ZeroTier now has link quality measurement. We are not using this yet but decided to put it in to prep for future QoS support and SD-WAN stuff.

include/ZeroTierOne.h

@@ -179,6 +179,11 @@ extern "C" {
  */
 #define ZT_CLUSTER_MAX_MESSAGE_LENGTH (1500 - 48)
 
+/**
+ * Maximum value for link quality (min is 0)
+ */
+#define ZT_PATH_LINK_QUALITY_MAX 0xff
+
 /**
  * Packet characteristics flag: packet direction, 1 if inbound 0 if outbound
  */
@@ -1036,6 +1041,11 @@ typedef struct
 	 */
 	uint64_t trustedPathId;
 
+	/**
+	 * Path link quality from 0 to 255 (always 255 if peer does not support)
+	 */
+	int linkQuality;
+
 	/**
 	 * Is path expired?
 	 */