fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
 629                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 630                 // minus one before dividing
 631                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 632                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 633                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 634                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 635                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 636                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 637                         let chunk_u16 = chunk.to_u8() as u16;
 638                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 639                         if new_byte_idx != length_bytes - 1 {
 640                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 641                         }
 642                 }
 643                 // Trim the highest feature bits.
 644                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 645                         res_bytes.pop();
 646                 }
 647                 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
 648         }
 649 }
 650
 651 impl<T: sealed::Context> Features<T> {
 652         /// Create a blank Features with no features set
 653         pub fn empty() -> Self {
 654                 Features {
 655                         flags: Vec::new(),
 656                         mark: PhantomData,
 657                 }
 658         }
 659
 660         /// Creates a Features with the bits set which are known by the implementation
 661         pub fn known() -> Self {
 662                 Self {
 663                         flags: T::KNOWN_FEATURE_FLAGS.to_vec(),
 664                         mark: PhantomData,
 665                 }
 666         }
 667
 668         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 669         /// included in the result.
 670         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 671                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 672                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 673                 let mut flags = Vec::new();
 674                 for (i, byte) in self.flags.iter().enumerate() {
 675                         if i < from_byte_count && i < to_byte_count {
 676                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 677                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 678                                 flags.push(byte & from_known_features & to_known_features);
 679                         }
 680                 }
 681                 Features::<C> { flags, mark: PhantomData, }
 682         }
 683
 684         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 685         /// most on-the-wire encodings.
 686         /// (C-not exported) as we don't support export across multiple T
 687         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 688                 Features {
 689                         flags,
 690                         mark: PhantomData,
 691                 }
 692         }
 693
 694         #[cfg(test)]
 695         /// Gets the underlying flags set, in LE.
 696         pub fn le_flags(&self) -> &Vec<u8> {
 697                 &self.flags
 698         }
 699
 700         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 701                 for f in self.flags.iter().rev() { // Swap back to big-endian
 702                         f.write(w)?;
 703                 }
 704                 Ok(())
 705         }
 706
 707         fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
 708                 flags.reverse(); // Swap to little-endian
 709                 Self {
 710                         flags,
 711                         mark: PhantomData,
 712                 }
 713         }
 714
 715         pub(crate) fn supports_any_optional_bits(&self) -> bool {
 716                 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
 717         }
 718
 719         /// Returns true if this `Features` object contains unknown feature flags which are set as
 720         /// "required".
 721         pub fn requires_unknown_bits(&self) -> bool {
 722                 // Bitwise AND-ing with all even bits set except for known features will select required
 723                 // unknown features.
 724                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 725                 self.flags.iter().enumerate().any(|(i, &byte)| {
 726                         let required_features = 0b01_01_01_01;
 727                         let unknown_features = if i < byte_count {
 728                                 !T::KNOWN_FEATURE_MASK[i]
 729                         } else {
 730                                 0b11_11_11_11
 731                         };
 732                         (byte & (required_features & unknown_features)) != 0
 733                 })
 734         }
 735
 736         pub(crate) fn supports_unknown_bits(&self) -> bool {
 737                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 738                 // both required and optional unknown features.
 739                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 740                 self.flags.iter().enumerate().any(|(i, &byte)| {
 741                         let unknown_features = if i < byte_count {
 742                                 !T::KNOWN_FEATURE_MASK[i]
 743                         } else {
 744                                 0b11_11_11_11
 745                         };
 746                         (byte & unknown_features) != 0
 747                 })
 748         }
 749 }
 750
 751 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 752         #[cfg(test)]
 753         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 754                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 755                 self
 756         }
 757 }
 758
 759
 760 impl<T: sealed::GossipQueries> Features<T> {
 761         #[cfg(test)]
 762         pub(crate) fn clear_gossip_queries(mut self) -> Self {
 763                 <T as sealed::GossipQueries>::clear_bits(&mut self.flags);
 764                 self
 765         }
 766 }
 767
 768 impl<T: sealed::InitialRoutingSync> Features<T> {
 769         // We are no longer setting initial_routing_sync now that gossip_queries
 770         // is enabled. This feature is ignored by a peer when gossip_queries has
 771         // been negotiated.
