_ Git - rust-lightning/blob - lightning/src/ln/features.rs

   1 // This file is Copyright its original authors, visible in version control
   2 // history.
   3 //
   4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
   5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
   7 // You may not use this file except in accordance with one or both of these
   8 // licenses.
   9
  10 //! Feature flag definitions for the Lightning protocol according to [BOLT #9].
  11 //!
  12 //! Lightning nodes advertise a supported set of operation through feature flags. Features are
  13 //! applicable for a specific context as indicated in some [messages]. [`Features`] encapsulates
  14 //! behavior for specifying and checking feature flags for a particular context. Each feature is
  15 //! defined internally by a trait specifying the corresponding flags (i.e., even and odd bits).
  16 //!
  17 //! Whether a feature is considered "known" or "unknown" is relative to the implementation, whereas
  18 //! the term "supports" is used in reference to a particular set of [`Features`]. That is, a node
  19 //! supports a feature if it advertises the feature (as either required or optional) to its peers.
  20 //! And the implementation can interpret a feature if the feature is known to it.
  21 //!
  22 //! The following features are currently required in the LDK:
  23 //! - `VariableLengthOnion` - requires/supports variable-length routing onion payloads
  24 //!     (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md) for more information).
  25 //! - `StaticRemoteKey` - requires/supports static key for remote output
  26 //!     (see [BOLT-3](https://github.com/lightning/bolts/blob/master/03-transactions.md) for more information).
  27 //!
  28 //! The following features are currently supported in the LDK:
  29 //! - `DataLossProtect` - requires/supports that a node which has somehow fallen behind, e.g., has been restored from an old backup,
  30 //!     can detect that it has fallen behind
  31 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  32 //! - `InitialRoutingSync` - requires/supports that the sending node needs a complete routing information dump
  33 //!     (see [BOLT-7](https://github.com/lightning/bolts/blob/master/07-routing-gossip.md#initial-sync) for more information).
  34 //! - `UpfrontShutdownScript` - commits to a shutdown scriptpubkey when opening a channel
  35 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#the-open_channel-message) for more information).
  36 //! - `GossipQueries` - requires/supports more sophisticated gossip control
  37 //!     (see [BOLT-7](https://github.com/lightning/bolts/blob/master/07-routing-gossip.md) for more information).
  38 //! - `PaymentSecret` - requires/supports that a node supports payment_secret field
  39 //!     (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md) for more information).
  40 //! - `BasicMPP` - requires/supports that a node can receive basic multi-part payments
  41 //!     (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md#basic-multi-part-payments) for more information).
  42 //! - `Wumbo` - requires/supports that a node create large channels. Called `option_support_large_channel` in the spec.
  43 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#the-open_channel-message) for more information).
  44 //! - `AnchorsZeroFeeHtlcTx` - requires/supports that commitment transactions include anchor outputs
  45 //!     and HTLC transactions are pre-signed with zero fee (see
  46 //!     [BOLT-3](https://github.com/lightning/bolts/blob/master/03-transactions.md) for more
  47 //!     information).
  48 //! - `RouteBlinding` - requires/supports that a node can relay payments over blinded paths
  49 //!     (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md#route-blinding) for more information).
  50 //! - `ShutdownAnySegwit` - requires/supports that future segwit versions are allowed in `shutdown`
  51 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  52 //! - `OnionMessages` - requires/supports forwarding onion messages
  53 //!     (see [BOLT-7](https://github.com/lightning/bolts/pull/759/files) for more information).
  54 //     TODO: update link
  55 //! - `ChannelType` - node supports the channel_type field in open/accept
  56 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  57 //! - `SCIDPrivacy` - supply channel aliases for routing
  58 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  59 //! - `PaymentMetadata` - include additional data in invoices which is passed to recipients in the
  60 //!      onion.
  61 //!      (see [BOLT-11](https://github.com/lightning/bolts/blob/master/11-payment-encoding.md) for
  62 //!      more).
  63 //! - `ZeroConf` - supports accepting HTLCs and using channels prior to funding confirmation
  64 //!      (see
  65 //!      [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#the-channel_ready-message)
  66 //!      for more info).
  67 //! - `Keysend` - send funds to a node without an invoice
  68 //!     (see the [`Keysend` feature assignment proposal](https://github.com/lightning/bolts/issues/605#issuecomment-606679798) for more information).
  69 //! - `Trampoline` - supports receiving and forwarding Trampoline payments
  70 //!     (see the [`Trampoline` feature proposal](https://github.com/lightning/bolts/pull/836) for more information).
  71 //!
  72 //! LDK knows about the following features, but does not support them:
  73 //! - `AnchorsNonzeroFeeHtlcTx` - the initial version of anchor outputs, which was later found to be
  74 //!     vulnerable (see this
  75 //!     [mailing list post](https://lists.linuxfoundation.org/pipermail/lightning-dev/2020-September/002796.html)
  76 //!     for more information).
  77 //!
  78 //! [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
  79 //! [messages]: crate::ln::msgs
  80
  81 #[allow(unused_imports)]
  82 use crate::prelude::*;
  83
  84 use crate::{io, io_extras};
  85 use core::{cmp, fmt};
  86 use core::borrow::Borrow;
  87 use core::hash::{Hash, Hasher};
  88 use core::marker::PhantomData;
  89
  90 use bitcoin::bech32;
  91 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
  92 use crate::ln::msgs::DecodeError;
  93 use crate::util::ser::{Readable, WithoutLength, Writeable, Writer};
  94
  95 mod sealed {
  96         #[allow(unused_imports)]
  97         use crate::prelude::*;
  98         use crate::ln::features::Features;
  99
 100         /// The context in which [`Features`] are applicable. Defines which features are known to the
 101         /// implementation, though specification of them as required or optional is up to the code
 102         /// constructing a features object.
 103         pub trait Context {
 104                 /// Bitmask for selecting features that are known to the implementation.
 105                 const KNOWN_FEATURE_MASK: &'static [u8];
 106         }
 107
 108         /// Defines a [`Context`] by stating which features it requires and which are optional. Features
 109         /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
 110         /// feature identifiers.
