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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <libgen.h>
#include <getopt.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <linux/if_tun.h>
#include <linux/if.h>
#include <linux/if_ether.h>
#include <arpa/inet.h>
static struct option long_options[] = {
{ "delete", no_argument, 0, 'd'},
{ "help", no_argument, 0, 'h'},
{ 0, 0, 0, 0}
};
void usage(char *prog) {
fprintf(stderr, "note: you must be root (except perhaps to delete "
"the interface)\n");
fprintf(stderr, "usage: %s [--help | -h] | [--delete | -d] "
"<interface_name>\n", basename(prog));
exit(-1);
}
int main(int argc, char **argv) {
struct ifreq ifr, ifw;
char if_name[IFNAMSIZ], *chan_name = "gsm";
int option_index = 0, c, delete_if = 0, persist = 1, fd, sd;
while((c = getopt_long(argc, argv, "dh?", long_options, &option_index))
!= -1) {
switch(c) {
case 'd':
delete_if = 1;
break;
case 'h':
case '?':
default:
usage(argv[0]);
break;
}
}
if(optind >= argc)
usage(argv[0]);
chan_name = argv[optind];
if(!delete_if && getuid() && geteuid())
usage(argv[0]);
// construct TUN interface
if((fd = open("/dev/net/tun", O_RDWR)) == -1) {
perror("open");
return -1;
}
memset(&ifr, 0, sizeof(ifr));
ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
snprintf(ifr.ifr_name, IFNAMSIZ, "%s", chan_name);
if(ioctl(fd, TUNSETIFF, (void *)&ifr) == -1) {
perror("TUNSETIFF");
close(fd);
return -1;
}
// save actual name
memcpy(if_name, ifr.ifr_name, IFNAMSIZ);
if(delete_if)
persist = 0;
if(ioctl(fd, TUNSETPERSIST, (void *)persist) == -1) {
perror("TUNSETPERSIST");
close(fd);
return -1;
}
if(delete_if) {
close(fd);
return 0;
}
// set interface up
if((sd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
perror("socket");
close(fd);
return -1;
}
// get current flags
memset(&ifr, 0, sizeof(ifr));
strncpy(ifr.ifr_name, if_name, IFNAMSIZ - 1);
if(ioctl(sd, SIOCGIFFLAGS, &ifr) == -1) {
perror("SIOCGIFFLAGS");
close(sd);
close(fd);
return -1;
}
// set up
memset(&ifw, 0, sizeof(ifw));
strncpy(ifw.ifr_name, if_name, IFNAMSIZ - 1);
ifw.ifr_flags = ifr.ifr_flags | IFF_UP | IFF_RUNNING;
if(ioctl(sd, SIOCSIFFLAGS, &ifw) == -1) {
perror("SIOCSIFFLAGS");
close(sd);
close(fd);
return -1;
}
close(sd);
close(fd);
return 0;
}
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