_ 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                                 }
 279
 280                                 /// Sets the feature's optional (odd) bit in the given flags.
 281                                 #[inline]
 282                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 283                                         if flags.len() <= Self::BYTE_OFFSET {
 284                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 285                                         }
 286
 287                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 288                                 }
 289
 290                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 291                                 /// flags.
 292                                 #[inline]
 293                                 fn clear_bits(flags: &mut Vec<u8>) {
 294                                         if flags.len() > Self::BYTE_OFFSET {
 295                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 296                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 297                                         }
 298
 299                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 300                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 301                                         flags.resize(size, 0u8);
 302                                 }
 303                         }
 304
 305                         impl <T: $feature> Features<T> {
 306                                 /// Set this feature as optional.
 307                                 pub fn $optional_setter(&mut self) {
 308                                         <T as $feature>::set_optional_bit(&mut self.flags);
 309                                 }
 310
 311                                 /// Set this feature as required.
 312                                 pub fn $required_setter(&mut self) {
 313                                         <T as $feature>::set_required_bit(&mut self.flags);
 314                                 }
 315
 316                                 /// Checks if this feature is supported.
 317                                 pub fn $supported_getter(&self) -> bool {
 318                                         <T as $feature>::supports_feature(&self.flags)
 319                                 }
 320                         }
 321
 322                         $(
 323                                 impl $feature for $context {
 324                                         // EVEN_BIT % 2 == 0
 325                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 326
 327                                         // ODD_BIT % 2 == 1
 328                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 329
 330                                         // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
 331                                         #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
 332                                         const ASSERT_BITS_IN_MASK: u8 =
 333                                                 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
 334                                                  >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
 335                                 }
 336                         )*
 337                 };
 338                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 339                  $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
 340                         define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
 341                         impl <T: $feature> Features<T> {
 342                                 /// Checks if this feature is required.
 343                                 pub fn $required_getter(&self) -> bool {
 344                                         <T as $feature>::requires_feature(&self.flags)
 345                                 }
 346                         }
 347                 }
 348         }
 349
 350         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 351                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 352                 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
 353         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 354         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 355                 set_initial_routing_sync_optional, set_initial_routing_sync_required,
 356                 initial_routing_sync);
 357         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 358                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 359                 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
 360                 requires_upfront_shutdown_script);
 361         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 362                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
 363                 supports_gossip_queries, requires_gossip_queries);
 364         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
 365                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 366                 set_variable_length_onion_required, supports_variable_length_onion,
 367                 requires_variable_length_onion);
 368         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
 369                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 370                 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
 371         define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
 372                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
 373                 supports_payment_secret, requires_payment_secret);
 374         define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext, Bolt12InvoiceContext],
 375                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
 376                 supports_basic_mpp, requires_basic_mpp);
 377         define_feature!(19, Wumbo, [InitContext, NodeContext],
 378                 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
 379                 supports_wumbo, requires_wumbo);
 380         define_feature!(23, AnchorsZeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
 381                 "Feature flags for `option_anchors_zero_fee_htlc_tx`.", set_anchors_zero_fee_htlc_tx_optional,
 382                 set_anchors_zero_fee_htlc_tx_required, supports_anchors_zero_fee_htlc_tx, requires_anchors_zero_fee_htlc_tx);
 383         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 384                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 385                 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
 386         define_feature!(39, OnionMessages, [InitContext, NodeContext],
 387                 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
 388                 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
 389         define_feature!(45, ChannelType, [InitContext, NodeContext],
 390                 "Feature flags for `option_channel_type`.", set_channel_type_optional,
 391                 set_channel_type_required, supports_channel_type, requires_channel_type);
 392         define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
 393                 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
 394                 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
 395         define_feature!(49, PaymentMetadata, [InvoiceContext],
 396                 "Feature flags for payment metadata in invoices.", set_payment_metadata_optional,
 397                 set_payment_metadata_required, supports_payment_metadata, requires_payment_metadata);
 398         define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
 399                 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
 400                 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
 401         define_feature!(55, Keysend, [NodeContext],
 402                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
 403                 supports_keysend, requires_keysend);
 404         // Note: update the module-level docs when a new feature bit is added!
