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    // Copyright 2015-2017 Parity Technologies (UK) Ltd.
    // This file is part of Parity.

    // Parity 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.

    // Parity 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 Parity.  If not, see <http://www.gnu.org/licenses/>.

    ///
    /// `BlockChain` synchronization strategy.
    /// Syncs to peers and keeps up to date.
    /// This implementation uses ethereum protocol v63
    ///
    /// Syncing strategy summary.
    /// Split the chain into ranges of N blocks each. Download ranges sequentially. Split each range into subchains of M blocks. Download subchains in parallel.
    /// State.
    /// Sync state consists of the following data:
    /// - s: State enum which can be one of the following values: `ChainHead`, `Blocks`, `Idle`
    /// - H: A set of downloaded block headers
    /// - B: A set of downloaded block bodies
    /// - S: Set of block subchain start block hashes to download.
    /// - l: Last imported / common block hash
    /// - P: A set of connected peers. For each peer we maintain its last known total difficulty and starting block hash being requested if any.
    /// General behaviour.
    /// We start with all sets empty, l is set to the best block in the block chain, s is set to `ChainHead`.
    /// If at any moment a bad block is reported by the block queue, we set s to `ChainHead`, reset l to the best block in the block chain and clear H, B and S.
    /// If at any moment P becomes empty, we set s to `ChainHead`, and clear H, B and S.
    ///
    /// Workflow for `ChainHead` state.
    /// In this state we try to get subchain headers with a single `GetBlockHeaders` request.
    /// On `NewPeer` / On `Restart`:
    /// 	If peer's total difficulty is higher and there are less than 5 peers downloading, request N/M headers with interval M+1 starting from l
    /// On `BlockHeaders(R)`:
    /// 	If R is empty:
    /// If l is equal to genesis block hash or l is more than 1000 blocks behind our best hash:
    /// Remove current peer from P. set l to the best block in the block chain. Select peer with maximum total difficulty from P and restart.
    /// Else
    /// 	Set l to l’s parent and restart.
    /// Else if we already have all the headers in the block chain or the block queue:
    /// 	Set s to `Idle`,
    /// Else
    /// 	Set S to R, set s to `Blocks`.
    ///
    /// All other messages are ignored.
    ///
    /// Workflow for `Blocks` state.
    /// In this state we download block headers and bodies from multiple peers.
    /// On `NewPeer` / On `Restart`:
    /// 	For all idle peers:
    /// Find a set of 256 or less block hashes in H which are not in B and not being downloaded by other peers. If the set is not empty:
    ///  	Request block bodies for the hashes in the set.
    /// Else
    /// 	Find an element in S which is  not being downloaded by other peers. If found: Request M headers starting from the element.
    ///
    /// On `BlockHeaders(R)`:
    /// If R is empty remove current peer from P and restart.
    /// 	Validate received headers:
    /// 		For each header find a parent in H or R or the blockchain. Restart if there is a block with unknown parent.
    /// 		Find at least one header from the received list in S. Restart if there is none.
    /// Go to `CollectBlocks`.
    ///
    /// On `BlockBodies(R)`:
    /// If R is empty remove current peer from P and restart.
    /// 	Add bodies with a matching header in H to B.
    /// 	Go to `CollectBlocks`.
    ///
    /// `CollectBlocks`:
    /// Find a chain of blocks C in H starting from h where h’s parent equals to l. The chain ends with the first block which does not have a body in B.
    /// Add all blocks from the chain to the block queue. Remove them from H and B. Set l to the hash of the last block from C.
    /// Update and merge subchain heads in S. For each h in S find a chain of blocks in B starting from h. Remove h from S. if the chain does not include an element from S add the end of the chain to S.
    /// If H is empty and S contains a single element set s to `ChainHead`.
    /// Restart.
    ///
    /// All other messages are ignored.
    /// Workflow for Idle state.
    /// On `NewBlock`:
    /// 	Import the block. If the block is unknown set s to `ChainHead` and restart.
    /// On `NewHashes`:
    /// 	Set s to `ChainHead` and restart.
    ///
    /// All other messages are ignored.
    ///

    use util::*;
    use rlp::*;
    use network::*;
    use ethcore::header::{BlockNumber, Header as BlockHeader};
    use ethcore::client::{BlockChainClient, BlockStatus, BlockId, BlockChainInfo, BlockImportError, BlockQueueInfo};
    use ethcore::error::*;
    use ethcore::snapshot::{ManifestData, RestorationStatus};
    use ethcore::transaction::PendingTransaction;
    use sync_io::SyncIo;
    use time;
    use super::SyncConfig;
    use block_sync::{BlockDownloader, BlockRequest, BlockDownloaderImportError as DownloaderImportError, DownloadAction};
    use rand::Rng;
    use snapshot::{Snapshot, ChunkType};
    use api::{EthProtocolInfo as PeerInfoDigest, WARP_SYNC_PROTOCOL_ID};
    use transactions_stats::{TransactionsStats, Stats as TransactionStats};

    known_heap_size!(0, PeerInfo);

    type PacketDecodeError = DecoderError;

    const PROTOCOL_VERSION_63: u8 = 63;
    const PROTOCOL_VERSION_62: u8 = 62;
    const PROTOCOL_VERSION_1: u8 = 1;
    const PROTOCOL_VERSION_2: u8 = 2;
    const MAX_BODIES_TO_SEND: usize = 256;
    const MAX_HEADERS_TO_SEND: usize = 512;
    const MAX_NODE_DATA_TO_SEND: usize = 1024;
    const MAX_RECEIPTS_TO_SEND: usize = 1024;
    const MAX_RECEIPTS_HEADERS_TO_SEND: usize = 256;
    const MIN_PEERS_PROPAGATION: usize = 4;
    const MAX_PEERS_PROPAGATION: usize = 128;
    const MAX_PEER_LAG_PROPAGATION: BlockNumber = 20;
    const MAX_NEW_HASHES: usize = 64;
    const MAX_TX_TO_IMPORT: usize = 512;
    const MAX_NEW_BLOCK_AGE: BlockNumber = 20;
    const MAX_TRANSACTION_SIZE: usize = 300*1024;
    // Maximal number of transactions in sent in single packet.
    const MAX_TRANSACTIONS_TO_PROPAGATE: usize = 64;
    // Min number of blocks to be behind for a snapshot sync
    const SNAPSHOT_RESTORE_THRESHOLD: BlockNumber = 100000;
    const SNAPSHOT_MIN_PEERS: usize = 3;

    const STATUS_PACKET: u8 = 0x00;
    const NEW_BLOCK_HASHES_PACKET: u8 = 0x01;
    const TRANSACTIONS_PACKET: u8 = 0x02;
    const GET_BLOCK_HEADERS_PACKET: u8 = 0x03;
    const BLOCK_HEADERS_PACKET: u8 = 0x04;
    const GET_BLOCK_BODIES_PACKET: u8 = 0x05;
    const BLOCK_BODIES_PACKET: u8 = 0x06;
    const NEW_BLOCK_PACKET: u8 = 0x07;

    const GET_NODE_DATA_PACKET: u8 = 0x0d;
    const NODE_DATA_PACKET: u8 = 0x0e;
    const GET_RECEIPTS_PACKET: u8 = 0x0f;
    const RECEIPTS_PACKET: u8 = 0x10;

    pub const ETH_PACKET_COUNT: u8 = 0x11;

    const GET_SNAPSHOT_MANIFEST_PACKET: u8 = 0x11;
    const SNAPSHOT_MANIFEST_PACKET: u8 = 0x12;
    const GET_SNAPSHOT_DATA_PACKET: u8 = 0x13;
    const SNAPSHOT_DATA_PACKET: u8 = 0x14;
    const CONSENSUS_DATA_PACKET: u8 = 0x15;

    pub const SNAPSHOT_SYNC_PACKET_COUNT: u8 = 0x16;

    const MAX_SNAPSHOT_CHUNKS_DOWNLOAD_AHEAD: usize = 3;

    const WAIT_PEERS_TIMEOUT_SEC: u64 = 5;
    const STATUS_TIMEOUT_SEC: u64 = 5;
    const HEADERS_TIMEOUT_SEC: u64 = 15;
    const BODIES_TIMEOUT_SEC: u64 = 10;
    const RECEIPTS_TIMEOUT_SEC: u64 = 10;
    const FORK_HEADER_TIMEOUT_SEC: u64 = 3;
    const SNAPSHOT_MANIFEST_TIMEOUT_SEC: u64 = 3;
    const SNAPSHOT_DATA_TIMEOUT_SEC: u64 = 60;

    #[derive(Copy, Clone, Eq, PartialEq, Debug)]
    /// Sync state
    pub enum SyncState {
    	/// Collecting enough peers to start syncing.
    	WaitingPeers,
    	/// Waiting for snapshot manifest download
    	SnapshotManifest,
    	/// Downloading snapshot data
    	SnapshotData,
    	/// Waiting for snapshot restoration progress.
    	SnapshotWaiting,
    	/// Downloading new blocks
    	Blocks,
    	/// Initial chain sync complete. Waiting for new packets
    	Idle,
    	/// Block downloading paused. Waiting for block queue to process blocks and free some space
    	Waiting,
    	/// Downloading blocks learned from `NewHashes` packet
    	NewBlocks,
    }

    /// Syncing status and statistics
    #[derive(Clone, Copy)]
    pub struct SyncStatus {
    	/// State
    	pub state: SyncState,
    	/// Syncing protocol version. That's the maximum protocol version we connect to.
    	pub protocol_version: u8,
    	/// The underlying p2p network version.
    	pub network_id: u64,
    	/// `BlockChain` height for the moment the sync started.
    	pub start_block_number: BlockNumber,
    	/// Last fully downloaded and imported block number (if any).
    	pub last_imported_block_number: Option<BlockNumber>,
    	/// Highest block number in the download queue (if any).
    	pub highest_block_number: Option<BlockNumber>,
    	/// Total number of blocks for the sync process.
    	pub blocks_total: BlockNumber,
    	/// Number of blocks downloaded so far.
    	pub blocks_received: BlockNumber,
    	/// Total number of connected peers
    	pub num_peers: usize,
    	/// Total number of active peers.
    	pub num_active_peers: usize,
    	/// Heap memory used in bytes.
    	pub mem_used: usize,
    	/// Snapshot chunks
    	pub num_snapshot_chunks: usize,
    	/// Snapshot chunks downloaded
    	pub snapshot_chunks_done: usize,
    	/// Last fully downloaded and imported ancient block number (if any).
    	pub last_imported_old_block_number: Option<BlockNumber>,
    }

    impl SyncStatus {
    	/// Indicates if snapshot download is in progress
    	pub fn is_snapshot_syncing(&self) -> bool {
    		self.state == SyncState::SnapshotManifest
    			|| self.state == SyncState::SnapshotData
    			|| self.state == SyncState::SnapshotWaiting
    	}

    	/// Returns max no of peers to display in informants
    	pub fn current_max_peers(&self, min_peers: u32, max_peers: u32) -> u32 {
    		if self.num_peers as u32 > min_peers {
    			max_peers
    		} else {
    			min_peers
    		}
    	}

    	/// Is it doing a major sync?
    	pub fn is_syncing(&self, queue_info: BlockQueueInfo) -> bool {
    		let is_syncing_state = match self.state { SyncState::Idle | SyncState::NewBlocks => false, _ => true };
    		let is_verifying = queue_info.unverified_queue_size + queue_info.verified_queue_size > 3;
    		is_verifying || is_syncing_state
    	}
    }

    #[derive(PartialEq, Eq, Debug, Clone)]
    /// Peer data type requested
    enum PeerAsking {
    	Nothing,
    	ForkHeader,
    	BlockHeaders,
    	BlockBodies,
    	BlockReceipts,
    	SnapshotManifest,
    	SnapshotData,
    }

    #[derive(PartialEq, Eq, Debug, Clone, Copy)]
    /// Block downloader channel.
    enum BlockSet {
    	/// New blocks better than out best blocks
    	NewBlocks,
    	/// Missing old blocks
    	OldBlocks,
    }
    #[derive(Clone, Eq, PartialEq)]
    enum ForkConfirmation {
    	/// Fork block confirmation pending.
    	Unconfirmed,
    	/// Peers chain is too short to confirm the fork.
    	TooShort,
    	/// Fork is confirmed.
    	Confirmed,
    }

    #[derive(Clone)]
    /// Syncing peer information
    struct PeerInfo {
    	/// eth protocol version
    	protocol_version: u8,
    	/// Peer chain genesis hash
    	genesis: H256,
    	/// Peer network id
    	network_id: u64,
    	/// Peer best block hash
    	latest_hash: H256,
    	/// Peer total difficulty if known
    	difficulty: Option<U256>,
    	/// Type of data currenty being requested from peer.
    	asking: PeerAsking,
    	/// A set of block numbers being requested
    	asking_blocks: Vec<H256>,
    	/// Holds requested header hash if currently requesting block header by hash
    	asking_hash: Option<H256>,
    	/// Holds requested snapshot chunk hash if any.
    	asking_snapshot_data: Option<H256>,
    	/// Request timestamp
    	ask_time: u64,
    	/// Holds a set of transactions recently sent to this peer to avoid spamming.
    	last_sent_transactions: HashSet<H256>,
    	/// Pending request is expired and result should be ignored
    	expired: bool,
    	/// Peer fork confirmation status
    	confirmation: ForkConfirmation,
    	/// Best snapshot hash
    	snapshot_hash: Option<H256>,
    	/// Best snapshot block number
    	snapshot_number: Option<BlockNumber>,
    	/// Block set requested
    	block_set: Option<BlockSet>,
    }

    impl PeerInfo {
    	fn can_sync(&self) -> bool {
    		self.confirmation == ForkConfirmation::Confirmed && !self.expired
    	}

    	fn is_allowed(&self) -> bool {
    		self.confirmation != ForkConfirmation::Unconfirmed && !self.expired
    	}

    	fn reset_asking(&mut self) {
    		self.asking_blocks.clear();
    		self.asking_hash = None;
    		// mark any pending requests as expired
    		if self.asking != PeerAsking::Nothing && self.is_allowed() {
    			self.expired = true;
    		}
    	}
    }

    #[cfg(not(test))]
    mod random {
    	use rand;
    	pub fn new() -> rand::ThreadRng { rand::thread_rng() }
    }
    #[cfg(test)]
    mod random {
    	use rand::{self, SeedableRng};
    	pub fn new() -> rand::XorShiftRng { rand::XorShiftRng::from_seed([0, 1, 2, 3]) }
    }

    /// Blockchain sync handler.
    /// See module documentation for more details.
    pub struct ChainSync {
    	/// Sync state
    	state: SyncState,
    	/// Last block number for the start of sync
    	starting_block: BlockNumber,
    	/// Highest block number seen
    	highest_block: Option<BlockNumber>,
    	/// All connected peers
    	peers: HashMap<PeerId, PeerInfo>,
    	/// Peers active for current sync round
    	active_peers: HashSet<PeerId>,
    	/// Block download process for new blocks
    	new_blocks: BlockDownloader,
    	/// Block download process for ancient blocks
    	old_blocks: Option<BlockDownloader>,
    	/// Last propagated block number
    	last_sent_block_number: BlockNumber,
    	/// Network ID
    	network_id: u64,
    	/// Optional fork block to check
    	fork_block: Option<(BlockNumber, H256)>,
    	/// Snapshot downloader.
    	snapshot: Snapshot,
    	/// Connected peers pending Status message.
    	/// Value is request timestamp.
    	handshaking_peers: HashMap<PeerId, u64>,
    	/// Sync start timestamp. Measured when first peer is connected
    	sync_start_time: Option<u64>,
    	/// Transactions propagation statistics
    	transactions_stats: TransactionsStats,
    	/// Enable ancient block downloading
    	download_old_blocks: bool,
    }

    type RlpResponseResult = Result<Option<(PacketId, RlpStream)>, PacketDecodeError>;

    impl ChainSync {
    	/// Create a new instance of syncing strategy.
    	pub fn new(config: SyncConfig, chain: &BlockChainClient) -> ChainSync {
    		let chain_info = chain.chain_info();
    		let mut sync = ChainSync {
    			state: if config.warp_sync { SyncState::WaitingPeers } else { SyncState::Idle },
    			starting_block: chain.chain_info().best_block_number,
    			highest_block: None,
    			peers: HashMap::new(),
    			handshaking_peers: HashMap::new(),
    			active_peers: HashSet::new(),
    			new_blocks: BlockDownloader::new(false, &chain_info.best_block_hash, chain_info.best_block_number),
    			old_blocks: None,
    			last_sent_block_number: 0,
    			network_id: config.network_id,
    			fork_block: config.fork_block,
    			download_old_blocks: config.download_old_blocks,
    			snapshot: Snapshot::new(),
    			sync_start_time: None,
    			transactions_stats: TransactionsStats::default(),
    		};
    		sync.update_targets(chain);
    		sync
    	}

