_ 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 /// This is not exported to bindings users but probably should be.
 444 impl<T: sealed::Context, Rhs: Borrow<Self>> core::ops::BitOrAssign<Rhs> for Features<T> {
 445         fn bitor_assign(&mut self, rhs: Rhs) {
 446                 let total_feature_len = cmp::max(self.flags.len(), rhs.borrow().flags.len());
 447                 self.flags.resize(total_feature_len, 0u8);
 448                 for (byte, rhs_byte) in self.flags.iter_mut().zip(rhs.borrow().flags.iter()) {
 449                         *byte |= *rhs_byte;
 450                 }
 451         }
 452 }
 453
 454 /// This is not exported to bindings users but probably should be.
 455 impl<T: sealed::Context> core::ops::BitOr for Features<T> {
 456         type Output = Self;
 457
 458         fn bitor(mut self, o: Self) -> Self {
 459                 self |= o;
 460                 self
 461         }
 462 }
 463
 464 impl<T: sealed::Context> Clone for Features<T> {
 465         fn clone(&self) -> Self {
 466                 Self {
 467                         flags: self.flags.clone(),
 468                         mark: PhantomData,
 469                 }
 470         }
 471 }
 472 impl<T: sealed::Context> Hash for Features<T> {
 473         fn hash<H: Hasher>(&self, hasher: &mut H) {
 474                 let mut nonzero_flags = &self.flags[..];
 475                 while nonzero_flags.last() == Some(&0) {
 476                         nonzero_flags = &nonzero_flags[..nonzero_flags.len() - 1];
 477                 }
 478                 nonzero_flags.hash(hasher);
 479         }
 480 }
 481 impl<T: sealed::Context> PartialEq for Features<T> {
 482         fn eq(&self, o: &Self) -> bool {
 483                 let mut o_iter = o.flags.iter();
 484                 let mut self_iter = self.flags.iter();
 485                 loop {
 486                         match (o_iter.next(), self_iter.next()) {
 487                                 (Some(o), Some(us)) => if o != us { return false },
 488                                 (Some(b), None) | (None, Some(b)) => if *b != 0 { return false },
 489                                 (None, None) => return true,
 490                         }
 491                 }
 492         }
 493 }
 494 impl<T: sealed::Context> PartialOrd for Features<T> {
 495         fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
 496                 self.flags.partial_cmp(&other.flags)
 497         }
 498 }
 499 impl<T: sealed::Context + Eq> Ord for Features<T> {
 500         fn cmp(&self, other: &Self) -> cmp::Ordering {
 501                 self.flags.cmp(&other.flags)
 502         }
 503 }
 504 impl<T: sealed::Context> fmt::Debug for Features<T> {
 505         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 506                 self.flags.fmt(fmt)
 507         }
 508 }
 509
 510 /// Features used within an `init` message.
 511 pub type InitFeatures = Features<sealed::InitContext>;
 512 /// Features used within a `node_announcement` message.
 513 pub type NodeFeatures = Features<sealed::NodeContext>;
 514 /// Features used within a `channel_announcement` message.
 515 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 516 /// Features used within an invoice.
 517 pub type Bolt11InvoiceFeatures = Features<sealed::Bolt11InvoiceContext>;
 518 /// Features used within an `offer`.
 519 pub type OfferFeatures = Features<sealed::OfferContext>;
 520 /// Features used within an `invoice_request`.
 521 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
 522 /// Features used within an `invoice`.
 523 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
 524 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
 525 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
 526
 527 /// Features used within the channel_type field in an OpenChannel message.
 528 ///
 529 /// A channel is always of some known "type", describing the transaction formats used and the exact
 530 /// semantics of our interaction with our peer.
 531 ///
 532 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
 533 /// the counterparty, only required features are allowed here.
 534 ///
 535 /// This is serialized differently from other feature types - it is not prefixed by a length, and
 536 /// thus must only appear inside a TLV where its length is known in advance.
