fix(epoch_sync) Prevent Block Header sync during Epoch sync (#12868)

Issue #12564. Epoch sync is restricted to nodes at genesis. At the
moment node will not initialize Block Header sync but it can handle
BlockHeadersResponse anyway.

The commit provides addtional check on processig BlockHeadersResponse to
ensure that receiver node is not at EpochSync state.

chain/client/src/client.rs

@@ -40,7 +40,7 @@ use near_chunks::client::ShardedTransactionPool;
 use near_chunks::logic::{decode_encoded_chunk, persist_chunk};
 use near_chunks::shards_manager_actor::ShardsManagerActor;
 use near_client_primitives::debug::ChunkProduction;
-use near_client_primitives::types::{Error, StateSyncStatus};
+use near_client_primitives::types::{Error, StateSyncStatus, SyncStatus};
 use near_epoch_manager::shard_assignment::{account_id_to_shard_id, shard_id_to_uid};
 use near_epoch_manager::shard_tracker::ShardTracker;
 use near_epoch_manager::EpochManagerAdapter;
@@ -1623,6 +1623,11 @@ impl Client {
         headers: Vec<BlockHeader>,
         signer: &Option<Arc<ValidatorSigner>>,
     ) -> Result<(), near_chain::Error> {
+        if matches!(self.sync_handler.sync_status, SyncStatus::EpochSync(_)) {
+            return Err(near_chain::Error::Other(
+                "Cannot sync block headers during an epoch sync".to_owned(),
+            ));
+        };
         let mut challenges = vec![];
         self.chain.sync_block_headers(headers, &mut challenges)?;
         self.send_challenges(challenges, signer);

integration-tests/src/tests/client/process_blocks.rs

@@ -36,6 +36,7 @@ use near_o11y::WithSpanContextExt;
 use near_parameters::{ActionCosts, ExtCosts};
 use near_parameters::{RuntimeConfig, RuntimeConfigStore};
 use near_primitives::block::Approval;
+use near_primitives::block::GenesisId;
 use near_primitives::block_header::BlockHeader;
 use near_primitives::errors::TxExecutionError;
 use near_primitives::errors::{ActionError, ActionErrorKind, InvalidTxError};
@@ -1889,6 +1890,56 @@ fn test_not_resync_old_blocks() {
     }
 }
 
+#[test]
+fn test_reject_block_headers_during_epoch_sync() {
+    let mut genesis = Genesis::test(vec!["test0".parse().unwrap(), "test1".parse().unwrap()], 1);
+    let epoch_length = 2;
+    genesis.config.epoch_length = epoch_length;
+    let mut env =
+        TestEnv::builder(&genesis.config).clients_count(2).nightshade_runtimes(&genesis).build();
+
+    let mut blocks = vec![];
+    for i in 1..=epoch_length + 1 {
+        let block = env.clients[0].produce_block(i).unwrap().unwrap();
+        env.process_block(0, block.clone(), Provenance::PRODUCED);
+        blocks.push(block);
+    }
+
+    let sync_client = &mut env.clients[1];
+    let status = &mut sync_client.sync_handler.sync_status;
+    let chain = &sync_client.chain;
+    let highest_height = sync_client.config.epoch_sync.epoch_sync_horizon + 1;
+    let highest_height_peers = vec![HighestHeightPeerInfo {
+        archival: false,
+        genesis_id: GenesisId::default(),
+        highest_block_hash: *blocks.last().unwrap().hash(),
+        highest_block_height: blocks.len() as u64,
+        tracked_shards: vec![],
+        peer_info: PeerInfo::random(),
+    }];
+
+    // Running epoch sync, sets SyncStatus::EpochSync
+    assert_matches!(
+        sync_client.sync_handler.epoch_sync.run(
+            status,
+            chain,
+            highest_height,
+            &highest_height_peers
+        ),
+        Ok(()),
+        "Epoch sync failure"
+    );
+
+    let headers = blocks.iter().map(|b| b.header().clone()).collect::<Vec<_>>();
+    let signer = sync_client.validator_signer.get();
+    // actual attempt to sync headers during ongoing epoch sync
+    assert_matches!(
+        sync_client.sync_block_headers(headers, &signer),
+        Err(_),
+        "Block headers accepted during epoch sync"
+    );
+}
+
 #[test]
 fn test_gc_tail_update() {
     let mut genesis = Genesis::test(vec!["test0".parse().unwrap(), "test1".parse().unwrap()], 1);