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

   1 // This file is Copyright its original authors, visible in version control
   2 // history.
   3 //
   4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
   5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
   7 // You may not use this file except in accordance with one or both of these
   8 // licenses.
   9
  10 //! Feature flag definitions for the Lightning protocol according to [BOLT #9].
  11 //!
  12 //! Lightning nodes advertise a supported set of operation through feature flags. Features are
  13 //! applicable for a specific context as indicated in some [messages]. [`Features`] encapsulates
  14 //! behavior for specifying and checking feature flags for a particular context. Each feature is
  15 //! defined internally by a trait specifying the corresponding flags (i.e., even and odd bits).
  16 //!
  17 //! Whether a feature is considered "known" or "unknown" is relative to the implementation, whereas
  18 //! the term "supports" is used in reference to a particular set of [`Features`]. That is, a node
  19 //! supports a feature if it advertises the feature (as either required or optional) to its peers.
  20 //! And the implementation can interpret a feature if the feature is known to it.
  21 //!
  22 //! The following features are currently required in the LDK:
  23 //! - `VariableLengthOnion` - requires/supports variable-length routing onion payloads
  24 //!     (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md) for more information).
  25 //! - `StaticRemoteKey` - requires/supports static key for remote output
  26 //!     (see [BOLT-3](https://github.com/lightning/bolts/blob/master/03-transactions.md) for more information).
  27 //!
  28 //! The following features are currently supported in the LDK:
  29 //! - `DataLossProtect` - requires/supports that a node which has somehow fallen behind, e.g., has been restored from an old backup,
  30 //!     can detect that it has fallen behind
  31 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  32 //! - `InitialRoutingSync` - requires/supports that the sending node needs a complete routing information dump
  33 //!     (see [BOLT-7](https://github.com/lightning/bolts/blob/master/07-routing-gossip.md#initial-sync) for more information).
  34 //! - `UpfrontShutdownScript` - commits to a shutdown scriptpubkey when opening a channel
  35 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#the-open_channel-message) for more information).
  36 //! - `GossipQueries` - requires/supports more sophisticated gossip control
  37 //!     (see [BOLT-7](https://github.com/lightning/bolts/blob/master/07-routing-gossip.md) for more information).
  38 //! - `PaymentSecret` - requires/supports that a node supports payment_secret field
  39 //!     (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md) for more information).
  40 //! - `BasicMPP` - requires/supports that a node can receive basic multi-part payments
  41 //!     (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md#basic-multi-part-payments) for more information).
  42 //! - `Wumbo` - requires/supports that a node create large channels. Called `option_support_large_channel` in the spec.
  43 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#the-open_channel-message) for more information).
  44 //! - `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 //!
  70 //! LDK knows about the following features, but does not support them:
  71 //! - `AnchorsNonzeroFeeHtlcTx` - the initial version of anchor outputs, which was later found to be
  72 //!     vulnerable (see this
  73 //!     [mailing list post](https://lists.linuxfoundation.org/pipermail/lightning-dev/2020-September/002796.html)
  74 //!     for more information).
  75 //!
  76 //! [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
  77 //! [messages]: crate::ln::msgs
  78
  79 use crate::{io, io_extras};
  80 use crate::prelude::*;
  81 use core::{cmp, fmt};
  82 use core::borrow::Borrow;
  83 use core::hash::{Hash, Hasher};
  84 use core::marker::PhantomData;
  85
  86 use bitcoin::bech32;
  87 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
  88 use crate::ln::msgs::DecodeError;
  89 use crate::util::ser::{Readable, WithoutLength, Writeable, Writer};
  90
  91 mod sealed {
  92         use crate::prelude::*;
  93         use crate::ln::features::Features;
  94
  95         /// The context in which [`Features`] are applicable. Defines which features are known to the
  96         /// implementation, though specification of them as required or optional is up to the code
  97         /// constructing a features object.
  98         pub trait Context {
  99                 /// Bitmask for selecting features that are known to the implementation.
 100                 const KNOWN_FEATURE_MASK: &'static [u8];
 101         }
 102
 103         /// Defines a [`Context`] by stating which features it requires and which are optional. Features
 104         /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
 105         /// feature identifiers.
 106         macro_rules! define_context {
 107                 ($context: ident, [$( $( $known_feature: ident )|*, )*]) => {
 108                         #[derive(Eq, PartialEq)]
 109                         pub struct $context {}
 110
 111                         impl Context for $context {
 112                                 const KNOWN_FEATURE_MASK: &'static [u8] = &[
 113                                         $(
 114                                                 0b00_00_00_00 $(|
 115                                                         <Self as $known_feature>::REQUIRED_MASK |
 116                                                         <Self as $known_feature>::OPTIONAL_MASK)*,
 117                                         )*
 118                                 ];
 119                         }
 120
 121                         impl alloc::fmt::Display for Features<$context> {
 122                                 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
 123                                         $(
 124                                                 $(
 125                                                         fmt.write_fmt(format_args!("{}: {}, ", stringify!($known_feature),
 126                                                                 if <$context as $known_feature>::requires_feature(&self.flags) { "required" }
 127                                                                 else if <$context as $known_feature>::supports_feature(&self.flags) { "supported" }
 128                                                                 else { "not supported" }))?;
 129                                                 )*
 130                                                 {} // Rust gets mad if we only have a $()* block here, so add a dummy {}
 131                                         )*
 132                                         fmt.write_fmt(format_args!("unknown flags: {}",
 133                                                 if self.requires_unknown_bits() { "required" }
 134                                                 else if self.supports_unknown_bits() { "supported" } else { "none" }))
 135                                 }
 136                         }
 137                 };
 138         }
 139
 140         define_context!(InitContext, [
 141                 // Byte 0
 142                 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
 143                 // Byte 1
 144                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 145                 // Byte 2
 146                 BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
 147                 // Byte 3
 148                 RouteBlinding | ShutdownAnySegwit | Taproot,
 149                 // Byte 4
 150                 OnionMessages,
 151                 // Byte 5
 152                 ChannelType | SCIDPrivacy,
 153                 // Byte 6
 154                 ZeroConf,
 155         ]);
 156         define_context!(NodeContext, [
 157                 // Byte 0
 158                 DataLossProtect | UpfrontShutdownScript | GossipQueries,
 159                 // Byte 1
 160                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 161                 // Byte 2
 162                 BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
 163                 // Byte 3
 164                 RouteBlinding | ShutdownAnySegwit | Taproot,
 165                 // Byte 4
 166                 OnionMessages,
 167                 // Byte 5
 168                 ChannelType | SCIDPrivacy,
 169                 // Byte 6
 170                 ZeroConf | Keysend,
 171         ]);
 172         define_context!(ChannelContext, []);
 173         define_context!(Bolt11InvoiceContext, [
 174                 // Byte 0
 175                 ,
 176                 // Byte 1
 177                 VariableLengthOnion | PaymentSecret,
 178                 // Byte 2
 179                 BasicMPP,
 180                 // Byte 3
 181                 ,
 182                 // Byte 4
 183                 ,
 184                 // Byte 5
 185                 ,
 186                 // Byte 6
 187                 PaymentMetadata,
 188         ]);
 189         define_context!(OfferContext, []);
 190         define_context!(InvoiceRequestContext, []);
 191         define_context!(Bolt12InvoiceContext, [
 192                 // Byte 0
 193                 ,
 194                 // Byte 1
 195                 ,
 196                 // Byte 2
 197                 BasicMPP,
 198         ]);
 199         define_context!(BlindedHopContext, []);
 200         // This isn't a "real" feature context, and is only used in the channel_type field in an
 201         // `OpenChannel` message.
