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.\"     $OpenBSD: inet_net.3,v 1.6 2000/04/21 15:38:17 aaron Exp $

.\"     $NetBSD: inet_net.3,v 1.1 1997/06/18 02:25:27 lukem Exp $

.\"

.\" Copyright (c) 1997 The NetBSD Foundation, Inc.

.\" All rights reserved.

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.\" This code is derived from software contributed to The NetBSD Foundation

.\" by Luke Mewburn.

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.Dd June 18, 1997

.Dt INET_NET 3

.Os

.Sh NAME

.Nm inet_net_ntop ,

.Nm inet_net_pton

.Nd Internet network number manipulation routines

.Sh SYNOPSIS

.Fd #include 

.Fd #include 

.Fd #include 

.Ft char *

.Fn inet_net_ntop "int af" "const void *src" "int bits" "char *dst" "size_t size"

.Ft int

.Fn inet_net_pton "int af" "const char *src" "void *dst" "size_t size"

.Sh DESCRIPTION

The

.Fn inet_net_ntop

function converts an Internet network number from network format (usually a

.Li struct in_addr

or some other binary form, in network byte order) to CIDR presentation format

(suitable for external display purposes).

.Fa bits

is the number of bits in

.Fa src

that are the network number.

It returns

.Dv NULL

if a system error occurs (in which case,

.Va errno

will have been set), or it returns a pointer to the destination string.

.Pp

The

.Fn inet_net_pton

function converts a presentation format Internet network number (that is,

printable form as held in a character string) to network format (usually a

.Li struct in_addr

or some other internal binary representation, in network byte order).

It returns the number of bits (either computed based on the class, or

specified with /CIDR), or \-1 if a failure occurred

(in which case

.Va errno

will have been set.

It will be set to

.Er ENOENT

if the Internet network number was not valid).

.Pp

The only value for

.Fa af

currently supported is

.Dv AF_INET .

.Fa size

is the size of the result buffer

.Fa dst .

.Sh NETWORK NUMBERS (IP VERSION 4)

Internet network numbers may be specified in one of the following forms:

.Bd -literal -offset indent

a.b.c.d/bits

a.b.c.d

a.b.c

a.b

a

.Ed

.Pp

When four parts are specified, each is interpreted

as a byte of data and assigned, from left to right,

to the four bytes of an Internet network number.

Note that when an Internet network number is viewed as a 32-bit

integer quantity on a system that uses little-endian

byte order (such as the Intel 386, 486, and Pentium processors)

the bytes referred to above appear as

.Dq Li d.c.b.a .

That is, little-endian bytes are ordered from right to left.

.Pp

When a three part number is specified, the last

part is interpreted as a 16-bit quantity and placed

in the rightmost two bytes of the Internet network number.

This makes the three part number format convenient

for specifying Class B network numbers as

.Dq Li 128.net.host .

.Pp

When a two part number is supplied, the last part

is interpreted as a 24-bit quantity and placed in

the rightmost three bytes of the Internet network number.

This makes the two part number format convenient

for specifying Class A network numbers as

.Dq Li net.host .

.Pp

When only one part is given, the value is stored

directly in the Internet network number without any byte

rearrangement.

.Pp

All numbers supplied as

.Dq parts

in a

.Ql \&.

notation

may be decimal, octal, or hexadecimal, as specified

in the C language (i.e., a leading 0x or 0X implies

hexadecimal; otherwise, a leading 0 implies octal;

otherwise, the number is interpreted as decimal).

.Sh SEE ALSO

.Xr byteorder 3 ,

.Xr inet 3 ,

.Xr networks 5

.Sh HISTORY

The

.Nm inet_net_ntop

and

.Nm inet_net_pton

functions first appeared in BIND 4.9.4.