1.\" $NetBSD: linkaddr.3,v 1.13 2017/07/03 21:32:49 wiz Exp $ 2.\" 3.\" Copyright (c) 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" This code is derived from software contributed to Berkeley by 7.\" Donn Seeley at BSDI. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. 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.\" @(#)linkaddr.3 8.1 (Berkeley) 7/28/93 34.\" 35.Dd December 7, 2016 36.Dt LINK_ADDR 3 37.Os 38.Sh NAME 39.Nm link_addr , 40.Nm link_ntoa 41.Nd elementary address specification routines for link level access 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In sys/types.h 46.In sys/socket.h 47.In net/if_dl.h 48.Ft void 49.Fn link_addr "const char *addr" "struct sockaddr_dl *sdl" 50.Ft char * 51.Fn link_ntoa "const struct sockaddr_dl *sdl" 52.Sh DESCRIPTION 53The routine 54.Fn link_addr 55interprets character strings representing link-level addresses, 56returning binary information suitable for use in system calls. 57The routine 58.Fn link_ntoa 59takes a link-level address and returns an 60.Tn ASCII 61string representing some of the information present, including the 62link level address itself, and the interface name or number, if present. 63This facility is experimental and is still subject to change. 64.Pp 65Prior to a call to 66.Fn link_addr , 67.Fa sdl->sdl_len 68must be initialized to the size of the link-level socket structure, 69typically 70.Fa sizeof(struct sockaddr_dl) . 71.Pp 72For 73.Fn link_addr , 74the string 75.Fa addr 76may contain 77an optional network interface identifier of the form 78.Dq "name unit-number" , 79suitable for the first argument to 80.Xr ifconfig 8 , 81followed in all cases by a colon and 82an interface address in the form of 83groups of hexadecimal digits 84separated by periods. 85Each group represents a byte of address; 86address bytes are filled left to right from 87low order bytes through high order bytes. 88.Pp 89.\" A regular expression may make this format clearer: 90.\" .Bd -literal -offset indent 91.\" ([a-z]+[0-9]+:)?[0-9a-f]+(\e.[0-9a-f]+)* 92.\" .Ed 93.\" .Pp 94Thus 95.Li le0:8.0.9.13.d.30 96represents an ethernet address 97to be transmitted on the first Lance ethernet interface. 98.Sh RETURN VALUES 99.Fn link_ntoa 100always returns a null terminated string. 101.Fn link_addr 102has no return value (See 103.Sx BUGS ) . 104.Sh SEE ALSO 105.Xr ethers 3 , 106.Xr iso 4 107.Sh HISTORY 108The 109.Fn link_addr 110and 111.Fn link_ntoa 112functions appeared in 113.Bx 4.3 Reno . 114.Sh BUGS 115The returned string for 116.Fn link_ntoa 117resides in a static memory area. 118If it would overflow this area, 119.Fn link_ntoa 120silently truncates the result. 121.Pp 122The function 123.Fn link_addr 124should diagnose improperly formed input, and there should be an unambiguous 125way to recognize this. 126.Pp 127If the 128.Va sdl_len 129field of the link socket address 130.Fa sdl 131is 0, 132.Fn link_ntoa 133will not insert a colon before the interface address bytes. 134If this translated address is given to 135.Fn link_addr 136without inserting an initial colon, 137the latter will not interpret it correctly. 138