 772         #[cfg(test)]
 773         pub(crate) fn clear_initial_routing_sync(&mut self) {
 774                 <T as sealed::InitialRoutingSync>::clear_bits(&mut self.flags)
 775         }
 776 }
 777
 778 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 779         #[cfg(test)]
 780         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 781                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 782                 self
 783         }
 784 }
 785
 786 impl<T: sealed::Wumbo> Features<T> {
 787         #[cfg(test)]
 788         pub(crate) fn clear_wumbo(mut self) -> Self {
 789                 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
 790                 self
 791         }
 792 }
 793
 794 macro_rules! impl_feature_len_prefixed_write {
 795         ($features: ident) => {
 796                 impl Writeable for $features {
 797                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 798                                 (self.flags.len() as u16).write(w)?;
 799                                 self.write_be(w)
 800                         }
 801                 }
 802                 impl Readable for $features {
 803                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 804                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
 805                         }
 806                 }
 807         }
 808 }
 809 impl_feature_len_prefixed_write!(InitFeatures);
 810 impl_feature_len_prefixed_write!(ChannelFeatures);
 811 impl_feature_len_prefixed_write!(NodeFeatures);
 812 impl_feature_len_prefixed_write!(InvoiceFeatures);
 813
 814 // Because ChannelTypeFeatures only appears inside of TLVs, it doesn't have a length prefix when
 815 // serialized. Thus, we can't use `impl_feature_len_prefixed_write`, above, and have to write our
 816 // own serialization.
 817 impl Writeable for ChannelTypeFeatures {
 818         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 819                 self.write_be(w)
 820         }
 821 }
 822 impl Readable for ChannelTypeFeatures {
 823         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 824                 let v = io_extras::read_to_end(r)?;
 825                 Ok(Self::from_be_bytes(v))
 826         }
 827 }
 828
 829 #[cfg(test)]
 830 mod tests {
 831         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures};
 832         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
 833
 834         #[test]
 835         fn sanity_test_known_features() {
 836                 assert!(!ChannelFeatures::known().requires_unknown_bits());
 837                 assert!(!ChannelFeatures::known().supports_unknown_bits());
 838                 assert!(!InitFeatures::known().requires_unknown_bits());
 839                 assert!(!InitFeatures::known().supports_unknown_bits());
 840                 assert!(!NodeFeatures::known().requires_unknown_bits());
 841                 assert!(!NodeFeatures::known().supports_unknown_bits());
 842
 843                 assert!(InitFeatures::known().supports_upfront_shutdown_script());
 844                 assert!(NodeFeatures::known().supports_upfront_shutdown_script());
 845                 assert!(!InitFeatures::known().requires_upfront_shutdown_script());
 846                 assert!(!NodeFeatures::known().requires_upfront_shutdown_script());
 847
 848                 assert!(InitFeatures::known().supports_gossip_queries());
 849                 assert!(NodeFeatures::known().supports_gossip_queries());
 850                 assert!(!InitFeatures::known().requires_gossip_queries());
 851                 assert!(!NodeFeatures::known().requires_gossip_queries());
 852
 853                 assert!(InitFeatures::known().supports_data_loss_protect());
 854                 assert!(NodeFeatures::known().supports_data_loss_protect());
 855                 assert!(!InitFeatures::known().requires_data_loss_protect());
 856                 assert!(!NodeFeatures::known().requires_data_loss_protect());
 857
 858                 assert!(InitFeatures::known().supports_variable_length_onion());
 859                 assert!(NodeFeatures::known().supports_variable_length_onion());
 860                 assert!(InvoiceFeatures::known().supports_variable_length_onion());
 861                 assert!(InitFeatures::known().requires_variable_length_onion());
 862                 assert!(NodeFeatures::known().requires_variable_length_onion());
 863                 assert!(InvoiceFeatures::known().requires_variable_length_onion());
 864
 865                 assert!(InitFeatures::known().supports_static_remote_key());
 866                 assert!(NodeFeatures::known().supports_static_remote_key());
 867                 assert!(InitFeatures::known().requires_static_remote_key());
