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ns: proc files for namespace naming policy.

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Create files under /proc/<pid>/ns/ to allow controlling the
namespaces of a process.

This addresses three specific problems that can make namespaces hard to
work with.
- Namespaces require a dedicated process to pin them in memory.
- It is not possible to use a namespace unless you are the child
  of the original creator.
- Namespaces don't have names that userspace can use to talk about
  them.

The namespace files under /proc/<pid>/ns/ can be opened and the
file descriptor can be used to talk about a specific namespace, and
to keep the specified namespace alive.

A namespace can be kept alive by either holding the file descriptor
open or bind mounting the file someplace else.  aka:
mount --bind /proc/self/ns/net /some/filesystem/path
mount --bind /proc/self/fd/<N> /some/filesystem/path

This allows namespaces to be named with userspace policy.

It requires additional support to make use of these filedescriptors
and that will be comming in the following patches.

Acked-by: Daniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2010-03-07 16:41:34 -08:00
parent 0ee5623f9a
commit 6b4e306aa3
6 changed files with 241 additions and 11 deletions
Download patch file Download diff file Expand all files Collapse all files

18
include/linux/proc_fs.h
View file

@ -179,6 +179,8 @@ extern void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file);
extern struct file *get_mm_exe_file(struct mm_struct *mm);
extern void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm);
extern struct file *proc_ns_fget(int fd);
#else
#define proc_net_fops_create(net, name, mode, fops) ({ (void)(mode), NULL; })
@ -239,6 +241,11 @@ static inline void dup_mm_exe_file(struct mm_struct *oldmm,
struct mm_struct *newmm)
{}
static inline struct file *proc_ns_fget(int fd)
{
return ERR_PTR(-EINVAL);
}
#endif /* CONFIG_PROC_FS */
#if !defined(CONFIG_PROC_KCORE)
@ -250,6 +257,15 @@ kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
extern void kclist_add(struct kcore_list *, void *, size_t, int type);
#endif
struct nsproxy;
struct proc_ns_operations {
const char *name;
int type;
void *(*get)(struct task_struct *task);
void (*put)(void *ns);
int (*install)(struct nsproxy *nsproxy, void *ns);
};
union proc_op {
int (*proc_get_link)(struct inode *, struct path *);
int (*proc_read)(struct task_struct *task, char *page);
@ -268,6 +284,8 @@ struct proc_inode {
struct proc_dir_entry *pde;
struct ctl_table_header *sysctl;
struct ctl_table *sysctl_entry;
void *ns;
const struct proc_ns_operations *ns_ops;
struct inode vfs_inode;
};