net/mlx5e: Check encap entry state when offloading tunneled flows

Encap entries cached by the driver could be invalidated due to
tunnel destination neighbour state changes.
When attempting to offload a flow that uses a cached encap entry,
we must check the entry validity and defer the offloading
if the entry exists but not valid.

When EAGAIN is returned, the flow offloading to hardware takes place
by the neigh update code when the tunnel destination neighbour
becomes connected.

Fixes: 232c0013 ("net/mlx5e: Add support to neighbour update flow")
Signed-off-by: Vlad Buslov <vladbu@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

@@ -1859,6 +1859,7 @@ static int mlx5e_attach_encap(struct mlx5e_priv *priv,
 		}
 	}
 
+	/* must verify if encap is valid or not */
 	if (found)
 		goto attach_flow;
 
@@ -1885,6 +1886,8 @@ static int mlx5e_attach_encap(struct mlx5e_priv *priv,
 	*encap_dev = e->out_dev;
 	if (e->flags & MLX5_ENCAP_ENTRY_VALID)
 		attr->encap_id = e->encap_id;
+	else
+		err = -EAGAIN;
 
 	return err;