_ 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 //! - `Wumbo` - requires/supports that a node create large channels. Called `option_support_large_channel` in the spec.
  43 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#the-open_channel-message) for more information).
  44 //! - `ShutdownAnySegwit` - requires/supports that future segwit versions are allowed in `shutdown`
  45 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  46 //! - `OnionMessages` - requires/supports forwarding onion messages
  47 //!     (see [BOLT-7](https://github.com/lightning/bolts/pull/759/files) for more information).
  48 //     TODO: update link
  49 //! - `ChannelType` - node supports the channel_type field in open/accept
  50 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  51 //! - `SCIDPrivacy` - supply channel aliases for routing
  52 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  53 //! - `PaymentMetadata` - include additional data in invoices which is passed to recipients in the
  54 //!      onion.
  55 //!      (see [BOLT-11](https://github.com/lightning/bolts/blob/master/11-payment-encoding.md) for
  56 //!      more).
  57 //! - `ZeroConf` - supports accepting HTLCs and using channels prior to funding confirmation
  58 //!      (see
  59 //!      [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#the-channel_ready-message)
  60 //!      for more info).
  61 //! - `Keysend` - send funds to a node without an invoice
  62 //!     (see the [`Keysend` feature assignment proposal](https://github.com/lightning/bolts/issues/605#issuecomment-606679798) for more information).
  63 //! - `AnchorsZeroFeeHtlcTx` - requires/supports that commitment transactions include anchor outputs
  64 //!     and HTLC transactions are pre-signed with zero fee (see
  65 //!     [BOLT-3](https://github.com/lightning/bolts/blob/master/03-transactions.md) for more
  66 //!     information).
  67 //!
  68 //! [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
  69 //! [messages]: crate::ln::msgs
  70
  71 use crate::{io, io_extras};
  72 use crate::prelude::*;
  73 use core::{cmp, fmt};
  74 use core::hash::{Hash, Hasher};
  75 use core::marker::PhantomData;
  76
  77 use bitcoin::bech32;
  78 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
  79 use crate::ln::msgs::DecodeError;
  80 use crate::util::ser::{Readable, WithoutLength, Writeable, Writer};
  81
  82 mod sealed {
  83         use crate::prelude::*;
  84         use crate::ln::features::Features;
  85
  86         /// The context in which [`Features`] are applicable. Defines which features are known to the
  87         /// implementation, though specification of them as required or optional is up to the code
  88         /// constructing a features object.
  89         pub trait Context {
  90                 /// Bitmask for selecting features that are known to the implementation.
  91                 const KNOWN_FEATURE_MASK: &'static [u8];
  92         }
  93
  94         /// Defines a [`Context`] by stating which features it requires and which are optional. Features
  95         /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
  96         /// feature identifiers.
  97         macro_rules! define_context {
  98                 ($context: ident, [$( $( $known_feature: ident )|*, )*]) => {
  99                         #[derive(Eq, PartialEq)]
 100                         pub struct $context {}
 101
 102                         impl Context for $context {
 103                                 const KNOWN_FEATURE_MASK: &'static [u8] = &[
 104                                         $(
 105                                                 0b00_00_00_00 $(|
 106                                                         <Self as $known_feature>::REQUIRED_MASK |
 107                                                         <Self as $known_feature>::OPTIONAL_MASK)*,
 108                                         )*
 109                                 ];
 110                         }
 111
 112                         impl alloc::fmt::Display for Features<$context> {
 113                                 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
 114                                         $(
 115                                                 $(
 116                                                         fmt.write_fmt(format_args!("{}: {}, ", stringify!($known_feature),
 117                                                                 if <$context as $known_feature>::requires_feature(&self.flags) { "required" }
 118                                                                 else if <$context as $known_feature>::supports_feature(&self.flags) { "supported" }
 119                                                                 else { "not supported" }))?;
 120                                                 )*
 121                                                 {} // Rust gets mad if we only have a $()* block here, so add a dummy {}
 122                                         )*
 123                                         fmt.write_fmt(format_args!("unknown flags: {}",
 124                                                 if self.requires_unknown_bits() { "required" }
 125                                                 else if self.supports_unknown_bits() { "supported" } else { "none" }))
 126                                 }
 127                         }
 128                 };
 129         }
 130
 131         define_context!(InitContext, [
