_ 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 //! - `ShutdownAnySegwit` - requires/supports that future segwit versions are allowed in `shutdown`
  45 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  46 //! - `OnionMessages` - requires/supports forwarding onion messages
  47 //!     (see [BOLT-7](https://github.com/lightning/bolts/pull/759/files) for more information).
  48 //!     TODO: update link
  49 //! - `ChannelType` - node supports the channel_type field in open/accept
  50 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  51 //! - `SCIDPrivacy` - supply channel aliases for routing
  52 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
  53 //! - `Keysend` - send funds to a node without an invoice
  54 //!     (see the [`Keysend` feature assignment proposal](https://github.com/lightning/bolts/issues/605#issuecomment-606679798) for more information).
  55 //!
  56 //! [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
  57 //! [messages]: crate::ln::msgs
  58
  59 use crate::{io, io_extras};
  60 use crate::prelude::*;
  61 use core::{cmp, fmt};
  62 use core::hash::{Hash, Hasher};
  63 use core::marker::PhantomData;
  64
  65 use bitcoin::bech32;
  66 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
  67 use crate::ln::msgs::DecodeError;
  68 use crate::util::ser::{Readable, WithoutLength, Writeable, Writer};
  69
  70 mod sealed {
  71         use crate::prelude::*;
  72         use crate::ln::features::Features;
  73
  74         /// The context in which [`Features`] are applicable. Defines which features are known to the
  75         /// implementation, though specification of them as required or optional is up to the code
  76         /// constructing a features object.
  77         pub trait Context {
  78                 /// Bitmask for selecting features that are known to the implementation.
  79                 const KNOWN_FEATURE_MASK: &'static [u8];
  80         }
  81
  82         /// Defines a [`Context`] by stating which features it requires and which are optional. Features
  83         /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
  84         /// feature identifiers.
  85         macro_rules! define_context {
  86                 ($context: ident, [$( $( $known_feature: ident )|*, )*]) => {
  87                         #[derive(Eq, PartialEq)]
  88                         pub struct $context {}
  89
  90                         impl Context for $context {
  91                                 const KNOWN_FEATURE_MASK: &'static [u8] = &[
  92                                         $(
  93                                                 0b00_00_00_00 $(|
  94                                                         <Self as $known_feature>::REQUIRED_MASK |
  95                                                         <Self as $known_feature>::OPTIONAL_MASK)*,
  96                                         )*
  97                                 ];
  98                         }
  99
 100                         impl alloc::fmt::Display for Features<$context> {
 101                                 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
 102                                         $(
 103                                                 $(
 104                                                         fmt.write_fmt(format_args!("{}: {}, ", stringify!($known_feature),
 105                                                                 if <$context as $known_feature>::requires_feature(&self.flags) { "required" }
 106                                                                 else if <$context as $known_feature>::supports_feature(&self.flags) { "supported" }
 107                                                                 else { "not supported" }))?;
 108                                                 )*
 109                                                 {} // Rust gets mad if we only have a $()* block here, so add a dummy {}
 110                                         )*
 111                                         fmt.write_fmt(format_args!("unknown flags: {}",
 112                                                 if self.requires_unknown_bits() { "required" }
 113                                                 else if self.supports_unknown_bits() { "supported" } else { "none" }))
 114                                 }
 115                         }
 116                 };
 117         }
 118
 119         define_context!(InitContext, [
 120                 // Byte 0
 121                 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
 122                 // Byte 1
 123                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 124                 // Byte 2
 125                 BasicMPP | Wumbo,
 126                 // Byte 3
 127                 ShutdownAnySegwit,
 128                 // Byte 4
 129                 OnionMessages,
 130                 // Byte 5
 131                 ChannelType | SCIDPrivacy,
 132                 // Byte 6
 133                 ZeroConf,
 134         ]);
 135         define_context!(NodeContext, [
 136                 // Byte 0
 137                 DataLossProtect | UpfrontShutdownScript | GossipQueries,
 138                 // Byte 1
 139                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 140                 // Byte 2
 141                 BasicMPP | Wumbo,
 142                 // Byte 3
 143                 ShutdownAnySegwit,
 144                 // Byte 4
 145                 OnionMessages,
 146                 // Byte 5
 147                 ChannelType | SCIDPrivacy,
 148                 // Byte 6
 149                 ZeroConf | Keysend,
 150         ]);
 151         define_context!(ChannelContext, []);
 152         define_context!(InvoiceContext, [
 153                 // Byte 0
 154                 ,
 155                 // Byte 1
 156                 VariableLengthOnion | PaymentSecret,
 157                 // Byte 2
 158                 BasicMPP,
 159         ]);
 160         define_context!(OfferContext, []);
 161         define_context!(InvoiceRequestContext, []);
 162         define_context!(Bolt12InvoiceContext, [
 163                 // Byte 0
 164                 ,
 165                 // Byte 1
 166                 ,
 167                 // Byte 2
 168                 BasicMPP,
 169         ]);
 170         define_context!(BlindedHopContext, []);
 171         // This isn't a "real" feature context, and is only used in the channel_type field in an
 172         // `OpenChannel` message.
