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 $()* block here, so add a dummy {}
111 fmt.write_fmt(format_args!("unknown flags: {}",
112 if self.requires_unknown_bits() { "required" }
113 else if self.supports_unknown_bits() { "supported" } else { "none" }))
119 define_context!(InitContext, [
121 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
123 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
131 ChannelType | SCIDPrivacy,
135 define_context!(NodeContext, [
137 DataLossProtect | UpfrontShutdownScript | GossipQueries,
139 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
147 ChannelType | SCIDPrivacy,
151 define_context!(ChannelContext, []);
152 define_context!(InvoiceContext, [
156 VariableLengthOnion | PaymentSecret,
160 define_context!(OfferContext, []);
161 define_context!(InvoiceRequestContext, []);
162 // This isn't a "real" feature context, and is only used in the channel_type field in an
163 // `OpenChannel` message.
164 define_context!(ChannelTypeContext, [
181 /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
182 /// useful for manipulating feature flags.
183 macro_rules! define_feature {
184 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
185 $required_setter: ident, $supported_getter: ident) => {
188 /// See [BOLT #9] for details.
190 /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
191 pub trait $feature: Context {
192 /// The bit used to signify that the feature is required.
193 const EVEN_BIT: usize = $odd_bit - 1;
195 /// The bit used to signify that the feature is optional.
196 const ODD_BIT: usize = $odd_bit;
198 /// Assertion that [`EVEN_BIT`] is actually even.
200 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
201 const ASSERT_EVEN_BIT_PARITY: usize;
203 /// Assertion that [`ODD_BIT`] is actually odd.
205 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
206 const ASSERT_ODD_BIT_PARITY: usize;
208 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
210 /// [`KNOWN_FEATURE_MASK`]: Context::KNOWN_FEATURE_MASK
211 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
212 const ASSERT_BITS_IN_MASK: u8;
214 /// The byte where the feature is set.
215 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
217 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
219 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
220 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
222 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
224 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
225 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
227 /// Returns whether the feature is required by the given flags.
229 fn requires_feature(flags: &Vec<u8>) -> bool {
230 flags.len() > Self::BYTE_OFFSET &&
231 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
234 /// Returns whether the feature is supported by the given flags.
236 fn supports_feature(flags: &Vec<u8>) -> bool {
237 flags.len() > Self::BYTE_OFFSET &&
238 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
241 /// Sets the feature's required (even) bit in the given flags.
243 fn set_required_bit(flags: &mut Vec<u8>) {
244 if flags.len() <= Self::BYTE_OFFSET {
245 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
248 flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
251 /// Sets the feature's optional (odd) bit in the given flags.
253 fn set_optional_bit(flags: &mut Vec<u8>) {
254 if flags.len() <= Self::BYTE_OFFSET {
255 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
258 flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
261 /// Clears the feature's required (even) and optional (odd) bits from the given
264 fn clear_bits(flags: &mut Vec<u8>) {
265 if flags.len() > Self::BYTE_OFFSET {
266 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
267 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
270 let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
271 let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
272 flags.resize(size, 0u8);
276 impl <T: $feature> Features<T> {
277 /// Set this feature as optional.
278 pub fn $optional_setter(&mut self) {
279 <T as $feature>::set_optional_bit(&mut self.flags);
282 /// Set this feature as required.
283 pub fn $required_setter(&mut self) {
284 <T as $feature>::set_required_bit(&mut self.flags);
287 /// Checks if this feature is supported.
288 pub fn $supported_getter(&self) -> bool {
289 <T as $feature>::supports_feature(&self.flags)
294 impl $feature for $context {
296 const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
299 const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
301 // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
302 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
303 const ASSERT_BITS_IN_MASK: u8 =
304 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
305 >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
309 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
310 $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
311 define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
312 impl <T: $feature> Features<T> {
313 /// Checks if this feature is required.
