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).
55 //! - `AnchorsZeroFeeHtlcTx` - requires/supports that commitment transactions include anchor outputs
56 //! and HTLC transactions are pre-signed with zero fee (see
57 //! [BOLT-3](https://github.com/lightning/bolts/blob/master/03-transactions.md) for more
60 //! [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
61 //! [messages]: crate::ln::msgs
63 use crate::{io, io_extras};
64 use crate::prelude::*;
66 use core::hash::{Hash, Hasher};
67 use core::marker::PhantomData;
70 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
71 use crate::ln::msgs::DecodeError;
72 use crate::util::ser::{Readable, WithoutLength, Writeable, Writer};
75 use crate::prelude::*;
76 use crate::ln::features::Features;
78 /// The context in which [`Features`] are applicable. Defines which features are known to the
79 /// implementation, though specification of them as required or optional is up to the code
80 /// constructing a features object.
82 /// Bitmask for selecting features that are known to the implementation.
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 {
90 ($context: ident, [$( $( $known_feature: ident )|*, )*]) => {
91 #[derive(Eq, PartialEq)]
92 pub struct $context {}
94 impl Context for $context {
95 const KNOWN_FEATURE_MASK: &'static [u8] = &[
98 <Self as $known_feature>::REQUIRED_MASK |
99 <Self as $known_feature>::OPTIONAL_MASK)*,
104 impl alloc::fmt::Display for Features<$context> {
105 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
108 fmt.write_fmt(format_args!("{}: {}, ", stringify!($known_feature),
109 if <$context as $known_feature>::requires_feature(&self.flags) { "required" }
110 else if <$context as $known_feature>::supports_feature(&self.flags) { "supported" }
111 else { "not supported" }))?;
113 {} // Rust gets mad if we only have a $()* block here, so add a dummy {}
115 fmt.write_fmt(format_args!("unknown flags: {}",
116 if self.requires_unknown_bits() { "required" }
117 else if self.supports_unknown_bits() { "supported" } else { "none" }))
123 define_context!(InitContext, [
125 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
127 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
129 BasicMPP | Wumbo | AnchorsZeroFeeHtlcTx,
135 ChannelType | SCIDPrivacy,
139 define_context!(NodeContext, [
141 DataLossProtect | UpfrontShutdownScript | GossipQueries,
143 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
145 BasicMPP | Wumbo | AnchorsZeroFeeHtlcTx,
151 ChannelType | SCIDPrivacy,
155 define_context!(ChannelContext, []);
156 define_context!(InvoiceContext, [
160 VariableLengthOnion | PaymentSecret,
164 define_context!(OfferContext, []);
165 define_context!(InvoiceRequestContext, []);
166 define_context!(Bolt12InvoiceContext, [
174 define_context!(BlindedHopContext, []);
175 // This isn't a "real" feature context, and is only used in the channel_type field in an
176 // `OpenChannel` message.
177 define_context!(ChannelTypeContext, [
183 AnchorsZeroFeeHtlcTx,
194 /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
195 /// useful for manipulating feature flags.
196 macro_rules! define_feature {
197 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
198 $required_setter: ident, $supported_getter: ident) => {
201 /// See [BOLT #9] for details.
203 /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
204 pub trait $feature: Context {
205 /// The bit used to signify that the feature is required.
206 const EVEN_BIT: usize = $odd_bit - 1;
208 /// The bit used to signify that the feature is optional.
209 const ODD_BIT: usize = $odd_bit;
211 /// Assertion that [`EVEN_BIT`] is actually even.
213 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
214 const ASSERT_EVEN_BIT_PARITY: usize;
216 /// Assertion that [`ODD_BIT`] is actually odd.
218 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
219 const ASSERT_ODD_BIT_PARITY: usize;
221 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
223 /// [`KNOWN_FEATURE_MASK`]: Context::KNOWN_FEATURE_MASK
224 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
225 const ASSERT_BITS_IN_MASK: u8;
227 /// The byte where the feature is set.
