40452493ee
The getaddrinfo(3), getipnodebyname(3) and resolver(3) can coincide now with what should be totally reentrant, and h_errno values will now be preserved correctly, but this does not affect interfaces such as gethostbyname(3) which are still mostly non-reentrant. In all of these relevant functions, the thread-safety has been pushed down as far as it seems possible right now. This means that operations that are selected via nsdispatch(3) (i.e. files, yp, dns) are protected still under global locks that getaddrinfo(3) defines, but where possible the locking is greatly reduced. The most noticeable improvement is that multiple DNS lookups can now be run at the same time, and this shows major improvement in performance of DNS-lookup threaded programs, and solves the "Mozilla tab serialization" problem. No single-threaded applications need to be recompiled. Multi-threaded applications that reference "_res" to change resolver(3) options will need to be recompiled, and ones which reference "h_errno" will also if they desire the correct h_errno values. If the applications already understood that _res and h_errno were not thread-safe and had their own locking, they will see no performance improvement but will not actually break in any way. Please note that when NSS modules are used, or when nsdispatch(3) defaults to adding any lookups of its own to the individual libc _nsdispatch() calls, those MUST be reentrant as well.
632 lines
14 KiB
Groff
632 lines
14 KiB
Groff
.\" $KAME: getaddrinfo.3,v 1.31 2001/08/05 18:19:38 itojun Exp $
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.\"
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.\" 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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.\" $FreeBSD$
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.\"
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.Dd May 25, 1995
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.Dt GETADDRINFO 3
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.Os
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.\"
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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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.\"
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/types.h
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.In sys/socket.h
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.In 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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.\"
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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 the 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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but in a more sophisticated manner.
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.Pp
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The
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.Li addrinfo
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structure is defined as a result of including the
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.In 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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(i.e., a dotted-decimal IPv4 address or an IPv6 hex address).
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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
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.Dv 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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|
(for a connection-oriented protocol)
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or either
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.Fn connect ,
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.Fn sendto ,
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or
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.Fn sendmsg
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(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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The arguments to
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.Fn getaddrinfo
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|
must be sufficiently consistent and unambiguous.
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|
Here are some problem cases you may encounter:
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.Bl -bullet
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.It
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|
The
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.Fn getaddrinfo
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|
function
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|
will fail if the members in the
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|
.Fa hints
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|
structure are not consistent.
|
|
For example, for internet address families,
|
|
.Fn getaddrinfo
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|
will fail if you specify
|
|
.Dv SOCK_STREAM
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|
to
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|
.Fa ai_socktype
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|
while you specify
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.Dv IPPROTO_UDP
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|
to
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|
.Fa ai_protocol .
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|
.It
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|
If you specify a
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.Fa servname
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|
which is defined only for certain
|
|
.Fa ai_socktype ,
|
|
.Fn getaddrinfo
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|
will fail because the arguments are not consistent.
|
|
For example,
|
|
.Fn getaddrinfo
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|
will return an error if you ask for
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|
.Dq Li tftp
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|
service on
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|
.Dv SOCK_STREAM .
|
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.It
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|
For internet address families, if you specify
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|
.Fa servname
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|
while you set
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|
.Fa ai_socktype
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|
to
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|
.Dv SOCK_RAW ,
|
|
.Fn getaddrinfo
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|
will fail, because service names are not defined for the internet
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|
.Dv SOCK_RAW
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|
space.
|
|
.It
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|
If you specify numeric
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|
.Fa servname ,
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|
while leaving
|
|
.Fa ai_socktype
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|
and
|
|
.Fa ai_protocol
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|
unspecified,
|
|
.Fn getaddrinfo
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|
will fail.
|
|
This is because the numeric
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|
.Fa servname
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|
does not identify any socket type, and
|
|
.Fn getaddrinfo
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|
is not allowed to glob the argument in such case.
|
|
.El
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|
.Pp
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|
All of the information returned by
|
|
.Fn getaddrinfo
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|
is dynamically allocated:
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|
the
|
|
.Li addrinfo
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|
structures, the socket address structures, and canonical node name
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|
strings pointed to by the addrinfo structures.
|
|
To return this information to the system the function
|
|
.Fn freeaddrinfo
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|
is called.
|
|
The
|
|
.Vt addrinfo
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|
structure pointed to by the
|
|
.Fa ai
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|
argument
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|
is freed, along with any dynamic storage pointed to by the structure.
|
|
This operation is repeated until a
|
|
.Dv NULL
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|
.Fa ai_next
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|
pointer is encountered.
|
|
.Pp
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|
To aid applications in printing error messages based on the
|
|
.Dv EAI_xxx
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|
codes returned by
|
|
.Fn getaddrinfo ,
|
|
.Fn gai_strerror
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|
is defined.
|
|
The argument is one of the
|
|
.Dv EAI_xxx
|
|
values defined earlier and the return value points to a string describing
|
|
the error.
|
|
If the argument is not one of the
|
|
.Dv EAI_xxx
|
|
values, the function still returns a pointer to a string whose contents
|
|
indicate an unknown error.
