_ 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 //! [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
  23 //! [messages]: crate::ln::msgs
  24
  25 use {io, io_extras};
  26 use prelude::*;
  27 use core::{cmp, fmt};
  28 use core::hash::{Hash, Hasher};
  29 use core::marker::PhantomData;
  30
  31 use bitcoin::bech32;
  32 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
  33 use ln::msgs::DecodeError;
  34 use util::ser::{Readable, Writeable, Writer};
  35
  36 mod sealed {
  37         use prelude::*;
  38         use ln::features::Features;
  39
  40         /// The context in which [`Features`] are applicable. Defines which features are required and
  41         /// which are optional for the context.
  42         pub trait Context {
  43                 /// Features that are known to the implementation, where a required feature is indicated by
  44                 /// its even bit and an optional feature is indicated by its odd bit.
  45                 const KNOWN_FEATURE_FLAGS: &'static [u8];
  46
  47                 /// Bitmask for selecting features that are known to the implementation, regardless of
  48                 /// whether each feature is required or optional.
  49                 const KNOWN_FEATURE_MASK: &'static [u8];
  50         }
  51
  52         /// Defines a [`Context`] by stating which features it requires and which are optional. Features
  53         /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
  54         /// feature identifiers.
  55         macro_rules! define_context {
  56                 ($context: ident {
  57                         required_features: [$( $( $required_feature: ident )|*, )*],
  58                         optional_features: [$( $( $optional_feature: ident )|*, )*],
  59                 }) => {
  60                         #[derive(Eq, PartialEq)]
  61                         pub struct $context {}
  62
  63                         impl Context for $context {
  64                                 const KNOWN_FEATURE_FLAGS: &'static [u8] = &[
  65                                         // For each byte, use bitwise-OR to compute the applicable flags for known
  66                                         // required features `r_i` and optional features `o_j` for all `i` and `j` such
  67                                         // that the following slice is formed:
  68                                         //
  69                                         // [
  70                                         //  `r_0` | `r_1` | ... | `o_0` | `o_1` | ...,
  71                                         //  ...,
  72                                         // ]
  73                                         $(
  74                                                 0b00_00_00_00 $(|
  75                                                         <Self as $required_feature>::REQUIRED_MASK)*
  76                                                 $(|
  77                                                         <Self as $optional_feature>::OPTIONAL_MASK)*,
  78                                         )*
  79                                 ];
  80
  81                                 const KNOWN_FEATURE_MASK: &'static [u8] = &[
  82                                         // Similar as above, but set both flags for each feature regardless of whether
  83                                         // the feature is required or optional.
  84                                         $(
  85                                                 0b00_00_00_00 $(|
  86                                                         <Self as $required_feature>::REQUIRED_MASK |
  87                                                         <Self as $required_feature>::OPTIONAL_MASK)*
  88                                                 $(|
  89                                                         <Self as $optional_feature>::REQUIRED_MASK |
  90                                                         <Self as $optional_feature>::OPTIONAL_MASK)*,
  91                                         )*
  92                                 ];
  93                         }
  94
  95                         impl alloc::fmt::Display for Features<$context> {
  96                                 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
  97                                         $(
  98                                                 $(
  99                                                         fmt.write_fmt(format_args!("{}: {}, ", stringify!($required_feature),
 100                                                                 if <$context as $required_feature>::requires_feature(&self.flags) { "required" }
 101                                                                 else if <$context as $required_feature>::supports_feature(&self.flags) { "supported" }
 102                                                                 else { "not supported" }))?;
 103                                                 )*
 104                                                 $(
 105                                                         fmt.write_fmt(format_args!("{}: {}, ", stringify!($optional_feature),
 106                                                                 if <$context as $optional_feature>::requires_feature(&self.flags) { "required" }
 107                                                                 else if <$context as $optional_feature>::supports_feature(&self.flags) { "supported" }
 108                                                                 else { "not supported" }))?;
 109                                                 )*
 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                 required_features: [
 121                         // Byte 0
 122                         ,
 123                         // Byte 1
 124                         VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 125                         // Byte 2
 126                         ,
 127                         // Byte 3
 128                         ,
 129                         // Byte 4
 130                         ,
 131                         // Byte 5
 132                         ,
 133                 ],
 134                 optional_features: [
