[NET]: netlink support for moving devices between network namespaces.

The simplest thing to implement is moving network devices between
namespaces.  However with the same attribute IFLA_NET_NS_PID we can
easily implement creating devices in the destination network
namespace as well.  However that is a little bit trickier so this
patch sticks to what is simple and easy.

A pid is used to identify a process that happens to be a member
of the network namespace we want to move the network device to.

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

1 files changed, 35 insertions, 0 deletions

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 44f91bb1ae8d..1b9c32d79917 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -35,6 +35,7 @@
 #include <linux/security.h>
 #include <linux/mutex.h>
 #include <linux/if_addr.h>
+#include <linux/nsproxy.h>
 
 #include <asm/uaccess.h>
 #include <asm/system.h>
@@ -727,6 +728,7 @@ const struct nla_policy ifla_policy[IFLA_MAX+1] = {
         [IFLA_WEIGHT]           = { .type = NLA_U32 },
         [IFLA_OPERSTATE]        = { .type = NLA_U8 },
         [IFLA_LINKMODE]         = { .type = NLA_U8 },
+        [IFLA_NET_NS_PID]       = { .type = NLA_U32 },
 };
 
 static const struct nla_policy ifla_info_policy[IFLA_INFO_MAX+1] = {
@@ -734,12 +736,45 @@ static const struct nla_policy ifla_info_policy[IFLA_INFO_MAX+1] = {
         [IFLA_INFO_DATA]        = { .type = NLA_NESTED },
 };
 
+static struct net *get_net_ns_by_pid(pid_t pid)
+{
+        struct task_struct *tsk;
+        struct net *net;
+
+        /* Lookup the network namespace */
+        net = ERR_PTR(-ESRCH);
+        rcu_read_lock();
+        tsk = find_task_by_pid(pid);
+        if (tsk) {
+                task_lock(tsk);
+                if (tsk->nsproxy)
+                        net = get_net(tsk->nsproxy->net_ns);
+                task_unlock(tsk);
+        }
+        rcu_read_unlock();
+        return net;
+}
+
 static int do_setlink(struct net_device *dev, struct ifinfomsg *ifm,
                       struct nlattr **tb, char *ifname, int modified)
 {
         int send_addr_notify = 0;
         int err;
 
+        if (tb[IFLA_NET_NS_PID]) {
+                struct net *net;
+                net = get_net_ns_by_pid(nla_get_u32(tb[IFLA_NET_NS_PID]));
+                if (IS_ERR(net)) {
+                        err = PTR_ERR(net);
+                        goto errout;
+                }
+                err = dev_change_net_namespace(dev, net, ifname);
+                put_net(net);
+                if (err)
+                        goto errout;
+                modified = 1;
+        }
+
         if (tb[IFLA_MAP]) {
                 struct rtnl_link_ifmap *u_map;
                 struct ifmap k_map;