staging_xcm/v3/traits.rs
1// Copyright (C) Parity Technologies (UK) Ltd.
2// This file is part of Polkadot.
3
4// Polkadot is free software: you can redistribute it and/or modify
5// it under the terms of the GNU General Public License as published by
6// the Free Software Foundation, either version 3 of the License, or
7// (at your option) any later version.
8
9// Polkadot is distributed in the hope that it will be useful,
10// but WITHOUT ANY WARRANTY; without even the implied warranty of
11// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12// GNU General Public License for more details.
13
14// You should have received a copy of the GNU General Public License
15// along with Polkadot. If not, see <http://www.gnu.org/licenses/>.
16
17//! Cross-Consensus Message format data structures.
18
19use crate::v5::Error as NewError;
20use core::result;
21use scale_info::TypeInfo;
22
23pub use sp_weights::Weight;
24
25// A simple trait to get the weight of some object.
26pub trait GetWeight<W> {
27 fn weight(&self) -> sp_weights::Weight;
28}
29
30use super::*;
31
32/// Error codes used in XCM. The first errors codes have explicit indices and are part of the XCM
33/// format. Those trailing are merely part of the XCM implementation; there is no expectation that
34/// they will retain the same index over time.
35#[derive(
36 Copy,
37 Clone,
38 Encode,
39 Decode,
40 DecodeWithMemTracking,
41 Eq,
42 PartialEq,
43 Debug,
44 TypeInfo,
45 MaxEncodedLen,
46)]
47#[scale_info(replace_segment("staging_xcm", "xcm"))]
48#[cfg_attr(feature = "json-schema", derive(schemars::JsonSchema))]
49pub enum Error {
50 // Errors that happen due to instructions being executed. These alone are defined in the
51 // XCM specification.
52 /// An arithmetic overflow happened.
53 #[codec(index = 0)]
54 Overflow,
55 /// The instruction is intentionally unsupported.
56 #[codec(index = 1)]
57 Unimplemented,
58 /// Origin Register does not contain a value value for a reserve transfer notification.
59 #[codec(index = 2)]
60 UntrustedReserveLocation,
61 /// Origin Register does not contain a value value for a teleport notification.
62 #[codec(index = 3)]
63 UntrustedTeleportLocation,
64 /// `MultiLocation` value too large to descend further.
65 #[codec(index = 4)]
66 LocationFull,
67 /// `MultiLocation` value ascend more parents than known ancestors of local location.
68 #[codec(index = 5)]
69 LocationNotInvertible,
70 /// The Origin Register does not contain a valid value for instruction.
71 #[codec(index = 6)]
72 BadOrigin,
73 /// The location parameter is not a valid value for the instruction.
74 #[codec(index = 7)]
75 InvalidLocation,
76 /// The given asset is not handled.
77 #[codec(index = 8)]
78 AssetNotFound,
79 /// An asset transaction (like withdraw or deposit) failed (typically due to type conversions).
80 #[codec(index = 9)]
81 FailedToTransactAsset(#[codec(skip)] &'static str),
82 /// An asset cannot be withdrawn, potentially due to lack of ownership, availability or rights.
83 #[codec(index = 10)]
84 NotWithdrawable,
85 /// An asset cannot be deposited under the ownership of a particular location.
86 #[codec(index = 11)]
87 LocationCannotHold,
88 /// Attempt to send a message greater than the maximum supported by the transport protocol.
89 #[codec(index = 12)]
90 ExceedsMaxMessageSize,
91 /// The given message cannot be translated into a format supported by the destination.
92 #[codec(index = 13)]
93 DestinationUnsupported,
94 /// Destination is routable, but there is some issue with the transport mechanism.
95 #[codec(index = 14)]
96 Transport(#[codec(skip)] &'static str),
97 /// Destination is known to be unroutable.
98 #[codec(index = 15)]
99 Unroutable,
100 /// Used by `ClaimAsset` when the given claim could not be recognized/found.
