git.bitcoin.ninja Git - rust-lightning/blob - lightning/src/ln/features.rs

   1 // This file is Copyright its original authors, visible in version control
   2 // history.
   3 //
   4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
   5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
   7 // You may not use this file except in accordance with one or both of these
   8 // licenses.
   9
  10 //! Feature flag definitions for the Lightning protocol according to [BOLT #9].
  11 //!
  12 //! Lightning nodes advertise a supported set of operation through feature flags. Features are
  13 //! applicable for a specific context as indicated in some [messages]. [`Features`] encapsulates
  14 //! behavior for specifying and checking feature flags for a particular context. Each feature is
  15 //! defined internally by a trait specifying the corresponding flags (i.e., even and odd bits).
  16 //!
  17 //! Whether a feature is considered "known" or "unknown" is relative to the implementation, whereas
  18 //! the term "supports" is used in reference to a particular set of [`Features`]. That is, a node
  19 //! supports a feature if it advertises the feature (as either required or optional) to its peers.
  20 //! And the implementation can interpret a feature if the feature is known to it.
  21 //!
  22 //! 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 //! LDK knows about the following features, but does not support them:
  69 //! - `AnchorsNonzeroFeeHtlcTx` - the initial version of anchor outputs, which was later found to be
  70 //!     vulnerable (see this
  71 //!     [mailing list post](https://lists.linuxfoundation.org/pipermail/lightning-dev/2020-September/002796.html)
  72 //!     for more information).
  73 //!
  74 //! [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
  75 //! [messages]: crate::ln::msgs
  76
  77 use crate::{io, io_extras};
  78 use crate::prelude::*;
  79 use core::{cmp, fmt};
  80 use core::borrow::Borrow;
  81 use core::hash::{Hash, Hasher};
  82 use core::marker::PhantomData;
  83
  84 use bitcoin::bech32;
  85 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
  86 use crate::ln::msgs::DecodeError;
  87 use crate::util::ser::{Readable, WithoutLength, Writeable, Writer};
  88
  89 mod sealed {
  90         use crate::prelude::*;
  91         use crate::ln::features::Features;
  92
  93         /// The context in which [`Features`] are applicable. Defines which features are known to the
  94         /// implementation, though specification of them as required or optional is up to the code
  95         /// constructing a features object.
  96         pub trait Context {
  97                 /// Bitmask for selecting features that are known to the implementation.
  98                 const KNOWN_FEATURE_MASK: &'static [u8];
  99         }
 100
 101         /// Defines a [`Context`] by stating which features it requires and which are optional. Features
 102         /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
 103         /// feature identifiers.
 104         macro_rules! define_context {
 105                 ($context: ident, [$( $( $known_feature: ident )|*, )*]) => {
 106                         #[derive(Eq, PartialEq)]
 107                         pub struct $context {}
 108
 109                         impl Context for $context {
 110                                 const KNOWN_FEATURE_MASK: &'static [u8] = &[
 111                                         $(
 112                                                 0b00_00_00_00 $(|
 113                                                         <Self as $known_feature>::REQUIRED_MASK |
 114                                                         <Self as $known_feature>::OPTIONAL_MASK)*,
 115                                         )*
 116                                 ];
 117                         }
 118
 119                         impl alloc::fmt::Display for Features<$context> {
 120                                 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
 121                                         $(
 122                                                 $(
 123                                                         fmt.write_fmt(format_args!("{}: {}, ", stringify!($known_feature),
 124                                                                 if <$context as $known_feature>::requires_feature(&self.flags) { "required" }
 125                                                                 else if <$context as $known_feature>::supports_feature(&self.flags) { "supported" }
 126                                                                 else { "not supported" }))?;
 127                                                 )*
 128                                                 {} // Rust gets mad if we only have a $()* block here, so add a dummy {}
 129                                         )*
 130                                         fmt.write_fmt(format_args!("unknown flags: {}",
 131                                                 if self.requires_unknown_bits() { "required" }
 132                                                 else if self.supports_unknown_bits() { "supported" } else { "none" }))
 133                                 }
 134                         }
 135                 };
 136         }
 137
 138         define_context!(InitContext, [
 139                 // Byte 0
 140                 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
 141                 // Byte 1
 142                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 143                 // Byte 2
 144                 BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
 145                 // Byte 3
 146                 ShutdownAnySegwit,
 147                 // Byte 4
 148                 OnionMessages,
 149                 // Byte 5
 150                 ChannelType | SCIDPrivacy,
 151                 // Byte 6
 152                 ZeroConf,
 153         ]);
 154         define_context!(NodeContext, [
 155                 // Byte 0
 156                 DataLossProtect | UpfrontShutdownScript | GossipQueries,
 157                 // Byte 1
 158                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 159                 // Byte 2
 160                 BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
 161                 // Byte 3
 162                 ShutdownAnySegwit,
 163                 // Byte 4
 164                 OnionMessages,
 165                 // Byte 5
 166                 ChannelType | SCIDPrivacy,
 167                 // Byte 6
 168                 ZeroConf | Keysend,
 169         ]);
 170         define_context!(ChannelContext, []);
 171         define_context!(Bolt11InvoiceContext, [
 172                 // Byte 0
 173                 ,
 174                 // Byte 1
 175                 VariableLengthOnion | PaymentSecret,
 176                 // Byte 2
 177                 BasicMPP,
 178                 // Byte 3
 179                 ,
 180                 // Byte 4
 181                 ,
 182                 // Byte 5
 183                 ,
 184                 // Byte 6
 185                 PaymentMetadata,
 186         ]);
 187         define_context!(OfferContext, []);
 188         define_context!(InvoiceRequestContext, []);
 189         define_context!(Bolt12InvoiceContext, [
 190                 // Byte 0
 191                 ,
 192                 // Byte 1
 193                 ,
 194                 // Byte 2
 195                 BasicMPP,
 196         ]);
 197         define_context!(BlindedHopContext, []);
 198         // This isn't a "real" feature context, and is only used in the channel_type field in an
 199         // `OpenChannel` message.