 405
 406         #[cfg(test)]
 407         define_feature!(123456789, UnknownFeature,
 408                 [NodeContext, ChannelContext, InvoiceContext, OfferContext, InvoiceRequestContext, Bolt12InvoiceContext, BlindedHopContext],
 409                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 410                 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
 411 }
 412
 413 /// Tracks the set of features which a node implements, templated by the context in which it
 414 /// appears.
 415 ///
 416 /// This is not exported to bindings users as we map the concrete feature types below directly instead
 417 #[derive(Eq)]
 418 pub struct Features<T: sealed::Context> {
 419         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 420         flags: Vec<u8>,
 421         mark: PhantomData<T>,
 422 }
 423
 424 impl <T: sealed::Context> Features<T> {
 425         pub(crate) fn or(mut self, o: Self) -> Self {
 426                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
 427                 self.flags.resize(total_feature_len, 0u8);
 428                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
 429                         *byte |= *o_byte;
 430                 }
 431                 self
 432         }
 433 }
 434
 435 impl<T: sealed::Context> Clone for Features<T> {
 436         fn clone(&self) -> Self {
 437                 Self {
 438                         flags: self.flags.clone(),
 439                         mark: PhantomData,
 440                 }
 441         }
 442 }
 443 impl<T: sealed::Context> Hash for Features<T> {
 444         fn hash<H: Hasher>(&self, hasher: &mut H) {
 445                 self.flags.hash(hasher);
 446         }
 447 }
 448 impl<T: sealed::Context> PartialEq for Features<T> {
 449         fn eq(&self, o: &Self) -> bool {
 450                 self.flags.eq(&o.flags)
 451         }
 452 }
 453 impl<T: sealed::Context> fmt::Debug for Features<T> {
 454         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 455                 self.flags.fmt(fmt)
 456         }
 457 }
 458
 459 /// Features used within an `init` message.
 460 pub type InitFeatures = Features<sealed::InitContext>;
 461 /// Features used within a `node_announcement` message.
 462 pub type NodeFeatures = Features<sealed::NodeContext>;
 463 /// Features used within a `channel_announcement` message.
 464 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 465 /// Features used within an invoice.
 466 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
 467 /// Features used within an `offer`.
 468 pub type OfferFeatures = Features<sealed::OfferContext>;
 469 /// Features used within an `invoice_request`.
 470 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
 471 /// Features used within an `invoice`.
 472 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
 473 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
 474 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
 475
 476 /// Features used within the channel_type field in an OpenChannel message.
 477 ///
 478 /// A channel is always of some known "type", describing the transaction formats used and the exact
 479 /// semantics of our interaction with our peer.
 480 ///
 481 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
 482 /// the counterparty, only required features are allowed here.
 483 ///
 484 /// This is serialized differently from other feature types - it is not prefixed by a length, and
 485 /// thus must only appear inside a TLV where its length is known in advance.
 486 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
 487
 488 impl InitFeatures {
 489         /// Writes all features present up to, and including, 13.
 490         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 491                 let len = cmp::min(2, self.flags.len());
 492                 (len as u16).write(w)?;
 493                 for i in (0..len).rev() {
 494                         if i == 0 {
 495                                 self.flags[i].write(w)?;
 496                         } else {
 497                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 498                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 499                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 500                         }
 501                 }
 502                 Ok(())
 503         }
 504
 505         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 506         /// are included in the result.
 507         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 508                 self.to_context_internal()
 509         }
 510 }
 511
 512 impl InvoiceFeatures {
 513         /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
 514         /// context `C` are included in the result.
