_ 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 const ANY_REQUIRED_FEATURES_MASK: u8 = 0b01_01_01_01;
 446 const ANY_OPTIONAL_FEATURES_MASK: u8 = 0b10_10_10_10;
 447
 448 /// Tracks the set of features which a node implements, templated by the context in which it
 449 /// appears.
 450 ///
 451 /// This is not exported to bindings users as we map the concrete feature types below directly instead
 452 #[derive(Eq)]
 453 pub struct Features<T: sealed::Context> {
 454         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 455         flags: Vec<u8>,
 456         mark: PhantomData<T>,
 457 }
 458
 459 impl<T: sealed::Context, Rhs: Borrow<Self>> core::ops::BitOrAssign<Rhs> for Features<T> {
 460         fn bitor_assign(&mut self, rhs: Rhs) {
 461                 let total_feature_len = cmp::max(self.flags.len(), rhs.borrow().flags.len());
 462                 self.flags.resize(total_feature_len, 0u8);
 463                 for (byte, rhs_byte) in self.flags.iter_mut().zip(rhs.borrow().flags.iter()) {
 464                         *byte |= *rhs_byte;
 465                 }
 466         }
 467 }
 468
 469 impl<T: sealed::Context> core::ops::BitOr for Features<T> {
 470         type Output = Self;
 471
 472         fn bitor(mut self, o: Self) -> Self {
 473                 self |= o;
 474                 self
 475         }
 476 }
 477
 478 impl<T: sealed::Context> Clone for Features<T> {
 479         fn clone(&self) -> Self {
 480                 Self {
 481                         flags: self.flags.clone(),
 482                         mark: PhantomData,
 483                 }
 484         }
 485 }
 486 impl<T: sealed::Context> Hash for Features<T> {
 487         fn hash<H: Hasher>(&self, hasher: &mut H) {
 488                 let mut nonzero_flags = &self.flags[..];
 489                 while nonzero_flags.last() == Some(&0) {
 490                         nonzero_flags = &nonzero_flags[..nonzero_flags.len() - 1];
 491                 }
 492                 nonzero_flags.hash(hasher);
 493         }
 494 }
 495 impl<T: sealed::Context> PartialEq for Features<T> {
 496         fn eq(&self, o: &Self) -> bool {
 497                 let mut o_iter = o.flags.iter();
 498                 let mut self_iter = self.flags.iter();
 499                 loop {
 500                         match (o_iter.next(), self_iter.next()) {
 501                                 (Some(o), Some(us)) => if o != us { return false },
 502                                 (Some(b), None) | (None, Some(b)) => if *b != 0 { return false },
 503                                 (None, None) => return true,
 504                         }
 505                 }
 506         }
 507 }
 508 impl<T: sealed::Context> PartialOrd for Features<T> {
 509         fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
 510                 self.flags.partial_cmp(&other.flags)
 511         }
 512 }
 513 impl<T: sealed::Context + Eq> Ord for Features<T> {
 514         fn cmp(&self, other: &Self) -> cmp::Ordering {
 515                 self.flags.cmp(&other.flags)
 516         }
 517 }
 518 impl<T: sealed::Context> fmt::Debug for Features<T> {
 519         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 520                 self.flags.fmt(fmt)
 521         }
 522 }
 523
 524 /// Features used within an `init` message.
 525 pub type InitFeatures = Features<sealed::InitContext>;
 526 /// Features used within a `node_announcement` message.
 527 pub type NodeFeatures = Features<sealed::NodeContext>;
 528 /// Features used within a `channel_announcement` message.
 529 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 530 /// Features used within an invoice.
 531 pub type Bolt11InvoiceFeatures = Features<sealed::Bolt11InvoiceContext>;
 532 /// Features used within an `offer`.
 533 pub type OfferFeatures = Features<sealed::OfferContext>;
 534 /// Features used within an `invoice_request`.
 535 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
 536 /// Features used within an `invoice`.
 537 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
 538 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
 539 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
 540
 541 /// Features used within the channel_type field in an OpenChannel message.
 542 ///
 543 /// A channel is always of some known "type", describing the transaction formats used and the exact
 544 /// semantics of our interaction with our peer.
 545 ///
 546 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
 547 /// the counterparty, only required features are allowed here.
