1.\" $NetBSD: inet_net.3,v 1.4 1999/03/22 19:44:52 garbled Exp $ 2.\" 3.\" Copyright (c) 1997 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Luke Mewburn. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. Neither the name of The NetBSD Foundation nor the names of its 18.\" contributors may be used to endorse or promote products derived 19.\" from this software without specific prior written permission. 20.\" 21.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 22.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 23.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 24.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 25.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 26.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 27.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 28.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 29.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 30.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 31.\" POSSIBILITY OF SUCH DAMAGE. 32.\" 33.\" $FreeBSD$ 34.\" 35.Dd August 18, 2016 36.Dt INET_NET 3 37.Os 38.Sh NAME 39.Nm inet_net_ntop , 40.Nm inet_net_pton 41.Nd Internet network number manipulation routines 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In sys/socket.h 46.In netinet/in.h 47.In arpa/inet.h 48.Ft char * 49.Fn inet_net_ntop "int af" "const void *src" "int bits" "char *dst" "size_t size" 50.Ft int 51.Fn inet_net_pton "int af" "const char *src" "void *dst" "size_t size" 52.Sh DESCRIPTION 53The 54.Fn inet_net_ntop 55function converts an Internet network number from network format (usually a 56.Vt "struct in_addr" 57or some other binary form, in network byte order) to CIDR presentation format 58(suitable for external display purposes). 59The 60.Fa bits 61argument 62is the number of bits in 63.Fa src 64that are the network number. 65It returns 66.Dv NULL 67if a system error occurs (in which case, 68.Va errno 69will have been set), or it returns a pointer to the destination string. 70.Pp 71The 72.Fn inet_net_pton 73function converts a presentation format Internet network number (that is, 74printable form as held in a character string) to network format (usually a 75.Vt "struct in_addr" 76or some other internal binary representation, in network byte order). 77It returns the number of bits (either computed based on the class, or 78specified with /CIDR), or \-1 if a failure occurred 79(in which case 80.Va errno 81will have been set. 82It will be set to 83.Er ENOENT 84if the Internet network number was not valid). 85.Pp 86The currently supported values for 87.Fa af 88are 89.Dv AF_INET 90and 91.Dv AF_INET6 . 92The 93.Fa size 94argument 95is the size of the result buffer 96.Fa dst . 97.Sh NETWORK NUMBERS (IP VERSION 4) 98Internet network numbers may be specified in one of the following forms: 99.Bd -literal -offset indent 100a.b.c.d/bits 101a.b.c.d 102a.b.c 103a.b 104a 105.Ed 106.Pp 107When four parts are specified, each is interpreted 108as a byte of data and assigned, from left to right, 109to the four bytes of an Internet network number. 110Note 111that when an Internet network number is viewed as a 32-bit 112integer quantity on a system that uses little-endian 113byte order (such as the 114.Tn Intel 386 , 486 , 115and 116.Tn Pentium 117processors) the bytes referred to above appear as 118.Dq Li d.c.b.a . 119That is, little-endian bytes are ordered from right to left. 120.Pp 121When a three part number is specified, the last 122part is interpreted as a 16-bit quantity and placed 123in the rightmost two bytes of the Internet network number. 124This makes the three part number format convenient 125for specifying Class B network numbers as 126.Dq Li 128.net.host . 127.Pp 128When a two part number is supplied, the last part 129is interpreted as a 24-bit quantity and placed in 130the rightmost three bytes of the Internet network number. 131This makes the two part number format convenient 132for specifying Class A network numbers as 133.Dq Li net.host . 134.Pp 135When only one part is given, the value is stored 136directly in the Internet network number without any byte 137rearrangement. 138.Pp 139All numbers supplied as 140.Dq parts 141in a 142.Ql \&. 143notation 144may be decimal, octal, or hexadecimal, as specified 145in the C language (i.e., a leading 0x or 0X implies 146hexadecimal; otherwise, a leading 0 implies octal; 147otherwise, the number is interpreted as decimal). 148.\" 149.\" .Sh NETWORK NUMBERS (IP VERSION 6) 150.\" XXX - document this! 151.\" 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