314 pub fn $required_getter(&self) -> bool {
315 <T as $feature>::requires_feature(&self.flags)
321 define_feature!(1, DataLossProtect, [InitContext, NodeContext],
322 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
323 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
324 // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
325 define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
326 set_initial_routing_sync_optional, set_initial_routing_sync_required,
327 initial_routing_sync);
328 define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
329 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
330 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
331 requires_upfront_shutdown_script);
332 define_feature!(7, GossipQueries, [InitContext, NodeContext],
333 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
334 supports_gossip_queries, requires_gossip_queries);
335 define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
336 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
337 set_variable_length_onion_required, supports_variable_length_onion,
338 requires_variable_length_onion);
339 define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
340 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
341 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
342 define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
343 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
344 supports_payment_secret, requires_payment_secret);
345 define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext],
346 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
347 supports_basic_mpp, requires_basic_mpp);
348 define_feature!(19, Wumbo, [InitContext, NodeContext],
349 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
350 supports_wumbo, requires_wumbo);
351 define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
352 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
353 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
354 define_feature!(39, OnionMessages, [InitContext, NodeContext],
355 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
356 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
357 define_feature!(45, ChannelType, [InitContext, NodeContext],
358 "Feature flags for `option_channel_type`.", set_channel_type_optional,
359 set_channel_type_required, supports_channel_type, requires_channel_type);
360 define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
361 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
362 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
363 define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
364 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
365 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
366 define_feature!(55, Keysend, [NodeContext],
367 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
368 supports_keysend, requires_keysend);
371 define_feature!(123456789, UnknownFeature,
372 [NodeContext, ChannelContext, InvoiceContext, OfferContext, InvoiceRequestContext],
373 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
374 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
377 /// Tracks the set of features which a node implements, templated by the context in which it
380 /// (C-not exported) as we map the concrete feature types below directly instead
382 pub struct Features<T: sealed::Context> {
383 /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
385 mark: PhantomData<T>,
388 impl <T: sealed::Context> Features<T> {
389 pub(crate) fn or(mut self, o: Self) -> Self {
390 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
391 self.flags.resize(total_feature_len, 0u8);
392 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
399 impl<T: sealed::Context> Clone for Features<T> {
400 fn clone(&self) -> Self {
402 flags: self.flags.clone(),
407 impl<T: sealed::Context> Hash for Features<T> {
408 fn hash<H: Hasher>(&self, hasher: &mut H) {
409 self.flags.hash(hasher);
412 impl<T: sealed::Context> PartialEq for Features<T> {
413 fn eq(&self, o: &Self) -> bool {
414 self.flags.eq(&o.flags)
417 impl<T: sealed::Context> fmt::Debug for Features<T> {
418 fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
423 /// Features used within an `init` message.
424 pub type InitFeatures = Features<sealed::InitContext>;
425 /// Features used within a `node_announcement` message.
426 pub type NodeFeatures = Features<sealed::NodeContext>;
427 /// Features used within a `channel_announcement` message.
428 pub type ChannelFeatures = Features<sealed::ChannelContext>;
429 /// Features used within an invoice.
430 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
431 /// Features used within an `offer`.
432 pub type OfferFeatures = Features<sealed::OfferContext>;
433 /// Features used within an `invoice_request`.
434 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
436 /// Features used within the channel_type field in an OpenChannel message.
438 /// A channel is always of some known "type", describing the transaction formats used and the exact
439 /// semantics of our interaction with our peer.
441 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
442 /// the counterparty, only required features are allowed here.
444 /// This is serialized differently from other feature types - it is not prefixed by a length, and
445 /// thus must only appear inside a TLV where its length is known in advance.
446 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
449 /// Writes all features present up to, and including, 13.
450 pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
451 let len = cmp::min(2, self.flags.len());
452 (len as u16).write(w)?;
453 for i in (0..len).rev() {
455 self.flags[i].write(w)?;
457 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
458 // up-to-and-including-bit-5, 0-indexed, on this byte:
459 (self.flags[i] & 0b00_11_11_11).write(w)?;
465 /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
466 /// are included in the result.
467 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
468 self.to_context_internal()
472 impl InvoiceFeatures {
473 /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
474 /// context `C` are included in the result.
475 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
476 self.to_context_internal()
479 /// Getting a route for a keysend payment to a private node requires providing the payee's
480 /// features (since they were not announced in a node announcement). However, keysend payments
481 /// don't have an invoice to pull the payee's features from, so this method is provided for use in
482 /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
483 /// `InvoiceFeatures` for [`find_route`].
485 /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
486 /// [`find_route`]: crate::routing::router::find_route
487 pub(crate) fn for_keysend() -> InvoiceFeatures {
488 let mut res = InvoiceFeatures::empty();
489 res.set_variable_length_onion_optional();
494 impl ChannelTypeFeatures {
495 /// Constructs the implicit channel type based on the common supported types between us and our
497 pub(crate) fn from_counterparty_init(counterparty_init: &InitFeatures) -> Self {
498 let mut ret = counterparty_init.to_context_internal();
499 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
500 // optional bits and then AND out the optional ones.
501 for byte in ret.flags.iter_mut() {
502 *byte |= (*byte & 0b10_10_10_10) >> 1;
503 *byte &= 0b01_01_01_01;
508 /// Constructs a ChannelTypeFeatures with only static_remotekey set
509 pub(crate) fn only_static_remote_key() -> Self {
510 let mut ret = Self::empty();
511 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
516 impl ToBase32 for InvoiceFeatures {
517 fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
518 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
519 // minus one before dividing
520 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
521 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
522 for (byte_idx, byte) in self.flags.iter().enumerate() {
523 let bit_pos_from_left_0_indexed = byte_idx * 8;
524 let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
525 let new_bit_pos = bit_pos_from_left_0_indexed % 5;
526 let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
527 let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
528 res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
530 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
531 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
534 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
535 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
538 // Trim the highest feature bits.