 135                         // Byte 0
 136                         DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
 137                         // Byte 1
 138                         ,
 139                         // Byte 2
 140                         BasicMPP,
 141                         // Byte 3
 142                         ShutdownAnySegwit,
 143                         // Byte 4
 144                         ,
 145                         // Byte 5
 146                         ChannelType,
 147                 ],
 148         });
 149         define_context!(NodeContext {
 150                 required_features: [
 151                         // Byte 0
 152                         ,
 153                         // Byte 1
 154                         VariableLengthOnion | StaticRemoteKey | PaymentSecret,
 155                         // Byte 2
 156                         ,
 157                         // Byte 3
 158                         ,
 159                         // Byte 4
 160                         ,
 161                         // Byte 5
 162                         ,
 163                         // Byte 6
 164                         ,
 165                 ],
 166                 optional_features: [
 167                         // Byte 0
 168                         DataLossProtect | UpfrontShutdownScript | GossipQueries,
 169                         // Byte 1
 170                         ,
 171                         // Byte 2
 172                         BasicMPP,
 173                         // Byte 3
 174                         ShutdownAnySegwit,
 175                         // Byte 4
 176                         ,
 177                         // Byte 5
 178                         ChannelType,
 179                         // Byte 6
 180                         Keysend,
 181                 ],
 182         });
 183         define_context!(ChannelContext {
 184                 required_features: [],
 185                 optional_features: [],
 186         });
 187         define_context!(InvoiceContext {
 188                 required_features: [
 189                         // Byte 0
 190                         ,
 191                         // Byte 1
 192                         VariableLengthOnion | PaymentSecret,
 193                         // Byte 2
 194                         ,
 195                 ],
 196                 optional_features: [
 197                         // Byte 0
 198                         ,
 199                         // Byte 1
 200                         ,
 201                         // Byte 2
 202                         BasicMPP,
 203                 ],
 204         });
 205         // This isn't a "real" feature context, and is only used in the channel_type field in an
 206         // `OpenChannel` message.
 207         define_context!(ChannelTypeContext {
 208                 required_features: [
 209                         // Byte 0
 210                         ,
 211                         // Byte 1
 212                         StaticRemoteKey,
 213                         // Byte 2
 214                         ,
 215                         // Byte 3
 216                         ,
 217                 ],
 218                 optional_features: [
 219                         // Byte 0
 220                         ,
 221                         // Byte 1
 222                         ,
 223                         // Byte 2
 224                         ,
 225                         // Byte 3
 226                         ,
 227                 ],
 228         });
 229
 230         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
 231         /// useful for manipulating feature flags.
 232         macro_rules! define_feature {
 233                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 234                  $required_setter: ident, $supported_getter: ident) => {
 235                         #[doc = $doc]
 236                         ///
 237                         /// See [BOLT #9] for details.
 238                         ///
 239                         /// [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
 240                         pub trait $feature: Context {
 241                                 /// The bit used to signify that the feature is required.
 242                                 const EVEN_BIT: usize = $odd_bit - 1;
 243
 244                                 /// The bit used to signify that the feature is optional.
 245                                 const ODD_BIT: usize = $odd_bit;
 246
 247                                 /// Assertion that [`EVEN_BIT`] is actually even.
 248                                 ///
 249                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
 250                                 const ASSERT_EVEN_BIT_PARITY: usize;
 251
 252                                 /// Assertion that [`ODD_BIT`] is actually odd.
 253                                 ///
 254                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
 255                                 const ASSERT_ODD_BIT_PARITY: usize;
 256
 257                                 /// The byte where the feature is set.
 258                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
 259
 260                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
 261                                 ///
 262                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 263                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
 264
 265                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
 266                                 ///
 267                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
 268                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
 269
 270                                 /// Returns whether the feature is required by the given flags.
 271                                 #[inline]
 272                                 fn requires_feature(flags: &Vec<u8>) -> bool {
 273                                         flags.len() > Self::BYTE_OFFSET &&
 274                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
 275                                 }
 276
 277                                 /// Returns whether the feature is supported by the given flags.
