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dmp.rs
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// Copyright 2020 Parity Technologies (UK) Ltd.
// This file is part of Polkadot.
// Polkadot is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Polkadot is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Polkadot. If not, see <http://www.gnu.org/licenses/>.
use crate::{
configuration::{self, HostConfiguration},
initializer,
};
use frame_support::pallet_prelude::*;
use primitives::v1::{DownwardMessage, Hash, Id as ParaId, InboundDownwardMessage};
use sp_runtime::traits::{BlakeTwo256, Hash as HashT, SaturatedConversion};
use sp_std::{fmt, prelude::*};
use xcm::latest::SendError;
pub use pallet::*;
/// An error sending a downward message.
#[cfg_attr(test, derive(Debug))]
pub enum QueueDownwardMessageError {
/// The message being sent exceeds the configured max message size.
ExceedsMaxMessageSize,
}
impl From<QueueDownwardMessageError> for SendError {
fn from(err: QueueDownwardMessageError) -> Self {
match err {
QueueDownwardMessageError::ExceedsMaxMessageSize => SendError::ExceedsMaxMessageSize,
}
}
}
/// An error returned by [`check_processed_downward_messages`] that indicates an acceptance check
/// didn't pass.
pub enum ProcessedDownwardMessagesAcceptanceErr {
/// If there are pending messages then `processed_downward_messages` should be at least 1,
AdvancementRule,
/// `processed_downward_messages` should not be greater than the number of pending messages.
Underflow { processed_downward_messages: u32, dmq_length: u32 },
}
impl fmt::Debug for ProcessedDownwardMessagesAcceptanceErr {
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
use ProcessedDownwardMessagesAcceptanceErr::*;
match *self {
AdvancementRule =>
write!(fmt, "DMQ is not empty, but processed_downward_messages is 0",),
Underflow { processed_downward_messages, dmq_length } => write!(
fmt,
"processed_downward_messages = {}, but dmq_length is only {}",
processed_downward_messages, dmq_length,
),
}
}
}
#[frame_support::pallet]
pub mod pallet {
use super::*;
#[pallet::pallet]
#[pallet::generate_store(pub(super) trait Store)]
pub struct Pallet<T>(_);
#[pallet::config]
pub trait Config: frame_system::Config + configuration::Config {}
/// The downward messages addressed for a certain para.
#[pallet::storage]
pub(crate) type DownwardMessageQueues<T: Config> = StorageMap<
_,
Twox64Concat,
ParaId,
Vec<InboundDownwardMessage<T::BlockNumber>>,
ValueQuery,
>;
/// A mapping that stores the downward message queue MQC head for each para.
///
/// Each link in this chain has a form:
/// `(prev_head, B, H(M))`, where
/// - `prev_head`: is the previous head hash or zero if none.
/// - `B`: is the relay-chain block number in which a message was appended.
/// - `H(M)`: is the hash of the message being appended.
#[pallet::storage]
pub(crate) type DownwardMessageQueueHeads<T: Config> =
StorageMap<_, Twox64Concat, ParaId, Hash, ValueQuery>;
#[pallet::call]
impl<T: Config> Pallet<T> {}
}
/// Routines and getters related to downward message passing.
impl<T: Config> Pallet<T> {
/// Block initialization logic, called by initializer.
pub(crate) fn initializer_initialize(_now: T::BlockNumber) -> Weight {
0
}
/// Block finalization logic, called by initializer.
pub(crate) fn initializer_finalize() {}
/// Called by the initializer to note that a new session has started.
pub(crate) fn initializer_on_new_session(
_notification: &initializer::SessionChangeNotification<T::BlockNumber>,
outgoing_paras: &[ParaId],
) {
Self::perform_outgoing_para_cleanup(outgoing_paras);
}
/// Iterate over all paras that were noted for offboarding and remove all the data
/// associated with them.
fn perform_outgoing_para_cleanup(outgoing: &[ParaId]) {
for outgoing_para in outgoing {
Self::clean_dmp_after_outgoing(outgoing_para);
}
}
/// Remove all relevant storage items for an outgoing parachain.
fn clean_dmp_after_outgoing(outgoing_para: &ParaId) {
<Self as Store>::DownwardMessageQueues::remove(outgoing_para);
<Self as Store>::DownwardMessageQueueHeads::remove(outgoing_para);
}
/// Enqueue a downward message to a specific recipient para.
///
/// When encoded, the message should not exceed the `config.max_downward_message_size`.
/// Otherwise, the message won't be sent and `Err` will be returned.
