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 //! LDK knows about the following features, but does not support them:
69 //! - `AnchorsNonzeroFeeHtlcTx` - the initial version of anchor outputs, which was later found to be
70 //! vulnerable (see this
71 //! [mailing list post](https://lists.linuxfoundation.org/pipermail/lightning-dev/2020-September/002796.html)
72 //! for more information).
74 //! [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
75 //! [messages]: crate::ln::msgs
77 use crate::{io, io_extras};
78 use crate::prelude::*;
80 use core::hash::{Hash, Hasher};
81 use core::marker::PhantomData;
84 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
85 use crate::ln::msgs::DecodeError;
86 use crate::util::ser::{Readable, WithoutLength, Writeable, Writer};
89 use crate::prelude::*;
90 use crate::ln::features::Features;
92 /// The context in which [`Features`] are applicable. Defines which features are known to the
93 /// implementation, though specification of them as required or optional is up to the code
94 /// constructing a features object.
96 /// Bitmask for selecting features that are known to the implementation.
97 const KNOWN_FEATURE_MASK: &'static [u8];
100 /// Defines a [`Context`] by stating which features it requires and which are optional. Features
101 /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
102 /// feature identifiers.
103 macro_rules! define_context {
104 ($context: ident, [$( $( $known_feature: ident )|*, )*]) => {
105 #[derive(Eq, PartialEq)]
106 pub struct $context {}
108 impl Context for $context {
109 const KNOWN_FEATURE_MASK: &'static [u8] = &[
112 <Self as $known_feature>::REQUIRED_MASK |
113 <Self as $known_feature>::OPTIONAL_MASK)*,
118 impl alloc::fmt::Display for Features<$context> {
119 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
122 fmt.write_fmt(format_args!("{}: {}, ", stringify!($known_feature),
123 if <$context as $known_feature>::requires_feature(&self.flags) { "required" }
124 else if <$context as $known_feature>::supports_feature(&self.flags) { "supported" }
125 else { "not supported" }))?;
127 {} // Rust gets mad if we only have a $()* block here, so add a dummy {}
129 fmt.write_fmt(format_args!("unknown flags: {}",
130 if self.requires_unknown_bits() { "required" }
131 else if self.supports_unknown_bits() { "supported" } else { "none" }))
137 define_context!(InitContext, [
139 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
141 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
143 BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
149 ChannelType | SCIDPrivacy,
153 define_context!(NodeContext, [
155 DataLossProtect | UpfrontShutdownScript | GossipQueries,
157 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
159 BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
165 ChannelType | SCIDPrivacy,
169 define_context!(ChannelContext, []);
170 define_context!(InvoiceContext, [
174 VariableLengthOnion | PaymentSecret,
186 define_context!(OfferContext, []);
187 define_context!(InvoiceRequestContext, []);
188 define_context!(Bolt12InvoiceContext, [
196 define_context!(BlindedHopContext, []);
197 // This isn't a "real" feature context, and is only used in the channel_type field in an
198 // `OpenChannel` message.
199 define_context!(ChannelTypeContext, [
205 AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
216 /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
217 /// useful for manipulating feature flags.
218 macro_rules! define_feature {
219 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
220 $required_setter: ident, $supported_getter: ident) => {
223 /// See [BOLT #9] for details.
225 /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
226 pub trait $feature: Context {
227 /// The bit used to signify that the feature is required.
228 const EVEN_BIT: usize = $odd_bit - 1;
230 /// The bit used to signify that the feature is optional.
231 const ODD_BIT: usize = $odd_bit;
233 /// Assertion that [`EVEN_BIT`] is actually even.
235 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
236 const ASSERT_EVEN_BIT_PARITY: usize;
238 /// Assertion that [`ODD_BIT`] is actually odd.
240 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
241 const ASSERT_ODD_BIT_PARITY: usize;
243 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
245 /// [`KNOWN_FEATURE_MASK`]: Context::KNOWN_FEATURE_MASK
246 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
247 const ASSERT_BITS_IN_MASK: u8;
249 /// The byte where the feature is set.
250 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
252 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
254 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
255 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
257 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
259 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
260 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
262 /// Returns whether the feature is required by the given flags.
264 fn requires_feature(flags: &Vec<u8>) -> bool {
265 flags.len() > Self::BYTE_OFFSET &&
266 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
269 /// Returns whether the feature is supported by the given flags.
