\"      $NetBSD: getaddrinfo.3,v 1.1.1.2 2012/09/09 16:07:46 christos Exp $
\"
\" Copyright (C) 2009  Internet Systems Consortium, Inc. ("ISC")
\"
\" Permission to use, copy, modify, and/or distribute this software for any
\" purpose with or without fee is hereby granted, provided that the above
\" copyright notice and this permission notice appear in all copies.
\"
\" THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
\" REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
\" AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
\" INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
\" LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
\" OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
\" PERFORMANCE OF THIS SOFTWARE.
\"
\"     Id: getaddrinfo.3,v 1.3 2009/01/22 23:49:23 tbox Exp
\"
Dd May 25, 1995
Dt GETADDRINFO @LIB_NETWORK_EXT@
Os KAME
Sh NAME
Nm getaddrinfo
Nm freeaddrinfo ,
Nm gai_strerror
Nd nodename-to-address translation in protocol-independent manner
Sh SYNOPSIS
Fd #include <sys/socket.h>
Fd #include <netdb.h>
Ft int
Fn getaddrinfo "const char *nodename" "const char *servname" \
"const struct addrinfo *hints" "struct addrinfo **res"
Ft void
Fn freeaddrinfo "struct addrinfo *ai"
Ft "char *"
Fn gai_strerror "int ecode"
Sh DESCRIPTION
The
Fn getaddrinfo
function is defined for protocol-independent nodename-to-address translation.
It performs functionality of
Xr gethostbyname @LIB_NETWORK_EXT@
and
Xr getservbyname @LIB_NETWORK_EXT@ ,
in more sophisticated manner.
Pp
The addrinfo structure is defined as a result of including the
Li <netdb.h>
header:
Bd -literal -offset
struct addrinfo {                                                  *
    int     ai_flags;     /* AI_PASSIVE, AI_CANONNAME, AI_NUMERICHOST */
    int     ai_family;    /* PF_xxx */
    int     ai_socktype;  /* SOCK_xxx */
    int     ai_protocol;  /* 0 or IPPROTO_xxx for IPv4 and IPv6 */
    size_t  ai_addrlen;   /* length of ai_addr */
    char   *ai_canonname; /* canonical name for nodename */
    struct sockaddr  *ai_addr; /* binary address */
    struct addrinfo  *ai_next; /* next structure in linked list */
};
Ed
Pp
The
Fa nodename
and
Fa servname
arguments are pointers to null-terminated strings or
Dv NULL .
One or both of these two arguments must be a
Pf non Dv -NULL
pointer.
In the normal client scenario, both the
Fa nodename
and
Fa servname
are specified.
In the normal server scenario, only the
Fa servname
is specified.
A
Pf non Dv -NULL
Fa nodename
string can be either a node name or a numeric host address string
(i.e., a dotted-decimal IPv4 address or an IPv6 hex address).
A
Pf non Dv -NULL
Fa servname
string can be either a service name or a decimal port number.
Pp
The caller can optionally pass an
Li addrinfo
structure, pointed to by the third argument,
to provide hints concerning the type of socket that the caller supports.
In this
Fa hints
structure all members other than
Fa ai_flags ,
Fa ai_family ,
Fa ai_socktype ,
and
Fa ai_protocol
must be zero or a
Dv NULL
pointer.
A value of
Dv PF_UNSPEC
for
Fa ai_family
means the caller will accept any protocol family.
A value of 0 for
Fa ai_socktype
means the caller will accept any socket type.
A value of 0 for
Fa ai_protocol
means the caller will accept any protocol.
For example, if the caller handles only TCP and not UDP, then the
Fa ai_socktype
member of the hints structure should be set to
Dv SOCK_STREAM
when
Fn getaddrinfo
is called.
If the caller handles only IPv4 and not IPv6, then the
Fa ai_family
member of the
Fa hints
structure should be set to
Dv PF_INET
when
Fn getaddrinfo
is called.
If the third argument to
Fn getaddrinfo
is a
Dv NULL
pointer, this is the same as if the caller had filled in an
Li addrinfo
structure initialized to zero with
Fa ai_family
set to PF_UNSPEC.
Pp
Upon successful return a pointer to a linked list of one or more
Li addrinfo
structures is returned through the final argument.
The caller can process each
Li addrinfo
structure in this list by following the
Fa ai_next
pointer, until a
Dv NULL
pointer is encountered.
