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, 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 $()* block here, so add a dummy {}
111 fmt.write_fmt(format_args!("unknown flags: {}",
112 if self.requires_unknown_bits() { "required" }
113 else if self.supports_unknown_bits() { "supported" } else { "none" }))
119 define_context!(InitContext, [
121 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
123 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
131 ChannelType | SCIDPrivacy,
135 define_context!(NodeContext, [
137 DataLossProtect | UpfrontShutdownScript | GossipQueries,
139 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
147 ChannelType | SCIDPrivacy,
151 define_context!(ChannelContext, []);
152 define_context!(InvoiceContext, [
156 VariableLengthOnion | PaymentSecret,
160 define_context!(OfferContext, []);
161 // This isn't a "real" feature context, and is only used in the channel_type field in an
162 // `OpenChannel` message.
163 define_context!(ChannelTypeContext, [
180 /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
181 /// useful for manipulating feature flags.
182 macro_rules! define_feature {
183 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
184 $required_setter: ident, $supported_getter: ident) => {
187 /// See [BOLT #9] for details.
189 /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
190 pub trait $feature: Context {
191 /// The bit used to signify that the feature is required.
192 const EVEN_BIT: usize = $odd_bit - 1;
194 /// The bit used to signify that the feature is optional.
195 const ODD_BIT: usize = $odd_bit;
197 /// Assertion that [`EVEN_BIT`] is actually even.
199 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
200 const ASSERT_EVEN_BIT_PARITY: usize;
202 /// Assertion that [`ODD_BIT`] is actually odd.
204 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
205 const ASSERT_ODD_BIT_PARITY: usize;
207 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
209 /// [`KNOWN_FEATURE_MASK`]: Context::KNOWN_FEATURE_MASK
210 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
211 const ASSERT_BITS_IN_MASK: u8;
213 /// The byte where the feature is set.
214 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
216 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
218 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
219 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
221 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
223 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
224 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
226 /// Returns whether the feature is required by the given flags.
228 fn requires_feature(flags: &Vec<u8>) -> bool {
229 flags.len() > Self::BYTE_OFFSET &&
230 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
233 /// Returns whether the feature is supported by the given flags.
235 fn supports_feature(flags: &Vec<u8>) -> bool {
236 flags.len() > Self::BYTE_OFFSET &&
237 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
240 /// Sets the feature's required (even) bit in the given flags.
242 fn set_required_bit(flags: &mut Vec<u8>) {
243 if flags.len() <= Self::BYTE_OFFSET {
244 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
247 flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
250 /// Sets the feature's optional (odd) bit in the given flags.
252 fn set_optional_bit(flags: &mut Vec<u8>) {
253 if flags.len() <= Self::BYTE_OFFSET {
254 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
257 flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
260 /// Clears the feature's required (even) and optional (odd) bits from the given
263 fn clear_bits(flags: &mut Vec<u8>) {
264 if flags.len() > Self::BYTE_OFFSET {
265 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
266 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
269 let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
270 let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
271 flags.resize(size, 0u8);
275 impl <T: $feature> Features<T> {
276 /// Set this feature as optional.
277 pub fn $optional_setter(&mut self) {
278 <T as $feature>::set_optional_bit(&mut self.flags);
281 /// Set this feature as required.
282 pub fn $required_setter(&mut self) {
283 <T as $feature>::set_required_bit(&mut self.flags);
286 /// Checks if this feature is supported.
287 pub fn $supported_getter(&self) -> bool {
288 <T as $feature>::supports_feature(&self.flags)
293 impl $feature for $context {
295 const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
298 const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
300 // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
301 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
302 const ASSERT_BITS_IN_MASK: u8 =
303 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
304 >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
308 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
309 $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
310 define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
311 impl <T: $feature> Features<T> {
312 /// Checks if this feature is required.
