net/mlx5e: Read neigh parameters with proper locking

The nud_state and hardware address fields are protected by the neighbour
lock, we should acquire it before accessing those parameters.

Use this lock to avoid inconsistency between the neighbour validity state
and it's hardware address.
Signed-off-by: Hadar Hen Zion <hadarh@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en_tc.c

@@ -1223,6 +1223,7 @@ static int mlx5e_create_encap_header_ipv4(struct mlx5e_priv *priv,
 	struct flowi4 fl4 = {};
 	char *encap_header;
 	int ttl, err;
+	u8 nud_state;
 
 	if (max_encap_size < ipv4_encap_size) {
 		mlx5_core_warn(priv->mdev, "encap size %d too big, max supported is %d\n",
@@ -1252,7 +1253,12 @@ static int mlx5e_create_encap_header_ipv4(struct mlx5e_priv *priv,
 	if (err)
 		goto out;
 
-	if (!(n->nud_state & NUD_VALID)) {
+	read_lock_bh(&n->lock);
+	nud_state = n->nud_state;
+	ether_addr_copy(e->h_dest, n->ha);
+	read_unlock_bh(&n->lock);
+
+	if (!(nud_state & NUD_VALID)) {
 		pr_warn("%s: can't offload, neighbour to %pI4 invalid\n", __func__, &fl4.daddr);
 		err = -EOPNOTSUPP;
 		goto out;
@@ -1261,8 +1267,6 @@ static int mlx5e_create_encap_header_ipv4(struct mlx5e_priv *priv,
 	e->n = n;
 	e->out_dev = out_dev;
 
-	neigh_ha_snapshot(e->h_dest, n, out_dev);
-
 	switch (e->tunnel_type) {
 	case MLX5_HEADER_TYPE_VXLAN:
 		gen_vxlan_header_ipv4(out_dev, encap_header,
@@ -1297,6 +1301,7 @@ static int mlx5e_create_encap_header_ipv6(struct mlx5e_priv *priv,
 	struct flowi6 fl6 = {};
 	char *encap_header;
 	int err, ttl = 0;
+	u8 nud_state;
 
 	if (max_encap_size < ipv6_encap_size) {
 		mlx5_core_warn(priv->mdev, "encap size %d too big, max supported is %d\n",
@@ -1327,7 +1332,12 @@ static int mlx5e_create_encap_header_ipv6(struct mlx5e_priv *priv,
 	if (err)
 		goto out;
 
-	if (!(n->nud_state & NUD_VALID)) {
+	read_lock_bh(&n->lock);
+	nud_state = n->nud_state;
+	ether_addr_copy(e->h_dest, n->ha);
+	read_unlock_bh(&n->lock);
+
+	if (!(nud_state & NUD_VALID)) {
 		pr_warn("%s: can't offload, neighbour to %pI6 invalid\n", __func__, &fl6.daddr);
 		err = -EOPNOTSUPP;
 		goto out;
@@ -1336,8 +1346,6 @@ static int mlx5e_create_encap_header_ipv6(struct mlx5e_priv *priv,
 	e->n = n;
 	e->out_dev = out_dev;
 
-	neigh_ha_snapshot(e->h_dest, n, out_dev);
-
 	switch (e->tunnel_type) {
 	case MLX5_HEADER_TYPE_VXLAN:
 		gen_vxlan_header_ipv6(out_dev, encap_header,