rtnl: add link netns id to interface messages

This patch adds a new attribute (IFLA_LINK_NETNSID) which contains the 'link'
netns id when this netns is different from the netns where the interface
stands (for example for x-net interfaces like ip tunnels).
With this attribute, it's possible to interpret correctly all advertised
information (like IFLA_LINK, etc.).

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

3 files changed, 16 insertions, 0 deletions

diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index e21b9f9653c0..6c6d5393fc34 100644
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -46,6 +46,7 @@ static inline int rtnl_msg_family(const struct nlmsghdr *nlh)
  *                          to create when creating a new device.
  *      @get_num_rx_queues: Function to determine number of receive queues
  *                          to create when creating a new device.
+ *      @get_link_net: Function to get the i/o netns of the device
  */
 struct rtnl_link_ops {
         struct list_head        list;
@@ -93,6 +94,7 @@ struct rtnl_link_ops {
         int                     (*fill_slave_info)(struct sk_buff *skb,
                                                    const struct net_device *dev,
                                                    const struct net_device *slave_dev);
+        struct net              *(*get_link_net)(const struct net_device *dev);
 };
 
 int __rtnl_link_register(struct rtnl_link_ops *ops);
diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index 2a8380edbb7e..0deee3eeddbf 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -146,6 +146,7 @@ enum {
         IFLA_PHYS_PORT_ID,
         IFLA_CARRIER_CHANGES,
         IFLA_PHYS_SWITCH_ID,
+        IFLA_LINK_NETNSID,
         __IFLA_MAX
 };
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 47b39f3e867c..bd6370f0cb31 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -875,6 +875,7 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev,
                + nla_total_size(1) /* IFLA_OPERSTATE */
                + nla_total_size(1) /* IFLA_LINKMODE */
                + nla_total_size(4) /* IFLA_CARRIER_CHANGES */
+               + nla_total_size(4) /* IFLA_LINK_NETNSID */
                + nla_total_size(ext_filter_mask
                                 & RTEXT_FILTER_VF ? 4 : 0) /* IFLA_NUM_VF */
                + rtnl_vfinfo_size(dev, ext_filter_mask) /* IFLA_VFINFO_LIST */
@@ -1169,6 +1170,18 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
                         goto nla_put_failure;
         }
 
+        if (dev->rtnl_link_ops &&
+            dev->rtnl_link_ops->get_link_net) {
+                struct net *link_net = dev->rtnl_link_ops->get_link_net(dev);
+
+                if (!net_eq(dev_net(dev), link_net)) {
+                        int id = peernet2id(dev_net(dev), link_net);
+
+                        if (nla_put_s32(skb, IFLA_LINK_NETNSID, id))
+                                goto nla_put_failure;
+                }
+        }
+
         if (!(af_spec = nla_nest_start(skb, IFLA_AF_SPEC)))
                 goto nla_put_failure;