101 #[codec(index = 16)]
102 UnknownClaim,
103 /// Used by `Transact` when the functor cannot be decoded.
104 #[codec(index = 17)]
105 FailedToDecode,
106 /// Used by `Transact` to indicate that the given weight limit could be breached by the
107 /// functor.
108 #[codec(index = 18)]
109 MaxWeightInvalid,
110 /// Used by `BuyExecution` when the Holding Register does not contain payable fees.
111 #[codec(index = 19)]
112 NotHoldingFees,
113 /// Used by `BuyExecution` when the fees declared to purchase weight are insufficient.
114 #[codec(index = 20)]
115 TooExpensive,
116 /// Used by the `Trap` instruction to force an error intentionally. Its code is included.
117 #[codec(index = 21)]
118 Trap(u64),
119 /// Used by `ExpectAsset`, `ExpectError` and `ExpectOrigin` when the expectation was not true.
120 #[codec(index = 22)]
121 ExpectationFalse,
122 /// The provided pallet index was not found.
123 #[codec(index = 23)]
124 PalletNotFound,
125 /// The given pallet's name is different to that expected.
126 #[codec(index = 24)]
127 NameMismatch,
128 /// The given pallet's version has an incompatible version to that expected.
129 #[codec(index = 25)]
130 VersionIncompatible,
131 /// The given operation would lead to an overflow of the Holding Register.
132 #[codec(index = 26)]
133 HoldingWouldOverflow,
134 /// The message was unable to be exported.
135 #[codec(index = 27)]
136 ExportError,
137 /// `MultiLocation` value failed to be reanchored.
138 #[codec(index = 28)]
139 ReanchorFailed,
140 /// No deal is possible under the given constraints.
141 #[codec(index = 29)]
142 NoDeal,
143 /// Fees were required which the origin could not pay.
144 #[codec(index = 30)]
145 FeesNotMet,
146 /// Some other error with locking.
147 #[codec(index = 31)]
148 LockError,
149 /// The state was not in a condition where the operation was valid to make.
150 #[codec(index = 32)]
151 NoPermission,
152 /// The universal location of the local consensus is improper.
153 #[codec(index = 33)]
154 Unanchored,
155 /// An asset cannot be deposited, probably because (too much of) it already exists.
156 #[codec(index = 34)]
157 NotDepositable,
158
159 // Errors that happen prior to instructions being executed. These fall outside of the XCM
160 // spec.
161 /// XCM version not able to be handled.
162 UnhandledXcmVersion,
163 /// Execution of the XCM would potentially result in a greater weight used than weight limit.
164 WeightLimitReached(Weight),
165 /// The XCM did not pass the barrier condition for execution.
166 ///
167 /// The barrier condition differs on different chains and in different circumstances, but
168 /// generally it means that the conditions surrounding the message were not such that the chain
169 /// considers the message worth spending time executing. Since most chains lift the barrier to
170 /// execution on appropriate payment, presentation of an NFT voucher, or based on the message
171 /// origin, it means that none of those were the case.
172 Barrier,
173 /// The weight of an XCM message is not computable ahead of execution.
