NETDEVICE
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 user 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. Setting the MTU to
too small values may cause kernel crashes.
- 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.
See also
packet(7)
for an alternative.
- 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.