plugins/linuxdisk/linuxdisk.c

   1 /* nbdkit
   2  * Copyright Red Hat
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *
  11  * * Redistributions in binary form must reproduce the above copyright
  12  * notice, this list of conditions and the following disclaimer in the
  13  * documentation and/or other materials provided with the distribution.
  14  *
  15  * * Neither the name of Red Hat nor the names of its contributors may be
  16  * used to endorse or promote products derived from this software without
  17  * specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  22  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  26  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  27  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  29  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <config.h>
  34
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <stdbool.h>
  38 #include <inttypes.h>
  39 #include <string.h>
  40 #include <unistd.h>
  41 #include <time.h>
  42
  43 #define NBDKIT_API_VERSION 2
  44
  45 #include <nbdkit-plugin.h>
  46
  47 #include "random.h"
  48 #include "regions.h"
  49
  50 #include "virtual-disk.h"
  51
  52 /* Directory, label, type, size parameters. */
  53 const char *dir;
  54 const char *label;
  55 const char *type = "ext2";
  56 int64_t size;
  57 bool size_add_estimate;  /* if size=+SIZE was used */
  58
  59 /* Virtual disk. */
  60 static struct virtual_disk disk;
  61
  62 /* Used to create a random GUID for the partition. */
  63 struct random_state random_state;
  64
  65 static void
  66 linuxdisk_load (void)
  67 {
  68   init_virtual_disk (&disk);
  69   xsrandom (time (NULL), &random_state);
  70 }
  71
  72 static void
  73 linuxdisk_unload (void)
  74 {
  75   free_virtual_disk (&disk);
  76 }
  77
  78 static int
  79 linuxdisk_config (const char *key, const char *value)
  80 {
  81   if (strcmp (key, "dir") == 0) {
  82     if (dir != NULL) {
  83       /* TODO: Support merging of multiple directories, like iso plugin. */
  84       nbdkit_error ("dir=<DIRECTORY> must only be set once");
  85       return -1;
  86     }
  87     /* We don't actually need to use realpath here because the
  88      * directory is only used in .get_ready, before we chdir.  Not
  89      * doing realpath is helpful because on Windows it will munge the
  90      * path in such a way that external mke2fs cannot parse it.
  91      */
  92     dir = value;
  93   }
  94   else if (strcmp (key, "label") == 0) {
  95     label = value;
  96   }
  97   else if (strcmp (key, "type") == 0) {
  98     if (strncmp (value, "ext", 3) != 0) {
  99       nbdkit_error ("type=<TYPE> must be an filesystem type "
 100                     "supported by e2fsprogs");
 101       return -1;
 102     }
 103     type = value;
 104   }
 105   else if (strcmp (key, "size") == 0) {
 106     if (value[0] == '+') {
 107       size_add_estimate = true;
 108       value++;
 109     }
 110     else
 111       size_add_estimate = false;
 112     size = nbdkit_parse_size (value);
 113     if (size == -1)
 114       return -1;
 115   }
 116   else {
 117     nbdkit_error ("unknown parameter '%s'", key);
 118     return -1;
 119   }
 120
 121   return 0;
 122 }
 123
 124 static int
 125 linuxdisk_config_complete (void)
 126 {
 127   if (dir == NULL) {
 128     nbdkit_error ("you must supply the dir=<DIRECTORY> parameter "
 129                   "after the plugin name on the command line");
 130     return -1;
 131   }
 132
 133   return 0;
 134 }
 135
 136 #define linuxdisk_config_help \
 137   "dir=<DIRECTORY>  (required) The directory to serve.\n" \
 138   "label=<LABEL>               The filesystem label.\n" \
 139   "type=ext2|ext3|ext4         The filesystem type.\n" \
 140   "size=[+]<SIZE>              The virtual filesystem size."
 141
 142 static int
 143 linuxdisk_get_ready (void)
 144 {
 145   return create_virtual_disk (&disk);
 146 }
 147
 148 static void *
 149 linuxdisk_open (int readonly)
 150 {
 151   return NBDKIT_HANDLE_NOT_NEEDED;
 152 }
 153
 154 #define THREAD_MODEL NBDKIT_THREAD_MODEL_PARALLEL
 155
 156 /* Get the file size. */
 157 static int64_t
 158 linuxdisk_get_size (void *handle)
 159 {
 160   return virtual_size (&disk.regions);
 161 }
 162
 163 /* Serves the same data over multiple connections. */
 164 static int
 165 linuxdisk_can_multi_conn (void *handle)
 166 {
 167   return 1;
 168 }
 169
 170 /* Cache. */
 171 static int
 172 linuxdisk_can_cache (void *handle)
 173 {
 174   /* Let nbdkit call pread to populate the file system cache. */
 175   return NBDKIT_CACHE_EMULATE;
 176 }
 177
 178 /* Read data from the virtual disk. */
 179 static int
 180 linuxdisk_pread (void *handle, void *buf, uint32_t count, uint64_t offset,
 181                  uint32_t flags)
 182 {
 183   while (count > 0) {
 184     const struct region *region = find_region (&disk.regions, offset);
 185     size_t len;
 186     ssize_t r;
 187
 188     /* Length to end of region. */
 189     len = region->end - offset + 1;
 190     if (len > count)
 191       len = count;
 192
 193     switch (region->type) {
 194     case region_file:
 195       /* We don't use region->u.i since there is only one backing
 196        * file, and we have that open already (in ‘disk.fd’).
 197        */
 198       r = pread (disk.fd, buf, len, offset - region->start);
 199       if (r == -1) {
 200         nbdkit_error ("pread: %m");
 201         return -1;
 202       }
 203       if (r == 0) {
 204         nbdkit_error ("pread: unexpected end of file");
 205         return -1;
 206       }
 207       len = r;
 208       break;
 209
 210     case region_data:
 211       memcpy (buf, &region->u.data[offset - region->start], len);
 212       break;
 213
 214     case region_zero:
 215       memset (buf, 0, len);
 216       break;
 217     }
 218
 219     count -= len;
 220     buf += len;
 221     offset += len;
 222   }
 223
 224   return 0;
 225 }
 226
 227 static struct nbdkit_plugin plugin = {
 228   .name              = "linuxdisk",
 229   .longname          = "nbdkit Linux virtual disk plugin",
 230   .version           = PACKAGE_VERSION,
 231   .load              = linuxdisk_load,
 232   .unload            = linuxdisk_unload,
 233   .config            = linuxdisk_config,
 234   .config_complete   = linuxdisk_config_complete,
 235   .config_help       = linuxdisk_config_help,
 236   .magic_config_key  = "dir",
 237   .get_ready         = linuxdisk_get_ready,
 238   .open              = linuxdisk_open,
 239   .get_size          = linuxdisk_get_size,
 240   .can_multi_conn    = linuxdisk_can_multi_conn,
 241   .can_cache         = linuxdisk_can_cache,
 242   .pread             = linuxdisk_pread,
 243   .errno_is_preserved = 1,
 244 };
 245
 246 NBDKIT_REGISTER_PLUGIN (plugin)