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[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 //! [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
69 //! [messages]: crate::ln::msgs
70
71 use crate::{io, io_extras};
72 use crate::prelude::*;
73 use core::{cmp, fmt};
74 use core::hash::{Hash, Hasher};
75 use core::marker::PhantomData;
76
77 use bitcoin::bech32;
78 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
79 use crate::ln::msgs::DecodeError;
80 use crate::util::ser::{Readable, WithoutLength, Writeable, Writer};
81
82 mod sealed {
83         use crate::prelude::*;
84         use crate::ln::features::Features;
85
86         /// The context in which [`Features`] are applicable. Defines which features are known to the
87         /// implementation, though specification of them as required or optional is up to the code
88         /// constructing a features object.
89         pub trait Context {
90                 /// Bitmask for selecting features that are known to the implementation.
91                 const KNOWN_FEATURE_MASK: &'static [u8];
92         }
93
94         /// Defines a [`Context`] by stating which features it requires and which are optional. Features
95         /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
96         /// feature identifiers.
97         macro_rules! define_context {
98                 ($context: ident, [$( $( $known_feature: ident )|*, )*]) => {
99                         #[derive(Eq, PartialEq)]
100                         pub struct $context {}
101
102                         impl Context for $context {
103                                 const KNOWN_FEATURE_MASK: &'static [u8] = &[
104                                         $(
105                                                 0b00_00_00_00 $(|
106                                                         <Self as $known_feature>::REQUIRED_MASK |
107                                                         <Self as $known_feature>::OPTIONAL_MASK)*,
108                                         )*
109                                 ];
110                         }
111
112                         impl alloc::fmt::Display for Features<$context> {
113                                 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
114                                         $(
115                                                 $(
116                                                         fmt.write_fmt(format_args!("{}: {}, ", stringify!($known_feature),
117                                                                 if <$context as $known_feature>::requires_feature(&self.flags) { "required" }
118                                                                 else if <$context as $known_feature>::supports_feature(&self.flags) { "supported" }
119                                                                 else { "not supported" }))?;
120                                                 )*
121                                                 {} // Rust gets mad if we only have a $()* block here, so add a dummy {}
122                                         )*
123                                         fmt.write_fmt(format_args!("unknown flags: {}",
124                                                 if self.requires_unknown_bits() { "required" }
125                                                 else if self.supports_unknown_bits() { "supported" } else { "none" }))
126                                 }
127                         }
128                 };
129         }
130
131         define_context!(InitContext, [
132                 // Byte 0
133                 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
134                 // Byte 1
135                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
136                 // Byte 2
137                 BasicMPP | Wumbo | AnchorsZeroFeeHtlcTx,
138                 // Byte 3
139                 ShutdownAnySegwit,
140                 // Byte 4
141                 OnionMessages,
142                 // Byte 5
143                 ChannelType | SCIDPrivacy,
144                 // Byte 6
145                 ZeroConf,
146         ]);
147         define_context!(NodeContext, [
148                 // Byte 0
149                 DataLossProtect | UpfrontShutdownScript | GossipQueries,
150                 // Byte 1
151                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
152                 // Byte 2
153                 BasicMPP | Wumbo | AnchorsZeroFeeHtlcTx,
154                 // Byte 3
155                 ShutdownAnySegwit,
156                 // Byte 4
157                 OnionMessages,
158                 // Byte 5
159                 ChannelType | SCIDPrivacy,
160                 // Byte 6
161                 ZeroConf | Keysend,
162         ]);
163         define_context!(ChannelContext, []);
164         define_context!(InvoiceContext, [
165                 // Byte 0
166                 ,
167                 // Byte 1
168                 VariableLengthOnion | PaymentSecret,
169                 // Byte 2
170                 BasicMPP,
171                 // Byte 3
172                 ,
173                 // Byte 4
174                 ,
175                 // Byte 5
176                 ,
177                 // Byte 6
178                 PaymentMetadata,
179         ]);
180         define_context!(OfferContext, []);
181         define_context!(InvoiceRequestContext, []);
182         define_context!(Bolt12InvoiceContext, [
183                 // Byte 0
184                 ,
185                 // Byte 1
186                 ,
187                 // Byte 2
188                 BasicMPP,
189         ]);
190         define_context!(BlindedHopContext, []);
191         // This isn't a "real" feature context, and is only used in the channel_type field in an
192         // `OpenChannel` message.
