inet_ntop (original) (raw)

The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.

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NAME

inet_ntop, inet_pton - convert IPv4 and IPv6 addresses between binary and text form

SYNOPSIS

`#include <arpa/inet.h>

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);
`

DESCRIPTION

The inet_ntop() function shall convert a numeric address into a text string suitable for presentation. The _af_argument shall specify the family of the address. This can be AF_INET [IP6] [Option Start] or AF_INET6. [Option End] The src argument points to a buffer holding an IPv4 address if the af argument is AF_INET,[IP6] [Option Start] or an IPv6 address if the af argument is AF_INET6; [Option End] the address must be in network byte order. The dst argument points to a buffer where the function stores the resulting text string; it shall not be NULL. The size argument specifies the size of this buffer, which shall be large enough to hold the text string (INET_ADDRSTRLEN characters for IPv4, [IP6] [Option Start] INET6_ADDRSTRLEN characters for IPv6). [Option End]

The inet_pton() function shall convert an address in its standard text presentation form into its numeric binary form. The af argument shall specify the family of the address. The AF_INET [IP6] [Option Start] and AF_INET6[Option End] address families shall be supported. The src argument points to the string being passed in. The dst argument points to a buffer into which the function stores the numeric address; this shall be large enough to hold the numeric address (32 bits for AF_INET, [IP6] [Option Start] 128 bits for AF_INET6). [Option End]

If the af argument of inet_pton() is AF_INET, the src string shall be in the standard IPv4 dotted-decimal form:

ddd.ddd.ddd.ddd

where "ddd" is a one to three digit decimal number between 0 and 255 (see inet_addr()). The inet_pton() function does not accept other formats (such as the octal numbers, hexadecimal numbers, and fewer than four numbers that inet_addr()accepts).

[IP6] [Option Start]If the af argument of inet_pton() is AF_INET6, the src string shall be in one of the following standard IPv6 text forms:

  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. Leading zeros in individual fields can be omitted, but there shall be at least one numeral in every field.
  2. A string of contiguous zero fields in the preferred form can be shown as "::". The "::" can only appear once in an address. Unspecified addresses ( "0:0:0:0:0:0:0:0" ) may be represented simply as "::".
  3. A third form that is sometimes more convenient when dealing with a mixed environment of IPv4 and IPv6 nodes is"x:x:x:x:x:x:d.d.d.d", where the 'x' s are the hexadecimal values of the six high-order 16-bit pieces of the address, and the 'd' s are the decimal values of the four low-order 8-bit pieces of the address (standard IPv4 representation).

Note:

A more extensive description of the standard representations of IPv6 addresses can be found in RFC 2373.

[Option End]

RETURN VALUE

The inet_ntop() function shall return a pointer to the buffer containing the text string if the conversion succeeds, and NULL otherwise, and set errno to indicate the error.

The inet_pton() function shall return 1 if the conversion succeeds, with the address pointed to by dst in network byte order. It shall return 0 if the input is not a valid IPv4 dotted-decimal string [IP6] [Option Start] or a valid IPv6 address string, [Option End] or -1 with errno set to [EAFNOSUPPORT] if the af argument is unknown.

ERRORS

The inet_ntop() and inet_pton() functions shall fail if:

[EAFNOSUPPORT]

The af argument is invalid.

[ENOSPC]

The size of the inet_ntop() result buffer is inadequate.

The following sections are informative.

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

The Base Definitions volume of IEEE Std 1003.1-2001, <arpa/inet.h>

CHANGE HISTORY

First released in Issue 6. Derived from the XNS, Issue 5.2 specification.

IPv6 extensions are marked.

The restrict keyword is added to the inet_ntop() and inet_pton() prototypes for alignment with the ISO/IEC 9899:1999 standard.

IEEE Std 1003.1-2001/Cor 1-2002, item XSH/TC1/D6/29 is applied, adding ``the address must be in network byte order'' to the end of the fourth sentence of the first paragraph in the DESCRIPTION.

End of informative text.

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