228 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
230 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
232 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
233 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
235 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
237 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
238 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
240 /// Returns whether the feature is required by the given flags.
242 fn requires_feature(flags: &Vec<u8>) -> bool {
243 flags.len() > Self::BYTE_OFFSET &&
244 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
247 /// Returns whether the feature is supported by the given flags.
249 fn supports_feature(flags: &Vec<u8>) -> bool {
250 flags.len() > Self::BYTE_OFFSET &&
251 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
254 /// Sets the feature's required (even) bit in the given flags.
256 fn set_required_bit(flags: &mut Vec<u8>) {
257 if flags.len() <= Self::BYTE_OFFSET {
258 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
261 flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
264 /// Sets the feature's optional (odd) bit in the given flags.
266 fn set_optional_bit(flags: &mut Vec<u8>) {
267 if flags.len() <= Self::BYTE_OFFSET {
268 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
271 flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
274 /// Clears the feature's required (even) and optional (odd) bits from the given
277 fn clear_bits(flags: &mut Vec<u8>) {
278 if flags.len() > Self::BYTE_OFFSET {
279 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
280 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
283 let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
284 let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
285 flags.resize(size, 0u8);
289 impl <T: $feature> Features<T> {
290 /// Set this feature as optional.
291 pub fn $optional_setter(&mut self) {
292 <T as $feature>::set_optional_bit(&mut self.flags);
295 /// Set this feature as required.
296 pub fn $required_setter(&mut self) {
297 <T as $feature>::set_required_bit(&mut self.flags);
300 /// Checks if this feature is supported.
301 pub fn $supported_getter(&self) -> bool {
302 <T as $feature>::supports_feature(&self.flags)
307 impl $feature for $context {
309 const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
312 const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
314 // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
315 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
316 const ASSERT_BITS_IN_MASK: u8 =
317 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
318 >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
322 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
323 $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
324 define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
325 impl <T: $feature> Features<T> {
326 /// Checks if this feature is required.
327 pub fn $required_getter(&self) -> bool {
328 <T as $feature>::requires_feature(&self.flags)
334 define_feature!(1, DataLossProtect, [InitContext, NodeContext],
335 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
336 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
337 // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
338 define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
339 set_initial_routing_sync_optional, set_initial_routing_sync_required,
340 initial_routing_sync);
341 define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
342 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
343 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
344 requires_upfront_shutdown_script);
345 define_feature!(7, GossipQueries, [InitContext, NodeContext],
346 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
347 supports_gossip_queries, requires_gossip_queries);
348 define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
349 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
350 set_variable_length_onion_required, supports_variable_length_onion,
351 requires_variable_length_onion);
352 define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
353 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
354 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
355 define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
356 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
357 supports_payment_secret, requires_payment_secret);
358 define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext, Bolt12InvoiceContext],
359 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
360 supports_basic_mpp, requires_basic_mpp);
361 define_feature!(19, Wumbo, [InitContext, NodeContext],
362 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
363 supports_wumbo, requires_wumbo);
364 define_feature!(23, AnchorsZeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
365 "Feature flags for `option_anchors_zero_fee_htlc_tx`.", set_anchors_zero_fee_htlc_tx_optional,
366 set_anchors_zero_fee_htlc_tx_required, supports_anchors_zero_fee_htlc_tx, requires_anchors_zero_fee_htlc_tx);
367 define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
368 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
369 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
370 define_feature!(39, OnionMessages, [InitContext, NodeContext],
371 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
372 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