 200         define_context!(ChannelTypeContext, [
 201                 // Byte 0
 202                 ,
 203                 // Byte 1
 204                 StaticRemoteKey,
 205                 // Byte 2
 206                 AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
 207                 // Byte 3
 208                 ,
 209                 // Byte 4
 210                 ,
 211                 // Byte 5
 212                 SCIDPrivacy,
 213                 // Byte 6
 214                 ZeroConf,
 215         ]);
 216
 217         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 218         /// useful for manipulating feature flags.
 219         macro_rules! define_feature {
 220                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 221                  $required_setter: ident, $supported_getter: ident) => {
 222                         #[doc = $doc]
 223                         ///
 224                         /// See [BOLT #9] for details.
 225                         ///
 226                         /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
 227                         pub trait $feature: Context {
 228                                 /// The bit used to signify that the feature is required.
 229                                 const EVEN_BIT: usize = $odd_bit - 1;
 230
 231                                 /// The bit used to signify that the feature is optional.
 232                                 const ODD_BIT: usize = $odd_bit;
 233
 234                                 /// Assertion that [`EVEN_BIT`] is actually even.
 235                                 ///
 236                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 237                                 const ASSERT_EVEN_BIT_PARITY: usize;
 238
 239                                 /// Assertion that [`ODD_BIT`] is actually odd.
 240                                 ///
 241                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 242                                 const ASSERT_ODD_BIT_PARITY: usize;
 243
 244                                 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
 245                                 ///
 246                                 /// [`KNOWN_FEATURE_MASK`]: Context::KNOWN_FEATURE_MASK
 247                                 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
 248                                 const ASSERT_BITS_IN_MASK: u8;
 249
 250                                 /// The byte where the feature is set.
 251                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 252
 253                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 254                                 ///
 255                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 256                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 257
 258                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 259                                 ///
 260                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 261                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 262
 263                                 /// Returns whether the feature is required by the given flags.
 264                                 #[inline]
 265                                 fn requires_feature(flags: &Vec<u8>) -> bool {
 266                                         flags.len() > Self::BYTE_OFFSET &&
 267                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
 268                                 }
 269
 270                                 /// Returns whether the feature is supported by the given flags.
 271                                 #[inline]
 272                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 273                                         flags.len() > Self::BYTE_OFFSET &&
 274                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 275                                 }
 276
 277                                 /// Sets the feature's required (even) bit in the given flags.
 278                                 #[inline]
 279                                 fn set_required_bit(flags: &mut Vec<u8>) {
 280                                         if flags.len() <= Self::BYTE_OFFSET {
 281                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 282                                         }
 283
 284                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
 285                                         flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 286                                 }
 287
 288                                 /// Sets the feature's optional (odd) bit in the given flags.
 289                                 #[inline]
 290                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 291                                         if flags.len() <= Self::BYTE_OFFSET {
 292                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 293                                         }
 294
 295                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 296                                 }
 297
 298                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 299                                 /// flags.
 300                                 #[inline]
 301                                 fn clear_bits(flags: &mut Vec<u8>) {
 302                                         if flags.len() > Self::BYTE_OFFSET {
 303                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 304                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 305                                         }
 306
 307                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 308                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 309                                         flags.resize(size, 0u8);
 310                                 }
 311                         }
 312
 313                         impl <T: $feature> Features<T> {
 314                                 /// Set this feature as optional.
 315                                 pub fn $optional_setter(&mut self) {
 316                                         <T as $feature>::set_optional_bit(&mut self.flags);
 317                                 }
 318
 319                                 /// Set this feature as required.
 320                                 pub fn $required_setter(&mut self) {
 321                                         <T as $feature>::set_required_bit(&mut self.flags);
 322                                 }
 323
 324                                 /// Checks if this feature is supported.
 325                                 pub fn $supported_getter(&self) -> bool {
 326                                         <T as $feature>::supports_feature(&self.flags)
 327                                 }
 328                         }
 329
 330                         $(
 331                                 impl $feature for $context {
 332                                         // EVEN_BIT % 2 == 0
 333                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 334
 335                                         // ODD_BIT % 2 == 1
 336                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 337
 338                                         // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
 339                                         #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
 340                                         const ASSERT_BITS_IN_MASK: u8 =
 341                                                 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
 342                                                  >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
 343                                 }
 344                         )*
 345                 };
 346                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 347                  $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
 348                         define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
 349                         impl <T: $feature> Features<T> {
 350                                 /// Checks if this feature is required.
