Limit arbitrary signature requests to 3 hops, just in case a bug caused any kind of circular broadcasting.

src/main/java/org/qortal/controller/arbitrary/ArbitraryDataFileManager.java

@@ -159,7 +159,7 @@ public class ArbitraryDataFileManager {
             // but only if these files are in accordance with our storage policy
             if (ArbitraryDataStorageManager.getInstance().canStoreData(arbitraryTransactionData)) {
                 // Use a null peer address to indicate our own
-                Message newArbitrarySignatureMessage = new ArbitrarySignaturesMessage(null, Arrays.asList(signature));
+                Message newArbitrarySignatureMessage = new ArbitrarySignaturesMessage(null, 0, Arrays.asList(signature));
                 Network.getInstance().broadcast(broadcastPeer -> newArbitrarySignatureMessage);
             }
         }

src/main/java/org/qortal/controller/arbitrary/ArbitraryDataManager.java

@@ -43,6 +43,9 @@ public class ArbitraryDataManager extends Thread {
 	/** Maximum time to hold information about an in-progress relay */
 	public static final long ARBITRARY_RELAY_TIMEOUT = 30 * 1000L; // ms
 
+	/** Maximum number of hops that an arbitrary signatures request is allowed to make */
+	private static int ARBITRARY_SIGNATURES_REQUEST_MAX_HOPS = 3;
+
 	private static ArbitraryDataManager instance;
 	private final Object peerDataLock = new Object();
 
@@ -369,7 +372,7 @@ public class ArbitraryDataManager extends Thread {
 
 			// Broadcast the list, using null to represent our peer address
 			LOGGER.info("Broadcasting list of hosted signatures...");
-			Message arbitrarySignatureMessage = new ArbitrarySignaturesMessage(null, hostedSignatures);
+			Message arbitrarySignatureMessage = new ArbitrarySignaturesMessage(null, 0, hostedSignatures);
 			Network.getInstance().broadcast(broadcastPeer -> arbitrarySignatureMessage);
 
 		} catch (DataException e) {
@@ -429,8 +432,12 @@ public class ArbitraryDataManager extends Thread {
 				// If at least one signature in this batch was new to us, we should rebroadcast the message to the
 				// network in case some peers haven't received it yet
 				if (containsNewEntry) {
-					LOGGER.debug("Rebroadcasting arbitrary signature list for peer {}", peerAddress);
+					int requestHops = arbitrarySignaturesMessage.getRequestHops();
-					Network.getInstance().broadcast(broadcastPeer -> broadcastPeer == peer ? null : arbitrarySignaturesMessage);
+					arbitrarySignaturesMessage.setRequestHops(++requestHops);
+					if (requestHops < ARBITRARY_SIGNATURES_REQUEST_MAX_HOPS) {
+						LOGGER.debug("Rebroadcasting arbitrary signature list for peer {}", peerAddress);
+						Network.getInstance().broadcast(broadcastPeer -> broadcastPeer == peer ? null : arbitrarySignaturesMessage);
+					}
 				} else {
 					// Don't rebroadcast as otherwise we could get into a loop
 				}

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

@@ -2,7 +2,6 @@ package org.qortal.network.message;
 
 import com.google.common.primitives.Ints;
 import org.qortal.data.network.PeerData;
-import org.qortal.transaction.DeployAtTransaction;
 import org.qortal.transform.TransformationException;
 import org.qortal.transform.Transformer;
 import org.qortal.utils.Serialization;
@@ -19,16 +18,18 @@ public class ArbitrarySignaturesMessage extends Message {
 	private static final int SIGNATURE_LENGTH = Transformer.SIGNATURE_LENGTH;
 
 	private String peerAddress;
+	private int requestHops;
 	private List<byte[]> signatures;
 
-	public ArbitrarySignaturesMessage(String peerAddress, List<byte[]> signatures) {
+	public ArbitrarySignaturesMessage(String peerAddress, int requestHops, List<byte[]> signatures) {
-		this(-1, peerAddress, signatures);
+		this(-1, peerAddress, requestHops, signatures);
 	}
 
-	private ArbitrarySignaturesMessage(int id, String peerAddress, List<byte[]> signatures) {
+	private ArbitrarySignaturesMessage(int id, String peerAddress, int requestHops, List<byte[]> signatures) {
 		super(id, MessageType.ARBITRARY_SIGNATURES);
 
 		this.peerAddress = peerAddress;
+		this.requestHops = requestHops;
 		this.signatures = signatures;
 	}
 
@@ -40,9 +41,19 @@ public class ArbitrarySignaturesMessage extends Message {
 		return this.signatures;
 	}
 
+	public int getRequestHops() {
+		return this.requestHops;
+	}
+
+	public void setRequestHops(int requestHops) {
+		this.requestHops = requestHops;
+	}
+
 	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException, TransformationException {
 		String peerAddress = Serialization.deserializeSizedString(bytes, PeerData.MAX_PEER_ADDRESS_SIZE);
 
+		int requestHops = bytes.getInt();
+
 		int signatureCount = bytes.getInt();
 
 		if (bytes.remaining() != signatureCount * SIGNATURE_LENGTH)
@@ -55,7 +66,7 @@ public class ArbitrarySignaturesMessage extends Message {
 			signatures.add(signature);
 		}
 
-		return new ArbitrarySignaturesMessage(id, peerAddress, signatures);
+		return new ArbitrarySignaturesMessage(id, peerAddress, requestHops, signatures);
 	}
 
 	@Override
@@ -65,6 +76,8 @@ public class ArbitrarySignaturesMessage extends Message {
 
 			Serialization.serializeSizedString(bytes, this.peerAddress);
 
+			bytes.write(Ints.toByteArray(this.requestHops));
+
 			bytes.write(Ints.toByteArray(this.signatures.size()));
 
 			for (byte[] signature : this.signatures)

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

@@ -228,7 +228,7 @@ public class ArbitraryTransaction extends Transaction {
 			if (ArbitraryDataStorageManager.getInstance().canStoreData(arbitraryTransactionData)) {
 				// Use a null peer address to indicate our own
 				byte[] signature = arbitraryTransactionData.getSignature();
-				Message arbitrarySignatureMessage = new ArbitrarySignaturesMessage(null, Arrays.asList(signature));
+				Message arbitrarySignatureMessage = new ArbitrarySignaturesMessage(null, 0, Arrays.asList(signature));
 				Network.getInstance().broadcast(broadcastPeer -> arbitrarySignatureMessage);
 			}
 		}