NAME
if_nametoindex,
if_indextoname,
if_nameindex,
if_freenameindex —
provide mappings between interface
names and indexes
SYNOPSIS
#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
Theif_nametoindex()
function maps the interface name specified in ifname to
its corresponding index. If the specified interface does not exist, it returns
0.
The
if_indextoname()
function maps the interface index specified in ifindex
to it corresponding name, which is copied into the buffer pointed to by
ifname, which must be of at least IFNAMSIZ bytes. This
pointer is also the return value of the function. If there is no interface
corresponding to the specified index, NULL is returned.
The
if_nameindex()
function returns an array of if_nameindex
structures, one structure per interface, as defined in the include file
<net/if.h>. The
if_nameindex structure contains at least the
following entries:
unsigned int if_index; /* 1, 2, ... */
char *if_name; /* null terminated name: "le0", ... */
The end of the array of structures is indicated by a structure
with an if_index of 0 and an
if_name of NULL. A NULL pointer is returned upon an
error.
The
if_freenameindex()
function frees the dynamic memory that was allocated by
if_nameindex().
RETURN VALUES
Upon successful completion,
if_nametoindex() returns the index number of the
interface. If the interface is not found, a value of 0 is returned and
errno is set to ENXIO. A value
of 0 is also returned if an error occurs while retrieving the list of
interfaces via
getifaddrs(3).
Upon successful completion,
if_indextoname() returns
ifname. If the interface is not found, a NULL pointer
is returned and errno is set to
ENXIO. A NULL pointer is also returned if an error
occurs while retrieving the list of interfaces via
getifaddrs(3).
The if_nameindex() returns a NULL pointer
if an error occurs while retrieving the list of interfaces via
getifaddrs(3), or if sufficient memory cannot be
allocated.
SEE ALSO
STANDARDS
The if_nametoindex(),
if_indextoname(),
if_nameindex(), and
if_freenameindex() functions conform to
IEEE Std 1003.1-2001 (“POSIX.1”),
X/Open Networking Services Issue 5.2
(“XNS5.2”), and RFC 3493.
HISTORY
The implementation first appeared in BSD/OS.