CONTENTS

SYNOPSIS

DESCRIPTION

The hostname and servname arguments are either pointers to NUL-terminated strings or the null pointer. An acceptable value for 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 servname is either a decimal port number or a service name listed in services(5). At least one of hostname and servname must be non-null.

hints is an optional pointer to a struct addrinfo, as defined by <netdb.h>:
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 */
};

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 hints:

All other elements of the addrinfo structure passed via hints must be zero or the null pointer.

If hints is the null pointer, getaddrinfo behaves as if the caller provided a struct addrinfo with ai_family set to PF_UNSPEC and all other elements set to zero or NULL.

After a successful call to getaddrinfo, *res is a pointer to a linked list of one or more addrinfo structures. The list can be traversed by following the ai_next pointer in each addrinfo structure until a null pointer is encountered. The three members ai_family, ai_socktype, and ai_protocol in each returned addrinfo structure are suitable for a call to socket(2). For each addrinfo structure in the list, the ai_addr member points to a filled-in socket address structure of length ai_addrlen.

This implementation of 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 sin6_scope_id field for addresses. This would make management of scoped addresses easier and allows cut-and-paste input of scoped addresses.

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 ( such as ne0 ). An example is "fe80::1%ne0", which means " fe80::1 on the link associated with the ne0 interface ".

The current implementation assumes a one-to-one relationship between the interface and link, which is not necessarily true from the specification.

All of the information returned by getaddrinfo is dynamically allocated: the addrinfo structures themselves as well as the socket address structures and the canonical host name strings included in the addrinfo structures.

EXAMPLES

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);

The following example tries to open a wildcard listening socket onto service "http", for all the address families available.
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);

STANDARDS