/* fatvpn daemon by eeeee
 * Public Domain */

#include "config.h"
#include "common.h"

#define LOGFILE "/tmp/fatvpnd.log"
#define MAX_PEERS 16
#define TIMEOUT_D  180 /* timeout (no packets) in seconds for disconnect */

struct {
	struct sockaddr_storage a;
	u32 lptime; /* time of last packet */
	u8 mac[6];  /* internal mac */
} peer[MAX_PEERS];

u32 ccnt;

int main(int argc, char *argv[]){
	u8  *pkt;
	s32 res, tap, fdmax, skt, i, psz;
	struct sockaddr_storage c;
	struct timespec         t;
	struct termios          attr;
	struct ifreq            ifr;
	fd_set rset;

	/* arguments */
	if (argc != 3 && argc != 4){
		fprintf(stderr, "Using:\n\t"
			"%s <tap name> [address] <port>\n\n"
		        "Example:\n\t"
			"%s tap0 2222\n\t%s tap0 127.0.0.1 2222\n\n",
		        argv[0], argv[0], argv[0]);
		exit(1);
	}

	memset(&c, 0, sizeof(c));
	c.ss_family = AF_INET;
	(*(struct sockaddr_in*)&c).sin_port = htons((u16)atoi(argv[argc-1]));
	if (argc == 4){
		res = inet_pton(AF_INET6, argv[2],
		                ((struct sockaddr_in6*)&c)->sin6_addr.s6_addr);
		if (res != 1){
			res = inet_pton(AF_INET, argv[2], &psz);
			if (res != 1){
				fprintf(stderr, "wrong addr: %s\n",argv[2]);
				exit(1);
			}
			memcpy(&((struct sockaddr_in*)&c)->sin_addr.s_addr, &psz, 4);
		} else {
			c.ss_family = AF_INET6;
		}
	}

	if (strlen(argv[1]) + 1 > IFNAMSIZ)
		fputs("tap name is too long\n", stderr), exit(1);

	if (password[0] == 0){
		/* TODO: test std streams redirected to file */
		/* get term attrs */
		res = tcgetattr(STDOUT_FILENO, &attr);
		ERRDIE(res, "tcgetattr");

		/* echo off */
		attr.c_lflag &= ~ECHO;
		res = tcsetattr(STDOUT_FILENO, TCSANOW, &attr);
		ERRDIE(res, "tcsetattr");

		/* get password */
		fputs("Password: ", stdout), fflush(stdout);
		pkt = fgets(password, PASSWORD_BUF_SZ, stdin);
		fputs("\n", stdout);
		if (pkt == NULL)
			fputs("can't read password\n", stderr), exit(1);

		/* echo on */
		attr.c_lflag |= ECHO;
		res = tcsetattr(STDOUT_FILENO, TCSANOW, &attr);
		ERRDIE(res, "tcsetattr");
	}

	/* password without '\r\n' */
	res = 0;
	while (password[res] != '\0'
	    && password[res] != '\r'
	    && password[res] != '\n') res++;

	/* hash password */
	sponge256_hash32(key, password, res);
	memset(password, 0, PASSWORD_BUF_SZ);

	/* feed prng with key and current time */
	duplex257_prng_feed(prng_state, ((u32*)key)[0]);
	duplex257_prng_feed(prng_state, ((u32*)key)[1]);
	duplex257_prng_feed(prng_state, ((u32*)key)[2]);
	duplex257_prng_feed(prng_state, ((u32*)key)[3]);
	duplex257_prng_feed(prng_state, ((u32*)key)[4]);
	duplex257_prng_feed(prng_state, ((u32*)key)[5]);
	duplex257_prng_feed(prng_state, ((u32*)key)[6]);
	duplex257_prng_feed(prng_state, ((u32*)key)[7]);
	clock_gettime(CLOCK_MONOTONIC, &t);
	duplex257_prng_feed(prng_state, (u32)t.tv_sec);
	duplex257_prng_feed(prng_state, (u32)t.tv_nsec);

	/* daemonize: redirect std streams */
	res = open("/dev/null", O_RDONLY); ERRDIE(res, "open(/dev/null)");
	close(STDIN_FILENO), dup(res), close(res);
	res = open(LOGFILE, O_CREAT|O_WRONLY|O_TRUNC, S_IRUSR | S_IWUSR);
	ERRDIE(res, "open(logfile)");
	close(STDOUT_FILENO);
	close(STDERR_FILENO);
	dup(res), dup(res), close(res);

