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#include "dnslib.h"
#include <netinet/in.h>
#include <arpa/inet.h>
/* make a full dns query including header. Returns length of packet.
*/
int
makequery (char *name, u_int16_t type, u_int8_t *buffer, u_int16_t id)
{
HEADER *head;
head = (HEADER *)buffer;
bzero (head, DNSHDRSIZE);
head->id = htons (id);
head->qr = 0;
head->opcode = 0;
head->aa = 0;
head->tc = 0;
head->rd = 1;
head->ra = 0;
head->rcode = 0;
head->qdcount = htons (1);
head->ancount = 0;
head->nscount = 0;
head->arcount = 0;
return (makeqbody (name, type, buffer + DNSHDRSIZE) + DNSHDRSIZE);
}
/* convert a \0-terminated string to a DNS domain name.
* www.yahoo.com(.) => \003www\005yahoo\003\com\000
*/
int
formatname (char *in, u_int8_t *out)
{
char *start = in, c = 0;
int n = strlen (in);
in += n - 1;
out += n + 1;
*out-- = 0;
n = 0;
while (in >= start) {
c = *in--;
if (c == '.') {
*out-- = n;
n = 0;
} else {
*out-- = c;
n++;
}
}
if (n)
*out-- = n;
return (strlen (out + 1) + 1);
}
/* simple function for making a, ptr and ns resource records
* doesn't support more complicated stuph.
*/
int
makeRR (char *name, u_int16_t type, u_int16_t class, u_int32_t ttl,
char *rdata, char *buf)
{
int n;
rrec_body *rec;
char *ptr = buf;
/* name the resource record pertains too */
ptr += formatname (name, ptr);
rec = (rrec_body *)ptr;
rec->type = htons (type);
rec->class = htons (class);
rec->ttl = htonl (ttl);
rec->rdlength = 0;
ptr += 10;
switch (type) {
case T_A:
*(u_int32_t *)ptr = inet_addr (rdata);
rec->rdlength = htons (4);
ptr += 4;
break;
case T_PTR:
case T_NS:
n = formatname (rdata, ptr);
ptr += n;
rec->rdlength = htons (n);
break;
default:
/**/
}
return (ptr - buf);
}
/* make just the body of a DNS query.
*/
int
makeqbody (char *name, u_int16_t type, u_int8_t *buffer)
{
int len;
len = formatname (name, buffer);
buffer += len;
PUTSHORT (type, buffer);
PUTSHORT (C_IN, buffer);
return (len + 4);
}
/* uncompress compressed dns names. ugh.
* works for normal formatted dns names too..
* returns the length of the first part of the compressed name (i.e.
* before redirection).
*/
int
uncompress (u_int8_t *in, char *out, u_int8_t *msg)
{
u_int8_t *start = in, *end = NULL;
u_int8_t len;
u_int16_t off;
while ((len = *in++)) {
if (len & INDIR_MASK) {
if (end == NULL)
end = in + 1;
off = (len & ~INDIR_MASK);
off |= *in++ << 8;
off = ntohs (off);
in = msg + off;
continue;
}
memcpy (out, in, len);
out += len;
in += len;
*out++ = '.';
}
if (end == NULL)
end = in;
*out++ = 0;
return (end - start);
}
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