 868                 assert!(NodeFeatures::known().requires_static_remote_key());
 869
 870                 assert!(InitFeatures::known().supports_payment_secret());
 871                 assert!(NodeFeatures::known().supports_payment_secret());
 872                 assert!(InvoiceFeatures::known().supports_payment_secret());
 873                 assert!(InitFeatures::known().requires_payment_secret());
 874                 assert!(NodeFeatures::known().requires_payment_secret());
 875                 assert!(InvoiceFeatures::known().requires_payment_secret());
 876
 877                 assert!(InitFeatures::known().supports_basic_mpp());
 878                 assert!(NodeFeatures::known().supports_basic_mpp());
 879                 assert!(InvoiceFeatures::known().supports_basic_mpp());
 880                 assert!(!InitFeatures::known().requires_basic_mpp());
 881                 assert!(!NodeFeatures::known().requires_basic_mpp());
 882                 assert!(!InvoiceFeatures::known().requires_basic_mpp());
 883
 884                 assert!(InitFeatures::known().supports_channel_type());
 885                 assert!(NodeFeatures::known().supports_channel_type());
 886                 assert!(!InitFeatures::known().requires_channel_type());
 887                 assert!(!NodeFeatures::known().requires_channel_type());
 888
 889                 assert!(InitFeatures::known().supports_shutdown_anysegwit());
 890                 assert!(NodeFeatures::known().supports_shutdown_anysegwit());
 891
 892                 assert!(InitFeatures::known().supports_scid_privacy());
 893                 assert!(NodeFeatures::known().supports_scid_privacy());
 894                 assert!(ChannelTypeFeatures::known().supports_scid_privacy());
 895                 assert!(!InitFeatures::known().requires_scid_privacy());
 896                 assert!(!NodeFeatures::known().requires_scid_privacy());
 897                 assert!(ChannelTypeFeatures::known().requires_scid_privacy());
 898
 899                 assert!(InitFeatures::known().supports_wumbo());
 900                 assert!(NodeFeatures::known().supports_wumbo());
 901                 assert!(!InitFeatures::known().requires_wumbo());
 902                 assert!(!NodeFeatures::known().requires_wumbo());
 903
 904                 assert!(InitFeatures::known().supports_zero_conf());
 905                 assert!(!InitFeatures::known().requires_zero_conf());
 906                 assert!(NodeFeatures::known().supports_zero_conf());
 907                 assert!(!NodeFeatures::known().requires_zero_conf());
 908                 assert!(ChannelTypeFeatures::known().supports_zero_conf());
 909                 assert!(ChannelTypeFeatures::known().requires_zero_conf());
 910
 911                 let mut init_features = InitFeatures::known();
 912                 assert!(init_features.initial_routing_sync());
 913                 init_features.clear_initial_routing_sync();
 914                 assert!(!init_features.initial_routing_sync());
 915         }
 916
 917         #[test]
 918         fn sanity_test_unknown_bits() {
 919                 let features = ChannelFeatures::empty();
 920                 assert!(!features.requires_unknown_bits());
 921                 assert!(!features.supports_unknown_bits());
 922
 923                 let mut features = ChannelFeatures::empty();
 924                 features.set_unknown_feature_required();
 925                 assert!(features.requires_unknown_bits());
 926                 assert!(features.supports_unknown_bits());
 927
 928                 let mut features = ChannelFeatures::empty();
 929                 features.set_unknown_feature_optional();
 930                 assert!(!features.requires_unknown_bits());
 931                 assert!(features.supports_unknown_bits());
 932         }
 933
 934         #[test]
 935         fn convert_to_context_with_relevant_flags() {
 936                 let init_features = InitFeatures::known().clear_upfront_shutdown_script().clear_gossip_queries();
 937                 assert!(init_features.initial_routing_sync());
 938                 assert!(!init_features.supports_upfront_shutdown_script());
 939                 assert!(!init_features.supports_gossip_queries());
 940
 941                 let node_features: NodeFeatures = init_features.to_context();
 942                 {
 943                         // Check that the flags are as expected:
 944                         // - option_data_loss_protect
 945                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
 946                         // - basic_mpp | wumbo
 947                         // - opt_shutdown_anysegwit
 948                         // -
