iodine/dns.c

/*
 * Copyright (c) 2006 Bjorn Andersson <flex@kryo.se>, Erik Ekman <yarrick@kryo.se>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <netdb.h>
#include <time.h>
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <ctype.h>

#include "dns.h"

static int host2dns(const char *, char *, int);

struct sockaddr_in peer;
char topdomain[256];

int 
open_dns() 
{
	int fd;
	int flag;
	struct sockaddr_in addr;

	bzero(&addr, sizeof(addr));
	addr.sin_family = AF_INET;
	addr.sin_port = htons(0);
	addr.sin_addr.s_addr = htonl(INADDR_ANY);

	fd = socket(AF_INET, SOCK_DGRAM, 0);
	if(fd < 0) {
		warn("Could not get UDP socket");
		return 0;
	}

	flag = 1;
#ifdef SO_REUSEPORT
	setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &flag, sizeof(flag));
#endif
	setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &flag, sizeof(flag));

	if(bind(fd, (struct sockaddr*)&addr, sizeof(addr)) < 0) {
		warn("Could not bind UDP socket locally");
		return 0;
	}

	printf("Opened UDP socket\n");

	return fd;
}

void
close_dns(int fd)
{
	close(fd);
}

void
dns_set_peer(const char *host)
{
	struct hostent *h;

	h = gethostbyname(host);
	bzero(&peer, sizeof(peer));
	peer.sin_family = AF_INET;
	peer.sin_port = htons(53);
	peer.sin_addr = *((struct in_addr *) h->h_addr);
}

void
dns_ping(int dns_fd)
{
	dns_query(dns_fd, "kryo.se", 1);
}

void 
dns_query(int fd, char *host, int type)
{
	char *p;
	int len;
	int peerlen;
	char buf[1024];
	HEADER *header;
	
	len = 0;
	memset(buf, 0, sizeof(buf));

	header = (HEADER*)buf;	
	
	header->id = 0;
	header->qr = 0;
	header->opcode = 0;
	header->aa = 0;
	header->tc = 0;
	header->rd = 1;
	header->ra = 0;

	header->qdcount = htons(1);

	p = buf + sizeof(HEADER);
	p += host2dns(host, p, strlen(host));	

	PUTSHORT(type, p);
	PUTSHORT(C_IN, p);

	peerlen = sizeof(peer);

	len = p - buf;
	sendto(fd, buf, len+1, 0, (struct sockaddr*)&peer, peerlen);
}

int
dns_read(int fd, char *buf, int len)
{
	int r;

	r = recv(fd, buf, len, 0);
	if (r < 0) {
		perror("recvfrom");
	}
	printf("Read %d bytes DNS reply\n", r);

	return r;
}

static int
host2dns(const char *host, char *buffer, int size)
{
	char *h;
	char *p;
	char *word;

	h = strdup(host);
	memset(buffer, 0, size);
	p = buffer;
	
	word = strtok(h, ".");
	while(word) {
		*p++ = (char)strlen(word);
		memcpy(p, word, strlen(word));
		p += strlen(word);

		word = strtok(NULL, ".");
	}

	*p++ = 0;

	free(h);

	return p - buffer;
}