Merge branch 'master' into sync-multiple-blocks

# Conflicts:
#	src/main/java/org/qortal/settings/Settings.java

src/main/java/org/qortal/block/Block.java

@@ -476,6 +476,16 @@ public class Block {
 		return this.minter;
 	}
 
+
+	public void setRepository(Repository repository) throws DataException {
+		this.repository = repository;
+
+		for (Transaction transaction : this.getTransactions()) {
+			transaction.setRepository(repository);
+		}
+	}
+
+
 	// More information
 
 	/**
@@ -524,8 +534,10 @@ public class Block {
 		long nonAtTransactionCount = transactionsData.stream().filter(transactionData -> transactionData.getType() != TransactionType.AT).count();
 
 		// The number of non-AT transactions fetched from repository should correspond with Block's transactionCount
-		if (nonAtTransactionCount != this.blockData.getTransactionCount())
+		if (nonAtTransactionCount != this.blockData.getTransactionCount()) {
+			LOGGER.error(() -> String.format("Block's transactions from repository (%d) do not match block's transaction count (%d)", nonAtTransactionCount, this.blockData.getTransactionCount()));
 			throw new IllegalStateException("Block's transactions from repository do not match block's transaction count");
+		}
 
 		this.transactions = new ArrayList<>();
 

src/main/java/org/qortal/controller/Controller.java

@@ -68,9 +68,11 @@ import org.qortal.network.Network;
 import org.qortal.network.Peer;
 import org.qortal.network.message.ArbitraryDataMessage;
 import org.qortal.network.message.BlockSummariesMessage;
+import org.qortal.network.message.BlocksMessage;
 import org.qortal.network.message.CachedBlockMessage;
 import org.qortal.network.message.GetArbitraryDataMessage;
 import org.qortal.network.message.GetBlockMessage;
+import org.qortal.network.message.GetBlocksMessage;
 import org.qortal.network.message.GetBlockSummariesMessage;
 import org.qortal.network.message.GetOnlineAccountsMessage;
 import org.qortal.network.message.GetPeersMessage;
@@ -101,6 +103,8 @@ import org.qortal.utils.Triple;
 
 import com.google.common.primitives.Longs;
 
+import static org.qortal.network.Peer.FETCH_BLOCKS_TIMEOUT;
+
 public class Controller extends Thread {
 
 	static {
@@ -222,6 +226,18 @@ public class Controller extends Thread {
 		}
 		public GetBlockMessageStats getBlockMessageStats = new GetBlockMessageStats();
 
+		public static class GetBlocksMessageStats {
+			public AtomicLong requests = new AtomicLong();
+			public AtomicLong cacheHits = new AtomicLong();
+			public AtomicLong unknownBlocks = new AtomicLong();
+			public AtomicLong cacheFills = new AtomicLong();
+			public AtomicLong fullyFromCache = new AtomicLong();
+
+			public GetBlocksMessageStats() {
+			}
+		}
+		public GetBlocksMessageStats getBlocksMessageStats = new GetBlocksMessageStats();
+
 		public static class GetBlockSummariesStats {
 			public AtomicLong requests = new AtomicLong();
 			public AtomicLong cacheHits = new AtomicLong();
@@ -1201,6 +1217,10 @@ public class Controller extends Thread {
 				onNetworkGetBlockMessage(peer, message);
 				break;
 
+			case GET_BLOCKS:
+				onNetworkGetBlocksMessage(peer, message);
+				break;
+
 			case TRANSACTION:
 				onNetworkTransactionMessage(peer, message);
 				break;
@@ -1315,6 +1335,54 @@ public class Controller extends Thread {
 		}
 	}
 
+	private void onNetworkGetBlocksMessage(Peer peer, Message message) {
+		GetBlocksMessage getBlocksMessage = (GetBlocksMessage) message;
+		byte[] parentSignature = getBlocksMessage.getParentSignature();
+		this.stats.getBlocksMessageStats.requests.incrementAndGet();
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+
+			// If peer's parent signature matches our latest block signature
+			// then we can short-circuit with an empty response
+			BlockData chainTip = getChainTip();
+			if (chainTip != null && Arrays.equals(parentSignature, chainTip.getSignature())) {
+				Message blocksMessage = new BlocksMessage(Collections.emptyList());
+				blocksMessage.setId(message.getId());
+				if (!peer.sendMessage(blocksMessage))
+					peer.disconnect("failed to send blocks");
+
+				return;
+			}
+
+			// Ensure that we don't serve more blocks than the amount specified in the settings
+			// Serializing multiple blocks is very slow, so by default we are using a low limit
+			int blockLimitPerRequest = Settings.getInstance().getMaxBlocksPerResponse();
+			int untrimmedBlockLimitPerRequest = Settings.getInstance().getMaxBlocksPerResponse();
+			int numberRequested = Math.min(blockLimitPerRequest, getBlocksMessage.getNumberRequested());
+
+			List<Block> blocks = new ArrayList<>();
+			BlockData blockData = repository.getBlockRepository().fromReference(parentSignature);
+
+			while (blockData != null && blocks.size() < numberRequested) {
+				// If we're dealing with untrimmed blocks, ensure we don't go above the untrimmedBlockLimitPerRequest
+				if (blockData.isTrimmed() == false && blocks.size() >= untrimmedBlockLimitPerRequest) {
+					break;
+				}
+				Block block = new Block(repository, blockData);
+				blocks.add(block);
+				blockData = repository.getBlockRepository().fromReference(blockData.getSignature());
+			}
+
+			Message blocksMessage = new BlocksMessage(blocks);
+			blocksMessage.setId(message.getId());
+			if (!peer.sendMessageWithTimeout(blocksMessage, FETCH_BLOCKS_TIMEOUT))
+				peer.disconnect("failed to send blocks");
+
+		} catch (DataException e) {
+			LOGGER.error(String.format("Repository issue while sending blocks after %s to peer %s", Base58.encode(parentSignature), peer), e);
+		}
+	}
+
 	private void onNetworkTransactionMessage(Peer peer, Message message) {
 		TransactionMessage transactionMessage = (TransactionMessage) message;
 		TransactionData transactionData = transactionMessage.getTransactionData();

