NETDEVICE(7)

NAME
netdevice - Low level access to Linux network devices.

SYNOPSIS
#include <net/if.h>

DESCRIPTION
This man page describes the sockets interface which is used to configure network devices. Linux supports some standard ioctls to configure network devices. They can be used on any socket's file descriptor regardless of the family or type. They pass an ifreq structure:
struct ifreq
{
	char	ifr_name[IFNAMSIZ];	/* Interface name */
	union {
		struct sockaddr	ifr_addr;
		struct sockaddr	ifr_dstaddr;
		struct sockaddr	ifr_broadaddr;
		struct sockaddr	ifr_netmask;
		struct sockaddr	ifr_hwaddr;
		short	ifr_flags;
		int	ifr_ifindex;
		int	ifr_metric;
		int	ifr_mtu;
		struct ifmap	ifr_map;
		char	ifr_slave[IFNAMSIZ];
		char	ifr_newname[IFNAMSIZ];
		char *	ifr_data;
	};
}
Normally, the ioctl specifies which device to affect by setting ifr_name to the name of the interface. All other members of the structure may share memory.

IOCTLS
If an ioctl is marked as privileged then using it requires an effective user id of 0 or the CAP_NET_ADMIN capability. If this is not the case EPERM will be returned.

SIOCGIFNAME
    Given the ifr_ifindex, return the name of the interface in ifr_name. This is the only ioctl which returns its result in ifr_name.

SIOCGIFINDEX
    Retrieve the interface index of the interface into ifr_ifindex.

SIOCGIFFLAGS, SIOCSIFFLAGS
    Get or set the active flag word of the device. ifr_flags contains a bitmask of the following values:
    Device flags
    IFF_UP | Interface is running.
    IFF_BROADCAST | Valid broadcast address set.
    IFF_DEBUG | Internal debugging flag.
    IFF_LOOPBACK | Interface is a loopback interface.
    IFF_POINTOPOINT | Interface is a point-to-point link.
    IFF_RUNNING | Resources allocated.
    IFF_NOARP | No arp protocol
    IFF_PROMISC | Interface is in promiscuous mode.
    IFF_NOTRAILERS | Avoid use of trailers.
    IFF_ALLMULTI | Receive all multicast packets.
    IFF_MASTER | Master of a load balancing bundle.
    IFF_SLAVE | Slave of a load balancing bundle.
    IFF_MULTICAST | Supports multicast
    IFF_PORTSEL | Is able to select media type via ifmap.
    IFF_AUTOMEDIA | Auto media selection active.
    IFF_DYNAMIC | The addresses are lost when the interface goes down.
    Setting the active flag word is a privileged operation, but any process may read it.

SIOCGIFMETRIC, SIOCSIFMETRIC
    Get or set the metric of the device using ifr_metric. This is currently not implemented; it sets ifr_metric to 0 if you attempt to read it and returns EOPNOTSUPP if you attempt to set it.

SIOCGIFMTU, SIOCSIFMTU
    Get or set the MTU (Maximum Transfer Unit) of a device using ifr_mtu. Setting the MTU is a privileged operation.

SIOCGIFHWADDR, SIOCSIFHWADDR
    Get or set the hardware address of a device using ifr_hwaddr. Setting the hardware address is a privileged operation.

SIOCSIFHWBROADCAST
    Set the hardware broadcast address of a device from ifr_hwaddr. This is a privileged operation.

SIOCGIFMAP, SIOCSIFMAP
    Get or set the interface's hardware parameters using ifr_map. Setting the parameters is a privileged operation.
    struct ifmap
    {
    	unsigned long	mem_start;
    	unsigned long	mem_end;
    	unsigned short	base_addr;
    	unsigned char	irq;
    	unsigned char	dma;
    	unsigned char	port;
    };
    The interpretation of the ifmap structure depends on the device driver and the architecture.

SIOCADDMULTI, SIOCDELMULTI
    Add an address to or delete an address from the device's link layer multicast filters using ifr_hwaddr. These are privileged operations.

SIOCGIFTXQLEN, SIOCSIFTXQLEN
    Get or set the transmit queue length of a device using ifr_qlen. Setting the transmit queue length is a privileged operation.

SIOCSIFNAME
    Changes the name of the interface specified in ifr_ifindex to ifr_newname. This is a privileged operation.

Most protocols support their own ioctls to configure protocol specific interface options. See the protocol man pages for a description.

In addition some devices support private ioctls. These are not described here.