rtnl: allow to create device with IFLA_LINK_NETNSID set

This patch adds the ability to create a netdevice in a specified netns and
then move it into the final netns. In fact, it allows to have a symetry between
get and set rtnl messages.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 22 insertions, 3 deletions

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index bd6370f0cb31..a12eecc0f976 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1248,6 +1248,7 @@ static const struct nla_policy ifla_policy[IFLA_MAX+1] = {
         [IFLA_PHYS_PORT_ID]     = { .type = NLA_BINARY, .len = MAX_PHYS_ITEM_ID_LEN },
         [IFLA_CARRIER_CHANGES]  = { .type = NLA_U32 },  /* ignored */
         [IFLA_PHYS_SWITCH_ID]   = { .type = NLA_BINARY, .len = MAX_PHYS_ITEM_ID_LEN },
+        [IFLA_LINK_NETNSID]     = { .type = NLA_S32 },
 };
 
 static const struct nla_policy ifla_info_policy[IFLA_INFO_MAX+1] = {
@@ -2021,7 +2022,7 @@ replay:
                 struct nlattr *slave_attr[m_ops ? m_ops->slave_maxtype + 1 : 0];
                 struct nlattr **data = NULL;
                 struct nlattr **slave_data = NULL;
-                struct net *dest_net;
+                struct net *dest_net, *link_net = NULL;
 
                 if (ops) {
                         if (ops->maxtype && linkinfo[IFLA_INFO_DATA]) {
@@ -2127,7 +2128,18 @@ replay:
                 if (IS_ERR(dest_net))
                         return PTR_ERR(dest_net);
 
-                dev = rtnl_create_link(dest_net, ifname, name_assign_type, ops, tb);
+                if (tb[IFLA_LINK_NETNSID]) {
+                        int id = nla_get_s32(tb[IFLA_LINK_NETNSID]);
+
+                        link_net = get_net_ns_by_id(dest_net, id);
+                        if (!link_net) {
+                                err =  -EINVAL;
+                                goto out;
+                        }
+                }
+
+                dev = rtnl_create_link(link_net ? : dest_net, ifname,
+                                       name_assign_type, ops, tb);
                 if (IS_ERR(dev)) {
                         err = PTR_ERR(dev);
                         goto out;
@@ -2155,9 +2167,16 @@ replay:
                         }
                 }
                 err = rtnl_configure_link(dev, ifm);
-                if (err < 0)
+                if (err < 0) {
                         unregister_netdevice(dev);
+                        goto out;
+                }
+
+                if (link_net)
+                        err = dev_change_net_namespace(dev, dest_net, ifname);
 out:
+                if (link_net)
+                        put_net(link_net);
                 put_net(dest_net);
                 return err;
         }