repsonse parser

This commit is contained in:
Bjorn Andersson 2006-06-05 15:36:13 +00:00
parent f9a37db26b
commit 54bacf5b80
1 changed files with 99 additions and 6 deletions

105
dns.c
View File

@ -35,6 +35,53 @@ static int host2dns(const char *, char *, int);
struct sockaddr_in peer;
char topdomain[256];
static int
readname(char *packet, char *dst, char *src)
{
char l;
int len;
int offset;
len = 0;
while(*src) {
l = *src++;
len++;
if(l & 0x80 && l & 0x40) {
offset = ((src[-1] & 0x3f) << 8) | src[0];
readname(packet, dst, packet + offset);
dst += strlen(dst);
break;
}
while(l) {
*dst++ = *src++;
l--;
len++;
}
*dst++ = '.';
}
*dst = '\0';
src++;
len++;
return len;
}
#define READNAME(packet, dst, src) (src) += readname((packet), (dst), (src));
#define READSHORT(dst, src) \
(dst) = ntohs(*(short*)(src)); (src)+=2;
#define READLONG(dst, src) \
(dst) = ntohl(*(long*)(src)); (src)+=4;
#define READDATA(dst, src, len) \
memcpy((dst), (src), (len)); (src)+=(len);
int
open_dns()
{
@ -130,17 +177,63 @@ dns_query(int fd, char *host, int type)
}
int
dns_read(int fd, char *buf, int len)
dns_read(int fd, char *buf, int buflen)
{
int i;
int r;
long ttl;
short rlen;
short type;
short class;
short port;
short ancount;
char *data;
char name[255];
char host[255];
char rdata[256];
HEADER *header;
char packet[64*1024];
r = recv(fd, packet, sizeof(packet), 0);
r = recv(fd, buf, len, 0);
if (r < 0) {
perror("recvfrom");
}
printf("Read %d bytes DNS reply\n", r);
return r;
if(r == -1) {
perror("recvfrom");
} else {
header = (HEADER*)packet;
data = packet + sizeof(HEADER);
if(header->qr) { /* qr=1 => response */
ancount = ntohs(header->ancount);
for(i=0;i<ancount;i++) {
READNAME(buf, name, data);
READSHORT(type, data);
READSHORT(class, data);
READLONG(ttl, data);
READSHORT(rlen, data);
READDATA(rdata, data, rlen);
if(type == T_SRV && rlen > 6) {
char *r;
short priority;
short weight;
r = rdata;
READSHORT(priority, r);
READSHORT(weight, r);
READSHORT(port, r);
READNAME(buf, host, r);
}
printf("%s\n", name);
}
}
}
return 0;
}
static int