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