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 //! - `PaymentMetadata` - include additional data in invoices which is passed to recipients in the
55 //! (see [BOLT-11](https://github.com/lightning/bolts/blob/master/11-payment-encoding.md) for
57 //! - `ZeroConf` - supports accepting HTLCs and using channels prior to funding confirmation
59 //! [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#the-channel_ready-message)
61 //! - `Keysend` - send funds to a node without an invoice
62 //! (see the [`Keysend` feature assignment proposal](https://github.com/lightning/bolts/issues/605#issuecomment-606679798) for more information).
63 //! - `AnchorsZeroFeeHtlcTx` - requires/supports that commitment transactions include anchor outputs
64 //! and HTLC transactions are pre-signed with zero fee (see
65 //! [BOLT-3](https://github.com/lightning/bolts/blob/master/03-transactions.md) for more
68 //! [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
69 //! [messages]: crate::ln::msgs
71 use crate::{io, io_extras};
72 use crate::prelude::*;
74 use core::hash::{Hash, Hasher};
75 use core::marker::PhantomData;
78 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
79 use crate::ln::msgs::DecodeError;
80 use crate::util::ser::{Readable, WithoutLength, Writeable, Writer};
83 use crate::prelude::*;
84 use crate::ln::features::Features;
86 /// The context in which [`Features`] are applicable. Defines which features are known to the
87 /// implementation, though specification of them as required or optional is up to the code
88 /// constructing a features object.
90 /// Bitmask for selecting features that are known to the implementation.
91 const KNOWN_FEATURE_MASK: &'static [u8];
94 /// Defines a [`Context`] by stating which features it requires and which are optional. Features
95 /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
96 /// feature identifiers.
97 macro_rules! define_context {
98 ($context: ident, [$( $( $known_feature: ident )|*, )*]) => {
99 #[derive(Eq, PartialEq)]
100 pub struct $context {}
102 impl Context for $context {
103 const KNOWN_FEATURE_MASK: &'static [u8] = &[
106 <Self as $known_feature>::REQUIRED_MASK |
107 <Self as $known_feature>::OPTIONAL_MASK)*,
112 impl alloc::fmt::Display for Features<$context> {
113 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
116 fmt.write_fmt(format_args!("{}: {}, ", stringify!($known_feature),
117 if <$context as $known_feature>::requires_feature(&self.flags) { "required" }
118 else if <$context as $known_feature>::supports_feature(&self.flags) { "supported" }
119 else { "not supported" }))?;
121 {} // Rust gets mad if we only have a $()* block here, so add a dummy {}
123 fmt.write_fmt(format_args!("unknown flags: {}",
124 if self.requires_unknown_bits() { "required" }
125 else if self.supports_unknown_bits() { "supported" } else { "none" }))
131 define_context!(InitContext, [
133 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
135 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
137 BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
143 ChannelType | SCIDPrivacy,
147 define_context!(NodeContext, [
149 DataLossProtect | UpfrontShutdownScript | GossipQueries,
151 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
153 BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
159 ChannelType | SCIDPrivacy,
163 define_context!(ChannelContext, []);
164 define_context!(InvoiceContext, [
168 VariableLengthOnion | PaymentSecret,
180 define_context!(OfferContext, []);
181 define_context!(InvoiceRequestContext, []);
182 define_context!(Bolt12InvoiceContext, [
190 define_context!(BlindedHopContext, []);
191 // This isn't a "real" feature context, and is only used in the channel_type field in an
192 // `OpenChannel` message.
193 define_context!(ChannelTypeContext, [
199 AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
210 /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
211 /// useful for manipulating feature flags.
212 macro_rules! define_feature {
213 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
214 $required_setter: ident, $supported_getter: ident) => {
217 /// See [BOLT #9] for details.
219 /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
220 pub trait $feature: Context {
221 /// The bit used to signify that the feature is required.
222 const EVEN_BIT: usize = $odd_bit - 1;
224 /// The bit used to signify that the feature is optional.
225 const ODD_BIT: usize = $odd_bit;
227 /// Assertion that [`EVEN_BIT`] is actually even.
229 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
230 const ASSERT_EVEN_BIT_PARITY: usize;
232 /// Assertion that [`ODD_BIT`] is actually odd.