373 define_feature!(45, ChannelType, [InitContext, NodeContext],
374 "Feature flags for `option_channel_type`.", set_channel_type_optional,
375 set_channel_type_required, supports_channel_type, requires_channel_type);
376 define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
377 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
378 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
379 define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
380 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
381 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
382 define_feature!(55, Keysend, [NodeContext],
383 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
384 supports_keysend, requires_keysend);
387 define_feature!(123456789, UnknownFeature,
388 [NodeContext, ChannelContext, InvoiceContext, OfferContext, InvoiceRequestContext, Bolt12InvoiceContext, BlindedHopContext],
389 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
390 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
393 /// Tracks the set of features which a node implements, templated by the context in which it
396 /// (C-not exported) as we map the concrete feature types below directly instead
398 pub struct Features<T: sealed::Context> {
399 /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
401 mark: PhantomData<T>,
404 impl <T: sealed::Context> Features<T> {
405 pub(crate) fn or(mut self, o: Self) -> Self {
406 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
407 self.flags.resize(total_feature_len, 0u8);
408 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
415 impl<T: sealed::Context> Clone for Features<T> {
416 fn clone(&self) -> Self {
418 flags: self.flags.clone(),
423 impl<T: sealed::Context> Hash for Features<T> {
424 fn hash<H: Hasher>(&self, hasher: &mut H) {
425 self.flags.hash(hasher);
428 impl<T: sealed::Context> PartialEq for Features<T> {
429 fn eq(&self, o: &Self) -> bool {
430 self.flags.eq(&o.flags)
433 impl<T: sealed::Context> fmt::Debug for Features<T> {
434 fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
439 /// Features used within an `init` message.
440 pub type InitFeatures = Features<sealed::InitContext>;
441 /// Features used within a `node_announcement` message.
442 pub type NodeFeatures = Features<sealed::NodeContext>;
443 /// Features used within a `channel_announcement` message.
444 pub type ChannelFeatures = Features<sealed::ChannelContext>;
445 /// Features used within an invoice.
446 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
447 /// Features used within an `offer`.
448 pub type OfferFeatures = Features<sealed::OfferContext>;
449 /// Features used within an `invoice_request`.
450 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
451 /// Features used within an `invoice`.
452 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
453 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
454 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
456 /// Features used within the channel_type field in an OpenChannel message.
458 /// A channel is always of some known "type", describing the transaction formats used and the exact
459 /// semantics of our interaction with our peer.
461 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
462 /// the counterparty, only required features are allowed here.
464 /// This is serialized differently from other feature types - it is not prefixed by a length, and
465 /// thus must only appear inside a TLV where its length is known in advance.
466 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
469 /// Writes all features present up to, and including, 13.
470 pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
471 let len = cmp::min(2, self.flags.len());
472 (len as u16).write(w)?;
473 for i in (0..len).rev() {
475 self.flags[i].write(w)?;
477 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
478 // up-to-and-including-bit-5, 0-indexed, on this byte:
479 (self.flags[i] & 0b00_11_11_11).write(w)?;
485 /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
486 /// are included in the result.
487 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
488 self.to_context_internal()
492 impl InvoiceFeatures {
493 /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
494 /// context `C` are included in the result.
495 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
496 self.to_context_internal()
499 /// Getting a route for a keysend payment to a private node requires providing the payee's
500 /// features (since they were not announced in a node announcement). However, keysend payments
501 /// don't have an invoice to pull the payee's features from, so this method is provided for use in
502 /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
503 /// `InvoiceFeatures` for [`find_route`].
505 /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
506 /// [`find_route`]: crate::routing::router::find_route
507 pub(crate) fn for_keysend() -> InvoiceFeatures {
508 let mut res = InvoiceFeatures::empty();
509 res.set_variable_length_onion_optional();
514 impl ChannelTypeFeatures {
515 // Maps the relevant `InitFeatures` to `ChannelTypeFeatures`. Any unknown features to
516 // `ChannelTypeFeatures` are not included in the result.
517 pub(crate) fn from_init(init: &InitFeatures) -> Self {
518 let mut ret = init.to_context_internal();
519 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
520 // optional bits and then AND out the optional ones.