///
/// It is possible to send a downward message to a non-existent para. That, however, would lead
/// to a dangling storage. If the caller cannot statically prove that the recipient exists
/// then the caller should perform a runtime check.
pub fn queue_downward_message(
config: &HostConfiguration<T::BlockNumber>,
para: ParaId,
msg: DownwardMessage,
) -> Result<(), QueueDownwardMessageError> {
let serialized_len = msg.len() as u32;
if serialized_len > config.max_downward_message_size {
return Err(QueueDownwardMessageError::ExceedsMaxMessageSize)
}
let inbound =
InboundDownwardMessage { msg, sent_at: <frame_system::Pallet<T>>::block_number() };
// obtain the new link in the MQC and update the head.
<Self as Store>::DownwardMessageQueueHeads::mutate(para, |head| {
let new_head =
BlakeTwo256::hash_of(&(*head, inbound.sent_at, T::Hashing::hash_of(&inbound.msg)));
*head = new_head;
});
<Self as Store>::DownwardMessageQueues::mutate(para, |v| {
v.push(inbound);
});
Ok(())
}
/// Checks if the number of processed downward messages is valid.
pub(crate) fn check_processed_downward_messages(
para: ParaId,
processed_downward_messages: u32,
) -> Result<(), ProcessedDownwardMessagesAcceptanceErr> {
let dmq_length = Self::dmq_length(para);
if dmq_length > 0 && processed_downward_messages == 0 {
return Err(ProcessedDownwardMessagesAcceptanceErr::AdvancementRule)
}
if dmq_length < processed_downward_messages {
return Err(ProcessedDownwardMessagesAcceptanceErr::Underflow {
processed_downward_messages,
dmq_length,
})
}
Ok(())
}
/// Prunes the specified number of messages from the downward message queue of the given para.
pub(crate) fn prune_dmq(para: ParaId, processed_downward_messages: u32) -> Weight {
<Self as Store>::DownwardMessageQueues::mutate(para, |q| {
let processed_downward_messages = processed_downward_messages as usize;
if processed_downward_messages > q.len() {
// reaching this branch is unexpected due to the constraint established by
// `check_processed_downward_messages`. But better be safe than sorry.
q.clear();
} else {
*q = q.split_off(processed_downward_messages);
}
});
T::DbWeight::get().reads_writes(1, 1)
}
/// Returns the Head of Message Queue Chain for the given para or `None` if there is none
/// associated with it.
#[cfg(test)]
fn dmq_mqc_head(para: ParaId) -> Hash {
<Self as Store>::DownwardMessageQueueHeads::get(¶)
}
/// Returns the number of pending downward messages addressed to the given para.
///
/// Returns 0 if the para doesn't have an associated downward message queue.
pub(crate) fn dmq_length(para: ParaId) -> u32 {
<Self as Store>::DownwardMessageQueues::decode_len(¶)
.unwrap_or(0)
.saturated_into::<u32>()
}
/// Returns the downward message queue contents for the given para.
///
/// The most recent messages are the latest in the vector.
pub(crate) fn dmq_contents(recipient: ParaId) -> Vec<InboundDownwardMessage<T::BlockNumber>> {
<Self as Store>::DownwardMessageQueues::get(&recipient)
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::mock::{new_test_ext, Configuration, Dmp, MockGenesisConfig, Paras, System};
use hex_literal::hex;
use parity_scale_codec::Encode;
use primitives::v1::BlockNumber;
pub(crate) fn run_to_block(to: BlockNumber, new_session: Option<Vec<BlockNumber>>) {
while System::block_number() < to {
let b = System::block_number();
Paras::initializer_finalize(b);
Dmp::initializer_finalize();
if new_session.as_ref().map_or(false, |v| v.contains(&(b + 1))) {
Dmp::initializer_on_new_session(&Default::default(), &Vec::new());
}
System::on_finalize(b);
System::on_initialize(b + 1);
System::set_block_number(b + 1);
Paras::initializer_finalize(b + 1);
Dmp::initializer_initialize(b + 1);
}
}
fn default_genesis_config() -> MockGenesisConfig {
MockGenesisConfig {
configuration: crate::configuration::GenesisConfig {
config: crate::configuration::HostConfiguration {
max_downward_message_size: 1024,
..Default::default()
},
},
..Default::default()
}
}
fn queue_downward_message(
para_id: ParaId,
msg: DownwardMessage,
) -> Result<(), QueueDownwardMessageError> {
Dmp::queue_downward_message(&Configuration::config(), para_id, msg)
}
#[test]
fn clean_dmp_works() {
let a = ParaId::from(1312);
let b = ParaId::from(228);
let c = ParaId::from(123);
new_test_ext(default_genesis_config()).execute_with(|| {
// enqueue downward messages to A, B and C.
