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
62 use core::hash::{Hash, Hasher};
63 use core::marker::PhantomData;
66 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
67 use ln::msgs::DecodeError;
68 use util::ser::{Readable, Writeable, Writer};
72 use ln::features::Features;
74 /// The context in which [`Features`] are applicable. Defines which features are required and
75 /// which are optional for the context.
77 /// Features that are known to the implementation, where a required feature is indicated by
78 /// its even bit and an optional feature is indicated by its odd bit.
79 const KNOWN_FEATURE_FLAGS: &'static [u8];
81 /// Bitmask for selecting features that are known to the implementation, regardless of
82 /// whether each feature is required or optional.
83 const KNOWN_FEATURE_MASK: &'static [u8];
86 /// Defines a [`Context`] by stating which features it requires and which are optional. Features
87 /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
88 /// feature identifiers.
89 macro_rules! define_context {
91 required_features: [$( $( $required_feature: ident )|*, )*],
92 optional_features: [$( $( $optional_feature: ident )|*, )*],
94 #[derive(Eq, PartialEq)]
95 pub struct $context {}
97 impl Context for $context {
98 const KNOWN_FEATURE_FLAGS: &'static [u8] = &[
99 // For each byte, use bitwise-OR to compute the applicable flags for known
100 // required features `r_i` and optional features `o_j` for all `i` and `j` such
101 // that the following slice is formed:
104 // `r_0` | `r_1` | ... | `o_0` | `o_1` | ...,
109 <Self as $required_feature>::REQUIRED_MASK)*
111 <Self as $optional_feature>::OPTIONAL_MASK)*,
115 const KNOWN_FEATURE_MASK: &'static [u8] = &[
116 // Similar as above, but set both flags for each feature regardless of whether
117 // the feature is required or optional.
120 <Self as $required_feature>::REQUIRED_MASK |
121 <Self as $required_feature>::OPTIONAL_MASK)*
123 <Self as $optional_feature>::REQUIRED_MASK |
124 <Self as $optional_feature>::OPTIONAL_MASK)*,
129 impl alloc::fmt::Display for Features<$context> {
130 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
133 fmt.write_fmt(format_args!("{}: {}, ", stringify!($required_feature),
134 if <$context as $required_feature>::requires_feature(&self.flags) { "required" }
135 else if <$context as $required_feature>::supports_feature(&self.flags) { "supported" }
136 else { "not supported" }))?;
139 fmt.write_fmt(format_args!("{}: {}, ", stringify!($optional_feature),
140 if <$context as $optional_feature>::requires_feature(&self.flags) { "required" }
141 else if <$context as $optional_feature>::supports_feature(&self.flags) { "supported" }
142 else { "not supported" }))?;
145 fmt.write_fmt(format_args!("unknown flags: {}",
146 if self.requires_unknown_bits() { "required" }
147 else if self.supports_unknown_bits() { "supported" } else { "none" }))
153 define_context!(InitContext {
158 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
172 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
182 ChannelType | SCIDPrivacy,
187 define_context!(NodeContext {
192 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
206 DataLossProtect | UpfrontShutdownScript | GossipQueries,
216 ChannelType | SCIDPrivacy,
221 define_context!(ChannelContext {
222 required_features: [],
223 optional_features: [],
225 define_context!(InvoiceContext {
230 VariableLengthOnion | PaymentSecret,
243 // This isn't a "real" feature context, and is only used in the channel_type field in an
244 // `OpenChannel` message.
245 define_context!(ChannelTypeContext {
280 /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
281 /// useful for manipulating feature flags.
282 macro_rules! define_feature {
283 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
284 $required_setter: ident, $supported_getter: ident) => {
287 /// See [BOLT #9] for details.
289 /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
290 pub trait $feature: Context {
291 /// The bit used to signify that the feature is required.
292 const EVEN_BIT: usize = $odd_bit - 1;
294 /// The bit used to signify that the feature is optional.
295 const ODD_BIT: usize = $odd_bit;
297 /// Assertion that [`EVEN_BIT`] is actually even.
299 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
300 const ASSERT_EVEN_BIT_PARITY: usize;
302 /// Assertion that [`ODD_BIT`] is actually odd.
304 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
305 const ASSERT_ODD_BIT_PARITY: usize;
307 /// The byte where the feature is set.
308 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
310 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
312 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
313 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
315 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
317 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
318 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
320 /// Returns whether the feature is required by the given flags.
