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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_NS_COMMON_TYPES_H
#define _LINUX_NS_COMMON_TYPES_H
#include <linux/atomic.h>
#include <linux/ns/nstree_types.h>
#include <linux/rbtree.h>
#include <linux/refcount.h>
#include <linux/types.h>
struct cgroup_namespace;
struct dentry;
struct ipc_namespace;
struct mnt_namespace;
struct net;
struct pid_namespace;
struct proc_ns_operations;
struct time_namespace;
struct user_namespace;
struct uts_namespace;
extern struct cgroup_namespace init_cgroup_ns;
extern struct ipc_namespace init_ipc_ns;
extern struct mnt_namespace init_mnt_ns;
extern struct net init_net;
extern struct pid_namespace init_pid_ns;
extern struct time_namespace init_time_ns;
extern struct user_namespace init_user_ns;
extern struct uts_namespace init_uts_ns;
extern const struct proc_ns_operations cgroupns_operations;
extern const struct proc_ns_operations ipcns_operations;
extern const struct proc_ns_operations mntns_operations;
extern const struct proc_ns_operations netns_operations;
extern const struct proc_ns_operations pidns_operations;
extern const struct proc_ns_operations pidns_for_children_operations;
extern const struct proc_ns_operations timens_operations;
extern const struct proc_ns_operations timens_for_children_operations;
extern const struct proc_ns_operations userns_operations;
extern const struct proc_ns_operations utsns_operations;
/*
* Namespace lifetimes are managed via a two-tier reference counting model:
*
* (1) __ns_ref (refcount_t): Main reference count tracking memory
* lifetime. Controls when the namespace structure itself is freed.
* It also pins the namespace on the namespace trees whereas (2)
* only regulates their visibility to userspace.
*
* (2) __ns_ref_active (atomic_t): Reference count tracking active users.
* Controls visibility of the namespace in the namespace trees.
* Any live task that uses the namespace (via nsproxy or cred) holds
* an active reference. Any open file descriptor or bind-mount of
* the namespace holds an active reference. Once all tasks have
* called exited their namespaces and all file descriptors and
* bind-mounts have been released the active reference count drops
* to zero and the namespace becomes inactive. IOW, the namespace
* cannot be listed or opened via file handles anymore.
*
* Note that it is valid to transition from active to inactive and
* back from inactive to active e.g., when resurrecting an inactive
* namespace tree via the SIOCGSKNS ioctl().
*
* Relationship and lifecycle states:
*
* - Active (__ns_ref_active > 0):
* Namespace is actively used and visible to userspace. The namespace
* can be reopened via /proc/<pid>/ns/<ns_type>, via namespace file
* handles, or discovered via listns().
*
* - Inactive (__ns_ref_active == 0, __ns_ref > 0):
* No tasks are actively using the namespace and it isn't pinned by
* any bind-mounts or open file descriptors anymore. But the namespace
* is still kept alive by internal references. For example, the user
* namespace could be pinned by an open file through file->f_cred
* references when one of the now defunct tasks had opened a file and
* handed the file descriptor off to another process via a UNIX
* sockets. Such references keep the namespace structure alive through
* __ns_ref but will not hold an active reference.
*
* - Destroyed (__ns_ref == 0):
* No references remain. The namespace is removed from the tree and freed.
*
* State transitions:
*
* Active -> Inactive:
* When the last task using the namespace exits it drops its active
* references to all namespaces. However, user and pid namespaces
* remain accessible until the task has been reaped.
*
* Inactive -> Active:
* An inactive namespace tree might be resurrected due to e.g., the
* SIOCGSKNS ioctl() on a socket.
*
* Inactive -> Destroyed:
* When __ns_ref drops to zero the namespace is removed from the
* namespaces trees and the memory is freed (after RCU grace period).
*
* Initial namespaces:
* Boot-time namespaces (init_net, init_pid_ns, etc.) start with
* __ns_ref_active = 1 and remain active forever.