 132                 // Byte 0
 133                 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
 134                 // Byte 1
 135                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 136                 // Byte 2
 137                 BasicMPP | Wumbo | AnchorsZeroFeeHtlcTx,
 138                 // Byte 3
 139                 ShutdownAnySegwit,
 140                 // Byte 4
 141                 OnionMessages,
 142                 // Byte 5
 143                 ChannelType | SCIDPrivacy,
 144                 // Byte 6
 145                 ZeroConf,
 146         ]);
 147         define_context!(NodeContext, [
 148                 // Byte 0
 149                 DataLossProtect | UpfrontShutdownScript | GossipQueries,
 150                 // Byte 1
 151                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 152                 // Byte 2
 153                 BasicMPP | Wumbo | AnchorsZeroFeeHtlcTx,
 154                 // Byte 3
 155                 ShutdownAnySegwit,
 156                 // Byte 4
 157                 OnionMessages,
 158                 // Byte 5
 159                 ChannelType | SCIDPrivacy,
 160                 // Byte 6
 161                 ZeroConf | Keysend,
 162         ]);
 163         define_context!(ChannelContext, []);
 164         define_context!(InvoiceContext, [
 165                 // Byte 0
 166                 ,
 167                 // Byte 1
 168                 VariableLengthOnion | PaymentSecret,
 169                 // Byte 2
 170                 BasicMPP,
 171                 // Byte 3
 172                 ,
 173                 // Byte 4
 174                 ,
 175                 // Byte 5
 176                 ,
 177                 // Byte 6
 178                 PaymentMetadata,
 179         ]);
 180         define_context!(OfferContext, []);
 181         define_context!(InvoiceRequestContext, []);
 182         define_context!(Bolt12InvoiceContext, [
 183                 // Byte 0
 184                 ,
 185                 // Byte 1
 186                 ,
 187                 // Byte 2
 188                 BasicMPP,
 189         ]);
 190         define_context!(BlindedHopContext, []);
 191         // This isn't a "real" feature context, and is only used in the channel_type field in an
 192         // `OpenChannel` message.
 193         define_context!(ChannelTypeContext, [
 194                 // Byte 0
 195                 ,
 196                 // Byte 1
 197                 StaticRemoteKey,
 198                 // Byte 2
 199                 AnchorsZeroFeeHtlcTx,
 200                 // Byte 3
 201                 ,
 202                 // Byte 4
 203                 ,
 204                 // Byte 5
 205                 SCIDPrivacy,
 206                 // Byte 6
 207                 ZeroConf,
 208         ]);
 209
 210         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 211         /// useful for manipulating feature flags.
 212         macro_rules! define_feature {
 213                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 214                  $required_setter: ident, $supported_getter: ident) => {
 215                         #[doc = $doc]
 216                         ///
 217                         /// See [BOLT #9] for details.
 218                         ///
 219                         /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
 220                         pub trait $feature: Context {
 221                                 /// The bit used to signify that the feature is required.
 222                                 const EVEN_BIT: usize = $odd_bit - 1;
 223
 224                                 /// The bit used to signify that the feature is optional.
 225                                 const ODD_BIT: usize = $odd_bit;
 226
 227                                 /// Assertion that [`EVEN_BIT`] is actually even.
 228                                 ///
 229                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 230                                 const ASSERT_EVEN_BIT_PARITY: usize;
 231
 232                                 /// Assertion that [`ODD_BIT`] is actually odd.
 233                                 ///
 234                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 235                                 const ASSERT_ODD_BIT_PARITY: usize;
 236
 237                                 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
 238                                 ///
 239                                 /// [`KNOWN_FEATURE_MASK`]: Context::KNOWN_FEATURE_MASK
 240                                 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
 241                                 const ASSERT_BITS_IN_MASK: u8;
 242
 243                                 /// The byte where the feature is set.
 244                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 245
 246                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 247                                 ///
 248                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 249                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 250
 251                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 252                                 ///
 253                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 254                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 255
 256                                 /// Returns whether the feature is required by the given flags.
