204 lines
6.4 KiB
Groff
204 lines
6.4 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: getnameinfo.3,v 1.2 1999/07/03 13:58:31 kleink Exp $
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.\"
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.Dd May 25, 1995
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.Dt GETNAMEINFO 3
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.Os KAME
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.Sh NAME
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.Nm getnameinfo
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.Nd address-to-nodename translation in protocol-independent manner
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.Sh LIBRARY
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.Lb libc
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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 getnameinfo "const struct sockaddr *sa" "socklen_t salen" \
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"char *host" "size_t hostlen" "char *serv" "size_t servlen" "int flags"
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.Sh DESCRIPTION
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The
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.Fn getnameinfo
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function is defined for protocol-independent address-to-nodename translation.
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Its functionality is a reverse conversion of
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.Xr getaddrinfo 3 ,
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and implements similar functionality with
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.Xr gethostbyaddr 3 and
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.Xr getservbyport 3
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in more sophisticated manner.
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.Pp
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This function looks up an IP address and port number provided by the
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caller in the DNS and system-specific database, and returns text
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strings for both in buffers provided by the caller.
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The function indicates successful completion by a zero return value;
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a non-zero return value indicates failure.
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.Pp
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The first argument,
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.Fa sa ,
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points to either a
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.Fa sockaddr_in
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structure (for IPv4) or a
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.Fa sockaddr_in6
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structure (for IPv6) that holds the IP address and port number.
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The
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.Fa salen
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argument gives the length of the
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.Fa sockaddr_in
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or
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.Fa sockaddr_in6
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structure.
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.Pp
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The function returns the nodename associated with the IP address in
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the buffer pointed to by the
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.Fa host
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argument.
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The caller provides the size of this buffer via the
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.Fa hostlen
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argument.
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The service name associated with the port number is returned in the buffer
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pointed to by
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.Fa serv ,
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and the
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.Fa servlen
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argument gives the length of this buffer.
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The caller specifies not to return either string by providing a zero
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value for the
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.Fa hostlen
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or
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.Fa servlen
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arguments.
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Otherwise, the caller must provide buffers large enough to hold the
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nodename and the service name, including the terminating null characters.
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.Pp
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Unfortunately most systems do not provide constants that specify the
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maximum size of either a fully-qualified domain name or a service name.
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Therefore to aid the application in allocating buffers for these two
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returned strings the following constants are defined in
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.Li <netdb.h> :
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.Bd -literal -offset
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#define NI_MAXHOST 1025
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#define NI_MAXSERV 32
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.Ed
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.Pp
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The first value is actually defined as the constant
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.Dv MAXDNAME
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in recent versions of BIND's
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.Li <arpa/nameser.h>
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header
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.Po
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older versions of BIND define this constant to be 256
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.Pc
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and the second is a guess based on the services listed in the current
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Assigned Numbers RFC.
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.Pp
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The final argument is a
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.Fa flag
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that changes the default actions of this function.
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By default the fully-qualified domain name (FQDN) for the host is
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looked up in the DNS and returned.
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If the flag bit
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.Dv NI_NOFQDN
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is set, only the nodename portion of the FQDN is returned for local hosts.
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.Pp
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If the
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.Fa flag
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bit
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.Dv NI_NUMERICHOST
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is set, or if the host's name cannot be located in the DNS,
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the numeric form of the host's address is returned instead of its name
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.Po
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e.g., by calling
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.Fn inet_ntop
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instead of
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.Fn getnodebyaddr
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.Pc .
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If the
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.Fa flag
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bit
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.Dv NI_NAMEREQD
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is set, an error is returned if the host's name cannot be located in the DNS.
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.Pp
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If the flag bit
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.Dv NI_NUMERICSERV
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is set, the numeric form of the service address is returned
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.Pq e.g., its port number
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instead of its name.
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The two
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.Dv NI_NUMERICxxx
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flags are required to support the
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.Li "-n"
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flag that many commands provide.
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.Pp
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A fifth flag bit,
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.Dv NI_DGRAM ,
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specifies that the service is a datagram service, and causes
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.Fn getservbyport
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to be called with a second argument of "udp" instead of its default of "tcp".
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This is required for the few ports (512-514)
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that have different services for UDP and TCP.
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.Pp
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These
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.Dv NI_xxx
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flags are defined in
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.Li <netdb.h> .
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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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The function indicates successful completion by a zero return value;
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a non-zero return value indicates failure.
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.Sh SEE ALSO
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.Xr getaddrinfo 3 ,
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.Xr gethostbyaddr 3 ,
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.Xr getservbyport 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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