lwres_getipnode man page on Alpinelinux
[printable version]
LWRES_GETIPNODE(3) BIND9 LWRES_GETIPNODE(3)
NAME
lwres_getipnodebyname, lwres_getipnodebyaddr, lwres_freehostent -
lightweight resolver nodename / address translation 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 (nicknames) 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 contains 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 protocol 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 suitable error
messages.
SEE ALSO
RFC2553(), lwres(3), lwres_gethostent(3), lwres_getaddrinfo(3),
lwres_getnameinfo(3), lwres_hstrerror(3).
COPYRIGHT
Copyright © 2004, 2005, 2007, 2014 Internet Systems Consortium, Inc.
("ISC")
Copyright © 2000, 2001, 2003 Internet Software Consortium.
BIND9 June 18, 2007 LWRES_GETIPNODE(3)
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