 173         define_context!(ChannelTypeContext, [
 174                 // Byte 0
 175                 ,
 176                 // Byte 1
 177                 StaticRemoteKey,
 178                 // Byte 2
 179                 ,
 180                 // Byte 3
 181                 ,
 182                 // Byte 4
 183                 ,
 184                 // Byte 5
 185                 SCIDPrivacy,
 186                 // Byte 6
 187                 ZeroConf,
 188         ]);
 189
 190         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 191         /// useful for manipulating feature flags.
 192         macro_rules! define_feature {
 193                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 194                  $required_setter: ident, $supported_getter: ident) => {
 195                         #[doc = $doc]
 196                         ///
 197                         /// See [BOLT #9] for details.
 198                         ///
 199                         /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
 200                         pub trait $feature: Context {
 201                                 /// The bit used to signify that the feature is required.
 202                                 const EVEN_BIT: usize = $odd_bit - 1;
 203
 204                                 /// The bit used to signify that the feature is optional.
 205                                 const ODD_BIT: usize = $odd_bit;
 206
 207                                 /// Assertion that [`EVEN_BIT`] is actually even.
 208                                 ///
 209                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 210                                 const ASSERT_EVEN_BIT_PARITY: usize;
 211
 212                                 /// Assertion that [`ODD_BIT`] is actually odd.
 213                                 ///
 214                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 215                                 const ASSERT_ODD_BIT_PARITY: usize;
 216
 217                                 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
 218                                 ///
 219                                 /// [`KNOWN_FEATURE_MASK`]: Context::KNOWN_FEATURE_MASK
 220                                 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
 221                                 const ASSERT_BITS_IN_MASK: u8;
 222
 223                                 /// The byte where the feature is set.
 224                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 225
 226                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 227                                 ///
 228                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 229                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 230
 231                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 232                                 ///
 233                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 234                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 235
 236                                 /// Returns whether the feature is required by the given flags.
 237                                 #[inline]
 238                                 fn requires_feature(flags: &Vec<u8>) -> bool {
 239                                         flags.len() > Self::BYTE_OFFSET &&
 240                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
 241                                 }
 242
 243                                 /// Returns whether the feature is supported by the given flags.
 244                                 #[inline]
 245                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 246                                         flags.len() > Self::BYTE_OFFSET &&
 247                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 248                                 }
 249
 250                                 /// Sets the feature's required (even) bit in the given flags.
 251                                 #[inline]
 252                                 fn set_required_bit(flags: &mut Vec<u8>) {
 253                                         if flags.len() <= Self::BYTE_OFFSET {
 254                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 255                                         }
 256
 257                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
 258                                 }
 259
 260                                 /// Sets the feature's optional (odd) bit in the given flags.
 261                                 #[inline]
 262                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 263                                         if flags.len() <= Self::BYTE_OFFSET {
 264                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 265                                         }
 266
 267                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 268                                 }
 269
 270                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 271                                 /// flags.
 272                                 #[inline]
 273                                 fn clear_bits(flags: &mut Vec<u8>) {
 274                                         if flags.len() > Self::BYTE_OFFSET {
 275                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 276                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 277                                         }
 278
 279                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 280                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 281                                         flags.resize(size, 0u8);
 282                                 }
 283                         }
 284
 285                         impl <T: $feature> Features<T> {
 286                                 /// Set this feature as optional.