 278                                 #[inline]
 279                                 fn supports_feature(flags: &Vec<u8>) -> bool {
 280                                         flags.len() > Self::BYTE_OFFSET &&
 281                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
 282                                 }
 283
 284                                 /// Sets the feature's required (even) bit in the given flags.
 285                                 #[inline]
 286                                 fn set_required_bit(flags: &mut Vec<u8>) {
 287                                         if flags.len() <= Self::BYTE_OFFSET {
 288                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 289                                         }
 290
 291                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
 292                                 }
 293
 294                                 /// Sets the feature's optional (odd) bit in the given flags.
 295                                 #[inline]
 296                                 fn set_optional_bit(flags: &mut Vec<u8>) {
 297                                         if flags.len() <= Self::BYTE_OFFSET {
 298                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
 299                                         }
 300
 301                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
 302                                 }
 303
 304                                 /// Clears the feature's required (even) and optional (odd) bits from the given
 305                                 /// flags.
 306                                 #[inline]
 307                                 fn clear_bits(flags: &mut Vec<u8>) {
 308                                         if flags.len() > Self::BYTE_OFFSET {
 309                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
 310                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
 311                                         }
 312
 313                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
 314                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
 315                                         flags.resize(size, 0u8);
 316                                 }
 317                         }
 318
 319                         impl <T: $feature> Features<T> {
 320                                 /// Set this feature as optional.
 321                                 pub fn $optional_setter(&mut self) {
 322                                         <T as $feature>::set_optional_bit(&mut self.flags);
 323                                 }
 324
 325                                 /// Set this feature as required.
 326                                 pub fn $required_setter(&mut self) {
 327                                         <T as $feature>::set_required_bit(&mut self.flags);
 328                                 }
 329
 330                                 /// Checks if this feature is supported.
 331                                 pub fn $supported_getter(&self) -> bool {
 332                                         <T as $feature>::supports_feature(&self.flags)
 333                                 }
 334                         }
 335
 336                         $(
 337                                 impl $feature for $context {
 338                                         // EVEN_BIT % 2 == 0
 339                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
 340
 341                                         // ODD_BIT % 2 == 1
 342                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
 343                                 }
 344                         )*
 345                 };
 346                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
 347                  $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
 348                         define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
 349                         impl <T: $feature> Features<T> {
 350                                 /// Checks if this feature is required.
 351                                 pub fn $required_getter(&self) -> bool {
 352                                         <T as $feature>::requires_feature(&self.flags)
 353                                 }
 354                         }
 355                 }
 356         }
 357
 358         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
 359                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
 360                 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
 361         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
 362         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
 363                 set_initial_routing_sync_optional, set_initial_routing_sync_required,
 364                 initial_routing_sync);
 365         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
 366                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
 367                 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
 368                 requires_upfront_shutdown_script);
 369         define_feature!(7, GossipQueries, [InitContext, NodeContext],
 370                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
 371                 supports_gossip_queries, requires_gossip_queries);
 372         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
 373                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
 374                 set_variable_length_onion_required, supports_variable_length_onion,
 375                 requires_variable_length_onion);
 376         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
 377                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
 378                 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
 379         define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
 380                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
 381                 supports_payment_secret, requires_payment_secret);
 382         define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext],
 383                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
 384                 supports_basic_mpp, requires_basic_mpp);
 385         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 386                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 387                 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
 388         define_feature!(45, ChannelType, [InitContext, NodeContext],
 389                 "Feature flags for `option_channel_type`.", set_channel_type_optional,
 390                 set_channel_type_required, supports_channel_type, requires_channel_type);
 391         define_feature!(55, Keysend, [NodeContext],
 392                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
 393                 supports_keysend, requires_keysend);
 394
 395         #[cfg(test)]
 396         define_feature!(123456789, UnknownFeature, [NodeContext, ChannelContext, InvoiceContext],
 397                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
 398                 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
 399 }
 400
 401 /// Tracks the set of features which a node implements, templated by the context in which it
 402 /// appears.
