_ 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 //! - `AnchorsZeroFeeHtlcTx` - requires/supports that commitment transactions include anchor outputs
  45 //!     and HTLC transactions are pre-signed with zero fee (see
  46 //!     [BOLT-3](https://github.com/lightning/bolts/blob/master/03-transactions.md) for more
  47 //!     information).
  48 //! - `RouteBlinding` - requires/supports that a node can relay payments over blinded paths
  49 //!     (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md#route-blinding) for more information).
  50 //! - `ShutdownAnySegwit` - requires/supports that future segwit versions are allowed in `shutdown`
  51 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  52 //! - `OnionMessages` - requires/supports forwarding onion messages
  53 //!     (see [BOLT-7](https://github.com/lightning/bolts/pull/759/files) for more information).
  54 //     TODO: update link
  55 //! - `ChannelType` - node supports the channel_type field in open/accept
  56 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  57 //! - `SCIDPrivacy` - supply channel aliases for routing
  58 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  59 //! - `PaymentMetadata` - include additional data in invoices which is passed to recipients in the
  60 //!      onion.
  61 //!      (see [BOLT-11](https://github.com/lightning/bolts/blob/master/11-payment-encoding.md) for
  62 //!      more).
  63 //! - `ZeroConf` - supports accepting HTLCs and using channels prior to funding confirmation
  64 //!      (see
  65 //!      [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#the-channel_ready-message)
  66 //!      for more info).
  67 //! - `Keysend` - send funds to a node without an invoice
  68 //!     (see the [`Keysend` feature assignment proposal](https://github.com/lightning/bolts/issues/605#issuecomment-606679798) for more information).
  69 //! - `Trampoline` - supports receiving and forwarding Trampoline payments
  70 //!     (see the [`Trampoline` feature proposal](https://github.com/lightning/bolts/pull/836) for more information).
  71 //!
  72 //! LDK knows about the following features, but does not support them:
  73 //! - `AnchorsNonzeroFeeHtlcTx` - the initial version of anchor outputs, which was later found to be
  74 //!     vulnerable (see this
  75 //!     [mailing list post](https://lists.linuxfoundation.org/pipermail/lightning-dev/2020-September/002796.html)
  76 //!     for more information).
  77 //!
  78 //! [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
  79 //! [messages]: crate::ln::msgs
  80
  81 #[allow(unused_imports)]
  82 use crate::prelude::*;
  83
  84 use crate::{io, io_extras};
  85 use core::{cmp, fmt};
  86 use core::borrow::Borrow;
  87 use core::hash::{Hash, Hasher};
  88 use core::marker::PhantomData;
  89
  90 use bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
  91 use crate::ln::msgs::DecodeError;
  92 use crate::util::ser::{Readable, WithoutLength, Writeable, Writer};
  93
  94 mod sealed {
  95         #[allow(unused_imports)]
  96         use crate::prelude::*;
  97         use crate::ln::features::Features;
  98
  99         /// The context in which [`Features`] are applicable. Defines which features are known to the
 100         /// implementation, though specification of them as required or optional is up to the code
 101         /// constructing a features object.
 102         pub trait Context {
 103                 /// Bitmask for selecting features that are known to the implementation.
 104                 const KNOWN_FEATURE_MASK: &'static [u8];
 105         }
 106
 107         /// Defines a [`Context`] by stating which features it requires and which are optional. Features
 108         /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
 109         /// feature identifiers.
 110         macro_rules! define_context {
 111                 ($context: ident, [$( $( $known_feature: ident )|*, )*]) => {
 112                         #[derive(Eq, PartialEq)]
 113                         pub struct $context {}
 114
 115                         impl Context for $context {
 116                                 const KNOWN_FEATURE_MASK: &'static [u8] = &[
 117                                         $(
 118                                                 0b00_00_00_00 $(|
 119                                                         <Self as $known_feature>::REQUIRED_MASK |
 120                                                         <Self as $known_feature>::OPTIONAL_MASK)*,
 121                                         )*
 122                                 ];
 123                         }
 124
 125                         impl alloc::fmt::Display for Features<$context> {
 126                                 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
 127                                         $(
 128                                                 $(
 129                                                         fmt.write_fmt(format_args!("{}: {}, ", stringify!($known_feature),
 130                                                                 if <$context as $known_feature>::requires_feature(&self.flags) { "required" }
 131                                                                 else if <$context as $known_feature>::supports_feature(&self.flags) { "supported" }
 132                                                                 else { "not supported" }))?;
 133                                                 )*
 134                                                 {} // Rust gets mad if we only have a $()* block here, so add a dummy {}
 135                                         )*
 136                                         fmt.write_fmt(format_args!("unknown flags: {}",
 137                                                 if self.requires_unknown_bits() { "required" }
 138                                                 else if self.supports_unknown_bits() { "supported" } else { "none" }))
 139                                 }
 140                         }
 141                 };
 142         }
 143
 144         define_context!(InitContext, [
 145                 // Byte 0
 146                 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
 147                 // Byte 1
 148                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 149                 // Byte 2
 150                 BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
 151                 // Byte 3
 152                 RouteBlinding | ShutdownAnySegwit | Taproot,
 153                 // Byte 4
 154                 OnionMessages,
 155                 // Byte 5
 156                 ChannelType | SCIDPrivacy,
 157                 // Byte 6
 158                 ZeroConf,
 159                 // Byte 7
 160                 Trampoline,
 161         ]);
 162         define_context!(NodeContext, [
 163                 // Byte 0
 164                 DataLossProtect | UpfrontShutdownScript | GossipQueries,
 165                 // Byte 1
 166                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 167                 // Byte 2
 168                 BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
 169                 // Byte 3
 170                 RouteBlinding | ShutdownAnySegwit | Taproot,
 171                 // Byte 4
 172                 OnionMessages,
 173                 // Byte 5
 174                 ChannelType | SCIDPrivacy,
 175                 // Byte 6
 176                 ZeroConf | Keysend,
 177                 // Byte 7
 178                 Trampoline,
 179         ]);
 180         define_context!(ChannelContext, []);
 181         define_context!(Bolt11InvoiceContext, [
 182                 // Byte 0
 183                 ,
 184                 // Byte 1
 185                 VariableLengthOnion | PaymentSecret,
 186                 // Byte 2
 187                 BasicMPP,
 188                 // Byte 3
 189                 ,
 190                 // Byte 4
 191                 ,
 192                 // Byte 5
 193                 ,
 194                 // Byte 6
 195                 PaymentMetadata,
 196                 // Byte 7
 197                 Trampoline,
 198         ]);
 199         define_context!(OfferContext, []);
 200         define_context!(InvoiceRequestContext, []);
 201         define_context!(Bolt12InvoiceContext, [
 202                 // Byte 0
 203                 ,
 204                 // Byte 1
 205                 ,
 206                 // Byte 2
 207                 BasicMPP,
 208         ]);
 209         define_context!(BlindedHopContext, []);
 210         // This isn't a "real" feature context, and is only used in the channel_type field in an
 211         // `OpenChannel` message.
