_ 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> core::ops::BitOr for Features<T> {
 426         type Output = Self;
 427
 428         fn bitor(mut self, o: Self) -> Self {
 429                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
 430                 self.flags.resize(total_feature_len, 0u8);
 431                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
 432                         *byte |= *o_byte;
 433                 }
 434                 self
 435         }
 436 }
 437
 438 impl<T: sealed::Context> Clone for Features<T> {
 439         fn clone(&self) -> Self {
 440                 Self {
 441                         flags: self.flags.clone(),
 442                         mark: PhantomData,
 443                 }
 444         }
 445 }
 446 impl<T: sealed::Context> Hash for Features<T> {
 447         fn hash<H: Hasher>(&self, hasher: &mut H) {
 448                 self.flags.hash(hasher);
 449         }
 450 }
 451 impl<T: sealed::Context> PartialEq for Features<T> {
 452         fn eq(&self, o: &Self) -> bool {
 453                 self.flags.eq(&o.flags)
 454         }
 455 }
 456 impl<T: sealed::Context> PartialOrd for Features<T> {
 457         fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
 458                 self.flags.partial_cmp(&other.flags)
 459         }
 460 }
 461 impl<T: sealed::Context + Eq> Ord for Features<T> {
 462         fn cmp(&self, other: &Self) -> cmp::Ordering {
 463                 self.flags.cmp(&other.flags)
 464         }
 465 }
 466 impl<T: sealed::Context> fmt::Debug for Features<T> {
 467         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 468                 self.flags.fmt(fmt)
 469         }
 470 }
 471
 472 /// Features used within an `init` message.
 473 pub type InitFeatures = Features<sealed::InitContext>;
 474 /// Features used within a `node_announcement` message.
 475 pub type NodeFeatures = Features<sealed::NodeContext>;
 476 /// Features used within a `channel_announcement` message.
 477 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 478 /// Features used within an invoice.
 479 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
 480 /// Features used within an `offer`.
 481 pub type OfferFeatures = Features<sealed::OfferContext>;
 482 /// Features used within an `invoice_request`.
 483 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
 484 /// Features used within an `invoice`.
 485 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
 486 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
 487 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
 488
 489 /// Features used within the channel_type field in an OpenChannel message.
 490 ///
 491 /// A channel is always of some known "type", describing the transaction formats used and the exact
 492 /// semantics of our interaction with our peer.
 493 ///
 494 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
 495 /// the counterparty, only required features are allowed here.
 496 ///
 497 /// This is serialized differently from other feature types - it is not prefixed by a length, and
 498 /// thus must only appear inside a TLV where its length is known in advance.
 499 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
 500
 501 impl InitFeatures {
 502         /// Writes all features present up to, and including, 13.
 503         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 504                 let len = cmp::min(2, self.flags.len());
 505                 (len as u16).write(w)?;
 506                 for i in (0..len).rev() {
 507                         if i == 0 {
 508                                 self.flags[i].write(w)?;
 509                         } else {
 510                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 511                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 512                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 513                         }
 514                 }
 515                 Ok(())
 516         }
 517
 518         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 519         /// are included in the result.
 520         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 521                 self.to_context_internal()
 522         }
 523 }
 524
 525 impl InvoiceFeatures {
 526         /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
 527         /// context `C` are included in the result.
 528         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 529                 self.to_context_internal()
 530         }
 531
 532         /// Getting a route for a keysend payment to a private node requires providing the payee's
 533         /// features (since they were not announced in a node announcement). However, keysend payments
 534         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 535         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
 536         /// `InvoiceFeatures` for [`find_route`].
 537         ///
 538         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
 539         /// [`find_route`]: crate::routing::router::find_route
 540         pub(crate) fn for_keysend() -> InvoiceFeatures {
 541                 let mut res = InvoiceFeatures::empty();
 542                 res.set_variable_length_onion_optional();
 543                 res
 544         }
 545 }
 546
 547 impl Bolt12InvoiceFeatures {
 548         /// Converts `Bolt12InvoiceFeatures` to `Features<C>`. Only known `Bolt12InvoiceFeatures` relevant
 549         /// to context `C` are included in the result.