313 pub fn $required_getter(&self) -> bool {
314 <T as $feature>::requires_feature(&self.flags)
320 define_feature!(1, DataLossProtect, [InitContext, NodeContext],
321 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
322 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
323 // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
324 define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
325 set_initial_routing_sync_optional, set_initial_routing_sync_required,
326 initial_routing_sync);
327 define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
328 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
329 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
330 requires_upfront_shutdown_script);
331 define_feature!(7, GossipQueries, [InitContext, NodeContext],
332 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
333 supports_gossip_queries, requires_gossip_queries);
334 define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
335 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
336 set_variable_length_onion_required, supports_variable_length_onion,
337 requires_variable_length_onion);
338 define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
339 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
340 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
341 define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
342 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
343 supports_payment_secret, requires_payment_secret);
344 define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext],
345 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
346 supports_basic_mpp, requires_basic_mpp);
347 define_feature!(19, Wumbo, [InitContext, NodeContext],
348 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
349 supports_wumbo, requires_wumbo);
350 define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
351 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
352 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
353 define_feature!(39, OnionMessages, [InitContext, NodeContext],
354 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
355 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
356 define_feature!(45, ChannelType, [InitContext, NodeContext],
357 "Feature flags for `option_channel_type`.", set_channel_type_optional,
358 set_channel_type_required, supports_channel_type, requires_channel_type);
359 define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
360 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
361 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
362 define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
363 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
364 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
365 define_feature!(55, Keysend, [NodeContext],
366 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
367 supports_keysend, requires_keysend);
370 define_feature!(123456789, UnknownFeature, [NodeContext, ChannelContext, InvoiceContext, OfferContext],
371 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
372 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
375 /// Tracks the set of features which a node implements, templated by the context in which it
378 /// (C-not exported) as we map the concrete feature types below directly instead
380 pub struct Features<T: sealed::Context> {
381 /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
383 mark: PhantomData<T>,
386 impl <T: sealed::Context> Features<T> {
387 pub(crate) fn or(mut self, o: Self) -> Self {
388 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
389 self.flags.resize(total_feature_len, 0u8);
390 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
397 impl<T: sealed::Context> Clone for Features<T> {
398 fn clone(&self) -> Self {
400 flags: self.flags.clone(),
405 impl<T: sealed::Context> Hash for Features<T> {
406 fn hash<H: Hasher>(&self, hasher: &mut H) {
407 self.flags.hash(hasher);
410 impl<T: sealed::Context> PartialEq for Features<T> {
411 fn eq(&self, o: &Self) -> bool {
412 self.flags.eq(&o.flags)
415 impl<T: sealed::Context> fmt::Debug for Features<T> {
416 fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
421 /// Features used within an `init` message.
422 pub type InitFeatures = Features<sealed::InitContext>;
423 /// Features used within a `node_announcement` message.
424 pub type NodeFeatures = Features<sealed::NodeContext>;
425 /// Features used within a `channel_announcement` message.
426 pub type ChannelFeatures = Features<sealed::ChannelContext>;
427 /// Features used within an invoice.
428 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
429 /// Features used within an offer.
430 pub type OfferFeatures = Features<sealed::OfferContext>;
432 /// Features used within the channel_type field in an OpenChannel message.
434 /// A channel is always of some known "type", describing the transaction formats used and the exact
435 /// semantics of our interaction with our peer.
437 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
438 /// the counterparty, only required features are allowed here.
440 /// This is serialized differently from other feature types - it is not prefixed by a length, and
441 /// thus must only appear inside a TLV where its length is known in advance.
442 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
445 /// Writes all features present up to, and including, 13.
446 pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
447 let len = cmp::min(2, self.flags.len());
448 (len as u16).write(w)?;
449 for i in (0..len).rev() {
451 self.flags[i].write(w)?;
453 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
454 // up-to-and-including-bit-5, 0-indexed, on this byte:
455 (self.flags[i] & 0b00_11_11_11).write(w)?;
461 /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
462 /// are included in the result.
463 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
464 self.to_context_internal()
468 impl InvoiceFeatures {
469 /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
470 /// context `C` are included in the result.
471 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
472 self.to_context_internal()
475 /// Getting a route for a keysend payment to a private node requires providing the payee's
476 /// features (since they were not announced in a node announcement). However, keysend payments
477 /// don't have an invoice to pull the payee's features from, so this method is provided for use in
478 /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
479 /// `InvoiceFeatures` for [`find_route`].
481 /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
482 /// [`find_route`]: crate::routing::router::find_route
483 pub(crate) fn for_keysend() -> InvoiceFeatures {
484 let mut res = InvoiceFeatures::empty();
485 res.set_variable_length_onion_optional();
490 impl ChannelTypeFeatures {
491 /// Constructs the implicit channel type based on the common supported types between us and our
493 pub(crate) fn from_counterparty_init(counterparty_init: &InitFeatures) -> Self {
494 let mut ret = counterparty_init.to_context_internal();
495 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
496 // optional bits and then AND out the optional ones.
497 for byte in ret.flags.iter_mut() {
498 *byte |= (*byte & 0b10_10_10_10) >> 1;
499 *byte &= 0b01_01_01_01;
504 /// Constructs a ChannelTypeFeatures with only static_remotekey set
505 pub(crate) fn only_static_remote_key() -> Self {
506 let mut ret = Self::empty();
507 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
512 impl ToBase32 for InvoiceFeatures {
513 fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
514 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
515 // minus one before dividing
516 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
517 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
518 for (byte_idx, byte) in self.flags.iter().enumerate() {
519 let bit_pos_from_left_0_indexed = byte_idx * 8;
520 let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
521 let new_bit_pos = bit_pos_from_left_0_indexed % 5;
522 let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
523 let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
524 res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
526 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
527 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
530 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
531 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
534 // Trim the highest feature bits.