 111         macro_rules! define_context {
 112                 ($context: ident, [$( $( $known_feature: ident )|*, )*]) => {
 113                         #[derive(Eq, PartialEq)]
 114                         pub struct $context {}
 115
 116                         impl Context for $context {
 117                                 const KNOWN_FEATURE_MASK: &'static [u8] = &[
 118                                         $(
 119                                                 0b00_00_00_00 $(|
 120                                                         <Self as $known_feature>::REQUIRED_MASK |
 121                                                         <Self as $known_feature>::OPTIONAL_MASK)*,
 122                                         )*
 123                                 ];
 124                         }
 125
 126                         impl alloc::fmt::Display for Features<$context> {
 127                                 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
 128                                         $(
 129                                                 $(
 130                                                         fmt.write_fmt(format_args!("{}: {}, ", stringify!($known_feature),
 131                                                                 if <$context as $known_feature>::requires_feature(&self.flags) { "required" }
 132                                                                 else if <$context as $known_feature>::supports_feature(&self.flags) { "supported" }
 133                                                                 else { "not supported" }))?;
 134                                                 )*
 135                                                 {} // Rust gets mad if we only have a $()* block here, so add a dummy {}
 136                                         )*
 137                                         fmt.write_fmt(format_args!("unknown flags: {}",
 138                                                 if self.requires_unknown_bits() { "required" }
 139                                                 else if self.supports_unknown_bits() { "supported" } else { "none" }))
 140                                 }
 141                         }
 142                 };
 143         }
 144
 145         define_context!(InitContext, [
 146                 // Byte 0
 147                 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
 148                 // Byte 1
 149                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 150                 // Byte 2
 151                 BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
 152                 // Byte 3
 153                 RouteBlinding | ShutdownAnySegwit | Taproot,
 154                 // Byte 4
 155                 OnionMessages,
 156                 // Byte 5
 157                 ChannelType | SCIDPrivacy,
 158                 // Byte 6
 159                 ZeroConf,
 160                 // Byte 7
 161                 Trampoline,
 162         ]);
 163         define_context!(NodeContext, [
 164                 // Byte 0
 165                 DataLossProtect | UpfrontShutdownScript | GossipQueries,
 166                 // Byte 1
 167                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 168                 // Byte 2
 169                 BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
 170                 // Byte 3
 171                 RouteBlinding | ShutdownAnySegwit | Taproot,
 172                 // Byte 4
 173                 OnionMessages,
 174                 // Byte 5
 175                 ChannelType | SCIDPrivacy,
 176                 // Byte 6
 177                 ZeroConf | Keysend,
 178                 // Byte 7
 179                 Trampoline,
 180         ]);
 181         define_context!(ChannelContext, []);
 182         define_context!(Bolt11InvoiceContext, [
 183                 // Byte 0
 184                 ,
 185                 // Byte 1
 186                 VariableLengthOnion | PaymentSecret,
 187                 // Byte 2
 188                 BasicMPP,
 189                 // Byte 3
 190                 ,
 191                 // Byte 4
 192                 ,
 193                 // Byte 5
 194                 ,
 195                 // Byte 6
 196                 PaymentMetadata,
 197                 // Byte 7
 198                 Trampoline,
 199         ]);
 200         define_context!(OfferContext, []);
 201         define_context!(InvoiceRequestContext, []);
 202         define_context!(Bolt12InvoiceContext, [
 203                 // Byte 0
 204                 ,
 205                 // Byte 1
 206                 ,
 207                 // Byte 2
 208                 BasicMPP,
 209         ]);
 210         define_context!(BlindedHopContext, []);
 211         // This isn't a "real" feature context, and is only used in the channel_type field in an
 212         // `OpenChannel` message.
 213         define_context!(ChannelTypeContext, [
 214                 // Byte 0
 215                 ,
 216                 // Byte 1
 217                 StaticRemoteKey,
 218                 // Byte 2
 219                 AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
 220                 // Byte 3
 221                 Taproot,
 222                 // Byte 4
 223                 ,
 224                 // Byte 5
 225                 SCIDPrivacy,
 226                 // Byte 6
 227                 ZeroConf,
 228         ]);
 229
 230         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 231         /// useful for manipulating feature flags.
 232         macro_rules! define_feature {
 233                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 234                  $required_setter: ident, $supported_getter: ident) => {
 235                         #[doc = $doc]
 236                         ///
 237                         /// See [BOLT #9] for details.
 238                         ///
 239                         /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
 240                         pub trait $feature: Context {
 241                                 /// The bit used to signify that the feature is required.
 242                                 const EVEN_BIT: usize = $odd_bit - 1;
 243
 244                                 /// The bit used to signify that the feature is optional.
 245                                 const ODD_BIT: usize = $odd_bit;
 246
 247                                 /// Assertion that [`EVEN_BIT`] is actually even.
 248                                 ///
 249                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 250                                 const ASSERT_EVEN_BIT_PARITY: usize;
 251
 252                                 /// Assertion that [`ODD_BIT`] is actually odd.
 253                                 ///
 254                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 255                                 const ASSERT_ODD_BIT_PARITY: usize;
 256
 257                                 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
 258                                 ///
 259                                 /// [`KNOWN_FEATURE_MASK`]: Context::KNOWN_FEATURE_MASK
 260                                 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
 261                                 const ASSERT_BITS_IN_MASK: u8;
 262
 263                                 /// The byte where the feature is set.
 264                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 265
 266                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 267                                 ///
 268                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 269                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 270
 271                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 272                                 ///
 273                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 274                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 275
 276                                 /// Returns whether the feature is required by the given flags.
 277                                 #[inline]
 278                                 fn requires_feature(flags: &Vec<u8>) -> bool {
 279                                         flags.len() > Self::BYTE_OFFSET &&
 280                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
 281                                 }
 282
 283                                 /// Returns whether the feature is supported by the given flags.
 284                                 #[inline]
 285                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 286                                         flags.len() > Self::BYTE_OFFSET &&
 287                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 288                                 }
 289
 290                                 /// Sets the feature's required (even) bit in the given flags.
 291                                 #[inline]
 292                                 fn set_required_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::REQUIRED_MASK;
 298                                         flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 299                                 }
 300
 301                                 /// Sets the feature's optional (odd) bit in the given flags.
 302                                 #[inline]
 303                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 304                                         if flags.len() <= Self::BYTE_OFFSET {
 305                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 306                                         }
 307
 308                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 309                                 }
 310
 311                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 312                                 /// flags.
 313                                 #[inline]
 314                                 fn clear_bits(flags: &mut Vec<u8>) {
 315                                         if flags.len() > Self::BYTE_OFFSET {
 316                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 317                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 318                                         }
 319
 320                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 321                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 322                                         flags.resize(size, 0u8);
 323                                 }
 324                         }
 325
 326                         impl <T: $feature> Features<T> {
 327                                 /// Set this feature as optional.
