\" $NetBSD: if_indextoname.3,v 1.12 2010/03/22 19:30:54 joerg Exp $
\" $KAME: if_indextoname.3,v 1.10 2000/11/24 08:13:51 itojun Exp $
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Dd March 11, 2005
Dt IF_NAMETOINDEX 3
Os
Sh NAME
Nm if_nametoindex ,
Nm if_indextoname ,
Nm if_nameindex ,
Nm if_freenameindex
Nd provide mappings between interface names and indexes
Sh SYNOPSIS
In net/if.h
Ft unsigned int
Fn if_nametoindex "const char *ifname"
Ft char *
Fn if_indextoname "unsigned int ifindex" "char *ifname"
Ft struct if_nameindex *
Fn if_nameindex "void"
Ft void
Fn if_freenameindex "struct if_nameindex *ptr"
Sh DESCRIPTION
The
Fn if_nametoindex
function maps the interface name specified in
Ar ifname
to its corresponding index.
If the specified interface does not exist, it returns 0.
Pp
The
Fn if_indextoname
function maps the interface index specified in
Ar ifindex
to it corresponding name, which is copied into the
buffer pointed to by
Ar 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.
Pp
The
Fn if_nameindex
function returns an array of
Nm if_nameindex
structures, one structure per interface, as
defined in the include file
In net/if.h .
The
Nm if_nameindex
structure contains at least the following entries:
Bd -literal
unsigned int if_index; /* 1, 2, ... */
char *if_name; /* null terminated name: "le0", ... */
Ed
Pp
The end of the array of structures is indicated by a structure with an
Nm if_index
of 0 and an
Nm if_name
of NULL.
A NULL pointer is returned upon an error.
Pp
The
Fn if_freenameindex
function frees the dynamic memory that was
allocated by
Fn if_nameindex .
Sh RETURN VALUES
Upon successful completion,
Fn if_nametoindex
returns the index number of the interface.
If the interface is not found, a value of 0 is returned and
Va errno
is set to
Er ENXIO .
A value of 0 is also returned if an error
occurs while retrieving the list of interfaces via
Xr getifaddrs 3 .
Pp
Upon successful completion,
Fn if_indextoname
returns
Ar ifname .
If the interface is not found, a NULL pointer is returned and
Va errno
is set to
Er ENXIO .
A NULL pointer is also returned if an error
occurs while retrieving the list of interfaces via
Xr getifaddrs 3 .
Pp
The
Fn if_nameindex
returns a NULL pointer if an error
occurs while retrieving the list of interfaces via
Xr getifaddrs 3 ,
or if sufficient memory cannot be allocated.
Sh SEE ALSO
Xr getifaddrs 3 ,
Xr networking 4
Sh STANDARDS
The
Fn if_nametoindex ,
Fn if_indextoname ,
Fn if_nameindex ,
and
Fn if_freenameindex
functions conform to
St -p1003.1-2001 ,
St -xns5.2 ,
and RFC 3493.
Sh HISTORY
The implementation first appeared in
Bsx .
