#include <sys/types.h>
#include <net/if_tun.h>
#include <net/if_types.h>
#include <sys/ioctl.h>
#include <sys/endian.h>
#include <sys/socket.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <err.h>
#include <string.h>
#include <sys/select.h>


#include <arpa/inet.h>
#include <netinet/in.h>

int
main(int ac, char *av[])
{
	int fd;
	int s;
	int mode;
	char buf[2052];
	int n, i;
	int endpt;
	struct sockaddr_in sin;
	fd_set rfdset;
	struct tuninfo ti;

	/* Run one end as 'qd_tun 1' and the other as 'qd_tun 2' */
	if (ac < 2)
		errx(1, "usage: 1/2");
	endpt = atoi(av[1]);
	if (endpt != 1 && endpt != 2)
		errx(1, "usage: 1/2");

	s = socket(PF_INET, SOCK_DGRAM, 0);
	if (s < 0)
		err(1, "socket");

	mode = 1;
	i = setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &mode, sizeof(mode));
	if (i < 0)
		err(1, "ioctl SO_REUSEADDR tun0");

	memset(&sin, 0, sizeof(sin));
	sin.sin_len = sizeof(sin);
	sin.sin_family = AF_INET;

	if (endpt == 1) {
		/* Endpoint 1 */
		inet_aton("10.1.1.1", &sin.sin_addr);
		sin.sin_port = htons(10001);
	} else {
		/* Endpoint 2 */
		inet_aton("10.2.2.2", &sin.sin_addr);
		sin.sin_port = htons(10002);
	}
	i = bind(s, (struct sockaddr *)&sin, sizeof(sin));
	if (i < 0)
		err(1, "bind. right endpt?");

	if (endpt == 1) {
		/* I am canning. his remote end. */
		inet_aton("216.145.52.172", &sin.sin_addr);
		sin.sin_port = htons(33926);
	} else {
		/* I am daintree. his remote end. */
		inet_aton("192.203.228.73", &sin.sin_addr);
		sin.sin_port = htons(53);
	}


	fd = open("/dev/tun0", O_RDWR | O_EXCL, 0);
	if (fd < 0)
		err(1, "open tun0");

	mode = 1;
	i = ioctl(fd, FIONBIO, &mode, sizeof(mode));
	if (i < 0)
		err(1, "ioctl FIONBIO tun0");
	mode = 1;
	i = ioctl(s, FIONBIO, &mode, sizeof(mode));
	if (i < 0)
		err(1, "ioctl FIONBIO sock");

	mode = 1;
	i = ioctl(fd, TUNSIFHEAD, &mode, sizeof(mode));
	if (i < 0)
		err(1, "ioctl TUNSIFHEAD");


	memset(&ti, 0, sizeof(ti));
	ti.baudrate = 100*1000*1000;
	ti.mtu = 1280;
	ti.type = IFT_TUNNEL;
	ti.dummy = 0;
	i = ioctl(fd, TUNSIFINFO, &ti, sizeof(ti));
	if (i < 0)
		err(1, "ioctl TUNSIFINFO");

	for (;;) {
		FD_ZERO(&rfdset);
		FD_SET(fd, &rfdset);
		FD_SET(s, &rfdset);
		n = select(FD_SETSIZE, &rfdset, NULL, NULL, NULL);
		if (n < 0)
			err(1, "select");
		if (n == 0)
			continue;
		if (FD_ISSET(fd, &rfdset)) {
			n = read(fd, buf, sizeof(buf));
			if (n > 0) {
				if (n >= 4) {
					mode = be32toh(*(uint32_t *)buf);
					/*printf("tun0 rcv protocol: %d\n", mode); */
					if (mode != AF_INET6)
						continue;
					i = sendto(s, buf, n, 0, (struct sockaddr *)&sin, sizeof(sin));
					if (i < 0)
						warn("sock sendto");
				}
			}
			if (n < 0) {
				err(1, "tun0 eof");
			}
			if (n == 0) {
				warn("tun0 short read");
			}
		}
		if (FD_ISSET(s, &rfdset)) {
			n = read(s, buf, sizeof(buf));
			if (n > 0) {
				if (n >= 4) {
					mode = be32toh(*(uint32_t *)buf);
					/* printf("sock rcv protocol: %d\n", mode); */
					if (mode != AF_INET6)
						continue;
					i = write(fd, buf, n);
					if (i < 0)
						warn("tun0 write");
				}
			}
			if (n < 0) {
				err(1, "sock eof");
			}
			if (n == 0) {
				warnx("sock short read");
			}
		}
	}
}