363 lines
10 KiB
Groff
363 lines
10 KiB
Groff
.\" $NetBSD: inet.3,v 1.1 2004/05/20 23:13:02 christos Exp $
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.\"
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.\" Copyright (c) 1983, 1990, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)inet.3 8.1 (Berkeley) 6/4/93
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.\"
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.Dd June 30, 2003
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.Dt INET 3
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.Os
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.Sh NAME
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.Nm inet_addr ,
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.Nm inet_aton ,
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.Nm inet_lnaof ,
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.Nm inet_makeaddr ,
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.Nm inet_netof ,
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.Nm inet_network ,
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.Nm inet_ntoa ,
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.Nm inet_ntop ,
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.Nm inet_pton ,
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.Nm addr ,
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.Nm ntoa ,
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.Nm network
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.Nd Internet address manipulation routines
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In arpa/inet.h
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.Ft in_addr_t
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.Fn inet_addr "const char *cp"
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.Ft int
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.Fn inet_aton "const char *cp" "struct in_addr *addr"
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.Ft in_addr_t
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.Fn inet_lnaof "struct in_addr in"
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.Ft struct in_addr
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.Fn inet_makeaddr "in_addr_t net" "in_addr_t lna"
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.Ft in_addr_t
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.Fn inet_netof "struct in_addr in"
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.Ft in_addr_t
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.Fn inet_network "const char *cp"
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.Ft char *
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.Fn inet_ntoa "struct in_addr in"
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.Ft const char *
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.Fn inet_ntop "int af" "const void * restrict src" "char * restrict dst" "socklen_t size"
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.Ft int
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.Fn inet_pton "int af" "const char * restrict src" "void * restrict dst"
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.Sh DESCRIPTION
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The routines
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.Fn inet_aton ,
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.Fn inet_addr
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and
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.Fn inet_network
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interpret character strings representing
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numbers expressed in the Internet standard
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.Qq dotted quad
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notation.
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.Pp
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The
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.Fn inet_pton
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function converts a presentation format address (that is, printable form
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as held in a character string) to network format (usually a
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.Ft struct in_addr
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or some other internal binary representation, in network byte order).
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It returns 1 if the address was valid for the specified address family, or
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0 if the address wasn't parsable in the specified address family, or -1
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if some system error occurred (in which case
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.Va errno
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will have been set).
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This function is presently valid for
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.Dv AF_INET
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and
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.Dv AF_INET6 .
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.Pp
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The
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.Fn inet_aton
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routine interprets the specified character string as an Internet address,
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placing the address into the structure provided.
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It returns 1 if the string was successfully interpreted,
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or 0 if the string is invalid.
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.Pp
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The
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.Fn inet_addr
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and
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.Fn inet_network
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functions return numbers suitable for use
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as Internet addresses and Internet network
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numbers, respectively.
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.Pp
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The function
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.Fn inet_ntop
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converts an address from network format (usually a
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.Ft struct in_addr
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or some other binary form, in network byte order) to presentation format
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(suitable for external display purposes).
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It returns NULL if a system error occurs (in which case,
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.Va errno
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will have been set), or it returns a pointer to the destination string.
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.Pp
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The routine
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.Fn inet_ntoa
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takes an Internet address and returns an
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.Tn ASCII
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string representing the address in
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.Qq dotted quad
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notation.
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.Pp
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The routine
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.Fn inet_makeaddr
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takes an Internet network number and a local network address (both in
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host order) and constructs an Internet address from it.
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Note that to convert only a single value to a
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.Ft struct in_addr
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form that value should be passed as the first parameter and
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.Ql 0L
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should be given for the second parameter.
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.Pp
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The routines
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.Fn inet_netof
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and
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.Fn inet_lnaof
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break apart Internet host addresses, returning the network number and
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local network address part, respectively (both in host order).
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.Pp
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All Internet addresses are returned in network
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order (bytes ordered from left to right).
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All network numbers and local address parts are
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returned as machine format integer values.
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.Sh INTERNET ADDRESSES (IP VERSION 4)
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Values specified using the
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.Qq dotted quad
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notation take one
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of the following forms:
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.Bd -literal -offset indent
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a.b.c.d
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a.b.c
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a.b
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a
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.Ed
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.Pp
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When four parts are specified, each is interpreted
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as a byte of data and assigned, from left to right,
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to the four bytes of an Internet address.
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Note that when an Internet address is viewed as a 32-bit
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integer quantity on a system that uses little-endian
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byte order (e.g.
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.Tn Intel i386, i486
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and
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.Tn Pentium
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processors) the bytes referred to above appear as
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.Dq Li d.c.b.a .
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That is, little-endian bytes are ordered from right to left.
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.Pp
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When a three part address is specified, the last
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part is interpreted as a 16-bit quantity and placed
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in the right-most two bytes of the network address.
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This makes the three part address format convenient
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for specifying Class B network addresses as
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.Dq Li 128.net.host .
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.Pp
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When a two part address is supplied, the last part
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is interpreted as a 24-bit quantity and placed in
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the right most three bytes of the network address.
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This makes the two part address format convenient
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for specifying Class A network addresses as
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.Dq Li net.host .
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.Pp
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When only one part is given, the value is stored
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directly in the network address without any byte
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rearrangement.