271 fn supports_feature(flags: &Vec<u8>) -> bool {
272 flags.len() > Self::BYTE_OFFSET &&
273 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
276 /// Sets the feature's required (even) bit in the given flags.
278 fn set_required_bit(flags: &mut Vec<u8>) {
279 if flags.len() <= Self::BYTE_OFFSET {
280 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
283 flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
284 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
287 /// Sets the feature's optional (odd) bit in the given flags.
289 fn set_optional_bit(flags: &mut Vec<u8>) {
290 if flags.len() <= Self::BYTE_OFFSET {
291 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
294 flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
297 /// Clears the feature's required (even) and optional (odd) bits from the given
300 fn clear_bits(flags: &mut Vec<u8>) {
301 if flags.len() > Self::BYTE_OFFSET {
302 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
303 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
306 let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
307 let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
308 flags.resize(size, 0u8);
312 impl <T: $feature> Features<T> {
313 /// Set this feature as optional.
314 pub fn $optional_setter(&mut self) {
315 <T as $feature>::set_optional_bit(&mut self.flags);
318 /// Set this feature as required.
319 pub fn $required_setter(&mut self) {
320 <T as $feature>::set_required_bit(&mut self.flags);
323 /// Checks if this feature is supported.
324 pub fn $supported_getter(&self) -> bool {
325 <T as $feature>::supports_feature(&self.flags)
330 impl $feature for $context {
332 const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
335 const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
337 // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
338 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
339 const ASSERT_BITS_IN_MASK: u8 =
340 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
341 >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
345 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
346 $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
347 define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
348 impl <T: $feature> Features<T> {
349 /// Checks if this feature is required.
350 pub fn $required_getter(&self) -> bool {
351 <T as $feature>::requires_feature(&self.flags)
357 define_feature!(1, DataLossProtect, [InitContext, NodeContext],
358 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
359 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
360 // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
361 define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
362 set_initial_routing_sync_optional, set_initial_routing_sync_required,
363 initial_routing_sync);
364 define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
365 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
366 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
367 requires_upfront_shutdown_script);
368 define_feature!(7, GossipQueries, [InitContext, NodeContext],
369 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
370 supports_gossip_queries, requires_gossip_queries);
371 define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
372 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
373 set_variable_length_onion_required, supports_variable_length_onion,
374 requires_variable_length_onion);
375 define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
376 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
377 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
378 define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
379 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
380 supports_payment_secret, requires_payment_secret);
381 define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext, Bolt12InvoiceContext],
382 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
383 supports_basic_mpp, requires_basic_mpp);
384 define_feature!(19, Wumbo, [InitContext, NodeContext],
385 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
386 supports_wumbo, requires_wumbo);
387 define_feature!(21, AnchorsNonzeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
388 "Feature flags for `option_anchors_nonzero_fee_htlc_tx`.", set_anchors_nonzero_fee_htlc_tx_optional,
389 set_anchors_nonzero_fee_htlc_tx_required, supports_anchors_nonzero_fee_htlc_tx, requires_anchors_nonzero_fee_htlc_tx);
390 define_feature!(23, AnchorsZeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
391 "Feature flags for `option_anchors_zero_fee_htlc_tx`.", set_anchors_zero_fee_htlc_tx_optional,
392 set_anchors_zero_fee_htlc_tx_required, supports_anchors_zero_fee_htlc_tx, requires_anchors_zero_fee_htlc_tx);
393 define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
394 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
395 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
396 define_feature!(39, OnionMessages, [InitContext, NodeContext],
397 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
398 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
399 define_feature!(45, ChannelType, [InitContext, NodeContext],
400 "Feature flags for `option_channel_type`.", set_channel_type_optional,
401 set_channel_type_required, supports_channel_type, requires_channel_type);
402 define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
403 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
404 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
405 define_feature!(49, PaymentMetadata, [InvoiceContext],
406 "Feature flags for payment metadata in invoices.", set_payment_metadata_optional,
407 set_payment_metadata_required, supports_payment_metadata, requires_payment_metadata);
408 define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
409 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
410 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
411 define_feature!(55, Keysend, [NodeContext],
412 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
413 supports_keysend, requires_keysend);
414 // Note: update the module-level docs when a new feature bit is added!
