static char *pico_dns_client_seek_suffix(char *suf, struct pico_dns_header *pre, struct pico_dns_query *q)
{
struct pico_dns_answer_suffix *asuffix = NULL;
uint16_t comp = 0, compression = 0;
uint16_t i = 0;
if (!suf)
return NULL;
while (i++ < short_be(pre->ancount)) {
comp = short_from(suf);
compression = short_be(comp);
switch (compression >> 14)
{
case PICO_DNS_POINTER:
while (compression >> 14 == PICO_DNS_POINTER) {
dns_dbg("DNS: pointer\n");
suf += sizeof(uint16_t);
comp = short_from(suf);
compression = short_be(comp);
}
break;
case PICO_DNS_LABEL:
dns_dbg("DNS: label\n");
suf = pico_dns_client_seek(suf);
break;
default:
dns_dbg("DNS ERROR: incorrect compression (%u) value\n", compression);
return NULL;
}
asuffix = (struct pico_dns_answer_suffix *)suf;
if (!asuffix)
break;
if (pico_dns_client_check_asuffix(asuffix, q) < 0) {
suf += (sizeof(struct pico_dns_answer_suffix) + short_be(asuffix->rdlength));
continue;
}
return suf;
}
return NULL;
}
static void pico_dns_client_callback(uint16_t ev, struct pico_socket *s)
{
char *q_qname, *q_suf, *a_hdr, *a_qname, *a_suf, *a_rdata;
struct dns_message_hdr *hdr;
struct dns_query_suffix query_suf;
struct dns_answer_suffix answer_suf;
struct pico_dns_key test, *key;
char *answer;
char dns_answer[PICO_DNS_MAX_RESPONSE_LEN] = {0};
uint8_t valid_suffix = 0;
uint16_t compression = 0;
int i = 0, r = 0;
if (ev & PICO_SOCK_EV_RD) {
r = pico_socket_read(s, dns_answer, PICO_DNS_MAX_RESPONSE_LEN);
pico_socket_close(s);
if (r == PICO_DNS_MAX_RESPONSE_LEN || r < (int)sizeof(struct dns_message_hdr)) {
dns_dbg("DNS ERROR: received incorrect number(%d) of bytes\n", r);
return;
}
/* Check header validity */
a_hdr = dns_answer;
hdr = (struct dns_message_hdr *) a_hdr;
pico_dns_client_hdr_ntoh(hdr);
if (GET_FLAG_QR(hdr) != PICO_DNS_QR_RESPONSE || GET_FLAG_OPCODE(hdr) != PICO_DNS_OPCODE_QUERY
|| GET_FLAG_TC(hdr) == PICO_DNS_TC_IS_TRUNCATED || GET_FLAG_RCODE(hdr) != PICO_DNS_RCODE_NO_ERROR) {
dns_dbg("DNS ERROR: OPCODE %d | TC %d | RCODE %d\n", GET_FLAG_OPCODE(hdr), GET_FLAG_TC(hdr), GET_FLAG_RCODE(hdr));
return;
}
if (hdr->ancount < 1 || r < (int)(sizeof(struct dns_message_hdr) + hdr->qdcount * sizeof(struct dns_query_suffix)
+ hdr->ancount * sizeof(struct dns_answer_suffix))) {
dns_dbg("DNS ERROR: ancount < 1 OR received number(%d) of bytes too low\n", r);
return;
}
/* Find DNS key */
test.id = hdr->id;
key = pico_tree_findKey(&DNSTable,&test);
if (!key) {
dns_dbg("DNS WARNING: key with id %u not found\n", hdr->id);
return;
}
key->retrans = 0;
/* Check query suffix validity */
q_qname = a_hdr + sizeof(struct dns_message_hdr);
q_suf = pico_dns_client_seek(q_qname);
query_suf = *(struct dns_query_suffix *) q_suf;
if (short_be(query_suf.qtype) != key->qtype || short_be(query_suf.qclass) != key->qclass) {
dns_dbg("DNS ERROR: received qtype (%u) or qclass (%u) incorrect\n", short_be(query_suf.qtype), short_be(query_suf.qclass));
return;
}
/* Seek answer suffix */
a_qname = q_suf + sizeof(struct dns_query_suffix);
a_suf = a_qname;
while(i++ < hdr->ancount) {
uint16_t comp_h = short_from(a_suf);
compression = short_be(comp_h);
switch (compression >> 14)
{
case PICO_DNS_POINTER:
while (compression >> 14 == PICO_DNS_POINTER) {
dns_dbg("DNS: pointer\n");
a_suf += sizeof(uint16_t);
comp_h = short_from(a_suf);
compression = short_be(comp_h);
}
break;
case PICO_DNS_LABEL:
dns_dbg("DNS: label\n");
a_suf = pico_dns_client_seek(a_qname);
break;
default:
dns_dbg("DNS ERROR: incorrect compression (%u) value\n", compression);
return;
}
/* Check answer suffix validity */
answer_suf = *(struct dns_answer_suffix *)a_suf;
if (short_be(answer_suf.qtype) != key->qtype || short_be(answer_suf.qclass) != key->qclass) {
dns_dbg("DNS WARNING: received qtype (%u) or qclass (%u) incorrect\n", short_be(answer_suf.qtype), short_be(answer_suf.qclass));
a_suf = a_suf + sizeof(struct dns_answer_suffix) + short_be(answer_suf.rdlength);
continue;
}
if (short_be(answer_suf.ttl) > PICO_DNS_MAX_TTL) {
dns_dbg("DNS WARNING: received TTL (%u) > MAX (%u)\n", short_be(answer_suf.ttl), PICO_DNS_MAX_TTL);
a_suf = a_suf + sizeof(struct dns_answer_suffix) + short_be(answer_suf.rdlength);
continue;
}
valid_suffix = 1;
break;
}
if (!valid_suffix) {
dns_dbg("DNS ERROR: invalid dns answer suffix\n");
return;
}
a_rdata = a_suf + sizeof(struct dns_answer_suffix);
if (key->qtype == PICO_DNS_TYPE_A) {
uint32_t ip_h = long_from(a_rdata);
dns_dbg("DNS: length %u | ip %08X\n", short_be(answer_suf.rdlength), long_be(ip_h));
answer = pico_zalloc(16);
pico_ipv4_to_string(answer, ip_h);
key->callback(answer, key->arg);
} else if (key->qtype == PICO_DNS_TYPE_PTR) {
pico_dns_client_reverse_label((char *) a_rdata);
dns_dbg("DNS: length %u | name %s\n", short_be(answer_suf.rdlength), (char *)a_rdata + 1);
answer = pico_zalloc(answer_suf.rdlength - 1);
memcpy(answer, (char *)a_rdata + 1, short_be(answer_suf.rdlength) - 1);
key->callback(answer, key->arg);
} else {
dns_dbg("DNS ERROR: incorrect qtype (%u)\n", key->qtype);
return;
}
}