 328                                 pub fn $optional_setter(&mut self) {
 329                                         <T as $feature>::set_optional_bit(&mut self.flags);
 330                                 }
 331
 332                                 /// Set this feature as required.
 333                                 pub fn $required_setter(&mut self) {
 334                                         <T as $feature>::set_required_bit(&mut self.flags);
 335                                 }
 336
 337                                 /// Checks if this feature is supported.
 338                                 pub fn $supported_getter(&self) -> bool {
 339                                         <T as $feature>::supports_feature(&self.flags)
 340                                 }
 341                         }
 342
 343                         $(
 344                                 impl $feature for $context {
 345                                         // EVEN_BIT % 2 == 0
 346                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 347
 348                                         // ODD_BIT % 2 == 1
 349                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 350
 351                                         // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
 352                                         #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
 353                                         const ASSERT_BITS_IN_MASK: u8 =
 354                                                 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
 355                                                  >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
 356                                 }
 357                         )*
 358                 };
 359                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 360                  $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
 361                         define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
 362                         impl <T: $feature> Features<T> {
 363                                 /// Checks if this feature is required.
 364                                 pub fn $required_getter(&self) -> bool {
 365                                         <T as $feature>::requires_feature(&self.flags)
 366                                 }
 367                         }
 368                 }
 369         }
 370
 371         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 372                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 373                 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
 374         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 375         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 376                 set_initial_routing_sync_optional, set_initial_routing_sync_required,
 377                 initial_routing_sync);
 378         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 379                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 380                 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
 381                 requires_upfront_shutdown_script);
 382         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 383                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
 384                 supports_gossip_queries, requires_gossip_queries);
 385         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, Bolt11InvoiceContext],
 386                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 387                 set_variable_length_onion_required, supports_variable_length_onion,
 388                 requires_variable_length_onion);
 389         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
 390                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 391                 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
 392         define_feature!(15, PaymentSecret, [InitContext, NodeContext, Bolt11InvoiceContext],
 393                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
 394                 supports_payment_secret, requires_payment_secret);
 395         define_feature!(17, BasicMPP, [InitContext, NodeContext, Bolt11InvoiceContext, Bolt12InvoiceContext],
 396                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
 397                 supports_basic_mpp, requires_basic_mpp);
 398         define_feature!(19, Wumbo, [InitContext, NodeContext],
 399                 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
 400                 supports_wumbo, requires_wumbo);
 401         define_feature!(21, AnchorsNonzeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
 402                 "Feature flags for `option_anchors_nonzero_fee_htlc_tx`.", set_anchors_nonzero_fee_htlc_tx_optional,
 403                 set_anchors_nonzero_fee_htlc_tx_required, supports_anchors_nonzero_fee_htlc_tx, requires_anchors_nonzero_fee_htlc_tx);
 404         define_feature!(23, AnchorsZeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
 405                 "Feature flags for `option_anchors_zero_fee_htlc_tx`.", set_anchors_zero_fee_htlc_tx_optional,
 406                 set_anchors_zero_fee_htlc_tx_required, supports_anchors_zero_fee_htlc_tx, requires_anchors_zero_fee_htlc_tx);
 407         define_feature!(25, RouteBlinding, [InitContext, NodeContext],
 408                 "Feature flags for `option_route_blinding`.", set_route_blinding_optional,
 409                 set_route_blinding_required, supports_route_blinding, requires_route_blinding);
 410         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 411                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 412                 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
 413         define_feature!(31, Taproot, [InitContext, NodeContext, ChannelTypeContext],
 414                 "Feature flags for `option_taproot`.", set_taproot_optional,
 415                 set_taproot_required, supports_taproot, requires_taproot);
 416         define_feature!(39, OnionMessages, [InitContext, NodeContext],
 417                 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
 418                 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
 419         define_feature!(45, ChannelType, [InitContext, NodeContext],
 420                 "Feature flags for `option_channel_type`.", set_channel_type_optional,
 421                 set_channel_type_required, supports_channel_type, requires_channel_type);
 422         define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
 423                 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
 424                 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
 425         define_feature!(49, PaymentMetadata, [Bolt11InvoiceContext],
 426                 "Feature flags for payment metadata in invoices.", set_payment_metadata_optional,
 427                 set_payment_metadata_required, supports_payment_metadata, requires_payment_metadata);
 428         define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
 429                 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
 430                 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
 431         define_feature!(55, Keysend, [NodeContext],
 432                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
 433                 supports_keysend, requires_keysend);
 434         define_feature!(57, Trampoline, [InitContext, NodeContext, Bolt11InvoiceContext],
 435                 "Feature flags for Trampoline routing.", set_trampoline_routing_optional, set_trampoline_routing_required,
 436                 supports_trampoline_routing, requires_trampoline_routing);
 437         // Note: update the module-level docs when a new feature bit is added!
 438
 439         #[cfg(test)]
 440         define_feature!(123456789, UnknownFeature,
 441                 [NodeContext, ChannelContext, Bolt11InvoiceContext, OfferContext, InvoiceRequestContext, Bolt12InvoiceContext, BlindedHopContext],
 442                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 443                 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
 444 }
 445
 446 const ANY_REQUIRED_FEATURES_MASK: u8 = 0b01_01_01_01;
 447 const ANY_OPTIONAL_FEATURES_MASK: u8 = 0b10_10_10_10;
 448
 449 /// Tracks the set of features which a node implements, templated by the context in which it
 450 /// appears.