src/main/java/org/qortal/controller/Synchronizer.java

@@ -25,8 +25,10 @@ import org.qortal.data.transaction.RewardShareTransactionData;
 import org.qortal.data.transaction.TransactionData;
 import org.qortal.network.Peer;
 import org.qortal.network.message.BlockMessage;
+import org.qortal.network.message.BlocksMessage;
 import org.qortal.network.message.BlockSummariesMessage;
 import org.qortal.network.message.GetBlockMessage;
+import org.qortal.network.message.GetBlocksMessage;
 import org.qortal.network.message.GetBlockSummariesMessage;
 import org.qortal.network.message.GetSignaturesV2Message;
 import org.qortal.network.message.Message;
@@ -40,12 +42,14 @@ import org.qortal.transaction.Transaction;
 import org.qortal.utils.Base58;
 import org.qortal.utils.NTP;
 
+import static org.qortal.network.Peer.FETCH_BLOCKS_TIMEOUT;
+
 public class Synchronizer {
 
 	private static final Logger LOGGER = LogManager.getLogger(Synchronizer.class);
 
 	/** Max number of new blocks we aim to add to chain tip in each sync round */
-	private static final int SYNC_BATCH_SIZE = 200; // XXX move to Settings?
+	private static final int SYNC_BATCH_SIZE = 1000; // XXX move to Settings?
 
 	/** Initial jump back of block height when searching for common block with peer */
 	private static final int INITIAL_BLOCK_STEP = 8;
@@ -58,6 +62,11 @@ public class Synchronizer {
 	/** Maximum number of block signatures we ask from peer in one go */
 	private static final int MAXIMUM_REQUEST_SIZE = 200; // XXX move to Settings?
 
+	/* Minimum peer version that supports syncing multiple blocks at once via GetBlocksMessage */
+	private static final long PEER_VERSION_160 = 0x0100060000L;
+
+
+
 
 	// Keep track of the size of the last re-org, so it can be logged
 	private int lastReorgSize;
@@ -790,7 +799,7 @@ public class Synchronizer {
 	}
 
 	private SynchronizationResult syncToPeerChain(Repository repository, BlockData commonBlockData, int ourInitialHeight,
-			Peer peer, final int peerHeight, List<BlockSummaryData> peerBlockSummaries) throws DataException, InterruptedException {
+												  Peer peer, final int peerHeight, List<BlockSummaryData> peerBlockSummaries) throws DataException, InterruptedException {
 		final int commonBlockHeight = commonBlockData.getHeight();
 		final byte[] commonBlockSig = commonBlockData.getSignature();
 		String commonBlockSig58 = Base58.encode(commonBlockSig);
@@ -820,19 +829,19 @@ public class Synchronizer {
 			if (Controller.isStopping())
 				return SynchronizationResult.SHUTTING_DOWN;
 
-            // Ensure we don't request more than MAXIMUM_REQUEST_SIZE
-            int numberRequested = Math.min(numberSignaturesRequired, MAXIMUM_REQUEST_SIZE);
+			// Ensure we don't request more than MAXIMUM_REQUEST_SIZE
+			int numberRequested = Math.min(numberSignaturesRequired, MAXIMUM_REQUEST_SIZE);
 
-            // Do we need more signatures?
+			// Do we need more signatures?
 			if (peerBlockSignatures.isEmpty() && numberRequested > 0) {
-                LOGGER.trace(String.format("Requesting %d signature%s after height %d, sig %.8s",
-                        numberRequested, (numberRequested != 1 ? "s" : ""), height, Base58.encode(latestPeerSignature)));
+				LOGGER.trace(String.format("Requesting %d signature%s after height %d, sig %.8s",
+						numberRequested, (numberRequested != 1 ? "s" : ""), height, Base58.encode(latestPeerSignature)));
 
