blacklist bad manifest hashes upon failure

sync/src/chain.rs

@@ -521,7 +521,8 @@ impl ChainSync {
 					sn > fork_block &&
 					self.highest_block.map_or(true, |highest| highest >= sn && (highest - sn) <= SNAPSHOT_RESTORE_THRESHOLD)
 				))
-				.filter_map(|(p, peer)| peer.snapshot_hash.map(|hash| (p, hash.clone())));
+				.filter_map(|(p, peer)| peer.snapshot_hash.map(|hash| (p, hash.clone())))
+				.filter(|&(_, ref hash)| !self.snapshot.is_known_bad(hash));
 
 			let mut snapshot_peers = HashMap::new();
 			let mut max_peers: usize = 0;
@@ -1075,10 +1076,18 @@ impl ChainSync {
 		}
 
 		// check service status
-		match io.snapshot_service().status() {
+		let status = io.snapshot_service().status();
+		match status {
 			RestorationStatus::Inactive | RestorationStatus::Failed => {
 				trace!(target: "sync", "{}: Snapshot restoration aborted", peer_id);
 				self.state = SyncState::WaitingPeers;
+
+				// only note bad if restoration failed.
+				if let (Some(hash), RestorationStatus::Failed) = (self.snapshot.snapshot_hash(), status) {
+					trace!(target: "sync", "Noting snapshot hash {} as bad", hash);
+					self.snapshot.note_bad(hash);
+				}
+
 				self.snapshot.clear();
 				self.continue_sync(io);
 				return Ok(());

sync/src/snapshot.rs

@@ -31,6 +31,7 @@ pub struct Snapshot {
 	downloading_chunks: HashSet<H256>,
 	completed_chunks: HashSet<H256>,
 	snapshot_hash: Option<H256>,
+	bad_hashes: HashSet<H256>,
 }
 
 impl Snapshot {
@@ -42,6 +43,7 @@ impl Snapshot {
 			downloading_chunks: HashSet::new(),
 			completed_chunks: HashSet::new(),
 			snapshot_hash: None,
+			bad_hashes: HashSet::new(),
 		}
 	}
 
@@ -109,6 +111,16 @@ impl Snapshot {
 		self.downloading_chunks.remove(hash);
 	}
 
+	// note snapshot hash as bad.
+	pub fn note_bad(&mut self, hash: H256) {
+		self.bad_hashes.insert(hash);
+	}
+
+	// whether snapshot hash is known to be bad.
+	pub fn is_known_bad(&self, hash: &H256) -> bool {
+		self.bad_hashes.contains(hash)
+	}
+
 	pub fn snapshot_hash(&self) -> Option<H256> {
 		self.snapshot_hash
 	}
@@ -205,5 +217,15 @@ mod test {
 		assert_eq!(snapshot.done_chunks(), snapshot.total_chunks());
 		assert_eq!(snapshot.snapshot_hash(), Some(manifest.into_rlp().sha3()));
 	}
+
+	#[test]
+	fn tracks_known_bad() {
+		let mut snapshot = Snapshot::new();
+		let hash = H256::random();
+
+		assert_eq!(snapshot.is_known_bad(&hash), false);
+		snapshot.note_bad(hash);
+		assert_eq!(snapshot.is_known_bad(&hash), true);
+	}
 }