193         define_context!(ChannelTypeContext, [
194                 // Byte 0
195                 ,
196                 // Byte 1
197                 StaticRemoteKey,
198                 // Byte 2
199                 AnchorsZeroFeeHtlcTx,
200                 // Byte 3
201                 ,
202                 // Byte 4
203                 ,
204                 // Byte 5
205                 SCIDPrivacy,
206                 // Byte 6
207                 ZeroConf,
208         ]);
209
210         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
211         /// useful for manipulating feature flags.
212         macro_rules! define_feature {
213                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
214                  $required_setter: ident, $supported_getter: ident) => {
215                         #[doc = $doc]
216                         ///
217                         /// See [BOLT #9] for details.
218                         ///
219                         /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
220                         pub trait $feature: Context {
221                                 /// The bit used to signify that the feature is required.
222                                 const EVEN_BIT: usize = $odd_bit - 1;
223
224                                 /// The bit used to signify that the feature is optional.
225                                 const ODD_BIT: usize = $odd_bit;
226
227                                 /// Assertion that [`EVEN_BIT`] is actually even.
228                                 ///
229                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
230                                 const ASSERT_EVEN_BIT_PARITY: usize;
231
232                                 /// Assertion that [`ODD_BIT`] is actually odd.
233                                 ///
234                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
235                                 const ASSERT_ODD_BIT_PARITY: usize;
236
237                                 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
238                                 ///
239                                 /// [`KNOWN_FEATURE_MASK`]: Context::KNOWN_FEATURE_MASK
240                                 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
241                                 const ASSERT_BITS_IN_MASK: u8;
242
243                                 /// The byte where the feature is set.
244                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
245
246                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
247                                 ///
248                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
249                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
250
251                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
252                                 ///
253                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
254                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
255
256                                 /// Returns whether the feature is required by the given flags.
257                                 #[inline]
258                                 fn requires_feature(flags: &Vec<u8>) -> bool {
259                                         flags.len() > Self::BYTE_OFFSET &&
260                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
261                                 }
262
263                                 /// Returns whether the feature is supported by the given flags.
264                                 #[inline]
265                                 fn supports_feature(flags: &Vec<u8>) -> bool {
266                                         flags.len() > Self::BYTE_OFFSET &&
267                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
268                                 }
269
270                                 /// Sets the feature's required (even) bit in the given flags.
271                                 #[inline]
272                                 fn set_required_bit(flags: &mut Vec<u8>) {
273                                         if flags.len() <= Self::BYTE_OFFSET {
274                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
275                                         }
276
277                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
278                                         flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
279                                 }
280
281                                 /// Sets the feature's optional (odd) bit in the given flags.
282                                 #[inline]
283                                 fn set_optional_bit(flags: &mut Vec<u8>) {
284                                         if flags.len() <= Self::BYTE_OFFSET {
285                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
286                                         }
287
288                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
289                                 }
290
291                                 /// Clears the feature's required (even) and optional (odd) bits from the given
292                                 /// flags.
293                                 #[inline]
294                                 fn clear_bits(flags: &mut Vec<u8>) {
295                                         if flags.len() > Self::BYTE_OFFSET {
296                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
297                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
298                                         }
299
300                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
301                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
302                                         flags.resize(size, 0u8);
303                                 }
304                         }
305
306                         impl <T: $feature> Features<T> {
307                                 /// Set this feature as optional.
308                                 pub fn $optional_setter(&mut self) {
309                                         <T as $feature>::set_optional_bit(&mut self.flags);
310                                 }
311
312                                 /// Set this feature as required.
313                                 pub fn $required_setter(&mut self) {
314                                         <T as $feature>::set_required_bit(&mut self.flags);
315                                 }
316
317                                 /// Checks if this feature is supported.
318                                 pub fn $supported_getter(&self) -> bool {
319                                         <T as $feature>::supports_feature(&self.flags)
320                                 }
321                         }
322
323                         $(
324                                 impl $feature for $context {
325                                         // EVEN_BIT % 2 == 0
326                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
327
328                                         // ODD_BIT % 2 == 1
329                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
330
331                                         // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
332                                         #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
333                                         const ASSERT_BITS_IN_MASK: u8 =
334                                                 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
335                                                  >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
336                                 }
337                         )*
338                 };
339                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
340                  $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
341                         define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
342                         impl <T: $feature> Features<T> {
343                                 /// Checks if this feature is required.