417 define_feature!(123456789, UnknownFeature,
418 [NodeContext, ChannelContext, InvoiceContext, OfferContext, InvoiceRequestContext, Bolt12InvoiceContext, BlindedHopContext],
419 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
420 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
423 /// Tracks the set of features which a node implements, templated by the context in which it
426 /// This is not exported to bindings users as we map the concrete feature types below directly instead
428 pub struct Features<T: sealed::Context> {
429 /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
431 mark: PhantomData<T>,
434 impl<T: sealed::Context> core::ops::BitOr for Features<T> {
437 fn bitor(mut self, o: Self) -> Self {
438 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
439 self.flags.resize(total_feature_len, 0u8);
440 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
447 impl<T: sealed::Context> Clone for Features<T> {
448 fn clone(&self) -> Self {
450 flags: self.flags.clone(),
455 impl<T: sealed::Context> Hash for Features<T> {
456 fn hash<H: Hasher>(&self, hasher: &mut H) {
457 self.flags.hash(hasher);
460 impl<T: sealed::Context> PartialEq for Features<T> {
461 fn eq(&self, o: &Self) -> bool {
462 self.flags.eq(&o.flags)
465 impl<T: sealed::Context> PartialOrd for Features<T> {
466 fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
467 self.flags.partial_cmp(&other.flags)
470 impl<T: sealed::Context + Eq> Ord for Features<T> {
471 fn cmp(&self, other: &Self) -> cmp::Ordering {
472 self.flags.cmp(&other.flags)
475 impl<T: sealed::Context> fmt::Debug for Features<T> {
476 fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
481 /// Features used within an `init` message.
482 pub type InitFeatures = Features<sealed::InitContext>;
483 /// Features used within a `node_announcement` message.
484 pub type NodeFeatures = Features<sealed::NodeContext>;
485 /// Features used within a `channel_announcement` message.
486 pub type ChannelFeatures = Features<sealed::ChannelContext>;
487 /// Features used within an invoice.
488 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
489 /// Features used within an `offer`.
490 pub type OfferFeatures = Features<sealed::OfferContext>;
491 /// Features used within an `invoice_request`.
492 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
493 /// Features used within an `invoice`.
494 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
495 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
496 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
498 /// Features used within the channel_type field in an OpenChannel message.
500 /// A channel is always of some known "type", describing the transaction formats used and the exact
501 /// semantics of our interaction with our peer.
503 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
504 /// the counterparty, only required features are allowed here.
506 /// This is serialized differently from other feature types - it is not prefixed by a length, and
507 /// thus must only appear inside a TLV where its length is known in advance.
508 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
511 /// Writes all features present up to, and including, 13.
512 pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
513 let len = cmp::min(2, self.flags.len());
514 (len as u16).write(w)?;
515 for i in (0..len).rev() {
517 self.flags[i].write(w)?;
519 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
520 // up-to-and-including-bit-5, 0-indexed, on this byte:
521 (self.flags[i] & 0b00_11_11_11).write(w)?;
527 /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
528 /// are included in the result.
529 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
530 self.to_context_internal()
534 impl InvoiceFeatures {
535 /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
536 /// context `C` are included in the result.
537 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
538 self.to_context_internal()
541 /// Getting a route for a keysend payment to a private node requires providing the payee's
542 /// features (since they were not announced in a node announcement). However, keysend payments
543 /// don't have an invoice to pull the payee's features from, so this method is provided for use in
544 /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
545 /// `InvoiceFeatures` for [`find_route`].
547 /// MPP keysend is not widely supported yet, so we parameterize support to allow the user to
548 /// choose whether their router should find multi-part routes.
550 /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
551 /// [`find_route`]: crate::routing::router::find_route
552 pub(crate) fn for_keysend(allow_mpp: bool) -> InvoiceFeatures {
553 let mut res = InvoiceFeatures::empty();
554 res.set_variable_length_onion_optional();
556 res.set_basic_mpp_optional();
562 impl Bolt12InvoiceFeatures {
563 /// Converts `Bolt12InvoiceFeatures` to `Features<C>`. Only known `Bolt12InvoiceFeatures` relevant
564 /// to context `C` are included in the result.
565 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
566 self.to_context_internal()
570 impl ChannelTypeFeatures {
571 // Maps the relevant `InitFeatures` to `ChannelTypeFeatures`. Any unknown features to
572 // `ChannelTypeFeatures` are not included in the result.