 212         define_context!(ChannelTypeContext, [
 213                 // Byte 0
 214                 ,
 215                 // Byte 1
 216                 StaticRemoteKey,
 217                 // Byte 2
 218                 AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
 219                 // Byte 3
 220                 Taproot,
 221                 // Byte 4
 222                 ,
 223                 // Byte 5
 224                 SCIDPrivacy,
 225                 // Byte 6
 226                 ZeroConf,
 227         ]);
 228
 229         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 230         /// useful for manipulating feature flags.
 231         macro_rules! define_feature {
 232                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 233                  $required_setter: ident, $supported_getter: ident) => {
 234                         #[doc = $doc]
 235                         ///
 236                         /// See [BOLT #9] for details.
 237                         ///
 238                         /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
 239                         pub trait $feature: Context {
 240                                 /// The bit used to signify that the feature is required.
 241                                 const EVEN_BIT: usize = $odd_bit - 1;
 242
 243                                 /// The bit used to signify that the feature is optional.
 244                                 const ODD_BIT: usize = $odd_bit;
 245
 246                                 /// Assertion that [`EVEN_BIT`] is actually even.
 247                                 ///
 248                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 249                                 const ASSERT_EVEN_BIT_PARITY: usize;
 250
 251                                 /// Assertion that [`ODD_BIT`] is actually odd.
 252                                 ///
 253                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 254                                 const ASSERT_ODD_BIT_PARITY: usize;
 255
 256                                 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
 257                                 ///
 258                                 /// [`KNOWN_FEATURE_MASK`]: Context::KNOWN_FEATURE_MASK
 259                                 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
 260                                 const ASSERT_BITS_IN_MASK: u8;
 261
 262                                 /// The byte where the feature is set.
 263                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 264
 265                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 266                                 ///
 267                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 268                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 269
 270                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 271                                 ///
 272                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 273                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 274
 275                                 /// Returns whether the feature is required by the given flags.
 276                                 #[inline]
 277                                 fn requires_feature(flags: &Vec<u8>) -> bool {
 278                                         flags.len() > Self::BYTE_OFFSET &&
 279                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
 280                                 }
 281
 282                                 /// Returns whether the feature is supported by the given flags.
 283                                 #[inline]
 284                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 285                                         flags.len() > Self::BYTE_OFFSET &&
 286                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 287                                 }
 288
 289                                 /// Sets the feature's required (even) bit in the given flags.
 290                                 #[inline]
 291                                 fn set_required_bit(flags: &mut Vec<u8>) {
 292                                         if flags.len() <= Self::BYTE_OFFSET {
 293                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 294                                         }
 295
 296                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
 297                                         flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 298                                 }
 299
 300                                 /// Sets the feature's optional (odd) bit in the given flags.
 301                                 #[inline]
 302                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 303                                         if flags.len() <= Self::BYTE_OFFSET {
 304                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 305                                         }
 306
 307                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 308                                 }
 309
 310                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 311                                 /// flags.
 312                                 #[inline]
 313                                 fn clear_bits(flags: &mut Vec<u8>) {
 314                                         if flags.len() > Self::BYTE_OFFSET {
 315                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 316                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 317                                         }
 318
 319                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 320                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 321                                         flags.resize(size, 0u8);
 322                                 }
 323                         }
 324
 325                         impl <T: $feature> Features<T> {
 326                                 /// Set this feature as optional.
 327                                 pub fn $optional_setter(&mut self) {
 328                                         <T as $feature>::set_optional_bit(&mut self.flags);
 329                                 }
 330
 331                                 /// Set this feature as required.
 332                                 pub fn $required_setter(&mut self) {
 333                                         <T as $feature>::set_required_bit(&mut self.flags);
 334                                 }
 335
 336                                 /// Checks if this feature is supported.
 337                                 pub fn $supported_getter(&self) -> bool {
 338                                         <T as $feature>::supports_feature(&self.flags)
 339                                 }
 340                         }
 341
 342                         $(
 343                                 impl $feature for $context {
 344                                         // EVEN_BIT % 2 == 0
 345                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 346
 347                                         // ODD_BIT % 2 == 1
 348                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 349
 350                                         // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
 351                                         #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
 352                                         const ASSERT_BITS_IN_MASK: u8 =
 353                                                 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
 354                                                  >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
 355                                 }
 356                         )*
 357                 };
 358                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 359                  $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
 360                         define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
 361                         impl <T: $feature> Features<T> {
 362                                 /// Checks if this feature is required.