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.Pp
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All numbers supplied as
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.Dq parts
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in a
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.Qq dotted quad
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notation
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may be decimal, octal, or hexadecimal, as specified
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in the C language (i.e., a leading 0x or 0X implies
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hexadecimal; otherwise, a leading 0 implies octal;
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otherwise, the number is interpreted as decimal).
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.Sh INTERNET ADDRESSES (IP VERSION 6)
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In order to support scoped IPv6 addresses,
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the use of
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.Xr getaddrinfo 3
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and
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.Xr getnameinfo 3
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is recommended rather than the functions presented here.
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.Pp
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The presentation format of an IPv6 address is given in RFC 2373:
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.Pp
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There are three conventional forms for representing IPv6 addresses as
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text strings:
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.Bl -enum
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.It
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The preferred form is x:x:x:x:x:x:x:x, where the 'x's are the
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hexadecimal values of the eight 16-bit pieces of the address.
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Examples:
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.Bd -literal -offset indent
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FEDC:BA98:7654:3210:FEDC:BA98:7654:3210
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1080:0:0:0:8:800:200C:417A
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.Ed
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.Pp
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Note that it is not necessary to write the leading zeros in an
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individual field, but there must be at least one numeral in
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every field (except for the case described in 2).
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.It
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Due to the method of allocating certain styles of IPv6
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addresses, it will be common for addresses to contain long
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strings of zero bits.
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In order to make writing addresses
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containing zero bits easier, a special syntax is available to
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compress the zeros.
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The use of ``::'' indicates multiple groups of 16-bits of zeros.
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The ``::'' can only appear once in an address.
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The ``::'' can also be used to compress the leading
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and/or trailing zeros in an address.
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.Pp
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For example the following addresses:
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.Bd -literal -offset indent
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1080:0:0:0:8:800:200C:417A a unicast address
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FF01:0:0:0:0:0:0:43 a multicast address
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0:0:0:0:0:0:0:1 the loopback address
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0:0:0:0:0:0:0:0 the unspecified addresses
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.Ed
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.Pp
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may be represented as:
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.Bd -literal -offset indent
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1080::8:800:200C:417A a unicast address
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FF01::43 a multicast address
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::1 the loopback address
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:: the unspecified addresses
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.Ed
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.It
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An alternative form that is sometimes more convenient when
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dealing with a mixed environment of IPv4 and IPv6 nodes is
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x:x:x:x:x:x:d.d.d.d, where the 'x's are the hexadecimal values
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of the six high-order 16-bit pieces of the address, and the 'd's
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are the decimal values of the four low-order 8-bit pieces of the
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address (standard IPv4 representation).
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Examples:
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.Bd -literal -offset indent
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0:0:0:0:0:0:13.1.68.3
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0:0:0:0:0:FFFF:129.144.52.38
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.Ed
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.Pp
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or in compressed form:
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.Bd -literal -offset indent
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::13.1.68.3
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::FFFF:129.144.52.38
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.Ed
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.El
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.Sh DIAGNOSTICS
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The constant
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.Dv INADDR_NONE
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is returned by
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.Fn inet_addr
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and
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.Fn inet_network
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for malformed requests.
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.Sh SEE ALSO
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.Xr byteorder 3 ,
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.Xr gethostbyname 3 ,
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.Xr getnetent 3 ,
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.Xr inet_net 3 ,
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.Xr hosts 5 ,
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.Xr networks 5
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.Rs
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.%R RFC 2373
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.%D July 1998
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.%T "IP Version 6 Addressing Architecture"
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.Re
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.Rs
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.%R RFC 3493
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.%D February 2003
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.%T "Basic Socket Interface Extensions for IPv6"
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.Re
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.Sh STANDARDS
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The
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.Nm inet_ntop
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and
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.Nm inet_pton
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functions conform to
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.St -p1003.1-2001 .
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Note that
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.Nm inet_pton
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does not accept 1-, 2-, or 3-part dotted addresses; all four parts
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must be specified.
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This is a narrower input set than that accepted by
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.Nm inet_aton .
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.Sh HISTORY
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The
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.Nm inet_addr ,
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.Nm inet_network ,
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.Nm inet_makeaddr ,
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.Nm inet_lnaof
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and
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.Nm inet_netof
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functions appeared in
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.Bx 4.2 .
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They were changed to use
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.Va in_addr_t
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in place of
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.Va unsigned long
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in
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.Nx 2.0 .
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The
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.Nm inet_aton
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and
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.Nm inet_ntoa
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functions appeared in
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.Bx 4.3 .
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The
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.Nm inet_pton
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and
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.Nm inet_ntop
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functions appeared in BIND 4.9.4 and thence
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.Nx 1.3 ;
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they were also in
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.St -xns5.2 .
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.Sh BUGS
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The value
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.Dv INADDR_NONE
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(0xffffffff) is a valid broadcast address, but
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.Fn inet_addr
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cannot return that value without indicating failure.
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The newer
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.Fn inet_aton
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function does not share this problem.
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.Pp
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The problem of host byte ordering versus network byte ordering is
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confusing.
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.Pp
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The string returned by
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.Fn inet_ntoa
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resides in a static memory area.
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.Pp
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.Fn inet_addr
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should return a
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.Fa "struct in_addr" .
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