tun_dev.c

Adhoc无线网络路由协议源码

#include "common.h"
#include "utils.h"
#include "tun_dev.h"


/*
 * tun_init():
 * 	prepare the tun device and return the handle (file descriptor)
 */
int tun_init()
{
  struct ifreq ifr;
  int fd, r;
  char cmd[256];
  unsigned char dev[IFNAMSIZ];
  
  // change to root --vikas
  if(setreuid(0, 0) < 0){
    fprintf(stderr, "setreuid to root failed : \n Please run as root.. ");
    return(-1);
  }

  /* FIXME : hardcoded dir name and perms */
  umask(0);
  mkdir("/dev/net", 0755);

  /* MISC_MAJOR and TUN_MINOR char nodes */
  mk_node("/dev/net/tun", 10, 200);

  // FIXME : should I do a manual insmod here : kmod should do automatically
  
	if ( (fd = open("/dev/net/tun", O_RDWR)) < 0 ) {
	 	fprintf(stderr, "tun_init(): Error openeing tun device :\n May be you have not configured tun device \n See /usr/src/linux/Documentation/networking/tuntap.txt\n");
		perror("Opening : /dev/net/tun");
		return -1;
	}

	memset(&ifr, 0, sizeof(ifr));

	/* Flags: IFF_TUN   - TUN device (no Ethernet headers) 
	 *        IFF_TAP   - TAP device  
	 *
	 *        IFF_NO_PI - Do not provide packet information  
	 */ 
	ifr.ifr_flags = IFF_TUN | IFF_NO_PI; 

	strcpy(ifr.ifr_name, TUN_DEV_NAME);

	if ((r = ioctl(fd, TUNSETIFF, (void *) &ifr)) < 0) {
		perror("ioctl(TUNSETIFF) failed");
        	close(fd);
        	return -1;
	}
	strcpy(dev, ifr.ifr_name);

	/* FIXME : Is there another way instead of using system */
	/* turn up the interface
	* Is it worth it ?? -vikas */
	sprintf(cmd, "/sbin/ifconfig %s %s netmask 255.255.255.255 up",
		dev, TUN_DEV_IP);
	system(cmd);
	

#ifdef DEBUG
	 fprintf(stderr, "tun_init() : device %s is now up\n", dev);
#endif
	 
	/* no checksum */
        if ((r = ioctl(fd, TUNSETNOCSUM, 1)) < 0) {
		perror("ioctl(TUNSETNOCSUM) failed");
        	close(fd);
        	return -1;
	}

	return (fd);
}

/*
 * tun_in(fd, buf):
 *	read the next packet from fd into buf, return the packet length
 */
int tun_in(int fd, unsigned char *buf)
{
  int r;

	r = read(fd, buf, BUFSIZE);
#ifdef DEBUG
	{ int i;
		fprintf(stderr, "IN: (%d) [ ", r);
		for (i = 0; i < 20; i++)
			fprintf(stderr, "%02x ", buf[i]);
		fprintf(stderr, "]\n");
	}
#endif
	return r;
}