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Merge pull request #2248 from TheBlueMatt/2023-04-gossip-check
[rust-lightning] / lightning / src / ln / features.rs
1 // This file is Copyright its original authors, visible in version control
2 // history.
3 //
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
8 // licenses.
9
10 //! Feature flag definitions for the Lightning protocol according to [BOLT #9].
11 //!
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).
16 //!
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.
21 //!
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).
27 //!
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).
48 //     TODO: update link
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
54 //!      onion.
55 //!      (see [BOLT-11](https://github.com/lightning/bolts/blob/master/11-payment-encoding.md) for
56 //!      more).
57 //! - `ZeroConf` - supports accepting HTLCs and using channels prior to funding confirmation
58 //!      (see
59 //!      [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#the-channel_ready-message)
60 //!      for more info).
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
66 //!     information).
67 //!
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).
73 //!
74 //! [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
75 //! [messages]: crate::ln::msgs
76
77 use crate::{io, io_extras};
78 use crate::prelude::*;
79 use core::{cmp, fmt};
80 use core::borrow::Borrow;
81 use core::hash::{Hash, Hasher};
82 use core::marker::PhantomData;
83
84 use bitcoin::bech32;
85 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
86 use crate::ln::msgs::DecodeError;
87 use crate::util::ser::{Readable, WithoutLength, Writeable, Writer};
88
89 mod sealed {
90         use crate::prelude::*;
91         use crate::ln::features::Features;
92
93         /// The context in which [`Features`] are applicable. Defines which features are known to the
94         /// implementation, though specification of them as required or optional is up to the code
95         /// constructing a features object.
96         pub trait Context {
97                 /// Bitmask for selecting features that are known to the implementation.
98                 const KNOWN_FEATURE_MASK: &'static [u8];
99         }
100
101         /// Defines a [`Context`] by stating which features it requires and which are optional. Features
102         /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
103         /// feature identifiers.
104         macro_rules! define_context {
105                 ($context: ident, [$( $( $known_feature: ident )|*, )*]) => {
106                         #[derive(Eq, PartialEq)]
107                         pub struct $context {}
108
109                         impl Context for $context {
110                                 const KNOWN_FEATURE_MASK: &'static [u8] = &[
111                                         $(
112                                                 0b00_00_00_00 $(|
113                                                         <Self as $known_feature>::REQUIRED_MASK |
114                                                         <Self as $known_feature>::OPTIONAL_MASK)*,
115                                         )*
116                                 ];
117                         }
118
119                         impl alloc::fmt::Display for Features<$context> {
120                                 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
121                                         $(
122                                                 $(
123                                                         fmt.write_fmt(format_args!("{}: {}, ", stringify!($known_feature),
124                                                                 if <$context as $known_feature>::requires_feature(&self.flags) { "required" }
125                                                                 else if <$context as $known_feature>::supports_feature(&self.flags) { "supported" }
126                                                                 else { "not supported" }))?;
127                                                 )*
128                                                 {} // Rust gets mad if we only have a $()* block here, so add a dummy {}
129                                         )*
130                                         fmt.write_fmt(format_args!("unknown flags: {}",
131                                                 if self.requires_unknown_bits() { "required" }
132                                                 else if self.supports_unknown_bits() { "supported" } else { "none" }))
133                                 }
134                         }
135                 };
136         }
137
138         define_context!(InitContext, [
139                 // Byte 0
140                 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
141                 // Byte 1
142                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
143                 // Byte 2
144                 BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
145                 // Byte 3
146                 ShutdownAnySegwit | Taproot,
147                 // Byte 4
148                 OnionMessages,
149                 // Byte 5
150                 ChannelType | SCIDPrivacy,
151                 // Byte 6
152                 ZeroConf,
153         ]);
154         define_context!(NodeContext, [
155                 // Byte 0
156                 DataLossProtect | UpfrontShutdownScript | GossipQueries,
157                 // Byte 1
158                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
159                 // Byte 2
160                 BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
161                 // Byte 3
162                 ShutdownAnySegwit | Taproot,
163                 // Byte 4
164                 OnionMessages,
165                 // Byte 5
166                 ChannelType | SCIDPrivacy,
167                 // Byte 6
168                 ZeroConf | Keysend,
169         ]);
170         define_context!(ChannelContext, []);
171         define_context!(Bolt11InvoiceContext, [
172                 // Byte 0
173                 ,
174                 // Byte 1
175                 VariableLengthOnion | PaymentSecret,
176                 // Byte 2
177                 BasicMPP,
178                 // Byte 3
179                 ,
180                 // Byte 4
181                 ,
182                 // Byte 5
183                 ,
184                 // Byte 6
185                 PaymentMetadata,
186         ]);
187         define_context!(OfferContext, []);
188         define_context!(InvoiceRequestContext, []);
189         define_context!(Bolt12InvoiceContext, [
190                 // Byte 0
191                 ,
192                 // Byte 1
193                 ,
194                 // Byte 2
195                 BasicMPP,
196         ]);
197         define_context!(BlindedHopContext, []);
198         // This isn't a "real" feature context, and is only used in the channel_type field in an
199         // `OpenChannel` message.