 257                                 #[inline]
 258                                 fn requires_feature(flags: &Vec<u8>) -> bool {
 259                                         flags.len() > Self::BYTE_OFFSET &&
 260                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
 261                                 }
 262
 263                                 /// Returns whether the feature is supported by the given flags.
 264                                 #[inline]
 265                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 266                                         flags.len() > Self::BYTE_OFFSET &&
 267                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 268                                 }
 269
 270                                 /// Sets the feature's required (even) bit in the given flags.
 271                                 #[inline]
 272                                 fn set_required_bit(flags: &mut Vec<u8>) {
 273                                         if flags.len() <= Self::BYTE_OFFSET {
 274                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 275                                         }
 276
 277                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
 278                                         flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 279                                 }
 280
 281                                 /// Sets the feature's optional (odd) bit in the given flags.
 282                                 #[inline]
 283                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 284                                         if flags.len() <= Self::BYTE_OFFSET {
 285                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 286                                         }
 287
 288                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 289                                 }
 290
 291                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 292                                 /// flags.
 293                                 #[inline]
 294                                 fn clear_bits(flags: &mut Vec<u8>) {
 295                                         if flags.len() > Self::BYTE_OFFSET {
 296                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 297                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 298                                         }
 299
 300                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 301                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 302                                         flags.resize(size, 0u8);
 303                                 }
 304                         }
 305
 306                         impl <T: $feature> Features<T> {
 307                                 /// Set this feature as optional.
 308                                 pub fn $optional_setter(&mut self) {
 309                                         <T as $feature>::set_optional_bit(&mut self.flags);
 310                                 }
 311
 312                                 /// Set this feature as required.
 313                                 pub fn $required_setter(&mut self) {
 314                                         <T as $feature>::set_required_bit(&mut self.flags);
 315                                 }
 316
 317                                 /// Checks if this feature is supported.
 318                                 pub fn $supported_getter(&self) -> bool {
 319                                         <T as $feature>::supports_feature(&self.flags)
 320                                 }
 321                         }
 322
 323                         $(
 324                                 impl $feature for $context {
 325                                         // EVEN_BIT % 2 == 0
 326                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 327
 328                                         // ODD_BIT % 2 == 1
 329                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 330
 331                                         // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
 332                                         #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
 333                                         const ASSERT_BITS_IN_MASK: u8 =
 334                                                 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
 335                                                  >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
 336                                 }
 337                         )*
 338                 };
 339                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 340                  $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
 341                         define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
 342                         impl <T: $feature> Features<T> {
 343                                 /// Checks if this feature is required.
 344                                 pub fn $required_getter(&self) -> bool {
 345                                         <T as $feature>::requires_feature(&self.flags)
 346                                 }
 347                         }
 348                 }
 349         }
 350
 351         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 352                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 353                 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
 354         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 355         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 356                 set_initial_routing_sync_optional, set_initial_routing_sync_required,
 357                 initial_routing_sync);
 358         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 359                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 360                 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
 361                 requires_upfront_shutdown_script);
 362         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 363                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
 364                 supports_gossip_queries, requires_gossip_queries);
 365         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
 366                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 367                 set_variable_length_onion_required, supports_variable_length_onion,
 368                 requires_variable_length_onion);
 369         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
 370                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 371                 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
 372         define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
 373                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
 374                 supports_payment_secret, requires_payment_secret);
 375         define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext, Bolt12InvoiceContext],
 376                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
 377                 supports_basic_mpp, requires_basic_mpp);
 378         define_feature!(19, Wumbo, [InitContext, NodeContext],
 379                 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
 380                 supports_wumbo, requires_wumbo);
 381         define_feature!(23, AnchorsZeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
 382                 "Feature flags for `option_anchors_zero_fee_htlc_tx`.", set_anchors_zero_fee_htlc_tx_optional,
 383                 set_anchors_zero_fee_htlc_tx_required, supports_anchors_zero_fee_htlc_tx, requires_anchors_zero_fee_htlc_tx);
 384         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 385                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 386                 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
 387         define_feature!(39, OnionMessages, [InitContext, NodeContext],
 388                 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
 389                 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
 390         define_feature!(45, ChannelType, [InitContext, NodeContext],
 391                 "Feature flags for `option_channel_type`.", set_channel_type_optional,
 392                 set_channel_type_required, supports_channel_type, requires_channel_type);
 393         define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
 394                 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
 395                 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
 396         define_feature!(49, PaymentMetadata, [InvoiceContext],
 397                 "Feature flags for payment metadata in invoices.", set_payment_metadata_optional,
 398                 set_payment_metadata_required, supports_payment_metadata, requires_payment_metadata);
 399         define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
 400                 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
 401                 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
 402         define_feature!(55, Keysend, [NodeContext],
 403                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
 404                 supports_keysend, requires_keysend);
 405         // Note: update the module-level docs when a new feature bit is added!
