The qsort() used in libads/dns.c is regularly trashing the list of Domain Controllers. This is because the comparison function dnssrvcmp() is using rand(). AFAIK, that's not recommended -- repeated calls to the qsort() comparison function with the same args _must_ return the same, consistent results.


See here: 

http://www.opengroup.org/onlinepubs/009695399/functions/qsort.html

Quote: When the same objects (consisting of width bytes, irrespective of their current positions in the array) are passed more than once to the comparison function, the results shall be consistent with one another. That is, they shall define a total ordering on the array. 


And discussions, along similar lines here:

http://www.thescripts.com/forum/thread212502.html
http://sourceware.org/ml/binutils/2004-06/msg00091.html

Quote: Finally, and if my crystal ball is working again, the third common problem is the one you are actually running into. If a comparison function is not 100% consistent in deciding that, when a<b, b>a, some qsort() variants will run wild. Hence this:

	int bad_compare(const void *l, const void *r) {
		return (rand() % 3) - 1;
	}

is a terrible function to use, and causes real qsort()s to run off into the weeds. 


A modified comparison routine like this works for me:

static int dnssrvcmp( struct dns_rr_srv *a, struct dns_rr_srv *b )
{
        if ( a->priority == b->priority ) {

                if ( a->weight == b->weight )
                    return 0;

                /* higher weights should be sorted lower */
                if ( a->weight > b->weight )
                        return -1;
                else
                        return 1;
        }

        if ( a->priority < b->priority )
                return -1;

        return 1;
}