 287                                 pub fn $optional_setter(&mut self) {
 288                                         <T as $feature>::set_optional_bit(&mut self.flags);
 289                                 }
 290
 291                                 /// Set this feature as required.
 292                                 pub fn $required_setter(&mut self) {
 293                                         <T as $feature>::set_required_bit(&mut self.flags);
 294                                 }
 295
 296                                 /// Checks if this feature is supported.
 297                                 pub fn $supported_getter(&self) -> bool {
 298                                         <T as $feature>::supports_feature(&self.flags)
 299                                 }
 300                         }
 301
 302                         $(
 303                                 impl $feature for $context {
 304                                         // EVEN_BIT % 2 == 0
 305                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 306
 307                                         // ODD_BIT % 2 == 1
 308                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 309
 310                                         // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
 311                                         #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
 312                                         const ASSERT_BITS_IN_MASK: u8 =
 313                                                 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
 314                                                  >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
 315                                 }
 316                         )*
 317                 };
 318                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 319                  $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
 320                         define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
 321                         impl <T: $feature> Features<T> {
 322                                 /// Checks if this feature is required.
 323                                 pub fn $required_getter(&self) -> bool {
 324                                         <T as $feature>::requires_feature(&self.flags)
 325                                 }
 326                         }
 327                 }
 328         }
 329
 330         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 331                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 332                 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
 333         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 334         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 335                 set_initial_routing_sync_optional, set_initial_routing_sync_required,
 336                 initial_routing_sync);
 337         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 338                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 339                 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
 340                 requires_upfront_shutdown_script);
 341         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 342                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
 343                 supports_gossip_queries, requires_gossip_queries);
 344         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
 345                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 346                 set_variable_length_onion_required, supports_variable_length_onion,
 347                 requires_variable_length_onion);
 348         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
 349                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 350                 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
 351         define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
 352                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
 353                 supports_payment_secret, requires_payment_secret);
 354         define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext, Bolt12InvoiceContext],
 355                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
 356                 supports_basic_mpp, requires_basic_mpp);
 357         define_feature!(19, Wumbo, [InitContext, NodeContext],
 358                 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
 359                 supports_wumbo, requires_wumbo);
 360         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 361                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 362                 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
 363         define_feature!(39, OnionMessages, [InitContext, NodeContext],
 364                 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
 365                 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
 366         define_feature!(45, ChannelType, [InitContext, NodeContext],
 367                 "Feature flags for `option_channel_type`.", set_channel_type_optional,
 368                 set_channel_type_required, supports_channel_type, requires_channel_type);
 369         define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
 370                 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
 371                 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
 372         define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
 373                 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
 374                 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
 375         define_feature!(55, Keysend, [NodeContext],
 376                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
 377                 supports_keysend, requires_keysend);
 378
 379         #[cfg(test)]
 380         define_feature!(123456789, UnknownFeature,
 381                 [NodeContext, ChannelContext, InvoiceContext, OfferContext, InvoiceRequestContext, Bolt12InvoiceContext, BlindedHopContext],
 382                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 383                 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
 384 }
 385
 386 /// Tracks the set of features which a node implements, templated by the context in which it
 387 /// appears.
 388 ///
 389 /// (C-not exported) as we map the concrete feature types below directly instead
 390 #[derive(Eq)]
 391 pub struct Features<T: sealed::Context> {
 392         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 393         flags: Vec<u8>,
 394         mark: PhantomData<T>,
 395 }
 396
 397 impl <T: sealed::Context> Features<T> {
 398         pub(crate) fn or(mut self, o: Self) -> Self {
 399                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
 400                 self.flags.resize(total_feature_len, 0u8);
 401                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
 402                         *byte |= *o_byte;
 403                 }
 404                 self
 405         }
 406 }
 407
 408 impl<T: sealed::Context> Clone for Features<T> {
 409         fn clone(&self) -> Self {
 410                 Self {
 411                         flags: self.flags.clone(),
 412                         mark: PhantomData,
 413                 }
 414         }
 415 }
 416 impl<T: sealed::Context> Hash for Features<T> {
 417         fn hash<H: Hasher>(&self, hasher: &mut H) {
 418                 self.flags.hash(hasher);
 419         }
 420 }
 421 impl<T: sealed::Context> PartialEq for Features<T> {
 422         fn eq(&self, o: &Self) -> bool {
 423                 self.flags.eq(&o.flags)
 424         }
 425 }
 426 impl<T: sealed::Context> fmt::Debug for Features<T> {
 427         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 428                 self.flags.fmt(fmt)
 429         }
 430 }
 431
 432 /// Features used within an `init` message.
