netdevice(7) - Linux manual page (original) (raw)
netdevice(7) Miscellaneous Information Manual netdevice(7)
NAME top
netdevice - low-level access to Linux network devicesSYNOPSIS top
**#include <sys/ioctl.h>**
**#include <net/if.h>**DESCRIPTION top
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. Most of them 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;
};
};
**AF_INET6** is an exception. It passes an _in6ifreq_ structure:
struct in6_ifreq {
struct in6_addr ifr6_addr;
u32 ifr6_prefixlen;
int ifr6_ifindex; /* Interface index */
};
Normally, the user specifies which device to affect by setting
_ifrname_ to the name of the interface or _ifr6ifindex_ to the index
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 _ifrifindex_, return the name of the interface in
_ifrname_. This is the only ioctl which returns its result
in _ifrname_.
**SIOCGIFINDEX**
Retrieve the interface index of the interface into
_ifrifindex_.
**SIOCGIFFLAGS**
**SIOCSIFFLAGS**
Get or set the active flag word of the device. _ifrflags_
contains a bit mask 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, 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 The addresses are lost when the interface
goes down.
IFF_LOWER_UP Driver signals L1 up (since Linux 2.6.17)
IFF_DORMANT Driver signals dormant (since Linux 2.6.17)
IFF_ECHO Echo sent packets (since Linux 2.6.25)
Setting the active flag word is a privileged operation, but any
process may read it.
**SIOCGIFPFLAGS**
**SIOCSIFPFLAGS**
Get or set extended (private) flags for the device.
_ifrflags_ contains a bit mask of the following values:
Private flags
IFF_802_1Q_VLAN Interface is 802.1Q VLAN device.
IFF_EBRIDGE Interface is Ethernet bridging device.
IFF_SLAVE_INACTIVE Interface is inactive bonding slave.
IFF_MASTER_8023AD Interface is 802.3ad bonding master.
IFF_MASTER_ALB Interface is balanced-alb bonding master.
IFF_BONDING Interface is a bonding master or slave.
IFF_SLAVE_NEEDARP Interface needs ARPs for validation.
IFF_ISATAP Interface is RFC4214 ISATAP interface.
Setting the extended (private) interface flags is a privileged
operation.
**SIOCGIFADDR**
**SIOCSIFADDR**
**SIOCDIFADDR**
Get, set, or delete the address of the device using
_ifraddr_, or _ifr6addr_ with _ifr6prefixlen_. Setting or
deleting the interface address is a privileged operation.
For compatibility, **SIOCGIFADDR** returns only **AF_INET**
addresses, **SIOCSIFADDR** accepts **AF_INET** and **AF_INET6**
addresses, and **SIOCDIFADDR** deletes only **AF_INET6** addresses.
A **AF_INET** address can be deleted by setting it to zero via
**SIOCSIFADDR**.
**SIOCGIFDSTADDR**
**SIOCSIFDSTADDR**
Get or set the destination address of a point-to-point
device using _ifrdstaddr_. For compatibility, only **AF_INET**
addresses are accepted or returned. Setting the
destination address is a privileged operation.
**SIOCGIFBRDADDR**
**SIOCSIFBRDADDR**
Get or set the broadcast address for a device using
_ifrbrdaddr_. For compatibility, only **AF_INET** addresses are
accepted or returned. Setting the broadcast address is a
privileged operation.
**SIOCGIFNETMASK**
**SIOCSIFNETMASK**
Get or set the network mask for a device using _ifrnetmask_.
For compatibility, only **AF_INET** addresses are accepted or
returned. Setting the network mask is a privileged
operation.
**SIOCGIFMETRIC**
**SIOCSIFMETRIC**
Get or set the metric of the device using _ifrmetric_. This
is currently not implemented; it sets _ifrmetric_ 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 _ifrmtu_. 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
_ifrhwaddr_. The hardware address is specified in a struct
_sockaddr_. _safamily_ contains the ARPHRD_* device type,
_sadata_ the L2 hardware address starting from byte 0.