 351                                 pub fn $required_getter(&self) -> bool {
 352                                         <T as $feature>::requires_feature(&self.flags)
 353                                 }
 354                         }
 355                 }
 356         }
 357
 358         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 359                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 360                 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
 361         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 362         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 363                 set_initial_routing_sync_optional, set_initial_routing_sync_required,
 364                 initial_routing_sync);
 365         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 366                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 367                 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
 368                 requires_upfront_shutdown_script);
 369         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 370                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
 371                 supports_gossip_queries, requires_gossip_queries);
 372         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, Bolt11InvoiceContext],
 373                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 374                 set_variable_length_onion_required, supports_variable_length_onion,
 375                 requires_variable_length_onion);
 376         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
 377                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 378                 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
 379         define_feature!(15, PaymentSecret, [InitContext, NodeContext, Bolt11InvoiceContext],
 380                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
 381                 supports_payment_secret, requires_payment_secret);
 382         define_feature!(17, BasicMPP, [InitContext, NodeContext, Bolt11InvoiceContext, Bolt12InvoiceContext],
 383                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
 384                 supports_basic_mpp, requires_basic_mpp);
 385         define_feature!(19, Wumbo, [InitContext, NodeContext],
 386                 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
 387                 supports_wumbo, requires_wumbo);
 388         define_feature!(21, AnchorsNonzeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
 389                 "Feature flags for `option_anchors_nonzero_fee_htlc_tx`.", set_anchors_nonzero_fee_htlc_tx_optional,
 390                 set_anchors_nonzero_fee_htlc_tx_required, supports_anchors_nonzero_fee_htlc_tx, requires_anchors_nonzero_fee_htlc_tx);
 391         define_feature!(23, AnchorsZeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
 392                 "Feature flags for `option_anchors_zero_fee_htlc_tx`.", set_anchors_zero_fee_htlc_tx_optional,
 393                 set_anchors_zero_fee_htlc_tx_required, supports_anchors_zero_fee_htlc_tx, requires_anchors_zero_fee_htlc_tx);
 394         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 395                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 396                 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
 397         define_feature!(39, OnionMessages, [InitContext, NodeContext],
 398                 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
 399                 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
 400         define_feature!(45, ChannelType, [InitContext, NodeContext],
 401                 "Feature flags for `option_channel_type`.", set_channel_type_optional,
 402                 set_channel_type_required, supports_channel_type, requires_channel_type);
 403         define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
 404                 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
 405                 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
 406         define_feature!(49, PaymentMetadata, [Bolt11InvoiceContext],
 407                 "Feature flags for payment metadata in invoices.", set_payment_metadata_optional,
 408                 set_payment_metadata_required, supports_payment_metadata, requires_payment_metadata);
 409         define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
 410                 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
 411                 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
 412         define_feature!(55, Keysend, [NodeContext],
 413                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
 414                 supports_keysend, requires_keysend);
 415         // Note: update the module-level docs when a new feature bit is added!
 416
 417         #[cfg(test)]
 418         define_feature!(123456789, UnknownFeature,
 419                 [NodeContext, ChannelContext, Bolt11InvoiceContext, OfferContext, InvoiceRequestContext, Bolt12InvoiceContext, BlindedHopContext],
 420                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 421                 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
 422 }
 423
 424 /// Tracks the set of features which a node implements, templated by the context in which it
 425 /// appears.
 426 ///
 427 /// This is not exported to bindings users as we map the concrete feature types below directly instead
 428 #[derive(Eq)]
 429 pub struct Features<T: sealed::Context> {
 430         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 431         flags: Vec<u8>,
 432         mark: PhantomData<T>,
 433 }
 434
 435 impl<T: sealed::Context, Rhs: Borrow<Self>> core::ops::BitOrAssign<Rhs> for Features<T> {
 436         fn bitor_assign(&mut self, rhs: Rhs) {
 437                 let total_feature_len = cmp::max(self.flags.len(), rhs.borrow().flags.len());
 438                 self.flags.resize(total_feature_len, 0u8);
 439                 for (byte, rhs_byte) in self.flags.iter_mut().zip(rhs.borrow().flags.iter()) {
 440                         *byte |= *rhs_byte;
 441                 }
 442         }
 443 }
 444
 445 impl<T: sealed::Context> core::ops::BitOr for Features<T> {
 446         type Output = Self;
 447
 448         fn bitor(mut self, o: Self) -> Self {
 449                 self |= o;
 450                 self
 451         }
 452 }
 453
 454 impl<T: sealed::Context> Clone for Features<T> {
 455         fn clone(&self) -> Self {
 456                 Self {
 457                         flags: self.flags.clone(),
 458                         mark: PhantomData,
 459                 }
 460         }
 461 }
 462 impl<T: sealed::Context> Hash for Features<T> {
 463         fn hash<H: Hasher>(&self, hasher: &mut H) {
 464                 self.flags.hash(hasher);
 465         }
 466 }
 467 impl<T: sealed::Context> PartialEq for Features<T> {
 468         fn eq(&self, o: &Self) -> bool {
 469                 self.flags.eq(&o.flags)
 470         }
 471 }
 472 impl<T: sealed::Context> PartialOrd for Features<T> {
 473         fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
 474                 self.flags.partial_cmp(&other.flags)
 475         }
 476 }
 477 impl<T: sealed::Context + Eq> Ord for Features<T> {
 478         fn cmp(&self, other: &Self) -> cmp::Ordering {
 479                 self.flags.cmp(&other.flags)
 480         }
 481 }
 482 impl<T: sealed::Context> fmt::Debug for Features<T> {
 483         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 484                 self.flags.fmt(fmt)
 485         }
 486 }
 487
 488 /// Features used within an `init` message.
