1 .\" $KAME: getaddrinfo.3,v 1.36 2005/01/05 03:23:05 itojun Exp $
2 .\" $OpenBSD: getaddrinfo.3,v 1.35 2004/12/21 03:40:31 jaredy Exp $
3 .\" $FreeBSD: src/lib/libc/net/getaddrinfo.3,v 1.29 2005/01/23 16:02:48 gnn Exp $
4 .\" $DragonFly: src/lib/libc/net/getaddrinfo.3,v 1.6 2007/08/18 20:48:47 swildner Exp $
6 .\" Copyright (C) 2004 Internet Systems Consortium, Inc. ("ISC")
7 .\" Copyright (C) 2000, 2001 Internet Software Consortium.
9 .\" Permission to use, copy, modify, and distribute this software for any
10 .\" purpose with or without fee is hereby granted, provided that the above
11 .\" copyright notice and this permission notice appear in all copies.
13 .\" THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
14 .\" REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
15 .\" AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
16 .\" INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
17 .\" LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
18 .\" OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
19 .\" PERFORMANCE OF THIS SOFTWARE.
27 .Nd socket address structure to host and service name
35 .Fn getaddrinfo "const char *hostname" "const char *servname" \
36 "const struct addrinfo *hints" "struct addrinfo **res"
38 .Fn freeaddrinfo "struct addrinfo *ai"
42 function is used to get a list of
44 addresses and port numbers for host
48 It is a replacement for and provides more flexibility than the
58 arguments are either pointers to NUL-terminated strings or the null pointer.
59 An acceptable value for
61 is either a valid host name or a numeric host address string consisting
62 of a dotted decimal IPv4 address or an IPv6 address.
65 is either a decimal port number or a service name listed in
74 is an optional pointer to a
80 int ai_flags; /* input flags */
81 int ai_family; /* protocol family for socket */
82 int ai_socktype; /* socket type */
83 int ai_protocol; /* protocol for socket */
84 socklen_t ai_addrlen; /* length of socket-address */
85 struct sockaddr *ai_addr; /* socket-address for socket */
86 char *ai_canonname; /* canonical name for service location */
87 struct addrinfo *ai_next; /* pointer to next in list */
91 This structure can be used to provide hints concerning the type of socket
92 that the caller supports or wishes to use.
93 The caller can supply the following structure elements in
95 .Bl -tag -width "ai_socktypeXX"
97 The protocol family that should be used.
102 it means the caller will accept any protocol family supported by the
105 Denotes the type of socket that is wanted:
112 is zero the caller will accept any socket type.
114 Indicates which transport protocol is desired,
120 is zero the caller will accept any protocol.
125 the following values:
126 .Bl -tag -width "AI_CANONNAMEXX"
130 bit is set, a successful call to
132 will return a NUL-terminated string containing the canonical name
133 of the specified hostname in the
138 .It Dv AI_NUMERICHOST
141 bit is set, it indicates that
143 should be treated as a numeric string defining an IPv4 or IPv6 address
144 and no name resolution should be attempted.
148 bit is set it indicates that the returned socket address structure
149 is intended for use in a call to
153 argument is the null pointer, then the IP address portion of the
154 socket address structure will be set to
156 for an IPv4 address or
162 bit is not set, the returned socket address structure will be ready
165 for a connection-oriented protocol or
170 if a connectionless protocol was chosen.
173 address portion of the socket address structure will be set to the
176 is the null pointer and
182 All other elements of the
186 must be zero or the null pointer.
192 behaves as if the caller provided a
198 and all other elements set to zero or
201 After a successful call to
204 is a pointer to a linked list of one or more
207 The list can be traversed by following the
211 structure until a null pointer is encountered.
219 structure are suitable for a call to
223 structure in the list, the
225 member points to a filled-in socket address structure of length
228 This implementation of
230 allows numeric IPv6 address notation with scope identifier,
231 as documented in chapter 11 of draft-ietf-ipv6-scoping-arch-02.txt.
232 By appending the percent character and scope identifier to addresses,
236 This would make management of scoped addresses easier
237 and allows cut-and-paste input of scoped addresses.
239 At this moment the code supports only link-local addresses with the format.
240 The scope identifier is hardcoded to the name of the hardware interface
252 on the link associated with the
257 The current implementation assumes a one-to-one relationship between
258 the interface and link, which is not necessarily true from the specification.
260 All of the information returned by
262 is dynamically allocated: the
264 structures themselves as well as the socket address structures and
265 the canonical host name strings included in the
269 Memory allocated for the dynamically allocated structures created by
279 structure created by a call to
283 returns zero on success or one of the error codes listed in
287 The following code tries to connect to
292 It loops through all the addresses available, regardless of address family.
293 If the destination resolves to an IPv4 address, it will use an
296 Similarly, if it resolves to IPv6, an
299 Observe that there is no hardcoded reference to a particular address family.
300 The code works even if
302 returns addresses that are not IPv4/v6.
303 .Bd -literal -offset indent
304 struct addrinfo hints, *res, *res0;
307 const char *cause = NULL;
309 memset(&hints, 0, sizeof(hints));
310 hints.ai_family = PF_UNSPEC;
311 hints.ai_socktype = SOCK_STREAM;
312 error = getaddrinfo("www.kame.net", "http", &hints, &res0);
314 errx(1, "%s", gai_strerror(error));
318 for (res = res0; res; res = res->ai_next) {
319 s = socket(res->ai_family, res->ai_socktype,
326 if (connect(s, res->ai_addr, res->ai_addrlen) < 0) {
333 break; /* okay we got one */
342 The following example tries to open a wildcard listening socket onto service
344 for all the address families available.
345 .Bd -literal -offset indent
346 struct addrinfo hints, *res, *res0;
350 const char *cause = NULL;
352 memset(&hints, 0, sizeof(hints));
353 hints.ai_family = PF_UNSPEC;
354 hints.ai_socktype = SOCK_STREAM;
355 hints.ai_flags = AI_PASSIVE;
356 error = getaddrinfo(NULL, "http", &hints, &res0);
358 errx(1, "%s", gai_strerror(error));
362 for (res = res0; res && nsock < MAXSOCK; res = res->ai_next) {
363 s[nsock] = socket(res->ai_family, res->ai_socktype,
370 if (bind(s[nsock], res->ai_addr, res->ai_addrlen) < 0) {
375 (void) listen(s[nsock], 5);
391 .Xr gethostbyname 3 ,
393 .Xr getservbyname 3 ,
406 .%T Basic Socket Interface Extensions for IPv6
416 .%T "IPv6 Scoped Address Architecture"
418 .%N draft-ietf-ipv6-scoping-arch-02.txt
419 .%O work in progress material
423 .%T Protocol Independence Using the Sockets API
424 .%B "Proceedings of the freenix track: 2000 USENIX annual technical conference"
430 function is defined by the
432 draft specification and documented in
434 .Dq Basic Socket Interface Extensions for IPv6 .
436 The implementation of