234 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
235 const ASSERT_ODD_BIT_PARITY: usize;
237 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
239 /// [`KNOWN_FEATURE_MASK`]: Context::KNOWN_FEATURE_MASK
240 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
241 const ASSERT_BITS_IN_MASK: u8;
243 /// The byte where the feature is set.
244 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
246 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
248 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
249 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
251 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
253 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
254 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
256 /// Returns whether the feature is required by the given flags.
258 fn requires_feature(flags: &Vec<u8>) -> bool {
259 flags.len() > Self::BYTE_OFFSET &&
260 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
263 /// Returns whether the feature is supported by the given flags.
265 fn supports_feature(flags: &Vec<u8>) -> bool {
266 flags.len() > Self::BYTE_OFFSET &&
267 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
270 /// Sets the feature's required (even) bit in the given flags.
272 fn set_required_bit(flags: &mut Vec<u8>) {
273 if flags.len() <= Self::BYTE_OFFSET {
274 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
277 flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
278 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
281 /// Sets the feature's optional (odd) bit in the given flags.
283 fn set_optional_bit(flags: &mut Vec<u8>) {
284 if flags.len() <= Self::BYTE_OFFSET {
285 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
288 flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
291 /// Clears the feature's required (even) and optional (odd) bits from the given
294 fn clear_bits(flags: &mut Vec<u8>) {
295 if flags.len() > Self::BYTE_OFFSET {
296 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
297 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
300 let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
301 let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
302 flags.resize(size, 0u8);
306 impl <T: $feature> Features<T> {
307 /// Set this feature as optional.
308 pub fn $optional_setter(&mut self) {
309 <T as $feature>::set_optional_bit(&mut self.flags);
312 /// Set this feature as required.
313 pub fn $required_setter(&mut self) {
314 <T as $feature>::set_required_bit(&mut self.flags);
317 /// Checks if this feature is supported.
318 pub fn $supported_getter(&self) -> bool {
319 <T as $feature>::supports_feature(&self.flags)
324 impl $feature for $context {
326 const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
329 const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
331 // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
332 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
333 const ASSERT_BITS_IN_MASK: u8 =
334 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
335 >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
339 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
340 $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
341 define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
342 impl <T: $feature> Features<T> {
343 /// Checks if this feature is required.
344 pub fn $required_getter(&self) -> bool {
345 <T as $feature>::requires_feature(&self.flags)
351 define_feature!(1, DataLossProtect, [InitContext, NodeContext],
352 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
353 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
354 // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
355 define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
356 set_initial_routing_sync_optional, set_initial_routing_sync_required,
357 initial_routing_sync);
358 define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
359 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
360 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
361 requires_upfront_shutdown_script);
362 define_feature!(7, GossipQueries, [InitContext, NodeContext],
363 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
364 supports_gossip_queries, requires_gossip_queries);
365 define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
366 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
367 set_variable_length_onion_required, supports_variable_length_onion,
368 requires_variable_length_onion);
369 define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
370 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
371 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
372 define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
373 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
374 supports_payment_secret, requires_payment_secret);
375 define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext, Bolt12InvoiceContext],
376 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
377 supports_basic_mpp, requires_basic_mpp);
378 define_feature!(19, Wumbo, [InitContext, NodeContext],
379 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
380 supports_wumbo, requires_wumbo);
381 define_feature!(21, AnchorsNonzeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
382 "Feature flags for `option_anchors_nonzero_fee_htlc_tx`.", set_anchors_nonzero_fee_htlc_tx_optional,
383 set_anchors_nonzero_fee_htlc_tx_required, supports_anchors_nonzero_fee_htlc_tx, requires_anchors_nonzero_fee_htlc_tx);
384 define_feature!(23, AnchorsZeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
385 "Feature flags for `option_anchors_zero_fee_htlc_tx`.", set_anchors_zero_fee_htlc_tx_optional,
386 set_anchors_zero_fee_htlc_tx_required, supports_anchors_zero_fee_htlc_tx, requires_anchors_zero_fee_htlc_tx);
387 define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
388 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
389 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
390 define_feature!(39, OnionMessages, [InitContext, NodeContext],
391 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
392 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
393 define_feature!(45, ChannelType, [InitContext, NodeContext],
394 "Feature flags for `option_channel_type`.", set_channel_type_optional,
395 set_channel_type_required, supports_channel_type, requires_channel_type);
396 define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
397 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
398 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
399 define_feature!(49, PaymentMetadata, [InvoiceContext],
400 "Feature flags for payment metadata in invoices.", set_payment_metadata_optional,
401 set_payment_metadata_required, supports_payment_metadata, requires_payment_metadata);
402 define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
403 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
404 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
405 define_feature!(55, Keysend, [NodeContext],
406 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
407 supports_keysend, requires_keysend);
408 // Note: update the module-level docs when a new feature bit is added!
