NETDEVICE (7)
Low level access to Linux network devices.
SYNOPSIS
#include <sys/ioctl.h>
#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:
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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;
};
}
struct ifconf
{
int ifc_len; /* size of buffer */
union {
char * ifc_buf; /* buffer address */
struct ifreq *ifc_req; /* array of structures */
};
};
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:
tab(:);
c s
l l.
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, L2 destination address not set.
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:T{
The addresses are lost when the interface goes down.
T}
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.
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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.
SIOCGIFCONF
Return a list of interface (transport layer) addresses. This currently
means only addresses of the AF_INET family for compatibility.
The user passes a
ifconf
structure as argument to the ioctl. It contains a pointer to an array of
ifreq
structures in
ifc_req
and its length in bytes in
ifc_len.
The kernel fills the ifreqs with all current L3 interface addresses that
are running:
ifr_name
contains the interface name (eth0:1 etc.),
ifr_addr
the address.
The kernel returns with the actual length in
ifc_len;
if it is equal the original length the user should assume that it overflowed
and retry with a bigger buffer. When no error occurs the ioctl returns 0;
otherwise -1. Overflow is no error.
\" XXX Slaving isn't supported in 2.2
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