344                                 pub fn $required_getter(&self) -> bool {
345                                         <T as $feature>::requires_feature(&self.flags)
346                                 }
347                         }
348                 }
349         }
350
351         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
352                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
353                 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
354         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
355         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
356                 set_initial_routing_sync_optional, set_initial_routing_sync_required,
357                 initial_routing_sync);
358         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
359                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
360                 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
361                 requires_upfront_shutdown_script);
362         define_feature!(7, GossipQueries, [InitContext, NodeContext],
363                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
364                 supports_gossip_queries, requires_gossip_queries);
365         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
366                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
367                 set_variable_length_onion_required, supports_variable_length_onion,
368                 requires_variable_length_onion);
369         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
370                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
371                 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
372         define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
373                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
374                 supports_payment_secret, requires_payment_secret);
375         define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext, Bolt12InvoiceContext],
376                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
377                 supports_basic_mpp, requires_basic_mpp);
378         define_feature!(19, Wumbo, [InitContext, NodeContext],
379                 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
380                 supports_wumbo, requires_wumbo);
381         define_feature!(23, AnchorsZeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
382                 "Feature flags for `option_anchors_zero_fee_htlc_tx`.", set_anchors_zero_fee_htlc_tx_optional,
383                 set_anchors_zero_fee_htlc_tx_required, supports_anchors_zero_fee_htlc_tx, requires_anchors_zero_fee_htlc_tx);
384         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
385                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
386                 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
387         define_feature!(39, OnionMessages, [InitContext, NodeContext],
388                 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
389                 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
390         define_feature!(45, ChannelType, [InitContext, NodeContext],
391                 "Feature flags for `option_channel_type`.", set_channel_type_optional,
392                 set_channel_type_required, supports_channel_type, requires_channel_type);
393         define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
394                 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
395                 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
396         define_feature!(49, PaymentMetadata, [InvoiceContext],
397                 "Feature flags for payment metadata in invoices.", set_payment_metadata_optional,
398                 set_payment_metadata_required, supports_payment_metadata, requires_payment_metadata);
399         define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
400                 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
401                 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
402         define_feature!(55, Keysend, [NodeContext],
403                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
404                 supports_keysend, requires_keysend);
405         // Note: update the module-level docs when a new feature bit is added!
406
407         #[cfg(test)]
408         define_feature!(123456789, UnknownFeature,
409                 [NodeContext, ChannelContext, InvoiceContext, OfferContext, InvoiceRequestContext, Bolt12InvoiceContext, BlindedHopContext],
410                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
411                 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
412 }
413
414 /// Tracks the set of features which a node implements, templated by the context in which it
415 /// appears.
416 ///
417 /// This is not exported to bindings users as we map the concrete feature types below directly instead
418 #[derive(Eq)]
419 pub struct Features<T: sealed::Context> {
420         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
421         flags: Vec<u8>,
422         mark: PhantomData<T>,
423 }
424
425 impl <T: sealed::Context> Features<T> {
426         pub(crate) fn or(mut self, o: Self) -> Self {
427                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
428                 self.flags.resize(total_feature_len, 0u8);
429                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
430                         *byte |= *o_byte;
431                 }
432                 self
433         }
434 }
435
436 impl<T: sealed::Context> Clone for Features<T> {
437         fn clone(&self) -> Self {
438                 Self {
439                         flags: self.flags.clone(),
440                         mark: PhantomData,
441                 }
442         }
443 }
444 impl<T: sealed::Context> Hash for Features<T> {
445         fn hash<H: Hasher>(&self, hasher: &mut H) {
446                 self.flags.hash(hasher);
447         }
448 }
449 impl<T: sealed::Context> PartialEq for Features<T> {
450         fn eq(&self, o: &Self) -> bool {
451                 self.flags.eq(&o.flags)
452         }
453 }
454 impl<T: sealed::Context> fmt::Debug for Features<T> {
455         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
456                 self.flags.fmt(fmt)
457         }
458 }
459
460 /// Features used within an `init` message.
