github.com/afumu/libc@v0.0.6/musl/src/network/res_mkquery.c (about)

     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);