521 for byte in ret.flags.iter_mut() {
522 *byte |= (*byte & 0b10_10_10_10) >> 1;
523 *byte &= 0b01_01_01_01;
528 /// Constructs a ChannelTypeFeatures with only static_remotekey set
529 pub(crate) fn only_static_remote_key() -> Self {
530 let mut ret = Self::empty();
531 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
536 impl ToBase32 for InvoiceFeatures {
537 fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
538 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
539 // minus one before dividing
540 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
541 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
542 for (byte_idx, byte) in self.flags.iter().enumerate() {
543 let bit_pos_from_left_0_indexed = byte_idx * 8;
544 let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
545 let new_bit_pos = bit_pos_from_left_0_indexed % 5;
546 let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
547 let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
548 res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
550 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
551 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
554 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
555 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
558 // Trim the highest feature bits.
559 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
562 writer.write(&res_u5s)
566 impl Base32Len for InvoiceFeatures {
567 fn base32_len(&self) -> usize {
568 self.to_base32().len()
572 impl FromBase32 for InvoiceFeatures {
573 type Err = bech32::Error;
575 fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
576 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
577 // minus one before dividing
578 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
579 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
580 for (u5_idx, chunk) in field_data.iter().enumerate() {
581 let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
582 let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
583 let new_bit_pos = bit_pos_from_right_0_indexed % 8;
584 let chunk_u16 = chunk.to_u8() as u16;
585 res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
586 if new_byte_idx != length_bytes - 1 {
587 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
590 // Trim the highest feature bits.
591 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
594 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
598 impl<T: sealed::Context> Features<T> {
599 /// Create a blank Features with no features set
600 pub fn empty() -> Self {
607 /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
608 /// included in the result.
609 fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
610 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
611 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
612 let mut flags = Vec::new();
613 for (i, byte) in self.flags.iter().enumerate() {
614 if i < from_byte_count && i < to_byte_count {
615 let from_known_features = T::KNOWN_FEATURE_MASK[i];
616 let to_known_features = C::KNOWN_FEATURE_MASK[i];
617 flags.push(byte & from_known_features & to_known_features);
620 Features::<C> { flags, mark: PhantomData, }
623 /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
624 /// most on-the-wire encodings.
625 /// (C-not exported) as we don't support export across multiple T
626 pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
634 /// Gets the underlying flags set, in LE.
635 pub fn le_flags(&self) -> &Vec<u8> {
639 fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
640 for f in self.flags.iter().rev() { // Swap back to big-endian
646 fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
647 flags.reverse(); // Swap to little-endian
654 pub(crate) fn supports_any_optional_bits(&self) -> bool {
655 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
658 /// Returns true if this `Features` object contains unknown feature flags which are set as
660 pub fn requires_unknown_bits(&self) -> bool {
661 // Bitwise AND-ing with all even bits set except for known features will select required
663 let byte_count = T::KNOWN_FEATURE_MASK.len();
664 self.flags.iter().enumerate().any(|(i, &byte)| {
665 let required_features = 0b01_01_01_01;
666 let unknown_features = if i < byte_count {
667 !T::KNOWN_FEATURE_MASK[i]
671 (byte & (required_features & unknown_features)) != 0
675 pub(crate) fn supports_unknown_bits(&self) -> bool {
676 // Bitwise AND-ing with all even and odd bits set except for known features will select
677 // both required and optional unknown features.
678 let byte_count = T::KNOWN_FEATURE_MASK.len();
679 self.flags.iter().enumerate().any(|(i, &byte)| {
680 let unknown_features = if i < byte_count {
681 !T::KNOWN_FEATURE_MASK[i]
685 (byte & unknown_features) != 0
689 // Returns true if the features within `self` are a subset of the features within `other`.
690 pub(crate) fn is_subset(&self, other: &Self) -> bool {
691 for (idx, byte) in self.flags.iter().enumerate() {
692 if let Some(other_byte) = other.flags.get(idx) {
693 if byte & other_byte != *byte {
694 // `self` has bits set that `other` doesn't.
