libunbound : ub_result from ub_resolve_event callback

[Antony Antony]

Hello,
I am using ub_resolve_event, with libvent. The result in the callback function is type  void* packet. Which is new to me. ub_resolve and ub_resolve_async return a type ub_result. 

How do I convert the 'void *packet' to 'struct ub_result*'?
 
from unbound-event.h
void callback(void* mydata, int rcode, void* packet, int packet_len,               int sec, char* why_bogus) 

The ub_result is documented. I couldn't find anything about packet.

The the program already use libevent and call event_base_loop. I gave try with ub_resolve_async. The forked thread get stuck in event loop. It never call the callback function or ub_process. tcpdump can see dns queries going out and replies coming back. Still 

regards,
-antony