[NET]: Implement network device movement between namespaces

This patch introduces NETIF_F_NETNS_LOCAL a flag to indicate
a network device is local to a single network namespace and
should never be moved.  Useful for pseudo devices that we
need an instance in each network namespace (like the loopback
device) and for any device we find that cannot handle multiple
network namespaces so we may trap them in the initial network
namespace.

This patch introduces the function dev_change_net_namespace
a function used to move a network device from one network
namespace to another.  To the network device nothing
special appears to happen, to the components of the network
stack it appears as if the network device was unregistered
in the network namespace it is in, and a new device
was registered in the network namespace the device
was moved to.

This patch sets up a namespace device destructor that
upon the exit of a network namespace moves all of the
movable network devices  to the initial network namespace
so they are not lost.

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

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 7353b3e1f4fc..407658c64fb6 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -449,6 +449,7 @@ struct net_device
 #define NETIF_F_VLAN_CHALLENGED 1024    /* Device cannot handle VLAN packets */
 #define NETIF_F_GSO             2048    /* Enable software GSO. */
 #define NETIF_F_LLTX            4096    /* LockLess TX */
+#define NETIF_F_NETNS_LOCAL     8192    /* Does not change network namespaces */
 #define NETIF_F_MULTI_QUEUE     16384   /* Has multiple TX/RX queues */
 #define NETIF_F_LRO             32768   /* large receive offload */
 
@@ -1016,6 +1017,8 @@ extern int		dev_ethtool(struct net *net, struct ifreq *);
 extern unsigned         dev_get_flags(const struct net_device *);
 extern int              dev_change_flags(struct net_device *, unsigned);
 extern int              dev_change_name(struct net_device *, char *);
+extern int              dev_change_net_namespace(struct net_device *,
+                                                 struct net *, const char *);
 extern int              dev_set_mtu(struct net_device *, int);
 extern int              dev_set_mac_address(struct net_device *,
                                             struct sockaddr *);