 406
 407         #[cfg(test)]
 408         define_feature!(123456789, UnknownFeature,
 409                 [NodeContext, ChannelContext, InvoiceContext, OfferContext, InvoiceRequestContext, Bolt12InvoiceContext, BlindedHopContext],
 410                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 411                 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
 412 }
 413
 414 /// Tracks the set of features which a node implements, templated by the context in which it
 415 /// appears.
 416 ///
 417 /// This is not exported to bindings users as we map the concrete feature types below directly instead
 418 #[derive(Eq)]
 419 pub struct Features<T: sealed::Context> {
 420         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 421         flags: Vec<u8>,
 422         mark: PhantomData<T>,
 423 }
 424
 425 impl <T: sealed::Context> Features<T> {
 426         pub(crate) fn or(mut self, o: Self) -> Self {
 427                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
 428                 self.flags.resize(total_feature_len, 0u8);
 429                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
 430                         *byte |= *o_byte;
 431                 }
 432                 self
 433         }
 434 }
 435
 436 impl<T: sealed::Context> Clone for Features<T> {
 437         fn clone(&self) -> Self {
 438                 Self {
 439                         flags: self.flags.clone(),
 440                         mark: PhantomData,
 441                 }
 442         }
 443 }
 444 impl<T: sealed::Context> Hash for Features<T> {
 445         fn hash<H: Hasher>(&self, hasher: &mut H) {
 446                 self.flags.hash(hasher);
 447         }
 448 }
 449 impl<T: sealed::Context> PartialEq for Features<T> {
 450         fn eq(&self, o: &Self) -> bool {
 451                 self.flags.eq(&o.flags)
 452         }
 453 }
 454 impl<T: sealed::Context> PartialOrd for Features<T> {
 455         fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
 456                 self.flags.partial_cmp(&other.flags)
 457         }
 458 }
 459 impl<T: sealed::Context + Eq> Ord for Features<T> {
 460         fn cmp(&self, other: &Self) -> cmp::Ordering {
 461                 self.flags.cmp(&other.flags)
 462         }
 463 }
 464 impl<T: sealed::Context> fmt::Debug for Features<T> {
 465         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 466                 self.flags.fmt(fmt)
 467         }
 468 }
 469
 470 /// Features used within an `init` message.
 471 pub type InitFeatures = Features<sealed::InitContext>;
 472 /// Features used within a `node_announcement` message.
 473 pub type NodeFeatures = Features<sealed::NodeContext>;
 474 /// Features used within a `channel_announcement` message.
 475 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 476 /// Features used within an invoice.
 477 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
 478 /// Features used within an `offer`.
 479 pub type OfferFeatures = Features<sealed::OfferContext>;
 480 /// Features used within an `invoice_request`.
 481 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
 482 /// Features used within an `invoice`.
 483 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
 484 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
 485 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
 486
 487 /// Features used within the channel_type field in an OpenChannel message.
 488 ///
 489 /// A channel is always of some known "type", describing the transaction formats used and the exact
 490 /// semantics of our interaction with our peer.
 491 ///
 492 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
 493 /// the counterparty, only required features are allowed here.
 494 ///
 495 /// This is serialized differently from other feature types - it is not prefixed by a length, and
 496 /// thus must only appear inside a TLV where its length is known in advance.