 515         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 516                 self.to_context_internal()
 517         }
 518
 519         /// Getting a route for a keysend payment to a private node requires providing the payee's
 520         /// features (since they were not announced in a node announcement). However, keysend payments
 521         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 522         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
 523         /// `InvoiceFeatures` for [`find_route`].
 524         ///
 525         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
 526         /// [`find_route`]: crate::routing::router::find_route
 527         pub(crate) fn for_keysend() -> InvoiceFeatures {
 528                 let mut res = InvoiceFeatures::empty();
 529                 res.set_variable_length_onion_optional();
 530                 res
 531         }
 532 }
 533
 534 impl ChannelTypeFeatures {
 535         // Maps the relevant `InitFeatures` to `ChannelTypeFeatures`. Any unknown features to
 536         // `ChannelTypeFeatures` are not included in the result.
 537         pub(crate) fn from_init(init: &InitFeatures) -> Self {
 538                 let mut ret = init.to_context_internal();
 539                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
 540                 // optional bits and then AND out the optional ones.
 541                 for byte in ret.flags.iter_mut() {
 542                         *byte |= (*byte & 0b10_10_10_10) >> 1;
 543                         *byte &= 0b01_01_01_01;
 544                 }
 545                 ret
 546         }
 547
 548         /// Constructs a ChannelTypeFeatures with only static_remotekey set
 549         pub(crate) fn only_static_remote_key() -> Self {
 550                 let mut ret = Self::empty();
 551                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 552                 ret
 553         }
 554 }
 555
 556 impl ToBase32 for InvoiceFeatures {
 557         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 558                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 559                 // minus one before dividing
 560                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 561                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 562                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 563                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 564                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 565                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 566                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 567                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 568                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 569                         if new_u5_idx > 0 {
 570                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 571                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 572                         }
 573                         if new_u5_idx > 1 {
 574                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 575                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 576                         }
 577                 }
 578                 // Trim the highest feature bits.
 579                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 580                         res_u5s.remove(0);
 581                 }
 582                 writer.write(&res_u5s)
 583         }
 584 }
 585
 586 impl Base32Len for InvoiceFeatures {
 587         fn base32_len(&self) -> usize {
 588                 self.to_base32().len()
 589         }
 590 }
 591
 592 impl FromBase32 for InvoiceFeatures {
 593         type Err = bech32::Error;
 594
 595         fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
 596                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 597                 // minus one before dividing
 598                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 599                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 600                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 601                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 602                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 603                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 604                         let chunk_u16 = chunk.to_u8() as u16;
 605                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 606                         if new_byte_idx != length_bytes - 1 {
 607                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 608                         }
 609                 }
 610                 // Trim the highest feature bits.
 611                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 612                         res_bytes.pop();
 613                 }
 614                 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
 615         }
 616 }
 617
 618 impl<T: sealed::Context> Features<T> {
 619         /// Create a blank Features with no features set
 620         pub fn empty() -> Self {
 621                 Features {
 622                         flags: Vec::new(),
 623                         mark: PhantomData,
 624                 }
 625         }
 626
 627         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 628         /// included in the result.
 629         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 630                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 631                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 632                 let mut flags = Vec::new();
 633                 for (i, byte) in self.flags.iter().enumerate() {
 634                         if i < from_byte_count && i < to_byte_count {
 635                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 636                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 637                                 flags.push(byte & from_known_features & to_known_features);
 638                         }
 639                 }
 640                 Features::<C> { flags, mark: PhantomData, }
 641         }
 642
 643         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 644         /// most on-the-wire encodings.
 645         ///
 646         /// This is not exported to bindings users as we don't support export across multiple T
 647         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 648                 Features {
 649                         flags,
 650                         mark: PhantomData,
 651                 }
 652         }
 653
 654         #[cfg(test)]
 655         /// Gets the underlying flags set, in LE.