 433 pub type InitFeatures = Features<sealed::InitContext>;
 434 /// Features used within a `node_announcement` message.
 435 pub type NodeFeatures = Features<sealed::NodeContext>;
 436 /// Features used within a `channel_announcement` message.
 437 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 438 /// Features used within an invoice.
 439 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
 440 /// Features used within an `offer`.
 441 pub type OfferFeatures = Features<sealed::OfferContext>;
 442 /// Features used within an `invoice_request`.
 443 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
 444 /// Features used within an `invoice`.
 445 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
 446 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
 447 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
 448
 449 /// Features used within the channel_type field in an OpenChannel message.
 450 ///
 451 /// A channel is always of some known "type", describing the transaction formats used and the exact
 452 /// semantics of our interaction with our peer.
 453 ///
 454 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
 455 /// the counterparty, only required features are allowed here.
 456 ///
 457 /// This is serialized differently from other feature types - it is not prefixed by a length, and
 458 /// thus must only appear inside a TLV where its length is known in advance.
 459 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
 460
 461 impl InitFeatures {
 462         /// Writes all features present up to, and including, 13.
 463         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 464                 let len = cmp::min(2, self.flags.len());
 465                 (len as u16).write(w)?;
 466                 for i in (0..len).rev() {
 467                         if i == 0 {
 468                                 self.flags[i].write(w)?;
 469                         } else {
 470                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 471                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 472                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 473                         }
 474                 }
 475                 Ok(())
 476         }
 477
 478         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 479         /// are included in the result.
 480         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 481                 self.to_context_internal()
 482         }
 483 }
 484
 485 impl InvoiceFeatures {
 486         /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
 487         /// context `C` are included in the result.
 488         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 489                 self.to_context_internal()
 490         }
 491
 492         /// Getting a route for a keysend payment to a private node requires providing the payee's
 493         /// features (since they were not announced in a node announcement). However, keysend payments
 494         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 495         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
 496         /// `InvoiceFeatures` for [`find_route`].
 497         ///
 498         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
 499         /// [`find_route`]: crate::routing::router::find_route
 500         pub(crate) fn for_keysend() -> InvoiceFeatures {
 501                 let mut res = InvoiceFeatures::empty();
 502                 res.set_variable_length_onion_optional();
 503                 res
 504         }
 505 }
 506
 507 impl ChannelTypeFeatures {
 508         /// Constructs the implicit channel type based on the common supported types between us and our
 509         /// counterparty
 510         pub(crate) fn from_counterparty_init(counterparty_init: &InitFeatures) -> Self {
 511                 let mut ret = counterparty_init.to_context_internal();
 512                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
 513                 // optional bits and then AND out the optional ones.
 514                 for byte in ret.flags.iter_mut() {
 515                         *byte |= (*byte & 0b10_10_10_10) >> 1;
 516                         *byte &= 0b01_01_01_01;
 517                 }
 518                 ret
 519         }
 520
 521         /// Constructs a ChannelTypeFeatures with only static_remotekey set
 522         pub(crate) fn only_static_remote_key() -> Self {
 523                 let mut ret = Self::empty();
 524                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 525                 ret
 526         }
 527 }
 528
 529 impl ToBase32 for InvoiceFeatures {
 530         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 531                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 532                 // minus one before dividing
 533                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 534                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 535                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 536                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 537                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 538                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 539                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 540                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 541                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 542                         if new_u5_idx > 0 {
 543                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 544                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 545                         }
 546                         if new_u5_idx > 1 {
 547                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 548                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 549                         }
 550                 }
 551                 // Trim the highest feature bits.