200         define_context!(ChannelTypeContext, [
201                 // Byte 0
202                 ,
203                 // Byte 1
204                 StaticRemoteKey,
205                 // Byte 2
206                 AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
207                 // Byte 3
208                 Taproot,
209                 // Byte 4
210                 ,
211                 // Byte 5
212                 SCIDPrivacy,
213                 // Byte 6
214                 ZeroConf,
215         ]);
216
217         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
218         /// useful for manipulating feature flags.
219         macro_rules! define_feature {
220                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
221                  $required_setter: ident, $supported_getter: ident) => {
222                         #[doc = $doc]
223                         ///
224                         /// See [BOLT #9] for details.
225                         ///
226                         /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
227                         pub trait $feature: Context {
228                                 /// The bit used to signify that the feature is required.
229                                 const EVEN_BIT: usize = $odd_bit - 1;
230
231                                 /// The bit used to signify that the feature is optional.
232                                 const ODD_BIT: usize = $odd_bit;
233
234                                 /// Assertion that [`EVEN_BIT`] is actually even.
235                                 ///
236                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
237                                 const ASSERT_EVEN_BIT_PARITY: usize;
238
239                                 /// Assertion that [`ODD_BIT`] is actually odd.
240                                 ///
241                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
242                                 const ASSERT_ODD_BIT_PARITY: usize;
243
244                                 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
245                                 ///
246                                 /// [`KNOWN_FEATURE_MASK`]: Context::KNOWN_FEATURE_MASK
247                                 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
248                                 const ASSERT_BITS_IN_MASK: u8;
249
250                                 /// The byte where the feature is set.
251                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
252
253                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
254                                 ///
255                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
256                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
257
258                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
259                                 ///
260                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
261                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
262
263                                 /// Returns whether the feature is required by the given flags.
264                                 #[inline]
265                                 fn requires_feature(flags: &Vec<u8>) -> bool {
266                                         flags.len() > Self::BYTE_OFFSET &&
267                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
268                                 }
269
270                                 /// Returns whether the feature is supported by the given flags.
271                                 #[inline]
272                                 fn supports_feature(flags: &Vec<u8>) -> bool {
273                                         flags.len() > Self::BYTE_OFFSET &&
274                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
275                                 }
276
277                                 /// Sets the feature's required (even) bit in the given flags.
278                                 #[inline]
279                                 fn set_required_bit(flags: &mut Vec<u8>) {
280                                         if flags.len() <= Self::BYTE_OFFSET {
281                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
282                                         }
283
284                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
285                                         flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
286                                 }
287
288                                 /// Sets the feature's optional (odd) bit in the given flags.
289                                 #[inline]
290                                 fn set_optional_bit(flags: &mut Vec<u8>) {
291                                         if flags.len() <= Self::BYTE_OFFSET {
292                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
293                                         }
294
295                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
296                                 }
297
298                                 /// Clears the feature's required (even) and optional (odd) bits from the given
299                                 /// flags.
300                                 #[inline]
301                                 fn clear_bits(flags: &mut Vec<u8>) {
302                                         if flags.len() > Self::BYTE_OFFSET {
303                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
304                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
305                                         }
306
307                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
308                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
309                                         flags.resize(size, 0u8);
310                                 }
311                         }
312
313                         impl <T: $feature> Features<T> {
314                                 /// Set this feature as optional.
315                                 pub fn $optional_setter(&mut self) {
316                                         <T as $feature>::set_optional_bit(&mut self.flags);
317                                 }
318
319                                 /// Set this feature as required.
320                                 pub fn $required_setter(&mut self) {
321                                         <T as $feature>::set_required_bit(&mut self.flags);
322                                 }
323
324                                 /// Checks if this feature is supported.
325                                 pub fn $supported_getter(&self) -> bool {
326                                         <T as $feature>::supports_feature(&self.flags)
327                                 }
328                         }
329
330                         $(
331                                 impl $feature for $context {
332                                         // EVEN_BIT % 2 == 0
333                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
334
335                                         // ODD_BIT % 2 == 1
336                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
337
338                                         // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
339                                         #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
340                                         const ASSERT_BITS_IN_MASK: u8 =
341                                                 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
342                                                  >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
343                                 }
344                         )*
345                 };
346                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
347                  $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
348                         define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
349                         impl <T: $feature> Features<T> {
350                                 /// Checks if this feature is required.
