net: add netdev_adjacent->private and allow to use it

Currently, even though we can access any linked device, we can't attach
anything to it, which is vital to properly manage them.

To fix this, add a new void *private to netdev_adjacent and functions
setting/getting it (per link), so that we can save, per example, bonding's
slave structures there, per slave device.

netdev_master_upper_dev_link_private(dev, upper_dev, private) links dev to
upper dev and populates the neighbour link only with private.

netdev_lower_dev_get_private{,_rcu}() returns the private, if found.

CC: "David S. Miller" <davem@davemloft.net>
CC: Eric Dumazet <edumazet@google.com>
CC: Jiri Pirko <jiri@resnulli.us>
CC: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 514045c704a8..75d5beac463b 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2839,8 +2839,15 @@ extern int netdev_upper_dev_link(struct net_device *dev,
                                  struct net_device *upper_dev);
 extern int netdev_master_upper_dev_link(struct net_device *dev,
                                         struct net_device *upper_dev);
+extern int netdev_master_upper_dev_link_private(struct net_device *dev,
+                                                struct net_device *upper_dev,
+                                                void *private);
 extern void netdev_upper_dev_unlink(struct net_device *dev,
                                     struct net_device *upper_dev);
+extern void *netdev_lower_dev_get_private_rcu(struct net_device *dev,
+                                              struct net_device *lower_dev);
+extern void *netdev_lower_dev_get_private(struct net_device *dev,
+                                          struct net_device *lower_dev);
 extern int skb_checksum_help(struct sk_buff *skb);
 extern struct sk_buff *__skb_gso_segment(struct sk_buff *skb,
         netdev_features_t features, bool tx_path);