-                peerBlockSignatures = this.getBlockSignatures(peer, latestPeerSignature, numberRequested);
+				peerBlockSignatures = this.getBlockSignatures(peer, latestPeerSignature, numberRequested);
 
-                if (peerBlockSignatures == null || peerBlockSignatures.isEmpty()) {
-                    LOGGER.info(String.format("Peer %s failed to respond with more block signatures after height %d, sig %.8s", peer,
-                            height, Base58.encode(latestPeerSignature)));
+				if (peerBlockSignatures == null || peerBlockSignatures.isEmpty()) {
+					LOGGER.info(String.format("Peer %s failed to respond with more block signatures after height %d, sig %.8s", peer,
+							height, Base58.encode(latestPeerSignature)));
 
 					// Clear our cache of common block summaries for this peer, as they are likely to be invalid
 					CommonBlockData cachedCommonBlockData = peer.getCommonBlockData();
@@ -842,7 +851,7 @@ public class Synchronizer {
                     // If we have already received newer blocks from this peer that what we have already, go ahead and apply them
                     if (peerBlocks.size() > 0) {
 						final BlockData ourLatestBlockData = repository.getBlockRepository().getLastBlock();
-                    	final Block peerLatestBlock = peerBlocks.get(peerBlocks.size() - 1);
+						final Block peerLatestBlock = peerBlocks.get(peerBlocks.size() - 1);
 						final Long minLatestBlockTimestamp = Controller.getMinimumLatestBlockTimestamp();
 						if (ourLatestBlockData != null && peerLatestBlock != null && minLatestBlockTimestamp != null) {
 
@@ -865,8 +874,8 @@ public class Synchronizer {
                     return SynchronizationResult.NO_REPLY;
                 }
 
-                numberSignaturesRequired = peerHeight - height - peerBlockSignatures.size();
-                LOGGER.trace(String.format("Received %s signature%s", peerBlockSignatures.size(), (peerBlockSignatures.size() != 1 ? "s" : "")));
+				numberSignaturesRequired = peerHeight - height - peerBlockSignatures.size();
+				LOGGER.trace(String.format("Received %s signature%s", peerBlockSignatures.size(), (peerBlockSignatures.size() != 1 ? "s" : "")));
 			}
 
 			if (peerBlockSignatures.isEmpty()) {
@@ -1003,8 +1012,108 @@ public class Synchronizer {
 	}
 
