INET(3) | Library Functions Manual | INET(3) |
inet_addr
, inet_aton
,
inet_lnaof
, inet_makeaddr
,
inet_netof
, inet_network
,
inet_ntoa
, inet_ntop
,
inet_pton
, addr
,
ntoa
, network
—
#include <arpa/inet.h>
in_addr_t
inet_addr
(const
char *cp);
int
inet_aton
(const
char *cp, struct in_addr
*addr);
in_addr_t
inet_lnaof
(struct
in_addr in);
struct in_addr
inet_makeaddr
(in_addr_t
net, in_addr_t
lna);
in_addr_t
inet_netof
(struct
in_addr in);
in_addr_t
inet_network
(const
char *cp);
char *
inet_ntoa
(struct
in_addr in);
const char *
inet_ntop
(int
af, const void * restrict
src, char * restrict
dst, socklen_t
size);
int
inet_pton
(int
af, const char * restrict
src, void * restrict
dst);
inet_aton
(),
inet_addr
() and inet_network
()
interpret character strings representing numbers expressed in the Internet
standard “dotted quad” notation.
The inet_pton
() function converts a
presentation format address (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 1 if the address was valid for the specified address family, or 0 if
the address wasn't parsable in the specified address family, or -1 if some
system error occurred (in which case errno will have
been set). This function is presently valid for
AF_INET
and AF_INET6
.
The inet_aton
() routine interprets the
specified character string as an Internet address, placing the address into
the structure provided. It returns 1 if the string was successfully
interpreted, or 0 if the string is invalid.
The inet_addr
() and
inet_network
() functions return numbers suitable for
use as Internet addresses and Internet network numbers, respectively.
The function inet_ntop
() converts an
address from network format (usually a struct in_addr
or some other binary form, in network byte order) to presentation format
(suitable for external display purposes). 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
size parameter is the size of the
buf argument.
The routine inet_ntoa
() takes an Internet
address and returns an ASCII string representing the address in
“dotted quad” notation.
The routine inet_makeaddr
() takes an
Internet network number and a local network address (both in host order) and
constructs an Internet address from it. Note that to convert only a single
value to a struct in_addr form that value should be
passed as the first parameter and ‘0L
’
should be given for the second parameter.
The routines inet_netof
() and
inet_lnaof
() break apart Internet host addresses,
returning the network number and local network address part, respectively
(both in host order).
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.
a.b.c.d a.b.c a.b a
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
address. Note that when an Internet address is viewed as a 32-bit integer
quantity on a system that uses little-endian byte order (e.g. Intel i386,
i486 and Pentium processors) the bytes referred to above appear as
“d.c.b.a
”. That is, little-endian
bytes are ordered from right to left.
When a three part address is specified, the last part is
interpreted as a 16-bit quantity and placed in the right-most two bytes of
the network address. This makes the three part address format convenient for
specifying Class B network addresses as
“128.net.host
”.
When a two part address is supplied, the last part is interpreted
as a 24-bit quantity and placed in the right most three bytes of the network
address. This makes the two part address format convenient for specifying
Class A network addresses as
“net.host
”.
When only one part is given, the value is stored directly in the network address without any byte rearrangement.
All numbers supplied as “parts” in a “dotted quad” 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).
The presentation format of an IPv6 address is given in RFC 2373:
There are three conventional forms for representing IPv6 addresses as text strings:
FEDC:BA98:7654:3210:FEDC:BA98:7654:3210 1080:0:0:0:8:800:200C:417A
Note that it is not necessary to write the leading zeros in an individual field, but there must be at least one numeral in every field (except for the case described in 2).
For example the following addresses:
1080:0:0:0:8:800:200C:417A a unicast address FF01:0:0:0:0:0:0:43 a multicast address 0:0:0:0:0:0:0:1 the loopback address 0:0:0:0:0:0:0:0 the unspecified addresses
may be represented as:
1080::8:800:200C:417A a unicast address FF01::43 a multicast address ::1 the loopback address :: the unspecified addresses
0:0:0:0:0:0:13.1.68.3 0:0:0:0:0:FFFF:129.144.52.38
or in compressed form:
::13.1.68.3 ::FFFF:129.144.52.38
INADDR_NONE
is returned by
inet_addr
() and inet_network
()
for malformed requests.
inet_ntop
() and inet_pton
()
functions may fail with
EAFNOSUPPORT
]AF_INET
or AF_INET6
.The inet_ntop
() function may fail with
ENOSPC
]IP Version 6 Addressing Architecture, RFC 2373, July 1998.
Basic Socket Interface Extensions for IPv6, RFC 3493, February 2003.
inet_ntop
() and inet_pton
()
functions conform to IEEE Std 1003.1-2001
(“POSIX.1”). Note that
inet_pton
() does not accept 1-, 2-, or 3-part dotted
addresses; all four parts must be specified. Additionally all four parts of a
dotted address must be decimal. This is a narrower input set than that
accepted by inet_aton
().
inet_addr
(), inet_network
(),
inet_makeaddr
(), inet_lnaof
()
and inet_netof
() functions appeared in
4.2BSD. They were changed to use
in_addr_t in place of unsigned
long in NetBSD 2.0. The
inet_aton
() and inet_ntoa
()
functions appeared in 4.3BSD. The
inet_pton
() and inet_ntop
()
functions appeared in BIND 4.9.4 and thence NetBSD
1.3; they were also in X/Open Networking Services
Issue 5.2 (“XNS5.2”).
INADDR_NONE
(0xffffffff) is a valid broadcast
address, but inet_addr
() cannot return that value
without indicating failure. The newer inet_aton
()
function does not share this problem.
The problem of host byte ordering versus network byte ordering is confusing.
The string returned by inet_ntoa
() resides
in a static memory area.
The function inet_addr
() should return a
struct in_addr.
The function inet_network
() does not
support byte rearrangement for one, two, and three part addresses.
July 25, 2012 | NetBSD 9.0 |