351                                 pub fn $required_getter(&self) -> bool {
352                                         <T as $feature>::requires_feature(&self.flags)
353                                 }
354                         }
355                 }
356         }
357
358         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
359                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
360                 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
361         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
362         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
363                 set_initial_routing_sync_optional, set_initial_routing_sync_required,
364                 initial_routing_sync);
365         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
366                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
367                 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
368                 requires_upfront_shutdown_script);
369         define_feature!(7, GossipQueries, [InitContext, NodeContext],
370                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
371                 supports_gossip_queries, requires_gossip_queries);
372         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, Bolt11InvoiceContext],
373                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
374                 set_variable_length_onion_required, supports_variable_length_onion,
375                 requires_variable_length_onion);
376         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
377                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
378                 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
379         define_feature!(15, PaymentSecret, [InitContext, NodeContext, Bolt11InvoiceContext],
380                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
381                 supports_payment_secret, requires_payment_secret);
382         define_feature!(17, BasicMPP, [InitContext, NodeContext, Bolt11InvoiceContext, Bolt12InvoiceContext],
383                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
384                 supports_basic_mpp, requires_basic_mpp);
385         define_feature!(19, Wumbo, [InitContext, NodeContext],
386                 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
387                 supports_wumbo, requires_wumbo);
388         define_feature!(21, AnchorsNonzeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
389                 "Feature flags for `option_anchors_nonzero_fee_htlc_tx`.", set_anchors_nonzero_fee_htlc_tx_optional,
390                 set_anchors_nonzero_fee_htlc_tx_required, supports_anchors_nonzero_fee_htlc_tx, requires_anchors_nonzero_fee_htlc_tx);
391         define_feature!(23, AnchorsZeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
392                 "Feature flags for `option_anchors_zero_fee_htlc_tx`.", set_anchors_zero_fee_htlc_tx_optional,
393                 set_anchors_zero_fee_htlc_tx_required, supports_anchors_zero_fee_htlc_tx, requires_anchors_zero_fee_htlc_tx);
394         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
395                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
396                 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
397         define_feature!(31, Taproot, [InitContext, NodeContext, ChannelTypeContext],
398                 "Feature flags for `option_taproot`.", set_taproot_optional,
399                 set_taproot_required, supports_taproot, requires_taproot);
400         define_feature!(39, OnionMessages, [InitContext, NodeContext],
401                 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
402                 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
403         define_feature!(45, ChannelType, [InitContext, NodeContext],
404                 "Feature flags for `option_channel_type`.", set_channel_type_optional,
405                 set_channel_type_required, supports_channel_type, requires_channel_type);
406         define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
407                 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
408                 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
409         define_feature!(49, PaymentMetadata, [Bolt11InvoiceContext],
410                 "Feature flags for payment metadata in invoices.", set_payment_metadata_optional,
411                 set_payment_metadata_required, supports_payment_metadata, requires_payment_metadata);
412         define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
413                 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
414                 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
415         define_feature!(55, Keysend, [NodeContext],
416                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
417                 supports_keysend, requires_keysend);
418         // Note: update the module-level docs when a new feature bit is added!
419
420         #[cfg(test)]
421         define_feature!(123456789, UnknownFeature,
422                 [NodeContext, ChannelContext, Bolt11InvoiceContext, OfferContext, InvoiceRequestContext, Bolt12InvoiceContext, BlindedHopContext],
423                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
424                 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
425 }
426
427 /// Tracks the set of features which a node implements, templated by the context in which it
428 /// appears.
429 ///
430 /// This is not exported to bindings users as we map the concrete feature types below directly instead
431 #[derive(Eq)]
432 pub struct Features<T: sealed::Context> {
433         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
434         flags: Vec<u8>,
435         mark: PhantomData<T>,
436 }
437
438 impl<T: sealed::Context, Rhs: Borrow<Self>> core::ops::BitOrAssign<Rhs> for Features<T> {
439         fn bitor_assign(&mut self, rhs: Rhs) {
440                 let total_feature_len = cmp::max(self.flags.len(), rhs.borrow().flags.len());
441                 self.flags.resize(total_feature_len, 0u8);
442                 for (byte, rhs_byte) in self.flags.iter_mut().zip(rhs.borrow().flags.iter()) {
443                         *byte |= *rhs_byte;
444                 }
445         }
446 }
447
448 impl<T: sealed::Context> core::ops::BitOr for Features<T> {
449         type Output = Self;
450
451         fn bitor(mut self, o: Self) -> Self {
452                 self |= o;
453                 self
454         }
455 }
456
457 impl<T: sealed::Context> Clone for Features<T> {
458         fn clone(&self) -> Self {
459                 Self {
460                         flags: self.flags.clone(),
461                         mark: PhantomData,
462                 }
463         }
464 }
465 impl<T: sealed::Context> Hash for Features<T> {
466         fn hash<H: Hasher>(&self, hasher: &mut H) {
467                 self.flags.hash(hasher);
468         }
469 }
470 impl<T: sealed::Context> PartialEq for Features<T> {
471         fn eq(&self, o: &Self) -> bool {
472                 self.flags.eq(&o.flags)
473         }
474 }
475 impl<T: sealed::Context> PartialOrd for Features<T> {
476         fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
477                 self.flags.partial_cmp(&other.flags)
478         }
479 }
480 impl<T: sealed::Context + Eq> Ord for Features<T> {
481         fn cmp(&self, other: &Self) -> cmp::Ordering {
482                 self.flags.cmp(&other.flags)
483         }
484 }
485 impl<T: sealed::Context> fmt::Debug for Features<T> {
486         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
487                 self.flags.fmt(fmt)
488         }
489 }
490
491 /// Features used within an `init` message.
