Deferred decode for HELLO to prevent HELLOcalypse under high load of new peers.

include/ZeroTierOne.h

@@ -1511,6 +1511,27 @@ void ZT_Node_clusterHandleIncomingMessage(ZT_Node *node,const void *msg,unsigned
  */
 void ZT_Node_clusterStatus(ZT_Node *node,ZT_ClusterStatus *cs);
 
+/**
+ * Do things in the background until Node dies
+ *
+ * This function can be called from one or more background threads to process
+ * certain tasks in the background to improve foreground performance. It will
+ * not return until the Node is shut down. If threading is not enabled in
+ * this build it will return immediately and will do nothing.
+ *
+ * This is completely optional. If this is never called, all processing is
+ * done in the foreground in the various processXXXX() methods.
+ *
+ * This does NOT replace or eliminate the need to call the normal
+ * processBackgroundTasks() function in your main loop. This mechanism is
+ * used to offload the processing of expensive mssages onto background
+ * handler threads to prevent foreground performance degradation under
+ * high load.
+ *
+ * @param node Node instance
+ */
+void ZT_Node_backgroundThreadMain(ZT_Node *node);
+
 /**
  * Get ZeroTier One version
  *