1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
|
.\" Copyright 2000 Sam Varshavchik <mrsam@courier-mta.com>
.\" and Copyright (c) 2008 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date. The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein. The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\" %%%LICENSE_END
.\"
.\" References: RFC 2553
.TH INET_PTON 3 2020-06-09 "Linux" "Linux Programmer's Manual"
.SH NAME
inet_pton \- convert IPv4 and IPv6 addresses from text to binary form
.SH SYNOPSIS
.nf
.B #include <arpa/inet.h>
.PP
.BI "int inet_pton(int " "af" ", const char *" "src" ", void *" "dst" );
.fi
.SH DESCRIPTION
This function converts the character string
.I src
into a network address structure in the
.I af
address family, then
copies
the network address structure to
.IR dst .
The
.I af
argument must be either
.B AF_INET
or
.BR AF_INET6 .
.IR dst
is written in network byte order.
.PP
The following address families are currently supported:
.TP
.B AF_INET
.I src
points to a character string containing an IPv4 network address in
dotted-decimal format, "\fIddd.ddd.ddd.ddd\fP", where
.I ddd
is a decimal number of up to three digits in the range 0 to 255.
The address is converted to a
.I struct in_addr
and copied to
.IR dst ,
which must be
.I sizeof(struct in_addr)
(4) bytes (32 bits) long.
.TP
.B AF_INET6
.I src
points to a character string containing an IPv6 network address.
The address is converted to a
.I struct in6_addr
and copied to
.IR dst ,
which must be
.I sizeof(struct in6_addr)
(16) bytes (128 bits) long.
The allowed formats for IPv6 addresses follow these rules:
.RS
.IP 1. 3
The preferred format is
.IR x:x:x:x:x:x:x:x .
This form consists of eight hexadecimal numbers,
each of which expresses a 16-bit value (i.e., each
.I x
can be up to 4 hex digits).
.IP 2.
A series of contiguous zero values in the preferred format
can be abbreviated to
.IR :: .
Only one instance of
.I ::
can occur in an address.
For example, the loopback address
.I 0:0:0:0:0:0:0:1
can be abbreviated as
.IR ::1 .
The wildcard address, consisting of all zeros, can be written as
.IR :: .
.IP 3.
An alternate format is useful for expressing IPv4-mapped IPv6 addresses.
This form is written as
.IR x:x:x:x:x:x:d.d.d.d ,
where the six leading
.IR x s
are hexadecimal values that define the six most-significant
16-bit pieces of the address (i.e., 96 bits), and the
.IR d s
express a value in dotted-decimal notation that
defines the least significant 32 bits of the address.
An example of such an address is
.IR ::FFFF:204.152.189.116 .
.RE
.IP
See RFC 2373 for further details on the representation of IPv6 addresses.
.SH RETURN VALUE
.BR inet_pton ()
returns 1 on success (network address was successfully converted).
0 is returned if
.I src
does not contain a character string representing a valid network
address in the specified address family.
If
.I af
does not contain a valid address family, \-1 is returned and
.I errno
is set to
.BR EAFNOSUPPORT .
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lb lb lb
l l l.
Interface Attribute Value
T{
.BR inet_pton ()
T} Thread safety MT-Safe locale
.TE
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
.SH NOTES
Unlike
.BR inet_aton (3)
and
.BR inet_addr (3),
.BR inet_pton ()
supports IPv6 addresses.
On the other hand,
.BR inet_pton ()
accepts only IPv4 addresses in dotted-decimal notation, whereas
.BR inet_aton (3)
and
.BR inet_addr (3)
allow the more general numbers-and-dots notation (hexadecimal
and octal number formats, and formats that don't require all
four bytes to be explicitly written).
For an interface that handles both IPv6 addresses, and IPv4
addresses in numbers-and-dots notation, see
.BR getaddrinfo (3).
.SH BUGS
.B AF_INET6
does not recognize IPv4 addresses.
An explicit IPv4-mapped IPv6 address must be supplied in
.I src
instead.
.SH EXAMPLES
The program below demonstrates the use of
.BR inet_pton ()
and
.BR inet_ntop (3).
Here are some example runs:
.PP
.in +4n
.EX
.RB "$" " ./a.out i6 0:0:0:0:0:0:0:0"
::
.RB "$" " ./a.out i6 1:0:0:0:0:0:0:8"
1::8
.RB "$" " ./a.out i6 0:0:0:0:0:FFFF:204.152.189.116"
::ffff:204.152.189.116
.EE
.in
.SS Program source
\&
.EX
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int
main(int argc, char *argv[])
{
unsigned char buf[sizeof(struct in6_addr)];
int domain, s;
char str[INET6_ADDRSTRLEN];
if (argc != 3) {
fprintf(stderr, "Usage: %s {i4|i6|<num>} string\en", argv[0]);
exit(EXIT_FAILURE);
}
domain = (strcmp(argv[1], "i4") == 0) ? AF_INET :
(strcmp(argv[1], "i6") == 0) ? AF_INET6 : atoi(argv[1]);
s = inet_pton(domain, argv[2], buf);
if (s <= 0) {
if (s == 0)
fprintf(stderr, "Not in presentation format");
else
perror("inet_pton");
exit(EXIT_FAILURE);
}
if (inet_ntop(domain, buf, str, INET6_ADDRSTRLEN) == NULL) {
perror("inet_ntop");
exit(EXIT_FAILURE);
}
printf("%s\en", str);
exit(EXIT_SUCCESS);
}
.EE
.SH SEE ALSO
.BR getaddrinfo (3),
.BR inet (3),
.BR inet_ntop (3)
.SH COLOPHON
This page is part of release 5.10 of the Linux
.I man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
\%https://www.kernel.org/doc/man\-pages/.
|
