[NET]: Basic network namespace infrastructure.

This is the basic infrastructure needed to support network
namespaces.  This infrastructure is:
- Registration functions to support initializing per network
  namespace data when a network namespaces is created or destroyed.

- struct net.  The network namespace data structure.
  This structure will grow as variables are made per network
  namespace but this is the minimal starting point.

- Functions to grab a reference to the network namespace.
  I provide both get/put functions that keep a network namespace
  from being freed.  And hold/release functions serve as weak references
  and will warn if their count is not zero when the data structure
  is freed.  Useful for dealing with more complicated data structures
  like the ipv4 route cache.

- A list of all of the network namespaces so we can iterate over them.

- A slab for the network namespace data structure allowing leaks
  to be spotted.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 68 insertions, 0 deletions

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
new file mode 100644
index 00000000000..6344b77f81a
--- /dev/null
+++ b/include/net/net_namespace.h
@@ -0,0 +1,68 @@
+/*
+ * Operations on the network namespace
+ */
+#ifndef __NET_NET_NAMESPACE_H
+#define __NET_NET_NAMESPACE_H
+
+#include <asm/atomic.h>
+#include <linux/workqueue.h>
+#include <linux/list.h>
+
+struct net {
+	atomic_t		count;		/* To decided when the network
+						 *  namespace should be freed.
+						 */
+	atomic_t		use_count;	/* To track references we
+						 * destroy on demand
+						 */
+	struct list_head	list;		/* list of network namespaces */
+	struct work_struct	work;		/* work struct for freeing */
+};
+
+extern struct net init_net;
+extern struct list_head net_namespace_list;
+
+extern void __put_net(struct net *net);
+
+static inline struct net *get_net(struct net *net)
+{
+	atomic_inc(&net->count);
+	return net;
+}
+
+static inline void put_net(struct net *net)
+{
+	if (atomic_dec_and_test(&net->count))
+		__put_net(net);
+}
+
+static inline struct net *hold_net(struct net *net)
+{
+	atomic_inc(&net->use_count);
+	return net;
+}
+
+static inline void release_net(struct net *net)
+{
+	atomic_dec(&net->use_count);
+}
+
+extern void net_lock(void);
+extern void net_unlock(void);
+
+#define for_each_net(VAR)				\
+	list_for_each_entry(VAR, &net_namespace_list, list)
+
+
+struct pernet_operations {
+	struct list_head list;
+	int (*init)(struct net *net);
+	void (*exit)(struct net *net);
+};
+
+extern int register_pernet_subsys(struct pernet_operations *);
+extern void unregister_pernet_subsys(struct pernet_operations *);
+extern int register_pernet_device(struct pernet_operations *);
+extern void unregister_pernet_device(struct pernet_operations *);
+
+#endif /* __NET_NET_NAMESPACE_H */