net/core/net_namespace.c

   1 #include <linux/workqueue.h>
   2 #include <linux/rtnetlink.h>
   3 #include <linux/cache.h>
   4 #include <linux/slab.h>
   5 #include <linux/list.h>
   6 #include <linux/delay.h>
   7 #include <linux/sched.h>
   8 #include <linux/idr.h>
   9 #include <net/net_namespace.h>
  10 #include <net/netns/generic.h>
  11
  12 /*
  13  *      Our network namespace constructor/destructor lists
  14  */
  15
  16 static LIST_HEAD(pernet_list);
  17 static struct list_head *first_device = &pernet_list;
  18 static DEFINE_MUTEX(net_mutex);
  19
  20 LIST_HEAD(net_namespace_list);
  21 EXPORT_SYMBOL_GPL(net_namespace_list);
  22
  23 struct net init_net;
  24 EXPORT_SYMBOL(init_net);
  25
  26 #define INITIAL_NET_GEN_PTRS    13 /* +1 for len +2 for rcu_head */
  27
  28 /*
  29  * setup_net runs the initializers for the network namespace object.
  30  */
  31 static __net_init int setup_net(struct net *net)
  32 {
  33         /* Must be called with net_mutex held */
  34         struct pernet_operations *ops;
  35         int error = 0;
  36
  37         atomic_set(&net->count, 1);
  38
  39 #ifdef NETNS_REFCNT_DEBUG
  40         atomic_set(&net->use_count, 0);
  41 #endif
  42
  43         list_for_each_entry(ops, &pernet_list, list) {
  44                 if (ops->init) {
  45                         error = ops->init(net);
  46                         if (error < 0)
  47                                 goto out_undo;
  48                 }
  49         }
  50 out:
  51         return error;
  52
  53 out_undo:
  54         /* Walk through the list backwards calling the exit functions
  55          * for the pernet modules whose init functions did not fail.
  56          */
  57         list_for_each_entry_continue_reverse(ops, &pernet_list, list) {
  58                 if (ops->exit)
  59                         ops->exit(net);
  60         }
  61
  62         rcu_barrier();
  63         goto out;
  64 }
  65
  66 static struct net_generic *net_alloc_generic(void)
  67 {
  68         struct net_generic *ng;
  69         size_t generic_size = sizeof(struct net_generic) +
  70                 INITIAL_NET_GEN_PTRS * sizeof(void *);
  71
  72         ng = kzalloc(generic_size, GFP_KERNEL);
  73         if (ng)
  74                 ng->len = INITIAL_NET_GEN_PTRS;
  75
  76         return ng;
  77 }
  78
  79 #ifdef CONFIG_NET_NS
  80 static struct kmem_cache *net_cachep;
  81 static struct workqueue_struct *netns_wq;
  82
  83 static struct net *net_alloc(void)
  84 {
  85         struct net *net = NULL;
  86         struct net_generic *ng;
  87
  88         ng = net_alloc_generic();
  89         if (!ng)
  90                 goto out;
  91
  92         net = kmem_cache_zalloc(net_cachep, GFP_KERNEL);
  93         if (!net)
  94                 goto out_free;
  95
  96         rcu_assign_pointer(net->gen, ng);
  97 out:
  98         return net;
  99
 100 out_free:
 101         kfree(ng);
 102         goto out;
 103 }
 104
 105 static void net_free(struct net *net)
 106 {
 107 #ifdef NETNS_REFCNT_DEBUG
 108         if (unlikely(atomic_read(&net->use_count) != 0)) {
 109                 printk(KERN_EMERG "network namespace not free! Usage: %d\n",
 110                         atomic_read(&net->use_count));
 111                 return;
 112         }
 113 #endif
 114         kfree(net->gen);
 115         kmem_cache_free(net_cachep, net);
 116 }
 117
 118 struct net *copy_net_ns(unsigned long flags, struct net *old_net)
 119 {
 120         struct net *new_net = NULL;
 121         int err;
 122
 123         get_net(old_net);
 124
 125         if (!(flags & CLONE_NEWNET))
 126                 return old_net;
 127
 128         err = -ENOMEM;
 129         new_net = net_alloc();
 130         if (!new_net)
 131                 goto out_err;
 132
 133         mutex_lock(&net_mutex);
 134         err = setup_net(new_net);
 135         if (!err) {
 136                 rtnl_lock();
 137                 list_add_tail(&new_net->list, &net_namespace_list);
 138                 rtnl_unlock();
 139         }
 140         mutex_unlock(&net_mutex);
 141
 142         if (err)
 143                 goto out_free;
 144 out:
 145         put_net(old_net);
 146         return new_net;
 147
 148 out_free:
 149         net_free(new_net);
 150 out_err:
 151         new_net = ERR_PTR(err);
 152         goto out;
 153 }
 154
 155 static void cleanup_net(struct work_struct *work)
 156 {
 157         struct pernet_operations *ops;
 158         struct net *net;
 159
 160         net = container_of(work, struct net, work);
 161
 162         mutex_lock(&net_mutex);
 163
 164         /* Don't let anyone else find us. */
 165         rtnl_lock();
 166         list_del(&net->list);
 167         rtnl_unlock();
 168
 169         /* Run all of the network namespace exit methods */
 170         list_for_each_entry_reverse(ops, &pernet_list, list) {
 171                 if (ops->exit)
 172                         ops->exit(net);
 173         }
 174
 175         mutex_unlock(&net_mutex);
 176
 177         /* Ensure there are no outstanding rcu callbacks using this
 178          * network namespace.
