Archipelago » blktap-utils

/*

 * Copyright (c) 2008, XenSource Inc.

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions are met:

 *     * Redistributions of source code must retain the above copyright

 *       notice, this list of conditions and the following disclaimer.

 *     * Redistributions in binary form must reproduce the above copyright

 *       notice, this list of conditions and the following disclaimer in the

 *       documentation and/or other materials provided with the distribution.

 *     * Neither the name of XenSource Inc. nor the names of its contributors

 *       may be used to endorse or promote products derived from this software

 *       without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER

 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF

 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING

 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include <stdio.h>

#include <errno.h>

#include <fcntl.h>

#include <stdlib.h>

#include <unistd.h>

#include <string.h>

#include <getopt.h>

#include <libgen.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <sys/ioctl.h>

#include <linux/major.h>

#include "tap-ctl.h"

#include "blktap2.h"

static int

tap_ctl_prepare_directory(const char *dir)

{

        int err;

        char *ptr, *name, *start;

        err = access(dir, W_OK | R_OK);

        if (!err)

                return 0;

        name = strdup(dir);

        if (!name)

                return ENOMEM;

        start = name;

        for (;;) {

                ptr = strchr(start + 1, '/');

                if (ptr)

                        *ptr = '\0';

                err = mkdir(name, 0755);

                if (err && errno != EEXIST) {

                        PERROR("mkdir %s", name);

                        err = errno;

                        break;

                }

                if (!ptr)

                        break;

                else {

                        *ptr = '/';

                        start = ptr + 1;

                }

        }

        free(name);

        return err;

}

static int

tap_ctl_make_device(const char *devname, const int major,

                    const int minor, const int perm)

{

        int err;

        char *copy, *dir;

        copy = strdup(devname);

        if (!copy)

                return ENOMEM;

        dir = dirname(copy);

        err = tap_ctl_prepare_directory(dir);

        free(copy);

        if (err)

                return err;

        if (!access(devname, F_OK))

                if (unlink(devname)) {

                        PERROR("unlink %s", devname);

                        return errno;

                }

        err = mknod(devname, perm, makedev(major, minor));

        if (err) {

                PERROR("mknod %s", devname);

                return errno;

        }

        return 0;

}

static int

tap_ctl_check_environment(void)

{

        FILE *f;

        int err, minor;

        char name[256];

        err = tap_ctl_prepare_directory(BLKTAP2_CONTROL_DIR);

        if (err)

                return err;

        if (!access(BLKTAP2_CONTROL_DEVICE, R_OK | W_OK))

                return 0;

        memset(name, 0, sizeof(name));

        f = fopen("/proc/misc", "r");

        if (!f) {

                EPRINTF("failed to open /proc/misc: %d\n", errno);

                return errno;

        }

        while (fscanf(f, "%d %256s", &minor, name) == 2)

                if (!strcmp(name, BLKTAP2_CONTROL_NAME)) {

                        err = tap_ctl_make_device(BLKTAP2_CONTROL_DEVICE,

                                                  MISC_MAJOR,

                                                  minor, S_IFCHR | 0600);

                        goto out;

                }

        err = ENOSYS;

        EPRINTF("didn't find %s in /proc/misc\n", BLKTAP2_CONTROL_NAME);

out:

        fclose(f);

        return err;

}

static int

tap_ctl_allocate_device(int *minor, char **devname)

{

        char *name;

        int fd, err;

        struct blktap2_handle handle;

        *minor = -1;

        if (!devname)

                return EINVAL;

        fd = open(BLKTAP2_CONTROL_DEVICE, O_RDONLY);

        if (fd == -1) {

                EPRINTF("failed to open control device: %d\n", errno);

                return errno;

        }

        err = ioctl(fd, BLKTAP2_IOCTL_ALLOC_TAP, &handle);

        close(fd);

        if (err == -1) {

                EPRINTF("failed to allocate new device: %d\n", errno);

                return errno;

        }

        err = asprintf(&name, "%s%d", BLKTAP2_RING_DEVICE, handle.minor);

        if (err == -1) {

                err = ENOMEM;

                goto fail;

        }

        err = tap_ctl_make_device(name, handle.ring,

                                  handle.minor, S_IFCHR | 0600);

        free(name);

        if (err) {

                EPRINTF("creating ring device for %d failed: %d\n",

                        handle.minor, err);

                goto fail;

        }

        if (*devname)

                name = *devname;

        else {

                err = asprintf(&name, "%s%d",

                               BLKTAP2_IO_DEVICE, handle.minor);

                if (err == -1) {

                        err = ENOMEM;

                        goto fail;

                }

                *devname = name;

        }

        err = tap_ctl_make_device(name, handle.device,

                                  handle.minor, S_IFBLK | 0600);

        if (err) {

                EPRINTF("creating IO device for %d failed: %d\n",

                        handle.minor, err);

                goto fail;

        }

        DBG("new interface: ring: %u, device: %u, minor: %u\n",

            handle.ring, handle.device, handle.minor);

        *minor = handle.minor;

        return 0;

fail:

        tap_ctl_free(handle.minor);

        return err;

}

int

tap_ctl_allocate(int *minor, char **devname)

{

        int err;

        *minor = -1;

        err = tap_ctl_check_environment();

        if (err)

                return err;

        err = tap_ctl_allocate_device(minor, devname);

        if (err)

                return err;

        return 0;

}