Added rate gates for QOS and ACK packets

node/Constants.hpp

@@ -274,6 +274,23 @@
  */
 #define ZT_MULTIPATH_BINDER_REFRESH_PERIOD 5000
 
+/**
+ * Time horizon for VERB_QOS_MEASUREMENT and VERB_ACK packet processesing cutoff
+ */
+#define ZT_PATH_QOS_ACK_CUTOFF_TIME 30000
+
+/**
+ * Maximum number of VERB_QOS_MEASUREMENT and VERB_ACK packets allowed to be
+ * processesed within cutoff time. Separate totals are kept for each type but
+ * the limit is the same for both.
+ *
+ * This limits how often this peer will compute statistical estimates
+ * of various QoS measures from a VERB_QOS_MEASUREMENT or VERB_ACK packets to
+ * CUTOFF_LIMIT times per CUTOFF_TIME milliseconds per peer to prevent
+ * this from being useful for DOS amplification attacks.
+ */
+#define ZT_PATH_QOS_ACK_CUTOFF_LIMIT 16
+
 /**
  * Path choice history window size. This is used to keep track of which paths were
  * previously selected so that we can maintain a target allocation over time.