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|
.\"
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|
.Sh EXTENSIONS
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|
This implementation supports numeric IPv6 address notation with the
|
|
experimental scope identifier.
|
|
By appending a percent sign and scope identifier to the address, you
|
|
can specify the value of the
|
|
.Li sin6_scope_id
|
|
field of the socket address.
|
|
This makes management of scoped address easier,
|
|
and allows cut-and-paste input of scoped addresses.
|
|
.Pp
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|
At the moment the code supports only link-local addresses in this format.
|
|
The scope identifier is hardcoded to name of hardware interface associated
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|
with the link,
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|
(such as
|
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.Li ne0 ) .
|
|
For example,
|
|
.Dq Li fe80::1%ne0 ,
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|
which means
|
|
.Do
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|
.Li fe80::1
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|
on the link associated with the
|
|
.Li ne0
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|
interface
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|
.Dc .
|
|
.Pp
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|
This implementation is still very experimental and non-standard.
|
|
The current implementation assumes a one-to-one relationship between
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interfaces and links, which is not necessarily true according to the
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|
specification.
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|
.\"
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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 stream socket.
|
|
It loops through all the addresses available, regardless of the address family.
|
|
If the destination resolves to an IPv4 address, it will use an
|
|
.Dv AF_INET
|
|
socket.
|
|
Similarly, if it resolves to IPv6, an
|
|
.Dv AF_INET6
|
|
socket is used.
|
|
Observe that there is no hardcoded reference to particular address family.
|
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The code works even if
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.Fn getaddrinfo
|
|
returns addresses that are not IPv4/v6.
|
|
.Bd -literal -offset indent
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|
struct addrinfo hints, *res, *res0;
|
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int error;
|
|
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);
|
|
if (error) {
|
|
errx(1, "%s", gai_strerror(error));
|
|
/*NOTREACHED*/
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|
}
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s = -1;
|
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cause = "no addresses";
|
|
errno = EADDRNOTAVAIL;
|
|
for (res = res0; res; res = res->ai_next) {
|
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s = socket(res->ai_family, res->ai_socktype,
|
|
res->ai_protocol);
|
|
if (s < 0) {
|
|
cause = "socket";
|
|
continue;
|
|
}
|
|
|
|
if (connect(s, res->ai_addr, res->ai_addrlen) < 0) {
|
|
cause = "connect";
|
|
close(s);
|
|
s = -1;
|
|
continue;
|
|
}
|
|
|
|
break; /* okay we got one */
|
|
}
|
|
if (s < 0) {
|
|
err(1, cause);
|
|
/*NOTREACHED*/
|
|
}
|
|
freeaddrinfo(res0);
|
|
.Ed
|
|
.Pp
|
|
The following example tries to open a wildcard listening socket onto service
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|
.Dq Li http ,
|
|
for all the address families available.
|
|
.Bd -literal -offset indent
|
|
struct addrinfo hints, *res, *res0;
|
|
int error;
|
|
int s[MAXSOCK];
|
|
int nsock;
|
|
const char *cause = NULL;
|
|
|
|
memset(&hints, 0, sizeof(hints));
|
|
hints.ai_family = PF_UNSPEC;
|
|
hints.ai_socktype = SOCK_STREAM;
|
|
hints.ai_flags = AI_PASSIVE;
|
|
error = getaddrinfo(NULL, "http", &hints, &res0);
|
|
if (error) {
|
|
errx(1, "%s", gai_strerror(error));
|
|
/*NOTREACHED*/
|
|
}
|
|
nsock = 0;
|
|
for (res = res0; res && nsock < MAXSOCK; res = res->ai_next) {
|
|
s[nsock] = socket(res->ai_family, res->ai_socktype,
|
|
res->ai_protocol);
|
|
if (s[nsock] < 0) {
|
|
cause = "socket";
|
|
continue;
|
|
}
|
|
|
|
if (bind(s[nsock], res->ai_addr, res->ai_addrlen) < 0) {
|
|
cause = "bind";
|
|
close(s[nsock]);
|
|
continue;
|
|
}
|
|
|
|
if (listen(s[nsock], SOMAXCONN) < 0) {
|
|
cause = "listen";
|
|
close(s[nsock]);
|
|
continue;
|
|
}
|
|
|
|
nsock++;
|
|
}
|
|
if (nsock == 0) {
|
|
err(1, cause);
|
|
/*NOTREACHED*/
|
|
}
|
|
freeaddrinfo(res0);
|
|
.Ed
|
|
.\"
|
|
.Sh FILES
|
|
.Bl -tag -width /etc/nsswitch.conf -compact
|
|
.It Pa /etc/hosts
|
|
.It Pa /etc/nsswitch.conf
|
|
.It Pa /etc/resolv.conf
|
|
.El
|
|
.\"
|
|
.Sh DIAGNOSTICS
|
|
Error return status from
|
|
.Fn getaddrinfo
|
|
is zero on success and non-zero on errors.
