IF(4N)IF(4N)NAMEif - general properties of network interfaces
DESCRIPTION
Each network interface in a system corresponds to a path through which
messages may be sent and received. A network interface usually has a
hardware device associated with it, though certain interfaces such as
the loopback interface, lo(4), do not.
At boot time each interface which has underlying hardware support makes
itself known to the system during the autoconfiguration process. Once
the interface has acquired its address it is expected to install a
routing table entry so that messages may be routed through it. Most
interfaces require some part of their address specified with an
SIOCSIFADDR ioctl before they will allow traffic to flow through them.
On interfaces where the network-link layer address mapping is static,
only the network number is taken from the ioctl; the remainder is found
in a hardware specific manner. On interfaces which provide dynamic
network-link layer address mapping facilities (for example, 10Mb/s
Ethernets using arp(4P),), the entire address specified in the ioctl is
used.
The following ioctl calls may be used to manipulate network interfaces.
Unless specified otherwise, the request takes an ifreq structure as its
parameter. This structure has the form
struct ifreq {
char ifr_name[16]; /* name of interface (e.g. "ec0") */
union {
struct sockaddr ifru_addr;
struct sockaddr ifru_dstaddr;
short ifru_flags;
} 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_flags ifr_ifru.ifru_flags /* flags */
};
SIOCSIFADDR
Set interface address. Following the address assignment, the
``initialization'' routine for the interface is called.
SIOCGIFADDR
Get interface address.
SIOCSIFDSTADDR
Set point to point address for interface.
SIOCGIFDSTADDR
Get point to point address for interface.
SIOCSIFFLAGS
Set interface flags field. If the interface is marked down, any
processes currently routing packets through the interface are
notified.
SIOCGIFFLAGS
Get interface flags.
SIOCGIFCONF
Get interface configuration list. This request takes an ifconf
structure (see below) as a value-result parameter. The ifc_len
field should be initially set to the size of the buffer pointed to
by ifc_buf. On return it will contain the length, in bytes, of
the configuration list.
/*
* Structure used in SIOCGIFCONF request.
* Used to retrieve interface configuration
* for machine (useful for programs which
* must know all networks accessible).
*/
struct ifconf {
int ifc_len; /* size of associated buffer */
union {
caddr_t ifcu_buf;
struct ifreq *ifcu_req;
} ifc_ifcu;
#define ifc_buf ifc_ifcu.ifcu_buf /* buffer address */
#define ifc_req ifc_ifcu.ifcu_req /* array of structures returned */
};
SEE ALSOarp(4P), ec(4S), lo(4)
25 July 1985 IF(4N)