net: Allow setting the network namespace by fd

Take advantage of the new abstraction and allow network devices
to be placed in any network namespace that we have a fd to talk
about.

Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Daniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index d7c4bb4..dca9602 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1043,6 +1043,7 @@
 	[IFLA_LINKMODE]		= { .type = NLA_U8 },
 	[IFLA_LINKINFO]		= { .type = NLA_NESTED },
 	[IFLA_NET_NS_PID]	= { .type = NLA_U32 },
+	[IFLA_NET_NS_FD]	= { .type = NLA_U32 },
 	[IFLA_IFALIAS]	        = { .type = NLA_STRING, .len = IFALIASZ-1 },
 	[IFLA_VFINFO_LIST]	= {. type = NLA_NESTED },
 	[IFLA_VF_PORTS]		= { .type = NLA_NESTED },
@@ -1091,6 +1092,8 @@
 	 */
 	if (tb[IFLA_NET_NS_PID])
 		net = get_net_ns_by_pid(nla_get_u32(tb[IFLA_NET_NS_PID]));
+	else if (tb[IFLA_NET_NS_FD])
+		net = get_net_ns_by_fd(nla_get_u32(tb[IFLA_NET_NS_FD]));
 	else
 		net = get_net(src_net);
 	return net;
@@ -1221,7 +1224,7 @@
 	int send_addr_notify = 0;
 	int err;
 
-	if (tb[IFLA_NET_NS_PID]) {
+	if (tb[IFLA_NET_NS_PID] || tb[IFLA_NET_NS_FD]) {
 		struct net *net = rtnl_link_get_net(dev_net(dev), tb);
 		if (IS_ERR(net)) {
 			err = PTR_ERR(net);