411 define_feature!(123456789, UnknownFeature,
412 [NodeContext, ChannelContext, InvoiceContext, OfferContext, InvoiceRequestContext, Bolt12InvoiceContext, BlindedHopContext],
413 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
414 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
417 /// Tracks the set of features which a node implements, templated by the context in which it
420 /// This is not exported to bindings users as we map the concrete feature types below directly instead
422 pub struct Features<T: sealed::Context> {
423 /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
425 mark: PhantomData<T>,
428 impl<T: sealed::Context> core::ops::BitOr for Features<T> {
431 fn bitor(mut self, o: Self) -> Self {
432 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
433 self.flags.resize(total_feature_len, 0u8);
434 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
441 impl<T: sealed::Context> Clone for Features<T> {
442 fn clone(&self) -> Self {
444 flags: self.flags.clone(),
449 impl<T: sealed::Context> Hash for Features<T> {
450 fn hash<H: Hasher>(&self, hasher: &mut H) {
451 self.flags.hash(hasher);
454 impl<T: sealed::Context> PartialEq for Features<T> {
455 fn eq(&self, o: &Self) -> bool {
456 self.flags.eq(&o.flags)
459 impl<T: sealed::Context> PartialOrd for Features<T> {
460 fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
461 self.flags.partial_cmp(&other.flags)
464 impl<T: sealed::Context + Eq> Ord for Features<T> {
465 fn cmp(&self, other: &Self) -> cmp::Ordering {
466 self.flags.cmp(&other.flags)
469 impl<T: sealed::Context> fmt::Debug for Features<T> {
470 fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
475 /// Features used within an `init` message.
476 pub type InitFeatures = Features<sealed::InitContext>;
477 /// Features used within a `node_announcement` message.
478 pub type NodeFeatures = Features<sealed::NodeContext>;
479 /// Features used within a `channel_announcement` message.
480 pub type ChannelFeatures = Features<sealed::ChannelContext>;
481 /// Features used within an invoice.
482 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
483 /// Features used within an `offer`.
484 pub type OfferFeatures = Features<sealed::OfferContext>;
485 /// Features used within an `invoice_request`.
486 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
487 /// Features used within an `invoice`.
488 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
489 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
490 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
492 /// Features used within the channel_type field in an OpenChannel message.
494 /// A channel is always of some known "type", describing the transaction formats used and the exact
495 /// semantics of our interaction with our peer.
497 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
498 /// the counterparty, only required features are allowed here.
500 /// This is serialized differently from other feature types - it is not prefixed by a length, and
501 /// thus must only appear inside a TLV where its length is known in advance.
502 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
505 /// Writes all features present up to, and including, 13.
506 pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
507 let len = cmp::min(2, self.flags.len());
508 (len as u16).write(w)?;
509 for i in (0..len).rev() {
511 self.flags[i].write(w)?;
513 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
514 // up-to-and-including-bit-5, 0-indexed, on this byte:
515 (self.flags[i] & 0b00_11_11_11).write(w)?;
521 /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
522 /// are included in the result.
523 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
524 self.to_context_internal()
528 impl InvoiceFeatures {
529 /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
530 /// context `C` are included in the result.
531 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
532 self.to_context_internal()
535 /// Getting a route for a keysend payment to a private node requires providing the payee's
536 /// features (since they were not announced in a node announcement). However, keysend payments
537 /// don't have an invoice to pull the payee's features from, so this method is provided for use in
538 /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
539 /// `InvoiceFeatures` for [`find_route`].
541 /// MPP keysend is not widely supported yet, so we parameterize support to allow the user to
542 /// choose whether their router should find multi-part routes.
