networking/tunctl.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * tun devices controller
   4  *
   5  * Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
   6  *
   7  * Original code:
   8  *      Jeff Dike
   9  *
  10  * Licensed under GPLv2, see file LICENSE in this source tree.
  11  */
  12 //config:config TUNCTL
  13 //config:       bool "tunctl (6.4 kb)"
  14 //config:       default y
  15 //config:       select PLATFORM_LINUX
  16 //config:       help
  17 //config:       tunctl creates or deletes tun devices.
  18 //config:
  19 //config:config FEATURE_TUNCTL_UG
  20 //config:       bool "Support owner:group assignment"
  21 //config:       default y
  22 //config:       depends on TUNCTL
  23 //config:       help
  24 //config:       Allow to specify owner and group of newly created interface.
  25 //config:       340 bytes of pure bloat. Say no here.
  26
  27 //applet:IF_TUNCTL(APPLET_NOEXEC(tunctl, tunctl, BB_DIR_SBIN, BB_SUID_DROP, tunctl))
  28
  29 //kbuild:lib-$(CONFIG_TUNCTL) += tunctl.o
  30
  31 //usage:#define tunctl_trivial_usage
  32 //usage:       "[-f device] ([-t name] | -d name)" IF_FEATURE_TUNCTL_UG(" [-u owner] [-g group] [-b]")
  33 //usage:#define tunctl_full_usage "\n\n"
  34 //usage:       "Create or delete tun interfaces\n"
  35 //usage:     "\n        -f name         tun device (/dev/net/tun)"
  36 //usage:     "\n        -t name         Create iface 'name'"
  37 //usage:     "\n        -d name         Delete iface 'name'"
  38 //usage:        IF_FEATURE_TUNCTL_UG(
  39 //usage:     "\n        -u owner        Set iface owner"
  40 //usage:     "\n        -g group        Set iface group"
  41 //usage:     "\n        -b              Brief output"
  42 //usage:        )
  43 //usage:
  44 //usage:#define tunctl_example_usage
  45 //usage:       "# tunctl\n"
  46 //usage:       "# tunctl -d tun0\n"
  47
  48 #include <netinet/in.h>
  49 #include <net/if.h>
  50 #include <linux/if_tun.h>
  51 #include "libbb.h"
  52
  53 /* TUNSETGROUP appeared in 2.6.23 */
  54 #ifndef TUNSETGROUP
  55 #define TUNSETGROUP _IOW('T', 206, int)
  56 #endif
  57
  58 #define IOCTL(a, b, c) ioctl_or_perror_and_die(a, b, c, NULL)
  59
  60 #if 1
  61
  62 int tunctl_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  63 int tunctl_main(int argc UNUSED_PARAM, char **argv)
  64 {
  65         struct ifreq ifr;
  66         int fd;
  67         const char *opt_name = "tap%d";
  68         const char *opt_device = "/dev/net/tun";
  69 #if ENABLE_FEATURE_TUNCTL_UG
  70         const char *opt_user, *opt_group;
  71         long user = -1, group = -1;
  72 #endif
  73         unsigned opts;
  74
  75         enum {
  76                 OPT_f = 1 << 0, // control device name (/dev/net/tun)
  77                 OPT_t = 1 << 1, // create named interface
  78                 OPT_d = 1 << 2, // delete named interface
  79 #if ENABLE_FEATURE_TUNCTL_UG
  80                 OPT_u = 1 << 3, // set new interface owner
  81                 OPT_g = 1 << 4, // set new interface group
  82                 OPT_b = 1 << 5, // brief output
  83 #endif
  84         };
  85
  86         opts = getopt32(argv, "^"
  87                         "f:t:d:" IF_FEATURE_TUNCTL_UG("u:g:b")
  88                         "\0"
  89                         "=0:t--d:d--t", // no arguments; t ^ d
  90                         &opt_device, &opt_name, &opt_name
  91                         IF_FEATURE_TUNCTL_UG(, &opt_user, &opt_group)
  92         );
  93
  94         // select device
  95         memset(&ifr, 0, sizeof(ifr));
  96         ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
  97         strncpy_IFNAMSIZ(ifr.ifr_name, opt_name);
  98
  99         // open device
 100         fd = xopen(opt_device, O_RDWR);
 101         IOCTL(fd, TUNSETIFF, (void *)&ifr);
 102
 103         // delete?
 104         if (opts & OPT_d) {
 105                 IOCTL(fd, TUNSETPERSIST, (void *)(uintptr_t)0);
 106                 printf("Set '%s' nonpersistent\n", ifr.ifr_name);
 107                 return EXIT_SUCCESS;
 108         }
 109
 110         // create
 111 #if ENABLE_FEATURE_TUNCTL_UG
 112         if (opts & OPT_g) {
 113                 group = xgroup2gid(opt_group);
 114                 IOCTL(fd, TUNSETGROUP, (void *)(uintptr_t)group);
 115         } else
 116                 user = geteuid();
 117         if (opts & OPT_u)
 118                 user = xuname2uid(opt_user);
 119         IOCTL(fd, TUNSETOWNER, (void *)(uintptr_t)user);
 120 #endif
 121         IOCTL(fd, TUNSETPERSIST, (void *)(uintptr_t)1);
 122
 123         // show info
 124 #if ENABLE_FEATURE_TUNCTL_UG
 125         if (opts & OPT_b) {
 126                 puts(ifr.ifr_name);
 127         } else {
 128                 printf("Set '%s' %spersistent", ifr.ifr_name, "");
 129                 printf(" and owned by uid %ld", user);
 130                 if (group != -1)
 131                         printf(" gid %ld", group);
 132                 bb_putchar('\n');
 133         }
 134 #else
 135         puts(ifr.ifr_name);
 136 #endif
 137         return EXIT_SUCCESS;
 138 }
 139
 140 #else
 141
 142 /* -210 bytes: */
 143
 144 int tunctl_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 145 int tunctl_main(int argc UNUSED_PARAM, char **argv)
 146 {
 147         struct ifreq ifr;
 148         int fd;
 149         const char *opt_name = "tap%d";
 150         const char *opt_device = "/dev/net/tun";
 151         unsigned opts;
 152
 153         enum {
 154                 OPT_f = 1 << 0, // control device name (/dev/net/tun)
 155                 OPT_t = 1 << 1, // create named interface
 156                 OPT_d = 1 << 2, // delete named interface
 157         };
 158
 159         opts = getopt32(argv, "^"
 160                         "f:t:d:u:g:b" // u, g, b accepted and ignored
 161                         "\0"
 162                         "=0:t--d:d--t", // no arguments; t ^ d
 163                         &opt_device, &opt_name, &opt_name, NULL, NULL
 164         );
 165
 166         // set interface name
 167         memset(&ifr, 0, sizeof(ifr));
 168         ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
 169         strncpy_IFNAMSIZ(ifr.ifr_name, opt_name);
 170
 171         // open device
 172         fd = xopen(opt_device, O_RDWR);
 173         IOCTL(fd, TUNSETIFF, (void *)&ifr);
 174
 175         // create or delete interface
 176         IOCTL(fd, TUNSETPERSIST, (void *)(uintptr_t)(0 == (opts & OPT_d)));
 177
 178         return EXIT_SUCCESS;
 179 }
 180
 181 #endif