 202         define_context!(ChannelTypeContext, [
 203                 // Byte 0
 204                 ,
 205                 // Byte 1
 206                 StaticRemoteKey,
 207                 // Byte 2
 208                 AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
 209                 // Byte 3
 210                 Taproot,
 211                 // Byte 4
 212                 ,
 213                 // Byte 5
 214                 SCIDPrivacy,
 215                 // Byte 6
 216                 ZeroConf,
 217         ]);
 218
 219         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 220         /// useful for manipulating feature flags.
 221         macro_rules! define_feature {
 222                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 223                  $required_setter: ident, $supported_getter: ident) => {
 224                         #[doc = $doc]
 225                         ///
 226                         /// See [BOLT #9] for details.
 227                         ///
 228                         /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
 229                         pub trait $feature: Context {
 230                                 /// The bit used to signify that the feature is required.
 231                                 const EVEN_BIT: usize = $odd_bit - 1;
 232
 233                                 /// The bit used to signify that the feature is optional.
 234                                 const ODD_BIT: usize = $odd_bit;
 235
 236                                 /// Assertion that [`EVEN_BIT`] is actually even.
 237                                 ///
 238                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 239                                 const ASSERT_EVEN_BIT_PARITY: usize;
 240
 241                                 /// Assertion that [`ODD_BIT`] is actually odd.
 242                                 ///
 243                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 244                                 const ASSERT_ODD_BIT_PARITY: usize;
 245
 246                                 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
 247                                 ///
 248                                 /// [`KNOWN_FEATURE_MASK`]: Context::KNOWN_FEATURE_MASK
 249                                 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
 250                                 const ASSERT_BITS_IN_MASK: u8;
 251
 252                                 /// The byte where the feature is set.
 253                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 254
 255                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 256                                 ///
 257                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 258                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 259
 260                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 261                                 ///
 262                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 263                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 264
 265                                 /// Returns whether the feature is required by the given flags.
 266                                 #[inline]
 267                                 fn requires_feature(flags: &Vec<u8>) -> bool {
 268                                         flags.len() > Self::BYTE_OFFSET &&
 269                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
 270                                 }
 271
 272                                 /// Returns whether the feature is supported by the given flags.
 273                                 #[inline]
 274                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 275                                         flags.len() > Self::BYTE_OFFSET &&
 276                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 277                                 }
 278
 279                                 /// Sets the feature's required (even) bit in the given flags.
 280                                 #[inline]
 281                                 fn set_required_bit(flags: &mut Vec<u8>) {
 282                                         if flags.len() <= Self::BYTE_OFFSET {
 283                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 284                                         }
 285
 286                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
 287                                         flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 288                                 }
 289
 290                                 /// Sets the feature's optional (odd) bit in the given flags.
 291                                 #[inline]
 292                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 293                                         if flags.len() <= Self::BYTE_OFFSET {
 294                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 295                                         }
 296
 297                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 298                                 }
 299
 300                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 301                                 /// flags.
 302                                 #[inline]
 303                                 fn clear_bits(flags: &mut Vec<u8>) {
 304                                         if flags.len() > Self::BYTE_OFFSET {
 305                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 306                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 307                                         }
 308
 309                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 310                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 311                                         flags.resize(size, 0u8);
 312                                 }
 313                         }
 314
 315                         impl <T: $feature> Features<T> {
 316                                 /// Set this feature as optional.
 317                                 pub fn $optional_setter(&mut self) {
 318                                         <T as $feature>::set_optional_bit(&mut self.flags);
 319                                 }
 320
 321                                 /// Set this feature as required.
 322                                 pub fn $required_setter(&mut self) {
 323                                         <T as $feature>::set_required_bit(&mut self.flags);
 324                                 }
 325
 326                                 /// Checks if this feature is supported.
 327                                 pub fn $supported_getter(&self) -> bool {
 328                                         <T as $feature>::supports_feature(&self.flags)
 329                                 }
 330                         }
 331
 332                         $(
 333                                 impl $feature for $context {
 334                                         // EVEN_BIT % 2 == 0
 335                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 336
 337                                         // ODD_BIT % 2 == 1
 338                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 339
 340                                         // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
 341                                         #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
 342                                         const ASSERT_BITS_IN_MASK: u8 =
 343                                                 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
 344                                                  >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
 345                                 }
 346                         )*
 347                 };
 348                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 349                  $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
 350                         define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
 351                         impl <T: $feature> Features<T> {
 352                                 /// Checks if this feature is required.