 550         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 551                 self.to_context_internal()
 552         }
 553 }
 554
 555 impl ChannelTypeFeatures {
 556         // Maps the relevant `InitFeatures` to `ChannelTypeFeatures`. Any unknown features to
 557         // `ChannelTypeFeatures` are not included in the result.
 558         pub(crate) fn from_init(init: &InitFeatures) -> Self {
 559                 let mut ret = init.to_context_internal();
 560                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
 561                 // optional bits and then AND out the optional ones.
 562                 for byte in ret.flags.iter_mut() {
 563                         *byte |= (*byte & 0b10_10_10_10) >> 1;
 564                         *byte &= 0b01_01_01_01;
 565                 }
 566                 ret
 567         }
 568
 569         /// Constructs a ChannelTypeFeatures with only static_remotekey set
 570         pub(crate) fn only_static_remote_key() -> Self {
 571                 let mut ret = Self::empty();
 572                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 573                 ret
 574         }
 575 }
 576
 577 impl ToBase32 for InvoiceFeatures {
 578         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 579                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 580                 // minus one before dividing
 581                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 582                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 583                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 584                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 585                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 586                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 587                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 588                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 589                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 590                         if new_u5_idx > 0 {
 591                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 592                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 593                         }
 594                         if new_u5_idx > 1 {
 595                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 596                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 597                         }
 598                 }
 599                 // Trim the highest feature bits.
 600                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 601                         res_u5s.remove(0);
 602                 }
 603                 writer.write(&res_u5s)
 604         }
 605 }
 606
 607 impl Base32Len for InvoiceFeatures {
 608         fn base32_len(&self) -> usize {
 609                 self.to_base32().len()
 610         }
 611 }
 612
 613 impl FromBase32 for InvoiceFeatures {
 614         type Err = bech32::Error;
 615
 616         fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
 617                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 618                 // minus one before dividing
 619                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 620                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 621                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 622                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 623                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 624                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 625                         let chunk_u16 = chunk.to_u8() as u16;
 626                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 627                         if new_byte_idx != length_bytes - 1 {
 628                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 629                         }
 630                 }
 631                 // Trim the highest feature bits.
 632                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 633                         res_bytes.pop();
 634                 }
 635                 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
 636         }
 637 }
 638
 639 impl<T: sealed::Context> Features<T> {
 640         /// Create a blank Features with no features set
 641         pub fn empty() -> Self {
 642                 Features {
 643                         flags: Vec::new(),
 644                         mark: PhantomData,
 645                 }
 646         }
 647
 648         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 649         /// included in the result.
 650         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 651                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 652                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 653                 let mut flags = Vec::new();
 654                 for (i, byte) in self.flags.iter().enumerate() {
 655                         if i < from_byte_count && i < to_byte_count {
 656                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 657                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 658                                 flags.push(byte & from_known_features & to_known_features);
 659                         }
 660                 }
 661                 Features::<C> { flags, mark: PhantomData, }
 662         }
 663
 664         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 665         /// most on-the-wire encodings.
 666         ///
 667         /// This is not exported to bindings users as we don't support export across multiple T
 668         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 669                 Features {
 670                         flags,
 671                         mark: PhantomData,
 672                 }
 673         }
 674
 675         #[cfg(test)]
 676         /// Gets the underlying flags set, in LE.
 677         pub fn le_flags(&self) -> &Vec<u8> {
 678                 &self.flags
 679         }
 680
 681         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 682                 for f in self.flags.iter().rev() { // Swap back to big-endian
 683                         f.write(w)?;
 684                 }
 685                 Ok(())
 686         }
 687
 688         fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
 689                 flags.reverse(); // Swap to little-endian
 690                 Self {
 691                         flags,
 692                         mark: PhantomData,
 693                 }
 694         }
 695
 696         pub(crate) fn supports_any_optional_bits(&self) -> bool {
 697                 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
 698         }
 699
 700         /// Returns true if this `Features` object contains required features unknown by `other`.
 701         pub fn requires_unknown_bits_from(&self, other: &Features<T>) -> bool {
 702                 // Bitwise AND-ing with all even bits set except for known features will select required
 703                 // unknown features.