 552                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 553                         res_u5s.remove(0);
 554                 }
 555                 writer.write(&res_u5s)
 556         }
 557 }
 558
 559 impl Base32Len for InvoiceFeatures {
 560         fn base32_len(&self) -> usize {
 561                 self.to_base32().len()
 562         }
 563 }
 564
 565 impl FromBase32 for InvoiceFeatures {
 566         type Err = bech32::Error;
 567
 568         fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
 569                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 570                 // minus one before dividing
 571                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 572                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 573                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 574                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 575                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 576                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 577                         let chunk_u16 = chunk.to_u8() as u16;
 578                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 579                         if new_byte_idx != length_bytes - 1 {
 580                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 581                         }
 582                 }
 583                 // Trim the highest feature bits.
 584                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 585                         res_bytes.pop();
 586                 }
 587                 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
 588         }
 589 }
 590
 591 impl<T: sealed::Context> Features<T> {
 592         /// Create a blank Features with no features set
 593         pub fn empty() -> Self {
 594                 Features {
 595                         flags: Vec::new(),
 596                         mark: PhantomData,
 597                 }
 598         }
 599
 600         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 601         /// included in the result.
 602         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 603                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 604                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 605                 let mut flags = Vec::new();
 606                 for (i, byte) in self.flags.iter().enumerate() {
 607                         if i < from_byte_count && i < to_byte_count {
 608                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 609                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 610                                 flags.push(byte & from_known_features & to_known_features);
 611                         }
 612                 }
 613                 Features::<C> { flags, mark: PhantomData, }
 614         }
 615
 616         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 617         /// most on-the-wire encodings.
 618         /// (C-not exported) as we don't support export across multiple T
 619         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 620                 Features {
 621                         flags,
 622                         mark: PhantomData,
 623                 }
 624         }
 625
 626         #[cfg(test)]
 627         /// Gets the underlying flags set, in LE.
 628         pub fn le_flags(&self) -> &Vec<u8> {
 629                 &self.flags
 630         }
 631
 632         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 633                 for f in self.flags.iter().rev() { // Swap back to big-endian
 634                         f.write(w)?;
 635                 }
 636                 Ok(())
 637         }
 638
 639         fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
 640                 flags.reverse(); // Swap to little-endian
 641                 Self {
 642                         flags,
 643                         mark: PhantomData,
 644                 }
 645         }
 646
 647         pub(crate) fn supports_any_optional_bits(&self) -> bool {
 648                 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
 649         }
 650
 651         /// Returns true if this `Features` object contains unknown feature flags which are set as
 652         /// "required".
 653         pub fn requires_unknown_bits(&self) -> bool {
 654                 // Bitwise AND-ing with all even bits set except for known features will select required
 655                 // unknown features.
 656                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 657                 self.flags.iter().enumerate().any(|(i, &byte)| {
 658                         let required_features = 0b01_01_01_01;
 659                         let unknown_features = if i < byte_count {
 660                                 !T::KNOWN_FEATURE_MASK[i]
 661                         } else {
 662                                 0b11_11_11_11
 663                         };
 664                         (byte & (required_features & unknown_features)) != 0
 665                 })
 666         }
 667
 668         pub(crate) fn supports_unknown_bits(&self) -> bool {
 669                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 670                 // both required and optional unknown features.