 363                                 pub fn $required_getter(&self) -> bool {
 364                                         <T as $feature>::requires_feature(&self.flags)
 365                                 }
 366                         }
 367                 }
 368         }
 369
 370         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 371                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 372                 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
 373         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 374         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 375                 set_initial_routing_sync_optional, set_initial_routing_sync_required,
 376                 initial_routing_sync);
 377         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 378                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 379                 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
 380                 requires_upfront_shutdown_script);
 381         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 382                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
 383                 supports_gossip_queries, requires_gossip_queries);
 384         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, Bolt11InvoiceContext],
 385                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 386                 set_variable_length_onion_required, supports_variable_length_onion,
 387                 requires_variable_length_onion);
 388         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
 389                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 390                 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
 391         define_feature!(15, PaymentSecret, [InitContext, NodeContext, Bolt11InvoiceContext],
 392                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
 393                 supports_payment_secret, requires_payment_secret);
 394         define_feature!(17, BasicMPP, [InitContext, NodeContext, Bolt11InvoiceContext, Bolt12InvoiceContext],
 395                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
 396                 supports_basic_mpp, requires_basic_mpp);
 397         define_feature!(19, Wumbo, [InitContext, NodeContext],
 398                 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
 399                 supports_wumbo, requires_wumbo);
 400         define_feature!(21, AnchorsNonzeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
 401                 "Feature flags for `option_anchors_nonzero_fee_htlc_tx`.", set_anchors_nonzero_fee_htlc_tx_optional,
 402                 set_anchors_nonzero_fee_htlc_tx_required, supports_anchors_nonzero_fee_htlc_tx, requires_anchors_nonzero_fee_htlc_tx);
 403         define_feature!(23, AnchorsZeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
 404                 "Feature flags for `option_anchors_zero_fee_htlc_tx`.", set_anchors_zero_fee_htlc_tx_optional,
 405                 set_anchors_zero_fee_htlc_tx_required, supports_anchors_zero_fee_htlc_tx, requires_anchors_zero_fee_htlc_tx);
 406         define_feature!(25, RouteBlinding, [InitContext, NodeContext],
 407                 "Feature flags for `option_route_blinding`.", set_route_blinding_optional,
 408                 set_route_blinding_required, supports_route_blinding, requires_route_blinding);
 409         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 410                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 411                 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
 412         define_feature!(31, Taproot, [InitContext, NodeContext, ChannelTypeContext],
 413                 "Feature flags for `option_taproot`.", set_taproot_optional,
 414                 set_taproot_required, supports_taproot, requires_taproot);
 415         define_feature!(39, OnionMessages, [InitContext, NodeContext],
 416                 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
 417                 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
 418         define_feature!(45, ChannelType, [InitContext, NodeContext],
 419                 "Feature flags for `option_channel_type`.", set_channel_type_optional,
 420                 set_channel_type_required, supports_channel_type, requires_channel_type);
 421         define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
 422                 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
 423                 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
 424         define_feature!(49, PaymentMetadata, [Bolt11InvoiceContext],
 425                 "Feature flags for payment metadata in invoices.", set_payment_metadata_optional,
 426                 set_payment_metadata_required, supports_payment_metadata, requires_payment_metadata);
 427         define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
 428                 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
 429                 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
 430         define_feature!(55, Keysend, [NodeContext],
 431                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
 432                 supports_keysend, requires_keysend);
 433         define_feature!(57, Trampoline, [InitContext, NodeContext, Bolt11InvoiceContext],
 434                 "Feature flags for Trampoline routing.", set_trampoline_routing_optional, set_trampoline_routing_required,
 435                 supports_trampoline_routing, requires_trampoline_routing);
 436         // Note: update the module-level docs when a new feature bit is added!
 437
 438         #[cfg(test)]
 439         define_feature!(123456789, UnknownFeature,
 440                 [NodeContext, ChannelContext, Bolt11InvoiceContext, OfferContext, InvoiceRequestContext, Bolt12InvoiceContext, BlindedHopContext],
 441                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 442                 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
 443 }
 444
 445 /// Tracks the set of features which a node implements, templated by the context in which it
 446 /// appears.
 447 ///
 448 /// This is not exported to bindings users as we map the concrete feature types below directly instead
 449 #[derive(Eq)]
 450 pub struct Features<T: sealed::Context> {
 451         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 452         flags: Vec<u8>,
 453         mark: PhantomData<T>,
 454 }
 455
 456 impl<T: sealed::Context, Rhs: Borrow<Self>> core::ops::BitOrAssign<Rhs> for Features<T> {
 457         fn bitor_assign(&mut self, rhs: Rhs) {
 458                 let total_feature_len = cmp::max(self.flags.len(), rhs.borrow().flags.len());
 459                 self.flags.resize(total_feature_len, 0u8);
 460                 for (byte, rhs_byte) in self.flags.iter_mut().zip(rhs.borrow().flags.iter()) {
 461                         *byte |= *rhs_byte;
 462                 }
 463         }
 464 }
 465
 466 impl<T: sealed::Context> core::ops::BitOr for Features<T> {
 467         type Output = Self;
 468
 469         fn bitor(mut self, o: Self) -> Self {
 470                 self |= o;
 471                 self
 472         }
 473 }
 474
 475 impl<T: sealed::Context> Clone for Features<T> {
 476         fn clone(&self) -> Self {
 477                 Self {
 478                         flags: self.flags.clone(),
 479                         mark: PhantomData,
 480                 }
 481         }
 482 }
 483 impl<T: sealed::Context> Hash for Features<T> {
 484         fn hash<H: Hasher>(&self, hasher: &mut H) {
 485                 let mut nonzero_flags = &self.flags[..];
 486                 while nonzero_flags.last() == Some(&0) {
 487                         nonzero_flags = &nonzero_flags[..nonzero_flags.len() - 1];
 488                 }
 489                 nonzero_flags.hash(hasher);
 490         }
 491 }
 492 impl<T: sealed::Context> PartialEq for Features<T> {
 493         fn eq(&self, o: &Self) -> bool {
 494                 let mut o_iter = o.flags.iter();
 495                 let mut self_iter = self.flags.iter();
 496                 loop {
 497                         match (o_iter.next(), self_iter.next()) {
 498                                 (Some(o), Some(us)) => if o != us { return false },
 499                                 (Some(b), None) | (None, Some(b)) => if *b != 0 { return false },
 500                                 (None, None) => return true,
 501                         }
 502                 }
 503         }
 504 }
 505 impl<T: sealed::Context> PartialOrd for Features<T> {
 506         fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
 507                 self.flags.partial_cmp(&other.flags)
 508         }
 509 }
 510 impl<T: sealed::Context + Eq> Ord for Features<T> {
 511         fn cmp(&self, other: &Self) -> cmp::Ordering {
 512                 self.flags.cmp(&other.flags)
 513         }
 514 }
 515 impl<T: sealed::Context> fmt::Debug for Features<T> {
 516         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 517                 self.flags.fmt(fmt)
 518         }
 519 }
 520
 521 /// Features used within an `init` message.