 179          */
 180         rcu_barrier();
 181
 182         /* Finally it is safe to free my network namespace structure */
 183         net_free(net);
 184 }
 185
 186 void __put_net(struct net *net)
 187 {
 188         /* Cleanup the network namespace in process context */
 189         INIT_WORK(&net->work, cleanup_net);
 190         queue_work(netns_wq, &net->work);
 191 }
 192 EXPORT_SYMBOL_GPL(__put_net);
 193
 194 #else
 195 struct net *copy_net_ns(unsigned long flags, struct net *old_net)
 196 {
 197         if (flags & CLONE_NEWNET)
 198                 return ERR_PTR(-EINVAL);
 199         return old_net;
 200 }
 201 #endif
 202
 203 static int __init net_ns_init(void)
 204 {
 205         struct net_generic *ng;
 206         int err;
 207
 208         printk(KERN_INFO "net_namespace: %zd bytes\n", sizeof(struct net));
 209 #ifdef CONFIG_NET_NS
 210         net_cachep = kmem_cache_create("net_namespace", sizeof(struct net),
 211                                         SMP_CACHE_BYTES,
 212                                         SLAB_PANIC, NULL);
 213
 214         /* Create workqueue for cleanup */
 215         netns_wq = create_singlethread_workqueue("netns");
 216         if (!netns_wq)
 217                 panic("Could not create netns workq");
 218 #endif
 219
 220         ng = net_alloc_generic();
 221         if (!ng)
 222                 panic("Could not allocate generic netns");
 223
 224         rcu_assign_pointer(init_net.gen, ng);
 225
 226         mutex_lock(&net_mutex);
 227         err = setup_net(&init_net);
 228
 229         rtnl_lock();
 230         list_add_tail(&init_net.list, &net_namespace_list);
 231         rtnl_unlock();
 232
 233         mutex_unlock(&net_mutex);
 234         if (err)
 235                 panic("Could not setup the initial network namespace");
 236
 237         return 0;
 238 }
 239
 240 pure_initcall(net_ns_init);
 241
 242 #ifdef CONFIG_NET_NS
 243 static int register_pernet_operations(struct list_head *list,
 244                                       struct pernet_operations *ops)
 245 {
 246         struct net *net, *undo_net;
 247         int error;
 248
 249         list_add_tail(&ops->list, list);
 250         if (ops->init) {
 251                 for_each_net(net) {
 252                         error = ops->init(net);
 253                         if (error)
 254                                 goto out_undo;
 255                 }
 256         }
 257         return 0;
 258
 259 out_undo:
 260         /* If I have an error cleanup all namespaces I initialized */
 261         list_del(&ops->list);
 262         if (ops->exit) {
 263                 for_each_net(undo_net) {
 264                         if (undo_net == net)
 265                                 goto undone;
 266                         ops->exit(undo_net);
 267                 }
 268         }
 269 undone:
 270         return error;
 271 }
 272
 273 static void unregister_pernet_operations(struct pernet_operations *ops)
 274 {
 275         struct net *net;
 276
 277         list_del(&ops->list);
 278         if (ops->exit)
 279                 for_each_net(net)
 280                         ops->exit(net);
 281 }
 282
 283 #else
 284
 285 static int register_pernet_operations(struct list_head *list,
 286                                       struct pernet_operations *ops)
 287 {
 288         if (ops->init == NULL)
 289                 return 0;
 290         return ops->init(&init_net);
 291 }
 292
 293 static void unregister_pernet_operations(struct pernet_operations *ops)
 294 {
 295         if (ops->exit)
 296                 ops->exit(&init_net);
 297 }
 298 #endif
 299
 300 static DEFINE_IDA(net_generic_ids);
 301
 302 /**
 303  *      register_pernet_subsys - register a network namespace subsystem
 304  *      @ops:  pernet operations structure for the subsystem
 305  *
 306  *      Register a subsystem which has init and exit functions
 307  *      that are called when network namespaces are created and
 308  *      destroyed respectively.