 403 ///
 404 /// (C-not exported) as we map the concrete feature types below directly instead
 405 #[derive(Eq)]
 406 pub struct Features<T: sealed::Context> {
 407         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
 408         flags: Vec<u8>,
 409         mark: PhantomData<T>,
 410 }
 411
 412 impl<T: sealed::Context> Clone for Features<T> {
 413         fn clone(&self) -> Self {
 414                 Self {
 415                         flags: self.flags.clone(),
 416                         mark: PhantomData,
 417                 }
 418         }
 419 }
 420 impl<T: sealed::Context> Hash for Features<T> {
 421         fn hash<H: Hasher>(&self, hasher: &mut H) {
 422                 self.flags.hash(hasher);
 423         }
 424 }
 425 impl<T: sealed::Context> PartialEq for Features<T> {
 426         fn eq(&self, o: &Self) -> bool {
 427                 self.flags.eq(&o.flags)
 428         }
 429 }
 430 impl<T: sealed::Context> fmt::Debug for Features<T> {
 431         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 432                 self.flags.fmt(fmt)
 433         }
 434 }
 435
 436 /// Features used within an `init` message.
 437 pub type InitFeatures = Features<sealed::InitContext>;
 438 /// Features used within a `node_announcement` message.
 439 pub type NodeFeatures = Features<sealed::NodeContext>;
 440 /// Features used within a `channel_announcement` message.
 441 pub type ChannelFeatures = Features<sealed::ChannelContext>;
 442 /// Features used within an invoice.
 443 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
 444
 445 /// Features used within the channel_type field in an OpenChannel message.
 446 ///
 447 /// A channel is always of some known "type", describing the transaction formats used and the exact
 448 /// semantics of our interaction with our peer.
 449 ///
 450 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
 451 /// the counterparty, only required features are allowed here.
 452 ///
 453 /// This is serialized differently from other feature types - it is not prefixed by a length, and
 454 /// thus must only appear inside a TLV where its length is known in advance.
 455 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
 456
 457 impl InitFeatures {
 458         /// Writes all features present up to, and including, 13.
 459         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 460                 let len = cmp::min(2, self.flags.len());
 461                 (len as u16).write(w)?;
 462                 for i in (0..len).rev() {
 463                         if i == 0 {
 464                                 self.flags[i].write(w)?;
 465                         } else {
 466                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
 467                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
 468                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
 469                         }
 470                 }
 471                 Ok(())
 472         }
 473
 474         /// or's another InitFeatures into this one.
 475         pub(crate) fn or(mut self, o: InitFeatures) -> InitFeatures {
 476                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
 477                 self.flags.resize(total_feature_len, 0u8);
 478                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
 479                         *byte |= *o_byte;
 480                 }
 481                 self
 482         }
 483
 484         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
 485         /// are included in the result.
 486         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 487                 self.to_context_internal()
 488         }
 489 }
 490
 491 impl InvoiceFeatures {
 492         /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
 493         /// context `C` are included in the result.
 494         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 495                 self.to_context_internal()
 496         }
 497
 498         /// Getting a route for a keysend payment to a private node requires providing the payee's
 499         /// features (since they were not announced in a node announcement). However, keysend payments
 500         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
 501         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
 502         /// `InvoiceFeatures` for [`find_route`].
 503         ///
 504         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
 505         /// [`find_route`]: crate::routing::router::find_route
 506         pub(crate) fn for_keysend() -> InvoiceFeatures {
 507                 let mut res = InvoiceFeatures::empty();
 508                 res.set_variable_length_onion_optional();
 509                 res
 510         }
 511 }
 512
 513 impl ChannelTypeFeatures {
 514         /// Constructs the implicit channel type based on the common supported types between us and our
 515         /// counterparty
 516         pub(crate) fn from_counterparty_init(counterparty_init: &InitFeatures) -> Self {
 517                 let mut ret = counterparty_init.to_context_internal();
 518                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
 519                 // optional bits and then AND out the optional ones.