 353                                 pub fn $required_getter(&self) -> bool {
 354                                         <T as $feature>::requires_feature(&self.flags)
 355                                 }
 356                         }
 357                 }
 358         }
 359
 360         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 361                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 362                 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
 363         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 364         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 365                 set_initial_routing_sync_optional, set_initial_routing_sync_required,
 366                 initial_routing_sync);
 367         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 368                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 369                 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
 370                 requires_upfront_shutdown_script);
 371         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 372                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
 373                 supports_gossip_queries, requires_gossip_queries);
 374         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, Bolt11InvoiceContext],
 375                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 376                 set_variable_length_onion_required, supports_variable_length_onion,
 377                 requires_variable_length_onion);
 378         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
 379                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 380                 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
 381         define_feature!(15, PaymentSecret, [InitContext, NodeContext, Bolt11InvoiceContext],
 382                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
 383                 supports_payment_secret, requires_payment_secret);
 384         define_feature!(17, BasicMPP, [InitContext, NodeContext, Bolt11InvoiceContext, Bolt12InvoiceContext],
 385                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
 386                 supports_basic_mpp, requires_basic_mpp);
 387         define_feature!(19, Wumbo, [InitContext, NodeContext],
 388                 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
 389                 supports_wumbo, requires_wumbo);
 390         define_feature!(21, AnchorsNonzeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
 391                 "Feature flags for `option_anchors_nonzero_fee_htlc_tx`.", set_anchors_nonzero_fee_htlc_tx_optional,
 392                 set_anchors_nonzero_fee_htlc_tx_required, supports_anchors_nonzero_fee_htlc_tx, requires_anchors_nonzero_fee_htlc_tx);
 393         define_feature!(23, AnchorsZeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
 394                 "Feature flags for `option_anchors_zero_fee_htlc_tx`.", set_anchors_zero_fee_htlc_tx_optional,
 395                 set_anchors_zero_fee_htlc_tx_required, supports_anchors_zero_fee_htlc_tx, requires_anchors_zero_fee_htlc_tx);
 396         define_feature!(25, RouteBlinding, [InitContext, NodeContext],
 397                 "Feature flags for `option_route_blinding`.", set_route_blinding_optional,
 398                 set_route_blinding_required, supports_route_blinding, requires_route_blinding);
 399         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 400                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 401                 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
 402         define_feature!(31, Taproot, [InitContext, NodeContext, ChannelTypeContext],
 403                 "Feature flags for `option_taproot`.", set_taproot_optional,
 404                 set_taproot_required, supports_taproot, requires_taproot);
 405         define_feature!(39, OnionMessages, [InitContext, NodeContext],
 406                 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
 407                 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
 408         define_feature!(45, ChannelType, [InitContext, NodeContext],
 409                 "Feature flags for `option_channel_type`.", set_channel_type_optional,
 410                 set_channel_type_required, supports_channel_type, requires_channel_type);
 411         define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
 412                 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
 413                 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
 414         define_feature!(49, PaymentMetadata, [Bolt11InvoiceContext],
 415                 "Feature flags for payment metadata in invoices.", set_payment_metadata_optional,
 416                 set_payment_metadata_required, supports_payment_metadata, requires_payment_metadata);
 417         define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
 418                 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
 419                 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
 420         define_feature!(55, Keysend, [NodeContext],
 421                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
 422                 supports_keysend, requires_keysend);
 423         // Note: update the module-level docs when a new feature bit is added!
 424
 425         #[cfg(test)]
 426         define_feature!(123456789, UnknownFeature,
 427                 [NodeContext, ChannelContext, Bolt11InvoiceContext, OfferContext, InvoiceRequestContext, Bolt12InvoiceContext, BlindedHopContext],
 428                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 429                 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
 430 }
 431
 432 /// Tracks the set of features which a node implements, templated by the context in which it
 433 /// appears.
 434 ///
 435 /// This is not exported to bindings users as we map the concrete feature types below directly instead
 436 #[derive(Eq)]
 437 pub struct Features<T: sealed::Context> {
 438         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 439         flags: Vec<u8>,
 440         mark: PhantomData<T>,
 441 }
 442
 443 impl<T: sealed::Context, Rhs: Borrow<Self>> core::ops::BitOrAssign<Rhs> for Features<T> {
 444         fn bitor_assign(&mut self, rhs: Rhs) {
 445                 let total_feature_len = cmp::max(self.flags.len(), rhs.borrow().flags.len());
 446                 self.flags.resize(total_feature_len, 0u8);
 447                 for (byte, rhs_byte) in self.flags.iter_mut().zip(rhs.borrow().flags.iter()) {
 448                         *byte |= *rhs_byte;
 449                 }
 450         }
 451 }
 452
 453 impl<T: sealed::Context> core::ops::BitOr for Features<T> {
 454         type Output = Self;
 455
 456         fn bitor(mut self, o: Self) -> Self {
 457                 self |= o;
 458                 self
 459         }
 460 }
 461
 462 impl<T: sealed::Context> Clone for Features<T> {
 463         fn clone(&self) -> Self {
 464                 Self {
 465                         flags: self.flags.clone(),
 466                         mark: PhantomData,
 467                 }
 468         }
 469 }
 470 impl<T: sealed::Context> Hash for Features<T> {
 471         fn hash<H: Hasher>(&self, hasher: &mut H) {
 472                 let mut nonzero_flags = &self.flags[..];
 473                 while nonzero_flags.last() == Some(&0) {
 474                         nonzero_flags = &nonzero_flags[..nonzero_flags.len() - 1];
 475                 }
 476                 nonzero_flags.hash(hasher);
 477         }
 478 }
 479 impl<T: sealed::Context> PartialEq for Features<T> {
 480         fn eq(&self, o: &Self) -> bool {
 481                 let mut o_iter = o.flags.iter();
 482                 let mut self_iter = self.flags.iter();
 483                 loop {
 484                         match (o_iter.next(), self_iter.next()) {
 485                                 (Some(o), Some(us)) => if o != us { return false },
 486                                 (Some(b), None) | (None, Some(b)) => if *b != 0 { return false },
 487                                 (None, None) => return true,
 488                         }
 489                 }
 490         }
 491 }
 492 impl<T: sealed::Context> PartialOrd for Features<T> {
 493         fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
 494                 self.flags.partial_cmp(&other.flags)
 495         }
 496 }
 497 impl<T: sealed::Context + Eq> Ord for Features<T> {
 498         fn cmp(&self, other: &Self) -> cmp::Ordering {
 499                 self.flags.cmp(&other.flags)
 500         }
 501 }
 502 impl<T: sealed::Context> fmt::Debug for Features<T> {
 503         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 504                 self.flags.fmt(fmt)
 505         }
 506 }
 507
 508 /// Features used within an `init` message.
