我正在关注http://backreference.org/2010/03/26/tuntap-interface-tutorial/
以下代码在我以 root 身份运行时成功获取 fd（通常为 3），但它不会创建 /dev/tun77 设备。
应该是？
#include <stdio.h>
#include <stdlib.h>
#include <net/if.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <string.h>
#include <linux/if_tun.h>
#include <linux/ioctl.h>
#define IFNAMSIZ 16
int tun_alloc(char *dev, int flags) {
struct ifreq ifr;
int fd, err;
char *clonedev = "/dev/net/tun";
/* Arguments taken by the function:
*
* char *dev: the name of an interface (or '\0'). MUST have enough
* space to hold the interface name if '\0' is passed
* int flags: interface flags (eg, IFF_TUN etc.)
*/
/* open the clone device */
if( (fd = open(clonedev, O_RDWR)) < 0 ) {
return fd;
}
/* preparation of the struct ifr, of type "struct ifreq" */
memset(&ifr, 0, sizeof(ifr));
ifr.ifr_flags = flags; /* IFF_TUN or IFF_TAP, plus maybe IFF_NO_PI */
if (*dev) {
/* if a device name was specified, put it in the structure; otherwise,
* the kernel will try to allocate the "next" device of the
* specified type */
strncpy(ifr.ifr_name, dev, IFNAMSIZ);
}
/* try to create the device */
if( (err = ioctl(fd, TUNSETIFF, (void *) &ifr)) < 0 ) {
close(fd);
return err;
}
/* if the operation was successful, write back the name of the
* interface to the variable "dev", so the caller can know
* it. Note that the caller MUST reserve space in *dev (see calling
* code below) */
strcpy(dev, ifr.ifr_name);
/* this is the special file descriptor that the caller will use to talk
* with the virtual interface */
return fd;
}
int main(void) {
char tun_name[IFNAMSIZ];
int nread, tun_fd;
char buffer[2048];
/* Connect to the device */
strcpy(tun_name, "tun77");
tun_fd = tun_alloc(tun_name, IFF_TUN | IFF_NO_PI); /* tun interface */
if (tun_fd < 0){
perror("Allocating interface");
exit(1);
} else {
printf("connected to %s on fd: %i\n", tun_name, tun_fd);
}
/* Now read data coming from the kernel */
while (1) {
/* Note that "buffer" should be at least the MTU size of the interface, eg 1500 bytes */
nread = read(tun_fd, buffer, sizeof(buffer));
if (nread < 0) {
perror("Reading from interface");
close(tun_fd);
exit(1);
}
/* Do whatever with the data */
printf("Read %d bytes from device %s\n", nread, tun_name);
}
return EXIT_SUCCESS;
}