NAME
inet_net_ntop
,
inet_net_pton
—
Internet network number manipulation
routines
SYNOPSIS
#include
<sys/socket.h>
#include <arpa/inet.h>
char *
inet_net_ntop
(int
af, const void
*src, int bits,
char *dst,
size_t size);
int
inet_net_pton
(int
af, const char
*src, void *dst,
size_t size);
DESCRIPTION
The
inet_net_ntop
()
function converts an Internet network number from network format (usually a
struct in_addr
or some other binary form, in network
byte order) to CIDR presentation format (suitable for external display
purposes). bits is the number of bits in
src that are the network number. It returns
NULL
if a system error occurs (in which case,
errno will have been set), or it returns a pointer to
the destination string.
The
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
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 errno will have been
set. It will be set to ENOENT
if the Internet
network number was not valid).
Caution: The dst field
should be zeroed before calling
inet_net_pton
()
as the function will only fill the number of bytes necessary to encode the
network number in network byte order.
The only values for af currently supported
are AF_INET
and AF_INET6
.
size is the size of the result buffer
dst.
NETWORK NUMBERS (IP VERSION 4)
The external representation of Internet network numbers may be specified in one of the following forms:
a a.b a.b.c a.b.c.d
Any of the above four forms may have
“/bits
” appended where
“bits
” is in the range
0-32
and is used to explicitly specify the number of
bits in the network address. When
“/bits
” is not specified, the number
of bits in the network address is calculated as the larger of the number of
bits in the class to which the address belongs and the number of bits
provided rounded up modulo 8. Examples:
10
- an 8-bit network number (class A), value
10.0.0.0
. 192
- a 24-bit network number (class C), value
192.0.0.0
. 10.10
- a 16-bit network number, value
10.10.0.0
. 10.1.2
- a 24-bit network number, value
10.1.2.0
. 10.1.2.3
- a 32-bit network number, value
10.1.2.3
. 10.1.2.3/24
- a 24-bit network number (explicit), value
10.1.2.3
.
Note that when the number of bits is
specified using “/bits
” notation, the
value of the address still includes all bits supplied in the external
representation, even those bits which are the host part of an Internet
address. Also, unlike
inet_pton(3) where the external representation is assumed to be a
host address, the external representation for
inet_net_pton
()
is assumed to be a network address. Thus
“10.1
” is assumed to be
“10.1.0.0
” not
“10.0.0.1
”
All numbers supplied as “parts” in a
‘.
’ 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).
NETWORK NUMBERS (IP VERSION 6)
See
inet_pton(3) for valid external representations of IP version 6
addresses. A valid external representation may have
“/bits
” appended where
“bits
” is in the range
0-128
and is used to explicitly specify the number
of bits in the network address. When
“/bits
” is not specified, 128 is used.
Note that when the number of bits is specified using
“/bits
” notation, the value of the
address still includes all bits supplied in the external representation,
even those bits which are the host part of an Internet address.
SEE ALSO
HISTORY
The inet_net_ntop
and
inet_net_pton
functions first appeared in BIND
4.9.4.