 309  *
 310  *      When registered all network namespace init functions are
 311  *      called for every existing network namespace.  Allowing kernel
 312  *      modules to have a race free view of the set of network namespaces.
 313  *
 314  *      When a new network namespace is created all of the init
 315  *      methods are called in the order in which they were registered.
 316  *
 317  *      When a network namespace is destroyed all of the exit methods
 318  *      are called in the reverse of the order with which they were
 319  *      registered.
 320  */
 321 int register_pernet_subsys(struct pernet_operations *ops)
 322 {
 323         int error;
 324         mutex_lock(&net_mutex);
 325         error =  register_pernet_operations(first_device, ops);
 326         mutex_unlock(&net_mutex);
 327         return error;
 328 }
 329 EXPORT_SYMBOL_GPL(register_pernet_subsys);
 330
 331 /**
 332  *      unregister_pernet_subsys - unregister a network namespace subsystem
 333  *      @ops: pernet operations structure to manipulate
 334  *
 335  *      Remove the pernet operations structure from the list to be
 336  *      used when network namespaces are created or destroyed.  In
 337  *      addition run the exit method for all existing network
 338  *      namespaces.
 339  */
 340 void unregister_pernet_subsys(struct pernet_operations *module)
 341 {
 342         mutex_lock(&net_mutex);
 343         unregister_pernet_operations(module);
 344         mutex_unlock(&net_mutex);
 345 }
 346 EXPORT_SYMBOL_GPL(unregister_pernet_subsys);
 347
 348 int register_pernet_gen_subsys(int *id, struct pernet_operations *ops)
 349 {
 350         int rv;
 351
 352         mutex_lock(&net_mutex);
 353 again:
 354         rv = ida_get_new_above(&net_generic_ids, 1, id);
 355         if (rv < 0) {
 356                 if (rv == -EAGAIN) {
 357                         ida_pre_get(&net_generic_ids, GFP_KERNEL);
 358                         goto again;
 359                 }
 360                 goto out;
 361         }
 362         rv = register_pernet_operations(first_device, ops);
 363         if (rv < 0)
 364                 ida_remove(&net_generic_ids, *id);
 365 out:
 366         mutex_unlock(&net_mutex);
 367         return rv;
 368 }
 369 EXPORT_SYMBOL_GPL(register_pernet_gen_subsys);
 370
 371 void unregister_pernet_gen_subsys(int id, struct pernet_operations *ops)
 372 {
 373         mutex_lock(&net_mutex);
 374         unregister_pernet_operations(ops);
 375         ida_remove(&net_generic_ids, id);
 376         mutex_unlock(&net_mutex);
 377 }
 378 EXPORT_SYMBOL_GPL(unregister_pernet_gen_subsys);
 379
 380 /**
 381  *      register_pernet_device - register a network namespace device
 382  *      @ops:  pernet operations structure for the subsystem
 383  *
 384  *      Register a device which has init and exit functions
 385  *      that are called when network namespaces are created and
 386  *      destroyed respectively.
 387  *
 388  *      When registered all network namespace init functions are
 389  *      called for every existing network namespace.  Allowing kernel
 390  *      modules to have a race free view of the set of network namespaces.
 391  *
 392  *      When a new network namespace is created all of the init
 393  *      methods are called in the order in which they were registered.