queue_downward_message(a, vec![1, 2, 3]).unwrap();
queue_downward_message(b, vec![4, 5, 6]).unwrap();
queue_downward_message(c, vec![7, 8, 9]).unwrap();
let notification = crate::initializer::SessionChangeNotification::default();
let outgoing_paras = vec![a, b];
Dmp::initializer_on_new_session(¬ification, &outgoing_paras);
assert!(<Dmp as Store>::DownwardMessageQueues::get(&a).is_empty());
assert!(<Dmp as Store>::DownwardMessageQueues::get(&b).is_empty());
assert!(!<Dmp as Store>::DownwardMessageQueues::get(&c).is_empty());
});
}
#[test]
fn dmq_length_and_head_updated_properly() {
let a = ParaId::from(1312);
let b = ParaId::from(228);
new_test_ext(default_genesis_config()).execute_with(|| {
assert_eq!(Dmp::dmq_length(a), 0);
assert_eq!(Dmp::dmq_length(b), 0);
queue_downward_message(a, vec![1, 2, 3]).unwrap();
assert_eq!(Dmp::dmq_length(a), 1);
assert_eq!(Dmp::dmq_length(b), 0);
assert!(!Dmp::dmq_mqc_head(a).is_zero());
assert!(Dmp::dmq_mqc_head(b).is_zero());
});
}
#[test]
fn dmp_mqc_head_fixture() {
let a = ParaId::from(2000);
new_test_ext(default_genesis_config()).execute_with(|| {
run_to_block(2, None);
assert!(Dmp::dmq_mqc_head(a).is_zero());
queue_downward_message(a, vec![1, 2, 3]).unwrap();
run_to_block(3, None);
queue_downward_message(a, vec![4, 5, 6]).unwrap();
assert_eq!(
Dmp::dmq_mqc_head(a),
hex!["88dc00db8cc9d22aa62b87807705831f164387dfa49f80a8600ed1cbe1704b6b"].into(),
);
});
}
#[test]
fn check_processed_downward_messages() {
let a = ParaId::from(1312);
new_test_ext(default_genesis_config()).execute_with(|| {
// processed_downward_messages=0 is allowed when the DMQ is empty.
assert!(Dmp::check_processed_downward_messages(a, 0).is_ok());
queue_downward_message(a, vec![1, 2, 3]).unwrap();
queue_downward_message(a, vec![4, 5, 6]).unwrap();
queue_downward_message(a, vec![7, 8, 9]).unwrap();
// 0 doesn't pass if the DMQ has msgs.
assert!(!Dmp::check_processed_downward_messages(a, 0).is_ok());
// a candidate can consume up to 3 messages
assert!(Dmp::check_processed_downward_messages(a, 1).is_ok());
assert!(Dmp::check_processed_downward_messages(a, 2).is_ok());
assert!(Dmp::check_processed_downward_messages(a, 3).is_ok());
// there is no 4 messages in the queue
assert!(!Dmp::check_processed_downward_messages(a, 4).is_ok());
});
}
#[test]
fn dmq_pruning() {
let a = ParaId::from(1312);
new_test_ext(default_genesis_config()).execute_with(|| {
assert_eq!(Dmp::dmq_length(a), 0);
queue_downward_message(a, vec![1, 2, 3]).unwrap();
queue_downward_message(a, vec![4, 5, 6]).unwrap();
queue_downward_message(a, vec![7, 8, 9]).unwrap();
assert_eq!(Dmp::dmq_length(a), 3);
// pruning 0 elements shouldn't change anything.
Dmp::prune_dmq(a, 0);
assert_eq!(Dmp::dmq_length(a), 3);
Dmp::prune_dmq(a, 2);
assert_eq!(Dmp::dmq_length(a), 1);
});
}
#[test]
fn queue_downward_message_critical() {
let a = ParaId::from(1312);
let mut genesis = default_genesis_config();
genesis.configuration.config.max_downward_message_size = 7;
new_test_ext(genesis).execute_with(|| {
let smol = [0; 3].to_vec();
let big = [0; 8].to_vec();
// still within limits
assert_eq!(smol.encode().len(), 4);
assert!(queue_downward_message(a, smol).is_ok());
// that's too big
assert_eq!(big.encode().len(), 9);
assert!(queue_downward_message(a, big).is_err());
});
}
#[test]
fn verify_dmq_mqc_head_is_externally_accessible() {
use hex_literal::hex;
use primitives::v1::well_known_keys;
let a = ParaId::from(2020);
new_test_ext(default_genesis_config()).execute_with(|| {
let head = sp_io::storage::get(&well_known_keys::dmq_mqc_head(a));
assert_eq!(head, None);
queue_downward_message(a, vec![1, 2, 3]).unwrap();
let head = sp_io::storage::get(&well_known_keys::dmq_mqc_head(a));
assert_eq!(
head,
Some(
hex!["434f8579a2297dfea851bf6be33093c83a78b655a53ae141a7894494c0010589"]
.to_vec()
)
);
});
}
}