l3mdev: add function to retreive upper master

Existing functions to retreive the l3mdev of a device did not walk the
master chain to find the upper master. This patch adds a function to
find the l3mdev, even indirect through e.g. a bridge:

+----------+
|          |
| vrf-blue |
|          |
+----+-----+
     |
     |
+----+-----+
|          |
| br-blue  |
|          |
+----+-----+
     |
     |
+----+-----+
|          |
|   eth0   |
|          |
+----------+

This will properly resolve the l3mdev of eth0 to vrf-blue.

Signed-off-by: Alexis Bauvin <abauvin@scaleway.com>
Reviewed-by: Amine Kherbouche <akherbouche@scaleway.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Tested-by: Amine Kherbouche <akherbouche@scaleway.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 22 insertions, 0 deletions

diff --git a/include/net/l3mdev.h b/include/net/l3mdev.h
index 3832099289c5..78fa0ac4613c 100644
--- a/include/net/l3mdev.h
+++ b/include/net/l3mdev.h
@@ -101,6 +101,17 @@ struct net_device *l3mdev_master_dev_rcu(const struct net_device *_dev)
 	return master;
 }
 
+int l3mdev_master_upper_ifindex_by_index_rcu(struct net *net, int ifindex);
+static inline
+int l3mdev_master_upper_ifindex_by_index(struct net *net, int ifindex)
+{
+	rcu_read_lock();
+	ifindex = l3mdev_master_upper_ifindex_by_index_rcu(net, ifindex);
+	rcu_read_unlock();
+
+	return ifindex;
+}
+
 u32 l3mdev_fib_table_rcu(const struct net_device *dev);
 u32 l3mdev_fib_table_by_index(struct net *net, int ifindex);
 static inline u32 l3mdev_fib_table(const struct net_device *dev)
@@ -208,6 +219,17 @@ static inline int l3mdev_master_ifindex_by_index(struct net *net, int ifindex)
 }
 
 static inline
+int l3mdev_master_upper_ifindex_by_index_rcu(struct net *net, int ifindex)
+{
+	return 0;
+}
+static inline
+int l3mdev_master_upper_ifindex_by_index(struct net *net, int ifindex)
+{
+	return 0;
+}
+
+static inline
 struct net_device *l3mdev_master_dev_rcu(const struct net_device *dev)
 {
 	return NULL;