544 /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
545 /// [`find_route`]: crate::routing::router::find_route
546 pub(crate) fn for_keysend(allow_mpp: bool) -> InvoiceFeatures {
547 let mut res = InvoiceFeatures::empty();
548 res.set_variable_length_onion_optional();
550 res.set_basic_mpp_optional();
556 impl Bolt12InvoiceFeatures {
557 /// Converts `Bolt12InvoiceFeatures` to `Features<C>`. Only known `Bolt12InvoiceFeatures` relevant
558 /// to context `C` are included in the result.
559 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
560 self.to_context_internal()
564 impl ChannelTypeFeatures {
565 // Maps the relevant `InitFeatures` to `ChannelTypeFeatures`. Any unknown features to
566 // `ChannelTypeFeatures` are not included in the result.
567 pub(crate) fn from_init(init: &InitFeatures) -> Self {
568 let mut ret = init.to_context_internal();
569 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
570 // optional bits and then AND out the optional ones.
571 for byte in ret.flags.iter_mut() {
572 *byte |= (*byte & 0b10_10_10_10) >> 1;
573 *byte &= 0b01_01_01_01;
578 /// Constructs a ChannelTypeFeatures with only static_remotekey set
579 pub(crate) fn only_static_remote_key() -> Self {
580 let mut ret = Self::empty();
581 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
586 impl ToBase32 for InvoiceFeatures {
587 fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
588 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
589 // minus one before dividing
590 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
591 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
592 for (byte_idx, byte) in self.flags.iter().enumerate() {
593 let bit_pos_from_left_0_indexed = byte_idx * 8;
594 let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
595 let new_bit_pos = bit_pos_from_left_0_indexed % 5;
596 let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
597 let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
598 res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
600 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
601 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
604 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
605 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
608 // Trim the highest feature bits.
609 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
612 writer.write(&res_u5s)
616 impl Base32Len for InvoiceFeatures {
617 fn base32_len(&self) -> usize {
618 self.to_base32().len()
622 impl FromBase32 for InvoiceFeatures {
623 type Err = bech32::Error;
625 fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
626 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
627 // minus one before dividing
628 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
629 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
630 for (u5_idx, chunk) in field_data.iter().enumerate() {
631 let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
632 let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
633 let new_bit_pos = bit_pos_from_right_0_indexed % 8;
634 let chunk_u16 = chunk.to_u8() as u16;
635 res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
636 if new_byte_idx != length_bytes - 1 {
637 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
640 // Trim the highest feature bits.
641 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
644 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
648 impl<T: sealed::Context> Features<T> {
649 /// Create a blank Features with no features set
650 pub fn empty() -> Self {
657 /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
658 /// included in the result.
659 fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
660 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
661 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
662 let mut flags = Vec::new();
663 for (i, byte) in self.flags.iter().enumerate() {
664 if i < from_byte_count && i < to_byte_count {
665 let from_known_features = T::KNOWN_FEATURE_MASK[i];
666 let to_known_features = C::KNOWN_FEATURE_MASK[i];
667 flags.push(byte & from_known_features & to_known_features);
670 Features::<C> { flags, mark: PhantomData, }
673 /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
674 /// most on-the-wire encodings.
676 /// This is not exported to bindings users as we don't support export across multiple T
677 pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
685 /// Gets the underlying flags set, in LE.
686 pub fn le_flags(&self) -> &Vec<u8> {
690 fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
691 for f in self.flags.iter().rev() { // Swap back to big-endian
697 fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
698 flags.reverse(); // Swap to little-endian
705 pub(crate) fn supports_any_optional_bits(&self) -> bool {
706 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
709 /// Returns true if this `Features` object contains required features unknown by `other`.
710 pub fn requires_unknown_bits_from(&self, other: &Features<T>) -> bool {
711 // Bitwise AND-ing with all even bits set except for known features will select required
713 self.flags.iter().enumerate().any(|(i, &byte)| {
714 const REQUIRED_FEATURES: u8 = 0b01_01_01_01;
715 const OPTIONAL_FEATURES: u8 = 0b10_10_10_10;
716 let unknown_features = if i < other.flags.len() {
717 // Form a mask similar to !T::KNOWN_FEATURE_MASK only for `other`
719 | ((other.flags[i] >> 1) & REQUIRED_FEATURES)
720 | ((other.flags[i] << 1) & OPTIONAL_FEATURES))
724 (byte & (REQUIRED_FEATURES & unknown_features)) != 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
759 // Returns true if the features within `self` are a subset of the features within `other`.
