37e8159125
get{addr,name} info are implemented to have as little impact to existing
resolver code as possible, so they are NOT the optimal implementation.
They are at this moment not very thread safe (as they call
gethostby{name,addr}).
(shlib minor version)++, as new interfaces are added.
TODO: getipnodeby{name,addr} - which needs total reimplementation of
gethostby{name,addr}.
upgrade rcmd.c for multiple af support (needed for IPv6-ready rsh/rlogin)
362 lines
9.6 KiB
Groff
362 lines
9.6 KiB
Groff
.\" Copyright (c) 1983, 1987, 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. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. 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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.\" From: @(#)gethostbyname.3 8.4 (Berkeley) 5/25/95
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.\" $Id: getaddrinfo.3,v 1.1 1999/07/01 18:23:54 itojun Exp $
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.\"
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.Dd May 25, 1995
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.Dt GETADDRINFO 3
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.Os KAME
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.Sh NAME
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.Nm getaddrinfo
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.Nm freeaddrinfo ,
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.Nm gai_strerror
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.Nd nodename-to-address translation in protocol-independent manner
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.Sh SYNOPSIS
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.Fd #include <sys/socket.h>
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.Fd #include <netdb.h>
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.Ft int
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.Fn getaddrinfo "const char *nodename" "const char *servname" \
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"const struct addrinfo *hints" "struct addrinfo **res"
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.Ft void
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.Fn freeaddrinfo "struct addrinfo *ai"
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.Ft "char *"
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.Fn gai_strerror "int ecode"
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.Sh DESCRIPTION
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The
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.Fn getaddrinfo
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function is defined for protocol-independent nodename-to-address translation.
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It performs functionality of
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.Xr gethostbyname 3
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and
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.Xr getservbyname 3 ,
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in more sophisticated manner.
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.Pp
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The addrinfo structure is defined as a result of including the
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.Li <netdb.h>
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header:
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.Bd -literal -offset
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struct addrinfo { *
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int ai_flags; /* AI_PASSIVE, AI_CANONNAME, AI_NUMERICHOST */
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int ai_family; /* PF_xxx */
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int ai_socktype; /* SOCK_xxx */
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int ai_protocol; /* 0 or IPPROTO_xxx for IPv4 and IPv6 */
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size_t ai_addrlen; /* length of ai_addr */
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char *ai_canonname; /* canonical name for nodename */
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struct sockaddr *ai_addr; /* binary address */
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struct addrinfo *ai_next; /* next structure in linked list */
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};
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.Ed
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.Pp
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The
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.Fa nodename
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and
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.Fa servname
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arguments are pointers to null-terminated strings or
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.Dv NULL .
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One or both of these two arguments must be a
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.Pf non Dv -NULL
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pointer.
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In the normal client scenario, both the
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.Fa nodename
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and
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.Fa servname
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are specified.
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In the normal server scenario, only the
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.Fa servname
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is specified.
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A
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.Pf non Dv -NULL
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.Fa nodename
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string can be either a node name or a numeric host address string
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.Po
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i.e., a dotted-decimal IPv4 address or an IPv6 hex address
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.Pc .
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A
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.Pf non Dv -NULL
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.Fa servname
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string can be either a service name or a decimal port number.
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.Pp
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The caller can optionally pass an
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.Li addrinfo
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structure, pointed to by the third argument,
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to provide hints concerning the type of socket that the caller supports.
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In this
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.Fa hints
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structure all members other than
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.Fa ai_flags ,
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.Fa ai_family ,
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.Fa ai_socktype ,
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and
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.Fa ai_protocol
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must be zero or a
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.Dv NULL
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pointer.
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A value of
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.Dv PF_UNSPEC
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for
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.Fa ai_family
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means the caller will accept any protocol family.
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A value of 0 for
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.Fa ai_socktype
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means the caller will accept any socket type.
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A value of 0 for
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.Fa ai_protocol
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means the caller will accept any protocol.
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For example, if the caller handles only TCP and not UDP, then the
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.Fa ai_socktype
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member of the hints structure should be set to
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.Dv SOCK_STREAM
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when
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.Fn getaddrinfo
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is called.
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If the caller handles only IPv4 and not IPv6, then the
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.Fa ai_family
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member of the
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.Fa hints
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structure should be set to
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.Dv PF_INET
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when
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.Fn getaddrinfo
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is called.
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If the third argument to
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.Fn getaddrinfo
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is a
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.Dv NULL
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pointer, this is the same as if the caller had filled in an
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.Li addrinfo
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structure initialized to zero with
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.Fa ai_family
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set to PF_UNSPEC.
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.Pp
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Upon successful return a pointer to a linked list of one or more
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.Li addrinfo
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structures is returned through the final argument.
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The caller can process each
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.Li addrinfo
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structure in this list by following the
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.Fa ai_next
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pointer, until a
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.Dv NULL
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pointer is encountered.
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In each returned
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.Li addrinfo
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structure the three members
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.Fa ai_family ,
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.Fa ai_socktype ,
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and
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.Fa ai_protocol
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are the corresponding arguments for a call to the
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.Fn socket
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function.
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In each
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.Li addrinfo
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structure the
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.Fa ai_addr
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member points to a filled-in socket address structure whose length is
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specified by the
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.Fa ai_addrlen
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member.