573 pub(crate) fn from_init(init: &InitFeatures) -> Self {
574 let mut ret = init.to_context_internal();
575 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
576 // optional bits and then AND out the optional ones.
577 for byte in ret.flags.iter_mut() {
578 *byte |= (*byte & 0b10_10_10_10) >> 1;
579 *byte &= 0b01_01_01_01;
584 /// Constructs a ChannelTypeFeatures with only static_remotekey set
585 pub(crate) fn only_static_remote_key() -> Self {
586 let mut ret = Self::empty();
587 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
592 impl ToBase32 for InvoiceFeatures {
593 fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
594 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
595 // minus one before dividing
596 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
597 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
598 for (byte_idx, byte) in self.flags.iter().enumerate() {
599 let bit_pos_from_left_0_indexed = byte_idx * 8;
600 let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
601 let new_bit_pos = bit_pos_from_left_0_indexed % 5;
602 let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
603 let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
604 res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
606 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
607 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
610 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
611 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
614 // Trim the highest feature bits.
615 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
618 writer.write(&res_u5s)
622 impl Base32Len for InvoiceFeatures {
623 fn base32_len(&self) -> usize {
624 self.to_base32().len()
628 impl FromBase32 for InvoiceFeatures {
629 type Err = bech32::Error;
631 fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
632 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
633 // minus one before dividing
634 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
635 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
636 for (u5_idx, chunk) in field_data.iter().enumerate() {
637 let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
638 let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
639 let new_bit_pos = bit_pos_from_right_0_indexed % 8;
640 let chunk_u16 = chunk.to_u8() as u16;
641 res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
642 if new_byte_idx != length_bytes - 1 {
643 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
646 // Trim the highest feature bits.
647 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
650 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
654 impl<T: sealed::Context> Features<T> {
655 /// Create a blank Features with no features set
656 pub fn empty() -> Self {
663 /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
664 /// included in the result.
665 fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
666 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
667 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
668 let mut flags = Vec::new();
669 for (i, byte) in self.flags.iter().enumerate() {
670 if i < from_byte_count && i < to_byte_count {
671 let from_known_features = T::KNOWN_FEATURE_MASK[i];
672 let to_known_features = C::KNOWN_FEATURE_MASK[i];
673 flags.push(byte & from_known_features & to_known_features);
676 Features::<C> { flags, mark: PhantomData, }
679 /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
680 /// most on-the-wire encodings.
682 /// This is not exported to bindings users as we don't support export across multiple T
683 pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
691 /// Gets the underlying flags set, in LE.
692 pub fn le_flags(&self) -> &Vec<u8> {
696 fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
697 for f in self.flags.iter().rev() { // Swap back to big-endian
703 fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
704 flags.reverse(); // Swap to little-endian
711 pub(crate) fn supports_any_optional_bits(&self) -> bool {
712 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
715 /// Returns true if this `Features` object contains required features unknown by `other`.
716 pub fn requires_unknown_bits_from(&self, other: &Features<T>) -> bool {
717 // Bitwise AND-ing with all even bits set except for known features will select required
719 self.flags.iter().enumerate().any(|(i, &byte)| {
720 const REQUIRED_FEATURES: u8 = 0b01_01_01_01;
721 const OPTIONAL_FEATURES: u8 = 0b10_10_10_10;
722 let unknown_features = if i < other.flags.len() {
723 // Form a mask similar to !T::KNOWN_FEATURE_MASK only for `other`
725 | ((other.flags[i] >> 1) & REQUIRED_FEATURES)
726 | ((other.flags[i] << 1) & OPTIONAL_FEATURES))
730 (byte & (REQUIRED_FEATURES & unknown_features)) != 0
734 /// Returns true if this `Features` object contains unknown feature flags which are set as
736 pub fn requires_unknown_bits(&self) -> bool {
737 // Bitwise AND-ing with all even bits set except for known features will select required
739 let byte_count = T::KNOWN_FEATURE_MASK.len();
740 self.flags.iter().enumerate().any(|(i, &byte)| {
741 let required_features = 0b01_01_01_01;
742 let unknown_features = if i < byte_count {
743 !T::KNOWN_FEATURE_MASK[i]
747 (byte & (required_features & unknown_features)) != 0
751 pub(crate) fn supports_unknown_bits(&self) -> bool {
752 // Bitwise AND-ing with all even and odd bits set except for known features will select
753 // both required and optional unknown features.