 489 pub type InitFeatures = Features<sealed::InitContext>;
 490 /// Features used within a `node_announcement` message.
 491 pub type NodeFeatures = Features<sealed::NodeContext>;
 492 /// Features used within a `channel_announcement` message.
 493 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 494 /// Features used within an invoice.
 495 pub type Bolt11InvoiceFeatures = Features<sealed::Bolt11InvoiceContext>;
 496 /// Features used within an `offer`.
 497 pub type OfferFeatures = Features<sealed::OfferContext>;
 498 /// Features used within an `invoice_request`.
 499 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
 500 /// Features used within an `invoice`.
 501 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
 502 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
 503 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
 504
 505 /// Features used within the channel_type field in an OpenChannel message.
 506 ///
 507 /// A channel is always of some known "type", describing the transaction formats used and the exact
 508 /// semantics of our interaction with our peer.
 509 ///
 510 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
 511 /// the counterparty, only required features are allowed here.
 512 ///
 513 /// This is serialized differently from other feature types - it is not prefixed by a length, and
 514 /// thus must only appear inside a TLV where its length is known in advance.
 515 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
 516
 517 impl InitFeatures {
 518         /// Writes all features present up to, and including, 13.
 519         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 520                 let len = cmp::min(2, self.flags.len());
 521                 (len as u16).write(w)?;
 522                 for i in (0..len).rev() {
 523                         if i == 0 {
 524                                 self.flags[i].write(w)?;
 525                         } else {
 526                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 527                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 528                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 529                         }
 530                 }
 531                 Ok(())
 532         }
 533
 534         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 535         /// are included in the result.
 536         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 537                 self.to_context_internal()
 538         }
 539 }
 540
 541 impl Bolt11InvoiceFeatures {
 542         /// Converts `Bolt11InvoiceFeatures` to `Features<C>`. Only known `Bolt11InvoiceFeatures` relevant to
 543         /// context `C` are included in the result.
 544         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 545                 self.to_context_internal()
 546         }
 547
 548         /// Getting a route for a keysend payment to a private node requires providing the payee's
 549         /// features (since they were not announced in a node announcement). However, keysend payments
 550         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 551         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
 552         /// `Bolt11InvoiceFeatures` for [`find_route`].
 553         ///
 554         /// MPP keysend is not widely supported yet, so we parameterize support to allow the user to
 555         /// choose whether their router should find multi-part routes.
 556         ///
 557         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
 558         /// [`find_route`]: crate::routing::router::find_route
 559         pub(crate) fn for_keysend(allow_mpp: bool) -> Bolt11InvoiceFeatures {
 560                 let mut res = Bolt11InvoiceFeatures::empty();
 561                 res.set_variable_length_onion_optional();
 562                 if allow_mpp {
 563                         res.set_basic_mpp_optional();
 564                 }
 565                 res
 566         }
 567 }
 568
 569 impl Bolt12InvoiceFeatures {
 570         /// Converts [`Bolt12InvoiceFeatures`] to [`Features<C>`]. Only known [`Bolt12InvoiceFeatures`]
 571         /// relevant to context `C` are included in the result.
 572         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 573                 self.to_context_internal()
 574         }
 575 }
 576
 577 impl ChannelTypeFeatures {
 578         // Maps the relevant `InitFeatures` to `ChannelTypeFeatures`. Any unknown features to
 579         // `ChannelTypeFeatures` are not included in the result.
 580         pub(crate) fn from_init(init: &InitFeatures) -> Self {
 581                 let mut ret = init.to_context_internal();
 582                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
 583                 // optional bits and then AND out the optional ones.
 584                 for byte in ret.flags.iter_mut() {
 585                         *byte |= (*byte & 0b10_10_10_10) >> 1;
 586                         *byte &= 0b01_01_01_01;
 587                 }
 588                 ret
 589         }
 590
 591         /// Constructs a ChannelTypeFeatures with only static_remotekey set
 592         pub(crate) fn only_static_remote_key() -> Self {
 593                 let mut ret = Self::empty();
 594                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 595                 ret
 596         }
 597
 598         /// Constructs a ChannelTypeFeatures with anchors support
 599         pub(crate) fn anchors_zero_htlc_fee_and_dependencies() -> Self {
 600                 let mut ret = Self::empty();
 601                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 602                 <sealed::ChannelTypeContext as sealed::AnchorsZeroFeeHtlcTx>::set_required_bit(&mut ret.flags);
 603                 ret
 604         }
 605 }
 606
 607 impl ToBase32 for Bolt11InvoiceFeatures {
 608         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 609                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 610                 // minus one before dividing
 611                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 612                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 613                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 614                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 615                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 616                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 617                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 618                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 619                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 620                         if new_u5_idx > 0 {
 621                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 622                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 623                         }
 624                         if new_u5_idx > 1 {
 625                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 626                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 627                         }
 628                 }
 629                 // Trim the highest feature bits.