 537 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
 538
 539 impl InitFeatures {
 540         /// Writes all features present up to, and including, 13.
 541         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 542                 let len = cmp::min(2, self.flags.len());
 543                 (len as u16).write(w)?;
 544                 for i in (0..len).rev() {
 545                         if i == 0 {
 546                                 self.flags[i].write(w)?;
 547                         } else {
 548                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 549                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 550                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 551                         }
 552                 }
 553                 Ok(())
 554         }
 555
 556         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 557         /// are included in the result.
 558         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 559                 self.to_context_internal()
 560         }
 561 }
 562
 563 impl Bolt11InvoiceFeatures {
 564         /// Converts `Bolt11InvoiceFeatures` to `Features<C>`. Only known `Bolt11InvoiceFeatures` relevant to
 565         /// context `C` are included in the result.
 566         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 567                 self.to_context_internal()
 568         }
 569
 570         /// Getting a route for a keysend payment to a private node requires providing the payee's
 571         /// features (since they were not announced in a node announcement). However, keysend payments
 572         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 573         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
 574         /// `Bolt11InvoiceFeatures` for [`find_route`].
 575         ///
 576         /// MPP keysend is not widely supported yet, so we parameterize support to allow the user to
 577         /// choose whether their router should find multi-part routes.
 578         ///
 579         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
 580         /// [`find_route`]: crate::routing::router::find_route
 581         pub(crate) fn for_keysend(allow_mpp: bool) -> Bolt11InvoiceFeatures {
 582                 let mut res = Bolt11InvoiceFeatures::empty();
 583                 res.set_variable_length_onion_optional();
 584                 if allow_mpp {
 585                         res.set_basic_mpp_optional();
 586                 }
 587                 res
 588         }
 589 }
 590
 591 impl Bolt12InvoiceFeatures {
 592         /// Converts [`Bolt12InvoiceFeatures`] to [`Features<C>`]. Only known [`Bolt12InvoiceFeatures`]
 593         /// relevant to context `C` are included in the result.
 594         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 595                 self.to_context_internal()
 596         }
 597 }
 598
 599 impl ChannelTypeFeatures {
 600         // Maps the relevant `InitFeatures` to `ChannelTypeFeatures`. Any unknown features to
 601         // `ChannelTypeFeatures` are not included in the result.
 602         pub(crate) fn from_init(init: &InitFeatures) -> Self {
 603                 let mut ret = init.to_context_internal();
 604                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
 605                 // optional bits and then AND out the optional ones.
 606                 for byte in ret.flags.iter_mut() {
 607                         *byte |= (*byte & 0b10_10_10_10) >> 1;
 608                         *byte &= 0b01_01_01_01;
 609                 }
 610                 ret
 611         }
 612
 613         /// Constructs a ChannelTypeFeatures with only static_remotekey set
 614         pub(crate) fn only_static_remote_key() -> Self {
 615                 let mut ret = Self::empty();
 616                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 617                 ret
 618         }
 619
 620         /// Constructs a ChannelTypeFeatures with anchors support
 621         pub(crate) fn anchors_zero_htlc_fee_and_dependencies() -> Self {
 622                 let mut ret = Self::empty();
 623                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 624                 <sealed::ChannelTypeContext as sealed::AnchorsZeroFeeHtlcTx>::set_required_bit(&mut ret.flags);
 625                 ret
 626         }
 627 }
 628
 629 impl ToBase32 for Bolt11InvoiceFeatures {
 630         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 631                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 632                 // minus one before dividing
 633                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 634                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 635                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 636                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 637                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 638                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 639                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 640                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 641                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 642                         if new_u5_idx > 0 {
 643                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 644                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 645                         }
 646                         if new_u5_idx > 1 {
 647                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 648                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 649                         }
 650                 }
 651                 // Trim the highest feature bits.
