-/* Get state from ifindex. Possible states: unknown, unmanaged, failed, configuring, configured */
-int sd_network_get_link_state(unsigned index, char**state);
+/* Get state from ifindex.
+ * Possible states: failed, configuring, configured
+ * Possible return codes:
+ * -ENODATA: networkd is not aware of the link
+ * -EUNATCH: networkd is not managing this link
+ * -EBUSY: udev is still processing the link, networkd does not yet know if it will manage it
+ */
+int sd_network_get_link_state(unsigned ifindex, char **state);
+
+/* Get operatinal state from ifindex.
+ * Possible states: unknown, dormant, carrier, degraded, routable
+ * Possible return codes:
+ * -ENODATA: networkd is not aware of the link
+ */
+int sd_network_get_link_operational_state(unsigned ifindex, char **state);
+
+/* Get overall opeartional state
+ * Possible states: unknown, dormant, carrier, degraded, routable
+ * Possible return codes:
+ * -ENODATA: networkd is not aware of any links
+ */
+int sd_network_get_operational_state(char **state);
+
+/* Returns true if link exists and is loopback, and false otherwise */
+int sd_network_link_is_loopback(unsigned ifindex);