From 9b4844e85361d66bd7e51f3a974a571a682ef27c Mon Sep 17 00:00:00 2001
From: Gavin Wood <gavin@parity.io>
Date: Thu, 8 Apr 2021 20:58:06 +0200
Subject: [PATCH] Introduce plurality XCM locations (#2846)
* Introduce plurality XCM locations
* Add RelayedFrom
---
polkadot/xcm/src/v0/junction.rs | 62 +++++++++++++++++++++++----
polkadot/xcm/src/v0/mod.rs | 18 +++++++-
polkadot/xcm/src/v0/multi_location.rs | 23 ++++++++++
polkadot/xcm/xcm-executor/src/lib.rs | 8 ++++
4 files changed, 101 insertions(+), 10 deletions(-)
diff --git a/polkadot/xcm/src/v0/junction.rs b/polkadot/xcm/src/v0/junction.rs
index b5493cd31fe..fd0104a48fe 100644
--- a/polkadot/xcm/src/v0/junction.rs
+++ b/polkadot/xcm/src/v0/junction.rs
@@ -32,6 +32,41 @@ pub enum NetworkId {
Kusama,
}
+/// An identifier of a pluralistic body.
+#[derive(Clone, Eq, PartialEq, Ord, PartialOrd, Encode, Decode, Debug)]
+pub enum BodyId {
+ /// The only body in its context.
+ Unit,
+ /// A named body.
+ Named(Vec<u8>),
+ /// An indexed body.
+ // TODO: parity-scale-codec#262: Change to be a tuple.
+ Index { #[codec(compact)] id: u32 },
+ /// The unambiguous executive body (for Polkadot, this would be the Polkadot council).
+ Executive,
+ /// The unambiguous technical body (for Polkadot, this would be the Technical Committee).
+ Technical,
+ /// The unambiguous legislative body (for Polkadot, this could be considered the opinion of a majority of
+ /// lock-voters).
+ Legislative,
+ /// The unambiguous judicial body (this doesn't exist on Polkadot, but if it were to get a "grand oracle", it
+ /// may be considered as that).
+ Judicial,
+}
+
+/// A part of a pluralistic body.
+#[derive(Clone, Eq, PartialEq, Ord, PartialOrd, Encode, Decode, Debug)]
+pub enum BodyPart {
+ /// The body's declaration, under whatever means it decides.
+ Voice,
+ /// A given number of members of the body.
+ Members { #[codec(compact)] count: u32 },
+ /// No less than the given proportion of members of the body.
+ AtLeastProportion { #[codec(compact)] nom: u32, #[codec(compact)] denom: u32 },
+ /// More than than the given proportion of members of the body.
+ MoreThanProportion { #[codec(compact)] nom: u32, #[codec(compact)] denom: u32 },
+}
+
/// A single item in a path to describe the relative location of a consensus system.
///
/// Each item assumes a pre-existing location as its context and is defined in terms of it.
@@ -85,21 +120,30 @@ pub enum Junction {
///
/// Not currently used except as a fallback when deriving ancestry.
OnlyChild,
+ /// A pluralistic body existing within consensus.
+ ///
+ /// Typical to be used to represent a governance origin of a chain, but could in principle be used to represent
+ /// things such as multisigs also.
+ Plurality { id: BodyId, part: BodyPart },
}
impl Junction {
- pub fn is_sub_consensus(&self) -> bool {
+ /// Returns true if this junction can be considered an interior part of its context. This is generally `true`,
+ /// except for the `Parent` item.
+ pub fn is_interior(&self) -> bool {
match self {
Junction::Parent => false,
- Junction::Parachain { .. } |
- Junction::AccountId32 { .. } |
- Junction::AccountIndex64 { .. } |
- Junction::AccountKey20 { .. } |
- Junction::PalletInstance { .. } |
- Junction::GeneralIndex { .. } |
- Junction::GeneralKey(..) |
- Junction::OnlyChild => true,
+ Junction::Parachain { .. }
+ | Junction::AccountId32 { .. }
+ | Junction::AccountIndex64 { .. }
+ | Junction::AccountKey20 { .. }
+ | Junction::PalletInstance { .. }
+ | Junction::GeneralIndex { .. }
+ | Junction::GeneralKey(..)