 497 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
 498
 499 impl InitFeatures {
 500         /// Writes all features present up to, and including, 13.
 501         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 502                 let len = cmp::min(2, self.flags.len());
 503                 (len as u16).write(w)?;
 504                 for i in (0..len).rev() {
 505                         if i == 0 {
 506                                 self.flags[i].write(w)?;
 507                         } else {
 508                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 509                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 510                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 511                         }
 512                 }
 513                 Ok(())
 514         }
 515
 516         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 517         /// are included in the result.
 518         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 519                 self.to_context_internal()
 520         }
 521 }
 522
 523 impl InvoiceFeatures {
 524         /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
 525         /// context `C` are included in the result.
 526         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 527                 self.to_context_internal()
 528         }
 529
 530         /// Getting a route for a keysend payment to a private node requires providing the payee's
 531         /// features (since they were not announced in a node announcement). However, keysend payments
 532         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 533         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
 534         /// `InvoiceFeatures` for [`find_route`].
 535         ///
 536         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
 537         /// [`find_route`]: crate::routing::router::find_route
 538         pub(crate) fn for_keysend() -> InvoiceFeatures {
 539                 let mut res = InvoiceFeatures::empty();
 540                 res.set_variable_length_onion_optional();
 541                 res
 542         }
 543 }
 544
 545 impl ChannelTypeFeatures {
 546         // Maps the relevant `InitFeatures` to `ChannelTypeFeatures`. Any unknown features to
 547         // `ChannelTypeFeatures` are not included in the result.
 548         pub(crate) fn from_init(init: &InitFeatures) -> Self {
 549                 let mut ret = init.to_context_internal();
 550                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
 551                 // optional bits and then AND out the optional ones.
 552                 for byte in ret.flags.iter_mut() {
 553                         *byte |= (*byte & 0b10_10_10_10) >> 1;
 554                         *byte &= 0b01_01_01_01;
 555                 }
 556                 ret
 557         }
 558
 559         /// Constructs a ChannelTypeFeatures with only static_remotekey set
 560         pub(crate) fn only_static_remote_key() -> Self {
 561                 let mut ret = Self::empty();
 562                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 563                 ret
 564         }
 565 }
 566
 567 impl ToBase32 for InvoiceFeatures {
 568         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 569                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 570                 // minus one before dividing
 571                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 572                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 573                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 574                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 575                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 576                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 577                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 578                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 579                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 580                         if new_u5_idx > 0 {
 581                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 582                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 583                         }
 584                         if new_u5_idx > 1 {
 585                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 586                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 587                         }
 588                 }
 589                 // Trim the highest feature bits.
 590                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 591                         res_u5s.remove(0);
 592                 }
 593                 writer.write(&res_u5s)
 594         }
 595 }
 596
 597 impl Base32Len for InvoiceFeatures {
 598         fn base32_len(&self) -> usize {
 599                 self.to_base32().len()
 600         }
 601 }
 602
 603 impl FromBase32 for InvoiceFeatures {
 604         type Err = bech32::Error;
 605
 606         fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
 607                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 608                 // minus one before dividing
 609                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 610                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 611                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 612                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 613                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 614                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 615                         let chunk_u16 = chunk.to_u8() as u16;
 616                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 617                         if new_byte_idx != length_bytes - 1 {
 618                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 619                         }
 620                 }
 621                 // Trim the highest feature bits.
 622                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 623                         res_bytes.pop();
 624                 }
 625                 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
 626         }
 627 }
 628
 629 impl<T: sealed::Context> Features<T> {
 630         /// Create a blank Features with no features set
 631         pub fn empty() -> Self {
 632                 Features {
 633                         flags: Vec::new(),
 634                         mark: PhantomData,
 635                 }
 636         }
 637
 638         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 639         /// included in the result.
 640         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 641                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 642                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 643                 let mut flags = Vec::new();
 644                 for (i, byte) in self.flags.iter().enumerate() {
 645                         if i < from_byte_count && i < to_byte_count {
 646                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 647                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 648                                 flags.push(byte & from_known_features & to_known_features);
 649                         }
 650                 }
 651                 Features::<C> { flags, mark: PhantomData, }
 652         }
 653
 654         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 655         /// most on-the-wire encodings.