 520                 for byte in ret.flags.iter_mut() {
 521                         *byte |= (*byte & 0b10_10_10_10) >> 1;
 522                         *byte &= 0b01_01_01_01;
 523                 }
 524                 ret
 525         }
 526
 527         /// Constructs a ChannelTypeFeatures with only static_remotekey set
 528         pub(crate) fn only_static_remote_key() -> Self {
 529                 let mut ret = Self::empty();
 530                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
 531                 ret
 532         }
 533 }
 534
 535 impl ToBase32 for InvoiceFeatures {
 536         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
 537                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
 538                 // minus one before dividing
 539                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
 540                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
 541                 for (byte_idx, byte) in self.flags.iter().enumerate() {
 542                         let bit_pos_from_left_0_indexed = byte_idx * 8;
 543                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
 544                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
 545                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
 546                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
 547                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
 548                         if new_u5_idx > 0 {
 549                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
 550                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
 551                         }
 552                         if new_u5_idx > 1 {
 553                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
 554                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
 555                         }
 556                 }
 557                 // Trim the highest feature bits.
 558                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
 559                         res_u5s.remove(0);
 560                 }
 561                 writer.write(&res_u5s)
 562         }
 563 }
 564
 565 impl Base32Len for InvoiceFeatures {
 566         fn base32_len(&self) -> usize {
 567                 self.to_base32().len()
 568         }
 569 }
 570
 571 impl FromBase32 for InvoiceFeatures {
 572         type Err = bech32::Error;
 573
 574         fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
 575                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
 576                 // minus one before dividing
 577                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
 578                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
 579                 for (u5_idx, chunk) in field_data.iter().enumerate() {
 580                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
 581                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
 582                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
 583                         let chunk_u16 = chunk.to_u8() as u16;
 584                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
 585                         if new_byte_idx != length_bytes - 1 {
 586                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
 587                         }
 588                 }
 589                 // Trim the highest feature bits.
 590                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
 591                         res_bytes.pop();
 592                 }
 593                 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
 594         }
 595 }
 596
 597 impl<T: sealed::Context> Features<T> {
 598         /// Create a blank Features with no features set
 599         pub fn empty() -> Self {
 600                 Features {
 601                         flags: Vec::new(),
 602                         mark: PhantomData,
 603                 }
 604         }
 605
 606         /// Creates a Features with the bits set which are known by the implementation
 607         pub fn known() -> Self {
 608                 Self {
 609                         flags: T::KNOWN_FEATURE_FLAGS.to_vec(),
 610                         mark: PhantomData,
 611                 }
 612         }
 613
 614         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
 615         /// included in the result.
 616         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
 617                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
 618                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
 619                 let mut flags = Vec::new();
 620                 for (i, byte) in self.flags.iter().enumerate() {
 621                         if i < from_byte_count && i < to_byte_count {
 622                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
 623                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
 624                                 flags.push(byte & from_known_features & to_known_features);
 625                         }
 626                 }
 627                 Features::<C> { flags, mark: PhantomData, }
 628         }
 629
 630         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
 631         /// most on-the-wire encodings.
 632         /// (C-not exported) as we don't support export across multiple T
 633         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
 634                 Features {
 635                         flags,
 636                         mark: PhantomData,
 637                 }
 638         }
 639
 640         #[cfg(test)]
 641         /// Gets the underlying flags set, in LE.
 642         pub fn le_flags(&self) -> &Vec<u8> {
 643                 &self.flags
 644         }
 645
 646         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 647                 for f in self.flags.iter().rev() { // Swap back to big-endian
 648                         f.write(w)?;
 649                 }
 650                 Ok(())
 651         }
 652
 653         fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
 654                 flags.reverse(); // Swap to little-endian
 655                 Self {
 656                         flags,
 657                         mark: PhantomData,
 658                 }
 659         }
 660
 661         pub(crate) fn supports_any_optional_bits(&self) -> bool {
 662                 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
 663         }
 664
 665         /// Returns true if this `Features` object contains unknown feature flags which are set as
 666         /// "required".
 667         pub fn requires_unknown_bits(&self) -> bool {
 668                 // Bitwise AND-ing with all even bits set except for known features will select required
 669                 // unknown features.