 451 ///
 452 /// This is not exported to bindings users as we map the concrete feature types below directly instead
 453 #[derive(Eq)]
 454 pub struct Features<T: sealed::Context> {
 455         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 456         flags: Vec<u8>,
 457         mark: PhantomData<T>,
 458 }
 459
 460 impl<T: sealed::Context, Rhs: Borrow<Self>> core::ops::BitOrAssign<Rhs> for Features<T> {
 461         fn bitor_assign(&mut self, rhs: Rhs) {
 462                 let total_feature_len = cmp::max(self.flags.len(), rhs.borrow().flags.len());
 463                 self.flags.resize(total_feature_len, 0u8);
 464                 for (byte, rhs_byte) in self.flags.iter_mut().zip(rhs.borrow().flags.iter()) {
 465                         *byte |= *rhs_byte;
 466                 }
 467         }
 468 }
 469
 470 impl<T: sealed::Context> core::ops::BitOr for Features<T> {
 471         type Output = Self;
 472
 473         fn bitor(mut self, o: Self) -> Self {
 474                 self |= o;
 475                 self
 476         }
 477 }
 478
 479 impl<T: sealed::Context> Clone for Features<T> {
 480         fn clone(&self) -> Self {
 481                 Self {
 482                         flags: self.flags.clone(),
 483                         mark: PhantomData,
 484                 }
 485         }
 486 }
 487 impl<T: sealed::Context> Hash for Features<T> {
 488         fn hash<H: Hasher>(&self, hasher: &mut H) {
 489                 let mut nonzero_flags = &self.flags[..];
 490                 while nonzero_flags.last() == Some(&0) {
 491                         nonzero_flags = &nonzero_flags[..nonzero_flags.len() - 1];
 492                 }
 493                 nonzero_flags.hash(hasher);
 494         }
 495 }
 496 impl<T: sealed::Context> PartialEq for Features<T> {
 497         fn eq(&self, o: &Self) -> bool {
 498                 let mut o_iter = o.flags.iter();
 499                 let mut self_iter = self.flags.iter();
 500                 loop {
 501                         match (o_iter.next(), self_iter.next()) {
 502                                 (Some(o), Some(us)) => if o != us { return false },
 503                                 (Some(b), None) | (None, Some(b)) => if *b != 0 { return false },
 504                                 (None, None) => return true,
 505                         }
 506                 }
 507         }
 508 }
 509 impl<T: sealed::Context> PartialOrd for Features<T> {
 510         fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
 511                 self.flags.partial_cmp(&other.flags)
 512         }
 513 }
 514 impl<T: sealed::Context + Eq> Ord for Features<T> {
 515         fn cmp(&self, other: &Self) -> cmp::Ordering {
 516                 self.flags.cmp(&other.flags)
 517         }
 518 }
 519 impl<T: sealed::Context> fmt::Debug for Features<T> {
 520         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 521                 self.flags.fmt(fmt)
 522         }
 523 }
 524
 525 /// Features used within an `init` message.
 526 pub type InitFeatures = Features<sealed::InitContext>;
 527 /// Features used within a `node_announcement` message.
 528 pub type NodeFeatures = Features<sealed::NodeContext>;
 529 /// Features used within a `channel_announcement` message.
 530 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 531 /// Features used within an invoice.
 532 pub type Bolt11InvoiceFeatures = Features<sealed::Bolt11InvoiceContext>;
 533 /// Features used within an `offer`.
 534 pub type OfferFeatures = Features<sealed::OfferContext>;
 535 /// Features used within an `invoice_request`.
 536 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
 537 /// Features used within an `invoice`.
 538 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
 539 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
 540 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
 541
 542 /// Features used within the channel_type field in an OpenChannel message.
 543 ///
 544 /// A channel is always of some known "type", describing the transaction formats used and the exact
 545 /// semantics of our interaction with our peer.
 546 ///
 547 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
 548 /// the counterparty, only required features are allowed here.
 549 ///
 550 /// This is serialized differently from other feature types - it is not prefixed by a length, and
 551 /// thus must only appear inside a TLV where its length is known in advance.
 552 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
 553
 554 impl InitFeatures {
 555         /// Writes all features present up to, and including, 13.
 556         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 557                 let len = cmp::min(2, self.flags.len());
 558                 (len as u16).write(w)?;
 559                 for i in (0..len).rev() {
 560                         if i == 0 {
 561                                 self.flags[i].write(w)?;
 562                         } else {
 563                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 564                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 565                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 566                         }
 567                 }
 568                 Ok(())
 569         }
 570
 571         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 572         /// are included in the result.
 573         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 574                 self.to_context_internal()
 575         }
 576 }
 577
 578 impl Bolt11InvoiceFeatures {
 579         /// Converts `Bolt11InvoiceFeatures` to `Features<C>`. Only known `Bolt11InvoiceFeatures` relevant to
 580         /// context `C` are included in the result.
 581         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 582                 self.to_context_internal()
 583         }
 584
 585         /// Getting a route for a keysend payment to a private node requires providing the payee's
 586         /// features (since they were not announced in a node announcement). However, keysend payments
 587         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 588         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
 589         /// `Bolt11InvoiceFeatures` for [`find_route`].
 590         ///
 591         /// MPP keysend is not widely supported yet, so we parameterize support to allow the user to
 592         /// choose whether their router should find multi-part routes.
 593         ///
 594         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
 595         /// [`find_route`]: crate::routing::router::find_route
 596         pub(crate) fn for_keysend(allow_mpp: bool) -> Bolt11InvoiceFeatures {
 597                 let mut res = Bolt11InvoiceFeatures::empty();
 598                 res.set_variable_length_onion_optional();
 599                 if allow_mpp {
 600                         res.set_basic_mpp_optional();
 601                 }
 602                 res
 603         }
 604 }
 605
 606 impl Bolt12InvoiceFeatures {
 607         /// Converts [`Bolt12InvoiceFeatures`] to [`Features<C>`]. Only known [`Bolt12InvoiceFeatures`]
 608         /// relevant to context `C` are included in the result.
 609         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 610                 self.to_context_internal()
 611         }
 612 }
 613
 614 impl ChannelTypeFeatures {
 615         // Maps the relevant `InitFeatures` to `ChannelTypeFeatures`. Any unknown features to
 616         // `ChannelTypeFeatures` are not included in the result.
 617         pub(crate) fn from_init(init: &InitFeatures) -> Self {
 618                 let mut ret = init.to_context_internal();
 619                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
 620                 // optional bits and then AND out the optional ones.
 621                 for byte in ret.flags.iter_mut() {
 622                         *byte |= (*byte & ANY_OPTIONAL_FEATURES_MASK) >> 1;
 623                         *byte &= ANY_REQUIRED_FEATURES_MASK;
 624                 }
 625                 ret
 626         }
 627
 628         /// Constructs a ChannelTypeFeatures with only static_remotekey set
 629         pub(crate) fn only_static_remote_key() -> Self {
 630                 let mut ret = Self::empty();
 631                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 632                 ret
 633         }
 634
 635         /// Constructs a ChannelTypeFeatures with anchors support
 636         pub(crate) fn anchors_zero_htlc_fee_and_dependencies() -> Self {
 637                 let mut ret = Self::empty();
 638                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 639                 <sealed::ChannelTypeContext as sealed::AnchorsZeroFeeHtlcTx>::set_required_bit(&mut ret.flags);
 640                 ret
 641         }
 642 }
 643
 644 impl ToBase32 for Bolt11InvoiceFeatures {
 645         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 646                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 647                 // minus one before dividing
 648                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 649                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 650                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 651                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 652                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 653                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 654                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 655                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 656                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 657                         if new_u5_idx > 0 {
 658                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 659                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 660                         }
 661                         if new_u5_idx > 1 {
 662                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 663                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 664                         }
 665                 }
 666                 // Trim the highest feature bits.