    	/// Returns synchonization status
    	pub fn status(&self) -> SyncStatus {
    		let last_imported_number = self.new_blocks.last_imported_block_number();
    		SyncStatus {
    			state: self.state.clone(),
    			protocol_version: PROTOCOL_VERSION_63,
    			network_id: self.network_id,
    			start_block_number: self.starting_block,
    			last_imported_block_number: Some(last_imported_number),
    			last_imported_old_block_number: self.old_blocks.as_ref().map(|d| d.last_imported_block_number()),
    			highest_block_number: self.highest_block.map(|n| max(n, last_imported_number)),
    			blocks_received: if last_imported_number > self.starting_block { last_imported_number - self.starting_block } else { 0 },
    			blocks_total: match self.highest_block { Some(x) if x > self.starting_block => x - self.starting_block, _ => 0 },
    			num_peers: self.peers.values().filter(|p| p.is_allowed()).count(),
    			num_active_peers: self.peers.values().filter(|p| p.is_allowed() && p.asking != PeerAsking::Nothing).count(),
    			num_snapshot_chunks: self.snapshot.total_chunks(),
    			snapshot_chunks_done: self.snapshot.done_chunks(),
    			mem_used:
    				self.new_blocks.heap_size()
    				+ self.old_blocks.as_ref().map_or(0, |d| d.heap_size())
    				+ self.peers.heap_size_of_children(),
    		}
    	}

    	/// Returns information on peers connections
    	pub fn peer_info(&self, peer_id: &PeerId) -> Option<PeerInfoDigest> {
    		self.peers.get(peer_id).map(|peer_data| {
    			PeerInfoDigest {
    				version: peer_data.protocol_version as u32,
    				difficulty: peer_data.difficulty,
    				head: peer_data.latest_hash,
    			}
    		})
    	}

    	/// Returns transactions propagation statistics
    	pub fn transactions_stats(&self) -> &H256FastMap<TransactionStats> {
    		self.transactions_stats.stats()
    	}

    	/// Updates transactions were received by a peer
    	pub fn transactions_received(&mut self, hashes: Vec<H256>, peer_id: PeerId) {
    		if let Some(mut peer_info) = self.peers.get_mut(&peer_id) {
    			peer_info.last_sent_transactions.extend(&hashes);
    		}
    	}

    	/// Abort all sync activity
    	pub fn abort(&mut self, io: &mut SyncIo) {
    		self.reset_and_continue(io);
    		self.peers.clear();
    	}

    	#[cfg_attr(feature="dev", allow(for_kv_map))] // Because it's not possible to get `values_mut()`
    	/// Reset sync. Clear all downloaded data but keep the queue
    	fn reset(&mut self, io: &mut SyncIo) {
    		self.new_blocks.reset();
    		self.snapshot.clear();
    		let chain_info = io.chain().chain_info();
    		if self.state == SyncState::SnapshotData {
    			debug!(target:"sync", "Aborting snapshot restore");
    			io.snapshot_service().abort_restore();
    		}
    		for (_, ref mut p) in &mut self.peers {
    			if p.block_set != Some(BlockSet::OldBlocks) {
    				p.reset_asking();
    				if p.difficulty.is_none() {
    					// assume peer has up to date difficulty
    					p.difficulty = Some(chain_info.pending_total_difficulty);
    				}
    			}
    		}
    		self.state = SyncState::Idle;
    		// Reactivate peers only if some progress has been made
    		// since the last sync round of if starting fresh.
    		self.active_peers = self.peers.keys().cloned().collect();
    	}

    	/// Restart sync
    	pub fn reset_and_continue(&mut self, io: &mut SyncIo) {
    		trace!(target: "sync", "Restarting");
    		self.reset(io);
    		self.continue_sync(io);
    	}

    	/// Remove peer from active peer set. Peer will be reactivated on the next sync
    	/// round.
    	fn deactivate_peer(&mut self, _io: &mut SyncIo, peer_id: PeerId) {
    		trace!(target: "sync", "Deactivating peer {}", peer_id);
    		self.active_peers.remove(&peer_id);
    	}

    	fn maybe_start_snapshot_sync(&mut self, io: &mut SyncIo) {
    		if self.state != SyncState::WaitingPeers {
    			return;
    		}
    		// Make sure the snapshot block is not too far away from best block and network best block and
    		// that it is higher than fork detection block
    		let our_best_block = io.chain().chain_info().best_block_number;
    		let fork_block = self.fork_block.as_ref().map(|&(n, _)| n).unwrap_or(0);

    		let (best_hash, max_peers, snapshot_peers) = {
    			//collect snapshot infos from peers
    			let snapshots = self.peers.iter()
    				.filter(|&(_, p)| p.is_allowed() && p.snapshot_number.map_or(false, |sn|
    					our_best_block < sn && (sn - our_best_block) > SNAPSHOT_RESTORE_THRESHOLD &&
    					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())));

    			let mut snapshot_peers = HashMap::new();
    			let mut max_peers: usize = 0;
    			let mut best_hash = None;
    			for (p, hash) in snapshots {
    				let peers = snapshot_peers.entry(hash).or_insert_with(Vec::new);
    				peers.push(*p);
    				if peers.len() > max_peers {
    					max_peers = peers.len();
    					best_hash = Some(hash);
    				}
    			}
    			(best_hash, max_peers, snapshot_peers)
    		};

    		let timeout = self.sync_start_time.map_or(false, |t| ((time::precise_time_ns() - t) / 1_000_000_000) > WAIT_PEERS_TIMEOUT_SEC);

    		if let (Some(hash), Some(peers)) = (best_hash, best_hash.map_or(None, |h| snapshot_peers.get(&h))) {
    			if max_peers >= SNAPSHOT_MIN_PEERS {
    				trace!(target: "sync", "Starting confirmed snapshot sync {:?} with {:?}", hash, peers);
    				self.start_snapshot_sync(io, peers);
    			} else if timeout {
    				trace!(target: "sync", "Starting unconfirmed snapshot sync {:?} with {:?}", hash, peers);
    				self.start_snapshot_sync(io, peers);
    			}
    		} else if timeout {
    			trace!(target: "sync", "No snapshots found, starting full sync");
    			self.state = SyncState::Idle;
    			self.continue_sync(io);
    		}
    	}

    	fn start_snapshot_sync(&mut self, io: &mut SyncIo, peers: &[PeerId]) {
    		self.snapshot.clear();
    		for p in peers {
    			if self.peers.get(p).map_or(false, |p| p.asking == PeerAsking::Nothing) {
    				self.request_snapshot_manifest(io, *p);
    			}
    		}
    		self.state = SyncState::SnapshotManifest;
    	}

    	/// Restart sync disregarding the block queue status. May end up re-downloading up to QUEUE_SIZE blocks
    	pub fn restart(&mut self, io: &mut SyncIo) {
    		self.update_targets(io.chain());
    		self.reset_and_continue(io);
    	}

    	/// Update sync after the blockchain has been changed externally.
    	pub fn update_targets(&mut self, chain: &BlockChainClient) {
    		// Do not assume that the block queue/chain still has our last_imported_block
    		let chain = chain.chain_info();
    		self.new_blocks = BlockDownloader::new(false, &chain.best_block_hash, chain.best_block_number);
    		self.old_blocks = None;
    		if self.download_old_blocks {
    			if let (Some(ancient_block_hash), Some(ancient_block_number)) = (chain.ancient_block_hash, chain.ancient_block_number) {

    				trace!(target: "sync", "Downloading old blocks from {:?} (#{}) till {:?} (#{:?})", ancient_block_hash, ancient_block_number, chain.first_block_hash, chain.first_block_number);
    				let mut downloader = BlockDownloader::with_unlimited_reorg(true, &ancient_block_hash, ancient_block_number);
    				if let Some(hash) = chain.first_block_hash {
    					trace!(target: "sync", "Downloader target set to {:?}", hash);
    					downloader.set_target(&hash);
    				}
    				self.old_blocks = Some(downloader);
    			}
    		}
    	}

    	/// Called by peer to report status
    	fn on_peer_status(&mut self, io: &mut SyncIo, peer_id: PeerId, r: &UntrustedRlp) -> Result<(), PacketDecodeError> {
    		self.handshaking_peers.remove(&peer_id);
    		let protocol_version: u8 = r.val_at(0)?;
    		let warp_protocol = io.protocol_version(&WARP_SYNC_PROTOCOL_ID, peer_id) != 0;
    		let peer = PeerInfo {
    			protocol_version: protocol_version,
    			network_id: r.val_at(1)?,
    			difficulty: Some(r.val_at(2)?),
    			latest_hash: r.val_at(3)?,
    			genesis: r.val_at(4)?,
    			asking: PeerAsking::Nothing,
    			asking_blocks: Vec::new(),
    			asking_hash: None,
    			ask_time: 0,
    			last_sent_transactions: HashSet::new(),
    			expired: false,
    			confirmation: if self.fork_block.is_none() { ForkConfirmation::Confirmed } else { ForkConfirmation::Unconfirmed },
    			asking_snapshot_data: None,
    			snapshot_hash: if warp_protocol { Some(r.val_at(5)?) } else { None },
    			snapshot_number: if warp_protocol { Some(r.val_at(6)?) } else { None },
    			block_set: None,
    		};

    		if self.sync_start_time.is_none() {
    			self.sync_start_time = Some(time::precise_time_ns());
    		}

    		trace!(target: "sync", "New peer {} (protocol: {}, network: {:?}, difficulty: {:?}, latest:{}, genesis:{}, snapshot:{:?})",
    			peer_id, peer.protocol_version, peer.network_id, peer.difficulty, peer.latest_hash, peer.genesis, peer.snapshot_number);
    		if io.is_expired() {
    			trace!(target: "sync", "Status packet from expired session {}:{}", peer_id, io.peer_info(peer_id));
    			return Ok(());
    		}

    		if self.peers.contains_key(&peer_id) {
    			debug!(target: "sync", "Unexpected status packet from {}:{}", peer_id, io.peer_info(peer_id));
    			return Ok(());
    		}
    		let chain_info = io.chain().chain_info();
    		if peer.genesis != chain_info.genesis_hash {
    			io.disable_peer(peer_id);
    			trace!(target: "sync", "Peer {} genesis hash mismatch (ours: {}, theirs: {})", peer_id, chain_info.genesis_hash, peer.genesis);
    			return Ok(());
    		}
    		if peer.network_id != self.network_id {
    			io.disable_peer(peer_id);
    			trace!(target: "sync", "Peer {} network id mismatch (ours: {}, theirs: {})", peer_id, self.network_id, peer.network_id);
    			return Ok(());
    		}
    		if (warp_protocol && peer.protocol_version != PROTOCOL_VERSION_1 && peer.protocol_version != PROTOCOL_VERSION_2) || (!warp_protocol && peer.protocol_version != PROTOCOL_VERSION_63 && peer.protocol_version != PROTOCOL_VERSION_62) {
    			io.disable_peer(peer_id);
    			trace!(target: "sync", "Peer {} unsupported eth protocol ({})", peer_id, peer.protocol_version);
    			return Ok(());
    		}

    		self.peers.insert(peer_id.clone(), peer);
    		// Don't activate peer immediatelly when searching for common block.
    		// Let the current sync round complete first.
    		self.active_peers.insert(peer_id.clone());
    		debug!(target: "sync", "Connected {}:{}", peer_id, io.peer_info(peer_id));
    		if let Some((fork_block, _)) = self.fork_block {
    			self.request_fork_header_by_number(io, peer_id, fork_block);
    		} else {
    			self.sync_peer(io, peer_id, false);
    		}
    		Ok(())
    	}

    	#[cfg_attr(feature="dev", allow(cyclomatic_complexity, needless_borrow))]
    	/// Called by peer once it has new block headers during sync
    	fn on_peer_block_headers(&mut self, io: &mut SyncIo, peer_id: PeerId, r: &UntrustedRlp) -> Result<(), PacketDecodeError> {
    		let confirmed = match self.peers.get_mut(&peer_id) {
    			Some(ref mut peer) if peer.asking == PeerAsking::ForkHeader => {
    				peer.asking = PeerAsking::Nothing;
    				let item_count = r.item_count();
    				let (fork_number, fork_hash) = self.fork_block.expect("ForkHeader request is sent only fork block is Some; qed").clone();
    				if item_count == 0 || item_count != 1 {
    					trace!(target: "sync", "{}: Chain is too short to confirm the block", peer_id);
    					peer.confirmation = ForkConfirmation::TooShort;
    				} else {
    					let header = r.at(0)?.as_raw();
    					if header.sha3() == fork_hash {
    						trace!(target: "sync", "{}: Confirmed peer", peer_id);
    						peer.confirmation = ForkConfirmation::Confirmed;
    						if !io.chain_overlay().read().contains_key(&fork_number) {
    							io.chain_overlay().write().insert(fork_number, header.to_vec());
    						}
    					} else {
    						trace!(target: "sync", "{}: Fork mismatch", peer_id);
    						io.disconnect_peer(peer_id);
    						return Ok(());
    					}
    				}
    				true
    			},
    			_ => false,
    		};
    		if confirmed {
    			self.sync_peer(io, peer_id, false);
    			return Ok(());
    		}

    		self.clear_peer_download(peer_id);
    		let expected_hash = self.peers.get(&peer_id).and_then(|p| p.asking_hash);
    		let allowed = self.peers.get(&peer_id).map(|p| p.is_allowed()).unwrap_or(false);
    		let block_set = self.peers.get(&peer_id).and_then(|p| p.block_set).unwrap_or(BlockSet::NewBlocks);
    		if !self.reset_peer_asking(peer_id, PeerAsking::BlockHeaders) || expected_hash.is_none() || !allowed {
    			trace!(target: "sync", "{}: Ignored unexpected headers, expected_hash = {:?}", peer_id, expected_hash);
    			self.continue_sync(io);
    			return Ok(());
    		}
    		let item_count = r.item_count();
    		trace!(target: "sync", "{} -> BlockHeaders ({} entries), state = {:?}, set = {:?}", peer_id, item_count, self.state, block_set);
    		if (self.state == SyncState::Idle || self.state == SyncState::WaitingPeers) && self.old_blocks.is_none() {
    			trace!(target: "sync", "Ignored unexpected block headers");
    			self.continue_sync(io);
    			return Ok(());
    		}
    		if self.state == SyncState::Waiting {
    			trace!(target: "sync", "Ignored block headers while waiting");
    			self.continue_sync(io);
    			return Ok(());
    		}

    		let result =  {
    			let mut downloader = match block_set {
    				BlockSet::NewBlocks => &mut self.new_blocks,
    				BlockSet::OldBlocks => {
    					match self.old_blocks {
    						None => {
    							trace!(target: "sync", "Ignored block headers while block download is inactive");
    							self.continue_sync(io);
    							return Ok(());
    						},
    						Some(ref mut blocks) => blocks,
    					}
    				}
    			};
    			downloader.import_headers(io, r, expected_hash)
    		};

    		match result {
    			Err(DownloaderImportError::Useless) => {
    				self.deactivate_peer(io, peer_id);
    			},
    			Err(DownloaderImportError::Invalid) => {
    				io.disable_peer(peer_id);
    				self.deactivate_peer(io, peer_id);
    				self.continue_sync(io);
    				return Ok(());
    			},
    			Ok(DownloadAction::Reset) => {
    				// mark all outstanding requests as expired
    				trace!("Resetting downloads for {:?}", block_set);
    				for (_, ref mut p) in self.peers.iter_mut().filter(|&(_, ref p)| p.block_set == Some(block_set)) {
    					p.reset_asking();
    				}

