1 /* tunctl.c - Control tap/tun network devices.
2  *
3  * Copyright 2016 Rob Landley <rob@landley.net>
4  *
5  * See http://kernel.org/doc/Documentation/networking/tuntap.txt
6  *
7  * This is useful for things like "kvm -netdev tap" and containers.
8  * See https://landley.net/lxc/02-networking.html for example usage.
9  *
10  * todo: bridge mode
11  *  -b	bridge daemon (forwards packets between NAME and NAME2 interfaces)
12 
13 
14 USE_TUNCTL(NEWTOY(tunctl, "<1>1t|d|u:T[!td]", TOYFLAG_USR|TOYFLAG_BIN))
15 
16 config TUNCTL
17   bool "tunctl"
18   default y
19   help
20     usage: tunctl [-dtT] [-u USER] NAME
21 
22     Create and delete tun/tap virtual ethernet devices.
23 
24     -T	Use tap (ethernet frames) instead of tun (ip packets)
25     -d	Delete tun/tap device
26     -t	Create tun/tap device
27     -u	Set owner (user who can read/write device without root access)
28 */
29 
30 #define FOR_tunctl
31 #include "toys.h"
32 #include <linux/if_tun.h>
33 
34 GLOBALS(
35   char *user;
36 )
37 
38 void tunctl_main(void)
39 {
40   struct ifreq *ifr = (void *)toybuf;
41   uid_t u = TT.user ?  xgetuid(TT.user) : 0;
42   int fd = xopen("/dev/net/tun", O_RDWR);
43 
44   // Associate filehandle with device
45   ifr->ifr_flags = ((toys.optflags&FLAG_T) ? IFF_TUN : IFF_TAP)|IFF_NO_PI;
46   strncpy(ifr->ifr_name, *toys.optargs, sizeof(ifr->ifr_name));
47   xioctl(fd, TUNSETIFF, toybuf);
48 
49   if (toys.optflags&FLAG_t) {
50     xioctl(fd, TUNSETPERSIST, (void *)1);
51     xioctl(fd, TUNSETOWNER, (void *)(long)u);
52   } else xioctl(fd, TUNSETPERSIST, (void *)0);
53 }
54