754 let byte_count = T::KNOWN_FEATURE_MASK.len();
755 self.flags.iter().enumerate().any(|(i, &byte)| {
756 let unknown_features = if i < byte_count {
757 !T::KNOWN_FEATURE_MASK[i]
761 (byte & unknown_features) != 0
765 // Returns true if the features within `self` are a subset of the features within `other`.
766 pub(crate) fn is_subset(&self, other: &Self) -> bool {
767 for (idx, byte) in self.flags.iter().enumerate() {
768 if let Some(other_byte) = other.flags.get(idx) {
769 if byte & other_byte != *byte {
770 // `self` has bits set that `other` doesn't.
775 // `self` has a non-zero byte that `other` doesn't.
783 /// Sets a required custom feature bit. Errors if `bit` is outside the custom range as defined
784 /// by [bLIP 2] or if it is a known `T` feature.
786 /// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
787 /// be set instead (i.e., `bit - 1`).
789 /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
790 pub fn set_required_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
791 self.set_custom_bit(bit - (bit % 2))
794 /// Sets an optional custom feature bit. Errors if `bit` is outside the custom range as defined
795 /// by [bLIP 2] or if it is a known `T` feature.
797 /// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
798 /// set instead (i.e., `bit + 1`).
800 /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
801 pub fn set_optional_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
802 self.set_custom_bit(bit + (1 - (bit % 2)))
805 fn set_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
810 let byte_offset = bit / 8;
811 let mask = 1 << (bit - 8 * byte_offset);
812 if byte_offset < T::KNOWN_FEATURE_MASK.len() {
813 if (T::KNOWN_FEATURE_MASK[byte_offset] & mask) != 0 {
818 if self.flags.len() <= byte_offset {
819 self.flags.resize(byte_offset + 1, 0u8);
822 self.flags[byte_offset] |= mask;
828 impl<T: sealed::UpfrontShutdownScript> Features<T> {
830 pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
831 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
836 impl<T: sealed::ShutdownAnySegwit> Features<T> {
838 pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
839 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
844 impl<T: sealed::Wumbo> Features<T> {
846 pub(crate) fn clear_wumbo(mut self) -> Self {
847 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
852 impl<T: sealed::SCIDPrivacy> Features<T> {
853 pub(crate) fn clear_scid_privacy(&mut self) {
854 <T as sealed::SCIDPrivacy>::clear_bits(&mut self.flags);
858 impl<T: sealed::AnchorsZeroFeeHtlcTx> Features<T> {
859 pub(crate) fn clear_anchors_zero_fee_htlc_tx(&mut self) {
860 <T as sealed::AnchorsZeroFeeHtlcTx>::clear_bits(&mut self.flags);
865 impl<T: sealed::UnknownFeature> Features<T> {
866 pub(crate) fn unknown() -> Self {
867 let mut features = Self::empty();
868 features.set_unknown_feature_required();
873 macro_rules! impl_feature_len_prefixed_write {
874 ($features: ident) => {
875 impl Writeable for $features {
876 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
877 (self.flags.len() as u16).write(w)?;
881 impl Readable for $features {
882 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
883 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
888 impl_feature_len_prefixed_write!(InitFeatures);
889 impl_feature_len_prefixed_write!(ChannelFeatures);
890 impl_feature_len_prefixed_write!(NodeFeatures);
891 impl_feature_len_prefixed_write!(InvoiceFeatures);
892 impl_feature_len_prefixed_write!(Bolt12InvoiceFeatures);
893 impl_feature_len_prefixed_write!(BlindedHopFeatures);
895 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
896 macro_rules! impl_feature_tlv_write {
897 ($features: ident) => {
898 impl Writeable for $features {
899 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
900 WithoutLength(self).write(w)
903 impl Readable for $features {
904 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
905 Ok(WithoutLength::<Self>::read(r)?.0)
911 impl_feature_tlv_write!(ChannelTypeFeatures);
913 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
914 // requires a length but the former does not.