 704                 self.flags.iter().enumerate().any(|(i, &byte)| {
 705                         const REQUIRED_FEATURES: u8 = 0b01_01_01_01;
 706                         const OPTIONAL_FEATURES: u8 = 0b10_10_10_10;
 707                         let unknown_features = if i < other.flags.len() {
 708                                 // Form a mask similar to !T::KNOWN_FEATURE_MASK only for `other`
 709                                 !(other.flags[i]
 710                                         | ((other.flags[i] >> 1) & REQUIRED_FEATURES)
 711                                         | ((other.flags[i] << 1) & OPTIONAL_FEATURES))
 712                         } else {
 713                                 0b11_11_11_11
 714                         };
 715                         (byte & (REQUIRED_FEATURES & unknown_features)) != 0
 716                 })
 717         }
 718
 719         /// Returns true if this `Features` object contains unknown feature flags which are set as
 720         /// "required".
 721         pub fn requires_unknown_bits(&self) -> bool {
 722                 // Bitwise AND-ing with all even bits set except for known features will select required
 723                 // unknown features.
 724                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 725                 self.flags.iter().enumerate().any(|(i, &byte)| {
 726                         let required_features = 0b01_01_01_01;
 727                         let unknown_features = if i < byte_count {
 728                                 !T::KNOWN_FEATURE_MASK[i]
 729                         } else {
 730                                 0b11_11_11_11
 731                         };
 732                         (byte & (required_features & unknown_features)) != 0
 733                 })
 734         }
 735
 736         pub(crate) fn supports_unknown_bits(&self) -> bool {
 737                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 738                 // both required and optional unknown features.
 739                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 740                 self.flags.iter().enumerate().any(|(i, &byte)| {
 741                         let unknown_features = if i < byte_count {
 742                                 !T::KNOWN_FEATURE_MASK[i]
 743                         } else {
 744                                 0b11_11_11_11
 745                         };
 746                         (byte & unknown_features) != 0
 747                 })
 748         }
 749
 750         // Returns true if the features within `self` are a subset of the features within `other`.
 751         pub(crate) fn is_subset(&self, other: &Self) -> bool {
 752                 for (idx, byte) in self.flags.iter().enumerate() {
 753                         if let Some(other_byte) = other.flags.get(idx) {
 754                                 if byte & other_byte != *byte {
 755                                         // `self` has bits set that `other` doesn't.
 756                                         return false;
 757                                 }
 758                         } else {
 759                                 if *byte > 0 {
 760                                         // `self` has a non-zero byte that `other` doesn't.
 761                                         return false;
 762                                 }
 763                         }
 764                 }
 765                 true
 766         }
 767
 768         /// Sets a required custom feature bit. Errors if `bit` is outside the custom range as defined
 769         /// by [bLIP 2] or if it is a known `T` feature.
 770         ///
 771         /// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
 772         /// be set instead (i.e., `bit - 1`).
 773         ///
 774         /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
 775         pub fn set_required_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 776                 self.set_custom_bit(bit - (bit % 2))
 777         }
 778
 779         /// Sets an optional custom feature bit. Errors if `bit` is outside the custom range as defined
 780         /// by [bLIP 2] or if it is a known `T` feature.
 781         ///
 782         /// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
 783         /// set instead (i.e., `bit + 1`).