461 pub type InitFeatures = Features<sealed::InitContext>;
462 /// Features used within a `node_announcement` message.
463 pub type NodeFeatures = Features<sealed::NodeContext>;
464 /// Features used within a `channel_announcement` message.
465 pub type ChannelFeatures = Features<sealed::ChannelContext>;
466 /// Features used within an invoice.
467 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
468 /// Features used within an `offer`.
469 pub type OfferFeatures = Features<sealed::OfferContext>;
470 /// Features used within an `invoice_request`.
471 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
472 /// Features used within an `invoice`.
473 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
474 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
475 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
476
477 /// Features used within the channel_type field in an OpenChannel message.
478 ///
479 /// A channel is always of some known "type", describing the transaction formats used and the exact
480 /// semantics of our interaction with our peer.
481 ///
482 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
483 /// the counterparty, only required features are allowed here.
484 ///
485 /// This is serialized differently from other feature types - it is not prefixed by a length, and
486 /// thus must only appear inside a TLV where its length is known in advance.
487 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
488
489 impl InitFeatures {
490         /// Writes all features present up to, and including, 13.
491         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
492                 let len = cmp::min(2, self.flags.len());
493                 (len as u16).write(w)?;
494                 for i in (0..len).rev() {
495                         if i == 0 {
496                                 self.flags[i].write(w)?;
497                         } else {
498                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
499                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
500                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
501                         }
502                 }
503                 Ok(())
504         }
505
506         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
507         /// are included in the result.
508         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
509                 self.to_context_internal()
510         }
511 }
512
513 impl InvoiceFeatures {
514         /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
515         /// context `C` are included in the result.
516         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
517                 self.to_context_internal()
518         }
519
520         /// Getting a route for a keysend payment to a private node requires providing the payee's
521         /// features (since they were not announced in a node announcement). However, keysend payments
522         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
523         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
524         /// `InvoiceFeatures` for [`find_route`].
525         ///
526         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
527         /// [`find_route`]: crate::routing::router::find_route
528         pub(crate) fn for_keysend() -> InvoiceFeatures {
529                 let mut res = InvoiceFeatures::empty();
530                 res.set_variable_length_onion_optional();
531                 res
532         }
533 }
534
535 impl ChannelTypeFeatures {
536         // Maps the relevant `InitFeatures` to `ChannelTypeFeatures`. Any unknown features to
537         // `ChannelTypeFeatures` are not included in the result.
538         pub(crate) fn from_init(init: &InitFeatures) -> Self {
539                 let mut ret = init.to_context_internal();
540                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
541                 // optional bits and then AND out the optional ones.
542                 for byte in ret.flags.iter_mut() {
543                         *byte |= (*byte & 0b10_10_10_10) >> 1;
544                         *byte &= 0b01_01_01_01;
545                 }
546                 ret
547         }
548
549         /// Constructs a ChannelTypeFeatures with only static_remotekey set
550         pub(crate) fn only_static_remote_key() -> Self {
551                 let mut ret = Self::empty();
552                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
553                 ret
554         }
555 }
556
557 impl ToBase32 for InvoiceFeatures {
558         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
559                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
560                 // minus one before dividing
561                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
562                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
563                 for (byte_idx, byte) in self.flags.iter().enumerate() {
564                         let bit_pos_from_left_0_indexed = byte_idx * 8;
565                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
566                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
567                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
568                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
569                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
570                         if new_u5_idx > 0 {
571                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
572                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
573                         }
574                         if new_u5_idx > 1 {
575                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
576                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
577                         }
578                 }
579                 // Trim the highest feature bits.
580                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
581                         res_u5s.remove(0);
582                 }
583                 writer.write(&res_u5s)
584         }
585 }
586
587 impl Base32Len for InvoiceFeatures {
588         fn base32_len(&self) -> usize {
589                 self.to_base32().len()
590         }
591 }
592
593 impl FromBase32 for InvoiceFeatures {
594         type Err = bech32::Error;
595
596         fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
597                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
598                 // minus one before dividing
599                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
600                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
601                 for (u5_idx, chunk) in field_data.iter().enumerate() {
602                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
603                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
604                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
605                         let chunk_u16 = chunk.to_u8() as u16;
606                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
607                         if new_byte_idx != length_bytes - 1 {
608                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
609                         }
610                 }
611                 // Trim the highest feature bits.
612                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
613                         res_bytes.pop();
614                 }
615                 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
616         }
617 }
618
619 impl<T: sealed::Context> Features<T> {
620         /// Create a blank Features with no features set
621         pub fn empty() -> Self {
622                 Features {
623                         flags: Vec::new(),
624                         mark: PhantomData,
625                 }
626         }
627
628         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
629         /// included in the result.
630         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
631                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
632                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
633                 let mut flags = Vec::new();
634                 for (i, byte) in self.flags.iter().enumerate() {
635                         if i < from_byte_count && i < to_byte_count {
636                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
637                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
638                                 flags.push(byte & from_known_features & to_known_features);
639                         }
640                 }
641                 Features::<C> { flags, mark: PhantomData, }
642         }
643
644         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
645         /// most on-the-wire encodings.
646         ///
647         /// This is not exported to bindings users as we don't support export across multiple T
648         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
649                 Features {
650                         flags,
651                         mark: PhantomData,
652                 }
653         }
654
655         #[cfg(test)]
656         /// Gets the underlying flags set, in LE.
657         pub fn le_flags(&self) -> &Vec<u8> {
658                 &self.flags
659         }
660
661         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
662                 for f in self.flags.iter().rev() { // Swap back to big-endian
663                         f.write(w)?;
664                 }
665                 Ok(())
666         }
667
668         fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
669                 flags.reverse(); // Swap to little-endian
670                 Self {
671                         flags,
672                         mark: PhantomData,
673                 }
674         }
675
676         pub(crate) fn supports_any_optional_bits(&self) -> bool {
677                 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
678         }
679
680         /// Returns true if this `Features` object contains unknown feature flags which are set as
681         /// "required".
682         pub fn requires_unknown_bits(&self) -> bool {
683                 // Bitwise AND-ing with all even bits set except for known features will select required
684                 // unknown features.
685                 let byte_count = T::KNOWN_FEATURE_MASK.len();
686                 self.flags.iter().enumerate().any(|(i, &byte)| {
687                         let required_features = 0b01_01_01_01;
688                         let unknown_features = if i < byte_count {
689                                 !T::KNOWN_FEATURE_MASK[i]
690                         } else {
691                                 0b11_11_11_11
692                         };
693                         (byte & (required_features & unknown_features)) != 0
694                 })
695         }
696
697         pub(crate) fn supports_unknown_bits(&self) -> bool {
698                 // Bitwise AND-ing with all even and odd bits set except for known features will select
699                 // both required and optional unknown features.
700                 let byte_count = T::KNOWN_FEATURE_MASK.len();
701                 self.flags.iter().enumerate().any(|(i, &byte)| {
702                         let unknown_features = if i < byte_count {
703                                 !T::KNOWN_FEATURE_MASK[i]
704                         } else {
705                                 0b11_11_11_11
706                         };
707                         (byte & unknown_features) != 0
708                 })
709         }
710
711         // Returns true if the features within `self` are a subset of the features within `other`.
712         pub(crate) fn is_subset(&self, other: &Self) -> bool {
713                 for (idx, byte) in self.flags.iter().enumerate() {
714                         if let Some(other_byte) = other.flags.get(idx) {
715                                 if byte & other_byte != *byte {
716                                         // `self` has bits set that `other` doesn't.
717                                         return false;
718                                 }
719                         } else {
720                                 if *byte > 0 {
721                                         // `self` has a non-zero byte that `other` doesn't.