Setting the hardware address is a privileged operation.
**SIOCSIFHWBROADCAST**
Set the hardware broadcast address of a device from
_ifrhwaddr_. This is a privileged operation.
**SIOCGIFMAP**
**SIOCSIFMAP**
Get or set the interface's hardware parameters using
_ifrmap_. 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 _ifrhwaddr_. These are
privileged operations. See also [packet(7)](../man7/packet.7.html) for an
alternative.
**SIOCGIFTXQLEN**
**SIOCSIFTXQLEN**
Get or set the transmit queue length of a device using
_ifrqlen_. Setting the transmit queue length is a
privileged operation.
**SIOCSIFNAME**
Changes the name of the interface specified in _ifrname_ to
_ifrnewname_. This is a privileged operation. It is
allowed only when the interface is not up.
**SIOCGIFCONF**
Return a list of interface (network layer) addresses. This
currently means only addresses of the **AF_INET** (IPv4) family
for compatibility. Unlike the others, this ioctl passes an
_ifconf_ structure:
struct ifconf {
int ifc_len; /* size of buffer */
union {
char *ifc_buf; /* buffer address */
struct ifreq *ifc_req; /* array of structures */
};
};
If _ifcreq_ is NULL, **SIOCGIFCONF** returns the necessary
buffer size in bytes for receiving all available addresses
in _ifclen_. Otherwise, _ifcreq_ contains a pointer to an
array of _ifreq_ structures to be filled with all currently
active L3 interface addresses. _ifclen_ contains the size
of the array in bytes. Within each _ifreq_ structure,
_ifrname_ will receive the interface name, and _ifraddr_ the
address. The actual number of bytes transferred is
returned in _ifclen_.
If the size specified by _ifclen_ is insufficient to store
all the addresses, the kernel will skip the exceeding ones
and return success. There is no reliable way of detecting
this condition once it has occurred. It is therefore
recommended to either determine the necessary buffer size
beforehand by calling **SIOCGIFCONF** with _ifcreq_ set to NULL,
or to retry the call with a bigger buffer whenever _ifclen_
upon return differs by less than _sizeof(struct ifreq)_ from
its original value.
If an error occurs accessing the _ifconf_ or _ifreq_
structures, **EFAULT** will be returned.
Most protocols support their own ioctls to configure protocol-
specific interface options. See the protocol man pages for a
description. For configuring IP addresses, see [ip(7)](../man7/ip.7.html).
In addition, some devices support private ioctls. These are not
described here.NOTES top
**SIOCGIFCONF** and the other ioctls that accept or return only
**AF_INET** socket addresses are IP-specific and perhaps should rather
be documented in [ip(7)](../man7/ip.7.html).
The names of interfaces with no addresses or that don't have the
**IFF_RUNNING** flag set can be found via _/proc/net/dev_.
**AF_INET6** IPv6 addresses can be read from _/proc/net/ifinet6_ or via
[rtnetlink(7)](../man7/rtnetlink.7.html). Adding a new IPv6 address and deleting an existing
IPv6 address can be done via **SIOCSIFADDR** and **SIOCDIFADDR** or via
[rtnetlink(7)](../man7/rtnetlink.7.html). Retrieving or changing destination IPv6 addresses
of a point-to-point interface is possible only via [rtnetlink(7)](../man7/rtnetlink.7.html).BUGS top
glibc 2.1 is missing the _ifrnewname_ macro in _<net/if.h>_. Add the
following to your program as a workaround:
#ifndef ifr_newname
#define ifr_newname ifr_ifru.ifru_slave
#endifSEE ALSO top
[proc(5)](../man5/proc.5.html), [capabilities(7)](../man7/capabilities.7.html), [ip(7)](../man7/ip.7.html), [rtnetlink(7)](../man7/rtnetlink.7.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-05-02 netdevice(7)
Pages that refer to this page:getifaddrs(3), ip(7), ipv6(7), packet(7), rtnetlink(7)