Sockets Library Functions inet(3SOCKET)
NAME
inet, inet6, inet_ntop, inet_pton, inet_aton, inet_addr,
inet_network, inet_makeaddr, inet_lnaof, inet_netof,
inet_ntoa - Internet address manipulation
SYNOPSIS
cc [ flag... ] file... -lsocket -lnsl [ library... ]
#include
#include
#include
#include
const char *inet_ntop(int af, const void *addr, char *cp,
size_t size);
int inet_pton(int af, const char *cp, void *addr);
int inet_aton(const char *cp, struct in_addr *addr);
in_addr_t inet_addr(const char *cp);
in_addr_t inet_network(const char *cp);
struct in_addr inet_makeaddr(const int net, const int lna);
int inet_lnaof(const struct in_addr in);
int inet_netof(const struct in_addr in);
char *inet_ntoa(const struct in_addr in);
DESCRIPTION
The inet_ntop() and inet_pton() functions can manipulate
both IPv4 and IPv6 addresses. The inet_aton(), inet_addr(),
inet_network(), inet_makeaddr(), inet_lnaof(),
inet_netof(), and inet_ntoa() functions can only manipulate
IPv4 addresses.The inet_ntop() function converts a numeric address into a
string suitable for presentation. The af argument specifiesthe family of the address which can be AF_INET or AF_INET6.
The addr argument points to a buffer that holds an IPv4SunOS 5.11 Last change: 28 Nov 2007 1
Sockets Library Functions inet(3SOCKET)address if the af argument is AF_INET. The addr argument
points to a buffer that holds an IPv6 address if the afargument is AF_INET6. The address must be in network byte
order. The cp argument points to a buffer where the function stores the resulting string. The application must specify anon-NULL cp argument. The size argument specifies the size
of this buffer. For IPv6 addresses, the buffer must be atleast 46-octets. For IPv4 addresses, the buffer must be at
least 16-octets. To allow applications to easily declare
buffers of the proper size to store IPv4 and IPv6 addresses in string form, the following two constants are defined in: #define INET_ADDRSTRLEN 16
#define INET6_ADDRSTRLEN 46
The inet_pton() function converts the standard text presen-
tation form of a function to the numeric binary form. The af argument specifies the family of the address. Currently, theAF_INET and AF_INET6 address families are supported. The cp
argument points to the string being passed in. The addr argument points to a buffer where the function stores the numeric address. The calling application must ensure that the buffer referred to by addr is large enough to hold thenumeric address, at least 4 bytes for AF_INET or 16 bytes
for AF_INET6.
The inet_aton(), inet_addr(), and inet_network() functions
interpret character strings that represent numbers expressedin the IPv4 standard '.' notation, returning numbers suit-
able for use as IPv4 addresses and IPv4 network numbers,respectively. The inet_makeaddr() function uses an IPv4 net-
work number and a local network address to construct an IPv4address. The inet_netof() and inet_lnaof() functions break
apart IPv4 host addresses, then return the network number and local network address, respectively.The inet_ntoa() function returns a pointer to a string in
the base 256 notation d.d.d.d. See the following section on IPv4 addresses. Internet addresses are returned in network order, bytes ordered from left to right. Network numbers and local address parts are returned as machine format integer values. IPv6 AddressesSunOS 5.11 Last change: 28 Nov 2007 2
Sockets Library Functions inet(3SOCKET) There are three conventional forms for representing IPv6 addresses as strings: 1. The preferred form is x:x:x:x:x:x:x:x, where the'x's are the hexadecimal values of the eight 16-bit
pieces of the address. For example: 1080:0:0:0:8:800:200C:417A It is not necessary to write the leading zeros in an individual field. There must be at least one numeral in every field, except when the special syntax described in the following is used. 2. It is common for addresses to contain long stringsof zero bits in some methods used to allocate cer-
tain IPv6 address styles. A special syntax is available to compress the zeros. The use of "::" indicates multiple groups of 16 bits of zeros. The :: may only appear once in an address. The :: can also be used to compress the leading and trailing zeros in an address. For example: 1080::8:800:200C:417A3. The alternative form x:x:x:x:x:x:d.d.d.d is some-
times more convenient when dealing with a mixed environment of IPv4 and IPv6 nodes. The x's in this form represent the hexadecimal values of the sixhigh-order 16-bit pieces of the address. The d's
represent the decimal values of the four low-order
8-bit pieces of the standard IPv4 address. For
example: ::FFFF:129.144.52.38 ::129.144.52.38 The ::FFFF:d.d.d.d and ::d.d.d.d pieces are thegeneral forms of an IPv4-mapped IPv6 address and an
IPv4-compatible IPv6 address.