 548 ///
 549 /// This is serialized differently from other feature types - it is not prefixed by a length, and
 550 /// thus must only appear inside a TLV where its length is known in advance.
 551 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
 552
 553 impl InitFeatures {
 554         /// Writes all features present up to, and including, 13.
 555         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 556                 let len = cmp::min(2, self.flags.len());
 557                 (len as u16).write(w)?;
 558                 for i in (0..len).rev() {
 559                         if i == 0 {
 560                                 self.flags[i].write(w)?;
 561                         } else {
 562                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 563                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 564                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 565                         }
 566                 }
 567                 Ok(())
 568         }
 569
 570         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 571         /// 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 Bolt11InvoiceFeatures {
 578         /// Converts `Bolt11InvoiceFeatures` to `Features<C>`. Only known `Bolt11InvoiceFeatures` relevant to
 579         /// context `C` are included in the result.
 580         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 581                 self.to_context_internal()
 582         }
 583
 584         /// Getting a route for a keysend payment to a private node requires providing the payee's
 585         /// features (since they were not announced in a node announcement). However, keysend payments
 586         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 587         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
 588         /// `Bolt11InvoiceFeatures` for [`find_route`].
 589         ///
 590         /// MPP keysend is not widely supported yet, so we parameterize support to allow the user to
 591         /// choose whether their router should find multi-part routes.
 592         ///
 593         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
 594         /// [`find_route`]: crate::routing::router::find_route
 595         pub(crate) fn for_keysend(allow_mpp: bool) -> Bolt11InvoiceFeatures {
 596                 let mut res = Bolt11InvoiceFeatures::empty();
 597                 res.set_variable_length_onion_optional();
 598                 if allow_mpp {
 599                         res.set_basic_mpp_optional();
 600                 }
 601                 res
 602         }
 603 }
 604
 605 impl Bolt12InvoiceFeatures {
 606         /// Converts [`Bolt12InvoiceFeatures`] to [`Features<C>`]. Only known [`Bolt12InvoiceFeatures`]
 607         /// relevant to context `C` are included in the result.
 608         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 609                 self.to_context_internal()
 610         }
 611 }
 612
 613 impl ChannelTypeFeatures {
 614         // Maps the relevant `InitFeatures` to `ChannelTypeFeatures`. Any unknown features to
 615         // `ChannelTypeFeatures` are not included in the result.
 616         pub(crate) fn from_init(init: &InitFeatures) -> Self {
 617                 let mut ret = init.to_context_internal();
 618                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
 619                 // optional bits and then AND out the optional ones.
 620                 for byte in ret.flags.iter_mut() {
 621                         *byte |= (*byte & ANY_OPTIONAL_FEATURES_MASK) >> 1;
 622                         *byte &= ANY_REQUIRED_FEATURES_MASK;
 623                 }
 624                 ret
 625         }
 626
 627         /// Constructs a ChannelTypeFeatures with only static_remotekey set
 628         pub(crate) fn only_static_remote_key() -> Self {
 629                 let mut ret = Self::empty();
 630                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 631                 ret
 632         }
 633
 634         /// Constructs a ChannelTypeFeatures with anchors support
 635         pub(crate) fn anchors_zero_htlc_fee_and_dependencies() -> Self {
 636                 let mut ret = Self::empty();
 637                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 638                 <sealed::ChannelTypeContext as sealed::AnchorsZeroFeeHtlcTx>::set_required_bit(&mut ret.flags);
 639                 ret
 640         }
 641 }
 642
 643 impl ToBase32 for Bolt11InvoiceFeatures {
 644         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 645                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 646                 // minus one before dividing
 647                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 648                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 649                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 650                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 651                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 652                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 653                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 654                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 655                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 656                         if new_u5_idx > 0 {
 657                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 658                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 659                         }
 660                         if new_u5_idx > 1 {
 661                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 662                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 663                         }
 664                 }
 665                 // Trim the highest feature bits.
