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 $()* block here, so add a dummy {}
111 fmt.write_fmt(format_args!("unknown flags: {}",
112 if self.requires_unknown_bits() { "required" }
113 else if self.supports_unknown_bits() { "supported" } else { "none" }))
119 define_context!(InitContext, [
121 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
123 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
131 ChannelType | SCIDPrivacy,
135 define_context!(NodeContext, [
137 DataLossProtect | UpfrontShutdownScript | GossipQueries,
139 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
147 ChannelType | SCIDPrivacy,
151 define_context!(ChannelContext, []);
152 define_context!(InvoiceContext, [
156 VariableLengthOnion | PaymentSecret,
160 define_context!(OfferContext, []);
161 define_context!(InvoiceRequestContext, []);
162 define_context!(Bolt12InvoiceContext, [
170 define_context!(BlindedHopContext, []);
171 // This isn't a "real" feature context, and is only used in the channel_type field in an
172 // `OpenChannel` message.
173 define_context!(ChannelTypeContext, [
190 /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
191 /// useful for manipulating feature flags.
192 macro_rules! define_feature {
193 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
194 $required_setter: ident, $supported_getter: ident) => {
197 /// See [BOLT #9] for details.
199 /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
200 pub trait $feature: Context {
201 /// The bit used to signify that the feature is required.
202 const EVEN_BIT: usize = $odd_bit - 1;
204 /// The bit used to signify that the feature is optional.
205 const ODD_BIT: usize = $odd_bit;
207 /// Assertion that [`EVEN_BIT`] is actually even.
209 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
210 const ASSERT_EVEN_BIT_PARITY: usize;
212 /// Assertion that [`ODD_BIT`] is actually odd.
214 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
215 const ASSERT_ODD_BIT_PARITY: usize;
217 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
219 /// [`KNOWN_FEATURE_MASK`]: Context::KNOWN_FEATURE_MASK
220 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
221 const ASSERT_BITS_IN_MASK: u8;
223 /// The byte where the feature is set.
224 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
226 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
228 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
229 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
231 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
233 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
234 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
236 /// Returns whether the feature is required by the given flags.
238 fn requires_feature(flags: &Vec<u8>) -> bool {
239 flags.len() > Self::BYTE_OFFSET &&
240 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
243 /// Returns whether the feature is supported by the given flags.
245 fn supports_feature(flags: &Vec<u8>) -> bool {
246 flags.len() > Self::BYTE_OFFSET &&
247 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
250 /// Sets the feature's required (even) bit in the given flags.
252 fn set_required_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::REQUIRED_MASK;
260 /// Sets the feature's optional (odd) bit in the given flags.
262 fn set_optional_bit(flags: &mut Vec<u8>) {
263 if flags.len() <= Self::BYTE_OFFSET {
264 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
267 flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
270 /// Clears the feature's required (even) and optional (odd) bits from the given
273 fn clear_bits(flags: &mut Vec<u8>) {
274 if flags.len() > Self::BYTE_OFFSET {
275 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
276 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
279 let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
280 let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
281 flags.resize(size, 0u8);
285 impl <T: $feature> Features<T> {
286 /// Set this feature as optional.
287 pub fn $optional_setter(&mut self) {
288 <T as $feature>::set_optional_bit(&mut self.flags);
291 /// Set this feature as required.
292 pub fn $required_setter(&mut self) {
293 <T as $feature>::set_required_bit(&mut self.flags);
296 /// Checks if this feature is supported.
297 pub fn $supported_getter(&self) -> bool {
298 <T as $feature>::supports_feature(&self.flags)
303 impl $feature for $context {
305 const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
308 const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
310 // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
311 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
312 const ASSERT_BITS_IN_MASK: u8 =
313 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
314 >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
318 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
319 $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
320 define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
321 impl <T: $feature> Features<T> {
322 /// Checks if this feature is required.