722                                         return false;
723                                 }
724                         }
725                 }
726                 true
727         }
728 }
729
730 impl<T: sealed::UpfrontShutdownScript> Features<T> {
731         #[cfg(test)]
732         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
733                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
734                 self
735         }
736 }
737
738 impl<T: sealed::ShutdownAnySegwit> Features<T> {
739         #[cfg(test)]
740         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
741                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
742                 self
743         }
744 }
745
746 impl<T: sealed::Wumbo> Features<T> {
747         #[cfg(test)]
748         pub(crate) fn clear_wumbo(mut self) -> Self {
749                 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
750                 self
751         }
752 }
753
754 impl<T: sealed::SCIDPrivacy> Features<T> {
755         pub(crate) fn clear_scid_privacy(&mut self) {
756                 <T as sealed::SCIDPrivacy>::clear_bits(&mut self.flags);
757         }
758 }
759
760 impl<T: sealed::AnchorsZeroFeeHtlcTx> Features<T> {
761         pub(crate) fn clear_anchors_zero_fee_htlc_tx(&mut self) {
762                 <T as sealed::AnchorsZeroFeeHtlcTx>::clear_bits(&mut self.flags);
763         }
764 }
765
766 #[cfg(test)]
767 impl<T: sealed::UnknownFeature> Features<T> {
768         pub(crate) fn unknown() -> Self {
769                 let mut features = Self::empty();
770                 features.set_unknown_feature_required();
771                 features
772         }
773 }
774
775 macro_rules! impl_feature_len_prefixed_write {
776         ($features: ident) => {
777                 impl Writeable for $features {
778                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
779                                 (self.flags.len() as u16).write(w)?;
780                                 self.write_be(w)
781                         }
782                 }
783                 impl Readable for $features {
784                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
785                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
786                         }
787                 }
788         }
789 }
790 impl_feature_len_prefixed_write!(InitFeatures);
791 impl_feature_len_prefixed_write!(ChannelFeatures);
792 impl_feature_len_prefixed_write!(NodeFeatures);
793 impl_feature_len_prefixed_write!(InvoiceFeatures);
794 impl_feature_len_prefixed_write!(BlindedHopFeatures);
795
796 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
797 macro_rules! impl_feature_tlv_write {
798         ($features: ident) => {
799                 impl Writeable for $features {
800                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
801                                 WithoutLength(self).write(w)
802                         }
803                 }
804                 impl Readable for $features {
805                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
806                                 Ok(WithoutLength::<Self>::read(r)?.0)
807                         }
808                 }
809         }
810 }
811
812 impl_feature_tlv_write!(ChannelTypeFeatures);
813
814 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
815 // requires a length but the former does not.
816
817 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
818         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
819                 self.0.write_be(w)
820         }
821 }
822
823 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
824         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
825                 let v = io_extras::read_to_end(r)?;
826                 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
827         }
828 }
829
830 #[cfg(test)]
831 mod tests {
832         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
833         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
834         use crate::util::ser::{Readable, WithoutLength, Writeable};
835
836         #[test]
837         fn sanity_test_unknown_bits() {
838                 let features = ChannelFeatures::empty();
839                 assert!(!features.requires_unknown_bits());
840                 assert!(!features.supports_unknown_bits());
841
842                 let mut features = ChannelFeatures::empty();
843                 features.set_unknown_feature_required();
844                 assert!(features.requires_unknown_bits());
845                 assert!(features.supports_unknown_bits());
846
847                 let mut features = ChannelFeatures::empty();
848                 features.set_unknown_feature_optional();
849                 assert!(!features.requires_unknown_bits());
850                 assert!(features.supports_unknown_bits());
851         }
852
853         #[test]
854         fn convert_to_context_with_relevant_flags() {
855                 let mut init_features = InitFeatures::empty();
856                 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
857                 // converted as it's only relevant in an init context).