916 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
917 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
922 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
923 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
924 let v = io_extras::read_to_end(r)?;
925 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
931 use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
932 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
933 use crate::util::ser::{Readable, WithoutLength, Writeable};
936 fn sanity_test_unknown_bits() {
937 let features = ChannelFeatures::empty();
938 assert!(!features.requires_unknown_bits());
939 assert!(!features.supports_unknown_bits());
941 let mut features = ChannelFeatures::empty();
942 features.set_unknown_feature_required();
943 assert!(features.requires_unknown_bits());
944 assert!(features.supports_unknown_bits());
946 let mut features = ChannelFeatures::empty();
947 features.set_unknown_feature_optional();
948 assert!(!features.requires_unknown_bits());
949 assert!(features.supports_unknown_bits());
953 fn requires_unknown_bits_from() {
954 let mut features1 = InitFeatures::empty();
955 let mut features2 = InitFeatures::empty();
956 assert!(!features1.requires_unknown_bits_from(&features2));
957 assert!(!features2.requires_unknown_bits_from(&features1));
959 features1.set_data_loss_protect_required();
960 assert!(features1.requires_unknown_bits_from(&features2));
961 assert!(!features2.requires_unknown_bits_from(&features1));
963 features2.set_data_loss_protect_optional();
964 assert!(!features1.requires_unknown_bits_from(&features2));
965 assert!(!features2.requires_unknown_bits_from(&features1));
967 features2.set_gossip_queries_required();
968 assert!(!features1.requires_unknown_bits_from(&features2));
969 assert!(features2.requires_unknown_bits_from(&features1));
971 features1.set_gossip_queries_optional();
972 assert!(!features1.requires_unknown_bits_from(&features2));
973 assert!(!features2.requires_unknown_bits_from(&features1));
975 features1.set_variable_length_onion_required();
976 assert!(features1.requires_unknown_bits_from(&features2));
977 assert!(!features2.requires_unknown_bits_from(&features1));
979 features2.set_variable_length_onion_optional();
980 assert!(!features1.requires_unknown_bits_from(&features2));
981 assert!(!features2.requires_unknown_bits_from(&features1));
983 features1.set_basic_mpp_required();
984 features2.set_wumbo_required();
985 assert!(features1.requires_unknown_bits_from(&features2));
986 assert!(features2.requires_unknown_bits_from(&features1));
990 fn convert_to_context_with_relevant_flags() {
991 let mut init_features = InitFeatures::empty();
992 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
993 // converted as it's only relevant in an init context).
994 init_features.set_initial_routing_sync_required();
995 init_features.set_data_loss_protect_required();
996 init_features.set_variable_length_onion_required();
997 init_features.set_static_remote_key_required();
998 init_features.set_payment_secret_required();
999 init_features.set_basic_mpp_optional();
1000 init_features.set_wumbo_optional();
1001 init_features.set_anchors_zero_fee_htlc_tx_optional();
1002 init_features.set_shutdown_any_segwit_optional();
1003 init_features.set_onion_messages_optional();
1004 init_features.set_channel_type_optional();
1005 init_features.set_scid_privacy_optional();
1006 init_features.set_zero_conf_optional();
1008 assert!(init_features.initial_routing_sync());
1009 assert!(!init_features.supports_upfront_shutdown_script());
1010 assert!(!init_features.supports_gossip_queries());
1012 let node_features: NodeFeatures = init_features.to_context();
1014 // Check that the flags are as expected:
1015 // - option_data_loss_protect (req)
1016 // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
1017 // - basic_mpp | wumbo | anchors_zero_fee_htlc_tx
1018 // - opt_shutdown_anysegwit
1020 // - option_channel_type | option_scid_alias
1021 // - option_zeroconf
1022 assert_eq!(node_features.flags.len(), 7);
1023 assert_eq!(node_features.flags[0], 0b00000001);
1024 assert_eq!(node_features.flags[1], 0b01010001);
1025 assert_eq!(node_features.flags[2], 0b10001010);
1026 assert_eq!(node_features.flags[3], 0b00001000);
1027 assert_eq!(node_features.flags[4], 0b10000000);
1028 assert_eq!(node_features.flags[5], 0b10100000);
1029 assert_eq!(node_features.flags[6], 0b00001000);
1032 // Check that cleared flags are kept blank when converting back:
1033 // - initial_routing_sync was not applicable to NodeContext
1034 // - upfront_shutdown_script was cleared before converting
1035 // - gossip_queries was cleared before converting
1036 let features: InitFeatures = node_features.to_context_internal();
1037 assert!(!features.initial_routing_sync());
1038 assert!(!features.supports_upfront_shutdown_script());
1039 assert!(!init_features.supports_gossip_queries());
1043 fn convert_to_context_with_unknown_flags() {
1044 // Ensure the `from` context has fewer known feature bytes than the `to` context.