760 pub(crate) fn is_subset(&self, other: &Self) -> bool {
761 for (idx, byte) in self.flags.iter().enumerate() {
762 if let Some(other_byte) = other.flags.get(idx) {
763 if byte & other_byte != *byte {
764 // `self` has bits set that `other` doesn't.
769 // `self` has a non-zero byte that `other` doesn't.
777 /// Sets a required custom feature bit. Errors if `bit` is outside the custom range as defined
778 /// by [bLIP 2] or if it is a known `T` feature.
780 /// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
781 /// be set instead (i.e., `bit - 1`).
783 /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
784 pub fn set_required_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
785 self.set_custom_bit(bit - (bit % 2))
788 /// Sets an optional custom feature bit. Errors if `bit` is outside the custom range as defined
789 /// by [bLIP 2] or if it is a known `T` feature.
791 /// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
792 /// set instead (i.e., `bit + 1`).
794 /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
795 pub fn set_optional_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
796 self.set_custom_bit(bit + (1 - (bit % 2)))
799 fn set_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
804 let byte_offset = bit / 8;
805 let mask = 1 << (bit - 8 * byte_offset);
806 if byte_offset < T::KNOWN_FEATURE_MASK.len() {
807 if (T::KNOWN_FEATURE_MASK[byte_offset] & mask) != 0 {
812 if self.flags.len() <= byte_offset {
813 self.flags.resize(byte_offset + 1, 0u8);
816 self.flags[byte_offset] |= mask;
822 impl<T: sealed::UpfrontShutdownScript> Features<T> {
824 pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
825 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
830 impl<T: sealed::ShutdownAnySegwit> Features<T> {
832 pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
833 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
838 impl<T: sealed::Wumbo> Features<T> {
840 pub(crate) fn clear_wumbo(mut self) -> Self {
841 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
846 impl<T: sealed::SCIDPrivacy> Features<T> {
847 pub(crate) fn clear_scid_privacy(&mut self) {
848 <T as sealed::SCIDPrivacy>::clear_bits(&mut self.flags);
852 impl<T: sealed::AnchorsZeroFeeHtlcTx> Features<T> {
853 pub(crate) fn clear_anchors_zero_fee_htlc_tx(&mut self) {
854 <T as sealed::AnchorsZeroFeeHtlcTx>::clear_bits(&mut self.flags);
859 impl<T: sealed::UnknownFeature> Features<T> {
860 pub(crate) fn unknown() -> Self {
861 let mut features = Self::empty();
862 features.set_unknown_feature_required();
867 macro_rules! impl_feature_len_prefixed_write {
868 ($features: ident) => {
869 impl Writeable for $features {
870 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
871 (self.flags.len() as u16).write(w)?;
875 impl Readable for $features {
876 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
877 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
882 impl_feature_len_prefixed_write!(InitFeatures);
883 impl_feature_len_prefixed_write!(ChannelFeatures);
884 impl_feature_len_prefixed_write!(NodeFeatures);
885 impl_feature_len_prefixed_write!(InvoiceFeatures);
886 impl_feature_len_prefixed_write!(Bolt12InvoiceFeatures);
887 impl_feature_len_prefixed_write!(BlindedHopFeatures);
889 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
890 macro_rules! impl_feature_tlv_write {
891 ($features: ident) => {
892 impl Writeable for $features {
893 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
894 WithoutLength(self).write(w)
897 impl Readable for $features {
898 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
899 Ok(WithoutLength::<Self>::read(r)?.0)
905 impl_feature_tlv_write!(ChannelTypeFeatures);
907 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
908 // requires a length but the former does not.