    			}
    			Ok(DownloadAction::None) => {},
    		}

    		self.collect_blocks(io, block_set);
    		// give a task to the same peer first if received valuable headers.
    		self.sync_peer(io, peer_id, false);
    		// give tasks to other peers
    		self.continue_sync(io);
    		Ok(())
    	}

    	/// Called by peer once it has new block bodies
    	fn on_peer_block_bodies(&mut self, io: &mut SyncIo, peer_id: PeerId, r: &UntrustedRlp) -> Result<(), PacketDecodeError> {
    		self.clear_peer_download(peer_id);
    		let block_set = self.peers.get(&peer_id).and_then(|p| p.block_set).unwrap_or(BlockSet::NewBlocks);
    		if !self.reset_peer_asking(peer_id, PeerAsking::BlockBodies) {
    			trace!(target: "sync", "{}: Ignored unexpected bodies", peer_id);
    			self.continue_sync(io);
    			return Ok(());
    		}
    		let item_count = r.item_count();
    		trace!(target: "sync", "{} -> BlockBodies ({} entries), set = {:?}", peer_id, item_count, block_set);
    		if item_count == 0 {
    			self.deactivate_peer(io, peer_id);
    		}
    		else if self.state == SyncState::Waiting {
    			trace!(target: "sync", "Ignored block bodies while waiting");
    		}
    		else
    		{
    			let result = {
    				let mut downloader = match block_set {
    					BlockSet::NewBlocks => &mut self.new_blocks,
    					BlockSet::OldBlocks => match self.old_blocks {
    						None => {
    							trace!(target: "sync", "Ignored block headers while block download is inactive");
    							self.continue_sync(io);
    							return Ok(());
    						},
    						Some(ref mut blocks) => blocks,
    					}
    				};
    				downloader.import_bodies(io, r)
    			};

    			match result {
    				Err(DownloaderImportError::Invalid) => {
    					io.disable_peer(peer_id);
    					self.deactivate_peer(io, peer_id);
    					self.continue_sync(io);
    					return Ok(());
    				},
    				Err(DownloaderImportError::Useless) => {
    					self.deactivate_peer(io, peer_id);
    				},
    				Ok(()) => (),
    			}

    			self.collect_blocks(io, block_set);
    			self.sync_peer(io, peer_id, false);
    		}
    		self.continue_sync(io);
    		Ok(())
    	}

    	/// Called by peer once it has new block receipts
    	fn on_peer_block_receipts(&mut self, io: &mut SyncIo, peer_id: PeerId, r: &UntrustedRlp) -> Result<(), PacketDecodeError> {
    		self.clear_peer_download(peer_id);
    		let block_set = self.peers.get(&peer_id).and_then(|p| p.block_set).unwrap_or(BlockSet::NewBlocks);
    		if !self.reset_peer_asking(peer_id, PeerAsking::BlockReceipts) {
    			trace!(target: "sync", "{}: Ignored unexpected receipts", peer_id);
    			self.continue_sync(io);
    			return Ok(());
    		}
    		let item_count = r.item_count();
    		trace!(target: "sync", "{} -> BlockReceipts ({} entries)", peer_id, item_count);
    		if item_count == 0 {
    			self.deactivate_peer(io, peer_id);
    		}
    		else if self.state == SyncState::Waiting {
    			trace!(target: "sync", "Ignored block receipts while waiting");
    		}
    		else
    		{
    			let result = {
    				let mut downloader = match block_set {
    					BlockSet::NewBlocks => &mut self.new_blocks,
    					BlockSet::OldBlocks => match self.old_blocks {
    						None => {
    							trace!(target: "sync", "Ignored block headers while block download is inactive");
    							self.continue_sync(io);
    							return Ok(());
    						},
    						Some(ref mut blocks) => blocks,
    					}
    				};
    				downloader.import_receipts(io, r)
    			};

    			match result {
    				Err(DownloaderImportError::Invalid) => {
    					io.disable_peer(peer_id);
    					self.deactivate_peer(io, peer_id);
    					self.continue_sync(io);
    					return Ok(());
    				},
    				Err(DownloaderImportError::Useless) => {
    					self.deactivate_peer(io, peer_id);
    				},
    				Ok(()) => (),
    			}

    			self.collect_blocks(io, block_set);
    			self.sync_peer(io, peer_id, false);
    		}
    		self.continue_sync(io);
    		Ok(())
    	}

    	/// Called by peer once it has new block bodies
    	#[cfg_attr(feature="dev", allow(cyclomatic_complexity))]
    	fn on_peer_new_block(&mut self, io: &mut SyncIo, peer_id: PeerId, r: &UntrustedRlp) -> Result<(), PacketDecodeError> {
    		if !self.peers.get(&peer_id).map_or(false, |p| p.can_sync()) {
    			trace!(target: "sync", "Ignoring new block from unconfirmed peer {}", peer_id);
    			return Ok(());
    		}
    		let difficulty: U256 = r.val_at(1)?;
    		if let Some(ref mut peer) = self.peers.get_mut(&peer_id) {
    			if peer.difficulty.map_or(true, |pd| difficulty > pd) {
    				peer.difficulty = Some(difficulty);
    			}
    		}
    		let block_rlp = r.at(0)?;
    		let header_rlp = block_rlp.at(0)?;
    		let h = header_rlp.as_raw().sha3();
    		trace!(target: "sync", "{} -> NewBlock ({})", peer_id, h);
    		let header: BlockHeader = header_rlp.as_val()?;
    		if header.number() > self.highest_block.unwrap_or(0) {
    			self.highest_block = Some(header.number());
    		}
    		let mut unknown = false;
    		{
    			if let Some(ref mut peer) = self.peers.get_mut(&peer_id) {
    				peer.latest_hash = header.hash();
    			}
    		}
    		let last_imported_number = self.new_blocks.last_imported_block_number();
    		if last_imported_number > header.number() && last_imported_number - header.number() > MAX_NEW_BLOCK_AGE {
    			trace!(target: "sync", "Ignored ancient new block {:?}", h);
    			io.disable_peer(peer_id);
    			return Ok(());
    		}
    		match io.chain().import_block(block_rlp.as_raw().to_vec()) {
    			Err(BlockImportError::Import(ImportError::AlreadyInChain)) => {
    				trace!(target: "sync", "New block already in chain {:?}", h);
    			},
    			Err(BlockImportError::Import(ImportError::AlreadyQueued)) => {
    				trace!(target: "sync", "New block already queued {:?}", h);
    			},
    			Ok(_) => {
    				// abort current download of the same block
    				self.complete_sync(io);
    				self.new_blocks.mark_as_known(&header.hash(), header.number());
    				trace!(target: "sync", "New block queued {:?} ({})", h, header.number());
    			},
    			Err(BlockImportError::Block(BlockError::UnknownParent(p))) => {
    				unknown = true;
    				trace!(target: "sync", "New block with unknown parent ({:?}) {:?}", p, h);
    			},
    			Err(e) => {
    				debug!(target: "sync", "Bad new block {:?} : {:?}", h, e);
    				io.disable_peer(peer_id);
    			}
    		};
    		if unknown {
    			if self.state != SyncState::Idle {
    				trace!(target: "sync", "NewBlock ignored while seeking");
    			} else {
    				trace!(target: "sync", "New unknown block {:?}", h);
    				//TODO: handle too many unknown blocks
    				self.sync_peer(io, peer_id, true);
    			}
    		}
    		self.continue_sync(io);
    		Ok(())
    	}

    	/// Handles `NewHashes` packet. Initiates headers download for any unknown hashes.
    	fn on_peer_new_hashes(&mut self, io: &mut SyncIo, peer_id: PeerId, r: &UntrustedRlp) -> Result<(), PacketDecodeError> {
    		if !self.peers.get(&peer_id).map_or(false, |p| p.can_sync()) {
    			trace!(target: "sync", "Ignoring new hashes from unconfirmed peer {}", peer_id);
    			return Ok(());
    		}
    		let hashes: Vec<_> = r.iter().take(MAX_NEW_HASHES).map(|item| (item.val_at::<H256>(0), item.val_at::<BlockNumber>(1))).collect();
    		if let Some(ref mut peer) = self.peers.get_mut(&peer_id) {
    			// Peer has new blocks with unknown difficulty
    			peer.difficulty = None;
    			if let Some(&(Ok(ref h), _)) = hashes.last() {
    				peer.latest_hash = h.clone();
    			}
    		}
    		if self.state != SyncState::Idle {
    			trace!(target: "sync", "Ignoring new hashes since we're already downloading.");
    			let max = r.iter().take(MAX_NEW_HASHES).map(|item| item.val_at::<BlockNumber>(1).unwrap_or(0)).fold(0u64, max);
    			if max > self.highest_block.unwrap_or(0) {
    				self.highest_block = Some(max);
    			}
    			self.continue_sync(io);
    			return Ok(());
    		}
    		trace!(target: "sync", "{} -> NewHashes ({} entries)", peer_id, r.item_count());
    		let mut max_height: BlockNumber = 0;
    		let mut new_hashes = Vec::new();
    		let last_imported_number = self.new_blocks.last_imported_block_number();
    		for (rh, rn) in hashes {
    			let hash = rh?;
    			let number = rn?;
    			if number > self.highest_block.unwrap_or(0) {
    				self.highest_block = Some(number);
    			}
    			if self.new_blocks.is_downloading(&hash) {
    				continue;
    			}
    			if last_imported_number > number && last_imported_number - number > MAX_NEW_BLOCK_AGE {
    				trace!(target: "sync", "Ignored ancient new block hash {:?}", hash);
    				io.disable_peer(peer_id);
    				continue;
    			}
    			match io.chain().block_status(BlockId::Hash(hash.clone())) {
    				BlockStatus::InChain  => {
    					trace!(target: "sync", "New block hash already in chain {:?}", hash);
    				},
    				BlockStatus::Queued => {
    					trace!(target: "sync", "New hash block already queued {:?}", hash);
    				},
    				BlockStatus::Unknown => {
    					new_hashes.push(hash.clone());
    					if number > max_height {
    						trace!(target: "sync", "New unknown block hash {:?}", hash);
    						if let Some(ref mut peer) = self.peers.get_mut(&peer_id) {
    							peer.latest_hash = hash.clone();
    						}
    						max_height = number;
    					}
    				},
    				BlockStatus::Bad => {
    					debug!(target: "sync", "Bad new block hash {:?}", hash);
    					io.disable_peer(peer_id);
    					return Ok(());
    				}
    			}
    		};
    		if max_height != 0 {
    			trace!(target: "sync", "Downloading blocks for new hashes");
    			self.new_blocks.reset_to(new_hashes);
    			self.state = SyncState::NewBlocks;
    			self.sync_peer(io, peer_id, true);
    		}
    		self.continue_sync(io);
    		Ok(())
    	}

    	/// Called when snapshot manifest is downloaded from a peer.
    	fn on_snapshot_manifest(&mut self, io: &mut SyncIo, peer_id: PeerId, r: &UntrustedRlp) -> Result<(), PacketDecodeError> {
    		if !self.peers.get(&peer_id).map_or(false, |p| p.can_sync()) {
    			trace!(target: "sync", "Ignoring snapshot manifest from unconfirmed peer {}", peer_id);
    			return Ok(());
    		}
    		self.clear_peer_download(peer_id);
    		if !self.reset_peer_asking(peer_id, PeerAsking::SnapshotManifest) || self.state != SyncState::SnapshotManifest {
    			trace!(target: "sync", "{}: Ignored unexpected/expired manifest", peer_id);
    			self.continue_sync(io);
    			return Ok(());
    		}

    		let manifest_rlp = r.at(0)?;
    		let manifest = match ManifestData::from_rlp(manifest_rlp.as_raw()) {
    			Err(e) => {
    				trace!(target: "sync", "{}: Ignored bad manifest: {:?}", peer_id, e);
    				io.disconnect_peer(peer_id);
    				self.continue_sync(io);
    				return Ok(());
    			}
    			Ok(manifest) => manifest,
    		};
    		self.snapshot.reset_to(&manifest, &manifest_rlp.as_raw().sha3());
    		io.snapshot_service().begin_restore(manifest);
    		self.state = SyncState::SnapshotData;

    		// give a task to the same peer first.
    		self.sync_peer(io, peer_id, false);
    		// give tasks to other peers
    		self.continue_sync(io);
    		Ok(())
    	}

    	/// Called when snapshot data is downloaded from a peer.
    	fn on_snapshot_data(&mut self, io: &mut SyncIo, peer_id: PeerId, r: &UntrustedRlp) -> Result<(), PacketDecodeError> {
    		if !self.peers.get(&peer_id).map_or(false, |p| p.can_sync()) {
    			trace!(target: "sync", "Ignoring snapshot data from unconfirmed peer {}", peer_id);
    			return Ok(());
    		}
    		self.clear_peer_download(peer_id);
    		if !self.reset_peer_asking(peer_id, PeerAsking::SnapshotData) || (self.state != SyncState::SnapshotData && self.state != SyncState::SnapshotWaiting) {
    			trace!(target: "sync", "{}: Ignored unexpected snapshot data", peer_id);
    			self.continue_sync(io);
    			return Ok(());
    		}

    		// check service status
    		match io.snapshot_service().status() {
    			RestorationStatus::Inactive | RestorationStatus::Failed => {
    				trace!(target: "sync", "{}: Snapshot restoration aborted", peer_id);
    				self.state = SyncState::WaitingPeers;
    				self.snapshot.clear();
    				self.continue_sync(io);
    				return Ok(());
    			},
    			RestorationStatus::Ongoing { .. } => {
    				trace!(target: "sync", "{}: Snapshot restoration is ongoing", peer_id);
    			},
    		}

    		let snapshot_data: Bytes = r.val_at(0)?;
    		match self.snapshot.validate_chunk(&snapshot_data) {
    			Ok(ChunkType::Block(hash)) => {
    				trace!(target: "sync", "{}: Processing block chunk", peer_id);
    				io.snapshot_service().restore_block_chunk(hash, snapshot_data);
    			}
    			Ok(ChunkType::State(hash)) => {
    				trace!(target: "sync", "{}: Processing state chunk", peer_id);
    				io.snapshot_service().restore_state_chunk(hash, snapshot_data);
    			}
    			Err(()) => {
    				trace!(target: "sync", "{}: Got bad snapshot chunk", peer_id);
    				io.disconnect_peer(peer_id);
    				self.continue_sync(io);
    				return Ok(());
    			}
    		}

    		if self.snapshot.is_complete() {
    			// wait for snapshot restoration process to complete
    			self.state = SyncState::SnapshotWaiting;
    		}
    		// give a task to the same peer first.
    		self.sync_peer(io, peer_id, false);
    		// give tasks to other peers
    		self.continue_sync(io);
    		Ok(())
    	}

    	/// Called by peer when it is disconnecting
    	pub fn on_peer_aborting(&mut self, io: &mut SyncIo, peer: PeerId) {
    		trace!(target: "sync", "== Disconnecting {}: {}", peer, io.peer_info(peer));
    		self.handshaking_peers.remove(&peer);
    		if self.peers.contains_key(&peer) {
    			debug!(target: "sync", "Disconnected {}", peer);
    			self.clear_peer_download(peer);
    			self.peers.remove(&peer);
    			self.active_peers.remove(&peer);
    			self.continue_sync(io);
    		}
    	}

    	/// Called when a new peer is connected
    	pub fn on_peer_connected(&mut self, io: &mut SyncIo, peer: PeerId) {
    		trace!(target: "sync", "== Connected {}: {}", peer, io.peer_info(peer));
    		if let Err(e) = self.send_status(io, peer) {
    			debug!(target:"sync", "Error sending status request: {:?}", e);
    			io.disable_peer(peer);
    		} else {
    			self.handshaking_peers.insert(peer, time::precise_time_ns());
    		}
    	}