535 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
538 writer.write(&res_u5s)
542 impl Base32Len for InvoiceFeatures {
543 fn base32_len(&self) -> usize {
544 self.to_base32().len()
548 impl FromBase32 for InvoiceFeatures {
549 type Err = bech32::Error;
551 fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
552 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
553 // minus one before dividing
554 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
555 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
556 for (u5_idx, chunk) in field_data.iter().enumerate() {
557 let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
558 let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
559 let new_bit_pos = bit_pos_from_right_0_indexed % 8;
560 let chunk_u16 = chunk.to_u8() as u16;
561 res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
562 if new_byte_idx != length_bytes - 1 {
563 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
566 // Trim the highest feature bits.
567 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
570 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
574 impl<T: sealed::Context> Features<T> {
575 /// Create a blank Features with no features set
576 pub fn empty() -> Self {
583 /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
584 /// included in the result.
585 fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
586 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
587 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
588 let mut flags = Vec::new();
589 for (i, byte) in self.flags.iter().enumerate() {
590 if i < from_byte_count && i < to_byte_count {
591 let from_known_features = T::KNOWN_FEATURE_MASK[i];
592 let to_known_features = C::KNOWN_FEATURE_MASK[i];
593 flags.push(byte & from_known_features & to_known_features);
596 Features::<C> { flags, mark: PhantomData, }
599 /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
600 /// most on-the-wire encodings.
601 /// (C-not exported) as we don't support export across multiple T
602 pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
610 /// Gets the underlying flags set, in LE.
611 pub fn le_flags(&self) -> &Vec<u8> {
615 fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
616 for f in self.flags.iter().rev() { // Swap back to big-endian
622 fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
623 flags.reverse(); // Swap to little-endian
630 pub(crate) fn supports_any_optional_bits(&self) -> bool {
631 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
634 /// Returns true if this `Features` object contains unknown feature flags which are set as
636 pub fn requires_unknown_bits(&self) -> bool {
637 // Bitwise AND-ing with all even bits set except for known features will select required
639 let byte_count = T::KNOWN_FEATURE_MASK.len();
640 self.flags.iter().enumerate().any(|(i, &byte)| {
641 let required_features = 0b01_01_01_01;
642 let unknown_features = if i < byte_count {
643 !T::KNOWN_FEATURE_MASK[i]
647 (byte & (required_features & unknown_features)) != 0
651 pub(crate) fn supports_unknown_bits(&self) -> bool {
652 // Bitwise AND-ing with all even and odd bits set except for known features will select
653 // both required and optional unknown features.
654 let byte_count = T::KNOWN_FEATURE_MASK.len();
655 self.flags.iter().enumerate().any(|(i, &byte)| {
656 let unknown_features = if i < byte_count {
657 !T::KNOWN_FEATURE_MASK[i]
661 (byte & unknown_features) != 0
666 impl<T: sealed::UpfrontShutdownScript> Features<T> {
668 pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
669 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
674 impl<T: sealed::ShutdownAnySegwit> Features<T> {
676 pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
677 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
682 impl<T: sealed::Wumbo> Features<T> {
684 pub(crate) fn clear_wumbo(mut self) -> Self {
685 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
691 impl<T: sealed::UnknownFeature> Features<T> {
692 pub(crate) fn unknown() -> Self {
693 let mut features = Self::empty();
694 features.set_unknown_feature_required();
699 macro_rules! impl_feature_len_prefixed_write {
700 ($features: ident) => {
701 impl Writeable for $features {
702 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
703 (self.flags.len() as u16).write(w)?;
707 impl Readable for $features {
708 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
709 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
714 impl_feature_len_prefixed_write!(InitFeatures);
715 impl_feature_len_prefixed_write!(ChannelFeatures);
716 impl_feature_len_prefixed_write!(NodeFeatures);
717 impl_feature_len_prefixed_write!(InvoiceFeatures);
719 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
720 macro_rules! impl_feature_tlv_write {
721 ($features: ident) => {
722 impl Writeable for $features {
723 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
727 impl Readable for $features {
728 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
729 let v = io_extras::read_to_end(r)?;
730 Ok(Self::from_be_bytes(v))
736 impl_feature_tlv_write!(ChannelTypeFeatures);
737 impl_feature_tlv_write!(OfferFeatures);
741 use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures, sealed};
742 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
745 fn sanity_test_unknown_bits() {
746 let features = ChannelFeatures::empty();
747 assert!(!features.requires_unknown_bits());
748 assert!(!features.supports_unknown_bits());
750 let mut features = ChannelFeatures::empty();
751 features.set_unknown_feature_required();
752 assert!(features.requires_unknown_bits());
753 assert!(features.supports_unknown_bits());
755 let mut features = ChannelFeatures::empty();
756 features.set_unknown_feature_optional();
757 assert!(!features.requires_unknown_bits());
758 assert!(features.supports_unknown_bits());
762 fn convert_to_context_with_relevant_flags() {
763 let mut init_features = InitFeatures::empty();
764 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
765 // converted as it's only relevant in an init context).