 666                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 667                         res_u5s.remove(0);
 668                 }
 669                 writer.write(&res_u5s)
 670         }
 671 }
 672
 673 impl Base32Len for Bolt11InvoiceFeatures {
 674         fn base32_len(&self) -> usize {
 675                 self.to_base32().len()
 676         }
 677 }
 678
 679 impl FromBase32 for Bolt11InvoiceFeatures {
 680         type Err = bech32::Error;
 681
 682         fn from_base32(field_data: &[u5]) -> Result<Bolt11InvoiceFeatures, bech32::Error> {
 683                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 684                 // minus one before dividing
 685                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 686                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 687                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 688                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 689                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 690                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 691                         let chunk_u16 = chunk.to_u8() as u16;
 692                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 693                         if new_byte_idx != length_bytes - 1 {
 694                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 695                         }
 696                 }
 697                 // Trim the highest feature bits.
 698                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 699                         res_bytes.pop();
 700                 }
 701                 Ok(Bolt11InvoiceFeatures::from_le_bytes(res_bytes))
 702         }
 703 }
 704
 705 impl<T: sealed::Context> Features<T> {
 706         /// Create a blank Features with no features set
 707         pub fn empty() -> Self {
 708                 Features {
 709                         flags: Vec::new(),
 710                         mark: PhantomData,
 711                 }
 712         }
 713
 714         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 715         /// included in the result.
 716         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 717                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 718                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 719                 let mut flags = Vec::new();
 720                 for (i, byte) in self.flags.iter().enumerate() {
 721                         if i < from_byte_count && i < to_byte_count {
 722                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 723                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 724                                 flags.push(byte & from_known_features & to_known_features);
 725                         }
 726                 }
 727                 Features::<C> { flags, mark: PhantomData, }
 728         }
 729
 730         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 731         /// most on-the-wire encodings.
 732         ///
 733         /// This is not exported to bindings users as we don't support export across multiple T
 734         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 735                 Features {
 736                         flags,
 737                         mark: PhantomData,
 738                 }
 739         }
 740
 741         #[cfg(test)]
 742         /// Gets the underlying flags set, in LE.
 743         pub fn le_flags(&self) -> &Vec<u8> {
 744                 &self.flags
 745         }
 746
 747         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 748                 for f in self.flags.iter().rev() { // Swap back to big-endian
 749                         f.write(w)?;
 750                 }
 751                 Ok(())
 752         }
 753
 754         /// Create a [`Features`] given a set of flags, in big-endian. This is in byte order from
 755         /// most on-the-wire encodings.
 756         ///
 757         /// This is not exported to bindings users as we don't support export across multiple T
 758         pub fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
 759                 flags.reverse(); // Swap to little-endian
 760                 Self {
 761                         flags,
 762                         mark: PhantomData,
 763                 }
 764         }
 765
 766         pub(crate) fn supports_any_optional_bits(&self) -> bool {
 767                 self.flags.iter().any(|&byte| (byte & ANY_OPTIONAL_FEATURES_MASK) != 0)
 768         }
 769
 770         /// Returns true if this `Features` object contains required features unknown by `other`.
 771         pub fn requires_unknown_bits_from(&self, other: &Self) -> bool {
 772                 // Bitwise AND-ing with all even bits set except for known features will select required
 773                 // unknown features.
 774                 self.flags.iter().enumerate().any(|(i, &byte)| {
 775                         let unknown_features = unset_features_mask_at_position(other, i);
 776                         (byte & (ANY_REQUIRED_FEATURES_MASK & unknown_features)) != 0
 777                 })
 778         }
 779
 780         pub(crate) fn required_unknown_bits_from(&self, other: &Self) -> Vec<usize> {
 781                 let mut unknown_bits = Vec::new();
 782
 783                 // Bitwise AND-ing with all even bits set except for known features will select required
 784                 // unknown features.
 785                 self.flags.iter().enumerate().for_each(|(i, &byte)| {
 786                         let unknown_features = unset_features_mask_at_position(other, i);
 787                         if byte & unknown_features != 0 {
 788                                 for bit in (0..8).step_by(2) {
 789                                         if ((byte & unknown_features) >> bit) & 1 == 1 {
 790                                                 unknown_bits.push(i * 8 + bit);
 791                                         }
 792                                 }
 793                         }
 794                 });
 795
 796                 unknown_bits
 797         }
 798
 799         /// Returns true if this `Features` object contains unknown feature flags which are set as
 800         /// "required".
 801         pub fn requires_unknown_bits(&self) -> bool {
 802                 // Bitwise AND-ing with all even bits set except for known features will select required
 803                 // unknown features.
