437 lines
10 KiB
Groff
437 lines
10 KiB
Groff
.\" $KAME: getaddrinfo.3,v 1.36 2005/01/05 03:23:05 itojun Exp $
|
|
.\" $OpenBSD: getaddrinfo.3,v 1.35 2004/12/21 03:40:31 jaredy Exp $
|
|
.\"
|
|
.\" Copyright (C) 2004 Internet Systems Consortium, Inc. ("ISC")
|
|
.\" Copyright (C) 2000, 2001 Internet Software Consortium.
|
|
.\"
|
|
.\" Permission to use, copy, modify, and 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.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd December 20, 2004
|
|
.Dt GETADDRINFO 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm getaddrinfo ,
|
|
.Nm freeaddrinfo
|
|
.Nd socket address structure to host and service name
|
|
.Sh SYNOPSIS
|
|
.Fd #include <sys/types.h>
|
|
.Fd #include <sys/socket.h>
|
|
.Fd #include <netdb.h>
|
|
.Ft int
|
|
.Fn getaddrinfo "const char *hostname" "const char *servname" \
|
|
"const struct addrinfo *hints" "struct addrinfo **res"
|
|
.Ft void
|
|
.Fn freeaddrinfo "struct addrinfo *ai"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn getaddrinfo
|
|
function is used to get a list of
|
|
.Tn IP
|
|
addresses and port numbers for host
|
|
.Fa hostname
|
|
and service
|
|
.Fa servname .
|
|
It is a replacement for and provides more flexibility than the
|
|
.Xr gethostbyname 3
|
|
and
|
|
.Xr getservbyname 3
|
|
functions.
|
|
.Pp
|
|
The
|
|
.Fa hostname
|
|
and
|
|
.Fa servname
|
|
arguments are either pointers to NUL-terminated strings or the null pointer.
|
|
An acceptable value for
|
|
.Fa hostname
|
|
is either a valid host name or a numeric host address string consisting
|
|
of a dotted decimal IPv4 address or an IPv6 address.
|
|
The
|
|
.Fa servname
|
|
is either a decimal port number or a service name listed in
|
|
.Xr services 5 .
|
|
At least one of
|
|
.Fa hostname
|
|
and
|
|
.Fa servname
|
|
must be non-null.
|
|
.Pp
|
|
.Fa hints
|
|
is an optional pointer to a
|
|
.Li struct addrinfo ,
|
|
as defined by
|
|
.Aq Pa netdb.h :
|
|
.Bd -literal
|
|
struct addrinfo {
|
|
int ai_flags; /* input flags */
|
|
int ai_family; /* protocol family for socket */
|
|
int ai_socktype; /* socket type */
|
|
int ai_protocol; /* protocol for socket */
|
|
socklen_t ai_addrlen; /* length of socket-address */
|
|
struct sockaddr *ai_addr; /* socket-address for socket */
|
|
char *ai_canonname; /* canonical name for service location */
|
|
struct addrinfo *ai_next; /* pointer to next in list */
|
|
};
|
|
.Ed
|
|
.Pp
|
|
This structure can be used to provide hints concerning the type of socket
|
|
that the caller supports or wishes to use.
|
|
The caller can supply the following structure elements in
|
|
.Fa hints :
|
|
.Bl -tag -width "ai_socktypeXX"
|
|
.It Fa ai_family
|
|
The protocol family that should be used.
|
|
When
|
|
.Fa ai_family
|
|
is set to
|
|
.Dv PF_UNSPEC ,
|
|
it means the caller will accept any protocol family supported by the
|
|
operating system.
|
|
.It Fa ai_socktype
|
|
Denotes the type of socket that is wanted:
|
|
.Dv SOCK_STREAM ,
|
|
.Dv SOCK_DGRAM ,
|
|
or
|
|
.Dv SOCK_RAW .
|
|
When
|
|
.Fa ai_socktype
|
|
is zero the caller will accept any socket type.
|
|
.It Fa ai_protocol
|
|
Indicates which transport protocol is desired,
|
|
.Dv IPPROTO_UDP
|
|
or
|
|
.Dv IPPROTO_TCP .
|
|
If
|
|
.Fa ai_protocol
|
|
is zero the caller will accept any protocol.
