1 // This file is Copyright its original authors, visible in version control
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
10 //! Feature flag definitions for the Lightning protocol according to [BOLT #9].
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).
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.
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).
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).
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).
56 //! [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
57 //! [messages]: crate::ln::msgs
59 use crate::{io, io_extras};
60 use crate::prelude::*;
62 use core::hash::{Hash, Hasher};
63 use core::marker::PhantomData;
66 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
67 use crate::ln::msgs::DecodeError;
68 use crate::util::ser::{Readable, WithoutLength, Writeable, Writer};
71 use crate::prelude::*;
72 use crate::ln::features::Features;
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.
78 /// Bitmask for selecting features that are known to the implementation.
79 const KNOWN_FEATURE_MASK: &'static [u8];
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 {}
90 impl Context for $context {
91 const KNOWN_FEATURE_MASK: &'static [u8] = &[
94 <Self as $known_feature>::REQUIRED_MASK |
95 <Self as $known_feature>::OPTIONAL_MASK)*,
100 impl alloc::fmt::Display for Features<$context> {
101 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
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" }))?;
109 {} // Rust gets mad if we only have a $()* block here, so add a dummy {}
111 fmt.write_fmt(format_args!("unknown flags: {}",
112 if self.requires_unknown_bits() { "required" }
113 else if self.supports_unknown_bits() { "supported" } else { "none" }))
119 define_context!(InitContext, [
121 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
123 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
131 ChannelType | SCIDPrivacy,
135 define_context!(NodeContext, [
137 DataLossProtect | UpfrontShutdownScript | GossipQueries,
139 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
147 ChannelType | SCIDPrivacy,
151 define_context!(ChannelContext, []);
152 define_context!(InvoiceContext, [
156 VariableLengthOnion | PaymentSecret,
160 define_context!(OfferContext, []);
161 define_context!(InvoiceRequestContext, []);
162 define_context!(Bolt12InvoiceContext, [
170 // This isn't a "real" feature context, and is only used in the channel_type field in an
171 // `OpenChannel` message.
172 define_context!(ChannelTypeContext, [
189 /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
190 /// useful for manipulating feature flags.
191 macro_rules! define_feature {
192 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
193 $required_setter: ident, $supported_getter: ident) => {
196 /// See [BOLT #9] for details.
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;
203 /// The bit used to signify that the feature is optional.
204 const ODD_BIT: usize = $odd_bit;
206 /// Assertion that [`EVEN_BIT`] is actually even.
208 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
209 const ASSERT_EVEN_BIT_PARITY: usize;
211 /// Assertion that [`ODD_BIT`] is actually odd.
213 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
214 const ASSERT_ODD_BIT_PARITY: usize;
216 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
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;
222 /// The byte where the feature is set.
223 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
225 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
227 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
228 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
230 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
232 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
233 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
235 /// Returns whether the feature is required by the given flags.
237 fn requires_feature(flags: &Vec<u8>) -> bool {
238 flags.len() > Self::BYTE_OFFSET &&
239 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
242 /// Returns whether the feature is supported by the given flags.
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
249 /// Sets the feature's required (even) bit in the given flags.
251 fn set_required_bit(flags: &mut Vec<u8>) {
252 if flags.len() <= Self::BYTE_OFFSET {
253 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
256 flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
259 /// Sets the feature's optional (odd) bit in the given flags.
261 fn set_optional_bit(flags: &mut Vec<u8>) {
262 if flags.len() <= Self::BYTE_OFFSET {
263 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
266 flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
269 /// Clears the feature's required (even) and optional (odd) bits from the given
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;
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);
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);
290 /// Set this feature as required.
291 pub fn $required_setter(&mut self) {
292 <T as $feature>::set_required_bit(&mut self.flags);
295 /// Checks if this feature is supported.
296 pub fn $supported_getter(&self) -> bool {
297 <T as $feature>::supports_feature(&self.flags)
302 impl $feature for $context {
304 const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
307 const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
309 // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
310 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
311 const ASSERT_BITS_IN_MASK: u8 =
312 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
313 >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
317 ($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)
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);
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);
385 /// Tracks the set of features which a node implements, templated by the context in which it
388 /// (C-not exported) as we map the concrete feature types below directly instead
390 pub struct Features<T: sealed::Context> {
391 /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
393 mark: PhantomData<T>,
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()) {
407 impl<T: sealed::Context> Clone for Features<T> {
408 fn clone(&self) -> Self {
410 flags: self.flags.clone(),
415 impl<T: sealed::Context> Hash for Features<T> {
416 fn hash<H: Hasher>(&self, hasher: &mut H) {
417 self.flags.hash(hasher);
420 impl<T: sealed::Context> PartialEq for Features<T> {
421 fn eq(&self, o: &Self) -> bool {
422 self.flags.eq(&o.flags)
425 impl<T: sealed::Context> fmt::Debug for Features<T> {
426 fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
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>;
446 /// Features used within the channel_type field in an OpenChannel message.