 667                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 668                         res_u5s.remove(0);
 669                 }
 670                 writer.write(&res_u5s)
 671         }
 672 }
 673
 674 impl Base32Len for Bolt11InvoiceFeatures {
 675         fn base32_len(&self) -> usize {
 676                 self.to_base32().len()
 677         }
 678 }
 679
 680 impl FromBase32 for Bolt11InvoiceFeatures {
 681         type Err = bech32::Error;
 682
 683         fn from_base32(field_data: &[u5]) -> Result<Bolt11InvoiceFeatures, bech32::Error> {
 684                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 685                 // minus one before dividing
 686                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 687                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 688                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 689                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 690                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 691                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 692                         let chunk_u16 = chunk.to_u8() as u16;
 693                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 694                         if new_byte_idx != length_bytes - 1 {
 695                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 696                         }
 697                 }
 698                 // Trim the highest feature bits.
 699                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 700                         res_bytes.pop();
 701                 }
 702                 Ok(Bolt11InvoiceFeatures::from_le_bytes(res_bytes))
 703         }
 704 }
 705
 706 impl<T: sealed::Context> Features<T> {
 707         /// Create a blank Features with no features set
 708         pub fn empty() -> Self {
 709                 Features {
 710                         flags: Vec::new(),
 711                         mark: PhantomData,
 712                 }
 713         }
 714
 715         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 716         /// included in the result.
 717         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 718                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 719                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 720                 let mut flags = Vec::new();
 721                 for (i, byte) in self.flags.iter().enumerate() {
 722                         if i < from_byte_count && i < to_byte_count {
 723                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 724                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 725                                 flags.push(byte & from_known_features & to_known_features);
 726                         }
 727                 }
 728                 Features::<C> { flags, mark: PhantomData, }
 729         }
 730
 731         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 732         /// most on-the-wire encodings.
 733         ///
 734         /// This is not exported to bindings users as we don't support export across multiple T
 735         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 736                 Features {
 737                         flags,
 738                         mark: PhantomData,
 739                 }
 740         }
 741
 742         #[cfg(test)]
 743         /// Gets the underlying flags set, in LE.
 744         pub fn le_flags(&self) -> &Vec<u8> {
 745                 &self.flags
 746         }
 747
 748         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 749                 for f in self.flags.iter().rev() { // Swap back to big-endian
 750                         f.write(w)?;
 751                 }
 752                 Ok(())
 753         }
 754
 755         /// Create a [`Features`] given a set of flags, in big-endian. This is in byte order from
 756         /// most on-the-wire encodings.
 757         ///
 758         /// This is not exported to bindings users as we don't support export across multiple T
 759         pub fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
 760                 flags.reverse(); // Swap to little-endian
 761                 Self {
 762                         flags,
 763                         mark: PhantomData,
 764                 }
 765         }
 766
 767         pub(crate) fn supports_any_optional_bits(&self) -> bool {
 768                 self.flags.iter().any(|&byte| (byte & ANY_OPTIONAL_FEATURES_MASK) != 0)
 769         }
 770
 771         /// Returns true if this `Features` object contains required features unknown by `other`.
 772         pub fn requires_unknown_bits_from(&self, other: &Self) -> bool {
 773                 // Bitwise AND-ing with all even bits set except for known features will select required
 774                 // unknown features.
 775                 self.flags.iter().enumerate().any(|(i, &byte)| {
 776                         let unknown_features = unset_features_mask_at_position(other, i);
 777                         (byte & (ANY_REQUIRED_FEATURES_MASK & unknown_features)) != 0
 778                 })
 779         }
 780
 781         pub(crate) fn required_unknown_bits_from(&self, other: &Self) -> Vec<usize> {
 782                 let mut unknown_bits = Vec::new();
 783
 784                 // Bitwise AND-ing with all even bits set except for known features will select required
 785                 // unknown features.
 786                 self.flags.iter().enumerate().for_each(|(i, &byte)| {
 787                         let unknown_features = unset_features_mask_at_position(other, i);
 788                         if byte & unknown_features != 0 {
 789                                 for bit in (0..8).step_by(2) {
 790                                         if ((byte & unknown_features) >> bit) & 1 == 1 {
 791                                                 unknown_bits.push(i * 8 + bit);
 792                                         }
 793                                 }
 794                         }
 795                 });
 796
 797                 unknown_bits
 798         }
 799
 800         /// Returns true if this `Features` object contains unknown feature flags which are set as
 801         /// "required".
 802         pub fn requires_unknown_bits(&self) -> bool {
 803                 // Bitwise AND-ing with all even bits set except for known features will select required
 804                 // unknown features.
 805                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 806                 self.flags.iter().enumerate().any(|(i, &byte)| {
 807                         let unknown_features = if i < byte_count {
 808                                 !T::KNOWN_FEATURE_MASK[i]
 809                         } else {
 810                                 0b11_11_11_11
 811                         };
 812                         (byte & (ANY_REQUIRED_FEATURES_MASK & unknown_features)) != 0
 813                 })
 814         }
 815
 816         pub(crate) fn supports_unknown_bits(&self) -> bool {
 817                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 818                 // both required and optional unknown features.
 819                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 820                 self.flags.iter().enumerate().any(|(i, &byte)| {
 821                         let unknown_features = if i < byte_count {
 822                                 !T::KNOWN_FEATURE_MASK[i]
 823                         } else {
 824                                 0b11_11_11_11
 825                         };
 826                         (byte & unknown_features) != 0
 827                 })
 828         }
 829
 830         // Returns true if the features within `self` are a subset of the features within `other`.
 831         pub(crate) fn is_subset(&self, other: &Self) -> bool {
 832                 for (idx, byte) in self.flags.iter().enumerate() {
 833                         if let Some(other_byte) = other.flags.get(idx) {
 834                                 if byte & other_byte != *byte {
 835                                         // `self` has bits set that `other` doesn't.
 836                                         return false;
 837                                 }
 838                         } else {
 839                                 if *byte > 0 {
 840                                         // `self` has a non-zero byte that `other` doesn't.