 671                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 672                 self.flags.iter().enumerate().any(|(i, &byte)| {
 673                         let unknown_features = if i < byte_count {
 674                                 !T::KNOWN_FEATURE_MASK[i]
 675                         } else {
 676                                 0b11_11_11_11
 677                         };
 678                         (byte & unknown_features) != 0
 679                 })
 680         }
 681 }
 682
 683 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 684         #[cfg(test)]
 685         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 686                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 687                 self
 688         }
 689 }
 690
 691 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 692         #[cfg(test)]
 693         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 694                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 695                 self
 696         }
 697 }
 698
 699 impl<T: sealed::Wumbo> Features<T> {
 700         #[cfg(test)]
 701         pub(crate) fn clear_wumbo(mut self) -> Self {
 702                 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
 703                 self
 704         }
 705 }
 706
 707 #[cfg(test)]
 708 impl<T: sealed::UnknownFeature> Features<T> {
 709         pub(crate) fn unknown() -> Self {
 710                 let mut features = Self::empty();
 711                 features.set_unknown_feature_required();
 712                 features
 713         }
 714 }
 715
 716 macro_rules! impl_feature_len_prefixed_write {
 717         ($features: ident) => {
 718                 impl Writeable for $features {
 719                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 720                                 (self.flags.len() as u16).write(w)?;
 721                                 self.write_be(w)
 722                         }
 723                 }
 724                 impl Readable for $features {
 725                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 726                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
 727                         }
 728                 }
 729         }
 730 }
 731 impl_feature_len_prefixed_write!(InitFeatures);
 732 impl_feature_len_prefixed_write!(ChannelFeatures);
 733 impl_feature_len_prefixed_write!(NodeFeatures);
 734 impl_feature_len_prefixed_write!(InvoiceFeatures);
 735 impl_feature_len_prefixed_write!(BlindedHopFeatures);
 736
 737 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
 738 macro_rules! impl_feature_tlv_write {
 739         ($features: ident) => {
 740                 impl Writeable for $features {
 741                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 742                                 WithoutLength(self).write(w)
 743                         }
 744                 }
 745                 impl Readable for $features {
 746                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 747                                 Ok(WithoutLength::<Self>::read(r)?.0)
 748                         }
 749                 }
 750         }
 751 }
 752
 753 impl_feature_tlv_write!(ChannelTypeFeatures);
 754
 755 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
 756 // requires a length but the former does not.
 757
 758 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
 759         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 760                 self.0.write_be(w)
 761         }
 762 }
 763
 764 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
 765         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 766                 let v = io_extras::read_to_end(r)?;
 767                 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
 768         }
 769 }
 770
 771 #[cfg(test)]
 772 mod tests {
 773         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
 774         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
 775         use crate::util::ser::{Readable, WithoutLength, Writeable};
 776
 777         #[test]
 778         fn sanity_test_unknown_bits() {
 779                 let features = ChannelFeatures::empty();
 780                 assert!(!features.requires_unknown_bits());
 781                 assert!(!features.supports_unknown_bits());
 782
 783                 let mut features = ChannelFeatures::empty();
 784                 features.set_unknown_feature_required();
 785                 assert!(features.requires_unknown_bits());
 786                 assert!(features.supports_unknown_bits());
 787
 788                 let mut features = ChannelFeatures::empty();
 789                 features.set_unknown_feature_optional();
 790                 assert!(!features.requires_unknown_bits());
 791                 assert!(features.supports_unknown_bits());
 792         }
 793
 794         #[test]
 795         fn convert_to_context_with_relevant_flags() {
 796                 let mut init_features = InitFeatures::empty();
 797                 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
 798                 // converted as it's only relevant in an init context).
 799                 init_features.set_initial_routing_sync_required();
 800                 init_features.set_data_loss_protect_optional();
 801                 init_features.set_variable_length_onion_required();
 802                 init_features.set_static_remote_key_required();
 803                 init_features.set_payment_secret_required();
 804                 init_features.set_basic_mpp_optional();
 805                 init_features.set_wumbo_optional();
 806                 init_features.set_shutdown_any_segwit_optional();
 807                 init_features.set_onion_messages_optional();
 808                 init_features.set_channel_type_optional();
 809                 init_features.set_scid_privacy_optional();
 810                 init_features.set_zero_conf_optional();
 811
 812                 assert!(init_features.initial_routing_sync());