 784         ///
 785         /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
 786         pub fn set_optional_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 787                 self.set_custom_bit(bit + (1 - (bit % 2)))
 788         }
 789
 790         fn set_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 791                 if bit < 256 {
 792                         return Err(());
 793                 }
 794
 795                 let byte_offset = bit / 8;
 796                 let mask = 1 << (bit - 8 * byte_offset);
 797                 if byte_offset < T::KNOWN_FEATURE_MASK.len() {
 798                         if (T::KNOWN_FEATURE_MASK[byte_offset] & mask) != 0 {
 799                                 return Err(());
 800                         }
 801                 }
 802
 803                 if self.flags.len() <= byte_offset {
 804                         self.flags.resize(byte_offset + 1, 0u8);
 805                 }
 806
 807                 self.flags[byte_offset] |= mask;
 808
 809                 Ok(())
 810         }
 811 }
 812
 813 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 814         #[cfg(test)]
 815         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 816                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 817                 self
 818         }
 819 }
 820
 821 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 822         #[cfg(test)]
 823         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 824                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 825                 self
 826         }
 827 }
 828
 829 impl<T: sealed::Wumbo> Features<T> {
 830         #[cfg(test)]
 831         pub(crate) fn clear_wumbo(mut self) -> Self {
 832                 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
 833                 self
 834         }
 835 }
 836
 837 impl<T: sealed::SCIDPrivacy> Features<T> {
 838         pub(crate) fn clear_scid_privacy(&mut self) {
 839                 <T as sealed::SCIDPrivacy>::clear_bits(&mut self.flags);
 840         }
 841 }
 842
 843 impl<T: sealed::AnchorsZeroFeeHtlcTx> Features<T> {
 844         pub(crate) fn clear_anchors_zero_fee_htlc_tx(&mut self) {
 845                 <T as sealed::AnchorsZeroFeeHtlcTx>::clear_bits(&mut self.flags);
 846         }
 847 }
 848
 849 #[cfg(test)]
 850 impl<T: sealed::UnknownFeature> Features<T> {
 851         pub(crate) fn unknown() -> Self {
 852                 let mut features = Self::empty();
 853                 features.set_unknown_feature_required();
 854                 features
 855         }
 856 }
 857
 858 macro_rules! impl_feature_len_prefixed_write {
 859         ($features: ident) => {
 860                 impl Writeable for $features {
 861                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 862                                 (self.flags.len() as u16).write(w)?;
 863                                 self.write_be(w)
 864                         }
 865                 }
 866                 impl Readable for $features {
 867                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 868                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
 869                         }
 870                 }
 871         }
 872 }
 873 impl_feature_len_prefixed_write!(InitFeatures);
 874 impl_feature_len_prefixed_write!(ChannelFeatures);
 875 impl_feature_len_prefixed_write!(NodeFeatures);
 876 impl_feature_len_prefixed_write!(InvoiceFeatures);
 877 impl_feature_len_prefixed_write!(Bolt12InvoiceFeatures);
 878 impl_feature_len_prefixed_write!(BlindedHopFeatures);
 879
 880 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
 881 macro_rules! impl_feature_tlv_write {
 882         ($features: ident) => {
 883                 impl Writeable for $features {
 884                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 885                                 WithoutLength(self).write(w)
 886                         }
 887                 }
 888                 impl Readable for $features {
 889                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 890                                 Ok(WithoutLength::<Self>::read(r)?.0)
 891                         }
 892                 }
 893         }
 894 }
 895
 896 impl_feature_tlv_write!(ChannelTypeFeatures);
 897
 898 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
 899 // requires a length but the former does not.
 900
 901 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
 902         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 903                 self.0.write_be(w)
 904         }
 905 }
 906
 907 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
 908         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 909                 let v = io_extras::read_to_end(r)?;
 910                 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
 911         }
 912 }
 913
 914 #[cfg(test)]
 915 mod tests {
 916         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
 917         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
 918         use crate::util::ser::{Readable, WithoutLength, Writeable};
 919
 920         #[test]
 921         fn sanity_test_unknown_bits() {
 922                 let features = ChannelFeatures::empty();
 923                 assert!(!features.requires_unknown_bits());
 924                 assert!(!features.supports_unknown_bits());
 925
 926                 let mut features = ChannelFeatures::empty();
 927                 features.set_unknown_feature_required();
 928                 assert!(features.requires_unknown_bits());
 929                 assert!(features.supports_unknown_bits());
 930
 931                 let mut features = ChannelFeatures::empty();
 932                 features.set_unknown_feature_optional();
 933                 assert!(!features.requires_unknown_bits());
 934                 assert!(features.supports_unknown_bits());
 935         }
 936
 937         #[test]
 938         fn requires_unknown_bits_from() {
 939                 let mut features1 = InitFeatures::empty();
 940                 let mut features2 = InitFeatures::empty();
 941                 assert!(!features1.requires_unknown_bits_from(&features2));
 942                 assert!(!features2.requires_unknown_bits_from(&features1));
 943
 944                 features1.set_data_loss_protect_required();
 945                 assert!(features1.requires_unknown_bits_from(&features2));
 946                 assert!(!features2.requires_unknown_bits_from(&features1));
 947
 948                 features2.set_data_loss_protect_optional();
 949                 assert!(!features1.requires_unknown_bits_from(&features2));
 950                 assert!(!features2.requires_unknown_bits_from(&features1));
 951
 952                 features2.set_gossip_queries_required();
 953                 assert!(!features1.requires_unknown_bits_from(&features2));
 954                 assert!(features2.requires_unknown_bits_from(&features1));
 955
 956                 features1.set_gossip_queries_optional();
 957                 assert!(!features1.requires_unknown_bits_from(&features2));
 958                 assert!(!features2.requires_unknown_bits_from(&features1));
 959
 960                 features1.set_variable_length_onion_required();
 961                 assert!(features1.requires_unknown_bits_from(&features2));
 962                 assert!(!features2.requires_unknown_bits_from(&features1));
 963
 964                 features2.set_variable_length_onion_optional();
 965                 assert!(!features1.requires_unknown_bits_from(&features2));
 966                 assert!(!features2.requires_unknown_bits_from(&features1));
 967
 968                 features1.set_basic_mpp_required();
 969                 features2.set_wumbo_required();
 970                 assert!(features1.requires_unknown_bits_from(&features2));
 971                 assert!(features2.requires_unknown_bits_from(&features1));
 972         }
 973
 974         #[test]
 975         fn convert_to_context_with_relevant_flags() {
 976                 let mut init_features = InitFeatures::empty();
 977                 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
 978                 // converted as it's only relevant in an init context).