|
|
Non-zero error codes are defined in
|
|
.In netdb.h ,
|
|
and as follows:
|
|
.Pp
|
|
.Bl -tag -width EAI_ADDRFAMILY -compact
|
|
.It Dv EAI_AGAIN
|
|
Temporary failure in name resolution.
|
|
.It Dv EAI_BADFLAGS
|
|
Invalid value for
|
|
.Fa ai_flags .
|
|
.It Dv EAI_FAIL
|
|
Non-recoverable failure in name resolution.
|
|
.It Dv EAI_FAMILY
|
|
The
|
|
.Fa ai_family
|
|
address family is
|
|
not supported.
|
|
.It Dv EAI_MEMORY
|
|
Memory allocation failure.
|
|
.It Dv EAI_NONAME
|
|
Neither
|
|
.Fa nodename
|
|
nor
|
|
.Fa servname
|
|
provided, or not known.
|
|
.It Dv EAI_SERVICE
|
|
The
|
|
.Fa servname
|
|
service name is
|
|
not supported for
|
|
.Fa ai_socktype .
|
|
.It Dv EAI_SOCKTYPE
|
|
The
|
|
.Fa ai_socktype
|
|
socket type is
|
|
not supported.
|
|
.It Dv EAI_SYSTEM
|
|
System error returned in
|
|
.Va errno .
|
|
.It Dv EAI_BADHINTS
|
|
Invalid value for
|
|
.Fa hints .
|
|
.It Dv EAI_PROTOCOL
|
|
Resolved protocol is unknown.
|
|
.It Dv EAI_MAX
|
|
Unknown error.
|
|
.El
|
|
.Pp
|
|
If called with an appropriate argument,
|
|
.Fn gai_strerror
|
|
returns a pointer to a string describing the given error code.
|
|
If the argument is not one of the
|
|
.Dv EAI_xxx
|
|
values, the function still returns a pointer to a string whose contents
|
|
indicate an unknown error.
|
|
.\"
|
|
.Sh SEE ALSO
|
|
.Xr gethostbyname 3 ,
|
|
.Xr getnameinfo 3 ,
|
|
.Xr getservbyname 3 ,
|
|
.Xr hosts 5 ,
|
|
.Xr resolv.conf 5 ,
|
|
.Xr services 5 ,
|
|
.Xr hostname 7 ,
|
|
.Xr named 8
|
|
.Pp
|
|
.Rs
|
|
.%A R. Gilligan
|
|
.%A S. Thomson
|
|
.%A J. Bound
|
|
.%A W. Stevens
|
|
.%T Basic Socket Interface Extensions for IPv6
|
|
.%R RFC2553
|
|
.%D March 1999
|
|
.Re
|
|
.Rs
|
|
.%A Tatsuya Jinmei
|
|
.%A Atsushi Onoe
|
|
.%T "An Extension of Format for IPv6 Scoped Addresses"
|
|
.%R internet draft
|
|
.%N draft-ietf-ipngwg-scopedaddr-format-02.txt
|
|
.%O work in progress material
|
|
.Re
|
|
.Rs
|
|
.%A Craig Metz
|
|
.%T Protocol Independence Using the Sockets API
|
|
.%B "Proceedings of the freenix track: 2000 USENIX annual technical conference"
|
|
.%D June 2000
|
|
.Re
|
|
.\"
|
|
.Sh HISTORY
|
|
The implementation first appeared in WIDE Hydrangea IPv6 protocol stack kit.
|
|
.\"
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn getaddrinfo
|
|
function is defined in
|
|
.St -p1003.1g-2000 ,
|
|
and documented in
|
|
.Dq Basic Socket Interface Extensions for IPv6
|
|
(RFC2553).
|
|
.\"
|
|
.Sh BUGS
|
|
Although the current implementation is otherwise thread-safe, using
|
|
.Fn getaddrinfo
|
|
in conjunction with
|
|
.Fn gethostby*
|
|
(see
|
|
.Xr gethostbyname 3 )
|
|
or
|
|
.Xr yp 8
|
|
breaks the thread-safety of both.
|
|
.Pp
|
|
The text was shamelessly copied from RFC2553.
|