 522 pub type InitFeatures = Features<sealed::InitContext>;
 523 /// Features used within a `node_announcement` message.
 524 pub type NodeFeatures = Features<sealed::NodeContext>;
 525 /// Features used within a `channel_announcement` message.
 526 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 527 /// Features used within an invoice.
 528 pub type Bolt11InvoiceFeatures = Features<sealed::Bolt11InvoiceContext>;
 529 /// Features used within an `offer`.
 530 pub type OfferFeatures = Features<sealed::OfferContext>;
 531 /// Features used within an `invoice_request`.
 532 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
 533 /// Features used within an `invoice`.
 534 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
 535 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
 536 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
 537
 538 /// Features used within the channel_type field in an OpenChannel message.
 539 ///
 540 /// A channel is always of some known "type", describing the transaction formats used and the exact
 541 /// semantics of our interaction with our peer.
 542 ///
 543 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
 544 /// the counterparty, only required features are allowed here.
 545 ///
 546 /// This is serialized differently from other feature types - it is not prefixed by a length, and
 547 /// thus must only appear inside a TLV where its length is known in advance.
 548 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
 549
 550 impl InitFeatures {
 551         /// Writes all features present up to, and including, 13.
 552         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 553                 let len = cmp::min(2, self.flags.len());
 554                 (len as u16).write(w)?;
 555                 for i in (0..len).rev() {
 556                         if i == 0 {
 557                                 self.flags[i].write(w)?;
 558                         } else {
 559                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 560                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 561                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 562                         }
 563                 }
 564                 Ok(())
 565         }
 566
 567         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 568         /// are included in the result.
 569         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 570                 self.to_context_internal()
 571         }
 572 }
 573
 574 impl Bolt11InvoiceFeatures {
 575         /// Converts `Bolt11InvoiceFeatures` to `Features<C>`. Only known `Bolt11InvoiceFeatures` relevant to
 576         /// context `C` are included in the result.
 577         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 578                 self.to_context_internal()
 579         }
 580
 581         /// Getting a route for a keysend payment to a private node requires providing the payee's
 582         /// features (since they were not announced in a node announcement). However, keysend payments
 583         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 584         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
 585         /// `Bolt11InvoiceFeatures` for [`find_route`].
 586         ///
 587         /// MPP keysend is not widely supported yet, so we parameterize support to allow the user to
 588         /// choose whether their router should find multi-part routes.
 589         ///
 590         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
 591         /// [`find_route`]: crate::routing::router::find_route
 592         pub(crate) fn for_keysend(allow_mpp: bool) -> Bolt11InvoiceFeatures {
 593                 let mut res = Bolt11InvoiceFeatures::empty();
 594                 res.set_variable_length_onion_optional();
 595                 if allow_mpp {
 596                         res.set_basic_mpp_optional();
 597                 }
 598                 res
 599         }
 600 }
 601
 602 impl Bolt12InvoiceFeatures {
 603         /// Converts [`Bolt12InvoiceFeatures`] to [`Features<C>`]. Only known [`Bolt12InvoiceFeatures`]
 604         /// relevant to context `C` are included in the result.
 605         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 606                 self.to_context_internal()
 607         }
 608 }
 609
 610 impl ChannelTypeFeatures {
 611         // Maps the relevant `InitFeatures` to `ChannelTypeFeatures`. Any unknown features to
 612         // `ChannelTypeFeatures` are not included in the result.
 613         pub(crate) fn from_init(init: &InitFeatures) -> Self {
 614                 let mut ret = init.to_context_internal();
 615                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
 616                 // optional bits and then AND out the optional ones.
 617                 for byte in ret.flags.iter_mut() {
 618                         *byte |= (*byte & 0b10_10_10_10) >> 1;
 619                         *byte &= 0b01_01_01_01;
 620                 }
 621                 ret
 622         }
 623
 624         /// Constructs a ChannelTypeFeatures with only static_remotekey set
 625         pub(crate) fn only_static_remote_key() -> Self {
 626                 let mut ret = Self::empty();
 627                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 628                 ret
 629         }
 630
 631         /// Constructs a ChannelTypeFeatures with anchors support
 632         pub(crate) fn anchors_zero_htlc_fee_and_dependencies() -> Self {
 633                 let mut ret = Self::empty();
 634                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 635                 <sealed::ChannelTypeContext as sealed::AnchorsZeroFeeHtlcTx>::set_required_bit(&mut ret.flags);
 636                 ret
 637         }
 638 }
 639
 640 impl ToBase32 for Bolt11InvoiceFeatures {
 641         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 642                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 643                 // minus one before dividing
 644                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 645                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 646                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 647                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 648                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 649                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 650                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 651                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 652                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 653                         if new_u5_idx > 0 {
 654                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 655                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 656                         }
 657                         if new_u5_idx > 1 {
 658                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 659                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 660                         }
 661                 }
 662                 // Trim the highest feature bits.
