getdns_hostname(3) getdns_hostname_sync


DNS Resolver library (libgetdns, -lgetdns)


#include <getdns.h>

getdns_hostname (getdns_context *context,

getdns_dict *address,
getdns_dict *extensions,
void *userarg,
getdns_transaction_t *transaction_id,
getdns_callback_t callbackfn)

getdns_hostname_sync (getdns_context *context,

getdns_dict *address,
getdns_dict *extensions,
getdns_dict **response)


The getdns_hostname(3) and getdns_hostname_sync functions provide public entry points into the getdns API library to retrieve the host name given an address.

A pointer to the previously created DNS context that is to be used with this DNS request. see getdns_context (3)

a getdns_dict structure containing two names: address_type (whose value is bindata and is either "IPv4" or "IPv6") and address_data whose value is bindata

extensions for this request, NULL if no extensions, see libgetdns (3) for a detailed description of extensions

returned to the callback function untouched, can be NULL

populated by the API and used to identify the callback (for example to getdns_cancel_callback), can be NULL, set to 0 if the function fails

non-NULL pointer to a callback function defined by the application, typically used to process the response. Only the asynchronous signature accepts a callback function, the synchronous signature does not include a callback. See libgetdns (3) for a more detailed discussion of callback functions.

A getdns_dict type is returned in response and always contains at least three names: replies_full (a list containing the DNS response as binary data), replies_tree (a list containing the parsed DNS response data) and status (an int). The storage associated with this must be freed by a call to getdns_free_sync_request_memory (3).


Upon successful completion the functions return GETDNS_RETURN_GOOD , otherwise the following error values are returned:

GETDNS_RETURN_BAD_CONTEXT if the context pointer is invalid or the context has internal deficiencies

GETDNS_RETURN_BAD_DOMAIN_NAME if the domain name passed to the function is invalid

GETDNS_RETURN_EXTENSION_MISFORMAT if the data type specified in one or more of the extensions does not match the specifications

GETDNS_RETURN_GENERIC_ERROR if some problem was encountered in the function not addressed by one of the more specific return codes

GETDNS_RETURN_INVALID PARAMETER if one or more parameters has an invalid value

GETDNS_RETURN_MEMORY_ERROR if unable to allocate the memory required

GETDNS_RETURN_NO_SUCH_EXTENSION if one or more of the strings specified in the extensions are not valid

The values of status included in the response parameter are:

GETDNS_RESPSTATUS_GOOD if at least one response was returned

GETDNS_RESPSTATUS_NO_NAME if queries for the name yielded all negative responses

GETDNS_RESPSTATUS_ALL_TIMEOUT if all queries for the name timed out

GETDNS_RESPSTATUS_NO_SECURE_ANSWERS if only secure replies accepted (per context) and at least one response was received but no DNS responses were secure through DNSSEC

For a more detailed explanation of the response object see libgetdns (3)