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(tunctl, BB_DIR_SBIN, BB_SUID_DROP))
  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         opt_complementary = "=0:t--d:d--t"; // no arguments; t ^ d
  87         opts = getopt32(argv, "f:t:d:" IF_FEATURE_TUNCTL_UG("u:g:b"),
  88                         &opt_device, &opt_name, &opt_name
  89                         IF_FEATURE_TUNCTL_UG(, &opt_user, &opt_group));
  90
  91         // select device
  92         memset(&ifr, 0, sizeof(ifr));
  93         ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
  94         strncpy_IFNAMSIZ(ifr.ifr_name, opt_name);
  95
  96         // open device
  97         fd = xopen(opt_device, O_RDWR);
  98         IOCTL(fd, TUNSETIFF, (void *)&ifr);
  99
 100         // delete?
 101         if (opts & OPT_d) {
 102                 IOCTL(fd, TUNSETPERSIST, (void *)(uintptr_t)0);
 103                 printf("Set '%s' nonpersistent\n", ifr.ifr_name);
 104                 return EXIT_SUCCESS;
 105         }
 106
 107         // create
 108 #if ENABLE_FEATURE_TUNCTL_UG
 109         if (opts & OPT_g) {
 110                 group = xgroup2gid(opt_group);
 111                 IOCTL(fd, TUNSETGROUP, (void *)(uintptr_t)group);
 112         } else
 113                 user = geteuid();
 114         if (opts & OPT_u)
 115                 user = xuname2uid(opt_user);
 116         IOCTL(fd, TUNSETOWNER, (void *)(uintptr_t)user);
 117 #endif
 118         IOCTL(fd, TUNSETPERSIST, (void *)(uintptr_t)1);
 119
 120         // show info
 121 #if ENABLE_FEATURE_TUNCTL_UG
 122         if (opts & OPT_b) {
 123                 puts(ifr.ifr_name);
 124         } else {
 125                 printf("Set '%s' %spersistent", ifr.ifr_name, "");
 126                 printf(" and owned by uid %ld", user);
 127                 if (group != -1)
 128                         printf(" gid %ld", group);
 129                 bb_putchar('\n');
 130         }
 131 #else
 132         puts(ifr.ifr_name);
 133 #endif
 134         return EXIT_SUCCESS;
 135 }
 136
 137 #else
 138
 139 /* -210 bytes: */
 140
 141 int tunctl_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 142 int tunctl_main(int argc UNUSED_PARAM, char **argv)
 143 {
 144         struct ifreq ifr;
 145         int fd;
 146         const char *opt_name = "tap%d";
 147         const char *opt_device = "/dev/net/tun";
 148         unsigned opts;
 149
 150         enum {
 151                 OPT_f = 1 << 0, // control device name (/dev/net/tun)
 152                 OPT_t = 1 << 1, // create named interface
 153                 OPT_d = 1 << 2, // delete named interface
 154         };
 155
 156         opt_complementary = "=0:t--d:d--t"; // no arguments; t ^ d
 157         opts = getopt32(argv, "f:t:d:u:g:b", // u, g, b accepted and ignored
 158                         &opt_device, &opt_name, &opt_name, NULL, NULL);
 159
 160         // set interface name
 161         memset(&ifr, 0, sizeof(ifr));
 162         ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
 163         strncpy_IFNAMSIZ(ifr.ifr_name, opt_name);
 164
 165         // open device
 166         fd = xopen(opt_device, O_RDWR);
 167         IOCTL(fd, TUNSETIFF, (void *)&ifr);
 168
 169         // create or delete interface
 170         IOCTL(fd, TUNSETPERSIST, (void *)(uintptr_t)(0 == (opts & OPT_d)));
 171
 172         return EXIT_SUCCESS;
 173 }
 174
 175 #endif