699 // `self` has a non-zero byte that `other` doesn't.
708 impl<T: sealed::UpfrontShutdownScript> Features<T> {
710 pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
711 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
716 impl<T: sealed::ShutdownAnySegwit> Features<T> {
718 pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
719 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
724 impl<T: sealed::Wumbo> Features<T> {
726 pub(crate) fn clear_wumbo(mut self) -> Self {
727 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
732 impl<T: sealed::SCIDPrivacy> Features<T> {
733 pub(crate) fn clear_scid_privacy(&mut self) {
734 <T as sealed::SCIDPrivacy>::clear_bits(&mut self.flags);
738 impl<T: sealed::AnchorsZeroFeeHtlcTx> Features<T> {
739 pub(crate) fn clear_anchors_zero_fee_htlc_tx(&mut self) {
740 <T as sealed::AnchorsZeroFeeHtlcTx>::clear_bits(&mut self.flags);
745 impl<T: sealed::UnknownFeature> Features<T> {
746 pub(crate) fn unknown() -> Self {
747 let mut features = Self::empty();
748 features.set_unknown_feature_required();
753 macro_rules! impl_feature_len_prefixed_write {
754 ($features: ident) => {
755 impl Writeable for $features {
756 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
757 (self.flags.len() as u16).write(w)?;
761 impl Readable for $features {
762 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
763 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
768 impl_feature_len_prefixed_write!(InitFeatures);
769 impl_feature_len_prefixed_write!(ChannelFeatures);
770 impl_feature_len_prefixed_write!(NodeFeatures);
771 impl_feature_len_prefixed_write!(InvoiceFeatures);
772 impl_feature_len_prefixed_write!(BlindedHopFeatures);
774 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
775 macro_rules! impl_feature_tlv_write {
776 ($features: ident) => {
777 impl Writeable for $features {
778 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
779 WithoutLength(self).write(w)
782 impl Readable for $features {
783 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
784 Ok(WithoutLength::<Self>::read(r)?.0)
790 impl_feature_tlv_write!(ChannelTypeFeatures);
792 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
793 // requires a length but the former does not.
795 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
796 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
801 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
802 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
803 let v = io_extras::read_to_end(r)?;
804 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
810 use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
811 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
812 use crate::util::ser::{Readable, WithoutLength, Writeable};
815 fn sanity_test_unknown_bits() {
816 let features = ChannelFeatures::empty();
817 assert!(!features.requires_unknown_bits());
818 assert!(!features.supports_unknown_bits());
820 let mut features = ChannelFeatures::empty();
821 features.set_unknown_feature_required();
822 assert!(features.requires_unknown_bits());
823 assert!(features.supports_unknown_bits());
825 let mut features = ChannelFeatures::empty();
826 features.set_unknown_feature_optional();
827 assert!(!features.requires_unknown_bits());
828 assert!(features.supports_unknown_bits());
832 fn convert_to_context_with_relevant_flags() {
833 let mut init_features = InitFeatures::empty();
834 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
835 // converted as it's only relevant in an init context).