 	private SynchronizationResult applyNewBlocks(Repository repository, BlockData commonBlockData, int ourInitialHeight,
+												 Peer peer, int peerHeight, List<BlockSummaryData> peerBlockSummaries) throws InterruptedException, DataException {
+
+		final BlockData ourLatestBlockData = repository.getBlockRepository().getLastBlock();
+		if (Settings.getInstance().isFastSyncEnabled() && peer.getPeersVersion() >= PEER_VERSION_160 && ourLatestBlockData.isTrimmed())
+			// This peer supports syncing multiple blocks at once via GetBlocksMessage, and it is enabled in the settings
+			return this.applyNewBlocksUsingFastSync(repository, commonBlockData, ourInitialHeight, peer, peerHeight, peerBlockSummaries);
+		else
+			// Older peer version, or fast sync is disabled in the settings - use slow sync
+			return this.applyNewBlocksUsingSlowSync(repository, commonBlockData, ourInitialHeight, peer, peerHeight, peerBlockSummaries);
+
+	}
+
+	private SynchronizationResult applyNewBlocksUsingFastSync(Repository repository, BlockData commonBlockData, int ourInitialHeight,
+												 Peer peer, int peerHeight, List<BlockSummaryData> peerBlockSummaries) throws InterruptedException, DataException {
+		LOGGER.debug(String.format("Fetching new blocks from peer %s using fast sync", peer));
+
+		final int commonBlockHeight = commonBlockData.getHeight();
+		final byte[] commonBlockSig = commonBlockData.getSignature();
+		byte[] latestPeerSignature = commonBlockSig;
+
+		int ourHeight = ourInitialHeight;
+
+		// Fetch, and apply, blocks from peer
+		int maxBatchHeight = commonBlockHeight + SYNC_BATCH_SIZE;
+
+		// Ensure that we don't request more blocks than specified in the settings
+		int maxBlocksPerRequest = Settings.getInstance().getMaxBlocksPerRequest();
+
+		while (ourHeight < peerHeight && ourHeight < maxBatchHeight) {
+			if (Controller.isStopping())
+				return SynchronizationResult.SHUTTING_DOWN;
+
+			int numberRequested = Math.min(maxBatchHeight - ourHeight, maxBlocksPerRequest);
+
+			LOGGER.trace(String.format("Fetching %d blocks after height %d, sig %.8s from %s", numberRequested, ourHeight, Base58.encode(latestPeerSignature), peer));
+			List<Block> blocks = this.fetchBlocks(repository, peer, latestPeerSignature, numberRequested);
+			if (blocks == null || blocks.isEmpty()) {
+				LOGGER.info(String.format("Peer %s failed to respond with more blocks after height %d, sig %.8s", peer,
+						ourHeight, Base58.encode(latestPeerSignature)));
+				return SynchronizationResult.NO_REPLY;
+			}
+			LOGGER.trace(String.format("Received %d blocks after height %d, sig %.8s from %s", blocks.size(), ourHeight, Base58.encode(latestPeerSignature), peer));
+
+			for (Block newBlock : blocks) {
+				++ourHeight;
+
+				if (Controller.isStopping())
+					return SynchronizationResult.SHUTTING_DOWN;
+
+				if (newBlock == null) {
+					LOGGER.info(String.format("Peer %s failed to respond with block for height %d, sig %.8s", peer,
+							ourHeight, Base58.encode(latestPeerSignature)));
+					return SynchronizationResult.NO_REPLY;
+				}
+
+				if (!newBlock.isSignatureValid()) {
+					LOGGER.info(String.format("Peer %s sent block with invalid signature for height %d, sig %.8s", peer,
+							ourHeight, Base58.encode(latestPeerSignature)));
+					return SynchronizationResult.INVALID_DATA;
+				}
+
+				// Set the repository, because we couldn't do that when originally constructing the Block
+				newBlock.setRepository(repository);
+
+				// Transactions are transmitted without approval status so determine that now
+				for (Transaction transaction : newBlock.getTransactions()) {
+					transaction.setInitialApprovalStatus();
+				}
+
+				ValidationResult blockResult = newBlock.isValid();
+				if (blockResult != ValidationResult.OK) {
+					LOGGER.info(String.format("Peer %s sent invalid block for height %d, sig %.8s: %s", peer,
+							ourHeight, Base58.encode(latestPeerSignature), blockResult.name()));
+					return SynchronizationResult.INVALID_DATA;
+				}
+
+				// Save transactions attached to this block
+				for (Transaction transaction : newBlock.getTransactions()) {
+					TransactionData transactionData = transaction.getTransactionData();
+					repository.getTransactionRepository().save(transactionData);
+				}
+
+				newBlock.process();
+
+				LOGGER.trace(String.format("Processed block height %d, sig %.8s", newBlock.getBlockData().getHeight(), Base58.encode(newBlock.getBlockData().getSignature())));
+
+				repository.saveChanges();
+
+				Controller.getInstance().onNewBlock(newBlock.getBlockData());
+
+				// Update latestPeerSignature so that subsequent batches start requesting from the correct block
+				latestPeerSignature = newBlock.getSignature();
+			}
+
+		}
+
+		return SynchronizationResult.OK;
+	}
+
+	private SynchronizationResult applyNewBlocksUsingSlowSync(Repository repository, BlockData commonBlockData, int ourInitialHeight,
 			Peer peer, int peerHeight, List<BlockSummaryData> peerBlockSummaries) throws InterruptedException, DataException {
-		LOGGER.debug(String.format("Fetching new blocks from peer %s", peer));
+		LOGGER.debug(String.format("Fetching new blocks from peer %s using slow sync", peer));
 
 		final int commonBlockHeight = commonBlockData.getHeight();
 		final byte[] commonBlockSig = commonBlockData.getSignature();
@@ -1125,6 +1234,22 @@ public class Synchronizer {
 		return new Block(repository, blockMessage.getBlockData(), blockMessage.getTransactions(), blockMessage.getAtStates());
 	}
 
+	private List<Block> fetchBlocks(Repository repository, Peer peer, byte[] parentSignature, int numberRequested) throws InterruptedException {
+		Message getBlocksMessage = new GetBlocksMessage(parentSignature, numberRequested);
+
+		Message message = peer.getResponseWithTimeout(getBlocksMessage, FETCH_BLOCKS_TIMEOUT);
+		if (message == null || message.getType() != MessageType.BLOCKS) {
+			return null;
+		}
+
+		BlocksMessage blocksMessage = (BlocksMessage) message;
+		if (blocksMessage == null || blocksMessage.getBlocks() == null) {
+			return null;
+		}
+
+		return blocksMessage.getBlocks();
+	}
+
 	private void populateBlockSummariesMinterLevels(Repository repository, List<BlockSummaryData> blockSummaries) throws DataException {
 		final int firstBlockHeight = blockSummaries.get(0).getHeight();
 

src/main/java/org/qortal/data/block/BlockData.java

@@ -9,7 +9,10 @@ import javax.xml.bind.annotation.XmlAccessorType;
 import javax.xml.bind.annotation.XmlElement;
 import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
 
+import org.qortal.block.BlockChain;
+import org.qortal.settings.Settings;
 import org.qortal.crypto.Crypto;
+import org.qortal.utils.NTP;
 
 // All properties to be converted to JSON via JAX-RS
 @XmlAccessorType(XmlAccessType.FIELD)
@@ -204,6 +207,13 @@ public class BlockData implements Serializable {
 		return this.onlineAccountsSignatures;
 	}
 