 670                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 671                 self.flags.iter().enumerate().any(|(i, &byte)| {
 672                         let required_features = 0b01_01_01_01;
 673                         let unknown_features = if i < byte_count {
 674                                 !T::KNOWN_FEATURE_MASK[i]
 675                         } else {
 676                                 0b11_11_11_11
 677                         };
 678                         (byte & (required_features & unknown_features)) != 0
 679                 })
 680         }
 681
 682         pub(crate) fn supports_unknown_bits(&self) -> bool {
 683                 // Bitwise AND-ing with all even and odd bits set except for known features will select
 684                 // both required and optional unknown features.
 685                 let byte_count = T::KNOWN_FEATURE_MASK.len();
 686                 self.flags.iter().enumerate().any(|(i, &byte)| {
 687                         let unknown_features = if i < byte_count {
 688                                 !T::KNOWN_FEATURE_MASK[i]
 689                         } else {
 690                                 0b11_11_11_11
 691                         };
 692                         (byte & unknown_features) != 0
 693                 })
 694         }
 695 }
 696
 697 impl<T: sealed::UpfrontShutdownScript> Features<T> {
 698         #[cfg(test)]
 699         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
 700                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
 701                 self
 702         }
 703 }
 704
 705
 706 impl<T: sealed::GossipQueries> Features<T> {
 707         #[cfg(test)]
 708         pub(crate) fn clear_gossip_queries(mut self) -> Self {
 709                 <T as sealed::GossipQueries>::clear_bits(&mut self.flags);
 710                 self
 711         }
 712 }
 713
 714 impl<T: sealed::InitialRoutingSync> Features<T> {
 715         // We are no longer setting initial_routing_sync now that gossip_queries
 716         // is enabled. This feature is ignored by a peer when gossip_queries has
 717         // been negotiated.
 718         #[cfg(test)]
 719         pub(crate) fn clear_initial_routing_sync(&mut self) {
 720                 <T as sealed::InitialRoutingSync>::clear_bits(&mut self.flags)
 721         }
 722 }
 723
 724 impl<T: sealed::ShutdownAnySegwit> Features<T> {
 725         #[cfg(test)]
 726         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
 727                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
 728                 self
 729         }
 730 }
 731 macro_rules! impl_feature_len_prefixed_write {
 732         ($features: ident) => {
 733                 impl Writeable for $features {
 734                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 735                                 (self.flags.len() as u16).write(w)?;
 736                                 self.write_be(w)
 737                         }
 738                 }
 739                 impl Readable for $features {
 740                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 741                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
 742                         }
 743                 }
 744         }
 745 }
 746 impl_feature_len_prefixed_write!(InitFeatures);
 747 impl_feature_len_prefixed_write!(ChannelFeatures);
 748 impl_feature_len_prefixed_write!(NodeFeatures);
 749 impl_feature_len_prefixed_write!(InvoiceFeatures);
 750
 751 // Because ChannelTypeFeatures only appears inside of TLVs, it doesn't have a length prefix when
 752 // serialized. Thus, we can't use `impl_feature_len_prefixed_write`, above, and have to write our
 753 // own serialization.
