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tun-driver.c
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tun-driver.c
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#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <net/if.h>
#include <linux/if_tun.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include "tun-driver.h"
int tun_alloc(char dev[IFNAMSIZ], short flags) {
// Interface request structure
struct ifreq ifr;
// File descriptor
int fileDescriptor;
// Open the tun device, if it doesn't exists return the error
char *cloneDevice = "/dev/net/tun";
if ((fileDescriptor = open(cloneDevice, O_RDWR)) < 0) {
perror("open /dev/net/tun");
return fileDescriptor;
}
// Initialize the ifreq structure with 0s and the set flags
memset(&ifr, 0, sizeof(ifr));
ifr.ifr_flags = flags;
// If a device name is passed we should add it to the ifreq struct
// Otherwise the kernel will try to allocate the next available
// device of the given type
if (*dev) {
strncpy(ifr.ifr_name, dev, IFNAMSIZ);
}
// Ask the kernel to create the new device
int err = ioctl(fileDescriptor, TUNSETIFF, (void *) &ifr);
if (err < 0) {
// If something went wrong close the file and return
perror("ioctl TUNSETIFF");
close(fileDescriptor);
return err;
}
// Write the device name back to the dev variable so the caller
// can access it
strcpy(dev, ifr.ifr_name);
// Return the file descriptor
return fileDescriptor;
}