+	public boolean isTrimmed() {
+		long onlineAccountSignaturesTrimmedTimestamp = NTP.getTime() - BlockChain.getInstance().getOnlineAccountSignaturesMaxLifetime();
+		long currentTrimmableTimestamp = NTP.getTime() - Settings.getInstance().getAtStatesMaxLifetime();
+		long blockTimestamp = this.getTimestamp();
+		return blockTimestamp < onlineAccountSignaturesTrimmedTimestamp && blockTimestamp < currentTrimmableTimestamp;
+	}
+
 	// JAXB special
 
 	@XmlElement(name = "minterAddress")

src/main/java/org/qortal/network/Network.java

@@ -155,9 +155,23 @@ public class Network {
         }
 
         // Load all known peers from repository
-        try (Repository repository = RepositoryManager.getRepository()) {
-            synchronized (this.allKnownPeers) {
-                this.allKnownPeers.addAll(repository.getNetworkRepository().getAllPeers());
+        synchronized (this.allKnownPeers) { List<String> fixedNetwork = Settings.getInstance().getFixedNetwork();
+            if (fixedNetwork != null && !fixedNetwork.isEmpty()) {
+                Long addedWhen = NTP.getTime();
+                String addedBy = "fixedNetwork";
+                List<PeerAddress> peerAddresses = new ArrayList<>();
+                for (String address : fixedNetwork) {
+                    PeerAddress peerAddress = PeerAddress.fromString(address);
+                    peerAddresses.add(peerAddress);
+                }
+                List<PeerData> peers = peerAddresses.stream()
+                        .map(peerAddress -> new PeerData(peerAddress, addedWhen, addedBy))
+                        .collect(Collectors.toList());
+                this.allKnownPeers.addAll(peers);
+            } else {
+                try (Repository repository = RepositoryManager.getRepository()) {
+                    this.allKnownPeers.addAll(repository.getNetworkRepository().getAllPeers());
+                }
             }
         }
 
@@ -513,14 +527,24 @@ public class Network {
         if (socketChannel == null) {
             return;
         }
+        PeerAddress address = PeerAddress.fromSocket(socketChannel.socket());
+        List<String> fixedNetwork = Settings.getInstance().getFixedNetwork();
+        if (fixedNetwork != null && !fixedNetwork.isEmpty() && ipNotInFixedList(address, fixedNetwork)) {
+            try {
+                LOGGER.debug("Connection discarded from peer {} as not in the fixed network list", address);
+                socketChannel.close();
+            } catch (IOException e) {
+                // IGNORE
+            }
+            return;
+        }
 
         final Long now = NTP.getTime();
         Peer newPeer;
 
         try {
             if (now == null) {
-                LOGGER.debug("Connection discarded from peer {} due to lack of NTP sync",
-                        PeerAddress.fromSocket(socketChannel.socket()));
+                LOGGER.debug("Connection discarded from peer {} due to lack of NTP sync", address);
                 socketChannel.close();
                 return;
             }
@@ -528,12 +552,12 @@ public class Network {
             synchronized (this.connectedPeers) {
                 if (connectedPeers.size() >= maxPeers) {
                     // We have enough peers
-                    LOGGER.debug("Connection discarded from peer {}", PeerAddress.fromSocket(socketChannel.socket()));
+                    LOGGER.debug("Connection discarded from peer {} because the server is full", address);
                     socketChannel.close();
                     return;
                 }
 
-                LOGGER.debug("Connection accepted from peer {}", PeerAddress.fromSocket(socketChannel.socket()));
+                LOGGER.debug("Connection accepted from peer {}", address);
 
                 newPeer = new Peer(socketChannel, channelSelector);
                 this.connectedPeers.add(newPeer);
@@ -541,6 +565,7 @@ public class Network {
         } catch (IOException e) {
             if (socketChannel.isOpen()) {
                 try {
+                    LOGGER.debug("Connection failed from peer {} while connecting/closing", address);
                     socketChannel.close();
                 } catch (IOException ce) {
                     // Couldn't close?
@@ -552,6 +577,16 @@ public class Network {
         this.onPeerReady(newPeer);
     }
 
+    private boolean ipNotInFixedList(PeerAddress address, List<String> fixedNetwork) {
+        for (String ipAddress : fixedNetwork) {
+            String[] bits = ipAddress.split(":");
+            if (bits.length >= 1 && bits.length <= 2 && address.getHost().equals(bits[0])) {
+                return false;
+            }
+        }
+        return true;
+    }
+
     private Peer getConnectablePeer(final Long now) throws InterruptedException {
         // We can't block here so use tryRepository(). We don't NEED to connect a new peer.
         try (Repository repository = RepositoryManager.tryRepository()) {
@@ -1145,6 +1180,10 @@ public class Network {
 
     private boolean mergePeers(Repository repository, String addedBy, long addedWhen, List<PeerAddress> peerAddresses)
             throws DataException {
+        List<String> fixedNetwork = Settings.getInstance().getFixedNetwork();
+        if (fixedNetwork != null && !fixedNetwork.isEmpty()) {
+            return false;
+        }
         List<PeerData> newPeers;
         synchronized (this.allKnownPeers) {
             for (PeerData knownPeerData : this.allKnownPeers) {

src/main/java/org/qortal/network/Peer.java

@@ -47,6 +47,11 @@ public class Peer {
      */
     private static final int RESPONSE_TIMEOUT = 3000; // ms
 
