res_mkquery.c raw

   1  #include <resolv.h>
   2  #include <string.h>
   3  #include <time.h>
   4  
   5  int __res_mkquery(int op, const char *dname, int class, int type,
   6  	const unsigned char *data, int datalen,
   7  	const unsigned char *newrr, unsigned char *buf, int buflen)
   8  {
   9  	int id, i, j;
  10  	unsigned char q[280];
  11  	struct timespec ts;
  12  	size_t l = strnlen(dname, 255);
  13  	int n;
  14  
  15  	if (l && dname[l-1]=='.') l--;
  16  	n = 17+l+!!l;
  17  	if (l>253 || buflen<n || op>15u || class>255u || type>255u)
  18  		return -1;
  19  
  20  	/* Construct query template - ID will be filled later */
  21  	memset(q, 0, n);
  22  	q[2] = op*8 + 1;
  23  	q[3] = 32; /* AD */
  24  	q[5] = 1;
  25  	memcpy((char *)q+13, dname, l);
  26  	for (i=13; q[i]; i=j+1) {
  27  		for (j=i; q[j] && q[j] != '.'; j++);
  28  		if (j-i-1u > 62u) return -1;
  29  		q[i-1] = j-i;
  30  	}
  31  	q[i+1] = type;
  32  	q[i+3] = class;
  33  
  34  	/* Make a reasonably unpredictable id */
  35  	clock_gettime(CLOCK_REALTIME, &ts);
  36  	id = ts.tv_nsec + ts.tv_nsec/65536UL & 0xffff;
  37  	q[0] = id/256;
  38  	q[1] = id;
  39  
  40  	memcpy(buf, q, n);
  41  	return n;
  42  }
  43  
  44  weak_alias(__res_mkquery, res_mkquery);
  45