 804                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 805                 self.flags.iter().enumerate().any(|(i, &byte)| {
 806                         let unknown_features = if i < byte_count {
 807                                 !T::KNOWN_FEATURE_MASK[i]
 808                         } else {
 809                                 0b11_11_11_11
 810                         };
 811                         (byte & (ANY_REQUIRED_FEATURES_MASK & unknown_features)) != 0
 812                 })
 813         }
 814
 815         pub(crate) fn supports_unknown_bits(&self) -> bool {
 816                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 817                 // both required and optional unknown features.
 818                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 819                 self.flags.iter().enumerate().any(|(i, &byte)| {
 820                         let unknown_features = if i < byte_count {
 821                                 !T::KNOWN_FEATURE_MASK[i]
 822                         } else {
 823                                 0b11_11_11_11
 824                         };
 825                         (byte & unknown_features) != 0
 826                 })
 827         }
 828
 829         // Returns true if the features within `self` are a subset of the features within `other`.
 830         pub(crate) fn is_subset(&self, other: &Self) -> bool {
 831                 for (idx, byte) in self.flags.iter().enumerate() {
 832                         if let Some(other_byte) = other.flags.get(idx) {
 833                                 if byte & other_byte != *byte {
 834                                         // `self` has bits set that `other` doesn't.
 835                                         return false;
 836                                 }
 837                         } else {
 838                                 if *byte > 0 {
 839                                         // `self` has a non-zero byte that `other` doesn't.
 840                                         return false;
 841                                 }
 842                         }
 843                 }
 844                 true
 845         }
 846
 847         /// Sets a required feature bit. Errors if `bit` is outside the feature range as defined
 848         /// by [BOLT 9].
 849         ///
 850         /// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
 851         /// be set instead (i.e., `bit - 1`).
 852         ///
 853         /// [BOLT 9]: https://github.com/lightning/bolts/blob/master/09-features.md
 854         pub fn set_required_feature_bit(&mut self, bit: usize) -> Result<(), ()> {
 855                 self.set_feature_bit(bit - (bit % 2))
 856         }
 857
 858         /// Sets an optional feature bit. Errors if `bit` is outside the feature range as defined
 859         /// by [BOLT 9].
 860         ///
 861         /// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
 862         /// set instead (i.e., `bit + 1`).
 863         ///
 864         /// [BOLT 9]: https://github.com/lightning/bolts/blob/master/09-features.md
 865         pub fn set_optional_feature_bit(&mut self, bit: usize) -> Result<(), ()> {
 866                 self.set_feature_bit(bit + (1 - (bit % 2)))
 867         }
 868
 869         fn set_feature_bit(&mut self, bit: usize) -> Result<(), ()> {
 870                 if bit > 255 {
 871                         return Err(());
 872                 }
 873                 self.set_bit(bit, false)
 874         }
 875
 876         /// Sets a required custom feature bit. Errors if `bit` is outside the custom range as defined
 877         /// by [bLIP 2] or if it is a known `T` feature.
 878         ///
 879         /// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
 880         /// be set instead (i.e., `bit - 1`).
 881         ///
 882         /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
 883         pub fn set_required_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 884                 self.set_custom_bit(bit - (bit % 2))
 885         }
 886
 887         /// Sets an optional custom feature bit. Errors if `bit` is outside the custom range as defined
 888         /// by [bLIP 2] or if it is a known `T` feature.
 889         ///
 890         /// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
 891         /// set instead (i.e., `bit + 1`).