    	/// Resume downloading
    	fn continue_sync(&mut self, io: &mut SyncIo) {
    		let mut peers: Vec<(PeerId, U256, u8)> = self.peers.iter().filter_map(|(k, p)|
    			if p.can_sync() { Some((*k, p.difficulty.unwrap_or_else(U256::zero), p.protocol_version)) } else { None }).collect();
    		random::new().shuffle(&mut peers); //TODO: sort by rating
    		// prefer peers with higher protocol version
    		peers.sort_by(|&(_, _, ref v1), &(_, _, ref v2)| v1.cmp(v2));
    		trace!(target: "sync", "Syncing with peers: {} active, {} confirmed, {} total", self.active_peers.len(), peers.len(), self.peers.len());
    		for (p, _, _) in peers {
    			if self.active_peers.contains(&p) {
    				self.sync_peer(io, p, false);
    			}
    		}
    		if (self.state != SyncState::WaitingPeers && self.state != SyncState::SnapshotWaiting && self.state != SyncState::Waiting && self.state != SyncState::Idle)
    			&& !self.peers.values().any(|p| p.asking != PeerAsking::Nothing && p.block_set != Some(BlockSet::OldBlocks) && p.can_sync()) {

    			self.complete_sync(io);
    		}
    	}

    	/// Called after all blocks have been downloaded
    	fn complete_sync(&mut self, io: &mut SyncIo) {
    		trace!(target: "sync", "Sync complete");
    		self.reset(io);
    		self.state = SyncState::Idle;
    	}

    	/// Enter waiting state
    	fn pause_sync(&mut self) {
    		trace!(target: "sync", "Block queue full, pausing sync");
    		self.state = SyncState::Waiting;
    	}

    	/// Find something to do for a peer. Called for a new peer or when a peer is done with its task.
    	fn sync_peer(&mut self, io: &mut SyncIo, peer_id: PeerId, force: bool) {
    		if !self.active_peers.contains(&peer_id) {
    			trace!(target: "sync", "Skipping deactivated peer {}", peer_id);
    			return;
    		}
    		let (peer_latest, peer_difficulty, peer_snapshot_number, peer_snapshot_hash) = {
    			if let Some(peer) = self.peers.get_mut(&peer_id) {
    				if peer.asking != PeerAsking::Nothing || !peer.can_sync() {
    					trace!(target: "sync", "Skipping busy peer {}", peer_id);
    					return;
    				}
    				if self.state == SyncState::Waiting {
    					trace!(target: "sync", "Waiting for the block queue");
    					return;
    				}
    				if self.state == SyncState::SnapshotWaiting {
    					trace!(target: "sync", "Waiting for the snapshot restoration");
    					return;
    				}
    				(peer.latest_hash.clone(), peer.difficulty.clone(), peer.snapshot_number.as_ref().cloned().unwrap_or(0), peer.snapshot_hash.as_ref().cloned())
    			} else {
    				return;
    			}
    		};
    		let chain_info = io.chain().chain_info();
    		let syncing_difficulty = chain_info.pending_total_difficulty;
    		let num_active_peers = self.peers.values().filter(|p| p.asking != PeerAsking::Nothing).count();

    		let higher_difficulty = peer_difficulty.map_or(true, |pd| pd > syncing_difficulty);
    		if force || higher_difficulty || self.old_blocks.is_some() {
    			match self.state {
    				SyncState::WaitingPeers => {
    					trace!(target: "sync", "Checking snapshot sync: {} vs {}", peer_snapshot_number, chain_info.best_block_number);
    					self.maybe_start_snapshot_sync(io);
    				},
    				SyncState::Idle | SyncState::Blocks | SyncState::NewBlocks => {
    					if io.chain().queue_info().is_full() {
    						self.pause_sync();
    						return;
    					}

    					let have_latest = io.chain().block_status(BlockId::Hash(peer_latest)) != BlockStatus::Unknown;
    					trace!(target: "sync", "Considering peer {}, force={}, td={:?}, our td={}, latest={}, have_latest={}, state={:?}", peer_id, force, peer_difficulty, syncing_difficulty, peer_latest, have_latest, self.state);
    					if !have_latest && (higher_difficulty || force || self.state == SyncState::NewBlocks) {
    						// check if got new blocks to download
    						trace!(target: "sync", "Syncing with peer {}, force={}, td={:?}, our td={}, state={:?}", peer_id, force, peer_difficulty, syncing_difficulty, self.state);
    						if let Some(request) = self.new_blocks.request_blocks(io, num_active_peers) {
    							self.request_blocks(io, peer_id, request, BlockSet::NewBlocks);
    							if self.state == SyncState::Idle {
    								self.state = SyncState::Blocks;
    							}
    							return;
    						}
    					}

    					if let Some(request) = self.old_blocks.as_mut().and_then(|d| d.request_blocks(io, num_active_peers)) {
    						self.request_blocks(io, peer_id, request, BlockSet::OldBlocks);
    						return;
    					}
    				},
    				SyncState::SnapshotData => {
    					if let RestorationStatus::Ongoing { state_chunks_done, block_chunks_done, .. } = io.snapshot_service().status() {
    						if self.snapshot.done_chunks() - (state_chunks_done + block_chunks_done) as usize > MAX_SNAPSHOT_CHUNKS_DOWNLOAD_AHEAD {
    							trace!(target: "sync", "Snapshot queue full, pausing sync");
    							self.state = SyncState::SnapshotWaiting;
    							return;
    						}
    					}
    					if peer_snapshot_hash.is_some() && peer_snapshot_hash == self.snapshot.snapshot_hash() {
    						self.request_snapshot_data(io, peer_id);
    					}
    				},
    				SyncState::SnapshotManifest | //already downloading from other peer
    					SyncState::Waiting | SyncState::SnapshotWaiting => ()
    			}
    		} else {
    			trace!(target: "sync", "Skipping peer {}, force={}, td={:?}, our td={}, state={:?}", peer_id, force, peer_difficulty, syncing_difficulty, self.state);
    		}
    	}

    	/// Perofrm block download request`
    	fn request_blocks(&mut self, io: &mut SyncIo, peer_id: PeerId, request: BlockRequest, block_set: BlockSet) {
    		match request {
    			BlockRequest::Headers { start, count, skip } => {
    				self.request_headers_by_hash(io, peer_id, &start, count, skip, false, block_set);
    			},
    			BlockRequest::Bodies { hashes } => {
    				self.request_bodies(io, peer_id, hashes, block_set);
    			},
    			BlockRequest::Receipts { hashes } => {
    				self.request_receipts(io, peer_id, hashes, block_set);
    			},
    		}
    	}

    	/// Find some headers or blocks to download for a peer.
    	fn request_snapshot_data(&mut self, io: &mut SyncIo, peer_id: PeerId) {
    		self.clear_peer_download(peer_id);
    		// find chunk data to download
    		if let Some(hash) = self.snapshot.needed_chunk() {
    			if let Some(ref mut peer) = self.peers.get_mut(&peer_id) {
    				peer.asking_snapshot_data = Some(hash.clone());
    			}
    			self.request_snapshot_chunk(io, peer_id, &hash);
    		}
    	}

    	/// Clear all blocks/headers marked as being downloaded by a peer.
    	fn clear_peer_download(&mut self, peer_id: PeerId) {
    		if let Some(ref mut peer) = self.peers.get_mut(&peer_id) {
    			match peer.asking {
    				PeerAsking::BlockHeaders => {
    					if let Some(ref hash) = peer.asking_hash {
    						self.new_blocks.clear_header_download(hash);
    						if let Some(ref mut old) = self.old_blocks {
    							old.clear_header_download(hash);
    						}
    					}
    				},
    				PeerAsking::BlockBodies => {
    					self.new_blocks.clear_body_download(&peer.asking_blocks);
    					if let Some(ref mut old) = self.old_blocks {
    						old.clear_body_download(&peer.asking_blocks);
    					}
    				},
    				PeerAsking::BlockReceipts => {
    					self.new_blocks.clear_receipt_download(&peer.asking_blocks);
    					if let Some(ref mut old) = self.old_blocks {
    						old.clear_receipt_download(&peer.asking_blocks);
    					}
    				},
    				PeerAsking::SnapshotData => {
    					if let Some(hash) = peer.asking_snapshot_data {
    						self.snapshot.clear_chunk_download(&hash);
    					}
    				},
    				_ => (),
    			}
    		}
    	}

    	/// Checks if there are blocks fully downloaded that can be imported into the blockchain and does the import.
    	#[cfg_attr(feature="dev", allow(block_in_if_condition_stmt))]
    	fn collect_blocks(&mut self, io: &mut SyncIo, block_set: BlockSet) {
    		match block_set {
    			BlockSet::NewBlocks => {
    				if self.new_blocks.collect_blocks(io, self.state == SyncState::NewBlocks) == Err(DownloaderImportError::Invalid) {
    					self.restart(io);
    				}
    			},
    			BlockSet::OldBlocks => {
    				if self.old_blocks.as_mut().map_or(false, |downloader| { downloader.collect_blocks(io, false) == Err(DownloaderImportError::Invalid) }) {
    					self.restart(io);
    				} else if self.old_blocks.as_ref().map_or(false, |downloader| { downloader.is_complete() }) {
    					trace!(target: "sync", "Background block download is complete");
    					self.old_blocks = None;
    				}
    			}
    		}
    	}

    	/// Request headers from a peer by block hash
    	#[cfg_attr(feature="dev", allow(too_many_arguments))]
    	fn request_headers_by_hash(&mut self, sync: &mut SyncIo, peer_id: PeerId, h: &H256, count: u64, skip: u64, reverse: bool, set: BlockSet) {
    		trace!(target: "sync", "{} <- GetBlockHeaders: {} entries starting from {}, set = {:?}", peer_id, count, h, set);
    		let mut rlp = RlpStream::new_list(4);
    		rlp.append(h);
    		rlp.append(&count);
    		rlp.append(&skip);
    		rlp.append(&if reverse {1u32} else {0u32});
    		self.send_request(sync, peer_id, PeerAsking::BlockHeaders, GET_BLOCK_HEADERS_PACKET, rlp.out());
    		let peer = self.peers.get_mut(&peer_id).expect("peer_id may originate either from on_packet, where it is already validated or from enumerating self.peers. qed");
    		peer.asking_hash = Some(h.clone());
    		peer.block_set = Some(set);
    	}

    	/// Request headers from a peer by block number
    	#[cfg_attr(feature="dev", allow(too_many_arguments))]
    	fn request_fork_header_by_number(&mut self, sync: &mut SyncIo, peer_id: PeerId, n: BlockNumber) {
    		trace!(target: "sync", "{} <- GetForkHeader: at {}", peer_id, n);
    		let mut rlp = RlpStream::new_list(4);
    		rlp.append(&n);
    		rlp.append(&1u32);
    		rlp.append(&0u32);
    		rlp.append(&0u32);
    		self.send_request(sync, peer_id, PeerAsking::ForkHeader, GET_BLOCK_HEADERS_PACKET, rlp.out());
    	}

    	/// Request snapshot manifest from a peer.
    	fn request_snapshot_manifest(&mut self, sync: &mut SyncIo, peer_id: PeerId) {
    		trace!(target: "sync", "{} <- GetSnapshotManifest", peer_id);
    		let rlp = RlpStream::new_list(0);
    		self.send_request(sync, peer_id, PeerAsking::SnapshotManifest, GET_SNAPSHOT_MANIFEST_PACKET, rlp.out());
    	}

    	/// Request snapshot chunk from a peer.
    	fn request_snapshot_chunk(&mut self, sync: &mut SyncIo, peer_id: PeerId, chunk: &H256) {
    		trace!(target: "sync", "{} <- GetSnapshotData {:?}", peer_id, chunk);
    		let mut rlp = RlpStream::new_list(1);
    		rlp.append(chunk);
    		self.send_request(sync, peer_id, PeerAsking::SnapshotData, GET_SNAPSHOT_DATA_PACKET, rlp.out());
    	}

    	/// Request block bodies from a peer
    	fn request_bodies(&mut self, sync: &mut SyncIo, peer_id: PeerId, hashes: Vec<H256>, set: BlockSet) {
    		let mut rlp = RlpStream::new_list(hashes.len());
    		trace!(target: "sync", "{} <- GetBlockBodies: {} entries starting from {:?}, set = {:?}", peer_id, hashes.len(), hashes.first(), set);
    		for h in &hashes {
    			rlp.append(&h.clone());
    		}
    		self.send_request(sync, peer_id, PeerAsking::BlockBodies, GET_BLOCK_BODIES_PACKET, rlp.out());
    		let peer = self.peers.get_mut(&peer_id).expect("peer_id may originate either from on_packet, where it is already validated or from enumerating self.peers. qed");
    		peer.asking_blocks = hashes;
    		peer.block_set = Some(set);
    	}

    	/// Request block receipts from a peer
    	fn request_receipts(&mut self, sync: &mut SyncIo, peer_id: PeerId, hashes: Vec<H256>, set: BlockSet) {
    		let mut rlp = RlpStream::new_list(hashes.len());
    		trace!(target: "sync", "{} <- GetBlockReceipts: {} entries starting from {:?}, set = {:?}", peer_id, hashes.len(), hashes.first(), set);
    		for h in &hashes {
    			rlp.append(&h.clone());
    		}
    		self.send_request(sync, peer_id, PeerAsking::BlockReceipts, GET_RECEIPTS_PACKET, rlp.out());
    		let peer = self.peers.get_mut(&peer_id).expect("peer_id may originate either from on_packet, where it is already validated or from enumerating self.peers. qed");
    		peer.asking_blocks = hashes;
    		peer.block_set = Some(set);
    	}

    	/// Reset peer status after request is complete.
    	fn reset_peer_asking(&mut self, peer_id: PeerId, asking: PeerAsking) -> bool {
    		if let Some(ref mut peer) = self.peers.get_mut(&peer_id) {
    			peer.expired = false;
    			peer.block_set = None;
    			if peer.asking != asking {
    				trace!(target:"sync", "Asking {:?} while expected {:?}", peer.asking, asking);
    				peer.asking = PeerAsking::Nothing;
    				return false;
    			} else {
    				peer.asking = PeerAsking::Nothing;
    				return true;
    			}
    		}
    		false
    	}

    	/// Generic request sender
    	fn send_request(&mut self, sync: &mut SyncIo, peer_id: PeerId, asking: PeerAsking,  packet_id: PacketId, packet: Bytes) {
    		if let Some(ref mut peer) = self.peers.get_mut(&peer_id) {
    			if peer.asking != PeerAsking::Nothing {
    				warn!(target:"sync", "Asking {:?} while requesting {:?}", peer.asking, asking);
    			}
    			peer.asking = asking;
    			peer.ask_time = time::precise_time_ns();
    			let result = if packet_id >= ETH_PACKET_COUNT {
    				sync.send_protocol(WARP_SYNC_PROTOCOL_ID, peer_id, packet_id, packet)
    			} else {
    				sync.send(peer_id, packet_id, packet)
    			};
    			if let Err(e) = result {
    				debug!(target:"sync", "Error sending request: {:?}", e);
    				sync.disable_peer(peer_id);
    			}
    		}
    	}

    	/// Generic packet sender
    	fn send_packet(&mut self, sync: &mut SyncIo, peer_id: PeerId, packet_id: PacketId, packet: Bytes) {
    		if let Err(e) = sync.send(peer_id, packet_id, packet) {
    			debug!(target:"sync", "Error sending packet: {:?}", e);
    			sync.disable_peer(peer_id);
    		}
    	}

