nsproxy.h 2.44 KB
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#ifndef _LINUX_NSPROXY_H
#define _LINUX_NSPROXY_H

#include <linux/spinlock.h>
#include <linux/sched.h>

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struct mnt_namespace;
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struct uts_namespace;
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struct ipc_namespace;
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struct pid_namespace;
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struct cgroup_namespace;
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struct fs_struct;
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/*
 * A structure to contain pointers to all per-process
 * namespaces - fs (mount), uts, network, sysvipc, etc.
 *
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 * The pid namespace is an exception -- it's accessed using
 * task_active_pid_ns.  The pid namespace here is the
 * namespace that children will use.
 *
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 * 'count' is the number of tasks holding a reference.
 * The count for each namespace, then, will be the number
 * of nsproxies pointing to it, not the number of tasks.
 *
 * The nsproxy is shared by tasks which share all namespaces.
 * As soon as a single namespace is cloned or unshared, the
 * nsproxy is copied.
 */
struct nsproxy {
	atomic_t count;
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	struct uts_namespace *uts_ns;
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	struct ipc_namespace *ipc_ns;
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	struct mnt_namespace *mnt_ns;
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	struct pid_namespace *pid_ns_for_children;
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	struct net 	     *net_ns;
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	struct cgroup_namespace *cgroup_ns;
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};
extern struct nsproxy init_nsproxy;

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/*
 * the namespaces access rules are:
 *
 *  1. only current task is allowed to change tsk->nsproxy pointer or
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 *     any pointer on the nsproxy itself.  Current must hold the task_lock
 *     when changing tsk->nsproxy.
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 *
 *  2. when accessing (i.e. reading) current task's namespaces - no
 *     precautions should be taken - just dereference the pointers
 *
 *  3. the access to other task namespaces is performed like this
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 *     task_lock(task);
 *     nsproxy = task->nsproxy;
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 *     if (nsproxy != NULL) {
 *             / *
 *               * work with the namespaces here
 *               * e.g. get the reference on one of them
 *               * /
 *     } / *
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 *         * NULL task->nsproxy means that this task is
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 *         * almost dead (zombie)
 *         * /
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 *     task_unlock(task);
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 *
 */

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int copy_namespaces(unsigned long flags, struct task_struct *tsk);
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void exit_task_namespaces(struct task_struct *tsk);
void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
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void free_nsproxy(struct nsproxy *ns);
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int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
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	struct cred *, struct fs_struct *);
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int __init nsproxy_cache_init(void);
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static inline void put_nsproxy(struct nsproxy *ns)
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{
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	if (atomic_dec_and_test(&ns->count)) {
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		free_nsproxy(ns);
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	}
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}

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static inline void get_nsproxy(struct nsproxy *ns)
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{
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	atomic_inc(&ns->count);
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}
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#endif