xref: /freebsd/lib/libc/net/inet_net.3 (revision 8ab2f5ecc596131f6ca790d6ae35540c06ed7985)
1.\"	$NetBSD: inet_net.3,v 1.4 1999/03/22 19:44:52 garbled Exp $
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6.\" This code is derived from software contributed to The NetBSD Foundation
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37.\" $FreeBSD$
38.\"
39.Dd June 18, 1997
40.Dt INET_NET 3
41.Os
42.Sh NAME
43.Nm inet_net_ntop ,
44.Nm inet_net_pton
45.Nd Internet network number manipulation routines
46.Sh LIBRARY
47.Lb libc
48.Sh SYNOPSIS
49.In sys/types.h
50.In sys/socket.h
51.In netinet/in.h
52.In arpa/inet.h
53.Ft char *
54.Fn inet_net_ntop "int af" "const void *src" "int bits" "char *dst" "size_t size"
55.Ft int
56.Fn inet_net_pton "int af" "const char *src" "void *dst" "size_t size"
57.Sh DESCRIPTION
58The
59.Fn inet_net_ntop
60function converts an Internet network number from network format (usually a
61.Vt "struct in_addr"
62or some other binary form, in network byte order) to CIDR presentation format
63(suitable for external display purposes).
64The
65.Fa bits
66argument
67is the number of bits in
68.Fa src
69that are the network number.
70It returns
71.Dv NULL
72if a system error occurs (in which case,
73.Va errno
74will have been set), or it returns a pointer to the destination string.
75.Pp
76The
77.Fn inet_net_pton
78function converts a presentation format Internet network number (that is,
79printable form as held in a character string) to network format (usually a
80.Vt "struct in_addr"
81or some other internal binary representation, in network byte order).
82It returns the number of bits (either computed based on the class, or
83specified with /CIDR), or \-1 if a failure occurred
84(in which case
85.Va errno
86will have been set.
87It will be set to
88.Er ENOENT
89if the Internet network number was not valid).
90.Pp
91The only value for
92.Fa af
93currently supported is
94.Dv AF_INET .
95The
96.Fa size
97argument
98is the size of the result buffer
99.Fa dst .
100.Pp
101.Sh NETWORK NUMBERS (IP VERSION 4)
102Internet network numbers may be specified in one of the following forms:
103.Bd -literal -offset indent
104a.b.c.d/bits
105a.b.c.d
106a.b.c
107a.b
108a
109.Ed
110.Pp
111When four parts are specified, each is interpreted
112as a byte of data and assigned, from left to right,
113to the four bytes of an Internet network number.
114Note
115that when an Internet network number is viewed as a 32-bit
116integer quantity on a system that uses little-endian
117byte order (such as the
118.Tn Intel 386 , 486 ,
119and
120.Tn Pentium
121processors) the bytes referred to above appear as
122.Dq Li d.c.b.a .
123That is, little-endian bytes are ordered from right to left.
124.Pp
125When a three part number is specified, the last
126part is interpreted as a 16-bit quantity and placed
127in the rightmost two bytes of the Internet network number.
128This makes the three part number format convenient
129for specifying Class B network numbers as
130.Dq Li 128.net.host .
131.Pp
132When a two part number is supplied, the last part
133is interpreted as a 24-bit quantity and placed in
134the rightmost three bytes of the Internet network number.
135This makes the two part number format convenient
136for specifying Class A network numbers as
137.Dq Li net.host .
138.Pp
139When only one part is given, the value is stored
140directly in the Internet network number without any byte
141rearrangement.
142.Pp
143All numbers supplied as
144.Dq parts
145in a
146.Ql \&.
147notation
148may be decimal, octal, or hexadecimal, as specified
149in the C language (i.e., a leading 0x or 0X implies
150hexadecimal; otherwise, a leading 0 implies octal;
151otherwise, the number is interpreted as decimal).
152.Sh SEE ALSO
153.Xr byteorder 3 ,
154.Xr inet 3 ,
155.Xr networks 5
156.Sh HISTORY
157The
158.Fn inet_net_ntop
159and
160.Fn inet_net_pton
161functions appeared in BIND 4.9.4.
162