539 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
542 writer.write(&res_u5s)
546 impl Base32Len for InvoiceFeatures {
547 fn base32_len(&self) -> usize {
548 self.to_base32().len()
552 impl FromBase32 for InvoiceFeatures {
553 type Err = bech32::Error;
555 fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
556 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
557 // minus one before dividing
558 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
559 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
560 for (u5_idx, chunk) in field_data.iter().enumerate() {
561 let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
562 let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
563 let new_bit_pos = bit_pos_from_right_0_indexed % 8;
564 let chunk_u16 = chunk.to_u8() as u16;
565 res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
566 if new_byte_idx != length_bytes - 1 {
567 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
570 // Trim the highest feature bits.
571 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
574 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
578 impl<T: sealed::Context> Features<T> {
579 /// Create a blank Features with no features set
580 pub fn empty() -> Self {
587 /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
588 /// included in the result.
589 fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
590 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
591 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
592 let mut flags = Vec::new();
593 for (i, byte) in self.flags.iter().enumerate() {
594 if i < from_byte_count && i < to_byte_count {
595 let from_known_features = T::KNOWN_FEATURE_MASK[i];
596 let to_known_features = C::KNOWN_FEATURE_MASK[i];
597 flags.push(byte & from_known_features & to_known_features);
600 Features::<C> { flags, mark: PhantomData, }
603 /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
604 /// most on-the-wire encodings.
605 /// (C-not exported) as we don't support export across multiple T
606 pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
614 /// Gets the underlying flags set, in LE.
615 pub fn le_flags(&self) -> &Vec<u8> {
619 fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
620 for f in self.flags.iter().rev() { // Swap back to big-endian
626 fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
627 flags.reverse(); // Swap to little-endian
634 pub(crate) fn supports_any_optional_bits(&self) -> bool {
635 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
638 /// Returns true if this `Features` object contains unknown feature flags which are set as
640 pub fn requires_unknown_bits(&self) -> bool {
641 // Bitwise AND-ing with all even bits set except for known features will select required
643 let byte_count = T::KNOWN_FEATURE_MASK.len();
644 self.flags.iter().enumerate().any(|(i, &byte)| {
645 let required_features = 0b01_01_01_01;
646 let unknown_features = if i < byte_count {
647 !T::KNOWN_FEATURE_MASK[i]
651 (byte & (required_features & unknown_features)) != 0
655 pub(crate) fn supports_unknown_bits(&self) -> bool {
656 // Bitwise AND-ing with all even and odd bits set except for known features will select
657 // both required and optional unknown features.
658 let byte_count = T::KNOWN_FEATURE_MASK.len();
659 self.flags.iter().enumerate().any(|(i, &byte)| {
660 let unknown_features = if i < byte_count {
661 !T::KNOWN_FEATURE_MASK[i]
665 (byte & unknown_features) != 0
670 impl<T: sealed::UpfrontShutdownScript> Features<T> {
672 pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
673 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
678 impl<T: sealed::ShutdownAnySegwit> Features<T> {
680 pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
681 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
686 impl<T: sealed::Wumbo> Features<T> {
688 pub(crate) fn clear_wumbo(mut self) -> Self {
689 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
695 impl<T: sealed::UnknownFeature> Features<T> {
696 pub(crate) fn unknown() -> Self {
697 let mut features = Self::empty();
698 features.set_unknown_feature_required();
703 macro_rules! impl_feature_len_prefixed_write {
704 ($features: ident) => {
705 impl Writeable for $features {
706 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
707 (self.flags.len() as u16).write(w)?;
711 impl Readable for $features {
712 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
713 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
718 impl_feature_len_prefixed_write!(InitFeatures);
719 impl_feature_len_prefixed_write!(ChannelFeatures);
720 impl_feature_len_prefixed_write!(NodeFeatures);
721 impl_feature_len_prefixed_write!(InvoiceFeatures);
723 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
724 macro_rules! impl_feature_tlv_write {
725 ($features: ident) => {
726 impl Writeable for $features {
727 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
731 impl Readable for $features {
732 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
733 let v = io_extras::read_to_end(r)?;
734 Ok(Self::from_be_bytes(v))
740 impl_feature_tlv_write!(ChannelTypeFeatures);
741 impl_feature_tlv_write!(OfferFeatures);
742 impl_feature_tlv_write!(InvoiceRequestFeatures);
746 use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures, sealed};
747 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
750 fn sanity_test_unknown_bits() {
751 let features = ChannelFeatures::empty();
752 assert!(!features.requires_unknown_bits());
753 assert!(!features.supports_unknown_bits());
755 let mut features = ChannelFeatures::empty();
756 features.set_unknown_feature_required();
757 assert!(features.requires_unknown_bits());
758 assert!(features.supports_unknown_bits());
760 let mut features = ChannelFeatures::empty();
761 features.set_unknown_feature_optional();
762 assert!(!features.requires_unknown_bits());
763 assert!(features.supports_unknown_bits());
767 fn convert_to_context_with_relevant_flags() {
768 let mut init_features = InitFeatures::empty();
769 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
770 // converted as it's only relevant in an init context).
