[patch -mm 16/17] net namespace: add unshare

[clg at fr.ibm.com]

From: Cedric Le Goater <clg at fr.ibm.com>

Signed-off-by: Cedric Le Goater <clg at fr.ibm.com>
---
 include/linux/net_namespace.h |   13 +++++++++++++
 kernel/nsproxy.c              |   25 ++++++++++++++++++++++---
 net/core/net_namespace.c      |   35 +++++++++++++++++++++++++++++++++++
 3 files changed, 70 insertions(+), 3 deletions(-)

Index: 2.6.19-rc6-mm2/include/linux/net_namespace.h
===================================================================
--- 2.6.19-rc6-mm2.orig/include/linux/net_namespace.h
+++ 2.6.19-rc6-mm2/include/linux/net_namespace.h
@@ -3,6 +3,7 @@
 
 #include <linux/kref.h>
 #include <linux/nsproxy.h>
+#include <linux/errno.h>
 
 struct net_namespace {
 	struct kref	kref;
@@ -19,6 +20,9 @@ static inline void get_net_ns(struct net
 	kref_get(&ns->kref);
 }
 
+extern int unshare_net_ns(unsigned long unshare_flags,
+			  struct net_namespace **new_net);
+
 extern int copy_net_ns(int flags, struct task_struct *tsk);
 
 extern void free_net_ns(struct kref *kref);
@@ -36,6 +40,15 @@ static inline void get_net_ns(struct net
 {
 }
 
+static inline int unshare_net_ns(unsigned long unshare_flags,
+				 struct net_namespace **new_net)
+{
+	if (unshare_flags & NS_NET)
+		return -EINVAL;
+
+	return 0;
+}
+
 static inline int copy_net_ns(int flags, struct task_struct *tsk)
 {
 	return 0;
Index: 2.6.19-rc6-mm2/kernel/nsproxy.c
===================================================================
--- 2.6.19-rc6-mm2.orig/kernel/nsproxy.c
+++ 2.6.19-rc6-mm2/kernel/nsproxy.c
@@ -329,6 +329,12 @@ static int switch_ns(int id, unsigned lo
 			put_pid_ns(new_ns->pid_ns);
 			new_ns->pid_ns = ns->pid_ns;
 		}
+		if (flags & NS_NET) {
+			get_net_ns(ns->net_ns);
+			put_net_ns(new_ns->net_ns);
+			new_ns->net_ns = ns->net_ns;
+		}
+
 	out_ns:
 		put_nsproxy(ns);
 	}
@@ -446,6 +452,7 @@ asmlinkage long sys_unshare_ns(unsigned 
  	struct uts_namespace *uts, *new_uts = NULL;
  	struct ipc_namespace *ipc, *new_ipc = NULL;
 	struct pid_namespace *pid, *new_pid = NULL;
+	struct net_namespace *net, *new_net = NULL;
  	unsigned long unshare_flags = 0;
 
  	/* Return -EINVAL for all unsupported flags */
@@ -475,17 +482,19 @@ asmlinkage long sys_unshare_ns(unsigned 
 
 	if ((err = unshare_pid_ns(unshare_ns_flags, &new_pid)))
 		goto bad_unshare_ns_cleanup_ipc;
+	if ((err = unshare_net_ns(unshare_ns_flags, &new_net)))
+		goto bad_unshare_ns_cleanup_pid;
 
-	if (new_mnt || new_uts || new_ipc || new_pid) {
+	if (new_mnt || new_uts || new_ipc || new_pid || new_net) {
  		old_nsproxy = current->nsproxy;
  		new_nsproxy = dup_namespaces(old_nsproxy);
  		if (!new_nsproxy) {
  			err = -ENOMEM;
- 			goto bad_unshare_ns_cleanup_pid;
+ 			goto bad_unshare_ns_cleanup_net;
  		}
  	}
 
- 	if (new_fs || new_mnt || new_uts || new_ipc || new_pid) {
+ 	if (new_fs || new_mnt || new_uts || new_ipc || new_pid || new_net) {
 
  		task_lock(current);
 
@@ -524,12 +533,22 @@ asmlinkage long sys_unshare_ns(unsigned 
 			new_pid = pid;
 		}
 
+		if (new_net) {
+			net = current->nsproxy->net_ns;
+			current->nsproxy->net_ns = new_net;
+			new_net = net;
+		}
+
  		task_unlock(current);
  	}
 
  	if (new_nsproxy)
  		put_nsproxy(new_nsproxy);
 
+bad_unshare_ns_cleanup_net:
+	if (new_net)
+		put_net_ns(new_net);
+
 bad_unshare_ns_cleanup_pid:
 	if (new_pid)
 		put_pid_ns(new_pid);
Index: 2.6.19-rc6-mm2/net/core/net_namespace.c
===================================================================
--- 2.6.19-rc6-mm2.orig/net/core/net_namespace.c
+++ 2.6.19-rc6-mm2/net/core/net_namespace.c
@@ -18,6 +18,41 @@ struct net_namespace init_net_ns = {
 
 #ifdef CONFIG_NET_NS
 
+/*
+ * Clone a new ns copying an original net ns, setting refcount to 1
+ * @old_ns: namespace to clone
+ * Return NULL on error (failure to kmalloc), new ns otherwise
+ */
+static struct net_namespace *clone_net_ns(struct net_namespace *old_ns)
+{
+	struct net_namespace *ns;
+
+	ns = kmalloc(sizeof(struct net_namespace), GFP_KERNEL);
+	if (!ns)
+		return NULL;
+
+	kref_init(&ns->kref);
+	return ns;
+}
+
+/*
+ * unshare the current process' net namespace.
+ */
+int unshare_net_ns(unsigned long unshare_flags,
+		   struct net_namespace **new_net)
+{
+	if (unshare_flags & NS_NET) {
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+
+		*new_net = clone_net_ns(current->nsproxy->net_ns);
+		if (!*new_net)
+			return -ENOMEM;
+	}
+
+	return 0;
+}
+
 int copy_net_ns(int flags, struct task_struct *tsk)
 {
 	struct net_namespace *old_ns = tsk->nsproxy->net_ns;

--