 652                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 653                         res_u5s.remove(0);
 654                 }
 655                 writer.write(&res_u5s)
 656         }
 657 }
 658
 659 impl Base32Len for Bolt11InvoiceFeatures {
 660         fn base32_len(&self) -> usize {
 661                 self.to_base32().len()
 662         }
 663 }
 664
 665 impl FromBase32 for Bolt11InvoiceFeatures {
 666         type Err = bech32::Error;
 667
 668         fn from_base32(field_data: &[u5]) -> Result<Bolt11InvoiceFeatures, bech32::Error> {
 669                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 670                 // minus one before dividing
 671                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 672                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 673                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 674                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 675                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 676                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 677                         let chunk_u16 = chunk.to_u8() as u16;
 678                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 679                         if new_byte_idx != length_bytes - 1 {
 680                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 681                         }
 682                 }
 683                 // Trim the highest feature bits.
 684                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 685                         res_bytes.pop();
 686                 }
 687                 Ok(Bolt11InvoiceFeatures::from_le_bytes(res_bytes))
 688         }
 689 }
 690
 691 impl<T: sealed::Context> Features<T> {
 692         /// Create a blank Features with no features set
 693         pub fn empty() -> Self {
 694                 Features {
 695                         flags: Vec::new(),
 696                         mark: PhantomData,
 697                 }
 698         }
 699
 700         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 701         /// included in the result.
 702         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 703                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 704                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 705                 let mut flags = Vec::new();
 706                 for (i, byte) in self.flags.iter().enumerate() {
 707                         if i < from_byte_count && i < to_byte_count {
 708                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 709                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 710                                 flags.push(byte & from_known_features & to_known_features);
 711                         }
 712                 }
 713                 Features::<C> { flags, mark: PhantomData, }
 714         }
 715
 716         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 717         /// most on-the-wire encodings.
 718         ///
 719         /// This is not exported to bindings users as we don't support export across multiple T
 720         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 721                 Features {
 722                         flags,
 723                         mark: PhantomData,
 724                 }
 725         }
 726
 727         #[cfg(test)]
 728         /// Gets the underlying flags set, in LE.
 729         pub fn le_flags(&self) -> &Vec<u8> {
 730                 &self.flags
 731         }
 732
 733         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 734                 for f in self.flags.iter().rev() { // Swap back to big-endian
 735                         f.write(w)?;
 736                 }
 737                 Ok(())
 738         }
 739
 740         /// Create a [`Features`] given a set of flags, in big-endian. This is in byte order from
 741         /// most on-the-wire encodings.
 742         ///
 743         /// This is not exported to bindings users as we don't support export across multiple T
 744         pub fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
 745                 flags.reverse(); // Swap to little-endian
 746                 Self {
 747                         flags,
 748                         mark: PhantomData,
 749                 }
 750         }
 751
 752         pub(crate) fn supports_any_optional_bits(&self) -> bool {
 753                 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
 754         }
 755
 756         /// Returns true if this `Features` object contains required features unknown by `other`.
 757         pub fn requires_unknown_bits_from(&self, other: &Self) -> bool {
 758                 // Bitwise AND-ing with all even bits set except for known features will select required
 759                 // unknown features.
 760                 self.flags.iter().enumerate().any(|(i, &byte)| {
 761                         const REQUIRED_FEATURES: u8 = 0b01_01_01_01;
 762                         const OPTIONAL_FEATURES: u8 = 0b10_10_10_10;
 763                         let unknown_features = if i < other.flags.len() {
 764                                 // Form a mask similar to !T::KNOWN_FEATURE_MASK only for `other`
 765                                 !(other.flags[i]
 766                                         | ((other.flags[i] >> 1) & REQUIRED_FEATURES)
 767                                         | ((other.flags[i] << 1) & OPTIONAL_FEATURES))
 768                         } else {
 769                                 0b11_11_11_11
 770                         };
 771                         (byte & (REQUIRED_FEATURES & unknown_features)) != 0
 772                 })
 773         }
 774
 775         /// Returns true if this `Features` object contains unknown feature flags which are set as
 776         /// "required".
