LWRES_HSTRERROR(3) BIND9 LWRES_HSTRERROR(3)NAME
lwres_herror, lwres_hstrerror - lightweight resolver error message generation
SYNOPSIS
#include <lwres/netdb.h>
void lwres_herror(const char *s);
const char * lwres_hstrerror(int err);
DESCRIPTION
lwres_herror() prints the string s on stderr followed by the string generated by lwres_hstrerror() for the error code stored in the global
variable lwres_h_errno.
lwres_hstrerror() returns an appropriate string for the error code gievn by err. The values of the error codes and messages are as follows:
NETDB_SUCCESS
Resolver Error 0 (no error)
HOST_NOT_FOUND
Unknown host
TRY_AGAIN
Host name lookup failure
NO_RECOVERY
Unknown server error
NO_DATA
No address associated with name
RETURN VALUES
The string Unknown resolver error is returned by lwres_hstrerror() when the value of lwres_h_errno is not a valid error code.
SEE ALSO herror(3), lwres_hstrerror(3).
COPYRIGHT
Copyright (C) 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC")
Copyright (C) 2000, 2001 Internet Software Consortium.
BIND9 Jun 30, 2000 LWRES_HSTRERROR(3)
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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 (C) 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC")
Copyright (C) 2000, 2001, 2003 Internet Software Consortium.
BIND9 Jun 30, 2000 LWRES_GETIPNODE(3)