 663                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 664                         res_u5s.remove(0);
 665                 }
 666                 writer.write(&res_u5s)
 667         }
 668 }
 669
 670 impl Base32Len for Bolt11InvoiceFeatures {
 671         fn base32_len(&self) -> usize {
 672                 self.to_base32().len()
 673         }
 674 }
 675
 676 impl FromBase32 for Bolt11InvoiceFeatures {
 677         type Err = bech32::Error;
 678
 679         fn from_base32(field_data: &[u5]) -> Result<Bolt11InvoiceFeatures, bech32::Error> {
 680                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 681                 // minus one before dividing
 682                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 683                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 684                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 685                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 686                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 687                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 688                         let chunk_u16 = chunk.to_u8() as u16;
 689                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 690                         if new_byte_idx != length_bytes - 1 {
 691                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 692                         }
 693                 }
 694                 // Trim the highest feature bits.
 695                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 696                         res_bytes.pop();
 697                 }
 698                 Ok(Bolt11InvoiceFeatures::from_le_bytes(res_bytes))
 699         }
 700 }
 701
 702 impl<T: sealed::Context> Features<T> {
 703         /// Create a blank Features with no features set
 704         pub fn empty() -> Self {
 705                 Features {
 706                         flags: Vec::new(),
 707                         mark: PhantomData,
 708                 }
 709         }
 710
 711         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 712         /// included in the result.
 713         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 714                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 715                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 716                 let mut flags = Vec::new();
 717                 for (i, byte) in self.flags.iter().enumerate() {
 718                         if i < from_byte_count && i < to_byte_count {
 719                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 720                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 721                                 flags.push(byte & from_known_features & to_known_features);
 722                         }
 723                 }
 724                 Features::<C> { flags, mark: PhantomData, }
 725         }
 726
 727         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 728         /// most on-the-wire encodings.
 729         ///
 730         /// This is not exported to bindings users as we don't support export across multiple T
 731         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 732                 Features {
 733                         flags,
 734                         mark: PhantomData,
 735                 }
 736         }
 737
 738         #[cfg(test)]
 739         /// Gets the underlying flags set, in LE.
 740         pub fn le_flags(&self) -> &Vec<u8> {
 741                 &self.flags
 742         }
 743
 744         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 745                 for f in self.flags.iter().rev() { // Swap back to big-endian
 746                         f.write(w)?;
 747                 }
 748                 Ok(())
 749         }
 750
 751         /// Create a [`Features`] given a set of flags, in big-endian. This is in byte order from
 752         /// most on-the-wire encodings.
 753         ///
 754         /// This is not exported to bindings users as we don't support export across multiple T
 755         pub fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
 756                 flags.reverse(); // Swap to little-endian
 757                 Self {
 758                         flags,
 759                         mark: PhantomData,
 760                 }
 761         }
 762
 763         pub(crate) fn supports_any_optional_bits(&self) -> bool {
 764                 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
 765         }
 766
 767         /// Returns true if this `Features` object contains required features unknown by `other`.
 768         pub fn requires_unknown_bits_from(&self, other: &Self) -> bool {
 769                 // Bitwise AND-ing with all even bits set except for known features will select required
 770                 // unknown features.
 771                 self.flags.iter().enumerate().any(|(i, &byte)| {
 772                         const REQUIRED_FEATURES: u8 = 0b01_01_01_01;
 773                         const OPTIONAL_FEATURES: u8 = 0b10_10_10_10;
 774                         let unknown_features = if i < other.flags.len() {
 775                                 // Form a mask similar to !T::KNOWN_FEATURE_MASK only for `other`
 776                                 !(other.flags[i]
 777                                         | ((other.flags[i] >> 1) & REQUIRED_FEATURES)
 778                                         | ((other.flags[i] << 1) & OPTIONAL_FEATURES))
 779                         } else {
 780                                 0b11_11_11_11
 781                         };
 782                         (byte & (REQUIRED_FEATURES & unknown_features)) != 0
 783                 })
 784         }
 785
 786         /// Returns true if this `Features` object contains unknown feature flags which are set as
 787         /// "required".
 788         pub fn requires_unknown_bits(&self) -> bool {
 789                 // Bitwise AND-ing with all even bits set except for known features will select required
 790                 // unknown features.
 791                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 792                 self.flags.iter().enumerate().any(|(i, &byte)| {
 793                         let required_features = 0b01_01_01_01;
 794                         let unknown_features = if i < byte_count {
 795                                 !T::KNOWN_FEATURE_MASK[i]
 796                         } else {
 797                                 0b11_11_11_11
 798                         };
 799                         (byte & (required_features & unknown_features)) != 0
 800                 })
 801         }
 802
 803         pub(crate) fn supports_unknown_bits(&self) -> bool {
 804                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 805                 // both required and optional unknown features.
 806                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 807                 self.flags.iter().enumerate().any(|(i, &byte)| {
 808                         let unknown_features = if i < byte_count {
 809                                 !T::KNOWN_FEATURE_MASK[i]
 810                         } else {
 811                                 0b11_11_11_11
 812                         };
 813                         (byte & unknown_features) != 0
 814                 })
 815         }
 816
 817         // Returns true if the features within `self` are a subset of the features within `other`.
 818         pub(crate) fn is_subset(&self, other: &Self) -> bool {
 819                 for (idx, byte) in self.flags.iter().enumerate() {
 820                         if let Some(other_byte) = other.flags.get(idx) {
 821                                 if byte & other_byte != *byte {
 822                                         // `self` has bits set that `other` doesn't.
 823                                         return false;
 824                                 }
 825                         } else {
 826                                 if *byte > 0 {
 827                                         // `self` has a non-zero byte that `other` doesn't.
 828                                         return false;
 829                                 }
 830                         }
 831                 }
 832                 true
 833         }
 834
 835         /// Sets a required feature bit. Errors if `bit` is outside the feature range as defined
 836         /// by [BOLT 9].
 837         ///
 838         /// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
 839         /// be set instead (i.e., `bit - 1`).