836 init_features.set_initial_routing_sync_required();
837 init_features.set_data_loss_protect_optional();
838 init_features.set_variable_length_onion_required();
839 init_features.set_static_remote_key_required();
840 init_features.set_payment_secret_required();
841 init_features.set_basic_mpp_optional();
842 init_features.set_wumbo_optional();
843 init_features.set_shutdown_any_segwit_optional();
844 init_features.set_onion_messages_optional();
845 init_features.set_channel_type_optional();
846 init_features.set_scid_privacy_optional();
847 init_features.set_zero_conf_optional();
848 init_features.set_anchors_zero_fee_htlc_tx_optional();
850 assert!(init_features.initial_routing_sync());
851 assert!(!init_features.supports_upfront_shutdown_script());
852 assert!(!init_features.supports_gossip_queries());
854 let node_features: NodeFeatures = init_features.to_context();
856 // Check that the flags are as expected:
857 // - option_data_loss_protect
858 // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
859 // - basic_mpp | wumbo
860 // - opt_shutdown_anysegwit
862 // - option_channel_type | option_scid_alias
864 assert_eq!(node_features.flags.len(), 7);
865 assert_eq!(node_features.flags[0], 0b00000010);
866 assert_eq!(node_features.flags[1], 0b01010001);
867 assert_eq!(node_features.flags[2], 0b10001010);
868 assert_eq!(node_features.flags[3], 0b00001000);
869 assert_eq!(node_features.flags[4], 0b10000000);
870 assert_eq!(node_features.flags[5], 0b10100000);
871 assert_eq!(node_features.flags[6], 0b00001000);
874 // Check that cleared flags are kept blank when converting back:
875 // - initial_routing_sync was not applicable to NodeContext
876 // - upfront_shutdown_script was cleared before converting
877 // - gossip_queries was cleared before converting
878 let features: InitFeatures = node_features.to_context_internal();
879 assert!(!features.initial_routing_sync());
880 assert!(!features.supports_upfront_shutdown_script());
881 assert!(!init_features.supports_gossip_queries());
885 fn convert_to_context_with_unknown_flags() {
886 // Ensure the `from` context has fewer known feature bytes than the `to` context.
887 assert!(<sealed::InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
888 <sealed::NodeContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
889 let mut invoice_features = InvoiceFeatures::empty();
890 invoice_features.set_unknown_feature_optional();
891 assert!(invoice_features.supports_unknown_bits());
892 let node_features: NodeFeatures = invoice_features.to_context();
893 assert!(!node_features.supports_unknown_bits());
897 fn set_feature_bits() {
898 let mut features = InvoiceFeatures::empty();
899 features.set_basic_mpp_optional();
900 features.set_payment_secret_required();
901 assert!(features.supports_basic_mpp());
902 assert!(!features.requires_basic_mpp());
903 assert!(features.requires_payment_secret());
904 assert!(features.supports_payment_secret());
908 fn encodes_features_without_length() {
909 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
910 assert_eq!(features.flags.len(), 8);
912 let mut serialized_features = Vec::new();
913 WithoutLength(&features).write(&mut serialized_features).unwrap();
914 assert_eq!(serialized_features.len(), 8);
916 let deserialized_features =
917 WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
918 assert_eq!(features, deserialized_features);
922 fn invoice_features_encoding() {
923 let features_as_u5s = vec![
924 u5::try_from_u8(6).unwrap(),
925 u5::try_from_u8(10).unwrap(),
926 u5::try_from_u8(25).unwrap(),
927 u5::try_from_u8(1).unwrap(),
928 u5::try_from_u8(10).unwrap(),
929 u5::try_from_u8(0).unwrap(),
930 u5::try_from_u8(20).unwrap(),
931 u5::try_from_u8(2).unwrap(),
932 u5::try_from_u8(0).unwrap(),
933 u5::try_from_u8(6).unwrap(),
934 u5::try_from_u8(0).unwrap(),
935 u5::try_from_u8(16).unwrap(),
936 u5::try_from_u8(1).unwrap(),
938 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
940 // Test length calculation.
941 assert_eq!(features.base32_len(), 13);
943 // Test serialization.
944 let features_serialized = features.to_base32();
945 assert_eq!(features_as_u5s, features_serialized);
947 // Test deserialization.
948 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
949 assert_eq!(features, features_deserialized);
953 fn test_channel_type_mapping() {
954 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
955 // required-StaticRemoteKey ChannelTypeFeatures.
956 let mut init_features = InitFeatures::empty();
957 init_features.set_static_remote_key_optional();
958 let converted_features = ChannelTypeFeatures::from_init(&init_features);
959 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
960 assert!(!converted_features.supports_any_optional_bits());
961 assert!(converted_features.requires_static_remote_key());