lwres_freeaddrinfo
LWRES_GETADDRINFO(3) LWRES_GETADDRINFO(3)
NAME
lwres_getaddrinfo, lwres_freeaddrinfo - socket address structure to
host and service name
SYNOPSIS
#include <lwres/netdb.h>
int lwres_getaddrinfo(const char *hostname, const char *servname,
const struct addrinfo *hints, struct addrinfo **res);
void lwres_freeaddrinfo(struct addrinfo *ai);
If the operating system does not provide a struct addrinfo, the fol-
lowing structure is used:
struct addrinfo {
int ai_flags; /* AI_PASSIVE, AI_CANONNAME */
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 hostname */
struct sockaddr *ai_addr; /* binary address */
struct addrinfo *ai_next; /* next structure in linked list */
};
DESCRIPTION
lwres_getaddrinfo() is used to get a list of IP addresses and port
numbers for host hostname and service servname. The function is the
lightweight resolver’s implementation of getaddrinfo() as defined in
RFC2133. hostname and servname are pointers to null-terminated
strings or NULL. hostname is either a host name or a numeric host
address string: a dotted decimal IPv4 address or an IPv6 address.
servname is either a decimal port number or a service name as listed
in /etc/services.
hints is an optional pointer to a struct addrinfo. 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 struc-
ture elements in *hints:
ai_family
The protocol family that should be used. When ai_family is set
to PF_UNSPEC, it means the caller will accept any protocol fam-
ily supported by the operating system.
ai_socktype
denotes the type of socket — SOCK_STREAM, SOCK_DGRAM or
SOCK_RAW — that is wanted. When ai_socktype is zero the caller
will accept any socket type.
ai_protocol
indicates which transport protocol is wanted: IPPROTO_UDP or
IPPROTO_TCP. If ai_protocol is zero the caller will accept any
protocol.
ai_flags
Flag bits. If the AI_CANONNAME bit is set, a successful call
to lwres_getaddrinfo() will return a null-terminated string
containing the canonical name of the specified hostname in
ai_canonname of the first addrinfo structure returned. Setting
the AI_PASSIVE bit indicates that the returned socket address
structure is intended for used in a call to bind(2). In this
case, if the hostname argument is a NULL pointer, then the IP
address portion of the socket address structure will be set to
INADDR_ANY for an IPv4 address or IN6ADDR_ANY_INIT for an IPv6
address.
When ai_flags does not set the AI_PASSIVE bit, the returned
socket address structure will be ready for use in a call to
connect(2) for a connection-oriented protocol or connect(2),
sendto(2), or sendmsg(2) if a connectionless protocol was cho-
sen. The IP address portion of the socket address structure
will be set to the loopback address if hostname is a NULL
pointer and AI_PASSIVE is not set in ai_flags.
If ai_flags is set to AI_NUMERICHOST it indicates that hostname
should be treated as a numeric string defining an IPv4 or IPv6
address and no name resolution should be attempted.
All other elements of the struct addrinfo passed via hints must be
zero.
A hints of NULL is treated as if the caller provided a struct addrinfo
initialized to zero with ai_familyset to PF_UNSPEC.
After a successful call to lwres_getaddrinfo(), *res is a pointer to a
linked list of one or more addrinfo structures. Each struct addrinfo
in this list cn be processed by following the ai_next pointer, until a
NULL pointer is encountered. The three members ai_family, ai_sock-
type, and ai_protocol in each returned addrinfo structure contain the
corresponding arguments 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.
All of the information returned by lwres_getaddrinfo() is dynamically
allocated: the addrinfo structures, and the socket address structures
and canonical host name strings pointed to by the addrinfostructures.
Memory allocated for the dynamically allocated structures created by a
successful call to lwres_getaddrinfo() is released by lwres_freead-
drinfo(). ai is a pointer to a struct addrinfo created by a call to
lwres_getaddrinfo().
RETURN VALUES
lwres_getaddrinfo() returns zero on success or one of the error codes
listed in gai_strerror(3) if an error occurs. If both hostname and
servname are NULL lwres_getaddrinfo() returns EAI_NONAME.
SEE ALSO
lwres(3), lwres_getaddrinfo(3), lwres_freeaddrinfo(3), lwres_gai_str-
error(3), RFC2133, getservbyname(3), bind(2), connect(2), sendto(2),
sendmsg(2), socket(2).
BIND9 Jun 30, 2000 LWRES_GETADDRINFO(3)
