Example

int my_dns_func(pblock *pb, Session *sn, Request *rq)
{
    char *host = pblock_findval("dns-host", rq->vars);
    struct hostent *hostent;
    hostent = gethostbyname(host);//replace with custom DNS implementation
    dns_set_hostent(hostent, sn, rq);
    return REQ_PROCEED;
}