 840         ///
 841         /// [BOLT 9]: https://github.com/lightning/bolts/blob/master/09-features.md
 842         pub fn set_required_feature_bit(&mut self, bit: usize) -> Result<(), ()> {
 843                 self.set_feature_bit(bit - (bit % 2))
 844         }
 845
 846         /// Sets an optional feature bit. Errors if `bit` is outside the feature range as defined
 847         /// by [BOLT 9].
 848         ///
 849         /// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
 850         /// set instead (i.e., `bit + 1`).
 851         ///
 852         /// [BOLT 9]: https://github.com/lightning/bolts/blob/master/09-features.md
 853         pub fn set_optional_feature_bit(&mut self, bit: usize) -> Result<(), ()> {
 854                 self.set_feature_bit(bit + (1 - (bit % 2)))
 855         }
 856
 857         fn set_feature_bit(&mut self, bit: usize) -> Result<(), ()> {
 858                 if bit > 255 {
 859                         return Err(());
 860                 }
 861                 self.set_bit(bit, false)
 862         }
 863
 864         /// Sets a required custom feature bit. Errors if `bit` is outside the custom range as defined
 865         /// by [bLIP 2] or if it is a known `T` feature.
 866         ///
 867         /// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
 868         /// be set instead (i.e., `bit - 1`).
 869         ///
 870         /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
 871         pub fn set_required_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 872                 self.set_custom_bit(bit - (bit % 2))
 873         }
 874
 875         /// Sets an optional custom feature bit. Errors if `bit` is outside the custom range as defined
 876         /// by [bLIP 2] or if it is a known `T` feature.
 877         ///
 878         /// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
 879         /// set instead (i.e., `bit + 1`).
 880         ///
 881         /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
 882         pub fn set_optional_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 883                 self.set_custom_bit(bit + (1 - (bit % 2)))
 884         }
 885
 886         fn set_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 887                 if bit < 256 {
 888                         return Err(());
 889                 }
 890                 self.set_bit(bit, true)
 891         }
 892
 893         fn set_bit(&mut self, bit: usize, custom: bool) -> Result<(), ()> {
 894                 let byte_offset = bit / 8;
 895                 let mask = 1 << (bit - 8 * byte_offset);
 896                 if byte_offset < T::KNOWN_FEATURE_MASK.len() && custom {
 897                         if (T::KNOWN_FEATURE_MASK[byte_offset] & mask) != 0 {
 898                                 return Err(());
 899                         }
 900                 }
 901
 902                 if self.flags.len() <= byte_offset {
 903                         self.flags.resize(byte_offset + 1, 0u8);
 904                 }
 905
 906                 self.flags[byte_offset] |= mask;
 907
 908                 Ok(())
 909         }
 910 }
 911
 912 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 913         #[cfg(test)]
 914         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 915                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 916                 self
 917         }
 918 }
 919
 920 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 921         #[cfg(test)]
 922         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 923                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 924                 self
 925         }
 926 }
 927
 928 impl<T: sealed::Wumbo> Features<T> {
 929         #[cfg(test)]
 930         pub(crate) fn clear_wumbo(mut self) -> Self {
 931                 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
 932                 self
 933         }
 934 }
 935
 936 impl<T: sealed::SCIDPrivacy> Features<T> {
 937         pub(crate) fn clear_scid_privacy(&mut self) {
 938                 <T as sealed::SCIDPrivacy>::clear_bits(&mut self.flags);
 939         }
 940 }
 941
 942 impl<T: sealed::AnchorsZeroFeeHtlcTx> Features<T> {
 943         pub(crate) fn clear_anchors_zero_fee_htlc_tx(&mut self) {
 944                 <T as sealed::AnchorsZeroFeeHtlcTx>::clear_bits(&mut self.flags);
 945         }
 946 }
 947
 948 impl<T: sealed::RouteBlinding> Features<T> {
 949         #[cfg(test)]
 950         pub(crate) fn clear_route_blinding(&mut self) {
 951                 <T as sealed::RouteBlinding>::clear_bits(&mut self.flags);
 952         }
 953 }
 954
 955 #[cfg(test)]
 956 impl<T: sealed::UnknownFeature> Features<T> {
 957         pub(crate) fn unknown() -> Self {
 958                 let mut features = Self::empty();
 959                 features.set_unknown_feature_required();
 960                 features
 961         }
 962 }
 963
 964 macro_rules! impl_feature_len_prefixed_write {
 965         ($features: ident) => {
 966                 impl Writeable for $features {
 967                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 968                                 (self.flags.len() as u16).write(w)?;
 969                                 self.write_be(w)
 970                         }
 971                 }
 972                 impl Readable for $features {
 973                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 974                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
 975                         }
 976                 }
 977         }
 978 }
 979 impl_feature_len_prefixed_write!(InitFeatures);
 980 impl_feature_len_prefixed_write!(ChannelFeatures);
 981 impl_feature_len_prefixed_write!(NodeFeatures);
 982 impl_feature_len_prefixed_write!(Bolt11InvoiceFeatures);
 983 impl_feature_len_prefixed_write!(Bolt12InvoiceFeatures);
 984 impl_feature_len_prefixed_write!(BlindedHopFeatures);
 985
 986 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
 987 macro_rules! impl_feature_tlv_write {
 988         ($features: ident) => {
 989                 impl Writeable for $features {
 990                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 991                                 WithoutLength(self).write(w)
 992                         }
 993                 }
 994                 impl Readable for $features {
 995                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 996                                 Ok(WithoutLength::<Self>::read(r)?.0)
 997                         }
 998                 }
 999         }
1000 }
1001
1002 impl_feature_tlv_write!(ChannelTypeFeatures);
1003
1004 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
1005 // requires a length but the former does not.