 630                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 631                         res_u5s.remove(0);
 632                 }
 633                 writer.write(&res_u5s)
 634         }
 635 }
 636
 637 impl Base32Len for Bolt11InvoiceFeatures {
 638         fn base32_len(&self) -> usize {
 639                 self.to_base32().len()
 640         }
 641 }
 642
 643 impl FromBase32 for Bolt11InvoiceFeatures {
 644         type Err = bech32::Error;
 645
 646         fn from_base32(field_data: &[u5]) -> Result<Bolt11InvoiceFeatures, bech32::Error> {
 647                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 648                 // minus one before dividing
 649                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 650                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 651                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 652                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 653                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 654                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 655                         let chunk_u16 = chunk.to_u8() as u16;
 656                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 657                         if new_byte_idx != length_bytes - 1 {
 658                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 659                         }
 660                 }
 661                 // Trim the highest feature bits.
 662                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 663                         res_bytes.pop();
 664                 }
 665                 Ok(Bolt11InvoiceFeatures::from_le_bytes(res_bytes))
 666         }
 667 }
 668
 669 impl<T: sealed::Context> Features<T> {
 670         /// Create a blank Features with no features set
 671         pub fn empty() -> Self {
 672                 Features {
 673                         flags: Vec::new(),
 674                         mark: PhantomData,
 675                 }
 676         }
 677
 678         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 679         /// included in the result.
 680         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 681                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 682                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 683                 let mut flags = Vec::new();
 684                 for (i, byte) in self.flags.iter().enumerate() {
 685                         if i < from_byte_count && i < to_byte_count {
 686                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 687                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 688                                 flags.push(byte & from_known_features & to_known_features);
 689                         }
 690                 }
 691                 Features::<C> { flags, mark: PhantomData, }
 692         }
 693
 694         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 695         /// most on-the-wire encodings.
 696         ///
 697         /// This is not exported to bindings users as we don't support export across multiple T
 698         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 699                 Features {
 700                         flags,
 701                         mark: PhantomData,
 702                 }
 703         }
 704
 705         #[cfg(test)]
 706         /// Gets the underlying flags set, in LE.
 707         pub fn le_flags(&self) -> &Vec<u8> {
 708                 &self.flags
 709         }
 710
 711         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 712                 for f in self.flags.iter().rev() { // Swap back to big-endian
 713                         f.write(w)?;
 714                 }
 715                 Ok(())
 716         }
 717
 718         fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
 719                 flags.reverse(); // Swap to little-endian
 720                 Self {
 721                         flags,
 722                         mark: PhantomData,
 723                 }
 724         }
 725
 726         pub(crate) fn supports_any_optional_bits(&self) -> bool {
 727                 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
 728         }
 729
 730         /// Returns true if this `Features` object contains required features unknown by `other`.
 731         pub fn requires_unknown_bits_from(&self, other: &Self) -> bool {
 732                 // Bitwise AND-ing with all even bits set except for known features will select required
 733                 // unknown features.
 734                 self.flags.iter().enumerate().any(|(i, &byte)| {
 735                         const REQUIRED_FEATURES: u8 = 0b01_01_01_01;
 736                         const OPTIONAL_FEATURES: u8 = 0b10_10_10_10;
 737                         let unknown_features = if i < other.flags.len() {
 738                                 // Form a mask similar to !T::KNOWN_FEATURE_MASK only for `other`
 739                                 !(other.flags[i]
 740                                         | ((other.flags[i] >> 1) & REQUIRED_FEATURES)
 741                                         | ((other.flags[i] << 1) & OPTIONAL_FEATURES))
 742                         } else {
 743                                 0b11_11_11_11
 744                         };
 745                         (byte & (REQUIRED_FEATURES & unknown_features)) != 0
 746                 })
 747         }
 748
 749         /// Returns true if this `Features` object contains unknown feature flags which are set as
 750         /// "required".
 751         pub fn requires_unknown_bits(&self) -> bool {
 752                 // Bitwise AND-ing with all even bits set except for known features will select required
 753                 // unknown features.
 754                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 755                 self.flags.iter().enumerate().any(|(i, &byte)| {
 756                         let required_features = 0b01_01_01_01;
 757                         let unknown_features = if i < byte_count {
 758                                 !T::KNOWN_FEATURE_MASK[i]
 759                         } else {
 760                                 0b11_11_11_11
 761                         };
 762                         (byte & (required_features & unknown_features)) != 0
 763                 })
 764         }
 765
 766         pub(crate) fn supports_unknown_bits(&self) -> bool {
 767                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 768                 // both required and optional unknown features.
 769                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 770                 self.flags.iter().enumerate().any(|(i, &byte)| {
 771                         let unknown_features = if i < byte_count {
 772                                 !T::KNOWN_FEATURE_MASK[i]
 773                         } else {
 774                                 0b11_11_11_11
 775                         };
 776                         (byte & unknown_features) != 0
 777                 })
 778         }
 779
 780         // Returns true if the features within `self` are a subset of the features within `other`.