 509 pub type InitFeatures = Features<sealed::InitContext>;
 510 /// Features used within a `node_announcement` message.
 511 pub type NodeFeatures = Features<sealed::NodeContext>;
 512 /// Features used within a `channel_announcement` message.
 513 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 514 /// Features used within an invoice.
 515 pub type Bolt11InvoiceFeatures = Features<sealed::Bolt11InvoiceContext>;
 516 /// Features used within an `offer`.
 517 pub type OfferFeatures = Features<sealed::OfferContext>;
 518 /// Features used within an `invoice_request`.
 519 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
 520 /// Features used within an `invoice`.
 521 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
 522 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
 523 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
 524
 525 /// Features used within the channel_type field in an OpenChannel message.
 526 ///
 527 /// A channel is always of some known "type", describing the transaction formats used and the exact
 528 /// semantics of our interaction with our peer.
 529 ///
 530 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
 531 /// the counterparty, only required features are allowed here.
 532 ///
 533 /// This is serialized differently from other feature types - it is not prefixed by a length, and
 534 /// thus must only appear inside a TLV where its length is known in advance.
 535 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
 536
 537 impl InitFeatures {
 538         /// Writes all features present up to, and including, 13.
 539         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 540                 let len = cmp::min(2, self.flags.len());
 541                 (len as u16).write(w)?;
 542                 for i in (0..len).rev() {
 543                         if i == 0 {
 544                                 self.flags[i].write(w)?;
 545                         } else {
 546                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 547                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 548                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 549                         }
 550                 }
 551                 Ok(())
 552         }
 553
 554         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 555         /// are included in the result.
 556         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 557                 self.to_context_internal()
 558         }
 559 }
 560
 561 impl Bolt11InvoiceFeatures {
 562         /// Converts `Bolt11InvoiceFeatures` to `Features<C>`. Only known `Bolt11InvoiceFeatures` relevant to
 563         /// context `C` are included in the result.
 564         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 565                 self.to_context_internal()
 566         }
 567
 568         /// Getting a route for a keysend payment to a private node requires providing the payee's
 569         /// features (since they were not announced in a node announcement). However, keysend payments
 570         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 571         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
 572         /// `Bolt11InvoiceFeatures` for [`find_route`].
 573         ///
 574         /// MPP keysend is not widely supported yet, so we parameterize support to allow the user to
 575         /// choose whether their router should find multi-part routes.
 576         ///
 577         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
 578         /// [`find_route`]: crate::routing::router::find_route
 579         pub(crate) fn for_keysend(allow_mpp: bool) -> Bolt11InvoiceFeatures {
 580                 let mut res = Bolt11InvoiceFeatures::empty();
 581                 res.set_variable_length_onion_optional();
 582                 if allow_mpp {
 583                         res.set_basic_mpp_optional();
 584                 }
 585                 res
 586         }
 587 }
 588
 589 impl Bolt12InvoiceFeatures {
 590         /// Converts [`Bolt12InvoiceFeatures`] to [`Features<C>`]. Only known [`Bolt12InvoiceFeatures`]
 591         /// relevant to context `C` are included in the result.
 592         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 593                 self.to_context_internal()
 594         }
 595 }
 596
 597 impl ChannelTypeFeatures {
 598         // Maps the relevant `InitFeatures` to `ChannelTypeFeatures`. Any unknown features to
 599         // `ChannelTypeFeatures` are not included in the result.
 600         pub(crate) fn from_init(init: &InitFeatures) -> Self {
 601                 let mut ret = init.to_context_internal();
 602                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
 603                 // optional bits and then AND out the optional ones.
 604                 for byte in ret.flags.iter_mut() {
 605                         *byte |= (*byte & 0b10_10_10_10) >> 1;
 606                         *byte &= 0b01_01_01_01;
 607                 }
 608                 ret
 609         }
 610
 611         /// Constructs a ChannelTypeFeatures with only static_remotekey set
 612         pub(crate) fn only_static_remote_key() -> Self {
 613                 let mut ret = Self::empty();
 614                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 615                 ret
 616         }
 617
 618         /// Constructs a ChannelTypeFeatures with anchors support
 619         pub(crate) fn anchors_zero_htlc_fee_and_dependencies() -> Self {
 620                 let mut ret = Self::empty();
 621                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 622                 <sealed::ChannelTypeContext as sealed::AnchorsZeroFeeHtlcTx>::set_required_bit(&mut ret.flags);
 623                 ret
 624         }
 625 }
 626
 627 impl ToBase32 for Bolt11InvoiceFeatures {
 628         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 629                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 630                 // minus one before dividing
 631                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 632                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 633                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 634                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 635                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 636                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 637                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 638                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 639                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 640                         if new_u5_idx > 0 {
 641                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 642                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 643                         }
 644                         if new_u5_idx > 1 {
 645                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 646                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 647                         }
 648                 }
 649                 // Trim the highest feature bits.
