.\" $OpenBSD: inet_net_ntop.3,v 1.4 2022/09/11 06:38:10 jmc Exp $ .\" $NetBSD: inet_net.3,v 1.1 1997/06/18 02:25:27 lukem Exp $ .\" .\" Copyright (c) 1997 The NetBSD Foundation, Inc. .\" All rights reserved. .\" .\" This code is derived from software contributed to The NetBSD Foundation .\" by Luke Mewburn. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS .\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED .\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE .\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR .\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF .\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS .\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN .\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE .\" POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: September 11 2022 $ .Dt INET_NET_NTOP 3 .Os .Sh NAME .Nm inet_net_ntop , .Nm inet_net_pton .Nd Internet network number manipulation routines .Sh SYNOPSIS .In sys/socket.h .In arpa/inet.h .Ft char * .Fn inet_net_ntop "int af" "const void *src" "int bits" "char *dst" "size_t size" .Ft int .Fn inet_net_pton "int af" "const char *src" "void *dst" "size_t size" .Sh DESCRIPTION The .Fn inet_net_ntop function converts an Internet network number from network format (usually a .Vt struct in_addr or some other binary form, in network byte order) to CIDR presentation format (suitable for external display purposes). .Fa bits is the number of bits in .Fa src that are the network number. It returns .Dv NULL if a system error occurs (in which case, .Va errno will have been set), or it returns a pointer to the destination string. .Pp The .Fn inet_net_pton function converts a presentation format Internet network number (that is, printable form as held in a character string) to network format (usually a .Vt struct in_addr or some other internal binary representation, in network byte order). It returns the number of bits (either computed based on the class, or specified with /CIDR), or \-1 if a failure occurred (in which case .Va errno will have been set. It will be set to .Er ENOENT if the Internet network number was not valid). .Pp Caution: The .Fa dst field should be zeroed before calling .Fn inet_net_pton as the function will only fill the number of bytes necessary to encode the network number in network byte order. .Pp The only values for .Fa af currently supported are .Dv AF_INET and .Dv AF_INET6 . .Fa size is the size of the result buffer .Fa dst . .Sh NETWORK NUMBERS (IP VERSION 4) The external representation of Internet network numbers may be specified in one of the following forms: .Bd -literal -offset indent a a.b a.b.c a.b.c.d .Ed .Pp Any of the above four forms may have .Dq Li /bits appended where .Dq Li bits is in the range .Li 0-32 and is used to explicitly specify the number of bits in the network address. When .Dq Li /bits is not specified, the number of bits in the network address is calculated as the larger of the number of bits in the class to which the address belongs and the number of bits provided rounded up modulo 8. Examples: .Pp .Bl -tag -width 10.1.2.3/24 -offset indent -compact .It Li 10 an 8-bit network number (class A), value .Li 10.0.0.0 . .It Li 192 a 24-bit network number (class C), value .Li 192.0.0.0 . .It Li 10.10 a 16-bit network number, value .Li 10.10.0.0 . .It Li 10.1.2 a 24-bit network number, value .Li 10.1.2.0 . .It Li 10.1.2.3 a 32-bit network number, value .Li 10.1.2.3 . .It Li 10.1.2.3/24 a 24-bit network number (explicit), value .Li 10.1.2.3 . .El .Pp Note that when the number of bits is specified using .Dq Li /bits notation, the value of the address still includes all bits supplied in the external representation, even those bits which are the host part of an Internet address. Also, unlike .Xr inet_pton 3 where the external representation is assumed to be a host address, the external representation for .Fn inet_net_pton is assumed to be a network address. Thus .Dq Li 10.1 is assumed to be .Dq Li 10.1.0.0 not .Dq Li 10.0.0.1 .Pp All numbers supplied as .Dq parts in a .Ql \&. notation may be decimal, octal, or hexadecimal, as specified in the C language (i.e., a leading 0x or 0X implies hexadecimal; otherwise, a leading 0 implies octal; otherwise, the number is interpreted as decimal). .Sh NETWORK NUMBERS (IP VERSION 6) See .Xr inet_pton 3 for valid external representations of IP version 6 addresses. A valid external representation may have .Dq Li /bits appended where .Dq Li bits is in the range .Li 0-128 and is used to explicitly specify the number of bits in the network address. When .Dq Li /bits is not specified, 128 is used. Note that when the number of bits is specified using .Dq Li /bits notation, the value of the address still includes all bits supplied in the external representation, even those bits which are the host part of an Internet address. .Sh SEE ALSO .Xr htonl 3 , .Xr inet_pton 3 , .Xr inet 4 , .Xr hosts 5 .Sh HISTORY The .Nm inet_net_ntop and .Nm inet_net_pton functions first appeared in BIND 4.9.4.