492 pub type InitFeatures = Features<sealed::InitContext>;
493 /// Features used within a `node_announcement` message.
494 pub type NodeFeatures = Features<sealed::NodeContext>;
495 /// Features used within a `channel_announcement` message.
496 pub type ChannelFeatures = Features<sealed::ChannelContext>;
497 /// Features used within an invoice.
498 pub type Bolt11InvoiceFeatures = Features<sealed::Bolt11InvoiceContext>;
499 /// Features used within an `offer`.
500 pub type OfferFeatures = Features<sealed::OfferContext>;
501 /// Features used within an `invoice_request`.
502 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
503 /// Features used within an `invoice`.
504 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
505 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
506 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
507
508 /// Features used within the channel_type field in an OpenChannel message.
509 ///
510 /// A channel is always of some known "type", describing the transaction formats used and the exact
511 /// semantics of our interaction with our peer.
512 ///
513 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
514 /// the counterparty, only required features are allowed here.
515 ///
516 /// This is serialized differently from other feature types - it is not prefixed by a length, and
517 /// thus must only appear inside a TLV where its length is known in advance.
518 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
519
520 impl InitFeatures {
521         /// Writes all features present up to, and including, 13.
522         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
523                 let len = cmp::min(2, self.flags.len());
524                 (len as u16).write(w)?;
525                 for i in (0..len).rev() {
526                         if i == 0 {
527                                 self.flags[i].write(w)?;
528                         } else {
529                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
530                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
531                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
532                         }
533                 }
534                 Ok(())
535         }
536
537         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
538         /// are included in the result.
539         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
540                 self.to_context_internal()
541         }
542 }
543
544 impl Bolt11InvoiceFeatures {
545         /// Converts `Bolt11InvoiceFeatures` to `Features<C>`. Only known `Bolt11InvoiceFeatures` relevant to
546         /// context `C` are included in the result.
547         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
548                 self.to_context_internal()
549         }
550
551         /// Getting a route for a keysend payment to a private node requires providing the payee's
552         /// features (since they were not announced in a node announcement). However, keysend payments
553         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
554         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
555         /// `Bolt11InvoiceFeatures` for [`find_route`].
556         ///
557         /// MPP keysend is not widely supported yet, so we parameterize support to allow the user to
558         /// choose whether their router should find multi-part routes.
559         ///
560         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
561         /// [`find_route`]: crate::routing::router::find_route
562         pub(crate) fn for_keysend(allow_mpp: bool) -> Bolt11InvoiceFeatures {
563                 let mut res = Bolt11InvoiceFeatures::empty();
564                 res.set_variable_length_onion_optional();
565                 if allow_mpp {
566                         res.set_basic_mpp_optional();
567                 }
568                 res
569         }
570 }
571
572 impl Bolt12InvoiceFeatures {
573         /// Converts [`Bolt12InvoiceFeatures`] to [`Features<C>`]. Only known [`Bolt12InvoiceFeatures`]
574         /// relevant to context `C` are included in the result.
575         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
576                 self.to_context_internal()
577         }
578 }
579
580 impl ChannelTypeFeatures {
581         // Maps the relevant `InitFeatures` to `ChannelTypeFeatures`. Any unknown features to
582         // `ChannelTypeFeatures` are not included in the result.
583         pub(crate) fn from_init(init: &InitFeatures) -> Self {
584                 let mut ret = init.to_context_internal();
585                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
586                 // optional bits and then AND out the optional ones.
587                 for byte in ret.flags.iter_mut() {
588                         *byte |= (*byte & 0b10_10_10_10) >> 1;
589                         *byte &= 0b01_01_01_01;
590                 }
591                 ret
592         }
593
594         /// Constructs a ChannelTypeFeatures with only static_remotekey set
595         pub(crate) fn only_static_remote_key() -> Self {
596                 let mut ret = Self::empty();
597                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
598                 ret
599         }
600
601         /// Constructs a ChannelTypeFeatures with anchors support
602         pub(crate) fn anchors_zero_htlc_fee_and_dependencies() -> Self {
603                 let mut ret = Self::empty();
604                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
605                 <sealed::ChannelTypeContext as sealed::AnchorsZeroFeeHtlcTx>::set_required_bit(&mut ret.flags);
606                 ret
607         }
608 }
609
610 impl ToBase32 for Bolt11InvoiceFeatures {
611         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
612                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
613                 // minus one before dividing
614                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
615                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
616                 for (byte_idx, byte) in self.flags.iter().enumerate() {
617                         let bit_pos_from_left_0_indexed = byte_idx * 8;
618                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
619                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
620                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
621                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
622                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
623                         if new_u5_idx > 0 {
624                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
625                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
626                         }
627                         if new_u5_idx > 1 {
628                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
629                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
630                         }
631                 }
632                 // Trim the highest feature bits.