 892         ///
 893         /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
 894         pub fn set_optional_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 895                 self.set_custom_bit(bit + (1 - (bit % 2)))
 896         }
 897
 898         fn set_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 899                 if bit < 256 {
 900                         return Err(());
 901                 }
 902                 self.set_bit(bit, true)
 903         }
 904
 905         fn set_bit(&mut self, bit: usize, custom: bool) -> Result<(), ()> {
 906                 let byte_offset = bit / 8;
 907                 let mask = 1 << (bit - 8 * byte_offset);
 908                 if byte_offset < T::KNOWN_FEATURE_MASK.len() && custom {
 909                         if (T::KNOWN_FEATURE_MASK[byte_offset] & mask) != 0 {
 910                                 return Err(());
 911                         }
 912                 }
 913
 914                 if self.flags.len() <= byte_offset {
 915                         self.flags.resize(byte_offset + 1, 0u8);
 916                 }
 917
 918                 self.flags[byte_offset] |= mask;
 919
 920                 Ok(())
 921         }
 922 }
 923
 924 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 925         #[cfg(test)]
 926         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 927                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 928                 self
 929         }
 930 }
 931
 932 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 933         #[cfg(test)]
 934         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 935                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 936                 self
 937         }
 938 }
 939
 940 impl<T: sealed::Wumbo> Features<T> {
 941         #[cfg(test)]
 942         pub(crate) fn clear_wumbo(mut self) -> Self {
 943                 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
 944                 self
 945         }
 946 }
 947
 948 impl<T: sealed::SCIDPrivacy> Features<T> {
 949         pub(crate) fn clear_scid_privacy(&mut self) {
 950                 <T as sealed::SCIDPrivacy>::clear_bits(&mut self.flags);
 951         }
 952 }
 953
 954 impl<T: sealed::AnchorsZeroFeeHtlcTx> Features<T> {
 955         pub(crate) fn clear_anchors_zero_fee_htlc_tx(&mut self) {
 956                 <T as sealed::AnchorsZeroFeeHtlcTx>::clear_bits(&mut self.flags);
 957         }
 958 }
 959
 960 impl<T: sealed::RouteBlinding> Features<T> {
 961         #[cfg(test)]
 962         pub(crate) fn clear_route_blinding(&mut self) {
 963                 <T as sealed::RouteBlinding>::clear_bits(&mut self.flags);
 964         }
 965 }
 966
 967 #[cfg(test)]
 968 impl<T: sealed::UnknownFeature> Features<T> {
 969         pub(crate) fn unknown() -> Self {
 970                 let mut features = Self::empty();
 971                 features.set_unknown_feature_required();
 972                 features
 973         }
 974 }
 975
 976 macro_rules! impl_feature_len_prefixed_write {
 977         ($features: ident) => {
 978                 impl Writeable for $features {
 979                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 980                                 (self.flags.len() as u16).write(w)?;
 981                                 self.write_be(w)
 982                         }
 983                 }
 984                 impl Readable for $features {
 985                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 986                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
 987                         }
 988                 }
 989         }
 990 }
 991 impl_feature_len_prefixed_write!(InitFeatures);
 992 impl_feature_len_prefixed_write!(ChannelFeatures);
 993 impl_feature_len_prefixed_write!(NodeFeatures);
 994 impl_feature_len_prefixed_write!(Bolt11InvoiceFeatures);
 995 impl_feature_len_prefixed_write!(Bolt12InvoiceFeatures);
 996 impl_feature_len_prefixed_write!(BlindedHopFeatures);
 997
 998 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
 999 macro_rules! impl_feature_tlv_write {
1000         ($features: ident) => {
1001                 impl Writeable for $features {
1002                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
1003                                 WithoutLength(self).write(w)
1004                         }
1005                 }
1006                 impl Readable for $features {
1007                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
1008                                 Ok(WithoutLength::<Self>::read(r)?.0)
1009                         }
1010                 }
1011         }
1012 }
1013
1014 impl_feature_tlv_write!(ChannelTypeFeatures);
1015
1016 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
1017 // requires a length but the former does not.