322 fn requires_feature(flags: &Vec<u8>) -> bool {
323 flags.len() > Self::BYTE_OFFSET &&
324 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
327 /// Returns whether the feature is supported by the given flags.
329 fn supports_feature(flags: &Vec<u8>) -> bool {
330 flags.len() > Self::BYTE_OFFSET &&
331 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
334 /// Sets the feature's required (even) bit in the given flags.
336 fn set_required_bit(flags: &mut Vec<u8>) {
337 if flags.len() <= Self::BYTE_OFFSET {
338 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
341 flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
344 /// Sets the feature's optional (odd) bit in the given flags.
346 fn set_optional_bit(flags: &mut Vec<u8>) {
347 if flags.len() <= Self::BYTE_OFFSET {
348 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
351 flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
354 /// Clears the feature's required (even) and optional (odd) bits from the given
357 fn clear_bits(flags: &mut Vec<u8>) {
358 if flags.len() > Self::BYTE_OFFSET {
359 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
360 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
363 let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
364 let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
365 flags.resize(size, 0u8);
369 impl <T: $feature> Features<T> {
370 /// Set this feature as optional.
371 pub fn $optional_setter(&mut self) {
372 <T as $feature>::set_optional_bit(&mut self.flags);
375 /// Set this feature as required.
376 pub fn $required_setter(&mut self) {
377 <T as $feature>::set_required_bit(&mut self.flags);
380 /// Checks if this feature is supported.
381 pub fn $supported_getter(&self) -> bool {
382 <T as $feature>::supports_feature(&self.flags)
387 impl $feature for $context {
389 const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
392 const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
396 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
397 $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
398 define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
399 impl <T: $feature> Features<T> {
400 /// Checks if this feature is required.
401 pub fn $required_getter(&self) -> bool {
402 <T as $feature>::requires_feature(&self.flags)
408 define_feature!(1, DataLossProtect, [InitContext, NodeContext],
409 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
410 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
411 // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
412 define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
413 set_initial_routing_sync_optional, set_initial_routing_sync_required,
414 initial_routing_sync);
415 define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
416 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
417 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
418 requires_upfront_shutdown_script);
419 define_feature!(7, GossipQueries, [InitContext, NodeContext],
420 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
421 supports_gossip_queries, requires_gossip_queries);
422 define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
423 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
424 set_variable_length_onion_required, supports_variable_length_onion,
425 requires_variable_length_onion);
426 define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
427 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
428 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
429 define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
430 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
431 supports_payment_secret, requires_payment_secret);
432 define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext],
433 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
434 supports_basic_mpp, requires_basic_mpp);
435 define_feature!(19, Wumbo, [InitContext, NodeContext],
436 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
437 supports_wumbo, requires_wumbo);
438 define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
439 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
440 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
441 define_feature!(39, OnionMessages, [InitContext, NodeContext],
442 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
443 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
444 define_feature!(45, ChannelType, [InitContext, NodeContext],
445 "Feature flags for `option_channel_type`.", set_channel_type_optional,
446 set_channel_type_required, supports_channel_type, requires_channel_type);
447 define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
448 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
449 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
450 define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
451 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
452 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
453 define_feature!(55, Keysend, [NodeContext],
454 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
455 supports_keysend, requires_keysend);
458 define_feature!(123456789, UnknownFeature, [NodeContext, ChannelContext, InvoiceContext],
459 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
460 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
463 /// Tracks the set of features which a node implements, templated by the context in which it
466 /// (C-not exported) as we map the concrete feature types below directly instead
468 pub struct Features<T: sealed::Context> {
469 /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
471 mark: PhantomData<T>,
474 impl <T: sealed::Context> Features<T> {
475 pub(crate) fn or(mut self, o: Self) -> Self {
476 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
477 self.flags.resize(total_feature_len, 0u8);
478 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
485 impl<T: sealed::Context> Clone for Features<T> {
486 fn clone(&self) -> Self {
488 flags: self.flags.clone(),
493 impl<T: sealed::Context> Hash for Features<T> {
494 fn hash<H: Hasher>(&self, hasher: &mut H) {
495 self.flags.hash(hasher);
498 impl<T: sealed::Context> PartialEq for Features<T> {
499 fn eq(&self, o: &Self) -> bool {
500 self.flags.eq(&o.flags)
503 impl<T: sealed::Context> fmt::Debug for Features<T> {
504 fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
509 /// Features used within an `init` message.
