1.\" Copyright (c) 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" Donn Seeley at BSDI. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" From: @(#)linkaddr.3 8.1 (Berkeley) 7/28/93 32.\" $FreeBSD: src/lib/libc/net/linkaddr.3,v 1.16 2007/02/28 21:18:38 bms Exp $ 33.\" 34.Dd February 28, 2007 35.Dt LINK_ADDR 3 36.Os 37.Sh NAME 38.Nm link_addr , 39.Nm link_ntoa 40.Nd elementary address specification routines for link level access 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In sys/types.h 45.In sys/socket.h 46.In net/if_dl.h 47.Ft void 48.Fn link_addr "const char *addr" "struct sockaddr_dl *sdl" 49.Ft char * 50.Fn link_ntoa "const struct sockaddr_dl *sdl" 51.Sh DESCRIPTION 52The routine 53.Fn link_addr 54interprets character strings representing 55link-level addresses, returning binary information suitable 56for use in system calls. 57The routine 58.Fn link_ntoa 59takes 60a link-level 61address and returns an 62.Tn ASCII 63string representing some of the information present, 64including the link level address itself, and the interface name 65or number, if present. 66This facility is experimental and is 67still subject to change. 68.Pp 69For 70.Fn link_addr , 71the string 72.Fa addr 73may contain 74an optional network interface identifier of the form 75.Dq "name unit-number" , 76suitable for the first argument to 77.Xr ifconfig 8 , 78followed in all cases by a colon and 79an interface address in the form of 80groups of hexadecimal digits 81separated by periods. 82Each group represents a byte of address; 83address bytes are filled left to right from 84low order bytes through high order bytes. 85.Pp 86.\" A regular expression may make this format clearer: 87.\" .Bd -literal -offset indent 88.\" ([a-z]+[0-9]+:)?[0-9a-f]+(\e.[0-9a-f]+)* 89.\" .Ed 90.\" .Pp 91Thus 92.Li lnc0:8.0.9.13.d.30 93represents an ethernet address 94to be transmitted on the first Lance ethernet interface. 95.Sh RETURN VALUES 96The 97.Fn link_ntoa 98function 99always returns a null terminated string. 100The 101.Fn link_addr 102function 103has no return value. 104(See 105.Sx BUGS . ) 106.Sh SEE ALSO 107.Xr getnameinfo 3 108.Sh HISTORY 109The 110.Fn link_addr 111and 112.Fn link_ntoa 113functions appeared in 114.Bx 4.3 Reno . 115.Sh BUGS 116The returned values for 117.Fn link_ntoa 118reside in a static memory area. 119.Pp 120The function 121.Fn link_addr 122should diagnose improperly formed input, and there should be an unambiguous 123way to recognize this. 124.Pp 125If the 126.Va sdl_len 127field of the link socket address 128.Fa sdl 129is 0, 130.Fn link_ntoa 131will not insert a colon before the interface address bytes. 132If this translated address is given to 133.Fn link_addr 134without inserting an initial colon, 135the latter will not interpret it correctly. 136