 650                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 651                         res_u5s.remove(0);
 652                 }
 653                 writer.write(&res_u5s)
 654         }
 655 }
 656
 657 impl Base32Len for Bolt11InvoiceFeatures {
 658         fn base32_len(&self) -> usize {
 659                 self.to_base32().len()
 660         }
 661 }
 662
 663 impl FromBase32 for Bolt11InvoiceFeatures {
 664         type Err = bech32::Error;
 665
 666         fn from_base32(field_data: &[u5]) -> Result<Bolt11InvoiceFeatures, bech32::Error> {
 667                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 668                 // minus one before dividing
 669                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 670                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 671                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 672                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 673                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 674                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 675                         let chunk_u16 = chunk.to_u8() as u16;
 676                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 677                         if new_byte_idx != length_bytes - 1 {
 678                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 679                         }
 680                 }
 681                 // Trim the highest feature bits.
 682                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 683                         res_bytes.pop();
 684                 }
 685                 Ok(Bolt11InvoiceFeatures::from_le_bytes(res_bytes))
 686         }
 687 }
 688
 689 impl<T: sealed::Context> Features<T> {
 690         /// Create a blank Features with no features set
 691         pub fn empty() -> Self {
 692                 Features {
 693                         flags: Vec::new(),
 694                         mark: PhantomData,
 695                 }
 696         }
 697
 698         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 699         /// included in the result.
 700         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 701                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 702                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 703                 let mut flags = Vec::new();
 704                 for (i, byte) in self.flags.iter().enumerate() {
 705                         if i < from_byte_count && i < to_byte_count {
 706                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 707                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 708                                 flags.push(byte & from_known_features & to_known_features);
 709                         }
 710                 }
 711                 Features::<C> { flags, mark: PhantomData, }
 712         }
 713
 714         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 715         /// most on-the-wire encodings.
 716         ///
 717         /// This is not exported to bindings users as we don't support export across multiple T
 718         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 719                 Features {
 720                         flags,
 721                         mark: PhantomData,
 722                 }
 723         }
 724
 725         #[cfg(test)]
 726         /// Gets the underlying flags set, in LE.
 727         pub fn le_flags(&self) -> &Vec<u8> {
 728                 &self.flags
 729         }
 730
 731         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 732                 for f in self.flags.iter().rev() { // Swap back to big-endian
 733                         f.write(w)?;
 734                 }
 735                 Ok(())
 736         }
 737
 738         /// Create a [`Features`] given a set of flags, in big-endian. This is in byte order from
 739         /// most on-the-wire encodings.
 740         ///
 741         /// This is not exported to bindings users as we don't support export across multiple T
 742         pub fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
 743                 flags.reverse(); // Swap to little-endian
 744                 Self {
 745                         flags,
 746                         mark: PhantomData,
 747                 }
 748         }
 749
 750         pub(crate) fn supports_any_optional_bits(&self) -> bool {
 751                 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
 752         }
 753
 754         /// Returns true if this `Features` object contains required features unknown by `other`.
 755         pub fn requires_unknown_bits_from(&self, other: &Self) -> bool {
 756                 // Bitwise AND-ing with all even bits set except for known features will select required
 757                 // unknown features.
 758                 self.flags.iter().enumerate().any(|(i, &byte)| {
 759                         const REQUIRED_FEATURES: u8 = 0b01_01_01_01;
 760                         const OPTIONAL_FEATURES: u8 = 0b10_10_10_10;
 761                         let unknown_features = if i < other.flags.len() {
 762                                 // Form a mask similar to !T::KNOWN_FEATURE_MASK only for `other`
 763                                 !(other.flags[i]
 764                                         | ((other.flags[i] >> 1) & REQUIRED_FEATURES)
 765                                         | ((other.flags[i] << 1) & OPTIONAL_FEATURES))
 766                         } else {
 767                                 0b11_11_11_11
 768                         };
 769                         (byte & (REQUIRED_FEATURES & unknown_features)) != 0
 770                 })
 771         }
 772
 773         /// Returns true if this `Features` object contains unknown feature flags which are set as
 774         /// "required".
 775         pub fn requires_unknown_bits(&self) -> bool {
 776                 // Bitwise AND-ing with all even bits set except for known features will select required
 777                 // unknown features.
 778                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 779                 self.flags.iter().enumerate().any(|(i, &byte)| {
 780                         let required_features = 0b01_01_01_01;
 781                         let unknown_features = if i < byte_count {
 782                                 !T::KNOWN_FEATURE_MASK[i]
 783                         } else {
 784                                 0b11_11_11_11
 785                         };
 786                         (byte & (required_features & unknown_features)) != 0
 787                 })
 788         }
 789
 790         pub(crate) fn supports_unknown_bits(&self) -> bool {
 791                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 792                 // both required and optional unknown features.
 793                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 794                 self.flags.iter().enumerate().any(|(i, &byte)| {
 795                         let unknown_features = if i < byte_count {
 796                                 !T::KNOWN_FEATURE_MASK[i]
 797                         } else {
 798                                 0b11_11_11_11
 799                         };
 800                         (byte & unknown_features) != 0
 801                 })
 802         }
 803
 804         // Returns true if the features within `self` are a subset of the features within `other`.
 805         pub(crate) fn is_subset(&self, other: &Self) -> bool {
 806                 for (idx, byte) in self.flags.iter().enumerate() {
 807                         if let Some(other_byte) = other.flags.get(idx) {
 808                                 if byte & other_byte != *byte {
 809                                         // `self` has bits set that `other` doesn't.
 810                                         return false;
 811                                 }
 812                         } else {
 813                                 if *byte > 0 {
 814                                         // `self` has a non-zero byte that `other` doesn't.
 815                                         return false;
 816                                 }
 817                         }
 818                 }
 819                 true
 820         }
 821
 822         /// Sets a required feature bit. Errors if `bit` is outside the feature range as defined
 823         /// by [BOLT 9].
