From: Tariq Toukan <tariqt@nvidia.com>

[ Upstream commit 719a402cf60311b1cdff3f6320abaecdcc5e46b7]

ndo_sk_get_lower_dev returns the lower netdev that corresponds to
a given socket.
Additionally, we implement a helper netdev_sk_get_lowest_dev() to get
the lowest one in chain.

Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Boris Pismenny <borisp@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ Keerthana: Backported the patch to v5.10.y ]
Signed-off-by: Keerthana K <keerthana.kalyanasundaram@broadcom.com>
---
 include/linux/netdevice.h |  4 ++++
 net/core/dev.c            | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index d3a3e77a18df..c9f2a88a6c83 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1435,6 +1435,8 @@ struct net_device_ops {
 	struct net_device*	(*ndo_get_xmit_slave)(struct net_device *dev,
 						      struct sk_buff *skb,
 						      bool all_slaves);
+	struct net_device*	(*ndo_sk_get_lower_dev)(struct net_device *dev,
+							struct sock *sk);
 	netdev_features_t	(*ndo_fix_features)(struct net_device *dev,
 						    netdev_features_t features);
 	int			(*ndo_set_features)(struct net_device *dev,
@@ -2914,6 +2916,8 @@ int init_dummy_netdev(struct net_device *dev);
 struct net_device *netdev_get_xmit_slave(struct net_device *dev,
 					 struct sk_buff *skb,
 					 bool all_slaves);
+struct net_device *netdev_sk_get_lowest_dev(struct net_device *dev,
+					    struct sock *sk);
 struct net_device *dev_get_by_index(struct net *net, int ifindex);
 struct net_device *__dev_get_by_index(struct net *net, int ifindex);
 struct net_device *dev_get_by_index_rcu(struct net *net, int ifindex);
diff --git a/net/core/dev.c b/net/core/dev.c
index c0dc524548ee..ad2be47b48a9 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8169,6 +8169,39 @@ struct net_device *netdev_get_xmit_slave(struct net_device *dev,
 }
 EXPORT_SYMBOL(netdev_get_xmit_slave);
 
+static struct net_device *netdev_sk_get_lower_dev(struct net_device *dev,
+						  struct sock *sk)
+{
+	const struct net_device_ops *ops = dev->netdev_ops;
+
+	if (!ops->ndo_sk_get_lower_dev)
+		return NULL;
+	return ops->ndo_sk_get_lower_dev(dev, sk);
+}
+
+/**
+ * netdev_sk_get_lowest_dev - Get the lowest device in chain given device and socket
+ * @dev: device
+ * @sk: the socket
+ *
+ * %NULL is returned if no lower device is found.
+ */
+
+struct net_device *netdev_sk_get_lowest_dev(struct net_device *dev,
+					    struct sock *sk)
+{
+	struct net_device *lower;
+
+	lower = netdev_sk_get_lower_dev(dev, sk);
+	while (lower) {
+		dev = lower;
+		lower = netdev_sk_get_lower_dev(dev, sk);
+	}
+
+	return dev;
+}
+EXPORT_SYMBOL(netdev_sk_get_lowest_dev);
+
 static void netdev_adjacent_add_links(struct net_device *dev)
 {
 	struct netdev_adjacent *iter;
-- 
2.43.7