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.
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.
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>;
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() {
465 self.flags[i].write(w)?;
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)?;
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()
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()
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`].
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();
504 impl ChannelTypeFeatures {
505 /// Constructs the implicit channel type based on the common supported types between us and our
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;
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);
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();
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();
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();
548 // Trim the highest feature bits.
549 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
552 writer.write(&res_u5s)
556 impl Base32Len for InvoiceFeatures {
557 fn base32_len(&self) -> usize {
558 self.to_base32().len()
562 impl FromBase32 for InvoiceFeatures {
563 type Err = bech32::Error;
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;
580 // Trim the highest feature bits.
581 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
584 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
588 impl<T: sealed::Context> Features<T> {
589 /// Create a blank Features with no features set
590 pub fn empty() -> Self {
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);
610 Features::<C> { flags, mark: PhantomData, }
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> {
624 /// Gets the underlying flags set, in LE.
625 pub fn le_flags(&self) -> &Vec<u8> {
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
636 fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
637 flags.reverse(); // Swap to little-endian
644 pub(crate) fn supports_any_optional_bits(&self) -> bool {
645 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
648 /// Returns true if this `Features` object contains unknown feature flags which are set as
650 pub fn requires_unknown_bits(&self) -> bool {
651 // Bitwise AND-ing with all even bits set except for known features will select required
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]
661 (byte & (required_features & unknown_features)) != 0
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]
675 (byte & unknown_features) != 0
680 impl<T: sealed::UpfrontShutdownScript> Features<T> {
682 pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
683 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
688 impl<T: sealed::ShutdownAnySegwit> Features<T> {
690 pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
691 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
696 impl<T: sealed::Wumbo> Features<T> {
698 pub(crate) fn clear_wumbo(mut self) -> Self {
699 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
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();
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)?;
721 impl Readable for $features {
722 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
723 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
728 impl_feature_len_prefixed_write!(InitFeatures);
729 impl_feature_len_prefixed_write!(ChannelFeatures);
730 impl_feature_len_prefixed_write!(NodeFeatures);
731 impl_feature_len_prefixed_write!(InvoiceFeatures);
733 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
734 macro_rules! impl_feature_tlv_write {
735 ($features: ident) => {
736 impl Writeable for $features {
737 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
738 WithoutLength(self).write(w)
741 impl Readable for $features {
742 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
743 Ok(WithoutLength::<Self>::read(r)?.0)
749 impl_feature_tlv_write!(ChannelTypeFeatures);
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.
754 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
755 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
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)))
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};
774 fn sanity_test_unknown_bits() {
775 let features = ChannelFeatures::empty();
776 assert!(!features.requires_unknown_bits());
777 assert!(!features.supports_unknown_bits());
779 let mut features = ChannelFeatures::empty();
780 features.set_unknown_feature_required();
781 assert!(features.requires_unknown_bits());
782 assert!(features.supports_unknown_bits());
784 let mut features = ChannelFeatures::empty();
785 features.set_unknown_feature_optional();
786 assert!(!features.requires_unknown_bits());
787 assert!(features.supports_unknown_bits());
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();
808 assert!(init_features.initial_routing_sync());
809 assert!(!init_features.supports_upfront_shutdown_script());
810 assert!(!init_features.supports_gossip_queries());
812 let node_features: NodeFeatures = init_features.to_context();
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
820 // - option_channel_type | option_scid_alias
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);
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());
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());
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());
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);
870 let mut serialized_features = Vec::new();
871 WithoutLength(&features).write(&mut serialized_features).unwrap();
872 assert_eq!(serialized_features.len(), 8);
874 let deserialized_features =
875 WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
876 assert_eq!(features, deserialized_features);
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(),
896 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
898 // Test length calculation.
899 assert_eq!(features.base32_len(), 13);
901 // Test serialization.
902 let features_serialized = features.to_base32();
903 assert_eq!(features_as_u5s, features_serialized);
905 // Test deserialization.
906 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
907 assert_eq!(features, features_deserialized);
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());