 824         ///
 825         /// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
 826         /// be set instead (i.e., `bit - 1`).
 827         ///
 828         /// [BOLT 9]: https://github.com/lightning/bolts/blob/master/09-features.md
 829         pub fn set_required_feature_bit(&mut self, bit: usize) -> Result<(), ()> {
 830                 self.set_feature_bit(bit - (bit % 2))
 831         }
 832
 833         /// Sets an optional feature bit. Errors if `bit` is outside the feature range as defined
 834         /// by [BOLT 9].
 835         ///
 836         /// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
 837         /// set instead (i.e., `bit + 1`).
 838         ///
 839         /// [BOLT 9]: https://github.com/lightning/bolts/blob/master/09-features.md
 840         pub fn set_optional_feature_bit(&mut self, bit: usize) -> Result<(), ()> {
 841                 self.set_feature_bit(bit + (1 - (bit % 2)))
 842         }
 843
 844         fn set_feature_bit(&mut self, bit: usize) -> Result<(), ()> {
 845                 if bit > 255 {
 846                         return Err(());
 847                 }
 848                 self.set_bit(bit, false)
 849         }
 850
 851         /// Sets a required custom feature bit. Errors if `bit` is outside the custom range as defined
 852         /// by [bLIP 2] or if it is a known `T` feature.
 853         ///
 854         /// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
 855         /// be set instead (i.e., `bit - 1`).
 856         ///
 857         /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
 858         pub fn set_required_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 859                 self.set_custom_bit(bit - (bit % 2))
 860         }
 861
 862         /// Sets an optional custom feature bit. Errors if `bit` is outside the custom range as defined
 863         /// by [bLIP 2] or if it is a known `T` feature.
 864         ///
 865         /// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
 866         /// set instead (i.e., `bit + 1`).
 867         ///
 868         /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
 869         pub fn set_optional_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 870                 self.set_custom_bit(bit + (1 - (bit % 2)))
 871         }
 872
 873         fn set_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 874                 if bit < 256 {
 875                         return Err(());
 876                 }
 877                 self.set_bit(bit, true)
 878         }
 879
 880         fn set_bit(&mut self, bit: usize, custom: bool) -> Result<(), ()> {
 881                 let byte_offset = bit / 8;
 882                 let mask = 1 << (bit - 8 * byte_offset);
 883                 if byte_offset < T::KNOWN_FEATURE_MASK.len() && custom {
 884                         if (T::KNOWN_FEATURE_MASK[byte_offset] & mask) != 0 {
 885                                 return Err(());
 886                         }
 887                 }
 888
 889                 if self.flags.len() <= byte_offset {
 890                         self.flags.resize(byte_offset + 1, 0u8);
 891                 }
 892
 893                 self.flags[byte_offset] |= mask;
 894
 895                 Ok(())
 896         }
 897 }
 898
 899 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 900         #[cfg(test)]
 901         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 902                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 903                 self
 904         }
 905 }
 906
 907 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 908         #[cfg(test)]
 909         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 910                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 911                 self
 912         }
 913 }
 914
 915 impl<T: sealed::Wumbo> Features<T> {
 916         #[cfg(test)]
 917         pub(crate) fn clear_wumbo(mut self) -> Self {
 918                 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
 919                 self
 920         }
 921 }
 922
 923 impl<T: sealed::SCIDPrivacy> Features<T> {
 924         pub(crate) fn clear_scid_privacy(&mut self) {
 925                 <T as sealed::SCIDPrivacy>::clear_bits(&mut self.flags);
 926         }
 927 }
 928
 929 impl<T: sealed::AnchorsZeroFeeHtlcTx> Features<T> {
 930         pub(crate) fn clear_anchors_zero_fee_htlc_tx(&mut self) {
 931                 <T as sealed::AnchorsZeroFeeHtlcTx>::clear_bits(&mut self.flags);
 932         }
 933 }
 934
 935 impl<T: sealed::RouteBlinding> Features<T> {
 936         #[cfg(test)]
 937         pub(crate) fn clear_route_blinding(&mut self) {
 938                 <T as sealed::RouteBlinding>::clear_bits(&mut self.flags);
 939         }
 940 }
 941
 942 #[cfg(test)]
 943 impl<T: sealed::UnknownFeature> Features<T> {
 944         pub(crate) fn unknown() -> Self {
 945                 let mut features = Self::empty();
 946                 features.set_unknown_feature_required();
 947                 features
 948         }
 949 }
 950
 951 macro_rules! impl_feature_len_prefixed_write {
 952         ($features: ident) => {
 953                 impl Writeable for $features {
 954                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 955                                 (self.flags.len() as u16).write(w)?;
 956                                 self.write_be(w)
 957                         }
 958                 }
 959                 impl Readable for $features {
 960                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 961                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
 962                         }
 963                 }
 964         }
 965 }
 966 impl_feature_len_prefixed_write!(InitFeatures);
 967 impl_feature_len_prefixed_write!(ChannelFeatures);
 968 impl_feature_len_prefixed_write!(NodeFeatures);
 969 impl_feature_len_prefixed_write!(Bolt11InvoiceFeatures);
 970 impl_feature_len_prefixed_write!(Bolt12InvoiceFeatures);
 971 impl_feature_len_prefixed_write!(BlindedHopFeatures);
 972
 973 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
 974 macro_rules! impl_feature_tlv_write {
 975         ($features: ident) => {
 976                 impl Writeable for $features {
 977                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 978                                 WithoutLength(self).write(w)
 979                         }
 980                 }
 981                 impl Readable for $features {
 982                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 983                                 Ok(WithoutLength::<Self>::read(r)?.0)
 984                         }
 985                 }
 986         }
 987 }
 988
 989 impl_feature_tlv_write!(ChannelTypeFeatures);
 990
 991 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
 992 // requires a length but the former does not.