1018
1019 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
1020         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
1021                 self.0.write_be(w)
1022         }
1023 }
1024
1025 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
1026         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
1027                 let v = io_extras::read_to_end(r)?;
1028                 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
1029         }
1030 }
1031
1032 pub(crate) fn unset_features_mask_at_position<T: sealed::Context>(other: &Features<T>, index: usize) -> u8 {
1033         if index < other.flags.len() {
1034                 // Form a mask similar to !T::KNOWN_FEATURE_MASK only for `other`
1035                 !(other.flags[index]
1036                         | ((other.flags[index] >> 1) & ANY_REQUIRED_FEATURES_MASK)
1037                         | ((other.flags[index] << 1) & ANY_OPTIONAL_FEATURES_MASK))
1038         } else {
1039                 0b11_11_11_11
1040         }
1041 }
1042
1043 #[cfg(test)]
1044 mod tests {
1045         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, Bolt11InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
1046         use bech32::{Base32Len, FromBase32, ToBase32, u5};
1047         use crate::util::ser::{Readable, WithoutLength, Writeable};
1048
1049         #[test]
1050         fn sanity_test_unknown_bits() {
1051                 let features = ChannelFeatures::empty();
1052                 assert!(!features.requires_unknown_bits());
1053                 assert!(!features.supports_unknown_bits());
1054
1055                 let mut features = ChannelFeatures::empty();
1056                 features.set_unknown_feature_required();
1057                 assert!(features.requires_unknown_bits());
1058                 assert!(features.supports_unknown_bits());
1059                 assert_eq!(features.required_unknown_bits_from(&ChannelFeatures::empty()), vec![123456788]);
1060
1061                 let mut features = ChannelFeatures::empty();
1062                 features.set_unknown_feature_optional();
1063                 assert!(!features.requires_unknown_bits());
1064                 assert!(features.supports_unknown_bits());
1065                 assert_eq!(features.required_unknown_bits_from(&ChannelFeatures::empty()), vec![]);
1066
1067                 let mut features = ChannelFeatures::empty();
1068                 features.set_unknown_feature_required();
1069                 features.set_custom_bit(123456786).unwrap();
1070                 assert!(features.requires_unknown_bits());
1071                 assert!(features.supports_unknown_bits());
1072                 assert_eq!(features.required_unknown_bits_from(&ChannelFeatures::empty()), vec![123456786, 123456788]);
1073
1074                 let mut limiter = ChannelFeatures::empty();
1075                 limiter.set_unknown_feature_optional();
1076                 assert_eq!(features.required_unknown_bits_from(&limiter), vec![123456786]);
1077         }
1078
1079         #[test]
1080         fn requires_unknown_bits_from() {
1081                 let mut features1 = InitFeatures::empty();
1082                 let mut features2 = InitFeatures::empty();
1083                 assert!(!features1.requires_unknown_bits_from(&features2));
1084                 assert!(!features2.requires_unknown_bits_from(&features1));
1085
1086                 features1.set_data_loss_protect_required();
1087                 assert!(features1.requires_unknown_bits_from(&features2));
1088                 assert!(!features2.requires_unknown_bits_from(&features1));
1089
1090                 features2.set_data_loss_protect_optional();
1091                 assert!(!features1.requires_unknown_bits_from(&features2));
1092                 assert!(!features2.requires_unknown_bits_from(&features1));
1093
1094                 features2.set_gossip_queries_required();
1095                 assert!(!features1.requires_unknown_bits_from(&features2));
1096                 assert!(features2.requires_unknown_bits_from(&features1));
1097
1098                 features1.set_gossip_queries_optional();
1099                 assert!(!features1.requires_unknown_bits_from(&features2));
1100                 assert!(!features2.requires_unknown_bits_from(&features1));
1101
1102                 features1.set_variable_length_onion_required();
1103                 assert!(features1.requires_unknown_bits_from(&features2));
1104                 assert!(!features2.requires_unknown_bits_from(&features1));
1105
1106                 features2.set_variable_length_onion_optional();
1107                 assert!(!features1.requires_unknown_bits_from(&features2));
1108                 assert!(!features2.requires_unknown_bits_from(&features1));
1109
1110                 features1.set_basic_mpp_required();
1111                 features2.set_wumbo_required();
1112                 assert!(features1.requires_unknown_bits_from(&features2));
1113                 assert!(features2.requires_unknown_bits_from(&features1));
1114         }
1115
1116         #[test]
1117         fn convert_to_context_with_relevant_flags() {
1118                 let mut init_features = InitFeatures::empty();
1119                 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
1120                 // converted as it's only relevant in an init context).
