mirror of https://github.com/mkerrisk/man-pages
Remove statement that inet_pton() extends inet_ntoa();
that's not really true, since inet_pton() doesn't support all of the string forms that are supported by inet_ntoa(); as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=482987. Describe IPv6 address formats. Describe dotted decimal format in more detail. Add an example program. Remove unneeded header files from SYNOPSIS. Make NAME line more precise. Make description of return value more precise. SEE ALSO: Add inet(3), Add getaddrinfo(3).
This commit is contained in:
Michael Kerrisk
parent
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178
man3/inet_pton.3
178
man3/inet_pton.3
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@ -1,4 +1,5 @@
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.\" Copyright 2000 Sam Varshavchik <mrsam@courier-mta.com>
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.\" and Copyright (c) 2008 Michael Kerrisk <mtk.manpages@gmail.com>
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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@ -21,13 +22,11 @@
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.\" References: RFC 2553
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.TH INET_PTON 3 2000-12-18 "Linux" "Linux Programmer's Manual"
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.TH INET_PTON 3 2008-06-18 "Linux" "Linux Programmer's Manual"
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.SH NAME
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inet_pton \- Create a network address structure
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inet_pton \- convert IPv4 and IPv6 addresses from text to binary form
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.SH SYNOPSIS
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.nf
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.B #include <sys/types.h>
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.B #include <sys/socket.h>
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.B #include <arpa/inet.h>
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.BI "int inet_pton(int " "af" ", const char *" "src" ", void *" "dst" );
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@ -41,69 +40,176 @@ address family, then
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copies
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the network address structure to
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.IR dst .
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The
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.I af
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argument must be either
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.B AF_INET
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or
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.BR AF_INET6 .
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.PP
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.BR inet_pton ()
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extends the
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.BR inet_addr (3)
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function to support multiple address families,
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.BR inet_addr (3)
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is now considered to be deprecated in favor of
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.BR inet_pton ().
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The following address families are currently supported:
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.TP
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.B AF_INET
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.I src
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points to a character string containing an IPv4 network address in
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the dotted-quad format, "\fIddd.ddd.ddd.ddd\fP".
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The address is converted
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to a
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dotted-decimal format, "\fIddd.ddd.ddd.ddd\fP", where
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.I ddd
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is a decimal number of up to three digits in the range 0 to 255.
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The address is converted to a
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.I struct in_addr
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and copied to
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.IR dst ,
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which must be
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.I sizeof(struct in_addr)
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bytes long.
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(4) bytes (32 bits) long.
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.TP
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.B AF_INET6
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.I src
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points to a character string containing an IPv6 network address in
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any allowed IPv6 address format.
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The address is converted
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to a
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points to a character string containing an IPv6 network address.
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The address is converted to a
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.I struct in6_addr
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and copied to
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.IR dst ,
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which must be
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.I sizeof(struct in6_addr)
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bytes long.
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.PP
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Certain legacy hex and octal formats of
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.B AF_INET
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addresses are not supported by
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.BR inet_pton (),
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which rejects them.
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(16) bytes (128 bits) long.
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The allowed formats for IPv6 addresses follow these rules:
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.RS
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.IP 1. 3
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The preferred format is
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.IR x.x.x.x.x.x.x.x .
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This form consists of eight hexadecimal numbers,
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each of which expresses a 16-bit value (i.e., each
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.I x
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can be up to 4 hex digits).
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.IP 2.
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A series of contiguous zero values in the preferred format
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can be abbreviated to
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.IR :: .
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Only one instance of
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.I ::
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can occur in an address.
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For example, the loopback address
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.I 0:0:0:0:0:0:0:1
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can be abbreviated as
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.IR ::1 .
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The wildcard address, consisting of all zeroes, can be written as
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.IR :: .
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.IP 3.
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An alternate format is useful for expressing IPv4-mapped IPv6 addresses.
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This form is written as
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.IR x:x:x:x:x:x:d.d.d.d ,
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where the six leading
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.IR x s
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are hexadecimal values that define the six most-significant
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16-bit pieces of the address (i.e., 96 bits), and the
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.IR d s
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express a value in dotted-decimal notation that
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defines the least significant 32 bits of the address.
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An example of such an address is
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.IR ::FFFF:204.152.189.116 .
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.RE
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.IP
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See RFC 2373 for further details on the representation of IPv6 addresses.
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.SH "RETURN VALUE"
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.BR inet_pton ()
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returns a negative value and sets
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.I errno
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to
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.B EAFNOSUPPORT
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if
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.I af
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does not contain a valid address family.
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returns 1 on success (network address was successfully converted).
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0 is returned if
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.I src
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does not contain a character string representing a valid network
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address in the specified address family.
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A positive value is returned if the network address was successfully
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converted.
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If
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.I af
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does not contain a valid address family, \-1 is returned and
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.I errno
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is set to
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.BR EAFNOSUPPORT .
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.SH "CONFORMING TO"
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POSIX.1-2001.
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.SH BUGS
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.B AF_INET6
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does not recognize IPv4 addresses.
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An explicit IPv6-mapped IPv4 address must be supplied in
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An explicit IPv4-mapped IPv6 address must be supplied in
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.I src
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instead.
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.SH NOTES
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Unlike
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.BR inet_aton (3)
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and
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.BR inet_addr (3),
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.BR inet_pton ()
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supports IPv6 addresses.
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On the other hand,
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.BR inet_pton ()
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only accepts IPv4 addresses in dotted-decimal notation, whereas
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.BR inet_aton (3)
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and
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.BR inet_addr (3)
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allow the more general numbers-and-dots notation (hexadecimal
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and octal number formats, and formats that don't require all
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four bytes to be explicitly written).
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For an interface that handles both IPv6 addresses, and IPv4
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addresses in numbers-and-dots notation, see
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.BR getaddrinfo (3).
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.SH EXAMPLE
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The program below demonstrates the use of
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.BR inet_pton ()
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and
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.BR inet_ntop (3).
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Here are some example runs:
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.in +4n
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.nf
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$ ./a.out i6 0:0:0:0:0:0:0:0
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::
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$ ./a.out i6 1:0:0:0:0:0:0:8
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1::8
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$ ./a.out i6 0:0:0:0:0:FFFF:204.152.189.116
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::ffff:204.152.189.116
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.fi
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.in
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.nf
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#include <arpa/inet.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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int
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main(int argc, char *argv[])
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{
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unsigned char buf[sizeof(struct in6_addr)];
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int domain, s;
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char str[INET6_ADDRSTRLEN];
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if (argc != 3) {
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fprintf(stderr, "Usage: %s {i4|i6|<num>} string\\n", argv[0]);
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exit(EXIT_FAILURE);
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}
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domain = (strcmp(argv[1], "i4") == 0) ? AF_INET :
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(strcmp(argv[1], "i6") == 0) ? AF_INET6 : atoi(argv[1]);
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s = inet_pton(domain, argv[2], buf);
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if (s <= 0) {
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if (s == 0)
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fprintf(stderr, "Not in presentation format");
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else
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perror("inet_pton");
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exit(EXIT_FAILURE);
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}
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if (inet_ntop(domain, buf, str, INET6_ADDRSTRLEN) == NULL) {
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perror("inet_ntop");
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exit(EXIT_FAILURE);
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}
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printf("%s\\n", str);
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exit(EXIT_SUCCESS);
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}
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.fi
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.SH "SEE ALSO"
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.BR getaddrinfo (3),
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.BR inet (3),
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.BR inet_ntop (3)
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