6617cf5778
Reviewed by: Kame Project (including Itojun-san, Jinmei-san and Suzuki-san) Approved by: Robert Watson (robert at freebsd dot org) Obtained from: Kame Project and OpenBSD Replace manual pages that may have violated the IETF's Copyright. All come from the Kame tree. Several were from OpenBSD except for ip6.4, and the inet6* pages which were rewritten by me. All of the text is new and drawn from reading the code and documentation.
436 lines
10 KiB
Groff
436 lines
10 KiB
Groff
.\" $KAME: getaddrinfo.3,v 1.36 2005/01/05 03:23:05 itojun Exp $
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.\" $OpenBSD: getaddrinfo.3,v 1.35 2004/12/21 03:40:31 jaredy Exp $
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.\" $FreeBSD$
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.\"
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.\" Copyright (C) 2004 Internet Systems Consortium, Inc. ("ISC")
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.\" Copyright (C) 2000, 2001 Internet Software Consortium.
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.\"
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.\" Permission to use, copy, modify, and distribute this software for any
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.\" purpose with or without fee is hereby granted, provided that the above
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.\" copyright notice and this permission notice appear in all copies.
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.\"
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.\" THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
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.\" REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
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.\" AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
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.\" INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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.\" LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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.\" OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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.\" PERFORMANCE OF THIS SOFTWARE.
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.\"
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.Dd December 20, 2004
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.Dt GETADDRINFO 3
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.Os
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.Sh NAME
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.Nm getaddrinfo ,
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.Nm freeaddrinfo
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.Nd socket address structure to host and service name
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.Sh SYNOPSIS
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.Fd #include <sys/types.h>
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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 *hostname" "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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.Sh DESCRIPTION
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The
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.Fn getaddrinfo
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function is used to get a list of
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.Tn IP
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addresses and port numbers for host
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.Fa hostname
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and service
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.Fa servname .
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It is a replacement for and provides more flexibility than the
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.Xr gethostbyname 3
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and
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.Xr getservbyname 3
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functions.
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.Pp
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The
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.Fa hostname
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and
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.Fa servname
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arguments are either pointers to NUL-terminated strings or the null pointer.
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An acceptable value for
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.Fa hostname
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is either a valid host name or a numeric host address string consisting
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of a dotted decimal IPv4 address or an IPv6 address.
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The
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.Fa servname
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is either a decimal port number or a service name listed in
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.Xr services 5 .
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At least one of
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.Fa hostname
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and
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.Fa servname
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must be non-null.
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.Pp
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.Fa hints
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is an optional pointer to a
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.Li struct addrinfo ,
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as defined by
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.Aq Pa netdb.h :
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.Bd -literal
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struct addrinfo {
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int ai_flags; /* input flags */
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int ai_family; /* protocol family for socket */
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int ai_socktype; /* socket type */
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int ai_protocol; /* protocol for socket */
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socklen_t ai_addrlen; /* length of socket-address */
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struct sockaddr *ai_addr; /* socket-address for socket */
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char *ai_canonname; /* canonical name for service location */
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struct addrinfo *ai_next; /* pointer to next in list */
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};
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.Ed
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.Pp
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This structure can be used to provide hints concerning the type of socket
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that the caller supports or wishes to use.
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The caller can supply the following structure elements in
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.Fa hints :
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.Bl -tag -width "ai_socktypeXX"
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.It Fa ai_family
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The protocol family that should be used.
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When
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.Fa ai_family
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is set to
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.Dv PF_UNSPEC ,
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it means the caller will accept any protocol family supported by the
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operating system.
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.It Fa ai_socktype
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Denotes the type of socket that is wanted:
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.Dv SOCK_STREAM ,
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.Dv SOCK_DGRAM ,
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or
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.Dv SOCK_RAW .
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When
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.Fa ai_socktype
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is zero the caller will accept any socket type.
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.It Fa ai_protocol
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Indicates which transport protocol is desired,
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.Dv IPPROTO_UDP
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or
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.Dv IPPROTO_TCP .
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If
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.Fa ai_protocol
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is zero the caller will accept any protocol.
