[Devel] [PATCH vz7 1/2] ms/net: add an ioctl to get a socket network namespace

[Kirill Tkhai]

Port ms commit c62cce2caee5

Each socket operates in a network namespace where it has been created,
so if we want to dump and restore a socket, we have to know its network
namespace.

We have a socket_diag to get information about sockets, it doesn't
report sockets which are not bound or connected.

This patch introduces a new socket ioctl, which is called SIOCGSKNS
and used to get a file descriptor for a socket network namespace.

A task must have CAP_NET_ADMIN in a target network namespace to
use this ioctl.

Cc: "David S. Miller" <davem at davemloft.net>
Cc: Eric W. Biederman <ebiederm at xmission.com>
Signed-off-by: Andrei Vagin <avagin at openvz.org>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 fs/proc/namespaces.c         |    2 +-
 include/linux/proc_ns.h      |    8 ++++++++
 include/uapi/linux/sockios.h |    1 +
 net/socket.c                 |   32 ++++++++++++++++++++++++++++++++
 4 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
index 626d943b23f8..d03078162944 100644
--- a/fs/proc/namespaces.c
+++ b/fs/proc/namespaces.c
@@ -130,7 +130,7 @@ static struct dentry *proc_ns_get_dentry(struct super_block *sb,
 	return __proc_ns_get_dentry(sb, ns, ns_ops);
 }
 
-static int open_related_ns(struct vfsmount *mnt, struct proc_ns *ns,
+int open_related_ns(struct vfsmount *mnt, struct proc_ns *ns,
 		const struct proc_ns_operations *relative_ns_ops,
 		void *(*get_ns)(void *ns,
 			const struct proc_ns_operations *ns_ops)) {
diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h
index af898ed6fbad..53d7aca52478 100644
--- a/include/linux/proc_ns.h
+++ b/include/linux/proc_ns.h
@@ -78,4 +78,12 @@ static inline bool proc_ns_inode(struct inode *inode) { return false; }
 
 #endif /* CONFIG_PROC_FS */
 
+struct vfsmount;
+int open_related_ns(struct vfsmount *mnt, struct proc_ns *ns,
+		    const struct proc_ns_operations *relative_ns_ops,
+		    void *(*get_ns)(void *ns,
+		    const struct proc_ns_operations *ns_ops));
+
+int open_net_ns_fd(struct net *net);
+
 #endif /* _LINUX_PROC_NS_H */
diff --git a/include/uapi/linux/sockios.h b/include/uapi/linux/sockios.h
index e888b1aed69f..cf0a25ebc74c 100644
--- a/include/uapi/linux/sockios.h
+++ b/include/uapi/linux/sockios.h
@@ -84,6 +84,7 @@
 #define SIOCWANDEV	0x894A		/* get/set netdev parameters	*/
 
 #define SIOCOUTQNSD	0x894B		/* output queue size (not sent only) */
+#define SIOCGSKNS	0x894C		/* get socket network namespace */
 
 /* ARP cache control calls. */
 		    /*  0x8950 - 0x8952  * obsolete calls, don't re-use */
diff --git a/net/socket.c b/net/socket.c
index b76a5da91122..b79c1d5efee5 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -67,6 +67,7 @@
 #include <linux/rcupdate.h>
 #include <linux/netdevice.h>
 #include <linux/proc_fs.h>
+#include <linux/proc_ns.h>
 #include <linux/seq_file.h>
 #include <linux/mutex.h>
 #include <linux/if_bridge.h>
@@ -1026,6 +1027,29 @@ static long sock_do_ioctl(struct net *net, struct socket *sock,
  *	what to do with it - that's up to the protocol still.
  */
 
+static void *get_net_ns(void *ns, const struct proc_ns_operations *ns_ops)
+{
+	struct net *net = ns;
+	return get_net(net);
+}
+
+int open_net_ns_fd(struct net *net)
+{
+	struct proc_ns ns = { .ns = net, .ns_ops = &netns_operations, };
+	struct vfsmount *proc_mnt;
+	int ret;
+
+	proc_mnt = mntget(task_active_pid_ns(current)->proc_mnt);
+	if (IS_ERR(proc_mnt))
+		return PTR_ERR(proc_mnt);
+
+	ret = open_related_ns(proc_mnt, &ns, ns.ns_ops, get_net_ns);
+	mntput(proc_mnt);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(open_net_ns_fd);
+
 static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
 {
 	struct socket *sock;
@@ -1093,6 +1117,13 @@ static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
 				err = dlci_ioctl_hook(cmd, argp);
 			mutex_unlock(&dlci_ioctl_mutex);
 			break;
+		case SIOCGSKNS:
+			err = -EPERM;
+			if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
+				break;
+
+			err = open_net_ns_fd(net);
+			break;
 		default:
 			err = sock_do_ioctl(net, sock, cmd, arg);
 			break;
@@ -3246,6 +3277,7 @@ static int compat_sock_ioctl_trans(struct file *file, struct socket *sock,
 	case SIOCSIFVLAN:
 	case SIOCADDDLCI:
 	case SIOCDELDLCI:
+	case SIOCGSKNS:
 		return sock_ioctl(file, cmd, arg);
 
 	case SIOCGIFFLAGS: