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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 //! - `Keysend` - send funds to a node without an invoice
54 //!     (see the [`Keysend` feature assignment proposal](https://github.com/lightning/bolts/issues/605#issuecomment-606679798) for more information).
55 //! - `AnchorsZeroFeeHtlcTx` - requires/supports that commitment transactions include anchor outputs
56 //!   and HTLC transactions are pre-signed with zero fee (see
57 //!   [BOLT-3](https://github.com/lightning/bolts/blob/master/03-transactions.md) for more
58 //!   information).
59 //!
60 //! [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
61 //! [messages]: crate::ln::msgs
62
63 use crate::{io, io_extras};
64 use crate::prelude::*;
65 use core::{cmp, fmt};
66 use core::hash::{Hash, Hasher};
67 use core::marker::PhantomData;
68
69 use bitcoin::bech32;
70 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
71 use crate::ln::msgs::DecodeError;
72 use crate::util::ser::{Readable, WithoutLength, Writeable, Writer};
73
74 mod sealed {
75         use crate::prelude::*;
76         use crate::ln::features::Features;
77
78         /// The context in which [`Features`] are applicable. Defines which features are known to the
79         /// implementation, though specification of them as required or optional is up to the code
80         /// constructing a features object.
81         pub trait Context {
82                 /// Bitmask for selecting features that are known to the implementation.
83                 const KNOWN_FEATURE_MASK: &'static [u8];
84         }
85
86         /// Defines a [`Context`] by stating which features it requires and which are optional. Features
87         /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
88         /// feature identifiers.
89         macro_rules! define_context {
90                 ($context: ident, [$( $( $known_feature: ident )|*, )*]) => {
91                         #[derive(Eq, PartialEq)]
92                         pub struct $context {}
93
94                         impl Context for $context {
95                                 const KNOWN_FEATURE_MASK: &'static [u8] = &[
96                                         $(
97                                                 0b00_00_00_00 $(|
98                                                         <Self as $known_feature>::REQUIRED_MASK |
99                                                         <Self as $known_feature>::OPTIONAL_MASK)*,
100                                         )*
101                                 ];
102                         }
103
104                         impl alloc::fmt::Display for Features<$context> {
105                                 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
106                                         $(
107                                                 $(
108                                                         fmt.write_fmt(format_args!("{}: {}, ", stringify!($known_feature),
109                                                                 if <$context as $known_feature>::requires_feature(&self.flags) { "required" }
110                                                                 else if <$context as $known_feature>::supports_feature(&self.flags) { "supported" }
111                                                                 else { "not supported" }))?;
112                                                 )*
113                                                 {} // Rust gets mad if we only have a $()* block here, so add a dummy {}
114                                         )*
115                                         fmt.write_fmt(format_args!("unknown flags: {}",
116                                                 if self.requires_unknown_bits() { "required" }
117                                                 else if self.supports_unknown_bits() { "supported" } else { "none" }))
118                                 }
119                         }
120                 };
121         }
122
123         define_context!(InitContext, [
124                 // Byte 0
125                 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
126                 // Byte 1
127                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
128                 // Byte 2
129                 BasicMPP | Wumbo | AnchorsZeroFeeHtlcTx,
130                 // Byte 3
131                 ShutdownAnySegwit,
132                 // Byte 4
133                 OnionMessages,
134                 // Byte 5
135                 ChannelType | SCIDPrivacy,
136                 // Byte 6
137                 ZeroConf,
138         ]);
139         define_context!(NodeContext, [
140                 // Byte 0
141                 DataLossProtect | UpfrontShutdownScript | GossipQueries,
142                 // Byte 1
143                 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
144                 // Byte 2
145                 BasicMPP | Wumbo | AnchorsZeroFeeHtlcTx,
146                 // Byte 3
147                 ShutdownAnySegwit,
148                 // Byte 4
149                 OnionMessages,
150                 // Byte 5
151                 ChannelType | SCIDPrivacy,
152                 // Byte 6
153                 ZeroConf | Keysend,
154         ]);
155         define_context!(ChannelContext, []);
156         define_context!(InvoiceContext, [
157                 // Byte 0
158                 ,
159                 // Byte 1
160                 VariableLengthOnion | PaymentSecret,
161                 // Byte 2
162                 BasicMPP,
163                 // Byte 3
164                 ,
165                 // Byte 4
166                 ,
167                 // Byte 5
168                 ,
169                 // Byte 6
170                 PaymentMetadata,
171         ]);
172         define_context!(OfferContext, []);
173         define_context!(InvoiceRequestContext, []);
174         define_context!(Bolt12InvoiceContext, [
175                 // Byte 0
176                 ,
177                 // Byte 1
178                 ,
179                 // Byte 2
180                 BasicMPP,
181         ]);
182         define_context!(BlindedHopContext, []);
183         // This isn't a "real" feature context, and is only used in the channel_type field in an
184         // `OpenChannel` message.
185         define_context!(ChannelTypeContext, [
186                 // Byte 0
187                 ,
188                 // Byte 1
189                 StaticRemoteKey,
190                 // Byte 2
191                 AnchorsZeroFeeHtlcTx,
192                 // Byte 3
193                 ,
194                 // Byte 4
195                 ,
196                 // Byte 5
197                 SCIDPrivacy,
198                 // Byte 6
199                 ZeroConf,
200         ]);
201
202         /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
203         /// useful for manipulating feature flags.
204         macro_rules! define_feature {
205                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
206                  $required_setter: ident, $supported_getter: ident) => {
207                         #[doc = $doc]
208                         ///
209                         /// See [BOLT #9] for details.
210                         ///
211                         /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
212                         pub trait $feature: Context {
213                                 /// The bit used to signify that the feature is required.
214                                 const EVEN_BIT: usize = $odd_bit - 1;
215
216                                 /// The bit used to signify that the feature is optional.
217                                 const ODD_BIT: usize = $odd_bit;
218
219                                 /// Assertion that [`EVEN_BIT`] is actually even.
220                                 ///
221                                 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
222                                 const ASSERT_EVEN_BIT_PARITY: usize;
223
224                                 /// Assertion that [`ODD_BIT`] is actually odd.
225                                 ///
226                                 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
227                                 const ASSERT_ODD_BIT_PARITY: usize;
228
229                                 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
230                                 ///
231                                 /// [`KNOWN_FEATURE_MASK`]: Context::KNOWN_FEATURE_MASK
232                                 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
233                                 const ASSERT_BITS_IN_MASK: u8;
234
235                                 /// The byte where the feature is set.
236                                 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
237
238                                 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
239                                 ///
240                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
241                                 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
242
243                                 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
244                                 ///
245                                 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
246                                 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
247
248                                 /// Returns whether the feature is required by the given flags.
249                                 #[inline]
250                                 fn requires_feature(flags: &Vec<u8>) -> bool {
251                                         flags.len() > Self::BYTE_OFFSET &&
252                                                 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
253                                 }
254
255                                 /// Returns whether the feature is supported by the given flags.
256                                 #[inline]
257                                 fn supports_feature(flags: &Vec<u8>) -> bool {
258                                         flags.len() > Self::BYTE_OFFSET &&
259                                                 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
260                                 }
261
262                                 /// Sets the feature's required (even) bit in the given flags.
263                                 #[inline]
264                                 fn set_required_bit(flags: &mut Vec<u8>) {
265                                         if flags.len() <= Self::BYTE_OFFSET {
266                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
267                                         }
268
269                                         flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
270                                 }
271
272                                 /// Sets the feature's optional (odd) bit in the given flags.
273                                 #[inline]
274                                 fn set_optional_bit(flags: &mut Vec<u8>) {
275                                         if flags.len() <= Self::BYTE_OFFSET {
276                                                 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
277                                         }
278
279                                         flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
280                                 }
281
282                                 /// Clears the feature's required (even) and optional (odd) bits from the given
283                                 /// flags.
284                                 #[inline]
285                                 fn clear_bits(flags: &mut Vec<u8>) {
286                                         if flags.len() > Self::BYTE_OFFSET {
287                                                 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
288                                                 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
289                                         }
290
291                                         let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
292                                         let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
293                                         flags.resize(size, 0u8);
294                                 }
295                         }
296
297                         impl <T: $feature> Features<T> {
298                                 /// Set this feature as optional.
299                                 pub fn $optional_setter(&mut self) {
300                                         <T as $feature>::set_optional_bit(&mut self.flags);
301                                 }
302
303                                 /// Set this feature as required.
304                                 pub fn $required_setter(&mut self) {
305                                         <T as $feature>::set_required_bit(&mut self.flags);
306                                 }
307
308                                 /// Checks if this feature is supported.
309                                 pub fn $supported_getter(&self) -> bool {
310                                         <T as $feature>::supports_feature(&self.flags)
311                                 }
312                         }
313
314                         $(
315                                 impl $feature for $context {
316                                         // EVEN_BIT % 2 == 0
317                                         const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
318
319                                         // ODD_BIT % 2 == 1
320                                         const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
321
322                                         // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
323                                         #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
324                                         const ASSERT_BITS_IN_MASK: u8 =
325                                                 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
326                                                  >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
327                                 }
328                         )*
329                 };
330                 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
331                  $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
332                         define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
333                         impl <T: $feature> Features<T> {
334                                 /// Checks if this feature is required.
335                                 pub fn $required_getter(&self) -> bool {
336                                         <T as $feature>::requires_feature(&self.flags)
337                                 }
338                         }
339                 }
340         }
341
342         define_feature!(1, DataLossProtect, [InitContext, NodeContext],
343                 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
344                 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
345         // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
346         define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
347                 set_initial_routing_sync_optional, set_initial_routing_sync_required,
348                 initial_routing_sync);
349         define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
350                 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
351                 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
352                 requires_upfront_shutdown_script);
353         define_feature!(7, GossipQueries, [InitContext, NodeContext],
354                 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
355                 supports_gossip_queries, requires_gossip_queries);
356         define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
357                 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
358                 set_variable_length_onion_required, supports_variable_length_onion,
359                 requires_variable_length_onion);
360         define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
361                 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
362                 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
363         define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
364                 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
365                 supports_payment_secret, requires_payment_secret);
366         define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext, Bolt12InvoiceContext],
367                 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
368                 supports_basic_mpp, requires_basic_mpp);
369         define_feature!(19, Wumbo, [InitContext, NodeContext],
370                 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
371                 supports_wumbo, requires_wumbo);
372         define_feature!(23, AnchorsZeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
373                 "Feature flags for `option_anchors_zero_fee_htlc_tx`.", set_anchors_zero_fee_htlc_tx_optional,
374                 set_anchors_zero_fee_htlc_tx_required, supports_anchors_zero_fee_htlc_tx, requires_anchors_zero_fee_htlc_tx);
375         define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
376                 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
377                 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
378         define_feature!(39, OnionMessages, [InitContext, NodeContext],
379                 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
380                 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
381         define_feature!(45, ChannelType, [InitContext, NodeContext],
382                 "Feature flags for `option_channel_type`.", set_channel_type_optional,
383                 set_channel_type_required, supports_channel_type, requires_channel_type);
384         define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
385                 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
386                 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
387         define_feature!(49, PaymentMetadata, [InvoiceContext],
388                 "Feature flags for payment metadata in invoices.", set_payment_metadata_optional,
389                 set_payment_metadata_required, supports_payment_metadata, requires_payment_metadata);
390         define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
391                 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
392                 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
393         define_feature!(55, Keysend, [NodeContext],
394                 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
395                 supports_keysend, requires_keysend);
396
397         #[cfg(test)]
398         define_feature!(123456789, UnknownFeature,
399                 [NodeContext, ChannelContext, InvoiceContext, OfferContext, InvoiceRequestContext, Bolt12InvoiceContext, BlindedHopContext],
400                 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
401                 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
402 }
403
404 /// Tracks the set of features which a node implements, templated by the context in which it
405 /// appears.
406 ///
407 /// This is not exported to bindings users as we map the concrete feature types below directly instead
408 #[derive(Eq)]
409 pub struct Features<T: sealed::Context> {
410         /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
411         flags: Vec<u8>,
412         mark: PhantomData<T>,
413 }
414
415 impl <T: sealed::Context> Features<T> {
416         pub(crate) fn or(mut self, o: Self) -> Self {
417                 let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
418                 self.flags.resize(total_feature_len, 0u8);
419                 for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
420                         *byte |= *o_byte;
421                 }
422                 self
423         }
424 }
425
426 impl<T: sealed::Context> Clone for Features<T> {
427         fn clone(&self) -> Self {
428                 Self {
429                         flags: self.flags.clone(),
430                         mark: PhantomData,
431                 }
432         }
433 }
434 impl<T: sealed::Context> Hash for Features<T> {
435         fn hash<H: Hasher>(&self, hasher: &mut H) {
436                 self.flags.hash(hasher);
437         }
438 }
439 impl<T: sealed::Context> PartialEq for Features<T> {
440         fn eq(&self, o: &Self) -> bool {
441                 self.flags.eq(&o.flags)
442         }
443 }
444 impl<T: sealed::Context> fmt::Debug for Features<T> {
445         fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
446                 self.flags.fmt(fmt)
447         }
448 }
449
450 /// Features used within an `init` message.
451 pub type InitFeatures = Features<sealed::InitContext>;
452 /// Features used within a `node_announcement` message.
453 pub type NodeFeatures = Features<sealed::NodeContext>;
454 /// Features used within a `channel_announcement` message.
455 pub type ChannelFeatures = Features<sealed::ChannelContext>;
456 /// Features used within an invoice.
457 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
458 /// Features used within an `offer`.
459 pub type OfferFeatures = Features<sealed::OfferContext>;
460 /// Features used within an `invoice_request`.
461 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
462 /// Features used within an `invoice`.
463 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
464 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
465 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
466
467 /// Features used within the channel_type field in an OpenChannel message.
468 ///
469 /// A channel is always of some known "type", describing the transaction formats used and the exact
470 /// semantics of our interaction with our peer.
471 ///
472 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
473 /// the counterparty, only required features are allowed here.
474 ///
475 /// This is serialized differently from other feature types - it is not prefixed by a length, and
476 /// thus must only appear inside a TLV where its length is known in advance.
477 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
478
479 impl InitFeatures {
480         /// Writes all features present up to, and including, 13.
481         pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
482                 let len = cmp::min(2, self.flags.len());
483                 (len as u16).write(w)?;
484                 for i in (0..len).rev() {
485                         if i == 0 {
486                                 self.flags[i].write(w)?;
487                         } else {
488                                 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
489                                 // up-to-and-including-bit-5, 0-indexed, on this byte:
490                                 (self.flags[i] & 0b00_11_11_11).write(w)?;
491                         }
492                 }
493                 Ok(())
494         }
495
496         /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
497         /// are included in the result.
498         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
499                 self.to_context_internal()
500         }
501 }
502
503 impl InvoiceFeatures {
504         /// Converts `InvoiceFeatures` to `Features<C>`. Only known `InvoiceFeatures` relevant to
505         /// context `C` are included in the result.
506         pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
507                 self.to_context_internal()
508         }
509
510         /// Getting a route for a keysend payment to a private node requires providing the payee's
511         /// features (since they were not announced in a node announcement). However, keysend payments
512         /// don't have an invoice to pull the payee's features from, so this method is provided for use in
513         /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
514         /// `InvoiceFeatures` for [`find_route`].
515         ///
516         /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
517         /// [`find_route`]: crate::routing::router::find_route
518         pub(crate) fn for_keysend() -> InvoiceFeatures {
519                 let mut res = InvoiceFeatures::empty();
520                 res.set_variable_length_onion_optional();
521                 res
522         }
523 }
524
525 impl ChannelTypeFeatures {
526         // Maps the relevant `InitFeatures` to `ChannelTypeFeatures`. Any unknown features to
527         // `ChannelTypeFeatures` are not included in the result.
528         pub(crate) fn from_init(init: &InitFeatures) -> Self {
529                 let mut ret = init.to_context_internal();
530                 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
531                 // optional bits and then AND out the optional ones.
532                 for byte in ret.flags.iter_mut() {
533                         *byte |= (*byte & 0b10_10_10_10) >> 1;
534                         *byte &= 0b01_01_01_01;
535                 }
536                 ret
537         }
538
539         /// Constructs a ChannelTypeFeatures with only static_remotekey set
540         pub(crate) fn only_static_remote_key() -> Self {
541                 let mut ret = Self::empty();
542                 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
543                 ret
544         }
545 }
546
547 impl ToBase32 for InvoiceFeatures {
548         fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
549                 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
550                 // minus one before dividing
551                 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
552                 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
553                 for (byte_idx, byte) in self.flags.iter().enumerate() {
554                         let bit_pos_from_left_0_indexed = byte_idx * 8;
555                         let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
556                         let new_bit_pos = bit_pos_from_left_0_indexed % 5;
557                         let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
558                         let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
559                         res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
560                         if new_u5_idx > 0 {
561                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
562                                 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
563                         }
564                         if new_u5_idx > 1 {
565                                 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
566                                 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
567                         }
568                 }
569                 // Trim the highest feature bits.
570                 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
571                         res_u5s.remove(0);
572                 }
573                 writer.write(&res_u5s)
574         }
575 }
576
577 impl Base32Len for InvoiceFeatures {
578         fn base32_len(&self) -> usize {
579                 self.to_base32().len()
580         }
581 }
582
583 impl FromBase32 for InvoiceFeatures {
584         type Err = bech32::Error;
585
586         fn from_base32(field_data: &[u5]) -> Result<InvoiceFeatures, bech32::Error> {
587                 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
588                 // minus one before dividing
589                 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
590                 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
591                 for (u5_idx, chunk) in field_data.iter().enumerate() {
592                         let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
593                         let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
594                         let new_bit_pos = bit_pos_from_right_0_indexed % 8;
595                         let chunk_u16 = chunk.to_u8() as u16;
596                         res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
597                         if new_byte_idx != length_bytes - 1 {
598                                 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
599                         }
600                 }
601                 // Trim the highest feature bits.
602                 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
603                         res_bytes.pop();
604                 }
605                 Ok(InvoiceFeatures::from_le_bytes(res_bytes))
606         }
607 }
608
609 impl<T: sealed::Context> Features<T> {
610         /// Create a blank Features with no features set
611         pub fn empty() -> Self {
612                 Features {
613                         flags: Vec::new(),
614                         mark: PhantomData,
615                 }
616         }
617
618         /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
619         /// included in the result.
620         fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
621                 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
622                 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
623                 let mut flags = Vec::new();
624                 for (i, byte) in self.flags.iter().enumerate() {
625                         if i < from_byte_count && i < to_byte_count {
626                                 let from_known_features = T::KNOWN_FEATURE_MASK[i];
627                                 let to_known_features = C::KNOWN_FEATURE_MASK[i];
628                                 flags.push(byte & from_known_features & to_known_features);
629                         }
630                 }
631                 Features::<C> { flags, mark: PhantomData, }
632         }
633
634         /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
635         /// most on-the-wire encodings.
636         ///
637         /// This is not exported to bindings users as we don't support export across multiple T
638         pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
639                 Features {
640                         flags,
641                         mark: PhantomData,
642                 }
643         }
644
645         #[cfg(test)]
646         /// Gets the underlying flags set, in LE.
647         pub fn le_flags(&self) -> &Vec<u8> {
648                 &self.flags
649         }
650
651         fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
652                 for f in self.flags.iter().rev() { // Swap back to big-endian
653                         f.write(w)?;
654                 }
655                 Ok(())
656         }
657
658         fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
659                 flags.reverse(); // Swap to little-endian
660                 Self {
661                         flags,
662                         mark: PhantomData,
663                 }
664         }
665
666         pub(crate) fn supports_any_optional_bits(&self) -> bool {
667                 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
668         }
669
670         /// Returns true if this `Features` object contains unknown feature flags which are set as
671         /// "required".
672         pub fn requires_unknown_bits(&self) -> bool {
673                 // Bitwise AND-ing with all even bits set except for known features will select required
674                 // unknown features.
675                 let byte_count = T::KNOWN_FEATURE_MASK.len();
676                 self.flags.iter().enumerate().any(|(i, &byte)| {
677                         let required_features = 0b01_01_01_01;
678                         let unknown_features = if i < byte_count {
679                                 !T::KNOWN_FEATURE_MASK[i]
680                         } else {
681                                 0b11_11_11_11
682                         };
683                         (byte & (required_features & unknown_features)) != 0
684                 })
685         }
686
687         pub(crate) fn supports_unknown_bits(&self) -> bool {
688                 // Bitwise AND-ing with all even and odd bits set except for known features will select
689                 // both required and optional unknown features.
690                 let byte_count = T::KNOWN_FEATURE_MASK.len();
691                 self.flags.iter().enumerate().any(|(i, &byte)| {
692                         let unknown_features = if i < byte_count {
693                                 !T::KNOWN_FEATURE_MASK[i]
694                         } else {
695                                 0b11_11_11_11
696                         };
697                         (byte & unknown_features) != 0
698                 })
699         }
700
701         // Returns true if the features within `self` are a subset of the features within `other`.
702         pub(crate) fn is_subset(&self, other: &Self) -> bool {
703                 for (idx, byte) in self.flags.iter().enumerate() {
704                         if let Some(other_byte) = other.flags.get(idx) {
705                                 if byte & other_byte != *byte {
706                                         // `self` has bits set that `other` doesn't.
707                                         return false;
708                                 }
709                         } else {
710                                 if *byte > 0 {
711                                         // `self` has a non-zero byte that `other` doesn't.
712                                         return false;
713                                 }
714                         }
715                 }
716                 true
717         }
718 }
719
720 impl<T: sealed::UpfrontShutdownScript> Features<T> {
721         #[cfg(test)]
722         pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
723                 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
724                 self
725         }
726 }
727
728 impl<T: sealed::ShutdownAnySegwit> Features<T> {
729         #[cfg(test)]
730         pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
731                 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
732                 self
733         }
734 }
735
736 impl<T: sealed::Wumbo> Features<T> {
737         #[cfg(test)]
738         pub(crate) fn clear_wumbo(mut self) -> Self {
739                 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
740                 self
741         }
742 }
743
744 impl<T: sealed::SCIDPrivacy> Features<T> {
745         pub(crate) fn clear_scid_privacy(&mut self) {
746                 <T as sealed::SCIDPrivacy>::clear_bits(&mut self.flags);
747         }
748 }
749
750 impl<T: sealed::AnchorsZeroFeeHtlcTx> Features<T> {
751         pub(crate) fn clear_anchors_zero_fee_htlc_tx(&mut self) {
752                 <T as sealed::AnchorsZeroFeeHtlcTx>::clear_bits(&mut self.flags);
753         }
754 }
755
756 #[cfg(test)]
757 impl<T: sealed::UnknownFeature> Features<T> {
758         pub(crate) fn unknown() -> Self {
759                 let mut features = Self::empty();
760                 features.set_unknown_feature_required();
761                 features
762         }
763 }
764
765 macro_rules! impl_feature_len_prefixed_write {
766         ($features: ident) => {
767                 impl Writeable for $features {
768                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
769                                 (self.flags.len() as u16).write(w)?;
770                                 self.write_be(w)
771                         }
772                 }
773                 impl Readable for $features {
774                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
775                                 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
776                         }
777                 }
778         }
779 }
780 impl_feature_len_prefixed_write!(InitFeatures);
781 impl_feature_len_prefixed_write!(ChannelFeatures);
782 impl_feature_len_prefixed_write!(NodeFeatures);
783 impl_feature_len_prefixed_write!(InvoiceFeatures);
784 impl_feature_len_prefixed_write!(BlindedHopFeatures);
785
786 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
787 macro_rules! impl_feature_tlv_write {
788         ($features: ident) => {
789                 impl Writeable for $features {
790                         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
791                                 WithoutLength(self).write(w)
792                         }
793                 }
794                 impl Readable for $features {
795                         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
796                                 Ok(WithoutLength::<Self>::read(r)?.0)
797                         }
798                 }
799         }
800 }
801
802 impl_feature_tlv_write!(ChannelTypeFeatures);
803
804 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
805 // requires a length but the former does not.
806
807 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
808         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
809                 self.0.write_be(w)
810         }
811 }
812
813 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
814         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
815                 let v = io_extras::read_to_end(r)?;
816                 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
817         }
818 }
819
820 #[cfg(test)]
821 mod tests {
822         use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
823         use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
824         use crate::util::ser::{Readable, WithoutLength, Writeable};
825
826         #[test]
827         fn sanity_test_unknown_bits() {
828                 let features = ChannelFeatures::empty();
829                 assert!(!features.requires_unknown_bits());
830                 assert!(!features.supports_unknown_bits());
831
832                 let mut features = ChannelFeatures::empty();
833                 features.set_unknown_feature_required();
834                 assert!(features.requires_unknown_bits());
835                 assert!(features.supports_unknown_bits());
836
837                 let mut features = ChannelFeatures::empty();
838                 features.set_unknown_feature_optional();
839                 assert!(!features.requires_unknown_bits());
840                 assert!(features.supports_unknown_bits());
841         }
842
843         #[test]
844         fn convert_to_context_with_relevant_flags() {
845                 let mut init_features = InitFeatures::empty();
846                 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
847                 // converted as it's only relevant in an init context).
848                 init_features.set_initial_routing_sync_required();
849                 init_features.set_data_loss_protect_optional();
850                 init_features.set_variable_length_onion_required();
851                 init_features.set_static_remote_key_required();
852                 init_features.set_payment_secret_required();
853                 init_features.set_basic_mpp_optional();
854                 init_features.set_wumbo_optional();
855                 init_features.set_shutdown_any_segwit_optional();
856                 init_features.set_onion_messages_optional();
857                 init_features.set_channel_type_optional();
858                 init_features.set_scid_privacy_optional();
859                 init_features.set_zero_conf_optional();
860                 init_features.set_anchors_zero_fee_htlc_tx_optional();
861
862                 assert!(init_features.initial_routing_sync());
863                 assert!(!init_features.supports_upfront_shutdown_script());
864                 assert!(!init_features.supports_gossip_queries());
865
866                 let node_features: NodeFeatures = init_features.to_context();
867                 {
868                         // Check that the flags are as expected:
869                         // - option_data_loss_protect
870                         // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
871                         // - basic_mpp | wumbo
872                         // - opt_shutdown_anysegwit
873                         // - onion_messages
874                         // - option_channel_type | option_scid_alias
875                         // - option_zeroconf
876                         assert_eq!(node_features.flags.len(), 7);
877                         assert_eq!(node_features.flags[0], 0b00000010);
878                         assert_eq!(node_features.flags[1], 0b01010001);
879                         assert_eq!(node_features.flags[2], 0b10001010);
880                         assert_eq!(node_features.flags[3], 0b00001000);
881                         assert_eq!(node_features.flags[4], 0b10000000);
882                         assert_eq!(node_features.flags[5], 0b10100000);
883                         assert_eq!(node_features.flags[6], 0b00001000);
884                 }
885
886                 // Check that cleared flags are kept blank when converting back:
887                 // - initial_routing_sync was not applicable to NodeContext
888                 // - upfront_shutdown_script was cleared before converting
889                 // - gossip_queries was cleared before converting
890                 let features: InitFeatures = node_features.to_context_internal();
891                 assert!(!features.initial_routing_sync());
892                 assert!(!features.supports_upfront_shutdown_script());
893                 assert!(!init_features.supports_gossip_queries());
894         }
895
896         #[test]
897         fn convert_to_context_with_unknown_flags() {
898                 // Ensure the `from` context has fewer known feature bytes than the `to` context.
899                 assert!(<sealed::ChannelContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
900                         <sealed::InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
901                 let mut channel_features = ChannelFeatures::empty();
902                 channel_features.set_unknown_feature_optional();
903                 assert!(channel_features.supports_unknown_bits());
904                 let invoice_features: InvoiceFeatures = channel_features.to_context_internal();
905                 assert!(!invoice_features.supports_unknown_bits());
906         }
907
908         #[test]
909         fn set_feature_bits() {
910                 let mut features = InvoiceFeatures::empty();
911                 features.set_basic_mpp_optional();
912                 features.set_payment_secret_required();
913                 assert!(features.supports_basic_mpp());
914                 assert!(!features.requires_basic_mpp());
915                 assert!(features.requires_payment_secret());
916                 assert!(features.supports_payment_secret());
917         }
918
919         #[test]
920         fn encodes_features_without_length() {
921                 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
922                 assert_eq!(features.flags.len(), 8);
923
924                 let mut serialized_features = Vec::new();
925                 WithoutLength(&features).write(&mut serialized_features).unwrap();
926                 assert_eq!(serialized_features.len(), 8);
927
928                 let deserialized_features =
929                         WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
930                 assert_eq!(features, deserialized_features);
931         }
932
933         #[test]
934         fn invoice_features_encoding() {
935                 let features_as_u5s = vec![
936                         u5::try_from_u8(6).unwrap(),
937                         u5::try_from_u8(10).unwrap(),
938                         u5::try_from_u8(25).unwrap(),
939                         u5::try_from_u8(1).unwrap(),
940                         u5::try_from_u8(10).unwrap(),
941                         u5::try_from_u8(0).unwrap(),
942                         u5::try_from_u8(20).unwrap(),
943                         u5::try_from_u8(2).unwrap(),
944                         u5::try_from_u8(0).unwrap(),
945                         u5::try_from_u8(6).unwrap(),
946                         u5::try_from_u8(0).unwrap(),
947                         u5::try_from_u8(16).unwrap(),
948                         u5::try_from_u8(1).unwrap(),
949                 ];
950                 let features = InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
951
952                 // Test length calculation.
953                 assert_eq!(features.base32_len(), 13);
954
955                 // Test serialization.
956                 let features_serialized = features.to_base32();
957                 assert_eq!(features_as_u5s, features_serialized);
958
959                 // Test deserialization.
960                 let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
961                 assert_eq!(features, features_deserialized);
962         }
963
964         #[test]
965         fn test_channel_type_mapping() {
966                 // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
967                 // required-StaticRemoteKey ChannelTypeFeatures.
968                 let mut init_features = InitFeatures::empty();
969                 init_features.set_static_remote_key_optional();
970                 let converted_features = ChannelTypeFeatures::from_init(&init_features);
971                 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
972                 assert!(!converted_features.supports_any_optional_bits());
973                 assert!(converted_features.requires_static_remote_key());
974         }
975 }