1121                 init_features.set_initial_routing_sync_required();
1122                 init_features.set_data_loss_protect_required();
1123                 init_features.set_variable_length_onion_required();
1124                 init_features.set_static_remote_key_required();
1125                 init_features.set_payment_secret_required();
1126                 init_features.set_basic_mpp_optional();
1127                 init_features.set_wumbo_optional();
1128                 init_features.set_anchors_zero_fee_htlc_tx_optional();
1129                 init_features.set_route_blinding_optional();
1130                 init_features.set_shutdown_any_segwit_optional();
1131                 init_features.set_onion_messages_optional();
1132                 init_features.set_channel_type_optional();
1133                 init_features.set_scid_privacy_optional();
1134                 init_features.set_zero_conf_optional();
1135
1136                 assert!(init_features.initial_routing_sync());
1137                 assert!(!init_features.supports_upfront_shutdown_script());
1138                 assert!(!init_features.supports_gossip_queries());
1139
1140                 let node_features: NodeFeatures = init_features.to_context();
1141                 {
1142                         // Check that the flags are as expected:
1143                         // - option_data_loss_protect (req)
1144                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
1145                         // - basic_mpp | wumbo | option_anchors_zero_fee_htlc_tx
1146                         // - option_route_blinding | opt_shutdown_anysegwit
1147                         // - onion_messages
1148                         // - option_channel_type | option_scid_alias
1149                         // - option_zeroconf
1150                         assert_eq!(node_features.flags.len(), 7);
1151                         assert_eq!(node_features.flags[0], 0b00000001);
1152                         assert_eq!(node_features.flags[1], 0b01010001);
1153                         assert_eq!(node_features.flags[2], 0b10001010);
1154                         assert_eq!(node_features.flags[3], 0b00001010);
1155                         assert_eq!(node_features.flags[4], 0b10000000);
1156                         assert_eq!(node_features.flags[5], 0b10100000);
1157                         assert_eq!(node_features.flags[6], 0b00001000);
1158                 }
1159
1160                 // Check that cleared flags are kept blank when converting back:
1161                 // - initial_routing_sync was not applicable to NodeContext
1162                 // - upfront_shutdown_script was cleared before converting
1163                 // - gossip_queries was cleared before converting
1164                 let features: InitFeatures = node_features.to_context_internal();
1165                 assert!(!features.initial_routing_sync());
1166                 assert!(!features.supports_upfront_shutdown_script());
1167                 assert!(!init_features.supports_gossip_queries());
1168         }
1169
1170         #[test]
1171         fn convert_to_context_with_unknown_flags() {
1172                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
1173                 assert!(<sealed::ChannelContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
1174                         <sealed::Bolt11InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
1175                 let mut channel_features = ChannelFeatures::empty();
1176                 channel_features.set_unknown_feature_optional();
1177                 assert!(channel_features.supports_unknown_bits());
1178                 let invoice_features: Bolt11InvoiceFeatures = channel_features.to_context_internal();
1179                 assert!(!invoice_features.supports_unknown_bits());
1180         }
1181
1182         #[test]
1183         fn set_feature_bits() {
1184                 let mut features = Bolt11InvoiceFeatures::empty();
1185                 features.set_basic_mpp_optional();
1186                 features.set_payment_secret_required();
1187                 assert!(features.supports_basic_mpp());
1188                 assert!(!features.requires_basic_mpp());
1189                 assert!(features.requires_payment_secret());
1190                 assert!(features.supports_payment_secret());
1191
1192                 // Set flags manually
1193                 let mut features = NodeFeatures::empty();
1194                 assert!(features.set_optional_feature_bit(55).is_ok());
1195                 assert!(features.supports_keysend());
1196                 assert!(features.set_optional_feature_bit(255).is_ok());
1197                 assert!(features.set_required_feature_bit(256).is_err());
1198         }
1199
1200         #[test]
1201         fn set_custom_bits() {
1202                 let mut features = Bolt11InvoiceFeatures::empty();
1203                 features.set_variable_length_onion_optional();
1204                 assert_eq!(features.flags[1], 0b00000010);
1205
1206                 assert!(features.set_optional_custom_bit(255).is_err());
1207                 assert!(features.set_required_custom_bit(256).is_ok());
1208                 assert!(features.set_required_custom_bit(258).is_ok());