+ | Junction::OnlyChild
+ | Junction::Plurality { .. }
+ => true,
}
}
}
diff --git a/polkadot/xcm/src/v0/mod.rs b/polkadot/xcm/src/v0/mod.rs
index e2add536425..3beb0ee98e8 100644
--- a/polkadot/xcm/src/v0/mod.rs
+++ b/polkadot/xcm/src/v0/mod.rs
@@ -227,6 +227,20 @@ pub enum Xcm<Call> {
#[codec(compact)] sender: u32,
#[codec(compact)] recipient: u32,
},
+
+ /// A message to indicate that the embedded XCM is actually arriving on behalf of some consensus
+ /// location within the origin.
+ ///
+ /// Safety: No concerns.
+ ///
+ /// Kind: *Instruction*
+ ///
+ /// Errors:
+ #[codec(index = 10)]
+ RelayedFrom {
+ who: MultiLocation,
+ message: alloc::boxed::Box<Xcm<Call>>,
+ },
}
impl<Call> From<Xcm<Call>> for VersionedXcm<Call> {
@@ -268,7 +282,9 @@ impl<Call> Xcm<Call> {
HrmpChannelClosing { initiator, sender, recipient}
=> HrmpChannelClosing { initiator, sender, recipient},
Transact { origin_type, require_weight_at_most, call}
- => Transact { origin_type, require_weight_at_most, call: call.into() }
+ => Transact { origin_type, require_weight_at_most, call: call.into() },
+ RelayedFrom { who, message }
+ => RelayedFrom { who, message: alloc::boxed::Box::new((*message).into()) },
}
}
}
diff --git a/polkadot/xcm/src/v0/multi_location.rs b/polkadot/xcm/src/v0/multi_location.rs
index f2ac7f891e5..2dd448c745b 100644
--- a/polkadot/xcm/src/v0/multi_location.rs
+++ b/polkadot/xcm/src/v0/multi_location.rs
@@ -539,6 +539,23 @@ impl MultiLocation {
}
}
+ /// Mutate `self` so that it is suffixed with `prefix`. The correct normalised form is returned, removing any
+ /// internal `Parent`s.
+ ///
+ /// Does not modify `self` and returns `Err` with `prefix` in case of overflow.
+ pub fn append_with(&mut self, suffix: MultiLocation) -> Result<(), MultiLocation> {
+ let mut prefix = suffix;
+ core::mem::swap(self, &mut prefix);
+ match self.prepend_with(prefix) {
+ Ok(()) => Ok(()),
+ Err(prefix) => {
+ let mut suffix = prefix;
+ core::mem::swap(self, &mut suffix);
+ Err(suffix)
+ }
+ }
+ }
+
/// Mutate `self` so that it is prefixed with `prefix`. The correct normalised form is returned, removing any
/// internal `Parent`s.
///
@@ -566,6 +583,12 @@ impl MultiLocation {
}
Ok(())
}
+
+ /// Returns true iff `self` is an interior location. For this it may not contain any `Junction`s for which
+ /// `Junction::is_interior` returns `false`. This
+ pub fn is_interior(&self) -> bool {
+ self.iter().all(Junction::is_interior)
+ }
}
impl From<MultiLocation> for VersionedMultiLocation {
diff --git a/polkadot/xcm/xcm-executor/src/lib.rs b/polkadot/xcm/xcm-executor/src/lib.rs
index 885b7a78c47..143ab111383 100644
--- a/polkadot/xcm/xcm-executor/src/lib.rs
+++ b/polkadot/xcm/xcm-executor/src/lib.rs
@@ -182,6 +182,14 @@ impl<Config: config::Config> XcmExecutor<Config> {
Config::ResponseHandler::on_response(origin, query_id, response);
None
}
+ (origin, Xcm::RelayedFrom { who, message }) => {
+ ensure!(who.is_interior(), XcmError::EscalationOfPrivilege);
+ let mut origin = origin;
+ origin.append_with(who).map_err(|_| XcmError::MultiLocationFull)?;
+ let surplus = Self::do_execute_xcm(origin, top_level, *message, weight_credit, None, trader)?;
+ total_surplus = total_surplus.saturating_add(surplus);
+ None
+ }
_ => Err(XcmError::UnhandledXcmMessage)?, // Unhandled XCM message.
};
--
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