 813                 assert!(!init_features.supports_upfront_shutdown_script());
 814                 assert!(!init_features.supports_gossip_queries());
 815
 816                 let node_features: NodeFeatures = init_features.to_context();
 817                 {
 818                         // Check that the flags are as expected:
 819                         // - option_data_loss_protect
 820                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
 821                         // - basic_mpp | wumbo
 822                         // - opt_shutdown_anysegwit
 823                         // - onion_messages
 824                         // - option_channel_type | option_scid_alias
 825                         // - option_zeroconf
 826                         assert_eq!(node_features.flags.len(), 7);
 827                         assert_eq!(node_features.flags[0], 0b00000010);
 828                         assert_eq!(node_features.flags[1], 0b01010001);
 829                         assert_eq!(node_features.flags[2], 0b00001010);
 830                         assert_eq!(node_features.flags[3], 0b00001000);
 831                         assert_eq!(node_features.flags[4], 0b10000000);
 832                         assert_eq!(node_features.flags[5], 0b10100000);
 833                         assert_eq!(node_features.flags[6], 0b00001000);
 834                 }
 835
 836                 // Check that cleared flags are kept blank when converting back:
 837                 // - initial_routing_sync was not applicable to NodeContext
 838                 // - upfront_shutdown_script was cleared before converting
 839                 // - gossip_queries was cleared before converting
 840                 let features: InitFeatures = node_features.to_context_internal();
 841                 assert!(!features.initial_routing_sync());
 842                 assert!(!features.supports_upfront_shutdown_script());
 843                 assert!(!init_features.supports_gossip_queries());
 844         }
 845
 846         #[test]
 847         fn convert_to_context_with_unknown_flags() {
 848                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
 849                 assert!(<sealed::InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
 850                         <sealed::NodeContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
 851                 let mut invoice_features = InvoiceFeatures::empty();
 852                 invoice_features.set_unknown_feature_optional();
 853                 assert!(invoice_features.supports_unknown_bits());
 854                 let node_features: NodeFeatures = invoice_features.to_context();
 855                 assert!(!node_features.supports_unknown_bits());
 856         }
 857
 858         #[test]
 859         fn set_feature_bits() {
 860                 let mut features = InvoiceFeatures::empty();
 861                 features.set_basic_mpp_optional();
 862                 features.set_payment_secret_required();
 863                 assert!(features.supports_basic_mpp());
 864                 assert!(!features.requires_basic_mpp());
 865                 assert!(features.requires_payment_secret());
 866                 assert!(features.supports_payment_secret());
 867         }
 868
 869         #[test]
 870         fn encodes_features_without_length() {
 871                 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
 872                 assert_eq!(features.flags.len(), 8);
 873
 874                 let mut serialized_features = Vec::new();
 875                 WithoutLength(&features).write(&mut serialized_features).unwrap();
 876                 assert_eq!(serialized_features.len(), 8);
 877
 878                 let deserialized_features =
 879                         WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
 880                 assert_eq!(features, deserialized_features);
 881         }
 882
 883         #[test]
 884         fn invoice_features_encoding() {
 885                 let features_as_u5s = vec![
 886                         u5::try_from_u8(6).unwrap(),
 887                         u5::try_from_u8(10).unwrap(),
 888                         u5::try_from_u8(25).unwrap(),
 889                         u5::try_from_u8(1).unwrap(),
 890                         u5::try_from_u8(10).unwrap(),
 891                         u5::try_from_u8(0).unwrap(),
 892                         u5::try_from_u8(20).unwrap(),
 893                         u5::try_from_u8(2).unwrap(),
 894                         u5::try_from_u8(0).unwrap(),
 895                         u5::try_from_u8(6).unwrap(),
 896                         u5::try_from_u8(0).unwrap(),
 897                         u5::try_from_u8(16).unwrap(),
 898                         u5::try_from_u8(1).unwrap(),
 899                 ];
 900                 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
 901
 902                 // Test length calculation.
 903                 assert_eq!(features.base32_len(), 13);
 904
 905                 // Test serialization.
 906                 let features_serialized = features.to_base32();
 907                 assert_eq!(features_as_u5s, features_serialized);
 908
 909                 // Test deserialization.
 910                 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
 911                 assert_eq!(features, features_deserialized);
 912         }
 913
 914         #[test]
 915         fn test_channel_type_mapping() {
 916                 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
 917                 // required-StaticRemoteKey ChannelTypeFeatures.
 918                 let mut init_features = InitFeatures::empty();
 919                 init_features.set_static_remote_key_optional();
 920                 let converted_features = ChannelTypeFeatures::from_counterparty_init(&init_features);
 921                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
 922                 assert!(!converted_features.supports_any_optional_bits());
 923                 assert!(converted_features.requires_static_remote_key());
 924         }
 925 }