/* Copyright 2014 Ivo Smits <Ivo@UCIS.nl>. All rights reserved.
   Redistribution and use in source and binary forms, with or without modification, are
   permitted provided that the following conditions are met:

   1. Redistributions of source code must retain the above copyright notice, this list of
      conditions and the following disclaimer.

   2. Redistributions in binary form must reproduce the above copyright notice, this list
      of conditions and the following disclaimer in the documentation and/or other materials
      provided with the distribution.

   THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
   WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
   FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR
   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
   ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
   ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

   The views and conclusions contained in the software and documentation are those of the
   authors and should not be interpreted as representing official policies, either expressed
   or implied, of Ivo Smits.*/

#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <string.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <net/if.h>
#ifdef linux
	#include <linux/if_tun.h>
	#include <linux/if_ether.h>
#else
	#define ETH_FRAME_LEN 1514
	#include <net/if_tun.h>
	#ifdef SOLARIS
		#include <sys/stropts.h>
		#include <sys/sockio.h>
	#endif
#endif
#include "include.h"

static unsigned char readbuffer[2000];

bool tunnel_write_data(tunnel_context* context, unsigned char* buffer, int len) {
	if (context->fake_pi) {
		if (len == 0) return true;
		int ipver = (*buffer >> 4) & 0xf;
		int pihdr = 0;
#if defined linux
		if (ipver == 4) pihdr = 0x0000 | (0x0008 << 16); //little endian: flags and protocol are swapped
		else if (ipver == 6) pihdr = 0x0000 | (0xdd86 << 16);
#else
		if (ipver == 4) pihdr = htonl(AF_INET);
		else if (ipver == 6) pihdr = htonl(AF_INET6);
#endif
		struct iovec iov[2];
		iov[0].iov_base = &pihdr;
		iov[0].iov_len = sizeof(pihdr);
		iov[1].iov_base = buffer;
		iov[1].iov_len = len;
		writev(context->fd, iov, 2);
	} else {
		write(context->fd, buffer, len);
	}
	return true;
}

bool tunnel_read(tunnel_context* context) {
	int len = read(context->fd, readbuffer, sizeof(readbuffer));
	if (len < 0) return errorexitp("read failure on tap device");
	if (!context->connection) return true;
	if (context->fake_pi) {
		if (len < 4) return errorexit("short packet received from tap device");
		connection_write_data(context->connection, readbuffer + 4, len - 4);
	} else {
		connection_write_data(context->connection, readbuffer, len);
	}
	return true;
}

bool tunnel_init(tunnel_context* context) {
	memset(context, 0, sizeof(tunnel_context));
	char* envval;
	fprintf(stderr, "Initializing tun/tap device...\n");
	int ttfd; //Tap device file descriptor
	int tunmode = 0;
	if ((envval = getconf("TUN_MODE"))) tunmode = atoi(envval);
#if defined(__linux__)
	struct ifreq ifr; //required for tun/tap setup
	memset(&ifr, 0, sizeof(ifr));
	if ((ttfd = open("/dev/net/tun", O_RDWR)) < 0) return errorexitp("Could not open tun/tap device file");
	if ((envval = getconf("INTERFACE"))) strcpy(ifr.ifr_name, envval);
	ifr.ifr_flags = tunmode ? IFF_TUN : IFF_TAP;
	ifr.ifr_flags |= IFF_NO_PI;
	if (ioctl(ttfd, TUNSETIFF, (void *)&ifr) < 0) return errorexitp("TUNSETIFF ioctl failed");
#elif defined SOLARIS
	int ip_fd = -1, if_fd = -1, ppa = 0;
	if ((ttfd = open("/dev/tun", O_RDWR)) < 0) return errorexitp("Could not open tun device file");
	if ((ip_fd = open("/dev/ip", O_RDWR, 0)) < 0) return errorexitp("Could not open /dev/ip");
	if ((envval = getconf("INTERFACE"))) {
		while (*envval && !isdigit((int)*envval)) envval++;
		ppa = atoi(envval);
	}
	if ((ppa = ioctl(ttfd, TUNNEWPPA, ppa)) < 0) return errorexitp("Could not assign new PPA");
	if ((if_fd = open("/dev/tun", O_RDWR, 0)) < 0) return errorexitp("Could not open tun device file again");
	if (ioctl(if_fd, I_PUSH, "ip") < 0) return errorexitp("Could not push IP module");
	if (ioctl(if_fd, IF_UNITSEL, (char *)&ppa) < 0) return errorexitp("Could not set PPA");
	if (ioctl(ip_fd, I_LINK, if_fd) < 0) return errorexitp("Could not link TUN device to IP");
#else
	if (!(envval = getconf("INTERFACE"))) envval = "/dev/tun0";
	if ((ttfd = open(envval, O_RDWR)) < 0) return errorexitp("Could not open tun device file");
	if (tunmode) {
		int i = IFF_POINTOPOINT | IFF_MULTICAST;
		ioctl(ttfd, TUNSIFMODE, &i);
#if defined(__OpenBSD__)
		context->fake_pi = true;
#else
		i = 1;
		ioctl(ttfd, TUNSIFHEAD, &i);
#endif
	}
#endif
	if ((envval = getconf("TUN_UP_SCRIPT"))) system(envval);
	context->fd = ttfd;
	return true;
}