    	/// Called when peer sends us new transactions
    	fn on_peer_transactions(&mut self, io: &mut SyncIo, peer_id: PeerId, r: &UntrustedRlp) -> Result<(), PacketDecodeError> {
    		// Accept transactions only when fully synced
    		if !io.is_chain_queue_empty() || (self.state != SyncState::Idle && self.state != SyncState::NewBlocks) {
    			trace!(target: "sync", "{} Ignoring transactions while syncing", peer_id);
    			return Ok(());
    		}
    		if !self.peers.get(&peer_id).map_or(false, |p| p.can_sync()) {
    			trace!(target: "sync", "{} Ignoring transactions from unconfirmed/unknown peer", peer_id);
    		}

    		let mut item_count = r.item_count();
    		trace!(target: "sync", "{:02} -> Transactions ({} entries)", peer_id, item_count);
    		item_count = min(item_count, MAX_TX_TO_IMPORT);
    		let mut transactions = Vec::with_capacity(item_count);
    		for i in 0 .. item_count {
    			let rlp = r.at(i)?;
    			if rlp.as_raw().len() > MAX_TRANSACTION_SIZE {
    				debug!("Skipped oversized transaction of {} bytes", rlp.as_raw().len());
    				continue;
    			}
    			let tx = rlp.as_raw().to_vec();
    			transactions.push(tx);
    		}
    		io.chain().queue_transactions(transactions, peer_id);
    		Ok(())
    	}

    	/// Send Status message
    	fn send_status(&mut self, io: &mut SyncIo, peer: PeerId) -> Result<(), NetworkError> {
    		let warp_protocol_version = io.protocol_version(&WARP_SYNC_PROTOCOL_ID, peer);
    		let warp_protocol = warp_protocol_version != 0;
    		let protocol = if warp_protocol { warp_protocol_version } else { PROTOCOL_VERSION_63 };
    		trace!(target: "sync", "Sending status to {}, protocol version {}", peer, protocol);
    		let mut packet = RlpStream::new_list(if warp_protocol { 7 } else { 5 });
    		let chain = io.chain().chain_info();
    		packet.append(&(protocol as u32));
    		packet.append(&self.network_id);
    		packet.append(&chain.total_difficulty);
    		packet.append(&chain.best_block_hash);
    		packet.append(&chain.genesis_hash);
    		if warp_protocol {
    			let manifest = match self.old_blocks.is_some() {
    				true => None,
    				false => io.snapshot_service().manifest(),
    			};
    			let block_number = manifest.as_ref().map_or(0, |m| m.block_number);
    			let manifest_hash = manifest.map_or(H256::new(), |m| m.into_rlp().sha3());
    			packet.append(&manifest_hash);
    			packet.append(&block_number);
    		}
    		io.respond(STATUS_PACKET, packet.out())
    	}

    	/// Respond to GetBlockHeaders request
    	fn return_block_headers(io: &SyncIo, r: &UntrustedRlp, peer_id: PeerId) -> RlpResponseResult {
    		// Packet layout:
    		// [ block: { P , B_32 }, maxHeaders: P, skip: P, reverse: P in { 0 , 1 } ]
    		let max_headers: usize = r.val_at(1)?;
    		let skip: usize = r.val_at(2)?;
    		let reverse: bool = r.val_at(3)?;
    		let last = io.chain().chain_info().best_block_number;
    		let number = if r.at(0)?.size() == 32 {
    			// id is a hash
    			let hash: H256 = r.val_at(0)?;
    			trace!(target: "sync", "{} -> GetBlockHeaders (hash: {}, max: {}, skip: {}, reverse:{})", peer_id, hash, max_headers, skip, reverse);
    			match io.chain().block_header(BlockId::Hash(hash)) {
    				Some(hdr) => {
    					let number = hdr.number().into();
    					debug_assert_eq!(hdr.sha3(), hash);

    					if max_headers == 1 || io.chain().block_hash(BlockId::Number(number)) != Some(hash) {
    						// Non canonical header or single header requested
    						// TODO: handle single-step reverse hashchains of non-canon hashes
    						trace!(target:"sync", "Returning single header: {:?}", hash);
    						let mut rlp = RlpStream::new_list(1);
    						rlp.append_raw(&hdr.into_inner(), 1);
    						return Ok(Some((BLOCK_HEADERS_PACKET, rlp)));
    					}
    					number
    				}
    				None => return Ok(Some((BLOCK_HEADERS_PACKET, RlpStream::new_list(0)))) //no such header, return nothing
    			}
    		} else {
    			trace!(target: "sync", "{} -> GetBlockHeaders (number: {}, max: {}, skip: {}, reverse:{})", peer_id, r.val_at::<BlockNumber>(0)?, max_headers, skip, reverse);
    			r.val_at(0)?
    		};

    		let mut number = if reverse {
    			min(last, number)
    		} else {
    			max(0, number)
    		};
    		let max_count = min(MAX_HEADERS_TO_SEND, max_headers);
    		let mut count = 0;
    		let mut data = Bytes::new();
    		let inc = (skip + 1) as BlockNumber;
    		let overlay = io.chain_overlay().read();

    		while number <= last && count < max_count {
    			if let Some(hdr) = overlay.get(&number) {
    				trace!(target: "sync", "{}: Returning cached fork header", peer_id);
    				data.extend_from_slice(hdr);
    				count += 1;
    			} else if let Some(hdr) = io.chain().block_header(BlockId::Number(number)) {
    				data.append(&mut hdr.into_inner());
    				count += 1;
    			} else {
    				// No required block.
    				break;
    			}
    			if reverse {
    				if number <= inc || number == 0 {
    					break;
    				}
    				number -= inc;
    			}
    			else {
    				number += inc;
    			}
    		}
    		let mut rlp = RlpStream::new_list(count as usize);
    		rlp.append_raw(&data, count as usize);
    		trace!(target: "sync", "{} -> GetBlockHeaders: returned {} entries", peer_id, count);
    		Ok(Some((BLOCK_HEADERS_PACKET, rlp)))
    	}

    	/// Respond to GetBlockBodies request
    	fn return_block_bodies(io: &SyncIo, r: &UntrustedRlp, peer_id: PeerId) -> RlpResponseResult {
    		let mut count = r.item_count();
    		if count == 0 {
    			debug!(target: "sync", "Empty GetBlockBodies request, ignoring.");
    			return Ok(None);
    		}
    		count = min(count, MAX_BODIES_TO_SEND);
    		let mut added = 0usize;
    		let mut data = Bytes::new();
    		for i in 0..count {
    			if let Some(body) = io.chain().block_body(BlockId::Hash(r.val_at::<H256>(i)?)) {
    				data.append(&mut body.into_inner());
    				added += 1;
    			}
    		}
    		let mut rlp = RlpStream::new_list(added);
    		rlp.append_raw(&data, added);
    		trace!(target: "sync", "{} -> GetBlockBodies: returned {} entries", peer_id, added);
    		Ok(Some((BLOCK_BODIES_PACKET, rlp)))
    	}

    	/// Respond to GetNodeData request
    	fn return_node_data(io: &SyncIo, r: &UntrustedRlp, peer_id: PeerId) -> RlpResponseResult {
    		let mut count = r.item_count();
    		trace!(target: "sync", "{} -> GetNodeData: {} entries", peer_id, count);
    		if count == 0 {
    			debug!(target: "sync", "Empty GetNodeData request, ignoring.");
    			return Ok(None);
    		}
    		count = min(count, MAX_NODE_DATA_TO_SEND);
    		let mut added = 0usize;
    		let mut data = Vec::new();
    		for i in 0..count {
    			if let Some(node) = io.chain().state_data(&r.val_at::<H256>(i)?) {
    				data.push(node);
    				added += 1;
    			}
    		}
    		trace!(target: "sync", "{} -> GetNodeData: return {} entries", peer_id, added);
    		let mut rlp = RlpStream::new_list(added);
    		for d in data {
    			rlp.append(&d);
    		}
    		Ok(Some((NODE_DATA_PACKET, rlp)))
    	}

    	fn return_receipts(io: &SyncIo, rlp: &UntrustedRlp, peer_id: PeerId) -> RlpResponseResult {
    		let mut count = rlp.item_count();
    		trace!(target: "sync", "{} -> GetReceipts: {} entries", peer_id, count);
    		if count == 0 {
    			debug!(target: "sync", "Empty GetReceipts request, ignoring.");
    			return Ok(None);
    		}
    		count = min(count, MAX_RECEIPTS_HEADERS_TO_SEND);
    		let mut added_headers = 0usize;
    		let mut added_receipts = 0usize;
    		let mut data = Bytes::new();
    		for i in 0..count {
    			if let Some(mut receipts_bytes) = io.chain().block_receipts(&rlp.val_at::<H256>(i)?) {
    				data.append(&mut receipts_bytes);
    				added_receipts += receipts_bytes.len();
    				added_headers += 1;
    				if added_receipts > MAX_RECEIPTS_TO_SEND { break; }
    			}
    		}
    		let mut rlp_result = RlpStream::new_list(added_headers);
    		rlp_result.append_raw(&data, added_headers);
    		Ok(Some((RECEIPTS_PACKET, rlp_result)))
    	}

    	/// Respond to GetSnapshotManifest request
    	fn return_snapshot_manifest(io: &SyncIo, r: &UntrustedRlp, peer_id: PeerId) -> RlpResponseResult {
    		let count = r.item_count();
    		trace!(target: "sync", "{} -> GetSnapshotManifest", peer_id);
    		if count != 0 {
    			debug!(target: "sync", "Invalid GetSnapshotManifest request, ignoring.");
    			return Ok(None);
    		}
    		let rlp = match io.snapshot_service().manifest() {
    			Some(manifest) => {
    				trace!(target: "sync", "{} <- SnapshotManifest", peer_id);
    				let mut rlp = RlpStream::new_list(1);
    				rlp.append_raw(&manifest.into_rlp(), 1);
    				rlp
    			},
    			None => {
    				trace!(target: "sync", "{}: No manifest to return", peer_id);
    				RlpStream::new_list(0)
    			}
    		};
    		Ok(Some((SNAPSHOT_MANIFEST_PACKET, rlp)))
    	}

    	/// Respond to GetSnapshotData request
    	fn return_snapshot_data(io: &SyncIo, r: &UntrustedRlp, peer_id: PeerId) -> RlpResponseResult {
    		let hash: H256 = r.val_at(0)?;
    		trace!(target: "sync", "{} -> GetSnapshotData {:?}", peer_id, hash);
    		let rlp = match io.snapshot_service().chunk(hash) {
    			Some(data) => {
    				let mut rlp = RlpStream::new_list(1);
    				trace!(target: "sync", "{} <- SnapshotData", peer_id);
    				rlp.append(&data);
    				rlp
    			},
    			None => {
    				RlpStream::new_list(0)
    			}
    		};
    		Ok(Some((SNAPSHOT_DATA_PACKET, rlp)))
    	}

    	fn return_rlp<FRlp, FError>(io: &mut SyncIo, rlp: &UntrustedRlp, peer: PeerId, rlp_func: FRlp, error_func: FError) -> Result<(), PacketDecodeError>
    		where FRlp : Fn(&SyncIo, &UntrustedRlp, PeerId) -> RlpResponseResult,
    			FError : FnOnce(NetworkError) -> String
    	{
    		let response = rlp_func(io, rlp, peer);
    		match response {
    			Err(e) => Err(e),
    			Ok(Some((packet_id, rlp_stream))) => {
    				io.respond(packet_id, rlp_stream.out()).unwrap_or_else(
    					|e| debug!(target: "sync", "{:?}", error_func(e)));
    				Ok(())
    			}
    			_ => Ok(())
    		}
    	}

    	/// Dispatch incoming requests and responses
    	pub fn dispatch_packet(sync: &RwLock<ChainSync>, io: &mut SyncIo, peer: PeerId, packet_id: u8, data: &[u8]) {
    		let rlp = UntrustedRlp::new(data);
    		let result = match packet_id {
    			GET_BLOCK_BODIES_PACKET => ChainSync::return_rlp(io, &rlp, peer,
    				ChainSync::return_block_bodies,
    				|e| format!("Error sending block bodies: {:?}", e)),

    			GET_BLOCK_HEADERS_PACKET => ChainSync::return_rlp(io, &rlp, peer,
    				ChainSync::return_block_headers,
    				|e| format!("Error sending block headers: {:?}", e)),

    			GET_RECEIPTS_PACKET => ChainSync::return_rlp(io, &rlp, peer,
    				ChainSync::return_receipts,
    				|e| format!("Error sending receipts: {:?}", e)),

    			GET_NODE_DATA_PACKET => ChainSync::return_rlp(io, &rlp, peer,
    				ChainSync::return_node_data,
    				|e| format!("Error sending nodes: {:?}", e)),

    			GET_SNAPSHOT_MANIFEST_PACKET => ChainSync::return_rlp(io, &rlp, peer,
    				ChainSync::return_snapshot_manifest,
    				|e| format!("Error sending snapshot manifest: {:?}", e)),

    			GET_SNAPSHOT_DATA_PACKET => ChainSync::return_rlp(io, &rlp, peer,
    				ChainSync::return_snapshot_data,
    				|e| format!("Error sending snapshot data: {:?}", e)),
    			CONSENSUS_DATA_PACKET => ChainSync::on_consensus_packet(io, peer, &rlp),
    			_ => {
    				sync.write().on_packet(io, peer, packet_id, data);
    				Ok(())
    			}
    		};
    		result.unwrap_or_else(|e| {
    			debug!(target:"sync", "{} -> Malformed packet {} : {}", peer, packet_id, e);
    		})
    	}

    	pub fn on_packet(&mut self, io: &mut SyncIo, peer: PeerId, packet_id: u8, data: &[u8]) {
    		if packet_id != STATUS_PACKET && !self.peers.contains_key(&peer) {
    			debug!(target:"sync", "Unexpected packet {} from unregistered peer: {}:{}", packet_id, peer, io.peer_info(peer));
    			return;
    		}
    		let rlp = UntrustedRlp::new(data);
    		let result = match packet_id {
    			STATUS_PACKET => self.on_peer_status(io, peer, &rlp),
    			TRANSACTIONS_PACKET => self.on_peer_transactions(io, peer, &rlp),
    			BLOCK_HEADERS_PACKET => self.on_peer_block_headers(io, peer, &rlp),
    			BLOCK_BODIES_PACKET => self.on_peer_block_bodies(io, peer, &rlp),
    			RECEIPTS_PACKET => self.on_peer_block_receipts(io, peer, &rlp),
    			NEW_BLOCK_PACKET => self.on_peer_new_block(io, peer, &rlp),
    			NEW_BLOCK_HASHES_PACKET => self.on_peer_new_hashes(io, peer, &rlp),
    			SNAPSHOT_MANIFEST_PACKET => self.on_snapshot_manifest(io, peer, &rlp),
    			SNAPSHOT_DATA_PACKET => self.on_snapshot_data(io, peer, &rlp),
    			_ => {
    				debug!(target: "sync", "{}: Unknown packet {}", peer, packet_id);
    				Ok(())
    			}
    		};
    		result.unwrap_or_else(|e| {
    			debug!(target:"sync", "{} -> Malformed packet {} : {}", peer, packet_id, e);
    		})
    	}

    	#[cfg_attr(feature="dev", allow(match_same_arms))]
    	pub fn maintain_peers(&mut self, io: &mut SyncIo) {
    		let tick = time::precise_time_ns();
    		let mut aborting = Vec::new();
    		for (peer_id, peer) in &self.peers {
    			let elapsed = (tick - peer.ask_time) / 1_000_000_000;
    			let timeout = match peer.asking {
    				PeerAsking::BlockHeaders => elapsed > HEADERS_TIMEOUT_SEC,
    				PeerAsking::BlockBodies => elapsed > BODIES_TIMEOUT_SEC,
    				PeerAsking::BlockReceipts => elapsed > RECEIPTS_TIMEOUT_SEC,
    				PeerAsking::Nothing => false,
    				PeerAsking::ForkHeader => elapsed > FORK_HEADER_TIMEOUT_SEC,
    				PeerAsking::SnapshotManifest => elapsed > SNAPSHOT_MANIFEST_TIMEOUT_SEC,
    				PeerAsking::SnapshotData => elapsed > SNAPSHOT_DATA_TIMEOUT_SEC,
    			};
    			if timeout {
    				trace!(target:"sync", "Timeout {}", peer_id);
    				io.disconnect_peer(*peer_id);
    				aborting.push(*peer_id);
    			}
    		}
    		for p in aborting {
    			self.on_peer_aborting(io, p);
    		}

