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(such as 61.Dq Li lo0 ) , 62and vice versa. 63.Pp 64.Fn if_nametoindex 65converts readable interface name to interface index 66.Pp positive integer value . 67If the specified interface does not exist, 0 will be returned. 68.Pp 69.Fn if_indextoname 70converts interface index to readable interface name. 71The 72.Fa ifname 73argument must point to a buffer of at least 74.Dv IF_NAMESIZE 75bytes into which the interface name corresponding to the specified index is 76returned. 77.Dv ( IF_NAMESIZE 78is also defined in 79.Aq Pa net/if.h 80and its value includes a terminating null byte at the end of the 81interface name.) 82This pointer is also the return value of the function. 83If there is no interface corresponding to the specified index, 84.Dv NULL 85is returned. 86.Pp 87.Fn if_nameindex 88returns an array of 89.Fa if_nameindex 90structures. 91.Fa if_nametoindex 92is also defined in 93.Aq Pa net/if.h , 94and is as follows: 95.Bd -literal -offset 96struct if_nameindex { 97 unsigned int if_index; /* 1, 2, ... */ 98 char *if_name; /* null terminated name: "le0", ... */ 99}; 100.Ed 101.Pp 102The end of the array of structures is indicated by a structure with 103an 104.Fa if_index 105of 0 and an 106.Fa if_name 107of 108.Dv NULL . 109The function returns a 110.Dv NULL 111pointer upon an error. 112The memory used for this array of structures along with the interface 113names pointed to by the 114.Fa if_name 115members is obtained dynamically. 116This memory is freed by the 117.Fn if_freenameindex 118function. 119.Pp 120.Fn if_freenameindex 121takes a pointer that was returned by 122.Fn if_nameindex 123as argument 124.Pq Fa ptr , 125and it reclaims the region allocated. 126.Sh DIAGNOSTICS 127.Fn if_nametoindex 128returns 0 on error, positive integer on success. 129.Fn if_indextoname 130and 131.Fn if_nameindex 132return 133.Dv NULL 134on errors. 135.Sh SEE ALSO 136R. Gilligan, S. Thomson, J. Bound, and W. Stevens, 137``Basic Socket Interface Extensions for IPv6,'' RFC2553, March 1999. 138.Sh HISTORY 139The implementation first appeared in WIDE Hydrangea IPv6 protocol stack kit. 140.Sh STANDARDS 141These functions are defined in ``Basic Socket Interface Extensions for IPv6'' 142.Pq RFC2533 . 143