766 init_features.set_initial_routing_sync_required();
767 init_features.set_data_loss_protect_optional();
768 init_features.set_variable_length_onion_required();
769 init_features.set_static_remote_key_required();
770 init_features.set_payment_secret_required();
771 init_features.set_basic_mpp_optional();
772 init_features.set_wumbo_optional();
773 init_features.set_shutdown_any_segwit_optional();
774 init_features.set_onion_messages_optional();
775 init_features.set_channel_type_optional();
776 init_features.set_scid_privacy_optional();
777 init_features.set_zero_conf_optional();
779 assert!(init_features.initial_routing_sync());
780 assert!(!init_features.supports_upfront_shutdown_script());
781 assert!(!init_features.supports_gossip_queries());
783 let node_features: NodeFeatures = init_features.to_context();
785 // Check that the flags are as expected:
786 // - option_data_loss_protect
787 // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
788 // - basic_mpp | wumbo
789 // - opt_shutdown_anysegwit
791 // - option_channel_type | option_scid_alias
793 assert_eq!(node_features.flags.len(), 7);
794 assert_eq!(node_features.flags[0], 0b00000010);
795 assert_eq!(node_features.flags[1], 0b01010001);
796 assert_eq!(node_features.flags[2], 0b00001010);
797 assert_eq!(node_features.flags[3], 0b00001000);
798 assert_eq!(node_features.flags[4], 0b10000000);
799 assert_eq!(node_features.flags[5], 0b10100000);
800 assert_eq!(node_features.flags[6], 0b00001000);
803 // Check that cleared flags are kept blank when converting back:
804 // - initial_routing_sync was not applicable to NodeContext
805 // - upfront_shutdown_script was cleared before converting
806 // - gossip_queries was cleared before converting
807 let features: InitFeatures = node_features.to_context_internal();
808 assert!(!features.initial_routing_sync());
809 assert!(!features.supports_upfront_shutdown_script());
810 assert!(!init_features.supports_gossip_queries());
814 fn convert_to_context_with_unknown_flags() {
815 // Ensure the `from` context has fewer known feature bytes than the `to` context.
816 assert!(<sealed::InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
817 <sealed::NodeContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
818 let mut invoice_features = InvoiceFeatures::empty();
819 invoice_features.set_unknown_feature_optional();
820 assert!(invoice_features.supports_unknown_bits());
821 let node_features: NodeFeatures = invoice_features.to_context();
822 assert!(!node_features.supports_unknown_bits());
826 fn set_feature_bits() {
827 let mut features = InvoiceFeatures::empty();
828 features.set_basic_mpp_optional();
829 features.set_payment_secret_required();
830 assert!(features.supports_basic_mpp());
831 assert!(!features.requires_basic_mpp());
832 assert!(features.requires_payment_secret());
833 assert!(features.supports_payment_secret());
837 fn invoice_features_encoding() {
838 let features_as_u5s = vec![
839 u5::try_from_u8(6).unwrap(),
840 u5::try_from_u8(10).unwrap(),
841 u5::try_from_u8(25).unwrap(),
842 u5::try_from_u8(1).unwrap(),
843 u5::try_from_u8(10).unwrap(),
844 u5::try_from_u8(0).unwrap(),
845 u5::try_from_u8(20).unwrap(),
846 u5::try_from_u8(2).unwrap(),
847 u5::try_from_u8(0).unwrap(),
848 u5::try_from_u8(6).unwrap(),
849 u5::try_from_u8(0).unwrap(),
850 u5::try_from_u8(16).unwrap(),
851 u5::try_from_u8(1).unwrap(),
853 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
855 // Test length calculation.
856 assert_eq!(features.base32_len(), 13);
858 // Test serialization.
859 let features_serialized = features.to_base32();
860 assert_eq!(features_as_u5s, features_serialized);
862 // Test deserialization.
863 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
864 assert_eq!(features, features_deserialized);
868 fn test_channel_type_mapping() {
869 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
870 // required-StaticRemoteKey ChannelTypeFeatures.
871 let mut init_features = InitFeatures::empty();
872 init_features.set_static_remote_key_optional();
873 let converted_features = ChannelTypeFeatures::from_counterparty_init(&init_features);
874 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
875 assert!(!converted_features.supports_any_optional_bits());
876 assert!(converted_features.requires_static_remote_key());