+ /* Returns the ifindex of 'netdev', if successful, as a positive number.
+ * On failure, returns a negative errno value.
+ *
+ * The desired semantics of the ifindex value are a combination of those
+ * specified by POSIX for if_nametoindex() and by SNMP for ifIndex. An
+ * ifindex value should be unique within a host and remain stable at least
+ * until reboot. SNMP says an ifindex "ranges between 1 and the value of
+ * ifNumber" but many systems do not follow this rule anyhow. */
+ int (*get_ifindex)(const struct netdev *);
+