 656         ///
 657         /// This is not exported to bindings users as we don't support export across multiple T
 658         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 659                 Features {
 660                         flags,
 661                         mark: PhantomData,
 662                 }
 663         }
 664
 665         #[cfg(test)]
 666         /// Gets the underlying flags set, in LE.
 667         pub fn le_flags(&self) -> &Vec<u8> {
 668                 &self.flags
 669         }
 670
 671         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 672                 for f in self.flags.iter().rev() { // Swap back to big-endian
 673                         f.write(w)?;
 674                 }
 675                 Ok(())
 676         }
 677
 678         fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
 679                 flags.reverse(); // Swap to little-endian
 680                 Self {
 681                         flags,
 682                         mark: PhantomData,
 683                 }
 684         }
 685
 686         pub(crate) fn supports_any_optional_bits(&self) -> bool {
 687                 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
 688         }
 689
 690         /// Returns true if this `Features` object contains unknown feature flags which are set as
 691         /// "required".
 692         pub fn requires_unknown_bits(&self) -> bool {
 693                 // Bitwise AND-ing with all even bits set except for known features will select required
 694                 // unknown features.
 695                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 696                 self.flags.iter().enumerate().any(|(i, &byte)| {
 697                         let required_features = 0b01_01_01_01;
 698                         let unknown_features = if i < byte_count {
 699                                 !T::KNOWN_FEATURE_MASK[i]
 700                         } else {
 701                                 0b11_11_11_11
 702                         };
 703                         (byte & (required_features & unknown_features)) != 0
 704                 })
 705         }
 706
 707         pub(crate) fn supports_unknown_bits(&self) -> bool {
 708                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 709                 // both required and optional unknown features.
 710                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 711                 self.flags.iter().enumerate().any(|(i, &byte)| {
 712                         let unknown_features = if i < byte_count {
 713                                 !T::KNOWN_FEATURE_MASK[i]
 714                         } else {
 715                                 0b11_11_11_11
 716                         };
 717                         (byte & unknown_features) != 0
 718                 })
 719         }
 720
 721         // Returns true if the features within `self` are a subset of the features within `other`.
 722         pub(crate) fn is_subset(&self, other: &Self) -> bool {
 723                 for (idx, byte) in self.flags.iter().enumerate() {
 724                         if let Some(other_byte) = other.flags.get(idx) {
 725                                 if byte & other_byte != *byte {
 726                                         // `self` has bits set that `other` doesn't.
 727                                         return false;
 728                                 }
 729                         } else {
 730                                 if *byte > 0 {
 731                                         // `self` has a non-zero byte that `other` doesn't.
 732                                         return false;
 733                                 }
 734                         }
 735                 }
 736                 true
 737         }
 738 }
 739
 740 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 741         #[cfg(test)]
 742         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 743                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 744                 self
 745         }
 746 }
 747
 748 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 749         #[cfg(test)]
 750         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 751                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 752                 self
 753         }
 754 }
 755
 756 impl<T: sealed::Wumbo> Features<T> {
 757         #[cfg(test)]
 758         pub(crate) fn clear_wumbo(mut self) -> Self {
 759                 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
 760                 self
 761         }
 762 }
 763
 764 impl<T: sealed::SCIDPrivacy> Features<T> {
 765         pub(crate) fn clear_scid_privacy(&mut self) {
 766                 <T as sealed::SCIDPrivacy>::clear_bits(&mut self.flags);
 767         }
 768 }
 769
 770 impl<T: sealed::AnchorsZeroFeeHtlcTx> Features<T> {
 771         pub(crate) fn clear_anchors_zero_fee_htlc_tx(&mut self) {
 772                 <T as sealed::AnchorsZeroFeeHtlcTx>::clear_bits(&mut self.flags);
 773         }
 774 }
 775
 776 #[cfg(test)]
 777 impl<T: sealed::UnknownFeature> Features<T> {
 778         pub(crate) fn unknown() -> Self {
 779                 let mut features = Self::empty();
 780                 features.set_unknown_feature_required();