 949                         // - option_channel_type | option_scid_alias
 950                         // - option_zeroconf
 951                         assert_eq!(node_features.flags.len(), 7);
 952                         assert_eq!(node_features.flags[0], 0b00000010);
 953                         assert_eq!(node_features.flags[1], 0b01010001);
 954                         assert_eq!(node_features.flags[2], 0b00001010);
 955                         assert_eq!(node_features.flags[3], 0b00001000);
 956                         assert_eq!(node_features.flags[4], 0b00000000);
 957                         assert_eq!(node_features.flags[5], 0b10100000);
 958                         assert_eq!(node_features.flags[6], 0b00001000);
 959                 }
 960
 961                 // Check that cleared flags are kept blank when converting back:
 962                 // - initial_routing_sync was not applicable to NodeContext
 963                 // - upfront_shutdown_script was cleared before converting
 964                 // - gossip_queries was cleared before converting
 965                 let features: InitFeatures = node_features.to_context_internal();
 966                 assert!(!features.initial_routing_sync());
 967                 assert!(!features.supports_upfront_shutdown_script());
 968                 assert!(!init_features.supports_gossip_queries());
 969         }
 970
 971         #[test]
 972         fn convert_to_context_with_unknown_flags() {
 973                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
 974                 assert!(InvoiceFeatures::known().flags.len() < NodeFeatures::known().flags.len());
 975                 let mut invoice_features = InvoiceFeatures::known();
 976                 invoice_features.set_unknown_feature_optional();
 977                 assert!(invoice_features.supports_unknown_bits());
 978                 let node_features: NodeFeatures = invoice_features.to_context();
 979                 assert!(!node_features.supports_unknown_bits());
 980         }
 981
 982         #[test]
 983         fn set_feature_bits() {
 984                 let mut features = InvoiceFeatures::empty();
 985                 features.set_basic_mpp_optional();
 986                 features.set_payment_secret_required();
 987                 assert!(features.supports_basic_mpp());
 988                 assert!(!features.requires_basic_mpp());
 989                 assert!(features.requires_payment_secret());
 990                 assert!(features.supports_payment_secret());
 991         }
 992
 993         #[test]
 994         fn invoice_features_encoding() {
 995                 let features_as_u5s = vec![
 996                         u5::try_from_u8(6).unwrap(),
 997                         u5::try_from_u8(10).unwrap(),
 998                         u5::try_from_u8(25).unwrap(),
 999                         u5::try_from_u8(1).unwrap(),
1000                         u5::try_from_u8(10).unwrap(),
1001                         u5::try_from_u8(0).unwrap(),
1002                         u5::try_from_u8(20).unwrap(),
1003                         u5::try_from_u8(2).unwrap(),
1004                         u5::try_from_u8(0).unwrap(),
1005                         u5::try_from_u8(6).unwrap(),
1006                         u5::try_from_u8(0).unwrap(),
1007                         u5::try_from_u8(16).unwrap(),
1008                         u5::try_from_u8(1).unwrap(),
1009                 ];
1010                 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1011
1012                 // Test length calculation.
1013                 assert_eq!(features.base32_len(), 13);
1014
1015                 // Test serialization.
1016                 let features_serialized = features.to_base32();
1017                 assert_eq!(features_as_u5s, features_serialized);
1018
1019                 // Test deserialization.
1020                 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
1021                 assert_eq!(features, features_deserialized);
1022         }
1023
1024         #[test]
1025         fn test_channel_type_mapping() {
1026                 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
1027                 // required-StaticRemoteKey ChannelTypeFeatures.
1028                 let mut init_features = InitFeatures::empty();
1029                 init_features.set_static_remote_key_optional();
1030                 let converted_features = ChannelTypeFeatures::from_counterparty_init(&init_features);
1031                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
1032                 assert!(!converted_features.supports_any_optional_bits());
1033                 assert!(converted_features.requires_static_remote_key());
1034         }
1035 }