633                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
634                         res_u5s.remove(0);
635                 }
636                 writer.write(&res_u5s)
637         }
638 }
639
640 impl Base32Len for Bolt11InvoiceFeatures {
641         fn base32_len(&self) -> usize {
642                 self.to_base32().len()
643         }
644 }
645
646 impl FromBase32 for Bolt11InvoiceFeatures {
647         type Err = bech32::Error;
648
649         fn from_base32(field_data: &[u5]) -> Result<Bolt11InvoiceFeatures, bech32::Error> {
650                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
651                 // minus one before dividing
652                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
653                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
654                 for (u5_idx, chunk) in field_data.iter().enumerate() {
655                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
656                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
657                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
658                         let chunk_u16 = chunk.to_u8() as u16;
659                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
660                         if new_byte_idx != length_bytes - 1 {
661                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
662                         }
663                 }
664                 // Trim the highest feature bits.
665                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
666                         res_bytes.pop();
667                 }
668                 Ok(Bolt11InvoiceFeatures::from_le_bytes(res_bytes))
669         }
670 }
671
672 impl<T: sealed::Context> Features<T> {
673         /// Create a blank Features with no features set
674         pub fn empty() -> Self {
675                 Features {
676                         flags: Vec::new(),
677                         mark: PhantomData,
678                 }
679         }
680
681         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
682         /// included in the result.
683         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
684                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
685                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
686                 let mut flags = Vec::new();
687                 for (i, byte) in self.flags.iter().enumerate() {
688                         if i < from_byte_count && i < to_byte_count {
689                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
690                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
691                                 flags.push(byte & from_known_features & to_known_features);
692                         }
693                 }
694                 Features::<C> { flags, mark: PhantomData, }
695         }
696
697         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
698         /// most on-the-wire encodings.
699         ///
700         /// This is not exported to bindings users as we don't support export across multiple T
701         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
702                 Features {
703                         flags,
704                         mark: PhantomData,
705                 }
706         }
707
708         #[cfg(test)]
709         /// Gets the underlying flags set, in LE.
710         pub fn le_flags(&self) -> &Vec<u8> {
711                 &self.flags
712         }
713
714         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
715                 for f in self.flags.iter().rev() { // Swap back to big-endian
716                         f.write(w)?;
717                 }
718                 Ok(())
719         }
720
721         fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
722                 flags.reverse(); // Swap to little-endian
723                 Self {
724                         flags,
725                         mark: PhantomData,
726                 }
727         }
728
729         pub(crate) fn supports_any_optional_bits(&self) -> bool {
730                 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
731         }
732
733         /// Returns true if this `Features` object contains required features unknown by `other`.
734         pub fn requires_unknown_bits_from(&self, other: &Self) -> bool {
735                 // Bitwise AND-ing with all even bits set except for known features will select required
736                 // unknown features.
737                 self.flags.iter().enumerate().any(|(i, &byte)| {
738                         const REQUIRED_FEATURES: u8 = 0b01_01_01_01;
739                         const OPTIONAL_FEATURES: u8 = 0b10_10_10_10;
740                         let unknown_features = if i < other.flags.len() {
741                                 // Form a mask similar to !T::KNOWN_FEATURE_MASK only for `other`
742                                 !(other.flags[i]
743                                         | ((other.flags[i] >> 1) & REQUIRED_FEATURES)
744                                         | ((other.flags[i] << 1) & OPTIONAL_FEATURES))
745                         } else {
746                                 0b11_11_11_11
747                         };
748                         (byte & (REQUIRED_FEATURES & unknown_features)) != 0
749                 })
750         }
751
752         /// Returns true if this `Features` object contains unknown feature flags which are set as
753         /// "required".
754         pub fn requires_unknown_bits(&self) -> bool {
755                 // Bitwise AND-ing with all even bits set except for known features will select required
756                 // unknown features.
757                 let byte_count = T::KNOWN_FEATURE_MASK.len();
758                 self.flags.iter().enumerate().any(|(i, &byte)| {
759                         let required_features = 0b01_01_01_01;
760                         let unknown_features = if i < byte_count {
761                                 !T::KNOWN_FEATURE_MASK[i]
762                         } else {
763                                 0b11_11_11_11
764                         };
765                         (byte & (required_features & unknown_features)) != 0
766                 })
767         }
768
769         pub(crate) fn supports_unknown_bits(&self) -> bool {
770                 // Bitwise AND-ing with all even and odd bits set except for known features will select
771                 // both required and optional unknown features.
772                 let byte_count = T::KNOWN_FEATURE_MASK.len();
773                 self.flags.iter().enumerate().any(|(i, &byte)| {
774                         let unknown_features = if i < byte_count {
775                                 !T::KNOWN_FEATURE_MASK[i]
776                         } else {
777                                 0b11_11_11_11
778                         };
779                         (byte & unknown_features) != 0
780                 })
781         }
782
783         // Returns true if the features within `self` are a subset of the features within `other`.
