.\" Copyright (c) 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" This code is derived from software contributed to Berkeley by .\" Donn Seeley at BSDI. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" From: @(#)linkaddr.3 8.1 (Berkeley) 7/28/93 .\" $FreeBSD: src/lib/libc/net/linkaddr.3,v 1.14 2004/07/03 22:30:08 ru Exp $ .\" .Dd June 17, 1996 .Dt LINK_ADDR 3 .Os .Sh NAME .Nm link_addr , .Nm link_ntoa .Nd elementary address specification routines for link level access .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In sys/types.h .In sys/socket.h .In net/if_dl.h .Ft void .Fn link_addr "const char *addr" "struct sockaddr_dl *sdl" .Ft char * .Fn link_ntoa "const struct sockaddr_dl *sdl" .Sh DESCRIPTION The routine .Fn link_addr interprets character strings representing link-level addresses, returning binary information suitable for use in system calls. The routine .Fn link_ntoa takes a link-level address and returns an .Tn ASCII string representing some of the information present, including the link level address itself, and the interface name or number, if present. This facility is experimental and is still subject to change. .Pp For .Fn link_addr , the string .Fa addr may contain an optional network interface identifier of the form .Dq "name unit-number" , suitable for the first argument to .Xr ifconfig 8 , followed in all cases by a colon and an interface address in the form of groups of hexadecimal digits separated by periods. Each group represents a byte of address; address bytes are filled left to right from low order bytes through high order bytes. .Pp .\" A regular expression may make this format clearer: .\" .Bd -literal -offset indent .\" ([a-z]+[0-9]+:)?[0-9a-f]+(\e.[0-9a-f]+)* .\" .Ed .\" .Pp Thus .Li le0:18.104.22.168.d.30 represents an ethernet address to be transmitted on the first Lance ethernet interface. .Pp The direct use of these functions is deprecated in favor of the .Xr addr2ascii 3 interface; however, portable programs cannot rely on the latter as it is not yet widely implemented. .Sh RETURN VALUES The .Fn link_ntoa function always returns a null terminated string. The .Fn link_addr function has no return value. (See .Sx BUGS . ) .Sh SEE ALSO .Xr addr2ascii 3 .\" .Xr iso 4 .Sh HISTORY The .Fn link_addr and .Fn link_ntoa functions appeared in .Bx 4.3 Reno . .Sh BUGS The returned values for link_ntoa reside in a static memory area. .Pp The function .Fn link_addr should diagnose improperly formed input, and there should be an unambiguous way to recognize this. .Pp If the .Va sdl_len field of the link socket address .Fa sdl is 0, .Fn link_ntoa will not insert a colon before the interface address bytes. If this translated address is given to .Fn link_addr without inserting an initial colon, the latter will not interpret it correctly.