In each returned
Li addrinfo
structure the three members
Fa ai_family ,
Fa ai_socktype ,
and
Fa ai_protocol
are the corresponding arguments for a call to the
Fn socket
function.
In each
Li addrinfo
structure the
Fa ai_addr
member points to a filled-in socket address structure whose length is
specified by the
Fa ai_addrlen
member.
Pp
If the
Dv AI_PASSIVE
bit is set in the
Fa ai_flags
member of the
Fa hints
structure, then the caller plans to use the returned socket address
structure in a call to
Fn bind .
In this case, if the
Fa nodename
argument is a
Dv NULL
pointer, then the IP address portion of the socket
address structure will be set to
Dv INADDR_ANY
for an IPv4 address or
Dv IN6ADDR_ANY_INIT
for an IPv6 address.
Pp
If the
Dv AI_PASSIVE
bit is not set in the
Fa ai_flags
member of the
Fa hints
structure, then the returned socket address structure will be ready for a
call to
Fn connect
Pq for a connection-oriented protocol
or either
Fn connect ,
Fn sendto ,
or
Fn sendmsg
Pq for a connectionless protocol .
In this case, if the
Fa nodename
argument is a
Dv NULL
pointer, then the IP address portion of the
socket address structure will be set to the loopback address.
Pp
If the
Dv AI_CANONNAME
bit is set in the
Fa ai_flags
member of the
Fa hints
structure, then upon successful return the
Fa ai_canonname
member of the first
Li addrinfo
structure in the linked list will point to a null-terminated string
containing the canonical name of the specified
Fa nodename .
Pp
If the
Dv AI_NUMERICHOST
bit is set in the
Fa ai_flags
member of the
Fa hints
structure, then a
Pf non Dv -NULL
Fa nodename
string must be a numeric host address string.
Otherwise an error of
Dv EAI_NONAME
is returned.
This flag prevents any type of name resolution service (e.g., the DNS)
from being called.
Pp
All of the information returned by
Fn getaddrinfo
is dynamically allocated:
the
Li addrinfo
structures, and the socket address structures and canonical node name
strings pointed to by the addrinfo structures.
To return this information to the system the function
Fn freeaddrinfo
is called.
The
Fa addrinfo
structure pointed to by the
Fa ai argument
is freed, along with any dynamic storage pointed to by the structure.
This operation is repeated until a
Dv NULL
Fa ai_next
pointer is encountered.
Pp
To aid applications in printing error messages based on the
Dv EAI_xxx
codes returned by
Fn getaddrinfo ,
Fn gai_strerror
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.
Sh FILES
Bl -tag -width /etc/resolv.conf -compact
It Pa /etc/hosts
It Pa /etc/host.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
Li <netdb.h> ,
and as follows:
Pp
Bl -tag -width EAI_ADDRFAMILY -compact
It Dv EAI_ADDRFAMILY
address family for nodename not supported
It Dv EAI_AGAIN
temporary failure in name resolution
It Dv EAI_BADFLAGS
invalid value for ai_flags
It Dv EAI_FAIL
non-recoverable failure in name resolution
It Dv EAI_FAMILY
ai_family not supported
It Dv EAI_MEMORY
memory allocation failure
It Dv EAI_NODATA
no address associated with nodename
It Dv EAI_NONAME
nodename nor servname provided, or not known
It Dv EAI_SERVICE
servname not supported for ai_socktype
It Dv EAI_SOCKTYPE
ai_socktype not supported
It Dv EAI_SYSTEM
system error returned in errno
El
Pp
If called with proper 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 getnameinfo @LIB_NETWORK_EXT@ ,
Xr gethostbyname @LIB_NETWORK_EXT@ ,
Xr getservbyname @LIB_NETWORK_EXT@ ,
Xr hosts @FORMAT_EXT@ ,
Xr services @FORMAT_EXT@ ,
Xr hostname @DESC_EXT@
Pp
R. Gilligan, S.  Thomson, J. Bound, and W. Stevens,
``Basic Socket Interface Extensions for IPv6,'' RFC2133, April 1997.
Sh HISTORY
The implementation first appeared in WIDE Hydrangea IPv6 protocol stack kit.
Sh STANDARDS
The
Fn getaddrinfo
function is defined IEEE POSIX 1003.1g draft specification,
and documented in ``Basic Socket Interface Extensions for IPv6''
(RFC2133).
Sh BUGS
The text was shamelessly copied from RFC2133.

You are viewing proxied material from ftp.icm.edu.pl. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.