 841                                         return false;
 842                                 }
 843                         }
 844                 }
 845                 true
 846         }
 847
 848         /// Sets a required feature bit. Errors if `bit` is outside the feature range as defined
 849         /// by [BOLT 9].
 850         ///
 851         /// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
 852         /// be set instead (i.e., `bit - 1`).
 853         ///
 854         /// [BOLT 9]: https://github.com/lightning/bolts/blob/master/09-features.md
 855         pub fn set_required_feature_bit(&mut self, bit: usize) -> Result<(), ()> {
 856                 self.set_feature_bit(bit - (bit % 2))
 857         }
 858
 859         /// Sets an optional feature bit. Errors if `bit` is outside the feature range as defined
 860         /// by [BOLT 9].
 861         ///
 862         /// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
 863         /// set instead (i.e., `bit + 1`).
 864         ///
 865         /// [BOLT 9]: https://github.com/lightning/bolts/blob/master/09-features.md
 866         pub fn set_optional_feature_bit(&mut self, bit: usize) -> Result<(), ()> {
 867                 self.set_feature_bit(bit + (1 - (bit % 2)))
 868         }
 869
 870         fn set_feature_bit(&mut self, bit: usize) -> Result<(), ()> {
 871                 if bit > 255 {
 872                         return Err(());
 873                 }
 874                 self.set_bit(bit, false)
 875         }
 876
 877         /// Sets a required custom feature bit. Errors if `bit` is outside the custom range as defined
 878         /// by [bLIP 2] or if it is a known `T` feature.
 879         ///
 880         /// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
 881         /// be set instead (i.e., `bit - 1`).
 882         ///
 883         /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
 884         pub fn set_required_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 885                 self.set_custom_bit(bit - (bit % 2))
 886         }
 887
 888         /// Sets an optional custom feature bit. Errors if `bit` is outside the custom range as defined
 889         /// by [bLIP 2] or if it is a known `T` feature.
 890         ///
 891         /// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
 892         /// set instead (i.e., `bit + 1`).
 893         ///
 894         /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
 895         pub fn set_optional_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 896                 self.set_custom_bit(bit + (1 - (bit % 2)))
 897         }
 898
 899         fn set_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
 900                 if bit < 256 {
 901                         return Err(());
 902                 }
 903                 self.set_bit(bit, true)
 904         }
 905
 906         fn set_bit(&mut self, bit: usize, custom: bool) -> Result<(), ()> {
 907                 let byte_offset = bit / 8;
 908                 let mask = 1 << (bit - 8 * byte_offset);
 909                 if byte_offset < T::KNOWN_FEATURE_MASK.len() && custom {
 910                         if (T::KNOWN_FEATURE_MASK[byte_offset] & mask) != 0 {
 911                                 return Err(());
 912                         }
 913                 }
 914
 915                 if self.flags.len() <= byte_offset {
 916                         self.flags.resize(byte_offset + 1, 0u8);
 917                 }
 918
 919                 self.flags[byte_offset] |= mask;
 920
 921                 Ok(())
 922         }
 923 }
 924
 925 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 926         #[cfg(test)]
 927         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 928                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 929                 self
 930         }
 931 }
 932
 933 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 934         #[cfg(test)]
 935         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 936                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 937                 self
 938         }
 939 }
 940
 941 impl<T: sealed::Wumbo> Features<T> {
 942         #[cfg(test)]
 943         pub(crate) fn clear_wumbo(mut self) -> Self {
 944                 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
 945                 self
 946         }
 947 }
 948
 949 impl<T: sealed::SCIDPrivacy> Features<T> {
 950         pub(crate) fn clear_scid_privacy(&mut self) {
 951                 <T as sealed::SCIDPrivacy>::clear_bits(&mut self.flags);
 952         }
 953 }
 954
 955 impl<T: sealed::AnchorsZeroFeeHtlcTx> Features<T> {
 956         pub(crate) fn clear_anchors_zero_fee_htlc_tx(&mut self) {
 957                 <T as sealed::AnchorsZeroFeeHtlcTx>::clear_bits(&mut self.flags);
 958         }
 959 }
 960
 961 impl<T: sealed::RouteBlinding> Features<T> {
 962         #[cfg(test)]
 963         pub(crate) fn clear_route_blinding(&mut self) {
 964                 <T as sealed::RouteBlinding>::clear_bits(&mut self.flags);
 965         }
 966 }
 967
 968 #[cfg(test)]
 969 impl<T: sealed::UnknownFeature> Features<T> {
 970         pub(crate) fn unknown() -> Self {
 971                 let mut features = Self::empty();
 972                 features.set_unknown_feature_required();
 973                 features
 974         }
 975 }
 976
 977 macro_rules! impl_feature_len_prefixed_write {
 978         ($features: ident) => {
 979                 impl Writeable for $features {
 980                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 981                                 (self.flags.len() as u16).write(w)?;
 982                                 self.write_be(w)
 983                         }
 984                 }
 985                 impl Readable for $features {
 986                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 987                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
 988                         }
 989                 }
 990         }
 991 }
 992 impl_feature_len_prefixed_write!(InitFeatures);
 993 impl_feature_len_prefixed_write!(ChannelFeatures);
 994 impl_feature_len_prefixed_write!(NodeFeatures);
 995 impl_feature_len_prefixed_write!(Bolt11InvoiceFeatures);
 996 impl_feature_len_prefixed_write!(Bolt12InvoiceFeatures);
 997 impl_feature_len_prefixed_write!(BlindedHopFeatures);
 998
 999 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
1000 macro_rules! impl_feature_tlv_write {
1001         ($features: ident) => {
1002                 impl Writeable for $features {
1003                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
1004                                 WithoutLength(self).write(w)
1005                         }
1006                 }
1007                 impl Readable for $features {
1008                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
1009                                 Ok(WithoutLength::<Self>::read(r)?.0)
1010                         }
1011                 }
1012         }
1013 }
1014
1015 impl_feature_tlv_write!(ChannelTypeFeatures);
1016
1017 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
1018 // requires a length but the former does not.