174 WeightNotComputable,
175 /// Recursion stack limit reached
176 ExceedsStackLimit,
177}
178
179impl TryFrom<NewError> for Error {
180 type Error = ();
181 fn try_from(new_error: NewError) -> result::Result<Error, ()> {
182 use NewError::*;
183 Ok(match new_error {
184 Overflow => Self::Overflow,
185 Unimplemented => Self::Unimplemented,
186 UntrustedReserveLocation => Self::UntrustedReserveLocation,
187 UntrustedTeleportLocation => Self::UntrustedTeleportLocation,
188 LocationFull => Self::LocationFull,
189 LocationNotInvertible => Self::LocationNotInvertible,
190 BadOrigin => Self::BadOrigin,
191 InvalidLocation => Self::InvalidLocation,
192 AssetNotFound => Self::AssetNotFound,
193 FailedToTransactAsset(s) => Self::FailedToTransactAsset(s),
194 NotWithdrawable => Self::NotWithdrawable,
195 LocationCannotHold => Self::LocationCannotHold,
196 ExceedsMaxMessageSize => Self::ExceedsMaxMessageSize,
197 DestinationUnsupported => Self::DestinationUnsupported,
198 Transport(s) => Self::Transport(s),
199 Unroutable => Self::Unroutable,
200 UnknownClaim => Self::UnknownClaim,
201 FailedToDecode => Self::FailedToDecode,
202 MaxWeightInvalid => Self::MaxWeightInvalid,
203 NotHoldingFees => Self::NotHoldingFees,
204 TooExpensive => Self::TooExpensive,
205 Trap(i) => Self::Trap(i),
206 ExpectationFalse => Self::ExpectationFalse,
207 PalletNotFound => Self::PalletNotFound,
208 NameMismatch => Self::NameMismatch,
209 VersionIncompatible => Self::VersionIncompatible,
210 HoldingWouldOverflow => Self::HoldingWouldOverflow,
211 ExportError => Self::ExportError,
212 ReanchorFailed => Self::ReanchorFailed,
213 NoDeal => Self::NoDeal,
214 FeesNotMet => Self::FeesNotMet,
215 LockError => Self::LockError,
216 NoPermission => Self::NoPermission,
217 Unanchored => Self::Unanchored,
218 NotDepositable => Self::NotDepositable,
219 _ => return Err(()),
220 })
221 }
222}
223
224impl From<SendError> for Error {
225 fn from(e: SendError) -> Self {
226 match e {
227 SendError::NotApplicable | SendError::Unroutable | SendError::MissingArgument =>
228 Error::Unroutable,
229 SendError::Transport(s) => Error::Transport(s),
230 SendError::DestinationUnsupported => Error::DestinationUnsupported,
231 SendError::ExceedsMaxMessageSize => Error::ExceedsMaxMessageSize,
232 SendError::Fees => Error::FeesNotMet,
233 }
234 }
235}
236
237pub type Result = result::Result<(), Error>;
238
239/// Outcome of an XCM execution.
240#[derive(Clone, Encode, Decode, Eq, PartialEq, Debug, TypeInfo)]
241#[scale_info(replace_segment("staging_xcm", "xcm"))]
242pub enum Outcome {
243 /// Execution completed successfully; given weight was used.
244 Complete(Weight),
245 /// Execution started, but did not complete successfully due to the given error; given weight
246 /// was used.
247 Incomplete(Weight, Error),
248 /// Execution did not start due to the given error.
249 Error(Error),
250}
251
252impl Outcome {
253 pub fn ensure_complete(self) -> result::Result<Weight, Error> {
254 match self {
255 Outcome::Complete(weight) => Ok(weight),
256 Outcome::Incomplete(_, e) => Err(e),
257 Outcome::Error(e) => Err(e),
258 }
259 }
260 pub fn ensure_execution(self) -> result::Result<Weight, Error> {
261 match self {
262 Outcome::Complete(w) => Ok(w),
263 Outcome::Incomplete(w, _) => Ok(w),
264 Outcome::Error(e) => Err(e),
265 }
266 }
267 /// How much weight was used by the XCM execution attempt.
268 pub fn weight_used(&self) -> Weight {
269 match self {
270 Outcome::Complete(w) => *w,
271 Outcome::Incomplete(w, _) => *w,
272 Outcome::Error(_) => Weight::zero(),
273 }
274 }
275}
276
277pub trait PreparedMessage {
278 fn weight_of(&self) -> Weight;
279}
280
281/// Type of XCM message executor.