1006
1007 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
1008         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
1009                 self.0.write_be(w)
1010         }
1011 }
1012
1013 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
1014         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
1015                 let v = io_extras::read_to_end(r)?;
1016                 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
1017         }
1018 }
1019
1020 #[cfg(test)]
1021 mod tests {
1022         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, Bolt11InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
1023         use bech32::{Base32Len, FromBase32, ToBase32, u5};
1024         use crate::util::ser::{Readable, WithoutLength, Writeable};
1025
1026         #[test]
1027         fn sanity_test_unknown_bits() {
1028                 let features = ChannelFeatures::empty();
1029                 assert!(!features.requires_unknown_bits());
1030                 assert!(!features.supports_unknown_bits());
1031
1032                 let mut features = ChannelFeatures::empty();
1033                 features.set_unknown_feature_required();
1034                 assert!(features.requires_unknown_bits());
1035                 assert!(features.supports_unknown_bits());
1036
1037                 let mut features = ChannelFeatures::empty();
1038                 features.set_unknown_feature_optional();
1039                 assert!(!features.requires_unknown_bits());
1040                 assert!(features.supports_unknown_bits());
1041         }
1042
1043         #[test]
1044         fn requires_unknown_bits_from() {
1045                 let mut features1 = InitFeatures::empty();
1046                 let mut features2 = InitFeatures::empty();
1047                 assert!(!features1.requires_unknown_bits_from(&features2));
1048                 assert!(!features2.requires_unknown_bits_from(&features1));
1049
1050                 features1.set_data_loss_protect_required();
1051                 assert!(features1.requires_unknown_bits_from(&features2));
1052                 assert!(!features2.requires_unknown_bits_from(&features1));
1053
1054                 features2.set_data_loss_protect_optional();
1055                 assert!(!features1.requires_unknown_bits_from(&features2));
1056                 assert!(!features2.requires_unknown_bits_from(&features1));
1057
1058                 features2.set_gossip_queries_required();
1059                 assert!(!features1.requires_unknown_bits_from(&features2));
1060                 assert!(features2.requires_unknown_bits_from(&features1));
1061
1062                 features1.set_gossip_queries_optional();
1063                 assert!(!features1.requires_unknown_bits_from(&features2));
1064                 assert!(!features2.requires_unknown_bits_from(&features1));
1065
1066                 features1.set_variable_length_onion_required();
1067                 assert!(features1.requires_unknown_bits_from(&features2));
1068                 assert!(!features2.requires_unknown_bits_from(&features1));
1069
1070                 features2.set_variable_length_onion_optional();
1071                 assert!(!features1.requires_unknown_bits_from(&features2));
1072                 assert!(!features2.requires_unknown_bits_from(&features1));
1073
1074                 features1.set_basic_mpp_required();
1075                 features2.set_wumbo_required();
1076                 assert!(features1.requires_unknown_bits_from(&features2));
1077                 assert!(features2.requires_unknown_bits_from(&features1));
1078         }
1079
1080         #[test]
1081         fn convert_to_context_with_relevant_flags() {
1082                 let mut init_features = InitFeatures::empty();
1083                 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
1084                 // converted as it's only relevant in an init context).
1085                 init_features.set_initial_routing_sync_required();
1086                 init_features.set_data_loss_protect_required();
1087                 init_features.set_variable_length_onion_required();
1088                 init_features.set_static_remote_key_required();
1089                 init_features.set_payment_secret_required();
1090                 init_features.set_basic_mpp_optional();
1091                 init_features.set_wumbo_optional();
1092                 init_features.set_anchors_zero_fee_htlc_tx_optional();
1093                 init_features.set_route_blinding_optional();
1094                 init_features.set_shutdown_any_segwit_optional();
1095                 init_features.set_onion_messages_optional();
1096                 init_features.set_channel_type_optional();
1097                 init_features.set_scid_privacy_optional();
1098                 init_features.set_zero_conf_optional();
1099
1100                 assert!(init_features.initial_routing_sync());
1101                 assert!(!init_features.supports_upfront_shutdown_script());
1102                 assert!(!init_features.supports_gossip_queries());
1103
1104                 let node_features: NodeFeatures = init_features.to_context();
1105                 {
1106                         // Check that the flags are as expected:
1107                         // - option_data_loss_protect (req)
1108                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
1109                         // - basic_mpp | wumbo | option_anchors_zero_fee_htlc_tx
1110                         // - option_route_blinding | opt_shutdown_anysegwit
1111                         // - onion_messages
1112                         // - option_channel_type | option_scid_alias
1113                         // - option_zeroconf
1114                         assert_eq!(node_features.flags.len(), 7);
1115                         assert_eq!(node_features.flags[0], 0b00000001);
1116                         assert_eq!(node_features.flags[1], 0b01010001);
1117                         assert_eq!(node_features.flags[2], 0b10001010);
1118                         assert_eq!(node_features.flags[3], 0b00001010);
1119                         assert_eq!(node_features.flags[4], 0b10000000);
1120                         assert_eq!(node_features.flags[5], 0b10100000);
1121                         assert_eq!(node_features.flags[6], 0b00001000);
1122                 }
1123
1124                 // Check that cleared flags are kept blank when converting back:
1125                 // - initial_routing_sync was not applicable to NodeContext
1126                 // - upfront_shutdown_script was cleared before converting
1127                 // - gossip_queries was cleared before converting
1128                 let features: InitFeatures = node_features.to_context_internal();
1129                 assert!(!features.initial_routing_sync());
1130                 assert!(!features.supports_upfront_shutdown_script());
1131                 assert!(!init_features.supports_gossip_queries());
1132         }
1133
1134         #[test]
1135         fn convert_to_context_with_unknown_flags() {
1136                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
1137                 assert!(<sealed::ChannelContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