858                 init_features.set_initial_routing_sync_required();
859                 init_features.set_data_loss_protect_optional();
860                 init_features.set_variable_length_onion_required();
861                 init_features.set_static_remote_key_required();
862                 init_features.set_payment_secret_required();
863                 init_features.set_basic_mpp_optional();
864                 init_features.set_wumbo_optional();
865                 init_features.set_shutdown_any_segwit_optional();
866                 init_features.set_onion_messages_optional();
867                 init_features.set_channel_type_optional();
868                 init_features.set_scid_privacy_optional();
869                 init_features.set_zero_conf_optional();
870                 init_features.set_anchors_zero_fee_htlc_tx_optional();
871
872                 assert!(init_features.initial_routing_sync());
873                 assert!(!init_features.supports_upfront_shutdown_script());
874                 assert!(!init_features.supports_gossip_queries());
875
876                 let node_features: NodeFeatures = init_features.to_context();
877                 {
878                         // Check that the flags are as expected:
879                         // - option_data_loss_protect
880                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
881                         // - basic_mpp | wumbo
882                         // - opt_shutdown_anysegwit
883                         // - onion_messages
884                         // - option_channel_type | option_scid_alias
885                         // - option_zeroconf
886                         assert_eq!(node_features.flags.len(), 7);
887                         assert_eq!(node_features.flags[0], 0b00000010);
888                         assert_eq!(node_features.flags[1], 0b01010001);
889                         assert_eq!(node_features.flags[2], 0b10001010);
890                         assert_eq!(node_features.flags[3], 0b00001000);
891                         assert_eq!(node_features.flags[4], 0b10000000);
892                         assert_eq!(node_features.flags[5], 0b10100000);
893                         assert_eq!(node_features.flags[6], 0b00001000);
894                 }
895
896                 // Check that cleared flags are kept blank when converting back:
897                 // - initial_routing_sync was not applicable to NodeContext
898                 // - upfront_shutdown_script was cleared before converting
899                 // - gossip_queries was cleared before converting
900                 let features: InitFeatures = node_features.to_context_internal();
901                 assert!(!features.initial_routing_sync());
902                 assert!(!features.supports_upfront_shutdown_script());
903                 assert!(!init_features.supports_gossip_queries());
904         }
905
906         #[test]
907         fn convert_to_context_with_unknown_flags() {
908                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
909                 assert!(<sealed::ChannelContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
910                         <sealed::InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
911                 let mut channel_features = ChannelFeatures::empty();
912                 channel_features.set_unknown_feature_optional();
913                 assert!(channel_features.supports_unknown_bits());
914                 let invoice_features: InvoiceFeatures = channel_features.to_context_internal();
915                 assert!(!invoice_features.supports_unknown_bits());
916         }
917
918         #[test]
919         fn set_feature_bits() {
920                 let mut features = InvoiceFeatures::empty();
921                 features.set_basic_mpp_optional();
922                 features.set_payment_secret_required();
923                 assert!(features.supports_basic_mpp());
924                 assert!(!features.requires_basic_mpp());
925                 assert!(features.requires_payment_secret());
926                 assert!(features.supports_payment_secret());
927         }
928
929         #[test]
930         fn encodes_features_without_length() {
931                 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
932                 assert_eq!(features.flags.len(), 8);
933
934                 let mut serialized_features = Vec::new();
935                 WithoutLength(&features).write(&mut serialized_features).unwrap();
936                 assert_eq!(serialized_features.len(), 8);
937
938                 let deserialized_features =
939                         WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
940                 assert_eq!(features, deserialized_features);
941         }
942
943         #[test]
944         fn invoice_features_encoding() {
945                 let features_as_u5s = vec![
946                         u5::try_from_u8(6).unwrap(),
947                         u5::try_from_u8(10).unwrap(),
948                         u5::try_from_u8(25).unwrap(),
949                         u5::try_from_u8(1).unwrap(),
950                         u5::try_from_u8(10).unwrap(),
951                         u5::try_from_u8(0).unwrap(),
952                         u5::try_from_u8(20).unwrap(),
953                         u5::try_from_u8(2).unwrap(),
954                         u5::try_from_u8(0).unwrap(),
955                         u5::try_from_u8(6).unwrap(),
956                         u5::try_from_u8(0).unwrap(),
957                         u5::try_from_u8(16).unwrap(),
958                         u5::try_from_u8(1).unwrap(),
959                 ];
960                 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
961
962                 // Test length calculation.
963                 assert_eq!(features.base32_len(), 13);
964
965                 // Test serialization.
966                 let features_serialized = features.to_base32();
967                 assert_eq!(features_as_u5s, features_serialized);
968
969                 // Test deserialization.
970                 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
971                 assert_eq!(features, features_deserialized);
972         }
973
974         #[test]
975         fn test_channel_type_mapping() {
976                 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
977                 // required-StaticRemoteKey ChannelTypeFeatures.
978                 let mut init_features = InitFeatures::empty();
979                 init_features.set_static_remote_key_optional();
980                 let converted_features = ChannelTypeFeatures::from_init(&init_features);
981                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
982                 assert!(!converted_features.supports_any_optional_bits());
983                 assert!(converted_features.requires_static_remote_key());
984         }
985 }