 777         pub fn requires_unknown_bits(&self) -> bool {
 778                 // Bitwise AND-ing with all even bits set except for known features will select required
 779                 // unknown features.
 780                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 781                 self.flags.iter().enumerate().any(|(i, &byte)| {
 782                         let required_features = 0b01_01_01_01;
 783                         let unknown_features = if i < byte_count {
 784                                 !T::KNOWN_FEATURE_MASK[i]
 785                         } else {
 786                                 0b11_11_11_11
 787                         };
 788                         (byte & (required_features & unknown_features)) != 0
 789                 })
 790         }
 791
 792         pub(crate) fn supports_unknown_bits(&self) -> bool {
 793                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 794                 // both required and optional unknown features.
 795                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 796                 self.flags.iter().enumerate().any(|(i, &byte)| {
 797                         let unknown_features = if i < byte_count {
 798                                 !T::KNOWN_FEATURE_MASK[i]
 799                         } else {
 800                                 0b11_11_11_11
 801                         };
 802                         (byte & unknown_features) != 0
 803                 })
 804         }
 805
 806         // Returns true if the features within `self` are a subset of the features within `other`.
 807         pub(crate) fn is_subset(&self, other: &Self) -> bool {
 808                 for (idx, byte) in self.flags.iter().enumerate() {
 809                         if let Some(other_byte) = other.flags.get(idx) {
 810                                 if byte & other_byte != *byte {
 811                                         // `self` has bits set that `other` doesn't.
 812                                         return false;
 813                                 }
 814                         } else {
 815                                 if *byte > 0 {
 816                                         // `self` has a non-zero byte that `other` doesn't.
 817                                         return false;
 818                                 }
 819                         }
 820                 }
 821                 true
 822         }
 823
 824         /// Sets a required feature bit. Errors if `bit` is outside the feature range as defined
 825         /// by [BOLT 9].
 826         ///
 827         /// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
 828         /// be set instead (i.e., `bit - 1`).
 829         ///
 830         /// [BOLT 9]: https://github.com/lightning/bolts/blob/master/09-features.md
 831         pub fn set_required_feature_bit(&mut self, bit: usize) -> Result<(), ()> {
 832                 self.set_feature_bit(bit - (bit % 2))
 833         }
 834
 835         /// Sets an optional feature bit. Errors if `bit` is outside the feature range as defined
 836         /// by [BOLT 9].
 837         ///
 838         /// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
 839         /// set instead (i.e., `bit + 1`).
 840         ///
 841         /// [BOLT 9]: https://github.com/lightning/bolts/blob/master/09-features.md
 842         pub fn set_optional_feature_bit(&mut self, bit: usize) -> Result<(), ()> {
 843                 self.set_feature_bit(bit + (1 - (bit % 2)))
 844         }
 845
 846         fn set_feature_bit(&mut self, bit: usize) -> Result<(), ()> {
 847                 if bit > 255 {
 848                         return Err(());
 849                 }
 850                 self.set_bit(bit, false)
 851         }
 852
 853         /// Sets a required custom feature bit. Errors if `bit` is outside the custom range as defined
 854         /// by [bLIP 2] or if it is a known `T` feature.
 855         ///
 856         /// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
 857         /// be set instead (i.e., `bit - 1`).
 858         ///
 859         /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
 860         pub fn set_required_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 861                 self.set_custom_bit(bit - (bit % 2))
 862         }
 863
 864         /// Sets an optional custom feature bit. Errors if `bit` is outside the custom range as defined
 865         /// by [bLIP 2] or if it is a known `T` feature.
 866         ///
 867         /// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
 868         /// set instead (i.e., `bit + 1`).