The IPv4 portion must be in the d.d.d.d form. The following forms are invalid: ::FFFF:d.d.d ::FFFF:d.d ::d.d.d ::d.d The ::FFFF:d form is a valid but unconventionalrepresentation of the IPv4-compatible IPv6 address
SunOS 5.11 Last change: 28 Nov 2007 3
Sockets Library Functions inet(3SOCKET) ::255.255.0.d. The ::d form corresponds to the general IPv6 address 0:0:0:0:0:0:0:d. IPv4 AddressesValues specified using `.' notation take one of the follow-
ing forms: d.d.d.d d.d.d d.d d When four parts are specified, each part is interpreted as a byte of data and assigned from left to right to the four bytes of an IPv4 address.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. The three part address format is convenient for specifying Class B network addresses such as 128.net.host.When a two-part address is supplied, the last part is inter-
preted as a 24-bit quantity and placed in the right most
three bytes of the network address. The two part address format is convenient for specifying Class A network addresses such as net.host. When only one part is given, the value is stored directly in the network address without any byte rearrangement.With the exception of inet_pton(), numbers supplied as parts
in '.' notation may be decimal, octal, or hexadecimal, as specified in C language. For example, a leading 0x or 0X implies hexadecimal. A leading 0 implies octal. Otherwise, the number is interpreted as decimal.For IPv4 addresses, inet_pton() accepts only a string in
standard IPv4 dot notation: d.d.d.dSunOS 5.11 Last change: 28 Nov 2007 4
Sockets Library Functions inet(3SOCKET) Each number has one to three digits with a decimal value between 0 and 255.The inet_addr() function has been obsoleted by inet_aton().
RETURN VALUES
The inet_aton() function returns nonzero if the address is
valid, 0 if the address is invalid.The inet_ntop() function returns a pointer to the buffer
that contains a string if the conversion succeeds. Other-
wise, NULL is returned. Upon failure, errno is set to EAF-
NOSUPPORT if the af argument is invalid or ENOSPC if the size of the result buffer is inadequate.The inet_pton() function returns 1 if the conversion
succeeds, 0 if the input is not a valid IPv4 dotted-decimal
string or a valid IPv6 address string. The function returns-1 with errno set to EAFNOSUPPORT if the af argument is
unknown.The value INADDR_NONE, which is equivalent to (in_addr_t)(-
1), is returned by inet_addr() and inet_network() for mal-
formed requests.The functions inet_netof() and inet_lnaof() break apart IPv4
host addresses, returning the network number and local net-
work address part, respectively.The function inet_ntoa() returns a pointer to a string in
the base 256 notation d.d.d.d, described in the section on IPv4 addresses.ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:SunOS 5.11 Last change: 28 Nov 2007 5
Sockets Library Functions inet(3SOCKET)____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Interface Stability | See below. ||_____________________________|_____________________________|
| MT-Level | Safe |
|_____________________________|_____________________________|
The inet_ntop(), inet_pton(), inet_aton(), inet_addr(), and
inet_network() functions are Committed. The inet_lnaof(),
inet_makeaddr(), inet_netof(), and inet_network() functions
are Committed (Obsolete).SEE ALSO
gethostbyname(3NSL), getipnodebyname(3SOCKET), getnetbyname(3SOCKET), inet.h(3HEAD), hosts(4), networks(4), attributes(5) NOTESThe return value from inet_ntoa() points to a buffer which
is overwritten on each call. This buffer is implemented asthread-specific data in multithreaded applications.
IPv4-mapped addresses are not recommended.
BUGS
The problem of host byte ordering versus network byte order-
ing is confusing. A simple way to specify Class C network addresses in a manner similar to that for Class B and Class A is needed.SunOS 5.11 Last change: 28 Nov 2007 6