dns-transp-client.c

   1 /**/
   2
   3 uint8_t qid[2];
   4
   5 #define PKT_PREPEND_START(pe, size, body) do{           \
   6     assert((pe)->ptr - (pe)->buf >= (size));            \
   7     const uint8_t *pkt_prepend_orig = (pe)->ptr;        \
   8     uint8_t *pkt = (pe)->ptr -= (size);                 \
   9     { body; }                                           \
  10     assert(pkt == pkt_prepend_orig);                    \
  11   }while(0)
  12
  13 #define PKT_ADDB(byte) (*pkt++ = (byte))
  14 #define PKT_ADDW(word) (*pkt++ = ((w) >> 8), *pkt++ = (w))
  15
  16 #define DNS_HDRLEN (6*2)
  17
  18 void dnsqueryenc_start(struct dnspacketenc *pe,
  19                        int mydompathlen, const char *mydompath) {
  20     dnspacketenc_start(pe);
  21
  22     PKT_PREPEND(pe, 4, {
  23         PKT_ADDW(QTYPE_CNAME);
  24         PKT_ADDW(QCLASS_IN);
  25     });
  26
  27     return dnsdomainenc_start(&pe->dom, pe->buf,
  28                               pe->ptr - pe->buf - DNS_HDRLEN,
  29                               mydompathlen, mydompath);
  30 }
  31
  32 void dnsqueryenc_finish(uint16_t qid, const uint8_t **result, int *reslen) {
  33     pe->ptr = dnsdomainenc_getresult(&pe->dom);
  34
  35     PKT_PREPEND(pe, DNS_HDRLEN, {
  36         PKT_ADDW(qid);
  37         PKT_ADDB(0x00); /* QR=0(q); Opcode=QUERY; !AA,!TC,!RD */
  38         PKT_ADDB(0x00); /* !RA; Z; RCODE=NOERROR */
  39         PKT_ADDW(0x01); /* QDCOUNT=1 */
  40         PKT_ADDW(0x00); /* ANCOUNT=0 */
  41         PKT_ADDW(0x00); /* NSCOUNT=0 */
  42         PKT_ADDW(0x00); *hdr++ = 0x00; /* ARCOUNT=0 */
  43     });
  44
  45     *result = pe->ptr;
  46     *reslen = (pe->buf + MAX_DNSPACKET_BYTES) - pe->ptr;
  47 }
  48