 979                 init_features.set_initial_routing_sync_required();
 980                 init_features.set_data_loss_protect_required();
 981                 init_features.set_variable_length_onion_required();
 982                 init_features.set_static_remote_key_required();
 983                 init_features.set_payment_secret_required();
 984                 init_features.set_basic_mpp_optional();
 985                 init_features.set_wumbo_optional();
 986                 init_features.set_anchors_zero_fee_htlc_tx_optional();
 987                 init_features.set_shutdown_any_segwit_optional();
 988                 init_features.set_onion_messages_optional();
 989                 init_features.set_channel_type_optional();
 990                 init_features.set_scid_privacy_optional();
 991                 init_features.set_zero_conf_optional();
 992
 993                 assert!(init_features.initial_routing_sync());
 994                 assert!(!init_features.supports_upfront_shutdown_script());
 995                 assert!(!init_features.supports_gossip_queries());
 996
 997                 let node_features: NodeFeatures = init_features.to_context();
 998                 {
 999                         // Check that the flags are as expected:
1000                         // - option_data_loss_protect (req)
1001                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
1002                         // - basic_mpp | wumbo | anchors_zero_fee_htlc_tx
1003                         // - opt_shutdown_anysegwit
1004                         // - onion_messages
1005                         // - option_channel_type | option_scid_alias
1006                         // - option_zeroconf
1007                         assert_eq!(node_features.flags.len(), 7);
1008                         assert_eq!(node_features.flags[0], 0b00000001);
1009                         assert_eq!(node_features.flags[1], 0b01010001);
1010                         assert_eq!(node_features.flags[2], 0b10001010);
1011                         assert_eq!(node_features.flags[3], 0b00001000);
1012                         assert_eq!(node_features.flags[4], 0b10000000);
1013                         assert_eq!(node_features.flags[5], 0b10100000);
1014                         assert_eq!(node_features.flags[6], 0b00001000);
1015                 }
1016
1017                 // Check that cleared flags are kept blank when converting back:
1018                 // - initial_routing_sync was not applicable to NodeContext
1019                 // - upfront_shutdown_script was cleared before converting
1020                 // - gossip_queries was cleared before converting
1021                 let features: InitFeatures = node_features.to_context_internal();
1022                 assert!(!features.initial_routing_sync());
1023                 assert!(!features.supports_upfront_shutdown_script());
1024                 assert!(!init_features.supports_gossip_queries());
1025         }
1026
1027         #[test]
1028         fn convert_to_context_with_unknown_flags() {
1029                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
1030                 assert!(<sealed::ChannelContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
1031                         <sealed::InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
1032                 let mut channel_features = ChannelFeatures::empty();
1033                 channel_features.set_unknown_feature_optional();
1034                 assert!(channel_features.supports_unknown_bits());
1035                 let invoice_features: InvoiceFeatures = channel_features.to_context_internal();
1036                 assert!(!invoice_features.supports_unknown_bits());
1037         }
1038
1039         #[test]
1040         fn set_feature_bits() {
1041                 let mut features = InvoiceFeatures::empty();
1042                 features.set_basic_mpp_optional();
1043                 features.set_payment_secret_required();
1044                 assert!(features.supports_basic_mpp());
1045                 assert!(!features.requires_basic_mpp());
1046                 assert!(features.requires_payment_secret());
1047                 assert!(features.supports_payment_secret());
1048         }
1049
1050         #[test]
1051         fn set_custom_bits() {
1052                 let mut features = InvoiceFeatures::empty();
