LWRES_GETIPNODE(3)LWRES_GETIPNODE(3)NAME
lwres_getipnodebyname, lwres_getipnodebyaddr, lwres_free-
hostent - lightweight resolver nodename / address transla-
tion API
SYNOPSIS
#include <lwres/netdb.h>
struct hostent * lwres_getipnodebyname(const char *name,
int af, int flags, int *error_num);
struct hostent * lwres_getipnodebyaddr(const void *src,
size_t len, int af, int *error_num);
void lwres_freehostent(struct hostent *he);
DESCRIPTION
These functions perform thread safe, protocol independent
nodename-to-address and address-to-nodename translation as
defined in RFC2553.
They use a struct hostent which is defined in namedb.h:
struct hostent {
char *h_name; /* official name of host */
char **h_aliases; /* alias list */
int h_addrtype; /* host address type */
int h_length; /* length of address */
char **h_addr_list; /* list of addresses from name server */
};
#define h_addr h_addr_list[0] /* address, for backward compatibility */
The members of this structure are:
h_name The official (canonical) name of the host.
h_aliases
A NULL-terminated array of alternate names (nick-
names) for the host.
h_addrtype
The type of address being returned - usually
PF_INET or PF_INET6.
h_length
The length of the address in bytes.
h_addr_list
A NULL terminated array of network addresses for
the host. Host addresses are returned in network
byte order.
lwres_getipnodebyname() looks up addresses of protocol
family af for the hostname name. The flags parameter con-
tains ORed flag bits to specify the types of addresses
that are searched for, and the types of addresses that are
returned. The flag bits are:
AI_V4MAPPED
This is used with an af of AF_INET6, and causes
IPv4 addresses to be returned as IPv4-mapped IPv6
addresses.
AI_ALL This is used with an af of AF_INET6, and causes all
known addresses (IPv6 and IPv4) to be returned. If
AI_V4MAPPED is also set, the IPv4 addresses are
return as mapped IPv6 addresses.
AI_ADDRCONFIG
Only return an IPv6 or IPv4 address if here is an
active network interface of that type. This is not
currently implemented in the BIND 9 lightweight
resolver, and the flag is ignored.
AI_DEFAULT
This default sets the AI_V4MAPPED and AI_ADDRCONFIG
flag bits.
lwres_getipnodebyaddr() performs a reverse lookup of
address src which is len bytes long. af denotes the pro-
tocol family, typically PF_INET or PF_INET6.
lwres_freehostent() releases all the memory associated
with the struct hostent pointer he. Any memory allocated
for the h_name, h_addr_list and h_aliases is freed, as is
the memory for the hostent structure itself.
RETURN VALUES
If an error occurs, lwres_getipnodebyname() and
lwres_getipnodebyaddr() set *error_num to an appropriate
error code and the function returns a NULL pointer. The
error codes and their meanings are defined in
<lwres/netdb.h>:
HOST_NOT_FOUND
No such host is known.
NO_ADDRESS
The server recognised the request and the name but
no address is available. Another type of request to
the name server for the domain might return an
answer.
TRY_AGAIN
A temporary and possibly transient error occurred,
such as a failure of a server to respond. The
request may succeed if retried.
NO_RECOVERY
An unexpected failure occurred, and retrying the
request is pointless.
lwres_hstrerror(3) translates these error codes to suit-
able error messages.
SEE ALSO
RFC2553, lwres(3), lwres_gethostent(3), lwres_getad-
drinfo(3), lwres_getnameinfo(3), lwres_hstrerror(3).
BIND9 Jun 30, 2000 LWRES_GETIPNODE(3)