+    /**
+     * Maximum time to wait for a peer to respond with blocks (ms)
+     */
+    public static final int FETCH_BLOCKS_TIMEOUT = 10000;
+
     /**
      * Interval between PING messages to a peer. (ms)
      * <p>
@@ -544,12 +549,22 @@ public class Peer {
     }
 
     /**
-     * Attempt to send Message to peer.
+     * Attempt to send Message to peer, using default RESPONSE_TIMEOUT.
      *
      * @param message message to be sent
      * @return <code>true</code> if message successfully sent; <code>false</code> otherwise
      */
     public boolean sendMessage(Message message) {
+        return this.sendMessageWithTimeout(message, RESPONSE_TIMEOUT);
+    }
+
+    /**
+     * Attempt to send Message to peer, using custom timeout.
+     *
+     * @param message message to be sent
+     * @return <code>true</code> if message successfully sent; <code>false</code> otherwise
+     */
+    public boolean sendMessageWithTimeout(Message message, int timeout) {
         if (!this.socketChannel.isOpen()) {
             return false;
         }
@@ -583,7 +598,7 @@ public class Peer {
                          */
                         Thread.sleep(1L); //NOSONAR squid:S2276
 
-                        if (System.currentTimeMillis() - sendStart > RESPONSE_TIMEOUT) {
+                        if (System.currentTimeMillis() - sendStart > timeout) {
                             // We've taken too long to send this message
                             return false;
                         }
@@ -604,7 +619,7 @@ public class Peer {
     }
 
     /**
-     * Send message to peer and await response.
+     * Send message to peer and await response, using default RESPONSE_TIMEOUT.
      * <p>
      * Message is assigned a random ID and sent.
      * If a response with matching ID is received then it is returned to caller.
@@ -618,6 +633,24 @@ public class Peer {
      * @throws InterruptedException if interrupted while waiting
      */
     public Message getResponse(Message message) throws InterruptedException {
+        return getResponseWithTimeout(message, RESPONSE_TIMEOUT);
+    }
+
+    /**
+     * Send message to peer and await response.
+     * <p>
+     * Message is assigned a random ID and sent.
+     * If a response with matching ID is received then it is returned to caller.
+     * <p>
+     * If no response with matching ID within timeout, or some other error/exception occurs,
+     * then return <code>null</code>.<br>
+     * (Assume peer will be rapidly disconnected after this).
+     *
+     * @param message message to send
+     * @return <code>Message</code> if valid response received; <code>null</code> if not or error/exception occurs
+     * @throws InterruptedException if interrupted while waiting
+     */
+    public Message getResponseWithTimeout(Message message, int timeout) throws InterruptedException {
         BlockingQueue<Message> blockingQueue = new ArrayBlockingQueue<>(1);
 
         // Assign random ID to this message
@@ -632,13 +665,13 @@ public class Peer {
         message.setId(id);
 
         // Try to send message
-        if (!this.sendMessage(message)) {
+        if (!this.sendMessageWithTimeout(message, timeout)) {
             this.replyQueues.remove(id);
             return null;
         }
 
         try {
-            return blockingQueue.poll(RESPONSE_TIMEOUT, TimeUnit.MILLISECONDS);
+            return blockingQueue.poll(timeout, TimeUnit.MILLISECONDS);
         } finally {
             this.replyQueues.remove(id);
         }

src/main/java/org/qortal/network/message/BlocksMessage.java

@@ -0,0 +1,91 @@
+package org.qortal.network.message;
+
+import com.google.common.primitives.Ints;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.qortal.block.Block;
+import org.qortal.data.at.ATStateData;
+import org.qortal.data.block.BlockData;
+import org.qortal.data.transaction.TransactionData;
+import org.qortal.transform.TransformationException;
+import org.qortal.transform.block.BlockTransformer;
+import org.qortal.utils.Triple;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.UnsupportedEncodingException;
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.List;
+
+public class BlocksMessage extends Message {
+
+	private static final Logger LOGGER = LogManager.getLogger(BlocksMessage.class);
+
+	private List<Block> blocks;
+
+	public BlocksMessage(List<Block> blocks) {
+		this(-1, blocks);
+	}
+
+	private BlocksMessage(int id, List<Block> blocks) {
+		super(id, MessageType.BLOCKS);
+
+		this.blocks = blocks;
+	}
+
+	public List<Block> getBlocks() {
+		return this.blocks;
+	}
+
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+
+		int count = bytes.getInt();
+		List<Block> blocks = new ArrayList<>();
+
+		for (int i = 0; i < count; ++i) {
+			int height = bytes.getInt();
+
+			try {
+				boolean finalBlockInBuffer = (i == count-1);
+
+				Triple<BlockData, List<TransactionData>, List<ATStateData>> blockInfo = null;
+				blockInfo = BlockTransformer.fromByteBuffer(bytes, finalBlockInBuffer);
+				BlockData blockData = blockInfo.getA();
+				blockData.setHeight(height);
+
+				// We are unable to obtain a valid Repository instance here, so set it to null and we will attach it later
+				Block block = new Block(null, blockData, blockInfo.getB(), blockInfo.getC());
+				blocks.add(block);
+
+			} catch (TransformationException e) {
+				return null;
+			}
+
+		}
+
+		return new BlocksMessage(id, blocks);
+	}
+
+	@Override
+	protected byte[] toData() {
+		try {
+			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+
+			bytes.write(Ints.toByteArray(this.blocks.size()));
+
+			for (Block block : this.blocks) {
+				bytes.write(Ints.toByteArray(block.getBlockData().getHeight()));
+				bytes.write(BlockTransformer.toBytes(block));
+			}
+			LOGGER.trace(String.format("Total length of %d blocks is %d bytes", this.blocks.size(), bytes.size()));
+
+			return bytes.toByteArray();
+		} catch (IOException e) {
+			return null;
+		} catch (TransformationException e) {
+			return null;
+		}
+	}
+
+}