*
* @ns_type: type of namespace (e.g., CLONE_NEWNET)
* @stashed: cached dentry to be used by the vfs
* @ops: namespace operations
* @inum: namespace inode number (quickly recycled for non-initial namespaces)
* @__ns_ref: main reference count (do not use directly)
* @ns_tree: namespace tree nodes and active reference count
*/
struct ns_common {
u32 ns_type;
struct dentry *stashed;
const struct proc_ns_operations *ops;
unsigned int inum;
refcount_t __ns_ref; /* do not use directly */
union {
struct ns_tree;
struct rcu_head ns_rcu;
};
};
#define to_ns_common(__ns) \
_Generic((__ns), \
struct cgroup_namespace *: &(__ns)->ns, \
const struct cgroup_namespace *: &(__ns)->ns, \
struct ipc_namespace *: &(__ns)->ns, \
const struct ipc_namespace *: &(__ns)->ns, \
struct mnt_namespace *: &(__ns)->ns, \
const struct mnt_namespace *: &(__ns)->ns, \
struct net *: &(__ns)->ns, \
const struct net *: &(__ns)->ns, \
struct pid_namespace *: &(__ns)->ns, \
const struct pid_namespace *: &(__ns)->ns, \
struct time_namespace *: &(__ns)->ns, \
const struct time_namespace *: &(__ns)->ns, \
struct user_namespace *: &(__ns)->ns, \
const struct user_namespace *: &(__ns)->ns, \
struct uts_namespace *: &(__ns)->ns, \
const struct uts_namespace *: &(__ns)->ns)
#define ns_init_inum(__ns) \
_Generic((__ns), \
struct cgroup_namespace *: CGROUP_NS_INIT_INO, \
struct ipc_namespace *: IPC_NS_INIT_INO, \
struct mnt_namespace *: MNT_NS_INIT_INO, \
struct net *: NET_NS_INIT_INO, \
struct pid_namespace *: PID_NS_INIT_INO, \
struct time_namespace *: TIME_NS_INIT_INO, \
struct user_namespace *: USER_NS_INIT_INO, \
struct uts_namespace *: UTS_NS_INIT_INO)
#define ns_init_ns(__ns) \
_Generic((__ns), \
struct cgroup_namespace *: &init_cgroup_ns, \
struct ipc_namespace *: &init_ipc_ns, \
struct mnt_namespace *: &init_mnt_ns, \
struct net *: &init_net, \
struct pid_namespace *: &init_pid_ns, \
struct time_namespace *: &init_time_ns, \
struct user_namespace *: &init_user_ns, \
struct uts_namespace *: &init_uts_ns)
#define ns_init_id(__ns) \
_Generic((__ns), \
struct cgroup_namespace *: CGROUP_NS_INIT_ID, \
struct ipc_namespace *: IPC_NS_INIT_ID, \
struct mnt_namespace *: MNT_NS_INIT_ID, \
struct net *: NET_NS_INIT_ID, \
struct pid_namespace *: PID_NS_INIT_ID, \
struct time_namespace *: TIME_NS_INIT_ID, \
struct user_namespace *: USER_NS_INIT_ID, \
struct uts_namespace *: UTS_NS_INIT_ID)
#define to_ns_operations(__ns) \
_Generic((__ns), \
struct cgroup_namespace *: (IS_ENABLED(CONFIG_CGROUPS) ? &cgroupns_operations : NULL), \
struct ipc_namespace *: (IS_ENABLED(CONFIG_IPC_NS) ? &ipcns_operations : NULL), \
struct mnt_namespace *: &mntns_operations, \
struct net *: (IS_ENABLED(CONFIG_NET_NS) ? &netns_operations : NULL), \
struct pid_namespace *: (IS_ENABLED(CONFIG_PID_NS) ? &pidns_operations : NULL), \
struct time_namespace *: (IS_ENABLED(CONFIG_TIME_NS) ? &timens_operations : NULL), \
struct user_namespace *: (IS_ENABLED(CONFIG_USER_NS) ? &userns_operations : NULL), \
struct uts_namespace *: (IS_ENABLED(CONFIG_UTS_NS) ? &utsns_operations : NULL))
#define ns_common_type(__ns) \
_Generic((__ns), \
struct cgroup_namespace *: CLONE_NEWCGROUP, \
struct ipc_namespace *: CLONE_NEWIPC, \
struct mnt_namespace *: CLONE_NEWNS, \
struct net *: CLONE_NEWNET, \
struct pid_namespace *: CLONE_NEWPID, \
struct time_namespace *: CLONE_NEWTIME, \
struct user_namespace *: CLONE_NEWUSER, \
struct uts_namespace *: CLONE_NEWUTS)
#endif /* _LINUX_NS_COMMON_TYPES_H */
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