 781         pub(crate) fn is_subset(&self, other: &Self) -> bool {
 782                 for (idx, byte) in self.flags.iter().enumerate() {
 783                         if let Some(other_byte) = other.flags.get(idx) {
 784                                 if byte & other_byte != *byte {
 785                                         // `self` has bits set that `other` doesn't.
 786                                         return false;
 787                                 }
 788                         } else {
 789                                 if *byte > 0 {
 790                                         // `self` has a non-zero byte that `other` doesn't.
 791                                         return false;
 792                                 }
 793                         }
 794                 }
 795                 true
 796         }
 797
 798         /// Sets a required custom feature bit. Errors if `bit` is outside the custom range as defined
 799         /// by [bLIP 2] or if it is a known `T` feature.
 800         ///
 801         /// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
 802         /// be set instead (i.e., `bit - 1`).
 803         ///
 804         /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
 805         pub fn set_required_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 806                 self.set_custom_bit(bit - (bit % 2))
 807         }
 808
 809         /// Sets an optional custom feature bit. Errors if `bit` is outside the custom range as defined
 810         /// by [bLIP 2] or if it is a known `T` feature.
 811         ///
 812         /// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
 813         /// set instead (i.e., `bit + 1`).
 814         ///
 815         /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
 816         pub fn set_optional_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 817                 self.set_custom_bit(bit + (1 - (bit % 2)))
 818         }
 819
 820         fn set_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 821                 if bit < 256 {
 822                         return Err(());
 823                 }
 824
 825                 let byte_offset = bit / 8;
 826                 let mask = 1 << (bit - 8 * byte_offset);
 827                 if byte_offset < T::KNOWN_FEATURE_MASK.len() {
 828                         if (T::KNOWN_FEATURE_MASK[byte_offset] & mask) != 0 {
 829                                 return Err(());
 830                         }
 831                 }
 832
 833                 if self.flags.len() <= byte_offset {
 834                         self.flags.resize(byte_offset + 1, 0u8);
 835                 }
 836
 837                 self.flags[byte_offset] |= mask;
 838
 839                 Ok(())
 840         }
 841 }
 842
 843 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 844         #[cfg(test)]
 845         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 846                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 847                 self
 848         }
 849 }
 850
 851 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 852         #[cfg(test)]
 853         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 854                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 855                 self
 856         }
 857 }
 858
 859 impl<T: sealed::Wumbo> Features<T> {
 860         #[cfg(test)]
 861         pub(crate) fn clear_wumbo(mut self) -> Self {
 862                 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
 863                 self
 864         }
 865 }
 866
 867 impl<T: sealed::SCIDPrivacy> Features<T> {
 868         pub(crate) fn clear_scid_privacy(&mut self) {
 869                 <T as sealed::SCIDPrivacy>::clear_bits(&mut self.flags);
 870         }
 871 }
 872
 873 impl<T: sealed::AnchorsZeroFeeHtlcTx> Features<T> {
 874         pub(crate) fn clear_anchors_zero_fee_htlc_tx(&mut self) {
 875                 <T as sealed::AnchorsZeroFeeHtlcTx>::clear_bits(&mut self.flags);
 876         }
 877 }
 878
 879 #[cfg(test)]
 880 impl<T: sealed::UnknownFeature> Features<T> {
 881         pub(crate) fn unknown() -> Self {
 882                 let mut features = Self::empty();
 883                 features.set_unknown_feature_required();
 884                 features
 885         }
 886 }
 887
 888 macro_rules! impl_feature_len_prefixed_write {
 889         ($features: ident) => {
 890                 impl Writeable for $features {
 891                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 892                                 (self.flags.len() as u16).write(w)?;
 893                                 self.write_be(w)
 894                         }
 895                 }
 896                 impl Readable for $features {
 897                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 898                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
 899                         }
 900                 }
 901         }
 902 }
 903 impl_feature_len_prefixed_write!(InitFeatures);
 904 impl_feature_len_prefixed_write!(ChannelFeatures);
 905 impl_feature_len_prefixed_write!(NodeFeatures);
 906 impl_feature_len_prefixed_write!(Bolt11InvoiceFeatures);
 907 impl_feature_len_prefixed_write!(Bolt12InvoiceFeatures);
 908 impl_feature_len_prefixed_write!(BlindedHopFeatures);
 909
 910 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
 911 macro_rules! impl_feature_tlv_write {
 912         ($features: ident) => {
 913                 impl Writeable for $features {
 914                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 915                                 WithoutLength(self).write(w)
 916                         }
 917                 }
 918                 impl Readable for $features {
 919                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 920                                 Ok(WithoutLength::<Self>::read(r)?.0)
 921                         }
 922                 }
 923         }
 924 }
 925
 926 impl_feature_tlv_write!(ChannelTypeFeatures);
 927
 928 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
 929 // requires a length but the former does not.
