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+.\"     $OpenBSD: link_addr.3,v 1.7 2000/04/18 03:01:32 aaron Exp $
+.\"
+.\" 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.
+.\"
+.Dd July 28, 1993
+.Dt LINK_ADDR 3
+.Os
+.Sh NAME
+.Nm link_addr ,
+.Nm link_ntoa
+.Nd elementary address specification routines for link level access
+.Sh SYNOPSIS
+.Fd #include <sys/types.h>
+.Fd #include <sys/socket.h>
+.Fd #include <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
+.Fn link_addr
+function interprets character strings representing
+link-level addresses, returning binary information suitable
+for use in system calls.
+.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 le0:8.0.9.13.d.30
+represents an Ethernet address
+to be transmitted on the first Lance Ethernet interface.
+.Sh RETURN VALUES
+.Fn link_ntoa
+always returns a null-terminated string.
+.Fn link_addr
+has no return value.
+(See
+.Sx BUGS . )
+.Sh SEE ALSO
+.Xr iso 4 ,
+.Xr ifconfig 8
+.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
+.Fa 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.