    		// Check for handshake timeouts
    		for (peer, ask_time) in &self.handshaking_peers {
    			let elapsed = (tick - ask_time) / 1_000_000_000;
    			if elapsed > STATUS_TIMEOUT_SEC {
    				trace!(target:"sync", "Status timeout {}", peer);
    				io.disconnect_peer(*peer);
    			}
    		}
    	}

    	fn check_resume(&mut self, io: &mut SyncIo) {
    		if self.state == SyncState::Waiting && !io.chain().queue_info().is_full() && self.state == SyncState::Waiting {
    			self.state = SyncState::Blocks;
    			self.continue_sync(io);
    		} else if self.state == SyncState::SnapshotWaiting {
    			match io.snapshot_service().status() {
    				RestorationStatus::Inactive => {
    					trace!(target:"sync", "Snapshot restoration is complete");
    					self.restart(io);
    					self.continue_sync(io);
    				},
    				RestorationStatus::Ongoing { state_chunks_done, block_chunks_done, .. } => {
    					if !self.snapshot.is_complete() && self.snapshot.done_chunks() - (state_chunks_done + block_chunks_done) as usize <= MAX_SNAPSHOT_CHUNKS_DOWNLOAD_AHEAD {
    						trace!(target:"sync", "Resuming snapshot sync");
    						self.state = SyncState::SnapshotData;
    						self.continue_sync(io);
    					}
    				},
    				RestorationStatus::Failed => {
    					trace!(target: "sync", "Snapshot restoration aborted");
    					self.state = SyncState::WaitingPeers;
    					self.snapshot.clear();
    					self.continue_sync(io);
    				},
    			}
    		}
    	}

    	/// creates rlp to send for the tree defined by 'from' and 'to' hashes
    	fn create_new_hashes_rlp(chain: &BlockChainClient, from: &H256, to: &H256) -> Option<Bytes> {
    		match chain.tree_route(from, to) {
    			Some(route) => {
    				let uncles = chain.find_uncles(from).unwrap_or_else(Vec::new);
    				match route.blocks.len() {
    					0 => None,
    					_ => {
    						let mut blocks = route.blocks;
    						blocks.extend(uncles);
    						let mut rlp_stream = RlpStream::new_list(blocks.len());
    						for block_hash in  blocks {
    							let mut hash_rlp = RlpStream::new_list(2);
    							let number = chain.block_header(BlockId::Hash(block_hash.clone()))
    								.expect("chain.tree_route and chain.find_uncles only return hahses of blocks that are in the blockchain. qed.").number();
    							hash_rlp.append(&block_hash);
    							hash_rlp.append(&number);
    							rlp_stream.append_raw(hash_rlp.as_raw(), 1);
    						}
    						Some(rlp_stream.out())
    					}
    				}
    			},
    			None => None
    		}
    	}

    	/// creates rlp from block bytes and total difficulty
    	fn create_block_rlp(bytes: &Bytes, total_difficulty: U256) -> Bytes {
    		let mut rlp_stream = RlpStream::new_list(2);
    		rlp_stream.append_raw(bytes, 1);
    		rlp_stream.append(&total_difficulty);
    		rlp_stream.out()
    	}

    	/// creates latest block rlp for the given client
    	fn create_latest_block_rlp(chain: &BlockChainClient) -> Bytes {
    		ChainSync::create_block_rlp(
    			&chain.block(BlockId::Hash(chain.chain_info().best_block_hash))
    				.expect("Best block always exists").into_inner(),
    			chain.chain_info().total_difficulty
    		)
    	}

    	/// creates given hash block rlp for the given client
    	fn create_new_block_rlp(chain: &BlockChainClient, hash: &H256) -> Bytes {
    		ChainSync::create_block_rlp(
    			&chain.block(BlockId::Hash(hash.clone())).expect("Block has just been sealed; qed").into_inner(),
    			chain.block_total_difficulty(BlockId::Hash(hash.clone())).expect("Block has just been sealed; qed.")
    		)
    	}

    	/// returns peer ids that have different blocks than our chain
    	fn get_lagging_peers(&mut self, chain_info: &BlockChainInfo) -> Vec<PeerId> {
    		let latest_hash = chain_info.best_block_hash;
    		self
    			.peers
    			.iter_mut()
    			.filter_map(|(&id, ref mut peer_info)| {
    				trace!(target: "sync", "Checking peer our best {} their best {}", latest_hash, peer_info.latest_hash);
    				if peer_info.latest_hash != latest_hash {
    					Some(id)
    				} else {
    					None
    				}
    			})
    			.collect::<Vec<_>>()
    	}

    	fn select_random_peers(peers: &[PeerId]) -> Vec<PeerId> {
    		// take sqrt(x) peers
    		let mut peers = peers.to_vec();
    		let mut count = (peers.len() as f64).powf(0.5).round() as usize;
    		count = min(count, MAX_PEERS_PROPAGATION);
    		count = max(count, MIN_PEERS_PROPAGATION);
    		random::new().shuffle(&mut peers);
    		peers.truncate(count);
    		peers
    	}

    	fn get_consensus_peers(&self) -> Vec<PeerId> {
    		self.peers.iter().filter_map(|(id, p)| if p.protocol_version == PROTOCOL_VERSION_2 { Some(*id) } else { None }).collect()
    	}

    	/// propagates latest block to a set of peers
    	fn propagate_blocks(&mut self, chain_info: &BlockChainInfo, io: &mut SyncIo, blocks: &[H256], peers: &[PeerId]) -> usize {
    		trace!(target: "sync", "Sending NewBlocks to {:?}", peers);
    		let mut sent = 0;
    		for peer_id in peers {
    			if blocks.is_empty() {
    				let rlp =  ChainSync::create_latest_block_rlp(io.chain());
    				self.send_packet(io, *peer_id, NEW_BLOCK_PACKET, rlp);
    			} else {
    				for h in blocks {
    					let rlp =  ChainSync::create_new_block_rlp(io.chain(), h);
    					self.send_packet(io, *peer_id, NEW_BLOCK_PACKET, rlp);
    				}
    			}
    			if let Some(ref mut peer) = self.peers.get_mut(peer_id) {
    				peer.latest_hash = chain_info.best_block_hash.clone();
    			}
    			sent += 1;
    		}
    		sent
    	}

    	/// propagates new known hashes to all peers
    	fn propagate_new_hashes(&mut self, chain_info: &BlockChainInfo, io: &mut SyncIo, peers: &[PeerId]) -> usize {
    		trace!(target: "sync", "Sending NewHashes to {:?}", peers);
    		let mut sent = 0;
    		let last_parent = &io.chain().best_block_header().parent_hash();
    		for peer_id in peers {
    			sent += match ChainSync::create_new_hashes_rlp(io.chain(), &last_parent, &chain_info.best_block_hash) {
    				Some(rlp) => {
    					{
    						if let Some(ref mut peer) = self.peers.get_mut(peer_id) {
    							peer.latest_hash = chain_info.best_block_hash.clone();
    						}
    					}
    					self.send_packet(io, *peer_id, NEW_BLOCK_HASHES_PACKET, rlp);
    					1
    				},
    				None => 0
    			}
    		}
    		sent
    	}

    	/// propagates new transactions to all peers
    	pub fn propagate_new_transactions(&mut self, io: &mut SyncIo) -> usize {
    		// Early out if nobody to send to.
    		if self.peers.is_empty() {
    			return 0;
    		}

    		let transactions = io.chain().ready_transactions();
    		if transactions.is_empty() {
    			return 0;
    		}

    		let (transactions, service_transactions): (Vec<_>, Vec<_>) = transactions.into_iter()
    			.partition(|tx| !tx.transaction.gas_price.is_zero());

    		// usual transactions could be propagated to all peers
    		let mut affected_peers = HashSet::new();
    		if !transactions.is_empty() {
    			let peers = self.select_peers_for_transactions(|_| true);
    			affected_peers = self.propagate_transactions_to_peers(io, peers, transactions);
    		}

    		// most of times service_transactions will be empty
    		// => there's no need to merge packets
    		if !service_transactions.is_empty() {
    			let service_transactions_peers = self.select_peers_for_transactions(|peer_id| accepts_service_transaction(&io.peer_info(*peer_id)));
    			let service_transactions_affected_peers = self.propagate_transactions_to_peers(io, service_transactions_peers, service_transactions);
    			affected_peers.extend(&service_transactions_affected_peers);
    		}

    		affected_peers.len()
    	}

    	fn select_peers_for_transactions<F>(&self, filter: F) -> Vec<PeerId>
    		where F: Fn(&PeerId) -> bool {
    		// sqrt(x)/x scaled to max u32
    		let fraction = (self.peers.len() as f64).powf(-0.5).mul(u32::max_value() as f64).round() as u32;
    		let small = self.peers.len() < MIN_PEERS_PROPAGATION;

    		let mut random = random::new();
    		self.peers.keys()
    			.cloned()
    			.filter(filter)
    			.filter(|_| small || random.next_u32() < fraction)
    			.take(MAX_PEERS_PROPAGATION)
    			.collect()
    	}

    	fn propagate_transactions_to_peers(&mut self, io: &mut SyncIo, peers: Vec<PeerId>, transactions: Vec<PendingTransaction>) -> HashSet<PeerId> {
    		let all_transactions_hashes = transactions.iter()
    			.map(|tx| tx.transaction.hash())
    			.collect::<HashSet<H256>>();
    		let all_transactions_rlp = {
    			let mut packet = RlpStream::new_list(transactions.len());
    			for tx in &transactions { packet.append(&tx.transaction); }
    			packet.out()
    		};

    		// Clear old transactions from stats
    		self.transactions_stats.retain(&all_transactions_hashes);

    		// sqrt(x)/x scaled to max u32
    		let block_number = io.chain().chain_info().best_block_number;

    		let lucky_peers = {
    			peers.into_iter()
    				.filter_map(|peer_id| {
    					let stats = &mut self.transactions_stats;
    					let peer_info = self.peers.get_mut(&peer_id)
    						.expect("peer_id is form peers; peers is result of select_peers_for_transactions; select_peers_for_transactions selects peers from self.peers; qed");

    					// Send all transactions
    					if peer_info.last_sent_transactions.is_empty() {
    						// update stats
    						for hash in &all_transactions_hashes {
    							let id = io.peer_session_info(peer_id).and_then(|info| info.id);
    							stats.propagated(*hash, id, block_number);
    						}
    						peer_info.last_sent_transactions = all_transactions_hashes.clone();
    						return Some((peer_id, all_transactions_hashes.len(), all_transactions_rlp.clone()));
    					}

    					// Get hashes of all transactions to send to this peer
    					let to_send = all_transactions_hashes.difference(&peer_info.last_sent_transactions)
    						.take(MAX_TRANSACTIONS_TO_PROPAGATE)
    						.cloned()
    						.collect::<HashSet<_>>();
    					if to_send.is_empty() {
    						return None;
    					}

    					// Construct RLP
    					let mut packet = RlpStream::new_list(to_send.len());
    					for tx in &transactions {
    						if to_send.contains(&tx.transaction.hash()) {
    							packet.append(&tx.transaction);
    							// update stats
    							let id = io.peer_session_info(peer_id).and_then(|info| info.id);
    							stats.propagated(tx.transaction.hash(), id, block_number);
    						}
    					}

    					peer_info.last_sent_transactions = all_transactions_hashes
    						.intersection(&peer_info.last_sent_transactions)
    						.chain(&to_send)
    						.cloned()
    						.collect();
    					Some((peer_id, to_send.len(), packet.out()))
    				})
    				.collect::<Vec<_>>()
    		};

    		// Send RLPs
    		let mut peers = HashSet::new();
    		if lucky_peers.len() > 0 {
    			let mut max_sent = 0;
    			let lucky_peers_len = lucky_peers.len();
    			for (peer_id, sent, rlp) in lucky_peers {
    				peers.insert(peer_id);
    				self.send_packet(io, peer_id, TRANSACTIONS_PACKET, rlp);
    				trace!(target: "sync", "{:02} <- Transactions ({} entries)", peer_id, sent);
    				max_sent = max(max_sent, sent);
    			}
    			debug!(target: "sync", "Sent up to {} transactions to {} peers.", max_sent, lucky_peers_len);
    		}

    		peers
    	}

    	fn propagate_latest_blocks(&mut self, io: &mut SyncIo, sealed: &[H256]) {
    		let chain_info = io.chain().chain_info();
    		if (((chain_info.best_block_number as i64) - (self.last_sent_block_number as i64)).abs() as BlockNumber) < MAX_PEER_LAG_PROPAGATION {
    			let mut peers = self.get_lagging_peers(&chain_info);
    			if sealed.is_empty() {
    				let hashes = self.propagate_new_hashes(&chain_info, io, &peers);
    				peers = ChainSync::select_random_peers(&peers);
    				let blocks = self.propagate_blocks(&chain_info, io, sealed, &peers);
    				if blocks != 0 || hashes != 0 {
    					trace!(target: "sync", "Sent latest {} blocks and {} hashes to peers.", blocks, hashes);
    				}
    			} else {
    				self.propagate_blocks(&chain_info, io, sealed, &peers);
    				self.propagate_new_hashes(&chain_info, io, &peers);
    				trace!(target: "sync", "Sent sealed block to all peers");
    			};
    		}
    		self.last_sent_block_number = chain_info.best_block_number;
    	}

    	/// Distribute valid proposed blocks to subset of current peers.
    	fn propagate_proposed_blocks(&mut self, io: &mut SyncIo, proposed: &[Bytes]) {
    		let peers = self.get_consensus_peers();
    		trace!(target: "sync", "Sending proposed blocks to {:?}", peers);
    		for block in proposed {
    			let rlp = ChainSync::create_block_rlp(
    				block,
    				io.chain().chain_info().total_difficulty
    			);
    			for peer_id in &peers {
    				self.send_packet(io, *peer_id, NEW_BLOCK_PACKET, rlp.clone());
    			}
    		}
    	}

    	/// Maintain other peers. Send out any new blocks and transactions
    	pub fn maintain_sync(&mut self, io: &mut SyncIo) {
    		self.maybe_start_snapshot_sync(io);
    		self.check_resume(io);
    	}

    	/// called when block is imported to chain - propagates the blocks and updates transactions sent to peers
    	pub fn chain_new_blocks(&mut self, io: &mut SyncIo, _imported: &[H256], invalid: &[H256], enacted: &[H256], _retracted: &[H256], sealed: &[H256], proposed: &[Bytes]) {
    		let queue_info = io.chain().queue_info();
    		let is_syncing = self.status().is_syncing(queue_info);

    		if !is_syncing || !sealed.is_empty() {
    			trace!(target: "sync", "Propagating blocks, state={:?}", self.state);
    			self.propagate_latest_blocks(io, sealed);
    			self.propagate_proposed_blocks(io, proposed);
    		}
    		if !invalid.is_empty() {
    			trace!(target: "sync", "Bad blocks in the queue, restarting");
    			self.restart(io);
    		}

    		if !is_syncing && !enacted.is_empty() && !self.peers.is_empty() {
    			// Select random peer to re-broadcast transactions to.
    			let peer = random::new().gen_range(0, self.peers.len());
    			trace!(target: "sync", "Re-broadcasting transactions to a random peer.");
    			self.peers.values_mut().nth(peer).map(|mut peer_info|
    				peer_info.last_sent_transactions.clear()
    			);
    		}
    	}

    	/// Called when peer sends us new consensus packet
    	fn on_consensus_packet(io: &mut SyncIo, peer_id: PeerId, r: &UntrustedRlp) -> Result<(), PacketDecodeError> {
    		trace!(target: "sync", "Received consensus packet from {:?}", peer_id);
    		io.chain().queue_consensus_message(r.as_raw().to_vec());
    		Ok(())
    	}