510 pub type InitFeatures = Features<sealed::InitContext>;
511 /// Features used within a `node_announcement` message.
512 pub type NodeFeatures = Features<sealed::NodeContext>;
513 /// Features used within a `channel_announcement` message.
514 pub type ChannelFeatures = Features<sealed::ChannelContext>;
515 /// Features used within an invoice.
516 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
518 /// Features used within the channel_type field in an OpenChannel message.
520 /// A channel is always of some known "type", describing the transaction formats used and the exact
521 /// semantics of our interaction with our peer.
523 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
524 /// the counterparty, only required features are allowed here.
526 /// This is serialized differently from other feature types - it is not prefixed by a length, and
527 /// thus must only appear inside a TLV where its length is known in advance.
528 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
531 /// Writes all features present up to, and including, 13.
532 pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
533 let len = cmp::min(2, self.flags.len());
534 (len as u16).write(w)?;
535 for i in (0..len).rev() {
537 self.flags[i].write(w)?;
539 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
540 // up-to-and-including-bit-5, 0-indexed, on this byte:
541 (self.flags[i] & 0b00_11_11_11).write(w)?;
547 /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
548 /// are included in the result.
549 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
550 self.to_context_internal()
554 impl InvoiceFeatures {
555 /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
556 /// context `C` are included in the result.
557 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
558 self.to_context_internal()
561 /// Getting a route for a keysend payment to a private node requires providing the payee's
562 /// features (since they were not announced in a node announcement). However, keysend payments
563 /// don't have an invoice to pull the payee's features from, so this method is provided for use in
564 /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
565 /// `InvoiceFeatures` for [`find_route`].
567 /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
568 /// [`find_route`]: crate::routing::router::find_route
569 pub(crate) fn for_keysend() -> InvoiceFeatures {
570 let mut res = InvoiceFeatures::empty();
571 res.set_variable_length_onion_optional();
576 impl ChannelTypeFeatures {
577 /// Constructs the implicit channel type based on the common supported types between us and our
579 pub(crate) fn from_counterparty_init(counterparty_init: &InitFeatures) -> Self {
580 let mut ret = counterparty_init.to_context_internal();
581 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
582 // optional bits and then AND out the optional ones.
583 for byte in ret.flags.iter_mut() {
584 *byte |= (*byte & 0b10_10_10_10) >> 1;
585 *byte &= 0b01_01_01_01;
590 /// Constructs a ChannelTypeFeatures with only static_remotekey set
591 pub(crate) fn only_static_remote_key() -> Self {
592 let mut ret = Self::empty();
593 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
598 impl ToBase32 for InvoiceFeatures {
599 fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
600 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
601 // minus one before dividing
602 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
603 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
604 for (byte_idx, byte) in self.flags.iter().enumerate() {
605 let bit_pos_from_left_0_indexed = byte_idx * 8;
606 let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
607 let new_bit_pos = bit_pos_from_left_0_indexed % 5;
608 let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
609 let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
610 res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
612 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
613 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
616 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
617 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
620 // Trim the highest feature bits.
621 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
624 writer.write(&res_u5s)
628 impl Base32Len for InvoiceFeatures {
629 fn base32_len(&self) -> usize {
630 self.to_base32().len()
634 impl FromBase32 for InvoiceFeatures {
635 type Err = bech32::Error;
637 fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
638 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
639 // minus one before dividing
640 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
641 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
642 for (u5_idx, chunk) in field_data.iter().enumerate() {
643 let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
644 let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
645 let new_bit_pos = bit_pos_from_right_0_indexed % 8;
646 let chunk_u16 = chunk.to_u8() as u16;
647 res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
648 if new_byte_idx != length_bytes - 1 {
649 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
652 // Trim the highest feature bits.
653 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
656 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
660 impl<T: sealed::Context> Features<T> {
661 /// Create a blank Features with no features set
662 pub fn empty() -> Self {
669 /// Creates a Features with the bits set which are known by the implementation
670 pub fn known() -> Self {
672 flags: T::KNOWN_FEATURE_FLAGS.to_vec(),
677 /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
678 /// included in the result.
