Don't validate a block announcement when syncing (#177)

cumulus/network/src/lib.rs

@@ -23,7 +23,7 @@ mod tests;
 
 use sp_api::ProvideRuntimeApi;
 use sp_blockchain::{Error as ClientError, HeaderBackend};
-use sp_consensus::block_validation::{BlockAnnounceValidator, Validation};
+use sp_consensus::{block_validation::{BlockAnnounceValidator, Validation}, SyncOracle};
 use sp_core::traits::SpawnNamed;
 use sp_runtime::{
 	generic::BlockId,
@@ -55,14 +55,20 @@ pub struct JustifiedBlockAnnounceValidator<B, P> {
 	phantom: PhantomData<B>,
 	polkadot_client: Arc<P>,
 	para_id: ParaId,
+	polkadot_sync_oracle: Box<dyn SyncOracle + Send>,
 }
 
 impl<B, P> JustifiedBlockAnnounceValidator<B, P> {
-	pub fn new(polkadot_client: Arc<P>, para_id: ParaId) -> Self {
+	pub fn new(
+		polkadot_client: Arc<P>,
+		para_id: ParaId,
+		polkadot_sync_oracle: Box<dyn SyncOracle + Send>,
+	) -> Self {
 		Self {
 			phantom: Default::default(),
 			polkadot_client,
 			para_id,
+			polkadot_sync_oracle,
 		}
 	}
 }
@@ -77,6 +83,10 @@ where
 		header: &B::Header,
 		mut data: &[u8],
 	) -> Result<Validation, Box<dyn std::error::Error + Send>> {
+		if self.polkadot_sync_oracle.is_major_syncing() {
+			return Ok(Validation::Success { is_new_best: false });
+		}
+
 		let runtime_api = self.polkadot_client.runtime_api();
 		let polkadot_info = self.polkadot_client.info();