282pub trait ExecuteXcm<Call> {
283 type Prepared: PreparedMessage;
284 fn prepare(message: Xcm<Call>) -> result::Result<Self::Prepared, Xcm<Call>>;
285 fn execute(
286 origin: impl Into<MultiLocation>,
287 pre: Self::Prepared,
288 id: &mut XcmHash,
289 weight_credit: Weight,
290 ) -> Outcome;
291 fn prepare_and_execute(
292 origin: impl Into<MultiLocation>,
293 message: Xcm<Call>,
294 id: &mut XcmHash,
295 weight_limit: Weight,
296 weight_credit: Weight,
297 ) -> Outcome {
298 let pre = match Self::prepare(message) {
299 Ok(x) => x,
300 Err(_) => return Outcome::Error(Error::WeightNotComputable),
301 };
302 let xcm_weight = pre.weight_of();
303 if xcm_weight.any_gt(weight_limit) {
304 return Outcome::Error(Error::WeightLimitReached(xcm_weight))
305 }
306 Self::execute(origin, pre, id, weight_credit)
307 }
308
309 /// Execute some XCM `message` with the message `hash` from `origin` using no more than
310 /// `weight_limit` weight.
311 ///
312 /// The weight limit is a basic hard-limit and the implementation may place further
313 /// restrictions or requirements on weight and other aspects.
314 fn execute_xcm(
315 origin: impl Into<MultiLocation>,
316 message: Xcm<Call>,
317 hash: XcmHash,
318 weight_limit: Weight,
319 ) -> Outcome {
320 let origin = origin.into();
321 tracing::trace!(
322 target: "xcm::execute_xcm",
323 ?origin,
324 ?message,
325 ?weight_limit,
326 );
327 Self::execute_xcm_in_credit(origin, message, hash, weight_limit, Weight::zero())
328 }
329
330 /// Execute some XCM `message` with the message `hash` from `origin` using no more than
331 /// `weight_limit` weight.
332 ///
333 /// Some amount of `weight_credit` may be provided which, depending on the implementation, may
334 /// allow execution without associated payment.
335 fn execute_xcm_in_credit(
336 origin: impl Into<MultiLocation>,
337 message: Xcm<Call>,
338 mut hash: XcmHash,
339 weight_limit: Weight,
340 weight_credit: Weight,
341 ) -> Outcome {
342 let pre = match Self::prepare(message) {
343 Ok(x) => x,
344 Err(_) => return Outcome::Error(Error::WeightNotComputable),
345 };
346 let xcm_weight = pre.weight_of();
347 if xcm_weight.any_gt(weight_limit) {
348 return Outcome::Error(Error::WeightLimitReached(xcm_weight))
349 }
350 Self::execute(origin, pre, &mut hash, weight_credit)
351 }
352
353 /// Deduct some `fees` to the sovereign account of the given `location` and place them as per
354 /// the convention for fees.
355 fn charge_fees(location: impl Into<MultiLocation>, fees: MultiAssets) -> Result;
356}
357
358pub enum Weightless {}
359impl PreparedMessage for Weightless {
360 fn weight_of(&self) -> Weight {
361 unreachable!()
362 }
363}
364
365impl<C> ExecuteXcm<C> for () {
366 type Prepared = Weightless;
367 fn prepare(message: Xcm<C>) -> result::Result<Self::Prepared, Xcm<C>> {
368 Err(message)
369 }
370 fn execute(
371 _: impl Into<MultiLocation>,
372 _: Self::Prepared,
373 _: &mut XcmHash,
374 _: Weight,
375 ) -> Outcome {
376 unreachable!()
377 }
378 fn charge_fees(_location: impl Into<MultiLocation>, _fees: MultiAssets) -> Result {
379 Err(Error::Unimplemented)
380 }
381}
382
383/// Error result value when attempting to send an XCM message.
384#[derive(
385 Clone, Encode, Decode, DecodeWithMemTracking, Eq, PartialEq, Debug, scale_info::TypeInfo,
386)]
387#[scale_info(replace_segment("staging_xcm", "xcm"))]
388pub enum SendError {
389 /// The message and destination combination was not recognized as being reachable.
390 ///
391 /// This is not considered fatal: if there are alternative transport routes available, then
392 /// they may be attempted.
