include/linux/nsproxy.h

   1 #ifndef _LINUX_NSPROXY_H
   2 #define _LINUX_NSPROXY_H
   3
   4 #include <linux/spinlock.h>
   5 #include <linux/sched.h>
   6
   7 struct mnt_namespace;
   8 struct uts_namespace;
   9 struct ipc_namespace;
  10 struct pid_namespace;
  11 struct fs_struct;
  12
  13 /*
  14  * A structure to contain pointers to all per-process
  15  * namespaces - fs (mount), uts, network, sysvipc, etc.
  16  *
  17  * The pid namespace is an exception -- it's accessed using
  18  * task_active_pid_ns.  The pid namespace here is the
  19  * namespace that children will use.
  20  *
  21  * 'count' is the number of tasks holding a reference.
  22  * The count for each namespace, then, will be the number
  23  * of nsproxies pointing to it, not the number of tasks.
  24  *
  25  * The nsproxy is shared by tasks which share all namespaces.
  26  * As soon as a single namespace is cloned or unshared, the
  27  * nsproxy is copied.
  28  */
  29 struct nsproxy {
  30         atomic_t count;
  31         struct uts_namespace *uts_ns;
  32         struct ipc_namespace *ipc_ns;
  33         struct mnt_namespace *mnt_ns;
  34         struct pid_namespace *pid_ns_for_children;
  35         struct net           *net_ns;
  36 };
  37 extern struct nsproxy init_nsproxy;
  38
  39 /*
  40  * the namespaces access rules are:
  41  *
  42  *  1. only current task is allowed to change tsk->nsproxy pointer or
  43  *     any pointer on the nsproxy itself.  Current must hold the task_lock
  44  *     when changing tsk->nsproxy.
  45  *
  46  *  2. when accessing (i.e. reading) current task's namespaces - no
  47  *     precautions should be taken - just dereference the pointers
  48  *
  49  *  3. the access to other task namespaces is performed like this
  50  *     task_lock(task);
  51  *     nsproxy = task->nsproxy;
  52  *     if (nsproxy != NULL) {
  53  *             / *
  54  *               * work with the namespaces here
  55  *               * e.g. get the reference on one of them
  56  *               * /
  57  *     } / *
  58  *         * NULL task->nsproxy means that this task is
  59  *         * almost dead (zombie)
  60  *         * /
  61  *     task_unlock(task);
  62  *
  63  */
  64
  65 int copy_namespaces(unsigned long flags, struct task_struct *tsk);
  66 void exit_task_namespaces(struct task_struct *tsk);
  67 void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
  68 void free_nsproxy(struct nsproxy *ns);
  69 int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
  70         struct cred *, struct fs_struct *);
  71 int __init nsproxy_cache_init(void);
  72
  73 static inline void put_nsproxy(struct nsproxy *ns)
  74 {
  75         if (atomic_dec_and_test(&ns->count)) {
  76                 free_nsproxy(ns);
  77         }
  78 }
  79
  80 static inline void get_nsproxy(struct nsproxy *ns)
  81 {
  82         atomic_inc(&ns->count);
  83 }
  84
  85 #endif