 754 impl Writeable for ChannelTypeFeatures {
 755         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 756                 self.write_be(w)
 757         }
 758 }
 759 impl Readable for ChannelTypeFeatures {
 760         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 761                 let v = io_extras::read_to_end(r)?;
 762                 Ok(Self::from_be_bytes(v))
 763         }
 764 }
 765
 766 #[cfg(test)]
 767 mod tests {
 768         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures};
 769         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
 770
 771         #[test]
 772         fn sanity_test_known_features() {
 773                 assert!(!ChannelFeatures::known().requires_unknown_bits());
 774                 assert!(!ChannelFeatures::known().supports_unknown_bits());
 775                 assert!(!InitFeatures::known().requires_unknown_bits());
 776                 assert!(!InitFeatures::known().supports_unknown_bits());
 777                 assert!(!NodeFeatures::known().requires_unknown_bits());
 778                 assert!(!NodeFeatures::known().supports_unknown_bits());
 779
 780                 assert!(InitFeatures::known().supports_upfront_shutdown_script());
 781                 assert!(NodeFeatures::known().supports_upfront_shutdown_script());
 782                 assert!(!InitFeatures::known().requires_upfront_shutdown_script());
 783                 assert!(!NodeFeatures::known().requires_upfront_shutdown_script());
 784
 785                 assert!(InitFeatures::known().supports_gossip_queries());
 786                 assert!(NodeFeatures::known().supports_gossip_queries());
 787                 assert!(!InitFeatures::known().requires_gossip_queries());
 788                 assert!(!NodeFeatures::known().requires_gossip_queries());
 789
 790                 assert!(InitFeatures::known().supports_data_loss_protect());
 791                 assert!(NodeFeatures::known().supports_data_loss_protect());
 792                 assert!(!InitFeatures::known().requires_data_loss_protect());
 793                 assert!(!NodeFeatures::known().requires_data_loss_protect());
 794
 795                 assert!(InitFeatures::known().supports_variable_length_onion());
 796                 assert!(NodeFeatures::known().supports_variable_length_onion());
 797                 assert!(InvoiceFeatures::known().supports_variable_length_onion());
 798                 assert!(InitFeatures::known().requires_variable_length_onion());
 799                 assert!(NodeFeatures::known().requires_variable_length_onion());
 800                 assert!(InvoiceFeatures::known().requires_variable_length_onion());
 801
 802                 assert!(InitFeatures::known().supports_static_remote_key());
 803                 assert!(NodeFeatures::known().supports_static_remote_key());
 804                 assert!(InitFeatures::known().requires_static_remote_key());
 805                 assert!(NodeFeatures::known().requires_static_remote_key());
 806
 807                 assert!(InitFeatures::known().supports_payment_secret());
 808                 assert!(NodeFeatures::known().supports_payment_secret());
 809                 assert!(InvoiceFeatures::known().supports_payment_secret());
 810                 assert!(InitFeatures::known().requires_payment_secret());
 811                 assert!(NodeFeatures::known().requires_payment_secret());
 812                 assert!(InvoiceFeatures::known().requires_payment_secret());
 813
 814                 assert!(InitFeatures::known().supports_basic_mpp());
 815                 assert!(NodeFeatures::known().supports_basic_mpp());
 816                 assert!(InvoiceFeatures::known().supports_basic_mpp());
 817                 assert!(!InitFeatures::known().requires_basic_mpp());
 818                 assert!(!NodeFeatures::known().requires_basic_mpp());
 819                 assert!(!InvoiceFeatures::known().requires_basic_mpp());
 820
 821                 assert!(InitFeatures::known().supports_channel_type());
 822                 assert!(NodeFeatures::known().supports_channel_type());
 823                 assert!(!InitFeatures::known().requires_channel_type());
 824                 assert!(!NodeFeatures::known().requires_channel_type());
 825
 826                 assert!(InitFeatures::known().supports_shutdown_anysegwit());
 827                 assert!(NodeFeatures::known().supports_shutdown_anysegwit());
 828
 829                 let mut init_features = InitFeatures::known();
 830                 assert!(init_features.initial_routing_sync());
 831                 init_features.clear_initial_routing_sync();
 832                 assert!(!init_features.initial_routing_sync());
 833         }
 834
 835         #[test]
 836         fn sanity_test_unknown_bits() {
 837                 let features = ChannelFeatures::empty();
 838                 assert!(!features.requires_unknown_bits());
 839                 assert!(!features.supports_unknown_bits());
 840
 841                 let mut features = ChannelFeatures::empty();
 842                 features.set_unknown_feature_required();
 843                 assert!(features.requires_unknown_bits());
 844                 assert!(features.supports_unknown_bits());
 845
 846                 let mut features = ChannelFeatures::empty();
 847                 features.set_unknown_feature_optional();
 848                 assert!(!features.requires_unknown_bits());
 849                 assert!(features.supports_unknown_bits());