323 pub fn $required_getter(&self) -> bool {
324 <T as $feature>::requires_feature(&self.flags)
330 define_feature!(1, DataLossProtect, [InitContext, NodeContext],
331 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
332 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
333 // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
334 define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
335 set_initial_routing_sync_optional, set_initial_routing_sync_required,
336 initial_routing_sync);
337 define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
338 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
339 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
340 requires_upfront_shutdown_script);
341 define_feature!(7, GossipQueries, [InitContext, NodeContext],
342 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
343 supports_gossip_queries, requires_gossip_queries);
344 define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
345 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
346 set_variable_length_onion_required, supports_variable_length_onion,
347 requires_variable_length_onion);
348 define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
349 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
350 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
351 define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
352 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
353 supports_payment_secret, requires_payment_secret);
354 define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext, Bolt12InvoiceContext],
355 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
356 supports_basic_mpp, requires_basic_mpp);
357 define_feature!(19, Wumbo, [InitContext, NodeContext],
358 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
359 supports_wumbo, requires_wumbo);
360 define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
361 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
362 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
363 define_feature!(39, OnionMessages, [InitContext, NodeContext],
364 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
365 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
366 define_feature!(45, ChannelType, [InitContext, NodeContext],
367 "Feature flags for `option_channel_type`.", set_channel_type_optional,
368 set_channel_type_required, supports_channel_type, requires_channel_type);
369 define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
370 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
371 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
372 define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
373 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
374 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
375 define_feature!(55, Keysend, [NodeContext],
376 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
377 supports_keysend, requires_keysend);
380 define_feature!(123456789, UnknownFeature,
381 [NodeContext, ChannelContext, InvoiceContext, OfferContext, InvoiceRequestContext, Bolt12InvoiceContext, BlindedHopContext],
382 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
383 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
386 /// Tracks the set of features which a node implements, templated by the context in which it
389 /// (C-not exported) as we map the concrete feature types below directly instead
391 pub struct Features<T: sealed::Context> {
392 /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
394 mark: PhantomData<T>,
397 impl <T: sealed::Context> Features<T> {
398 pub(crate) fn or(mut self, o: Self) -> Self {
399 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
400 self.flags.resize(total_feature_len, 0u8);
401 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
408 impl<T: sealed::Context> Clone for Features<T> {
409 fn clone(&self) -> Self {
411 flags: self.flags.clone(),
416 impl<T: sealed::Context> Hash for Features<T> {
417 fn hash<H: Hasher>(&self, hasher: &mut H) {
418 self.flags.hash(hasher);
421 impl<T: sealed::Context> PartialEq for Features<T> {
422 fn eq(&self, o: &Self) -> bool {
423 self.flags.eq(&o.flags)
426 impl<T: sealed::Context> fmt::Debug for Features<T> {
427 fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
432 /// Features used within an `init` message.
433 pub type InitFeatures = Features<sealed::InitContext>;
434 /// Features used within a `node_announcement` message.
435 pub type NodeFeatures = Features<sealed::NodeContext>;
436 /// Features used within a `channel_announcement` message.
437 pub type ChannelFeatures = Features<sealed::ChannelContext>;
438 /// Features used within an invoice.
439 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
440 /// Features used within an `offer`.
441 pub type OfferFeatures = Features<sealed::OfferContext>;
442 /// Features used within an `invoice_request`.
443 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
444 /// Features used within an `invoice`.
445 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
446 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
447 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
449 /// Features used within the channel_type field in an OpenChannel message.
451 /// A channel is always of some known "type", describing the transaction formats used and the exact
452 /// semantics of our interaction with our peer.
454 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
455 /// the counterparty, only required features are allowed here.
457 /// This is serialized differently from other feature types - it is not prefixed by a length, and
458 /// thus must only appear inside a TLV where its length is known in advance.
459 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
462 /// Writes all features present up to, and including, 13.
463 pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
464 let len = cmp::min(2, self.flags.len());
465 (len as u16).write(w)?;
466 for i in (0..len).rev() {
468 self.flags[i].write(w)?;
470 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
471 // up-to-and-including-bit-5, 0-indexed, on this byte:
472 (self.flags[i] & 0b00_11_11_11).write(w)?;
478 /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
479 /// are included in the result.