910 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
911 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
916 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
917 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
918 let v = io_extras::read_to_end(r)?;
919 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
925 use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
926 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
927 use crate::util::ser::{Readable, WithoutLength, Writeable};
930 fn sanity_test_unknown_bits() {
931 let features = ChannelFeatures::empty();
932 assert!(!features.requires_unknown_bits());
933 assert!(!features.supports_unknown_bits());
935 let mut features = ChannelFeatures::empty();
936 features.set_unknown_feature_required();
937 assert!(features.requires_unknown_bits());
938 assert!(features.supports_unknown_bits());
940 let mut features = ChannelFeatures::empty();
941 features.set_unknown_feature_optional();
942 assert!(!features.requires_unknown_bits());
943 assert!(features.supports_unknown_bits());
947 fn requires_unknown_bits_from() {
948 let mut features1 = InitFeatures::empty();
949 let mut features2 = InitFeatures::empty();
950 assert!(!features1.requires_unknown_bits_from(&features2));
951 assert!(!features2.requires_unknown_bits_from(&features1));
953 features1.set_data_loss_protect_required();
954 assert!(features1.requires_unknown_bits_from(&features2));
955 assert!(!features2.requires_unknown_bits_from(&features1));
957 features2.set_data_loss_protect_optional();
958 assert!(!features1.requires_unknown_bits_from(&features2));
959 assert!(!features2.requires_unknown_bits_from(&features1));
961 features2.set_gossip_queries_required();
962 assert!(!features1.requires_unknown_bits_from(&features2));
963 assert!(features2.requires_unknown_bits_from(&features1));
965 features1.set_gossip_queries_optional();
966 assert!(!features1.requires_unknown_bits_from(&features2));
967 assert!(!features2.requires_unknown_bits_from(&features1));
969 features1.set_variable_length_onion_required();
970 assert!(features1.requires_unknown_bits_from(&features2));
971 assert!(!features2.requires_unknown_bits_from(&features1));
973 features2.set_variable_length_onion_optional();
974 assert!(!features1.requires_unknown_bits_from(&features2));
975 assert!(!features2.requires_unknown_bits_from(&features1));
977 features1.set_basic_mpp_required();
978 features2.set_wumbo_required();
979 assert!(features1.requires_unknown_bits_from(&features2));
980 assert!(features2.requires_unknown_bits_from(&features1));
984 fn convert_to_context_with_relevant_flags() {
985 let mut init_features = InitFeatures::empty();
986 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
987 // converted as it's only relevant in an init context).
988 init_features.set_initial_routing_sync_required();
989 init_features.set_data_loss_protect_required();
990 init_features.set_variable_length_onion_required();
991 init_features.set_static_remote_key_required();
992 init_features.set_payment_secret_required();
993 init_features.set_basic_mpp_optional();
994 init_features.set_wumbo_optional();
995 init_features.set_anchors_zero_fee_htlc_tx_optional();
996 init_features.set_shutdown_any_segwit_optional();
997 init_features.set_onion_messages_optional();
998 init_features.set_channel_type_optional();
999 init_features.set_scid_privacy_optional();
1000 init_features.set_zero_conf_optional();
1002 assert!(init_features.initial_routing_sync());
1003 assert!(!init_features.supports_upfront_shutdown_script());
1004 assert!(!init_features.supports_gossip_queries());
1006 let node_features: NodeFeatures = init_features.to_context();
1008 // Check that the flags are as expected:
1009 // - option_data_loss_protect (req)
1010 // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
1011 // - basic_mpp | wumbo | anchors_zero_fee_htlc_tx
1012 // - opt_shutdown_anysegwit
1014 // - option_channel_type | option_scid_alias
1015 // - option_zeroconf
1016 assert_eq!(node_features.flags.len(), 7);
1017 assert_eq!(node_features.flags[0], 0b00000001);
1018 assert_eq!(node_features.flags[1], 0b01010001);
1019 assert_eq!(node_features.flags[2], 0b10001010);
1020 assert_eq!(node_features.flags[3], 0b00001000);
1021 assert_eq!(node_features.flags[4], 0b10000000);
1022 assert_eq!(node_features.flags[5], 0b10100000);
1023 assert_eq!(node_features.flags[6], 0b00001000);
1026 // Check that cleared flags are kept blank when converting back:
1027 // - initial_routing_sync was not applicable to NodeContext
1028 // - upfront_shutdown_script was cleared before converting
1029 // - gossip_queries was cleared before converting
1030 let features: InitFeatures = node_features.to_context_internal();
1031 assert!(!features.initial_routing_sync());
1032 assert!(!features.supports_upfront_shutdown_script());
1033 assert!(!init_features.supports_gossip_queries());
1037 fn convert_to_context_with_unknown_flags() {
1038 // Ensure the `from` context has fewer known feature bytes than the `to` context.