 869         ///
 870         /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
 871         pub fn set_optional_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 872                 self.set_custom_bit(bit + (1 - (bit % 2)))
 873         }
 874
 875         fn set_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 876                 if bit < 256 {
 877                         return Err(());
 878                 }
 879                 self.set_bit(bit, true)
 880         }
 881
 882         fn set_bit(&mut self, bit: usize, custom: bool) -> Result<(), ()> {
 883                 let byte_offset = bit / 8;
 884                 let mask = 1 << (bit - 8 * byte_offset);
 885                 if byte_offset < T::KNOWN_FEATURE_MASK.len() && custom {
 886                         if (T::KNOWN_FEATURE_MASK[byte_offset] & mask) != 0 {
 887                                 return Err(());
 888                         }
 889                 }
 890
 891                 if self.flags.len() <= byte_offset {
 892                         self.flags.resize(byte_offset + 1, 0u8);
 893                 }
 894
 895                 self.flags[byte_offset] |= mask;
 896
 897                 Ok(())
 898         }
 899 }
 900
 901 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 902         #[cfg(test)]
 903         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 904                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 905                 self
 906         }
 907 }
 908
 909 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 910         #[cfg(test)]
 911         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 912                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 913                 self
 914         }
 915 }
 916
 917 impl<T: sealed::Wumbo> Features<T> {
 918         #[cfg(test)]
 919         pub(crate) fn clear_wumbo(mut self) -> Self {
 920                 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
 921                 self
 922         }
 923 }
 924
 925 impl<T: sealed::SCIDPrivacy> Features<T> {
 926         pub(crate) fn clear_scid_privacy(&mut self) {
 927                 <T as sealed::SCIDPrivacy>::clear_bits(&mut self.flags);
 928         }
 929 }
 930
 931 impl<T: sealed::AnchorsZeroFeeHtlcTx> Features<T> {
 932         pub(crate) fn clear_anchors_zero_fee_htlc_tx(&mut self) {
 933                 <T as sealed::AnchorsZeroFeeHtlcTx>::clear_bits(&mut self.flags);
 934         }
 935 }
 936
 937 #[cfg(test)]
 938 impl<T: sealed::UnknownFeature> Features<T> {
 939         pub(crate) fn unknown() -> Self {
 940                 let mut features = Self::empty();
 941                 features.set_unknown_feature_required();
 942                 features
 943         }
 944 }
 945
 946 macro_rules! impl_feature_len_prefixed_write {
 947         ($features: ident) => {
 948                 impl Writeable for $features {
 949                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 950                                 (self.flags.len() as u16).write(w)?;
 951                                 self.write_be(w)
 952                         }
 953                 }
 954                 impl Readable for $features {
 955                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 956                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
 957                         }
 958                 }
 959         }
 960 }
 961 impl_feature_len_prefixed_write!(InitFeatures);
 962 impl_feature_len_prefixed_write!(ChannelFeatures);
 963 impl_feature_len_prefixed_write!(NodeFeatures);
 964 impl_feature_len_prefixed_write!(Bolt11InvoiceFeatures);
 965 impl_feature_len_prefixed_write!(Bolt12InvoiceFeatures);
 966 impl_feature_len_prefixed_write!(BlindedHopFeatures);
 967
 968 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
 969 macro_rules! impl_feature_tlv_write {
 970         ($features: ident) => {
 971                 impl Writeable for $features {
 972                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 973                                 WithoutLength(self).write(w)
 974                         }
 975                 }
 976                 impl Readable for $features {
 977                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 978                                 Ok(WithoutLength::<Self>::read(r)?.0)
 979                         }
 980                 }
 981         }
 982 }
 983
 984 impl_feature_tlv_write!(ChannelTypeFeatures);
 985
 986 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
 987 // requires a length but the former does not.