480 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
481 self.to_context_internal()
485 impl InvoiceFeatures {
486 /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
487 /// context `C` are included in the result.
488 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
489 self.to_context_internal()
492 /// Getting a route for a keysend payment to a private node requires providing the payee's
493 /// features (since they were not announced in a node announcement). However, keysend payments
494 /// don't have an invoice to pull the payee's features from, so this method is provided for use in
495 /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
496 /// `InvoiceFeatures` for [`find_route`].
498 /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
499 /// [`find_route`]: crate::routing::router::find_route
500 pub(crate) fn for_keysend() -> InvoiceFeatures {
501 let mut res = InvoiceFeatures::empty();
502 res.set_variable_length_onion_optional();
507 impl ChannelTypeFeatures {
508 /// Constructs the implicit channel type based on the common supported types between us and our
510 pub(crate) fn from_counterparty_init(counterparty_init: &InitFeatures) -> Self {
511 let mut ret = counterparty_init.to_context_internal();
512 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
513 // optional bits and then AND out the optional ones.
514 for byte in ret.flags.iter_mut() {
515 *byte |= (*byte & 0b10_10_10_10) >> 1;
516 *byte &= 0b01_01_01_01;
521 /// Constructs a ChannelTypeFeatures with only static_remotekey set
522 pub(crate) fn only_static_remote_key() -> Self {
523 let mut ret = Self::empty();
524 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
529 impl ToBase32 for InvoiceFeatures {
530 fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
531 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
532 // minus one before dividing
533 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
534 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
535 for (byte_idx, byte) in self.flags.iter().enumerate() {
536 let bit_pos_from_left_0_indexed = byte_idx * 8;
537 let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
538 let new_bit_pos = bit_pos_from_left_0_indexed % 5;
539 let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
540 let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
541 res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
543 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
544 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
547 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
548 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
551 // Trim the highest feature bits.
552 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
555 writer.write(&res_u5s)
559 impl Base32Len for InvoiceFeatures {
560 fn base32_len(&self) -> usize {
561 self.to_base32().len()
565 impl FromBase32 for InvoiceFeatures {
566 type Err = bech32::Error;
568 fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
569 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
570 // minus one before dividing
571 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
572 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
573 for (u5_idx, chunk) in field_data.iter().enumerate() {
574 let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
575 let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
576 let new_bit_pos = bit_pos_from_right_0_indexed % 8;
577 let chunk_u16 = chunk.to_u8() as u16;
578 res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
579 if new_byte_idx != length_bytes - 1 {
580 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
583 // Trim the highest feature bits.
584 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
587 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
591 impl<T: sealed::Context> Features<T> {
592 /// Create a blank Features with no features set
593 pub fn empty() -> Self {
600 /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
601 /// included in the result.
602 fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
603 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
604 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
605 let mut flags = Vec::new();
606 for (i, byte) in self.flags.iter().enumerate() {
607 if i < from_byte_count && i < to_byte_count {
608 let from_known_features = T::KNOWN_FEATURE_MASK[i];
609 let to_known_features = C::KNOWN_FEATURE_MASK[i];
610 flags.push(byte & from_known_features & to_known_features);
613 Features::<C> { flags, mark: PhantomData, }
616 /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
617 /// most on-the-wire encodings.
618 /// (C-not exported) as we don't support export across multiple T
619 pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
627 /// Gets the underlying flags set, in LE.