 656         pub fn le_flags(&self) -> &Vec<u8> {
 657                 &self.flags
 658         }
 659
 660         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 661                 for f in self.flags.iter().rev() { // Swap back to big-endian
 662                         f.write(w)?;
 663                 }
 664                 Ok(())
 665         }
 666
 667         fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
 668                 flags.reverse(); // Swap to little-endian
 669                 Self {
 670                         flags,
 671                         mark: PhantomData,
 672                 }
 673         }
 674
 675         pub(crate) fn supports_any_optional_bits(&self) -> bool {
 676                 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
 677         }
 678
 679         /// Returns true if this `Features` object contains unknown feature flags which are set as
 680         /// "required".
 681         pub fn requires_unknown_bits(&self) -> bool {
 682                 // Bitwise AND-ing with all even bits set except for known features will select required
 683                 // unknown features.
 684                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 685                 self.flags.iter().enumerate().any(|(i, &byte)| {
 686                         let required_features = 0b01_01_01_01;
 687                         let unknown_features = if i < byte_count {
 688                                 !T::KNOWN_FEATURE_MASK[i]
 689                         } else {
 690                                 0b11_11_11_11
 691                         };
 692                         (byte & (required_features & unknown_features)) != 0
 693                 })
 694         }
 695
 696         pub(crate) fn supports_unknown_bits(&self) -> bool {
 697                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 698                 // both required and optional unknown features.
 699                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 700                 self.flags.iter().enumerate().any(|(i, &byte)| {
 701                         let unknown_features = if i < byte_count {
 702                                 !T::KNOWN_FEATURE_MASK[i]
 703                         } else {
 704                                 0b11_11_11_11
 705                         };
 706                         (byte & unknown_features) != 0
 707                 })
 708         }
 709
 710         // Returns true if the features within `self` are a subset of the features within `other`.
 711         pub(crate) fn is_subset(&self, other: &Self) -> bool {
 712                 for (idx, byte) in self.flags.iter().enumerate() {
 713                         if let Some(other_byte) = other.flags.get(idx) {
 714                                 if byte & other_byte != *byte {
 715                                         // `self` has bits set that `other` doesn't.
 716                                         return false;
 717                                 }
 718                         } else {
 719                                 if *byte > 0 {
 720                                         // `self` has a non-zero byte that `other` doesn't.
 721                                         return false;
 722                                 }
 723                         }
 724                 }
 725                 true
 726         }
 727 }
 728
 729 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 730         #[cfg(test)]
 731         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 732                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 733                 self
 734         }
 735 }
 736
 737 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 738         #[cfg(test)]
 739         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 740                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 741                 self
 742         }
 743 }
 744
 745 impl<T: sealed::Wumbo> Features<T> {
 746         #[cfg(test)]
 747         pub(crate) fn clear_wumbo(mut self) -> Self {
 748                 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
 749                 self
 750         }
 751 }
 752
 753 impl<T: sealed::SCIDPrivacy> Features<T> {
 754         pub(crate) fn clear_scid_privacy(&mut self) {
 755                 <T as sealed::SCIDPrivacy>::clear_bits(&mut self.flags);
 756         }
 757 }
 758
 759 impl<T: sealed::AnchorsZeroFeeHtlcTx> Features<T> {
 760         pub(crate) fn clear_anchors_zero_fee_htlc_tx(&mut self) {
 761                 <T as sealed::AnchorsZeroFeeHtlcTx>::clear_bits(&mut self.flags);
 762         }
 763 }
 764
 765 #[cfg(test)]
 766 impl<T: sealed::UnknownFeature> Features<T> {
 767         pub(crate) fn unknown() -> Self {
 768                 let mut features = Self::empty();
 769                 features.set_unknown_feature_required();
 770                 features
 771         }
 772 }
 773
 774 macro_rules! impl_feature_len_prefixed_write {
 775         ($features: ident) => {
 776                 impl Writeable for $features {
 777                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 778                                 (self.flags.len() as u16).write(w)?;
 779                                 self.write_be(w)
 780                         }
 781                 }
 782                 impl Readable for $features {
 783                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 784                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
 785                         }
 786                 }
 787         }
 788 }
 789 impl_feature_len_prefixed_write!(InitFeatures);
 790 impl_feature_len_prefixed_write!(ChannelFeatures);
 791 impl_feature_len_prefixed_write!(NodeFeatures);
 792 impl_feature_len_prefixed_write!(InvoiceFeatures);
 793 impl_feature_len_prefixed_write!(BlindedHopFeatures);
 794
 795 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
 796 macro_rules! impl_feature_tlv_write {
 797         ($features: ident) => {
 798                 impl Writeable for $features {
 799                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 800                                 WithoutLength(self).write(w)
 801                         }
 802                 }
 803                 impl Readable for $features {
 804                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 805                                 Ok(WithoutLength::<Self>::read(r)?.0)
 806                         }
 807                 }
 808         }
 809 }
 810
 811 impl_feature_tlv_write!(ChannelTypeFeatures);
 812
 813 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
 814 // requires a length but the former does not.