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.It Fa ai_flags
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.Fa ai_flags
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is formed by
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.Tn OR Ns 'ing
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the following values:
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.Bl -tag -width "AI_CANONNAMEXX"
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.It Dv AI_CANONNAME
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If the
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.Dv AI_CANONNAME
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bit is set, a successful call to
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.Fn getaddrinfo
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will return a NUL-terminated string containing the canonical name
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of the specified hostname in the
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.Fa ai_canonname
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element of the first
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.Li addrinfo
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structure returned.
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.It Dv AI_NUMERICHOST
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If the
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.Dv AI_NUMERICHOST
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bit is set, it indicates that
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.Fa hostname
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should be treated as a numeric string defining an IPv4 or IPv6 address
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and no name resolution should be attempted.
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.It Dv AI_PASSIVE
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If the
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.Dv AI_PASSIVE
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bit is set it indicates that the returned socket address structure
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is intended for use in a call to
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.Xr bind 2 .
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In this case, if the
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.Fa hostname
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argument is the null pointer, then the IP address portion of the
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socket 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, the returned socket address structure will be ready
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for use in a call to
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.Xr connect 2
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for a connection-oriented protocol or
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.Xr connect 2 ,
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.Xr sendto 2 ,
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or
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.Xr sendmsg 2
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if a connectionless protocol was chosen.
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The
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.Tn IP
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address portion of the socket address structure will be set to the
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loopback address if
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.Fa hostname
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is the null pointer and
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.Dv AI_PASSIVE
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is not set.
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.El
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.El
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.Pp
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All other elements of the
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.Li addrinfo
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structure passed via
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.Fa hints
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must be zero or the null pointer.
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.Pp
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If
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.Fa hints
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is the null pointer,
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.Fn getaddrinfo
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behaves as if the caller provided a
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.Li struct addrinfo
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with
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.Fa ai_family
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set to
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.Dv PF_UNSPEC
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and all other elements set to zero or
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.Dv NULL .
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.Pp
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After a successful call to
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.Fn getaddrinfo ,
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.Fa *res
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is a pointer to a linked list of one or more
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.Li addrinfo
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structures.
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The list can be traversed by following the
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.Fa ai_next
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pointer in each
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.Li addrinfo
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structure until a null pointer is encountered.
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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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in each returned
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.Li addrinfo
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structure are suitable for a call to
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.Xr socket 2 .
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For each
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.Li addrinfo
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structure in the list, the
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.Fa ai_addr
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member points to a filled-in socket address structure of length
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.Fa ai_addrlen .
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.Pp
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This implementation of
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.Fn getaddrinfo
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allows numeric IPv6 address notation with scope identifier,
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as documented in chapter 11 of draft-ietf-ipv6-scoping-arch-02.txt.
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By appending the percent character and scope identifier to addresses,
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one can fill the
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.Li sin6_scope_id
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field for addresses.
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This would make management of scoped addresses easier
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and allows cut-and-paste input of scoped addresses.
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.Pp
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At this moment the code supports only link-local addresses with the format.
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The scope identifier is hardcoded to the name of the hardware interface
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associated
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with the link
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.Po
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such as
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.Li ne0
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.Pc .
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An example is
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.Dq Li fe80::1%ne0 ,
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which means
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.Do
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.Li fe80::1
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on the link associated with the
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.Li ne0
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interface
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.Dc .
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.Pp
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The current implementation assumes a one-to-one relationship between
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the interface and link, which is not necessarily true from the specification.
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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: the
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.Li addrinfo
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structures themselves as well as the socket address structures and
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the canonical host name strings included in the
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.Li addrinfo
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structures.
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.Pp
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Memory allocated for the dynamically allocated structures created by
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a successful call to
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.Fn getaddrinfo
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is released by the
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.Fn freeaddrinfo
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function.
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The
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.Fa ai
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pointer should be a
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.Li addrinfo
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structure created by a call to
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.Fn getaddrinfo .
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.Sh RETURN VALUES
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.Fn getaddrinfo
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returns zero on success or one of the error codes listed in
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.Xr gai_strerror 3
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if an error occurs.
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.Sh EXAMPLES
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The following code tries to connect to
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.Dq Li www.kame.net
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service
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.Dq Li http
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via a stream socket.
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It loops through all the addresses available, regardless of address family.
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If the destination resolves to an IPv4 address, it will use an
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.Dv AF_INET
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socket.