393 NotApplicable,
394 /// Destination is routable, but there is some issue with the transport mechanism. This is
395 /// considered fatal.
396 /// A human-readable explanation of the specific issue is provided.
397 Transport(#[codec(skip)] &'static str),
398 /// Destination is known to be unroutable. This is considered fatal.
399 Unroutable,
400 /// The given message cannot be translated into a format that the destination can be expected
401 /// to interpret.
402 DestinationUnsupported,
403 /// Message could not be sent due to its size exceeding the maximum allowed by the transport
404 /// layer.
405 ExceedsMaxMessageSize,
406 /// A needed argument is `None` when it should be `Some`.
407 MissingArgument,
408 /// Fees needed to be paid in order to send the message and they were unavailable.
409 Fees,
410}
411
412/// A hash type for identifying messages.
413pub type XcmHash = [u8; 32];
414
415/// Result value when attempting to send an XCM message.
416pub type SendResult<T> = result::Result<(T, MultiAssets), SendError>;
417
418/// Utility for sending an XCM message to a given location.
419///
420/// These can be amalgamated in tuples to form sophisticated routing systems. In tuple format, each
421/// router might return `NotApplicable` to pass the execution to the next sender item. Note that
422/// each `NotApplicable` might alter the destination and the XCM message for to the next router.
423///
424/// # Example
425/// ```rust
426/// # use codec::Encode;
427/// # use staging_xcm::v3::{prelude::*, Weight};
428/// # use staging_xcm::VersionedXcm;
429/// # use std::convert::Infallible;
430///
431/// /// A sender that only passes the message through and does nothing.
432/// struct Sender1;
433/// impl SendXcm for Sender1 {
434/// type Ticket = Infallible;
435/// fn validate(_: &mut Option<MultiLocation>, _: &mut Option<Xcm<()>>) -> SendResult<Infallible> {
436/// Err(SendError::NotApplicable)
437/// }
438/// fn deliver(_: Infallible) -> Result<XcmHash, SendError> {
439/// unreachable!()
440/// }
441/// }
442///
443/// /// A sender that accepts a message that has an X2 junction, otherwise stops the routing.
444/// struct Sender2;
445/// impl SendXcm for Sender2 {
446/// type Ticket = ();
447/// fn validate(destination: &mut Option<MultiLocation>, message: &mut Option<Xcm<()>>) -> SendResult<()> {
448/// match destination.as_ref().ok_or(SendError::MissingArgument)? {
449/// MultiLocation { parents: 0, interior: X2(j1, j2) } => Ok(((), MultiAssets::new())),
450/// _ => Err(SendError::Unroutable),
451/// }
452/// }
453/// fn deliver(_: ()) -> Result<XcmHash, SendError> {
454/// Ok([0; 32])
455/// }
456/// }
457///
458/// /// A sender that accepts a message from a parent, passing through otherwise.
459/// struct Sender3;
460/// impl SendXcm for Sender3 {
461/// type Ticket = ();
462/// fn validate(destination: &mut Option<MultiLocation>, message: &mut Option<Xcm<()>>) -> SendResult<()> {
463/// match destination.as_ref().ok_or(SendError::MissingArgument)? {
464/// MultiLocation { parents: 1, interior: Here } => Ok(((), MultiAssets::new())),
465/// _ => Err(SendError::NotApplicable),
466/// }
467/// }
468/// fn deliver(_: ()) -> Result<XcmHash, SendError> {
469/// Ok([0; 32])
470/// }
471/// }
472///
473/// // A call to send via XCM. We don't really care about this.
474/// # fn main() {
475/// let call: Vec<u8> = ().encode();
476/// let message = Xcm(vec![Instruction::Transact {
477/// origin_kind: OriginKind::Superuser,
478/// require_weight_at_most: Weight::zero(),
479/// call: call.into(),
480/// }]);
481/// let message_hash = message.using_encoded(sp_io::hashing::blake2_256);
482///
483/// // Sender2 will block this.