 930
 931 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
 932         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 933                 self.0.write_be(w)
 934         }
 935 }
 936
 937 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
 938         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 939                 let v = io_extras::read_to_end(r)?;
 940                 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
 941         }
 942 }
 943
 944 #[cfg(test)]
 945 mod tests {
 946         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, Bolt11InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
 947         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
 948         use crate::util::ser::{Readable, WithoutLength, Writeable};
 949
 950         #[test]
 951         fn sanity_test_unknown_bits() {
 952                 let features = ChannelFeatures::empty();
 953                 assert!(!features.requires_unknown_bits());
 954                 assert!(!features.supports_unknown_bits());
 955
 956                 let mut features = ChannelFeatures::empty();
 957                 features.set_unknown_feature_required();
 958                 assert!(features.requires_unknown_bits());
 959                 assert!(features.supports_unknown_bits());
 960
 961                 let mut features = ChannelFeatures::empty();
 962                 features.set_unknown_feature_optional();
 963                 assert!(!features.requires_unknown_bits());
 964                 assert!(features.supports_unknown_bits());
 965         }
 966
 967         #[test]
 968         fn requires_unknown_bits_from() {
 969                 let mut features1 = InitFeatures::empty();
 970                 let mut features2 = InitFeatures::empty();
 971                 assert!(!features1.requires_unknown_bits_from(&features2));
 972                 assert!(!features2.requires_unknown_bits_from(&features1));
 973
 974                 features1.set_data_loss_protect_required();
 975                 assert!(features1.requires_unknown_bits_from(&features2));
 976                 assert!(!features2.requires_unknown_bits_from(&features1));
 977
 978                 features2.set_data_loss_protect_optional();
 979                 assert!(!features1.requires_unknown_bits_from(&features2));
 980                 assert!(!features2.requires_unknown_bits_from(&features1));
 981
 982                 features2.set_gossip_queries_required();
 983                 assert!(!features1.requires_unknown_bits_from(&features2));
 984                 assert!(features2.requires_unknown_bits_from(&features1));
 985
 986                 features1.set_gossip_queries_optional();
 987                 assert!(!features1.requires_unknown_bits_from(&features2));
 988                 assert!(!features2.requires_unknown_bits_from(&features1));
 989
 990                 features1.set_variable_length_onion_required();
 991                 assert!(features1.requires_unknown_bits_from(&features2));
 992                 assert!(!features2.requires_unknown_bits_from(&features1));
 993
 994                 features2.set_variable_length_onion_optional();
 995                 assert!(!features1.requires_unknown_bits_from(&features2));
 996                 assert!(!features2.requires_unknown_bits_from(&features1));
 997
 998                 features1.set_basic_mpp_required();
 999                 features2.set_wumbo_required();
1000                 assert!(features1.requires_unknown_bits_from(&features2));
1001                 assert!(features2.requires_unknown_bits_from(&features1));
1002         }
1003
1004         #[test]
1005         fn convert_to_context_with_relevant_flags() {
1006                 let mut init_features = InitFeatures::empty();
1007                 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
1008                 // converted as it's only relevant in an init context).
1009                 init_features.set_initial_routing_sync_required();
1010                 init_features.set_data_loss_protect_required();
1011                 init_features.set_variable_length_onion_required();
1012                 init_features.set_static_remote_key_required();
1013                 init_features.set_payment_secret_required();
1014                 init_features.set_basic_mpp_optional();
1015                 init_features.set_wumbo_optional();
1016                 init_features.set_anchors_zero_fee_htlc_tx_optional();
1017                 init_features.set_shutdown_any_segwit_optional();
1018                 init_features.set_onion_messages_optional();
1019                 init_features.set_channel_type_optional();
1020                 init_features.set_scid_privacy_optional();
1021                 init_features.set_zero_conf_optional();
1022
1023                 assert!(init_features.initial_routing_sync());
1024                 assert!(!init_features.supports_upfront_shutdown_script());
1025                 assert!(!init_features.supports_gossip_queries());
1026
1027                 let node_features: NodeFeatures = init_features.to_context();
1028                 {
1029                         // Check that the flags are as expected:
1030                         // - option_data_loss_protect (req)
1031                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
1032                         // - basic_mpp | wumbo | anchors_zero_fee_htlc_tx
1033                         // - opt_shutdown_anysegwit
1034                         // - onion_messages
1035                         // - option_channel_type | option_scid_alias
1036                         // - option_zeroconf
1037                         assert_eq!(node_features.flags.len(), 7);
1038                         assert_eq!(node_features.flags[0], 0b00000001);
1039                         assert_eq!(node_features.flags[1], 0b01010001);
1040                         assert_eq!(node_features.flags[2], 0b10001010);
1041                         assert_eq!(node_features.flags[3], 0b00001000);
1042                         assert_eq!(node_features.flags[4], 0b10000000);
1043                         assert_eq!(node_features.flags[5], 0b10100000);
1044                         assert_eq!(node_features.flags[6], 0b00001000);
1045                 }
1046
1047                 // Check that cleared flags are kept blank when converting back:
1048                 // - initial_routing_sync was not applicable to NodeContext