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.Pp
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If the
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.Dv AI_PASSIVE
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bit is set in the
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.Fa ai_flags
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member of the
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.Fa hints
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structure, then the caller plans to use the returned socket address
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structure in a call to
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.Fn bind .
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In this case, if the
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.Fa nodename
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argument is a
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.Dv NULL
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pointer, then the IP address portion of the socket
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address structure will be set to
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.Dv INADDR_ANY
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for an IPv4 address or
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.Dv IN6ADDR_ANY_INIT
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for an IPv6 address.
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.Pp
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If the
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.Dv AI_PASSIVE
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bit is not set in the
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.Fa ai_flags
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member of the
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.Fa hints
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structure, then the returned socket address structure will be ready for a
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call to
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.Fn connect
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.Pq for a connection-oriented protocol
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or either
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.Fn connect ,
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.Fn sendto , or
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.Fn sendmsg
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.Pq for a connectionless protocol .
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In this case, if the
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.Fa nodename
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argument is a
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.Dv NULL
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pointer, then the IP address portion of the
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socket address structure will be set to the loopback address.
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.Pp
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If the
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.Dv AI_CANONNAME
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bit is set in the
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.Fa ai_flags
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member of the
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.Fa hints
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structure, then upon successful return the
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.Fa ai_canonname
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member of the first
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.Li addrinfo
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structure in the linked list will point to a null-terminated string
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containing the canonical name of the specified
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.Fa nodename .
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.Pp
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If the
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.Dv AI_NUMERICHOST
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bit is set in the
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.Fa ai_flags
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member of the
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.Fa hints
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structure, then a
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.Pf non Dv -NULL
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.Fa nodename
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string must be a numeric host address string.
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Otherwise an error of
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.Dv EAI_NONAME
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is returned.
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This flag prevents any type of name resolution service (e.g., the DNS)
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from being called.
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.Pp
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All of the information returned by
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.Fn getaddrinfo
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is dynamically allocated:
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the
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.Li addrinfo
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structures, and the socket address structures and canonical node name
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strings pointed to by the addrinfo structures.
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To return this information to the system the function
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.Fn freeaddrinfo
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is called.
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The
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.Fa addrinfo
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structure pointed to by the
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.Fa ai argument
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is freed, along with any dynamic storage pointed to by the structure.
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This operation is repeated until a
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.Dv NULL
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.Fa ai_next
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pointer is encountered.
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.Pp
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To aid applications in printing error messages based on the
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.Dv EAI_xxx
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codes returned by
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.Fn getaddrinfo ,
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.Fn gai_strerror
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is defined.
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The argument is one of the
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.Dv EAI_xxx
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values defined earlier and the return value points to a string describing
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the error.
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If the argument is not one of the
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.Dv EAI_xxx
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values, the function still returns a pointer to a string whose contents
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indicate an unknown error.
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.Sh FILES
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.Bl -tag -width /etc/resolv.conf -compact
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.It Pa /etc/hosts
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.It Pa /etc/host.conf
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.It Pa /etc/resolv.conf
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.El
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.Sh DIAGNOSTICS
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Error return status from
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.Fn getaddrinfo
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is zero on success and non-zero on errors.
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Non-zero error codes are defined in
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.Li <netdb.h> ,
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and as follows:
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.Pp
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.Bl -tag -width EAI_ADDRFAMILY -compact
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.It Dv EAI_ADDRFAMILY
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address family for nodename not supported
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.It Dv EAI_AGAIN
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temporary failure in name resolution
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.It Dv EAI_BADFLAGS
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invalid value for ai_flags
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.It Dv EAI_FAIL
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non-recoverable failure in name resolution
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.It Dv EAI_FAMILY
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ai_family not supported
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.It Dv EAI_MEMORY
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memory allocation failure
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.It Dv EAI_NODATA
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no address associated with nodename
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.It Dv EAI_NONAME
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nodename nor servname provided, or not known
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.It Dv EAI_SERVICE
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servname not supported for ai_socktype
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.It Dv EAI_SOCKTYPE
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ai_socktype not supported
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.It Dv EAI_SYSTEM
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system error returned in errno
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.El
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.Pp
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If called with proper argument,
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.Fn gai_strerror
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returns a pointer to a string describing the given error code.
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If the argument is not one of the
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.Dv EAI_xxx
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values, the function still returns a pointer to a string whose contents
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indicate an unknown error.
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.Sh SEE ALSO
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.Xr getnameinfo 3 ,
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.Xr gethostbyname 3 ,
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.Xr getservbyname 3 ,
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.Xr hosts 5 ,
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.Xr services 5 ,
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.Xr hostname 7 ,
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.Xr named 8
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.Pp
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R. Gilligan, S. Thomson, J. Bound, and W. Stevens,
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``Basic Socket Interface Extensions for IPv6,'' RFC2553, March 1999.
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.Sh HISTORY
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The implementation first appeared in WIDE Hydrangea IPv6 protocol stack kit.
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.Sh STANDARDS
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The
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.Fn getaddrinfo
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function is defined IEEE POSIX 1003.1g draft specification,
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and documented in ``Basic Socket Interface Extensions for IPv6''
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.Pq RFC2533 .
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.Sh BUGS
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The text was shamelessly copied from RFC2553.
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