628 pub fn le_flags(&self) -> &Vec<u8> {
632 fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
633 for f in self.flags.iter().rev() { // Swap back to big-endian
639 fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
640 flags.reverse(); // Swap to little-endian
647 pub(crate) fn supports_any_optional_bits(&self) -> bool {
648 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
651 /// Returns true if this `Features` object contains unknown feature flags which are set as
653 pub fn requires_unknown_bits(&self) -> bool {
654 // Bitwise AND-ing with all even bits set except for known features will select required
656 let byte_count = T::KNOWN_FEATURE_MASK.len();
657 self.flags.iter().enumerate().any(|(i, &byte)| {
658 let required_features = 0b01_01_01_01;
659 let unknown_features = if i < byte_count {
660 !T::KNOWN_FEATURE_MASK[i]
664 (byte & (required_features & unknown_features)) != 0
668 pub(crate) fn supports_unknown_bits(&self) -> bool {
669 // Bitwise AND-ing with all even and odd bits set except for known features will select
670 // both required and optional unknown features.
671 let byte_count = T::KNOWN_FEATURE_MASK.len();
672 self.flags.iter().enumerate().any(|(i, &byte)| {
673 let unknown_features = if i < byte_count {
674 !T::KNOWN_FEATURE_MASK[i]
678 (byte & unknown_features) != 0
683 impl<T: sealed::UpfrontShutdownScript> Features<T> {
685 pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
686 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
691 impl<T: sealed::ShutdownAnySegwit> Features<T> {
693 pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
694 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
699 impl<T: sealed::Wumbo> Features<T> {
701 pub(crate) fn clear_wumbo(mut self) -> Self {
702 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
708 impl<T: sealed::UnknownFeature> Features<T> {
709 pub(crate) fn unknown() -> Self {
710 let mut features = Self::empty();
711 features.set_unknown_feature_required();
716 macro_rules! impl_feature_len_prefixed_write {
717 ($features: ident) => {
718 impl Writeable for $features {
719 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
720 (self.flags.len() as u16).write(w)?;
724 impl Readable for $features {
725 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
726 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
731 impl_feature_len_prefixed_write!(InitFeatures);
732 impl_feature_len_prefixed_write!(ChannelFeatures);
733 impl_feature_len_prefixed_write!(NodeFeatures);
734 impl_feature_len_prefixed_write!(InvoiceFeatures);
735 impl_feature_len_prefixed_write!(BlindedHopFeatures);
737 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
738 macro_rules! impl_feature_tlv_write {
739 ($features: ident) => {
740 impl Writeable for $features {
741 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
742 WithoutLength(self).write(w)
745 impl Readable for $features {
746 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
747 Ok(WithoutLength::<Self>::read(r)?.0)
753 impl_feature_tlv_write!(ChannelTypeFeatures);
755 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
756 // requires a length but the former does not.
758 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
759 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
764 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
765 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
766 let v = io_extras::read_to_end(r)?;
767 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
773 use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
774 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
775 use crate::util::ser::{Readable, WithoutLength, Writeable};
778 fn sanity_test_unknown_bits() {
779 let features = ChannelFeatures::empty();
780 assert!(!features.requires_unknown_bits());
781 assert!(!features.supports_unknown_bits());
783 let mut features = ChannelFeatures::empty();
784 features.set_unknown_feature_required();
785 assert!(features.requires_unknown_bits());
786 assert!(features.supports_unknown_bits());
788 let mut features = ChannelFeatures::empty();
789 features.set_unknown_feature_optional();
790 assert!(!features.requires_unknown_bits());
791 assert!(features.supports_unknown_bits());
795 fn convert_to_context_with_relevant_flags() {
796 let mut init_features = InitFeatures::empty();
797 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
798 // converted as it's only relevant in an init context).