 815
 816 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
 817         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 818                 self.0.write_be(w)
 819         }
 820 }
 821
 822 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
 823         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 824                 let v = io_extras::read_to_end(r)?;
 825                 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
 826         }
 827 }
 828
 829 #[cfg(test)]
 830 mod tests {
 831         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
 832         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
 833         use crate::util::ser::{Readable, WithoutLength, Writeable};
 834
 835         #[test]
 836         fn sanity_test_unknown_bits() {
 837                 let features = ChannelFeatures::empty();
 838                 assert!(!features.requires_unknown_bits());
 839                 assert!(!features.supports_unknown_bits());
 840
 841                 let mut features = ChannelFeatures::empty();
 842                 features.set_unknown_feature_required();
 843                 assert!(features.requires_unknown_bits());
 844                 assert!(features.supports_unknown_bits());
 845
 846                 let mut features = ChannelFeatures::empty();
 847                 features.set_unknown_feature_optional();
 848                 assert!(!features.requires_unknown_bits());
 849                 assert!(features.supports_unknown_bits());
 850         }
 851
 852         #[test]
 853         fn convert_to_context_with_relevant_flags() {
 854                 let mut init_features = InitFeatures::empty();
 855                 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
 856                 // converted as it's only relevant in an init context).
 857                 init_features.set_initial_routing_sync_required();
 858                 init_features.set_data_loss_protect_optional();
 859                 init_features.set_variable_length_onion_required();
 860                 init_features.set_static_remote_key_required();
 861                 init_features.set_payment_secret_required();
 862                 init_features.set_basic_mpp_optional();
 863                 init_features.set_wumbo_optional();
 864                 init_features.set_shutdown_any_segwit_optional();
 865                 init_features.set_onion_messages_optional();
 866                 init_features.set_channel_type_optional();
 867                 init_features.set_scid_privacy_optional();
 868                 init_features.set_zero_conf_optional();
 869                 init_features.set_anchors_zero_fee_htlc_tx_optional();
 870
 871                 assert!(init_features.initial_routing_sync());
 872                 assert!(!init_features.supports_upfront_shutdown_script());
 873                 assert!(!init_features.supports_gossip_queries());
 874
 875                 let node_features: NodeFeatures = init_features.to_context();
 876                 {
 877                         // Check that the flags are as expected:
 878                         // - option_data_loss_protect
 879                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
 880                         // - basic_mpp | wumbo
 881                         // - opt_shutdown_anysegwit
 882                         // - onion_messages
 883                         // - option_channel_type | option_scid_alias
 884                         // - option_zeroconf
 885                         assert_eq!(node_features.flags.len(), 7);
 886                         assert_eq!(node_features.flags[0], 0b00000010);
 887                         assert_eq!(node_features.flags[1], 0b01010001);
 888                         assert_eq!(node_features.flags[2], 0b10001010);
 889                         assert_eq!(node_features.flags[3], 0b00001000);
 890                         assert_eq!(node_features.flags[4], 0b10000000);
 891                         assert_eq!(node_features.flags[5], 0b10100000);
 892                         assert_eq!(node_features.flags[6], 0b00001000);
 893                 }
 894
 895                 // Check that cleared flags are kept blank when converting back:
 896                 // - initial_routing_sync was not applicable to NodeContext
 897                 // - upfront_shutdown_script was cleared before converting
 898                 // - gossip_queries was cleared before converting