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Similarly, if it resolves to IPv6, an
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.Dv AF_INET6
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socket is used.
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Observe that there is no hardcoded reference to a particular address family.
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The code works even if
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.Fn getaddrinfo
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returns addresses that are not IPv4/v6.
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.Bd -literal -offset indent
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struct addrinfo hints, *res, *res0;
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int error;
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int s;
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const char *cause = NULL;
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memset(&hints, 0, sizeof(hints));
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hints.ai_family = PF_UNSPEC;
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hints.ai_socktype = SOCK_STREAM;
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error = getaddrinfo("www.kame.net", "http", &hints, &res0);
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if (error) {
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errx(1, "%s", gai_strerror(error));
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/*NOTREACHED*/
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}
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s = -1;
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for (res = res0; res; res = res->ai_next) {
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s = socket(res->ai_family, res->ai_socktype,
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res->ai_protocol);
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if (s < 0) {
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cause = "socket";
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continue;
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}
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if (connect(s, res->ai_addr, res->ai_addrlen) < 0) {
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cause = "connect";
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close(s);
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s = -1;
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continue;
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}
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break; /* okay we got one */
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}
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if (s < 0) {
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err(1, "%s", cause);
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/*NOTREACHED*/
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}
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freeaddrinfo(res0);
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.Ed
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.Pp
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The following example tries to open a wildcard listening socket onto service
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.Dq Li http ,
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for all the address families available.
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.Bd -literal -offset indent
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struct addrinfo hints, *res, *res0;
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int error;
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int s[MAXSOCK];
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int nsock;
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const char *cause = NULL;
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memset(&hints, 0, sizeof(hints));
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hints.ai_family = PF_UNSPEC;
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hints.ai_socktype = SOCK_STREAM;
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hints.ai_flags = AI_PASSIVE;
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error = getaddrinfo(NULL, "http", &hints, &res0);
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if (error) {
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errx(1, "%s", gai_strerror(error));
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/*NOTREACHED*/
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}
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nsock = 0;
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for (res = res0; res && nsock < MAXSOCK; res = res->ai_next) {
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s[nsock] = socket(res->ai_family, res->ai_socktype,
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res->ai_protocol);
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if (s[nsock] < 0) {
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cause = "socket";
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continue;
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}
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if (bind(s[nsock], res->ai_addr, res->ai_addrlen) < 0) {
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cause = "bind";
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close(s[nsock]);
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continue;
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}
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(void) listen(s[nsock], 5);
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nsock++;
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}
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if (nsock == 0) {
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err(1, "%s", cause);
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/*NOTREACHED*/
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}
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freeaddrinfo(res0);
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.Ed
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.Sh SEE ALSO
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.Xr bind 2 ,
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.Xr connect 2 ,
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.Xr send 2 ,
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.Xr socket 2 ,
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.Xr gai_strerror 3 ,
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.Xr gethostbyname 3 ,
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.Xr getnameinfo 3 ,
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.Xr getservbyname 3 ,
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.Xr resolver 3 ,
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.Xr hosts 5 ,
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.Xr resolv.conf 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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.Rs
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.%A R. Gilligan
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.%A S. Thomson
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.%A J. Bound
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.%A J. McCann
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.%A W. Stevens
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.%T Basic Socket Interface Extensions for IPv6
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.%R RFC 3493
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.%D February 2003
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.Re
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.Rs
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.%A S. Deering
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.%A B. Haberman
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.%A T. Jinmei
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.%A E. Nordmark
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.%A B. Zill
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.%T "IPv6 Scoped Address Architecture"
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.%R internet draft
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.%N draft-ietf-ipv6-scoping-arch-02.txt
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.%O work in progress material
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.Re
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.Rs
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.%A Craig Metz
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.%T Protocol Independence Using the Sockets API
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.%B "Proceedings of the freenix track: 2000 USENIX annual technical conference"
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.%D June 2000
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.Re
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.Sh STANDARDS
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The
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.Fn getaddrinfo
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function is defined by the
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.St -p1003.1g-2000
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draft specification and documented in
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.Dv "RFC 3493" ,
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.Dq Basic Socket Interface Extensions for IPv6 .
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.Sh BUGS
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The implementation of
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.Fn getaddrinfo
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is not thread-safe.
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