484/// assert!(send_xcm::<(Sender1, Sender2, Sender3)>(Parent.into(), message.clone()).is_err());
485///
486/// // Sender3 will catch this.
487/// assert!(send_xcm::<(Sender1, Sender3)>(Parent.into(), message.clone()).is_ok());
488/// # }
489/// ```
490pub trait SendXcm {
491 /// Intermediate value which connects the two phases of the send operation.
492 type Ticket;
493
494 /// Check whether the given `message` is deliverable to the given `destination` and if so
495 /// determine the cost which will be paid by this chain to do so, returning a `Validated` token
496 /// which can be used to enact delivery.
497 ///
498 /// The `destination` and `message` must be `Some` (or else an error will be returned) and they
499 /// may only be consumed if the `Err` is not `NotApplicable`.
500 ///
501 /// If it is not a destination which can be reached with this type but possibly could by others,
502 /// then this *MUST* return `NotApplicable`. Any other error will cause the tuple
503 /// implementation to exit early without trying other type fields.
504 fn validate(
505 destination: &mut Option<MultiLocation>,
506 message: &mut Option<Xcm<()>>,
507 ) -> SendResult<Self::Ticket>;
508
509 /// Actually carry out the delivery operation for a previously validated message sending.
510 fn deliver(ticket: Self::Ticket) -> result::Result<XcmHash, SendError>;
511}
512
513#[impl_trait_for_tuples::impl_for_tuples(30)]
514impl SendXcm for Tuple {
515 for_tuples! { type Ticket = (#( Option<Tuple::Ticket> ),* ); }
516
517 fn validate(
518 destination: &mut Option<MultiLocation>,
519 message: &mut Option<Xcm<()>>,
520 ) -> SendResult<Self::Ticket> {
521 let mut maybe_cost: Option<MultiAssets> = None;
522 let one_ticket: Self::Ticket = (for_tuples! { #(
523 if maybe_cost.is_some() {
524 None
525 } else {
526 match Tuple::validate(destination, message) {
527 Err(SendError::NotApplicable) => None,
528 Err(e) => { return Err(e) },
529 Ok((v, c)) => {
530 maybe_cost = Some(c);
531 Some(v)
532 },
533 }
534 }
535 ),* });
536 if let Some(cost) = maybe_cost {
537 Ok((one_ticket, cost))
538 } else {
539 Err(SendError::NotApplicable)
540 }
541 }
542
543 fn deliver(one_ticket: Self::Ticket) -> result::Result<XcmHash, SendError> {
544 for_tuples!( #(
545 if let Some(validated) = one_ticket.Tuple {
546 return Tuple::deliver(validated);
547 }
548 )* );
549 Err(SendError::Unroutable)
550 }
551}
552
553/// Convenience function for using a `SendXcm` implementation. Just interprets the `dest` and wraps
554/// both in `Some` before passing them as mutable references into `T::send_xcm`.
555pub fn validate_send<T: SendXcm>(dest: MultiLocation, msg: Xcm<()>) -> SendResult<T::Ticket> {
556 T::validate(&mut Some(dest), &mut Some(msg))
557}
558
559/// Convenience function for using a `SendXcm` implementation. Just interprets the `dest` and wraps
560/// both in `Some` before passing them as mutable references into `T::send_xcm`.
561///
562/// Returns either `Ok` with the price of the delivery, or `Err` with the reason why the message
563/// could not be sent.
564///
565/// Generally you'll want to validate and get the price first to ensure that the sender can pay it
566/// before actually doing the delivery.
567pub fn send_xcm<T: SendXcm>(
568 dest: MultiLocation,
569 msg: Xcm<()>,
570) -> result::Result<(XcmHash, MultiAssets), SendError> {
571 let (ticket, price) = T::validate(&mut Some(dest), &mut Some(msg))?;
572 let hash = T::deliver(ticket)?;
573 Ok((hash, price))
574}