679 fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
680 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
681 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
682 let mut flags = Vec::new();
683 for (i, byte) in self.flags.iter().enumerate() {
684 if i < from_byte_count && i < to_byte_count {
685 let from_known_features = T::KNOWN_FEATURE_MASK[i];
686 let to_known_features = C::KNOWN_FEATURE_MASK[i];
687 flags.push(byte & from_known_features & to_known_features);
690 Features::<C> { flags, mark: PhantomData, }
693 /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
694 /// most on-the-wire encodings.
695 /// (C-not exported) as we don't support export across multiple T
696 pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
704 /// Gets the underlying flags set, in LE.
705 pub fn le_flags(&self) -> &Vec<u8> {
709 fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
710 for f in self.flags.iter().rev() { // Swap back to big-endian
716 fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
717 flags.reverse(); // Swap to little-endian
724 pub(crate) fn supports_any_optional_bits(&self) -> bool {
725 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
728 /// Returns true if this `Features` object contains unknown feature flags which are set as
730 pub fn requires_unknown_bits(&self) -> bool {
731 // Bitwise AND-ing with all even bits set except for known features will select required
733 let byte_count = T::KNOWN_FEATURE_MASK.len();
734 self.flags.iter().enumerate().any(|(i, &byte)| {
735 let required_features = 0b01_01_01_01;
736 let unknown_features = if i < byte_count {
737 !T::KNOWN_FEATURE_MASK[i]
741 (byte & (required_features & unknown_features)) != 0
745 pub(crate) fn supports_unknown_bits(&self) -> bool {
746 // Bitwise AND-ing with all even and odd bits set except for known features will select
747 // both required and optional unknown features.
748 let byte_count = T::KNOWN_FEATURE_MASK.len();
749 self.flags.iter().enumerate().any(|(i, &byte)| {
750 let unknown_features = if i < byte_count {
751 !T::KNOWN_FEATURE_MASK[i]
755 (byte & unknown_features) != 0
760 impl<T: sealed::UpfrontShutdownScript> Features<T> {
762 pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
763 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
769 impl<T: sealed::GossipQueries> Features<T> {
771 pub(crate) fn clear_gossip_queries(mut self) -> Self {
772 <T as sealed::GossipQueries>::clear_bits(&mut self.flags);
777 impl<T: sealed::InitialRoutingSync> Features<T> {
778 // Note that initial_routing_sync is ignored if gossip_queries is set.
780 pub(crate) fn clear_initial_routing_sync(mut self) -> Self {
781 <T as sealed::InitialRoutingSync>::clear_bits(&mut self.flags);
786 impl<T: sealed::ShutdownAnySegwit> Features<T> {
788 pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
789 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
794 impl<T: sealed::Wumbo> Features<T> {
796 pub(crate) fn clear_wumbo(mut self) -> Self {
797 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
802 macro_rules! impl_feature_len_prefixed_write {
803 ($features: ident) => {
804 impl Writeable for $features {
805 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
806 (self.flags.len() as u16).write(w)?;
810 impl Readable for $features {
811 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
812 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
817 impl_feature_len_prefixed_write!(InitFeatures);
818 impl_feature_len_prefixed_write!(ChannelFeatures);
819 impl_feature_len_prefixed_write!(NodeFeatures);
820 impl_feature_len_prefixed_write!(InvoiceFeatures);
822 // Because ChannelTypeFeatures only appears inside of TLVs, it doesn't have a length prefix when
823 // serialized. Thus, we can't use `impl_feature_len_prefixed_write`, above, and have to write our
824 // own serialization.