784         pub(crate) fn is_subset(&self, other: &Self) -> bool {
785                 for (idx, byte) in self.flags.iter().enumerate() {
786                         if let Some(other_byte) = other.flags.get(idx) {
787                                 if byte & other_byte != *byte {
788                                         // `self` has bits set that `other` doesn't.
789                                         return false;
790                                 }
791                         } else {
792                                 if *byte > 0 {
793                                         // `self` has a non-zero byte that `other` doesn't.
794                                         return false;
795                                 }
796                         }
797                 }
798                 true
799         }
800
801         /// Sets a required custom feature bit. Errors if `bit` is outside the custom range as defined
802         /// by [bLIP 2] or if it is a known `T` feature.
803         ///
804         /// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
805         /// be set instead (i.e., `bit - 1`).
806         ///
807         /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
808         pub fn set_required_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
809                 self.set_custom_bit(bit - (bit % 2))
810         }
811
812         /// Sets an optional custom feature bit. Errors if `bit` is outside the custom range as defined
813         /// by [bLIP 2] or if it is a known `T` feature.
814         ///
815         /// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
816         /// set instead (i.e., `bit + 1`).
817         ///
818         /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
819         pub fn set_optional_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
820                 self.set_custom_bit(bit + (1 - (bit % 2)))
821         }
822
823         fn set_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
824                 if bit < 256 {
825                         return Err(());
826                 }
827
828                 let byte_offset = bit / 8;
829                 let mask = 1 << (bit - 8 * byte_offset);
830                 if byte_offset < T::KNOWN_FEATURE_MASK.len() {
831                         if (T::KNOWN_FEATURE_MASK[byte_offset] & mask) != 0 {
832                                 return Err(());
833                         }
834                 }
835
836                 if self.flags.len() <= byte_offset {
837                         self.flags.resize(byte_offset + 1, 0u8);
838                 }
839
840                 self.flags[byte_offset] |= mask;
841
842                 Ok(())
843         }
844 }
845
846 impl<T: sealed::UpfrontShutdownScript> Features<T> {
847         #[cfg(test)]
848         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
849                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
850                 self
851         }
852 }
853
854 impl<T: sealed::ShutdownAnySegwit> Features<T> {
855         #[cfg(test)]
856         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
857                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
858                 self
859         }
860 }
861
862 impl<T: sealed::Wumbo> Features<T> {
863         #[cfg(test)]
864         pub(crate) fn clear_wumbo(mut self) -> Self {
865                 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
866                 self
867         }
868 }
869
870 impl<T: sealed::SCIDPrivacy> Features<T> {
871         pub(crate) fn clear_scid_privacy(&mut self) {
872                 <T as sealed::SCIDPrivacy>::clear_bits(&mut self.flags);
873         }
874 }
875
876 impl<T: sealed::AnchorsZeroFeeHtlcTx> Features<T> {
877         pub(crate) fn clear_anchors_zero_fee_htlc_tx(&mut self) {
878                 <T as sealed::AnchorsZeroFeeHtlcTx>::clear_bits(&mut self.flags);
879         }
880 }
881
882 #[cfg(test)]
883 impl<T: sealed::UnknownFeature> Features<T> {
884         pub(crate) fn unknown() -> Self {
885                 let mut features = Self::empty();
886                 features.set_unknown_feature_required();
887                 features
888         }
889 }
890
891 macro_rules! impl_feature_len_prefixed_write {
892         ($features: ident) => {
893                 impl Writeable for $features {
894                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
895                                 (self.flags.len() as u16).write(w)?;
896                                 self.write_be(w)
897                         }
898                 }
899                 impl Readable for $features {
900                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
901                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
902                         }
903                 }
904         }
905 }
906 impl_feature_len_prefixed_write!(InitFeatures);
907 impl_feature_len_prefixed_write!(ChannelFeatures);
908 impl_feature_len_prefixed_write!(NodeFeatures);
909 impl_feature_len_prefixed_write!(Bolt11InvoiceFeatures);
910 impl_feature_len_prefixed_write!(Bolt12InvoiceFeatures);
911 impl_feature_len_prefixed_write!(BlindedHopFeatures);
912
913 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
914 macro_rules! impl_feature_tlv_write {
915         ($features: ident) => {
916                 impl Writeable for $features {
917                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
918                                 WithoutLength(self).write(w)
919                         }
920                 }
921                 impl Readable for $features {
922                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
923                                 Ok(WithoutLength::<Self>::read(r)?.0)
924                         }
925                 }
926         }
927 }
928
929 impl_feature_tlv_write!(ChannelTypeFeatures);
930
931 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
932 // requires a length but the former does not.