 781                 features
 782         }
 783 }
 784
 785 macro_rules! impl_feature_len_prefixed_write {
 786         ($features: ident) => {
 787                 impl Writeable for $features {
 788                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 789                                 (self.flags.len() as u16).write(w)?;
 790                                 self.write_be(w)
 791                         }
 792                 }
 793                 impl Readable for $features {
 794                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 795                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
 796                         }
 797                 }
 798         }
 799 }
 800 impl_feature_len_prefixed_write!(InitFeatures);
 801 impl_feature_len_prefixed_write!(ChannelFeatures);
 802 impl_feature_len_prefixed_write!(NodeFeatures);
 803 impl_feature_len_prefixed_write!(InvoiceFeatures);
 804 impl_feature_len_prefixed_write!(BlindedHopFeatures);
 805
 806 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
 807 macro_rules! impl_feature_tlv_write {
 808         ($features: ident) => {
 809                 impl Writeable for $features {
 810                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 811                                 WithoutLength(self).write(w)
 812                         }
 813                 }
 814                 impl Readable for $features {
 815                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 816                                 Ok(WithoutLength::<Self>::read(r)?.0)
 817                         }
 818                 }
 819         }
 820 }
 821
 822 impl_feature_tlv_write!(ChannelTypeFeatures);
 823
 824 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
 825 // requires a length but the former does not.
 826
 827 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
 828         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 829                 self.0.write_be(w)
 830         }
 831 }
 832
 833 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
 834         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 835                 let v = io_extras::read_to_end(r)?;
 836                 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
 837         }
 838 }
 839
 840 #[cfg(test)]
 841 mod tests {
 842         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
 843         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
 844         use crate::util::ser::{Readable, WithoutLength, Writeable};
 845
 846         #[test]
 847         fn sanity_test_unknown_bits() {
 848                 let features = ChannelFeatures::empty();
 849                 assert!(!features.requires_unknown_bits());
 850                 assert!(!features.supports_unknown_bits());
 851
 852                 let mut features = ChannelFeatures::empty();
 853                 features.set_unknown_feature_required();
 854                 assert!(features.requires_unknown_bits());
 855                 assert!(features.supports_unknown_bits());
 856
 857                 let mut features = ChannelFeatures::empty();
 858                 features.set_unknown_feature_optional();
 859                 assert!(!features.requires_unknown_bits());
 860                 assert!(features.supports_unknown_bits());
 861         }
 862
 863         #[test]
 864         fn convert_to_context_with_relevant_flags() {
 865                 let mut init_features = InitFeatures::empty();
 866                 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
 867                 // converted as it's only relevant in an init context).
 868                 init_features.set_initial_routing_sync_required();
 869                 init_features.set_data_loss_protect_required();
 870                 init_features.set_variable_length_onion_required();
 871                 init_features.set_static_remote_key_required();
 872                 init_features.set_payment_secret_required();
 873                 init_features.set_basic_mpp_optional();
 874                 init_features.set_wumbo_optional();
 875                 init_features.set_shutdown_any_segwit_optional();
 876                 init_features.set_onion_messages_optional();
 877                 init_features.set_channel_type_optional();
 878                 init_features.set_scid_privacy_optional();
 879                 init_features.set_zero_conf_optional();
 880                 init_features.set_anchors_zero_fee_htlc_tx_optional();
 881
 882                 assert!(init_features.initial_routing_sync());
 883                 assert!(!init_features.supports_upfront_shutdown_script());
 884                 assert!(!init_features.supports_gossip_queries());
 885
 886                 let node_features: NodeFeatures = init_features.to_context();
 887                 {
 888                         // Check that the flags are as expected:
 889                         // - option_data_loss_protect (req)
 890                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
 891                         // - basic_mpp | wumbo
 892                         // - opt_shutdown_anysegwit
 893                         // - onion_messages
 894                         // - option_channel_type | option_scid_alias
 895                         // - option_zeroconf