825 impl Writeable for ChannelTypeFeatures {
826 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
830 impl Readable for ChannelTypeFeatures {
831 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
832 let v = io_extras::read_to_end(r)?;
833 Ok(Self::from_be_bytes(v))
839 use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures};
840 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
843 fn sanity_test_known_features() {
844 assert!(!ChannelFeatures::known().requires_unknown_bits());
845 assert!(!ChannelFeatures::known().supports_unknown_bits());
846 assert!(!InitFeatures::known().requires_unknown_bits());
847 assert!(!InitFeatures::known().supports_unknown_bits());
848 assert!(!NodeFeatures::known().requires_unknown_bits());
849 assert!(!NodeFeatures::known().supports_unknown_bits());
851 assert!(InitFeatures::known().supports_upfront_shutdown_script());
852 assert!(NodeFeatures::known().supports_upfront_shutdown_script());
853 assert!(!InitFeatures::known().requires_upfront_shutdown_script());
854 assert!(!NodeFeatures::known().requires_upfront_shutdown_script());
856 assert!(InitFeatures::known().supports_gossip_queries());
857 assert!(NodeFeatures::known().supports_gossip_queries());
858 assert!(!InitFeatures::known().requires_gossip_queries());
859 assert!(!NodeFeatures::known().requires_gossip_queries());
861 assert!(InitFeatures::known().supports_data_loss_protect());
862 assert!(NodeFeatures::known().supports_data_loss_protect());
863 assert!(!InitFeatures::known().requires_data_loss_protect());
864 assert!(!NodeFeatures::known().requires_data_loss_protect());
866 assert!(InitFeatures::known().supports_variable_length_onion());
867 assert!(NodeFeatures::known().supports_variable_length_onion());
868 assert!(InvoiceFeatures::known().supports_variable_length_onion());
869 assert!(InitFeatures::known().requires_variable_length_onion());
870 assert!(NodeFeatures::known().requires_variable_length_onion());
871 assert!(InvoiceFeatures::known().requires_variable_length_onion());
873 assert!(InitFeatures::known().supports_static_remote_key());
874 assert!(NodeFeatures::known().supports_static_remote_key());
875 assert!(InitFeatures::known().requires_static_remote_key());
876 assert!(NodeFeatures::known().requires_static_remote_key());
878 assert!(InitFeatures::known().supports_payment_secret());
879 assert!(NodeFeatures::known().supports_payment_secret());
880 assert!(InvoiceFeatures::known().supports_payment_secret());
881 assert!(InitFeatures::known().requires_payment_secret());
882 assert!(NodeFeatures::known().requires_payment_secret());
883 assert!(InvoiceFeatures::known().requires_payment_secret());
885 assert!(InitFeatures::known().supports_basic_mpp());
886 assert!(NodeFeatures::known().supports_basic_mpp());
887 assert!(InvoiceFeatures::known().supports_basic_mpp());
888 assert!(!InitFeatures::known().requires_basic_mpp());
889 assert!(!NodeFeatures::known().requires_basic_mpp());
890 assert!(!InvoiceFeatures::known().requires_basic_mpp());
892 assert!(InitFeatures::known().supports_channel_type());
893 assert!(NodeFeatures::known().supports_channel_type());
894 assert!(!InitFeatures::known().requires_channel_type());
895 assert!(!NodeFeatures::known().requires_channel_type());
897 assert!(InitFeatures::known().supports_shutdown_anysegwit());
898 assert!(NodeFeatures::known().supports_shutdown_anysegwit());
900 assert!(InitFeatures::known().supports_scid_privacy());
901 assert!(NodeFeatures::known().supports_scid_privacy());
902 assert!(ChannelTypeFeatures::known().supports_scid_privacy());
903 assert!(!InitFeatures::known().requires_scid_privacy());
904 assert!(!NodeFeatures::known().requires_scid_privacy());
905 assert!(ChannelTypeFeatures::known().requires_scid_privacy());
907 assert!(InitFeatures::known().supports_wumbo());
908 assert!(NodeFeatures::known().supports_wumbo());
909 assert!(!InitFeatures::known().requires_wumbo());
910 assert!(!NodeFeatures::known().requires_wumbo());
912 assert!(InitFeatures::known().supports_onion_messages());
913 assert!(NodeFeatures::known().supports_onion_messages());
914 assert!(!InitFeatures::known().requires_onion_messages());
915 assert!(!NodeFeatures::known().requires_onion_messages());
917 assert!(InitFeatures::known().supports_zero_conf());
918 assert!(!InitFeatures::known().requires_zero_conf());
919 assert!(NodeFeatures::known().supports_zero_conf());
920 assert!(!NodeFeatures::known().requires_zero_conf());
921 assert!(ChannelTypeFeatures::known().supports_zero_conf());
922 assert!(ChannelTypeFeatures::known().requires_zero_conf());