933
934 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
935         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
936                 self.0.write_be(w)
937         }
938 }
939
940 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
941         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
942                 let v = io_extras::read_to_end(r)?;
943                 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
944         }
945 }
946
947 #[cfg(test)]
948 mod tests {
949         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, Bolt11InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
950         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
951         use crate::util::ser::{Readable, WithoutLength, Writeable};
952
953         #[test]
954         fn sanity_test_unknown_bits() {
955                 let features = ChannelFeatures::empty();
956                 assert!(!features.requires_unknown_bits());
957                 assert!(!features.supports_unknown_bits());
958
959                 let mut features = ChannelFeatures::empty();
960                 features.set_unknown_feature_required();
961                 assert!(features.requires_unknown_bits());
962                 assert!(features.supports_unknown_bits());
963
964                 let mut features = ChannelFeatures::empty();
965                 features.set_unknown_feature_optional();
966                 assert!(!features.requires_unknown_bits());
967                 assert!(features.supports_unknown_bits());
968         }
969
970         #[test]
971         fn requires_unknown_bits_from() {
972                 let mut features1 = InitFeatures::empty();
973                 let mut features2 = InitFeatures::empty();
974                 assert!(!features1.requires_unknown_bits_from(&features2));
975                 assert!(!features2.requires_unknown_bits_from(&features1));
976
977                 features1.set_data_loss_protect_required();
978                 assert!(features1.requires_unknown_bits_from(&features2));
979                 assert!(!features2.requires_unknown_bits_from(&features1));
980
981                 features2.set_data_loss_protect_optional();
982                 assert!(!features1.requires_unknown_bits_from(&features2));
983                 assert!(!features2.requires_unknown_bits_from(&features1));
984
985                 features2.set_gossip_queries_required();
986                 assert!(!features1.requires_unknown_bits_from(&features2));
987                 assert!(features2.requires_unknown_bits_from(&features1));
988
989                 features1.set_gossip_queries_optional();
990                 assert!(!features1.requires_unknown_bits_from(&features2));
991                 assert!(!features2.requires_unknown_bits_from(&features1));
992
993                 features1.set_variable_length_onion_required();
994                 assert!(features1.requires_unknown_bits_from(&features2));
995                 assert!(!features2.requires_unknown_bits_from(&features1));
996
997                 features2.set_variable_length_onion_optional();
998                 assert!(!features1.requires_unknown_bits_from(&features2));
999                 assert!(!features2.requires_unknown_bits_from(&features1));
1000
1001                 features1.set_basic_mpp_required();
1002                 features2.set_wumbo_required();
1003                 assert!(features1.requires_unknown_bits_from(&features2));
1004                 assert!(features2.requires_unknown_bits_from(&features1));
1005         }
1006
1007         #[test]
1008         fn convert_to_context_with_relevant_flags() {
1009                 let mut init_features = InitFeatures::empty();
1010                 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
1011                 // converted as it's only relevant in an init context).
1012                 init_features.set_initial_routing_sync_required();
1013                 init_features.set_data_loss_protect_required();
1014                 init_features.set_variable_length_onion_required();
1015                 init_features.set_static_remote_key_required();
1016                 init_features.set_payment_secret_required();
1017                 init_features.set_basic_mpp_optional();
1018                 init_features.set_wumbo_optional();
1019                 init_features.set_anchors_zero_fee_htlc_tx_optional();
1020                 init_features.set_shutdown_any_segwit_optional();
1021                 init_features.set_onion_messages_optional();
1022                 init_features.set_channel_type_optional();
1023                 init_features.set_scid_privacy_optional();
1024                 init_features.set_zero_conf_optional();
1025
1026                 assert!(init_features.initial_routing_sync());
1027                 assert!(!init_features.supports_upfront_shutdown_script());
1028                 assert!(!init_features.supports_gossip_queries());
1029
1030                 let node_features: NodeFeatures = init_features.to_context();
1031                 {
1032                         // Check that the flags are as expected:
1033                         // - option_data_loss_protect (req)
1034                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
1035                         // - basic_mpp | wumbo | anchors_zero_fee_htlc_tx
1036                         // - opt_shutdown_anysegwit
1037                         // - onion_messages
1038                         // - option_channel_type | option_scid_alias
1039                         // - option_zeroconf
1040                         assert_eq!(node_features.flags.len(), 7);
1041                         assert_eq!(node_features.flags[0], 0b00000001);
1042                         assert_eq!(node_features.flags[1], 0b01010001);
1043                         assert_eq!(node_features.flags[2], 0b10001010);
1044                         assert_eq!(node_features.flags[3], 0b00001000);
1045                         assert_eq!(node_features.flags[4], 0b10000000);
1046                         assert_eq!(node_features.flags[5], 0b10100000);
1047                         assert_eq!(node_features.flags[6], 0b00001000);
1048                 }
1049
1050                 // Check that cleared flags are kept blank when converting back:
1051                 // - initial_routing_sync was not applicable to NodeContext
