static int dns_q_format(struct dns_q *query, char *buff, size_t buff_sz) {
int ret;
size_t bytes_left, field_sz;
uint16_t field_val;
bytes_left = buff_sz;
ret = name_to_label(&query->qname[0], buff, buff_sz);
field_sz = (strlen(&query->qname[0]) + 2) * sizeof(uint8_t);
if (ret != 0) {
return ret;
}
bytes_left -= field_sz;
buff += field_sz;
field_sz = sizeof query->qtype;
if (field_sz > bytes_left) {
return -ENOMEM;
}
field_val = htons(query->qtype);
memcpy(buff, &field_val, sizeof field_sz);
bytes_left -= field_sz;
buff += field_sz;
field_sz = sizeof query->qclass;
if (field_sz > bytes_left) {
return -ENOMEM;
}
field_val = htons(query->qclass);
memcpy(buff, &field_val, sizeof field_sz);
return 0;
}
// lookup list is made of jdns_packet_labels
static int writelabel(const jdns_string_t *name, int at, int left, unsigned char **bufp, jdns_list_t *lookup)
{
unsigned char label[MAX_LABEL_LENGTH];
int n, i, len;
unsigned char *l;
unsigned char *ref;
int refsize;
len = name_to_label(name, label);
if(len == -1)
return 0;
ref = *bufp - at;
refsize = at + left;
for(n = 0; label[n]; n += label[n] + 1)
{
for(i = 0; i < lookup->count; ++i)
{
jdns_packet_label_t *pl = (jdns_packet_label_t *)lookup->item[i];
if(matchlabel(label + n, len - n, pl->value->data, pl->value->size, ref, refsize, 8, 8))
{
// set up a pointer right here, overwriting
// the length byte and the first content
// byte of this section within 'label'.
// this is safe, because the length value
// will always be greater than zero,
// ensuring we have two bytes available to
// use.
l = label + n;
short2net((unsigned short int)pl->offset, &l);
label[n] |= 0xc0;
len = n + 2; // cut things short
break;
}
}
if(label[n] & 0xc0) // double loop, so break again
break;
}
if(left < len)
return 0;
// copy into buffer, point there now
memcpy(*bufp, label, len);
l = *bufp;
*bufp += len;
// for each new label, store its location for future compression
for(n = 0; l[n]; n += l[n] + 1)
{
jdns_string_t *str;
jdns_packet_label_t *pl;
if(l[n] & 0xc0)
break;
pl = jdns_packet_label_new();
str = jdns_string_new();
jdns_string_set(str, l + n, len - n);
pl->offset = l + n - ref;
pl->value = str;
jdns_list_insert(lookup, pl, -1);
}
return 1;
}