 394  *
 395  *      When a network namespace is destroyed all of the exit methods
 396  *      are called in the reverse of the order with which they were
 397  *      registered.
 398  */
 399 int register_pernet_device(struct pernet_operations *ops)
 400 {
 401         int error;
 402         mutex_lock(&net_mutex);
 403         error = register_pernet_operations(&pernet_list, ops);
 404         if (!error && (first_device == &pernet_list))
 405                 first_device = &ops->list;
 406         mutex_unlock(&net_mutex);
 407         return error;
 408 }
 409 EXPORT_SYMBOL_GPL(register_pernet_device);
 410
 411 int register_pernet_gen_device(int *id, struct pernet_operations *ops)
 412 {
 413         int error;
 414         mutex_lock(&net_mutex);
 415 again:
 416         error = ida_get_new_above(&net_generic_ids, 1, id);
 417         if (error) {
 418                 if (error == -EAGAIN) {
 419                         ida_pre_get(&net_generic_ids, GFP_KERNEL);
 420                         goto again;
 421                 }
 422                 goto out;
 423         }
 424         error = register_pernet_operations(&pernet_list, ops);
 425         if (error)
 426                 ida_remove(&net_generic_ids, *id);
 427         else if (first_device == &pernet_list)
 428                 first_device = &ops->list;
 429 out:
 430         mutex_unlock(&net_mutex);
 431         return error;
 432 }
 433 EXPORT_SYMBOL_GPL(register_pernet_gen_device);
 434
 435 /**
 436  *      unregister_pernet_device - unregister a network namespace netdevice
 437  *      @ops: pernet operations structure to manipulate
 438  *
 439  *      Remove the pernet operations structure from the list to be
 440  *      used when network namespaces are created or destroyed.  In
 441  *      addition run the exit method for all existing network
 442  *      namespaces.
 443  */
 444 void unregister_pernet_device(struct pernet_operations *ops)
 445 {
 446         mutex_lock(&net_mutex);
 447         if (&ops->list == first_device)
 448                 first_device = first_device->next;
 449         unregister_pernet_operations(ops);
 450         mutex_unlock(&net_mutex);
 451 }
 452 EXPORT_SYMBOL_GPL(unregister_pernet_device);
 453
 454 void unregister_pernet_gen_device(int id, struct pernet_operations *ops)
 455 {
 456         mutex_lock(&net_mutex);
 457         if (&ops->list == first_device)
 458                 first_device = first_device->next;
 459         unregister_pernet_operations(ops);
 460         ida_remove(&net_generic_ids, id);
 461         mutex_unlock(&net_mutex);
 462 }
 463 EXPORT_SYMBOL_GPL(unregister_pernet_gen_device);
 464
 465 static void net_generic_release(struct rcu_head *rcu)
 466 {
 467         struct net_generic *ng;
 468
 469         ng = container_of(rcu, struct net_generic, rcu);
 470         kfree(ng);
 471 }
 472
 473 int net_assign_generic(struct net *net, int id, void *data)
 474 {
 475         struct net_generic *ng, *old_ng;
 476
 477         BUG_ON(!mutex_is_locked(&net_mutex));
 478         BUG_ON(id == 0);
 479
 480         ng = old_ng = net->gen;
 481         if (old_ng->len >= id)
 482                 goto assign;
 483
 484         ng = kzalloc(sizeof(struct net_generic) +
 485                         id * sizeof(void *), GFP_KERNEL);
 486         if (ng == NULL)
 487                 return -ENOMEM;
 488
 489         /*
 490          * Some synchronisation notes:
 491          *
 492          * The net_generic explores the net->gen array inside rcu
 493          * read section. Besides once set the net->gen->ptr[x]
 494          * pointer never changes (see rules in netns/generic.h).
 495          *
 496          * That said, we simply duplicate this array and schedule
 497          * the old copy for kfree after a grace period.
 498          */
 499
 500         ng->len = id;
 501         memcpy(&ng->ptr, &old_ng->ptr, old_ng->len * sizeof(void*));
 502
 503         rcu_assign_pointer(net->gen, ng);
 504         call_rcu(&old_ng->rcu, net_generic_release);
 505 assign:
 506         ng->ptr[id - 1] = data;
 507         return 0;
 508 }
 509 EXPORT_SYMBOL_GPL(net_assign_generic);