IF_NAMETOINDEX(3) OpenBSD Programmer's Manual IF_NAMETOINDEX(3)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.
DIAGNOSTICSif_nametoindex() returns 0 on error, positive integer on success.
if_indextoname() and if_nameindex() return NULL on errors.
SEE ALSOgetifaddrs(3), networking(4)
R. Gilligan, S. Thomson, J. Bound, and W. Stevens, Basic Socket Interface
Extensions for IPv6, RFC 2553, March 1999.
STANDARDS
These functions are defined in ``Basic Socket Interface Extensions for
IPv6'' (RFC 2533).
OpenBSD 4.9 May 31, 2007 OpenBSD 4.9