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