    	/// Broadcast consensus message to peers.
    	pub fn propagate_consensus_packet(&mut self, io: &mut SyncIo, packet: Bytes) {
    		let lucky_peers = ChainSync::select_random_peers(&self.get_consensus_peers());
    		trace!(target: "sync", "Sending consensus packet to {:?}", lucky_peers);
    		for peer_id in lucky_peers {
    			self.send_packet(io, peer_id, CONSENSUS_DATA_PACKET, packet.clone());
    		}
    	}
    }

    /// Checks if peer is able to process service transactions
    fn accepts_service_transaction(client_id: &str) -> bool {
    	// Parity versions starting from this will accept service-transactions
    	const SERVICE_TRANSACTIONS_VERSION: (u32, u32) = (1u32, 6u32);
    	// Parity client string prefix
    	const PARITY_CLIENT_ID_PREFIX: &'static str = "Parity/v";

    	if !client_id.starts_with(PARITY_CLIENT_ID_PREFIX) {
    		return false;
    	}
    	let ver: Vec<u32> = client_id[PARITY_CLIENT_ID_PREFIX.len()..].split('.')
    		.take(2)
    		.filter_map(|s| s.parse().ok())
    		.collect();
    	ver.len() == 2 && (ver[0] > SERVICE_TRANSACTIONS_VERSION.0 || (ver[0] == SERVICE_TRANSACTIONS_VERSION.0 && ver[1] >= SERVICE_TRANSACTIONS_VERSION.1))
    }

    #[cfg(test)]
    mod tests {
    	use std::collections::{HashSet, VecDeque};
    	use network::PeerId;
    	use tests::helpers::*;
    	use tests::snapshot::TestSnapshotService;
    	use util::{Uint, U256, Address, RwLock};
    	use util::sha3::Hashable;
    	use util::hash::{H256, FixedHash};
    	use util::bytes::Bytes;
    	use rlp::{Rlp, RlpStream, UntrustedRlp, View, Stream};
    	use super::*;
    	use ::SyncConfig;
    	use super::{PeerInfo, PeerAsking};
    	use ethkey;
    	use ethcore::header::*;
    	use ethcore::client::*;
    	use ethcore::transaction::UnverifiedTransaction;
    	use ethcore::miner::MinerService;

    	fn get_dummy_block(order: u32, parent_hash: H256) -> Bytes {
    		let mut header = Header::new();
    		header.set_gas_limit(0.into());
    		header.set_difficulty((order * 100).into());
    		header.set_timestamp((order * 10) as u64);
    		header.set_number(order as u64);
    		header.set_parent_hash(parent_hash);
    		header.set_state_root(H256::zero());

    		let mut rlp = RlpStream::new_list(3);
    		rlp.append(&header);
    		rlp.append_raw(&::rlp::EMPTY_LIST_RLP, 1);
    		rlp.append_raw(&::rlp::EMPTY_LIST_RLP, 1);
    		rlp.out()
    	}

    	fn get_dummy_blocks(order: u32, parent_hash: H256) -> Bytes {
    		let mut rlp = RlpStream::new_list(1);
    		rlp.append_raw(&get_dummy_block(order, parent_hash), 1);
    		let difficulty: U256 = (100 * order).into();
    		rlp.append(&difficulty);
    		rlp.out()
    	}

    	fn get_dummy_hashes() -> Bytes {
    		let mut rlp = RlpStream::new_list(5);
    		for _ in 0..5 {
    			let mut hash_d_rlp = RlpStream::new_list(2);
    			let hash: H256 = H256::from(0u64);
    			let diff: U256 = U256::from(1u64);
    			hash_d_rlp.append(&hash);
    			hash_d_rlp.append(&diff);

    			rlp.append_raw(&hash_d_rlp.out(), 1);
    		}

    		rlp.out()
    	}

    	fn queue_info(unverified: usize, verified: usize) -> BlockQueueInfo {
    		BlockQueueInfo {
    			unverified_queue_size: unverified,
    			verified_queue_size: verified,
    			verifying_queue_size: 0,
    			max_queue_size: 1000,
    			max_mem_use: 1000,
    			mem_used: 500
    		}
    	}

    	fn sync_status(state: SyncState) -> SyncStatus {
    		SyncStatus {
    			state: state,
    			protocol_version: 0,
    			network_id: 0,
    			start_block_number: 0,
    			last_imported_block_number: None,
    			highest_block_number: None,
    			blocks_total: 0,
    			blocks_received: 0,
    			num_peers: 0,
    			num_active_peers: 0,
    			mem_used: 0,
    			num_snapshot_chunks: 0,
    			snapshot_chunks_done: 0,
    			last_imported_old_block_number: None,
    		}
    	}

    	#[test]
    	fn is_still_verifying() {
    		assert!(!sync_status(SyncState::Idle).is_syncing(queue_info(2, 1)));
    		assert!(sync_status(SyncState::Idle).is_syncing(queue_info(2, 2)));
    	}

    	#[test]
    	fn is_synced_state() {
    		assert!(sync_status(SyncState::Blocks).is_syncing(queue_info(0, 0)));
    		assert!(!sync_status(SyncState::Idle).is_syncing(queue_info(0, 0)));
    	}

    	#[test]
    	fn return_receipts_empty() {
    		let mut client = TestBlockChainClient::new();
    		let queue = RwLock::new(VecDeque::new());
    		let ss = TestSnapshotService::new();
    		let io = TestIo::new(&mut client, &ss, &queue, None);

    		let result = ChainSync::return_receipts(&io, &UntrustedRlp::new(&[0xc0]), 0);

    		assert!(result.is_ok());
    	}

    	#[test]
    	fn return_receipts() {
    		let mut client = TestBlockChainClient::new();
    		let queue = RwLock::new(VecDeque::new());
    		let sync = dummy_sync_with_peer(H256::new(), &client);
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);

    		let mut receipt_list = RlpStream::new_list(4);
    		receipt_list.append(&H256::from("0000000000000000000000000000000000000000000000005555555555555555"));
    		receipt_list.append(&H256::from("ff00000000000000000000000000000000000000000000000000000000000000"));
    		receipt_list.append(&H256::from("fff0000000000000000000000000000000000000000000000000000000000000"));
    		receipt_list.append(&H256::from("aff0000000000000000000000000000000000000000000000000000000000000"));

    		let receipts_request = receipt_list.out();
    		// it returns rlp ONLY for hashes started with "f"
    		let result = ChainSync::return_receipts(&io, &UntrustedRlp::new(&receipts_request.clone()), 0);

    		assert!(result.is_ok());
    		let rlp_result = result.unwrap();
    		assert!(rlp_result.is_some());

    		// the length of two rlp-encoded receipts
    		assert_eq!(603, rlp_result.unwrap().1.out().len());

    		io.sender = Some(2usize);
    		ChainSync::dispatch_packet(&RwLock::new(sync), &mut io, 0usize, super::GET_RECEIPTS_PACKET, &receipts_request);
    		assert_eq!(1, io.packets.len());
    	}

    	#[test]
    	fn return_block_headers() {
    		use ethcore::views::HeaderView;
    		fn make_hash_req(h: &H256, count: usize, skip: usize, reverse: bool) -> Bytes {
    			let mut rlp = RlpStream::new_list(4);
    			rlp.append(h);
    			rlp.append(&count);
    			rlp.append(&skip);
    			rlp.append(&if reverse {1u32} else {0u32});
    			rlp.out()
    		}

    		fn make_num_req(n: usize, count: usize, skip: usize, reverse: bool) -> Bytes {
    			let mut rlp = RlpStream::new_list(4);
    			rlp.append(&n);
    			rlp.append(&count);
    			rlp.append(&skip);
    			rlp.append(&if reverse {1u32} else {0u32});
    			rlp.out()
    		}
    		fn to_header_vec(rlp: ::chain::RlpResponseResult) -> Vec<Bytes> {
    			Rlp::new(&rlp.unwrap().unwrap().1.out()).iter().map(|r| r.as_raw().to_vec()).collect()
    		}

    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(100, EachBlockWith::Nothing);
    		let blocks: Vec<_> = (0 .. 100)
    			.map(|i| (&client as &BlockChainClient).block(BlockId::Number(i as BlockNumber)).map(|b| b.into_inner()).unwrap()).collect();
    		let headers: Vec<_> = blocks.iter().map(|b| Rlp::new(b).at(0).as_raw().to_vec()).collect();
    		let hashes: Vec<_> = headers.iter().map(|h| HeaderView::new(h).sha3()).collect();

    		let queue = RwLock::new(VecDeque::new());
    		let ss = TestSnapshotService::new();
    		let io = TestIo::new(&mut client, &ss, &queue, None);

    		let unknown: H256 = H256::new();
    		let result = ChainSync::return_block_headers(&io, &UntrustedRlp::new(&make_hash_req(&unknown, 1, 0, false)), 0);
    		assert!(to_header_vec(result).is_empty());
    		let result = ChainSync::return_block_headers(&io, &UntrustedRlp::new(&make_hash_req(&unknown, 1, 0, true)), 0);
    		assert!(to_header_vec(result).is_empty());

    		let result = ChainSync::return_block_headers(&io, &UntrustedRlp::new(&make_hash_req(&hashes[2], 1, 0, true)), 0);
    		assert_eq!(to_header_vec(result), vec![headers[2].clone()]);

    		let result = ChainSync::return_block_headers(&io, &UntrustedRlp::new(&make_hash_req(&hashes[2], 1, 0, false)), 0);
    		assert_eq!(to_header_vec(result), vec![headers[2].clone()]);

    		let result = ChainSync::return_block_headers(&io, &UntrustedRlp::new(&make_hash_req(&hashes[50], 3, 5, false)), 0);
    		assert_eq!(to_header_vec(result), vec![headers[50].clone(), headers[56].clone(), headers[62].clone()]);

    		let result = ChainSync::return_block_headers(&io, &UntrustedRlp::new(&make_hash_req(&hashes[50], 3, 5, true)), 0);
    		assert_eq!(to_header_vec(result), vec![headers[50].clone(), headers[44].clone(), headers[38].clone()]);

    		let result = ChainSync::return_block_headers(&io, &UntrustedRlp::new(&make_num_req(2, 1, 0, true)), 0);
    		assert_eq!(to_header_vec(result), vec![headers[2].clone()]);

    		let result = ChainSync::return_block_headers(&io, &UntrustedRlp::new(&make_num_req(2, 1, 0, false)), 0);
    		assert_eq!(to_header_vec(result), vec![headers[2].clone()]);

    		let result = ChainSync::return_block_headers(&io, &UntrustedRlp::new(&make_num_req(50, 3, 5, false)), 0);
    		assert_eq!(to_header_vec(result), vec![headers[50].clone(), headers[56].clone(), headers[62].clone()]);

    		let result = ChainSync::return_block_headers(&io, &UntrustedRlp::new(&make_num_req(50, 3, 5, true)), 0);
    		assert_eq!(to_header_vec(result), vec![headers[50].clone(), headers[44].clone(), headers[38].clone()]);
    	}

    	#[test]
    	fn return_nodes() {
    		let mut client = TestBlockChainClient::new();
    		let queue = RwLock::new(VecDeque::new());
    		let sync = dummy_sync_with_peer(H256::new(), &client);
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);

    		let mut node_list = RlpStream::new_list(3);
    		node_list.append(&H256::from("0000000000000000000000000000000000000000000000005555555555555555"));
    		node_list.append(&H256::from("ffffffffffffffffffffffffffffffffffffffffffffaaaaaaaaaaaaaaaaaaaa"));
    		node_list.append(&H256::from("aff0000000000000000000000000000000000000000000000000000000000000"));

    		let node_request = node_list.out();
    		// it returns rlp ONLY for hashes started with "f"
    		let result = ChainSync::return_node_data(&io, &UntrustedRlp::new(&node_request.clone()), 0);

    		assert!(result.is_ok());
    		let rlp_result = result.unwrap();
    		assert!(rlp_result.is_some());

    		// the length of one rlp-encoded hashe
    		let rlp = rlp_result.unwrap().1.out();
    		let rlp = Rlp::new(&rlp);
    		assert_eq!(1, rlp.item_count());

    		io.sender = Some(2usize);

    		ChainSync::dispatch_packet(&RwLock::new(sync), &mut io, 0usize, super::GET_NODE_DATA_PACKET, &node_request);
    		assert_eq!(1, io.packets.len());
    	}

    	fn dummy_sync_with_peer(peer_latest_hash: H256, client: &BlockChainClient) -> ChainSync {
    		let mut sync = ChainSync::new(SyncConfig::default(), client);
    		insert_dummy_peer(&mut sync, 0, peer_latest_hash);
    		sync
    	}

    	fn insert_dummy_peer(sync: &mut ChainSync, peer_id: PeerId, peer_latest_hash: H256) {
    		sync.peers.insert(peer_id,
    			PeerInfo {
    				protocol_version: 0,
    				genesis: H256::zero(),
    				network_id: 0,
    				latest_hash: peer_latest_hash,
    				difficulty: None,
    				asking: PeerAsking::Nothing,
    				asking_blocks: Vec::new(),
    				asking_hash: None,
    				ask_time: 0,
    				last_sent_transactions: HashSet::new(),
    				expired: false,
    				confirmation: super::ForkConfirmation::Confirmed,
    				snapshot_number: None,
    				snapshot_hash: None,
    				asking_snapshot_data: None,
    				block_set: None,
    			});

    	}

    	#[test]
    	fn finds_lagging_peers() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(100, EachBlockWith::Uncle);
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(10), &client);
    		let chain_info = client.chain_info();

    		let lagging_peers = sync.get_lagging_peers(&chain_info);

    		assert_eq!(1, lagging_peers.len());
    	}

    	#[test]
    	fn calculates_tree_for_lagging_peer() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(15, EachBlockWith::Uncle);

    		let start = client.block_hash_delta_minus(4);
    		let end = client.block_hash_delta_minus(2);

    		// wrong way end -> start, should be None
    		let rlp = ChainSync::create_new_hashes_rlp(&client, &end, &start);
    		assert!(rlp.is_none());

    		let rlp = ChainSync::create_new_hashes_rlp(&client, &start, &end).unwrap();
    		// size of three rlp encoded hash-difficulty
    		assert_eq!(107, rlp.len());
    	}

    	#[test]
    	fn sends_new_hashes_to_lagging_peer() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(100, EachBlockWith::Uncle);
    		let queue = RwLock::new(VecDeque::new());
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);
    		let chain_info = client.chain_info();
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);

    		let peers = sync.get_lagging_peers(&chain_info);
    		let peer_count = sync.propagate_new_hashes(&chain_info, &mut io, &peers);

    		// 1 message should be send
    		assert_eq!(1, io.packets.len());
    		// 1 peer should be updated
    		assert_eq!(1, peer_count);
    		// NEW_BLOCK_HASHES_PACKET
    		assert_eq!(0x01, io.packets[0].packet_id);
    	}

    	#[test]
    	fn sends_latest_block_to_lagging_peer() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(100, EachBlockWith::Uncle);
    		let queue = RwLock::new(VecDeque::new());
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);
    		let chain_info = client.chain_info();
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);
    		let peers = sync.get_lagging_peers(&chain_info);
    		let peer_count = sync.propagate_blocks(&chain_info, &mut io, &[], &peers);

    		// 1 message should be send
    		assert_eq!(1, io.packets.len());
    		// 1 peer should be updated
    		assert_eq!(1, peer_count);
    		// NEW_BLOCK_PACKET
    		assert_eq!(0x07, io.packets[0].packet_id);
    	}

    	#[test]
    	fn sends_sealed_block() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(100, EachBlockWith::Uncle);
    		let queue = RwLock::new(VecDeque::new());
    		let hash = client.block_hash(BlockId::Number(99)).unwrap();
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);
    		let chain_info = client.chain_info();
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);
    		let peers = sync.get_lagging_peers(&chain_info);
    		let peer_count = sync.propagate_blocks(&chain_info, &mut io, &[hash.clone()], &peers);

    		// 1 message should be send
    		assert_eq!(1, io.packets.len());
    		// 1 peer should be updated
    		assert_eq!(1, peer_count);
    		// NEW_BLOCK_PACKET
    		assert_eq!(0x07, io.packets[0].packet_id);
    	}

