#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);
}