/* vi: set sw=4 ts=4: */
/*
 * tun devices controller
 *
 * Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
 *
 * Original code:
 *      Jeff Dike
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */
//config:config TUNCTL
//config:       bool "tunctl (6.2 kb)"
//config:       default y
//config:       help
//config:       tunctl creates or deletes tun devices.
//config:
//config:config FEATURE_TUNCTL_UG
//config:       bool "Support owner:group assignment"
//config:       default y
//config:       depends on TUNCTL
//config:       help
//config:       Allow to specify owner and group of newly created interface.
//config:       340 bytes of pure bloat. Say no here.

//applet:IF_TUNCTL(APPLET_NOEXEC(tunctl, tunctl, BB_DIR_SBIN, BB_SUID_DROP, tunctl))

//kbuild:lib-$(CONFIG_TUNCTL) += tunctl.o

//usage:#define tunctl_trivial_usage
//usage:       "[-f DEVICE] [-t NAME | -d NAME]" IF_FEATURE_TUNCTL_UG(" [-u USER] [-g GRP] [-b]")
//usage:#define tunctl_full_usage "\n\n"
//usage:       "Create or delete TUN/TAP interfaces\n"
//usage:     "\n        -f DEV  TUN device (default /dev/net/tun)"
//usage:     "\n        -t NAME Create iface (default: tapN)"
//usage:     "\n        -d NAME Delete iface"
//usage:        IF_FEATURE_TUNCTL_UG(
//usage:     "\n        -u USER Set iface owner"
//usage:     "\n        -g GRP  Set iface group"
//usage:     "\n        -b      Brief output"
//usage:        )
//usage:
//usage:#define tunctl_example_usage
//usage:       "# tunctl\n"
//usage:       "# tunctl -d tun0\n"

#include <netinet/in.h>
#include <net/if.h>
#include <linux/if_tun.h>
#include "libbb.h"

/* TUNSETGROUP appeared in 2.6.23 */
#ifndef TUNSETGROUP
#define TUNSETGROUP _IOW('T', 206, int)
#endif

#define IOCTL(a, b, c) ioctl_or_perror_and_die(a, b, c, NULL)

#if 1

int tunctl_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int tunctl_main(int argc UNUSED_PARAM, char **argv)
{
        struct ifreq ifr;
        int fd;
        const char *opt_name = "tap%d";
        const char *opt_device = "/dev/net/tun";
#if ENABLE_FEATURE_TUNCTL_UG
        const char *opt_user, *opt_group;
        long user = -1, group = -1;
#endif
        unsigned opts;

        enum {
                OPT_f = 1 << 0, // control device name (/dev/net/tun)
                OPT_t = 1 << 1, // create named interface
                OPT_d = 1 << 2, // delete named interface
#if ENABLE_FEATURE_TUNCTL_UG
                OPT_u = 1 << 3, // set new interface owner
                OPT_g = 1 << 4, // set new interface group
                OPT_b = 1 << 5, // brief output
#endif
        };

        opts = getopt32(argv, "^"
                        "f:t:d:" IF_FEATURE_TUNCTL_UG("u:g:b")
                        "\0"
                        "=0:t--d:d--t", // no arguments; t ^ d
                        &opt_device, &opt_name, &opt_name
                        IF_FEATURE_TUNCTL_UG(, &opt_user, &opt_group)
        );

        // select device
        memset(&ifr, 0, sizeof(ifr));
        ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
        strncpy_IFNAMSIZ(ifr.ifr_name, opt_name);

        // open device
        fd = xopen(opt_device, O_RDWR);
        IOCTL(fd, TUNSETIFF, (void *)&ifr);

        // delete?
        if (opts & OPT_d) {
                IOCTL(fd, TUNSETPERSIST, (void *)(uintptr_t)0);
                printf("Set '%s' nonpersistent\n", ifr.ifr_name);
                return EXIT_SUCCESS;
        }

        // create
#if ENABLE_FEATURE_TUNCTL_UG
        if (opts & OPT_g) {
                group = xgroup2gid(opt_group);
                IOCTL(fd, TUNSETGROUP, (void *)(uintptr_t)group);
        } else
                user = geteuid();
        if (opts & OPT_u)
                user = xuname2uid(opt_user);
        IOCTL(fd, TUNSETOWNER, (void *)(uintptr_t)user);
#endif
        IOCTL(fd, TUNSETPERSIST, (void *)(uintptr_t)1);

        // show info
#if ENABLE_FEATURE_TUNCTL_UG
        if (opts & OPT_b) {
                puts(ifr.ifr_name);
        } else {
                printf("Set '%s' %spersistent", ifr.ifr_name, "");
                printf(" and owned by uid %ld", user);
                if (group != -1)
                        printf(" gid %ld", group);
                bb_putchar('\n');
        }
#else
        puts(ifr.ifr_name);
#endif
        return EXIT_SUCCESS;
}

#else

/* -210 bytes: */

int tunctl_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int tunctl_main(int argc UNUSED_PARAM, char **argv)
{
        struct ifreq ifr;
        int fd;
        const char *opt_name = "tap%d";
        const char *opt_device = "/dev/net/tun";
        unsigned opts;

        enum {
                OPT_f = 1 << 0, // control device name (/dev/net/tun)
                OPT_t = 1 << 1, // create named interface
                OPT_d = 1 << 2, // delete named interface
        };

        opts = getopt32(argv, "^"
                        "f:t:d:u:g:b" // u, g, b accepted and ignored
                        "\0"
                        "=0:t--d:d--t", // no arguments; t ^ d
                        &opt_device, &opt_name, &opt_name, NULL, NULL
        );

        // set interface name
        memset(&ifr, 0, sizeof(ifr));
        ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
        strncpy_IFNAMSIZ(ifr.ifr_name, opt_name);

        // open device
        fd = xopen(opt_device, O_RDWR);
        IOCTL(fd, TUNSETIFF, (void *)&ifr);

        // create or delete interface
        IOCTL(fd, TUNSETPERSIST, (void *)(uintptr_t)(0 == (opts & OPT_d)));

        return EXIT_SUCCESS;
}

#endif