1039 assert!(<sealed::ChannelContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
1040 <sealed::InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
1041 let mut channel_features = ChannelFeatures::empty();
1042 channel_features.set_unknown_feature_optional();
1043 assert!(channel_features.supports_unknown_bits());
1044 let invoice_features: InvoiceFeatures = channel_features.to_context_internal();
1045 assert!(!invoice_features.supports_unknown_bits());
1049 fn set_feature_bits() {
1050 let mut features = InvoiceFeatures::empty();
1051 features.set_basic_mpp_optional();
1052 features.set_payment_secret_required();
1053 assert!(features.supports_basic_mpp());
1054 assert!(!features.requires_basic_mpp());
1055 assert!(features.requires_payment_secret());
1056 assert!(features.supports_payment_secret());
1060 fn set_custom_bits() {
1061 let mut features = InvoiceFeatures::empty();
1062 features.set_variable_length_onion_optional();
1063 assert_eq!(features.flags[1], 0b00000010);
1065 assert!(features.set_optional_custom_bit(255).is_err());
1066 assert!(features.set_required_custom_bit(256).is_ok());
1067 assert!(features.set_required_custom_bit(258).is_ok());
1068 assert_eq!(features.flags[31], 0b00000000);
1069 assert_eq!(features.flags[32], 0b00000101);
1071 let known_bit = <sealed::InvoiceContext as sealed::PaymentSecret>::EVEN_BIT;
1072 let byte_offset = <sealed::InvoiceContext as sealed::PaymentSecret>::BYTE_OFFSET;
1073 assert_eq!(byte_offset, 1);
1074 assert_eq!(features.flags[byte_offset], 0b00000010);
1075 assert!(features.set_required_custom_bit(known_bit).is_err());
1076 assert_eq!(features.flags[byte_offset], 0b00000010);
1078 let mut features = InvoiceFeatures::empty();
1079 assert!(features.set_optional_custom_bit(256).is_ok());
1080 assert!(features.set_optional_custom_bit(259).is_ok());
1081 assert_eq!(features.flags[32], 0b00001010);
1083 let mut features = InvoiceFeatures::empty();
1084 assert!(features.set_required_custom_bit(257).is_ok());
1085 assert!(features.set_required_custom_bit(258).is_ok());
1086 assert_eq!(features.flags[32], 0b00000101);
1090 fn encodes_features_without_length() {
1091 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1092 assert_eq!(features.flags.len(), 8);
1094 let mut serialized_features = Vec::new();
1095 WithoutLength(&features).write(&mut serialized_features).unwrap();
1096 assert_eq!(serialized_features.len(), 8);
1098 let deserialized_features =
1099 WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
1100 assert_eq!(features, deserialized_features);
1104 fn invoice_features_encoding() {
1105 let features_as_u5s = vec![
1106 u5::try_from_u8(6).unwrap(),
1107 u5::try_from_u8(10).unwrap(),
1108 u5::try_from_u8(25).unwrap(),
1109 u5::try_from_u8(1).unwrap(),
1110 u5::try_from_u8(10).unwrap(),
1111 u5::try_from_u8(0).unwrap(),
1112 u5::try_from_u8(20).unwrap(),
1113 u5::try_from_u8(2).unwrap(),
1114 u5::try_from_u8(0).unwrap(),
1115 u5::try_from_u8(6).unwrap(),
1116 u5::try_from_u8(0).unwrap(),
1117 u5::try_from_u8(16).unwrap(),
1118 u5::try_from_u8(1).unwrap(),
1120 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1122 // Test length calculation.
1123 assert_eq!(features.base32_len(), 13);
1125 // Test serialization.
1126 let features_serialized = features.to_base32();
1127 assert_eq!(features_as_u5s, features_serialized);
1129 // Test deserialization.
1130 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
1131 assert_eq!(features, features_deserialized);
1135 fn test_channel_type_mapping() {
1136 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
1137 // required-StaticRemoteKey ChannelTypeFeatures.
1138 let mut init_features = InitFeatures::empty();
1139 init_features.set_static_remote_key_optional();
1140 let converted_features = ChannelTypeFeatures::from_init(&init_features);
1141 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
1142 assert!(!converted_features.supports_any_optional_bits());
1143 assert!(converted_features.requires_static_remote_key());