1019
1020 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
1021         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
1022                 self.0.write_be(w)
1023         }
1024 }
1025
1026 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
1027         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
1028                 let v = io_extras::read_to_end(r)?;
1029                 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
1030         }
1031 }
1032
1033 pub(crate) fn unset_features_mask_at_position<T: sealed::Context>(other: &Features<T>, index: usize) -> u8 {
1034         if index < other.flags.len() {
1035                 // Form a mask similar to !T::KNOWN_FEATURE_MASK only for `other`
1036                 !(other.flags[index]
1037                         | ((other.flags[index] >> 1) & ANY_REQUIRED_FEATURES_MASK)
1038                         | ((other.flags[index] << 1) & ANY_OPTIONAL_FEATURES_MASK))
1039         } else {
1040                 0b11_11_11_11
1041         }
1042 }
1043
1044 #[cfg(test)]
1045 mod tests {
1046         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, Bolt11InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
1047         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
1048         use crate::util::ser::{Readable, WithoutLength, Writeable};
1049
1050         #[test]
1051         fn sanity_test_unknown_bits() {
1052                 let features = ChannelFeatures::empty();
1053                 assert!(!features.requires_unknown_bits());
1054                 assert!(!features.supports_unknown_bits());
1055
1056                 let mut features = ChannelFeatures::empty();
1057                 features.set_unknown_feature_required();
1058                 assert!(features.requires_unknown_bits());
1059                 assert!(features.supports_unknown_bits());
1060                 assert_eq!(features.required_unknown_bits_from(&ChannelFeatures::empty()), vec![123456788]);
1061
1062                 let mut features = ChannelFeatures::empty();
1063                 features.set_unknown_feature_optional();
1064                 assert!(!features.requires_unknown_bits());
1065                 assert!(features.supports_unknown_bits());
1066                 assert_eq!(features.required_unknown_bits_from(&ChannelFeatures::empty()), vec![]);
1067
1068                 let mut features = ChannelFeatures::empty();
1069                 features.set_unknown_feature_required();
1070                 features.set_custom_bit(123456786).unwrap();
1071                 assert!(features.requires_unknown_bits());
1072                 assert!(features.supports_unknown_bits());
1073                 assert_eq!(features.required_unknown_bits_from(&ChannelFeatures::empty()), vec![123456786, 123456788]);
1074
1075                 let mut limiter = ChannelFeatures::empty();
1076                 limiter.set_unknown_feature_optional();
1077                 assert_eq!(features.required_unknown_bits_from(&limiter), vec![123456786]);
1078         }
1079
1080         #[test]
1081         fn requires_unknown_bits_from() {
1082                 let mut features1 = InitFeatures::empty();
1083                 let mut features2 = InitFeatures::empty();
1084                 assert!(!features1.requires_unknown_bits_from(&features2));
1085                 assert!(!features2.requires_unknown_bits_from(&features1));
1086
1087                 features1.set_data_loss_protect_required();
1088                 assert!(features1.requires_unknown_bits_from(&features2));
1089                 assert!(!features2.requires_unknown_bits_from(&features1));
1090
1091                 features2.set_data_loss_protect_optional();
1092                 assert!(!features1.requires_unknown_bits_from(&features2));
1093                 assert!(!features2.requires_unknown_bits_from(&features1));
1094
1095                 features2.set_gossip_queries_required();
1096                 assert!(!features1.requires_unknown_bits_from(&features2));
1097                 assert!(features2.requires_unknown_bits_from(&features1));
1098
1099                 features1.set_gossip_queries_optional();
1100                 assert!(!features1.requires_unknown_bits_from(&features2));
1101                 assert!(!features2.requires_unknown_bits_from(&features1));
1102
1103                 features1.set_variable_length_onion_required();
1104                 assert!(features1.requires_unknown_bits_from(&features2));
1105                 assert!(!features2.requires_unknown_bits_from(&features1));
1106
1107                 features2.set_variable_length_onion_optional();
1108                 assert!(!features1.requires_unknown_bits_from(&features2));
1109                 assert!(!features2.requires_unknown_bits_from(&features1));
1110
1111                 features1.set_basic_mpp_required();
1112                 features2.set_wumbo_required();
1113                 assert!(features1.requires_unknown_bits_from(&features2));
1114                 assert!(features2.requires_unknown_bits_from(&features1));
1115         }
1116
1117         #[test]
1118         fn convert_to_context_with_relevant_flags() {
1119                 let mut init_features = InitFeatures::empty();
1120                 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
1121                 // converted as it's only relevant in an init context).
1122                 init_features.set_initial_routing_sync_required();
1123                 init_features.set_data_loss_protect_required();
1124                 init_features.set_variable_length_onion_required();
1125                 init_features.set_static_remote_key_required();
1126                 init_features.set_payment_secret_required();
1127                 init_features.set_basic_mpp_optional();
1128                 init_features.set_wumbo_optional();
1129                 init_features.set_anchors_zero_fee_htlc_tx_optional();
1130                 init_features.set_route_blinding_optional();
1131                 init_features.set_shutdown_any_segwit_optional();
1132                 init_features.set_onion_messages_optional();
1133                 init_features.set_channel_type_optional();
1134                 init_features.set_scid_privacy_optional();
1135                 init_features.set_zero_conf_optional();
1136
1137                 assert!(init_features.initial_routing_sync());
1138                 assert!(!init_features.supports_upfront_shutdown_script());
1139                 assert!(!init_features.supports_gossip_queries());
1140
1141                 let node_features: NodeFeatures = init_features.to_context();
1142                 {
1143                         // Check that the flags are as expected:
1144                         // - option_data_loss_protect (req)
1145                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
1146                         // - basic_mpp | wumbo | option_anchors_zero_fee_htlc_tx
1147                         // - option_route_blinding | opt_shutdown_anysegwit
1148                         // - onion_messages
1149                         // - option_channel_type | option_scid_alias
1150                         // - option_zeroconf
1151                         assert_eq!(node_features.flags.len(), 7);
1152                         assert_eq!(node_features.flags[0], 0b00000001);
1153                         assert_eq!(node_features.flags[1], 0b01010001);
1154                         assert_eq!(node_features.flags[2], 0b10001010);
1155                         assert_eq!(node_features.flags[3], 0b00001010);
1156                         assert_eq!(node_features.flags[4], 0b10000000);
1157                         assert_eq!(node_features.flags[5], 0b10100000);
1158                         assert_eq!(node_features.flags[6], 0b00001000);
1159                 }
1160
1161                 // Check that cleared flags are kept blank when converting back:
1162                 // - initial_routing_sync was not applicable to NodeContext