1053                 features.set_variable_length_onion_optional();
1054                 assert_eq!(features.flags[1], 0b00000010);
1055
1056                 assert!(features.set_optional_custom_bit(255).is_err());
1057                 assert!(features.set_required_custom_bit(256).is_ok());
1058                 assert!(features.set_required_custom_bit(258).is_ok());
1059                 assert_eq!(features.flags[31], 0b00000000);
1060                 assert_eq!(features.flags[32], 0b00000101);
1061
1062                 let known_bit = <sealed::InvoiceContext as sealed::PaymentSecret>::EVEN_BIT;
1063                 let byte_offset = <sealed::InvoiceContext as sealed::PaymentSecret>::BYTE_OFFSET;
1064                 assert_eq!(byte_offset, 1);
1065                 assert_eq!(features.flags[byte_offset], 0b00000010);
1066                 assert!(features.set_required_custom_bit(known_bit).is_err());
1067                 assert_eq!(features.flags[byte_offset], 0b00000010);
1068
1069                 let mut features = InvoiceFeatures::empty();
1070                 assert!(features.set_optional_custom_bit(256).is_ok());
1071                 assert!(features.set_optional_custom_bit(259).is_ok());
1072                 assert_eq!(features.flags[32], 0b00001010);
1073
1074                 let mut features = InvoiceFeatures::empty();
1075                 assert!(features.set_required_custom_bit(257).is_ok());
1076                 assert!(features.set_required_custom_bit(258).is_ok());
1077                 assert_eq!(features.flags[32], 0b00000101);
1078         }
1079
1080         #[test]
1081         fn encodes_features_without_length() {
1082                 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1083                 assert_eq!(features.flags.len(), 8);
1084
1085                 let mut serialized_features = Vec::new();
1086                 WithoutLength(&features).write(&mut serialized_features).unwrap();
1087                 assert_eq!(serialized_features.len(), 8);
1088
1089                 let deserialized_features =
1090                         WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
1091                 assert_eq!(features, deserialized_features);
1092         }
1093
1094         #[test]
1095         fn invoice_features_encoding() {
1096                 let features_as_u5s = vec![
1097                         u5::try_from_u8(6).unwrap(),
1098                         u5::try_from_u8(10).unwrap(),
1099                         u5::try_from_u8(25).unwrap(),
1100                         u5::try_from_u8(1).unwrap(),
1101                         u5::try_from_u8(10).unwrap(),
1102                         u5::try_from_u8(0).unwrap(),
1103                         u5::try_from_u8(20).unwrap(),
1104                         u5::try_from_u8(2).unwrap(),
1105                         u5::try_from_u8(0).unwrap(),
1106                         u5::try_from_u8(6).unwrap(),
1107                         u5::try_from_u8(0).unwrap(),
1108                         u5::try_from_u8(16).unwrap(),
1109                         u5::try_from_u8(1).unwrap(),
1110                 ];
1111                 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1112
1113                 // Test length calculation.
1114                 assert_eq!(features.base32_len(), 13);
1115
1116                 // Test serialization.
1117                 let features_serialized = features.to_base32();
1118                 assert_eq!(features_as_u5s, features_serialized);
1119
1120                 // Test deserialization.
1121                 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
1122                 assert_eq!(features, features_deserialized);
1123         }
1124
1125         #[test]
1126         fn test_channel_type_mapping() {
1127                 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
1128                 // required-StaticRemoteKey ChannelTypeFeatures.
1129                 let mut init_features = InitFeatures::empty();
1130                 init_features.set_static_remote_key_optional();
1131                 let converted_features = ChannelTypeFeatures::from_init(&init_features);
1132                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
1133                 assert!(!converted_features.supports_any_optional_bits());
1134                 assert!(converted_features.requires_static_remote_key());
1135         }
1136 }