 993
 994 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
 995         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 996                 self.0.write_be(w)
 997         }
 998 }
 999
1000 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
1001         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
1002                 let v = io_extras::read_to_end(r)?;
1003                 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
1004         }
1005 }
1006
1007 #[cfg(test)]
1008 mod tests {
1009         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, Bolt11InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
1010         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
1011         use crate::util::ser::{Readable, WithoutLength, Writeable};
1012
1013         #[test]
1014         fn sanity_test_unknown_bits() {
1015                 let features = ChannelFeatures::empty();
1016                 assert!(!features.requires_unknown_bits());
1017                 assert!(!features.supports_unknown_bits());
1018
1019                 let mut features = ChannelFeatures::empty();
1020                 features.set_unknown_feature_required();
1021                 assert!(features.requires_unknown_bits());
1022                 assert!(features.supports_unknown_bits());
1023
1024                 let mut features = ChannelFeatures::empty();
1025                 features.set_unknown_feature_optional();
1026                 assert!(!features.requires_unknown_bits());
1027                 assert!(features.supports_unknown_bits());
1028         }
1029
1030         #[test]
1031         fn requires_unknown_bits_from() {
1032                 let mut features1 = InitFeatures::empty();
1033                 let mut features2 = InitFeatures::empty();
1034                 assert!(!features1.requires_unknown_bits_from(&features2));
1035                 assert!(!features2.requires_unknown_bits_from(&features1));
1036
1037                 features1.set_data_loss_protect_required();
1038                 assert!(features1.requires_unknown_bits_from(&features2));
1039                 assert!(!features2.requires_unknown_bits_from(&features1));
1040
1041                 features2.set_data_loss_protect_optional();
1042                 assert!(!features1.requires_unknown_bits_from(&features2));
1043                 assert!(!features2.requires_unknown_bits_from(&features1));
1044
1045                 features2.set_gossip_queries_required();
1046                 assert!(!features1.requires_unknown_bits_from(&features2));
1047                 assert!(features2.requires_unknown_bits_from(&features1));
1048
1049                 features1.set_gossip_queries_optional();
1050                 assert!(!features1.requires_unknown_bits_from(&features2));
1051                 assert!(!features2.requires_unknown_bits_from(&features1));
1052
1053                 features1.set_variable_length_onion_required();
1054                 assert!(features1.requires_unknown_bits_from(&features2));
1055                 assert!(!features2.requires_unknown_bits_from(&features1));
1056
1057                 features2.set_variable_length_onion_optional();
1058                 assert!(!features1.requires_unknown_bits_from(&features2));
1059                 assert!(!features2.requires_unknown_bits_from(&features1));
1060
1061                 features1.set_basic_mpp_required();
1062                 features2.set_wumbo_required();
1063                 assert!(features1.requires_unknown_bits_from(&features2));
1064                 assert!(features2.requires_unknown_bits_from(&features1));
1065         }
1066
1067         #[test]
1068         fn convert_to_context_with_relevant_flags() {
1069                 let mut init_features = InitFeatures::empty();
1070                 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
1071                 // converted as it's only relevant in an init context).
1072                 init_features.set_initial_routing_sync_required();
1073                 init_features.set_data_loss_protect_required();
1074                 init_features.set_variable_length_onion_required();
1075                 init_features.set_static_remote_key_required();
1076                 init_features.set_payment_secret_required();
1077                 init_features.set_basic_mpp_optional();
1078                 init_features.set_wumbo_optional();
1079                 init_features.set_anchors_zero_fee_htlc_tx_optional();
1080                 init_features.set_route_blinding_optional();
1081                 init_features.set_shutdown_any_segwit_optional();
1082                 init_features.set_onion_messages_optional();
1083                 init_features.set_channel_type_optional();
1084                 init_features.set_scid_privacy_optional();
1085                 init_features.set_zero_conf_optional();
1086
1087                 assert!(init_features.initial_routing_sync());
1088                 assert!(!init_features.supports_upfront_shutdown_script());
1089                 assert!(!init_features.supports_gossip_queries());
1090
1091                 let node_features: NodeFeatures = init_features.to_context();
1092                 {
1093                         // Check that the flags are as expected:
1094                         // - option_data_loss_protect (req)
1095                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
1096                         // - basic_mpp | wumbo | option_anchors_zero_fee_htlc_tx
1097                         // - option_route_blinding | opt_shutdown_anysegwit
1098                         // - onion_messages
1099                         // - option_channel_type | option_scid_alias
1100                         // - option_zeroconf
1101                         assert_eq!(node_features.flags.len(), 7);
1102                         assert_eq!(node_features.flags[0], 0b00000001);
1103                         assert_eq!(node_features.flags[1], 0b01010001);
1104                         assert_eq!(node_features.flags[2], 0b10001010);
1105                         assert_eq!(node_features.flags[3], 0b00001010);
1106                         assert_eq!(node_features.flags[4], 0b10000000);
1107                         assert_eq!(node_features.flags[5], 0b10100000);
1108                         assert_eq!(node_features.flags[6], 0b00001000);
1109                 }
1110
1111                 // Check that cleared flags are kept blank when converting back:
1112                 // - initial_routing_sync was not applicable to NodeContext
1113                 // - upfront_shutdown_script was cleared before converting
1114                 // - gossip_queries was cleared before converting
1115                 let features: InitFeatures = node_features.to_context_internal();
1116                 assert!(!features.initial_routing_sync());
1117                 assert!(!features.supports_upfront_shutdown_script());
1118                 assert!(!init_features.supports_gossip_queries());
1119         }
1120
1121         #[test]
1122         fn convert_to_context_with_unknown_flags() {
1123                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
1124                 assert!(<sealed::ChannelContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
