1.\" Copyright (c) 1983, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" From: @(#)rcmd.3 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD$ 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 LIBRARY 45.Lb libc 46.Sh SYNOPSIS 47.Fd #include <sys/types.h> 48.Fd #include <sys/socket.h> 49.Fd #include <net/if.h> 50.Ft "unsigned int" 51.Fn if_nametoindex "const char *ifname" 52.Ft "char *" 53.Fn if_indextoname "unsigned int ifindex" "char *ifname" 54.Ft "struct if_nameindex *" 55.Fn if_nameindex "void" 56.Ft "void" 57.Fn if_freenameindex "struct if_nameindex *ptr" 58.Sh DESCRIPTION 59The functions map interface index to readable interface name 60.Po 61such as 62.Li ``lo0'' 63.Pc 64, and vice versa. 65.Pp 66.Fn if_nametoindex 67converts readable interface name to interface index 68.Pp positive integer value . 69If the specified interface does not exist, 0 will be returned. 70.Pp 71.Fn if_indextoname 72converts interface index to readable interface name. 73The 74.Fa ifname 75argument must point to a buffer of at least 76.Dv IF_NAMESIZE 77bytes into which the interface name corresponding to the specified index is 78returned. 79.Po 80.Dv IF_NAMESIZE 81is also defined in 82.Li <net/if.h> 83and its value includes a terminating null byte at the end of the 84interface name. 85.Pc 86This pointer is also the return value of the function. 87If there is no interface corresponding to the specified index, 88.Dv NULL 89is returned. 90.Pp 91.Fn if_nameindex 92returns an array of 93.Fa if_nameindex 94structures. 95.Fa if_nametoindex 96is also defined in 97.Li <net/if.h> , 98and is as follows: 99.Bd -literal -offset 100struct if_nameindex { 101 unsigned int if_index; /* 1, 2, ... */ 102 char *if_name; /* null terminated name: "le0", ... */ 103}; 104.Ed 105.Pp 106The end of the array of structures is indicated by a structure with 107an 108.Fa if_index 109of 0 and an 110.Fa if_name 111of 112.Dv NULL . 113The function returns a 114.Dv NULL 115pointer upon an error. 116The memory used for this array of structures along with the interface 117names pointed to by the 118.Fa if_name 119members is obtained dynamically. 120This memory is freed by the 121.Fn if_freenameindex 122function. 123.Pp 124.Fn if_freenameindex 125takes a pointer that was returned by 126.Fn if_nameindex 127as argument 128.Pq Fa ptr , 129and it reclaims the region allocated. 130.Sh DIAGNOSTICS 131.Fn if_nametoindex 132returns 0 on error, positive integer on success. 133.Fn if_indextoname 134and 135.Fn if_nameindex 136return 137.Dv NULL 138on errors. 139.Sh SEE ALSO 140R. Gilligan, S. Thomson, J. Bound, and W. Stevens, 141``Basic Socket Interface Extensions for IPv6,'' RFC2553, March 1999. 142.Sh HISTORY 143The implementation first appeared in WIDE Hydrangea IPv6 protocol stack kit. 144.Sh STANDARDS 145These functions are defined in ``Basic Socket Interface Extensions for IPv6'' 146.Pq RFC2533 . 147