struct	ifreq {
#define IFNAMSIZ 16
	char	ifr_name[IFNAMSIZ];	/* if name, e.g. "en0" */
	union {
		struct	sockaddr	ifru_addr;
		struct	sockaddr	ifru_dstaddr;
		struct	sockaddr	ifru_broadaddr;
		short			ifru_flags;
		int			ifru_metric;
		uint64_t		ifru_media;
		caddr_t			ifru_data;
	} ifr_ifru;
#define	ifr_addr	ifr_ifru.ifru_addr	/* address */
#define	ifr_dstaddr	ifr_ifru.ifru_dstaddr	/* other end of p-to-p link */
#define	ifr_broadaddr	ifr_ifru.ifru_broadaddr	/* broadcast address */
#define	ifr_flags	ifr_ifru.ifru_flags	/* flags */
#define	ifr_metric	ifr_ifru.ifru_metric	/* metric */
#define	ifr_mtu		ifr_ifru.ifru_metric	/* mtu (overload) */
#define	ifr_hardmtu	ifr_ifru.ifru_metric	/* hardmtu (overload) */
#define	ifr_media	ifr_ifru.ifru_media	/* media options */
#define	ifr_rdomainid	ifr_ifru.ifru_metric	/* VRF instance (overload) */
#define	ifr_vnetid	ifr_ifru.ifru_metric	/* Virtual Net Id (overload) */
#define	ifr_ttl		ifr_ifru.ifru_metric	/* tunnel TTL (overload) */
#define	ifr_data	ifr_ifru.ifru_data	/* for use by interface */
};