ns: proc files for namespace naming policy.

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>

1 files changed, 18 insertions, 0 deletions

diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index c03e8d3..96245a1 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -119,3 +119,21 @@ struct inode *proc_get_inode(struct super_block *, struct proc_dir_entry *);
  */
 int proc_readdir(struct file *, void *, filldir_t);
 struct dentry *proc_lookup(struct inode *, struct dentry *, struct nameidata *);
+
+
+
+/* Lookups */
+typedef struct dentry *instantiate_t(struct inode *, struct dentry *,
+				struct task_struct *, const void *);
+int proc_fill_cache(struct file *filp, void *dirent, filldir_t filldir,
+	const char *name, int len,
+	instantiate_t instantiate, struct task_struct *task, const void *ptr);
+int pid_revalidate(struct dentry *dentry, struct nameidata *nd);
+struct inode *proc_pid_make_inode(struct super_block * sb, struct task_struct *task);
+extern const struct dentry_operations pid_dentry_operations;
+int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat);
+int proc_setattr(struct dentry *dentry, struct iattr *attr);
+
+extern const struct inode_operations proc_ns_dir_inode_operations;
+extern const struct file_operations proc_ns_dir_operations;
+