1049                 // - upfront_shutdown_script was cleared before converting
1050                 // - gossip_queries was cleared before converting
1051                 let features: InitFeatures = node_features.to_context_internal();
1052                 assert!(!features.initial_routing_sync());
1053                 assert!(!features.supports_upfront_shutdown_script());
1054                 assert!(!init_features.supports_gossip_queries());
1055         }
1056
1057         #[test]
1058         fn convert_to_context_with_unknown_flags() {
1059                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
1060                 assert!(<sealed::ChannelContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
1061                         <sealed::Bolt11InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
1062                 let mut channel_features = ChannelFeatures::empty();
1063                 channel_features.set_unknown_feature_optional();
1064                 assert!(channel_features.supports_unknown_bits());
1065                 let invoice_features: Bolt11InvoiceFeatures = channel_features.to_context_internal();
1066                 assert!(!invoice_features.supports_unknown_bits());
1067         }
1068
1069         #[test]
1070         fn set_feature_bits() {
1071                 let mut features = Bolt11InvoiceFeatures::empty();
1072                 features.set_basic_mpp_optional();
1073                 features.set_payment_secret_required();
1074                 assert!(features.supports_basic_mpp());
1075                 assert!(!features.requires_basic_mpp());
1076                 assert!(features.requires_payment_secret());
1077                 assert!(features.supports_payment_secret());
1078         }
1079
1080         #[test]
1081         fn set_custom_bits() {
1082                 let mut features = Bolt11InvoiceFeatures::empty();
1083                 features.set_variable_length_onion_optional();
1084                 assert_eq!(features.flags[1], 0b00000010);
1085
1086                 assert!(features.set_optional_custom_bit(255).is_err());
1087                 assert!(features.set_required_custom_bit(256).is_ok());
1088                 assert!(features.set_required_custom_bit(258).is_ok());
1089                 assert_eq!(features.flags[31], 0b00000000);
1090                 assert_eq!(features.flags[32], 0b00000101);
1091
1092                 let known_bit = <sealed::Bolt11InvoiceContext as sealed::PaymentSecret>::EVEN_BIT;
1093                 let byte_offset = <sealed::Bolt11InvoiceContext as sealed::PaymentSecret>::BYTE_OFFSET;
1094                 assert_eq!(byte_offset, 1);
1095                 assert_eq!(features.flags[byte_offset], 0b00000010);
1096                 assert!(features.set_required_custom_bit(known_bit).is_err());
1097                 assert_eq!(features.flags[byte_offset], 0b00000010);
1098
1099                 let mut features = Bolt11InvoiceFeatures::empty();
1100                 assert!(features.set_optional_custom_bit(256).is_ok());
1101                 assert!(features.set_optional_custom_bit(259).is_ok());
1102                 assert_eq!(features.flags[32], 0b00001010);
1103
1104                 let mut features = Bolt11InvoiceFeatures::empty();
1105                 assert!(features.set_required_custom_bit(257).is_ok());
1106                 assert!(features.set_required_custom_bit(258).is_ok());
1107                 assert_eq!(features.flags[32], 0b00000101);
1108         }
1109
1110         #[test]
1111         fn encodes_features_without_length() {
1112                 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1113                 assert_eq!(features.flags.len(), 8);
1114
1115                 let mut serialized_features = Vec::new();
1116                 WithoutLength(&features).write(&mut serialized_features).unwrap();
1117                 assert_eq!(serialized_features.len(), 8);
1118
1119                 let deserialized_features =
1120                         WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
1121                 assert_eq!(features, deserialized_features);
1122         }
1123
1124         #[test]
1125         fn invoice_features_encoding() {
1126                 let features_as_u5s = vec![
1127                         u5::try_from_u8(6).unwrap(),
1128                         u5::try_from_u8(10).unwrap(),
1129                         u5::try_from_u8(25).unwrap(),
1130                         u5::try_from_u8(1).unwrap(),
1131                         u5::try_from_u8(10).unwrap(),
1132                         u5::try_from_u8(0).unwrap(),
1133                         u5::try_from_u8(20).unwrap(),
1134                         u5::try_from_u8(2).unwrap(),
1135                         u5::try_from_u8(0).unwrap(),
1136                         u5::try_from_u8(6).unwrap(),
1137                         u5::try_from_u8(0).unwrap(),
1138                         u5::try_from_u8(16).unwrap(),
1139                         u5::try_from_u8(1).unwrap(),
1140                 ];
1141                 let features = Bolt11InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1142
1143                 // Test length calculation.
1144                 assert_eq!(features.base32_len(), 13);
1145
1146                 // Test serialization.
1147                 let features_serialized = features.to_base32();
1148                 assert_eq!(features_as_u5s, features_serialized);
1149
1150                 // Test deserialization.
1151                 let features_deserialized = Bolt11InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
1152                 assert_eq!(features, features_deserialized);
1153         }
1154
1155         #[test]
1156         fn test_channel_type_mapping() {
1157                 // If we map an Bolt11InvoiceFeatures with StaticRemoteKey optional, it should map into a
1158                 // required-StaticRemoteKey ChannelTypeFeatures.
1159                 let mut init_features = InitFeatures::empty();
1160                 init_features.set_static_remote_key_optional();
1161                 let converted_features = ChannelTypeFeatures::from_init(&init_features);
1162                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
1163                 assert!(!converted_features.supports_any_optional_bits());
1164                 assert!(converted_features.requires_static_remote_key());
1165         }
1166 }