    	#[test]
    	fn sends_proposed_block() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(2, EachBlockWith::Uncle);
    		let queue = RwLock::new(VecDeque::new());
    		let block = client.block(BlockId::Latest).unwrap().into_inner();
    		let mut sync = ChainSync::new(SyncConfig::default(), &client);
    		sync.peers.insert(0,
    			PeerInfo {
    				// Messaging protocol
    				protocol_version: 2,
    				genesis: H256::zero(),
    				network_id: 0,
    				latest_hash: client.block_hash_delta_minus(1),
    				difficulty: None,
    				asking: PeerAsking::Nothing,
    				asking_blocks: Vec::new(),
    				asking_hash: None,
    				ask_time: 0,
    				last_sent_transactions: HashSet::new(),
    				expired: false,
    				confirmation: super::ForkConfirmation::Confirmed,
    				snapshot_number: None,
    				snapshot_hash: None,
    				asking_snapshot_data: None,
    				block_set: None,
    			});
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);
    		sync.propagate_proposed_blocks(&mut io, &[block]);

    		// 1 message should be sent
    		assert_eq!(1, io.packets.len());
    		// NEW_BLOCK_PACKET
    		assert_eq!(0x07, io.packets[0].packet_id);
    	}

    	#[test]
    	fn propagates_transactions() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(100, EachBlockWith::Uncle);
    		client.insert_transaction_to_queue();
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(1), &client);
    		let queue = RwLock::new(VecDeque::new());
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);
    		let peer_count = sync.propagate_new_transactions(&mut io);
    		// Try to propagate same transactions for the second time
    		let peer_count2 = sync.propagate_new_transactions(&mut io);
    		// Even after new block transactions should not be propagated twice
    		sync.chain_new_blocks(&mut io, &[], &[], &[], &[], &[], &[]);
    		// Try to propagate same transactions for the third time
    		let peer_count3 = sync.propagate_new_transactions(&mut io);

    		// 1 message should be send
    		assert_eq!(1, io.packets.len());
    		// 1 peer should be updated but only once
    		assert_eq!(1, peer_count);
    		assert_eq!(0, peer_count2);
    		assert_eq!(0, peer_count3);
    		// TRANSACTIONS_PACKET
    		assert_eq!(0x02, io.packets[0].packet_id);
    	}

    	#[test]
    	fn does_not_propagate_new_transactions_after_new_block() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(100, EachBlockWith::Uncle);
    		client.insert_transaction_to_queue();
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(1), &client);
    		let queue = RwLock::new(VecDeque::new());
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);
    		let peer_count = sync.propagate_new_transactions(&mut io);
    		io.chain.insert_transaction_to_queue();
    		// New block import should not trigger propagation.
    		// (we only propagate on timeout)
    		sync.chain_new_blocks(&mut io, &[], &[], &[], &[], &[], &[]);

    		// 2 message should be send
    		assert_eq!(1, io.packets.len());
    		// 1 peer should receive the message
    		assert_eq!(1, peer_count);
    		// TRANSACTIONS_PACKET
    		assert_eq!(0x02, io.packets[0].packet_id);
    	}

    	#[test]
    	fn does_not_fail_for_no_peers() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(100, EachBlockWith::Uncle);
    		client.insert_transaction_to_queue();
    		// Sync with no peers
    		let mut sync = ChainSync::new(SyncConfig::default(), &client);
    		let queue = RwLock::new(VecDeque::new());
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);
    		let peer_count = sync.propagate_new_transactions(&mut io);
    		sync.chain_new_blocks(&mut io, &[], &[], &[], &[], &[], &[]);
    		// Try to propagate same transactions for the second time
    		let peer_count2 = sync.propagate_new_transactions(&mut io);

    		assert_eq!(0, io.packets.len());
    		assert_eq!(0, peer_count);
    		assert_eq!(0, peer_count2);
    	}

    	#[test]
    	fn propagates_transactions_without_alternating() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(100, EachBlockWith::Uncle);
    		client.insert_transaction_to_queue();
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(1), &client);
    		let queue = RwLock::new(VecDeque::new());
    		let ss = TestSnapshotService::new();
    		// should sent some
    		{
    			let mut io = TestIo::new(&mut client, &ss, &queue, None);
    			let peer_count = sync.propagate_new_transactions(&mut io);
    			assert_eq!(1, io.packets.len());
    			assert_eq!(1, peer_count);
    		}
    		// Insert some more
    		client.insert_transaction_to_queue();
    		let (peer_count2, peer_count3) = {
    			let mut io = TestIo::new(&mut client, &ss, &queue, None);
    			// Propagate new transactions
    			let peer_count2 = sync.propagate_new_transactions(&mut io);
    			// And now the peer should have all transactions
    			let peer_count3 = sync.propagate_new_transactions(&mut io);
    			(peer_count2, peer_count3)
    		};

    		// 2 message should be send (in total)
    		assert_eq!(2, queue.read().len());
    		// 1 peer should be updated but only once after inserting new transaction
    		assert_eq!(1, peer_count2);
    		assert_eq!(0, peer_count3);
    		// TRANSACTIONS_PACKET
    		assert_eq!(0x02, queue.read()[0].packet_id);
    		assert_eq!(0x02, queue.read()[1].packet_id);
    	}

    	#[test]
    	fn should_maintain_transations_propagation_stats() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(100, EachBlockWith::Uncle);
    		client.insert_transaction_to_queue();
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(1), &client);
    		let queue = RwLock::new(VecDeque::new());
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);
    		sync.propagate_new_transactions(&mut io);

    		let stats = sync.transactions_stats();
    		assert_eq!(stats.len(), 1, "Should maintain stats for single transaction.")
    	}

    	#[test]
    	fn should_propagate_service_transaction_to_selected_peers_only() {
    		let mut client = TestBlockChainClient::new();
    		client.insert_transaction_with_gas_price_to_queue(U256::zero());
    		let block_hash = client.block_hash_delta_minus(1);
    		let mut sync = ChainSync::new(SyncConfig::default(), &client);
    		let queue = RwLock::new(VecDeque::new());
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);

    		// when peer#1 is Geth
    		insert_dummy_peer(&mut sync, 1, block_hash);
    		io.peers_info.insert(1, "Geth".to_owned());
    		// and peer#2 is Parity, accepting service transactions
    		insert_dummy_peer(&mut sync, 2, block_hash);
    		io.peers_info.insert(2, "Parity/v1.6".to_owned());
    		// and peer#3 is Parity, discarding service transactions
    		insert_dummy_peer(&mut sync, 3, block_hash);
    		io.peers_info.insert(3, "Parity/v1.5".to_owned());
    		// and peer#4 is Parity, accepting service transactions
    		insert_dummy_peer(&mut sync, 4, block_hash);
    		io.peers_info.insert(4, "Parity/v1.7.3-ABCDEFGH".to_owned());

    		// and new service transaction is propagated to peers
    		sync.propagate_new_transactions(&mut io);

    		// peer#2 && peer#4 are receiving service transaction
    		assert!(io.packets.iter().any(|p| p.packet_id == 0x02 && p.recipient == 2)); // TRANSACTIONS_PACKET
    		assert!(io.packets.iter().any(|p| p.packet_id == 0x02 && p.recipient == 4)); // TRANSACTIONS_PACKET
    		assert_eq!(io.packets.len(), 2);
    	}

    	#[test]
    	fn should_propagate_service_transaction_is_sent_as_separate_message() {
    		let mut client = TestBlockChainClient::new();
    		let tx1_hash = client.insert_transaction_to_queue();
    		let tx2_hash = client.insert_transaction_with_gas_price_to_queue(U256::zero());
    		let block_hash = client.block_hash_delta_minus(1);
    		let mut sync = ChainSync::new(SyncConfig::default(), &client);
    		let queue = RwLock::new(VecDeque::new());
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);

    		// when peer#1 is Parity, accepting service transactions
    		insert_dummy_peer(&mut sync, 1, block_hash);
    		io.peers_info.insert(1, "Parity/v1.6".to_owned());

    		// and service + non-service transactions are propagated to peers
    		sync.propagate_new_transactions(&mut io);

    		// two separate packets for peer are queued:
    		// 1) with non-service-transaction
    		// 2) with service transaction
    		let sent_transactions: Vec<UnverifiedTransaction> = io.packets.iter()
    			.filter_map(|p| {
    				if p.packet_id != 0x02 || p.recipient != 1 { // TRANSACTIONS_PACKET
    					return None;
    				}

    				let rlp = UntrustedRlp::new(&*p.data);
    				let item_count = rlp.item_count();
    				if item_count != 1 {
    					return None;
    				}

    				rlp.at(0).ok().and_then(|r| r.as_val().ok())
    			})
    			.collect();
    		assert_eq!(sent_transactions.len(), 2);
    		assert!(sent_transactions.iter().any(|tx| tx.hash() == tx1_hash));
    		assert!(sent_transactions.iter().any(|tx| tx.hash() == tx2_hash));
    	}

    	#[test]
    	fn handles_peer_new_block_malformed() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(10, EachBlockWith::Uncle);

    		let block_data = get_dummy_block(11, client.chain_info().best_block_hash);

    		let queue = RwLock::new(VecDeque::new());
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);
    		//sync.have_common_block = true;
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);

    		let block = UntrustedRlp::new(&block_data);

    		let result = sync.on_peer_new_block(&mut io, 0, &block);

    		assert!(result.is_err());
    	}

    	#[test]
    	fn handles_peer_new_block() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(10, EachBlockWith::Uncle);

    		let block_data = get_dummy_blocks(11, client.chain_info().best_block_hash);

    		let queue = RwLock::new(VecDeque::new());
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);

    		let block = UntrustedRlp::new(&block_data);

    		let result = sync.on_peer_new_block(&mut io, 0, &block);

    		assert!(result.is_ok());
    	}

    	#[test]
    	fn handles_peer_new_block_empty() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(10, EachBlockWith::Uncle);
    		let queue = RwLock::new(VecDeque::new());
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);

    		let empty_data = vec![];
    		let block = UntrustedRlp::new(&empty_data);

    		let result = sync.on_peer_new_block(&mut io, 0, &block);

    		assert!(result.is_err());
    	}

    	#[test]
    	fn handles_peer_new_hashes() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(10, EachBlockWith::Uncle);
    		let queue = RwLock::new(VecDeque::new());
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);

    		let hashes_data = get_dummy_hashes();
    		let hashes_rlp = UntrustedRlp::new(&hashes_data);

    		let result = sync.on_peer_new_hashes(&mut io, 0, &hashes_rlp);

    		assert!(result.is_ok());
    	}

    	#[test]
    	fn handles_peer_new_hashes_empty() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(10, EachBlockWith::Uncle);
    		let queue = RwLock::new(VecDeque::new());
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);

    		let empty_hashes_data = vec![];
    		let hashes_rlp = UntrustedRlp::new(&empty_hashes_data);

    		let result = sync.on_peer_new_hashes(&mut io, 0, &hashes_rlp);

    		assert!(result.is_ok());
    	}

    	// idea is that what we produce when propagading latest hashes should be accepted in
    	// on_peer_new_hashes in our code as well
    	#[test]
    	fn hashes_rlp_mutually_acceptable() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(100, EachBlockWith::Uncle);
    		let queue = RwLock::new(VecDeque::new());
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);
    		let chain_info = client.chain_info();
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);

    		let peers = sync.get_lagging_peers(&chain_info);
    		sync.propagate_new_hashes(&chain_info, &mut io, &peers);

    		let data = &io.packets[0].data.clone();
    		let result = sync.on_peer_new_hashes(&mut io, 0, &UntrustedRlp::new(data));
    		assert!(result.is_ok());
    	}

    	// idea is that what we produce when propagading latest block should be accepted in
    	// on_peer_new_block  in our code as well
    	#[test]
    	fn block_rlp_mutually_acceptable() {
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(100, EachBlockWith::Uncle);
    		let queue = RwLock::new(VecDeque::new());
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);
    		let chain_info = client.chain_info();
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);

    		let peers = sync.get_lagging_peers(&chain_info);
    		sync.propagate_blocks(&chain_info, &mut io, &[], &peers);

    		let data = &io.packets[0].data.clone();
    		let result = sync.on_peer_new_block(&mut io, 0, &UntrustedRlp::new(data));
    		assert!(result.is_ok());
    	}

    	#[test]
    	fn should_add_transactions_to_queue() {
    		fn sender(tx: &UnverifiedTransaction) -> Address {
    			ethkey::public_to_address(&tx.recover_public().unwrap())
    		}

    		// given
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(98, EachBlockWith::Uncle);
    		client.add_blocks(1, EachBlockWith::UncleAndTransaction);
    		client.add_blocks(1, EachBlockWith::Transaction);
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);

    		let good_blocks = vec![client.block_hash_delta_minus(2)];
    		let retracted_blocks = vec![client.block_hash_delta_minus(1)];

    		// Add some balance to clients and reset nonces
    		for h in &[good_blocks[0], retracted_blocks[0]] {
    			let block = client.block(BlockId::Hash(*h)).unwrap();
    			let sender = sender(&block.transactions()[0]);;
    			client.set_balance(sender, U256::from(10_000_000_000_000_000_000u64));
    			client.set_nonce(sender, U256::from(0));
    		}

    		// when
    		{
    			let queue = RwLock::new(VecDeque::new());
    			let ss = TestSnapshotService::new();
    			let mut io = TestIo::new(&mut client, &ss, &queue, None);
    			io.chain.miner.chain_new_blocks(io.chain, &[], &[], &[], &good_blocks);
    			sync.chain_new_blocks(&mut io, &[], &[], &[], &good_blocks, &[], &[]);
    			assert_eq!(io.chain.miner.status().transactions_in_future_queue, 0);
    			assert_eq!(io.chain.miner.status().transactions_in_pending_queue, 1);
    		}
    		// We need to update nonce status (because we say that the block has been imported)
    		for h in &[good_blocks[0]] {
    			let block = client.block(BlockId::Hash(*h)).unwrap();
    			client.set_nonce(sender(&block.transactions()[0]), U256::from(1));
    		}
    		{
    			let queue = RwLock::new(VecDeque::new());
    			let ss = TestSnapshotService::new();
    			let mut io = TestIo::new(&client, &ss, &queue, None);
    			io.chain.miner.chain_new_blocks(io.chain, &[], &[], &good_blocks, &retracted_blocks);
    			sync.chain_new_blocks(&mut io, &[], &[], &good_blocks, &retracted_blocks, &[], &[]);
    		}

    		// then
    		let status = client.miner.status();
    		assert_eq!(status.transactions_in_pending_queue, 1);
    		assert_eq!(status.transactions_in_future_queue, 0);
    	}

    	#[test]
    	fn should_not_add_transactions_to_queue_if_not_synced() {
    		// given
    		let mut client = TestBlockChainClient::new();
    		client.add_blocks(98, EachBlockWith::Uncle);
    		client.add_blocks(1, EachBlockWith::UncleAndTransaction);
    		client.add_blocks(1, EachBlockWith::Transaction);
    		let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);

    		let good_blocks = vec![client.block_hash_delta_minus(2)];
    		let retracted_blocks = vec![client.block_hash_delta_minus(1)];

    		let queue = RwLock::new(VecDeque::new());
    		let ss = TestSnapshotService::new();
    		let mut io = TestIo::new(&mut client, &ss, &queue, None);

    		// when
    		sync.chain_new_blocks(&mut io, &[], &[], &[], &good_blocks, &[], &[]);
    		assert_eq!(io.chain.miner.status().transactions_in_future_queue, 0);
    		assert_eq!(io.chain.miner.status().transactions_in_pending_queue, 0);
    		sync.chain_new_blocks(&mut io, &[], &[], &good_blocks, &retracted_blocks, &[], &[]);

    		// then
    		let status = io.chain.miner.status();
    		assert_eq!(status.transactions_in_pending_queue, 0);
    		assert_eq!(status.transactions_in_future_queue, 0);
    	}
    }

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