 988
 989 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
 990         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 991                 self.0.write_be(w)
 992         }
 993 }
 994
 995 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
 996         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 997                 let v = io_extras::read_to_end(r)?;
 998                 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
 999         }
1000 }
1001
1002 #[cfg(test)]
1003 mod tests {
1004         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, Bolt11InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
1005         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
1006         use crate::util::ser::{Readable, WithoutLength, Writeable};
1007
1008         #[test]
1009         fn sanity_test_unknown_bits() {
1010                 let features = ChannelFeatures::empty();
1011                 assert!(!features.requires_unknown_bits());
1012                 assert!(!features.supports_unknown_bits());
1013
1014                 let mut features = ChannelFeatures::empty();
1015                 features.set_unknown_feature_required();
1016                 assert!(features.requires_unknown_bits());
1017                 assert!(features.supports_unknown_bits());
1018
1019                 let mut features = ChannelFeatures::empty();
1020                 features.set_unknown_feature_optional();
1021                 assert!(!features.requires_unknown_bits());
1022                 assert!(features.supports_unknown_bits());
1023         }
1024
1025         #[test]
1026         fn requires_unknown_bits_from() {
1027                 let mut features1 = InitFeatures::empty();
1028                 let mut features2 = InitFeatures::empty();
1029                 assert!(!features1.requires_unknown_bits_from(&features2));
1030                 assert!(!features2.requires_unknown_bits_from(&features1));
1031
1032                 features1.set_data_loss_protect_required();
1033                 assert!(features1.requires_unknown_bits_from(&features2));
1034                 assert!(!features2.requires_unknown_bits_from(&features1));
1035
1036                 features2.set_data_loss_protect_optional();
1037                 assert!(!features1.requires_unknown_bits_from(&features2));
1038                 assert!(!features2.requires_unknown_bits_from(&features1));
1039
1040                 features2.set_gossip_queries_required();
1041                 assert!(!features1.requires_unknown_bits_from(&features2));
1042                 assert!(features2.requires_unknown_bits_from(&features1));
1043
1044                 features1.set_gossip_queries_optional();
1045                 assert!(!features1.requires_unknown_bits_from(&features2));
1046                 assert!(!features2.requires_unknown_bits_from(&features1));
1047
1048                 features1.set_variable_length_onion_required();
1049                 assert!(features1.requires_unknown_bits_from(&features2));
1050                 assert!(!features2.requires_unknown_bits_from(&features1));
1051
1052                 features2.set_variable_length_onion_optional();
1053                 assert!(!features1.requires_unknown_bits_from(&features2));
1054                 assert!(!features2.requires_unknown_bits_from(&features1));
1055
1056                 features1.set_basic_mpp_required();
1057                 features2.set_wumbo_required();
1058                 assert!(features1.requires_unknown_bits_from(&features2));
1059                 assert!(features2.requires_unknown_bits_from(&features1));
1060         }
1061
1062         #[test]
1063         fn convert_to_context_with_relevant_flags() {
1064                 let mut init_features = InitFeatures::empty();
1065                 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
1066                 // converted as it's only relevant in an init context).