 850         }
 851
 852         #[test]
 853         fn convert_to_context_with_relevant_flags() {
 854                 let init_features = InitFeatures::known().clear_upfront_shutdown_script().clear_gossip_queries();
 855                 assert!(init_features.initial_routing_sync());
 856                 assert!(!init_features.supports_upfront_shutdown_script());
 857                 assert!(!init_features.supports_gossip_queries());
 858
 859                 let node_features: NodeFeatures = init_features.to_context();
 860                 {
 861                         // Check that the flags are as expected:
 862                         // - option_data_loss_protect
 863                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
 864                         // - basic_mpp
 865                         // - opt_shutdown_anysegwit
 866                         // -
 867                         // - option_channel_type
 868                         assert_eq!(node_features.flags.len(), 6);
 869                         assert_eq!(node_features.flags[0], 0b00000010);
 870                         assert_eq!(node_features.flags[1], 0b01010001);
 871                         assert_eq!(node_features.flags[2], 0b00000010);
 872                         assert_eq!(node_features.flags[3], 0b00001000);
 873                         assert_eq!(node_features.flags[4], 0b00000000);
 874                         assert_eq!(node_features.flags[5], 0b00100000);
 875                 }
 876
 877                 // Check that cleared flags are kept blank when converting back:
 878                 // - initial_routing_sync was not applicable to NodeContext
 879                 // - upfront_shutdown_script was cleared before converting
 880                 // - gossip_queries was cleared before converting
 881                 let features: InitFeatures = node_features.to_context_internal();
 882                 assert!(!features.initial_routing_sync());
 883                 assert!(!features.supports_upfront_shutdown_script());
 884                 assert!(!init_features.supports_gossip_queries());
 885         }
 886
 887         #[test]
 888         fn convert_to_context_with_unknown_flags() {
 889                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
 890                 assert!(InvoiceFeatures::known().flags.len() < NodeFeatures::known().flags.len());
 891                 let mut invoice_features = InvoiceFeatures::known();
 892                 invoice_features.set_unknown_feature_optional();
 893                 assert!(invoice_features.supports_unknown_bits());
 894                 let node_features: NodeFeatures = invoice_features.to_context();
 895                 assert!(!node_features.supports_unknown_bits());
 896         }
 897
 898         #[test]
 899         fn set_feature_bits() {
 900                 let mut features = InvoiceFeatures::empty();
 901                 features.set_basic_mpp_optional();
 902                 features.set_payment_secret_required();
 903                 assert!(features.supports_basic_mpp());
 904                 assert!(!features.requires_basic_mpp());
 905                 assert!(features.requires_payment_secret());
 906                 assert!(features.supports_payment_secret());
 907         }
 908
 909         #[test]
 910         fn invoice_features_encoding() {
 911                 let features_as_u5s = vec![
 912                         u5::try_from_u8(6).unwrap(),
 913                         u5::try_from_u8(10).unwrap(),
 914                         u5::try_from_u8(25).unwrap(),
 915                         u5::try_from_u8(1).unwrap(),
 916                         u5::try_from_u8(10).unwrap(),
 917                         u5::try_from_u8(0).unwrap(),
 918                         u5::try_from_u8(20).unwrap(),
 919                         u5::try_from_u8(2).unwrap(),
 920                         u5::try_from_u8(0).unwrap(),
 921                         u5::try_from_u8(6).unwrap(),
 922                         u5::try_from_u8(0).unwrap(),
 923                         u5::try_from_u8(16).unwrap(),
 924                         u5::try_from_u8(1).unwrap(),
 925                 ];
 926                 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
 927
 928                 // Test length calculation.
 929                 assert_eq!(features.base32_len(), 13);
 930
 931                 // Test serialization.
 932                 let features_serialized = features.to_base32();
 933                 assert_eq!(features_as_u5s, features_serialized);
 934
 935                 // Test deserialization.
 936                 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
 937                 assert_eq!(features, features_deserialized);
 938         }
 939
 940         #[test]
 941         fn test_channel_type_mapping() {
 942                 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
 943                 // required-StaticRemoteKey ChannelTypeFeatures.
 944                 let mut init_features = InitFeatures::empty();
 945                 init_features.set_static_remote_key_optional();
 946                 let converted_features = ChannelTypeFeatures::from_counterparty_init(&init_features);
 947                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
 948                 assert!(!converted_features.supports_any_optional_bits());
 949                 assert!(converted_features.requires_static_remote_key());
 950         }
 951 }