Grandpa revert procedure (#11162)

* Grandpa revert procedure

* Trigger ci pipeline

* Test rename

* Update client/finality-grandpa/src/authorities.rs

Co-authored-by: André Silva <123550+andresilva@users.noreply.github.com>

substrate/client/finality-grandpa/src/lib.rs

@@ -63,6 +63,7 @@ use parking_lot::RwLock;
 use prometheus_endpoint::{PrometheusError, Registry};
 use sc_client_api::{
 	backend::{AuxStore, Backend},
+	utils::is_descendent_of,
 	BlockchainEvents, CallExecutor, ExecutionStrategy, ExecutorProvider, Finalizer, LockImportRun,
 	StorageProvider, TransactionFor,
 };
@@ -71,7 +72,7 @@ use sc_telemetry::{telemetry, TelemetryHandle, CONSENSUS_DEBUG, CONSENSUS_INFO};
 use sc_utils::mpsc::{tracing_unbounded, TracingUnboundedReceiver};
 use sp_api::ProvideRuntimeApi;
 use sp_application_crypto::AppKey;
-use sp_blockchain::{Error as ClientError, HeaderBackend, HeaderMetadata};
+use sp_blockchain::{Error as ClientError, HeaderBackend, HeaderMetadata, Result as ClientResult};
 use sp_consensus::SelectChain;
 use sp_core::crypto::ByteArray;
 use sp_keystore::{SyncCryptoStore, SyncCryptoStorePtr};
@@ -1162,3 +1163,49 @@ fn local_authority_id(
 			.map(|(p, _)| p.clone())
 	})
 }
+
+/// Reverts protocol aux data to at most the last finalized block.
+/// In particular, standard and forced authority set changes announced after the
+/// revert point are removed.
+pub fn revert<Block, Client>(client: Arc<Client>, blocks: NumberFor<Block>) -> ClientResult<()>
+where
+	Block: BlockT,
+	Client: AuxStore
+		+ HeaderMetadata<Block, Error = sp_blockchain::Error>
+		+ HeaderBackend<Block>
+		+ ProvideRuntimeApi<Block>,
+{
+	let best_number = client.info().best_number;
+	let finalized = client.info().finalized_number;
+	let revertible = blocks.min(best_number - finalized);
+
+	let number = best_number - revertible;
+	let hash = client
+		.block_hash_from_id(&BlockId::Number(number))?
+		.ok_or(ClientError::Backend(format!(
+			"Unexpected hash lookup failure for block number: {}",
+			number
+		)))?;
+
+	let info = client.info();
+	let persistent_data: PersistentData<Block> =
+		aux_schema::load_persistent(&*client, info.genesis_hash, Zero::zero(), || unreachable!())?;
+
+	let shared_authority_set = persistent_data.authority_set;
+	let mut authority_set = shared_authority_set.inner();
+
+	let is_descendent_of = is_descendent_of(&*client, None);
+	authority_set.revert(hash, number, &is_descendent_of);
+
+	// The following has the side effect to properly reset the current voter state.
+	let (set_id, set_ref) = authority_set.current();
+	let new_set = Some(NewAuthoritySet {
+		canon_hash: info.finalized_hash,
+		canon_number: info.finalized_number,
+		set_id,
+		authorities: set_ref.to_vec(),
+	});
+	aux_schema::update_authority_set::<Block, _, _>(&authority_set, new_set.as_ref(), |values| {
+		client.insert_aux(values, None)
+	})
+}