src/main/java/org/qortal/network/message/GetBlocksMessage.java

@@ -0,0 +1,65 @@
+package org.qortal.network.message;
+
+import com.google.common.primitives.Ints;
+import org.qortal.transform.Transformer;
+import org.qortal.transform.block.BlockTransformer;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.UnsupportedEncodingException;
+import java.nio.ByteBuffer;
+
+public class GetBlocksMessage extends Message {
+
+	private static final int BLOCK_SIGNATURE_LENGTH = BlockTransformer.BLOCK_SIGNATURE_LENGTH;
+
+	private byte[] parentSignature;
+	private int numberRequested;
+
+	public GetBlocksMessage(byte[] parentSignature, int numberRequested) {
+		this(-1, parentSignature, numberRequested);
+	}
+
+	private GetBlocksMessage(int id, byte[] parentSignature, int numberRequested) {
+		super(id, MessageType.GET_BLOCKS);
+
+		this.parentSignature = parentSignature;
+		this.numberRequested = numberRequested;
+	}
+
+	public byte[] getParentSignature() {
+		return this.parentSignature;
+	}
+
+	public int getNumberRequested() {
+		return this.numberRequested;
+	}
+
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+		if (bytes.remaining() != BLOCK_SIGNATURE_LENGTH + Transformer.INT_LENGTH)
+			return null;
+
+		byte[] parentSignature = new byte[BLOCK_SIGNATURE_LENGTH];
+		bytes.get(parentSignature);
+
+		int numberRequested = bytes.getInt();
+
+		return new GetBlocksMessage(id, parentSignature, numberRequested);
+	}
+
+	@Override
+	protected byte[] toData() {
+		try {
+			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+
+			bytes.write(this.parentSignature);
+
+			bytes.write(Ints.toByteArray(this.numberRequested));
+
+			return bytes.toByteArray();
+		} catch (IOException e) {
+			return null;
+		}
+	}
+
+}

src/main/java/org/qortal/network/message/Message.java

@@ -25,7 +25,7 @@ public abstract class Message {
 	private static final int MAGIC_LENGTH = 4;
 	private static final int CHECKSUM_LENGTH = 4;
 
-	private static final int MAX_DATA_SIZE = 1024 * 1024; // 1MB
+	private static final int MAX_DATA_SIZE = 10 * 1024 * 1024; // 10MB
 
 	@SuppressWarnings("serial")
 	public static class MessageException extends Exception {
@@ -80,7 +80,10 @@ public abstract class Message {
 		GET_ONLINE_ACCOUNTS(81),
 
 		ARBITRARY_DATA(90),
-		GET_ARBITRARY_DATA(91);
+		GET_ARBITRARY_DATA(91),
+
+		BLOCKS(100),
+		GET_BLOCKS(101);
 
 		public final int value;
 		public final Method fromByteBufferMethod;

src/main/java/org/qortal/settings/Settings.java

@@ -5,6 +5,7 @@ import java.io.FileNotFoundException;
 import java.io.FileReader;
 import java.io.IOException;
 import java.io.Reader;
+import java.util.List;
 import java.util.Locale;
 
 import javax.xml.bind.JAXBContext;
@@ -137,6 +138,17 @@ public class Settings {
 	/** Maximum time (in seconds) that we should attempt to remain connected to a peer for */
 	private int maxPeerConnectionTime = 20 * 60; // seconds
 
+	/** Whether to sync multiple blocks at once in normal operation */
+	private boolean fastSyncEnabled = true;
+	/** Whether to sync multiple blocks at once when the peer has a different chain */
+	private boolean fastSyncEnabledWhenResolvingFork = true;
+	/** Maximum number of blocks to request at once */
+	private int maxBlocksPerRequest = 100;
+	/** Maximum number of blocks this node will serve in a single response */
+	private int maxBlocksPerResponse = 200;
+	/** Maximum number of untrimmed blocks this node will serve in a single response */
+	private int maxUntrimmedBlocksPerResponse = 10;
+
 	// Which blockchains this node is running
 	private String blockchainConfig = null; // use default from resources
 	private BitcoinNet bitcoinNet = BitcoinNet.MAIN;
@@ -152,6 +164,7 @@ public class Settings {
 	private String repositoryPath = "db";
 	/** Repository connection pool size. Needs to be a bit bigger than maxNetworkThreadPoolSize */
 	private int repositoryConnectionPoolSize = 100;
+	private List<String> fixedNetwork;
 