|
|
.It Fa ai_flags
|
|
.Fa ai_flags
|
|
is formed by
|
|
.Tn OR Ns 'ing
|
|
the following values:
|
|
.Bl -tag -width "AI_CANONNAMEXX"
|
|
.It Dv AI_CANONNAME
|
|
If the
|
|
.Dv AI_CANONNAME
|
|
bit is set, a successful call to
|
|
.Fn getaddrinfo
|
|
will return a NUL-terminated string containing the canonical name
|
|
of the specified hostname in the
|
|
.Fa ai_canonname
|
|
element of the first
|
|
.Li addrinfo
|
|
structure returned.
|
|
.It Dv AI_NUMERICHOST
|
|
If the
|
|
.Dv AI_NUMERICHOST
|
|
bit is set, it indicates that
|
|
.Fa hostname
|
|
should be treated as a numeric string defining an IPv4 or IPv6 address
|
|
and no name resolution should be attempted.
|
|
.It Dv AI_PASSIVE
|
|
If the
|
|
.Dv AI_PASSIVE
|
|
bit is set it indicates that the returned socket address structure
|
|
is intended for use in a call to
|
|
.Xr bind 2 .
|
|
In this case, if the
|
|
.Fa hostname
|
|
argument is the 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, the returned socket address structure will be ready
|
|
for use in a call to
|
|
.Xr connect 2
|
|
for a connection-oriented protocol or
|
|
.Xr connect 2 ,
|
|
.Xr sendto 2 ,
|
|
or
|
|
.Xr sendmsg 2
|
|
if a connectionless protocol was chosen.
|
|
The
|
|
.Tn IP
|
|
address portion of the socket address structure will be set to the
|
|
loopback address if
|
|
.Fa hostname
|
|
is the null pointer and
|
|
.Dv AI_PASSIVE
|
|
is not set.
|
|
.El
|
|
.El
|
|
.Pp
|
|
All other elements of the
|
|
.Li addrinfo
|
|
structure passed via
|
|
.Fa hints
|
|
must be zero or the null pointer.
|
|
.Pp
|
|
If
|
|
.Fa hints
|
|
is the null pointer,
|
|
.Fn getaddrinfo
|
|
behaves as if the caller provided a
|
|
.Li struct addrinfo
|
|
with
|
|
.Fa ai_family
|
|
set to
|
|
.Dv PF_UNSPEC
|
|
and all other elements set to zero or
|
|
.Dv NULL .
|
|
.Pp
|
|
After a successful call to
|
|
.Fn getaddrinfo ,
|
|
.Fa *res
|
|
is a pointer to a linked list of one or more
|
|
.Li addrinfo
|
|
structures.
|
|
The list can be traversed by following the
|
|
.Fa ai_next
|
|
pointer in each
|
|
.Li addrinfo
|
|
structure until a null pointer is encountered.
|
|
The three members
|
|
.Fa ai_family,
|
|
.Fa ai_socktype,
|
|
and
|
|
.Fa ai_protocol
|
|
in each returned
|
|
.Li addrinfo
|
|
structure are suitable for a call to
|
|
.Xr socket 2 .
|
|
For each
|
|
.Li addrinfo
|
|
structure in the list, the
|
|
.Fa ai_addr
|
|
member points to a filled-in socket address structure of length
|
|
.Fa ai_addrlen .
|
|
.Pp
|
|
This implementation of
|
|
.Fn getaddrinfo
|
|
allows numeric IPv6 address notation with scope identifier,
|
|
as documented in chapter 11 of draft-ietf-ipv6-scoping-arch-02.txt.
|
|
By appending the percent character and scope identifier to addresses,
|
|
one can fill the
|
|
.Li sin6_scope_id
|
|
field for addresses.
|
|
This would make management of scoped addresses easier
|
|
and allows cut-and-paste input of scoped addresses.
|
|
.Pp
|
|
At this moment the code supports only link-local addresses with the format.
|
|
The scope identifier is hardcoded to the name of the hardware interface
|
|
associated
|
|
with the link
|
|
.Po
|
|
such as
|
|
.Li ne0
|
|
.Pc .
|
|
An example is
|
|
.Dq Li fe80::1%ne0 ,
|
|
which means
|
|
.Do
|
|
.Li fe80::1
|
|
on the link associated with the
|
|
.Li ne0
|
|
interface
|
|
.Dc .
|
|
.Pp
|
|
The current implementation assumes a one-to-one relationship between
|
|
the interface and link, which is not necessarily true from the specification.
