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dnsquery
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Make query generation a function.

This commit is contained in:
Érico Nogueira 2021-08-18 11:28:55 -03:00
parent 88234ad8fc
commit 00449157c7
1 changed files with 39 additions and 22 deletions
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61
dnsquery.c
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@ -53,6 +53,39 @@ static void iter_name(const uint8_t *buf, size_t buf_len, char *name, size_t *na
*index = i;
}
#define QTYPE_A 1
#define QTYPE_AAAA 28
#define QCLASS_IN 1
static void add_q(uint8_t *q, size_t *index, const char *qname, uint16_t qtype, uint16_t qclass, uint16_t *qdcount_written)
{
size_t i = *index;
for (;;) {
const char *dot = strchr(qname, '.');
/* fragment length */
size_t f = dot ? dot - qname : strlen(qname);
if (f >= UINT8_MAX) e("bad qname");
q[i++] = f;
memcpy(q+i, qname, f);
i+=f;
if (dot) qname = dot+1;
else break;
}
/* terminator */
q[i++] = 0;
q[i++] = BYTE2(qtype);
q[i++] = BYTE1(qtype);
q[i++] = BYTE2(qclass);
q[i++] = BYTE1(qclass);
*index = i;
*qdcount_written += 1;
}
int main()
{
uint8_t q[256], r[1024];
@ -66,9 +99,7 @@ int main()
/* RA(1) Z(3) RCODE(4) */
q[3] = 0;
uint16_t qdcount = 1, ancount = 0, nscount = 0, arcount = 0;
q[4] = BYTE2(qdcount);
q[5] = BYTE1(qdcount);
uint16_t ancount = 0, nscount = 0, arcount = 0;
q[6] = BYTE2(ancount);
q[7] = BYTE1(ancount);
q[8] = BYTE2(nscount);
@ -78,25 +109,11 @@ int main()
size_t i = 12;
/* QNAME
* length and then content */
q[i++] = 6;
memcpy(q+i, "google", 6);
i+=6;
q[i++] = 3;
memcpy(q+i, "com", 3);
i+=3;
/* terminator */
q[i++] = 0;
/* QTYPE
* A record */
q[i++] = 0;
q[i++] = 1;
/* QCLASS
* IN class */
q[i++] = 0;
q[i++] = 1;
uint16_t qdcount = 0;
add_q(q, &i, "google.com", QTYPE_A, QCLASS_IN, &qdcount);
//add_q(q, &i, "google.com", QTYPE_AAAA, QCLASS_IN, &qdcount);
q[4] = BYTE2(qdcount);
q[5] = BYTE1(qdcount);
int s = socket(AF_INET, SOCK_DGRAM, 0);
struct sockaddr_in addr = {.sin_family=AF_INET, .sin_port=htons(53), .sin_addr=inet_addr("127.0.0.1")};