1067                 init_features.set_initial_routing_sync_required();
1068                 init_features.set_data_loss_protect_required();
1069                 init_features.set_variable_length_onion_required();
1070                 init_features.set_static_remote_key_required();
1071                 init_features.set_payment_secret_required();
1072                 init_features.set_basic_mpp_optional();
1073                 init_features.set_wumbo_optional();
1074                 init_features.set_anchors_zero_fee_htlc_tx_optional();
1075                 init_features.set_route_blinding_optional();
1076                 init_features.set_shutdown_any_segwit_optional();
1077                 init_features.set_onion_messages_optional();
1078                 init_features.set_channel_type_optional();
1079                 init_features.set_scid_privacy_optional();
1080                 init_features.set_zero_conf_optional();
1081
1082                 assert!(init_features.initial_routing_sync());
1083                 assert!(!init_features.supports_upfront_shutdown_script());
1084                 assert!(!init_features.supports_gossip_queries());
1085
1086                 let node_features: NodeFeatures = init_features.to_context();
1087                 {
1088                         // Check that the flags are as expected:
1089                         // - option_data_loss_protect (req)
1090                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
1091                         // - basic_mpp | wumbo | option_anchors_zero_fee_htlc_tx
1092                         // - option_route_blinding | opt_shutdown_anysegwit
1093                         // - onion_messages
1094                         // - option_channel_type | option_scid_alias
1095                         // - option_zeroconf
1096                         assert_eq!(node_features.flags.len(), 7);
1097                         assert_eq!(node_features.flags[0], 0b00000001);
1098                         assert_eq!(node_features.flags[1], 0b01010001);
1099                         assert_eq!(node_features.flags[2], 0b10001010);
1100                         assert_eq!(node_features.flags[3], 0b00001010);
1101                         assert_eq!(node_features.flags[4], 0b10000000);
1102                         assert_eq!(node_features.flags[5], 0b10100000);
1103                         assert_eq!(node_features.flags[6], 0b00001000);
1104                 }
1105
1106                 // Check that cleared flags are kept blank when converting back:
1107                 // - initial_routing_sync was not applicable to NodeContext
1108                 // - upfront_shutdown_script was cleared before converting
1109                 // - gossip_queries was cleared before converting
1110                 let features: InitFeatures = node_features.to_context_internal();
1111                 assert!(!features.initial_routing_sync());
1112                 assert!(!features.supports_upfront_shutdown_script());
1113                 assert!(!init_features.supports_gossip_queries());
1114         }
1115
1116         #[test]
1117         fn convert_to_context_with_unknown_flags() {
1118                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
1119                 assert!(<sealed::ChannelContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
1120                         <sealed::Bolt11InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
1121                 let mut channel_features = ChannelFeatures::empty();
1122                 channel_features.set_unknown_feature_optional();
1123                 assert!(channel_features.supports_unknown_bits());
1124                 let invoice_features: Bolt11InvoiceFeatures = channel_features.to_context_internal();
1125                 assert!(!invoice_features.supports_unknown_bits());
1126         }
1127
1128         #[test]
1129         fn set_feature_bits() {
1130                 let mut features = Bolt11InvoiceFeatures::empty();
1131                 features.set_basic_mpp_optional();
1132                 features.set_payment_secret_required();
1133                 assert!(features.supports_basic_mpp());
1134                 assert!(!features.requires_basic_mpp());
1135                 assert!(features.requires_payment_secret());
1136                 assert!(features.supports_payment_secret());
1137
1138                 // Set flags manually
1139                 let mut features = NodeFeatures::empty();
1140                 assert!(features.set_optional_feature_bit(55).is_ok());
1141                 assert!(features.supports_keysend());
1142                 assert!(features.set_optional_feature_bit(255).is_ok());
1143                 assert!(features.set_required_feature_bit(256).is_err());
1144         }
1145
1146         #[test]
1147         fn set_custom_bits() {
1148                 let mut features = Bolt11InvoiceFeatures::empty();
1149                 features.set_variable_length_onion_optional();
1150                 assert_eq!(features.flags[1], 0b00000010);
1151
1152                 assert!(features.set_optional_custom_bit(255).is_err());
1153                 assert!(features.set_required_custom_bit(256).is_ok());
1154                 assert!(features.set_required_custom_bit(258).is_ok());