924 let mut init_features = InitFeatures::known();
925 assert!(init_features.initial_routing_sync());
926 init_features = init_features.clear_initial_routing_sync();
927 assert!(!init_features.initial_routing_sync());
931 fn sanity_test_unknown_bits() {
932 let features = ChannelFeatures::empty();
933 assert!(!features.requires_unknown_bits());
934 assert!(!features.supports_unknown_bits());
936 let mut features = ChannelFeatures::empty();
937 features.set_unknown_feature_required();
938 assert!(features.requires_unknown_bits());
939 assert!(features.supports_unknown_bits());
941 let mut features = ChannelFeatures::empty();
942 features.set_unknown_feature_optional();
943 assert!(!features.requires_unknown_bits());
944 assert!(features.supports_unknown_bits());
948 fn convert_to_context_with_relevant_flags() {
949 let init_features = InitFeatures::known().clear_upfront_shutdown_script().clear_gossip_queries();
950 assert!(init_features.initial_routing_sync());
951 assert!(!init_features.supports_upfront_shutdown_script());
952 assert!(!init_features.supports_gossip_queries());
954 let node_features: NodeFeatures = init_features.to_context();
956 // Check that the flags are as expected:
957 // - option_data_loss_protect
958 // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
959 // - basic_mpp | wumbo
960 // - opt_shutdown_anysegwit
962 // - option_channel_type | option_scid_alias
964 assert_eq!(node_features.flags.len(), 7);
965 assert_eq!(node_features.flags[0], 0b00000010);
966 assert_eq!(node_features.flags[1], 0b01010001);
967 assert_eq!(node_features.flags[2], 0b00001010);
968 assert_eq!(node_features.flags[3], 0b00001000);
969 assert_eq!(node_features.flags[4], 0b10000000);
970 assert_eq!(node_features.flags[5], 0b10100000);
971 assert_eq!(node_features.flags[6], 0b00001000);
974 // Check that cleared flags are kept blank when converting back:
975 // - initial_routing_sync was not applicable to NodeContext
976 // - upfront_shutdown_script was cleared before converting
977 // - gossip_queries was cleared before converting
978 let features: InitFeatures = node_features.to_context_internal();
979 assert!(!features.initial_routing_sync());
980 assert!(!features.supports_upfront_shutdown_script());
981 assert!(!init_features.supports_gossip_queries());
985 fn convert_to_context_with_unknown_flags() {
986 // Ensure the `from` context has fewer known feature bytes than the `to` context.
987 assert!(InvoiceFeatures::known().flags.len() < NodeFeatures::known().flags.len());
988 let mut invoice_features = InvoiceFeatures::known();
989 invoice_features.set_unknown_feature_optional();
990 assert!(invoice_features.supports_unknown_bits());
991 let node_features: NodeFeatures = invoice_features.to_context();
992 assert!(!node_features.supports_unknown_bits());
996 fn set_feature_bits() {
997 let mut features = InvoiceFeatures::empty();
998 features.set_basic_mpp_optional();
999 features.set_payment_secret_required();
1000 assert!(features.supports_basic_mpp());
1001 assert!(!features.requires_basic_mpp());
1002 assert!(features.requires_payment_secret());
1003 assert!(features.supports_payment_secret());
1007 fn invoice_features_encoding() {
1008 let features_as_u5s = vec![
1009 u5::try_from_u8(6).unwrap(),
1010 u5::try_from_u8(10).unwrap(),
1011 u5::try_from_u8(25).unwrap(),
1012 u5::try_from_u8(1).unwrap(),
1013 u5::try_from_u8(10).unwrap(),
1014 u5::try_from_u8(0).unwrap(),
1015 u5::try_from_u8(20).unwrap(),
1016 u5::try_from_u8(2).unwrap(),
1017 u5::try_from_u8(0).unwrap(),
1018 u5::try_from_u8(6).unwrap(),
1019 u5::try_from_u8(0).unwrap(),
1020 u5::try_from_u8(16).unwrap(),
1021 u5::try_from_u8(1).unwrap(),
1023 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1025 // Test length calculation.
1026 assert_eq!(features.base32_len(), 13);
1028 // Test serialization.
1029 let features_serialized = features.to_base32();
1030 assert_eq!(features_as_u5s, features_serialized);
1032 // Test deserialization.
1033 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
1034 assert_eq!(features, features_deserialized);
1038 fn test_channel_type_mapping() {
1039 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
1040 // required-StaticRemoteKey ChannelTypeFeatures.
1041 let mut init_features = InitFeatures::empty();
1042 init_features.set_static_remote_key_optional();
1043 let converted_features = ChannelTypeFeatures::from_counterparty_init(&init_features);
1044 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
1045 assert!(!converted_features.supports_any_optional_bits());
1046 assert!(converted_features.requires_static_remote_key());