1163                 // - upfront_shutdown_script was cleared before converting
1164                 // - gossip_queries was cleared before converting
1165                 let features: InitFeatures = node_features.to_context_internal();
1166                 assert!(!features.initial_routing_sync());
1167                 assert!(!features.supports_upfront_shutdown_script());
1168                 assert!(!init_features.supports_gossip_queries());
1169         }
1170
1171         #[test]
1172         fn convert_to_context_with_unknown_flags() {
1173                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
1174                 assert!(<sealed::ChannelContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
1175                         <sealed::Bolt11InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
1176                 let mut channel_features = ChannelFeatures::empty();
1177                 channel_features.set_unknown_feature_optional();
1178                 assert!(channel_features.supports_unknown_bits());
1179                 let invoice_features: Bolt11InvoiceFeatures = channel_features.to_context_internal();
1180                 assert!(!invoice_features.supports_unknown_bits());
1181         }
1182
1183         #[test]
1184         fn set_feature_bits() {
1185                 let mut features = Bolt11InvoiceFeatures::empty();
1186                 features.set_basic_mpp_optional();
1187                 features.set_payment_secret_required();
1188                 assert!(features.supports_basic_mpp());
1189                 assert!(!features.requires_basic_mpp());
1190                 assert!(features.requires_payment_secret());
1191                 assert!(features.supports_payment_secret());
1192
1193                 // Set flags manually
1194                 let mut features = NodeFeatures::empty();
1195                 assert!(features.set_optional_feature_bit(55).is_ok());
1196                 assert!(features.supports_keysend());
1197                 assert!(features.set_optional_feature_bit(255).is_ok());
1198                 assert!(features.set_required_feature_bit(256).is_err());
1199         }
1200
1201         #[test]
1202         fn set_custom_bits() {
1203                 let mut features = Bolt11InvoiceFeatures::empty();
1204                 features.set_variable_length_onion_optional();
1205                 assert_eq!(features.flags[1], 0b00000010);
1206
1207                 assert!(features.set_optional_custom_bit(255).is_err());
1208                 assert!(features.set_required_custom_bit(256).is_ok());
1209                 assert!(features.set_required_custom_bit(258).is_ok());
1210                 assert_eq!(features.flags[31], 0b00000000);
1211                 assert_eq!(features.flags[32], 0b00000101);
1212
1213                 let known_bit = <sealed::Bolt11InvoiceContext as sealed::PaymentSecret>::EVEN_BIT;
1214                 let byte_offset = <sealed::Bolt11InvoiceContext as sealed::PaymentSecret>::BYTE_OFFSET;
1215                 assert_eq!(byte_offset, 1);
1216                 assert_eq!(features.flags[byte_offset], 0b00000010);
1217                 assert!(features.set_required_custom_bit(known_bit).is_err());
1218                 assert_eq!(features.flags[byte_offset], 0b00000010);
1219
1220                 let mut features = Bolt11InvoiceFeatures::empty();
1221                 assert!(features.set_optional_custom_bit(256).is_ok());
1222                 assert!(features.set_optional_custom_bit(259).is_ok());
1223                 assert_eq!(features.flags[32], 0b00001010);
1224
1225                 let mut features = Bolt11InvoiceFeatures::empty();
1226                 assert!(features.set_required_custom_bit(257).is_ok());
1227                 assert!(features.set_required_custom_bit(258).is_ok());
1228                 assert_eq!(features.flags[32], 0b00000101);
1229         }
1230
1231         #[test]
1232         fn encodes_features_without_length() {
1233                 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1234                 assert_eq!(features.flags.len(), 8);
1235
1236                 let mut serialized_features = Vec::new();
1237                 WithoutLength(&features).write(&mut serialized_features).unwrap();
1238                 assert_eq!(serialized_features.len(), 8);
1239
1240                 let deserialized_features =
1241                         WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
1242                 assert_eq!(features, deserialized_features);
1243         }
1244
1245         #[test]
1246         fn invoice_features_encoding() {
1247                 let features_as_u5s = vec![
1248                         u5::try_from_u8(6).unwrap(),
1249                         u5::try_from_u8(10).unwrap(),
1250                         u5::try_from_u8(25).unwrap(),
1251                         u5::try_from_u8(1).unwrap(),
1252                         u5::try_from_u8(10).unwrap(),
1253                         u5::try_from_u8(0).unwrap(),
1254                         u5::try_from_u8(20).unwrap(),
1255                         u5::try_from_u8(2).unwrap(),
1256                         u5::try_from_u8(0).unwrap(),
1257                         u5::try_from_u8(6).unwrap(),
1258                         u5::try_from_u8(0).unwrap(),
1259                         u5::try_from_u8(16).unwrap(),
1260                         u5::try_from_u8(1).unwrap(),
1261                 ];
1262                 let features = Bolt11InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1263
1264                 // Test length calculation.
1265                 assert_eq!(features.base32_len(), 13);
1266
1267                 // Test serialization.
1268                 let features_serialized = features.to_base32();
1269                 assert_eq!(features_as_u5s, features_serialized);
1270
1271                 // Test deserialization.
1272                 let features_deserialized = Bolt11InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
1273                 assert_eq!(features, features_deserialized);
1274         }
1275
1276         #[test]
1277         fn test_channel_type_mapping() {
1278                 // If we map an Bolt11InvoiceFeatures with StaticRemoteKey optional, it should map into a
1279                 // required-StaticRemoteKey ChannelTypeFeatures.
1280                 let mut init_features = InitFeatures::empty();
1281                 init_features.set_static_remote_key_optional();
1282                 let converted_features = ChannelTypeFeatures::from_init(&init_features);
1283                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
1284                 assert!(!converted_features.supports_any_optional_bits());
1285                 assert!(converted_features.requires_static_remote_key());
1286         }
1287
1288         #[test]
1289         #[cfg(feature = "std")]
1290         fn test_excess_zero_bytes_ignored() {
1291                 // Checks that `Hash` and `PartialEq` ignore excess zero bytes, which may appear due to
1292                 // feature conversion or because a peer serialized their feature poorly.
1293                 use std::collections::hash_map::DefaultHasher;
1294                 use std::hash::{Hash, Hasher};
1295
1296                 let mut zerod_features = InitFeatures::empty();
1297                 zerod_features.flags = vec![0];
1298                 let empty_features = InitFeatures::empty();
1299                 assert!(empty_features.flags.is_empty());
1300
1301                 assert_eq!(zerod_features, empty_features);
1302
1303                 let mut zerod_hash = DefaultHasher::new();
1304                 zerod_features.hash(&mut zerod_hash);
1305                 let mut empty_hash = DefaultHasher::new();
1306                 empty_features.hash(&mut empty_hash);
1307                 assert_eq!(zerod_hash.finish(), empty_hash.finish());
1308         }
1309 }