Don't intentionally disconnect peers if we are currently syncing with them.

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

@@ -722,6 +722,7 @@ public class Controller extends Thread {
 				hasStatusChanged = true;
 			}
 		}
+		peer.setSyncInProgress(true);
 
 		if (hasStatusChanged)
 			updateSysTray();
@@ -801,6 +802,7 @@ public class Controller extends Thread {
 			return syncResult;
 		} finally {
 			isSynchronizing = false;
+			peer.setSyncInProgress(false);
 		}
 	}
 

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

@@ -645,10 +645,15 @@ public class Network {
         }
 
         // Find peers that have reached their maximum connection age, and disconnect them
-        List<Peer> peersToDisconnect = this.connectedPeers.stream().filter(peer -> peer.hasReachedMaxConnectionAge()).collect(Collectors.toList());
+        List<Peer> peersToDisconnect = this.connectedPeers.stream()
+                .filter(peer -> !peer.isSyncInProgress())
+                .filter(peer -> peer.hasReachedMaxConnectionAge())
+                .collect(Collectors.toList());
+
         if (peersToDisconnect != null && peersToDisconnect.size() > 0) {
             for (Peer peer : peersToDisconnect) {
-                LOGGER.debug("Forcing disconnect of peer {} because connection age ({} ms) has reached the maximum ({} ms)", peer, peer.getConnectionAge(), peer.getMaxConnectionAge());
+                LOGGER.info("Forcing disconnection of peer {} because connection age ({} ms) " +
+                        "has reached the maximum ({} ms)", peer, peer.getConnectionAge(), peer.getMaxConnectionAge());
                 peer.disconnect("Connection age too old");
             }
         }

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

@@ -97,6 +97,8 @@ public class Peer {
 
     byte[] ourChallenge;
 
+    private boolean syncInProgress = false;
+
     // Versioning
     public static final Pattern VERSION_PATTERN = Pattern.compile(Controller.VERSION_PREFIX
             + "(\\d{1,3})\\.(\\d{1,5})\\.(\\d{1,5})");
@@ -340,6 +342,14 @@ public class Peer {
         }
     }
 
+    public boolean isSyncInProgress() {
+        return this.syncInProgress;
+    }
+
+    public void setSyncInProgress(boolean syncInProgress) {
+        this.syncInProgress = syncInProgress;
+    }
+
     @Override
     public String toString() {
         // Easier, and nicer output, than peer.getRemoteSocketAddress()