1138                         <sealed::Bolt11InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
1139                 let mut channel_features = ChannelFeatures::empty();
1140                 channel_features.set_unknown_feature_optional();
1141                 assert!(channel_features.supports_unknown_bits());
1142                 let invoice_features: Bolt11InvoiceFeatures = channel_features.to_context_internal();
1143                 assert!(!invoice_features.supports_unknown_bits());
1144         }
1145
1146         #[test]
1147         fn set_feature_bits() {
1148                 let mut features = Bolt11InvoiceFeatures::empty();
1149                 features.set_basic_mpp_optional();
1150                 features.set_payment_secret_required();
1151                 assert!(features.supports_basic_mpp());
1152                 assert!(!features.requires_basic_mpp());
1153                 assert!(features.requires_payment_secret());
1154                 assert!(features.supports_payment_secret());
1155
1156                 // Set flags manually
1157                 let mut features = NodeFeatures::empty();
1158                 assert!(features.set_optional_feature_bit(55).is_ok());
1159                 assert!(features.supports_keysend());
1160                 assert!(features.set_optional_feature_bit(255).is_ok());
1161                 assert!(features.set_required_feature_bit(256).is_err());
1162         }
1163
1164         #[test]
1165         fn set_custom_bits() {
1166                 let mut features = Bolt11InvoiceFeatures::empty();
1167                 features.set_variable_length_onion_optional();
1168                 assert_eq!(features.flags[1], 0b00000010);
1169
1170                 assert!(features.set_optional_custom_bit(255).is_err());
1171                 assert!(features.set_required_custom_bit(256).is_ok());
1172                 assert!(features.set_required_custom_bit(258).is_ok());
1173                 assert_eq!(features.flags[31], 0b00000000);
1174                 assert_eq!(features.flags[32], 0b00000101);
1175
1176                 let known_bit = <sealed::Bolt11InvoiceContext as sealed::PaymentSecret>::EVEN_BIT;
1177                 let byte_offset = <sealed::Bolt11InvoiceContext as sealed::PaymentSecret>::BYTE_OFFSET;
1178                 assert_eq!(byte_offset, 1);
1179                 assert_eq!(features.flags[byte_offset], 0b00000010);
1180                 assert!(features.set_required_custom_bit(known_bit).is_err());
1181                 assert_eq!(features.flags[byte_offset], 0b00000010);
1182
1183                 let mut features = Bolt11InvoiceFeatures::empty();
1184                 assert!(features.set_optional_custom_bit(256).is_ok());
1185                 assert!(features.set_optional_custom_bit(259).is_ok());
1186                 assert_eq!(features.flags[32], 0b00001010);
1187
1188                 let mut features = Bolt11InvoiceFeatures::empty();
1189                 assert!(features.set_required_custom_bit(257).is_ok());
1190                 assert!(features.set_required_custom_bit(258).is_ok());
1191                 assert_eq!(features.flags[32], 0b00000101);
1192         }
1193
1194         #[test]
1195         fn encodes_features_without_length() {
1196                 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1197                 assert_eq!(features.flags.len(), 8);
1198
1199                 let mut serialized_features = Vec::new();
1200                 WithoutLength(&features).write(&mut serialized_features).unwrap();
1201                 assert_eq!(serialized_features.len(), 8);
1202
1203                 let deserialized_features =
1204                         WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
1205                 assert_eq!(features, deserialized_features);
1206         }
1207
1208         #[test]
1209         fn invoice_features_encoding() {
1210                 let features_as_u5s = vec![
1211                         u5::try_from_u8(6).unwrap(),
1212                         u5::try_from_u8(10).unwrap(),
1213                         u5::try_from_u8(25).unwrap(),
1214                         u5::try_from_u8(1).unwrap(),
1215                         u5::try_from_u8(10).unwrap(),
1216                         u5::try_from_u8(0).unwrap(),
1217                         u5::try_from_u8(20).unwrap(),
1218                         u5::try_from_u8(2).unwrap(),
1219                         u5::try_from_u8(0).unwrap(),
1220                         u5::try_from_u8(6).unwrap(),
1221                         u5::try_from_u8(0).unwrap(),
1222                         u5::try_from_u8(16).unwrap(),
1223                         u5::try_from_u8(1).unwrap(),
1224                 ];
1225                 let features = Bolt11InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1226
1227                 // Test length calculation.
1228                 assert_eq!(features.base32_len(), 13);
1229
1230                 // Test serialization.
1231                 let features_serialized = features.to_base32();
1232                 assert_eq!(features_as_u5s, features_serialized);
1233
1234                 // Test deserialization.
1235                 let features_deserialized = Bolt11InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
1236                 assert_eq!(features, features_deserialized);
1237         }
1238
1239         #[test]
1240         fn test_channel_type_mapping() {
1241                 // If we map an Bolt11InvoiceFeatures with StaticRemoteKey optional, it should map into a
1242                 // required-StaticRemoteKey ChannelTypeFeatures.
1243                 let mut init_features = InitFeatures::empty();
1244                 init_features.set_static_remote_key_optional();
1245                 let converted_features = ChannelTypeFeatures::from_init(&init_features);
1246                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
1247                 assert!(!converted_features.supports_any_optional_bits());
1248                 assert!(converted_features.requires_static_remote_key());
1249         }
1250
1251         #[test]
1252         #[cfg(feature = "std")]
1253         fn test_excess_zero_bytes_ignored() {
1254                 // Checks that `Hash` and `PartialEq` ignore excess zero bytes, which may appear due to
1255                 // feature conversion or because a peer serialized their feature poorly.
1256                 use std::collections::hash_map::DefaultHasher;
1257                 use std::hash::{Hash, Hasher};
1258
1259                 let mut zerod_features = InitFeatures::empty();
1260                 zerod_features.flags = vec![0];
1261                 let empty_features = InitFeatures::empty();
1262                 assert!(empty_features.flags.is_empty());
1263
1264                 assert_eq!(zerod_features, empty_features);
1265
1266                 let mut zerod_hash = DefaultHasher::new();
1267                 zerod_features.hash(&mut zerod_hash);
1268                 let mut empty_hash = DefaultHasher::new();
1269                 empty_features.hash(&mut empty_hash);
1270                 assert_eq!(zerod_hash.finish(), empty_hash.finish());
1271         }
1272 }