 	// Auto-update sources
 	private String[] autoUpdateRepos = new String[] {
@@ -460,6 +473,20 @@ public class Settings {
 		return this.repositoryConnectionPoolSize;
 	}
 
+	public boolean isFastSyncEnabled() {
+		return this.fastSyncEnabled;
+	}
+
+	public boolean isFastSyncEnabledWhenResolvingFork() {
+		return this.fastSyncEnabledWhenResolvingFork;
+	}
+
+	public int getMaxBlocksPerRequest() { return this.maxBlocksPerRequest; }
+
+	public int getMaxBlocksPerResponse() { return this.maxBlocksPerResponse; }
+
+	public int getMaxUntrimmedBlocksPerResponse() { return this.maxUntrimmedBlocksPerResponse; }
+
 	public boolean isAutoUpdateEnabled() {
 		return this.autoUpdateEnabled;
 	}
@@ -516,4 +543,7 @@ public class Settings {
 		return this.onlineSignaturesTrimBatchSize;
 	}
 
+	public List<String> getFixedNetwork() {
+		return fixedNetwork;
+	}
 }

src/main/java/org/qortal/transaction/Transaction.java

@@ -315,6 +315,10 @@ public abstract class Transaction {
 		return this.transactionData;
 	}
 
+	public void setRepository(Repository repository) {
+		this.repository = repository;
+	}
+
 	// More information
 
 	public static long getDeadline(TransactionData transactionData) {

src/main/java/org/qortal/transform/block/BlockTransformer.java

@@ -74,19 +74,30 @@ public class BlockTransformer extends Transformer {
 	}
 
 	/**
-	 * Extract block data and transaction data from serialized bytes.
-	 * 
+	 * Extract block data and transaction data from serialized bytes containing a single block.
+	 *
 	 * @param bytes
 	 * @return BlockData and a List of transactions.
 	 * @throws TransformationException
 	 */
 	public static Triple<BlockData, List<TransactionData>, List<ATStateData>> fromByteBuffer(ByteBuffer byteBuffer) throws TransformationException {
+		return BlockTransformer.fromByteBuffer(byteBuffer, true);
+	}
+
+	/**
+	 * Extract block data and transaction data from serialized bytes containing one or more blocks.
+	 * 
+	 * @param bytes
+	 * @return the next block's BlockData and a List of transactions.
+	 * @throws TransformationException
+	 */
+	public static Triple<BlockData, List<TransactionData>, List<ATStateData>> fromByteBuffer(ByteBuffer byteBuffer, boolean finalBlockInBuffer) throws TransformationException {
 		int version = byteBuffer.getInt();
 
-		if (byteBuffer.remaining() < BASE_LENGTH + AT_BYTES_LENGTH - VERSION_LENGTH)
+		if (finalBlockInBuffer && byteBuffer.remaining() < BASE_LENGTH + AT_BYTES_LENGTH - VERSION_LENGTH)
 			throw new TransformationException("Byte data too short for Block");
 
-		if (byteBuffer.remaining() > BlockChain.getInstance().getMaxBlockSize())
+		if (finalBlockInBuffer && byteBuffer.remaining() > BlockChain.getInstance().getMaxBlockSize())
 			throw new TransformationException("Byte data too long for Block");
 
 		long timestamp = byteBuffer.getLong();
@@ -210,7 +221,8 @@ public class BlockTransformer extends Transformer {
 			byteBuffer.get(onlineAccountsSignatures);
 		}
 
-		if (byteBuffer.hasRemaining())
+		// We should only complain about excess byte data if we aren't expecting more blocks in this ByteBuffer
+		if (finalBlockInBuffer && byteBuffer.hasRemaining())
 			throw new TransformationException("Excess byte data found after parsing Block");
 
 		// We don't have a height!

tools/block-timings.sh

@@ -69,11 +69,13 @@ function fetch_and_process_blocks {
     online_accounts_count=$(echo "${block_minting_info}" | jq -r .onlineAccountsCount)
     key_distance_ratio=$(echo "${block_minting_info}" | jq -r .keyDistanceRatio)
     time_delta=$(echo "${block_minting_info}" | jq -r .timeDelta)
+    timestamp=$(echo "${block_minting_info}" | jq -r .timestamp)
 
     time_offset=$(calculate_time_offset "${key_distance_ratio}")
     block_time=$((target-deviation+time_offset))
 
     echo "=== BLOCK ${height} ==="
+    echo "Timestamp: ${timestamp}"
     echo "Minter level: ${minter_level}"
     echo "Online accounts: ${online_accounts_count}"
     echo "Key distance ratio: ${key_distance_ratio}"