	/* daemonize: fork 1 */
	res = fork(); ERRDIE(res, "fork 1");
	if (res != 0) exit(0);

	/* daemonize: become session leader */
	setsid();

	/* daemonize: fork 2 */
	res = fork(); ERRDIE(res, "fork 2");
	if (res != 0) exit(0); /* kill session leader */

	/* daemonized! */

	/* cur pkt buf */
	pkt = malloc(MAX_PKT_SZ);
	if (pkt == NULL) fputs("pkt = malloc() failed\n",stderr), exit(1);

	/* socket, setsockopt */
	skt = socket(c.ss_family, SOCK_DGRAM, 0); ERRDIE(skt, "socket");
	res = 1;
	res = setsockopt(skt, SOL_SOCKET, SO_REUSEADDR, &res, sizeof(res));
	ERRDIE(res, "SO_REUSEADDR");

	/* bind */
	res = bind(skt, (struct sockaddr*) &c, sizeof(c));
	ERRDIE(res, "bind");

	/* tap */
	tap = open("/dev/net/tun", O_RDWR);
	ERRDIE(tap, "open(/dev/net/tun)");

	memset(&ifr, 0, sizeof(ifr));
	ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
	strncpy(ifr.ifr_name, argv[1], IFNAMSIZ);
	res = ioctl(tap, TUNSETIFF, &ifr);
	ERRDIE(res, "TUNSETIFF");

	fdmax = (tap > skt) ? tap+1 : skt+1;

inf_loop:
	/* "disconnect" peers with timeout */
	clock_gettime(CLOCK_MONOTONIC, &t);
	for (i=0; i < ccnt; i++){
		if (t.tv_sec - peer[i].lptime < TIMEOUT_D) continue;
		if (i != ccnt-1)
			memcpy(&peer[i], &peer[ccnt-1], sizeof(peer[0]));

		ccnt--, i--;
		memset(&peer[ccnt], 0, sizeof(peer[0]));
	}

	/* select */
	FD_ZERO(&rset);
	FD_SET(skt, &rset);
	FD_SET(tap, &rset);

	select(fdmax, &rset, NULL, NULL, NULL);

	/* read packet from tap */
	if (FD_ISSET(tap, &rset)){
		psz = read(tap, pkt, MAX_PKT_SZ);
		ERRDIE(psz, "read(tap)");

		for (i=0; i < ccnt; i++){
			if (0 == memcmp(peer[i].mac, pkt, 6)){
				send_pkt(skt, pkt, psz, &peer[i].a);
				break;
			}
		}
	}

	/* recv packet from client */
	if (0 == FD_ISSET(skt, &rset)) goto inf_loop;

	psz = recv_pkt(skt, pkt, MAX_PKT_SZ, &c);

	switch (c.ss_family)
	{
	case AF_INET:
		for (i=0; i < ccnt; i++)
			if (((struct sockaddr_in*)&c)->sin_port ==
					((struct sockaddr_in*)&peer[i].a)->sin_port &&
				((struct sockaddr_in*)&c)->sin_addr.s_addr ==
					((struct sockaddr_in*)&peer[i].a)->sin_addr.s_addr) break;
		break;
	case AF_INET6:
		for (i=0; i < ccnt; i++)
			if (((struct sockaddr_in6*)&c)->sin6_port ==
					((struct sockaddr_in6*)&peer[i].a)->sin6_port &&
				0 == memcmp(((struct sockaddr_in6*)&c)->sin6_addr.s6_addr,
					((struct sockaddr_in6*)&peer[i].a)->sin6_addr.s6_addr, 16)) break;
		break;
	}

	if (i == ccnt){
		/* client not connected */
		if (psz <= 14) /* ethernet header len == 14 */
			goto inf_loop;

		if (ccnt == MAX_PEERS) goto inf_loop;

		/* add peer to array */
		memcpy(&peer[i].a, &c, sizeof(c));
		memcpy(&peer[i].mac, &pkt[6], 6);
		ccnt++;
	}

	/* client connected */
	clock_gettime(CLOCK_MONOTONIC, &t);
	duplex257_prng_feed(prng_state, t.tv_nsec);
	peer[i].lptime = t.tv_sec;

	/* if connected peer send small packet, it's a ping packet for NAT
	 * keepalive, all i need to do is update lptime */
	if (psz <= 14) goto inf_loop;

	i = write(tap, pkt, psz);
	if (i == -1) perror("write(tap)");
	if (i < psz)
		fprintf(stderr, "i < psz, i=%d, psz=%d\n", i, psz), exit(1);

	goto inf_loop;

	return 0;
}