 899                 let features: InitFeatures = node_features.to_context_internal();
 900                 assert!(!features.initial_routing_sync());
 901                 assert!(!features.supports_upfront_shutdown_script());
 902                 assert!(!init_features.supports_gossip_queries());
 903         }
 904
 905         #[test]
 906         fn convert_to_context_with_unknown_flags() {
 907                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
 908                 assert!(<sealed::ChannelContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
 909                         <sealed::InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
 910                 let mut channel_features = ChannelFeatures::empty();
 911                 channel_features.set_unknown_feature_optional();
 912                 assert!(channel_features.supports_unknown_bits());
 913                 let invoice_features: InvoiceFeatures = channel_features.to_context_internal();
 914                 assert!(!invoice_features.supports_unknown_bits());
 915         }
 916
 917         #[test]
 918         fn set_feature_bits() {
 919                 let mut features = InvoiceFeatures::empty();
 920                 features.set_basic_mpp_optional();
 921                 features.set_payment_secret_required();
 922                 assert!(features.supports_basic_mpp());
 923                 assert!(!features.requires_basic_mpp());
 924                 assert!(features.requires_payment_secret());
 925                 assert!(features.supports_payment_secret());
 926         }
 927
 928         #[test]
 929         fn encodes_features_without_length() {
 930                 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
 931                 assert_eq!(features.flags.len(), 8);
 932
 933                 let mut serialized_features = Vec::new();
 934                 WithoutLength(&features).write(&mut serialized_features).unwrap();
 935                 assert_eq!(serialized_features.len(), 8);
 936
 937                 let deserialized_features =
 938                         WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
 939                 assert_eq!(features, deserialized_features);
 940         }
 941
 942         #[test]
 943         fn invoice_features_encoding() {
 944                 let features_as_u5s = vec![
 945                         u5::try_from_u8(6).unwrap(),
 946                         u5::try_from_u8(10).unwrap(),
 947                         u5::try_from_u8(25).unwrap(),
 948                         u5::try_from_u8(1).unwrap(),
 949                         u5::try_from_u8(10).unwrap(),
 950                         u5::try_from_u8(0).unwrap(),
 951                         u5::try_from_u8(20).unwrap(),
 952                         u5::try_from_u8(2).unwrap(),
 953                         u5::try_from_u8(0).unwrap(),
 954                         u5::try_from_u8(6).unwrap(),
 955                         u5::try_from_u8(0).unwrap(),
 956                         u5::try_from_u8(16).unwrap(),
 957                         u5::try_from_u8(1).unwrap(),
 958                 ];
 959                 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
 960
 961                 // Test length calculation.
 962                 assert_eq!(features.base32_len(), 13);
 963
 964                 // Test serialization.
 965                 let features_serialized = features.to_base32();
 966                 assert_eq!(features_as_u5s, features_serialized);
 967
 968                 // Test deserialization.
 969                 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
 970                 assert_eq!(features, features_deserialized);
 971         }
 972
 973         #[test]
 974         fn test_channel_type_mapping() {
 975                 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
 976                 // required-StaticRemoteKey ChannelTypeFeatures.
 977                 let mut init_features = InitFeatures::empty();
 978                 init_features.set_static_remote_key_optional();
 979                 let converted_features = ChannelTypeFeatures::from_init(&init_features);
 980                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
 981                 assert!(!converted_features.supports_any_optional_bits());
 982                 assert!(converted_features.requires_static_remote_key());
 983         }
 984 }