NAME
if_nametoindex,
if_indextoname,
if_nameindex,
if_freenameindex —
convert interface index to name, and
vice versa
SYNOPSIS
#include
<sys/types.h>
#include <sys/socket.h>
#include <net/if.h>
unsigned int
if_nametoindex(const
char *ifname);
char *
if_indextoname(unsigned
int ifindex, char
*ifname);
struct if_nameindex *
if_nameindex(void);
void
if_freenameindex(struct
if_nameindex *ptr);
DESCRIPTION
These functions map interface indexes to interface names (such as “lo0”), and vice versa.
The
if_nametoindex()
function converts an interface name specified by the
ifname argument to an interface index (positive
integer value). If the specified interface does not exist, 0 will be
returned.
if_indextoname()
converts an interface index specified by the ifindex
argument to an interface name. The ifname argument
must point to a buffer of at least IF_NAMESIZE bytes
into which the interface name corresponding to the specified index is
returned. (IF_NAMESIZE is also defined in
<net/if.h> and its value
includes a terminating NUL byte at the end of the interface name.) This
pointer is also the return value of the function. If there is no interface
corresponding to the specified index, NULL is
returned.
if_nameindex()
returns an array of if_nameindex structures.
if_nameindex is also defined in
<net/if.h>, and is as
follows:
struct if_nameindex {
unsigned int if_index; /* 1, 2, ... */
char *if_name; /* NUL-terminated name */
};
The end of the array of structures is
indicated by a structure with an if_index of 0 and an
if_name of NULL. The function
returns a null pointer on error. The memory used for this array of
structures along with the interface names pointed to by the
if_name members is obtained dynamically. This memory
is freed by the
if_freenameindex()
function.
if_freenameindex()
takes a pointer that was returned by if_nameindex()
as argument (ptr), and it reclaims the region
allocated.
DIAGNOSTICS
if_nametoindex() returns 0 on error,
positive integer on success. if_indextoname() and
if_nameindex() return NULL
on errors.
SEE ALSO
STANDARDS
R. Gilligan, S. Thomson, J. Bound, J. McCann, and W. Stevens, Basic Socket Interface Extensions for IPv6, RFC 3493, February 2003.