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.\" $OpenBSD: inet_lnaof.3,v 1.2 2014/04/19 16:46:32 jmc Exp $
.\" $NetBSD: inet.3,v 1.7 1997/06/18 02:25:24 lukem Exp $
.\"
.\" Copyright (c) 1983, 1990, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" 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. 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.
.\"
.\" @(#)inet.3 8.1 (Berkeley) 6/4/93
.\"
.Dd $Mdocdate: April 19 2014 $
.Dt INET_LNAOF 3
.Os
.Sh NAME
.Nm inet_makeaddr ,
.Nm inet_netof ,
.Nm inet_lnaof
.Nd routines for manipulating classful Internet Protocol version 4 (IPv4) addresses
.Sh SYNOPSIS
.In arpa/inet.h
.Ft struct in_addr
.Fn inet_makeaddr "in_addr_t net" "in_addr_t lna"
.Ft in_addr_t
.Fn inet_netof "struct in_addr in"
.Ft in_addr_t
.Fn inet_lnaof "struct in_addr in"
.Sh DESCRIPTION
As originally designed,
IP version 4 split each address into a network part and local network
address part, encoding that split into the address itself.
It is frequency-encoded;
the most-significant bit is clear in Class A addresses,
in which the high-order 8 bits are the network number.
Class B addresses use the high-order 16 bits as the network field,
and Class C addresses have a 24-bit network part.
.Pp
The routine
.Fn inet_makeaddr
takes an Internet network number and a local
network address and constructs an Internet address
from it.
.Pp
The routines
.Fn inet_netof
and
.Fn inet_lnaof
break apart Internet host addresses, returning
the network number and local network address part,
respectively.
.Pp
All Internet addresses are returned in network
order (bytes ordered from left to right).
All network numbers and local address parts are
returned as machine format integer values.
.Sh SEE ALSO
.Xr getnetent 3 ,
.Xr inet_addr 3 ,
.Xr inet_net 3 ,
.Xr hosts 5 ,
.Xr networks 5
.Sh HISTORY
The
.Nm inet_makeaddr ,
.Nm inet_lnaof ,
and
.Nm inet_netof
functions appeared in
.Bx 4.2 .
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