1209                 assert_eq!(features.flags[31], 0b00000000);
1210                 assert_eq!(features.flags[32], 0b00000101);
1211
1212                 let known_bit = <sealed::Bolt11InvoiceContext as sealed::PaymentSecret>::EVEN_BIT;
1213                 let byte_offset = <sealed::Bolt11InvoiceContext as sealed::PaymentSecret>::BYTE_OFFSET;
1214                 assert_eq!(byte_offset, 1);
1215                 assert_eq!(features.flags[byte_offset], 0b00000010);
1216                 assert!(features.set_required_custom_bit(known_bit).is_err());
1217                 assert_eq!(features.flags[byte_offset], 0b00000010);
1218
1219                 let mut features = Bolt11InvoiceFeatures::empty();
1220                 assert!(features.set_optional_custom_bit(256).is_ok());
1221                 assert!(features.set_optional_custom_bit(259).is_ok());
1222                 assert_eq!(features.flags[32], 0b00001010);
1223
1224                 let mut features = Bolt11InvoiceFeatures::empty();
1225                 assert!(features.set_required_custom_bit(257).is_ok());
1226                 assert!(features.set_required_custom_bit(258).is_ok());
1227                 assert_eq!(features.flags[32], 0b00000101);
1228         }
1229
1230         #[test]
1231         fn encodes_features_without_length() {
1232                 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1233                 assert_eq!(features.flags.len(), 8);
1234
1235                 let mut serialized_features = Vec::new();
1236                 WithoutLength(&features).write(&mut serialized_features).unwrap();
1237                 assert_eq!(serialized_features.len(), 8);
1238
1239                 let deserialized_features =
1240                         WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
1241                 assert_eq!(features, deserialized_features);
1242         }
1243
1244         #[test]
1245         fn invoice_features_encoding() {
1246                 let features_as_u5s = vec![
1247                         u5::try_from_u8(6).unwrap(),
1248                         u5::try_from_u8(10).unwrap(),
1249                         u5::try_from_u8(25).unwrap(),
1250                         u5::try_from_u8(1).unwrap(),
1251                         u5::try_from_u8(10).unwrap(),
1252                         u5::try_from_u8(0).unwrap(),
1253                         u5::try_from_u8(20).unwrap(),
1254                         u5::try_from_u8(2).unwrap(),
1255                         u5::try_from_u8(0).unwrap(),
1256                         u5::try_from_u8(6).unwrap(),
1257                         u5::try_from_u8(0).unwrap(),
1258                         u5::try_from_u8(16).unwrap(),
1259                         u5::try_from_u8(1).unwrap(),
1260                 ];
1261                 let features = Bolt11InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1262
1263                 // Test length calculation.
1264                 assert_eq!(features.base32_len(), 13);
1265
1266                 // Test serialization.
1267                 let features_serialized = features.to_base32();
1268                 assert_eq!(features_as_u5s, features_serialized);
1269
1270                 // Test deserialization.
1271                 let features_deserialized = Bolt11InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
1272                 assert_eq!(features, features_deserialized);
1273         }
1274
1275         #[test]
1276         fn test_channel_type_mapping() {
1277                 // If we map an Bolt11InvoiceFeatures with StaticRemoteKey optional, it should map into a
1278                 // required-StaticRemoteKey ChannelTypeFeatures.
1279                 let mut init_features = InitFeatures::empty();
1280                 init_features.set_static_remote_key_optional();
1281                 let converted_features = ChannelTypeFeatures::from_init(&init_features);
1282                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
1283                 assert!(!converted_features.supports_any_optional_bits());
1284                 assert!(converted_features.requires_static_remote_key());
1285         }
1286
1287         #[test]
1288         #[cfg(feature = "std")]
1289         fn test_excess_zero_bytes_ignored() {
1290                 // Checks that `Hash` and `PartialEq` ignore excess zero bytes, which may appear due to
1291                 // feature conversion or because a peer serialized their feature poorly.
1292                 use std::collections::hash_map::DefaultHasher;
1293                 use std::hash::{Hash, Hasher};
1294
1295                 let mut zerod_features = InitFeatures::empty();
1296                 zerod_features.flags = vec![0];
1297                 let empty_features = InitFeatures::empty();
1298                 assert!(empty_features.flags.is_empty());
1299
1300                 assert_eq!(zerod_features, empty_features);
1301
1302                 let mut zerod_hash = DefaultHasher::new();
1303                 zerod_features.hash(&mut zerod_hash);
1304                 let mut empty_hash = DefaultHasher::new();
1305                 empty_features.hash(&mut empty_hash);
1306                 assert_eq!(zerod_hash.finish(), empty_hash.finish());
1307         }
1308 }