|
|
.Pp
|
|
All of the information returned by
|
|
.Fn getaddrinfo
|
|
is dynamically allocated: the
|
|
.Li addrinfo
|
|
structures themselves as well as the socket address structures and
|
|
the canonical host name strings included in the
|
|
.Li addrinfo
|
|
structures.
|
|
.Pp
|
|
Memory allocated for the dynamically allocated structures created by
|
|
a successful call to
|
|
.Fn getaddrinfo
|
|
is released by the
|
|
.Fn freeaddrinfo
|
|
function.
|
|
The
|
|
.Fa ai
|
|
pointer should be a
|
|
.Li addrinfo
|
|
structure created by a call to
|
|
.Fn getaddrinfo .
|
|
.Sh RETURN VALUES
|
|
.Fn getaddrinfo
|
|
returns zero on success or one of the error codes listed in
|
|
.Xr gai_strerror 3
|
|
if an error occurs.
|
|
.Sh EXAMPLES
|
|
The following code tries to connect to
|
|
.Dq Li www.kame.net
|
|
service
|
|
.Dq Li http
|
|
via a stream socket.
|
|
It loops through all the addresses available, regardless of 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 a particular address family.
|
|
The code works even if
|
|
.Fn getaddrinfo
|
|
returns addresses that are not IPv4/v6.
|
|
.Bd -literal -offset indent
|
|
struct addrinfo hints, *res, *res0;
|
|
int error;
|
|
int s;
|
|
const char *cause = NULL;
|
|
|
|
memset(&hints, 0, sizeof(hints));
|
|
hints.ai_family = PF_UNSPEC;
|
|
hints.ai_socktype = SOCK_STREAM;
|
|
error = getaddrinfo("www.kame.net", "http", &hints, &res0);
|
|
if (error) {
|
|
errx(1, "%s", gai_strerror(error));
|
|
/*NOTREACHED*/
|
|
}
|
|
s = -1;
|
|
for (res = res0; res; res = res->ai_next) {
|
|
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, "%s", cause);
|
|
/*NOTREACHED*/
|
|
}
|
|
freeaddrinfo(res0);
|
|
.Ed
|
|
.Pp
|
|
The following example tries to open a wildcard listening socket onto service
|
|
.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;
|
|
}
|
|
(void) listen(s[nsock], 5);
|
|
|
|
nsock++;
|
|
}
|
|
if (nsock == 0) {
|
|
err(1, "%s", cause);
|
|
/*NOTREACHED*/
|
|
}
|
|
freeaddrinfo(res0);
|
|
.Ed
|
|
.Sh SEE ALSO
|
|
.Xr bind 2 ,
|
|
.Xr connect 2 ,
|
|
.Xr send 2 ,
|
|
.Xr socket 2 ,
|
|
.Xr gai_strerror 3 ,
|
|
.Xr gethostbyname 3 ,
|
|
.Xr getnameinfo 3 ,
|
|
.Xr getservbyname 3 ,
|
|
.Xr resolver 3 ,
|
|
.Xr hosts 5 ,
|
|
.Xr resolv.conf 5 ,
|
|
.Xr services 5 ,
|
|
.Xr hostname 7 ,
|
|
.Xr named 8
|
|
.Rs
|
|
.%A R. Gilligan
|
|
.%A S. Thomson
|
|
.%A J. Bound
|
|
.%A J. McCann
|
|
.%A W. Stevens
|
|
.%T Basic Socket Interface Extensions for IPv6
|
|
.%R RFC 3493
|
|
.%D February 2003
|
|
.Re
|
|
.Rs
|
|
.%A S. Deering
|
|
.%A B. Haberman
|
|
.%A T. Jinmei
|
|
.%A E. Nordmark
|
|
.%A B. Zill
|
|
.%T "IPv6 Scoped Address Architecture"
|
|
.%R internet draft
|
|
.%N draft-ietf-ipv6-scoping-arch-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 STANDARDS
|
|
The
|
|
.Fn getaddrinfo
|
|
function is defined by the
|
|
.St -p1003.1g-2000
|
|
draft specification and documented in
|
|
.Dv "RFC 3493" ,
|
|
.Dq Basic Socket Interface Extensions for IPv6 .
|
|
.Sh BUGS
|
|
The implementation of
|
|
.Fn getaddrinfo
|
|
is not thread-safe.
|