799 init_features.set_initial_routing_sync_required();
800 init_features.set_data_loss_protect_optional();
801 init_features.set_variable_length_onion_required();
802 init_features.set_static_remote_key_required();
803 init_features.set_payment_secret_required();
804 init_features.set_basic_mpp_optional();
805 init_features.set_wumbo_optional();
806 init_features.set_shutdown_any_segwit_optional();
807 init_features.set_onion_messages_optional();
808 init_features.set_channel_type_optional();
809 init_features.set_scid_privacy_optional();
810 init_features.set_zero_conf_optional();
812 assert!(init_features.initial_routing_sync());
813 assert!(!init_features.supports_upfront_shutdown_script());
814 assert!(!init_features.supports_gossip_queries());
816 let node_features: NodeFeatures = init_features.to_context();
818 // Check that the flags are as expected:
819 // - option_data_loss_protect
820 // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
821 // - basic_mpp | wumbo
822 // - opt_shutdown_anysegwit
824 // - option_channel_type | option_scid_alias
826 assert_eq!(node_features.flags.len(), 7);
827 assert_eq!(node_features.flags[0], 0b00000010);
828 assert_eq!(node_features.flags[1], 0b01010001);
829 assert_eq!(node_features.flags[2], 0b00001010);
830 assert_eq!(node_features.flags[3], 0b00001000);
831 assert_eq!(node_features.flags[4], 0b10000000);
832 assert_eq!(node_features.flags[5], 0b10100000);
833 assert_eq!(node_features.flags[6], 0b00001000);
836 // Check that cleared flags are kept blank when converting back:
837 // - initial_routing_sync was not applicable to NodeContext
838 // - upfront_shutdown_script was cleared before converting
839 // - gossip_queries was cleared before converting
840 let features: InitFeatures = node_features.to_context_internal();
841 assert!(!features.initial_routing_sync());
842 assert!(!features.supports_upfront_shutdown_script());
843 assert!(!init_features.supports_gossip_queries());
847 fn convert_to_context_with_unknown_flags() {
848 // Ensure the `from` context has fewer known feature bytes than the `to` context.
849 assert!(<sealed::InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
850 <sealed::NodeContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
851 let mut invoice_features = InvoiceFeatures::empty();
852 invoice_features.set_unknown_feature_optional();
853 assert!(invoice_features.supports_unknown_bits());
854 let node_features: NodeFeatures = invoice_features.to_context();
855 assert!(!node_features.supports_unknown_bits());
859 fn set_feature_bits() {
860 let mut features = InvoiceFeatures::empty();
861 features.set_basic_mpp_optional();
862 features.set_payment_secret_required();
863 assert!(features.supports_basic_mpp());
864 assert!(!features.requires_basic_mpp());
865 assert!(features.requires_payment_secret());
866 assert!(features.supports_payment_secret());
870 fn encodes_features_without_length() {
871 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
872 assert_eq!(features.flags.len(), 8);
874 let mut serialized_features = Vec::new();
875 WithoutLength(&features).write(&mut serialized_features).unwrap();
876 assert_eq!(serialized_features.len(), 8);
878 let deserialized_features =
879 WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
880 assert_eq!(features, deserialized_features);
884 fn invoice_features_encoding() {
885 let features_as_u5s = vec![
886 u5::try_from_u8(6).unwrap(),
887 u5::try_from_u8(10).unwrap(),
888 u5::try_from_u8(25).unwrap(),
889 u5::try_from_u8(1).unwrap(),
890 u5::try_from_u8(10).unwrap(),
891 u5::try_from_u8(0).unwrap(),
892 u5::try_from_u8(20).unwrap(),
893 u5::try_from_u8(2).unwrap(),
894 u5::try_from_u8(0).unwrap(),
895 u5::try_from_u8(6).unwrap(),
896 u5::try_from_u8(0).unwrap(),
897 u5::try_from_u8(16).unwrap(),
898 u5::try_from_u8(1).unwrap(),
900 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
902 // Test length calculation.
903 assert_eq!(features.base32_len(), 13);
905 // Test serialization.
906 let features_serialized = features.to_base32();
907 assert_eq!(features_as_u5s, features_serialized);
909 // Test deserialization.
910 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
911 assert_eq!(features, features_deserialized);
915 fn test_channel_type_mapping() {
916 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
917 // required-StaticRemoteKey ChannelTypeFeatures.
918 let mut init_features = InitFeatures::empty();
919 init_features.set_static_remote_key_optional();
920 let converted_features = ChannelTypeFeatures::from_counterparty_init(&init_features);
921 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
922 assert!(!converted_features.supports_any_optional_bits());
923 assert!(converted_features.requires_static_remote_key());