1.\" $OpenBSD: if_indextoname.3,v 1.4 2000/03/01 17:31:23 todd Exp $ 2.\" Copyright (c) 1983, 1991, 1993 3.\" The Regents of the University of California. All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 3. All advertising materials mentioning features or use of this software 14.\" must display the following acknowledgement: 15.\" This product includes software developed by the University of 16.\" California, Berkeley and its contributors. 17.\" 4. Neither the name of the University nor the names of its contributors 18.\" may be used to endorse or promote products derived from this software 19.\" without specific prior written permission. 20.\" 21.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31.\" SUCH DAMAGE. 32.\" 33.\" From: @(#)rcmd.3 8.1 (Berkeley) 6/4/93 34.\" 35.Dd May 21, 1998 36.Dt IF_NAMETOINDEX 3 37.Os 38.Sh NAME 39.Nm if_nametoindex , 40.Nm if_indextoname , 41.Nm if_nameindex , 42.Nm if_freenameindex 43.Nd convert interface index to name, and vice versa 44.Sh SYNOPSIS 45.Fd #include <net/if.h> 46.Ft "unsigned int" 47.Fn if_nametoindex "const char *ifname" 48.Ft "char *" 49.Fn if_indextoname "unsigned int ifindex" "char *ifname" 50.Ft "struct if_nameindex *" 51.Fn if_nameindex "void" 52.Ft "void" 53.Fn if_freenameindex "struct if_nameindex *ptr" 54.Sh DESCRIPTION 55These functions map interface indexes to interface names (such as 56.Dq lo0 ) , 57and vice versa. 58.Pp 59The 60.Fn if_nametoindex 61function converts an interface name specified by the 62.Fa ifname 63argument to an interface index (positive integer value). 64If the specified interface does not exist, 0 will be returned. 65.Pp 66.Fn if_indextoname 67converts an interface index specified by the 68.Fa ifindex 69argument to an interface name. 70The 71.Fa ifname 72argument must point to a buffer of at least 73.Dv IF_NAMESIZE 74bytes into which the interface name corresponding to the specified index is 75returned. 76.Pf ( Dv IF_NAMESIZE 77is also defined in 78.Aq Pa net/if.h 79and its value includes a terminating null byte at the end of the 80interface name.) 81This pointer is also the return value of the function. 82If there is no interface corresponding to the specified index, 83.Dv NULL 84is returned. 85.Pp 86.Fn if_nameindex 87returns an array of 88.Fa if_nameindex 89structures. 90.Fa if_nametoindex 91is also defined in 92.Aq Pa net/if.h , 93and is as follows: 94.Bd -literal -offset 95struct if_nameindex { 96 unsigned int if_index; /* 1, 2, ... */ 97 char *if_name; /* null terminated name: "le0", ... */ 98}; 99.Ed 100.Pp 101The end of the array of structures is indicated by a structure with 102an 103.Fa if_index 104of 0 and an 105.Fa if_name 106of 107.Dv NULL . 108The function returns a null pointer on error. 109The memory used for this array of structures along with the interface 110names pointed to by the 111.Fa if_name 112members is obtained dynamically. 113This memory is freed by the 114.Fn if_freenameindex 115function. 116.Pp 117.Fn if_freenameindex 118takes a pointer that was returned by 119.Fn if_nameindex 120as argument 121.Pq Fa ptr , 122and it reclaims the region allocated. 123.Sh DIAGNOSTICS 124.Fn if_nametoindex 125returns 0 on error, positive integer on success. 126.Fn if_indextoname 127and 128.Fn if_nameindex 129return 130.Dv NULL 131on errors. 132.Sh SEE ALSO 133R. Gilligan, S. Thomson, J. Bound, and W. Stevens, 134``Basic Socket Interface Extensions for IPv6,'' RFC2553, March 1999. 135.Sh STANDARDS 136These functions are defined in ``Basic Socket Interface Extensions for IPv6'' 137.Pq RFC2533 . 138