1052                 // - upfront_shutdown_script was cleared before converting
1053                 // - gossip_queries was cleared before converting
1054                 let features: InitFeatures = node_features.to_context_internal();
1055                 assert!(!features.initial_routing_sync());
1056                 assert!(!features.supports_upfront_shutdown_script());
1057                 assert!(!init_features.supports_gossip_queries());
1058         }
1059
1060         #[test]
1061         fn convert_to_context_with_unknown_flags() {
1062                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
1063                 assert!(<sealed::ChannelContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
1064                         <sealed::Bolt11InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
1065                 let mut channel_features = ChannelFeatures::empty();
1066                 channel_features.set_unknown_feature_optional();
1067                 assert!(channel_features.supports_unknown_bits());
1068                 let invoice_features: Bolt11InvoiceFeatures = channel_features.to_context_internal();
1069                 assert!(!invoice_features.supports_unknown_bits());
1070         }
1071
1072         #[test]
1073         fn set_feature_bits() {
1074                 let mut features = Bolt11InvoiceFeatures::empty();
1075                 features.set_basic_mpp_optional();
1076                 features.set_payment_secret_required();
1077                 assert!(features.supports_basic_mpp());
1078                 assert!(!features.requires_basic_mpp());
1079                 assert!(features.requires_payment_secret());
1080                 assert!(features.supports_payment_secret());
1081         }
1082
1083         #[test]
1084         fn set_custom_bits() {
1085                 let mut features = Bolt11InvoiceFeatures::empty();
1086                 features.set_variable_length_onion_optional();
1087                 assert_eq!(features.flags[1], 0b00000010);
1088
1089                 assert!(features.set_optional_custom_bit(255).is_err());
1090                 assert!(features.set_required_custom_bit(256).is_ok());
1091                 assert!(features.set_required_custom_bit(258).is_ok());
1092                 assert_eq!(features.flags[31], 0b00000000);
1093                 assert_eq!(features.flags[32], 0b00000101);
1094
1095                 let known_bit = <sealed::Bolt11InvoiceContext as sealed::PaymentSecret>::EVEN_BIT;
1096                 let byte_offset = <sealed::Bolt11InvoiceContext as sealed::PaymentSecret>::BYTE_OFFSET;
1097                 assert_eq!(byte_offset, 1);
1098                 assert_eq!(features.flags[byte_offset], 0b00000010);
1099                 assert!(features.set_required_custom_bit(known_bit).is_err());
1100                 assert_eq!(features.flags[byte_offset], 0b00000010);
1101
1102                 let mut features = Bolt11InvoiceFeatures::empty();
1103                 assert!(features.set_optional_custom_bit(256).is_ok());
1104                 assert!(features.set_optional_custom_bit(259).is_ok());
1105                 assert_eq!(features.flags[32], 0b00001010);
1106
1107                 let mut features = Bolt11InvoiceFeatures::empty();
1108                 assert!(features.set_required_custom_bit(257).is_ok());
1109                 assert!(features.set_required_custom_bit(258).is_ok());
1110                 assert_eq!(features.flags[32], 0b00000101);
1111         }
1112
1113         #[test]
1114         fn encodes_features_without_length() {
1115                 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1116                 assert_eq!(features.flags.len(), 8);
1117
1118                 let mut serialized_features = Vec::new();
1119                 WithoutLength(&features).write(&mut serialized_features).unwrap();
1120                 assert_eq!(serialized_features.len(), 8);
1121
1122                 let deserialized_features =
1123                         WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
1124                 assert_eq!(features, deserialized_features);
1125         }
1126
1127         #[test]
1128         fn invoice_features_encoding() {
1129                 let features_as_u5s = vec![
1130                         u5::try_from_u8(6).unwrap(),
1131                         u5::try_from_u8(10).unwrap(),
1132                         u5::try_from_u8(25).unwrap(),
1133                         u5::try_from_u8(1).unwrap(),
1134                         u5::try_from_u8(10).unwrap(),
1135                         u5::try_from_u8(0).unwrap(),
1136                         u5::try_from_u8(20).unwrap(),
1137                         u5::try_from_u8(2).unwrap(),
1138                         u5::try_from_u8(0).unwrap(),
1139                         u5::try_from_u8(6).unwrap(),
1140                         u5::try_from_u8(0).unwrap(),
1141                         u5::try_from_u8(16).unwrap(),
1142                         u5::try_from_u8(1).unwrap(),
1143                 ];
1144                 let features = Bolt11InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1145
1146                 // Test length calculation.
1147                 assert_eq!(features.base32_len(), 13);
1148
1149                 // Test serialization.
1150                 let features_serialized = features.to_base32();
1151                 assert_eq!(features_as_u5s, features_serialized);
1152
1153                 // Test deserialization.
1154                 let features_deserialized = Bolt11InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
1155                 assert_eq!(features, features_deserialized);
1156         }
1157
1158         #[test]
1159         fn test_channel_type_mapping() {
1160                 // If we map an Bolt11InvoiceFeatures with StaticRemoteKey optional, it should map into a
1161                 // required-StaticRemoteKey ChannelTypeFeatures.
1162                 let mut init_features = InitFeatures::empty();
1163                 init_features.set_static_remote_key_optional();
1164                 let converted_features = ChannelTypeFeatures::from_init(&init_features);
1165                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
1166                 assert!(!converted_features.supports_any_optional_bits());
1167                 assert!(converted_features.requires_static_remote_key());
1168         }
1169 }