771 init_features.set_initial_routing_sync_required();
772 init_features.set_data_loss_protect_optional();
773 init_features.set_variable_length_onion_required();
774 init_features.set_static_remote_key_required();
775 init_features.set_payment_secret_required();
776 init_features.set_basic_mpp_optional();
777 init_features.set_wumbo_optional();
778 init_features.set_shutdown_any_segwit_optional();
779 init_features.set_onion_messages_optional();
780 init_features.set_channel_type_optional();
781 init_features.set_scid_privacy_optional();
782 init_features.set_zero_conf_optional();
784 assert!(init_features.initial_routing_sync());
785 assert!(!init_features.supports_upfront_shutdown_script());
786 assert!(!init_features.supports_gossip_queries());
788 let node_features: NodeFeatures = init_features.to_context();
790 // Check that the flags are as expected:
791 // - option_data_loss_protect
792 // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
793 // - basic_mpp | wumbo
794 // - opt_shutdown_anysegwit
796 // - option_channel_type | option_scid_alias
798 assert_eq!(node_features.flags.len(), 7);
799 assert_eq!(node_features.flags[0], 0b00000010);
800 assert_eq!(node_features.flags[1], 0b01010001);
801 assert_eq!(node_features.flags[2], 0b00001010);
802 assert_eq!(node_features.flags[3], 0b00001000);
803 assert_eq!(node_features.flags[4], 0b10000000);
804 assert_eq!(node_features.flags[5], 0b10100000);
805 assert_eq!(node_features.flags[6], 0b00001000);
808 // Check that cleared flags are kept blank when converting back:
809 // - initial_routing_sync was not applicable to NodeContext
810 // - upfront_shutdown_script was cleared before converting
811 // - gossip_queries was cleared before converting
812 let features: InitFeatures = node_features.to_context_internal();
813 assert!(!features.initial_routing_sync());
814 assert!(!features.supports_upfront_shutdown_script());
815 assert!(!init_features.supports_gossip_queries());
819 fn convert_to_context_with_unknown_flags() {
820 // Ensure the `from` context has fewer known feature bytes than the `to` context.
821 assert!(<sealed::InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
822 <sealed::NodeContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
823 let mut invoice_features = InvoiceFeatures::empty();
824 invoice_features.set_unknown_feature_optional();
825 assert!(invoice_features.supports_unknown_bits());
826 let node_features: NodeFeatures = invoice_features.to_context();
827 assert!(!node_features.supports_unknown_bits());
831 fn set_feature_bits() {
832 let mut features = InvoiceFeatures::empty();
833 features.set_basic_mpp_optional();
834 features.set_payment_secret_required();
835 assert!(features.supports_basic_mpp());
836 assert!(!features.requires_basic_mpp());
837 assert!(features.requires_payment_secret());
838 assert!(features.supports_payment_secret());
842 fn invoice_features_encoding() {
843 let features_as_u5s = vec![
844 u5::try_from_u8(6).unwrap(),
845 u5::try_from_u8(10).unwrap(),
846 u5::try_from_u8(25).unwrap(),
847 u5::try_from_u8(1).unwrap(),
848 u5::try_from_u8(10).unwrap(),
849 u5::try_from_u8(0).unwrap(),
850 u5::try_from_u8(20).unwrap(),
851 u5::try_from_u8(2).unwrap(),
852 u5::try_from_u8(0).unwrap(),
853 u5::try_from_u8(6).unwrap(),
854 u5::try_from_u8(0).unwrap(),
855 u5::try_from_u8(16).unwrap(),
856 u5::try_from_u8(1).unwrap(),
858 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
860 // Test length calculation.
861 assert_eq!(features.base32_len(), 13);
863 // Test serialization.
864 let features_serialized = features.to_base32();
865 assert_eq!(features_as_u5s, features_serialized);
867 // Test deserialization.
868 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
869 assert_eq!(features, features_deserialized);
873 fn test_channel_type_mapping() {
874 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
875 // required-StaticRemoteKey ChannelTypeFeatures.
876 let mut init_features = InitFeatures::empty();
877 init_features.set_static_remote_key_optional();
878 let converted_features = ChannelTypeFeatures::from_counterparty_init(&init_features);
879 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
880 assert!(!converted_features.supports_any_optional_bits());
881 assert!(converted_features.requires_static_remote_key());