236 lines
5.8 KiB
Groff
236 lines
5.8 KiB
Groff
.\"
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.\" Copyright 1996 Massachusetts Institute of Technology
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.\"
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.\" Permission to use, copy, modify, and distribute this software and
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.\" its documentation for any purpose and without fee is hereby
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.\" granted, provided that both the above copyright notice and this
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.\" permission notice appear in all copies, that both the above
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.\" copyright notice and this permission notice appear in all
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.\" supporting documentation, and that the name of M.I.T. not be used
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.\" in advertising or publicity pertaining to distribution of the
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.\" software without specific, written prior permission. M.I.T. makes
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.\" no representations about the suitability of this software for any
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.\" purpose. It is provided "as is" without express or implied
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.\" warranty.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''. M.I.T. DISCLAIMS
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.\" ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
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.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
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.\" SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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.\" USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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.\" ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $ANA: addr2ascii.3,v 1.1 1996/06/13 18:41:46 wollman Exp $
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.\" $FreeBSD$
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.\"
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.Dd June 13, 1996
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.Dt ADDR2ASCII 3
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.Os
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.Sh NAME
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.Nm addr2ascii ,
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.Nm ascii2addr
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.Nd Generic address formatting routines
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In arpa/inet.h
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.Ft "char *"
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.Fn addr2ascii "int af" "const void *addrp" "int len" "char *buf"
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.Ft int
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.Fn ascii2addr "int af" "const char *ascii" "void *result"
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.Sh DESCRIPTION
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The routines
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.Fn addr2ascii
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and
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.Fn ascii2addr
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are used to convert network addresses between binary form and a
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printable form appropriate to the address family.
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Both functions take
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an
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.Fa af
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argument, specifying the address family to be used in the conversion
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process.
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(Currently, only the
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.Dv AF_INET
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and
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.Dv AF_LINK
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address families are supported.)
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.Pp
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The
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.Fn addr2ascii
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function
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is used to convert binary, network-format addresses into printable
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form.
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In addition to
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.Fa af ,
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there are three other arguments.
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The
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.Fa addrp
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argument is a pointer to the network address to be converted.
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The
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.Fa len
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argument is the length of the address.
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The
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.Fa buf
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argument is an optional pointer to a caller-allocated buffer to hold
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the result; if a null pointer is passed,
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.Fn addr2ascii
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uses a statically-allocated buffer.
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.Pp
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The
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.Fn ascii2addr
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function performs the inverse operation to
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.Fn addr2ascii .
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In addition to
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.Fa af ,
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it takes two arguments,
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.Fa ascii
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and
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.Fa result .
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The
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.Fa ascii
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argument is a pointer to the string which is to be converted into
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binary.
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The
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.Fa result
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argument is a pointer to an appropriate network address structure for
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the specified family.
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.Pp
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The following gives the appropriate structure to use for binary
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addresses in the specified family:
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.Pp
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.Bl -tag -width AF_INETxxxx -compact
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.It Dv AF_INET
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.Vt "struct in_addr"
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(in
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.In arpa/inet.h )
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.It Dv AF_LINK
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.Vt "struct sockaddr_dl"
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(in
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.In net/if_dl.h )
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.\" .It Dv AF_INET6
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.\" .Vt "struct in6_addr"
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.\" (in
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.\" .In netinet6/in6.h )
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.El
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.Pp
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.Dv AF_INET
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and
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.Dv AF_LINK
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constants are defined in
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.In sys/socket.h .
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.Sh RETURN VALUES
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The
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.Fn addr2ascii
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function returns the address of the buffer it was passed, or a static
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buffer if the a null pointer was passed; on failure, it returns a null
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pointer.
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The
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.Fn ascii2addr
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function returns the length of the binary address in bytes, or -1 on
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failure.
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.Sh EXAMPLES
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The
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.Xr inet 3
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functions
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.Fn inet_ntoa
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and
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.Fn inet_aton
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could be implemented thusly:
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.Bd -literal -offset indent
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#include <sys/socket.h>
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#include <arpa/inet.h>
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char *
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inet_ntoa(struct in_addr addr)
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{
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return addr2ascii(AF_INET, &addr, sizeof addr, 0);
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}
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int
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inet_aton(const char *ascii, struct in_addr *addr)
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{
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return (ascii2addr(AF_INET, ascii, addr)
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== sizeof(*addr));
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}
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.Ed
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.Pp
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In actuality, this cannot be done because
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.Fn addr2ascii
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and
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.Fn ascii2addr
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are implemented in terms of the
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.Xr inet 3
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functions, rather than the other way around.
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.Sh ERRORS
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When a failure is returned,
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.Va errno
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is set to one of the following values:
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.Bl -tag -width Er
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.It Bq Er ENAMETOOLONG
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The
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.Fn addr2ascii
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routine was passed a
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.Fa len
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argument which was inappropriate for the address family given by
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.Fa af .
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.It Bq Er EPROTONOSUPPORT
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Either routine was passed an
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.Fa af
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argument other than
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.Dv AF_INET
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or
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.Dv AF_LINK .
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.It Bq Er EINVAL
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The string passed to
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.Fn ascii2addr
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was improperly formatted for address family
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.Fa af .
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.El
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.Sh SEE ALSO
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.Xr inet 3 ,
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.Xr linkaddr 3 ,
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.Xr inet 4
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.Sh HISTORY
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An interface close to this one was originally suggested by Craig
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Partridge.
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This particular interface originally appeared in the
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.Tn INRIA
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.Tn IPv6
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implementation.
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.Sh AUTHORS
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Code and documentation by
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.An Garrett A. Wollman ,
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MIT Laboratory for Computer Science.
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.Sh BUGS
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The original implementations supported IPv6.
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This support should
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eventually be resurrected.
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The
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.Tn NRL
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implementation also included support for the
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.Dv AF_ISO
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and
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.Dv AF_NS
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address families.
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.Pp
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The genericity of this interface is somewhat questionable.
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A truly
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generic interface would provide a means for determining the length of
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the buffer to be used so that it could be dynamically allocated, and
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would always require a
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.Vt "struct sockaddr"
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to hold the binary address.
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Unfortunately, this is incompatible with existing
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practice.
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This limitation means that a routine for printing network
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addresses from arbitrary address families must still have internal
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knowledge of the maximum buffer length needed and the appropriate part
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of the address to use as the binary address.
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