1155                 assert_eq!(features.flags[31], 0b00000000);
1156                 assert_eq!(features.flags[32], 0b00000101);
1157
1158                 let known_bit = <sealed::Bolt11InvoiceContext as sealed::PaymentSecret>::EVEN_BIT;
1159                 let byte_offset = <sealed::Bolt11InvoiceContext as sealed::PaymentSecret>::BYTE_OFFSET;
1160                 assert_eq!(byte_offset, 1);
1161                 assert_eq!(features.flags[byte_offset], 0b00000010);
1162                 assert!(features.set_required_custom_bit(known_bit).is_err());
1163                 assert_eq!(features.flags[byte_offset], 0b00000010);
1164
1165                 let mut features = Bolt11InvoiceFeatures::empty();
1166                 assert!(features.set_optional_custom_bit(256).is_ok());
1167                 assert!(features.set_optional_custom_bit(259).is_ok());
1168                 assert_eq!(features.flags[32], 0b00001010);
1169
1170                 let mut features = Bolt11InvoiceFeatures::empty();
1171                 assert!(features.set_required_custom_bit(257).is_ok());
1172                 assert!(features.set_required_custom_bit(258).is_ok());
1173                 assert_eq!(features.flags[32], 0b00000101);
1174         }
1175
1176         #[test]
1177         fn encodes_features_without_length() {
1178                 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1179                 assert_eq!(features.flags.len(), 8);
1180
1181                 let mut serialized_features = Vec::new();
1182                 WithoutLength(&features).write(&mut serialized_features).unwrap();
1183                 assert_eq!(serialized_features.len(), 8);
1184
1185                 let deserialized_features =
1186                         WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
1187                 assert_eq!(features, deserialized_features);
1188         }
1189
1190         #[test]
1191         fn invoice_features_encoding() {
1192                 let features_as_u5s = vec![
1193                         u5::try_from_u8(6).unwrap(),
1194                         u5::try_from_u8(10).unwrap(),
1195                         u5::try_from_u8(25).unwrap(),
1196                         u5::try_from_u8(1).unwrap(),
1197                         u5::try_from_u8(10).unwrap(),
1198                         u5::try_from_u8(0).unwrap(),
1199                         u5::try_from_u8(20).unwrap(),
1200                         u5::try_from_u8(2).unwrap(),
1201                         u5::try_from_u8(0).unwrap(),
1202                         u5::try_from_u8(6).unwrap(),
1203                         u5::try_from_u8(0).unwrap(),
1204                         u5::try_from_u8(16).unwrap(),
1205                         u5::try_from_u8(1).unwrap(),
1206                 ];
1207                 let features = Bolt11InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1208
1209                 // Test length calculation.
1210                 assert_eq!(features.base32_len(), 13);
1211
1212                 // Test serialization.
1213                 let features_serialized = features.to_base32();
1214                 assert_eq!(features_as_u5s, features_serialized);
1215
1216                 // Test deserialization.
1217                 let features_deserialized = Bolt11InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
1218                 assert_eq!(features, features_deserialized);
1219         }
1220
1221         #[test]
1222         fn test_channel_type_mapping() {
1223                 // If we map an Bolt11InvoiceFeatures with StaticRemoteKey optional, it should map into a
1224                 // required-StaticRemoteKey ChannelTypeFeatures.
1225                 let mut init_features = InitFeatures::empty();
1226                 init_features.set_static_remote_key_optional();
1227                 let converted_features = ChannelTypeFeatures::from_init(&init_features);
1228                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
1229                 assert!(!converted_features.supports_any_optional_bits());
1230                 assert!(converted_features.requires_static_remote_key());
1231         }
1232
1233         #[test]
1234         #[cfg(feature = "std")]
1235         fn test_excess_zero_bytes_ignored() {
1236                 // Checks that `Hash` and `PartialEq` ignore excess zero bytes, which may appear due to
1237                 // feature conversion or because a peer serialized their feature poorly.
1238                 use std::collections::hash_map::DefaultHasher;
1239                 use std::hash::{Hash, Hasher};
1240
1241                 let mut zerod_features = InitFeatures::empty();
1242                 zerod_features.flags = vec![0];
1243                 let empty_features = InitFeatures::empty();
1244                 assert!(empty_features.flags.is_empty());
1245
1246                 assert_eq!(zerod_features, empty_features);
1247
1248                 let mut zerod_hash = DefaultHasher::new();
1249                 zerod_features.hash(&mut zerod_hash);
1250                 let mut empty_hash = DefaultHasher::new();
1251                 empty_features.hash(&mut empty_hash);
1252                 assert_eq!(zerod_hash.finish(), empty_hash.finish());
1253         }
1254 }