1125                         <sealed::Bolt11InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
1126                 let mut channel_features = ChannelFeatures::empty();
1127                 channel_features.set_unknown_feature_optional();
1128                 assert!(channel_features.supports_unknown_bits());
1129                 let invoice_features: Bolt11InvoiceFeatures = channel_features.to_context_internal();
1130                 assert!(!invoice_features.supports_unknown_bits());
1131         }
1132
1133         #[test]
1134         fn set_feature_bits() {
1135                 let mut features = Bolt11InvoiceFeatures::empty();
1136                 features.set_basic_mpp_optional();
1137                 features.set_payment_secret_required();
1138                 assert!(features.supports_basic_mpp());
1139                 assert!(!features.requires_basic_mpp());
1140                 assert!(features.requires_payment_secret());
1141                 assert!(features.supports_payment_secret());
1142
1143                 // Set flags manually
1144                 let mut features = NodeFeatures::empty();
1145                 assert!(features.set_optional_feature_bit(55).is_ok());
1146                 assert!(features.supports_keysend());
1147                 assert!(features.set_optional_feature_bit(255).is_ok());
1148                 assert!(features.set_required_feature_bit(256).is_err());
1149         }
1150
1151         #[test]
1152         fn set_custom_bits() {
1153                 let mut features = Bolt11InvoiceFeatures::empty();
1154                 features.set_variable_length_onion_optional();
1155                 assert_eq!(features.flags[1], 0b00000010);
1156
1157                 assert!(features.set_optional_custom_bit(255).is_err());
1158                 assert!(features.set_required_custom_bit(256).is_ok());
1159                 assert!(features.set_required_custom_bit(258).is_ok());
1160                 assert_eq!(features.flags[31], 0b00000000);
1161                 assert_eq!(features.flags[32], 0b00000101);
1162
1163                 let known_bit = <sealed::Bolt11InvoiceContext as sealed::PaymentSecret>::EVEN_BIT;
1164                 let byte_offset = <sealed::Bolt11InvoiceContext as sealed::PaymentSecret>::BYTE_OFFSET;
1165                 assert_eq!(byte_offset, 1);
1166                 assert_eq!(features.flags[byte_offset], 0b00000010);
1167                 assert!(features.set_required_custom_bit(known_bit).is_err());
1168                 assert_eq!(features.flags[byte_offset], 0b00000010);
1169
1170                 let mut features = Bolt11InvoiceFeatures::empty();
1171                 assert!(features.set_optional_custom_bit(256).is_ok());
1172                 assert!(features.set_optional_custom_bit(259).is_ok());
1173                 assert_eq!(features.flags[32], 0b00001010);
1174
1175                 let mut features = Bolt11InvoiceFeatures::empty();
1176                 assert!(features.set_required_custom_bit(257).is_ok());
1177                 assert!(features.set_required_custom_bit(258).is_ok());
1178                 assert_eq!(features.flags[32], 0b00000101);
1179         }
1180
1181         #[test]
1182         fn encodes_features_without_length() {
1183                 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1184                 assert_eq!(features.flags.len(), 8);
1185
1186                 let mut serialized_features = Vec::new();
1187                 WithoutLength(&features).write(&mut serialized_features).unwrap();
1188                 assert_eq!(serialized_features.len(), 8);
1189
1190                 let deserialized_features =
1191                         WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
1192                 assert_eq!(features, deserialized_features);
1193         }
1194
1195         #[test]
1196         fn invoice_features_encoding() {
1197                 let features_as_u5s = vec![
1198                         u5::try_from_u8(6).unwrap(),
1199                         u5::try_from_u8(10).unwrap(),
1200                         u5::try_from_u8(25).unwrap(),
1201                         u5::try_from_u8(1).unwrap(),
1202                         u5::try_from_u8(10).unwrap(),
1203                         u5::try_from_u8(0).unwrap(),
1204                         u5::try_from_u8(20).unwrap(),
1205                         u5::try_from_u8(2).unwrap(),
1206                         u5::try_from_u8(0).unwrap(),
1207                         u5::try_from_u8(6).unwrap(),
1208                         u5::try_from_u8(0).unwrap(),
1209                         u5::try_from_u8(16).unwrap(),
1210                         u5::try_from_u8(1).unwrap(),
1211                 ];
1212                 let features = Bolt11InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1213
1214                 // Test length calculation.
1215                 assert_eq!(features.base32_len(), 13);
1216
1217                 // Test serialization.
1218                 let features_serialized = features.to_base32();
1219                 assert_eq!(features_as_u5s, features_serialized);
1220
1221                 // Test deserialization.
1222                 let features_deserialized = Bolt11InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
1223                 assert_eq!(features, features_deserialized);
1224         }
1225
1226         #[test]
1227         fn test_channel_type_mapping() {
1228                 // If we map an Bolt11InvoiceFeatures with StaticRemoteKey optional, it should map into a
1229                 // required-StaticRemoteKey ChannelTypeFeatures.
1230                 let mut init_features = InitFeatures::empty();
1231                 init_features.set_static_remote_key_optional();
1232                 let converted_features = ChannelTypeFeatures::from_init(&init_features);
1233                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
1234                 assert!(!converted_features.supports_any_optional_bits());
1235                 assert!(converted_features.requires_static_remote_key());
1236         }
1237
1238         #[test]
1239         #[cfg(feature = "std")]
1240         fn test_excess_zero_bytes_ignored() {
1241                 // Checks that `Hash` and `PartialEq` ignore excess zero bytes, which may appear due to
1242                 // feature conversion or because a peer serialized their feature poorly.
1243                 use std::collections::hash_map::DefaultHasher;
1244                 use std::hash::{Hash, Hasher};
1245
1246                 let mut zerod_features = InitFeatures::empty();
1247                 zerod_features.flags = vec![0];
1248                 let empty_features = InitFeatures::empty();
1249                 assert!(empty_features.flags.is_empty());
1250
1251                 assert_eq!(zerod_features, empty_features);
1252
1253                 let mut zerod_hash = DefaultHasher::new();
1254                 zerod_features.hash(&mut zerod_hash);
1255                 let mut empty_hash = DefaultHasher::new();
1256                 empty_features.hash(&mut empty_hash);
1257                 assert_eq!(zerod_hash.finish(), empty_hash.finish());
1258         }
1259 }