1045 assert!(<sealed::ChannelContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
1046 <sealed::InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
1047 let mut channel_features = ChannelFeatures::empty();
1048 channel_features.set_unknown_feature_optional();
1049 assert!(channel_features.supports_unknown_bits());
1050 let invoice_features: InvoiceFeatures = channel_features.to_context_internal();
1051 assert!(!invoice_features.supports_unknown_bits());
1055 fn set_feature_bits() {
1056 let mut features = InvoiceFeatures::empty();
1057 features.set_basic_mpp_optional();
1058 features.set_payment_secret_required();
1059 assert!(features.supports_basic_mpp());
1060 assert!(!features.requires_basic_mpp());
1061 assert!(features.requires_payment_secret());
1062 assert!(features.supports_payment_secret());
1066 fn set_custom_bits() {
1067 let mut features = InvoiceFeatures::empty();
1068 features.set_variable_length_onion_optional();
1069 assert_eq!(features.flags[1], 0b00000010);
1071 assert!(features.set_optional_custom_bit(255).is_err());
1072 assert!(features.set_required_custom_bit(256).is_ok());
1073 assert!(features.set_required_custom_bit(258).is_ok());
1074 assert_eq!(features.flags[31], 0b00000000);
1075 assert_eq!(features.flags[32], 0b00000101);
1077 let known_bit = <sealed::InvoiceContext as sealed::PaymentSecret>::EVEN_BIT;
1078 let byte_offset = <sealed::InvoiceContext as sealed::PaymentSecret>::BYTE_OFFSET;
1079 assert_eq!(byte_offset, 1);
1080 assert_eq!(features.flags[byte_offset], 0b00000010);
1081 assert!(features.set_required_custom_bit(known_bit).is_err());
1082 assert_eq!(features.flags[byte_offset], 0b00000010);
1084 let mut features = InvoiceFeatures::empty();
1085 assert!(features.set_optional_custom_bit(256).is_ok());
1086 assert!(features.set_optional_custom_bit(259).is_ok());
1087 assert_eq!(features.flags[32], 0b00001010);
1089 let mut features = InvoiceFeatures::empty();
1090 assert!(features.set_required_custom_bit(257).is_ok());
1091 assert!(features.set_required_custom_bit(258).is_ok());
1092 assert_eq!(features.flags[32], 0b00000101);
1096 fn encodes_features_without_length() {
1097 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1098 assert_eq!(features.flags.len(), 8);
1100 let mut serialized_features = Vec::new();
1101 WithoutLength(&features).write(&mut serialized_features).unwrap();
1102 assert_eq!(serialized_features.len(), 8);
1104 let deserialized_features =
1105 WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
1106 assert_eq!(features, deserialized_features);
1110 fn invoice_features_encoding() {
1111 let features_as_u5s = vec![
1112 u5::try_from_u8(6).unwrap(),
1113 u5::try_from_u8(10).unwrap(),
1114 u5::try_from_u8(25).unwrap(),
1115 u5::try_from_u8(1).unwrap(),
1116 u5::try_from_u8(10).unwrap(),
1117 u5::try_from_u8(0).unwrap(),
1118 u5::try_from_u8(20).unwrap(),
1119 u5::try_from_u8(2).unwrap(),
1120 u5::try_from_u8(0).unwrap(),
1121 u5::try_from_u8(6).unwrap(),
1122 u5::try_from_u8(0).unwrap(),
1123 u5::try_from_u8(16).unwrap(),
1124 u5::try_from_u8(1).unwrap(),
1126 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1128 // Test length calculation.
1129 assert_eq!(features.base32_len(), 13);
1131 // Test serialization.
1132 let features_serialized = features.to_base32();
1133 assert_eq!(features_as_u5s, features_serialized);
1135 // Test deserialization.
1136 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
1137 assert_eq!(features, features_deserialized);
1141 fn test_channel_type_mapping() {
1142 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
1143 // required-StaticRemoteKey ChannelTypeFeatures.
1144 let mut init_features = InitFeatures::empty();
1145 init_features.set_static_remote_key_optional();
1146 let converted_features = ChannelTypeFeatures::from_init(&init_features);
1147 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
1148 assert!(!converted_features.supports_any_optional_bits());
1149 assert!(converted_features.requires_static_remote_key());