 896                         assert_eq!(node_features.flags.len(), 7);
 897                         assert_eq!(node_features.flags[0], 0b00000001);
 898                         assert_eq!(node_features.flags[1], 0b01010001);
 899                         assert_eq!(node_features.flags[2], 0b10001010);
 900                         assert_eq!(node_features.flags[3], 0b00001000);
 901                         assert_eq!(node_features.flags[4], 0b10000000);
 902                         assert_eq!(node_features.flags[5], 0b10100000);
 903                         assert_eq!(node_features.flags[6], 0b00001000);
 904                 }
 905
 906                 // Check that cleared flags are kept blank when converting back:
 907                 // - initial_routing_sync was not applicable to NodeContext
 908                 // - upfront_shutdown_script was cleared before converting
 909                 // - gossip_queries was cleared before converting
 910                 let features: InitFeatures = node_features.to_context_internal();
 911                 assert!(!features.initial_routing_sync());
 912                 assert!(!features.supports_upfront_shutdown_script());
 913                 assert!(!init_features.supports_gossip_queries());
 914         }
 915
 916         #[test]
 917         fn convert_to_context_with_unknown_flags() {
 918                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
 919                 assert!(<sealed::ChannelContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
 920                         <sealed::InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
 921                 let mut channel_features = ChannelFeatures::empty();
 922                 channel_features.set_unknown_feature_optional();
 923                 assert!(channel_features.supports_unknown_bits());
 924                 let invoice_features: InvoiceFeatures = channel_features.to_context_internal();
 925                 assert!(!invoice_features.supports_unknown_bits());
 926         }
 927
 928         #[test]
 929         fn set_feature_bits() {
 930                 let mut features = InvoiceFeatures::empty();
 931                 features.set_basic_mpp_optional();
 932                 features.set_payment_secret_required();
 933                 assert!(features.supports_basic_mpp());
 934                 assert!(!features.requires_basic_mpp());
 935                 assert!(features.requires_payment_secret());
 936                 assert!(features.supports_payment_secret());
 937         }
 938
 939         #[test]
 940         fn encodes_features_without_length() {
 941                 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
 942                 assert_eq!(features.flags.len(), 8);
 943
 944                 let mut serialized_features = Vec::new();
 945                 WithoutLength(&features).write(&mut serialized_features).unwrap();
 946                 assert_eq!(serialized_features.len(), 8);
 947
 948                 let deserialized_features =
 949                         WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
 950                 assert_eq!(features, deserialized_features);
 951         }
 952
 953         #[test]
 954         fn invoice_features_encoding() {
 955                 let features_as_u5s = vec![
 956                         u5::try_from_u8(6).unwrap(),
 957                         u5::try_from_u8(10).unwrap(),
 958                         u5::try_from_u8(25).unwrap(),
 959                         u5::try_from_u8(1).unwrap(),
 960                         u5::try_from_u8(10).unwrap(),
 961                         u5::try_from_u8(0).unwrap(),
 962                         u5::try_from_u8(20).unwrap(),
 963                         u5::try_from_u8(2).unwrap(),
 964                         u5::try_from_u8(0).unwrap(),
 965                         u5::try_from_u8(6).unwrap(),
 966                         u5::try_from_u8(0).unwrap(),
 967                         u5::try_from_u8(16).unwrap(),
 968                         u5::try_from_u8(1).unwrap(),
 969                 ];
 970                 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
 971
 972                 // Test length calculation.
 973                 assert_eq!(features.base32_len(), 13);
 974
 975                 // Test serialization.
 976                 let features_serialized = features.to_base32();
 977                 assert_eq!(features_as_u5s, features_serialized);
 978
 979                 // Test deserialization.
 980                 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
 981                 assert_eq!(features, features_deserialized);
 982         }
 983
 984         #[test]
 985         fn test_channel_type_mapping() {
 986                 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
 987                 // required-StaticRemoteKey ChannelTypeFeatures.
 988                 let mut init_features = InitFeatures::empty();
 989                 init_features.set_static_remote_key_optional();
 990                 let converted_features = ChannelTypeFeatures::from_init(&init_features);
 991                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
 992                 assert!(!converted_features.supports_any_optional_bits());
 993                 assert!(converted_features.requires_static_remote_key());
 994         }
 995 }